JPH03238984A - Electronic still camera - Google Patents

Abstract

PURPOSE:To prevent production of flicker due to uneven brightness for each field by applying idle readout for a period being an integral number of multiple of fields for a prescribed field scanning readout period after the exposure and applying field scanning readout to a picture element signal. CONSTITUTION:Idle readout is implemented through vertical charge transfer lines l1-lm and a horizontal charge transfer line HCCD without field shift for a period corresponding to the scanning period of KXi fields after exposure and each field scanning readout is implemented sequentially from the field scanning succeeding to the end of idle readout to read a picture element signal. Thus, smear component is excluded for the idle read period and the effect of a dark current onto the picture element signal corresponding to each field is uniformized and production of flicker of the reproduced picture is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic still camera that captures still images using a charge-coupled solid-state imaging device, and in particular provides high-definition still images without flicker. Regarding electronic still cameras.

[Conventional technology]

Conventional electronic still cameras have used charge-coupled stationary image devices having a vertical resolution that complies with standard television systems, such as the NTSC system, with a scan line count of 525, for example.

However, in order to perform high-resolution imaging that can be used in high-definition television systems that have approximately twice the vertical resolution of NTSC television systems, conventional solid-state imaging devices are required. However, the vertical resolution was insufficient, and for this reason, there was a desire to develop an electronic still camera using a solid-state imaging device with a larger number of pixels.

Therefore, the inventors of the present application used an interline transfer type charge-coupled solid-state imaging device that doubles the number of pixels in the vertical direction compared to the conventional one and reads out the pixel signals of all pixels by four field scanning readouts. Researched and developed electronic still cameras.

The structure of such a solid-state imaging device will be described based on FIG. 9. In the figure, there are photodiodes At, B!, corresponding to a total of 800,000 pixels, 1000 rows in the vertical direction X and 8'00 columns in the horizontal direction Y. , A2°B2 are formed in a matrix, and vertical charge transfer paths 11 to 1m are formed adjacent to the photodiode groups arranged in each column, and horizontal charge transfer paths are formed at the ends of the vertical charge transfer paths 11 to 1m. RoadHCCD
is formed, and each pixel signal is read out in time series in synchronization with the timing of dot sequential scanning via an output amplifier (AMP) formed at the end of the horizontal charge transfer path HCCD.

Further, the photodiode A4 arranged in the 40-3rd row (where n is a natural number) is the first field, the photodiode B1 arranged in the 4n-2nd row is the second field,
The photodiode A2 arranged in the 4n-1th row is
field, and the photodiode B2 arranged in the 4th nth row is defined as corresponding to the 4th field,
By performing field scanning readout four times in order, it operates to read out all pixel signals for one image.

A series of imaging operations from exposure to scanning readout of pixel signals will be explained based on the tie chart in FIG. 10.
The solid-state imaging device is configured for each field scanning period (IV
) Each field scanning readout is performed in synchronization with a vertical synchronizing signal VD representing the field. That is, in FIG. 10, a field shift operation is performed for each field in synchronization with the vertical synchronizing signal VD inverting to the "'H" level (FSI, FS2, FS3, FS4 or "'H" in the figure). °
The next vertical synchronizing signal VD is "H".

■V until it becomes Rehel! During tJ1, the pixel signals corresponding to each field are read out.

For example, as shown in FIG. 10, at a certain time t during the second field scanning period (between time t0 and t2), the shutter release button of the camera is pressed and a predetermined shutter period (“H” in the figure) is pressed. If exposure is performed for a period indicated by "," readout of pixel signals starts from continuous field scanning immediately after the end of exposure. That is, first, the pixel signal qAz generated in the photodiode A2 corresponding to the third field is field-shifted from time t2 to the vertical charge transfer path side during the period when FS3 is "H", and then,
Vertical charge transfer path 421-1m in synchronization with a predetermined drive signal
The horizontal charge transfer path HCCD reads out the pixel signal qaz in time series, thereby scanning and reading out the third field in the period from time point L2 to L:l.

