JP4372961B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that captures a subject image using an imaging element such as a CCD.
[0002]
[Prior art]
In recent years, various attempts have been proposed to obtain a captured image with a wide dynamic range by combining two images having different exposure amounts. In particular, even when a destructive readout type image sensor such as a CCD is used in order to prevent processing failure that occurs when a subject moves during the shooting of two images, A reading method devised so as to minimize the timing shift is described in, for example, Japanese Patent Laid-Open No. Hei 4-207581.
[0003]
Such two-image continuous imaging technology with a minimum time difference is not limited to the above wide dynamic range imaging, and has the potential to be applied to various image quality enhancement and new imaging functions by image processing using two images. As such, the technical expectations are great.
[0004]
[Problems to be solved by the invention]
In the application of synthesizing two images obtained by two-image continuous imaging, naturally, while satisfying special constraints different from general imaging in which two images can be obtained without timing deviation, of course, for normal one-image imaging. The image quality should not be degraded. Further, even if a slight deterioration in image quality is allowed, it is generally required that the image quality of the two images is the same, and this is a problem when one image quality is deteriorated. .
[0005]
However, since the above-mentioned special constraints are imposed, there are limited methods that can deal with various image quality degradation factors as compared with the case of taking a single image. It was. From this point of view, the present applicant is able to significantly reduce the occurrence of smear as compared with the prior art while satisfying the above-mentioned special restriction conditions by the previous patent application (Japanese Patent Application No. 2000-77136). Has proposed.
[0006]
However, even in such an imaging technique, particularly in the second image, the saturation level of the image signal is reduced as compared with the image obtained by capturing only one normal image or the first image when two images are continuously captured. The problem arises. More specifically, this phenomenon is caused by charge leakage in the photoelectric conversion accumulation region. Here, the above-described charge leakage which is a problem of the present invention becomes prominent after light shielding of the mechanical shutter, for example, and a part of the accumulated charge below the overflow level is lost with time in the charge accumulation unit of the image sensor. This is a phenomenon in which the saturation level of the signal in the charge storage portion is lowered.
[0007]
This is because the charge is discharged to the substrate side by overcoming the overflow level due to the quantum mechanical fluctuation of electrons. At this time (if no new photocharge is generated), the potential of the charge accumulating portion decreases as the charge leaks, so that the leakage current attenuates with the passage of time after light shielding. As a result, the accumulated charge amount, that is, the saturation signal amount of the image sensor output shows a logarithmic decay characteristic with respect to the elapsed time after light shielding, and the value is, for example, the saturation level after 1-2 ms. It drops to about 70%. Naturally, this is a quantum mechanical effect, so it can be ignored if the amount of charge handled is sufficiently large. However, since the amount of charge per pixel has become extremely small due to the recent increase in the number of pixels in the image sensor, it has become apparent. It is a phenomenon that is going on.
By the way, the existence of this phenomenon has been known per se. For example, in the interlaced scanning CCD image sensor, a technique for taking measures against the problem that the accumulated charge amounts in the odd field and the even field do not match and a line step is generated. The applicant himself has proposed (Japanese Patent Laid-Open No. 09-163239).
[0008]
On the other hand, in the progressive scanning CCD image pickup device, such a problem does not occur in principle because the shutter is electronically closed by a single charge transfer pulse (TG pulse). This is because the decrease in the saturation level due to this leak occurs during the period until the electric charge is transferred from the charge storage section to the vertical transfer path, so that in the sequential scanning type imaging device, the input light is irradiated. Even when a TG is output or when a mechanical shutter is used together, the TG is output almost simultaneously with the closing of the shutter so that the saturation level does not decrease, and the TG is output after a long time from the closing of the mechanical shutter. This is because even if the saturation level is lowered by this, there is no line step difference at least as in the interlaced scanning type imaging device, so that only a slight deterioration in image quality with respect to only that one image has occurred.
[0009]
However, regarding the two-image continuous imaging technique, even if a progressive scanning CCD imaging device is used, the above-mentioned special restriction condition is still imposed. The problem due to the decrease in the temperature will be noticeable. Moreover, since this occurs only in the second image, even if the deterioration is tolerable in general imaging, there is a problem that the image quality of the first image and the second image is not uniform. Will be invited.
