HK1063551B - Image reading apparatus and its driving method - Google Patents

Description

Image reading apparatus and method of driving the same

Technical Field

The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus which brings a subject into contact with a sensor array in which a plurality of sensors are arranged in a matrix, detects a contact state of a specific subject such as a human body, and executes an operation of reading an image pattern of the subject, and a driving method thereof.

Background

Conventionally, as a two-dimensional image reading apparatus for reading a printed material, a photograph, a fingerprint, and other fine uneven shapes, there is a reading structure including: for example, an object to be detected is placed on a detection surface provided on an optical sensor array configured by arranging photoelectric conversion elements (optical sensors) in a matrix, and brought into contact with the detection surface, and an image pattern of the object to be detected is read.

In order to perform an appropriate image reading operation while suppressing deterioration of characteristics of the photosensor element, an image reading apparatus having a function of detecting a contact state of the object with the detection surface and starting the image reading operation (hereinafter referred to as a contact detection function) is known as an image reading apparatus in which the object directly contacts the detection surface. Further, there is also known an image reading apparatus having a function of discharging and removing static electricity (hereinafter referred to as a static electricity removing function) in order to suppress the occurrence of element destruction or erroneous operation due to static electricity charged to an object.

Here, a conventional configuration of an image reading apparatus having the above-described contact detection function and static electricity removal function will be briefly described with reference to the drawings. Here, a fingerprint reading apparatus is shown as an example of the configuration of the image reading apparatus.

First, a conventional contact detection function is explained.

Fig. 25 is a schematic configuration diagram showing a configuration example of a conventional contact detection function in the image reading apparatus, and fig. 26 is a schematic configuration diagram showing another configuration example. The contact detection function shown in fig. 25 is referred to as an impedance detection mode.

This aspect is configured to substantially include: a photosensor array 300A in which a plurality of photosensors 310 are arranged in a matrix on one surface side of a transparent insulating substrate; transparent electrode layers 320x and 320y formed on at least an array region where the plurality of photosensors 310 are arranged, 2 dividing the array region and spaced apart from each other by a fine gap GP; a detection circuit 330a for applying a dc voltage to one of the transparent electrode layers 320x and 320y (for example, the transparent electrode layer 320x) via the lead line PLx and applying a ground potential to the other transparent electrode layer (for example, the transparent electrode layer 320y) via the lead line Ply, detecting a voltage change caused by the finger FG or the like being placed on the transparent electrode layers 320x and 320y and contacting the transparent electrode layers, and starting an image reading operation by the image reading apparatus; and a surface light source (not shown) disposed on the back surface side of the photosensor array 300A.

In such an image reading apparatus, when an object to be detected, such as a finger FG, is placed across and brought into contact with the transparent electrode layers 320x and 320y, the transparent electrode layers 320x and 320y are electrically connected via the resistance of the finger FG, and a voltage change caused thereby is observed by the detection circuit 330a, whereby the placement of the finger on the photosensor array 100p is detected, various drivers and surface light sources, not shown, are operated, and an image reading operation for reading an image pattern (fingerprint) of the object to be detected is automatically performed.

The contact detection function shown in fig. 26 is referred to as a capacity detection method.

This embodiment schematically includes: a photosensor array 300B in which a plurality of photosensors 310 are arranged in a matrix; a transparent electrode layer 320z formed to cover the entire array region; a detection circuit 330b connected to the transparent electrode layer 320z via a lead line PLz, for detecting a change in capacitance caused by the transparent electrode layer 320z being placed on or brought into contact with an object to be detected, and starting an image reading operation by the image reading apparatus; and a surface light source (not shown) disposed on the back surface side of the photosensor array 300B.

In such an image reading apparatus, when an object to be detected such as a finger FG is placed on and brought into contact with the transparent electrode layer 320z, a change in capacitance due to the finger (human body) FG which is a dielectric substance being brought into contact with or added to the capacitance originally included in the photosensor array 300B is observed, and the image reading operation for reading a fingerprint is automatically executed by detecting the placement of the finger on the photosensor array 300B.

Next, a conventional static electricity removing function will be described.

Fig. 27A is a schematic configuration diagram showing a configuration example of a conventional static electricity removing function in the image reading apparatus.

In this structure, there are generally: a photosensor array 300C in which a plurality of photosensors 310 are arranged in an array on one surface side of a transparent insulating substrate; a transparent electrode layer 320z formed to cover at least an array region where the plurality of photosensors 310 are arranged; a lead-out wiring PLp connecting the transparent electrode layer 320z to a ground potential; and a surface light source (not shown) disposed on the back surface side of the photosensor array 300C. In the drawing, Rp is a wiring resistance of the lead-out wiring PLp.

In such an image reading apparatus, when an object to be detected such as a finger FG is placed on and brought into contact with the transparent electrode layer 320z, electric charges (static electricity) charged in the finger (human body) FG are discharged to the ground potential through the lead-out wiring PLp. That is, an excessive current due to the charge on the finger FG flows to the ground potential through the lead-out wiring PLp (wiring resistance Rp) having a low resistance, and thus, the element destruction of the photosensor 310 due to static electricity and the occurrence of an erroneous operation of the image reading apparatus can be suppressed. Here, since it is known that the discharge voltage by the finger contact is about 3 to 4kV, the electrostatic withstand voltage is considered to be larger than 5 kV. In order to obtain the electrostatic withstand voltage, the film impedance of the transparent electrode layer 320z is set to a value lower than 50 Ω/□, preferably 15 to 20 Ω/□.

Further, an image reading apparatus having both the contact detection function and the static electricity removal function is also known. Fig. 27B is a schematic configuration diagram showing an example of a configuration in a case where the image reading apparatus has both the contact detection function and the static electricity removal function.

At this time, the transparent electrode layer 330z formed on the photosensor array region is connected to the detection circuit 330b via the lead-out wiring PLp, and at the same time, the anti-parallel diode circuit 340z, for example, in which a pair of diodes are connected in parallel in opposite directions, is connected between the lead-out wiring PLp and the ground potential, and an excessive current due to the electric charge charged in the finger FG flows to the ground potential through the wiring PLp having the wiring resistance Rp and the diode of the anti-parallel diode circuit 340 z.

However, the conventional image reading apparatus described above has the following problems.

In the image reading apparatus (fingerprint reading apparatus) of the impedance detection method shown in fig. 25, a method of detecting a contact state of an object to be detected from a value when the object is in contact with both of the transparent electrode layers 320x and 320y spaced apart by the gap GP is applied, but when the object to be detected is a human body, the resistance value inherent to the object to be detected (human body) greatly varies due to an individual difference such as a physical constitution or a condition of the human body, or an external environment such as an air temperature or humidity. Therefore, the contact state of the object cannot be detected accurately, and the start control of the image reading operation is not uniform and unstable.

On the other hand, in the image reading apparatus of the capacitance detection system shown in fig. 26, as an example of a method for accurately detecting the contact state of the object, there is a method for reading a weak signal voltage change that is displaced in accordance with a capacitance component of the object, but in order to determine such a weak voltage change, it is desirable that the capacitance of the transparent electrode layer, and further the parasitic capacitance generated between the optical sensor and the transparent electrode layer, be extremely small. However, in order to improve the electrostatic resistance of the photosensor and the peripheral circuit, it is necessary to form the transparent electrode layer thick so that the transparent electrode layer has a sufficiently small film resistance. Here, when a general metal oxide is applied as the transparent electrode layer, since the transparent electrode layer has a characteristic of high impedance, if the transparent electrode layer is deposited thick to reduce the thin-film impedance as described above, the capacitance of the transparent electrode layer itself greatly increases, and the parasitic capacitance between the photosensor and the transparent electrode layer increases, so that the signal-to-noise ratio (S/N) of the capacitance change caused by the contact with the subject becomes small, and it is difficult to favorably detect the capacitance change when the subject (human body) is placed on the detection surface.

Further, the impedance detection method or the capacitance detection method of the contact detection function focuses only on the resistance value or the capacitance value of the object to be detected, and detects a change based on the resistance value or the capacitance value, so that it is difficult to determine whether the object is a proper object to be detected when a foreign object is touched or a foreign object is touched.

In the image reading apparatus having the static electricity eliminating function shown in fig. 27A and 27B, the film material of the transparent electrode layer 330C needs to have light transmittance and conductivity for discharging static electricity through the lead line PLp. Usually, tin oxide (SnO)₂) Film or ITO (Indium-Tin-Oxide: indium tin oxide) film, and the like.

As described above, it has been known that a predetermined electrostatic withstand voltage can be obtained when the film resistance of the transparent electrode layer is a value lower than 50. omega./□, preferably 15 to 20. omega./□, and that such a value can be obtained when the ITO film is used as the transparent electrode layer by setting the film thickness to approximately 1500. sup. -. 2000. sup./2000 *.

However, the condition of the film resistance of the transparent electrode layer is, as described above, a discharge voltage by finger contact is determined under the condition that the electrostatic withstand voltage is preferably greater than 5 kV. However, as a result of intensive studies by the inventors of the present application, it has been found that the human body sometimes takes electricity of 10kV or more. It is also known that a value higher than 10kV, specifically, a value of about 10kV to 15kV is required as the corresponding electrostatic withstand voltage.

On the contrary, in consideration of the conventional technology, it is assumed that the necessary electrostatic withstand voltage can be obtained by making the transparent electrode layer low in resistance, but in this case, the film thickness of the transparent electrode layer needs to be further increased. However, since the transparent electrode layer must have good light transmittance and not obstruct reading of an object image pattern, the film thickness cannot be excessively increased. In addition, when a capacitance detection method using a transparent electrode layer is applied as the contact detection function, as described above, if the thickness of the transparent electrode layer is increased, the parasitic capacitance between the optical sensor and the transparent electrode layer increases, and it is difficult to favorably detect a change in capacitance when the subject (human body) is placed on the detection surface.

Disclosure of Invention

The present invention is advantageous in that, in an image reading apparatus for reading an image pattern of an object to be detected, a contact state of a specific object to be detected placed on or in contact with a detection surface can be detected well, and an image pattern reading operation is started, and static electricity charged to the object to be detected is discharged well, thereby preventing element destruction or system malfunction due to the static electricity.

In order to obtain the above advantages, an image reading apparatus according to the present invention includes: a detection surface on which a subject is placed; a sensor array in which a plurality of sensors that read an image pattern of the object placed on the detection surface are arrayed; a 1 st detection electrode provided at least on an upper portion of the sensor array and having the detection surface; a 2 nd detection electrode electrically insulated from and spaced apart from the 1 st detection electrode; an opposite electrode provided opposite to the 1 st detection electrode via an interlayer insulating film; a signal voltage applying circuit for applying a signal voltage having a 1 st signal waveform that periodically fluctuates to the counter electrode and exciting a 2 nd signal waveform in the 1 st detection electrode through the interlayer insulating film; a contact detection device for determining whether or not the subject in contact with the detection surface is a specific subject based on a 2 nd signal waveform state excited in the 2 nd detection electrode in response to the subject contacting both the 1 st detection electrode and the 2 nd detection electrode; and a drive control device that performs an image reading operation of reading an image pattern of the subject placed on the detection surface by supplying a predetermined drive control signal to each sensor of the sensor array based on a result of determination of whether or not the subject is the specific subject by the contact detection device, wherein the specific subject is, for example, a human body, and the image pattern specific to the human body is read.

Each sensor of the sensor array is an optical sensor, the 1 st detection electrode and the interlayer insulating film have optical transparency, and the 1 st detection electrode is a transparent conductive film provided at least on the upper portion of the light-sensing surface of the sensor array via the interlayer insulating film, and the transparent conductive film is made of a material mainly containing indium tin oxide, for example.

The 1 st detection electrode is a conductive film provided on the sensor array, the 2 nd detection electrode is a conductive member provided near at least a part of the periphery of the conductive film, the conductive member is, for example, a conductive case member surrounding the periphery of the sensor array, and the 1 st detection electrode and the 2 nd detection electrode are arranged so as to contact the subject over the entire periphery thereof.

The detection circuit further includes an amplitude limiting circuit, and the voltage value that defines the upper limit and the lower limit of the 2 nd signal waveform excited in the 1 st detection circuit is formed of, for example, an anti-parallel diode circuit provided between the 1 st detection electrode and a ground electrode.

The signal voltage applying circuit applies a voltage component having a predetermined voltage amplitude and a periodic pulse-like signal waveform to the counter electrode.

The contact detection device determines whether or not the object is a specific object based on the voltage amplitude and the amplitude center voltage value of the 3 rd signal waveform excited in the 2 nd detection electrode. The contact detection device determines whether or not the specific object is detected based on a comparison between a threshold voltage set in advance based on a capacitance component and a resistance component of the specific object and the 3 rd signal waveform excited in the 2 nd detection electrode. The contact detection device includes a threshold voltage setting circuit that sets the threshold voltage, and a comparison circuit that compares the magnitude relationship between the threshold voltage and the 3 rd signal waveform. The contact detection device determines that the object is the specific object when the threshold voltage is included in a voltage amplitude range of the 3 rd signal waveform excited in the 2 nd detection electrode based on a comparison result of the comparison circuit.

The 3 rd signal waveform is a waveform that fluctuates periodically, and the contact detection device includes a counter circuit that counts the number of times the 3 rd signal waveform passes through the threshold voltage level based on a comparison result of the comparator circuit, and determines that the subject is the specific subject when a continuous count value of the counter circuit exceeds a preset number of times.

