HK1027653B - Fingerprint reading apparatus - Google Patents

Description

Fingerprint reading apparatus

Technical Field

The present invention relates to a reading apparatus for reading a target object having a fine concave or convex pattern such as a fingerprint.

Background

A typical reading apparatus for reading a target object having a fine concave or convex pattern, such as a fingertip, has a structure like that disclosed in US patent No.5635723, in which a two-dimensional photosensor is formed on a surface light source, and an optical component is formed on this two-dimensional photosensor. The invention of this reference detects a change in capacitance when a finger touches the optical member, and sequentially detects as a result of detection of electric charges generated by the photosensor devices arranged in two dimensions and corresponding to the amount of light incident from the optical member. In this structure, a plurality of optical fibers are mounted on the two-dimensional photosensor without any optical lens, so that the entire apparatus can be reduced in size. At present, another type of structure is examined in which an optical component composed of a plurality of optical fibers is made thinner to enter a light scattering film, or in which the upper surface of a photosensitive device is covered with a transparent resin layer having a rough surface without any optical component. This type of structure is disclosed, for example, in US patent application No.09/128237 filed by the applicant (8/3/1998).

In the reading apparatus, a finger directly touches an upper surface of the two-dimensional photosensor. If the finger is charged with static electricity, such static electricity may cause malfunction of the two-dimensional photosensor or in the worst case damage it. If the pattern of the fingerprint is copied to a sheet by any means, the reading device is determined to be in agreement as long as the pattern is the same, since the device is not provided with any means for distinguishing a sheet from a human finger. When such fingerprint match is set as a registration condition for a personal computer or a host computer of a network, the computer cannot reliably prevent entry of a third party.

Disclosure of Invention

A first object of the present invention is to provide a reading apparatus which prevents a photosensitive device from being erroneously operated or damaged due to static electricity. A second object of the present invention is to provide a reading apparatus capable of ensuring reliability thereof by reading a pattern after, for example, detecting whether or not the object is a person.

According to the present invention, there is provided a fingerprint reading apparatus comprising: a light source; a photosensor device having a plurality of photosensors formed on said light source; each photosensitive device comprising a semiconductor layer and an electrode electrically connected to the semiconductor layer, characterized in that: the apparatus further includes a transparent conductive layer formed on a surface of the photo-sensor device so as to completely cover the photo-sensor device and be contacted by a finger, the transparent conductive layer being grounded to dissipate static electricity.

According to the present invention, there is provided a fingerprint reading apparatus comprising: a light source; a photosensor device having a plurality of photosensors formed on the light source and an outer layer film formed on the photosensors; each photosensitive device comprising a semiconductor layer and an electrode electrically connected to the semiconductor layer, characterized in that: the apparatus further includes a transparent conductive layer formed on an outer film of the photo-sensor device to cover the photo-sensors, and the photo-sensors are disposed proximate to a surface of the transparent conductive layer such that when light is emitted substantially perpendicular to the photo-sensors, some of the photo-sensors located near the finger prominences become bright and some of the photo-sensors located near the finger recessions become dark.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate presently preferred embodiments of the invention and, together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention:

fig. 1 is an enlarged cross-sectional view of a portion of a fingerprint reading device according to a first embodiment of the present invention;

FIG. 2 is a plan view of a portion of the fingerprint reading device shown in FIG. 1;

FIG. 3 is a block diagram of the fingerprint reading device of FIG. 1;

FIG. 4 is a circuit diagram of the photosensitive device portion and the photosensitive device driver shown in FIG. 3;

FIG. 5 is an equivalent circuit diagram of a single photosensitive device shown in FIG. 1;

fig. 6A to 6D are circuit diagrams illustrating voltages applied to respective electrodes of the photosensitive device shown in fig. 5 and changes in the state of the photosensitive device;

figure 7 is a plan view of a part of a fingerprint reading device according to a second embodiment of the present invention;

FIG. 8 is a circuit diagram of a portion of the fingerprint reading device shown in FIG. 7;

figure 9 is a plan view of a part of a fingerprint reading device according to a third embodiment of the present invention;

FIG. 10 is a circuit diagram of a portion of the fingerprint reading device shown in FIG. 9; and

fig. 11 is a plan view illustrating a modification of the fingerprint reading device shown in fig. 9.

