MXPA00003188A - Optical disc and apparatus for scanning the optical disc - Google Patents

Abstract

An optical disc is described for recording data, which disc has a recording area subdivided in coaxial annular zones comprising circular or spiral tracks. Each track within one of the zones is arranged for storing a same predetermined amount of data, and the first track of each zone stores an amount of data proportional to the radial position, resulting on average in a substantially constant density, the so called CLV (Constant Linear Velocity) density. The tracks comprise periodic characteristics, e.g. a wobble, which are radially aligned within each one of the zones, the periodicity being indicative of the track recording density for the track concerned. Hence the data recording and reading speed can be synchronised to the periodic characteristics, whereas any cross-talk of the periodic characteristics of neighbouring tracks is avoided.

Description

OPTICAL DISC AND APPARATUS FOR EXPLORING THE OPTICAL DISC This invention relates to an optical disc comprising a recording area for recording data at a substantially constant density, the recording area being subdivided into a plurality of coaxial annular zones comprising circular or spiral tracks, each track within one of the areas for storing the same predetermined amount of data at a track density, the average of the track densities within a zone is substantially equal to said constant density. The invention further relates to a recording device for recording data at a substantially constant density on an optical disk, comprising a recording area comprising circular or spiral tracks, recording area which is divided into a plurality of zones. annular or axial, device which comprises a registration head and recording control means. The invention also relates to a reading device for reading data from an optical disk recorded at a substantially constant density, the optical disk comprises a recording area comprising circular or spiral tracks, recording area which is subdivided into a plurality of coaxial annular zones, device which comprises a reading head and reading control means. Such a carrier and recording apparatus are known from the European Patent Application EP 0 587 019, document DI in the list of related documents. The document describes a record carrier in the form of an optical disk having a recording area comprising a pattern of grooves of a substrate, which constitute a servo pattern of circular or spiral tracks. The recording area is subdivided into coaxial ring zones, and within a zone each track comprises the same amount of data. Consequently, the density of data storage decreases when one moves radially outward, while at the beginning of the next zone the density is restored. The average density over the entire surface is substantially equal, usually known as a density of CLV (Constant Linear Velocity), for example, as used in compact discs (audio CD). However, within an area the amount of data in each turn of the track is constant, usually called CAV density (Constant Angular Velocity). The disc comprises a number of servodepressions aligned radially in each turn, constituting what is known as a sampled servopattron. The servopattern comprises aligned elements called constant angular velocity servopatron (CAV), and must be explored by a servo system that has a phase locked circuit (PLL) to generate a blocked servo frequency at the disk rotation frequency. The servodepressions are sized to be read in a synchronized manner by the rotary servo frequency of the disk. The servodepresiones are sized to be read in a synchronized manner by servo frequency. In addition, a phase locked data circuit is provided to generate a locked data clock at a speed of read / write operations, which are performed at a substantially constant linear density. When jumping to a new radial position, the fixation point of the rotation frequency or the data clock setting point is adjusted to the new position,. but the servo circuit blocked by phase remains locked to the CAV servopattern. Consequently servodepresiones are always read to servo frequency. The recording apparatus comprises an optical system for recording or reading information generating a point via a beam of radiation on a track of the record carrier. The optical disk is rotated and the point is placed in the radial direction on the center of the track by servomedios to explore the track. During the scan the servo circuit blocked by phase is locked to the rotation frequency of the disk to read the servopatron CAV. The phase locked data circuit is blocked at the CLV data rate. The known carrier and recording device has the problem, that for the reliable operation a first phase-locked circuit must be blocked to the CAV servopattern, and a second phase-locked circuit must be locked to the CLV data density. An object of the invention is to provide an optical disk, a read and write device arranged for a more reliable recording and / or recovery operation while the data is recorded at a substantially constant density. For this purpose, an optical disk as described in the opening paragraph is