JPH0446477A - Driving method for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To uniformize the sensitivity of a photoelectric conversion element, to uniformize the amount of the maximum store electric charge and to reduce the absolute amount by setting all the vertical electric charge transmission paths to a peening state after the end of the vertical electric charge transmission during the abandonment processing of unnecessary electric charge before exposure. CONSTITUTION:A CCD driving part 4 generating a driving signal to perform the scanning reading, etc., of signal electric charge is connected to a solid-state image pickup device 3, and the outputted signal is transmitted to a signal processing part 5. In the processing part 5, the processing of color separation, gamma compensation, etc., is performed, and also a color difference signal and a luminance signal are formed to output. The picture is reproduced on an electronic finder 7 by switching a contact to an 'a' side at the time of monitoring operation by using a changeover circuit 6, and video data is stored in the recording medium of a recording part 8 by swithing the contact to a 'b' side at the time of photographing. A mechanical type shutter 2, the CCD driving part 4, the signal. processing part 5, the charageover circuit 6, the recording part 8, etc., are synchronized at prescribed timing to be operated by a control part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving an interline transfer type charge-coupled solid-state imaging device, and particularly to a method for reducing flicker in a reproduced image.

[Conventional technology]

A method of driving a conventional interline transfer type charge-coupled solid-state imaging device will be described with reference to a device having a structure shown in FIG.

First, to explain the structure, AI is placed on the surface of the semiconductor substrate.
, Bl are arranged in a matrix along the row direction (X direction) and the column direction (X direction), and a vertical charge is formed adjacent to the photodiode group arranged along each column direction. Transfer route 11~! ! , or is formed. Further, the vertical charge transfer paths 11 to 1. For example, a gate electrode (not shown) is formed to transfer signal charges in synchronization with a drive signal of a four-phase drive force type, and a light-shielding film or a laminated layer is formed on the upper surface of the gate electrode to block the incidence of external light. has been done.

Furthermore, vertical charge transfer paths l, ~I! A horizontal charge transfer path HCCD is formed at the end of the output amplifier A.
MP is formed. The horizontal charge transfer path HCCD is provided with a gate electrode for transferring signal charges in synchronization with, for example, a two-phase driving force drive signal φ14L+φH2, and a light shielding film is laminated on the upper surface thereof.

Then, it is defined that the photodiode A1 is arranged in an odd field and the photodiode B1 is arranged in an even field, and the signal charges generated in these photodiodes AI and Bl are read out by field scanning.

Next, a driving method when a charge-coupled solid-state imaging device having such a structure is applied to an electronic camera will be described.

Such an electronic camera is provided with a mechanical shutter behind the imaging lens, etc., and further provided with an imaging optical system in which the light receiving surface of the imaging device shown in FIG. 9 is arranged behind the mechanical shutter.

Then, with the mechanical shutter always open, the NT
By repeating field scanning and readout in synchronization with the vertical and horizontal synchronization timing of standard television systems such as the SC system, it is possible to record videos, etc. On the other hand, the mechanical shutter can be activated in synchronization with pressing the shutter release button. Exposure is performed at a desired shutter speed by opening and closing, and by this exposure, the pixel signals accumulated on the photodiode are read out twice by field scanning (2) A still image corresponding to one frame image is photographed.

The photographing operation of an electronic camera having two photographing modes for video photographing and still image photographing is shown in the flowchart of FIG. 10 and the timing chart of FIG. 1I. Note that the flow in FIG. 10 and the timing chart in FIG. 1I are shown in temporal correspondence.

In FIG. 1O, the operation starts in synchronization with turning on the power switch of the electronic camera, and the camera enters the video shooting mode. That is, in step 100, the mechanical shutter is set to be always open and receives light from the subject. next,
In step 110, the internal control circuit determines whether or not the shutter release button for instructing still image photography has been pressed. If the release button has not been pressed, steps 120 to 130 are performed. That is, in step 120, the pixel signal of the photodiode A1 corresponding to an odd field is transferred to the vertical charge transfer paths 11 to 1 during a period corresponding to, for example, one field period (1/60 second) of the NTSC system. After the heft field shift, the vertical charge transfer path I! t~1. By the charge transfer operation of the horizontal charge transfer path HCCD, pixel signals for one field are read out.

Similarly, in step 130, the pixel signals of the photodiodes B1 corresponding to the even field are read out during the next 1/60 second period.

