JP2001119627A - Infrared imaging device - Google Patents

Abstract

(57) [Problem] To detect a temperature distribution in an imaging region of an infrared imaging element as a change in capacitance and to obtain a high-quality signal without being affected by wiring resistance or resistance of a switch unit. . Kind Code: A1 Abstract: Thermosensitive capacitors 3 (1, 1), 3 (2, 2)
1), 3 (2, 1), and 3 (2, 2) are regularly arranged on the imaging surface, and the capacitance changes depending on the temperature. Switch 2 (1, 1), 2 (2, 1), 2 (2, 1), 2
(2, 2), amplifier 4 (1), 4 (2), capacitor 5
(1), 5 (2), switches 6 (1), 6 (2), 7
The reading means according to (1) and (2) converts the capacitance of the temperature-sensitive capacitor into an electric signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging device, and more particularly to an uncooled infrared imaging device.

[0002]

2. Description of the Related Art In recent years, infrared imaging devices have attracted attention in security applications such as intruder monitoring and the like, and in operation systems of automobiles. In particular, non-cooling type infrared imaging devices that are easy to maintain are desired.

As a non-cooling type infrared imaging apparatus, a sensor that irradiates a resistor with an electromagnetic wave called a bolometer, converts electromagnetic wave energy into heat, and detects an electromagnetic wave intensity by a change in resistance value is mainly used.

In order to form an infrared imaging device, for example, as shown in FIG. 8, resistors 101 for detection are arranged in a matrix, and the output of a vertical scanning circuit 106 causes a switch 102 for vertical scanning to use one row at a time. Select sequential. Then, the current flowing through the resistor 101 is passed through the vertical signal line 103,
The resistance-voltage conversion circuit 104 converts the voltage into a voltage value. By sequentially turning on the horizontal scanning circuit 107 and the horizontal scanning switch 105 during one horizontal period, a scanning video signal converted into a voltage value is obtained from the output terminal 108.

[0005]

Since the resistance value of each pixel is connected to the resistance-voltage conversion circuit 104 via the switch 102 and the vertical signal line 103, when the resistance value of each pixel is detected. An error occurs due to the resistance between the switch 102 and the vertical signal line 103. Since the resistance of the switch 102 is a function of the pixel temperature similarly to the pixel resistance, there is little problem. However, the resistance of the vertical signal line 103 indicates the position of the row to be scanned and the vertical signal passing therethrough. The correction is difficult because the resistance value changes depending on the length of the line 103 and the temperature.

Accordingly, an object of the present invention is to provide an image pickup apparatus in which an error does not occur in a signal read from a pixel.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical system for forming an infrared light image on an imaging surface to form a temperature distribution, and regularly disposing the optical system on the imaging surface. The temperature control device includes at least a plurality of temperature-sensitive capacitors whose capacitances change with temperature, and a detection amplifier that converts the capacitances of the plurality of temperature-sensitive capacitors into electric signals.

Thus, the temperature distribution of each pixel can be grasped as a change in capacitance, so that a detection error does not occur even if the resistance value of the passing switch signal line or the like fluctuates.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit connection diagram of an infrared imaging device according to a first embodiment of the present invention. In this example, four pixels arranged in a matrix are shown to simplify the description. One pixel is a thermosensitive capacitor 3
(X, y) and a switch 2 (x, y). In the figure, the thermosensitive capacitors 3 (1, 1), 3 (2,
1), 3 (1, 2), 3 (2, 2) and switch 2
(1,1), 2 (2,1), 2 (1,2), 2 (2,2)
2) is shown.

The pixels arranged in the horizontal direction are driven one row at a time by a vertical scanning circuit 201. That is, the vertical scanning circuit 201 is provided with selection lines SEL1 and SEL2, and a pulse appearing on the selection line SEL1. Is
The switches in the first row are driven, and the pulse appearing on the selection line SEL2 drives the switches in the second row.

The output from the switch in the first column appears on the read line RL1, and the output from the switch in the second column is
Appears on read line RL2. Read line RL1
Is connected to the inverting input terminal of the amplifier 4 (1), and is connected to a capacitor 5 (1) provided in parallel with the amplifier 4 (1) and one end of a switch 6 (1).
The read line RL2 is connected to the inverting input terminal of the amplifier 4 (2), and a capacitor 5 (2) and a switch 6 (2) provided in parallel with the amplifier 4 (2).
Is connected to one end.

Control pulses from a pulse generator 202 are applied to the other input terminals of the amplifiers 4 (1) and 4 (2). Output terminals of the amplifiers 4 (1) and 4 (2) are connected to output terminals 203 via switches 7 (1) and 7 (2), respectively.
Are connected in common. Switches 7 (1), 7 (2)
Are driven by the horizontal scanning circuit 204 so as to be turned on once in each horizontal period.

FIG. 2 shows pulse timings for explaining the operation of the above configuration.

