JP2955676B2 - Electronic shutter control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic shutter control device used for a still video camera or the like.

[Prior art] A so-called electronic shutter using a CCD, which is a solid-state imaging device, is generally used as a shutter for a still video camera or the like. Is read out in synchronization with the vertical synchronizing signal of the video processing circuit (for example, see "Television Technology", August 1987, pp. 37-39).

This necessity is based on the fact that the vertical transfer section of the CCD is in a state of receiving the signal charges of the photoelectric conversion section,
This is due to the need to read signals from the CCD and the fact that image recording is basically a movie operation.

However, if the signal charges are read out to the vertical transfer unit in this manner, the timing corresponding to the shutter closing is fixed if the signal is synchronized with the video vertical synchronizing signal. Is restricted by the vertical synchronizing signal. For this reason, the time from the arbitrary timing of the release to the timing of the shutter opening varies, and furthermore, the shutter opening time is calculated by the pre-metering data. In particular, when the flash emission is required, the exposure control is likely to vary.

As described above, real-time photometry cannot be performed with the conventional device, and there is a limit in improving photometric accuracy.

A method of driving an electronic shutter in synchronization with a release switch is also known (for example, Japanese Patent Application Laid-Open No. Sho 60-5217).
No consideration is given to making it possible to always output the shutter opening timing.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned conventional problems, and can open and close an electronic shutter irrespective of the timing of a video vertical synchronizing signal. It is an object of the present invention to provide an electronic shutter control device capable of improving the photometric accuracy by making it possible.

Means for Solving the Problems The present invention is an electronic shutter provided in a camera that performs electronic still photography, and includes a photoelectric conversion unit, and a vertical transfer unit that reads out charges accumulated in the photoelectric conversion unit. The image pickup device, a drive circuit for driving and controlling the image pickup device, an exposure control circuit for outputting an exposure end signal to the drive circuit at the end of exposure, and during the exposure, the potential of the vertical transfer unit from the photoelectric conversion unit. This is an intermediate state between the state in which the electric charge cannot be received and the state in which the electric charge is read out. The state in which the electric charge can be received but the readout from the photoelectric conversion unit is not performed and the exposure from the exposure control circuit is completed. A control unit that waits for a signal and controls the drive circuit so as to read out the accumulated charge of the photoelectric conversion unit to the vertical transfer unit according to an exposure end signal independent of the vertical synchronization signal. And

Furthermore, the control unit starts exposure in synchronization with a signal for reading unnecessary charges of the photoelectric conversion unit to a vertical transfer unit,
Further, after the unnecessary charges are swept out of the vertical transfer unit, the drive circuit is controlled so as to hold the potential of the vertical transfer unit in the intermediate state.

According to another aspect of the present invention, there is provided an electronic shutter provided in a camera for performing electronic still photography, wherein a photoelectric conversion unit, a first state in which the charge stored in the photoelectric conversion unit is read out, and a charge can be received. An image pickup device including a vertical transfer unit capable of taking a second state in which the charge stored in the photoelectric conversion unit is not read out; a driving circuit for driving and controlling the image pickup device; An exposure control circuit for outputting to a drive circuit; and during exposure, the vertical transfer unit is held so as to be in the second state and waits for an exposure end signal from the exposure control circuit. And a control unit that controls the drive circuit to be in the first state in response to an end signal.

Furthermore, the control unit starts exposure in synchronization with a signal for reading unnecessary charges of the photoelectric conversion unit to a vertical transfer unit,
Further, after the unnecessary charges are swept out of the vertical transfer unit, the drive circuit is controlled so as to hold the vertical transfer unit in the second state.

[Operation] According to this configuration, the potential of the vertical transfer unit is fixed to a state in which the accumulated charge can be received at any time, and a signal for closing the shutter is awaited.

In addition, the timing of opening the shutter can be synchronized with the timing of reading out unnecessary charges to the vertical transfer unit, and after sweeping out unnecessary charges, the potential of the vertical transfer unit is fixed to a state in which accumulated charge can be received at any time, and the shutter closes. You will have to wait for a signal.

[Embodiment] Fig. 1 shows a configuration in which the electronic shutter control device of the present invention is applied to a still video camera.

In FIG. 1, reference numeral 1 denotes an image sensor that performs photoelectric conversion.
CCD is the core of the electronic shutter.

As shown in FIG. 2, the CCD 1 has a photoelectric conversion unit 22 and a memory unit 24, and a vertical transfer CCD 23 (hereinafter, vertical is abbreviated to V) of the photoelectric conversion unit 22 and a V transfer CCD 25 of the memory unit 24, respectively. Drive control can be performed by giving drive pulses FI and FS (details will be described later). 2,3 are the above CCDs respectively
1 is a photoelectric transfer unit V-transfer CCD driver and a memory unit V-transfer CCD driver, 4 is a horizontal (hereinafter abbreviated as H) transfer CCD drive synchronization pulse generation circuit, and 5 is both V-transfer CCD drivers 2, 3 , And outputs a signal to the electronic shutter to control the opening / closing timing of the electronic shutter.

