US3896333A - Electronic flash device - Google Patents

Electronic flash device Download PDF

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Publication number
US3896333A
US3896333A US358522A US35852273A US3896333A US 3896333 A US3896333 A US 3896333A US 358522 A US358522 A US 358522A US 35852273 A US35852273 A US 35852273A US 3896333 A US3896333 A US 3896333A
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United States
Prior art keywords
flash
capacitor
conductive
discharge
tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US358522A
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English (en)
Inventor
Zenzo Nakamura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
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Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
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Publication of US3896333A publication Critical patent/US3896333A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
    • H05B41/32—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation
    • H05B41/325—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation by measuring the incident light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
    • H05B41/32—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation

Definitions

  • ABSTRACT The device controls the amount of light emitted by a flash illumination tube by interrupting the energization of the tube during a flash discharge.
  • a main condenser is charged to apredetermined voltage from a suitable source, and is arranged to be discharged through the flash illumination tube when a thyristor, connected in series with the flash illumination tube, is triggered conductive responsive to actuation of a camera element.
  • a discharge preventing condenser is also charged from the source and is arranged to be discharged through a switch element connected in series therewith responsive to a flash preventing trigger signal.
  • the flash preventing condenser When the flash preventing condenser is thus discharged, it triggers the thyristor non-conductive to block discharging of the flash illumination tube.
  • a charging signal-trigger circuit and a charging thyristor, having its gateconnected to the charging signal trigger circuit, are connected in parallel with the illumination or discharge preventing condenser.
  • the charging sig nal trigger circuit is activated responsive to discharge of the illumination preventing condenser to trigger the connected thyristor conductive for a rapid re-charging of the illumination preventing condenser.
  • the present invention relates to an electronic flash device, particularly to an electronic flash device suitable as an auxiliary light source for picture taking.
  • the present invention employs particularly a light 1 amount control system of the series type to control the illumination time of the flash discharge tube corresponding to a distance from a camera to an object or corresponding to the film sensitivity.
  • the discharge current is shielded by converting a switching element, connected in series to a discharge tube, to the non-conductive state.
  • FIG. 1 illustrates a conventional flash illumination device of the series control type.
  • the illustrated device includes a booster circuit 1, of a conventional type, such as a dc. converter, or the like, a main storage condenser 2, and a flash discharge tube 3 having a trigger electrode 3'J
  • the circuit also includes a silicon control element 4 having a gate 4' and a cathode 4".
  • a trigger circuit 5 is included and is connected to a flash starting signal input terminal 6.
  • a discharge preventing condenser 9 is connected in the circuit in association with fixed resistors 7 and 10 and diodes 8 and 11.
  • a switching element 12 is connected operatively with the discharge preventing condenser 9 and is switched by a flash preventing trigger circuit 13 responsive to a signal provided at a terminal 14.
  • a further fixed resistance 15 is connected in series with trigger circuit 5, and the power source 1 is connected to the circuit upon closure of a power source switch 16.
  • the purpose of providing diode 8 is to prevent current from flowing through resistance 7 and discharge tube 3 when condenser 9 is discharged, and the purpose of diode 11 is to prevent current from flowing through the circuit of discharge preventing condenser 9, switching element 12, such as a quenching discharge tube or the like, and resistance 10.
  • switching element 12 such as a quenching discharge tube or the like
  • resistance 10 in the circuit shown in FIG. 1, condenser 9 is discharged with switching element 12 to trigger silicon control element 4 nonconductive.
  • the preparation time from the first illumination to the second illumination will be determined by a time constant factor of the product of the sum of the resistance values of resistances 7 and 10 and the capacity of the condensor 9.
