WO2012025973A1 - Method of recording data on multi-layer optical disc and optical disc device - Google Patents

Abstract

The present invention is a data recording method that records data onto a multi-layer optical disc, which comprises a plurality of information recording layers, the number of such layers being N (where N is an integer greater than one). The kth information recording layer away from the bottom end side of a multi-layer optical disc (where k is an integer that satisfies the formula 1 ≤ k ≤ N) is treated as information recording layer k. The method comprises: step A (distinguish disc), wherein the number of information recording layers of an optical disc that is loaded into an optical disc device is obtained; step B (execute OPC), wherein, when the number of layers is X (where X is an integer greater than one), a test data recording is carried out in a test recording region and a tentative initial beam power determined in an information recording layer m (where m is an integer that satisfies the formula 1 ≤ m ≤ X-1); step C, wherein a correction coefficient is selected according to which information recording layer is the target information recording layer wherein data is to be recorded, and the tentative initial recording beam power is corrected on the basis of the selected correction coefficient, setting an initial recording beam power; and step D, wherein data recording commences on the target information recording layer at the initial recording beam power.

Description

Data recording method for multilayer optical disc and optical disc apparatus

The present invention relates to a data recording method performed on a multilayer optical disc having a plurality of information recording layers. The present invention also relates to an optical disk apparatus that executes this data recording method.

The data recorded on the optical disc is reproduced by irradiating a relatively weak light beam of constant intensity onto the rotating optical disc and detecting the reflected light modulated by the optical disc. Information in the form of pits is recorded in advance spirally on the reproduction-only optical disc at the manufacturing stage of the optical disc. On the other hand, in the case of a rewritable optical disc, a recording material film capable of optically recording / reproducing data is deposited by a method such as vapor deposition on the surface of a base material on which a track having a spiral land or groove is formed. It is done. When recording data on a rewritable optical disk, the optical disk is irradiated with a light beam whose light intensity is modulated according to the data to be recorded, thereby locally changing the characteristics of the recording material film, thereby writing the data. Do.

The pit depth, track depth, and recording material film thickness are smaller than the thickness of the optical disk substrate. Therefore, the portion of the optical disc on which the data is recorded constitutes a two-dimensional surface, and may be referred to as a "recording surface" or an "information surface". In the present specification, in view of the fact that such a surface has a physical size in the depth direction, instead of using the term "recording surface (information surface)", "information recording layer" We will use the words The optical disc has at least one such information recording layer. One information recording layer may actually include a plurality of layers such as a phase change material layer and a reflective layer.

In a recordable optical disc or a rewritable optical disc, when recording data in the information recording layer, the crystalline phase change material layer is formed by irradiating the information recording layer with a light beam whose light intensity is modulated as described above. An amorphous recording mark is formed. This amorphous recording mark is formed by rapid cooling after a portion of the information recording layer irradiated with the recording light beam rises to a temperature above the melting point. When the light intensity when irradiating the light beam to the recording mark is set lower, the temperature of the recording mark irradiated with the light beam does not exceed the melting point, and returns to the crystalline state after rapid cooling (erasing of the recording mark). In this way, it is possible to rewrite the recording mark many times. If the magnitude of the light intensity (recording light power) of the light beam when recording data is inadequate, the shape of the recording mark may be distorted, making it difficult to reproduce the data.

Since the reflectance of the amorphous recording mark is different from the reflectance of the surrounding crystalline portion, the intensity of the reflected light at the time of reproduction changes depending on the presence or absence of the recording mark. In the area in which data is recorded (recorded area), there are lines of recording marks and spaces having different lengths according to the content of the data to be recorded. Therefore, the optical characteristics (light reflectance and transmittance) of the recorded area are different from the optical characteristics of the area (unrecorded area) in which the data is not recorded.

When reproducing data recorded on an optical disk or recording data on a recordable optical disk, it is necessary for the light beam to be always in a predetermined focused state on a target track in the information recording layer. For this purpose, "focus control" and "tracking control" are required. The "focus control" refers to the position of the objective lens in the normal direction of the information surface (hereinafter referred to as "the substrate depth direction" so that the position of the focal point (focusing point) of the light beam is always located on the information recording layer. There is a case) to control. On the other hand, tracking control is to control the position of the objective lens in the radial direction of the optical disc (hereinafter referred to as “disc radial direction”) so that the spot of the light beam is positioned on a predetermined track.

In order to perform the focus control and the tracking control described above, it is necessary to detect a focus shift or a track shift based on the light reflected from the optical disc and adjust the position of the light beam spot so as to reduce the shift. It is. The magnitudes of defocusing and tracking deviation are respectively indicated by "focus error (FE) signal" and "tracking error (TE) signal" generated based on the reflected light from the optical disc.

In recent years, an optical disc in which two information recording layers are stacked is put on the market, and a multilayer optical disc in which three or more information recording layers are stacked is being developed. In the present specification, an optical disc in which N layers (N is an integer of 2 or more) are stacked will be referred to as a "multilayer optical disc".

When reproducing data from the target information recording layer of a multilayer optical disc or writing data into the target information recording layer, the optical disc apparatus aligns the focus position of the light beam on the target information recording layer, It is necessary to form a small light spot on the information recording layer. Since a plurality of information recording layers exist in one multi-layered optical disc, for example, when the focus position of the light beam is aligned with the information recording layer located farthest, the light beam passes through the information recording layer located in front. It will be.

If the light beam intensity (recording light power) at the time of writing the data is not optimized, as described above, the shape of the recording mark becomes inappropriate, and the rate of the reproduction error becomes high. In order to optimize the recording light power, it is performed to record a plurality of data with different recording light powers in the test recording area of the information recording layer of the optical disc and reproduce the data. Thus, an index such as a reproduction error is measured in the test recording area, and the recording light power indicating the most preferable value of the index is determined. Strictly speaking, such optimization of the recording light power is optimization of the “initial recording light power”. After recording of data in the user area is started with the initial recording light power determined by the above method, the recording light power is more appropriately determined from the initial recording light power, for example, based on the β value described later. Can be corrected. In the present specification, the processing performed by the optical disk device to determine the initial recording light power in the test recording area is referred to as optimum power control (OPC).

