KR100879311B1 - Record carrier and apparatus for scanning the record carrier - Google Patents

Abstract

A servo track 4 representing an information track 9 for recording a plurality of information blocks represented by a plurality of marks, wherein the servo track 4 is provided with a periodic variation of a physical parameter at a first frequency. A record carrier 1 having modulation portions for encoding record carrier information is disclosed. These modulation portions have a bit synchronization component consisting of phase modulation of periodic variation and a data portion comprising data bits of record carrier information encoded by direct digital modulation. Alternatively, the modulation portions comprise a second frequency different from the first frequency for encoding the data bits of the record carrier information, the second frequency being an integer multiple N of the first frequency. The recording and / or reproducing apparatus has means for recording / reading information blocks and for reading the recording medium information.

Record carrier, physical parameter, periodic variation, bit sync, digital modulation

Description

Record carrier and record carrier injection device {RECORD CARRIER AND APPARATUS FOR SCANNING THE RECORD CARRIER}             

The present invention has a servo track representing an information track for recording a plurality of information blocks represented by marks having a length expressed in channel bits, the servo track having a periodic variation in physical parameters, the recording medium A recording medium in which this periodic variation is modulated to encode information.

Moreover, the present invention includes means for recording / reading a plurality of information blocks represented by marks having a length represented by channel bits, means for scanning a servo track, and means for retrieving recording medium information. It relates to a recording / reproducing apparatus.

The present invention also relates to a method of manufacturing this recording medium.

Recording media and devices as defined at the outset for reading / writing information are known from WO 00/43996 (PHN 17323). The information is encoded into an information signal that includes time codes and can be divided into a plurality of information blocks according to the time codes, which are used as addresses in a CD-ROM or a DVD + RW or the like. The record carrier has a servo track, usually called a pregroove, which allows servo signals to be generated when scanning the track. The physical parameters of the preliminary groove, for example the radial position, are changed to constitute a so-called wobble. During the scan of the track, this wobble causes a change in the servo signal. This variation is modulated by record carrier information, for example sync symbols and encoded position information, which indicates the absolute length of the track from the start position. During recording, since the positions of the information blocks are synchronized as much as possible with the synchronization symbols, the information blocks are recorded on the recording medium at the position corresponding to their address.

The problem with this conventional system is that the pre-home wobble signal cannot be reliably demodulated to recover the encoded position information.

After all, it is an object of the present invention to provide a recording medium and an apparatus in which the recording medium information can be easily recorded and read.

According to the invention, the recording medium as described at the outset has the features described in claim 1. The recording / playback apparatus described at the outset has the same features as described in claim 12. This configuration has the effect that data bits can be detected regardless of the modulation type which has a significant difference from the unmodulated periodic variation. Another advantage is that since significantly different modulation in adjacent tracks has little effect on unmodulated variation compared to modulated variation such as frequency modulation, it is important to note the periodic variation that can be used to position the marks at the time of recording. The disturbance in the detection of the physical position is precise.

Another embodiment of the recording medium is characterized in that the length of one periodic variation corresponds to a predetermined third number of channel bits. The effect of this is that the nominal position of the nth channel bit corresponds exactly to the physical position of the nth periodic variation divided by a predetermined third number. This has the advantage that the recording position can be synchronized with the periodic variation. The relatively small predetermined third number of channel bits per periodic variation allows high precision of positioning. In particular, 32 is a reasonable number since 32 is considerably longer than the longest mark with a value smaller than 16 used in general channel coding, and can facilitate address computation in binary systems.

Still other preferred embodiments of the method, apparatus and recording medium according to the invention are described in the dependent claims.

The invention will become more apparent from the following examples given with reference to the accompanying drawings in which:

1 shows a recording medium,

2 shows servo track frequency modulation,

3 illustrates servo track digital modulation,

4 shows bit synch and word sync,

5 shows a playback device,

6 shows a recording apparatus,

7 shows an address symbol set,

8 shows the contents of the address word,

9 shows the wobble of a DVD + RW,             

10 shows reverse word sync,

11 shows servo track on / off modulation,

12 illustrates servo track on / off modulation with bit sync.

Corresponding elements in these different figures bear the same reference numbers.