The sensor is an optical sensor, and has a source electrode and a drain electrode formed by sandwiching a channel region formed of a semiconductor layer, the counter electrode is the drain electrode and a drain line connected to the drain electrode, and the 1 st signal voltage applied to the counter electrode by the signal voltage applying circuit is a pulse voltage applied to the drain line, for example, a precharge pulse.

A time constant defined by a resistance component between the detection surface and a ground potential and a capacitance component added to the detection surface is set to a value of 0.3 μ sec or less, preferably 0.25 μ sec or less than 0.25 μ sec, the resistance component includes a resistance of the 1 st detection electrode and is set to a resistance value of 30 Ω or less than 30 Ω, and the capacitance component includes a capacitance formed between the 1 st detection electrode and the counter electrode facing each other via the interlayer insulating film and between the 1 st detection electrode and the sensor, and is set to a capacitance value of 10nF or less than 10 nF.

The sensors of the sensor array are photosensors each having a predetermined light-receiving surface, and the 1 st detection electrode is a transparent conductive film having an area larger than that of the light-receiving surface and provided on the upper portion of the light-receiving surface of the sensor array via the interlayer insulating film. In addition, a conductive member having a resistance value lower than that of the transparent conductive film is provided in the transparent conductive film in an area excluding at least an area corresponding to the light-sensing surface, the resistance component includes a resistance formed by the transparent conductive film and the conductive member, and the conductive member is made of a conductive material which is one of chromium, aluminum, an alloy material containing chromium, and an alloy material containing aluminum.

In order to obtain the above advantages, the method for driving the image reading apparatus of the present invention includes the steps of: applying a signal voltage having a 1 st signal waveform that periodically fluctuates to a counter electrode provided opposite to a 1 st detection electrode provided on the sensor array and having the detection surface via an interlayer insulating film, and exciting a 2 nd signal waveform in the 1 st detection electrode; detecting a 3 rd signal waveform excited in the 2 nd detection electrode based on the object contacting both the 1 st detection electrode and a 2 nd detection electrode electrically insulated from and spaced apart from the 1 st detection electrode; judging whether the detected object contacting the detection surface is a specific object according to the state of the detected 3 rd signal waveform; and when the detected body is determined to be the specific detected body, the drive control device starts reading the image pattern,

the step of determining whether or not the subject is a specific subject includes a comparison step of comparing a threshold voltage set in advance based on a capacitance component and a resistance component of the specific subject with the 3 rd signal waveform excited in the 2 nd detection electrode, and the step of comparing the threshold voltage with the 3 rd signal waveform includes the steps of: judging whether the threshold voltage is included in a voltage amplitude range of the 3 rd signal waveform; when it is determined that the threshold voltage is included in the voltage amplitude range of the 3 rd signal waveform, it is determined that the subject is the specific subject.

Drawings

Fig. 1 is a schematic block diagram showing an embodiment 1 of a contact detection device for realizing the contact detection function of the present invention.

Fig. 2 is a schematic circuit diagram showing an example of a detection circuit configuration applied to embodiment 1 of the contact detection device.

Fig. 3A to D are schematic diagrams showing an example of the contact detection operation of the contact detection device according to embodiment 1.

Fig. 4A to D are schematic diagrams showing another example of the contact detection operation of the contact detection device according to embodiment 1.

Fig. 5 is a schematic block diagram showing embodiment 2 of a contact detection device for realizing the contact detection function of the present invention.

Fig. 6A to C are schematic diagrams showing an example of the contact detection operation of embodiment 2 of the contact detection device.

Fig. 7A, B is a cross-sectional structural view and an equivalent circuit showing a schematic structure of a double gate (double gate) type optical sensor.

Fig. 8 is a timing chart showing an example of a basic drive control method of the dual-gate photosensor.

Fig. 9 is a schematic configuration diagram of an optical sensor system including an optical sensor array configured by two-dimensionally arranging dual-gate optical sensors.

Fig. 10 is a sectional view of a main part at the time of fingerprint reading in a fingerprint reading apparatus based on an image reading apparatus to which an optical sensor system is applied.

Fig. 11A, B is a schematic configuration diagram showing an embodiment in which the contact detection device according to each embodiment is applied to a fingerprint reading device using an image reading device.

Fig. 12A, B is a schematic view showing a state in which a finger is placed on the fingerprint reading device of fig. 11A, B.

Fig. 13A is a schematic configuration diagram showing a configuration example of a drain driver applicable to a fingerprint reading apparatus to which the contact detecting apparatus according to each embodiment is applied.

Fig. 13B is a schematic configuration diagram showing another configuration example of a drain driver applicable to a fingerprint reading apparatus to which the contact detecting device of each embodiment is applied.

Fig. 14 is a schematic diagram illustrating a contact detection operation of a fingerprint reading apparatus to which the contact detection apparatus according to each embodiment is applied.

Fig. 15 is an equivalent circuit diagram showing the photosensor array in the touch detection operation.

Fig. 16A, B is a schematic configuration diagram showing an example of a conventional fingerprint reading apparatus as a comparison target of the image reading apparatus according to the embodiments of the present invention.

Fig. 17 is a schematic circuit diagram showing an example of a detection circuit applied to the conventional fingerprint reading apparatus of fig. 16A, B.

Fig. 18 is a schematic configuration diagram showing embodiment 1 of a configuration for realizing the static electricity removing function according to the present invention.

Fig. 19 is a schematic cross-sectional view showing a main part structure of embodiment 1 of the static electricity removing function.

Fig. 20A, B is a schematic diagram showing a test method applied when measuring the relationship between the electrostatic withstand voltage and the time constant in the image reading apparatus.

Fig. 21 is a graph showing a relationship between a time constant and a withstand voltage of the image reading apparatus.

Fig. 22 is a schematic configuration diagram showing a configuration example of embodiment 2 of the configuration for realizing the static electricity removing function of the present invention.

Fig. 23 is a schematic cross-sectional view showing a main part of embodiment 2 of the static electricity removing function.

Fig. 24A, B is a schematic configuration diagram showing another configuration example of embodiment 2 of the static electricity eliminating function.

Fig. 25 is a schematic configuration diagram showing a configuration example of a conventional contact detection function in the image reading apparatus.

Fig. 26 is a schematic configuration diagram showing another configuration example of the conventional touch detection function.

Fig. 27A is a schematic configuration diagram showing a configuration example of a conventional static electricity removing function in the image reading apparatus.

Fig. 27B is a schematic configuration diagram showing a configuration example in the case where both the contact detection function and the static electricity removal function are provided in the image reading apparatus.

Detailed Description

An image reading apparatus having a contact detection function and a static electricity removal function according to the present invention and a method of driving the image reading apparatus will be described below with reference to the embodiments shown in the drawings.

First, a configuration for realizing the contact detection function of the present invention will be described with reference to an embodiment.

(embodiment 1 of contact detection function)

Fig. 1 is a schematic block diagram showing embodiment 1 of a contact detection device for realizing the contact detection function of the present invention, and fig. 2 is a schematic circuit diagram showing an example of a detection circuit configuration applied to the contact detection device of the present embodiment.

As shown in fig. 1, the contact detection device of the present embodiment roughly includes: a 1 st detection electrode 10 and a 2 nd detection electrode 20 which are provided at a distance from each other and are in contact with each other across both sides by the object OBJ; an opposite electrode 30 provided opposite to the 1 st detection electrode 10 via an interlayer insulating film (insulating layer); a pulse generating circuit (signal voltage applying circuit) 40 that applies a signal voltage having a predetermined signal waveform to the counter electrode 30; an amplitude limiting circuit (amplitude limiting circuit) 50 for limiting the voltage amplitude of the signal component excited in the 1 st detection voltage 10 to a predetermined voltage range; and a detection circuit (contact detection device) 60 for detecting a change in the signal component excited in the 2 nd detection electrode 20 and determining a state in which the subject OBJ is in contact with the 1 st detection electrode 10 and the 2 nd detection electrode 20.

The 1 st detection electrode 30 is, for example, a transparent conductive film (tin oxide (SnO)₂) Film or ITO (Indium-Tin-Oxide: indium tin oxide) film) is provided so as to cover the entire region of the region where the object OBJ to be contacted is placed or contacted.

The 2 nd detection electrode 20 is made of a low-resistance conductive material such as metal, and is provided to be spaced apart from and electrically insulated from the 1 st detection electrode 10 via an insulator such as air. Here, the 2 nd detection electrode 20 is provided so as to protrude in a region close to, for example, the 1 st detection electrode 10, and is brought into contact with the subject OBJ in a state where the subject OBJ is placed in contact with the 1 st detection electrode 10. Specific configuration examples of the 1 st detection electrode 10 and the 2 nd detection electrode 20 will be described later.

Thus, as shown in fig. 1, the 1 st detection electrode 10 and the 2 nd detection electrode 20 are electrically connected only when the subject OBJ is placed and contacted across the 1 st detection electrode 10 and the 2 nd detection electrode 20.

The counter electrode 30 is, for example, a conductive thin film provided to face the 1 st detection electrode 10 with an insulating film as a dielectric interposed therebetween, and a capacitance having a predetermined capacitance value is formed by the 1 st detection electrode 10, the insulating film, and the counter electrode 30. Here, as described above, the counter electrode 30 may be provided as a thin film layer having a single shape and the same size as the 1 st detection electrode 10 formed in the entire region where the subject OBJ is placed and contacted, or may be provided as a thin film layer formed in a band shape or the like so as to have a predetermined arrangement path with respect to the 1 st detection electrode 10. Specific configuration examples of the counter electrode 30 will be described later.

The pulse generating circuit 40 generates a pulse-like signal voltage (1 st signal waveform) having a predetermined voltage amplitude Δ Vp (e.g., O-Vp) and a predetermined signal period, and applies the generated voltage to the counter electrode 30.

For example, as shown in fig. 1, the amplitude limiting circuit 50 includes an anti-parallel diode circuit portion 50a in which a pair of diodes is connected in anti-parallel between the 1 st detection electrode 10 and the ground potential, and an impedance element 50b connected in parallel to the anti-parallel diode circuit portion 50 a.

Thus, in the 1 st detection electrode 10, the excitation signal waveform corresponds to the 2 nd signal waveform of the 1 st signal waveform based on the capacitance component via the insulating film of the pulse-like 1 st signal waveform applied to the counter electrode 30 by the pulse generation circuit 40. The anti-parallel diode circuit portion 50a of the amplitude limiting circuit 50 defines the voltage amplitude Δ va (the upper limit voltage and the lower limit voltage) of the 2 nd signal waveform within a voltage range + Vf to Vf corresponding to the forward voltage Vf of the diode, and controls the impedance element 50b so that the positive and negative ac voltage waveforms are centered around the ground potential.

Here, since the 2 nd detection electrode has a structure in which it is spaced apart from and electrically insulated from the 1 st detection electrode 10 by a gap, the capacitance component formed by the 1 st detection electrode 10 and the 2 nd detection electrode 20 is very small. Therefore, in a state where the object OBJ is not in contact with the object, the signal waveform (3 rd signal waveform) excited on the 2 nd detection electrode 20 side by the 2 nd signal waveform excited by the pulse generating circuit 40 at the 1 st detection electrode 10 is set to be extremely small, and cannot be detected by the detection circuit 60. The details are as described later.

By exciting the 2 nd signal waveform whose voltage amplitude Δ Va is limited by the amplitude limiting circuit 50 at the 1 st detection electrode 10 and defining the voltage range within + Vf to Vf by the voltage amplitude Δ Va, even when an electrical disturbance factor exceeding the voltage range (a voltage greater than the amplitude upper limit voltage + Vf and a voltage less than the amplitude lower limit voltage-Vf) is applied to the 1 st detection electrode, an electric current can be passed to the ground current flow by the antiparallel diode 50a connected to the amplitude limiting circuit 50, and only a voltage within the predetermined voltage range (+ Vf to Vf) defined by the voltage amplitude Δ Va can be applied to the 1 st detection electrode 10. Therefore, for example, an excessive voltage larger than the above-described upper limit amplitude voltage + Vf can be prevented from being applied to the counter electrode 30 via the insulating film, and electrostatic breakdown of the contact detection device and the peripheral circuit can be appropriately prevented.

The detection circuit 60 constantly monitors the signal waveform excited in the 2 nd detection electrode 20, determines that the specific object OBJ is in contact across both the 1 st detection electrode 10 and the 2 nd detection electrode 20 when a predetermined signal waveform is detected, and outputs the determination result as a contact detection signal.

Specifically, as shown in fig. 2, the detection circuit 60 generally includes: a resistance R11 connected between the contact N1 connected to the 2 nd detection electrode 20 and the high potential power supply Vdd; a resistor R12 connected between the node N1 and ground potential; resistors R21 and R22 connected in series between the high-potential power supply Vdd and the ground potential via a junction N2; and a comparator CMP, the contact N1 being connected to the non-inverting input terminal (+), and the contact N2 being connected to the inverting input terminal (-).

In the detection circuit having such a circuit configuration, the comparator CMP compares the voltage component of the 3 rd signal waveform (the signal voltage V α at the node N1) excited in the 2 nd detection electrode 20 with the reference voltage (threshold voltage) Vref generated by dividing the voltage at the node N2, and outputs a touch detection signal when the signal voltage V α is larger than the reference voltage Vref.

(method of detecting contact detecting device)

Next, the contact state detection operation of the object to be detected by the contact detection device having the above-described configuration will be described in detail with reference to the drawings.

Fig. 3A to D are schematic diagrams showing an example of the contact detection operation of the contact detection device according to the present embodiment. Here, fig. 3A corresponds to a state when the object OBJ is not in contact, and fig. 3B to D correspond to states when the object OBJ is in contact.

