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Method of evaluating a readout signal, and optical disc apparatus

A technology for regenerating signals and evaluating methods, which is applied in digital recording/reproducing, electrical components, code conversion, etc., and can solve problems such as inability to evaluate data patterns

Inactive Publication Date: 2005-11-09
HITACHI CONSUMER ELECTRONICS CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] In addition, from the viewpoint of optimizing the recording strategy, it is ideal to use MLSE to decompose into a table corresponding to the mark length and space length to evaluate the reproduced signal. The probability of error is fundamental, so, as described in the above-mentioned literature, it is impossible to evaluate the data pattern structured by the minimum run length blank and the minimum run length mark

Method used

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  • Method of evaluating a readout signal, and optical disc apparatus
  • Method of evaluating a readout signal, and optical disc apparatus
  • Method of evaluating a readout signal, and optical disc apparatus

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Embodiment 1

[0186] Correspondence to various PR categories

[0187] In the above description, PR(1,2,2,1) corresponding to RLL(1,7) encoding is decoded, and the calculation method of S-SEAT and V-SEAT is explained. In the following, PR(1,2,1), PR(12221), PR(123321) corresponding to RLL(1,7) coding, and PR(3,4,4 corresponding to RLL(2,10) , 3) The embodiment of the class.

[0188] First, the PR class corresponding to the RLL (1, 7) encoding of a blue laser disc or the like will be described.

[0189] Fig. 12 is for PR (1, 2, 1) corresponding to RLL (1, 7) encoding and PR (a, b, c) 1-bit error pattern, summarizing the relationship between Euclidean distance and edge shift direction diagram. As shown in the figure, there are two types of code pattern combinations for 1-bit error, and the Euclidean distance is 6 in the case of a fixed target level. The definition of the edge shift direction for each code pattern is as shown in the figure.

[0190] First, calculation of S-SEAT will be des...

Embodiment 2

[0244] Next, an embodiment will be described with reference to the drawings regarding an appropriate circuit configuration for calculating S-SEAT and V-SEAT.

[0245] FIG. 1 illustrates the structure of the S-SEAT calculation circuit mounted in the optical disc device of the present invention. The overall configuration is composed of a decoding unit 10 , a target level learning unit 20 and a signal evaluation unit 30 .

[0246] First, the decoding unit 10 will be described. The decoding unit 10 is composed of a waveform equalizer 11 , a branch metric calculation unit 12 , an ACS (Add Select Compare) unit 13 , a path memory 14 (pass memory), and an object level table 17 . The reproduced signal 50 is converted into a digital value by an AD converter in advance, and after being equalized by the FIR filter in the waveform equalizer 11, in the branch metric calculation unit 12, the 2 times of the error between the target value and each bit array is calculated. square (branch metr...

Embodiment 3

[0296] Cases where branch metric calculation is implemented by absolute value

[0297] As described above, in order to obtain the most accurate binarization result in the Viterbi decoder, branch metric values ​​obtained by multiplying the difference between the reproduced signal and the target value to the power of 2 are used. Such a Viterbi decoder is called a quadratic system. The second power Δ2 of the difference between the reproduced signal and the target level becomes:

[0298] 【Number 14】

[0299] Δ 2 =(V signal [t]-V target [n]) 2

[0300] (Formula A-1)

[0301] =(V signal [t]) 2 -2V signal [t]V target [n]+(V target [n]) 2

[0302] Here, Vsignal[t] represents the reproduced signal level at time t, and Vtarget[n] represents the target signal level corresponding to the bit array. In the Viterbi decoder, binarization is performed such that Δ 2 The multiplied value becomes the minimum. The first item ...

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Abstract

A method of evaluating the quality of a read signal from the viewpoint of the detection margin of a Viterbi decoder in the PRML method in which a target signal level varies depending on the read signal, and an optical disc apparatus implementing the method. A method of evaluating the quality of a signal pattern comprising a combination of minimum run lengths from the viewpoint of edge shift, and an optical disc apparatus implementing the method. From the target signal level that varies depending on the read signal, a target signal is generated based on a decoding result, and an error target signal is generated in which the decoding result is edge-shifted. The signal quality is evaluated by calculating a Euclidean distance between these signals and the read signal. A virtual state that is not included in the Viterbi decoder and that is less than the minimum run length is defined, and a target signal level for the virtual state is generated using a target signal level table inside the Viterbi decoder, based on the concept of convolution. In this way, the signal quality can be evaluated by the same method as mentioned above even in cases where the pattern of a combination of the minimum run lengths has edge-shifted.

Description

technical field [0001] The present invention relates to an optical disc device for recording information by forming recording marks different in physical properties from other parts on a recording medium. Background technique [0002] With the increase in speed and density of optical discs, the PRML (Partial Response MaximumLikehood) reproduction signal processing method has become an essential technology. One of the PRML methods is an adaptive PRML or a compensation PRML method in which a target signal level is adaptively changed according to a reproduced signal. According to "Tech.Digest ISOM'03, pp.34", it is shown that by using such a PRML method, by compensating the asymmetry of the reproduced signal and the thermal interference during recording, it is possible for Blu-ray compatible devices to High density equivalent to 35GB can be achieved. [0003] In an optical disc device using a PRML device, it is important to properly learn (1) playback equalization conditions,...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G11B20/10
Inventor 峰邑浩行
Owner HITACHI CONSUMER ELECTRONICS CORP
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