JP5644530B2 - Infrared imaging device - Google Patents

Description

  The present invention relates to an infrared imaging device.

  For example, there is an infrared imaging device including an infrared image sensor in which each pixel is configured by a quantum infrared photodetector such as a quantum well infrared photodetector (QWIP).

Leonard Chen et al., “Overview of advances in high performance ROIC designs for use with IRFPAs”, Proceedings of SPIE, Vol.4028 (2000), pp.124-138

By the way, in the infrared image sensor, if the area of each pixel is reduced in order to achieve high resolution, the signal intensity of each pixel is relatively reduced, and this has caused noise that was not a problem in the past. The S / N ratio (Signal to Noise ratio) decreases.
For example, when there is a luminance distribution in the imaging target, that is, when there is an incident amount distribution in infrared rays incident on the infrared image sensor, this causes noise.

In other words, a part of the infrared light incident on each pixel of the infrared image sensor is converted into heat inside the infrared detection element that constitutes each pixel, and the temperature of the infrared detection element depends on the heat capacity or thermal resistance of the infrared detection element. Will rise.
In the infrared detection element, since the element resistance has temperature dependence, when the element temperature changes, the element resistance changes, and the dark current and the photocurrent change.

  In this case, if there is a variation in the amount of infrared rays incident on each pixel of the infrared image sensor, a temperature difference occurs between the infrared detection elements constituting each pixel. For example, in a pixel where strong light is incident, the temperature of the infrared detection element rises compared to a pixel where weak light is incident, and a temperature difference occurs between the infrared detection elements constituting each pixel. . As a result, a resistance difference occurs between the infrared detection elements constituting each pixel, which affects the dark current and the photocurrent and causes noise.

  Therefore, it is desired to prevent the S / N ratio from being lowered due to a temperature difference between the infrared detection elements constituting each pixel of the infrared image sensor.

The infrared imaging device includes an infrared detection element array including a plurality of infrared detection elements, a compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength that can be detected by the infrared detection elements; A plurality of compensation infrared irradiating units so that the total amount of infrared light from the imaging target and the compensation infrared light incident on each of the plurality of infrared sensing elements is the same within a sensing period for detecting the current flowing through the infrared sensing element. The intensity of the infrared rays for compensation irradiated to each of the infrared detector elements is controlled, and the intensity of the infrared rays detected by each of the plurality of infrared detector elements and each of the plurality of infrared detector elements are irradiated by the infrared irradiation unit for compensation Based on the intensity of the compensating infrared ray, the infrared ray incident on each of the plurality of infrared detection elements from the imaging target Further comprising a control arithmetic unit for determining the degree to requirements.

The infrared imaging device includes an infrared detection element array including a plurality of infrared detection elements, and a compensation infrared that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength other than a wavelength that can be detected by the infrared detection element. Compensation infrared irradiation so that the total amount of infrared light from the imaging object and the compensation infrared light incident on each of the plurality of infrared detection elements is the same within the detection period for detecting the current flowing through the irradiation unit and the infrared detection element. And a control operation unit for controlling the intensity of the compensating infrared ray irradiated to each of the plurality of infrared detection elements by the unit.

  The infrared imaging device includes an infrared detection element array including a plurality of infrared detection elements, a compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength that can be detected by the infrared detection elements; Compensation for irradiating each of the plurality of infrared detection elements by the infrared irradiation unit for compensation so that the total amount of current flowing to each of the plurality of infrared detection elements becomes the same within a detection period for detecting the current flowing to the infrared detection element And controlling the intensity of infrared rays for imaging, and imaging based on the intensity of infrared rays detected by each of the plurality of infrared detecting elements and the intensity of compensating infrared rays irradiated to each of the plurality of infrared detecting elements by the compensating infrared irradiation unit A control operation unit for obtaining the intensity of infrared rays incident on each of a plurality of infrared detection elements from a target. And requirements.

  The infrared imaging device includes an infrared detection element array including a plurality of infrared detection elements, and a compensation infrared that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength other than a wavelength that can be detected by the infrared detection element. The compensation infrared irradiation unit causes each of the plurality of infrared detection elements to have the same total current flowing through each of the plurality of infrared detection elements within the detection period for detecting the current flowing through the irradiation unit and the infrared detection element. It is necessary to include a control calculation unit that controls the intensity of the compensating infrared ray to be irradiated.

  Therefore, according to the present infrared imaging device, there is an advantage that it is possible to prevent the S / N ratio from being lowered due to a temperature difference between the infrared detection elements constituting each pixel of the infrared image sensor.

It is a schematic diagram which shows the structure of the infrared imaging device concerning 1st Embodiment. It is a schematic diagram which shows the structure of the infrared imaging device concerning 1st Embodiment. It is a schematic diagram which shows the structure of the infrared imaging device concerning 1st Embodiment. (A)-(D) are the figures for demonstrating operation | movement of the infrared imaging device concerning 1st Embodiment. (A)-(C) are schematic diagrams which show the structure of the infrared detection element array of the infrared image sensor with which the infrared imaging device concerning 1st Embodiment is equipped. (A), (B) is a schematic diagram which shows the structure of the read-out circuit chip | tip of the infrared image sensor with which the infrared imaging device concerning 1st Embodiment is equipped. It is a schematic diagram which shows the structure of the infrared irradiation part for compensation with which the infrared imaging device concerning 1st Embodiment is equipped. (A), (B) is a schematic diagram which shows the structure of the infrared irradiation part for compensation with which the infrared imaging device concerning 1st Embodiment is equipped. It is a block diagram which shows the structure of the infrared imaging device concerning 1st Embodiment. It is a figure for demonstrating the output conversion circuit of the control calculating part with which the infrared imaging device concerning 1st Embodiment is equipped. It is a figure for demonstrating the compensation infrared intensity determination circuit of the control calculating part with which the infrared imaging device concerning 1st Embodiment is equipped. (A)-(G) are time charts for demonstrating operation | movement of the infrared imaging device concerning 1st Embodiment. It is a figure for demonstrating the effect by the infrared imaging device concerning 1st Embodiment. It is a schematic diagram which shows the structure of the modification of the infrared irradiation part for compensation with which the infrared imaging device concerning 1st Embodiment is equipped. It is a figure for demonstrating the modification of the output conversion circuit of the control calculating part with which the infrared imaging device concerning 1st Embodiment is equipped. It is a figure for demonstrating the modification of the infrared rays intensity determination circuit for compensation of the control calculating part with which the infrared imaging device concerning 1st Embodiment is equipped. It is a schematic diagram which shows the structure of the infrared imaging device concerning 2nd Embodiment. (A)-(C) are the figures for demonstrating operation | movement of the infrared imaging device concerning 2nd Embodiment. It is a schematic diagram which shows the structure of the temperature plate of the infrared irradiation part for compensation with which the infrared imaging device concerning 2nd Embodiment is equipped. It is a schematic diagram which shows the structure of the modification of the infrared imaging device concerning 2nd Embodiment.

Hereinafter, an infrared imaging device according to an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
First, the infrared imaging device according to the first embodiment will be described with reference to FIGS.
As shown in FIG. 1, the infrared imaging apparatus according to the present embodiment includes an infrared image sensor 1, a compensating infrared irradiation unit 2, and a control calculation unit 3. In FIG. 1, reference numerals 37 and 41 denote lenses.

  Here, as shown in FIGS. 5A and 5B, the infrared image sensor includes an infrared detection element array 4 including a plurality of infrared detection elements (pixels) 7 and a plurality of infrared detection elements 7. And a read circuit chip 5 including a read circuit connected to each. The infrared detection element array 4 and the readout circuit chip 5 are connected via a conductive metal bump electrode 6 (here, In bump electrode). That is, the infrared detection element array 4 and the readout circuit chip 5 are joined by flip chip bonding.

  The infrared detection element array 4 is also referred to as a sensor element array, a sensor array, a photoelectric conversion element array, an infrared focal plane array (IRFPA), or a QWIP focal plane array (QWIP-FPA). The infrared detection element 7 is also referred to as a quantum infrared detection element, a photosensitive element, a light receiving element, a sensor element, or a QWIP element. The read circuit chip 5 is also referred to as a read circuit array. The reading circuit is also referred to as a ROIC (readout integrated circuit) or a signal processing circuit.

