Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
1998-04-20
2001-11-27
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064200, C428S064400, C428S064800, C428S447000, C428S913000, C430S270140, C430S495100, C430S945000, C369S283000, C369S288000
Reexamination Certificate
active
06322868
ABSTRACT:
This invention relates to the enhancement of performance of optical storage media by applying a thin layer coating containing liquid mixtures of polymers and dyes in organic solvents on the surface of transparent plastic separating it from the recording layer.
BACKGROUND OF THE INVENTION
Field of Invention: Fundamentals of the Compact Disc Optical Storage Technology—a Brief Summary
Optical information storage media such as CDs rely on high accuracy writing and readout of the encoded information by the optical devices (optical pick-ups) in dedicated apparatuses such as CD-ROM drives, CD and DVD recorders and players, etc. Information in such storage media can be encoded by a variety of physical and chemical means which change the structure of the information layer. The most widely used format of digital encoding is physical alteration of the data (information) layer expressed in the form of precisely defined pits and lands, waves, bubbles, etc. The accuracy of the writing and readout of the encoded information depends upon fidelity of the laser optics device for recording and playback as well as upon optical characteristics of the transparent layer of plastic (usually polycarbonate) of the CD/DVD.
While sophisticated error correction algorithms, e.g., Cross Interleave Reed Solomon code—CIRC, are used to compensate successfully for the inevitable random and spike errors during optical storage media readout, significant variables exist in the ability of CD players and CD-ROM drives to accurately reproduce all of the encoded information. Variations in the quality and light transmitting characteristic of the transparent polycarbonate layer of the optical storage media also contribute to such inaccuracies.
The optical characteristics of the transparent polycarbonate layer are critical also during the recording process on recordable and re-writeable CD-R/CD-RW/DVD for the optimization of the geometry of the physical traces of the laser burning action on the recordable information layers in such recordable media.
In some cases, variations in the optical disc manufacturing process, the efficiency of error correction algorithums used as well as in optical and mechanical properties of the readout devices introduce noticeable errors in the readout. For reasons well understood by those versed in the art description of which is beyond the coverage of this submission, low amplitude signals as well as those of high frequency and short duration are particularly prone to reproduction distortions due to the less than optimal error correction of such encoded sounds during readout (J Halliday, 1996).
Likewise, during recording on optical discs in appropriate recorders, variation in or the presence of noise in the laser beam characteristics will result in distortion of timing and the pit geometry to a relatively greater extent affecting the smaller pits rather than longer pits (J Halliday, 1996). Consequently, the information content carried in the smaller pits (more abundant in encoded high frequency audio signals) will be disproportionately affected during playback (J Halliday, 1996) . On the other hand, strong signals of high amplitude and relatively longer duration are less prone to be distorted (see for example: Pohlmann, 1995).
In the case of audio optical storage media (eg CDs), such deficiencies are perceived as frequency distortions, audible imperfections of sound resulting in apparent loss of the encoded information. Various causes related to the laser light transmission process and reflection of the beams from the data layer of the optical storage media via the transparent (polycarbonate) layer of the optical storage media may account for this deficiency.
Among such causes can be, but not limited to, the unwanted light scattering, diffraction and reduced reflection from the data layer, reflection from an interfering object, media and surfaces not intended to produce these optical aberrations.
The Role of Jitter in Signal Deterioration
The principle cause of audible imperfections is jitter. Essentially there are three main causes of jitter:
First, imperfect geometry of the recorded pits themselves. “Anything which causes unwanted variations in the sizes of the pits will come out as jitter. One thing that can be significant is laser noise; that is, high-frequency variations in the power of the recording spot. Not surprisingly, if the power varies, the pits also vary in width and length, so when the CD is played the apparent pit lengths vary” (J Halliday, 1996).
The second “source of jitter is the influence of other pits nearby in the same track. The readout spot is broad enough that when the center of the spot reaches the beginning of a short pit, the end of the pit lies within the fringes of the spot. So the apparent position of the one pit end is slightly dependent on where the other end is. The same applies to short lands. This is called inter-symbol interference. The jitter which arises from this is not truly random, but is associated with the pattern of recorded pit and land lengths” (J Halliday, 1996).
“Inter-symbol interference is worse at low recording velocities, because the pits are shorter and closer together. And it is the cause of “deviation” of the pit lengths”. . . . “If the shortest pits appear too short on playback, it is only because most of them are next to lands which are longer” (J Halliday, 1996).
The “third source of jitter is the crosstalk between pits in adjacent tracks, because the readout spot does not fall wholly on one track. It is a largely random contribution. It is worse at lower recorded velocities, because the highest frequency components of the readout signal in the wanted track, with which the crosstalk is competing, are weaker” (italics and emphasis are ours) (J Halliday, 1996).
In order to reduce the undesirable effects of jitter one can give “a gentle boost of the higher frequencies (so it relatively strengthens the signals from the shorter pits and lands), and to some extent it has the effect of correcting for the effects of the optical resolution limitations which cause inter-symbol interference and crosstalk. The deviation of the shorter pit lengths is likewise reduced” (italics and emphasis are ours) (J Halliday, 1996).
These timing aberrations result in unwanted digital noise and deterioration of information retrieval from CDs/LDs/CD-Rs/CD-Rs/CD-RWs/DVDs particularly demonstrable in transients.
The accuracy of readout depends among other things also upon on adequate reflection (and in part resulting cancellation) of the diode laser beam from the transition points of the pits and lands of submicron dimensions in the metallized data layer. The minimum degree of expected reflectance beam is 70%. Reflectance of the recordable and re-writeable optic media (CD-Rs, CD-RW) is even lower. It is obvious, therefore, that improvement of the readout would occur if the data layer would have high reflectance while the exterior polycarbonate surface of the optical storage media does not contribute to light scattering and reflectance.
BACKGROUND ART
Numerous reports and inventions are known related to coating processes in the optical storage media field. Our search of the patent literature as well as of published reports in scientific and technical fields related to optical storage media, laser beam treatment and/or coating processes revealed no evidence of either existing or claimed surface coating technology, or compositions similar to or distinct from those described in the present invention that are specifically intended to, designed for or claim to achieve enhancement of efficiency of recording on and readout of encoded information from optical storage media as a result of surface coating such as described in the present invention.
All of these describe technologies, uses and/or compositions either
a) relate to application of complex polymer-dye containing coating layers to serve as substrates for encoding digital information in these layers the latter being an integral part of the physical structure of the optical storage media in the process of its manufa
Bernstam Victor A.
Bernstam Victor A.
Evans Elizabeth
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