Then, the process moves to step 110 again, and step 110
By repeating the processes from 130 to 130 at a cycle of 1/30 seconds, a video signal for playing a moving image on an NTSC monitor television is output.

Incidentally, the odd field scanning readout in step 120 is performed during the vertical blanking period MTva (VD or "H") within the l field period TV+1 (1/60 seconds), as shown at time t1 to t2 in FIG. When A□ becomes "H" during the period rWI), only the pixel signals corresponding to the odd field are field-shifted to the vertical charge transfer paths 11 to 1, and the timing signal HD indicating the horizontal scanning period becomes "H". During the IH period, the vertical charge transfer paths 11 to 1. transfers one row of pixel signals to the horizontal charge transfer path HCCD, then Hcc
During the period when o is "H", pixel signals for one row are output by reading from the horizontal charge transfer path HCCD, and this I
Odd field scanning is completed by repeating the operation during the H period until all pixel signals are read. The even field scanning readout in step 130 is also performed in the same way as the odd field scanning readout (times t1 to ts) as shown at time points t2 to t3 in FIG. However, B vs.
At the timing when the signal becomes "H", only the pixel signals corresponding to even fields are field shifted.

Then, by repeating field scanning at time t in FIG. 11 and thereafter at time t1 to time t, a moving image is captured.

Next, when the press of the shutter release button is detected in step 11O of FIG. 10, the process moves to step 140, and the still image shooting mode is entered.

First, in step 140, the mechanical shutter is closed to prohibit light from entering, and then, in the step knob 150, the imaging device is caused to perform a charge transfer operation while remaining in this closed state. As a result, dark current components and smear components existing in all the photodiodes, vertical transfer paths 1, to 11, and horizontal charge transfer path HCCD are discarded to the outside.

That is, if the shutter release button is pressed at a certain time t5 in FIG. 11, a press signal S is generated. , 4 occurs, and in synchronization with this, the control signal STI+ changes from "H" to "L" to close the mechanical shutter, and at time t6 during the next vertical blanking period, Aps and B F5
As shown in the figure, all the charges are transferred to the vertical charge transfer path It~! by performing field shifts for all the photodiodes in the odd and even fields. ! . Transfer to. Then, by performing the same field scanning readout as usual from time t6 to time t, unnecessary charges such as dark current and smear components are discarded.

In addition, during this dark current and smear component disposal period, the 11th
As shown in the figure, the period τ corresponding to the shutter speed
37. Exposure is performed by opening the mechanical shutter (for the period from time t7 to t8) and closing it again.

After completing this exposure and dark current discard processing, next, in step 160 (see time tlo in FIG. 11),
The pixel signal of photodiode A1 corresponding to the odd field is transferred to the vertical charge transfer path! , ~1, Hefield shift, and then in step 170, time ti'' of FIG.
As shown in ``tl+'', the vertical charge transfer path 11~! ! , and a horizontal charge transfer path HCCD to output odd field pixel signals. Note that the pixel signals read out sequentially are converted into, for example, digital signals and stored in a semiconductor memory or the like.

Next, in step 180 (see time t1□ in FIG. 11), the photodiode B corresponding to the even field is
1 pixel signal is transferred to the vertical charge transfer path l, ~1. In step 190, the vertical charge transfer paths 11 to 11 are shifted as shown at time points t+z to tlff in FIG.
1. And pixel signals of even fields are outputted by the transfer operation by the horizontal charge transfer path HCCD. Then, the sequentially read pixel signals are converted into digital signals and stored in a semiconductor memory or the like.

As described above, when a still image is captured electronically by executing the processes of steps 140 to 190, step 100 is performed again.
The camera switches to video shooting mode.

[Invention or problem to be solved]

According to such a conventional driving method of an imaging device, when shooting a still image, the period from the end of exposure to the start of even field scanning is longer than the period from the end of exposure to the start of odd field scanning. is long (NT
(1/60 seconds in the case of the SC system), so the influence of the smear component on pixel signals corresponding to even fields is greater than the influence of smear components on pixel signals corresponding to odd fields. As a result, when image reproduction is performed by interlaced scanning according to the read pixel signals, so-called field flicker occurs, where the brightness differs between fields.
This results in deterioration of image quality.