Here, the infrared detection element array 4 is a two-dimensional infrared detection element array in which a plurality of pixels configured by an infrared detection element 7 that generates a photocurrent according to the amount of incident infrared rays is two-dimensionally arranged. .
Here, the infrared detection element array 4 is a quantum type infrared detection element array including a quantum type infrared photodetector such as QWIP as the infrared detection element 7. For this reason, this infrared image sensor is also called a quantum infrared image sensor.

For example, the quantum well infrared detection element array 4 is configured as follows.
That is, as shown in FIGS. 5B and 5C, the quantum well-type infrared detection element array 4 includes an n-GaAs lower contact layer 9 and an AlGaAs / GaAs multiple quantum well on a GaAs substrate 8. A structure in which an (MQW) layer 10 and an n-GaAs upper contact layer 11 are stacked is provided. In addition, each infrared detection element 7 (each pixel) is separated by a separation groove 12. An In bump electrode 6 is provided on the n-GaAs upper contact layer 11 of each pixel 7. In addition, an In bump electrode 6 as a common electrode is provided on the n-GaAs lower contact layer 9 extending to the side of each pixel 7. The quantum well infrared detecting element array 4 is connected to the readout circuit chip 5 through these In bump electrodes 6.

For example, when the quantum well infrared detecting element array 4 having sensitivity to infrared having a wavelength of about 7 μm is configured, the following configuration may be used.
That is, the n-GaAs lower contact layer 9 and the n-GaAs upper contact layer 11 have a thickness of, for example, about 1 μm, use, for example, Si as an n-type dopant, and a concentration of, for example, about 1 × 10 ¹⁸ cm ⁻³ . Just do it. The AlGaAs / GaAs-MQW layer 10 is formed by alternately stacking 20 layers of i-Al _0.3 Ga _0.7 As layers 13 having a thickness of 40 nm and i-GaAs layers 14 having a thickness of 4 nm. It ’s fine.

The configuration of the infrared detection element array 4 is not limited to this.
The readout circuit chip 5 sequentially reads out the output voltage corresponding to the amount of current that has flowed through each infrared detection element 7 when infrared rays are incident. Here, the readout circuit chip 5 is formed on, for example, a Si substrate. As shown in FIGS. 6A and 6B, a plurality of driving circuits provided for each pixel 7 are provided as the readout circuit 17. A circuit 15 and a switching circuit 16 for sequentially reading the output of each drive circuit 15 are provided. Here, an AD converter 18 is further integrated in the readout circuit chip 5.

The AD converter 18 is also referred to as an analog / digital conversion circuit, an AD conversion circuit, or an AD circuit. The read circuit chip 5 is also referred to as a Si integrated circuit chip.
Here, the plurality of drive circuits 15 are connected to each of the infrared detection elements 7 of the infrared detection element array 4 via the bump electrodes 6. The drive circuit 15 is an integration circuit that integrates the current flowing in the infrared detection element 7 by the incidence of infrared rays over time, converts the current into voltage, and outputs the voltage.

  Here, the drive circuit 15 includes a capacitor 19 (integration capacitor), a switch 20 (transistor) for connecting the capacitor 19 to the infrared detection element 7, and a switch 21 (transistor) for connecting the capacitor 19 to a bias power source. With. That is, the drive circuit 15 includes a switch 20 connected to one side of the infrared detection element 7 via the bump electrode 6, a switch 21 connected to a bias power source, and a capacitor 19 connected to these switches 20 and 21. With. The output terminal 22 is connected to a contact X connecting the terminals of the capacitor 19 and the switches 20 and 21. A common electrode 6 is connected to the other side of the infrared detection element 7.

The switching circuit 16 is connected to the output terminal 22 of each drive circuit 15.
That is, the switching circuit 16 includes a plurality of source follower transistors 23, a plurality of row selection transistors 24, a plurality of row lines 25, a plurality of column lines 26, a plurality of column selection transistors 27, a readout line 28, A load transistor 29, an amplifier 30, a vertical scanning shift register 31, and a horizontal scanning shift register 32 are provided. The output terminal 22 of each drive circuit 15 is connected to the gate terminal of each source follower transistor 23.

Note that the column line 26 and the readout line 28 are also referred to as output lines. The amplifier 30 is also referred to as a final output stage amplifier, an output amplifier, a voltage buffer, a DC amplifier, or an impedance conversion circuit. The row selection transistor 24 is also referred to as a vertical selection switch. The column selection transistor 27 is also referred to as a horizontal selection switch.
Here, the source follower transistor 23 has the gate terminal connected to the output terminal 22 of the drive circuit 15 and operates according to the output of the drive circuit 15. Note that the drain terminal of each source follower transistor 23 is connected to a power supply (not shown) and is supplied with a power supply voltage.

Each row selection transistor 24 is connected to each of the source terminals of the plurality of source follower transistors 23. Each row line 25 is connected to the gate terminal of the row selection transistor 24 in each row.
Each column line 26 is connected to a source follower transistor 23 via a row selection transistor 24. That is, each column line 26 is connected to the source follower transistor 23 of each column via the row selection transistor 24. Each column selection transistor 27 is connected to each of the plurality of column lines 26. Further, the read line 28 is connected to all the column selection transistors 27.

  The vertical scanning shift register 31 is connected to all the row lines 25, sequentially drives each row line 25, and performs conduction / non-conduction control of the row selection transistor 24 connected to each row line 25. Yes. The horizontal scanning shift register 32 is connected to all the column selection transistors 27 and sequentially drives each column selection transistor 27 to control conduction / non-conduction of each column selection transistor 27.

One of the read lines 28 is connected to the output terminal _VOUT through the amplifier 30, and the other is connected to the ground potential (GND) through the load transistor 29.
When a pixel selection signal is input from the control calculation unit 3 and the row line 25 is selected by the vertical scanning shift register 31, the row selection transistor 24 connected to the selected row line 25 is in a conductive state (ON state). ) When the row selection transistor 24 becomes conductive, an output signal from each infrared detection element 7 (each pixel) is output to the column line 26 via the drive circuit 15, the source follower transistor 23, and the row selection transistor 24.

On the other hand, when a pixel selection signal is input from the control calculation unit 3 and the column selection transistor 27 is selected by the horizontal scanning shift register 32, the selected column selection transistor 27 is turned on (on state). When the column selection transistor 27 becomes conductive, the output signal output to each column line 26 as described above is output to the readout line 28 via the column selection transistor 27. The output signal output to the readout line 28 is output to the output terminal _VOUT via the amplifier 30.

In this embodiment, the AD converter 18 is connected to the output terminal _VOUT of the switching circuit 16, the analog electrical signal that is the output signal from the switching circuit 16 is converted into a digital electrical signal, and the digital electrical signal is read out. The signal is output from the circuit chip 5 to the control calculation unit 3.
By the way, in this embodiment, the infrared image sensor 1 including the infrared detection element array 4 and the readout circuit chip 5 configured as described above has a vacuum container having a window 33A through which infrared rays can enter as shown in FIG. It is installed in a cold shield 34 provided in 33 and is cooled by a cooling system (cooler) 35. That is, the infrared image sensor 1 is a cooling infrared image sensor.

  Furthermore, in order to form an infrared image of the wavelength desired to be imaged on the infrared image sensor 1 among the infrared rays from the imaging target (observation target), the present infrared imaging device only includes the infrared rays of the wavelength desired to be imaged among the infrared rays from the imaging target. A band pass filter 36 and a lens 37 are provided. The infrared rays from the imaging target pass through the band-pass filter 36 and then form an image on the infrared detection element array 4 by the lens 37. The lens 37 is also referred to as an optical lens, a lens system, or an optical system.

By the way, in the infrared image sensor 1, if the area of each pixel 7 is reduced in order to achieve high resolution, the signal intensity of each pixel 7 becomes relatively small. As a result, the S / N ratio decreases.
In particular, in the cooling infrared image sensor 1 including the cooling system, when the number of pixels is increased, the area of each pixel 7 is reduced so as not to increase the volume of the costly cooling unit. N ratio will fall.

