JP4367289B2 - Infrared imaging device - Google Patents

Description

  The present invention relates to an infrared imaging apparatus that captures a desired image using a thermal infrared detection element, and more particularly, to an infrared imaging apparatus that can reduce a switching noise generated at the time of scanning switching and obtain a clear image.

  A thermal infrared sensor is known as an example of an infrared sensor used in an infrared imaging device or the like. The thermal infrared sensor is a sensor that utilizes the fact that the temperature of the element rises due to the thermal effect of infrared rays, which changes the electrical properties of the element, and it is not necessary to cool the element to a cryogenic temperature and can be used at room temperature Because it can, it is easy to use and widely used. A thermal infrared sensor usually has a detection element whose temperature is increased by infrared rays, a reference element for reference, an offset adjustment circuit, etc., and a configuration in which an amplifier is further arranged in the subsequent stage to amplify the detection output. There are many.

Such a thermal infrared sensor is easily affected by ambient temperature and the like, and offset and sensitivity change when an environmental change such as a temperature change occurs during measurement. Therefore, it is desirable to correct offset and sensitivity unevenness as needed.
Therefore, in a conventional infrared imaging apparatus using such a thermal infrared sensor, for example, by measuring the output of the reference element every cycle, even if an environmental change such as a temperature change occurs during operation, the amplifier The offset is corrected immediately (for example, see Patent Document 1).
Japanese Patent No. 3339291

  However, in such an infrared imaging device, when a detection element having a high output impedance such as a thermopile (thermocouple) is used, switching noise may be superimposed on the output signal during scanning. In such a case, the output signal of the detection element cannot be accurately extracted, and it is difficult to accurately measure the output signal of the reference element having the same electrical characteristics as the detection element. As a result, there is a problem that an error occurs in the offset correction.

  The present invention has been made in view of such a problem, and an object of the present invention is to reduce switching noise generated at the time of scanning and to obtain an amplified output signal of a high-accuracy reference element. It is an object of the present invention to provide an infrared imaging device capable of accurately correcting an offset of an amplifier even when a temperature change occurs, and thereby capturing a desired image with high accuracy.

In order to solve the above-described problems, an infrared imaging device according to the present invention is two-dimensionally arranged in a first direction and a second direction, and has a detection element having predetermined electrical characteristics and sensitivity, and a proximity to the detection element. An infrared imaging element that is arranged in a line in the first direction and has the same electrical characteristics as the detection element, but includes a first reference element that has a different sensitivity and does not change a signal value even when infrared rays are incident thereon;
A second reference element that is arranged in a line in the first direction in the vicinity of the infrared imaging element, has the same electrical characteristics as the detection element, but does not change the signal value even when infrared rays are incident with different sensitivity. When,
First scanning means for sequentially scanning the infrared imaging element in the first direction and the second direction, and scanning and reading the detection element and the first reference element;
Second scanning means for scanning and reading the second reference element in synchronization with scanning reading in the first direction of the scanning means;
A differential amplifier circuit for detecting a difference between an output of the scanning readout in the first direction of the first scanning unit and an output of the scanning readout by the second scanning unit, amplifying the difference, and outputting the difference;
Offset setting means for setting an offset of the differential amplifier circuit based on a difference between the output of the first reference element and the output of the second reference element detected in the differential amplifier circuit. An infrared imaging device.

  In the infrared imaging device having such a configuration, a reference element having the same electrical characteristics as that of the detection element disposed in each pixel of the infrared imaging element is provided inside the infrared imaging element (first reference element). And a first scanning means disposed outside (second reference element), scanning and selecting each element (detection element and first reference element) of the infrared imaging element, and sequentially outputting an output signal thereof; The second scanning means for scanning and selecting each reference element and sequentially outputting the output signals is operated in synchronism. In the differential amplifier circuit, a difference between the output signals read out synchronously by the first and second scanning means is detected, and an imaging signal of each pixel is obtained based on the difference, and the differential amplifier circuit The offset correction value is detected. Therefore, even if switching noise is superimposed on each output signal, the waveform of the noise is the same, and the noise is canceled by detecting the difference in the differential amplifier. Therefore, an appropriate offset correction value can be detected, and the offset can be canceled appropriately. In addition, a highly accurate imaging signal can be obtained by appropriately canceling the offset.