FIG. 1A is a view showing a multilayer optical disc 10, and FIG. 1B is a schematic cross-sectional view thereof. The multilayer optical disc 10 shown in FIG. 1 includes a first information recording layer L0 located farthest from the disc surface 10a on which the light beam is incident, and a second information recording layer L1 closest to the disc surface 10a. ing. The multilayer optical disc 10 is provided with a user data area in which user data is recorded, and a test recording area (PCA: Power Calibration Area) located on the inner peripheral side of the user area. The multilayer optical disc 10 is also provided with a management area other than PCA, but is not shown in FIG. 1 for the sake of simplicity.

FIG. 2 is a view showing a part of the cross section of the multilayer optical disc 10 shown in FIG. 1 (b) in more detail. In FIG. 2, light beams focused on three different regions a, b and c in the information recording layer L0 are schematically shown. The area a is an area (unrecorded area) in which data is not recorded in any of the information recording layers L0 and L1 in the PCA. Similarly, the area b is an area (unrecorded area) in which data is not recorded in any of the information recording layers L0 and L1 in the user data area. On the other hand, the area c is an area (recorded area) in which data is recorded in the information recording layer L1 in the user data area.

The light transmittance of the region where data is recorded in the information recording layer L1 is different from the light transmittance of the region where data is not recorded. In many optical disks, the light transmittance of the area where data is recorded is lower than the light transmittance of the area where data is not recorded. For this reason, the light beam focused on the information recording layer L0 in the region c is transmitted through the portion where the light transmittance is relatively lowered in the information recording layer L1. As a result, the intensity of the light beam on the information recording layer L0 is lower in the area c than in the area b.

Thus, the amount of light that the light beam focused on the information recording layer L0 can be given to the information recording layer L0 is on the information recording layer L1 located in front of the information recording layer L0 (closer to the disk surface). It will change depending on whether or not the data is recorded.

FIG. 3 is a graph showing the relationship between the error rate and the recording light power when the data recorded in the information recording layer L0 is reproduced. The horizontal axis of the graph is the recording light power (power), and the vertical axis is the error rate during reproduction (error rate of L0). In FIG. 3, curves showing the results in the regions a and b which are unrecorded regions shown in FIG. 2 and curves showing the results in the region c which is the recorded region shown in FIG. 2 are described.

As can be seen from FIG. 3, in the regions a and b, when the recording light power is PWb, the error rate is minimized. That is, it is understood that it is preferable to set the recording light power to PWb in the unrecorded area (areas a and b). On the other hand, in the region c, the error rate is minimized when the recording light power is PWc. That is, in the recorded area (area c), it is preferable to set the recording light power to PWc larger than PWb. As described above, in the area c which is a recorded area, it is preferable to write data with a recording light power higher than the recording light power for the areas a and b which are unrecorded areas.

Conventionally, when data is recorded at a specific address position in a user data area of an optical disc, it is unclear whether the position is in a recorded area or in an unrecorded area. Therefore, the initial recording light power at the time of starting to record data is set to the optimum value (PWb in the example of FIG. 3) in the unrecorded area. In this case, after recording of data is started in the user data area, while the data is reproduced at short time intervals, correction of recording light power is performed based on the index indicating the waveform of the reproduction signal.

FIG. 4A is a view showing a cross section of the multilayer optical disc 10, and corresponds to FIG. FIG. 4B is a diagram showing temporal transition due to the correction of the recording light power when the initial recording light power PWb starts recording data in the area b which is an unrecorded area. On the other hand, FIG. 4C is a diagram showing a temporal transition due to the correction of the recording light power when the data is started to be recorded in the area c which is the recorded area with the initial recording light power PWb.

In the example of FIG. 4B, the recording light power is held at PWb which is the optimum value in the region b. On the other hand, in the example of FIG. 4C, the correction is performed so that the recording light power increases toward the optimum value PWc in the region c.

As the number of information recording layers provided in the multilayer optical disc increases, for example, when the information recording layer L0 located at the far end is in focus, the number of information recording layers located in front of it increases to 2 or more. . For this reason, in the recorded areas where data is recorded in the plurality of information recording layers positioned in front of them, the decrease in light transmittance becomes remarkable.

FIG. 5A is a schematic cross-sectional view of a multilayer optical disc provided with three information recording layers L0, L1, and L2. FIG. 5B is a diagram showing temporal transition due to the correction of the recording light power when the initial recording light power PWb starts recording data in the area b which is an unrecorded area. On the other hand, FIG. 5C is a diagram showing a temporal transition due to the correction of the recording light power when the data is started to be recorded in the area e which is the recorded area with the initial recording light power PWb.

In the example of FIG. 5C, the recording light power is corrected to increase toward the optimum value PWe in the region e, but a longer time is required to reach the optimum value PWe. It is thought that there is. The reason is that, in the area e, since data are recorded in both of the two information recording layers L1 and L2, the degree of decrease in light transmittance due to them is large, and the optimum value PWe of the recording light power in the area e is This is because there is a possibility that they are significantly different from the optimum value PWb of the recording light power in the regions a and b.

In the future, it is expected that the number of information recording layers included in the multilayer optical disc will further increase, for example, to four or more. Even in such a multilayer optical disc, when data recording is started with the recording light power PWb optimized in the area a which is an unrecorded area, the problem that the recording light power can not be corrected to a more preferable size in a short time is there. Thus, Patent Document 1 discloses a technique of performing OPC using PCA for each of the possible combinations of the recorded area and the unrecorded area.

Patent Document 2 determines the recorded area or unrecorded area by managing the addresses of the recorded area and the unrecorded area in addition to the disclosed contents of Patent Document 1, and the initial recording is performed according to the judgment result. A technique for changing the optical power is disclosed.

JP 2008-108388 A JP 2008-192258 A

According to the technique of Patent Document 1, many parts are consumed for test recording in PCA, and the time required for test recording also increases. These have the problem that they increase geometrically as the number of layers of the optical disk increases.

According to the technology of Patent Document 2, management of the recorded area / unrecorded area in each information recording layer is performed based on the address, so that positional deviation (sticking error) occurs in the upper and lower information recording layers to be stacked. The positions of the recorded area and the unrecorded area can not be accurately determined based on the address. For example, when recording data at a specified address position of the information recording layer L0, an area before the address position in the information recording layer L1 is determined based on the address, and whether data is recorded in the area If there is a physical deviation between the information recording layer L0 and the information recording layer L1, the correspondence based on the address may not be correct.

