| 摘要 |
PURPOSE:To shorten the focal length of a grating lens device by using a substrate which has a reflection mirror surface or forming the reflection mirror surface on the substrate, and loading a grating lens on the reflection mirror surface. CONSTITUTION:A reflection film 31 is formed on the substrate 30 and the grating lens 32 is mounted on the reflection film 31. Light which is incident vertically on the surface where the grating lens 32 is formed is converged by the lens 32 and reflected by the reflection film 31 to form a spot at a position (focus O) of the focal length (f) on the incidence side. Light P1 incident on the peak part of the lens 32 and light P2 incident on the bottom travels forth and back in the grating lens 32, so the phase difference between them is 2X2piX(d/lambda), where (d) is the thickness of the grating 32. Consequently, the focal length (f) is 1/2 as long as before. |
