JPS62107578A - Electronic still camera - Google Patents

Abstract

PURPOSE:To securely prevent photographing failure due to smears by vertically transferring an unnecessary charge going around to a vertical transfer part from the interior of a substrate to a horizontal transfer part so as to accumulate and output it outside, prior to the image pickup action of an electronic shutter composed of an image pickup element. CONSTITUTION:A smear detection signal obtained by a CCD 12's smear detection and drive is taken out in a sample holding circuit 17, and inputted to a smear detection circuit 40 enclosed by broken lines. In a comparator 45, a reference voltage source 46 sets, as a comparison reference, a permissible smear voltage (permissible smear quantity) becoming the upper limit of a smear voltage which cannot be identified on a television screen at the time of reproduction. If a detection smear signal from a peak holding circuit 44 exceeds the permissible smear voltage given by the reference voltage source 46, an output discriminating whether smears arise is outputted to a holding circuit 47.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to an electronic still camera in which the original image sensor itself, such as a COD, has a shutter function. Regarding electronic still cameras.

(Background of the Invention) Conventionally, in an electronic still camera using an image carrying element such as a COD, by controlling the charge accumulation time (exposure time) of the light receiving section passing through the image carrying element, It has a shutter function and operates as a so-called electronic shutter, and since a mechanical shutter is not required, the camera can be made more compact, and it has the advantage of easily realizing dark shadow functions such as high-speed continuous shooting. There is.

Figure 4 shows an outline of an interline transfer type CCD (IT-CCD) having a MOS diode structure in the light receiving section as an image carrier used in an electronic still camera. The shutter function is explained as follows.

First, to explain the structure and function of the T-COD, in Fig. 4, 1 is a light receiving section, and the light receiving section 1 is not a pn junction photodiode, but a signal charge photoelectrically converted using a MOS diode. It is structured to store. 2
is a vertical transfer section, which transfers the signal charge of the light receiving section 1 to the horizontal transfer section 3.

The horizontal transfer section 3 transfers the signal charge of one horizontal line transferred from the vertical transfer section 2 to a floating defension amplifier 4.
The signal charge sent from the horizontal transfer section 3 is converted into a signal voltage and output.

On the other hand, 5 is an overflow drain (hereinafter referred to as rOFD) and an overflow control gate (hereinafter referred to as rOFD).
(referred to as FcGJ), and when signal charges exceeding those that can be transferred by the vertical transfer section 2 are generated in the light receiving section 1, the function is to discharge the excess charges.

FIG. 5 shows a V-V cross-sectional structure including the light receiving section 1 and the vertical transfer section 2 shown in FIG. 4, and its potential structure.

First, in the structure shown in FIG. 5(a), the aluminum 7 shields the vertical transfer section 2 from light.
A transparent polysilicon electrode 8a forming a sensor 1 no goo 1~ (hereinafter referred to as rsGJ) is provided below. Further, a polysilicon electrode 8b surrounded by silicon oxide (SiO) 9 becomes an electrode of the vertical transfer section 2.

In such a cross-sectional structure, 1 Herans Fargate T
G is also used by the polysilicon electrode 8b of the vertical transfer section 2, and the electrode voltage of the polysilicon electrode 8b is operated in units of 3, and when the voltage is the highest]・Lansf 7G 1-T G
It is designed to perform the same movements. Also, 0FCG
5a is common to the SG formed of the polysilicon electrode 8a, and therefore 0FCG 5a cannot be controlled.

Furthermore, looking at the structure of the light receiving section 1, it has a laminated structure of an SG made of a polysilicon electrode 8a, a silicon oxide (SiO) 9, and a P-type silicon substrate 10, and is not a pn junction photodiode but an MO8 structure. It forms a photodiode.

FIG. 6 shows the charge distribution depending on the gate voltage in the MO8 structure of the P-type silicon substrate 10 serving as the light receiving section 1.

FIG. 6(a) shows the charge distribution when a voltage of 10 VQ is applied to the SGN pole, and electrons are stored at the interface of the P-type silicon substrate 10. However, the potential of the P-type silicon substrate 10 is O.
It is set as V.

The signal charge accumulation state shown in FIG. 6(a) is called an inversion type.