Also, because there is a difference between the amount of dark current leaking into the photodiode corresponding to the odd field and the amount of dark current leaking into the photodiode corresponding to the even field, field flicker may occur similar to smear, and false color may occur. There are problems such as the occurrence of That is, even during exposure, the vertical charge transfer paths 11 to
1. continues the transfer operation in an empty reading state, but the potential level of the vertical charge transfer path adjacent to the photodiode AI corresponding to the odd field and the potential level of the vertical charge transfer path adjacent to the photodiode Bl corresponding to the even field Since the levels are different, the electrical influence from the vertical charge transfer path on the photodiode in each field is different, and this results in a difference in the amount of dark current leaking into the photodiode in each field.

The present invention has been made in view of these problems,
An object of the present invention is to provide a method for driving a solid-state imaging device that does not cause field flicker even when pixel signals are read out by field scanning readout.

[Means to solve the problem]

In order to achieve such an object, the present invention provides a plurality of photoelectric conversion elements corresponding to a plurality of pixels arranged in a matrix in the row and column directions, and a plurality of photoelectric conversion elements arranged in each column direction. a vertical charge transfer path formed adjacent to;
A horizontal charge transfer path is provided that outputs signal charges transferred from these vertical charge transfer paths in time series, and after field-shifting unnecessary charges remaining in the photoelectric conversion element to the vertical charge transfer path, Discarding unnecessary charges by scanning readout using a charge transfer path and a horizontal charge transfer path, and generating a pixel signal in a photoelectric conversion element by exposing to light at a predetermined time during the discard processing period or at a predetermined time after the completion of the discard processing, Next, a method for driving a solid-state imaging device that performs image sensing by field-shifting the pixel signal to the vertical charge transfer path and then performing scanning readout using the vertical charge transfer path and the horizontal charge transfer path is targeted.

With respect to such a driving method of a solid-state imaging device, the present invention provides that during the disposal period, after all unnecessary charges are transferred to the horizontal charge transfer path from the vertical charge transfer path, all the vertical charge transfer paths are transferred to the horizontal charge transfer path. is set in the pinning state and unnecessary charges are discarded by scanning and reading out the horizontal charge transfer path, and the exposure is performed at an appropriate time while the vertical charge transfer path is set in the pinning state.

[Effect]

According to the present invention using such a driving method, during unnecessary signal discard processing, during the period from the end of continuous vertical charge transfer for dark current discard to the start of the next field shift,
Since the vertical charge transfer path is set in a pinning state, the potential level of the vertical charge transfer path adjacent to all photoelectric conversion elements in each field is equalized, and the sensitivity of all photoelectric conversion elements and the maximum The amount of accumulated charge is also made uniform.

Furthermore, since the surface level of the vertical charge transfer path is inactivated by the pinning state, leakage of dark current can also be reduced.

As a result of these, the occurrence of flicker in reproduced images can be significantly reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, the schematic configuration of an electronic camera to which the driving method of the present invention is applied will be explained based on FIG. 1. In FIG. Lens 1, mechanical shutter 2
, the solid-state imaging devices 3 are arranged on the same optical axis. The solid-state imaging device 3 has an interline transfer structure similar to that shown in FIG.

Reference numeral 4 denotes a CCD driving section that generates a drive signal for causing the solid-state imaging device 3 to scan and read out the signal charge', and transfers the signal outputted by the scanning and readout to the signal processing section 5. The signal processing unit 5 performs processing such as color separation and γ correction, and also forms and outputs a color difference signal and a luminance signal.

Reference numeral 6 denotes a switching circuit, which reproduces an image on the electronic viewfinder 7 by switching to the contact a side during monitor operation, and outputs video data to the recording medium of the recording unit 8 by switching to the contact side during shooting. Make me remember.

Then, the control section 9 controls the mechanical shutter 2, the CCD drive section 4, the signal processing section 5, the switching circuit 6, the recording section 8, etc. to operate in synchronization with a predetermined timing.

In addition, the mechanical shutter must be kept open at all times, and NTSC
By repeating field scanning and readout in synchronization with the vertical and horizontal synchronization timing of standard television systems, it is possible to record videos, etc. On the other hand, the mechanical shutter can be opened and closed in synchronization with pressing the shutter release button. By doing this, exposure is performed at a desired shutter speed, and the pixel signals accumulated in the photodiode due to this exposure are controlled to be scanned and read out twice to capture a still image corresponding to one frame image. .

