JPS634194Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flash camera that integrates an electronic flash device and a camera, and is particularly designed to control the amount of light emitted from a flash discharge tube in accordance with the distance to the object without receiving the object light. Regarding the flash camera.

For example, there is a system that controls the amount of light emitted from a flash discharge tube according to the setting of the subject distance.
As shown in Publication No. 10646, a thyristor is further connected to the flash discharge tube and a resistor connected in series with it, and the current from the main discharge capacitor flowing through this resistor is controlled to reach the time corresponding to the subject distance. Then, the thyristor bypasses the light and emits a large amount of light.
Also known are devices in which a plurality of main discharge capacitors with different capacitance values are provided and switched, or in which the charging voltage of the main discharge capacitor is varied, and in which a resistor is connected in series with the flash discharge tube.

However, with a thyristor that bypasses the current flowing through a resistor connected in series with the flash discharge tube, there is a risk that the film may be exposed, especially in close-up photography, due to the light emitted until the thyristor becomes conductive. In the case of switching the main discharge capacitor, the size becomes large due to the provision of multiple main discharge capacitors with large capacitance values, and in the case of switching the main discharge capacitor directly with a switch, the switch must have a large contact capacity and is expensive. Moreover, in devices that adjust the charging voltage of the main discharge capacitor, if the set distance changes for some reason after charging at the specified charging voltage, it is not possible to quickly adjust the voltage to an appropriate value. This has the problem of being difficult and requiring time to adjust.

Furthermore, in the case of a resistance adjustment device that is directly connected to a flash discharge tube, the resistance adjustment is thought to be done by either switching multiple resistors with different resistance values or by varying the resistance value of a variable resistor. It will be done. However, in the former case, an expensive switch with a large capacity contact must be used, similar to the above-mentioned switch that switches the main discharge capacitor, and in the latter case, the discharge circuit must be The resistance provided is usually from several ohms to several tens of ohms, so the amount of light emitted per ohm increases, and if the resistance value set for distance adjustment changes even slightly due to vibration etc., the amount of light will increase. There is a problem that the light emission fluctuates and accurate light emission control cannot be performed.

The present invention was developed to solve these problems, and examples thereof will be described below with reference to the drawings.

The flash camera of this embodiment includes a main discharge capacitor 1, a flash discharge tube 2 that consumes the charging energy of the main discharge capacitor 1 to emit a flash, and a well-known trigger circuit 3 that applies a trigger voltage to the flash discharge tube 2. an electronic flash device 5 consisting of a trigger switch 4; a camera integrated with the electronic flash device 5; a knob 7 for adjusting the focal length of a lens 6 of the camera; and a lever 8 to which the knob 7 is attached. , a switch 12 consisting of an electric contact piece 9 and contacts 10 and 11 provided at the tip of this lever 8, and a switch 12 that operates according to the on/off state of this switch 12 and controls the light emission of the flash discharge tube 2 of the electronic flash device 5. It also includes a light amount control device 13 that controls the amount of light.

The light amount control device 13 includes a resistor 14 connected to one electrode of the flash discharge tube 2, a series body of a resistor 15 and a thyristor 16 connected to the other electrode, and a resistor 17 connected to the gate of the thyristor 16.
The connection point between one electrode of the flash discharge tube 2 and the resistor 14 is electrically connected to the contact point 10 of the switch 12.

Next, the operation of this flash camera will be explained.

A power switch (not shown) is closed and the main discharge capacitor 1 is charged. On the other hand, when adjusting the focal length of the camera lens 6 for long-distance photography, when the scale of the knob 7 is set to "far" displayed on the camera body, the electric contact 9 of the switch 12
contacts contact 10.

When the trigger switch 4 of the electronic flash device 5 is closed in this state, the flash discharge tube 2 becomes conductive, but since no voltage is applied to the gate of the thyristor 16, the thyristor 16 maintains the non-conductive state. do. Therefore, the charging energy of the main discharge capacitor 1 is released through the flash discharge tube 2 and the small resistor 14, and most of the charging energy is consumed in the flash discharge tube 2, so that the flash discharge tube 2 emits a large amount of light.

Next, for close-up photography, the camera lens 6
When the scale of the knob 7 is set to "Near" in order to adjust the focal length, the lever 8 moves to the right and the contact piece 9 of the switch 12 connects the contacts 10 and 11.

When the trigger switch 4 is closed in this state, the trigger circuit 3 is operated and the flash discharge tube 2 is made conductive.

At this time, since the contacts 10 and 11 of the switch 12 are short-circuited, current flows through the resistor 17 connected to the gate of the thyristor 16, and the voltage generated across the resistor 17 makes the thyristor 16 conductive.

Therefore, the charging energy of the main discharge capacitor 1 is the same as that of the flash discharge tube 2, the resistor 15, and the thyristor 1.
The light is divided into 6 series bodies and consumed, and depending on the value of the resistor 15, an appropriate amount of light is given to a subject at a close distance.

Note that an inductance may be used instead of the resistor 14.

As explained above, the present invention forms a light emitting circuit with a flash discharge tube, a main discharge capacitor, and a fixed resistor or inductance, and supplies current to a gate circuit of a thyristor in series with a resistor connected in parallel to the main discharge capacitor. is controlled prior to light emission, and the current supply to the gate circuit is performed by a switch corresponding to the distance to the subject, so that stable light emission control can be performed and an inexpensive and compact flash camera can be provided.

[Brief explanation of drawings]

The figure is an electrical circuit diagram of a flash camera that is an embodiment of the present invention. 5...Electronic flash device, 6...Lens, 7...Adjustment knob, 12...Switch, 13...Light amount control device.

Claims (1)

[Scope of utility model registration request] a series body in which a flash discharge tube and a first resistor or inductance are connected in series; a main discharge capacitor connected in parallel with the series body to store charging energy; a thyristor connected in parallel with the main discharge capacitor; a series body with a resistor, connected to a camera lens focal length adjustment knob, and turning on an electrical connection between a connection point between the flash discharge tube and the first resistor or inductance and the gate of the thyristor;
A flash camera equipped with a switch to turn it off.