JP5017895B2 - Infrared detector - Google Patents

Description

  The present invention relates to an infrared detection apparatus that images a temperature distribution of a subject using a plurality of infrared detection elements that convert incident infrared light into an electrical signal.

  2. Description of the Related Art Conventionally, an infrared detection device that detects a temperature distribution of a subject in real time by arranging a plurality of infrared detection elements side by side is widely known. In such an infrared detection device, various methods for reducing noise mixed in the signal output have been proposed. For example, Patent Document 1 discloses an infrared detection device that reduces scanning switching noise using dummy pixels arranged on a line. Patent Document 2 discloses a bolometer-type infrared detection device that reduces 1 / f noise and fixed pattern noise generated when a MOSFET is used.

JP 7-87399 A JP-A-8-105794

  For example, in an infrared detector with a weak sensor output signal, such as a thermopile type infrared detector using a thermocouple for the sensor part of the infrared detector, an amplifier is provided for each element, and the sensor output signal is amplified by the amplifier. Needs to be output. A transistor is generally used for this amplifier, and when there is no input from the sensor output signal, an output called an offset voltage is generated. The output signal from each element obtained by amplifying the sensor output signal by the amplifier of each element includes the offset voltage component as an offset component, but infrared detection disclosed in Patent Documents 1 and 2 The apparatus cannot correct the offset component of the output signal.

The infrared detection device according to the present invention is arranged on a semiconductor substrate, and a predetermined reference voltage is constant.
A plurality of thermopile type infrared detection elements that are applied to the end and output a voltage value corresponding to the incident light intensity to the other end as a detection signal, are provided corresponding to each of the infrared detection elements. Amplifying the detection signal output according to the intensity of the incident infrared rays, and sequentially selecting a plurality of amplifying means for outputting an output signal including an offset component according to the characteristic difference for each individual, and the plurality of amplifying means A control unit that is connected in parallel with the infrared detection element between both ends of the infrared detection element and the differential amplification unit that constitutes the differential amplifier by being connected to either the selection unit or the amplification unit according to the change of the signal, the reference voltage is short-circuited across the infrared detection element to be output to the amplifying means, or the detection signal is outputted to the amplification means from the infrared detection element And a short-circuit switch to open between both ends of the infrared detection element. The control signal is changed each time one of the amplification means is selected by the selection means, and the connection state between both ends of the infrared detection element is amplified by the short-circuit switch within the selection period of each amplification means, and the detection signal is amplified from the infrared detection element. The circuit is sequentially switched to an open state output to the means, a short circuit state where the reference voltage is output to the amplifying means, and an open state where the detection signal is output again from the infrared detection element to the amplifying means. Then, the amplifying means selected by the selecting means and the differential amplifying means are connected, and a differential amplifier constituted by the connected amplifying means and the differential amplifying means is used to connect between both ends of the infrared detecting element by a short-circuit switch. Output from the amplifying means based on the output signal output from the amplifying means when short-circuited and the output signal output from the amplifying means when both ends of the infrared detecting element are opened by the short-circuit switch. The offset component included in the output signal is corrected.
Alternatively, the infrared detection device according to the present invention is arranged on a semiconductor substrate, and a plurality of thermopile types that apply a predetermined reference voltage to one end and output a voltage value corresponding to the incident light intensity to the other end as a detection signal. An infrared detection element and an infrared detection element are provided corresponding to each of the infrared detection elements, amplifying the detection signal output from each infrared detection element according to the incident infrared intensity, and an offset corresponding to the individual characteristic difference A plurality of amplifying means each for outputting an output signal including components, a selecting means for sequentially selecting the plurality of amplifying means, and an infrared detecting element connected in parallel between both ends of the infrared detecting element are inputted from the outside. depending on the change in the control signals that, the reference voltage is short-circuited across the infrared detection element to be output to the amplifying means, or the detection signal is outputted to the amplification means from the infrared detection element And a short-circuit switch to open between both ends of the infrared detection element as. The control signal is changed each time one of the amplification means is selected by the selection means, and the connection state between both ends of the infrared detection element is amplified by the short-circuit switch within the selection period of each amplification means, and the detection signal is amplified from the infrared detection element. The circuit is sequentially switched to an open state output to the means, a short circuit state where the reference voltage is output to the amplifying means, and an open state where the detection signal is output again from the infrared detection element to the amplifying means. An output and an output signal outputted from the amplification means selected when the short-circuit the two ends of the infrared detection element by short-circuiting switch, the amplifying means is selected when you open across the infrared detection element by short-circuiting switch Based on the output signal, the offset component included in the output signal output from the selected amplification means is corrected .

  According to the present invention, the offset component in the output signal of the infrared detection device can be corrected.

