JP4454771B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an imaging apparatus such as a digital camera, and more particularly to an imaging apparatus having a pixel defect compensation function.
[0002]
[Prior art]
  Imaging devices such as video cameras have been widely used conventionally. In recent years, electronic still cameras that mainly capture and record still images have become widely used as digital cameras, and video movies that are mainly intended for moving image recording have a still image shooting and recording function. The long-time exposure used for still image shooting increases the exposure time by increasing the charge accumulation time in the image sensor, thereby enabling shooting without using auxiliary lighting such as a strobe even under low illumination. It is known as a technology that enables it to be done.
[0003]
  On the other hand, in a solid-state image pickup device such as a CCD, there is a dark output due to the presence of a so-called dark current, which is superimposed on an image signal, resulting in image quality degradation. When there is a pixel with a high dark output level, it is called a pixel defect, and it is widely put into practice that image information is complemented using output information of neighboring pixels without using output information of that pixel. Hereinafter, in the present specification, such a complementary process is referred to as pixel defect compensation. For example, with a predetermined standard exposure time (1/60 seconds for NTSC, or a predetermined margin based on this, for example, 1/15 seconds for a quadruple margin) determined on the premise of moving image drive at the used frame rate The dark defect is evaluated, and the pixel defect compensation is applied to a pixel having a large level as a defective pixel.
[0004]
  Further, since a pixel defect is accompanied by temperature dependence and a change with time, it is also possible to improve the technique that it is not sufficient to evaluate a defective pixel before shipment from the factory. It is disclosed in the publication. This publication describes a technique for compensating for defects by closing the iris immediately after turning on the power to shield the light receiving surface and detecting the defective pixels by evaluating the CCD dark output prior to using the camera. ing.
[0005]
  By the way, as in the technique disclosed in the above publication, if a defective pixel is detected and compensated for in a camera device as a finished product after factory shipment, there is a risk that the image quality of the recorded image is degraded. This is because when a defective pixel is newly detected due to an increase in dark current caused by temperature dependence or a change with time, the occurrence of the defective pixel is generally difficult to predict. This is a serious problem particularly when the above-described conventional technique is further developed and applied to long-time exposure.
[0006]
  On the other hand, “In the case of long exposure exceeding the standard exposure time, the dark output level of the pixel is further increased due to the dark current accumulation effect. `` A method for detecting and compensating for defects '' can be considered, but in such a case, the defects that occur increase in proportion to the approximate exposure time due to the dark current accumulation effect, so in the worst case it is determined to be a defect. A large number of pixels may be generated. If the number of defective pixels is too large, no matter how the above pixel defect compensation is applied, there may be no pixel having image information to be used for complementation in the neighborhood. However, there is a problem that it is impossible to obtain an image with a quality that can withstand viewing.
[0007]
  This problem is particularly serious from the following points. In other words, in order to actually perform defect compensation, the address of the detected defective pixel is temporarily registered in a predetermined memory area in the camera, and complementation processing is performed using peripheral pixel information based on the registered address information. It will be. In this case, since the allocation area (capacity) of the address registration memory is limited, if there are more defective pixels than the capacity allows, a system error occurs during registration of the defective pixel address, which is the worst case. In this case, the camera function cannot be maintained.
[0008]
  In order to solve such a problem, the present inventor previously solved the problem associated with a large number of defective pixels in pixel defect compensation in Japanese Patent Application No. 11-327217, and applied a certain restraint to image quality degradation. At the same time, we have proposed an imaging device that prevents system failures.
[0009]
  That is, the proposed imaging apparatus includes an imaging element for imaging a subject image, an exposure control unit that controls exposure to the imaging element, an accumulation time control unit that controls a charge accumulation time in the imaging element, The defective pixel detection means for detecting a defective pixel in a predetermined operation state of the image sensor under the control of the exposure control means and the accumulation time control means, and information on the defective pixel detected by the defective pixel detection means In an imaging apparatus including a pixel defect compensation unit that compensates for this by pixel information, the defective pixel detection unit includes a defective pixel number limiting unit that limits the number of defective pixels to be detected to a predetermined value or less. It is a feature.
[0010]
  In the imaging apparatus configured as described above, since the defect pixel number limiting unit that limits the number of defective pixels detected by the defective pixel detection unit to a predetermined value or less is provided, the image quality deterioration can be fixed to a certain level, It is possible to prevent a system from failing due to detecting more defects than can be stored.
