JP2010200109A - Imaging device, control method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device capable of reducing strip-like noise due to power fluctuation or the like occurring in an imaging element while suppressing influence of increase of sensitivity of the imaging element, and improving image quality in the imaging device; a control method; and a program. <P>SOLUTION: This imaging device includes: the imaging element 1 having a horizontal OB region 51, a vertical OB region 52 and an effective pixel region 53; a memory 4; and a control part 6. The control part 6 executes a process of reducing noise by an image processing part 5 to a pixel output value of the horizontal OB region 51 of the imaging element 1, and determines whether the output level of the pixel output value after the process is within a set range. When there is a pixel output value of which the output level exceeds the set range, the control part 6 calculates a correction value for bringing the output level exceeding the set range of the pixel output value close to a reference output level, and corrects the pixel output value of which the output level exceeds the set range based on the correction value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that captures an image of a subject using an imaging element, a control method, and a program.

  In recent years, imaging devices (digital cameras, video cameras, etc.) that capture an image of a subject using an imaging device (CCD image sensor, CMOS image sensor, etc.) have become widespread. In an image pickup apparatus provided with this type of image pickup device, an image pickup operation is generally performed by a series of operations of charge accumulation by the image pickup device, charge transfer, and charge read-out to a subsequent circuit. It is known.

  In addition, many of the image pickup devices include a region composed of reference pixels that are not affected by light used for shooting. In order to set the output of the reference pixel to the dark level, there are many image pickup devices that perform a clamping operation in which the output of the reference pixel is clamped by a circuit at a subsequent stage and is adjusted to be substantially constant as a reference of an effective pixel region used for imaging. As the reference pixel, it is common to use a pixel called an optical black (OB) pixel in which a pixel having the same structure as the effective pixel region is shielded by an aluminum film or the like.

  First, a CMOS type image pickup device and an image pickup apparatus including the image pickup device will be described. The CMOS type image sensor is composed of a known horizontal OB area (HOB) where pixels are shielded from light, a known vertical OB area (VOB) where pixels are shielded from light, and an effective pixel area where pixels are not shielded from light. . In addition, the imaging apparatus includes an imaging element, an analog front end (AFE), an image processing unit, a control unit, a timing generation unit, a memory, and the like.

  FIG. 14 is a block diagram illustrating an internal configuration of the AFE of the imaging apparatus according to the conventional example.

  In FIG. 14, the AFE 100 includes a gain control amplifier 101, a horizontal OB clamp / low pass filter 102, and an A / D converter 103. The gain control amplifier 101 is used for sensitivity adjustment. The horizontal OB clamp / low-pass filter 102 gradually follows the offset between the OB output and the black level of each row in the horizontal OB region of the image sensor by a coefficient. This is intended to correct minute and gentle dark shading. The A / D converter 103 converts the analog signal output from the gain control amplifier 101 into a digital signal.

  Next, charge accumulation, transfer, and readout in the imaging operation of the CMOS image sensor will be described with reference to FIGS.

  FIG. 15 is a diagram illustrating a general configuration example of a pixel unit circuit of a CMOS image sensor.

  In FIG. 15, a photodiode (PD) 114-1, a transfer switch (TX) 114-2, and a reset switch (TRES) 114-3 are provided in the pixel. Further, a source follower (SF) 114-10 and a row selection switch (TSEL) 114-6 constituting a pixel amplifier are provided. The gate of the transfer switch (TX) 114-2 is connected to ΦTX (n, n + 1) from the vertical scanning circuit 114-14. The gate of the reset switch 114-3 is connected to ΦRES (n, n + 1) from the vertical scanning circuit 114-14. The gate of the row selection switch 114-6 is connected to ΦSEL (n, n + 1) from the vertical scanning circuit 114-14.

  Photoelectric conversion is performed by the photodiode 114-1, and the transfer switch 114-2 is in the OFF state during the charge accumulation period corresponding to the received light quantity. The charge photoelectrically converted by the photodiode 114-1 is not transferred to the gate 114-11 (floating diffusion (FD)) of the source follower 114-10.

  The gate 114-11 of the source follower 114-10 is basically initialized to an appropriate voltage by turning on the reset switch 114-3 before the start of charge accumulation. That is, this is a dark level. Next, when the row selection switch 114-6 is turned on simultaneously with the reset switch 114-3 (or), the source follower circuit constituted by the load current source 114-7 and the source follower 114-10 enters an operating state. By turning on the transfer switch 114-2 in the source follower circuit, the charge accumulated in the photodiode 114-1 is transferred to the gate 114-11 of the source follower 114-10. In addition, 114-4 is a reset power source, and 114-5 is a power source for driving the source follower 114-10.

  Here, the output of the selected row is generated on the vertical output line 114-13. This output is accumulated in the signal accumulation unit 15 via the transfer gates 114-15a and 114-15b. The output temporarily stored in the signal storage unit 114-15 is sequentially read out to an output amplifier unit (not shown) by the horizontal scanning circuit 114-16.

  FIG. 16 is a diagram illustrating an example of general operation timing of the CMOS image sensor.

  In FIG. 16, first, resetting of the pixel portion is started at the timing of T0. At T0, ΦTX (n), ΦTX (n + 1), ΦRES (n), and ΦRES (n + 1) are activated. In this state, the cathode charge of the photodiode 114-1 is shifted to the gate of the source follower 114-10 and averaged, but the capacitance component of the capacitor 114-9 at the gate of the source follower 114-10 is increased. . As a result, the level is the same as the level at which the cathode of the photodiode 114-1 is reset.

  Subsequently, ΦTX (n), ΦTX (n + 1), ΦRES (n), and ΦRES (n + 1) are turned off at the timing of T1. At this stage, an operation for accumulating charges in the pixel portion is started (however, a mechanical shutter (not shown) is closed). Next, a mechanical shutter that guides the light amount of the target image is opened at the timing of T2, and an actual exposure operation is started. The mechanical shutter is closed at timing T3. That is, an interval between T2 and T3 is an exposure period (charge accumulation period) as the imaging device.

  In the exposure period (charge accumulation period), if a leakage of charge to the gate 114-11 of the source follower 114-10 occurs due to exposure of a high-brightness object, and the charge exceeds a predetermined value, a determination unit (comparison) The comparator, the comparison potential, and the OR circuit) transmits information to the memory control circuit 22. As a result, the row in which the charge leaked (≈saturated row) is stored in the memory.