Next, the driving method will be explained in detail according to the flowchart of FIG. 2 and the timing chart of FIG. 3.

In FIG. 2, the operation starts in synchronization with turning on the power switch of the electronic camera, and the camera enters the video shooting mode. That is, in step 200, the mechanical shutter is set to be always open and receives light from the subject. Next, in step 210, the internal control circuit determines whether or not the shutter release button for instructing still image shooting has been pressed, and if the release button has not been pressed, the processes of steps 220 to 230 are repeated. .

That is, the odd field scanning readout process in step 220 is performed at the timings t to t2 in FIG. 3, and the even field scanning readout process in step 230 is performed at the timings t2 to t in FIG. It is carried out at the timing of l. In addition, in FIG. 3, each period of TVD corresponds to each one field scanning period, and the period of time when VD is "H"
B is a vertical blanking period, HD is a horizontal synchronization signal that becomes “H” every horizontal scanning period (IH), and S
Mechanical shutter is released when TR is “H”, “L”
It is closed when , and the field shift of the odd field is performed at the timing when A P s becomes "H", and B6
The field shift of even fields is performed at the timing when VCCD becomes "H", and the vertical charge transfer paths l, to 1 . Transfer the signal charge for one line or H
The horizontal charge transfer path HCCD transfers the signal charge for one line during the period when the CCD is "H", and the signal charge is S in synchronization with pressing the shutter release button. N or “H” shall be shouted.

If the shutter release button is pressed at a certain point during such a moving image shooting mode, the process moves to step 240, and the still image shooting mode is entered.

First, step 240 begins at time t in FIG.

In synchronization with the pressing of the shutter release button, the signal SA or "L" is generated, and the mechanical shutter is closed, thereby prohibiting the entry of external light.

Next, dark current components remaining in all photodiodes are discarded by processing steps 250 to 330. That is, at a predetermined time t4 within the vertical blanking period that follows time t in FIG. ), then at time t
Vertical charge transfer paths 11-f at high speed during the predetermined period 5-t6
.

By vertical transfer operation, all unnecessary charges are transferred to the horizontal charge transfer path HCCD (step 260).

Next, during a period from time t6 to start time t9 of the next vertical blanking period, vertical charge transfer paths 11 to I! , all drive signals φ1. applied to the gate electrodes of φ1. ~φv4“
By setting it to L” level, all vertical charge transfer paths !1 to 1o are set to the pinning (Pi old ng) state (
step 270).

This pinning state means that all the vertical charge transfer paths 11 to 1
．． , is set at the potential barrier level, and the surface levels of all vertical charge transfer paths A, -1 are inactivated by holes.

Furthermore, the potential levels of the vertical charge transfer paths adjacent to all the photodiodes AI and Bl in the odd and even fields are made uniform.

Furthermore, during the period from time t7 to t8 (equal to the LH period),
The horizontal charge transfer path HCCD performs a horizontal transfer operation to discard unnecessary charges corresponding to odd fields (step 280).

Next, one field period T at time t, ~t17
vo, photodiode B corresponding to even field
Discard the dark current in step 1. That is, at time t, the vertical charge transfer path 11~! ! , to release the pinning state of , and set it to a state where charge transfer is possible (step 290).
Next, at time t1° during the vertical blanking period, the charge of the photodiode B1 corresponding to the even field is transferred to the vertical charge transfer path! ,~1. Hefield shift (step 300). Then, the period from time tll to t12 (
Vertical charge transfer paths 11-1 . By vertical transfer operation, all unnecessary charges are transferred to the horizontal charge transfer path HCCD (step 310).

Next, time point 1. During the period from □ to the start time t1□ of the next vertical blanking period, the vertical charge transfer paths l, to 1. All the vertical charge transfer paths 11 to 16 are set to the pinning state by setting all the drive signals φv1 to φv4 applied to the gate electrodes of the gate electrodes to the "L" level (step 320), and the driving signals φv1 to φv4 are set to the "L" level. Reduce the effect of dark current on all applicable photodiodes.

Then, in this pinning state, from time t13 to t1
During the period 4 (equal to the period 17 to t), the horizontal charge transfer path HCCD performs a transfer operation to discard the dark current (step 330).

