Identifier tag to track layers in a multi-layer optical disc

Method and apparatus for tracking layers in a multi-layer optical disc. The disc includes a first layer which stores a first set of user data and a table of contents (TOC) for the disc. A second layer stores a second set of user data and an identifier tag which identifies the second layer as corresponding to the first layer. The identifier tag can comprise a portion of, or a complete copy of the TOC, or can comprise a reference value which, among other things, identifies a revision level of the second layer. Preferably, the first layer is also provided with a reference value. In this way, a database or other mechanism can be used to track the history of the various layers of the disc. Stampers form the respective layers and the ID tags further serve to ensure correspondence thereof in the formation of the disc.

FIELD OF THE INVENTION

The present invention relates generally to the field of optical disc technology and more particularly, but without limitation, to the identification of multiple layers within a multi-layer optical disc.

BACKGROUND

Optical discs are media used to store a wide variety of digitally encoded data. Such discs are usually portable in nature and can be played in a variety of settings (personal computers, car audio players, home theater systems, handheld personal entertainment devices, home gaming systems, etc.).

A typical optical disc comprises a circular disc having one or more recording layers of light reflective material embedded in a refractive substrate. Each recording layer is disposed along a plane substantially normal to an axis about which the disc is rotated and stores data in the form of localized pits and lands along a continuously extending spiral track. A data transducing head uses a laser or similar light source to output a readback signal based on the different reflectivities of the pit and land areas. Decoding circuitry decodes the user data for output by the appropriate playback device.

An optical disc typically has a lead-in area, a program area and then a lead-out area. Table of contents or similar information are typically stored in the lead-in area to allow the readback system to identify the contents of the playback area. Multi-layer discs, popular for certain types of formats such as DVD-9, use multiple embedded, semi-translucent layers that can be accessed by switching the focal length of the readback system.

In a multi-layer disc, the readback system typically moves the transducing head radially across the disc (such as from inner diameter, ID to outer diameter, OD). When the first layer is completed, the readback system switches the focal length of the head and continues reading the next layer in the disc back across the radius of the disc (such as from OD to ID). The first layer has a lead-in area that stores a table of contents identifying the program area contents of all of the layers in the disc. The end of the final layer has a lead out area to indicate playback is complete.

Since the content information for an entire multi-layer disc is presently only stored on the first layer (in the lead-in area), there is generally no effective way to verify the contents of a second layer absent the first layer. This makes individual testing of layers difficult, and also makes it harder to ensure that the correct layers are assembled into the final replicated disc.

SUMMARY OF THE INVENTION

In accordance with preferred embodiments, the present invention is generally directed to tracking layers in a multi-layer optical disc.

In one aspect, a stamper is configured to form pits and lands in a non-first layer in a multi-layer optical disc. The pits and lands define data including an identifier tag. The identifier tag identifies the stamper as corresponding to a second stamper configured to form pits and lands in a first layer of the disc.

Preferably, the pits and lands in the first layer of the disc define data including a table of contents (TOC) for the disc, and the identifier tag comprises at least a portion of the TOC. Alternatively, the identifier tag can comprise a complete copy of the TOC.

In accordance with other preferred embodiments, the identifier tag comprises a reference value that is associated with the contents of the disc. Among other characteristics, the reference value facilitates identification of a revision level of the stamper using, for example, a network accessible database.

In another aspect, a replicated article is provided as formed by the stamper, and a multi-layer optical disc is provided as formed from the replicated article.

In another aspect, a multi-layer optical disc is provided that comprises a first layer which stores a first set of user data and a table of contents (TOC) for the disc. The disc further comprises a second layer aligned adjacent the first layer and which stores a second set of user data and an identifier tag, the identifier tag identifying the second layer as corresponding to the first layer.

In some preferred embodiments, as before the identifier tag comprises at least a portion of, or a complete copy of, the TOC. In other preferred embodiments, the identifier tag is a reference value associated with the contents of the disc and can be used to identify a revision level of the second layer.

