JP2000232613A - Still picture pickup device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a still picture with a wide dynamic range without the use of an exclusive CCD image sensor or without combination of plural CCD image sensors and a complicated optical system. SOLUTION: When a change in a signal SUB resulting from discharging electric charges of a photo cell to a substrate is lost, the charge being stored in the photo cell is gradually increased. After the lapse of a prescribed time (before a change in a succeeding vertical synchronizing signal V-SYNC), a signal SG2 resulting from transferring charges stored on an even number rows of the photo cells to a vertical CCD is changed to transfer the charge stored on the even number rows of the photo cells to the vertical CCD (i). Then odd number rows of the photo cells successively store charges until a change in a succeeding vertical synchronizing signal V-SYNC and the even number rows of the photo cells having stored no charge store again charges. Thus, a different electronic shutter speed from the rows of the photo cells can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a still image pickup apparatus for picking up a still image using a CCD image sensor as a solid-state image pickup device and a method therefor.

[0002]

2. Description of the Related Art Since a CCD image sensor used in a still image pickup device has a narrow dynamic range, whiteout or blackout occurs in an image pickup scene having a large luminance difference.

In order to obtain a still image with a wide dynamic range, a conventional CCD image sensor has conventionally been used (see Japanese Patent Application Laid-Open Nos.
Japanese Patent Application Laid-Open No. 322142), a plurality of images are taken by changing the exposure amount of the CCD image sensor, and the taken images are combined, or images with different exposure amounts are taken simultaneously using a plurality of CCDs and the corresponding optical system. And then combine the captured images.

[0004]

However, a dedicated CCD is required.
The conventional technology using an image sensor has a disadvantage that the manufacturing cost is high. Further, the conventional technique of performing image capturing a plurality of times requires a device for fixing a still image capturing device such as a tripod, and has a problem that it is impossible to capture a moving object. Further, in the conventional technology using an optical system corresponding to a plurality of CCD image sensors, the cost increases,
There is a problem that the configuration becomes complicated.

An object of the present invention is to obtain a wide dynamic range still image without using a dedicated CCD image sensor or using a plurality of CCD image sensors in combination with a complicated optical system. Is to do.

Another object of the present invention is to obtain a still image with a high vertical resolution when the luminance difference in the screen is small, and to obtain an image without whiteout and blackout when the luminance difference in the screen is large. Is to be able to do it.

[0007]

According to a first aspect of the present invention, there is provided a still image pickup apparatus for picking up a still image using a CCD image sensor as a solid-state image pickup device.
A CCD image sensor capable of simultaneously capturing a still image at a different electronic shutter speed depending on the row of the photocells by changing the timing of starting the accumulation of charges in the photocells of the image sensor for each row of the photocells. A still image pickup device comprising a driving unit.

Therefore, a still image with a wide dynamic range can be obtained by simultaneously capturing still images at different electronic shutter speeds depending on the row of photocells and synthesizing the obtained images.

According to a second aspect of the present invention, in the still image capturing apparatus according to the first aspect, there is provided an evaluation means for evaluating a luminance difference in a screen captured by the CCD image sensor,
CCD image sensor driving means, when the evaluation means is evaluated that the brightness difference is greater than a predetermined degree,
A still image is simultaneously captured at different electronic shutter speeds depending on the row of photocells.

Therefore, when the luminance difference in the screen is small, a still image with a high vertical resolution can be obtained, and when the luminance difference in the screen is large, an image without whiteout and blackout can be obtained.

According to a third aspect of the present invention, in the still image pickup apparatus according to the second aspect, the CCD image sensor driving means changes the electronic shutter speed for each row of the photocells according to the evaluation of the luminance difference by the evaluation means. Is characterized by changing the ratio.

Therefore, by changing the ratio of the different electronic shutter speeds depending on the row of photocells, it is possible to optimize an image for synthesizing images having different electronic shutter speeds depending on the row of photocells for each shooting scene.

According to a fourth aspect of the present invention, in the still image pickup method for picking up a still image using a CCD image sensor as a solid-state image pickup device, the timing for starting the accumulation of electric charges in the photocell of the CCD image sensor is determined. A still image capturing method characterized in that it is possible to simultaneously capture a still image at a different electronic shutter speed depending on the row of the photo cells by changing the row for each photo cell.

Therefore, a still image with a wide dynamic range can be obtained by simultaneously capturing still images at different electronic shutter speeds depending on the row of photocells and synthesizing the obtained images.

[0015]