[0011]
[Problems to be solved by the invention]
  However, the previously proposed imaging apparatus limits the number of defective pixels to be detected to a predetermined value or less, thereby preventing image degradation due to defect compensation and preventing system failure. However, if the defect determination level is increased without restriction in order to avoid system failure, there is a problem that image quality eventually fails and an image whose image quality has failed is recorded unintentionally.
[0012]
  The present invention has been made in order to solve the above-described problems in the previously proposed imaging apparatus. In the case where the allowable limit value of the determination level is determined and the number of defective pixels exceeds the predetermined number even at the allowable limit level. An object of the present invention is to provide an imaging apparatus capable of performing a predetermined image quality failure handling process and avoiding a problem of unintentionally recording an image with an image quality failure.
[0013]
[Means for Solving the Problems]
  In order to solve the above problem, the invention according to claim 1 controls an image pickup device for picking up a subject image, exposure control means for controlling exposure to the image pickup device, and charge accumulation time in the image pickup device. An accumulation time control means; a defective pixel detection means for detecting a defective pixel in a predetermined operation state of the image sensor under the control of the exposure control means and the accumulation time control means; and a defective pixel detected by the defect pixel detection means. With respect to information, in an imaging apparatus including a pixel defect compensation unit that compensates for this by pixel information in the vicinity of the pixel, the defective pixel detection unit is configured so that the exposure control unit blocks exposure to the imaging element, and Test imaging means for executing charge accumulation and readout operations in the imaging device, and output from the imaging device obtained corresponding to the test imaging A defect determination unit that determines a defective pixel by comparing the level with a predetermined pixel defect determination level, and the pixel defect determination level when the number of defective pixels once determined by the defect determination unit exceeds a predetermined value By changing the number of defective pixels to be less than or equal to the predetermined value by making the determination by the defect determination unit again after the change, and the pixel defect determination level has reached the allowable limit level An image quality failure state detection means for determining that the image quality is in a failure state when the number of defective pixels determined by the defect determination means in the state exceeds the predetermined value;Image quality failure handling processing execution means for executing predetermined image quality failure handling processing when the image quality failure status detection means detects an image quality failure status;It is characterized by having.
[0014]
  In the imaging apparatus configured as described above, in the defective pixel number limiting unit, an allowable limit level is set as the defect determination level in the defect determination unit for limiting the number of defective pixels to be detected to a predetermined value or less. If the number of defective pixels exceeds the predetermined number even at the allowable limit level, the image quality failure state detection means determines that the image quality is in a failure state. As a result, it is possible to execute the image quality failure handling process, and it is possible to avoid the problem of unintentionally recording an image whose image quality has failed.In addition, when the image quality failure state detection unit determines that the image quality is in a failed state, the image quality failure handling process is executed by the image quality failure handling process execution unit, and thus an image in which the image quality is broken unintentionally is recorded. Does not happen.
[0015]
  Claims2The invention according to claim1In the image pickup apparatus, image quality failure handling processing by the image quality failure handling processing execution means isTo shorten the exposure time in actual shootingIt is an exposure time shortening process.
[0016]
  In the imaging apparatus configured as described above, when it is determined that the image quality is in a failed state,In the actual shootingSince the occurrence of pixel defects is reduced by shortening the exposure time, it is possible to prevent failure of the image quality of the recorded image.
[0017]
  Claims3The invention according to claim1In the image pickup apparatus, the image quality failure handling process by the image quality failure handling process execution means is a shooting prohibition process.
[0018]
  In the image pickup apparatus configured as described above, if it is determined that the image quality is in a broken state, the photographing itself is prohibited, so that an image with a broken image quality is not recorded.
[0019]
  Claims4The invention according to claim1~3In the image pickup apparatus according to any one of the above, the image quality failure handling processing execution means includes a warning processing unit.
[0020]
  In the imaging apparatus configured as described above, the user can determine the setting related to shooting and whether or not shooting is possible after recognizing the image quality failure state by a warning, so that the intention can be maximized.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
  Next, embodiments will be described. FIG. 1 is a block diagram showing a circuit configuration of a digital camera according to an embodiment of an imaging apparatus of the present invention. In FIG. 1, 1 is a lens system composed of various lenses, 2 is a lens system drive mechanism for driving the lens system 1, 3 is an exposure control mechanism for controlling the aperture / shutter device of the lens system 1, and 4 is an LPF. And the like, 5 is a CCD image pickup device with a built-in color filter, 6 is a CCD driver for driving the image pickup device 5, 7 is a preprocess circuit including an A / D converter, and 8 is provided with a memory. A digital process circuit for performing various digital processes to be described, 9 is a memory card interface, 10 is a memory card, 11 is an LCD image display system, 12 is a system controller for centralized control including a microcomputer as a main configuration , 13 is an operation switch system composed of various SWs, 14 is an operation display system for displaying the operation state and mode state, and 15 is for controlling the lens system drive mechanism 2. Lens driver for, 16 flash, the exposure control driver 17, 18 denotes an EEPROM.