The timing control circuit 5 includes a circuit 51 that generates a drive pulse FIN (FI1 to FI4) for the photoelectric conversion unit V transfer CCD driver 2 and a drive pulse FSN for the memory unit V transfer CCD driver 3 that constitute a V-system timing control unit. (FS1-F
The charge accumulated in the circuit 52 that generates S4) and the photoelectric conversion unit is V
Circuit for generating pulses FSAN and FSBN (corresponding to the first field and the second field, respectively) for reading to the transfer CCD
53 and a TV synchronization pulse generator 54.

Reference numeral 6 denotes an exposure (AE) control circuit which measures an actual exposure amount from the start of exposure, and outputs an exposure end signal to the timing control circuit 5 when the exposure amount reaches the set exposure amount. The AE control circuit 6 includes a photometric element 7 for monitoring an exposure amount,
A capacitor 8, an open / close switch 9 provided in parallel with the capacitor 8, an amplifier 10, a comparator 11, a reference power supply 12 for determining a set level, and a signal for opening / closing an electronic shutter, that is, for starting and ending exposure. It comprises an exposure (EXP) output circuit 13 to be generated and a timer 14 for measuring the time of the start of flash emission.

Reference numeral 15 denotes a release switch for giving an instruction to open the electronic shutter, and reference numeral 16 denotes circuits 51 and 52 for generating pulses FIN and FSN after waiting for a power-on time by turning on the release switch 15.
And a timer for giving a start signal (START) for entering a still sequence to the EXP output circuit 13, a video processing circuit 17 for transferring a signal from the CCD 1 at a video rate, and a writing and recording process signal by the circuit 17 on a magnetic disk or the like. Is a flash control circuit for performing flash emission when it is determined that the set exposure amount is not reached despite exposure for a predetermined time.

FIG. 2 shows the configuration of the CCD 1 used in this embodiment. This CC
D1 includes a photoelectric conversion unit 22 in which a large number of photodiodes 21 are arranged in a plurality of columns, a vertical (V) transfer CCD 23 provided corresponding to each column of the photoelectric conversion unit 22, and the V transfer CCD 23. A V transfer CCD 25 forming a memory unit 24 in which the stored signal charges are transferred at high speed and temporarily storing the same charges, and a photoelectric conversion unit 22
And a drain 26 for reversely transferring unnecessary charges of the memory unit 24 through the V transfer CCD 23 to discharge the unnecessary charges.
And a horizontal readout CCD 27 transferred to the video processing circuit 17 at a video rate.

The operation of the electronic shutter having the above configuration will be described below in the third.
The description will be made based on the time charts of FIGS. 4 and 5 show a part of FIG. 3 in an enlarged manner on the time axis.

In these figures, times t0pt1 and t2 correspond to the main switch S0, the photometry switch S1, and the release switch S2, respectively.
ON timing. At time t3, after the release switch S2 is turned on, the FSAN pulse (a) and the FSBN pulse (b) for reading out the accumulated charges (unnecessary charges) of the photoelectric conversion unit 22 and the memory unit 24 into the V transfer CCD 23 based on the start signal. A plurality of FIN and FSN pulses (c) for high-speed reverse transfer to the drain 26
This is the timing at which the first pulse of (b) occurs.

At time t4, as can be seen from FIG. 4, the FSAN pulse (a) and FSB for reading the unnecessary charges to the V transfer CCD 23 are used.
This is the generation timing of the last pulse of the N pulse (b), and this FSBN pulse b is the EXP output circuit 13 of the AE control circuit 6.
, An exposure (EXP) output signal is generated in synchronization with this, and exposure starts, that is, accumulation of signal charges in the CCD 1 starts.

Note that the unnecessary charges are swept out an appropriate number of times (for example, 10 times) according to the structure of the CCD 1.

The start of the above exposure is a timing indicated by EXP (open) in FIG. 4, and corresponds to the opening of the shutter. Then, for the real time measurement of the shutter opening, the switch 9 of the AE control circuit 6 is opened and the charge accumulation in the capacitor 8 by the photometric element 7 is started simultaneously with the start of accumulation of the signal charges.