On the other hand, when a voltage of -VQ is applied to the polysilicon electrode 8a constituting the sensor gate SG, the charge distribution becomes the potential state shown in FIG. i O) 9 is driven into the inside of the P-type silicon substrate 10, and in return, holes are stored at the interface. This state is called the accumulation type.

In this way, by applying the sensor gate voltage -VQ to an accumulation type state, all signal charge electrons can be discharged to the substrate side without being discharged to the OFD, and a state where there is no signal charge at all in the light receiving section 1 is achieved. This can be realized by controlling the sensor gate voltage to -V(+).

By the way, in actual CCD driving, Fig. 5(a)
As is clear from the cross-sectional structure of , the SG potential given by the polysilicon electrode 8a of the light receiving section 1 is deeply related to the potential state of the surrounding vertical transfer section 2, etc., so that not only the SG lightning voltage control but also It is also necessary to control the vertical transfer gate voltage applied by the polysilicon electrode 8a.

The potential state of each part by controlling the vertical transfer gate voltage corresponding to this SG lightning voltage controller 1 to roll will be explained with reference to the potential state diagrams in FIGS. 5(b) to 5(d).

First, during normal video operation, since the electrode voltage Vg is always applied to the SG of the light receiving section 1, the potential of TG6 is the same as that of the light receiving section 1 and 0FCG, as shown in FIG. 5(b).
It is in a state higher than the potential of 5a.

Here, if only the SG lightning voltage of the light receiving part 1 is changed to -vg,
As shown in FIG. 5(C), the potential of the light receiving section 1 changes to the state shown by the broken line, and the potential of the 0FCG6 becomes lower than the potential of the light receiving section 1 and 0FCG5a, and from the light receiving section 1 to the vertical transfer section. This causes charge leakage to 2. Therefore, it is necessary to make the potential of the TG 6 higher than that of the light receiving section 1, and it is necessary to increase the potential by applying a voltage (negative voltage) lower than the SG lightning voltage to the vertical transfer section 2.

The potential state when a negative voltage is applied to the vertical transfer section 2 in this way is shown in FIG. Since the potential inside the substrate is necessarily in a low state and the potential inside the substrate is also in a state where the potential is lower than that, it is possible to reliably discharge the signal charges of the light receiving section 1 to the inside of the substrate of the light receiving section 1.

Here, FIGS. 5(b) to 5(d) show only the potential state in the interface region, and do not take into account the potential state inside the substrate. However, in reality, when the potential state shown in FIG. 5(d) is established, a phenomenon occurs in which a portion of the charge discharged into the substrate goes around to the vertical transfer section.

Next, a driving method of providing the interline transfer type COD itself with a shutter function and operating it as an electronic shutter, as shown in FIG. 4.5.6, will be explained with reference to the time chart of FIG. 7.

In FIG. 7, FLD is a frame synchronization signal, and the day state indicates an odd field, and the 1- state indicates an even field. Also, BLK is a blanking signal, 1-ID
is the horizontal synchronization signal, SG is the sensor gate voltage, ■1 to ■4
indicates the vertical transfer electrode voltage.

Note that the number of the horizontal synchronization signal HD indicates the number of horizontal lines.

The operation to realize the electronic shutter begins with the sensor gate voltage SG of the light receiving section becoming a negative voltage at time T1, as shown in Fig. 6(b).
), all of the signal charges accumulated in the light receiving section are swept out into the substrate, and some of them go around to the vertical transfer section. However, since the vertical transfer section also performs high-speed charge transfer from time T1, the charges that have leaked from within the substrate are discharged to the outside at high speed.

Next, at time T2, the sensor gate voltage SG becomes the original positive voltage again, and from time T2, accumulation of newly photoelectrically converted signal charges is started (exposure start).

High-speed charge transfer from time T1 to the vertical transfer section begins at time T5.
During this period, at least one of the field signals is
263 stages of vertical transfer corresponding to one scan are performed, and therefore, at time t5, there is no unnecessary charge in the vertical transfer section.

Next, from time T6 to T7, the voltage of vertical transfer electrode V1 is 3
This becomes the highest voltage among the voltages that can reach the level, and the signal charges accumulated in the light receiving section are transferred to the vertical transfer section. The exposure period of the signal charge obtained at this time is from time T2 to T7, which is the shutter time, and the shutter time can be changed by changing the positions of times T1 and T2.