characterized according to the invention because the tracks comprise periodic characteristics, which are radially aligned within each of the zones, the periodicity being indicative of the recording density of the track for the track in question. This has the effect that the speed of recording and reading data can be blocked directly to a signal generated by the detection of the periodic characteristics. When you jump within a zone, the speed does not change, whereas when you jump to a different zone the speed changes a known amount. There is no need for a second circuit blocked per phase, only one blocked circuit per locked phase is required at the data rate. As a result, the registry is less complex and more reliable. For the purposes mentioned above, a recording device as described in the opening paragraph is characterized according to the invention because, although the tracks comprise periodic characteristics, which are radially aligned within each of the zones and the periodicity is indicative of a track density for the track concerned, the average track density within a zone is substantially equal to said constant density, the recording control means are arranged to detect the periodic characteristics and to record depending on these same predetermined amount of data in each track within one of the zones at such density of the track. A reading device as described in the opening paragraph is characterized according to the invention because, although the tracks comprise periodic characteristics, which are radially aligned within each of the zones and the periodicity is indicative of a density of the track for the track in question, the average of the track densities within a zone is substantially equal to such a constant density, the reading control means are arranged to detect the periodic characteristics and to read the same predetermined amount depending on them. of data of each track within one of the zones at such track density. This has the effect that the data, although positioned corresponding to a CAV pattern within a zone, have a substantially average CLV density, and can be recorded and read by means directly synchronized to a signal generated by the detection of the periodic characteristics. The invention is also based on the following recognition related to the reliability of servo signal detection in a high density optical register. To achieve the high density the distance between the tracks, the depressions of the tracks, are designed as small as possible for the available exploration system and the size of the scanning point. When the servoelements, for example the depressions or other periodic characteristics of the track, are then explored and a servo signal is generated, the servo elements of the neighboring tracks also have influences on the servo signal, which is known as a replica. However for a CLV density the amount of data stored in a track must be increased radially. The inventors have * observed that by aligning the periodic characteristics within a zone the replica within the zone can be eliminated. At the beginning of the next zone, the density increases gradually, so that on average the density is substantially equal to the density of CLV. The replication problem is now only present in the boundary track between two zones. The boundary track can be skipped, or it can be taken against special measures to control interference problems at the boundary of the area. An optical disk modality is characterized in that the size of the zones is such that the difference in the number of periodic characteristics in a lap of the track in the boundaries of adjacent zones is relatively low in relation to the number of periodic characteristics in a lap of track. A difference in periodicity produces an interference pattern that includes (partial) extinctions in a limit signal generated from the periodic characteristics when a track is scanned at the boundary of two zones. A minor difference in the periodicity relationship results in the limit signal having only a few extinctions, which can be positioned by selecting the phase difference of the periodic characteristics. The additional advantages, the preferred embodiments of the apparatus and the detection unit according to the invention are given in the dependent claims. These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which Figure 1 shows a record carrier. , Figure 2 shows a prior art optical disk with a CLV header pattern, Figure 3 shows an optical disk divided into zones, Figure 4 shows a diagram of a header and a sector, Figure 5 shows an apparatus to read a record carrier, Figure 6 shows an apparatus for writing and reading a record carrier, Figure 7 shows a servo pattern of areas / slots in the boundary of a zone, Figure 8 shows an optical disk having a track eccentric, and Figure 9 shows servo signals generated at the boundary of a zone. The corresponding elements in the different Figures have identical numerical references. The Figure shows a record carrier in the form of a disk 1 having a track 9 intended to be used for recording and a central hole 10. The track 9 is arranged according to a pattern