Title of Invention	DISC DRIVE APPARATUS, AND METHOD FOR TIMING RECALIBRATION IN A DISC DRIVE APPARATUS
Abstract	A disc drive apparatus (1) is described, for writing/reading information into/from a storage medium (2), such as an optical disc. After start-up, multiple recalibration processes are executed, wherein the recalibration processes are executed more frequently during an early phase of the write/read operation than during a later phase of the write/read operation.

Full Text

FIELD OF THE INVENTJON The present Invention relates in general to the art of storage devices such as optical storage discs. More particularly, the present invention relates in general to a disc drive apparatus for writing/reading information into/from an optical storage disc; hereinafter, sudi disc drive apparatus will also be indicated as "optical disc drive". BACKGROUND OF THE INVENTION As is commonly known, an optical storage disc comprises at least one track, either in the form of a continuous spiral or in the form of multiple concentric circles, of storage space where information may be stored in the form of a data pattern. Optical discs may be read-only type, where information is recorded during manufiicturing, vAiich information can only be read by a user. The optical storage disc may also be a writable type, where information may be stored by a user, For reading/writing information from^into the storage space of the optical storage disc, an optical disc drive comprises, on the one hand, rotating means for receiving and rotating an optical disc, and on the other hand optical means for generating an optical beam, typically a laser beam, and for scanning the storage track with said laser beam. Since the technology of optical discs in general, the way in which information can be stored in an optical disc, and the way in which optical data can be read tom an optica! disc, is commonly known, it is not necessary here to describe this technology in more detail. In a disc drive, several operational parameters need to be calibrated, i.e. set to an optimal value for optimal performance. For example, a tilt angle of an optical lens is calibrated, a focus offset of an optical pickup unit is calibrated, a radial error amplitude is calibrated, etc. Particularly, in the case of a write operation, the optical write power is calibrated. Said parameters are commonly known to persons skilled in this art, as is the requirement for calibration. Further, calibration procedures for the above-mentioned and other parameters are known per se, and may be used in implementing the present invention. Therefore, a more detailed description of calibration procedures is not necessary here. It is already known in practice to perform calibration procedures as part of a start-up procedure or initiation procedure, i.e. when a new disc cs inbxxluced in the disc drive, and/or when a new read/write command is given in respect of a disc already present in the drive. However, it may be that the parameter values as set during start-up calibration are no longer optima) values at a later stage of the readAvriie process. This may, for instance, be due to changing circumstances like changing temperature, changing read/write location on disc, etc. Therefore, it may be desirable to also perform calibration procedures at a later stage, when a write or read process is in proffxss. Such calibrE^ion procedures will be indicated by the phrase "recalibration", to make a distinction from calibration during the start-up phase. An important aspect in recalibration is its timing. On the one hand, more frequent recalibration procedures may improve ^e si^tal quality, but it involves a reduction in data throughput. On the other hand, if recalibration procedures are performed not often enough, errors may occur. Further, recalibration procedures interrupt the write or read process which is in progress, so they could afiGsct the proper data transfer. SUMMARY OF THE INVENTION The present invention relates specifically to the timing of recalibration. It is a general objective of the present invention to provide a disc drive Eq)paratus in which an optimal signal quality is maintained as much as possible. It also is a general objective of the present invention to provide a disc drive apparatus in which the numlser of recalibration procedures performed is as few as possible. It is a further general objective of the present invention to provide a disc drive apparatus in which recalibration procedures are performed as efficiently as possible, i.e. in which the timing of recalibration procedures for a certain parameter is determined in relation to a chance that this parameter actually needs to be recalibrated. It is a specific objective of the present invention to provide a disc drive apparatus with a recalibration management fecility which provides an efficient timing of recalibration procedures for parameters which are temperature-sensitive. According to an important aspect of the present invention, at least in an early phase of a write or read operation, the recalibration timing is more frequent than in a later phase of the write or read operation. Or, the time intervals between successive recalibration timings may increase with the passing of time since tiie beginning of a write or read operation. Such change of successive recalibration timings is based on the insight that relatively large changes in temperature are expected during the first moments of a write or read operation, due