Device for homogenizing laser radiation
View Patent ↗The assembly to homogenize a light beam, especially from an excimer laser, has at least two optical functional surfaces ( 26 ) in succession along the light path (z). Two groups of refractive or diffractive imaging elements are at the optical surfaces as cylinder lenses ( 30, 30′, 32 ), with at least two imaging elements of different characteristics within at least one of the groups. The light beam is finally carried through a Fourier lens ( 28 ) to the working plane ( 29 ).
1. A device for homogenizing laser radiation ( 100 ), comprising:
a first lens array ( 1 ) having a first optically functional boundary surface ( 10 ) through which the laser radiation ( 100 ), which has an intensity profile in form of a Gaussian profile, enters the first lens array ( 1 ), and a second optically functional boundary surface ( 11 ) through which the laser radiation ( 100 ) exits from the first lens array ( 1 ), wherein at least one of the two optically functional boundary surfaces ( 10 , 11 ) comprises a plurality of lenses ( 3 ) splitting the laser radiation ( 100 ) into a plurality of sub-beams ( 101 , 102 , 103 ), as well as
a second lens array ( 2 ), which is arranged in a beam path behind the first lens array ( 1 ), with a first optically functional boundary surface ( 20 ), through which the sub-beams ( 101 , 102 , 103 ) enter the second lens array ( 2 ), and with a second optically functional boundary surface ( 21 ), through which the sub-beams ( 101 , 102 , 103 ) exit the second lens array ( 2 ), wherein at least one of the first and second optically functional boundary surfaces ( 20 , 21 ) of the second lens array ( 2 ) comprises a plurality of lens ( 4 ) configured to refract the sub-beams ( 101 , 102 , 103 ),
wherein the plurality of lenses ( 3 ) of the first lens array ( 1 ) are designed to split the laser radiation ( 100 ) into the plurality of sub-beams ( 101 , 102 , 103 ) in such a way to illuminate the plurality of lenses ( 4 ) of the second lens array ( 2 ) substantially homogeneously, wherein cross-sectional profiles transverse to axes of the first lens array ( 1 ) of at least some of the plurality of lenses ( 3 ) of the first lens array ( 1 ) are shaped aspherically or acylindrically,
wherein the plurality of lenses ( 3 ) of the first lens array ( 1 ) are cylindrical lenses ( 3 ), whose cylinder axes extend parallel to each other in a first direction and split the laser radiation ( 100 ) into the plurality of sub-beams ( 101 , 102 , 103 ), and/or
the plurality of lenses ( 4 ) of the second lens array ( 2 ) are cylindrical lenses ( 4 ), whose cylinder axes extend parallel to each other in the first direction and refract the plurality of sub-beams ( 101 , 102 , 103 ),
wherein the cross-sectional profiles of at least some of the cylindrical lenses ( 3 ) of the first lens array ( 1 ) are designed asymmetrically.
2. The device according to claim 1 , wherein the cross-sectional profiles transverse to the axes of the first lens array ( 1 ) of all the plurality of lenses ( 3 ) of the first lens array ( 1 ) are shaped aspherically or acylindrically.
3. The device according to claim 1 , wherein the plurality of lenses ( 3 ) of the first lens array ( 1 ) have a focal length f 1 , and the lenses ( 4 ) of the second lens array ( 2 ) have a focal length f 2 , wherein the focal lengths are selected such that f 1 =f 2 .
4. The device according to claim 1 , wherein the plurality of lenses ( 3 ) of the first lens array ( 1 ) have a focal length f 1 , and the plurality of lenses ( 4 ) of the second lens array ( 2 ) have a focal length f 2 , wherein the focal lengths are selected such that f 1 >f 2 .
5. The device according to claim 1 , wherein the plurality of lenses ( 3 ) of the first lens array ( 1 ) have a focal length f 1 , and the plurality of lenses ( 4 ) of the second lens array ( 2 ) have a focal length f 2 , wherein the focal lengths are selected such that f 1 <f 2 .
6. The device according to claim 4 , wherein the first lens array ( 1 ) and the second lens array ( 2 ) are arranged at a distance d to each other, wherein the distance d is chosen so that d=f 2 .
7. The device according to claim 1 , wherein the plurality of lenses ( 3 , 4 ) of the first lens array ( 1 ) and/or the second lens array ( 2 ) are formed as micro lenses.
8. The device according to claim 1 , wherein the device comprises a Fourier lens ( 5 ), which is designed and arranged in the beam path behind the second lens array ( 2 ) so as to superimpose the sub-beams ( 101 , 102 , 103 ) refracted by the plurality of lenses ( 4 ) of the second lens array ( 2 ) in a working plane ( 6 ).
9. The device according to claim 1 , wherein at least some of the cylindrical lenses ( 3 ) of the first lens array ( 1 ) have an aspheric cross-sectional profile when viewed transversely to their respective cylinder axes.
10. The device according to claim 9 , wherein all the cylindrical lenses ( 3 ) of the first lens array ( 1 ) have an aspheric cross-sectional profile when viewed transversely to their respective cylinder axes.
11. The device according to claim 9 , wherein the plurality of cylindrical lenses ( 4 ) of the second lens array ( 2 ) have a spherical cross-sectional profile when view perpendicular to their respective cylinder axes.