JPH01277224A - Flash photographing device - Google Patents

Abstract

PURPOSE:To reduce the number of comparators for detection by switching the gain of an integrating circuit, which generates an output corresponding to the quantity of received light, for the purpose of controlling the quantity of emitted light at each time in accordance with each light emission. CONSTITUTION:A light emission stopping circuit and a switching circuit are provided, and the output of the integrating circuit which generates the output corresponding to the quantity of received light is inputted to the light emission stopping circuit and is compared with a reference value, and the light emission stopping circuit stops each light emission when the output of the integrating circuit reaches the reference value, and the switching circuit successively changes the gain of the integrating circuit to a value corresponding to each light emission at each time of light emission. Since the reference value is switched for each light emission when the output of the received light quantity integrating circuit is compared with the reference value to stop the flash, the number of comparators for detection is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a flash photography bag σ, particularly a type of flash photography in which light is emitted multiple times during one exposure, and the amount of light emitted each time is arbitrarily adjusted. Regarding equipment.

[Prior art]

Conventionally, in the above-mentioned type of flash photography device, a number of comparators corresponding to the number of times of each light emission are provided as a configuration for detecting whether or not the amount of light emission for each time reaches a set amount of light emission. This system is configured to detect the amount using individual comparators, which has the disadvantage that the number of detection comparators increases.

〔the purpose〕

In view of the above, in order to regulate the amount of light emitted each time in response to each light emission, the present invention switches the gain of an integrating circuit that generates an output according to the amount of light received each time the light is emitted, and transmits it to the same comparator. It is an object of the present invention to provide a flash photography device which eliminates the drawbacks of the conventional device by detecting the amount of light emitted each time using one comparator.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a flash light emission control device according to the present invention.

In the figure, ■ indicates the camera side configuration, FIash, l
.

FIash2 indicates first and second strobe devices connected to the camera (2).

Since the above-mentioned strobe device is a well-known device, a detailed explanation will be omitted, but a flash (not shown) is produced in response to an on signal or a high level signal of a synchro switch inputted through terminals T, , ', and TIL, respectively. Trigger circuit 'TGI, TG2 and terminal Tb I' + to trigger the tube
a commutation circuit (light emission stop circuit) LC that stops flash emission in response to a light emission stop signal inputted via Tb□';
, LC2.

On the camera side l, X is a synchro switch that is turned on in conjunction with the shutter front curtain, MM is a one-shot circuit that outputs a high-level signal for a predetermined period of time when the switch is turned on, and the output of this circuit is connected to terminals T & Fal through l
Trigger the shl trigger circuit TGI. SW1 is a switch that is turned off while the high level signal is being sent out in response to a high level signal inputted through the OR gate OR, and a capacitor Ci is connected in parallel to the switch SWI. PD is a light receiving element connected to the input of the operational amplifier OP. The light receiving element is arranged so as to receive the reflected light on the film surface of the light incident on the camera through the photographic lens. A well-known transistor Tr includes the photodetector PD, an operational amplifier OP, a diode D1 connected to the output and input of the amplifier OP, and a transistor Tr whose base is connected to the output of the amplifier OP and whose collector is connected to the integrating capacitor Ci. An integral circuit is formed.

Vcl or Vc2 connected to a voltage (not shown) is applied to the emitter of the transistor through a switch 5W-2, and by applying Vcl or Vc2, the gain of the known integrating circuit changes.

COMP connects the power to the output of the above integration circuit,
The reference voltage Vre is connected to a reference signal source (not shown).
It is a comparator to which f is applied.

The comparator outputs the light emission stop signal, and the light emission stop circuit LC of each strobe device F1a5hl, F1a5h2 is output via the AND gate AND or switch SW3.
,, is transmitted to the LC2 to stop the light emission of each strobe device.

DL is a play circuit that responds to the output (high level signal) of the one-shot circuit MM, sets the output to high level after a predetermined time, and holds the high level signal for a predetermined time. The output of the play circuit DL is connected to the OR gate OR and the switch SW2. SW3, Antogame) AND is connected to the inverter INV.

The switch SW2 switches the switch terminal from the a side to the b side in response to a high level signal from the play circuit DL, and maintains this state while the signal is at a high level. Also switch S
W3 responds to the high level signal of the play circuit DL,
The signal is on while the signal is at high level.

