JPH0563996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a driving device for an image sensor in an electronic still camera that can continuously monitor in movie mode and record one image at a time in still mode.

"Prior Art and its Problems" In recent years, various electronic still cameras have been developed that use CCD image sensors instead of conventional silver halide films. This CCD image sensor has a shutter speed control function similar to that of a conventional mechanical shutter by changing the time interval at which the charge accumulated in the light receiving section is transferred to the vertical transfer CCD (vertical transfer section), that is, the accumulation time. can get. Recently, efforts have been made to reduce the weight of cameras by adopting pure electronic shutters that actively utilize this charge accumulation time adjustment.

In order to reduce costs, conventional electronic still cameras use an interline transfer type CCD image pickup device and drive device, which is similar to the image pickup unit used in video cameras.

This CCD imaging unit for video cameras has
The signal charges accumulated in the light receiving section are periodically (every 1/60 seconds) transferred all at once to the vertical transfer CCD (vertical transfer section), and this signal charge is used for the periodic transfer of the next signal charge. They are read out sequentially before being read out.
Transfer to the vertical transfer CCD is performed by a periodic accumulation control signal, and reading is performed by a read signal consisting of vertical and horizontal transfer signals.

During electronic shutter operation, electronic charges are forcibly transported at a predetermined timing, and exposure is started. The unnecessary charge transferred to the vertical transfer CCD is swept out in a short time immediately before the periodic accumulation control signal is output. After the above forced transfer,
The signal charges accumulated in the light receiving section until the periodic transfer (exposure time) are transferred to the vertical transfer CCD by a periodic accumulation control signal, and then sequentially from the vertical transfer CCD by a periodic readout signal. It is being read.

When such a pure electronic shutter is adopted, the signal charge accumulated in the light receiving section is periodically read out at the smear level in the movie mode, and during electronic shutter operation, the charge is accumulated for a time corresponding to the shutter speed. Thereafter, the smear level in the still mode in which signal charges accumulated within this time are read out is different, and the image becomes unbalanced.

For example, in the movie mode, a periodic accumulation control signal is outputted from the light receiving section every 1/60 seconds to transfer signal charges to the vertical transfer CCD, and then read out by a readout signal. Therefore, signal charges that could not be read out in the previous frame are used for vertical transfer.
There were cases where some remained on the CCD.

However, when capturing an image at a shutter speed of 1/60 seconds in still mode, after the forced accumulation control signal is output and immediately before the periodic accumulation control signal is output, the charge transferred to the vertical transfer CCD is be swept away. Therefore, unnecessary charges are used for vertical transfer.
Almost no residue remained on the CCD.

In other words, the smear level tends to be higher in the movie mode, even though the charge accumulation time is the same.

This kind of imbalance is not desirable, so
Although it is necessary to perform circuit adjustment, this circuit adjustment is extremely difficult and time-consuming.

``Object of the Invention'' The present invention has been made in view of these conventional problems, and it is possible to control the charge accumulation time of the imaging means, and also to adjust the smear level in movie mode and still mode. It is an object of the present invention to provide a driving device for an image sensor that can be easily adjusted to be the same at different times.

"Summary of the Invention" To achieve the above object, the present invention provides an imaging means including a light receiving section and a vertical transfer section that converts a subject image into signal charges and accumulates them, and a signal charge that can be accumulated in the light receiving section. periodically outputting a periodic accumulation control signal for transferring the signal charges to the vertical transfer section, and a readout signal for the signal charges transferred to the vertical transfer section;
A pulse signal output that can be used to input a high-speed sweep signal to sweep out the charges in the vertical transfer section periodically after stopping the output of the read signal and before outputting the next periodic accumulation control signal, or when inputting a sweep request signal from the outside. means for outputting a forced accumulation control signal for transferring the signal charge of the light receiving section to the vertical transfer section at any time, and outputting the sweep-out request signal after outputting the forced accumulation control signal; The present invention is characterized by comprising a sweep request switch means for turning on/off the output of the high-speed sweep signal output to the controller.

Therefore, in normal times (movie mode), the regular accumulation control signal and the readout signal are periodically output from the pulse signal output means to the imaging means, and the signal charge is outputted from the vertical transfer section at a normal speed. transfer is performed.

