WO2009012405A1

WO2009012405A1 - Data storage medium authentication using speed-sensitive artifacts

Info

Publication number: WO2009012405A1
Application number: PCT/US2008/070363
Authority: WO
Inventors: Douglas M. Carson
Original assignee: Doug Carson & Associates, Inc.
Priority date: 2007-07-17
Filing date: 2008-07-17
Publication date: 2009-01-22

Abstract

Method (1000) and apparatus (100) for authenticating a storage medium (102), such as an optical disc. At least one speed-sensitive artifact (504, 606, 716, 718, 804, 902, 904) is placed in a data sequence (700) on the storage medium, the speed-sensitive artifact configured to provide a first error response when the data sequence is read at a first speed and a second error response different from the first error response when the data sequence is read at a second speed (1002). The first and second error responses are used to authenticate the medium as an authorized copy (1004, 1006). Preferably, access is granted to the medium if the artifact is detected (1008), and access is denied if the artifact is not detected (1010).

Description

DATA STORAGE MEDIUM AUTHENTICATION USING SPEED-SENSITIVE ARTIFACTS

Background

Some types of data storage media are in the form of discs, which are rotated at a specified rate adjacent a data transducer. For example, data are often written to an optical disc as a pattern sequence of pits and lands (marks) that provide different optically reflective responses to an optical pickup mechanism.

The transitions between adjacent pits and lands are detected in relation to changes in reflectivity of these respective areas. The transitions are generally used to provide a readback signal that, when processed, returns the originally written data to a user. The disc is controllably rotated at a velocity sufficient to cause transitions to occur at a selected frequency rate, enabling readback circuitry to establish a frequency lock with the data. Data storage schemes can include constant linear velocity (CLV), zoned constant linear velocity (ZCLV), constant angular velocity (CAV), etc. Data channel transfer rates (both reading and writing) are often specified at a standard rate (sometimes referred to as a "IX" rate). For most compact discs (CDs), the IX rate nominally provides a 4.3128 MHz channel rate. Generally, CLV rotation is supplied to the medium at a linear velocity of around 1.2 to 1.4 meters/sec (m/s) to maintain this 4.3128 MHz channel rate. For most digital versatile discs (DVDs), the IX rate nominally provides a 26.16 MHz channel rate using CLV rotation with a constant linear velocity of about 3.49 m/s. It will be appreciated that other media can provide other standard channel frequencies and rotational rates. The efficiency of reading and writing operations can be enhanced using systems that operate at an increased rotational rate for the medium. Commonly employed enhanced rates include 4X, 16X, 32X, 4OX, etc. For example, a CD writer that writes data to a recordable CD (CD-R) at 4OX writes the data at 40 times the nominal rate, or at a transfer rate of around 172.5 MHz (i.e., 40*4.3128 MHz). Such 4OX reading can be achieved by rotating the medium at an enhanced rate, such a variable revolutions per minute (RPM) profile that provides linear velocities generally in the range of around 48-56 m/s (1.2*40 and 1.4*40 m/s, respectively). Thus, instead of rotating the CD at perhaps between 250 and 500 RPM for IX reading as the transducer is moved between the ID and OD, at 4OX reading the RPM profile may be more on the order of from about 10,000 to 20,000 RPM.

Summary

Various embodiments of the present invention are generally directed to a method and apparatus for authenticating a storage medium, such as an optical disc, through the placement of one or more speed-sensitive artifacts on the medium.

In accordance with various embodiments, the speed-sensitive artifacts generally operate such that a first error response is achieved during readback at a first relative velocity between the medium and a read mechanism. The speed- sensitive artifacts further provide a different second error response during readback at a different second relative velocity between the medium and the read mechanism.

Preferably, the first and second velocities are achieved by rotating the medium at different rotational velocities.

The presence of the artifact is preferably detected by reading the medium at the respective first and/or second velocities. The presence of the artifact is thereafter preferably used to verify that the storage medium is an authentic copy and not, for example, an illegally pirated copy.

Brief Description of Drawings

FIG. 1 provides a generalized functional block representation of a readback system that reads back data from an optical disc.

FIG. 2 provides a generalized functional block representation of a writer system that writes data to an optical disc.

