Optical disc reading apparatus

Abstract

Disclosed is an optical disc reading apparatus, which samples an analog read signal read from an information recording medium by means of a sampler; an adaptive filter performs filtering and shaping processing on the output of the sampler, and adaptively updates a coefficient of the filter on the basis of the output of the adaptive filter; a filter coefficient calculation unit performs calculation on a filter coefficient of the adaptive filter, generates phase error information of a read clock and outputs the phase error information; a read clock generation unit generates a read clock period on the basis of the output of the filter coefficient calculation unit; the read clock period is used as a sampling clock for the sampler performing sampling operation. When the shortest mark length is close to the optical resolution limit and inter-symbol interference significantly increases, the read clock is stably generated by means of a simple structure. In addition, the read clock of each track can also be independently generated by means of a simple structure when track density increases and crosstalk influence between adjacent tracks is very large, thereby achieving high-precision crosstalk elimination.

Description

Optical disc reading device Technical Field

[0001] The present invention relates to the technical field of optical disc reading, and in particular to an optical disc reading device. Background Art

[0002] In recent years, the amount of data generated worldwide has increased dramatically, spurring a surge in demand for high-capacity storage. High-capacity optical storage, with its low storage costs, low power consumption, and long lifespan, is highly anticipated as the next generation of mainstream data storage systems. To increase the capacity of optical discs, the recording density must be increased. Increasing recording density requires shortening the minimum mark length to increase linear density and reducing the track pitch to increase track density. While shortening the minimum mark length can improve linear density, in recent years the minimum mark length has approached the limit of optical resolution, significantly increasing intersymbol interference.

[0003] When an optical disc reader reads data, it generates a read clock signal synchronized with the read signal. This clock signal must be synchronized with the decoded digital signal when the read signal is decoded. Typically, information related to the read clock signal is contained within the edges of the recorded marks. The optical disc reader generates the read clock signal by detecting phase information related to the lead or lag of the edges. However, when reading a recorded signal with a linear density exceeding the optical resolution limit, intersymbol interference (ISI) can prevent the phase information contained within the edges from being correctly detected, making it impossible to generate a read clock signal.

[0004] At this point, according to JP 4987843, the analog read signal read from the information recording medium can be sampled, and the resulting digital read signal can be shaped by an adaptive filter. The output of the adaptive filter can then be decoded by a maximum likelihood decoder. The phase error can be detected by the digital read signal shaped by the adaptive filter and the maximum likelihood decoded signal generated by the maximum likelihood decoder, thereby generating a read clock signal. In addition, if the track density is increased, the crosstalk effect of adjacent tracks also becomes significant. To reduce the impact of crosstalk, the read signal of the target track can be subtracted from the read signal of the adjacent track. However, if the time relationship between the read signal of the target track and the read signal of the adjacent track is misaligned, the impact of crosstalk will not be effectively reduced. At this point, according to JP 2008-108325, the phase difference between the read signal of the target track and the read signal of the adjacent track can be calculated by calculating the cross-correlation function between the two, and the timing of the crosstalk signal can be corrected.

[0005] The shortest mark length currently recorded by existing technologies is already approaching the limit of optical resolution. Due to intersymbol interference, the phase information contained in the edges of recorded data whose line density exceeds the optical resolution limit cannot be accurately detected. To accurately read the data, the analog read signal from the information recording medium must be sampled. The resulting digital read signal is then shaped by an adaptive filter. The output of the adaptive filter is then decoded by a maximum likelihood decoder. Phase errors can be detected from the adaptively filtered digital read signal and the maximum likelihood decoded signal generated by the maximum likelihood decoder, thereby generating a read clock signal.

[0006] However, this method suffers from a poor signal-to-noise ratio (SNR) of the analog reproduced signal read from the information recording medium, leading to frequent errors in the decoding results of the maximum likelihood decoder. This directly impacts phase error detection, often leading to erroneous phase error detection and inability to generate a stable read clock signal. Furthermore, phase error detection requires calculating the difference in metric values ​​between the digital read signal shaped by the adaptive filter and the maximum likelihood decoded signal generated by the maximum likelihood decoder, resulting in a larger circuit size.

[0007] Furthermore, as track density increases, the crosstalk effect from adjacent tracks becomes more pronounced. To reduce the impact of crosstalk, the read signal from the target track can be subtracted from the read signal from the adjacent track. However, if the timing relationship between the read signal from the target track and the read signal from the adjacent track is misaligned, the crosstalk effect cannot be effectively reduced. Because the read signal from the adjacent track lacks its own maximum likelihood decoder, the read clock for the adjacent track read signal cannot use the aforementioned method to detect the phase error between the digital read signal shaped by the adaptive filter and the maximum likelihood decoded signal generated by the maximum likelihood decoder to generate the read clock signal. Instead, the cross-correlation function between the read signal from the target track and the read signal from the adjacent track must be used to calculate the phase difference between the two to correct the timing of the crosstalk signal.

[0008] However, this method requires using the cross-correlation function between the read signal of the target track and the read signal of the adjacent track to calculate the phase difference between the two, which also has the disadvantage of increasing the circuit scale. In addition, when the optical disc reading device is searching, the optical head moves and changes position, and the time relationship between the read signal of the target track and the regenerated signal of the adjacent track changes. Therefore, during each search, it is necessary to use the cross-correlation function between the read signal of the target track and the read signal of the adjacent track to calculate the phase difference between the two to correct the timing of the crosstalk signal. Because this correction process occurs before the signal reading process, it will cause the overall processing speed to decrease.

[0009] Summary of the Invention

[0010] The present invention provides an optical disc reading device to overcome the above technical problems.

[0011] In order to achieve the above object, the technical solution of the present invention is:

[0012] An optical disc reading device comprises: an optical head, a sampler, an adaptive filter, a filter coefficient calculation unit and a reading clock generation unit;

[0013] The optical head is used to read the information recorded on the information recording medium and output an analog read signal;

[0014] The sampler is used to perform a sampling operation on the analog read signal read from the information recording medium according to the sampling clock;

[0015] The adaptive filter is used to perform filtering and shaping processing on the output of the sampler, and adaptively update the coefficients of the filter according to the output of the adaptive filter and the expected target signal;

[0016] The filter coefficient calculation unit is used to calculate the filter coefficient of the adaptive filter, generate phase error information of the read clock and output it to the read clock generation unit;

[0017] The read clock generating unit is used to generate a read clock cycle according to the output of the filter coefficient operation unit;

[0018] The read clock cycle is used as a sampling clock for the sampler to perform a sampling operation.

[0019] Furthermore, the adaptive filter is one or more FIR filters and is provided with one or more adaptive coefficient updating units;

[0020] The adaptive coefficient updating unit is used to adaptively update the filter coefficients of the FIR filter according to the output of the FIR filter and the expected target signal.

[0021] Furthermore, the filter coefficient operation unit operates the filter coefficient of the adaptive filter to generate the phase error information of the read clock.

[0022] Defining and numbering a center tap of the FIR filter and a plurality of tap pairs symmetrically arranged on both sides of the center tap;

[0023] The filter coefficient calculation unit performs a difference operation on coefficients of at least one group of taps on both sides of the center tap of the adaptive filter with the same distance from the center tap, with the center tap as the axis;

[0024] Or perform weighted summation on multiple sets of data after difference operation;

[0025] The data after the difference operation or the data after the weighted summation is used as phase error information to obtain the read clock error period.

[0026] Furthermore, the sampler is an AD converter;

[0027] or an AD converter and memory connected in sequence;

[0028] or any one of an AD converter, a memory and an interpolation operator connected in sequence;

[0029] The AD converter is used to perform analog-to-digital conversion on the analog read signal read by the optical head according to the output of the read clock generation unit;

[0030] The memory is used to store the digital read signal after analog-to-digital conversion in the memory according to the output of the read clock generation unit;

[0031] The interpolation operator is used to read the data stored in the memory and perform interpolation processing according to the output of the reading clock generation unit.

[0032] Furthermore, the filter coefficient calculation unit is one or more;

[0033] And the number of the read clock generating unit is one or more;

[0034] And the number of the samplers is one or more;

[0035] The optical head reads one or more analog read signals from the information recording medium and samples the read analog read signals through one or more samplers;

[0036] and inputting the output of the sampler into an adaptive filter provided with one or more FIR filters;

[0037] The filter coefficient operation unit calculates and obtains phase error information of the read clock using coefficients of one or more FIR filters, and the read clock generation unit generates a read clock cycle through the output of the filter coefficient operation unit;

[0038] The samplers all perform sampling using a read clock cycle generated by the same read clock generation unit;

[0039] Or each of the samplers performs sampling using a read clock cycle generated by the read clock generation unit.

[0040] Furthermore, the analog read signal read from the information recording medium is a read signal on a target track to be read on the information recording medium and a read signal on a track adjacent to the target track to be read.

[0041] Furthermore, it also includes a maximum likelihood decoder, a target signal generating unit and one or more preamplifiers;

[0042] The maximum likelihood decoder is used to perform maximum likelihood decoding on the adaptive filter output and output the decoding result as a digital signal;

[0043] The target signal generating unit is used to obtain the target signal according to the output of the maximum likelihood decoder;

[0044] The target signal is a desired target signal obtained by adjusting the output of the maximum likelihood decoder;

[0045] The preamplifier is used to perform gain amplification on the analog read signal and transmit the gain-amplified analog read signal to the sampler.