-First embodiment-
A first embodiment of the present invention will be described. FIG. 1 is a circuit configuration diagram of an infrared detection device according to the first embodiment. The infrared detection apparatus shown in FIG. 1 includes an infrared detection element unit 1, a counter 2, a vertical direction decoder 3, a horizontal direction decoder 4, and a black pixel unit 5.

  In the infrared detection element section 1, m pixels in the vertical direction, that is, the column direction, and n pixels in the horizontal direction, that is, the row direction, are two-dimensionally arranged on the semiconductor substrate. In FIG. 1, a pixel located at the p-th in the vertical direction and the q-th in the horizontal direction is represented as a pixel pq (p = 1 to m, q = 1 to n). Each pixel is provided with thermopiles (thermocouples) T11a to Tmna that convert incident infrared rays into electric signals by outputting a voltage value corresponding to the intensity of incident infrared rays as a detection signal. The thermopiles T11a to Tmna can be expressed as an equivalent circuit in which a reference voltage Vref is applied in series with a resistor and a voltage source as shown in FIG. Such an infrared detection element is called a thermopile type two-dimensional infrared detection element.

  The thermopile type infrared detection element used in the infrared detection element unit 1 is placed in a hollow space by supporting a heat receiving unit that absorbs incident infrared light and converts it into heat via a beam, It has a structure in which a thermopile is wired in the beam. Such a structure is realized by micromachining. In the pixels 11 to mn having such a structure, incident infrared light is converted into an electrical signal by detecting a voltage generated in each thermopile due to a temperature difference between the heat receiving portion and the substrate portion. The magnitude of the voltage generated at this time varies depending on the intensity of the incident infrared light, but the thermopile infrared detection element is as small as about ± several tens of μV, so that it is weak to noise and difficult to handle as it is. Therefore, it is necessary to amplify and output the detection signal from each pixel.

  The gate terminals of signal amplification transistors M11a to Mmna using N-type MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are connected to the thermopiles T11a to Tmna provided in each pixel of the infrared detection element unit 1, respectively. ing. The power supply voltage Vcc is input to the drain terminals of the amplification transistors M11a to Mmna, and the drain terminals of switching transistors M11 to Mmn using N-type MOSFETs are connected to the source terminals. The switching operations of the switches M11 to Mmn are controlled by vertical direction selection signals Y1 to Ym input from the vertical direction decoder 3 to the gate terminals. Constant current sources I1 to In are connected to the source terminals of the switches M11 to Mmn for each pixel column, respectively.

  The counter 2 outputs an address count signal corresponding to the number of pixels of the infrared detection element unit 1 to the vertical direction decoder 3 and the horizontal direction decoder 4 based on the input clock signal (CLK). The vertical direction decoder 3 outputs vertical direction selection signals Y1 to Ym to each pixel of the infrared detection element unit 1 based on the address count signal output from the counter 2. On the other hand, the horizontal decoder 4 outputs horizontal direction selection signals X1 to Xn to each pixel of the black pixel unit 5 based on the address count signal output from the counter 2.

  The black pixel unit 5 is disposed adjacent to the lowermost row of the infrared detection element unit 1, that is, the row constituted by the pixels m1 to mn, and has n black pixels in the horizontal direction. The n black pixels (represented as black pixel 1 to black pixel n) have the same structure and circuit configuration as the pixels of the infrared detection element unit 1, but the pixels of the infrared detection element unit 1 Is a pixel that does not output an electrical signal according to the intensity of incident infrared rays. As shown in FIG. 1, each of the black pixels 1 to black pixels n includes resistors R1a to Rna to which a reference voltage Vref is applied, amplification transistors M1a to Mna using N-type MOSFETs, and switches M1 to Mn. ing. Each of these components is provided in pairs for each column of the pixels 11 to mn arranged in a two-dimensional manner. Such black pixels are also called standard pixels, optical black pixels, dummy pixels, or the like.

  The drain terminals of the amplification transistors M1a to Mna provided in the black pixels 1 to n of the black pixel unit 5 are connected to the output voltage Vp. An output resistor RL is connected between the power supply voltage Vcc and the output voltage Vp. The horizontal direction selection signals X1 to Xn from the horizontal decoder are respectively input to the gate terminals of the switches M1 to Mn, and thereby the switching operations of the switches M1 to Mn are controlled.

  The black pixel portion 5 is provided in the same semiconductor chip as the infrared detection element portion 1, that is, on the same semiconductor substrate. FIG. 2 shows an example of a chip floor plan diagram of the infrared detection element unit 1 and the black pixel unit 5. In this figure, as described above, the black pixel portion 5 (black pixel 1 to black pixel n) is disposed and connected adjacent to the lowermost row (pixel m1 to pixel mn) of the infrared detection element portion 1. It is shown. In this way, by providing the amplification transistors M11a to Mmna of the infrared detection element unit 1 and the amplification transistors M1a to Mna of the black pixel unit 5 on the same semiconductor substrate, the same characteristics can be obtained.

