JP2017135597A - Imaging apparatus, camera and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of acquiring image information in which an afterimage is reduced and which is shorter than a time interval determined by a frame rate, a camera and a vehicle.SOLUTION: An imaging apparatus comprises: M (M≥2) pieces of first wiring; N (N≥1) pieces of second wiring across the M pieces of first wiring; multiple pixels which are provided in an intersection region of the first wiring and the second wiring, each of which includes first and second terminals and of which the first terminal is connected to corresponding first wiring and the second terminal is connected to corresponding second wiring; a first selection circuit for successively selecting K (M>K≥1) pieces of first wiring from one piece of first wiring in the plurality of first wiring and applying a voltage; and a second selection circuit for successively selecting the K pieces of first wiring from the one piece of first wiring after the K pieces of first wiring are successively selected by the first selection circuit, and applying a voltage.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an imaging device, a camera, and a car.

  Since infrared rays have a feature of being more permeable to smoke and fog than visible light, infrared imaging is possible regardless of day or night. In addition, since infrared imaging can also obtain temperature information of a subject, it has a wide range of applications such as surveillance cameras and fire detection cameras in the defense field.

  In recent years, the development of “uncooled infrared imaging devices” that do not require a cooling mechanism has become active. An uncooled type or thermal type infrared imaging device converts incident infrared rays having a wavelength of about 10 μm into heat by an absorption structure, and converts a temperature change of the heat sensitive part caused by the weak heat into an electric signal by a thermoelectric conversion element. The uncooled infrared imaging apparatus obtains infrared image information by reading out the electrical signal. Here, when the incident infrared rays are converted into heat, it is necessary to insulate the absorption structure of the incident infrared rays from the substrate. Usually, the thermal infrared imaging element is supported and operated in the air.

  One index representing the performance of the infrared sensor is NETD (Noise Equivalent Temperature Difference) that expresses the temperature resolution of the infrared sensor. It is important to reduce NETD, that is, to reduce the temperature difference of the infrared detection element corresponding to noise. Further, the thermal infrared detection element has a constant thermal time constant when changing infrared rays to temperature, and cannot follow a subject that changes at high speed. There is a trade-off between pixel sensitivity and thermal time constant. For example, if the heat insulation is increased in order to improve the sensitivity, it becomes difficult for heat to escape and the thermal time constant deteriorates. That is, only an infrared image including an afterimage can be obtained due to the deterioration of the thermal time constant.

  A technique is known in which the afterimage amount of the entire screen is regarded as constant, and the afterimage is reduced by subtracting the image of the immediately preceding frame at a constant rate. However, with this technique, image information shorter than the time interval determined by the frame rate cannot be acquired.

JP 2011-153994 A

  The present embodiment provides an imaging apparatus, a camera, and a car that have few afterimages and can acquire image information that is shorter than a time interval determined by a frame rate.

  The imaging apparatus according to the present embodiment includes M (M ≧ 2) first wirings, N (N ≧ 1) second wirings intersecting the M first wirings, the first wirings, and the first wirings. Provided in a region intersecting with the second wiring, each having a first and second terminal, the first terminal is connected to the corresponding first wiring, and the second terminal is connected to the corresponding second wiring. A first selection circuit for sequentially selecting a plurality of pixels and K (M> K ≧ 1) first wirings from one of the plurality of first wirings and applying a voltage; A second selection circuit for sequentially selecting the K first wirings from the one first wiring and applying a voltage after the K first wirings are sequentially selected by the first selection circuit; ing.

