JPH04340528A - Camera provided with red-eye phenomenon relieving function - Google Patents

Abstract

PURPOSE:To obtain a camera capable of photographing with appropriate exposure without complicating a stroboscopic device, while a red-eye phenomenon is relieved in the case of photographing with strobe light. CONSTITUTION:This camera is provided with a means for detecting charge voltage VF for a main capacitor C11 and a sub capacitor C12 which are charged to make a light emission tube Xe emit light, a means for outputting a trigger signal TRG to make the light emission tube Xe emit light by comparing the charge voltage VF with light emission permission voltage, a means for setting the light emission permission voltage, and a means for setting the light emission permission voltage higher than ordinary time by specified voltage in the case of relieving the red-eye phenomenon. These means are provided in a central processing unit CPU, and the specified voltage is set at least as voltage equivalent to the charge voltage which is lowered by preliminary light emission.

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 includes means for detecting the charging voltage of a capacitor that is charged to cause the arc tube to emit light, and a means for detecting the charging voltage of a capacitor that is charged to cause the arc tube to emit light, and a means for comparing this charging voltage with a light emission permission voltage to cause the arc tube to emit light. The apparatus includes means for outputting a trigger signal to enable the light emission, means for setting the light emission permission voltage, and means for setting the light emission permission voltage to be higher by a predetermined voltage than normal during red-eye reduction. In this case, the predetermined voltage is set to a voltage corresponding to at least the charging voltage lowered by pre-emission.

[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 to reduce the red-eye phenomenon.

FIG. 1 shows a circuit diagram of a strobe device built into the camera body CAB. central processing unit CP
are for controlling the flash operation, and include a photometry switch SWS that is turned on when the shutter button SB is pressed down halfway, and a shutter switch SW that is turned on when the shutter button SB is pressed down completely.
R 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, a charging permission signal CHEN when charging the strobe device,
Trigger signal TRG when firing the strobe and pre-flash signal PRE when performing pre-flash to reduce red-eye
and a voltage detection signal CHCK for detecting the charging voltage of the capacitor provided in the strobe device. or,
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 charges charged in the sub-capacitor C12 and the main capacitor C11 flow through the resistor R9.
A portion of the charge is supplied to the xenon tube Xe to perform pre-light emission with a small amount of light. Also, pre-emission switch SWP
When the main capacitor C11 is turned on, a large amount of main light emission is performed due to 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 C
If the charging voltage of 11 is 270V or more, the voltage detection signal C
After a predetermined delay time has elapsed from HCK, the neon tube Ne is turned on, and 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 N of the resistor R4
The voltage on the e side is the voltage (VF-VN) obtained by subtracting VN (approximately 220V) from the charging voltage VF.

Next, when the voltage detection signal CHCK is set to "L" level, the transistor Tr3 is turned off.
The current flowing through transistor TR3 is transferred to capacitor C3.
and flows through resistor R7, charging capacitor C3,
And the transistor Tr4 is turned on. Simultaneously with turning on the transistor Tr4, the collector potential of the transistor Tr4, which was connected to VDD via the resistor R8, is lowered, and the charging voltage signal RLS, which had been at the "H" level, becomes the "L" level. As the charging of the capacitor C3 progresses, the voltage across the capacitor C3 increases, and as the voltage drop across the capacitor C3 increases, the current flowing through the neon tube Ne decreases, and the neon tube N
The neon tube Ne was no longer able to keep e lit.
is turned off, and at the same time, the transistor Tr4 is turned off. Therefore, the collector of the transistor Tr4 is again connected to VD.
A potential of D is generated, and the charging voltage signal RLS becomes “
It 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 voltage 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 and the aperture, shutter, etc. of the camera based on the charging voltage detected by the charging voltage detection section.
A light emission permission voltage for outputting the trigger signal TRG is set here. That is, in the central processing unit CPU,
When the main capacitor C11 is fully charged (330V), the light emission permission voltage for outputting the trigger signal TRG is set to 290V, and the main capacitor C11
By outputting a trigger signal TRG to cause the xenon tube Xe to emit light when the charging voltage VF is equal to or higher than the light emission permission voltage, it is possible to secure the required amount of light and take pictures with proper exposure. Further, during so-called standby charging, in which photography is performed immediately after charging is completed, the light emission permission voltage is set to 280V.

