JPS5980069A - Image pickup system using solid state image pickup element - Google Patents

Abstract

PURPOSE:To ensure a shutter function without using a mechanical mechanism, by discharging the electric charge stored at a photosensitive part to a transfer part and then transferring the electric charge stored newly at the photosensitive part to the transfer part when a prescribed period of time elapses after the first discharge of the electric charge. CONSTITUTION:When a shutter button 9 is pushed, a pulse 15 delivered from a rise detector 13 in the timing of the front edge of a pulse signal 12 delivered from a monostable-multivibrator 11 is applied to a gate pulse generator 17 in the form of a gate pulse GP. Therefore a transfer gate of a solid state image pickup element 3 is opened, and the electric charge so far stored at a photosensitive part is discharged via a transfer part. From this time point the storage of the electric charge corresponding to an object image 1 is started. Then the rear edge of the signal 12 is detected by a fall detector 14 when the time T corresponding to a shutter speed elapses, and an output pulse 16 is applied to the transfer gate as a pulse GP. Therefore the electric charge corresponding to the image 1 and stored at the photosensitive part for the time T is delivered via the transfer part in the form of a picture signal and recorded to a frame memory 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for capturing still images or moving images using a solid-state imaging device such as a CCD, and particularly to an imaging system in which a shutter function is added using pure electronic means.

[Technical background of the invention and its problems]

2. Description of the Related Art In recent years, research and development of imaging devices called electronic cameras, which electronically capture still images using solid-state imaging devices using COD or MOS, have been actively conducted. This is to record an image signal obtained from a solid-state image pickup device as a still image in a magnetic disk memory, semiconductor memory, etc. in units of frames or fields.

In such an electronic camera, as a solid-state image sensor, a device similar to a video camera for capturing moving images can be used in principle. However, since the image formed on the photosensitive surface of the image sensor is usually moving, in order to capture and record a still image in such a state, one frame from the image signal continuously obtained from the output of the image sensor is required. Alternatively, the signal for one field must be extracted and supplied to the memory. Such processing is similar to fixing the shutter speed to 1/30 second or 1/60 second. These shutter speeds are slow and slow for a still camera, so camera shake is likely to occur unless a fixed means such as a tripod is used.
Furthermore, even if a tripod or the like is used to photograph a fast-moving subject, subject blur may occur in the resulting image.

Due to these circumstances, in practical terms, electronic cameras have a speed of 1/125 seconds, just like general cameras that use film. 1/
It is desired to provide a variable speed shutter mechanism including high speed shutters such as 250 seconds, I1500 seconds, and 1/1.000 seconds. However, the shutter mechanism conventionally used in general film-based cameras is mechanical, and applying such a shutter mechanism to electronic cameras takes advantage of electronic cameras' advantages of being small, lightweight, and highly reliable. This is not desirable as it may damage the

One possible method for substantially increasing the shutter speed of an electronic camera without using a mechanical shutter mechanism is to shorten the time for one frame by increasing the readout frequency of the solid-state image sensor. However, the readout frequency of a CCD image sensor of 500 vertical pixels x 400 horizontal pixels, which is often used in electronic cameras, is 7. The shutter speed is 16 MHz, and even if this could be doubled to 14.32 Iz, the shutter speed would not be at most 1/60 second, which would still be insufficient.

On the other hand, even in video cameras that are used to capture moving images, when capturing a subject moving at high speed with a solid-state image sensor, the subject moves while the photosensitive element is accumulating charge, resulting in poor quality of the image. There is a problem that images cannot be obtained. For example, baseball and golf balls are smeared and blurred, resulting in an afterimage-like appearance, and the sharpness of the image is significantly impaired. Therefore, even in such a video camera, a mechanical shutter mechanism may be provided in the optical system to intermittently interrupt the incident light of the image sensor, but this type of solid-state imaging video camera intended for home use However, there are problems that hinder miniaturization and weight reduction.

[Purpose of the invention]

It is an object of the invention to obtain a shutter function which can be set to virtually any speed by purely electronic means.
An object of the present invention is to provide an imaging method using a solid-state imaging device.

[Summary of the invention]

The present invention provides an imaging command source when capturing a still image or a moving image using a solid-state image sensor in which a two-dimensional array of photosensitive sections and a transfer section for transferring accumulated charges of the photosensitive sections are formed on a semiconductor substrate. From the time when the charges already accumulated in the #j are transferred to the transfer section, charges corresponding to the subject image are newly accumulated in the photosensitive section for a predetermined period that can be arbitrarily set, and this accumulated charge #j is transferred to the transfer section. , it is characterized in that it is taken out as an image signal through a transfer section.

