JP2008219649A - Infrared imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared imaging apparatus capable of precisely imaging an object to be imaged without reference to whether the temperature of a shutter is high or low. <P>SOLUTION: Infrared rays from the shutter are made incident on an infrared sensor Det.101 by closing the shutter, and switches SW1(111) to SW5(115) are closed at the same time to supply currents to five transistors Tr0(121) to Tr4(125). Then only the switch SW5(115) which is closed is opened. A charge storage capacitor 130 is charged with currents applied to respective gates of the transistors Tr0(121) to Tr4(125). The shutter is opened to start imaging operation. At this point, the same currents as those when the shutter is closed continue to flow to the transistors Tr0(121) to Tr4(125). One of the switches SW1(111) to SW4(114) is opened to discharge currents by the four transistors and then the current charged in the charge storage capacitor 130 can be reduced to 4/5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an infrared imaging device having an infrared detection unit that detects infrared radiation of an imaging target by an infrared sensor array in which an input circuit that senses an infrared detection element (sensor) is arranged in a mesh pattern, and in particular, an offset in an input circuit. The present invention relates to a technique for appropriately removing and increasing a signal charge accumulation amount.

  2. Description of the Related Art In recent years, infrared imaging devices have been remarkably improved in performance and price, and there is a demand for infrared imaging devices that are smaller, simpler, and more accurate in usage. FIG. 17A is a diagram illustrating a configuration of an input circuit in an infrared detection unit according to a conventional infrared imaging device. FIG. 17B is a chart showing the operation timing of the input circuit in the conventional infrared detector shown in FIG. 17A. The operation of the conventional input circuit will be described with reference to FIGS. 17A and 17B.

  First, the control voltage ΦR applied to the gate of the transistor 52 is reset to a low level in order to reset the capacitor for storing signal charges (hereinafter simply referred to as “signal charge storage capacitor”) CInt (54) (see FIG. 17B). Then, the voltage of the node N1 (55) becomes the reset level. The reset level is determined by the VR voltage. VS is the substrate voltage, usually ground.

  After returning the control voltage ΦR applied to the gate of the transistor 52 to the high level, the control voltage ΦInt applied to the gate of the transistor 53 is set to the high level for a predetermined time (integration time), and the infrared detection element (sensor) Det. (51) (See FIG. 17B). A bias voltage Vbias is applied to the gate of the transistor 58 so that an appropriate current flows through the infrared detection element Det. (51). The voltage at the node N1 (55) continues to decrease while the control voltage ΦInt is at a high level. As the current flowing through the infrared detection element Det. (51) increases, the voltage at the node N1 (55) decreases faster. That is, the voltage of the node N1 (55) decreases faster as more infrared rays are incident on the infrared detection element Det. (51). After the control voltage ΦInt is set to the low level and the current supply to the infrared detection element Det. (51) is stopped, the voltage of the node N1 (55) is read through the transistors 56 and 57 (see FIG. 17B). Transistor 56 is configured to function as a source follower amplifier.

18A and 18B are diagrams showing the basic configuration and operation of a conventional infrared imaging device. The conventional infrared imaging apparatus shown in FIG. 18A operates as follows.
As shown in FIG. 18B, the shutter 33 is first closed, and the infrared radiation of the shutter 33 is incident on the input circuit 32 of the infrared detector 31. The output of the infrared detector 31 reflects the temperature of the shutter 33. The signal detected at this time is stored as an offset in the memory unit 43 for each infrared detection element Det. Provided in the input circuit 32 of the infrared detection unit 31. The memory unit 43 is composed of, for example, a RAM (Random Access Memory), and the infrared detection unit is composed of a large number of infrared detection elements Det. Of the input circuit shown in FIG. The signal detected for each Det. Is digitized via the A / D converter 41 and stored in the memory 43.

Thereafter, as shown in FIG. 18B, the shutter 33 is opened, and the infrared radiation from the imaging target 35 is incident on the infrared detection element Det. Of the input circuit 32. At this time, it is assumed that the output of each infrared detection element Det. Becomes the voltage indicated by a circle 62 shown in FIG. An offset (signal voltage when the shutter 33 is closed = voltage stored in the memory unit 43) is subtracted from the voltage of the circle 62 by the calculation unit 42 shown in FIG. 18A. If the signal voltage obtained by closing the shutter 33 is the voltage of the square mark 61 shown in FIG. 19A, the length from the square mark 61 to the round mark 62 shown in FIG. The difference is expressed in FIG. The calculation unit 42 amplifies the voltage difference shown in FIG. 19B through the D / A conversion unit 44 and converts it into an analog value, and further, as an image having a luminance proportional to the voltage difference. Displayed on the display unit (monitor) 45.

  The reason why the conventional infrared imaging device requires complicated signal processing is that infrared radiation emitted from the imaging target 35 in a normal temperature environment (about 300 K) is transmitted to each infrared detection element Det. Of the infrared detection unit 31. This is because a process for detecting and removing the offset from the detected infrared radiation is performed. In practical infrared imaging devices, since temperature measurement accuracy of several tens of mK to 100 mK is required, offset removal is an absolutely indispensable issue.

  However, if the offset removal is performed outside the input circuit as in the conventional method, further improvement in accuracy cannot be expected. This is because the signal charge storage capacitor CInt (54) in the input circuit is configured to store not only the signal but also the offset together. In other words, it is desirable that only the charge that contributes to the accuracy of display luminance is originally stored, but the offset, that is, the charge corresponding to the infrared radiation of the shutter 33 mainly fills the signal charge storage capacitor CInt (54). Therefore, there has been a problem that the amount of accumulated charge cannot be increased and improvement in accuracy cannot be expected.

