JP2011229102A - Imaging apparatus and temperature characteristic correction method of imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus and a temperature characteristic correction method of the imaging apparatus such that an object is imaged always with a predetermined dynamic range without reference to temperature characteristics of an A/D conversion unit.SOLUTION: The present invention relates to the imaging apparatus which includes an imaging device for imaging a subject image formed by an imaging optical system and an analog/digital (A/D) conversion unit for converting the picked-up subject image into digital imaging data, and the temperature characteristic correction method of the imaging apparatus. The imaging apparatus also includes an A/D conversion characteristic detection unit which detects A/D conversion characteristics of the A/D conversion unit, and an A/D conversion characteristic correction unit which corrects the A/D conversion characteristics of the A/D conversion unit based upon a detection result of the A/D conversion characteristic detection unit so as to approximate reference A/D conversion characteristics, and thereby can perform imaging always with the predetermined dynamic range without reference to the temperature characteristics of the A/D conversion unit.

Description

  The present invention relates to an image pickup apparatus and a temperature characteristic correction method for the image pickup apparatus, and more particularly to an image pickup apparatus having an analog-digital conversion unit having temperature characteristics and a temperature characteristic correction method for the image pickup apparatus.

  There is known a linear logarithmic conversion type imaging device having a photoelectric conversion characteristic in which two characteristics of a linear characteristic and a logarithmic characteristic are switched according to the amount of incident light. This image sensor can achieve both high sensitivity and a wide dynamic range. However, in the vicinity of the inflection point where the photoelectric conversion characteristic is switched from the linear characteristic to the logarithmic characteristic, the MOS transistor that constitutes the pixel of the image sensor As a result, output errors due to variations in the characteristics of photodiodes and photodiodes increase, and the position of the inflection point changes with temperature.

  Therefore, for example, in Patent Document 1, the correction value for each pixel including the temperature coefficient is stored, and the output value of each pixel is corrected based on the correction value, so that the output values of all the pixels can be matched. A signal processing apparatus is disclosed.

JP 11-298799 A

  However, when the offset or inflection point of the pixel output changes due to the temperature characteristics of the photoelectric conversion characteristics of the image sensor, the dynamic range of the image sensor itself changes. However, as in Patent Document 1, the output value output from the image sensor is In the method of correcting by post-processing, the change of the dynamic range itself cannot be corrected.

  In addition, the image signal output from the image sensor is converted into digital data by an analog-to-digital converter and calculated, but the analog-to-digital converter itself also has temperature characteristics, and the dynamic range changes depending on the temperature characteristics. Therefore, it is necessary to correct the temperature characteristics of the analog-digital converter. The temperature characteristics of the analog-digital converter do not depend on the photoelectric conversion characteristics of the image sensor.

  The present invention has been made in view of the above circumstances, and an imaging apparatus and an imaging device capable of always imaging in a predetermined dynamic range regardless of the temperature characteristics of the analog-digital conversion unit and the photoelectric conversion characteristics of the imaging device. An object of the present invention is to provide a method for correcting temperature characteristics of an apparatus.

  The object of the present invention can be achieved by the following constitution.

1. An imaging optical system for forming a subject image;
An image sensor that captures a subject image formed by the imaging optical system;
In an imaging apparatus including an analog-digital (A / D) conversion unit that converts a subject image captured by the imaging element into digital imaging data,
An A / D conversion characteristic detector for detecting an A / D conversion characteristic of the A / D converter;
An A / D conversion characteristic correction unit configured to correct the A / D conversion characteristic of the A / D conversion unit so as to approach the reference A / D conversion characteristic based on the detection result of the A / D conversion characteristic detection unit; An imaging apparatus characterized by that.

2. An A / D input switching unit that switches input to the A / D conversion unit;
The A / D conversion characteristic detector is
Using the A / D input switching unit, a reference voltage having a predetermined potential independent of temperature is applied to the A / D conversion unit to perform an A / D conversion operation. 2. The imaging apparatus according to 1 above, which detects a / D conversion characteristic.

  3. The imaging apparatus according to 1 or 2, wherein the A / D conversion characteristic detection unit detects an A / D conversion characteristic of the A / D conversion unit every time a predetermined time elapses.

4). A temperature detection unit for detecting the temperature of the A / D conversion unit;
The A / D conversion characteristic detection unit detects an A / D conversion characteristic of the A / D conversion unit when a detection result of the temperature detection unit changes by a predetermined value or more from a previous detection result. The imaging apparatus according to any one of 1 to 3, wherein:

5). The image sensor includes the A / D converter and a temperature sensor.
5. The imaging apparatus according to 4, wherein the temperature detection unit detects the temperature of the imaging element based on an output of the temperature sensor.

  6). The said A / D conversion characteristic detection part detects the A / D conversion characteristic of the said A / D conversion part during the vertical blanking period of imaging operation | movement, The said any one of 1-5 characterized by the above-mentioned. Imaging device.

7). The A / D converter includes an A / D converter that converts upper bits in a successive approximation type and converts lower bits including redundant bits in an integral type,
The A / D conversion characteristic detector is
Applying a reference voltage of at least two predetermined potentials independent of temperature to the A / D conversion unit to detect A / D conversion characteristics;
Using the detected A / D conversion characteristics,
An A / D offset correction value for bringing the offset of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
Calculating an A / D inclination correction value for bringing the inclination of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
The A / D conversion characteristic correction unit is
Based on the A / D offset correction value, the offset of the A / D conversion characteristic is brought close to the reference A / D conversion characteristic, and
The imaging apparatus according to any one of 2 to 6, wherein the slope of the A / D conversion characteristic is made closer to the reference A / D conversion characteristic based on the A / D inclination correction value.

8). The image sensor has a photoelectric conversion characteristic detection pixel,
A photoelectric conversion characteristic detection unit that detects a photoelectric conversion characteristic of the imaging element based on a photoelectric conversion output of the photoelectric conversion characteristic detection pixel corrected by the A / D conversion characteristic correction unit;
The photoelectric conversion characteristic correction unit that corrects the photoelectric conversion characteristic of the image sensor so as to approach the reference photoelectric conversion characteristic based on the detection result of the photoelectric conversion characteristic detection unit. The imaging device according to any one of the above.

9. An imaging optical system for forming a subject image;
An image sensor that captures a subject image formed by the imaging optical system and outputs an imaging signal;
In the temperature characteristic correction method for an imaging apparatus, comprising: an A / D conversion unit that converts the imaging signal into digital imaging data;
An A / D conversion characteristic detection step of detecting an A / D conversion characteristic of the A / D conversion unit;
An A / D conversion characteristic correction step of correcting the A / D conversion characteristic of the A / D conversion unit so as to approach the reference A / D conversion characteristic based on the detection result of the A / D conversion characteristic detection step. A method for correcting temperature characteristics of an imaging apparatus, characterized in that:

10. An A / D input switching unit that switches input to the A / D conversion unit;
The A / D conversion characteristic detection step includes
Using the A / D input switching unit, a reference voltage having a predetermined potential independent of temperature is applied to the A / D conversion unit to perform an A / D conversion operation. 10. The method for correcting a temperature characteristic of an imaging apparatus as described in 9 above, which is a step of detecting a / D conversion characteristic.

