MXPA00009444A - Record carrier, playback device and method of recording information - Google Patents

Abstract

A record carrier has substantially parallel tracks, which exhibit first variations of a first physical parameter and second variations of a second physical parameter of the track. The first variations represent information recorded on the record carrier, which information is recoverable by means of a controllable type of data processing. A modulation pattern of the second variations represents a code for controlling said type of data processing. In respect of a code track that comprises themodulation pattern, the modulation pattern in the left neighbouring track (41, 44) is aligned to the modulation pattern in the right neighbouring track (43, 46). Thereby crosstalk due to the second variations is decreased, and at least two tracks have the same modulation pattern. The playback device has a demodulator and a control unit (56) for retrieving the code from at least two tracks.

Description

REGISTRAR CARRIER, REPRODUCTION DEVICE AND METHOD FOR REGISTERING INFORMATION FIELD OF THE INVENTION The present invention relates to a record carrier comprising substantially parallel tracks exhibiting variations of a first physical parameter of the track, the first variations represent recorded information about the record carrier, information which is recoverable by means of a controllable type of data processing; and second variations of a second physical parameter of the track, a modulation pattern of the second variations represents a code for controlling the type of data processing. The invention also relates to a method for recording information about a record carrier, a method in which the record carrier is provided with substantially parallel tracks, and the information is encoded in first variations of a first physical parameter of the track. , information which is recordable by means of a controllable type of data processing; and a code for controlling the type of data processing is encoded in a modulation pattern of second variations of a second physical parameter of the track.

The invention also relates to a reproduction device for recovering information from the record carrier, the device comprises reading means for generating a reading signal depending on the first variations, and modulation means for recovering the modulation pattern code of the second variations, and data processing means for processing the forward signal to retrieve the information depending on the code.

BACKGROUND OF THE INVENTION A system for recording information comprising a record carrier, a recording method and a reproduction device is known from US 5,724,327. The record carrier comprises tracks in which the information is represented in a predefined form by optically readable marks of first variations of a first physical parameter, such as the reflectivity of the scanned surface. The track also has second variations of a second physical parameter, such as a periodic excursion of the track in a transverse direction (denoted, moreover, as undulation), a variation in the depth, shape or width of the marks. The second variations are modulated and the modulation pattern represents a code which is used to retrieve the information, for example a demixing code to retrieve information stored as mixed information. The code can be a mark of useful means in a system or copy protection, because the ripple of the track can not be copied to a recordable disc in the standard recording equipment. The reproduction device comprises reading means for reading the optical marks and demodulation means for recovering the modulation code of the second variations. The player and the information carrier form a system for the controlled reproduction of information. For this purpose, the player comprises data processing means for reproducing the information depending on the retrieved code. If the information is copied on a writable information carrier, the information of this copy will not be reproduced by the player, because during the copying process only the information represented by the first variations is written to the bearer of writable information. The copied information carrier does not contain the code, since the second variations can not be produced by the standard registration devices. However, the known system can not be applied to an existing high density recording carrier such as DVD, because such high density recording carrier systems have very narrow tolerances on the parameters of the track and the required modulation of a second physical parameter would disturb the reading of the marks and cause errors in the information retrieved.

BRIEF DESCRIPTION OF THE INVENTION An object of the invention is to provide a high density record carrier with a media mark, and recording and reproduction means for such a record carrier. For this purpose, the record carrier described in the opening paragraph is characterized in that, with respect to a code track comprising the modulation pattern, the modulation pattern in the left neighboring track is aligned with the modulation pattern in the track. neighboring right. The code is a track that contains in its modulation pattern the code to control the processing of data when a recorded information is retrieved. One or more (or all) of the tracks on the record carrier can be code tracks. The modulation patterns aligned in the tracks adjacent to the code track have the effect that the second variations in the left neighboring track are complementary to the second variations in the right neighboring track, due to irregularities in the second variations due to the modulation present in both neighboring tracks. Consequently, any increase in the disturbance caused by a second variation in the left neighboring track is compensated for by a decrease in the disturbance by the complementary variation in the right neighboring track. Therefore, narrow tolerances on track parameters can be effectively maintained and crosstalk remains limited to acceptable values. The invention is also based on the following recognition. The amplitude of the second variations must be strong enough to detect the modulation pattern. However, in a high density recording carrier, the modulation of the second variation in neighboring tracks causes crosstalk, and therefore produces noise, which degrades the detection of the recorded information and the detection of the modulation pattern itself. Consequently, the amplitude of the second variation should be as low as possible. The inventors have recognized that, by using aligned modulation on neighboring tracks, the maximum noise contribution of the left track does not coincide with the maximum noise contribution of the right track. Consequently, a relatively low amplitude of the second variations is sufficient for reliable detection of the modulation pattern. Due to the low amplitude the disturbance of the reading of the marks and errors in the recovered information is reduced to a minimum.

