| 摘要 |
A line narrowed laser system (42) having a spatial filter (44) to filter light at wavelengths greater and/or smaller than a desired range of wavelengths. The laser system is line narrowed with a line narrowing mechanism (8,10,12,14,16) having a dispersive element which disperses laser light into wavelength dependent directions. By spatially filtering the resulting beam the bandwidth of the beam can be reduced substantially. There is also a reduction of beam energy as a result of the spatial filtering but this reduction is substantially less than some other known techniques for reducing bandwidths. A preferred spatial filter (44), for reducing the bandwidth of a line narrowed gas discharge laser, includes two cylindrical focusing lenses (46 and 48) separated by a distance equal to their focal lengths with a slit aperture (50) positioned at the common focal line. The spatial filtering technique of the present invention is a low cost technique, relatively easy to implement and does not significantly complicate laser operation as compared to some more elaborate systems for reducing laser bandwidth. <IMAGE> |
