Optical encoder
Optical encoders as signal encoders have a glass element (4) on which there is a pattern of transparent and opaque areas (lines). A light-sensitive sensor (5) records the intensity of the light beam dependent on the position of the glass element.
If the glass element as signal encoder moves relative to the sensor, this generates a sine-shaped periodic signal in the sensor.
The number or periods through a rotor rotation is decisive for the accuracy of the actual position value.
The position of the rotor cannot be uniquely determined with a single sine signal. Two sensors, electrically offset by 90° are used that generate a sine and a cosine signal. Through evaluation of both signals, the rotor position and direction of rotation can be uniquely determined.
Optical encoders can have very high resolutions but are susceptible to polluted environment due to dust and oil.
The following illustration shows the principle of an optical encoder.
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With this design, the following signal pattern results:
