US 6,041,193 A · Real-image zoom finder with rotationally asymmetric surface

Abstract

A high-performance real-image finder with a zoom objective optical system wherein a power is given to a reflecting surface of an image-inverting optical system to reduce the size in the direction of the thickness, and at the same time, a rotationally asymmetric surface is used in the image-inverting optical system to correct rotationally asymmetric decentration aberrations. The zoom objective optical system Ob has a first lens unit G1 of negative power, a second lens unit G2 of positive power, and a third lens unit G3 of positive or negative power. The real-image finder further includes an image-inverting optical system PP for erecting an intermediate image formed by the objective optical system Ob, and an ocular optical system Oc having a positive refracting power. At least one of reflecting surfaces S.sub.8 and S.sub.9 of the image-inverting optical system PP is a curved reflecting mirror having an optical power and has a rotationally asymmetric surface configuration that corrects decentration aberrations produced by the curved reflecting mirror.

Claims23

Dependent claims

A real-image finder comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;
an image-inverting optical system having a reflecting surface, said image-inverting optical system erecting an intermediate image formed by said objective optical system;
and
an ocular optical system having a positive refracting power;
wherein said objective optical system includes, in order from an object side thereof, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, and a third lens unit having one of a positive refracting power and a negative refracting power,
wherein when zooming from a wide-angle end to a telephoto end is performed, a spacing between each pair of lens units among said first, second and third lens units is changed, and
wherein said reflecting surface of said image-inverting optical system is arranged in a form of a curved reflecting mirror having an optical power and having a rotationally asymmetric surface configuration that corrects decentration aberrations produced by said curved reflecting mirror.

4 more elements

Dependencies are inferred from the claim text.

Real-image zoom finder with rotationally asymmetric surface

Life of this patent

Real-image zoom finder with rotationally asymmetric surface

Life of this patent

Abstract

Claims23