Signal processing circuit of anti-pollution optical encoder

A signal processing circuit of an optical encoder, the optical encoder comprising a first index photodiode, a second index photodiode and a reference index photodiode, the signal processing circuit comprising:

• a trans-impedance amplifier (TIA), electrically coupled to the first index photodiode, the second index photodiode and the reference index photodiode, and configured to convert a first photocurrent generated by the first index photodiode, a second photocurrent generated by the second index photodiode and a reference photocurrent generated by the reference index photodiode respectively to a first voltage, a second voltage and a reference voltage;
• a first comparator, configured to compare the first voltage and the reference voltage to output a first comparison voltage;
• a second comparator, configured to compare the second voltage and the reference voltage to output a second comparison voltage;
• and
• an AND gate, configured to receive the first comparison voltage and the second comparison voltage to accordingly generate an index output.