Diffraction type optical pickup lens and optical pickup apparatus using the same

摘要

In a diffraction type optical pickup lens, at least one surface of a convergent lens is formed with such an aspheric surface that a luminous flux having a wavelength lambda₁ is converged at a first predetermined position. At least one surface of the convergent lens is formed with a zone plate having such a wavelength selectivity that a luminous flux having a wavelength lambda₂ is converged at a second predetermined position whereas the luminous flux having a wavelength lambda₁ is transmitted therethrough as it is. The convergent lens is transparent to the luminous fluxes having the wavelengths lambda₁ and lambda₂.