Page 233 - Concise Encyclopedia of Robotics

through the chopping wheel. The wheel has radial bands, alternately trans-
parent and opaque (see illustration). The wheel is attached to the shaft.
As the shaft turns,the light beam is interrupted.Each interruption actuates
a counting circuit. The number of pulses is a direct function of the extent
to which the shaft has rotated. The frequency of pulses is a direct function
of the rotational speed. Two LEDs, placed in the correct positions, allow
the encoder to indicate the direction (clockwise or counterclockwise) in
which the shaft rotates.
Continuous Optical Interferometer
light beams
LEDs
Interrupted
light beams

Chopping wheel

Photoreceptors

To frequency
control circuit
Optical encoder

Optical encoders are used in various robotic applications. In particular,
they are used in manipulators to measure the extent of joint rotation.
See also ARTICULATED GEOMETRY and ROBOT ARM.

OPTICAL INTERFEROMETER
See PRESENCE SENSING.

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