| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain an aperture-limiting element, in which the phase of the transmitted light in the element peripheral region where a grating is formed is made equal to that in the element central region where the grating is not formed, so that difference in the phase is not generated, even when the wavelength of the light transmitted by both regions is fluctuated, and to make an optical head device, having the element which is stable in recording/reproducing information. <P>SOLUTION: The aperture-limiting element 1 is obtained, in which the sectional shape of the grating 13 of the aperture-limiting element is of unevenness shape. The difference in the phase of the transmitted light between the projected part and the recessed part is an integral multiple of the wavelength λ<SB>2</SB>of the incident light. The mean phase of the transmitted light of the projected and recessed parts match with the phase of the transmitted light, in the central region that is a phase adjustment layer 14. The aperture-limiting element 1 is loaded into the optical head device. <P>COPYRIGHT: (C)2004,JPO |
