US 20060120231 A1
During manufacturing of optical disks, mastering equipment inserts marks (“high frequency wobble marks” or “HFWMs”) into the wobble of the groove on optical disks to store data. The presence of a HFWM at a zero crossing of the wobble indicates an active bit and the absence of the HFWM indicates an inactive bit. The zero crossing is, for example, a negative zero crossing. A matched filter is used to detect the shape of the HFWMs. If a HFWM is detected during a wobble cycle, an active bit is saved in a register or a memory. If a HFWM is not detected during a wobble cycle, an inactive bit is saved in a register or a memory. The active and inactive bits may be coded bits that must be decoded to data bits. The data bits include information such as a synchronization mark, a sector identification data, and an error detection code.
1. A method of storing data on an optical disk, comprising:
creating a spiral groove with a sinusoidal deviation from a centerline of the spiral groove on the optical disk, the sinusoidal deviation having a first frequency; and
creating sinusoidal marks in zero crossings of the spiral groove, the sinusoidal marks having a second frequency.
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receiving data bits;
encoding data bits to code bits according to an encoding scheme; and
generating sinusoidal marks in wobble cycles to represent code bits.
9. The method of
10. A method for reading information on an optical disk, comprising:
detecting zero crossings of a wobble on the optical disk;
detecting sinusoidal marks in the wobble;
outputting an inactive bit upon detecting a wobble cycle and not the sinusoidal mark; and
outputting an active bit upon detecting a sinusoidal mark.
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17. A method for reading information on an optical disk, comprising:
determining a wobble frequency of a wobble;
detecting sinusoidal marks in the wobble according to the wobble frequency;
outputting an active bit upon detecting the sinusoidal mark; and
outputting an inactive bit when the sinusoidal mark is not detected.
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This application is a Divisional Application of U.S. patent application Ser. No. 09/542,681, filed Apr. 3, 2000. The contents of this application is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a method to store data on writeable optical disks, and more particularly to the use of marks in the wobble of the groove to store data.
2. Description of Related Art
To determine the linear velocity of the tracks, the tracks in the writable area contain a deviation from the averaged centerline of the groove called “wobble”.
Writable optical disks must have a reliable method for reading radial and rotational positions of the tracks so that optical drives can read from and write to the appropriate locations in the tracks. Radial and rotational information may be communicated through prewritten data in the tracks called pre-embossed headers. In this addressing scheme, the mastering equipment creates the optical disks with radial and rotational information written in the groove during the manufacturing of the optical disks. This addressing scheme displaces some storage area that can be otherwise used to store user data in order to store radial and rotational information. For further details, see for example Standard ECMA-272 from ECMA located at 114 Rue du Rhône-CH-1204 Geneva Switzerland (“ECMA”), which is hereby incorporated by reference.
Radial and rotational information may also be communicated by modulating the frequency of the wobble. The wobble frequency is modulated between a first frequency and a second frequency to communicate an active or inactive bit (e.g., a “1” or a “0” bit). This addressing scheme is inefficient because multiple wobble cycles are required to convey an active or inactive bit. As
Radial and rotational information may further be communicated through a series of pits (“land pre-pits”) on the land areas between the tracks. Land pre-pits create cross talk into the data because optical drives detect the land pre-pits in the land areas between the tracks. Closely aligned land pre-pits in adjacent tracks also create cancellation problems as their presence cancels their detection by optical drives. Land pre-pits further require a 2-beam mastering system that can generate the groove and the land pre-pits simultaneously during the mastering of the optical disks. For further details, see for example Standard ECMA-279 from ECMA, which is hereby incorporated by reference.
A master optical disk is formed by coating a glass substrate with a photoresist, exposing the photoresist to a laser beam recorder, developing the photoresist, removing the photoresist, and coating the remaining material with a thin seed-layer of metal to form the master optical disk. These steps are known as “mastering”. A stamper is made by electroplating nickel onto the master and removing the nickel from the master to form the stamper. These steps are known as “electroforming”. Optical disks are produced from the stamper by placing the stamper in a mold cavity of an injection molding press and injecting molten plastic into the mold. The resulting molded disks have an imprint of the stamper. These steps are known as “molding”. The molded disks are then coated with a variety of thin films (e.g., reflective layers, active layers, overcoats) depending on their type. The molded disks can be coated by a variety of methods, such as sputtering, spin coating, and chemical vapor deposition (CVD). Manufacturers of optical disks include Ritek of Taiwan, Sony of Japan, Matsushita of Japan, and Imation of Oakdale, Minn.
