Abstract:
A method for controlling an optical drive to record data onto a disc. The optical recorder has a pick up head for emitting laser onto the disc to record data onto the disc. The method includes adjusting a write power and a write strategy of the optical drive according to a linear velocity of the disc when passing by the pick up head.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method of controlling an optical drive to write data, more specifically, a method of adjusting a write-in strategy and a write-in power according to a linear velocity of an optical disc operating on the optical drive.  
           [0003]    2. Description of the Prior Art  
           [0004]    With the rapid development of computer technology, most data can be transformed into digital form for convenience of transmitting and storing.  
           [0005]    In order to help users store data more conveniently, various data storage devices, such as CD recorders, are being introduced. A CD-R drive, due to a low price, small volume, and large capacity of a disc, can record data onto the CD, letting the user store data more easily.  
           [0006]    The conventional CD-R drive rotates at a zone constant linear velocity (ZCLV). When a pickup head of the CD-R drive is passing through different zones of a disc, for keeping a constant linear velocity, the angular velocity of the operating CD-R drive also changes so as to accurately record the data on the disc. In addition, a fixed-angular-velocity-operated CD-R drive does not need to frequently adjust the motor turns, and has also become a widely used drive in recent years.  
           [0007]    Please refer to FIG. 1, which shows a schematic diagram of the CD-R drive  10  recording data onto an optical disc  20 . The disc  20  has a spiral track  22  covered by a photoresist layer from the center outward. The drive  10  comprises a pickup head  12 . While the drive  10  writes data onto the disc  20 , the pickup head  12  makes the photoresist layer of the track  22  on the disc  20  be intermittently exposed to an on-and-off laser according to the data. The exposed photoresist layer of the track  22  will cause pits to form. On the contrary, the unexposed photoresist layer will be kept as lands. Reflections of the pits and the lands are not similar, in this way, the different data (for example, the digital “0” or “1”) can be represented by the pits and the lands respectively, and stored in the disc  20 . While reading the data stored in the disc  20 , the drive  10  can receives reflecting laser from the disc  20  to read the data stored in the disc  20 .  
           [0008]    The extended length of the pit and the land represent the times of the particular repetition bit in disc  20 , a length for continuing representative data. For example, if the pit represents bit “1”, the three repetition bits “1 1 1” is represented by longer extended pits. As above-mentioned, when the disc  20  passes through the pickup head  12 , the pickup head  12  will apply energy onto the disc  20  with a laser so as to write data onto the disc  20 . Both the applied energy (that is, the laser power) and the applied time of the energy can affect the extended length of the pits and further affect the precision of the written data on the disc  20 .  
           [0009]    Please refer to FIG. 2, which shows a relation plot of an amount of exposure of the photoresist layer against the fragment position relative to the pickup head  12  while the disc  20  is rotating. When the drive  10  is going to write data into the disc  20 , the pickup head  12  begins to emit a laser while passing through the fragment of p 0 . At this moment, the received energy of the disc  20  is not enough to form a pit. As the disc  20  is rotating, the pickup head  12  constantly supplies energy onto the disc  20 . While the fragment of p 1  is passing through the pickup head  12 , a temperature of the photoresist layer of the fragment reaches a threshold temperature Eth and a pit is formed. While passing through the fragment of p 2 , the pickup head  12  stops emitting a laser and the temperature of the disc  20  decreases gradually. While the pickup head  12  is passing through the p 3 , the temperature of the photoresist layer is lower than threshold temperature Eth and a pit is no longer formed. In other words, a real extended length of the pit is from position p 1  to p 3 . From FIG. 2, a length from p 0  to p 1  is obviously different from a length from p 2  to p 3 , that is, if a pit intends to be formed from p 1  to p 3 , the pickup head  12  of the drive  10  must begin/stop emitting a laser while passing through the position p 0  and p 2  respectively. In addition, the energy applied from the pickup head  12  affects the formed pit as well. For instance, the larger energy the pickup head  12  applies to the disc  20 , the closer to the initial position, where the pickup head  12  begins to apply energy, the reaching threshold temperature Eth position of the photoresist layer is. Generally speaking, while writing data into the disc  20 , the drive  10  can determine a position and a length of a pit, i.e. the position of p 1  and p 3 , according to the data. As to the position where the pickup head  12  actually applies energy, i.e. the position of p 0  and p 2 , are determined by a specific write-in strategy along with an optimal write-in power based on the position p 1  and p 3 . Because the data within the disc  20  has direct relation to the extended length of the pit, an over-length or an under-length of the pit is incapable of correctly recording data onto the disc  20 .  
