Variable power lens systems for producing small images
First Claim
1. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and comprising:
- (a) a first lens unit having a negative power and a focal length f1 ;
(b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, and (iii) has a focal length f2 ; and
(c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ;
wherein;
the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit;
the ratio of f2 to fmin is greater than about 1.3; and
the first lens unit includes only negative lens elements, has a negative power Φ
U1 equal to 1/f1, and includes a lens surface that;
(i) is concave to the image, and(ii) has a negative power Φ
U1S, the ratio of Φ
U1S to Φ
U1 being greater than 1.0.
2 Assignments
0 Petitions
Accused Products
Abstract
Variable power lens systems for use with electronic imaging systems, e.g., systems employing CCDs, are provided. The systems take advantage of the fact that the images detected by electronic imaging systems are small, e.g., the image diagonal can be 5.5 millimeters or less. The lens systems employ thick lens elements, whose diameters and thicknesses are large relative to the image size, and large air spaces between lens elements. The systems also employ weak lens units. In this way, simplified lens designs having excellent optical properties at less cost are provided. In certain embodiments, the lens systems contain only three lens elements, e.g., a negative first lens element, a positive second lens element for zooming, and a positive third lens element, with the first and/or the third lens element serving as a compensator.
148 Citations
35 Claims
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1. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and comprising:
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(a) a first lens unit having a negative power and a focal length f1 ; (b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, and (iii) has a focal length f2 ; and (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ; wherein; the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit; the ratio of f2 to fmin is greater than about 1.3; and the first lens unit includes only negative lens elements, has a negative power Φ
U1 equal to 1/f1, and includes a lens surface that;(i) is concave to the image, and (ii) has a negative power Φ
U1S, the ratio of Φ
U1S to Φ
U1 being greater than 1.0. - View Dependent Claims (2, 3, 4, 13, 14, 15, 16, 17, 25, 28, 29, 30, 31)
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5. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin, a maximum effective focal length fmax, and comprising:
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(a) a first lens unit having a negative power and a focal length f1 ; (b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, and (iii) has a focal length f2 ; and (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ; wherein; the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit; the ratio of f2 to fmin is greater than about 1.3; the first lens unit includes only negative lens elements; the second lens unit is moveable to change the magnification of the lens system and includes only positive lens elements; at least one of the first and third lens units is moveable; and the movement of the second lens unit provides the majority of the change in focal length of the lens system between its maximum and minimum effective focal lengths.
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6. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and comprising:
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(a) a first lens unit having a negative power and a focal length f1 ; (b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, and (iii) has a focal length f2 ; (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ; and (d) a fourth lens unit on the object side of the first lens unit, said fourth lens unit having a positive power; wherein; the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit; and the ratio of f2 to fmin is greater than about 1.3.
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7. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and comprising:
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(a) a first lens unit having a negative power and a focal length f1 ; (b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, (iii) has a focal length f2, and (iv) consists of a single lens element; and (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ; wherein; the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit; the ratio of f2 to fmin is greater than about 1.3; the second lens unit has a positive optical power Φ
U2 equal to 1/f2, and includes a lens surface that;(i) is concave to the image, and (ii) has a positive optical power Φ
U2S, the ratio of Φ
U2S to Φ
U2 being greater than 1.0; andthe third lens unit has a positive optical power. - View Dependent Claims (12)
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8. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and comprising:
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(a) a first lens unit having a negative power and a focal length f1 ; (b) a second lens unit which (i) is on the image side of said first lens unit, (ii) has a positive power, and (iii) has a focal length f2 ; and (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a focal length f3 ; wherein; the focal length of the lens system is changed by changing the spacing between the first lens unit and the second lens unit; and the lens system includes at least one lens element for which the ratio of the thickness of the element to fmin is greater than about 0.5. - View Dependent Claims (9, 10, 11)
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18. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and consisting of, from the object side:
- a positive first lens element;
a negative second lens element that moves for zooming;
a positive third lens element that moves for compensating; and
a positive lens unit, wherein the positive third lens element has a thickness which is greater than about 0.5 times fmin. - View Dependent Claims (27)
- a positive first lens element;
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19. A variable power lens system for forming an image of an object, said system consisting of, from the object side:
- a positive first lens element;
a negative second lens element that moves for zooming;
a positive third lens element that moves for compensating; and
a positive lens unit, wherein the positive third lens element is a meniscus element. - View Dependent Claims (20)
- a positive first lens element;
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21. A variable power lens system for forming an image of an object, said system comprising:
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(a) a first lens unit having a negative power and including only negative lens elements; (b) a second lens unit which is on the image side of said first lens unit and has a positive power, said second lens unit being moveable to change the magnification of the lens system and including only positive lens elements; and (c) a third lens unit which is on the image side of said second lens unit, said third lens unit including means for correcting the lens system'"'"'s chromatic aberration. - View Dependent Claims (22, 23, 24)
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26. A variable power lens system for forming an image of an object, said system having a minimum focal length fmin and consisting of, from the best side:
- a positive first lens element;
a negative second lens element that moves for zooming;
a positive third lens element that moves for compensating; and
a positive lens unit, wherein the negative second lens element has a thickness which is greater than about 0.5 times fmin.
- a positive first lens element;
- 32. An optical system comprising a variable power lens system for forming an image of an object and an electronic imaging system for detecting said image, said lens system comprising three lens units at least one of which consists of a single lens element whose thickness is at least about 0.5 times the diagonal of the image.
- 34. An optical system comprising a variable power lens system for forming an image of an object and an electronic imaging system for detecting said image, said electronic imaging system comprising an electronic component having a light sensitive surface and said lens system comprising three lens units at least one of which consists of a single lens element whose thickness is at least about 0.5 times the maximum transverse dimension of said light sensitive surface.
Specification