WO2008044176A2 - Optimizing a parameter for reading-out / recording of an optical data carrier - Google Patents
Optimizing a parameter for reading-out / recording of an optical data carrier Download PDFInfo
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- WO2008044176A2 WO2008044176A2 PCT/IB2007/054057 IB2007054057W WO2008044176A2 WO 2008044176 A2 WO2008044176 A2 WO 2008044176A2 IB 2007054057 W IB2007054057 W IB 2007054057W WO 2008044176 A2 WO2008044176 A2 WO 2008044176A2
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0945—Methods for initialising servos, start-up sequences
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/094—Methods and circuits for servo offset compensation
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0956—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
Abstract
The present invention relates to a device and a method for determining an approximated optimum of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter based on three measurements covering a range of said parameter, about a minimum, about a maximum and a medium, wherein a circle is defined by the data pairs of parameter and corresponding result. The center is of this circle is used for an approximated optimization of said parameter.
Description
Optimizing a parameter for reading-out / recording of an optical data carrier
FIELD OF THE INVENTION
The present invention relates to a device and a method for determining an approximated optimum of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter.
BACKGROUND OF THE INVENTION
For recording to and for reading-out from an optical data carrier a laser beam is directed to the optical data carrier. The positioning accuracy of this laser beam is crucial for the performance of the playback- or recording- system. In particular, in case of a DVD media a deviation of the focal point of the laser beam, i.e. a de-focus, in z-direction may cause a poor performance, especially in terms of jitter. This de-focus is also referred to as a focus offset.
For compensation this focus offset, along with the wide range of data carriers available in the market, front-end internal ICs introduce an offset to the focus error signal. Further, to some extent a de-focus may be compensated during playback with an increased laser power. However, it is practically impossible to playback throughout the whole disc with these compensating methods.
In common playback- / recording-systems, during an initial recognition of the media an optimum focus offset point for minimum jitter is calculated based on jitter measurements usually done at 13 different focus offset positions. By creating an index of jitter measured at corresponding focus offset positions a "bathtub"-curve is approximated mathematically. From this derived approximated "bathtub" the optimum focus offset point is determined. This calibration is generally done during start-up and subsequently the laser beam is focused using this optimum focus offset during playback along the disc. In some cases the above is performed at various predetermined locations and different optimum focus offsets are obtained for different areas of the data carrier, for example for 6 regions from inside to outside, wherein each calibration is limited to its specific region.
Focus offset curves are categorized basically into four different types as illustrated in Fig. 1.
The symmetric or center symmetric curve 11 shows a symmetry resulting in the optimum focus offset, i.e. in this case, the focus offset resulting in the lowest jitter, at or close to a zero offset. Best performance in terms of jitter is to be achieved at or around a focus offset of zero. In case of a left-asymmetric 12 or a right-asymmetric 13 curve the optimum focus offset is shifted to the left or right, respectively, wherein the shape of the curve generally corresponds to that of a symmetric curve. The fourth type 14 is non symmetric, showing no particular symmetry. The curves shown in Fig. 1 are representations of extreme conditions of focus offsets. In practice the actual focus offset to jitter curves will be in between these conditions.
Anyway, the calibration methods as described above require a significant amount of system time due to the number of measurements, i.e. 13 measurements, needed for determining a optimum focus offset for each region and the complexity of the "bathtub"- approximation. This problem becomes even more severe with an increasing number of different regions for which optimum focus offsets are to be determined and with the additional provision of optimizing a tilt of the data carrier.
In particular for a direct dual layer DVD recording it is desired that the time required by the system for adapting to the switched layer is as short as possible. After finishing a recording on a first layer (layerO) and before starting a recording on a second layer (layer 1) the recorder has to obtain good values for tilt and focus offset for the second layer in order to allow the switching of layers. Typically, the time for calibration before starting a recording on a new layer is about 7 to 8 seconds, with 2+ seconds for a first optimum power calibration, about 1.3 seconds for a focus offset calibration, about 1.3 seconds for a tilt calibration, and further 2+ seconds for a second optimum power calibration using the outcome of the focus offset calibration and the tilt calibration. Thus, a buffer has to be provided being capable of buffering a sufficient amount of data during a on-the-fly recording in order to prevent a data loss. Either, the buffer made large enough, resulting in higher costs, or the live recording performance is poor due to lost data during a layer switching, both of which including the risk of not satisfying the consumer.
