Photoelectric incident light distance measuring device
Shaped plastic articles having replicated microstructure surfaces Patent #: 4576850
ApplicationNo. 06/736275 filed on 05/20/1985
US Classes:356/499Having wavefront division (e.g., by diffraction)
ExaminersPrimary: Willis, Davis L.
Assistant: Koren, Matthew W.
Attorney, Agent or Firm
International ClassesG01D 5/38 (20060101)
G01D 5/26 (20060101)
Foreign Application Priority Data1984-05-31 GB
AbstractDisplacement 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).