Zoom lens using elements made of plastic materials

Claim 2

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens and wherein said detection means has an autofocus function and said first lens group is shifted in correspondence with an in focus signal from said detection means.

Claim 3

A zoom lens according to claim 1, wherein said member of a plastic material arranged in said first lens group consists of at least one positive lens and at least one negative lens.

Claim 4

A zoom lens according to claim 1, wherein the means for shifting said first lens group has a stop and said stop is arranged at a position which is further beyond a position within said first lens group corresponding to an infinitely distant object.

Claim 5

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens and wherein said detection means has an electronic viewfinder.

Claim 6

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens and wherein said detection means has an electronic viewfinder.

Claim 7

A zoom lens according to claim 4, wherein said member of a plastic material arranged in said first lens group consists of at least one positive lens and at least one negative lens.

Claim 8

A zoom lens according to claim 4, wherein the means for shifting said first lens group has a stop and said stop is arranged at a position which is further beyond a position within said first lens group corresponding to an infinitely distant object.

Claim 9

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, and wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjugate to an image plane.

Claim 10

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, and wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjugate to an image plane.

Claim 11

A zoom lens according to claim 7, wherein said member of a plastic material arranged in said first lens group consists of at least one positive lens and at least one negative lens.

Claim 12

A zoom lens according to claim 7, wherein the means for shifting said first lens group has a stop and said stop is arranged at a position which is further beyond a position within said first lens group corresponding to an infinitely distant object.

Claim 13

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjugate to an image plane and wherein said focusing detection mechanism consists of a split prism.

Claim 14

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjugate to an image plane and wherein said focusing detection mechanism consists of a split prism.

Claim 15

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group poisitioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjutage to an image plane and wherein said focusing detection mechanism consists of a micro-prism.

Claim 16

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group poisitioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a position conjutage to an image plane and wherein said focusing detection mechanism consists of a micro-prism.

Claim 17

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a positon conjugate to an image plane and wherein said focusing mechanism comprises a matt surface or matt surfaces.

Claim 18

A photographic apparatus having a zoom lens, comprising: a zoom lens which can change its focal length continuously within a predetermined range wherein a first lens group positioned at the frontmost side within said zoom lens has at least one plastic lens and lens systems subsequent to said first lens group having no plastic lenses; means for receiving a light bundle from said zoom lens to detect whether or not an image of an object is in an in focus state or not; and means for shifting said first lens group in the direction of the optical axis relative to said lens systems subsequent to said first lens group corresponding to the in focus state obtained from said detection means for having the light bundle image at an optically conjugate position with a fixed image plane position of said zoom lens, wherein said detection means comprises a viewfinder, a mirror for guiding at least a portion of a light bundle passing through said photo-taking system toward said viewfinder and a focusing detection mechanism arranged at a positon conjugate to an image plane and wherein said focusing mechanism comprises a matt surface or matt surfaces.