| 摘要 |
PURPOSE:To obtain >=34% logical diffraction efficiency, by constituting the diffraction grating so that the refractive index of a medium forming the diffraction grating, the depth of the grating, and intervals of the grating satisfy prescribed conditions for a used wavelength. CONSTITUTION:The laser luminous flux emitted from a laser light source 2 becomes a parallel luminous flux through a lens 3, an object lens 4, a pinhole 5, and a lens 6. The parallel luminous flux has a uniform intensity distribution through a filter 7 having a reverse Gaussian transmittance distribution and is divided into two by a beam splitter 8 to irradiate a recording material 10 through mirrors 91 and 92. Processings such as development are performed to obtain a diffraction grating 1 where a relief is formed on a light transmittive resin 1B on a transparent substrate 1A. h/lambda>0.4 and D/lambda>1/(no+1) are satisfied when the refractive index of the meidum 1B, the wavelength of the incident light, the depth of the diffraction grating 1, and intervals of the grating are denoted as no, lambda, (h), and D respectively, thereby obtaining >=34% diffraction efficiency. |