1 shows a disc-shaped recording medium 1 with a continuous track 9 for recording, which is arranged in a spiral pattern consisting of a plurality of windings 3. These windings may be arranged concentrically instead of helically. The track 9 on the record carrier is represented, for example, by a servo track which allows the preliminary groove to allow the read / write head to follow the track 9 during the scanning process. This servo track may also consist of a plurality of regularly distributed subtracks which cause the signal to occur periodically, for example in a servo track system. FIG. 1B shows a cross sectional view along the line b-b of the recording medium 1, wherein the transparent substrate 5 is covered with a recording layer 6 and a protective layer 7. In addition, the preliminary groove 4 may be arranged in a land or may have material properties different from its periphery. The recording layer 6 may be stacked optically, magneto-optically, or magnetically by an apparatus for reading and / or recording information such as a known CD recordable or a hard disk for a computer. 1C and 1D show two examples of periodic modulation (commonly called wobble) of a reserve groove. This wobble causes additional signals to be generated in the servo track recorder. In the prior art, the wobble is, for example, frequency modulated and the disc information is modulated and encoded. Extensive contents of recordable CD systems including disc information obtained in this manner are described in US 4,901,3000 (PHN 12.398) and US 5,187,699 (PHQ 88.002).

2 shows servo track frequency modulation. Most of the servo tracks are modulated with a constant wobble frequency called so-called monotones. Monotone portions are alternated with the small modulated portions shown in FIG. The upper trajectory represents the modulated portion of the word sync pattern, and the second and third portions represent the modulated portion for data bits data = 0 and data = 1. Each modulated portion begins with a bit sync component (bit sync) with lengths corresponding to one wobble period. Bit and word synchronization consists of a significantly higher frequency, which is twice the wobble frequency in the figure. The data bits have two parts, and one part at this frequency can be easily detected due to its substantial difference.

3 illustrates servo track digital modulation. The top trajectory represents a monotone wobble that can be used as a reference wobble for locking a phase locked loop (PLL) inside the decoder. The second trajectory is shown using an inverted wobble for the timing signal bit sync and address bits. It is robust in detecting from monotone wobble. The address bits are encoded using direct digital modulation, and RLL wobble modulation is applied in FIG. 3, which is robust because the position is known from the timing signal. This Run Length Limited modulation has a maximum length of consecutive zeros and ones, which has the advantage that the signal can be easily decoded since signal inversion occurs in a short period of time. Moreover, since this modulation is different from phase modulation, it can be easily detected. There are four steps in wobble detection, where step 1 locks the wobble PLL to the long monotone portion, and step 2 locks to the bit sync, which is an equidistant inverted wobble. Step 3 is locking to word sync, which is a pattern of equidistant inverted wobble corresponding to an inverted wobble pattern different from the bit sync. Step 4 is to read the address data for the digitally modulated wobble. For a particular implementation, the actual choice of the relationship between the length of the encoded address and the data to be written is as follows:

The bit sinks are equidistant, which is necessary to lock the decoder to the bit sink. This distance is one bit sync to 71 wobble, each wobble is 69 T, where T is the channel bit period of the data to be written. One address word includes a plurality of bit sinks, and the length of the address word is 49 bit sinks. The bit sink itself corresponds to one inverted wobble as shown in FIG. Data is recorded in a plurality of blocks (RUBs). The RUB is the smallest unit for recording and consists of 496 data frames and one concatenated frame. In this case, since the RUB includes 497 frames of 1932 channel bits, 497 * 1932/68 = 13916 wobbles are provided for each RUB. In addition, four addresses are arranged in each RUB, resulting in 3479 (49 * 71) wobble / address. Digital modulation of address symbols can be RLL modulation as follows. For the digital zero value ("0"), the mastering beam (and thus the servo track) is moved inside the recording medium, and for the digital one value ("1"), the mastering beam is moved outside. Preferably, the length of the data bit of the write information (address and auxiliary codes for controlling the writing process) is equal to the wobble period. Detection can be performed by integration, while integration time can be easily derived from the wobble PLL. Moreover, the data bits are encoded in a DC-free manner, ie with the same number of "0" s and "1" s. No effect is obtained on the servo signal as follows: k = 1 (k + 1 is the maximum number of consecutive "0s" and "1s"), and the k constraint limits the low frequency components and suppresses the high frequency filtering. Allow.

In wobble encoding address and auxiliary data, it is presented to combine multiple address bits into an address bit symbol following a bit sink. In FIG. 3, a plurality of address bits are scattered inside an address symbol. In DVD + RW, only one address bit is encoded after each bit sync. At this time, in order to further prevent errors during reading, the address symbols are selected to constitute a set suitable for error detection and correction (ECC). For ECC based on 4 bit symbols, it is desirable to store 4 bits or 1 nibble after each bit sync, due to the lower sensitivity to short burst errors.