In other words, the operation of transferring and discharging the charges already accumulated in the photosensitive section to the transfer section and the operation of transferring the charges newly accumulated on the photoconductor to the transfer section after a predetermined period of time have elapsed have effectively caused the shutter to close. This realizes opening and closing operations.

〔Effect of the invention〕

According to this invention, a shutter function can be added without using a structurally complicated mechanical shutter mechanism,
Moreover, the shutter speed, that is, the time for which the shutter is "open" can be arbitrarily set by a simple time designation operation.

Therefore, when applied to an electronic camera, the shutter speed is
/125 or less can prevent camera shake. Also, for fast-moving subjects, you can use fast shutter speeds such as 1/250 seconds and IA00 seconds, and for dark subjects, you can shoot at a fraction of a second. It is also possible to prevent underexposure by using a slow shutter speed of 1 second or more.

On the other hand, since a solid-state imaging video camera can also achieve a high-speed shutter without using a mechanical shutter mechanism, it is possible to obtain clear images even in the case of a fast-moving subject.

[Embodiments of the invention]

FIG. 1 shows an embodiment in which the present invention is applied to a solid-state imaging device for capturing still images, a so-called electronic camera.

In the figure, a subject image 1 is formed on the photosensitive surface of a solid-state image sensor 3 via an imaging optical system 2 (simply represented by a convex lens symbol in the figure). The solid-state image sensor 3 is driven by a drive circuit 4 and generates a still image signal related to the subject image 1 at its output. , this still image signal is input to a frame memory 6 via an amplifier 5.

The frame memory 6 uses, for example, a magnetic disk as a recording medium, and records the still image signal supplied from the amplifier 5 onto the magnetic disk through a magnetic head. The still image signal thus recorded in the frame memory 6 is appropriately reproduced frame by frame, taken out to the output terminal 7, and then reproduced as a hard copy or a CRT.
It may be displayed on a display device, etc. Note that a semiconductor memory can also be used as the frame memory 6.

The solid-state image sensor 3 is constructed using, for example, a CCD, and preferably an interline transfer type CCD image sensor constructed on a single semiconductor substrate as shown in FIG. 2 is used. This image sensor has a photosensitive section Pij (1; 1., .21 . . . ) corresponding to m pixels in the horizontal direction and n pixels in the vertical direction.
m + j "1 + 2 + "'n) are arranged in a two-dimensional array to form a photosensitive surface.

Each photosensitive section P1j has a photoelectric conversion and charge storage function, and is usually composed of a photodiode. Adjacent to each photosensitive part Pth and adjacent to transfugu-)Gij,
A vertical transfer section CV1%CVm is provided so as to be inserted between the columns of the photosensitive sections P13 in the vertical direction. Further, a horizontal transfer section CH is provided at one end of the vertical transfer sections CV1 to CVm, and an output section 0 is provided at one end of the horizontal transfer section CH.

Returning to FIG. 1, the drive circuit 4 drives the solid-state image sensor 3 as shown in FIG. It is used to generate still image signals and is configured as follows.

In the drive circuit 4, a monostable multivibrator (hereinafter referred to as mono-multi) 11 has a shutter speed setting dial 8.
CR according to the shutter speed set by the operator via
The shutter button 9 is provided so that the time constant of the shutter button 9 changes.
An imaging command pulse 12 as shown in FIG. 3(b) is generated by an imaging command pulse 10 as shown in FIG. 3(,) which is generated when the button is pressed. The time width T of this pulse signal 12 matches the set shutter speed.

The output pulse signal 12 of the monomulti 11 is sent to the rising edge detector 1
3 and fall detector 14, and its rising edge (leading edge) and falling edge (trailing edge) are detected, as shown in FIG. 3(C).
A detection pulse of 15°16 as shown in FIG. These detection pulses J5 and 16 are applied to the transfer dart GB of the solid-state image sensor 3 as dart cruise GP. Further, the rising detection pulse 15 is also given to the dart pulse generator 17, and from the dart pulse generator 17, as shown in FIG. 3(d).
A dirt/gurus 18 is generated with a certain time width t shown in FIG.

