| 摘要 |
PURPOSE:To increase the life of luminous elements and improve the speed of response by a method wherein a light detecting circuit and a comparison circuit of a controller are shared, and circuit constitution is simplified while currents not less than necessary currents are not supplied to the luminous elements. CONSTITUTION:A plurality of semiconductor elements LD1-LDn of a semiconductor laser array 1 are selectively driven by means of switch circuits 21-1-21-n, and back beams BL1-BLn that the elements LD1-LDn radiate are detected by means of a light detecting circuit 11. Signals detected by means of the circuit 11 are compared with reference signals from a reference level setting circuit 13 by means of a comparison circuit 14 of a luminous energy controller, and the results of comparison are added to a change-over circuit 15. Control circuits 16-1-16-n controlling the circuits 21-1-21-n are selected by timing signals from a terminal TM by means of the circuit 15. Counters counting signals from an oscillation circuit 17 and D/A converters are mounted to the circuits 16-1-16-n, and the currents of the elements LD1-LDn can be controlled in response to the results of comparison of the circuit 15, thus lengthening the life of the elements LD1-LDn. |