1 is a block diagram illustrating an imaging apparatus according to a first embodiment. FIG. 6 is a diagram for explaining an example of a reading operation in the imaging apparatus according to the first embodiment. FIG. 3 is a circuit diagram illustrating a specific example of a selection circuit in the imaging apparatus according to the first embodiment. FIG. 4 is a waveform diagram for explaining the operation of the selection circuit of one specific example shown in FIG. 3. The top view which shows the infrared rays detection element part which concerns on 1st Embodiment. Sectional drawing of the infrared element part cut | disconnected by the cutting line VV shown in FIG. The figure which shows the relationship between the voltage of a thermoelectric conversion part (pn junction diode), and an electric current. The figure which shows typically the temperature rise of this thermoelectric conversion part when a thermoelectric conversion part receives the pulse-form infrared rays from a heat source. The figure which represents typically the contribution with respect to the image information in the present | current time at the heat | fever which generate | occur | produced in the present flame | frame and the frame immediately before it. The schematic diagram which developed and drawn the past afterimage information in the present frame to the corresponding past time. The block diagram which shows the structure of the digital signal processing part which concerns on 1st Embodiment. FIG. 6 is a circuit diagram showing a selection circuit of an imaging apparatus according to a second embodiment. The perspective view which shows an example of the car provided with the camera carrying the imaging device of 1st or 2nd embodiment. The perspective view which shows the other example of the vehicle provided with the camera carrying the imaging device of 1st or 2nd embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
An imaging apparatus according to the first embodiment is shown in FIG. The imaging apparatus 1 according to the first embodiment includes an infrared detection element unit 10 and a digital signal processing unit 50. Infrared detector unit 10 includes a pixel array 11 having a plurality of heat-sensitive pixels ₁₂ 11 _{to 12 33} which are arranged in a matrix, for example 3 × 3, a row wire _{131-134 3,} signal lines ₁₄ 1 to 14 ₃ Current sources 16 _{1 to} 16 ₃ provided corresponding to the signal lines 14 _{1 to} 14 ₃ , a selection circuit 20 having a first row selection circuit 21 and a second row selection circuit 22, and signal lines 14 ₁ to 14 ₃ . and _{ADC (Analog to Digital Converter) 30} 1 ~30 3 provided corresponding to the 14 _3, and a horizontal selection circuit 40,. In FIG. 1, the thermal pixels are arranged in a 3 × 3 matrix. However, when m and n are natural numbers, they may be arranged in an m × n matrix.

Each thermal pixel 12 _ij (i, j = 1, 2, 3) has at least one PN junction diode, for example. When each thermal pixel 12 _ij (i, j = 1, 2, 3) has a plurality of PN junction diodes, these PN junction diodes are connected in series. That is, each thermal pixel 12 _ij (i, j = 1, 2, 3) is a two-terminal element including an anode side terminal and a cathode side terminal. In FIG. 1, each thermal pixel 12 _ij (i, j = 1, 2, 3) is composed of one PN junction diode.

Same thermal pixels arranged in rows _{12 i1, 12 i2, 12 i3} (i = 1,2,3) is the anode-side terminal is connected to the same row line 13 _i, the row wiring 13 _i is first The first row selection circuit 21 and the second row selection circuit 22 are connected.

The thermal pixels 12 _1j , 12 _2j , 12 _3j (j = 1, 2, 3) arranged in the same column have anode-side terminals connected to the same signal line 14 _j .

Each signal line 14 _j (j = 1, 2, 3) has one end connected to the corresponding constant current source 16 _i and the other end connected to the corresponding ADC 30 _j . The ADCs 30 ₁ to 30 ₃ are connected to the horizontal selection circuit 40. The horizontal selection circuit 40 is connected to the digital signal processing unit 50.

  Next, the reading operation of the thermal pixels arranged in the 3 × 3 matrix shown in FIG. 1 will be described.

Each of the first row selection circuit 21 and the second row selection circuit 22 sequentially selects one row wiring from among a plurality (three in FIG. 1) of row wirings 13 ₁ , 13 ₂ , and 13 ₃ . However, the first row selection circuit 21 and the second row selection circuit 22 select different row wirings.

Selected row wirings by any of the first row selection circuit 21 or the second row selection circuit 22, a bias voltage Vd is applied to the example row wiring 13 _1. The bias voltage Vd to the row wiring 13 ₁ is applied, the constant current If flows through the constant current sources ₁₆ j (j = 1,2,3), the heat-sensitive pixel coupled to the row wiring 13 ₁ selected 12 The forward voltage Vf of the PN junctions ₁₁ , 12 ₁₂ , and 12 ₁₃ is determined. The cathode side terminals of the thermal pixels 12 ₁₁ , 12 ₁₂ , 12 ₁₃ are connected to the vertical signal lines 14 ₁ , 14 ₂ , 14 ₃ , respectively, and the potential thereof is Vd−Vf.