to the warming-up of the laser system or the apparatus as a whole, whereas relatively litiJe changes in lemperatureare exjwcted during later moments of a write or read operation, because then the laser system or the apparatus as a whole will have {almost) reached a steady state. In a ^ecific embodiment, a recalibration due time is determined on the basis of the amount of time lapsed since a. particular event. This particular event may be, for instance, tiie previous recalibration due time, or the start of the previous recalibration procedure, or the end of the previous recalibration procedure. Recalibration may start immediately at the recalibration due times, or after ^Ifihnent of recalibration permission conditions. The time interval between said particular event and tfie next recalibration due time increases for subsequent recalibration due times. In a specific embodiment, a disc drive apparatus comprises a data engine system and a data processing system. The data engine system provides an interfece between disc drive apparatus and disc, as it handles all incoming and outgoing communication between disc drive and disc. The data processing system processes the data present in incoming and outgoing signals from and to the disc, respectively, and processes the data for communication to and from a host system such as a PC, respectively. The data engine system determines the recalibration due times, i.e. the moments in time when a recalibration is desirable. If the actual recalibration is postponed until fulfilment of recalibration perniission conditions, it may be that the check for such conditions is done by the data processing system. BRIEF DESCRIPTrON OF THE DRAWINGS These and other aspects, features and advantages of the present invention will be further explained by the following description of a preferred embodiment of the present invention with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which: Figure 1 schematically shows a block diagram illustrating relevant parts of a disc drive apparatus; Figure 2 schematically shows a block diagram illustrating relevant parts of a control circuit; Figures 3A and 3B are graphs illustrating the development of temperatiire as a function of time; Figure 4A is a flow dif^ram schematically illustrating a first method of detennining recalibration starting times in accordance with the present invention; Figure 4B is a flow diagram schematically illustrating a second method of determining recalibration starting times in accordance with the present invention; Figures SA and SB are graphs illustrating the timing of the methods illustrated in figures 4A and 4B, respectively; Figure 6A is a flow diagram schematically illustrating a third method of determining recalibration starting times in accordance vjtih the present invention; Figure 6B is a flow diagram schematically illustrating a fourth method of determining recalibration starting times in accordance with the present invention; Figure 6C is a flow diagram schematically illustrating a fifth method of determining recalibration starting times in accordance with the present invention; Figures 7A-C are graphs illustrating the timing of the methods illustrated in figures 6A-C, respectively. DESCRIPTION OF THE INVENTION Figure 1 schematically shows a diagram which illustrates some parts of a disc drive apparatus 1, capable of handling a disc 2. For instance, the disc 2 is an optical (including magneto-optical) disc, such as a CD, a DVD, etc. The disc drive 1 comprises a motor 4 for rotating Oie disc 2, and an optica) pickup unit 5 for scanning tracks (not shown) of the disc 2 widi an optical beam 6. The disc drive 1 fiirther comprises a control circuit 10, having a first output 11 for controlling the motor 4, and having a second output 12 for controlling the optical pickup unit 5. The control circuit 10 fiirther has a data input port 13 and a data output port 14. In a reading mode, the data input port 13 receives a data read signal SR fixim the optical pickup unit 5. In a writing mode, the control circuit 10 provides a data write signal Sw at its data output port 14, The control circuit ]0 fiirther has a data communication port 15 for data communication witii a host system, generally indicated at H. The host system H may for instance be a PC or the like. The disc drive I may be separate from the host 1, communicating over a long-distance communication path, or it may be built-in in the host H. When the disc drive 1 is started, for instance when a new disc 2 is introduced into the drive, a start-up procedure is executed, which includes a calibration procedure for certain parameters, as is known per se. Assume that the disc drive 1 is in a stand-by modus for some time, and its temperature is substantially equal to ambient temperature. When a read/write procedure is started, the temperature of the laser device and its immediate surroundings rises, and also the temperature of the disc drive apparatus as a whole rises. Some of the calibrated parameters arc sensitive to temperature. Examples of temperature-sensitive parameters are focus-offeet and optimal power control (OPC). OPC relates to the optimal laser power for performing a write operation: this optimal power depends inter alia on the temperature of the laser device. When the temperature within the housing of the disc drive apparatus rises, the exact sh^e of the optical path changes, so tiie focus-offset needs to be calibrated. In this respect, it is noted