In WO 2004/105003 Al a method is described for compensating tilt of an optical disc. An optical lens, which is pivotably mounted, is pivoted to an optimum pivot position such that the amplitude of the push-pull tracking error signal is maximal. Said optimum pivot position is determined by measuring said amplitude at different pivot
positions and calculating a maximum point of a best parabolic fit through the measurements. Further details on tilt may be found in WO 2004/105003 Al which to some extent apply mutatis mutandis as well for a focus offset.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device and a method for determining an approximated optimum of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter, wherein the determining is performed fast and of low complexity, in particular faster than a conventional optimization as described above.
In a first aspect of the present invention a device is presented determining an approximated optimum of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter, said device comprising: an actuator for setting said parameter to a lower parameter value at or around a lower limit of said range, to an upper parameter value at or around an upper limit of said range and to an intermediate parameter value between said lower parameter value and said upper parameter value; a detector for detecting a lower result value, an upper result value and an intermediate result value with said parameter being set to said lower parameter value, said upper parameter value and said intermediate parameter value, respectively; and a determination unit for determining said approximated optimum as an abscissa of a midpoint of a circle defined by three points having said parameter values as abscissas and said result values as ordinates, respectively.
In a further aspect of the present invention a method of determining an approximated optimum (pm) of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter is presented, said method comprising the steps of: measuring a lower result value using a lower parameter value at or around a lower limit of said range; - measuring an upper result value using an upper parameter value at or around an upper limit of said range; measuring an intermediate result value using an intermediate parameter value between said lower parameter value and said upper parameter value; and
determining said approximated optimum as an abscissa of a midpoint of a circle defined by three points having said parameter values as abscissas and said result values as ordinates, respectively.
According to a further aspect of the invention, a computer program is proposed comprising program code means for causing a computer to carry out the steps of a method according to the invention when said computer program is carried out on a computer. Preferred embodiments of the invention are defined in the dependent claims. According to the present invention an approximated optimum of a parameter for recording and/or reading-out an optical data carrier is determined based on three measurements covering a range of said parameter, about a minimum, about a maximum and a medium, wherein a circle is defined by the data pairs of parameter and corresponding result. The center is of this circle is used for an approximated optimization of said parameter. Thus, by minimizing the number of measurements, the present invention allows for an increased speed in comparison to conventional methods. Unlike with conventional methods and devices there is no need for a correlation or fitting of a polynom to a rather large number of measured data pairs. Thus, the determination of said approximated optimum is done merely by solving a first-order solution without employing any parabolic or higher order fit. Accordingly, by reducing the complexity of the calculation the time needed for optimization is further reduced. In comparison to the above conventional scenario the proposed 3 -point circle fit method is much faster by taking less than 300msec to provide about the same result as conventional 13 point algorithm for each of tilt and focus offset calibration. Accordingly a total of about 2 seconds of time saving is achieved, allowing for a smaller buffer, i.e. for reduced costs. According to the invention merely the parameter itself is optimized wherein the result corresponding to this parameter it is neither measured nor calculated for this optimization. It has been realized by the inventors that for the optimization purpose only the knowledge of the parameter value is relevant while the result corresponding to this value may be ignored. In contrast thereto, for conventional optimization a curve is fitted to the measured data pairs of parameter and result which give a lot of information not needed for optimization, i.e. for determining an (approximated) optimum of the parameter. When a data pair comprising the optimum and the result should be needed at a later point in time, the result, e.g. the jitter, may just be measured using the optimum.
