JP3093324B2 - Slave flash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slave flash which emits light in synchronization with the emission of another flash.

[0002]

2. Description of the Related Art A slave flash which emits light in synchronization with another flash is conventionally used when one flash is insufficient in light quantity or when it is desired to project light from a plurality of different directions. .

A conventional slave flash automatically emits light by detecting the light emission of another flash by a light receiving means,
When the light emission amount reaches a preset light emission amount, the light emission is stopped.

[0004]

[0005] In a general single-lens reflex camera, a TTL auto strobe is used as a main flash to which a slave flash is subordinate. The TTL auto strobe is a system that measures the amount of light reflected from a subject and reaches the film surface, and stops light emission when a certain exposure is obtained. Such a TTL
With the auto strobe, the photographer does not need to set the light emission amount itself.

However, in the conventional slave flash as described above, the photographer himself has to set the timing of stopping the light emission, so that the setting is complicated. Further, the main flash is controlled including the light amount by the slave flash. However, since the slave flash functions without receiving such control, it is difficult to make settings for obtaining an appropriate exposure as a whole. In addition, conventional thread
The light detected by the light receiving means
When the rising edge of the
There is something that is determined to be flash light emission. However
Such a slave flash has such a large amount of light
There is no flickering external light, but if its rise is steep
False recognition of a flash and malfunction
There is a problem that there is.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems in the conventional technology, the <br/> slave flash that can prevent a malfunction due to external light makes it possible to automatically control the emission stop The purpose is to provide.

[0007]

In order to achieve the above object, a slave flash according to the present invention has a light emitting section for emitting a flash, a light receiving section for receiving a flash of another flash, and a light receiving section for receiving the light. The amount of light change speed is the first
Outputs the first level when the speed exceeds a predetermined speed, and
The second level when the activating speed falls below the second predetermined speed.
A first comparison operation circuit for outputting a signal,
Compare the amount of received light with the predetermined amount of light, and the amount of received light exceeds the predetermined amount of light.
Output the first level when the light level is
A second comparison that outputs a second level when:
An operation circuit, an output of the first comparison operation circuit, and a second comparison operation
Issued when the output of the arithmetic circuit is at the first level.
A light emission start circuit for starting light emission of the light unit, and a first comparative performance
Of the output of the arithmetic circuit and the output of the second comparison
And a light emission stop circuit for stopping light emission of the light emitting unit when at least one of the light emission levels reaches the second level .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
1 to 4 show one embodiment of the present invention.

As shown in FIG. 1, a single-lens reflex camera 10 is electrically connected to a strobe 20 for emitting light toward a subject. Further, independently of the single-lens reflex camera 10, the slave flash 30 is arranged so as to illuminate the subject S from different directions.

A strobe 20 connected to the camera 10 includes a light receiving element 11 provided inside the single-lens reflex camera 10 and a light control circuit.
Together with 12, it constitutes a TTL auto strobe system. The dimming circuit 12 includes an integrating circuit 12a that integrates the voltage of the light receiving element (photodiode) 11, as shown in FIG. 2, and an exposure setting circuit 12b that sets a voltage corresponding to an appropriate exposure based on the film sensitivity Sv. And a comparator 12c for comparing the integration output of the integration circuit 12a with the set voltage of the exposure setting circuit 12b.

When the shutter is opened and the strobe 20 emits light, the light control circuit 12 integrates the amount of light reaching the film 14 from the subject S via the photographic lens 13 based on the output of the light receiving element 11. A light emission stop (quench) signal is output from the output terminal of the comparator 12c when the integral voltage exceeds the set voltage and a light amount necessary for exposure is obtained, and light emission of the strobe 20 is stopped.

On the other hand, as shown in FIG. 1, the slave flash 30 includes a light emitting section 31 and a light receiving section which receives light from the strobe 20.
32, a light emission start circuit 33 for starting light emission of the light emitting unit 31 in response to a signal from the light receiving unit, and a light emission stop circuit 34 for stopping light emission.

The TTL auto strobe stops emitting light when proper exposure is obtained, including not only the amount of light of the strobe 20 itself but also the amount of light of the slave flash 30. This is the timing at which the proper exposure is obtained regardless of the presence or absence of the image.

When the light emission start circuit 33 receives the signal from the light receiving section 32 and detects the start of light emission of the strobe 20, the slave flash 30 starts the light emission of the light emission section 31 in synchronism therewith, and the light emission stop circuit 34 Receives the signal from the light receiving unit 32 and detects the stop of the emission of the strobe light 20, and in synchronization with this, stops the emission of the light emitting unit 31. As a result, an appropriate exposure is obtained for the film 14.

FIG. 3 shows an example of a circuit of the slave flash 30.

When the charging switch SW is turned on, the voltage of the battery BATT is boosted by the transformer and is charged in the main capacitor C1, and when the charging voltage exceeds a certain value, the neon tube Ne is turned on.