[0022]
  In the digital camera according to the present embodiment, the system controller 12 performs all the control, and in particular controls the drive of the CCD image pickup device 5 by the shutter device included in the exposure control mechanism 3 and the CCD driver 6. Then, exposure (charge accumulation) and signal readout are performed, and pixel defects described below are detected using the output level information stored in the digital process circuit 8 via the preprocess circuit 7. is there. Therefore, the system controller 12 further includes a defective pixel detection unit 19, in which the charge in the CCD image pickup device 5 is stored in a state where exposure to the CCD image pickup device 5 is blocked by the exposure control mechanism 3. A test imaging unit 19-1 that performs storage and readout operations, and a defect determination unit 19 that determines a defective pixel by comparing the output level of the CCD imaging device 5 obtained by this test imaging with a predetermined pixel defect determination level. -2, and when the number of defective pixels once determined by the defect determination unit 19-2 exceeds a predetermined value, the determination by the defect determination unit 19-2 is performed again after changing the pixel defect determination level The defective pixel number limiting unit 19-3 that limits the number of defective pixels to be detected to the predetermined value or less, and the defect determination in a state where the pixel defect determination level has reached an allowable limit level. When the number of defective pixels determined by the unit 19-2 exceeds the predetermined value, the image quality failure state detection unit 19-4 that determines that the image quality failure state exists, and the image quality failure state detection unit 19-4 When an image quality failure state is detected, a failure handling processing unit 19-5 that executes an exposure time reduction process as an image quality failure handling process is provided. As described later, the image quality failure handling processing includes shooting prohibition processing, warning processing, and the like, but here, exposure time reduction processing will be described as an example.
[0023]
  In addition, the digital process circuit 8 in the digital camera according to the present embodiment has a pixel defect compensation unit 20,
  (a) Address data of defective pixels relating to normal defects (hereinafter referred to as normal defects) stored in the EEPROM 18 in advance;
  (b) At the time of long exposure, pixel address data of a defective pixel relating to a defect (hereinafter referred to as a detection defect) as a result of detecting a pixel defect by the defective pixel detection unit 19 prior to photographing.
Based on the above, this pixel defect compensation processing is performed.
[0024]
  Next, processing directly related to pixel defect detection and compensation, defective pixel number limitation, and image quality failure state detection in the present embodiment will be described with reference to the flowchart of FIG. However, in this camera, the digital processing of the signal level is performed with 8 bits (0 to 255). In addition, the description will be made on the assumption that the operation is performed at room temperature except for the specially described portion.
[0025]
  Prior to shooting, an exposure time Ttotal required for shooting is set based on manual settings or photometric results (however, the maximum exposure time is 10 seconds as the spec of this camera). It is determined whether or not this exposure time Ttotal is shorter than the standard exposure time Tstd in this camera (which can be arbitrarily set, but in this example, 1/15 seconds), that is, whether Ttotal ≦ Tstd ( S1).
[0026]
  (1) In the case of Ttotal ≦ Tstd, the imaging trigger command for main imaging is awaited in particular as in the prior art, and exposure based on a predetermined exposure control value is received in response to the command (S2), and the imaging signal is read out After performing predetermined signal processing, it is recorded in the memory card 10 (S4). At that time, pixel defect compensation corresponding to the above (a), that is, only for the normally defective pixel is accompanied by pixel defect compensation in the pixel defect compensation unit 20 (S3).
[0027]
  (2) When Ttotal> Tstd (long exposure), the defective pixel detection unit 19 first detects a pixel defect prior to actual main imaging. This pixel defect detection processing includes test imaging described below, defect determination using the result, processing for limiting the number of defective pixels, pixel failure state detection processing, and image quality failure handling processing.