FIG. 3 generally depicts different analog readback signals transduced from an optical disc at different linear velocities of the disc. FIG. 4 generally represents portions of a read channel used to process readback signals such as shown in FIG. 3. FIG. 5 generally illustrates a speed-sensitive artifact that can be advantageously used for disc authentication purposes, the artifact in FIG. 5 generally characterized as a size related artifact.

FIG. 6 sets forth a radial deviation artifact. FIG. 7 provides an alternative series of focus deviation artifacts.

FIG. 8 sets forth additional focus deviation artifacts.

FIG. 9 generally illustrates a warpage related artifact.

FIG. 10 is a flow chart for a MEDIA AUTHENTICATION routine generally illustrative of steps carried out in accordance with various embodiments of the present invention.

Detailed Discussion

FIG. 1 provides a generalized representation of a readback system 100 used to read back data from an exemplary storage medium 102. For purposes of the present discussion, the readback system 100 will be contemplated as comprising a

DVD reader and the medium 102 will be contemplated as a multi-layer optical disc generally configured as a DVD-9. Such is not limiting, however.

A motor 104 selectively rotates the medium 102 at a selected rate, in this case at some multiple of the specified DVD rate. A readback mechanism 106, characterized as an optical pickup, includes a linear actuator 108 which radially advances a light emitting transducer (head) 110 to follow circumferentially extending tracks defined on the respective recording layers of the DVD. It is contemplated that the tracks in each layer are arranged as a continuous spiral from one radial extent of the medium 102 to the other, such as from the innermost diameter (ID) to the outermost diameter (OD).

A readback signal is transduced from the transducer 110 and provided to a readback processor block 112. The readback processor block 112 applies appropriate pattern detection, demodulation and error correction to recover the originally stored content from the medium 102. The recovered data are thereafter sequentially provided to an associated I/O device 114. The content can take any number of forms, such as audio, video, computer programming, etc. The I/O device 114 can accordingly comprise an audio receiver, a video processor, a television display, a personal computer, etc. FIG. 2 shows a generalized functional block diagram of a writer system 200 used to write data to a storage medium 202. As before, the storage medium 202 will be contemplated as comprising a recording layer of a DVD-9, although such is not limiting. As set forth below, the system 200 can be a part of a disc manufacturing operation in which prerecorded discs are formed. Alternatively, the system 200 can be viewed as a stand-alone writer for recordable media (such as DVD-R, DVD-R/W, DVD-HD-R, Bluray-R/W, etc.).

Input data (content) to be written to the medium 102 are denoted at storage location 204 and are provided to a signal processing block 206. The signal processing block 206 operates under the control of a top-level control processor block 208, which also controllably rotates the medium 202 at a desired velocity via motor 210.

The input data are processed by the signal processing block 206 and forwarded to an encoder block 212, which applies an appropriate run length limiting (RLL) encoding to generate a PWM output driver signal. For DVDs, the output of the encoder 212 may be an EFM+ signal with 8/16 encoding. The modulation signal from the encoder operates to selectively modulate a light transducer 214, which selectively exposes the medium 202 in relation thereto as the transducer 214 is radially advanced across the medium via actuator 216. With 8/16 encoding, symbol lengths (pit/land durations) will generally range from a minimum of 3T to a maximum of 14T in length, where T is the channel rate.

In a prerecorded environment, the medium 202 can be realized as a glass master which has a layer of photoresist or other material that reacts to the selective exposure supplied by the transducer 214. The exposed master is thereafter processed as is known in the art to form a series of stampers which are then used in an injection molding or similar process to form a population of nominally identical discs. It will be appreciated that for purposes herein, the term data storage medium will be read broadly to include a finished prerecorded disc, as well as intermediate media used in the formation thereof including glass masters and stampers. In a recordable environment, the medium 202 is a recordable style medium and may have a wiggle pregroove or similar formed therein that is followed by the system 200 in the writing of data to the medium. In such case, a layer of dye or similar may be provided within the medium which, when exposed to the modulated recording light, provides a sequence of marks that operate as pits and lands similar to a prerecorded disc.