For example, when there is an incident amount distribution in the infrared light incident on the infrared image sensor 1, that is, when there is a received light amount distribution in the infrared light received by the infrared image sensor 1, this causes noise.
In other words, a part of the infrared light incident on each pixel 7 of the infrared image sensor 1 is converted into heat inside the infrared detection element constituting each pixel 7, and the infrared detection is performed by the heat capacity or thermal resistance of the infrared detection element 7. The temperature of the element 7 will rise.

Normally, the heat generated in each infrared detecting element 7 is released to the reading circuit chip 5 side via the In bump electrode 6, but the infrared detecting element array 4 and the reading circuit chip are increased as the number of pixels increases. Since the In-buff electrode 6 connected to the semiconductor device 5 is miniaturized, the thermal resistance of this portion also increases. As a result, the temperature of the infrared detection element 7 rises.
Further, when the readout circuit chip 5 having the same function is used due to the reduction in the area of each pixel 7 with the increase in the number of pixels, it is necessary to increase the number of wiring layers. The thermal conductivity tends to decrease, and as a result, the temperature of the infrared detection element 7 increases.

In addition, since the element resistance of the infrared detection element 7 such as QWIP has temperature dependence, the element resistance changes when the element temperature changes, and the dark current and the photocurrent change.
In this case, if there is a variation in the amount of infrared rays incident on each pixel 7 of the infrared image sensor 1, a temperature difference occurs between the infrared detection elements constituting each pixel 7. For example, in the pixel 7 where the strong light is incident, the temperature of the infrared detection element 7 is increased compared to the pixel 7 where the weak light is incident, and a temperature difference is generated between the infrared detection elements.

  As a result, a resistance difference is generated between the infrared detection elements constituting each pixel 7, which affects the dark current and the photocurrent and causes noise. Thereby, when there is a luminance distribution in the imaging target, the S / N ratio is reduced as compared with the case where a uniform temperature surface is observed. That is, if the intensity of infrared rays incident on each pixel 7 of the infrared image sensor 1 varies in the plane, the S / N ratio is lowered.

Therefore, in order to suppress the occurrence of a temperature difference between the infrared detection elements constituting each pixel 7 of the infrared image sensor 1, the infrared imaging device includes a plurality of infrared detection elements 7 provided in the infrared detection element array 4. Each is provided with a compensating infrared irradiation unit 2 that emits a compensating infrared ray.
Then, as will be described later, the compensating infrared irradiation unit 2 causes the total amount of infrared light incident on each of the plurality of infrared detection elements 7 to be the same within a detection period in which a current flowing through the infrared detection element 7 is detected. The intensity of the compensating infrared ray irradiated to each of the plurality of infrared detecting elements 7 is controlled.

For example, by irradiating the compensation infrared ray by the compensation infrared irradiating unit 2 to a pixel whose intensity of the infrared ray from the imaging target is weak and the total amount of infrared rays incident on the infrared detection element 7 is small during the detection period, The total amount of infrared light incident on each infrared detection element 7 during the detection period is made constant.
In the present embodiment, a compensation infrared irradiation unit 2 that irradiates a compensation infrared having a wavelength that can be detected by the infrared detection element 7 is provided.

Specifically, the compensating infrared irradiating unit 2 includes a light emitting element array 38 including a plurality of light emitting elements 39 that emit compensating infrared rays, an array drive circuit chip 40 connected to the light emitting element array 38, a lens 41, and the like. And the half mirror 42.
The light emitting element 39 is also referred to as an infrared source or a compensation light source. The light emitting element array 38 is also referred to as an infrared source array or a compensation light source array. The lens 41 is also referred to as an optical lens, a lens system, or an optical system. The half mirror is also called an optical system. The array drive circuit chip 40 is also referred to as a Si integrated circuit chip.

Here, in the light emitting element array 38, the light emitting elements 39 are provided corresponding to the plurality of infrared detection elements 7. The light emitting element array 38 has the same element arrangement as the infrared detecting element array 4, and each element 39 constituting the light emitting element array 38 and each element 7 constituting the infrared detecting element array 4 are in a one-to-one relationship. It comes to correspond to.
Here, the light emitting element array 38 is an LED array including a plurality of LEDs (Light emitting diodes) that emit compensating infrared rays. In this embodiment, since the band-pass filter 36 that transmits only the infrared ray having the wavelength to be imaged among the infrared rays from the imaging target is used, the infrared ray having the same wavelength as the infrared ray having the wavelength that passes through the band-pass filter 36 is emitted. An LED array 38 having a plurality of LEDs 39 is used.

  Specifically, as shown in FIG. 7, the semiconductor device has a compound semiconductor stacked structure 44 formed on the compound semiconductor substrate 43, and each LED 39 (each element) is separated by a separation groove 45. A bump electrode 46 is provided on the contact layer of each element 39, and a bump electrode 47 as a common electrode is provided on the contact layer extending to the side of each element 39. Yes. The LED array 38 is connected to the array drive circuit chip 40 via these bump electrodes 46 and 47.

  The array drive circuit chip 40 is for driving the light emitting element array 38. The array drive circuit chip 40 is formed on, for example, a Si substrate 48 and includes an array drive circuit 49 and a plurality of PWM (Pulse width modulation) circuits 50 provided for each light emitting element 39. The plurality of PWM circuits 50 are connected to the respective light emitting elements 39 of the light emitting element array 38 via the bump electrodes 46. That is, the light emitting element array 38 and the array drive circuit chip 40 are joined by flip chip bonding.

As described above, the array driving circuit chip 40 includes the PWM circuit 50 for each light emitting element 39, and each PWM circuit 50 is driven by the array driving circuit 49, so that each PWM circuit 50 increases the light emission intensity for each light emitting element 39. It can be controlled.
Here, as shown in FIG. 8A, a pixel selection signal is input to the array drive circuit 49 from a timing control circuit 65 included in the control calculation unit 3 described later, and the control calculation unit 3 described later. The compensation infrared intensity setting value of each pixel 7 read out from the memory circuit 63 included in is input. The array drive circuit 49 outputs the compensation infrared intensity setting value for the pixel to the PWM circuit 50 connected to the selected pixel.

  The PWM circuit 50 includes a PWM conversion circuit 51 and an LED drive circuit 52 as shown in FIG. The PWM circuit 50 performs PWM conversion on the compensation infrared intensity setting value from the array drive circuit 49 by the PWM conversion circuit 51 and outputs the PWM converted signal to the LED 39 by the LED drive circuit 52. In this way, the LED 39 is driven. The LED drive circuit 52 is also referred to as a light emitting element drive circuit.

  As shown in FIG. 3, the compensating infrared rays emitted from the light emitting elements 39 constituting the light emitting element array 38 of the compensating infrared irradiation unit 2 configured as described above pass through the lens 41 and are half mirrors. Each of the infrared detection elements 7 constituting the infrared detection element array 4 is reflected by 42 and irradiated. On the other hand, the infrared rays from the imaging target pass through the band-pass filter 36 and the lens 37, pass through the half mirror 42, and enter the infrared detection elements 7 together with the compensation infrared rays.

By the way, as shown in FIG. 9, the infrared imaging apparatus processes an output signal from the readout circuit chip 5 and performs various controls including control for the compensating infrared irradiation unit 2, and an imaging unit. And a monitor 60 for displaying the processed image.
In the present embodiment, the control arithmetic unit 3 compensates infrared rays so that the total amount of infrared rays incident on each of the plurality of infrared detection elements 7 is the same during a detection period in which a current flowing through the infrared detection element 7 is detected. The irradiation part 2 controls the intensity of the compensating infrared rays irradiated to each of the plurality of infrared detection elements 7. The control calculation unit 3 is configured by a computer or a controller.

In this way, by making the total amount of infrared rays incident on each infrared detection element 7 within the detection period equal, the total amount of heat received by each infrared detection element within the detection period becomes the same, and the infrared detection element It is possible to prevent the temperature difference between the seven.
Here, as shown in FIG. 2, when there is a variation in the intensity of infrared rays incident on each of the plurality of infrared detection elements 7 from the imaging target within the detection period, the total of infrared rays incident on each of the infrared detection elements 7 is different. The intensity of the compensation infrared rays irradiated to each of the infrared detection elements 7 is controlled by the compensation infrared irradiation unit 2 so that the light amount becomes a target value.