The vertical scanning circuit 201 (row selection circuit) sequentially selects pixels arranged in a matrix one by one. First,
The case where the pixel in the bottom row is selected will be described.
The horizontal scanning circuit 201 includes a row selection switch 2 (1,
1) Output a control signal for turning on 2 (2, 1). The temperature-sensitive capacitor 3 (1, 1) is connected to the readout line (vertical signal line) RL1, and the temperature-sensitive capacitor 3 (2, 1)
1) is connected to the read line (vertical signal line) RL2.

Next, reset switches 6 (1), 6
Turn on (2). Then, the thermosensitive capacitor 3 (1,
1) The operational amplifier 4 (1) uses a pulse generator 20
2 is charged to the output voltage VsL. Further, the temperature-sensitive capacitor 3 (2, 1) is charged to the output voltage VsL of the pulse generator 202 by the operational amplifier 4 (2). next,
The reset switches 6 (1) and 6 (2) are turned off, and the output voltage of the pulse generator 202 is set to VsH. Then
The operational amplifier 4 is connected to the temperature-sensitive capacitor 3 (1, 1).
(1) Charging is performed via the capacitor 5 (1).
The temperature-sensitive capacitor 3 (2, 1) is connected to the operational amplifier 4
(2) Charging is performed via the capacitor 5 (2).

In these charging operations, the capacitor 3
(1, 1) is completed when the potential becomes VsH. The potential of the capacitor 3 (2, 1) is also VsH.
It is completed when it becomes.

Here, capacitors 3 (1, 1), 3
In (2, 1), the charged amount of charge can be expressed as follows.

(Electrostatic capacitance of the capacitor 3) × (VsH−VsL) The charge amount of each of the capacitors 3 (1, 1) and 3 (2, 1) is also stored in the capacitors 5 (1) and 5 (2). Charged. Here, when the output voltage of the pulse generator 202 is returned to VsL after the selection switches 2 (1, 1) and 2 (2, 1) are turned off, the charges of the capacitors 5 (1) and 5 (2) are held. Therefore, the output voltage of the operational amplifier 4 (1) is [(capacitance of capacitor 3 (1,1)) / (capacitance of capacitor 5 (1))] × (VsH−VsL) + Vs
L The output voltage of the operational amplifier 4 (2) is [(capacitance of capacitor 3 (2,1)) / (capacitance of capacitor 5 (2))] × (VsH−VsL) + Vs
L.

That is, the change in capacitance is converted into a voltage signal. This voltage is applied to switches 7 (1), 7
The video signal is sequentially selected in (2) and is output to the output terminal 203 as a video signal. The output signal voltage is determined by the capacitance ratio,
Since the ON resistance of the signal line and the switch does not affect the output signal voltage, a high-quality infrared image can be easily obtained.

FIG. 3 shows an example of the structure of a temperature-sensitive capacitor.

First wiring electrode 111 of semiconductor chip 101
This can be realized by providing the cavity 102 between the first wiring electrode 112 and the second wiring electrode 112 and forming the second wiring electrode 112 in a bimetal structure. Since the electrode 112 having a bimetal structure is displaced by a change in temperature, the first wiring electrode 111 and the second wiring electrode 112 are displaced.
And the interval changes. Therefore, the capacitance changes with temperature.

FIG. 4 shows an example of manufacturing the above-mentioned temperature-sensitive capacitor.

As shown in FIG. 4A, a lower metal layer 301 of a bimetal is formed on a SiO2 insulating film by vapor deposition. The metal film other than the bimetal component is removed by photoetching (FIG. 4B). A contact hole 302 is opened by photoetching for connection with the lower wiring 113 (FIG. 4).
(C)). An upper metal layer 303 of the bimetal is deposited, and the bimetal portion and the wiring metal are patterned by etching (FIG. 5A). At this time, in order to form a cavity below the bimetal portion, a bimetal electrode is formed in a mesh shape so that the SiO2 etching solution can pass therethrough (FIG. 5).
(B)).

A resist 305 is formed in a portion excluding the temperature-sensitive capacitor (FIG. 5C), and when SiO2 is isotropically etched, it is also etched in the lateral direction, and the SiO2 cavity 10 is etched.
2 (FIG. 3) can be produced.

With such a structure, when infrared rays hit the bimetal portion, the temperature rises, the bimetal electrode bends, and the distance to the lower electrode changes, so that the intensity of infrared rays can be detected as a change in capacitance.

FIG. 6 is a circuit block diagram of an infrared imaging apparatus showing another embodiment of the present invention. This embodiment also shows four pixels arranged in a matrix. Since the configuration of each pixel is the same, one pixel will be described as a representative.

In this image pickup apparatus as well, for simplicity of description, four pixels 60 arranged in a matrix are used.
(1, 1), 60 (2, 1), 60 (1, 2), 60
(2, 2) is shown. The configuration of one pixel 60 (1, 1) will be described as a representative.

SEL1 is a first row selection line. 6
1 (a1) is a temperature-sensitive capacitor. One electrode of the temperature-sensitive capacitor 61 (a1) is connected to the ground line, and the other electrode is connected to a switch 64 (a1).
1), 65 (a1), the previous row selection line SEL1
It is connected to the.