FIG. 1 is a block diagram of a still image pickup apparatus according to an embodiment of the present invention. The still image pickup apparatus 1 includes a lens 2, a mechanical shutter 3, an aperture 4 for adjusting the amount of light passing therethrough, a CCD image sensor 5 for converting light into an electric signal, and a CCD image sensor 5
CD that removes noise components contained in a signal and amplifies signal components
S circuit, A / D converter 6 for converting a shaped and amplified analog signal into a digital signal, and image processing circuit 7 for performing image processing such as pixel interpolation, gain correction for each color, γ correction, and aperture correction A DCT / coder 8 for compressing and decompressing image data, a memory 9 for storing image data, an LCD 10 for displaying image data to be shot at the time of photographing and reproducing and displaying the image data stored in the memory 9, not shown. A lens drive circuit 11 that changes the focus position of an image formed on the CCD image sensor 5 by moving the lens 2 with a motor or the like, a shutter drive circuit 12 that opens and closes a mechanical shutter, and a diaphragm (not shown) Aperture drive circuit 13 for changing the aperture, and light incident on CCD image sensor 5 from the output of image processing circuit 7 Automatic exposure control circuit 14 for controlling the
An automatic focus detection circuit 15 for detecting a focus position of an image to be captured from an output of the image processing circuit 7;
A white balance control circuit 16 for controlling a white balance of an image picked up from the output of the CCD image sensor 5, the CCD image sensor 5, the CDS
A timing generator 17 for generating a drive pulse for the circuit and the A / D converter 6 and a microcomputer 18 for controlling the operation of each section are provided.

The operation of recording an image by the still image pickup apparatus 1 having the above configuration is as follows. When a shutter button (not shown) is half-pressed after turning on a power button (not shown) to set the image recording mode, the microcomputer 18 opens the mechanical shutter 3 via the shutter drive circuit 12. Then, it passes through the lens 2 and the aperture 4
The image formed on the CCD image sensor 5 by adjusting the light amount is converted into a voltage signal corresponding to the light amount for each pixel by the CCD image sensor 5 and sequentially output at regular intervals.
The arrangement of the lens 2, the mechanical shutter 3, and the diaphragm 4 is shown in FIG.
And the mechanical shutter 3 and / or the diaphragm 4 may be arranged in the space between the plurality of lenses 2. Further, the aperture 4 may also serve as the mechanical shutter 3. CCD image sensor 5
The image data output from is converted to digital signal image data by removing noise components and amplifying the signal by the CDS circuit and A / D converter 6. Here, when the CCD image sensor 5 is a color CCD, the image data has color data of a color filter formed on a light receiving element of the CCD such as R, G, B for each pixel.

Next, the image data is subjected to pixel interpolation by the image processing circuit 7 (when the color filter of the CCD image sensor 5 is other than R, G, B, conversion to R, G, B is also performed). R, G, and B signals for each color. Then, image processing such as gain correction, γ correction, and aperture correction for each color is performed, and further converted into a luminance signal and a color difference signal and output to the LCD 10. The LCD 10 displays a monitor image recorded by the still image capturing device 1. Then, this monitor image is updated at regular intervals.

The image processing circuit 7 includes an automatic exposure control circuit 14, an automatic focus detection circuit 15
The image data obtained by converting the R, G, and B image data of each pixel into a luminance signal is output to the white balance control circuit 16 as the R, G, and B image data of each pixel. Note that these circuits 14, 15, and 16 determine conditions for capturing an image to be actually captured by pressing the shutter button.

The automatic exposure control circuit 14 includes an image processing circuit 7
The exposure amount of the CCD image sensor 5 is calculated for a preset range in the image data input from the CPU, and the result is output to the microcomputer 18. The microcomputer 18 changes the gain of the CDS circuit and the amplifier of the A / D converter 6 based on the calculation result so that the exposure amount of the CCD image sensor 5 becomes appropriate, operates the aperture driving circuit 13, and sets the timing. The electronic shutter speed of the CCD image sensor 5 is varied via the generator 17.

The automatic focus detection circuit 15 includes an image processing circuit 7
The amount of high-frequency components contained in the image data is calculated for a preset range in the image data input from.
This operation is performed by moving the lens 2 by the lens driving circuit 11 and C
This is performed at a plurality of positions while changing the focus position of the image formed on the CD image sensor 5 from infinity to a close distance (or from the close distance to infinity). Then, the focus position of the image formed on the CCD image sensor 5 is output to the microcomputer 18 where the calculation result becomes maximum. The microcomputer 18 operates the lens drive circuit 11 to move the lens 2 so as to be at the input focus position.

The white balance control circuit 16 adjusts the color deviation of the input image from the distribution of the R, G, and B colors of the input image data in a predetermined range in the image data input from the image processing circuit 7. Image processing circuit 7 so that
Change the gain of the gain correction for each color.

After the photographing conditions are determined by the automatic exposure control circuit 14, the automatic focus detection circuit 15, and the white balance control circuit 16 (usually, the photographer is informed by turning on an LED (not shown)), a shutter button (not shown) is further activated. When pressed, a still image is captured. When capturing a still image, CC
Imaging is performed at a different electronic shutter speed for each row of photocells of the D image sensor 5.

When the photographing of the still image is completed, the microcomputer 18 closes the mechanical shutter 3 via the shutter drive circuit 12 so that no extra light enters the CCD image sensor 5. The image formed on the CCD image sensor 5 is converted into an electric signal and sequentially output at regular time intervals. The image processing circuit 7 interpolates the pixel by a method different from that of the monitor image, and converts the R, G, B colors for each pixel. Of a wide dynamic range. Then, image processing such as gain correction, γ correction, and aperture correction for each color is performed, and further converted into a luminance signal and a color difference signal.
The data is compressed by the T / coder 8 and stored in the memory 9.

Next, the CCD image sensor 5 will be described.

