US 5,119,235 AGranted

Focusing screen and method of manufacturing same

AssigneeNikon Corporation

InventorsToshiro Umeda, Hiroyuki Sugimura, Shinichi Tsukada, Noboru Yoneya, Akira Adachi, Asaji Masuko

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Abstract

A focusing screen of the type composed of a multitude of micro-lens-like curved surfaces arranged on a given plane is substantially regular in terms of their two-dimensional arrangement on the above-mentioned plane but exhibits some variation in terms of the height of the microscopic surface roughness formed by the micro-lens-like curved surfaces. The variation range is determined in correspondence with the pitch of the above-mentioned two-dimensional arrangement. Also disclosed is a method of manufacturing a focusing screen exhibiting an appropriate degree of randomness in terms of its surface configuration.

Claims6

Dependent claims

In a focusing screen having of a multitude of micro-lens-like curved surfaces arranged on a given plane, wherein the improvement comprises:

(a) that the arrangement pitch P of said multitude of micro-lens-like curved surfaces is a value which is in the range:
8 .mu.m.ltoreq.P.ltoreq.30 .mu.m
(b) that the projection of the vertex of each of said multitude of micro-lens-like curved surfaces onto said plane is positioned at a periodical lattice point having plane coordinates (X, Y) determined from the following equations by using said pitch P and a pair of integers (I, J):
##EQU2## (c) that the distance between the vertex of each of said multitude of micro-lens-like curved surfaces and said plane varies within a certain variation range, which can be expressed as:
P.times.H (.mu.m), where H is a constant determined within the following range:
0. 01.ltoreq.H.ltoreq.0.1.

3 more elements

Dependencies are inferred from the claim text.