It is contemplated that the rotational rate at which the motor 104 in FIG. 1, and motor 210 in FIG. 2, respectively rotate the respective media 102, 202 can be selectively varied depending on the requirements of a given application. For example, the readback system 100 of FIG. 1 may have a maximum readback capability of 16X, meaning that a nominal readback channel rate can be achieved of as much as about 418.56 MHz (or 418.56 Mbytes/sec). The writer system 200 of FIG. 2 may similarly have a maximum write speed capability of 4OX, meaning that a nominal write channel rate of as much as around 1046.4 MHz (or 1.046 Gbytes/sec) can be sustained.

Of course, just because the data are written to the medium 202 by the system 200 at first velocity, it does not mean that the readback system 100 must read the medium 202 at that same velocity. Rather, the respective systems nominally operate to write and read data that, apart from as disclosed herein, have physical characteristics that enable recovery at any suitable speed.

Having said that, it will be recognized that the resulting readback signals can have characteristics that vary in relation to the velocity of the medium during the readback sequence. For example, FIG. 3 provides two different readback signals 300, 302 taken from a selected medium (in this case, the DVD 102 of FIG. 1). The first signal 300 is generally representative of a readback sequence at a nominal IX readback rate, and the second signal 302 is generally representative of the same readback sequence at a nominal 1OX readback rate.

It will be noted that the analog saw-tooth, or eye-pattern characteristics of the respective signals 300, 302 in FIG. 3 are merely exemplary of the types of signals that may be transduced from the medium, and that other types of signals can readily be recovered. Moreover, it will be noted that the 1OX signal 302 has been normalized (stretched) to align with the IX signal 300, for purposes of comparison; as will be appreciated, using a common x-axis time reference the 1OX signal 302 would only occupy 1/lOth of the elapsed time extent of the IX signal 300.

Two observations can be made from FIG. 3 with regard to the readback signals 300, 302. First, with regard to a given readback signal, it will be noted that some variability will usually exist with regard to signal amplitude as compared to symbol length. Generally, longer symbol eye patterns tend to provide greater peak- to-peak amplitudes (Vpp) than shorter symbol eye patterns. For example, a 14T pattern at IX will often provide a greater gain-normalized Vpp, such as around 2 V, whereas a 3T pattern at IX might provide a reduced amplitude range, such as Vpp=0.75V.

Second, it will be noted that the overall signal amplitudes of the 1OX signal 302 are generally reduced as compared to the overall signal amplitudes of the IX signal 300. This may be particularly true for shorter eye patterns, such as denoted at 304 and 306, respectively. There are a number of factors that can influence this response, including the fact that at the higher rotational speeds, there is less elapsed time for the readback system to both emit and recover energy sufficient to detect the various transitions, and this is generally more pronounced with shorter symbol lengths. Accordingly, the 3T pattern of the IX readback curve 300 may be more reliably detected than the same 3T pattern of the 1OX readback curve 302, as generally represented by respective detection levels 308, 310.

The respective relationships between symbol lengths, speed and signal amplitude may be non-linear; that is, the reduction in signal amplitude of shorter symbols (such as 3T symbols) between IX and 1OX speeds may be substantially greater than the reduction in signal amplitude of longer symbols (such as 14T symbols).

FIG. 4 generally illustrates a top-level view of a processing circuit 400 which operates to apply signal reconstruction processing to readback signals such as 300, 302 from FIG. 3 by the readback processor 112 of FIG. 1. Generally, a pattern detection block 402 applies signal processing to the input signal, including the application of thresholding to recover an EFM type readback signal. A demodulation block 404 applies 16/8 demodulation to the recovered sequence, and an error correction block applies suitable error detection and correction to the data prior to output.

The storage media 102, 202 of FIGS. 1-2 are preferably arranged to include one or more speed-sensitive artifacts that enable the media to be authenticated as an authorized copy. A number of different types of artifacts are proposed herein, and can be used singly or in combination. It will be appreciated, however, that other types of artifacts similar to those set forth herein may occur to the skilled artisan in view of the present disclosure, and therefore the following discussion is illustrative and not limiting.

A first type of artifact is generally characterized in FIG. 5 as a symbol-size related artifact. A standard size 3T (or 13) symbol is denoted at 502, and a reduced 3T symbol is denoted at 504. It will be appreciated that the symbols 502, 504 are characterized as pits, but the respective artifacts can be additionally and/or alternatively realized as lands.