Next, the photodiode corresponding to the fourth field
The pixel signal '182 generated at B2 is converted to FS from time L3.
4 is "H", the field is shifted to the vertical charge transfer path side, and then, in synchronization with a predetermined drive signal, the vertical charge transfer path j21-ffim and the horizontal charge transfer path HCCD time-series the pixel signal QB□. The fourth field is scanned and read out during the period from time t3 to L4.

Next, the photodiode At corresponding to the first field
The pixel signal qAI generated in 1 is field-shifted to the vertical charge transfer path side during the period when FSI is “H” at time L4, and then, in synchronization with a predetermined drive signal, the vertical charge transfer path 11=1m and the horizontal charge transfer The pixel signal qA is
By reading I chronologically, time t, ~t,
The scanning readout of the first field is performed during the period of .

Next, photodiode B1 corresponding to the second field
The pixel signal qg+ generated at
++ field shift to the vertical charge transfer path side, and then, in response to a predetermined drive signal, the vertical charge transfer path f
fl-ffm and horizontal charge transfer path HCCD or pixel signal q
1 in time series, time t5 to L6
The scanning readout of the first field is performed during the period of .

In this way, by performing field scanning readout four times immediately after exposure, all pixel signals for one image are read out.

[Problems to be Solved by the Invention] However, when pixel signals are scanned and read out at the timing shown in FIG. 10, smear components are generated in the pixel signals of the phototiorute corresponding to the field that is first scanned and read out immediately after exposure. This causes the problem that field flicker occurs when an image is reproduced, resulting in deterioration of image quality. For example, according to the timing shown in FIG. 10, the largest amount of smear is mixed in the pixel signal qA2 corresponding to the third field, which is scanned and read out first, and the fourth field, which is scanned and read out subsequently. Since the smear on the pixel signal corresponding to the first and second fields is almost no problem, the brightness of the field image corresponding to the third field will be high and cause color unevenness. , which caused deterioration in image quality.

By the way, as a method to prevent such smear from being mixed into pixel signals, after the exposure is completed, the vertical charge transfer path nl-
/! By causing the horizontal charge transfer path HCCD to perform scanning readout, unnecessary charges that cause smear are discharged to the outside, and then by performing normal field scanning readout, the pixel signal Hesmear of all fields is mixed in. It may be possible to avoid this.

That is, to explain the method based on the timing chart of FIG. 11, if exposure is performed at a certain time t4, the first field shift operation after the end of the exposure (that is, the field shift operation in the third field) is performed. By masking (period T6 in the figure),
During the period C (time t, to t6) in which the transfer of pixel signals from the photodiode to the vertical charge transfer path is prohibited and scanning readout of the third field is originally performed, the vertical charge transfer path and the water are in a so-called idle reading state. + Charge transfer path ↓ This scanning readout operation is performed, and what is read out during this period (period from time L5 to time t6) is discarded without being used as a pixel signal. As a result, smear components in the vertical charge transfer path and the horizontal charge transfer path are removed.

Then, scanning readout of the fourth field is started from time t6, and the scanning readout of the first field is started. Second. By scanning and reading out the third field in order, all pixel signals for four fields are read out.

