JPH05173229A - Red eye preventive device - Google Patents

Abstract

PURPOSE:To prevent the red-eye, and at the same time, prevent generation of trigger noises, shortage of the trigger voltage, and misconception between the preliminary light emission and the true light emission. CONSTITUTION:A red-eye preventive device is provided with a trigger pulse generating means 13 to generate the specified trigger pulse signal, a light emitting means Xe to make the discharge light emission by the trigger pulse signal, and a discharge current control means 14 to control the discharge current of the light emitting means Xe, and an arrangement is made so that the preliminary light emission by the light emitting means is achieved before the true light emission may be realized while the light emitting condition of the light emitting means Xe being maintained from one time application of the trigger pulse signal to the completion of the light emission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a red-eye prevention device for a camera in flash photography, and more particularly to a red-eye prevention device for a camera which preliminarily emits light prior to main flash emission, and more particularly to a preliminary light emission mechanism thereof.

[0002]

2. Description of the Related Art As a red-eye prevention method for flash photography of a camera, for example, a method in which an auxiliary lamp provided separately is lit for a certain period of time immediately before flash synchronization photography (Japanese Patent Publication Sho 58)
No. 48088), and a method of performing preliminary light emission a plurality of times prior to main light emission by the same flash (light emitting means) (see Japanese Patent Application Laid-Open No. 2-157733).

[0003]

However, such a conventional camera red-eye prevention device has the following problems.

That is, in the system described in Japanese Patent Publication No. 58-48088, since an auxiliary lamp is provided in addition to the flash, there is a restriction on the space of the camera, and a wide range of irradiation angles is required when performing group photographing. There was a problem that a large amount of power was required because of the demand.

On the other hand, in the method described in Japanese Patent Laid-Open No. 2-157733, a sufficient flashing angle can be secured by using the same flash for preliminary light emission, and in the case of a compact camera with a built-in zoom lens, the zoom ratio is increased. By changing the light distribution characteristics of the flash, the preliminary flash emission angle can be automatically set to a value suitable for the subject, but on the other hand, the trigger voltage can be applied multiple times to the light emitting means. However, since the light emitting means was made to emit light a plurality of times intermittently, there were the following drawbacks.

In recent years, microcomputers have been used to control the operation of cameras, and malfunctions due to noise have become the most problematic in the highly electronicized world. The largest source of noise inside a camera is The above trigger voltage reaches 1,000 V. Therefore, when applying the trigger voltage multiple times as described above, a sufficient shield is necessary to prevent the influence of noise, but when this shield is applied, there is a restriction on the space of the camera. Become.

Further, when light is emitted a plurality of times, the charging time of the main capacitor for light emission and discharge is shortened.
Each time the light is emitted, the charging voltage of the main capacitor for light emission and discharge of the flash circuit drops, and the subsequent trigger voltage also drops at the same time. For this reason, there occurs a problem that the subsequent light emission trigger is less likely to be applied. To prevent this problem, a voltage doubler circuit may be used as the trigger circuit, but the number of circuit elements will increase. On the other hand, if the number of pre-flashes is reduced to reduce the energy consumption of the main capacitor of the flash circuit (one or two times), the required amount of light cannot be obtained to prevent red eye, and There is a problem that the intended picture cannot be obtained because the user mistakenly thinks that the picture has been taken.

The present invention has been made in view of the above problems, and an inexpensive camera capable of preventing red eye, preventing trigger noise, trigger voltage shortage, and misrecognition of preliminary light emission or main light emission. It is intended to provide a red-eye prevention device.

[0009]

SUMMARY OF THE INVENTION A red-eye prevention device according to the present invention comprises a trigger pulse generating means for generating a predetermined trigger pulse signal, a light emitting means for discharging and emitting light according to the trigger pulse signal, and a discharge current of the light emitting means. And a discharge current control means for controlling the discharge current control means.
While the light emitting state of the light emitting means is maintained from the application of the number of times to the end of the main light emission, the preliminary light emission by the light emitting means is performed before the main light emission.