Marks (“high frequency wobble marks” or “HFWMs”) in the wobble of the groove on an optical disk are used to store data. The presence of a HFWM at a negative zero crossing of the wobble indicates an active bit while the absence of a HFWM at a negative zero crossing of the wobble indicates an inactive bit. Alternatively, the presence of a HFWM at a positive zero crossing of the wobble indicates an active bit while the absence of a HFWM at a positive zero crossing of the wobble indicates an inactive bit. A matched filter outputs an active signal to a decoder logic when the matched filter detects the shape of a HFWM. The decoder logic records an active bit when it receives an active signal from the matched filter. If the logic device does not receive an active signal from the matched filter within a wobble cycle, the logic device records an inactive bit. The stored bits include information such as a synchronization mark used for timing, physical sector information including a physical sector address, and an error correction code for correcting misread of the physical sector information.
Other aspects and advantages of the present invention will become apparent from the following detailed description and accompanying drawings.
Use of the same reference symbols in different drawings indicates similar or identical items.
In accordance with one aspect of the invention, the presence of a mark in a wobble cycle (“high frequency wobble mark” or “HFWM”) indicates an active bit (e.g., a “1” bit”) and the absence of a HFWM indicates an inactive bit (e.g., a “0” bit). The active and inactive bits (“HFWM bits”) are decoded to generate data bits. During the manufacturing of an optical disk, a conventional mastering equipment inserts the HFWMs in the wobble of the tracks to save data such a synchronization mark, physical sector information, and an error correction code. The conventional mastering equipment can make a conventional disk stamper from the above-described optical disk and use the conventional disk stamper to make optical disks in large quantity. The optical disk includes, for example, a small optical disk 32 mm in diameter. Optical drives read the synchronization mark and the physical sector information from optical disks to determine the appropriate sectors for read and write operations. Optical drives read the error correction code to detect and correct errors from the reading of the physical sector information.
In one embodiment illustrated in
In one implementation illustrated in
In another implementation, the mastering equipment inserts HFWMs at points on the optical disk where the wobble would cross the centerline of the tracks from a region closer to the outer diameter to a region closer to the inner diameter (“positive zero crossings”). In this implementation, the absence of HFWMs at positive zero crossings indicate inactive HFWM bits. In this implementation, optical drives detect the negative zero crossings of the wobble to determine the wobble cycles, wobble frequencies, and the linear velocities of the tracks.
The HFWMs may have a frequency, for example, three to five times the frequency of the wobble. It is preferred to choose a frequency that is far from the frequencies of the data so there is less cross talk between HFWM detection and data detection. The HFWMs cannot have the same frequency as the wobble because optical drives will not be able to detect the zero crossings of the wobble to determine the wobble cycles, the wobble frequencies, and the linear velocities of the tracks. The HFWMs cannot have a frequency that is too large because the mastering equipment may not have the precision to generate the shape of such HFWMs. The frequency limit of the mastering equipment is, for example, 106 Hz. Furthermore, optical drives may not have the precision to detect such HFWMs.
In one implementation, each HFWM is in phase with the HFWMs in adjacent tracks. Since the amplitude of the HFWMs is no greater than the amplitude of the wobble, the cross talk between HFWMs in adjacent tracks is no greater than the cross talk between the wobbles of the tracks. Using HFWMs that are in phase allows simpler manufacturing processes as compared to using marks that are not in phase with adjacent marks.
A direct current coupled amplifier 30 adds currents Ia and Ib and outputs current I1. A direct current coupled amplifier 31 adds the currents Ic and Id and outputs current I2. A direct current coupled amplifier 28 adds currents I1 and I2 and outputs a current I3, which represents the data that is stored on a track. A direct current coupled amplifier 29 subtracts current I2 from current I1 and outputs a current I4, which represents the wobble of the track. The output of direct current coupled amplifier 29 is coupled to an analog-to-digital converter 41. Analog-to-digital converter 41 converts the amplitude of Current I4 to discrete values at a specified interval, thereby creating a stream of digital values. Analog-to-digital converter 41 passes these values to a matched filter 32, a wobble detector 34, and a synchronization detector 40.
