Illumination portion for an adaptable resolution optical encoder

摘要

An illumination portion of an optical encoder comprising a scale track extending along a measuring axis direction, an imaging portion, and a detector configuration. The illumination portion comprises: a light source configured to output source light; a collimation portion; and a structured illumination generating portion comprising a beam-separating portion and an illumination grating and configured to input the source light and output structured illumination to the scale track. The beam-separating portion is arranged to input the source light and output a first source light portion and a second source light portion to the illumination grating, such that they form beams that are spaced apart from one another along the measuring axis direction. The illumination grating is configured to diffract the first and second source light portions to the scale track such that only two orders of diffracted light overlap within an imaged region.

主权项

1. An illumination portion for an optical encoder which comprises a scale track extending along a measuring axis direction, an imaging configuration, and a detector configuration, the illumination portion comprising:
a light source configured to output source light having a wavelength λ; and a structured illumination-generating portion configured to input the source light and provide structured illumination, wherein the structured illumination comprises an illumination fringe pattern oriented transversely to the measuring axis direction which is input to the scale track, wherein:
the scale track is configured to spatially modulate the input illumination fringe pattern and output scale light comprising spatially modulated image light;the detector configuration and imaging configuration are configured such that only scale light arising from an imaged region of the scale track is imaged to the detector configuration;the structured illumination-generating portion comprises a beam-separating portion and an illumination grating;the beam-separating portion is arranged to input the source light and is configured to output a first source light portion and a second source light portion to the illumination grating, such that the first and second source light portions form beams that are spaced apart from one another along the measuring axis direction at a plane proximate to the illumination grating; andthe illumination grating is configured to diffract the first and second source light portions across an operating gap to the scale track such that only two orders of diffracted light overlap within the imaged region at a plane coinciding with the scale track, and provide the illumination fringe pattern in the imaged region.