JP2804782B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to, for example, a still video camera system, and more particularly, to an image pickup apparatus for expanding a dynamic range of a solid-state image pickup device.

[Related Art] In recent years, still video cameras (electronic still cameras) using a still video disk having the same structure as a floppy disk as a recording medium have appeared. In this camera, for example, an image playback processor is configured to be electrically and mechanically detachable, and an image taken while being carried by the camera alone is recorded on a still video disk built in the camera, and the camera is used for image playback. Connected to a processor for playback of recorded images on a still video disc, and display or obtain a hard copy so that the images can be viewed.

By the way, in such a still video camera, an imaging device such as a CCD (solid-state imaging device) is used as an imaging device for capturing an image.

In such an image sensor, as shown in FIG.
There is a predetermined saturation level LS of the image sensor. In a still video camera, light accumulation is a maximum LS within a horizontal scanning period 1H of the television, and this LS becomes a saturation level.
Therefore, the output is saturated when light with a light amount Lm exceeding the saturation level LS is incident within the 1H period. In such a case, as a method of expanding the dynamic range, there is a method of reading out the accumulated charges of the image sensor twice and adding them to obtain a video signal for one image.

However, in this method, the shutter speed is doubled so that one screen is imaged twice, that is, two consecutive shots, and the video output for each image is added and synthesized. That is, as shown in FIG. 10, the first read output video signal photographed by the first shutter operation and the second read output video signal photographed by the second shutter operation are added, and each shutter operation is performed. The exposure time is set to half of the normal exposure time, and the amount of incident light during each exposure time does not exceed the saturation level LS so that the added video signal becomes the original level and the effect of the saturation level LS Is excluded.

[Problems to be Solved by the Invention] As described above, the image sensor has a saturation level with respect to the incident light amount, and is saturated with respect to the light amount exceeding this saturation level, so that the resolution is deteriorated. Therefore, in order to eliminate the influence of the saturation, there has been a method in which one image is photographed twice by two shutter operations to obtain respective video signals, and the two are added to obtain one image. However, a still video camera is configured to execute a series of sequences in synchronization with a television synchronization signal so that a captured image can be reproduced and viewed as a television image. In the case of the NTSC system, the vertical synchronization is 1/60 second in one field in the case of the field sequential system, and therefore, the reading time is at most once per field. In this case, if the above-described dynamic range expansion method is adopted, two shots are performed to obtain one image, so that the second shot is delayed by 1/60 second from the first shot. This delay is not a problem for photographing a still object or a slow-moving subject, but causes a serious problem when photographing a fast-moving subject.

For example, as can be clearly understood from a case in which an image is blurred unless the shutter speed is set to a high speed such as 1/500 or 1/1000, the shutter is shuttered twice at an exposure time of half the shutter speed. Even if it is cut, a shift of 1/60 second is inevitable between the two, and therefore, the first and second images have a large shift. Then, if these two images are added, an image with large blur will result due to the difference between the two, and as a result, a clear photograph cannot be taken when a moving subject is to be photographed.

Accordingly, an object of the present invention is to provide an optimal image pickup apparatus which can be applied to a still video camera or the like which can expand a dynamic range of an image pickup device and can obtain a clear image even with a fast moving subject. To provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention has taken the following measures. That is, in an image sensor, an output signal of the same pixel is read out at least twice and added to obtain a video signal for one screen. Means for controlling readout separately for each of the first and second halves, taking the difference between these readout signals, taking the signal of the absolute value of the difference as a base clip to obtain the correction amount of the added signal, and performing the subtraction correction And a correcting means for outputting. Second, the correction means detects the movement of the subject from the two signals read by the read control means, and when the movement is equal to or less than a predetermined value, adds the read signals. Third, the correction means selects whether or not to add the two read signals in accordance with the incident amount information or the focal length information of the photographing lens, and performs the addition correction.

