JPH0546753B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electronic camera that obtains still images using a solid-state imaging device such as a CCD, and in particular, the invention relates to an electronic camera that obtains a still image using a solid-state imaging device such as a CCD. Regarding an electronic camera that allows you to obtain

[Technical background of the invention and its problems]

BACKGROUND ART In recent years, research and development have been conducted on imaging devices called electronic cameras that electronically capture static images using solid-state imaging devices using CCD or MOS. This is to record an image signal obtained from a solid-state image sensor in a frame or field unit as a still image in a magnetic disk memory, semiconductor memory, or the like.

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 corresponds to fixing the shutter speed to 1/30 second or 1/60 second. These shutter speeds are slow for a still camera, so camera shake is likely to occur unless a fixed means such as a tripod is used, and when shooting a fast-moving subject,
Even if a tripod or the like is used, subject blur will occur in the resulting image.

Due to these circumstances, in practical terms, electronic cameras as well as general cameras using film have a 1/12
It is desirable to have a variable speed shutter mechanism including high speed shutters of 5 seconds, 1/250 seconds, 1/1500 seconds, and 1/1000 seconds.

On the other hand, in the case of an electronic camera, it is necessary to accurately obtain a single still image, and it must also be able to capture the image immediately without missing a shot. Generally, electronic cameras are designed to operate on batteries, but from the viewpoint of power consumption, it is preferable to keep the power off at all times and turn on the power when capturing an image. However, even when the power is turned on, since the signal path of the camera is an analog circuit, the correct signal cannot be obtained immediately and becomes distorted, and the correct signal is usually obtained only after several fields have elapsed. Therefore, if the user presses the shutter by feeling until the circuit is stabilized, there remains the problem that the user may miss the shutter release or be unable to capture a desired scene. Further, as a matter of course, there is a problem in that if the power is turned on in advance, the battery is consumed rapidly and is not practical.

[Purpose of the invention]

This invention was made to address the above-mentioned circumstances, and is capable of instantaneously capturing a still image at any shutter speed. The purpose is to obtain a stable imaging signal without missing anything.

[Summary of the invention]

Immediately after the power switch 28 is turned on, the present invention prohibits normal readout clocks from being applied to the solid-state image sensor 3 from the gate circuits 25 and 26 while the amplifier 5, frame memory 6, etc. are stabilized. In order not to miss a shot, unnecessary charges accumulated in the solid-state image sensor 3 are swept out and the exposure is performed immediately.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, an image of a subject 1 is formed on the photosensitive surface of a solid-state image sensor 3 by light input through 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 a subject image at its output. This still image signal is
The 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. In this way, frame memory 6
The still image signal recorded at
It may be displayed on a CRT display device, etc. Note that a semiconductor memory can also be used as the frame memory 6.

As shown in FIG. 2, the solid-state image sensor 3 has photosensitive parts {P ₁₁ , P ₂₁ , P ₃₁ ,...Pm ₁ ,
_P11 , _{P12 , P13} , . The transfer unit is a vertical transfer unit that corresponds to the photosensitive area in the column direction.
It has CV ₁ , CV ₂ , CV ₃ , . . . CVm, and a horizontal transfer section CH that transfers the outputs of the vertical transfer sections CV ₁ , CV ₂ , CV ₃ , . . . CVm in the horizontal direction. Also {G ₁₁ , G ₂₁ , G ₃₁ ...Cm ₁ , G ₁₁ , G ₁₂ , G ₁₃ ...G ₁ n}
is a transfer gate. Horizontal transfer section
The output of CH is derived via an output amplifier O.

Returning to FIG. 1, the drive circuit 4 drives the solid-state image sensor 3 based on signals from the shutter speed setting dial 8 and the shutter button 9, and generates a still image signal as its output. be.

In the drive circuit 4, a monostable multivibrator (hereinafter referred to as a first monomulti) 11 is configured such that the CR time constant changes in response to the shutter speed set by the operator via the shutter speed setting dial 8. The imaging command pulse 10 (shown in FIG. 3a) generated when the shutter button 9 is pressed generates a rectangular pulse signal 12 (shown in FIG. 3b) with a time width T determined by the time constant. occurs. The time width T of this rectangular pulse signal 12 matches the set shutter speed.

Output pulse signal 12 of first monomulti 11
is input to a rising edge detector 13 and a falling edge detector 14, and its rising edge (leading edge) and falling edge (trailing edge) are detected, resulting in pulses 15 and 16 as shown in FIG. 3d. These detection pulses 15,1
6 is a transfer gate of the solid-state image sensor 3
Gij is given as gate pulse GP. Also,
The rising detection pulse 15 is generated by the gate pulse generator 1.
7, and causes the gate pulse generator 17 to generate a gate pulse 18 having a constant time width t shown in FIG. 3e.