In additional preferred embodiments, the first layer also stores a second reference value associated with the contents of the disc, with the reference value of the first layer being the same as, or different from, the reference value of the second layer. When additional layers are included in the disc, a third layer also includes an identifier tag which identifies the third layer as corresponding to the first and second layers.

In yet another aspect, a method includes a step of forming a first layer for a multi-layer optical disc which stores a first set of user data and a table of contents (TOC) for the disc. The method further includes a step of forming a second layer for the disc configured to be aligned adjacent the first layer and which stores a second set of user data and an identifier tag which identifies the second layer as corresponding to the first layer.

The method further preferably comprises a step of attaching the second layer to the first layer. The method further preferably comprises forming a third layer for the disc configured to be aligned adjacent the second layer and which stores a third set of user data and a second identifier tag which identifies the third layer as corresponding to the first and second layers.

The method further preferably comprises using the identifier tag to test the second layer apart from the first layer. The method further preferably comprises using the identifier tag to identify a revision level of the second set of user data.

In this way, a global history of the individual layers can readily be maintained, and errors with regard to the improper joining of layers from different titles, and/or the use of layers of incorrect revision level, can be detected and eliminated.

These and various other features and advantages which characterize the claimed invention will become apparent upon reading the following detailed description and upon reviewing the associated drawings.

DETAILED DESCRIPTION

FIG. 1shows a readback system100used to read back data from an optical disc102. For purposes of the present discussion, the disc102is contemplated as having a multi-layer, digital versatile disc (DVD) compatible format such as DVD-9, although the claimed invention is not so limited.

The readback system100includes a readback processor104which communicates with an input/output (I/O) device106. Depending upon the type of data stored on the disc102(i.e., DVD-ROM, DVD audio, DVD video, etc.), the device106can comprise a personal computer, an optical disc audio or video player, a gaming system, etc.

The readback processor104controls an actuator108, optical pickup (transducing head)110and disc motor112. During a readback operation the readback processor104processes a modulated signal transduced by the head110to provide originally stored data from the disc102to the device106.

FIG. 2provides a generalized representation of a data structure of the disc102. The disc102includes two adjacent data recording layers114,116, denoted as “layer0” and “layer1” respectively. Other numbers and configurations of layers can alternatively be used as desired.

The first layer114(layer0) has a lead-in area118followed by a program area120and a middle area122. The second layer116(layer1) has a middle area124, a program area126and a lead-out area128. As will be recognized, the respective sizes of the various areas shown inFIG. 2in terms of data storage capacity are not represented to scale; rather, the data capacities of the program areas are very large as compared to the lead-in, lead-out and middle areas.

Content information for the disc102is stored in the lead-in area118in the form of a table of contents, TOC. As will be recognized, the TOC identifies the collective contents of the program areas120,126in a standardized manner in terms of title, length, elapsed times, number and locations of chapter divisions, etc.

During a sequential readback operation, the respective layers114,116are read in the direction shown. The head110(FIG. 1) will locate the lead-in area118, access the TOC and initiate recovery of the contents of the program area120on layer0. At the end of the program area120, the head110will adjust focal depth to the appropriate level to read layer1, and continue with the recovery of the contents of the program area126until the lead-out area128is reached, signifying the end of the disc102. The middle areas122,124serve as buffer areas and are typically skipped.

The respective layers114,116are preferably formed using a recording system such as represented at130inFIG. 3. The recording system130, preferably characterized as a laser beam recorder (LBR), includes a signal processing block132which processes input data from a source134. The signal processing block132provides encoded data to a modulation (MOD) circuit136, which in turn outputs a frequency modulated signal to a light emitting transducer138.

