JPH0767159B2 - Solid-state electronic imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state electronic image pickup device with a so-called electronic shutter, which is used in, for example, an electronic still camera, a video camera and the like.

Generally, in a camera, adjustment of the shutter speed and the diaphragm is indispensable in order to obtain a subject image with an appropriate exposure charge. Photometric information is required for these adjustments,
Conventionally, the serial video signal obtained from the image sensor is directly used to obtain photometric information, or one or several photo
A method has been adopted in which a photometric element such as a diode is provided and its output signal is used as photometric information. In the former method, since the video signal flows serially, it is difficult to extract and process only the desired information necessary for control and adjustment, and read the video signal for at least one field. It takes 1/60 second to get out. Further, the latter method has a problem that only photometric information only at a certain place in the field of view or information on the average value of the incident light amount can be obtained. A photometric element for so-called multi-photometry, which measures the amount of incident light in each of a plurality of cases in the field of view, has also been recently developed.
It is expensive and the pattern of photometric locations (division pattern of the light receiving area) is limited.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid-state electronic image pickup device capable of performing photometry without necessarily requiring a photometry element, capable of multi-photometry, and further completing photometry relatively quickly. To do.

The present invention is a photoelectric conversion element that is two-dimensionally arrayed on a light receiving region of a substrate and performs photoelectric conversion to store signal charges according to the amount of received light, and a vertical transfer unit that vertically transfers the signal charges stored in the photoelectric conversion element. In a solid-state electronic image pickup device comprising a transfer section and a horizontal transfer section for horizontally transferring the signal charge input from the vertical transfer section, the signal charge accumulated in the photoelectric conversion element in preliminary imaging is transferred to the light receiving region. Mutually isolated sweep electrodes for sweeping to the substrate for each of the divided regions, a scanning circuit for sequentially scanning the sweep electrodes for sweeping to the substrate for each of the divided regions, and It is characterized by comprising a photometric circuit for photometrically measuring each of the divided regions based on the signal charges swept onto the substrate by the scanning by the scanning circuit.

In the solid-state electronic image pickup device according to the present invention, when the voltage applied to the photoelectric conversion element is lowered to clear the signal charge accumulated in the MOS capacitor type photoelectric conversion element, the signal charge is swept out to the substrate side. We are using. Photometry using the solid-state electronic image pickup device according to the present invention is performed through preliminary photographing. The signal charge accumulated in the preliminary imaging is swept to the substrate side by applying the clear signal, and the swept signal charge amount is measured. Then, the shutter speed and the aperture value are determined based on the measured values.

Since photometry is performed using a solid-state electronic image pickup device for picking up a subject image, accurate photometry is possible and appropriate exposure amount adjustment can be performed. In addition, since the signal charges accumulated in the preliminary photographing are swept out by lowering the voltage applied to the MOS capacitor type photoelectric conversion element, rapid photometry can be performed.

According to the present invention, photometry is performed using the solid-state electronic image pickup device for picking up a subject image, and therefore it is not always necessary to provide a photodetector or other light receiving element dedicated to photometry. However, the present invention does not exclude the provision of a light receiving element dedicated to photometry. It is also possible to determine an approximate exposure amount based on the photometric signal from the photometric light receiving element, and then determine the optimum exposure amount according to the present invention.

Further, according to the present invention, the light receiving region of the solid-state electronic image pickup device is divided into a plurality of regions, which are insulated from each other, and the signal charges accumulated by the preliminary photographing are swept out for each divided region. The amount of light is obtained separately (multi-metering). As a result, it becomes possible to perform exposure control suitable for a desired divided area. Particularly, according to the present invention, the signal charge is accumulated in the photoelectric conversion element during the preliminary photographing. A photometric value is obtained for each of the divided areas by scanning the sweep electrode with the accumulated signal charges by the scanning circuit.

The signal charges are accumulated in the photoelectric conversion element, swept onto the substrate, and photometrically measured, so that they are hardly affected by ambient light.