  After the timing of T4, the charge transfer operation for each row is started. That is, the charges are read sequentially from the nth row and the (n + 1) th row. At the timing of T4, ΦSEL (n) becomes active, the row selection switch 114-6 is turned on, and the source follower circuit composed of the source followers 114-10 of all the pixels connected to the nth row is activated. . At the same time, ΦTN (n) is activated, and the transfer gate 114-15b is turned on until the timing of T7. At this timing, the transfer gate 114-15b starts transferring charges to the signal storage unit 114-15.

  Subsequently, at the timing of T5, ΦRES (n) becomes active, the reset switch 114-3 is turned on, and the charge of the gate 114-11 of the source follower 114-10 is initialized to the dark level. The reset switch 114-3 is turned off at the timing of T6, but waits for the charge of the gate 114-11 of the source follower 114-10 to be stabilized (to the dark level) in the period Tn from T6 to T7.

  Next, ΦTN (n) is turned off at the timing of T7. The electric charge due to this timing becomes the final electric charge transferred to the signal storage unit 114-15. This operation is performed simultaneously in parallel for all pixels connected to n rows. A period from T4 to T7 (including a stabilization waiting period Tn) in which a dark level signal is transferred to the signal storage unit 114-15 and held stable is called “N reading”.

  After the dark level signal transfer (N reading) to the signal storage unit 114-15 is completed (T7), ΦTS is activated only during the period T5-T6 at the timing T8, and the transfer gate 114-15a is at the timing T11. Turn on until. At this timing, the transfer gate 114-15b starts transferring charges to the signal storage unit 114-15.

  Subsequently, ΦTX (n) is activated at the timing of T9 and the transfer switch 114-2 is turned on, whereby the charge (signal charge) accumulated in the photodiode 114-1 is changed to the gate of the source follower 114-10. 114-11. At this time, the potential of the gate 114-11 of the source follower 114-10 changes from the initialization level (dark level) by an amount corresponding to the transferred charge, and the signal level is determined. The transfer switch 114-2 is turned off at the timing of T10, but waits for the charge of the gate 114-11 of the source follower 114-10 to be stabilized (to the output signal level) in the period Ts until T10-T11.

  Next, ΦTS (n) is turned off at the timing of T11. The amount of charge due to this timing becomes the final amount of charge at the signal output level transferred to the signal storage unit 114-15. This operation is performed simultaneously in parallel for all pixels connected to n rows. A period from T8 to T11 in which the signal output of the signal level is transferred to the signal accumulating unit 114-15 to be stabilized and held (including the stabilization waiting period Ts) is referred to as “S reading”. The “N reading” period and the “S reading” period are collectively referred to as a “charge transfer period”.

  When the operation of the charge transfer period is completed (T11), the signal accumulation unit 114-15 holds the dark level and the signal level of all the pixels connected to the n rows. The following signals are obtained by taking the comparison difference between the dark level and the signal level between the pixels. A signal obtained by canceling fixed pattern noise (FPN) due to variations in the threshold voltage (threshold voltage) Vth of the source follower and KTC noise generated when the reset switch 114-3 is reset, and removing a noise component having a high S / N. can get.

  The horizontal scanning circuit 114-16 horizontally scans the difference signal between the dark level and the signal level accumulated in the signal accumulation unit 114-15. As a result, a signal is output in time series at the timing of T11-T12. This completes the output of the nth row signal. Similarly, as shown in FIG. 16, by driving ΦSEL (n + 1), ΦRES (n + 1), ΦTX (n + 1), ΦTN, and ΦTS in the same manner as the nth row, the signal of the n + 1th row can be read out.

  The following technologies have been proposed as related technologies in the above technical fields (see, for example, Patent Document 1 and Patent Document 2).

JP 2001-230974 A JP 2007-300999 A

  However, an image pickup apparatus including a CMOS image pickup element that performs the above-described driving includes a power supply voltage stabilization waiting time that fluctuates due to ON / OFF of the transfer switch during the charge transfer period. Therefore, in a situation where the charge transfer period is short, the power supply fluctuation cannot be settled and charge transfer occurs in an unstable state, and the image quality of the image captured and recorded by the imaging device may deteriorate.

  In particular, a high-intensity part corresponding to a high-intensity subject to be photographed in an effective pixel area of a CMOS image sensor has a large amount of charge movement and a large amount of power fluctuation. When a scene with a subject is photographed, the following problem occurs. If the charge transfer period is short, N reading and S reading are performed in a state where the power supply is not stable, and therefore, there is a difference in output voltage level between the dark pixel / OB portion and the row with the high luminance portion. As a result, a belt-like output fluctuation occurs in the vicinity of the high-luminance portion of the CMOS image sensor (see Patent Document 1 “Problem to be Solved by the Invention”).

  The output fluctuation of the CMOS image sensor is similar to, for example, a smear phenomenon that occurs in a CCD image sensor, but the configuration and generation factors are different. The CCD type image sensor has a vertical (vertical) band, but the CMOS type image sensor has a horizontal (horizontal) band.

  For example, as shown in FIG. 17, when there is a high brightness portion 122 corresponding to a high brightness subject to be photographed in the effective pixel region 121 of the CMOS type image sensor 120, the output of the effective portion / OB portion is changed to become a reference. The OB output greatly deviates from the reference level (dark level). As a result, an offset image in which the output increases or decreases only in a row having a high luminance portion corresponding to the high luminance subject is obtained. Reference numeral 123 denotes a calculation area.

  In order to reduce the effect of shading in the vertical direction (vertical direction) of the image sensor, an OB clamp that clamps the output level of the light-shielded reference pixel (OB pixel) of the CMOS image sensor to a predetermined level in a subsequent circuit There is also a corresponding method. However, the OB clamp is intended to suppress low frequency components of shading, and in order to avoid output fluctuations due to random noise etc., a predetermined coefficient (feedback coefficient) is applied to the deviation between the output level of each row and the predetermined level. It is common to follow. When the deviation from a predetermined level is large, such as the band-like output fluctuation in the vicinity of the high-luminance part as described above, the output fluctuation cannot often be suppressed (because of the influence of the feedback coefficient).

  In addition, since the follow-up is delayed due to the OB clamping, the CMOS image sensor does not change in the output in a certain direction in the vicinity of the high-luminance part, and changes to the sinking direction after changing in the floating direction with respect to the reference. Etc.

  As a technique for dealing with the above-described band-shaped output fluctuation, the following technique has been proposed in an image pickup apparatus using a CCD image pickup element, although it is different from a CMOS image pickup element (see Patent Document 2). That is, as a technique corresponding to smear (smear: noise such as light streaks appearing when a high-luminance subject is photographed) generated in the vertical direction (vertical direction) of the image sensor, refer to the horizontal reference level, There has been proposed a technique for performing an offset process when a predetermined level is exceeded.