The reduced size 3T symbol 504 is selected to be shorter than the standard size 3T symbol 502, as shown. As desired, a corresponding width of the pit denoted at 504 can also be reduced as compared to the standard size of 502, although such is not required.

It is contemplated that the standard size 3T symbols 502 will be preferably used in most places on the medium, and the non-standard size 3T symbols 504 will be placed at selected locations thereon. The shorter length of the reduced size 3T symbols 504 is preferably selected such that error-free, or near error-free, readback is achieved of these symbols by the reconstruction circuit 400 at a lower rotational speed.

At the same time, the shorter length of the symbols 504 is controllably selected to provide an enhanced number of errors during readback at a higher rotational speed. That is, the shorter length symbols 504 will provide signal amplitude responses that tend to be too low to be reliably detected by the thresholding applied by the pattern detection block 402 (FIG. 4) for at least some higher speeds.

Appropriate symbol length adjustments can be readily determined via empirical testing. Individual adjustments in pit and land lengths to implement the respectively adjusted symbols can be carried out, for example, as described in U.S.

Patent No. 6,469,969 assigned to the assignee of the present application. It is noted that such tailoring can be carried out for all symbols on the medium; that is, during initial signal processing prior to the writing of the medium, a first set of adjustments can be established to adjust individual pit and land transitions to provide optimum readback performance, and then selected ones of the transitions can be further subjected to a second set of adjustments to induce the desired speed-sensitive artifacts. Referring again to FIG. 4, it will be appreciated that some number of errors can be "tolerated" in the readback system 400 and corrected by the error correction circuitry 406. Using the current example, a sufficient number and spacing of the reduced size 3T symbols 504 can be preferably added, however, such that at a higher rotational speed, too many errors are encountered that can be fully compensated by the readback circuitry 400 and an error in the readback data is declared.

Thus, a conventional readback system such as 100 in FIG. 1 can readily be used to determine whether a particular medium 102 is an authentic copy. This can be done in a number of ways. In a preferred embodiment, a selected portion of the medium is read at a first speed, such as IX, and then that portion of the medium is re-read at a second speed, such as 10X. In some embodiments, the data will be successfully recovered at the first speed but not at the second speed. The inability of data recovery at the second speed can be used as an indication that the medium 102 is an authentic copy. Multiple readings can be taken, including of areas that have standard sized symbols, in order to calibrate the system. For example, an area known to have standard size symbols can first be read at each of a succession of incrementally higher speeds until a maximum speed is achieved that still enables successful recovery of the standard sized patterns. Identification of this "maximum successful speed" may require successive operation at speeds higher than this speed and at which errors begin to be exhibited. In some embodiments, a table of predetermined speeds can be sequentially applied and the results for each can be recorded to obtain an error profile across the respective speeds. In other embodiments, a single speed can be applied and the results therefor can be used. The system 100 can then access an area known to have controllably adjusted- size symbols and an attempt can be made to read this area at the previously identified speed (or speeds). If errors are consistently identified in this area, then the medium can be adjudged to be an authentic copy. Hence, it will be understood that it is not necessarily required that the speed related artifacts herein be actually read at multiple speeds; rather, at least some embodiments presented herein contemplate that the area containing the speed-sensitive artifacts may only require reading of that area at a single speed. In some embodiments, the same sequence of data symbols (e.g., multiple copies of the same data) is provided in multiple locations on the media, with one or more locations having the speed-sensitive artifacts therein and one or more other locations not having the speed-sensitive artifacts therein. The reading of the data at these respective locations can provide further confirmation during the foregoing calibration and authentication operations that the medium is an authentic copy. While exemplary T3 patterns are shown in FIG. 5, it is not necessarily required that such be at the shorter end of the pattern range. Any symbols, including intermediate symbol lengths (e.g., 5T, 7T, etc.) or the longest symbol lengths (e.g., 14T) can be adjusted in order to induce such speed related artifacts, as desired.

Moreover, the speed-sensitive artifact can be a selective lengthening, rather than a shortening, of the respective symbols.