Here, when a bias voltage Vd is applied to the thermal pixels 12 ₁₁ , 12 ₁₂ , and 12 ₁₃ on the row wiring 13 ₁ at a certain time t1, the thermal pixels 12 ₁₁ , 12 ₁₂ , and 12 ₁₃ are used as signals of the subject, respectively. Accordingly, since the temperature Tp (t) is different, each forward voltage Vf, that is, Vd−Vf is also different. The voltage Vd−Vf of the thermal pixels 12 _1j and (j = 1, 2, 3) is input to the ADC 30 _j through the vertical signal line 14 _j and is converted into a digital signal. These digital signals are sequentially read for each column by the horizontal selection circuit 40 and are sent to the digital signal processing unit 50 as serial signals.

Then, the subsequent time, the bias voltage Vd is applied to the thermal pixel _{12 21,} 12 22, _{12 23} on the row wirings 14 _2, corresponding voltage Vd-Vf of the thermal pixels _{12 21,} 12 22, _{12 23} is sent to the vertical signal lines _{14 1,} 14 2, 14 ₃ corresponding through ADC 30 _{1, 30} 2, 30 ₃ is converted into a digital signal, these digital signals are sequentially read out for each column by the horizontal selection circuit 40 A serial signal is sent to the digital signal processing unit 50.

Furthermore, after which the bias voltage Vd to the row thermal pixels ₁₂ 31 on the wiring 13 _3, 12 32, _{12 33} is applied, the heat-sensitive pixels _{12 31,} 12 32, _{12 33} vertical signal line voltage Vd-Vf corresponding to 14 ₁ , 14 ₂ , and 14 ₃ are sent to the corresponding ADCs 30 ₁ , 30 ₂ , and 30 ₃ to be converted into digital signals. These digital signals are sequentially read out by the horizontal selection circuit 40 for each column, And sent to the digital signal processing unit 50.

In the above embodiment, the ADCs 30 ₁ to 30 ₃ and the horizontal selection circuit 40 form a column parallel read circuit.

  In the present embodiment, the selection circuit 20 has two systems as a function of selecting a row. That is, the row selected by the first row selection circuit 21 and the row selected by the second row selection circuit 22 can be selected separately. This will be described with reference to FIG.

  For example, the first row selection circuit 21 selects the fourth row (broken line (1) shown in FIG. 2), and then the second row selection circuit 22 selects the second row (shown in FIG. 2 (1 ′) ) Solid line).

  Next, the first row selection circuit 21 selects the fifth row (broken line (2) shown in FIG. 2), and then the second row selection circuit 22 selects the third row ((2 shown in FIG. 2). ') Solid line).

  The first row selection circuit 21 selects the sixth row (broken line (3) shown in FIG. 2), and then the second row selection circuit 22 selects the fourth row ((3 ′) shown in FIG. 2). solid line).

  As described above, the fourth row is selected again and read out after a time interval corresponding to the selection of the fifth row. Usually, the frame interval is longer than the time until all rows are selected. Thus, in this embodiment, the same row can be selected twice at a time interval shorter than the frame interval.

A specific example of the selection circuit 20 having the first and second row selection circuits 21 and 22 has the configuration shown in FIG. FIG. 3 shows a case where there are m (≧ 2) row wirings. The selection circuit 20 of this specific example includes a first row selection circuit 21, a second row selection circuit 22, and OR gates 24 _{1 to} 24 _m . The first row selection circuit 21 includes a shift register 210 and AND gates 212 _{1 to} 212 _m . The second row selection circuit 22 includes a shift register 220 and AND gates 222 _{1 to} 222 _m .

The shift register 210 has a configuration in which n flip-flops (for example, D-type flip-flops) 210 _{1 to} 210 _m provided corresponding to the row wirings 13 _{1 to} 13 _m are connected in series. The output terminal (Q terminal) of the flip-flop 210 _i-1 is connected to the input terminal (D terminal) of the flip-flop 210 _i (i = 2,..., M). The input terminal of the flip-flop 210 _1, the first row selection start signal IN1 is input. The clock signal VCLK is input to the clock input terminal (CK terminal) of each flip-flop 210 _i (i = 1,..., M). AND gate _{212 i (i = 1, ···} , m) is the output signal OUTA _i of the flip-flop 210 _i to the first input terminal is input, the first enable signal ENA is input to the second input terminal.