[Operation] By taking such a measure, the following effects are exhibited. That is, the output signal of the same pixel in the image sensor is read out at least twice, and they are added to obtain a video signal for one screen, thereby expanding the dynamic range of the image sensor. The video signal for one screen is divided into two exposure periods for one photographing and read separately for the first half and the second half, and is obtained in the form of two video signals. Then, correction is performed by a correction unit to remove blur after addition and synthesis when there is a shift between the two images. In the case of the first invention, the correction is performed by subtracting the difference between these read signals. Then, the signal of the absolute value of the difference is base-clipped to obtain the correction amount of the added signal, and the signal is subtracted and output. As a result, the portion corresponding to the displacement is removed by the subtraction correction, and only the portion without the displacement is synthesized. Therefore, the dynamic range of the image sensor can be expanded, and the occurrence of blur due to image shift can be suppressed.

In the case of the second invention, the correction means detects the movement of the subject from the two signals read from the read control means, and when the movement is equal to or less than a predetermined value, adds the read signals. When the motion is equal to or greater than a certain value, one of the video signals obtained by reading twice and obtaining each without performing the addition process is amplified by a factor of two and output. Thereby, the second
In the case of the invention, when the motion is equal to or less than a predetermined value, the addition and synthesis are performed as it is, and when the motion is equal to or more than the predetermined value, one of the video signals is amplified by a factor of 2 without being added and output. The dynamic range of the image sensor can be expanded only by the correction operation, and the occurrence of blur due to image shift can be suppressed.

In the case of the third invention, the correction means selects whether or not to add the two read signals in accordance with the incident light amount information or the focal length information of the photographing lens, and performs the addition correction. That is, when the exposure time or the focal length is long, there is a high possibility that the two video signals will be shifted. In this case, without addition correction, one of the video signals obtained by reading twice and obtaining each of the two video signals is used. The signal is amplified by a factor of two and output. Otherwise, the two video signals are added. As a result, the dynamic range of the imaging element can be expanded with only a simple operation, and the occurrence of blur due to image shift can be suppressed.

Therefore, according to the present invention, it is possible to provide an optimal image pickup apparatus that can be applied to a still video camera or the like by being able to expand the dynamic range of the image pickup device and obtain a clear image even with a fast-moving subject. I can do it.

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

Here, the technology underlying the present device, which will be described below, is referred to as a still video camera.
It modulates, amplifies, and applies the image signal from the image sensor to a magnetic recording medium to perform magnetic recording. Readout from the image sensor to enable playback as TV video,
1/60 which is the time of one field in the case of field sequential
It is synchronized with the vertical synchronization signal VD every second. Since the still video disk is used as the magnetic recording medium, the same applies to the drive system of the magnetic recording medium. In the magnetic recording medium, image information is concentrically recorded on a magnetic surface of a magnetic disk based on a flexible thin circular plastic film by a recording / reproducing magnetic head moving in a radial direction by a head access mechanism. When recording image information in a still video camera, this concentric recording track is, for example, the maximum.
Fifty lines are formed at equal intervals, and a field image is recorded on each track for one frame. In order to record a field image for one frame per track, the drive system of the magnetic recording medium rotates the magnetic recording medium once in 1/60 second, and generates a pulse for each rotation. Used as a synchronization pulse corresponding to the vertical synchronization signal VD.

The trigger button of the camera, which is a shutter button, is a two-stage switch. When the trigger button is pressed, the first stage operates first, whereby the photometric system functions and the drive of the magnetic recording medium rotates. The metering system and the AF (autofocus) system measured the exposure and distance of the subject, and based on the measurement results, the system controller determined the exposure and shutter speed, and set the exposure and shutter speed and set autofocus. Then, in the second stage, the shutter is driven in synchronization with the synchronization pulse, exposure is performed, an image is captured, a video signal is read from the image sensor, modulated, and the modulated signal is sent to a drive of a magnetic recording medium to transmit the modulated signal. It is applied to a magnetic head and recorded on a recording track. For reproduction, the recording signal of the recording track is read by the magnetic head,
Demodulates, performs predetermined process processing such as dropout compensation and skew distortion correction, adds and outputs a synchronization signal, gives it to a TV monitor, etc. and displays it as an image, or hard copies it with a video printer etc. Launch as

The apparatus of the present invention is such a still video camera system in which the configuration of an image pickup / recording system is configured as shown in FIG. That is, 1 is a camera lens, 2 is an aperture, 3 is a shutter, 4 is a half mirror, 5 is a solid-state image sensor, 6 is an A / D converter, 7 is a changeover switch, 8 is a drive control signal generator, and 9 is a drive control signal generator. A field memory, 10 is an addition circuit, 11 is a mirror for reflection, 12 is a photometry unit, 13 is a system controller, and 14 is a signal correction unit.

