JP3518181B2 - Thermal infrared image sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal infrared image sensor, and in particular, in a thermal infrared image sensor using a bolometer, infrared radiation can be accurately detected by a simple device configuration without being affected by self-heating. Regarding the technology that was done.

[0002]

2. Description of the Related Art Conventionally, various types of infrared image sensors have been developed to detect infrared radiation emitted from a warm human body. One example of an infrared image sensor uses a bolometer as a heat sensor, and for example, the one disclosed in Japanese Patent Laid-Open No. 2-196929 is known. A bolometer is an element whose resistance value changes according to temperature rise (change) due to infrared irradiation.

FIG. 5 shows a schematic configuration of the infrared image system disclosed in Japanese Patent Laid-Open No. 2-196929. In the configuration of the figure, infrared radiation from warm human body 116 is incident on array of bolometers 106 via infrared lens system 102 and chopper 104.
The array of bolometers 106 is scanned by drive and readout electronics 108 to obtain a signal corresponding to an infrared image of a warm human body 116, which is then converted by a video processor 110 into a suitable signal format before display 11.
It is displayed as 2.

FIG. 6 shows the configuration of the array of bolometers 106 in the infrared image system of FIG. 5, and FIG. 7 shows the configuration of one pixel in the array of bolometers 106 in cross section. As described with reference to FIG. 5, an infrared image of a subject 116, such as a warm human body, is imaged through the infrared lens system 102 and the chopper 104 onto the array of bolometers 106. In the array 106 of the bolometer, as shown in FIG. 6, in each pixel 140, infrared infrared image incident is irradiated to the bolometer resistance R _B, the resistance value by the temperature of the bolometer resistance R _B is changed Change. As a result, the voltage obtained from the connection point of the bolometer resistance R _B and the fixed resistance R _L connected in series between the bias voltage 182 (V) and the ground changes. This change in voltage is taken out from the row read circuit 128 via the capacitor 122, the amplifier 120, and the switch 132, and is supplied to the driving and reading electronic device 108 in FIG.

[0005]

In the conventional infrared image sensor described above, in order to obtain an image with a good signal-to-noise ratio (S / N), the resistors R _B and R _L in each pixel 140 in FIG. It was necessary to make them smaller and to pass a large amount of current through these resistors.

The reason is that the resistance R is generally expressed by the following equation 1
This can be explained by generating the thermal noise Vn indicated by.

## EQU1 ## Vn = 2 (kTRΔf) ^1/2 where k is the Boltzmann constant, T is the temperature of the resistor, R is the resistance of the resistor, and Δf is the frequency bandwidth of the electronic circuit.
Therefore, it can be seen from Equation 1 that the noise Vn decreases as the resistance value R of the resistor is reduced.

On the other hand, the voltage of the connection point of the resistors R _B and R _L in the circuit of FIG. 6, the ratio of the resistance R _B and R _L is constant as long as it and a bias voltage V is constant constant. That is, if the resistance ratio and the bias voltage V are constant, the signal Vs
Is constant, and the signal-to-noise ratio S / N is improved as the resistance value is lowered.

However, with the bias voltage V kept constant,
When the resistance value of each resistor is lowered, the current I increases and the power W = V × I consumed by the resistor increases. The electric power W consumed by the resistance is converted into heat. Therefore, this heat causes a self-heating phenomenon in which the temperature of the resistor rises.

Since the thermal infrared image sensor using the bolometer obtains an infrared image by utilizing the temperature rise of the bolometer due to the received infrared rays, such a self-heating phenomenon causes an offset of the image signal.

Therefore, in view of the problems in the conventional device, the present invention suppresses the self-heating of the thermal infrared image sensor using the bolometer and removes the offset of the image signal with a simple device configuration. To obtain a high-fidelity and high-quality infrared image.

