JPS6336676A - Image pickup system by change coupled device - Google Patents

Abstract

PURPOSE:To attain the frame pickup with high accuracy and exposure control by moving once a stored charge of a photodetection section to a transfer section, returning the charge of both fields to the photodetection section shutting the light and reading the charge by one field each. CONSTITUTION:In depressing a release button, a shutter is opened, the electric charge of photoelectric conversion section 1 ODD, 1 EVEN are swept-out, and signal charge is stored in the photoelectric conversion section. Each electric charge of the photoelectric conversion section 1 ODD, 1 EVEN is moved to the transfer section 3 after a prescribed time and then the shutter is closed. After the shutter is closed completely, all the stored charge of the transfer section 3 is returned to the photoelectric conversion section 1 and the electric charge of the conversion section 1 ODD belonging to one field in the photoelectric conversion section. After the end of the read, the signal charge left in the section 1 EVEN is moved again to the transfer section 3 for read.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a solid-state imaging system using a COD (charge-coupled device), and particularly to a signal charge accumulation and transfer system for exposure control.

Background of the Invention - As an imaging means in video cameras and still video cameras, solid-state imaging is used to accumulate photoelectric charges for each pixel through +:electronic light conversion, and to read out the accumulated charges to obtain image values. What solid-state imaging method do you get? It is becoming popular.

In this solid-state imaging system, a mechanical shutter, an electronic shutter, a strobe light, and an aperture adjustment are used to control the exposure gNj of the light-receiving part of the solid-state imaging device.

When the mechanical shutter opens, it starts exposing the light-receiving part of the solid-state image sensor, and when it closes, it starts exposing the photoelectric charge of the solid-state image sensor. The movement of the signal charge in this solid-state image sensor to the COD for transfer, which performs exposure control by completing the M product, is performed every 1760 seconds in synchronization with the vertical synchronization signal, but during the period when the shutter is open. By prohibiting this movement, it is possible to cope with long exposures.

On the other hand, with an electronic shutter, the mechanical shutter of the optical system is left open for a longer time than the exposure time, or the solid-state image sensor is exposed to light without a mechanical shutter.
The exposure time is controlled by controlling the potential of the solid-state image sensor. Specifically, first, the potential of the overflow control cable (OFCG) of the COD is lowered, and all charges generated by light from the optical system at the light receiving section are drained to the overflow drain (OFD) to reduce the charges i and ta. At the start of exposure, the potential of the overflow control gate is raised to start accumulation, and after a set time when the accumulation of signal charges reaches a maximum level, the charges of the light receiving section are transferred to the transfer CCD, and the exposure is completed.

Furthermore, in the method using a strobe and aperture, the aperture is set according to the light amount of the strobe and the distance to the subject, or the exposure amount is adjusted by using an auto strobe that matches the aperture of the camera.

Problems to be Solved by the Invention - With conventional mechanical shutters, the latitude of solid-state image sensors is much narrower than that of silver halide film, so the shutter precision of silver halide film cameras does not provide sufficient exposure time. There was a problem that accuracy could not be obtained.

In addition, with the electronic shutter method, only one field's worth of signals is transferred to the transfer COD at a time, and the signals of other fields remain in the light receiving section, resulting in overexposure, and as a result, only field photography is possible. There was a problem that I couldn't do it.

In addition, with the method using a strobe and aperture, even if you know the amount of light from the strobe and the distance to the subject, the amount of light incident on the light receiving section changes depending on the reflectance of the subject, making it impossible to accurately set the optimal aperture. Even if it were possible, there was a problem in that it took time to set up. Furthermore, auto strobes required high precision, something that IIN's auto strobes were unable to meet.

Therefore, according to Japanese Patent Application No. 81-134360, in an electronic shutter system, the accumulated charges in the light receiving section are moved once to the transfer section, one field's worth of charges are returned to the light receiving section, and the remaining one field's worth of charges in the transfer section is read out. After that, an invention was made in which the charges in the light receiving section were transferred to a transfer section and read out. However, according to this method, since the transfer efficiency from the light receiving section to the transfer section is not 10 oz, flicker occurs every reyield due to differences in the readout procedure.

The purpose of the present invention is 1! Easy! 1. To provide a solid-state imaging system capable of highly accurate exposure control and precise frame photography while providing a light shielding means in an optical system.

A means to solve a problem - One aspect of the present invention is to achieve the above-mentioned objects.

