COMPOUND OBJECTIVE LENS, OPTICAL HEAD DEVICE, OPTICAL INFORMATION DEVICE AND INFORMATION PROCESSING DEVICE

摘要

Disclosed are a compound objective lens, optical head device, optical information device, and information processing device capable of suppressing occurrence of aberration even if the light source wavelength is offset from the design value. Upon a region (R10) and a region (R20), a diffractive structure having a sawtooth or stepped cross-section is formed. The height of the sawtooth or stepped cross-section formed upon the region (R10), for a predetermined wavelength of light, imparts an optical path length difference of N times a predetermined wavelength compared to transmission through air; the height of the sawtooth or stepped cross-section formed for the region (R20), for the predetermined wavelength of light, imparts an optical path length difference of J times the predetermined wavelength compared to transmission through air; and either the height difference of both ends of a border zone (RB) provided between the region (R10) and the region (R20) and/or the width of the border zone (RB) imparts an optical path length difference of (N+J)/2 (where N and J are mutually different natural numbers) times the predetermined wavelength compared to transmission through air.