JPH01288070A - Electronic image pickup device - Google Patents

Abstract

PURPOSE:To keep the consecutive shot speed set by a photographer and to obtain a picture of proper luminous quantity by supplying a signal representing a value corresponding to the deficient quantity of an actual exposure with respect to a prescribed exposure as a gain control signal. CONSTITUTION:The gain relating to a photoelectric conversion output from an image pickup means 6 depending on the exposure is controlled in response to the gain control signal given by a gain control means 34 to obtain a signal representing a value corresponding to the deficient quantity of the actual exposure with respect to the prescribed exposure from a gain control signal generating means and the signal is fed to the control means as its gain control signal. That is, when an output of a shutter second time monitor means 27 is led to a data storage means 31 at the end or exposure, the output data or a differential amplifier 24 is digitized and held by the data holding means 31, a digital function in response to the holding data is outputted from a digital function generating means 32 and the gain of a GCA circuit 34 is varied in response to the digital function. Thus, the shutter time set by the photographer is kept to obtain a picture of proper luminous quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electronic imaging device, more specifically, to continuous imaging (
The present invention relates to an electronic imaging device capable of continuous shooting (hereinafter referred to as continuous shooting).

[Prior Art] Generally, exposure control modes in an automatic exposure camera include an aperture priority mode, a program mode, a shutter priority mode, and the like. In the aperture priority mode, when the photographer sets an aperture value, the camera determines the appropriate shutter speed based on the set aperture value and the brightness of the subject. Also,
In the program mode, the shutter speed and aperture value are determined according to the brightness of the subject. Furthermore, in shutter priority mode, if the photographer sets the shutter speed,
The appropriate aperture value is determined on the camera side based on the set shutter speed and the brightness of the subject.

On the other hand, a camera with each exposure control mode like this
Most of them allow continuous shooting.

However, if you try to perform continuous shooting in such conventional exposure control modes, for example in aperture priority mode or program mode, the shutter speed will change depending on the external light condition, so it will not be possible to perform continuous shooting as a result. The shooting speed, that is, the number of consecutive frames that can be taken per second, changes.

However, in general, when performing continuous shooting, there is a desire to keep the continuous shooting speed constant.For example, there is a desire to capture still images at regular intervals, such as a series of golf swing movements or the form of a running person. The above-mentioned demand is strong in cases where it is desired to record the process of change over time in an experiment. Therefore, in such a case, changing the continuous shooting speed means changing the time interval between each frame, which makes it difficult to compare and analyze the images of each frame obtained during continuous shooting. This will cause trouble.

In the shutter priority mode, the continuous shooting speed is also set by setting the shutter speed, so the continuous shooting speed remains unchanged unless the shutter speed is changed. However, if the brightness of the subject changes during continuous shooting, only the aperture value will change because the shutter speed is completely fixed.
Simply changing the aperture has a narrow control range for obtaining proper exposure, and can easily result in underexposure or overexposure.

In view of this, an electronic still camera having a configuration as shown in FIG. 5 can be considered as an electronic imaging device that can always maintain the continuous shooting speed set by the photographer.