11. The A / D converter is an A / D converter that converts upper bits in a successive approximation type and converts lower bits including redundant bits in an integral type.
The A / D conversion characteristic detection step includes
Applying a reference voltage of at least two predetermined potentials independent of temperature to the A / D conversion unit to detect A / D conversion characteristics;
Using the detected A / D conversion characteristics,
An A / D offset correction value for bringing the offset of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
A step of calculating an A / D inclination correction value for bringing the inclination of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
The A / D conversion characteristic correction step includes:
Based on the A / D offset correction value, the offset of the A / D conversion characteristic is brought close to the reference A / D conversion characteristic, and
11. The temperature characteristic correction method for an image pickup apparatus according to 10, wherein the method is a step of bringing the inclination of the A / D conversion characteristic closer to the reference A / D conversion characteristic based on the A / D inclination correction value.

12 The image sensor has a photoelectric conversion characteristic detection pixel,
A photoelectric conversion characteristic detection step of detecting a photoelectric conversion characteristic of the image sensor based on a photoelectric conversion output of the photoelectric conversion characteristic detection pixel corrected by the A / D conversion characteristic correction step;
The photoelectric conversion characteristic correction step of correcting the photoelectric conversion characteristic of the image sensor so as to approach the reference photoelectric conversion characteristic based on the detection result of the photoelectric conversion characteristic detection step. The temperature characteristic correction method for an imaging apparatus according to any one of the preceding claims.

  According to the present invention, an imaging device that includes an imaging device that captures a subject image formed by the imaging optical system and an analog-digital (A / D) conversion unit that converts the captured subject image into digital imaging data. In the apparatus, an A / D conversion characteristic detection unit that detects an A / D conversion characteristic of the A / D conversion unit, and an A / D conversion of the A / D conversion unit based on a detection result of the A / D conversion characteristic detection unit By providing an A / D conversion characteristic correction unit that corrects the characteristic so as to approach the reference A / D conversion characteristic, it is possible to always capture images in a predetermined dynamic range regardless of the temperature characteristic of the A / D conversion unit. An imaging apparatus and a temperature characteristic correction method for the imaging apparatus can be provided.

  Furthermore, since the photoelectric conversion characteristics of the image sensor are detected based on the imaging data corrected by the A / D conversion characteristics correction unit, the imaging data does not include the temperature characteristics of the A / D conversion unit. It is possible to provide an image pickup apparatus and a temperature characteristic correction method for the image pickup apparatus that can accurately perform the above correction.

It is a block diagram which shows an example of a structure of an imaging device. It is a block diagram which shows an example of a structure of an image pick-up element, an image process part, and a control part. It is a block diagram (1/2) which shows an example of an internal configuration of an image sensor. It is a block diagram (2/2) which shows an example of an internal structure of an image pick-up element. It is a schematic diagram which shows an example of a structure of a pixel, and a characteristic. It is a circuit schematic diagram which shows an example of a structure of a monitor pixel. It is the main routine of the flowchart which shows the 1st example of operation | movement of embodiment of an imaging device. This is the subroutine (1/2) in FIG. This is the subroutine (2/2) in FIG. It is a graph which shows the calculation method of the temperature correction value in this invention. It is the main routine of the flowchart which shows the 2nd example of operation | movement of embodiment of an imaging device. It is a schematic diagram which shows the subject which this invention solves.

  Hereinafter, the present invention will be described based on the illustrated embodiment, but the present invention is not limited to the embodiment. In the drawings, the same or equivalent parts are denoted by the same reference numerals, and redundant description may be omitted.

  First, the problem to be solved by the present invention will be confirmed with reference to FIG. 12A and 12B are schematic diagrams showing the problems to be solved by the present invention. FIG. 12A shows the temperature characteristics of the photoelectric conversion characteristics of the image sensor, and FIG. 12B shows analog / digital (hereinafter referred to as A / D). Say) shows the temperature characteristics of the A / D conversion characteristics of the converter.

  In FIG. 12A, the imaging device according to the present invention has a photoelectric conversion characteristic (hereinafter referred to as a linear log characteristic) in which two characteristics of a linear characteristic and a logarithmic characteristic are switched according to the amount of incident light. The horizontal axis of the graph represents the imaging surface illuminance L of the image sensor on the logarithmic axis, and the vertical axis represents the output voltage VL of the image sensor on the linear axis.

A reference photoelectric conversion characteristic PC ₀ indicated by a solid line in the graph is a photoelectric conversion characteristic at a reference temperature, for example, a temperature T ₀ at the time of preliminary measurement, and shows a linear characteristic in the low illuminance area A1 and a logarithmic characteristic in the high illuminance area A2. Indicates. Linear characteristic inflection point Pt ₀ is switched point with logarithmic characteristic, the output voltage of the illuminance Lpt ₀ is Vpt _0.

On the other hand, the photoelectric conversion characteristics PCh at high temperature, as indicated by the broken line in the graph, the reference photoelectric conversion characteristic PC _0, offset occurs lifted output voltage (1) low illuminance side, (2) The inflection point Pth moves to the low illuminance side, and (3) the logarithmic characteristic has an inclination. Accordingly, the width of the output voltage VL becomes narrower than the range of the imaging surface illuminance L that can be photoelectrically converted, and the contrast of the image is lowered.

On the contrary, the photoelectric conversion characteristic PCl at a low temperature has (1) the output voltage decreases on the low illuminance side and a negative offset occurs, as shown by the alternate long and short dash line in the graph, and (2) the inflection point Ptl is high. It moves to the illuminance side, and (3) the slope of the logarithmic characteristic lies down. Accordingly, the scope of the imaging surface illuminance L can be converted photoelectrically, i.e. dynamic range, it is narrowed with respect to the reference photoelectric conversion characteristic PC _0.

The offset Vos in (1) is caused by an increase in dark current due to temperature, and is an inherent phenomenon that occurs in the entire imaging device. The movement of the inflection point Pt in (2) is caused by a decrease in the potential of the transfer gate due to temperature, and is a phenomenon inherent to the linear log characteristics. The change in the slope of the logarithmic characteristic of (3) includes a term in which the theoretical formula of the slope of the logarithmic transformation includes (k _B T / q) (k _B is the Boltzmann constant, T is the absolute temperature, and q is the charge element of the electron. Therefore, the slope is proportional to the absolute temperature T, which is a phenomenon unique to the logarithmic conversion characteristic.