[0011]

In order to achieve the above object, in the thermal infrared image sensor according to the first aspect of the present invention, a plurality of bolometers each of which causes a temperature rise by infrared irradiation and each of the bolometers are provided. A plurality of charge storage means provided correspondingly and a plurality of switch elements connected between each of the bolometers and the corresponding charge storage means are provided. Then, each of the switch elements is turned on to discharge the charge of the charge storage means through the bolometer for a predetermined time, and then a signal corresponding to the residual charge of each charge storage means is output.

That is, according to the present invention, as a method for detecting the change in the resistance value of the bolometer in this way, in the current mode reading in which a constant voltage is applied to the resistance and the change in the resistance value is known from the change in the current as in the conventional method. Instead, the electric charge accumulated in the electric charge accumulating means is discharged through the bolometer for a predetermined time, and a signal corresponding to the residual electric charge is output to know the change in the resistance value. Therefore, the influence of self-heating of the bolometer can be removed, and an infrared image with less offset can be obtained.

In this case, further, a second switch element having one end connected to the charge storage means, and a load resistor connected to a circuit between the other end of the second switch element and the power supply are provided. Conveniently, the output signal is obtained based on the dielectric current flowing in the charge storage means via the load resistor.

In such a structure, after the charge of the charge storage means is discharged through the bolometer for a predetermined time, the second charge
The switch element is turned on, and the charge storage means is recharged from the power source through the load resistor. The magnitude of the charging current during this recharging increases as the residual charge in the charge storage means decreases. Therefore, the voltage developed across the load resistance by this charging current is related to the amount of residual charge in the charge storage means and thus to the resistance of the bolometer. Thus, by extracting the voltage of the load resistance, it is possible to know the change in the resistance value of the bolometer, and it is possible to obtain an infrared image signal accurately with a simple device configuration.

In the thermal infrared image sensor according to the second aspect of the present invention, a plurality of bolometers arranged in a matrix along the row and column directions, each of which raises a temperature by infrared irradiation, and each of the bolometers. A plurality of charge storage capacitors provided in correspondence with the plurality of first switch elements connected between each of the bolometers and the corresponding charge storage capacitors, and a plurality of vertical switches provided for each column. And a plurality of second switch elements connected between the line and a vertical line corresponding to each of the charge storage capacitors.

In such a thermal infrared image sensor, the first switch element is turned on for each row to discharge the charge of the storage capacitor through the corresponding bolometer for a predetermined time. Then, after that, the second switch is turned on to charge the storage capacitor through each vertical line,
A signal corresponding to the charging current during the charging is sequentially output through the vertical line.

As a result, an image signal corresponding to an image of a human body or other infrared radiation can be obtained by the bolometers arranged in a matrix, and in this case as well, there is almost no self-heating of each bolometer, and therefore a high-quality image is obtained. It can be obtained with low power consumption.

In the thermal infrared image sensor according to the third aspect of the present invention, a plurality of bolometers arranged in a matrix along the row and column directions, each of which raises the temperature by infrared irradiation, and each of the bolometers. And a plurality of switch elements each having one end connected to a corresponding bolometer, and the other end of each of the switch elements corresponding to the bolometers arranged in each column connected in common. A plurality of vertical lines and a storage capacitor provided for each vertical line and connected to the corresponding vertical line.

In such a thermal infrared image sensor, the switch elements in each row are sequentially turned on to discharge the electric charge of the storage capacitors provided in each vertical line through the bolometer for a predetermined time. After that, each storage capacitor is charged through the vertical line, and a signal corresponding to the residual charge of the storage capacitor is sequentially output from the charging current at this time through the vertical line.

Also in this case, as in the case of the second aspect, an image signal corresponding to an image of a human body or other infrared radiation can be obtained with high quality without causing an adverse effect due to self-heating. Further, since the storage capacitor need only be provided for each vertical line, the device configuration is simplified, the area occupied by the storage capacitor on the integrated circuit board can be reduced, and high-density mounting can be performed. .

In this case, the storage capacitor may be configured by providing a separate capacitance element for each vertical line, but as another method, at least a part of the storage capacitor is configured by the parasitic capacitance of the vertical line. You can also In this case, the device configuration can be simplified, it is not necessary to provide a space for the storage capacitor on the integrated circuit, or the space can be reduced.