Time T when the next vertical blanking starts after time T7
The driving up to 9 is the same as normal video operation, and the images taken at the shutter times from time T2 to T7 are displayed as the reproduced images on the television screen.

On the other hand, regarding the other field, which is an even field, during the period from time T1 to time T3, which is the output period of the video signal, the unnecessary charge is swept out from the vertical transfer section as described above. It cannot be used as a signal. Therefore, in the photographing operation shown in FIG. 7, only the odd field video signals are valid.

(Problems to be Solved by the Invention) However, in electronic still cameras in which the solid-state image sensor itself has a shutter function and is not equipped with a mechanical shutter, it is difficult to capture a photograph of a subject with sharp eyes because there is no light shielding by the mechanical shutter. If there is a high-brightness area in a part of the image, a smear with white lines above and below the high-brightness area will occur.

In other words, smear is a phenomenon in which a white line is drawn in the vertical direction of the high-brightness area on the TV screen when there is a high-brightness area in a part of the shape wave image, and the cause of this is the vertical This occurs because, when signal charges are transferred using the transfer section, charges generated deep in the light receiving section leak into the vertical transfer section, and this amount is proportional to the brightness of the subject. Note that since the vertical transfer section transfers signal charges toward the horizontal transfer section, that is, upward or downward on the television screen, it appears as a white line in the vertical direction.

Also, in the case of electronic still cameras that use an electronic shutter method,
Since there is no light shielding by a mechanical shutter, light is always shining on the image sensor, and the intensity of that light is determined only by the aperture value, assuming the brightness of the subject is constant. Therefore, when obtaining the same exposure value, the image output is the same when the aperture is closed with a slow shutter speed and when the aperture is open with a high speed shutter, but the amount of smear that appears in the image is different, and the amount of smear that appears in the image is different. Since the aperture is wider, the amount of smear increases. That is, if the exposure amount is the same, the amount of smear increases in proportion to the shutter speed.

In response to the deterioration of image quality due to the occurrence of smear, the amount of smear has decreased with advances in sensor structure, and in the case of video operation with a shutter time of 1/30 second or 1/60 second, high brightness Almost no smear is observed on the subject.

However, as mentioned above, the amount of smear occurs in proportion to the brightness of the subject. For example, if we consider a high-speed shutter with a shutter time of 1/2000 seconds, the brightness of the subject incident on the light receiving section is proportional to the brightness of the subject. Compared to seconds, the brightness is (1/30)/(1/2000)': 67 times higher, and the amount of smear also increases to 67 times the amount of smear when the shutter time is 1/30 seconds.

As a result, smear is still noticeable when photographing subjects with high brightness, deteriorating image quality, and especially when shooting still shots using high shutter times, there is a very high possibility of image quality deterioration due to smear and shooting failure. was there.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and detects the amount of smear expected to be included in the video signal before the pupil shadow. The purpose is to provide an electronic still camera that can prevent failures.

(Summary of the Invention) In order to achieve this object, in the present invention, prior to the photographing operation using the electronic shutter, the transfer of signal charges from the light receiving section to the vertical transfer section is prohibited, and the signal charges are transferred from the inside of the substrate to the vertical transfer section. Unnecessary charges that cause smear that come around are sent to the horizontal transfer unit for a certain period of time, for example, one field period, and the unnecessary charges are accumulated in the horizontal transfer unit, and after a certain period of time, the horizontal transfer unit is transferred to the horizontal transfer unit for one horizontal period. The technical point is to output to the outside a signal representing the horizontal distribution of the amount of smear, that is, the cumulative amount of smear in the vertical direction of the screen, by driving the sensor.For example, this detected amount of smear is compared with a preset allowable amount of smear. However, when the amount of smear exceeds the allowable amount, it is possible to issue a smear warning or control the aperture.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention having a smear detection function.

First, to explain the configuration, numeral 12 is a COD as an image carrying element which itself has a shutter function.
An IT-CCD as shown in the figure is used. CCD1
2 causes the COD drive circuit 13 to perform a smear detection operation in addition to the photographing operation shown in the time chart of FIG.
This is done in response to a signal from. In addition, an optical image of the subject is formed on the light receiving surface of the CCD 12 via a lens 15 and an aperture 16, and since a mechanical shutter is not required due to the shutter function of the CCD 12 itself, an optical image is always formed. I'm in the middle of the day.