  For the reasons described above, the temperature characteristics (1) to (3) are the same temperature characteristics in all the pixels 31a of the image sensor 3, and the same correction can be performed in all the pixels 31a.

  In the imaging apparatus, since it is necessary to perform A / D conversion in real time in synchronization with imaging, in the embodiment described below, the high-order bits are converted in a successive approximation type as a high-speed A / D converter. An A / D converter called a column type that converts lower-order bits including redundant bits by an integral type is used. This type of A / D converter is described in detail in, for example, Japanese Patent Application Laid-Open No. 2008-244716.

In FIG. 12B, a reference A / D conversion characteristic AD ₀ indicated by a solid line in the graph is an A / D conversion characteristic at a reference temperature, for example, a temperature T ₀ at the time of preliminary measurement, and is relative to the input voltage Vin. Shows a linear A / D conversion characteristic.

On the other hand, A / D conversion characteristic ADh at high temperature, as indicated by the broken line in the graph, the reference A / D conversion characteristic AD _0, (4) the output ADout value low side of the input voltage Vin is increased Offset (hereinafter referred to as AD offset) occurs, and (5) the slope of the A / D conversion characteristic (hereinafter referred to as AD slope) stands. Therefore, the input range of the A / D conversion, i.e., A / D converter dynamic range of, narrowed with respect to the reference A / D conversion characteristic AD _0.

Conversely, the A / D conversion characteristic ADl at low temperature, as indicated by a chain line in the graph, the reference A / D conversion characteristic AD _0, the output ADout value (4) low side of input voltage Vin It becomes smaller and negative AD offset occurs, and (5) AD tilt is laid down. Therefore, the output width becomes narrower than the input range where A / D conversion is possible, and the contrast of the image is lowered.

  The causes of the change in the AD offset in (4) and the A / D slope in (5) are allowed for the temperature characteristics of the capacitor used in the successive approximation conversion method for converting the upper bits and the A / D conversion. This is due to the fact that the potential of the capacitor is in an unsaturated state due to the short period of time required for the capacitor. In other words, this is an error that occurs due to the capacitance of the capacitor increasing and the unsaturated state increasing at a high temperature, and the capacitor capacitance decreasing and the unsaturated state decreasing at a low temperature.

  The above is a problem to be solved by the present invention. In the embodiment described below, (1) and (2) are corrected in an analog manner before A / D conversion, and (3), (4) and (5) ) Is digitally corrected after A / D conversion to solve the problem.

  It is desirable to make the photoelectric conversion characteristics and A / D conversion characteristics in the temperature environment coincide with the reference photoelectric conversion characteristics and the reference A / D conversion characteristics by correcting the problems (1) to (5). Even if they cannot be matched with each other, the effect is great if they can be brought close to the reference photoelectric conversion characteristics and the reference A / D conversion characteristics.

  Next, an embodiment of the imaging apparatus according to the present invention will be described with reference to FIG. 1. FIG. 1 is a block diagram illustrating an example of the configuration of the embodiment of the imaging apparatus.

  In FIG. 1, an imaging apparatus 1 includes an imaging optical system 2, an imaging element 3, an image processing unit 4, a control unit 5, a storage unit 6, a display unit 7, an interface unit (hereinafter referred to as an I / F unit) 8, and the like. Composed. The display unit 7 and the I / F unit 8 are not essential.

  The imaging optical system 2 is composed of a lens or the like, and forms an image of a subject on the imaging surface of the imaging element 3 disposed on the optical axis 21.

  The image pickup device 3 is arranged so that the image pickup surface is located at the image formation position on the optical axis 21 of the image pickup optical system 2, and photoelectrically converts the subject image formed by the image pickup optical system 2 to generate an analog image pickup signal. Output. As will be described in detail with reference to FIG. 2 and subsequent figures, in this example, the image pickup device 3 includes an A / D converter, and the image pickup device 3 performs A / D conversion of the image pickup signal and outputs it as digital image pickup data 3s. To do.

  The A / D converter is not necessarily built in the image sensor 3 and may be separately provided between the image sensor 3 and the image processor 4.

  The image processing unit 4 performs image processing on the imaging data 3s output from the imaging device 3 under the control of the control unit 5 described later, and outputs image data 4s.

  The control unit 5 includes, for example, a CPU and a calculation memory. The control unit 5 controls the operation of the imaging device 1 according to a program stored in a storage unit 6 described later, and the imaging device 1 is connected via the I / F unit 8. Communicates with connected external systems. The image sensor 3, the image processing unit 4, and the control unit 5 will be described in detail with reference to FIG.

  The storage unit 6 includes a ROM, a RAM, and the like, stores a program that defines the operation of the CPU that constitutes the control unit 5, and image data 4 s output from the image processing unit 4 under the control of the control unit 5. Are stored and output, and adjustment data and the like relating to each part of the imaging apparatus 1 are stored and output.

  The display unit 7 displays an image stored in the storage unit 6, information about the image, and the like under the control of the control unit 5.

  The I / F unit 8 performs communication between the imaging device 1 and an external system under the control of the control unit 5.

  Next, the image sensor, the image processing unit, and the control unit will be described with reference to FIGS. FIG. 2 is a block diagram illustrating an example of the configuration of the image sensor, the image processing unit, and the control unit.

  In FIG. 2, the image sensor 3 includes a pixel unit 31, a monitor pixel unit 32, a temperature sensor 33, a vertical scanning circuit 34, an A / D conversion unit 35, a horizontal shift register 36, an output amplifier 37, an offset shift unit 38, and an A / D. It consists of a D input switching unit 39 and the like.

  As described above, the pixel unit 31 has a photoelectric conversion characteristic of a linear log characteristic. Imaging data 3 s is output from the imaging device 3 toward the image processing unit 4. Details of the internal configuration of the image sensor 3 will be described with reference to FIGS.

The image processing unit 4 performs image processing on the image data 3s output from the image sensor 3 or outputs the image data 4s to the control unit 5 as it is without performing any processing. In addition, the image processing unit 4 sets the A / D offset Vados between the A / D conversion characteristic A / D of the A / D conversion unit 35 of the image sensor 3 and the reference A / D conversion characteristic AD ₀ to 0 (zero). An A / D offset correction unit 41 that approaches, an A / D inclination correction unit 42 that approximates the inclination of the A / D conversion characteristic A / D of the A / D conversion unit 35 to the inclination of the reference A / D conversion characteristic AD ₀ , and imaging and a logarithmic characteristic correcting unit 43 to approach the slope of the logarithmic characteristic of the photoelectric conversion characteristics PC elements 3 on the slope of the logarithmic characteristic of the reference light photoelectric conversion characteristics PC _0.

  The control unit 5 controls the operation of the entire imaging apparatus 1 such as controlling the operation of the imaging device 3 to output the imaging data 3 s and storing the image data 4 s output from the image processing unit 4 in the storage unit 6. .

