US 2003/0193723 A1 · Zoom lens system, and image pickup system using the same

Abstract

The invention provides a zoom lens system much more reduced in size and cost than ever before and best-suited for use on portable information terminals of small size. The zoom lens system comprises, in order from an object side thereof, a first lens group G1 having positive refracting power and designed to be fixed during zooming, a second lens group G2 having negative refracting power and designed to move from the object side to an image plane side of the system for zooming from a wide-angle end to a telephoto end of the system, a third lens group having refracting power and designed to move from the image plane side to the object side for zooming from the wide-angle end to the telephoto end, and a fourth lens group G4 having positive refracting power and designed to be movable during zooming. Condition (1) with respect to the power of the third lens group G3, condition (2) with respect to the amount of zooming movement of the third lens group G3 or condition (3) with respect to the composite power of the third and fourth lens groups G3 and G4 and condition (10) with respect to the actual value of the back focus are satisfied.

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Claims33

Dependent claims

A zoom lens system comprising, in order from an object side of said zoom lens system, a first lens group having positive refracting power and designed to be fixed during zooming, a second lens group having negative refracting power and designed to move from the object side to an image plane side of the zoom lens system for zooming from a wide-angle end to a telephoto end of said zoom lens system, a third lens group having positive refracting power and designed to move from the image plane side to the object side for zooming from the wide-angle end to the telephoto end, and a fourth lens group having positive refracting power and designed to be movable for zooming, wherein the following conditions are satisfied:

0.5<|F2/F3|<1.2 (1)2.5 mm<fB(min)<4.8 mm (10)
where Fi is a focal length of an i-th lens group and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

A zoom lens system comprising, in order from an object side of said zoom lens system, a first lens group having positive refracting power, a second lens group having negative refracting power and designed to move from the object side to an image plane side of said zoom lens system for zooming a wide-angle end to a telephoto end of said zoom lens system, a third lens group having positive refracting power and a fourth lens group having positive refracting power and designed to be movable for zooming, wherein said third lens group comprises, in order from an object side thereof, a positive lens component convex on an object side thereof and a cemented lens consisting of a positive lens element convex on an object side thereof and a negative lens element concave on an image plane side thereof, and both the object-side positive lens component and the cemented lens in said third lens group are held in a lens barrel while the object-side convex surfaces thereof abut peripherally or at peripheral several spots against said lens barrel, and the following condition is satisfied:

2.5 mm<fB(min)<4.8 mm (10)
where fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

0.5<|F2/F3|<1.2 (1)0.49<|L3/L2|<1 (2)2.5 mm<fB(min)<4.8 mm (10)
where Fi is a focal length of an i-th lens group, Li is an amount of an i-th lens group from the wide-angle end to the telephoto end, and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

0.5<|F2/F3|<1.2 (1)2<(F3.4W)/IH<3.3 (3)2.5 mm<fB(min)<4.8 mm (10)
where Fi is a focal length of an i-th lens group, (F3.4W) is a composite focal length of the third and forth lens groups at the wide-angle end, IH is a radius of an image circle, and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

0.49<|L3/L2|<1 (2)2<(F3.4W)/IH<3.3 (3)2.5 mm<fB(min)<4.8 mm (10)
where Li is an amount of movement of an i-th lens group, (F3.4W) is a composite focal length of the third and forth lens groups at the wide-angle end, IH is a radius of an image circle, and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

0.5<|F2/F3|<1.2 (1)0.49<|L3/L2|<1 (2)2<(F3.4W)/IH|<3.3 (3)2.5 mm<fB(min)<4.8 mm (10)
where Fi is a focal length of an i-th lens group, Li is an amount of movement of an i-th lens group, (F3.4W) is a composite focal length of the third and forth lens groups at the wide-angle end, IH is a radius of an image circle, and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

ν21<40 (7)2.5 mm<fB(min)<4.8 mm (10)
where ν21 is an Abbe's number of said negative lens element located nearest to the object side in said second lens group, and fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

A zoom lens system comprising, in order from an object side of said zoom lens system, a first lens group having positive refracting power and designed to be fixed during zooming, a second lens group having negative refracting power and designed to move from the object side to an image plane side of said zoom lens system for zooming from a wide-angle end to a telephoto end of said zoom lens system, a third lens group having positive refracting power and designed to move constantly from the image plane side to the object side for zooming from the wide-angle end to the telephoto end, and a fourth lens group having positive refracting power and designed to be movable during zooming, wherein said third lens group comprises a cemented lens consisting of a positive lens element and a negative lens element, said fourth lens group consists of one positive lens element, and the following condition (10) is satisfied:

2.5 mm<fB(min)<4.8 mm (10)
where fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