On the other hand, when the electronic shutter is operating (in still mode)
In this case, a forced accumulation control signal is outputted from the control means to the imaging means, and a sweep request signal is outputted to the pulse signal output means, so that unnecessary charges in the light receiving section are swept out to the vertical transfer section in a short time. . As a result, an electronic shutter using only the imaging means is realized.

When the sweep request signal output means is activated in the movie mode, the pulse signal output means outputs a sweep signal for each field.
Unnecessary charges remaining in the vertical transfer section are swept out in a short time.

As a result, the smear level in movie mode and still mode is made uniform, and uniform images can be obtained in movie mode and still mode.

"Embodiments of the Invention" Examples of an image sensor driving device according to the present invention will be described in detail below with reference to the drawings.

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

As shown in the figure, a driver 12 for driving the CCD image sensor 11 is connected to a CCD image sensor 11 serving as an imaging means. Driver 12
A CCD driving clock generator 13 as a pulse signal output means and a microprocessing unit (MPU) 14 as a control means are connected via changeover switch circuits 20A and 20B.
is connected. Note that the MPU 14 and the changeover switch circuits 20A and 20B constitute a control means.

The CCD image sensor 11 uses an interline transfer method, and a subject image that enters from the photographing lens 15 and passes through the aperture 16 is formed on each photodiode constituting the light receiving section, and the subject image is converted into a signal charge. captured in the form of Aperture 16 is MPU
The aperture adjusting circuit 23, which is driven and controlled by the aperture adjusting circuit 14, constitutes an aperture adjusting means.

The signal charges accumulated in the photodiodes are transferred all at once to a vertical transfer CCD serving as a vertical transfer section. The charge transferred to the vertical transfer CCD is
When reading, data is sequentially transferred to the horizontal transfer CCD,
It is read out from the horizontal transfer CCD for each horizontal line,
At the time of sweeping out, it is swept out to a sweeping drain provided on the opposite side from the horizontal transfer CCD.

A recording/reproducing section 18 is connected to the CCD for horizontal transfer of the CCD image sensor 11 . This recording/playback section 18 is
Information regarding signal charges output from the CCD image sensor 11 is recorded as a video signal on the magnetic disk 17, or the video signal recorded on the magnetic disk 17 is read out and reproduced. The operation of the magnetic disk 17 and the recording/reproducing section 18 is controlled by the MPU 14.
controlled by.

An electronic viewfinder 28 is connected to the recording/playback section 18 , and images input to the recording/playback section 18 can be viewed on this electronic viewfinder 27 .

The MPU 14 logarithmically compresses the side light signal from the photometric element 21 that measures the brightness of the subject, and the A/D
A photometry section 22 that converts the data and outputs it as digital photometry data is connected. The MPU 14 calculates the optimum aperture value and shutter speed (charge accumulation time) based on the photometric data.

Further, the MPU 14 is connected to a release button 24 and a sweep switch 25 as a sweep request signal output means. When an on signal is output from the release button 24, the MPU 14
The above photometric calculation is performed on the aperture 1 via the aperture drive circuit 23.
6, driving the CCD image sensor 11, recording, etc.

When the on signal is output from the sweep switch 25, the MPU 14 outputs a sweep request signal to the clock generator 13 via the PHV.

Next, the configuration and operation related to the signals that drive the CCD image sensor 11 will be explained.

From the clock generator 13, periodically,
An accumulation control pulse as a regular accumulation signal, a relatively low-speed transfer pulse, and a read pulse as a read signal for reading signal charges transferred to the vertical transfer CCD are output.

The periodic accumulation control pulse and the low-speed transfer pulse are output at constant intervals (1/60 second intervals), and the charges accumulated in the light receiving section of the CCD image sensor 11 are transferred all at once to the vertical transfer CCD.

The read pulse is output periodically while the regular accumulation control pulse is output, and reads out the charge transferred to the vertical transfer CCD. Note that the read pulse is a vertical transfer pulse that sequentially moves the signal charge transferred to the vertical transfer CCD to the horizontal transfer CCD, and
Although it consists of a horizontal transfer pulse for reading out the signal charge of one horizontal line transferred to the horizontal transfer CCD, in this embodiment, for the sake of simplicity, the horizontal transfer pulse will not be explained.

Further, the clock generator 13 outputs a high-speed transfer pulse as a sweep signal for discharging the charge of the vertical transfer CCD in a short time. This high-speed transfer pulse is output for a predetermined period of time after the output of the above-mentioned read pulse is completed, provided that the sweep request pulse is input from the MPU 14, and the output ends before the output of the next periodic accumulation control pulse. do.

