JP2002049083A - Stroboscopic device for electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit a light receiving sensor used only for controlling strobe light and a strobe light control circuit by using a CCD image sensor also as a sensor for controlling the electronic flash. SOLUTION: The strobe light is emitted from the xenon tube of the stroboscopic device 50 at strobe-photographing. Whether or not a signal charge accumulated in the light receiving part of the CCD image sensor 14 while the strobe light is emitted overflows is detected by a current detecting unit 49 for detecting an OFD current. In the case of detecting by the current detecting unit 49 that the charge overflows in the CCD image sensor 14, the emission of the xenon tube of the stroboscopic device 50 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strobe device for an electronic camera, and more particularly, to a strobe device for an electronic camera having no dedicated light receiving sensor for strobe light control or a strobe light control circuit.

[0002]

2. Description of the Related Art A conventional strobe device has a dedicated light receiving sensor for strobe light control and a strobe light control circuit.
At the time of auto flash photography, flash light is emitted from a flash light emitting unit toward a subject, and reflected light from the subject is detected by a light receiving sensor. The strobe light control circuit integrates an electric charge corresponding to the amount of light received by the light receiving sensor with an integrating capacitor, and stops the strobe light emission when the integrated value reaches a reference value corresponding to a preset light emission amount. I have.

[0003]

In the above-mentioned conventional strobe device, it is necessary to mount a light receiving sensor for strobe light control on the exterior of the front of the camera. There is also the problem of being restricted above.

Further, since a light receiving sensor for strobe light control and an image sensor for image capture are different, it is necessary to adjust a strobe light control circuit to match the characteristics of the image sensor.

The present invention has been made in view of such circumstances, and uses a CCD image sensor as a sensor for strobe light control and omits a dedicated light receiving sensor for strobe light control and a strobe light control circuit. It is another object of the present invention to provide a strobe device for an electronic camera that can perform strobe multiple exposure shooting.

[0006]

According to a first aspect of the present invention, there is provided a strobe device of an electronic camera for obtaining an image signal indicating a subject image via a CCD image sensor. Detecting means for detecting whether or not the signal charges accumulated in the light receiving portion of the sensor have overflown; and emitting strobe light from a strobe light emitting portion during strobe shooting, and the detecting means detects overflow of the CCD image sensor. And strobe control means for stopping light emission of the strobe light emitting section.

That is, when the strobe light is emitted from the strobe light emitting section, the reflected light from the subject irradiated with the strobe light is incident on the CCD image sensor, and the charge corresponding to the amount of incident light is transferred to each light receiving section of the CCD image sensor. Is accumulated in Then, during the strobe light emission, the signal charges are gradually accumulated in the respective light receiving sections of the CCD image sensor, and are saturated in the order of the light receiving sections that receive light from the subject having a high reflectance, and the signal charges overflow. The overflowed charge flows to the overflow drain, and when this is detected by the detecting means, the light emission of the strobe light emitting unit is stopped. Even if the light receiving portion of the CCD image sensor is saturated and the signal charge overflows as described above, the strobe light emitting portion emits light only when the light receiving portion that receives light from an object having a high reflectance is saturated. If stopped, the image will not be overexposed to the detriment of image quality.

The detecting means detects overflow of the CCD image sensor on the basis of the magnitude of signal charges flowing to the overflow drain of the CCD image sensor.

According to a third aspect of the present invention, in a strobe device of an electronic camera for obtaining an image signal indicating a subject image through a CCD image sensor, whether signal charges accumulated in a light receiving portion of the CCD image sensor overflow. Detection means for detecting whether or not the CCD image sensor overflows, and setting means for setting the overflow drain voltage of the CCD image sensor to a reference voltage or a voltage which is more likely to overflow than at the time of the reference voltage. First strobe control means for emitting strobe light from the strobe light emitting unit after the voltage is set, and stopping emission of the strobe light emitting unit when the detection means detects an overflow of the CCD image sensor; By one strobe control means Calculating means for calculating an optimal flash light emission time when setting the overflow drain voltage of the CCD image sensor to the reference voltage on the basis of the control by the flash light emission time, the C during flash photography
A second step of setting the overflow drain voltage of the CD image sensor to the reference voltage to emit strobe light from the strobe light emitting unit and stopping the light emission of the strobe light emitting unit after the elapse of the optimum strobe light emission time obtained by the arithmetic means. And strobe control means.