Detailed Description

(first embodiment)

Fig. 1 is a cross-sectional view of a part of a reading device according to a first embodiment of the invention. The reading apparatus can read any form of target object having a fine concave or convex pattern. In the following embodiments, this reading apparatus will exemplify a fingerprint reading apparatus for reading a fingerprint. This fingerprint reading apparatus has a two-dimensional photosensor (photosensor device) 2 on a surface light source 1. A transparent conductive layer 3 made of ITO or the like is formed on this two-dimensional photosensor 2. The surface light source 1 is made to be electroluminescent or configured as an edge-light type backlight used in a liquid crystal display device. Although not shown, this edge-light type backlight typically has a light reflection plate on the lower surface of a light guide plate, one or several point light sources such as light emitting diodes are arranged next to the light guide plate, and the surface of the point light source not coinciding with the light guide plate is covered with a light reflection thin layer. The transparent conductive layer 3 dissipates static electricity and is grounded in a certain area (not shown). The transparent conductive layer 3 is formed by, for example, vapor deposition on the upper surface of the outer layer film 23 of the two-dimensional photosensor 2 (to be described later). The transparent conductive layer 3 is made slightly larger than

The square sensor region 4 of the two-dimensional photosensor 2 is indicated in fig. 2 by a single-dot line. It should be noted that the two-dot line in fig. 2 represents a finger 5.

This two-dimensional photosensor 2 is now described. The two-dimensional photosensor 2 has a structure in which a plurality of photosensors 11 are arranged in a matrix (only one photosensor is illustrated in fig. 1). The two-dimensional photosensor 2 has a transparent substrate 12 made of acrylic resin, glass, or the like. A bottom gate 13 made of chromium or aluminum serving as a light shielding electrode is formed for each photosensitive device 11 on the upper surface of the transparent substrate 12. A light-transmitting bottom gate insulating film 14 made of silicon nitride is formed on the entire upper surface of the bottom gate electrode 13 and the upper surface of the transparent substrate 12. A semiconductor layer 15 made of amorphous silicon is formed on an upper surface portion of the bottom gate insulating film 14 corresponding to the bottom gate electrode 13. N + -type silicon layers 16 and 17 are formed on both sides of the semiconductor layer 15 on the upper surface of the bottom gate insulating film 14, respectively. A light-transmitting barrier layer 18 made of silicon nitride is formed on the upper surface of the semiconductor layer 15. Source and drain electrodes 19 and 20 made of chromium or aluminum as light shielding electrodes are formed on both sides of the upper surface of the barrier layer 18, on the upper surfaces of the n + -type silicon layers 16 and 17, and on the upper surface of the bottom gate insulating film 14. A light-transmitting top gate insulating film 21 made of silicon nitride is formed on the entire upper surfaces of the source and drain electrodes 19 and 20 and the exposed surface of the barrier layer 18. A top gate electrode 22 made of ITO or the like as a transparent electrode is formed on an upper surface portion of this top gate insulating film 21 corresponding to the semiconductor layer 15. A light-transmitting outer layer film 23 made of silicon nitride is formed on the entire upper surface of the top gate electrode 22 and the upper surface of the insulating film 21. In this two-dimensional photosensor 2, when light beams are incident randomly from the lower surface side, a part of the light beams is shielded by the bottom gate electrode 13, and the other part of the light beams passes through the light-transmitting layer other than the source and drain electrodes 19 and 20, so that the light beams are not incident directly on the semiconductor layer 15.

