Compatible optical scanning device.

摘要

A device is described in which a radiation source generates a radiation beam of a first wavelength. The scanning spot 7 generated by this radiation beam follows the centreline 13 of a track 8 to be scanned on a first type of record carrier designed for this wavelength. When a second type of record carrier is being read, in which the information is stored in a phase structure designed for a wavelength which is longer than the first wavelength, the read spot 7, according to the invention, follows the edge of a track 38 to be read instead of the centreline 18. In this way it is possible to generate a satisfactory information signal not only of the first type of record carrier but also of the second type of record carrier. <IMAGE> <IMAGE>