초록 ▼

In a range finder, a capacitor for light emission is charged by turning off first and second switching elements and turning on third and fourth switching elements before light is emitted from a light emitting diode. A sum of a charging voltage of the capacitor for light emission and the voltage of a

In a range finder, a capacitor for light emission is charged by turning off first and second switching elements and turning on third and fourth switching elements before light is emitted from a light emitting diode. A sum of a charging voltage of the capacitor for light emission and the voltage of a direct current power source is applied to the light emitting diode by turning on the first and second switching elements and turning off the third and fourth switching elements when light is emitted from the light emitting diode. At this time, an operation of the second switching element is controlled with a constant electric current by a constant current control circuit constructed by a transistor, a resistor for current limitation, a diode, etc. so that an electric current flowing through the light emitting diode is constant and a light emitting amount of the light emitting diode becomes constant.

대표청구항 ▼

A range finder for obtaining measured distance information by emitting light to a photographed subject and detecting reflected light from the photographed subject in synchronization with the light emission; the range finder comprising: a direct current power source of a low voltage; a series circuit

A range finder for obtaining measured distance information by emitting light to a photographed subject and detecting reflected light from the photographed subject in synchronization with the light emission; the range finder comprising: a direct current power source of a low voltage; a series circuit constructed by a light emitting element and a capacitor for light emission; first and second switching means respectively connected between both ends of said direct current power source and the series circuit constructed by said light emitting element and the capacitor for light emission; the first and second switching means being simultaneously turned on so that a discharging electric current flows from said capacitor for light emission in a first direction; third and fourth switching means respectively connected between both the ends of said direct current power source and the capacitor for light emission of said series circuit; the third and fourth switching means being simultaneously turned on so that a charging electric current flows to said capacitor for light emission in a second direction different from said first direction; constant current control means for operating the series circuit of the light emitting element and the capacitor for light emission with a constant electric current when said first and second switching means are turned on; and light emitting control means for charging the capacitor for light emission by turning off said first and second switching means and turning on said third and fourth switching means before light is emitted from said light emitting element; the light emitting control means applying a sum of a charging voltage of said capacitor for light emission and a voltage of said direct current power source to said light emitting element by turning on said first and second switching means and turning off said third and fourth switching means when light is emitted from said light emitting element; and the light emitting control means emitting light from said light emitting element with a constant electric current provided by said constant current control means.