PHASE LAG ELEMENT AND AN OPTICAL PICK-UP COMPRISING THE SAME, CAPABLE OF OPTIMIZING THE RATIO OF THE PHASE LAG VALUE OF A FIRST PHASE LAG LAYER TO THE PHASE LAG VALUE OF A SECOND LAG LAYER BY STACKING THE FIRST AND SECOND PHASE LAG LAYERS

摘要

PURPOSE: A phase lag element and an optical pick-up comprising the same are provided to retard the phases by 1/4 of wavelength respectively for different wavelength of laser lights triggered from DVD light source.;CONSTITUTION: A phase lag element(13) comprises first and second phase lag layers(17,18). The first and second phase lag layers are mutually stacked. The phase lag value of the second phase lag layer is 140~190nm and the phase lag value of the first phase lag layer is 450~1300nm. The ratio of the phase lag value of the first phase lag layer to the phase lag value of the second phase lag layer is 1:3.8~1:7.7. The ellipticity of the light coming out from the phase lag element is 0.89 or greater.;COPYRIGHT KIPO 2010