Zoom lens with short back focal length

Claim 2

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, said second lens unit having a greater magnification ratio than said second sub-unit and upon movement providing the majority of change of overall lens power.

Claim 3

The lens of claim 1 where said second positive sub-unit of said first lens unit comprises a biconvex element.

Claim 4

The lens of claim 1 where said first lens unit first sub-unit is of overall meniscus form.

Claim 5

The lens of claim 3 where said first lens sub-unit is concave toward the object end.

Claim 6

The lens of claim 1 where said first lens sub-unit of said first lens unit is concave toward the object end.

Claim 7

The lens of claim 1 where said second lens unit consists of a single element concave toward the object end.

Claim 8

The lens of claim 1 where said first sub-unit of said first lens unit is a single element.

Claim 9

The lens of claim 1 where said second sub-unit of said first lens unit is a single element.

Claim 10

The lens of claim 1 where said sub-units of said first lens group move differentially during zooming.

Claim 11

The lens of claim 1 where said lens further includes a stationary field flattening element adjacent the image plane of the lens.

Claim 12

The lens of claim 1 where said second lens unit comprises two sub-units which move differentially during zooming.

Claim 13

The lens of claim 1 where the entrance pupil of said lens is located on the object side of said lens.

Claim 14

The lens of claim 1 where said second lens unit comprises a negative element strongly concave to the object.

Claim 15

The lens of claim 1 where the second principal point of said first lens unit is closely adjacent or outside of the rear vertex of said first lens unit.

Claim 16

The zoom lens of claim 1 where said first sub-unit is configured to provide a monotonic increase of the marginal ray height from the optical axis determined by an axial ray emanating from a distant object and traversing said first sub-unit.

Claim 17

The lens of claim 1 wherein said first lens unit first sub-unit comprises a meniscus concave to the object.

Claim 18

The lens of claim 1 where said second sub-unit is overall biconvex.

Claim 19

The lens of claim 1 where said first lens sub-unit of said first lens unit is overall biconcave.

Claim 20

The lens of claim 18 where said first lens sub-unit of said first lens unit comprises a biconcave element and a positive meniscus.

Claim 21

The lens of claim 1 where said second sub-unit of said first lens unit comprises a doublet of overall biconvex shape.

Claim 22

The lens of claim 20 where said second sub-unit of said first lens unit further includes a thick positive meniscus.

Claim 23

The lens of claim 1 where said second sub-unit of said first lens unit comprises a biconvex element and a meniscus.

Claim 24

The lens of claim 1 where said second sub-unit comprises a negative element concave toward the object end and a positive meniscus.

Claim 25

The lens of claim 1 where said first lens sub-unit of said first lens unit includes a doublet concave to the object end.

Claim 26

The lens of claim 24 where said first sub-unit of said first lens unit includes a component of overall meniscus form.

Claim 27

The lens of claim 24 where said first sub-unit of said first lens unit includes a doublet of overall biconcave form.

Claim 28

The zoom lens of claim 1 where said first lens unit comprises a negative meniscus element concave to the object side and a biconvex element.

Claim 29

The lens of claim 1 where said first sub-unit of said first lens unit comprises a negative meniscus concave to the object and said second sub-unit consists of an overall biconvex air spaced doublet.

Claim 30

The lens of claim 1 wherein said first sub-unit of said first lens unit comprises a doublet of overall meniscus form concave to the object and said second sub-unit is overall biconvex and comprises a positive element followed by a doublet.

Claim 31

The lens of claim 1 where said first sub-unit is a doublet.

Claim 32

The lens of claim 30 where said first sub-unit is overall biconcave.

Claim 33

The lens of claim 30 where said first sub-unit is a doublet comprising a biconcave element and a positive meniscus.

Claim 34

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said second lens unit upon movement providing the majority of change of overall lens power, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, the second principal point of said first lens unit being essentially at or outside of the image side surface of said first lens unit, said first lens sub-unit being configured to provide an increase of the marginal ray height from the optical axis determined by an axial ray emanating from a distant object and traversing said first sub-unit.

Claim 35

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said second lens unit upon movement providing the majority of change of overall lens power, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, the second principal point of said first lens unit being essentially at or outside of the image side surface of said first lens unit, said first lens sub-unit being configured to provide an increase of the marginal ray height from the optical axis determined by an axial ray emanating from a distant object and traversing said first sub-unit.

Claim 36

The lens of claim 33 where the entrance pupil of said lens is positioned on the object side of the front vertex of said lens.

Claim 37

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, said second lens unit having a greater magnification ratio than said second sub-unit and upon movement providing the majority of change of overall lens power, said first sub-unit being concave toward the object, said second sub-unit including at least one biconvex element.

Claim 38

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, said second lens unit having a greater magnification ratio than said second sub-unit and upon movement providing the majority of change of overall lens power, said first sub-unit being concave toward the object, said second sub-unit including at least one biconvex element.

Claim 39

The lens of claim 35 where said sub-units of said first lens group move differentially during zooming.

Claim 40

The lens of claim 35 where said second lens unit comprises two sub-units which move differentially during zooming.

Claim 41

The lens of claim 35 where the entrance pupil of said lens is located on the object side of said lens.

Claim 42

The zoom lens of claim 35 where said first sub-unit is configured to provide an increase of the marginal ray height from the optical axis determined by an axial ray emanating from a distant object and traversing said first sub-unit.

Claim 43

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said second lens unit upon movement providing the majority of change of overall lens power, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, said second lens unit comprising a negative element concave to the object.

Claim 44

A zoom lens comprising from the object end a first lens unit of overall positive power, and a second lens unit of negative power, both of said lens units being axially movable to vary the equivalent focal length of the lens, said second lens unit upon movement providing the majority of change of overall lens power, said first lens unit comprising from the object end first and second sub-units, said first sub-unit being of negative power and said second sub-unit being of positive power, said second lens unit comprising a negative element concave to the object.