JP2004022010A - Disk reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reading accuracy of a prepit string arranged at the intermediate position between a land track and a groove track. <P>SOLUTION: This device is provided with a pickup (PUH) consisting of a laser diode for irradiating a disk with a laser beam and a detector 21 which is arranged for detecting the light reflected from the disk and bisected in the radial direction of the disk, a differential amplifier 24 for producing a signal of the difference between both detection areas of the bisected detector 21, a summing amplifier 25 for producing a signal of the sum of both detection areas of the detector 21, a controller 29 for evaluating about which output signal of the differential amplifier 24 or the summing amplifier 25 is suitable for reproducing the information of the prepit, and a switch circuit 26 for selecting either one out of the differential amplifier 24 and the summing amplifier 25 for reproducing the information of the prepit in accordance with the evaluation result of the controller 29. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording / reproducing apparatus for an optical disc which records data using both or one of a land track and a groove track as a recording track.
[0002]
[Prior art]
A so-called DVD-RAM is known as an optical disk using a phase change medium.
[0003]
The DVD-RAM adopts a single spiral format in which land tracks and groove tracks are alternately arranged on one spiral. In the user area, data is recorded as marks on both land tracks and groove tracks.
[0004]
On the other hand, in the header area, ID information such as address information is recorded as a pre-pit string at a position １ ／ track away from the center of the land track and the groove track in the disk radial direction, that is, an intermediate position between the land track and the groove track. Have been. Such an arrangement of the header area is called a CAPA (Complementary Allocated Pit Address) format. In the header area, ID information such as address information is recorded.
[0005]
That is, the header information includes a sector number indicating an address number, a track number, and land / groove identification information. The sector number indicates a physical address of the sector on the optical disk. The track number represents, for example, the number of a physical track on the optical disk. The track number may not only represent the number of a physical track on the optical disc, but may also represent the number of a logical track in which one track corresponds to the number of sectors for one track. The land / groove identification information is information indicating whether the corresponding track is a land track or a groove track.
[0006]
In the DVD-RAM standard, 2.6 GB and 4.7 GB disks are defined, and the track pitch of the disk is set to 0.74 μm for 2.6 GB and 0.615 μm for 4.7 GB. ing.
[0007]
As described above, address information (referred to as CAPA) indicating an absolute position on the disk is recorded on these disks in advance, and this signal is staggered in the track direction around the track. Are located. To read this, a photodetector divided into two in the track direction was used to obtain the electric signal output of each of the divided photodetectors, and in the case of a 2.6 GB DVD-RAM disk, the difference was taken and address demodulation was performed. . In the case of a 4.7 GB DVD-RAM disk, address demodulation is performed after the sum of the electric signal outputs of the two divided photodetectors is obtained.
[0008]
Such a reproducing process is recommended in the disc standard and is disclosed in Japanese Patent Application Laid-Open No. H11-273084.
[0009]
That is, JP-A-11-273084 discloses that a reflected light from an optical disk is detected by a two-divided detector, and a difference signal and a sum signal of output signals from each light receiving area of the detector are generated by a differential amplifier and an addition amplifier. When the optical disk is a first disk having a relatively wide track pitch, a difference signal is selected, and when the optical disk is a second disk having a relatively narrow track pitch, a sum signal is selected by a switching circuit 26 and processed by a signal processing circuit. Further, there is disclosed an apparatus for reproducing information recorded by a pit string.
[0010]
In a disc reproducing apparatus that reads two discs of 2.6 GB and 4.7 GB, light irradiated on the disc is small so that the reading performance of 4.7 GB with a narrow track pitch is improved. A light spot is generally considered. In particular, since the 4.7G disk has a narrow track pitch, it is necessary to set so that the light spot becomes narrow in the track direction in order to reduce crosstalk.
[0011]
By the way, as a result of the inventor's various experiments, since the CAPAs are arranged on the disk with respect to the tracks, the smaller the spot size, the smaller the amount of light irradiated to the CAPAs and the lower the reading rate. It was found that a problem of lowering occurred. It has also been found that the difference signal for a 2.6 GB disc and the sum signal for a 4.7 GB disc do not always maximize the readability of address information.
[0012]
That is, the track pitch of the disk varies from disk to disk due to errors in the manufacturing process of the disk, and the size of the read spot varies from pickup to pickup. As a result, in particular, the address of the 2.6 G disk is affected. If the information reading rate fluctuates and is extreme, there is a problem that the address information cannot be read at all.