The predetermined range may or may not coincide with a maximum range which is possible for setting said parameter, i.e. said predetermined range may correspond to, but may as well be smaller than a maximum range, e.g. defined by constraints of the actuator. However, if it is possible to obtain meaningful results, e.g. a jitter or a signal to noise ratio, using the most extreme parameter values possible, said predetermined range may correspond to said maximum range. In some cases said possible maximum range may extend beyond limits in which meaningful results may be obtained or which are preferable for safety reasons. Under such circumstances the predetermined range is smaller than said maximum range. Preferable ranges for tilt and focus offset are defined in claims 5 and 8. It was found those limits define a range justifying a confidence that the readout signal can be reconstructed, i.e. that a meaningful result can be obtained, and that the desired optimum is comprised in said range. However, besides using the maximum range or using a range based on experience there are further ways to determine the predetermined range. For example, during an initialization the predetermined range may be defined based on an identification of the present data carrier together with a set of corresponding ranges stored in the device. Another possibility is to adapt the limits based on actual measurements as trial and error. Further, the predetermined range may be limited to the range in which the bit clock can be reconstructed corresponding to the lock- in condition of the bit detector. Still further, the range may be dynamically adapted, e.g. if the readout signal cannot be reconstructed at one of the ends or if the minimum is determined to be outside of the range. Combinations of these approaches may also be used.
A further problem of the known techniques has been realized by the inventors. Commonly, the optimum parameter is determined only once (for each region). However, this determination may be based on flawed data, either due to incorrect measurements or to some unpredictable artifacts during data processing. Even if the data is correct for the particular point is was measured for this does not necessarily imply that is also correct or reliable for other parts of the (region of the) data carrier. Thus, a wrong "optimum" parameter may be determined resulting a poor or even fatal performance. Conventionally, this problem may be countered by repeated measurements for a large number or regions of the data carrier. This, however, is very time consuming.
In order to allow for a continuous and repeated determination of an approximated optimum of said parameter it is proposed to provide a detector which is
adapted for detecting an operation result value resulting from reading-out and/or recording of said optical data carrier using an operation parameter value, wherein said device further comprises: a memory unit for storing first data comprising a first operation parameter value and a first operation result value obtained at a predetermined point in time, and a calculation unit for obtaining second data comprising a second operation parameter value and a second operation result value later after said storing and for calculating an approximated operation optimum based on said second operation parameter value, a difference between said first operation parameter value and said second operation parameter value, and a difference between said first operation result value and said second operation result value, wherein said memory unit is adapted for storing said second data as a replacement for said first data after said calculating said approximated operation optimum.
Thus, subsequent to a first approximation of the optimum parameter, e.g. a focus offset, said approximated optimum parameter is further adjusted / fine tuned along the recording and/or reading-out of the data carrier, e.g. continuously on-the-fly and / or at given number of blocks or at given locations on the data carrier, e.g. every 20 ECC blocks or multiple of 20 ECC blocks or every lmm on the data carrier.
It has to be noted that this continuous or repeated determination of the an approximated optimum parameter may also be implemented without the need for a first determination of an approximated optimum parameter, i.e. this technique may also be used based on a conventionally obtained starting parameter.
BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. In the following drawings Fig. 1 shows four basic types of relations between focus offset and jitter; Fig. 2 shows a set of three data pairs, a resulting circle and the construction for calculating a midpoint of the circle; Fig. 3 shows schematically an embodiment of a device according to the present invention;
Fig. 4 shows a flow chart illustrating an embodiment of a method according to the present invention;
Fig. 5 shows a flow chart illustrating further steps of a second embodiment of a method according to the present invention;
Fig. 6 shows a flow chart illustrating yet further steps of the second embodiment of a method according to the present invention; and Fig. 7 shows a illustration of the method show in Fig. 6.
DETAILED DESCRIPTION OF EMBODIMENTS
Fig. 1 shows four basic types of relations between focus offset and jitter. Fig. 1 is described above. Fig. 2 shows a set of three data pairs, a resulting circle and the construction for calculating a midpoint of the circle. According to the present invention, measurements of results for three different parameter values are done giving three data pairs each comprising a parameter value and a result corresponding to this parameter value.
