JP2016111615A - Imaging apparatus, control method, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate a correction coefficient appropriate for an effective pixel even if primary shading is present in a pixel plane of an imager.SOLUTION: An imaging apparatus comprises: an effective pixel area; a dummy pixel area provided outside the effective pixel area; an A/D converter that A/D converts by comparing a pixel signal with a first lamp signal or a second lamp signal that has a gradient greater than the first lamp signal; a correction part that makes corrections to a first conversion signal obtained by A/D conversion through a comparison with the first lamp signal or a second conversion signal obtained by A/D conversion through a comparison with the second lamp signal; a calculating section that, during a period of time that a dummy pixel is read, inputs a reference signal to the A/D converter and calculates a correction value for correction on the basis of an A/D converted signal; and a control section that changes, for each frame, a period of time that a reference signal is input to the A/D converter and that causes a calculating section to calculate a correction value for each frame.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus and a control method thereof.

  In recent years, the standard of television is that the number of pixels of horizontal 1920 pixels and vertical 1080 pixels (hereinafter referred to as 1920 × 1080) called full high-definition is 4840 times as many as HD, 3840 × 2160 pixels called 4K2K. It has changed to something with. As a next generation after 4K2K, there is a standard called 8K4K or Super Hi-Vision, which has a pixel number of 7680 × 4320 pixels. Along with the increase in the number of pixels, the frame rate continues to increase. Along with such changes, an imaging device that captures a television image is also required to have a higher pixel count and a higher frame rate of a recordable image.

  In order to satisfy this requirement, also in an image sensor that converts light into an electrical signal, it is one of the important issues to increase the readout time of the video signal, and in particular, A / D conversion of the image sensor. The speed of the vessel is required.

  In Patent Document 1, a comparison unit that compares an analog signal with a predetermined voltage is provided, a reference voltage having different gradation accuracy is selected, and the time required for A / D conversion is reduced without reducing the gradation. Further, in Patent Document 2, non-linearity variation at the time of A / D conversion of the image sensor is corrected. Specifically, two reference voltages are input to a dummy pixel provided in the image pickup device, and the A / D conversion is repeated a plurality of times to read out the non-linearity while suppressing an increase in the number of dummy pixels. Correct.

JP 2013-251677 A JP 2012-147163 A

  In the case of an imaging apparatus in which a reference voltage used for correction of an A / D converter is input to a dummy pixel as in Patent Document 2 and a correction coefficient is calculated with reference to the result of the A / D conversion, There is a problem like this. That is, if there is near one-dimensional shading or the like in one frame pixel, the value to be corrected fluctuates within one frame. For example, even if a correction coefficient is calculated before one frame, Accurate correction is difficult. The dummy pixel cannot be physically disposed within the effective pixel range, and the dummy pixel signal readout period cannot be included in the effective pixel signal readout period. Therefore, conventionally, when there is near one-dimensional shading in one frame pixel, it is difficult to obtain a correct correction coefficient for correcting an effective pixel signal.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to calculate an appropriate correction coefficient for an effective pixel even when there is one-dimensional shading in the pixel plane of the image sensor. It is to be.

  The image pickup apparatus according to the present invention is configured such that the effective pixel region, the dummy pixel region provided outside the effective pixel region, and the signal of the pixel are the first ramp signal or the first ramp signal having a larger slope than the first ramp signal. An A / D converter that performs A / D conversion by comparing with the second ramp signal, and the first converted signal or the second ramp signal that has been A / D converted by comparing with the first ramp signal. Correction means for correcting the second conversion signal obtained by A / D conversion by comparing the first conversion signal and the second conversion signal, which change according to the amount of light incident on the pixel, in succession. A calculation means for inputting a reference signal to the A / D converter during a dummy pixel reading period and calculating a correction value for the correction based on the A / D converted signal; and the A / D converter The period during which the reference signal is input to Varied from frame, characterized in that it comprises a control means for calculating said correction value for each frame to the calculation means.