  However, the above proposal relating to an image pickup apparatus using a CCD type image pickup device has a problem that it is not possible to suppress horizontal band fluctuations that occur in a CMOS type image pickup device. Further, since the correction processing is performed for a predetermined level or more, only one side of the band-like output fluctuation in which the floating / sinking with respect to the reference fluctuates is corrected, so that the correction effect is insufficient. There's a problem.

  In addition, when correction is performed in a subsequent circuit, an OB pixel region that is a reference pixel is used. However, due to the effect of increasing random noise due to the recent increase in sensitivity, if the correction is simply performed on the value of the OB pixel area in the same row, the correction includes a random noise component. There is a high possibility of correction. As a result, horizontal stripe noise may increase. In particular, there is a problem that the tendency is remarkably generated with the recent increase in sensitivity.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image pickup apparatus and a control method capable of reducing band-like noise caused by power supply fluctuation or the like generated in the image pickup element while suppressing the influence of high sensitivity of the image pickup element and improving the image quality in the image pickup apparatus. And providing a program.

  In order to achieve the above object, the present invention provides an imaging having an effective pixel region in which a plurality of pixels are two-dimensionally arranged and a reference pixel region arranged adjacent to the effective pixel region to obtain a reference signal An image pickup apparatus including an element, a storage unit that stores a pixel output value of the reference pixel region, a processing unit that performs a process of reducing noise on the pixel output value stored in the storage unit, and the processing Output determination means for determining whether or not the output level of the pixel output value of the reference pixel area processed by the means is within a set range, and a pixel output value whose output level exceeds the set range by the output determination means When it is determined that there is a pixel output value that exceeds the set range, a correction value for approximating the reference output level is calculated, and a pixel output value that exceeds the set range based on the correction value Characterized in that it comprises a correction means for correcting.

  According to the present invention, a pixel output value whose output level exceeds the set range is calculated as a correction value for approaching the reference output level, and the pixel output value that exceeds the set range is corrected based on the correction value. As a result, it is possible to reduce the band-like noise caused by the power supply fluctuation or the like generated in the image sensor while suppressing the influence of the high sensitivity of the image sensor. As a result, it is possible to improve the image quality of the image captured by the imaging apparatus.

It is a figure which shows schematic structure of the CMOS type image pick-up element with which the imaging device which concerns on the 1st Embodiment of this invention is provided. It is a block diagram which shows the structure of an imaging device. It is a flowchart which shows the schematic sequence at the time of imaging | photography operation | movement of an imaging device. It is a flowchart which shows the detail of the correction process with respect to the strip | belt-shaped output fluctuation | variation in the image processing of step S107 of FIG. (A) is a figure which shows the calculation area | region of a CMOS type image pick-up element. (B) is a figure which shows the state fixed to the upper limit or the lower limit in the average value of the value of each row read from the horizontal OB area | region of a CMOS type image pick-up element. (C) is a figure which shows the state which took the moving average of the orthogonal | vertical direction of the average value of a horizontal OB area | region. (D) is a figure which shows the correction value for correct | amending a strip | belt-shaped output fluctuation | variation. It is a flowchart which shows the detail of the correction process with respect to the strip | belt-shaped output fluctuation | variation which concerns on the modification 1 of 1st Embodiment. (A) is a figure which shows the correction value for correct | amending the strip | belt-shaped output fluctuation | variation which generate | occur | produces with the image pick-up element which concerns on 1st Embodiment. (B) is a figure which shows the correction value for correct | amending the strip | belt-shaped output fluctuation | variation which generate | occur | produces with the image pick-up element which concerns on the modification 1. FIG. (C) is a figure which shows the correction value for correct | amending the strip | belt-shaped output fluctuation | variation which generate | occur | produces with the image pick-up element which concerns on the modification 2. FIG. It is a flowchart which shows the schematic sequence at the time of imaging | photography preparation operation | movement of the imaging device which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the schematic sequence at the time of imaging | photography operation | movement of an imaging device. It is a figure which shows schematic structure of the CMOS type image pick-up element with which the imaging device which concerns on the 3rd Embodiment of this invention is provided. It is a flowchart which shows the schematic sequence at the time of imaging | photography operation | movement of an imaging device. 12 is a flowchart showing details of correction processing for band-like output fluctuation in the image processing in step S608 of FIG. (A) is a figure which shows the calculation area | region of a CMOS type image pick-up element. (B) is a diagram showing a case where there is a correlation between the value of the first horizontal OB area and the value of the second horizontal OB area. (C) is a diagram showing a case where there is no correlation between the value of the first horizontal OB area and the value of the second horizontal OB area. It is a block diagram which shows the internal structure of the analog front end (AFE) of the imaging device which concerns on a prior art example. It is a figure which shows the general structural example of the pixel part circuit of a CMOS type image pick-up element. It is a figure which shows the example of the general operation | movement timing of a CMOS type image pick-up element. It is a figure which shows the example of the strip | belt-shaped output fluctuation | variation of a CMOS type image sensor, and the calculation area | region of a CMOS type image sensor.

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

[First Embodiment]
FIG. 1 is a diagram showing a schematic configuration of a CMOS type image sensor provided in the imaging apparatus according to the first embodiment of the present invention.

  In FIG. 1, a CMOS image sensor (hereinafter referred to as an image sensor) 1 includes a horizontal OB area (reference pixel area) 51, a vertical OB area (reference pixel area) 52, and an effective pixel area 53. The horizontal OB area 51 and the vertical OB area 52 are disposed adjacent to the effective pixel area 53. Further, the horizontal OB area 51 and the vertical OB area 52 are pixel areas for obtaining a reference signal, and each is composed of a plurality of reference pixels whose front face is shielded by an aluminum film or the like. The effective pixel region 53 is a pixel region for extracting effective signal charges, and is composed of two-dimensionally arranged effective pixels that are not shielded from light. The horizontal OB area 51 includes a calculation area (see FIG. 5A).

  FIG. 2 is a block diagram illustrating a configuration of the imaging apparatus.

  In FIG. 2, the imaging device includes an imaging device 1, an analog front end (AFE) 2, a memory 4, an image processing unit 5, a control unit 6, an operation unit 7, a display unit 8, a recording unit 9, a timing generation unit 10, and an imaging. A lens and a mechanical shutter (not shown) are provided. The imaging element 1 photoelectrically converts an optical image of a subject to be photographed by the imaging device into an electrical signal. The AFE 2 performs sensitivity adjustment, dark shading correction, analog / digital conversion of the output of the image sensor 1, and the like.