The configuration of the CCD image sensor 5 for capturing a black-and-white image allows the timing of reading charges from the photocells to the vertical CCDs to be performed independently for odd rows and even rows. Charge can be directly discharged from the substrate to the substrate (vertical overflow drain structure), the vertical CCD operates at high speed, and the vertical CCD is moved from its end (horizontal CCD side or opposite side of horizontal CCD).
It is necessary to use an IT-CCD or a FIT-CCD capable of discharging unnecessary charges from the inside (high-speed sweep mode).

An example of the configuration will be described with reference to FIG. FIG. 2A is an overall circuit diagram of the CCD image sensor 5, in which 20 is a photocell, 21 is a vertical CCD, 22 is a horizontal CCD, 23 is an output amplifier, and 24 is a substrate. Also,
φV1 to φV4 are signals for driving the vertical CCD 21; SG1 is a signal for transferring the charge accumulated in the odd-numbered row of photocells 20 to the vertical CCD 21; SG2 is a signal for accumulating the charge accumulated in the even-numbered row of photocells 20. Vertical CCD 21
ΦH1 and φH2 are horizontal CCD2
2 is a signal for driving the second signal. SUB discharges the electric charge accumulated in the photocell 20 by changing the voltage with the substrate voltage of the substrate 24.

FIG. 2B shows the vertical CCD 2 shown in FIG.
1 is an enlarged view of a portion φ1 to φV4, SG1, SG2.
FIG. Reference numeral 25 denotes a transfer gate for transferring the charge stored in the photocell 20 to the vertical CCD 21.

In FIG. 2, charges generated and accumulated in the photocell 20 according to the intensity of light incident from the outside are transferred to the vertical CCD 21. Then, the data is transferred from the vertical CCD 21 to the horizontal CCD 22 for each row. Horizontal CCD 22
Is transferred to the output amplifier 23 for each pixel, converted into a voltage proportional to the amount of electric charge input to the output amplifier 23, and output to the outside.

Next, how charges are transferred from the vertical CCD 21 in the CCD image sensor 5 will be described with reference to FIGS. In FIG. 3 and subsequent figures, white circles and black circles represent electric charges.

FIG. 3 shows a state in which the power of the still image pickup apparatus 1 is turned on until a shutter button (not shown) is pressed to start the pickup of a still image, or a still image is picked up and its signal is output to the outside. After that, the vertical CCD 2 is operated until the shutter button is pressed again to capture a still image (normal mode).
1 shows the operation of the charge transfer. Also, FIG.
FIG. 6 is a timing chart of operation timings of signals and the like in a normal mode and a still image mode to be described later, wherein a to f in FIG. 5 correspond to (a) to (f) in FIG. I have.

First, when the vertical synchronizing signal V-SYNC changes, SG1 changes immediately and the electric charge (shown by a black circle) stored in the odd-numbered row of the photocell 20 is changed to the vertical CCD2.
1 (FIG. 3A).

Photocell 2 transferred to vertical CCD 21
The charges in the odd-numbered rows of 0 are stored in the horizontal CCD 22 and the output amplifier 23.
Are output to the outside one pixel at a time. Each time a charge for one row is output to the outside as a voltage signal and a horizontal synchronization signal H-SYNC (not shown) changes, φV1 to φV
4 so that charges on the vertical CCD 21 are transferred from the vertical CCD 21 to the horizontal CCD 22 one row at a time.
Each time, two rows of the photocells 20 are driven. During this time, charges are accumulated in the photocell 20 in accordance with the intensity of the incident light, but each time the horizontal synchronization signal H-SYNC changes, S
While the UB is changing, the charge accumulated every time the SUB changes is discharged to the substrate 24 (FIG. 3B).

When the change of SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 3).
(C)).

When V-SYNC changes again after outputting the charge for one screen as a voltage signal to the outside, this time, S
The electric charge (indicated by a white circle) stored in the even-numbered row of the photocell 20 is transferred to the vertical CCD 21 by changing G2 (FIG. 3D).

Photocell 2 transferred to vertical CCD 21
The charges in the even-numbered rows of 0 are stored in the horizontal CCD 22 and the output amplifier 23.
Are output to the outside one pixel at a time. Each time a charge for one row is output to the outside as a voltage signal and a horizontal synchronization signal H-SYNC (not shown) changes, φV1 to φV
4 so that charges on the vertical CCD 21 are transferred from the vertical CCD 21 to the horizontal CCD 22 one row at a time.
Each time, two rows of the photocells 20 are driven. During this time, charges are accumulated in the photocell 20 in accordance with the intensity of the incident light, but each time the horizontal synchronization signal H-SYNC changes, S
While the UB is changing, the charge accumulated every time the SUB changes is discharged to the substrate 24 (FIG. 3E).

Then, when the change of SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 3).
(F)).

Thereafter, the above-described processing shown in FIGS. 3A to 3F is repeated until a shutter button (not shown) is pressed.

FIG. 4 shows the vertical C from the time when the shutter button (not shown) is pressed to start capturing a still image until the signal of the captured still image is output to the outside (still image mode).
This shows the operation of the charge transfer of the CD 21. Further, g to n in FIG. 5 correspond to the respective time points shown in (g) to (n) in FIG.