[0046] Advantageous Effects: The present invention provides an optical disc reading device. When the shortest mark length approaches the optical resolution limit and intersymbol interference (ISI) increases significantly, the read signal of a target track to be read and the read signal of its adjacent tracks are independently sampled. Samplers synchronize their respective optimal read clocks obtained by a read clock generation unit, eliminating the need to use a cross-correlation function to calculate timing correction for crosstalk signals. Simple calculations are performed on the read signal of the target track and the read signal of the adjacent tracks, resulting in stable read clock generation using a simple circuit configuration. Furthermore, when track density increases and crosstalk from adjacent tracks significantly affects the performance, the timing relationship between the read signal of the target track and the read signal of the adjacent tracks no longer needs to be calculated and corrected during each search. The read signals of each track are automatically and independently sampled synchronously using their respective optimal read clocks, eliminating the need for redundant processing and slowing down the overall processing speed, thereby achieving high-precision crosstalk cancellation. Furthermore, due to the advantages of low storage cost, low power consumption, and long life of large-capacity optical storage, the device can meet the rapidly growing demand for data generation in recent years. This device can increase optical disc linear density and track density, thereby achieving high-density recording, i.e., a large-capacity optical disc device. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0048] FIG1 is a schematic structural diagram of a first embodiment of an optical disc reading device according to the present invention;

[0049] FIG2 is a schematic structural diagram of a second embodiment of an optical disc reading device according to the present invention;

[0050] FIG3 is a schematic structural diagram of a third embodiment of an optical disc reading device according to the present invention;

[0051] FIG4 is a schematic structural diagram of a fourth embodiment of an optical disc reading device according to the present invention;

[0052] FIG5 is a schematic diagram of the structure of the FIR filter in this embodiment;

[0053] FIG6 is a line diagram of the output of the filter operation unit in this embodiment;

[0054] FIG7 is a schematic structural diagram of a read clock generating unit in this embodiment;

[0055] FIG8 is a schematic diagram of difference operation of the difference operator in this embodiment;

[0056] FIG9 is a response waveform diagram of the output signal of the filter coefficient operation unit in this embodiment;

[0057] FIG10 is a schematic diagram of a detector of the optical head in this embodiment;

[0058] FIG. 11 is a diagram showing the improvement effect of crosstalk between adjacent tracks on the information recording medium in this embodiment. DETAILED DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0060] A disc reading device comprises: an optical head, a sampler, an adaptive filter, a filter coefficient operation unit and a read clock generation unit; the optical head is used to read information recorded on an information recording medium and output an analog read signal; the sampler is used to sample the analog read signal read from the information recording medium according to the sampling clock; the adaptive filter is used to filter and shape the output of the sampler, and adaptively update the filter coefficient according to the output of the adaptive filter and the expected target signal; the filter coefficient operation unit is used to operate on the filter coefficient of the adaptive filter, generate phase error information of the read clock and output it to the read clock generation unit; the read clock generation unit is used to generate a read clock cycle according to the output of the filter coefficient operation unit; the read clock cycle is used as a sampling clock for the sampler to perform sampling operations.

[0061] Preferably, the adaptive filter is one or more FIR filters and is provided with one or more adaptive coefficient updating units; the adaptive coefficient updating units are used to adaptively update the filter coefficients of the FIR filter according to the output of the FIR filter and the desired target signal;

[0062] The expression of the filter coefficient of the adaptively updated FIR filter is:

[0063] e(n)=d(n)-y(n)

[0064] km(n+1)=km(n)+μe(n)x(nm)

[0065] Where: μ represents the gain coefficient; x(nm) represents the input of the nmth filter; k m represents the coefficient of the mth filter; d(n) represents the target signal; y(n) represents the output of the FIR filter; e(n) represents the error between the target signal and the output of the FIR filter; km(n) represents the coefficient value of the filter before the coefficient is updated; km(n+1) represents the coefficient value of the filter after the coefficient is updated.

[0066] Preferably, the filter coefficient operation unit operates the filter coefficient of the adaptive filter to generate the phase error information of the read clock.

[0067] Define and number the center tap of the FIR filter and multiple groups of tap pairs symmetrically arranged on both sides of the center tap; use the filter coefficient calculation unit to take the center tap as the axis and perform a difference operation on the coefficients of at least one group of tap pairs on both sides of the center tap of the adaptive filter with the same distance as the center tap; or perform a weighted summation on the multiple groups of data after the difference operation; and use the data after the difference operation or the data after the weighted summation as phase error information to obtain the read clock error period.

[0068] Preferably, the read clock generation unit includes a loop filter, a loop gain coefficient module, and an adder connected in sequence; the loop filter is used to input the output of the filter coefficient operation unit into the loop gain coefficient module to achieve loop gain compensation and phase compensation of the read clock error period; the adder is used to add the output of the loop gain coefficient module and a preset read clock reference period to obtain the read clock period;

[0069] Furthermore, the number of the read clock generation units and the number of the filter coefficient calculation units are one or more.

[0070] Preferably, the sampler is an AD converter; or an AD converter and a memory connected in sequence;

[0071] or any one of an AD converter, a memory and an interpolation operator connected in sequence;

[0072] The AD converter is used to perform analog-to-digital conversion on the analog read signal read by the optical head according to the output of the read clock generating unit to obtain a digital read signal;

[0073] The memory is used to store the digital read signal after analog-to-digital conversion in the memory according to the output of the read clock generation unit and record it in the corresponding memory;

[0074] The interpolation operator is used to read the data of the storage address in the memory and perform interpolation processing according to the output of the reading clock generation unit.

[0075] In addition, the filter coefficient calculation unit is one or more;

[0076] And the number of the read clock generating unit is one or more;

[0077] And the number of the samplers is one or more;

[0078] The optical head reads one or more analog read signals from the information recording medium and samples the read analog read signals through one or more samplers;

[0079] and inputting the output of the sampler into an adaptive filter provided with one or more FIR filters;

[0080] The filter coefficient operation unit calculates and obtains phase error information of the read clock using coefficients of one or more FIR filters, and the read clock generation unit generates a read clock cycle through the output of the filter coefficient operation unit;

[0081] Sampling is performed by an optical method, that is, the samplers all perform sampling using a read clock cycle generated by the same read clock generation unit;

[0082] Alternatively, sampling is performed by an optical segmentation method, that is, each of the samplers performs sampling using a read clock cycle generated by the read clock generation unit.

[0083] When the phase error information of the read clock is output through the filter coefficient calculation unit of the adaptive filter, even if the signal-to-noise ratio (SNR) of the analog read signal read from the information recording medium is poor or the decoding result of the maximum likelihood decoder is erroneous, the adaptive filter's adaptive algorithm (e.g., the LMS algorithm) prevents the coefficients of the adaptive filter from fluctuating significantly. The noise of the analog read signal or the errors of the maximum likelihood decoder will not directly appear in the phase error information, thereby achieving the purpose of stably generating the read clock. In addition, the phase error detection only requires simple operations such as taking the difference between the coefficients of at least one set of symmetrical taps on both sides of the center tap of the adaptive filter, and can be composed of a very simple circuit.

[0084] The sampler performs a sampling operation according to the read clock cycle obtained by the read clock generation unit.

[0085] Preferably, the analog read signal read from the information recording medium is a read signal on a target track to be read on the information recording medium and a read signal on a track adjacent to the target track to be read.

[0086] When the optical disc reading device is searching, when the optical head moves and changes its position, the time relationship between the read signal of the target track and the read signal of the adjacent track changes. The read signal of the target track to be read and the read signal of the track adjacent to it are independent of each other and are sampled synchronously with their respective optimal read clocks. There is no need to use a cross-correlation function to calculate the timing correction of the crosstalk signal. The read signal of the target track and the read signal of the adjacent track are respectively performed, such as simple operations such as the difference of the coefficients of at least one group of symmetrical taps on both sides of the center tap of the adaptive filter. They can be composed of very simple circuits. There is no need to calculate the time relationship between the read signal of the target track and the read signal of the adjacent track for correction every time the search is performed. Instead, during the signal reading process, the read signal of the target track and the read signal of the adjacent track are automatically and independently sampled synchronously with their respective optimal read clocks. No redundant processing is required and the overall processing speed will not be slowed down.

[0087] Preferably, the method further comprises a maximum likelihood decoder, a target signal generating unit and one or more preamplifiers; wherein the maximum likelihood decoder is used to perform maximum likelihood decoding on the output of the adaptive filter and output the decoding result as a digital signal;

[0088] The target signal generating unit is used to obtain the target signal according to the output of the maximum likelihood decoder;

[0089] The target signal is a desired target signal obtained by adjusting the output of the maximum likelihood decoder; and the preamplifier is used to gain-amplify the analog read signal and transmit the gain-amplified analog read signal to the sampler.

[0090] The optical disc reading device disclosed in the present invention achieves stable read clock generation through a simple structure even when the shortest mark length approaches the optical resolution limit and intersymbol interference increases significantly. Furthermore, even when track density increases and crosstalk from adjacent tracks significantly affects the read clock, the simple structure can independently generate a read clock for each track, achieving high-precision crosstalk cancellation. Furthermore, due to the advantages of high-capacity optical storage, such as low storage costs, low power consumption, and long life, it can meet the rapidly growing demand for data generation in recent years. This device can increase the linear density of the optical disc and the track density, thereby achieving high-density recording, thus enabling the design of a large-capacity optical disc device.

[0091] Embodiment 1: As shown in FIG1 , it includes: an optical head 102 , a preamplifier 103 , a sampler 107 , an adaptive filter 110 , a filter coefficient calculation unit 111 , a read clock generation unit 112 , a maximum likelihood decoder 113 , and a target signal generation unit 114 ;

[0092] The optical head 102 is connected to the input end of the preamplifier 103, and is used to read the information recorded on the information recording medium 101 and output an analog read signal, and transmit the analog read signal to the preamplifier 103; the output end of the preamplifier 103 is connected to the input end of the sampler 107, and is used to perform gain amplification on the analog read signal, obtain a gain analog read signal, and transmit the gain analog read signal to the sampler 107;

[0093] The adaptive filter 110 includes an FIR filter 108 and an adaptive coefficient updating unit 109; the output of the sampler 107 is connected to the input of the FIR filter 108; the output of the FIR filter 108 is connected to the input of the filter coefficient calculation unit 111, the maximum likelihood decoder 113, and the adaptive coefficient updating unit 109 respectively;

[0094] The output end of the filter coefficient calculation unit 111 is connected to the input end of the read clock generation unit 112, and the output end of the read clock generation unit 112 is connected to the sampler 107.

