Focusing screen including different height microlenses arranged in a cyclical pattern

• US 5,177,637 A
• Filed: 09/06/1991
• Issued: 01/05/1993
• Est. Priority Date: 09/11/1990
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tsukada, Shinichi
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US07/756,031
• Time in Patent Office: 487 Days
• Field of Search: 359/619, 359/625, 359/626, 359/599, 359/569, 359/707, 359/837, 359/831, 359/900, 359/893
• US Class Current: 359/599
• CPC Class Codes: G03B 13/24 Focusing screens
• CPC Class Codes: G03B 2217/005 Blur detection

Abstract

In a focusing screen having a large number of microlenses regularly arranged thereon, heights of microlenses are n different values. The microlenses having the same height are cyclically arranged. In another aspect, the heights of the microlenses in a similar focusing screen are randomly distributed over ranges centered on n central values, and the microlenses having the same central value are cyclically arranged. In still another aspect, in a method of manufacturing a focusing screen having micropatterned projections by a so-called proximity exposure method, dimensions of the micropatterns of the mask vary centered on the n different values, and the micropatterns having the same central values are cyclically arranged.

Claims

1. In a focusing screen having a large number of microlenses regularly distributed in an array, the improvement wherein said microlenses are substantially uniformly cross-dimensioned and arranged as a plurality of intermingled groups, with the microlenses of each group having a predetermined height different from that of the microlenses of each other group and occupying a respective cyclical pattern of positions within said array.

2. In a focusing screen having a large number of microlenses regularly distributed in an array, the improvement wherein said microlenses are arranged as a plurality of intermingled groups, with the microlenses of each group having heights which are randomly distributed within a predetermined range about a predetermined central height value, the central height value being different for each group, and the microlenses of each group occupying a respective cyclical pattern of positions within said array.

3. A focusing screen according to claim 2, wherein the microlenses of said array are substantially uniformly cross-dimensioned.

4. A focusing screen according to claim 2, wherein a width of said predetermined range is the same for each said group.

5. A focusing screen according to claim 4, wherein the microlenses of said array are substantially uniformly cross-dimensioned.

6. A focusing screen according to claim 2, wherein for each said group, a width R of said predetermined range is defined as follows:

space="preserve" listing-type="equation">0<

R<

1.5Q/(n-1)

where Q is the difference between the maximum and minimum central height values and n is the number of said groups.

7. A focusing screen according to claim 6, wherein the width of said predetermined range is the same for each said group.

8. A focusing screen according to claim 7, wherein the microlenses of said array are substantially uniformly cross-dimensioned.