However, although scanning readout with the timing shown in FIG. 11 improves the smear problem, the influence of dark current cannot be ignored. In other words, dark current is a noise component that is constantly generated from the surface of a semiconductor substrate or photodiode, and the pixel signal (the pixel signal corresponding to the fourth field in FIG. 11) that is first subjected to field scanning readout is a photodetector. Since the time spent in the diode is short, the effect of dark current is small, and the last field scanning readout (pixel signal corresponding to the third field in FIG. 1) is affected by dark current because the time spent in the diode is long. That is, in the case of FIG. 11, the pixel signal corresponding to the fourth field is at time t, ~
Dark electricity proportional to 4V period up to L6? The pixel signal corresponding to the first field is mixed with JL (supposed to be 4Q), and the pixel signal corresponding to the second field is mixed with a dark current (supposed to be 4Q) proportional to the 4V period from time t2 to L7. The signal has a dark current (4V) proportional to the 4V period from time t3 to t9.
Q), and the pixel signal corresponding to the third field is prohibited from field shifting at time t, so that the pixel signal corresponding to the third field is mixed at time 1, -1 . A dark current (assumed to be 8Q) proportional to the 8V period up to this point is mixed in, and clearly the amount of dark current mixed into the pixel signal corresponding to the third field is larger than in the other fields. If an image is reproduced based on the pixel signals read out in this way, uneven brightness and color may occur depending on the amount of dark current mixed in each field, resulting in deterioration of image quality. becomes.

The present invention was developed in view of these problems,
An object of the present invention is to provide an electronic still camera that uses a charge-coupled solid-state imaging device with a large number of pixels and is capable of capturing images without causing image quality deterioration such as flicker in reproduced images.

[Means to solve the problem]

To achieve such an object, the present invention forms a plurality of photoelectric conversion elements corresponding to pixels in a matrix shape along the row direction and the column direction, and vertically aligns the photoelectric conversion elements arranged in each column. In an electronic still camera that captures an image using an interline transfer type charge-coupled solid-state imaging device that forms charge transfer paths and also forms horizontal charge transfer paths connected to the terminal ends of these vertical charge transfer paths, The photoelectric conversion element group is divided into k fields (k is a natural number), and the pixel signals generated in the photoelectric conversion elements arranged in each field are scanned and read out several times in order every predetermined field scanning readout period. , controls to read out all pixel signals, and during imaging, the vertical charge transfer path and A scanning readout is performed using a horizontal charge transfer path, and after the k x i field scanning readouts, pixel signals generated in the photoelectric conversion elements arranged in each field are sequentially read out every predetermined field scanning readout period. I decided to do so.

[Operation] According to the electronic still camera of the present invention having such a configuration, after exposure, a blank sequence is performed in a period that is an integral multiple of the number of fields with respect to a predetermined field scanning readout period, and then pixels are scanned. Since the signal is scanned continuously in fields, it is possible to eliminate smear components, and it is also possible to equalize the influence of dark current on the pixel signals of each field, so when the image is reproduced, it is possible to eliminate unevenness in brightness from field to field. It is possible to prevent flicker from occurring.

In addition, by setting the number of fields to 4 and the coefficient i to about l, that is, by dividing it into 4 fields and making the blank reading period correspond to the 4-field period, the imaging speed can be increased. This is effective in that the absolute amount of dark current relative to the pixel signal can be reduced.

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

First, to explain the entire electronic still camera +S based on Fig. 1, 1 is an imaging lens, 2 is an aperture mechanism, 3 is a beam splitter, 4 is a shutter mechanism, and 5 is an interline transfer type charge-coupled solid state. These are imaging devices, each of which is arranged in order along the optical axis.

Reference numeral 6 denotes a light receiving element, which measures the light from the beam splitter 3 and manually inputs a measurement signal representing the subject brightness to the exposure control circuit 7. Then, the exposure control circuit 7 automatically sets the aperture value of the aperture mechanism 2 and the shunter speed of the shutter mechanism 4 based on the measurement signal.

Reference numeral 8 denotes an imaging device drive circuit, which includes a drive signal for controlling the scanning readout timing of the charge-coupled solid-state imaging device 5, that is, a drive signal φ9 for driving the vertical charge transfer path, and a drive signal φ9 for driving the horizontal charge transfer path. drive signal φ8
, the exposure control circuit 7 generates a field shift synchronization signal FS for performing a field shift operation in each field scan readout G, and also generates a synchronization signal for synchronizing the scan readout of the charge-coupled solid-state imaging device 5.
supply to

9 is a system controller for controlling the operation timing of the entire camera, and a shutter release button 1
When a synchronization signal synchronized with the pressing timing of 0 is received from the release operation detection circuit 10, the operations of the exposure control circuit 7 and the imaging device drive circuit 5 are operated in synchronization with the synchronization signal, and the charge-coupled solid-state imaging device 5 is operated in synchronization with the synchronization signal. The timing for signal processing the pixel signals read out from and recording them on the recording medium is controlled.