7 illustrates a set of suitable address symbols. In order to have at least 16 different symbols with a Hamming distance of at least 4, address symbols with a length of 10 wobble periods are needed. Hamming distance 4 between address symbols allows good discrimination between different words. The number of address symbols is chosen as follows: For sufficient addressing, it is proposed to use 48 address bits encoded into 12 address symbols each containing 1 nibble of 4 bits. Preferably, isolated bit sinks that are not followed by an address symbol are included within the address word. The advantage of this is that locking to the bit sink can be improved because fewer false bit sinks are detected. When detecting a bit sink adjacent to the modulated address data bits, the detector may confuse the address bit with the bit sink. An isolated bit sink cannot be confused because only unmodulated wobbles surround the isolated bit sink.

The practical choice is to have an address symbol after one bit of the four bit sinks and a word sink after one bit of sync so that the total length is a 49 bit sink (as described above).

8 illustrates contents of an address word according to another exemplary embodiment. The address word is 15 address symbols each containing 60 address bits, i.e. 1 nibble. At this time, more bits may be used for data and / or ECC, and a maximum number of bits exist for nibble-based ECC. At this time, in order to maintain the entire address word length limited to the same length of the 49-bit sink, an address symbol is located after one bit of the three bit sinks.

4 shows a bit sync and a word sync. The upper trajectory a represents the bit sync of one inverted wobble. Trajectory b represents the stronger beat sync of the two inverted wobbles. Another configuration is shown in trajectory c, where the bit sync is not adjacent to the digitally modulated region but farther to the left. The characteristics of this word sync are as follows: This is based on the pattern of inverted wobble, for example four consecutive inverted wobble shown in FIG. Alternatively, word sync may be based on special "address symbols" that do not occur in the set of address symbols used to encode the address bits. Such word sinks based only on special address symbols have the problem that the detection of word sinks may be as strong as the detection of only one nibble out of additional data nibbles, and thus may not be sufficient. This can be improved by using larger hamming distances or by violating other constraints of the code (such as k constraints). It is proposed to include a word sink after at least one bit sink among the 49 bit sinks, but by including word sinks after more than one bit sink in each address word, detection can be made more reliable. Slightly different word sinks may be used to distinguish the location of the word sink within the address word. For example, the trace d of FIG. 4 represents the first word sync wordSync0 composed of one inverted wobble and the trace e represents the second word sync wordSync1 composed of four inverted wobble. Such word syncs based on inverted wobbles are preferred over special symbols inside the address symbol region because there are more wobble and less digital modulation. Alternatively, word sinks may be placed in front of the bit sink.

5 and 6 show an apparatus according to the invention for scanning a record carrier 1. Recording and reading of information on optical discs, and formatting, error correction and channel coding rules are known in the art, for example from CD systems. The apparatus shown in FIG. 5 is configured to read the recording medium 1, which is the same as the recording medium shown in FIG. The apparatus comprises a read head 52 for scanning a track on a record carrier, a driver 55 for rotating the record carrier 1, for example a read circuit 53 comprising a channel decoder and an error corrector, and a tracking unit ( 51) and a read control unit including the system control unit 56. The read head comprises optical elements of the conventional type which generate a radiation spot 66 focused on a track of the recording layer of the recording medium via a radiation beam 65 guided through the optical elements. The radiation beam 65 is generated by a radiation source, for example a laser diode. The read head further includes a focusing actuator for focusing the radiation beam 65 on the recording layer and a tracking actuator 59 for adjusting the fine position of the spot 66 in the radial direction from the center of the track. The apparatus has a positioning unit 54 for rough positioning of the read head 52 in the radial direction on the track. The tracking actuator 59 includes coils for radially moving the optical member, or changes the angle of the reflecting member on the movable portion of the read head or on a portion in a fixed position when the optical system is mounted at a fixed position. It can be configured to. The radiation reflected by the recording layer is detected by a conventional type of detector, for example four quadrant diodes, to generate a detection signal 57 comprising a read signal, a tracking signal and a focus error signal. In order to receive the tracking error signal from the read head and to control the tracking actuator 59, the tracking part 51 is connected to the read head. During reading, the read signal is converted into the output information indicated by the arrow 64 inside the read circuit 53. The apparatus includes an address detector 57 for detecting and retrieving address information from the detection signal 57 when scanning the servo track of the recording medium. The apparatus receives a command from a control computer system or a user, and controls a control line 58, for example, a drive unit 55, a positioning unit 54, an address detector 50, a tracking unit 51 and a readout circuit. A system control unit 56 is further provided for controlling the device via the system bus connected to 53. To this end, the system control unit includes a control circuit for performing the above-described process, for example, a microprocessor, a program memory, and control gates. The system controller 56 may be implemented as a state machine of a logic circuit. The reading device is configured to read a disc having a plurality of tracks having periodic fluctuations, for example, continuous wobble. The reading control section is configured to detect periodic variation and read out a predetermined amount of data from the track in dependence thereon. In particular, the address detector 50 is configured to read recording medium information, for example position information and recording control data, from the modulated servo signal. A suitable embodiment of the address detector is a synchronous frequency detector for detecting the frequency used to modulate the write control information according to FIG. Digital RLL modulation can be detected by a digital demodulator that is switched on after the bit sync is detected. Moreover, other modulations to the modulated servo signal can also be used. The address detector further includes a word detector for searching for words of the recording medium information, as described with reference to FIGS. 3 and 4. The starting position of such a word is detected from a predetermined number of inverted wobbles that appear in the word sync following a long sequence of unmodulated wobbles.