that the rise in laser temperature is very fast after start of a write or read operation, or when switching from reading to writing: the time constant is in ^e order of approximately I to 2 minutes. During this relatively short period, laser power variations piay a large role in the writing process. On the other hand, drifts in the focus offset are caused in the CPU by changes in temperature of the surroundings, which is a much slower process. Thus, it is desirable to perform a recaiibration of the temperature-sensitive parameters, or at least one of the parameters belonging to the group of temperature-sensitive parameters, some time after start of a read operation or write operation. In the case of prolonged duration of such read operation or write operation, it is desirable that such recaiibration procedure is repeated regularly. As mentioned before, recaiibration processes are known per se, and the present invention is not directed to improving a recaiibration process as such. In fact, known per se recaiibration processes may be applied when implementing the present invention; therefore, recaiibration processes as such will not be explained in further detail here. The present invention relates specifically to the timing of the recaiibration processes. According to an important aspect of the present invention, a recaiibration process is initiated on the basis of an amount of time lapsed since the previous calibration or recaiibration. Thus, it may be thai the time intervals between successive recaiibration processes are constant. However, according to a further important aspect of the present invention, the successive recaiibration processes are preferably performed with a decreasing repetition frequency, or increasing interval between successive recaiibration processes. Immediately after start of a read procedure or write procedure, the change in laser temperature will be larger than in a later stage, so that the need of recaiibration diminishes with time. Figure 3A is a graph illustrating generally the development of temperature T at a certain location within the housing of the disc drive 1, as a flinction of time t For instance, the graph of figure 3 A is illustrative for the temperature rise of the Laser device. It is assumed that the disc drive 1 has been switched off for some time, so that on time t=0, when a read procedure or write procedure is started, the temperature T is equal to ambient temperature Ta. After time t=0, the temperature rises quickly, but the temperature rising speed (derivative dT/dt) decreases, and eventually the temperature approaches a new equilibrium temperature Te. It is easily serai that the temperature rise within an early time interval [tl, tl+At] is larger than the temperature rise within a later time interval [t2, t2+At] of same duration. Thus, it is expected that a temperature-sensitive parameter (such as for instance optimal laser power) will change more during such early time interval than during such later time interval, so that fewer recalibration processes are sufFicient during the later time interval as compared with the early time interval. It is noted that the development of ambient temperature within the disc drive housing, causing changes in the focus offset, has a similar shape as the curve of figure 3A but at a larger time scale. Thus, ttie lapse of a certain amount of time since a particular event is considered to be an indication that it would be desirable to execute a recalibration process. The moment in time when such recalibration process becomes desirable will be indicated as recalibration due time t^. Figure 3B is a graph comparable to figure 3A, now illustrating successive calibration due times tol, to^, tpB,... selected in accordance with the present invention. It is clearly shown that the time interval (tD4-tD3) between later calibration due times toS and tjyi is larger than the time interval (toS-tol) between early calibration due times tpl and tD2. In the following, time intervals between successive calibration due times toi and tD(i-l) will be IndicaWd as Atoi. In one exemplary implementation of the present invention, the time intervals Atoi have a first constant value Al for a first number of successive calibration due times and have a second, larger constant value A2 for a second number of successive calibration due times following the first number of successive calibration due times, as illustrated in figure 3C. After that, a third number of successive calibration due times can have lime intervals Atoi having a third constant value larger than the second constant value, etc. In another exemplary implementation of the present invention, the time intervals Atoi are selected such that the corresponding absolute temperature changes 'i-(T(i-1)) are substantially constant, as illustrated in figure 3B. [n figure 3B, the empcratures at times toi are indicated at Ti. ft is clearly seen in figure 3B that T4-T3 is ipproximately equal to T2-TI. In yet another exemplary implementation of the present invention, the time ntcrvals Atoi are selected such that the corresponding relative temperature changes (Ti-(T(i-l))}/T(i-l) are substantially constant. Then, (T4-T3)/T3 would be approximately squal to Cn-TOH"!, but this is not illustrated in the figures. It is possible that the calibration due times toi are determined on the basis of a measurement of the actual temperature T. However, this would involve the use of a temperature sensor, which is not