Machine Design

Laser encoder delivers nanometer accuracy

Laser encoders used to measure position can be complicated and difficult to install.

A simplified design, the RLE10, from Renishaw Inc., Hoffman Estates, Ill. (, combines multiaxis capabilities with a compact detector that holds the interferometer, reference-path optics, fringe detector, and beam steerer. Fiber optics deliver laser light from a single source to detectors measuring different axes, which simplifies the optical path and facilitates alignment and installation. Only one external optic is needed. Placing the laser source outside the detector also saves space and keeps heat away from the measurement axis to reduce thermal drift.

The detector is available in versions for planar or linear applications, and they can be used on axes of up to 4 m. It also provides RS-422-format, digital quadrature outputs and analog 1-Vpps sin/cos signals. Resolutions to subnanometer levels can be obtained with external interpolation of analog signals. An optional real-time compensation system for "in-air" applications gives accuracies on the order of 1 ppm.

TAGS: Technologies
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