First, in a state where the subject OBJ is not in contact with the 1 st and 2 nd detection electrodes 10 and 20, the 2 nd detection electrode 20 is not substantially affected by the 2 nd signal waveform excited in the 1 st detection electrode 10, and therefore the signal voltage V α input to the non-inverting input terminal (+) of the comparator CMP becomes a signal waveform having an amplitude center voltage Vc and a minute amplitude substantially at a predetermined voltage Vr (for example, Vdd/2 when the resistance values of the resistance elements R11 and R12 are equal) generated by dividing the voltage by the resistance elements R11 and R12 connected to the contact point N1. Here, by arbitrarily setting the voltage division ratio by the resistance elements R11 and R12, the reference voltage Vref input to the inverting input terminal (-) is made larger than the signal voltage V α (═ Vr), and the contact detection signal cannot be output from the comparator CMP.

On the other hand, in a state where the subject OBJ is placed in contact with the subject OBJ across the 1 st and 2 nd detection electrodes 10 and 20, the 1 st and 2 nd detection electrodes 10 and 20 are electrically connected to each other through a resistance component and a capacitance component inherent in the subject OBJ, as shown in fig. 1 and 2. Accordingly, a 3 rd signal waveform is excited in the 2 nd detection electrode 20 according to the resistance component and the capacitance component of the object OBJ, and the 3 rd signal waveform corresponds to the 2 nd signal waveform excited in the 1 st detection electrode 10.

Here, the voltage amplitude Δ Vq of the 3 rd signal waveform excited in the 2 nd detection electrode 20 is affected by the capacitance component of the subject OBJ, and as described above, when the subject OBJ is not in contact, the capacitance component between the 1 st detection electrode 10 and the 2 nd detection electrode 20 is very small, and therefore the voltage amplitude Δ Vq is an extremely small value, but when the subject OBJ is in contact and the capacitance value of the subject OBJ is added, capacitive coupling occurs between the 1 st detection electrode 10 and the 2 nd detection electrode 20, and the magnitude of the voltage amplitude Δ Vq increases. The larger the capacitance value of the object OBJ, the larger the amplitude of the voltage amplitude Δ Vq. However, the maximum value (amplitude upper limit voltage) (+ Vmax to Vmin) of the voltage amplitude Δ Vq of the 3 rd signal waveform excited in the 2 nd detection electrode 20 is limited to the voltage amplitude Δ Va of the 2 nd signal waveform excited in the 1 st detection electrode 10, that is, a voltage range (+ Vf to Vf) defined by the forward voltage Vf of the antiparallel diode 50a provided in the amplitude limiting circuit 50 connected to the 1 st detection electrode 10.

The resistance component of the object OBJ is connected to the ground potential via the impedance element 50b of the amplitude limiting circuit 50, and is substantially connected in parallel to the impedance element R12 of the detection circuit 60, whereby the resistance value between the resistance component and the ground potential decreases, and acts in a direction in which the amplitude center voltage Vc of the signal waveform excited in the 2 nd detection electrode 20 decreases, and the smaller the resistance value, the lower the amplitude center voltage Vc.

Therefore, the 3 rd signal waveform excited by the 2 nd detection electrode 20 and input to the non-inverting input terminal (+) of the comparator CMP through the contact N1 has a predetermined amplitude center voltage Vc defined by the resistance component of the object OBJ and a predetermined voltage amplitude Δ Vq defined by the capacitance component of the object OBJ.

At this time, the reference voltage Vref input to the inverting input terminal (-) of the comparator CMP is appropriately set in advance, and by comparing the relationship between the magnitude of the reference voltage Vref and the signal waveform having the amplitude center voltage Vc and the voltage amplitude Δ Vq, the 3 rd signal waveform is detected based on the change in the resistance component and the capacitance component specific to the specific object OBJ (for example, finger FG), and only the state where the specific object OBJ is placed in contact can be detected.

Specifically, when focusing attention on the capacitance component of the object OBJ, in a state where the object OBJ is not in contact with the 1 st detection electrode 10 and the 2 nd detection electrode 20, as shown in fig. 3A, the reference voltage Vref generated by dividing the voltage by the impedance elements R11 and R12 is set in advance so that the reference voltage Vref is higher than the maximum value of the 3 rd signal waveform excited in the 2 nd detection electrode 20. On the other hand, as described above, the 3 rd signal waveform excited in the 2 nd detection electrode 20 has the amplitude center voltage Vc generated by voltage division by the impedance elements R11, R12 provided in the detection circuit 60, and has the minute voltage amplitude Δ Vqa. Therefore, in the comparator CMP provided in the detection circuit 60, the waveform of the signal inputted to the non-inverting input terminal (+) is smaller than the reference voltage Vref inputted to the inverting input terminal (-), and it is determined that the magnitude relationship is not inverted at all, and a low-level output signal is outputted.

Next, when the object OBJ makes contact across the 1 st and 2 nd detection electrodes 10 and 20, the voltage amplitude Δ Vqa of the 3 rd signal waveform input to the non-inverting input terminal (+) of the comparator CMP changes to Δ Vqb due to the capacitance component of the object OBJ as shown in fig. 3B. At this time, as described above, the voltage amplitude Δ Vqb greatly increases from the voltage amplitude Δ Vqa due to the capacitance component of the object OBJ, because the capacitance value added to the 1 st detection electrode 10 greatly increases. When the maximum value (amplitude upper limit voltage) + Vmax of the voltage amplitude Δ Vqa is larger than the reference voltage Vref, that is, when the 3 rd signal waveform crosses the reference voltage Vref, the comparator CMP outputs a high-level output signal, and the output of the comparator CMP changes, thereby detecting the object OBJ contact.

Here, as shown in fig. 3C and 3D, the object OBJ having the capacitance component that increases the voltage amplitude Δ Vqa of the 3 rd signal waveform substantially decreases the resistance value applied to the 1 st detection electrode 10 due to the resistance component, the amplitude center voltage Vc of the signal waveform decreases (Vca → Vcb), and as shown in fig. 3D, the comparator CMP outputs a low-level output signal when the maximum value (amplitude upper limit voltage) + Vmax of the voltage amplitude Δ Vqb becomes smaller than the reference voltage Vref, that is, when the 3 rd signal waveform and the reference voltage Vref do not intersect with each other. That is, the contact detection signal is not output.

That is, even when the subject is brought into contact across the 1 st and 2 nd detection electrodes 10 and 20, the contact detection device can determine that the subject is not in contact with the actual subject to be detected when the subject does not have a capacitance component and a resistance component specific to a substance to be brought into contact with the detection object in advance, for example, when the resistance value is extremely low although the subject has a predetermined capacitance value. In other words, when a forged finger or the like is used as the subject without using the actual subject, or when a conductive or capacitive foreign substance (rubber or the like) is added, the foreign substance can be excluded as a different object from the actual subject, and thus improper use or erroneous damage can be prevented.

Therefore, according to the contact detection device and the detection method thereof of the present embodiment, since it is possible to determine that the object is the main object to be detected only when the signal waveform changing in association with both of the resistance component and the capacitance component of the object exceeds the predetermined threshold value, it is possible to suppress the influence of the inherent state of the object to be detected, the external environment, and the like when detecting the contact state of the object to be detected, unlike the case shown in the related art, to perform more accurate detection and determination, and to improve the reliability of the contact detection device.

Next, another embodiment of the contact detection method of the present invention will be described with reference to the drawings.

Fig. 4A to D are schematic diagrams showing another example of the contact detection operation of the contact detection device according to the present embodiment. Here, the configuration of the contact detection device is equivalent to that of the above embodiment, and therefore, the description thereof is omitted. Even in the contact detection operation, the same methods as those of the above embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

In the detection method of the contact detection device shown in the above embodiment, the reference voltage Vref is set to be larger than the signal waveform excited in the 2 nd detection electrode 20 in advance, but in the present embodiment, for example, the reference voltage Vref is set to be smaller than the signal waveform excited in the 2 nd detection electrode 20 in advance.

Specifically, in a state where the object OBJ is not in contact with the 1 st detection electrode 10 and the 2 nd detection electrode 20, as shown in fig. 4A, the reference voltage Vref, and the amplitude center voltage Vc and the voltage amplitude Δ Vqa of the 3 rd signal waveform excited in the 2 nd detection electrode 20 are set in advance such that the reference voltage Vref becomes lower than the minimum value (amplitude lower limit voltage) -Vmin of the signal waveform excited in the 2 nd detection electrode 20. In this state, the comparator CMP provided in the detection circuit 60 outputs a high-level output signal when the signal waveform inputted to the non-inverting input terminal (+) is larger than the reference voltage Vref inputted to the inverting input terminal (-), and it is determined that the magnitude relationship is not inverted at all.

On the other hand, when the object OBJ makes contact across the 1 st and 2 nd detection electrodes 10 and 20, the voltage amplitude Δ Vqa of the 3 rd signal waveform input to the non-inverting input terminal (+) of the comparator CMP changes to Δ Vqb due to the capacitance component of the object OBJ as shown in fig. 4B. At this time, when the minimum value (lower limit amplitude voltage) -Vmin of the voltage amplitude Δ Vqb of the signal waveform increased by the capacitance component of the object OBJ is smaller than the reference voltage Vref, that is, when the 3 rd signal waveform crosses the reference voltage Vref, the comparator CMP outputs a low-level output signal, the output of the comparator CMP changes, and the object OBJ contact is detected.

Here, even if the object OBJ has a small capacitance component specific to the object OBJ and does not substantially have the capacitance component that increases the voltage amplitude Δ Vqa of the signal waveform, as shown in fig. 4C and 4D, the resistance value added to the 1 st detection electrode 10 is substantially reduced by the resistance component, the amplitude center voltage Vc of the signal waveform is lowered (Vca → Vcb), and when the minimum value (amplitude lower limit voltage) -Vmin of the voltage amplitude Δ Vqa becomes smaller than the reference voltage Vref, that is, when the 3 rd signal waveform crosses the reference voltage Vref, the comparator CMP outputs the output signal of a low level. That is, the output of the comparator CMP changes, and the object OBJ contact is detected.

That is, when the subject is contacted across the 1 st and 2 nd detection electrodes 10 and 20, the contact detection device determines that the subject is contacted when a capacitance component and a resistance component (particularly, a resistance component in a predetermined range) specific to a substance to be contacted are present in advance. In other words, even when the capacitance component of the object has the same value as the capacitance component specific to the substance to be detected, the signal waveform excited in the 2 nd detection electrode does not intersect the reference voltage Vref when the resistance component is much higher or much lower than the resistance component specific to the substance to be detected, and therefore the output of the comparator CMP does not change, and it is determined that the object is not actually in contact.

According to this contact detection method, as in the above-described embodiment, since the contact determination condition of the object to be detected that is the object of contact detection can be set relatively strictly while suppressing the influence of the intrinsic state of the object, the external environment, and the like, the contact state of the subject can be detected and determined relatively accurately.

(embodiment 2 of contact detecting device)

Next, embodiment 2 of the structure for realizing the contact detection function of the present invention will be described with reference to the drawings.

Fig. 5 is a schematic block diagram showing embodiment 2 of the contact detection device for realizing the contact detection function of the present invention, and fig. 6A to C are schematic diagrams showing an example of the contact detection operation of the contact detection device of the present embodiment. Here, the same configurations and methods as those of embodiment 1 are denoted by the same reference numerals, and the description thereof is simplified or omitted. Fig. 6A corresponds to a state where the object OBJ is not in contact, and fig. 6B, C corresponds to a state where the object OBJ is in contact.

As shown in fig. 5, the contact detection device of the present embodiment includes a contact determination circuit 70 in an output portion of a detection circuit 60 provided in the contact detection device shown in fig. 1 and 2.

Here, the contact determination circuit 70 counts the output signal of a specific signal level output from the detection circuit when the object is in contact with the 1 st detection electrode and the 2 nd detection electrode, and outputs a contact detection signal when the output signal is output more than a predetermined threshold number of times.

Specifically, for example, as in the case shown in fig. 3A, as shown in fig. 6A, the detection circuit 60 sets the reference voltage Vref in advance so that the reference voltage Vref becomes larger than the 3 rd signal waveform (the amplitude center voltage Vc, the voltage amplitude Δ vqa) excited in the 2 nd detection electrode 20, and sets the comparator CMP not to output the contact detection signal when the object OBJ is not in contact.

Next, when the object OBJ makes contact across the 1 st detection electrode 10 and the 2 nd detection electrode 20, the voltage amplitude Δ vqa and the amplitude center voltage Vc of the signal waveform change due to the capacitance component and the resistance component of the object OBJ, and as shown in fig. 6B, the comparator CMP provided in the detection circuit 60 detects a state where the magnitude relationship between the 3 rd signal waveform and the reference voltage Vref is reversed, that is, a state where the signal waveform crosses the reference voltage Vref, and outputs a contact detection signal from the comparator CMP. At this time, the contact determination circuit 70 counts the number of times the contact detection signal outputted from the detection circuit 60 (comparator CMP) is in a predetermined period, and determines that the object is actually in contact when the counted value exceeds a predetermined threshold (for example, 5 consecutive times).

According to this contact detection method, it is possible to realize a contact detection device with extremely high reliability, which can judge that the subject is the main subject only when the subject having a specific capacitance component and resistance component is continuously and stably contacted, and can favorably judge that the main subject and the foreign object are removed from the object of the contact detection operation when the conductive or capacitive foreign object is contacted between the 1 st detection electrode and the 2 nd detection electrode, and can prevent an erroneous operation such as an erroneous judgment that the subject is the main contact state and a contact detection signal is output even when the subject is erroneously temporarily contacted, for example, while suppressing the influence of the inherent state of the subject or the external environment.

