Rca Inc.

Ping Sheng

William Ronald Roach

Arthur Herbert Firester

William J Burke

Recovery from a record of data recorded in an elongated information track, comprising depressed areas of various lengths alternating with non-depressed areas, is effected by an optical playback system. The playback system employs apparatus for focusing a laser source as a light spot on the information track. A light detector, responsive to light diffracted by the information track as relative motion is established between the light spot and the information track, is used in the playback apparatus to translate the depressions in the information track into frequency-modulated electrical signals. When the light spot size or depression spacing becomes comparable to the wavelength of the laser source, the signal strength at the detector output becomes dependent upon the polarization of the light spot incident on the information track. In the playback system, apparatus is provided for orienting the polarization of the light spot on the information track to enhance the signal strength of the detector output.

Optimal polarization for the optical readout of high density video

An incident light beam illuminates the surface of a disc, having signal elements recorded therein in the form of a succession of spaced apart depressions, with a light spot that spans a plurality of depressions. The structure of the depressions serves as a diffraction grating which reflects the incident light beam into a plurality of substantially coplanar diverging fans of light. Polarizers are interposed between the light beam source and the surface to polarize the light beam in orthogonal directions. Photodetectors, positioned to intercept the reflected fans, provide outputs corresponding to the light power in the reflected fans. The photodetectors provide a first output of the reflected light power of the light beam polarized in a first direction and a second output of the light power of the reflected light beam polarized in a direction orthogonal to the first direction. The ratio of the first output to the second output is indicative of the depression depth.

Diffractometer for measuring signal depth and width

Recovery from a record of information recorded in an elongated information track comprising depressed areas alternating along the length of the track with relatively non-depressed areas, is effected by an optical playback system. The playback system employs means for illuminating a focusing lens with a light beam having a cross-section forming a closed band of light, such as an annulus, to thereby increase the depth-of-field of the resulting focused spot formed on the information track. Light detection means, responsive to light diffracted by the track provides an output signal representative of the recorded data.

Optical playback system having increased depth-of-field

A moveable mask with a pin hole therethrough is disposed between a source of an object beam and a holographic recording medium. The pin hole limits the angular range of rays of the object beam transmitted to the medium, thereby preventing intermodulation distortion caused by rays of the object beam that have large angles therebetween. The mask may be moved to cause all of the rays of the object beam to pass through the pin hole, whereby a hologram is recorded.

Growing community of inventors

Princeton, NJ, United States of America

Ping Sheng