摘要:
Recording and/or reading of information on an optical record carrier is effected by scanning such record carrier with a radiation beam which is focussed by an objective lens into a scanning spot of a size which is diffraction-limited by the aperture of the objective lens. The effective size of the scanning spot is considerably reduced by including a layer of non-linear optical material in the record carrier, such material having an optical characteristic which changes with changes in intensity of the radiation incident thereon. The read/write resolution of information on the record carrier is thereby substantially increased.
摘要:
When information is recorded on a record carrier (1) of the thermomagnetic type, the thermomagnetic recording layer (4) is scanned by a magnetic field generated by a magnetic-field modulator (7). The magnetic field is modulated depending on an information signal (Vi). Moreover, the scanned portion of the record carrier (1) is at the same time locally heated by radiation pulses (10) generated by an optical scanning device (5). By means of radiation pulses (10) the record carrier is heated above a write temperature (Ts), above which temperature the magnetization of the record carrier assumes the direction dictated by the magnetic field. A synchronizing circuit (9) generates the control signal (Vm) for modulating the magnetic field and the control signal (Vr) for generating the radiation pulses, in such a way that at the end of the radiation pulses the field strength is sufficiently high for the heated area of the record carrier to be magnetized in the directio dictated by the magnetic field.
摘要:
A method and apparatus are revealed for recording information on a record carrier (1) having a magneto-optical recording layer (2), a pattern of magnetic domains (23, 24) having a first and a second direction of magnetization being formed in the recording layer (2). In accordance with the method, areas (22) of the recording layer are heated by the radiation pulses (20). The heated areas (22) are magnetized by means of a coil (12) which is energized with energizing-current pulses (21) which lag the radiation pulses (20) to such an extent that cooling of the areas (22) takes place substantially during the generation of the energizing pulses (12).
摘要:
A display tube comprising in an evacuated envelope (1) a display screen (7) provided on the inside of a display window (2) in the wall of the envelope (1), which display screen (7) comprises luminescent material (13), and a multilayer interference filter (12) is provided between this material and the display window and compises a number of layers (HL) which alternately are manufactured from a material having a high (H) and a material having a low (L) refractive index. If the filter is composed substantially of 14 to 30 layers, each having an optical thickness nd, wherein n is the refractive index of the material and d is the thickness, which optical thickness is between 0.2 .lambda..sub.f and 0.3 .lambda..sub.f and preferably between 0.23 .lambda..sub.f and 0.27 .lambda..sub.f, wherein .lambda..sub.f is equal to p x .lambda., wherein .lambda. is the desired central wavelength which is selected from the spectrum emitted by the luminescent material (13) and p is a number between 1.18 and 1.36, a display tube is obtained in which the luminous efficiency in the forward direction and at small angles for the central wavelength of the phosphor is at least 40% larger than in a tube without such a filter. Color improvement and gain in contrast also occur.