Furthermore, the vertical charge transfer path 1. -4. The period from a predetermined point in time (t12 to t, 7) to the point corresponding to the shutter speed (t15 to t
Exposure is performed by opening the mechanical shutter by 16) and closing it again.

In this way, when the dark current of all fields has been discarded, in the next one field scanning period t17 to t+s,
By performing normal vertical and horizontal charge transfer without field shifting, vertical charge transfer paths l, ~1. ．． Then, the smear component in the horizontal charge transfer path HCCD is discarded (step 340).

Next, during one field scanning period at time tI m-i 2o, pixel signals generated in photodiodes AI corresponding to odd fields are scanned and read out (step 3
50). That is, at a predetermined time t1 during the vertical blanking period
9, pixel signals corresponding to odd fields are transferred to vertical charge transfer paths 11 to 1 by field shifting. , and then read out by normal vertical and horizontal charge transfer operations.

Next, during one field scanning period at time t20""'t2□, pixel signals generated in the photodiodes Bl corresponding to even fields are scanned and read out (step 360). That is, at a predetermined time point t2 during the vertical blanking period, pixel signals corresponding to even fields are transferred to the vertical charge transfer path by field shifting! ! +~1
．． , and then read out by normal vertical and horizontal charge transfer operations.

As described above, pixel signals of a still image corresponding to one frame are obtained in two fields by processing from time t when the shutter release button is pressed to discarding unnecessary charges, exposure, and reading out pixel signals.

When this still image shooting is completed, the process moves to step 200 in FIG. 2, and the moving image shooting operation is repeated until time t22), when the mechanical shutter remains open.

As described above, according to this embodiment, during the period from the end of continuous vertical charge transfer for dark current disposal to the next field shift, the vertical charge transfer path! 1-1. Since the pinning state is set for the photodiodes A1, . The sensitivity of Bl and the maximum direct product charge amount are made uniform. Also, depending on the pinning state, a vertical charge transfer path! ! 1-1. Since the surface level of is inactivated, leakage of dark current can also be reduced.

As a result of these, the occurrence of flicker in reproduced images can be significantly reduced.

Next, a second example will be described. Conventional solid-state imaging devices have mainly had a relatively low vertical resolution compatible with the NTSC system, etc., but this second embodiment improves the vertical resolution by about twice, and has a vertical resolution equivalent to a pixel. The photodiode is divided into four fields, and when shooting a video, the pixel signals for one frame are read out by performing two field scanning readouts, and when shooting still images, the pixel signals are read out by four field scanning readouts. By doing this, one frame of pixel signals is read out.

First, to explain the structure based on FIG. 4, the light receiving area includes photodiodes PAI for a total of 800,000 pixels, 1000 rows in the vertical direction X and 800 columns in the horizontal direction.
, PBl, PA2. PB2 are arranged and formed in a matrix, and 800 vertical charge transfer paths i7+ to A are formed between photodiode groups arranged along the vertical direction. A horizontal charge transfer path HCCD is formed at the end of the vertical charge transfer path, and an output amplifier AMP is formed at the end.

Then, the photodiode FAI of the (4n-3)th row (here, n is a natural number) of the 1st row, 5th row, etc. is replaced with the (4n-2)th row of the 1st field, 2nd row, 6th row, etc. The photodiode in the row is the second field, the photodiode in the (4n-1) row is in the third field, the third row, the seventh row, etc., and the photodiode in the (4n) row is the third field, the fourth row, the eighth row, etc. It is defined that photodiodes are arranged in the fourth field.

Further, the vertical charge transfer path L-1- has a gate electrode VAI corresponding to the photodiode PAIi of the first field.
and v2, gate electrodes VBI and V4 for the photodiode PBI in the second field, gate electrodes VBI and V4 for the photodiode PA2 in the third field, and gate electrodes VB2 and V4 for the photodiode PB2 in the fourth field, respectively. At the same time, by applying a drive signal φA1 to the gate electrode VAI, a drive signal φ2 to the gate electrode V2, a drive signal φB1 to the gate electrode VBI, and a drive signal φ4 to the gate electrode V4, the vertical charge transfer path! , to generate a potential well and a potential barrier at predetermined timing to vertically transfer signal charges to the horizontal charge transfer path HCCD side. Horizontal charge transfer path HC
CD is a drive signal φ□, ~φ□4 using a 4-phase drive force formula.
The signal charge is transferred to the output amplifier AMP side in synchronization with .