Also, the last FSAN to read out unnecessary charges to the V-transfer CCD23
In order to sweep out unnecessary charges read by the pulse (a) and the FSBN pulse (b), the last one FIN,
FSN pulses (c) and (d) are output, which is EXP (open)
Located at the beginning of

After the unnecessary charges are swept out by the high-speed reverse transfer, the exposure end signal generated when the exposure amount measured by the AE control circuit 6 reaches the set appropriate exposure amount, that is, EXP (close) corresponding to shutter closing. Is given to the timing control circuit 5, and FSAN, F
When the SBN pulse appears, the V-transfer CCD 23 is held at an appropriate potential without outputting the FIN and FSN pulses so that the accumulated signal charge of the CCD 1 can be immediately read out to the V-transfer CCD 23. In other words, while CCD1 accumulates signal charges,
At the same time as EXP (closed), it stands by in a readable state.

That is, when the EXP (open) signal is input, the timing control circuit 5 uses the V transfer control unit to control the FI1N to FI4N, FS1.
After sweeping out unnecessary charges as shown in FIG. 4, the N to FS4N pulses are fixed and wait for an EXP (close) signal. This V transfer control unit can be composed of, for example, a shift register in which D flip-flops are arranged.
It has a function of performing desired timing control in response to an XP signal, a “read out” signal described later, or the like.

Here, the photodiode 21 of the photoelectric conversion unit 22 and the V transfer
The operation of the CCD 23 will be described with reference to FIGS. 6 (a) and 6 (b).

In FIG. 7A, assuming that vertical portions of the V transfer CCD 23 to which the four-phase drive pulses FI1 to FI4 are given are V1 to V4, the photodiodes PD are connected to V1 and V3.
V transfer CCD23 is L (low), M (middle), H (high)
Are driven in four phases by the three types of pulses. FIG. 3B shows the potential at the portion indicated by the broken line X in FIG. 3A, and FIG. 3C shows the potential at the portion indicated by the broken line Y in FIG.

As can be seen from these figures, the readout of the stored
This is performed by setting the drive pulses FI1 and FI3 respectively corresponding to 1 and V3 to the ternary level H. V transfer section CCD driver
Pulses FI1N, FI3N, FSA
By inputting N and FSBN, the pulses FI1 and FI3 become H.

Immediately before reading the stored charge, the pulses FI1N and FI1N
By setting 3N to L, the pulses FI1 and FI3 are set to the M level. In this way, the pulse FI
1. FI3 can be a ternary level H. Further, the pulse FI2 is set to L and the pulse FI4 is set to M in order to absorb potential fluctuation at the time of reading and to prevent unnecessary mixing of the read charges. To do this,
The pulse FI2N is set to H, and the pulse FI4N is set to L.

Thus, the potential of the pulses FI1N to FI4N is L,
It becomes H, L, L and is in a readable state. The pulses FS1N to FS4N are in a state where they can be matched with the above-mentioned FI1N to FI4N.

After the exposure is started by opening the shutter, if the proper exposure amount is not reached even if a predetermined time has elapsed, or if it is predicted that the exposure amount will not be reached, a flash emission start signal is output to the flash control circuit 19. Flash emission is performed as shown in FIG. This flash fires
Due to the structure of the CCD 1, exposure for an excessively long time increases the dark current, which is not preferable. Therefore, it is necessary to keep the exposure time within a predetermined time.

Here, the flash firing start timing may be obtained by turning on the photometering switch S1 before turning on the release switch S2 and calculating by a microcomputer outside the figure based on the pre-metered information. Flash boosting is performed in advance as shown in FIG.

Next, time t5 is a timing at which EXP (close), which is an exposure end signal corresponding to shutter closing, is output from the EXP output circuit 13, and this signal outputs FSAN and FSBN pulses (a ', b'). Thus, the signal charges stored in the photoelectric conversion unit 22 are read out to the V transfer CCD 23. Further, subsequently, the memory unit 2 receives the FIN pulse (e) and the FSN pulse (f).
4. High-speed transfer to the V-transfer CCD 25 is performed. At this time, CCD1
The reading of signals from to the outside is prohibited.

During the high-speed reverse transfer of the unnecessary charges to the drain 26, the EXP (closed) signal cannot be output. Therefore, the high-speed reverse transfer time becomes the shortest shutter speed.

In the present embodiment, a flash emission stop signal is also output at the same time as the EXP (close) signal. However, the flash stop operation may be omitted and the flash may be fully emitted.

A time t6 indicates a timing at which a signal read output “read out” is given from the microcomputer (not shown) to the timing control circuit 5 after a lapse of time required to complete the transfer of the accumulated signal charge to the memory unit 24. Before the “read out” output is supplied, the timing control circuit 5 for driving and controlling the CCD 1 is generated from the synchronizing pulse generating circuit 54 and operates in synchronism with the vertical (in which the video processing circuit 17 and the image recording unit 18 operate). V) Synchronous operation is performed separately from the horizontal (H) synchronization signal. However, after the “read out” output is given, the operation is performed in synchronization with the TV synchronization signal, and the signal is read out to the outside. Will be.

