Photographic flashlight apparatus with improved automatic light termination means

Claim 2

In a photographic flashlight apparatus comprising: a flash capacitor connected across a dc source of a predetermined voltage; a flashlight source connected across said flash capacitor and including a flash tube and a thyristor which are simultaneously rendered conductive upon the shutter operation of a photographic camera so as to initiate a light emission by said flash tube; and an automatic light termination means disposed across said flash capacitor and including a quench element, a timer circuit coupled with said quench element so as to cause said quench element to be turned on a predetermined period of time after the emission of light is initiated by said flash tube, and a flash termination capacitor coupled with said thyristor included in said flashlight source and said quench element and precharged with voltage corresponding to that of said dc source for effecting discharge upon the conduction of said quench element by said timer circuit through said conducting quench element, said flash capacitor and said flashlight source so as to turn off said thyristor; the improvement comprising: an exposure correction means including a series arrangement which is connected across said flash capacitor and which includes a switch element coupled with said timer circuit so as to be made conductive simultaneously with said quench element, and a parallel circuit which includes a resistor and a bypass capacitor coupled in parallel with said resistor, said parallel circuit being operative to shunt through said conducting switch element at least part of an over-flash current which might otherwise flow into said flash tube upon the flash termiNation thereof.

Claim 3

Apparatus as claimed in claim 1, wherein said series arrangement further includes a diode connected in series with said switch element and with a forward polarity with respect to said dc source.

Claim 4

Apparatus as claimed in claim 1, wherein said switch element as well as said quench element comprises a thyristor.

Claim 5

Apparatus as claimed in claim 1, wherein said switch element as well as said quench element comprises a quench tube.

Claim 6

Apparatus as claimed in claim 1 further including an inductor connected between a power source line for said flash capacitor and a power source line for the remaining elements.

Claim 7

Apparatus as claimed in claim 1 further including a diode connected in parallel with said inductor with a backward polarity relative to said dc source.

Claim 8

Apparatus as claimed in claim 1, wherein said timer circuit included in said automatic light termination means comprises a photoelectric conversion element which is connected to a dc source via a normally open switch which is closed interlockingly with the shutter operation of said camera, and which is disposed to receive light emitted by said flash tube and reflected from a foreground subject so as to produce photocurrent proportional to the received amount of light; and an integration capacitor coupled with said photoelectric conversion element and said quench element for integrating with time the photocurrent flowing through said photoelectric conversion element, said quench element being turned on responsive to the integrated voltage.

Claim 9

Apparatus as claimed in claim 1, wherein said timer circuit included in said automatic light termination means comprises a relaxation oscillator which includes a series circuit having a first resistor and a capacitor connected in series with said first resistor, said series circuit being connected to a dc source via a normally open switch which is closed interlockingly with the shutter operation of said camera; and a double base diode whose emitter is connected to the junction of said capacitor with said first resistor, one of the bases of said double base diode being connected to one end of said series circuit via a second resistor and coupled with said quench element, and the other base of said double base diode being connected to the other end of said series circuit via a third resistor.

Claim 10

Apparatus as claimed in claim 1 further including an availability-confirming means which comprises an indicator lamp having one electrode thereof connected to the junction of said flash termination capacitor with said quench element as well as to the high potential side of said dc source via a resistor and a diode, the diode being connected with a backward polarity relative to said dc source, the other electrode of said indicator lamp being connected to the low potential side of said dc source via another resistor, said indicator lamp being turned on only when sufficient voltage to permit the emission of light by said flash tube is precharged on said flash capacitor and also sufficient discharging voltage to cause said quench element to be turned off is precharged on said flash termination capacitor.

Claim 11

Apparatus as claimed in claim 9, comprising a trigger source for said flashlight source, and wherein said availability-confirming means further includes a further diode coupled between said trigger source and said other electrode of said indicator lamp and being operative to shunt part of the current from said trigger source only upon an erroneous shutter operation of an associated camera under the condition where insufficient voltage to permit the optimum emission of light by said flash tube is precharged on said flash capacitor so as to prevent said flash tube from being triggered.

