| 摘要 |
PURPOSE:To obtain a high diffraction efficiency, by making light incident so that the incident angle satisfies a specified conditional equation, in a diffraction grating which is a one-dimensional grating and has a symmetrical section of each minute projecting part for forming a grating whose interval is fixed. CONSTITUTION:Two luminous fluxes from a laser light source 5, which pass through a light shielding plate 8, are divided into two by a splitter 111 and are reflected by mirrors 12, 13 interfere with each other and are made incident onto a recording medium 1', and form a diffraction grating corresponding to a sensitized stripe pattern on a glass substrate 10' to which a photoresist 11' is applied. When incident angles theta1, theta2 of said two luminous fluxes are made equal, a section of a minute projecting part for forming the grating becomes symmetrical. When an incident angle theta of laser light and a diffraction angle phi of primary diffracted light are nearly equal to this diffraction grating, the diffraction efficiency becomes maximum. When wavelength of incident light and a grating interval are denoted as lambda and D, respectively, the incident angle theta obtained from the equation of sin theta=lambdadivided by D decides an incident angle for giving the maximum diffraction efficiency. |