[0095] The filter coefficient operation unit 111 is used to operate the filter coefficients of the adaptive filter 110 to generate phase error information of the read clock; and the read clock generation unit 112 is used to obtain the read clock period according to the phase error information of the read clock; the sampler 107 is used to read the read clock period output by the clock generation unit 112, sample the gain analog read signal output by the preamplifier 103, obtain a digital read signal and input it into the adaptive filter 110;

[0096] The adaptive filter 110 is used to perform filtering and shaping processing on the digital read signal; the output end of the maximum likelihood decoder 113 is used to perform maximum likelihood decoding on the digital read signal after filtering and shaping processing output by the adaptive filter 110, and output the decoding result as digital data;

[0097] The input end of the target signal generating unit 114 is connected to the output end of the maximum likelihood decoder 113, and is used to obtain the target signal according to the output of the maximum likelihood decoder 113;

[0098] The target signal is a desired target signal obtained by adjusting the output of the maximum likelihood decoder;

[0099] The target signal is transmitted to the adaptive coefficient updating unit 109 ; the adaptive coefficient updating unit 109 is used to adaptively adjust the filter coefficients of the FIR filter 108 according to the output of the adaptive filter 110 and the output of the target signal generating unit 114 .

[0100] The sampler 107 is composed of the AD converter 104 , the memory 105 , and the interpolation operator 106 .

[0101] The output of preamplifier 103 is A / D converted by AD converter 104, and the converted A / D data is sequentially stored in memory 105. Based on the output of read clock generator 112, the read address of memory 105 is controlled, and the A / D converted data stored in memory 105 is read out and input to interpolator 106. Interpolator 106 uses the data read from memory 105 to output sampled data from preamplifier 103. The timing of this sampled data is based on the read clock cycle output by read clock generator 112.

[0102] FIG8 illustrates an embodiment of the interpolation operator 106. When the output of the read clock generation unit 112 is displayed as ΔT time after the k-1th AD conversion, the output of the interpolation operator is mem(k-1)+(mem(k)-mem(k-1))·ΔT / T. Here, mem(k) is the value of the memory storing the kth AD conversion data, and T is the AD conversion period.

[0103] In addition, the interpolation processing in FIG8 is linear interpolation, and other interpolation processing methods may also be used.

[0104] Sampler 107 in Figure 1 is composed of AD converter 104, memory 105, and interpolation operator 106. Alternatively, it may be composed solely of AD converter 104, or of AD converter 104 and memory 105. When the sampling timing varies slightly or when high sampling timing accuracy is not required, the circuit may be reduced by using only AD converter 104 or by combining AD converter 104 and memory 105.

[0105] Specifically, the sampler 107 includes an AD converter 104, a memory 105 and an interpolation operator 106 connected in sequence; and the AD converter 104, the memory 105 and the interpolation operator 106 are respectively connected to the read clock generation unit 112; the AD converter 104 is used to perform analog-to-digital conversion on the gain analog read signal output by the preamplifier 103 according to the read clock cycle of the read clock generation unit 112, and based on the output time sequence of the preamplifier 103, the gain analog read signal after analog-to-digital conversion is stored in the memory 105 according to the read clock cycle of the read clock generation unit 112 and the corresponding storage address is recorded; the interpolation operator 106 is used to read the data of the storage address in the memory 105 according to the read clock cycle of the read clock generation unit 112, perform interpolation processing, and transmit the interpolated data to the adaptive filter 110.

[0106] The output of the sampler 107 is waveform-shaped by the adaptive filter 110 and input into the maximum likelihood decoder 113. The target signal generating unit 114 uses the output of the maximum likelihood decoder 113 to generate a target signal. In order to make the output of the adaptive filter 110 closer to the target signal generated by the target generating unit 114, the adaptive filter 110 changes its filter characteristics successively.

[0107] The adaptive filter 110 is composed of the FIR filter 108 and the adaptive coefficient updating unit 109 .

[0108] The output y(n) of the FIR filter 108 is as follows:

[0109] y(n)=k N x(nN)+…+k m x(nm)+…+k1x(n-1)+k0x(n)

[0110] x(n) is the input of the nth filter, k N ,···k m ,···,k0 is the filter coefficient.

[0111] d(n) is the output of the target signal generating unit 114. The relationship between d(n) and the error e(n) of the output y(n) of the adaptive filter 110 is as follows:

[0112] e(n)=d(n)-y(n)

[0113] The coefficients of the FIR filter 108 are shown below and are updated sequentially:

[0114] km(n+1)=km(n)+μe(n)x(nm)

[0115] μ is the gain coefficient, which should be set appropriately based on stability and convergence speed. μ represents the gain coefficient; y(n) represents the output of the FIR filter; e(n) represents the error between the output of the target signal generation unit and the output of the FIR filter; km(n) represents the value of the filter coefficient before the update; and km(n+1) represents the value of the filter coefficient after the update.

[0116] When the signal-to-noise ratio (SNR) of the analog read signal read from the information recording medium is very poor, or when the maximum likelihood decoding result of the maximum likelihood decoder has many errors, there will be noise in the output y(n) of the FIR filter 108 or the output d(n) of the target signal generating unit 114. By setting an appropriate μ value, the coefficients of the FIR filter 108 can be slowly changed, thereby reducing the impact of the noise.

[0117] The adaptive algorithm of the adaptive filter 110 in this embodiment is LMS, and other adaptive algorithms can also be used here.

[0118] The maximum likelihood decoder 113 performs maximum likelihood decoding on the shaped digital read signal output by the adaptive filter 110, and outputs the decoding result as digital data. The maximum likelihood decoder 113 can utilize, for example, a Viterbi decoder. The digital data obtained after demodulation and error correction on the data output by the maximum likelihood decoder 113 is the information recorded on the information recording medium 101 that was finally read.

[0119] Specifically, based on the characteristic that the filter coefficients are symmetrical about the center tap when the sampling timing error of the signal is 0, the sampling timing error information of the signal, that is, the phase error information, can be obtained by calculating the difference between the coefficients of the tap pairs at symmetrical positions on both sides of the center tap.

[0120] FIG5 shows the configuration of the FIR filter 108 when the number of filter taps is 25. ...

[0121] Among them, when the number of taps is 25, the 13th tap k 12 is the center tap, center tap k12 The tap pairs at symmetrical positions on both sides are: k 11 and k 13 (±1 on both sides of the center tap), k 10 and k 14 (±2 on either side of the center tap), k9 and k 15 (±3 on either side of the center tap), k8 and k 16 (±4 on either side of the center tap), k7 and k 17 (±5 on either side of the center tap), k6 and k 18 (±6 on either side of the center tap), k5 and k 19 (±7 on either side of the center tap), k4 and k 20 (±8 on either side of the center tap), k3 and k 21 (±9 on either side of the center tap), k2 and k 22 (±10 on either side of the center tap), k1 and k 23 (±11 on either side of the center tap), k0 and k 24 (±12 on either side of the center tap).

[0122] In this embodiment, at least one set of center taps k is used. 12 The difference between the two symmetrical tap pairs is calculated as phase error information. For example, using the center tap k 12 k at ±1 position on both sides 11 ,k 13 , then the output of the filter coefficient operation unit 111 is k 11 -k 13 ; Use center tap k 12 k at the ±1 and ±2 positions on both sides 11 ,k 13 and k 10 ,k 14 , then the output of the filter coefficient operation unit 111 is (k 11 -k 13 )+(k 10 -k 14 ); In addition, a weight coefficient can be added to the output calculation of the filter coefficient operation unit according to the distance between the two sides of the center tap. By setting the weight coefficient for weighted calculation, the detection range of the phase error can be expanded, and the linear relationship between the phase error and the output of the filter coefficient operation unit 111 can be improved. At this time, the output of the filter coefficient operation unit is a(k 11 -k 13 )+b(k 10 -k 14 ), a, b are weighting coefficients.

[0123] FIG6 shows the relationship between the phase error and the output of filter coefficient calculation unit 111 when the number of FIR filter taps is 25. This diagram illustrates the changing relationship between the phase error and the output of filter coefficient calculation unit 111. Clearly, the linear relationship between the phase error and the output of filter coefficient calculation unit 111 is very good. Thus, phase error information can be calculated using a very simple method: calculating the difference between at least one set of filter coefficients at symmetrical positions around the center tap of the adaptive filter.

[0124] The adaptive filter includes an odd number of filter taps and is at least three. For example, when the adaptive filter has three filter taps, the middle filter tap is used as the center tap, and the coefficient difference of the filter taps at the symmetrical positions on both sides is calculated as the phase error information.

[0125] When the number of filter taps of the adaptive filter is greater than three, the middle filter tap is taken as the center tap, and the differences between the two filter tap coefficients at symmetrical positions on both sides of the center tap are calculated respectively, and the corresponding weight coefficients are set, and then weighted as phase error information; in addition, even when the signal-to-noise ratio (SNR) of the read analog read signal is very poor or the decoding result of the maximum likelihood decoder has many errors, the coefficients of the adaptive filter will change very slowly through adaptive algorithms such as LMS, thereby reducing the influence of the noise of the analog read signal or the maximum likelihood decoding error.

[0126] As shown in Figure 7, the read clock generation unit 112 includes a loop filter 701, a loop gain coefficient module 702, and an adder 703, which are connected in sequence. The loop filter 701 is used to input the read clock error period output by the filter coefficient calculation unit 111 into the loop gain coefficient module 702 and perform loop gain compensation and phase compensation on the read clock error period using PLL technology. The purpose of gain compensation and phase compensation is to stabilize the read clock loop and reduce the error in the read clock period. Furthermore, the high-frequency attenuation characteristics of the loop filter 701 can reduce the impact of noise contained in the output of the filter coefficient calculation unit 111. The adder 703 is used to sum the output data of the loop gain coefficient module 702 with a preset read clock reference period to obtain the read clock period.