The shift register 220 has a configuration in which n flip-flops (for example, D-type flip-flops) 220 _{1 to} 220 _m provided corresponding to the row wirings 13 _{1 to} 13 _m are connected in series. The output terminal (Q terminal) of the flip-flop 220 _i-1 is connected to the input terminal (D terminal) of the flip-flop 220 _i (i = 2,..., M). The input terminal of the flip-flop 220 _1, the second row selection start signal IN2 is inputted. The clock signal VCLK is input to the clock input terminal (CK terminal) of each flip-flop 220 _i (i = 1,..., M). AND gate _{222 i (i = 1, ···} , m) is the first input terminal receives the output signal OUTB _i of the flip-flop 220 _i, the second enable signal ENB is input to the second input terminal.

The OR gate 24 _i (i = 1,..., M) has a first input terminal connected to the output terminal of the AND gate 212 _i, a second input terminal connected to the output terminal of the AND gate 222 _i , and an output. The terminal is connected to the row wiring 13 _i . An output signal OUT _i is output from the output terminal of the OR gate 24 _i (i = 1,..., M).

  Next, the operation of the selection circuit 20 shown in FIG. 3 will be described with reference to FIG.

The signals IN1 and IN2 define the sweep start time of the shift registers 210 and 220, and the signal propagates to the lower flip-flop each time the clock signal VCLK is input. An output set (OUTA _i , OUTB _i ) of flip-flops 210 _i , 220 _i (i = 1,..., M) at each stage of the shift registers 210 and 220 is an AND circuit 212 installed at the subsequent stage thereof. _i and 222 are input to the OR circuit 24 _i at the timing when _i is turned on. The AND circuits 212 _i and 222 _i (i = 1,..., M) pass signals when the enable signals ENA and ENB become high (H) levels, respectively. As shown in FIG. 4, for example, when an output signal OUTA ₁ is a high level of the flip-flop 210 _1, and the enable signal ENA is at the high level, the output signal OUT ₁ of the OR gate 24 ₁ becomes high level . Since the shift registers 210 and 220 always select one of the rows, the set of outputs (OUTA ₁ , OUTB ₁ ) of the flip-flops 210 _i , 220 _i (i = 1,..., M) at each stage. , (OUTA ₂ , OUTB ₂ )... (OUTA _m , OUTB _m ), two signals are always at a high level. However, when two rows are selected at the same time, the pixel array 11 cannot output signals for two rows at the same time. For this reason, the enable signal ENA and the enable signal ENB have complementary pulse timings so that the output signals of two or more rows among the output signals OUT _{1 to} OUT _m of the selection circuit 20 do not become high level simultaneously.

  With this configuration, it is possible to realize the selection circuit 20 that combines and outputs the outputs of the two systems of shift registers 210 and 220 with an OR gate.

Next, the structure of each thermal pixel 12 _ij (i, j = 1, 2, 3) of the infrared detection element unit 10 according to the present embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 shows each thermal pixel 12 _ij (i, j = 1, 2, 3) of the infrared detection element unit 10 according to the present embodiment as the thermal pixel 12 and is a plan view specifically showing the structure of the thermal pixel 12. is there. FIG. 6 is a cross-sectional view of the thermal pixel 12 taken along the cutting line VV shown in FIG.

  The thermal pixel 12 is formed on an SOI substrate. This SOI substrate has a support substrate 110, a buried insulating layer (BOX layer) 115, and an SOI (Silicon-On-Insulator) layer 114 made of silicon single crystal, and a recess 120 is formed on the surface portion. Yes. The thermal pixel 12 includes a thermoelectric conversion unit 161 formed in the SOI layer 114 and a support structure 162 that supports the thermoelectric conversion unit 161 above the recess 120. The thermoelectric converter 161 includes a plurality of (two in FIG. 5 and FIG. 6) pn junction diodes 192 connected in series, a wiring 194 connecting these pn junction diodes 192, and these pn junction diodes 192 and wiring. And an infrared absorption film 191 formed so as to cover 194.