[0013]
[Problems to be solved by the invention]
As described above, the present invention solves the problem that the reading accuracy of a pre-pit row arranged at an intermediate position between a land track and a groove track varies depending on the type of a disc, and is arranged at an intermediate position between a land track and a groove track. It is an object of the present invention to provide an optical disk recording / reproducing apparatus capable of improving the reading accuracy of a pre-pit string.
[0014]
According to the present invention, there is provided a disk reproducing apparatus for reproducing a disk having a prepit formed at an intermediate position between a land track and a groove track. A light source, a pickup arranged to detect light reflected from the land track or groove track, and a detector divided into at least two in the radial direction of the disk, and a detector divided in the disk radial direction Difference detecting means for generating a signal of the difference between the two, a sum detecting means for generating a sum signal of the detectors divided in the disk radial direction, and an output signal of the difference detecting means and an output signal of the sum detecting means. Means for evaluating which of the difference detection means and the sum detection means is suitable for reproducing the information of the pre-pits; Either one of said difference detecting means or sum detector based on the evaluation result of the evaluation means and selecting means for selecting for reproduction of information of the pre-pits.
[0015]
Further, the present invention provides a disc reproducing apparatus for reproducing a disc having a prepit formed at an intermediate position between a land track and a groove track, a light source for irradiating the disc with laser light, and a reflected light from the land track or groove track. A pickup comprising: a detector arranged to detect the disk; and a detector divided at least into two parts in the radial direction of the disk; a difference detecting means for generating a signal of a difference between the detectors divided in the disk radial direction; Sum detection means for generating a signal of the sum of the detectors divided in the radial direction, means for reading the information of the pre-pits from the output signal of the difference detection means or the output signal of the sum detection means, When the information of the pre-pit cannot be read, the difference detection means and the sum detection means are switched and the difference is read again. That.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a block diagram of a disk recording / reproducing apparatus 1 according to the first embodiment of the present invention.
[0018]
As shown in FIG. 1, in a disk recording / reproducing apparatus 1, an optical disk 10 is rotated at an appropriate rotation speed by a spindle motor 11 driven by a motor driving circuit 12 during recording / reproduction, and a semiconductor laser is driven by an LD driving circuit 13. The (LD) 14 is driven to emit a light beam.
[0019]
The light beam emitted from the semiconductor laser 14 is collimated by a collimating lens 15, and then enters an objective lens 18 via a polarizing beam splitter (PBS) 16 and a 波長 wavelength plate 17 in order. Thus, the optical disk 10 is irradiated with a light beam. At this time, the objective lens 18 is controlled by a focus servo system (not shown) so that the light beam applied to the optical disk 10 forms a minute beam spot on the recording layer 19.
[0020]
The light beam focused on the recording layer 19 of the optical disk 10 is reflected by the reflection film formed on the recording layer 19, returns to the objective lens 18, and becomes parallel light again.
The reflected light converted into parallel light has a polarization perpendicular to the light incident on the ４ wavelength plate 17 by transmitting through the 波長 wavelength plate 17, and is reflected by the polarization beam splitter 16. You. The light beam reflected by the polarization beam splitter 16 is converged by the condenser lens 20 and is incident on the detector 21.
[0021]
The light receiving surface of the detector 21 is divided into at least two light receiving regions 22a and 22b by at least one dividing line including a dividing line parallel to the track tangential direction. The reflected light from the optical disk 10 that has entered the detector 21 is photoelectrically converted, and a current substantially proportional to the amount of incident light in each of the light receiving regions 22a and 22b is generated separately for each of the light receiving regions 22a and 22b and output.
[0022]
FIG. 2 shows a relative arrangement of a pit row, a beam spot, and a divided detector 21 on the optical disk of FIG. The reflected light from the beam spot irradiated on the optical disk is kicked by the aperture of the objective lens, and then passes through an optical system (not shown) to enter the detector 21. As shown in FIG. 2, the light receiving surface of the detector 21 is divided into two by a dividing line parallel to the track tangential direction.
[0023]
Output signals (currents) from the detector 21 corresponding to the light receiving regions 22a and 22b are converted into voltage signals by a current-voltage conversion amplifier (not shown), and then input to the input terminals of the differential amplifier 24 and the addition amplifier 25. Is entered. Accordingly, signals (A) and (B) of voltages corresponding to the detection currents of the detectors 22 a and 22 b divided into two in the track direction of the disk by the detector 21 are input to each of the differential amplifier 24 and the addition amplifier 25. Is done.