           [0010]    Please refer to FIG. 3. FIG. 3 is an enlarged plot according to a dotted line section of the disc  20  shown in FIG. 1. For a rewritable disc  20 , its track  22  can be divided into two kinds of tracks, one is a data track  26  for use to record data, and the other is a wobble track  28  for use to record relative information of each frame on the disc  20 . The data track  26  is an arc along the disc  20  and around the center of the disc  20 , like the track  22 . Because FIG. 3 is an enlarged plot of a tiny part of the arc track, the data track  26  shown in FIG. 3 is a straight line. However, the wobble track  28  is not only an arc along the disc  20  and around the center of the disc  20 , from a view of FIG. 3, but also appears as crawl-shaped with small amplitude along the track  22 . The pickup head  12  of the drive  10  can receive reflected light from the wobble track  28  and forms a wobble signal. The drive  10  can detect which part of data on the disc  20  is being read by the pickup head  12  based on the wobble signal.  
           [0011]    According to the orange book regulating the specification of the disc  20 , while the emitted laser power from the pickup head  12  has optimal power, the reflected signal measured by the pickup head  12  is an AC coupled high frequency (HF) signal with a perfect symmetrical amplitude. Please refer to FIG. 4 which shows a waveform of the HF signal reflected from the disc  20  while the pickup head  12  of the drive  10  writes data onto the disc  20  based on an optimal write-in power, where the horizontal axis represents time, the vertical axis represents amplitude, and the place marked as level dc represents a corresponding amplitude of a long-term average of the waveform. If a laser is reflected from a pit, the HF signal shows an upper amplitude A 1  over the level dc. If a laser is reflected from a land, the HF signal shows a lower amplitude A 2  below the level dc. A measurement amplitude parameter β=(A 1 −A 2 )/(A 1 +A 2 ) is for use to compare the A 1  and A 2 . During writing data into the disc  20 , the drive  10  will encodethe data, resulting in a total extended length of pits equaling to a total extended length of lands. In other words, a total spent time of the laser reflecting from pits and a total spent time of the laser reflecting from lands are the same, which causes a long-term average level dc of the reflected HF signal to be exactly in the middle of the upper amplitude A 1  and the lower amplitude A 2 , that is β=0. If the laser power emitted from the pickup head  12  is lower than the optimal power or if the laser-emitting time is too short, either causes the insufficient extended pits, which makes the waveform of the HF signal move downward and causes A 1  to be less than A 2 , leading to β&lt;0. On the contrary, if the laser power emitted from the pickup head  12  is higher than the optimal power or if the laser-emitting time is too long, either forms an over-length of an extended pit, which makes the waveform of the HF signal move upward and causes A 1  to be more than A 2 , leading to β&gt;0. In other words, β represents an amount of the pits matching an amount of the lands during encoding. When β does not equal to 0, it means either the length of the pit or that of the land is incorrect, resulting in errors during encoding. Besides β, a signal jitter in the duration of data-reading also can be used to judge a correction of data-writing. If there is something wrong when the disc  20  is written, even identical bits, the last time of signal-reading (that is, the extended length of the pits or the lands), are not the same, which increases the signal jitter.  