Here, the target value is set to an allowable value of the infrared detecting element 7, that is, an arbitrary value within the full range of the infrared detecting element 7. The target value is also referred to as a reference value, a constant value, or a total amount adjustment reference amount.
As a result, the total amount of infrared light incident on each of the infrared detection elements 7 is within a certain range near the target value or the target value. That is, the total amount of infrared light incident on each of the infrared detection elements 7 within the detection period is the same or substantially the same, that is, the total amount of infrared light becomes uniform within the surface of the light receiving region of the infrared detection element array, It is possible to prevent a temperature difference from occurring between the infrared detection elements 7. As a result, it is possible to prevent a resistance difference from occurring between the infrared detection elements 7, and thus it is possible to prevent the S / N ratio from being lowered.

  For example, when the intensity of the compensating infrared light is controlled using an LED, the intensity of the compensating infrared light does not need to be statically changed, and the LED is blinked at a period sufficiently shorter than the sensing period to within the sensing period. It is sufficient to control the total amount of light. Note that the detection period is included in the imaging frame period. That is, the imaging frame period includes a detection period and a reading period. Note that the imaging frame period is also referred to as an imaging frame or a frame.

In addition, the total amount of infrared light incident from the imaging target is obtained as follows.
Here, as shown in FIG. 4A, it is assumed that the total amount of infrared light incident from the imaging target for each imaging frame changes with time in a certain pixel. Note that the numbers in FIG. 4A indicate frame numbers.

Immediately after the activation of the infrared imaging device, the compensating infrared irradiation unit 2 is not used to irradiate the compensating infrared ray, and therefore the pixel 7 is incident upon imaging of the first frame as shown in FIG. The total amount of infrared light is the total amount of infrared light incident from the imaging target.
Next, as shown in FIGS. 4B and 4C, the amount of deviation between the total amount of infrared light incident on the pixel 7 and the target value when the first frame is imaged, that is, when the first frame is imaged. The compensation infrared irradiation unit 2 emits a compensation infrared ray having a light amount corresponding to the difference between the total amount of infrared rays incident on the pixel 7 and the target value.

Here, as the target value, a value obtained by subtracting a margin corresponding to a change in the amount of infrared light from the imaging target that is expected to change in one frame from the full range in which the infrared detection element 7 operates normally is set. desirable.
Similarly, at the time of imaging after the third frame, the compensation infrared irradiating unit 2 irradiates the compensation infrared irradiation unit 2 with the amount of light corresponding to the difference between the total amount of infrared light incident from the imaging target and the target value in the immediately preceding frame. .

In this case, at the time of imaging from the second frame onward, the total amount of infrared light incident from the imaging target can be obtained by the following equation, and based on this, the image captured on the monitor 60 can be displayed.
The total amount of infrared light incident from the imaging target = the total amount of infrared light detected by the pixel−the total amount of infrared light for compensation irradiated from the compensation infrared irradiation unit In the above case, the infrared light detected by the pixel 7 in all frames The total amount of infrared light, that is, the total amount of infrared light incident on the pixel 7 from the imaging target and the compensating infrared irradiation unit 2 is near the target value. Therefore, here, the conversion characteristic of the AD converter 18 that converts the total amount of infrared light (analog signal) detected by the pixel 7 into a digital signal is a non-linear curve characteristic as shown in FIG. It is fine and rough. That is, the quantization delimiter of the AD converter 18 is fine near the target value, and rough elsewhere. By using such conversion characteristics as the conversion characteristics of the AD converter 18, high resolution can be obtained over the full range. In other words, by giving a fine resolution near the target value, the output from the pixel 7 that is near the target value in all frames can be converted into a digital signal with high resolution, and the change in the intensity of infrared rays from the imaging target for each frame is assured. Can be detected.

In the present embodiment, the control calculation unit 3 is based on the intensity of the infrared rays detected by each infrared detection element 7 and the intensity of the compensation infrared ray irradiated to each infrared detection element 7 by the compensation infrared irradiation unit 2. Thus, the intensity of the infrared light incident on each infrared detecting element 7 is obtained.
Here, the control calculation unit 3 obtains a difference between the intensity of the infrared rays detected by each infrared detection element 7 and the intensity of the infrared rays for compensation irradiated to each infrared detection element 7 by the compensation infrared irradiation unit 2. The intensity of infrared rays incident on each infrared detection element 7 from the object is obtained.

Specifically, as shown in FIG. 9, the control calculation unit 3 includes an output conversion circuit 61, a compensating infrared intensity determination circuit 62, a memory circuit 63, a display circuit 64, and a timing control circuit 65. Configured as a thing.
The control calculation unit 3 is also referred to as a control calculation circuit. The output conversion circuit 61 and the compensating infrared intensity determination circuit 62 are also referred to as an arithmetic circuit. The output conversion circuit 61, the compensating infrared intensity determination circuit 62, the memory circuit 63, and the display circuit 64 are also referred to as signal processing circuits. The timing control circuit 65 is also referred to as a control circuit or a controller.

Here, the output conversion circuit 61 uses the compensation infrared intensity setting value of each pixel 7 stored in the memory circuit 63 as the output signal of each pixel 7 from the readout circuit chip 5 of the infrared image sensor 7. This is converted into an output signal of each pixel 7 corresponding to the intensity of infrared rays incident on each pixel 7 from the imaging target.
Here, the output conversion circuit 61 reads the AD conversion value (digital signal value) of each pixel converted by the AD converter 18 included in the reading circuit chip 5 and converts it into a conversion characteristic (here, shown in FIG. 10). And a circuit that outputs the signal corresponding to the intensity of the infrared light incident on each pixel 7. In this case, the signal corresponding to the intensity of the infrared light incident on each pixel 7 is a combination of the signal corresponding to the intensity of the infrared light from the imaging target and the signal corresponding to the intensity of the compensating infrared light from the compensating infrared irradiation unit 2. It is a thing.

  Then, as shown in FIG. 10, the output conversion circuit 61 calculates the intensity of the infrared light incident on each pixel 7 described above and the compensation infrared intensity setting value applied to each pixel 7 read from the memory circuit 63. The difference is obtained, and a signal corresponding to the intensity of the infrared light incident on each pixel 7 from the object to be imaged is obtained. A signal corresponding to the intensity of infrared light incident on each pixel 7 from the imaging target thus obtained is referred to as an output of each pixel 7 after conversion.

As shown in FIG. 9, the compensation infrared intensity determination circuit 62 uses the compensation infrared irradiation unit 2 to output each pixel 7 based on the output of each pixel 7 converted by the output conversion circuit 61 and the target infrared intensity value. The intensity of the compensation infrared ray to be irradiated to the laser beam is determined, and the determined compensation infrared ray intensity setting value is stored in the memory circuit 63.
Here, as shown in FIG. 11, the compensation infrared intensity determination circuit 62 calculates the difference between the output of each pixel 7 converted by the output conversion circuit 61 and the target infrared intensity value by the compensation infrared irradiation unit 2. The intensity of the compensation infrared ray irradiated to the pixel 7, that is, the compensation infrared intensity setting value is determined.

As shown in FIG. 9, the memory circuit 63 stores the compensation infrared intensity setting value for each pixel determined by the compensation infrared intensity determination circuit 62.
The display circuit 64 is a circuit that converts the output of each pixel 7 obtained by the output conversion circuit 61 in order to display the captured image on the monitor 60, and is, for example, a format conversion circuit or a DA conversion circuit. .

The timing control circuit 65 includes an output conversion circuit 61 of the control calculation unit 3, a compensation infrared intensity determination circuit 62, a memory circuit 63 and a display circuit 64, a readout circuit chip 5 of the infrared image sensor 1, and a compensation infrared irradiation. A pixel selection signal is output as a control signal to the array drive circuit chip 40 of the section 2 at a predetermined timing.
In the infrared imaging apparatus configured as described above, the following processing is performed.

In the infrared imaging device, the output (AD conversion value) of each pixel 7 is switched by sequentially switching the pixel selection signal output from the timing control circuit 65 within the reading period of one frame including the detection period and the reading period. Are sequentially read and processed.
Here, an example in which the output of i pixels is read and processed in the j frame and the j + 1 frame will be described with reference to FIG.