That is, the overflow drain voltage of the CCD image sensor is set to a voltage that easily overflows, strobe light is emitted from the strobe light emitting section to cause the overflow, and C is determined based on the strobe emission time at that time.
An optimum flash emission time when the overflow drain voltage of the CD image sensor is set to the reference voltage is obtained. Thereafter, at the time of actual flash photography, the flash time is controlled so that the flash time becomes the optimum flash time obtained above. By setting the overflow drain voltage to a voltage that easily overflows, the amount of flash light emission before actual flash photography is suppressed.

According to a fourth aspect of the present invention, there is provided a selecting means for selecting a subject to be dimmed, and the CCD image sensor corresponding to the subject selected by the selecting means at the time of strobe control by the first strobe control means. Means for detecting a charge accumulation amount in a light receiving region, wherein the calculation means includes a strobe emission time controlled by the first strobe control means and the detected charge accumulation amount. When the overflow drain voltage is set to the reference voltage, a strobe light emission time is calculated so that the charge accumulation amount of the selected subject becomes optimum. This allows
The strobe light emission time is controlled so that the amount of light to a preselected dimming subject is optimized.

According to a fifth aspect of the present invention, in a strobe device of an electronic camera for obtaining an image signal indicating a subject image via a CCD image sensor, whether signal charges accumulated in a light receiving portion of the CCD image sensor overflow. Detection means for detecting whether or not the CCD image sensor overflows, and setting means for setting the overflow drain voltage of the CCD image sensor to a reference voltage or a voltage which is more likely to overflow than at the time of the reference voltage. First strobe control means for emitting strobe light from the strobe light emitting unit after the voltage is set, and stopping emission of the strobe light emitting unit when the detection means detects an overflow of the CCD image sensor; By one strobe control means Calculating means for calculating an optimal flash light emission time when setting the overflow drain voltage of the CCD image sensor to the reference voltage on the basis of the control by the flash light emission time, the C during flash photography
After setting the overflow drain voltage of the CD image sensor to the reference voltage, the plurality of strobe light emitting units are intermittently arranged so that the total of the light emitting times of the strobe light emitting units becomes the optimum strobe light emitting time obtained by the arithmetic means. And second strobe control means for emitting light once. As in the case of the invention according to claim 3 of the present application, it is possible to obtain the optimum flash emission time,
Thereafter, the strobe light-emitting unit is intermittently caused to emit light a plurality of times so that the total of the light-emitting time in the strobe light-emitting unit becomes the optimum strobe light-emitting time, so that the photographing can be performed by the strobe multiple exposure.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a strobe device of an electronic camera according to the present invention.

FIG. 1 is a block diagram showing an embodiment of an electronic camera including a strobe device according to the present invention.

The electronic camera shown in FIG. 1 mainly includes a photographing lens 10, an aperture 12, a CCD image sensor 14, an analog signal processing circuit 16, a digital signal processing circuit 20, a memory (DRAM) 22, a compression / expansion circuit 24, and a memory card 26. , LCD monitor 30, central processing unit (CPU) 4
0, operation unit 42 such as release switch, current detector 4
9 and a strobe device 50 and the like.

The CPU 40 controls and controls the respective circuits of the camera. When a release switch in the operation section 42 is pressed, the CPU 40 detects this and a strobe device 50.
A strobe ON signal is output to the controller, the aperture 12 is controlled, and the drive of the CCD image sensor is controlled via a timing generation circuit.

Through a photographing lens 10 and an aperture 12, CC
The subject light incident on the light receiving surface of the D image sensor 14 is
Here, the signal charge is converted into an amount of signal charge corresponding to the amount of light incident on each light receiving portion of the CCD image sensor 14. The signal charge stored in each light receiving section of the CCD image sensor 14 is
The vertical transfer pulses φV _{1 to} φV ₁ applied from the timing generation circuit 44 to the vertical CCD shift register via the vertical driver 46,
Horizontal transfer pulse φH _1, φ applied to D shift register
H2 _, sequentially read out as a CCD output signal (image signal) of a voltage corresponding to the signal charge based on _the reset pulse RS.