6 shows the use of a beam 65 of electromagnetic radiation to record information on a record carrier according to the invention, for example in the form of magneto-optical or optically (re) recordable (via phase change or dye). The device is shown. This device also has a readout device and has the same components as the readout control means, with the exception of the write / readhead 62 and the write circuit 60, for example with a formatter, error encoder and channel encoder. Except having one write control means, it has the same components as the reading apparatus described above with reference to FIG. The write / read head 62 has the same function as the read head 52 together with the write function, and is connected to the write circuit 60. The information given to the input of the recording circuit 60 (indicated by arrow 63) is distributed in logical and physical sectors according to the formatting and encoding rules, and converted into a recording signal 61 for the recording / reading head 62. . The system controller 56 is configured to control the recording circuit 60 and to perform the position information restoration and positioning process as described for the reading apparatus. During the recording operation, marks indicating information are formed on the recording medium. The recording control means is configured to detect the periodic variation, for example by locking the phase locked loop to its periodicity. A certain fixed number of channel bits are recorded corresponding to each instant of the periodic characteristic, for example 32 channel bits for one wobble. Thus, during the recording of the block, the recording of the marks representing the information is exactly synchronized to the corresponding wobble. In one embodiment of the recording apparatus, the positioning unit is configured to position the block to be recorded based on the exact correspondence of the wobble length to a predetermined number of channel bits, for example, according to the DVD format, And a calculating unit configured to calculate the position based on the relationship between the address word in the wobble and the address of the information block.

In one embodiment, the reading and / or writing device has, for example, a phase locked loop housed inside the address detector, which locks in accordance with the periodic fluctuations of the track, such as wobble, during the scanning process. After the jump of the heads 52 and 62 to the new scan position, the phase locked loop may be preset to the data clock value at the new position, or the bandwidth of the phase locked loop described above may be increased to quickly lock to the new wobble frequency. have.

Note that the DVD + RW disc has wobbled grooves. These wobbles have two functions: generation of a precise and stable recording clock and retrieval of address information. This presents conflicting requirements for wobbles. The first is that for the generation of an optimal write clock, the wobble should be as monotone as possible, where it is easiest to lock the PLL with high precision. Secondly, for robustly high-speed robust retrieval of address information, wobble is used in one or the other way (phase modulation is used for DVD + RW, but the same applies to other modulation schemes, such as frequency modulation). Must be modulated by). Modulation means that the wobble is not completely monotone.

9 shows the wobble of a DVD + RW. The disc contains 93 wobble structures consisting of 85 monotone wobbles and 8 wobble ADIP sections. This structure is repeated 52 times to form an ADIP word. Each ADIP word begins with an ADIP portion that includes a word sink followed by 51 ADIP portions containing zero or one data. The ADIP portion with word sink has three inverted wobbles in the word sync area of length 3, and the ATIP portion with data has two inverted wobbles in the data area of length 4. 9 shows that each ADIP portion 91 starts with a bit sync area 92 having a length of one wobble that is always inverted. This gives the average number of inverted wobbles in the following areas: Bit sink region 92: 100% inverted wobbles; Word sync region 93: 2% inverted wobbles; Data area 94: 49% inverted wobbles; Monotone Wobble Region 95: 0% inverted wobbles. The problem is that for the generation of the write clock, all wobbles are used and you can choose to accept that the phase error in the modulated portion degrades the clock jitter. In the preferred embodiment, only the monotone wobble region 95 is used for clock generation and ignores the modulated portion of the PLL (leave blank). This configuration has the advantage that the PLL does not see the phase error in the modulated portion, but has the disadvantage that the phase information in the portion of the positive wobble is discarded. Another possible way is to use both monotone wobble region 95 and word sync region 93. According to this, by adding a very small number of inverted wobbles, the number of positive wobbles is increased compared to the second method. The problem with this last method is that the word sync region 93 and the monotone wobble region 95 are not adjacent, which complicates the construction.