In the first change of the vertical synchronizing signal V-SYNC after the shutter button is pressed, SG1 and SG2 do not change. Therefore, the electric charges accumulated in the photocell 20 are not transferred to the vertical CCD 21 but Each time the horizontal synchronizing signal H-SYNC (not shown) changes, it is discharged to the substrate 24 while the SUB changes (FIG. 4 (g)).

When the change of SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 4).
(H)).

After a lapse of a predetermined time (before the next change of the vertical synchronizing signal V-SYNC), the electric charge accumulated in the even-numbered rows of the photocell 20 due to the change of SG2 is
(FIG. 4 (i)).

Thereafter, the next vertical synchronizing signal V-SYNC
, The odd-numbered rows of the photocells 20 continue to accumulate charges, and the even-numbered rows of the photocells 20 accumulate charges again from 0. As described above, the change of SG2 shown in FIG. 4 (i) makes it possible to simultaneously capture a still image at a different electronic shutter speed depending on the row of the photocell 20, and implements the CCD image sensor driving means of the present invention. I have. In addition, the vertical CCD 21 overflows the charges transferred from the even-numbered rows of the photocells 20 during the operation time described with reference to FIG. 4 (i) from the end of the horizontal CCD 22 or the end opposite thereto during high-speed operation. It is discharged to the substrate through the drain (FIG. 4 (j)). It is not necessary to discharge the electric charges in this operation immediately after the change of SG2, but it is performed so that the discharge is completed by the second change of the vertical synchronization signal V-SYNC after the shutter button (not shown) is pressed. There is a need.

Then, after the shutter button is pressed, 2
With the vertical change of the vertical synchronizing signal V-SYNC, the mechanical shutter 3 is closed at the same time, and the accumulation of electric charges is completed. Immediately after that, SG1 changes and the electric charges accumulated in the odd-numbered rows of the photocell 20 are reduced. The data is transferred to the vertical CCD 21 (FIG. 4 (k)).

Photocell 2 transferred to vertical CCD 21
The charges in the odd-numbered rows of 0 are stored in the horizontal CCD 22 and the output amplifier 23.
Are output to the outside one pixel at a time. And 1
Each time a row of charges is output to the outside as a voltage signal and the horizontal synchronization signal H-SYNC (not shown) changes, φV1
.About..phi.V4 drives two rows of photocells 20 at a time so that the charges on the vertical CCD 21 are transferred from the vertical CCD 21 to the horizontal CCD 22 one row at a time. During this time, the charges in the even-numbered rows of the photocell 20 are held as they are (FIG. 4 (l)).

Then, after the shutter button is pressed, 3
Immediately after the change of the vertical synchronizing signal V-SYNC, S
As G2 changes, the electric charges accumulated in the even-numbered rows of the photocell 20 are transferred to the vertical CCD 21 (FIG. 4 (m)).

Photocell 2 transferred to vertical CCD 21
The charge in the even-numbered row of 1 is stored in the horizontal CCD 22 and the output amplifier 23.
Are output to the outside one pixel at a time. And 1
Each time a row of charges is output to the outside as a voltage signal and the horizontal synchronization signal H-SYNC (not shown) changes, φV1
.About..phi.V4 drives two rows of photocells 20 at a time so that the charges on the vertical CCD 21 are transferred one row at a time from the vertical CCD 21 to the horizontal CCD 22 (FIG. 4).
(N)).

Then, after the shutter button is pressed,
The mechanical shutter 3 is opened at the same time as the change of the vertical synchronizing signal V-SYNC for the third time, the mode shifts from the still image mode to the normal mode, and the accumulation of charges in the photocell 20 is started again.

Here, in the odd-numbered rows of the photocells 20 in the still image mode, charges are accumulated for the sum of the period h and the period j shown in FIG. In contrast, the photocell 20
In the even-numbered rows, the charges accumulated in the period h are transferred to the vertical CCD 21 in the period i, and only the charges in the period j are accumulated. Therefore, the charge accumulation time is shorter than that in the odd-numbered rows of the photocell 20. Become. Therefore, by performing post-processing on the read output to generate R, G, and B signals for each pixel,
The dynamic range can be expanded according to the ratio of the charge accumulation time. Note that SG in the period i shown in FIG.
When 2 is not changed, a still image as in the related art can be captured. In the period of i, SG2 instead of SG2
When the CCD image sensor 5 is similarly driven while changing the value of 1, the charge amount stored in the odd and even rows of the photocell 20 can be reversed.

Next, the CCD image sensor 5 for picking up a color image will be described. C that captures color images
The CD image sensor 5 can independently read the charge from the photocell to the vertical CCD every four rows, and can directly discharge the charge from the photocell to the substrate (vertical). Type overflow drain structure), operate the vertical CCD at a high speed, and start the vertical CCD from the end (horizontal CCD side or the opposite side of the horizontal CCD).
It is an IT-CCD or a FIT-CCD capable of discharging unnecessary charges from the inside (high-speed sweep mode).