of turns constituting substantially parallel spiral tracks. The track 9 on the record carrier is indicated by a pre-stamped track structure provided during the manufacture of the blank record carrier. The structure of the track is constituted, for example, by a pre-slot 4, which allows a read / write head to follow the track 9 during the scan. The invention is applicable correspondingly to other track patterns having substantially parallel tracks, in which the turns are concentric instead of spirals forming circular tracks. Figure lb is a cross section taken along the line bb of the record carrier 1, in which a transparent substrate 5 with a recording layer 6 and a protective layer 7 is provided. The pre-race 4 can be implemented as a indentation or elevation, or as a material property that deviates from its surroundings. The recording layer 6 can be optically or magneto-optically (MO) writable by means of a device for writing information, for example as the known recordable CD system. During writing, the recording layer is locally heated by a beam of electromagnetic radiation, such as a laser light. The registration layer in a rewritable record carrier is constituted, for example, by a material by phase change, which acquires an amorphous or crystallized state when heated to the correct degree. The Figure shows an alternative track structure consisting of raised tracks and alternating depressions, called spaces 11 and slots 12. It should be noted, that both spaces 11 and slots 12 serve as record tracks. Each turn has at least one area that interrupts the spaces and slots that make up the header area. For a spiral pattern, the slots can be continued as slots once in each turn after the area of the header that constitutes a double spiral by the concatenated spaces and the concatenated slots. Alternatively, at least once per turn, a transition from space to slot or vice versa is established by switching to the other type after the header area. According to the invention, the tracks are subdivided into recordable track portions 3 by radially aligned headers 2. The. Track portions 3 are for reading or recording optical marks representing user information, and are preceded by headings for individual access to each portion of track. The headers comprise position information indicative of the heading position and the attached track portion relative to the beginning of the track or radial and angular parameters, for example address markings representing the address information. Address markings on a type of recordable record carrier are usually stamped during manufacturing to allow the positioning of a read / write head anywhere on the record carrier not yet registered. The headings are located in a few, that is, four, angular positions in each turn of the track, which corresponds to the heading locations used in the Constant Angular Velocity System (CAV). However, the position information in the headers in the CAV places is written at a CLV density, ie, the marks encode the position information at a constant density. This is indicated schematically by the rectangular header areas 2 of Figure la. Due to the CAV location of the headers, the track portions have a length proportional to the radial position, ie, the distance to the middle part of the central hole 10. The track portions are recorded at a constant density, and therefore both the amount of data in a track portion is proportional to the radial position, which is known as CLV format. The data within the track portions and the position information in the attached header are recorded at the same density and can be read with the same reading means. The data to be recorded is subdivided into sectors of a fixed length, which are recorded from a first angularly arbitrary position and radial to a second arbitrary position, such positions are between the headers. In the disc format according to the invention, there is no requirement to have a fixed sector number exactly in one revolution, which gives additional advantages in the average data density, because zoning can not be used. small areas. Arbitrary positions can be calculated according to a few formulas by knowing the amounts of recordable data in each track portion. Consequently, a reduced overload of the header is achieved by using a few headings aligned by CAV per turn and writing sectors to the CLV data density, sectors which are not aligned with the headers. Figure 2 shows an optical disc of the prior art 21, such as a DVD-RAM using a CLV format by zones (CLV = Constant Linear Velocity, ie the constant recording density is independent of the radial position). Headers 22 are provided, 23, 24 for each sector, and the record area of the disk is subdivided into annular or axial zones. Each lane portion within one of the zones accommodates a sector, and the associated header comprises a physical address for that sector. Each zone has a fixed number of sectors in a turn, and the number of zones increases by one for each next zone radically outward. The headers 24, of the first sector in each turn are aligned radially. The additional headers 22, 23 are aligned within the zone, and within