[0010]
Of the above-mentioned problems, an example of a problem caused by irregular image quality is given as a reference. For example, there is a technique for detecting the movement of a subject by comparing the correlation between two images. For example, a reference window of a predetermined size is provided in the center of the first image, for example, the same size as the reference window in the vicinity of the center of the second image, and the relative position coordinates from the reference window are (i, j). A plurality of detection windows are provided, and for each (i, j), the total amount of difference absolute values for each pixel of the image signal of the reference window and the image signal of the detection window is calculated, and this total amount is minimum. (I, j) that obtains the maximum image correlation in the region to be compared is obtained and used as a motion vector (x, y). For example, prior to combining the two images, it may be used for an auxiliary purpose such as combining after correcting the shift between the two images due to movement, or canceling the combining if the shift is large. It can also be used to detect motion information independently of synthesis. In such a correlation comparison, it will be apparent that a malfunction may be caused if the image quality of the two comparison images is not uniform.
[0011]
Of course, before such a problem of uneven image quality, even if only one of the two images is used, it is a problem that image quality deterioration cannot be avoided under the constraint conditions of two-image shooting. In applications where random noise is reduced by adding and averaging to improve the image quality, the image quality of the second image is reduced, so that the image quality of the total image is lower than the originally obtained image quality. Is clear.
[0012]
The present invention has been made in view of the above-mentioned circumstances. While satisfying the constraint that two images can be obtained without timing shift, the first does not cause a decrease in the saturation level, and the second temporarily. An object of the present invention is to provide an imaging apparatus that can realize high-quality two-image continuous imaging in which the image quality of two images is uniformed by aligning the degree of lowering of the saturation level between the two images.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a solid-state imaging device, a driving unit that drives the solid-state imaging device, and an optical that can switch between a transmission state and a light-shielding state of a subject image with respect to an imaging surface of the solid-state imaging device. And an imaging control unit that controls exposure and image signal readout by controlling the driving unit and the shutter unit, and the imaging control unit is configured to control the shutter when imaging an image to be captured. Full exposure relating to the imaging is started by switching the light shielding state from the light shielding state by the means to the transmission state or outputting the final charge discharge pulse SUB by the driving means in the transmission state of the shutter means, and the light transmission state by the shutter means is shielded. Switch to the state to end all exposure related to the imaging, and from the start of all exposure to the total exposure The first exposure is finished by outputting the first charge transfer pulse TG1 by the driving means during the period of time, and the second exposure is started simultaneously with the first exposure. The transfer path driving of the solid-state imaging device for reading the generated first image signal is started after the completion of all exposures, and after the reading of the first image signal is finished, the second exposure is performed. The generated second image signal is transferred to the transfer path of the solid-state imaging device by the output of the second charge transfer pulse TG2, and then the transfer path is driven to read it out. Then, the set value of the substrate bias voltage VSUB of the solid-state imaging device is controlled to a different value, and the overflow level determined corresponding to the set value of the substrate bias voltage VSUB is set. In the first exposure period before the output of the first charge transfer pulse TG1, the first level is reached, and in the period from the end of all exposure to the output time of the second charge transfer pulse TG2, the first charge transfer pulse TG1 is output. The saturation level after the reading of the first image signal and the second image signal is kept equal to each other by setting each of the second level and the second level higher than the second level. To do.
[0014]
In this imaging apparatus, control is performed to set the overflow level of the solid-state imaging device to be larger in the period from the end of all exposures to the output point of the second charge transfer pulse TG2 than in the first exposure period. . As a result, the saturation level of the second image before the occurrence of the leak can be relatively increased with respect to the first image, so that at least the saturation levels of both the first and second images can be set to be equal, and the image quality of the two images is uniform. It is possible to realize continuous image pickup with high image quality.
[0015]
Further, the setting level change from the first level to the second level of the overflow level is started and completed within the transition period from the transmission state to the light-shielding state of the shutter unit related to the end of all exposure. It is preferable to control.
[0016]
In the transition period in which the shutter means is closed, the plate surface illuminance of the solid-state image sensor gradually decreases, so this period can be considered as a transition period from the adverse effect of blooming to the adverse effect of leak. On the other hand, increasing the overflow level corresponds to switching from the blooming suppression state to the leak suppression state. Therefore, by starting and completing the change of the overflow level during the transition period in which the shutter means is closed, it is possible to suppress the influence of blooming due to the increase of the overflow level, and to solve the problem due to the charge leak after the light is cut off. It becomes possible to improve.
[0017]
In particular, by using the control of gradually changing the overflow level from the first level to the second level in accordance with the transition from the transmission state to the light shielding state of the shutter unit, the transition from the blooming problem to the leakage problem can be achieved. Combined with the transition from the blooming suppression state to the leak suppression state, it is possible to obtain an optimal suppression effect according to the degree of occurrence of the problem.
