| 摘要 |
A diffraction element may include a grating region where a plurality of groove parts and a plurality of protruded parts are alternately formed on a surface of the diffraction element and flat regions where the surface of the diffraction element is formed to be a flat face. The flat regions are formed on both sides of the grating region and are formed at a height of "nlambda" from the center position in the depth direction of the groove part; wherein "lambda" is the wavelength of an incident light beam to the diffraction element and "n" is an integer number. The diffraction element may be disposed at a midway position in the forward path as a three-beam generating element.
|