  Next, the operation of the infrared detection apparatus described above will be described. FIG. 3 shows a time chart of signals output in the infrared detection apparatus of FIG. The counter 2 counts the number of pixels corresponding to the number of pixels of the infrared detection element unit 1, that is, m × n, based on the input reference clock CLK, and outputs it to the vertical direction decoder 3 and the horizontal direction decoder 4 as address count signals. To do.

  The vertical direction decoder 3 decodes the address count signal from the counter 2 and switches the vertical direction selection signals Y1 to Ym indicated by reference numeral 11 in FIG. 3 to the switches M11 provided in the pixels 11 to mn of the infrared detection element unit 1. Output for ~ Mmn. Further, the horizontal direction decoder 4 decodes the address count signal from the counter 2, and the horizontal direction selection signals X1 to Xn indicated by reference numeral 12 in FIG. 3 are provided to the black pixels 1 to black pixels n of the black pixel unit 5. Output to the switches M1 to Mn.

  The vertical direction selection signals Y1 to Ym and the horizontal direction selection signals X1 to Xn are sequentially set to the H (high) level at timings indicated by reference numerals 11 and 12. First, the vertical direction selection signal Y1 and the horizontal direction selection signal X1 become H level. As a result, the switch M11 of the pixel 11 and the switch M1 of the black pixel 1 are turned on, and the drain-source is conducted, and the pixel 11 is selected for scanning. At this time, a voltage corresponding to the intensity of the incident infrared ray detected in the pixel 11 is output as an output signal of the pixel 11 to the output voltage Vp.

  Next, the horizontal direction selection signals X2 to Xn sequentially become H level while the vertical direction selection signal Y1 is at H level, whereby the switches M12 to M1n of the pixels 12 to 1n and the switches M1 to M1 of the black pixel 1 are obtained. Mn is turned on, and the pixels 12 to 1n are sequentially scanned and selected. Thereby, the voltage according to the intensity | strength of the incident infrared rays of the pixels 12-1n is sequentially output to the output voltage Vp as an output signal of the pixels 12-1n. Thereafter, the vertical direction selection signals Y2, Y3,... Ym are sequentially set to H level, and the horizontal direction selection signals X1 to Xn are sequentially set to H level, so that the pixels mn are sequentially scanned and selected. Is output to the output voltage Vp as an output signal.

  As described above, an output voltage Vp having a waveform as indicated by reference numeral 14 is obtained by sequentially scanning and selecting pixels 11 to mn. The value of the output voltage Vp fluctuates according to the incident infrared intensity of each pixel at a timing according to the scanning selection interval. As indicated by reference numeral 13, the reference voltage Vref is always constant. When scanning is selected up to the pixel mn, scanning selection is repeated from the pixel 11 again.

  Next, a circuit operation when each pixel is selected for scanning will be described. FIG. 4 is a diagram showing a circuit configuration when focusing on the pixel 11 and the black pixel 1 of FIG. As shown in FIG. 4, the drain terminal of the amplification transistor M11a of the pixel 11 is connected to the power supply voltage Vcc, and the drain terminal of the amplification transistor M1a of the black pixel 1 is connected to the power supply voltage Vcc via the resistor RL. . The source terminals of the amplification transistors M11a and M1a are connected to the constant current source I1 through the switch M11 or M1. Further, the thermopile T11a of the pixel 11 and the resistor R1a of the black pixel 1 are connected to the gate terminals of the amplification transistors M11a and M1a, respectively. A reference voltage Vref is applied to the other ends of the thermopile T11a and the resistor R1a.

  In the circuit shown in FIG. 4, when the switches M11 and M1 are turned on by selecting the pixel 11, the sources and drains of the switches M11 and M1 become conductive. At this time, the circuit of FIG. 4 can be represented by the equivalent circuit of FIG. 5 in which the switches M11 and M1 are omitted.

  In the equivalent circuit shown in FIG. 5, since the amplification transistor M11a and the amplification transistor M1a are connected, an electromotive voltage ΔV generated according to the intensity of incident infrared light from the voltage source of the thermopile T11a is applied to the amplification transistor M11a. A differential voltage ΔV is generated between the amplification transistor M11a and the amplification transistor M1a. This difference voltage ΔV represents a variation with respect to the reference voltage Vref. At this time, the equivalent circuit of FIG. 5 operates as a differential amplifier having the amplification transistors M11a and M1a as a differential pair. As a result, the generated difference voltage ΔV is differentially amplified and output to the output voltage Vp. In this way, the detection signal from the pixel 11 is amplified and output.