As described above, Patent Documents 1 and 2 both have problems and are not practical. Therefore, the inventor did not seek the best recording characteristics as a concept not disclosed in either of Patent Documents 1 and 2, but considered that it would be acceptable if the recording characteristics could be guaranteed within an acceptable range. That is, the first initial optimum recording light power for recording data under the condition where data is not written in all other information recording layers in the multilayer optical disk, and the data is written in all other information recording layers in the multilayer optical disk The initial recording light power is determined so as to be located between the second initial optimum recording light power for recording data under the situation where the data is recorded, and after the initial recording using the initial recording light power, The concept of dynamically changing the recording light power is adopted accordingly. According to this concept, PCA is not increased according to the number of layers of the optical disc, and the recording characteristics can be guaranteed within an allowable range regardless of whether the other layer is a recorded area or an unrecorded area.

The present invention has been made to solve the above-mentioned problems, and its main purpose is to correspond to the position where the data is recorded and the thickness direction when the data is recorded in the user data area, and to the data The present invention provides a data recording method that can be promptly corrected to the optimum size regardless of whether the position in the other information recording layer located in front of the information recording layer on which the information is recorded is within the recorded area or the unrecorded area. It is. Another object of the present invention is to provide an optical disc apparatus which executes the data recording method.

A data recording method according to the present invention is a data recording method for recording data on a multilayer optical disc provided with a plurality of information recording layers having N layers (N is an integer of 2 or more). Step k for determining the number of information recording layers provided in the optical disc loaded in the optical disc device, where k is the kth information recording layer (k is an integer satisfying 1 ≦ k ≦ N); When the number of layers is X (X is an integer of 2 or more), data is stored in the test recording area in the m-th information recording layer (m is an integer satisfying 1 ≦ m ≦ X−1) on which test recording is performed. Test recording, the step B of determining the temporary initial recording light power, the target information recording layer for recording the data, the correction coefficient is selected according to the information recording layer, and the selected correction The provisional first based on the factor Comprising a step C of determining the initial recording optical power of the recording light power is corrected, and a step D to start recording data on the target information recording layer in the initial recording light power.

In one embodiment, when the number of layers is X (X is an integer of 2 or more), the step B satisfies an m-th information recording layer (m satisfies 1 ≦ m ≦ X−1) on which test recording is performed. Data is recorded in an unrecorded area in which data is not written in all the information recording layers from the (m + 1) th information recording layer to the Xth information recording layer among the test recording areas in the integer). A tentative initial recording light power is determined.

In one embodiment, the step C selects the correction coefficient depending on the type of the optical disk loaded in addition to the information recording layer of the target information recording layer.

In one embodiment, for each of the information recording layers provided in each of the multilayer optical disks supported by the optical disk device, correction coefficient information in which the value of the correction coefficient is given for each type of multilayer optical disk is recorded in the memory of the optical disk device. Including the step of

In one embodiment, the initial recording light power determined in the step C is larger than the provisional initial recording light power in the case of a light transmittance reduced type multilayer optical disc.

In one embodiment, after starting recording data in the step D, the method further includes the step of changing the recording light power from the initial recording light power as needed based on the signal waveform obtained from the optical disc.

In one embodiment, after starting recording data in the step D, the recording light power is adjusted so that the β value indicating the symmetry of the signal amplitude related to the average value of the reproduction signal obtained from the optical disc approaches the target β value. The method further includes the step of correcting.

In one embodiment, m = 1.

An optical disc apparatus according to the present invention is an optical disc apparatus for recording data on a multilayer optical disc comprising a plurality of information recording layers having N layers (N is an integer of 2 or more), and optically accesses the multilayer optical disc An optical pickup, a memory for storing correction coefficient information to which a correction coefficient value is given for each type of multilayer optical disc for each information recording layer included in each multilayer optical disc supported by the optical disk device, and loaded multilayer After performing test recording of data in a test recording area in a certain information recording layer included in an optical disc and determining a tentative initial recording light power, what number information recording layer is the target information recording layer for recording data? Select the correction coefficient from the memory according to the correction, and correct the provisional initial recording light power based on the selected correction coefficient. And a recording processing unit for determining the period recording optical power.

According to the present invention, when data is recorded in the user data area, another information recording layer corresponding to the position where the data is recorded and the thickness direction and located in front of the information recording layer in which the data is recorded It is possible to provide a data recording method that can be corrected to the optimum size promptly regardless of whether the position in the recording area is within the recorded area or the unrecorded area.

