Scott B. Chase

Write noise from optical heads with nonachromatic beam expansion prisms

The purposes for achromatizing the optics in an optical recording head are: (a) to reduce focal shifts of the spot at the disk and in the focus sensing system, and (b) to eliminate lateral shifts of the spot at the disk when the laser wavelength shifts. Reference 1 discusses the use of a very low dispersion glass in the fabrication of molded singlet lenses for use in optical data storage. This paper discusses an effect of a lateral shift of the focal spot that occurs, due to the dispersion in the beam expansion prism, when the laser mode hops.