  Preferably, the first scanning unit scans the infrared imaging element in the second direction, and scans and reads the detection element or the first reference element for each column in the first direction. And the detection element or the first reference element for each column in the first direction scanned and read by the second direction scanning unit is scanned in the first direction, and the detection is performed for each column in the first direction. A first direction scanning unit that scans and reads an element or the first reference element, and the second scanning unit scans and reads the second reference element in synchronization with the scan reading of the first direction scanning unit. To do.

  Preferably, the first direction scanning unit and the second scanning unit do not output a signal of an element that performs scanning reading in the first direction at the same time when scanning reading in the second direction scanning unit is switched. .

  In addition, another infrared imaging device according to the present invention is two-dimensionally arranged in a first direction and a second direction, and includes an infrared imaging device having detection elements having predetermined electrical characteristics and sensitivity, and proximity to the infrared imaging device. A reference element that is arranged in a line in the first direction and has the same electrical characteristics as the detection element, but has a different sensitivity and the signal value does not change even when infrared rays are incident thereon, and the infrared imaging element. First scanning means that sequentially scans in the first direction and the second direction to scan and read the detection element; and scanning and reading of the reference element in synchronization with the scanning reading in the first direction of the scanning means A difference between the second scanning means and the output of the detection element read by the first scanning means and the output of the reference element read by the second scanning means is detected, and based on the detected difference. And an output circuit which outputs as an imaging signal Ku signal.

  According to the present invention, the offset noise of the amplifier can be accurately corrected even if a temperature change occurs during operation of the infrared imaging device by reducing switching noise generated during scanning and obtaining a highly accurate amplified output signal of the reference element. Thus, it is possible to provide an infrared imaging device capable of capturing a desired image with high accuracy.

An embodiment of the present invention will be described with reference to FIGS.
First, an infrared imaging apparatus having a normal configuration related to the infrared imaging apparatus of the present invention will be described with reference to FIGS.
FIG. 1 is a circuit diagram showing a configuration of the infrared imaging device 100.
As shown in FIG. 1, the infrared imaging device 100 includes an infrared imaging device unit 1, a counter 2, a vertical direction decoder 3, a horizontal direction decoder 4, a horizontal direction scanner 5, a processing unit 6, and a differential amplifier 9.

As shown in the figure, the infrared imaging element unit 1 is configured by two-dimensionally arranging n × n detection elements corresponding to the pixels 11 to nn. In addition, one pixel sl provided with a reference element for outputting a reference output signal is disposed at a position close to the detection element of each pixel arranged in two dimensions.
The specific structures of the detection element and the reference element will be described in detail later with reference to FIGS. 5 and 6. However, assuming that a detection element such as a thermocouple (thermocouple) as will be described later is assumed, its equivalent is assumed. The circuit can be represented as a series circuit of a resistor and a voltage source as shown in FIG. In this case, the equivalent circuit of the reference element can be expressed as a resistor as shown in FIG.

In the infrared imaging element unit 1, N-type MOSFET switches M11 to Mnn serving as a vertical scanner are connected to the plus terminals (114) of the respective detection elements (detection elements 211 (see FIG. 5)). Similarly, N-type MOSFET switches M1 to Mn are connected to the horizontal scanner 5 for each detection element array. The reference voltage Vref1 is input to the minus terminals (115) of all the detection elements (211).
In the reference element (reference element 212 (see FIG. 6)) arranged in the reference pixel sl, an N-type MOSFET switch Msly serving as a vertical scanner is connected to the plus terminal (114) of the reference element (212). The N-type MOSFET switch Mslx of the horizontal scanner 5 is connected to the end. The reference voltage Vref1 is also input to the minus terminal (115) of the reference element (212).