The output obtained by the smear detection drive and photography drive of the CCD 12 by the COD drive circuit 13 is given to the video signal processing circuit 18 via the sample hold circuit 17.
Further, the video signal processing circuit 18 sends a signal to the recording signal processing circuit 19, and after performing FM modulation, the signal is sent to the magnetic head 21 installed in the moving mechanism 20, which is moved in the radial direction of the magnetic disk 23 by the DC motor 22. The video signals for one screen are recorded on the 11th track (field recording) or the 2nd track (frame recording) of the magnetic disk 23. The movement of the magnetic head 21 is controlled by drive control of the DC motor 22 by the head position control section 24 . Further, the magnetic disk 23 is rotated by a DC motor 25 at a constant speed of, for example, 3600 rl)m, and the DC motor 25 is rotated by a rotation speed phase control section 26.
It is controlled to maintain constant speed rotation.

In addition, in order to obtain a video signal with a constant exposure amount during travel photography, the brightness of the subject measured by the photometric element 27 is given to the photometric circuit 28 to determine the exposure value, and the exposure value obtained by the photometric circuit 2B and the aperture 16 The arithmetic circuit 29 calculates the shutter time based on the aperture value.

Furthermore, a release switch 30 and a half-press switch 32 are provided for performing a photographing operation, and when the shirt button is pressed halfway, the half-press switch 32 is activated to perform a photographing preparation operation. As a photographing preparation operation accompanying the operation of the half-press switch 32, it is desirable to have the CCD drive circuit 13 drive the CCD 12 for smear detection. Further, when the release button is pressed halfway and then pressed further, the release switch 30 is activated, and the CCD drive circuit 13 drives the CCD 12 to take an image.

The operation timing associated with a series of these smear detection drives and photographing drives is performed under the control of a timing signal generator 36 that receives a clock from a synchronization signal generator 34.

Next, to explain the circuit section for smear detection performed prior to photographing drive, the smear detection signal obtained with the smear detection drive of the CCD 12
7 and input to a smear detection circuit 40 surrounded by a broken line. The smear detection circuit 40 includes an amplifier 41 that amplifies the smear detection signal, an analog switch 42 that handles the smear signal for a certain period, for example, one field period, and a clamp circuit that clamps the smear signal picked up by the analog switch 42 at the black level. 43, and further includes a peak hold circuit 44 that detects and holds the peak level of the smear detection signal clamped at the black level. Furthermore, the output of the peak hold 44 is input to a comparator 45,
The comparator 45 has a permissible smear voltage (between permissible smears), which is the upper limit of the smear voltage that cannot be identified on the TV screen during playback, set as a comparison standard by a reference voltage source 46, and the detection from the peak hold circuit 44 When the smear signal exceeds the allowable smear voltage given by the reference voltage source 46, an output for determining the occurrence of smear is output to the hold circuit 47. The smear discrimination output held by the hold circuit 47 is given to a smear warning section 48, which issues a smear warning to the photographer by sounding a buzzer or displaying it in the finder.

Next, the smear detection drive and photographing drive in the embodiment shown in FIG. 1 will be explained with reference to the timing chart shown in FIG. 2.

First, the timing signal generating section 36 controls the release switch 3
The smear detection drive is performed until the release signal due to the 0 operation is received.

During this smear detection driving period, signal charges are not transferred from the light receiving section to the vertical transfer section in the CCD 12, that is, the transfer gates 1 to 1 are closed and the vertical transfer section is operating normally. That is, the vertical transfer section is always in an operating state in which it performs idle transfer to the horizontal transfer section. Even when the vertical transfer section is being fed idly in this way, unnecessary charge that causes smear leaks into the vertical transfer section from the deep part of the substrate in the light-receiving section, which is constantly exposed to light. The transfer section does not actually perform idle feeding, but transfers the leaked smear charge to the horizontal transfer section. On the other hand, the transfer drive of the horizontal transfer section during the smear detection drive period is controlled so that charge transfer for one horizontal line is performed only once within one field period. By driving the vertical transfer section and the horizontal transfer section with such characteristics, the smear charges are collected in the horizontal transfer section over one field period (16,7m5), and the smear charges are collected in the horizontal transfer section over one field period (16,7m5).
It is read out to the outside in a 1H period (63.5 μs>263).