           [0012]    Please again refer to FIG. 1. The drive  10  further includes an absolute time in pregroove decoder (ATIP decoder)  14  for decoding the absolute time code acquired from pickup head  12  and an eight-to fourteen modulator (EFM)  16  for modulating the data into EFM data. The drive  10  includes a table  18 , which shows write-in strategies corresponding to write-in powers. The drive  10  adjusts the write-in strategy and the write-in power based on both a time code and the table  18 . The drive  10  can be a constant-angular-velocity-operated drive. While the drive  10  rotates the disc  20 , the rotation angular velocity of the drive  10  stays constant. Due to the fixed angular velocity of the drive  10 , when the drive  10  is operating, a linear velocity of an inner orbit of the disc  20  is smaller, but a linear velocity of an outer orbit of the disc  20  is larger. If intending to write data into the inner orbit of the disc  20 , due to a smaller linear velocity of an inner orbit, the pickup head  12  has enough time to emit a laser exposing the photoresist layers on the inner orbits, therefore the emitted laser power from the pickup head  12  is not too large. On the other hand, if intending to write data into the outer orbit of the disc  20 , due to a larger linear velocity of an outer orbit, the pickup head  12  has to augment the laser power or increase the heating time so that the photoresist layer on the outer orbit of the disc  20  can complete exposure in a predetermined time. As a result, the write-in strategy and the write-in power have to be adjusted adequately along with the process of data-writing.  
           [0013]    Please refer to FIG. 5, FIG. 6, and FIG. 7. FIG. 5 is a schematic diagram of distribution frames along the disc  20 . FIG. 6 is a relation plot showing the linear velocity of the rotating disc  20  against the record time of the drive  10  while the pickup head  10  is passing through the disc  20 . FIG. 7 is a relation diagram showing the value of β against time. The track for recording data on the disc  20  can be divided into a plurality of frames, each having identical data capacity. In CD-R/CD-RW, a linear length of each frame (an arc along the track) is identical. Two frames FA and FB are marked in FIG. 5, where the inner frame FA is from Fa 0  to Fa 1  and the outer frame FB is from Fb 0  to Fb 1 . In the prior art, the drive  10  adjusts the laser power emitted from the pickup head  12  according to the frames, that is, the emitted laser powers from the pickup head  12  are the same in an identical frame. The emitted laser powers from the pickup head  12  changes as a change of frames.  
           [0014]    As a curve  50  shows in FIG. 6, while the pickup head  12  is moving from the inner part of the disc  20  outward, the linear velocity of the disc  20  skipping the pickup head  12  is increasing. On the other hand, even though the linear length of each frame is identical, the spread angle of the center of the disc  20  corresponding to the frame distributed in the inner disc  20  (like frame FA) is also larger and each point within the frame corresponding to the radius of the center of the disc  20  has a larger difference. As inner frame FA shows in FIG. 5, the radius from the center to the start point of Fa 0  is different from that from the center to the end point of Fa 1 . Relatively, the spread angle of the center of the disc  20  corresponding to the frame FB distributed in the outer disc  20  is smaller, and the radius from the center to the point Fb 0  and Fb 1  are almost the same. That the radius from each point to the center has a larger difference means while the pickup head  12  passes through different points within the frame FA, the linear velocity changes more greatly. As shown in FIG. 6, where an interval between the time t 0  and t 1  represents the spent time of the pickup head  12  passing through the inner frame FA, an interval of the time t 5  and t 6  represents the spent time between the pickup head  12  passing through the outer frame FB. Despite the change of the linear velocity among different points within the inner frame of the disc  20  being larger, the write-in strategy and the write-in power are adjusted according to the frames in prior art, resulting in the same write-in strategy and the write-in power are used to write data into the inner frame. In this way, the linear velocity at the end fragment of the inner frame is faster than that at the start fragment of the inner frame during writing data into the inner frame. For the end fragment of the frame, the write-in strategy and the write-in power adapted to the start fragment of the frame can cause a lack of absorption energy, which leads to too short a length of the pits. Similarly, for the start fragment of the frame, the write-in strategy and the write-in power adapted to the end fragment of the frame can cause over-absorption energy, which leads to too long a length of the pits. From FIG. 7, while the pickup head  12  writes data into the end of the inner orbit, the absolute value of β being maximum, that is, the laser power emitted from the pickup head  12  at this moment is most far from the optimal power, meaning that the pickup head  12  is prone to generate errors at this position of the disc  20 .  
