Diffuse surface interference position sensor
AssigneeMicroE, Inc.
InventorsWilliam G. Thorburn, Donald K. Mitchell, Bruce A. Horwitz
Life of this patent
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Abstract
Position of a diffusely scattering surface is detected by interfering backscattered light from respective input beams which illuminate a common spot. Through polarization of the input beams and appropriate filtering, backscattered light is isolated from specularly reflected light and interfered to form a fringe pattern on a detector. The position sensor has particular applicability as a push pin sensor in a hard disk servo system.
Claims20
A position sensor for sensing position of a diffusely scattering surface comprising:
- a source of coherent illumination which illuminates the diffusely scattering surface with first and second input beams angled toward the surface forwardly and rearwardly, respectively, relative to surface motion;
- a fringe detector;
- and
- optics to direct light, scattered from the surface in rearward and forward directions, respectively, relative to surface motion, to the detector to form a fringe pattern in the plane of the detector resulting from interference of diffusely scattered light, movement of the surface being detected by the fringe detector through movement of the fringe pattern.
A position sensor for sensing position of a diffusely scattering surface comprising:
- a source of coherent illumination which illuminates a spot of the diffusely scattering surface with separate polarized input beams from forward and reverse directions, respectively;
- a fringe detector;
- and
- optics to direct light, backscattered from the surface, to form a fringe pattern in the plane of the detector resulting from interference of diffusely scattered light, backscattered light being isolated from specularly reflected light through polarization filters.
A method of sensing position of a diffusely scattering surface comprising:
- illuminating the surface with coherent illumination in first and second input beams angled toward the surface forwardly and rearwardly, respectively, relative to surface motion;
- directing light diffusely scattered from the surface in rearward and forward directions, respectively, relative to surface movement to a fringe detector;
- and
- sensing position of a fringe pattern from the diffusely scattered light interfering at the fringe detector as an indication of position of the diffusely reflecting surface.
Dependencies are inferred from the claim text.