JP2796817B2 - Driving device for image sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving device of an image sensor, and more specifically, to a driving device of an image sensor capable of controlling a charge accumulation time of an image sensor such as a CCD.

[Prior art and its problems] In recent years, various electronic still cameras using a CCD image sensor instead of a conventional silver halide film have been developed. This type of electronic still camera uses a mechanical shutter similar to a conventional camera, and mechanically adjusts the shutter speed, that is, the time during which the light receiving unit of the CCD image sensor receives the subject light.

By the way, the CCD image sensor can obtain a shutter speed control function similar to that of a conventional mechanical shutter by changing the time interval for transferring the charges accumulated in the light receiving unit to the vertical transfer CCD, that is, the accumulation time. Therefore, recently, it has been attempted to reduce the weight of the camera by adopting a pure electronic shutter that actively utilizes the adjustment of the charge accumulation time.

However, a CCD image sensor used in a conventional electronic still camera has a configuration in which an accumulation control signal for transferring signal charges accumulated in a light receiving unit to a vertical transfer CCD is periodically output. Therefore, a device capable of outputting the accumulation control signal at a desired time is newly provided. Providing such a device newly leads to an increase in the cost of the camera, which is not preferable.

[Object of the Invention] The present invention has been made in view of such conventional problems, and an image pickup device driving device capable of controlling a shutter speed only by an existing device without providing a new device is provided. The purpose is to provide.

[Summary of the Invention] The present invention for achieving the above object includes: an image pickup unit having a light receiving unit and a vertical transfer unit for converting a subject image into electric charges and storing the charges; periodically synchronizing signals, transfer pulses, The transfer pulse is output as an accumulation control pulse as a readout pulse for reading out the electric charge transferred to the vertical transfer unit. When an external sweep request signal is received, the transfer pulse is transferred to the vertical transfer unit instead of the transfer pulse. Pulse signal output means for outputting a high-speed sweeping pulse for sweeping out charged electric charges;
A transfer pulse different from the transfer pulse of the pulse signal output means and a forced accumulation control pulse, which are used as a forced accumulation control signal for transferring the signal charges of the light receiving section to the vertical transfer section, and thereafter, the sweep request signal Imaging control means for outputting a signal; and a first switching means for selecting an accumulation control pulse output from the pulse signal output means and a forced accumulation control pulse output from the control means and connecting to the imaging means. A second switching means for selecting a transfer pulse or a high-speed sweeping pulse output from the pulse signal output means and a transfer pulse output from the control means and connecting to the image pickup means; And means for synchronizing with the synchronizing signal output from the pulse signal output means after the ON signal is output from the release switch. 2 operating the switching means, connecting the imaging means to the control means, outputting the forcible accumulation control pulse, the transfer pulse and the sweep-out request signal, and then operating the first and second switching means to generate the pulse. It is characterized in that the signal output means is connected to the imaging means.

According to this configuration, the regular accumulation control signal and the readout signal (vertical and horizontal transfer signals) are periodically output from the pulse signal output unit to the image pickup unit.

On the other hand, when the control means starts the shutter operation, a forced accumulation control signal is output from the control means to the imaging means at the shutter time start reference, unnecessary charges are transferred to the vertical transfer section, and a sweep-out request is sent to the pulse signal output means. A signal is output, and a sweep signal (high-speed vertical reverse transfer signal) is output from the pulse signal output means, and unnecessary charges in the vertical transfer unit are swept out at high speed.

Then, the signal charge accumulated in the light receiving section after the forced accumulation control signal is output from the control means is read out by the periodic accumulation control signal and the readout signal output from the pulse signal output means.

The forced accumulation control signal output from the output control means can be output at an appropriate timing according to the brightness of the subject or at a timing set by the photographer.

With the above operation, a pure electronic shutter using only the imaging unit can be realized.

Also, since the pulse signal output means and the control means use the existing ones and there is no need to newly provide them, the electronic shutter can be constituted only by changing the control program without increasing the cost.

[Explanation of Embodiment] An embodiment of a driving device for an image sensor according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a driving device of an image sensor.

As shown in the figure, a driver 12 for driving the CCD image pickup device 11 is connected to the CCD image pickup device 11 as an image pickup means. The driver 12 includes a CCD drive clock generator 13 as a pulse signal output unit and a microprocessing unit (MPU) as a control unit via switching switch circuits 20A and 20B as first and second switching units. 14 are connected.

