Electronic flash intensity control circuits

Claim 2

An electronic flash intensity control circuit for controlling the light output of a discharge tube, comprising: a discharge tube and a resistive impedance connected together as a series circuit; a storage capacitor connected in parallel with said series circuit; trigger circuit means connected to said discharge tube for discharging said discharge tube and to thereby discharge said storage capacitor at least partially through said resistive impedance; a voltage-dividing tap on said resistive impedance for dividing a voltage applied across said resistive impedance by the discharge of said storage capacitor; control means for controlling the output of said discharge tube, including a semiconductor control element having an anodE, a cathode and a gate and connected in parallel with said resistive impedance, said voltage-dividing tap being connected to said cathode for applying a voltage on the voltage-dividing tap to the cathode; and control voltage applying means connected to said semiconductor control element for applying a control voltage to the gate thereof; wherein said semiconductor control element becomes conductive when the difference between the voltage on said voltage dividing means and said control voltage reaches a predetermined value.

Claim 3

An electronic flash intensity control circuit for controlling the light output of a discharge tube, comprising: a discharge tube and a resistive impedance connected together as a series circuit; a storage capacitor connected in parallel with said series circuit; trigger circuit means connected to said discharge tube for discharging said discharge tube and to thereby discharge said storage capacitor at least partially through said resistive impedance; a voltage-dividing tap on said resistive impedance for dividing a voltage applied across said resistive impedance by the discharge of said storage capacitor; control means for controlling the output of said discharge tube, including a semiconductor control element having an anodE, a cathode and a gate and connected in parallel with said resistive impedance, said voltage-dividing tap being connected to said cathode for applying a voltage on the voltage-dividing tap to the cathode; and control voltage applying means connected to said semiconductor control element for applying a control voltage to the gate thereof; wherein said semiconductor control element becomes conductive when the difference between the voltage on said voltage dividing means and said control voltage reaches a predetermined value.

Claim 4

An electronic flash intensity control circuit for controlling the light output of a discharge tube, comprising: a discharge tube and a resistive impedance connected together as a series circuit; a storage capacitor connected in parallel with said series circuit; trigger circuit means connected to said discharge tube for discharging said discharge tube and to thereby discharge said storage capacitor at least partially through said resistive impedance; a voltage-dividing tap on said resistive impedance for dividing a voltage applied across said resistive impedance by the discharge of said storage capacitor; control means for controlling the output of said discharge tube, including a semiconductor control element having an anodE, a cathode and a gate and connected in parallel with said resistive impedance, said voltage-dividing tap being connected to said cathode for applying a voltage on the voltage-dividing tap to the cathode; and control voltage applying means connected to said semiconductor control element for applying a control voltage to the gate thereof; wherein said semiconductor control element becomes conductive when the difference between the voltage on said voltage dividing means and said control voltage reaches a predetermined value.

Claim 5

The electronic flash intensity control circuit according to claim 1, further comprising: a second capacitor connected in parallel with said resistive impedance, a portion of the discharge of said storage capacitor being applied across said resistive impedance and said second capacitor at the start of the discharge of said storage capacitor to cause said discharge tube to produce a light output to be directed to an object; light signal storage circuit means connected to said control voltage applying means for storing a representative voltage which is representative of the distance between said discharge tube and said object, a voltage derived from said representative voltage being applied to the gate of said semiconductor control element as said control voltage; and light responsive means for applying at least a portion of said light output reflected from said object to said light signal storage circuit means.

Claim 6

The electronic flash intensity control circuit according to claim 2, wherein a power source for said light signal storage circuit means comprises the voltage applied across said resistive impedance.

Claim 7

The electronic flash intensity control circuit according to claim 2, wherein said control voltage applying means includes a transistor, said light signal storage circuit means is connected to said transistor for controlling the current flowing through said transistor by said representative voltage, and the output of said transistor is connected to said control means, wherein said control voltage applied to the gate of said semiconductor control element varies with said representative voltage.

Claim 8

An electronic flash intensity control circuit for controlling the light output of a flash discharge tube, comprising: a first discharge tube; a first storage capacitor connected in parallel with said first discharge tube; a series circuit comprising a second discharge tube in series with a parallel circuit of a resistor and a second capacitor, said series circuit being connected in parallel with said first capacitor; means to discharge said first capacitor at least partially through said series circuit to produce a light output from said second tube which is directed to an object; voltage-dividing means connected to said resistor for dividing the voltage applied across said resistor; trigger circuit means connected to said first discharge tube for generating a trigger pulse to discharge said first tube; control means controlling the operation of said trigger circuit means, said control means including a semiconductor control element, having an anode, a cathode and a gate, connected to said trigger circuit means and said resistor, said cathode being connected to said voltage-dividing means; control voltage applying means connected to said semiconductor control element for applying a control voltage to the gate thereof to cause said semiconductor control element to conduct and trigger said trigger circuit means; light signal storage circuit means connected to said control voltage applying means for storing a representative voltage which is representative of the distance between said pilot discharge tube and said object; light responsive means applying at least a portion of said light output reflected from said object to said light signal storage circuit means; and means applying a voltage derived from said representative voltage to the gate of said semiconductor control element as said control voltage, wherein said semiconductor control eLement becomes conductive when the voltage between said voltage dividing means and said control voltage applying means reaches a predetermined value.

Claim 9

An electronic flash intensity control circuit for controlling the light output of a flash discharge tube, comprising: a first discharge tube; a first storage capacitor connected in parallel with said first discharge tube; a series circuit comprising a second discharge tube in series with a parallel circuit of a resistor and a second capacitor, said series circuit being connected in parallel with said first capacitor; means to discharge said first capacitor at least partially through said series circuit to produce a light output from said second tube which is directed to an object; voltage-dividing means connected to said resistor for dividing the voltage applied across said resistor; trigger circuit means connected to said first discharge tube for generating a trigger pulse to discharge said first tube; control means controlling the operation of said trigger circuit means, said control means including a semiconductor control element, having an anode, a cathode and a gate, connected to said trigger circuit means and said resistor, said cathode being connected to said voltage-dividing means; control voltage applying means connected to said semiconductor control element for applying a control voltage to the gate thereof to cause said semiconductor control element to conduct and trigger said trigger circuit means; light signal storage circuit means connected to said control voltage applying means for storing a representative voltage which is representative of the distance between said pilot discharge tube and said object; light responsive means applying at least a portion of said light output reflected from said object to said light signal storage circuit means; and means applying a voltage derived from said representative voltage to the gate of said semiconductor control element as said control voltage, wherein said semiconductor control eLement becomes conductive when the voltage between said voltage dividing means and said control voltage applying means reaches a predetermined value.