Title: Photoelectric grating displacement measuring apparatus

Abstract: A measuring system includes a scale grating carried on one of two relatively movable bodies and an index grating carried on the other. The scale grating is illuminated directly in such a way that light passing from it to the index grating is at least partially diffuse. Detector means are provided to respond to the resulting spatially periodic distribution of illumination.

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Inventors: Brake, David George (Welwyn Garden City, EN)

Application Number: 716229
Filing Date: 1976-08-20
Publication_date: 1978-03-14
Assignee: Ferranti Limited (Hollinwood, EN)
Primary Class(es): 250/237G 356/619
Other Classes:
US Patent Ref:

3578979	May, 1971	Kawaguchi et al.	356/170.
3599004	Aug, 1971	Grendelmeier	250/237.
3748043	Jul, 1973	Zipin	250/237.
3796498	Mar, 1974	Post	250/237.
3812352	May, 1974	MacGovern	356/169.

Other Refs:
Primary Examiner: Helms, David C.
Assistant Examiner:
Attorney: Cameron, Kerkam, Sutton, Stowell & Stowell