Further, in this central processing unit CPU, when the red-eye reduction switch SWD is turned on, each light emission permission voltage is increased by 20V during full charging and standby charging, and increases to 310V during full charging, and increases to 310V during standby charging. The battery is configured to be set to 300V during charging. This 2
The value of 0V is approximately equal to the voltage at which the charging voltage VF of the main capacitor C11 is reduced by pre-emission of the xenon tube Xe. This was obtained from an experiment conducted by the present inventors using a strobe circuit such as this example, in which the charging voltage VF decreased by approximately 20 V due to pre-light emission.
This is based on the fact that if the light emission permission voltage is increased by 20 V in advance in this way, the charging voltage VF can be maintained at a level higher than the light emission permission voltage for normal photography even during pre-light emission. Note that changing this light emission permission voltage is done by comparing it with the detected charging voltage in the central processing unit CPU and setting the trigger signal T.
This problem can be easily dealt with by setting the software in the central processing unit CPU to change the reference voltage value of the comparison circuit that outputs RG.

The operation of strobe photography by the camera configured as above will be explained based on the flowcharts of FIGS. 1 and 5. First, when a photographer performs normal flash photography, he or she keeps the red-eye reduction switch off. Then, since no information from the red-eye reduction switch SWD is input to the central processing unit CPU, the pre-emission signal PRE from the central processing unit CPU remains at the "L" level, and the pre-emission switch SWP is turned on. For this reason, the central processing unit CP
When the trigger signal TRG is output from U, the trigger circuit T
Due to the RC, the xenon tube Xe emits main light with a large amount of light due to the charges of the main capacitor C11 and the sub-capacitor C12, and photographing is executed. At this time, central processing unit C
In the PU, the charging voltage VF is set based on the charging voltage signal RLS.
is detected, and this detected voltage is set as the light emission permission voltage 29 at that time.
By comparing with 0V or 280V, the trigger signal TRG
output. If the charging voltage VF is lower than the light emission permission voltage, charging is continued. At this time, the trigger signal T
Figure 7 shows a time chart showing the relationship between RG and shutter operation.
Shown in (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 the "L" level, and the pre-emission switch SWP is also returned to the on state.

Then, when the trigger signal TRG is output from the central processing unit CPU again 750ms 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, a large amount of light is emitted. The main light is emitted depending on the amount of light, and the shutter is operated at the same time to take a picture. Therefore, the pupil of the person as the subject begins to close due to the pre-emission described above, and by performing photography using the main emission 750 ms after the pupil closes, red eye can be reduced. Also, at this time, the central processing unit CPU detects the charging voltage VF based on the charging voltage signal RLS, compares this detected voltage with the light emission permission voltage 310V or 300V, which is approximately 20V higher than normal, and determines the charging voltage VF. is larger than the light emission permission voltage, a trigger signal TRG is output. A time chart showing the relationship between the trigger signal TRG and the shutter operation at this time is shown in FIG. 7(b).

Therefore, in this camera, when performing red-eye reduction photography, the light emission enabling voltage in the central processing unit CPU is set 20V higher than the normal light emission enabling voltage. Even if the charging voltage VF is reduced by approximately 20V, the charging voltage can be maintained above the normal flash permission voltage, and even if you continue to take flash photography using the main flash in this state, underexposure will occur. Never.

Here, in FIG. 1, the sub-capacitor C1
The resistor R9 connected in series with 2 may be omitted. Further, the pre-emission switch SWP is configured using 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 emission permission voltage to be increased during red-eye reduction is not limited to 20V as in the above embodiment,
Needless to say, this is changed depending on various factors constituting the strobe circuit, such as the capacitance values of the main capacitor C11 and the sub-capacitor C12, and the charging voltage at full charge.

As explained above, the present invention detects the charging voltage of a capacitor, and sets the light emission permission voltage, which is compared when outputting a trigger signal based on this charging voltage, to a predetermined value during red-eye reduction compared to normal times. In other words, the configuration is such that the voltage is set high at least by the voltage equivalent to the charging voltage lowered by pre-flash, so even if pre-flash is performed to reduce red-eye, a predetermined charging voltage can be secured. Immediately after that, even if flash photography is performed using the main flash, the exposure will not be insufficient, and photography can be performed with proper exposure. Moreover, since most of the means constituting the present invention can be installed in the central processing unit as software, the circuitry 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.

[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. In the camera equipped with the camera, the capacitor includes a means for detecting a charging voltage of the capacitor, a means for comparing the charging voltage with a light emission permission voltage and outputting a trigger signal for causing the arc tube to emit light, and a means for setting the light emission permission voltage. A camera with a red-eye reduction function, comprising means for setting the emission permission voltage to be higher by a predetermined voltage than in normal times during red-eye reduction. 2. The means for setting the light emission permission voltage high during red-eye reduction, wherein the predetermined voltage is set to a voltage corresponding to at least a charging voltage lowered by pre-light emission.
A camera with red-eye reduction function.