Flash unit for use with camera

Claim 2

A flash unit for cameras comprising a. a DC power supply for supplying a high DC voltage, b. at least one flash lamp provided with an auxiliary or trigger electrode arranged in circuit for application of a trigger pulse thereto and an anode and a cathode arranged in circuit for application of a discharge current thereto, and c. a constant current circuit means interconnected in series between said DC power supply and said at least one flash lamp for maintaining the current supplied from said DC power supply to said at least one flash lamp at a constant level for a period of time after application of a triggering pulse as aforesaid.

Claim 3

A flash unit as defined in claim 1 wherein said constant current circuit means comprises a Darlington circuit comprising at least two transistors, and a bias circuit for applying a predetermined current to said Darlington circuit.

Claim 4

A flash unit as defined in claim 1 wherein said constant current circuit means comprises a switching circuit means and transistor means arranged to be turned on or off by said switching circuit means in such a manner as to give a constant current output, the input of said transistor means being connected to said switching circuit.

Claim 5

A flash unit as defined in claim 1 wherein at least two series-connected flash lamps are arranged in such a manner that an anode of one of said at least two flash lamps and a cathode of the other flash lamp are connecteD to said DC power supply through said constant current circuit means, and the trigger signal is applied simultaneously to the parallel-connected trigger electrodes of said at least two flash lamps.

Claim 6

A flash unit as defined in claim 3 wherein said constant current circuit further comprises variable resistive means adjustable, means for varying said resistive means in accordance with the distance from the camera to the subject, a time constant circuit comprising said variable resistor means, and a capacitor one terminal of which is connected to said switching circuit.

Claim 7

A flash unit as defined in claim 3 wherein said switching means comprises a. a time constant circuit comprising a photoconductive cell means and a capacitor, and a first switching circuit having its output connected to the input of said time constant circuit; b. short-circuiting switch means connected in parallel with said capacitor in said time constant circuit and arranged to be opened when the shutter of the camera is opened, and electromagnet means connected to the output of said first switching circuit for closing the shutter.

Claim 8

A flash unit for cameras comprising a. power supply means for generating high-voltage DC current, said power supply means comprising a step-up circuit, and a main capacitor connected to the output of said step-up circuit; b. at least one flash lamp provided with an auxiliary or trigger electrode arranged in circuit for application of a trigger signal and an anode and a cathode arranged in circuit for application of a discharge current; c. a constant current circuit means interconnected between said power supply means and said at least one flash lamp so that a constant current may be supplied to said at least one flash lamp from said power supply means; d. switching means inserted in the discharge circuit of said at least one flash lamp and provided with a switching input arranged to receive the trigger signal pulse whenever such a signal is applied to said trigger electrode of said at least one flash lamp; and e. flash interruption means comprising a discharge switching circuit connected in parallel with said main capacitor so that the flash produced by said at least one flash lamp may be interrupted under control of said discharge switching circuit.

Claim 9

A flash unit for cameras comprising a. power supply means for generating high-voltage DC current, said power supply means comprising a step-up circuit, and a main capacitor connected to the output of said step-up circuit; b. at least one flash lamp provided with an auxiliary or trigger electrode arranged in circuit for application of a trigger signal and an anode and a cathode arranged in circuit for application of a discharge current; c. a constant current circuit means interconnected between said power supply means and said at least one flash lamp so that a constant current may be supplied to said at least one flash lamp from said power supply means; d. switching means inserted in the discharge circuit of said at least one flash lamp and provided with a switching input arranged to receive the trigger signal pulse whenever such a signal is applied to said trigger electrode of said at least one flash lamp; and e. flash interruption means comprising a discharge switching circuit connected in parallel with said main capacitor so that the flash produced by said at least one flash lamp may be interrupted under control of said discharge switching circuit.

Claim 10

A flash unit as defined in claim 7 wherein said flash interruption means comprises a quenching tube connected in parallel with said main capacitor and provided with an anode, a cathode and a trigger electrode, a commutation capacitor interconnected between said anode of said quenching tube and the input of said switching means, and an interruption signal generating circuit for generating the interruption signal to said trigger electrode of said quenching tube.

Claim 11

A flash unit as defined in claim 7, wherein said switching means is a thyristor.

Claim 12

A flash unit as defined in claim 7, wherein said flash interruption means comprises a pulse oscillator circuit an output of which is connected to an input of said switching means to continually interrupt said switching means.

Claim 13

A flash unit as defined in claim 10, wherein said pulse oscillator circuit is an astable multivibrator.

Claim 14

A flash unit as defined in claim 10, wherein said pulse oscillator circuit is a monostable multivibrator.

Claim 15

A flash unit for cameras comprising: a first DC power supply having a capacitor for storage electrical energy for flashing; at least one triple-electrode discharge lamp comprising an auxiliary electrode for flash triggering, an anode arranged to be supplied with a discharge current from said first DC power supply, an auxiliary anode and a cathode; a second DC power supply having a capacitor for storing electrical energy for auxiliary flashing, the voltage of said second power supply being set to a value higher than a lower limit of flashing of said discharge lamp, and the outputs of said second power supply being connected across said auxiliary electroDe and said cathode; and a constant current circuit interconnected in series between said first DC power supply and said at least one flash lamp for maintaining the current supplied from said first DC power supply to said at least one flash lamp at a constant level after flash triggering.

Claim 16

A flash unit for cameras comprising: a first DC power supply having a capacitor for storage electrical energy for flashing; at least one triple-electrode discharge lamp comprising an auxiliary electrode for flash triggering, an anode arranged to be supplied with a discharge current from said first DC power supply, an auxiliary anode and a cathode; a second DC power supply having a capacitor for storing electrical energy for auxiliary flashing, the voltage of said second power supply being set to a value higher than a lower limit of flashing of said discharge lamp, and the outputs of said second power supply being connected across said auxiliary electroDe and said cathode; and a constant current circuit interconnected in series between said first DC power supply and said at least one flash lamp for maintaining the current supplied from said first DC power supply to said at least one flash lamp at a constant level after flash triggering.

Claim 17

A flash unit for cameras comprising: a DC power supply for supplying a high DC voltage; at least one flash lamp provided with an auxiliary or trigger electrode arranged for application thereto of a trigger pulse and an anode and a cathode arranged for application thereto of a discharge current; and a constant current circuit serially connected between said DC power supply and said flash lamp for maintaining the current at a constant level for a period after application of a trigger pulse as aforesaid, said circuit comprising a variable resistance means for setting the magnitude of said discharge current supplied from said DC power supply at a predetermined level, said variable resistance means being so connected in said constant current circuit that at most a very small portion of said discharge current passes through said variable resistance means.

Claim 18

A flash unit for cameras comprising: a DC power supply for supplying a high DC voltage; at least one flash lamp provided with an auxiliary or trigger electrode arranged for application thereto of a trigger pulse and an anode and a cathode arranged for application thereto of a discharge current; and a constant current circuit serially connected between said DC power supply and said flash lamp for maintaining the current at a constant level for a period after application of a trigger pulse as aforesaid, said circuit comprising a variable resistance means for setting the magnitude of said discharge current supplied from said DC power supply at a predetermined level, said variable resistance means being so connected in said constant current circuit that at most a very small portion of said discharge current passes through said variable resistance means.