On the other hand, the output pulse signal 12 of the first monomulti 11 is given to the synchronization pulse generator 19 as a starting signal, and the synchronization pulse generator 19 uses the signal from the oscillator 20 to perform horizontal scanning of the television. Generates a synchronization pulse corresponding to the period. The oscillator 20 oscillates at 14MHz, for example, and its output is given to the synchronous pulse generator 19 and also input to the 1/7 frequency divider 21 and the 1/2 frequency divider 22, The frequency is divided into 2MHz and 7MHz frequencies. The 2MHz signal from the 1/7 frequency divider 21 is input to the 4-phase shift register 23, and the 2MHz signal is input to the 4-phase shift register 23.
This is a 4-phase clock. The 7MHz signal from the 1/2 frequency divider 22 is input to the two-phase shift register 24, and becomes a 7MHz two-phase clock.

These four-phase clocks and two-phase clocks are input to gate circuits 25 and 26, respectively. The gate circuit 25 receives the synchronizing pulse from the synchronizing pulse generator 19, and normally extracts and outputs one four-phase clock for each horizontal scanning period .tau., as shown in FIG. 3 f to i. However, when the gate pulse 18 (shown in FIG. 3e) is applied from the gate pulse generator 17, the period t changes the 4-phase clock to 31, 32, 33, and 34 of FIG. Output as shown without sampling. This corresponds to refreshing the photosensitive section for approximately one horizontal period at the moment the shutter button 19 is pressed. Another gate circuit 26 is
The gate pulse 18 is not applied, and the input two-phase clock is extracted and outputted one by one every horizontal scanning period τ by the synchronizing pulse from the periodic pulse generator 19. However, as will be described later, the period during which the output of the monostable multivibrator (hereinafter referred to as the second monomulti) 27 exists immediately after the power is turned on (Fig. 3C
), the horizontal and vertical reading pulse outputs are stopped after pulse 16.

The four-phase clocks subjected to gate processing as _shown in _{FIG .} The two-phase clock processed by the gate circuit 26 is applied to the horizontal transfer section CH of the solid-state image sensor 3 as a transfer clock.

In this case, a part of the output of the first mono multi 11 is also input to the second mono multi 27, and immediately after the power is turned on, a pulse signal delayed by about 100 ms is sent from the second mono multi 27. The signal is output and given to the synchronization pulse generator 19 as a second activation signal. Then, after the regulation of the second activation signal is released, the vertical and horizontal transfer of the charges accumulated in the image is actually started. An output pulse from a power switch 28 is applied to the second monomulti 27, and the monomulti 27 is set to operate only immediately after the power switch 28 is turned on.

Next, the operation of this embodiment will be explained step by step.

First, the power switch 28 is turned on. As a result, the second monomulti 27 is operable immediately after the power is turned on.

Next, when the shutter button 9 is pressed, the first monomulti 11 is activated by the imaging command pulse 10, and a rectangular pulse signal 12 is obtained. A pulse 15 is obtained from the rising edge detector 13 at the timing of the leading edge of this rectangular pulse signal 12. This causes the transfer gates Gij to open all at once.
The residual charges accumulated in the photosensitive portion Pij are simultaneously transferred to the vertical transfer portions CV ₁ to CVm. The charges transferred to the vertical transfer units CV ₁ to CVm are transferred to 31, 32, and 32 in FIG. 3 during the period t of the gate pulse 18.
The vertical transfer clocks Vφ ₁ to Vφ ₄ that are continuously generated at 2 MHz as shown in 33 and 34 perform high-speed transfer in the direction of arrow V in FIG.
CH is transferred in the direction of arrow H in FIG. 2 using horizontal transfer clocks Hφ ₁ and Hφ ₂ . By this, first,
The residual charges in the image sensor 3 and the transfer section are cleared, and unnecessary signals are ejected from the output terminal of the solid-state image sensor 3 as shown at 35 in FIG. 3J.

As described above, the period from when the residual accumulated charge in the photosensitive section Pij is simultaneously transferred to the vertical transfer sections CJ ₁ to CVm until the pulse 16 is obtained corresponds to the shutter being "open".

Next, when the trailing edge of the output pulse signal 12 is detected by the fall detector 14 and the output pulse 16 is obtained, this output pulse 16 is again converted into a gate pulse.
Given to transfer gate Gij as GP.

