The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 05, 1982
Filed:
Jul. 14, 1981
Toshihiro Sasaya, Kawasaki, JP;
Nippon Kogaku K.K., Tokyo, JP;
Abstract
In a focusing screen capable of passing light therethrough and disposed between an objective lens and an eyepiece to enable the focused condition of the objective lens with respect to an object to be observed through the eyepiece and having a surface formed with a number of pyramidical faces, the angle of inclination .alpha. of each of said pyramids satisfies an inequality that ##EQU1## where F represents the F-number of the optical system from the objective lens to the focusing screen, f the focal length of the eyepiece, n the refractive index of the focusing screen and .DELTA. the required range finding accuracy, and the focusing screen satisfies ##EQU2## where A represents the visual angle whereat a length cos .alpha. times as great as the length of the slant face extending from the bottom surface to the vertex of the pyramid at the angle of inclination .alpha. is seen through said eyepiece.