preferred. In a preferred embodiment, the controller 10 comprises a timer 40 for determining calibration due times toi. Such timer can be started at the said particular event. This particular event may be, for instance, the previous recalibration due lime, or the start of the previous recalibration procedure, or the end of the previous recalibration procedure, i.e. when the previous actual calibration process has been completed. In one implementation of the present invention, a recalibration process starts immediately at a recalibration due time. In such case, the recalibration due time is the same as the starting time of the recalibration process. Two examples of this imptementaticm will be explained with reference to figures 4A-B. Figure 4A is a flow diagram schematically illustrating one m^od of determining recalibmtion due times in accordance with the pnssent invention. After start-up [step 101], an initial timer value is defined [step 102j. When a read command or write command is received [step 110] at time tO, the timer 40 is set at this initial timer value [step III], which determines the time interval Atol until the first recalibration due time to). During the write/read procedure [step 112], the timer condition is monitored [step 113]. If the timer 40 has reached the timer value, it is determined that a recalibration due time has been reached, and a recalibration process is executed [step 120]. After completion of the recalibration process, the timer value is increased with a certain timer increment [step 132], and the process is repeated, indicated as a Jump back to step 111. Thus, in this embodiment, the particular event for starting the timer for calculating the next recalibration due time is the end of Uie previous recalibration procedure. When increasing the timer value in step 132, the timer increment may always have the same value, but it is also possible that an expected temperature development characteristic like the gr^h of figure 3A-B is taken into account and the timer increment increases, such that successive absolute or relative temperature changes between successive recalibration initiation times are substantially constant, as explained above. It is also possible that the timer value is only increased up to a predefined maximum value, as illustrated by step 131 before step 132 in figure 4A. Figure SA is a timing sraph, schematically showing the timing of this example. At time toCi-l). indicated at (a), a recalibration process starts. At completion of this recalibration process, indicated at (b), the read or write process continues, and tiie new timer interval starts. At time tD{i), indicated at (c), the timer interval ends, and a next recalibration process starts. Figure 4B is a flow diagram schematically (tlustrating another method of determining recalibration due times in accordance with the present invention. After start-up [step 201], an initial timer value is defined [step 202], When a read command or write command is received [step 210] at time tO, llie timer 40 is set at this initial timer value [step 211], which determines the time interval Atpl until the first recalibration due time tol-During the write/read procedure [step 212], the timer condition is monitored [step213J. If the timer 40 has reached (he timer value, it is detCTmined that a recalibration due time has been reached. Now, the timer value is increased with a certain timer increment [step 232], and the timer 40 is set at this tinier value [step 233]. Then, a recalibration process is executed [step 220], after which the process is repeated, indicated as a jump back to step 212. Thus, in this embodiment, the particular event for starting the timer for calculating the next recalibration due time is the previous recalibration due time. When increasing the timer value in step 232, the timer increment may always have the same value, but it is also possible that an expected temperature development characteristic like the graph of figure 3A-B is teken into account and the timer increment increases, such that successive absolute or relative temperature changes between successive recalibration Initiation times are substantially constant, as explained above. It is also possible that the timer value is only increased up to a predefined maximum value, as illustrated by step 231 before step 232 in figure 4B. Figure SB is a timing graph, schematically showing the timing of this example. At time toCi-l), indicated at (a), a recalibration process starts, and also the new timer interval starts. At completion of this recalibration process, indicated at (b), the read or write process continues. At time toCi), indicated at (c), the timer interval ends, and a next recalibration process starts. In another implementation of the present invention, a recalibration process »s not necessarily start immediately at a recalibration due time. First, it is checked whether e readAvrite process should be continued and the recalibration process should be postponed itil a more suitable moment. In such case, the recalibration due time marks the beginning of check for recalibration permission conditions, while die actual recalibration process only arts when all recalibration permission conditions are fulfilled. It may even be that the actual calibration process does not start at all, because at least one of the recalibration permission 3nditions is not f\ilfilled. By way of example of a recalibration permission condition, it may be that the isc