JP2003222555A - Thermal-type infrared solid image pickup element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal-type infrared solid image pickup element less affected by a voltage drop caused by resistance of a drive line and less fluctuated in output by fluctuation in power supply voltage or fluctuation in element temperature. <P>SOLUTION: A second constant current source 18 connected in common by a bias line 17 is provided in the proximity of a first constant current source 2 connected to pixels 1. Difference between a voltage across the first source 2 and a voltage across the second source 18 is integrated for a fixed period of time by a differential integration circuit 7 and outputted, thereby cancelling voltage distribution appearing in the drive line. From a reference signal output circuit 11 driven by a pixel power supply 6, a reference signal corresponding to the temperature of the whole element is inputted into the bias line 17. Drifts of the signal caused by fluctuation in power supply voltage and fluctuation in element temperature are subtracted by the differential integration circuit, thereby preventing the drifts from being outputted to the exterior. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal infrared solid-state image sensor in which temperature changes due to incident infrared rays are detected by a two-dimensionally arranged semiconductor sensor, and in particular, an electric signal from the semiconductor sensor is integrated by a signal processing circuit. The present invention relates to a thermal infrared solid-state imaging device that outputs after processing.

[0002]

2. Description of the Related Art FIGS. 10 and 11 show Proc.SPIE Vol.36.
98 1999 Conventional thermal infrared solid-state imaging device described on pages 556 to 564. As shown in FIGS. 10A and 10B, in the pixel 1 of the infrared imaging device, the PN junction diode 902 serving as the temperature sensor has two long support legs 11
01 is supported on the hollow portion 1103 provided in the silicon substrate 1102, and the electrode wiring 1104 of the diode 902 is embedded in the support leg 1101.
A plurality of PN junction diodes 902 are connected in series to increase sensitivity. The hollow portion 1103 increases the thermal resistance between the diode 902 and the silicon substrate 1102 to form a heat insulating structure. The diode 902 is
Since it needs to be a layer independent of the substrate 1102, SOI
It is formed on the SOI layer using the substrate, and the buried oxide film under the SOI layer is a part of the structure supporting the hollow structure. Further, the infrared absorbing structure 1106 that is in thermal contact with the diode portion has a structure protruding above the support leg 1101 so that infrared rays incident from above in the drawing can be efficiently absorbed. In addition, in FIG. 10B, in order to make the lower structure easy to understand, the infrared absorption structure in the front portion of the drawing is omitted.

When infrared rays are incident on the pixel 1, they are absorbed by the infrared absorbing structure 1106, and the heat insulating structure described above allows the pixel 1 to be absorbed.
Changes, and the forward voltage characteristic of the diode 902 serving as a temperature sensor changes. By reading the change amount of the forward voltage characteristic of the diode 902 with a predetermined detection circuit, an output signal according to the incident infrared ray amount can be taken out. In the thermal infrared solid-state imaging device, a large number of pixels 1 are two-dimensionally arranged, and the pixels 1 are sequentially accessed. In such an element, uniformity of characteristics between pixels is important. The forward voltage of the diode and its temperature dependence have very little variation between solids, and it is particularly effective for the thermal infrared imaging element to use the diode as the temperature sensor for achieving uniform characteristics.

FIG. 11 shows a circuit configuration of a thermal infrared solid-state image pickup device. The pixels 1 are two-dimensionally arranged, and are connected by a drive line 3 for each row and connected by a signal line 5 for each column. The drive line 3 is sequentially selected by the vertical scanning circuit 4 and the switch 9, and the pixel 1 is energized from the power supply 6 via the selected drive line 3. Since the constant current source 2 is provided at the end of the signal line 5 connected to the cathode side of the pixel 1, the pixel 1 is driven by constant current. The voltage across the constant current source 2 is integrated and amplified by the integrating circuit 39, and is output to the output terminal 10 sequentially by the horizontal scanning circuit 8 and the switch 9.