From the clock generator 13, the charges accumulated in each light receiving element (photodiode) of the CCD image sensor 11 are simultaneously transferred to the vertical transfer CCD as a vertical transfer unit at a fixed cycle (usually about 1/60 second cycle) The periodic accumulation control pulse and the relatively low-speed transfer pulse as the periodic accumulation control signal are respectively transmitted to the switch circuit 20A via the CTG, and
Is output to the switch circuit 20B via the CV ₁ ~CV _4. Note that the clock generator 13 also periodically outputs a vertical synchronization signal (vertical synchronization pulse VD) and a horizontal synchronization signal (not shown) as is well known. In the case of the present embodiment, the clock generator 13 outputs a vertical synchronization pulse VD to the MPU 14 and the recording / reproducing unit 18, and outputs a periodic accumulation control pulse in synchronization with the vertical synchronization pulse VD.

Further, the clock generator 13 outputs horizontal and vertical transfer signals as read signals for reading the signal charges transferred to the vertical transfer CCD. Incidentally, among the read signal, but the vertical transfer signal is output via the CV ₁ ~CV _4, constituting about a horizontal transfer signal is omitted in the description of this embodiment for simplicity of explanation.

The transfer pulses of CV _{1 to} CV ₄ are either an accumulation control signal or a vertical transfer signal (read signal or high-speed sweep signal) according to the level of the accumulation control pulse of the CTG.

 Next, a configuration which is a feature of the present invention will be described.

The MPU 14 generally controls the operation of the entire driving device, and from this, a switching signal that causes the switching circuit 20A, 20B to perform a switching operation is output via the PS. The connection position of the switch circuits 20A and 20B, that is, whether the MPU 14 is connected to the driver 12 or the clock generator 13 is connected, depending on whether the switching signal output to the PS is "H" or "L". Is determined.

Further, the MPU 14 outputs a forced accumulation control pulse and a transfer pulse as a forced accumulation control signal for simultaneously transferring the signal charges accumulated in each photodiode of the light receiving unit of the CCD image sensor 11 to the vertical transfer CCD. You. Force storage control pulse is output to the change-over switch 20A via the PTG, the transfer pulse is output to the change-over switch 20B via the PV ₁ ~PV _4.

Further, the MPU 14 sends a sweep request pulse as a sweep request signal to the clock generator 13 as a PH signal.
Output via V. When the sweep-out request pulse is output, the clock generator 13, high-speed vertical transfer pulses as high-speed sweep signal which swept unnecessary charges at a high speed, CV ₁ ~CV ₄ a through switching switch circuit 20
Output to B.

From the changeover switch circuit 20A to the driver 12,
The CTG or PTG accumulation control pulse output from the MPU 14 or the clock generator 13 is output via the TG.

For the driver 12 from the switch circuit 20B, CV ₁ ~CV
Transfer pulses ₄ or PV ₁ ~PV ₄ is output through the V ₁ ~V _4.

And for the CCD image sensor 11 from the driver 12, as accumulation control signal, or the transfer pulses as read signal or high-speed sweep signal is output via the ΦV ₁ ~ΦV _4.

As mentioned above, clock generator 13 or MPU1
Which storage control pulse output from 4 is used, and which transfer pulse output from MPU 14 or clock generator 13 is used, is determined by a switching signal output from MPU 14 to PS.

The transfer pulse of ΦV ₁ to ΦV ₄ output from the driver 12 is, depending on the level of the TG accumulation control pulse, an accumulation control signal for transferring the charge of the photodiode to the vertical transfer CCD, or It becomes a read signal for vertically transferring charges or a high-speed sweep signal. That is,
When the transfer pulse is output together with the accumulation control pulse, it becomes an accumulation control signal, and otherwise, it becomes a read signal or a sweep signal.

Note that the sweeping out of the accumulated charges transferred to the vertical transfer CCD is performed to a charge sweeping drain provided in a direction opposite to the horizontal transfer CCD.

The photodiode constituting the light receiving element of the CCD image sensor 11 is formed with an image of a subject incident from the photographing lens 15 and passing through the aperture 16, and the subject image is captured in the form of signal charges. The horizontal transfer CCD of the CCD image sensor 11 has
The recording / reproducing unit 18 is connected. The recording / reproducing unit 18 records information on signal charges output from the CCD image pickup device 11 on the magnetic disk 17 as a video signal, or reads and reproduces a video signal recorded on the magnetic disk 17. The operations of the magnetic disk 17 and the recording / reproducing unit 18 are controlled by the MPU 14.

Further, the MPU 14 is connected to a photometry unit 22 that logarithmically compresses the photometry signal from the photometry element 21 that measures the brightness of the subject, performs A / D conversion, and outputs the result as digital photometry data. The MPU 14 calculates an optimal aperture value and shutter speed (charge accumulation time) based on the photometric data.

