| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a spatial intensity distribution of laser light which has been converged weakly at its center part and intensely at its peripheral part by arranging a specific composite Fresnel zone plate right before or behind a condenser lens. SOLUTION: The composite Fresnel zone plate 1 has a unit cell obtained by providing a Fresnel zone plate, which is optically different in pitch, concentrically in a Fresnel zone plate together. Then this unit cell and a complementary unit cell which is opposite in phase difference of 0 andπradian from the unit cell are arranged in quantities at random on the same plate so that they are in half-and-half proportion. The obtained composite Fresnel zone plate 1 is arranged right before or behind the condenser lens. For example, the laser light L outputted from a large-output laser after passing through the composite Fresnel zone plate 1 is converged by the condenser lens 2. An object 3 is placed almost at a distance of the focal length (f) of the condenser lens 2.</p> |