the zone the amount of data recorded in one revolution remains constant according to the CAV (Constant Angular Rate) system. The format of this disc is known as ZCLV (CLV per Zone). However, the prior art ZCLV disks have a significant loss of data storage capacity due to the large number of headers. This loss is known as overload, overload which is reduced by the invention. Figure 3 shows an optical disk divided into zones according to the invention. The disk has a registration area 31 of an internal diameter 32 to an external diameter 33. The record comprises circular or spiral tracks (as shown in Figure 1) and the tracks are interrupted by headers 34 that form track portions. The headers are radially aligned, in particular the start of the headings is aligned along straight radial lines 36. The record area 31 of the disk is subdivided into coaxial annular zones, and within each zone the track portions are arranged to register the same amount of data. Within a zone the density begins at a nominal level, say the density of CLV, and decreases proportional to the radial proportion of the portion of the track in question, and at the beginning of a next zone the density is fixed at the nominal level. Consequently, the density within each zone is according to the CAV system. The average density of the total recording area is a little lower than the nominal CLV level, such loss of zones depends on the number of zones, for example it is greater with only a few large zones. Accordingly, each track portion within one of the zones is arranged to record the same predetermined amount of data at a track portion density, and the average track portion density within a zone is substantially equal to the density of CLV. The headers are written to the data density, which decreases outwardly within a zone according to the CAV system, the final portions 35 of the headers are aligned in radial linear pieces 35 at a different angle that constitutes a structure similar to teeth of saw on each ray. In one embodiment of the disc, the track portions are provided with periodic characteristics indicative of the density for the respective track portion. During scanning in a reading device, the periodic characteristics generate a periodic signal in a scanning unit, for example, in servo signals or the data reading signal. The periodic signals can be used to synchronize the recording or reading of data, for example by a blocked circuit per phase blocked to the periodic signal. Periodic characteristics may be a variation of the track position in a direction transverse to the track called eccentric turn, or other variations in the width or depth of the track. The eccentric rotation for a track on a CLV disc without headers, for example a CD-R, is described in US 4,901,300 (D2). In an embodiment of the disk divided into zones according to the invention, the eccentric turns of the track within the zone are aligned radially. The number of eccentric turns within a track portion is constant, and a fixed amount of data corresponds to an eccentric rotation, for example, an eccentric turn is 324 channel bits, and a frame is 6 eccentric turns or 1944 channel bits or 155 bytes of data for a given channel code. Figure 4 shows a header and sector diagram. Figure 4a shows a pattern of spaces / slots interrupted by headers in an elongated and schematic form. A first slot 41 is interrupted by a header area 40. A first space 42 is adjacent to the first slot 41, and additional slots and spaces follow. The grooves are provided with a transverse variation of the place, the so-called eccentric turn, which is aligned between the grooves. The header area is subdivided into a first portion 43 used for slot headers and a second portion 44 for space headers. Accordingly, the reading of address markings 45 representing the position information is not disturbed by the interference of the address markings in a radially neighboring area. Figure 4b shows a header diagram and track portion indicating the logical allocation of the stored information. The unit of length is the period of eccentric rotation, which corresponds to a fixed amount of channel bits as explained above. First a header 40 is given, subdivided into a header portion 43, and a space header portion 44. Subsequently a control portion 46 of the eccentric turn 5 follows to control the reading of the stored data. The control portion 46 is subdivided into a Vacuum (unwritten area directly adjacent to the header area), a Protection area to initiate the writing operation (some variation at the initial point followed to prevent wear), a VFO area for block a Variable Frequency Oscillator, and a SINC pattern to logically synchronize the channel code. After the control portion 46 follows a DATA area 47 for storing user data, DATA area which has a length that depends on the radial position of the track portion. The last part 48 of the track portion before the next header area is divided into a PA, a Tapping to close the channel code coding, a second Protection and Vacuum with similar functions as the Vacuum and Protection in the portion of control 46. Figure 4c shows the logical data format.