[0127] Figure 9 shows the response waveforms when a phase error is initially applied in this embodiment. Figure 9a shows the response waveform of the output signal of the filter coefficient calculation unit 111, Figure 9b shows the response waveform of the read clock cycle output by the read clock generation unit 112, and Figure 9c shows the response waveform of the phase error. The phase error causes the output of the filter coefficient calculation unit to change, and the read clock cycle responds to this change, eventually causing the phase error to converge toward zero.

[0128] The optical disc reading device of this embodiment can generate good and stable phase error information with a simple structure by calculating the tap coefficient difference of at least one group of symmetrical positions on both sides of the center tap of the adaptive filter even when the shortest mark length is close to the optical resolution limit and the inter-symbol interference is significantly increased. Even when the signal-to-noise ratio (SNR) of the analog read signal read from the information recording medium is very poor or the decoding result of the maximum likelihood decoder has many errors, the adaptive algorithm of the adaptive filter (such as LMS) can be used to make the coefficient change smooth, and the noise of the analog read signal and the error of the maximum likelihood decoder are not directly reflected in the phase error information, so that the read clock can be generated stably.

[0129] Example 2: An optical disc reader device that divides the optical head's photodetector into multiple areas, thereby reducing the effects of crosstalk between adjacent tracks and interference from preceding and following recording marks. Figure 2 is a block diagram of the optical disc reader device structure according to a second embodiment of the present invention. Information recording medium 201 is used to record and read optical information.

[0130] The optical disc reader device shown in FIG. 2 of this embodiment includes an optical head 202, preamplifiers 203a, 203b, 203c, and 203d, a sampler 207, an adaptive filter 210, a filter coefficient calculation unit 211, a read clock generation unit 212, a maximum likelihood decoder 213, and a target signal generation unit 214. The sampler 207 includes AD converters 204a, 204b, 204c, and 204d, memories 205a, 205b, 205c, and 205d, and interpolation units 206a, 206b, 206c, and 206d. The adaptive filter 210 includes FIR filters 208a, 208b, 208c, and 208d, an adaptive coefficient update unit 209, and an adder 215. FIG. 10 shows an example of a detector mounted on the optical head 202. The light spot irradiated onto the information recording medium 201 is divided into four regions for detection. The amount of crosstalk from adjacent tracks and interference from preceding and following recording marks varies in the signals detected in different areas. By properly dividing the light spot into multiple areas and performing appropriate calculations on the resulting read signals, crosstalk from adjacent tracks and interference from preceding and following recording marks can be reduced.

[0131] Specifically, in this embodiment, four regions are used as an example, but the number of divided regions is not limited to 4. The optical head 202 reads the information recorded on the information recording medium 201 and outputs the information independently to the detectors in the four regions.

[0132] Preamplifiers 203a, 203b, 203c, and 203d amplify the four analog read signals output by the optical head 202 at a specific gain and then input them to the sampler 207. Sampler 207 samples the outputs of preamplifiers 203a, 203b, 203c, and 203d using the output of the read clock generator 212 as a read clock cycle, generating digital signals that are input to the adaptive filter 210. Sampler 207 is comprised of A / D converters 204a, 204b, 204c, and 204d, memories 205a, 205b, 205c, and 205d, and interpolation units 206a, 206b, 206c, and 206d.

[0133] The outputs of preamplifiers 203a, 203b, 203c, and 203d are converted by AD converters 204a, 204b, 204c, and 204d before being sequentially stored in memories 205a, 205b, 205c, and 205d. The read addresses of memories 205a, 205b, 205c, and 205d are controlled by the output of a read clock generator 212. The AD-converted data stored in memories 205a, 205b, 205c, and 205d are read and input to interpolation operators 206a, 206b, 206c, and 206d.

[0134] Interpolation operators 206 a , 206 b , 206 c , and 206 d use data read from memories 205 a , 205 b , 205 c , and 205 d to sample and output the outputs of preamplifiers 203 a , 203 b , 203 c , and 203 d based on the read clock cycle output by read clock generator 212 .

[0135] The operations of interpolation calculators 206a, 206b, 206c, and 206d are the same as those in the first embodiment. When the output of read clock generator 212 indicates a time ΔT after the k-1th AD conversion, the output of the interpolation calculator is mem(k-1)+(mem(k)-mem(k-1))·ΔT / T. Here, mem(k) is the value of the memory storing the kth AD conversion data, and T is the AD conversion period. While the interpolation process in the above equation is linear interpolation, other interpolation methods may also be used.

[0136] The sampler 207 in Figure 2 is composed of AD converters 204a, 204b, 204c, 204d, memories 205a, 205b, 205c, 205d and interpolation operators 206a, 206b, 206c, 206d. It can also be composed of only AD converters 204a, 204b, 204c, 204d, or AD converters 204a, 204b, 204c, 204d and memories 205a, 205b, 205c, 205d.

[0137] When the sampling timing variation is very small, or when the sampling timing does not require very high precision, it can be composed of AD converters 204a, 204b, 204c, 204d, or AD converters 204a, 204b, 204c, 204d and memories 205a, 205b, 205c, 205d to reduce the circuit scale.

[0138] In addition, the memory is composed of four memories 205a, 205b, 205c, and 205d. Alternatively, one memory may be divided into four areas to store the data of the AD converters 204a, 204b, 204c, and 204d.

[0139] The output of sampler 207 is waveform-shaped by adaptive filter 210 and input to maximum likelihood decoder 213. Target signal generator 214 generates a target signal using the output of maximum likelihood decoder 213. To make the output of adaptive filter 210 closer to the target signal generated by target generator 214, adaptive filter 210 gradually changes its filter characteristics.

[0140] The adaptive filter 210 is composed of FIR filters 208a, 208b, 208c, and 208d, an adaptive coefficient updating unit 209, and an adder 215. The outputs y of the FIR filters 208a, 208b, 208c, and 208d are a (n),y b (n),y c (n),y d (n) is as follows:

[0141] y a (n) = k aN x a (nN)+…+k am x a (nm)+…+k a1 x a (n-1)+k a0 x a (n)

[0142] y b (n) = kbN x b (nN)+…+k bm x b (nm)+…+k b1 x b (n-1)+k b0 x b (n)

[0143] y c (n) = k cN x c (nN)+…+k cm x c (nm)+…+k c1 x c (n-1)+k c0 x c (n)

[0144] y d (n) = k dN x d (nN)+…+k dm x d (nm)+…+k d1 x d (n-1)+k d0 x d (n)

[0145] Among them, x a (n),x b (n),x c (n),x d (n) is the input of the nth filter of FIR filters 208a, 208b, 208c, and 208d, respectively, and k aN ,…,k am ,…,k a0 is the coefficient of filter 208a, k bN ,…,k bm ,…,k b0 is the coefficient of filter 208b, k cN ,…,k cm ,…,k c0 is the coefficient of filter 208c, k dN ,…,k dm ,…,k d0 are the coefficients of filter 208d.

[0146] The output of the adder 215, that is, the output y(n) of the adaptive filter 210, is as follows:

[0147] y(n)=y a (n)+y b (n)+yc (n)+y d (n)

[0148] d(n) is the output of the target signal generating unit 214. The relationship between d(n) and the error e(n) of the output y(n) of the adaptive filter 210 is as follows:

[0149] e(n)=d(n)-y(n)

[0150] The coefficients of the FIR filters 208a, 208b, 208c, and 208d are shown in the following equations and are updated in sequence:

[0151] k am (n+1)=k am (n)+μe(n)x a (nm)

[0152] k bm (n+1)=k bm (n)+μe(n)x b (nm)

[0153] k cm (n+1)=k cm (n)+μe(n)x c (nm)

[0154] k dm (n+1)=k dm (n)+μe(n)x d (nm)

[0155] Where: μ is the gain coefficient, and the appropriate value is set according to stability and convergence speed.

[0156] When the signal-to-noise ratio (SNR) of the analog read signal from the information recording medium is poor, or when the maximum likelihood decoding result of the maximum likelihood decoder is erroneous, the outputs y of the FIR filters 208a, 208b, 208c, and 208d are a (n),y b (n),y c (n),y d There may be noise in the output d(n) or the target signal generating unit 214. By setting an appropriate μ value, the coefficients of the FIR filters 208a, 208b, 208c, and 208d can be changed slowly, thereby reducing the influence of the noise.

[0157] The adaptive algorithms in the above-described embodiment include, but are not limited to, the LMS adaptive algorithm; other adaptive algorithms may also be used herein. The maximum likelihood decoder 213 performs maximum likelihood decoding on the shaped digital read signal output by the adaptive filter 210, and outputs the decoding result as digital data. The maximum likelihood decoder 213 may utilize, for example, a Viterbi decoder. The digital data obtained after demodulation and error correction of the data output by the maximum likelihood decoder 213 is the information recorded on the information recording medium 201 that was finally read. The filter coefficient calculation unit 211 calculates the filter coefficients of the adaptive filter 210 to generate phase error information of the read clock.

[0158] Specifically, based on the characteristic that the filter coefficients are symmetrical about the center tap when the sampling timing error of the signal is 0, the sampling timing error information of the signal, that is, the phase error information, can be obtained by calculating the difference between the coefficients of the tap pairs at symmetrical positions on both sides of the center tap.

[0159] When the number of taps of FIR filters 208a, 208b, 208c, and 208d is 25, the 13th tap k a12 、k b12 、k c12 、k d12 are the center taps respectively.

[0160] The tap pairs symmetrically located on either side of the center tap are:

[0161] FIR filter 208a:

[0162] k a11 and k a13 、k a10 and k a14 、k a9 and k a15 、k a8 and k a16 、k a7 and k a17 、k a6 and k a18 、k a5 and k a19 、k a4 and k a20 、k a3 and k a21 、k a2 and k a22 、k a1 and k a23 、k a0 and k a24 .

[0163] FIR filter 208b:

[0164] k b11 and k b13 、k b10 and k b14 、k b9 and k b15 、k b8 and k b16 、k b7 and k b17 、k b6 and k b18 、k b5 and k b19 、k b4 and k b20 、k b3 and k b21 、k b2 and k b22 、k b1 and k b23 、k b0 and k b24 .

