Optical disc device

Abstract

The invention discloses an optical disc device, which realizes accurate recording of user data through a recording pulse generation circuit module which forms a recording mark based on a recording code signal through a laser irradiation track. The data reading unit is used for detecting and recording a read signal of the mark from reflected light irradiated by the laser to the track, generating an equalization signal obtained by correcting the waveform of the read signal through a waveform equalization circuit module, and performing error correction on the processed equalization signal to obtain final decoding data; the method comprises the following steps of: performing convolution operation on an expected signal and a recorded coded signal through a recording condition control unit to obtain a result containing a base signal item and a squared signal item after squaring the base signal, thereby realizing stable reading of data, and realizing stable reading of the data through different noise states of reading signal amplitude corresponding to reflectivity. According to the present invention, data recorded on an optical disc can be stably read at a high linear density without reducing a linear density condition by extending a linear direction length in a cell direction or reducing the number of levels of multi-valued recording, and the like, by adjusting the size of a recording mark.

Description

Technical Field

[0001] The present invention relates to the technical field of recording and reading data on optical discs and optical recording data, and particularly relates to an optical disc device. Background Art

[0002] Currently, as information recording media for storing images, data, etc., there are various optical discs such as DVDs and Blu-ray (registered trademark) discs (hereinafter referred to as BDs). From the perspective of space efficiency during data storage, as technologies for increasing the recording capacity per unit volume without increasing the cost of optical discs, there are technologies for increasing the track density and the line density.

[0003] As a technology for increasing the line density, the Partial Response Most Likelihood (hereinafter referred to as PRML) signal processing technology is widely used. During the recording process on an optical disc track, binary signals are represented using marks and spaces. When reading this binary signal, based on the frequency characteristics detected in the light beam, the detected read signal is limited to low frequencies. This is due to the diffraction limit of the light beam reading multiple marks and spaces simultaneously, which is called inter-symbol interference. The PRML signal processing technology is a maximum likelihood decoding technology that estimates the recorded binary signal by comparing and selecting the expected waveform and the read signal waveform, where the expected waveform assumes inter-symbol interference. As the line density increases, the PRML signal processing technology with an extended inter-symbol interference width has been used. In addition, by strongly emitting the light beam with a time width corresponding to the length of the mark to record the binary signal represented by the mark and the space, an appropriate mark is recorded. Based on the PRML signal processing technology, adjustments are made to the light emission time width and the delay position corresponding to the mark to achieve good reading.

[0004] In addition, as a technology for increasing the line density, for example, there is a multi-value recording method that virtually sets cells at certain intervals in the track extension direction (line direction) and records marks of three or more different sizes for each cell. By expanding from binary signals to multi-value code signals of three values or more, the line density is increased. The above PRML signal processing technology can also be used to read the original multi-value code signal from the multi-value recording track.

[0005] [Prior Art Documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-339765

[0007] [Patent Document 2] International Publication WO2020—100777

[0008] [Patent Document 3] International Publication WO2022—158237

[0009] In the reading of traditional PRML signal processing techniques for recording binary signals, it is necessary to appropriately control the start position and end position of a mark in order to reduce the error rate of the read data. Compared with the start and end positions, the state of the middle position of the mark has a smaller impact on the error rate.

[0010] However, in the PRML signal processing techniques for multi-value recording shown in Patent Document 1 and Patent Document 3, the influence degrees of all waveform shapes of the read signal on the data error rate are roughly the same. In addition, it can be known from Patent Document 2 that even in binary signal recording, when the linear density increases, for short marks whose length exceeds the diffraction limit, the influence degrees of all waveform shapes of the read signal on the data error rate increase not only at the start and end of the mark.

[0011] The information recording on an optical disc is achieved by the change in reflectivity caused by recording marks. Compared with the reflectivity in the state where no mark is recorded on the track, the reflectivity of the recorded mark part decreases. When the track is irradiated with laser light from a pickup head, the reflectivity of the recorded mark part decreases, so that the amount of light reflected from the track decreases. The pickup head detects the reflected light and converts it into a read signal according to the amount of light.

[0012] In such optical recording and reading, multiple noise elements appear in the read signal. Laser noise generated by the change in irradiation laser power, optical disc noise generated by the roughness of the track surface state, recording noise generated by the roughness of the state of forming the mark, and circuit noise generated by the circuit after the reflected light is detected in the pickup head and becomes a read signal. Among them, when the laser noise, optical disc noise, and recording noise finally appear in the read signal in the form of noise, they are affected by the change in reflectivity because noise is generated before it becomes reflected light. That is to say, it has amplitude asymmetry, where the amplitude of the noise increases in the high reflectivity part and decreases in the low reflectivity part. In maximum likelihood decoding techniques including PRML signal processing techniques, the error rate usually deteriorates correspondingly according to the magnitude of the noise amplitude. When the noise characteristic is white, the effect of the maximum likelihood decoding technique is ideally demonstrated. As described above, there is a problem that the effect of the PRML signal processing technique cannot be ideally demonstrated in a state where the noise amplitude is asymmetric and the error rate deteriorates.