An embodiment of the record carrier according to the invention is characterized in that the second variations are offsets of the track in a direction transverse to the longitudinal direction of the track, and the displacements of the left neighboring track coincide with offsets of the right neighboring track. in the same direction. This has the advantage, that the crosstalk of the first variations in adjacent tracks is reduced, because if the exclusion in one of the adjacent tracks is towards the position of a reading point on the code track and consequently causes some additional crosstalk, the excursion of the other adjacent track is far from the reading point and consequently causes less crosstalk. An embodiment of the record carrier according to the invention is characterized in that the modulation patterns in the code track and the neighboring tracks represent the same code. This has the advantage that the detection signal of the code track will be stronger because the neighboring tracks have the same modulation. Also, if the second parameter is an excursion to a transverse direction, the distance between the tracks, also called separation, in the modulated parts of the track is still the same, because both tracks have the same transversal excursion. Alternatively, the modulation pattern in the code track is substantially inverse to the modulation pattern in the left neighboring track. This has the advantage for some types of modulation, for example, a ripple in a pre-slot, that the detection signal of the code track is stronger. An embodiment of the record carrier according to the invention is characterized in that the second variations are periodic and the modulation pattern comprises phase modulation, and phase differences between modulation patterns in adjacent tracks limited to a predetermined amount. Such predetermined amount is selected to be smaller than the phase differences that occur in the phase modulation. This has the advantage that any disturbance of the neighboring tracks is substantially in phase with a read signal of the modulation pattern in the code track. According to the invention, the method as described in the opening paragraph is characterized in that, with respect to a code track comprising the modulation pattern, the modulation pattern in the left neighboring track is aligned with the modulation pattern in the right neighboring track. The effects and advantages of the method have been previously explained by difference to the record carrier. The reproduction device as described in the opening paragraph is characterized in that the device comprises means for recovering the code of at least two tracks. In the record carrier the alienating modulation patterns result in at least two tracks having the same modulation pattern and therefore representing the same code. In the reproduction device, the code retrieved from a first track is verified by reading an additional track, which comprises the same code. This has the advantage that the code recovery is more reliable. The most preferred embodiments of the method, devices and information carrier according to the invention are given in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be apparent from, and elucidated better 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 schematic map of the recording area and the amplitude of undulation or oscillation, Figure 3 shows parts of a modulation pattern, Figure 4 shows the distribution of a record carrier, the Figure 5 shows a reproduction device, and Figure 6 shows a recording device. The corresponding elements in different Figures have identical numerical references.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The figure shows a disc-shaped record carrier 1 having a track 9 and a central hole 10. The track 9 is arranged according to a spiral pattern of turns constituting substantially parallel tracks on a information layer. The record carrier may be an optical disk having an information layer of a recordable type or a pre-registered type. Examples of a recordable disc are the CD-R and the CD-RW, and the DVD + RW, while the audio CD or the DVD video are examples of pre-registered discs. The pre-registered type can be manufactured in a well-known way by first registering a master disk and via intermediate steps later pressing discs for the consumer. The track 9 on the recordable type of the record carrier is indicated by a pre-stamped track structure provided during the manufacture of the blank record carrier, for example a pre-race. The information is represented on the information layer by optically detectable marks recorded along the track. The marks are constituted by variations of a first physical parameter and therefore have different optical properties or magnetic direction than their surroundings, for example variations in height called depressions and areas on a CD. Figure Ib is a cross-section taken along the line bb of the registration carrier 1 of the recordable type, in which a transparent substrate 5 is provided with a registration layer 6 and a protective layer 7. The registration structure is constituted, for example, by a pre-slotted track 4, which allows a read / write head to follow track 9 during the scan. The pre-scored track 4 may be implemented as an indentation or an elevation, it may consist of a material having a different optical property than the surrounding material. The preset track allows a read / write head to follow the pit 9 during the scan. A track structure can also be formed by regularly scattered servomars, which cause them to periodically occur servo signals. The record carrier may contain information in real time, for example video or audio information, or other information, such as computer data.