Similarly, the speed-sensitive artifacts can utilize nominally the same lengths of symbols, but provide other changes in characteristics that tend to induce errors at higher speeds, such as different widths, different shapes of leading and trailing edges, etc. While the speed-sensitive artifacts are preferably selected so as to provide degraded performance at higher speeds, this also is not necessarily required; under some situations it may be desirable to configure the symbols to provide acceptable readback performance at higher speeds, and degraded performance at lower speeds. Both higher and lower speed artifacts can further be utilized on the same medium.

A second exemplary type of speed related artifact is generally set forth by FIG. 6, which provides a radial deviation artifact. Generally, a first track 602, denoted as TRACK N, is shown to be at a substantially constant (or constantly varying) radius with respect to the associated medium. An adjacent track 604, denoted as TRACK N+l, includes a radial deviation zone at 606. A third normal track is shown at 608 and denoted as TRACK N+2.

The radial deviation zone 606 is contemplated as deviating inwardly toward the ID in a direction so as to approach adjacent TRACK N. It will be appreciated that the deviation zone 606 could alternatively, or additionally, deviate toward

TRACK N+2. The rate in change of the radial deviation zone 606 is selected such that the tracking servo system of the readback system 100 (FIG. 1) can successfully follow the path delineated by TRACK N+l at a lower speed, but not at a higher speed. That is, the deviation zone 606 provides an input response to the servo tracking system which cannot be accommodated by the servo response function of the system, so that tracking is temporarily lost at higher speeds.

Some types of media, such as recordable media, provide a frequency modulated wiggle pre-groove to provide state information to the system (such as writer 200, FIG. 2) during the writing of data thereto. Hence, some types of media access systems can accommodate a selected range (both frequency and amplitude) of radial deviation. It is therefore contemplated that the amount and type of radial deviation presented by a deviation zone such as 606 is such that the deviation is greater than that normally obtained in such wiggle pre-groove configurations.

While the radial deviation zone 606 is represented as a symmetrical "bump," other shapes, configurations and trajectories can readily be used as desired, including paths that meet or even cross over other adjacent tracks.

FIGS. 7 and 8 show different types of exemplary focus deviation artifacts. In FIG. 7, a data sequence 700 is formed in an embedded recording layer generally denoted at 702. Light emitting and detection portions of an optical pickup 704 access the recording layer to detect differences in elevation (depth) to distinguish between pits and lands in the recording layer 702. For reference, a standard sized pit is denoted at 706, and a standard sized land is denoted at 708. Generally, the relative depth between the pits and lands 706, 708 is shown by the interval between dashed lines 710 and 712. This interval is a suitable value such as 1/4 of the wavelength QJ 4) of the coherent wavelength of the light from pickup 704. In this way, the pickup 704 can nominally distinguish between the pits and lands due to different levels of reflectivity in the reflected light, since the light reflected from one feature (pit or land) will be about 180 degrees ((λ/2) out of phase as compared to the reflected light from the other feature (land or pit).

The focus related artifacts in FIG. 7 are shown to include a shallow pit 714 and a shallow land 716. The shallow pit 714 has a recessed base surface 718 that deviates from the normal pit depth 710. Similarly, the shallow land 716 has a base surface 720 that deviates from the normal land depth 712. While the respective base surfaces 718 and 720 are shown to fall within the interval between 710 and 712, such is not required. Generally, the deviations provided by the base surfaces 718, 720 are preferably selected such that, at higher speeds, the readback processing circuitry 400 (FIG. 4) cannot reliably detect the deviated pits and lands 714, 716. It is contemplated that the readback system will have an adaptive focus mechanism to enable it to make continuous focus depth adjustments. However, at higher speeds, the response of this focus mechanism may be insufficient to be able to properly focus and detect these respective features.

In FIG. 8, another focus deviation is set forth in an embedded recording layer 802. Particularly, a localized thickness variation zone 804 is presented within the medium, such as by varying various bonding layers within the medium. As with

FIG. 7, the variation of the zone 804 causes the optical pickup (not shown in FIG. 8) to lose focus control at higher speeds.