(A) is a figure which shows the multilayer optical disk 10, (b) is the cross-sectional schematic diagram. It is a figure which shows a part of cross section of the multilayer optical disk 10 shown in FIG.1 (b) in more detail. It is a graph which shows the relationship between the error rate at the time of reproducing | regenerating the data recorded on the information recording layer L0, and recording light power. The horizontal axis of the graph is the recording light power (power), and the vertical axis is the error rate at the time of reproduction (error rate of the information recording layer L0). (A) is a schematic cross-sectional view of a multilayer optical disc provided with two information recording layers L0 and L1, (b) is an information recording layer L0 of an area b where the information recording layer L1 is an unrecorded area with an initial recording light power PWb. (C) shows the information recording layer L0 of the area c where the information recording layer L1 is the recorded area at the initial recording light power PWb when the recording light power is corrected when the data recording is started. FIG. 7 is a diagram showing a temporal transition due to the correction of the recording light power when the recording of data is started. (A) is a schematic cross-sectional view of a multilayer optical disc provided with three information recording layers L0, L1, and L2, (b) is an unrecorded area of the information recording layer L1 and the information recording layer L2 at an initial recording light power PWb The figure which shows the time transition by correction | amendment of recording light power when recording data in the information recording layer L0 of the area | region b, (c) is the information recording layer L1 and the information recording layer L2 by initial recording light power PWb. The figure which shows a temporal transition by correction | amendment of recording light power at the time of starting recording data in the information recording layer L0 of the area | region e which is a recorded area, (d) is with information recording layer L1 by initial recording light power PWmid. The figure which shows a time transition by correction | amendment of recording light power when the information recording layer L2 starts recording data in the information recording layer L0 of the area | region b which is an unrecorded area | region, (e) is initial recording light power PWmid. With information recording layer L1 It is a timing chart showing a sequence by the correction of the recording light power when the broadcast recording layer L2 begins to record data on the information recording layer L0 of the region e is recorded area. (A) is a schematic cross-sectional view of a multilayer optical disc provided with three information recording layers L0, L1, L2, (b) is an error when data recorded in the information recording layer L0 is reproduced in the case of a three-layer optical disc It is a graph which shows the relationship between a rate and recording light power. (A) is a schematic cross-sectional view of a multilayer optical disc provided with three information recording layers L0, L1 and L2 in which the light transmittance of the recorded area is higher than the light transmittance of the unrecorded area; (b) is this three-layer It is a graph which shows the relationship between the error rate at the time of reproducing | regenerating the data recorded on the non-information recording layer L0 in an optical disk, and recording light power. (A) is a schematic cross-sectional view of a multilayer optical disc provided with four information recording layers L0, L1, L2, and L3, and (b) is a case where data recorded in the information recording layer L0 in the case of a four-layer optical disc is reproduced. Is a graph showing the relationship between the error rate of and the recording light power. It is a table which shows an example of a correction coefficient. It is a graph which shows typically the waveform of the reproduction | regeneration signal (RF signal) obtained from the area | region where data were recorded. It is a graph which shows the relationship of the error rate when recording the data recorded on the information recording layer L0 in the case of 3 layer optical disk, and recording light power. It is a graph which shows typically the relationship between (beta) value and recording light power. It is a block diagram showing an example of composition of an embodiment of an optical disk device by the present invention. It is a flowchart which shows an example of the power setting method in this embodiment. It is a flowchart which shows the prior art example of the power setting method. It is a flowchart which shows an example of the data recording method in this embodiment. It is a figure which shows typically the cross section of an optical disk to which sensitivity falls toward an outer peripheral side from the disk inner peripheral side. It is a graph which shows the relationship between the error rate in area | region a, b, b ', e, e', and recording light power. It is a graph which shows the relationship between (beta) value and recording light power in area | region a, b, b ', e, e'. FIG. 7 is a diagram showing an example of changes in the β value, recording light power, and error rate when data is recorded in the regions e, b, c, d, e, b in the embodiment of the present invention. In the embodiment of the present invention, the β value, recording light power, and error rate in the case of recording data in the regions e ′, b ′, c ′, d ′, e ′, b ′ relatively lower in sensitivity than PCA It is a figure which shows an example of a change of.

The data recording method of the present invention is a method of recording data on a multilayer optical disc provided with a plurality of information recording layers in which the number of layers is N (N is an integer of 2 or more). Here, the k-th (k is an integer satisfying 1 ≦ k ≦ N) information recording layer from the information recording layer on the innermost side (position far from the light incident surface) of the multilayer optical disc is used as the k-th information recording layer. . For example, in the case of the three-layered optical disc shown in FIG. 5A, the information recording layer L0 is the "first information recording layer" and the information recording layer L1 is the "second information recording layer". When the total number of layers of the multilayer optical disc is X (X is an integer of 2 or more), a test recording area in the m-th information recording layer (m is an integer satisfying 1 ≦ m ≦ X−1) on which test recording is performed Among the above, an area in which data is not written in all the information recording layers from the (m + 1) th information recording layer to the X-th information recording layer is referred to as “unrecorded area”. In the following description, the information recording layer on which test recording for OPC is performed is the “first information recording layer” located at the far end, but the present invention is not limited to this example. For example, test recording for OPC may be performed in the second information recording layer, or test recording for OPC may be performed in each information recording layer.

First, the basic operation principle of the present invention will be described with reference to FIGS. 5 (d) and 5 (e). In the present invention, as shown in FIGS. 5D and 5E, an intermediate value (PWmid) of the recording light power in the area b and the area e is used as the initial recording light power. Therefore, in any of the area b and the area e, after the start of data recording, correction to the optimum power is required based on, for example, the β value. However, it becomes possible to reduce the time required to complete such correction. The correction based on the β value is sometimes referred to as running optimum power control (ROPC) to distinguish it from the OPC performed in PCA.

The initial recording light power at the start of the above data recording can be obtained by multiplying the “provisional initial recording light power” by a correction coefficient to be described later. The “provisional initial recording light power” is the optimum value (Pwa = PWb) of the recording light power obtained by performing the OPC in the unrecorded area in the test recording area.

In current optical disk technology, while forming one recording mark by light beam irradiation, the light intensity of the light beam is not constant but changes like a pulse. The type of pulse waveform used to form the recording mark is determined by the write strategy. The “recording light power” in the present specification means the peak value of each pulse constituting the recording light beam. The peak value of each pulse is common to one recording mark.

Next, the relationship between the initial recording light power and the provisional initial recording light power (PWa = PWb) will be described with reference to FIGS. 6 (a) and 6 (b). FIG. 6 relates to an optical transmission reduced type optical disc in which the light transmission of the recorded area is lower than the light transmission of the unrecorded area. FIG. 6 (a) is a diagram corresponding to FIG. 5 (a), and FIG. 6 (b) is an error rate when data recorded in the non-information recording layer L0 is reproduced in the case of a three-layer optical disc. It is a graph which shows a relation with recording light power. In FIG. 6B, a curve showing the results in the areas a and b which are unrecorded areas and a curve showing the results in the area e which is a recorded area are described. A similar curve can also be obtained by changing the error rate to jitter on the vertical axis.

As can be seen from FIG. 6B, in the regions a and b, the error rate becomes the minimum value when the recording light power is PWb. On the other hand, in the area e, the error rate becomes the minimum value when the recording light power is PWe. In the example of FIG. 6B, the minimum value of the error rate is the level R1. When data is recorded in the area e with the recording light power set to PWb, the error rate at the time of reproduction reaches the level R2. Similarly, when data is recorded in the area b with the recording light power set to PWe, the error rate at the time of reproduction reaches the level R2. If the level R2 exceeds the reproduction limit, the data recording is performed in a state where the reproduction can not be normally performed when the data recording is started.

