Optical pickup device using optical lens coated with antireflection film whose spectral reflectance changes in accordance with wavelength

Abstract

An optical pickup device capable of maintaining a sufficient amount of laser beam light when recording information on an optical disc and stabilizing the light emission of the semiconductor laser when reproducing information. Each optical component constituting an optical system for an optical pickup device used for both information recording and reproducing is coated with an antireflection film whose spectral reflectance changes in accordance with the wavelength of an incident light. The antireflection film has a high spectral reflectance at a shorter wavelength in the whole range of light emission wavelength covered by the semiconductor laser light source and a low spectral reflectance at a longer wavelength, and is formed on the incident surface or outgoing surface of at least one optical transparent element. In recording information on an optical disc wherein a laser beam is emitted at a high output power and at a wavelength shifted to a longer peak wavelength, the transmission coefficient of a laser beam becomes high. Furthermore, in reproducing information wherein a laser beam is emitted at a low output power and at a wavelength shifted to a shorter peak wavelength, the transmission coefficient of a laser beam becomes low, reducing the amount of light returned to the semiconductor laser.

Dependencies are inferred from the claim text.