The operation of the infrared imaging apparatus 100 having such a configuration will be described with reference to FIG.
FIG. 2 is a time chart showing waveforms of output signals of the vertical decoder 3, the horizontal decoder 4, and the horizontal scanner 5 shown in FIG.
First, the counter 2 generates addresses for the number of pixels of the infrared imaging element unit 1 (detection element n × n + one reference element) based on the input reference clock CLK, and the vertical decoder 3 and the horizontal direction It is output to the decoder 4.

In the vertical direction decoder 3 and the horizontal direction decoder 4, the address generated by the counter 2 is decoded, and the vertical direction selection signals Y1 to Yn and Ysl for each row and the horizontal direction selection signals X1 to Xn and Xsl for each column. Is generated. The generated vertical direction selection signals Y1 to Yn and Ysl are respectively applied to the gate terminals of the N-type MOSFET switches M11 to Mnn and Msly of the vertical scanner for the infrared imaging element unit 1 and the reference pixel sl. The generated horizontal direction selection signals X1 to Xn and Xsl are applied to the gate terminals of the N-type MOSFET switches M1 to Mn and Mslx of the horizontal scanner 5, respectively.
Here, as shown in the time chart of FIG. 2, when the vertical direction selection signals Y1 to Yn and Ysl and the horizontal direction selection signals X1 to Xn and Xsl are respectively set to the H (high) level, each connected signal is connected. The N-type MOSFET switch is turned on.

  Specifically, when the vertical direction selection signal Y1 becomes H level, the N-type MOSFET switches M11 to M1n are turned on, and the output signals V1 to Vn of the pixels 11 to 1n are sent to the horizontal scanner 5. . At the same time, the horizontal direction selection signal X1 becomes H level, the N-type MOSFET switch M1 is turned on, and the output signal of the pixel 11 is output as the output signal Vdt of the horizontal scanner 5. Thereafter, the horizontal direction selection signals X2 to Xn sequentially become H level, and as the output signal Vdt, the output signals of the pixels 12 to 1n are sequentially output following the output signal of the pixel 11.

Next, the vertical direction selection signal Y2 becomes H level, and in accordance with this, the horizontal direction selection signals X1 to Xn sequentially become H level, and the output signals of the pixels 21 to 2n are sequentially outputted as the output signal Vdt. Selected.
By repeating such an operation, as the output signal Vdt, the output signals of the pixels are output in the order of the pixels 11 to 1n, the pixels 21 to 2n, and the pixels n1 to nn.
Finally, the vertical direction selection signal Ysl and the horizontal direction selection signal Xsl simultaneously become H level, and the output signal of the reference pixel sl is selected as the output signal Vdt.
Then, the scanning from the pixel 11 is repeated again.

The difference between the signal Vdt output from the horizontal scanner 5 and Vref1, which is a constant reference voltage, is obtained in the differential amplifier 9. The obtained difference value is amplified after the offset is corrected by the offset correction value input from the processing unit 8, and is output to the AD converter (ADC) 8b of the processing unit 8 as an output signal of the imaging result.
The processing unit 8 calculates an offset correction value necessary for infrared imaging and removing the offset of the differential amplifier 9 from the signal input from the differential amplifier 9 to the ADC 8b. The calculated offset correction value is output from the DA converter (DAC) 8a to the differential amplifier 9 (Vref2) and is used for removing the offset of the differential amplifier 9.

In the infrared imaging device having such a configuration, operations at the time of rising and falling of the vertical direction selection signals Y1 to Yn and Ysl and the horizontal direction selection signals X1 to Xn and Xsl will be described with reference to FIG.
FIG. 3 is a diagram for explaining the operation when the horizontal direction selection signal X2 falls and when the horizontal direction selection signal X3 rises.
As shown in FIG. 3, it is assumed that the vertical direction selection signal Y2 is at the H level, the pixel in the second row in the vertical direction is selected, and the horizontal direction selection signal X2 is rising. In this situation, as shown in FIG. 3, when the horizontal direction selection signal X2 falls and at the same time the horizontal direction selection signal X3 rises, the N-type MOSFET switch M2 in the second row in the horizontal direction is turned off, and at the same time in the third row. The N-type MOSFET switch M3 is turned on.