(image reading apparatus)

An image reading apparatus using the contact detection apparatus of the present invention will be described below with reference to embodiments.

First, a sensor structure applicable to the image reading apparatus of the present invention is explained.

A sensor suitable for the image reading apparatus of the present invention can favorably use a solid-state imaging Device such as a CCD (charge coupled Device).

As is well known, a CCD has a structure in which photo sensors such as photodiodes and Thin Film Transistors (TFTs) are arranged in a matrix, and the amount of electron-hole pairs (the amount of charge) generated in accordance with the amount of light applied to the light-receiving portions of each photo sensor is detected by a horizontal scanning circuit and a vertical scanning circuit, thereby detecting the luminance of the light applied.

However, in the optical sensor system using such a CCD, it is necessary to separately provide a selection transistor for switching each scanned sensor to a selected state, and therefore, there is a problem that the number of detection pixels increases and the system itself becomes large.

Therefore, as a structure for solving such a problem in recent years, a thin film transistor (hereinafter referred to as a double-gate transistor) having a so-called double-gate structure has been developed, in which a photosensor itself has a photosensitive function and a selection transistor function, and miniaturization of a system and high density of pixels have been attempted. Therefore, the double-pass transistor can be preferably used also in the image reading apparatus of the present invention.

Here, a photosensor (hereinafter referred to as a double gate photosensor) formed of a double gate transistor, which is applicable to the image reading apparatus of the present invention, will be described in detail with reference to the drawings.

(Dual gate type optical sensor)

Fig. 7A, B is a cross-sectional configuration diagram showing a schematic configuration of a dual-gate type optical sensor and an equivalent circuit.

As shown in fig. 7A, the dual-gate type optical sensor 110 includes: a semiconductor layer (channel layer) 111 such as amorphous silicon which generates electron-hole pairs when excitation light (visible light in this case) enters; impurity layers 117 and 118 each formed of n + silicon and provided at both ends of the semiconductor layer 111; a drain electrode 112 and a source electrode 113 which are selected from chromium, a chromium alloy, aluminum, an aluminum alloy, and the like formed on the impurity layers 117 and 118 and are opaque to visible light; a top (top) gate electrode (1 st gate electrode) 121 formed above (above the drawing) the semiconductor layer 111 through a block (block) insulating film 114 and an upper (top) gate insulating film (insulating layer) 115, and formed of a transparent electrode layer of ITO or the like, and having transparency to visible light; a bottom gate electrode (2 nd gate electrode) 122 which is selected from chromium, a chromium alloy, aluminum, an aluminum alloy, and the like formed below (below the drawing) the semiconductor layer 111 through a lower gate insulating film (insulating layer) 116 and is opaque to visible light; and an uppermost transparent electrode layer 130 formed on the top gate electrode 121 via a protective insulating film (insulating layer; dielectric) 120. The dual-gate type photosensor 110 having such a structure is formed on a transparent insulating substrate 119 such as a glass substrate.

In fig. 7A, the top gate insulating film 115, the block insulating film 114, the bottom gate insulating film 116, the protective insulating film (dielectric) 120 provided on the top gate electrode 121, and the transparent electrode layer 130 of the uppermost layer are all made of a material having a high transparency to visible light of the excitation semiconductor layer 111, for example, silicon nitride, silicon oxide, ITO, or the like, and have a structure of detecting only light incident from above the drawing. As described later, the upper surface of the uppermost transparent electrode layer 130 serves as a detection surface DT on which an object is placed and contacted.

Such a dual-gate type photosensor 110 is generally represented by an equivalent circuit shown in fig. 7B. Here, TG is a top gate terminal electrically connected to the top gate electrode 121, BG is a bottom gate terminal electrically connected to the bottom gate electrode 122, S is a source terminal electrically connected to the source electrode 113, and D is a drain terminal electrically connected to the drain electrode 112.

Next, a driving control method of the above-described double-pass type photosensor will be described with reference to the drawings.

Fig. 8 is a timing chart showing an example of a basic drive control method of the dual-gate photosensor. Here, the structure of the double-pass type photosensor described above (fig. 7) is appropriately referred to for explanation.

As shown in fig. 8, first, in a reset operation (initialization operation), a pulse voltage (hereinafter referred to as a reset pulse; for example, Vtg is a high level of +15V) Φ Ti is applied to the top gate terminal TG of the double-pass photosensor 110, and carriers (here, holes) accumulated in the vicinity of the interface with the semiconductor layer 111 in the semiconductor layer 111 and the bulk insulating film 114 are released (reset period Trst).

Next, in the charge accumulation operation (light accumulation operation), a bias Φ Ti of a low level (for example, Vtg is-15V) is applied to the top gate terminal TG, thereby terminating the reset operation and starting a charge accumulation period Ta of the carrier accumulation operation. In the charge accumulation period Ta, electron-hole pairs are generated in the carrier generation region, which is the effective region for incidence of the semiconductor layer 111, in accordance with the amount of light incident from the top gate electrode 121 side, and holes are accumulated in the vicinity of the interface with the semiconductor layer 111 in the semiconductor layer 111 and the bulk insulating film 114, that is, around the channel region.

In the precharge operation, in parallel with the charge accumulation period Ta, a predetermined voltage (precharge voltage) Vpg is applied to the drain terminal D in accordance with the precharge signal Φ pg, and the drain electrode 112 holds the charge (precharge period Tprch).

After the precharge period Tprch elapses in the read operation, a bias voltage (read select signal; hereinafter referred to as a read pulse) Φ bi (selected state) of a high level (for example, Vbg +10V) is applied to the bottom gate terminal BG, and the double pass photosensor 110 is turned ON (read period Tread).

Here, in the readout period Tread, carriers (holes) accumulated in the channel region move in a direction of relaxing Vtg (-15V) applied to the top gate terminal TG of the opposite polarity, so Vbg (+15V) of the bottom gate terminal BG forms an n-channel, and the voltage (drain voltage) VD of the drain terminal D tends to correspond to the drain current, and gradually falls from the precharge voltage Vpg as time passes.

That is, in the case where the light accumulation state in the charge accumulation period Ta is the bright state, since carriers (holes) corresponding to the amount of incident light are trapped in the channel region, the negative bias of the top gate terminal TG is cancelled, and the double pass type photosensor 110 becomes the ON state by the positive bias of the bottom gate terminal BG of a magnitude equal to the cancelling portion. The drain voltage VD decreases according to the ON resistance corresponding to the amount of incident light.

On the other hand, when carriers (holes) are not accumulated in the channel region in the dark state of the light accumulation state, the positive bias of the bottom gate terminal BG is cancelled by applying a negative bias to the top gate terminal TG, the dual pass type photosensor 110 becomes an OFF state, and the drain voltage VD is kept substantially constant.

Therefore, the trend of the change in the drain voltage VD is closely related to the amount of light received during the time (charge accumulation period Ta) from the reset operation termination time when the reset pulse Φ Ti is applied to the top gate terminal TG to the read pulse Φ bi being applied to the bottom gate terminal BG, and tends to decrease rapidly when a large number of carriers are accumulated (bright state) and to decrease slowly when a small number of carriers are accumulated (dark state). Therefore, the readout period Tread starts, and the amount of light (irradiation light) incident on the double-pass photosensor 110 is converted by detecting the drain voltage VD (Vrd) after a predetermined time has elapsed or by detecting the time until the drain voltage VD reaches a predetermined threshold voltage.

The same processing steps are repeated for the dual-pass optical sensor 110 in the i +1 th row, using the above-described series of image reading operations as one cycle, whereby the dual-pass optical sensor 110 can be operated as a two-dimensional sensor system.

(optical sensor system)

Next, an optical sensor system including an optical sensor array in which the above-described dual-gate type optical sensors are arranged in a predetermined pattern will be described with reference to the drawings. Here, although the optical sensor array configured by two-dimensionally arranging a plurality of double-gate type optical sensors is shown and described, it is needless to say that a linear sensor array may be configured by one-dimensionally arranging a plurality of double-gate type optical sensors in the X direction, and the linear sensor array may be moved in the Y direction perpendicular to the X direction to scan (scan) a two-dimensional area.

Fig. 9 is a schematic configuration diagram of an optical sensor system including an optical sensor array configured by two-dimensionally arranging dual-gate optical sensors.

As shown in fig. 9, the optical sensor system generally has: a photosensor array 100 in which a plurality of dual-gate photosensors 110 are arranged in a matrix of, for example, n rows × m columns (n and m are arbitrary natural numbers); a top gate line 101 and a bottom gate line 102 extending to connect and extend a top gate terminal TG (top gate electrode 121) and a bottom gate terminal BG (bottom gate electrode 122) of each of the dual-gate photosensors 110 in the row direction; drain lines (data lines) 103 connecting drain terminals D (drain electrodes 12) of the respective dual-gate photosensors 110 in the column direction; a source line (common line) 104 connected to the source terminal S (source electrode 13) in the column direction and to the ground potential; a top gate driver 210 connected to the top gate line 101; a bottom gate driver 220 connected to the bottom gate line 102; and a drain driver 230 connected to the drain line 103, and including a column switch, a precharge switch, an output amplifier, and the like, which are not shown.

Here, the top gate line 101 is formed integrally with a top gate electrode 121 and a transparent electrode layer such as ITO as shown in fig. 7, and the bottom gate line 102, the drain line 103, and the source line 104 are formed integrally with a material opaque to excitation light, which is the same as the bottom gate electrode 122, the drain electrode 112, and the source electrode 113. The source line 104 is applied with the constant voltage Vss set in accordance with the precharge voltage Vpg described later, but may be the ground potential (GND).

In fig. 9, Φ tg is a control signal for generating selection output signals Φ T1, Φ T2,.. Φ Ti, and.. Φ Tn as either the reset voltage or the photo carrier accumulation voltage, Φ bg is a control signal for generating selection output signals Φ B1, Φ B2,.. Φ Bi, and.. Φ Bn as either the read voltage or the non-read voltage, and Φ pg is a precharge signal for controlling the timing of applying the precharge voltage Vpg. In addition, the structure of the drain driver 230 applicable to the present invention is described in detail later.

In this configuration, a photosensitive function is realized by applying a signal Φ Ti (i is an arbitrary natural number, i is 1, 2, and.. n) from the top gate driver 210 to the top gate terminal TG via the top gate line 101, and a selective read function is realized by applying a signal Φ bi from the bottom gate driver 220 to the bottom gate terminal BG via the bottom gate line 102, and taking a detection signal into the drain driver 230 via the drain line 103 to output the detection signal as an output voltage Vout of serial data or parallel data.

Fig. 10 is a sectional view of a main part of a configuration when an image pattern of a fingerprint is read in a fingerprint reading apparatus based on an image reading apparatus to which the optical sensor system is applied. Here, for convenience of explanation and illustration, a cross-sectional line portion showing a cross-sectional portion of the optical sensor system is omitted.

As shown in fig. 10, in an image reading apparatus for reading an image pattern such as a fingerprint, irradiation light is incident from a rear lamp (surface light source) BL provided below an insulating substrate 119 such as a glass substrate on which a double-pass type photosensor 110 is formed, and the irradiation light La is irradiated to a finger (object to be detected) FG placed on a fingerprint detection surface (detection surface) DT on a transparent electrode layer 130 through the transparent insulating substrate 119 and insulating films 115, 116, and 120 excluding a formation region of the double-pass type photosensor 110 (specifically, a bottom gate electrode 122, a drain electrode 112, and a source electrode 113).

When the fingerprint reading device detects a fingerprint, the translucent layer of the skin surface layers FGs of the finger FG contacts the transparent electrode layer 130 formed in the uppermost layer of the photosensor array 100, so that there is no air layer having a low refractive index in the interface between the transparent electrode layer 130 and the skin surface layers FGs. Here, since the thickness of the skin surface layer FGs is greater than 650nm, the light La incident on the inside of the convex portion Fpa of the fingerprint FP is scattered, reflected, and propagated inside the skin surface layer FGs. A part of the propagating light Lb passes through the transparent electrode layer 130, the transparent insulating films 120, 115, and 114, and the top gate electrode 121, and enters the semiconductor layer 111 of the dual-gate photosensor 110 as excitation light. Therefore, by accumulating carriers (holes) generated by the incident light to the semiconductor layer 111 of the dual-gate type photosensor 110 arranged at a position corresponding to the convex portion Fpa of the finger FG, the image pattern of the finger FG can be read as light and dark information according to the above-described series of drive control methods.

In addition, in the concave portion FPb of the fingerprint FG, the irradiated light La passes through the interface between the detection surface DT on the transparent electrode layer 130 and the air layer, reaches the finger FG at the end of the air layer, and is scattered in the skin surface layer FGs, but since the refractive index of the skin surface layer FGs is higher than that of air, the light Lc incident at a certain angle into the skin surface layer FGs on the interface is less likely to escape from the air layer, and the incidence to the semiconductor layer 111 of the dual-gate type photosensor 110 disposed at a position corresponding to the concave portion FPb is suppressed.

Therefore, by using a transparent conductive material such as ITO for the transparent electrode layer 130, light scattered or reflected by the finger FG placed on the transparent electrode layer 130 being irradiated is favorably made incident on the semiconductor layer 111 of each of the dual-gate type photosensors 110, so that the image pattern (fingerprint) of the subject can be favorably read without deteriorating the read trial characteristics in the reading operation of the finger FG.

