摘要:
An optical scanning device for scanning an optical record carrier comprising an information layer. Crosstalk cancellation is provided using a phase modulating element (40, 140) for generating a non-rotationally-symmetric phase profile in a subsidiary radiation beam. The phase profile varies with an azimuthal angle measured about the optical axis of the beam portion, the phase profile varying such that successively different phases are introduced in at least five locations which are each at successive azimuthal angles (φ1, φ2, φN) and each at a given radial distance from the optical axis, wherein the phase profile is such that the phases introduced, when taken in modulo 2π form, successively cycle through 0 to 2π at least twice, whereby the subsidiary beam spot is provided with an intensity distribution on the information layer which overlaps that of the side-lobe of the main beam spot.
摘要:
A branch metric calculation unit calculates a set of branch metric values for subsequent samples of the sampled input signal. Each of the set of branch metric values is an indication for the likelihood that an amplitude value of a sample corresponds to a particular state, a state being defined as a sequence of n-ary digits. A delay unit, which forms part of a delay chain of delay units, includes a first delay unit of the delay chain which is coupled to the branch metric calculation unit. A path metric calculation chain of path metric calculation units includes one or more path metric calculation units having first inputs coupled to a delay unit and second inputs coupled to a preceding path metric calculation unit. The path metric calculation unit calculates the path metric values from the branch metric values, a path metric value being on indication for the likelihood that a sequence of samples corresponds to a sequence of states.
摘要:
A detector (30) is described for detecting a digital signal (Bio) out of an input information signal (Ai) which represents a runlength limited sequence, the runlength having a minimal value m. The detector (30) generates (60, 62) a preliminary binary signal (Bi) out of the input information signal (Ai). A composed sequence of subsequent bits is identified (86) within the preliminary binary signal (Bi) which subsequently includes at least a first neighboring bit of a run of length greater or equal than m+1, one or more further runs of length m and at least a second neighboring bit of a run of length greater or equal than intl. A set of sequences are generated (84, 86). These sequences can be obtained from said composed sequence by changing polarities of binary values within the composed sequence without violating the runlength constraint. The set includes the composed sequence obtained from the preliminary binary signal. A path metric (D) is calculated (94, 96) for two or more sequences of the set, said path metric (D) being the sum of the branch metrics (d) for the path through the trellis corresponding to the sequence of binary values. The sequence from the set which has the highest likelihood of corresponding to the input sequence represented by the input information signal (Ai) is identified (86, 98, 100) on the basis of the path metric.
摘要:
A device and associated method for processing a digital information signal from a channel signal. The digital information signal is runlength limited with one or more constraints. The device comprises receiving means for receiving the channel signal and means for comparing a detected runlength with a predetermined value indicative of a minimum runlength constraint or a maximum runlength constraint of the channel signal and for generating a control signal when the detected runlength violates said constraint. The device further comprises substitute means for in response to the control signal deleting or inserting an element in the channel signal.
摘要:
A method of converting a stream of databits of a binary information signal into a stream of databits of a constrained binary channel signal. This stream of databits of the information signal is divided into n-bit information words. These information words are converted into m1-bit channel words in accordance with a channel code C1, or m2-bit channel words in accordance with a channel code C2, where m1, m2, and n are intergers such that m2>m1≧n. The m2-bit channel word is chosen from of at least two m2-bit channel words, at least two of which have opposite parities. The concatenated m1-bit channel words and the m2-bit channel words comply with a runlength constraint of the constrained binary channel signal. The constrained binary channel signal may be recorded on a record carrier.
摘要翻译:一种将二进制信息信号的数据位流转换成受限二进制信道信号的数据位流的方法。 该信息信号的数据流流被分成n位信息字。 这些信息字根据信道码C1或m2位信道字根据信道码C2转换成m1位信道字,其中m1,m2和n是间隔,使得m2> m1> = n 。 从至少两个m2位通道字中选择m2位通道字,其中至少两个通道字具有相反的奇偶校验。 级联的m1位通道字和m2位通道字符合受限二进制通道信号的游程长度约束。 受限二进制信道信号可以被记录在记录载体上。
摘要:
A method of measuring a phase difference between two regions in an aberration function: Reference structures are produced on a substrate using illumination that minimizes effects of phase aberration. A grating is produced on the substrate using a phase-shift grating reticle to produce, in the exit pupil, a pair of diffracted non-zero orders, while forbidding other diffracted orders and produces interference fringes formed by interference between the pair. The interference contributes to a first grating on the substrate. Overlay error is measured between the grating and the reference structure using diffraction-based or image-based overlay measurements. A phase aberration function for the exit pupil of the lithographic apparatus can then be determined from the measured overlay errors.
摘要:
A method of measuring a phase difference between two regions in an aberration function: Reference structures are produced on a substrate using illumination that minimizes effects of phase aberration. A grating is produced on the substrate using a phase-shift grating reticle to produce, in the exit pupil, a pair of diffracted non-zero orders, while forbidding other diffracted orders and produces interference fringes formed by interference between the pair. The interference contributes to a first grating on the substrate. Overlay error is measured between the grating and the reference structure using diffraction-based or image-based overlay measurements. A phase aberration function for the exit pupil of the lithographic apparatus can then be determined from the measured overlay errors.
摘要:
This invention relates to a method of converting a user bitstream into a coded bitstream by means of a runlengh limited (d, k) channel code where the channel code has a constraint of d=1. In order to ensure an improvement in bit detection performance an additional RMTR constraint of r=2 is imposed limiting to two the maximum number of minimum runs allowed by the d=1 constraint. An additional advantage of such a code is a limitation of the back-tracking depth of a Viterbi bit-detector Based on two different k constraints the construction of such d=1 and r=2 codes is disclosed.
摘要:
On existing DVD and CD players a control loop is required for the adaptation and timing recovery. For Two-Dimensional Optical Storage such a control loop has drawbacks because PRML detection in the form of a stripe-wise Viterbi detector is used. Such a detector introduces an increasing detection delay when going from the outer rows towards the center of the broad spiral. A feedback loop is arranged to determining an error signal from a first area of the data block where the first area is that area where the error signal can be determined within the shortest period of time. This reduces the duration of the detection step and thus increases the stability of the control loop.
摘要:
The invention relates to a method of storing a number of data bits of a secondary channel (30) in the frame of a main channel (20) and to a method of decoding a stream of bits relating to a secondary channel (30) embedded in the frames of a main channel (20) into a stream of data bits (62). In order to enable a certain synchronization and to guarantee a fixed amount of storage capacity in the secondary channel as well as to be able to correct deletions or insertions of bits in the secondary channel it is proposed according to the invention to form a secondary frame (11) having a fixed number of frame bits, to fill a fixed part of the secondary frame (11) with data bits (113), an end-bit (114) set to a first bit-value and, if necessary, with filling bits (115) set to a second bit-value, to encode the secondary frame (11) producing encoded data bits (113) and parity bits (112), which are finally embedded in the frame of the main channel (20). The invention relates also to a device for storing a number of data bits of the secondary channel (30) in the frame of a main channel (20) and to a device for decoding a stream of bits of relating to a secondary channel (30) embedded in the frames of a main channel (20).