JP2614129B2 - Electronic still camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic still camera that captures a still image using a charge-coupled solid-state imaging device, and particularly provides a high-definition still image without flicker. To an electronic still camera.

[Conventional technology]

A conventional electronic still camera uses a charge-coupled solid-state device having a vertical resolution of such a degree as to conform to a standard television system such as the NTSC system having 525 scanning lines, for example.

However, in order to perform high-resolution imaging that can be applied to a high-definition television system having about twice the vertical resolution as compared to an NTSC television system, a conventional solid-state imaging device must be used. Therefore, the vertical resolution is insufficient. For this reason, there has been a demand for the development of an electronic still camera using a solid-state imaging device having a larger number of pixels.

Therefore, the inventor of the present application has used an interline transfer type charge-coupled fixed imaging device in which the number of pixels in the vertical direction is about twice as large as that of the related art, and pixel signals of all pixels are read out by performing field scanning and reading four times. Research and development of electronic still cameras.

The structure of such a solid-state imaging device will be described with reference to FIG. 9. In FIG. 9, photodiodes A1, B1, A2, and 1000 corresponding to 1000 rows in the vertical direction X and 800 columns in the horizontal direction Y correspond to a total of 800,000 pixels. B2 is formed in a matrix shape, and the vertical charge transfer paths l1 to
and a horizontal charge transfer path HCCD is formed at the end of the vertical charge transfer paths l1 to lm. Each pixel signal is output via an output amplifier (AMP) formed at the end of the horizontal charge transfer path HCCD. The data is read out in time series at the same time as the point-sequential scanning timing.

Further, the photodiodes A1 arranged in the (4n-3) th row (where n is a natural number) are in the first field, the photodiodes B1 arranged in the (4n-2) th row are in the second field, and the photodiodes A1 are arranged in the fourth field.
The photodiode A2 arranged in the first row is defined as the third field, and the photodiode B2 arranged in the fourth nth row is defined as the fourth field, and the field scanning and reading are performed four times in order. 1 operates to read out all pixel signals for one image.

A series of imaging operations from exposure to scanning and reading of pixel signals will be described with reference to the timing chart of FIG.
For solid-state imaging devices, each field scan period (1V)
The respective fields are scanned and read out in synchronization with a vertical synchronization signal VD representing the following. That is, in FIG. 10, a field shift operation for each field is performed in synchronization with the inversion of the vertical synchronization signal VD to the “H” level (FS in FIG. 10).
1, FS2, FS3, and FS4 become “H” level during the field shift period of each field), and the next vertical synchronization signal VD
The pixel signal corresponding to each field is read during the 1 V period until the signal becomes “H” level.

For example, as shown in FIG. 10, at time t ₁ with a second field scanning period (between times t ₀ ~t _2), a predetermined shutter time by pressing the camera shutter release button (in the figure " If exposure is performed only during the period indicated by H "), reading of pixel signals starts from field scan reading immediately after the end of the exposure. That is, first, the pixel signal q generated in the photodiode A2 corresponding to the third field
Field shifted to the vertical charge transfer path side of _A2 from the time t ₂ during a period in which FS3 becomes "H", then a given pixel is the vertical charge transfer paths l1~lm and horizontal charge transfer path HCCD in synchronization with the drive signal By reading out the signal q _A2 in time series, the time t
Performing scan reading of the third field in a period of ₂ ~t _3.

Next, the photodiode B2 corresponding to the fourth field
The pixel signal q _B2 generated at the time t is shifted from the time t ₃ to the vertical charge transfer path during the period when the FS4 becomes “H”,
Predetermined vertical charge transfer path in synchronization with the drive signal l1~lm and horizontal charge transfer path HCDD is by reading the pixel signals q _B2 chronologically, scan reading of the fourth field period from time t ₃ ~t ₄ I do.

Next, the photodiode A1 corresponding to the first field
To field shift to the vertical charge transfer path side pixel signal q _A1 in the period in which FS1 at time t ₄ becomes "H" generated, then, predetermined vertical charge transfer paths l1~lm and horizontal synchronization with the drive signal by charge transfer path HCCD reads a pixel signal q _A1 in time series, performs a scan reading of the first field in the period from time t ₄ ~t _5.