[0018]
A means for detecting a change in a subject based on a difference between the first image signal and the second image signal, wherein the exposure time is set to be equal between the first exposure and the second exposure; By providing, it becomes possible to detect the change of the subject with high accuracy from two images with uniform image quality.
[0019]
Furthermore, by providing means for setting the exposure time to be equal between the first exposure and the second exposure, and averaging and outputting the first image signal and the second image signal, S / A high-quality image signal with a high N can be obtained.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an imaging apparatus according to an embodiment of the present invention. Here, the case where it implement | achieves as a digital camera is illustrated and demonstrated.
[0021]
In the figure, 101 is a lens system composed of various lenses, 102 is a lens driving mechanism for driving the lens system 101, 103 is an exposure control mechanism for controlling the aperture of the lens system 101, 104 is a mechanical shutter, and 105 is a color filter. Built-in CCD color image sensor, 106 is a CCD driver for driving the image sensor 105, 107 is a preprocess circuit including an A / D converter, 108 is a color signal generation process, matrix conversion process, and other various digital processes A digital process circuit for performing the processing, 109 is a card interface, 110 is a memory card, and 111 is an LCD image display system.
[0022]
In the figure, 112 is a system controller (CPU) for comprehensively controlling each part, 113 is an operation switch system including various operation buttons, 114 is an operation display system for displaying operation states and mode states, Reference numeral 115 denotes a lens driver for controlling the lens driving mechanism 102, 116 denotes a strobe as a light emitting means, 117 denotes an exposure control driver for controlling the strobe 116, and 118 denotes a nonvolatile memory for storing various setting information and the like. EEPROM).
[0023]
In the digital camera of the present embodiment, the system controller 112 performs all the control, and in particular, controls the mechanical shutter 104 and the CCD image sensor 105 driven by the CCD driver 106 to control exposure (charge accumulation) and signals. Is read into the digital process circuit 108 via the pre-process circuit 107 and subjected to various signal processing, and then recorded on the memory card 110 via the card interface 109.
[0024]
The drive control of the CCD image sensor 105 is performed using various drive signals (charge transfer pulse TG, vertical drive pulse, horizontal drive pulse, substrate voltage VSUB, etc.) output from the CCD driver 106. The CCD color imaging device 105 includes a charge storage unit arranged in a matrix and charge transfer paths (vertical charge transfer path, horizontal charge transfer path) arranged horizontally and vertically, for example, progressive scan ( A sequential scanning type vertical overflow drain (VOFD) structure or the like is used.
[0025]
When the charge transfer pulse TG is output, a transfer gate provided between each charge storage unit and the vertical charge transfer path is opened, and charge is transferred from each charge storage unit to the corresponding vertical charge transfer path. The substantial exposure time is controlled by the output timing of the charge transfer pulse TG. The substrate voltage VSUB is a substrate bias voltage for determining the maximum charge accumulation level (overflow level OFL) of the charge accumulating unit, and this VSUB is obtained by superimposing a large value pulse on the total charge on the substrate. It is also used for forced discharge.
[0026]
In the digital camera of the present embodiment, operations and controls similar to those of a normal digital camera are performed except for an imaging control sequence related to two-image continuous imaging described in detail below, particularly a portion related to variable control of the overflow level OFL. The description of such known parts is omitted.
[0027]
FIG. 2 shows a cross-sectional structure of an interline CCD having a vertical overflow drain structure, which is used as the image sensor 105 of the present embodiment.
The n-type semiconductor substrate 400 is formed of a first region 401 with a shallow junction and a second region 402 with a deep junction. The region of the first region 401 where the junction n-type region is formed functions as a photodiode, so-called photoelectric conversion region (charge storage portion) 403.
[0028]
In the second region 402, a vertical shift register or transfer electrode 405 including a buried channel 404 is formed. A transfer electrode 405 is disposed on the main surface through an insulating layer 406. The photoelectric conversion region 403 and the buried channel 404 are separated by a channel stop region 407 made of a high p-type impurity layer.
[0029]
A transfer gate region 408 is disposed between the photoelectric conversion region 403 and the corresponding buried channel 404. Further, light is shielded by the metal layer 409 except for the photoelectric conversion region 403. In order to suppress blooming, a substrate bias voltage VSUB 411, which is a reverse bias voltage, is applied to the junction between the N-type semiconductor substrate 400 and the first region 401 and the second region 402 of the P well, and the first well of the P well immediately below the photoelectric conversion region 403 is applied. This is realized by completely depleting the region 401 (depletion layer). Further, as described above, all charges can be forcibly discharged by superimposing a high potential pulse on VSUB.