12 is a video signal processing circuit which performs processes such as self-balance adjustment and T correction on pixel signals read out at predetermined timing from the charge-coupled solid-state imaging device 5;
A predetermined modulation process or the like is performed to form a recordable video signal.

A buffer circuit 13 amplifies the video signal output from the video signal processing circuit 12 and transfers the amplified video signal to the recording device 14.

I5 is a recording control circuit, which controls the operation of the buffer circuit 13 and the recording device 14 according to the timing control signal from the system controller 9, and controls the operation of the recording device 14.
A video signal is recorded on a magnetic recording medium or a semiconductor memory of a memory card.

Next, the structure of the charge-coupled solid-state imaging device 5 will be explained based on FIG. 2. This imaging device is a charge-coupled solid-state imaging device manufactured by semiconductor integrated circuit technology on a semiconductor substrate with impurities at a predetermined concentration, and the light receiving area has 1000 rows in the vertical direction X4 and 1000 rows in the horizontal direction Y. Photodiode A with 800 columns for a total of 800,000 pixels
l, BIA2. B2 is provided in a matrix, and 80
Zero vertical charge transfer paths 11 to 1m are formed. On the upper surface of each of the vertical charge transfer paths 11 to 1m, a gate electrode VAl is provided for the photodiode At arranged in the 40-3rd row (n is a natural number), and a photodiode arranged in the 40th-3rd row (n is a natural number) is provided. Gate electrode VBI for diode Bl
, a gate electrode VA2 is provided for the photodiode A2 arranged in the 4nth row, a gate electrode VB2 is provided for the photodiode F'B2 arranged in the 4nth row, and a gate electrode VB2 is provided between the gate electrode VA1 and VBI. and gate electrode VA2
A gate electrode V2 is provided between the gate electrodes VBI and VA2, and a gate electrode 4 is provided between the gate electrodes VBI and VA2 and between the gate electrodes VB2 and VAI.

The gate electrodes in the same row are formed of a common polysilicon layer, and the gate electrode VAI is connected to the drive signal φ1,
Drive signal φ2 is applied to gate electrode V2, drive signal φ□ is applied to gate electrode VBI, drive signal φ4 is applied to gate electrode ■4, drive signal φ4□ is applied to gate electrode VA2, and drive signal φ4 is applied to gate electrode VB2.
↓Here, drive signal φ8z is applied, and these drive signals φ
□, φ2. φ8φ4. φ, 2. Signal charges are transferred by generating a potential well (hereinafter, the potential well portion is referred to as a transfer element) and a potential barrier of a potential level corresponding to the applied voltage of φ8□ in the vertical charge transfer path ff1-ff1m↓. It has become. Note that one driving word φ shown in FIG.

are these drive signals φAl+φ2. φKun, φ4゜φ
A2+φ8□ is shown as a representative.

Further, a horizontal charge transfer path HCCD is formed at the end of the vertical charge transfer paths 11 to 2m, and an output amplifier AMP is provided at the output end of the horizontal charge transfer path HCCD.
is formed. The horizontal charge transfer path HCCD is driven by four-phase drive signals φM+ +φ, 12, φ83 . φH
The pixel signal is transferred horizontally in synchronization with 4, and the output amplifier (AM
P). It should be noted that the drive signal φi shown in FIG.
．． φH4 is shown as a representative.