The operation of this fingerprint reading device is briefly described below. The light beam emitted from the upper surface of the surface light source 1 passes through the light-transmitting portion of the two-dimensional photosensor 2 and the transparent conductive layer 3. A finger 5 (see fig. 2) in contact with the transparent conductive layer 3 is randomly irradiated with this emission light beam from the lower surface side. The light beam reflected by the surface of the finger 5 passes through the transparent conductive layer 3 and the adjacent top gate electrode 22 serving as a transparent electrode, and is incident on the incident surface (exposed surface) of the semiconductor layer 15 between the source and drain electrodes 19 and 20. In this case, a portion corresponding to a protrusion (bump) of the skin surface of the finger 5 in contact with the surface of the transparent conductive layer 3 becomes bright. The portion of the recess (valley) corresponding to the skin surface of the finger 5 becomes dark. As a result, an image whose contrast is optically apparent in accordance with the ridges and valleys of the skin surface of the finger 5 can be obtained to read the fingerprint of the finger 5.

In this fingerprint reading apparatus, since the transparent conductive layer 3 is formed and grounded on the two-dimensional photosensor 2, static electricity discharged from the finger 5 in contact with the transparent conductive layer 3 on the two-dimensional photosensor 2 can be dissipated through the transparent conductive layer 3. This can prevent the two-dimensional photosensor 2 from malfunctioning or being damaged due to such static electricity.

Fig. 3 is a block diagram showing portions of a fingerprint reading apparatus. This fingerprint reading apparatus includes a photosensor section 31, a photosensor driver 32, a CTR (controller) 33, a clock generation section 34, an a/D (analog-to-digital) conversion section 35, an S/P (serial-parallel) conversion section 36, a standard pattern memory 37, a collation section 38, a determination section 39, and the like.

As shown in fig. 4, the photosensor section 31 has a structure in which the photosensors 11 constituting the two-dimensional photosensor shown in fig. 1 are arranged in a matrix. As shown in fig. 1, this photosensor has a bottom-gate type transistor composed of a Bottom Gate (BG)13, a semiconductor layer 15, a source (S)19, a drain (D)20, and the like, and a top-gate type transistor composed of a Top Gate (TG)22, a semiconductor layer 15, a source (S)19, a drain (D)20, and the like. That is, this photosensor device is constituted by a photoelectric conversion thin film transistor in which a Bottom Gate (BG)13 and a Top Gate (TG)22 are formed below and above a semiconductor layer 15, respectively. The equivalent circuit of such a transistor is shown in fig. 5.

Referring back to fig. 4, the Bottom Gate (BG) of each photosensor 11 is connected to one of a plurality of bottom electrode lines 41 extending in the row direction. The drain (D) of each photosensor 11 is connected to one of the plurality of signal lines 42 extending in the column direction. The Top Gate (TG) of each photosensitive device 11 is connected to one of a plurality of top electrode lines 43 extending in the row direction. The source (S) of each photosensitive device 11 is grounded.

As shown in fig. 4, the photosensor driver 32 shown in fig. 3 includes a bottom address decoder 44 connected to the bottom electrode lines 42 functioning as a vertical scanning circuit, a column switch 45 connected to the signal lines 14 functioning as a horizontal scanning circuit, and a top address decoder 46 connected to the top electrodes 43. The bottom address decoder 44 applies a bottom gate voltage V to the corresponding bottom electrode line 41_BGTo the Bottom Gates (BG) of the photosensitive devices 11 arranged in rows. The top address decoder 46 applies a top gate voltage V_TGTo the Top Gates (TG) of the photosensitive devices 11 arranged in each row through the corresponding top electrode lines 43.

Column switch 45 receives drain voltage V through precharge transistor 47_DDThe column switch 45 outputs an output signal V through a buffer 48_out. Each time the precharge transistor 47 receives the precharge voltage V_pcAnd when turned on, the column switch 45 outputs the output from each photosensor 11 connected to the signal line 42 as an output signal V via the buffer 48_out。

The clock generation section 34 shown in fig. 3 includes an oscillation circuit and a frequency dividing circuit, and outputs a clock having a predetermined frequency and a reset signal to the CTR 33. The CTR33 converts the bottom and top gate voltages V according to the clock and reset signals from the clock generating part 34_BGAnd V_TGOutputs to the photosensor driver 32 as a read and reset signal, and outputs a precharge and drain voltage V_PCAnd V_DDTo the precharge transistor 47 shown in fig. 4.