In the graph of FIG. 6 (b), the curves showing the results in the regions a and b have the same shape as the curves showing the results in the region e for the sake of simplicity, but the actual curves are different. Also good. In that case, the local minimum of the curve showing the result in the regions a, b is not equal to the local minimum of the curve showing the result in the region e.

In the embodiment of the present invention, the recording light power at the start of data recording is set not to PWb but to PWmid (= PWb × correction coefficient). In the example of FIG. 6B, the correction coefficient is a numerical value larger than one. As can be seen from FIG. 6B, when data is recorded in the area b with the recording light power set to PWmid, the error rate at the time of reproduction becomes the level R3. Similarly, even if data is recorded in the area e with the recording light power set to PWmid, the error rate at the time of reproduction is suppressed to the level R3. As a result, even when data is recorded in any of the areas b and e, it is possible to prevent the data from being recorded in a bad state so as to exceed the reproduction limit.

Furthermore, according to the present embodiment, when data recording is started, the difference between the initial value and the optimum value of the recording light power, that is, the value of “PWe-PWmid” or “PWmid-PWb” is “PWe-PWb”. It is smaller than enough. Therefore, it also becomes possible to shorten the time required for the subsequent correction based on the β value. This is apparent when FIG. 5 (c) is compared with FIGS. 5 (d) and 5 (e). In the examples of FIGS. 5D and 5E, even when data is recorded in any of the areas b and e, correction based on the β value is necessary, but the time required for the correction is shown in FIG. 5C. It won't be too long like the example.

Next, FIGS. 7A and 7B will be referred to. FIG. 7 relates to a light transmittance increasing type optical disc in which the light transmittance of the recorded area is higher than the light transmittance of the unrecorded area. In such an optical disc, in the area e which is a recorded area, it is possible to form a recording mark of a preferable shape with lower recording light power than the areas a and b which are unrecorded areas. In this case, the optimum value PWe in the recorded area is smaller than the optimum value PWb in the unrecorded area. Also in the example shown in FIG. 7, in the present embodiment, the recording light power is set to PWmid (= PWb × correction coefficient). The correction coefficient at this time is smaller than one.

Next, FIGS. 8A and 8B will be referred to. FIG. 8A schematically shows a cross section of a four-layer disc, and relates to an optical transmission reduced type optical disc. In an area f which is a recorded area, data is recorded in three information recording layers L1, L2, and L3. FIG. 8 (b) is a graph showing the relationship between the error rate and the recording light power when data recorded in the information recording layer L0 is reproduced in the case of a four-layer optical disc, which is an area a which is an unrecorded area, A curve showing the result in b and a curve showing the result in the area f which is a recorded area are described.

In the example shown in FIG. 8B, the difference between the optimum values PWf and PWb of the recording light power is large. Therefore, the correction coefficient by which PWb is multiplied to obtain the intermediate value PWmid also becomes relatively large.

FIG. 9 is a table showing an example of the correction coefficient. In the example shown in FIG. 9, since there are differences in the structure and materials of the optical disc among the disc manufacturers, the correction coefficients are set to different values. The value of the correction coefficient also changes depending on how many information recording layers are present before the information recording layer for which data is to be recorded. For example, in the case of a BD-R triple-layer disc manufactured by company A, when recording data in the information recording layer L0, the correction coefficient is 1.30, but data is recorded in the information recording layer L1 of the same optical disc The correction factor is 1.15. The reason is as follows.

When recording data in the information recording layer L0, two information recording layers L1 and L2 exist in front of the information recording layer L0. Therefore, the light beam focused on the information recording layer L0 is transmitted through the two information recording layers L1 and L2. On the other hand, when recording data in the information recording layer L1, only one information recording layer L2 exists in front of the information recording layer L1. Therefore, the light beam focused on the information recording layer L0 passes through only one information recording layer L2. The less the information recording layer passes through, the smaller the absolute value of the difference between the optimum value PWe in the recorded area and the optimum value PWb in the recorded area. As a result, the value of the intermediate value PWmid can be set to a value close to PWb, and the correction coefficient also approaches 1. When the total number of layers in the multilayer optical disc apparatus is X (X is an integer of 2 or more), the correction coefficient when recording data in the X-th information recording layer may be 1.

As described above, since the correction factor depends on the type of multilayer optical disc including the above-described disc type, it is necessary to determine the correction factor for each different type of optical disc in advance. For this purpose, test recording is performed on a plurality of optical disks of different types, and the relationship between the index (for example, error rate or jitter) of the reproduced signal and the recording light power is measured. It is necessary to determine PWb. Furthermore, the correction coefficient (PWmid / PWb) is calculated by determining PWmid for each information recording layer of the optical disc. Thus, for example, data of the correction coefficient shown in FIG. 9 can be obtained. The magnitude of PWmid may be determined by, for example, two curves as shown in FIG. 6B by test recording, and the median value of the minimum values PWb and PWe of these curves may be determined by calculation. However, PWmid does not necessarily have to be equal to (PWb + PWe) / 2, and may be between minimum values PWb and PWe.

The data of the correction coefficient is preferably stored in a memory included in the optical disk device. The correction coefficient stored in the memory of the optical disc drive can be updated, for example, via communication and broadcasting, for an optical disc that is to be newly manufactured after the optical disc drive is purchased by the user. Also, the correction coefficient for each optical disc may be recorded on the optical disc itself. In that case, the optical disk apparatus may read out the data of the correction coefficient from the loaded optical disk and calculate the initial recording light power using the correction coefficient.

The optical disk apparatus in the preferred embodiment of the present invention determines the type of the optical disk loaded in the optical disk apparatus in order to appropriately select the “correction coefficient” used when calculating PWmid from PWb. Then, the correction coefficient most suitable for the optical disc is read out from a memory in which data as shown in FIG. 9 is recorded, for example. If there is no corresponding disk in the memory, the disk is updated at that time, or the correction coefficient of the disk having the same number of recording layers is substituted. The type of the optical disc may be determined by any known method, but the type of the optical disc may be determined by reading disc information from the management area of the reference layer (for example, the information recording layer L0).

Next, the β value will be described with reference to FIG. FIG. 10 is a graph schematically showing the waveform of a reproduction signal (RF signal) obtained from the area where data is recorded. Assuming that the upper and lower amplitudes are P and B with reference to the average value A of the RF signal, the β value is represented by (P−B) / (P + B). The higher the upper and lower symmetries with respect to the average value A, the closer to zero the β value. In the example shown in FIG. 10, since P> B, the β value is positive. If P <B, the β value is negative.