Also, each photodiode PAL, PBl, PA
2. PB2 and the gate electrodes VAI, VBI, VA2 .corresponding to those of the vertical charge transfer path. Transfer gate (represented by Tg in the figure) between the transfer elements below VB2
is formed, and each transfer gate has a gate electrode VA
1. VB1. VA2. VB2 (knee) becomes conductive by applying a predetermined high voltage field shift signal.

Next, the operation of such a solid-state imaging device will be explained based on the flowchart of FIG. 5 and the timing charts of FIGS. 6 to 8. Note that a photographing operation when applied to an electronic camera having a configuration similar to that of the first embodiment will be explained.

In FIG. 5, operation starts in synchronization with turning on the power switch of the electronic camera, and the camera enters the video shooting mode. That is, in step 370, the mechanical shutter is set to be always open and receives light from the subject. Next, in step 380, the internal image production circuit determines whether or not the shutter release button for instructing still image shooting has been pressed, and if the release button has not been pressed, the processing in steps 390 to 400 is performed. By repeating
Shoot a video.

First, in step 390, the first. The pixel signals of the third field are scanned and read out. That is, the vertical blanking period T11. during the period T V D l. Then, the drive signal φ and φA2 become high voltage “HH” necessary for field shift, so that the first
Field and 3rd field photodiode FAI
, PA2 pixel signals are transferred to the vertical charge transfer paths 11 to 1m, and then the vertical charge transfer paths 2. -2. , and the horizontal charge transfer path F (CCD performs a transfer operation at a predetermined timing to perform scanning readout. Note that each period T in FIG.
) II) and the vertical charge transfer path t! I=1. The pixel signals for each two rows are vertically transferred to the horizontal charge transfer path HCCD, and the horizontal charge transfer path HCC is transferred vertically until the next vertical transfer is started.
Perform D or horizontal scanning readout. Therefore, the first. Since the pixel signals of the third field are mixed and read out one row at a time, in video shooting, the vertical resolution is half the number of pixels.

In step 400, the second. The pixel signals of the fourth field are scanned and read out.

That is, the vertical blanking period TVI during the period T vo2
1, the drive signals φB1 and φB2 become the high voltage "HH" necessary for field shifting, so that the photodiodes PA2 and PB of the second field and the fourth field
2 pixel signal to the vertical charge transfer path I! 1-1. After transferring to vertical charge transfer path l,~11 and horizontal charge transfer path HCC
Scanning readout is performed by performing a transfer operation at a predetermined timing. In addition, the vertical charge transfer path is established at each predetermined period THD in FIG. 1-j2. Pixel signals for every two rows are vertically transferred to the horizontal charge transfer path HCCD, and horizontal scanning readout is performed from the horizontal charge transfer path HCCD until the next vertical transfer is started. 2nd thing I wanted to do. Since the pixel signals of the fourth field are mixed and read out one row at a time, in video shooting, the vertical resolution is half of the number of pixels.

Then, by repeating field scanning and reading out every 1/60 seconds in this way, a moving image is photographed.

Further, as shown in FIG. 7, if the shutter release button is pressed at a certain time t1 during the video shooting mode, the "H" level press signal S is generated. In synchronization with the occurrence of "N", the process moves to step 410, and the control signal STR is set to "
When set to L'' level, the mechanical shutter is closed and light is prohibited from entering, thereby entering the still image shooting mode.

In the still image shooting mode, first, as shown in Figure 7,
For each field, unnecessary charges are discarded at a cycle TvD of 1/60 seconds.

In the first cycle (period from time t2 to t6), from time t2 to
At a predetermined time within t3, the drive signal φA1 becomes a predetermined high voltage level "HH", so that the photodiode P
Unnecessary charges in AI are transferred to vertical charge transfer paths 11-1. Hefield shift (step 420), then step 430
(period between time points t3 and t4), the vertical charge transfer path I! , ~
I! By performing the horizontal transfer operation, unnecessary charges are transferred to the horizontal charge transfer path HCCD.

Next, in step 440 (times t4 to ta), the vertical charge transfer paths l, to l. The voltage level of all drive signals of “
By setting it to L” level, the vertical charge transfer path f!
+”!!, is set to the pinning state, and at the time t4
By performing a charge transfer operation in the horizontal charge transfer path HCCD during the period from ~t5, the dark current of the photodiode PAL related to the first field is discarded.