The a/D conversion section 35 shown in fig. 3 pairs the output signal V output by the photosensor section 31 through the photosensor driver 32 (i.e., the column switch 45 shown in fig. 4)_outA/D conversion is performed. The S/P conversion section 36 converts the serial output signal from the a/D conversion section 35 into a parallel output signal. Fingerprint image signals corresponding to fingerprints of a plurality of specific persons are stored in advance in the standard pattern memory 37 as standard pattern signals. The collating section 38 collates with the standard pattern signals sequentially read out from the standard pattern memory 37An output signal from the S/P converting section 36, and outputs each of the collation signals to the determining section 39. The determination section 39 determines whether or not a fingerprint image signal corresponding to the signal Vout output from the photosensor section 31 matches a standard pattern signal of a specific person stored in advance in the standard pattern memory 37 based on the collation signal from the collation section 38.

The operation of the photosensor 11 will now be described with reference to fig. 5 and 1. When a positive voltage (e.g., +10V) is applied to the Bottom Gate (BG) while a positive voltage (e.g., +5V) is maintained between the source (S) and drain (D) of the photosensitive device 11, a channel is formed in the semiconductor layer 15 to flow a drain current. In this state, when a negative voltage (e.g., -20V) of a level sufficient to make the channel formed by the electric field of the Bottom Gate (BG) disappear is applied to the Top Gate (TG), the electric field generated by the Top Gate (TG) acts in a direction to eliminate the channel formed by the electric field of the bottom Gate (GB), thereby pinching off the channel. At this time, when the semiconductor layer 15 is irradiated with a light beam from the Top Gate (TG) side, electron-hole pairs are introduced into the semiconductor layer 15 on the Top Gate (TG) side. The electron-hole pairs are accumulated in the channel region of the semiconductor layer 15 to cancel out the electric field of the Top Gate (TG). A channel is then formed in the semiconductor layer 15 to flow a drain current. This drain current varies with a change in the amount of incident light of the semiconductor layer 15. As described above, in this two-dimensional photosensor 2, the electric field generated by the Top Gate (TG) acts in a direction to prevent the channel from being formed by the electric field of the Bottom Gate (BG) to pinch off the channel. The drain current obtained in the absence of incident light beam can be greatly reduced, e.g. by 10^-14A. The difference between the drain current obtained when no light beam is incident and the drain current obtained when a light beam is incident can be made sufficiently large. At this time, the amplification factor of the bottom-gate transistor can be changed in accordance with the change in the amount of incident light to increase the S/N ratio.

In this two-dimensional photosensor 2, one photosensor 11 may have both a sensor function and a selection transistor function. These functions will be generally described below. When a voltage, for example, 0V is applied to the Top Gate (TG) while the Bottom Gate (BG) is maintained to be applied with a positive voltage (+10V), holes are discharged from the trap level between the semiconductor layer 15 and the top gate insulating film 21 so that a refresh or reset operation can be performed. More specifically, in the continuous application of the reading device, the trap level between the semiconductor layer 15 and the top gate insulating film 21 is masked by holes generated by irradiation and holes injected from the drain electrode (D). The channel resistance established in the absence of light beam incidence is reduced and the resulting drain current in the absence of light beam incidence is increased. Therefore, setting the Top Gate (TG) to 0V discharges these holes to enable the reset operation.

When a positive voltage is not applied to the Bottom Gate (BG), no channel is formed in the bottom gate transistor. Even if a light beam is incident, no drain current flows to establish a non-selected state. More specifically, the selected and non-selected states are controlled by controlling the voltage applied to the Bottom Gate (BG). In the non-selected state, when 0V is applied to the Top Gate (TG), holes can be discharged from the trap level between the semiconductor layer 15 and the top gate insulating film 21 so that the reset operation can be performed in the same state as described above.