The MPU 14 has an aperture driving circuit 23 for driving the aperture 16.
And the release button 24 are in contact with each other. When an ON signal is output from the release button 24, the MPU 14 performs the photometric calculation, controls the aperture of the aperture 16 via the aperture drive circuit 23, and drives the CCD image sensor 11.

FIG. 2 shows an example of a specific circuit of the inversion type driver 12. As shown in FIG.

As shown in the figure, a plurality of sets of pulse signals are output to ΦV ₁ to ΦV ₄ for driving the CCD image sensor 11 by a combination of a TG accumulation control pulse and a transfer pulse of CV ₁ to CV _4. It has become.

When the accumulation control pulse level of the TG is “L”, the changeover switch element 30 is in a state of connection with V _H as shown in FIG.
When the same pulse level is "H", the switches to connect to the V _M.

Changeover switch element 31 is in a connection state of the switch 30 as shown at the time of transfer pulse level V ₁ is "L", when the same level of "H" switches to connect the V _L.

Changeover switch element 32 may, when the transfer pulse level V ₂ is "L", is in connection state between V _M 'as shown,
When the level is “H”, the connection is switched to _VL .

The levels of V _H , V _M (V _M ′), and V _L are V _H > V _M >
_VL .

V ₃ and the circuit relating to V _4, respectively the V ₁ and V ₂
The circuit is configured identically.

A specific timing chart of the driver 12 is shown in FIG.
It is shown in the figure. When there is no input of TG accumulation control pulses, since the changeover switch element 30 is switched to V _M,
From? V _1, transfer pulses V ₁ is output is inverted.

From ΦV ₂ , ΦV ₃ , ΦV ₄ , transfer pulses of V ₂ , V ₃ , V ₄ are inverted and output in the same manner as V ₁ .

In the above case, the “H” level of V _{1 to} V ₄ is ΦV ₁
V _M of ~ΦV _4, the V _M 'level, the "L" level corresponding to V _L level.

Further, when there is an input of the storage control pulse TG, since the changeover switch element 30 is switched to the V _H as shown, V _1, V ₃
When the level of "L" is,? V _1, the level of? V ₃ is V _H.

As described above, ΦV ₁ and ΦV ₃ are ternary signals,
When ΦV ₁ and ΦV ₃ are at the highest level, _VH , the signal becomes an accumulation control signal, and the electric charge accumulated in the photodiode is transferred to the vertical transfer CCD. On the other hand, the level of ΦV _{1 to} ΦV ₄ is V
_M, becomes the vertical transfer pulse when taking a V _M 'and V _L, the charges transferred to the CCD for vertical transfer, and transfers the vertical transfer CCD top.

Next, a specific operation of the image pickup device control device of the present invention thus configured will be described with reference to the flowchart shown in FIG. Note that the flowchart will be described with reference to the schematic configuration diagram of FIG. 1 and the timing charts of FIG. 5 and FIG.

First, when the release button 24 is turned on, the MPU 14
The S switching pulse is set to “H”, and the PHV sweep request signal is set to “L” (steps 51 and 52). With this setting, a clock generator 13 is connected to the driver 12, and a periodic accumulation control pulse is generated from the clock generator 13 at a period of 1/60 second, as shown in FIG.
G and the transfer pulse is output to CV ₁ to CV ₄ . That is, 1/6
An image of the subject is read from the CCD image sensor 11 at a cycle of 0 seconds and output to the recording / reproducing unit 18.

Then, the MPU 14 performs a photometric calculation based on the photometric data on the brightness of the subject output from the photometric unit 22 (step 53), and obtains an optimal aperture value AV and shutter speed TV. And the aperture drive circuit based on the optimal aperture value AV
23 is controlled to set the aperture 16 to an optimal aperture value (steps 54 and 55).

When the setting of the diaphragm 16 is completed, the MPU 14 sets the switching pulse PS to "L" after waiting for the VD pulse shown in FIG. 5 to become "H" (steps 56 and 57). by this,
The switch circuits 20A and 20B perform a switching operation, and the MPU 14 is connected to the driver 12, so that the MPU 14 can output a forced accumulation control pulse and a transfer pulse. That is, the driver 12 is ready to output an accumulation control signal.

The MPU 14 calculates the optimal shutter speed T calculated in step 53.
When V is obtained, as shown in FIGS. 5 and 6, P
The forced accumulation control pulses to the TG, the PV ₁ ~PV ₄ outputs a transfer pulse. As a result, unnecessary charges accumulated in the light receiving section of the CCD image sensor 11 are simultaneously transferred to the vertical transfer CCD. (Step 58). When the forced accumulation control pulse is output, when the shutter speed TV is faster than 1/60 second, the clock generator 13 outputs the next periodic accumulation control pulse. It can be obtained by back-calculating the shutter speed TV from the time when the pulse is output.