FIG. 6A is an overall circuit diagram of the CCD image sensor 5, in which reference numeral 20 denotes a photocell, and reference numeral 21 denotes a vertical CC.
D and 22 are horizontal CCDs, 23 is an output amplifier, and 24 is a substrate. ΦV1 to φV4 are signals for driving the vertical CCD 21. SG1 has 4n + 1 rows (n = 0, 1,
2,...) Are stored in the vertical CC
SG2 is a signal to be transferred to D21, and SG2 is 4n + 2 rows (n
= 0, 1, 2,...) Are transferred to the vertical CCD 21. SG3 is 4n.
.. Are signals for transferring the charges accumulated in the photocells 20 in the +3 rows (n = 0, 1, 2,...) To the vertical CCD 21.
G4 is a signal for transferring charges accumulated in the photocells 20 of 4n + 4 rows (n = 0, 1, 2,...) To the vertical CCD 21. φH1 and φH2 are signals for driving the horizontal CCD 22. SUB discharges the electric charge accumulated in the photocell 20 by changing the voltage with the substrate voltage of the substrate 24.

FIG. 6B shows the vertical CCD 2 shown in FIG.
1 is an enlarged view of a portion φ1 to φV4, SG1 to SG4.
FIG. Reference numeral 25 denotes a transfer gate for transferring the charge stored in the photocell 20 to the vertical CCD 21.

In FIG. 6, charges generated and accumulated according to the intensity of light incident on the photocell 20 from the outside are stored in a vertical CCD.
21. Then, the data is transferred from the vertical CCD 21 to the horizontal CCD 22 for each row, and transferred from the horizontal CCD 22 to the output amplifier 23 for each pixel.
Is converted into a voltage proportional to the input charge amount and output to the outside.

Next, how charges are transferred from the vertical CCD 21 in the CCD image sensor 5 will be described with reference to FIGS.

FIG. 7 shows a state in which the power of the still image pickup apparatus 1 is turned on until a shutter button (not shown) is depressed to start picking up a still image, or a still image is picked up and its signal is output to the outside. After that, the vertical CCD 2 is operated until the shutter button is pressed again to capture a still image (normal mode).
1 shows the operation of the charge transfer. Also, FIG.
FIG. 10 is a timing chart of operation timings of signals and the like in a normal mode and a still image mode to be described later, wherein A to F in FIG. 9 correspond to (A) to (F) in FIG. I have.

First, when the vertical synchronizing signal V-SYNC changes, immediately after that, SG1 and SG3 change, and the electric charges accumulated in the 4n + 1th row and 4n + 3th row of the photocell 20 are transferred to the vertical CCD 21 (FIG. 7). (A)).

Photocell 2 transferred to vertical CCD 21
0 of the 4n + 1th row and 4n + 3th row are charged in the horizontal CCD 2
2. Output to the outside one pixel at a time via the output amplifier 23. Each time a charge of one row is output to the outside as a voltage signal and a horizontal synchronizing signal H-SYNC (not shown) changes, φV1 to φV4 change the charge on the vertical CCD 21 one row at a time from the vertical CCD 21. The two rows of the photocells 20 are driven at one time so that they are transferred to the horizontal CCD 22. During this time, the photocell 20 accumulates electric charges in accordance with the intensity of the incident light. However, while the SUB changes each time the horizontal synchronization signal H-SYNC (not shown) changes, the charge accumulates every time the SUB changes. The discharged charges are discharged to the substrate 24 (FIG. 7B).

Then, when the change of SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 7).
(C)).

When V-SYNC changes again after the output of the charges for one screen as a voltage signal to the outside, the signal S
G2 and SG4 change to 4n + 2 rows of the photocell 20,
The electric charges (shown by white circles) accumulated in the 4n + 4 rows are transferred to the vertical CCD 21 (FIG. 7D).

Photocell 2 transferred to vertical CCD 21
The charges in the even-numbered rows of 0 are stored in the horizontal CCD 22 and the output amplifier 23.
Are output to the outside one pixel at a time. Each time a charge for one row is output to the outside as a voltage signal and a horizontal synchronization signal H-SYNC (not shown) changes, φV1 to φV
4 so that charges on the vertical CCD 21 are transferred from the vertical CCD 21 to the horizontal CCD 22 one row at a time.
Each time, two rows of the photocells 20 are driven. During this time, charges are accumulated in the photocell 20 in accordance with the intensity of the incident light, but each time the horizontal synchronization signal H-SYNC changes, S
While the UB is changing, the charge accumulated every time the SUB changes is discharged to the substrate 24 (FIG. 7E).

When the change in SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 7).
(F)).

Thereafter, the above-described processing shown in FIGS. 7A to 7F is repeated until a shutter button (not shown) is pressed.

FIG. 8 shows the vertical C during the period from when a shutter button (not shown) is pressed to start capturing a still image to when a signal of the captured still image is output to the outside (still image mode).
This shows the operation of the charge transfer of the CD 21. Also, G to N in FIG. 9 correspond to the time points (G) to (N) in FIG. 8, respectively.

In the first change of the vertical synchronizing signal V-SYNC after the shutter button is pressed, SG1, SG2, SG2
Since SG3 and SG4 do not change, photocell 2
The electric charge accumulated in 0 is not transferred to the vertical CCD 21, but is discharged to the substrate 24 while the SUB changes each time the horizontal synchronization signal H-SYNC (not shown) changes (FIG. 8 (G)). .

When the change of SUB stops, the charge stored in the photocell 20 gradually increases (FIG. 8).
(H)).