As a result, as shown in FIGS. 6A to 6D, for example, the top gate voltage V is controlled_TGTo 0V and-20V to control the reading state and the reset state. Will bottom gate voltage V_BGControl to 0V and +10V and control of selected and non-selected states. That is, by controlling the top gate voltage V_TGAnd bottom gate voltage V_BGOne photosensor 11 can have both a function as a photosensor and a function as a selection transistor.

The operation of the two-dimensional photosensor 2 is now explained with reference to fig. 3 and 4. The clock generation section 34 outputs a clock having a predetermined frequency and a reset signal to the CTR 33. The CTR33 outputs bottom and top gate voltages V according to the clock and reset signals from the clock generating part 34_BGAnd V_TGAs read and reset signals to the photosensor driver 32 and outputs precharge and drain voltages V_PCAnd V_DDTo precharge transistor 47.

The photosensitive devices on the first row are activated by setting the bottom and top gate voltages V_BGAnd V_TGTo 0V and reset. During this reset period, the precharge voltage V is set_PCTo precharge transistor 47 to a predetermined levelTime, and the drain voltage V_DD(+5V) is applied to all signal lines 42 to precharge the photosensitive devices 11. The top gate voltage V_TGSet to-20V to change the photosensor 11 to the reading state. Will bottom gate voltage V_BGSet to +10V to change the photosensitive device 11 to a selected state. The signal V output by each photosensitive device 11_outDepending on the amount of incident light (luminous flux), changes to 0V or remains at + 5V. The signal V output by each photosensitive device 11_outOutput from the column switch 45 through a buffer 48. The same is done for the photosensitive devices 11 on the second to last rows. The subsequent operation will not be described.

(second embodiment)

Fig. 7 is a plan view illustrating a portion of a fingerprint reading apparatus according to a second embodiment of the present invention. In this fingerprint reading apparatus, a pair of transparent conductive films 3A and 3B in the shape of a comb tooth are formed on and around the upper surface of the outer layer film 23 of the two-dimensional photosensor 2 within the sensor region 4. When the finger 5 touches the two-dimensional photosensor 2 including the pair of transparent conductive films 3A and 3B, the pair of transparent conductive films 3A and 3B detects the resistance of the touching finger 5 and thus detects a signal to start a fingerprint reading operation (described later). The pair of transparent conductive films 3A and 3B may also have an antistatic function. The pair of transparent conductive films 3A and 3B are formed in a comb-like shape in order to be able to detect the resistance of the finger 5 which is relatively small with high sensitivity.

Fig. 8 illustrates part of the circuitry of a fingerprint reading device. In fig. 8, the same reference numerals as in fig. 4 denote the same parts, and their description will be omitted accordingly. A transparent conductive film 3A is connected to the CTR33 (see FIG. 3) through a resistor 51 for outputting a drain voltage V_DDAnd the other transparent conductive film 3B is grounded. CTR33 is connected between a transparent conductive film 3A and the resistor 51 through the inverter 52. The CTR33 outputs the switching signal to the switch controller 53 upon receiving an H-level signal from the inverter 52. The switch controller 53 outputs a switch control signal to the switch 54 after receiving the conversion signal from the CTR 33. Switch 54 is a normally-on switch formed between column switch 45 and precharge transistor 47.

In this fingerprint reading apparatus, when the finger 5 touches the two-dimensional photosensor 2 including the pair of transparent conductive films 3A and 3B, a resistance corresponding to the contact portion of the finger 5 is generated between the pair of transparent conductive films 3A and 3B to lower the potential between the transparent conductive film 3A and the resistance 51 to a potential divided by the resistance 51 and the resistance value of the finger. The input of the inverter 52 is lowered from the H level to the L level to change the output of the inverter 52 to the H level, and this H level signal is output to the CTR 33. The CTR33 outputs a switching signal to the switch controller 53 upon receiving an H-level signal from the inverter 52. Receiving the changeover signal from CTR33, switch controller 53 outputs a switch control signal to switch 54 to close switch 54. Then, column switch 45 is connected to precharge transistor 47 through switch 54, and the same state as shown in fig. 4 is set to start the fingerprint reading operation.