  The memory 4 (storage means) stores various data (including pixel output values of the image sensor 1), and has a plurality of storage areas described later. The image processing unit 5 performs image processing such as correction and development on the output of the AFE 2. The control unit 6 (processing unit, output determination unit, correction unit, exposure determination unit, correlation determination unit) controls each unit of the imaging apparatus. Moreover, the control part 6 performs the process shown to each below-mentioned flowchart based on a program.

  The operation unit 7 is for an operator to give various instructions to the imaging apparatus. A shooting start switch for instructing start of shooting, a power switch for instructing power on / off, and various modes (AF mode, strobe mode) , A continuous shooting mode, etc.). The display unit 8 displays an image or the like that has been developed by the image processing unit 5. The recording unit 9 stores an image of the photographed subject. The timing generator 10 supplies a driving timing signal to the image sensor 1, the AFE 2, and the like. The mechanical shutter is controlled to be opened and closed by the control unit 6.

  Next, the operation of the imaging apparatus of the present embodiment having the above configuration will be described with reference to FIGS.

  First, a schematic sequence during the shooting operation of the imaging apparatus will be described with reference to FIG.

  FIG. 3 is a flowchart illustrating a schematic sequence during the shooting operation of the imaging apparatus. In addition, since operations such as photometry and distance measurement that are normally performed in the imaging operation of the imaging apparatus are known, the description thereof is omitted in the present embodiment.

  In FIG. 3, the control unit 6 of the imaging apparatus starts to accumulate charges (signal charges) in the imaging device 1 via the timing generation unit 10 (step S <b> 101), opens the mechanical shutter, and performs exposure on the imaging device 1. (Step S102). Next, the control unit 6 closes the mechanical shutter, ends charge accumulation in the image sensor 103 (step S103), and reads out the charge accumulated in the image sensor 1 to a subsequent circuit (step S104). . During the read operation, the AFE 2 performs a clamp operation and A / D conversion on the output of the horizontal OB region 51 of the image sensor 1, and outputs the result to a subsequent circuit.

  Next, the control unit 6 averages the pixel output values of a predetermined region of the horizontal OB region 51 in the horizontal line V of the image sensor 1, and the averaged pixel output value (OB average value of each row) in the memory 4. 1 is stored in the storage area M1 (step S105). Here, when obtaining the average value of the pixel output values in the predetermined area of the horizontal OB area 51, the pixel output values that exceed the predetermined level or fall below the predetermined level are excluded as calculated values, or the upper and lower limits of the pixel output value Apply clip restrictions. As a result, even when the calculated value varies greatly due to random noise or the like, the influence on the correction is reduced.

  Next, the control unit 6 determines whether or not the reading operation of the charge accumulated in the image sensor 1 has been completed up to the last row (step S106). If the charge reading operation has not been completed until the last row, the process returns to step S104, and the control unit 6 performs the charge reading operation for the next row. If the charge reading operation has been completed up to the last row, the control unit 6 performs the next image processing by the image processing unit 5 (step S107). In other words, the control unit 6 performs image processing such as correction processing (smear correction processing, interpolation processing of an abnormal portion, etc.) and development processing for reducing noise by the image processing unit 5 with respect to the pixel output value that has been read out. Do. Thereby, this process (process related to a series of photographing operations) is completed.

  Next, details of the correction processing for the band-shaped output fluctuation generated in the image sensor 1 in the image processing in step S107 of FIG. 3 and the correction value for correcting the band-shaped output fluctuation will be described with reference to FIGS.

  FIG. 4 is a flowchart showing details of the correction processing for the belt-like output fluctuation in the image processing in step S107 of FIG. FIG. 5A is a diagram showing a calculation area of the image sensor 1, and FIG. 5B is fixed to an upper limit value or a lower limit value in the average value of the values of each row read from the horizontal OB area 51 of the image sensor 1. It is a figure which shows the state which carried out the clip. FIG. 5C is a diagram showing a state in which the average value of the horizontal OB area 51 is taken in the vertical direction, and FIG. 5D is a diagram showing a correction value for correcting the belt-like output fluctuation. is there.

  4, the control unit 6 of the imaging apparatus averages the pixel output values of the horizontal OB area 51 stored in the first storage area M1 of the memory 4 in step S105 of FIG. 3 (OB average value of each row). ) (See step S201, FIG. 5B). Next, the control unit 6 performs a check (upper limit / lower limit check) as to whether or not each of the read average values of each row of the horizontal OB area 51 is within a predetermined setting range (step S202).

  If each of the average values of each row in the horizontal OB area 51 is within the set range, the process proceeds to step S204. For pixel output values that exceed the set range among the average values of each row in the horizontal OB area 51, the control unit 6 sets the data to a value obtained by fixing (clipping) the pixel output to the upper limit value or lower limit value of the set range. Replacement processing is performed (see the arrow in step S203, FIG. 5B). Thereafter, the process proceeds to step S204.

  Next, the control unit 6 takes the moving average in the vertical direction of the average value of each row of the horizontal OB area 51 whose output is clipped to the upper limit value or the lower limit value obtained in steps S201 to S203, and smooths the data. Processing is performed (see FIG. 5C). Further, the smoothed data is stored in the memory 4 as correction calculation data (step S204). By performing the processing from step S201 to step S204, components that fluctuate locally due to abnormal pixels or random noise components in the image sensor 1 can be excluded, and a band-shaped noise (smear) component can be found effectively.

  Next, the control unit 6 determines whether or not the correction calculation data stored in the memory 4 in step S204 is out of the preset correction determination range for each row, and sets the correction calculation data in the determination target row. It is determined whether or not to correct (step S205). If the correction calculation data of the determination target row is within the correction determination range, the control unit 6 stores the correction calculation data of the determination target row as it is in the memory 4 as a correction value (no correction), and the process proceeds to step S207. To do.

  When the correction calculation data in the determination target row is out of the correction determination range, the control unit 6 performs a calculation to calculate a correction value based on the correction calculation data, and stores the calculated correction value in the memory 4. (See step S206, FIG. 5 (d)). Thereafter, the process proceeds to step S207. Here, the correction value is a value for bringing the pixel output value exceeding the set range in the image sensor 1 close to the reference output level.

  As an example of the calculation method, find the value obtained by multiplying the difference between the dark output design value and the correction calculation data by the overcorrection suppression coefficient, and add or subtract that value from the correction calculation data. There is a method for making the data close to the output design value. Specifically, the correction amount X may be obtained by (A−d) × c when the reference value A, the pixel output value d obtained by taking a moving average, and the overcorrection suppression coefficient c are used. The correction amount X is an amount for calculating a correction value (for suppressing a deviation of the reference output level due to a band-like output fluctuation in the image sensor).