The image signal output from the CCD 14 is applied to an analog signal processing circuit 16. The analog signal processing circuit 16 has a CDS clamp, a gain control amplifier, and the like, where sampling of an image signal, white balance adjustment, and the like are performed. The image signal processed by the analog signal processing circuit 16 is converted into R, G, B digital signals by an A / D converter 18 and applied to a digital signal processing circuit 20.

The digital signal processing circuit 20 includes a gamma correction circuit, a YC signal generation circuit, etc., and performs gamma correction of the R, G, B digital signals, and YC signals of the R, G, B signals (the luminance signal Y and the chroma signal). Processing such as conversion into a signal C) is performed, and the YC signal is stored in the memory 22. The YC signal stored in the memory 22 is compressed into a predetermined format by a compression / expansion circuit 24, and is attached to a memory card 26 detachable from the camera.
Will be recorded.

The LCD controller 28 controls the R, G, and R signals based on the YC signal input from the memory 22 during photographing.
A B signal and a pulse necessary for liquid crystal display are generated and output to the LCD monitor 30 to display an image on the LCD monitor 30. At the time of reproduction, a YC signal read from the memory card 26 and expanded by the compression / expansion circuit 24 is converted into a YC signal. The reproduced image is displayed on the LCD monitor 30 based on the received image.

Next, control of the strobe device 50 will be described.

FIG. 2 is a circuit diagram showing the internal configuration of the strobe device 50. First, when a power supply (not shown) of the camera is turned on, the CPU 40 outputs a charge ON signal to the DC / DC converter 51. Thereby, the DC / DC converter 51 boosts the voltage of the battery 52 to a high voltage (about 300 V), and charges the main capacitor MC with the boosted voltage. When the charging voltage of the main capacitor MC becomes equal to or higher than a predetermined voltage at which strobe light can be emitted, a charging OK signal is output to CP.
Output to U40.

After inputting the charge OK signal, the CPU 40
When the shutter release button is pressed, for example, for 1/60 second, in synchronization with the operation of the shutter release button.
A strobe ON signal (H level signal) is output to the AND circuit 55 to enable the AND circuit 55. A detection signal from the current detector 49 is applied to another input of the AND circuit 55.

The current detector 49 becomes operable only when a detection ON signal is applied from the CPU 40.
As shown in (5), when the charge accumulated in the light receiving portion of the CCD image sensor 14 is saturated and overflows, the current width and the magnitude of the current flowing to the overflow drain (OFD) are detected. The current detector 49 normally outputs an H level signal, and when detecting an overflow from the current width and the current flowing through the OFD, outputs a strobe OFF signal (L level signal) and at least a detection ON signal from the CPU 40. Output during input period. The detection ON signal is a signal corresponding to, for example, a strobe ON signal.

Accordingly, when the strobe ON signal is input from the CPU 40, the AND circuit 55 satisfies the AND condition, outputs an H level signal to the insulated gate bipolar transistor (IGBT) 53, and turns on the IGBT 53.

When the IGBT 53 is turned on, at the same time, a current flows through the transformer in the trigger circuit 54, and a high voltage is applied to the trigger electrode of the xenon tube Xe. As a result, arc discharge occurs between the poles of the xenon tube Xe, and the xenon tube Xe emits light.

When the strobe light is emitted from the xenon tube Xe, the reflected light of the strobe light on the subject (subject light)
Is incident on the light receiving surface of the CCD image sensor 14 via the photographing lens 10 and the aperture 12, and an amount of signal charge corresponding to the amount of incident light is accumulated in each light receiving portion of the CCD image sensor 14.

As described above, the CCD is used during the flash emission.
When signal light is gradually accumulated in each light receiving portion of the image sensor 14, and as a result, the light receiving portion that receives light from an object having high reflectance is saturated, the signal charge overflows and flows to the OFD. Upon detecting the OFD current, the current detector 49 outputs a strobe OFF (L level signal) to the AND circuit 55. Thereby, the AND circuit 55
Outputs an L level signal to the IGBT 53,
To stop the light emission of the xenon tube Xe.
As described above, a part of the light receiving unit of the CCD image sensor 14 (a light receiving unit that receives light from a subject having a high reflectance)
Even if is saturated, if the light emission of the xenon tube Xe is immediately stopped, the image will not be overexposed to the detriment of the image quality.