Next, the photodiode B1 corresponding to the second field
To field shift to the vertical charge transfer path side pixel signals q _B1 from time t ₅ in the period in which FS2 becomes "H" generated, then, predetermined vertical charge transfer paths l1~lm and horizontal synchronization with the drive signal by charge transfer path HCCD reads a pixel signal q _B1 in a time series, performs a scan reading of the first field in the period from time t ₅ ~t _6.

As described above, by performing field scan reading four times immediately after exposure, all pixel signals for one image are read.

[Problems to be solved by the invention]

However, if the pixel signal is scanned and read at the timing shown in FIG. 10, the smear component is most mixed in the pixel signal of the photodiode corresponding to the field which is first scanned and read immediately after the exposure, and the image is reproduced. Then, there is a problem that the field flicker occurs and the image quality is deteriorated. For example, according to the timing of FIG. 10, the smear is most mixed into the pixel signal q _A2 corresponding to the third field first scan reading is performed,
Since the smear is hardly mixed into the pixel signals corresponding to the fourth, first, and second fields scanned and read out thereafter, only the luminance of the field image corresponding to the third field increases, Color unevenness occurs, which causes deterioration of image quality.

By the way, as a method of preventing such smear from being mixed into the pixel signal, first, after the exposure is completed, first, the vertical charge transfer paths l1 to
lm and the horizontal charge transfer path HCCD perform scanning readout, thereby discharging unnecessary charges causing smear to the outside,
Then, it is conceivable that smear is prevented from being mixed into all the fields and pixel signals by performing normal field scan reading.

That is, if explaining the technique based on the timing chart of FIG. 11, when exposure was performed at some point in time t _4, the first field shift operation after the end of exposure (i.e., field shift operation in the third field) masking by (period T _MS in the figure) that prohibits the transfer of the pixel signal from the photodiode to the vertical charge transfer path, a period of time (time t ₅ ~t ₆ for performing scanning reading of the third field-body in), to perform the operation of the scanning read to the vertical charge transfer paths and horizontal charge transfer path in a so-called pre-read state, without the pixel signals that are read out in this period (period from time t ₅ ~t ₆₎ waste I do. As a result, smear components in the vertical charge transfer path and the horizontal charge transfer path are removed. Then, the scanning reading of the fourth field starting from point t _6, by performing the first, second, the scanning reading of the third field in turn, to read all of the pixel signals of the four fields.

However, according to the scanning reading at the timing as shown in FIG. 11, the problem of smear is improved, but the influence of dark current cannot be ignored. That is, the dark current is a noise component that is constantly generated from the surface of the semiconductor substrate or the photodiode, and the pixel signal for which the field scan reading is performed first (the pixel signal corresponding to the fourth field in FIG. 11) is the photocurrent. Since the staying time in the diode is short, the influence of the dark current is small, and the last field scanning readout (the pixel signal corresponding to the third field in FIG. 11) is affected by the dark current since the staying time is long. That is, in the case of FIG. 11, the pixel signals corresponding to the fourth field, up to the time t ₁ ~t ₆
4V (a 4Q) dark current proportional to the period are mixed, the pixel signals corresponding to the first field, (a 4Q) proportional to the current to 4V period until time t ₂ ~t ₇ is mixed, the pixel signals corresponding to two fields, (to 4Q) dark current proportional to 4V period until time point t ₃ ~t ₉ is mixed, and the pixel signals corresponding to the third field, field at time t ₅ since the shift is inhibited, will be dark in proportion to 8V period until time point t ₀ ~t ₉ current (and 8Q) is mixed, apparently, dark current to the pixel signals corresponding to the third field The amount of contamination is greater than others. Then, when an image is reproduced based on the pixel signals thus read out, according to the difference in the amount of dark current mixed in each field,
This causes luminance and color unevenness, which leads to deterioration of image quality.

The present invention has been made in view of such a problem, and it is an object of the present invention to use a charge-coupled solid-state imaging device having a large number of pixels and perform imaging so as not to cause deterioration in image quality such as flicker in a reproduced image. It is an object of the present invention to provide an electronic still camera capable of performing the following.

