Optical configuration for imaging-type optical encoders

Details Optical configuration for imaging-type optical encoders Optical configuration for imaging-type optical encoders

2006-06-26

2008-10-14

Epps, Georgia Y. (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

C250S23700G, C356S616000, C341S011000

Reexamination Certificate

active

07435945

ABSTRACT:
A displacement measuring device including a scale, and an optical readhead including an index pattern and a light receiving element is provided. A bright/dark pattern arising from a scale grating is detected by the readhead to measure displacement. In various embodiments, a magnification of the pattern is adjusted by the spacing between at least a lens element, aperture element, and detection plane of the readhead. An aperture can be designed to provide a diffraction-limited telecentric imaging configuration that filters an image of the scale grating to provide a sinusoidal intensity pattern that supports highly interpolated measurements. An aperture dimension, selected in relation to the grating pitch and other parameters, can provide a desirable combination of readhead operating characteristics including one or more of a desired depth of field; degree of spatial filtering; and optical signal power.

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