JPH0432381A - Electronic image pickup device - Google Patents

Abstract

PURPOSE:To obtain a stable exposure level even when the brightness of an object is changed by providing a means reading an effective picture charge to a vertical transfer register and repeating the discharge of the undesired optical storage range for a set number of times only and a means reading the effective picture charge stored in the vertical transfer register to the image pickup device. CONSTITUTION:An externally photometric element 11 applies direct photometry to a video signal asynchronously therewith and a stored charge in an optical charge storage section 46 of an image pickup element 3 obtained by shutter operation is read out to a vertical transfer register 47 to which no transfer clock is applied. Then an undesired charge is discharged and the electronic shutter operation by direct photometry is implemented again and the charge obtained in this way is mixed by the vertical transfer register 47. Then a picture subjected to multiplex exposure is obtained by repeating the operation continuously by number of times of multiplex exposure. Thus, the stable exposure level is obtained without use of a special memory even when the lightness of the object is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic imaging device, and more particularly, to an electronic imaging device with excellent characteristics when performing multiple consecutive exposures.

[Prior Art] A first means for multiple exposure in a conventional electronic imaging device is applicable to an electronic imaging device having a mechanical shutter, and involves continuously operating the shutter mechanism for the number of multiple exposures. This is a method of multiplexing images. Also the second
This method is a method in which a shutter speed is determined in advance by blur photometry or from an image output from an imaging device, and the shutter is operated at that shutter speed for the number of times of multiple exposure to perform multiple exposure. Furthermore, the third
This means is applicable to an electronic imaging device equipped with a memory IC, and is a method of obtaining multiple images by sequentially adding and writing image information for the number of multiple exposure ports to the memory IC.

[Problems to be Solved by the Invention] However, in the first method of operating the mechanical shutter mechanism for the number of times of multiple exposure, the scale of the apparatus becomes large and complicated, resulting in an increase in cost. In addition, in the second method described above, in which the shutter speed is determined in advance and the shutter is operated as many times as the number of multiple exposures at that shutter speed, the shutter speed is constant, so for example, as the subject moves, the brightness changes from moment to moment. When a subject is subjected to multiple exposure, the brightness of each multiple-exposed scene varies, resulting in an unsightly multiple image. Furthermore, 1. adds image information for the number of multiple exposure apertures to the memory IC and then writes it. In the third method, it is necessary to mount a memory IC in the electronic imaging device, and the circuit size including input/output control for this increases, resulting in an increase in cost. In addition,
It is necessary to synchronize the timing of writing to or reading from the memory IC with the video rate, which results in constraints on the shutter timing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, to be able to add and hold image information associated with multiple shutter operations in multiple exposure mode without providing a special memory means, and to be able to add and hold image information associated with multiple shutter operations in multiple exposure mode, and to To provide an electronic imaging device that can obtain a stable exposure level even if the exposure level changes.

[Means for Solving the Problems] The electronic imaging device of the present invention discharges unnecessary charges from the photocharge storage section and starts charge accumulation in the photocharge storage section when a recording start signal is applied. means for accumulating effective image charges for a time determined by direct photometry, reading out the charges to the vertical transfer register 1, and then discharging unnecessary photoaccumulated charges for a set number of times; and accumulating them in the vertical transfer registers. and means for reading out the effective image charge.

[Function] In this electronic imaging device, during multiple still shutter operations in multiple exposure mode, the effective image charge accumulated in the photocharge storage section is transferred and locked for a time determined by direct photometry. It is read and added to the vertical transfer register.

[Example] The present invention will be explained below with reference to illustrated embodiments.

First, prior to a detailed explanation of the present invention, a detailed explanation of the present invention will be given. That is, direct photometry is performed asynchronously with the video signal by an external photometry element, and the accumulated charge in the photocharge storage section of the image sensor obtained by this shutter operation is held in the vertical transfer register whose transfer lock has been stopped, and then the charge is transferred again. An electronic shutter operation is performed using direct photometry, and the charges obtained are mixed in the vertical transfer register. By continuously repeating these operations the number of times of multiple exposure, a multiple exposed image is obtained. The above is an overview of the present invention. Next, a first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 11 is a block diagram of an electronic imaging device showing a first embodiment of the present invention. The object light is imaged on the light receiving surface of the image sensor 3 via the lens 1 and the diaphragm mechanism 2 . The video signal photoelectrically converted by the same element 3 is sent to the video signal processing unit 5
After being subjected to camera processing, the signal is supplied to the recording section 6 and recorded on a recording medium such as an Sv (still video) floppy disk.