  By the circuit operation similar to that described above, for each of the other pixels, a differential amplifier in which the amplification transistor of the pixel and the amplification transistor of any one of the black pixels 1 to black pixels n are configured as a differential pair The output from the thermopile is amplified and sequentially output to the output voltage Vp. As described above, among the amplifying transistors M11a to Mmna of the pixels 11 to mn and the amplifying transistors M1a to Mna of the black pixels 1 to n, any one corresponding to each other configured to obtain the same characteristics. Are connected to form a differential amplifier, which is used to amplify and output the detection signal of each pixel. In this way, the detection signal of each pixel is amplified using a differential amplifier in which amplification transistors having the same characteristics are configured as a differential pair.

  Generally, there is an individual difference in the threshold voltage of the transistor. Due to the individual difference in the threshold voltage, there is a characteristic difference for each individual in the amplification transistors M11a to Mmna of each pixel. Since an output signal obtained by amplifying the detection signal of each pixel includes an offset component due to an offset voltage, even if the intensity of incident infrared rays is the same, due to the characteristic difference between the amplification transistors M11a to Mmna as described above. There is a difference in the magnitude of the offset component, and the output signal from each element is not constant. As described above, if the output signals output from the amplification transistors M11a to Mmna are used as they are, an error due to the difference in offset component for each individual occurs. Such an error is called an offset error.

  However, when a differential amplifier having an amplification transistor with the same characteristics as a differential pair as described above is used, the offset component is canceled by the operation of the differential amplifier, and only the fluctuation of the output signal is amplified. In this way, the offset component of the output signal can be corrected. Therefore, a correct output signal without an offset error can be obtained.

According to the first embodiment described above, the following operational effects can be achieved.
(1) The switches M11 to Mmn and the switches M1 to Mn are controlled by the vertical direction selection signals Y1 to Ym output from the vertical direction decoder 3 and the horizontal direction selection signals X1 to Xn output from the horizontal direction decoder 4. Thus, the amplification transistors M11a to Mmna provided in the pixels 11 to mn are sequentially selected. Then, any one of the selected amplification transistors M11a to Mmna and any one of the amplification transistors M1a to Mna of the black pixels 1 to n are connected to form a differential amplifier. Using the differential amplifier configured in this manner, the offset component included in the output signal output from the selected amplification transistor is corrected. Since it did in this way, the offset component in the output signal of an infrared detector can be corrected.

(2) The amplification transistors M11a to Mmna of the pixels 11 to mn and the amplification transistors M1a to Mna of the black pixels 1 to n are provided on the same semiconductor substrate. Since it did in this way, the same characteristic can be acquired with both amplification transistors. Therefore, a differential amplifier that can appropriately correct the offset component can be configured.

(3) The amplification transistors M1a to Mna of the black pixel 1 to the black pixel n are provided for each column of the pixels 11 to mn and the amplification transistors M11a to Mmna arranged two-dimensionally. Since it did in this way, the number of the amplification transistors for comprising a differential amplifier can be minimized.

  In the first embodiment described above, an example is described in which each pair of the black pixels 1 to the black pixels n is provided for each column of the pixels 11 to mn arranged in a two-dimensional manner. did. However, by replacing the vertical and horizontal sides of the infrared detection element unit 1, a pair of each of the black pixels 1 to the black pixels n is provided for each row of the pixels 11 to the pixels mn arranged two-dimensionally. Also good. Even if it does in this way, the effect similar to the above can be acquired.

-Second Embodiment-
Next, a second embodiment of the present invention will be described. FIG. 6 is a circuit configuration diagram of the infrared detection device according to the second embodiment, and includes an infrared detection element unit 1A, a counter 2, a vertical direction decoder 3, a horizontal direction decoder 4, and a black pixel unit 5A. Among these, the counter 2, the vertical direction decoder 3, and the horizontal direction decoder 4 are the same as those of the infrared detection apparatus according to the first embodiment shown in FIG. Hereinafter, the present embodiment will be described focusing on differences from the first embodiment.

  In the infrared detection element unit 1A, pixels 11 to mn are arranged as in the infrared detection element unit 1 of FIG. The pixels 11 to mn are provided with the thermopiles T11a to Tmna, amplification transistors M11a to Mmna, and switches M11 to Mmn described in FIG. The pixels 11 to mn are further provided with thermopile short-circuit switches M11b to Mmnb using N-type MOSFETs. The short-circuit switches M11b to Mmnb are switched between the on state and the off state in accordance with a change in the control signal Vchk input from the outside, thereby short-circuiting the input and output of the thermopiles T11a to Tmna or their infrared detection elements. Works to connect through.

  The black pixel portion 5A also has the same structure as the infrared detection element portion 1A. That is, black pixels 1 to black pixels n are arranged adjacent to the pixels m1 to mn of the infrared detection element unit 1A, and resistors R1a to Rna, amplification transistors M1a to Mna, and switches M1 to Mn are provided in each of them. ing. The black pixels 1 to n are further provided with short-circuit switches M1b to Mnb that are turned on when the control signal Vchk is input and operate to short-circuit the resistors R1a to Rna.