Figures I and I d show two examples of track variations. The Figure shows a periodic variation of the lateral position of track 4, also called ripple. Figure Id shows a variation in the width of the track 4. Variations cause an additional signal to emerge in the reading head, for example in a servo tracking detector, of a recorder. The undulation or oscillation is, for example, frequency modulated and the information of the disk is encoded in the modulation. A complete description of a writable CD system comprising the disc information encoded in such a way can be found in US 4,901,300 (PHN 12,398) and US 5,187,699 (PHQ 88,002). For the optical record carriers of the read-only type, track 4 as shown schematically in the Figure is constituted by a series of depressions, and the ripple of the track in that case is the periodic variation of the lateral position of the depressions. According to the invention, the undulation comprises a code, which is an identifier for supporting the control against copying, anti-piracy, and / or other mechanisms. The code contains data for copy protection and anti-piracy mechanisms. It should be noted, that in a recordable disk, the pre-race or track structure is undulated, whereas in a prerecorded record carrier the detectable marks are undulated, for example, a ripple of depressions. During the production process of the master disk, the ripple is written by a laser beam recorder, imposing a small lateral deviation from the center of the depressions. The ripple is detectable by the optical pickup, using the servo control signals. Figure 2 shows a schematic map of the recording area in the amplitude of the undulation or oscillation. The schematic map 21 shows the first part of the recording area and indicates the amplitude A of the undulation. A corresponding address map 22 is shown on one side. The waviness or oscillation is located only in a limited area of total recording, for example in an area within the front area of a co disk or is indicated in Figure 2 from SI to S4. Preferably, the limited area does not comprise essential information, for example zero or redundant data. On a DVD-type disc, the ripple is provided in specific directions at the end of the initial zone of the front zone, between the SI sector, which is greater than or equal to 0x02E15C and sector S4, which is less than or equal to 0x02FF7C It should be noted, that if the amplitude of the undulation is nominal in a track and zero in the neighboring track, that in such bordering tracks the crosstalk is not compensated as described in the introduction. Consequently, an increased noise level is found in such tracks. In a modality of the record carrier, the amplitude of the undulation in the boundary areas (in Figure 2: SI to S2 and S3 to S4) will depend on the radial position as it increases gradually from zero to the nominal amplitude and vice versa. The area of the center that comprises the nominal amplitude (from S2 to S3) can be used to detect and recover the code, while in the border areas the disturbance caused by the ripple decreases to zero, but does not substantially exceed a level in the area limited. In a practical embodiment, the amplitude of the undulation depends on the direction of the sector number as follows. The maximum amplitude is A = 30 nm. This should take its full amplitude A (only) between the SI sector, with SI + 0x100 < S2 < 0x02f00, and S3"with 0x02FE00 <S3 <S4 - 0x100.This implies the interval where the full amplitude is applied (S3-S2), it must cover at least one reference code area, buffer zone 1 and the control data zone The rise and fall of the ripple amplitude takes at least 256 sectors (approximately 16 turns), the amplitude must be zero for sector numbers less than SI and beyond S 4. Linearity increases With the sector number from zero to A between SI and S2, it must have a constant value of A between sector S2 and S3, which decreases linearly from A to zero between r3 and r 4. In tical modalities, it is permissible that the amplitude of the undulation is gradually increased by the sector number, step by disc revolution or continuously, preferably the jumps in the amplitude of the undulation should not exceed 3 nm, and at any point on two successive turns, the difference in amplitude no d It should exceed 3 nm. In tice on a disc of the CD type the location of the undulation corresponds to radii of 23 to 24 nm. In one embodiment, the undulation or oscillation takes the form of a sinusoidal deviation (in relation to the center of the track) from the position of the depressions encoding the information. The undulation is written with a constant angular velocity (CAV), and each track is modulated with the same code and additional control bits. Consequently, each turn of the disk contains the same waveform of the ripple, except possibly for a difference of one minute in the amplitude or phase error. In a tical embodiment, the number of sinusoids of the ripple per track is 1152. The phase deviation between two neighboring tracks is as small as possible. In tice for a reading signal of sufficient quality, the phase difference may not exceed 30 degrees, where 360 degrees correspond to a complete undulation sinusoid (1 / 1152th of a turn of disk).