The transducer138selectively exposes a thin layer of spun photoresist on a glass master disc140. The disc140is controllably rotated by a motor142and the transducer138is advanced radially across the disc140by an actuator144, both under the control of a control block146. In this way, a selected pattern of exposed and non-exposed photoresist is generated in relation to the input data from the source134.

Subsequent processing steps are carried out on the glass master disc140to create stampers used to form replicated discs. At this point it will be noted that a glass master disc140is formed for each of the layers114,116of the disc102in turn.

As previously mentioned, the manufacture of multi-layer optical discs in a high volume manufacturing environment poses a number of challenges. Conventionally, non-zero layers are not provided with information that readily identifies such layers as belonging with other non-zero and zero layers for a given disc title. Because the program contents on non-zero layers (such as in the program area126) have a starting point that is somewhere in the “middle” of the overall disc contents, it is generally not possible to accurately test a particular non-zero layer and verify that the contents are correct without knowing the TOC information from the associated zero layer, as such information is generally required to ascertain where the non-zero layer data should start and where it should end.

Another problem that has arisen relates to detecting layer mismatches during manufacturing; that is, situations where the zero layer from a first disc title is improperly joined with a non-zero layer from a second disc title. While it may be possible to compare the length of the non-zero layer program area contents to the TOC in the zero layer in order to detect such a mismatch, this approach will only generally tend to work if the non-zero layer program area contents are in fact significantly longer or shorter that what is expected by the TOC.

Thus, non-zero layers with the same amount of data from different titles could be readily attached to a given zero layer, and reference to the length information in the TOC would not enable detection of this error.

Yet another problem relates to the fact that updated versions of individual layers may be formed from time to time during the course of the production life of a given disc title. Such updated versions may be generated to provide altered program area contents for a given layer (e.g., the addition of additional features, the correction of noted errors, etc.). Such updated versions may also relate to a remastering of a particular layer to form a new generation of stampers, etc. At present, there is generally no effective way to track whether a given set of layers belongs together, and to readily identify the status (including revision level) of the various individual layers in a given disc.

Accordingly, preferred embodiments of the present invention are generally directed to the incorporation of identifier tags into the various layers of a multi-layer disc. The manner in which this approach advantageously solves these and various other problems of the prior art will now be discussed.

FIG. 4provides a generalized representation of relevant portions of the second layer116(layer1) ofFIG. 2. The layer is more generally referred to as layer N>0 inFIG. 4, since the format shown can apply to any non-zero layer (i.e., a third layer, a fourth layer, etc.) and is not just limited to the second layer in a disc.

Preferably, the middle area124inFIG. 4is provided with a field150which stores an identifier tag assigned to the layer. The identifier (ID) tag is expressed within the layer as a sequence of pits and lands that, when decoded, provides a multi-bit representation of information that relates to the contents of the layer116.

The ID tag indicates that the layer1corresponds to (i.e., belongs with) layer0. While the ID tag field150is conveniently located in and is accessible from the middle area124, other locations can readily be used including the program area126or the lead-out area128(FIG. 2). It is important to note that the ID tag does not merely constitute the program area contents per se, but rather serves as a separate identifier thereof.

In one preferred approach, the ID tag comprises at least a portion of the TOC from the first layer114, such as relating to that portion of the title contents resident in the program area126on the layer116. In this way, this information can be used during stand-alone testing of the layer116without the need to access the TOC from the associated layer114. Alternatively, a copy of the complete TOC from the first layer114can be easily stored in the ID tag field150.

In another approach, the ID tag additionally, or alternatively, includes a particular reference value that is assigned to the layer116. Generally, the reference value is a unique identifier (such as an encoded or nonencoded alphanumeric string) that, through access to a database, enables identification of the title, contents, revision level, mastering date, and other relevant history characteristics of the layer116.

Preferably, all of the layers of the disc102are provided with ID tags, including the first layer114(layer0).FIG. 5shows the first layer114in this embodiment to include an ID tag field152in the middle area122. As before, the ID tag field152can alternatively be placed elsewhere within the first layer114, such as in the lead-in area118or the program area120. It is noted that the ID tag field152is provided in addition to the aforementioned TOC in a TOC field154in the lead-in area118.