In the present specification, the β value obtained when the shape or size of the recording mark is optimum will be described as “β_best”. In a preferred embodiment of the present invention, the recording light power is corrected from the initial setting value (PWmid) to another value using the β value as an index. This correction changes the recording light power so as to reduce the β value when the β value is larger than β_best. When the β value is smaller than β_best, the recording light power is changed so as to increase the β value. Thus, the correction of the recording light power is performed so that the β value becomes approximately equal to β_best. Such correction of recording light power is performed in the process of recording user data in the user data area.

Next, the relationship between the β value and the recording light power will be described with reference to FIG. 11 and FIG. FIG. 11 is a graph corresponding to FIG. In FIG. 11, the lower limit PWlow and the upper limit PWhigh which define the range of the recording light power at which the error rate is equal to or less than the reproduction limit are described. Also, the error rates b_PWb and e_PWb at the optimum value PWb of the recording light power in the unrecorded area, the error rates e_PWe and b_PWe at the optimum value PWe of the recording light power in the recorded area, and the error rate e_PWmid at the intermediate value PWmid of both recording light powers , B_PWmid are also shown.

The PWmid may be set equal to the average value of the recording light powers PWlow and PWhigh which become the reproduction limit. When the shape of the curve shown in FIG. 11 is significantly asymmetrical, it is preferable to use, as PWmid, an average value of the recording light powers PWlow and PWhigh, which become the reproduction limit. The intermediate value does not have to be an average value in a strict sense, and is preferably a value as far as possible from both the upper limit value and the lower limit value of the recording light power as the reproduction limit. For example, when the left part of the curve in FIG. 11 is sharp and the right part has a gentle shape, recording data in area e with the recording light power of the average value of PWb and PWe may exceed the reproduction limit. Becomes higher. However, if the average value of PWlow and PWhigh is set to Pmid and data is recorded with the recording light power of that size, it becomes easy to realize reproducible recording in both the area b and the area e.

The setting of PWmid is performed in advance for each optical disc. That is, for various optical disks, the relationship between the recording light power and the error rate needs to be obtained by measurement in both the unrecorded area and the recorded area. The correction coefficient (PWmid / PWb) is obtained by calculating how many times the minimum value PWb (= PWa) obtained in the unrecorded area is obtained by multiplying the minimum value PWb (= PWa) by the above method. On the other hand, in the OPC performed when the optical disc is loaded into the optical disc apparatus, the test recording may be performed only in the unrecorded area in the PCA of the optical disc. That is, in the OPC, the PWmid can be obtained by multiplying the PWb obtained in the unrecorded area by the correction coefficient.

The method of obtaining PWmid is not limited to the case of multiplying PWb by the correction coefficient. The PWe may be obtained in the recorded area of the PCA, and the PWmid may be calculated from the PWe. In that case, the value of PWmid / PWe is obtained in advance as a correction coefficient, and stored in the memory.

FIG. 12 is a graph schematically showing the relationship between the β value and the recording light power. The straight line which shows the relation in field a and b and the straight line which shows the relation in field e are described. In regions a and b, the β value is equal to β_best when the recording light power is PWb, whereas in region e, the β value is equal to β_best when the recording light power is PWe. In any region, the β value increases as the recording light power increases. This is because B in FIG. 10 tends to decrease as the recording light power increases. In FIG. 12, β_b_PWlow and β_e_PWhigh, which are β values at the time of the regeneration limit, are also shown.

Next, referring to FIG. 13, an exemplary configuration of the embodiment of the optical disc apparatus according to the present invention will be described.

The optical disk apparatus of the present embodiment includes an optical head 11 for optically accessing the optical disk 10, a front end processor (FEP) 20 connected to the optical head, and a laser drive circuit 30.

The optical disc 10 is a recordable optical disc. Examples of such optical disks include BE-R and BD-RE. When the optical disc 10 is inserted into the optical disc apparatus, the optical disc 10 is rotated by a motor (not shown), and then the optical head 11 emits a light beam to the optical disc 10.

The optical head 11 includes a laser light source (not shown) that emits a light beam and a light detector (not shown) that receives the reflected light from the optical disk 10.

The FEP 20 receives a signal output from the optical head 11 and performs amplification and waveform equalization on this signal. The FEP 20 outputs the processed analog signal to the reproduction processing unit 21. The reproduction processing unit 21 converts an analog signal received from the FEP 20 into a digital signal. The decoder 22 reproduces and outputs user data (for example, video data) recorded on the optical disc 10 by demodulating the digital signal received from the reproduction processing unit 21.

The laser drive circuit 30 drives the laser light source in the optical head 11 according to the recording waveform received from the recording processing unit 31 and causes the optical head 11 to emit a light beam. The recording processing unit 31 receives a recording signal from the encoder 32 and sets a recording waveform. When recording user data on the optical disc 10, the encoder 32 receives data to be recorded (for example, video data), modulates the data to generate an encoded recording signal, and inputs the generated recording signal to the recording processing unit 31. Do.

The target β value storage memory 23 receives the target β value obtained by test recording after the OPC from the reproduction processing unit 21 and holds it. The target β value is used for laser power correction during the recording operation.

The optical disk apparatus of the present embodiment includes a target β value storage memory 23 and a correction coefficient storage memory 33. The target β value storage memory 23 receives the target β value obtained by test recording after OPC from the reproduction processing unit 21 and holds it. As described above, this target β value is used to correct the recording light power during recording of user data. On the other hand, the correction coefficient storage memory 33 stores the correction coefficient of the initial recording light power. The correction coefficient may be stored in the correction coefficient storage memory 33 as data shown in the table of FIG. 9 described above. When setting the recording waveform, the recording processing unit 31 receives the correction coefficient of the initial recording light power from the correction coefficient storage memory 33, and sets the initial recording light power.

The FEP 20 has means for detecting the average value A and the amplitudes B and P necessary for the β value calculation shown in FIG.

The reproduction processing unit 21 uses the average value A and the amplitudes B and P detected by the FEP 20 to calculate the β value as described above. Then, when recording user data, the recording processing unit 31 corrects the recording waveform based on the β value (ROPC).