[0010]

According to the present invention, after the light emitting means emits light by one trigger pulse signal, it is not necessary to apply a voltage pulse for each preliminary light emission or main light emission, but only control of the discharge current value. Thus, preliminary light emission and main light emission can be performed. As a result, the problem of insufficient trigger voltage is solved and the chance of trigger noise being generated is reduced.

Further, since the light emitting state is maintained, it is possible to prevent misidentification of the preliminary light emission or the main light emission. Further, since the same light emitting means is used for the preliminary light emission and the main light emission, an auxiliary lamp is provided. Compared with, the number of parts is smaller and the price is lower.

[0012]

First, the principle of the present invention will be described with reference to FIG. 1. The flash circuit 1 includes a discharge capacitor MC, a discharge tube (light emitting means) Xe connected in series to the discharge capacitor MC, and Discharge resistance (discharge current control means) R
And a trigger circuit (trigger pulse generating means) 2 for the discharge tube Xe. Here, the plus (+) pole of the discharge capacitor MC is the plus (+) pole of the discharge tube Xe, and the minus (-) pole of the discharge tube Xe is the minus (-) of the discharge capacitor MC via the discharge resistor R. -) Is connected to the pole. Then, in this red-eye prevention device, a voltage pulse (trigger pulse signal) of several thousand V is applied to the discharge tube Xe by the trigger circuit 2, thereby discharging the electric charge charged in the discharge capacitor MC through the discharge tube Xe. It is supposed to be done.

The discharge current value in this case is determined by the size of the discharge resistance R connected in series with the discharge tube Xe. However, here, the discharge resistance R is configured as a variable resistance, and this discharge resistance R is 1 when the discharge tube Xe has a resistance value corresponding to the minimum sustainable discharge current value as Rmax.
The resistance value can be arbitrarily or stepwise changed between the application of the voltage pulse once and the end of the main light emission, for example, between 0Ω and Rmax. In this red-eye prevention device, preliminary light emission and main light emission can be performed by controlling the resistance value of the discharge resistor R and by controlling the discharge current value. In other words, the resistance value of the discharge resistance R can be changed to be temporarily reduced, and strong light emission (preliminary light emission) can be temporarily performed, and at the time when the preliminary light emission for red-eye prevention is finished, the shutter of the camera is released. The main light emission can be performed in synchronization with the opening by setting the resistance value to 0Ω.

According to this red-eye prevention device, since the maximum resistance value of the discharge resistor R is Rmax, after the discharge tube Xe emits light by one voltage pulse, the discharge tube Xe is discharged with the minimum discharge current.
Will continue to emit light, so that it is not necessary to apply a voltage pulse each time preliminary discharge or main emission after the discharge tube Xe emits light, but simply by controlling the resistance value of the discharge resistor R. The preliminary light emission and the main light emission can be performed.
An embodiment of a red-eye prevention device according to the present invention that embodies this basic principle will be described below with reference to the drawings.

(First Embodiment) FIG. 2 is a view showing a first embodiment of a red-eye prevention device for a camera according to the present invention. The same parts as those shown in the principle explanatory view of FIG. It is attached.

In the figure, reference numeral 11 is a camera control circuit 1.
0 is a red-eye prevention device for a camera controlled by outputs from output terminals A, B, and C.
Is a booster circuit 12 that boosts the voltage of the power supply battery E and supplies it to a circuit in the subsequent stage, and a discharge tube (light emitting means) Xe and a discharge capacitor MC that are connected to the booster circuit 12 via a rectifying diode D. The discharge tube Xe includes a trigger circuit (trigger pulse generating means) 13 and a discharge control circuit 14 that controls a discharge current flowing through the discharge tube Xe.

