Patent ID: 7440191

Claim:
A method for manufacturing a cross prism, comprising the steps of: preparing glass assembly units each comprised of a first glass member in the shape of a narrow square pole and a second glass member similar to said first glass member in cross-sectional shape but shorter than the latter in length, a lateral side of said first glass member being cemented to a lateral side of said second glass member through a first optical coating deposited on a surface of said lateral side of said first glass member or of said second glass member, leaving an alignment reference plane at opposite longitudinal ends of said first glass member; grinding a lateral side of said glass assembly unit, on the side perpendicular to said optical coating, in preparation of a plane surface on the bottom side of a prism member to be produced; grinding two edge lines of said glass assembly unit on the opposite side from said bottom side to produce a prism member in the shape of an isosceles triangle in cross section to form a first prism member; producing a second prism member by depositing a second optical coating on the bottom side of a prism member in the same shape of said first prism member; joining said first and second prism members by aligning reference surfaces of first glass members in the first and second prism member in such a manner as to form one and same plane to prepare a parent material of cross prism; and cutting said parent material of cross prism with a predetermined length to form a cross prism.