As one measure for solving this problem, an input circuit that is proposed in Patent Document 1 and increases the accuracy of autofocus in a camera can be used as a reference. In the proposal of Patent Document 1, a circuit for storing an unnecessary current such as background light is provided in the input circuit, and the stored current is continuously supplied even during signal measurement to discharge the unnecessary current, and only the necessary charge is discharged. Accumulation increases the accuracy of autofocus. That is, in Patent Document 1, as shown in FIGS. 20A and 20B, the voltage between the source and gate of the transistor 6 obtained through the light receiving element 24 (photodiode 2) when the light projection by the light source 20 is off is shown. The capacitor 7 stores, and when the light projection by the light source 20 is on, that is, when the signal is measured, the transistor 6 operates so as to continue to flow the current by the background light stored in the capacitor 7. As a result, only necessary charges are accumulated in the storage capacitor element 5 and unnecessary current such as background light is discharged by the transistor 6 so that unnecessary charges are not accumulated in the storage capacitor element 5.
Japanese Patent Laid-Open No. 7-203319 (page 10, FIGS. 1 and 17)

  Here, considering the case where the technique proposed in Patent Document 1 is applied to an infrared imaging device, when the temperature of the shutter 33 shown in FIG. There is a problem that signal charges are not accumulated in the charge accumulation capacitor CInt (54). This corresponds to the case where the current discharged by the transistor 6 is larger than the current flowing through the photodiode 2 in FIG. 20A. Since the charge is excessively subtracted, no signal charge is accumulated in the storage capacitor element 5. There arises a problem that a signal cannot be obtained.

  By using a Peltier element (not shown) or the like to keep the temperature of the shutter 33 shown in FIG. 18A lower than the temperature of the object to be imaged 35, the charge is not excessively subtracted. When the housing temperature of the apparatus rises, the temperature may be higher than that of the imaging target 35 even on the low temperature side of the Peltier element. Further, the heat generated on the high temperature side of the Peltier element further increases the temperature inside the casing of the infrared imaging device, making it more difficult to solve the problem. In order to cope with this problem, it is necessary to provide a heat radiating means from the inside of the casing of the infrared imaging apparatus to the outside of the casing, resulting in a problem that the apparatus becomes more complicated and expensive. In any case, the problem cannot be solved only by the use of Peltier elements.

Conversely, even when the temperature of the shutter 33 shown in FIG. 18A is too lower than the imaging target 35, a large amount of signal charge cannot be stored in the signal charge storage capacitor CInt (54). The amount of subtraction of the charge is too small, and a large amount of charge remains after the offset removal, and CInt (54) is filled with the accumulated charge. Therefore, the high-temperature imaging object 35 cannot be imaged with high accuracy. In order to accurately image the high-temperature imaging object 35, it is necessary to heat the shutter 33 with a heater (not shown) or the like. A problem arises that a shutter having good heat resistance must be used, and the apparatus becomes more complicated and expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an infrared imaging device that can accurately image an imaging target regardless of the shutter temperature.

  The infrared imaging device of the present invention includes a current discharge amount adjusting unit that discharges current so that unnecessary charge accumulation does not occur in an input circuit of an infrared detection unit. Further, the current discharge amount adjusting means is constituted by a plurality of transistors for discharging current so that unnecessary charge accumulation does not occur, and excessive subtraction does not occur by changing the number of transistors used according to the temperature of the shutter. It is characterized by.

  Thus, according to the present invention, since the current discharge amount adjusting means is provided in the input circuit of the infrared detection unit, it is possible to appropriately perform offset removal according to the relationship between the shutter temperature and the imaging target temperature. As a result, unnecessary offset charges stored in the signal charge storage capacitor CInt can be reduced and the amount of signal charges stored can be increased, so that the luminance accuracy of the image related to the infrared radiation to be imaged can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a block diagram showing the configuration of an input circuit of an infrared detection unit according to an embodiment of the present invention, and FIG. 1B is a waveform diagram for explaining the operation of the input circuit of the infrared detection unit according to an embodiment of the present invention. It is. FIG. 2 is a schematic diagram showing the basic configuration of the infrared imaging apparatus according to the embodiment of the present invention, and FIG. 3 is a block diagram of the configuration of the infrared imaging apparatus according to the embodiment of the present invention. 2 and 3, the infrared imaging device according to the embodiment of the present invention includes an infrared detection unit 100 and a shutter 300 in order from the imaging target 500 in a housing (not shown) in order to obtain infrared radiation from the imaging target 500. , Equipped with lens 400, infrared radiation data detected by infrared detection unit 100 outside the housing is signal processed by signal processing unit 800 and displayed on display unit (monitor) 900, and receives an instruction from control unit 600 to detect infrared radiation The drive unit 700 is configured to drive and control the input circuit 200 of the unit 100. An input circuit 200 is housed in the infrared detection unit 100 and is driven and controlled by a drive unit 700.

  The image related to the infrared radiation displayed on the display unit (monitor) 900 is monitored, and the operation of the infrared detection unit 100 is controlled from the control unit 600 via the drive unit 700. A drive unit 700 that drives and controls the input circuit 200 (see FIG. 1A) of the infrared detection unit 100 has an interface with the control unit 600, and switches SW1 (111) to SW5 (115) in the input circuit shown in FIG. 1A. Controls such as on / off, length of integration time (integration time), bias voltage of infrared detector (Det.) 101 are set by the control unit 600 to control the amount of current discharged and the amount of charge accumulated as a signal. Adjustable. The control unit 600 can be configured with a personal computer, a sequencer, or the like.

  The operation of the infrared imaging apparatus of the present invention will be described with reference to FIGS. 1A, 1B, 2 and 3. As shown in FIG. 1B, first, the shutter 300 shown in FIGS. 2 and 3 is closed, and infrared radiation from the shutter 300 is incident on the infrared detection element (sensor) Det. 101 (see FIG. 1A), and the switch SW1 (111). ... SW5 (115) (see FIG. 1A) are simultaneously closed, and a current flows through transistors Tr0 (121) to Tr4 (125) (see FIG. 1A) (see FIG. 1B).

Next, only the closed switch SW5 (115) (see FIG. 1A) is opened. At this time, the current applied to the gates of the transistors Tr0 (121) to Tr4 (125) is stored in the charge storage capacitor CMem (130) of the analog storage / subtraction circuit 110 shown in FIG. 1A.

  Next, the shutter 300 shown in FIGS. 2 and 3 is opened to start imaging. A predetermined voltage is applied to the transistors Tr0 (121) to Tr4 (125) by the charges stored in the charge storage capacitor CMem (130) in the transistors Tr0 (121) to Tr4 (125) of the analog storage / subtraction circuit 110 shown in FIG. 1A. ), The same current as when the shutter 300 is closed continues to flow.