Therefore, such a traless far gate vertical transfer section,
The smear signal obtained by the smear detection drive of the horizontal transfer section is the sum of the smear amount for one field period, so it is possible to obtain a detection signal with a smear amount that is 262 times the normal amount, and the sensitivity of the smear detection signal can be increased. can be significantly increased.

The smear signal read out from the horizontal transfer section of the CCD 12 to the outside in 1H period is transferred to the sample hold circuit 17.
After being applied to the smear detection circuit 40 via the smear detection circuit 40 and handled by the analog switch 42 of the smear detection circuit 40,
A clamp circuit 43 clamps the black level, and a peak hold circuit 44 detects the peak level of the smear detection signal. By detecting this peak level, the maximum value of the smear signal for the aperture value at this time is obtained.

The comparator 45 compares the smear voltage with a permissible smear voltage set by the reference voltage source 46 which limits the smear voltage that cannot be discerned on a television screen, and the result of the comparison is held in the hold circuit 47 for one field period. Therefore, when the comparator 45 obtains a peak level of the detected smear signal that exceeds the allowable smear voltage, the hold output of the hold circuit 47 becomes a smear warning signal, and the smear warning section 48
A smear warning operation is performed to the photographer.

These series of smear detection operations are repeated every field period until a release signal is received by the release switch 30.

Next, the smear detection drive and dark shadow drive will be explained in more detail with reference to the time chart of FIG. 2.

In Figure 2, VD is a vertical synchronization signal, FLD is a frame synchronization signal (H state is odd field, L state is even field), SG is sensor gate voltage, ■ is vertical transfer electrode voltage, 1-1 is horizontal transfer electrode voltage, and S is CCD1
This is the senna output of 2.

First, the period from time T1 to time T3 shows a state in which the aperture is opened and an attempt is made to photograph an extremely bright subject at the center of the screen using a high shutter time. Here, since the light-receiving section of the image sensor is constantly exposed to light, photocharges generated deep in the substrate of the light-receiving section have already seeped into the vertical transfer section. That is, smear has already occurred. Then, as described above, the vertical transfer section is driven for a certain period (for example, one field period) with the transfer gate closed to prevent the charge in the light receiving section from being transferred to the vertical transfer section, and the charge is accumulated in the horizontal transfer section. At this time, since the aperture is open, the amount of charge due to smear accumulated in the horizontal transfer section is large. Therefore, the signal level of 1 in the smear signal obtained as the sensor output S after horizontal transfer for 1H period is large, and the smear detection circuit 40
Since the peak-held smear peak hold signal exceeds the preset allowable smear voltage, the smear warning signal becomes H level and a smear warning is issued to the photographer.

On the other hand, after time T4, the signal state is shown after the photographer has closed the aperture several steps based on the smear warning up to time T3. Of course, since the exposure value is always kept constant by closing the aperture several steps, the shutter time is calculated to be longer depending on the number of steps the aperture is closed.

FIG. 2a is an enlarged view of J in FIG. 2.

By closing the diaphragm based on the smear warning in this way, at time T5 when the amount of light to the light receiving surface of the COD decreases, the smear signal obtained as the sensor output S is
The smear peak hold signal based on the voltage also decreases and becomes below the allowable smear voltage, so that the smear warning signal becomes L level and the smear warning is canceled.

When the shutter is released after the smear warning is canceled in this way, the same CCD photographing drive as shown in the timing chart of FIG. 7 is performed, and an image without smear can be recorded.