On the other hand, the output pulse signal 12 of the monomulti 11 is synchronous A?
The synchronizing pulse generator 19 generates a synchronizing pulse corresponding to the horizontal scanning period of the television based on the signal from the oscillator 20. The oscillator 20 oscillates at, for example, 14 MHz, and its output is given to the synchronous pulse generator 19 as described above, and is also input to the 1/7 frequency divider 21 and the IA frequency divider 22, each of which has a frequency of 2 Fi' The frequency is divided into 1Hz and 7MHz. The 2Iz signal from the 1/7 frequency divider 21 is input to the 4-phase shift register 23, and becomes a 2MHz 4-phase clock. Also, 7 MH from the frequency divider 22
The z signal is input to the two-phase shift register 24, and the 7MH
It becomes a two-phase clock of Z. These 4-phase clocks and 2
The phase clocks are input to gate circuits 25 and 26, respectively. The gate circuit 25 receives the synchronization pulse from the synchronization clock generator 19, and normally outputs one four-phase clock for every horizontal scanning period τ, as shown in FIG. 3(,) to (h). However, when the f-tooth i4 pulse 18 shown in FIG. 3(d) is given from the Noculus generator 17, the input four-phase clock is 311.32 , , ? , ? in Figure 3 (e) to (h).
, 34, it is output as is without sampling. The other dart circuit 26 is not provided with the dart pulse 18 from the Gutnoculus generator 18;
2 of the input by the synchronization pulse from the synchronization pulse generator 19
One phase clock is extracted and outputted every horizontal scanning period τ.

In this way, the four-phase clocks subjected to dart processing as shown in FIGS. 3(a) to (h) by the gate circuit 25 are applied to the vertical transfer sections Cv1 to CV□ of the solid-state image sensor 3. Transfer lock Vφ1 to Vφ
The two-phase clock processed by the dirt circuit 26 is transferred to the horizontal transfer section CH of the solid-state image sensor 3 and is provided as a lock.

Next, the operation of this embodiment will be explained. Now, when the shutter release button 9 is pressed, the monomulti 11 is activated by the imaging command Noculus 10 generated accordingly, and a rectangular/2-lust signal 12 is output.

At the timing of the leading edge of this pulse signal 12, the pulse 15 outputted from the rising edge detector 13 is given as a dirt pulse GP, thereby transferring )r'-)G
ij open all at once, and the charges that had been accumulated in the photosensitive portion Pij are simultaneously transferred to the vertical transfer portions Cv1 to Cvm. The charges transferred to the vertical transfer units CV, . . . , . . . , 31, . 9
After being transferred at high speed in the direction of arrow V by the vertical transfer locks Vφl to Vφ4 that are continuously generated at 2 MHz as shown in 233.34, the horizontal transfer section CH is transferred to the horizontal transfer locks Hφl and Hφ2 in the direction of arrow H. direction, output section 0
The liquid is discharged as shown at 35 in FIG. 3 (0).

As mentioned above, the accumulated charge in the photosensitive part Pij is transferred to the vertical transfer part C.
The operation of simultaneous transfer to V1 to Cvm corresponds to "opening the shutter", and from this point on, the accumulation of charge corresponding to the subject image 1 begins anew in the photosensitive section Pij.After this, the shutter speed is set using the shutter speed setting dial 8. When the time T corresponding to the shutter speed has elapsed, the trailing edge of the output pulse signal 12 of the monomulti 1 is detected by the falling edge detector 14, and the output i
4 pulse 16 is given to the transfer gate G31 as a dirt pulse GP, charges corresponding to the subject image 1 accumulated in the photosensitive part 1) tj during the time T are simultaneously transferred to the vertical transfer parts CV, ~Cvm. be done. This transfer operation corresponds to "closing" the shirt. At this time, the dart/volume 18 is not given to the start circuit 25, and the date circuit 2
From 5 onwards, the clock Vφ, - is applied every horizontal scanning period τ as usual.
Since Vφ4 is output, the charges transferred to the vertical transfer sections CV, to Cv4 are transferred in the direction of arrow V in the horizontal scanning period, and then transferred through the horizontal transfer section CH in the direction of arrow H, and then transferred to the output section 0, and is converted into a voltage signal, for example, and taken out as an output Vout as a still image signal as shown at 36 in FIG. 3 (0). The still image signal of one frame or one field obtained in this way is amplified by an amplifier 5 and then recorded by a frame memory 6 whose operation is started by an output signal 16 of a fall detector 14.

In this way, the shutter operation can be realized with equal constraints by purely electronic processing in the process of driving the solid-state image sensor 3 by the drive circuit 4. Moreover, the shutter speed in this case is
It can be arbitrarily set steplessly by simply changing the time constant of the monomulti 11.

The present invention is applicable not only to the above-mentioned electronic camera for capturing still images, but also to a video camera for normal moving image capturing, and an example of the operation in this case is shown in the time chart of FIG. .

That is, in this case, the monomulti 11 in FIG. 1 is replaced by the monomulti 11 in FIG.
By being repeatedly activated by the pulse 1o at constant time intervals shown in a), pulse wandering signals 12 with a time width T corresponding to the shutter speed are generated at constant time intervals as shown in FIG. 4(b). .