  According to the present invention, it is possible to calculate an appropriate correction coefficient for an effective pixel signal even when there is one-dimensional shading in the pixel plane of the image sensor.

1 is a block diagram showing a configuration of an imaging apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration and operation timing of a comparison unit in the image sensor of the first embodiment. The figure which shows the operation | movement of A / D conversion by multiple slopes. The figure regarding correction | amendment of the A / D conversion result by multiple slopes. FIG. 3 is a diagram illustrating a pixel portion of an imaging element. The figure which shows the operation | movement of A / D conversion of a dummy pixel. The figure which shows the operation | movement of A / D conversion of a dummy pixel. The figure regarding correction | amendment of the A / D conversion result by multiple slopes. The figure which shows a mode that the shading of offset property generate | occur | produces within 1 frame. The figure which shows the timing of correction value acquisition. The flowchart which shows the correction | amendment operation | movement of the A / D conversion result by multiple slopes. The figure which shows the timing of correction value acquisition. The figure which shows the timing of correction value acquisition.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to the first embodiment of the present invention. In FIG. 1, an image sensor 1 is a CMOS type image sensor on which a parallel A / D converter (parallel ADC) is mounted. The image processing LSI 2 performs development processing such as white balance processing and gamma processing on the image data output from the image sensor 1, and records the processed image data on a recording medium. The image processing LSI 2 has a built-in CPU. The CPU communicates with the image sensor (for example, serial communication) according to the operation mode of the image capturing apparatus, and controls the image sensor 1.

  The image sensor 1 includes a pixel unit 110, a vertical scanning circuit 120, a column AMP 130, a ramp circuit 140, a column A / D converter (column ADC) 150, a horizontal transfer circuit 160, a signal processing circuit 170, an external output circuit 180, and a controller circuit. 300.

  The controller circuit 300 is an I / F unit with the image processing LSI 2 and communicates with the CPU of the image processing LSI 2 using serial communication or the like to control the entire image sensor 1. In the pixel portion 110, a plurality of photoelectric conversion elements (photodiodes) that perform photoelectric conversion according to the amount of incident light and output the accumulated charges as voltages are arranged in a matrix. A color filter and a microlens are mounted on the surface of each photoelectric conversion element. By using three primary color filters of R (red), G (green), and B (blue) as the color filter, a so-called RGB primary color Bayer array periodic structure is adopted.

  The timing control unit 100 supplies an operation clock (CLK) and a timing signal to each block of the image sensor 1 and controls its operation. The vertical scanning circuit 120 performs timing control for sequentially reading out pixel signals accumulated in the two-dimensional photoelectric conversion elements in the pixel unit 110 in one frame. In general, video signals are sequentially read in units of rows from the upper row to the lower row in one frame.

  The column amplifier 130 is used to electrically amplify the pixel signal read from the pixel unit 110. By amplifying the signal level of the pixel signal by the column amplifier 130, the signal level of the pixel signal with respect to the noise level output from the ramp circuit 140 or the column ADC 150 is relatively increased, and SN is equivalently improved. However, the column amplifier 130 is not necessarily required in a circuit structure in which the noise generated by the ramp circuit 140 and the column ADC 150 is sufficiently small with respect to the noise generated from the pixel unit 110.

  The constant voltage input circuit 400 applies a predetermined constant voltage to a signal output line from which the pixel signal is output from the pixel unit 110 before being input to the column amplifier 130. Although described as a constant voltage input circuit in this embodiment, a circuit applicable to a clipping circuit that clips a signal with a certain voltage may be used. The ramp circuit 140 is a signal generator that generates a ramp-shaped voltage signal (ramp signal) having a constant slope (slope) in the time direction.

  The column ADC 150 is a dual slope type A / D converter. Detailed operation will be described later. The AD-converted image data for one row is sequentially read out from the end pixels by the horizontal transfer circuit 160.

