JPS5922037A - Electronic flash device - Google Patents

Abstract

PURPOSE:To make a circuit simple, by allowing to keep difference in time at the start of light emission of two flash discharge tubes and by controlling the stop of light emission of each discharge tube. CONSTITUTION:Flash discharge tubes 15, 16 are parallelly connected, and receive 37 reflected light from an object to be photographed, and a photometric means 37 converting a switching element 17 to the state that the tube 16 starts to emit light when the amount of received light reaches the first prescribed level and the light emission of the tubes 15, 16 are stopped when the amount of received light reaches the second prescribed level, is provided. The difference in time is kept for start of light emission of the tubes 15, 16, and it is arranged to control to stop light emission of the tubes 15, 16 by the element 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved self-adjustable electronic flash device having first and second flash discharge tubes.

In so-called bounce photography, where the flash from an electronic flash device is reflected off the ceiling, walls, etc., when photographing subjects such as people, the lower half of the face may be in shadow or there may be no light in the eyes. Sometimes it is not possible to obtain a realistic photograph. For this reason, it has already been proposed to provide two flash discharge tubes in one electronic flash device and use one for bounce and the other for direct irradiation to illuminate the front of the subject.

As an example, the one shown in Utility Model Application Publication No. 55-164624 is shown in FIGS. 1 and 2. A flash discharge tube 1 for bounce, a flash discharge tube 2 for direct irradiation, and a thyristor 3 are connected in series, and a thyristor is connected in parallel to the flash discharge tube 2 or in parallel to the series circuit of the flash discharge tube 2 and thyristor 3. 4
Or 5 are connected. As the thyristor 3 becomes conductive, the flash discharge tubes 1 and 2 start emitting light at the same time. When the amount of received light reaches a relatively small first predetermined level, the flash discharge tube 2 for direct irradiation stops emitting light due to conduction of the thyristor 4 or 5, and the amount of received light reaches a second predetermined level at which the appropriate exposure amount is reached. When reaching , the thyristor 3 or 5 becomes non-conductive,
The bounce flash discharge tube l stops emitting light.

Such an electronic flash device requires a plurality of switching elements to control the flash current (thyristors 3 and 4 in Figure 1, thyristors 3 and 5 in Figure 2), which poses the problem of complicating the circuit. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic flash device that can solve two problems and simplify one circuit.

In order to achieve this object, the present invention connects an if flash discharge tube and a second flash discharge tube in parallel, receives reflected light from a subject, and the amount of received light reaches a first predetermined level. When the second flash discharge tube starts emitting light, the amount of light received reaches the second flash discharge tube.
reaches a predetermined level, the first flash discharge tube and the second
A photometric means is provided for switching a switching element for flash current control to a state in which the flash discharge tube stops emitting light;
In addition to creating a time difference between the start of light emission of the two flash discharge tubes,
The present invention is characterized in that the one switching element controls the stopping of light emission of the two flash discharge tubes.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 3 shows a serial dimming type electronic flash device which is an embodiment of the present invention. 6 is a high voltage power supply, 7 is a resistor, 8 is a diode, 9 is a main capacitor, 10 is a synchro contact, 11 is a first
This trigger circuit is formed by a resistor 12, a trigger capacitor 13, and a trigger transformer 14. A first flash discharge tube 15 for bounce and a second flash discharge tube 1 for direct irradiation.
6 is connected in parallel with the main thyristor 17, and then connected in series with the main thyristor 17. Reference numerals 18 and 19 are trigger terminals, and 20 is a light amount control circuit, which is formed by a main thyristor 17, a sub-thyristor 21, resistors 22 to 26, a commutating capacitor 27, and a capacitor 28. A second trigger circuit 29 is formed by a trigger transformer 30, a trigger capacitor 31, a thyristor 32, and resistors 33 and 34. 35 and 36 are resistors, 37 are photometric circuits, comparators 38 and 39, voltage dividing resistors 40 to 42, photodiodes 43, integral capacitors 44, transistors 45, capacitors 46, resistors 47.
48, a diode 49 and a local power supply 50.

Next, the operation will be explained. Main capacitor 9 is charged by high voltage power supply 6 via resistor 7 and diode 8. When the synchro contact 10 is closed in a sufficiently charged state, the first flash discharge tube 15 is triggered by the circuit 11, and the inside of the tube is ionized. A current due to this ionization flows through the commutation capacitor 27. Resistor 24 and capacitor 28
is applied to the gate of the main thyristor 17 through the main thyristor 17, and the main thyristor 17 becomes conductive. This allows the main capacitor 9
The charge of the first flash discharge tube 15 and the main thyristor 1
7, the flash discharge tube 15 starts emitting light.