The step-up circuit 12 is composed of, for example, a blocking oscillator and a step-up transformer, and the step-up output from the step-up circuit 12 is rectified by a diode D and discharged to the discharge tube X.
It is supplied to the plus (+) side of e, the plus (+) side of the discharging capacitor MC, and the trigger circuit 13. The plus (+) side of the discharge capacitor MC is connected to the plus (+) side of the discharge tube Xe, and the minus (-) side is grounded G.
ND is done. The trigger circuit 13 includes a trigger coil T. C, a trigger capacitor C, a trigger thyristor SCR1 and resistors R1, R2 and R3,
The rectifying output side of the rectifying diode D is connected to the trigger coil T.P. via a resistor R3 and a trigger capacitor C. The primary winding of C is connected in series with GND, and the anode of the trigger thyristor SCR1 is connected to the resistor R3 and SC.
The cathode of R1 is connected to GND. A protection resistor R2 is connected between the gate of SCR1 and GND, and SC
The gate of R1 is connected to the output terminal A of the camera control circuit 10 via the resistor R1. In addition, the trigger coil T. C
The secondary winding of is connected to the trigger electrode of the luminous discharge tube Xe.

On the other hand, the discharge control circuit 14 includes a light emitting thyristor SCR2, a transistor Q1 and a resistor R4.
It is composed of R5, R6, R7, R8, R9,
A weak discharge resistor R6 is connected between the negative (−) pole of the discharge tube Xe and GND, and one terminal of a strong discharge resistor R7 is connected to the (−) pole of the discharge tube Xe. The other terminal of the resistor R7 is connected to GND by the emitter via the collector of the transistor Q1. The base of the transistor Q1 is connected to the output terminal C of the camera control circuit 10 via the resistor R9 and is also connected to GND via the resistor R8. The negative (-) pole of the discharge tube Xe is connected to the anode of the light emitting thyristor SCR2, and the cathode of the SCR2 is connected to GND.
The gate of the SCR2 is connected to the GND via the resistor R5 and is also connected to the output terminal B of the camera control circuit 10 via the resistor R4. The value of the resistor R6 is
The discharge tube Xe is set so as to have a minimum discharge current value capable of sustaining discharge.

The operation of the red-eye prevention device for a camera constructed as above will be described.

The boosted output of the booster circuit 12 connected to the power supply battery E is rectified by the diode D and is discharged to the discharge capacitor M.
C is usually charged to 300 to 350V. At this time, the trigger capacitor C is also charged to the same voltage via the resistor R3.

The first step of the release operation of the camera (not shown) performs photometry, distance measurement, etc., and the subsequent second step release operation performs the exposure operation. The timing waveform of each part at this time is shown in FIG. That is, by the second stage of the release operation (FIG. 3A), the trigger pulse shown in FIG. 3B is output from the output terminal A of the camera control circuit 10 to the gate of the trigger thyristor SCR1 via the resistor R1. As a result, SCR1 turns on and 300 to 350
The electric charge of the trigger capacitor C charged to V is S
CR1 anode-cathode and trigger coil T.C. Discharge through the primary winding of C. At this time, the trigger coil T. A voltage pulse of several thousand V is generated in the secondary winding of C and is applied to the trigger electrode of the discharge tube Xe.

The application of this voltage pulse causes the discharge tube Xe to start the light emission discharge. At this time, since the SCR2 and the transistor Q1 are in the OFF state, the discharge capacitor Me.
The electric charge of C is discharged through the discharge tube Xe and the resistor R6. However, since the value of the resistor R6 is set so that the discharge tube Xe has a minimum discharge current value capable of sustaining discharge,
The discharge tube Xe will emit weak light. Next, during the weak emission discharge of the discharge tube Xe, a base current is periodically supplied from the output terminal C of the camera control circuit 10 to the base of the transistor Q1 via the resistor R9 as shown in FIG. 3 (d). By doing so, the transistor Q1 is periodically turned on.
N When the transistor Q1 is turned on, the strong discharge resistance R7 and the weak discharge resistance R6 become parallel resistances, the resistance value is reduced and the discharge current (Xe current) is increased as compared with the case of only the weak discharge resistance R6 (see FIG. 3 ( See e)). As a result, strong light emission is performed with a sufficient amount of light to prevent red eye. Although not particularly limited here, the time during which the transistor Q1 is ON is 100 μm.
By shortening the time from s to 500 μs, the energy taken out from the discharging capacitor MC is suppressed and
The amount of light necessary to prevent red eye is secured by repeating strong discharge light emission.