In the thermal infrared image sensor according to the fourth aspect of the present invention, a plurality of bolometers arranged in a matrix along the row and column directions, each of which raises the temperature by infrared irradiation, and each of the bolometers. A plurality of charge storage capacitors provided corresponding to the plurality of charge storage capacitors, a plurality of first switch elements connected between the respective bolometers and the corresponding charge storage capacitors, and the respective charge storage capacitors and the first charge storage capacitors. A plurality of second switch elements each having one end connected to a connection point of one switch element, and provided for each column,
A plurality of vertical lines to which the other ends of the second switch elements corresponding to the bolometers arranged in each column are commonly connected, and a horizontal switch connected between each of the vertical lines and a horizontal output line. An element, a vertical scanning circuit that sequentially connects the first and second switch elements in a predetermined order for each row, a horizontal scanning circuit that sequentially drives the horizontal switch element, and the other terminal of the charge storage capacitor. Bias voltage supply means for supplying a bias voltage to the horizontal output line via a load resistor.

In such a thermal infrared image sensor, the first switch elements are sequentially turned on for each row to discharge the charges of the charge storage capacitors through the corresponding bolometers for a predetermined time. After that, the second switch element and the horizontal switch element are sequentially turned on to supply the charge current to the charge storage capacitors of each column through the load resistor and output a signal corresponding to the magnitude of the charge current.

With such a structure, as in the case of the thermal infrared image sensor according to the second aspect, it is possible to obtain an image signal corresponding to a two-dimensional image due to infrared radiation of the human body or the like. Moreover, the image signal is not offset by the self-heating of the bolometer, and an image of high quality and high fidelity can be obtained.

In the thermal infrared image sensor according to the fifth aspect of the present invention, a plurality of bolometers arranged in a matrix along the row and column directions, each of which raises the temperature by infrared irradiation, and each of the bolometers. Corresponding to the plurality of switch elements, one end of which is connected to one end of the corresponding bolometer, and the other end of the switch element, which is provided for each column and corresponds to the bolometers arranged in each column, are common. Multiple vertical lines connected to
A charge storage capacitor provided for each vertical line and connected to a corresponding vertical line, a horizontal switch element connected between each of the vertical lines and a horizontal output line, and a bolometer arranged in each row. A vertical scanning circuit that sequentially connects the connected switch elements row by row, a horizontal scanning circuit that sequentially drives the horizontal switch elements, and a load resistor between the other terminal of the bolometer and the horizontal output line. And a bias voltage supply means for supplying a bias voltage.

In such a thermal infrared image sensor, the switch elements are sequentially turned on for each row, and the charges of the charge storage capacitors provided on each vertical line are discharged for a predetermined time through each bolometer. After that, the horizontal switch elements are sequentially turned on to supply the charge current to the charge storage capacitors of each column through the load resistors, and the signal corresponding to the magnitude of the charge current is output.

Also in this case, the same advantages as those of the thermal infrared image sensor according to the fourth aspect can be obtained, and in addition to the above, the accumulation can be performed similarly to the case of the thermal infrared image sensor according to the third aspect. Since the capacitance need only be provided for each vertical line, the area occupied by the storage capacitance on the integrated circuit substrate can be reduced, and an image sensor with a high degree of integration can be obtained.

Further, also in this case, at least a part of the charge storage capacitors can be formed by the parasitic capacitance of the vertical line, and the area occupied by the charge storage capacitors on the integrated circuit substrate can be reduced or eliminated to achieve high density. Can be implemented.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to describing a thermal infrared image sensor according to a preferred embodiment of the present invention, a thermal infrared image sensor according to the present invention and a conventional image sensor shown in FIGS. Power consumption and noise between the two will be compared and examined.