[Means for solving the problem]

According to the present invention for achieving the above object, a plurality of photoelectric exchange elements corresponding to pixels are formed in a matrix in a row direction and a column direction, and are vertically formed along the photoelectric conversion elements arranged in each column. An electronic still camera that forms an electric charge transfer path and performs imaging by an interline transfer type charge-coupled solid-state imaging device formed by forming a horizontal electric charge transfer path connected to an end portion of these vertical electric charge transfer paths, K (where k is a natural number)
The pixel signals generated in the photoelectric conversion elements arranged in each field are divided into fields, and the pixel signals generated by the photoelectric conversion elements are sequentially scanned and read k times in each predetermined field scanning readout period, so that all the pixel signals are read out. During imaging, during the k × i (i is a natural number) number of field scan readout periods after exposure, scan readout is performed by the vertical charge transfer path and the horizontal charge transfer path with the field shift stopped. After k × i times of field scan reading, pixel signals generated in the photoelectric conversion elements arranged in each field are sequentially scanned and read at predetermined field scan read periods.

[Action]

According to the electronic still camera of the present invention having such a configuration, after exposure, idle reading is performed during a period obtained by performing a predetermined field scan by an integral multiple of the number of fields with respect to the reading period, and then the pixel signal is output to the field. Scanning and reading can eliminate smear components and can even out the effect of dark current on pixel signals in each field. Therefore, when an image is reproduced, flicker due to uneven brightness in each field can be prevented. Can be prevented.

It is to be noted that the number of fields k is set to 4 and the coefficient i is set to about 1, that is, dividing into four fields and setting the period of the idle reading to a period corresponding to the four field period can increase the imaging speed and increase the darkness. This is effective in that the absolute amount of the current with respect to the pixel signal can be reduced.

〔Example〕

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

First, the overall structure of an electronic still camera will be described with reference to 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 imaging. Devices, each of which is sequentially arranged along the optical axis.

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

Reference numeral 8 denotes an imaging device driving circuit, which is a driving signal for controlling the scanning readout timing of the charge-coupled solid-state imaging device 5, that is, a driving signal φ _V for driving a vertical charge transfer path, and driving a horizontal charge transfer path. Drive signal φ for
_H. A field shift synchronizing signal FS or the like for performing a field shift operation in each field scan reading is generated, and a synchronizing signal for synchronizing with the scan reading of the charge-coupled solid-state imaging device 5 is supplied to the exposure control circuit 7. I do.

Reference numeral 9 denotes a system controller for controlling the operation timing of the entire camera, and a shutter release button 9
When a synchronization signal synchronized with the pressing timing of 10 is received from the release operation detection circuit 10, the operations of the exposure control circuit 7 and the imaging device driving circuit 5 are operated in synchronization with the synchronization signal, or the charge-coupled solid-state imaging device 5 is operated. The timing for controlling the pixel signal read from the memory device and recording it on a recording medium is controlled.

Reference numeral 12 denotes a video signal processing circuit, which performs processing such as white balance adjustment and γ correction on a pixel signal read out from the charge-coupled solid-state imaging device 5 at a predetermined timing.
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.

Reference numeral 15 denotes a recording control circuit which controls the operations of the buffer circuit 13 and the recording device 14 according to a timing control signal from the system controller 9, and sends an image to a magnetic recording medium or a semiconductor memory of a memory card to the recording device 14. Record the signal.

Next, the structure of the charge-coupled solid-state imaging device 5 will be described with reference to FIG. This imaging device is a charge-coupled solid-state imaging device manufactured by semiconductor integrated circuit technology on a semiconductor substrate having a predetermined concentration of impurities. 80
Photodiodes A1, B1, A2, and B2 for a total of 800,000 pixels in column 0 are provided in a matrix, and 800 vertical charge transfer paths l1 are provided between photodiode groups arranged along the vertical direction X.
~ Lm is formed. And each vertical charge transfer path
On the upper surface of l1 to lm, the gate electrode VA1 and the 4nth photodiode are arranged on the 4n-3rd row (n is a natural number).
The gate electrode VB1 for the photodiode B1 arranged in the -2nd row, and the photodiode A2 arranged in the 4n-1st row
A gate electrode VA2, and a gate electrode VB2 for the photodiode B2 arranged in the fourth n-th row.
A gate electrode V2 is provided between the gate electrodes VA1 and VB1 and between the gate electrodes VA2 and VB2, and a gate electrode V4 is provided between the gate electrodes VB1 and VA2 and between the gate electrodes VB2 and VA1.

