Signal processing algorithm of a position sensitive detector using amplitude modulation/demodulation

The signal processing algorithm for a position sensitive detector (PSD) using an amplitude modulation/demodulation algorithm is addressed in this article. Dark currents and the external noises such as daylight and fluorescent lights are eliminated by using the amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for the PSD sensor is compared with a pulse amplitude modulation method (PAM). The proposed amplitude modulation method is proved to be more accurate and robust than the PAM method by using analysis and experiments. Multiple measurements technique using one PSD sensor by the amplitude modulation/demodulation is also addressed. The power variation of light source is compensated by the normalization process using a divider.