Next, a specific configuration in a case where the contact detecting device according to each of the above embodiments is applied to a fingerprint reading device based on the above-described image reading device will be described. In the embodiments shown below, a case where the sensor is the above-described double-pass optical sensor will be described.

Fig. 11A, B is a schematic configuration diagram showing an embodiment in which the contact detecting device of each embodiment is applied to a fingerprint reading device using an image reading device, and fig. 12A, B is a schematic diagram showing a state in which a finger is set in the fingerprint reading device of fig. 11A, B. Here, the description is given with reference to the configurations of the optical sensor and the optical sensor system (fig. 7 and 9) as appropriate. The same reference numerals are given to the same components as those shown in fig. 7 and 9, and the description thereof will be simplified or omitted.

As shown in fig. 11A, B, the fingerprint reading device of the present embodiment includes: a sensor device PD including a photosensor array 100 in which the dual-gate photosensors 110 having the above-described structure are arranged in a matrix on one surface side of an insulating substrate 119, and a protective insulating film 120 formed in the entire array region in which the dual-gate photosensors 110 are arranged (the top gate insulating film 115 of the photosensor 111 and the protective insulating film 120 correspond to the interlayer insulating film); a transparent electrode layer 130 (transparent conductive film; corresponding to the 1 st detection electrode) formed on the protective insulating film 120; a surface light source BL disposed on the other surface side of the sensor device PD and configured to irradiate a subject (finger FG) in contact with the upper surface (detection surface DT) of the transparent electrode layer 130 with uniform light; a conductive case member (conductive member; corresponding to the 2 nd detection electrode) 240 provided so as to be electrically insulated from the sensor device PD and the transparent electrode layer 130 and so as to surround the sensor device PD and the transparent electrode layer 130; an amplitude limiting circuit (amplitude limiting means) 250 for limiting the voltage amplitude of the signal waveform (equal to the 2 nd signal waveform) excited in the transparent electrode layer 130 to a predetermined voltage range as shown in the above embodiment; and a detection circuit (contact detection means) 260 for detecting a change in a signal waveform (corresponding to the 3 rd signal waveform) excited in the case member 240 and determining a state in which the subject (finger FG) is in contact with both the transparent electrode layer 130 and the case member 240.

As shown in fig. 11B, the case member 240 is electrically insulated by a space interval (i.e., via an insulator such as air) from the transparent electrode layer 130. As shown in fig. 11A, the case member 240 surrounds the sensor device PD and the transparent electrode layer 130, and includes an opening 240a having a predetermined shape so as to expose the detection surface DT on the transparent electrode layer 130. The case member 240 is made of a single-layer or multi-layer conductor made of a material having a lower impedance than a transparent conductive material such as ITO constituting the transparent electrode layer 130, for example, chromium, aluminum, tungsten, or the like. Thus, the film impedance of can be realized by reducing the thickness of the board or the film thickness, and the signal-to-noise ratio (S/N) can be sufficiently increased.

Specifically, as shown in fig. 12A, B, the opening 240a of the case member 240 has a shape such that, in a state where a finger FG is placed on the detection surface DT of the transparent electrode layer 130, the finger FG simultaneously contacts the case member 240 near the end of the opening 240 a. That is, it has a shape suitable for the finger FG to contact both the transparent electrode layer 130 and the case member 240.

As described later, the case member 240 functions not only as a structure for detecting a state in which the finger FG contacts the detection surface DT, but also as a shield case for protecting the sensor device PD from an electric interference factor, a physical impact, or the like, and also as a guide member for inducing or guiding a finger as an object to be detected to well contact the detection surface DT on the transparent electrode layer 130.

Further, the detection circuit 260 constantly monitors a change in the signal waveform (3 rd signal waveform) excited in the case member 240, and contacts the finger FG across both the transparent electrode layer 130 and the case member 240, and when a predetermined change in the signal waveform is detected from the capacitance component and the resistance component specific to the finger FG, it is determined that the finger FG is placed on the fingerprint detection surface 30a on the transparent electrode layer 130, and the determination result is output as a contact detection signal to, for example, a controller (drive control circuit) that controls the operation of the fingerprint reading apparatus, thereby controlling the start timing of the fingerprint reading operation.

Specifically, as shown in the above-described contact detection device (see fig. 2), the detection circuit 260 compares the magnitude relationship between the reference voltage Vref set in advance based on the capacitance component and the resistance component of the finger FG as the subject and the voltage amplitude and the amplitude center voltage of the signal waveform (3 rd signal waveform) excited in the case member 240, and outputs the contact detection signal when the magnitude relationship with the reference voltage Vref changes (reverses) (see fig. 3A to D, fig. 4A to D, and fig. 6A to C).

Next, a drain driver applied to the fingerprint reading device (see fig. 9) according to the present embodiment will be described in detail with reference to the drawings.

Fig. 13A is a schematic configuration diagram showing one configuration example of a drain driver applicable to a fingerprint reading apparatus to which the contact detecting device of each embodiment is applied, and fig. 13B is a schematic configuration diagram showing another configuration example of the drain driver. Here, the description is made with reference to the above-described optical sensor system configuration (fig. 9) as appropriate. Note that the same components as those shown in fig. 9 are denoted by the same reference numerals, and description thereof is simplified or omitted.

As shown in the above-described embodiment (see, for example, fig. 1), the contact detection device of the present invention includes a counter electrode for exciting a predetermined signal waveform (2 nd signal waveform) to the 1 st detection electrode that is in contact with a subject, and a pulse generation circuit. When the contact detection device having such a structure is applied to an image reading device (fingerprint reading device) including a dual-pass type photosensor, for example, in the dual-pass type photosensor shown in fig. 7 and 9, the drain electrode 112 and the drain line 103 connecting the drain electrodes are used as the counter electrodes, and the drain driver 230 is used as the pulse generation circuit (signal voltage application circuit).

As shown in fig. 13A, the fingerprint reading apparatus of the present embodiment includes a drain driver 230 in addition to the photosensor array 100, the top gate driver 210, and the bottom gate driver 220, which are substantially equivalent to the configuration shown in fig. 7, and the driver includes: a column switch 231 connected to the drain lines 103, an output amplifier 232 provided at an output end of the column switch 231, a switch group 233 having one end connected to each drain line 103, a single switch 234 commonly connected to the other end of the switch group 232, and a plurality of power supply voltages Vpg, Vgnd connected in parallel to the switch 234.

Here, the column switches 231 and the output amplifiers 232 constituting the drain driver 230 read the amount of electric charge (carriers) accumulated in the dual-pass photosensors 110 in accordance with the subject image pattern collectively for each row by the column switches 231 via the drain lines 103 in accordance with the operation control procedure of the dual-pass photosensors 110, amplify the electric charge to a predetermined signal voltage by the output amplifiers 232 as a change in drain voltage, and output the amplified signal voltage as serial data or parallel data from the output terminals Vout to a peripheral circuit (for example, an image processing apparatus such as a fingerprint collating apparatus).

The switch group 233 has one end connected to each drain line constituting the photosensor array 100 and the other end connected to the single switch 234, and controls on/off states based on a precharge signal Φ pg supplied from a controller, not shown. On the other hand, the switch 234 is connected to the plurality of power supply voltages Vpg and Vgnd, and is selectively connected to one of the power supply voltages Vpg and Vgnd in accordance with a switching control signal Φ sw supplied from a controller, not shown, for control.

In the drain driver 230 having such a configuration, first, a case will be described in which the image reading operation is performed, and in the precharge operation performed in the charge accumulation period of the dual-pass photosensor, the switch 234 is switched to the precharge voltage Vpg side by the switching control signal Φ sw, and then the switch group 233 is turned on all at once at a predetermined timing by the precharge signal Φ pg, and the precharge voltage Vpg is applied to each of the dual-pass photosensors via the switch group 233 and the drain line 103.

In the reading operation of the double-pass type photosensor, the switch group 233 is turned off at once by the precharge signal Φ pg, and thereby the drain voltage corresponding to the amount of electric charges (carriers) accumulated in each of the double-pass type photosensors in the electric charge accumulation period in accordance with the image pattern of the subject (finger FG) is collectively taken into the column switch 231 through each drain line 103 and is output from the output terminal through the output amplifier 232 as serial data or parallel data.

On the other hand, in the contact detection operation executed before the image reading operation, first, the switch group 233 is turned on at a predetermined timing by the precharge signal Φ pg at a time, and the control switch 234 is repeatedly switched by the switching control signal Φ sw at a predetermined timing, so that the switch 234 is periodically and selectively connected to the reference charging voltage Vpg and the ground potential Vgnd side, and a pulse signal having a voltage amplitude in which the lower limit amplitude voltage is defined to OV and the upper limit amplitude voltage is defined to the precharge voltage Vpg (for example, 3.3V) is applied to the drain electrodes of all the double-gate type photosensors constituting the photosensor array 100 via the drain lines 103.

In the embodiment shown in fig. 13A and the method of applying the pulse signal to each drain line 103, the switch 234 controlled by the switching control signal Φ sw is used to select the precharge voltage Vpg and the ground potential Vgnd periodically, thereby generating and supplying the pulse signal having the voltage amplitude OV-Vpg, however, the present invention is not limited to this, and as shown in FIG. 13B, a pulse generating circuit 235 for generating a pulse signal having a predetermined voltage amplitude may be provided separately, and a switch 236 provided between the other end of the switch group 233 and the switch 234 and switching the connection between the switch group 233 and the switch 234 or the pulse generating circuit 235, in the contact detection operation, the control switch 236 is switched by the switch control signal Psw, the pulse generation circuit 235 is connected to the other end of the switch group 233, and the pulse signal output from the pulse generation circuit 235 is supplied to each drain line 103.

Next, a contact detection operation in the fingerprint reading device according to the present embodiment will be described in detail with reference to the drawings.

Fig. 14 is a schematic diagram illustrating a contact detection operation of a fingerprint reading apparatus to which the contact detection device according to each embodiment is applied, and fig. 15 is an equivalent circuit diagram illustrating an optical sensor array in the contact detection operation.

As described above, in the fingerprint reading apparatus of the present embodiment, in the contact detection operation, the drain driver 230 functions as the pulse generation circuit 40 in the contact detection apparatus shown in the above-described embodiment (see fig. 1), and the drain line 103 and the drain electrode 112 function as the counter electrode 30, so that, as shown in fig. 14, a signal waveform (2 nd signal waveform) corresponding to a pulse signal (1 st signal waveform) applied to the drain line 103 and the drain electrode 112 is excited in the transparent electrode layer 130 formed so as to cover the entire array region through the upper gate insulating film 115 and the protective insulating film 120.

Specifically, as shown in fig. 15, the photosensor array 100 has parasitic capacitances formed between a transparent electrode layer 130 constituting the uppermost layer and the top gate line 101, the bottom gate line 102, the drain line 103, and the source line 104, which are formed on the transparent electrode layer 130 through the protective insulating film 120, the upper gate insulating film 115, the lower gate insulating film 116, and the like, and also formed between the top gate line 101, the bottom gate line 102, the drain line 103, and the source line 104.

On the other hand, since the amplitude limiting circuit 250 is provided between the transparent electrode layer 130 and the ground potential as shown in fig. 14 and 15, the signal waveform (ac voltage waveform; 2 nd signal waveform) (-Vf to + Vf) excited in the transparent electrode layer 130 is limited by the forward voltage Vf in the anti-parallel diode circuit provided in the amplitude limiting circuit 250 as shown in fig. 14.

As shown in fig. 15, top gate line 101 connected to top gate driver 210 and bottom gate line 102 connected to bottom gate driver 220 are connected to the ground potential via output impedances Rt and Rb of drivers 210 and 220, and source line 104 is also connected to the ground potential.

Therefore, in such an equivalent circuit, when a pulse signal having a predetermined voltage amplitude is applied through the drain line 103 by the drain driver 230, no potential is excited in the top gate line 101, the bottom gate line 102, and the source line 104, and only the drain line 103 is excited with a predetermined signal waveform having a predetermined voltage amplitude by the amplitude limiting circuit 250.

Accordingly, even when an electrical disturbance factor other than the voltage amplitude range defined by the amplitude limiting circuit 250 (a voltage greater than the amplitude upper limit voltage + Vf and a voltage less than the amplitude lower limit voltage-Vf) is applied to the transparent electrode layer 130, it is possible to suppress an excessive voltage from being applied to the top gate line 101, the bottom gate line 102, or the like through the protective insulating film 120, and thus it is possible to appropriately prevent electrostatic breakdown of the photosensor array 100 or the drivers 210, 220, and 230.

In the state where the predetermined signal waveform is excited in the transparent electrode layer 130, as shown in fig. 14, when the finger FG is brought into contact with both the transparent electrode layer 130 and the case member 240, the transparent electrode layer 130 and the case member 240 are electrically connected via a capacitance component and a resistance component inherent to the finger FG. Therefore, as in the detection method of the contact detection device, the waveform of the signal excited in the case member changes due to the capacitance component and the resistance component unique to the finger FG, and the comparator (see fig. 2) provided in the detection circuit 260 performs the comparison process with the reference voltage set in advance, and when the voltage component of the signal waveform intersects the reference voltage, it is determined that the formal object (finger FG) to be detected is placed on and in contact with the transparent electrode layer 130, and the contact detection signal is output to the controller of the fingerprint reading device (not shown). The controller executes the above-described series of image reading operations based on the contact detection signal, and then starts an operation of reading an image pattern (fingerprint) of the finger FG placed on the transparent electrode layer 130 (photosensor array 100).