  Since the voltages applied to the gates of the transistors Tr0 (121) to Tr4 (125) of the analog storage / subtraction circuit 110 shown in FIG. 1A are the same, the charge storage capacitor CMem (130) has five identical transistors. The current when the shutter 300 is closed is stored, and one of the switches SW1 (111) to SW4 (114) of the analog storage / subtraction circuit 110 is opened, and the current is discharged by four transistors. By doing so, the current stored in the charge storage capacitor CMem (130) can be reduced 4/5 times (80%). Thereby, it is possible to prevent oversubtraction when the shutter 300 becomes hotter than the imaging object 500.

  Also, open any one of the switches SW1 (111) to SW4 (114) of the analog memory / subtraction circuit 110 shown in FIG. 1A, and close the switches SW5 (115) other than the opened switches together. Current is stored in the charge storage capacitor CMem (130) using four transistors, and the switches SW1 (111) to SW4 (114) of the analog storage / subtraction circuit 110 are closed, and five transistors Tr0 (121 ) To Tr4 (125), the current accumulated in the charge storage capacitor CMem (130) can be increased 5/4 times (125%). When the imaging target 500 becomes hotter than the shutter 300, the luminance accuracy of the image related to the infrared radiation of the imaging target can be improved by increasing the discharge current amount.

  1A and 1B, the control voltage ΦR applied to the gate of the transistor 102 in the input circuit is controlled to turn the transistor 102 on and off, and the control voltage ΦInt (integration time) applied to the gate of the transistor 103 in the input circuit is controlled. Then, the transistor 103 is turned on / off to pass a current through the infrared detection element Det. (101), and the charge (corresponding to the signal) from which the offset is removed by controlling the voltage of the node 105 is the signal charge storage capacitor CInt (104). To accumulate. Then, the charge (corresponding to a signal) stored in the signal charge storage capacitor CInt (104) is read and transmitted to the signal processing unit 800. The signal processing unit 800 processes the detected signal, and the display unit 900 displays an image related to the infrared radiation of the imaging target based on the processed signal.

  As described above, the input circuit of the infrared detection unit according to the embodiment of the present invention includes means for discharging a current proportional to the current that flows when the shutter 300 is closed at the time of signal detection (at the time of imaging), By controlling so that the charge flowing into the storage capacitor CInt (104) does not include the offset, the display luminance accuracy can be improved, and as a result, the S / N can be increased.

FIG. 4 is a block diagram illustrating a configuration of the infrared detection unit illustrated in FIGS. 2 and 3. In FIG. 4, the infrared detection unit is configured to detect infrared radiation of the imaging object 500 by an infrared sensor array in which input circuits 200 that sense infrared detection elements (sensors) are arranged in a mesh pattern. Each input circuit 200 has the configuration shown in FIG. 1A, and the infrared selection data 171 selected by the vertical shift register 170 through the transistors 106 and 107 is the infrared radiation data detected by the infrared detection element Det. (101). And a vertical bus 181 selected by the horizontal shift register 180 to guide to the output line. In this case, when functioning as an infrared sensor array, the horizontal input circuit 200 selected by the vertical selection line 171 is guided to the output line 182 by the vertical bus 181 selected by the horizontal shift register 180, and then the vertical selection line Similarly, the horizontal input circuit 200 is led to the output line 182 by the vertical bus 181 selected by the horizontal shift register 180 by changing the selection position of 171, and this is repeated thereafter. In addition, driving of the transistors Tr11 (111), Tr12 (112), Tr13 (113), Tr14 (114), etc. of each input circuit 200 is performed by the driving unit 700 in parallel with each horizontal input circuit 200 selected by the vertical selection line 171. It is realized by driving to. Note that the transistor 106 functions as a source follower amplifier. Also, the switches SW1 (111) to SW4 (114) in FIGS. 1A and 1B are realized by transistors Tr11 (111), Tr12 (112), Tr13 (113), and Tr14 (114) in FIG. Further, the output line 182 of the infrared detection unit 100 is connected to the signal processing unit 800, and the signal output to the output line 182 is signal-processed by the signal processing unit 800.

  FIG. 5 is a block diagram illustrating a configuration of the drive unit illustrated in FIGS. 2 and 3. In FIG. 5, the drive unit includes a microprocessor system (MPU) 701 that includes a memory (not shown), a serial data interface 702 that controls an interface with the control unit 600, and transistors in the input circuit 200 of the infrared detection unit 100. A parallel I / O port 703 that outputs a gate signal to be controlled, and a pulse generation circuit 704 that outputs a control voltage for controlling a transistor in the input circuit 200 of the infrared detection unit 100 are configured. The MPU 701 can store programs and various data in a built-in memory (not shown), and is coupled to a serial data interface 702 and a parallel I / O port 703 via an internal bus 703. Then, the MPU 701 receives a command from the control unit 600 via the serial data interface 702, and applies a current discharge amount (Tr11 (111) to Tr14 (114) gate application as control to the parallel I / O port 703 and the pulse generation circuit 705). Voltage), integration time (time when the control voltage ΦInt is at a high level) and element bias voltage (voltage of the control voltage Vbias) are set. The parallel I / O port 703 includes transistors Tr11 (111), Tr12 (112), Tr13 (113), and Tr14 (114) of the horizontal input circuit 200 selected by the vertical selection line 171 as described in FIG. The gate application voltage and the element bias voltage can be driven in parallel. Similarly, the pulse generation circuit 705 can be controlled by applying a voltage to the gates of the transistors Tr11 (102) and Tr12 (103) of the horizontal input circuit 200 at a predetermined timing.