Control unit 5, the other, a correction value for detecting the A / D conversion characteristic of AD with the use temperature environment of the A / D converter 35 of the image pickup element 3, close to the reference A / D conversion characteristic AD ₀ The photoelectric conversion characteristic PC under the operating temperature environment of the A / D conversion correction value calculation unit 51 to be calculated and the pixel unit 31 of the image pickup device 3 is detected, and a correction value for approximating the reference photoelectric conversion characteristic PC ₀ is calculated. And a photoelectric conversion correction value calculation unit 52.

  Here, the A / D input switching unit 39 and the A / D conversion correction value calculation unit 51 function as an A / D conversion characteristic detection unit in the present invention, and the monitor pixel unit 32 and the photoelectric conversion correction value calculation unit 52 It functions as a photoelectric conversion characteristic detector in the present invention.

Further, the control unit 5 adjusts the temperature deviation of the offset due to the temperature characteristic of the photoelectric conversion characteristic PC of the image sensor 3 to the reference photoelectric conversion characteristic PC ₀ and the temperature characteristic of the photoelectric conversion characteristic PC of the image sensor 3. Using the output of the inflection point control unit 54 that brings the deviation of the inflection point Pt caused to approach the inflection point Pt ₀ of the reference photoelectric conversion characteristic PC ₀ and the temperature sensor 33 built in the image sensor 3, the image sensor 3. The temperature detection part 55 which detects the temperature of this is provided.

  Here, the offset shift unit 38 and the offset control unit 53 function as an offset correction unit in the present invention, and the vertical scanning circuit 34 and the inflection point control unit 54 function as an inflection point correction unit in the present invention. Furthermore, the logarithmic characteristic correction unit 43, the offset shift unit 38 and the offset control unit 53, the vertical scanning circuit 34, and the inflection point control unit 54 function as a photoelectric conversion characteristic correction unit in the present invention.

  3 and 4 are block diagrams showing an example of the internal configuration of the image sensor 3. FIG. 3 shows the pixel unit 31, the monitor pixel unit 32, the temperature sensor 33, and the vertical scanning circuit 34, and FIG. 4 shows the A / D. A conversion unit 35, a horizontal shift register 36, an output amplifier 37, an offset correction circuit 38, and an A / D input switching unit 39 are shown.

  In FIG. 3, the pixel unit 31 includes pixels 31 a and the like arranged in a two-dimensional matrix of m rows and n columns (m and n are positive integers) on the image pickup surface of the image pickup device 3. 2 subjects the image of the subject formed on the optical axis 21 to photoelectric conversion and outputs an imaging signal.

  FIG. 5 shows the configuration and photoelectric conversion characteristics of the pixel 31a. FIG. 5 is a schematic diagram showing an example of the configuration and characteristics of the pixel 31a. FIG. 5A shows an example of the circuit configuration of the pixel 31a, and FIG. 5B shows the photoelectric conversion characteristics of the pixel 31a.

  In FIG. 5A, the pixel 31a includes a photodiode PD, a transfer transistor Q1, a reset transistor Q2, a floating diffusion FD, an output transistor Q3, a selection transistor Q4, and the like.

  PVDD and PVSS are power supply potentials of the pixel 31a. First, in a state where the transfer transistor Q1 is off, the row reset signal φRST is output from the vertical scanning circuit 34, the reset transistor Q2 is turned on, and the potential of the floating diffusion FD is reset.

  After the elapse of a predetermined time from the reset, the row selection signal φVSEN is output from the vertical scanning circuit 34 and the selection transistor Q4 is turned on, so that the potential of the floating diffusion FD in the reset state becomes the vertical of the pixel 31a via the output transistor Q3. The noise signal 31n is output to the common vertical signal line 31b for each column.

  Subsequently, when the transfer signal φTX of the transfer transistor Q1 is set to a predetermined potential, the light of the subject image incident on the pixel 31a is photoelectrically converted by the photodiode PD to become a photocurrent Ip, and is floated via the transfer transistor Q1. Accumulated in the diffusion FD.

  When the amount of incident light, that is, the imaging surface illuminance L is low, the accumulation of the photocurrent Ip in the floating diffusion FD has a linear characteristic. When the imaging surface illuminance L is high, a potential obtained by logarithmically converting the photocurrent Ip is generated in the floating diffusion FD due to the subthreshold characteristic of the transfer transistor Q1. The switching point between the linear characteristic and the logarithmic characteristic, that is, the value Lpt of the photocurrent Ip that becomes the inflection point Pt can be arbitrarily set by setting the transfer signal φTX of the transfer transistor Q1.

Therefore, in order to match the inflection point Pt with the inflection point Pt ₀ of the reference photoelectric conversion characteristic, based on the inflection point correction value σ output from the inflection point correction unit 54 of the control unit 5, the transfer transistor Q 1 This can be done by controlling the transfer signal φTX.

  Again, the row selection signal φVSEN is output from the vertical scanning circuit 34 and the selection transistor Q4 is turned on, so that the potential in the imaging state of the floating diffusion FD is supplied to the pixel signal 31p via the output transistor Q3 to the vertical signal line 31b. Is output as

  Imaging in which noise has been canceled by taking the difference between the pixel signal 31p and the noise signal 31n by a correlated double sampling (hereinafter referred to as CDS) method or the like in a subsequent circuit, for example, the A / D converter 35 or the like. A signal 31s (31s = 31p−31n) can be obtained.

  The photoelectric conversion characteristics are shown in FIG. The horizontal axis of the graph represents the imaging surface illuminance L on the logarithmic axis, and the vertical axis represents the output voltage VL on the linear axis. In a state where the illuminance is lower than the imaging surface illuminance Lpt at the inflection point Pt (A1 region), the output voltage VL is linear with respect to the imaging surface illuminance L, and is higher than the imaging surface illuminance Lpt at the inflection point Pt. In a high illuminance state (A2 region), the output voltage VL is logarithmic with respect to the imaging surface illuminance L.

  Returning to FIG. 3, the monitor pixel unit 32 includes a monitor pixel 32 a for monitoring the temperature characteristics of the photoelectric conversion characteristics of the pixel unit 31. In the example of FIG. 3, the monitor pixel 32 a is provided with n pixels for one horizontal row adjacent to the region of the pixel portion 31 on the imaging surface of the imaging device 3, but is not limited thereto. It is sufficient if at least one pixel is provided, and several rows may be provided. An example of the configuration of the monitor pixel 32a is shown in FIG.

  In FIG. 6, the monitor pixel 32a has a constant current source ID that supplies a current Id having a predetermined current value independent of temperature in parallel with the photodiode PD of the pixel 31a. Further, at least the photodiode PD is shielded from light so that only the dark current is generated without generating the photocurrent Ip. The rest of the configuration is the same as that of the pixel 31a. The current Id having a predetermined current value that does not depend on the temperature can be created by using a known circuit as a band gap circuit, for example.