Since the resistor 47 has a high resistance and the resistor 48 has a relatively low resistance, the capacitor 46 is charged to the voltage of the main capacitor 9 before the flash discharge tube 15 emits light. Further, since the base current is applied to the transistor 45 through the resistors 47 and 48, the transistor 45 is turned on and prevents the integration capacitor 44 from being charged. When the flash discharge tube 15 starts emitting light, the electric charge in the capacitor 46 is transferred to the flash discharge tube 1.
5. Since the current flows through the closed circuit of the main thyristor 17, the diode 49, and the resistor 48, the base and emitter of the transistor 45 are reverse biased, the transistor 45 is turned off, and the integrating capacitor 44 becomes ready for charging.

The light reflected from the subject by the flash discharge tube 15 is received by the photodiode 43, and a voltage corresponding to the amount of received light is generated in the integrating capacitor 44. The potential at the voltage dividing point of the voltage dividing resistors 41 and 42 is determined to correspond to a first predetermined level where the amount of received light is relatively large, and the potential at the voltage dividing point of the voltage dividing resistors 40 and 41 is determined to correspond to the appropriate exposure amount. Therefore, when the amount of received light reaches the first predetermined level, the voltage of the integrating capacitor 44 is set to correspond to the voltage dividing resistor 4.
1 and 42, the comparator 39 outputs a high-level light emission command signal P1. This causes the trigger circuit 29 to operate and trigger the second flash discharge tube 16 to start one light emission.

When the amount of received light further increases and reaches a second predetermined level, the comparator 38 issues a high-level light emission stop command (iM No. P
Outputs 2. As a result, the secondary resistor 21 becomes conductive, and due to the action of the commutating capacitor 27) the secondary resistor 1
7 becomes non-conductive and two flash discharges 'I'i'15.1
6 both stop emitting light.

The flash discharge %'15 of fJ'S1 uses reflections from walls, etc. to indirectly illuminate the subject, and the second flash) li and electric tube 16 directly illuminate the subject. It is. Therefore, indirect light is photometered up to the first predetermined level of the amount of received light, and from the first predetermined level to the second predetermined level, the first indirect light and the direct light are A11l light. However, the subject due to indirect light! ! ((Since the emitted light is sufficiently low compared to that caused by direct light, from the first predetermined level to the second predetermined level, only the direct light is used)
It is equivalent to one light being emitted, and the ratio of the subject's il (+light gutter) between indirect light and direct light is constant regardless of the subject distance.

Also, flash discharge? Compared to the emission sustaining voltage of 1115.

If the light emission sustaining voltage of the flash discharge tube 16 is set 4 minutes lower, when the flash discharge tube 16 starts emitting light, the flash discharge tube 15
Since the light emission is stopped, only direct light can be completely photometered from the first predetermined level to the second predetermined level.

In the embodiment shown in FIG. 3, the main switch 17 corresponds to the switching element of the present invention, but the present invention is not limited to this, and a bidirectional switch, a transistor, or the like may also be used.

The present invention is applicable not only to the series dimming type shown in FIG. 3 but also to the parallel dimming type. In that case, a switching element is connected in parallel to the flash discharge tubes 15, 16, and light emission is stopped by conduction of the switching element.

As described above, according to the present invention, the h's 1 flash discharge tube and the second flash discharge tube are connected in parallel, and the reflected light from the subject is received, and the received light beam is connected to the first flash discharge tube. When the amount of received light reaches a predetermined level, the second flash discharge tube starts emitting light, and when the amount of received light reaches a second predetermined level, the flash discharge tube of il and the second flash discharge tube start emitting light. A photometric means is provided to switch the switching element for controlling the flash current in the stopped state, so as to provide a time difference in the start of light emission of the twenty-four flash discharge tubes, and to control the light emission of the two flash discharge tubes by the switching element. Since the stop is controlled, the circuit can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of the main parts of a conventional two-pair electronic flash device, Fig. 2 is a circuit diagram showing another example of the main parts of a conventional two-pair electronic flash device, and Fig. 3 is a circuit diagram showing an example of the main parts of a conventional two-pair electronic flash device. FIG. 1 is a circuit diagram showing an embodiment of the present invention. 9...Main capacitor, 10...Synchro contact, 11...Trigger circuit, 15...
・First flash discharge tube, 16...Second flash discharge tube, 17...Main thyristor, 29...
Trigger circuit, 37...A111 optical circuit, 38.
39...Comparator, 43...Photograph), 44...Integration capacitor. Patent Applicant Canon Co., Ltd. Representative Minoru Nakamura Figure 1 Figure 2

Claims (1)

[Claims] / In an electronic flash device 1V7 comprising a first flash discharge tube that starts emitting light by closing a synchro contact, a second flash discharge tube, and a switching element that controls a flash current, the first flash discharge The tube and a second flash discharge tube are connected in parallel, and when the reflected light from the subject is received and the amount of light received reaches a first predetermined level, the second flash discharge tube starts emitting light; When the amount of received light reaches a second predetermined level,
1. An electronic flash device characterized in that a photometric means is provided for switching the switching element to a state where the first flash discharge tube and the second flash discharge tube stop emitting light.