JPH04348332A - Camera provided with red-eye reducing function - Google Patents

Abstract

PURPOSE:To obtain a camera where photographing with appropriate exposure can be performed without complicating a stroboscopic device, while a red-eye phenomenon at the time of photographing with strobe light is reduced. CONSTITUTION:In order to prevent underexposure at the time of photographing with main light emission caused by the lowering of the charged voltage of a capacitor which occurs in the case of allowing a light emitting tube to preliminarily emit light to reduce the red-eye phenomenon, a diaphragm value at the time of photographing with the main light emission is corrected by as much as the lowering of the voltage. In such a case, it is good to detect the charged voltage before the main light emission and calculate a correction value in accordance with the detected voltage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera equipped with a strobe device, and more particularly to a camera having a function of reducing red-eye phenomenon.

0002

[Prior Art] Red eye phenomenon is a phenomenon in which when a person is photographed with a strobe light, the person's eyes appear red, and this is said to be caused by the person's pupils being dilated when the photograph is taken. . In other words, in relatively dark situations such as when using a strobe, the pupils of the human eye are often in a dilated state, so if you take a strobe photograph in this state, the strobe light will pass through the pupil and reach the retina. The light reflected from the retina causes the human eye to appear red. The human pupil functions to close in response to light, but the time required for it to close after sensing light is generally 0.5 to 1 second, so it is difficult for the camera shutter to close after the strobe fires. The red eye phenomenon occurs because it does not open in time. Conventionally, as one method for reducing this red-eye phenomenon, a method has been proposed in which pre-flash is performed once or several times immediately before flash photography is performed. In this method, a person's pupils are closed by pre-flash, and then the main flash is used to take the picture, thereby avoiding taking pictures with the pupils dilated and reducing the red-eye phenomenon.

0003

[Problems to be Solved by the Invention] By the way, commonly used camera strobe devices have a structure in which a capacitor is charged with an electric charge, and the charged electric charge is used to cause an arc tube (xenon tube) to emit light. is taken. The amount of light emitted by this arc tube is determined by the amount of charge charged in the capacitor, and usually by the charging voltage generated across the capacitor. When photographing with the camera, the aperture of the camera is determined to provide appropriate exposure according to the amount of light emitted from the arc tube.

Therefore, when such a strobe device is used to emit a pre-flash to reduce the red-eye phenomenon described above, a portion of the charge charged in the capacitor is consumed by the pre-flash, and the charging voltage of the capacitor decreases. As a result, the amount of light emitted during the next main flash will be reduced.
As a result, there is a risk that the exposure will be insufficient and it will not be possible to take pictures with proper exposure. To solve this problem, a circuit configuration that quickly charges the capacitor to restore the charging voltage at the same time as pre-flashing can be considered, but including this type of circuit would complicate the configuration of the strobe device and also It is extremely difficult to restore the charging voltage within the minute time between light emission and main light emission. SUMMARY OF THE INVENTION An object of the present invention is to provide a camera that reduces the red-eye phenomenon, does not complicate the strobe device, and allows photographing with proper exposure.

[0005]

[Means for Solving the Problems] The camera of the present invention is provided with means for correcting the aperture value of the camera by an amount corresponding to the charging voltage lowered by pre-emission during red-eye reduction. For example, a means for detecting the charging voltage of a capacitor, a means for calculating a correction value for a strobe guide number based on this charging voltage, a means for setting a correction value for red-eye reduction shooting, and a means for calculating a correction value for a flash guide number based on the charging voltage, a means for setting a correction value for red-eye reduction shooting, and a means for calculating a correction value for a flash guide number based on this charging voltage, a means for setting a correction value for red-eye reduction shooting, and a means for calculating a correction value for a flash guide number based on the charging voltage. and means for performing aperture calculation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 2 is an external view showing an example of a camera to which the present invention is applied, in which a strobe STB is integrally provided in a camera body CAB having a zoom lens ZL, and a shutter button SB
The strobe STB is configured to emit light by pressing down the button. Also, on the back of the camera body CAB, there is a zoom lever Z for adjusting the focal length of the zoom lens ZL.
LL, a finder FN for determining the photographic field of view, various operation buttons B1 and B2 for mode setting, a display section LCD, etc., as well as a red-eye reduction switch SWD for performing strobe photography with reduced red-eye phenomenon.

FIG. 1 shows a circuit diagram of a strobe device built into the camera body CAB. central processing unit CP
U is for controlling the strobe operation, and includes a photometry switch SWS that is turned on when the shutter button SB is pressed down halfway, and a shutter switch that is turned on when the shutter button is pressed down completely. S
WR and the on/off states of the red-eye reduction switch SWD, which is turned on during red-eye reduction photography, are input. On the other hand, there is a charging permission signal CHEN when charging the strobe device, a trigger signal TRG when firing the strobe, and a pre-flash signal PR when performing pre-flash to reduce red-eye.
E and a voltage detection signal CHCK for detecting the charging voltage of a capacitor provided in the strobe device. Further, a charging voltage signal RLS detected corresponding to this voltage detection signal CHCK is input.