The periodic accumulation control pulse is sent via CTG, and both transfer pulses and readout pulses are sent via CV ₁ to _{CV 4} to changeover switch circuits 20A and 20, respectively.
It is output to B.

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

The MPU 14 comprehensively controls the operation of the entire drive device, and from here the switching pulses are
Output via PS. Depending on whether the switching pulse output to this PS is “H” or “L”,
Connection position of changeover switch circuits 20A and 20B,
In other words, connect the MPU 14 to the driver 12,
It is determined whether to connect the clock generator 13.

The MPU 14 outputs forced accumulation control pulses and transfer pulses as forced accumulation control signals that cause the signal charges accumulated in each photodiode of the light receiving section of the CCD image sensor 11 to be transferred all at once to the vertical transfer CCD. The forced accumulation control pulse is
The transfer pulse is outputted to the changeover switch circuit 20A via PTG, and the transfer pulse is outputted to the changeover switch circuit 20B via _PV1 to _PV4 .

Further, the MPU 14 outputs a sweep request pulse as a sweep request signal to the clock generator 13 via the PHV. When this sweep request pulse is output, the clock generator 13 outputs a high-speed operation pulse as a high-speed sweep signal that sweeps out unnecessary charges at high speed as described above to the changeover switch circuit via CV ₁ to _{CV 4} . It is output to 20B.

As already explained, when the on signal is output from the sweep switch 25, the MPU 14 outputs a sweep request pulse to the clock generator 13 via the PHV. The clock generator 13 that receives this sweep request pulse PHV outputs the signal via the changeover switch circuit 20B.
A high-speed sweep pulse that sweeps out the charge of the vertical transfer CCD at high speed is outputted to the CCD image sensor 11 for a predetermined time after the end of output of the read pulse for each field, and is outputted to the vertical transfer CCD for each frame. Sweeping is executed.

FIG. 2 shows the area around the sweep switch 25.
A specific circuit of the MPU 14 is shown. A sweep switch 25 is connected to one input of the OR gate 26.
is input, and a still/movie switching signal inside the MPU 14 is input to the other input. Still/movie switching signal is MPU14
This signal is “H” in still mode and “L” in movie mode.

The output of the OR gate 26 is input to one of the inputs of the AND gate 27. A sweep request signal within the MPU 14 is input to the other input of the AND gate. This sweeping request signal is output periodically at a predetermined timing in the movie mode, and is output once at a predetermined timing in the still mode. And gate 27
The output is PHV.

Therefore, in the movie mode, the PHV periodically outputs a sweep request pulse on the condition that the "H" signal (on signal) is output from the sweep switch 25, and in the still mode, the sweep request pulse is output at a predetermined period. A sweep request pulse is output.

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

From the switch circuit 20B to the driver 12, the MPU 14 or the clock generator 13
Transfer pulses CV ₁ to CV ₄ or P ₁ to _{P 4} outputted from are alternatively outputted via V ₁ to _{V 4} .

Transfer pulses are output from the driver 12 to the CCD image sensor 11 as an accumulation control signal, a readout signal, or a high-speed sweep signal via ФV ₁ to ФV ₄ .

As mentioned above, which accumulation control pulse output from the clock generator 13 or the MPU 14 is used, and which transfer pulse is used depends on the switching pulse output from the MPU 14 via the PS. It is determined.

The transfer pulse of ФV ₁ to ФV ₄ output from the driver 12 transfers the charge of the photodiode to the CCD for vertical transfer according to the accumulation control pulse level of the TG.
Accumulation control signal to be transferred to or for vertical transfer
This serves as a readout signal or high-speed sweep signal that vertically transfers the charge on the CCD. That is, when the transfer pulse is output together with the accumulation control pulse, it becomes an accumulation control signal, and when not, it becomes a readout signal or a sweep signal.

FIG. 3 shows an example of a specific circuit of the inverting type driver 12.

As shown in the figure, the CCD image sensor 11
Plural sets of pulse signals are output to ФV ₁ to _{ФV 4} that drive the TG by combining the TG accumulation control pulse and the transfer pulses CV ₁ to _{CV 4} .

When the TG accumulation control pulse level is "L", the changeover switch element 30 switches V _H as shown in the figure.
When the pulse level is "H", the connection is switched to V _M.