[0030]
FIG. 3 shows a change characteristic of the saturation signal amount (overflow level OFL) of the charge storage unit with respect to the substrate bias voltage VSUB. As shown in the figure, the overflow level OFL can be lowered by increasing the absolute value of the substrate bias voltage VSUB.
[0031]
(Imaging control sequence 1)
Hereinafter, a first example of the imaging control sequence during continuous imaging of two images will be described with reference to the timing chart of FIG.
[0032]
Here, the substrate bias value corresponding to OFL is distinguished as VSUB, and the superimposed pulse at the time of discharging the charge is distinguished as a SUB pulse. In order to obtain a high saturation level, the OFL may be increased, but this is not possible because excessive charge overflows and blooms. Therefore, “OFL during normal imaging” described below is set to the maximum level of OFL within a range where blooming does not occur. The VSUB value corresponding to this is VN. VD is a vertical synchronization signal (however, since it is reset if necessary, it can also be called a start reference signal for one frame operation in that sense), V transfer is a vertical drive pulse for driving a vertical transfer path, The mechanical shutter indicates the open / close state of the mechanical shutter 104.
[0033]
When a shutter trigger (shooting start command) is input, an image pickup operation is started in synchronization with the first VD thereafter. A known high-speed charge discharge drive is started by the vertical drive pulse, and at the same time, a high-voltage SUB pulse is output, thereby discharging unnecessary charges in the vertical transfer path and the charge storage unit. Then, at the start time of the main exposure 1, a final SUB pulse is output to start full exposure for two-image continuous imaging. At this time, the mechanical shutter 104 is already open.
[0034]
Subsequently, the first charge transfer pulse TG1 is output while the mechanical shutter 104 is kept open to transfer the photocharge to the vertical transfer path, thereby completing the main exposure 1 and starting the second main exposure 2 at the same time. . At this time, in order to prevent the occurrence of the streaking smear, the reading of the first image obtained by the main exposure 1 is not started yet, i.e., the vertical drive pulse is stopped and the transfer of the signal charge is stopped. Then, after the main exposure 2 is completed by shielding the mechanical shutter 104, transfer path driving for reading the first image by the main exposure 1 is started. Further, after the reading of the first image is completed, the second image by the main exposure 2 is transferred to the vertical transfer path by the second charge transfer pulse TG2, and then the transfer path driving for reading it is started. Since there is no transfer driving during exposure in this way, even if smear occurs in the first image, it does not cause streaking smear. Further, the reading of the second image is performed in a state where unnecessary charges such as smear are not present in the transfer path by reading the first image.
[0035]
Here, when VSUB is fixed to the normal value VN as in the conventional case, the first image read in TG1 is the same as the conventional one, but the second image is several millimeters to 10 until TG2 after the main exposure 2 ends (light shielding). Since it takes several milliseconds, the saturation level is lowered.
[0036]
In this example, the VSUB setting change is started after the light shielding by the mechanical shutter 104 is started, and the VN reaches a lower VL than the VN before the light shielding is completed. That is, in the period of the main exposure 1 before the output of TG1, “OFL at the time of normal imaging” is set, but from the end of all exposure due to light shielding of the mechanical shutter 104 to the output time of TG2, “at the time of normal imaging” Is set to a level higher than “OFFL”. Here, VL is a value several tens of percent lower than VN, and if it is lowered to this level, the saturation level hardly decreases.
[0037]
Note that the VSUB set value may be further lowered than VL after the completion of light shielding. This is because there is no light incident after the light is blocked, so that the problem of blooming does not occur, and even if the OFL is increased, there is no adverse effect on the image quality.
[0038]
Since the plate surface illuminance gradually decreases during the transition period in which the shutter 104 is closed, it can be said to be a transition period from the adverse effect of blooming to the adverse effect of leakage. On the other hand, lowering VSUB from VN to VL corresponds to switching from the blooming suppression state to the leak suppression state. Therefore, it is necessary to start and complete voltage switching during this period. As shown in the figure, gradually changing the value of VSUB along with this period is a particularly effective control in the sense that a suppression effect according to the degree of occurrence of the failure can be obtained.