Further, among the horizontal charge transfer paths 11 to I'm, the portion VV connected to the horizontal charge transfer path HCCD is connected to the transfer element formed under the gate electrode VB2 located next to the horizontal charge transfer path F(CCD). There is a gate section for controlling the connection between the terminal and the terminal, and becomes conductive or non-conductive in synchronization with a gate signal (not shown) at a predetermined timing.

Furthermore, each photodiode /M, B4°A2. B2
and the corresponding gate electrode VAI of the vertical charge transfer path,
VBI, VA2. A transfer gate (represented by Tg in the figure) is formed between the transfer elements below VB2, and each transfer gate has a gate electrode VAI stacked over the transfer gate.

VBI, VA2. Field shift synchronization signal F to VB2
A field shift operation is performed by applying a predetermined high voltage drive signal in synchronization with S to make the transfer gate conductive.

And these photodiodes Al and Bl.

A2. An impurity region with a predetermined concentration formed around B2, the transfer gate, the vertical charge transfer paths 21 to 2m, and the horizontal charge transfer path HCCD serves as a channel stomp.

Further, the photodiode At is the first field, the photodiode Bl is the second field, and the photodiode A2
is defined as being arranged in the third field, and photodiode B2 is arranged in the fourth field.

Next, the imaging operation of such an electronic still camera will be explained.

This electronic still camera has an Al photodiode formed in a charge-coupled solid-state imaging device 5.

The pixel signals generated in BI A2 B2 are read out by sequentially performing field scanning readout for each field defined above, and the period (1 V) when the timing signal VD in FIG. 3 becomes "H" Each field has a scanning period.

Then, in synchronization with the timing signal VD, field shifting in each field scanning readout is performed in order. Incidentally, when FSI in the figure becomes "H", a field shift in the first field scan succession period is performed,
Other FS2. Similarly, FS3FS4 performs each field shift in the 2nd, 3rd, and 4th field scanning readout periods when the signal becomes H".

If it is determined that exposure is performed by pressing the shutter release button at a certain point L4, a masking period TMS starts from that point L4 for a period (4V) that is four times the period of the field scanning readout period (1■). , this period T, 4. In this case, all field shift operations are prohibited. Therefore, time t6. t6. t7. In LB,
No field shift operation is performed, and the pixel signals are held as they are in the three photodiodes AI, Bl, A2°B2 corresponding to each field.

Then, the vertical charge transfer paths 21 to 1m and the horizontal charge transfer path HCCD perform scanning readout four times during the period t to tlo (v), and all signals read during this period are discarded. Therefore, unnecessary charges that cause smear are discarded.

Next, at time t. Normal field scanning readout starts from this point. That is, first, at time tlo, the pixel signal qA□ of photodiode A2 corresponding to the third field, which is the first field, is transferred to the vertical charge transfer path ffl~1m.
field soft to a predetermined transfer element of
Drive signal φAl+ φ2. at a predetermined timing. φ1. φ
4. φ, 2. By reading in synchronization with φ8□, φiφ82 +φ83 +φ, time L10"""tl
All pixel signals qAZ corresponding to the third field are read out during +.

Next, at time 111, the pixel signal 'IB□ of the photodiode B2 corresponding to the fourth field is field-shifted to a predetermined transfer element of the vertical charge transfer paths 11 to 1m, and then the drive signal φ□ at a predetermined timing , φ2.
φB1. φ4. φA□, φ8□.

φ□, φ, +2, φH3+φ8. By reading out in synchronization with , all pixel signals corresponding to the fourth field are read out during time tz-t+□.

Next, at time t, the pixel signal (IAI) of the photodiode At corresponding to the first field is field-shifted to a predetermined transfer element of the vertical charge transfer paths 21 to 1m, and then the drive signal φ, 1.φ2.
φ89. φ4. φAZ+ φ82゜φH1, φH2,
By reading out in synchronization with φH3+φ□, all pixel signals QAI corresponding to the first field are read out between time points L1□ to L13.