  The support structure 162 includes a connection wiring 162b connected to one end of a series circuit composed of a pn junction diode 192 having one end connected to a corresponding row wiring and the other end connected in series, and an insulating film 162a covering the connection wiring 162b. And.

The infrared absorption film 191 generates heat due to incident infrared rays. The diode 192 converts heat generated in the infrared absorption film 191 into an electric signal. The support structure part 162 is formed in an elongated shape so as to surround the periphery of the thermoelectric conversion part 161. Thereby, the thermoelectric conversion part 161 is supported on the SOI substrate 110 in a state of being substantially insulated from the SOI substrate. By having such a hollow heat separation structure, the thermal pixel 12 can store heat generated according to incident infrared rays and output a voltage based on this heat to the signal line. The bias voltage Vd from the row wiring is transmitted to the diode 192 through the wiring 162b. The cathode side voltage of the diode 192, that is, the signal voltage is transmitted to the signal lines 14 ₁ , 14 ₂ , and 14 ₃ shown in FIG. 1 through the wiring 162b.

  By having such a structure, the thermal pixel 12 can store heat generated according to incident infrared rays and output a voltage based on this heat.

  FIG. 7 is a diagram illustrating the relationship between voltage and current in the pn junction diode 192 of the thermoelectric conversion unit 161 according to the first embodiment. The pn junction diode 192 is used in a region having a forward characteristic in the relationship between the voltage V and the current I, that is, a region having a characteristic in which a current increases when a voltage supplied in the forward direction is increased. A constant current is passed through such a pn junction diode 192 and the change in voltage is measured, thereby functioning as an infrared detection element. For example, as shown in FIG. 7, when infrared light is not received, that is, when the temperature of the pn junction diode 192 is T1, between the anode and the cathode of the pn junction diode 192 when a constant current is passed. Assume that the voltage is V1. When infrared rays are incident on the infrared absorption film 191 that covers the pn junction diode 192, the infrared absorption film 191 generates heat due to the incident infrared rays, whereby the temperature of the pn junction diode 192 rises and becomes T2. Then, as shown in FIG. 7, the IV characteristic of the pn junction diode 192 changes. Under the condition that the constant current Ib flows, the voltage between the anode and the cathode of the pn junction diode 192 after the incidence of infrared rays is, for example, from V1 to V2 (<V1), that is, as shown in FIG. Shift to the voltage side. In this manner, the pn junction diode 192 in the thermoelectric conversion unit 161 converts the temperature change of the pn junction diode 192 due to the heat generated in the infrared absorption film 191 into a voltage change. The bias current of the pn junction diode 192 can be kept constant, and the change in the forward voltage can be extracted as a signal.

  Next, the temperature rise of the thermoelectric conversion part 161 when the thermoelectric conversion part 161 receives infrared rays from a heat source will be considered quantitatively. FIG. 8 is a diagram schematically showing an increase in temperature of the thermoelectric converter 161 when the thermoelectric converter 161 receives infrared rays from a heat source. As shown in FIG. 8, each thermal pixel 12 receives an infrared input that changes with time from the outside. One thermal pixel receives infrared rays of a pulse T (s) Δs or T · δ (s−t) at a certain instant s. Here, Δs is the pulse width, T (s) is the pulse intensity at time s, and δ (s−t) is the delta function.

  The thermal pixel 12 receiving such pulsed infrared rays generates heat of T (s) Δs · exp (s−t) as a response output. The heat generated in one thermal pixel 12 is attenuated exponentially in time, but since infrared pulse input comes in one after another, the heat generated and attenuated in the past in the same thermal pixel is also stored. The This is shown in FIG. 9 when viewed in relation to the imaging frame of the imaging device.