Here, the contact detecting apparatus and the detecting method thereof of the present invention and the effectiveness of the image reading apparatus to which the contact detecting apparatus is applied will be specifically described in comparison with other configurations.

Fig. 16A, B is a schematic configuration diagram showing an example of a conventional fingerprint reading apparatus using an impedance detection method as a comparison target of an image reading apparatus according to each embodiment of the present invention, and fig. 17 is a schematic circuit diagram showing an example of a detection circuit applied to the conventional fingerprint reading apparatus of fig. 16A, B. Here, the same components as those of the above embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

As shown in fig. 16A, B, for example, a fingerprint reading device to be compared with the image reading device of the present embodiment includes, as in the above-described embodiment: a sensor device PD provided with a photosensor array 100 having a transparent electrode layer 130 formed on the uppermost surface; a surface light source BL disposed on the back surface of the sensor device PD; and a conductive case member 240 provided around the sensor device PD in an electrically insulated manner, and the detection circuit 260 is connected to the transparent electrode layer 130 while a ground potential is connected to the case member 240. Here, at least the transparent electrode layer 130 and the case member 240 are electrically insulated via air or the like.

As shown in fig. 17, the detection circuit 260 roughly includes: an input protection diode 261 and an impedance element 262 connected in parallel between a contact Na connected to the transparent electrode layer 430 and a ground potential; an impedance element 263 connected between a contact Na and the power voltage Vdd; a voltage follower 264 for amplifying the potential of the contact Na with an amplification factor of 1; a variable impedance element 265 connected between the power supply voltage Vdd and the ground potential; a comparator 266 for comparing the voltage Vr generated by the variable impedance element 265 with the output potential Vo of the voltage follower 264 and outputting a binary logic signal corresponding to the comparison result as a touch detection signal; and a pull-up (pull up) impedance 267 connected between the output of the comparator 266 and the supply voltage Vdd.

In the fingerprint reading device having such a structure, in the case where the finger FG does not commonly contact on the transparent electrode layer 130 and the case member 240, the resistance value between the transparent electrode layer 130 and the case member 240 exhibits a high value substantially equivalent to infinity.

On the other hand, in the case where the finger FG is in contact with the transparent electrode layer 130 and the case member 240 in common, the resistance value between the transparent electrode layer 130 and the case member 240 shows a value based on the resistance component of the finger FG, that is, a low resistance value corresponding to the skin impedance of the finger FG.

Accordingly, in the image reading apparatus having such a configuration, since the potential of the contact Na changes according to the state in which the finger FG contacts the transparent electrode layer 130 and the case member 240, the reference voltage Vr inputted to the comparator 266 is appropriately set by the variable impedance, whereby the contact state of the finger FG can be outputted as a contact detection signal composed of a binary logic signal. In addition, the fingerprint reading device starts an operation of reading the image pattern (fingerprint) of the finger FG placed on the transparent electrode layer 130 (photosensor array 100) in accordance with the contact detection signal.

However, as described above, in the image reading apparatus (fingerprint reading apparatus) including the conductive case member 240 provided around the sensor device PD in an electrically insulated manner, when the detection circuit 260 detects the potential of the change only from the resistance component specific to the finger FG which is in contact between the transparent electrode layer 130 and the case member 240, and detects the contact state of the finger FG, the resistance value change detected from the finger resistance component is small, and the resistance value difference increases depending on the finger state (muscle state, personal difference, external environment, and the like), so that it is difficult to detect the voltage change in a correspondingly wide range, and it is difficult to always normally detect the presence or absence of contact. In addition, conductive foreign matter (dirt, etc.) having a resistance value similar to the resistance component of the actual subject (finger) is erroneously detected as the actual subject.

In contrast, in the contact detecting device, the detecting method thereof, and the image reading device according to the present invention, since the state where the object is in contact with the transparent electrode layer is detected and judged by performing the comparison processing of the signal waveform that changes based on both the capacitance component and the resistance component unique to the object (finger) and the reference voltage that is set in advance, it is possible to provide a highly reliable contact detecting device and image reading device that can favorably and uniformly judge the actual object to be detected as the object to be detected and other conductive or capacitive foreign matter, and at the same time, can suppress erroneous detection due to the foreign matter and suppress erroneous operation of the image reading device.

The following description will explain the structure for realizing the static electricity removing function according to the present invention by showing an embodiment.

(embodiment 1 of static eliminating function)

Fig. 18 is a schematic configuration diagram of embodiment 1 showing a configuration for realizing the static electricity removing function of the present invention, and fig. 19 is a schematic cross-sectional view showing a main part configuration of the present embodiment. Here, the description will be made with reference to the configurations of the above-described dual-gate type optical sensor and optical sensor system as appropriate.

The image reading apparatus of the present invention has both the contact detection function and the static electricity elimination function as described above, and as in the above-described embodiments of the contact detection apparatus, the image reading apparatus includes the transparent electrode layer formed on the sensor device corresponding to the 1 st detection electrode, the 2 nd detection electrode, the counter electrode, and the like, the conductive case member, the drain electrode, the pulse generation circuit, the amplitude limitation circuit, the detection circuit, and the like, but the configuration for realizing the static electricity elimination function shown below relates to the transparent conductive film structure formed on the photosensor device corresponding to the 1 st detection electrode, and for convenience, only the portion relating to the transparent conductive film structure is shown in an emphasized manner.

The same components as those in the above embodiments are denoted by the same reference numerals, and the description thereof is simplified or omitted.

As shown in fig. 18 and 19, the image reading apparatus according to the present embodiment includes: a photosensor device PD including a photosensor array 100 formed by arranging the dual-gate photosensors 110 having the above-described structure in a matrix on one surface side of an insulating substrate 119, and a protective insulating film (light-transmitting insulating film) 120 formed on the photosensor array 100; a transparent electrode layer (transparent electrode film) 430 formed on the protective insulating film 120 on one surface as a region including the array region of the photosensor array 100, and corresponding to the transparent electrode layer 130 in each embodiment of the contact detection device having the detection surface DT formed thereon; a top gate driver 210 connected to a top gate line 101 arranged on the photo sensor device PD (photo sensor array 100), and applying a reset pulse Φ Ti to the group of the double-pass photo sensors 110 in a specific row during a reset period Trst; a bottom gate driver 220 connected to the bottom gate line 102 disposed on the photosensor device PD, and configured to apply a readout pulse Φ Bi to the group of the dual-gate photosensors 110 in the specific row during a readout period Tread; and a drain driver 230 connected to the drain line 103 arranged in the photosensor device PD, for applying a precharge voltage in a precharge period Tprch and detecting, as an output voltage, an amount of carriers accumulated in the group of the dual-gate photosensors 110 in the specific row in a readout period Tread.

Here, as shown in fig. 18, the respective structures (the photosensor device PD, the transparent electrode layer 430, the top gate driver 210, the bottom gate driver 220, and the drain driver 230) of the image reading apparatus are mounted on one surface side of a transparent insulating substrate 400 such as a glass substrate or a thin film substrate, and lead lines LNt, LNb, and LNd are disposed on the insulating substrate 400 to electrically connect the top gate driver 210, the bottom gate driver 220, the drain driver 230, and an external controller or a power supply circuit, which are not shown. Further, a lead line LNg is disposed on the insulating substrate 400, and the transparent electrode layer 430 formed on the photosensor device PD is electrically connected to a ground potential. The structure in which the transparent electrode layer 430 is connected to the ground potential via the lead-out wiring substantially corresponds to the structure in which the 1 st detection electrode is connected to the ground potential via the amplitude limiting circuit, as compared with the structure of each embodiment of the contact detection device.

Here, the lead lines LNt, LNb, LNd, and LNg may be connected to an external controller, a power supply circuit, or the like via a connection terminal group (not shown) provided on one end side of the insulating substrate 400. Instead of providing the insulating substrate 400, for example, the insulating substrate 119 may be extended in the left and right and lower portions thereof to form predetermined wirings, and the top gate driver 210, the bottom gate driver 220, and the drain driver 230 may be mounted thereon, or the bottom gate driver 220 and the drain driver 230 may be formed integrally with the photosensor array 100 on the insulating substrate 119.

As shown in fig. 19, on the other surface of the photosensor device PD (the other surface of the insulating substrate 400), a surface light source BL for emitting uniform light to a subject (for example, a finger) placed on or in contact with the detection surface DT on the upper surface of the transparent electrode layer 130 is disposed. Therefore, the insulating substrate 119 shown in the structure of the photo sensor device PD (dual-pass photo sensor 110) and the insulating substrate 200 shown in fig. 18 and 19 may be formed of the same glass substrate or the like.

Next, the static electricity removing function applied to the image reading apparatus according to the present embodiment will be specifically described.

First, it is considered that the image reading apparatus having the above-described configuration is equivalent to the circuit configuration shown in fig. 19, and the resistance component R composed of the impedance of the transparent electrode layer 430 and the wiring impedance of the lead-out wiring LNg is formed between the transparent electrode layer 430 and the ground potential, and the capacitance component Co composed of the capacitance (parasitic capacitance) formed by the insulating films such as the transparent electrode layer 430 and the protective insulating film 120 and the electrodes of the dual-pass photosensors (specifically, the bottom gate line 102 formed integrally with the top gate line 101 and the bottom gate electrode 122 formed integrally with the top gate electrode 121, the drain line 103 formed integrally with the drain electrode 112, and the source line 104 formed integrally with the source electrode 113) is distributed and added to the transparent electrode layer 430. Here, the total capacitance of the capacitance components Co is assumed to be C.

As described in the related art, in an image reading apparatus for reading an image pattern of an object (such as a human body) to be detected, which is likely to be electrostatically charged, it is required to have a withstand voltage (electrostatic withstand voltage) higher than that of the object to be detected in order to prevent an element from being broken due to static electricity or an erroneous operation of the image reading apparatus when the object to be detected is placed on or brought into contact with a detection surface DT. As described above, since it is determined that a human body is a subject and it is substantially charged with static electricity of more than 10kV to 15kV, the image reading apparatus (fingerprint reading apparatus) having the above-described configuration is also required to have a static electricity withstand voltage of more than or equal to the above-described charging voltage.

Therefore, the present inventors have conducted various experiments on the relationship between the resistance component R and the capacitance component C and the withstand voltage based on such a viewpoint, and have studied the relationship, and as a result, have found that the withstand voltage of the image reading apparatus is closely related to the time constant τ (C × R) defined by the product of the resistance component R and the capacitance component C. From this viewpoint, it is found that the numerical range of the optimal time constant τ is secured in an image reading apparatus (fingerprint reading apparatus) in which a human body is used as a subject, and a sufficient electrostatic withstand voltage is secured.

Next, a test method applied to the image reading apparatus of the present embodiment will be described.

Fig. 20A, B is a schematic diagram showing a test method used for measuring the relationship between the electrostatic withstand voltage and the time constant in the image reading apparatus according to the present embodiment.

In the present embodiment, the ESD (electrostatic discharge) test method by the human body electrification module is applied to the image reading apparatus having the above-described configuration, and as the test method, there are two types of the all-terminal-grounded state in which all the electrodes of the transparent electrode layer 430 and the dual-pass type photosensor 100 are connected to the ground potential as shown in fig. 20A and the transparent electrode-grounded state in which only the transparent electrode layer 430 is connected to the ground potential as shown in fig. 20B, and the values of the impedance and the electrostatic capacitance of the transparent electrode layer 430 and the value of the applied voltage corresponding to the withstand voltage are measured for the predetermined time constant τ, respectively. Here, as a method of arbitrarily setting the time constant τ, the resistance value of the transparent electrode layer 430 is arbitrarily set by changing the film thickness of the transparent electrode layer 430, and the capacitance value added to the transparent electrode layer 430 is arbitrarily set by changing the film thickness of the protective insulating film 120, so that the time constant τ is changed.

Specifically, in the ESD test in the all-terminal grounded state, as shown in fig. 20A, the following states are set: the photosensor device PD in which the transparent electrode layer 430 and the protective insulating film 120 are formed with arbitrary thicknesses is placed on the test stand STG, the transparent electrode layer 430 is connected to the ground potential via the lead wire LNg, and the electrodes of the double-pass photosensor 110 are also connected to the ground potential. Next, the discharge gun is brought into contact with the detection surface DT on the transparent electrode layer 430, and an arbitrary voltage is applied to bring the charged object into contact therewith.

In the ESD test in which the transparent electrode is grounded, as shown in fig. 20B, the following states are set: in the photosensor device PD provided on the test stand STG, the transparent electrode layer 430 is connected to the ground potential only via the lead line LNg, and the electrodes of the dual-gate photosensor 110 are in a floating state (floating voltage state). Next, the discharge gun SP is brought into contact with the detection surface DT on the transparent electrode layer 430, and an arbitrary voltage is applied.

In this test method, electric charges based on the voltage applied to the transparent electrode layer 430 are held and accumulated in the electrostatic capacitance formed by the protective insulating film 120 and the like according to the potential difference between the transparent electrode layer 430 and each electrode of the dual-gate photosensor 110, and the electric charges gradually flow to the test stand STG connected to the ground potential through the lead-out wiring LNg having a wiring impedance lower than that of the transparent electrode layer 430 while jumping over the potential difference between the transparent electrode layer 430 and the ground potential. When the applied voltage generated by the discharge gun SP is changed, the measurement photosensor device PD (the dual-pass photosensor 110) is not broken, and the maximum applied voltage that is well maintained is measured as the electrostatic withstand voltage.