At this time, the step change of the rising edge of the horizontal direction selection signal X3 is output as rising direction switching noise via the gate-drain capacitance Cgd3 and the gate-source capacitance Cgs3 of the N-type MOSFET switch M3 in the third column. Superposed on Vdt.
In addition, the step change of the falling edge of the horizontal direction selection signal X2 is superimposed on the Vdt output as falling edge switching noise via the gate-source capacitance Cgs2 of the N-type MOSFET switch M2 in the second column. The
The reason why the switching noise via the gate-drain capacitance Cgd2 is not superimposed is that the drain-source is open (non-conductive) because the N-type MOSFET switch M2 in the second column is off.

As a result, the switching noise superimposed on the output signal Vdt is, as shown in FIG. 3, the rising direction switching noise via the capacitors Cgd3 and Cgs3, and the falling direction switching noise via the capacitor Cgs2. Are superimposed on each other.
These two MOSFETs are both of the same conductivity type (N type), and the transistor sizes of the N type MOSFET switches M2 and M3 are equivalent. Furthermore, since the gate-drain capacitance and the gate-source capacitance of the MOSFET are generally equal, the relationship between the gate-drain capacitance and the gate-source capacitance of the two MOSFETs is expressed by the following equation (1). The rising noise for Cgd3 is superimposed on the output signal Vdt.

Number 1
Cgd3 + Cgs3-Cgs2 = Cgd3 (1)
However, Cgs3 = Cgs2,
"+" For rising, "-" for falling,
And

As a result, as shown in FIG. 3, the differential amplifier 9 receives the signal Vdt on which the rising noise is superimposed and the reference signal Vref1, which is a constant level, and the output signal Vout of the differential amplifier 9 is , The signal Vdt is a signal on which rising switching noise is superimposed.
The processing unit 8 calculates an offset correction value based on the signal Vout input from the differential amplifier 9 to the processing unit 8 when the reference element sl is scanned and the output signal Vsl is input to the differential amplifier 9. is doing. Therefore, when switching noise is superimposed on the signal Vdt input to the differential amplifier based on the output signal Vsl from the reference element sl, the switching noise is also superimposed on the signal Vout input to the processing unit 8. Thus, an accurate amplified output signal of the reference element (reference pixel sl) cannot be obtained, and an accurate offset correction value cannot be calculated.
Such a disadvantage may occur in the infrared imaging apparatus 100 having a normal configuration as shown in FIG.

Next, an infrared imaging apparatus according to the present invention that solves such a problem will be described with reference to FIGS.
FIG. 4 is a circuit diagram showing the configuration of the infrared imaging apparatus according to the present invention.
As shown in FIG. 4, the infrared imaging device 101 includes an infrared imaging element unit 1, a counter 2, a vertical direction decoder 3, a horizontal direction decoder 4, a horizontal direction scanner 5, a second reference pixel array 6, and a second reference element. An array scanner 7, a processing unit 8, and a differential amplifier 9 are provided.

Here, first, the structure of the detection element and the reference element used in the infrared imaging device 101 and the second reference pixel array 6 will be described.
5A and 5B are diagrams showing the structure of the detection element 211 used in the infrared imaging apparatus 101, FIG. 5A is a plan view of one detection element 211, and FIG. 5B is a cross section taken along the line AA in FIG. FIG.

  In the detection element 211, the substrate 116 is a substrate having a (100) plane as a surface, and a SiN thin film layer 118 is formed on the surface. On the thin film layer 118, a P-type thermopile 110 made of polysilicon or the like and doped in P-type and an N-type thermopile 111 doped in N-type are alternately and connected in series. The thin film layer 118 is formed with etching holes 119 in the space between the thermopile rows for removing a part of the substrate 116 by anisotropic etching to improve thermal separation.