FIG. 9 is a diagram schematically showing the contribution of the heat generated during the current measurement and the measurement immediately before that to the image information at the current time. The information at the time of the current measurement includes the information at the time of the previous past measurement. In FIG. 9, according to the present embodiment, the time interval tf between the previous past measurement time (t1−tf) and the current measurement time (t1) is adjusted to the nine thermal pixels 12 _{11 to} 12 ₃₃ , Divided into 9 equal parts. The heat at the current time t1 includes the heat generated at the past time among the heat signals included in the signal at the current measurement (information A in the current frame in FIG. 9) and the heat signal included at the past measurement ( In FIG. 9, it consists of information (afterimage information) B) in the previous frame. As shown in FIG. 9, the information at the time of the current measurement includes the information B at the time of the previous measurement as an afterimage.

で表される。ここで、τは感熱画素の熱時定数であり、通常１０ｍｓ〜１００ｍｓ程度となる。式（１）は被写体温度Ｔｔ（ｔ）を、指数関数で畳み込み積分した計算結果が熱電変換部１６１の温度Ｔｐ（ｔ）となることを表している。式（１）で表される畳み込み積分は、以下の式（２）に示すように、変形できる。

Here, assuming that the temperature change of the subject at a certain time t is Tt (t) and the temperature change of the thermoelectric converter 161 is Tp (t), the relationship thereof is expressed by the following equation (1).

It is represented by Here, τ is a thermal time constant of the thermal pixel and is usually about 10 ms to 100 ms. Formula (1) represents that the calculation result obtained by convolving and integrating the subject temperature Tt (t) with an exponential function becomes the temperature Tp (t) of the thermoelectric converter 161. The convolution integral represented by the equation (1) can be modified as shown in the following equation (2).

In equation (2), the first term is the contribution from all past times multiplied by exp (−tf / τ), and the second term is information corresponding to the time between the current measurement and the past measurement. . The first term is afterimage information before the past measurement. That is, Equation (2) represents that afterimage information can be removed by subtracting information obtained by multiplying exp (−tf / τ) from information obtained during the previous measurement from information obtained during the current measurement. In other words, the afterimage signal is accurate,
α _th = exp (−tf / τ)
The pixel is included in the ratio represented by.

  FIG. 10 is a schematic representation along the time axis in FIG. 9 including the contribution of the signal (afterimage signal) from the past time. FIG. 10 is a schematic diagram in which the contribution of the equation (1) to the integration, that is, each black circle and white circle drawn on the time t1 axis in FIG. 9 is developed to a past time corresponding to each. In FIG. 10, the shaded portion is infrared information emitted by the subject from the past of −∞ to the current time t1, and the inside of the bold line is subject information that does not include an afterimage obtained in the present embodiment. The subject information not including an afterimage is subject information integrated from reading at time t1-tf of the previous frame to reading at time t1 (current) of the current measurement when attention is paid to a certain pixel.

  The hatched part other than the part surrounded by the thick line is the thermal information included in the past measurement, and constitutes a part of the infrared image information held by the current measurement. In the present embodiment, this afterimage information can be removed by a digital signal processing unit 50 described later.

Furthermore, the part shown with the broken line of FIG. 10 represents the infrared image information immediately before represented by Formula (1). In other words, the image information represented by Expression (1) is output from the infrared detection element unit every time measurement is performed. Equation (1) is the same as the equation representing the output voltage Vout (t) when the signal voltage Vin (t) is input to the RC filter circuit, and the thermal infrared sensor can be regarded thermally as an RC filter circuit. Means that. Assuming that Rth is the thermal resistance of the thermal pixel, this Rth becomes larger as the support structure 162 is thinner and longer. Assuming that Cth is the heat capacity of the thermal pixel, this heat capacity increases as the volume of the thermoelectric converter 161 increases. Thermal time constant τ of thermal pixel is τ = Rth · Cth
It is expressed.

Next, functions of the digital signal processing unit 50 will be described. FIG. 11 is a diagram illustrating a configuration of the digital signal processing unit 50 according to the first embodiment. The serial signal output from the infrared detection element unit 10 is converted from an analog signal to a digital signal in the AD converters 30 ₁ to 30 ₃ to be an image signal. Hereinafter, the image value of the row y and the column x selected by the first row selection circuit 21 is M (x, y), and the image value of the row y and the column x selected by the second row selection circuit 22 is S (x , Y). Since the first row selection circuit 21 operates by several lines more than the second row selection circuit 22, the signal representing the former image value M (x, y) is the latter image value S (x, y). ) Is selected several lines ahead of the signal representing).