Finally, at time t13, the pixel signal qg+ of the photodiode Bl corresponding to the second field is field-shifted to a predetermined transfer element of the vertical charge transfer paths 11 to Qm, and then the drive signal φ□ at a predetermined timing is ,
φ2. φB++ φ4. φq2φB□1 φ□, φ8
2 +φ0. By reading out in synchronization with φH'4, all pixel signals q corresponding to the second field are read out between times tlff and t14.

Note that each read pixel signal is finally recorded on a predetermined recording medium in the recording device 14.

In this way, the 4-field scanning readout period (
In step 4), pixel signals are held in the photodiodes corresponding to each field and then scanned and read out. The pixel signal (lA2) read out during the period ~tl+ includes the dark current (lA2) that affected the photodiode 'A2 over the period of 8v from time to ~LIG.
81) will be mixed in, and at the time ' + 1''
"" = 1. The pixel signal Qsz read out during the period lz contains the dark current (8[
)? It was decided to go to Kunjin, and at point 1. □～t+3
The pixel signal QA+ read out during the period is affected by the dark current (81) that influenced the photodiode At over the 8-hour period from time L2 to L+z, and The pixel signal Qg□ read out at the time point L3 to L+3g
The dark current (assumed to be 8I) that affected the photodiode B1 over the period of 8.5 times increases by one order of magnitude.

In this way, a uniform dark current will be mixed into the pixel signals corresponding to all fields, so when the image is reproduced, the dark current caused by the brightness difference between each field will be reduced.
7 mosquitoes do not survive. As of now.

Since the smear component is discarded between and Loo, no flicker occurs due to the smear.

Next, in response to the increase in the number of pixels in order to improve the vertical resolution, each field scanning readout is shown in Figure 4~
This is done at the timing shown in FIG. Note that FIG. 4 shows the first field scanning sequence timing for reading out pixel signals from photodiode A1 corresponding to the first field, and FIG. 5 shows the timing for reading out pixel signals from photodiode B1 corresponding to the second field. 2nd field scan readout timing, Figure 6 shows the 3rd field scan readout timing for reading out pixel signals from photodiode A2 corresponding to the 3rd field, and Figure 7 shows the 4th field scan readout timing.
The fourth field scanning readout timing for reading out pixel signals from the photodiode B2 corresponding to the field is shown, and FIG. 8 shows an enlarged view of the timing of the field shift operation during the period τ in FIGS. 4 to 7. There is.

In addition, the period in each figure T FAI + TFBI =
TFA□ and TFB□ correspond to the period (1V) of each field scanning readout, and are each set to 1/60 seconds. Also, period Tfsl) Tfs□, T(53, T(s< is FSI FS2.FS3.FS4 or "'H" in Fig. 3)
It corresponds to the field shift period with ``, and the period T.ut
This is the scanning readout period that continues after the field shift operation.

First, the operation of the first field scanning readout will be explained based on FIG. 4.Field shift=x interval T"fsl
As shown in FIG. a, the drive signals φAlφ1. φ,
2. φ8□, φ2. The logical value level of φ4 changes, and at time S1 in the figure, the drive signal φA1 is applied to the transformer gate T.
The pixel signal of the photodiode At corresponding to the first field is field-shifted to the transfer element below the gate electrode VAl by reaching a high enough voltage to turn on the gate electrode VAl. Once this field shift is finished,
Next, by performing the operation for the period τ (between time points 32 and S3), the pixel signal Q is transferred to the vertical charge transfer paths 21 to 1m.
The entire AI is connected to the horizontal charge transfer path HCCD for one line.
Transfer to the side. That is, each drive signal in the period τ is divided from two periods of rectangular signals, and as shown in FIG. 8, the drive signal φ□ changes from "H" to "L" to "H" to "H
In contrast, the drive signal φ2 is set to the same waveform delayed by a predetermined phase Δ, and the drive signal φ2 is set to the same waveform delayed by a predetermined phase Δ from the drive signal φ2. The drive signal φ4 is further set to the same waveform delayed by the phase Δ from the drive signal φB1, the drive signal φA2 is further set to the same waveform delayed by the phase Δ from the drive signal φ4, and the drive signal φ8□ is set to the same waveform delayed by the phase Δ. Furthermore, the phase Δ is determined from the drive signal φA2.
is set to the same waveform delayed by Then, the vertical charge transfer path i1 is activated by the drive signal at such timing.
~ When f2m is driven, the pixel signal qAI for one row closest to the horizontal charge transfer path HCCD is transferred to the horizontal charge transfer path HCCD.
The data is transferred to a predetermined transfer element of the CD.