That is, at time T7, sensor gates 1 to SG change to -Vg and the light receiving section becomes an accumulation type, thereby discharging unnecessary charges into the substrate, and when sensor gate SG returns to 10VQ again, accumulation of signal charges starts. . Simultaneously at time T7, high-speed charge transfer using the vertical transfer electrode voltage {circle around (2)} is started, and unnecessary charges flowing into the vertical transfer section from inside the substrate are discharged. This discharge of unnecessary charges continues until time T8. Then time T
When reaching time 9 based on the shutter time set from 7, the vertical transfer electrode voltage V becomes the highest voltage of the 3 units, and is accumulated in the light receiving section over the shutter time until shutter time T10. Transfers signal charges to the vertical transfer section. On the other hand, since the normal horizontal transfer operation is performed by the horizontal transfer electrode voltage H from time 6, the video signal is transferred from the horizontal transfer section to time T10 when the transfer from the light receiving section to the vertical transfer section is completed. is outputted to the outside as the sensor output S, and the output of the video signal ends at time T11.

When the output of the video signal photographed at time T11 is finished in this manner, the drive state returns to the smear detection drive state again.

FIG. 3 is a timing chart showing smear detection drive and photographing drive according to another embodiment of the present invention.

That is, in the smear detection drive and photographing drive shown in the timing chart of FIG. 2, the amount of smear at the time of photographing is detected before the photographing drive, but the amount of video signal at the time of photographing is not detected. Therefore, it was necessary to provide a photometric element 27 as shown in the block diagram of FIG. On the other hand, in an embodiment that implements the driving operation shown in the timing chart of FIG. 3, a driving method is adopted in which both the amount of smear and the amount of video signal at the time of photographing are detected before the image is captured.

That is, in the embodiment shown in FIG. 3, the smear detection drive and photographing drive are performed within one frame period consisting of an even field and an odd field. In this case, in order to perform both smear detection drive in the even field period and high-speed transfer of unnecessary charges from the vertical transfer section during the exposure period set by the shutter time, the unnecessary charge It is necessary to allocate drive time for high-speed transfer within an even field period.

Therefore, in the embodiment shown in the time chart of FIG. 3, in order to make the smear signal 100 times the normal readout,
The smear charge is stored in the horizontal transfer section for a period of 100H (6.35ms) and then read out.
Therefore, the shutter time is the time of one field (16,
6n+s) to 100H (6,35
m s ), that is, the shutter time is limited to a time shorter than 'l Qm s (1/125 seconds) or less.

However, even if the shutter time is limited by allocating the smear detection operation and the high-speed transfer drive for discharging unnecessary charges within such an even field period,
Since smear occurs when the shutter time is high, it is sufficient if the smear detection drive is performed at a shutter time of 1/125 seconds from the high speed side.

To explain the timing chart of FIG. 3, first, at time T1, which is the start of an even field, the horizontal transfer drive indicated by the horizontal transfer electrode voltage H is stopped, and the smear detection drive is started. The smear charge is transferred through the vertical transfer unit until the smear signal is read at time T2, when a preset 100H period has elapsed, and is added and accumulated in the horizontal transfer unit of the CCD, and at time 2, the smear amount is 100 (r; The signal is read out from the horizontal transfer unit in a 1H period, and a smear warning is issued based on a comparison between the smear peak bold signal and the allowable smear signal, similar to the timing chart of FIG.

Next, from time T3 to time T4, a photographing operation is performed by operating as an electronic shutter, and a video signal is obtained as the sensor output S. Of course, the shutter time can be changed within a range of 10 m5 by changing the timing of time T3 with respect to time T2.

In this way, when the smear detection drive and the shooting drive shown in Fig. 3 are performed alternately, it becomes possible to constantly detect the amount of smear and the amount of video signal at the time of shooting during one frame period. This is done by recording the video signal output obtained after the shutter button is pressed and the release switch is engaged. Therefore, in the embodiment shown in FIG. 3, it is possible to detect not only the amount of smear at the time of shooting but also the amount of video signal prior to the w1 shadow, and based on the amount of detected video signal, it is possible to detect the amount of video signal without using a photometric element. You can perform exposure compensation and automatic exposure control.

Furthermore, in the above embodiment, a smear warning is issued when the detected smear amount exceeds the allowable smear amount, but in other embodiments, a smear warning signal is used to increase the detected smear amount. Of course, the aperture may be automatically controlled so that the amount of smear is within the allowable amount.

In the embodiment shown in FIG. 1, the vertical transfer section is driven for one field to transfer and accumulate unnecessary charges to the horizontal transfer section, but the invention is not limited to this, and the horizontal transfer section is driven for multiple fields. It is also possible to transfer and accumulate unnecessary charges to the transfer section. Furthermore, the vertical transfer section may be driven once or multiple times to transfer unnecessary charges to the horizontal transfer section, and then the horizontal transfer section may be driven.