  The image value is input into the digital signal processing unit 50. The digital signal processing unit 50 includes a memory 51, a constant multiplier 52, a subtractor 53, a constant multiplier 54, and an output unit 55.

  First, the pixel value M (x, y) of the coordinates (x, y) selected by the first row selection circuit 21 is sequentially stored in the memory 51. The memory 51 only needs to have a capacity for storing the pixel values for several rows selected by the first row selection circuit 21 and read out to the signal lines prior to the operation of the second row selection circuit.

  The constant multiplier 42 multiplies the value M (x, y) stored in the memory 51 by a predetermined constant α. The multiplier α represents an afterimage reduction rate. When one thermal pixel generates an afterimage signal of αth = 30%, for example, if α = 20% (0.2) is set, the afterimage is accurately 0.3-0. .2 = 0.1 (10%).

が残像低減後の画像値として出力部５５から出力される。 Subsequently, the signal value S (x, y) of the pixel selected by the second row selection circuit 22 at the time of the current measurement is stored in the memory 51 in the same row as the pixel selected by the second row selection circuit 22. A value αM (x, y) obtained by multiplying the pixel value M (x, y) of the pixel by a constant α is subtracted by the subtractor 43. As a result, S (x, y) −αM (x, y) is output from the subtracting unit 43. Here, for example, when S (x, y) = 100, M (x, y) = 100, and α = 20%, the calculation result of S (x, y) −αM (x, y) is 80, and the afterimage It becomes lower than the case where no reduction is performed. In order to adjust the luminance, the constant multiplier 54 multiplies the constant 1 / (1-α). This is 1.25 when α = 20%, and the calculation result 80 is restored to 80 × 1.25 = 100. as a result,

Is output from the output unit 55 as an image value after afterimage reduction.

  Even when the infrared detection element unit 10 captures an image of a subject with very strong infrared rays, the temperature rise of the thermoelectric conversion unit 161 is very small, so the thermal time constant τ is always constant. That is, the afterimage signal is constant, and there is almost no problem even if α is set uniformly for all pixels in advance.

As described above, according to the present embodiment, it is possible to provide an imaging apparatus that can acquire image information with less afterimages and shorter than the time interval determined by the frame rate.

(Second Embodiment)
An imaging apparatus according to the second embodiment will be described with reference to FIG. The imaging apparatus according to the second embodiment has a configuration in which the selection circuit 20 is replaced with a selection circuit 20A illustrated in FIG. 12 in the imaging apparatus 1 according to the first embodiment.

The selection circuit 20A includes shift registers 210 and 220, AND gates 212 _{1 to} 212 _m , AND gates 222 _{1 to} 222 _m , and OR gates 24 _{1 to} 24 _{m in the} selection circuit 20 shown in FIG. Instead, the decoders 25 ₁ and 25 ₂ , demultiplexers 26 ₁ and 26 ₂ , and NOR gates 27 _{1 to} 27 _m are newly provided.

The decoders 25 ₁ and 25 ₂ receive the encoded row number signals IN 1 and IN ₂ , respectively, convert them into parallel signals of a plurality of bits, for example, 8 bits, and send them to the demultiplexers 26 ₁ and 26 ₂ . For example, a value such as 15 for the signal IN1 and 156 for the signal IN2 is input, and this specifies the row number. The demultiplexer 26 ₁ outputs a signal value of only the high level (Hi) in the row corresponding to the line number value input of the m output OUTA ₁ ~OUTA _m. The demultiplexer 26 ₂ outputs a signal value of only the high level (Hi) in the row corresponding to the line number value input of the m output OUTB ₁ ~OUTB _m. NOR gate _{27 i (i = 1, ···} , m) performs a NOR operation on the basis of an output OUTA _i of Demaruchipukuresa 26 _1, and the output OUTB _i of Demaruchipukuresa 26 _2, and outputs an output signal OUT _i. The output signal OUT _i (i = 1,..., M) is sent to the corresponding row wiring 13 _i .

  With this configuration, the row selection order that is impossible with the selection circuit 20 including the shift register shown in FIG.