The user data is subdivided into sectors 142 of a fixed length of 2 kBytes, each of which requires, for example, 98 eccentric spins when registering. A number of sectors, for example 32, are joined forming an ECC block, in which Error Correction Codes are included to correct errors anywhere in the ECC block. Such a long ECC block provides better protection against burst errors, and constitutes the minimum amount of data to be written. Also if only one sector should be changed, the entire ECC block to be rewritten including the newly calculated error codes. A linking sector 141, which is only a few eccentric turns, is reserved as a buffer between the ECC blocks to allow independent writing of such blocks. Usually the linking sector is written with padding data to ensure that blank intermediate areas do not remain. Obviously, the ECC block is not placed in a track portion, the block may be larger or smaller than the DATA 47 area within a track portion. The actual start of an ECC block can be easily calculated from the length of the block, the direction of the block and the size of the track portions, which vary by default depending on the radial position. Such a calculation gives a track number, a heading number within the track and a distance from that heading, for example expressed as a number of eccentric turns. In an embodiment of the optical disc, the position information in the header comprises a track number indicative of the radial position of the track and a heading number indicative of the angular position of the header. It should be noted that a specific heading will always be within a block with a specific address and that it will always be located near a block at a known distance from that header. In an embodiment of the optical disk, the position information in a header comprises a block address indicative of the location of the block in the header and an indicator of the next block indicating the distance of the header at the beginning of the next block. The address of the block can be the beginning of the block before and including the header, or it can be the address of the next initial block. Figures 5 and 6 show an apparatus according to the invention for scanning a record carrier 1. The apparatus of Figure 5 is arranged to read the record carrier 1, record carrier which is identical to the record carriers shown in Figure 1 or Figure 3. The device is provided with a read head 52 for scanning the track on the record carrier and reading control means comprising drive means 55 for rotating the record carrier 1, a reading unit 53, comprising for example a channel decoder and an error corrector, tracking means 51 and a system control unit 56. The reading head comprises an optical system of a known type for generating a radiation point 66 focused on a track of the recording layer of the record carrier via a radiation beam 65 guided through optical elements. The radiation beam 65 is generated by a radiation source, for example, a laser diode. The read head further comprises a focusing actuator for focusing the radiation beam 65 on the recording layer and a tracking actuator 59 for fine positioning of the point 66 in a radial direction over the center of the track. The tracking actuator 59 may comprise coils for radially moving an optical element or may be arranged to change the angle of a reflective element on a moving part of the read head or a part on a fixed position in the part of the case or frame of the optical system, which is mounted on a fixed position. The radiation reflected by the recording layer is detected by a detector of a usual type, for example, a four-quadrant diode, for generating detector signals 57 that include a read signal, a tracking error and a focus error signal. The apparatus is provided with tracking means 51 coupled to the read head for receiving the tracking error signal of the read head and controlling the tracking actuator 59. During reading, the read signal is converted into output information, indicated by the arrow 64, in the reading unit 53. The apparatus is provided with a header detector to detect the header areas and retrieve the address information of the detector signals 57 when scanning the header areas of the tracks of the record carrier. The header detection means is arranged to read the position information of the headers substantially at the data density, which corresponds substantially to the constant density used in the CLV. The apparatus has passivation means 54 for the approximate positioning of the read head 52 in the radial direction on the track, the fine positioning is effected by the tracking means 59. The device is further provided with a control unit of the system 56 for receiving commands from a control computer system or from a user to control the apparatus via control lines 58, for example a collective conductor of the system collected to the drive means 55, the positioning means 54, the detector of the header 50, the tracking means 51 and the reading unit 53. For this purpose, the control unit of the system comprises control circuits, for example a microprocessor, a program memory and control gates to perform the procedures described below . The control unit of the system 56 can also be implemented as a state machine in logic circuits. It should be noted, that the headers are located in CAV positions, and therefore, the amount of data in the track portions depends on the radial position. The reading unit 53 is arranged to eliminate the headers of the data reading, elimination which can be controlled via the control lines 58 by the detector of the header 50. Alternatively, the reading means are provided with means to eliminate the format, which recognizes and removes the headers in additional control information of the data flow. In one embodiment, the reading device is arranged to read a disk having tracks with continuous eccentric turns, as described below with reference to Figure 8. The read control means are arranged to detect the periodic characteristics and to read depending on them the same predetermined amount of data of each track within one of the zones. A read clock is synchronized with the periodic characteristics and the read unit 53 reads a fixed number of channel bits per case of the periodic characteristics. In one embodiment, the read control means is arranged to retrieve the data from an area of the track after an unregistered area. The reading clock is synchronized with the periodic characteristics in the unregistered area and consequently the reading speed is adjusted during scanning of the unregistered area. The control unit of the system 56 is arranged to effect the retrieval of the position information and the positioning procedure as follows. An address of the desired block is derived from an order received from the user or from a control computer. The position of the block expressed in a track number and the header number and distance of the header is calculated based on the known amounts of data stored in each track portion. A table can be used for a zone format, giving each zone the first direction of the block and the length of the track portions, which is fixed during a zone. The radial distance from the current position to the desired track number is determined and a control signal for the positioning means 54 is generated to radially move the read head 52 to the desired track.