Fig. 21 is a graph showing a relationship between a time constant and a withstand voltage of the image reading apparatus based on the above-described test method. The electrostatic withstand voltage (maximum applied voltage) was measured in the following cases: an ITO film was used as the transparent electrode layer 430, the film thickness of the transparent electrode layer 430 was set to 50nm (500 *) and 150nm (1500 *), a silicon nitride film was used as the protective insulating film 120, and the film thickness of the protective insulating film 120 was set to 600nm (6000 *), 800nm (8000 *), and 1000nm (1 μm).

First, table 1 shows the relationship between the film resistance of the transparent electrode layer 430 and the capacitance of the protective insulating film 120 and the time constant τ, and the measurement data of the withstand voltage at the time constant τ.

TABLE 1

As shown in table 1, the ITO film forming transparent electrode layer 430 tends to have a lower film resistance as the film thickness is increased. In the present embodiment, since the transparent electrode layer 430 is formed in a substantially square shape, the resistance value of the transparent electrode layer 430 is the same as the film resistance. Therefore, the impedance of the transparent electrode layer 430 is hereinafter expressed by a film impedance. On the other hand, the silicon nitride film forming the protective insulating film 120 tends to have a smaller electrostatic capacitance as the film thickness is larger. Therefore, as the film thickness of the transparent electrode layer 430 is thicker (i.e., the film resistance is set lower) and the film thickness of the protective insulating film 120 is thicker (i.e., the capacitance is set lower), the time constant τ defined by the product of the film resistance (resistance component R) and the capacitance (capacitance component C) is smaller.

In the image reading apparatus set to have the film resistance and the capacitance having the values shown in table 1, when the electrostatic withstand voltage is measured according to the above-described test method, it is determined that as shown in table 1 and fig. 21, the smaller the time constant τ, the larger the electrostatic withstand voltage tends to be.

Thus, when the image reading apparatus of the present embodiment is applied to a fingerprint reading apparatus or the like in which a human body is used as a subject, it is found that, in order to realize a withstand voltage higher than static electricity (10 to 15kV) charged to the human body, it is effective to increase the film thickness of the transparent electrode layer 430 and set the film impedance low, and at the same time, it is effective to increase the film thickness of the protective insulating film 120 and set the capacitance low, and to reduce the time constant τ as much as possible.

However, as described above, in order to make light corresponding to the image pattern of the object incident on each of the dual-gate type photosensors 110 well, the transparent electrode layer 430, the protective insulating film 120, and the like must have high light transmittance, and therefore, in order to improve the above-described electrostatic withstand voltage (reduce the time constant τ), the film thicknesses of the transparent electrode layer 430, the protective insulating film 120, and the like are formed thick, and there is a possibility that the light transmittance characteristics are deteriorated by reflection, scattering, attenuation, and the like of light inside the film, and the reading sensitivity or accuracy of the photosensor device is lowered. Therefore, it is necessary to determine the numerical range of the time constant τ that can achieve appropriate read sensitivity while sufficiently securing the withstand voltage.

Therefore, the present inventors have found that, as shown in fig. 21, in order to realize a withstand voltage (static electricity removing function) of more than 10 to 10kV and favorable device characteristics (read sensitivity or accuracy), it is effective to set the film resistance of the transparent electrode 403 and the electrostatic capacitance of the protective insulating film 120 so that the time constant τ is substantially less than 0.3 microseconds (in the case of a withstand voltage of more than 10 kV), and more preferably less than 0.25 microseconds (μm) (in the case of a withstand voltage of more than 15kV), based on the experimental results and conditions such as the read sensitivity required for the optical sensor device. In this case, in order to make the time constant τ less than 0.3 μ sec, the film thicknesses of the transparent electrode layer 430, the protective insulating film 120, and the like are preferably formed to be extremely thick, and the numerical range of the time constant τ is preferably realized by an extremely thin film thickness depending on the film formation conditions, material composition, and the like.

Here, when it is verified from the measurement data shown in table 1 that 0.3 μ sec defining the numerical range of the time constant τ is defined, it is equivalent to make the film resistance of the transparent electrode layer 430 substantially less than 30 Ω/□ and the capacitance formed by the protective insulating film 120 substantially less than 10 nF. In the present embodiment, as shown in table 1, the numerical ranges of the thin-film impedance and the electrostatic capacitance correspond to the formation of the ITO film constituting the transparent conductive layer 30, the formation of the silicon nitride film constituting the protective insulating film 120 with a film thickness of substantially more than 150nm (1500 *), and the formation of the silicon nitride film constituting the protective insulating film 120 with a film thickness of substantially more than 600nm (6000 *), but the relationship between the thin-film impedance or the electrostatic capacitance and the film thickness greatly depends on the film formation conditions, the material composition, the crystal state, and the like, and therefore, there is no need to have a unique relationship, and the time constant τ or the electrostatic withstand voltage cannot be uniquely determined only by the film thicknesses because the film thicknesses (thin-film impedance and electrostatic capacitance) of the transparent electrode 430 and the.

Therefore, in the image reading apparatus of the present embodiment, by setting the time constant defined by the product of the resistance component of the transparent electrode layer and the capacitance component (electrostatic capacitance) of the protective insulating film or the like within a numerical range of less than 0.3 microseconds, even when the image reading apparatus is applied to a fingerprint reading apparatus or the like in which an object having a large static charge (10 to 15kV) such as a human body is used as the object, the static charge applied to the detection surface can be discharged to the ground potential well, and thus, the element destruction of the optical sensor or the occurrence of malfunction of the system can be prevented or suppressed well.

In the image reading apparatus of the present embodiment, a specific structure is not added to the conventional structure, and a structure having a desired time constant τ can be realized relatively easily and inexpensively by controlling only the film qualities (film thickness, film formation conditions, material composition, and the like) of the transparent electrode layer, the protective insulating film, and the like, so that an image reading apparatus having a good static electricity removing function which is well suited to the conventional structure can be provided.

(embodiment 2 of static eliminating function)

Next, embodiment 2 of the present invention for realizing the static electricity removing function will be described.

Fig. 22 is a schematic configuration diagram of embodiment 2 showing a configuration for realizing the static electricity removing function of the present invention, and fig. 23 is a schematic cross-sectional view showing a configuration of a main part of the image reading apparatus according to the present embodiment. Fig. 24A, B is a schematic configuration diagram showing another configuration example of the present embodiment. Here, the description will be made with reference to the configurations of the above-described dual-gate type optical sensor and optical sensor system as appropriate.

As shown in fig. 22 and 23, the image reading apparatus according to the present embodiment forms a transparent electrode layer 430 formed on the photosensor device PD having the same structure as that of embodiment 1 (see fig. 18) extending outside the light sensing region (array region) AR of the photosensor array 100, and a conductive member FR electrically connected to the transparent electrode layer 430 and the ground potential is provided in an arbitrary region of the transparent electrode layer 430.

Here, the conductive member FR is not particularly limited to the installation region, and for example, as shown in fig. 22 and 23, even in a state where the subject is placed on and in contact with the peripheral portion of the transparent electrode layer 430, the detection surface DT on the transparent electrode layer 430 is a region not overlapping the array region AR of the photosensor array 100, the subject can be formed in a region not in direct contact with the conductive member FR. That is, the conductive member FR is provided on the transparent electrode layer 430 around the array area AR so as to expose at least the array area AR.

The conductive member FR is electrically connected to the ground potential of the insulating substrate 200 via a lead line LNf extending from an arbitrary portion, and thereby electrically connects the transparent electrode layer 430 to the ground potential. Here, as the conductive material constituting the conductive member FR, a good conductor having a smaller electric resistance than the ITO film, the tin oxide film, or the like constituting the transparent electrode layer 430 can be preferably used, and for example, a conductive material selected from chromium, aluminum, an alloy material containing chromium, an alloy material containing aluminum, or the like can be preferably used.

However, in the image reading apparatus of the present embodiment, the film resistance of the transparent electrode layer 430 is not provided with the conductive member FR, and is required to be less than 30 Ω/□, since it is the same as in the embodiment 1. In order to set the film resistance of the transparent electrode layer 430 to be substantially less than 30 Ω/□, it is necessary to have a film thickness of substantially more than 150nm (1500 *) as described above, although the film formation conditions, material composition, and the like of the transparent electrode layer 430 are also used. However, as described in embodiment 1 above, when the film thickness of the transparent electrode layer 430, the protective insulating film 120, or the like on the photosensor array 100 is made thick, the light transmittance of the transparent electrode layer 430, the protective insulating film 120, or the like may deteriorate, and the reading sensitivity or accuracy of the photosensor device may deteriorate.

Therefore, in the present embodiment, the conductive member FR made of a low-resistance material is provided in the peripheral portion of the transparent electrode layer 430, and the transparent electrode layer 430 and the conductive member FR are electrically connected. Accordingly, the resistance component is constituted by the transparent electrode layer 430 and the conductive member FR being bonded to each other, and therefore, the resistance of the transparent electrode layer 430 can be substantially reduced.

That is, for example, when the film thickness of the transparent electrode layer 430 is made thin (for example, about 50nm (500 *)), even when the resistance of the transparent electrode layer 430 itself becomes high, the resistance component R bonded to the low-resistance conductive member FR can be reduced, and electrical characteristics (discharge characteristics) substantially the same as those when the film resistance of the transparent electrode layer 430 is set to be less than about 30 Ω/□ can be obtained.

Therefore, by connecting the peripheral portion of the transparent electrode layer 430 to the ground potential via the conductive member FR made of a good conductor and the lead-out wiring LNf, the film impedance of the transparent electrode layer 430 can be set to be substantially low, and the film thickness of the transparent electrode layer 430 can be made thin because the resistance value in the entire current path from the transparent electrode layer 430 to the ground potential via the conductive member FR and the lead-out wiring LNf is set to be low. Therefore, even when an object (finger or the like) to be detected, such as a human body, having static electricity of a relatively high voltage (more than 10 to 15kV) is placed on and brought into contact with the detection surface DT on the transparent electrode layer 430, the electric discharge from the transparent electrode layer 430 to the ground potential via the conductive member FR and the lead-out wiring LNf is favorable, the application of an excessive voltage to the photosensor device PD or the flow of an excessive current is suppressed, the destruction of the elements of the double-pass photosensor 110 or the occurrence of malfunction of the system is favorably prevented or suppressed, and the reading sensitivity or accuracy of the photosensor device is favorably ensured.

In the present embodiment, as shown in fig. 22 and 23, a case where the conductive member FR is formed in the peripheral portion of the transparent electrode layer 430, in the region which is not overlapped with the array region AR of the photosensor array 100, and in the region which is not directly contacted by the object to be detected is described, but the present invention is not limited to this, and the object to be detected may be contacted with both the detection surface DT and the conductive member FR in a state where the object to be detected (for example, finger FG) is placed on and contacted with the detection surface DT on the transparent electrode layer 430, as shown in fig. 24A, B, for example. In this case, it is preferable to contact the conductive member FR by appropriately setting the installation region or shape before the object contacts the detection surface DT.

According to the image reading apparatus having such a configuration, when the object is placed on and brought into contact with the detection surface on the transparent electrode layer, the object is brought into contact with the detection surface (transparent electrode layer), and at the same time, or before the object is brought into contact with the detection surface, the object is brought into contact with the conductive member having a low resistance, so that the static electricity charged in the object can be favorably discharged to the ground potential via the conductive member having a low resistance and the lead-out wiring, and the element destruction of the photosensor or the occurrence of an erroneous operation of the system can be favorably prevented or suppressed.

In the present embodiment, the case where the conductive member FR is laminated on the transparent electrode layer 430 extending to the periphery of the array region AR has been described, but the present invention is not limited thereto, and at least a part of the conductive member FR may electrically contact the transparent electrode layer 430.

(embodiment 3 of static eliminating function)

Next, embodiment 3 of the present invention for realizing the static electricity removing function will be described.

In this embodiment, the structure in which the time constant is set within a predetermined numerical range to improve the electrostatic withstand voltage as shown in the above-described electrostatic removal function embodiment 1 and the structure in which the low-resistance conductive member is provided in the peripheral portion of the transparent electrode layer and the thin-film resistance of the transparent electrode layer is substantially reduced to improve the electrostatic withstand voltage as shown in the electrostatic removal function embodiment 2 are provided.

Specifically, in the configuration shown in embodiment 2 (fig. 22 and 23), the conductive member FR having a lower impedance than the transparent electrode layer 430 is provided in the peripheral portion of the transparent electrode layer 430 formed to extend to the outside of the array region AR of the photosensor array 100, and the substantial value of the time constant τ defined by the thin-film impedance (resistance component) of the transparent electrode layer 430 and the capacitance (capacitance component) formed by the protective insulating film 129 and the like is set to be substantially less than 0.3 μ sec.

However, in the image reading apparatus of the present embodiment, as shown in embodiment 2, by electrically connecting the conductive member FR having a lower impedance than the transparent electrode layer 430 to the peripheral portion of the transparent electrode layer 430, the resistance value in the current path from the transparent electrode layer 430 to the ground potential via the conductive member FR and the lead-out wiring LNf can be reduced as a whole, and therefore, an effect equivalent to that in the case where the film impedance of the transparent electrode layer 430 is substantially set low can be obtained.