The gate electrodes on the same row are formed of a common polysilicon layer, and the gate electrode VA1 has driving signals φ _A1 ,
Drive signal φ ₂ for gate electrode V2, drive signal < _{B1 for} gate electrode VB1, drive signal φ _{4 for} gate electrode V4, drive signal φ _{A2 for} gate electrode VA2, drive signal φ for gate electrode VB2.
_B2 is applied, and these drive signals φ _A1 , φ ₂ , φ _B1 , φ ₄ , φ
_A2, phi _B2 potential level of the potential well corresponding to the applied voltage (hereinafter, referred to as transfer element a part of the potential well) and by generating a vertical charge transfer path l1~lm Potenshan barriers, to transfer signal charges It has become. The drive signal φ _V shown in FIG.
Shows these drive signals φ _A1 , φ ₂ , φ _B1 , φ ₄ , φ _A2 , φ _B2 as representatives.

A horizontal charge transfer path HCCD is formed at the end of the vertical charge transfer paths l1 to lm, and an output amplifier AMP is formed at the output end. Note that the horizontal charge transfer path HCCD transfers pixel signals in the horizontal direction in synchronization with the drive signals φ _H1 , φ _H2 , φ _H3 , φ _H4 of the four-phase drive system, and in synchronization with the transfer cycle, that is, the point-sequential timing. To read the pixel signal from the output amplifier (AMP). The drive signal φ _H shown in FIG. 1 is representative of these drive signals φ _H1 , φ _H2 , φ _H3 , φ _H4 .

Also, among the horizontal charge transfer paths l1 to lm, the horizontal charge transfer path HCC
The portion VV connected to D is the gate electrode V located next to it.
The transfer element formed below B2 and the horizontal charge transfer path H
A gate unit for controlling connection with the CCD, which is turned on or off in synchronization with a gate signal (not shown) at a predetermined timing.

Further, each photodiode A1, B1, A2, B2 and the corresponding gate electrode VA1, VB1, VA2, VB2 of the vertical charge transfer path.
, Transfer gates (represented by Tg in the figure) are formed between the transfer elements, and each of the transfer gates has a gate electrode VA1, VB1, VA2, A field shift operation is performed by applying a predetermined high voltage drive signal to VB2 in synchronization with the field shift synchronization signal FS to make the transfer gate conductive.

And these photodiodes A1, B1, A2, B2,
The transfer gate and impurity regions of a predetermined concentration formed around the vertical charge transfer paths l1 to lm and the horizontal charge transfer path HCCD serve as channel stops.

Further, it is defined that the photodiode A1 is arranged in the first field, the photodiode B1 is arranged in the second field, the photodiode A2 is arranged in the third field, and the photodiode B2 is arranged in the fourth field.

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

This electronic still camera reads out pixel signals generated in the photodiodes A1, B1, A2, and B2 formed in the charge-coupled solid-state imaging device 5 by sequentially performing field scan reading for each of the fields defined above. The period (1 V) in which the timing signal VD in FIG. 3 becomes “H” is each field scanning period. Then, in synchronization with the timing signal VD, the field shift in each field scanning readout is sequentially performed. still,
When FS1 in the figure becomes "H", the field shift is performed in the first field scanning readout period, and the other FS2, FS
Similarly, when FS4 becomes "H", each field shift is performed in the second, third, and fourth field scanning readout periods.

When exposed by pressing the shutter release button has been performed at some point t _4, the masking period T _MS next over a period of 4 times the period (4V) of the field scanning readout period (1V) from that point t _4, this period In _TMS , all field shift operations are prohibited. Thus, at time _{t 5, t 6 t 7,} t 8, field shift operation is not performed, the pixel signals as it is held in the photodiode A1, B1, A2, B2 corresponding to each field.

Then, a four scans read in a period l1~lm and horizontal charge transfer path HCCD to the vertical charge transfer paths is the time t ₅ ~t _10, the read signal is discarded all during this period. Therefore, unnecessary charges that cause smear are discarded.

Next, normal field scan reading is started from the time t _10. That is, first, at time t _10, and field shift to a predetermined transfer elements of the first field in a third corresponding to the field pixel signals q _A2 the vertical charge transfer paths l1~lm photodiode A2, then, Drive signals φ _A1 , φ ₂ , φ _B1 , φ ₄ , φ _A2 , φ _B2 , φ _H1 , φ for predetermined teaming
_By reading in synchronization with _H2 , _φH3 , _φH4 , time t
Read all ₁₀ ~t pixel signals q _A2 corresponding to the third field during _11.

