| 摘要 |
PURPOSE:To obtain a composite grating lens which provides desired diffracted light with a simple construction and easy operation by forming grating-shaped ruggedness at a specified grating interval and step on one surface of a light transmittable base plate, and providing the ruggedness corresponding to the pattern of a Fresnel zone plate in superposition thereon. CONSTITUTION:Grating-shaped ruggedness 11 is formed at a specified grating interval and step on one surface of a lens base plate 11 consisting of an acrylic resin or PVC which is a light transmission medium and ruggedness 31 having the fine period corresponding to the pattern of a Fresnel lens plate is formed in superposition thereon. The step d1 of the ruggedness 31 is set at the value at which the optical path difference equivalent to 1/2 wavelength given by the following equation where the refractive index of the lens material is designated as n: d1=lambda0/2(n-1) is produced. If a light emitting source such as a semiconductor laser which can be regarded nearly a spot light source is placed in the focal position of the lens constituted with the pattern of such a Fresnel zone plate, the primary light of the light past the lens is diffracted to parallel luminous fluxes. Further, the ruggedness 31 is formed superpositively on a grating-shaped ruggedness 21 having a period A0, so that the light past the lens is converted to the diffracted light of 0 order and n-th order by a linear diffraction grating 21 and is at the same time converted to parallel luminous fluxes. |
