Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Light polarizing article or holographic article
Reexamination Certificate
2000-09-20
2003-12-02
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Light polarizing article or holographic article
C264S002500, C425S810000
Reexamination Certificate
active
06656392
ABSTRACT:
BACKGROUND INFORMATION
Optical disks for storing information, e.g., in binary form, are provided with a plurality of optical “features”, i.e., marks and/or shapes which can be optically detected and used, e.g. for read and/or write operations. Features may represent content information, such as information which can be ultimately provided to the user (regardless of whether the user is a human, a computer or other device), but may also include other information such as information used for purposes such as focus or tracking (or other servo functions), sector navigation or addressing (or other access operations), testing purposes, data security purposes, quality control purposes and any of a number of other purposes, as will be understood by those of skill in the art after understanding the present disclosure.
Disks with features thereon can be formed using any of a number of processes. One operable process falls generally in the category of injection molding. In injection molding (of any of a number of objects, including optical disks), a mold cavity having a size and shape corresponding to (e.g. after thermal shrinking) the size and shape of a final object, is injected with heated (fluid) thermoplastic material. After cooling e.g. to the glass transition temperature, the mold is opened and the object is removed.
In some situations, features on an optical disk may represent binary digits (bits), or groups of bits. In most situations, features can be considered to be either in the form of a protrusion or in the form of a depression. The difference can be most readily described in the context of a “stamper” (i.e. a device used in a molding device for forming a disk, the stamper having a generally planar surface and a plurality of protrusions extending from the planar surface into the mold cavity or depressions receding from the planar surface away from the mold cavity. Protrusions on a stamper provide depressions in the molded disk and depressions in the stamper provide protrusions in the molded disk. Features can be formed on one surface of the disk, or on both surfaces (in which case, two opposed stampers are used in the molding device. Although descriptions of a stamper-formed disk are believed useful in describing the difference between protrusion disk features and depression disk features, the present inventions, described below, is not limited to use in disks which are molded, but can be used in disks where features are formed in other fashions (such as by ablation, injection-compression, etching, or other methods).
In typical applications, bits or bit groups are represented by bumps (small protrusions) or pits, (small depressions). Typically, such bumps or pits are positioned along one or more spiral or circular tracks on at least one surface or layer of the disk. Disks may also contain features which do not directly represent data bits. For example, there may be features such as grooves or lands, typically in an extended circular or spiral pattern, e.g. for defining one or more tracks. In some cases, the tracks may have small-scale periodic or other deviations from a circular or spiral pattern (e.g. “wobbled” grooves), such as for tracking and/or timing purposes.
When optical read/write devices include some type of detection of reflectivity (or some other parameter related to reflectivity) as the read/write beam is successively in alignment with lands, bumps, pits, grooves, and the like, typically, reflectivity changes detectably as the beam crosses a leading or trailing edge of a feature. Accordingly, if, e.g., a read/write beam is maintained aligned with a track which bears pits or bumps, a reflectivity transition will ideally be detected near the (track-wise) leading edge and trailing edge of each bump or pit along the track and accordingly, the difference in timing between leading edge and trailing edge transitions in reflectivity are indicative of the (track-wise) length of the bump or pit. In this way, the presence and/or length of a bump or pit can be detected and converted to bits or bit patterns (according to any of a number of encoding schemes).
A number of aspects of the size, shape, distribution or arrangement of features on the disk (and/or of electrical, optical or other parameters associated with their detection) are of significance in the read/write operations. Among these are the as-detected track-wise or radial size of the features, the z-dimension size of the features, the radial spacing of features, the track-wise spacing of features and/or the DC offset of detection signals, particularly for high frequency (short-length) marks compared to relatively longer marks. The design of encoding schemes and design of the read/write device (including size and shape of the medium, wavelength of the read/write beam and other factors) place constraints on the size and/or shape of features which are desired and/or operable in an optical disk data storage system.
Many previous disk configurations provide a relatively thick, substantially transparent, plastic or other substrate through which the read/write beam passes, before reaching a data layer (i.e., a layer which has readable or writeable features formed or formable thereon). As used herein, “read/write” refers to beams, devices or processes which involve only reading, only writing, or both. In previous typical optical disk configurations, the effective thickness of such substrate (or other relatively thick covering layer) was sufficiently large that the surface of the interface which does not contact the data layer (e.g. the air-substrate interface) was substantially outside the depth-of-field of the optical system used to read or write data, and accordingly, at least some important optical parameters were substantially unaffected (within tolerances required for successful operation of read/write operations) by the presence of the layer (i.e., by the requirement that the read/write beam traverse the substrate before reaching the data layer).
However, it is believed certain limitations on performance arise from the provision of a relatively thick substrate or similar layer. Accordingly, it would be useful to provide a system, method and apparatus which can achieve desired as-detected feature sizes and/or shapes without being limited to relatively thick substrates (or other layers through which the read/write beam must pass before reaching the data layer) for the read/write medium.
SUMMARY OF THE INVENTION
The present invention includes a recognition of the existence, nature and/or source of certain problems, including as described herein.
According to one aspect of the present invention, it is recognized that, in at least some situations, providing a relatively thin film over some or all of an optical disk data layer can affect items such as the “as-detected” size or shape of bumps or pits or other features (e.g., compared to the actual physical size of the feature, e.g. as molded) and that, accordingly, it can be advantageous to correct for and/or account for such effects. As used herein, “as-detected” size, spacing or magnitude refers to whatever feature size, spacing or magnitude is detected by (or indicated by or derivable from electrical or digital signals indicative of beam reflectivity or other feature-indicative parameters) an optical disk read/write device (e.g. based on time difference between a beam crossing a leading feature edge and a trailing feature edge, including as described below). In one embodiment, the effect of a thin film is corrected-for by forming features which have an actual, physical, size different from the desired as-detected feature size, e.g., so that after providing the thin film, the as-detected size of the feature (including effects caused by the presence or thickness of the film) is equal to the desired as-detected feature size. The desired as-detected feature size may be the size for any of a number of different features (including bumps, pits, grooves, lands and the like), may be sizes or shapes in any of a number of different dimensions or spacings (including, e.g., track-w
Blankenbeckler David L.
Medower Brian S.
DPHI Acquisitions, Inc.
MacPherson Kwok & Chen & Heid LLP
Vargot Mathieu D.
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