Next, another embodiment of a strobe device for an electronic camera according to the present invention will be described.

First, before flash photography, a subject to be dimmed (for example, a human face) is selected from the subjects. The subject to be dimmed is displayed on the LCD monitor 30 by, for example, a moving image shooting function of an electronic camera, and a touch panel 32 on the LCD monitor 30 (see FIG. 1)
Can be selected by touching the subject whose light is to be adjusted.

Next, the strobe device 50 is pre-flashed,
An optimum flash emission time at which the subject to be dimmed has appropriate brightness is determined.

Here, the preliminary light emission of the strobe device 50 is performed as follows. First, the OFD driver 48
Then, a voltage that easily overflows from the voltage (reference voltage) during normal shooting is applied to the OFD electrode of the CCD image sensor 14. As shown in the graph of FIG.
The amount of electricity at which the light receiving portion of the D image sensor is saturated is OFD
The voltage varies with the voltage VOFD applied to the electrode,
The higher the FD, the more likely it is to be saturated. Therefore, in this embodiment, the voltage VOFD is set to a high voltage that easily overflows during the preliminary light emission, and the voltage VOFD is set to a low voltage (reference voltage) during the main light emission.

After applying a voltage that easily overflows the reference voltage to the OFD electrode of the CCD image sensor 14 as described above, the shutter is turned on (FIG. 4).
(E)). A flash ON signal is output in synchronization with the shutter ON (FIG. 4 (F)), and the flash device 50 emits light (FIG. 4 (B)).

Thereafter, when a current is detected from the OFD of the CCD image sensor 14 by the current detector 49, the strobe light emission is stopped (FIGS. 4G and 4B), and the image data at this time is taken in. FIG. 4 (J)), the light emission time is measured. Subsequently, based on the captured image data, the brightness of an area corresponding to a preselected dimming subject is measured.

Next, prior to the main light emission, the CCD image sensor 14 is reset (charges are discharged to the OFD) (FIG. 4 (H)).
The voltage applied to the D electrode is returned to the reference voltage (see FIG. 4).
(I)) The strobe light emission time at which the brightness of the subject to be dimmed is optimized is determined by the light emission time during the preliminary light emission, the amount of saturation electricity at a high voltage at which overflow easily occurs, and saturation at a reference voltage. It is obtained based on the relationship with the quantity of electricity (Fig. 4
(K)). In calculating the optimal flash emission time, it is preferable to consider the relationship between the emission time and the emission intensity of the xenon tube Xe.

Thereafter, the shutter is turned on again (FIG. 4).
(E)), in response to the strobe ON signal synchronized with this shutter ON (FIG. 4 (F)), the strobe device 50 is caused to perform main emission for the above determined optimum strobe emission time (FIG. 4 (B), (F)), the image data at this time is captured (FIG. 4 (J)).

In this embodiment, the subject to be dimmed is selected and the flash emission time is determined so that the subject has the optimum brightness. However, the present invention is not limited to this. For example, a CCD image sensor may be used. It is also possible to determine the maximum strobe light emission time or the like at which the flashlight 14 does not overflow, and to perform the main light emission with this strobe light emission time.

In the above-described embodiment, the strobe device 50 continuously emits light for the above-described optimum strobe light emission time. However, the present invention is not limited to this. The xenon tube Xe is set so that the optimum strobe emission time obtained above will be obtained.
May be controlled intermittently a plurality of times. According to this, stroboscopic multiple exposure can be performed within a range in which the CCD image sensor does not overflow.

[0039]

As described above, according to the present invention, C
The CD image sensor can be used in combination as a sensor for strobe light control, and a dedicated light receiving sensor for strobe light control and a strobe light control circuit can be omitted. Also,
It is also possible to perform flash photography so that the brightness of the selected subject is optimal, or photography using flash multiple exposure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic camera including a strobe device according to the present invention.

FIG. 2 is a circuit diagram showing an internal configuration of the strobe device shown in FIG.