[0039]
With the above imaging control, the saturation levels of two temporally adjacent images can be made the same as usual, so that the image quality of the two images can be kept equal. Although the occurrence of blooming due to an increase in OFL is a concern, the control does not substantially cause a problem as described above. In addition, the exposure time of the main exposure 2 is set longer than that of the main exposure 1. This is because a good pixel portion is extracted from each of the two images and synthesized to obtain a recorded image with a wide dynamic range. Because.
[0040]
(Imaging control sequence 2)
Next, a second example of the imaging control sequence at the time of two-image continuous imaging will be described with reference to the timing chart of FIG.
[0041]
Here, it is assumed that VSUB is not controlled to be lower than VN. That is, since the saturation level of the second image is lowered, during the first image exposure (until TG1 output is completed), VH corresponding to a low OFL corresponding to this is set, and VSUB is immediately set after TG1 output is completed. Change from VH to VN and reset to “OFL during normal imaging”. In this case, the saturation level of the two images is lower than usual, but can be kept equal. Also, there is no concern that blooming will increase.
[0042]
Note that the decrease in the saturation level in the second image changes depending on the delay time from light shielding to TG2, but since this is constant in one frame period, during the first image exposure (until TG1 output is completed) What is necessary is just to set to the value of VH corresponding to this.
[0043]
Also, if the delay in changing to VN increases with respect to the period of the main exposure 2, the saturation level of the second image may be lowered accordingly, but it can usually be ignored by quick setting.
[0044]
(Motion detection and averaging of two images)
Next, an example of subject motion detection will be described as a function to which two-image continuous imaging according to the imaging control sequence 1 or 2 described above is applied.
[0045]
(1) First, an appropriate exposure is calculated by a known photometric unit included in the system controller 112 using an image output of preliminary exposure in advance, and an exposure time t1 based on the aperture value to be used is determined.
(2) After controlling the aperture to that value, the imaging control 1 or 2 sets the exposure times of the main exposure 1 and the main exposure 2 to the same t1, and performs imaging.
[0046]
(3) A motion vector (x, y) is obtained by correlation calculation for the captured first image and second image. Specifically, a reference window having a predetermined size is provided in the center of the first image, the same size as the reference window is provided in the vicinity of the center of the second image, and the relative position coordinates from the reference window are (i, j). A plurality of detection windows are provided, and for each (i, j), the sum of absolute difference values for each pixel of the image signal of the reference window and the image signal of the detection window is calculated, and this sum is minimized. (I, j) is obtained and this is set as a motion vector (x, y).
[0047]
(4) The amount of movement m is expressed as m = (x2 + y2) ^1/2 Ask for.
(5) The state of shooting is determined by m ≦ 2 (numerical value 2 is an example and can be set to an arbitrary value). That is, the amount of movement corresponds to image blur (motion blur), but if this is within 2 pixels, it is judged good, and if it exceeds, it is judged that the blur is large.
(6) An average calculation is performed for each pixel of the first image and the second image, and the result of the addition average is recorded as a recorded image.
(7) A warning is issued if “blur is large” in (5) above.
[0048]
According to this example, it is possible to obtain a high-quality image in which random noise is reduced by the average addition of two images, and the saturation level does not decrease despite the use of the two-image shooting technique. It is possible to realize a high-functionality and high-quality camera that can detect and warn of image blur caused by camera shakes more accurately.
[0049]
Note that two-image continuous imaging may be used only for motion detection, and actual imaging for actually obtaining a recorded image may be performed by normal single imaging after two-image continuous imaging. In this case, as the exposure time t2 at the time of single imaging, a value different from the exposure time t1 of each imaging at the time of continuous imaging of two images can be used. It is effective to use m ′ (m ′ = m × t2 / t1) obtained by converting the exposure time ratio. In other words, the value of the motion amount m detected by the two-image continuous imaging is converted into an exposure time at the time of actual imaging performed after the two-image continuous imaging to obtain m ′, and it is determined whether m ′ ≦ 2. By doing so, the degree of blurring of the image during actual imaging is detected.
[0050]
Furthermore, in (6), a process for correcting the movement deviation between the first and second images (for example, a coordinate shift process of (−x, −y) with respect to the entire second image) is added to obtain the movement deviation. It is possible to configure so as to perform an average calculation of the two images after correcting. As a result, only a motion blur is generated during one exposure period, which is a very preferable modification.
[0051]
In addition, the following various application examples are conceivable.
-The mechanical shutter 104 may be kept open in advance, and exposure may be started by a SUB pulse. In this case, it is necessary to continuously perform the charge discharging drive of the transfer path before the output of TG1, but the control of the mechanical shutter 104 can be simplified to only the closing operation. Needless to say, the exposure can be started by opening the mechanical shutter 104 by switching the order of the mechanical shutter opening and the final SUB pulse output in the previous embodiment.