  The output of the horizontal transfer circuit 160 is input to the signal processing circuit 170. The signal processing circuit 170 is a circuit that performs digital signal processing, and in addition to adding a fixed amount of offset value by digital processing, gain calculation can be easily performed by performing shift calculation or multiplication. Further, a pixel area that is intentionally shielded from light may be provided in the pixel unit 110, and a digital black level clamping operation using the output may be performed.

  The output of the signal processing circuit 170 is passed to the external output circuit 180. The external output circuit 180 has a serializer function, and converts the multi-bit parallel signal output from the signal processing circuit 170 into a serial signal. In addition, the serial signal is converted into, for example, an LVDS signal and output as image information to an external device (in this case, the image processing LSI 2). Next, A / D conversion using the column ADC 150 of the image sensor 1 in the present embodiment will be described with reference to FIG.

  The column ADC 150 includes a comparison unit 151 and a counter / latch circuit 152 therein. The comparison unit 151 compares the pixel signal VAMP amplified by the column amplifier 130 with the ramp signal VRAMP output from the ramp circuit 140, and outputs a comparison result. The counter / latch circuit 152 performs a count operation until the output of the comparison unit 151 is inverted after the count is reset, that is, until the signal level of the pixel signal matches the signal level of the ramp signal. Holds the count value when matches. By this operation, a count value proportional to the read signal level from the column amplifier 130 can be obtained, so this count value becomes an A / D conversion result and is output as digital data (conversion signal).

  FIG. 2B is a diagram showing a state where the slope (slope) of the ramp signal VRAMP output from the ramp circuit 140 is changed. By changing the slope, the timing at which the output of the comparison unit is inverted is changed, and by changing the count time, the gain of the A / D converted digital signal can be changed.

  FIG. 3 is an operation timing chart of the column ADC 150 when the horizontal axis is time. The operation of changing the slope of the ramp signal VRAMP in accordance with the level of the output signal of the column amplifier 130 will be described with reference to FIG.

  In general, in A / D conversion of a pixel signal output from a unit pixel, first, N signal (noise signal) is read and A / D converted, and then S signal (noise signal + light signal) is converted. Read and A / D conversion. With respect to these two signals, the signal processing circuit 170 calculates the S signal-N signal and cancels the noise component, whereby a signal having a good S / N can be acquired.

  First, in the A / D conversion period of the N signal, the N signal is counted with the first ramp signal. Since the N signal is smaller than the S signal, the count operation is performed using the first ramp signal having a small slope.

  Next, the S signal corresponding to the electric charge accumulated in the pixel unit 110 is read out, and after the output of the column amplifier 130 indicated by the dotted line becomes the level of the S signal, the ramp circuit 140 has a constant level lamp in the level determination period. The signal is output to the comparison unit 151 and compared with the level of the S signal. The counter / latch circuit 152 receives the result and determines whether the S signal is larger or smaller than the certain level (S signal determination level). When the S signal is smaller than a certain level, A / D conversion is performed with the same first ramp signal as the N signal to obtain a digital signal. When the S signal is larger than a certain level, the second ramp signal whose slope is α times that of the first ramp signal is used to perform A / D conversion of the S signal to obtain a digital signal. Thus, by changing the slope of the ramp signal according to the magnitude of the signal level, the count time of the counter at the time of A / D conversion is optimized and shortened, and as a result, the signal readout time from the image sensor is shortened. Can do. This is an advantage of the dual slope type A / D converter.

  FIG. 4 shows a digital value after A / D conversion with respect to the amount of light incident on the pixel unit 110 (that is, the output signal level of the column amplifier 130). The horizontal axis in FIG. 4 is the amount of light incident on the pixel unit 110 (the output signal level of the column amplifier 130), and the vertical axis is the digital value after A / D conversion. The solid line in FIG. 4 represents a digital value that is A / D converted by the comparison unit 151 and the counter / latch circuit 152 and input to the signal processing circuit 170 via the horizontal transfer circuit 160. A signal smaller than the S signal determination level is A / D converted using the first ramp signal, and a signal larger than the S signal determination level is A / D converted using the second ramp signal. Therefore, the A / D conversion value is not matched with the light quantity before and after that.

