JP2005093014A - Optical disk drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive device which is capable of reading the data recorded on an optical disk with higher reproducing quality. <P>SOLUTION: A synchronous code that is an identification code is added at every certain interval for recorded data on an optical disk. In the driver, an amplitude detecting circuit 30 extracts portions corresponding to the synchronous codes from RF signals which are generated based on the information read by an optical pickup 10 and a DSP 40 computes every modulation degree of the recorded data based on an amplitude value of the extracted synchronous code. Then, amplitudes of the RF signals are corrected in real time by an equalizer 50 based on the computed modulation degree so that amplitudes of the RF signals are maintained within a prescribed range. The RF signals which are corrected in real time are demodulated through a demodulator 60. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc drive apparatus that performs reproduction or recording / reproduction of an optical disc.

  Currently, there are CD optical disks such as CD, CD-ROM, and CD-R / RW, and DVD optical disks such as DVD, DVD-ROM, DVD-RAM, DVD-R / -RW, and DVD + R / + RW.

  Among these, reproduction-only standards include CD, CD-ROM, DVD, DVD-ROM and the like. Also, standards that enable recording include CD-R / RW, DVD-RAM, DVD-R / -RW, and DVD + R / + RW. Furthermore, among these standards that allow recording, there are CD-RW, DVD-RAM, DVD-RW, DVD + RW, and the like that can be overwritten using phase change. There are CD-R, DVD-R, DVD + R and the like.

  By the way, these optical discs are shipped from a plurality of disc manufacturers so as to satisfy the standard values. However, the recording quality and the reproducing quality when recording / reproducing is performed for each manufacturer or each production lot. Usually it is slightly different.

So, in the past, to keep the recording quality at least constant,
(A) A method of correcting a strategy pulse at the time of recording by an optical disk drive based on pulse strategy information previously recorded by each disk manufacturer on the lead-in of the optical disk. (B) The drive manufacturer searches for the optimal pulse strategy for each disk manufacturer's optical disk, records this in advance in the drive memory, and reads the disk manufacturer's ID from the lead-in information when reading the disk. A method of searching for the relevant pulse strategy from the drive memory and using it during recording.
Etc. have been proposed.

  In general, the recording quality with respect to the optical disc is maintained substantially constant by correcting the above-described strategy pulse and adopting an appropriate pulse strategy according to the disc used. However, as a matter of fact, even if the disc is optimally recorded for each maker, if there are fingerprints or scratches on it, the effect may cause overwriting or overwriting. The recording quality is not always constant. And the reproduction quality of the disc recorded in such a manner is not constant.

  Strictly speaking, the optimum laser power during recording varies depending on the temperature. Generally, an attempt is made to secure the optimum laser power by a method called running OPC (optimum recording power adjustment). However, if the temperature changes before and after switching the laser power, the recording quality is improved. You may not be able to keep it constant. Also in this case, the reproduction quality deteriorates.

  Furthermore, the playback quality is not constant even when the disc is warped. Normally, efforts are made to maintain reproduction quality on the drive side by tilt adjustment, focus offset adjustment, etc., but the influence of such warpage cannot be completely absorbed.

  In addition, the reproduction quality is not constant due to acquired scratches after recording, adhesion of fingerprints, or aging of the film forming the recording layer (reflection layer) of the disk.

  When the reproduction quality varies as described above, a large inconvenience arises in operating the optical disc, such as the recorded data not being read out normally.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical disc drive apparatus that can read data recorded on an optical disc with higher reproduction quality.

  In order to achieve these objects, the invention described in claim 1 is directed to an optical disc drive apparatus for reproducing data recorded on an optical disc with an identification code provided at regular intervals via the optical pickup. Extracting a portion corresponding to the identification code of the RF signal generated based on the read information, calculating the degree of modulation of the recording data each time based on the amplitude value of the extracted identification code, and Pre-processing means for correcting the RF signal in real time so that the amplitude of the RF signal falls within a predetermined range based on the calculated degree of modulation is provided. The RF signal corrected in real time by the pre-processing means is demodulated and recorded. The gist is to reproduce the recorded data.

