Patent ID: 6052541
Filing Date: 2000-04-18
Classification: G03B

Abstract:
A viewfinder optical system comprising, in order from an object side to an observation side:an objective optical system for forming a real image;a first optical member, said first optical member having a reflective surface by which to change a direction in which a light beam from said objective optical system advances;a second optical member, the real image being converted into an erecting image through said first optical member and said second optical member; andan eyepiece optical system for observing the erecting image,wherein the real image is formed on or near an exit surface of said first optical member, and the exit surface of said first optical member is a curved surface convex toward the observation side, andwherein said viewfinder optical system satisfies the following conditions:TABLE 1  Numerical Example Condition 1 2 3 4 5  (1) (R1 + R2)/(R2 - R1) -1.31 -1.16 -1.46 0.03 -0.35 (2) (R3 + R4)/(R4 - R3) -0.56 -0.51 -0.56 -0.60 -0.51 (3) D2/f1 -0.73 -0.76 -0.64 -1.21 -0.85 (4) f2/f1 -0.69 -0.71 -0.63 -1.02 -0.75 (5) DI/Fe 0 0 0 0 0 (6) fe/R7 -1.23 -0.93 -1.09 -0.78 -1.09 (7) N3 1.57 1.57 1.57 1.57 1.57  where DI is a distance from the exit surface of said first optical member to the real image, R7 is a radius of curvature of the exit surface of said first optical member, and fe is a focal length of said eyepiece optical system.