The optical disk turns with the shaft of the encoder. The infrared-light beam emitted by the LED is picked up by sensors after having passed through the index grating and the disk grating. The index grating is fixed to the main body. The smallest turn of the disk generates a modulation of the light which is received by the sensors. This is processed by the electronic circuit of the encoder and transformed into an electrical signal, which is compatible with most measuring and controlling systems. The number of pulses (PPR) generated from a complete shaft rotation, corresponds to the number of lines on the disk. The quality and stability of the signal and the reliability of the encoder during service depends on:

the accuracy of the production and assembly of the mechanical parts.
the accuracy and stability of the optical disk.
the dimensional stability of the main body.
the strict selection of the electronic components.