JPH0440761A - Electronic still camera - Google Patents

Abstract

PURPOSE:To prevent the smear caused at transfer of the charge by transferring the undesired charge stored in a charge store part right before the exposure, discharging the stored charge at a high speed within an exposure time, discontinuing the transfer of the charge until the light is shielded to an image pickup element, and transferring and reading out the signal charge out of the charge store part right after the exposure. CONSTITUTION:When a system control circuit 17 stops the drive of an aperture blade 2 via a stepping motor drive circuit 5, a CCD drive circuit 6 transfers the undesired charge stored in a photodiode to a vertical transfer register to discharge the undesired charge to the outside of a CCD 3. Then the circuit 17 revolves the blade 2 via the circuit 5 in order to shield the incident light to the CCD 3. When the light is shielded by the blade 2 to the CCD 3, the circuit 6 actuates the vertical transfer register and transfers the signal charge successively and vertically to output the change via a horizontal transfer register. The read signals are processed by a signal processing circuit 7 and a recording circuit 8 and then recorded to a video floppy 9 via a magnetic head.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic still camera that uses an image sensor to capture and record instantaneous images of a subject using an electronic camera.

2. Description of the Related Art Electronic still cameras have been put into practical use that capture and record instantaneous images of objects by combining an imaging device such as a CCD and a recording device that records on a floppy disk. Unlike conventional film cameras, these electronic still cameras do not require any processing for developing or printing, and have the advantage of allowing you to instantly check the images you have taken on a monitor, etc. There is.

By the way, this type of electronic still camera, like an optical film camera, requires so-called exposure control to control the amount of exposure on the image plane during shooting, and the aperture also uses a shutter to control the amount of exposure to the image sensor. ing. As a method for controlling the shutter speed when opening and closing the shutter, two methods are widely used: (1) a method using a mechanical shutter, and (2) a method using an electronic shutter.

This method using a mechanical shutter is a method such as a well-known lens shutter or focal brain shutter, in which the shutter curtain is mechanically opened for a predetermined period of time to perform exposure.

On the other hand, in the method using an electronic shutter, the charges accumulated in the light-receiving part (photodiode) of the image sensor immediately before exposure are swept out, and the accumulated charges are transferred after a predetermined period of time (equivalent to the shutter speed) has elapsed after this sweeping operation. I'm trying to read it out. This electronic shutter does not use any mechanical elements, and has the advantage that it can be made smaller in size than the above-mentioned mechanical shutter, and the accuracy of the shutter speed can be significantly increased.

Problems to be Solved by the Invention However, in the conventional mechanical shutter method described above, in the case of a lens shutter, the shutter blades suddenly try to close during the opening operation of the shutter blades, so the inertia and friction of the shutter blades are reduced. Due to the effects of
It was difficult to ensure exposure accuracy within (EV). In addition, in the case of a focal brain shutter, the accuracy of the shutter speed is better than that of a lens shutter, but because there are mechanical elements, it is difficult to achieve the above exposure accuracy at high speeds, and there is also the problem of changes over time. There is, and again,
When considered as an exposure mechanism, since there is also an aperture mechanism, there is also the problem that the size becomes large and the cost increases.

Next is the conventional method using an electronic shutter, but since there are no mechanical elements in the shutter mechanism, the shutter accuracy can be sufficiently high compared to a mechanical shutter, and it is possible to achieve the above exposure accuracy, but It has the following problems.

In other words, in an electronic shutter using an interline transfer type image sensor, the electric charge accumulated in the light receiving part (photodiode-F) of the image sensor until just before exposure is swept out,
Immediately after this sweeping operation has elapsed, the accumulated charge is transferred to the vertical transfer register and read out after a predetermined period of time (corresponding to C shutter seconds, the end point of the shutter seconds is approximately aligned with the vertical synchronization signal). . With this type of mechanism, if light continues to be irradiated onto the image sensor during charge transfer in the stacked transfer register, the vertical transfer register will not be completely shielded from light. (very difficult), smearing occurs, especially when the subject has high-brightness areas such as sunlight filtering through trees or sunlight reflecting off.
As is well known, when there is a spotlight (such as a spotlight), this smear charge causes a white tail to appear on the playback screen as the smear charge is added to the signal charge and transferred from this high brightness area towards the bottom of the screen. There was a problem. One possible solution to this problem is to block the light to the image sensor immediately after transferring the vertical transfer register signal charge.
It takes a certain amount of time to completely block light, and the above-mentioned tailing appears for that amount of time, so this is not a perfect solution.

