Importance

Loading Importance Indicators...

Abstract

An objective lens and optical pickup device that uses it is disclosed having an optical diffraction surface on its surface nearest a light source which may be switched in wavelength for either CD or DVD recording/replaying. The optical diffraction surface causes a selected wavelength beam to converge or diverge more than the other wavelength beam. Superimposed in a peripheral region of the diffraction grating is a step change in height (higher or lower) which causes destructive interference for light in the peripheral region for only one of the beams. In this way, an objective lens is provided that, with a simple and compact structure, enables a light beam to be converged accurately into a spot on a selected recording medium, despite the need to have the converged beam have different wavelengths and numerical apertures, depending on the recording medium used.

Loading the Abstract Image...

First Claim