A light receiving section having a photoelectric conversion section for each pixel, an overflow electrode that can control discharge of accumulated charges in the light receiving section, a light-shielded transfer section that accumulates, reads out and transfers accumulated charges in the light receiving section for each pixel, and an optical system. and a light blocking means capable of blocking light input from the light receiving section to the light receiving section, and after releasing the light blocking by the light blocking means, discharging the accumulated charge by the overflow electrode is stopped, and after a set time from this point, each of the light receiving section The accumulated charges are transferred to the transfer section, and after the light-receiving section is shielded from light by the light-shielding means, the M accumulation front of the light-receiving section is discharged by controlling the overflow electrode, and after this discharge is completed, all of the accumulated charges in the transfer section are is returned to the light-receiving section, the charge of the pixel subjected to one G field is read out from the light-receiving section, and after this reading is completed, the charge corresponding to the other one field remaining in the light-receiving section is moved to the transfer section to read out the charge. This is what I do.

One embodiment - Figure 4 (A) shows a four-phase driving force type C0D ('i'fi charge coupling element coupling element plan view, and its cross-sectional view along the line A-A' is shown in Figure 4 CB). The accumulated charges in the photoelectric conversion parts l ODD and I EVEN of each pixel, which become light receiving parts, are transferred to the light-shielded transfer part 3 by the voltage control of the transfer gate 2 on one side, and are provided on the other side. By controlling the voltage of the overflow control gate 4, the overflow is swept to the overflow drain 5, and the transfer electrodes 61 to 64 are swept out.
The signal charges transferred to the transfer section 3 are read out by controlling the voltages of phases φ1 to φ4 applied to the transfer section 3. The formation of voltage wells and the load transfer to the transfer electrodes 61 to 64 are as shown in FIG.

In the figure, the shaded area is shown as the amount of charge.

In a charge-coupled device having such a structure, exposure control according to this embodiment is performed together with light shielding control by a shutter (or iris) provided in the optical system. The control procedure is to open the shank when the release button is pressed, sweep out the ``heavy load'' of the Ku'ichi conversion unit 1000 and IVEN, and
After this, the photoelectric conversion section starts accumulating signal charges, and after a set time ("A light time), the photoelectric conversion section 1 [conversion section l ODD]
, l EVEN are transferred to the transfer unit 3, and then the shutter is closed. After the shutter is completely closed, all of the accumulated charges in the transfer section 3 are transferred to the photoelectric conversion section 10DD, l
EVEN, and the charge of the converter 10DD belonging to one field among the optical converters is read out. After this reading is completed, the signal charges remaining in the photoelectric conversion section I-- EVEN are moved to II-- and the transfer section 3 and read out. Exposure control to the north will be explained in detail below.

FIG. 1 shows a time chart according to this embodiment, in which the shutter is opened by operating the release button (time 1+
) At the same time, signals φ1 to φ4 are applied to the transfer electrodes 61 to 64! j
Then, all the signal charges in the transfer section 3 are read out to make it empty ('charge zero) (period T+). As shown in FIG. 2(a), charges are generated in the photoelectric conversion unit 1000 and IEVEN during this period T1 due to the opening of the shutter, but by keeping the level of the overflow control gate 4 low, all charges are transferred to the overflow drain 5 side. to prevent accumulation.

At the point in time (t2) when the transfer unit 3 has finished sweeping out, the state shown in FIG.
), by increasing the level of the overflow control gate 4, the photoelectric conversion unit 101][], I
Charge accumulation at EVEN begins, that is, exposure begins.

When a set time (exposure time) has elapsed from the start of L accumulation (time t3), the photoelectric conversion unit 1000 and IEVEN
The accumulated charges are transferred to the transfer section 3, respectively. This situation is shown in Fig. 3 (a) and (b), and the charge is transferred to the photoelectric conversion unit I EVEN.
and from the state ff accumulated in 10DD (Fig. 3g),
The transfer electrodes 62, 64 and tJ are moved to the transfer section 3 by lowering the level of the transfer gate 2 (FIG. 3b). Next, the transfer electrode 62 is moved to the transfer section 3 (FIG. 3b).

64 and the transfer gate 2 to separate the transfer section 3 and the photoelectric conversion sections 10DD and IEVEN (FIG. 3c), and also lowered the level of the overflow control gate 4 to separate the photoelectric conversion sections 10DD and IEVEN.
EN's '-' charge is prevented from accumulating (Fig. 3d). In this state, wait until the shutter is completely closed.