  Next, the control unit 6 determines whether or not the correction value calculation has been completed up to the last line of the correction calculation data (step S207). If the correction value calculation has not been completed up to the last line of the correction calculation data, the next line to be determined in the correction calculation data is set, and the process returns to step S205. When the correction value calculation has been completed up to the last line of the correction calculation data, the control unit 6 uses the correction values calculated and stored in steps S206 to S207 to set the dark level of the effective pixel area for each line. Correction is performed (step S208). Thereby, this process is complete | finished.

  As shown in FIG. 4, by performing correction processing on the band-like output fluctuation that occurs in the imaging device 1, it is possible to suppress the deviation of the reference output level due to the band-like output fluctuation and reduce the influence on the image quality.

<Modification 1>
Next, Modification 1 of the present embodiment will be described.

  In the present embodiment, the method of uniformly performing the same correction on the correction calculation data that exceeds the correction determination range (threshold value) in step S205 of FIG. 4 has been described. When correction is performed by this method, the level differs between the output that has not been corrected in the vicinity of the correction determination range (threshold) and the output that has been corrected and corrected to approach the reference value. Therefore, although there is a correction effect on the belt-like output fluctuation, the output difference from the location adjacent to the correction region causes linear noise as an edge (see the broken line circle in FIG. 5D). ).

  On the other hand, in the first modification, in order to avoid the above problem, when the output level of the pixel output value of the image sensor 1 exceeds the correction determination range (threshold), the level (amount) exceeding the correction determination range. ) To perform a weighting process for changing the correction amount.

  FIG. 6 is a flowchart showing details of the correction process for the belt-like output fluctuation according to the first modification of the present embodiment.

  In FIG. 6, the control unit 6 of the imaging apparatus reads the average value of each row in the horizontal OB area stored in the first storage area M1 of the memory 4 in step S105 of FIG. 3 (step S301). Next, the control unit 6 performs a check (upper / lower limit check) as to whether or not each of the read average values of each row in the horizontal OB area is within the set range (step S302).

  If each of the average values of each row in the horizontal OB area 51 is within the set range, the process proceeds to step S304. For pixel output values that exceed the set range among the average values of each row in the horizontal OB area 51, the control unit 6 sets the data to a value obtained by fixing (clipping) the pixel output to the upper limit value or lower limit value of the set range. A replacement process is performed (step S303). Thereafter, the process proceeds to step S304.

  Next, the control unit 6 takes the moving average in the vertical direction of the average value of each row of the horizontal OB area 51 whose output is clipped to the upper limit value or the lower limit value obtained in steps S301 to S303, and smoothes the data. Process. Further, the smoothed data is stored in the memory 4 as correction calculation data (step S304). By performing the processing from step S301 to step S304, components that fluctuate locally due to abnormal pixels or random noise components in the image sensor 1 can be excluded, and a band-shaped noise (smear) component can be found effectively.

  Next, the control unit 6 determines whether or not the correction calculation data stored in the memory 4 in step S304 is out of the first correction determination range L0 set in advance for each row (output determination 0) ( Step S305). When the correction calculation data in the determination target row is within the first correction determination range L0, the process proceeds to step S312. When the correction calculation data in the determination target row is out of the first correction determination range L0, the control unit 6 performs the following determination. It is determined whether the correction calculation data stored in the memory 4 in step S304 is out of the preset second correction determination range L1 line by line (output determination 1) (step S306).

  When the correction calculation data of the determination target row is within the second correction determination range L1, the control unit 6 sets the correction coefficient c1 used for calculating the correction value (step S308). When the correction calculation data in the determination target row is out of the second correction determination range L1, the control unit 6 performs the following determination. It is determined whether the correction calculation data stored in the memory 4 in step S304 is out of the preset third correction determination range L2 line by line (output determination 2) (step S307).

  When the correction calculation data of the determination target row is within the third correction determination range L2, the control unit 6 sets the correction coefficient c2 used for calculating the correction value (step S309). When the correction calculation data of the determination target row is out of the third correction determination range L2, the control unit 6 sets a correction coefficient c3 used for calculating the correction value (step S310). Note that the correction determination ranges are L0, L1, and L2 from the closest order to the reference value. The correction coefficients are c1, c2, and c3 in ascending order.

  Next, the control unit 6 performs a calculation for calculating a correction value based on the correction coefficient set in the above step S308, step S309, or step S310, and stores the calculated correction value in the memory 4 (step S311). Thereafter, the process proceeds to step S312.

  As an example of the calculation method, find the value obtained by multiplying the difference between the dark output design value and the correction calculation data by the overcorrection suppression coefficient, and add or subtract that value from the correction calculation data. There is a method for making the data close to the output design value. Specifically, when the correction amount X is a reference value A, a pixel output value d obtained by taking a moving average, and an overcorrection suppression coefficient C (any one of the set correction coefficients c1, c2, and c3), What is necessary is just to obtain | require by (Ad) * C.

  Next, the control unit 6 determines whether or not the correction value calculation has been completed up to the last line of the correction calculation data (step S312). If the correction value calculation has not been completed up to the last line of the correction calculation data, the next line to be determined in the correction calculation data is set, and the process returns to step S305. When the correction value calculation has been completed up to the last row of the correction calculation data, the control unit 6 corrects the dark level of the effective pixel area for each row using the correction value calculated and stored in step S311 ( Step S313). Thereby, this process is complete | finished.

  FIG. 7A is a diagram showing correction values for correcting the belt-like output fluctuation that occurs in the image sensor according to the present embodiment (reprinted in FIG. 5D). In FIG. 7A, an edge due to the reverse of the output is generated at the boundary between the uncorrected area where correction is not performed and the correction area where correction is performed. When correction is performed using data in which the edge is generated, the horizontal direction In other words, linear noise is generated.

  FIG. 7B is a diagram illustrating a correction value for correcting the belt-like output fluctuation that occurs in the image sensor according to the first modification. In FIG. 7B, the correction amount at a location near the uncorrected area of the image sensor 1 (close to the reference value A) is small, and the correction amount is increased as the deviation from the reference value A is larger. Thereby, while suppressing the shift | offset | difference of the reference level by the strip | belt-shaped output fluctuation | variation which generate | occur | produces in the image pick-up element 1, the boundary of an uncorrected area | region and a correction | amendment area | region can be made smooth and the edge (linear noise) can be suppressed.