In Fig. 2 three data pairs are shown, one corresponding to a measurement around a lower limit of the parameter range, one corresponding to a measurement around an upper limit of the parameter range and one corresponding to a measurement between the upper limit and the lower limit. Preferably, this intermediate measurement is done in the middle of the parameter range, i.e. with a focus offset of 0 nm or a tilt of 0 mrad. However, as it can be seen from Fig. 2 it is necessary to have the third measurement exactly in the middle between the two others. In other words, also the range does not have to be symmetric around a zero value of the parameter. Further, the order of measurements is not restricted to the present example, e.g. the measurements may also be performed in order with rising parameter values or with falling parameter values.
The coordinates of the three points are composed of focus offset as the parameter and jitter as the result as follows: (pi , η) denotes the coordinates of the left point where "pf represents the focus offset of the left end point and "η" represents the jitter measured corresponding to the focus offset pi. (pr, rr) is the coordinate of the right point. "pr" represents the focus offset of the right end point and "rr" represents the jitter measured corresponding to the focus offset pr. (p0, r0) denote the coordinates of the zero focus offset point, "po" represents the focus offset of the zero point and 'V represents the jitter measured corresponding to the focus offset p0.
With these three points a circle 21 is well defined as shown in Fig. 2. In the following an equation for determining the abscissa or x-coordinate of the midpoint (pm, rm) of the circle 21 is derived:
A line L is drawn to pass through point (pi , η) and point (po , ro). A line R is drawn to pass through point (pr , rr) and point (po , ro). The slope of line L is represented by the following equation:
The Slope of line R is represented by the following equation:
A line Lp is drawn perpendicular to the line L and passes through the center of the coordinates (pi, η) and (po, ro). A line Rp is drawn perpendicular to the line R and passes through the center of the coordinates (pr, rr) and (po, ro). The slopes of the lines Lp and Rp are represented by the following equation:
The center of the circle is the point where lines Lp and Rp intersect with each other. The coordinate of the center or midpoint of the circle is represented by the coordinates (pm, rm). From the above equations [3] and [4] the value of rm is derived as below:
As the coordinate rm is the same at the point of intersection of lines Lp and Rp equation [5] is thus equal to equation [6], so
Therefore the value of pm is obtained by the equation
The value of rm could be derived by substituting the value of pm in either equation [5] or equation [6] to obtain the coordinates (pm, rm) of center of the circle 21. However, here only pm is of interest as the approximated optimum of the parameter.
Fig. 3 shows schematically an embodiment of a device according to the present invention. A playback apparatus 30 comprises a controller 31, a read-out unit 32 and a device 33 for determining an approximated optimum of a parameter according to the present invention. Said device 33 comprises an actuator 35, a detector 36 and a determination unit 37 connected to said detector 36 and to said controller 31.
Said actuator 35 is controlled for setting a focus offset and/or a tilt as a parameter for reading-out a data carrier to three different parameter values. Using this parameter settings three measurements are conducted. Said detector 36 detects the result values from these measurements. The detector 36 is connected to said determination unit 37 for transferring said data. Based on the obtained data said determination unit 37 determines an approximated optimum of said parameter, i.e. the focus offset or tilt, by calculation the parameter value corresponding to a midpoint of a circle defined by the data pairs obtained by the measurements. The determined approximated optimum is transferred to said controller 31 which controls the read-out unit 32 based on said approximated optimum for reading out the data carrier and outputting the content of the data carrier.
In an extended embodiment said device 33 is replaced by a device 34 which comprises said actuator 35, said detector 36 and said determination unit 37 connected to said detector 36 and to said controller 31. Said device 34 further comprises a calculation unit 38 connected to said detector 36 and a memory unit 39 connected to said calculation unit 38. Based on an initial approximated optimum of the parameter for reading out the data carrier, preferably obtained as above and further described below, the playback or reproduction of data on the data carrier is started, thus a result value corresponding to said initial parameter is measured and the resulting data pair is stored in said memory unit 39. A different parameter value is used subsequently and again a data pair comprising said parameter value and the corresponding result value is obtained. These two data pairs are used by said calculation unit 38 to calculate therefrom a further parameter value which is expected to lead to an improved result value. Upon use of this further parameter value by said controller 31 and the read-out unit 32 a new further result value is measured, again, wherein the second data pair is stored in said memory unit 39 for the next calculation.