When the transfer pulse level of _V1 is "L", the changeover switch element 31 is connected to the switch 30 as shown in the figure, and when the same level is "H", it is switched to the connection with _VL .

When the transfer pulse level of V ₂ is "L", the changeover switch element 32 is in a continuous state with V _M ' as shown in the figure, and when the same level is "H", it is in a continuous state with V _L
The connection will be switched to

Note that the levels of V _H , V _M (V _M ′), and V _L mentioned above are V _H
The relationship is >V _M (V _M ′) > V _L.

The circuits for V ₃ and V ₄ are respectively the above V ₁
and is configured identically to the circuit of V ₂ .

A specific timing chart of the driver 12 is shown in FIG. When there is no input of the TG accumulation control pulse, the changeover switch element 30
is switched to _VM , so the transfer pulse of _V1 is inverted and output from _ФV1 .

From ФV ₂ , ФV ₃ and ФV ₄ , respectively, V ₂ , V ₃ ,
The transfer pulse of _V4 is inverted and output similarly to the above _V1 .

In the above case, the "H" level of V ₁ to V ₄ corresponds to the _{VM and VM'} levels of ФV ₁ to ФV ₄ , and the " _L " level corresponds to the V _L level.

Also, when the TG accumulation control pulse is input,
Since the changeover switch element 30 switches to _VH as shown, when the levels of _V1 and _V3 are "L", the levels of _ФV1 and _ФV3 become _VH .

As explained above, ФV ₁ and ФV ₃ are three-level signals, and ФV ₁ and ФV ₃ are the highest level V _H
When , it becomes an accumulation control signal and causes the charge accumulated in the photodiode to be transferred to the vertical transfer CCD. On the other hand, when the levels of ФV ₁ to ФV ₄ take V _M , V _M ′ and V _L , it becomes a vertical transfer pulse,
The charges transferred to the vertical transfer CCD are sequentially transferred on the vertical transfer CCD.

Next, the specific electronic shutter operation of the image sensor control device of the present invention configured as described above will be described in the fifth section.
The explanation will be based on the flowchart shown in the figure.
Note that this flowchart will be explained with reference to the schematic configuration diagram of FIG. 1 and the timing chart of FIG. 6.

First, when the release button 24 is turned on,
The MPU 14 sets the PS switching pulse to "H" and the PHV sweep request pulse to "L" (steps 51 and 52). With this set,
A clock generator 13 is connected to the driver 12, and a sixth clock generator 13 is connected to the driver 12.
As shown in the figure, the periodic accumulation control pulse is applied to CTG at a cycle of 1/60 seconds, and the transfer pulse is applied to CV ₁ to _{CV 4.}
is output to. In other words, the image of the subject is read out from the CCD image sensor 11 at a cycle of 1/60 seconds and output to the recording/reproducing section 18.

Then, the MPU 14 performs photometry calculations based on the photometry data regarding the brightness of the subject output from the photometry section 22 (step 53), and calculates the optimum aperture value AV.
and find the shutter speed TV. Then, the aperture drive circuit 23 is controlled based on the optimum aperture value AV, and the aperture 16 is set to the optimum aperture value (steps 54 and 55).

When the setting of the aperture 16 is completed, as shown in Fig. 5.
Wait for the VD pulse to become “H”, then MP1
Step 4 sets the PS switching pulse to "L" (steps 56 and 57). As a result, switch circuit 2
0A and 20B are switched, the MPU 14 is connected to the driver 12, and the MPU 14 is in a state where it can output forced accumulation control pulses and transfer pulses. In other words, the driver 12 is in a state where it can output the accumulation control signal.

When the optimal shutter mode TV calculated in step 53 is obtained, the MPU 14 outputs a forced adhesion control pulse to PTG and transfer pulses to PV ₁ to PV ₄ , as shown in Figures 6 and 7. do. As a result, unnecessary charges accumulated in the light receiving section of the VVD image sensor 11 are transferred all at once to the vertical transfer CCD (step 58). When the forced accumulation control pulse is outputted, when the shutter speed TV is faster than 1/60 seconds, the periodic accumulation control pulse is output from the clock generator 13, and when the shutter speed TV is slower than 1/60 second, the periodic accumulation control pulse is output from the next periodic accumulation control pulse. It can be determined by calculating backward the shutter speed TV from the time when the accumulation control pulse is output.