  FIG. 7 shows a time chart of signals output in the infrared detection apparatus described above. 3, the vertical direction decoder 3 decodes the address count signal from the counter 2 and outputs vertical direction selection signals Y1 to Ym indicated by reference numeral 21. The horizontal direction decoder 4 decodes the address count signal from the counter 2 and outputs horizontal direction selection signals X1 to Xn indicated by reference numeral 22.

  The vertical direction selection signals Y1 to Ym and the horizontal direction selection signals X1 to Xn are sequentially set to the H (high) level at timings indicated by reference numerals 21 and 22, respectively. First, the vertical direction selection signal Y1 and the horizontal direction selection signal X1 become H level. As a result, the switch M11 of the pixel 11 and the switch M1 of the black pixel 1 are turned on, and the drain-source is conducted, and the pixel 11 is selected for scanning. At this time, a voltage corresponding to the intensity of the incident infrared ray detected in the pixel 11 is output as an output signal of the pixel 11 to the output voltage Vp.

  When the control signal Vchk changes from L level to H level when the output signal of the pixel 11 is output as described above, the short-circuit switch M11b is turned on and both ends of the thermopile T11a are short-circuited. Is done. At this time, the offset voltage by the amplification transistor M11a is output to the output voltage Vp by a circuit operation as described later. When the control signal Vchk returns to the L level, the output signal of the pixel 11 is output to the output voltage Vp again.

  Next, while the vertical direction selection signal Y1 is at the H level, the horizontal direction selection signals X2 to Xn are sequentially at the H level, and the control signal Vchk changes from the L level to the H level. Accordingly, the pixels 12 to 1n are sequentially scanned and selected, and an output signal thereof is output to the output voltage Vp, and an offset voltage by the amplification transistors M12a to M1na of the pixels 12 to 1n is output to the output voltage Vp. Thereafter, the vertical direction selection signals Y2, Y3... Ym are sequentially set to H level, and the horizontal direction selection signals X1 to Xn are sequentially set to H level to change the control signal Vchk. Are sequentially scanned and a voltage corresponding to the intensity of incident infrared rays of each pixel and an offset voltage of the amplification transistor are output as an output signal to the output voltage Vp.

  As described above, the scanning voltage is sequentially selected from the pixel 11 to the pixel mn, and the control signal Vchk is changed during that time, whereby the output voltage Vp having a waveform as indicated by reference numeral 25 is obtained. The value of the output voltage Vp fluctuates according to the incident infrared intensity of each pixel at a timing according to the scanning selection interval, and fluctuates according to the offset voltage of the amplification transistor at the timing when the control signal Vchk changes. . As indicated by reference numeral 24, the reference voltage Vref is always constant. When scanning is selected up to the pixel mn, scanning selection is repeated from the pixel 11 again.

  Next, a circuit operation when each pixel is selected for scanning will be described. FIG. 8 is a diagram showing a circuit configuration when focusing on the pixel 11 and the black pixel 1 of FIG. This circuit configuration is the same as the circuit configuration shown in FIG. 4 except that the pixel 11 is provided with a short-circuit switch M11b and the black pixel 1 is provided with a short-circuit switch M1b. The control signal Vchk is input to the gate terminals of the short-circuit switches M11b and M1b.

  In the circuit shown in FIG. 8, when the switches M11 and M1 are turned on by selecting the pixel 11, the sources and drains of the switches M11 and M1 are brought into conduction. At this time, in the circuit of FIG. 8, when the control signal Vchk is at L level, that is, when the short-circuit switches M11b and M1b are off and the source and drain are not conducting, the switches M11 and M1 and the short-circuit switch M11b , M1b can be represented by the equivalent circuit of FIG. This equivalent circuit is the same as the equivalent circuit shown in FIG. That is, by the circuit operation as described above, the detection signal from the pixel 11 is amplified and output to the output voltage Vp.

  Further, in the circuit of FIG. 8, when the pixel 11 is selected and the control signal Vchk is at the H level, that is, the switches M11 and M1 and the short-circuit switches M11b and M1b are all on, and the source and drain are conductive. The case can be represented by the equivalent circuit of FIG. In this equivalent circuit, the switches M11 and M1, and the thermopile T11a and the resistor R1a whose both ends are short-circuited are omitted.

  In the equivalent circuit shown in FIG. 10, since the differential voltage from the voltage source is not applied to the amplification transistors M11a and M1a forming the differential pair, the amplified voltage is output if the characteristics of the amplification transistors M11a and M1a are exactly the same. Not. However, since the characteristics of the amplification transistors M11a and M1a are actually varied, an offset voltage corresponding to the variation is output as the output voltage Vp. Thus, the offset voltage detected when the control signal Vchk is at the H level is subtracted from the output signal when the control signal Vchk is at the L level, that is, the output signal including the offset component, thereby removing the offset component. 11 can be obtained as a true output signal.