Claim 12

A photographic flashlight apparatus comprising: a flash capacitor connected across a dc source of a predetermined voltage; a flashlight source connected across said flash capacitor and including a flash tube and a thyristor which are simultaneoUsly rendered conductive upon the shutter operation of a photographic camera so as to initiate a light emission by said flash tube; an automatic light termination means disposed across said flash capacitor and including a quench element; a timer circuit coupled with said quench element so as to cause said quench element to be turned on a predetermined period of time after the emission of light is initiated by said flash tube; and a flash termination capacitor coupled with said thyristor included in said flashlight source and said quench element and precharged with voltage corresponding to that of said dc source for effecting discharge upon the conduction of said quench element by said timer circuit through said conducting quench element, said flash capacitor and said flashlight source so as to turn off said thyristor; an exposure correction means including a resistor connected in parallel with a bypass capacitor, said parallel circuit being coupled substantially in parallel with said flash tube and being operative to shunt at least part of an over-flash current which might otherwise flow into said flash tube upon the flash termination thereof; and an availability-confirming means which comprises an indicator lamp having one electrode thereof connected to the junction of said flash termination capacitor with said quench element as well as to the high potential side of said dc source via a resistor and a diode, the diode being connected with a backward polarity relative to said dc source, the other electrode of said indicator lamp being connected to the low potential side of said dc source via another resistor, said indicator lamp being turned on only when sufficient voltage to permit the emission of light by said flash tube is precharged on said flash capacitor and also sufficient discharging voltage to cause said quench element to be turned off is precharged on said flash termination capacitor.

Claim 13

A photographic flashlight apparatus comprising: a flash capacitor connected across a dc source of a predetermined voltage; a flashlight source connected across said flash capacitor and including a flash tube and a thyristor which are simultaneoUsly rendered conductive upon the shutter operation of a photographic camera so as to initiate a light emission by said flash tube; an automatic light termination means disposed across said flash capacitor and including a quench element; a timer circuit coupled with said quench element so as to cause said quench element to be turned on a predetermined period of time after the emission of light is initiated by said flash tube; and a flash termination capacitor coupled with said thyristor included in said flashlight source and said quench element and precharged with voltage corresponding to that of said dc source for effecting discharge upon the conduction of said quench element by said timer circuit through said conducting quench element, said flash capacitor and said flashlight source so as to turn off said thyristor; an exposure correction means including a resistor connected in parallel with a bypass capacitor, said parallel circuit being coupled substantially in parallel with said flash tube and being operative to shunt at least part of an over-flash current which might otherwise flow into said flash tube upon the flash termination thereof; and an availability-confirming means which comprises an indicator lamp having one electrode thereof connected to the junction of said flash termination capacitor with said quench element as well as to the high potential side of said dc source via a resistor and a diode, the diode being connected with a backward polarity relative to said dc source, the other electrode of said indicator lamp being connected to the low potential side of said dc source via another resistor, said indicator lamp being turned on only when sufficient voltage to permit the emission of light by said flash tube is precharged on said flash capacitor and also sufficient discharging voltage to cause said quench element to be turned off is precharged on said flash termination capacitor.

Claim 14

Apparatus as claimed in claim 11, comprising a trigger source for said flashlight source, and wherein said availability-confirming means further includes a further diode coupled between said trigger source and said other electrode of said indicator lamp and being operative to shunt part of the current from said trigger source only upon an erroneous shutter operation of an associated camera under the condition where insufficient voltage to permit the optimum emission of light by said flash tube is precharged on said flash capacitor so as to prevent said flash tube from being triggered.

Claim 15

In a photographic flashlight apparatus comprising: a flash capacitor connected across a dc source of a predetermined voltage; a flashlight source connected across said flash capacitor and including a flash tube and a thyristor which are simultaneously rendered conductive upon the shutter operation of a photographic camera so as to initiate a light emission by said flash tube; and an automatic light termination means disposed across said flash capacitor and including a quench element; a timer circuit coupled with said quench element so as to cause said quench element to be turned on a predetermined period of time after the emission of light is initiated by said flash tube; and a flash termination capacitor coupled with said thyristor included in said flashlight source and said quench element and precharged with voltage corresponding to that of said dc source for effecting discharge upon the conduction of said quench element by said timer circuit through said conducting quench element, said flash capacitor and said flashlight source so as to turn off said thyristor; the improvement comprising: an exposure correction means including a parallel circuit which is coupled substantially in parallel with said flash tube between the high potential side of said dc source and the junction of said flash termination capacitor with said quench element, said parallel circuit including a resistor and a bypass capacitor connected in parallel with said resistor, Said parallel circuit being operative to shunt at least part of an over-flash current which might otherwise flow into said flash tube upon the flash termination thereof.