  In the first modification, the correction value calculation is weighted by providing a plurality of correction determination ranges (threshold values), but the present invention is not limited to this. For example, there is no problem even if weighting is performed by calculating a correction value using an approximate expression or the like.

<Modification 2>
Next, a second modification of the present embodiment will be described.

  As a method of suppressing the edge (linear noise) between the uncorrected area and the correction area of the image sensor 1 for the same purpose as that of the first modification, the correction amount target is a value different from the design standard (reference value A). There is a way to set. In Modification 2, the correction amount target is set to a value other than the reference value.

  In the present embodiment, the correction amount X, the reference value A, the pixel output value d obtained by taking a moving average, and the overcorrection suppression coefficient c are obtained as X = (A−d) × c.

  On the other hand, in the second modification, the correction amount target is set as the determination threshold L (threshold that defines the setting range for determining the reference pixel region output level), and all of the portions exceeding the determination threshold L are the determination threshold. Clip to L. Specifically, when a correction amount X, a reference value A, a threshold value L (difference from the reference value A), and a pixel output value d obtained by taking a moving average, X = ((A + L) −d) is obtained. The difference up to is corrected by adding or subtracting as it is.

  FIG. 7C is a diagram illustrating a correction value for correcting the belt-like output fluctuation that occurs in the imaging device according to the second modification obtained by the above calculation method. In FIG. 7C, as in the first modification, an edge due to the reverse of the output does not occur at the boundary between the uncorrected area and the corrected area of the image sensor 1. As a result, the boundary between the uncorrected area and the corrected area is smooth, and edges (linear noise) can be suppressed.

  As described above in detail, according to the present embodiment, it is possible to reduce the band-like noise caused by the power supply fluctuation or the like generated in the image sensor while suppressing the effect of increasing the sensitivity of the image sensor. As a result, it is possible to improve the image quality of the image captured by the imaging apparatus.

[Second Embodiment]
The second embodiment of the present invention is different from the first embodiment in the following points. Since the other elements of the present embodiment are the same as the corresponding ones of the first embodiment (FIGS. 1 and 2), description thereof is omitted.

  In this embodiment, when correcting the belt-like output fluctuation generated in the image sensor, the control is performed as follows in order to avoid the possibility of an edge or the like due to the correction as in the first embodiment. Do. That is, control is performed so that correction is not performed in a situation where it is assumed that the belt-like output fluctuation has little influence on the image quality.

  FIG. 8 is a flowchart showing a schematic sequence during the shooting preparation operation of the imaging apparatus according to the present embodiment.

  In FIG. 8, the control unit 6 of the imaging apparatus starts this processing when an imaging preparation switch (not shown) is turned on by the operator. First, the control unit 6 measures the luminance of a subject to be photographed using a known photometry circuit (step S401). In general, a photometry circuit divides an image area captured by an image sensor into a plurality of areas and determines exposure control items (shutter time, aperture, ISO sensitivity, etc.) based on the photometry output for each of the divided photometry areas. To do. Next, the control unit 6 determines the exposure of the brightness of the subject that has been measured (step S402).

  When determining the exposure of the luminance of the subject, the exposure may be determined based on the number of photometric areas that exceed a predetermined set value among the plurality of divided photometric areas, or the average value may be determined. It may be determined whether or not the exposure exceeds a predetermined exposure value. Further, in determining the exposure of the luminance of the subject, the entire photometric area may be used, or only a part of the photometric area may be used.

  When it is determined that the luminance exposure of the subject is equal to or higher than the set value (exposure brighter than the predetermined value), the control unit 6 determines that the subject to be photographed is a bright subject and the band-like output variation is difficult to recognize as the image quality. Then, the control unit 6 stores a correction determination flag “0” for not correcting the belt-like output fluctuation in a predetermined area of the memory 4 (step S403).

  When it is determined that the exposure is less than the set value (exposure darker than the predetermined value), the control unit 6 determines that the subject to be imaged is dark and the band-like output fluctuation is easily recognized as the image quality. Then, the control unit 6 stores a correction determination flag “1” for correcting the belt-like output fluctuation in a predetermined area of the memory 4 (step S404).

  When the process of step S403 or the process of step S404 ends, the control unit 6 measures the subject distance by a known distance measuring circuit (step S405). Next, the control unit 6 drives the photographic lens to adjust the focus of the photographic lens to the subject distance measured in step S405, and performs focus adjustment (step S406). Thereby, this process is complete | finished.

  FIG. 9 is a flowchart illustrating a schematic sequence during the shooting operation of the imaging apparatus.

  In FIG. 9, the processing related to the basic operation of the imaging apparatus among the processes common to FIG. 3 is simplified. The control unit 6 of the imaging apparatus starts accumulation of charges (signal charges) in the imaging device 1 (step S501), performs exposure (step S502), and ends the accumulation of charges (step S503). Next, the control unit 6 reads out the charges accumulated in the image sensor 1 (step S504).

  Next, the control unit 6 averages the pixel output values of a predetermined area of the horizontal OB area 51 in the horizontal line V of the image sensor 1, and stores the averaged pixel output value in the first storage area M 1 in the memory 4. (Step S505). Here, when obtaining the average value of the pixel output values in the predetermined area of the horizontal OB area 51, the pixel output values that exceed the predetermined level or fall below the predetermined level are excluded as calculated values, or the upper and lower limits of the pixel output value Apply clip restrictions. As a result, even when the calculated value varies greatly due to random noise or the like, the influence on the correction is reduced.

  Next, the control unit 6 determines whether or not the reading operation of the charge accumulated in the image sensor 1 has been completed up to the last row (step S506). If the charge reading operation is not completed up to the last row, the process returns to step S504, and the control unit 6 performs the charge reading operation for the next row. If the charge read operation has been completed up to the last row, the control unit 6 checks the correction determination flag stored in the memory 4 in step S403 or step S404 in FIG. 8 (step S507).

  If the correction determination flag is the correction determination flag “0” for not correcting the belt-like output fluctuation, the process proceeds to step S509 without performing correction. If the correction determination flag is the correction determination flag “1” for correcting the belt-like output fluctuation, the next image processing is performed to perform correction (step S508). That is, the control unit 6 performs band-shaped output fluctuation correction (smear correction) on the pixel output value for which reading has been completed. Since the belt-like output fluctuation correction has been described in the first embodiment, a detailed description thereof will be omitted.

  Next, the control unit 6 performs image processing such as correction processing for reducing noise (interpolation processing for an abnormal portion or the like) and development processing (step S509). Thereby, this process (process related to a series of photographing operations) is completed.