  An Al electrode is used to connect the P-type thermopile 110 and the N-type thermopile 111, and the center portion is a hot junction 113 and the peripheral portion is a cold junction 112. In the region surrounding the hot junction 113, a part of the substrate 116 is removed from the etching hole 119 in a quadrangular pyramid shape having the (111) plane 121 as a side surface by anisotropic etching, and is formed into a thermal separation structure. Further, an infrared absorption film 117 made of an Au black film or the like is provided on the hot contact 113 via the interlayer insulating film 120.

  When infrared rays are incident on the infrared absorption film 117 in such a detection element 12, a temperature difference is generated between the hot junction 113 and the cold junction 112 according to the intensity, and as a result, an electromotive force corresponding to the temperature difference is generated. Is generated between the positive terminal 114 and the negative terminal 115. Thereby, the signal according to the amount of infrared rays irradiated is detected.

6A and 6B are diagrams showing the structure of the reference element 212 used in the infrared imaging apparatus 101 according to the present embodiment shown in FIG. 4, FIG. 6A is a plan view of one reference element 212, and FIG. It is sectional drawing in AA of (A).
The reference element 212 also has a P-type thermopile 110, an N-type thermopile 111, a cold junction 112, and a hot junction 113, similar to the detection element 211 described above, and these are arranged and connected in the same manner as the detection element 211. Has been.

However, the thin film layer 118 of the reference element 212 does not have an etching hole 119 that is formed in the space between the thermopile rows of the detection element 211, and is anisotropically etched by the etching hole 119 to form the substrate 116. There is no quadrangular pyramid shaped removal hole formed in part. As a result, the reference element 212 has a structure in which the hot junction 113 and the substrate 116 are not thermally separated. As a result, in the reference element 212, there is no temperature difference between the hot junction 113 and the cold junction 112, and no electromotive force is generated between the plus terminal 114 and the minus terminal 115 even when infrared rays are incident. .
As described above, the reference element 212 has the same electrical characteristics as the detection element 211, but is configured as an element that does not output a signal corresponding to its intensity even when infrared rays are incident.

Returning to FIG. 4, the infrared imaging element unit 1 of the infrared imaging device 101 is configured by two-dimensionally arranging the detection elements 211 or the reference elements 212 described above corresponding to n × n pixels (pixels 11 to nn). Is done. The detection elements 211 are arranged in the pixels 11 to (n−1) n to form a detection pixel unit, and only the last line in the vertical direction among the pixels n1 to nn, that is, n × n pixels, is included. The reference elements 212 are arranged in a line, which constitutes a first reference pixel array 10 described later.
In the infrared imaging device 101, the second reference pixel array 6 is configured by arranging reference elements 212 in a line so as to be close to the infrared imaging element unit 1.

  As in the infrared imaging apparatus 100 described above, assuming a thermopile (thermocouple) as the detection element 211, the equivalent circuit can be represented as a series circuit of a resistor and a voltage source as shown in FIG. In that case, the equivalent circuit of the reference element 212 can be expressed as a resistor as shown in FIG.

In the infrared imaging element unit 1, N-type MOSFET switches M <b> 11 to Mnn that function as a vertical scanner are connected to the plus terminals 114 of the detection element 211 and the reference element 212. Similarly, N-type MOSFET switches M1 to Mn are connected to the horizontal scanner 5 for each element array.
The reference voltage Vref1 is input to all the detection elements 211 of the infrared imaging element unit 1 and the minus terminal 115 of the reference element 212.

  In the second reference pixel array 6, horizontal direction selection signals X 1 to Xn output from the horizontal direction decoder 4 are respectively supplied to gate terminals of N-type MOSFET switches B 1 to Bn of the second reference element array scanner 7. Applied. As a result, the output signal Vst of the second reference element array scanner 7 is output in synchronization with the output signal Vdt of the horizontal scanner 5 in the horizontal direction.

  In order to make the output impedances of the pixels (including the detection element 211 and the reference element 212) of the infrared imaging element unit 1 and the pixels (including the reference element 212) of the second reference element array 6 equal, The reference element array 6 is provided with N-type MOSFET switches A1 to An. The N-type MOSFET switches A1 to An are always given an H level signal Von to their gate terminals, and are always in an on state.

