Method and apparatus for homogenizing a collimated light beam

Apparatus for homogenising a collimated input light beam having a non-uniform cross-sectional intensity distribution, comprising:

• focusing means for focusing the input beam into a line;
• and
• a spatial filter disposed adjacent the line for filtering the beam to produce an output beam, the spatial filter comprising a longitudinal gap defined between opposing edges of generally coplanar plate members constructed of a material with a high resistance to excimer laser oblation;
• whereby the output beam is homogenised such that the output beam has a relatively uniform cross-sectional intensity distribution;
• wherein the input light beam is generated by an excimer laser.

A method for homogenising a collimated input light beam having a non-uniform cross-section intensity distribution defined by the function U.sub.1 (x.sub.1), where x.sub.1 is a cross-sectional dimension of the input beam, comprising the steps of:

• focusing the input beam to produce a transformed beam, the intensity distribution function U.sub.2 (.omega..sub.x) of which is defined by the Fourier transform of U.sub.1 (x.sub.1), such that
• U.sub.2 (.omega..sub.x)=.intg.U.sub.1 (x.sub.1) exp [-i.omega..sub.x x.sub.1 ]dx.sub.1 ;
• filtering the transformed beam by means of a spatial filter having an aperture defined by the aperture function S(x.sub.2), where ##EQU10## where 2b is the width of the aperture of said spatial filter and x.sub.2 is a cross-sectional dimension of the transformed beam;
• whereby to remove from the transformed beam spatial frequencies .omega..sub.x which are greater than a threshold Kb, where K is a positive constant, and produce a filtered beam, the intensity distribution of which is defined by the function U.sub.s (.omega..sub.x), where ##EQU11## said filtered beam having substantially greater homogeneity of cross-sectional intensity distribution than said input beam.

A method for homogenising a collimated input light beam having a non-uniform cross-sectional intensity distribution, comprising the steps of:

• generating the input light beam via an excimer laser;
• focusing the beam into a line;
• and,
• filtering the beam by means of a spatial filter disposed adjacent the line so as to produce an output beam, the spatial filter comprising a longitudinal gap formed between portions of material having a high resistance to excimer laser ablation, the gap being aligned with said line and substantially uniform in the dimension orthogonal to the line and the focused beam along at least the majority of the line;
• whereby the output beam is homogenised such that the output beam has a relatively uniform cross-sectional intensity distribution.

Apparatus for homogenising a collimated input light beam having a non-uniform cross-sectional intensity distribution, comprising:

• focusing means for focusing the input beam into a line;
• and,
• a spatial filter disposed adjacent the line for filtering the beam to produce an output beam, the spatial filter comprising a longitudinal gap formed between portions of material having a high resistance to excimer laser ablation, the gap being aligned with said line and substantially uniform in the dimension orthogonal to the line and the focused beam along at least the majority of the line;
• whereby the output beam is homogenised such that the output beam has a relatively uniform cross-sectional intensity distribution;
• wherein the input light beam is generated by an excimer laser.