Then, the MPU 14 waits until the VD pulse shown in FIG. 5 rises to “H”, and sets the PS switching pulse and the PHV sweep request signal to “H” (steps 59 and 6).
0). As a result, CV ₁ to CV
₄ a high-speed sweep pulse is output for a predetermined time,
The transfer pulse as a high-speed sweep pulse from ΦV ₁
Unnecessary charges that are output to the CCD image sensor 11 via ΦV ₂ and transferred to the vertical transfer CCD of the CCD image sensor 11 are swept out at high speed. The high-speed sweep pulse ends before the clock generator 13 outputs the next periodic accumulation control pulse.

From the clock generator 13 is next periodic accumulation control pulse is output to the CTG, transfer pulse when it is output to the CV ₁ ~CV _4, the signal charges accumulated in the optimal shutter speed TV time is transferred to the vertical transfer CCD. After the transfer, the MPU 14
The REC gate 18 is opened to start recording the signal charge (step 61). That is, the vertical and horizontal transfer signals output from the clock generator 13
The signal charges sequentially output from the CCD are recorded on the magnetic disk as video signals via the recording / reproducing section 18.

When the recording for one screen is completed, the PHV sweep request pulse is set to "L" to return to the initial state (step 6).
2, 63).

As described above, according to the present embodiment, the forced accumulation control signal for controlling the shutter time and the sweeping request signal for sweeping out unnecessary charges are output from the existing MPU 14, and the high-speed sweeping signal for sweeping out unnecessary charges is based on the existing MPU 14. Since the signal is output from the clock generator 13, a pure electronic shutter can be obtained only by changing the software of the existing system.

In the above embodiment, the type of the CCD image sensor is an interline transfer type having no memory area. However, the present invention is not limited to this. Is applicable.

Further, in the present embodiment, an example of the automatic exposure control in which the shutter speed changes according to the brightness of the subject has been described, but the present invention may be configured to set the shutter speed manually.

[Effects of the Invention] As is clear from the above description, the present invention provides a forced accumulation control pulse for arbitrarily controlling an exposure time (charge accumulation time) in an imaging device such as a CCD driven by an existing pulse signal output unit. The transfer pulse and a sweep request signal for sweeping out unnecessary charges in the vertical transfer unit in a short time are output from the control unit, and are transferred to the vertical transfer unit after the forcible accumulation control pulse and the transfer pulse are output. The unnecessary signal is swept out, the signal charge stored in the light receiving unit is transferred to the vertical transfer unit, and the signal charge transferred to the vertical transfer unit is read out by the pulse signal output unit. Since it is executed by the transfer pulse, without providing a new signal output means,
An electronic shutter whose shutter speed can be controlled by existing pulse signal output means and control means can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a driving device for an image sensor according to the present invention. FIG. 2 is a diagram showing an example of a specific circuit of an inversion type driver. FIG. 3 is a timing chart of the inversion type driver shown in FIG. 2, FIG. 4 is an operation flowchart of the driving device of the image pickup device shown in FIG. 1, and FIGS. 4 is a timing chart of each unit of the image sensor driving device illustrated in FIG. 11: CCD image sensor (imaging means), 12: driver (pulse signal output means), 13: clock generator (pulse signal output means), 14: MPU (control means), 20A, 20B: switch circuit (control means) .

Claims (1)

(57) [Claims] 1. An imaging means comprising a light receiving unit and a vertical transfer unit for converting a subject image into electric charges and storing the charge; and periodically transferring a synchronization signal, a transfer pulse, and the transfer pulse to the vertical transfer unit. A pulse for outputting a storage control pulse as a read pulse for reading out the stored charge, and outputting a high-speed sweep pulse for sweeping the charge transferred to the vertical transfer unit instead of the transfer pulse when receiving a sweep request signal from outside. And a signal output means for outputting a transfer pulse different from the transfer pulse of the pulse signal output means and a forced storage control pulse used as a forced storage control signal for transferring the signal charge of the light receiving section to the vertical transfer section, and thereafter Imaging control means for outputting the sweep request signal to the storage means; an accumulation control pulse output from the pulse signal output means; A first switching means for selecting a forced accumulation control pulse to be connected to the imaging means; a transfer pulse or a high-speed sweep pulse output from the pulse signal output means; and a transfer pulse output from the control means. And a second switching means for connecting to the imaging means, and wherein the control means outputs an ON signal from a release switch, and then outputs the synchronization signal from the pulse signal output means. After the first and second switching means are operated in synchronization with the control circuit, the imaging means is connected to the control means, and the forced accumulation control pulse, the transfer pulse and the sweep request signal are output. And a pulse signal output unit connected to the imaging unit by operating the switching unit.