First, as shown in FIG. 12A, when the output of the i pixel is read in the j frame, the timing control circuit 65 outputs a control signal for selecting the i pixel as the pixel selection signal. The period during which the control signal for selecting the i pixel is output is the readout period for reading the output of the i pixel.
Next, as shown in FIG. 12B, the output conversion circuit 61 converts the i pixel AD converted by the AD converter 18 included in the readout circuit chip 5 based on the control signal for selecting the i pixel. The conversion value is read out, converted based on the conversion characteristics as shown in FIG. 10, and output as a signal corresponding to the intensity of the infrared light incident on the i pixel. Note that the signal corresponding to the intensity of the infrared light incident on the i pixel is denoted by reference numeral (1) in FIG.

  In this example, as shown in FIG. 12C, the compensation infrared irradiating unit 2 includes a compensation infrared ray having an intensity based on the compensation infrared intensity setting value of the i pixel stored in the memory circuit 63. It is assumed that the i pixel is irradiated by the LED 39 provided at a position corresponding to the i pixel. For this reason, the signal corresponding to the intensity of the infrared ray incident on the i pixel is a signal corresponding to the intensity of the infrared ray from the imaging target and a signal corresponding to the intensity of the infrared ray from the LED 39 provided at the position corresponding to the i pixel. Are combined. In FIG. 12C, reference numeral (2) is added to the compensation infrared intensity setting value for i pixel, that is, the intensity of the compensation infrared radiation emitted from the compensation infrared irradiation unit 2 based on this. Yes.

  Next, the output conversion circuit 61 reads the compensation infrared intensity setting value for i pixel from the memory circuit 63. Then, as shown in FIG. 12D, the difference between the signal corresponding to the intensity of the infrared light incident on the above-described i pixel and the compensation infrared intensity setting value of the i pixel read from the memory circuit 63 is obtained, and imaging is performed. A signal corresponding to the intensity of infrared rays incident on the i pixel from the object, that is, the output of the converted i pixel is obtained. Note that the converted i pixel output is denoted by reference numeral (3) in FIG.

  Thus, the output of the i pixel obtained by the output conversion circuit 61 is sent to the display circuit 64 and displayed on the monitor 60. That is, as shown in FIG. 12F, the output of the i pixel output from the output conversion circuit 61 in the previous j-1 frame is output by the output of the i pixel output from the output conversion circuit 61 in the current j frame. Will be replaced and displayed on the monitor 60. Note that the output of the i pixel output from the output conversion circuit 61 in the current j frame is again replaced by the output of the i pixel output from the output conversion circuit 61 in the next j + 1 frame. In FIG. 12F, reference numeral (5) is attached to the output of the i pixel.

  Next, as shown in FIG. 12E, the compensation infrared intensity determination circuit 62 sets the difference between the output of the i pixel from the output conversion circuit 61 and the target infrared intensity value to a position corresponding to the i pixel. This is determined as the intensity of the compensating infrared ray that is emitted to the i pixel by the LED 39 provided. The determined compensation infrared intensity setting value is stored in the memory circuit 63. The target infrared intensity value is indicated by reference numeral (7) in FIG. 12E, and the determined infrared intensity value for compensation is indicated by reference numeral (4) in FIG. 12E. That is, the compensation infrared intensity setting value for i pixel determined in the previous j−1 frame is rewritten with the compensation infrared intensity setting value for i pixel determined in the current j frame, and stored in the memory circuit 63. Update the compensation infrared intensity setting value of i pixel.

  Next, the updated infrared intensity setting value for i pixel stored in the memory circuit 63 is input to the array drive circuit chip 40 of the infrared irradiation unit 2 for compensation. Then, as shown in FIG. 12G, the signal PWM-converted by the PWM circuit 50 connected to the i pixel is output by the LED drive circuit 52 to the LED 39 provided at the position corresponding to the i pixel. The As a result, the LED 39 provided at the position corresponding to the i pixel is driven, and the i-pixel is irradiated with the compensation infrared ray having an intensity based on the updated compensation infrared intensity setting value of the i-pixel.

Therefore, according to the infrared imaging device according to the present embodiment, it is possible to prevent the S / N ratio from being lowered due to a temperature difference between the infrared detection elements constituting each pixel 7 of the infrared image sensor 1. There is an advantage that you can. In particular, a high-resolution infrared imaging device in which each pixel 7 is fine can be realized while maintaining a high S / N ratio.
Further, as described above, by making the total amount of infrared light incident on each infrared detection element 7 within the detection period the same, the total amount of current flowing through each infrared detection element 7 within the detection period is the same. Thus, the total potential accumulated in the capacitor 19 in the readout circuit chip 5 connected to each infrared detection element 7 is also the same. For this reason, it is possible to prevent the S / N ratio from being lowered due to fluctuations in power consumption inside the readout circuit chip 5.

That is, if there is a variation in the total amount of infrared light incident on each infrared detection element 7 within the detection period, the total amount of current flowing through the circuits in the readout circuit chip 5 also varies.
As shown in FIG. 13, in the readout circuit chip 5, the current flowing through each pixel (infrared detecting element) 7 provided in the sensor array 4 is integrated for a certain time by the capacitor 19 provided in the integration circuit 15, and then the impedance conversion circuit. 30 is converted into a digital signal by the AD converter 18 and output. For example, see Libin Yao, “CMOS readout circuit design for infrared image sensors”, Proc. Of SPIE, Vol. 7384, 73841B (2009).

The impedance conversion circuit 30 and the AD converter 18 are not provided in each of the pixels 7 but are switched by the switching circuit 16 (multiplexer) so that the output signals from the pixels 7 are sequentially read out sequentially. ing.
In this case, if the total amount of current flowing through each pixel 7 varies, the total potential accumulated in the capacitor 19 connected to each pixel 7 also varies, and the circuit after the switching circuit 16 corresponds to a different potential for each pixel. Thus, charging / discharging is repeated. As a result, the power consumption inside the reading circuit chip 5 fluctuates, which causes noise, and the S / N ratio decreases.

  In the cooled infrared image sensor, the readout circuit chip 5 is installed in the cooling system 35, and the subsequent circuits are installed outside. In this case, it is difficult to make the wiring for connecting the external power source to the readout circuit chip 5 a low resistance wiring because of heat conduction. That is, a thin electric wire is used for wiring for connecting an external power source to the readout circuit chip 5 in order to reduce heat conduction. For example, see Mark D. Nelson et al., “General noise processes in hybrid infrared focal plane arrays”, OPTICAL ENGINEERING, Vol. 30, No. 11, pp.1682-1700, November 1991. For this reason, when the power consumption (current consumption) inside the read circuit chip 5 fluctuates, the power supply voltage inside the read circuit chip 5 tends to fluctuate due to the impedance of the wiring portion, which causes noise. The S / N ratio will decrease.

  On the other hand, as described above, by making the total amount of infrared light incident on each infrared detection element 7 within the detection period equal, the total amount of current flowing through each infrared detection element 7 within the detection period can be reduced. Can be the same. As a result, the total potential accumulated in the capacitor 19 in the readout circuit chip 5 connected to each infrared detection element 7 is also the same, so that the S / N is caused by fluctuations in the power consumption inside the readout circuit chip 5. It can prevent that ratio falls.

  In the above-described embodiment, in order to prevent the S / N ratio from being lowered due to a temperature difference between the infrared detection elements constituting each pixel 7 of the infrared image sensor 1, the detection period is set. The total amount of infrared light incident on each infrared detecting element 7 is made equal. As a result, since the total amount of current flowing through each infrared detection element 7 during the detection period is the same, it is possible to prevent the S / N ratio from being reduced due to fluctuations in power consumption inside the readout circuit chip 5. can do.

  On the other hand, in order to prevent the S / N ratio from decreasing due to fluctuations in power consumption inside the readout circuit chip 5, the total amount of current flowing through each infrared detection element 7 within the detection period is the same. It should have become. In other words, the control calculation unit 3 causes the compensating infrared irradiation unit 2 to make a plurality of currents flowing through each of the plurality of infrared detection elements 7 within the detection period for detecting the current flowing through the infrared detection element 7. While controlling the intensity | strength of the compensation infrared rays irradiated to each of the infrared detection elements 7, the infrared intensity detected by each of the plurality of infrared detection elements 7 and each of the plurality of infrared detection elements 7 by the compensation infrared irradiation unit 2 The intensity of the infrared rays incident on each of the plurality of infrared detection elements from the imaging target may be obtained based on the intensity of the compensating infrared rays applied to the.