  According to such a configuration as the optical disk drive device, the modulation degree for each time is calculated based on the identification code, and before the amplitude of the RF signal is corrected in real time based on the calculated modulation degree. Processing is performed. For this reason, the amplitude of the RF signal is naturally stabilized, so that even if the above-described factors affecting the reproduction quality are present, stable data reproduction that is not affected by those factors is performed. Become.

  According to a second aspect of the present invention, in the optical disk drive device according to the first aspect, the preprocessing means extracts a portion corresponding to the identification code of the RF signal based on the demodulated data. The gist is to have a closed loop structure.

  Various methods are conceivable for extracting the portion of the RF signal corresponding to the identification code. However, according to the above configuration in which the portion is extracted based on the demodulated data, the identification code is more reliably added to the identification code. Corresponding portions can be extracted, and as a result, the calculation accuracy can be improved in calculating the modulation factor.

  According to a third aspect of the present invention, in the optical disc drive apparatus according to the second aspect, the optical disc is a DVD standard optical disc, and the preprocessing means uses the demodulated signal as 32 as the identification code. A sync code detection circuit for detecting a sync code having a channel bit length, and a window signal corresponding to each of a 4-channel bit length (4T) portion and a 14-channel bit length (14T) portion included in the code from the detected sync code , An amplitude detection circuit for extracting the RF signal from each of the generated window signals and detecting the amplitude thereof, and an amplitude value (4T amplitude) of the RF signal corresponding to the detected 4T portion ) And the amplitude value of the RF signal corresponding to the 14T portion (14T amplitude) is multiplied by a predetermined correction value each time. Means for calculating a modulation factor and outputting a gain adjustment command based on the calculated modulation factor, and an equalizer for correcting the amplitude of the RF signal based on the output gain adjustment command Is the gist.

In the case of a DVD standard optical disc, the sync code having the 32-channel bit length can be used as the identification code. The sync code includes the 4 channel bit length (4T) portion and the 14 channel bit length (14T) portion described above. Therefore, the amplitude corresponding to each of those portions of the RF signal is detected to By calculating the modulation factor, the modulation factor can be obtained each time under the same conditions. For this reason, the stability of the RF signal whose amplitude is corrected through the equalizer is also ensured, and at least the reproduction quality of the DVD standard optical disc is suitably maintained.

  According to a fourth aspect of the present invention, in the optical disk drive device according to the third aspect, a correction value for multiplying a ratio of 4T amplitude to 14T amplitude “4T amplitude / 14T amplitude” in order to calculate the degree of modulation. Is a value less than “1.0” for conversion to the modulation degree “I3 / I14” as an index in the DVD standard.

  In the DVD standard optical disc, a desirable modulation degree is thus defined as “I3 / I14”. That is, when converted into the amplitude ratio, the value is “3T amplitude / 14T amplitude”. Therefore, by adopting a correction value less than “1.0” for converting “4T” to “3T” as in the above configuration, a more desirable modulation degree as a DVD standard optical disk can be obtained. As a result, even an RF signal whose amplitude is corrected through the equalizer can be a more desirable form as an RF signal extracted from the optical disc of the DVD standard.

  According to a fifth aspect of the present invention, in the optical disc drive device according to the third or fourth aspect, the equalizer includes a five-tap equalizer that sequentially propagates the RF signal, and the first tap of the equalizers. The third tap and the fifth tap are configured so that tap coefficients can be changed, and the sum of signals from taps whose tap coefficients can be changed is output as the RF signal corrected in real time. The gist of the gain adjustment command is a tap coefficient change command for the first tap, the third tap, and the fifth tap in which the tap coefficient can be changed.