Lens 1, aperture 2, shutter 3, half mirror 4,
The mirror 11 constitutes an optical system, and an optical image of a subject passes through the lens 1, is distributed by the half mirror 4, and is guided to the solid-state imaging device 5 and the mirror 11. The distribution light incident on the mirror 11 is guided to the photometry unit 12. The photometry unit 12 detects the exposure light amount from the distributed light and measures the distance of the subject image. The system controller 13 receives the distance measurement data and the exposure light amount data and, if the shutter speed is manually set, sets the exposure light amount data. If the aperture value is manually set, the shutter speed is determined based on the data of the exposure light amount, and a setting signal of the aperture value is given to the aperture driving mechanism, and the setting is performed. The focus control is performed by giving a control signal to the drive mechanism of the lens 1 so that the subject image is focused on the light receiving surface of the solid-state imaging device 5 based on the distance measurement data. The shutter speed is obtained by stopping the drive command when the elapsed time from the application of the shutter drive command reaches the shutter speed set time corresponding time, thereby obtaining a shutter speed corresponding to the set time.

The system controller 13 plays a central role in controlling the entire camera, and the solid-state imaging device 5 uses, for example, a CCD, and the time when half of the exposure time determined by the shutter speed has elapsed and the exposure time. At the end of the time, control is performed so as to read out the accumulated charges. This read control is performed by the drive control signal generator (SSG; sync signal generator) 8 which generates a synchronization signal for CCD read drive. The control of the drive control signal generator 8 is controlled by the system controller 13. Done. That is, the system controller 13 outputs a read pulse at the time when half of the exposure time determined by the shutter speed has elapsed after the start of the shutter drive and at the end of the exposure time, and upon receiving the read pulse, the drive control signal generator 8 Generates a synchronization pulse for driving the CCD readout. When the trigger button is operated, the drive control signal generator 8 performs a process of performing unnecessary charge release control of the CCD in accordance with a command from the system controller 13, and performs an electronic shutter release drive control. It is assumed that the CCD is controlled so that it can be exposed for a maximum of two fields. In addition, it has a mechanical shutter, which is controlled to be opened after the trigger button is operated until the opening time of the electronic shutter reaches the exposure time.

The A / D converter 6 converts a read video signal of the solid-state imaging device 5 into a digital signal. The changeover switch 7 is used to supply the read video signal to one of the adder circuit 10 and the field memory 9. This is for performing path switching. The field memory 9 is a memory having a capacity for one field, and among the image signals read out twice from the solid-state imaging device 5 for each photographing, the first
The changeover switch 7 is switched to supply the first readout output video signal to the field memory 9 and to supply the second readout output video signal to the adder circuit 10. At the output timing of the second readout output video signal, the system controller 13 is configured to read out the first readout output video signal from the field memory 9 in synchronism with the second readout output video signal and control the readout output video signal to be supplied to the adder circuit 10. It is.

The first reading of the video signal from the solid-state imaging device 5 is based on a reading pulse output at the time when half of the exposure time has elapsed. And the second reading of the video signal is performed after the end of the exposure time. That is, in the CCD, as shown in FIG. 3, a charge corresponding to the amount of incident light is accumulated in a cell CL which is a pixel formed in a grid pattern, and when the readout control is performed, each cell CL group in the same column is read out. The charge is transferred to the vertical transfer path VT provided, and the charge in the vertical transfer path VT is output to the outside by output control. And the vertical transfer path
The output of the VT charge to the outside is synchronized with the TV system.
The time when the first vertical synchronization pulse is generated after the transfer to the vertical transfer path VT, and one vertical period (one field period) from this time, and the CCD generates the vertical synchronization pulse at the time when the one vertical period elapses Second vertical transfer path VT from
Then, the system controller 13 performs a control of transferring the charges to the outside of the vertical transfer path VT for one vertical period from this point. Also, in this system, the first
The second reading of the video signal is at the time when half of the exposure time has elapsed, but since the exposure time is still the other half, charge accumulation continues during that time, and therefore, the second charge reading is performed. Will be possible.