  In this case, in the above-described embodiment, each pixel 7 is irradiated by the compensating infrared intensity determination circuit 62 of the control calculation unit 3 so that the total amount of infrared light incident on each infrared detection element 7 is the same during the detection period. As the target infrared intensity value used to determine the compensation infrared intensity setting value to be used, the same target infrared intensity value is used for all pixels in one frame, and the same target infrared intensity value is used in all frames. As a target value used for determining the compensation infrared intensity setting value to be irradiated to each pixel 7 by the compensation infrared intensity determination circuit 62 of the control calculation unit 3, all the values in one frame are used. The same target value may be used for the pixels, and it is not necessary to use the same target value in all frames. That is, a different target value may be used for each frame. As a result, the total amount of current flowing through each infrared detection element 7 within the detection period can be made the same. In this case, the amount of current flowing to each pixel 7, that is, the compensation applied to each pixel 7 so that the output of each pixel 7 before conversion by the output conversion circuit 61 becomes a target current amount as a target value. This will control the intensity of the infrared.

In the above-described embodiment, the compensation infrared irradiation unit 2 is configured to include the light emitting element array 38, the array drive circuit chip 40, the lens 41, and the half mirror 42. However, the present invention is not limited to this. It is not something that can be done.
For example, instead of the light emitting element array 38 and the array drive circuit chip 40 in the above-described embodiment, the compensating infrared irradiation unit 2 is replaced with a heating resistor element array 70 including a plurality of heating resistor elements 72 as shown in FIG. The band-pass filter 71 may be provided. That is, the compensating infrared irradiation unit 2 is provided corresponding to each of the plurality of infrared detection elements 7, and radiates from the heating resistance element array 70 including the plurality of heating resistance elements 72 that emit infrared rays. A band pass filter 71 that passes only the wavelength of the compensating infrared ray among the infrared rays that have been emitted may be included. Also in this case, it is preferable to include a lens and a half mirror as in the above-described embodiment. The heating resistance element 72 is also referred to as a heater element or a resistance element.

  Specifically, the heating resistor element array 70 is connected to each of the PWM circuits 75 on the surface of a Si integrated circuit substrate including, for example, an array drive circuit 74 and a plurality of PWM circuits 75 on a Si substrate 73. For example, the heating resistance element 72 is formed of a metal thin film or the like. That is, the heating resistor element array 70 is formed on, for example, the Si substrate 73, and includes a plurality of heating resistor elements 72 made of, for example, a metal thin film, and a plurality of PWM circuits 75 connected to the heating resistor elements 72, And an array drive circuit 74. As described above, the heating resistor element array 70 includes the PWM circuit 75 for each heating resistor element 72, and by controlling the current (electric power) flowing through each heating resistor element 72 by the PWM circuit 75, the heating resistor element 72. The temperature can be controlled every time. In this way, by controlling the temperature for each heating resistance element 72, the intensity of infrared rays emitted from the heating resistance element 72 can be controlled for each heating resistance element 72. In this case, the infrared rays radiated from the heating resistor element 72 include infrared rays having a wavelength other than that of the infrared rays incident on the infrared detection element 7 from the imaging target via the band pass filter 36 (see FIG. 3). For this reason, a band pass filter 71 that transmits infrared light having the same wavelength as the infrared light incident on the infrared detecting element 7 from the imaging target via the band pass filter 35 is used. As a result, infrared light having the same wavelength as the infrared light incident on the infrared detecting element 7 from the imaging target via the bandpass filter 35 is transmitted from the compensating infrared irradiation unit 2, that is, from the heating resistor element array 70 via the bandpass filter 71. Thus, it is emitted as a compensating infrared ray.

  In the above-described embodiment, the compensation infrared irradiation unit 2 that emits the compensation infrared radiation having a wavelength that can be detected by the infrared detection element 7 is used. However, the present invention is not limited to this. For example, a compensation infrared irradiation unit that emits compensation infrared light having a wavelength other than the wavelength that can be detected by the infrared detection element may be used. That is, a light-emitting element array including a plurality of light-emitting elements that emit compensating infrared rays having wavelengths other than those that can be detected by the infrared detection elements may be used. For example, a band-pass filter provided between the imaging target and the infrared detection element array, that is, a wavelength other than a wavelength that transmits a band-pass filter that transmits only infrared light having a wavelength to be imaged among infrared rays from the imaging target. You may use the LED array provided with several LED which radiate | emits infrared rays.

In this case, the intensity of the infrared rays detected by each infrared detection element changes depending on the intensity of the infrared rays incident from the imaging target, regardless of the intensity of the compensating infrared ray.
For this reason, the infrared imaging device has a plurality of infrared detection elements arranged by the infrared irradiation unit so that the total amount of light incident on each of the plurality of infrared detection elements is the same within a detection period in which a current flowing through the infrared detection element is detected. What is necessary is just to provide the control calculating part which controls the intensity | strength of the compensation infrared rays irradiated to each. That is, as in the above-described embodiment, the control calculation unit sets the intensity of the infrared rays detected by each of the plurality of infrared detection elements and the intensity of the infrared rays for compensation irradiated to each of the plurality of infrared detection elements by the infrared irradiation unit. Based on this, it is not necessary to obtain the intensity of the infrared light incident on each of the plurality of infrared detection elements from the imaging target.

  In this case, instead of the output conversion circuit 61 in the above-described embodiment, the output conversion circuit corresponds to the output of each pixel from the readout circuit chip of the infrared image sensor, and the intensity of infrared light incident on each pixel from the imaging target. It shall be converted into a signal. That is, the output conversion circuit reads the AD conversion value (digital signal value) of each pixel converted by the AD converter included in the reading circuit chip, and converts it into a conversion characteristic (here, linear conversion characteristic) as shown in FIG. ) To obtain a signal corresponding to the intensity of infrared light incident on each pixel from the imaging target. A signal corresponding to the intensity of infrared light incident on each pixel from the imaging target is referred to as an output of each pixel after conversion.

  Further, the infrared detecting element has no sensitivity to the compensating infrared light having a wavelength other than the wavelength that can be detected by the infrared detecting element. That is, compensation infrared light having a wavelength other than the wavelength that can be detected by the infrared detection element is not absorbed by the infrared detection element. On the other hand, the infrared detection element has sensitivity to infrared rays incident on the infrared detection element from the object to be imaged and is absorbed by the infrared detection element. For this reason, the infrared detecting element is irradiated with a compensating infrared ray having a wavelength other than the wavelength change that can be detected by the infrared detecting element due to the change in temperature of the infrared detecting element caused by the infrared ray from the imaging target entering the infrared detecting element. This is different from the temperature change of the infrared detecting element.

Therefore, in place of the compensation infrared intensity determination circuit 62 in the above-described embodiment, the difference between the output of each pixel converted by the output conversion circuit and the target infrared intensity value is shown in FIG. Conversion is performed using a conversion table (conversion table) having the conversion characteristics as shown, the intensity of the compensation infrared rays irradiated to each pixel is determined by the compensation infrared irradiation unit, and the determined infrared intensity setting value for compensation is stored in the memory It is stored in the circuit. In this case, as a conversion table having conversion characteristics as shown in FIG. 16, the temperature change amount of the infrared detection element with respect to the intensity of infrared having a wavelength that can be detected by the infrared detection element, and the wavelength other than the wavelength that can be detected by the infrared detection element Based on the correspondence relationship between the temperature change amount of the infrared detection element with respect to the intensity of the infrared ray having the wavelength, the intensity of the infrared ray having the wavelength that can be detected by the infrared detection element (element detection infrared intensity) A relationship with the intensity of infrared rays having a wavelength other than the wavelength that can be detected by the infrared detection element (element non-detection infrared intensity) is obtained in advance.
[Second Embodiment]
Next, an infrared imaging device according to the second embodiment will be described with reference to FIGS.