  6A is an example of the input circuit of the infrared detection unit according to the embodiment of the present invention, and FIG. 6B is a waveform diagram for explaining the operation of the example of the input circuit shown in FIG. 6A. 6A, the charge storage capacitor CMem130 stores a current when the shutter 300 shown in FIGS. 2 and 3 is closed, and the transistors Tr00 (141) to Tr04 (145) are proportional to the current stored in the charge storage capacitor CMem130. The transistors Tr11 (151) to Tr14 (154) are used to discharge current, and the switches SW1 (111) to SW4 (114) in FIGS. 1A and 1B are embodied to adjust the current to be discharged. The transistor Tr15 (155) embodies the switch SW5 (115) in FIGS. 1A and 1B, and is used to charge the charge storage capacitor CMem130 when the shutter 300 shown in FIG. 2 is closed. The operation waveform diagram of the embodiment of the input circuit shown in FIG. 6B is basically the same as that described with reference to FIG. 1B, so that the description thereof is omitted here. However, in FIG. 6B, FIG. 6A only shows the configuration of the input circuit related to the accumulation of signal charges for one selected infrared sensor, and this is also used for the infrared sensors of other input circuits. It is added that the signal reading is repeatedly performed.

Below, the relationship between the discharge amount of the accumulated current and the specific specifications of the input circuit according to the embodiment of the present invention will be described.
FIG. 7 shows the ratio of the current due to the radiation of the imaging object 500 and the current due to the radiation of the shutter 300 when the temperature of the shutter 300 shown in FIGS. 2 and 3 is higher than the temperature of the imaging object 500, and the shutter 300 and the imaging object 500. It is a graph which shows the relationship of the difference of temperature. As can be seen from FIG. 7, when the temperature of the shutter 300 and the temperature of the imaging target 500 shown in FIGS. 2 and 3 are equal, the radiation from both is equal and the current ratio is 1. As can be seen from FIG. 7, when the temperature of the shutter 300 shown in FIGS. 2 and 3 increases and the temperature difference from the imaging object 500 increases, the current ratio decreases. That is, the current that must be discharged is reduced compared to the current stored with the shutter 300 closed. Further, the current ratio decreases as the temperature of the imaging object 500 decreases, and the current that must be discharged decreases.

The condition that the temperature of the shutter 300 shown in FIGS. 2 and 3 is always higher than the temperature of the imaging target 500, but never higher than 30 ° C., and the temperature of the imaging target 500 does not fall below −20 ° C. Then, it can be seen from FIG. 7 that the current that must be discharged is 50% or more of the current when the shutter 300 is closed, and approaches 100% as the temperature of the shutter 300 approaches the temperature of the imaging object 500.
[Input circuit design example 1]
8A and 8B are diagrams illustrating a first design example for realizing specific specifications of the input circuit according to the embodiment of the present invention. That is, in the first design example shown in FIGS. 8A and 8B, the current flowing through Tr00 (141) is the sum of the current flowing through Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145). Designed to be equal. With this design, when the shutter 300 shown in FIGS. 2 and 3 is closed, the gate of the Tr15 (155) shown in FIG. 8A is set to the low level, and the Tr11 (151), Tr12 (152), and Tr13 (153) are set. When the gates of Tr14 (154) are all set to a low level and the current is stored in the charge storage capacitor CMem130, and the shutter 300 shown in FIGS. 2 and 3 is opened and imaging is started, Tr15 (155) shown in FIG. By setting the gate to high level and setting the gates of Tr11 (151), Tr12 (152), Tr13 (153), and Tr14 (154) to high level, it contributes to the discharge of the current accumulated in the charge storage capacitor CMem130. Since the transistor is only Tr00 (141), 50% of the stored current is discharged.

  As shown in FIG. 8B, the ratio of the current that flows when the same voltage is applied to the gates of the transistors Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145) that contribute to the discharge of current is 1: 2: 4: 8. At this time, the current to be discharged can be commanded from the control unit 600 shown in FIGS. 2 and 3 by combining the high and low gates of the transistors Tr11 (151) to Tr14 (154) for adjusting the current discharge amount. . In this example, 50% to 100% of the stored current can be adjusted in 3.3% (= 50% / 15) increments.

By doing so, even if the temperature of the shutter 300 shown in FIGS. 2 and 3 is 30 ° C. higher than the temperature of the imaging object 500, it is possible to prevent excessive charge subtraction.
9 shows the ratio of the current due to the radiation of the imaging object 500 and the current due to the radiation of the shutter 300 when the temperature of the shutter 300 shown in FIGS. 2 and 3 is lower than the temperature of the imaging object 500, and the shutter 300 and the imaging object 500. It is a graph which shows the relationship of the difference of temperature. As can be seen from FIG. 9, when the temperature of the shutter 300 and the temperature of the imaging target 500 shown in FIGS. 2 and 3 are equal, the radiation from both is equal and the current ratio is 1. As can be seen from FIG. 9, if the temperature of the imaging target 500 shown in FIGS. 2 and 3 increases and the temperature difference (absolute value) from the shutter 300 increases, the radiation from the imaging target 500 increases, so that the current The ratio of increases and the current that must be discharged increases. As the temperature of the shutter 300 shown in FIGS. 2 and 3 decreases, the current ratio increases, and the current that must be discharged increases.

Under the condition that the temperature of the shutter 300 is always 0 ° C or higher and the temperature of the imaging target 500 is not higher than 30 ° C higher than the temperature of the shutter 300, the current is discharged up to 1.8 times when the shutter 300 is closed during imaging. It can be seen from FIG.
[Input circuit design example 2]
10A and 10B are diagrams illustrating a second design example for realizing the specific specification of the input circuit according to the embodiment of the present invention. That is, in the second design example shown in FIGS. 10A and 10B, the current flowing through Tr00 (141) is 1.25 of the current added to Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145). Designed to be equal to double. With this design, when the shutter 300 shown in FIGS. 2 and 3 is closed, the gate of the Tr15 (155) shown in FIG. 10A is set to the low level, and the Tr11 (151), Tr12 (152), and Tr13 (153) are set. When all the gates of Tr14 (154) are set to the high level, current is supplied only to Tr00 (141) and stored in the charge storage capacitor CMem130, and the shutter 300 shown in FIGS. 2 and 3 is opened to start imaging. 10A, the gate of Tr15 (155) shown in FIG. 10A is set to the high level, and then the gates of Tr11 (151), Tr12 (152), Tr13 (153), and Tr14 (154) are all set to the low level. All transistors Tr00 (141) to Tr04 (145) shown in FIG. 5 contribute to the discharge of the current stored in the charge storage capacitor CMem130, and 180% of the stored current is discharged.