[0028]
  Specifically, when a test trigger command is received by the test imaging unit 19-1, first, test imaging is performed in a state where the light receiving surface of the CCD imaging device 5 is shielded by a shutter device included in the exposure control mechanism 3. That is, the CCD driver 6 performs a charge accumulation operation for the exposure time Ttotal in the dark to read a test imaging signal (dark output signal) and store it in the digital process circuit 8.
[0029]
  Next, with respect to the effective output pixels excluding at least normal defective pixels among all the stored data, the defect determination unit 19-2 examines each output level and performs a digital comparison with a predetermined pixel defect determination level TH. Make a decision. The initial criteria are as follows. That is, assuming that the output level of the target pixel is S,
    S> TH
In the case of (1), it is a defect. In this camera, 25 is adopted as the initial value of the pixel defect determination level TH.
[0030]
  This means that in the initial determination, the dark output level at the time of actual imaging is allowed up to 25 (about 10% of the full range 255) (S5). Here, the judgment level of output level 25 (about 10%) is not the only absolute level, and can be set arbitrarily according to the circumstances at the time of design. If, for example, about 5% is also effective) is selected, the possibility of revealing the influence of dark output superimposed on the image is sufficiently low.
[0031]
  In addition, if the pixel defect determination level TH is selected as the dark output 0%, it is possible to completely eliminate the pixel on which the dark output is superimposed, and in this respect, this may also be cited as one preferred embodiment. Since only a small amount of dark current is present as a defective pixel and the number of pixels that are complemented (that is, the image information is completely invalidated) increases, the image quality is liable to deteriorate. In reality, the initial reference level is set in consideration of these trade-off factors. In particular, a numerical range of 5 to 10% is extremely effective as a value at which this trade-off effect is usually sufficiently exhibited.
[0032]
  Next, regarding the detected defect, S> TH is determined as described above, and the number of defective pixels is calculated (S6). Since the defect compensation is performed in the same manner for both the normal defect and the detected defect, these defect addresses are processed in an integrated manner as the same defect address in this determination. Next, the defective pixel number limiting unit 19-3 determines whether or not the number of defective pixels is equal to or less than a predetermined number (S7). In the camera of the present embodiment, a memory area in the digital process circuit 8 is secured so that a maximum of 255 defective addresses can be stored. Therefore, if the number of detected defective pixels is 255 or less, the defective pixel address is stored in the defective address storage area, and the pixel defect detection is terminated (S8).
[0033]
  If the number of detected defective pixels is 256 or more, TH = TH + 10 is set (S9), and the second defect determination is performed. That is, in the case of the initial determination, the allowable dark output level is set to 25 as described above. However, since the number of defective pixels did not fall within the predetermined value, the defective dark output level was unavoidably raised and the defect was detected. Pixel determination is performed again.
[0034]
  At that time, the image quality failure state detection unit 19-4 determines whether the set pixel defect determination level TH exceeds a preset allowable limit level THL, that is, whether TH> THL. Performed (S10). In the present camera, the TH allowable limit level THL is set to 105 (≈40% with respect to the full range 255). Since the initial value of the pixel defect determination level TH is 25, TH = 35, that is, TH ≦ THL at this time, and the process returns to the calculation of the number of defective pixels in step S6. If the number of detected defective pixels is 255 or less, the defective pixel address at that time is stored in the defective address storage area, and the pixel defect detection is completed.
[0035]
  Similarly, if the number of defective pixels detected in each determination is 256 or more, TH is incremented by 10 and the next defect determination is performed. If the number of defective pixels is 255 or less, the current The defective pixel address is stored in the defective address storage area, and the pixel defect detection is finished.
[0036]
  In this embodiment, since THL = 105, THL is reached when TH change is repeated eight times. Even if TH reaches THL, if the number of defective pixels exceeds 255, that is, 256 or more, the image quality failure state detection unit 19-4 determines that the image quality is in failure state (S10).
[0037]
  If the image quality failure state detection unit 19-4 determines that the image quality failure state is present, the image quality failure response processing unit 19-5 executes image quality failure handling processing. In this embodiment, the exposure time Ttotal is changed (shortening process) (S11).
[0038]
  In this Ttotal changing process, it is not necessary to perform test imaging again, the pixel defect determination level TH is changed to exceed the allowable limit level THL (= 105), the number of defective pixels is repeatedly detected, and the number of defective pixels is 255. The final pixel defect judgment level TH (fin) (but less than 255) when it falls within the range is obtained. Then, the exposure time Ttotal (fin) after the change at that time is obtained by Ttotal × THL / TH (fin), and actual photographing is performed with exposure based on the changed exposure time Ttotal (fin). fin), pixel defect compensation corresponding to the defective pixel and the normal defective pixel detected at the time of setting is performed. In the flowchart, the above-described exposure time Ttotal (fin) is calculated every time in step S11, and then returned to step S6.