The inside of the integrating circuit 39 is shown in FIG. MO
The S transistor 40 is an integrating transistor whose gate serves as an input terminal. The integrating capacitor 40 is connected to the transistor 40 and is periodically reset by the transistor 26. A bias voltage that determines the operating point of the transistor 40 is applied from the bias line 41. The MOS transistor 40 and the integration capacitor 25 constitute a so-called gate modulation integration circuit. The output of this integration circuit is sampled by the sample hold (S / H) circuit 27,
It is output via the buffer amplifier 28.

[0006]

However, the above-mentioned conventional thermal infrared solid state image pickup device has the following problems. First, in FIG. 11, the voltage across the constant current source 2 is input to the input of the integrating circuit 39. This voltage drops from the voltage across the power source 6 across the pixel 1 and the voltage across the drive line 3. Is the value obtained by subtracting. However, since the amount of voltage drop on the drive line 3 differs for each pixel column, the output of the integrating circuit 39 also has a different value for each pixel column. For this reason,
An offset distribution due to the resistance of the drive line 3 occurs in the captured image. Further, since the response of the thermal infrared solid-state imaging device to infrared light, that is, the change in the voltage across the pixel 1 is much smaller than the voltage drop component on the drive line 3, the amplifier is affected by the voltage drop distribution on the drive line 3. There is also a problem that the required amplification degree cannot be secured due to saturation or the like.

Further, since the output of the integrating circuit 39 is directly affected by the voltage fluctuation of the power source 6, the output tends to be unstable. That is, when the detection is performed using the integrating circuit configured by the MOS transistor and the integrating capacitor as shown in FIG. 12, the voltage across the constant current source 2 is changed by the voltage fluctuation of the power source 6 for driving the pixel in FIG. Changes, the output voltage of the integration circuit 39 changes.

Further, since the response of the pixel 1 includes the response due to the change in the element temperature in addition to the response of the infrared light, the phenomenon that the element output drifts with the change in the element temperature appears if the element temperature control is not precisely performed and is stable. There is also a problem that the acquired image cannot be acquired. That is, in the pixel 1 shown in FIG. 10, it is ideal that the diode 902 and the substrate 1102 are completely insulated so that the output voltage of the pixel 1 is not affected by the temperature change of the substrate 1102. However, since the thermal resistance of the heat insulation structure including the support legs 1101 and the hollow portion 1103 has a finite value, the output voltage of the pixel 1 is the substrate 1102.
It also changes with changes in temperature. For this reason, when the ambient temperature of the infrared imaging device changes and the temperature of the substrate 1102 changes during the detection operation, the output of the detection unit 902 also changes. This change in output due to changes in environmental temperature cannot be distinguished from the change in incident infrared light, so the accuracy of infrared measurement decreases and stable image acquisition is not possible.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a thermal infrared solid-state image pickup element which is less affected by a voltage drop due to the resistance of a drive line. Another object of the present invention is to provide a thermal infrared solid-state image pickup device that is capable of stable image acquisition with little output change due to power supply voltage change and element temperature change.

[0010]

In order to achieve the above object, at least one semiconductor device of the present invention is connected in series, and a pixel is constituted by a diode having a heat insulating structure and an infrared absorbing structure. A pixel area arranged two-dimensionally, a plurality of drive lines in which the anodes of the pixels are commonly connected in each row, and a cathode in the pixels are commonly connected in each column,
A plurality of signal lines provided with a first constant current conversion unit at the end of each column, a vertical scanning circuit that sequentially selects the drive lines and connects the selected drive lines to a pixel power source, and the signal lines sequentially. A thermal infrared solid-state image sensor including a horizontal drive circuit that outputs a voltage across the first constant current conversion unit to a selected signal line via an integrating circuit provided for each signal line. A second constant current conversion unit that is provided in the vicinity of the first constant current conversion unit for each signal line and flows substantially the same current as the first constant current conversion unit; A bias line having an input end of the second constant current converting means commonly connected in parallel to the drive line and having a resistance substantially the same as that of the drive line;
A bias voltage output circuit for applying a bias voltage to the bias line, wherein the integration circuit integrates a difference between the voltages across the first constant current conversion means and the second constant current conversion means for a certain period of time. It is characterized by outputting.