[0024]
From the output terminal of the differential amplifier 24, a signal proportional to the difference between the amounts of light incident on the respective light receiving regions 22a and 22b of the detector 21, that is, a difference signal of AB = C, and from the output terminal of the addition amplifier 25 A signal proportional to the sum of the amounts of light incident on the light receiving regions 22a and 22b of the detector 21, that is, a sum signal of A + B = D is obtained as a reproduction signal.
[0025]
As for the difference signal (C) and the sum signal (D) output from the differential amplifier 24 and the addition amplifier 25, either one of the difference signal / sum signal is selected by the switching circuit 26 and input to the ID reproduction circuit 27. You.
[0026]
The signal (E: difference signal or sum signal) selected by the switching circuit 26 is input to the ID reproduction circuit 27 as a reproduction signal for reproducing information from prepits. The ID reproduction circuit 27 generates a clock signal by performing appropriate equalization, binarization, and other processing on the reproduction signal input via the difference signal / sum signal switching circuit 26, and generates the clock signal. The reproduction data (F) corresponding to the upper pre-pit is generated and output.
[0027]
The output signal of the ID reproducing circuit 27 is input to an error detecting circuit 28 for confirming the reliability of the ID information reproduced from the prepit. The error detection circuit 28 determines an error in the ID information reproduced from the pre-pits, and supplies the ID data and the error information (G) to the controller 29.
[0028]
On the disc, four identical data per block are recorded in the pre-pits as ID information. Therefore, if at least one ID data can be read, the position on the disk can be specified as a system. Even if no ID data can be read, the ID data of the previous or subsequent block can be determined. If so, it can be estimated by continuity.
[0029]
Therefore, the error detection circuit 28 determines that the ID data is an error when the ID data cannot be read, and when the continuity with the IDs of the preceding and following blocks is incorrect even when the ID data can be read. .
[0030]
The system controller 29 selects either the difference signal or the sum signal based on the error information (G) output from the error detection circuit 28,
By outputting the switch control signal H, the switching control of the difference signal / sum signal switching circuit 26 is performed.
[0031]
As for the recording data, the beam spot of the light beam irradiated on the optical disk 10 scans the track center line of the land and the groove, so that the sum of the output signals corresponding to the two light receiving areas 22a and 22b of the two-divided detector 21 is obtained. The signal is used as a reproduction signal, and the equalization, binarization, and the like are similarly performed on the reproduction signal by the signal processing circuit 26, so that the user information recorded in the recording area can be reproduced.
[0032]
FIG. 3 is a diagram showing a disk format on a DVD-RAM. A recording area for recording user information such as images, sounds, and data is composed of lands and grooves, and a header area for recording address information and the like is composed of pit strings formed as prepits. This pre-pit row is formed in a form offset in the disk radial direction such that its center line is located on an extension of the boundary between the land and the groove.
[0033]
The beam spot of the light beam applied to the optical disk scans over the track center line of the land and groove in the recording area, and deviates by a fixed distance (1/2 of the track pitch tp) from the center line of the pit row in the header area. Scan the moved position.
[0034]
Thus, the reflected light from the optical disk scanned by the beam spot is detected by the detector, and the information is reproduced from the land, the groove and the pit row.
[0035]
In FIG. 1, a portion surrounded by a chain line is unitized as a pickup head (PUH).
[0036]
Next, the operation of the apparatus shown in the block diagram of FIG. 1 will be described based on the flowchart of FIG.
[0037]
When the tray on which the disk is mounted is opened and closed, and when a system reset occurs, it is determined whether the disk is mounted (ST1).
[0038]
If a disk is mounted, it is determined whether the next mounted disk is a 2.6 GB DVD-RAM disk (ST2).
[0039]
If the mounted disk is not a 2.6 GB DVD-RAM disk, it is determined whether the mounted disk is a 4.7 GB DVD-RAM disk (ST3). Various methods are known for discriminating the disc type in step 2 and step 3, such as a method of reading information recorded in the lead-in area of the disc and a disc type determined from a reproduced signal of the disc. , Any method may be adopted.
[0040]
If the loaded disk is neither a 2.6 GB DVD-RAM disk nor a 4.7 GB DVD-RAM disk, processing of another disk is performed (ST4).
[0041]
When it is determined that the loaded disk is a 2.6 GB DVD-RAM disk (Yes in ST2), the controller 29 switches the switching circuit 26 to the (subtraction) output of the differential amplifier 24 by the switch control signal H. Set. That is, the switching circuit 26 selects the difference signal (C) which is the output of the differential amplifier 24, and is set so that C = E (ST5).