Description of Embodiments FIG. 1 shows an embodiment in which a solid-state electronic image pickup device according to the present invention is applied to an electronic still camera. Figure 2 is II of Figure 1.
The enlarged sectional view is shown on the line II.

The solid-state electronic image pickup device is provided with a plurality of light receiving section rows 2 in which a MOS capacitor type for accumulating signal charges according to the amount of incident light and photoelectric conversion elements are arranged in a row, and is arranged adjacent to each light receiving section row 2. It is composed of a large number of vertical transfer sections 4, a horizontal transfer section 10 connected to the output terminals of all the vertical transfer sections 4, and a charge amplification circuit 11 connected to the output side of the horizontal transfer sections 10.

A charge sweep line 13 is connected to a substrate 30 provided with the light receiving section array 2, the vertical transfer section 4, and the like. The charge sweep line 13 is connected to the A / D conversion circuit 15, and the output side of the A / D conversion circuit 15 is connected to the CPU 16. The CPU 16 outputs a scanning pulse timing signal to control the charge sweeping of this solid-state electronic image pickup device, and at the same time takes in a signal output from the A / D conversion circuit 15 and based on this signal, a shutter speed control signal, Outputs the aperture control signal. A transparent electrode 1 to be described later of the light receiving section array 2 is connected to a scanning circuit 18 via a switching element 17, and a predetermined voltage E is applied. Scanning circuit
18 inputs the scanning pulse timing signal from the CPU 16 and outputs the scanning pulse according to the signal.

Referring to FIG. 2, the photoelectric conversion element of the light-receiving section array 2 has a MOS capacitor structure and is formed by forming an insulating film 31 and a transparent electrode 1 on a substrate 30. In the vertical transfer unit 4, there is a transfer electrode 9 for transferring signal charges in the insulating film 31, and a four-phase transfer signal φ _V1 is transferred to this electrode 9.
Signal charge is transferred by applying ~ φ _V4 . The electrode 9 also has a function of a gate electrode and is transferred with a transfer gate pulse to transfer the signal charge accumulated in the light receiving section array 2 to the vertical transfer section 4.

There is a light-shielding film 3 on the upper surface of the transfer electrode 9, which is shown by hatching in FIG. Also in the light-receiving section array 2, the light-shielding film 3a is provided for each pixel (one photoelectric conversion element).
Are separated by. That is, under the light shielding film 3a (a boundary surface between the insulating film 31 and the substrate 30), although not shown, a channel stopper is formed so that signal charges of vertically adjacent pixels do not coexist. There is.

Returning to FIG. 2, a channel stopper 6 and an overflow drain 7 are formed at the boundary between the substrate 30 and the insulating film 31 to prevent excess charges from overflowing to the adjacent vertical transfer section 4 and causing blooming. Has been done. Further, an overflow gate 8 for controlling the overflow drain 7 is formed.

In the vertical transfer section 4, an N layer 5 is formed for transferring charges inside the substrate 30, not at the boundary surface between the substrate 30 and the insulating film 31. This structure is called a buried channel device (BCCD).

Referring again to FIG. 1, in such a solid-state image pickup device, the transparent electrode 1 is divided into four regions on the entire substrate 30 and insulated from each other. A scanning circuit 18 can separately control the signal charge clearing (sweeping) operation via the switching element 17 for each of the four divided regions.

Next, the transfer operation of the signal charge accumulated by the light applied to the light receiving section array 2 to the vertical transfer section 4 and the signal charge are transferred to the substrate 30.
The operation of sweeping to the side will be described.

By applying a predetermined voltage E to the transparent electrode 1, a potential well 32 is formed on the upper surface of the substrate 30 as shown by the chain line in FIG. When the light receiving section 2 is irradiated with light, electric charges are accumulated in the potential well 32 according to the irradiation light amount. In order to transfer the accumulated signal charges to the transfer section 4, first, a transfer gate pulse is applied to the transfer electrode 9. As a result, a potential well (not shown) deeper than the potential well 32 generated under the light receiving section 2 is generated under the vertical transfer section 4. And the potential well under the light receiving part 2
The signal charge accumulated in 32 is transferred to the potential well generated below the vertical transfer unit 4. The signal charges transferred to the vertical transfer unit 4 are transferred to the horizontal transfer unit 10 in the vertical transfer unit 4 by transfer signals φ _{V1 to} φ _V4 .