  Therefore, for example, in the signal processing circuit 170, a signal larger than the S signal determination level is multiplied by a slope ratio α of the first ramp signal and the second ramp signal, and an offset β is added. Thereby, the relationship between the incident light quantity and the A / D conversion value is corrected so as to be primarily continuous before and after the S signal determination level. If an image of an effective pixel is output in a state where this correction is not performed, an image with a sense of incongruity with a difference in brightness before and after the S signal determination level is obtained. As described above, the dual slope type A / D converter has the advantage of shortening the signal readout time from the image sensor, but it is necessary to perform such correction. Since this correction value varies depending on the temperature of the image sensor, the drive timing of the image sensor, or the drive setting (operation state such as the gain of the column amplifier 130, power supply setting, etc.), it is necessary to periodically acquire the correction value.

  Next, an example of calculating the slope ratio α as the correction value and the offset amount β to be added will be described. The operation for calculating the correction value is hereinafter referred to as a correction value acquisition operation.

  FIG. 5 is a diagram illustrating a pixel configuration of the pixel unit 110. As shown in FIG. 5, a dummy pixel area (correction value calculation area) is arranged at the top, followed by an optical black area and an effective pixel area for reading an actual video signal. In the present embodiment, the dummy pixel region arranged outside the effective pixel region is used for calculating a correction value composed of the inclination ratio α and the offset amount β.

  The dummy pixel does not have a photodiode and is connected to a column signal line which is an input of the column amplifier 130 shown in FIG. A fixed voltage (reference signal) is input from the constant voltage input circuit 400 during the time of reading the signal of the dummy pixel, and the voltage input from the column amplifier 130 to the comparison unit 151 is a fixed voltage (in this embodiment, V1 and V2). , V2> V1).

  6A and 6B show the flow of A / D conversion of the dummy pixel output signal. In FIG. 6A (a), the fixed voltage V1 is A / D converted. Unlike FIG. 3, it is not necessary to provide an A / D conversion period for the N signal. In FIG. 6A (a), the level of the ramp signal VRAMP in the level determination period is increased to the maximum value so that the fixed voltage V1 is always lower than the S signal determination level, and the first ramp signal VRAMP always having a small slope is used. Thus, A / D conversion of the fixed voltage V1 is performed. The result of A / D conversion is V1L.

  Subsequently, in FIG. 6A (b), the ramp signal VRAMP in the level determination period is set to the minimum value, and the fixed voltage V1 is always higher than the S signal determination level, and is always fixed using the second ramp signal VRAMP having a large slope. A / D conversion of the voltage V1 is performed. The result of A / D conversion is V1H. 6B (c) and 6B (d), the fixed voltage is changed to V2 larger than V1, and A / D conversion is performed in the same manner as in FIGS. 6A (a) and 6A (b). The results are V2L and V2H.

  The digital values after A / D conversion for these fixed voltages V1 and V2 are as shown in FIG. 7, where the horizontal axis represents the incident light quantity (output signal level of the column amplifier 130) and the vertical axis represents the A / D conversion value. Represented. FIG. 7 is an enlarged view of a portion smaller than the S signal determination level. FIG. 7 shows the A / D conversion values of the first ramp signal and the second ramp signal with respect to the fixed voltages V1 and V2 on the vertical axis.

  The slope ratio α and the offset amount β can be obtained from the coordinates of the four points (V1L, V2L, V1H, V2H) shown in FIG. For example, the slope ratio α can be obtained by the following equation.

α = (V2L−V1L) / (V2H−V1H)
After obtaining the slope ratio α, the offset amount β can be determined so that the two straight lines intersect at the S signal determination level. Hereinafter, the inclination ratio α and the offset correction value β are simply referred to as correction values. The above calculation may be performed inside the image sensor or may be performed by an image processing LSI.

