| 摘要 |
PROBLEM TO BE SOLVED: To provide a coupling lens of a plastic material which is not changed in the diversion angle of an exit luminous flux even if a temperature fluctuation occurs, an optical pickup device which is not changed in an object position with respect to an objective lens even if the temperature fluctuates and is not deteriorated in the spherical aberration of the objective lens, and a semiconductor laser collimating device which can emit stable parallel luminous fluxes even if a temperature fluctuation occurs. SOLUTION: This coupling lens 2 consists of a plastic material, has a diffraction face on which a level difference is formed in a ring band form on at least either one of a first face or second face and satisfies the equation |c1+(c2-c1).ϕD/ϕC|/fc<0.15 λ (mm). The optical pickup device and the semiconductor laser collimating device include the coupling lens. |