The code which is encoded in the ripple can be used as the disk mark. The master placement of the disk should affect a plated disk mark (e.g., a 64-bit number), from which the ripple code is created, preferably using a cryptographic function. For security reasons, facilities for directly inserting the ripple coding are not allowed. A cryptographic relationship can be used between the ripple code and the registered information about the record carrier, for example a one-way function between the mark of the disk and a watermark, i.e. the control information included in the information of audio and / or video. Additional details of creating and using a disc brand and checking the brand of the disc against additional control information (for example the so-called control ticket) for a controllable type of data processing can be found in the WO 98/33176 and WO 98/33325. In one embodiment, the record carrier contains several annular areas with undulating tracks separated by transit areas. Each transit area may have a different modulation pattern, while the modulation pattern within each individual area is the same. Accordingly, the number of codes in the second variations can be coded. The transit areas may or may not have a ripple or have a transit pattern that gradually changes the modulation pattern of a first annular area in the modulation pattern of a second annular area. In one embodiment, the code is provided with error correction symbols to correct reading errors. For the correction of errors a Reed-Solomon code [8,4,5] on F24 with a speed R = 1/2 can be used. The 64 bits of the cryptographic function are grouped into 4 symbols 4 times. A symbol contains 4 bits. The Reed Solomon encoder operates on 4 symbols at a time. Four user symbols xi, x2, x3, x, expand to x4, x3, x2, Xi, 0, 0, 0, 0, 0, 0, 0, (of length 11). Four ECC symbols X12, p, X? 4, 15 are obtained using the polynomial x4 + x + 1. The error correction encoder is the 8 symbols Xi, x2, x3, x4, x12, xi3, x? 4, X15 . Figure 3 shows parts of a modulation pattern. The code is represented by data bits, which are converted to a waveform and encoded in the ripple, and are provided with synchronization words to locate the start of the code. Figure 3a shows an example of modulation of data bits to channel bits, and the corresponding waveform 31. The data bits are encoded by Two Phase Marks. In the Two Phase Marks code, two data bits represent one data bit. The code always O "at the beginning of a data bit, a second transition will occur in the middle part of the dice bits in case it has a value of" 1. "In addition, data bits of the synchronization words are added. of the code to detect the beginning of the code Each group of 4 data symbols will be preceded by a specific 8-bit synchronization word (channel) Figure 3b shows a modulated undulation Modulation is the so-called Binary Phase Deviation modulation (PSK) One channel bit contains four ripple sinusoid periods The bit transitions 36 occur only at the zero crossings of the ripple sinusoids A first bit of channel 32 has the value of 0, one second channel bit is also 0, a third bit of channel 34 is 1 and the fourth bit of channel 35 is 0. Due to the coding of the Two-Phase Mark, one data bit is 8 carrier periods, and the Figure 3b shows two data bits. Due to the error correction R = 1/2, the effective bit period is 16 periods of the corrugated carrier. For detection, it is permissible for the modulated waveform reading signal to be filtered by bandpass or highpass, provided that the characteristics of the bandpass remain substantially flat, for example, within 3 dB.