  The driving method is the same. The difference is that the transfer signal φTX of the transfer transistor Q1 is set to a predetermined potential, so that a constant current Id corresponding to the photocurrent Ip is accumulated in the floating diffusion FD via the transfer transistor Q1. It is a point to be done.

  When the value of the constant current Id is low, the accumulation of the constant current Id in the floating diffusion FD has a linear characteristic. When the value of the constant current Id is high, a potential obtained by logarithmically converting the constant current Id is generated in the floating diffusion FD due to the subthreshold characteristic of the transfer transistor Q1. Other operations are the same as those of the pixel 31a. Therefore, the photoelectric conversion characteristic of the pixel unit 31 can be detected by supplying the monitor pixel unit 32 with a constant current Id corresponding to the photocurrent Ip.

  Returning to FIG. 3, the temperature sensor includes, for example, a diode and a constant current circuit, and outputs a forward voltage Vf of the diode to the output line 33 b. The temperature detection unit 55 described with reference to FIG. 2 can detect the temperature by detecting a change from the value of the diode forward voltage Vf under the reference temperature. The temperature sensor 33 is preferably provided in the vicinity of the A / D conversion unit 35, and by doing so, the temperature of the A / D conversion unit 35 can be accurately detected.

  The vertical scanning circuit 34 supplies the three drive signals (row reset signal φRST, transfer signal φTX, and row selection signal φVSEN) described in the above-described operation of the pixel 31b to each row of the pixel unit 31 and the monitor pixel unit 32. Then, each row of the pixel unit 31 and, if necessary, the monitor pixel unit 32 are sequentially scanned to perform an imaging operation and a photoelectric conversion characteristic detection operation.

In FIG. 4, the offset shift unit 38 generates a pixel signal 31p or noise signal 31n output from each pixel 31a to the vertical signal line 31b based on the offset correction value κ output from the offset control unit 53 of the control unit 5. The offset is corrected and the corrected pixel signal 38p or the corrected noise signal 38n is output. Thereby, it is possible to make the offset value of the pixel 31a to the offset value of the reference photoelectric conversion characteristic PC _0.

  The A / D input switching unit 39 switches the input of the A / D conversion unit 35 to the correction pixel signal 38p or the correction noise signal 38n, which is the output of the offset correction circuit 38, and the reference voltage 39v, and the temperature. And a reference voltage circuit 39b that outputs a reference voltage 39v that is a predetermined potential that does not depend on the reference voltage.

  The switch 39a is set on the output side of the offset correction circuit 38 in the imaging state, and is switched to the reference voltage 39v side when measuring the A / D conversion characteristics of the A / D conversion unit 35. Switching of the switch 39a is controlled by a switching signal 39h output from the A / D conversion correction value calculation unit 51 of the control unit 5.

  The value of the reference voltage 39v output from the reference voltage circuit 39b is controlled by the reference potential switching signal 39j output from the A / D conversion correction value calculation unit 51 of the control unit 5.

  The A / D converter 35 includes a total of (n + 1) A / D converters (ADC in the figure), n provided for each column of the pixel unit 31 and one provided for the output of the temperature sensor 33. The A / D conversion signal 35s is output. Each A / D converter 35a is, for example, a 14-bit A / D converter that converts the upper 4 bits in a successive approximation type and converts the lower 11 bits including 1 redundant bit in an integral type.

  Each A / D converter 35a has a CDS function that takes the difference between the correction pixel signal 38p, which is the output of the offset correction circuit 38, and the correction noise signal 38n, and noise after the difference is taken is cancelled. The captured image signal 31s is A / D converted.

  The horizontal shift register 36 converts the A / D conversion signal 35 s for one row of the pixel unit 31 into serial data and outputs it as imaging data 3 s via the output amplifier 37.

  Next, a first example of the operation of the embodiment of the imaging apparatus of the present invention will be described with reference to FIGS. FIG. 7 is a main routine of a flowchart showing a first example of the operation of the embodiment of the imaging apparatus, and FIGS. 8 and 9 are subroutines of FIG. In the first example of the operation, the imaging apparatus 1 captures a moving image, and the A / D conversion characteristic AD and the photoelectric conversion characteristic PC of the imaging apparatus 1 are set to the vertical block of the moving image capturing operation every predetermined time. Detect during the ranking period.

  In FIG. 7, the timer timing starts in step S11. In step S13, it is confirmed whether or not the timer value is greater than or equal to a predetermined time. The predetermined time is a period for detecting the A / D conversion characteristic AD and the photoelectric conversion characteristic PC of the imaging apparatus 1, and may be appropriately determined according to the application.

  When the time value of the timer is smaller than the predetermined time (step S13; No), the process proceeds to step S27 and a normal imaging operation is performed. When the time value of the timer is greater than or equal to the predetermined time (step S13; Yes), in step S15, it is confirmed whether or not the timing of the imaging operation of the imaging device 1 is the vertical blanking period. When it is not the vertical blanking period (step S15; No), the process proceeds to step S27, and a normal imaging operation is performed.

  If it is the vertical blanking period (step S15; Yes), step S17 “A / D conversion characteristic detection subroutine” shown in FIG. 8 is executed.

  In FIG. 8, in step S171, the A / D conversion correction value calculation unit 51 of the control unit 5 outputs (n + 1) switches 39a of the A / D input switching unit 39 of the image sensor 3 from the reference voltage circuit 39b. Is switched to the reference voltage 39v side. In step S172, the reference voltage 39v is set to the first reference potential V1 and input to the (n + 1) A / D converters 35a of the A / D converter 35.

  In step S173, the first reference potential V1 is A / D converted to obtain (n + 1) first A / D converted values A1. Similarly, the reference voltage 39v is set to the second reference potential V2 in step S174, and (n + 1) second A / D conversion values A2 are obtained in step S175. The straight line connecting the above two data (V1, A1) and (V2, A2) is the current A / D conversion characteristic AD of each A / D converter 35a.

In step S176, the reference A / D conversion characteristic AD ₀ for each A / D converter 35a is read. The reference A / D conversion characteristic AD ₀ is represented by data of at least (V1, A1 ₀ ) and (V2, A2 ₀ ) at least two points measured in advance by performing each operation from step S173 to step S175. in reference characteristic of the a / D converter 35a, it is the temperature T ₀ at the time of measurement that have been stored in the storage unit 6.

Subsequently, in step S177, by using the A / D conversion characteristic AD with the reference A / D conversion characteristic AD _0, the correction value is calculated.

First, a certain A / D converter 35a, and the current A / D conversion characteristic AD determined in step S175 from step S173, the reference A / D conversion characteristic AD ₀ read out from the storage unit 6, FIG. 10 (a). FIG. 10 is a graph showing a method for calculating a temperature correction value in the present invention.