[0165] FIR filter 208c:

[0166] k c11 and k c13 、k c10 and k c14 、k c9 and k c15 、k c8 and k c16 、k c7 and k c17 、k c6 and k c18 、k c5 and k c19 、k c4 and k c20 、k c3 and k c21 、k c2 and k c22 、k c1 and k c23 、k c0 and k c24 .

[0167] FIR filter 208d:

[0168] k d11 and k d13 、k d10 and k d14 、k d9 and k d15 、k d8 and k d16 、k d7 and kd17 、k d6 and k d18 、k d5 and k d19 、k d4 and k d20 、k d3 and k d21 、k d2 and k d22 、k d1 and k d23 、k d0 and k d24 .

[0169] The difference is calculated using at least one group of tap pairs symmetrical on both sides of the center tap of at least one FIR filter as the phase error information.

[0170] For example, when using the coefficients at ±1 positions on both sides of the center tap of the FIR filters 208a, 208b, 208c, and 208d, the output of the filter coefficient calculation unit 211 is (k a11 -k a13 )+(k b11 -k b13 )+(k c11 -k c13 )+(k d11 -k d13 ).

[0171] For example, when using the filter coefficients at the ±1 and ±2 positions on both sides of the center tap of the FIR filters 208a, 208b, 208c, and 208d, the output of the filter coefficient calculation unit 211 is

[0172] ((k a11 -k a13 )+(k a10 -k a14 ))+((k b11 -k b13 )+(k b10 -k b14 ))+((k c11 -k c13 )+(k c10 -k c14 ))+((k d11 -k d13 )+(k d10 -k d14 )).

[0173] For example, when using the filter coefficients at ±1 positions on both sides of the center tap of the FIR filters 208a and 208b, the output of the filter coefficient calculation unit 211 is (k a11 -k a13)+(k b11 -k b13 )

[0174] In addition, when using multiple FIR filter coefficients, weights may be added to each FIR filter coefficient to correct errors in detection sensitivity of each photodetector of the optical head 201 and errors in detection characteristics caused by different light spot partitions.

[0175] In addition, weights can be added to the FIR filter coefficients according to the distances on both sides of the center tap. By appropriate weighted calculations, the detection range of the phase error can be expanded, and the linear relationship between the phase error and the output of the filter coefficient operation unit 211 can be improved.

[0176] For example, when using the filter coefficients at positions ±1 and ±2 on either side of the center tap of FIR filters 208a, 208b, 208c, and 208d, after adding weights to the coefficients of each FIR filter and at different positions from the center tap, the output of the filter coefficient calculation unit 211 is:

[0177] A(a(k a11 -k a13 )+b(k a10 -k a14 ))+B(a(k b11 -k b13 )+b(k b10 -k b14 ))+C(a(k c11 -k c13 )+b(k c 10 -k c14 ))+D(a(k d11 -k d13 )+b(k d10 -k d14 )), where A, B, C, D, a, and b are weighting coefficients.

[0178] In this embodiment, when the optical head 202's photodetector is divided into multiple regions, the time difference between the multiple outputs of the photodetector is almost zero, eliminating the need to calculate phase error information for each photodetector. The filter coefficient calculation unit 211 can generate phase error information using a simple method: calculating the coefficient differences between at least one pair of taps located symmetrically on either side of the center tap of at least one FIR filter constituting the adaptive filter 210. Furthermore, even when the analog read signal's signal-to-noise ratio (SNR) is poor or the maximum likelihood decoder's decoding results are erroneous, the adaptive filter coefficients change very slowly due to adaptive algorithms such as LMS, minimizing the impact of analog read signal noise or maximum likelihood decoding errors.

[0179] Read clock generation unit 212 generates a read clock cycle, i.e., sampling timing information, based on the output of filter coefficient calculation unit 211. The structure and operation of the read clock generation unit are identical to those in the first embodiment. Sampler 207 has four inputs, all based on the output of filter coefficient calculation unit 211, and all sampled using the same timing.

[0180] In the above-mentioned embodiment, under the condition that the light detector of the optical head is divided into multiple areas, the optical disc reading device can generate stable phase error information with a good linear relationship in a simple way by calculating the coefficient difference of the tap pairs at symmetrical positions on both sides of the center tap of at least one group of FIR filters constituting the adaptive filter. Moreover, under the condition that the signal-to-noise ratio (SNR) of the analog read signal read from the information recording medium is very poor or the decoding result of the maximum likelihood decoder has many errors, the adaptive algorithm of the adaptive filter (such as LMS) can also be used to make the coefficient change smooth, and the noise of the analog read signal and the error of the maximum likelihood decoder are not directly reflected in the phase error information, so that the read clock can be generated stably.

[0181] Embodiment 3: An optical disc reading device with a crosstalk cancellation function can reduce the impact of crosstalk by calculating the difference between the read signal of the target track and the read signal of its adjacent track when the track density becomes higher and the crosstalk signal impact of adjacent tracks becomes obvious.

[0182] FIG3 is a block diagram of the structure of an optical disc reading device in a third embodiment of the present invention.

[0183] The information recording medium 301 is an information recording medium for recording and reading optical information.

[0184] The optical disc reading device of FIG3 includes an optical head 302, preamplifiers 303a, 303b, and 303c, samplers 307a, 307b, and 307c, an adaptive filter 310, filter coefficient calculation units 311a, 311b, and 311c, read clock generation units 312a, 312b, and 312c, a maximum likelihood decoder 313, and a target signal generation unit 314. The sampler 307a includes an AD converter 304a, a memory 305a, and an interpolation operator 306a; the sampler 307b includes an AD converter 304b, a memory 305b, and an interpolation operator 306b; the sampler 307c includes an AD converter 304c, a memory 305c, and an interpolation operator 306c; and the adaptive filter 310 includes FIR filters 308a, 308b, and 308c, an adaptive coefficient update unit 309, and an adder 315.

[0185] Optical head 302 emits a three-part beam toward information recording medium 301, outputting signals for the target track on information recording medium 301 and the tracks adjacent to it. The signal from the target track contains crosstalk from the adjacent tracks. To reduce this crosstalk, the signals from the adjacent tracks are subtracted from the signal from the target track to minimize the impact of the crosstalk.

[0186] However, the signals from the target track, the track adjacent to the left of the target track, and the track adjacent to the right of the target track are read by separate beams, resulting in a temporal misalignment among the three signals. To minimize crosstalk after subtracting the signals from the target track and the tracks adjacent to the target track, the signals from the target track, the track adjacent to the left of the target track, and the track adjacent to the right of the target track need to be sampled using separate timing sequences to ensure that the temporal misalignment among the three signals is not present.

[0187] The signal of the read target track on the information recording medium 301 read by the optical head 302 is amplified by a preamplifier 303a with a specific gain and then input to the sampler 307a.

[0188] The signal of the track adjacent to the left of the target track on the information recording medium 301 read by the optical head 302 is amplified by a preamplifier 303b with a specific gain and then input into the sampler 307b.

[0189] The signal of the track adjacent to the right of the target track on the information recording medium 301 read by the optical head 302 is amplified by a preamplifier 303c with a specific gain and then input into the sampler 307c.

[0190] The sampler 307 a samples the output of the preamplifier 303 a using the output of the read clock generating unit 312 a as a read clock cycle, and generates a digital signal which is input to the FIR filter 308 a .

[0191] The sampler 307b uses the output of the read clock generating unit 312b as a read clock cycle to sample the output of the preamplifier 303b, and generates a digital signal which is input to the FIR filter 308b.

[0192] The sampler 307c uses the output of the read clock generating unit 312c as a read clock cycle to sample the output of the preamplifier 303c, and generates a digital signal which is input to the FIR filter 308c.

[0193] The sampler 307a is composed of an AD converter 304a, a memory 305a, and an interpolation operator 306a.

[0194] The output of preamplifier 303a is converted by A / D converter 304a and then stored in memory 305a. The read address of memory 305a is controlled based on the output of read clock generator 312a, and the A / D converted data stored in memory 305a is read out and input to interpolator 306a. Interpolator 306a uses the data read from memory 305a and samples the output of preamplifier 303a based on the read clock cycle output by read clock generator 312a, and outputs the result.

[0195] The sampler 307b is composed of an AD converter 304b, a memory 305b, and an interpolation operator 306b.

[0196] The output of preamplifier 303b undergoes A / D conversion via A / D converter 304b and is subsequently stored in memory 305b. The read address of memory 305b is controlled based on the output of read clock generator 312b, and the A / D converted data stored in memory 305b is read out and input to interpolator 306b. Interpolator 306b uses the data read from memory 305b and samples the output of preamplifier 303b based on the read clock cycle output by read clock generator 312b, and outputs the result.

[0197] The sampler 307c is composed of an AD converter 304c, a memory 305c, and an interpolation operator 306c.

[0198] The output of preamplifier 303c undergoes A / D conversion via A / D converter 304c and is subsequently stored in memory 305c. The read address of memory 305c is controlled based on the output of read clock generator 312c, and the A / D converted data stored in memory 305c is read out and input to interpolator 306c. Interpolator 306c uses the data read from memory 305c and samples the output of preamplifier 303c based on the read clock cycle output by read clock generator 312c, and outputs the sampled data.

[0199] The operation of interpolation calculators 306a, 306b, and 306c is the same as in the first embodiment. When the outputs of read clock generators 312a, 312b, and 312c indicate a time ΔT after the k-1th AD conversion, the output of the interpolation calculator is mem(k-1) + (mem(k) - mem(k-1)) ΔT / T. Here, mem(k) is the value of the memory storing the kth AD conversion data, and T is the AD conversion period.

[0200] In addition, the interpolation processing in the above formula is linear interpolation, and other interpolation processing methods can also be used.

[0201] The samplers 307a, 307b, 307c in Figure 3 are composed of AD converters 304a, 304b, 304c, memories 305a, 305b, 305c and interpolation operators 306a, 306b, 306c, or can be composed of only AD converters 304a, 304b, 304c, or of AD converters 304a, 304b, 304c and memories 305a, 305b, 305c.