Next, in steps 450 to 470 (period TvD from time t to t8), the dark of the photodiode FBI related to the second field is Discard current. However, the vertical charge transfer path l.

~1. ．． At a predetermined time point before time t7 when vertical charge transfer is started, the drive signal φ is set to 1 or a predetermined high voltage level “HH”.
By doing so, unnecessary charges in the photodetector 1' and FPBI are transferred to the vertical charge transfer paths 11 to 1. , Hefield shift.

Next, in steps 480 to 500 (cycle T vo from time t1 to tlo), the previous cycle (time t2 to tlo)
The dark current of the photodiode PA2 related to the third field is discarded by performing the same process as in period 6).

However, at a predetermined time point before time t9 when the vertical charge transfer paths 11 to 1 start vertical charge transfer, the drive signal φA2 becomes a predetermined high voltage level "HH" (=therefore) the voltage in the odd diode PA2 Transfer unnecessary charges to the vertical charge transfer path it~
1. Hefield shift.

Next, in steps 510 to 530 (cycle TV from time tlo to t15), the previous cycle (time t2 to t
The dark current of the photodiode PB2 related to the fourth field is discarded by performing the same process as in period 6).

However, the vertical charge transfer path! 1-1. At a predetermined time point before time t11 when vertical charge transfer is started, the drive signal φ8□ becomes a predetermined high voltage level "HH", thereby transferring unnecessary charges in the photodiode PB2 to the vertical charge transfer paths 11 to 11.
1. , Hefield shift.

Note that exposure is performed by opening the mechanical shutter for a period (1, □ to t1.) corresponding to the shutter speed between time tll when the field shift operation is completed in the last cycle and time t14.

After the exposure and unnecessary charge disposal processing are completed in this way, the vertical charge transfer paths 11 to 1. and horizontal charge transfer path H
The CCD performs a transfer operation to discard unnecessary charges remaining in these transfer paths (step 540).
).

Next, by performing the processing of steps 550 to 580, the pixel signals generated in each photodiode are scanned and read out at the timing shown in the period from time tls to t0 in FIG.

First, during the predetermined period t+s~tag during the 1/60 second period t+s-t+i (step 550), the pixel signal of the photodiode PAI is changed by setting the drive signal φ^ to the "F (H") level. Vertical charge transfer path!!1
~! ! , after field shifting, vertical charge transfer path 1
The horizontal charge transfer path HCCD performs horizontal transfer every time pixel signals for + to 17 rows are transferred, and by repeating this, all pixel signals corresponding to the first field are output.

Next, in step 560, a period of 1/60 seconds t1□~
During a predetermined period from t17 to t's during t19, by setting the drive signal φB1 to the "HH" level, the pixel signals of the photodiodes PBI are transferred to the vertical charge transfer paths 11 to 1. After the heft field shift, vertical charge transfer paths 11-1. horizontal charge transfer path HCC each time transfers one row of pixel signals.
D is horizontally transferred, and by repeating this, all pixel signals corresponding to the second field are output.

Next, in step 570, a period of l/60 seconds tea~
During a predetermined period t19 to t20 during t21, by setting the drive signal φA2 to the "HH" level, the pixel signal of the odd diode PA2 is transferred to the vertical charge transfer path β1~! , after field shifting, the horizontal charge transfer path HCC is transferred every time pixel signals for one row of the vertical charge transfer path l, ~1m are transferred.
D is horizontally transferred, and by repeating this, all pixel signals corresponding to the third field are output.

Next, in step 580, a period of 1/60 seconds t21~
During a predetermined period t21 to t22 during t22, by setting the drive signal φ8□ to the "HH" level, the pixel signal of the photodiode PB2 is transferred to the vertical charge transfer paths l, -1. ．．
Vertical charge transfer path after Hefield shift! ,~l,
Each time pixel signals for one row are transferred, the horizontal charge transfer path HC
By horizontally transferring the CD and repeating this process, all pixel signals corresponding to the fourth field are output.

In this way, by scanning and reading out pixel signals for each field, the pixel signals of all photodiodes are output, so it is possible to provide a high-resolution still image.

When the still image shooting mode is ended, the process returns to step 370 and the moving image shooting mode is started.