As can be seen from the graph of FIG. 10 (a), the current A / D conversion characteristic AD, relative to the reference A / D conversion characteristic AD _0, with shifts upward slope is standing.

The current A / D conversion characteristic AD
ADout = α ・ Vin + β
Then,
α = (A2-A1) / (V2-V1)
β = A1-α · V1 = A1- (A2-A1) · V1 / (V2-V1)
It becomes.

Similarly, the reference A / D conversion characteristic AD ₀ is
ADout = γ · Vin
Then,
γ == (A2 ₀ −A1 ₀ ) / (V2 ₀ −V1 ₀ )
It becomes.

Therefore, in order to bring the current A / D conversion characteristic AD closer to the reference A / D conversion characteristic AD ₀ , first, the current A / D conversion characteristic AD is translated (subtracted) by the A / D offset correction value β. Later, it is necessary to multiply the inclination α by the A / D inclination correction value δ to convert it to the inclination γ.

Therefore, the A / D offset correction value β and the A / D inclination correction value δ are
β = A1- (A2-A1) .V1 / (V2-V1) (1 formula)
δ = γ / α = (A2 ₀ −A1 ₀ ) · (V2−V1) / (V2 ₀ −V1 ₀ ) · (A2−A1) (Expression 2)
It becomes.

  In step S178, the A / D offset correction value β and the A / D inclination correction value δ of each of the (n + 1) A / D converters 35a are stored in the storage unit 6. In step S179, the (n + 1) switches 39a of the A / D input switching unit 39 of the image sensor 3 are switched to the output side of the offset correction circuit 38 by the A / D conversion correction value calculation unit 51 of the control unit 5. The imaging state is set, and the process returns to step S17 in FIG.

  Here, step S17 “A / D conversion characteristic detection subroutine” functions as an A / D conversion characteristic detection step in the present invention.

  Subsequently, step S19 “photoelectric conversion characteristic detection subroutine” shown in FIG. 9 is executed. In FIG. 9, the parameter k is set to 0 (zero) in step S191. In step S192, 1 is added to the parameter k.

  In step S193, the kth current Ik is supplied as a current Id having a predetermined current value independent of temperature to all the monitor pixels 32a. In step S194, the kth current Ik is photoelectrically converted in the monitor pixel 32a. A / D conversion is performed by the A / D converter 35 to obtain a kth photoelectric conversion output Bk.

  In step S195, the A / D offset correction unit 41 of the image processing unit 4 translates the kth photoelectric conversion output Bk by the A / D offset correction value β calculated in step S17, so that A / D offset correction is performed. Is given.

  Subsequently, in step S196, the A / D inclination correction unit 42 of the image processing unit 4 converts the A / D inclination correction value δ calculated in step S17 into the k-th photoelectric conversion subjected to A / D offset correction. By multiplying the output Bk, A / D inclination correction is performed, and a k-th corrected photoelectric conversion output Bk2 is generated.

  Since the corrected photoelectric conversion output from which the temperature characteristic of the A / D conversion characteristic AD is removed can be obtained by steps S195 and S196, a more accurate temperature characteristic of the photoelectric conversion characteristic is detected and corrected in step S198 and subsequent steps. be able to.

  In step S197, it is confirmed whether parameter k ≧ 4. Until the parameter k becomes equal to 4, the operations from step S192 to S195 are repeated four times.

  Here, the first current I1 is a current value slightly larger than the photocurrent Ip at the minimum illuminance of the pixel 31a, and the second current I2 is photoelectric conversion of the pixel 31a in the entire use temperature range of the imaging device 1. The current value is a little smaller than the maximum value of the photocurrent Ip whose characteristic is a linear characteristic. The current linear characteristic of the photoelectric conversion characteristic PC is detected using the first current I1 and the second current I2.

  Similarly, the third current I3 is a current value slightly larger than the minimum value of the photocurrent Ip in which the photoelectric conversion characteristic of the pixel 31a becomes a logarithmic characteristic in the entire use temperature range of the imaging device 1, and the fourth current I4. Is a current value slightly smaller than the photocurrent Ip at the maximum illuminance of the pixel 31a. Using the third current I3 and the fourth current I4, the logarithmic characteristic of the current photoelectric conversion characteristic PC is detected.

When the parameter k becomes 4 (Step S197; Yes), in step S198, the reference photoelectric conversion characteristic PC ₀ of each monitor pixel 32a is read out. The reference photoelectric conversion characteristic value PC ₀ is measured in advance by performing the operations of steps S192 to S195, and is at least (I1, B1 ₀ ), (I2, B2 ₀ ), (I3, B3 ₀ ), and (I4, B4 0 at the reference characteristics of each monitor pixel 32a represented by data of four _points), in which is stored in the storage unit 6 as the temperature T ₀ at the time of measurement.

Temperature characteristics of the A / D converter 35 to the current of the photoelectric conversion characteristics PC is corrected, the relation of the current correction photoelectric conversion characteristic PC2 and the reference photoelectric conversion characteristic PC _0, shown in Figure 10 (b).

In step S199, by using the current correction photoelectric conversion characteristic PC2 and the reference photoelectric conversion characteristic PC ₀ that temperature characteristics have been corrected A / D converter 35, the correction value is calculated. First, the linear characteristic LN ₀ of the reference photoelectric conversion characteristic PC ₀ is
LN ₀ = ε · Id + φ
Then, since the slope of the linear characteristic is always constant, the linear characteristic LNh of the current corrected photoelectric conversion characteristic PC2 is
LNh = ε · Id + ξ
It is represented by Here, φ and ξ are output values at a current I 0 (zero) sufficiently smaller than the first current I 1 of the linear characteristic LN ₀ of the reference photoelectric conversion characteristic PC ₀ and the linear characteristic LNh of the current corrected photoelectric conversion characteristic PC 2. It is. Therefore,
B1 ₀ = ε · I1 + φ
B2 ₀ = ε · I2 + φ
B12 = ε · I1 + ξ
B22 = ε · I2 + ξ
And
ε = (B2 ₀ −B1 ₀ ) / (I2−I1) = (B22−B12) / (I2−I1)
φ = B1 ₀ −ε · I1
ξ = B12−ε · I1
It becomes.

Therefore, the offset correction value κ is
κ = ξ−φ = B12−B1 ₀ (3 formulas)
It is.

  Note that the offset correction value κ does not supply the current Id having a predetermined current value that does not depend on the temperature, and the current photoelectric conversion characteristic output and the reference photoelectric in the state where only the dark current from the photodiode PD flows. A difference from the output of the conversion characteristic may be used.

