Displacement measuring apparatus and method
Patent 4776701 Issued on October 11, 1988. Estimated Expiration Date: 
October 11, 2005. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
October 11, 2005. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesPhotoelectric incident light distance measuring device Shaped plastic articles having replicated microstructure surfaces Patent #: 4576850 InventorAssigneeApplicationNo. 06/736275 filed on 05/20/1985US Classes:356/499Having wavefront division (e.g., by diffraction)ExaminersPrimary: Willis, Davis L.Assistant: Koren, Matthew W. Attorney, Agent or FirmInternational ClassesG01D 5/38 (20060101)G01D 5/26 (20060101) Foreign Application Priority Data1984-05-31 GBAbstractDisplacement measuring apparatus comprises a light source (10), a lens (12), and index grating (14), a reflective scale grating (16), and three photodetectors (18) at positions corresponding to the zero order and positive and negative first order images of the source (10). The index grating (14) has a castellated surface profile with a mark/space ratio (a/b, FIG. 3) and a castellation height (h, FIG. 3) chosen so that the three photodetectors (18) see wavefronts having a phase separation of 120. The electrical signals from the photodetectors (18) are used to sense the magnitude and direction of movement of a reading head carrying the components (10, 12, 14 and 18) with respect to the scale grating (16).Other References
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