  • the capacity of V the condensor is made small or the resistance value is a diode 8 and switching element 12.
  • the current will flow through the circuit including flash discharge, tube 3, resistance 10 and a diode 11, so that illumination cannot be. interrupted.
  • FIG. 1 is an electric circuit diagram of a conventional electronic flash device.
  • FIG. 2 is an electric circuit diagram of one embodiment of the electronic flash device according to the present invention.
  • FIG. 3 is a wave form diagram of the function of the circuit shown in FIG. 2.
  • FIG. 4 is an electric circuit diagram of another embodiment of the electronic flash device according to the present invention.
  • a charging signal trigger circuit 1 17 and a charging silicon control element 1 18, having its gate terminal connected to a trigger circuit output 117, are additionally connected in parallel with illumination prevention condenser 109.
  • the circuitry of trigger circuit 117 is such that the behavior of the terminal voltage is detected as condenser 109 is discharged, and a control signal for applying a gate signal to silicon control element 118 is generated.
  • the current flows to the circuit containing the flash discharge tube 103, a connecting point 120, the discharge preventing condensor 109, a connecting point 119, and the switching element 112.
  • a positive potential is applied to the connecting point 120 and a negative potential to the connecting point 119.
  • the charging signal trigger circuit 117 is actuated by the positive potential at the connecting point 120, so as to supply a trigger signal to the gate.
  • the ordinate axis shows the charge magnitude, wherein the positive direction represents a case when the positive potential is applied to connecting point 119, and the negative direction illustrates the case when a positive potential is supplied to the connecting point 120.
  • charging of condenser 109 increases in accordance with the curve determined by the time constant of the resistance value and the capacity value, and the charge is carried out to a value sufficient to convert discharge preventingsilicon control element 104 from the conductive state to the nonconductive state.
  • condensor 109 When the flash discharge tube discharges to emit I light, condensor 109 is discharged in accordance with a flash preventing signal at the point C to actuate control element 104 to stop or interrupt flash discharge tube 103 from emitting light. Then, as the first charging of condensor 102 is started through flash discharge tube 103 from the point D and reaches the pointE, the
  • charging signal trigger circuit is actuated and condensor 109 is re-charged through control element 118. Thereby the direction of the electric charge is reversed and, at the same time, the voltage is elevated instantaneously and the next flash starting preparation is com pleted at the point B. 1
  • FIG. 4 shows another example of the present invention.
  • 201 is a power source cell, for example a low voltage small size dry cell, a Ni-cd battery, etc.
  • 202 is a power source switch.
  • 203 is adirect current voltage booster circuit consisting of,,for example,
  • a transistor oscillation circuit and a rectification circuit for generating a high voltage directcurrentfrom a low voltage direct current power source.
  • 204 is a main capacitor
  • 205 is a transformer inserted in a discharge path of the main capacitor.
  • 206' is a flash discharge tube
  • 207 is a triggertransforrner forthe discharge tube
  • 208 is a condensor for the same.
  • 209 is a synchronizing contact and is closed, forexample, in synchronism with the shutter running by a release button of a camera.
  • 210 is a semi-conductor switching element- (thyristor) connected in series with the flash discharge tube 206.
  • 211 to 223 are elements composing a light amount control circuit for controlling the switching of element 206, wherein 211 is arectifyingdiode, 212 is a smoothing condensor, and 213 is a variable resistance for setting the light amount of the discharge tube at a desired value, 214 is a control switching element which is a programmable uni-junction transistor (PUT). 216
  • 219 is a thyristor.
  • 217, 218, 220, 221 and 222 are elements composing a circuit to turn off the series thyristor 210, and compose the charging circuit of the commutation condensor 220.
  • 223 is an auxiliary capacitor connected in parallel with the flash discharge tube 206.
  • 224, 225 are the trigger condensor and, resistance, respectively, of the thyrister 210.
  • 226 is a thyristor
  • 227 is a conductance signal generation circuit having its output terminal connected to the gate of the thyristor 226 and corresponds to the member 117 of FIG. 2.
  • the function of this device shall be explained.
  • the power source switch 202 When the power source switch 202 is put ON, the power is supplied to the direct current booster circuit 203 from the battery 201, and direct current high voltage is generated at the output of the circuit 203 by the transistor oscillation circuit and the rectification circuit, whereby the main capacitor 204 is charged.