When the radial movement is completed, a header is read by the header detector 50. The header read signal is processed to detect if the desired track is being read. If so, the system control unit waits until the desired header arrives. After this header, any data before the calculated distance of the header is discarded, and the data of the desired block is read from a linking position within the linking sector described with reference to Figure 4c. In practice, all the data that starts in the header will be read, and any data before the start of the requested block will be discarded, and for reading, the linking position is equally effective for the start of the block. Preferably, the control unit of the system 56 is arranged to combine the first data amount of a first track portion with at least one additional amount of data from a first consecutive track portion, the at least one additional amount. of data comprising a final amount of data retrieved from a track portion to the next link position. Accordingly, the total ECC block comprises a first quantity of part of the first track portion read, a final amount of part of the last track portion read and many intermediate quantities of the track portions between the first and last track portions. . Figure 6 shows a device for writing information about a record carrier according to the invention of a type, which is (re) writable in, for example magneto-optical or optical form (via phase change or dye) by means of of a beam 65 of electromagnetic radiation. The device is also equipped to read and comprises the same elements as the reading apparatus described above in Figure 5, except that it has a write / read head 62 and recording control means, which comprise drive means 55 for making rotating the record carrier 1, a writing unit 60, which comprises for example, a device for formatting, an error encoder and a channel encoder, tracking means 51 and a control unit of the system 56. The head Write / read 62 has the same function as the read head 52 together with a write function and is coupled to the writing unit 60. The information presented at the input of the writing means 60 (indicated by arrow 63) is distributed over logical and physical sectors according to the rules for formatting and coding and is converted to a writing signal 61 by the write / read head 62. The unit The control system 56 is arranged to control the writing means 60 and effect the retrieval of the position information and the positioning procedure as described above by the reading apparatus. During the write operation, the marks representing the information are formed on the record carrier. The writing and reading of information for optical disc registration and the rules for formatting, correcting errors and coding by useful channel, as is well known in the art, for example for the CD system. In particular, the means detecting the header 50 are arranged to read the position information of the headers substantially at the data density, which corresponds substantially to the constant density used in the CLV. In the recording device or the reading device, the means detecting the header are synchronized with a data clock, which clock is generated by the clock generation means. The data clock is also used to control the writing means. 60 and / or the reading unit 53. The clock generation means can be controlled by the control unit of the system 56 based on the radial position, the area and the speed of rotation of the disk. In one embodiment of the device, the clock generation means comprises a phase-locked circuit, for example accommodated in the header detection means, phase-locked circuit which is blocked to the periodic characteristics of the track, such as rotation eccentric, during the scan. After a head jump 52, 62 to a new scanning location, the clock generation means may display the value of the data clock at the new location, or the bandwidth of the blocked circuit per phase may be increased to block quickly to the new eccentric rotation frequency. Accordingly, the recording control means are arranged to detect the periodic characteristics and to block the circuit blocked by phase to the periodicity thereof. A fixed, predetermined number of channel bits is recorded in correspondence to each case of the periodic characteristics, and as within a zone the number of periodic characteristics in a turn of the track is constant, a same predetermined amount of data in each track within one of the zones. Figure 7 shows a servo pattern of spaces / slots in a zone boundary. Tracks marked L (space) and G (slot) must be scanned from left to right and are connected via a spiral (not shown) to the side left of the Figure. The tracks are provided with eccentric turns or other preformed variations indicative of the data storage density of the track portion. A first track of slots 71 is the last track of a first zone and has an eccentric rotation corresponding to the data density of that zone, the last part of the first track of slots is shown on the left side of the Figure. After the interruption by the header area 70 the first track of slots 71 continues as the second track of slots 73 belonging to the next zone, which is provided with an eccentric turn according to that next zone, and consequently the track of intermediate spaces 72 forms the boundary of zone 74. From zone to zone the number of eccentric turns in a track portion may be increased, for example in an eccentric rotation or by a frame of 6 eccentric rotations. In the space / slot format, the eccentric rotation is implemented in the slot, and over space the eccentric turns of both neighboring slots are added to the servo signal. On space 72 between the two zones there is interference between the two eccentric turns of slightly different period, for example, when