In the present invention, since the method of discharging the capacitance by the resistance of the bolometer is adopted, the mechanism of generating noise and power consumption is different from the conventional one. Now, for example, when the capacitance of the capacitance value C is charged to the voltage V ₀ , and considering the case of discharging it by the resistance of the resistance value R, the time t is used as a variable, and the capacitance voltage V is given by the following formula. To be

[Number 2] _{V = V 0 exp (-t /} CR)

Integrating Equation 2 from time 0 to t ₀ gives
The amount of charge Q ₀ discharged at time t ₀ is obtained.

## EQU3 ## Q ₀ = CV ₀ {1-exp (-t ₀ / CR)}

In addition, the power W consumed by the resistor R during this period
₀ is given by the following equation.

## EQU00004 ## W ₀ = CV ₀ ² {1-exp (-2t ₀ / CR)}

Next, the power consumption of the conventional method and the method according to the present invention in the standard NTSC television format will be compared. As a condition, for example,
Consider a case where the signal when the resistance value of the bolometer changes by 1% is 100 times the noise.

First, in the conventional method, assuming that R _B and R _L (FIG. 6) are equal, when the resistance R _B changes by 1%, the output changes by 0.25% of the bias voltage V. On the other hand, as for noise, Δf = 4.2 MHz, k = 1.
Substituting 38 × 10 ⁻²³ and T = 300 gives the following equation.

(5) Vn = 2.637 × 10 ⁻⁷ × (R) ^1/2

Further, assuming that the bias voltage V is 1 (V), since the signal Vs is 2.5 × 10 ⁻³ V, the following equation is obtained from the equation 5 and Vs is 100 times Vn. To be

[Equation 6] R = 9 (kΩ)

The power consumption W is given by the following equation based on the bias voltage of 1 V and the resistance value of the equation (6).

## EQU7 ## W = 5.6 × 10 ^-5 (W)

On the other hand, in the present invention, as an example, t ₀
= CR and the resistance R changes by 1%, the difference ΔQ ₀ of the discharged electric charges is as follows.

ΔQ ₀ = 3.66 × 10 ⁻³ × CV ₀

Converting this charge difference ΔQ ₀ into the number of electrons, the number of signal electrons Ns is given by the following equation.

Ns = 3.66 × 10 ⁻³ × CV ₀ / q where q is the electron charge amount and is 1.6 × 10 ⁻¹⁹ (C).

Since the noise becomes shot noise, it can be obtained as follows. That is, t
Substituting ₀ = CR into Equation 3 above, the following equation is obtained.

## EQU10 ## Q ₀ = 0.632 × CV ₀

Converting Q ₀ shown in Equation 10 into the number of electrons, N ₀ is obtained by the following equation.

## EQU11 ## N ₀ = 0.632 × CV ₀ / q

The square root of N ₀ expressed by the equation 11 becomes the number Nn of noise electrons and is obtained by the following equation.

## EQU12 ## Nn = (0.632 × CV ₀ / q) ^1/2

Therefore, as in the conventional case, Ns is 1 of Nn.
Under the condition of 00 times, CV ₀ is obtained by the following equation from the above equations 9 and 12.

CV ₀ = 7.55 × 10 ⁻¹¹

The bias voltage V _{0 is set} to 1 as in the conventional case.
If V is set, the capacitance C is obtained by the following equation.

## EQU14 ## C = 75.5 (pF)

Therefore, the power consumption is C =
Substituting 75.5 pF, V ₀ = 1V, t ₀ = CR, it is obtained by the following equation.

## ^EQU15 ## W ₀ = 6.5 × 10 ^-11 (W)

In the standard NTSC television system,
Since an image of 30 frames is output per second, in the present invention, the electric power W consumed by one pixel is 30 times that of W ₀ and is given by the following equation.

(16) W = 1.95 × 10 ⁻⁹ (W)

Therefore, the power consumption according to the present invention is 1/2 that of the conventional power consumption expressed by the equation (7).
It will be reduced by 8,000 times.