An external photometry element 11 that measures the illuminance of a subject and starts photometry in response to an integral reset signal supplied from a photometry exposure control section 14, which will be described later. When the integral value of the photometric output of the element 11 exceeds a predetermined threshold level, it changes from "L' to "H", and the comparator 13, which detects the shutter end timing, performs photometry control, exposure calculation, shutter speed control, etc. The control unit 14 instructs the aperture mechanism 2 to perform aperture control, takes in the aperture information obtained as a result, and also controls the image sensor 3 at a predetermined shutter speed. It instructs shutter speed control to the image sensor drive signal generating section 4 which causes the electronic shutter operation to be performed.Furthermore, the strobe light emitting section 7 is controlled to start and stop emitting light through the strobe control section 8.

A system control unit 15 that controls the operation sequence of the entire electronic imaging device includes a shutter trigger switch 1
When the shutter trigger signal is received from 6, a still shutter command asynchronous to the vertical synchronization signal of the video signal and an exposure mode command for switching between the multiple mode and the normal mode are sent.
The signals are sent to the photometry/exposure control section 14 and the image sensor drive signal generation section 4, respectively. In addition, the control section 1
5 includes a mode switching command from the exposure mode operation section 17 for setting the exposure mode as multiple exposure mode or one-shot mode which is normal exposure, and a multiple exposure number operation section for setting the number of exposures in the multiple exposure mode. Exposure frequency setting commands from 18 are respectively input, and the exposure mode and exposure frequency are displayed on a monitor on a display section 19, and a still recording signal for still recording is sent to the recording section 6.

Next, the multiple exposure operation in the electronic imaging device according to the present embodiment configured as described above will be explained below based on the timing chart of FIG. 2.

In addition, in this FIG. 2, it is assumed that the image sensor is a CCD image sensor having an overflow drain, and the unnecessary charges in the photocharge storage section are discharged to the overflow drain.1. I will explain.

At time t1, the exposure mode operation section 17 switches the mode from the one-shot mode, which is normal exposure, to the multiple exposure mode. At time t2, when the trigger switch 16 is fully pressed and the trigger signal is received by the system control unit 5, the control unit 15 instructs each part of the device to operate the asynchronous still shutter using the direct photometry method. , This starts the first series of shutter operations in the multiple exposure mode. Immediately, the logic level of the signal supplied from the control section 15 to the photometric exposure control section 14 and the image sensor drive signal generation section 4 is set to L.
2 → "H2", thereby sending out the first still shutter command 23 in the multiple exposure mode.Then, the photometric element output 1 novel changes to the straight line 12 by the integral reset signal 24.
At the same time as the image sensor 3 is reset as shown in FIG. This will be done directly. In other words, the photometering element 1 and the image sensor 3 are reset to the initial state at the same time, and from this time t2, the photometer 1 calculates the light intensity integral of the subject light by direct photometry, and the image sensor 3 uses the asynchronous shutter. The first exposure operation is started respectively.

The photometric element 1] gradually integrates the amount of light and its output level rises as shown by straight line 1!3, and when it reaches the threshold level of the comparator 13 (see Figure 1) at time t3, the comparator output signal 26 becomes active. "H"
As a result, the first still shutter command 23 in the multiple exposure mode becomes inactive "L", and the exposure operation based on the first still shutter command ends. Then, the charge readout 27 of the effective image from the photocharge storage section of the image sensor 11 to the vertical transfer register is started, so the first still shutter exposure time TI by the asynchronous shutter is from time t2 to time t3.

In this way, the effective image charge Q accumulated in the photocharge storage section of the image sensor 3 during the first still shutter exposure time T1 in the multiple exposure mode and transferred to the vertical transfer register at time t3 is locked to the vertical transfer register at the same time t3. 28 is stopped, so it is held in the vertical transfer register. Note that the on/off state of the vertical transfer lock 28 is controlled by the image pickup element drive signal generation section 4 based on a command from the system control section 15.

When the first still shutter operation in the multiple exposure mode is completed, the system control unit 15 instructs the start of the second still shutter operation in the multiple exposure mode at time t4. This second still shutter operation is the same as the first still shutter operation described above, and is at time t4.
At , the photometric element output level is reset by the photometric element integral reset signal 24a, and unnecessary charge is discharged from the image sensor 2.
5a are performed simultaneously. Then, time t5 when the photometric element output level reaches a predetermined threshold level.
When this happens, the second still shutter operation ends.