In FIG. 5, when the continuous shooting speed is set by the continuous shooting speed setting means 55 of the system control circuit (hereinafter abbreviated as system controller) 8 consisting of a microcomputer, the shirt shutter speed monitoring means 57 sets the shirt speed according to the continuous shooting speed. The seconds range is limited. For example, if the number of continuous shooting frames is set to 20 frames/second as the continuous shooting speed, the shutter speed corresponds to the time required to complete one cycle of the series of shooting operations of exposure, recording, and head movement. Limited to speeds faster than 1/60 second. When the release is performed, the exposure start signal generating means 56 outputs the exposure start signal to CC.
A start signal is sent to the D image pickup device 6 to start exposure, and also to the shutter speed monitoring means 57 and the light amount integrator 51 of the photometry circuit 7. When the shutter speed monitoring means 57 receives the start signal, it generates an output at a shutter speed of 1/60 second, and this output is input to the CCD image pickup device 6 through the OR gate 59. In addition, the light amount integrator 51
When receiving the start signal, it starts integrating the photoelectric conversion output of the photometric element 4, and this integrated output is led to the comparator 53 and compared with the reference voltage of the reference voltage generating means 52. When the integrated output exceeds the reference voltage, the output of the comparator 53 is input to the CCD image sensor 6 through the OR gate 59 as an exposure end signal. By inputting the output of the shutter speed monitoring means 57 or the output of the comparator 53 to the CCD image sensor 6, the exposure of the CCD image sensor 6 is completed. Thereafter, the charge accumulated in the CCD image sensor 6 is read out by the readout start timing signal VD from the readout start signal generation means 58, and the charge is processed by the process circuit 10 to become an image signal, and then recorded. It is led to circuit 11.

[Problems to be Solved by the Invention] By the way, in the electronic still camera having the configuration shown in FIG.
If the appropriate exposure amount is not reached even after 1/60 seconds and the exposure end signal is not output from the comparator 53, the exposure is ended by the output of the shutter time monitoring means 57 when 1/60 seconds have elapsed. Although the number of continuous shooting frames of 20 frames/second is ensured in any case, the photographic screen becomes dark due to insufficient exposure.

In view of these problems, an object of the present invention is to provide an electronic imaging device that can maintain the shutter speed (or continuous shooting speed in the case of continuous shooting) set by the photographer and can obtain images with an appropriate amount of light. is to provide.

[Means and Effects for Solving the Problems] The electronic imaging device of the present invention controls the gain related to the photoelectric conversion output from the imaging means depending on the exposure amount in accordance with the gain control signal given by the gain control means. Then, a signal representing a value corresponding to a shortage of the actual exposure amount with respect to a predetermined exposure amount is obtained from the gain control signal generating means, and this signal is supplied to the control means as the gain control signal. Furthermore, a continuous shooting speed priority operation mode maintaining means is provided, and even in a condition range that deviates from the maximum exposure condition, the operation is continued while maintaining the continuous shooting speed set at that point in time.

Embodiment FIG. 2 is a block diagram of an electric circuit showing an embodiment of an electronic still camera to which the electronic imaging device of the present invention is applied.

In FIG. 2, subject light entering from a photographic lens 1 passes through an aperture 2, part of the light is reflected by a half mirror 3 and guided to a photometric element 4, and the remaining light is transmitted to a half mirror 3.
The light passes through the shutter mechanism 5 and is guided to the CCD image sensor 6. The shutter mechanism 5 may be either an element shutter of the CCD image sensor 6 or a mechanical shutter.

The photoelectric conversion output of the photometric element 4 is integrated and photometered by a photometric circuit 7, and the photometric output is input to a system controller 8.

The system controller 8 performs calculations based on the photometric output, sends the calculation outputs to the aperture drive circuit 9 and the shutter mechanism 5, and controls the aperture 2 and shutter mechanism 5 to a predetermined aperture value and shutter speed. Further, the output of the CCD image sensor 6 whose storage and transfer of photoelectric charges are driven and controlled by the clock pulse from the system controller 8 is led to the process circuit 1o, processed into an image signal, and then sent to the recording circuit 11. The output of the recording circuit 11 is supplied to the recording head 12 in synchronization with timing pulses from the system controller 8, thereby recording an image signal of the object on a recording medium 13 such as a magnetic disk. The recording head 12 is moved in the radial direction of the recording medium 13 by a head drive circuit 14 controlled by the system controller 8, and the recording medium 13 is rotated at a predetermined speed by a motor drive circuit 15 controlled by the system controller 8.

