| 摘要 |
PURPOSE:To obtain a blaze diffraction grating with double exposure which permits easy positioning in a two-beam interference method by performing the 1st exposure in air and performing the 2nd exposure through a transparent body having an isosceles triangular section and the refractive index twice higher than the refractive index of air. CONSTITUTION:The light from a laser 1 is split to two luminous fluxes with a beam splitter 2 and the split fluxes are collimated 3, 4 to parallel luminous fluxes of a large beam diameter which are reflected by mirrors 5, 6 and are made incident to a photosensitive material 8 on a substrate 7. A transparent body 9 having a section of an isosceles triangle and the refractive index twice higher than the refractive index of air is placed in the position where the origin coincides with the surface of the material 8 and the faces KL, KM are beforehand so determined that the two luminous fluxes are made incident perpendicularly to the faces KL and KM, then the 2nd exposure is performed. Then the wave number of the light in the 2nd exposure is made two-fold the wave number in the 1st exposure, and the grating contour by the binominal approximation in the Fourier series expansion of the grating contour is obtained, whereby the blaze grating is formed. |