[0202] When the sampling timing variation is small or the sampling timing does not require high precision, the circuit can be composed of AD converters 304a, 304b, 304c, or AD converters 304a, 304b, 304c and memories 305a, 305b, 305c to reduce the circuit scale.

[0203] In addition, the memory is composed of three memories 305a, 305b, and 305c. Alternatively, one memory may be divided into three areas to store the data of the AD converters 304a, 304b, and 304c.

[0204] In the adaptive filter 310 , the outputs of the samplers 307 a , 307 b , and 307 c are waveform-shaped by the FIR filters 308 a , 308 b , and 308 c , and are summed by the adder 315 before being input into the maximum likelihood decoder 313 .

[0205] The input to the FIR filter 308a is the read target track signal containing the crosstalk component of the left and right adjacent tracks, and the input to the FIR filters 308b and 308c are the read signals of the left and right adjacent tracks of the read target track, respectively.

[0206] Target signal generation unit 314 generates a target signal using the output of maximum likelihood decoder 313. The filter characteristics of FIR filters 308a, 308b, and 308c are sequentially changed to bring the outputs closer to the target signal generated by target generation unit 314. As a result, the filter characteristics of FIR filters 308a, 308b, and 308c adaptively remove crosstalk components from the summed signal of FIR filters 308a, 308b, and 308c.

[0207] The adaptive filter 310 is composed of FIR filters 308 a , 308 b , 308 c , an adaptive coefficient updating unit 309 , and an adder 315 .

[0208] The outputs y of the FIR filters 308a, 308b, 308c a (n),y b (n),y c(n) is as follows:

[0209] y a (n) = k aN x a (nN)+…+k am x a (nm)+…+k a1 x a (n-1)+k a0 x a (n)

[0210] y b (n) = k bN x b (nN)+…+k bm x b (nm)+…+k b1 x b (n-1)+k b0 x b (n)

[0211] y c (n) = k cN x c (nN)+…+k cm x c (nm)+…+k c1 x c (n-1)+k c0 x c (n)

[0212] x a (n),x b (n),x c (n) is the n-th filter input of FIR filters 308a, 308b, and 308c, respectively, and k aN ,…,k am ,…,k a0 is the coefficient of filter 308a, k bN ,…,k bm ,…,k b0 is the coefficient of filter 308b, k cN ,…,k cm ,…,k c0 are the coefficients of filter 308c.

[0213] The output of the adder 315, that is, the output y(n) of the adaptive filter 310, is as follows:

[0214] y(n)=y a (n)+y b (n)+y c (n)

[0215] d(n) is the output of the target signal generating unit 314. The relationship between d(n) and the error e(n) of the output y(n) of the adaptive filter 310 is as follows:

[0216] e(n)=d(n)-y(n)

[0217] The coefficients of the FIR filters 308a, 308b, and 308c are updated in sequence as shown below:

[0218] k am (n+1)=k am (n)+μe(n)x a (nm)

[0219] k bm (n+1)=k bm (n)+μe(n)x b (nm)

[0220] k cm (n+1)=k cm (n)+μe(n)x c (nm)

[0221] Where: μ is the gain coefficient, and the appropriate value is set according to stability and convergence speed.

[0222] When the signal-to-noise ratio (SNR) of the analog read signal from the information recording medium 301 is poor, or when the maximum likelihood decoding result of the maximum likelihood decoder 313 has many errors, the outputs y of the FIR filters 308a, 308b, and 308c are a (n),y b (n),y c There may be noise in the output d(n) or the target signal generating unit 314. By setting an appropriate μ value, the coefficients of the FIR filters 308a, 308b, and 308c can be changed slowly, thereby reducing the influence of the noise.

[0223] The adaptive algorithm in the above embodiment is LMS, but other adaptive algorithms can also be used here.

[0224] The maximum likelihood decoder 313 performs maximum likelihood decoding on the shaped digital read signal output by the adaptive filter 310 and outputs the decoding result as digital data.

[0225] The maximum likelihood decoder 313 may use a Viterbi decoder, for example. The digital data obtained after demodulation and error correction of the data output by the maximum likelihood decoder 313 is the information recorded in the information recording medium 301 that is finally read.

[0226] Filter coefficient calculation unit 311a calculates the filter coefficients of FIR filter 308a to generate phase error information of the read clock used by sampler 307a. Filter coefficient calculation unit 311b calculates the filter coefficients of FIR filter 308b to generate phase error information of the read clock used by sampler 307b. Filter coefficient calculation unit 311c calculates the filter coefficients of FIR filter 308c to generate phase error information of the read clock used by sampler 307c.

[0227] Specifically, based on the characteristic that the filter coefficients are symmetrical about the center tap when the sampling timing error of the signal is 0, the sampling timing error information of the signal, that is, the phase error information, can be obtained by calculating the difference between the coefficients of the tap pairs at symmetrical positions on both sides of the center tap.

[0228] When the number of taps of FIR filters 308a, 308b, and 308c is 25, the 13th tap k a12 、k b12 、k c12 are the center taps respectively.

[0229] In the FIR filter 308a, the tap pairs at symmetrical positions on both sides of the center tap are:

[0230] k a11 and k a13 、k a10 and k a14 、k a9 and k a15 、k a8 and k a16 、k a7 and k a17 、k a6 and k a18 、k a5 and k a19 、k a4 and k a20 、k a3 and k a21 、k a2 and k a22 、k a1 and k a23 、k a0 and k a24 .

[0231] The filter coefficient calculation unit 311a calculates the difference as phase error information using at least one set of tap pairs that are symmetrical on both sides of the center tap.

[0232] For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 311a is ka11 -k a13 .

[0233] For example, when using the coefficients at the ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient calculation unit 311a is (k a11 -k a13 )+(k a10 -k a14 ).

[0234] In the FIR filter 308b, the tap pairs at symmetrical positions on both sides of the center tap are:

[0235] k b11 and k b13 、k b10 and k b14 、k b9 and k b15 、k b8 and k b16 、k b7 and k b17 、k b6 and k b18 、k b5 and k b19 、k b4 and k b20 、k b3 and k b21 、k b2 and k b22 、k b1 and k b23 、k b0 and k b24 .

[0236] The filter coefficient calculation unit 311b calculates the difference as phase error information using at least one set of tap pairs that are symmetrical on both sides of the center tap.

[0237] For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 311b is k b11 -k b13 .

[0238] For example, when using the coefficients at the ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient operation unit 311b is (k b11 -k b13 )+(k b10 -k b14 ).

[0239] In the FIR filter 308c, the tap pairs at symmetrical positions on both sides of the center tap are:

[0240] k c11 and kc13 、k c10 and k c14 、k c9 and k c15 、k c8 and k c16 、k c7 and k c17 、k c6 and k c18 、k c5 and k c19 、k c4 and k c20 、k c3 and k c21 、k c2 and k c22 、k c1 and k c23 、k c0 and k c24 .

[0241] The filter coefficient calculation unit 311c uses at least one set of tap pairs that are symmetrical on both sides of the center tap to calculate the difference as phase error information.

[0242] For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 311c is k c11 -k c13 .

[0243] For example, when using the coefficients at ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient calculation unit 311c is (k c11 -k c13 )+(k c10 -k c14 ).

[0244] In addition, weights can be added to the FIR filter coefficients according to the distances on both sides of the center tap. By appropriate weighted calculations, the detection range of the phase error can be expanded, and the linear relationship between the phase error and the output of the filter coefficient operation units 311a, 311b, and 311c can be improved.

[0245] In the specific embodiment of FIG3 , the signal from the target track, the signal from the track adjacent to the left of the target track, and the signal from the track adjacent to the right of the target track are each independent, single signals. Alternatively, as in specific embodiment 2, the detectors for each track can be divided into multiple groups, with each track outputting multiple read signals. In this case, the read signals for each track are filtered using multiple FIR filters. Each track is then grouped, and the filter coefficient calculation unit for each group uses at least one pair of taps symmetrically located on either side of the center tap of at least one FIR filter within the group to calculate the coefficient difference as phase error information.

[0246] When using multiple FIR filter coefficients, a weight may be added to each FIR filter coefficient to correct errors in detection sensitivity of each light detector of the optical head 301 and errors in detection characteristics caused by different light spot partitions.

[0247] When the light beam of the optical head 302 is divided into multiple beams in this embodiment, the signal of reading the target track, the signal of reading the track adjacent to the left of the target track, and the signal of reading the track adjacent to the right of the target track are read separately using independent light beams. Since the phase error information of the signal of reading the target track, the signal of reading the track adjacent to the left of the target track, and the signal of reading the track adjacent to the right of the target track are independently detected and sampled, the time relationship of each signal will not be misaligned, which can achieve the purpose of fully reducing the crosstalk component of the adjacent tracks contained in the signal of reading the target track.

[0248] The filter coefficient calculation units 311a, 311b, and 311c can independently calculate and generate phase error information for the signal reading the target track, the signal reading the track adjacent to the left of the target track, and the signal reading the track adjacent to the right of the target track using a simple method. Specifically, they calculate the coefficient differences between the tap pairs located symmetrically on either side of the center tap of at least one set of FIR filters 308a, 308b, and 308c that constitute the adaptive filter 310. Furthermore, even when the signal-to-noise ratio (SNR) of the analog read signal is poor or the maximum likelihood decoder decodes a number of errors, the adaptive filter coefficients change very slowly due to the presence of adaptive algorithms such as LMS, thereby minimizing the impact of analog read signal noise or maximum likelihood decoding errors.

[0249] Read clock generation units 312a, 312b, and 312c generate read clock cycles, i.e., sampling timing information, based on the outputs of filter coefficient calculation units 311a, 311b, and 311c. The structure and operation of the read clock generation units are the same as those in the first embodiment. Samplers 307a, 307b, and 307c independently perform sampling using the optimal timing based on the outputs of filter coefficient calculation units 311a, 311b, and 311c.