The electronic still camera configured as described above is further provided with a mode changeover switch 17, which can be switched to set continuous shooting mode or single shooting mode, and can be set to either continuous shooting mode or single shooting mode. In,
Additionally, shutter priority mode, aperture priority mode, and program mode can be set. In the continuous shooting mode, it is also possible to set a continuous shooting frame number priority mode. In addition, the continuous shooting frame number setting switch 1
8 and a display section 19 are provided, and the number of continuous shooting frames set by the switch 18 is displayed on the display section 19. The display section 19 also displays underexposure and overexposure.

FIG. 1 shows a more detailed configuration of the main parts of the electronic still camera. In FIG. 1, the photometric circuit 7 includes a light amount integrator 21 that integrates the photoelectric conversion output of the photometric element 4. Reference voltage generating means 22 for generating a reference voltage. This light amount integrator 21
A comparator 23 that compares the output of the light intensity integrator 21 with the reference voltage of the reference voltage generating means 22, and a differential amplifier 24 that outputs the difference between the output of the light amount integrator 21 and the reference voltage are provided.

The system controller 8 also includes the continuous shooting frame number setting switch 18.
Continuous shooting speed setting means 25 for setting a continuous shooting speed according to the number of continuous shooting frames. Exposure start signal generating means 26 activated by pressing the release button. Shutter time monitoring means 27 for setting the limit shutter time according to the continuous shooting speed set by the continuous shooting speed setting means 25. Readout start signal generating means 28 for reading out signals accumulated in the CCD image sensor 6. An OR gate 29 for guiding either the output of the comparator 23 or the output of the shutter speed monitoring means 27 to the CCD image pickup device 6 as an exposure end signal. A/D converter 30 for converting the output of the differential amplifier 24 into a digital signal. Digitally converted differential amplifier 2
Data holding means 31 for holding the output of 4 for a certain period of time when the two OR gates output. A digital function generating means 32 for converting the held data into a certain function and a D/A converter 33 for converting the output of the digital function generating means 32 back into an analog signal are provided.

The 71-log output of this D/A converter 33 is the gain control (hereinafter abbreviated as OCA) of the process circuit 10.
A control terminal of circuit 34 is provided.

Next, the operation of the electronic still camera shown in FIG. 1.2 will be explained. Now, if the photographer sets the mode changeover switch 17 to continuous shooting frame number priority mode, the number of continuous shooting frames set by the continuous shooting frame number setting switch 18 is read into the system controller 8, and this number of continuous shooting frames is At the same time, the continuous shooting speed is set by the continuous shooting speed setting means 25 in the system controller 8, and the shooting speed is set by the continuous shooting speed monitoring means 27 according to the number of continuous shooting frames (continuous shooting speed). Tolerance is limited. This allowable range of shutter speed is determined by the system controller 8 in accordance with the photographing operation sequence set in the system at that time. For example, the sequence of photographing operations is set to proceed sequentially without overlapping timing, such as exposure-recording-head feeding shown in the time chart of FIG. 3, and the recording and head feeding operations are 1/hour each
If it is assumed that 60 seconds (this corresponds to the interval of the timing signal, VD, which will be explained in detail later) is required, then the allowable range of shutter speed seconds will be limited as shown in Figure 4. . This is based on the fact that the time required to complete each shooting sequence is limited depending on the number of consecutive shooting frames (frames/second). That is, FIG. 4 shows that, for example, when the number of continuous shooting frames is set to 15 frames/second, the shutter speed is limited to the range of faster speeds than 1/30 second, and when the number of continuous shooting frames is set to 15 frames/second, When set, the shutter speed is limited to a range faster than 1/60 second (the exposure time in FIG. 3 is an example that satisfies this condition).

Now, when the photographer selects the continuous shooting frame number priority mode and releases the camera as described above, the exposure start signal generating means 26 sends an exposure start signal to the CCD image sensor 6 to start exposure, and the above-mentioned The exposure start signal is also sent to the shutter speed monitoring means 27 and the light amount integrator 21 of the photometry circuit 7. When the continuous shooting frame number priority mode is selected and the photographer has set 20 frames/second as the number of continuous shooting frames, the shutter speed monitoring means 27 starts from the time when it receives the exposure start signal. A timing operation is started, and an output signal indicating the end of exposure is generated when 1/60 second has elapsed. This output signal is OR gate 2
At the same time, it is input to the CCD imaging probe 6 through 9.
It is also provided to the data holding means 31.