A zoom lens system comprising, in order from an object side of said zoom lens, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power and a fourth lens group having positive refracting power, wherein a spacing between said first lens group and said second lens group, a spacing between said second lens group and said third lens group, and a spacing between said third lens group and said fourth lens group varies upon zooming, said first lens group consists of one positive lens component, said second lens group comprises three lens elements or one single lens element and a cemented lens consisting of a negative lens element and a positive lens element in order from an object side thereof, said third lens group comprises three lens elements or a single lens element and a cemented lens consisting of a positive lens element and a negative lens element in order from an object side thereof, said fourth lens group consists of one positive lens element, and the following condition (10) is satisfied:

2.5 mm<fB(min)<4.8 mm (10)
where fB(min) is a length, as calculated on an air basis, of a final surface of a lens having power in said zoom lens system to an image plane of said zoom lens system, representing a figure at which said zoom lens system becomes shortest in a whole zooming space.

Dependencies are inferred from the claim text.

Description14,741 words

Summary7,206 words

#This application claims benefit of Japanese Application(s) No. Hei 11-316827 filed in Japan on Nov. 8, 1999, the contents of which are incorporated by this reference.

#The present invention relates generally to a zoom lens system and an image pickup system using the same, and more particularly to a compact yet low-cost zoom lens system for cameras using an electronic image pickup means, for instance, camcorders, digital cameras, surveillance monitor cameras and cameras incorporated in portable telephones or PCs.

#For zoom lens systems which belong to this field and are reduced in size and cost for consumer-oriented purposes, there has been proposed a four-group zoom lens system of +−++ construction in order from its object side, as shown in JP-A's 4-43311 and 4-78806. In this zoom lens system, the first and third lens groups are fixed during zooming, and the second lens group having negative power moves on an optical axis for zooming while the fourth lens group moves on the optical axis for correction of fluctuations of an image plane position with zooming. In zoom lens systems as set forth in JP-A's 6-94997 and 6-194572, on the other hand, the third lens group is moved from the image plane side to the object side for zooming from the wide-angle end to the telephoto end for the purpose of aiding in zoom action, thereby achieving further size reductions. These publications show zoom lenses having a relatively high zoom ratio of the order of 8 to 12. For a zoom lens system reduced exclusively in size and cost at the expense of zoom ratios, however, such prior art systems are still less than satisfactory because no sufficient size reductions are achievable thanks to an increased number of lenses.

Brief description of the drawings20 figures

#FIG. 1 is a sectional schematic illustrative of Example 1 of the zoom lens system according to the present invention, as viewed at the wide-angle end.

#FIG. 2 is a sectional schematic illustrative of Example 2 of the zoom lens system according to the present invention, as viewed at the wide-angle end.

#FIG. 3 is a sectional schematic illustrative of Example 3 of the zoom lens system according to the present invention, as viewed at the wide-angle end.

Detailed description7,035 words

#Examples 1 to 10 of the zoom lens system according to the present invention are now explained.

#FIGS. 1 through 10 are sectional views, as viewed at the wide-angle ends, of Examples 1 to 10 of the zoom lens system according to the present invention. Numerical data on each example will be set out later. Throughout the embodiments shown in FIGS. 1 to 10, plane-parallel plates are located between the fourth lens groups G4 and image planes. These, for instance, include an image pickup device cover glass, and filters such as an IR cut filter and a low-pass filter. These plane-parallel plates are omitted from the numerical data given later.

#Example 1 is directed to a zoom lens system having a focal length of 3.643 to 10.420 mm and a field angle of 66.42° to 24°. As shown in FIG. 1, the first lens group G1 is made up of a cemented lens consisting of a negative meniscus lens convex on an object side thereof and a double-convex lens and a positive meniscus lens convex on an object side thereof. The second lens group G2 is made up of a negative meniscus lens convex on an object side thereof and a cemented lens consisting of a double-concave lens and a double-convex lens. In the rear of the second lens group G2 there is located a stop S. The third lens group G3 is made up of two double-convex lenses and a negative meniscus lens convex on an object side thereof, and the fourth lens group G4 is made up of one positive meniscus lens convex on an object side thereof. One aspehrical surface is used for the surface located nearest to the object side in the third lens group G3. For zooming from the wide-angle end to the telephoto end, the first lens group G1 and the stop S remain fixed, the second lens group G2 moves from the object side to the image plane side, and the third and fourth lens groups G3 and G4 move from the image plane side to the object side while the space therebetween becomes wide, as indicated by arrows.

Zoom lens system, and image pickup system using the same

Life of this patent

Zoom lens system, and image pickup system using the same

Life of this patent

Life of this patent

Abstract

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Drawings

Claims33

Description14,741 words

Drawings

Classification3 codes

Life of this patent

Description14,741 words