Thus, as shown in embodiment 1, since the time constant τ defined by the product of the film resistance of the transparent electrode layer 430 and the capacitance of the protective insulating film 120 or the like can be set substantially low without performing the film quality change control such as the increase in the film thickness of the transparent electrode layer 430, the electrostatic withstand voltage can be improved as shown in table 1 and fig. 21. Therefore, it is possible to provide an image reading apparatus having a relatively simple configuration, in which the thickness of the transparent electrode layer constituting the detection surface is formed thin, the film resistance is set substantially low, the time constant of the detection surface is reduced, and the electrostatic discharge characteristics are improved, so that the element destruction of the photosensor and the occurrence of malfunction in the system can be prevented or suppressed, and the reading sensitivity and accuracy of the photosensor device can be ensured.

In the above-described embodiments, the case where the dual-gate type optical sensor is applied to the sensor applied to the optical sensor system is described, but the sensor applied to the present invention is not limited to this, and the present invention is also applicable to an optical sensor system using an optical sensor having another structure such as a photodiode or a TFT.

In the above description, a finger is shown as an example of the object to be detected and a fingerprint is shown as an example of the image to be read, but the present invention is not limited to this, and a specific part of a human body other than a finger or another object may be the object to be detected. Further, since a good electrostatic withstand voltage can be obtained, the present invention can be suitably applied to a subject having the above-described property of being easily electrostatically charged.

Film resistance and film thickness of transparent electrode conductor (ITO)	Electrostatic capacity and film thickness of protective insulating film	Time constant τ	Electrostatic withstand voltage
					All-terminal grounding	Transparent electrode grounding
			50Ω/□(50nm)	11nF(600nm)			0.55μsec	-	5.0kV
30Ω/□(150nm)	11nF(600nm)	0.33μsec			10.67kV	12.00kV
			30Ω/□(150nm)	9nF(800nm)			0.27μsec	11.33kV	21.60kV
30Ω/□(150nm)	7nF(1000nm)	0.21μsec			20.00kV	25.60kV

TABLE 1

Claims (44)

1. An image reading apparatus is characterized by comprising:

a detection surface on which a subject is placed;

a sensor array in which a plurality of sensors that read an image pattern of the object placed on the detection surface are arrayed;

a 1 st detection electrode provided at least on an upper portion of the sensor array and having the detection surface;

a 2 nd detection electrode electrically insulated from the 1 st detection electrode and spaced apart from a peripheral side of the 1 st detection electrode;

an opposite electrode disposed below the 1 st detection electrode and opposite to the 1 st detection electrode via an interlayer insulating film;

a signal voltage applying circuit for applying a signal voltage having a 1 st signal waveform that periodically fluctuates to the counter electrode and exciting a 2 nd signal waveform in the 1 st detection electrode through the interlayer insulating film; and

and a contact detection device connected to the 2 nd detection electrode, for determining whether or not the subject in contact with the detection surface is a specific subject based on a state of a 3 rd signal waveform excited in the 2 nd detection electrode in response to the subject contacting both the 1 st detection electrode and the 2 nd detection electrode.

2. The image reading apparatus according to claim 1, characterized in that:

the image processing apparatus further includes a drive control device that supplies a predetermined drive control signal to each sensor of the sensor array and performs an image reading operation of reading an image pattern of the object placed on the detection surface.

3. The image reading apparatus according to claim 2, characterized in that:

the drive control device controls the image reading operation based on a result of determination by the contact detection device whether or not the subject is the specific subject.

4. The image reading apparatus according to claim 1, characterized in that:

said sensors of said sensor array are light sensors,

the 1 st detection electrode and the interlayer insulating film have optical transparency.

5. The image reading apparatus according to claim 4, wherein:

the 1 st detection electrode is a transparent conductive film provided at least on the upper part of the light-sensing surface of the sensor array via the interlayer insulating film.

6. The image reading apparatus according to claim 5, characterized in that:

the transparent conductive film is made of a material mainly containing indium tin oxide.

7. The image reading apparatus according to claim 1, characterized in that:

the 1 st detection electrode is a conductive film disposed on the upper portion of the sensor array,

the 2 nd detection electrode is a conductive member provided in proximity to at least a part of the periphery of the conductive film.

8. The image reading apparatus according to claim 7, wherein:

the conductive member is a conductive case member that surrounds the sensor array and has an opening having a shape that exposes the detection surface of the conductive film.

9. The image reading apparatus according to claim 1, characterized in that:

the specific object to be detected is a human body, and an image pattern unique to the human body is read.

10. The image reading apparatus according to claim 1, characterized in that:

the 1 st detection electrode and the 2 nd detection electrode are configured to be contacted straddling by the object.

11. The image reading apparatus according to claim 1, characterized in that:

the amplitude limiting circuit is further provided for defining upper and lower voltage values of the 2 nd signal waveform excited in the 1 st detection circuit.

12. The image reading apparatus according to claim 11, characterized in that:

the amplitude limiting circuit includes an anti-parallel diode circuit provided at least between the 1 st detection electrode and a ground potential,

the upper limit and the lower limit of the 2 nd signal waveform excited in the 1 st detection electrode are defined by the forward voltage of each diode constituting the anti-parallel diode circuit.

13. The image reading apparatus according to claim 1, characterized in that:

the signal voltage applying circuit applies a voltage component having a predetermined voltage amplitude and a periodic pulse-like signal waveform to the counter electrode.

14. The image reading apparatus according to claim 1, characterized in that:

the contact detection device determines whether or not the object to be detected is a specific object to be detected based on a comparison between a voltage amplitude of the 3 rd signal waveform excited by the 2 nd detection electrode and a central voltage value of the voltage amplitude with a reference voltage value.

15. The image reading apparatus according to claim 1, characterized in that:

the contact detection device determines whether or not the object is the specific object based on a comparison between a threshold voltage set in advance based on a capacitance component and a resistance component of the specific object and the 3 rd signal waveform excited in the 2 nd detection electrode.

16. The image reading apparatus according to claim 15, wherein:

the contact detection device determines that the object is the specific object when the threshold voltage is included in a voltage amplitude range of the 3 rd signal waveform excited by the 2 nd detection electrode.

17. The image reading apparatus according to claim 15, wherein:

the threshold voltage is set to a voltage higher than an upper limit value of the 3 rd signal waveform excited in the 2 nd detection voltage in a state where at least the object does not contact the detection surface.

18. The image reading apparatus according to claim 15, wherein:

the threshold voltage is set to a voltage lower than a lower limit value of the 3 rd signal waveform excited in the 2 nd detection voltage in a state where at least the object does not contact the detection surface.

19. The image reading apparatus according to claim 15, wherein:

the contact detection device at least comprises

A threshold voltage setting circuit that sets the threshold voltage; and

a comparison circuit that compares the threshold voltage with the 3 rd signal waveform.

20. The image reading apparatus according to claim 19, wherein:

the contact detection device judges whether the threshold voltage is included in a voltage amplitude range of the 3 rd signal waveform according to a comparison result of the comparison circuit,

and outputting a contact detection signal indicating that the subject is the specific subject when it is determined that the threshold voltage is included in the voltage amplitude range of the 3 rd signal waveform.

21. The image reading apparatus according to claim 19, wherein:

the 3 rd signal waveform is a periodically varying waveform,

the contact detection device includes a detection device for detecting whether or not the 3 rd signal waveform has passed the threshold voltage level based on a comparison result of the comparison circuit; and

a counting circuit counting a number of times the 3 rd signal waveform passes the threshold voltage level,

when the continuous count value of the count circuit exceeds a preset number, a contact detection signal indicating that the detected object is the specific detected object is output.

22. The image reading apparatus according to claim 1, characterized in that:

the sensor is a light sensor and the light sensor,

comprising: a source electrode and a drain electrode formed with a channel region formed of the semiconductor layer interposed therebetween;

a 1 st gate electrode and a 2 nd gate electrode formed above and below at least the channel region via gate insulating films, respectively;

applying a reset pulse to the 1 st gate electrode to initialize the sensor, applying a precharge pulse to the drain electrode, and then applying a readout pulse to the 2 nd gate electrode to accumulate charges corresponding to an irradiation light amount in the channel region during a charge accumulation period from the termination of initialization to the application of the readout pulse, and outputting a voltage corresponding to the accumulated charge amount as an output voltage,

reading an image pattern of the subject placed on the detection surface based on a difference between a signal voltage based on the precharge pulse and the output voltage.

23. The image reading apparatus according to claim 22, wherein:

the sensor is formed on an insulating substrate having light transmittance,

a protective insulating film is formed on the side of the sensor opposite to the insulating substrate,

the interlayer insulating film includes the protective insulating film and the gate insulating film.

24. The image reading apparatus according to claim 23, wherein:

forming a transparent conductive film on the protective insulating film,

the 1 st detection electrode is the transparent conductive film.

25. The image reading apparatus according to claim 22, wherein:

the counter electrode is the drain electrode,

the 1 st signal voltage applied to the counter electrode by the signal voltage applying circuit is a pulse voltage applied to the drain electrode.

26. The image reading apparatus according to claim 25, wherein:

the pulse voltage is the precharge pulse.

27. The image reading apparatus according to claim 22, wherein:

the sensor array includes at least a plurality of drain lines connected to drain electrodes of the plurality of photosensors,

the counter electrode is the drain electrode and the drain line,

the 1 st signal voltage applied to the opposite electrode by the signal voltage applying circuit is a pulse voltage applied to the drain line.

28. The image reading apparatus according to claim 27, wherein:

the pulse voltage is the precharge pulse.

29. The image reading apparatus according to claim 1, characterized in that:

a time constant defined by a resistance component between the detection surface and a ground potential and a capacitance component added to the detection surface is set to a value of 0.3 μ sec or less than 0.3 μ sec.

30. The image reading apparatus according to claim 29, wherein:

the resistance component includes the resistance of the 1 st detection electrode.

31. The image reading apparatus according to claim 29, wherein:

the capacitance component includes electrostatic capacitances formed between the 1 st detection electrode and the counter electrode facing each other through the interlayer insulating film, and between the 1 st detection electrode and the sensor.

32. The image reading apparatus according to claim 29, wherein:

the time constant is set to 0.25 μ sec or a value less than 0.25 μ sec.

33. The image reading apparatus according to claim 29, wherein:

the resistance component is set to a resistance value of 30 Ω/□ or less than 30 Ω/□.

34. The image reading apparatus according to claim 29, wherein:

the capacitance component is set to a capacitance value of 10nF or less than 10 nF.

35. The image reading apparatus according to claim 29, wherein:

each of the sensors of the sensor array is a photosensor having a prescribed photosurface,

the 1 st detection electrode is a transparent conductive film having an area larger than that of the light-sensing surface and provided on the upper part of the light-sensing surface of the sensor array via the interlayer insulating film.

36. The image reading apparatus according to claim 35, wherein:

a conductive member having a resistance value lower than that of the transparent conductive film is provided in the transparent conductive film so as to be electrically connected to at least a region excluding a region corresponding to the light-sensing surface.

37. The image reading apparatus according to claim 36, wherein:

the resistance component includes a resistance formed by the transparent conductive film and the conductive member.

38. The image reading apparatus according to claim 36, wherein:

the conductive member is made of a conductive material which is one of chromium, aluminum, an alloy material containing chromium, and an alloy material containing aluminum.

39. A method for driving an image reading apparatus, the image reading apparatus comprising: a sensor array having a detection surface on which an object to be detected is placed; and a drive control device that reads an image pattern of the subject placed on the detection surface, the method including the steps of:

applying a signal voltage having a 1 st signal waveform that periodically fluctuates to a counter electrode provided in opposition to the 1 st detection electrode via an interlayer insulating film at a lower portion of the 1 st detection electrode provided above the sensor array and having the detection surface, and exciting a 2 nd signal waveform in the 1 st detection electrode;

detecting a 3 rd signal waveform excited in the 2 nd detection electrode based on the object contacting the 1 st detection electrode and a 2 nd detection electrode electrically insulated from the 1 st detection electrode and provided at an interval from a peripheral side of the 1 st detection electrode;

judging whether the object to be detected contacting the detection surface is a specific object to be detected or not according to the state of the detected 3 rd signal waveform; and

when it is determined that the subject is the specific subject, the drive control device starts reading the image pattern.

40. The image reading apparatus driving method according to claim 39, wherein:

the step of determining whether or not the subject is a specific subject includes a comparison step of comparing a threshold voltage set in advance based on a capacitance component and a resistance component of the specific subject with the 3 rd signal waveform excited in the 2 nd detection electrode.

41. The image reading apparatus driving method according to claim 40, wherein:

the step of comparing the threshold voltage with the 3 rd signal waveform comprises the steps of:

judging whether the threshold voltage is included in a voltage amplitude range of the 3 rd signal waveform; and

when it is determined that the threshold voltage is included in the voltage amplitude range of the 3 rd signal waveform, it is determined that the subject is the specific subject.

42. The image reading apparatus driving method according to claim 40, wherein:

the step of comparing the 3 rd signal waveform with the threshold voltage comprises the steps of:

detecting whether the 3 rd signal waveform passes the threshold voltage level; and

the number of times the 3 rd signal waveform passes through the threshold voltage level is counted, and when the number of times that the continuous count value exceeds a preset number of times, it is determined that the subject is the specific subject.

43. The image reading apparatus driving method according to claim 40, wherein:

the threshold voltage is set to a voltage higher than an upper limit value of the 3 rd signal waveform excited in the 2 nd detection voltage in a state where at least the object does not contact the detection surface.

44. The image reading apparatus driving method according to claim 40, wherein:

the threshold voltage is set to a voltage lower than a lower limit value of the 3 rd signal waveform excited in the 2 nd detection voltage in a state where at least the object does not contact the detection surface.