[0042]
The controller 29 controls the disk motor 12 to a required number of revolutions, and controls a focus servo tracking servo (not shown) and an access system (not shown) to position the read beam spot at a desired disk position. . Thereafter, the ID is reproduced by the ID reproduction circuit 27 while performing the ID reading operation sequentially along the disk track, and the reproduction error detection circuit 28 determines the error of the reproduced ID.
[0043]
Then, based on the output of the reproduction error detection circuit 28, the controller 29 counts the number of IDs having no ID error or the number of read IDs from a predetermined number of necessary blocks, and sets the value as the ID read rate A ( ST6).
[0044]
Subsequently, the controller 29 is set by the switch control signal H so that the switching circuit 26 selects the (addition) output of the addition amplifier 25. That is, the switching circuit 26 selects the sum signal (D), which is the output of the addition amplifier 25, and is set so that D = E (ST7).
[0045]
The controller 29 controls the disk motor 12 to a required number of revolutions, and controls a focus servo tracking servo (not shown) and an access system (not shown) to position the read beam spot at a desired disk position. . Thereafter, the ID is reproduced by the ID reproduction circuit 27 while performing the ID reading operation sequentially along the disk track, and the reproduction error detection circuit 28 determines the error of the reproduced ID.
[0046]
Then, based on the output of the reproduction error detection circuit 28, the controller 29 counts the number of IDs that have no ID error or the number of IDs that can be read from a required number of blocks, and sets the value as the ID read rate B ( ST8).
[0047]
In this step 8 (ST8), the same reading position as when the difference signal (C) is set and the ID reading rate A is measured (ST6) is read, and the ID reading rate B is measured, so that both reading rates are compared. To improve the accuracy of
[0048]
On the other hand, if it is determined in step 2 that the loaded disk is a 2.6 GB DVD-RAM disk (ST2 Yes), the controller 29 switches the switching circuit 26 to the addition amplifier 25 by the switch control signal H. Is set to select the sum signal (D), which is the output of (ST9), and the ID reading rate B is measured (ST10). Subsequently, the controller 29 sets the switching circuit 26 to select the difference signal (C) output from the subtraction amplifier 24 by the switch control signal H (ST10), and measures the ID reading rate A (ST12). .
[0049]
When the measurement of the ID reading rate A and the ID reading rate B is completed, the controller 29 compares the ID reading rate A and the ID reading rate B and determines which of the difference signal (C) and the sum signal (D). Is determined to be suitable for reproducing the pre-pit ID information (ST13).
[0050]
When the number of the ID reading rates A is larger than the ID reading rate B (Step 13 Yes), setting the difference signal (C) as the subtraction output corresponds to the case where the ID reading rate is higher. Is set to select the difference signal (C) which is the output of the differential amplifier 24 (ST14).
[0051]
On the other hand, when the number of the ID reading rates B is larger than the ID reading rate A (No in Step 13), setting the sum signal (D) as the addition output corresponds to the case where the ID reading rate is higher. The circuit 26 is set to select the sum signal (D) which is the output of the addition amplifier 25 (ST15).
[0052]
At this time, it is necessary to determine what to do when A = B. That is, in order to improve the reproducibility of the determination, when the absolute value | AB | of the difference between the reading rate A and the reading rate B is equal to or less than a certain value, it is determined that A = B. It is effective to forcibly set either the predetermined difference signal (C) or the sum signal (D),
Therefore, prior to step 13, it is determined whether the absolute value | AB | of the difference between the reading rates A and B is equal to or less than a certain value (ST16).
[0053]
When the absolute value | A−B | of the difference between the reading rate A and the reading rate B is equal to or less than a certain value, a difference signal (C) for a 2.6 GB disc and a sum signal for a 4.7 GB disc. As shown in (D), the signal is set to a signal recommended in the disk specification (ST17).
[0054]
By the above steps 1 (ST1) to 17 (ST17), the setting for reading the ID information recorded in the pre-pit is completed, and thereafter, the reading or recording operation of the recording data recorded on the track of the disc is completed. It goes into a standby state.
[0055]
Next, control during a reading operation or a recording operation of recording data recorded on a track will be described with reference to a flowchart of FIG.