The first, second and third constant current means are
A constant current source or load resistance can be used. Since the bias line and the drive line have substantially the same resistance, and the currents of the first constant current conversion unit and the second constant current conversion unit connected for each column are substantially the same, the voltage appearing on the bias line and the drive line. The distribution is essentially the same. Then, the two are subtracted from each other by the differential integrator circuit connected for each column, so that the voltage distribution appearing on the drive line and the bias line is canceled by the output of the integrator circuit. Therefore, the offset distribution due to the resistance of the drive line can be reduced from the captured image, and the saturation of the amplifier due to the voltage drop distribution on the drive line can be prevented and the necessary amplification degree can be easily ensured.

The bias voltage output circuit includes a reference signal output circuit that is driven by the pixel power source and outputs a reference signal according to the temperature of the entire element, and a buffer amplifier connected to the output of the reference signal output circuit. It is preferable to have. Thus, the reference signal for calibrating the signal output change due to the power supply voltage change and the temperature change of the entire element is input to the bias line. Therefore, it is possible to subtract the signal drift caused by the power supply voltage fluctuation and the element temperature fluctuation by the differential integration circuit and prevent the signal from being output to the outside.

Further, it is preferable that the bias voltage output circuit includes a low pass filter on at least one of an input side and an output side of the buffer amplifier. By inserting a low-pass filter between the output of the reference signal output circuit and the input terminal of the differential integrator circuit, and allowing only voltage fluctuations due to environmental temperature and drift of the power supply circuit to pass, the reference signal output circuit Noise can be suppressed, and noise increase due to differential can be suppressed.

Further, the reference signal output circuit has a temperature sensitive element whose electric characteristics change according to temperature, and a third constant current-generating means connected to the cathode side of the temperature sensitive element, It is preferable to output the voltage across the third constant current conversion means as a reference signal. As a result, the reference signal output circuit can output the reference signal for calibrating the temperature drift of the element that does not depend on infrared absorption.

Furthermore, the reference signal output circuit is N
A plurality of (N is a natural number) the temperature sensitive elements, and one of the third constant current conversion means commonly connected to the cathode side of the N number of the temperature sensitive elements, the third constant current The current conversion unit may flow N times as much current as the first constant current conversion unit. When the element area is wide to some extent, a temperature distribution may exist in the element surface. Further, there may be variations in the characteristics of the temperature sensitive element. By providing a plurality of temperature sensitive elements, it is possible to average the influence of the temperature distribution in the element plane and the characteristic variation of the temperature sensitive elements.

Further, the number of reference signal output circuits is N (N
Is a natural number), the N third constant current conversion means connected to each cathode side of the temperature detection element, and the voltage across the N third constant current conversion means. May be averaged and output as a reference signal.

The temperature sensitive element may be, for example, a reference pixel having substantially the same structure as the pixel except that it does not have at least one of a heat insulating structure and an infrared absorbing structure.
This makes it possible to detect only the temperature change of the element due to the environment or the like, regardless of the incident infrared rays. Further, instead of the reference pixel, a thermistor may be used as the temperature sensitive element.

The integrator circuit converts a difference in voltage between both ends of the first constant current conversion unit and the second constant current conversion unit into a current by a differential voltage-current conversion amplifier, and converts the current into the differential voltage. It is preferable to integrate the capacitance connected to the voltage-current conversion amplifier and periodically reset to a constant voltage. This simplifies the configuration of the integrating circuit as compared with the case where an operational amplifier is used.

[0019]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the same or corresponding members as the conventional ones are denoted by the same reference numerals as those in FIGS. Embodiment 1. 1 is a circuit diagram showing a circuit configuration of a thermal infrared solid-state imaging device according to a first embodiment of the present invention.
Similar to the conventional thermal infrared solid-state imaging device, a plurality of pixels are connected in series and each pixel 1 is composed of a diode having an infrared absorption structure and a heat insulation structure.
Form a two-dimensionally arranged pixel area. The drive line 3 is commonly connected to each row of the pixels 1.
The signal line 5 is commonly connected to each column of the pixels 1, and the constant current source 2 is connected to the terminal end of each signal line 5. Further, the drive line 3 is formed by the vertical scanning circuit 4 and the switch 9.
Are sequentially selected, the voltage across the constant current source 2 is integrated and amplified by the integrating circuit 7, and the voltage is sequentially output to the output terminal 10 by the horizontal scanning circuit 8 and the switch 9.