  Here, when the above correction value is calculated by an image sensor that needs to perform A / D conversion correction using the two ramp signals having different slopes described above, shading that is nearly one-dimensional within one frame pixel, etc. A coping method when there is an error will be described. Specifically, when the power consumption of the image sensor changes within the vertical synchronization signal VD, offset shading due to fluctuations in the power supply voltage may occur within one frame.

  FIG. 8 shows an operation transition of the image sensor in which the pixel signal reading period and the power saving period for reducing power consumption are within one vertical synchronization period (1VD) of the vertical synchronization signal VD. The horizontal axis in FIG. 8 is the time axis and indicates the timing at which the vertical synchronization signal VD is output. In the pixel signal readout period, since almost all circuits in the image sensor are operating, power consumption is high and the power supply voltage tends to be low. When the reading of the pixel signal is completed, the power of the circuit related to the reading is turned off to reduce power consumption. When the power consumption in the pixel signal readout period is large, the power supply voltage is likely to fluctuate due to switching to the power saving period.

  When the power supply voltage fluctuates, the pixel readout circuit is affected, and offset shading may occur in the video output from the image sensor. Therefore, the correction values for the A / D conversion of the plurality of ramp signals described above, particularly the correction coefficient for the offset amount β, change at the beginning (upper screen of the video) and the end (lower screen of the video) of the pixel signal. End up.

  Therefore, in this embodiment, the reading method of the image sensor is changed as shown in FIG. In FIG. 9, the horizontal axis represents time, and shows the timing of outputting the vertical synchronization signal VD. The vertical axis is a vertical readout line and indicates the timing of reading out the pixel signal of each line.

  In an odd frame (N = 2n-1: n is a natural number), a dummy pixel signal readout and a correction value acquisition operation for calculating a correction value are executed before the effective pixel signal readout period, and the acquired correction value is output. In an even frame (N = 2n: n is a natural number), the correction value acquisition operation is executed after the effective pixel readout period, and the acquired correction value is output. The correction values calculated for the odd and even frames are averaged and applied to the correction of the effective pixel signal from the next frame.

  The calculation of the correction value using such a dummy pixel signal and the correction operation using the calculated correction value will be described with reference to the flowchart of FIG. Here, β_ * represents the correction value β obtained in the * th frame.

  In step S1, output of a video signal from the image sensor is started. Let N = 1 for the number of frames. In step S2, it is determined whether the frame number N is an odd-numbered frame or an even-numbered frame. If it is an odd frame, a correction value acquisition period is set before reading out the effective pixel signal in step S3, and the correction value is acquired in that period.

  When the number of frames N (= 2n−1) is the first in step S4 (n = 1), the correction value obtained in that frame is applied to the correction of the effective pixel signal of the next frame (step S5). When the frame number N is an odd number other than the first in step S4, an average value of the correction value β_2n-1 obtained in that frame and the correction value β_2n-2 obtained in the immediately previous even frame is calculated in step S6. To do. Then, the calculated average value is applied as a correction value for the next frame.

  In step S2, if it is an even frame, the correction value β_2n is obtained in steps S7 and S8 in the same manner as in the odd frame, and the average value of the correction value β_2n-1 obtained in the immediately preceding odd frame is calculated. Then, the calculated average value is applied as a correction value for the next frame. In step S9, it is determined whether or not the video signal output is finished. If it is finished, this flow is finished. If not finished, N = N + 1 is set in step S10 and the process returns to step S2.

  An image sensor that needs to perform A / D conversion correction using a plurality of ramp signals having different slopes by the method described above, and is suitable for the effective video period even when the image has one-dimensional shading. The correction value can be calculated and obtained.

  In this embodiment, the ramp signal having two slopes is described. However, since the same treatment can be performed for a plurality of slopes, the number of slopes is not limited to two. Further, the correction value acquisition method and calculation method are not limited to the method of the present embodiment. Further, although the correction values obtained in the odd frames and the even frames are averaged, the calculation method is not limited to the method of the present embodiment, such as weighted averaging or calculation with a time constant. The order in which correction value acquisition operations are performed can be switched between odd-numbered frames and even-numbered frames.