The signal correction unit 14 is a processing circuit for correcting a shift in the case of a moving image with respect to the signal output from the addition circuit 10, and sends the corrected video signal to a subsequent process processing unit. Necessary process processing as a video signal is performed. Then, after modulation, the data is recorded on a recording medium.

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

When the trigger button of the camera is pressed, the mechanical shutter opens at the first step of the operation of the trigger button, and the optical image of the subject passes through the lens 1 and is distributed by the half mirror 4 to be guided to the solid-state imaging device 5 and the mirror 11. Then, the distribution light that has entered the mirror 11 is guided to the photometry unit 12. The photometry unit 12 detects the exposure light amount from the distributed light and measures the distance of the subject image. The system controller 13 receives the distance measurement data and the exposure light amount data and, if the shutter speed is manually set, sets the exposure light amount data. If the aperture value is manually set, the shutter speed is determined based on the data of the exposure light amount, and a setting signal of the aperture value is given to the aperture driving mechanism, and the setting is performed. Then, based on the distance measurement data, a control signal is given to the drive mechanism of the lens 1 so that the subject image is focused on the light receiving surface of the solid-state imaging device 5, and focus control is performed. The electronic shutter speed is obtained by giving a drive command to close the mechanical shutter when the elapsed time from the issuance of the shutter drive command reaches the shutter speed set time corresponding time, thereby obtaining a shutter speed corresponding to the set time. (FIGS. 2 (b) and 2 (c)).

On the other hand, the solid-state imaging device 5 uses, for example, a CCD, and is controlled so as to read the accumulated charge at a time when half of the exposure time determined by the shutter speed has elapsed and at a time when the exposure time ends. The read control is performed by the drive control signal generator 8 which generates a synchronization signal for CCD read drive.
Is controlled by the system controller 13.
That is, the system controller 13 outputs a read pulse at the time when half of the exposure time determined by the shutter speed has elapsed after the start of the shutter drive and at the end of the exposure time (FIG. 2 (d)). Upon receiving the signal, the drive control signal generator 8 generates a synchronization signal for driving to read out the CCD. In addition, the drive control signal generator 8 performs a process of performing unnecessary charge release control of the CCD according to a command from the system controller 13 when the trigger button is operated, and after the shutter release drive control is performed. The CCD is controlled so that it can be exposed for a maximum of two fields. The read image signal of the solid-state image pickup device 5 is converted into a digital signal by the A / D converter 6, and the digitalized read image signal is sent to one of the adder circuit 10 and the field memory 9 by the changeover switch 7. give. The field memory 9 is a memory having a capacity for one field, and stores a first read output video signal among image signals read out twice from the solid-state imaging device 5 for each photographing. Therefore, the changeover switch 7 is controlled by the system controller 13 so that the first readout output video signal is supplied to the field memory 9 and the second readout output video signal is supplied to the adder circuit 10. At the output timing, the first read output video signal is read from the field memory 9 in synchronization with the second read output video signal, and is supplied to the adder circuit 10.

As shown in FIG. 2D, the first reading of the video signal from the solid-state imaging device 5 is based on a read pulse output at the time when half of the exposure time has elapsed. The solid-state imaging device 5 transfers the current accumulated charge to the vertical transfer path, and the second reading of the video signal is performed after the end of the exposure time. That is, in the CCD, as shown in FIG. 3, a charge corresponding to the amount of incident light is accumulated in a cell CL which is a pixel formed in a grid pattern, and when the readout control is performed, each cell CL group in the same column is read out. The charge is transferred to the vertical transfer path VT provided, and the charge in the vertical transfer path VT is output to the outside by output control. Then, in order to synchronize the output of the vertical transfer path VT to the outside with the television system, as shown in FIG. 2 (e), the first vertical synchronization pulse after the transfer to the vertical transfer path VT is generated. One vertical period (period of one field) from this point in time, the charge transfer from the CCD to the second vertical transfer path VT is performed at the vertical synchronization pulse generation timing at the time when the one vertical period has elapsed, and subsequently, From this point on, for one vertical period, the system controller 13 controls to output the electric charge of the vertical transfer path VT to the outside. Further, in the present system, the first reading of the video signal from the solid-state imaging device 5 is at the time when half of the exposure time has elapsed, but since the exposure time is still the other half, the electric charge is accumulated during that time. , So that the second charge reading can be performed.