After a lapse of a predetermined time (before the next change of the vertical synchronizing signal V-SYNC), SG3 and SG4 change and the electric charges accumulated in the 4n + 3 rows and 4n + 4 rows of the photocell 20 are stored in the vertical CCD 21. Transferred (Fig. 8
(I)).

Thereafter, the next vertical synchronizing signal V-SYNC
4n + 1, 4n + 2 rows of the photocell 20 continue to accumulate charges until the change, and the 4n + 3 rows,
The 4n + 4 rows again store charge from zero. in this way,
The change of SG3 and SG4 shown in FIG. 8 (I) makes it possible to simultaneously capture a still image at a different electronic shutter speed depending on the row of the photocell 20, and implements the CCD image sensor driving means of the present invention. Also, vertical CC
D21 is a high-speed operation, during the operation time described with reference to FIG. 8I, the 4n + 3 rows and 4n +
The electric charges transferred from the four rows are discharged to the substrate from the end of the horizontal CCD 22 or the end opposite thereto via the overflow drain (FIG. 8 (J)). It is not necessary to discharge the electric charges in this operation immediately after the change of SG2, but it is performed so that the discharge is completed by the second change of the vertical synchronization signal V-SYNC after the shutter button (not shown) is pressed. There is a need.

Then, after the shutter button is pressed, 2
At the time of the change of the vertical synchronization signal V-SYNC at the same time, the mechanical shutter 3 is closed at the same time, and the accumulation of the electric charge is completed. Immediately after that, SG1 changes and the electric charge accumulated in the row 4n + 1 of the photocell 20 becomes Vertical CCD 21
(K1 in FIG. 8). And immediately vertical C
Insert the CD 21 in the photocell 2 in the direction opposite to the horizontal CCD 22.
After driving one row of 0, SG2 changes and photocell 2
The electric charges accumulated in the 4n + 2 rows of 0 are transferred to the vertical CCD 21 (FIG. 8 (K2)).

Photocell 2 transferred to vertical CCD 21
0 of the 4n + 1th row and 4n + 2th row are charged in the horizontal CCD 2
2. Output to the outside one pixel at a time via output amplifier 23. Each time a charge of one row is output to the outside as a voltage signal and a horizontal synchronizing signal H-SYNC (not shown) changes, φV1 to φV4 change the charge on the vertical CCD 21 one row at a time from the vertical CCD 21. Horizontal CCD2
2, so that two rows of the photocells 20 are driven at one time. During this time, 4n + 3 rows, 4n
The charges in the +4 rows are held as they are (FIG. 8 (L)).

Then, after the shutter button is pressed,
Immediately after the change of the vertical synchronizing signal V-SYNC, S
G3 changes, and the charges accumulated in the 4n + 3 rows of the photocell 20 are transferred to the vertical CCD 21 (FIG. 8 (M
1)). Then, the vertical CCD 21 is immediately replaced with the horizontal CCD 2
After driving one row of the photocell 20 in the direction opposite to the direction 2, SG4 changes, and the charges accumulated in the 4n + 4 rows of the photocell 20 are transferred to the vertical CCD 21 (FIG. 8 (M
2)).

Photocell 2 transferred to vertical CCD 21
1 of the 4n + 3 rows and the 4n + 4 rows are charged in the horizontal CCD 2
2. Output to the outside one pixel at a time via output amplifier 23. Each time a charge of one row is output to the outside as a voltage signal and a horizontal synchronizing signal H-SYNC (not shown) changes, φV1 to φV4 change the charge on the vertical CCD 21 one row at a time from the vertical CCD 21. Horizontal CCD2
Then, two rows of the photocells 20 are driven at a time so as to be transferred to (2) in FIG. 8 (N).

Then, the mechanical shutter 3 is opened at the same time as the fourth change of the vertical synchronizing signal V-SYNC after the shutter button is pressed, the mode shifts from the still image mode to the normal mode, and the electric charge is stored in the photocell 20 again. To start.

Here, in the still image mode, the 4n + 1-th row and the 4n + 2-th row of the photocell 20 have the period H shown in FIG.
The charge is accumulated for the sum of the periods. On the contrary,
In the 4n + 3 rows and 4n + 4 rows of the photocell 20, the charges accumulated in the H period are transferred to the vertical CCD 21 in the I period, and only the charges in the J period are accumulated. The charge accumulation time is shorter than 4n + 2 rows. Therefore, the image processing circuit 7
A memory having a capacity equal to or more than half the number of pixels of the CD image sensor 5 is provided, and 4n + 1 rows and 4n read during the period L
By generating R, G, and B signals in addition to the signals for each pixel in the +2 rows, or by providing a memory having a capacity equal to or larger than the number of pixels of the CCD image sensor 5 in the image processing circuit 7, The output signal for each pixel of the 4n + 1th and 4n + 2 rows and the signal for each pixel of the 4n + 3th and 4n + 4th rows read out during the period N are temporarily stored, and then R,
By creating the G and B signals, the dynamic range can be expanded according to the ratio of the charge accumulation time. When SG3 and SG4 are not changed during the period I shown in FIG. 9, a still image as in the related art can be captured. Also, in the period of I, not SG3 and SG4, but SG
1, SG2 is changed, and the CCD image sensor 5 is similarly driven, so that the 4n + 1 row, 4n + 2
It is possible to reverse the charge amounts stored in the row and the 4n + 3 rows and the 4n + 4 rows.