[0013] Especially in multi-value recording, all waveform shapes of the read signal are equally important. In a state where the noise amplitude is different between the high-amplitude side and the low-amplitude side of the read signal corresponding to the reflectivity, due to the high-amplitude side (high reflectivity side) of the read signal, the noise amplitude increases, and many errors will occur in the decoding result. In fact, in order to maintain a low bit error rate, there is a problem that the linear density condition must be reduced, and thus it is impossible to efficiently and stably read the recorded data on a high linear density optical disc, such as increasing the line direction length of the unit or reducing the number of multi-value levels in multi-value recording.

[0014] Therefore, there is an urgent need to provide an optical disc device capable of stably reading the data recorded on a high linear density optical disc. Summary of the Invention

[0015] The present invention provides an optical disc device to overcome the above technical problems.

[0016] To achieve the above object, the technical solution of the present invention is:

[0017] An optical disc device includes an optical head, a data recording unit, a data reading unit, a data storage unit, a recording condition control unit, and a device control unit;

[0018] The data recording unit includes an error correction coding circuit module, a modulation circuit module, and a recording pulse generation circuit module;

[0019] The error correction coding circuit module is used to obtain coded data according to the user data for optical disc recording in the data storage unit;

[0020] The modulation circuit module is used to receive the coded data and obtain a recording code signal modulated based on a predetermined multi-value modulation code;

[0021] The recording pulse generation circuit module is used to obtain a recording pulse signal according to the recording code signal, and drive the optical head through the device control unit to form a recording mark on the optical disc with the recording pulse signal;

[0022] The data reading unit includes a waveform equalization circuit module, a decoding circuit module, and an error correction decoding circuit module;

[0023] The waveform equalization circuit module is used to correct the waveform of the analog read signal with a predetermined expected signal as the target signal to obtain an equalized signal;

[0024] The analog read signal is an analog read signal obtained by driving the optical head through the device control unit and originating from the recording mark at the desired target position on the optical disc;

[0025] The decoding circuit module is used to decode the equalized signal processed by the maximum likelihood decoding circuit module and obtain an initial decoded signal;

[0026] The error correction and decoding circuit module is used to correct the error of the initial decoding signal, obtain the final decoded data, i.e., the read user data, and transmit it to the data storage unit for caching;

[0027] The recording condition control unit is used to obtain the measurement error based on the expected recording pulse signal according to the equalization signal and the recording code signal, so as to call the device control unit to adjust the signal condition of the expected recording pulse signal, and is used to correct the error of the initial decoding signal through the error correction and decoding circuit module, so as to ensure the stable recording and reading of the user data;

[0028] And the signal condition includes the luminous power and the luminous width.

[0029] Further, the acquisition formula for the expected signal for correcting the waveform of the analog read signal to obtain the equalization signal is

[0030] E=(P - K·P 2 )÷(1 - K)

[0031] In the formula: E represents the predetermined expected signal; P represents the base signal term obtained by performing convolution calculation on the expected recording pulse signal and the recording code signal; P 2 represents the square signal term of P; K represents the design constant and K = 0 or 0 < K < 1.

[0032] Further, the waveform equalization circuit module includes a first equalization filter, a second equalization filter, and a filter coefficient controller;

[0033] The first equalization filter is used to filter the analog read signal;

[0034] The second equalization filter is used to filter the square signal term of the analog read signal;

[0035] The filter coefficient controller is used to reduce the signal amplitude error between the equalization signal and the expected signal, and adaptively adjust the filter coefficients of the first equalization filter and the second equalization filter.

[0036] Further, the method for obtaining the equalization signal is

[0037] Confirm the value of the design constant K;

[0038] If the design constant K = 0, then add the output signals of the first equalization filter and the second equalization filter as the output equalization signal;

[0039] If the value range of the design constant K is 0 < K < 1, then use the output signal of the first equalization filter as the output equalization signal.

[0040] Further, the modulation circuit module is configured to receive encoded data and obtain a recording code signal modulated based on a predetermined multi-value modulation code, where the predetermined multi-value modulation code is a multi-value code including three or more encoding values.

[0041] Further, the data storage unit includes a host, an I / F circuit module, and a buffer;

[0042] The I / F circuit module is bidirectionally communicatively connected to the host, the buffer, and the device control unit respectively;

[0043] The I / F circuit module is connected to the input end of the error correction coding circuit module, the output end of the recording condition control unit, and the output end of the error correction decoding circuit module respectively;

[0044] And the I / F circuit module is configured to receive user data recorded on the optical disc from the host and store it in the buffer, or to send the user data stored in the buffer obtained by copying from the optical disc to the host.

[0045] Further, the device control unit includes a spindle motor, a servo controller, a system controller, and a ROM memory;

[0046] The servo controller is connected to the spindle motor and the optical head respectively,

[0047] The servo controller is configured to drive the rotation of the optical disc by controlling the spindle motor to realize the recording or reading of user data;

[0048] The servo controller is further configured to move and focus the laser emitted by the optical head onto the target track of the optical disc for scanning of user data.

[0049] Advantageous Effects: The present invention provides an optical disc device. The optical disc device in the present invention is an optical disc device that records and reads information on an optical disc track. A modulation circuit module generates a recording code signal based on a predetermined code in the information, and a recording pulse generation circuit module forms a recording mark based on the recording code signal by irradiating the track with a laser, thereby achieving accurate recording of user data; a data reading unit detects a reading signal of the recording mark from the reflected light of the laser irradiating the track, and uses an expected signal as a target signal. A waveform equalization circuit module generates an equalized signal obtained by correcting the waveform of the reading signal, and respectively passes the processed equalized signal through a maximum likelihood decoding circuit module and an error correction decoding circuit module to perform error correction on the equalized signal to obtain the final decoded data. The recording condition control unit performs a convolution operation on the expected signal and the recorded code signal to obtain a result including a base signal term and a square signal term obtained by squaring the base signal, thereby achieving stable reading of data. The present invention can adjust the size of the recording mark according to different noise states of the amplitude of the reading signal corresponding to the reflectivity, without reducing the line density condition by extending the line direction length of the unit or reducing the number of levels of multi-value recording, that is, it can stably read the data recorded on the optical disc under high line density. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 Structural schematic diagram of the optical disc device of the present invention;

[0052] Figure 2 Relationship diagram among the recording symbol signal, the recording pulse signal, and the recording mark in this embodiment;

[0053] Figure 3 Relationship diagram among the recording mark, the equalized signal, and the decoded signal in this embodiment;

[0054] Figure 4 Chart showing the cause of noise in this embodiment;

[0055] Figure 5 Expected value waveform diagram of PRML signal processing in this embodiment;

[0056] Figure 6 Expected value waveform diagram of recording adjustment in this embodiment.

[0057] In the figure: 10, optical disc device; 100, optical disc; 101, optical head; 102, spindle motor; 103, servo controller; 104, recording pulse generation circuit module; 105, modulation circuit module; 106, error correction coding circuit module; 107, waveform equalization circuit module; 108, maximum likelihood circuit module; 109, decoding circuit module; 110, error correction decoding circuit module; 111, recording condition control circuit module; 112, interface circuit module; 113, buffer; 114, system controller; 115, ROM buffer; 116, host; 201, recording encoded signal; 202, recording pulse signal; 203, first track; 301, second track; 204, first recording mark; 302, second recording mark; 303, equalization signal; 304, decoded signal. Detailed implementation manners

[0058] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0059] This embodiment provides an optical disc device, including an optical head 101, a data recording unit, a data reading unit, a data storage unit, a recording condition control unit, and a device control unit;

[0060] Specifically, the optical disc 100 device in this embodiment records and reads user data (an example of recorded data) on the optical disc 100. In the optical disc 100, a spiral track is formed from the inner circumference to the outer circumference, and the track is composed of a bottom track formed by the bottom of the groove and a top track formed between an adjacent bottom track, and user data can be recorded on the bottom track and the top track.

[0061] In a specific embodiment, the device control unit includes a spindle motor 102, a servo controller 103, a system controller 114, and a ROM memory 115; the servo controller 103 is respectively connected to the spindle motor 102 and the optical head 101. The servo controller 103 is configured to drive the rotation of the optical disc 100 at a preset speed by controlling the spindle motor 102 to record or read user data. The servo controller 103 is further configured to move and focus the laser emitted by the optical head 101 onto the target track of the optical disc 100 to scan user data. While the spindle motor 102 rotates the optical disc 100, the optical head 101 records user data by irradiating the optical disc 100 with laser light and reads user data from the optical disc 100. The ROM memory 115 consists of a flash memory. The ROM memory 115 stores a control program for the system controller 114 to control the entire optical disc 100 device. The programming and acquisition method of the control program stored in the ROM memory 115 are well-known prior art means and will not be elaborated here.

[0062] In a specific embodiment, the data storage unit includes a host 116, an I / F circuit module, and a buffer 113; the I / F circuit module is in bidirectional communication connection with the host 116, the buffer 113, and the device control unit respectively; the I / F circuit module is respectively connected to the input end of the error correction coding circuit module 106, the output end of the recording condition control unit, and the output end of the error correction decoding circuit module 109; and the I / F circuit module is configured to receive user data recorded on the optical disc 100 from the host 116 and store it in the buffer 113, or to send the user data stored in the buffer 113 obtained by copying from the optical disc 100 to the host 116. In addition, the user data stored in the buffer 113 can be transmitted to other internal modules, and conversely, the user data received from other internal modules can also be stored in the buffer 113.

[0063] The data recording unit includes an error correction coding circuit module 106, a modulation circuit module 105, and a recording pulse generation circuit module 104.

[0064] The error correction coding circuit module 106 is configured to obtain encoded data according to the user data for recording on the optical disc 100 in the data storage unit. Specifically, the error correction coding circuit module 106 generates encoded data by adding parity check codes for error correction to the user data received from the I / F circuit module. The method of adding parity check codes for error correction to the user data to generate encoded data is well-known prior art means and will not be elaborated here.

[0065] The modulation circuit module 105 is used to receive encoded data and obtain a recording code signal modulated based on a predetermined multi - value modulation code; and through the modulation circuit module 105, the modulation method of the recording code signal obtained by modulating the received encoded data based on the predetermined multi - value modulation code is multi - value coding including three or more encoding values.

[0066] The recording pulse generation circuit module 104 is used to obtain a recording pulse signal according to the recording code signal, and drive the optical head 101 through the device control unit to form a recording mark on the optical disc 100 with the recording pulse signal; specifically, the recording pulse generation circuit module 104 generates a recording pulse signal from the recording code signal generated by the modulation circuit module 105, and drives the semiconductor laser tube of the optical head 101. Due to the heat of the irradiated laser, a recording mark is formed on the optical disc 100; wherein, the optical head 101 includes a semiconductor laser tube that emits light with a wavelength of λ, an objective lens with a numerical aperture of N, and a photodetector for detecting the reflected light, etc. The optical head 101 irradiates the optical disc 100 with laser and detects the reflected light from the optical disc 100. The optical head 101 outputs a read signal based on the detected reflected light;

[0067] The data reading unit includes a waveform equalization circuit module 107, a decoding circuit module 109, and an error - correction decoding circuit module 110.

[0068] The waveform equalization circuit module 107 is used to correct the waveform of the analog read signal with a predetermined expected signal as the target signal to obtain an equalized signal;

[0069] The analog read signal is an analog read signal obtained by driving the optical head 101 through the device control unit, which is derived from the recording mark at the desired target position on the optical disc;

[0070] Specifically, the waveform equalization circuit module 107 includes a first equalization filter, a second equalization filter, and a filter coefficient controller;

[0071] The first equalization filter is used to filter the analog read signal;

[0072] The second equalization filter is used to filter the square - signal term of the analog read signal;

[0073] The filter coefficient controller is used to reduce the signal amplitude error between the equalized signal and the expected signal and adaptively adjust the filter coefficients of the first equalization filter and the second equalization filter;

[0074] In a specific embodiment, the method for obtaining the equalized signal is

[0075] Confirm the value of the design constant K;

[0076] If the design constant K = 0, the output signals of the first equalization filter and the second equalization filter are added together as the output equalization signal;

[0077] If the value range of the design constant K is 0 < K < 1, the output signal of the first equalization filter is used as the output equalization signal;

[0078] Specifically, the formula for obtaining the expected signal of the equalization signal by correcting the waveform of the analog read signal is

[0079] E = (P - K·P 2 ) ÷ (1 - K)

[0080] In the formula: E represents the predetermined expected signal; P represents the base signal term obtained by performing convolution calculation on the expected recording pulse signal and the recording code signal; P 2 represents the square signal term of P; K represents the design constant and K = 0 or 0 < K < 1;

[0081] The decoding circuit module 109 is used to decode the equalization signal processed by the maximum likelihood decoding circuit module 108 and obtain the initial decoded signal;

[0082] In this embodiment, the waveform equalization circuit module 107 and the maximum likelihood decoding circuit module 108 decode the recording code signal from the read signal and output it as the decoded signal; specifically, PRML signal processing (an example of maximum likelihood decoding) selects the closest expected value waveform from the comparison between the read signal and multiple expected value waveforms, and outputs the recording code signal as the decoded signal, which is the source of the expected value waveform, and the characteristics of the expected value waveform consider the influence of the frequency band limitation caused by the frequency characteristics of laser detection;

[0083] The error correction decoding circuit module 110 is used to perform error correction on the initial decoded signal, obtain the final decoded data, which is the restored read user data, and transmit it to the data storage unit for caching;

[0084] The recording condition control unit is used to obtain the measurement error based on the expected recording pulse signal according to the equalization signal and the recording code signal, so as to call the device control unit to adjust the signal conditions of the expected recording pulse signal for error correction of the initial decoded signal by the error correction decoding circuit module, thereby ensuring the stable recording and reading of user data, and the signal conditions include the luminous power and the luminous width. In addition, in this embodiment, the system controller 114 controls each circuit module and controls the communication with the host 116 by reading and executing the program stored in the ROM memory 115; Figure 1In this case, for convenience, the arrows indicating that the system controller 114 controls each component are omitted. In this embodiment, the system controller 114 of the optical disc 100 device controls the operations of each circuit related to the recording and reading of user data.

[0085] The working principle of the optical disc device in this embodiment is as follows:

[0086] First, the operation of the optical disc device 10 in this embodiment for performing track recording on the data area of the optical disc 100 will be described.

[0087] The user data sent from the host 116 and the logical address of the recording destination are obtained through the I / F circuit module 112. The user data is divided into data blocks of a predetermined unit, and each data block is sent to the error correction coding circuit module 106;

[0088] An error correction parity check code is added to the user data in each data block through the error correction coding circuit module 106 for error correction during the reading process, thereby obtaining coded data;

[0089] The coded data with the parity check code added to the recording code signal is modulated by the modulation circuit module 105 according to a predetermined multi-value modulation code;

[0090] A recording pulse signal is generated from the recording code signal generated by the modulation circuit module 105 through the recording pulse generation circuit module 104, and the semiconductor laser tube of the optical head 101 is driven. By the heat of the irradiated laser, recording marks corresponding to the recording pulse signal are continuously formed on the track of the optical disc 100; As Figure 2 The relationship between the recording code signal, the recording pulse signal, and the recording marks formed on the track is shown; the modulation circuit module 105 uses a five-value modulation code and generates a five-value recording code signal 201 composed of five values of 0 / 1 / 2 / 3 / 4. The recording pulse signal 202 is generated by the recording pulse generation circuit module 104 based on the recording coding signal 201. The emission of the laser is controlled according to the recording pulse signal 202, and the heat of the laser forms the first recording mark 204 on the first track 203; Preferably, the laser wavelength λ emitted by the semiconductor laser tube of the optical head 101 is 405 nm, the numerical aperture N of the objective lens is 0.85, and the servo controller 103 uses the photodetector of the optical head 101 to detect a signal from the reflected light of the first track 203, focuses the laser on the first track 203, and controls tracking and focusing; Under the conditions of the wavelength λ and the numerical aperture N, in order to stably perform tracking and focusing control, the width of the first track 203 of the optical disc is formed at about 160 nm or more; On the other hand, in order to increase the line density to be recorded, the length of one unit is shorter than the width of the first track 203, about 100 nm or less;

[0091] Recording is performed based on the five - value recording code signal 201, where 0 represents a smaller recording mark and 4 represents a larger recording mark. To stably read in different noise environments, ideally, the size range between the small mark and the large mark should be increased as much as possible. Because when the size range is large enough, it is easier to decode the recorded five - value recording code signal from the read signal; on the contrary, when the size range is small, it is more difficult to distinguish the five values from the read signal. For the first track 203, the small recording mark (0) can fit within a frame of one unit length, while the large recording mark (4) cannot fit within a frame of one unit length and will interfere with the recording of the front and back units. In addition, the recording film on the surface of the first track 203 will have its temperature rise due to laser heating, and the heat gradually accumulates, resulting in thermal interference between consecutive units. As described above, the formation of the first recording mark 204 cannot be controlled within one unit and is interfered with by the front and back units. Therefore, based on considering this interference, the shape of the recording pulse signal for controlling laser emission needs to be controlled; the shape of the recording pulse signal 202 is not determined solely by corresponding one - to - one with the unit values of the recording coding signal 201, but is determined according to the combination pattern of 3 or 5 unit values including the front and back units. If 5 - value modulation coding is used and the values of 5 unit intervals are combined, then there will be 3125 shapes of the recording pulse signal 202. The recording pulse signal 202 is equivalent to the laser emission waveform, and its laser emission power ( Figure 2 the height of the recording pulse signal 202 in Figure 2 and the pulse time width of the recording pulse signal 202 in

[0092] are variably controlled. Increasing the emission power and extending the emission width will form a larger recording mark; reducing the emission power and shortening the emission width will form a smaller recording mark;

[0092] The system controller 114 controls the recording operation of the above - mentioned user data. The system controller 114 determines the position to be recorded on the optical disc 100 and controls the servo controller 103 to move the optical head 101 to the preset target position. Before reaching the track of the target position, the error - correction coding circuit module 106 starts to operate. Starting from the point of reaching the target position, the modulation circuit module 105 and the recording pulse generation circuit module 104 are operated for recording, and then the recording of user data on the optical disc is completed.

[0093] The reading operation of the optical disc device 10 in this embodiment is described as follows:

[0094] The waveform equalization circuit module 107 and the maximum - likelihood decoding circuit module 108 decode the read signal output by the optical head 101 through the PRIML signal processing technology to generate a decoded signal. The demodulation circuit module 109 demodulates the decoded signal according to the five - value modulation code, and the error - correction decoding circuit module 110 corrects the errors in the demodulated coded data and restores the user data;

[0095] As Figure 3 shown, the relationship is shown between the recording marks formed on the track, the equalized signal processed by the waveform equalization circuit module 107 (where the read signal detected by the optical head 101 is processed by the waveform equalization circuit module 107), and the decoded signal decoded by the maximum likelihood decoding circuit module 108;

[0096] Since the laser wavelength λ of the optical head 101 is 405 nm and the numerical aperture N of the objective lens is 0.85, the frequency characteristics of the read signal detected from the second recording marks 302 continuously formed on the second track 301 can generally be determined. In PRML signal processing, the impulse response waveform obtained from a single recording mark of one unit is defined;

[0097] The frequency characteristics of the read signal are corrected by the waveform equalization circuit module 107 to approach the frequency characteristics of the defined impulse response waveform, and the equalized signal 303 is output; the maximum likelihood decoding circuit module 108 decodes by selecting the waveform closest to the equalized signal 303 from among a plurality of expected waveforms obtained from the defined impulse response waveform and the pattern of the recorded code signal, and outputs the decoded signal 304; in Figure 3 it, the impulse response waveform is defined in (1, 2, 1) and has a length of 3 units. By combining the five-value modulation code with the (1, 2, 1) impulse response, the expected waveform of the equalized signal 303 is a signal waveform having 17 amplitude levels as shown in the equalized signal 303; due to the warping and eccentricity of the optical disc 100, the residual of the servo controller 103's scanning control of the laser with respect to the second track 301, and the error in the shape of the recording marks recorded on the second track 301, the amplitude and frequency characteristics of the read signal change successively; in the waveform equalization circuit module 107, it is necessary to adaptively correct this change so as to approach the defined expected waveform; therefore, the waveform equalization circuit module 107 is configured as an adaptive equalization circuit, which has an FIR filter for correcting the signal waveform and a coefficient control circuit for sequentially controlling the filter coefficients of the FIR filter. By appropriately controlling the adaptive equalization of the waveform equalization circuit module 107, the decoding of the maximum likelihood decoding circuit module 108 also remains with the minimum error, and the error correction decoding circuit module 110 can stably read the user data within a range where sufficient correction can be made;

[0098] The system controller 114 controls the read operation: The system controller 114 controls the servo controller 103 to move the optical head 101 to a preset target position. When the target position is reached, the waveform equalization circuit module 107, the maximum likelihood decoding circuit module 108, and the demodulation circuit module 109 are turned on to work, and then the error correction decoding circuit module 110 is enabled to work to recover the user data; the recovered user data is stored in the buffer 113, and the user data is transmitted to the host 116 through the I / F circuit module 112 to complete the copying operation;

[0099] In addition, the recording condition control circuit module 111 measures the deviation of the recording condition by comparing the equalization signal 303 shown in Figure 3 with the recorded recording code signal and the expected value waveform obtained from the (1, 2, 1) impulse response; and based on the measurement result, the system controller 114 adjusts the Figure 2 conditions of the emission power and emission width of the recording pulse signal 202 shown; Ideally, the formation of recording marks on the track is always carried out under stable conditions, but the warping of the optical disc 100, the thickness of the recording film on the track surface, and the temperature around the optical disc device 10 and other conditions affecting recording will change; in order to stably read the user data in this embodiment, it is also necessary to ensure a stable recording state, that is, to measure through the recording condition control circuit module 111 and adjust the conditions of the recording pulse signal 202 through the system controller 114 to achieve the control to ensure a stable recording state; in this embodiment, in the reading of the PRML signal processing technology for conventional binary signal recording, it is very important to appropriately control the start and end positions of the recording marks to maintain a low error rate of the read data, and the influence of the middle position of the recording marks on the error rate is less than that of the start and end positions. However, as described in Patent Document 1, Patent Document 3, and the above Embodiment 1, in the PRML signal processing technology for multi-value recording, all waveform shapes of the read signal have an approximately equal degree of influence on the error rate of the data.

[0100] As Figures 2 to 3 shown, by recording recording marks on the optical disc 100, information recording is achieved through the change in reflectivity, and it is opposite to the reflectivity in the state where no recording marks are recorded on the track, while the reflectivity of the part where the recording marks are recorded will decrease. In the part where the recording marks are recorded and the reflectivity has decreased, the amount of light reflected from the track decreases, and the reflected light is detected by the photodetector of the optical head 101 and converted into a read signal according to the amount of light; As Figure 4The figure shows the noise components that appear in the read signal during such optical recording and reading. Laser noise generated by the power variation of the irradiated laser, disc noise generated by the roughness of the track surface state, recording noise generated by the roughness of the state of the formed recording marks, and circuit noise generated by the circuit after detecting the reflected light in the optical head 101, etc. are all the main factors of noise. Among them, when the laser noise, disc noise, and recording noise finally appear in the read signal in the form of noise, they are affected by the change in reflectivity. That is to say, it has amplitude asymmetry, where the amplitude of the noise increases in the part with high reflectivity and decreases in the part with low reflectivity. In the maximum likelihood decoding circuit module 108, the bit error rate usually deteriorates as the noise amplitude increases. When the noise characteristic is white, the effect of PRML signal processing is ideally demonstrated; as described above, in the state of noise amplitude asymmetry, the effect of PRML signal processing cannot be effectively exerted, and the bit error rate also deteriorates. In multi-value recording, all waveform shapes of the read signal are equally important. In the state where the noise amplitude is different between the high amplitude and the low amplitude of the read signal corresponding to the reflectivity, on the side where the noise amplitude increases (the side with high reflectivity), many errors will appear in the decoding result. In fact, in order to maintain a low bit error rate, it is necessary to reduce the line density condition, such as increasing the line direction length of the unit or reducing the number of multi-level levels in multi-value recording, etc.

[0101] As Figure 5 shown, this embodiment provides the expected value waveform of PRML signal processing based on the waveform equalization circuit module 107 and the maximum likelihood decoding circuit module 108, which is similar to Figure 3 the equalization signal 303. The impulse response waveform is defined in (1, 2, 1) and has a length of 3 units; by combining the 5-value recorded code signal and a (1, 2, 1) impulse response, the expected waveform will become a signal waveform with 17 amplitude levels. As Figure 5 (1) shows the waveform in the 100-unit interval, Figure 5 (2) shows the waveform in the 12000-unit interval for easier understanding of the 17 amplitude levels; the vertical axis represents the signal amplitude. When the pattern of the 3-cell part of the recorded symbol series is 000 and the size of the recording mark is small, the signal amplitude is 0; when the pattern of the 3-cell part is 444, the signal amplitude is 1, and the size of the recording mark is large; from Figure 5 (2), it can be seen that the 17 amplitude levels are evenly distributed. In Figure 5 , on the side with high reflectivity and the side where the signal amplitude is close to 0 (the recording mark is small), the amplitude increases and asymmetric noise overlaps; in this state, the side with larger noise has a greater impact, and the bit error rate in the maximum likelihood decoding circuit module 108 deteriorates.

[0102] The optical disc device 10 provided in this embodiment can adjust the size of the recording mark to be recorded according to the asymmetry of the noise amplitude; as Figure 6 shown, the expected waveform used as the target value when adjusting the size of the recording mark according to the emission width of the recording pulse signal is shown; Figure 6 (1) shows the waveform in the 100-cell interval, Figure 6 (2) shows the waveform in the 12,000-cell interval; it can be seen from Figure 6 (2) that the spacing of each amplitude level is not uniform, the spacing on the large recording mark side is narrower, and the spacing on the small recording mark side is wider, which is consistent with the fact that the noise amplitude on the large recording mark side is small and the noise amplitude on the small recording mark side is large, as Figure 6 shown, the acquisition formula for the expected signal of the equalization signal is

[0103] E = (P - K·P 2 ) ÷ (1 - K)

[0104] In the formula: E represents the predetermined expected signal; P represents the base signal term obtained by performing a convolution calculation on the expected recording pulse signal and the recording code signal, that is, the value obtained by performing a convolution calculation on the 5-value recording symbol signal in the 3-cell interval and the impulse response (1, 2, 1) calculation; P 2 represents the square signal term of P; K represents a design constant and K = 0 or 0 < K < 1; as Figure 5 shown, the expected waveforms are equal when k = 0; Figure 6 shown, the expected waveform is k = 0.3; as Figure 6 (1) shows the waveform in the 100-cell interval; Figure 6 (2) shows the waveform in the 12,000-cell interval; the value of k is determined according to the ratio of the noise amplitudes when measuring the noise on the large recording mark side and the small recording mark side respectively, or according to the reflectance ratio of the large recording mark side and the small recording mark side.

[0105] The recording condition control circuit module 111 measures the error of the recording state through the Figure 6 shown expected waveform and the equalization signal obtained from the waveform equalization circuit module 107, and adjusts the recording pulse signal width of the recording pulse generation circuit 104 through the system controller 114 to reduce the measured error; the waveform equalization circuit module 107 is as Figure 1 shown, composed of the FIR filter 1 corresponding to the P term in the acquisition formula of the expected signal and corresponding to K·P in the acquisition formula of the expected signal with the square of the reproduced signal as the input 2It is composed of the FIR filter 2 of the term; when measuring the recording state error through the recording condition control circuit module 111, only the FIR filter 1 (the first equalization filter) works, and the output of the FIR filter 2 (the second equalization filter) without the square term is not included. This is to match the expected waveform E shown in the expected signal acquisition formula only by adjusting the recording state, and not to use the FIR filter 2 in the waveform equalization circuit module 107 for square term correction; in order to make the equalization signal output from the waveform equalization circuit module 107 become the expected waveform E of the expected signal acquisition formula with the square term, and to make the FIR filter 1 in this state adaptively work correctly, the expected waveform in the coefficient control circuit and the expected waveform for decoding in the maximum likelihood decoding circuit 108 should also correspond to the expected signal acquisition formula; operating the optical disc device 10 under this condition can adjust the small recording marks and large recording marks on the track of the optical disc 100, and no longer form them in equal proportion as Figure 5 shown, but as Figure 6 shown in the expected signal acquisition formula, the size ratio difference of the small recording marks is large, and the size ratio difference of the large recording marks is small.

[0106] On the other hand, when reading user data by operating the demodulation circuit module 109 or the error correction decoding circuit module 110 instead of adjusting the recording state by reading, both the FIR filter 1 and the FIR filter 2 of the waveform equalization circuit module 107 operate; in the expected waveform of the square term distortion shown in the expected signal acquisition formula, the difference between the signal waveform patterns is larger on the small recording mark side and smaller on the large recording mark side. That is to say, in the maximum likelihood decoding circuit module 108, the larger the recording mark, the greater the possibility of decoding error. In addition to Figure 4 the noise factors shown in, when the size of the recording marks shows an average deviation or when the adaptive control of the waveform equalization circuit module 107 is in the transient response situation, many errors will occur on the large recording mark side.

[0107] In order to prevent this situation from occurring in this embodiment, for the read signal adjusted from the recording state to conform to the second-order distortion characteristics in the expected signal acquisition formula, by using the FIR filter 2 identical to the expected signal acquisition formula to compensate the waveform equalization circuit module 107 with second-order distortion, it can be appropriately adaptively equalized into an equalization signal with the same amplitude level as Figure 5 shown; among them, the expected waveform of the recording state adjustment is determined by the expected signal acquisition formula. Similarly, the FIR filter of the read waveform equalization circuit module 107 is set to the same structure as the expected signal acquisition formula. Thus, the amplitude levels of the equalization signals are the same and the noise amplitudes are symmetric, and the maximum likelihood decoding circuit module 108 can perform decoding most effectively, thereby preventing the deterioration of the bit error rate.

[0108] The optical disc device of this embodiment is an optical disc device that records and reads information on an optical disc track. It includes a modulation circuit module that generates a recording code signal based on a predetermined code in the information, and a recording pulse generation circuit module that forms recording marks based on the recording code signal by irradiating the track with a laser to achieve accurate recording of user data; a data reading unit that detects the recording marks from the reflected light of the laser irradiating the track, and uses the expected signal as the target signal. A waveform equalization circuit module generates an equalized signal obtained by correcting the waveform of the reading signal, and respectively passes the processed equalized signal through a maximum likelihood decoding circuit module and an error correction decoding circuit module to perform error correction on the equalized signal to obtain the final decoded data. The recording condition control unit performs a convolution operation on the expected signal and the recorded coded signal to obtain a result including a base signal term and a squared signal term obtained by squaring the base signal, thereby achieving stable data reading. The present invention can adjust the size of the recording marks according to different noise states of the amplitude of the reading signal corresponding to the reflectivity, without reducing the line density conditions by means such as extending the line direction length of the unit direction or reducing the number of levels of multi-value recording, that is, it can stably read the data recorded on the optical disc under high line density conditions.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical disc apparatus, characterized in that, It includes an optical head, a data recording unit, a data reading unit, a data storage unit, a recording condition control unit, and a device control unit; The data recording unit includes an error correction coding circuit module, a modulation circuit module, and a recording pulse generation circuit module; The error correction coding circuit module is used to obtain coded data according to the user data for optical disc recording in the data storage unit; The modulation circuit module is used to receive the coded data and obtain a recording code signal modulated based on a predetermined multi-value modulation code; The recording pulse generation circuit module is used to obtain a recording pulse signal according to the recording code signal, and drive the optical head through the device control unit to form recording marks of the recording pulse signal on the optical disc; The data reading unit includes a waveform equalization circuit module, a decoding circuit module, and an error correction decoding circuit module; The waveform equalization circuit module is used to correct the waveform of the analog reading signal with a predetermined expected signal as the target signal to obtain an equalized signal; The analog reading signal is an analog signal of the recording mark from the desired target position on the optical disc obtained by driving the optical head through the device control unit; The decoding circuit module is used to decode the equalized signal processed by the maximum likelihood decoding circuit module and obtain an initial decoded signal; The error correction decoding circuit module is used to correct the error of the initial decoded signal, obtain the final decoded data, i.e., the read user data, and transmit it to the data storage unit for caching; The recording condition control unit is used to obtain a measurement error based on the expected recording pulse signal according to the equalized signal and the recording code signal, so as to call the device control unit to adjust the signal conditions of the expected recording pulse signal for error correction of the initial decoded signal by the error correction decoding circuit module, thereby ensuring the stable recording and reading of user data; And the signal conditions include luminous power and luminous width.

2. The optical disc apparatus according to claim 1, wherein The acquisition formula for the expected signal of the equalization signal obtained by correcting the waveform of the analog read signal is E = (P - K·P 2 ) ÷ (1 - K) Where: E represents a predetermined expected signal; P represents a base signal term obtained by performing a convolution calculation on the expected recorded pulse signal and the recorded code signal; P 2 represents the square signal term of P; K represents a design constant and K = 0 or 0 < K < 1.

3. The optical disc apparatus according to claim 1, wherein The waveform equalization circuit module includes a first equalization filter, a second equalization filter, and a filter coefficient controller; The first equalization filter is used to filter the analog reading signal; The second equalization filter is used to filter the square signal term of the analog reading signal; The filter coefficient controller is used to reduce the signal amplitude error between the equalized signal and the expected signal and adaptively adjust the filter coefficients of the first equalization filter and the second equalization filter.

4. An optical disc apparatus according to claim 3, wherein, The method for obtaining the equalized signal is Confirm the value of the design constant K; If the design constant K = 0, add the output signals of the first equalization filter and the second equalization filter as the output equalized signal; If the value range of the design constant K is 0 < K < 1, use the output signal of the first equalization filter as the output equalized signal.

5. An optical disc apparatus according to claim 1, wherein, The modulation circuit module is used to receive the coded data, and the predetermined multi-value modulation code in the recording code signal modulated based on the predetermined multi-value modulation code is a multi-value code including three or more coding values.

6. The optical disc apparatus according to claim 1, wherein, The data storage unit includes a host, an I / F circuit module, and a buffer; The I / F circuit module is bidirectionally communicatively connected to the host, the buffer, and the device control unit respectively; The I / F circuit module is respectively connected to the input end of the error correction coding circuit module, the output end of the recording condition control unit, and the output end of the error correction decoding circuit module; The I / F circuit module is used to receive user data recorded on the optical disc from the host and store it in the buffer, or to send the user data stored in the buffer obtained by copying from the optical disc to the host.

7. The optical disc apparatus according to claim 1, wherein The device control unit includes a spindle motor, a servo controller, a system controller, and a ROM memory; The servo controller is respectively connected to the spindle motor and the optical head, The servo controller is used to drive the rotation of the optical disc by controlling the spindle motor to realize the recording or reading of user data; The servo controller is also used to move and focus the laser emitted by the optical head onto the target track of the optical disc for scanning user data.

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