Sharp Kabushiki Kaisha Corporation

Hitoshi Takeuchi

Junsaku Nakajima

Masaru Nomura

Kenji Ohta

Eiji Yamada

Chiaki Yamawaki

Tetsuo Iwaki

Taizo Sasada

An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit stringof pits of different depths is formed in the lead in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

Optical recording medium recorded with information in depth direction, and method and apparatus of reproduction therefrom

On an optical disk, a string of a plurality of pits having two different depths is formed. Quantity of light reflected from the pit string is detected by a photoreceptor element, and based on the detected quantity of reflected light, a pit depth detecting unit detects depth of each pit. Based on the detected quantity of reflected light, a servo signal generating unit generates a tracking servo signal. An output control unit supplies the generated tracking servo signal when a pit of such depth that is to be reproduced is tracked, and holds and supplies an immediately preceding tracking servo signal when a pit of different depth is being tracked, based on the result of detection by the pit depth detecting unit.

Optical disk having pits of different depths formed therein, optical disk reproducing apparatus for reproducing the optical disk, and method of tracking the optical disk

On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Optical disc having pits of different depth formed therein, optical disc device for reproducing the same, and method of reproduction

An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit stringof pits of different depths is formed in the lead-in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

An optical device to control the output power of a laser on recording and reproduction without expensive high-speed circuits is provided. The optical disk device of the present invention comprises monitor portion for monitoring the power of laser light, averaged light quantity calculating portion for calculating the averaged light quantity of the power of the laser light, memory portion for memorizing the averaged light quantity, error quantity calculated portion for calculating the difference between the output signals of the averaged light quantity calculating portion and the memory portion, and laser power control portion for controlling the power of the laser light in response to the output signal from the error quantity calculating portion.

Optical disk device

An optical recording medium capable of obtaining a large reproduced signal from the recoded mark, a large reproduced signal of a pre-pit and a large tracking signal both in an area of the grooves and an area of the pre-pits, which provides a sufficient time allowance for switching tracking to that suitable for the area of the grooves or to that suitable for the area of the pre-pits. An optical recording medium comprising a substrate whereon tracks each comprising at least of writable grooves and pre-pits deeper than or equal to the grooves are formed and areas of a relatively shallow pits are each provided between an area of the deep pits and an area of the grooves. The depth Dg of the grooves, the depth Dsp of the shallow pits and the depth Ddp of the deep pits satisfy the following conditions: Dg<&lgr;/(8n), &lgr;/(8n)<Ddp<&lgr;/(4n) and Dg&lE;Dsp<Ddp. Tracking method is switched over in the shallow pit area when recording or reproducing information on the optical recoding medium.

Optical recording medium, media tracking method and recording/reproducing apparatus

In a multi-track magnetic signal reproducing apparatus, a plurality of MR heads including MR (Magneto Resistance Effect) elements are provided correspondingly to tracks on a magnetic tape. At the time of reproduction, constant current from a constant current power supply is sequentially supplied as pulse-shaped current for detecting a signal to each MR element by a switching operation by switch in response to a prescribed clock signal, and output voltage from each MR element related to reproduction of a magnetic signal on a corresponding track is sequentially provided to one input side of a differential amplifier. In differential amplifier, the offset voltage of each MR element provided to the other input side and the above-described output voltage are differentially amplified and only voltage due to the reproducing magnetic signal of each track is accurately extracted. Accordingly, the supply of pulse-shaped current effectively suppresses increase in the amount of consumption current regardless of the number of tracks on the tape (or the number of heads), and since amplifier is shared between the tracks, the number of necessary terminals for such a multi-track MR head is reduced.

Multi-track magnetic signal reproducing apparatus

A digital data detector samples a signal at twice the data rate and calculates a phase interval from a zero crossing point to the current sampling point. The phase of the current sampling point is predicted based on the phase of a sampling point located before the current sampling point, the phase of a sampling point located at least two points before the current sampling point, and a zero crossing detection signal. A predicted error is calculated between a calculated phase interval and a predicted current phase. The frequency band of the predicted error is limited, and the phase of the current sampling point is calculated according to the band-limited predicted error, the predicted current phase, and the zero crossing detection signal. A data detection clock is detected in synchronization with a received digital data according to the calculated phase of each sampling point. A digital data value is detected using the phase interval, the calculated current phase, and sampling data. The predicted error is band-limited, and the phase of the current sampling point is calculated to follow only fluctuation due to wow and flutter in a relatively low frequency band. Since a clock signal is detected for data detection according to the calculated phase, digital data can be detected with a small data error rate even from received digital data having a low signal to noise ratio.

Digital data detector

A digital receive signal is sampled by an A/D converter, and the position of a point at which the receive signal crosses a reference level is obtained in response to sampling data by an exclusive OR gate. A phase interval between the present sampling point and the point at which the receive signal crosses the reference level is obtained by an arithmetic circuit, and the phase of the present sampling point is obtained in accordance with the position of the crossing point, the phase interval P between the present sampling point and the crossing point obtained by arithmetic circuit, the phase of a preceding sampling point obtained by an I-bit parallel delay circuit, and the phase of a sampling point which is two points preceding to the present sampling point and obtained by an I-bit j-stage parallel delay circuit. A data detection clock signal and digital data are detected in accordance with the computed phase of each sampling point, an MSB of sampling data, and the phase interval between the present sampling point and the point at which the receive signal crosses the reference level.

Digital data detector for reducing errors due to frequency variations

A digital modulation signal is sampled by an A/D converter in a predetermined cycle. A phase interval P between a zero level crossing and the current sampling point using sampling data S.sub.i+1 at the current sampling point and sampling data S.sub.i at a sampling point which is located one point before the current sampling point. A phase P.sub.i+1 of the current sampling point is found using the phase interval P, a phase P.sub.i of the sampling point which is located one point before the current sampling point, a phase P.sub.i -1 of a sampling point which is located two points before the current sampling point and a phase P.sub.i-2 of a sampling point which is located three points before the current sampling point. A clock signal is detected using the phases P.sub.i+1 and P.sub.i. Digital data is detected using the phase interval P, the phase P.sub.i+1 and the sampling data S.sub.i at the sampling point which is located one point before the current sampling point.

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Kitakatsuragi-gun, Japan

Hitoshi Takeuchi