  As shown in FIG. 10A, the ratio of the current that flows when the same voltage is applied to the transistors Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145) that contribute to the current discharge is 1: 2: 4: 8. At this time, the current to be discharged can be commanded from the control unit 600 shown in FIGS. 2 and 3 by combining the high and low levels of the gates of the transistors Tr11 (151) to Tr14 (154) for adjusting the current discharge amount. it can. In this example, the stored current can be adjusted from 100% to 180% in increments of 5.3% (= 80% / 15).

By doing so, even when the temperature of the imaging target 500 is 30 ° C. higher than the temperature of the shutter 300, the current can be discharged stepwise, so that the luminance accuracy of the image related to the infrared radiation of the imaging target can be improved.
[Input circuit design example 3]
FIG. 11A and FIG. 11B are diagrams showing a third design example for realizing specific specifications of the input circuit according to the embodiment of the present invention. That is, in the third design example shown in FIGS. 11A and 11B, the current flowing through Tr00 (141) is 0.341, although the current flowing through Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145) is added. Designed to be equal to double (= 46/135 times). The ratio of the current that flows when the same voltage is applied to Tr01 (142), Tr02 (143), Tr03 (144), and Tr04 (145) is 1: 2: 4: 8. 11A and 11B, when the shutter 300 shown in FIGS. 2 and 3 is closed, the gate of Tr15 (155) is set to low level, the gates of Tr11 (151) and Tr14 (154) are set to high level, Tr12 (152), the gate of Tr13 (153) is set to low level, a current is passed through Tr00 (141), Tr02 (143), and Tr03 (144), and the current is stored in the charge storage capacitor CMem130. As a result, 100% of current is shared by Tr00 (141) at 46%, Tr02 (143) at 18% (= 2 × 9%), and Tr03 (144) at 36% (= 4 × 9%). Remember.

  When the shutter 300 shown in FIGS. 2 and 3 is opened and imaging is started, the gate of the Tr15 (155) shown in FIG. 11A is set to the high level, and then the transistors Tr11 (151) and Tr12 (152 which contribute to the current discharge) ), Tr13 (153), Tr14 (154) gates are all set to high level, so only the transistor of Tr00 (141) contributes to the current drain, and 46% of the current stored in the charge storage capacitor CMem130 is drained Is done. The gate of Tr15 (155) shown in FIG. 11A is set to high level, and then the gates of transistors Tr11 (151), Tr12 (152), Tr13 (153), and Tr14 (154) that contribute to current discharge are all set to low level. Thus, all the transistors Tr00 (141) to Tr04 (145) for adjusting the current discharge amount contribute to the current discharge, and 181% of the current stored in the charge storage capacitor CMem130 is discharged. By combining the high and low gates of the transistors Tr11 (151) to Tr14 (154) that contribute to the current discharge shown in FIG. 11A, the current discharged from the current stored in the charge storage capacitor CMem130 is reduced from 46%. It can be commanded from the control unit 600 shown in FIGS. 2 and 3 in increments of 9% up to 181%.

  In this way, charge subtraction can be prevented even when the temperature of the shutter 300 is 30 ° C. higher than the temperature of the imaging object 500, and the current is reduced even when the temperature of the imaging object 500 is 30 ° C. higher than the temperature of the shutter 300. Therefore, the luminance accuracy of the image related to the infrared radiation of the imaging target can be improved.

As described above, three design examples for realizing the specific specifications of the input circuit according to the embodiment of the present invention have been shown. However, the number of transistors used for discharging current is not limited to five, and if there are a plurality, the discharge current It is possible to adjust. Further, the ratio of the current flowing through each transistor is not limited to the ratio 1: 2: 4: 8 shown in the above design example. If the number of transistors is increased, the adjustment range can be widened and the resolution can be made finer. However, if the number of transistors is increased, the mounting area of the input circuit is increased and the configuration becomes complicated.
It is important to select an appropriate number according to the design purpose.
[Embodiment 1]
FIG. 12 is a flowchart for explaining the adjustment procedure of the infrared imaging apparatus according to the first embodiment of the present invention. The configuration of the infrared imaging device itself is the same as that shown in FIGS. 2 and 3, and will not be described again here. In step S11 in the adjustment procedure of FIG. 12, it is checked whether the object surface at the lowest temperature has been imaged. If the object surface with the lowest temperature has not been imaged, the process proceeds to step S12. In step S12, control is performed to reduce the discharge current, and the process returns to step S11. If the lowest temperature object surface has been imaged in step S11, the process proceeds to step S13. In step S13, it is checked whether the highest temperature object surface has been imaged. If the object surface with the highest temperature has not been imaged, the process proceeds to step S14. In step S14, control is performed to reduce the accumulated charge, and the process returns to step S13. If the highest temperature object surface has been imaged in step S13, the process proceeds to step S15. In step S15, it is checked whether the highest temperature object surface can be imaged even if the accumulated charge is increased. If the highest temperature object surface can be imaged, the process proceeds to step S16. In step S16, the control to increase the accumulated charge is performed, and the process returns to step S13. If the surface of the hottest object can be imaged in step S13 and if the surface of the hottest object cannot be imaged even if the accumulated charge is increased in step S15, the process proceeds to step S17, and even if the discharge current is increased in step S17, the lowest temperature is reached. It is examined whether the surface of the object can be imaged. If the object surface with the lowest temperature can be imaged, the process proceeds to step S18. In step S18, control is performed to increase the discharge current, the process returns to step S11, and the processes in steps S11 to S16 are executed again. On the other hand, if the lowest temperature object surface cannot be imaged in step S17, the process ends.

  Summarizing the adjustment procedure described above, in the adjustment procedure of the infrared imaging device according to the first embodiment of the present invention, the temperature distribution of the lowest temperature object surface to be imaged is recognized in the imaging screen. Check if it is done. In this case, it is desirable to increase the current discharge amount as much as possible. However, if the shape of the object at the lowest temperature is not correctly captured and the image is as if there is no temperature distribution in that part, the current discharge amount Therefore, the gates of transistors Tr11 (151) to Tr14 (154) are closed and controlled to reduce the discharge current, while the shape of the coldest object is correctly imaged. For example, the current discharge amount is increased and adjusted so that the shape of the object at the lowest temperature is the maximum current discharge amount that can be correctly imaged.