  Further, the invention according to claim 6 is the optical disk drive device according to claim 5, wherein the means for calculating the modulation factor and outputting the gain adjustment command has the calculated modulation factor below a predetermined range. When outputting a command to change the tap coefficient set to the first tap and the fifth tap to a larger tap coefficient, when the calculated modulation degree exceeds a predetermined range, The gist is to output a command to change the tap coefficient set to the first tap and the fifth tap to a smaller tap coefficient.

  In particular, according to the configuration described in claim 5, the configuration as the equalizer can be simplified, and according to the configuration described in claim 6, the amplitude of the RF signal by the equalizer Correction processing can also be performed very simply.

  According to a seventh aspect of the present invention, in the optical disc drive device according to any one of the third to sixth aspects, the amplitude detection circuit outputs an RF signal extracted from the generated window signals. The gist of the present invention is to provide a peak hold circuit and a bottom hold circuit, respectively.

  According to such a configuration as the amplitude detection circuit, the above-described amplitude detection of the RF signal can be performed more easily and accurately.

  According to an eighth aspect of the present invention, in the optical disc drive apparatus according to any one of the third to seventh aspects, the means for generating the window signal has its channel bit based on the detected sync code. The gist of the invention is that it comprises a timing counter that outputs an active window signal corresponding to each of the 4-channel bit length (4T) portion and the 14-channel bit length (14T) portion while counting the length.

  If such a timing counter is used as means for generating the window signal, the window signal corresponding to the 4-channel bit length (4T) portion or the 14-channel bit length (14T) portion can be used. Even the window signal to be generated can be easily realized.

  According to the present invention, the degree of modulation for each time is calculated based on the identification code, and the pre-processing is performed in which the amplitude of the RF signal is corrected in real time based on the calculated degree of modulation. For this reason, the amplitude of the RF signal is naturally stabilized, and even if there are factors that affect the reproduction quality, stable data reproduction that is not influenced by those factors is performed.

  Hereinafter, an optical disk drive device according to an embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, an apparatus for reproducing data written on a DVD + R standard optical disc will be described as an example.

  The DVD-type optical disc is subjected to 8/16 modulation at the time of recording, and modulates 8 bits of original data into a 16-bit code defined by a modulation table. The basic modulation rule is to set the number of consecutive “0” s between code bits “1” and “1” to “2” or more and “10” or less. On the disc, the data of the modulation code string is inverted by “0” and the data bit modulation not inverted by “1”, that is, a channel bit pulse string converted by NRZI (Non-Return To Zero Inverse) is recorded. Assuming that one channel bit width is T, the shortest pulse width of the recording channel bit pulse train is 3T and the longest pulse width is 11T according to the modulation rule. At the time of reproducing the optical disc, 8/16 modulation is demodulated. In the demodulation process, the reproduced channel bit string is subjected to inverse NRZI conversion to obtain a 16-bit unit modulation code. This is inversely converted by an 8/16 modulation table and demodulated into 8-bit original data. However, some modulation codes can be demodulated into two original data bytes, and such modulation codes can be identified by the number of “0” at the end thereof. In this case, the original data byte is determined with reference to two specific bits of the next successive modulation code.

  First, a schematic configuration of the optical disc drive apparatus according to this embodiment will be described with reference to FIGS.

  In the optical disk drive apparatus shown in FIG. 1, a pickup (optical pickup) 10 is a part that reads data recorded on an optical disk OD by laser light and converts it into an electrical signal. An optical system including a lens, a mirror, a beam splitter, and the like, and a light receiving element. Then, the pit row formed in the recording layer of the optical disc OD is irradiated with laser light, and the laser light reflected from the pit row is received by the light receiving element and converted into an electric signal. The converted electrical signal is sent to the RF amplifier 20, where it is appropriately amplified, and then sent to the amplitude detection circuit 30 and the equalizer 50 as an RF signal (RF0).

  The amplitude detection circuit 30 is a circuit for peak-holding and bottom-holding the RF signal (RF0) extracted by the 4T window signal 4TW and the 14T window signal 14TW generated by the timing counter 80 described later. That is, the amplitude detection circuit 30 basically includes four circuits: a 4T peak hold circuit 31, a 4T bottom hold circuit 32, a 14T peak hold circuit 33, and a 14T bottom hold circuit.