Although not shown in FIG. 1, the signal sent from the switch 7 to the addition circuit 10 and the read signal from the field memory 9 are given to a signal correction unit 14, which has a motion for both signals. It is checked whether or not the image is an image based on a shift between the two signals. If the image has a motion, the signal output from the adding circuit 10 is corrected to remove the shift. The video signal that has passed through the signal correction unit 14 is sent to a subsequent processing unit, where necessary processing is performed as a video signal, modulated, and recorded on a recording medium.

 Here, an example of the configuration of the signal correction unit 14 is shown in FIG.

As shown in the figure, the signal correction unit 14 includes a difference extraction circuit 14a for obtaining absolute value data of a difference between the video signal data a sent from the changeover switch 7 to the addition circuit 10 and the video signal data b read from the field memory 9. This difference extraction circuit 14a
Of the absolute value of the difference between the video signal data a and b output by the clip level processing unit 14b, which cuts a portion equal to or less than a predetermined value, and subtracts the output of the clip level processing unit 14b from the output of the addition circuit 10. And an adding circuit 14c.

The operation of such a circuit will be described with reference to FIG. 5. The difference extraction circuit 14a outputs the data a of the second read-out output video signal (5
(A) and data b of the first read output video signal which is a read output from the field memory 9 (FIG. 5 (b))
Then, the difference between them (FIG. 5 (d)) is obtained, and then the absolute value data is obtained (FIG. 5 (e)). In the case of a moving subject, there is a difference between the two data a and b. If the two are simply added and synthesized, a level difference occurs by the amount S of the image movement as shown in FIG. Will appear. Then, in order to remove this blur, the difference between the two data a and b (FIG. 5 (d)) is obtained as described above, and then the absolute value data is obtained (FIG. 5 (e)). , Image data equivalent to blurring, and
By passing through 14b, a portion below a predetermined value is cut. This is an image in which the data a and b originally have a time lag, and since it is inevitable that a difference in luminance level occurs even in the same pixel portion, it is only digital processing to remove even a slight level difference. On the contrary, there is a fear that the image becomes unnatural. Therefore, the clip level LV (=
L2) to avoid this by cutting the parts below this level.

Then, the data clipped by the clip level processing unit 14 is given to the adder circuit 14c as L1 as negative data, and the output from the adder circuit 10 (added value of the data a and b) is given here.
The correction is performed by adding (FIG. 5 (c)). If there is a movement between the data a and b, simply adding the two reveals the part where the deviation has occurred. However, when the above-described correction is applied, the deviation is substantially eliminated (FIG. 5 (f)). )), The blur can be prevented. Of course, of the deviation data,
If the clip data is equal to or more than the clip level, the shift data of the level equal to or less than the clip level remains, but this is not a problem because it is small.

FIG. 6 shows another embodiment of the signal correction unit 14. In this example, the object data movement is detected by comparing the first and second readout output video signals a and b corresponding to the cells of the image sensor, that is, the pixels, and only when there is no motion, both video signal data a , b are added, and a correction is made so that the luminance change in the area of the displaced part in the case of movement is smooth, and the addition and synthesis are performed. In this case, the adder circuit 10 used in the embodiments described above is unnecessary, and the signal correction unit 14 includes the video signal data a sent from the changeover switch 7 and the video signal read from the field memory 9 synchronized with the data a. A motion detector 141 which receives the data b in correspondence with each pixel, detects the presence or absence of a difference between the data values of the two, and outputs a coefficient value K so as to perform correction when it is detected that there is motion;
And first and second correction circuits 142 and 143 that receive the output coefficient value of the motion detection unit 141 and correct data corresponding to the coefficient value K, 2-K times, and among these correction circuits 142 and 143, the correction circuit 142 Adder 144 for adding and synthesizing the second read-out output video signal data a obtained through the control circuit 143 and the first read-out output video signal data b obtained through the correction circuit 143.
It consists of:

Such a circuit receives the data a of the second readout output video signal input from the changeover switch 7 and the data b of the first readout output video signal, which is a readout output from the field memory 9, in a pixel-by-pixel manner. The detecting unit 141 detects the difference between the two, and if there is a difference, determines that there is movement. And
When the motion detecting unit 141 determines that there is a motion, the motion detecting unit 141 generates a coefficient value K for performing correction, and supplies the coefficient value K to the correction circuits 142 and 143.