[0056]
From a standby state of data reading or recording operation, normally used access and data reading operation, and recording operation via a recording control system (not shown) are performed based on an instruction from the controller 29. Here, not only in the reading operation but also in the recording operation, the land pre-pit is read prior to recording (ST21), and the signal processing at that time is the same as in normal reproduction. The switching circuit 26 selects one of the output of the subtraction amplifier 24 (difference signal (C)) or the output of the addition amplifier 25 (sum-difference signal (D)) according to the signal (H) from the controller 29. .
[0057]
The ID reproducing circuit 27 outputs ID information based on the output signal (E) of the switching circuit 26 at the time of reproducing the land pre-pits. The reproducing error detecting circuit 28 determines the presence or absence of a reproducing error. Is determined (ST22). In this determination, as in the case of the reading rate measurement in the steps 6, 8, 10, and 12 in FIG. 4, the ID data is output from the reproduction error detection circuit 28 and the ID data is reliable even with the continuity with the preceding and following data. If not, it is assumed that the ID information could not be read correctly.
[0058]
If it is determined that the ID information could not be read correctly (Yes in step 22 (ST22)), it is determined whether the switching circuit 26 has been set to the subtraction output (difference signal (C)) of the subtraction amplifier 24 ( ST23).
[0059]
When the switching circuit 26 is set to the subtraction output (difference signal (C)) of the subtraction amplifier 24 (Yes in step 23 (ST23)), the controller 29 switches the switching circuit 26 to the addition amplifier 25 by the switch control signal H. It is set to select the (addition) output (sum signal (D)) (ST24).
[0060]
Then, the process returns to step 21 (ST21), and the reading of the land prepit is retried.
[0061]
On the other hand, if the switching circuit 26 is not set to the (subtraction) output (difference signal (C)) of the subtraction amplifier 24 in step 23, the switching circuit 26 sets the addition output (sum signal (D )) Is determined (ST25).
When the switching circuit 26 is set to the addition output (sum signal (D)) of the addition amplifier 25 (Yes in ST25), the controller 29 causes the switching circuit 26 to output the (subtraction) output of the subtraction amplifier 24 by the switch control signal H. It is set to select (difference signal (C)) (ST26).
[0062]
Then, the process returns to step 21 (ST21), and the reading of the land prepit is retried.
[0063]
In the first embodiment, first, by the process shown in the flowchart of FIG. 4, the ID information recorded in the pre-pit is actually read, and the difference signal (C) or the sum signal ( Since the setting D) is performed, it is possible to minimize a decrease in the ID reading rate due to a variation in the track pitch due to a manufacturing error of the disk and a variation in the spot size of the pickup.
[0064]
Further, in the first embodiment, the quality of the ID information recorded in the pre-pits is determined by the processing shown in the flowchart of FIG. 5 at the time of reproducing and recording the data recorded on the disk. Since the switching of the difference signal (C) or the sum signal (D) is performed, it is possible to minimize variations in track pitch in the same disk and a decrease in the ID reading rate due to disk tilt.
[0065]
In the processing shown in the flowchart of FIG. 4 in the first embodiment, when it is determined that the loaded disk is a 2.6 GB DVD-RAM disk, the difference signal (C) is output in step 5. When the disc is determined to be a 4.7 GB DVD-RAM disc, the sum signal (D) is set in step 9; however, the sum signal (D) is set first to the signal recommended in the disc specification. , Whichever may be set first.
[0066]
That is, as shown in the flow chart of FIG. 6, steps 9 to 12 in the flow chart of FIG. 4 are deleted, and whether the mounted disc is a 2.6 GB DVD-RAM disc or a 4.7 GB disc is performed. Regardless, the difference signal (C) may be set in step 5. In the flowchart of FIG. 6, steps 5 and 6 (ST5 and ST6) and steps 7 and 8 (ST7 and ST8) may be exchanged to set the sum signal (D) first.
[0067]
In the flowcharts of FIGS. 4 and 6, one of the differential amplifier 24 and the addition amplifier 25 is selected based on the ID reading rates A and B. However, the present invention is not limited to this. Alternatively, the ID error rate may be measured and used for the determination. The operation of the disc recording / reproducing apparatus 1 in this case will be described with reference to the flowchart of FIG. In the flowchart of FIG. 7, the same parts as those in the flowchart of FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted.
[0068]
As shown in the flowchart of FIG. 7, the measurement of the ID reading rate in steps 6, 8, 10, and 12 in the flowchart of FIG. 4 is changed to an ID error rate measurement step (ST6a, ST8a, ST10a, ST12a). In the measurement of each ID error rate, the number of ID errors output from the reproduction error detection circuit 28 when reading IDs from a required number of predetermined blocks, and the total number of IDs that could be read but were not reliable due to continuity , And the values are set as ID error rates A2 and B2.