On the other hand, the circuit configuration of the strobe uses a battery as a power source BATT, and the voltage of this battery BATT is stabilized by a regulator REG to VDD, which is then supplied to the central processing unit CPU and a charging voltage detection section to be described later. Also, Tr
1 is an oscillation transistor, Tr2 is a switching transistor, R1, R2, R3 are resistors, C is a capacitor, D1
, D2 are diodes, and TNS is a step-up transformer, the switching transistor Tr2 is turned on in response to the charging permission signal CHEN from the central processing unit CPU, and an alternating current signal is generated by turning on and off the oscillation transistor Tr1.
This is boosted by a step-up transformer TNS, and diode D2
A high voltage of 330V or more is obtained by rectifying the voltage.

[0009] Also, C11 is a large-capacity main capacitor,
C12 is a small-capacity sub-capacitor connected in parallel with this main capacitor C11 via resistor R9, Xe is a xenon tube as a light emitting tube, SWP is a pre-emission switch connected in series with the xenon tube Xe, and TRC is a trigger circuit. , the main capacitor C11 and the sub capacitor C12
is charged by the high voltage. Here, the main capacitor C11 is fully charged at 330V. and,
When the trigger signal TRG from the central processing unit CPU is input to the trigger circuit TRC, the xenon tube Xe is caused to emit light. At this time, when the pre-emission switch SWP is turned off by the pre-emission signal PRE from the central processing unit CPU, the charge charged in the sub-capacitor C12 and a part of the charge in the main capacitor C11 flowing through the resistor are transferred to the xenon tube Xe. A small amount of pre-light emission is performed by supplying the light to the light source. Further, when the pre-light emission switch SWP is turned on, main light emission with a large amount of light is performed by the charge stored in the main capacitor C11.

Furthermore, Ne is a neon tube that lights up when a voltage of 270V or more is applied, and thereafter maintains a voltage around 220V regardless of the current value, and this neon tube Ne and transistors Tr3 and Tr4, The resistors R4 to R8 and the capacitor C3 constitute a charging voltage detection section that detects the charging voltage of the main capacitor C11. That is, FIG. 3 is a diagram for explaining the operation of this charging voltage detection section, and shows the voltage detection signal CHCK output from the central processing unit CPU.
When the voltage is set to the "H" level, the transistor Tr3 is turned on and the capacitor C3 is discharged, and at the same time, the negative side of the neon tube Ne is connected to the ground via the resistor R4 and the transistor Tr3. At this time, the main capacitor C1
If the charging voltage of 1 is 270V or more, the voltage detection signal CH
After a predetermined delay time has elapsed from CK, the neon tube Ne is turned on, and a current flows through the neon tube Ne, the resistor R4, and the transistor Tr3. At this time, the voltage VN across the neon tube Ne is approximately 220V, so the neon tube Ne of the resistor R4
The voltage on the side becomes the voltage (VF-VN) obtained by subtracting VN (approximately 220V) from the charging voltage VF.

Next, the voltage detection signal CHCK is set to “L, .
level, the transistor Tr3 is turned off, so the current flowing through the transistor TR3 is reduced to the capacitor C
3 and the resistor R7, the capacitor C3 is charged, and the transistor Tr4 is turned on. At the same time as this transistor Tr4 is turned on, the collector potential of the transistor Tr4, which was connected to VDD via the resistor R8, is lowered, and the charging detection signal RLS, which had been at "H" level, is
becomes “L” level. Then, as the charging of the capacitor C3 progresses, the voltage across the capacitor C3 increases,
When the voltage drop caused by the capacitor C3 becomes large, the current flowing through the neon tube Ne decreases, making it impossible to keep the neon tube Ne lit.
e is turned off, and at the same time, the transistor Tr4 is turned off. Therefore, the collector of the transistor Tr4 is again supplied with V.
A potential of DD is generated, and the charging voltage signal RLS becomes "H" level.

Therefore, the higher the charging voltage VF of the main capacitor C11 is, the less the voltage drop caused by the capacitor C3 will affect the neon tube Ne, and the timing of extinguishing the neon tube Ne will be delayed. Utilizing this, the charging voltage VF can be detected by measuring the time T during which the charging detection signal RLS is at the "L" level. FIG. 4 is a characteristic diagram showing the relationship between the time T and the charging voltage VF. In addition, when the charging voltage VF is 270V or less, even if the transistor Tr3 is turned on, the neon tube N
Since e does not light up, the charging voltage signal RLS remains at the "H" level.