Further, the on-time T of the one-shot circuit MM is set almost simultaneously with the full light emission time of the strobe device F1a5hl, and furthermore, the output of the play circuit DL is set to the one-shot circuit MM.
The time Tb from when the high level signal is output to when the high level signal is output is set to be slightly longer than the above T,
Moreover, the high level signal sending time of this play circuit DL is set to be approximately equal to the full light emission time of the strobe device F1a5h2.

Next, the operation of the embodiment shown in FIG. 1 will be explained using the waveform diagram shown in FIG.

Now, the strobe device F1a5h is connected to terminals T&, , Tb, , T, l, , Tb2゜ of camera L and ground G, , G2.
1. Each terminal of F1a5h2 T gLI ' r T b
I' + Ta2'lTb2',G,
This is what G2 is connected to.

When the camera is released in this state, the front curtain of the shutter moves and the cyclo switch X is turned on as shown in FIG. 2. With this, the output of the one-shot circuit MM outputs a high level signal as shown in FIG. 2A, and the strobe device Ela
Activate the shl trigger circuit TGI and F I a
A flash of light occurs from S h 1.

Further, the high level signal of the one-shot circuit MM is transmitted to the switch SW1, and the switch SW is turned off. The reflected light from the subject of the flash by F1a5hl is irradiated onto the film surface through the camera lens, and the reflected light from the film surface is received by the light receiving element PD.
The amount of light received by D is shown in Figure 2 C4 (condenser C
It appears as the output of i. The integrated output of the capacitor 〇i is compared with the reference voltage Vref, and the integrated output is equal to the above Vr.
When reaching ef, the comparator COMP inverts the output to a high level signal as shown in FIG. 2B, which is transmitted to the light emission stop circuit LC of F1a5hl via the AND gate AND, and the light emission by F1a5hl is stopped.

After that, when the output of the one-shot circuit MM is reversed to low level, the switch SW is turned on and the capacitor C is turned on.
The charge of i is discharged and the output of capacitor Ci is returned to its initial state.

Thereafter, the play circuit DL outputs a high level signal as shown in the second diagram, so that the trigger circuit TG2 of the strobe device F1a5h2 is activated, and F1a5h2 generates a flash. Further, the high level signal of the play circuit DL is transmitted to the switch SW1, which turns off, and the amount of light received by the light receiving element due to the flash of light F1a5h2 is integrated.

Also, the high level signal of the play circuit is sent to switch SW3.
Therefore, the switch SW3 is turned on and the switch SW2 is switched to the contact point.

By changing the contact point of the switch SW2 from a to b, the gain of the integrating circuit also changes from a value corresponding to the potential Vcl of the emitter of the transistor Tr to a value corresponding to Vc2.

When the integrated value of the amount of light received by the light receiving element due to the flash of F1a5h2 reaches the reference voltage Vref, the comparator COMP sends out a high level signal, and the switch SW3
is transmitted to the light emission stop circuit LC2 of F1a5h2 via
The flash caused by F1a5h2 stops. Voltages Vcl and V
Since c2 can be set to any value, F1a5hl and F
The light emission amount of 1a5h2 can be adjusted independently to any value. In the embodiment, the amount of light emitted from each of the two strobe devices is controlled, but the amount of light emitted by each of the strobe devices may be controlled so that one strobe device repeatedly emits light.

〔effect〕

As described above, in the present invention, when the output of the received light amount integrating circuit is compared with the reference value and the flash is stopped, the reference value is changed for each light emission, so the light emission amount for each time of multiple light emission is changed. This simplifies the configuration of a flash device that controls the value to an arbitrary value.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a flash photography device according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. 1. PD...light receiving element, Ci...condenser, COMP...comparator, SW2...switch, F1a5hl, F1a5h2-stroboscopic device. Patent applicant: Canon Co., Ltd. Day 1

Claims (1)

[Scope of Claims] A flash photography device that sequentially fires a plurality of flashes includes an integrating circuit that receives reflected light from the flash and generates an output according to the amount of the received light, and the integrating circuit is activated for each flash. A control circuit that operates from the initial state and returns to the initial state at the end of each light emission, and the output of the above-mentioned integrating circuit are input, and the output is compared with a reference value, and the light is emitted when the output of the integrating circuit reaches the reference value. A comparison circuit that outputs a stop signal, a light emission stop circuit that stops each light emission in response to the light emission stop signal, and a switch that sequentially changes the gain of the integrating circuit to a value corresponding to each light emission for each light emission. A flash photography device characterized by being provided with a circuit.