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 quasi-monochromatic 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 a position encoder application, 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.
Claims20
Apparatus for indicating the position of a movable element along a motion axis, said apparatus comprising:
- A. interference pattern generating means for generating a first diffraction and a second diffraction that are of different order, that have equal strength and that overlap thereby to produce a first high contrast, low noise interference fringe pattern in a first area of overlap,
- B. first detection means positioned to view the first interference fringe pattern for producing signals dependent upon the first interference fringe pattern, and
- C. motion means for producing relative movement of said generating means and said detection means along the motion axis thereby to move said first interference fringe pattern with respect to said detection means.
Apparatus for indicating the position of a movable element along a motion axis, said apparatus comprising
- A. light source means for producing spatially coherent, quasi-monchromatic light,
- B. holographically recorded, single frequency grating means
- (1) positioned to receive light from the light source directed along an axis perpendicular to the motion axis, and
- (2) having a substantially pure sinusoidal phase transmission function whose peak-to-peak phase delay produces first, second and third diffractions, the first and second diffractions being of a different order and equal strength and overlapping so as to interfere to produce a first high-contrast low-noise interference pattern, the first and third diffractions being of a different order and equal strength and overlapping so as to interfere to produce a second high-contrast low-noise interference pattern, said second pattern being 180.degree. out of phase with respect to the first pattern,
- C. first detection means positioned to view the first interference pattern for producing position signals, and
- D. first motion means for producing relative movement of the grating means and the first detection means along said motion axis thereby to move the first interference fringe pattern relative to the detection means.
Dependencies are inferred from the claim text.