Albert Smid

Design and production technology of replicated aspheric objective lenses for optical disk systems

A design is presented for an objective lens for the Compact Disc system. The objective is a single-element glass lens with one aspheric replicated surface and one flat surface. The temperature behavior of the lens is studied and compared with that of a plastic lens. The aspheric surface is manufactured by replication and is suitable for high-quality mass production.

Scanning optical microscope

In a scanning optical microscope a beam splitter (120) is arranged in the radiation path of the scanning beam with which splitter a reference beam synchronously moving with the scanning spot (21) is split off to a reference plane (140). The movement of the scanning spot (21) can be checked by measuring, with the aid of a radiation detector (160), the movement of a reference spot (121) formed by the reference beam in the reference plane. In this way an accurate determination of the position of the scanning spot (21) is possible while using simple beam-deflecting elements (40,42) having a relatively low accuracy. A cylindrical lens (131) gives the scanning spot the shape of a line, so that sensitivity to dust and other contaminations on the reference plane is reduced considerably.