Furthermore, if the number of continuous shooting frames is set to a value other than the above (20 frames/second), the duration of the timing operation in the shutter speed monitoring means 27 will also be a corresponding value. Of course. In the device of this embodiment, the time of this timing operation corresponds to the value of the shutter time in seconds corresponding to the left end of the solid line (indicated by a hollow point) corresponding to each continuous shooting frame number in FIG. 4. .

On the other hand, upon receiving the exposure start signal, the light amount integrator 21 starts integrating the photoelectric conversion output of the photometric element 4 at the time of receiving this signal. This dip output is led to the comparator 23, where it is compared with the reference voltage of the reference voltage generating means 220. The integrated output is made to match the reference voltage at the time when the amount of exposure to the CCD imaging element 6 reaches an appropriate value,
When this match is obtained, the output of the comparator 23 is sent as an exposure end signal to the CCD image sensor 6 through the OR gate 29.
and is guided to the data holding means 31.

Here, if the subject is bright and the appropriate amount of light is given to the CCD imaging probe 6 at a time earlier than the above-mentioned 1/60 second,
The comparator 23 has priority over the output of the shutter speed monitoring means 27.
Since the output is sent to the CCD imaging element 6 as an exposure end signal, the exposure of the CCD imaging element 6 ends at the same time. Thereafter, the charge accumulated in the CCD image sensor 6 from the start of exposure to the end of exposure is read out by the readout start timing signal VD from the readout start signal generation means 26, and the charge is processed by the process circuit 10. After being made into an image signal, it is guided to the recording circuit 11. Also, comparator 2
3 is guided to the data holding means 31 at the end of exposure, but at this time, the output of the light amount integrator 21 is equal to the reference voltage and the output of the differential amplifier 24 is zero, so the data holding means 31 is guided to the data holding means 31. The digital function generating means 3 holds the input data and generates a digital function according to the held data.
Output from 2. This digital function is converted back to an analog signal by the D/A converter 33 and guided to the control terminal of the GCA circuit 34 of the process circuit 10, but the digital function corresponding to the held data of zero at this time is 1,
The gain of the OCA circuit 34 is not changed.

Next, if the subject is dark and the appropriate amount of light is not given to the CCD imaging element 6 even after 1/60 seconds have passed from the start of exposure, priority is given to the output of the comparator 23 at 1/60 seconds. At the same time, the output of the shutter speed monitoring means 27 is sent to the CCD image sensor 6 as an exposure end signal.
Exposure of the CCD image sensor 6 is completed. Further, the output of the shutter speed monitoring means 27 is output from the data holding means 3 at the end of exposure.
1, the output of the differential amplifier 24 at this time has a value corresponding to the difference between the output of the light intensity integrator 21 and the reference voltage, so the output value data of the differential amplifier 24 is converted into A/
The data is digitized by the D converter 30 and stored in the data holding means 3.
1 is held, and the digital function generating means 32 outputs a digital function corresponding to the held data. Therefore, when this digital function is converted back into an analog signal by the D/A converter 33 and guided to the control terminal of the GCA circuit 34 of the process circuit 10, the GCA circuit 34 is converted into an analog signal according to this digital function.
The gain of circuit 34 changes. Therefore, when the charge of the CCD imaging probe 6 read out by the timing signal VD from the readout start signal generation means 28 is converted into an image signal by the process circuit 10, the image signal is converted to the digital function by the OCA circuit 34. Since the gain is increased by a gain factor of , even an underexposed image signal is made into an image signal with optimum brightness and is led to the recording circuit 11.

To explain the time chart of FIG. 3, the time chart shows the photographing operation when the number of continuous shooting frames is set to 20 frames/second.

