Low thermal stress birefringence imaging lens
First Claim
1. A lens system having reduced susceptibility to thermally-induced stress birefringence for imaging an object plane onto an image plane comprising;
- a plurality of lens elements arranged to image the object plane onto the image plane,wherein the lens element that experiences a highest optical power density from transiting light when the lens system is used to image the object plane onto the image plane is fabricated using a glass having a negligible susceptibility to thermal stress birefringence as characterized by a thermal stress birefringence metric;
wherein the other lens elements are fabricated using glasses having a negligible or a moderate susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric, at least one of the other lens elements being fabricated using a glass having a moderate susceptibility to thermal stress birefringence;
wherein the thermal stress birefringence metric has the form;
M1=ρ
κ
α
E/(K·
(1−
μ
).where ρ
is a coefficient of thermal expansion of the glass, κ
is a stress optical coefficient of the glass, α
is a light absorption coefficient of the glass, E is a modulus of elasticity of the glass, K is a thermal conductivity of the glass, and μ
is a Poisson'"'"'s ratio of the glass; and
wherein the glasses having the negligible susceptibility to thermal stress birefringence satisfy the condition that M1≦
0.1×
10−
6 W−
1 and the glasses having the moderate susceptibility to thermal stress birefringence satisfy the condition that 0.1×
10−
6 W−
1≦
M1<
1.6×
10−
6 W−
1.
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Accused Products
Abstract
An imaging lens having reduced susceptibility to thermally-induced stress birefringence for imaging an object plane to an image plane; comprising a plurality of lens elements. The lens element that experiences a highest optical power density is fabricated using a glass having a negligible susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric. The other lens elements are fabricated using glasses having a negligible or a moderate susceptibility to thermal stress birefringence, at least one of the other lens elements being fabricated using a glass having a moderate susceptibility to thermal stress birefringence.
29 Citations
17 Claims
-
1. A lens system having reduced susceptibility to thermally-induced stress birefringence for imaging an object plane onto an image plane comprising;
-
a plurality of lens elements arranged to image the object plane onto the image plane, wherein the lens element that experiences a highest optical power density from transiting light when the lens system is used to image the object plane onto the image plane is fabricated using a glass having a negligible susceptibility to thermal stress birefringence as characterized by a thermal stress birefringence metric; wherein the other lens elements are fabricated using glasses having a negligible or a moderate susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric, at least one of the other lens elements being fabricated using a glass having a moderate susceptibility to thermal stress birefringence; wherein the thermal stress birefringence metric has the form;
M1=ρ
κ
α
E/(K·
(1−
μ
).where ρ
is a coefficient of thermal expansion of the glass, κ
is a stress optical coefficient of the glass, α
is a light absorption coefficient of the glass, E is a modulus of elasticity of the glass, K is a thermal conductivity of the glass, and μ
is a Poisson'"'"'s ratio of the glass; andwherein the glasses having the negligible susceptibility to thermal stress birefringence satisfy the condition that M1≦
0.1×
10−
6 W−
1 and the glasses having the moderate susceptibility to thermal stress birefringence satisfy the condition that 0.1×
10−
6 W−
1≦
M1<
1.6×
10−
6 W−
1.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
where I0 is an optical power density in the glass, and L is a thickness of the lens element.
-
-
6. The lens system of claim 1 wherein all of the other lens elements are fabricated using glasses that satisfy the condition that M1≦
- 0.8×
10−
6 W−
1.
- 0.8×
-
7. The lens system of claim 1 wherein at least one of the other lens elements is fabricated using a glass that satisfies the condition that 0.8×
- 10−
6 W−
1≦
M1≦
1.6×
10−
6 W−
1.
- 10−
-
8. The lens system of claim 1 where the glasses used to fabricate the lens elements are also selected for properties that relate to achieving adequate image quality performance, including refractive index and chromatic dispersion properties.
-
9. The lens system of claim 1 wherein one or more surfaces of one or more of the lens elements have an aspheric surface profile.
-
10. The lens system of claim 1 wherein the lens system is used to image polarized light.
-
11. The lens system of claim 1 wherein the lens system is a relay lens or a projection lens for a digital projection system.
-
12. The lens system of claim 1 wherein the lens system is an imaging lens system or an illumination lens system.
-
13. The lens system of claim 1 wherein the lens system is a combined reflective-refractive optical system that includes at least one reflective optical element.
-
14. A lens system having reduced susceptibility to thermally-induced stress birefringence for imaging an object plane onto an image plane comprising;
-
a plurality of lens elements arranged to image the object plane onto the image plane; wherein the lens element that experiences a highest optical power density from transiting light when the lens system is used to image the object plane onto the image plane is fabricated using a glass having a negligible susceptibility to thermal stress birefringence as characterized by a thermal stress birefringence metric; wherein the other lens elements are fabricated using glasses having a negligible or a moderate susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric, at least one of the other lens elements being fabricated using a glass having a moderate susceptibility to thermal stress birefringence; wherein the thermal stress birefringence metric is given by;
M1′
=ρ
κ
α
.where ρ
is the coefficient of thermal expansion, κ
is the stress optical coefficient, and α
is the light absorption coefficient; andwherein the glasses having the negligible susceptibility to thermal stress birefringence satisfy the condition that M1′
≦
0.0008×
10−
12 mm/(N K) and the glasses having the moderate susceptibility to thermal stress birefringence satisfy the condition that 0.0008×
10−
12 mm/(N K)≦
M1′
≦
0.01×
10−
12 mm/(N K).- View Dependent Claims (15, 16, 17)
-
Specification