Canon Kabushiki Kaisha

Kunio Takeshi

Chiaki Terasawa

Fumiaki Usui

Jun Hosoya

Kazuo Tanaka

Mikichi Ban

Shigeru Oshima

Yoshiya Matsui

Kyoji Nariai

An aberration correction system having a first lens disposed at an object side; and a second lens disposed at an image side, wherein the first and second lenses have different dispersions (Abbe numbers) with respect to each other, the surface of the object side of the first lens and the surface of the image side of the second lens which is adjacent to the image have substantially common center of curvature and the first and second lenses rotate around the center of curvature.

Aberration correction system and astronomical telescope having the same

A high range zoom lens is disclosed, comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive or negative refractive power and a fourth lens unit of positive refractive power, the second and third lens units being movable for zooming, wherein an aspheric surface is introduced into the second or third lens unit at a specified location so that the variation of aberrations with zooming is as far reduced for high performance as possible.

Zoom lens

A chromatic aberration correcting lens assembly arranged on the image side of a photographic lens which is used in combination with a prism of a predetermined thickness on the image side thereof to correct the chromatic aberrations of the entire system, is constructed in the form of an assembly of three lens elements made of at least two different materials and cemented together at their adjoining surfaces, each of the cemented surfaces being made concave toward the image side.

Performance correcting optical assembly for photographic lens for

A zoom lens comprising a front lens group, a plurality of movable lens groups and an image forming lens group, the front lens group having three sub-groups. The first sub-group counting from the front has a negative refractive power and is movable for focusing purposes. The intermediate or second sub-group has a positive refractive power and is movable for focusing to the front of the third sub-group which has a positive refractive power and which is stationary during focusing. The front lens group is characterized by fulfilling the following relationships: ##EQU1## WHEREIN F.sub.1 AND F.sub.2 ARE THE FOCAL LENGTHS OF THE FIRST AND SECOND SUB-GROUPS RESPECTIVELY; D IS THE AXIAL SEPARATION BETWEEN THE REAR PRINCIPOINT OF THE FIRST SUB-GROUP AND THE FRONT PRINCIPAL POINT OF THE SECOND SUB-GROUP OCCURRING WHEN THE ENTIRE SYSTEM IS FOCUSED FOR OBJECT AT INFINITY; A' IS THE OBJECT DISTANCE MEASURED FROM THE FRONT PRINCIPOINT OF THE FIRST SUB-GROUP WHEN THE ENTIRE SYSTEM IS FOCUSED FOR AN OBJECT AT A FINITE DISTANCE; AND S and t are the amounts of movement of the first and second sub-groups resulted during focusing from infinity to a closeup at an object distance a' respectively.

Growing community of inventors

Kanagawa-ken, Japan

Kunio Takeshi