Next, the thermal infrared image sensor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic structure of a thermal infrared image sensor using a bolometer according to the first embodiment of the present invention. The thermal infrared image sensor shown in FIG. 1 includes a bolometer 1, a capacitor 2, and a MOS switch 3 connecting one end of the bolometer 1 and one end of the capacitor 2, and between the one end of the capacitor 2 and the vertical signal line 5. A plurality of pixels composed of other connected MOS switches 4 are arranged in a matrix. In FIG. 1, the pixels are shown as a matrix of 2 rows × 2 columns for simplification of the description, but in reality, more pixels such as several hundreds of pixels are arranged. Each of the MOS switches 3 and 4 is a switch element composed of a MOS transistor.

The thermal infrared image sensor of FIG. 1 further includes a vertical drive circuit 6, a horizontal drive circuit 7, a read circuit 8, and a horizontal MOS switch 11 composed of, for example, a MOS transistor.

One end of the bolometer 1 is connected to the source of the MOS switch 3, the gate of the MOS switch 3 is connected to the vertical drive circuit 6 in common for each row, and the drain is connected to one end of the capacitor 2. The other end of the bolometer 1 and the other end of the capacitor 2 are grounded.

One end of the capacitor 2, that is, the MOS switch 3
The drain of is connected to the source of the MOS switch 4,
The gates of the OS switches 4 are commonly connected to the vertical drive circuit 6 in each row, and the drains are connected to the sources of the horizontal MOS switches 11 in the respective columns through the vertical signal lines 5.

The gate of the horizontal MOS switch 11 is connected to the horizontal drive circuit 7, and the drain is connected to the output terminal OS via the horizontal signal line 12.

The output terminal OS is connected to the readout circuit 8 outside the thermal infrared image sensor in this embodiment. The read circuit 8 includes a resistor 9 and a power supply 10 that are connected in series between the output terminal OS and the ground. In addition,
The resistor 9 of the read circuit 8 may be provided inside the image sensor.

FIG. 2 shows the signal waveform of each part of the thermal infrared image sensor of FIG. It is assumed that each MOS switch in FIG. 1 is composed of an N-type MOS transistor, and therefore each MOS switch is opened, that is, turned on when the pulse is at a high level.

First, at time T0, the vertical drive pulse V11 from the vertical drive circuit 6 becomes high level, and the MOS switch 4 of the pixel on the first row is turned on. Further, at time T1, the horizontal drive pulse H1 from the horizontal drive circuit 7 becomes high level, and the horizontal MO connected to the signal vertical signal line 5 of the first column is connected.
The S switch 11 is turned on. This allows the power supply 1
0, the resistor 9, the output terminal OS, the horizontal signal line 12, the horizontal MOS switch 11 in the first column, and the MO of the pixel in the first row and the first column.
The capacitor 2 in the first row, first column is connected to the power source 1 via the S switch 4.
It is charged to zero voltage.

Next, at time T2, with the vertical drive pulse V11 from the vertical drive circuit 6 at the high level, the horizontal drive pulse H2 from the horizontal drive circuit 7 becomes the high level, and the pixel in the first row, second column The capacitor 2 (upper left pixel in FIG. 1) is similarly charged to the voltage of the power supply 10.

Next, at time T3, the vertical drive pulse V11 becomes low level, the first row MOS switch 4 is turned off, and instead the vertical drive pulse V12 becomes high level and the first row MOS switch is turned on. 3 turns on. As a result, the charges stored in the capacitor 2 in the pixels on the first row start to be discharged through the resistance of the bolometer 1. This discharge is performed at a later time T0 by the vertical drive pulse V12.
Continues until goes low. The magnitude of the discharge current during this discharge changes according to the resistance of the bolometer 1.

Next, from time T4 to T7, the vertical drive pulse V21 from the vertical drive circuit 6 becomes high level, and the capacitors 2 of the pixels on the second row are sequentially charged to the voltage of the power supply 10. This operation is similar to that described above for the pixels on the first row. After this charging, the process returns to the time T0 again.

