| 摘要 |
<p>PURPOSE: To improve the efficiency and service life of a light emitting diode(LED) by enabling switching between an on-position, where an optical pulse is outputted to each associated LED at the optical device of N×M rectangular arrays, and an off-position not to output any optical pulse to each associated LED. CONSTITUTION: Optical devices 1-8 are provided with one or a plurality of LED and each LED is driven so as to output a string of optical pulses separated at the intervals of luminosity '0'. Since the temperature of LED cathode is decreased during the respective intervals of zero luminosity, the average temperature over the operating cycles of respective LED gets lower than the case of having zero luminosity intervals outputted for shorter duration time. Since a driving circuit has a finite non-zero RC constant and has capacitors C1 -C8 serially connected with the LED, the long duration time having the zero luminosity intervals between light emitting pulses. Each driving circuit is provided with switches T1 -T8 for changing over the circuit between ON mode and OFF mode. The respective switches are controlled by continuous digital signals L1 -L8 outputted from an interface device. Thus, the efficiency and service life of each LED are improved.</p> |