Even if the strong discharge light emission ends in a short time, the weak discharge light emission is maintained by the resistor R6. Therefore, even if the re-trigger is not applied to the discharge tube Xe, the transistor Q1 is continuously turned on. It is possible to repeat strong discharge light emission.

Then, when the preliminary irradiation by the flash for preventing red eye is performed as in the above-mentioned operation and is completed, the shutter of the camera (not shown) starts opening and exposure is started (see FIG. 3 (f)). Then, when the shutter opening diameter reaches the aperture value determined by the subject distance and the flash guide number, the flash emission signal shown in FIG. 3C is output from the output terminal B of the camera control circuit 10 via the resistor R4. It

As a result, the main flash emission signal is applied to the gate of the light emitting thyristor SCR2, and the SCR2 is turned on.
To do. Since the resistance value of this SCR2 is extremely small,
2 and the parallel resistance value of the weak discharge resistor R6 are significantly lower than those of the parallel resistors R7 and R6, and the discharge current (X
(e current) instantaneously increases (see FIG. 3E), and the flash (discharge tube Xe) emits light. Even in this case, since the weak discharge light emission by the resistor R6 is maintained, it is not necessary to trigger the discharge tube Xe.

As described above, in this embodiment, the discharge tube Xe emits light by one voltage pulse, and thereafter, the discharge tube Xe continues to emit light with at least the minimum discharge current. It is not necessary to apply a voltage pulse for each preliminary light emission or main light emission, and the preliminary light emission and the main light emission can be performed simply by controlling the discharge current (Xe current). As a result, the chance of trigger noise being generated is reduced.

Further, by keeping the light emitting state, it is possible to prevent the misidentification of the preliminary light emission or the main light emission. Further, since the same discharge tube Xe is used for the preliminary light emission and the main light emission, an auxiliary lamp is provided. Compared with the case, the number of parts is reduced and the cost is reduced.

In this embodiment, the light emission is started by applying the voltage pulse to the discharge tube Xe once, but the point is that the light emission of the discharge tube Xe is started by one voltage pulse. Therefore, if the light emission is not successful, the voltage pulse applied thereafter becomes the first voltage pulse.

(Second Embodiment) The red-eye prevention device of the second embodiment differs from that of the first embodiment in that the transistor Q1 and the resistor R of the discharge current control circuit 14 of the first embodiment are different.
Instead of 7, R8 and R9, a diode D1, a capacitor C1 and resistors R10 and R11 are provided. That is, the diode D1, the resistor R10 and the capacitor C
1 is the negative (-) pole of the discharge tube Xe and the GN in this order.
It is connected to D. Further, one end of the resistor R11 is connected between the resistor R10 and the capacitor C1, and the other end is connected to GND. Here, the resistor R10 and the capacitor C1 form a charging time constant circuit, and the resistor R11 and the capacitor C1 form a discharging time constant circuit. Also, the diode D1
Functions as a reverse current blocking diode. In order to secure the amount of light necessary for preventing red eye, the resistance value of the resistor R11 is set to be larger than that of the resistor R10, and the discharge time is set to be longer than the charging time. Also, the resistance R
The resistance value of 10 is extremely smaller than that of the weak discharge resistance R6. For example, the resistance value of the resistor R10 is about 10Ω.

In the red-eye prevention device of this embodiment, when the discharge tube Xe starts to emit light by one voltage pulse, most of the discharge current (Xe current) flows to the capacitor C1 via the resistor R10 and the capacitor C1. Is charged.
In this case, since the resistance value of the resistor R10 is extremely smaller than that of the resistor R6, the discharge current (Xe current) becomes large (see FIG. 5).
(D)), Xe discharge resistance becomes small, and the arc tube Xe emits strong light. Then, when the charging of the capacitor C1 is completed, the input side potential of the capacitor C1 rises, so that most of the discharge current is now weak discharge resistance R.
It comes to flow through 6. Of course, the capacitor C1 is discharged after the charging is completed, but since the discharging is performed slowly, the discharging current flows into the capacitor C1 via the diode D1 and the resistor 10 to compensate for the discharging. However, since the Xe current flowing into the capacitor C1 side is small, the Xe discharge resistance increases, and Xe discharge resistance increases.
The e current will gradually decrease to near the minimum discharge current value.