The present invention solves the above-mentioned conventional problems. It eliminates the mechanical shutter mechanism and uses the electronic shutter function of the solid-state image sensor to perform high-precision exposure control. It also eliminates the trailing phenomenon caused by smear that occurs during charge transfer. The purpose of this is to provide an electronic still camera that does not require an electronic still camera.

Means for Solving the Problems In order to solve the above problems, the electronic still camera of the present invention includes an image sensor having a charge storage section and a charge transfer section by photoelectric conversion, and a charge storage device that has a charge storage section and a charge transfer section by photoelectric conversion, and an image pickup device that has a charge storage section and a charge transfer section. a transfer means for transferring the unnecessary charges accumulated in the charge storage section to the charge transfer section; and a transfer means for transferring the unnecessary charges accumulated in the charge storage section to the charge transfer section; a charge transfer means for transferring at high speed using a high frequency transfer clock; a light shielding means for blocking light incident on the image sensor after the exposure; and a light shielding means at least after the charge transfer means transmits unnecessary charges at high speed. The device is equipped with a charge transfer stop means for stopping charge transfer of the charge transfer section for a period of time until the light is almost uniformly distributed.

Furthermore, in addition to the above-mentioned configuration, the electronic still camera of the present invention is configured such that the end of the high speed transmission of unnecessary charges by the charge transfer means is made to coincide with the end of the exposure time corresponding to the shutter time, and the transfer means is connected to the exposure time. The structure is such that the signal charges accumulated in the charge storage section of the image pickup element within the time are transferred to the charge transfer section immediately after the above-mentioned arrow speed transfer.

Effect With the above configuration, during imaging, first, the transfer means transfers the unnecessary charges accumulated in the wL charge storage section to the charge transfer section immediately before the start of exposure, and then at any timing within the predetermined time required for subsequent exposure. By transferring unnecessary charges from the charge transfer unit at high speed using the charge transfer means, the unnecessary charges are discharged.
Further, the charge transfer stopping means stops the charge transfer from the end of the high-speed transfer until at least the light incident on the image sensor is blocked by the post-exposure light transmitting means, and
The signal charge accumulated in the charge storage section is transferred to the charge transfer section immediately after exposure by making the end of the high-speed transfer of unnecessary charges approximately coincide with the end time of the lightning, so that the transfer function is operated again at a predetermined timing after the exposure. This allows signal charges to be read out, eliminates the trailing phenomenon caused by smear that occurs during charge transfer, and allows highly accurate exposure control using the electronic shutter function of the image sensor.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. III is a block diagram showing the configuration of an electronic still camera according to an embodiment of the present invention. In FIG. 1, 1 is a photographing lens, 2 is an aperture blade C (311 in this embodiment) provided with a plurality of holes of different diameters (described later), and 3 is an interline transfer type CCD (hereinafter simply referred to as CCD).
), 4 is the aperture blade IR to select the desired aperture.
2 is a stepping motor for rotationally driving the stepping motor 4, 5 is an IR-based stepping motor W71 circuit mainly consisting of switching transistors for driving the stepping motor 4, and 6 is various pulses and charge transfer for driving the CCD 3. CCD that generates clocks etc.
A drive circuit 7 processes the signal obtained from the CCD to obtain a luminance signal and a color difference line sequential signal, a signal processing circuit 8 frequency modulates the signal obtained by the signal processing circuit 7, and the magnetic head 1
11 is a motor for rotationally driving the video floppy 9; 12 is a motor 111t which rotates at a constant rotation speed and a constant rotational phase; 13 is a PG bin provided in the center core of the video floppy 9 and indicates the phase of rotation; 14 is a PG bin 13; 15 is placed in the center core of the video floppy 9 and is configured in a fill shape to detect its rotational phase. 16 is a phase shifter for delaying the signal output from the amplifier circuit 15 by a predetermined value; 17 is a system control circuit that controls these systems and is composed of a micro combinator and its peripheral circuits; 18 is a so-called release that provides a trigger for photographing.