FIG. 4(c) shows the rising edge detection signal f for the pulse signal 12.
(d)
The r-to-harse 18 which is outputted from the pj-ruth generator 17 is shown. Therefore, in this example, after the residual charges on the photosensitive area P1j are discharged at a high speed at regular time intervals, the charges corresponding to the subject image newly accumulated on the photosensitive area Pij during the subsequent time T are generated as image signals. It will be output.

FIG. 4(,) is a signal based on residual charge, and L(f) is an image signal.

In this example, there is no problem if the time T is set shorter than the vertical blanking period, but if it is longer than this, the image signal cannot be obtained normally with standard scanning, and a separate scan conversion device is required. . However, in order to image a subject moving at high speed without blur, it is necessary to use a high-speed shutter of, for example, T = 11,500 seconds or less, which is shorter than the vertical blanking period, so a scan conversion device is not required.

As described above, when the present invention is applied to a video camera, it is possible to image a subject moving at high speed without causing an afterimage without using a mechanical shutter mechanism.

This invention is not limited to the above embodiments,
For example, in Fig. 1, the time constant of the monomulti 11, that is,
Although it was explained that the operator manually sets the e-yata speed, an automatic exposure system can be configured by detecting the brightness of the subject using an appropriate photoreceptor and automatically setting the shutter speed based on that. is also possible.

The ift monomulti 110 part may be replaced with something like a counter.

Furthermore, it goes without saying that the present invention is applicable not only to monochrome imaging devices but also to, for example, single-chip type color imaging devices that combine a solid-state image sensor with a color filter array, or multi-chip color image pickup devices that use a plurality of solid-state image sensors.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an imaging device according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing the configuration of a solid-state imaging device,
FIG. 3 is a time chart for explaining the operation of this embodiment, and FIG. 4 is a time chart for explaining another embodiment. DESCRIPTION OF SYMBOLS 1... Subject image, 3... Solid-state image sensor, 4... Drive circuit, 6... Frame memory, 8... Shirt button, 9... Shutter speed variable dial, 11...
Monostable multivibrator, 13...rise detector,
14... Falling edge detector, 17... Dirt pulse generator, 19... Synchronization/Gruss generator, 2o... Oscillator, 21.22... Frequency divider, 23... 4-phase shift register, 24...2-phase shift register, 25.26...
・Dirt circuit, Plj...photosensitive section, G eye...transfer gate, CV, ~CVm...vertical transfer section, CH
...Horizontal transfer section, 0...Output section.

Claims (6)

[Claims] (1) Using a solid-state image sensor in which a two-dimensional array of photosensitive parts and a transfer part that transfers the accumulated charge of the photosensitive parts are formed on a semiconductor substrate, a subject image is formed on the photosensitive parts to produce a still image or a moving image. When an imaging command is received, the charges already accumulated in the photosensitive section are transferred to the transfer section and discharged through the transfer section, and the charges already accumulated in the photosensitive section are transferred to the transfer section. A charge corresponding to the subject image is newly accumulated in the photosensitive section for a predetermined period that can be arbitrarily set from the time of transfer to the transfer section, and the accumulated charge is transferred to the transfer section and taken out as an image signal through the transfer section. An imaging method using a distinctive solid-state imaging device. (2) The solid-state image sensor is arranged between columns of photosensitive sections in the vertical direction, and includes a vertical transfer section where the accumulated charges of the photosensitive sections are transferred via a transfer T-gate, and these vertical transfer sections. The solid-state imaging device according to claim 1 is used, characterized in that the device has a horizontal transfer section that receives the transferred charges in parallel and transfers them in series and supplies them to the output section. The imaging method used. (3) It has means for generating a pulse signal with an arbitrarily settable time width in response to an imaging command, and transfers the charge already accumulated in the photosensitive section at the timing of the leading edge of this pulse signal. 1, and simultaneously transfers charges newly accumulated in the photosensitive area corresponding to the subject image to the transfer unit over the time width of the pulse signal at the timing of the trailing edge. Imaging method using the solid-state imaging device described in Section 1. (4) An imaging system using a solid-state imaging device according to claim 3, wherein the pulse signal is generated intermittently at regular time intervals. (5) Claim 3, characterized in that the time width of the pulse signal is set in accordance with a designated shutter speed.
An imaging method using the solid-state imaging device according to item 1 or 4. (6) Claims 3 to 4, characterized in that the means for generating the /'e pulse signal is a monostable multivibrator.
An imaging method using the solid-body imaging device according to any one of Item 5.