The signal charge accumulated in the potential well 32 formed in the MOS capacitor is swept out as follows. Switching element
By turning on 17, the voltage applied to the transparent electrode 1 is lowered. As a result, the potential well 32 generated in the substrate 30 is removed. Then, the signal charges accumulated in the potential well 32 are injected into the substrate 30. Then, it is recombined with the majority carriers to become a current and is swept from the charge sweep line 13. Switching element 17 for four divided regions
Are connected, it is possible to separately sweep out charges for each divided region.

FIG. 3 shows photometry using the solid-state electronic image pickup device shown in FIG.
6 is a time chart showing an example of exposure control and shooting operations. An image pickup operation in an electronic still camera incorporating this solid-state electronic image pickup device will be described with reference to this drawing.

The video floppy of the electronic still camera is 1/60 (s)
The rotation is controlled to rotate once. Since it is necessary to synchronize the rotation phase of the video floppy and the shooting timing, a transfer gate pulse (field shift pulse; this is called a synchronous transfer gate pulse) is applied to the transfer electrode 9 every 1/60 (s). ) P ₁ , P ₂ and P ₃ are given. Between the pulses P ₁ and P ₂ is (1/60) × n (s) (n is a positive integer)
Is set to. It goes without saying that when n ≧ 2, (n−1) transfer gate pulses are given every 1/60 (s) between the pulses P ₁ and P ₂ .

Preliminary shooting for photometry is performed. Some timing (pulse P ₁
The scanning pulse Q ₁ is applied to all the switching elements 17 from the scanning circuit 18 at the time t ₁ ) between P ₂ and P ₂ . This pulse Q ₁
It is preferable that the time until the next four scanning pulses Q ₂₁ , Q ₂₂ , Q ₂₃ and Q _{24 be} fixedly set. However although the output time t ₁ of the pulse Q ₁ may be variable based on the output of the photometric light receiving element, which is the photometric signal supplied to CPU16 it means that the shutter speed of the pre-photographing is variable It is necessary to perform a process of converting the expressed light amount into a certain light amount per unit time.

By applying the scan pulse Q ₁ , unnecessary charges accumulated in the potential well 32 before the time t ₁ are swept out to the substrate 30 side.

After the output of pulse Q _{1, the} next four scan pulses Q ₂₁ , Q
Time until ₂₂ , Q ₂₃ , Q ₂₄ is output (for example, t ₁ to t ₂
Each time) is fixed, and preliminary shooting is performed within this time, and photometry is performed in this preliminary shooting.

The charge accumulated in the potential well 32 as a result of the preliminary photographing is accumulated in each divided region by sequentially applying four scanning pulses Q ₂₁ , Q ₂₂ , Q ₂₃ , and Q ₂₄ to each switching element 17. The generated signal charges are sequentially swept through the charge sweep line 13. The signal charges swept to each charge sweep line 13 are sequentially A /
It is converted into a digital signal by the D conversion circuit 15 and taken into the CPU 16.

The CPU 16 performs exposure control based on the captured signal charge amount for each divided area. The exposure amount to the solid-state electronic image pickup device is controlled by the aperture value and the shutter speed. There are the following methods for controlling the aperture value and shutter speed based on the measured incident light amount. One of them is a table (program diagram) that predetermines the optimum aperture value and the optimum shutter speed for the illuminance, and stores it in the RAM or ROM of the CPU 16.
The optimum aperture value and the optimum shutter speed are read from this table by using the photometric value as a key. The other is to calculate the optimum aperture value and the optimum shutter speed by incorporating the calculation formula for calculating the optimum aperture value and the optimum shutter speed into the program of the CPU16. is there. At this time, generally, the optimum aperture value is first obtained by the photometric amount, and then the shutter speed is calculated using the obtained aperture value. Either the aperture value or the shutter speed may be fixed and the other may be adjusted, or both may be adjusted to the optimum values. The aperture value may be adjusted by well-known aperture control. In the case of an electronic shutter, the shutter speed is controlled by adjusting the output timing of the scanning pulse Q ₃ described later.