Next, in the logarithmic characteristic region, the logarithmic characteristic LOG ₀ of the reference photoelectric conversion characteristic PC ₀ and the logarithmic characteristic LOGh of the current correction photoelectric conversion characteristic PC 2 are set as follows: LOG ₀ = μ · log (Id) + ν
LOGh = χ · log (Id) + ψ
And ν is the logarithmic characteristic LOG ₀ output value at the photocurrent Ipt ₀ giving the inflection point Pt ₀ of the reference photoelectric conversion characteristic PC ₀ . Also, [psi is also present logarithmic characteristic LOGh output value of the correction photoelectric conversion characteristic PC2 of photocurrent Ipt _0. Therefore,
B3 ₀ = μ · log (I3) + ν
B4 ₀ = μ · log (I4) + ν
B32 = χ · log (I3) + ψ
B42 = χ · log (I4) + ψ
And from these,
μ = (B4 ₀ −B3 ₀ ) / (log (I4) −log (I3))
ν = B3 ₀ −μ · log (I3)
χ = (B42−B32) / (log (I4) −log (I3))
ψ = B32−χ · log (I3)
It is.

Therefore, the inflection point correction value σ is
σ = ν−ψ = B3 ₀ −B32− (μ−χ) · log (I3) (Expression 4)
The logarithmic characteristic slope correction value θ is
θ = χ / μ = (B42−B32) / (B4 ₀ −B3 ₀ ) (Expression 5)
It is.

  In step S200, the offset correction value κ, the inflection point correction value σ, and the logarithmic characteristic slope correction value θ calculated in step S199 are stored in the storage unit 6, and the process returns to step S19 in FIG. Here, step S19 “photoelectric conversion characteristic detection subroutine” functions as a photoelectric conversion characteristic detection step in the present invention.

  In step S21, the timer is reset and the timer starts counting again.

  In step S23, the offset of the pixel signal 31p or the noise signal 31n output from each pixel 31a of the pixel unit 31 is corrected by the offset shift unit 38 based on the offset correction value κ calculated in step S19. Next, the corrected offset value is held until the offset correction value 38h is changed. Here, step S23 functions as an offset correction step in the present invention.

In step S25, the potential of the transfer signal φTX of the transfer transistor Q1 during imaging output from the vertical scanning circuit 34 is controlled based on the inflection point correction value σ calculated in step S19, thereby the pixel unit 31. inflection point Pt of the photoelectric conversion characteristics PC of each pixel 31a of the matches to the reference inflection point Pt ₀ reference photoelectric conversion characteristic PC _0. Next, the corrected potential of the transfer signal φTX is held until the inflection point correction value σ is changed. Here, step S25 functions as an inflection point correction step in the present invention.

  In step S27, imaging is performed with the corrected offset value and the corrected transfer signal φTX, and imaging data 3s is output from the imaging device 3.

  In step S29, the A / D offset correction unit 41 of the image processing unit 4 translates the imaging data 3s by the A / D offset correction value β calculated in step S17 and performs A / D offset correction. Imaging data 3so is generated. Next, the current A / D offset correction value β is held until the A / D offset correction value β is changed.

Subsequently, in step S31, the A / D inclination correction unit 42 of the image processing unit 4 multiplies the imaging data 3so subjected to A / D offset correction by the A / D inclination correction value δ calculated in step S17. As a result, A / D inclination correction is performed, and A / D corrected imaging data 3sad is generated. Thus, A / D conversion characteristic AD matches the reference A / D conversion characteristic AD _0. Next, the current A / D inclination correction value is held until the A / D inclination correction value is changed.

  In step S33, the logarithmic characteristic correction unit 43 of the image processing unit 4 performs logarithmic characteristic inclination correction on the A / D-corrected imaging data 3sad using the logarithmic characteristic inclination correction value calculated in step S19. 4s is generated. Here, Step S33 functions as a logarithmic characteristic correction step in the present invention. Steps S23, S25 and S33 function as a photoelectric conversion characteristic correction step in the present invention.

  In step S35, the image data 4s is stored in the storage unit 6. In step S37, it is confirmed whether or not imaging is to be ended. If not (step S37; No), the process returns to step S13 and the above-described operations are repeated. When the process ends (step S37; Yes), the process ends as it is.

  Note that when still image capturing and still image continuous shooting are performed, steps S11, S13, S15, and S21 may be omitted, and steps S17 to S37 may be performed in accordance with the release operation.

  Next, a second example of the operation of the embodiment of the imaging apparatus of the present invention will be described with reference to FIG. FIG. 11 is a main routine of a flowchart showing a second example of the operation of the embodiment of the imaging apparatus. In the second example of the operation, the A / D conversion characteristic AD and the photoelectric conversion characteristic PC of the image pickup apparatus 1 are not detected every predetermined time as in the first example, but the temperature of the image pickup device 3 is the last time. This is detected when the temperature changes from the temperature at the time of detection by a predetermined value or more.

  In FIG. 11, in step S15, it is confirmed whether or not the timing of the imaging operation of the imaging apparatus 1 is the vertical blanking period. If it is not the vertical blanking period (step S15; No), the process proceeds to step S27.

  If it is the vertical blanking period (step S15; Yes), the temperature of the image sensor 3 is detected by the temperature sensor 33 built in the image sensor 3 and the temperature detector 55 of the controller 5 in step S41.

  In step S43, it is confirmed whether or not the difference between the temperature of the image sensor 3 detected in step S41 and the temperature at the previous detection, that is, whether the temperature change of the image sensor 3 is greater than or equal to a predetermined value. The predetermined value of the temperature change may be appropriately determined from the allowable value of the temperature characteristic of the A / D conversion characteristic and the photoelectric conversion characteristic.

  When the temperature change is smaller than the predetermined value (step S43; No), the process proceeds to step S27. When the temperature change is greater than or equal to the predetermined value (step S43; Yes), the process proceeds to step S17 “A / D conversion characteristic detection subroutine”. Subsequent operations are the same as those in the first example, and a description thereof will be omitted.

  Further, when the temperature of the image sensor 3 is detected every predetermined time by combining the first example and the second example, and the temperature of the image sensor 3 changes by a predetermined value or more from the temperature at the previous detection. The A / D conversion characteristic AD and the photoelectric conversion characteristic PC of the imaging device 1 may be detected.

  As described above, according to the present invention, the image sensor that captures the subject image formed by the imaging optical system and the analog digital (A / D) that converts the captured subject image into digital image data. In an imaging apparatus including a conversion unit, an A / D conversion characteristic detection unit that detects an A / D conversion characteristic of the A / D conversion unit, and an A / D conversion based on a detection result of the A / D conversion characteristic detection unit By providing an A / D conversion characteristic correction unit that corrects the A / D conversion characteristic of the conversion unit so as to approach the reference A / D conversion characteristic, a predetermined dynamic is always obtained regardless of the temperature characteristic of the A / D conversion unit. It is possible to provide an imaging apparatus capable of imaging in a range and a temperature characteristic correction method for the imaging apparatus.