As described above, in this fingerprint reading apparatus, when a finger touches the two-dimensional photosensor 2 including the pair of transparent conductive films 3A and 3B, the resistance of the touching finger 5 is detected to initiate a fingerprint reading operation by this detection signal. The fingerprint reading operation can be conveniently initiated automatically. Since the other transparent conductive film 3B applied to most of the sensor region 4 of the two-dimensional photosensor 2 is grounded as shown in fig. 7, the antistatic function is enhanced. Note that, when, for example, a copy sheet on which a fingerprint image of a finger 5 is copied is placed on the two-dimensional photosensor 2 including the pair of transparent conductive films 3A and 3B, resistance is not detected by the pair of transparent conductive films 3A and 3B because the copy sheet is insulated, and thus illegal use by the copy sheet can be prevented.

(third embodiment)

Fig. 9 is a plan view of a part of a fingerprint reading device according to a third embodiment of the present invention. In this fingerprint reading apparatus, pairs of transparent conductive films 3A and 3B in comb-teeth shape are formed at four corners of a square sensor area 4 on the upper surface of an outer layer film 23 of a two-dimensional photosensor 2, respectively. When the finger 5 touches the two-dimensional photosensor 2 including the four pairs of transparent conductive films 3A and 3B, the four pairs of transparent conductive films 3A and 3B detect the resistance of the touching finger 5 and thus detect a signal to start a fingerprint reading operation (described later). These transparent conductive film pairs 3A and 3B may also have an antistatic function.

Fig. 10 illustrates the main parts of the circuit of the fingerprint reading device. In fig. 10, the same reference numerals as in fig. 8 denote the same components, and their description will be omitted accordingly. The output sides of the four inverters 52 corresponding to the four pairs of transparent conductive films 3A and 3B are connected to the CTR33 and the input side of the one and circuit 55. The output side of the and circuit 55 is connected to the CTR 33.

In this fingerprint reading apparatus, when the finger 5 touches the two-dimensional photosensor 2 including the four pairs of transparent conductive films 3A and 3B, a resistance corresponding to the contact portion of the fingerprint 5 is generated between each pair of transparent conductive films 3A and 3B, the outputs of the four inverters 52 are changed from L-level signals to H-level signals, and these H-level signals are output to the and circuit 55. The and circuit 55 outputs an and signal to the CTR33 when it receives H-level signals from all four inverters 52. In these cases, inverter 52 outputs this H-level signal directly to CTR33, but CTR33 disregards these H-level signals. Referring to fig. 8, the CTR33 outputs a switching signal to the switch controller 53 upon receiving this and signal from the and circuit 55. Receiving this switching signal from CTR33, switch controller 53 outputs a switch control signal to switch 54 to close switch 54. Column switch 45 is then connected to precharge transistor 47 through switch 54 to set the same state as shown in fig. 4 and initiate a fingerprint reading operation.

In this fingerprint reading apparatus, when the contact position and state of the finger 5 (whether or not the finger 5 is properly touched) with respect to the sensor region 4 of the two-dimensional photosensor 2 are incorrect, that is, the finger 5 does not touch all of the four pairs of transparent conductive films 3A and 3B, the and circuit 55 will not output an and signal. In this case, the finger 5 contacts one to three pairs of transparent conductive films 3A and 3B among the four pairs of transparent conductive films 3A and 3B, and the inverter 52 corresponding to these pairs of transparent conductive films 3A and 3B touched by the finger 5 outputs an H-level signal to the CTR 33. The CTR33 outputs a finger touch error signal to a controller (not shown) based on the absence of the and signal from the and circuit 55 and the presence of the H-level signal from the inverter 52. The controller informs the operator of an incorrect contact position or state of the finger 5 with respect to the sensor area 4 of the two-dimensional light-sensitive device 2 by means of any annunciating means, such as a display "please reposition your finger" or a sound.