That is, as shown in FIG. 5, the FSN pulse (g) is output from time t7 to t8 after waiting for the V synchronization signal, and synchronization is performed at the video rate from the V transfer CCD 25 of the memory unit 24 to the horizontal read CCD 27. Therefore, the signal information is sequentially read out,
The image is recorded by the image recording unit 18 via the video processing circuit 17. In FIG. 3, this recording operation is shown as disk writing. Here, the disk is driven by a spindle motor started up by turning on the photometric switch S1.

Note that the pulses of FS1N to FS4N are strictly slightly out of phase, and image data on one scanning line can be obtained by a set of temporally continuous pulses of FS1N to FS4N. One screen is formed by the read data at t8.

Also, by changing the phase of each of the four phases of FIN and FSN, the high-speed reverse transfer of charges to the drain 26 and the memory section can be performed.
It is possible to switch between high-speed transfer of charges to the 24 V transfer CCDs 25.

[Effects of the Invention] As described above, according to the present invention, accumulated charges can be read out to the vertical transfer unit at the same time as when the shutter is closed.

Further, after the shutter is opened, the vertical transfer unit is reset after the unnecessary charges are swept out so that the stored charge of the photoelectric conversion unit is synchronized with the signal for reading the stored charge to the vertical transfer unit, and the stored charge can be read to the vertical transfer unit at the same time as the shutter is closed. Since the signal is fixed to be readable, the opening of the shutter and the actual start of signal charge accumulation can be made coincident, and the signal charge can be read out to the vertical transfer unit at the same time as the shutter is closed. As a result, real-time photometry becomes possible, and accurate exposure control by highly accurate photometry becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of a still video camera implementing an electronic shutter control device of the present invention, FIG. 2 is a diagram of a CCD used in the electronic shutter, and FIG. 3 is a time chart for explaining the operation of the device. , FIG. 4 and FIG. 5 are enlarged time charts of a part of FIG. 3, and FIG.
FIGS. 3B and 3C are diagrams illustrating a configuration for explaining operations of a photoelectric conversion unit and a V transfer CCD, respectively, and showing a potential state of each unit. 1 ... CCD, 5 ... Timing control circuit (drive circuit), 6 ... A
E control circuit, 7 photometric element, 17 video processing circuit, 22 photoelectric conversion unit, 23 vertical transfer CCD, 24 memory unit, 25 vertical transfer CCD, 26 drain drain, 27 horizontal read CCD.

Continuation of front page (72) Inventor Kazunori Sato 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-60-149270 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/335 H04N 5/225 H04N 5/238

Claims (4)

(57) [Claims] An electronic shutter provided in a camera for performing electronic still photography, comprising: a photoelectric conversion unit; and a vertical transfer unit for reading out charges accumulated in the photoelectric conversion unit. A drive circuit for controlling the driving of the exposure circuit; an exposure control circuit for outputting an exposure end signal to the drive circuit at the end of exposure; and a state in which the potential of the vertical transfer unit cannot be received from the photoelectric conversion unit during the exposure. An intermediate state between the state in which the charge is read and the state in which the charge can be received but the reading from the photoelectric conversion unit is not performed, and the exposure end signal from the exposure control circuit is awaited, and the vertical synchronization signal is output. According to the exposure end signal independent of
An electronic shutter control device, comprising: a control unit that controls the drive circuit so as to read out the accumulated charges of the photoelectric conversion unit to the vertical transfer unit. 2. The control section starts exposure in synchronization with a signal for reading unnecessary charges of the photoelectric conversion section to a vertical transfer section, and sweeps out the unnecessary charges from the vertical transfer section, and then controls the vertical transfer. 2. The electronic shutter control device according to claim 1, wherein the control circuit controls the drive circuit so as to hold the potential of the unit in the intermediate state. 3. An electronic shutter provided in a camera for performing electronic still photography, comprising: a photoelectric conversion unit; a first state in which electric charges stored in the photoelectric conversion unit are read; An image pickup device including a vertical transfer unit capable of taking a second state in which the charge stored in the photoelectric conversion unit is not read out; a drive circuit for driving and controlling the image pickup device; An exposure control circuit for outputting to the circuit; during exposure, the vertical transfer unit is held so as to be in the second state, and waits for an exposure end signal from the exposure control circuit; A control unit that controls the drive circuit to be in the first state in accordance with a signal. 4. The control section starts exposure in synchronization with a signal for reading out unnecessary charges of the photoelectric conversion section to a vertical transfer section, and sweeps out the unnecessary charges from the vertical transfer section, and then performs the vertical transfer. The electronic shutter control device according to claim 1, wherein the electronic shutter control device controls the drive circuit so as to hold the unit in the second state.