Next, the operation of the infrared imaging apparatus 101 according to the present invention will be described with reference to FIGS.
FIG. 7 is a time chart showing waveforms of output signals of the vertical direction decoder 3, the horizontal direction decoder 4, the horizontal direction scanner 5, and the reference element array scanner 7 of the infrared imaging device 101.

First, in the counter 2, based on the input reference clock CLK, the detection elements 211 and the first reference pixel array of the number of pixels of the infrared imaging element section 1 (detection pixel sections (pixels 11 to (n-1) n)). 10 (total number of reference elements 212 of pixels n1 to nn) are generated and output to the vertical direction decoder 3 and the horizontal direction decoder 4.
The vertical direction decoder 3 and the horizontal direction decoder 4 decode the address generated by the counter 2 to generate vertical direction selection signals Y1 to Yn for each row and horizontal direction selection signals X1 to Xn for each column. The generated vertical direction selection signals Y1 to Yn are applied to the gate terminals of the N-type MOSFET switches M11 to Mnn of the vertical direction scanner in the infrared imaging device section 1, respectively. The generated horizontal direction selection signals X1 to Xn are respectively applied to the gate terminals of the N-type MOSFET switches M1 to Mn of the horizontal scanner 5 and the gate terminals of the N-type MOSFET switches B1 to Bn of the reference element array scanner 7. Applied.
Here, as shown in the time chart of FIG. 7, when the vertical direction selection signals Y1 to Yn and the horizontal direction selection signals X1 to Xn become H (high) level, the connected N-type MOSFET switches are turned on. .

More specifically, like the infrared imaging device 100 described above, first, when the vertical direction selection signal Y1 becomes H level, the N-type MOSFET switches M11 to M1n are turned on, and the output signals V1 of the pixels 11 to 1n. ˜Vn is sent to the horizontal scanner 5. At the same time, the horizontal direction selection signal X 1 becomes H level, the N-type MOSFET switch M 1 is turned on, and the signal from the pixel 11 is output as the output signal Vdt of the horizontal scanner 5.
Thereafter, when the horizontal direction selection signals X2 to Xn are sequentially set to the H level, the signals of the pixels 12 to 1n are sequentially output as the output signal Vdt.

Next, when the vertical direction selection signal Y2 becomes the H level and the horizontal direction selection signals X1 to Xn sequentially become the H level in accordance with this, the signals of the pixels 21 to 2n are sequentially output as the output signal Vdt. . By repeating these operations, the output signals of the respective pixels are scanned and selected as the signal Vdt in the order of the pixels 11 to 1n, the pixels 21 to 2n, and the pixels n1 to nn.
In addition, the signal at this time is an output signal corresponding to the selection signals Y1 to Y (n-1) is an output from the detection element 211, and an output signal corresponding to the selection signal Yn in the last row is the first signal. It is an output signal of pixels (pixel n1 to pixel nn) of the reference pixel array 10.

On the other hand, the outputs Vs1 to Vsn of the reference pixels 1 to n of the second reference pixel array 6 are sent to the second reference element array scanner 7 via the N-type MOSFET switches A1 to An that are always on.
The second reference element array scanner 7 always operates in synchronization with the horizontal scanner 5 by horizontal direction selection signals X1 to Xn input from the coder 4 in the horizontal direction. As a result, the output signals of the reference pixels 1 to n of the second reference pixel array 6 are output from the second reference element array scanner 7 in synchronization with the horizontal scanning of the infrared imaging element unit 1.

When the horizontal direction decoder 4 sequentially switches the horizontal direction selection signals X1 to Xn, the output signal Vdt of the infrared imaging element unit 1 and the output signal Vst of the second reference element array 6 are described above with reference to FIG. As described above, switching noise is superimposed.
This switching noise is generated by the scanning selection operation of the N-type MOSFET and the electrical characteristics of the detection element 211 and the reference element 212. In the infrared imaging apparatus 101, as described above, the detection element 211 and the reference element 212 have the same electrical characteristics, and these elements are connected to the N-type MOSFET of the same size. The switching noise waveform superimposed on the output Vdt from the infrared imaging element unit 1 via 5 and the output Vst from the second reference element array 6 via the second reference element array scanner 7 is a similar waveform.