Returning to time T0, the vertical drive pulse V11 from the vertical drive circuit 6 becomes high level again, and the MOS switch 4 of the pixel on the first row is turned on. Then, at times T1 and T2, the horizontal drive pulses H1 and H2 from the horizontal drive circuit 7 sequentially become high level, and the horizontal MOS switch 5 is sequentially turned on. Therefore, at times T1 and T2, the capacitors 2 in the first and second columns are recharged from the power supply 10 via the resistor 9, respectively.

The charge amount of this recharge changes according to the residual charge of the bolometer 1. That is, if the residual charge of the capacitor 2 is large, the recharged charge is small, and the recharged current flowing through the resistor 9 is also small. On the contrary, if the residual charge of the capacitor 2 is small, the recharged charge amount is large and the resistance 9
The recharge current flowing through the device also increases. Therefore, the resistance 9
A signal corresponding to the residual charge of each capacitance, that is, an output corresponding to the resistance value of the bolometer 1 can be obtained by taking the recharge current flowing through the output as an output. The recharge current flowing through the resistor 9 has a downward signal waveform as shown by OS in FIG. A necessary image signal can be obtained by holding the downward peak of this signal waveform by a peak hold circuit (not shown).

FIG. 3 shows a schematic structure of a thermal infrared image sensor according to the second embodiment of the present invention. In the thermal infrared image sensor of FIG. 3, each pixel is a bolometer 1
Switch 1 consisting of
3 and arranged in a matrix. Figure 3
In order to simplify the description and the drawing, the pixels are shown arranged in a matrix of 2 rows × 2 columns, but in actuality, more rows and columns are provided.

In each pixel, one end of the bolometer 1 is M
It is connected to the source of the OS switch 13, and the gate of the MOS switch 13 is commonly connected to the vertical drive circuit 13 for each row. Each drain of the MOS switch 13 is commonly connected to a vertical signal line for each column. The other end of the bolometer 1 is grounded.

A capacitor 14 common to each column is connected between each vertical signal line 5 and the ground. Each vertical signal line 5 is connected to the source of the horizontal MOS switch 5.
The gate of the horizontal MOS switch 5 is connected to the horizontal drive circuit 7, and the drain is connected to the output terminal OS via the horizontal signal line 12. The output terminal OS is connected to, for example, an external read circuit 8 as in the case of FIG. The read circuit 8 includes a resistor 9 connected in series between the output terminal OS and the ground.
And a power supply 10.

Next, the operation of the thermal infrared image sensor according to the second embodiment will be described with reference to FIG.
First, at time T1, the horizontal drive pulse H1 supplied from the horizontal drive circuit 7 becomes high level, and the horizontal MO of the first column is moved.
The S switch 11 is turned on. As a result, the capacitor 14 connected to the vertical signal line 5 in the first column from the power source 10 via the resistor 9, the horizontal signal line 12, and the horizontal MOS switch 11 in the first column is charged to the voltage of the power source 10. . Next, time T
2, the horizontal drive pulse H2 supplied from the horizontal drive circuit 7
Becomes high level, and the capacitor 14 connected to the vertical signal line 5 in the second column is charged to the voltage of the power supply 10.

Next, at time T3, the vertical drive pulse V2 supplied from the vertical drive circuit 15 becomes high level, and the second
The MOS switch 13 of the pixel on the row is turned on. As a result, the charges of the capacitors 14 in each column start to be discharged through the bolometer 1 in the second row. The magnitude of the discharge current during this discharge is determined by the resistance value of each bolometer 1.

At time T4, the vertical drive pulse V2 becomes low level, and the discharge of the capacitors 12 in each column is completed. Therefore, the residual charge accumulated in the capacitors 14 in each column at this point is smaller as the resistance value of the corresponding bolometer 1 is lower.