Then, at time t _11, the pixel signals q _B2 the vertical charge transfer paths of the photodiode B2 corresponding to the fourth field l1
Lmlm to a predetermined transfer element, and then drive signals φ _A1 , φ ₂ , φ _B1 , φ ₄ ,
_{φ A2, φ B2, φ H1} , φ H2, φ H3, by reading in synchronism with phi _H4, reads all the pixel signals corresponding to the fourth field between the time point t ₁₁ ~t _12.

Then, at time t _9, the vertical charge transfer path to the pixel signal q _A1 photodiodes A1 corresponding to the first field l1~l
m to a predetermined transfer element, and then drive signals φ _A1 , φ ₂ , φ _B1 , φ ₄ ,
_{φ A2, φ B2, φ H1} , φ H2, φ H3, by reading in synchronism with phi _H4, reads all the pixel signals q _A1 corresponding to the first field between the point ₁₂ ~t _13.

Finally, at time t _13, the pixel signal q _B1 of the photodiodes B1 corresponding to the second field to a predetermined transfer elements off i Rudoshifuto of vertical charge transfer paths L1～lm, then, the drive signal of a predetermined Tamingu φ _{A1, φ 2, φ B1,} φ 4,
_{φ A2, φ B2, φ H1} , φ H2, φ H3, by reading in synchronism with phi _H4, reads all the pixel signals q _B1 corresponding to the second field between the time point t ₁₃ ~t _14.

Note that the read pixel signals are finally recorded in a predetermined medium recording in the recording device 14.

Thus, the pixel signals in the 4 field scanning reading period (4V) after exposure is performed scanning reading was held in the photodiode corresponding to each field, pixels read at a period of time t ₁₀ ~t ₁₁ the signal q _A2, will be dark current effects over 8V period up to the time t ₀ ~t ₁₀ to the photodiode A2 (and 8I) is mixed, the pixel signals read out in a period of time t ₁₁ ~t ₁₂ the q _B2, will be dark current affects the photodiode B2 over 8V period up to the time t ₁ ~t ₁₁ (and 8I) is mixed pixel signal q to be read in a period of time t ₁₂ ~t ₁₃ the _A1, will be dark current affects the photo die auto A1 over 8V period up to the time t ₂ ~t ₁₂ (and 8I) is mixed, and, pixels read at a period of time t ₁₃ ~t ₁₄ Faith The q _B1, the time t ₃ ~t ₁₃
The dark current (referred to as 8I) affecting the photo die auto B1 is mixed over the period of 8 V up to 8 V. As described above, since a uniform dark current is mixed in the pixel signals corresponding to all the fields, flicker due to a luminance difference between the fields does not occur when an image is reproduced. Since smear component is between t ₁₀ from the time t ₅ is discarded, it does not occur flicker caused by smear.

Next, in response to the increase in the number of pixels in order to improve the vertical resolution, each field scan readout is performed as shown in FIGS.
This is performed at the timing shown in FIG. FIG. 4 is a first field scanning readout timing for reading out a pixel signal from the photodiode A1 corresponding to the first field, and FIG. 5 is a timing chart for reading out a pixel signal from the photodiode B1 corresponding to the second field. FIG. 6 shows a third field for reading pixel signals from the photodiode A2 corresponding to the third field.
FIG. 7 shows the fourth field scanning read timing for reading out the pixel signal from the photodiode B2 corresponding to the fourth field. FIG. 8 shows the timing in the period τ in FIGS. 4 to 7. The timing of the field shift operation is shown in an enlarged manner.
Note that the periods T _FA1 , T _FB1 , T _FA2 , and T _FB2 in each figure correspond to the respective field scan reading periods (1 V), and are each set to 1/60 second. Further, the periods T _fs1 , T _fs2 , T _fs3 and T _{fs4 correspond} to F
S1, FS2, FS3, and FS4 correspond to a field shift period during which the signal is at "H", and a period _Tout is a period of scanning and reading that continues after the field shift operation.