[0039]
  Such a change in the exposure time Ttotal can be performed without redoing the test imaging until Ttotal (fin) ≧ 0.4 × Ttotal (the numerical value 0.4 is due to THL being approximately 40% of 105≈full range 255). However, in other cases, the change of TH exceeding THL reaches 255, so it is not possible to know the setting of the determination level as to how much the defective pixels can be reduced by reducing the exposure time. Set the exposure time to about 0.1 x Ttotal (the numerical value 0.1 is about 10% of the initial value of TH is 25 ≒ full range 255), perform test imaging again, and Ttotal (fin) based on the result You can ask for. (Note that the processing for redoing the test imaging is omitted in the flowchart of FIG. 2)
[0040]
  Now, after the pixel defect detection process is completed as described above, the case (2) is based on a predetermined exposure control value, that is, the exposure time, exactly as in the case (1) after the shooting trigger command. The total exposure of Ttotal or Ttotal (fin) is performed (S2), the image pickup signal is read and subjected to predetermined signal processing, and then recorded in the memory card 10 (S4). At this time, first, known pixel defect compensation is performed based on the defective pixel address data stored in the defect address storage area in step S8 (S3). The video signal processing in the subsequent circuit up to recording after defect compensation is common to both (1) and (2). Such processing includes balance processing, conversion to a luminance-color difference signal by matrix calculation or its inverse conversion processing, false color removal or reduction processing by band limitation, various non-linear processing represented by γ conversion, various information compression processing, and the like.
[0041]
  Thus, according to the present embodiment, an allowable limit level is set for the pixel defect determination level, and if the number of detected defective pixels exceeds the predetermined number (255) even at the allowable limit level, it is determined that the image quality is broken. However, since the exposure time is shortened, the exposure time is different from the originally planned one, but the occurrence of pixel defects is reduced and the image quality of the recorded image is prevented from being destroyed. Can do. That is, it is possible to avoid the problem of unintentionally recording an image whose image quality is broken.
[0042]
  In the above embodiment, when the image quality failure state detection unit 19-4 determines the image quality failure state, the image quality failure handling processing unit 19-5 performs processing with a reduced exposure time. However, if the exposure time is shortened, the shutter time will be shortened and a dark image will be captured. (In this case, if there is a margin in the aperture, this can be opened to compensate for the decrease in exposure value. However, when the aperture is fully open, it is invalid). Therefore, in the case where such dark image capturing is not originally planned, a measure to prohibit image capturing when an image quality failure state is detected is taken. You may comprise so that it may take.
[0043]
  Also, when the image quality failure state is determined, a warning is displayed with a buzzer (not shown), LCD image display system 11 or operation display system 14, etc. Imaging processing may be performed when the number of pixels becomes equal to or less than a predetermined value (255).
[0044]
  This warning process can be used in combination when the exposure time shortening process or the imaging prohibition process according to the present embodiment is performed. That is, when the exposure time shortening process is performed, a warning is displayed indicating that the shutter time has been shortened, and when the image capturing prohibition process is performed, a combined warning is given that the image cannot be captured even by operating the image capturing button. You may do it.
[0045]
  In the description of the above embodiment, for the sake of simplicity, the charge accumulation time and the exposure time are regarded as the same, but strictly speaking, charge accumulation is started before the start of exposure using a mechanical shutter. In the case of using a so-called delayed readout method in which the charge is transferred to the transfer path after a predetermined time after the exposure is completed or the stored charge is transferred to the transfer path and then transferred after a predetermined time. The two may not necessarily match. However, since the difference between the two is managed and recognized by the system controller 12, it may be applied to the above-described embodiment in consideration of this difference as necessary.
[0046]
  Various modifications other than the modification of the above-described embodiment are conceivable. First, as for the exposure time setting at the time of test imaging, the exposure time Ttotal of the main exposure is used as it is in the above embodiment. However, the test exposure time can be shortened by setting it to Ttotal / 2 or Ttotal / 10, for example. it can. In this case, the determination level TH may be set to 1/2 or 1/10 using the fact that the dark charge is substantially proportional to the accumulation time. Of course, if a similar correction is applied to the method of determination, a fixed value can be adopted as the test imaging exposure time at least until Ttotal is within a predetermined value or less.