  Among these, the 4T peak hold circuit 31 is a circuit for peak-holding the RF signal (RF0) extracted by the 4T window signal 4TW, and the amplitude value (4T amplitude) of the RF signal (RF0) corresponding to the 4T portion. ) Is output. The held 4T peak value is converted to a digital signal by the A / D converter 35 and sent to a DSP (digital signal processor) 40.

  Similarly, the 4T bottom hold circuit 32 is a circuit that bottom-holds the RF signal (RF0) extracted by the 4T window signal 4TW, and the amplitude value (4T amplitude) of the RF signal (RF0) corresponding to the 4T portion. Output the bottom value of. The held 4T bottom value is converted into a digital signal by the A / D converter 36 and sent to the DSP 40.

  The 14T peak hold circuit 33 is a circuit for peak-holding the RF signal (RF0) extracted from the 14T window signal 14TW, and the amplitude value (14T amplitude) of the RF signal (RF0) corresponding to the 14T portion. The peak value of is output. The held 14T peak value is converted to a digital signal by the A / D converter 37 and sent to the DSP 40.

  The 14T bottom hold circuit 34 is also a circuit that bottom-holds the RF signal (RF0) extracted by the 14T window signal 14TW, and the amplitude value (14T amplitude) of the RF signal (RF0) corresponding to the 14T portion. Output the bottom value of. The held 14T bottom value is converted into a digital signal by the A / D converter 38 and sent to the DSP 40.

  The DSP 40 to which the 14T peak value, the bottom value, and the 14T peak value and the bottom value are input calculates 4T amplitude and 14T amplitude, respectively, and on the basis of each amplitude value, the recording data is modulated each time. This is the part that calculates degrees. In this calculation, first, the 4T amplitude is calculated as “(4T peak hold value) − (4T bottom hold value)” from the 4T peak hold value and the 4T bottom hold value detected (held) by the amplitude detection circuit 30. . Next, the 14T amplitude is calculated as “(14T peak hold value) − (14T bottom hold value)” from the 14T peak hold value and the 14T bottom hold value. Then, the modulation degree is calculated from these 4T amplitude and 14T amplitude as “modulation degree (I3 / I14) = α × 4T amplitude / 14T amplitude”. In the DVD standard optical disc, a desirable modulation degree is thus defined as “I3 / I14”. That is, when converted into the amplitude ratio, the value is “3T amplitude / 14T amplitude”. Therefore, in this embodiment, by adopting a correction value α less than “1.0” for converting “4T” to “3T” as in the above calculation formula, a more desirable modulation degree as an optical disc of the DVD standard is adopted. Asking for.

  The DSP 40 includes means for outputting a tap coefficient change signal TC (gain adjustment command) to the equalizer 50 based on the modulation degree thus calculated. Basically, when the calculated degree of modulation falls below a predetermined range, a command for changing the tap coefficient to a larger tap coefficient is output to the equalizer 50. When the calculated degree of modulation exceeds a predetermined range, a command for changing the tap coefficient to a smaller tap coefficient is output to the equalizer 50.

  The equalizer 50 is a part that corrects the amplitude of the RF signal (RF0) output from the RF amplifier 20 in real time based on the tap coefficient change signal TC thus provided from the DSP 40 so that the amplitude is within a predetermined range. . FIG. 2 shows an example of the internal structure of the equalizer 50. Next, the configuration and function of the equalizer 50 will be described with reference to FIG.

  As shown in FIG. 2, the equalizer 50 includes a 5-tap equalizer having taps 51 to 55 that sequentially propagate the RF signal (RF0) output from the RF amplifier 20. Of these, the first tap 51, the third tap 53, and the fifth tap 55 are configured such that tap coefficients can be changed through tap coefficient changing multipliers Tap1, Tap2, and Tap3, respectively. Based on the tap coefficient change signal TC, the values of the first, third, and fifth taps 51, 53, and 55 multiplied by the tap coefficients set in the multipliers Tap1, Tap2, and Tap3 are added. 59, and the added value is output to the demodulator 60 (FIG. 1) as a final RF signal (RF) corrected in real time.