[0069]
Then, it is determined whether the absolute value | A2-B2 | of the difference between the ID error rate A2 and the ID error rate B2 is equal to or less than a certain value (step 16a). If the absolute value difference between the ID error rates A2 and B2 is equal to or less than a predetermined value. In the same manner as in the flowchart of FIG. 4, a signal recommended in the disk specification is set, such as a difference signal (C) for a 2.6 GB disk and a sum signal (D) for a 4.7 GB disk ( ST17).
[0070]
If the absolute value | A2-B2 | of the difference between the ID error rate A2 and the ID error rate B2 is not smaller than a certain value, the ID error rate A2 and the ID error rate B2 are compared (ST13a).
[0071]
When the ID error rate A is larger than the ID error rate B (Yes in step 13a), setting the sum signal (D) as an addition output corresponds to a higher ID reading rate. A setting is made to select the sum signal (D) which is the output of the amplifier 25 (ST15a).
[0072]
When the ID error rate B is greater than the ID error rate A (No in step 13a), setting the difference signal (C) as the subtraction output corresponds to a case where the ID reading rate is higher. A setting is made to select the difference signal (C) that is the output of the dynamic amplifier 24 (ST14a).
Next, a second embodiment of the present invention will be described with reference to the drawings. In the second embodiment, the processing shown in the flowchart of FIG. 4 in the first embodiment is omitted, and the processing shown in the flowchart of FIG. 8 is performed independently. Since the configuration is the same as that of the first embodiment shown in FIG. 1, the description of the configuration of the device is omitted.
[0073]
In the second embodiment, the quality of the ID information recorded in the pre-pits is determined at the time of reproducing and recording the data recorded on the disk, and the switching of the difference signal (C) or the sum signal (D) is performed. The operation of the apparatus will be described with reference to the flowchart of FIG.
[0074]
When the tray on which the disk is mounted is opened and closed, and when a system reset occurs, it is determined whether the disk is mounted (ST31).
[0075]
If a disk is mounted, it is determined whether the next mounted disk is a 2.6 GB DVD-RAM disk (ST32).
[0076]
If the mounted disk is not a 2.6 GB DVD-RAM disk, it is determined whether or not the mounted disk is a 4.7 GB DVD-RAM disk (ST33). Various methods are known for discriminating the disc type in step 2 and step 3, such as a method of reading information recorded in the lead-in area of the disc and a disc type determined from a reproduced signal of the disc. , Any method may be adopted.
[0077]
If the mounted disk is neither a 2.6 GB DVD-RAM disk nor a 4.7 GB DVD-RAM disk, processing of another disk is performed (ST34).
[0078]
When it is determined that the loaded disk is a 2.6 GB DVD-RAM disk (Yes in ST32), the controller 29 switches the switching circuit 26 to the (subtraction) output of the differential amplifier 24 by the switch control signal H. Set. That is, the switching circuit 26 selects the difference signal (C) which is the output of the differential amplifier 24, and is set so that C = E (ST35).
[0079]
On the other hand, if it is determined in step 33 that the loaded disk is a 2.6 GB DVD-RAM disk (ST32 Yes), the controller 29 switches the switching circuit 26 to the addition amplifier 25 by the switch control signal H. The sum signal (D) which is the output of is selected and set so that D = E (ST36).
The initial setting is completed by the above steps 31 to 36, and thereafter, the apparatus enters a standby state for reading or recording operation of the recording data recorded on the track of the disk.
[0080]
At the time of reading operation or recording operation of the recording data recorded on the track, the same control as in the flowchart shown in FIG. 5 is performed, and at the time of reproducing and recording of the data recorded on the disk, the data recorded on the pre-pit is recorded. The quality of the given ID information is determined, and the difference signal (C) or the sum signal (D) is switched.
[0081]
In the second embodiment, as described with reference to the flowchart of FIG. 8, the initial setting of the difference signal (C) or the sum signal (D) is performed for a DVD-RAM disk having a 2.6 GB disk and a 4.7 GB DVD-RAM disk. The difference from the first embodiment is that the setting is uniquely performed depending on which of the DVD-RAM discs the disc is. However, the controller 29 switches the switching circuit 26 to the preferred one of the difference signal (C) and the sum signal (D) when reproducing and recording the data recorded on the disk, thereby minimizing the decrease in the ID reading rate. It becomes possible to.