Then, the MPU 14 waits for the VD pulse shown in FIG. 6 to rise to "H", and then sets the PS switching pulse and the PHV sweep request pulse to "H" (steps 59 and 60). As a result, a high-speed sweep pulse is output from the clock generator 13 to CV ₁ to _{CV 4} for a predetermined time, and a high-speed transfer pulse is output from the driver 12 via ФV ₁ to ФV ₂ .
Unnecessary charges that are output to the CCD image sensor 11 and transferred to the vertical transfer CCD of the CCD image sensor 11 are swept out at high speed. This high speed transfer pulse ends before the next periodic accumulation control pulse is output from the clock generator 13.

When the next periodic accumulation control pulse is output from the clock generator 13 to the CTG, the image charges accumulated during the optimal shutter speed TV time are transferred to the vertical transfer CCD. After the transfer, the MPU 14 opens the REC gate of the recording/reproducing section 18 and starts recording the image charge (step 61). That is, the signal charges sequentially output from the vertical transfer CCD in response to the read pulse output from the clock generator 13 are recorded (recorded) on the magnetic disk 17 as a video signal via the recording/reproducing section 18.

When one screen worth of recording is completed, the PHV sweep request pulse is set to "L" and the process returns to the initial state (steps 62 and 63).

The above is the shutter operation in a state where the sweep switch 25 is not turned on. When the sweep switch 25 is turned on, a sweep request pulse is constantly output to the clock generator 13 as shown in FIG. It is output for a predetermined period of time. Therefore, the smear level can be easily adjusted between the still mode and the movie mode by turning on the switch 25.

Furthermore, when a high-brightness subject is being monitored in the movie mode, turning on the sweep switch 25 lowers the smear level of the image on the electronic viewfinder 28, making it less unsightly. Furthermore, power consumption can be saved by turning off the sweep switch 25.

In the above embodiments, an interline transfer type CCD image sensor without a memory area was exemplified, but the present invention is not limited to this, and even a frame interline transfer type with a memory area can be used. The invention is applicable.

Alternatively, the forced accumulation control pulse and the transfer pulse may be configured to be output from the clock generator 13, and the MPU 14 may be configured to output a control signal for outputting the forced accumulation control pulse and the transfer pulse.

"Effects of the Invention" As is clear from the above description, according to the present invention, the charge accumulation time of the imaging means can be controlled according to the brightness of the subject, and moreover, in the movie mode, the sweep request switch means can be controlled. When turned on, the pulse signal output means outputs a regular high-speed sweep signal after outputting the read signal for each field, and the charges in the vertical transfer section are swept out in a short time. Therefore, the difference in smear level between movie mode and still mode is eliminated, and it is possible to obtain an equal image in both modes.Moreover, there is no need to adjust the smear level, and even if it is necessary, it can be easily adjusted. can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an image sensor driving device according to the present invention, and FIG. 2 is a specific circuit diagram of the driving device around a sweep switch.
FIG. 3 is a diagram showing an example of a specific circuit of the inverting type driver, FIG. 4 is a timing chart of the inverting type driver shown in FIG. 3, and FIG.
6 is a timing chart of each part of the image sensor driving device shown in FIG. 1. FIG. 11... CCD element (imaging means), 12... driver (pulse signal output means), 13... CCD driving clock generator (pulse signal output means),
14...MPU (control means), 20A, 20B...
Changeover switch circuit, 25... sweep switch (sweep request signal output means).

Claims (1)

[Scope of Claims] 1. Imaging means equipped with a light receiving section and a vertical transfer section that convert a subject image into signal charges and store them, and a periodic accumulation that transfers the signal charges accumulated in the light receiving section to the vertical transfer section. A control signal and a readout signal for reading out the signal charge transferred to the vertical transfer section are periodically output, and a high-speed sweep signal for sweeping out the charge in the vertical transfer section is applied to the next periodic accumulation after the output of the readout signal is stopped. A pulse signal output means that can be output periodically before outputting a control signal and when a sweep request signal is input from the outside, and a forced accumulation control signal that causes the signal charge of the light receiving section to be transferred to the vertical transfer section at any time. and a control means for outputting the sweep request signal after outputting the forced control accumulation control signal, and a switch means for turning on/off the output of the high-speed sweep signal that is periodically output. A driving device for an image sensor.