  As described above in detail, according to the present embodiment, it is determined whether or not to correct the belt-like output fluctuation according to the brightness of the subject, and correction is performed in a situation where the belt-like output fluctuation is difficult to recognize as an image. Control not to. Thereby, it is possible to reduce the occurrence of an unfavorable effect due to the correction.

[Third Embodiment]
The third embodiment of the present invention is different from the first embodiment in the following points. Since the other elements of the present embodiment are the same as the corresponding ones of the first embodiment (FIG. 2), description thereof is omitted.

  In the present embodiment, the following control is performed in view of the fact that there are many structures having the reference pixel region on both the left and right sides in the image sensor recently. It is determined whether a band-like output fluctuation has occurred in the image sensor or a fluctuation in the reference pixel due to other factors (random noise or the like), and the band-like output fluctuation has occurred, as in the second embodiment. The control is performed so that the correction is not performed in a situation where the influence on the image quality is assumed to be small.

  FIG. 10 is a diagram illustrating a schematic configuration of a CMOS type image pickup element provided in the image pickup apparatus according to the present embodiment.

  In FIG. 10, a CMOS image sensor (hereinafter referred to as an image sensor) 11 includes a horizontal OB area (reference pixel area) 51, a vertical OB area (reference pixel area) 52, and an effective pixel area 53. Further, the horizontal OB area 51 is composed of a first horizontal OB area 51a and a second horizontal OB area 51b. The first horizontal OB area 51 a, the second horizontal OB area 51 b, and the vertical OB area 52 are disposed adjacent to the effective pixel area 53. The first horizontal OB area 51 a and the second horizontal OB area 51 b are arranged at positions facing each other with the effective pixel area 53 interposed therebetween.

  The first horizontal OB area 51a, the second horizontal OB area 51b, and the vertical OB area 52 are pixel areas for obtaining a reference signal, and each of the plurality of reference pixels has its front face shielded by an aluminum film or the like. It is composed of The effective pixel region 53 is a pixel region for extracting effective signal charges, and is composed of two-dimensionally arranged effective pixels that are not shielded from light. Note that each of the first horizontal OB area 51a and the second horizontal OB area 51b includes a calculation area (see FIG. 13A).

  FIG. 11 is a flowchart illustrating a schematic sequence during a shooting operation of the imaging apparatus.

  In FIG. 11, among the processes common to FIG. 3, the processes related to the basic operation of the imaging apparatus are simplified. The control unit 6 of the imaging apparatus starts accumulation of charges (signal charges) in the imaging element 1 (step S601), performs exposure (step S602), and ends the accumulation of charges (step S603). Next, the control unit 6 reads out the charges accumulated in the image sensor 1 (step S604).

  Next, the control unit 6 averages the pixel output values of the predetermined area of the first horizontal OB area 51 a in the horizontal line V of the image sensor 1, and the averaged pixel output value is the first storage area in the memory 4. Store in M1 (step S605). Here, when calculating the average value of the pixel output values in the predetermined area of the first horizontal OB area 51a, the pixel output values that exceed the predetermined level or fall below the predetermined level are excluded as calculated values, or the pixel output values Apply clip restrictions to the upper and lower limits. As a result, even when the calculated value varies greatly due to random noise or the like, the influence on the correction is reduced.

  Next, the same processing as in step S605 is performed. That is, the control unit 6 averages the pixel output values in a predetermined area of the second horizontal OB area 51 b in the horizontal line V of the image sensor 1, and uses the averaged pixel output value in the second storage area M 2 in the memory 4. (Step S606). Here, when obtaining the average value of the pixel output values in the predetermined area of the second horizontal OB area 51b, pixel output values that exceed the predetermined level or fall below the predetermined level are excluded as calculated values, or Apply clip restrictions to the upper and lower limits. As a result, even when the calculated value varies greatly due to random noise or the like, the influence on the correction is reduced.

  Next, the control unit 6 determines whether or not the reading operation of the charge accumulated in the image sensor 1 has been completed up to the last row (step S607). If the charge reading operation is not completed until the last row, the process returns to step S604, and the control unit 6 performs the charge reading operation for the next row. If the charge read operation has been completed up to the last row, the control unit 6 performs the next image processing (step S608). That is, the control unit 6 performs image processing such as correction processing (smear correction processing / interpolation processing of a non-normal part) or development processing on the pixel output value that has been read out. Thereby, this process (process related to a series of photographing operations) is completed.

  Next, the details of the correction processing for the band-like output fluctuation generated in the image sensor 11 in the image processing in step S608 of FIG. 11 and the correction value for correcting the band-like output fluctuation will be described with reference to FIGS.

  FIG. 12 is a flowchart showing details of correction processing for band-like output fluctuation in the image processing in step S608 of FIG. FIG. 13A is a diagram illustrating a calculation area of the CMOS image sensor. FIG. 13B is a diagram illustrating a case where there is a correlation between the value of the first horizontal OB region and the value of the second horizontal OB region. FIG. 13C is a diagram illustrating a case where there is no correlation between the value of the first horizontal OB area and the value of the second horizontal OB area.

  In FIG. 12, the control unit 6 of the imaging apparatus reads the value stored in the memory 4 in step S605 and step S606 in FIG. That is, the pixel output values of the first horizontal OB area 51a stored in the first storage area M1 of the memory 4 and the second horizontal OB area 51b stored in the second storage area M2 of the memory 4 are averaged. The read value is read (step S701). Next, the control unit 6 performs a check (upper limit / lower limit check) as to whether or not each of the read average values of the first horizontal OB area 51a and the second horizontal OB area 51b is within the set range. (Step S702).

  When each of the average values of the respective rows of the first horizontal OB area 51a and the second horizontal OB area 51b is within the set range, the process proceeds to step S704. Regarding the pixel output value that exceeds the set range among the average values of the rows of the first horizontal OB region 51a and the second horizontal OB region 51b, the control unit 6 outputs the pixel output to the upper limit value or the lower limit value of the set range. A replacement process for replacing the data with the fixed (clip) value is performed (step S703). Thereafter, the process proceeds to step S704.

  Next, the control unit 6 calculates the average value of each row of the first horizontal OB area 51a and the second horizontal OB area 51b whose output is clipped to the upper limit value or the lower limit value obtained in steps S701 to S703. The moving average in the vertical direction is taken and the data is smoothed. Further, each data subjected to the smoothing process is stored in the memory 4 as correction calculation data (step S704). By performing the processing from step S701 to step S704, it is possible to exclude components that fluctuate locally due to abnormal pixels or random noise components in the image sensor 1, and to effectively find a band noise (smear) component.