The optical disk apparatus of the present embodiment is different from the conventional optical disk apparatus in that the correction coefficient necessary for determining the initial recording light power is stored in the memory, but the other components are It may be similar to the components of the conventional optical disc.

Next, an example of a power setting method according to the present embodiment will be described with reference to FIG. 14A.

First, in step ST1, when an optical disc is loaded into the optical disc device, disc discrimination is executed. Here, it is assumed that the optical disc having the three information recording layers as shown in FIG. 6 is loaded. In this case, the disc information is read from the management area of the information recording layer L0 in a state where the information recording layer L0 is in focus, and the type of the loaded optical disc is grasped thereby. Specifically, based on the information read from the management area, for example, the total number of layers of the manufacturer and the information recording layer is obtained.

Next, in step ST2, OPC is performed by PCA of the information recording layer L0. At this time, test recording is performed in an area (unrecorded area) in which data is not recorded in all the information recording layers present before the information recording layer L0. In OPC, test recording of data is performed while changing the magnitude of the recording light power in multiple steps. As a result, the recording light power PWb with the smallest error rate can be obtained. Then, after test recording, in step ST3, the data recorded using the recording light power PWb is reproduced to obtain a target β value (β_best). In addition, the relationship between the β value and the recording light power using the beta value obtained by reproducing the data recorded using the recording light power other than the recording light power PWb and the target β value described above (for example, FIG. The straight line of the region a at 12 is also determined.

Next, at step ST4, the correction coefficient is read out from the correction coefficient storage memory 33 of FIG. 13 according to the type of disk obtained by disk discrimination and the information recording layer to be recorded. Then, in step ST5, a value (correction power) obtained by multiplying the optimum value PWb of the recording light power in the regions a and b by the correction coefficient is calculated. In step ST6, this correction power is set as the initial recording light power.

FIG. 14B is a flowchart showing an example of a conventional power setting method for reference. In the example of FIG. 14B, steps ST20 to 22 are the same as steps ST1 to 3, and when the power setting is performed in step ST23 after obtaining the target β value, the optimum of the recording light power in the area a obtained by test recording The value PWb is set as the initial recording light power.

Next, a data recording method in the present embodiment will be described with reference to FIG.

First, it is assumed that the setting of the initial recording light power is completed by the method described with reference to FIG. 14A. In the present embodiment, recording of user data is started at step ST10 with the recording light power of PWmid (= PWb × correction coefficient). If the recording end position has not been reached, the β value of the immediately preceding recording position is measured (steps ST11 and ST12).

At step ST13, the measured β value is compared with the target β value. Then, if the measured β value is larger than the target β value, the recording light power is decreased, and conversely, if the measured β value is smaller than the target β value, the recording light power is increased. At this time, when the difference .DELTA..beta. Between the measured .beta. Value and the target .beta. Value is known from the slope of the straight line shown in FIG. 12, the change amount .DELTA.PW of the recording light power is calculated from the slope of the straight line shown in FIG. be able to. That is, if the slope of the straight line in FIG. 12 is h, the relationship of ΔPW × h = Δβ is established. Therefore, when Δβ is known by measurement, the recording light power may be increased or decreased by Δβ / h. However, in the present embodiment, instead of changing the recording light power by Δβ / h at one time, data is recorded with the recording light power changed by 0.8 × Δβ / h (steps ST14 and ST15). Then, when reproducing the data recorded in that state, the β value is measured, and the recording light power is changed again by 0.8 × Δβ / h. As described above, by adjusting the recording light power so that the measured β value approaches the target β value in a stepwise manner, the recording light power can be reliably optimized in the range not exceeding the reproduction limit.

After recording data in this manner, the recording position is confirmed. Then, when the recording end position is reached in step ST11, the data recording is ended. If the recording end position has not been reached, the above operation is repeated.

In an actual optical disc, the sensitivity to the recording light power of the information recording layer may differ depending on the location. The example shown in FIG. 16 schematically shows a cross section of an optical disk of reduced light transmittance type in which the sensitivity decreases from the inner peripheral side to the outer peripheral side of the disk. Regions b ', c', d 'and e' correspond to the regions b, c, d and e, respectively, but their sensitivities are relatively lowered. This will be further described with reference to FIGS. 17 and 18. FIG. 17 is a graph showing the relationship between the error rate and the recording light power in the regions a, b, b ', e and e'. Similarly, FIG. 18 is a graph showing the relationship between the β value and the recording light power in the regions a, b, b ', e, e'.

In the regions b 'and e', the recording light power for achieving the same error rate or β value is relatively large compared to the regions b and e. This is because the sensitivity of the regions b 'and e' is relatively low, and a larger recording light power is required to realize the same state.

In the embodiment of the present invention, the initial recording light power is determined by test recording in the area a having the same sensitivity as the area b. In order to set the initial recording light power to PWmid (= PWb × correction coefficient), when data recording is started in area e ′, the error rate in area e ′ is e′_PWmid, as can be seen from FIG. Become. Assuming that the initial recording light power is set to PWb and data recording is started in the area e 'as in the conventional case, in the example of FIG. 17, the error rate in the area e' exceeds the reproduction limit e ' It will reach _PWb. As described above, according to the present embodiment, even when the data recording is started in a region where the sensitivity is relatively low, the possibility that the error rate exceeds the reproduction limit can be reduced.

Next, an example of changes in the β value, recording light power, and error rate during data recording will be described with reference to FIG.

In the example shown in FIG. 19, in the light transmittance reduced type optical disc, the areas for recording data are changed in the order of areas e, b, c, d, e, b. In the example of the figure, the area for starting data recording is the area e, and the initial recording light power is PWmid. When the recording light power is PWmid, the β value in the region e is smaller than β_best, for example, as shown in FIG. At the timing shown at the bottom of FIG. 19, the β value is measured, and the correction (β correction) of the recording light power is executed based on the difference between the measured β value and the target β value. The recording light power rises from PWmid to a level close to PWe by the β correction performed first. As a result, the error rate decreases and the β value can approach β_best. As a result of such β correction, the recording light power in the area e approaches the optimum value PWe in the area e. When the area for recording data transitions from the area e to the area b, the recording light power approaching the optimum value PWe in the area e has a value separated from the optimum value PWb in the area b. Therefore, in the region b, the β value of the data recorded with the recording light power of the PWe rises to β_b_PWe larger than the target β value β_best. At this time, in the example of FIG. 19, the error rate approaches the reproduction limit. However, since the β correction is performed quickly, the recording light power can eventually approach PWb, which is the optimum value in the region b.