FIG. 3 is a graph showing a relationship between a voltage applied to an OFD electrode of a CCD image sensor and an amount of electricity at which a light receiving portion of the CCD image sensor is saturated.

FIG. 4 is a timing chart used to explain an operation at the time of flash photography including preliminary light emission and main light emission;

[Explanation of symbols]

14: CCD image sensor, 30: LCD monitor, 3
2 ... touch panel, 40 ... CPU (central processing unit), 4
8 OFD driver, 49 current detector, 50 strobe device, 51 DC / DC converter, 52 battery, 5
3. Insulated gate bipolar transistor (IGBT),
54: trigger circuit, 55: AND circuit, Xe: xenon tube, MC: main capacitor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H002 CD00 HA24 JA07 2H053 AD08 BA54 DA03 2H054 AA01 5C022 AA13 AB03 AB15 AB17 AC03 AC42 AC52 AC69

Claims (5)

[Claims] 1. A strobe device for an electronic camera that obtains an image signal indicating a subject image via a CCD image sensor, wherein a detection unit detects whether signal charges accumulated in a light receiving unit of the CCD image sensor have overflowed. And strobe control means for emitting strobe light from a strobe light emitting unit during strobe shooting, and stopping emission of the strobe light emitting unit when the detecting means detects overflow of the CCD image sensor. Electronic electronic flash device. 2. The electronic camera according to claim 1, wherein said detecting means detects an overflow of said CCD image sensor based on a magnitude of a signal charge flowing to an overflow drain of said CCD image sensor. . 3. A strobe device of an electronic camera for obtaining an image signal indicating a subject image via a CCD image sensor, wherein a detecting means for detecting whether signal charges accumulated in a light receiving portion of the CCD image sensor overflows. Setting means for setting the overflow drain voltage of the CCD image sensor to a reference voltage or a voltage which is more likely to overflow than at the time of the reference voltage; and strobe light emission after setting the overflow drain voltage of the CCD image sensor to a voltage which easily overflows. A flash unit that emits strobe light; and when the detection unit detects overflow of the CCD image sensor, the first unit stops emitting light of the strobe light emitting unit.
Calculating means for calculating an optimal flash emission time when the overflow drain voltage of the CCD image sensor is set to the reference voltage based on the flash emission time controlled by the first flash control means. Setting the overflow drain voltage of the CCD image sensor to the reference voltage at the time of flash photography, and then emitting flash light from the flash emission unit, and emitting the flash emission unit after the optimal flash emission time obtained by the arithmetic unit has elapsed. And a second flash control means for stopping the electronic flash. 4. A selecting means for selecting a subject to be dimmed,
The C corresponding to the subject selected by the selection means at the time of flash control by the first flash control means
Means for detecting a charge accumulation amount in a light receiving area of the CD image sensor, wherein the calculating means is configured to calculate the charge amount based on the strobe light emission time controlled by the first strobe control means and the detected charge accumulation amount. 4. The electronic camera according to claim 3, wherein when the overflow drain voltage of the CCD image sensor is set to the reference voltage, the flash emission time is calculated so that the charge accumulation amount of the selected subject becomes optimum. apparatus. 5. A strobe device of an electronic camera for obtaining an image signal indicating a subject image via a CCD image sensor, wherein a detecting means for detecting whether signal charges accumulated in a light receiving portion of the CCD image sensor overflows. Setting means for setting the overflow drain voltage of the CCD image sensor to a reference voltage or a voltage which is more likely to overflow than at the time of the reference voltage; and strobe light emission after setting the overflow drain voltage of the CCD image sensor to a voltage which easily overflows. A flash unit that emits strobe light; and when the detection unit detects overflow of the CCD image sensor, the first unit stops emitting light of the strobe light emitting unit.
Calculating means for calculating an optimal flash emission time when the overflow drain voltage of the CCD image sensor is set to the reference voltage based on the flash emission time controlled by the first flash control means. And setting the overflow drain voltage of the CCD image sensor to the reference voltage at the time of flash shooting so that the total flash time of the flash light emitting unit becomes the optimum flash light time obtained by the arithmetic means.
A second strobe control means for intermittently causing the strobe light emitting unit to emit light a plurality of times; and a strobe device for an electronic camera.