When a light emission start signal is output from the light emission control circuit 100 when the charge voltage is equal to or higher than a predetermined value, a current flows from the main capacitor C1 and the slave flash
The xenon tube Xe as the light emitting part 31 of 30 emits light. When a light emission stop signal is output from the light emission control circuit 100, the xenon tube Xe turns off.

The light emission control circuit 100 includes a phototransistor 32a constituting the light receiving section 32, a voltage dividing resistor R1 connected in series with the phototransistor 32, resistors R2 and R3 for setting a reference voltage, a time constant circuit 101, It comprises comparators A and B as first and second comparison operation circuits , and an AND circuit C for taking AND of these.

The inverting input terminal of the first comparator A
The reference voltage divided by the two resistors is applied, and the voltage divided by the phototransistor 32a and the resistor R1 is applied to the non-inverting input terminal. The output of the first comparator A rises when the amount of light received by the phototransistor 32a exceeds a threshold level determined by the reference voltage.

The same reference voltage as described above is applied to the inverting input terminal of the second comparator B, and the voltage of the time constant circuit 101 is applied to the non-inverting input terminal. The second comparator B functions as a differentiating circuit, and its output is inverted when the amount of light received by the phototransistor 32a changes rapidly.

Next, the operation of the light emission control circuit 100 will be described with reference to FIG. In FIG. 4, (A) shows the emission intensity of the strobe 20,
(B) is the output signal of the first comparator A, (C) is the output signal of the second comparator B, (D) is the output signal of the AND circuit C, and (E) is the xenon tube of the slave flash 30. The luminescence amount is shown.

At time t0, the strobe 20 provided in the camera starts emitting light. First, the output of the second comparator B goes high due to the rapid change in the amount of light,
At t1, the amount of strobe light, that is, the phototransistor 32
When the light reception amount of “a” exceeds the threshold level SH of the first comparator A, the output of the first comparator A also rises. At the same time, the output of the AND circuit C becomes high level, and the insulated gate bipolar transistor IGBT
Turns on, and the xenon tube Xe starts emitting light.

At time t2, when the flash on the camera side stops emitting light due to the quench signal on the camera side, the flash 20
The output of the second comparator B becomes low level because the light amount of the second comparator B sharply decreases. At the same time, the output of AND circuit C goes low, turning off the power transistor IGBT.
Then, the xenon tube Xe stops emitting light.

Thereafter, at time t3, the light quantity of the strobe 20 becomes lower than the threshold level, and the output of the first comparator A also falls to the low level.

As described above , the light received by the phototransistor
The strobe 20 emits light in combination with the light amount level and the light amount change speed.
By judging, the steady state other than the light by the strobe 20
Slave flash by light, for example, large amount of steady illumination light
The malfunction of the menu 30 or the sudden change of the minute light amount, for example,
When the minute illumination light other than ROBO 20 blinks momentarily
Malfunction of the slave flash 30 can be prevented.
Only the start / stop of the flash 20 is accurately detected.
I can get out .

[0026]

As described above, according to the present invention, since the slave flash detects the start and stop of the flash of the camera by itself and controls the flash, the user manually sets the flash amount. It is not necessary. In addition, large light intensity
Malfunction due to malfunction due to ordinary light or slight sudden change in ambient light level
Movement can also be prevented.

In particular, when a TTL auto strobe is used on the camera side, an appropriate exposure including the light amount of the slave flash can be obtained by the operation of the TTL auto strobe.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of the present invention.

FIG. 2 is a circuit diagram of a dimming circuit on the camera side.

FIG. 3 is a circuit diagram of a slave flash according to the embodiment.

FIG. 4 is a graph showing a relationship between a light emission amount of a flash on a camera side, outputs of respective circuits on a slave flash side, and a light emission amount of a slave flash.

[Explanation of symbols]

 10 Camera 20 Flash 30 Slave flash 31 Light emitting unit 32 Light receiving unit 33 Light emission start circuit 34 Light emission stop circuit

Claims (1)

(57) [Claims] 1. A light emitting unit for emitting a flash, a light receiving unit for receiving a flash of another flash, and a light amount changing speed of an amount of light received by the light receiving unit is a first predetermined value.
When the speed is exceeded, the first level is output and the light amount change
A second level when the speed falls below a second predetermined speed;
A first comparison operation circuit that outputs the light quantity, and compares the amount of light received by the light receiving unit with a predetermined amount of light.
When the received light amount exceeds the predetermined light amount, the first
Level, and the received light amount is equal to or less than the predetermined light amount.
A second comparison operation for outputting the second level when the
Circuit, an output of the first comparison operation circuit, and the second comparison operation circuit.
A light emission start circuit for starting light emission of the light emitting unit when both the output of the road and the first level are at the first level; and an output of the first comparison operation circuit and the second comparison operation time.
At least one of the outputs of the road is the second level
A slave flash having a light emission stop circuit for stopping light emission of the light emitting unit when the light emission becomes .