BigPatents India

A detecting device for detecting the rotation of a motor rotor includes a light source, an identification mark means positioned around the motor rotor, and a sensor for detecting the light beams emitted by the light source and coming from the identification mark means. The identification mark means can be positioned on a cylindrical shoulder formed around the rotor thereby rotating with the motor rotor synchronously. The light source can emit light beams at two different wavelengths, and the sensor can thus receive and read the light beams with the two different wavelengths respectively reflected from the identificatin mark means thereby producing according binary code signals carrying more detailed information thereof, whereby the detecting device can achieve very precise detection of the rotation of the motor rotor.