The infrared imaging device according to the present embodiment is different in the configuration of the compensating infrared irradiation unit 2 from the above-described first embodiment and the modifications thereof.
That is, as shown in FIG. 17, the infrared imaging device includes a compensating infrared irradiation unit including temperature plates 80 and 81 that emit infrared rays, a band-pass filter 82, and a micromirror array 83.

Here, the temperature plates 80 and 81 are constant temperature plates that are at a constant temperature.
Here, two temperature plates, that is, a low temperature plate 80 and a high temperature plate 81 are used as the temperature plates. Here, the low temperature plate 80 is a temperature plate having a temperature equal to or higher than the temperature of the infrared detecting element 7. The high temperature plate 81 is a temperature plate having a temperature higher than that of the low temperature plate 80.

  Further, as shown in FIG. 19, the temperature plates 80 and 81 are plates having a good thermal conductivity such as Al, for example, and are attached with a heater 85 and a temperature sensor 86. A temperature control circuit 87 is connected to the heater 85 and the temperature sensor 86, and the temperature control circuit 87 controls the output of the heater 85 based on the detected value from the temperature sensor 86, whereby the temperature plates 80 and 81 are controlled. Can be maintained at a constant temperature. Here, the temperature control circuit 87 controls the output of the heater 85 so that the detection value from the temperature sensor 86 becomes a constant value.

The temperature plates 80 and 81 are also referred to as an infrared source, an infrared radiation source, or a compensation light source. The constant temperature plate is also referred to as a uniform temperature plate or a constant temperature plate. The temperature control circuit 87 is also referred to as a temperature controller.
As shown in FIG. 17, the band pass filter 82 passes only the wavelength of the compensating infrared ray out of the infrared rays radiated from the temperature plates 80 and 81.

Here, as the compensation infrared ray, an infrared ray having a wavelength that can be detected by the infrared detection element 7 may be used as in the first embodiment described above, or as a modification of the first embodiment described above. Infrared rays having wavelengths other than those that can be detected by the infrared detecting element 7 may be used.
When infrared light having a wavelength that can be detected by the infrared detection element 7 is used as compensation infrared light, the bandpass filter 82 includes a bandpass filter 36 (see FIG. 3) provided between the imaging target and the infrared detection element array 4. In other words, the same band pass filter as the band pass filter that transmits only the infrared ray having the wavelength to be imaged among the infrared rays from the imaging target may be used. In this case, the compensating infrared irradiating unit 2 is a compensating infrared irradiating unit that emits a compensating infrared ray having a wavelength that can be detected by the infrared detecting element 7.

  On the other hand, when an infrared ray having a wavelength other than the wavelength that can be detected by the infrared detection element 7 is used as the compensation infrared ray, the bandpass filter 82 is a bandpass filter 36 (between the imaging target and the infrared detection element array). If a band-pass filter different from that shown in FIG. 3 is used, that is, a band-pass filter that transmits infrared light having a wavelength other than the wavelength transmitted by the band-pass filter 36 provided between the imaging target and the infrared detection element array 4. good. In this case, the compensating infrared irradiating unit 2 is an infrared irradiating unit that irradiates a compensating infrared ray having a wavelength other than the wavelength that can be detected by the infrared detecting element 7.

The band pass filter 82 is provided between the temperature plates 80 and 81 and the micromirror array 83. The band pass filter 82 may be provided between the micromirror array 83 and the infrared detection element array 4.
The micromirror array 83 is provided corresponding to each of the plurality of infrared detection elements 7, and includes a plurality of micromirrors 84 that reflect the infrared rays radiated from the temperature plates 80 and 81 toward the infrared detection elements 7. . In addition, as the micromirror 84 which comprises the micromirror array 83, what is disclosed by patent 3512963, for example can be used.

Here, the micromirror array 83 includes a micromirror array 83 such that each micromirror 84 constituting the micromirror array 83 and each infrared detection element 7 constituting the infrared detection element array 4 correspond one-to-one. The infrared detecting element array 4 has the same arrangement configuration.
The micromirror array 83 is connected to a drive circuit (not shown) for driving it. Then, by driving the micromirror array 83 by the drive circuit based on the control signal from the control calculation unit 3, the intensity of the compensating infrared ray irradiated to each infrared detection element 7 can be controlled. .

  Here, as shown in FIG. 18A, the direction of each of the micromirrors 84 constituting the micromirror array 83 is changed to the low temperature plate 80 side and the drive circuit based on the control signal from the control calculation unit 3. By switching to either one of the high temperature plate 81 side, the intensity of the compensating infrared rays irradiated to each infrared detecting element 7 is controlled. Thereby, the total amount of infrared rays incident on each of the plurality of infrared detection elements 7 within the detection period is made the same.

Specifically, the drive circuit includes a PWM circuit for each micromirror 84. Then, the direction of the micromirror 84 is switched according to the on / off state of the pulse signal output from the PWM circuit, and is output from the PWM circuit based on the compensation infrared intensity setting value set by the control calculation unit 3. The width of the pulse signal is adjusted.
Here, FIG. 18B shows a compensation infrared intensity setting value set for each detection period (frame) with respect to a certain pixel, and FIG. 18C shows from the PWM circuit of the drive circuit, The control signal (pulse signal) output to the micromirror corresponding to a certain pixel is shown. Here, when the pulse signal is on, the micromirror 84 faces the high temperature plate 81 side. Therefore, the total time during which the pulse signal is on is the time during which the micromirror 84 faces the high temperature plate 81 side.

  As shown in FIGS. 18 (B) and 18 (C), when the compensation infrared intensity setting value is a large value, that is, when the intensity of the compensation infrared light applied to the infrared detection element 7 is large, the micromirror What is necessary is just to set the width | variety of a pulse signal so that the time for 84 to face the high temperature board 81 side may become long. Conversely, when the compensation infrared intensity setting value is a small value, that is, when the intensity of the compensation infrared ray applied to the infrared detection element 7 is small, it takes a long time for the micromirror 84 to face the low temperature plate 80 side. The width of the pulse signal may be set narrow so that

Thereby, the intensity | strength of the infrared rays for compensation irradiated to each infrared rays detection element 7 is controllable.
Therefore, a pixel selection signal is input from the timing control circuit 65 included in the control calculation unit 3 as a control signal from the control calculation unit 3 to the drive circuit, and the memory circuit 63 included in the control calculation unit 3. The compensation infrared intensity setting value of each pixel 7 read out from is input. The drive circuit adjusts the on / off and pulse width of the pulse signal output from the PWM circuit connected to the selected pixel, and drives each micromirror 84 based on this. Yes.

  In this case, the total amount of infrared light incident on each infrared detection element 7 within the detection period when irradiated with the compensation infrared rays is the total amount of infrared light for compensation from the low temperature plate 80 and the high temperature plate 81. The total amount of infrared light for compensation from is combined. Therefore, by adjusting the ratio of the time that each micromirror 84 constituting the micromirror array 83 faces the low temperature plate 80 side and the time that the micromirror 84 faces the high temperature plate 81 side, the compensating infrared ray Can adjust the total amount of infrared light incident on each infrared detection element 7 within the detection period. As a result, as shown in FIG. 17, even if there is a variation in the total amount of infrared light incident on each infrared detection element 7 within the detection period due to the incidence of infrared light from the imaging target, within the detection period. The total amount of infrared light incident on each of the plurality of infrared detection elements 7 can be made the same.

Since other details are the same as those in the first embodiment, the description thereof is omitted here.
Therefore, according to the infrared imaging device according to the present embodiment, as in the case of the first embodiment described above, a temperature difference is generated between the infrared detection elements constituting each pixel 7 of the infrared image sensor 1. There is an advantage that it is possible to prevent the S / N ratio from being lowered. In addition, a high-resolution infrared imaging device in which each pixel 7 is fine can be realized while maintaining a high S / N ratio.

  In particular, in the present embodiment, the compensation infrared irradiation unit 2 is relatively large as compared with the case where the compensation infrared source is individually provided corresponding to each infrared detection element 7 as in the first embodiment. Become. On the other hand, since infrared rays from the same temperature plates 80 and 81 are irradiated to all infrared detecting elements 7, it is possible to prevent the S / N ratio from being lowered due to variations in the intensity of the compensating infrared rays. can do.