The switches 64 (a1) and 65 (a1) are turned on and off by pulses φRD and φRS, respectively. A capacitor 62 (a1) is connected between the connection point of the switches 64 (a1) and 65 (a1) and the ground line. The switches 64 (a1) and 65 (a1)
Are connected to the buffer amplifier 63 (a1), the switch 6
6 (a1) is connected to the read line 70 (1).

The other pixels 60 (1, 2), 60 (2,
1) and 60 (2, 2) have the same configuration. Note that the outputs of the pixels 60 (1, 1) and 60 (2, 1) are output to the readout line 70 (1), but the pixels 60 (1, 2),
The output of 60 (2,2) is directed to read line 70 (2).

Read lines 70 (1), 70 (2)
Are connected to the input terminal of the buffer amplifier 69 via the capacitors 68 (1) and 68 (2), respectively.
A capacitor 71 and a switch 72 are connected to the output amplifier 69 in parallel. Switches 68 (1) and 68
(2) is controlled by the horizontal scanning circuit 302 so as to be turned on once in one horizontal period. The read signal appears at the output terminal 73.

FIG. 7 shows the operation timing of the above-described image pickup apparatus.

By setting all the select lines SEL1 and SEL2 to low level and setting the signals φRS and φRD to high level, the capacitors 61 and 62 are discharged and set to the voltage VSL.

The description will focus on the pixel 60 (1, 1).

Next, the row selection line SEL1 is set to the high level VsH, the capacitor 62 (a1) is charged to VsH via the reset switch 65 (a1), and the switch 66 (a1) is turned on to turn on the buffer amplifier 63 (a).
The output of 1) is applied to the vertical signal line (readout line) 70 (1)
(Time t1).

Next, after the reset switch 65 (a1) is turned off, the scanning switch 68 (1) and the output amplifier 69
Turn on the reset switch 72 of the
In (1), the output voltage variation of the buffer amplifier 63 (a1) at the time of no signal is removed by the clamp operation (at time t).
2).

Next, after the switches 68 (1) and 72 are turned off, the read switch 64 (a1) is turned on (time t3). Then, the input voltage Vdet of the buffer amplifier 63 (a1) becomes [VsL × (capacitance of 61 (a1)) + VsH × (6
2 (a1)) / [(61 (a1) capacitance) + (62 (a1) capacitance)] = VsH − [(V
sH-VsL) / (1+ (capacitance of 62 (a1)) /
(Capacitance of 601 (a1)))].

Therefore, the voltage change due to the capacitance change of the capacitor 61 (a1) is not
It can be extracted as the output Vsig of 1).

This voltage change is amplified by the capacitance ratio of the capacitors 67 (1) and 71 by alternately turning on the scanning switch 68 and the reset switch 72 of the output amplifier 69 which are sequentially selected. From the video signal voltage V
It can be taken out.

This output signal voltage can also be determined by the capacitance ratio,
Since the ON resistance of the signal line and the switch does not affect the output signal voltage, a high-quality infrared image can be easily obtained.

[0042]

As described above, according to the present invention, since the temperature distribution in the imaging region of the infrared imaging device is detected as a change in capacitance, a high image quality which is not affected by the wiring resistance or the resistance of the switch unit is obtained. An infrared imaging device can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart shown for explaining the operation of the circuit in FIG. 1;

FIG. 3 is a diagram showing a configuration example of a pixel according to the present invention.

FIG. 4 is an explanatory view for explaining an example of manufacturing a pixel according to the present invention.

FIG. 5 is an explanatory view showing a continuation of FIG. 4;

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a timing chart for explaining the operation of the circuit in FIG. 6;

FIG. 8 is a diagram showing a configuration of a conventional infrared imaging device.

[Explanation of symbols]

2 (1,1), 2 (2,1), 2 (2,1), 2 (2,2
2) Switch, 3 (1, 1), 3 (2, 1), 3
(2, 1), 3 (2, 2) ... temperature-sensitive condenser, 4
(1), 4 (2) ... amplifier, 5 (1), 5 (2) ... capacitor, 6 (1), 6 (2), 7 (1), 7 (2) ... switch, 201 ... vertical scanning circuit , 202 ... pulse generator, 204 ... horizontal scanning circuit.

Claims (4)

[Claims] 1. An optical system for forming an infrared light image on an imaging surface to form a temperature distribution, and a plurality of temperature-sensitive devices which are regularly arranged on the imaging surface and whose capacitance changes with temperature. An infrared imaging apparatus comprising at least a conductive capacitor and a detection amplifier that converts capacitance of the plurality of temperature-sensitive capacitors into an electric signal. 2. The temperature-sensitive capacitor includes a first electrode that is physically fixed, and a second electrode that faces the first electrode and changes the distance between the first electrode and the first electrode depending on temperature. The infrared imaging device according to claim 1, wherein: 3. A second electrode of the temperature-sensitive capacitor,
3. The infrared imaging device according to claim 2, wherein the infrared imaging device is made of a bimetal. 4. The method according to claim 1, wherein the detection amplifier converts a charge amount when a voltage applied to the temperature-sensitive capacitor is changed by a predetermined voltage into a voltage signal by a capacitor having a fixed capacitance. Item 7. The infrared imaging device according to Item 1.