On the other hand, the central processing unit CPU controls the flash device, the aperture, the shutter, etc. of the camera based on the charging voltage detected by the charging voltage detection section. In particular, when controlling the aperture, detailed explanations are omitted, but the standard light amount of the strobe device, that is, the standard guide number,
Aperture value AVS is calculated based on the distance to the subject. At this time, the reference guide number is set based on the light intensity when the charging voltage of the arc tube Xe is 270V, and if the charging voltage is higher than this, a correction value of the guide number is calculated and this is used as It is configured to be used for correction when calculating the value AVS. Furthermore, in this central processing unit CPU, when the red-eye reduction switch SWD is turned on, the charging voltage VF of the main capacitor C11 is reduced due to the pre-light emission of the xenon tube Xe, and according to the inventor's experiments, this embodiment In this case, the voltage decreases by about 20V, so the guide number corresponding to this decreased voltage is subtracted from the calculated guide number of the strobe device.

The operation of strobe photography by the camera configured as above will be explained based on the flowcharts of FIGS. 1 and 5. First, the central processing unit CPU detects the charging voltage VF and continues charging until it reaches at least 280V. When the photographer takes normal flash photography,
Keep the red eye reduction switch off. Then, since the information from the red-eye reduction switch SWD is not input to the central processing unit CPU, the pre-flash signal P from the central processing unit CPU is
RE remains at “L” level, and the pre-emission switch S
WP is turned on. For this reason, the central processing unit CPU
When the trigger signal TRG is output from the trigger circuit TR
C, the xenon tube Xe emits light with a large capacity due to the charges of the main capacitor C11 and the sub-capacitor C12,
Shooting is executed. At this time, the central processing unit CPU detects the charging voltage VF based on the charging voltage signal RLS, and converts this detected voltage into threshold voltages 330V, 315V, 2
Compare sequentially with 85V. And the charging voltage VF is 330
When the voltage is above V, the guide number correction value is set to 1EV, when it is 315 to 330V, the correction value is set to 2/4EV, when it is 285 to 315V, the correction value is set to 1/4EV, and when it is below 285V, the correction value is set to 0EV. Add the correction value DGV to the aperture value AVS (aperture value AVS
The corrected aperture value AVS is calculated. Then, based on the corrected aperture value AVS, photographing is performed using main light emission. Incidentally, a time chart showing the relationship between the trigger signal TRG and the shutter operation at this time is shown in FIG. 7(a).

On the other hand, when the photographer performs red-eye reduction photography, he turns on the red-eye reduction switch SWD. Then, information from the red-eye reduction switch SWD is input to the central processing unit CPU. As shown in a detailed flowchart in FIG. 6, when the shutter switch SWR is turned on by the shutter button, the pre-flash signal PRE from the central processing unit CPU becomes "H" level, and the pre-flash switch SWP is turned off. . Therefore, when the trigger signal TRG is output from the central processing unit CPU and its level becomes "H", the trigger circuit TRC causes the xenon tube
e is the charge of sub capacitor C12 and main capacitor C
11, it emits light with a small amount of light due to the charge of a part of it. At this time,
Shutter does not work. The trigger signal TRG goes to "L" level after 5ms, and then the pre-emission signal PRE
is also returned to “L,, level,” and the pre-emission switch SWP
is also returned to the on state.

Next, when the trigger signal TRG is output from the central processing unit CPU again 750 ms after the pre-emission, the xenon tube Xe emits light again by the trigger circuit TRC, but at this time, due to the charge of the main capacitor C11, the The main light is emitted depending on the amount of light, and the shutter is operated at the same time to take a picture. Due to this pre-emission, the pupil of the person as the subject begins to close, and the pupil closes at 750.
It goes without saying that red-eye can be reduced by performing photography using the main flash after ms. Also during this red-eye reduction shooting, the central processing unit CPU uses the charging voltage V based on the charging voltage signal RLS as in the normal time described above.
F is detected, and the aperture value AVS is corrected using this detected voltage. In this case, correction is further performed using a preset correction value DGVx by the amount of the charging voltage lowered by the pre-emission. In the case of this embodiment, since the charging voltage VF is lowered by approximately 20V due to pre-emission, the correction value DGVx corresponding to this voltage is set to the aperture value A by 2/4EV.
Based on the corrected aperture value AVS, which is subtracted from VS (corrected in the direction of opening the aperture by reducing the aperture value AVS), photographing is performed using main light emission. Furthermore, at this time,
A time chart showing the relationship between the trigger signal TRG and the shutter operation is shown in FIG. 7(b).

[0017] In both the above-mentioned normal shooting and red-eye reduction shooting, after correcting the aperture value AVS based on the correction of the guide number of the strobe device, the guide number based on the film sensitivity SV and the zooming of the strobe itself is corrected. Correction of the amount of change ZDGV, and furthermore, the amount of change α of the open F number based on the focal length of the zoom lens ZL
Needless to say, the final aperture value is set by making corrections and the like.