In the thermal infrared solid-state image pickup device according to this embodiment, (1) the differential integrating circuit 7 is used as the integrating circuit,
(2) Bias line 17 whose resistance is substantially the same as that of drive line 3
Is provided outside the pixel area in parallel with the drive line 3, and a constant current source 18 for flowing substantially the same current as the constant current source 2 is provided for each pixel column of the bias line, (3) The difference between the constant-current sources 2 and 18 is input to the differential integration circuit, which is a big difference from the conventional thermal infrared solid-state imaging device.

The constant current source 2 and the constant current source 18 supply the same current, and the bias line 17 and the drive line 3 have substantially the same resistance. Therefore, the voltage drop on the bias line 17 is the voltage on the drive line 3. It will be the same as the descent. Therefore, the voltage difference distribution due to the resistance of the drive line 3 is subtracted by the differential integrator circuit by integrating and outputting the difference between the voltages across the constant current source 2 and the constant current source 18 in the differential integrator circuit 7 for a certain period of time. , It is possible not to output to the outside.

Further, in the thermal infrared solid-state image pickup device according to the present embodiment, (4) a reference signal output circuit 11 is provided which is driven by the power source 6 common to the driving of the pixels and outputs an output according to the temperature change of the device. Also, in the point that it has a circuit configuration (“bias voltage output circuit”) for inputting the output of the reference signal output circuit 11 to the bias line 17 via the buffer 15, it is also significantly different from the conventional thermal infrared solid-state imaging device. ing.

A bias line 17 receives a voltage output of the power source 6 for driving the pixel 1 and a signal output change in response to a temperature change of the entire element. The signal is supplied to the differential integrator circuit 17 as a voltage across the constant current source 18. Is entered. Therefore, the signal drift due to the power supply voltage fluctuation and the element temperature fluctuation can be subtracted by the differential integration circuit 7 so as not to be output to the outside. Hereinafter, a specific configuration of the thermal infrared solid-state imaging device according to this embodiment will be described in detail.

[Bias Voltage Output Circuit] First, the bias voltage output circuit will be described. In the present embodiment, the bias voltage output circuit is the reference signal output circuit 11,
It comprises a buffer amplifier 15 and low-pass filters 14 and 16.

The reference signal output circuit 11 has a configuration in which a reference pixel 12 provided outside the pixel area and a constant current source 13 for supplying a constant current to the reference pixel 12 are connected in series.
The voltage difference between the two terminals is output. The reference pixel 12 has a structure excluding either or both of the infrared absorbing structure and the heat insulating structure so that only the temperature change of the element due to the environment or the like can be detected regardless of the incident infrared ray.
To form a pixel that does not have a heat insulating structure, for example, as shown in FIG.
In the detector structure shown in FIGS. 0 (a) and 0 (b), the substrate 1
The hollow portion 1103 may not be formed in 102, or the length of the support leg 1101 may be made sufficiently shorter than that of the pixel 1.
Further, to form a pixel having no infrared absorption structure,
For example, the formation of the infrared absorption structure 1106 may be omitted in the pixel 1 of FIGS. The current of the current source 13 is substantially the same as that of the constant current source 2 for the pixel 1. Therefore, from the reference signal output circuit 11,
It is possible to output a reference signal for calibrating the temperature drift of the element that does not depend on infrared absorption.

