Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1997-03-26
1998-10-20
Le, Que
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25055929, H01J 314
Patent
active
058250239
ABSTRACT:
An auto-focus laser incremental encoder for measuring linear or rotary motion or position of an object is described. An optical read head focuses three laser beams on the surface of a scaling grating. The grating is a reflection type grating where the height difference between adjacent pixels is one quarter of the wavelength of the laser light whereby the pitch of the grating can be detected by interferometric reflection. There are two sections of grating displaced with respect to each other so that a direction of movement can be readily determined. The third beam acts to provide an autofocus and is reflected from a smooth part of the grating between the two sections of reflective grating.
Cai Lilong
Zhang Jihua
Le Que
The Hong Kong University of Science & Technology
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