Therefore, in this camera, when performing red-eye reduction photography, the main flash is When shooting at , it is possible to shoot at the optimal aperture value, and underexposure will not occur.

FIG. 8 is a flowchart showing another embodiment of the present invention. In this embodiment, during normal photography, aperture correction is performed in accordance with the charging voltage, similar to the embodiment described above. On the other hand, in red-eye reduction photography, the charging voltage VF is detected after the pre-emission is completed, and aperture correction is performed based on the charging voltage at that time. That is, after pre-emission is performed, the charging voltage detection section detects the charging voltage VF. Then, the charging voltage VF at this time is sequentially compared with the threshold voltages of 310V, 295V, and 265V. When the charging voltage VF is 310V or more, the correction value DG
Vy is set to 1EV, when the voltage is 295 to 310V, the correction value DGVy is set to 2/4EV, when the voltage is 265 to 295V, the correction value DGVy is set to 1/4EV, and when the voltage is 265V or less, the correction value DGVy is set to 0EV, and these correction values D
Aperture value AVS is calculated based on GVy. This threshold value is set based on the inventor's experiment in which the charging voltage VF is lowered by approximately 20 V due to pre-light emission. In this case, approximately 50m is required to correct the aperture value after pre-flash.
s processing time is required, so in this processing, the waiting time of 750 ms shown in FIG. 6 is changed to 700 ms here.
The waiting time is assumed to be ms.

Therefore, in this embodiment, even if the charging voltage is lowered due to the pre-emission, the charging voltage VF is detected immediately before the main emission, and the correction value D obtained according to this detected voltage is
Since the aperture value AVS is corrected based on GVy, when shooting with main light emission, shooting is performed with exposure according to the charging voltage at that time, making it possible to shoot with proper exposure. Further, in this embodiment, more accurate aperture correction can be realized than in the previous embodiment in which the aperture value AVS is fixedly corrected after pre-emission.

Here, in FIG. 1, sub-capacitor C1
The resistor R9 connected in series with 2 may be omitted. Further, the pre-emission switch SWP may be an electronic device such as a thyristor, and the pre-emission switch SWP may be configured to be turned off by the "L" level of the pre-emission signal PRE. Furthermore, the correction value by pre-emission during red-eye reduction is not limited to 2/4EV as in the above embodiment, but also includes the capacitance value of the main capacitor C11 and the sub-capacitor C12, the power consumption of the arc tube Xe, etc. Needless to say, this may be changed depending on various factors constituting the circuit.

As explained above, the present invention is provided with means for correcting the aperture value of the camera by an amount corresponding to the charging voltage lowered by the pre-flash, so that the pre-flash is performed to reduce red-eye. Since the aperture value is corrected as the flash light intensity decreases, it is possible to avoid underexposure and take pictures with proper exposure. Further, since the means constituting the present invention can be installed in the central processing unit as software, the circuit of the strobe device does not have to be complicated and can be easily configured.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a strobe device provided in a camera of the present invention.

FIG. 2 is an external view of a camera to which the present invention is applied, seen diagonally from behind.

FIG. 3 is a time chart for explaining the operation of a charging voltage detection section.

FIG. 4 is a characteristic diagram showing the relationship between time T of a charging voltage signal and charging voltage VF.

FIG. 5 is a flowchart of strobe operation according to the present invention.

FIG. 6 is a detailed flowchart of a pre-emission operation.

FIGS. 7(a) and 7(b) are time charts during normal photography and red-eye reduction photography, respectively.

FIG. 8 is a flowchart of another embodiment of the invention.

[Explanation of symbols]

CPU Central processing unit SWD red eye reduction switch SWP Pre-emission switch C11 Main capacitor C12 Sub capacitor Xe xenon tube (luminous tube) TRC trigger circuit VF Charging voltage CHCK voltage detection signal RLS Charging voltage signal TRG Trigger signal PRE Pre-emission signal

Claims (2)

[Claims] 1. A red-eye reduction function comprising a strobe device that causes an arc tube to emit light with an amount of light corresponding to the charging voltage of a capacitor, and causes the arc tube to pre-emit immediately before performing strobe photography using the arc tube. A camera with a red-eye reduction function, characterized in that the camera is equipped with means for correcting the aperture value of the camera by an amount corresponding to the charging voltage lowered due to pre-flash. 2. Means for detecting a charging voltage of a capacitor, means for calculating a correction value for a strobe guide number based on the charging voltage, means for setting a correction value for red-eye reduction shooting, and each of the correction implants. 2. The camera with red-eye reduction function according to claim 1, further comprising means for calculating the aperture based on the red-eye reduction function.