  In the above-described embodiment, the two temperature plates 80 and 81 are used as the temperature plate. However, the present invention is not limited to this. For example, one temperature plate may be used as the temperature plate. In this case, the temperature plate is a temperature plate having a temperature higher than the temperature of the infrared detection element. Then, instead of the two temperature plates of the above-described embodiment, this temperature plate and a region in the apparatus that is at a lower temperature than the temperature plate may be used.

  In the above-described embodiment, the micromirror 84 is driven by a PWM circuit so that the orientation of the micromirror 84 can be alternately switched alternately between the low temperature plate 80 side and the high temperature plate 81 side. However, it is not limited to this. For example, the micromirror may be driven so that the micromirror is oriented toward the low temperature plate during a certain period within the detection period and the high temperature plate during the remaining period.

  In the above-described embodiment, the temperature plate that emits infrared rays is used. However, the present invention is not limited to this, and an infrared lamp 90 may be used instead of this temperature plate as shown in FIG. . In this case, the compensating infrared irradiation unit 2 includes an infrared lamp 90, a bandpass filter 82, and a micromirror array 83 including a plurality of micromirrors 84. Specifically, the compensating infrared irradiation unit 2 includes an infrared lamp 90, a bandpass filter 82, a micromirror array 83, an elliptical lens 91, a compound eye lens structure 92, and a collimating lens 93. It is preferable to do this.

Here, the compound eye lens structure 92 is for uniformizing the intensity of infrared rays emitted from the infrared lamp 90, and has a structure in which a projection lens element group and a condenser lens element group are arranged to face each other. Yes. For example, optical technology information magazine “Light Edge” No. 15 (1998) p. See FIGS. 2-13 and 2-15 of 7-45.
The collimating lens 93 is for making infrared rays from the infrared lamp 90 into parallel light.

In the case of using the compensating infrared irradiating unit 2 configured in this way, the infrared rays emitted from the infrared lamp 90 are condensed by the elliptical lens 91 via the bandpass filter 82 onto the compound eye lens structure 92 to obtain the compound eye lens structure. After the intensity is made uniform at 92, the light is collimated by the collimator lens 93 and guided to the micromirror array 83.
[Others]
Note that the present invention is not limited to the configurations described in the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Infrared image sensor 2 Compensation infrared irradiation part 3 Control operation part 4 Infrared sensing element array 5 Reading circuit chip 6 Bump electrode 7 Infrared sensing element (pixel)
8 GaAs substrate 9 n-GaAs lower contact layer 10 AlGaAs / GaAs multiple quantum well (MQW) layer 11 n-GaAs upper contact layer 12 separation groove 13 i-Al _0.3 Ga _0.7 As layer 14 i-GaAs layer DESCRIPTION OF SYMBOLS 15 Drive circuit 16 Switching circuit 17 Reading circuit 18 AD converter 19 Capacitor (integral capacity)
20, 21 Switch (transistor)
22 output terminal 23 source follower transistor 24 row selection transistor 25 row line 26 column line 27 column selection transistor 28 readout line 29 load transistor 30 amplifier (impedance conversion circuit)
31 Vertical Scan Shift Register 32 Horizontal Scan Shift Register 33 Vacuum Container 33A Window 34 Cold Shield 35 Cooling System 36 Band Pass Filter 37 Lens 38 Light Emitting Element Array (LED Array)
39 Light Emitting Element (LED)
40 Array drive circuit chip 41 Lens 42 Half mirror 43 Compound semiconductor substrate 44 Compound semiconductor laminated structure 45 Separation groove 46, 47 Bump electrode 48 Si substrate 49 Array drive circuit 50 PWM circuit 51 PWM conversion circuit 52 LED drive circuit 60 Monitor 61 Output conversion Circuit 62 Compensation infrared intensity determination circuit 63 Memory circuit 64 Display circuit 65 Timing control circuit 70 Heating resistance element array 71 Band pass filter 72 Heating resistance element 73 Si substrate 74 Array drive circuit 75 PWM circuit 80 Low temperature plate 81 High temperature Plate 82 Bandpass filter 83 Micromirror array 84 Micromirror 85 Heater 86 Temperature sensor 87 Temperature control circuit 90 Infrared lamp 91 Ellipse lens 92 Compound eye lens structure 93 Collimating lens

Claims (8)

An infrared detection element array comprising a plurality of infrared detection elements;
A compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength that can be detected by the infrared detection element;
The compensation infrared irradiation so that the total light quantity of the infrared ray from the imaging target incident on each of the plurality of infrared detection elements and the compensation infrared ray is the same within a detection period in which a current flowing through the infrared detection element is detected. And controlling the intensity of the compensation infrared rays irradiated to each of the plurality of infrared detection elements by the unit, and the intensity of the infrared rays detected by each of the plurality of infrared detection elements and the plurality of infrared rays by the compensation infrared irradiation unit An infrared imaging apparatus, comprising: a control calculation unit that obtains the intensity of infrared rays incident on each of the plurality of infrared detection elements from an imaging target based on the intensity of compensation infrared rays applied to each of the detection elements. An infrared detection element array comprising a plurality of infrared detection elements;
A compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength other than the wavelength that can be detected by the infrared detection element;
The compensation infrared irradiation so that the total light quantity of the infrared ray from the imaging target incident on each of the plurality of infrared detection elements and the compensation infrared ray is the same within a detection period in which a current flowing through the infrared detection element is detected. An infrared imaging device comprising: a control calculation unit that controls the intensity of the compensating infrared ray irradiated to each of the plurality of infrared detection elements by the unit. An infrared detection element array comprising a plurality of infrared detection elements;
A compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength that can be detected by the infrared detection element;
Each of the plurality of infrared detection elements is arranged by the compensating infrared irradiation unit so that the total amount of current flowing through each of the plurality of infrared detection elements is the same within a detection period for detecting the current flowing through the infrared detection element. The intensity of the compensating infrared ray to be irradiated is controlled, the intensity of the infrared ray detected by each of the plurality of infrared detecting elements and the amount of the compensating infrared ray irradiated to each of the plurality of infrared detecting elements by the compensating infrared ray irradiating unit. An infrared imaging apparatus, comprising: a control calculation unit that obtains the intensity of infrared light incident on each of the plurality of infrared detection elements from an imaging target based on intensity. An infrared detection element array comprising a plurality of infrared detection elements;
A compensation infrared irradiation unit that irradiates each of the plurality of infrared detection elements with a compensation infrared having a wavelength other than the wavelength that can be detected by the infrared detection element;
Each of the plurality of infrared detection elements is arranged by the compensating infrared irradiation unit so that the total amount of current flowing through each of the plurality of infrared detection elements is the same within a detection period for detecting the current flowing through the infrared detection element. An infrared imaging apparatus comprising: a control calculation unit that controls the intensity of the compensating infrared ray to be irradiated.   2. The compensation infrared irradiating unit includes a light emitting element array provided with a plurality of light emitting elements that emit compensation infrared rays, corresponding to each of the plurality of infrared detection elements. The infrared imaging device of any one of -4. The compensating infrared irradiator is
A heating resistor element array provided corresponding to each of the plurality of infrared detection elements, and comprising a plurality of heating resistor elements that emit infrared rays; and
The infrared imaging device according to any one of claims 1 to 4, further comprising a band-pass filter that allows only a wavelength of a compensating infrared ray out of the infrared rays radiated from the heating resistor element. The compensating infrared irradiator is
A temperature plate that emits infrared rays;
A band pass filter that passes only the wavelength of the compensating infrared ray out of the infrared ray radiated from the temperature plate;
A micromirror array including a micromirror provided corresponding to each of the plurality of infrared detection elements and configured to reflect infrared rays radiated from the temperature plate toward the infrared detection elements. The infrared imaging device according to any one of 1 to 4. The compensating infrared irradiator is
An infrared lamp that emits infrared rays;
A band-pass filter that passes only the wavelength of the infrared ray for compensation among the infrared rays emitted from the infrared lamp;
A micromirror array including a plurality of micromirrors provided corresponding to each of the plurality of infrared detection elements and reflecting infrared rays emitted from the infrared lamp toward the infrared detection elements; The infrared imaging device according to any one of claims 1 to 4.

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