FIG. 9 provides yet another exemplary speed related artifact generally characterized as intentionally induced media warpage. A first exemplary medium 902 includes a substantially constant amount of warpage across the diameter thereof, whereas a second exemplary medium 904 shows a radially exending warpage zone 906. It will be appreciated that the amount of warpage depicted in FIG. 9 is exaggerated for clarity of illustration. Such warpage can readily be controllably induced during media manufacturing. Generally, the warpage is selected such that as the media 902, 904 is rotated, such as depicted at 906, centrifugal forces will tend to cause the media to flatten. The warpage is preferably selected such that, at higher RPM rates, the media will be substantially flat as depicted in FIG. 9, thereby permitting the readback system to successfully read data therefrom. Conversely, at lower rotational rates, the centrifugal forces will not be sufficient to fully flatten the media, resulting in tracking and/or focus style errors as discussed above.

From FIG. 9 it can be seen that while in some embodiments the speed related artifacts are selected to prevent successful data readback at higher velocities, such is not necessarily required. Rather, FIG. 9 provides examples where the media can be successfully accessed at higher speeds, but not necessarily at lower speeds.

Various focus related deviations such as exemplified by FIGS. 7-9 can be implemented in a variety of ways. Focus deviations can be made by varying the voltage of the modulation signal being fed to a laser beam recorder write transducer to either increase or decrease the exposure and therefore depth of the pits and/or the lands.

Variations in the bonding layer or spacer layer on a two or more layer optical disc can be implemented such as by introducing thickness variations during a stamper creation process, such as during metal deposition, back sanding, machining, or by mechanically deforming a portion of the stamper (e.g., creation of a small, localized dimple, etc.). Another method would be to introduce thickness variations during the bonding process. Variations in thickness can be made at a particular sector, a particular XY location or at a certain radius or radius range. In the case of variations made to a specific radius or radius range, the optical pick-up head would be able to track the target radius at low speeds, but would exhibit failures at higher speeds.

Speed-sensitive artifacts as disclosed herein can be used to determine authenticity in pre-recorded media, blank recordable media and post written recordable media. Authenticity is preferably determined when the media exhibits two or more different read-back results at two or more different read-back speeds or rates. Although the above examples contemplate an artifact that is more easily read at lower speeds and not readable at higher speeds, it is also contemplated that other artifacts could be created which are not readable at lower speeds, but are more readable at higher speeds. An example would be a disc that has high initial warpage, but when spun at higher speeds tends to flatten out and thus become easier for a pick-up head to track as illustrated in FIG. 9.

There are several methods which can be used to create such warpage. One approach would be to introduce thickness variations during the stamper creation process, either during metal deposition or in the back sanding or machining process.

Another approach would be to introduce thickness variations in the mold cavity. One way to introduce these variations would be to have the mirror block and stamper mounted non parallel to each other such that the molded disc exhibits thickness variations due to the non parallel mounting. Yet another way to induce warpage would to create a clamping region portion of the molding cavity which is not in the same plane as the stamper or mirror block. As optical read/write devices often mount the optical disc based on the clamping region and not the data region, discs manufactured in this way would exhibit high vertical deviation when rotated slowly, however normal centrifugal forces will cause the data area to "flatten out" into one plane of rotation at higher speeds. Any number of types of artifacts, and ways to implement the same, will be readily apparent to the skilled artisan in view of the present discussion, so the foregoing are exemplary and not limiting.

FIG. 10 provides a flow chart for a MEDIA AUTHENTICATION routine 1000, generally illustrative of steps carried out in accordance with the foregoing embodiments to authenticate a data storage medium as an authorized copy, such as but not limited to the DVD-9 media 102, 202 discussed above. At step 1002, one or more speed-sensitive artifacts are placed upon a storage medium. This can be carried out as set forth above, and can include a combination of multiple types of artifacts on the same medium. The medium of step 1002 can take any number of forms such as a prerecorded or recordable optical disc, a glass master, a stamper, etc.. Other types of media can be used as well, such as magnetic tape, a magnetic recording disc, etc. This operation is preferably carried out by a writer, such as illustrated in FIG. 2.

At step 1004, the medium is accessed in order to detect the presence of the speed-sensitive artifact(s) thereon. This is preferably carried as discussed above, and may include rotating or otherwise moving the medium relative to a transducer at one or more selected speeds while accessing (or attempting to access) data from the medium.

