Optical device for beam shaping
The invention concerns an optical device and its application to generate an adjustable wave front deformation of a laser beam and thus to generate an adjustable beam spot geometry in the focal plane of laser optics. For this purpose, a device is provided which allows adjusting and modifying a laser beam in such a way that a beam spot, the shape of which can be adjusted continuously based on the original focal shape, is generated after focusing the beam, i.e. at least one dimension parameter of the shape of the beam spot has to be variable and adjustable so that the beam parameter product of the beam can also be modified without having to modify the focal position.
1. An optical device comprising at least two plate-like optical elements, which have a position dependent thickness and which are positioned in a row at short distance in the optical path of a position limited ray beam, wherein both plate-like elements are arranged displaceable along an axis transversal to the propagation direction of the ray beam, wherein x is the coordinate in the direction along the displacement axis, y is the coordinate vertically to the displacement axis, and z is the coordinate in the direction along the optical axis, and wherein a position of the plate-like elements called zero position is defined at which the thickness profiles are inverse to each other, wherein:
a. the total sum of the thickness profiles of both optical elements together describes in a centre cross section along the x coordinate with y=0 a profile, which corresponds to an isosceles triangle, and wherein the inclination of the laterals of said isosceles triangle in said centre cross section is adjustable by displacement of both optical elements against each other in direction of the x coordinate, and
b. both plate-like elements provide a thickness profile that shows a constant absolute value of the second derivative in a centre cross section along the x coordinate with y=0, which is constantly positive in one half of the centre cross section and constantly negative in the other half, and the absolute value of the curvature is the same on both sides.
2. The device according to claim 1 , wherein the sum of the position dependent thicknesses of both optical elements describes a cone surface.
3. The device according to claim 2 , wherein the cone angle of the cone surface can be adjusted by displacement of both optical elements against each other.
4. The device according to claim 1 , wherein the position dependent thickness D xy of a single plate-like element is defined for both elements by the following equation:
D xy =D 0 +( a/ 2){ x ( x 2 +y 2 ) 1/2 +y 2 [ln( x +( x 2 +y 2 ) 1/2 −ln| y|]}bx
wherein x is the coordinate in the direction of the displacement axis, y is the coordinate vertically to the displacement axis, D 0 is the thickness of the element on the optical axis with x=y=0, and a and b are two constant parameters.
5. The device according to claim 1 , wherein the sum of the position dependent thicknesses of both optical elements together describes an isosceles triangular cross section.
6. The device according to claim 5 , wherein the inclination angle of the lateral surfaces of the pitched roof surface is adjustable by displacement of both optical elements against each other.
7. The device according to claim 1 , wherein position dependent thickness D xy of a single plate-like element is defined for both elements by the following equation:
D xy =D 0 +( a/ 2)×| x|+bx
wherein x is the coordinate in the direction of the displacement axis, D 0 is the thickness of the element on the optical axis with x=y=0, and a and b are two constant parameters.
8. The device according to claim 1 , wherein the thickness profile of both plate-like elements is identical and that one element is arranged rotated by 180° along the y-axis with respect to the other element, and the y-axis is the axis which is positioned both vertically to the displacement axis of the elements and vertically to the optical axis.
9. The device according to claim 1 , wherein the thickness profile of both plate-like elements is identical and one element is rotated by 180° along the z-axis with respect to the other element, and the z-axis corresponds to the optical axis.
10. The device according to claim 1 , wherein a focusing lens is arranged behind both plate-like elements in the beam direction.
11. The device according to claim 1 , wherein a collimation lens is arranged in front of both plate-like elements in the beam direction.
12. The device according to claim 1 , wherein the maximum displacement of both plate-like elements against each other corresponds to maximal 10% of the lateral dimensions of the plates.
13. The device according to claim 1 , wherein the maximum displacement of both plate-like elements against each other corresponds to maximal 20% of the diameter of the beam.
14. The device according to claim 1 , wherein the plate-like elements are made of zinc sulphide.
15. A use of a device according to claim 1 , for modifying at least one dimension parameter of the beam spot in the focal plane without modifying the focal position itself.
16. A use of a device according to claim 1 , for generating a wave front deformation with the beam parameter product of the beam being continuously adjustable and magnifiable beginning with its original value.
17. A use of a device according to claim 1 , in an assembly for joining or cutting components as well as to fill up materials on workpieces.