Next, in a period from time point 33 to S4, the horizontal charge transfer path HCCD horizontally transfers one row's worth of pixel signals 9Al in synchronization with the drive signals φ□ to φH4, and reads out each pixel signal in time series.

Then, by repeating the same operations as those at time points 32 to S4 described above until all remaining pixel signals q□ are read out, scanning readout of all pixel signals corresponding to the first field is completed. In FIG. 4, it is assumed that reading is completed at time S5.

Next, photodiode 1B corresponding to the second field
The field scanning readout for No. 1 will be explained based on the number in FIG. As shown in the field shift period T, 5□B, the drive signal φ.

φ,, φA2+ φ, 2. φ2. The logic value level of φ4 changes, and at time S6 in the figure, the drive signal φ81 becomes a high enough voltage to make the transformer hTg conductive, so that the pixel signal of the photodiode BL corresponding to the second field changes. Field shift q1 to the transfer element below the gate electrode VBI. When this field shift ends, next is period T in FIG. ut
The same operation for charge transfer is performed, and at time S7 in the figure, all pixel signals q from the photodiode B1 hitting the second field are read out.

Next, photodiode A2 corresponding to the third field
The field scanning readout will be explained based on FIG. As shown in the field shift period T fs3, the drive signal φ,.

φll++ φA2. φ1121 φ2. φ4
The logic level of the photodiode A2 corresponding to the third field changes, and the drive signal φ4□ becomes a high enough voltage to make the transformer gate 1-Tg conductive at time S8 in the figure. Field shift the pixel signal qAz to the transfer element below the gate electrode VA2. When this field shift ends, next is period T in FIG. 7. Performs the same operation for charge transfer as
At time S9 in the figure, all pixel signals (IAZ) from the photodiode A2 corresponding to the third field are read out.

Next, the photodiode corresponding to the fourth field - F B
The field scanning readout for No. 2 will be explained based on FIG. As shown in the field shift period T fs4, the drive signal φ□.

φm l + φA2+ φB21 φZ7 φ
4 changes, and at time SIO in the figure, the drive signal φB2 becomes a high enough voltage to make the transformer gate Tg conductive, so that the photodiode B2 corresponding to the fourth field changes. Pixel signal qIl□
is field-shifted to the transfer element below the gate electrode VB2. Once this field shift is finished, then
Period T in Figure 4. The same operation as ut is performed for charge transfer, and all pixel signals qg□ from the photodiode B2 corresponding to the fourth field are read out at time Sll in the figure.

Note that each of the field shift operations shown in FIGS. 4 to 7 is stopped during the masking period, as described above, so the pixel signal remains held in the photodiode for the period T. U.

The transfer operation shown in FIG. 1 results in a series of empty transfers.

In this way, the vertical charge transfer paths 21 to 1m are connected to the six-phase drive signals φAI+φ, φ^2. φg2・φ2・φ4
When driven by
Effects such as simplification of wiring can be obtained. Incidentally, if we assume that the conventional four-phase drive method used for boat fishing can be applied to the imaging device of this embodiment with twice the vertical resolution, an eight-phase drive method will be applied. , eight types of drive signals are required. On the other hand, since this embodiment uses a six-phase drive system, the above-mentioned effects can be obtained.