A determination is made at decision step 1006 whether the speed-sensitive artifacts are present on the medium. This preferably is carried out by obtaining an error response from step 1004, such as the detection of a particular number of errors during the reading step. If so, the medium is authenticated at step 1008 and access is granted to the content stored on remaining portions of the medium. Conversely, if the speed-sensitive artifacts are not found to be present, the flow passes to step 1010 where access is denied.

Preferably, an executable program is stored by a writer (such as 200 in FIG. 2) onto the storage medium in accordance with steps 1004 through 1010 of FIG. 10.

Upon initialization of the medium by a reader system (such as 100 in FIG. 1), a processor (such as 112) will execute the program to command a rotation of the medium at a selected velocity, a reading of the pattern sequence at said selected velocity to obtain an associated error response, and an identification of the storage medium as an authorized copy when the error response indicates the presence of the speed-sensitive artifact in the pattern sequence. The program will further preferably grant access to the storage medium when the presence of the speed-sensitive artifact is detected, and deny access to the storage medium when the presence of the speed- sensitive artifact is not detected.

It will be appreciated that the styles and types of artifacts exemplified herein are generally of the type that will not be transferred from an original copy to an unauthorized copy. Thus, whether a copy is made onto a recordable medium, or a new prerecorded set of unauthorized copies are produced, it will be difficult to detect and provide the same artifacts to the unauthorized copies. This is particularly true if multiple types of artifacts are presented on a medium, and the medium initialization routine accesses different ones of the artifacts each time the medium is accessed. While the media exemplified herein are characterized as optical discs, such is not limiting as any number of different types of media can be utilized as desired.

Moreover, while the media as configured herein can be adapted for use in a specially configured readback system, such as a proprietary gaming system or similar, it will be appreciated that such is not required; rather, the media authentication can be adaptively configured to successfully operate on any number of different types of conventional, commercially available readback systems.

For purposes of the appended claims, the phrase "speed-sensitive artifact" will be understood consistent with the foregoing discussion as an alteration to an otherwise conventional data sequence placed onto a storage medium so that the same artifact produces a first error response, such as a first number of read errors

(including zero read errors) while the storage medium is read at a first speed (velocity) and a different, second error response, such as a different, second number of read errors while the storage medium is read at a second speed (velocity). The speed-sensitive artifact is further configured such that the presence of the artifact is detectable in relation to differences between the first and second error responses, and the presence of the artifact is used to authenticate the medium.

Claims

CLAIMS:

1. A method comprising: placing at least one speed-sensitive artifact in a data sequence on a storage medium configured to provide a first error response when the data sequence is read at a first speed and a second error response different from the first error response when the data sequence is read at a second speed; and using the first and second error responses to authenticate the medium as an authorized copy.

2. The method of claim 1 , wherein the using step comprises: reading the data sequence at the first speed; re-reading the data sequence at the second speed; and authenticating the medium as an authorized copy in relation to differences in the respective first and second error responses.

3. The method of claim 1 , wherein the first error response comprises a first number of read errors, wherein the second error response comprises a second number of read errors, and wherein the using step comprises comparing the first number of read errors to the second number of read errors.

4. The method of claim 1, wherein the using step comprises reading the data sequence at a selected one of the first and second speeds, and authenticating the medium as an authorized copy when a number of read errors detected during the reading step exceeds a predetermined threshold number of read errors.

5. The method of claim 1, wherein the speed-sensitive artifact permits successful transfer of the data sequence at the first speed and prevents successful transfer of the data sequence at the second speed.

6. The method of claim 1, wherein the second speed is at least twice the first speed.

7. The method of claim 1, wherein the speed-sensitive artifact of the placing step comprises a deviation from a nominal pit or land geometry used in remaining portions of the storage medium.

8. The method of claim 1, wherein the speed-sensitive artifact of the placing step comprises a deviation from a nominal circumferential path of a track on the medium.

9. The method of claim 1, wherein the speed-sensitive artifact of the placing step comprises a variation from a nominal depth of a pit or land of the pattern sequence used in remaining portions of the storage medium.