According to the red-eye prevention device configured as described above, the same effect as that of the red-eye prevention device of the first embodiment can be obtained, and the pulse signal is input from the camera control circuit 10. Since it is not provided, the circuit configuration is simplified correspondingly, and the preliminary light emission is performed only once, so energy can be saved.

Incidentally, as shown in FIG. 6, a discharge current control circuit 14 of the second embodiment in which the diode D1 and the resistor R11 are removed can be considered, but in this discharge current control circuit 14, the capacitor C1 is charged. As it proceeds, the Xe current becomes smaller and the Xe discharge resistance becomes larger. Then, the potential drop of the weak discharge resistor R6 becomes small, and the charge of the capacitor C1 is discharged through the weak discharge resistor R6. As a result, the potential drop of the weak discharge resistor R6 becomes large, but due to the increase of the potential drop of the weak discharge resistor R6, X
e The discharge current is further reduced. Then, the capacitor C
1 discharge is promoted. By repeating these, the light emission of the discharge tube Xe is stopped in an instant. Therefore, FIG.
In the case of (1), the amount of light necessary for preventing red eye may not be obtained. On the other hand, in the discharge current control circuit 14 of the second embodiment, due to the presence of the reverse current blocking diode D1 and the resistor R11, the discharge of the electric charge of the capacitor C1 hardly affects the potential drop of the weak discharge resistor R6. On the other hand, since the preliminary light emission time can be arbitrarily controlled by changing the resistance value of the resistor R11 and the like, it is possible to easily obtain the amount of light necessary for preventing red eye.

Although two embodiments made by the present inventor have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the gist of the present invention. Needless to say.

[0034]

The red-eye prevention device according to the present invention comprises a trigger pulse generating means for generating a predetermined trigger pulse signal, a light emitting means for discharging and emitting light according to the trigger pulse signal, and a discharge for controlling a discharge current of the light emitting means. Current control means, and by the discharge current control by the discharge current control means, while maintaining the light emission state of the light emission means from one application of the trigger pulse signal to the end of main light emission, before the main light emission. In addition, since the preliminary light emission is performed by the light emitting means, the problem of insufficient trigger voltage is eliminated, and the chance of trigger noise generation is reduced. In addition, it is possible to prevent erroneous recognition of preliminary light emission or main light emission, and since the same light emitting means is used for preliminary light emission and main light emission, the number of parts is reduced compared to the case where an auxiliary lamp is provided, and it is inexpensive. Becomes

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention,

FIG. 2 is a circuit diagram of the red-eye prevention device according to the first embodiment.

FIG. 3 is a timing chart thereof.

FIG. 4 is a circuit diagram of a red-eye prevention device according to a second embodiment.

FIG. 5 is a timing chart thereof.

FIG. 6 is a circuit diagram of a red-eye prevention device shown for explaining the effect of the red-eye prevention device according to the second embodiment.

[Explanation of symbols]

 1 Flash circuit (camera red-eye prevention device) 2, 13 Trigger circuit (pulse generation means) 10 Camera control circuit 11 Camera red-eye prevention device 14 Discharge control circuit (discharge current control means) Xe Discharge tube (light-emitting means) MC For discharge Capacitor R Discharge resistance (Discharge current control means) R6 Weak discharge resistance R7 Strong discharge resistance

Claims (1)

[Claims] 1. A camera comprising: a trigger pulse generating means for generating a predetermined trigger pulse signal; a light emitting means for discharging and emitting light according to the trigger pulse signal; and a discharge current control means for controlling a discharge current of the light emitting means. In the red-eye prevention device, the discharge current control means maintains the light emitting state of the light emitting means from one application of the trigger pulse signal to the end of main light emission, and before the main light emission,
A red-eye prevention device for a camera, which is configured to cause preliminary light emission by the light emitting means.