Optical system with compensated spatial dispersion

• US 20040008427A1
• Filed: 07/12/2002
• Published: 01/15/2004
• Est. Priority Date: 07/12/2002
• Status: Active Grant

• Current Assignee: Hellma Materials GmbH & Co. KG.
• Original Assignee: Schott AG (Carl-Zeiss-Stiftung)
• Inventors: Nattermann, Kurt, Moersen, Ewald
• Granted Patent: US 6,816,326 B2
• Time in Patent Office: Days
• US Class Current: 359/796
• CPC Class Codes: G02B 1/02 made of crystals, e.g. rock-salt, semi-conductors G02B1/08 takes precedence
• CPC Class Codes: G02B 13/143 for use with ultraviolet radiation
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties

Abstract

The optical system has a first optical element (11, 17, 19, 26) and a second optical element (12, 18, 20, 27) arranged along an optic axis (10). The optical elements are preferably made from crystalline material with a cubic crystal structure. The first and second optical elements have first and second orientations in relation to the optic axis, which are preferably rotated with respect to each other according to the rotational symmetry of the material. At least one of the first optical element and second optical element is pre-stressed by applying a compressive stress (σ,σ1,σ2) thereto. The compressive stress is applied radially symmetrically relative to the optic axis (10) and compensates for spatial dispersion.

Claims

1. An optical system with compensated spatial dispersion, said optical system comprising a first optical element (11, 17, 19, 26) and a second optical element (12, 18, 20, 27) arranged along an optic axis (10), wherein the first optical element has a first orientation in relation to the optic axis and the second optical element has a second orientation in relation to the optic axis, wherein at least one of the first optical element and second optical element is pre-stressed by applying a compressive stress (σ

,σ

1,σ

2) thereto and said compressive stress is applied radially symmetrically relative to the optic axis (10) in order to compensate for the spatial dispersion.

2. The optical system as defined in claim 1, wherein said compressive stress (σ

,σ

1,σ

2) is isotropic and homogenous.

3. The optical system as defined in claim 1, wherein said compressive stress (σ

,σ

1,σ

2) is from 0.5 to 50 MPa.

4. The optical system as defined in claim 3, wherein said compressive stress is from 0.6 to 1.6 MPa.

5. The optical system as defined in claim 1, wherein said at least one of the first optical element and second optical element is in a planar pre-stressed state in a plane perpendicular to the optic axis (10).

6. The optical system as defined in claim 1, further comprising means (C) for producing said compressive stress (σ

,σ

1,σ

2).

7. The optical system as defined in claim 1, further comprising means (C) for producing said compressive stress (σ

,σ

1,σ

2) and means (S) for adjusting said compressive stress.

8. The optical system as defined in claim 1, wherein said compressive stress (σ

, σ

1,σ

2) includes a first compressive stress (σ

1) applied to said first optical element and a second compressive stress (σ

2) applied to said second optical element.

9. The optical system as defined in claim 1, wherein the first and second optical elements are made from a crystalline material with a cubic crystal structure.

10. The optical system as defined in claim 9, wherein said crystalline material with said cubic crystal structure is CaF₂ or BaF₂.

11. The optical system as defined in claim 1, wherein said first optical element has a slow axis, said second optical element has a fast axis and said fast axis coincides with said slow axis.

12. The optical system as defined in claim 1, wherein said first optical element has a slow axis, said second optical element has a fast axis and said fast axis is directed in a direction opposite from that of said slow axis.

13. The optical system as defined in claim 1, wherein the first and second optical elements are made from a material with a four-fold rotational symmetry and said first optical element and said second optical element are twisted or rotated relative to each other by a rotation angle of 45°

, 135°

, 225°

or 315°

.

14. The optical system as defined in claim 1, wherein the first and second optical elements are made from a material with a three-fold rotational symmetry and said first optical element and said second optical element are twisted or rotated relative to each other by a rotation angle of 60°

, 180°

or 300°

.

15. The optical system as defined in claim 1, wherein said first and second optical elements have a cubic crystal structure with a [100]-axis, a [010]-axis, a [001]-axis, a [111]-axis, a [-1-11]-axis and a [1-11]-axis and wherein said [100]axis, said [010]-axis, said [001]-axis, said [111]-axis, said [-1-11]-axis or said [1-11]-axis are parallel to the first orientation and the second orientation.

16. The optical system as defined in claim 1, wherein said first optical element and said second optical element have respective plane surfaces facing each other.

17. The optical system as defined in claim 1, wherein said first optical element has a concave surface and said second optical element has a convex surface and said concave surface and said convex surface face each other.

18. The optical system as defined in claim 1, wherein said first optical element has a convex surface and said second optical element has a concave surface and said concave surface and said convex surface face each other.

19. The optical system as defined in claim 1, wherein said first optical element and said second optical element form an end group of an objective.

20. The optical system as defined in claim 1, wherein said first optical element and said second optical element form a planar corrective element.

21. The optical system as defined in claim 1, wherein said first optical element and said second optical element have equal thickness.

22. An apparatus comprising

an optical device with compensated spatial dispersion, said optical device including a first optical element (11, 17, 19, 26) and a second optical element (12, 18, 20, 27) arranged along an optic axis (10), wherein the first optical element has a first orientation in relation to the optic axis and the second optical element has a second orientation in relation to the optic axis, wherein at least one of the first optical element and second optical element is pre-stressed by applying a compressive stress (σ

,σ

1,σ

2) thereto and said compressive stress is applied radially symmetrically relative to the optic axis (10) in order to compensate for the spatial dispersion; and

at least one of a lens, a prism, a light conducting rod, an optical window, an optical component for DUV-photolithography, a stepper and an excimer laser.

23. An apparatus comprising a computer chip, an integrated circuit or an electronic unit and including an optical device with compensated spatial dispersion, said optical device including a first optical element (11, 17, 19, 26) and a second optical element (12, 18, 20, 27) arranged along an optic axis (10), wherein the first optical element has a first orientation in relation to the optic axis and the second optical element has a second orientation in relation to the optic axis, wherein at least one of the first optical element and second optical element is pre-stressed by applying a compressive stress (σ

,σ

1,σ

2) thereto and said compressive stress is applied radially symmetrically relative to the optic axis (10) in order to compensate for the spatial dispersion.