FIGS. 2(a) to 2(h) are timing charts showing the timing from photographing to recording in this embodiment. Figure 2 (
In Figure 2 (h), a is the PC signal that is the output of the phase shifter 16, and b is the ■ signal! [! PGnA No. a and
The phase relationship of the signals is adjusted by the phase shifter 16 so that the PG signal a takes the lead. 6 is a timing diagram showing the operating time of the aperture blade 2.

The inclined portion C1 indicates that the aperture blade 2 is operating,
This shows that the aperture stops at a flat portion C2 at a predetermined aperture. Ll is a vertical transfer 5TOP signal that gives a command to stop the vertical transfer clock after high-speed transmission, which will be described later.
is the shutter pulse that determines the exposure time (shabuta seconds),
f is a vertical transfer clock for transferring signal charges of the vertical transfer register 303, which will be described later; 1 normal drive' indicates the normal transfer cycle clock fl; The period is shorter than the normal transfer period, that is, it indicates a high frequency clock f2, and is a part for performing high-speed transmission (C drive), and when this clock stops, the transfer of signal charges stops.

g is a photodiode 301.3 of CCD 3, which will be described later.
A transfer gate pulse %1 for transferring signal charges accumulated in 02 to a vertical transfer register 303, which will be described later, is a recording gate for recording an instantaneous image of the object obtained by photographing on the video floppy disk 9.

FIG. 3 is an operational diagram for explaining the structure and operation of the aperture blade 2 of this embodiment. 19 indicates a part of the lens barrel (not shown); light is guided to the CCD 3 through this hole;
Naturally, by closing this hole, CCD 3
The incident light is blocked. 20.21.22 is aperture blade 2
This is a round hole-shaped fixed aperture provided with a diameter that provides a predetermined aperture value, respectively.

The aperture blades 2 are rotationally driven by a stepping motor 4 in the direction of the arrow (A).

Figure 4 shows the CCD used in the electronic still camera of this example.
3, 301 and 302 are photodiodes that accumulate charges, 303 is a vertical transfer register that vertically transfers signal charges that have not been accumulated in the photodiodes 301 and 302, and 30
4 is a horizontal transfer register, and 305 and 306 are transfer gates.

Each transfer gate 305.30 by transfer gate pulse g
6 is opened, the signal charges accumulated in the photodiodes 301 and 302 are transferred to the vertical transfer register 303.

The signal charge that has not been transferred to the vertical transfer register 303 is normally transferred vertically to the horizontal transfer register 304 by one horizontal line for each IH by the vertical transfer clock f synchronized with the horizontal synchronization signal, and in the horizontal transfer register 304, one horizontal line is transferred during the IH. Charges for a horizontal line are transferred to the output terminal of CCD 3.

The signal charges accumulated in the photodiodes 301 and 302 in this way are sequentially read out as described above.

By the way, just before the start of exposure, the photodiode 30
The structure is such that the unnecessary charges accumulated at 1.302 can be transferred by the transfer gate pulse g and then discharged at high speed via the vertical transfer register 303 using a vertical transfer clock having a higher frequency than usual.

This frequency is determined based on the transfer efficiency of the CCD 3, and is set to about 800 (KHz) in this embodiment.

The operation of the electronic still camera of this embodiment configured as described above will be described below.

First, when power is supplied to each circuit and a vertical transfer clock f and a horizontal transfer clock (not shown) are output from the CCD drive circuit 6, the photodiodes 301.
The dark charge, which is an unnecessary charge generated at 302, is transferred to the vertical transfer register 303 by the transfer gate pulse g generated at every superposition period C (period of the vertical synchronization signal), and is generated in the vertical transfer register 303 and the horizontal transfer register 304. The system control circuit 17 adjusts the aperture at the time of photographing according to the output of a photometering sensor (not shown) (which measures the brightness of the subject). Calculate and determine the value and shutter speed (shutter time). The following description will be made assuming that as a result of the calculation, the aperture value is determined to be the aperture 21, and the shutter speed is determined to be Tl.

When the release 5W1B is pressed after the power is turned on, the system control circuit 17 turns on the motor drive control circuit 12 and rotates the video floppy disk 9 through the motor 11.

Once the rotation of the video floppy 9 has stabilized at the specified rotation speed,
Next, the system control circuit 17 drives the stepping motor 4 via the stepping motor drive circuit 5 to rotate the aperture blade 2 from the initial position (FIG. 113(a)) in the direction of the arrow force. Furthermore, the aperture blades 2 are shown in Fig. 3 (
When it rotates to a predetermined position and stops as shown in b), the system side dividing circuit 17 sends the shutter time T to the CCD drive circuit 6.
The CCD drive circuit 6 outputs the transfer gate pulse g1 at the timing of the rising edge of the shutter pulse e. to open the transfer gates 305 and 306 of CCD 3,
Unnecessary charges accumulated in photodiodes 301 and 302 are transferred to vertical transfer register 303.