Fig. 4 shows a flow chart illustrating an embodiment of a method according to the present invention. After a startup-procedure an initialization step 405 is performed for
setting the variables of the procedure. In step 410 measurements are performed to obtain and store three data pairs each comprising a parameter value and a corresponding result value. In the present embodiment the parameter value (pi, p0, pr) is the focus offset and the corresponding result value (rls r0, rr)is the jitter resulting from a read-out using the given focus offset. In step 415 it is checked whether the result value ro of the medium parameter value po is smaller than either one of the two other values. (This applies for cases in which a minimal result value is desirable. If the result value is to be maximized, it is to be checked whether result value ro of the medium parameter value po is larger than either one of the two other values.) If it is, another check follows in step 420 to make sure that these data pairs do not present collinear points. Using the equation [8] derived above an approximated optimum pm is determined in step 425 from the midpoint of a circle defined by the three data pairs. For safety reasons it is checked in steps 430 and 435 if the determined optimum is within the bounds given by an upper threshold tu and a lower threshold ti. If necessary, in step 440 or step 445 the optimum pm is set to the respective threshold. Either step 435, step 445 or step 450 leads to point (1). If it is found in steps 415 or 420 that due to the particular data pairs a meaningful optimization does not seem to be possible a retry counter R is increased in step 450. In following step 455 an exceeding of the maximum number of retries is checked. Depending on the outcome the measurement is either repeated (step 410) or the approximated optimum pm is set to the medium parameter value po in step 460 leading to point (1). At point (1) an approximated optimum for reading-out and/or recording is determined and may be used for operation of an recorder or playback device.
Fig. 5 shows a flow chart illustrating further steps of a second embodiment of a method according to the present invention. The present embodiment corresponds to that shown in Fig. 4 and the method is continued at point (1). In step 505, a jitter value rm is measure using said approximated optimum pm determined before. In step 510 this result value or jitter value rm is compared to the result value ro obtained with parameter value or focus offset po in step 410 above. If the difference lies within in a range given by the limit d2 the process continues with step 515, otherwise with step 520. In step 515 the step size S is set to a value S2 corresponding to said limit d2. In step 520 the step size S is set to a value S1 (corresponding to another larger limit di). Both, step 515 and step 520, are followed by another comparison in step 525. If pm is larger than po the next step is step 530, otherwise the next step is step 535. In step 530 a further parameter value p2 is calculated by subtracting S from parameter value pm, in step 535 the parameter value p2 is calculated by adding S to parameter value pm. Thus, depending on the difference between the results corresponding to
the intermediate parameter value po and the approximated optimum pm a further parameter value p2 is calculated. Since the approximated optimum pm is a parameter value resulting in a better result value than the intermediate parameter value p0, the new calculated parameter value may result in a further improvement, i.e. an even better result value. Step 530 and step 535 lead to point (2).
Fig. 6 shows a flow chart illustrating yet further steps of the second embodiment of a method according to the present invention. Following point (2) in step 605 the first approximated optimum pm is stored together with the corresponding result rm, here a focus offset value together with a jitter value, to the data pair (pls ri). A counter x is set to 2. In step 610 the parameter px (denoted by said counter x, p2 is calculated above) is used for a measurement of the corresponding result value rx. In steps 615 and 620 an absolute difference between rx and rx_i is compared to limits d2 and di to determine a sub range of possible differences it is in. Depending on the outcome of the comparisons in steps 625, 630 and 635 a step size is set to predetermined values s0, S1, S2. In the present embodiment, the value so is 108 nm. The value of S1 is set as So/2 = 54 nm while S2 is set as So/3 = 36 nm. The limit d2 is set to 0.5% and the limit di is 1.%. Accordingly, for example, with a difference between rx and rx_i of 0.7% the step size S is set to 54 nm in step 630. In steps 640 the parameter value px is compared to parameter value px_i used before. If px is greater than px_i the next step is 645 in which the result value rx is compared to result value rx_i . With px being greater than px_i and rx being smaller than rx_i the next parameter value px+i is obtained by increasing the present value px by the step size S in step 650. If rx is greater than rx_i the next parameter value is obtained by decreasing px by S in step 655. Corresponding steps 660 - 670 are provided for parameter value px being smaller than px_i . It is self-evident that in case of an optimization for a maximum result instead of a minimum result, either the comparisons have to be changed or the decreasing steps have to be swapped with the increasing steps. Steps 650, 655, 665, 670 are followed by step 675 in which the counter x is increased by one. In following step 680 it is waited till 20 ECC blocks are read during playback as a condition for repeating the above steps. After 20 ECC blocks being read the process is resumed in step 610. Other conditions may be any given number of ECC blocks or reaching a predetermined radius on the data carrier.