The ID tag in field152on layer0can be the same as, or different from, the ID tag in field150on layer1. In this way, accessing the ID tags can readily allow a determination that the particular layers114,116belong together.

The ID tags in the fields150,152are formed in a straightforward manner, as will now be discussed.FIG. 6provides a simplified representation of a first stamper156for layer1. The first stamper156, more generally referred to inFIG. 6as stamper N>0 to represent a non-zero layer stamper, is formed using the system130ofFIG. 3.

More particularly, with reference again toFIG. 3, input data from source134relating to the data to be stored on layer1, including the ID tag, are utilized to cut a glass master140. Appropriate metallization and stamper growing processes are thereafter carried out in a substantially conventional manner to provide the first stamper156.

The first stamper156thus includes a sequence of pits and lands that embody the ID tag. The ID tag, as well as remaining data stored on the stamper, can readily be read using suitable stamper reading equipment. The pit and land pattern on the stamper is transferred to a layer1substrate158, as shown inFIG. 6, during manufacturing using a suitable injection molding or similar pressing process. As a result, the layer1substrate158(which includes the layer1data along a boundary thereof), also includes the ID tag as expressed as a sequence of pits and lands as shown.

Similarly,FIG. 7shows a second stamper160, also referred to as stamper0, which is likewise formed using the system130ofFIG. 3. As before, the second stamper160preferably includes a readable pit and land sequence that includes the TOC and the ID tag for layer0, which are also transferred to a layer0substrate162during manufacturing. The layer0substrate162includes the layer0data along a boundary thereof, as shown.

At this point it will be noted that the ID tag from the pits and lands on the first stamper156advantageously enables the first stamper156to be identified as corresponding to the second stamper158, which can be very useful during manufacturing processing. For example, prior to a pressing operation wherein multiple substrates are run, a quick verification of the ID tag on the first stamper156(or the second stamper158) can confirm that the correct stamper is being used to provide the desired title, contents, revision level, etc. for the associated layers about to be formed.

Likewise, the provision of the ID tags on the substrates158,162facilitate the testing and verification of these substrates individually (separately) prior to assembly into the disc102. Advantageously, the ID tags are also accessible after the substrates have been incorporated into the disc102, as depicted byFIG. 8.

FIG. 8provides a simplified, exaggerated representation of the disc102as formed by the joining together of the substrates158,162ofFIGS. 6 and 7using an intermediary layer of epoxy164.FIG. 8is useful in illustrating how that, during further processing of the completed disc102, the TOC, the ID tag for layer0(represented inFIG. 8as ID tag0), and the ID tag for layer1(ID tag1) can be accessed by a reader system such as the system100inFIG. 1. These various values can be immediately verified as constituting an appropriate set for the given disc title, thereby ensuring the disc has been properly assembled without the need to access the program area contents.

FIG. 9provides a functional block representation of a manufacturing and testing environment200used to form a population of discs such as nominally identical to the assembled disc102ofFIG. 8. A generalized process flow is represented by a number of operational stations.

These operational stations include a stamper generation block202in which stampers (such as156,160) are formed for a given title, a layer fabrication block204in which substrates, or articles (such as158,162) for the individual layers are fabricated from the stampers using a pressing operation, and a layer testing block206which individually tests the substrates for manufacturing defects.

The substrates are assembled into completed discs at a disc assembly block208, and the assembled discs are tested at a disc testing block210. It will be recognized that the various blocks202-210inFIG. 9may be carried out in a single facility, or may be spread out among a number of different facilities, locations and/or entities.

