GB754590A - Improvements in or relating to optical prism assemblies - Google Patents

Abstract

754,590. Optical apparatus. TECHNICOLOR MOTION PICTURE CORPORATION. June 3, 1954 [July 14, 1953], No. 16433/54. Class 97 (1). In a method for joining two triangular prisms together, one face A1, B2 of each prism A, B is placed on an optical flat 5 and cement 10 is applied between the faces A2, B1. Preferably, strips 6 of Lucite are temporarily cemented on the faces A1, B2 to prevent the cement from spreading and a recess is provided in the optical flat 5. Two pairs of prisms may then be joined to make an X-type four prism assembly. Faces A2 and D1 are made parallel by means of an auto-collimator arranged to project light perpendicularly into face C3. Two partial reflections, for example, at faces A2 and D1, and a total reflection at temporarily silvered face B3 returns the light to the collimator and enables this adjustment to be made. Faces A2 and D1 are aligned by adjustments made from the microscopic observations through faces A3 and D3 of the relative position of the gaps between the faces B2, A1 and C1, D2. Coatings R, G, which may be multi-layer interference coatings, are applied to the surfaces of the prisms before cementing. Coating G is applied as a continuous layer between prisms A and D, before the prisms are cemented together in pairs, a soluble mask of polyisobutyl methacrylate or polycyclohexyl methacrylate being used to prevent the coating from reaching the juxtaposed faces. Coating R is applied after the cementing process of Fig. 3. The completed prism may be used in a three-colour camera. Specification 731,865 is referred to.