  On the other hand, the demodulator 60 shown in FIG. 1 is a known circuit that performs demodulation processing on the data recorded on the optical disc OD based on the RF signal (RF) input in this way. That is, in this example, the demodulator 60 performs a process of inversely transforming 16-bit data 8 / 16-modulated at the time of recording using an 8/16 modulation table and demodulating it into 8-bit original data. One of the data demodulated 8/16 by the demodulator 60 is output to the sync code detection circuit 70, and the other is output to the decoder 90.

  The sync code detection circuit 70 shown in FIG. 1 is a circuit that detects a sync code added to recording data based on the data demodulated by the demodulator 60 in this way. By the way, the optical disc OD of the DVD standard is configured to have a physical sector of 26 sync frames in which a sync code of 32T is inserted for every 1456T of recording sectors (2976T × 13 rows).

  Here, the concept of the sync frame and sync code will be described with reference to FIGS.

  FIG. 3 shows the physical sector having the 26 sync frame structure, in which the number indicating the frame length indicates the channel bit length T, and “SY0” to “SY7” indicate the sync code. As described above, the sync code has a 32-channel bit length (32T). One of these sync codes “SY0” to “SY7” functions as a mark of a constant interval so as not to mistake the boundary of 16 channel bits during demodulation.

  Next, a sync code recording pattern, a circuit for detecting the sync code, and a circuit for generating the window signals 4TW and 14TW based on the detected sync code will be described with reference to FIG.

  FIG. 4A is an enlarged time chart of any one of the sync codes (“SY0” to “SY7”). As shown in FIG. 4A, a pulse having a 14 channel bit length (14T) that is sufficiently longer than the longest pulse width (11 channel bit length) that appears during data modulation is embedded in the sync code. Therefore, the sync code detection circuit 70 basically detects a sync code (identification code) based on the 14T. As described above, this sync code is provided at regular intervals. Once this sync code is detected, the sync code can be detected every 1456T thereafter. The sync code detection circuit 70 outputs the sync detection signal SYS to the timing counter 80 every time the sync code is detected in this way (FIG. 4B).

Similarly, the timing counter 80 shown in FIG. 1 is based on the sync detection signal SYS supplied from the sync code detection circuit 70 in the manner shown in FIGS. 4 (c) and 4 (d). This is the part that generates 4TW and 14TW. As shown in FIGS. 4 (c) and 4 (d), the window signals 4TW and 14TW respectively have a channel bit length based on the detected sync code (32T) and a 4T channel bit length (4T) portion. And 14T channel bit length (14T) portions corresponding to the active signals. Then, the generated window signals 4TW and 14TW are sent to the amplitude detection circuit 30 and used for amplitude detection of the RF signal (RF0) described above.

The decoder 90 to which the demodulated data is input from the demodulator 60 is a circuit that decodes the demodulated data by performing error correction or the like. When the optical disc is reproduced, the demodulated / decoded data is transferred to an external processor unit (such as a personal computer or a player) via the interface (I / F) 100. By the way, as this interface, for example, ATAPI (AT
(Attachment Packet Interface) and SCSI (Small)
A circuit corresponding to a standard such as Computer System Interface can be appropriately employed.

  Hereinafter, the modulation degree correcting operation of the optical disc drive apparatus according to this embodiment having the above-described configuration will be described in more detail with reference to FIGS.

  The correction of the modulation degree is executed with the reproduction of the optical disc OD. That is, as described above, the data read by the pickup 10 and converted into an electrical signal is amplified by the RF amplifier 20 to become an RF signal (RF0), and then the amplitude detection circuit 30 on the other hand, Amplitudes corresponding to the 4T portion and the 14T portion are detected and taken into the DSP 40.