           [0015]    While writing data into the outer frame of the disc  20 , owing to little linear velocity change at each position of the outer frame, the pickup head  12  is unable to make mistakes, even when writing data into a sequence of two or three frames with the same write-in strategy and the write-in power. From FIG. 7, β is approximate to 0 when the pickup head  12  writes data into the outer orbit of the disc  20 . As a result, it is not necessary to store too many write-in strategies and the write-in powers in the table  18  in prior art.  
           [0016]    In addition to the above defect, a change of the drive  10  operation speed makes the table  18  useless. For example, the table  18  adapted to the two-times drive is not suitable for the four-times drive. Even at the same frame, while the operation speed of the drive changes, the linear velocity of the pickup head passing the frame changes, and the corresponding write-in strategy and the write-in power also change. In this way, arising from a promotion of the drive operation speed, the conventional drives have to test new write-in strategies and write-in powers again, resulting in a wasted time and a cost increase of the drive development.  
         SUMMARY OF INVENTION  
         [0017]    It is therefore a primary objective of the claimed invention to provide a method for recording data with a drive so as to promote an accuracy of recording data onto a disc with the drive.  
           [0018]    Briefly summarized, the claimed invention provides a method of controlling an optical drive to write data onto an optical disc, the optical drive includes a pickup head for providing energy onto the disc. While the received energy of the disc is over a threshold, a mark for recording data is formed on the disc. During forming a mark on a data-location on the disc, the optical recorder determines when to start to provide energy based on the write-in strategy before the data-location passes through the pickup head. The method comprises adjusting the write-in strategy based on the linear velocity of the disc when the disc is passing through the pickup head.  
           [0019]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the invention, which is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0020]    [0020]FIG. 1 is a schematic diagram of a conventional drive recording data into a rewritable disc.  
         [0021]    [0021]FIG. 2 shows a physical characteristic of a photoresist layer within a disc.  
         [0022]    [0022]FIG. 3 is an enlarged diagram of a dotted line section of the disc shown in FIG. 1.  
         [0023]    [0023]FIG. 4 shows a waveform of a high frequency signal reflecting from the disc received by a pickup head of the drive.  
         [0024]    [0024]FIG. 5 shows distribution frames along a track on the disc.  
         [0025]    [0025]FIG. 6 shows a spent time of the conventional drive recording against the linear velocity of the pickup head passing through the disc.  
         [0026]    [0026]FIG. 7 shows β value of the drive against the time according to prior art.  
         [0027]    [0027]FIG. 8 shows a block diagram of the present invention.  
         [0028]    [0028]FIG. 9 is a flow chart of changing the write-in strategy and the write-in power according to the present invention.  
         [0029]    [0029]FIG. 10 is a flow chart of resetting a table according to the present invention.  
         [0030]    [0030]FIG. 11 shows a spent time of the drive recording against the linear velocity of the pickup head passing through the disc according to the present invention.  