Then, the output of the reference signal output circuit 11 is noise-removed by the low-pass filter 14, the current driving capability is increased by the buffer 15, the noise is again removed by the low-pass filter 16, and the result is given to the bias line 17. To be

The low-pass filters 14 and 16 are used for the reference pixel 1
This is for cutting noise of 2 and the constant current source 13 and extracting only the temperature drift component. That is, the low pass filters 14 and 16 play a role of preventing an increase in noise due to the provision of the reference signal output circuit 11. Generally, in an infrared detector aiming at a high S / N, the noise of the power supply system is sufficiently reduced by the power supply circuit, and the noise from the detection unit becomes the main noise component of the device. Therefore, when the outputs of the pixel 1 and the reference pixel 12 having the same configuration are input to the differential integration circuit 7, the noises of both are uncorrelated, and the noise becomes √2 times that of the conventional one. On the other hand, changes in the output of the detector due to changes in the ambient temperature and changes in the power supply voltage due to changes in the power supply circuit characteristics due to changes in the ambient temperature are generally gradual, on the order of seconds or more. Therefore, the band of the bias voltage output circuit for monitoring it may be sufficiently narrower than the band required for the signal line for detecting infrared rays. Therefore, if low-pass filters 14 and 16 are inserted between the output of the reference signal output circuit 11 and the input terminal of the differential integrator circuit 7, only voltage fluctuations due to environmental temperature, drift of the power supply circuit, etc. can be passed. ,
Noise from the reference signal output circuit 11 can be suppressed, and noise increase due to differential can be suppressed.

Since the typical value of the noise bandwidth for a pixel of such an infrared solid-state image pickup device is several KHz, the cutoff frequency may be set to 1/100 or less thereof. From the viewpoint of power supply voltage fluctuations and temperature fluctuations, the fluctuation cycle is short and on the order of seconds, so a band of several Hz is sufficient. Further, although the low-pass filter is inserted before and after the buffer 15 in the present embodiment, only one of them may be inserted.

[Reference Signal Output Circuit] In the present embodiment,
Although the reference signal output circuit 11 has a configuration in which the reference pixel 12 and the current source 13 are connected in series, configuration examples of other reference signal output circuits are shown in FIGS. 2 to 5. In FIG. 2, a plurality of reference pixels 12 are arranged in parallel, and a constant current source 19 whose current is equal to the number of the reference pixels 12 is connected in series. That is, when the N reference pixels 12 are arranged in parallel, the N times the current of the constant current source 2 is made to flow by the constant current source 19. The temperature of the thermal infrared solid-state imaging device may have a distribution in a device region having a finite size, so if a plurality of reference pixels 12 are appropriately distributed and installed in the device region, the temperature is reflected in the average temperature. Can output the output.

The same purpose can be realized by the reference signal output circuit 11 having the configuration of FIG. In FIG. 3, the reference pixel 1
2 and constant current source 13 are connected in series as a set,
The combined configuration itself is appropriately installed in the element region, and the respective outputs are averaged by the averaging circuit 20. The averaging circuit 20 can be realized by a combination of an adding circuit and a dividing circuit, which are well-known circuits using operational amplifiers.

The reference signal output circuit 11 of FIG. 4 is an example in which, instead of the reference pixel 12, a thermistor 21 whose resistance changes with temperature is driven by a constant current source 22 at a constant current. In this configuration, it is necessary to set the resistance of the thermistor 21 or the current of the constant current source 22 so that the output voltage of the buffer amplifier 15 becomes the same as in the case of FIG. Also,
By including the level shift operation in the buffer amplifier 15, the output voltage of the buffer circuit 15 may be the same as that in the case of FIG.

Further, the reference signal output circuit 11 of FIG.
This is an example in which the thermistor 21 is driven with a constant current by using a load resistor 23 instead of the constant current source 22 in the configuration of FIG. Also in this example, it is necessary to set the resistances of the thermistor 21 and the load resistor 23 so that the output voltage of the buffer circuit 15 is the same as in the case of FIG. 1, or to include the level shift operation in the buffer amplifier 15.

[Low-pass filter] Low-pass filter 1
Examples of the circuit configurations of 4 and 16 are shown in FIGS. 6 (a) and 6 (b).
The configuration shown below can be used for both the low-pass filters 14 and 16. The low-pass filter of FIG. 6A uses passive elements, 33 is a resistance or reactance, and 34 is a capacitance. A filter (= low-pass filter 1 to be inserted on the rear side of the buffer amplifier 15
As 6), a reactance with no DC voltage drop is preferable. On the other hand, as the filter (= low-pass filter 14) provided on the front side of the buffer amplifier 15, it is desirable to use a resistor that easily obtains the characteristics as a filter.
Further, the resistor 33 may be substituted with the internal resistance of the power supply circuit 6 or the internal resistance of the buffer amplifier 15.