When the shutter is completely closed (61ta in Figure 1)
, increase the level of overflow control Kate 4 (
In FIG. 3e), the level of the transfer electrodes 64 and 62 is lowered, and the level of the transfer gate 2 is lowered. to this,
Therefore, the accumulated charges of the transfer electrodes 64 and 62) are both spread to the photoelectric conversion parts I EVEN and I ODD (FIG. 3f). Next, the levels of the transfer electrodes 62 and 64 are raised and all the charges under the transfer electrodes are transferred to the optical layer conversion section I EVEN.
and 1000 (Fig. 3g), and further increase the level of the transfer gate 2 (Fig. 3h). As a result, the charges accumulated in the photoelectric conversion parts I EVEN and 10DD due to exposure are returned to their respective parts. At this time, since the shutter is closed, the photoelectric conversion part I E
There is no charge variation in both VEN and lOD[l, and the charge variation due to dark current is the same amount of variation in both converters.

Next, by lowering the level of the transfer gate 2 and the level of the transfer electrode 64, the photoelectric conversion is10
The charge on DD is transferred to the transfer section 3 (FIG. 3i), and the level of the transfer gate 2 is raised (FIG. 3J).

In this state, the charge under the transfer electrode 64, that is, the photoelectric conversion part +
The accumulated charges of 0DD are read out in synchronization with the vertical synchronizing signal V5YNC by the aforementioned signals φ1 to φ4 (period T2 in FIG. 1). After this reading is completed (time t5), the level of the transfer electrode 82 and the level of the transfer gate 2 are lowered to move the accumulated charge of the photoelectric conversion unit I EVEN to the transfer unit 3,
By raising the level of , and subsequently raising the level of the transfer electrode 62, the charges in the transfer section 3 are read out by the signals φ1 to φ4 (period T3 in FIG. 1).

Here, the accumulated charges in the photoelectric conversion units 10[]OD and IEVEN are both transferred to and from the transfer unit in the same process, and there is no difference in charge fluctuation between the two fields due to the existence of transfer efficiency due to this movement. Can be read.

Effects of the Invention - As is clear from the above description, the present invention, in an electronic shutter system, temporarily moves the accumulated charges in the light receiving section to the transfer section, and once returns the charges for both fields to the light receiving section, which is shielded from light. Because the charge is read out for each field, it is possible to take frame shots while using a single shutter for highly accurate control of exposure time, and the charge transfer efficiency for both fields is the same, eliminating flicker. This has the effect of making it possible to obtain high-quality images without -.

[Brief explanation of drawings]

FIG. 1 is a time chart of exposure control in the present invention, FIG. 2 is a diagram showing the control mode of COD up to the shutter opening in FIG. 1, and FIG.
4(A) is a plan view of the main part of the COD, FIG. 4(B) is a sectional view taken along line A-A' in FIG. 4(A), and FIG. FIG. 2 is a diagram showing transfer electrodes and charge states of a transfer section. 10DII, IEVEN,...photoelectric conversion section, 2
...Transfer gate, 3...Transfer section, 4.
... O8 flow control gate, 5... Overflow train, (31, 62, 63, 6a... Transfer electrode. Patent applicant Konishi Roku Photo Industry Co., Ltd. Figure 1 Figure 2 (b) Trunk "Figure 4 (A) Figure 4 (B)

Claims (1)

[Claims] 1) a light receiving section having a photoelectric conversion section for each pixel, an overflow electrode that can control discharge of accumulated charges in the light receiving section, and a light-shielded transfer section that accumulates, reads out, and transfers accumulated charges in the light receiving section for each pixel; and a light shielding means capable of blocking light input from the optical system to the light receiving section, and after the light shielding by the light blocking means is released, discharging of the accumulated charge by the overflow electrode is stopped and the light receiving section is operated after a set time from this point. transfer each of the accumulated charges of the light receiving section to the transfer section, and after the light blocking means blocks the light receiving section, the accumulated charges of the light receiving section are discharged by controlling the overflow electrode, and after this discharging is completed, all of the accumulated charges of the transfer section are transferred. return to the light receiving section,
The electric charge is characterized in that the charge of a pixel belonging to one field is read out from the light receiving section, and after this reading is completed, the charge corresponding to one field of the other remaining in the light receiving section is moved to the transfer section to read out the charge. Imaging method using coupling elements.