Fig. 7 shows a illustration of the method shown in Fig. 6. The calibration parameter, in this case the tilt, is measured and adjusted continuously while the disc is played back. The continuous calibration or optimization is done by taking into account the measured tilt and jitter at the previous two locations to determine a new tilt value. The step size and
direction of adjustment are determined by the amount of change in the jitter values measured. If the difference in the jitter values is high then a bigger adjustment is done in the tilt values. This way the proposed mechanism adapts to the disc condition and ensures a smooth playback. The step size determination and the method of continuous adjustment are described in detail with the help of a example shown in Fig. 7. A step size S of 0.75 mrad is defined in this example. If the absolute difference in jitter measured between the two previous locations is greater than 1%, then the step size of S is applied. If the difference is between 0.5-1% then the step size of S/2=0.375 mrad is applied. If the difference is less than 0.5% a step of S/3 is applied. The step size is applied in the direction of lower jitter. To calculate the tilt for the current location the tilt and jitter values for the previous 2 locations are taken into account. The new tilt value is calculated by adding or subtracting a step size to the previous tilt. The step size is determined by the difference between the two previous jitter values measured. In the figure 7, point C is assumed to be the current location. Point B and point N are the previous locations. The tilt at point B is 1.5 mrad and jitter measured was 8.2% and the jitter measured at point N 8.4%. Hence the difference in the jitters is 0.2%. So a step size of S/3 is applied. The tilt at point C can now be calculated as 1.5 mrad - 0.25 mrad=1.25 mrad. With this tilt applied the jitter is measured at point C during further playback. To calculate the tilt at the next location of point D, the jitter and tilt values of point B and C are used. It is proposed according to the invention to use a gap of 20 ECC blocks between each successive measurement. This will ensure that the shape of the disc is followed throughout playback, and at the same time not be affected by burst disturbances. The 20 ECC blocks gap is sufficiently small to ensure that the variations can always be kept track of, and hence provide a best playback scenario.
The jitter is not the only possibility for a result value. Other characteristics of the recording process may also be used, as for example, push pull signal amplitude, wobble signal amplitude, RL offset, or wobble to noise signal ratio.
The RL offset value is to eliminate electrical DC unbalance between the left and the right channel at the input signals of the PP -balancer processing the signals from the left and right pupil halves of the central photo diode. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.
Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.
A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. The invention can be applied generally to all types of optical recording media including but not limited to CD, DVD, BD and near- field optical media. Any reference signs in the claims should not be construed as limiting the scope.
Claims
1. Device for determining an approximated optimum (pm) of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter, said device comprising: an actuator (35) for setting said parameter to a lower parameter value (pi) at or around a lower limit of said range, to an upper parameter value (pr) at or around an upper limit of said range and to an intermediate parameter value (po) between said lower parameter value (pi) and said upper parameter value (pr); a detector (36) for detecting a lower result value (η), an upper result value (rr) and an intermediate result value (r0) with said parameter being set to said lower parameter value (pi), said upper parameter value (pr) and said intermediate parameter value (p0), respectively; and a determination unit (37) for determining said approximated optimum (pm) as an abscissa of a midpoint of a circle defined by three points having said parameter values (pi, po, Pr) as abscissas and said result values (η, r0, rr) as ordinates, respectively.
