U.S. Philips Corporation

U.S. Phillips Corporation

Bernardus A Jacobs

Johannes H Spruit

Guo-Fu Zhou

Cornelis M Van Uijen

James H Coombs

Pieter Zalm

Adriaan W De Poorter

Gerard E Van Rosmalen

Josephus J Braat

Gijsbertus Bouwhuis

Coen T Liedenbaum

Wilfred A Snijders

Jan G Dil

Johannes C Rijpers

Hendricus F Van Tongeren

Gerrit B Gerritsen

Johan P Duchateau

Wilma Van Es-Spiekman

Hermanus Johannes Borg

Johannes Van Der Wal

Petrus A Van Grinsven

Adrianus P Jongenelis

Piet F Bongers

Guofu F Zhou

Franciscus J Greidanus

Wilhelmus H Bardoel

A rewritable optical information medium has a phase-change recording layer on the basis of an alloy of Ge--Sb--Te, which composition is situated within the pentagonal area PQRST in a triangular ternary composition diagram. These alloys show a complete erase time of 50 ns or less. CET-values below 45 ns are obtained with alloys situated on the tie-line connecting Te and the compound GeSb.sub.2 Te.sub.4 within the area PQRST. Such a medium is suitable for high speed recording (i.e. at least six times the CD-speed), such as for DVD-RAM and optical tape.

Rewritable optical information medium

A rewritable optical information medium has a phase-change recording layer (3) on the basis of an alloy of Ge-Sb-Te-O, having the composition (Ge.sub.a Sb.sub.b Te.sub.c).sub.1-d O.sub.d, wherein:

An optical recording medium has a phase-change recording layer embedded in a stack of thin layers arranged on a substrate. At least one of the dielectric layers adjacent to the recording layer comprises a carbide. The carbide layer is separated from the substrate and/or from a reflecting layer in the stack by a dielectric layer not containing a carbide. The thickness of the carbide layer either lies in a range from 2 to 8 nm or is substantially equal to the thickness of the adjacent dielectric layer.

Optical recording medium

A method is described for recording an optical information carrier, in which marks representing recorded data are written at different writing speeds by radiation pulse of equal length and power, independent of the writing speed. The number of pulses per unit length of the written mark is a constant independent of the writing speed.

Method and device for recording a mark having a substantially constant

A radiation beam is generated by a radiation source such as laser. An optical system focuses the radiation beam at a recording layer (in a disc-shaped carrier) of a type in which an optically detectable change is caused to take place if the recording layer is heated to above a write temperature. The recording layer is scanned by the radiation beam by means of a motor. A control circuit feeds the radiation source with electric power which is converted in the radiation source partly into heat and partly into radiation for the radiation beam. The control circuit operates in a read mode in which the power supplied to the radiation source has a value at which the rise in temperature of the recording layer caused by the radiation beam is insufficient to cause an optically detectable change to take place. The control circuit also operates in a write mode in which the radiation source is intermittently fed with power pulses having a strength at which the rise in temperature of the recording layer caused by the radiation beam is sufficiently large to cause an optically detectable change to take place. The power pulses generated in the write mode have a strength and a duration for which the corresponding mean heat dissipation in the radiation source is substantially equal to the mean heat dissipation in the radiation soure in the read mode. As a result, the wavelengths of the generated radiation in the read mode and write mode are equal, thereby avoiding problems with a wavelength dispersion in the optical path of the optical system.

Optical reading and recording device containing a radiation source which

A description is given of an optical information carrier comprising a substrate (1), a thin reflective layer (5), a dielectric layer (7), a phase-change recording layer on the basis of GeTeSe (9), a dielectric layer (11), an opaque metal reflective layer (13) and a protective layer (15). The information carrier can be inscribed, erased and read by means of a laser-light beam a and, in the inscribed state, complies with the CD-industrial standard. The recording layer (9) comprises an alloy having the composition Ge.sub.x Te.sub.y Se.sub.z, in atom %, wherein

Optical information carrier

A magneto-optical record carrier having a recording track structure which enables recording with an increased information density. Information areas which are smaller than the write spot supplied by a first diode laser can be written by means of a switched magnetic field. The areas can then be read with a read spot which is smaller than the write spot, which read spot is formed by radiation from, for example, the combination of a second diode laser and a frequency doubler. The width of the recording tracks determines the width of the information areas recorded thereon.

Magneto-optical record carrier with recording track structure suited for

An apparatus for writing and reading a magneto-optical record carrier (1) with an increased information density are described. Information areas (4) which are smaller than the write spot (V.sub.w) supplied by a first diode laser (40) can be written by a switched magnetic field. The areas can be read with a read spot (V.sub.r) which is smaller than the write spot, which read spot is formed by radiation from, for example an assembly of a second diode laser (42) and a frequency doubler (43).

Apparatus for writing and reading a magneto-optical record carrier

A method and apparatus for writing and reading information in the form of a pattern of magnetic domains in an information layer of a record carrier. An optical scanning beam is focused to a diffraction-limited radiation spot, and a magnetic field is generated by a coil supplied with an energizing current the amplitude of which is modulated by the information signal to be recorded. The magnetic field is thereby modulated, and produces magnetic domains in the information layer such that each domain has a variable number of sub-domains and consequently a variable magnetization ratio, as determined by the information signal. This permits recording at an information density exceeding that corresponding to the size of the radiation spot.

Method and apparatus for writing and reading a magneto-optical record

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. As a result, the power of the radiation beam decreases during the radiation pulses and increases during the radiation intervals, and the influence exerted by previous radiation pulses on the temperature at the scanning area is taken into account.

Method of and device for recording information on a record carrier

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.

Magneto-optical scanning device with small coil

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. This produces a frozen-in net magnetization in the scanned local area of one of the recording layers, which aids the external magnetic field in producing a similar frozen-in net magnetization of the superposed local area in the other recording layer. This allows use of a relatively weak external magnetic field, which is more economical and capable of operation at higher frequencies. Any pre-existing magnetization of the latter superposed local area is erased in consequence of magnetization thereof in accordance with the external magnetic field.

Direct over-write magneto-optical recording medium having multiple

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.

Method of recording information on a record carrier of the

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. Read-out is based on the 'grey' level produced by the recorded information areas under the scanning spot at each position thereof, so that the same size scanning spot can be used for both writing and reading the record carrier.

Method of and apparatus for writing and reading a magneto-optical record

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).

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Eindhoven, Netherlands

Bernardus A Jacobs