Figure 3c specifies four different synchronization words. Synchronization words violate the rule of the previous Two-Phase Mark code, so that they can be easily recognized. A synchronization word always starts with a reversal of the phase. A synchronization word has two possible appearances that are each inverse to each other (channel bit). Appearance which is used depending on the last bit of the previous channel bits. Figures 3d and 3e show aligned modulation patterns. These Figures give details of a few neighboring tracks, and a transversal excursion modulation pattern, which is not drawn to scale (in fact the excursion is from 3% to 10% of the track separation). According to the invention, the modulation patterns are aligned from track to track, that is to say that for this type of modulation, the zero crossings are in a corresponding longitudinal position. In the Figures, the average track 42, 45 is a code track comprising the modulated pattern representing the code, which is going to be read from left to right according to what is indicated in arrow 40. In Figure 3d, the left neighbor track 41 and right neighbor track 43 have the same modulation pattern as code track 42. In a mode shown in Figure 3c the modulation pattern of left neighbor track 44 is inverse to the modulation pattern in the track. of code 45. The right neighboring track 46 again has the polarity of the left neighboring track 44. Consequently, the modulation is inverted from track to track. In an additional mode that uses the track width modulation as shown in Figure Id, the modulation of the left neighboring track is inverse to the modulation of the right neighboring track to achieve the optimal compensation of crosstalk. In this case, a maximum width of the left neighboring track is aligned with a minimum width of the right neighboring track. Since such pattern is formed each time from two equal modulated tracks followed by two reverse modulated tracks. Figure 4 shows the distribution of a record carrier. A lap of the track is encoded with four segments of code words, alternating with synchronization words. The laps begin with the word of zero synchronization, followed by 64 channel bits, followed by Synchronization 1, 64 channel bits, Synchronization 2, 64 channel bits, Synchronization 3 and 64 channel bits. The next round contains precisely the same code. The absence of a reverse wave phase between the data bits is permissible between the end of any return and the start of the next return, although this violates the modulation of the two-phase mark. Consequently, the same modulation pattern is present in each corrugated track. In one embodiment of the record carrier, the polarity of the modulation is inverse from track to track, as shown in Figure 3c. This improves the strength of the read signal for the detection of the ripple of certain track configurations, for example the detection of servo signals by push-pull detectors used in recordable CD systems. In a practical embodiment of the record carrier, the tracks contain 64 code bits for the 64-bit modulation key for ECC, and (4 * 8) / 2 synchronization bits. In total, one turn of the track contains precisely 4 * [2 * (64 + 64) + 4 * 8] = 1152 ripple periods. When the disk rotates approximately 25 Hz to read the front area, the ripple frequency is fw = 1152 * 25 Hz = 28.8 kHz. Such a ripple or oscillation frequency is about 30 kHz has the advantage, that the information encoded in the track by the first variations, has substantially no frequency components in this range, and is also outside the bandwidth of the tracking servo system . Therefore, the detection of the modulation pattern is not disturbed by the first variations. Figures 5 and 6 show apparatuses according to the invention for screening a record carrier. 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. The device is provided with reading means comprising a read head 52 for scanning track 54 on the record carrier, a drive unit 55 for rotating the record carrier 1, a reading unit 53 and comprising for example a channel encoder and an error corrector, a tracking unit 51 and a system control unit 56. The reading head comprises a optical system of a known type for generating a radiation point 66 focused on a track of the registration layer of the record carrier via a beam of radiation 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 the fine positioning of 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 case the part of the Optical system is mounted in a fixed position. The radiation reflected by the recording layer is detected by a conventional type, for example a four quadrant diode, to generate detection signals 57 which include a read signal, a tracking error and a focus error signal. The apparatus is provided with a tracking unit 51 coupled to the read head for receiving the tracking signal of the read head and controlling the tracking actuator 59. The tracking unit may, for example, be of a type of phase detection (PDP) different, in which the deviation of the reading head in relation to the centerline of the track is detected from the phase differences that occur between the signals of the detectors when a mark is scanned ( for example a depression) on the track. Alternatively, the tracking unit may be of the well-known phase type, in which the deviation is detected on the basis of the detector signals on the left and right sides of the track. During reading, the reading signal is converted into output information, indicated by arrow 64, in reading unit 53. For this purpose, reading unit 53 comprises data processing of a controllable type, which is controlled on the basis of a code of the record carrier, for example, access control can be performed based on the code retrieved from the record carrier. The apparatus has positioning means 54 for approximately positioning the read head 52 in the radial direction on the track, if fine positioning is performed by the tracking actuator 59. The apparatus is provided with a code detector 50 for detecting and demodulating the code of the detector signals 57 when scanning a code track comprising the modulation pattern. For example, the track can be modulated by periodic excursions transverse to the direction of the longitudinal track as described with reference to Figure 3. Such modulation can be detected from the radial tracking servos. The device is further provided with a control unit 56 for receiving commands from the