the number of eccentric turns in a track portion is increased by one frame (6 eccentric turns) in a zone limit. , the servo signal will be extinguished 0 or 6 times. The advantage of having only one increment of an eccentric turn per portion of track in a zone limit is that only one extinction of the servo signal occurs. Having one or only a few extinctions in a portion of the boundary track gives a sufficiently large area before a header, where the servo signal is present at a sufficient amplitude to keep the circuit blocked by phase locked. Accordingly, it is also possible to read the header in the limited track portions and still it is possible to record data in such track portions. Alternatively, such limit track portions may be evaded, and even at least one header directly after a limit turn. The servo signal of the space track 72 has an interference of two different eccentric rotations and is not easily useful for data storage. Additional measures may be taken in the recording and reading device to counteract the effects of the interference, but in a practical embodiment, the space track 72 is not used for data storage for a full revolution, the unused return forms the limit. of zone 74. It should be noted, that in the limit 74 the first header of the space 76, the second header of the space 77, etc., until the last header of the space 78, can not be read reliably due to such interference. In a disk mode (for reliable operation) two additional headers are not used, resulting in 1.25 unused tracks in eight headers in one round. In a disk mode (for symmetry reasons, ie the same total storage capacity for the space and the track), the capacity of the slot tracks is also limited by evading the same number of slot tracks in each zone boundary , shown in Figure 7 as the track of slots 73. Figure 8 shows an optical disk 1 having a track with an eccentric rotation. The recording area 81 is subdivided into three coaxial, annular zones 82, 83 and 84. Each zone is provided with circular or spiral tracks 85, with eccentric rotations. The inner zone 84 has for example n eccentric rotation periods, the middle zone 3 has n + 8 periods and the outer zone n + 16 periods. The number of eccentric turns and the increment were selected solely for the purposes of the drawing. The number of periodic characteristics at the beginning of a zone must be proportional to the radial distance to the center of the disk. By selecting the appropriate size of the zones, the difference in the number of periodic characteristics from zone to zone can be selected so that it is low in relation to the total number of periodic characteristics in a turn. For example, for a large number of zones (100) a difference of only a few periods (1% for a radial interval of diameter from n to 2n) can be achieved from zone to zone. The resulting signal has a component strongly related to the periodicity (for example the frequency of the eccentric rotation), and is modulated by amplitude with a relatively low frequency due to the replication or sum of the signals of neighboring tracks. For practical reasons the difference in periodicity is selected to be even, for example, 4, 6, 8, 16, 32, 48 or 64, while the number of eccentric turns is approximately 3200 in the innermost zone. By selecting such a low difference, the interference signal can be controlled and the maximum interference can be located at predetermined positions. In a format in the format of the disk with the headers, formats which were described with reference to Figures la and 3, the maximum interference can be located in relation to the headers. In particular, the maximum interference is located as far as possible before the headers, so that the headers can be detected reliably, because the phase locked circuit has a broad signal to synchronize. Consequently, in one embodiment, the disk has the format of spaces and slots and the phase difference of the eccentric turns confining a space between two adjacent zones is substantially zero near the headers. An advantageous choice is a difference of only one eccentric turn in each of the track portions, so that the maximum interference can be located in the middle part of the limit track portion and the minimum in a header. Figure 9 shows servo signals generated in a boundary zone. The first signal 91 has a number of periods n, and can be generated by scanning the last track of an area for a full revolution. The third signal 93 is generated from the first track within the next zone, and has n + 4 periods. The second signal 92 is generated from the boundary track between two zones, and shows the interference of combining the servo signals of two different eccentric rotation frequencies. When the difference in the number of periods is 4, the signal shows an extinction 94 in 4 places. The second signal 92 is generated when an intermediate space is explored between two zones having eccentric rotation grooves, so that the signal is the sum of two eccentric turns and complete extinctions occur. In a different modality, the interference is caused by the replica of the neighboring track, and partial extinctions (amplitude variations) instead of complete extinctions. Limit tracks can be bypassed when data is recorded, or a phase-locked circuit can be controlled to remain blocked, when a (partial) extinction occurs 94. Although the invention has been explained by modalities using four or eight headers in each round, it should be clear that other numbers or combination of numbers may be employed in the invention. For example, a disc of a recordable type has been described, but the invention can also be applied to dicomprising registered data, or disks of a read-only type. In addition, the invention is found in each and every one of the characteristics or combinations of novel features.