[0250] In the above-mentioned embodiment, in order to reduce the influence of adjacent track crosstalk caused by the increase in track density, the optical head of the optical disc reading device reads the target track signal and the signal of the track adjacent to it with independent light beams respectively. Under this condition, by calculating the coefficient difference of the tap pairs at symmetrical positions on both sides of at least one group of center taps of the FIR filter that constitutes the adaptive filter of each read signal, stable phase error information with a good linear relationship can be generated in a simple way. Moreover, since the various read signals are sampled independently of each other, the time relationship of each read signal can perform high-precision adjacent track crosstalk component reduction without any misalignment.

[0251] Example 4: An optical disc reading device with a crosstalk cancellation function can reduce the impact of crosstalk by calculating the difference between the read signal of the target track and the read signal of its adjacent track when the track density becomes higher and the crosstalk signal impact of adjacent tracks becomes obvious.

[0252] FIG4 is a block diagram of the structure of an optical disc reading device in a fourth embodiment of the present invention.

[0253] The information recording medium 401 is an information recording medium for recording and reading optical information.

[0254] The optical disc reader of FIG4 includes an optical head 402, a preamplifier 403, samplers 407a, 407b, and 407c, an adaptive filter 410, filter coefficient calculation units 411a, 411b, and 411c, read clock generation units 412a, 412b, and 412c, a maximum likelihood decoder 413, and a target signal generation unit 414. The AD converter 404 is shared by the samplers 407a, 407b, and 407c. The sampler 407a includes an AD converter 404, a memory 405a, and an interpolation operator 406a; the sampler 407b includes an AD converter 404, a memory 405b, and an interpolation operator 406b; the sampler 407c includes an AD converter 404, a memory 405c, and an interpolation operator 406c; the adaptive filter 410 includes FIR filters 408a, 408b, 408c, an adaptive coefficient update unit 409, and an adder 415.

[0255] The optical head 402 emits a light beam to the information recording medium 401 and outputs a read signal of the information recording medium 401; the read signal of the information recording medium 401 read by the optical head 402 is amplified with a specific gain by the preamplifier 403 and input into the AD converter 404; through the movement of the optical head 402, a light beam can be emitted to the target track and the signal can be read.

[0256] A light beam is emitted toward the target track to be read, and the output of the AD converter 404 is sequentially stored in the memory 405a; a light beam is emitted toward the track adjacent to the left of the target track to be read, and the output of the AD converter 404 is sequentially stored in the memory 405b; a light beam is emitted toward the track adjacent to the right of the target track to be read, and the output of the AD converter 404 is sequentially stored in the memory 405c.

[0257] When reading data, the signal of the read target track stored in the memory 405a is sampled in the memory 405a and the interpolation operator 406a using the output of the read clock generation unit 412a as the read clock cycle, and the digital read signal is input into the FIR filter 408a.

[0258] At the same time, the signal of the adjacent track to the left of the read target track stored in the memory 405b is sampled and output in the memory 405b and the interpolation operator 406b with the output of the read clock generation unit 412b as the read clock cycle, and the digital read signal is input into the FIR filter 408b; the signal of the adjacent track to the right of the read target track stored in the memory 405c is sampled and output in the memory 405c and the interpolation operator 406c with the output of the read clock generation unit 412c as the read clock cycle, and the digital read signal is input into the FIR filter 408c.

[0259] The operation of interpolation calculators 406a, 406b, and 406c is the same as in the first embodiment. When the outputs of read clock generators 412a, 412b, and 412c indicate a time ΔT after the k-1th AD conversion, the output of the interpolation calculator is mem(k-1) + (mem(k) - mem(k-1)) · ΔT / T. Here, mem(k) is the value of the memory storing the kth AD conversion data, and T is the AD conversion period.

[0260] In addition, the interpolation processing in the above formula is linear interpolation, and other interpolation processing methods can also be used.

[0261] The sampler 407a in FIG4 is composed of the AD converter 404, the memory 405a and the interpolation operator 406a, but may be composed of only the AD converter 404, or of the AD converter 404 and the memory 405a.

[0262] When the variation range of the sampling timing is very small, or when the sampling timing does not require very high accuracy, it can be composed of the AD converter 404, or the AD converter 404 and the memory 405a, so as to reduce the circuit scale.

[0263] In Figure 4 , samplers 407b and 407c are composed of AD converter 404, memories 405b and 405c, and interpolation units 406b and 406c. Alternatively, they can consist solely of AD converter 404 or of AD converter 404 and memories 405b and 405c. When the sampling timing varies slightly or when high precision is not required, the circuit can be reduced by consisting of AD converter 404 or of AD converter 404 and memories 405b and 405c. Furthermore, the memory can consist of three memories, namely memories 405a, 405b, and 405c, or a single memory divided into three areas can be used to store data from AD converters 405a, 405b, and 405c.

[0264] In the adaptive filter 410, the outputs of the samplers 407a, 407b, and 407c are waveform-shaped by the FIR filters 408a, 408b, and 408c, and are added by the adder 415 and input into the maximum likelihood decoder 413; the input into the FIR filter 408a is the read target track signal containing the crosstalk components of the left and right adjacent tracks, and the input into the FIR filters 408b and 408c is the read signals of the two adjacent tracks on the left and right of the read target track, respectively.

[0265] Target signal generation unit 414 generates a target signal using the output of maximum likelihood decoder 413. To bring the outputs of FIR filters 408a, 408b, and 408c closer to the target signal generated by target generation unit 414, the filter characteristics are sequentially modified. Consequently, the filter characteristics of FIR filters 408a, 408b, and 408c adaptively remove crosstalk components from the summed signal of FIR filters 408a, 408b, and 408c. Adaptive filter 410 comprises FIR filters 408a, 408b, and 408c, adaptive coefficient update unit 409, and adder 415.

[0266] The outputs y of the FIR filters 408a, 408b, 408c a (n),y b (n),y c (n) is as follows:

[0267] y a (n) = k aN x a (nN)+…+k am x a (nm)+…+k a1 x a (n-1)+k a0 x a (n)

[0268] y b (n) = k bN x b (nN)+…+k bm x b (nm)+…+k b1 x b (n-1)+k b0 x b (n)

[0269] y c (n) = k cN x c (nN)+…+k cm x c (nm)+…+k c1 x c (n-1)+k c0 x c (n)

[0270] Among them, x a (n),x b (n),x c (n) is the input of the nth filter of FIR filters 408a, 408b, and 408c, respectively, and k aN ,…,k am ,…,k a0 is the coefficient of filter 408a, k bN ,…,k bm ,…,k b0 is the coefficient of filter 408b, k cN ,…,k cm ,…,k c0 are the coefficients of filter 408c.

[0271] The output of the adder 415, that is, the output y(n) of the adaptive filter 410, is as follows:

[0272] y(n)=y a (n)+y b (n)+y c (n)

[0273] Define d(n) as the output of the target signal generating unit 414, then the relationship between d(n) and the error e(n) of the output y(n) of the adaptive filter 410 is as follows:

[0274] e(n)=d(n)-y(n)

[0275] The coefficients of FIR filters 408a, 408b, and 408c are updated in sequence as shown below:

[0276] k am(n+1)=k am (n)+μe(n)x a (nm)

[0277] k bm (n+1)=k bm (n)+μe(n)x b (nm)

[0278] k cm (n+1)=k cm (n)+μe(n)x c (nm)

[0279] Where: μ is the gain coefficient, and the appropriate value is set according to stability and convergence speed.

[0280] When the signal-to-noise ratio (SNR) of the analog read signal from the information recording medium 401 is poor, or when the maximum likelihood decoding result of the maximum likelihood decoder 413 has many errors, the outputs y of the FIR filters 408a, 408b, and 408c are a (n),y b (n),y c There may be noise in the output d(n) or the target signal generating unit 414. By setting an appropriate μ value, the coefficients of the FIR filters 408a, 408b, and 408c can be slowly changed, thereby reducing the influence of the noise.

[0281] The adaptive algorithm in the above embodiment is LMS, but other adaptive algorithms can also be used here.

[0282] Maximum likelihood decoder 413 performs maximum likelihood decoding on the shaped digital read signal output by adaptive filter 410, and outputs the decoding result as digital data. Maximum likelihood decoder 413 can utilize, for example, a Viterbi decoder. The digital data obtained after demodulation and error correction on the data output by maximum likelihood decoder 413 is the information recorded on information recording medium 401 that was finally read.

[0283] The filter coefficient operation unit 411a operates on the filter coefficients of the FIR filter 408a to generate the phase error information of the read clock used by the sampler 407a; the filter coefficient operation unit 411b operates on the filter coefficients of the FIR filter 408b to generate the phase error information of the read clock used by the sampler 407b; the filter coefficient operation unit 411c operates on the filter coefficients of the FIR filter 408c to generate the phase error information of the read clock used by the sampler 407c.

[0284] Specifically, based on the characteristic that the filter coefficients are symmetrical about the center tap when the sampling timing error of the signal is 0, the sampling timing error information of the signal, that is, the phase error information, can be obtained by calculating the difference between the coefficients of the tap pairs at symmetrical positions on both sides of the center tap.

[0285] When the number of taps of FIR filters 408a, 408b, and 408c is 25, the 13th tap k a12 、k b12 、k c12 are the center taps respectively.

[0286] In the FIR filter 408a, the tap pairs symmetrically located on either side of the center tap are:

[0287] k a11 and k a13 、k a10 and k a14 、k a9 and k a15 、k a8 and k a16 、k a7 and k a17 、k a6 and k a18 、k a5 and k a19 、k a4 and k a20 、k a3 and k a21 、k a2 and k a22 、k a1 and k a23 、k a0 and k a24 .

[0288] The filter coefficient calculation unit 411 a calculates a difference as phase error information using at least one set of tap pairs that are symmetrical on both sides of the center tap.

[0289] For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411a is k a11 -k a13 .

[0290] For example, when using the coefficients at the ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411a is (k a11 -k a13 )+(k a10 -k a14 ).

