Digitizing circuit of light amount receiving from strobe and control circuit of light amount emitted from strobe

A circuit that digitizes a quantity of light received from a strobe, comprising:

• a photoelectric conversion device that receives light from the strobe and outputs a current corresponding to an intensity of the received light;
• a current/voltage conversion device that stores the current output by said photoelectric conversion device and converts the current to a voltage value;
• a constant current discharge device that holds the voltage value output by said current/voltage conversion device close to a specific voltage level by discharging a constant current from said current/voltage conversion device over a specific period which is in synchronization with a specific sampling frequency and is shorter than the sampling cycle when the voltage value output by said current/voltage conversion device exceeds a predetermined threshold value and by implementing feedback control on the voltage output by said current/voltage conversion device;
• and
• a received light quantity output device that outputs one or more pulse signals when the voltage value output by said current/voltage conversion device exceeds the predetermined threshold value.

A circuit that controls a quantity of light emitted by a strobe, comprising:

• a photoelectric conversion device that receives light from the strobe and outputs a current corresponding to an intensity of the received light;
• a current/voltage conversion device that stores the current output by said photoelectric conversion device and converts the current to a voltage value;
• a constant current discharge device that holds the voltage value output by said current/voltage conversion device close to a specific voltage level by discharging a constant current from said current/voltage conversion device over a specific period which is in synchronization with a specific sampling frequency and is shorter than the sampling cycle when the voltage value output by said current/voltage conversion device exceeds a predetermined threshold value and by implementing feedback control on the voltage output by said current/voltage conversion device;
• a received light quantity output device that outputs one or more pulse signals when the voltage value output by said current/voltage conversion device exceeds the predetermined threshold value;
• and
• a strobe light emission stop device that counts said one or more pulse signals and outputs a light emission stop signal to the strobe when the count value exceeds a predetermined reference value.

A circuit that controls a quantity of light emitted by a strobe, comprising:

• a photoelectric conversion device that receives light from the strobe and outputs a current corresponding to an intensity of the received light;
• a current/voltage conversion device that stores the current output by said photoelectric conversion device and converts the current to a voltage value;
• a constant current discharge device that holds the voltage value output by said current/voltage conversion device close to a specific voltage level by discharging a constant current from said current/voltage conversion device when the voltage value output by said current/voltage conversion device exceeds a predetermined threshold value and by implementing feedback control on the voltage output by said current/voltage conversion device;
• a pulse signal output device that outputs one or more pulse signals when the constant current is discharged from said current/voltage conversion device;
• and
• a split light emission execution device that counts said one or more pulse signals, outputs a light emission temporary halt signal for stopping a strobe light emission over a specific length of time and resets a count value when the count value matches a first value and then repeatedly executes and stops strobe light emission.

A photoelectric current digitizing circuit, comprising:

• a light-receiving element that generates a photoelectric current corresponding to an intensity of received light;
• a capacitor connected in series with said light-receiving element, at which an electrical charge is stored by the photoelectric current;
• a reference source;
• a comparator that compares a voltage at said capacitor and a voltage at said reference source and outputs a first signal when the stored charge is equal to or greater than a specific quantity;
• a reference clock generating circuit;
• a latch circuit that latches an output of said first signal from said comparator in synchronization with the reference lock;
• a gate circuit that outputs one pulse signal in correspondence to one cycle of said reference clock as a digitized photoelectric current signal while said latch circuit is latching the output of said first signal from said comparator, based upon said reference clock and an output from said latch circuit;
• and
• a constant current circuit that discharges the charge t said capacitor at a specific current level and implements one discharge in correspondence to one pulse signal output by said gate circuit.

An electronic flash unit, comprising:

• a light-emitting device;
• a light-receiving element that generates a photoelectric current corresponding to an intensity of received light;
• a capacitor connected in series with said light-receiving element, at which an electrical charge is stored by the photoelectric current;
• a reference source;
• a comparator that compares a voltage at said capacitor and a voltage at said reference source and outputs a first signal when the stored charge is equal to or greater than a specific quantity;
• a reference clock generating circuit that generates a reference clock;
• a latch circuit that latches an output of said first signal from said comparator in synchronization with said reference clock;
• a gate circuit that outputs one pulse signal in correspondence to one cycle of said reference clock as a digitized photoelectric current signal while said latch circuit is latching the output of said first signal from said comparator, based upon said reference clock and an output from said latch circuit;
• a constant current circuit that discharges the charge at said capacitor at a specific current level and implements one discharge in correspondence to one pulse signal output by said gate circuit;
• a counter that counts said pulse signal;
• and
• a control device that controls said light-emitting device to start a light emission and controls said light-emitting device to stop the light emission when the count value at said counter exceeds a specific reference value after the light emission starts at said light-emitting device.