(Second Embodiment)
In the first embodiment, the configuration in which the dummy pixel signal is read only once in 1 VD (one vertical synchronization period) has been described in order to minimize the reading period of the dummy pixel signal. However, the present invention is not limited to this, and the dummy pixel signal may be read a plurality of times in 1 VD, and the correction value may be acquired for each dummy pixel reading period.

  In the present embodiment, the reading method of the image sensor is changed as shown in FIG. In FIG. 11, the horizontal axis is the time axis, and shows the timing of outputting the vertical synchronization signal VD. The vertical axis is a vertical readout line and indicates the timing of reading out the pixel signal of each line.

  In this embodiment, in each frame, the correction value acquisition operation for reading the dummy pixel signal and calculating the correction value is performed before and after the effective pixel signal reading period to acquire the correction value. The correction values acquired before and after the effective pixel signal readout period are averaged and applied to the correction of the effective pixel signal of the next frame.

  With such a correction value calculation operation, the calculation of the correction value can be completed within one frame. However, since there is a period in which the dummy pixel signal is read out twice or more in one frame (1VD), Compared with the embodiment, the drive time of the image sensor becomes longer. In addition, since the correction value is calculated a plurality of times within one frame, the circuit scale of the image sensor and the image processing LSI increases. On the other hand, since the timing for reading out the effective pixels does not change in each frame, there is an advantage that the influence of shading on the effective pixels does not change from frame to frame.

(Third embodiment)
In the second embodiment, in order to prevent an increase in circuit scale, a correction value acquisition operation may be performed only once per frame (1VD), and a dummy pixel signal may be read twice.

  In the present embodiment, the reading method of the image sensor is changed as shown in FIG. FIG. 12 shows the timing of outputting the vertical synchronization signal VD on the horizontal axis. The vertical axis is a vertical readout line and indicates the timing of reading out the pixel signal of each line.

  In this embodiment, dummy pixel signals are read out before and after the effective pixel signal reading period in each frame, but correction value acquisition is performed only once in each frame, and correction values are acquired in odd frames and even frames. The readout period of the dummy pixel signal accompanying the operation is changed. In an odd frame (N = 2n-1: n is a natural number), the correction value acquisition operation is performed in the dummy pixel signal reading period earlier than the effective pixel signal reading period, and the correction value is output. In an even frame (N = 2n: n is a natural number), the correction value acquisition operation is performed in the dummy pixel signal readout period after the effective pixel signal readout period, and the correction value is output. The correction values actually set in the image sensor are averaged from the correction values calculated for the odd and even frames and applied to the image sensor from the next frame.

  With this operation, the timing of acquiring the correction value and reading the effective pixel signal in each frame does not change while preventing an increase in the circuit scale of the image sensor and the image processing LSI for calculating the correction value multiple times. There is an advantage that the influence of shading on the effective pixel signal does not change from frame to frame.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1: imaging device, 2: image processing LSI, 100: timing control unit, 110: pixel unit, 120: vertical scanning circuit, 130: column amplifier, 140: ramp circuit, 150: column ADC, 151: comparison unit, 152: Counter / latch circuit, 160: horizontal transfer circuit, 300: controller circuit, 400: constant voltage input circuit

Claims (14)