         [0031]    [0031]FIG. 12 shows β value of the drive against the time according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0032]    Please refer to FIG. 8, which shows a block diagram of the drive  50  according to the present invention. The drive  50  includes a pickup head  52  for emitting a laser onto a disc  70  and for receiving the reflected laser from the disc  70  so as to read data and the wobble signal stored in the disc  70 , an ATIP decoder  54  for decoding the received wobble signal from the pickup head  52  into absolute time code and measuring the frequency of wobble signal to obtain the linear velocity, an eight-to-fourteen modulator (EFM)  56  for modulating the data into EFM data, and a table  18  for storing various linear velocities against write-in strategies and write-in powers. The drive  50  can be a constant-angular-velocity-operated drive, that is, the angular velocity is a constant when the drive  50  drives the disc  70  rotating.  
         [0033]    A difference between the present invention and prior art lies in that the drive  50  finds the corresponding write-in strategy and the corresponding write-in power stored in the table  58  based on the linear velocity when the disc  70  is passing through the pickup head  52 . Please refer to FIG. 9. FIG. 9 is a flow chart of changing the write-in strategy and the write-in power according to a change of the linear velocity of the disc  70  when the disc  70  is passing through the pickup head  52 . The flow occurs as follows:  
         [0034]    Step  100 : Start; (at this time, the disc  70  has been placed on the drive  50 )  
         [0035]    Step  110 : Read a wobble signal stored on the disc  70  with the pickup head  50 , and send the wobble signal to the ATIP decoder  54 ;  
         [0036]    Step  120 : Decode the sent wobble signal with the ATIP decoder  54 ; (The ATIP decoder  54  will decode the wobble signal into absolute time code and measure the frequency of wobble signal to obtain the linear velocity)  
         [0037]    Step  130 : Modulate write data into EFM data, and send the EFM data and the linear velocity data to the table  58 ;  
         [0038]    Step  140 : Determine the write-in strategy and the write-in power corresponding to the linear velocity based on the table  58 ; (If the linear velocity data is between a first linear velocity data and a second linear velocity data both stored in the table  58 , determine the write-in power and the write-in strategy with an interpolation method)  
         [0039]    Step  150 : Control the pickup head  52  based on the write-in strategy and the in power;  
         [0040]    (In other words, the emitted laser power from the pickup head  52  is controlled by the write-in power, and the beginning and the finishing emitting times of the pickup head  52  are controlled by the write-in strategy)  
         [0041]    Step  160 : End. (At this time, the pickup head  52  has recorded data accurately in the disc  70 )  
         [0042]    In above steps, it is assumed that the linear velocity of the pickup head  52  passing through the disc  70  is V 1 . When the drive  50  determines a write-in power WP 1  and a write-in strategy WS 1  corresponding to the linear velocity V 1  with an interpolation method, in the meantime, the linear velocity of the disc  70  passing through pickup head  52  is increasing to V 2 . If the write-in power WP 1  and the write-in strategy WS 1  corresponding to the linear velocity V 1  continues to be used to emit laser onto the disc  70 , errors occur. So the write-in power WP 1  and the write-in strategy WS 1  requires a predetermined weight so as to meet the optimal write-in power and optimal write-in strategy while the linear velocity of the disc  70  passing through pickup head  52  is V 1 .  