The low pass filter shown in FIG. 6 (b) is an integrating circuit using an operational amplifier 35 which is an active element. Since this circuit configuration is also a general low pass filter, detailed description thereof will be omitted. .

The low-pass filters 14 and 16 in the present invention are not limited to those illustrated in FIGS. 6A and 6B, and other filters (for example, switched capacitor circuits) may be used. it can. Further, the low-pass filters 14 and 16 may be provided only on either the front side or the rear side of the buffer amplifier 15, but in that case, the filter on the front side of the buffer amplifier 15 (= filter 1)
It is preferable to leave 4). This is because a large current flows on the rear side of the buffer amplifier 15, and the voltage drop in the filter causes fluctuations in the bias voltage.

[Differential Integrator Circuit] Next, a specific configuration example of the differential integrator circuit 7 will be described. A configuration example of the differential integration circuit 7 is shown in FIGS. 7 and 8. In FIG. 7, reference numeral 24 is a differential voltage-current conversion amplifier which converts the difference between input signals into a current and integrates it into an integration capacitor 25 which is periodically reset by a transistor 26. FIG. 8 shows an example using the operational amplifiers 31 and 32. The circuit unit 29 is a differential amplifier circuit, and the circuit unit 30 is an integrating circuit. In either case, the output after integration is sampled by the S / H circuit 27 and is buffered by the buffer 28.
Is output via.

FIG. 7 is a patent application (Japanese Patent Application No. 2000-386974) previously filed by the inventor of the present application, which has the effect of simplifying the configuration as compared with the case of using an operational amplifier described later.
Hereinafter, the differential integration circuit 7 shown in FIG. 7 will be described in detail.

The differential integration circuit shown in FIG. 7 includes a differential voltage-current conversion amplifier 24 in which the voltage across the constant current source 2 and the voltage across the constant current source 18 are connected to the input side, and a differential voltage-current conversion amplifier 24. Of the integrating capacitor 25 and a reset transistor 26 connected so as to periodically reset the integrating capacitor 25 to the voltage V _ref . The differential voltage-current conversion amplifier 24 is connected without negative feedback, and the product (= time constant) of its output impedance and the capacitance C _i of the integration capacitor 25 is five times or more the integration time T _i. Is set.

A sample and hold circuit 27 including a sample and hold transistor and a sample and hold capacitor is connected to the input terminal of the integration capacitor 25. The output after integration is sampled by the sample hold circuit 27,
It is output via the buffer 28.

In the differential integration circuit 7 of FIG. 7, since the integration circuit is configured using the differential voltage-current conversion amplifier 24 in the state where negative feedback is not performed, the integration using the operational amplifier as shown in FIG. 8 is performed. The circuit configuration can be greatly simplified as compared with the circuit. It will be described that the differential voltage-current conversion amplifier 24 shown in FIG. 7 performs an integration operation. The input / output response characteristics Av of a voltage amplifier without general feedback are the transconductance of the voltage amplifier, gm, and the output impedance.
R _out , where the integration time is T _i , A _v = gm R _out {1−exp (−T _i / T _a )} (1) T _a = R _out C _i (2) Here, T _a is a time constant. If T _a >> T _i (3), A _v = gm R _out T _i / T _a = gm T _i / C _i (4), which is the response characteristic of the integrator.

The equation (3) shows that the time constant represented by the product of the output impedance R _out and the integration capacitance is sufficiently longer than the integration time. For example, the time constant T _{a is set} to the integration time T _i
If it is at least 5 times or more, the deviation from the response characteristic of the integrator can be kept within 10%. In order to increase the time constant T _a , _a voltage amplifier with a very large output impedance R _out may be used. Generally, the voltage gain gm
· Single amplifier without using the large negative feedback of R _out is the output impedance R _out is increased. For example, the differential voltage-current conversion amplifier 24 can be constructed by taking out only the differential amplifier 31 of the operational amplifier shown in FIG. 8 and connecting it as shown in FIG. 7 without negative feedback or input resistance. it can. Therefore, according to the differential integration circuit of FIG.
With a much simpler circuit configuration than the integration circuit shown in
An integrating circuit can be constructed.

