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US 4,904,086 AGranted
Light alignment detection device
AssigneeThe Marconi Company Limited
InventorPaul E. G. Cope
Life of this patent
Estimating the term…
Abstract
An optical alignment detector uses a Fresnel bi-prism (12) on the base of which an incoming beam of light is focussed. When the beam is in alignment, it strikes the base substantially normally and is brought to a focus adjacent a ridge (13) of the bi-prism (12). To cope with a second axis of alignment, a second bi-prism (14) having a ridge (15) is placed beneath the first, with the two ridges (13,15) arranged orthogonally so as to produce four possible pupil entrance images which can be received by four photodetectors (17,18,19,20).
Claims5
An optical alignment detector device comprising:
- means for focussing an incoming beam of light, a Fresnel bi-prism mounted with its base towards the focussing means such that when the beam is in alignment with the optical axis of the focussing means the beam strikes the base substantially normally and is brought to a focus adjacent the ridge of bi-prism, and a pair of photodetectors disposed to receive light transmitted through the prism and located on either side of the plane containing the ridge of the bi-prism.
Dependencies are inferred from the claim text.