  In this way, in order to investigate the possibility of further improving the S / N, the integration time (the time when the control voltage ΦInt is at a high level) is lengthened, or the element bias voltage (the voltage of the control voltage Vbias) is applied to increase the infrared By increasing the amount of current flowing through the sensor, the signal charge storage amount in the signal charge storage capacitor CInt is increased. The maximum amount of charge that can be stored is limited. If the integration time is lengthened, the amount of stored charge increases and the S / N is improved, but the temperature range that can be imaged is narrowed. Even if the element bias voltage is increased to increase the current flowing through the infrared sensor, the S / N ratio is improved, but the temperature range that can be imaged is similarly reduced. Therefore, it is confirmed whether or not the temperature distribution on the surface of the highest temperature object to be imaged can be recognized in the imaging screen. In this case, it is desirable to improve the S / N by increasing the charge accumulation as much as possible, but when the shape of the highest temperature object is not captured correctly and it is captured as if there is no temperature distribution of that part , Control to reduce charge accumulation, while increasing the charge accumulation amount if the shape of the highest temperature object is correctly imaged, so that the shape of the highest temperature object is the maximum amount of charge accumulation to be correctly imaged Adjust the integration time or device bias voltage. In addition, since the amount of current to be discharged may increase due to the increase in the amount of accumulated charge for improving the S / N, it is necessary to adjust the current discharge amount described above again.

As described above, the infrared imaging device according to the first embodiment of the present invention alternately adjusts the current discharge amount and the charge accumulation amount, so that the charge flowing into the signal charge storage capacitor is offset by adjusting the discharge current amount. In addition, the portion corresponding to the offset is reduced from the electric charge stored in the signal charge storage capacitor, so the integration time is extended, or the device bias voltage is increased to increase the S / V in the range from the lowest temperature to the highest temperature. It is possible to improve the accuracy of display brightness by adjusting N so as to improve.
[Embodiment 2]
FIG. 13 is a schematic diagram showing a basic configuration of an infrared imaging device according to the second embodiment of the present invention, and FIG. 14 is a diagram for explaining an adjustment procedure of the infrared imaging device according to the second embodiment of the present invention. It is a flowchart of. FIG. 15 is a graph for explaining the adjustment width in the adjustment procedure shown in FIG.

  In FIG. 13, the infrared imaging apparatus according to the second embodiment of the present invention is basically the same as the configuration of the infrared imaging apparatus according to the first embodiment shown in FIGS. In the infrared imaging device according to the second embodiment, the control unit 600 acquires the output voltage (output voltage of the input circuit) of each infrared sensor from the signal processing unit 800, calculates the average value thereof, and calculates the average value and a predetermined set value. And the current discharge amount is automatically adjusted so that the average value of the output voltage of the input circuit approaches a predetermined set value. Therefore, the control unit 600 uses a microprocessor, a sequencer, or the like so that the adjustment of the current discharge amount can be executed in a procedure, and the discharge current amount is automatically adjusted by a program or a sequence.

  An example of procedural adjustment of the current discharge amount will be described below. In step S21 in the adjustment procedure of FIG. 14, the infrared detector 100 measures the output voltage of each infrared sensor. The measured output voltage of each infrared sensor is sent to the control unit 600 through the signal processing unit 800. In step S22, the controller 600 calculates the average value of the infrared sensor output voltage. Next, in step S23, it is checked whether the average value is larger than a predetermined set value A. The predetermined set value A is set to a portion where linearity is ensured in the graph showing the relationship between the signal charge accumulation amount and the output voltage of the input circuit (output voltage of the infrared sensor) as shown in FIG. In FIG. 15, the set value A is set in the middle where the vertical width is defined by the predetermined set value B. In the adjustment procedure of FIG. 14, the current so that the average value of the output voltage of the input circuit approaches the set value A. Emissions are adjusted.

  If it is larger than the predetermined set value A in step S23, the process proceeds to step S24. In step S24, it is checked if the absolute value of the difference from the set value A is larger than the set value B. Ends the process and proceeds to step S25 if larger, and in step S25, the current discharge amount is controlled so that the preset set value C is subtracted from the current to be discharged, and the process returns to step S23. And the process after step S23 is performed.

  On the other hand, if it is not larger than the predetermined set value A in step S23, the process proceeds to step S26. In step S26, the average value is checked whether the absolute value of the difference from the set value A is larger than the set value B. If it is not larger, the process ends and if it is larger, the process proceeds to step S27. In step S27, the current discharge amount is controlled to increase the preset value C to the current to be discharged, and the process returns to step S23. And the process after step S23 is performed. Note that, in the above, the set value C serves as a reference for the current discharge amount when the current discharge amount is increased or decreased, and the value of the set value C differs depending on the individual infrared imaging device and is determined individually by the infrared imaging device. .

As described above, the infrared imaging apparatus according to the second embodiment of the present invention is configured to automatically adjust the current discharge amount by executing the adjustment procedure as shown in FIG. In this case, as shown in the graph of FIG. 15, the output voltage of the input circuit does not reflect the charge accumulation amount even if the charge accumulation amount is too large or too small. Therefore, the current discharge amount is automatically adjusted so that the average value of the output voltage of the input circuit falls within the set value B centering on the set value A in the graph of FIG. Reflect it.
[Embodiment 3]
FIG. 16 is a schematic diagram showing the fundamental configuration of an infrared imaging device according to the third embodiment of the present invention, and means for measuring the shutter temperature and means for measuring the temperature of the imaging target (close environmental temperature). Current discharge amount is set from the relationship between the measured shutter temperature and the temperature of the imaging target (neighboring ambient temperature) and the shutter temperature and imaging target temperature shown in the graphs of FIGS. Is configured to automatically adjust.

