| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase type optical element in which a function to expand the depth tolerance is given to a diffraction optical element without expanding beam spot diameter and without increasing cost, and the beam spot diameter is further stabilized. SOLUTION: The phase type optical element 10 has an optical face which is made discrete by splitting the optical face of an optical element 11 into a plurality of regions, and the phase difference between adjacent regions at split parts is set to be an integral multiple of 2πof a used wavelength, wherein a discrete region 12 is provided at a part (a part of a plurality of ring bands, for example) of the optical element 11, the phase difference between the discrete region 12 and its peripheral part is set to be different from an integral multiple of 2πof the used wavelength. Thus, the depth tolerance is expanded without expanding the beam spot diameter and the beam spot diameter is stabilized. COPYRIGHT: (C)2008,JPO&INPIT
|