  In the DSP 40, as shown in FIG. 5, first, from the 4T peak hold value and the 4T bottom hold value detected by the amplitude detection circuit 30, “(4T peak hold value) − (4T bottom hold value)”. ) ", 4T amplitude is calculated (step S1). Next, similarly, the 14T amplitude is calculated as “(14T peak hold value) − (14T bottom hold value)” from the 14T peak hold value and the 14T bottom hold value detected by the amplitude detection circuit 30 (step S2). ). Then, the modulation degree is calculated from these 4T amplitude and 14T amplitude as “modulation degree (I3 / I14) = α × 4T amplitude / 14T amplitude” (step S3).

  Thereafter, it is determined whether or not the modulation degree is within the standard range (step S4). Here, the lower limit is determined by the disc standard and is, for example, “0.15”. Although the upper limit value is not particularly determined in the standard, it is necessary to appropriately determine the degree of modulation, that is, the value of “α × 4T amplitude / 14T amplitude” so that it does not become too large. Here, the upper limit value is, for example, “0.8” to “0.9”.

  When it is determined in the condition determination in step S4 that the modulation degree is lower than the lower limit value, the DSP 40 is set to the first tap 51 and the fifth tap 55 of the equalizer 50 through the tap coefficient change signal TC. A command for changing the tap coefficient to a larger tap coefficient is issued (step S5). If the degree of modulation is within the specified value range, the tap coefficients set in the first tap 51 and the fifth tap 55 are left as they are (step S6). When the modulation degree exceeds the upper limit value, the DSP 40 also changes the tap coefficients set in the first tap 51 and the fifth tap 55 to smaller tap coefficients through the tap coefficient change signal TC. A command is issued (step S7).

  FIG. 6 shows an example of the amplitude correction mode by the equalizer 50 accompanying such a change of the tap coefficient.

As described above, the equalizer 50 is a tap for the first tap 51, the third tap 53, and the fifth tap 55 among the taps 51 to 55 that receive the RF signal (RF0) from the RF amplifier 20. The coefficient is set to be changeable. Here, for example, as shown in FIG. 6A, when the tap coefficient change signal TC from the DSP 40 is set to −10a for Tap1, 100a for Tap2, and −10a for Tap3 (a is an arbitrary coefficient value). As shown in FIG. 6B, the amplitude of the synthesized waveform of the RF signal added by the adder 59 rises at the center. Note that FIG. 6B is a schematic diagram, and actually the amplitude slightly increases in the multiplication part of Tap1 and Tap3.

  For this reason, when the modulation degree falls below the lower limit in the condition determination of the modulation degree in step S4, the tap coefficients of Tap1 and Tap3 are changed to “−11a”, for example, through the tap coefficient change signal TC. Thereby, the amplitude as the RF signal (RF) can be raised. Further, when the modulation degree exceeds the upper limit value in the same condition determination, for example, the tap coefficients of Tap1 and Tap3 are changed to “−9a” through the tap coefficient change signal TC. Thereby, the amplitude as the RF signal (RF) can be lowered. As a specific method of changing the tap coefficients, it is possible to gradually correct the amplitude in real time by incrementing / decrementing the tap coefficient values of Tap1 and Tap3 by “1a”.

  In any case, the data recorded on the optical disk can be reproduced with higher quality by applying such pre-processing to the RF signal and supplying it to the demodulator 60. It becomes like this.

  As described above in detail, according to the optical disk drive device of this embodiment, many excellent effects listed below can be obtained.

  (1) In the case of a DVD standard optical disc OD, a sync code of 32 channel bit length (32T) can be used as the identification code. Since this sync code includes a 4-channel bit length (4T) portion and a 14-channel bit length (14T) portion, the amplitude corresponding to each of those portions of the RF signal is detected to determine the modulation degree. Since the calculation is performed, the degree of modulation can be obtained each time under the same conditions. For this reason, the stability of the RF signal whose amplitude is corrected through the equalizer 50 is also ensured, and at least the reproduction quality of the optical disc OD of the DVD standard is suitably maintained.