  That is, the infrared imaging apparatus according to the third embodiment of the present invention shown in FIG. 16 has an infrared detector 100 in order from the imaging target 500 in a housing (not shown) in order to obtain infrared radiation from the imaging target 500. In addition, the shutter 300 and the lens 400 are provided, and the infrared radiation data detected by the infrared detector 100 is signal-processed by the signal processor 800 and displayed on the display (monitor) 900 outside the casing, and a command from the controller 600 is received. From the driving unit 700 that drives and controls the input circuit 200 (see FIG. 1A, etc.) of the infrared detection unit 100, the temperature sensor 760 that detects the temperature of the shutter 300, and the temperature sensor 770 that detects the ambient temperature close to the imaging target 500 A temperature sensor interface unit 750 for inputting the obtained temperature to the control unit 600 is provided. The temperature sensor 770 that detects the environmental temperature in the vicinity of the imaging target 500 is preferably a sensor that can detect the temperature with the imaging target 500 as a target. Then, the control unit 600 sets the conditions of the input circuit 200 of the infrared detection unit 100 based on the temperatures detected by the temperature sensors 760 and 770 through the temperature sensor interface unit 750, that is, switches in the input circuit shown in FIGS. 1A and 1B. SW1 (111) to SW5 (115) on / off, length of accumulation time (integration time), bias voltage, etc. are automatically set and commands are issued to the drive unit 700 to reduce the current discharge amount and charge accumulation amount adjust.

  The automatic adjustment in the infrared imaging apparatus according to the third embodiment of the present invention will be described in detail. When the temperature of the shutter 300 is higher than the temperature of the imaging target 500, it is necessary to reduce the current discharged from FIG. I understand that. The magnitude of the discharged current can be determined from the graph of FIG. For example, when the temperature of the imaging object 500 is 0 ° C. and the temperature of the shutter 300 is 20 ° C., about 60% of the stored current may be discharged with the shutter 300 closed.

  On the contrary, when the temperature of the shutter 300 is lower than the temperature of the imaging target 500, it can be seen from FIG. The magnitude of the discharged current can be obtained from the graph of FIG. For example, when the temperature of the imaging target 500 is 30 ° C. and the temperature of the shutter 300 is 10 ° C., about 1.4 times the current stored by closing the shutter 300 may be discharged.

  The temperature of the shutter, the temperature of the imaging target (close environmental temperature), and the current discharge amount stored by closing the shutter are tabulated and stored in a ROM (Read Only Memory) etc., which is stored in the controller 600. A microprocessor or the like that holds a table (not shown) in a storage device (not shown) and controls the control unit 600 appropriately refers to the table (not shown), and obtains a current obtained from the table (not shown). Set the ON / OFF of transistors Tr11 (151) to Tr14 (154) provided in the input circuit 200 of the infrared detector 100, set the length of the integration time (integration time), bias voltage, etc. Automatic adjustment can be performed by instructing the input circuit 200 of the infrared detection unit 100 via the unit 700.

In summary, the present invention has the following configuration.
(Additional remark 1) The infrared detection part which detects the infrared radiation of imaging object by the infrared sensor array which arranged the input circuit which senses an infrared sensor in the shape of a network, the drive part which drives the input circuit of the infrared detection part, In an infrared imaging device having a control unit that controls a drive unit, a signal processing unit that performs signal processing on the output of the infrared detection unit, and a display unit that displays the output of the signal processing unit as an image,
The input circuit is disposed in front of the infrared detection unit, and stores current stored in the infrared sensor when the shutter that closes only the infrared radiation to be imaged to the infrared sensor is closed. It has a current discharge adjustment means that discharges a constant multiple of the current,
The control unit sends a command for adjusting the current discharge amount adjusting means of the input circuit to the drive unit so that the display S / N reflecting the output of the infrared detection unit is good. An infrared imaging device characterized by the above.

  (Supplementary note 2) The infrared imaging device according to supplementary note 1, wherein the current discharge amount adjusting means includes a plurality of transistors that discharge current so that unnecessary charge accumulation does not occur.

  (Supplementary Note 3) The current discharge amount adjusting means is configured so that gate lengths of a plurality of transistors that discharge current are set to a predetermined ratio so that unnecessary charge accumulation does not occur, and the plurality of transistors are turned on. The infrared imaging device according to appendix 2, wherein the amount of current discharged is adjusted by combining / off.

  (Supplementary Note 4) The control unit obtains an output voltage of the input circuit from the signal processing unit and calculates an average value thereof, and compares the average value with a predetermined set value to compare the output average of the input circuit. The infrared imaging apparatus according to appendix 1, further comprising means for automatically adjusting the amount of discharge current so that the value approaches a predetermined set value.

  (Additional remark 5) It has a means to measure the temperature of the said shutter, and a means to measure the temperature of imaging object, or the environmental temperature close | similar to it, The said control part measures the temperature of the said shutter and the temperature of imaging object, or it The current discharge amount in the current discharge amount adjusting means is extracted by referring to a table using the adjacent environmental temperature as a key, and a command for adjusting the current discharge amount adjusting means of the input circuit is sent to the drive unit. The infrared imaging device according to appendix 1.

(Additional remark 6) The said control part is comprised with a personal computer or a sequencer, The infrared imaging device in any one of Additional remark 1 thru | or 5 characterized by making the said adjustment into a procedure and performing automatically.
(Appendix 7) Checking whether the object surface with the lowest temperature has been imaged, reducing the discharge current if the object surface with the lowest temperature has not been imaged, and imaging the object surface with the lowest temperature For example, if the highest temperature object surface is imaged, and if the highest temperature object surface is not imaged, reducing the accumulated charge, if the highest temperature object surface is imaged, Checking whether the highest temperature object surface can be imaged even if the accumulated charge is increased, and if the highest temperature object surface can be imaged even if the accumulated charge is increased, increasing the accumulated charge, and increasing the accumulated charge. If the highest temperature object surface can be imaged and the highest temperature object surface cannot be imaged, the step of checking whether the lowest temperature object surface can be imaged even if the discharge current is increased, and the discharge current is increased. If it is possible to image the object surface at the lowest temperature, an infrared imaging method comprising the steps of increasing the discharge current and reexamining whether the object surface at the lowest temperature can be imaged.

