JPH0246435A - electronic flash device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electronic flash device.

[Conventional technology]

Conventionally, still cameras have used electronic flash devices as auxiliary light sources. FIG. 3 shows a schematic configuration diagram of a conventional electronic flash device. 10 is a DC power supply, 12 is a main capacitor, 14 is a flash discharge tube, 16 is a trigger circuit for discharging the flash discharge tube 14, and 18 is a synchronization switch.

First, the main capacitor 12 is charged by the DC power supply 10,
Additionally, a trigger capacitor (not shown) in the trigger circuit 16 is also charged. When the synchro switch 18 is closed, the trigger capacitor is discharged through the synchro switch 18, and the flash discharge tube 14 is discharged.
excite. As a result, the flash discharge tube 14 emits light.

[Problem to be solved by the invention]

In an electronic flash device with such a structure, the main capacitor 12 must be recharged to a predetermined amount or more in order to emit light again after the first flash. The charging period was relatively long. Therefore, it is insufficient to be used in combination with a still camera having a high-speed continuous shooting function, a so-called quick-shooting function. In other words, the main capacitor 12 cannot be sufficiently charged during the frame interval during continuous shooting (for example, 0.2 seconds in the case of 5 frames per second), so the amount of light emitted is appropriate for each frame of continuous shooting. can't get it.

The exposure control of still cameras is generally set to a fixed state during continuous shooting, so in the first shot, the correct exposure is obtained by flash firing, but as the later frames are taken, the amount of light is insufficient due to afterglow. become.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electronic flash device that can emit light while following high-speed continuous shooting.

[Means to solve the problem]

An electronic flash device according to the present invention includes a flash discharge tube, a plurality of main capacitors for supplying a discharge current of the flash discharge tube, and a plurality of trigger capacitors for supplying a trigger current for exciting the flash discharge tube. It is characterized by comprising a capacitor and a selection means for selectively using the main capacitor and the trigger capacitor.

[Effect]

By providing the above selection means and switching between the main capacitor and trigger capacitor used for light emission, it is possible to cause the flash discharge tube to emit flash light at extremely short time intervals even if the charging time of each capacitor is long enough. Can be done.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a configuration block diagram of an embodiment of the present invention capable of following continuous shooting of three frames per second. 20 is DC power supply, 22A
, 22B, 22C are main capacitors, 24 is a flash discharge tube,
26 is a protection resistor, 28 is a trigger circuit, 30 is a synchro switch, 32A, 32B, and 32C are switches that connect the DC power supply 10 to the main capacitors 22A, 22B, and 22C, respectively; 34A, 34B, and 34C are each, the main capacitor 22A , 22B, and 22C for supplying the charged charges to the flash discharge tube 24 via the protective resistor 26; 36 is a camera photography control circuit; 38 is photography frame interval information and shutter release from the photography control circuit 36; This is a switch control circuit that controls switching of switches 32A, 32B, 32C, switches 34A, 34B, 34C, and a later-described switch in trigger circuit 28 according to a signal.

FIG. 2 shows details of the trigger circuit 28. 4゜A, 40
B and 40C are 1 to rigger capacitors, 42 is a trigger transformer, 44A, 44B, and 44C are controlled to open and close by control signals from the switch control circuit 38, and trigger the charging charges of trigger capacitors 4OA, 40B, and 40C, respectively. - A switch connected to the transformer 42.

Next, the operation will be explained with reference to FIGS. 1 and 2. First, the switch control circuit 38 controls the switches 32A and 32B.
, 32C, and the main capacitors 22A, 22B, 2
2C and trigger capacitors 40A, 40B, 40C
After charging a predetermined amount, switch 32A, 32B
, 32. Release C. Preparation for shooting is now complete.

Next, when photographing the first frame, the switch control circuit 38 closes the switches 32A, 34A, and 44A, uses the main capacitor 22A for the flash current, and closes the trigger capacitor 4. Use OA for trigger current and start the next shooting (1/
3 seconds later), switches 32B, 34B, and 44B are closed, and for the next shooting (2/3 seconds in total), switch 3 is closed.
Close 2C, 34C, and 44C. Similarly for the next second, first close the switches 32A, 34A, 44A,
Next, switches 32B, 34B, and 44B are closed, followed by switches 32A, 34A, and 44A.

In this way, the switches 32A, 34A, 44A; 32B,
By sequentially closing 34B, 44B12A, 34A, and 44A, in the first frame, the main capacitor 22A discharges, and in the second frame, the main capacitor 22B discharges,
In the third frame, the main capacitor 22C discharges,
A sufficient amount of light can be obtained in each frame. Further, by sequentially selecting the main capacitors 22A, 22B, and 22C for discharging, the flash discharge tube 24 can be discharged at short time intervals.

The charging period for the main capacitors 22A, 22B, 22C is a short period after their discharge or until the start of the next discharge, during which the associated switches 32A, 32B, 32
What is necessary is to keep C closed. Of course, switch 3
2A, 32B, and 32C may be a single switch, which is closed from the time the power is turned on until the time the power is turned off. Also,
When the main capacitor (for example, 22A) is discharging, disconnect this main capacitor from the DC power supply and
Switches 32A, 32B, and 32C may be controlled to charge the next main capacitor to be discharged (eg, 22B) and/or the next main capacitor to be discharged (eg, 22C).

For a silver halide camera, the maximum speed is usually 5 frames per second, so five of these main capacitors can be connected in parallel and discharged in sequence in the same way. Furthermore, since an electronic still camera is capable of continuous shooting at 10 frames per second, it is sufficient to connect 100 main capacitors in parallel. Of course, it should be understood that depending on the charging time of each individual main capacitor, it may be possible to use fewer main capacitors in circulation.

For example, when using an electronic flash device with 10 main capacitors connected in parallel and performing continuous shooting at 2 frames per second or 5 frames per second, switches 32A, 32B, 32C;
, 34C; 44A, 44B.

These switches may be controlled so that switching of 44C is completed in one or four times, or all main capacitors are cycled at corresponding second intervals.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, it is possible to emit a flash with a sufficient amount of light even for high-speed continuous shooting, and therefore it is possible to shoot with appropriate exposure for each frame. becomes possible

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a concrete example of the trigger circuit 28 shown in FIG. 1, and FIG. 3 is a block diagram of a conventional electronic flash device. .

Claims (1)

[Claims] A flash discharge tube, a plurality of main capacitors for supplying a discharge current of the flash discharge tube, a plurality of trigger capacitors for supplying a trigger current for exciting the flash discharge tube, the main capacitor and the trigger. - An electronic flash device characterized by comprising a selection means for selectively using a capacitor.