10. The method of claim 1, wherein the placing step comprises inducing a warpage condition into the storage medium during manufacture thereof, wherein at lower rotational velocities the warpage condition is pronounced and at higher rotational velocities the warpage condition is reduced.

11. The method of claim 10, wherein the medium of the placing step comprises an optical disc configured to be selectively rotated at the first and second speeds.

12. In a data storage medium in which data are stored as a pattern sequence and transduced by a read mechanism to provide a readback signal, the improvement characterized as comprising: a speed-sensitive artifact placed at a selected location within said pattern sequence, the speed-sensitive artifact selected to exhibit a first error response while the pattern sequence is accessed when the storage medium is moved adjacent the read mechanism at a first velocity, and to exhibit a different, second error response while the pattern sequence is accessed when the storage medium is moved adjacent the read mechanism at a different second velocity; and programming stored on the medium which, when executed, commands a rotation of the medium at a selected velocity, a reading of the pattern sequence at said selected velocity to obtain an associated error response, and an identification of the storage medium as an authorized copy when the error response indicates the presence of the speed-sensitive artifact in the pattern sequence.

13. The improvement of claim 12, wherein the program further operates to grant access to the storage medium when the presence of the speed-sensitive artifact is detected and to deny access to the storage medium when the presence of the speed-sensitive artifact is not detected.

14. The improvement of claim 12, wherein the selected velocity comprises a selected one of the first or second velocities, wherein the program further operates to command rotation of the medium and reading of the pattern sequence at the remaining one of the first or second velocities, and wherein the program further operates to compare a number of errors detected at the first velocity to a number of errors detected at the second velocity.

15. The improvement of claim 12, wherein the selected velocity comprises a selected one of the first or second velocities, and wherein the programming authenticates the medium as an authorized copy when a number of read errors detected during said reading exceeds a predetermined threshold number of read errors.

16. The improvement of claim 12, wherein the speed-sensitive artifact permits successful transfer of the data sequence at the first speed and prevents successful transfer of the data sequence at the second speed.

17. The improvement of claim 12, wherein the second speed is at least twice the first speed.

18. The improvement of claim 12, wherein the speed-sensitive artifact comprises at least a selected one the following types of artifacts: a deviation from a nominal pit or land geometry used in remaining portions of the storage medium, a deviation from a nominal circumferential path of a track on the medium, a variation from a nominal depth of a pit or land of the pattern sequence used in remaining portions of the storage medium, or a warpage condition induced into the storage medium during manufacture thereof wherein at lower rotational velocities the warpage condition is pronounced and at higher rotational velocities the warpage condition is reduced.

19. The improvement of claim 18, wherein the speed-sensitive artifact comprises a plurality of said following types of defects.

20. The improvement of claim 19, wherein the programming is further configured to access a first one of said following types of defects during a first initialization of the storage medium, and wherein the programming is further configured to access a different, second one of said following types of defects during a subsequent initialization of the storage medium.

21. The improvement of claim 12, wherein the storage medium is characterized as an optical disc.

22. An apparatus comprising a writer system configured to place at least one speed-sensitive artifact into a data sequence on a storage medium, the speed- sensitive artifact configured to produce a first number of read errors when the data sequence is read at a first speed and to produce a different, second number of read errors when the data sequence is read at a second speed, the writer system further placing programming on the storage medium which, when executed, authenticates the medium as an authorized copy in relation to the first and second numbers of read errors.

23. The apparatus of claim 22, wherein the writer system comprises a motor which rotates the storage medium and a write transducer which selectively exposes the rotating storage medium to write said speed-sensitive artifact and said programming.

24. The apparatus of claim 22, wherein the storage medium comprises an optical disc.

25. The apparatus of claim 22, wherein the speed-sensitive artifact comprises at least a selected one the following types of artifacts: a deviation from a nominal pit or land geometry used in remaining portions of the storage medium, a deviation from a nominal circumferential path of a track on the medium, a variation from a nominal depth of a pit or land of the data sequence used in remaining portions of the storage medium, or a warpage condition induced into the storage medium during manufacture thereof wherein at lower rotational velocities the warpage condition is pronounced and at higher rotational velocities the warpage condition is reduced.