control computer or user system or for controlling the apparatus via control lines 58, for example a collective bus system conductor connected to the drive unit 55. , the positioning means 54, a code detector 50, the tracking unit 51 and the reading unit 53. For this purpose, the control unit comprises control circuits, for example a microprocessor, a program memory and control gates, to carry out the procedures described below. The control unit 56 can also be implemented as a state machine in logic circuits. The control unit 56 is arranged to recover the code of the track via the code detector 50, and to control the type of data processing in the reading unit 53. For example, the code may be a demixing key, the which is used to decrypt copy-protected video information. For reliable detection of the code, the control unit 56 is arranged to detect the code of at least two tracks. A first code track is located by placing the read head in a predetermined track, for example in a predetermined radial position or a predetermined direction. Next, the code is detected from the first code track. To verify the detected code, a second code track is scanned, for example the next turn of the track. The second detected code is compared to the first code, and if it is the same, the code is passed over the data processing unit. In one embodiment of the system, the code may be provided with error detection symbols, and the control unit may decide to read the code of a different code track only if errors are indicated by such error symbols. Alternatively, the control unit may be arranged to read two tracks, which are in different radial positions and comparing the recovered codes. In the event that the retrieved codes are not equal, additional tracks are read and the retrieved codes (or the read signals) are kept in the memory until the code can be determined with sufficient certainty, for example that at least 4 of 5 Tracks have the same code. In one embodiment, the reading device comprises means for locating a modulated area, i.e. a limited area of the record carrier comprising tracks modulated according to what is described with reference to Figure 2. The device may have a memory containing information Default modulated area address to locate the modulated area. Alternatively, such address information may be provided on the record carrier, for example in an information area system. The control unit 56 is arranged to control the positioning means 54 and the tracking actuator 59 to access a code track of the modulated area of the record carrier as indicated by the modulated area address information. 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 a magneto-optical or optical form (via phase change or dye) by means of a beam 65 of electromagnetic radiation. The device is also usually equipped to read and comprises the same elements as the reading apparatus described above with Figure 5, except that it comprises writing means, which include a write / read head 62 and a written signal processing unit. 60, which comprises for example a device for formatting, error encoder and a channel encoder. The write / read head 62 has the same function as the read head 62 together with a writing function and is coupled with the writing signal processing unit 60. The information presented to the input of the processing unit of the write signal 60 (indicated by the arrow 63) is distributed over logical and physical sectors according to the coding formats and rules and converted into a written signal 61 by the write / read head 62. The control unit of the system 56 is arranged to control the processing unit of the writing unit 60 to effect the retrieval of the position information and the processing procedure as described above for the reading apparatus. During the writing operation, marks are formed that represent information about the record carrier. The writing and reading of information to record on optical discs and to format useful, error correcting rules and channel coding, are well known in the art, for example of the CD system. In particular, the code detecting means 50 is arranged to recover the code of the modulated tracks as described with the playback apparatus. A data clock is used to control the processing unit of the writing unit and / or the reading unit 53. The means generating the data clock can be controlled by the control unit of the system 56 on the basis of the radial position, for example, on a zone and the speed of rotation of the disk and / or may be immobilized in the modulation. A registration method for providing a blank record carrier with modulated tracks comprises the following steps. In the method the record carrier is the one provided with substantially parallel tracks, the information is recorded in first variations of a first physical parameter of the track, information which is recoverable by means of a controllable type of data processing; and a code for controlling the type of data processing is encoded in a modulation pattern of second variations of a second physical parameter of the track. With respect to a code track comprising modulation pattern, the modulation pattern in the left neighboring track is aligned with the right neighboring track. This can be achieved by controlling exactly the modulation of the second variations, for example the radial positioning of the track in relation to the rotational position of the record carrier in the form of a disc. Alternatively, a second read head may be used to read the modulation pattern at a two track position before the track is written. In one embodiment, the record carrier is rotated and the modulation is controlled depending on the rotational position. Such control is achieved using tacho pulses from an engine that rotates the record carrier, and holding a waveform generator to the tacho pulses. The waveform generator further comprises the code for modulating the second variations during writing. Although the invention has been explained mainly by modalities using the undulation (a variable modulated transverse excursion), any suitable modulation of a track parameter can be modulated, for example reflection by means of a written part or the form of certain depressions. Also, for the information carrier an optical disk has been described, but other means, such as a disk or magnetic tape, can be used. In addition, the invention depends on each of the features or combination of novel features described above.