List of related documents (DI) EP-A- 587 019 Optical disk system and information processing system (D2) US 4,901,300 CLV optical disk with eccentric turns (PHN 12.398)

Claims (16)

CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, what is contained in the following CLAIMS is claimed:

1. An optical disk comprising a recording area for recording data at a substantially constant density, the recording area is divided into a plurality of coaxial annular zones comprising circular or spiral tracks, each track within one of the zones for storing the same predetermined amount of data at a track density, the average of the track densities within a zone is substantially equal to such a constant density, characterized in that the tracks comprise periodic characteristics, which are aligned radially within each of the zones, the periodicity being indicative of the density of track record for the track in question.

2. The optical disk according to claim 1, characterized in that the periodic characteristics comprise an eccentric radial track rotation.

3. The optical disc according to claim 1 or 2, characterized in that the size of the zones is such that the difference in the number of periodic characteristics in a lap of the track in the limits of the adjacent areas is relatively low in relation to the number of periodic characteristics in a turn of the track.

4. The optical disk according to claim 3, characterized in that the difference is 1,2,4,6,8,16,32,48 or 64.

5. The optical disk according to claim 2, 3 or 4 , characterized in that in the registration area comprises grooves and spaces, both of which constitute the tracks, the grooves exhibit the eccentric rotation of the radial track, and the eccentric rotation is aligned between the groove of each of the zones.

6. The optical disk according to claim 1, 2, 3, 4 or 5, characterized in that the servopattern comprises alternating headings with track portions, and because the phase difference of the periodic characteristics, in the limit of two adjacent zones is substantially zero near the headers. The optical disk according to claim 6, characterized in that the difference in the periodicity between the attached zones results in 1 or 2 extinctions within a track portion. The optical disk according to any of claims 1 to 7, characterized in that the recording area comprises recorded data. The optical disk according to claim 8, characterized in that the optical disk is of the read-only type. 10. A recording device for recording data at a substantially constant density on an optical disk, comprising a recording area comprising circular or spiral tracks, with the recording area being subdivided into a plurality of coaxial ring zones, which device it comprises a record header and record control means, characterized in that, although the tracks comprise periodic characteristics, which are radially aligned within each of the zones and the periodicity are indicative of a track density for the track to be In other words, the average of the track densities within a zone is substantially equal to the constant density, the recording control means are arranged to detect the periodic characteristics and to record a same predetermined amount of data in each track within them depending on them. from one of the zones to said track density. The recording device according to claim 10, characterized in that the recording control means are arranged to record a predetermined amount of channel bits per case of the periodic characteristics. The recording device according to claim 10 or 11, characterized in that the recording control means are arranged to control the recording speed depending on the periodic characteristics. 13. The device according to claim 10, characterized in that the record control means are arranged to skip a boundary track turn in a boundary zone during registration. The recording device according to claim 13, characterized in that the registration control means are arranged to also skip a turn of track of slots adjacent to the return of the limit space track. 15. A reading device for reading data from an optical disk recorded at a substantially constant density, the optical disk comprises a recording area comprising circular or spiral tracks, recording area which is subdivided into a plurality of coaxial ring zones, device which comprises a reading head and reading control means, characterized in that, although the tracks comprise periodic characteristics, which are aligned radially within each of the zones and the periodicity is indicative of a track density for the track in question, the average of the track densities within a zone being substantially equal to the constant density, the reading control means are arranged to detect the periodic characteristics and to read depending on them the same predetermined amount of data of each track within one of the zones at said track density. The reading device according to claim 15, characterized in that the read control means is arranged to recover the data of a track area after an unregistered area, by adjusting the reading speed during the scanning of the area not registered depending on the periodic characteristics.