Abstract: Method of and device for recording information on a record carrier having a recording layer by scanning the recording layer with a radiation beam whose power has a pulsatory variation, including radiation pulses of high power, each having decreasing power, relative to and alternating with radiation intervals of low power, each having increasing power. As a result of the heat produced by the radiation pulses, the recording layer undergoes an optically detectable change. A write signal generating circuit converts an information signal into a write signal having a pulsatory pattern, including pulses of high signal values relative to and alternating with intervals of low signal values. A control circuit sets the power of the radiation beam to values fixed by the signal values of the write signal. The signal values of each of the pulses of the write signal decrease and the signal values of each of the intervals of the write signal increase.

Abstract: A device for writing, reading or erasing a record carrier has a coil with a winding arranged between an objective lens and the record carrier. Optical radiation is focused to a spot, the converging beam passing through the coil opening. A core of a transparent material, having an index of refraction which significantly decreases vergence of the focused beam, is placed in the winding opening. As a result the diameter of the coil can be reduced, and permit increase of the generated magnetic field.

Abstract: A magneto-optical recording medium on which new information can be directly over-written over pre-existing recorded information. Such medium comprises two magneto-optical recording layers which have a difference in Curie temperature in the range of 0.degree. C. -25.degree. C. and which are separated from each other by a metal layer for the transfer of heat, such as aluminum. Recording is effected by scanning the medium with a write spot produced by a pulsed laser beam concurrently with application of an external magnetic field which is modulated in accordance with the information to be recorded. The layers may have equal Curie temperatures if they behave thermally asymmetrically. At any scanning position of the write spot the scanned superposed local areas of the two recording layers are heated thereby above the Curie temperature of at least one of such layers and then permitted to cool while being subjected to the external magnetic field.

Abstract: 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.

Abstract: 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.

Abstract: A method and apparatus for optically writing and reading information as a pattern of magnetic domains in the information recording layer of a record carrier. An optical scanning beam is focused to a diffraction-limited radiation spot for scanning the recording layer, and the region under the spot is subjected to a magnetic field generated by a magnetizing coil energized with a square-wave energizing current having a duty cycle which is modulated in accordance with the information signal. The frequency and amplitude of the energizing current are independent of the information signal, and the frequency thereof exceeds the optical cut-off frequency determined by the size of the radiation spot. Several different values of the information signal can therefore be recorded within a distance equal to the width of the radiation spot in the scanning direction at each position thereof, so that the recorded information density exceeds that corresponding the width of the scanning spot.

Abstract: Projection television display device includes three monochrome projection television display tubes (20, 21, 22) each having a display screen (24, 25, 26) which is provided on the inside of the display window (23) and luminesces in a different color. Each tube has an optical axis extending perpendicularly from the center of the display screen, the optical axes (33, 34, 35) of the three display screens being co-planar. The axes (34, 33) of the display screens of the first and second tubes (20, 22) coincide and the axis (35) of the display window of the third tube (21) constitutes the main axis of the device, the axis being perpendicular to the two coincident axes (33, 34). Two flat dichroic intersecting reflective mirrors (27, 29) extend perpendicularly of the plane and through the point of intersection of the axes, each at an angle of 45.degree. with the main axis.

Abstract: 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).

Abstract: A projection color television system having an improved resolution and luminance comprises red, green and blue color emitting tubes, the electron beams of which are focused onto their respective screens. In order to compensate for the strong saturation of the blue phosphor, and simultaneously to take advantage of the relatively fast decay of this phosphor, the blue color emitting tube is a single gun, multispot display tube. The increase in light output obtainable from the blue color emitting tube is matched by providing interference filters in the red and green color emitting display tubes and optionally in all three red, green and blue emitting tubes.

Abstract: A projection television system comprising an array of three projection television display tubes (14) luminescing in red, green and blue, a focusing lens (16) associated with each tube and a display screen (12) on which the respective optical images are merged to form a single multicolored image. At least one of the display tubes (14) has a multilayer interference filter (46) between the phosphor (30) and the faceplate (20). In order to imprve the light output at the corners of the display screen (12), the cut-off angle of the first filter layers is varied between the center and the corners thereof, for example by increasing the optical thickness of the filter layers relative to the center.

Abstract: A projection television display tube comprising in an evacuated envelope a display screen on the convexly curved inside of a display window in the wall of the envelope, which display screen comprises a layer of luminescent material and a multilayer interference filter between said material layer and the display window, the filter comprising a number of layers which are alternately high refractive index (H) and low refractive index (L). The filter is composed of at least 6 layers, each having an optical thickness nd, wherein n is the refractive index of the material of the layer and d is the thickness, which optical thickness is between 0.2.lambda..sub.f and 0.3.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 and p is a number between 1.18 and 1.32.

Abstract: 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.

Abstract: 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 comprises 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 6 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 0.25.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 1.15 and 1.

Abstract: A projection television system comprising an array of three projection television display tubes (14) luminescing in red, green and blue, a focusing lens (16) associated with each tube and a display screen (12) on which the respective optical images are merged to form a single multicolored image. At least one of the display tubes (14) has a multilayer interference filter (46) between the phosphor (30) and the faceplate (20). In order to imprve the light output at the corners of the display screen (12), the cut-off angle of the first filter layers is varied between the center and the corners thereof, for example by increasing the optical thickness of the filter layers relative to the center.