[0052]
The main exposure 2 may be started after a SUB pulse for forcibly discharging charges is output immediately after TG1 output. (Including such a case, the object can be achieved if the end of the first exposure and the start of the second exposure are substantially at the same time, which are included in the scope of the claims of the present invention.)
[0053]
【The invention's effect】
As described above, according to the present invention, it is possible to realize high-quality imaging that does not cause a decrease in saturation level while satisfying the condition that two images can be obtained without timing deviation.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a cross-sectional structure of an image sensor used in the image pickup apparatus of the embodiment.
FIG. 3 is a view showing a relationship between a substrate voltage and an overflow level of the image sensor used in the embodiment.
FIG. 4 is a timing chart showing a first imaging control sequence used in the embodiment.
FIG. 5 is a timing chart showing a second imaging control sequence used in the embodiment.
[Explanation of symbols]
101 ... Imaging lens
102: Lens drive mechanism
103. Exposure control mechanism
104 ... Mechanical shutter
105 ... CCD color image sensor
106 ... CCD driver
107: Preprocess circuit
108: Digital process circuit
112 ... System controller

Claims (5)

A solid-state imaging device; a driving unit for driving the solid-state imaging device; an optical shutter unit capable of switching between a transmission state and a light-shielding state of a subject image with respect to an imaging surface of the solid-state imaging device; and the driving unit and the shutter unit Imaging control means for controlling the exposure and readout of the image signal by controlling
The imaging control unit switches the light shielding state from the light shielding state to the transmission state by the shutter unit or outputs the final charge discharge pulse SUB by the driving unit in the transmission state of the shutter unit when imaging the image to be captured. Starts full exposure related to the imaging, ends the total exposure related to the imaging by switching the transmission state by the shutter means to a light shielding state, and the driving means during the period from the start of the full exposure to the end of the full exposure. The first exposure is finished by outputting the first charge transfer pulse TG1, and the second exposure is started at the same time, and the first image signal generated by the first exposure is read out. The transfer path driving of the solid-state imaging device for the first time is started after the completion of the entire exposure, and the first After the readout of the image signal is completed, the second image signal generated by the second exposure is transferred to the transfer path of the solid-state imaging device by the output of the second charge transfer pulse TG2, and then read out. And is configured to perform transfer path driving for
The set value of the substrate bias voltage VSUB of the solid-state imaging device is controlled to a different value, and the overflow level determined corresponding to the set value of the substrate bias voltage VSUB is set to the first level before the output of the first charge transfer pulse TG1. In the exposure period, the first level is set, and in the period from the end of all exposure to the output time of the second charge transfer pulse TG2, it is set to a second level higher than the first level. Thus, the image pickup apparatus is configured to keep the saturation level after reading the first image signal and the second image signal equal to each other. The change of the setting level from the first level to the second level of the overflow level is started and completed within the transition period from the transmission state to the light-shielding state of the shutter unit related to the end of all exposure. The imaging apparatus according to claim 1. The first exposure and the second exposure are further set to have the same exposure time, and further includes means for detecting a change in the subject based on the difference between the first image signal and the second image signal. The imaging apparatus according to claim 1. The apparatus further comprises means for setting the exposure time to be equal between the first exposure and the second exposure, and adding and averaging the first image signal and the second image signal. The imaging device according to claim 1. An imaging apparatus capable of continuously capturing two images using a solid-state imaging device,
An optical shutter means capable of switching between a transmission state and a light-shielding state of a subject image with respect to an imaging surface of the solid-state imaging device;
By outputting the first charge transfer pulse TG1 during the entire exposure period for continuous imaging of the two images, the first exposure is terminated at the same time as the second exposure is started, and the first exposure is performed. The second exposure is started after the transfer path driving of the solid-state imaging device for reading the generated first image signal is started after the whole exposure period is finished, and after the reading of the first image signal is finished. And an image pickup control means for driving the transfer path for reading out the second image signal generated by the transfer to the transfer path of the solid-state imaging device by the output of the second charge transfer pulse TG2. ,
The image pickup control means has a second overflow level higher than the first level from the first level in accordance with the transition from the transmissive state to the light-shielded state of the shutter means at the end of the entire exposure. An image pickup apparatus configured to control a set value of a substrate bias voltage VSUB of the solid-state image pickup device so as to gradually change to a level of the solid state image pickup device.

Images