  Next, the control unit 6 determines whether or not the correction calculation data of the first horizontal OB area 51a stored in the memory 4 in step S704 is out of the preset correction determination range line by line (step S704). S705). Furthermore, the control unit 6 determines whether or not to correct the correction calculation data in the determination target row. When the correction calculation data of the determination target row is within the correction determination range, the control unit 6 stores the correction calculation data of the determination target row as it is in the memory 4 as a correction value (without correction), and the process proceeds to step S708. To do.

  When the correction calculation data of the determination target row is out of the correction determination range, the control unit 6 stores each of the first horizontal OB area 51a and the second horizontal OB area 51b stored in the memory 4 in step S704. The correction calculation data are compared (step S706). Further, the control unit 6 determines a correlation (correlation confirmation) as to whether or not both correction calculation data are within a predetermined level. If there is no correlation between the two correction calculation data, the process proceeds to step S708. When there is a correlation between both the correction calculation data, the control unit 6 calculates a correction value based on the correction calculation data, stores the correction value in the memory 4 (step S707), and proceeds to step S708.

  Regarding the correlation determination, for example, as shown in FIGS. 13B and 13C, the value of the first horizontal OB area 51a and the value of the second horizontal OB area 51b are both set in step S705. It is determined whether or not the current correction determination range is outside. If both are out of the correction determination range, it is determined that there is a correlation (see FIG. 13B), and if both are not out of the value of the second horizontal OB area 51b, it is determined that there is no correlation (FIG. 13C). )reference).

  Note that the correlation determination is not limited to the above. For example, the determination may be made based on whether the value of the second horizontal OB area 51b is within a predetermined ratio (for example, within the first horizontal OB area ± 0.25%) with reference to the value of the first horizontal OB area 51a. Good. Alternatively, the determination may be made based on whether or not the value is within a set value (for example, within the first horizontal OB region ± 2 counts after A / D conversion by AFE2).

  Next, the control unit 6 determines whether or not the correction value calculation has been completed up to the last line of the correction calculation data (step S708). If the correction value calculation has not been completed up to the last line of the correction calculation data, the next line to be determined in the correction calculation data is set, and the process returns to step S705. When the correction value calculation has been completed up to the last row of the correction calculation data, the control unit 6 uses the correction values calculated and stored in steps S707 to S708 to set the dark level of the effective pixel area for each row. Correction is performed (step S709). Thereby, this process is complete | finished.

  When calculating the first horizontal OB area 51a and the second horizontal OB area 51b (left and right horizontal OB area), depending on the configuration of the image sensor and the peripheral circuit, there is a difference in how the noise is received in the left and right horizontal OB area. May occur. For this reason, when performing the above correlation check, there is no problem even if processing such as multiplying by a coefficient taking into account the noise intensity of the left and right horizontal OB regions is performed.

  As described above in detail, according to the present embodiment, the band-like output fluctuation is generated only when the fluctuations in the first horizontal OB area 51a and the second horizontal OB area 51b of the image sensor 11 are correlated. It is possible to perform correction as if there is. Further, when there is no correlation, it is possible to limit so as not to perform correction.

[Other Embodiments]
The object of the present invention is achieved by executing the following processing. That is, a storage medium in which a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code read from the storage medium itself realizes the functions of the above-described embodiments, and the storage medium storing the program code and the program code constitutes the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, a flexible disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, etc. . Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, the present invention includes a case where the functions of the above-described embodiment are realized by the following processing. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

DESCRIPTION OF SYMBOLS 1, 11 CMOS type image pick-up element 4 Memory 6 Control part 51 Horizontal OB area | region 51a 1st horizontal OB area | region 51b 2nd horizontal OB area | region 53 Effective pixel area | region

Claims (8)

An imaging apparatus comprising an imaging device having an effective pixel area in which a plurality of pixels are arranged two-dimensionally and a reference pixel area arranged adjacent to the effective pixel area to obtain a reference signal,
Storage means for storing a pixel output value of the reference pixel region;
Processing means for performing noise reduction processing on the pixel output value stored in the storage means;
Output determination means for determining whether or not the output level of the pixel output value of the reference pixel region processed by the processing means is within a predetermined setting range;
When it is determined by the output determination means that there is a pixel output value whose output level exceeds the set range, a correction value for calculating a pixel output value that exceeds the set range is approximated to a reference output level, Correction means for correcting a pixel output value exceeding the set range based on the correction value;
An imaging apparatus comprising:   The processing means performs a process of fixing a pixel output value exceeding the set range to an upper limit value or a lower limit value of the set range, and a process of averaging a plurality of pixel output values in the horizontal direction and the vertical direction. The imaging apparatus according to claim 1, characterized in that:   The correction means performs a weighting process for changing a correction amount in accordance with a level of the pixel output value that is determined by the output determination means to exceed the set range and that exceeds the set range. The imaging apparatus according to claim 1, characterized in that:   The imaging apparatus according to claim 3, wherein the correction unit sets the target of the correction amount to a threshold value that defines the setting range used by the output determination unit. Exposure determining means for determining the brightness exposure of the subject to be photographed;
The correction means performs the correction when the exposure determination means determines that the exposure is less than a predetermined set value, and performs the correction when the exposure determination means determines that the exposure is equal to or greater than the set value. The imaging apparatus according to claim 1, wherein the imaging apparatus is not provided. The reference pixel region is configured as a plurality of reference pixel regions arranged at positions facing each other across the effective pixel region,
Correlation determining means for determining a correlation between output levels of pixel output values of each of the plurality of reference pixel regions,
The correction means performs the correction when the correlation determination means determines that there is a correlation, and does not perform the correction when the correlation determination means determines that there is no correlation. The imaging apparatus according to 1. A control method for an image pickup apparatus including an image pickup device having an effective pixel region in which a plurality of pixels are two-dimensionally arranged and a reference pixel region arranged adjacent to the effective pixel region for obtaining a reference signal. ,
Storing a pixel output value of the reference pixel region;
A processing step for performing a process of reducing noise on the pixel output value stored in the storing step;
An output determination step for determining whether or not the output level of the pixel output value of the reference pixel region processed by the processing step is within a predetermined setting range;
When it is determined in the output determination step that there is a pixel output value whose output level exceeds the set range, a correction value for calculating a pixel output value that exceeds the set range is approximated to a reference output level; And a correction step of correcting a pixel output value exceeding the set range based on the correction value.   A program having computer-readable program code for causing a computer to execute the control method for an imaging apparatus according to claim 7.

Images