Focusing characteristics of an optical head with superresolution using a high-aspect-ratio red laser diode

The focusing characteristics, when using a superresolution technique, for a high-aspect-ratio laser beam were investigated theoretically. The spot size, sidelobe intensity, and laser beam transmission efficiency were calculated against the shading mask width, fill factor, and optical disc tilt. It was revealed that, for a given transmittance, performing superresolution in the region of fill factors greater than 1 is effective both for reducing the spot size and for increasing the laser beam transmission efficiency. However, since superresolution sharply increases the sidelobe, it must be carried out in a practical range.