  The afterimage reduction processing described in the first embodiment can be performed by configuring the signals IN1 and IN2 so that the row selected by the signal IN1 is selected again by the signal IN2 after a certain delay.

  Similarly to the first embodiment, the second embodiment can provide an imaging apparatus that has few afterimages and can acquire image information that is shorter than the time interval determined by the frame rate.

  The imaging devices of the first and second embodiments can be used for cameras such as surveillance cameras.

(Third embodiment)
FIG. 13 is a perspective view illustrating an example of a car 600 including the camera 620 on which the imaging device 1 according to the first or second embodiment is mounted. The car 600 includes a camera 620 and a display 630. The camera 620 is provided at the front end of the car 600 and can photograph the front of the car 600. The display 630 is provided in front of the driver's seat of the car 600 and can display an image captured by the camera 620. By confirming an image captured by the camera 620 on the display 630, for example, when parking, a blind spot can be confirmed.

(Eighth embodiment)
FIG. 14 is a perspective view showing another example of a car 700 including a camera 720 equipped with the imaging device of the first or second embodiment. The car 700 includes a camera 720 and a display 730. The camera 720 is provided at the rear end of the car 700 and can photograph the back of the car 700. The display 730 is provided in front of the driver's seat of the car 700 and can display an image captured by the camera 720. By confirming an image captured by the camera 720 on the display 730, the rear side can be confirmed.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

1 imaging apparatus 10 infrared detector unit 11 pixel array 12, 12 _{11-12 33} thermal pixels _{131-134 3} row wirings 14 ₁ to 14 ₃ signal lines 16 ₁ to 16 ₃ current source 20 selection circuit 21 first row selection circuit 22 second row selection circuit 30 ₁ to 30 ₃ ADC (AD converter)
40 horizontal selection circuit 50 digital signal processing unit 51 line memory 52 constant multiplier 53 subtractor 54 constant multiplier 55 output unit

Claims (10)

M (M ≧ 2) first wirings;
N (N ≧ 1) second wirings intersecting the M first wirings;
Provided in the intersection region of the first wiring and the second wiring, each having first and second terminals, the first terminal is connected to the corresponding first wiring, and the second terminal corresponds A plurality of pixels connected to the second wiring;
A first selection circuit that sequentially selects K (M> K ≧ 1) first wirings from one first wiring among the plurality of first wirings and applies a voltage;
A second selection circuit for sequentially selecting the K first wirings from the one first wiring and applying a voltage after the K first wirings are sequentially selected by the first selection circuit;
An imaging apparatus comprising: A readout circuit that reads out the signal value of the corresponding pixel from each of the N second wirings;
A signal processing unit for processing a signal value read by the reading circuit;
The imaging apparatus according to claim 1, further comprising:   The readout circuit selects N conversion circuits that convert analog signal values arranged corresponding to the N second wirings into digital signal values, and digital signal values from the N conversion circuits. The imaging device according to claim 2, further comprising: a third selection circuit that transmits the signal processing unit. The signal processing unit
A memory for storing, as a first acquired pixel value, a signal from the pixel read by the readout circuit of the K first wirings selected by the first selection circuit;
A first multiplier for multiplying the first acquired pixel value stored in the memory by a constant α (0 <α <1);
From the signal value from the pixel read by the readout circuit of the K first wirings selected by the second selection circuit, to the first acquired pixel value corresponding to the pixel, the first multiplier A subtractor for subtracting the value multiplied by the constant α by
A second multiplier for multiplying the output from the subtractor by 1 / (1-α);
The imaging device according to claim 2, further comprising:   The imaging apparatus according to claim 1, wherein each of the first and second selection circuits includes a shift register.   The imaging apparatus according to claim 1, wherein each of the first and second selection circuits includes a demultiplexer.   The imaging according to claim 1, wherein each of the plurality of pixels includes an infrared absorption film that absorbs infrared light, and a thermoelectric conversion unit that converts heat from the infrared absorption film into an electrical signal. apparatus.   The imaging apparatus according to claim 7, wherein the thermoelectric conversion unit includes at least one PN junction diode.   A camera comprising the imaging device according to claim 1.   A vehicle comprising the camera according to claim 9.

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