drive is currently writing data from a data buffer (in a writing mode), and that the flow f data may not be disturbed until the buffer is empty. Or, it may be that, in a reading mode, le disc drive is outputting data to the host from a buffer which is almost empty and which hould first be filled again in order to assure an undisturbed flow of data to the host. Three examples of this implementation will be explained with reference to igures 6A-C. Figure 6A is a flow diagram schematically Illustrating one method of ietermining recalibration due times in accordance with the present invention. After start-up step 301], an initial timer value is defined [step 302]. When a read command or write ;ommand is received [step 310] at time tO, the timer 40 is set at this initial timer value [step 511], which detemiines die time interval Atol until the first recalibration due time tol. During the write/read procedure [step 312], the timer condition is monitored [step 313]. If the £imer 40 has reached the timer value, it is determined that a recalibration due time ha^ been reached, and a recalibration initiation procedure is executed [step 320]. After this recalibration initiation procedure, the write/read procedure continues [step 34!], during which the recalibration pennission conditions are checked [step 342]. Only when all recalibration permission conditions are fulfilled, a recalibration process is executed [step 350]. Thus, the actual start of the recalibration process is later than the corresponding recalibration due time. After completion of the recalibration process, the timer value is increased with a certain timer increment [step 362], and the process is repeated, indicated as a jump back to step 311. Thus, in this embodiment, the particular event for starting the timer for calculating the next recalibration due time is the end of the previous recalibration procedure. When increasing the timer value in step 362, the timer increment may always have the same value, but it is also pc»sible that an expected temperature development characteristic like the graph of figure 3A-B is taken into account and the timer increment increases, such that successive absolute or relative temperature changes between successive recalibration initiation times are substantially constant, as explained above. Lt is also possible that the timer value is only increased up to a predefined maximum value, as illustrated by step 361 before step 362 in figure 6A. Figure 7A is a timing graph, schematically showing the timing of this example. At time toCi-l), indicated at (a), a recalibration process starts. At completion of this recalibration process, indicated at (b), the read or vmte process continues, and the new timer interval starts. At time toil), indicated at (c), the timer interval ends, but the read or write process continues until such time when all recalibration permission conditions are fulfilled, indicated at (d), at which moment a next recalibration process starts. Figure 6B is a flow diagram schematically illustrating another method of detennining calibration due times in accordance with the present invention. After start-up [step 401], an initial timer value is defined [step 402]. When a read command or write command is received [step 410] at time tO, the timer 40 is set at ^is initial timer value [step 411], which determines the time interval Atol until the first recalibration due time tol. During the write/read procedure [step 412], the timer condition is monitored [step 413]. If the timer 40 has reached the timer value, it is determined that a recalibration due time has been reached. Now, the timer value is increased with a certain timer increment [step 432], and the timer 40 is set at this timer value [step 433], Then, a recalibration initiation procedure is executed [step 420]. After this recalibration Initiation procedure, the write/read procedure continues [step44]], during which the recalibration permission conditions are checked [step 442]. Only when all recalibration permission conditions are fiilfiUed, a recalibration process is executed [step 450], Thus, the actual start of the recalibration process is later than the corresponding recalibration due time. After completion of the recalibration process, the process is repeated, indicated as a Jump back to step 412. Thus, in this embodiment, the particular event for starting the timer for calculating the next recalibration due time is the previous recalibration due time. When increasing the timer value in step 432, the timer increment may always have the same value, but it is also possible that an expected temperature development characteristic like tiie graph of figure 3A-B Is taken into account and the timer increment increases, such that successive absolute or relative temperature changes between successive recallbration initiation limes are substantially constant, as explained above. It is also possible that the timer value is only increased up to a predefined maximum value, as illustrated by step 431 before step 432 in figure 6B. Figure 7B is a timing graph, schematically showing the timing of this example. AttlmetD(i-l), indicated at (a), a recallbration process starts. At completion of this recallbration process, indicated at (b), the read or write process continues. At time 1^(1), indicated at (c), the timer interval ends, and the new timer interval starts, but the read or vmte process continues until such time when all recallbration permission conditions