| 摘要 |
The emission intensity of each light emitting element in a light source comprising a plurality of light emitting elements can be finely adjusted. Parallel connected variable resistors R1, R2 are connected in series to a monitor diode PD for detecting the emission intensity of light emitting elements LD1, LD2. The voltages Vr1, Vr2 generated at the movable contact of the variable resistors R1, R2 are supplied to the non-inversion input terminals of differential amplifiers OP1, OP2 respectively, while reference voltages Vref1, Vref2 are applied to the inversion input terminals of the differential amplifiers OP1, OP2. When adjusting the emission intensity of the light emitting element LD1, a switching element SW1 is set to a conducting state and a switching element SW2 is set to a non-conducting state, so as to finely adjust the resistance value of the variable resistor R1. When the emission intensity of the light emitting element LD2 is to be adjusted, the switching element SW1 is set to a non-conducting state and the switching element SW2 is set to a conducting state, and the resistance value of the variable resistor R2 is adjusted finely. By this type of fine adjustments, driving currents Id1, Id2 of the light emitting elements LD1, LD2 can be set to values proportional with the resistance values of the variable resistors R1, R2, enabling the emission intensities to be set at desired levels.
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