Embodiment 2. FIG. 9 shows another embodiment of the thermal infrared solid-state imaging device according to the present invention. Instead of the constant current sources 2, 13 and 18, load resistors 36, 37 and 3
8 is the same as that of the first embodiment except that 8 is used. If the load resistors 36, 37 and 38 have substantially the same resistance, the same effect as in the first embodiment can be obtained.

[0043]

Since the present invention is constructed as described above, it has the following effects. In the semiconductor device of the present invention, a second constant current source commonly connected by a bias line is provided in the vicinity of the first constant current source connected to the pixel, and the first constant current source and the second constant current source are provided. Since the difference between the voltages across the source is integrated and output for a certain period of time, the voltage distribution appearing on the drive line can be canceled by the output of the integrating circuit. As a result, the offset distribution due to the resistance of the drive line can be reduced from the captured image, and the saturation of the amplifier due to the voltage drop distribution on the drive line can be prevented to easily secure the required amplification degree.

Further, the bias voltage output circuit is composed of a reference signal output circuit which is driven by the pixel power source and outputs a reference signal according to the temperature of the entire element, and a buffer amplifier which is connected to the output of the reference signal output circuit. By doing
It is possible to subtract the signal drift due to the power supply voltage fluctuation and the element temperature fluctuation by the differential integration circuit so as not to be output to the outside.

Further, since the bias voltage output circuit is provided with a low-pass filter on either the input side or the output side of the buffer amplifier, the noise from the reference signal output circuit is suppressed and the noise increase due to the differential is suppressed. can do.

Further, the reference signal output circuit is composed of a temperature sensitive element whose electric characteristics change according to temperature, and a third constant current source connected to the cathode side of the temperature sensitive element. By outputting the difference between the voltages across the current source as the reference signal, it is possible to output the reference signal for calibrating the temperature drift of the element that is not due to infrared absorption.

Furthermore, by providing a plurality of temperature sensitive elements as the reference signal output circuit, it is possible to average the influence of the temperature distribution in the element plane and the characteristic variation of the temperature sensitive elements.

In addition, the temperature sensitive element is a reference pixel having substantially the same structure as the pixel except that it does not have a heat insulating structure, so that only the temperature change of the element due to the environment or the like does not occur regardless of incident infrared rays. Can be detected. Also,
If a thermistor is used as the temperature sensitive element instead of the reference pixel, the reference signal output circuit can be formed with a simple configuration.

Further, by integrating the current converted by the differential voltage / current conversion amplifier into the capacitance connected to the differential voltage / current conversion amplifier and periodically reset to a constant voltage, an integrating circuit can be formed with a simple structure. Can be configured.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a thermal infrared solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing another example of the reference signal output circuit.

FIG. 3 is a circuit diagram showing still another example of the reference signal output circuit.

FIG. 4 is a circuit diagram showing still another example of the reference signal output circuit.

FIG. 5 is a circuit diagram showing still another example of the reference signal output circuit.

FIG. 6A and FIG. 6B are circuit diagrams showing an example of a low-pass filter.

FIG. 7 is a circuit diagram showing an example of a differential integration circuit.

FIG. 8 is a circuit diagram showing another example of the differential integration circuit.

FIG. 9 is a circuit diagram showing a thermal infrared solid-state imaging device according to a second embodiment of the present invention.

10A and 10B are a cross-sectional view and a perspective view showing a pixel structure of a conventional thermal infrared solid-state imaging device.

FIG. 11 is a circuit diagram showing a conventional thermal infrared solid-state imaging device.

FIG. 12 is a circuit diagram showing an integrating circuit of a conventional thermal infrared solid-state imaging device.