Further, in the above description, 4n
+1 row and 4n + 2 row signals simultaneously, and 4n + 3
Although the signals of the row and the 4n + 4 row are read at the same time, even if the 4n + 1 row, 4n + 3 row, 4n + 2 row and 4n + 4 row are read simultaneously at the same time as in the normal mode, an image having a similarly expanded dynamic range can be obtained. . FIG. 14 is a timing chart of the operation timing of each signal in that case. The timing chart of FIG. 14 differs from the timing chart of FIG. 9 in a period from after the period J to before the next period A.

The operation during this period is as follows. SG1 and SG3 change during the period K 'immediately after the second change of the vertical synchronizing signal V-SYNC after the shutter button is pressed after the period J as in the normal mode period A, and the photocell 20
Of the charges accumulated in the 4n + 1 and 4n + 3 rows of
After the transfer to D21, the charges transferred to the vertical CCDs 22 in the period L 'in the same manner as in the normal mode period C are transferred to the horizontal CCD line by line.
The data is output to the outside one pixel at a time via the CD 22 and the output amplifier 23.

Then, 3 after the shutter button is pressed.
SG2 and SG4 change in the period M 'immediately after the change of the vertical synchronization signal V-SYNC in the same manner as in the period D in the normal mode, and the electric charges accumulated in the 4n + 2 and 4n + 4 rows of the photocell 20 are transferred to the vertical CCD 21. After the transfer to
In the same manner as in the normal mode period F, the charges transferred to the vertical CCD 21 are output to the outside one pixel at a time via the vertical CCD 22 and the output amplifier 23 one row at a time. The state of charge transfer from K ′ to N ′ is as shown in FIG.

In FIG. 6, the signals φV1 to φV4 for driving the vertical CCD 21 and the signals SG1 to SG4 for transferring the electric charge stored in the photocell 20 to the vertical CCD 21 are separated, but actually the signals φV1 to φV4 Is often used as a signal to be transferred to the vertical CCD 21 as a ternary logic. In that case, vertical CC from photocell 20
The charge is transferred from the photocell 20 to the vertical CCD 21 at the H level of the drive signal also serving as the transfer signal to D21,
The electric charge on the vertical CCD 21 is transferred at the M and L levels of the drive signal also serving as the transfer signal from the photocell 20 to the vertical CCD 21 and at the H and L levels of the drive signal not serving as the transfer signal.
Note that the M level of the drive signal also serving as the transfer signal from the photocell 20 to the vertical CCD 21 corresponds to the H level of the drive signal which is not so, and the L level of the drive signal which also serves as the transfer signal is the L level of the drive signal which is not so. Corresponding to FIG. 10 shows the configuration of the CCD image sensor 5 in this case.

Next, a description will be given, with reference to the flow chart of FIG. 11, of a process of switching between normal imaging performed based on a luminance difference in a screen and imaging performed at a different shutter speed depending on the row of the photocells 20 described above. I do.

First, imaging conditions such as an aperture and a shutter speed are initialized (step S1), and imaging is performed (step S2). Then, as shown in FIG. 12, the screen is divided into a plurality of blocks (the example of FIG. 12 is divided into three vertically and three horizontally), and an AE evaluation value is calculated for each block. Then, the maximum and minimum values of the AE evaluation value for each block are calculated (step S4).

Next, the maximum value of the AE evaluation value for each block is compared with a preset reference value V1 (step S5). If the maximum value of the AE evaluation value for each block is smaller than V1 (N in step S5), the imaging mode is set to the normal mode in which the row of the photocell 20 has the same shutter speed (step S6). A per block
When the maximum value of the E evaluation value is equal to or more than the reference value V1 (Y in step S5), the minimum value of the AE evaluation value for each block is calculated as follows:
A comparison is made with a preset reference value V2 that is smaller than the reference value V1 (step S7). And AE for each block
When the minimum value of the evaluation value is larger than the reference value V2 (N in step S7), the imaging mode is set to the normal mode (step S6). When the minimum value of the AE evaluation value for each block is equal to or smaller than the reference value V2 (Y in step S7), it is determined that the luminance difference in the screen is large, and therefore, imaging is performed at a different shutter speed for each row of the photocell 20. (Wide DR mode) (step S8).

The evaluation means of the present invention is implemented by steps S5 and S7. Further, by switching between the normal mode and the wide DR mode based on the luminance difference in the screen, the CCD image sensor driving means of the present invention is realized. As a result, a still image with a high vertical resolution can be obtained when the luminance difference in the screen is small, and an image without whiteout and blackout can be obtained when the luminance difference in the screen is large.

After steps S6 and S8, the AE program corresponding to the imaging mode is executed, and a predetermined calculation is performed from the distribution of the AE evaluation value for each block, and the AE evaluation value in each mode is calculated. The deviation from the target value is calculated (step S9), and the imaging conditions such as the aperture and the shutter speed are changed so as to eliminate the deviation from the calculated AE evaluation value (step S10).

The processes of steps S2 to S10 described above are repeatedly executed except when a shutter button (not shown) is pressed to capture a still image.