  By the circuit operation similar to that described above, for each of the other pixels, a differential amplifier in which the amplification transistor of the pixel and the amplification transistor of any one of the black pixels 1 to black pixels n are configured as a differential pair, The amplified detection signal and offset voltage are sequentially output to the output voltage Vp. Using this, a true output signal from which the offset component has been removed can be obtained for each pixel.

According to the second embodiment described above, in addition to the functions and effects described in the first embodiment, the following functions and effects can be further achieved.
(1) The input and output of the thermopiles T11a to Tmna are short-circuited or connected via each thermopile by the switch operation of the short-circuit switches M11b to Mmnb. Then, when the input and output of the thermopiles T11a to Tmna are short-circuited, the output signal output from the amplification transistor selected from the amplification transistors M11a to Mmna and the input and output of the thermopiles T11a to Tmna are connected via each thermopile. The offset component included in the output signal output from the amplification transistor is corrected based on the output signal output from the amplification transistor. In other words, the offset component is corrected by subtracting the output signal at the time of the short circuit representing the offset voltage from the output signal at the time of the latter connection including the offset component. Since it did in this way, the true output signal which removed the offset component can be calculated | required about each pixel. Therefore, the offset component in the output signal of the infrared detection device can be corrected more accurately.

(2) The switches M11 to Mmn and the switches M1 to Mn are controlled by the vertical direction selection signals Y1 to Ym and the horizontal direction selection signals X1 to Xn, thereby selecting any of the amplification transistors M11a to Mmna. In this way, the control signal Vchk is changed every time one of the amplification transistors M11a to Mmna is selected, and the connection state between the input and output of the thermopiles T11a to Tmna is short-circuited by the short-circuit switches M11b to Mmnb within the selection period of each amplification transistor. And switching to both connection states. Since this is done, the offset error can be reliably corrected every time each pixel is selected for scanning.

  In the above example, as shown in the time chart of FIG. 7, the control signal Vchk can take both L level and H level states while one pixel is selected for scanning. Thus, an example in which the connection state between the input and output of the thermopiles T11a to Tmna is switched between the short-circuit state and the connection state by the short-circuit switches M11b to Mmnb within the selection period of each amplification transistor has been described. However, the control signal Vchk may be changed every time scanning is selected for all the pixels without changing the control signal Vchk while one pixel is selected for scanning.

  FIG. 11 shows a time chart of signals output from the infrared detecting device when the control signal Vchk is changed as described above. When the vertical direction selection signals Y1 to Ym sequentially become H level at the timing indicated by reference numeral 31, as indicated by reference numeral 32, the control signal Vchk does not change at a constant L level in the first period. At this time, the output signal of each pixel is sequentially output as the output signal Vp indicated by reference numeral 34. However, in the next cycle, the control signal Vchk is switched to the H level and becomes constant. At this time, the offset signal of each pixel is sequentially output as the output signal Vp indicated by reference numeral 34. By subtracting the offset voltage thus obtained from the output signal, a true output signal from which the offset voltage has been removed is obtained for each pixel. In FIG. 11, the horizontal direction selection signals X1 to Xn are omitted. Further, as indicated by reference numeral 33, the reference voltage Vref is always constant.

  As described above, the control signal Vchk is changed each time all of the amplification transistors M11a to Mmna are selected, and the thermopile T11a to Tmna is turned on by the short-circuit switches M11b to Mmnb within the selection period of each amplification transistor. The connection state between the outputs can be either a short circuit or a connection. In this way, the offset component can be reliably corrected even if the interval for scanning and selecting each pixel is shortened.

  Further, the control signal Vchk may be kept constant at the L level during normal times, and the control signal Vchk may be changed to the H level only when a specific condition is satisfied. For example, the ambient temperature is measured in order to check the temperature environment where the infrared detection device is placed, and when the measured ambient temperature fluctuates by a predetermined value or more, the control signal Vchk is changed to the H level to detect the offset voltage. Can be. As described above, if the change of the control signal Vchk is permitted or prohibited based on the ambient temperature, the offset component can be appropriately corrected according to the temperature characteristic of the offset voltage. As a result, the offset component can be corrected efficiently at an appropriate timing.

-Third embodiment-
Next, a third embodiment of the present invention will be described. FIG. 12 is a circuit configuration diagram of an infrared detection device according to the third embodiment, and includes an infrared detection element unit 1B, a counter 2, a vertical decoder 3, a horizontal decoder 4, and a horizontal scanner 6. Among them, the counter 2, the vertical direction decoder 3 and the horizontal direction decoder 4 are the same as the infrared detection apparatus according to the first embodiment shown in FIG. 1 and the infrared detection apparatus according to the second embodiment shown in FIG. . Hereinafter, the present embodiment will be described focusing on the differences from the first and second embodiments.

