Apparatus for position encoding
AssigneeRandwal Instrument Co., Inc.
InventorPaul W. Remijan
Life of this patent
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Abstract
A position encoder including a holographically recorded, single-frequency, phase grating. When this phase grating is illuminated by a spatially coherent light source, it acts as a basic common path interferometer and constitutes a highly efficient source of high contrast, stable, interference fringe patterns. In the position encoder, a carrier moves the grating in a plane that is orthogonal to an axis from the light source. Motion of the carrier is detected as the fringe pattern moves past detecting means thereby to sense motion and provide position information in the form of electrical signals.
Claims14
Apparatus for indicating the position of a movable element along a motion axis, said apparatus comprising:
- A. source means for producing a spatially coherent light at a focal point along an axis that is normal to the motion axis,
- B. holographically recorded grating means for producing a first diffraction and a second diffraction of equal strengths and which overlap and the absolute values of whose order numbers are different thereby to produce a high contrast, low noise interference pattern in the area of overlap,
- C. detection means positioned in the area of overlap for producing signals dependent upon the interference pattern that impinges said detection means, and
- D. motion means for producing relative movement of said grating means and said detection means thereby to move the interference pattern with respect to said detection means.
Apparatus for indicating the position of a movable element along a motion axis, said apparatus comprising:
- A. optically thin grating means for projecting, along an axis perpendicular to the motion axis, multiple diffractions to include a first diffraction and a second diffraction of equal strengths and which overlap and the absolute values of whose order numbers are different thereby to produce a high contrast, low noise interference pattern in the area of overlap,
- B. detection means positioned in the area of overlap for producing signals dependent upon the interference pattern that impinges said detection means, and
- C. motion means for producing relative movement of said grating means and said detection means thereby to move the interference pattern with respect to said detection means.
Dependencies are inferred from the claim text.