An effective pixel area;
A dummy pixel region provided outside the effective pixel region;
An A / D converter that performs A / D conversion by comparing the pixel signal with a first ramp signal or a second ramp signal having a larger slope than the first ramp signal;
The amount of light incident on the pixel is converted into a first converted signal A / D converted by comparison with the first ramp signal or a second converted signal A / D converted by comparison with the second ramp signal. Correction means for performing correction so that the first conversion signal and the second conversion signal that change in response to each other are continuous;
A calculation means for inputting a reference signal to the A / D converter during a period of reading out the dummy pixels, and calculating a correction value for the correction based on the A / D converted signal;
Control means for changing a period for inputting the reference signal to the A / D converter for each frame, and for causing the calculation means to calculate the correction value for each frame;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the correction value is a gain and an offset value added to the first conversion signal or the second conversion signal.   The correction value calculated by the calculation unit for odd frames and a value obtained by averaging the correction values calculated by the calculation unit for even frames are used for correction by the correction unit. The imaging device described in 1.   The imaging apparatus according to claim 1, wherein the control unit inputs two reference signals having different voltages to the A / D converter.   The A / D converter performs A / D conversion by comparing each of the two reference signals with the first ramp signal and the second ramp signal, and the calculation means performs the A / D conversion. The imaging apparatus according to claim 4, wherein the correction value is calculated based on a signal obtained in this way. An effective pixel area;
A dummy pixel region provided outside the effective pixel region;
An A / D converter that performs A / D conversion by comparing the pixel signal with a first ramp signal or a second ramp signal having a larger slope than the first ramp signal;
The amount of light incident on the pixel is converted into a first converted signal A / D converted by comparison with the first ramp signal or a second converted signal A / D converted by comparison with the second ramp signal. Correction means for performing correction so that the first conversion signal and the second conversion signal that change in response to each other are continuous;
Calculation means for inputting a reference signal to the A / D converter during a period for reading dummy pixels before and after the effective pixel reading period, and calculating a correction value for the correction based on the A / D converted signal When,
An imaging apparatus comprising:   The imaging apparatus according to claim 6, wherein the correction value is a gain and an offset value to be added to the first conversion signal or the second conversion signal.   The correction value calculated by the calculation unit during a period of reading the dummy pixel before the effective pixel readout period and the calculation unit calculated by the calculation unit during the period of reading the dummy pixel after the effective pixel readout period. The imaging apparatus according to claim 6 or 7, wherein a value obtained by averaging correction values is used for correction by the correction means.   The imaging apparatus according to claim 6, wherein the calculation unit inputs two reference signals having different voltages to the A / D converter.   The A / D converter performs A / D conversion by comparing each of the two reference signals with the first ramp signal and the second ramp signal, and the calculation means performs the A / D conversion. The image pickup apparatus according to claim 9, wherein the correction value is calculated based on a signal obtained in this way. The effective pixel region, the dummy pixel region provided outside the effective pixel region, and the signal of the pixel are compared with the first ramp signal or the second ramp signal having a larger slope than the first ramp signal. A method for controlling an imaging apparatus including an A / D converter that performs A / D conversion by:
The amount of light incident on the pixel is converted into a first converted signal A / D converted by comparison with the first ramp signal or a second converted signal A / D converted by comparison with the second ramp signal. A correction step of performing correction so that the first conversion signal and the second conversion signal that change in response to each other are continuous;
A calculation step of inputting a reference signal to the A / D converter during a period of reading out the dummy pixels and calculating a correction value for the correction based on the A / D converted signal;
A control step of changing a period for inputting the reference signal to the A / D converter for each frame, and causing the calculation step to calculate the correction value for each frame;
A method for controlling an imaging apparatus, comprising: The effective pixel region, the dummy pixel region provided outside the effective pixel region, and the signal of the pixel are compared with the first ramp signal or the second ramp signal having a larger slope than the first ramp signal. A method for controlling an imaging apparatus including an A / D converter that performs A / D conversion by:
The amount of light incident on the pixel is converted into a first converted signal A / D converted by comparison with the first ramp signal or a second converted signal A / D converted by comparison with the second ramp signal. A correction step of performing correction so that the first conversion signal and the second conversion signal that change in response to each other are continuous;
A calculation step of inputting a reference signal to the A / D converter during a period of reading dummy pixels before and after the effective pixel reading period, and calculating a correction value for the correction based on the A / D converted signal When,
A method for controlling an imaging apparatus, comprising:   The program for making a computer perform each process of the control method of Claim 11 or 12.   A computer-readable storage medium storing a program for causing a computer to execute each step of the control method according to claim 11 or 12.

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