For example, as shown in FIG. 7, assuming that the luminance of the pixels P1 to P6 has changed, the luminance value of the pixels P1 to P3 does not change, so that the coefficient value K is set to “1”. Is also "1", and it is determined for the first time that there is a pixel change at the position of the pixel P4. Then, at the time of pixel P5, P4
, It is determined that there is a pixel change. In this case, there is a continuous change, so here the coefficient value K is changed by “「 ”for the first time. Therefore, in the example of the figure, the coefficient value K is “1 (1/1 /
2) ", and the coefficient value 2-K is" 1/2 ". Further, since it is determined that there is a change even at the time of P5, K, 2-K at the time of P6.
Both are further changed by “1/2”, and the coefficient value K is set to “2” and the coefficient value 2-K is set to “0”. Using this as a multiplier, the input data a and b at that time are multiplied by the multiplier, and the result is added to an adder circuit 144.
And outputs the result. The coefficient value is not limited to the above example, but the point is that if there is a change in the pixels, the data is corrected so that the luminance changes smoothly. In the above example, the luminance of the data a is large. However, when the luminance of the data a becomes equal to the data b, the coefficient value K is changed from “2” to “1 (1 / 2) "and" 1 ", and the coefficient value 2-K changes from" 0 "to" 1/2 "and" 1 ". As a result, the luminance of the shifted portion changes smoothly.

By the way, when the exposure time or the focal length of the lens is long, there is a high possibility that the two video signals are shifted, so an example to deal with this case will be described below. Since the system controller 13 performs autofocus and exposure control of the camera, the system controller 13 controls the changeover switch 7 shown in FIG. 8 according to the exposure time or the focal length. The changeover switch 7 is configured to select any one of the three directions.
An amplifier 15 having an amplification factor of is provided. When the exposure time or the focal length is short, the first readout output video signal is stored in the field memory 9, and when the second readout output video signal is output, the first readout output video signal and the first readout video signal stored in the field memory 9 are stored.
The readout output video signal is supplied to an adder circuit 10, added and synthesized, and output.

On the other hand, if the exposure time or focal length is long, 2
Since there is a high possibility that two video signals will be displaced, in this case, no addition correction is performed. For example, the first read output video signal is sent to the amplifier 15, where it is amplified by 6 dB and output. In this system, the period is divided into two during the same shutter opening / closing period from the image sensor, and the data is read out twice before and after the addition and combined, so that the combined data is doubled. Therefore, the amplifier 15 needs to amplify the input twice. Therefore, there is a gain of 6 dB. As described above, when the exposure time or the focal length is long, there is a high possibility that the two video signals are shifted. In this case, the addition is not corrected and one of the video signals obtained by reading twice is used. Is amplified twice, and the other two video signals are added, so that the dynamic range of the image sensor can be expanded with only simple operation, and the occurrence of blur due to image shift is suppressed. become able to.

As described above, the present system reads out the output signals of the same pixel in the image sensor at least twice, adds them, and
In obtaining a video signal for a screen, first, the above 1
The video signal for the screen is divided into two exposure periods,
Means for separately controlling reading in the latter half, and correcting means for taking the difference between these read signals, base-clipping the signal of the absolute value of the difference as a correction amount of the added signal, and performing subtraction correction for output. To be configured or
The correction means detects the movement of the subject from the two signals read by the read control means, and when the movement is equal to or less than a certain value, adds the read signal. One of the two read signals may be doubled and output, or the correction means may add the two read signals in accordance with incident light amount information or focal length information of a photographing lens. If the exposure time or the focal length is long, there is a high possibility that two video signals will be displaced. In this case, the addition is not corrected and the video obtained by reading twice is obtained. One of the signals is amplified by a factor of two and output, and in the other case, two video signals are added and output. In such a configuration, the output signal of the same pixel in the image sensor is read out at least twice and added to obtain a video signal for one screen, thereby expanding the dynamic range of the image sensor. Then, the readout control means divides the exposure signal of one screen into two and divides the exposure period of one photographing into two parts, and reads them out separately for the first half and the second half. Correction is made by the correction means in order to remove the blur after addition and synthesis in the case where there is, but in the case of the first invention, the difference between these read signals is obtained, and the signal of the absolute value of the difference is obtained. The base clip is used as the correction amount of the added signal, and the corrected signal is subtracted and output. By doing so, the portion corresponding to the deviation is removed by the subtraction correction, and only the portion without the deviation is synthesized. Becomes, therefore, it is possible to expand the dynamic range of the image pickup device, moreover,
This makes it possible to suppress the occurrence of blur due to image shift.