Now, the second still shutter exposure time T2 from time t4 to t5 is determined by direct photometry in which the exposure operation ends when the total exposure amount of the subject light incident on the photometry element 11 reaches a predetermined value. Therefore, as a matter of course, if the subject illuminance changes, the exposure time will differ from the first exposure time T1. Then, the effective image charge Q2 accumulated in the photocharge storage section of the image sensor 3 during the exposure time T2 is transferred to the vertical transfer register by the effective image charge readout 27a from the image sensor. In this vertical transfer register, since the first effective image charge Q1 is already held as described above, the second effective image charge Q2 is added to this, and the result and 17 are used as a moving image. Charge (Ql+Q2) will be held.

By repeating this still shutter operation by the number n of multiple exposures set in the multiple exposure number operating section 18, Q, +Q2+----- when the multiple exposure mode ends.
-+Qn effective image charges (hereinafter referred to as multiple exposure image charges) are held in the vertical transfer register of the image sensor 3. Upon completion of a series of still shutter operations in such multiple exposure mode, the system control unit 15 synchronizes with the video rate vertical blanking signal 29 (7) and activates the vertical transfer lock 30 toward the vertical transfer register of the image sensor. As a result, the charges Q1+Q2+...Qn of the multiple exposure image are read out as the image sensor output 31. This image sensor output 3]2 is transmitted to the video signal processing section 5 (see FIG. 1). The still recording signal 32 is applied to the recording unit 6 through the camera, and is sent from the system control unit 15 at this timing. The charge of the exposed image will be recorded.In this timing chart, the vertical blanking signal is written at such a long time rate, but it is written at a shorter time rate, that is, within one field period. It goes without saying that the still shutter operation in the multiple exposure mode described above may be performed at a timing such that it is performed many times.

The above is the first embodiment of the present invention, and according to this, even if the illuminance of the subject changes from moment to moment because the subject is moving, the shutter is activated by direct metering for each frame in the multiple exposure mode. Since it is operating, it is possible to obtain a multiple exposure image with no variation in shading. Furthermore, since a vertical transfer register with no transfer lock supplied is used to add and hold the effective image charges for each frame, no additional components such as memory means are required.

However, in the first embodiment, the shutter speed changes for each frame in the multiple exposure mode depending on the brightness of the subject, so the shutter speed at which multiple exposures can be made varies depending on the subject. Therefore, in the second embodiment described below, the approximate number of shots that can be taken during multiple exposure is displayed on the monitor in advance by the display unit 19 of the multiple exposure number operation unit 182 shown in FIG. 1, prior to the shutter operation. ing. The operation of the second embodiment will be explained below according to the flowchart of FIG.

In FIG. 3, when a desired value for the number of multiple exposures is set in the multiple exposure number operating section 18 (step S1), this desired value is taken into the system control section]5. Then, the system control unit 15 controls the comparator 1
3, if the number of multiple exposures is large, the threshold level of the comparator is set to a low value, and if the number of multiple exposures is small, the threshold level of the comparator is set to a high value (step S2). after that,
The brightness of the subject is determined in advance by pre-metering with the photometering element 11 (step S3), and the system control unit 15 determines whether it is possible to take a frame-by-frame image every second based on this metered value and the number of multiple exposures.
is predicted and displayed on the display unit 19 (step S4). 12) Then, wait until the shutter trigger signal is received (Step S5);) When the camera is activated, the shutter operation by direct photometry for each frame in the multiple exposure mode explained in FIG. 2 above is performed a set number of times; Step S
6) Still recording in the recording section 6 (step S7)
.

According to this second embodiment, the photographer can check whether multiple exposures can be performed at the shutter speed of the previous frame every second in the multiple exposure mode using the multiple exposure number control unit] 8 attached to the camera body and the display unit. 19, it can be recognized in advance.

Next, the multiple exposure mode under strobe light irradiation will be explained below using a third embodiment of the present invention and j-.