Next, at time T5, the horizontal drive pulse H1 from the horizontal drive circuit 7 becomes high level, and the horizontal MOS switch 11 in the first column is turned on. As a result, the capacitor 14 is recharged from the power supply 10 through the load resistor 9 and via the horizontal signal line 12 and the horizontal MOS switch 11. This recharged electric charge becomes equal to the electric charge discharged by the bolometer 1 in the first column, second row from time T3 to T4 as described above. The current at the time of this recharge, that is, the recharge current flows from the resistor 9 to the terminal OS, and appears as an output signal voltage waveform OS at the terminal OS.

Next, at time T6, the horizontal drive pulse H2 from the horizontal drive circuit 7 becomes high level, and the horizontal MOS switch 11 in the second column is turned on. As a result, the power source 10 to the resistor 9, the horizontal signal line 12, the horizontal M
The second-row capacitors 14 are recharged through the OS switch 11. Due to this recharging current, the output terminal OS is the same as before.
A downward peak waveform appears at.

Similarly, from time T7 to T0, the capacitors 14 in each column are discharged by the bolometer 1 of the pixel in the first row, and the time T is reached.
1 and T2 recharge from the power supply 10. As a result, output signal waveforms corresponding to the resistance values of the bolometers in the first and second columns of the first row are sequentially obtained at the output terminal OS.

By holding the downward peak signal waveform output to the output terminal OS in this manner, image signals from each pixel are sequentially output.

In the thermal infrared image sensor according to the embodiment of FIG. 3, since the capacitors 14 are commonly provided for each column, the area on the integrated circuit for forming the capacitors is smaller than that of the configuration of FIG. The number can be reduced and the configuration can be simplified. Further, since each capacitor 14 is connected between the vertical signal line 5 and the ground, the parasitic capacitance of the vertical signal line 5 can be used instead of the capacitor 14 or can be used in addition to the capacitor 14. As a result, the area on the integrated circuit substrate required for forming the capacitor 14 can be further reduced.

[0072]

As described above, according to the present invention, it is not necessary to constantly supply a large current to the bolometer as in the conventional case, and the charge accumulated in the capacitor is discharged through the bolometer and the capacitance is reduced. Since the output is obtained based on the current at the time of recharging and recharging, the self-heating of the bolometer becomes extremely small as shown in the above-mentioned formula 16. Therefore, it is possible to faithfully detect the temperature change of the bolometer without causing an offset due to self-heating and obtain a high-quality infrared image.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a thermal infrared image sensor according to a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the thermal infrared image sensor of FIG.

FIG. 3 is a block circuit diagram showing a schematic configuration of a thermal infrared image sensor according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of the thermal infrared image sensor of FIG.

FIG. 5 is a block diagram schematically showing an infrared detection system using a bolometer array.

FIG. 6 is a block circuit diagram showing a schematic configuration of a conventional thermal infrared image sensor.

7 is a sectional view showing a detailed configuration of a pixel portion of the thermal infrared image sensor of FIG.

[Explanation of symbols]

1 bolometer 2 capacity 3,4 pixel MOS switch 5 Vertical signal line 6,15 Vertical drive circuit 7 Horizontal drive circuit 8 readout circuit 9 load resistance 10 power supplies 11 Horizontal MOS switch 12 horizontal signal lines 13-pixel MOS switch Capacity provided for every 14 rows

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 1/00-1/60 G01J 5/00-5/62 H04N 5/33 JISST file (JOIS) WPI / L Web of Science

Claims (8)