Claims (12)

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

1. A record carrier comprising substantially parallel tracks exhibiting first variations of a first physical parameter of the track, the first variations represent recorded information about the record carrier, information which is recoverable by means of a controllable type of data processing; and second variations of a second physical parameter of the track, the modulation pattern of second variations represents a code for controlling the type of data processing, characterized in that, with respect to a code track comprising the modulation pattern, the pattern The modulation of the left neighboring track is aligned with the modulation pattern on the right neighboring track.

The record carrier according to claim 1, characterized in that the second variations are displacements of the track in a direction transverse to the longitudinal direction of the track and the displacements of the left neighboring track with displacements of the right neighboring track in the same direction.

3. The record carrier according to claim 1 or 2, characterized in that the modulation patterns in the code track and the neighboring tracks represent the same code.

4. The record carrier according to claim 3, characterized in that the modulation pattern in the code track is substantially inverse to the modulation pattern in the left neighboring track.

5. The record carrier according to claim 3, characterized in that the second variations are periodic and the modulation pattern comprises phase modulation, and the phase differences between the modulation patterns in adjacent tracks are limited to a predetermined amount.

The record carrier according to claim 1, characterized in that the tracks constitute a spiral or concentric pattern of tracks, and the adjacent tracks in the track pattern exhibit the same number of second variations.

7. The record carrier according to claim 1, characterized in that only limited tracks in a recording area exhibit the second variations.

The record carrier according to claim 7, characterized in that the limited areas comprise a boundary zone between the area exhibiting no second variations and a central area exhibiting the second variations at a predetermined amplitude, a boundary zone in which the amplitude of the second variations increases from zero to the predetermined amplitude.

9. A method for recording information about a record carrier, method in which the record carrier is provided with substantially parallel tracks, and the information is encoded in first variations of a first physical parameter of the track, information which is recoverable by means of a controllable type of data processing; and a code for controlling the type of data processing is encoded in a modulation pattern of second variations of a physical parameter of the track, characterized in that, with respect to a code track comprising the modulation pattern, the modulation pattern The left neighbor track is aligned with the modulation pattern on the right neighboring track.

10. The method according to claim 9, characterized in that the record carrier is rotated and the modulation pattern is generated depending on such rotation.

11. The playback device for retrieving information from a record carrier according to any of claims 1 to 8, the device comprising - reading means for generating a read signal depending on the first variations, and demodulation means for recovering the modulation pattern code of the second variations, and - data processing means for processing the read signal to retrieve the code information, characterized in that the device comprises means for recovering the code of at least two tracks. The reproduction device according to claim 11, which serves to retrieve information from a record carrier according to claim 7, characterized in that the device comprises means for locating the limited part.