| 摘要 |
PROBLEM TO BE SOLVED: To provide a continuous ND filer which easily gives laser beams, having desired intensity distribution by controlling the thickness of the filter. SOLUTION: A filtering device 3 contains a first lens 10 made of a light- absorbing material and a second lens 11 made of a transparent material and coupled with the first lens 10. The beam radiating face 12b of the first lens 10 is formed, to show a curved line according to the preliminarily determined distribution function of the density of light and the thickness of the first lens 10 changes from the center to the periphery. A beam entrance face 13a of the second lens 11 has the identical curved line, so that the entrance face matches the beam radiating face 12b of the first lens 10.
|