  Pixels 11 to mn are arranged in the infrared detection element unit 1B in the same manner as the infrared detection element unit 1A in FIG. 6, and the thermopiles T11a to Tmna, the switches M11 to Mmn, and the thermopile are arranged in the pixels 11 to mn, respectively. Short-circuit switches M11b to Mmnb are provided. The pixels 11 to mn are further provided with amplification transistors M11c to Mmnc and resistors R11 to Rmn using N-type MOSFETs.

  The amplification transistors M11c to Mmnc have thermopiles T11a to Tmna and short-circuit switches M11b to Mmnb connected to their gate terminals, resistors R11 to Rmn connected to their drain terminals, and their source terminals connected to the ground and grounded. The resistors R11 to Rmn are all connected to the power supply voltage Vcc. The drain terminals of the switches M11 to Mmn and the amplification transistors M11c to Mmnc are connected to each other.

  The horizontal scanner 6 is composed of switches M1 to Mn made of N-type MOSFETs. The switches M1 to Mn are sequentially turned on according to the horizontal direction selection signals X1 to Xn output from the horizontal direction decoder 4. By the operations of the switches M1 to Mn of the horizontal decoder 4 and the switches M11 to Mmn provided for each pixel, the pixels 11 to mn are sequentially scanned and selected as described above.

  Next, the operation of the circuit selected for scanning will be described. For example, when the pixel 11 is selected for scanning, if the control signal Vchk is at the L level and the short-circuit switch M11b is off, the operation of the inverting amplifier including the amplification transistor M11c and the resistor R11 causes the thermopile T11a to operate. Is inverted and amplified and output as an output voltage Vp. On the other hand, when the control signal Vchk is at the H level and the short-circuit switch M11b is on, the reference voltage Vref is amplified by the inverting amplifier and output as the offset voltage to the output voltage Vp. Thereby, a true output signal from the pixel 11 from which the offset voltage is removed can be obtained as in the second embodiment.

  For the other pixels, the detection signal and the offset voltage amplified by the inverting amplifier are sequentially output to the output voltage Vp by changing the control signal Vchk as in the pixel 11. Using this, a true output signal from which the offset voltage is removed can be obtained for each pixel.

  According to the third embodiment described above, the same operational effects as those of the second embodiment can be achieved.

  In the third embodiment described above, as in the second embodiment, all pixels are scanned without changing the control signal Vchk while one pixel is selected for scanning. The control signal Vchk may be changed every time it is selected. Further, normally, the control signal Vchk is kept at the L level constant, and when a specific condition is satisfied, for example, when the measured ambient temperature fluctuates by a predetermined value or more, the control signal Vchk is changed to the H level and the offset voltage is changed. May be detected. In this way, the same effects as those described in the second embodiment can be obtained.

  In each of the embodiments described above, an example in which a thermopile is used as an infrared detecting element that converts incident infrared light into an electrical signal has been described. However, the present invention is not limited to this content, and the infrared detecting element A thing may be used. Moreover, although the example in which the infrared detection elements are arranged in a two-dimensional manner has been described, a one-dimensional arrangement may be used. In that case, for example, in the first embodiment, the infrared detection element unit 1 of FIG. 1 is configured by one row of pixels 11 to 1n, and the vertical decoder 3 and the vertical scanner in the infrared detection element unit 1 The switches M11 to M1n serving as roles are omitted. Other than this, the configuration is the same as that of the infrared detection device of FIG. Therefore, the same effect as the above-described effect can be obtained. The same applies to other embodiments.

  In each of the embodiments described above, the configuration using the MOSFET for the amplification transistor and the switch has been described. However, the same configuration can be realized even if a bipolar transistor is used.

  In each of the embodiments described above, the infrared detection elements are the thermopiles T11a to Tmna, the amplification means are the amplification transistors M11a to Mmna or M11c to Mmnc, the selection means is the counter 2, the vertical decoder 3, the horizontal decoder 4, and the switches M11 to M11. Mmn and switches M1 to Mn, differential amplification means are realized by amplification transistors M1a to Mna, and short-circuit means are realized by short-circuit switches M11b to Mmnb, respectively. However, the above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

  Each embodiment and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired.