[0047]
  Further, the test imaging timing is preferably just before the main imaging, but is not limited to this. For example, when the power is turned on, when the camera can be switched to the playback mode, when switching to the shooting mode, when operating the first stage of the two-stage release switch camera (second stage is the shooting trigger), when operating the test imaging switch provided separately For example, it may be configured to be performed at an arbitrary time depending on the purpose.
[0048]
  In addition, supplementing the quantization level of the A / D converter in the preprocess circuit used in the above embodiment, in reality, the existence of error characteristics possessed by the hardware of the A / D converter, Even if there is no A / D converter used in actual quantization in the above embodiment, considering that in principle the quantization error is relatively equivalent to 100% near the minimum quantization level. Is more preferable than the number of quantization bits (8 bits in this embodiment) of the image processing system, for example, about 10 bits or 12 bits (or more). It is possible to sufficiently reduce the influence of errors when calculating each arithmetic expression.
[0049]
  Although several embodiments and modifications of the present invention have been specifically described above, the present invention is not limited to these, and can take any form as long as it is described in the claims. Needless to say.
[0050]
【The invention's effect】
  As described above based on the embodiments, according to the present invention, an allowable limit level is set as a defect determination level in the defect determination means for limiting the number of defective pixels to be detected to a predetermined value or less. Image quality failure state detection means for determining an image quality failure state when the number of defective pixels exceeds a predetermined number even at the levelAnd image quality failure handling processing execution means for executing predetermined image quality corruption handling processing when the image quality failure status detection means detects the image quality failure status.Therefore, it is possible to execute image quality failure handling processing, and avoid the problem of unintentionally recording an image whose image quality has failed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of a digital camera according to an embodiment of an imaging apparatus of the present invention.
FIG. 2 is a flowchart for explaining the operation of the digital camera shown in FIG. 1;
[Explanation of symbols]
  1 Lens system
  2 Lens system drive mechanism
  3 Exposure control mechanism
  4 Filter system
  5 CCD image sensor
  6 CCD driver
  7 Preprocess circuit
  8 Digital process circuit
  9 Memory card interface
  10 Memory card
  11 LCD image display system
  12 System controller
  13 Operation switch system
  14 Operation display system
  15 Lens driver
  16 Strobe
  17 Exposure control driver
  18 EEPROM
  19 Defective pixel detector
  19-1 Test imaging unit
  19-2 Defect judgment section
  19-3 Defect pixel limit
  19-4 Image quality failure detection unit
  19-5 Image Quality Correspondence Processing Department
  20 Pixel defect compensation unit

Claims (4)

An image sensor for capturing a subject image, an exposure control means for controlling exposure to the image sensor, an accumulation time control means for controlling a charge accumulation time in the image sensor, and the exposure control means and the accumulation time control means. Defective pixel detection means for detecting a defective pixel in a predetermined operation state of the image pickup device under control, and pixel defect that compensates for the information on the defective pixel detected by the defective pixel detection means by pixel information in the vicinity of the pixel In the imaging apparatus including the compensation unit, the defective pixel detection unit performs a charge accumulation and readout operation in the imaging element in a state where exposure to the imaging element is blocked by the exposure control unit; Compare the image sensor output level obtained in response to this test imaging with a predetermined pixel defect judgment level. If the number of defective pixels once determined by the defect determination means exceeds a predetermined value, the determination by the defect determination means is performed again after changing the pixel defect determination level. A defective pixel number limiting unit that limits the number of defective pixels to be detected to be equal to or less than the predetermined value, and a defective pixel determined by the defect determination unit in a state where the pixel defect determination level has reached an allowable limit level. If the number of images exceeds the predetermined value, the image quality failure state detecting means for determining that the image quality failure state is detected, and when the image quality failure state detection means detects the image quality failure state, predetermined image quality failure handling processing is performed. An image pickup apparatus comprising: an image quality corruption handling process execution unit to execute . 2. The image pickup apparatus according to claim 1 , wherein the image quality failure handling process by the image quality failure handling process execution unit is an exposure time shortening process for shortening an exposure time in actual photographing. 2. The image pickup apparatus according to claim 1 , wherein the image quality failure handling process by the image quality corruption handling process execution unit is a shooting prohibition process. The imaging apparatus according to any one of claims 1 to 3 , wherein the image quality corruption handling processing execution unit includes a warning processing unit.

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