Once this unnecessary charge is transferred, it is discharged to the outside of the CCD 3 using the normal vertical transfer clock r until the shutter pulse falls. When the 1 o'clock opening Tl has elapsed, the system control circuit 17 lowers the shutter pulse. At the same time, C rises to output vertical transfer 5TOP signal d), CC
The D drive circuit 6 receives the vertical transfer clock f when the shutter pulse C falls (vertical transfer 5 TOP signal d rises).
Switch from normal drive to high-speed drive by increasing the frequency of
After the unnecessary charges in the vertical transfer register 303 are discharged at high speed, the vertical transfer clock f is stopped.

By the way, the photodiode of CCD 3 is 301°30
In the second part, immediately after unnecessary charges are transferred to the vertical transfer register 303 by the transfer gate pulse gl, accumulation of signal charges corresponding to the subject image by photoelectric conversion is started. This accumulation is continued until the COD drive circuit 6 outputs the transfer gate pulse g2 after the high-speed transfer of unnecessary charges is completed.

That is, the transfer gate pulse g2 causes the time Ts
The signal charges accumulated in the photodiodes 301 and 302 due to the exposure during mth S1 and S1 are transferred to the vertical transfer register 303.

With the above operation, while the aperture blades 2 are rotating, the CCD 3
Incident light is irradiated on the photodiodes 301 and 302, but until just before the shutter pulse, unnecessary charges in the photodiodes 301 and 302 are transferred to the vertical transfer register 303 by the transfer gate pulse GO synchronized with the signal and discharged by normal driving. ,
Furthermore, at the rising timing of the shutter pulse e, unnecessary charges accumulated in the photodiodes 301 and 302 are transferred to the vertical transfer register 303 by the transfer gate pulse gl, and after the elapse of time Tss, the shutter pulse e After the time-opening Tax, which discharges unnecessary charges by high-speed driving as described above, has elapsed since the rise of the vertical transfer register 30 by the transfer gate pulse g2.
3, the signal charge is immediately transferred to 3, so that the pulse width of this layer pulse 〒II and the open time during high-speed driving are actually reduced.
The sum of S3 corresponds to shutter time (C exposure time) Ts.

Next, when the system control circuit 17 brings down the shirt j t
is driven, and the aperture blades 2 are rotated in the direction of arrow (a) to change from the state shown in FIG. 3(b) to the state shown in FIG. 3(+). 1!3 Figure (6) shows a state in which the incident light to the CCD 3 is used in the area between the aperture hole 20 and the aperture hole 21. The shorter the time required for this light shielding, the better, and the allowable longer time-opening range is determined by the allowable amount of charge that becomes a noise source such as dark current generated in the vertical transfer register 303 of the CCD 3 while the transfer is stopped. come.

When the light to the CCD 3 is blocked by the aperture blade 2 to an extent that there is no problem, the system control circuit 17 performs vertical transfer 5TOP.
Set the signal d to "L" level. Vertical transfer 5TOP signal d
When the signal becomes L" level, the CCD drive circuit 6 generates a vertical transfer clock f with a normal cycle in synchronization with the next rising signal, operates the vertical transfer register 303, and transfers the signal charge. It is sequentially transferred vertically and outputted via the horizontal transfer register 304. At this time, at the timing of the rise of the paa No. 1 signal immediately before this signal (2), the system control circuit 17 sets a recording gate for a time corresponding to the rotation period of the video vinyl 901. h, this read signal is processed by the signal processing circuit 7 and the recording circuit 8,
The data is recorded on a video floppy disk 9 via a magnetic spatula 10. In this case, the aperture blades 2 have returned to their initial positions, so J
: A series of shooting sequences will end with the record.

As described above, according to this embodiment, the unnecessary charge immediately before photographing is discharged by normal driving plus high-speed driving, and after exposure,
During the vertical transfer operation of signal charges by the vertical transfer registers 303, the CCD 3 is shielded from light by the aperture blades 2, and when light is incident on the CCD 3, the vertical transfer register 303 is stopped. Therefore, it is possible to record a signal without causing the trailing phenomenon caused by smear charges that occurs when light continues to enter the vertical transfer register 303 during transfer, as in the conventional case.

