Abstract: An optical drive provides an internal routine for automatically optimizing the common mode rejection ratio of the magneto-optic data output signal. A microprocessor provides control to a controller module which in turn supplies a plurality of calibration signals to a data detecting portion. The calibration signals modify predetermined parameters of the data detecting portion based upon measuring a predetermined parameter indicative of the common mode rejection ratio. The common mode rejection ratio optimization corrects for mismatches in both the optical elements and in the electronic data circuits.

Abstract: An apparatus and method is described for detecting focus errors in an optical head by positioning a prism in the optical path of a return light beam reflected from an optical recording medium. The prism reduces the beam in one dimension by a factor of M and concurrently increases the divergence/convergence angle associated with a focus-error of the beam by a factor of M in this dimension, thereby desirably enhancing the focus error signal by a factor of M.sup.2. A focus error is detected by a segmented photodetector having inner and outer photosensitive regions. The photodetector generates an electrical signal indicative of the focus error from the difference in light intensities at the inner and outer regions. The photodetector preferably is segmented in such manner as to also provide a track error signal.

Abstract: A fiber optic writing head delivers light from the ends of a close-packed array of optical fibers through a small inexpensive lens which images the light onto the writing surface. The ends of the individual fibers in the array are fixed at various angular positions to form a surface that is the image of the writing surface through the lens. The ends of the fibers are spaced along the surface so that the image that is produced on the writing surface has uniform spacing. The angular positions of the fibers are chosen such that the axis of the refracted beam emitted by each fiber is directed at the center of the entrance pupil of the lens.

Abstract: A color display is produced by overlaying two images from a single light valve. Filters are used to select the two primary colors used in the display. The two projection beams are folded and merged onto a dichroic mirror where they combine so that they follow an identical path to the screen. The dichroic mirror is positioned so that the two projection beams are equivalent when they strike the dichroic mirror. The dichroic mirror is an interference filter which reflects the spectral band passed by the first filter over a range of incident angles and transmits the spectral band passed by the second filter over the same range of angles.

Abstract: An interactive projection display system having a light pen device for use thereon is described. The projection display system has an image of a light valve on a projection screen which is formed by visible light of specified wavelengths. The projection screen also has a translatable crosswire image thereon which is formed by radiation which includes the visible light used to form the light valve image and an additional spectral component. The light pen device is sensitive to this additional spectral component. In a preferred embodiment, the image of the light valve and the crosswires are formed with white light (0.3 to 0.7 microns). The additional spectral component used for the crosswire image and the light pen sensing is a band of near-IR radiation (0.7 to 1 micron).