In other words, when the number of shooting frames is set to 20 frames/second,
As mentioned above, the shutter speed is limited to a range faster than 1/60 second (see Figure 4), so when continuous shooting starts, the shutter speed is 1/60 seconds faster than 1/60 second. 60
In synchronization with the timing signal VD every second, the shutter mechanism 5 is opened within the first field period (1/60 second) to perform exposure. Then, during the next one field period, the output of the recording circuit 11 is sent to the recording head 12 and recording on the recording medium 13 is performed. Furthermore, the next one
During the field period, the recording head 12 is driven by the head drive circuit 1.
4, the head is sent to the next track on the recording medium 13. And also the next field period, i.e.
Exposure is performed in the fourth field period, recording is performed in the fifth field period, and head feeding is performed in the sixth field period.

Thereafter, a series of photographing operations over a three-field period (1/20 second) of exposure, recording, and head movement are repeated in the same manner. In other words, continuous shooting is performed at a speed of 2o frames/second.

Furthermore, when the number of continuous shooting frames is set to 15 frames/second, as mentioned above, the shutter speed is limited to the shutter speed range faster than 1/3o second (see Figure 4). In this case, exposure is started in synchronization with the timing signal VD,
Exposure ends within the first field period or second field period (1/30 second or less), and other recording and head feeding are performed in the same way as in the case of 20 frames/second.
This series of photographing operations is performed sequentially every one field period, and is repeatedly performed.

When shooting is performed with the number of continuous shooting frames set by the photographer, as described above, even if the subject is dark, the OCA circuit 34 performs gain-up processing to compensate for the underexposure, resulting in an image signal with appropriate brightness. becomes.

In the above-described embodiments, the continuous shooting mode has been described, but the present invention is not limited to the continuous shooting mode, but can also be applied to the single shooting mode. In other words, in single shot mode,
As is clear from the explanation for the continuous shooting mode mentioned above, when the photographer sets the shutter speed, the exposure ends at the set shutter speed, and at this time, the shutter speed is such that underexposure occurs. If so, gain control is performed on the read image signal according to the amount of underexposure, and the gain of the image signal is increased.

[Effects of the Invention] As described above, according to the present invention, it is possible to maintain the continuous shooting speed set by the photographer, and when underexposure occurs at the same continuous shooting speed, this underexposure is compensated for in the image signal. This can be supplemented by gain control to obtain an image with an appropriate amount of light.

[Brief explanation of the drawing]

1 is a block diagram of an electric circuit showing an embodiment of the main part of the electronic still camera shown in FIG. 2 to which the present invention is applied; FIG. 2 is an electronic still camera to which the present invention is applied. A block diagram of an electric circuit showing an example; FIG. 3 is a time chart for explaining an example of continuous shooting operation timing; FIG. 4 is a line showing the relationship between shutter speed and the number of continuous shooting frames. FIG. 5 is a block diagram of an electric circuit showing an example of the essential parts of an electronic still camera that can be used for boat fishing. 6... CCD image sensor (imaging means) 24
...Differential amplifier (gain control signal generation means) 30
...A/D converter (gain control signal generation means) 3
1...Data holding means (gain control signal generation means) 32...Digital function generation means (gain control signal generation means)

Claims (2)

[Claims] (1) An imaging means for obtaining a photoelectric conversion output depending on the exposure amount, a gain control means for controlling the gain regarding the output of the imaging means in accordance with a given gain control signal, and a gain control means for controlling the gain regarding the output of the imaging means in accordance with a given gain control signal; An electronic imaging device comprising: gain control signal generating means for obtaining a signal representing a value corresponding to the amount of shortage and supplying this signal to the control means as its gain control signal. (2) Claim (1) further comprising continuous shooting speed priority operation mode maintaining means for maintaining the continuous shooting speed set at the time and continuing operation even in a condition range that deviates from the optimum exposure condition. Electronic imaging device as described.