  Furthermore, since the photoelectric conversion characteristics of the image sensor are detected based on the imaging data corrected by the A / D conversion characteristics correction unit, the imaging data does not include the temperature characteristics of the A / D conversion unit. It is possible to provide an image pickup apparatus and a temperature characteristic correction method for the image pickup apparatus that can accurately perform the above correction.

  It should be noted that the detailed configuration and detailed operation of each component constituting the imaging apparatus and the temperature characteristic correction method for the imaging apparatus according to the present invention can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Imaging optical system 21 Optical axis 3 Imaging element 31 Pixel part 31a Pixel 32 Monitor pixel part 32a Monitor pixel 33 Temperature sensor 34 Vertical scanning circuit 35 Analog digital (A / D) conversion part 35a Analog digital (A / D) Converter 36 Horizontal shift register 37 Output amplifier 38 Offset shift unit 39 A / D input switching unit 3s Imaging data 4 Image processing unit 41 A / D offset correction unit 42 A / D tilt correction unit 43 Logarithmic characteristic correction unit 4s Image data 5 Control unit 51 A / D conversion correction value calculation unit 52 Photoelectric conversion correction value calculation unit 53 Offset control unit 54 Inflection point control unit 55 Temperature detection unit 6 Storage unit 7 Display unit 8 Interface unit (I / F unit)

Claims (12)

An imaging optical system for forming a subject image;
An image sensor that captures a subject image formed by the imaging optical system;
In an imaging apparatus including an analog-digital (A / D) conversion unit that converts a subject image captured by the imaging element into digital imaging data,
An A / D conversion characteristic detector for detecting an A / D conversion characteristic of the A / D converter;
An A / D conversion characteristic correction unit configured to correct the A / D conversion characteristic of the A / D conversion unit so as to approach the reference A / D conversion characteristic based on the detection result of the A / D conversion characteristic detection unit; An imaging apparatus characterized by that. An A / D input switching unit that switches input to the A / D conversion unit;
The A / D conversion characteristic detector is
Using the A / D input switching unit, a reference voltage having a predetermined potential independent of temperature is applied to the A / D conversion unit to perform an A / D conversion operation. The imaging apparatus according to claim 1, wherein a / D conversion characteristic is detected.   The imaging apparatus according to claim 1, wherein the A / D conversion characteristic detection unit detects an A / D conversion characteristic of the A / D conversion unit every time a predetermined time elapses. A temperature detection unit for detecting the temperature of the A / D conversion unit;
The A / D conversion characteristic detection unit detects an A / D conversion characteristic of the A / D conversion unit when a detection result of the temperature detection unit changes by a predetermined value or more from a previous detection result. The imaging apparatus according to any one of claims 1 to 3. The image sensor includes the A / D converter and a temperature sensor.
The imaging apparatus according to claim 4, wherein the temperature detection unit detects a temperature of the imaging element based on an output of the temperature sensor.   The said A / D conversion characteristic detection part detects the A / D conversion characteristic of the said A / D conversion part during the vertical blanking period of imaging operation | movement, The any one of Claim 1 to 5 characterized by the above-mentioned. The imaging device described. The A / D converter includes an A / D converter that converts upper bits in a successive approximation type and converts lower bits including redundant bits in an integral type,
The A / D conversion characteristic detector is
Applying a reference voltage of at least two predetermined potentials independent of temperature to the A / D conversion unit to detect A / D conversion characteristics;
Using the detected A / D conversion characteristics,
An A / D offset correction value for bringing the offset of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
Calculating an A / D inclination correction value for bringing the inclination of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
The A / D conversion characteristic correction unit is
Based on the A / D offset correction value, the offset of the A / D conversion characteristic is brought close to the reference A / D conversion characteristic, and
7. The imaging apparatus according to claim 2, wherein an inclination of the A / D conversion characteristic is brought close to the reference A / D conversion characteristic based on the A / D inclination correction value. The image sensor has a photoelectric conversion characteristic detection pixel,
A photoelectric conversion characteristic detection unit that detects a photoelectric conversion characteristic of the imaging element based on a photoelectric conversion output of the photoelectric conversion characteristic detection pixel corrected by the A / D conversion characteristic correction unit;
8. A photoelectric conversion characteristic correction unit that corrects the photoelectric conversion characteristic of the image sensor so as to approach a reference photoelectric conversion characteristic based on a detection result of the photoelectric conversion characteristic detection unit. The imaging device according to any one of the above. An imaging optical system for forming a subject image;
An image sensor that captures a subject image formed by the imaging optical system and outputs an imaging signal;
In the temperature characteristic correction method for an imaging apparatus, comprising: an A / D conversion unit that converts the imaging signal into digital imaging data;
An A / D conversion characteristic detection step of detecting an A / D conversion characteristic of the A / D conversion unit;
An A / D conversion characteristic correction step of correcting the A / D conversion characteristic of the A / D conversion unit so as to approach the reference A / D conversion characteristic based on the detection result of the A / D conversion characteristic detection step. A method for correcting temperature characteristics of an imaging apparatus, characterized in that: An A / D input switching unit that switches input to the A / D conversion unit;
The A / D conversion characteristic detection step includes
Using the A / D input switching unit, a reference voltage having a predetermined potential independent of temperature is applied to the A / D conversion unit to perform an A / D conversion operation. The method for correcting a temperature characteristic of an imaging apparatus according to claim 9, wherein the method is a step of detecting a / D conversion characteristic. The A / D converter is an A / D converter that converts upper bits in a successive approximation type and converts lower bits including redundant bits in an integral type.
The A / D conversion characteristic detection step includes
Applying a reference voltage of at least two predetermined potentials independent of temperature to the A / D conversion unit to detect A / D conversion characteristics;
Using the detected A / D conversion characteristics,
An A / D offset correction value for bringing the offset of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
A step of calculating an A / D inclination correction value for bringing the inclination of the A / D conversion characteristic closer to the reference A / D conversion characteristic;
The A / D conversion characteristic correction step includes:
Based on the A / D offset correction value, the offset of the A / D conversion characteristic is brought close to the reference A / D conversion characteristic, and
The temperature characteristic correction method for an imaging apparatus according to claim 10, wherein the step is a step of bringing the slope of the A / D conversion characteristic closer to the reference A / D conversion characteristic based on the A / D inclination correction value. . The image sensor has a photoelectric conversion characteristic detection pixel,
A photoelectric conversion characteristic detection step of detecting a photoelectric conversion characteristic of the image sensor based on a photoelectric conversion output of the photoelectric conversion characteristic detection pixel corrected by the A / D conversion characteristic correction step;
12. A photoelectric conversion characteristic correction step for correcting the photoelectric conversion characteristic of the image sensor so as to approach a reference photoelectric conversion characteristic based on a detection result of the photoelectric conversion characteristic detection step. The temperature characteristic correction method for an imaging apparatus according to any one of the above.

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