(Effects of the Invention) As described above, according to the present invention, prior to the vi shadow operation by the electronic shutter of the image sensor, the transfer of signal charges from the light receiving part to the vertical transfer part is prohibited from the inside of the substrate. The unnecessary charge that causes smear that enters the transfer section is vertically transferred, sent to the horizontal transfer section, accumulated, and then output from the horizontal transfer section as a detection signal for the amount of smear, so that the amount of smear can be detected in advance. can be known. Therefore, for example, as in the embodiment, this detected smear amount and a preset allowable smear amount are compared and determined, and when the allowable smear amount is exceeded, the aperture control is performed to issue a smear warning or cancel the smear warning. If you try to darken a bright subject with a high shutter time setting, a smear warning will be issued before the pupil shadow appears, so you can close the aperture based on the smear warning until the smear warning is canceled. It is possible to reliably prevent photographing failures due to smears.

Furthermore, as in the first embodiment, the detection sensitivity of the smear amount can be improved by sending unnecessary charges that cause smear from the vertical transfer section to the horizontal transfer section and cumulatively adding them over a certain period of time, such as one field period. It is possible to significantly increase the SN
A smear detection signal with a high ratio can be obtained. Furthermore, as in the second embodiment, by adopting a driving method in which both smear detection driving and pupil shadow driving are distributed within one frame period, in addition to detecting the amount of smear, the amount of video signal can also be detected as a pupil shadow. Since the amount of video signal can be obtained by driving the image carrier element, exposure correction and automatic exposure control can be performed without providing a photometric element.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the embodiment of FIG. 1, and FIG.
Figure a is a partially enlarged view of Figure 2, Figure 3 is a time chart showing the operation of another embodiment of the present invention, and Figure 4 is an interline transfer type CO used in the electronic still camera of the present invention.
A schematic diagram of D, Figure 5 is an explanatory diagram showing the v-■ cross section of Figure 4 and its potential state, and Figure 6 is an illustration of the principle of accumulation and discharge of signal charges in the light receiving section of Figure 4. The charge distribution diagram shown in FIG. 7 is a time chart showing the pupil shadow operation in FIG. 4. 1: Light receiving section 2: Vertical transfer section 3: Horizontal transfer section 4: Floating diffusion amplifier 5: 0FC
G and 0FD 6: Transfer gate I ~ (TG) 7: Aluminum 8a: Polysilicon electrode (sensor gate 5G) 8b: Polysilicon electrode (vertical transfer gate) 9 Silicon dioxide (
Sin) 10: P-type silicon substrate 12: CCD 13: CCD drive circuit 14: Shutter time controller 1 to roll unit 15: Lens 16 and second aperture 17: Sample hold circuit 18: Video signal processing circuit 19: Recording signal processing circuit 21: Magnetic head 23: Magnetic disk 30 Release switch 32: Half-press switch 36: Timing signal generator 40: Smear detection circuit 41: Amplifier 42: Analog switch 43: Clamp circuit 44: Peak hold circuit 45: Comparator 46 Two reference voltage sources 47: Hold circuit 48: Smear warning section

Claims (2)

[Claims] (1) A solid-state image sensor having a light receiving section, a vertical transfer section, and a horizontal transfer section is used, and by controlling the charge accumulation time of the light receiving section, the solid-state image sensor itself has a shutter function and operates as an electronic shutter. In a still camera, the vertical transfer section is driven with charge transfer from the light receiving section to the vertical transfer section prohibited to transfer unnecessary charges to the horizontal transfer section, and then the horizontal transfer section is driven to transfer unnecessary charges to the horizontal transfer section. 1. An electronic still camera comprising: a solid-state image sensor control means for controlling a signal charge such that the signal charge is output as a smear amount at the time of photographing. (2) The solid-state image sensor control means controls the vertical transfer section in a state in which charge transfer from the light receiving section to the vertical transfer section is prohibited.
2. The electronic still camera according to claim 1, wherein the horizontal transfer section is driven after driving for a field to transfer and accumulate unnecessary charges to the horizontal transfer section.