Regardless, it is contemplated that each of the various blocks202-210communicate over a computer network (represented by communication path212) with a server214that maintains a database216. The database216preferably functions as described above to assign and track the ID tags for the various individual layers. Preferably, the database maintains data history records for each layer, so that each of the stations202-210can both provide data from the database216when a particular ID tag is accessed, as well as can update the database216at the conclusion of a particular operation to update the history of the layer.

It will now be appreciated that the presently preferred embodiments discussed herein provide advantages over the prior art. The ID tags presented herein can be readily incorporated into any number of different disc formats in a straightforward and inexpensive manner.

The ID tags provide global history capabilities in that the ID tags are preferably accessible at the stamper level, the individual layer (substrate) level, and at the completed disc level, allowing a full history associated with a given disc title to be easily determined, even years after the manufacture of the disc.

The ID tags provide significantly improved manufacturing processing in that the correspondence of particular layers within a given title set can be immediately and easily established. The layers can also be independently and separately tested and processed in an efficient manner.

In view of the foregoing, the present invention (as embodied herein and as claimed below) is generally directed to tracking layers in a multi-layer optical disc.

In one aspect, a stamper (such as156) is configured to form pits and lands in a non-first layer (such as116) in a multi-layer optical disc (such as102). The pits and lands define data including an identifier tag (such as stored in field150) which identifies the stamper as corresponding to a second stamper (such as160) configured to form pits and lands in a first layer (such as114) of the disc.

Preferably, the pits and lands in the first layer of the disc define data including a table of contents (TOC) for said disc (such as stored in field154), and wherein the identifier tag comprises at least a portion of the TOC. Alternatively, the identifier tag can comprise a complete copy of the TOC.

In accordance with other preferred embodiments, the identifier tag comprises a reference value that is associated with the contents of the disc, and which facilitates identification of a revision level of the stamper.

In another aspect, a replicated article (such as158) is provided as formed by the stamper, and a multi-layer optical disc (such as102) is formed from the replicated article.

In another aspect, a multi-layer optical disc is provided that comprises a first layer (such as114) which stores a first set of user data (such as at120) and a table of contents (TOC) for the disc (such as at154). The disc further comprises a second layer (such as116) aligned adjacent the first layer which stores a second set of user data (such as at126) and an identifier tag (such as at150) which identifies the second layer as corresponding to the first layer.

In some preferred embodiments, the identifier tag comprises at least a portion of, or a complete copy of, the TOC. In other preferred embodiments, the identifier tag is a reference value associated with the contents of the disc and which can be used to identify a revision level of the second layer.

In additional preferred embodiments, the first layer also stores a second reference value associated with the contents of the disc, with the reference value of the first layer being the same as, or different from, the reference value of the second layer. When additional layers are included in the disc, a third layer (such as layer N>0 inFIG. 3) also includes an identifier tag which identifies the third layer as corresponding to the first and second layers.

In yet another aspect, a method includes a step of forming a first layer (such as114) for a multi-layer optical disc (such as102) which stores a first set of user data (such as at120) and a table of contents (TOC) for the disc (such as at154). The method further includes a step of forming a second layer (such as116) for the disc configured to be aligned adjacent the first layer and which stores a second set of user data (such as at126) and an identifier tag (such as at150) which identifies the second layer as corresponding to the first layer.

The method further preferably comprises a step of attaching the second layer to the first layer (as depicted inFIG. 8). The method further preferably comprises forming a third layer for the disc configured to be aligned adjacent the second layer and which stores a third set of user data and a second identifier tag which identifies the third layer as corresponding to the first and second layers.

The method further preferably comprises using the identifier tag to test the second layer apart from the first layer (such as at block206). The method further preferably comprises using the identifier tag to identify a revision level of the second set of user data (such as at steps202-210).

For purposes of the appended claims, the term “corresponding to” will be defined consistent with the foregoing discussion to describe the correct association of the contents of the recited layer/stamper with the contents of the other recited layer/stamper, and not merely identifying, for example, a focal depth or other characteristic of the respective stamper/layer.