First, based on FIG. 4, when the operation of the first field scan reading, as shown in field shift period T _fs1, driving signals _{φ A1, φ B1, φ A2} , φ B2, φ 2,
phi ₄ logical value level is changed, the driving signals phi _A1 at time S1 in figure by a sufficiently high voltage to the conductive state transformer gate Tg, photodiodes A1 corresponding to the first field The pixel signal is field-shifted to the transfer element below the gate electrode VA1. When this field shift is completed, the operation for the next period τ (between the time points S2 and S3) is performed, whereby the vertical charge transfer paths l1 to lm
Only one line overall pixel signals q _A1 in transferred to the horizontal charge transfer path HCCD side. That is, each drive signal in the period τ is composed of a rectangular signal for two cycles, and as shown in FIG. 8, the drive signal φ _A1 is changed from “H” → “L” → “H” → “L” →
Whereas changes to "H", the driving signal phi ₂ is set to the same waveform delayed by a predetermined phase Δ than the drive signal phi
_B1 is set to further drive signal phi ₂ from only the phase Δ delayed same waveform, the driving signal phi ₄ is further driving signal phi _B1 from the phase Δ
Drive signal φ _A2 is further set to the same waveform delayed by a phase Δ from drive signal φ ₄ ,
The drive signal φ _B2 is set to have the same waveform that is further delayed from the drive signal φ _A2 by the phase Δ. Then transfer the driving signals of such timing when driving the vertical charge transfer path L1～lm, most horizontal charge transfer path predetermined transfer elements of the pixel signal q _A1 of one line in the vicinity of the horizontal charge transfer path HCCD to HCCD Is done.

Next, during the period from time S3 to S4, the horizontal charge transfer path H
The CCD drives the pixel signals q for one row in synchronization with the drive signals φ _{H1 to} φ _H4.
A1 is horizontally transferred, and each pixel signal is read out in time series.

Then, by repeating the same operation as the time S2~S4 described above until reading all remaining pixel signals q _A1,
The scanning and reading of all the pixel signals corresponding to the first field are completed. In FIG. 4, it is assumed that the reading is completed at time S5.

Next, the photodiode B1 corresponding to the second field
Will be described with reference to FIG. As shown in the field shift period T _fs2 , the logic values of the drive signals φ _A1 , φ _B1 , φ _A2 , φ _B2 , φ ₂ , φ ₄ change, and at time S6 in the figure, the drive signal φ _B1 by a sufficiently high voltage to the gate Tg conductive, field shifts the pixel signal q _B1 of the photodiodes B1 corresponding to the second field to the transfer element under the gate electrode VB1. When this field shift is completed, next, the same charge transfer operation as in the period _Tout is performed in FIG. 4, and at time S7 in FIG. 4, all pixel signals from the photodiode B1 corresponding to the second field are output. q _B1
Is read.

Next, the photodiode A2 corresponding to the third field
Will be described with reference to FIG. As shown in the field shift period T _fs3 , the logic levels of the drive signals φ _A1 , φ _B1 , φ _A2 , φ _B2 , φ ₂ , φ ₄ change, and at time S8 in the figure, the drive signal φ _A2 by a high enough voltage to the gate Tg conductive, field shifts the pixel signals q _A2 of photodiode A2 corresponding to the third field to the transfer element under the gate electrode VA2. When the field shift is completed, the same operation for charge transfer as in the period _{Tout in} FIG. 4 is performed, and all pixel signals from the photodiode A2 corresponding to the third field at time S9 in FIG. q _{Read A2} .

Next, the photodiode B2 corresponding to the fourth field
Will be described with reference to FIG. As illustrated in the field shift period T _fs4 , the logical values of the drive signals φ _A1 , φ _B1 , φ _A2 , φ _B2 , φ ₂ , φ ₄ change, and at time S10 in the figure, the drive signal φ _B2 by a sufficiently high voltage to the gate Tg conductive, field shifts the pixel signals q _B2 photodiodes B2 corresponding to the fourth field to the transfer element under the gate electrode VB2. When this field shift is completed, next, the same charge transfer operation as during the period _{Tout in} FIG. 4 is performed, and at time S11 in FIG. 4, all pixel signals from the photodiode B2 corresponding to the fourth field are output.
q _{Read B2} .

Since the respective field shift operations shown in FIGS. 4 to 7 are stopped during the masking period as described above, the pixel signals remain held in the photodiodes and are shown in the period _Tout . The idle read is performed by the transfer operation.

Thus, the driving signal phi _A1 six-phase vertical charge transfer path _{l1~lm, φ B1, φ A2,} φ B2, φ 2, when is driven by the phi _4,
Since only a small number of types of drive signals are required, effects such as simplification of the configuration of the imaging device drive circuit 8 and simplification of wiring can be obtained. By the way, if it is assumed that the concept of the four-phase driving method, which has been conventionally performed once, is applied to the imaging device of the present embodiment in which the vertical resolution is doubled, the eight-phase driving method is applied. Eight types of drive signals are required. On the other hand, in this embodiment, since the six-phase driving method is used, the above-described effects can be obtained.