  (2) In the calculation of the modulation factor, a correction value less than “1.0” for converting the 4-channel bit length (4T) to the 3-channel bit length (3T) is adopted, so that a more desirable modulation factor as the DVD standard is adopted. Can be requested. In addition, an RF signal whose amplitude is corrected via the equalizer 50 can be a more desirable signal as an RF signal extracted from the optical disc of the DVD standard.

  (3) The equalizer 50 is a 5-tap equalizer that sequentially propagates the RF signal, and the tap coefficient of the first tap 51, the third tap 53, and the fifth tap 55 can be changed. Configured. The sum of signals from taps whose tap coefficients can be changed is output as an RF signal corrected in real time. Thereby, the structure as the equalizer 50 can be simplified. At the same time, the amplitude correction processing of the RF signal by the equalizer 50 can be performed very simply.

  (4) The amplitude detection circuit 30 includes a circuit that holds the RF signal extracted by the window signals 4TW and 14TW in a peak hold and bottom hold, respectively. Thereby, the amplitude detection of the RF signal can be performed more easily and accurately.

  (5) The window signals 4TW and 14TW are generated based on the sync code detected from the actually demodulated data. In other words, a closed loop structure was adopted. As a result, it is possible to more accurately extract the RF signal corresponding to the sync code as the identification code, and as a result, the calculation accuracy can be improved when calculating the modulation factor.

  Note that the optical disk drive device according to the present invention is not limited to the above-described embodiment, and can be implemented as, for example, the following forms obtained by appropriately changing the embodiment.

  -The method of changing tap variables is not limited to increment / decrement of tap coefficient values, but a method of referring to a table for changing tap coefficients, a method of obtaining a predetermined calculation for each tap coefficient, etc. Can be adopted. Further, the configuration of the equalizer 50 is not limited to the configuration illustrated in FIG. 2, and the tap coefficient and the like are arbitrary.

  In the above embodiment, the lower limit value of the modulation degree is set to “0.15”, and the upper limit value is set to “0.8” to “0.9”, but these values depend on the optical disc to be reproduced. Can be changed arbitrarily.

In the above embodiment, the modulation factor is obtained as “modulation factor (I3 / I14) = α × 4T amplitude / 14T amplitude”. However, if the change in the modulation factor calculated each time (currently) suddenly increases, for example,
Modulation factor = {(4 × past average modulation factor) + current modulation factor} / 5 (1)
It is possible to appropriately adopt the method of obtaining such as. By adopting such a method for obtaining the modulation degree, even if the current modulation degree changes suddenly, it can be suitably gradually changed. In addition, the gradual change effect becomes larger by increasing the denominator (value of “5”) and the numerator (value of “4”) of the above formula (1).

  In the above embodiment, the amplitude detection circuit 30, the DSP 40, the equalizer 50, the sync code detection circuit 70, and the timing counter 80 that constitute the preprocessing means have a closed loop structure via the demodulator 60. However, when a timing generation circuit or the like capable of generating and outputting the window signals 4TW and 14TW independently is provided, the preprocessing means does not include the sync code detection circuit 70 and the timing counter 80. It can also be configured as an open loop structure.

In the above embodiment, an apparatus for reproducing data written on a DVD + R standard optical disk has been described. However, an optical disk to be reproduced is not limited to a CD system and a DVD system, and is arbitrary. In recent years, in particular, the Blu-ray standard and AOD (Advanced Optical
Disc) standards and other optical discs of a standard that realizes further higher density and larger capacity have been proposed, but the present invention can also be applied to such optical discs.

