A flat major surface of a disc-shaped substrate (e.g., of glass) is coated with a light-reflective layer (e.g., of aluminum) which is coated with a dielectric material (e.g., silicon dioxide) highly transparent for light of a frequency supplied by a recording laser, which dielectric material is coated with a thin layer of a material absorptive for light of the frequency supplied by the recording laser (e.g., titanium). The coating parameters are chosen to establish an anti-reflection condition for the coated record blank at the recording light frequency. The light output of the laser, which is intensity modulated in accordance with a signal to be recorded, is focused upon the coated surface of the disc as the disc is rotated. With the peak intensity of the focused light sufficient to at least cause melting of the absorptive layer, an information track is formed as a succession of spaced pits in which the reflective layer is effectively exposed through the layer of dielectric material. For playback, light of a constant intensity is focused on the information track as the disc is rotated. The focused light is of insufficient intensity to effect melting of the remaining absorptive layer, but is of a frequency at which the undisturbed regions of the coated disc exhibit an anti-reflection condition. A photodetector, positioned to receive light reflected from the information track as the pits pass through the path of the focused light, develops a signal representative of the recorded information.
Thermo-optical writing of information used for such applications as archival storage is performed on a medium in which a ductile metal film layer is stretched beyond the elastic limit under the pressure exerted by a contiguous layer of thermally deforming organic substance and is partially permeable to radiation produced by a light beam. An optical cavity formed between the ductile layer and a reflecting metal film layer is tuned so that the reflection factor of the information medium at the light-radiation wavelength increases with the deformation induced by the light beam.
An optical recording media having a thermally insulating film to minimize heat loss wherein the thickness of the film is not critical for recording. The thermally insulating film is disposed between a metal coated substrate and a dielectric-like film to form the optical recording media. When a spot on the dielectric-like film is exposed to a focused laser the coloration thereof changes to store multiple bits of information at a single spot.
An erasable optical disc medium on which information is recorded and read by using a laser beam, which comprises (i) a phase transition type information recording layer, (ii) an optical interference layer and (iii) an optical reflection layer, formed in this order on a transparent substrate, in such a state that a reflectance of the medium is higher before information is recorded and a reflectance of the recorded portions of the medium is lower after recording.
A memory medium includes a memory layer of a polymer liquid crystal and a reflection layer disposed on a substrate. A record part having a different refractive index from that of a non-record part is formed in the memory layer so that the record part and the non-record part have a difference in optical thickness of the memory layer. In a reproduction step, the memory medium is irradiated with a reproduction beam of coherent light so that the reproduction beam is transmitted through the memory layer, reflected at the reflection layer and re-transmitted through the memory layer, during which the reproduction beam is subjected to interferential diffraction due to the optical thickness difference between the record part and the non-record part to allow readout of the recorded data.
An image-forming composite image member and subtractive photo process employing that composite, in which composite, a spectrally reflective light-blocking layer, a secondary thin optically functional layer and a subtractive photosensitive layer are carried on a base in an association, in which the reflective layer and the secondary layer cooperate after imagewise exposure and development to define an image member in which the secondary layer and reflector layer may provide a guide to orientation of the composite and may provide a unique polarity-reversing ability to display both a negative and a positive image. In a preferred form, the reflective and secondary layers provide superior uniform light-blocking with a minimum combined thickness, and also cooperate in the photo process during the development to insure rapid and complete clearing of areas with at most minimal mechanical action under portions of the photosensitive layer which are soluble after imagewise exposure and have been removed in development.