In this embodiment, the case where the idle reading is performed during the period corresponding to the four-field scanning period after the exposure has been described.
The pixel signal may be read after performing the idle reading during a period corresponding to a field scanning period of an integral multiple of (for example, 8, 12, 16, etc.). That is, even if the idle reading is performed during a period corresponding to a field scanning period that is an integral multiple of four, the smear component can be removed, and at the same time, the effect of the dark current on the pixel signal corresponding to each field is made uniform. Can be.

Further, in this embodiment, the scanning readout for removing flicker when the array of photodiodes corresponding to pixels is divided into four fields has been described. However, in general, the field is divided into k (k is a natural number) fields. Then, if the pixel signal is read out after performing the idle reading in a period corresponding to k × i (i is a natural number) times the field scanning reading period, smear can be removed and dark current can be made uniform. And flicker can be prevented.

〔The invention's effect〕

As described above, according to the present invention, all the pixel signals are divided into k fields of the photoelectric conversion elements corresponding to the pixels, and the pixel signals of the photoelectric conversion elements corresponding to the respective fields are read out k times by field scanning. In an electronic still camera to which a read-out charge-coupled solid-state imaging device is applied, an idle reading operation is performed on a vertical charge transfer path and a horizontal charge transfer path without performing a field shift during a scan period of k × i fields after exposure. And all the pixel signals are read out by sequentially performing field scan reading from the next field scan after the completion of the idle reading operation, so that smear components are eliminated during the idle reading period, and The effect of dark current on pixel signals corresponding to the field of the image can be made uniform, and the occurrence of flicker in reproduced images can be prevented. It can be. Further, the present invention is extremely effective in realizing an electronic still camera to which a charge-coupled solid-state imaging device in which the number of pixels is increased to improve the vertical resolution is applied.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of one embodiment of the present invention, FIG. 2 is a configuration diagram showing a configuration of a charge-coupled solid-state imaging device applied to one embodiment, and FIG. FIG. 4 is a timing chart showing a first field scan readout timing in one embodiment; FIG. 5 is a timing chart showing a second field scan readout timing in one embodiment; 6 is a timing chart showing a third field scanning readout timing in one embodiment, FIG. 7 is a timing chart showing a fourth field scanning readout timing in one embodiment, and FIG. 8 is a period in FIGS. 4 to 7. Timing chart showing enlarged timing of τ. Fig. 9 is applied to a conventional electronic still camera. And FIG. 10 is a timing chart for explaining a problem of smear contamination in a conventional electronic still camera, and FIG. 11 is a timing chart for explaining a problem of smear contamination in a conventional electronic still camera. 6 is a timing chart for explaining the problem of dark current mixing in FIG. Reference numerals in the drawing: 1; imaging lens 2; aperture mechanism 3; beam splitter 4; shutter mechanism 5; charge-coupled solid-state imaging device 6; light receiving element 7; exposure control circuit 8; imaging device driving circuit 9; Shutter release button 11; release operation detection circuit 12; video signal processing circuit 13; buffer circuit 14; recording device 15; recording control circuit A1, B1, A2, B2; photodiode VA1, VB1, VA2, VB2; gate electrode l1 to lm; Vertical charge transfer path HCCD; Horizontal charge transfer path AMP; Output amplifier

Claims (1)

(57) [Claims] 1. A plurality of photoelectric exchange elements corresponding to pixels are formed in a matrix in a row direction and a column direction, and a vertical charge transfer path is formed along the photoelectric conversion elements arranged in each column. In an electronic still camera in which an image is captured by an interline transfer type charge-coupled solid-state imaging device formed by forming a horizontal charge transfer path connected to an end portion of the vertical charge transfer path, the photoelectric conversion element group is k (k Is a natural number) field, and the pixel signals generated in the photoelectric conversion elements arranged in each field are sequentially scanned and read k times in each predetermined field scanning and reading period so that all the pixel signals are read. In addition to the control, during the imaging, the field shift is stopped during k × i (i is a natural number) field scanning readout periods after exposure. In the stopped state, scanning readout is performed by the vertical charge transfer path and the horizontal charge transfer path, and after k × i field scan readouts, pixel signals generated in photoelectric conversion elements arranged in each field are scanned in a predetermined field. An electronic still camera wherein all pixel signals are read out by sequentially performing scanning readout in each readout period.