         [0043]    The present invention also can be used for resetting the table  58 . Please refer to FIG. 10. FIG. 10 is flow chart of resetting the table  58  according to the present invention, the flow occurs as follows:  
         [0044]    Step  200 : Start; (at this time, the disc  70  has been placed on the drive  50 )  
         [0045]    Step  210 : Select a linear velocity; (control the drive  50  so that the disc  70  can pass through the pickup head  52  by the selected linear velocity)  
         [0046]    Step  220 : Adjust a write-in strategy and a write-in power so as to ensure both the write-in strategy and the write-in power are optimal; (that is, the value of β of the received reflected wave from the disc  70  is 0)  
         [0047]    Step  230 : Store the optimal write-in power, the write-in strategy and the linear velocity data in the table  58 ; (certainly, a predetermined weight also can be added into the optimal write-in power and the optimal write-in strategy and then stored in the table  58 )  
         [0048]    Step  240 : Check the drive  50  to see whether the memory space is enough or not to store an additional group of a linear velocity against a write-in strategy/a write-in power, if it is, go to step  210 ; If not, go to step  250 ; (Under a circumstances of not retarding a normal operation of the drive  50 , simultaneously selecting many groups of linear velocities against write-in strategies/write-in powers can efficiently promote an accuracy of the drive&#39;s  50  writing data)  
         [0049]    Step  250 : End. (at this time, the drive  50  can record data onto the disc  70  according to the table  58 )  
         [0050]    Please refer to FIG. 11 and FIG. 12 together (and compare with FIG. 6 and FIG. 7). FIG. 11 shows a spent time of the drive  50  recording against the linear velocity when the pickup head  52  is passing through the disc  70  according to the present invention. FIG. 12 shows β of the drive  50  against the time according to the present invention. As shown in FIG. 11, because the present method adjusts the write-in strategy and the write-in power based on the linear velocity when the disc  70  is passing through the pickup head  52 . If the linear velocity is between V 1  and V 2 , a first write-in strategy/a first write-in power can be used; if the linear velocity is between V 2  and V 3 , a second write-in strategy/a second write-in power can be used etc. Compare to FIG. 12 and FIG. 7, β of the present method shown in FIG. 12 is more approximate to 0, in other words, the write-in strategy and the write-in power of the present method are closer to the optimal write-in strategy and the optimal write-in power than those of prior art are. From FIG. 11, while the inner frame of the disc  70  is passing through the pickup head  52 , the pickup head  52 , due to a greater change of the linear velocity, the write-in strategy and the write-in power are frequently adjusted to achieve better effects. While the outer frame of the disc  70  is passing through the pickup head  52 , the pickup head  52 , due to a smooth change of the linear velocity, need not frequently alter the write-in strategy and the write-in power. Such arrangement of the write-in strategy and the write-in power not only efficiently make use of a memory inside the drive  50 , but also ensure an accuracy of data-writing. On account of various linear velocities available to different write conditions, the present method is more suitable to a constant-angular-velocity-operated drive.  
         [0051]    While establishing the table  58  of the present invention, select a highest velocity of a high-speed drive as a benchmark, selecting a plurality of linear velocities under the highest velocity, then testing the high-speed drive by means of testing the highest velocity and the plurality of linear velocities in turn to determine a corresponding optimal write-in power and a corresponding optimal write-in strategy, and storing the highest velocity, the plurality of linear velocities, both the optimal write-in power and the optimal write-in strategy corresponding to each linear velocity to a table together. While the drive intends to record data to a disc, the drive can determine a write-in power and a write-in strategy stored in the table with an interpolation method, based on the linear velocity when the disc is passing through a pickup head of the drive, adding a predetermined weight to the write-in power and the write-in strategy, the pickup head can record data based on the weighted write-in power and the weighted write-in strategy.  
         [0052]    In contrast to the prior art, it is an advantage of the claimed invention that the claimed invention can adjust the write-in power and the write-in strategy according to the linear velocity of the disc  70  passing through the pickup head  52 . While the inner orbit of the disc  70  is passing through the pickup head  52 , the drive  50  can more frequently adjust the write-in power and the write-in strategy so as to adapt to a greater change of the linear velocity. Such can promote an accuracy of recording data. In other aspects, owing to less change of linear velocity, it is not necessary to store too many groups of the write-in power and the write-in strategy. Such can save memory spaces of the drive  50 . Furthermore, in present invention, while a higher-speed drive appears, the table storing the write-in power and the write-in strategy is no longer necessarily updated. This is because the present method defines the table according to the linear velocity. If an operation speed of the drive is rising, which only promote a linear velocity, the drive can determine both the write-in power and the write-in strategy corresponding to the higher linear velocity from the original table, in this way, such can reduce a cost and a spent time of a drive development.  
         [0053]    Those skilled in the art will readily observe that numerous modifications and alterations of the method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.