Furthermore, by having the aperture function and the light shielding function using the aperture blades 2 as in this embodiment, the configuration of the optical section can be made very simple.

However, the diaphragm/shading means is configured like a so-called diaphragm/lens shutter in which the diameter of the diaphragm is changed using multiple diaphragm blades, as in the past. It goes without saying that the object of the present invention can be achieved even if the above is used.

In addition, in this embodiment, the timing at which the aperture blade 2 finishes transmitting light after exposure is made close to the rising edge of the signal S for restarting the vertical transfer clock f, as shown in FIG. . This makes it possible to further shorten the period of time Tl in which the vertical transfer register 303 is stopped.
This has the advantage that the amount of dark charge generated in the vertical transfer register 303 is small, which is advantageous in terms of S/N.

However, in COD where the generation of dark charges in the vertical transfer register 303 is not a problem, it is not necessary to take such operation timing.

Furthermore, in this embodiment, regarding the drive of the CCD 3, the reference for the V rate of the COD drive circuit 6 was explained using the ■ signal. However, there is no problem with the present invention as long as the signal is replaced with VSYNC or a signal with the same period related to VSYNC.

In addition, in this embodiment, the initial position of the aperture blades 2 is set to a light-shielding state, but unnecessary charges accumulated in the photodiodes 301 and 302 immediately after the start of exposure C (shutter time) are quickly discharged via the vertical transfer register 303. Therefore, there is no problem even if the initial position is set to a position where the CCD 3 is irradiated with light.

Incidentally, in this embodiment, the end of the high-speed discharge of unnecessary charges is timed to approximately coincide with the end of the shutter time T-, but this high-speed discharge is performed at the timing of the shutter opening (C shutter time), that is, the transfer gate nozzle. (It goes without saying that the purpose of the present invention can be achieved no matter where the dark timing of pulse g1 and transfer gate pulse g2 is. However, in this case, the vertical transfer register 3
It is unavoidable that the amount of dark charges and smear generated in 03 will increase. At this time, it goes without saying that the shutter pulse Ts should be set long within the range of TS1≦Ta.

Effects of the Invention As described above, according to the present invention, since exposure is controlled not by a mechanical shutter but by an electronic shutter, it is not affected by the accuracy of the shutter mechanism and can achieve highly accurate exposure control. It is possible to provide an electronic still camera that can record an instantaneous image without causing a trailing phenomenon due to smear even if there is a high-luminance part in the subject, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an electronic still camera according to an embodiment of the present invention, FIG. An operation diagram for explaining the operation of the aperture blades in the same electronic still camera, and FIG. 4 is a schematic diagram of an interline transfer type CCD.
CD, 4--stepping motor, 5--stepping motor drive circuit, 6--CCD l[movement circuit, 17
... System system first circuit, 301, 302... Photodiode, 303... Vertical transfer register, 304...
...Horizontal transfer register, 305/306...Transfer gate.

Claims (1)

[Scope of Claims] 1. An image sensor having a charge storage section and a charge transfer section by photoelectric conversion, and an unnecessary charge accumulated in the charge storage section until immediately before the start of exposure corresponding to a shutter time during photographing is removed from the charge storage section. a transfer unit for transferring to a transfer unit; a charge transfer unit for transferring unnecessary charges transferred by the transfer unit of the charge transfer unit at high speed using a transfer clock having a higher frequency than a normal frequency within the predetermined exposure time; a light shielding means for shielding light incident on the image sensor after the exposure; and a light shielding means for blocking light incident on the image sensor after the exposure; and a light shielding means for blocking the charge transfer of the charge transfer unit for at least the time from the high speed transfer of unnecessary charges by the charge transfer means until the light is substantially shielded by the light shielding means. An electronic still camera comprising charge transfer stopping means for stopping the charge transfer. 2. The end of the high-speed transfer of unnecessary charge by the charge transfer means is made to substantially coincide with the end time of the exposure time corresponding to the shutter time, and the transfer means transfers the signal charge accumulated in the charge storage section during the exposure time at the high speed. 2. The electronic still camera according to claim 1, wherein the electronic still camera is configured to be transferred to the charge storage section immediately after being transferred.