In the processing shown in the flowchart, the switching of the shutter speed ratio for each field may be switched based on the luminance difference in the screen. That is, when the minimum value of the AE evaluation value for each block is equal to or less than the reference value V2 in step S7, the reference values V3 and V4 are smaller than V2 and the reference values V4 and V4 are smaller than V3.
By setting a plurality of reference values to be compared with the minimum value of the AE evaluation value, such as a smaller reference value V5, to increase the number of cases, and to change the ratio of the shutter speed different for each field in each case. I just need.

Thus, the CCD image sensor driving means of the present invention can be implemented. By changing the ratio of the different electronic shutter speeds depending on the rows of the photocells 20, different electronic shutter speeds depending on the rows of the photocells 20 can be used. Can be optimized for each shooting scene.

[0085]

According to the first aspect of the present invention, a still image with a wide dynamic range is obtained by simultaneously capturing still images at different electronic shutter speeds depending on the row of photocells and synthesizing the obtained images. Therefore, a wide dynamic range still image can be obtained without using a dedicated CCD image sensor or using a plurality of CCD image sensors in combination with a complicated optical system.

According to a second aspect of the present invention, in the still image pickup apparatus according to the first aspect, when the luminance difference in the screen is small, a still image with a high vertical resolution is obtained, and the luminance difference in the screen is large. In some cases, an image without overexposure and underexposure can be obtained.

According to a third aspect of the present invention, in the still image pickup apparatus according to the second aspect, by changing the ratio of the different electronic shutter speeds depending on the row of the photocells, the different electronic shutter speeds depending on the rows of the photocells. The image at the time of combining the images can be optimized for each shooting scene.

According to the fourth aspect of the present invention, a still image with a wide dynamic range can be obtained by simultaneously capturing still images at different electronic shutter speeds depending on the row of photocells and synthesizing the obtained images. Because it is possible, exclusive C
A still image with a wide dynamic range can be obtained without using a CD image sensor or using a combination of a plurality of CCD image sensors and a complicated optical system.

[Brief description of the drawings]

FIG. 1 is a block diagram of a still image pickup apparatus according to an embodiment of the present invention.

FIGS. 2A and 2B are an overall circuit diagram of a CCD image sensor of the still image pickup device, and an enlarged view of a vertical CCD portion thereof.

FIG. 3 is a diagram showing the charge transfer operation of the vertical CCD step by step.

FIG. 4 is a diagram showing the charge transfer operation of the vertical CCD step by step.

FIG. 5 is a timing chart showing signals for driving the CCD image sensor, accumulated charges of the CCD image sensor, and the like.

FIG. 6A is a circuit diagram of the entire CCD image sensor of the still image pickup device, and FIG. 6B is an enlarged view of a vertical CCD portion thereof.

FIG. 7 is a diagram showing the charge transfer operation of the vertical CCD step by step.

FIG. 8 is a diagram showing the charge transfer operation of the vertical CCD step by step.

FIG. 9 is a timing chart showing signals for driving the CCD image sensor, accumulated charges of the CCD image sensor, and the like.

FIG. 10 is an enlarged view of a vertical CCD part showing another example of the CCD image sensor of the still image pickup device.

FIG. 11 is a timing chart showing the operation of the still image pickup device.

FIG. 12 is a plan view of a screen for explaining the operation of the still image pickup device.

FIG. 13 is a diagram showing the charge transfer operation of the vertical CCD step by step.

FIG. 14 is a timing chart showing signals for driving the CCD image sensor, electric charges stored in the CCD image sensor, and the like.

[Explanation of symbols]

 Reference Signs List 1 still image pickup device 5 CCD image sensor 20 photocell

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5C022 AA13 AB00 AB03 AB12 AB17 AB32 AB52 AC01 AC42 AC69 5C024 AA01 CA03 CA11 CA15 CA17 DA04 FA01 FA11 GA11 GA16 GA17 GA26 GA41 GA48 GA50 HA08 HA11 HA14 HA17 HA18 HA24 HA27 JA04 JA31

Claims (4)

[Claims] 1. A still image pickup apparatus for picking up a still image using a CCD image sensor as a solid-state image pickup device, wherein a timing for starting to accumulate electric charges in a photocell of the CCD image sensor is changed for each row of the photocell. A still image pickup device comprising: a CCD image sensor driving means for simultaneously picking up a still image at a different electronic shutter speed depending on the row of the photocells. 2. An evaluation means for evaluating a luminance difference in a screen picked up by the CCD image sensor, wherein the CCD image sensor driving means is adapted to execute the evaluation when the evaluation means judges that the luminance difference is larger than a predetermined value. ,
2. A still image is simultaneously picked up at different electronic shutter speeds depending on the row of photocells.
3. The still image pickup device according to claim 1. 3. The still image pickup apparatus according to claim 2, wherein the CCD image sensor driving means changes the ratio of the different electronic shutter speeds depending on the row of the photocell in accordance with the evaluation of the luminance difference by the evaluation means. . 4. A still image pickup method for picking up a still image using a CCD image sensor as a solid-state image pickup device, wherein a timing to start accumulating charges in a photocell of the CCD image sensor is changed for each row of the photocell. Thus, it is possible to simultaneously capture a still image at a different electronic shutter speed depending on the row of the photocells.