10 shows reverse word sync. The reverse order of the word sync area 101 and the data area 100 such that the word sink area 101 and the monotone wobble area 102 are adjacent causes the use of all wobble information to lock the wobble PLL to restore the wobble frequency. To be able. This configuration allows a simple implementation of the detector according to the last method described above for wobbles with reversed word sync.             

11 shows servo track on / off modulation. The sync signal for bit sync and word sync is encoded by so-called on / off modulation by turning off the wobble signal. Moreover, the data bits are encoded by the combination of wobble periods and off region. This format is suitable as an address format of a recording medium having only a groove. The signal-to-noise ratio can be smaller than the phase-modulated wobbles, but this is not appropriate unless this signal-to-noise ratio is a significant factor for system robustness, and the detection is simpler. In one embodiment, inverted wobbles may be used in word sync and / or bit sync for timing purposes.

12 illustrates servo track on / off modulation with bit sync. Bit sync is encoded by inverted wobble.

Although the present invention has been described with an embodiment using wobble modulation, other suitable parameters of the track, such as track width for example, may be modulated. In addition, although the optical disk has been described for the recording medium, other media such as a magnetic disk or a tape may be used. Herein, the term 'comprises' does not exclude the presence of other components or steps other than those described, and the terms 'a' and 'an' in front of the components do not exist. It is to be noted that reference numbers do not limit the scope of the claims, and that multiple 'means' may be represented by the same item of hardware. Moreover, the scope of the present invention is not limited to this embodiment, and the present invention covers all novel features or combinations of the above-described features.

Claims (15)

A recording medium having a servo track 4 representing an information track 9 for recording a plurality of information blocks represented by marks having a length represented by channel bits, wherein the servo track 4 is a first carrier. A recording medium having periodic variations of physical parameters in frequency and modulation portions for encoding recording medium information, And wherein said modulation portions comprise a second frequency different from said first frequency for encoding data bits of record carrier information, said second frequency being an integer multiple of said first frequency. The method of claim 1, And when the M periods of the periodic variation correspond to one bit of recording medium information, the second frequency is a multiple of N divided by M. The method of claim 1, And the modulation portions comprise low frequency components that directly represent digital bits, the low frequency being at least four times lower than the first frequency. The method of claim 1, Wherein said modulating portions comprise a sink portion and a data portion, said sink portion comprising said periodic variation of at least one period having a phase opposite to that of an unmodulated periodic variation. The method of claim 1, And the length of one periodic variation coincides with a predetermined third number of channel bits. delete delete delete delete delete delete Means for recording / reading a plurality of information blocks represented by marks having a length represented by channel bits in the information track 9 on the servo track 4 of the recording medium according to claim 1, and the servo A recording / reproducing apparatus having means for scanning the track 4 and retrieving means for retrieving the recording medium information, And said retrieving means comprises demodulation means for retrieving data bits of record carrier information from said modulation portions. The method of claim 12, The apparatus comprises synchronizing means for synchronizing with the sink portion included in the modulation portions, wherein the synchronization portion includes at least one variation having a phase opposite to that of the unmodulated periodic variation. Recording / playback device. The method of claim 12, The apparatus is based on the physical position of one periodic variation among the periodic variations corresponding to the address of the information block by calculating a physical position from the length of one periodic variation corresponding to a predetermined third number of channel bits. And recording position designating means for designating a position of the information block to be recorded. Providing a recording medium having a servo track 4 representing an information track 9 for recording a plurality of information blocks represented by marks having a length expressed in channel bits; Converting the physical parameters of the servo track 4 into periodic fluctuations at a first frequency, 10. A method of manufacturing a record carrier comprising modulating portions of the servo track to encode record carrier information. And wherein said modulating portions comprise a second frequency different from said first frequency for encoding data bits of record carrier information, said second frequency being an integer multiple of said first frequency.

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