[0291] In the FIR filter 408b, the tap pairs at symmetrical positions on both sides of the center tap are:

[0292] k b11 and k b13 、k b10 and k b14 、k b9 and k b15 、k b8 and k b16 、k b7 and k b17 、k b6 and k b18 、k b5 and k b19 、k b4 and k b20 、k b3 and k b21 、k b2 and k b22 、k b1 and k b23 、k b0 and k b24 .

[0293] The filter coefficient calculation unit 411b uses at least one set of tap pairs symmetrical on both sides of the center tap to calculate the difference as phase error information. For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411b is k b11 -k b13 For example, when using the coefficients at ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411b is (k b11 -k b13 )+(k b10 -k b14 ).

[0294] In the FIR filter 408c, the tap pairs symmetrically located on either side of the center tap are:

[0295] k c11 and k c13 、k c10 and k c14 、k c9 and k c15 、k c8 and k c16 、k c7 and k c17 、k c6 and k c18 、k c5 and k c19 、k c4 and k c20 、k c3 and k c21 、k c2 and kc22 、k c1 and k c23 、k c0 and k c24 .

[0296] The filter coefficient calculation unit 411c uses at least one set of tap pairs that are symmetrical on both sides of the center tap to calculate the difference as phase error information.

[0297] For example, when using the coefficients at ±1 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411c is k c11 -k c13 .

[0298] For example, when using the coefficients at the ±1 and ±2 positions on both sides of the center tap, the output of the filter coefficient calculation unit 411c is (k c11 -k c13 )+(k c10 -k c14 ).

[0299] In addition, weights can be added to the FIR filter coefficients based on the distance between the center taps. By appropriate weighted calculations, the detection range of the phase error can be expanded, and the linear relationship between the phase error and the output of the filter coefficient calculation units 411a, 411b, and 411c can be improved.

[0300] In the specific embodiment of FIG4 , the signal from the target track, the signal from the track adjacent to the left of the target track, and the signal from the track adjacent to the right of the target track are each independent, single signals. Alternatively, as in specific embodiment 2, the detectors for each track can be divided into multiple groups, with each track outputting multiple read signals. In this case, the read signals for each track are filtered using multiple FIR filters. Each track is then grouped, and the filter coefficient calculation unit for each group uses at least one pair of taps symmetrically positioned on either side of the center tap of at least one FIR filter within the group to calculate the coefficient difference as phase error information.

[0301] When using multiple FIR filter coefficients, a weight may be added to each FIR filter coefficient to correct errors in detection sensitivity of each light detector of the optical head 401 and errors in detection characteristics caused by different light spot partitions.

[0302] FIG. 11 shows the improvement effect of adjacent track crosstalk in this specific embodiment.

[0303] The horizontal axis is the signal-to-noise ratio (SNR) of the read signal, and the vertical axis is the bit error rate. For the same SNR, the lower the bit error rate, the better the improvement.

[0304] The four broken lines in FIG11 represent the target track signal read in this specific embodiment, and the situations where the target track signal and the left and right adjacent track signals are sampled using the same timing when there is a time difference of 2T, 4T, and 8T between the target track signal and the left and right adjacent track signals, respectively. T is the read clock period.

[0305] When the target track signal and the left and right adjacent track signals are sampled using the same timing, the greater the time difference, the greater the bit error rate. If this specific implementation is adopted, the bit error rate can be significantly reduced.

[0306] In this embodiment, the target track signal and the signals of the left and right adjacent tracks of the target track read by the optical head 402 are respectively stored in the memory, and then the target track signal and the signals of the left and right adjacent tracks of the target track are read from the memory in parallel. Since the phase error information of the signal of the target track, the signal of the left adjacent track of the target track, and the signal of the right adjacent track of the target track are independently detected and sampled, the time relationship of each signal will not be misaligned, which can achieve the purpose of fully reducing the crosstalk component of the adjacent tracks contained in the target track signal.

[0307] The filter coefficient calculation units 411a, 411b, and 411c can independently calculate and generate phase error information for the signal reading the target track, the signal reading the track adjacent to the left of the target track, and the signal reading the track adjacent to the right of the target track using a simple method. Specifically, they calculate the coefficient differences between the tap pairs located symmetrically on either side of the center tap of at least one set of FIR filters 408a, 408b, and 408c that constitute the adaptive filter 410. Furthermore, even when the signal-to-noise ratio (SNR) of the analog read signal is poor or the maximum likelihood decoder decodes a number of errors, the adaptive filter coefficients change very slowly due to the presence of adaptive algorithms such as LMS, thereby minimizing the impact of analog read signal noise or maximum likelihood decoding errors. The read clock generation units 412a, 412b, and 412c generate read clock cycles, i.e., sampling timing information, based on the outputs of the filter coefficient operation units 411a, 411b, and 411c. The composition and operation of the read clock generation units are the same as those in the first specific implementation. The samplers 407a, 407b, and 407c independently use the optimal timing for sampling based on the outputs of the filter coefficient operation units 411a, 411b, and 411c.

[0308] In the above-described embodiment, to reduce the impact of adjacent track crosstalk caused by increased track density, an optical head in an optical disc reader device separately reads and stores the target track signal and the signals of the adjacent tracks in a memory, and then simultaneously reads the target track signal and the signals of the adjacent tracks from the memory. Under these conditions, by calculating the coefficient differences of at least one pair of taps symmetrically located on either side of the center tap of a FIR filter constituting an adaptive filter for each read signal, stable phase error information with excellent linearity can be generated using a simple method. Furthermore, because the read signals are sampled independently, the temporal relationship between each read signal is not misaligned, enabling high-precision adjacent track crosstalk reduction. Furthermore, even when the signal-to-noise ratio (SNR) of the analog read signal from the information recording medium is poor or the decoding result of the maximum likelihood decoder is erroneous, the adaptive filter's adaptive algorithm (e.g., LMS) can smooth the coefficient changes, preventing the noise of the analog read signal and the errors of the maximum likelihood decoder from being directly reflected in the phase error information, thereby enabling stable read clock generation.

[0309] Furthermore, when the optical head of the optical disc reading device moves and changes its radial position during retrieval, the time relationship between the read signal of the target track and the read signal of the adjacent track changes. By applying this construction method, it is no longer necessary to calculate the time relationship between the read signal of the target track and the read signal of the adjacent track for correction during each retrieval. Instead, during the signal reading process, the read signal of the target track and the read signal of the adjacent track are automatically and independently sampled in synchronization with their respective optimal read clocks, without the need for redundant processing and without slowing down the overall processing speed.

[0310] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical disc reading device, characterized in that: include: An optical head, a sampler, an adaptive filter, a filter coefficient operation unit, and a read clock generation unit; The optical head is used to read the information recorded on the information recording medium and output an analog read signal; The sampler is used to perform a sampling operation on an analog read signal read from the information recording medium according to a sampling clock; The adaptive filter is used to perform filtering and shaping processing on the output of the sampler, and adaptively update the coefficients of the filter according to the output of the adaptive filter and the expected target signal; The filter coefficient operation unit is used to operate the filter coefficient of the adaptive filter, generate the phase error information of the read clock and output it to the read clock generation unit; The read clock generating unit is used to generate a read clock cycle according to the output of the filter coefficient operation unit; The read clock cycle is used as a sampling clock for the sampler to perform a sampling operation.

2. The optical disc reading device according to claim 1, characterized in that: The adaptive filter is one or more FIR filters and is provided with one or more adaptive coefficient updating units; The adaptive coefficient updating unit is used to adaptively update the filter coefficients of the FIR filter according to the output of the FIR filter and the expected target signal.

3. The optical disc reading device according to claim 2, characterized in that: The filter coefficient operation unit operates the filter coefficient of the adaptive filter to generate the phase error information of the read clock. Define and number a center tap of the FIR filter and a plurality of tap pairs symmetrically arranged on both sides of the center tap; By means of the filter coefficient operation unit, taking the center tap as an axis, a difference operation is performed on coefficients of at least one group of taps on both sides of the center tap of the adaptive filter with the same distance as the center tap; Or weighted sum of multiple sets of data after difference operation; The data after the difference operation or the data after the weighted summation is used as the phase error information to obtain the read clock error period.

4. The optical disc reading device according to claim 1, characterized in that: The sampler is an AD converter; or an AD converter and a memory connected in sequence; or any one of an AD converter, a memory and an interpolation operator connected in sequence; The AD converter is used to perform analog-to-digital conversion on the analog read signal read by the optical head according to the output of the read clock generation unit; The memory is used to store the digital read signal after analog-to-digital conversion in the memory according to the output of the read clock generation unit; The interpolation operator is used to read the data stored in the memory and perform interpolation processing according to the output of the read clock generation unit.

5. The optical disc reading device according to claim 3, characterized in that: The filter coefficient calculation unit is one or more; And the reading clock generating unit is one or more; And the number of the samplers is one or more; The optical head reads one or more analog read signals from the information recording medium, and samples the read analog read signals through one or more samplers; and inputting the output of the sampler into an adaptive filter provided with one or more FIR filters; The filter coefficient operation unit uses one or more FIR filter coefficients to calculate and obtain the phase error information of the read clock, and the read clock generation unit generates a read clock cycle through the output of the filter coefficient operation unit; The samplers all perform sampling with a read clock cycle generated by the same read clock generation unit; Or each of the samplers uses a read clock cycle generated by the read clock generation unit to perform sampling.

6. The optical disc reading device according to claim 5, characterized in that: The analog read signal read from the information recording medium is a read signal on a target track to be read on the information recording medium and a read signal on a track adjacent to the target track to be read.

7. The optical disc reading device according to claim 1, characterized in that: Also includes a maximum likelihood decoder, a target signal generating unit and one or more preamplifiers; The maximum likelihood decoder is used to perform maximum likelihood decoding on the output of the adaptive filter and output the decoding result as a digital signal; The target signal generating unit is used to obtain the target signal according to the output of the maximum likelihood decoder; The target signal is a desired target signal obtained by adjusting the output of the maximum likelihood decoder; The preamplifier is used to perform gain amplification on the analog read signal and transmit the gain-amplified analog read signal to the sampler.

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