  • the oscillation of the booster circuit 203 As the charged voltage of the main capacitor 4 reaches a certain value, the oscillation of the booster circuit 203 is stopped by an oscillation control circuit which is not shown in the drawing and the electric charge of the main capacitor will maintain a constant value this state.
  • the condensors 208, 220, 223 at are also charged. At this state, the thyristor 210 and the thyristor 219 and PUT 214 are placed in OFF state.
  • the electric charge of the condensor 208 of the trigger circuit flows to the trigger transformer 207 and a trigger pulse is impressed onto the flash discharge tube 206.
  • the thyristor 210 becomes ON by the voltage generated at the resistance 225 and the condensor 224.
  • the electric charge of the main capacitor 204 and the auxiliary capacitor 223 is discharged by the flash discharge tube 206, which emits light.
  • the discharge is made certain by the action of the small capacity auxiliary capacitor 223 which is directly connected in parallel with the dis charge tube.
  • the discharge current from the main capacitor 204 flows to a primary coil of the transformer 205 in a pulse shape, thereby generating pulse wave form output at its secondary coil.
  • This output is rectified by the diode 211 of the control circuit and is smoothed by the condensor 212, and at the same time, with the trigger of the flash discharge tube 206, direct current constant voltage is generated.
  • This voltage works as a power source actuating the control circuit, and the PUT 214 is triggered with the time constant set beforehand at the variable resistance 213, that is, the delay time provided by the condensor 216 and the resistance 213, etc., and the thyristor 219 is switched ON by the terminal voltage of the output load resistance 215 of the PUT.
  • the terminal voltage of the commutation condensor 220 charged with the circuit of the resistance 217, the diode 218, the resistance 221, and the diode 222, is impressed on the thyristor 210 through the thyristor 219 with reverse polarity, whereby the thyristor 210 turns from ON to OFF blocking the discharge path of the flash discharge tube 206. Therefore, the flashing of the discharge tube 206 is stopped and the amount of light emitted is controlled.
  • the residual electric charge of the main capacitor 204 at this state remains undischarged, the capacitor is charged to a predetermined value with the power from the direct current booster circuit, so that preparation for next flashing is than that in the device of parallel type control system.
  • While the delay time in the control circuit of this device can be manually adjusted by setting the photographing information of flash photographing at the variable resistance 213, it can be automatically controlled by receiving light reflected from an object.
  • the thyristor 226 is triggered conductive through from the gate signal generation circuit 227 and charging current flows to the discharge preventing condensor 220, and the charging of the condensor 220 rapidly proceeds in preparation for the next flashing.
  • a circuit is provided which obviates the difficulties in a conventional flash device having a series type control circuit, that is, the uncertainty in the function at start up and the fact that the control circuit is started at the same time with the trigger of the flash discharge tube, further power consumption is small as a characteristic of a series type control system. Thus it is very effective especially as a small size light control flash device.
  • An electronic flash device for a photographic cam era, operable to control the amount of light emitted by a flash tube by interrupting the discharge of a flash tube after initiation of the discharge thereof, said electronic flash device comprising, in combination, a source of electric potential; a first capacitor connected across said source for charging thereby; a flash tube having one terminal connected to one terminal of said first capacitor; a first switching means connected in series to the other terminal of said flash tube, at a junction point, and to the other terminal of said first capacitor, and operable to effectively connect and disconnect said flash tube from said first capacitor; trigger means connected to said first switching means and operable to trigger said first switching means conductive for discharging said first capacitor through said flash tube; impedance means; a second capacitor; said impedance means connecting one end of said second capacitor with one terminal of said source of electric potential; the other end of said second capacitor being connected to said junction point of said first switching means and said flash tube, and to the other terminal of said source of electric potential, for charging of said second capacitor through said impedance means; signal
  • said second switching means is an SCR.