  The differential amplifier 9 receives the output signal Vdt of the infrared imaging element unit 1 and the output signal Vst of the second reference element array 6, detects the difference between them, and amplifies and outputs after the offset is canceled. Is done. Therefore, in the infrared imaging device 101 of the present embodiment, since the waveforms of the switching noise superimposed on the output signal Vdt and the output signal Vst are the same, these switching noises are canceled by the differential amplifier 9. As a result, the output signal Vout from the differential amplifier 9 is an appropriate signal that is not affected by the switching noise.

The offset measurement of the differential amplifier 9 is performed when the processing unit 8 scans and selects the first reference element array 10 and the second reference element array 6 in the infrared imaging element unit 1. The signal obtained at this time also has the switching noise canceled as described above in the infrared imaging apparatus 101 of the present embodiment. Therefore, the processing unit 8 can obtain the output signal of the reference element 212 with high accuracy, and can perform offset measurement with high accuracy. As a result, the offset can be canceled appropriately.
In the imaging apparatus 101 of the present embodiment, as shown in FIG. 4, the reference pixels are arranged in a line in the horizontal direction in the infrared imaging element unit 1 as the first reference pixel array 10. As a result, the number of samplings of the output signal of the reference element can be increased, and the offset measurement of the differential amplifier 9 can be performed with high accuracy.

  As described above, in the infrared imaging device 101 of the present embodiment, switching noise generated at the time of scanning selection can be reduced, and a highly accurate output signal of the reference element 212 can be obtained. In addition, the number of samplings can be increased by arranging the reference elements 212 in a line. Therefore, even if an environmental change such as a temperature change occurs during the operation of the infrared imaging device, the offset of the differential amplifier 9 can be measured with high accuracy, and the offset of the differential amplifier 9 can be corrected with high accuracy.

Further, since the amplified outputs of the first reference element array 10 and the second reference element array 6 can be obtained in each frame, when an environmental change such as a temperature change occurs during the operation of the infrared imaging device, the change is followed. Thus, the offset of the differential amplifier 9 can be corrected with high accuracy.
In addition, since switching noise included in the output signal of the detection element 211 can be removed, a clearer image can be obtained.

When the vertical scanning is selected, the vertical scanning signal and the horizontal scanning signal are switched at the same time. Therefore, the output Vdt of the infrared imaging element unit 1 includes switching noise and horizontal scanning selected by the vertical scanning selection. Switching noise due to is superimposed. However, only the switching noise due to the horizontal scanning selection is superimposed on the output signal Vst of the second reference element array 6. Therefore, switching noise is not completely canceled in the differential amplifier 9. Therefore, it is preferable to skip the reading immediately after such vertical scanning selection is performed and not output the element signal to the image.
In this way, a clearer image that does not include switching noise can be obtained.

  In addition, this Embodiment was described in order to make an understanding of this invention easy, and does not limit this invention at all. Each element disclosed in the present embodiment includes all design changes and equivalents belonging to the technical scope of the present invention, and various suitable modifications are possible.