It is a block diagram which shows the structure of the input circuit of the infrared rays detection part which concerns on embodiment of this invention. It is a wave form diagram for demonstrating operation | movement of the input circuit of the infrared rays detection part which concerns on embodiment of this invention. It is the schematic which shows the fundamental structure of the infrared imaging device which concerns on embodiment of this invention. 1 is a configuration block diagram of an infrared imaging device according to an embodiment of the present invention. It is a block diagram which shows the structure of the infrared detection part which concerns on embodiment of this invention. It is a block diagram which shows the structure of the drive part which concerns on embodiment of this invention. It is a figure which shows the Example of the input circuit of the infrared rays detection part which concerns on embodiment of this invention. It is a wave form diagram explaining the operation | movement of the Example of the input circuit of the infrared rays detection part which concerns on embodiment of this invention. It is a graph which shows the relationship between the ratio of the electric current by the radiation of the imaging object, and the electric current by the radiation of the shutter, and the temperature difference between the shutter and the imaging object when the temperature of the shutter according to the present invention is higher than the temperature of the imaging object. It is a figure which shows the example of an input circuit which concerns on the 1st design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a figure which shows the specification of the example of an input circuit which concerns on the 1st design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a graph which shows the relationship between the ratio of the electric current by the radiation of the imaging object, the electric current by the radiation of the shutter, and the temperature of the shutter and the imaging object when the temperature of the shutter according to the present invention is lower than the temperature of the imaging object. It is a figure which shows the input circuit example which concerns on the 2nd design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a figure which shows the specification of the example of an input circuit which concerns on the 2nd design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a figure which shows the input circuit example which concerns on the 3rd design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a figure which shows the specification of the example of an input circuit which concerns on the 3rd design example for implement | achieving the specific specification of the input circuit which concerns on embodiment of this invention. It is a flowchart for demonstrating the adjustment procedure of the infrared imaging device which concerns on 1st Embodiment of this invention. It is the schematic which shows the fundamental structure of the infrared imaging device which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the adjustment procedure of the infrared imaging device which concerns on 2nd Embodiment of this invention. It is a graph explaining the adjustment width | variety in the adjustment procedure of the infrared imaging device which concerns on 2nd Embodiment of this invention. It is the schematic which shows the principle structure of the infrared imaging device which concerns on 3rd Embodiment of this invention. It is a figure which shows the structure of the input circuit in the infrared rays detection part which concerns on the conventional infrared imaging device. It is a chart figure which shows the operation timing of the input circuit in the conventional infrared rays detection part. It is a figure which shows the fundamental structure of the conventional infrared imaging device. It is a figure which shows the principle of operation of the conventional infrared imaging device. It is a figure which shows the mode before and after the offset removal in the conventional infrared imaging device. It is a figure which shows the structure of the conventional input circuit for autofocus. It is a timing diagram explaining the operation of a conventional autofocus input circuit.

Explanation of symbols

100 Infrared detector
101 Infrared detector (sensor)
102 Reset voltage application transistor
103 Integration time setting transistor
104 Signal charge storage capacitor
108 Bias voltage application transistor
110 Analog memory / subtraction circuit
111 to 115 Current discharge adjustment switch
121 to 125 Current drain contribution transistor
130 Charge storage capacitor
170 Vertical shift register
171 vertical selection line
180 Horizontal shift register
181 Vertical bus
182 output line
200 input circuit
300 Shutter
400 lenses
500 Imaging target
600 Control unit
700 Drive unit
701 MPU (microprocessor system)
702 Serial data interface
703 Internal bus
704 Parallel I / O port
705 Pulse generator
750 Temperature sensor interface
760 Temperature sensor (shutter temperature)
770 Temperature sensor (ambient temperature)
800 Signal processor
900 Display (Monitor)

Claims (5)

An infrared detection unit that detects infrared radiation of an imaging target by an infrared sensor array in which an input circuit that senses an infrared sensor is arranged in a mesh pattern, a drive unit that drives the input circuit of the infrared detection unit, and a control of the drive unit An infrared imaging device having a control unit, a signal processing unit that performs signal processing on the output of the infrared detection unit, and a display unit that displays the output of the signal processing unit as an image.
The input circuit is disposed in front of the infrared detection unit, and stores current that flows through the infrared sensor when a shutter that closes only infrared radiation to be imaged to the infrared sensor is closed. It has a current discharge adjustment means that discharges a constant multiple of the current,
The control unit sends a command for adjusting the current discharge amount adjusting means of the input circuit to the drive unit so that the display S / N reflecting the output of the infrared detection unit is good. An infrared imaging device characterized by the above.   2. The infrared imaging apparatus according to claim 1, wherein the current discharge amount adjusting means includes a plurality of transistors that discharge current so that unnecessary charge accumulation does not occur.   The control unit obtains an output voltage of the input circuit from the signal processing unit and calculates an average value thereof, and compares the average value with a predetermined set value to obtain an average value of the output voltage of the input circuit. The infrared imaging apparatus according to claim 1, further comprising means for adjusting a current discharge amount so as to approach a predetermined set value.   The shutter includes a means for measuring the temperature of the shutter and a means for measuring the temperature of the imaging target or the environmental temperature close thereto, and the control unit measures the measured temperature of the shutter and the temperature of the imaging target or the environmental temperature close thereto. A command for extracting the current discharge amount in the current discharge amount adjusting means by referring to a table using as a key and sending the command to adjust the current discharge amount adjusting means of the input circuit is sent to the drive unit. The infrared imaging device according to 1.   The step of checking whether the object surface with the lowest temperature has been imaged, the step of reducing the discharge current if the object surface with the lowest temperature has not been imaged, and the highest temperature if the object surface with the lowest temperature has been imaged. A step of checking whether the object surface is imaged, a step of reducing the accumulated charge if the object surface of the highest temperature is not imaged, and a step of increasing the accumulated charge if the object surface of the highest temperature is imaged. Even if the highest temperature object surface can be imaged, and if the highest temperature object surface can be imaged even if the accumulated charge is increased, the accumulated temperature is increased and the highest temperature is increased even if the accumulated charge is increased. If the object surface can be imaged and the object surface at the highest temperature cannot be imaged, the step of examining whether the object surface at the lowest temperature can be imaged even when the discharge current is increased, and the lowest temperature even when the discharge current is increased. The body surface imaging possible, infrared imaging method which comprises the steps of increasing the discharge current, the steps to investigate the coldest surface of an object or again it is possible to image pickup, a.