are fulfilled, indicated at (d), at which moment a next recallbration process starts. Figure 6C Is a flow diagram schematically Illustrating yet another method of determining calibration due times in accordance with the present invention. After start-up [step 501], an initial timer value is defined [step 502]. When a read command or write command is received [step 510] at time tO, the timer 40 is set at this initial timer value [step 511], which determines the time interval Atul until the first recallbration due time tol. During the write/read procedure [step 512], the timer condition is monitored [step 513]. If the timer 40 has reached the timer value, it is determined that a recallbration due time has been reached, and a recalibration initiation procedure is executed [step 520]. After this recalibration initiation procedure, the write/read procedure continues [step 541], during which the recalibration permission conditions are checked [step 542]. Only when all recalibration permission conditions are fulfilled, the timer value is increased with a certain timer increment [step 532], the timer 40 is set at this timer value [step 533], and a recalibration process is executed [step 550]. Thus, the actual start of the recalibration process is later than the corresponding recalibration due time. After completion of the recalibration process, the process is repeated, indicated as a jump back to step 512. Thus, in this embodiment, the particular event for starting the timer for calculating the next recalibration due time is the actual start of the previous recalibration process. When increasing the timer value in step 532, the timer increment may always have the same value, but it is also possible that an expected temperature development characteristic like the graph of figure 3A-B is taken Into account and the timer increment increases, such that successive absolute or relative temperature dianges between successive recalibration initiation times are substantially constant, as explained above. It is also possible that the timer value is only increased up to a predefined maximum value, as illustrated by step 531 before step 532 in figure 6C. Figure 7B is a timing graph, schematically showing the timing of this example. AttimetD(i-l), indicated at (a), a recalibration process starts. At completion of this recalibration process, indicated at (b), the read or write process continues. At time tD(i), indicated at (c), the timer interval ends, but the read or write process continues until such time when all recalibration permission conditions are flilfilled, indicated at (d), at which moment a next recalibration process starts and the new timer interval starts. In the recalibration process mentioned above, i,e. the steps 120, 220,350,450, or 550 of the above-described examples, at least one temperature-sensitive parameter is calibrated. In fact, it is possible that for each individual temperature-sensitive parameter an individual timing procedure is executed. However, it is preferred ttiat in the recalibration process all temperature-sensitive parameters are calibrated. It is even more preferred that in the recalibration process all calibrateable parameters are calibrated, i.e. that the same calibrations are performed as during the start-up procedure. Figure 2 schematically shows a diagram which illustrates a possible embodiment of the control circuit 10 in somewhat more detail. Specifically, in this embodiment, the control circuit 10 comprises a data engine system 20 and a data processing system 30. The data engine system 20, hereinafter simply indicated as "engine", provides an interne between disc drive apparatus and disc, as it handles alt incoming and outgoing communication between disc drive I and disc 2. The data processing system 30, hereinafter simply indicated as "processor". processes the data present in incoming and outgoing signals SR and Sw from and to the disc, respectively, and processes the data for communication to and from a host system such as a PC, respectively. In such design, the recalibration initiation procedure (I.e. steps 320,420 or 520 in the above examples) and the recalibration process (i.e. steps 120,220, 350, 450, or 550 in the above exampjes) may be executed by the data engine ^stem 20, whereas the recalibration permission conditions are handled by the processor 30. The recalibration initiation procedure may comprise a step of the engine 20 sending a recalibration request signal to the processor 30. When the processor 30 finds that all recalibration permission conditions are fulfilled, it may send a recalibration pennission signal to the engine 20, which. upon receiving this recalibration pennjssion signal, will enter a calibration mode (i.e. steps 350,450, or 550 in the above examples). It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that various variations and modifications are possible within the protective scope of the Invention as defmed in the appending claims. For instance, the present invention has been explained in the context of optical storage discs. However, the gist of ttie present invention is not restricted to optical storage discs, but is generally applicable to slorage devices in general. In the above, the present invention has been explained with reference to block diagrams, which illustrate functional blocks of the device according to the present invention. It is to be understood that one or more of these fiinctional blocks may be implemented in hardware, where the function of such functional block is performed by individual hardware components, but it is also possible that one or more of these functional blodcs are implemented in software, so that the function of such functional biock is performed by one or more program lines of a computer program or a programmable device such as a microprocessor, microcontroller, etc. WE CLAIM: 1. A method for timing multiple recalibration processes in a storage write/read apparatus (1) when writing/reading information into/from a storage medium (2), wherein the recalibration processes are executed more frequently during an early phase of the write/read operation than during a later phase of the write/read operation. 