Generally, the accuracy of strobe light emission varies considerably, so even if the strobe light is emitted continuously at regular time intervals, the amount of strobe light emission will vary each time. Therefore, when performing multiple exposures in synchronization with strobe light, direct light metering is used to start and stop the strobe light, making it possible to take continuous strobe multiple exposure photographs without variations in the exposure level for each scene. The concrete means for this purpose are the same as those shown in FIGS. 1-2 in the first embodiment described in section 1, and there is no difference in their operation and effect, so the explanation thereof will be omitted.

Each of the above embodiments has been described assuming that the image sensor and 17 are CCD image sensors having an overflow drain. This is because unnecessary charges can be discharged from the overflow drain, which is another path, without disturbing the effective image charges transferred from the photocharge accumulation section to the vertical transfer register.

Generally, CCD image sensors are of interline transfer type, frame transfer type,
Furthermore, there is a 1 norm interline transfer type (hereinafter abbreviated as FIT). Among these, the above-mentioned CCD image sensor called FIT can perform a shutter operation in such a multiple exposure mode without discharging unnecessary charges to an overflow drain.

That is, to briefly explain using FIG. 4 which shows the outline of the device configuration of the FIT, this FIT consists of vertical transfer registers 4 that are shielded from subject light, such as a photocharge storage section 46.
7 are two-dimensionally arranged; a memory section 42 in which a vertical transfer register 47a is arranged and shielded from subject light; an unnecessary charge discharge drain 43 for discharging unnecessary charges; It is composed of a horizontal transfer register 44 and a buffer circuit 45 which are led out to an external circuit. When an exposure operation is performed by the first still shutter command in the multiple exposure mode in the FIT having such a configuration, the effective image charge Q photoelectrically converted in the photocharge storage section 46 is
1 is temporarily saved and held in the memory section 42 from the vertical transfer register 47. After that, the photocharge storage section 46
The unnecessary photo-accumulated charges generated in the vertical transfer register 47
is transferred upward in the figure at high speed and is discharged to the outside via the unnecessary charge discharge drain 43 (5).Then, the effective image charge Q1 that had been temporarily saved in the memory section 42 is vertically transferred to the imaging section 41 again. The data is reversely transferred to the register 47, and the second still shutter operation in the multiple exposure mode is performed.

Then, in addition to the effective image charge Q1 from the first shutter operation, the effective image charge Q2 from the second shutter operation is added to the register 47, resulting in (Q1
102) effective image charges are accumulated. After that, the effective image charge (Q1 + Q2) is
By temporarily saving the data in the memory section and then performing the same operation as the previous time, the multiple exposure of the present invention can also be performed by discharging through the vertical transfer path without using an overflow drain.

According to each of the embodiments described above, since the accumulation of effective image charge in the photocharge storage section of the image sensor is controlled by direct photometry using an external photometry element, the brightness of the subject changes depending on the movement of the subject or changes in the amount of light from the light source. Even if the exposure level changes, the exposure amount for each scene in the multiple exposure mode can always be maintained at the optimum value, thereby making it possible to capture images at the optimum exposure level. Additionally, since it can be used in synchronization with a strobe, it is possible to capture images with optimal exposure even when using a strobe. Furthermore, since multiplexing is performed using the vertical transfer register of the image sensor, there is no need to provide an external memory or the like for multiplexing, which is advantageous in terms of cost and scale.

[Effects of the Invention] As described above, according to the present invention, effective image charges are accumulated in the charge accumulation section at a time determined by direct photometry, the accumulated effective image charges are read out to the vertical transfer register, and then Unnecessary accumulated charges are discharged, and this series of operations is repeated a set number of times for multiple shooting. Therefore, the effective image charge can be accumulated and added using the vertical transfer register with the transfer lock stopped, without using any special memory means. Furthermore, a remarkable effect is achieved in that a stable exposure level can be obtained even if the brightness of the subject changes.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of an electronic imaging device showing a first embodiment of the present invention. FIG. 2 is a timing chart of multiple exposure operation in the first embodiment. FIG. Timing Chart of Multiple Exposure Operation in Electronic Imaging Device Showing Second Embodiment FIG. 4 is a plan view schematically showing the device configuration of a frame interline transfer type CCD imaging device.

Claims (1)

[Claims] (1) means for discharging unnecessary charge from the photocharge storage section and starting charge accumulation in the photocharge storage section when a recording start signal is given; means for repeatedly accumulating the charges, reading the charges to the vertical transfer register, and then discharging the unnecessary photoaccumulated charges a set number of times; and means for reading the effective image charges accumulated in the vertical transfer registers. Characteristic electronic imaging device.