FIG. 1 is a circuit diagram showing a configuration of a normal infrared imaging apparatus related to the present invention. FIG. 2 is a time chart showing waveforms of output signals of the vertical direction decoder, horizontal direction decoder, and horizontal direction scanner of the infrared imaging apparatus shown in FIG. FIG. 3 is a diagram for explaining switching noise generated in the infrared imaging apparatus shown in FIG. FIG. 4 is a circuit diagram showing a configuration of an infrared imaging device according to an embodiment of the present invention. 5A and 5B are diagrams showing the structure of the detection element used in the infrared imaging apparatus shown in FIG. 4, wherein FIG. 5A is a plan view of the detection element, and FIG. 5B is a cross-sectional view taken along line AA in FIG. It is. 6A and 6B are diagrams showing the structure of a reference element used in the infrared imaging device shown in FIG. 4, wherein FIG. 6A is a plan view of the reference element, and FIG. 6B is a cross-sectional view taken along line AA in FIG. It is. FIG. 7 is a time chart showing waveforms of output signals of the vertical direction decoder, the horizontal direction decoder, the horizontal direction scanner, and the reference element array scanner of the infrared imaging apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,101 ... Infrared imaging device 1 ... Infrared imaging device part 2 ... Counter 3 ... Vertical direction decoder 4 ... Horizontal direction decoder 5 ... Horizontal direction scanner 6 ... 2nd reference element array 7 ... 2nd reference element array scanner 8 ... Processing unit 8a ... DA converter (DAC)
8b AD converter (ADC)
DESCRIPTION OF SYMBOLS 9 ... Differential amplifier 10 ... 1st reference element array 211 ... Detection element 212 ... Reference element 110 ... P-type thermopile 111 ... N-type thermopile 112 ... Cold junction 113 ... Hot junction 114 ... Plus terminal 115 ... Minus terminal 116 ... Substrate 117 ... Infrared absorbing film 118 ... Thin film layer 119 ... Etching hole 120 ... Interlayer insulating film 121 ... (111) surface

Claims (2)

Two-dimensionally arranged in the first direction and the second direction, and having a predetermined electrical characteristic and sensitivity, and arranged in a line in the first direction in the vicinity of the detection element, the same as the detection element An infrared imaging device comprising a first reference element having electrical characteristics but having a different sensitivity and no change in signal value even when infrared rays are incident;
A second reference element that is arranged in a line in the first direction in the vicinity of the infrared imaging element, has the same electrical characteristics as the detection element, but does not change the signal value even when infrared rays are incident with different sensitivity. When,
First scanning means for sequentially scanning the infrared imaging element in the first direction and the second direction, and scanning and reading the detection element and the first reference element;
Second scanning means for scanning and reading the second reference element in synchronization with scanning reading in the first direction of the scanning means;
A differential amplifier circuit for detecting a difference between an output of the scanning readout in the first direction of the first scanning unit and an output of the scanning readout by the second scanning unit, amplifying the difference, and outputting the difference;
Offset setting means for setting an offset of the differential amplifier circuit based on a difference between the output of the first reference element and the output of the second reference element detected in the differential amplifier circuit ;
The first scanning means scans the infrared imaging element in the second direction, and scans and reads the detection element or the first reference element for each column in the first direction;
The detection element or the first reference element for each column in the first direction scanned and read out by the second direction scanning unit is scanned in the first direction, and the detection element for each column in the first direction.
Or a first direction scanning means for scanning and reading the first reference element,
The second scanning unit performs scanning and reading of the second reference element in synchronization with the scanning and reading of the first direction scanning unit;
The first direction scanning unit and the second scanning unit do not output a signal of an element that performs scanning reading in the first direction at the same time when scanning reading in the second direction scanning unit is switched. Infrared imaging device. An infrared imaging device having detection elements that are two-dimensionally arranged in a first direction and a second direction and have predetermined electrical characteristics and sensitivity;
A reference element that is arranged in a line in the first direction in the vicinity of the infrared imaging element, has the same electrical characteristics as the detection element but has a different sensitivity, and the signal value does not change even when infrared rays are incident thereon,
First scanning means for sequentially scanning the infrared imaging element in the first direction and the second direction, and scanning and reading the detection element;
Second scanning means for scanning and reading the reference element in synchronization with scanning reading in the first direction of the scanning means;
An output for detecting a difference between an output of the detection element read by the first scanning unit and an output of the reference element read by the second scanning unit, and outputting a signal based on the detected difference as an imaging signal and a circuit,
The first and second scanning units do not output a signal of an element that performs scanning reading in the first direction at the same time when scanning scanning in the second direction by the first scanning unit is switched. Infrared imaging device.

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