2. The method as claimed in claim 1, wherein the time interval between successive recalibration processes increases during the course of the write/read operation. 3. The method as claimed in claim 1, wherein at least one temperature-sensitive parameter is recalibrated in the recalibration processes. 4. The method as claimed in claim 1, wherein some parameters are calibrated during a start-up phase, and wherein the same parameters are also recalibrated in the recalibration processes. 5. The method as claimed in claim 1, the method comprising the step of calculating a recalibration due time (toCi)) on the basis of a time interval (AtD(i)) which starts at a particular event. 6. The method as claimed in claim 5, wherein recalibration due times (toCi)) are calculated such that expected absolute or relative increments of a temperature at a certain location within the disc drive apparatus in the time intervals between successive recalibration due times are substantially constant. 7. The method as claimed in claim 5, wherein the time intervals between successive recalibration due times have a first constant value during a first phase of the write/read operation, and have a second constant value during a second phase of the write/read operation, the second constant value being larger than the first constant value. 8. The method as claimed in claim 5, wherein the time intervals between successive recalibration due times increase up to a predetermined maximum value. 9. The method as claimed in claim 5, wherein increment in duration of two successive time intervals between successive recalibration due times is always substantially constant. 10. The method as claimed in claim 5, wherein a recalibration process is started substantially immediately at a recalibration due time (tofi)). 11. The method as claimed in claim 10, wherein said particular event substantially coincides with a previous recalibration due time (toCi)). 12. The method as claimed in claim 10, wherein said particular event substantially coincides with the end of a previous recalibration process. 13. The method as claimed in claim 5, wherein, at a recalibration due time (tD(i)), a check is made regarding predetermined recalibration permission conditions, and the start of an actual recalibration process is postponed until such time when all said predetermined recalibration permission conditions are fulfilled. 14. The method as claimed in claim 13, wherein the write/read operation is continued until the start of an actual recalibrafion process. 15. The method as claimed in claim 13, wherein said particular event substantially coincides with a previous recalibration due time (tD(i)). 16. The method as claimed in claim 13, wherein said particular event substantially coincides with the end of a previous recalibration process. 17. The method as claimed in claim 13, wherein said particular event substantially coincides with the actual start of a previous recalibration process. 18. A Storage write/read apparatus (I) for writing/reading information into/from a storage medium (2), the apparatus being designed for performing the method as claimed in any of the previous claims. 19. The storage write/read apparatus (1) as claimed in claim 18, the apparatus being a disc drive apparatus for writing/reading information into/from a storage disc (2), for instance an optical storage disc. 20. A storage write/read apparatus (1) for writing/reading information into/from a storage medium (2), the apparatus being designed for performing the method as claimed in claim 13, the apparatus comprising a control circuit (10) designed to perform multiple recalibration processes during a write or read process; the apparatus comprising a data engine system (20) and a data processing system (30) in data communication with each other; wherein the data engine system is designed, in a reading mode, for receiving read signals (SR), deriving data signals from the read signals, and communicating the data signals to the data processing system, and in a writing mode, for receiving data signals from the data processing system and generating write signals (SW); wherein the data processing system is designed, in a reading mode, for receiving data signals from the data engine system and processing the data for communication to a host system (H), and in a writing mode, for communication with a host system, processing data signals in the communication signals received from the host system, and communicating data signals to the data engine system; wherein the data engine system is designed for calculating the recalibration due times, and wherein the data processing system is designed for determining the recalibration permission conditions.

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