| 摘要 |
PURPOSE:To effective correct the aberration of a hologram lens or a grating lens with the aberration caused at a base board by constituting an objective lens by installing the hologram lens or the grating lens on the surface of one side, at least, of the base board having refractive index distribution. CONSTITUTION:The objective lens 1 is constituted of the hologram lens constructed by installing a hologram pattern 3 on the surface 2a of one side of the base board 2 having the refractive index distribution and uniting them integrally. Then, when the focal length of the base board is expressed by fB, and the focal length of the hologram lens is expressed by fH, (1/fB).(1/fH)>0 is satisfied. By constituting the objective lens by using a refractive index distribution type lens made by giving a parallel flat plate the refractive index distribution with ion exchange, etc., in such a manner, the reduction of size and weight can be realized, and simultaneously, the aberration caused at the hologram lens or the grating lens by the variation of the wavelength of a light source can be corrected with the aberration caused at the base board. |