[0082]
Finally, a disc recording / reproducing apparatus 80 according to a third embodiment of the present invention will be described. In the third embodiment, a four-divided detector 30 is used as shown in FIG. 9 instead of the two-divided detector 21 in the above-described embodiment. In FIG. 9, the same components as those in FIG. 1 are denoted by the same reference numerals.
[0083]
In the disc recording / reproducing device 80, the detector 30 is configured such that the light receiving surface is not only divided into two by a dividing line parallel to the track tangential direction as shown in FIG. It is divided and is a four-divided detector composed of the light receiving areas 30a, 30b, 30c, and 30d.
[0084]
A tracking coil 32 is arranged around the objective lens 18, and by driving the tracking coil, the objective lens 18 is moved in the tracking direction.
[0085]
In FIG. 9, a portion surrounded by a chain line is unitized as a pickup head (PUH), and the pickup head is movable in a tracking direction by driving a thread motor 33.
[0086]
Output signals (currents) corresponding to the detectors 30a and 30c are added by an adder 31a and converted into a voltage signal by a current-to-voltage conversion amplifier (not shown). Are input to the two input terminals.
[0087]
Output signals (currents) corresponding to the detectors 30b and 30d are added by an adder 31b and converted into a voltage signal by a current-to-voltage conversion amplifier (not shown). 25 are input to two input terminals.
[0088]
The signal processing after the differential amplifier 24 and the addition amplifier 25 is the same as that of the first embodiment. In FIG. 9, the same reference numerals as those in FIG. 1 denote the same as those in FIG. Omitted.
[0089]
In the third embodiment, tracking control of the pickup is performed using the four-divided detector 30. Therefore, output signals (currents) corresponding to the detectors 30b and 30c are added by an adder 31c, converted into a voltage signal by a current-voltage conversion amplifier (not shown), and then input to an input terminal of the phase detection circuit 34. You.
[0090]
The output signals (currents) corresponding to the detectors 30a and 30d are added by an adder 31d, converted into a voltage signal by a current-voltage conversion amplifier (not shown), and input to the other input terminal of the phase detection circuit 34. Is done.
[0091]
The phase detection circuit 34 compares the phase of the output signal corresponding to the detectors 30a and 30d with the phase of the output signal corresponding to the detectors 30b and 30c, and outputs a tracking error signal to the tracking control circuit 35.
[0092]
A method using the above-described phase detection circuit 34 as a method of generating a tracking error signal is known as a Differential Phase Detection (DPD) method of generating a tracking error signal using pit diffraction.
[0093]
The tracking control circuit 35 outputs a signal to the sled motor drive circuit 36 and the tracking coil 32 to perform tracking control of the pickup head (PUH) based on the tracking error signal output from the phase detection circuit 34.
[0094]
The sled motor drive circuit 36 drives the sled motor 33 based on a signal from the tracking control circuit 35 to move the pickup head (PUH). The tracking coil 32 is driven by a signal from the tracking control circuit 35 to move the objective lens 18 in the tracking direction.
[0095]
The tracking control circuit 35 may use not only the tracking error signal output from the phase detection circuit 34 but also the difference signal (C) output from the subtraction amplifier 24 as a Push Pull (hereinafter referred to as PP) tracking error signal. . That is, in the case of a DVD-ROM in which pits are formed, the DPD method is employed using the tracking error signal output from the phase detection circuit 34. In the case of a DVD-RAM in which no pits are formed, the subtraction amplifier 24 The PP method can be adopted using the output difference signal (C). Alternatively, by using the DPD method and the PP method together, it is possible to perform tracking control while interpolating defects of both companies.
[0096]
The difference between the third embodiment and the first and second embodiments has been described above. However, in the third embodiment, the processing shown in FIG. 4 or FIG. 5 and FIG. And the same effect as in the first embodiment can be obtained.
[0097]
Further, in the third embodiment, the same processing as the processing shown in FIGS. 8 and 5 of the second embodiment is executed, and the same effect as in the first embodiment can be obtained.
[0098]
As described above, according to the present invention, when reading the ID information of a disk having ID information positioned radially from a track, a decrease in the ID reading rate due to variations in the track pitch of the disk or the spot size of the pickup. Is effective because it can be minimized.
[0099]
Further, by applying the present invention to a disk reproducing apparatus using a blue laser, it is possible to reduce a reading error due to a small spot diameter of a laser beam or a small track pitch of a disk.
[0100]
The spot diameter of the laser beam varies depending on the temperature of the laser diode. However, according to the present invention, it is possible to improve the reading rate even when the temperature of the laser diode changes.