In the case of the second embodiment, the correction means detects the movement of the subject from the two signals read from the read control means, and when the movement is equal to or less than a certain value, adds the read signals. In this way, when the motion is equal to or more than a certain value, one of the video signals obtained by reading twice and obtaining each without performing the addition process is amplified by a factor of two and output. Is smaller than a certain value, the signal is added and synthesized as it is. When the motion is larger than a certain value, the image sensor is subjected to only a simple operation of amplifying and outputting one of the video signals twice without performing addition processing. The dynamic range can be expanded, and the occurrence of blur due to image shift can be suppressed.

In the case of the third embodiment, the correcting means selects whether or not to add the two read signals in accordance with the incident light amount information or the focal length information of the photographing lens, and performs the addition correction. In other words, if the exposure time or the focal length is long, there is a high possibility that two video signals will be shifted. In this case, no addition correction is performed and one of the video signals obtained by reading twice is obtained. Is amplified by a factor of two and output, and otherwise the two video signals are added. With this, the dynamic range of the image sensor can be expanded with only a simple operation, and furthermore, the image shift caused by image shift The blurring can be suppressed.

Therefore, according to the present apparatus, the dynamic range of the image sensor can be expanded, and a clear image can be obtained even for a fast-moving subject, so that an optimum image pickup apparatus applicable to a still video camera or the like can be provided. I can do it.

Note that the present invention can be implemented by appropriately modifying the embodiments described above and shown in the drawings without departing from the spirit of the invention. For example, in the above embodiment, a still video disk is used as a recording medium. Although used, any other storage medium, such as a memory card, can be used as long as it records video signals.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to expand the dynamic range of the image sensor, obtain a clear and blur-free image even with a fast-moving subject, and simultaneously obtain a two-dimensional image. It is possible to provide an optimal image pickup apparatus applied to a still video camera or the like, such as obtaining a noise reduction effect by adding two signals.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation thereof, FIG. 3 is a diagram showing a configuration of a CCD, and FIG. 4 is another embodiment of the present invention. Block diagram showing an example, FIG. 5 is a timing chart for explaining the operation, FIG. 6 is a block diagram showing still another embodiment of the present invention, FIG. 7 is a diagram for explaining the operation, FIG. 8 is a block diagram showing another embodiment of the present invention, and FIGS. 9 and 10 are diagrams for explaining a dynamic range and a technique for expanding the dynamic range. 1 ... camera lens, 2 ... aperture, 3 ... shutter,
4 Half mirror, 5 Solid-state image sensor, 6 A / D,
Converter 7 Changeover switch 8 Drive control signal generator 9 Field memory 10 Adder circuit 11
... Reflecting mirror, 12 Photometry unit, 13 System controller, 14 Signal correction unit.

Claims (3)

(57) [Claims] An output signal of the same pixel in an image sensor is read out at least twice and added to obtain a video signal for one screen, wherein the video signal for one screen corresponds to an exposure period of one photographing. Means for controlling readout separately for each of the first and second halves, taking the difference between these readout signals, taking the signal of the absolute value of the difference as a base clip to obtain the correction amount of the added signal, and performing the subtraction correction An image pickup apparatus comprising: a correction unit that outputs a signal. 2. An image pickup device according to claim 1, wherein an output signal of the same pixel in the image sensor is read out at least twice and added to obtain a video signal for one screen. Means for controlling readout separately for each of the first and second halves and detecting the movement of the subject from these two read signals, and adding the read signals when the movement is equal to or less than a predetermined value; An imaging device comprising: 3. An image pickup device, wherein output signals of the same pixel in an image pickup element are read out at least twice and added to obtain a video signal for one screen. Means for dividing the signal into two and reading control separately for the first half and the second half; and correcting means for selecting whether or not to add the two read signals in accordance with the incident light amount information or the focal length information of the photographing lens, and correcting the addition. An imaging device comprising: