JPH11312366A - Data read-out device for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk drive capable of coping with the skew, scratches, damages and jitters due to the irregularity of a reflecting film, or the like as to the individual optical disks. SOLUTION: When the read-in area of the optical disk is read out, the amount of jitter is obtained in a digital PLL 16, and a cut-off frequency as the equalizer constant of a variable equalizer 15 and a detection means of the jitter amount are corrected in accordance with this jitter amount, then these corrected values are fixed thereafter. Also, the equalizer constant is characterized by being the cut-off frequency and/or the boost amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reading device for reading data from an optical disk, and more particularly to a data reading device for an optical disk having an improved RF signal waveform equalization process.

[0002]

2. Description of the Related Art In an optical disk data reading device,
The optical disk is irradiated with a beam spot, an RF signal is generated from the amount of reflected light, and data is read out through processes such as waveform equalization, synchronization clock signal extraction, and synchronization modulation signal extraction using the synchronization clock signal. ing. On the other hand, in order to increase the data transfer rate from the optical disc,
A multi-beam type data reading device has been already proposed in which a plurality of beam spots are radiated to different positions in the radial direction of an optical disc, and data at each beam spot position is simultaneously read out from the reflected light.

In a conventional optical disk data reading device, an equalizer constant in a waveform equalizer is fixed. Further, in the multi-beam type data reading device, the same equalizer constant is set for each waveform equalizer for each RF signal, and the equalizer constant is fixed.

[0004]

Problems to be solved by the present invention are described below.
Scratches or breaks in the optical disk, unevenness in the reflective film of the optical disk, and increased density of pits or tracks on the optical disk cause waveform interference of the RF signal and disturbance of the waveform. In the conventional optical disk data reading device, since the equalizer constant in the waveform equalizer is fixed, it is difficult to sufficiently equalize the waveform with respect to the waveform interference factor of each optical disk. In particular, in the multi-beam type data reading device, the amount of jitter increases as the RF signal of the outer or inner sub beam with respect to the main beam increases, so that the equalizer constants of a plurality of waveform equalizers are equal to a predetermined value. Is not preferred.

An object of the present invention is to provide a data reading apparatus for an optical disk which overcomes the above-mentioned problems.

[0006]

The data reading apparatus (10) for an optical disk according to the present invention has the following (a) to (c). (A) An optical pickup (11) that irradiates a beam spot (34) to an optical disc (30) and generates an RF signal from reflected light thereof. (B) An RF signal input from the optical pickup (11) is converted based on an equalizer constant. Waveform equalizer (1
5) (c) Equalizer constant setting means (17) for detecting a jitter amount of an RF signal output from the waveform equalizer (15) and setting an equalizer constant in the waveform equalizer (15) based on the jitter amount.

[0007] The optical disc (30) has at least CD, D
VD, MD, PD (Phase Change Disk), MO, etc. are included. The setting of the equalizer constant by the equalizer constant setting means (17) is performed only for a predetermined specific period for each optical disc (30), and thereafter, the equalizer constant may be fixed to the value at that time, or each optical disc (30 )
It may be performed and changed as appropriate.

The setting of the equalizer constant includes, in addition to directly setting the equalizer constant, indirect setting of the equalizer constant by setting the correction amount of the equalizer constant.

An optical disk data reading device (10)
Includes both single-beam and multi-beam data readers. That is, the beam spot (3) that the optical pickup (11) irradiates the optical disc (30)
4) may be only one or plural. When there are a plurality of beam spots (34), an RF signal is generated from each reflected light from each beam spot (34).

The equalizer constant in the waveform equalizer (15) is not fixed, and the amount of jitter is detected for each optical disk (30) and is set based on the amount of jitter. ), An appropriate equalizer constant is set, and good equalization waveform processing can be performed.

An optical disk data reading apparatus (10) of the present invention has the following (a) to (c). (A) A plurality of beam spots (34) are radiated to different positions in the radial direction of the optical disc (30), and each of the reflected light beams
Optical pickup (11) for generating F signal (b) A plurality of waveform equalizers (15) provided for each RF signal input from the optical pickup (11) and performing waveform equalization processing of each RF signal based on an equalizer constant. (C) Equalizer constant setting means (17) for detecting an amount of jitter for each RF signal and setting an equalizer constant in each waveform equalizer (15) based on the amount of jitter.

This optical disk data reading device (10)
Then, a plurality of beam spots (34) are irradiated to different positions in the radial direction of the optical disc (30), and data at each position is read at the same time, so that the data transfer rate is greatly improved. Such an optical disk data reading device (1.
In (0), the jitter amount of the RF signal is determined by comparing the RF signal relating to the radially inner beam spot (34) and the outer beam spot (3).
Although the amount of jitter differs from the RF signal according to 4), the amount of jitter can be reduced by setting the equalizer constant to an appropriate value for each waveform equalizer (15) for each RF signal.

According to the optical disk data reading device (10) of the present invention, the equalizer constant is a cutoff frequency and / or a boost amount.

That is, in the waveform equalizer (15), not only the case where both the cutoff frequency and the boost amount are corrected, but also the case where only the cutoff frequency is corrected and the case where only the boost amount is corrected are included in the technical scope. Shall be included.

According to the data reading apparatus for an optical disk (10) of the present invention, the equalizer constant setting means (17) includes the RF
The amount of jitter is detected based on the phase difference between the corresponding signal of the synchronization clock signal extracted from the signal by the PLL (16) and the corresponding signal of the reference frequency signal of the rotation frequency of the spindle motor.

An optical disk data reading device (10)
To extract the rotation servo of the spindle motor and the synchronous modulation signal, a corresponding signal of a synchronization clock signal extracted from the RF signal by a PLL (16), and a corresponding signal of a reference frequency signal of a reference frequency for the rotation servo of the spindle motor. Are detected. The equalizer constant setting means (17)
Since the amount of jitter is easily detected using the phase difference,
The configuration can be simplified.

According to the optical disk data reading device (10) of the present invention, the equalizer constant setting means (17) is adapted to read the data in the lead-in area of the optical disk (30) when reading data.
An equalizer constant is calculated based on the F signal, and thereafter, the equalizer constant is fixed to the calculated value.

An optical disk data reading device (10)
When the optical disc (30) is set on the spindle motor, data in the lead-in area of the optical disc (30) is read first. Using this reading time, RF
The amount of jitter in the signal is detected, and an equalizer constant is calculated. By fixing the equalizer constant to this calculated value and coping with the subsequent data reading of the program area, it is possible to achieve good equalized waveform processing.

According to the optical disk data reading device (10) of the present invention, the optical pickup (11) applies each light beam for generating each beam spot (34) to the main beam and the main beam on both sides thereof. The sub-beams are arranged symmetrically, and R
The equalizer constant of the waveform equalizer (15) for the F signal is set to an equal value.

The sub beam can be generated by passing a part of the main beam through a hologram or a diffraction grating. By arranging the hologram and the diffraction grating symmetrically with respect to a portion through which the main beam passes as it is, it is possible to easily create a sub beam having a symmetric relationship with the main beam.

The amount of jitter of the RF signal relating to the sub-beam having a symmetrical relationship has substantially the same value despite a slight optical path difference caused by passing through an optical element such as a beam splitter in the optical pickup (11). By setting the equalizer constants of the sub-beams having a symmetrical relationship to be equal, the calculation of the equalizer constant can be simplified.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical disk drive 10
It is a schematic block diagram of. The optical pickup 11 is a 7ch photodiode that detects reflected light for each channel.
R as the output of the 7ch photodiode 12
The F signal is sent to the I / V amplifier 13, where it is amplified while being subjected to current / voltage conversion. The RF signals of a total of six channels related to the sub beam are directly sent to the variable equalizer 15, and the RF signals of one channel related to the main beam are sent to the microcomputer 17 via the 1ch RF amplifier 14. R for each channel
The F signal is waveform-equalized in the variable equalizer 15 and then sent to the digital PLL 16 to be converted into a synchronous modulation signal such as EFM (when the optical disk is a CD) and EFM + (when the optical disk is a DVD). The microcomputer 17
The DRAM 18 is used to read and write data during arithmetic processing.
Digital PLL 16, servo 19, and signal processing
It sends and receives data to and from the variable equalizer 24 and sends data to the variable equalizer 15. The servo 19 receives the main channel RF signal amplified by the 1ch RF amplifier 14,
Perform track servo and focus servo. The signal processor 24 demodulates and decodes the synchronous modulation signal input from the digital PLL 16 and sends it to the ATAPI interface 25. The ATAPI interface 25 sends and receives data to and from a personal computer 26.

FIG. 2 shows an irradiation state of the beam spot 34 on the optical disk 30. The track 31 extends in the direction of rotation of the optical disk 30 and has bits 32 as recording data. The beam splitter 33 is formed between the tracks 31. A total of seven beam spots 34 are generated on the seven tracks 31 arranged in order in the radial direction of the optical disc 30. For the following description, for the seven beam spots 34, M, E, F, G, H, I,
Name it J. The optical pickup 11 includes one laser light source, and passes a light beam (hereinafter, referred to as a “main beam”) therefrom through a hologram or a diffraction grating to further generate six light beams (hereinafter, referred to as “main beam”). Sub beam). This optical disk drive
Reference numeral 10 indicates seven light beams, but other numbers may be used. M corresponds to one main beam in the optical pickup 11, and E, F, G, H, I, and J correspond to the optical pickup 11.
Correspond to the six sub-beams at With respect to the M main beam, the E and F, G and H, and I and J sub beams travel symmetrically.

FIG. 3 is a detailed view of the 7ch photodiode 12 of FIG. 4 x A, B, C, D in a 2x2 array
The photodiodes 37 are disposed in the center. E, F,
The six photodiodes G, H, I, and J have dimensions approximately twice as large as the photodiodes 37 in the vertical and horizontal directions, respectively, and are sandwiched between the four photodiodes 37 by three on each side. They are arranged so as to form an array with the photodiodes 37. The reflected light from the M beam spot 34 is divided into four photodiodes 37 of A, B, C, and D.
The reflected light from each of the beam spots 34 of E, F, G, H, I, and J is incident on each photodiode 38 of E, F, G, H, I, and J. The sum of the outputs of the four photodiodes A, B, C, and D is the R of the main channel.
The output of each photodiode 38 of E, F, G, H, I, and J becomes a total of six RF signals of each sub-channel.

FIG. 4 is a detailed block diagram of the equalizer 15. The equalizer 15 includes low-pass filters 40, 41, 42,
High-frequency noise is removed by passing through a total of four stages of low-pass filters 43 and 44. The buffers 47 and 48 are provided on the output side of the low-pass filters 42 and 44, respectively. A closed loop is formed by the low-pass filters 50 and 51 and the buffer 52,
The capacitor of the low-pass filter 51 is connected to the output of the buffer 47. The gain control amplifier 54 boosts the cutoff frequency corresponding to the input from the buffer 52. The operational amplifier 56 amplifies the output from the buffer 48 with a gain corresponding to the output of the gain control amplifier 54, and outputs it as a new RF signal. The control 57 to the D / A converter 60 will be described later.

FIG. 5 is a detailed block diagram of the digital PLL 16. The type of the optical disc 30 (for example,
A clock signal of a crystal oscillator having a frequency corresponding to a CD, a DVD, or the like is input, and is divided into 1 / M (M is an integer). The frequency divider 63 is a PLLK from the digital PLL 71.
(Reproduced clock signal) is input and frequency-divided into 1 / N (N is an integer). The phase comparator 64 outputs a signal relating to the phase difference between the frequency dividers 62 and 63, and the output is sent to the VCO 68 via the low-pass filter amplifier 65.
68 outputs a frequency signal corresponding to the phase difference between the frequency dividers 62 and 63. The divider 69 divides the frequency signal of the VCO 68 by 1 / K
(K is an integer), and the slicing circuit 70 slices the RF signal as the output of the variable equalizer 15. The digital PLL 71 processes the input from the slice circuit 70 using the input from the frequency divider 69 as a synchronizing signal while generating the PLCK based on the input from the slice circuit 70, and outputs EFM or EFM + as a synchronous modulation signal. Generate The output of the low-pass filter amplifier 65 is a voltage corresponding to the amount of jitter, and this voltage is sent to the microcomputer 17. Microcomputer 17
Performs processing based on the digital value of the jitter amount converted via the built-in A / D converter.

FIG. 6 shows the relationship between the input data of the microcomputer 17 (the voltage input to the microcomputer 17 from the low-pass filter amplifier 65 of the digital PLL 16 in FIG. 5), the ratio of the jitter amount, the boost amount correction, and the (cut-off) frequency correction. Is shown. An A / D converter is provided at the input terminal of the microcomputer 17 from the low-pass filter amplifier 65. Since the A / D converter converts the input voltage from the low-pass filter amplifier 65 to 16 bits, 5V / 16 = 0. 3I3V, and the input data of the microcomputer 17 is actually from 0V to 0.313V.
The voltage is set up to 5 V in increments, and the amount of boost correction and the amount of frequency correction are set in advance for the input data of the microcomputer 17, and these data are stored in a flash ROM.
It is recorded in. The microcomputer 17 is a digital PLL 16
4 is sent to the control 57 in FIG. 4 as a serial 16-bit signal (DATA) corresponding to the correction amount obtained from the output of the low-pass filter amplifier 65. Control 57 is the microcomputer 17
Further, PLCK (output of the digital PLL 71 in FIG. 5) and WCK are input. Control 57 is a PL
In synchronization with the pulse of CK, DATA is fetched one bit at a time, and when 16 bits are fetched, a pulse is input to WCK and reset by this WCK.

In FIG. 4, control 57 is DATA
The digital value corresponding to the equalizer input data is output in parallel to the D / A converters 58 and 60, and the D / A converter
The analog output voltage 58 is converted into a current by a V / I converter 59, and the output current of the V / I converter 59 is sent to low-pass filters 40, 41, 42, 43, 44, 50, 51. As a result, the cutoff frequency of the variable equalizer 15 is corrected by the correction amount of the jitter amount with respect to the preset initial value. The analog output voltage of the D / A converter 60 is
Sent to the gain control amplifier 54, the gain control amplifier 54 corrects the boost amount for the corrected cutoff frequency by an amount corresponding to the jitter amount. Thus, the RF signal as the output of the variable equalizer 15 is
In response to reading data from the optical disc 30 at that time,
The cutoff frequency and the boost amount of the variable equalizer 15 are set so that the jitter amount becomes zero. This setting
This is performed when the optical disk 30 is set on the spindle motor and the data in the lead-in area is first read, and the data relating to the set value is written in the DRAM 18, and thereafter, the same set value is used for the equalizer constant. I do. The variable equalizer 15 and the digital PLL 16
There are as many signal channels as there are (in this case, seven), and an equalizer constant is set for each variable equalizer 15.

FIG. 7 shows the correspondence between the phase difference (corresponding to the output of the phase comparator 64) and the amount of jitter in each digital PLL 16 when the equalizer constant of the sub beam is set equal to the equalizer constant of the main beam. The reflected light of the main beam is A, B, C, D photodiode 37
Is detected by Since the six sub-beams are arranged symmetrically with respect to the central main beam in pairs, a slight optical path difference occurs in the optical pickup 11, but as shown in FIG. 7, the jitter amounts have substantially the same value. FIG. 7 exemplifies a symmetric relationship between the amounts of jitter of the RF signals of the I and J pairs, but the same applies to the other E and F pairs and the G and H pairs. That is, the amount of jitter of the RF signal of each sub-beam on one side with respect to the main beam is detected, and an equalizer constant for the amount of jitter is obtained.
It can be seen that the signal can be used as it is as an equalizer constant of the signal jitter amount.

FIG. 8 shows input / output signals in the main beam and sub beam variable equalizers 15. RF
The signal processing circuit 27 is built in the 1ch RF amplifier 14, and adds the A, B, C, and D RF signals. The variable equalizers 15m, 15e, 15f, 15g, 15h, 15i, and 15j correspond to the main beam M and the sub beams E, F, G, H, I, and J, respectively. EQF and EQB are variable equalizers respectively
15m, 15e, 15f, 15g, 15h, 15i, and 15j are signals related to the cutoff frequency correction amount and the boost amount correction amount.
There are four, one is the variable equalizer 15m, two is the variable equalizers 15e and 15f, three is the variable equalizers 15g and 15h, and four is the EQF and EQB of the variable equalizers 15i and 15j. RF
O means RF output, MAIN, E, F, G,
There are H, I, J RF outputs. As described with reference to FIG. 7, the sub-beams symmetrical with respect to the main beam M have the same amount of jitter and can set the same equalizer constant, so that the EQF and EQB sent from the microcomputer 17 to the variable equalizer 15 can be shared.

FIGS. 9 and 10 are flowcharts of a process for setting an equalizer constant. When the optical disk 30 is set on the tray (S80) and the power of the optical disk drive 10 is turned on (S81), the DVD beam is activated (S8).
2), the type of the optical disk 30 is determined (S83).
If it can be read with a DVD beam, the optical disk 30 can be determined to be a DVD. If it is not a DVD, this time, the CD beam is activated (S85), and the optical disk 30 is determined (S86). In this way, DVD or C
Optical discs 30 other than D, for example, MD, PD (phase change type disc), and MO optical disc 30 can also be identified. Further, if a compatible beam that can be transformed into various beams is adopted, the type of the optical disc 30 can be determined without switching to another beam source. When the type of the optical disc 30 cannot be determined, the process returns to S80, and when it can be determined, the process proceeds to S84. Next, an error correction method according to the type of the optical disk 30 is selected (S84), and the lead-in area of the optical disk 30 is read according to the error correction method (S8).
7). Thereby, the fine type of the optical disc 30 is further determined (for example, in S83 and S84,
Is identified as a CD, a CD-ROM,
CD-RW, music CD, photo CD, and VID
It is determined which of EOCD and the like. )

In this way, for the optical disc 30 identified to the type whose data structure is known, the variable equalizer 15 performs waveform equalization by substituting the initial value for the equalizer constant (S94). Note that the initial value of the equalizer constant is recorded in advance in the flash ROM for each type of the optical disc 30. At the same time, the amount of jitter is detected by the digital PLL 16 (S95). At this time, in order to ensure the reliability of the setting of the equalizer constant, S95 is performed a plurality of times, for example, 5 times.
Times, the amount of jitter is detected. That is, five tracks are read out for one beam. When the amount of jitter is detected for each channel, the processing in S95 is 7 channels × 5.
Only track = 35 tracks are read. Assuming that the jitter amount of the sub-beams having a symmetrical relationship is the same, the number of channels of the four sub-beams on one side is reduced by 3 channels, and only 4 channels × 5 tracks = 20 tracks are read. About 1300 in the lead-in area
Since the track exists, the equalizer constant setting method can be executed without any trouble. Then, while maintaining the initial value of the equalizer constant for each channel, a total of 5
The amount of jitter is detected each time, and the boost amount correction and the cut frequency correction (FIG. 6) corresponding to the minimum amount of jitter are selected (S96), and the correction values are sent from the microcomputer 17 to the control 57 of the variable equalizer 15. A new output is made (S97), and the correction value is fixed as an optimum equalizer constant while being stored in a memory (S98). That is, thereafter, the fixed equalizer constant is used for the optical disc 30 without detecting the jitter amount and resetting the equalizer constant again.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an optical disk drive.

FIG. 2 is a diagram showing an irradiation state of a beam spot on an optical disc.

FIG. 3 is a detailed view of the 7ch photodiode of FIG. 1;

FIG. 4 is a detailed block diagram of a digital PLL.

FIG. 5 is a detailed block diagram of an equalizer.

FIG. 6 is a diagram illustrating a relationship among input data of a microcomputer, a ratio of a jitter amount, boost amount correction, and (cut) frequency correction.

FIG. 7 shows each digital PL when the equalizer constant of the sub-beam is set equal to the equalizer constant of the main beam.
The correspondence between the phase difference and the amount of jitter in L is shown.

FIG. 8 is a diagram showing input / output signals in main beam and sub beam variable equalizers.

FIG. 9 is a flowchart of the first half of a process for setting an equalizer constant.

FIG. 10 is a flowchart of a latter half of a process for setting an equalizer constant.

[Explanation of symbols]

Reference Signs List 10 optical disk drive (optical disk data reading device) 11 optical pickup 15 variable equalizer (waveform equalizer) 16 digital PLL (jitter amount detecting means, PL
L) 17 microcomputer (equalizer constant setting means) 30 optical disk 34 beam spot

Claims (6)

[Claims] 1. A beam spot on an optical disk (30)
(34) An optical pickup (11) that irradiates (34) and generates an RF signal from the reflected light, (b) Waveform equalization that performs an equalization waveform process on the RF signal input from the optical pickup (11) based on an equalizer constant. (15) and (c) the waveform equalizer (15)
An optical disc characterized by having equalizer constant setting means (17) for detecting an amount of jitter of an RF signal output from the apparatus and setting an equalizer constant in the waveform equalizer (15) based on the amount of jitter. Data reading device. 2. An optical pickup (11) which irradiates a plurality of beam spots (34) to different positions in a radial direction of an optical disc (30) and generates respective RF signals from each reflected light;
(B) a plurality of waveform equalizers (15) provided for each RF signal input from the optical pickup (11) and performing waveform equalization processing of each RF signal based on an equalizer constant; and (c) each RF signal An equalizer constant setting unit (17) for detecting an amount of jitter for each of the waveform equalizers and setting an equalizer constant in each of the waveform equalizers (15) based on the amount of jitter. apparatus. 3. The optical disk data reading device according to claim 1, wherein the equalizer constant is a cutoff frequency and / or a boost amount. 4. An equalizer constant setting means (17) comprising:
The amount of jitter is detected based on a phase difference between a signal corresponding to a synchronization clock signal extracted from the F signal by a PLL (16) and a signal corresponding to a reference frequency signal of a reference frequency for rotation servo of a spindle motor. Claims 1-3
An optical disk data reading device according to any one of the above. 5. The equalizer constant setting means (17) calculates an equalizer constant based on an RF signal when reading data in a lead-in area of the optical disc (30), and thereafter calculates the equalizer constant based on the calculated value. The optical disk data reading device according to any one of claims 1 to 4, wherein the data reading device is fixed. 6. The optical pickup (11), wherein each light beam generating each beam spot (34) is a main beam and sub-beams symmetrically arranged on both sides of the main beam with respect to the main beam. 3. The data reading device for an optical disk according to claim 2, wherein the equalizer constants of the RF signal waveform equalizers (15) related to the sub-beams are set to the same value.