It is a circuit block diagram of the infrared rays detection apparatus by the 1st Embodiment of this invention. It is an example of a chip floor plan diagram. It is a time chart of the signal output in the infrared rays detection apparatus by 1st Embodiment. It is a figure which shows a circuit structure when paying attention to the pixel 11 and the black pixel 1 in 1st Embodiment. FIG. 5 is a diagram showing an equivalent circuit when switches M11 and M1 are turned on in the circuit configuration of FIG. It is a circuit block diagram of the infrared rays detection apparatus by the 2nd Embodiment of this invention. It is a time chart of the signal output in the infrared rays detection apparatus by 2nd Embodiment. It is a figure which shows a circuit structure when paying attention to the pixel 11 and the black pixel 1 in 2nd Embodiment. FIG. 9 is a diagram showing an equivalent circuit when switches M11 and M1 are turned on and short-circuit switches M11b and M1b are turned off in the circuit configuration of FIG. FIG. 9 is a diagram showing an equivalent circuit when switches M11 and M1 are turned on and short-circuit switches M11b and M1b are turned on in the circuit configuration of FIG. It is a time chart of the signal output in the infrared rays detection apparatus by the modification of 2nd Embodiment. It is a circuit block diagram of the infrared rays detection apparatus by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A, 1B: Infrared detection element part 2: Counter 3: Vertical direction decoder 4: Horizontal direction decoder 5, 5A: Black pixel part 6: Horizontal direction scanner

Claims (6)

A plurality of thermopile infrared detectors arranged on a semiconductor substrate , a predetermined reference voltage is applied to one end, and a voltage value corresponding to the incident light intensity is output to the other end as a detection signal ;
The infrared each is provided corresponding to the detector element, and amplifies the detection signal from the infrared detecting element is outputted in response to the incident infrared radiation intensity, including an offset component corresponding to the characteristic difference of each individual A plurality of amplifying means for outputting each output signal;
Selection means for sequentially selecting the plurality of amplification means;
Differential amplification means constituting a differential amplifier by being connected to any of the amplification means;
The infrared detection element is connected in parallel with the infrared detection element between both ends of the infrared detection element, and the reference voltage is output to the amplifying unit in response to a change in a control signal input from the outside. the short-circuiting between the two ends, or a short-circuit switch for the detection signal to open between both ends of the infrared detection element to be output to the amplifying means from the infrared detection element,
The control signal is changed every time one of the amplification means is selected by the selection means, and the connection state between both ends of the infrared detection element is selected by the short-circuit switch within the selection period of each amplification means. The open state output from the infrared detection element to the amplification means, the short circuit state where the reference voltage is output to the amplification means, and the open state where the detection signal is output again from the infrared detection element to the amplification means. switching,
The amplifying means selected by the selecting means and the differential amplifying means are connected, and a differential amplifier constituted by the connected amplifying means and the differential amplifying means is used, and the infrared detection element is connected by the short-circuit switch . Based on the output signal output from the amplification means when both ends are short-circuited and the output signal output from the amplification means when both ends of the infrared detection element are opened by the short-circuit switch An infrared detecting device, wherein an offset component included in an output signal output from the means is corrected. The infrared detection device of claim 1,
The infrared detecting device, wherein the amplifying means and the differential amplifying means are provided on the same semiconductor substrate. The infrared detection device according to claim 1 or 2,
The infrared detecting element and the amplifying means are arranged two-dimensionally on the semiconductor substrate,
The differential amplifying means is provided for each row or column of two-dimensionally arranged infrared detecting elements and amplifying means. In the infrared detection device according to any one of claims 1 to 3 ,
A temperature measuring means for measuring the ambient temperature;
An infrared detecting device, wherein the change of the control signal is permitted or prohibited based on the ambient temperature measured by the temperature measuring means. A plurality of thermopile infrared detectors arranged on a semiconductor substrate , a predetermined reference voltage is applied to one end, and a voltage value corresponding to the incident light intensity is output to the other end as a detection signal ;
The infrared each is provided corresponding to the detector element, and amplifies the detection signal from the infrared detecting element is outputted in response to the incident infrared radiation intensity, including an offset component corresponding to the characteristic difference of each individual A plurality of amplifying means for outputting each output signal;
Selection means for sequentially selecting the plurality of amplification means;
The infrared detection element is connected in parallel with the infrared detection element between both ends of the infrared detection element, and the reference voltage is output to the amplifying unit in response to a change in a control signal input from the outside. the short-circuiting between the two ends, or a short-circuit switch for the detection signal to open between both ends of the infrared detection element to be output to the amplifying means from the infrared detection element,
The control signal is changed every time one of the amplification means is selected by the selection means, and the connection state between both ends of the infrared detection element is selected by the short-circuit switch within the selection period of each amplification means. The open state output from the infrared detection element to the amplification means, the short circuit state where the reference voltage is output to the amplification means, and the open state where the detection signal is output again from the infrared detection element to the amplification means. switching,
An output signal outputted from the selected amplifying means when short circuit between both ends of the infrared detection element by the short-circuit switch, said selected when opened across the infrared detection element by the short-circuit switch An infrared detection apparatus, wherein an offset component included in an output signal output from the selected amplification means is corrected based on an output signal output from the amplification means. The infrared detection device of claim 5 ,
A temperature measuring means for measuring the ambient temperature;
An infrared detecting device, wherein the change of the control signal is permitted or prohibited based on the ambient temperature measured by the temperature measuring means.

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