JPH0629932B2 - Flash starter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash starting device, and more particularly to an electronic circuit flash starting device used together with an imaging device.

(Prior Art) Conventionally, in a trigger circuit of a flash light emitting device, flash light is emitted at a timing suitable for imaging by a contact provided in the imaging device. There are two types of trigger circuits, one that requires a high voltage and a large current to flow through the contacts depending on the flash device (called a high voltage trigger), and one that requires a low voltage and a small current (called a low voltage trigger). The latter is currently the mainstream, but it is necessary to satisfy both of them as a contact point of a general-purpose image pickup device.

In conventional imaging devices such as film cameras: ・ High voltage and large current can be easily passed. ・ The on / off timing of contacts is linked to the operating force of the shutter, and there is a powerful mechanism to drive the shutter. For many reasons, mechanical contacts were often used. However, (i) a large contact current must be applied to the mechanical contact as well, so that the contact resistance must be low, so that the contact pressure must be high and a material with a low contact resistance must be used, which makes the contact component expensive.

(Ii) Still, the spark oxidizes the contact surface,
Reliability is insufficient due to increased contact resistance and seizure.

(Iii) Light emission failure may occur due to chattering or the like.

(Iv) In an image pickup device that does not have a strong shutter mechanism such as a physical property shutter, a contact drive mechanism must be provided separately, which is complicated, large, and expensive.

On the other hand, if this contact is made electronic, the following problems occur. That is, it is necessary for the contact to have a structure that can handle both a high voltage trigger and a low voltage trigger. A switching element for the contact may be a transistor or a thyristor, but both have problems.

In the case of a transistor, the low-voltage trigger can emit light without any problem, but the effective on-resistance is too high for the high-voltage trigger, and the flash device cannot emit light.

In the case of thyristors, the on-resistance is sufficiently low, so there is no problem in that respect. However, if a constant current (holding current) or more flows steadily to this element after it has been turned on once, it has no ability to turn it off again. There was a disadvantage that you could not shoot with flash.

(Object) The present invention has been made in view of such drawbacks of the conventional device, and an object of the present invention is to provide a flash activation device which is small in size while using an electronic circuit and is compatible with both a high voltage trigger and a low voltage trigger.

(Example) The content of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a first embodiment of the apparatus of the present invention. In the figure, reference numeral 1 denotes a transistor, the base of which is connected to a control output terminal of the image pickup device, and the positive voltage is applied at an appropriate timing synchronized with the release from the image pickup device. To receive the pulse. The collector and the emitter are the positive and negative trigger terminals X of the flash light emitting device.
+ And X- are respectively connected. A series circuit of thyristor 2 and diode 3 is connected to X + and X-. The anode of the thyristor 2 is connected to X +, the cathode of the diode 3 is connected to X−, and the cathode of the thyristor 2 and the diode 3 are connected.
Of the thyristor 2 is connected, and the gate of the thyristor 2 is connected to X-. A series circuit of a resistor 4 and a capacitor 5 is connected in parallel with the anode / cathode of the thyristor 2.
The above is the configuration of one embodiment of the present invention, and its operation will be described below.

When a flash light emitting device (not shown) is connected to the image pickup device and the power is turned on, high voltage and low voltage are generated between X + and X- depending on whether the flash device is a high voltage trigger type or a low voltage trigger tap, respectively. Is charged to a voltage between X + and X- through the resistor 4 and the diode 3.

In the case of a low-voltage trigger, a positive pulse is applied from the image pickup device to the base of the transistor 1 through A in synchronization with the release, the transistor 1 is turned on, short-circuits between X + and X-, and the flash device emits light. In the case of a low voltage trigger, the current flowing between X + and X- is very small, so that the transistor 1 alone can suffice.

On the other hand, in the case of the high voltage trigger, the flash light emitting device does not emit light because the current flowing only in the transistor 1 is insufficient, but X +, X
The voltage across both terminals of − decreases. Along with this, the electric charge stored in the capacitor 5 is discharged through the resistor → transistor 1 → gate of the thyristor 2 → cathode of the thyristor 2, and a gate current flows through the thyristor 2 to turn on the thyristor 2. Then, a large current sufficient for light emission of the flash light emitting device flows through the thyristor 2 and the diode 3, and the flash light emitting device emits light. The current flowing from X + to X- after the light emission of the flash light emitting device is relatively small even if it may exceed the holding current of the thyristor 2, and can be made to flow if the transistor 1 is continuously turned on. Current can be made equal to or less than the holding current, and the thyristor 2 can be reliably turned off, so that flash photography from the next time can be performed without any problem.

FIG. 2 shows another embodiment improved from the embodiment shown in FIG. The structure of FIG. 2 is almost the same as that of FIG. 1, and the only difference is that the diode 6 is connected in parallel with the resistor 4.

Before explaining the operation of FIG. 2, the problem of FIG. 1 is mentioned. In the device of FIG. 1, when the capacitor 4 discharges for turning on the thyristor 2, the loss of the resistor 4 is large. The timing to turn on is delayed. If this timing is delayed, the voltage between X + and X- will decrease with the delay, and along with that, the electrical energy stored in the trigger capacitor of the flash light emitting device will also decrease, and in the worst case, it will be insufficient for the flash device to emit light. Could be. Meanwhile, resistance 4
If the resistance value of is too low, the flash light emitting device may emit light because the charging flow of the capacitor 5 is large when the flash light emitting device is connected to the imaging device. FIG. 2 shows a circuit improved to eliminate this kind of problem.

In FIG. 2, the capacitor 5 is charged through the resistor 4. Therefore, if the resistance value of the resistor 4 is made sufficiently large, it will not accidentally emit light even if the flash light emitting device in a charged state is connected. On the other hand, the discharge of the capacitor 5 which becomes the gate current of the thyristor 2 is performed through the diode 6, and the forward resistance of the diode is low, so that the loss does not delay the on-timing of the thyristor 2.