2. Device as claimed in claim 1, wherein said approximated optimum (pm) is determined according to the equation _ m1(p0 + pr) - mr(p0 + p1 ) + m1mr(rr - r1 ) pm = -
2(Hi1 - In1 ) with Hi1 = 
wherein po is said intermediate parameter value, pi is said lower parameter value, pr is said upper parameter value, r0 is said intermediate result value, x\ is said lower result value and rr is said upper result value.
3. Device as claimed in claim 1, wherein said intermediate parameter value (p0) is at or around a center of said range.
4. Device as claimed in claim 1, wherein said parameter is a focus offset.
5. Device as claimed in claim 4, wherein said range has an upper limit between 300 nm and 720 nm, preferably between 400 nm and 650 nm, an a lower limit between -300 nm and -720 nm, preferably between -400 nm and -650 nm.
6. Device as claimed in claim 4, wherein said determination unit (37) is adapted for setting said determined approximated optimum (pm) to a upper or lower threshold (tu, ti) if said approximated optimum (pm) exceeds said upper or lower threshold (tu, ti), wherein preferably said upper threshold is 600 nm and said lower threshold is -600 nm.
7. Device as claimed in claim 1, wherein said parameter is a tilt.
8. Device as claimed in claim 7, wherein said range has an upper limit between 4.5 mrad and 12 mrad, preferably between 5 mrad and 9 mrad, and a lower limit between -4.5 mrad and -12 mrad, preferably between -5 mrad and -9 mrad.
9. Device as claimed in claim 7, wherein said determination unit (37) is adapted for setting said determined approximated optimum (pm) to a upper or lower threshold (tu, ti) if said approximated optimum (pm) exceeds said upper or lower threshold (tu, ti), wherein preferably said upper threshold is 7.5 mrad and said lower threshold is -7.5 mrad.
10. Device as claimed in claim 1, wherein said detector is adapted for detecting, as result value (η, r0, rr), at least one of jitter, push pull signal amplitude, wobble signal amplitude, RL offset, and wobble signal to noise ratio.
11. Device as claimed in claim 1 , wherein said device is adapted for repeating a determination of an approximated optimum (pm) with a further predetermined range, wherein the determined approximated optimum (pm) is a center value of said further range.
12. Device as claimed in claim 1, wherein said detector (36) is adapted for detecting an operation result value resulting from reading-out and/or recording of said optical data carrier using an operation parameter value, wherein said device further comprises: a memory unit (39) for storing first data comprising a first operation parameter value and a first operation result value obtained at a predetermined point in time, and a calculation unit (38) for obtaining second data comprising a second operation parameter value and a second operation result value later after said storing and for calculating an approximated operation optimum based on said second operation parameter value, a difference between said first operation parameter value and said second operation parameter value, and a difference between said first operation result value and said second operation result value, wherein said memory unit (39) is adapted for storing said second data as a replacement for said first data after said calculating said approximated operation optimum.
13. Device as claimed in claim 14, wherein said calculation unit (38) is adapted for calculating said approximated operation optimum by increasing or decreasing said second operation parameter value depending on the sign of said difference between said first operation result value and said second operation result value.
14. Device as claimed in claim 13, wherein said calculation unit (38) is adapted for increasing or decreasing said second operation parameter depending on the absolute value of said difference between said first operation result value and said second operation result value.
15. Device as claimed in claim 13, wherein said calculation unit is provided with a set of non overlapping result ranges covering all possible operation result value differences, wherein said calculation unit is adapted for increasing or decreasing said second operation parameter depending on the result range which includes said difference between said first operation result value and said second operation result value.
16. Recording and/or read-out apparatus (30) for recording and/or reading out an optical data carrier using a parameter within a predetermined range comprising a device as claimed in claim 1 for determining an approximated optimum of said parameter, wherein said recording and/or read-out device is adapted for using said approximated optimum during recording and/or read-out.