(57) [Claims] 1. A plurality of bolometers each of which raises a temperature by infrared irradiation, a plurality of charge storage means provided corresponding to each of the bolometers, and a charge storage means corresponding to each of the bolometers. A plurality of connected switch elements, each of which is turned on to discharge the charge of the charge storage means through the bolometer for a predetermined time, and then outputs a signal corresponding to the residual charge of each charge storage means. A thermal infrared image sensor characterized by: 2. A second switch element having one end connected to the charge storage means, and a load resistor connected to a circuit between the other end of the second switch element and a power supply. The thermal infrared image sensor according to claim 1, wherein an output signal is obtained based on a charging current flowing through the charge storage means via the load resistor. 3. A plurality of bolometers arranged in a matrix along the row and column directions, each of which raises a temperature by infrared irradiation, and a plurality of charge storage capacitors provided corresponding to each of the bolometers, A plurality of first switch elements connected between each bolometer and a corresponding charge storage capacity, a plurality of vertical lines provided for each column, and a vertical line corresponding to each of the charge storage capacity A plurality of second switch elements connected between the first switch element and the second switch element after the charge of the storage capacitor is discharged through the bolometer for a predetermined time. To charge the storage capacitor and sequentially output a signal corresponding to a charging current at the time of charging through the vertical line. 4. A plurality of bolometers arranged in a matrix along the row and column directions, each of which raises a temperature by infrared irradiation, and provided corresponding to each of the bolometers, one end of which is connected to the corresponding bolometer. A plurality of switch elements, and a plurality of vertical lines that are provided for each column, and the other ends of the switch elements corresponding to the bolometers that are arranged in each column are commonly connected, and provided for each of the vertical lines. Corresponding to the residual charge of the storage capacitor after discharging the charge of the storage capacitor through the bolometer for a predetermined time by sequentially connecting the switch elements in each row to each other. A thermal infrared image sensor, which sequentially outputs the signals to be output through the vertical lines. 5. The thermal infrared image sensor according to claim 4, wherein at least a part of the storage capacitor is composed of a parasitic capacitance of the vertical line. 6. A plurality of bolometers arranged in a matrix along the row and column directions, each of which raises a temperature by infrared irradiation, and a plurality of charge storage capacitors provided corresponding to each of the bolometers, A plurality of first switch elements connected between the respective bolometers and the corresponding charge storage capacitors, and a plurality of first switch elements each having one end connected to a connection point of each of the charge storage capacitors and the first switch element. A second switch element, a plurality of vertical lines that are provided for each column, and the other ends of the second switch elements corresponding to the bolometers arranged in each column are commonly connected to each other; A horizontal switch element connected between each of them and a horizontal output line; and a vertical scanning circuit for electrically connecting the first and second switch elements in a predetermined order for each row. A horizontal scanning circuit for sequentially driving the horizontal switch elements; and a bias voltage supply unit for supplying a bias voltage between the other terminal of the charge storage capacitor and the horizontal output line via a load resistor. Then, the first switch elements are sequentially turned on for each row to discharge the charges of the charge storage capacitors through the respective bolometers for a predetermined time, and then the second switch elements and the horizontal switch elements are sequentially turned on for each column. A thermal infrared image sensor, wherein a charge current is supplied to the charge storage capacity of the battery via the load resistor and a signal corresponding to the magnitude of the charge current is output. 7. A plurality of bolometers arranged in a matrix along the row and column directions, each of which raises the temperature by infrared irradiation, and one bolometer provided corresponding to each of the bolometers, one end of which corresponds to one end of the corresponding bolometer. A plurality of connected switch elements, a plurality of vertical lines provided for each column, and a plurality of vertical lines to which the other ends of the switch elements corresponding to the bolometers arranged in each column are commonly connected, and for each vertical line A charge storage capacitance connected to a corresponding vertical line, a horizontal switch element connected between each of the vertical lines and a horizontal output line, and a switch element connected to a bolometer arranged in each row. A vertical scanning circuit for sequentially conducting each row, a horizontal scanning circuit for sequentially driving the horizontal switch elements, and the other of the bolometers. A bias voltage supply means for supplying a bias voltage between a child and the horizontal output line via a load resistance, and sequentially connecting the switch elements row by row to charge the charge storage capacitor. After discharging for a predetermined time through each bolometer, the horizontal switch elements are sequentially turned on to supply a charge current to the charge storage capacitors in each column through the load resistor, and a signal corresponding to the magnitude of the charge current is output. A thermal infrared image sensor characterized by: 8. The thermal infrared image sensor according to claim 7, wherein at least a part of the charge storage capacitance is composed of a parasitic capacitance of the vertical line.