(modification of the third embodiment)

This fingerprint reading apparatus can exhibit an antistatic function because the other transparent conductive film 3B of each pair is grounded as in fig. 10. However, in the third embodiment, the central portion of the sensor region 4 is inferior in antistatic performance because the transparent conductive film pairs 3A and 3B are formed at the four corners of the square sensor region 4 of the two-dimensional photosensor 2, respectively, as shown in fig. 9. Therefore, the static electricity dissipative transparent conductive film 3C having an almost cross shape can be formed in the central portion of the sensor region 4 as shown in fig. 11.

Note that, in the fingerprint reading apparatus in fig. 1, a transparent substrate 12 is disposed on a surface light source 1, and a photosensor section 31 having a photoelectric conversion thin film transistor is formed on this transparent substrate 12. Alternatively, the transparent substrate 12 may be omitted, and the photosensor section 31 having a photoelectric conversion thin film transistor may be formed directly on the light guide plate constituting the surface light source 1. Each photosensitive device is not limited to the double-gate type photoelectric conversion thin film transistor described in the above embodiments, and may be a single-gate type thin film transistor or a diode type thin film transistor.

As described above, according to the present invention, since the transparent conductive layer formed on the photosensor device has a static electricity dissipating function, even if, for example, a finger in contact with the transparent conductive layer on the photosensor device is electrostatically charged, such static electricity can be dissipated through the transparent conductive layer. It is possible to prevent the photosensitive device from malfunctioning or being damaged due to static electricity. In addition, a pair of transparent conductive layers are formed to be spaced apart from each other. The resistance value of the target object placed between the conductive layers is measured to determine whether the resistance value is within a predetermined range. The checkup is started only when a checkup pair is reached. Duplicate checks can be avoided to improve reliability.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims (8)

1. A fingerprint reading device comprising:

a light source (1);

a photosensor device (2) having a plurality of photosensors formed on said light source (1); each photosensitive device comprising a semiconductor layer (15) and electrodes (19, 20) electrically connected to the semiconductor layer (15), characterized in that:

the device further comprises a transparent conductive layer (3) formed on the surface of said light-sensitive device means (2) so as to completely cover the light-sensitive device and be contacted by a finger, the transparent conductive layer being grounded to dissipate static electricity.

2. A fingerprint reading device comprising:

a light source (1);

a photosensor device (2) having a plurality of photosensors formed on the light source (1) and an outer layer film formed on the photosensors; each photosensitive device comprising a semiconductor layer (15) and electrodes (19, 20) electrically connected to the semiconductor layer (15), characterized in that:

the apparatus further comprises a transparent conductive layer (3) formed on an outer film of the photosensor device (2) to cover the photosensor, and

the light-sensitive devices are arranged in close proximity to the surface of the transparent conductive layer (3) such that when light is emitted substantially perpendicular to the light-sensitive devices, some light-sensitive devices located near the finger protrusions become bright and some light-sensitive devices located near the finger recesses become dark.

3. A reading device as claimed in claim 2, characterized in that the transparent conductive layer dissipates static electricity.

4. The reading apparatus according to claim 2, wherein said transparent conductive layer comprises a pair of transparent conductive layers spaced apart from each other, and said pair of transparent conductive layers detects the resistance of the target object when the target object simultaneously touches said pair of transparent conductive layers.

5. A reading apparatus according to claim 4, further comprising detecting means for detecting whether the resistance value of the target object is within a predetermined value, and means for starting reading the target object when the resistance value is within the predetermined value.

6. A reading device according to claim 2, wherein said transparent conductive layer comprises a transparent conductive layer pair portion formed in a plurality of peripheral portions in a sensor area of said light-sensitive device means.

7. The reading apparatus according to claim 6, further comprising detecting means for detecting whether or not the resistance values of a plurality of contact portions of the target object are within a predetermined value when the target object simultaneously touches the pair of transparent conductive layers, and means for starting reading of the target object when all detection results are within the predetermined value.

8. The reading device according to claim 6, wherein said transparent conductive layer further comprises a static dissipative transparent conductive layer formed in a central portion of a sensor area of said photosensor device.