In this embodiment, a case has been described in which empty reading is performed during a period corresponding to 4 field scanning periods after exposure. The pixel signal may be read out after empty reading is performed during the period. That is, even if empty reading is performed during a period corresponding to a field scanning period that is an integral multiple of 4,
Smear components can be removed, and at the same time, the influence of dark current on pixel signals corresponding to each field can be equalized.

Furthermore, in this embodiment, scanning readout for flicker removal was explained when the array of photodiodes corresponding to pixels was divided into four fields.
Generally speaking, if the field is divided into k fields (k is a natural number), the pixel signal is read out after blank reading is performed during a period corresponding to k x i (i is a natural number) times the field scanning readout period. ; smear can be removed and dark current can be made uniform, and flicker can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, photoelectric conversion elements corresponding to pixels are divided into fields, and pixel signals of the photoelectric conversion elements corresponding to each field are scanned repeatedly for all pixels. In an electronic still camera that uses a charge-coupled solid-state imaging device to read out signals, blank reading is performed on the vertical charge transfer path and the horizontal charge transfer path without performing a field shift during a period equivalent to the k x iX yield scan period after exposure. All pixel signals are read out by reading out each field scan in order from the next field scan after the idle reading operation is completed. It is possible to equalize the influence of dark current on pixel signals corresponding to each field, and it is possible to prevent flicker from occurring in a reproduced image. Furthermore, it is extremely effective in realizing an electronic still camera that uses a charge-coupled solid-state imaging device with an increased number of pixels to improve vertical resolution.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention, Fig. 2 is a block diagram showing a configuration of a charge-coupled solid-state imaging device applied to an embodiment, and Fig. 3 is an electronic still image during imaging. A timing chart for explaining the operation of the camera, FIG. 4 is a timing chart showing the first field scan readout timing in one embodiment, FIG. 5 is a timing chart showing the second field scan readout timing in one embodiment, and FIG. 6 is a timing chart showing the readout timing of the 3rd field scan in one embodiment, FIG. 7 is a timing chart showing the evening and timing of the 47th field scan readout in one embodiment, and FIG. Fig. 7 is a timing chart showing an enlarged timing of the period τ in Fig. 9; The figure is a timing chart for explaining the problem of smear contamination in a conventional electronic still camera, and the figure '411 is a timing chart for explaining the problem of dark current in a conventional electronic still camera. Symbols in the figure: l; Imaging lens 2; Aperture mechanism 3; Beam splitter IJ holder 4; Shutter mechanism 5; Charge-coupled solid-state imaging device 6; Light receiving element 7; Exposure control circuit 8; Stem controller 10; shutter release button 11; release operation detection circuit 12; video signal processing circuit 13; Hanwha circuit 14; recording device 15; recording control circuits At, Bl, A2. B2; Photodiode VAN,,
VBI, VA2. VB2; Gate electrode 11-1m; Vertical charge transfer path HCCD; Horizontal charge transfer path AMP, output amplifier

Claims (1)

[Claims] A plurality of photoelectric conversion elements corresponding to pixels are formed in a matrix along the row and column directions, and a vertical charge transfer path is formed along the photoelectric conversion elements arranged in each column,
In an electronic still camera that captures an image using an interline transfer type charge-coupled solid-state imaging device formed by forming a horizontal charge transfer path connected to the terminal end of these vertical charge transfer paths, the photoelectric conversion element group is k (k is a natural number), and the pixel signals generated in the photoelectric conversion elements arranged in each field are sequentially read out k times in each predetermined field scanning readout period, so that all pixel signals are read out. At the same time, during imaging, the scanning readout using the vertical charge transfer path and the horizontal charge transfer path is performed with the field shift stopped during the field scanning readout period of k x i (i is a natural number) times after exposure. After performing the k x i field scanning readouts, all pixel signals are read out by sequentially scanning and reading out the pixel signals generated in the photoelectric conversion elements arranged in each field every predetermined field scanning readout period. An electronic still camera featuring