Matched filter 32 processes the stream of digital values to look for a HFWM mark. When matched filter 32 finds a HFWM mark, matched filter 32 outputs an active signal (e.g., a pulse) to a logic 33 (described later) for conversion to a HFWM bit. Matched filter 32 is known to one skilled in the art and is for example described in “Digital and Analog Communication Systems” by Leon W. Couch II, 1990, p. 497 to 508.
Wobble detector 34 processes the stream of digital values to extract the wobble frequency. Wobble detector 34 phase locks to the wobble frequency and generates a square wave clock signal. Wobble detector 34 passes this clock signal to logic 33, which uses the clock signal and the signals from matched filter 32 to extract the HFWM bits (described later). A decoder 43 also uses this clock signal to divide the HFWM bits into frames of encoded bits that decoder 43 decodes to data bits according to the coding scheme described below in reference to Tables 1 and 2.
Synchronization detector 40 processes the input digital stream to look for the synchronization pattern that is encoded at the start of each information field (described later). When synchronization detector 40 finds the synchronization pattern, it outputs an active signal (e.g., a pulse) to decoder 43, indicating to decoder 43 to start decoding the HFWM bits to data bits, build the resulting data bits into data bytes 42, and store data bytes 42 in a memory 35 for later use by a system microprocessor.
D flip-flop 45 also has a reset input terminal 49 coupled to the wobble clock signal from wobble detector 34, which is delayed by a buffer 54. Thus, a delayed active wobble clock signal resets D flip-flop 45. Once reset, D flip-flop 45 outputs an inactive signal (e.g., a “0”) until it receives another active signal at its clock input terminal 48 from matched filter 32.
Output line 47 of D flip-flop 45 is coupled to a data input terminal 51 of a D flip-flop 50. On receipt of an active wobble clock signal from wobble detector 34 on clock input terminal 53, D flip-flop 50 outputs the data it receives on terminal 51 from D flip-flop 45 to an output line 52 to decoder 43. Decoder 43 decodes the data it receives from D flip-flop 50 to data bits.
Each time matched filter 32 detects a HFWM mark in the wobble, matched filter 32 outputs an active signal. For example in cycle 2, matched filter 32 outputs an active signal 57 when it detects HFWM 56. Each time logic 33 receives an active wobble clock signal, logic 33 outputs an active signal if it has received an active signal from matched filter 32 in the last wobble cycle. For example in cycle 2, D flip-flop 45 of logic 33 (
The system microprocessor that controls optical drive 20 reads data bytes 42 in memory 35 to read physical sector information 37. The system microprocessor uses the detection of synchronization mark 36 and the read of physical sector information 37 to read from and write to the appropriate sectors on optical disk 26. The system microprocessor uses the error correction code to detect and correct errors from the read of the physical sector address. Alternatively, a hardware instead of the system microprocessor can be used to detect and correct errors in physical sector information 37.
In one implementation, a data bit is encoded in two consecutive HFWM bits (e.g., a 2-bit frame of HFWM bits) in accordance with Table 1.
In another implementation, mastering equipment uses an encoding scheme to change each 4 data bits to 15 code bits (e.g., a 15 bit frame of HFWM bits) where the 15 code bits are selected from a maximum length binary sequence (MLBS) generated from a four bit primary polynomial of “1001”. MLBS is known to one skilled in the art and is for example described in “Error-Correcting Codes” by Peterson et al., 1991, p. 222 to 223. By using 15 code bits selected from a MLBS, the chances of reading error are reduced as the 15 code bits are distinctly different from one and another. Table 2 illustrates frames of code bits generated from the MLBS and the data bits they represent. A negative sign before the code name designates a frame of code bits generated by inverting the frame of code bits of a corresponding positive code name.
During manufacturing of optical disks, the mastering equipment uses code bits from Table 2 to encode HFWM bits for identification data 37 and error correction code 38 in the wobble. In one implementation, a 63 bit MLBS is generated from a six bit primary polynomial of “100001”. This 63 bit MLBS is used as synchronization mark 36. The 63 bit MLBS is, for example, “010101100110111011010010011100010111100101000110000100000111111”. By using a different MLBS for synchronization mark 36, the encoded identification data 37 and error correction code 38 are less likely to be read as synchronization mark 36. One skilled in the art will recognize that other MLBS may be used. Furthermore, other encoding schemes may be used to decrease the chances of reading error.
In one implementation illustrated in
Although the invention has been described with reference to particular embodiments, the description is only an example of the invention's application and should not be taken as a limitation. In particular, other waveforms of HFWMs can be used. In addition, other types of encoding schemes may be used to encode the data. Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.