Real-time, fine adjustment of driver current of a light emitting device of an optical rain sensor

A method for fine adjustment of a driving current of a light emitting element of an optical rain sensor, comprising:

• providing the optical sensor including a first light emitting element adapted to emit a first light pulse toward an inner surface of a transparent substrate, a second light emitting element adapted to emit a second light pulse toward the inner surface of the transparent substrate, a photodetector adapted to detect a light from the first light pulse and the second light pulse that is reflected by the inner surface of the transparent substrate, and a rain sensor controller including a first driver adapted to output a first driver current pulse on a first channel for driving the first light emitting element to emit the first light pulse, and a second driver adapted to output a second driver current pulse on a second channel for driving the second light emitting element to emit the second light pulse;
• receiving an amplitude of a first photodetection signal corresponding to the reflected first light pulse and an amplitude of a second photodetection signal corresponding to the reflected second light pulse;
• deciding whether a difference between the amplitudes of the first photodetection signal and the second photodetection signal satisfies a compensation condition associated with an imbalance between the first light pulse and the second light pulse;
• and
• applying, with an external regulated current source, a compensation current signal on the second channel while the compensation condition is satisfied, the compensation current signal is adapted to increase or decrease a total current across the second light emitting element based on a relation between the amplitudes to reduce an imbalance between the first photodetection signal and the second photodetection signal.