[Explanation of symbols]

1 pixel, 2, 13, 18 constant current source, 3 drive line, 4
Vertical scanning circuit, 5 signal lines, 6 power supply, 7 differential integration circuit, 8 horizontal scanning circuit, 9 switch, 10 output terminal, 11 reference signal output circuit, 12 reference pixel, 14,
16 low pass filter, 15 buffer amplifier, 17
Bias line.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01J 5/48 G01J 5/48 E H01L 27/14 H04N 5/33 27/146 H01L 27/14 K H04N 5 / 33 AF term (reference) 2G065 AA04 AA08 AB02 BA02 BA06 BA12 BA20 BA34 BC05 BC08 BC15 CA21 DA18 2G066 BA09 BA13 BB11 BC02 BC11 4M118 AA10 AB01 BA14 BA30 CA03 CA23 DD09 DD10 FA06 GA10 GB09 5C024 AX06 CX03 HX29 H29H

Claims (9)

[Claims] 1. A pixel area in which at least one or more of the pixels are connected in series and each of which has a heat insulating structure and an infrared absorbing structure, and the pixels are arranged two-dimensionally. A plurality of drive lines commonly connected to each other and a cathode of the pixel are commonly connected to each column,
A plurality of signal lines having constant current conversion means, a vertical scanning circuit that sequentially selects the drive lines and connects the selected drive lines to a pixel power supply, and the signal lines that are sequentially selected and selected Regarding the above, the thermal infrared solid-state image sensor including: a horizontal drive circuit that outputs the voltage across the first constant current generating means through an integrating circuit provided for each signal line; And a second constant current converting unit that is provided near the first constant current converting unit and flows substantially the same current as the first constant current converting unit. An input terminal of the means is commonly connected in parallel to the drive line, and has a bias line having substantially the same resistance as the drive line, and a bias voltage output circuit for applying a bias voltage to the bias line, wherein the integration circuit is , The first constant current conversion means and the second constant current conversion means Thermal-type infrared solid-state imaging device and outputs the difference between the voltage across a fixed time integrated to. 2. A reference signal output circuit in which the bias voltage output circuit is driven by the pixel power source to output a reference signal according to the temperature of the entire element, and a buffer amplifier connected to the output of the reference signal output circuit. The thermal infrared solid-state imaging device according to claim 1, further comprising: 3. The thermal infrared solid-state image pickup device according to claim 2, wherein the bias voltage output circuit includes a low-pass filter on at least one of an input side and an output side of the buffer amplifier. 4. The reference signal output circuit includes a temperature sensitive element whose electrical characteristics change according to temperature, and a third constant current-generating unit connected to the cathode side of the temperature sensitive element, The thermal infrared solid-state imaging device according to claim 2 or 3, wherein the voltage across the third constant current means is output as a reference signal. 5. The reference signal output circuit includes N (N is a natural number) the temperature sensitive elements, and one third constant current commonly connected to the cathode side of the N temperature sensitive elements. 5. The thermal infrared solid-state image pickup device according to claim 4, further comprising: a current conversion unit, wherein the third constant current conversion unit supplies N times as much current as the first constant current conversion unit. 6. The reference signal output circuit comprises N (N is a natural number) the temperature sensitive elements, and N third constant current converting means connected to respective cathode sides of the temperature sensitive elements. And the above N
5. The thermal infrared solid-state imaging device according to claim 4, further comprising an averaging circuit for averaging the voltages across the third constant current generating means and outputting the averaged voltage as a reference signal. 7. The reference pixel according to claim 4, wherein the temperature sensitive element is a reference pixel having substantially the same structure as the pixel except that the temperature sensitive element does not have at least one of a heat insulating structure and an infrared absorbing structure. The thermal infrared solid-state image sensor according to item 1. 8. The thermal infrared solid-state imaging device according to claim 4, wherein the temperature sensitive device is a thermistor. 9. The integrator circuit converts a difference in voltage between both ends of the first constant current conversion unit and the second constant current conversion unit into a current by a differential voltage-current conversion amplifier, and the current is converted into the current. 9. The thermal infrared solid-state imaging device according to claim 1, wherein the thermal infrared solid-state imaging device is connected to a differential voltage-current conversion amplifier and is integrated into a capacitance that is periodically reset to a constant voltage.