Optical element, optical lens, optical head apparatus, optical information apparatus, computer, optical information medium player, car navigation system, optical information medium recorder, and optical information medium server

摘要

An optical lens includes a hologram, a refractive lens, and a phase level difference. The hologram has a sawtooth shape grating having a sawtooth shape in cross-section, and generates +2nd-order diffracted light most strongly with respect to blue light and +1st-order diffracted light most strongly with respect to red light, by setting a height of the sawtooth shape grating. The +2nd-order diffracted light of blue light is condensed through a substrate with a thickness t1, and the +1st-diffracted light of red light is condensed through a substrate with a thickness t2 (t1<T2). The difference in optical path length occurring when the blue light passes through the phase level difference is five times the wavelength of the blue light.