1 is a block diagram showing an embodiment of an optical disc drive apparatus according to the present invention. The block diagram which shows the internal structural example of the equalizer of the apparatus of the embodiment. The format figure which shows the data format example of the optical disk of DVD specification. (A) is a sync code recording pattern, (b) is a sync detection signal SYS, (c) is a 4T window signal 4TW, and (d) is a time chart showing a 14T window signal 14TW. The flowchart which shows the process sequence by DSP. (A) is a graph showing an RF signal after amplitude correction, and (b) is a graph showing an RF signal after amplitude correction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Pickup, 20 ... RF amplifier, 30 ... Amplitude detection circuit, 31 ... 4T peak hold circuit, 32 ... 4T bottom hold circuit, 33 ... 14T peak hold circuit, 34 ... 14T bottom hold circuit, 35, 36, 37, 38 ... A / D converter, 40 ... DSP, 50 ... Equalizer, 51, 52, 53, 54, 55 ... Tap, 59 ... Adder, 60 ... Demodulator, 70 ... Sync code detection circuit, 80 ... Timing counter, 90 ... Decoder, 100 ... Interface (I / F), OD ... Optical disc.

Claims (8)

In an optical disc drive apparatus for reproducing data recorded on an optical disc with an identification code given at regular intervals via an optical pickup,
A portion corresponding to the identification code of the RF signal generated based on the information read out through the optical pickup is extracted, and the degree of modulation of the recording data each time based on the amplitude value of the extracted identification code And pre-processing means for correcting the RF signal in real time so that the amplitude of the RF signal falls within a predetermined range based on the calculated degree of modulation, and the RF signal corrected in real time by the pre-processing means An optical disc drive apparatus for demodulating and reproducing the recorded data. The optical disc drive apparatus according to claim 1, wherein the preprocessing means has a closed loop structure for extracting a portion corresponding to the identification code of the RF signal based on the demodulated data. The optical disk is a DVD standard optical disk, and the preprocessing means detects a sync code detection circuit that detects a sync code of 32-channel bit length as the identification code from the demodulated signal, and the detected sync code. Means for generating window signals respectively corresponding to a 4-channel bit length (4T) portion and a 14-channel bit length (14T) portion included in the code, and extracting the RF signal from each of the generated window signals Each of the amplitude detection circuits for detecting the amplitude and a ratio between the detected amplitude value of the RF signal corresponding to the 4T portion (4T amplitude) and the amplitude value of the RF signal corresponding to the 14T portion (14T amplitude) are predetermined. Means for multiplying the correction value to calculate the degree of modulation each time and outputting a gain adjustment command based on the calculated degree of modulation; Optical disc drive apparatus according to comprised claim 2 and a equalizer for correcting the amplitude of the RF signal based on the gain adjustment command outputted. A correction value that is multiplied by the ratio “4T amplitude / 14T amplitude” of 4T amplitude to 14T amplitude in order to calculate the modulation degree is converted to “I3 / I14” as an index in the DVD standard. The optical disk drive device according to claim 3, wherein the value is less than 1.0. The equalizer is composed of a 5-tap equalizer that sequentially propagates the RF signal, and the tap coefficient of the first tap, the third tap, and the fifth tap can be changed. In addition, the sum of signals from taps whose tap coefficients can be changed is output as the RF signal corrected in real time, and the gain adjustment command includes the first tap and the second tap whose tap coefficients can be changed. The optical disc drive apparatus according to claim 3 or 4, wherein the command is a tap coefficient change command for the tap 3 and the fifth tap. The means for calculating the degree of modulation and outputting the gain adjustment command, when the calculated degree of modulation falls below a predetermined range, sets the tap coefficients set for the first tap and the fifth tap. A command to change to a larger tap coefficient is output, and when the calculated modulation degree exceeds a predetermined range, the tap coefficient set for the first tap and the fifth tap is set to a smaller tap. The optical disc drive apparatus according to claim 5, wherein a command for changing to a coefficient is output. The optical disc drive apparatus according to any one of claims 3 to 6, wherein the amplitude detection circuit includes a circuit that holds a peak hold and a bottom hold of an RF signal extracted from each of the generated window signals. The means for generating the window signal counts the channel bit length based on the detected sync code, and corresponds to the 4 channel bit length (4T) portion and the 14 channel bit length (14T) portion, respectively. The optical disc drive apparatus according to claim 3, further comprising a timing counter that outputs an active window signal.

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