17. Recording and/or read-out apparatus (30) for recording and/or reading out an optical data carrier using a parameter within a predetermined range comprising a device as claimed in claim 12 for determining an approximated optimum of said parameter, wherein said recording and/or read-out device is adapted for using said approximated optimum as a starting parameter for said recording and/or read-out and further adapted for using said approximated operation optimum during said recording and/or read-out.
18. Method of determining an approximated optimum (pm) of a parameter for reading-out and/or recording of an optical data carrier within a predetermined range of said parameter, comprising the steps of: measuring a lower result value (η) using a lower parameter value (pi) at or around a lower limit of said range; measuring an upper result value (rr) using an upper parameter value (pr) at or around an upper limit of said range; - measuring an intermediate result value (r0) using an intermediate parameter value (po) between said lower parameter value (pi) and said upper parameter value (pr); and determining said approximated optimum (pm) as an abscissa of a midpoint of a circle defined by three points having said parameter values (pi, p0, pr) as abscissas and said result values (η, r0, rr) as ordinates, respectively.
19. Computer program comprising program code means for causing a computer to carry out the steps of the method as claimed in claim 18 when said computer program is carried out on a computer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP06121969.7 | 2006-10-09 | ||
| EP06121969 | 2006-10-09 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| WO2008044176A2 true WO2008044176A2 (en) | 2008-04-17 |
| WO2008044176A3 WO2008044176A3 (en) | 2010-09-30 |
Family
ID=39048017
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/IB2007/054057 WO2008044176A2 (en) | 2006-10-09 | 2007-10-05 | Optimizing a parameter for reading-out / recording of an optical data carrier |
Country Status (2)
| Country | Link |
|---|---|
| TW (1) | TW200837732A (en) |
| WO (1) | WO2008044176A2 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0478367A2 (en) * | 1990-09-28 | 1992-04-01 | International Business Machines Corporation | Control of light beam focusing system in optical data storage apparatus |
| US5251194A (en) * | 1989-04-17 | 1993-10-05 | Mitsubishi Denki Kabushiki Kaisha | Techniques for controlling beam position and focus in optical disk drives |
| EP0612063A1 (en) * | 1993-02-15 | 1994-08-24 | Kabushiki Kaisha Toshiba | Focus balance automatic adjusting device and method |
| US20030179665A1 (en) * | 2002-03-19 | 2003-09-25 | Nec Corporation | Optical disk drive having a tilt compensator |
| WO2004105003A1 (en) * | 2003-05-21 | 2004-12-02 | Koninklijke Philips Electronics N.V. | Disc drive apparatus, and tilt compensation method |
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2007
- 2007-10-05 WO PCT/IB2007/054057 patent/WO2008044176A2/en active Application Filing
- 2007-10-05 TW TW96137379A patent/TW200837732A/en unknown
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5251194A (en) * | 1989-04-17 | 1993-10-05 | Mitsubishi Denki Kabushiki Kaisha | Techniques for controlling beam position and focus in optical disk drives |
| EP0478367A2 (en) * | 1990-09-28 | 1992-04-01 | International Business Machines Corporation | Control of light beam focusing system in optical data storage apparatus |
| EP0612063A1 (en) * | 1993-02-15 | 1994-08-24 | Kabushiki Kaisha Toshiba | Focus balance automatic adjusting device and method |
| US20030179665A1 (en) * | 2002-03-19 | 2003-09-25 | Nec Corporation | Optical disk drive having a tilt compensator |
| WO2004105003A1 (en) * | 2003-05-21 | 2004-12-02 | Koninklijke Philips Electronics N.V. | Disc drive apparatus, and tilt compensation method |
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| Title |
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| VANGALA VENKATA RAMANA ET AL: "A continuous calibration scheme to improve playability on optical media" IEEE TRANSACTIONS ON CONSUMER ELECTRONICS, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 53, no. 1, February 2007 (2007-02), pages 159-165, XP011175937 ISSN: 0098-3063 * |
Also Published As
| Publication number | Publication date |
|---|---|
| TW200837732A (en) | 2008-09-16 |
| WO2008044176A3 (en) | 2010-09-30 |
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