Zoom lens system with temperature compensation function and video camera using the same
First Claim
1. A zoom lens system comprising:
- a first lens group;
a second lens group that moves along an optical axis;
a third lens group that has a positive refractive power, a negative temperature coefficient of refractive index and a predetermined focal length;
a fourth lens group that moves along said optical axis;
a first lens barrel which extends from said first lens group to said third lens group; and
a second lens barrel which extends from said third lens group to an image pickup element;
wherein said first and second lens barrels each has a respective predetermined linear expansion coefficient, and variation of image location caused by temperature change in said first, second, third and fourth lens groups is cancelled by image location variation caused by expansion or contraction of at least one of said first lens barrel and said second lens barrel.
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Accused Products
Abstract
A zoom lens system with temperature compensation function includes the first lens group having a positive refractive power, the second lens group that has negative refractive power and moves along an optical axis, the third lens group having a plastic lens of positive refractive power, the fourth lens group that has positive refractive power and moves along the optical axis, the first lens barrel which extends from the first lens group to the third lens group, and the second lens barrel which extends from the third lens group to an image pickup element, and expansion or contraction of at least one of lens barrels in accordance with temperature change cancels variation of image location caused by temperature change of the lens groups.
15 Citations
18 Claims
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1. A zoom lens system comprising:
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a first lens group;
a second lens group that moves along an optical axis;
a third lens group that has a positive refractive power, a negative temperature coefficient of refractive index and a predetermined focal length;
a fourth lens group that moves along said optical axis;
a first lens barrel which extends from said first lens group to said third lens group; and
a second lens barrel which extends from said third lens group to an image pickup element;
wherein said first and second lens barrels each has a respective predetermined linear expansion coefficient, and variation of image location caused by temperature change in said first, second, third and fourth lens groups is cancelled by image location variation caused by expansion or contraction of at least one of said first lens barrel and said second lens barrel. - View Dependent Claims (2, 3, 11, 12, 13)
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4. A zoom lens system comprising:
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a first lens group having a positive refractive power;
a second lens group that has negative refractive power and moves along an optical axis;
a third lens group having a further positive refractive power and fixed relative to a first lens barrel;
a fourth lens group that has positive refractive power and moves along said optical axis;
said first lens barrel which extends from said first lens group to said third lens group; and
a second lens barrel which extends from said third lens group to an image pickup element;
wherein variation of image location caused by temperature change in said first, second, third and fourth lens groups is cancelled by variation of image location caused by expansion or contraction of at least one of said first lens barrel and said second lens barrel. - View Dependent Claims (5, 6, 7, 8, 9, 10, 14, 15, 16)
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17. A video camera including a zoom lens system, said zoom lens system comprising:
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a first lens group having a positive refractive power;
a second lens group that has negative refractive power and moves along an optical axis;
a third lens group having a further positive refractive power and fixed relative to a first lens barrel;
a fourth lens group that has positive refractive power and moves along said optical axis;
said first lens barrel which extends from said first lens group to said third lens group; and
a second lens barrel which extends from said third lens group to an image pickup element;
wherein variation of image location caused by temperature change in said first, second, third and fourth lens groups is cancelled by variation of image location caused by expansion or contraction of at least one of said first lens barrel and second lens barrel. - View Dependent Claims (18)
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Specification