As a result of performing the β correction to the recording light power in this way, the recording light power is optimized even if the data recording area changes from area b → area c → area d → area e → area b. It runs quickly.

Next, with reference to FIG. 20, an example of changes in the β value, recording light power, and error rate when recording data in a low sensitivity area will be described. FIG. 20 corresponds to FIG. 19, but differs in that the area in which data is recorded changes in the order of areas e ', b', c ', d', e ', b'. . In FIG. 20, not only the optimum values PWb 'and PWe' of the recording light power in the regions b 'and e' but also the optimum values PWb and PWe of the recording light power in the regions b and e are shown for comparison. .

In this embodiment, since the initial recording light power is set to PWmid (= PWb × correction coefficient), the error rate does not exceed the reproduction limit even when the data recording is started in the low sensitivity region e ′ first. It is possible to quickly approach the optimum value by β correction. The operation after the region e is basically as described with reference to FIG. 19, but the recording light power determined by the β correction is adjusted to a level higher than the level shown in FIG. This is to compensate for the low sensitivity with a stronger recording light power.

As in the prior art, when the initial optical disc apparatus is set to PWb and recording of data in a low-sensitivity recorded area starts, the error rate may exceed the reproduction limit. According to this, it is possible to reduce the possibility sufficiently.

In the above embodiment, data is recorded in the information recording layer L0, but when data is recorded in the information recording layer L1, the correction coefficient that was in the information recording layer is read from the memory, and the provisional initial recording light The initial recording light power can be calculated by multiplying the power. The correction coefficient may be set to 1 when data is recorded on the information recording layer L2 in the information recording layer located at the foremost position and on the three-layer optical disc.

In the above embodiment, information is recorded in PCA when recording is performed, for example, on the information recording layer L0 of the light transmittance decreasing type or light transmittance increasing type multilayer optical disc having the number of layers N (N is an integer of 2 or more). The test recording of data was performed in the unrecorded area where data is not written in all the information recording layers from the recording layer L1 to the information recording layer L (N-1), and the provisional initial recording light power (PWb) was determined. Performs test recording of data in the recording area where data is written in all the information recording layers from the information recording layer L1 to the information recording layer L (N-1) in PCA, and provisional initial recording light power (PWe) Then, the initial recording light power (PWmid) can be calculated by multiplying the temporary recording light power (PWe) temporarily with the correction coefficient (PWmid / PWe). Also, instead of the intermediate value between PWb and PWe, a value between PWlow and PWhigh may be adopted as the correction coefficient.

The present invention can be widely applied to an optical disc apparatus which records computer data and / or video / sound data on a multilayer optical disc such as BD-R or BD-RE.

10 optical disc 11 optical head (optical pickup)
20 Front End Processor (FEP)
21 reproduction processing unit 22 decoder 30 laser drive circuit 31 recording processing unit 32 encoder

Claims (9)

1. A data recording method for recording data on a multilayer optical disc comprising a plurality of information recording layers having N layers (N is an integer of 2 or more), and the k-th (k is 1) from the deepest side of the multilayer optical disc When an information recording layer of integers satisfying ≦ k ≦ N is the kth information recording layer,
   Step A of determining the number of information recording layers included in the optical disc loaded in the optical disc apparatus;
   When the number of layers is X (X is an integer of 2 or more), test of data in a test recording area in the m-th information recording layer (m is an integer satisfying 1 ≦ m ≦ X−1) on which test recording is performed Step B of performing recording and determining temporary initial recording light power;
   The correction coefficient is selected in accordance with the information recording layer of the target information recording layer for recording data, and the initial recording light power is corrected based on the selected correction coefficient to obtain the initial recording light power. Step C to determine
   And D. starting to record data in the target information recording layer with the initial recording light power.
2. The step B is
   When the number of layers is X (X is an integer of 2 or more), the test recording area in the m-th information recording layer (m is an integer satisfying 1 ≦ m ≦ X−1) on which test recording is performed Data is recorded in an unrecorded area where data is not written in all the information recording layers from the (m + 1) th information recording layer to the X-th information recording layer, and a tentative initial recording light power is determined The data recording method according to Item 1.
3. The data recording according to claim 1, wherein said step C selects said correction coefficient depending on the information recording layer of said target information recording layer, and also on the type of said loaded optical disc. Method.
4. The method includes the step of recording correction coefficient information in which the value of the correction coefficient is given for each type of multilayer optical disc for each of the information recording layers included in each multilayer optical disc supported by the optical disc device in the memory of the optical disc device. A data recording method according to item 3.
5. The data recording method according to claim 1, wherein the initial recording light power determined in the step C is larger than the provisional initial recording light power in the case of a light transmittance reduced type multilayer optical disc.
6. The data recording method according to claim 1, further comprising the step of changing the recording light power from the initial recording light power as needed based on the signal waveform obtained from the optical disc after starting to record the data in the step D.
7. After starting recording data in the step D, the step of correcting the recording light power is further performed such that the β value indicating the symmetry of the signal amplitude related to the average value of the reproduction signal obtained from the optical disc approaches the target β value. The data recording method according to claim 1, further comprising:
8. The data recording method according to claim 1, wherein m = 1.
9. An optical disc apparatus for recording data on a multilayer optical disc comprising a plurality of information recording layers having N layers (N is an integer of 2 or more).
   An optical pickup for optically accessing the multilayer optical disc;
   A memory for storing correction coefficient information to which a value of a correction coefficient is given for each type of multilayer optical disc for each information recording layer provided in each multilayer optical disc supported by the optical disc apparatus;
   Data is recorded in a test recording area in a certain information recording layer included in the loaded multi-layered optical disc, and after determining a tentative initial recording light power, the target information recording layer on which data is recorded is the information recording layer A recording processing unit which selects the correction coefficient from the memory according to whether it is a layer and corrects the provisional initial recording light power based on the selected correction coefficient to determine an initial recording light power;
   An optical disc apparatus comprising:

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