As already mentioned, the low-voltage trigger flash light-emitting device is currently in the mainstream, and the transistor 1 alone is sufficient for that, and the circuits other than the transistor 1 can operate completely independently of the imaging device. The size of the image pickup device can be reduced by taking it out of the image pickup device and forming an adapter so that the flashlight emitting device of the high-voltage trigger is connected and used only.

FIG. 3 is a diagram showing an example of the configuration of such an image pickup system, and the same reference numerals as those in FIGS. 1 and 2 indicate the same elements.

The adapter 14 composed of 1 to 6 has a signal input terminal 14a and an output terminal 14b.

Reference numeral 7 denotes an image pickup element as an image pickup means provided in the image pickup device 13, which includes a CCD, an XY address type image sensor, an image pickup tube, and the like.

Reference numeral 8 is a signal processing circuit for applying various corrections to the output of the image pickup device 7, 9 is a recording device for recording the output of the signal processing circuit 8, and 10 is a periodic drive for driving the image pickup device 7 with a clock driver. Supply a signal.

A sequence control circuit 11 controls the sequence of the entire image pickup apparatus. Reference numeral 12 denotes a release switch, and when this switch is turned on, an image for one shot using the flash device 15 is recorded in the recording device.

Reference numeral 13a is an output terminal for outputting the flash device synchro trigger signal from the sequence control circuit 11.

In the figure, 201 is a battery, which is connected to the low-voltage input side of a DC-DC converter 202 that boosts a DC voltage. The high voltage side output of the DC-DC converter is connected to the resistor 205 and the trigger capacitor 206 via the rectifying diode 203.
A known trigger circuit 204 including a trigger transformer 207, a trigger thyristor 208, and a resistor 209, and a resistor 2
11, 212, 213, 214, 218, 219, commutation capacitor 213, capacitor 215, and main thyristor 2
It is connected to a well-known light amount control circuit 220 including 16 and a sub thyristor 217, and a parallel circuit of a main capacitor 221. The flash discharge tube 210 has an anode and a cathode connected between the rectifier diode 203 and the main thyristor 216, and its trigger electrode is connected to the high voltage terminal of the trigger transformer 207. Terminal 15b and resistor 22 which are closed by a synchro signal
The series circuit of 3 is the anode of the battery 201 and the trigger thyristor 2.
It is connected between the gates of 08. Also commutation thyristor 2
The gate of 17 is connected to the output terminal of the photometric circuit 16.

15b is a synchro trigger signal input terminal of the flash device 15.

The above is the configuration of FIG. 3. Next, the operation will be described with the terminals 13a and 14a connected and the terminals 14b and 15b connected. Power switch 20 for flash device
When 0 is turned on, the DC-DC converter 202 operates to charge the trigger capacitor 206, the commutation capacitor 213, the capacitor 215, and the main capacitor 221 to the same polarity as shown in the figure. When the release switch is turned on by directing the image pickup device toward a predetermined subject while the charging voltage is at a level sufficient for flashing, a pulse as shown in FIG. 4 (a) is input to the sequence control circuit.

On the other hand, since the image pickup apparatus is turned on in advance, the clock driver 10 periodically outputs the vertical synchronizing signal of the standard television signal as shown in FIG. 4 (b).

The sequence control circuit outputs a synchro trigger signal as shown in FIG. 4 (d) in synchronization with, for example, the first vertical synchronizing signal after the release signal. This signal is on terminal 13
It is input to the transistor 1 via a and 14a, and the terminals 14b, that is, 15b are short-circuited as described above.

As a result, the gate current is supplied from the battery 201 to the trigger thyristor 208 via the resistor 223, the trigger thyristor 208 is turned on, the well-known trigger circuit 204 is activated, and the flash discharge tube 210 is ionized to make it conductive. A high voltage is applied to the anode of 216, which causes a gate current to flow to the main thyristor 216 via the commutation capacitor 213, the resistor 214, and the capacitor 215, and the main thyristor 216 is turned on and flash emission starts as shown in FIG. 4 (e). .

Next, the dimming operation will be described.

First, the light reflected by the subject of flash emission is detected and integrated by the photometric circuit. When this integrated signal exceeds a predetermined level, a high-level signal is output from the photometric circuit 16, and a gate current is passed through the sub-thyristor 217 to cause the sub-thyristor 217 to flow.
Turn on. Then, the known light amount control circuit 220
Is activated and the light emission stops instantly as shown in FIG. 4 (e).

The flash activation device of the present invention includes both such an adapter that can be attached to and detached from the image pickup device, and one that is incorporated in the image pickup device.

Of course, even in the case of an adapter, a part of the circuit in the adapter 14 may be included in the imaging device or the flash device.

(Effect) As described above, by using the device of the present invention, both the high-voltage trigger type and the low-voltage trigger type flash light emitting devices can be surely caused to emit light by one simple trigger signal from the imaging device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the device of the present invention, FIG. 2 is a second embodiment diagram which is an improvement of FIG. 1, and FIG. 3 is a configuration diagram of a system using the flash starting device of the present invention. , FIG. 4 shows the timing chart. In the figure, 1 is a transistor, 2 is a thyristor, 3 is a diode, 4 is a resistor, 5 is a capacitor, 6 is a diode, 1
Reference numeral 3 is an image pickup device, 14 is an adapter, and 15 is a flash light emitting device.

Claims (1)

[Claims] 1. A flash starting device in which a high voltage control circuit including a thyristor and a low voltage control circuit including a transistor are connected in parallel between trigger contacts of a flash device.