[0101]
Further, according to the present invention, even if the spot diameter of the laser beam applied to the disk changes due to the tilt of the disk, the read rate can be improved by switching between addition (sum signal) and subtraction (difference signal).
[0102]
In the above embodiment, the DVD-RAM has been described. However, in a recording / reproducing apparatus for a medium such as a DVD-R or a DVD-RW, which is a groove recording medium in which prepit information is recorded between a land and a groove. It goes without saying that the same effects as those described above can be obtained by applying the present invention.
[0103]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an optical disk recording / reproducing apparatus capable of improving the reading accuracy of a pre-pit row arranged at an intermediate position between a land track and a groove track.
[Brief description of the drawings]
FIG. 1 is a block diagram of a disk recording / reproducing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a relative arrangement of a beam spot on an optical disk and a detector.
FIG. 3 is a view showing a disk format on a DVD-RAM.
FIG. 4 is a flowchart for explaining the operation of the disc recording / reproducing apparatus of FIG. 1;
FIG. 5 is a flowchart for explaining the recording / reproducing operation of the disc recording / reproducing apparatus of FIG. 1;
FIG. 6 is a flowchart illustrating a modification of the flowchart of FIG. 4;
FIG. 7 is a flowchart illustrating a modification of the flowchart of FIG. 4;
FIG. 8 is a flowchart for explaining the operation of the disc recording / reproducing apparatus according to the second embodiment of the present invention.
FIG. 9 is a block diagram of a disk recording / reproducing apparatus according to a third embodiment of the present invention.
[Explanation of symbols]
1,80 ... Disc recording / reproducing device
14 Laser Diode
21, 30 Detector
24 ... Differential amplifier
25 ... Additional amplifier
26 Switching circuit
27 ID playback circuit
28 Reproduction error detection circuit
29 ... Controller
PUH …… Pickup head

Claims (5)

In a disk reproducing apparatus for reproducing a disk in which a prepit is formed at an intermediate position between a land and a groove,
A light source for irradiating the disk with laser light, and a pickup comprising a detector arranged to detect reflected light from the land or groove and divided into at least two in the radial direction of the disk,
Difference detection means for generating a signal of the difference between the detectors divided in the disk radial direction,
Sum detection means for generating a sum signal of the detector divided in the disk radial direction,
Means for evaluating which of the difference detection means or the sum detection means is suitable for reproducing the information of the pre-pits based on the output signal of the difference detection means and the output signal of the sum detection means,
A disc reproducing device comprising: a selecting unit that selects one of the difference detecting unit and the sum detecting unit for reproducing the pre-pit information based on the evaluation result of the evaluating unit. 2. The disc reproducing apparatus according to claim 1, wherein said evaluation means has an error detection means for detecting an error of said pre-pit information obtained from an output signal of said difference detection means and an output signal of a sum detection means, A disc reproducing apparatus comprising: means for determining which of the output signals of the difference detecting means or the sum detecting means is to be used for reproducing the information of the pre-pit based on the output of the error detecting means. 3. The disk reproducing apparatus according to claim 2, wherein a reading ratio based on an output signal of the difference detecting unit and a reading ratio based on an output signal of the sum detecting unit are measured based on an output of the error detecting unit, and the two companies are compared and read. A disc reproducing apparatus characterized in that the discriminating means selects the signal having a higher rate as a signal for reproducing the pre-pit by the selecting means. 3. The disk reproducing apparatus according to claim 2, wherein an error rate of the output signal of the difference detecting means and an error rate of the output signal of the sum detecting means are measured based on an output of the error detecting means, and the two companies are compared for error. A disc reproducing apparatus characterized in that the discriminating means selects the signal having a lower rate as a signal for reproducing the pre-pit by the selecting means. In a disk reproducing apparatus for reproducing a disk in which a prepit is formed at an intermediate position between a land and a groove,
A light source for irradiating the disk with laser light, and a pickup including a detector arranged to detect reflected light from the land track or groove track and divided into at least two in the radial direction of the disk,
Difference detection means for generating a signal of the difference between the detectors divided in the disk radial direction,
Sum detection means for generating a sum signal of the detector divided in the disk radial direction,
Means for reading the information of the pre-pit from the output signal of the difference detection means or the output signal of the sum detection means,
A disk reproducing apparatus characterized in that when the information of the pre-pit cannot be read by the reading means, the difference is detected by switching between the difference detecting means and the sum detecting means.

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