摘要:
An information recording and reproducing method is provided with an information recording method of optically recording digital data onto an information recording medium such as an optical disc etc., by forming a pit having a shape corresponding to the digital data, and an information reproducing method of optically reproducing the recorded digital data from the information recording medium. The information recording method is provided with: a record code generating process of applying an encoding process using a convolutional code onto the digital data, to thereby convert the digital data into a record code; a multi-level symbol generating process of converting the generated record code corresponding to a plurality of bits into a multi-level symbol having a plurality of values; a record symbol generating process of applying a logical converting process onto the generated multi-level symbol to thereby convert the multi-level symbol into a record symbol; and a recording process of recording the record symbol onto the information recording medium by optically forming the pit on the information recording medium while changing the shape of the pit by several steps in correspondence with a value of the generated record symbol. The information reproducing method is provided with: an irradiating process of irradiating a light beam for reproducing the digital data so that an irradiation range of the light beam on the information recording medium covers a plurality of pits.
摘要:
A semiconductor laser module comprises a light-emitting element 35 having a pair of opposed edge faces. One of edge face forms a reflective surface, and the other one thereof forms a low reflective surface. An optical fiber 20 has a diffraction grating 20a which functions as a deflector optically coupled to the low reflective surface of the light-emitting element 35. The diffraction grating 20a is formed close to the end portion of the optical fiber. The reflective surface of the light-emitting element 35 and the diffraction grating 20a formed in the optical fiber are used to form an optical resonator. The refraction grating 20a is formed so as to be positioned within a ferrule 60 fitted to the end portion of the optical fiber 20. The light-emitting element 35 is mounted in a package 10 not via temperature control member. The ferrule 60 is mechanically fixed to the package 10.
摘要:
An optical information recording and playback apparatus for recording and playing back an optical information recording medium having a transparent protective layer comprises a tilt detection device and an off-track adding device, and includes means for determining an optimum direction in which the center of a light spot is to be displaced from the centerline of an information track on the optical information recording medium to compensate for the tilting of the optical information recording medium relative to the light beam, means for setting the amount of displacement as fixed values, and means for splitting the optical information recording medium into a number of areas and for activating a tilt detection function each time switching is made from one area to another during recording or playback. In this way, by scanning the light spot on the optical information recording medium with the center of the light spot displaced from the centerline of the information track on the optical information recording medium, the degradation of recording/playback signal quality due to the tilting of the recording surface of the optical information recording medium can be reduced.
摘要:
An optical disk on which digital data is recorded by a pit edge multi-value recording system includes: a plurality of data areas formed with a plurality of data pits with a predetermined pit period, each of the plurality of data pits including one of a plurality of pit edge positions each corresponding to the digital data; and a plurality of servo areas formed with servo reference pits used for servo control. The data areas and the servo areas are formed alternately with each other in a circumferential direction of the optical disk. The servo area includes synchronization pits functioning as synchronization reference in reproducing the optical disk. A pit period 2L of the data pit and a pit length P of the synchronization pit satisfy the following equation: P=N×L (N is an integer not less than 2).
摘要:
An information reproducing apparatus for reproducing digital record information recorded on an information record medium is provided with: a generating device for reading out the digital record information from the information record medium to thereby output a reproduction signal; a sampling device for sampling the reproduction signal by using a sampling clock signal having a predetermined sampling frequency to thereby output the sampled reproduction signal; a detection device for detecting a direct current level of the sampled reproduction signal by extracting a zero-cross sample value, which is a sample value contained in the sampled reproduction signal and is the closest sample value to a zero level in the sampled reproduction signal, from the sampled reproduction signal; a correcting device for correcting the sampled reproduction signal by subtracting the detected direct current level from each sample value of the sampled reproduction signal to thereby output the corrected sampled reproduction signal; and a reproducing device for decoding the corrected sampled reproduction signal to thereby reproduce the digital record information.
摘要:
An optical head apparatus which records or reproduces signals stably on optical disks having different thicknesses. A correction hologram element or a correction filter is provided between a light source and a 2-focus lens in order to decrease optical intensity at a portion distant from the optical axis or to change the optical path length. The light which passes the correction hologram element or a correction filter is converged by the 2-focus lens as a micro-spot on an optical disk. The 2-focus lens comprises a hologram lens which diffracts a part of the light beam and an object lens.
摘要:
The device is equipped with a taper shank (23), a stationary member axially tapered shape (33), and a connecting member (49). The taper shank (23) is fitted in a deep portion of a shank receiving portion with a taper bore (5) formed at the tip portion of a spindle in such a manner that installation and removal are possible, and is fixedly connected to the spindle (3). The stationary member (33) is rotatably connected to the taper shank (23), and is located in the taper bore (5) with a clearance (35) and has a spray nozzle (37) for spraying cleaning fluid into the taper bore (5) and an inside passage (39). The connecting member (49) is connected, at one end thereof, to the stationary member (33) and is connected, at the other end thereof, to a supply block (13) located at the tip portion of a spindle head (1), and has a connecting passage (53) for continuously connecting a supply hole (15) and the spray nozzle (37).
摘要:
A crosstalk canceler cancels crosstalk components mixed into a reproduced signal of a target track from a first and a second neighboring tracks positioned on both sides of the target track formed on an optical disc. The crosstalk canceler includes: unit for reproducing a signal recorded on the tracks of the optical disc; unit for processing the reproduced signal to produce 1-bit binary data indicating data recorded on the first neighboring track and outputting first binary data; unit for producing a first pseudo crosstalk component which mixes into the reproduced signal of the target track from the first neighboring track based on the first binary data; unit for delaying an output signal corresponding to a pure recorded signal of the track preceding the target track to produce second binary data indicating data recorded on the second neighboring track and outputting second binary data; unit for producing a second pseudo crosstalk component which mixes into the reproduced signal of the target track from the second neighboring track based on the second binary data; and unit for subtracting the first and the second pseudo crosstalk components from the reproduced signal of the target track and outputting a pure recorded signal of the target track.
摘要:
An optical disk having a recording format for a sampled servo system and including a servo field which is preformatted, including synchronous marks for synchronizing detection, and a data field for recording data on each track. The length of the synchronous mark is defined to render the detection of the synchronous pattern possible by making it easily distinguishable from the maximum inversion interval in the data even if the optical disk is of the constant-linear-velocity (CLV) type.
摘要:
Disclosed is a digital signal reproducing apparatus, which outputs the read signal after changing its signal level by using the non-linear circuit whose amplifying characteristic changes in accordance with the difference between the center level of the amplitude of that signal pattern in the read signal which varies in a relatively short period and the center level of the amplitude of that signal pattern in the read signal which varies in a relatively long period. Accordingly, the adverse influence of asymmetry can be reduced in the form of a read signal quantized with multiple values, so that a Viterbi decoder or the like which decodes such a multivalue-quantized signal can be connected directly to the apparatus.