Claim 16

In a photographic flashlight apparatus comprising: a flash capacitor connected across a dc source of a predetermined voltage; a flashlight source connected across said flash capacitor and including a flash tube and a thyristor which are simultaneously rendered conductive upon the shutter operation of a photographic camera so as to initiate a light emission by said flash tube; and an automatic light termination means disposed across said flash capacitor and including a quench element; a timer circuit coupled with said quench element so as to cause said quench element to be turned on a predetermined period of time after the emission of light is initiated by said flash tube; and a flash termination capacitor coupled with said thyristor included in said flashlight source and said quench element and precharged with voltage corresponding to that of said dc source for effecting discharge upon the conduction of said quench element by said timer circuit through said conducting quench element, said flash capacitor and said flashlight source so as to turn off said thyristor; the improvement comprising: an exposure correction means including a parallel circuit which is coupled substantially in parallel with said flash tube between the high potential side of said dc source and the junction of said flash termination capacitor with said quench element, said parallel circuit including a resistor and a bypass capacitor connected in parallel with said resistor, Said parallel circuit being operative to shunt at least part of an over-flash current which might otherwise flow into said flash tube upon the flash termination thereof.

Claim 17

Apparatus as claimed in claim 13, wherein said exposure correction means further includes a diode connected between said parallel circuit and said flashlight source with a forward polarity with respect to said dc source.

Claim 18

Apparatus as claimed in claim 13, wherein said timer circuit included in said automatic light termination means comprises a photoelectric conversion element which is connected to a dc source via a normally open switch which is closed interlockingly with the shutter operation of said camera, and which is disposed to receive light emitted by said flash tube and reflected from a foreground subject so as to produce photocurrent proportional to the received amount of light; and an integration capacitor coupled with said photoelectric conversion element and said quench element for integrating with time the photocurrent flowing through said photoelectric conversion element, said quench element being turned on responsive to the integrated voltage.

Claim 19

Apparatus as claimed in claim 13, wherein said timer circuit included in said automatic light termination means comprises a relaxation oscillator which includes a series circuit having a first resistor and a capacitor connected in series with said first resistor, said series circuit being connected to a dc source via a normally open switch which is closed interlockingly with the shutter operation of said camera; and a double base diode whose emitter is connected to the junction of said capacitor with said first resistor, one of the bases of said double base diode being connected to one end of said series circuit via a second resistor and coupled with said quench element, and the other base of said double base diode being connected to the other end of said series circuit via a third resistor.

Claim 20

Apparatus as claimed in claim 13 wherein said quench element comprises a thyristor.

Claim 21

Apparatus as claimed in claim 13 wherein said quench element comprises a quench tube.

Claim 22

Apparatus as claimed in claim 13 further including an inductor connected between a power source line for said flash capacitor and a power source line for the remaining elements.

Claim 23

Apparatus as claimed in claim 19 further including a diode connected in parallel with said inductor with a backward polarity relative to said dc source.

Claim 24

Apparatus as claimed in claim 13 further including an availability-confirming means which comprises an indicator lamp having one electrode thereof connected to the junction of said flash termination capacitor with said quench element as well as to the high potential side of said dc source via a resistor and a diode, the diode being connected with a backward polarity relative to said dc source, the other electrode of said indicator lamp being connected to the low potential side of said dc source via another resistor, said indicator lamp being turned on only when sufficient voltage to permit the emission of light by said flash tube is precharged on said flash capacitor and also sufficient discharging voltage to cause said quench element to be turned off is precharged on said flash termination capacitor.

Claim 25

Apparatus as claimed in claim 21, comprising a trigger source for said flashlight source, and wherein said availability-confirming means further includes a further diode coupled between said trigger source and said other electrode of said indicator lamp and being operative to shunt part of the current from said trigger source only upon an erroneous shutter operation of an associated camera under the condition where insufficient voltage to permit the optimum emission of light by said flash tube is precharged on said flash capacitor so as to prevent said flash tube from being triggered.