As a result, charges corresponding to the actual image of the subject 1 accumulated in the photosensitive portion Pij during the time T are simultaneously transferred to the vertical transfer portions CV ₁ to CVm. This corresponds to the shutter being "closed".

In this case, since the power switch 28 is turned on for the first time, the second monomulti 27 operates, and after pulse 16, the synchronous pulse generator 19 is activated during the period when the output of the second monomulti 27 is present. An operation stop pulse is applied to the gate circuits 25 and 26 via the gate circuit, and vertical and horizontal transfers are interrupted. That is,
Immediately after the power switch 28 is turned on, the operation is stopped until approximately 100 ms has elapsed after the residual charge is discharged. No operation stop pulse is generated after the 100 ms elapses, and the next operation continues after pulse 16.

Next, when the predetermined period of 100 ms of the operation stop pulse has elapsed, the gate circuit 25 outputs clocks Vφ ₁ to Vφ ₄ for each horizontal scanning period τ as usual, so the clocks are transferred to the vertical transfer units CV ₁ to CV ₄ . The generated charges are transferred in the direction of arrow V in the horizontal scanning period, and further,
It is transferred through the horizontal transfer section CH in the direction of the arrow H, output as a voltage signal via the output amplifier O, and the third
The signal is extracted as a still image signal as shown at 36 in FIG. The still image signal of one frame or one field thus obtained is amplified by the amplifier 5, and then output pulse 16 of the fall detector 14 or
It is stored in the frame memory 6 which starts its operation at the falling edge of the output of the second monomulti 27 (priority is given to the falling pulse of the output of the second mono multi 27).

As described above, according to this embodiment, immediately after the power is turned on, the read operation in the drive process of the solid-state image sensor 3 by the drive circuit 4 is regulated for a certain period of time, so that the amplifier 5 and the frame memory 6 are controlled. is in a state where it can operate stably, and a still image signal for one frame is obtained. Immediately after the power is turned on, the residual charge is first discharged for a short period of time, and then the subject image is captured and stored. If the power has just been turned on, the charge is not read out from the solid-state image sensor immediately, but after waiting for the amplifier 5 and frame memory 6 to become stable. Therefore, the signal read out and stored without missing a shutter chance becomes stable without distortion.

Furthermore, this eliminates the need to keep the power on all the time, making it possible to use the battery efficiently. Immediately after the power is turned on, it takes about 100 ms to read out the signal after capturing and storing images, but this is not a problem compared to the shutter start time.

In the above embodiment, it was explained that a signal is obtained from the solid-state image sensor 3 100ms after the power is turned on, but this time may be the shortest time required for the stability of the electronic circuit, and may vary depending on the circuit performance on the output side. Designed with Also, depending on the shutter time, the stabilization time of the circuit may have already passed when the trailing edge pulse 16 is obtained, so reading out the imaged charge on the photosensitive section starts immediately after the trailing edge pulse 16. be done. Further, although the shutter has been described as an electronic shutter, it may be a mechanical shutter. Further, although a monomulti was used as a time setting means, a means using a counter may also be used.

[Effects of the Invention] As explained above, according to the present invention, the shutter chance immediately after the power is turned on is not missed;
It is possible to realize the important functions required of a camera.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an electronic camera according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing the configuration of a solid-state image sensor, and FIG. 3 is a diagram for explaining the operation of the embodiment. It is a signal waveform diagram. 3... Solid-state image sensor, 4... Drive circuit, 5... Amplifier, 6... Frame memory, 8... Shutter speed setting dial, 9... Shutter button, 11, 27... Monostable multivibrator, 13... Rise detector,
14... Fall detector, 17... Gate pulse generator, 19... Synchronous pulse generator, 25, 26... Gate circuit.

Claims (1)

[Scope of Claims] 1. A solid-state image pickup device in which a photosensitive section is arranged two-dimensionally on a semiconductor substrate and a transfer section that transfers the accumulated charge of the photosensitive section is used, and an object image is formed on the photosensitive section. In an electronic camera that obtains a still image using a shutter, a transfer section of the solid-state image sensor is configured to release residual charges already accumulated in the photosensitive section via the transfer section in response to an imaging command pulse generated by a shutter operation. a high-speed readout means for providing a high-speed readout clock having a higher frequency than a normal readout clock; an exposure control means for setting the exposure time of the solid-state image sensor between the leading edge and the trailing edge of the imaging command pulse; , the operation of the high-speed readout means and the exposure control means are allowed to compensate for the shutter speed, but the output of the solid-state image sensor is inputted during a period in which the normal readout clock is applied to the transfer section of the solid-state image sensor. and a gate means that is set after a period in which the circuit is stabilized.