As described above, according to this embodiment, it is possible to provide a still image with high vertical resolution, and furthermore, during the period of discarding unnecessary charges before exposure, it is possible to provide a still image with high vertical resolution. During the period, the vertical charge transfer path 1+-
β. Since all photodiodes PAL, PBl, PA2. P.B.
The potential level of the vertical charge transfer path for the photodiodes PA1. P.B.
l, PA2. The sensitivity and maximum accumulated charge amount of PB2 can also be made uniform, and the absolute amount can also be reduced. Furthermore, since the surface levels of the vertical charge transfer paths l to l are inactivated by the pinning state, leakage of dark current can also be reduced. As a result of these, the occurrence of flicker in reproduced images can be significantly reduced.

In both of the above two embodiments, exposure is performed during a predetermined period when the vertical charge transfer path is set to the pinning state and unnecessary charges are swept out, but the invention is not limited to this. The exposure may be performed after the sweep-out process is completed.

〔Effect of the invention〕

As explained above, according to the present invention, all the vertical charge transfer paths are set to the pinning state after the vertical charge transfer is completed during the period of discarding unnecessary charges before exposure. The potential level of the vertical charge transfer path with respect to the conversion element becomes uniform, and the sensitivity and maximum accumulated charge amount of the photoelectric conversion element can be equalized and the absolute amount can be reduced. The absolute amount of leakage into the photoelectric conversion element can be reduced by the pinning state of the path.

As a result, when an image is reproduced based on the read pixel signals, it is possible to provide an excellent image with significantly reduced occurrence of flicker.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing a schematic structure of an electronic camera according to an embodiment of the present invention, Fig. 2 is a flowchart showing a driving method of the first embodiment, and Fig. 3 @ corresponds to the flowchart in Fig. 2. A timing chart showing the driving method of the first embodiment, FIG. 4 is a timing chart showing the driving method of the first embodiment.
A structural explanatory diagram showing the structure of the solid-state imaging device in the embodiment, FIG. 5 is a flowchart showing the driving method of the second embodiment, and FIGS. 6, 7, and 8 correspond to the flowchart in FIG. 2. FIG. 9 is a conventional structural explanatory diagram showing the structure of a solid-state imaging device to which the conventional driving method is applied, and FIG. 10 is a timing chart showing the driving method of the second embodiment. FIG. 11 is a timing chart showing a conventional driving method corresponding to the flowchart shown in FIG. Symbols in the figure: ■D: Vertical synchronization timing signal, HD: Horizontal synchronization timing signal, S7. : Shutter timing signal, APS, BFS; Field shift timing signal, V
CCD: Vertical transfer timing signal, HCCD
: Horizontal transfer timing signal, S ON : Shutter press timing signal, φ1 φB1 φ2 φA
2 φs2 φ4: Drive signal for vertical charge transfer path, φold φH2φH2φH4: Drive signal for horizontal charge transfer path. Agent Patent Attorney (6642) Toshio Fukasawa (External 3
(name) S・ also 1φ Fig. 10

Claims (1)

[Scope of Claims] A plurality of photoelectric conversion elements corresponding to a plurality of pixels arranged in a matrix in the row and column directions, and a plurality of photoelectric conversion elements arranged adjacent to each other in each column direction. It is equipped with a vertical charge transfer path and a horizontal charge transfer path that outputs signal charges transferred from these vertical charge transfer paths in time series, and fields unnecessary charges remaining in the photoelectric conversion element to the vertical charge transfer path. After the shifting, unnecessary charges are discarded by scanning readout using the vertical charge transfer path and the horizontal charge transfer path, and the photoelectric conversion element is exposed to light at a predetermined time during the discard processing period or at a predetermined time after completion. In a method for driving a solid-state imaging device, which generates a pixel signal, then field-shifts the pixel signal to a vertical charge transfer path, and performs scanning readout through the vertical charge transfer path and horizontal charge transfer path to perform imaging. , during the disposal processing period, after all unnecessary charges are transferred from the vertical charge transfer path to the horizontal charge transfer path, all the vertical charge transfer paths are set to a pinning state and scanning readout is performed to the horizontal charge transfer path. A method for driving a solid-state imaging device, characterized in that the exposure is performed at an appropriate time when the vertical charge transfer path is set in a pinning state, and unnecessary charges are discarded by causing the exposure to occur.