In this embodiment, the light-receiving area is divided into four, and the amount of incident light at each location can be measured individually.
It is possible to control the total exposure amount based on the measured light amount at that location by specifying one with the input means, and the photographing operator can take an image by optimizing the exposure amount at the desired location. Like It goes without saying that the exposure amount can be determined based on the sum or average value of the photometric amounts at the four places.

After this, at a specified time t ₃ (when the shutter speed is fixed) or at a time corresponding to the determined shutter speed
At t ₃ , when the scanning pulse Q ₃ is output, all switching elements 17 are turned on, and four pulses Q ₂₁ , Q ₂₂ , Q ₂₃ ,
The charge accumulated in the potential well 32 from the time of Q ₂₄ is swept out as unnecessary. The time from the pulse Q ₃ to the next synchronous transfer gate pulse P ₂ (time from t ₃ to t ₄ ) is the time zone of the main shooting. The signal charges accumulated in the potential well 32 by being exposed in this time zone are transferred to the vertical transfer unit 4 by applying the synchronous transfer gate pulse P ₂ to the transfer electrode 9. Since the transfer signals φ _{V1 to} φ _V4 are given to the vertical transfer unit 4, the charges transferred to the vertical transfer unit 4 are sequentially transferred to the horizontal transfer unit 10, and
The video signal is output from 10 through the output unit 11. One field of the video signal is read out at 1/60 (s), and is subjected to predetermined processing such as FM modulation as described above, and then recorded on a video floppy. Although illustration is omitted, it goes without saying that the horizontal transfer pulse is also applied to the horizontal transfer unit 10.

In the above embodiment, the interline transfer type is shown as the solid-state electronic image pickup device. However, in addition to this, for example, a zigzag transfer (ZT) type, etc., a MOS capacitor.
The present invention can be applied to all types of solid-state electronic image pickup devices using types. Further, the transfer pulse is not limited to four phases, but can be applied to two-phase, three-phase, etc. imaging devices.

Further, although the above embodiment does not refer to interlaced scanning or non-interlaced scanning, the present invention can be applied to both types, and the present invention can be applied regardless of whether it is monochrome or color.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a solid-state electronic image pickup device according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II--II of FIG. 1, and FIG. 3 is an operation of the embodiment shown in FIG. Showing time
It is a chart. 1 ... Transparent electrode, 2 ... Receiving unit array (receiving unit), 4 ... Vertical transfer unit, 10 ... Horizontal transfer unit, 11 ... Output unit, 13 ... Charge sweep line, 15 ... A / D Conversion circuit, 16 …… CPU, 18 …… scanning circuit.

Claims (1)

[Claims] 1. A photoelectric conversion element which is two-dimensionally arrayed on a light receiving region of a substrate and performs photoelectric conversion to accumulate signal charges according to the amount of received light, and transfers the signal charges accumulated in the photoelectric conversion element in the vertical direction. In a solid-state electronic image pickup device comprising a vertical transfer section and a horizontal transfer section for horizontally transferring the signal charge input from the vertical transfer section, the signal charge accumulated in the photoelectric conversion element during preliminary imaging is received by the light receiving section. Mutually insulated sweep electrodes for sweeping to the substrate for each of the divided regions, a scanning circuit for sequentially scanning the sweep electrodes for sweeping to the substrate for each of the divided regions, And a photometric circuit for performing photometry for each of the divided areas based on the signal charges swept onto the substrate by scanning by the scanning circuit.