Landscapes

  • Stroboscope Apparatuses (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
  • Exposure Control For Cameras (AREA)
US358522A 1972-05-10 1973-05-09 Electronic flash device Expired - Lifetime US3896333A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4612972A JPS5729686B2 (fr) 1972-05-10 1972-05-10

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US3896333A true US3896333A (en) 1975-07-22

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JP (1) JPS5729686B2 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
DE2812939A1 (de) * 1977-03-25 1979-02-15 West Electric Co Aussenbefindlicher messfuehler fuer einen elektronenblitz
US4155031A (en) * 1976-09-09 1979-05-15 Toshiba Photo Products Co., Ltd. Electronic flash apparatus
US4288722A (en) * 1978-09-07 1981-09-08 Canon Kabushiki Kaisha Electronic flash device
US4344020A (en) * 1979-09-04 1982-08-10 West Electric Co., Ltd. Electronic flash device capable of automatic flash duration adjustment
US4591762A (en) * 1983-05-31 1986-05-27 Olympus Optical, Co. Electronic flash
US4994716A (en) * 1985-08-28 1991-02-19 U.S. Philips Corporation Circuit arrangement for starting and operating gas discharge lamps

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5337374A (en) * 1977-09-07 1978-04-06 Hitachi Ltd Test piece operating unit for scanning type electronic microscope or equivalent
JPS5478122A (en) * 1977-12-05 1979-06-22 Mamiya Camera Trigger circuit for strobe generator
JPS5638031A (en) * 1979-09-04 1981-04-13 West Electric Co Ltd Automatic dimming electronic flash device
JPH0712979Y2 (ja) * 1987-12-17 1995-03-29 株式会社ニコン 持続放電防止電子閃光装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3519879A (en) * 1968-07-25 1970-07-07 Honeywell Inc Flash apparatus with automatic light termination having gating and anticipation means
US3541387A (en) * 1968-04-23 1970-11-17 Bosch Elektronik Gmbh Control system for terminating the discharge of a flash lamp
US3591829A (en) * 1967-04-20 1971-07-06 Minolta Camera Kk Automatic control device for electronic flash
US3818266A (en) * 1968-02-13 1974-06-18 Ponder & Best Load current pulse control devices

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4421102Y1 (fr) * 1967-01-23 1969-09-08

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3591829A (en) * 1967-04-20 1971-07-06 Minolta Camera Kk Automatic control device for electronic flash
US3818266A (en) * 1968-02-13 1974-06-18 Ponder & Best Load current pulse control devices
US3541387A (en) * 1968-04-23 1970-11-17 Bosch Elektronik Gmbh Control system for terminating the discharge of a flash lamp
US3519879A (en) * 1968-07-25 1970-07-07 Honeywell Inc Flash apparatus with automatic light termination having gating and anticipation means

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
US4155031A (en) * 1976-09-09 1979-05-15 Toshiba Photo Products Co., Ltd. Electronic flash apparatus
DE2812939A1 (de) * 1977-03-25 1979-02-15 West Electric Co Aussenbefindlicher messfuehler fuer einen elektronenblitz
US4288722A (en) * 1978-09-07 1981-09-08 Canon Kabushiki Kaisha Electronic flash device
US4344020A (en) * 1979-09-04 1982-08-10 West Electric Co., Ltd. Electronic flash device capable of automatic flash duration adjustment
US4591762A (en) * 1983-05-31 1986-05-27 Olympus Optical, Co. Electronic flash
US4994716A (en) * 1985-08-28 1991-02-19 U.S. Philips Corporation Circuit arrangement for starting and operating gas discharge lamps

Also Published As

Publication number Publication date
JPS5729686B2 (fr) 1982-06-24
JPS498221A (fr) 1974-01-24

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