JP2005100610A - Laser power control device and method, optical disk device and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that recording interruption is required in an optical disk device for recording information on the optical disk having multiple layers in order to perform the recording at a constant transfer rate when laser power for each of the layers is adjusted in accordance with a temperature change because an adjusting time is required for the multiple layers. <P>SOLUTION: A laser power control device 100 is equipped with a power control part 32 for controlling a laser element 12 so that the laser beam power comes closer to a level for a control target, a variation detection part 17 for detecting a change in a recording condition for an optical disk 101a, and a power adjustment part 143 for adjusting the laser beam power to a recording film for a first layer 101. The power adjustment part 143 decides the laser beam power to the recording film for a second layer 101b based on the laser beam power adjusted to the recording film for the first layer 101a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser power control apparatus and method used in an optical disc apparatus for recording information on an optical disc having a plurality of layers, an optical disc apparatus for recording information on the optical disc, and a recording method for recording information on the optical disc.

  As a method for adjusting the power of laser light in a conventional optical disk apparatus, there is a method of adjusting the power of laser light in accordance with the temperature and the position along the radial direction of the optical disk to create a laser light power data table. . For example, Patent Document 1 describes a method for determining the power of laser light using the data table. This prior art will be described with reference to FIG.

  FIG. 12 is a block diagram showing a configuration of a conventional optical disc apparatus for recording information on the optical disc 1.

  The optical disc 1 includes a single layer 1a. The layer 1a is provided with a recording film.

  The optical pickup 10 converges the laser beam on the recording film of the layer 1a. A part of the laser light emitted from the laser element 12 passes through the reflection plate 15 and is detected by the emitted light detector 13. Further, the laser light emitted from the laser element 12 is reflected by the reflecting plate 15, passes through the deflection hologram 16, and is converged on the recording film of the optical disc 1 by the converging lens 11. Laser light (reflected light) reflected by the recording film of the optical disc 1 passes through the converging lens 11, is deflected by the deflection hologram 16, passes through the reflecting plate 15, and is detected by the reflected light detector 14.

  The laser light detected by the emitted light detector 13 is AD-converted by an AD converter 31 built in a DSP 30 (Digital Signal Processor). An output from the AD conversion unit 31 is supplied to a power control unit 32 built in the DSP 30. The power control unit 32 generates a laser drive value so that the power of the laser light detected by the emitted light detector 13 approaches the control target level, and controls the laser element 12 according to the laser drive value. Such control is performed, for example, by DA converting the laser drive value generated by the power control unit 32 by the DA conversion unit 33 incorporated in the DSP 30 and supplying the output from the DA conversion unit 33 to the drive circuit 2. Achieved. The control target level is determined by the power adjustment unit 43 and set in the power control unit 32. The drive circuit 2 drives the laser element 12 according to the output from the DA converter 33.

  The laser light (reflected light) detected by the reflected light detector 14 is AD-converted by an AD conversion unit 41 built in the DSP 30. An output from the AD conversion unit 41 is supplied to an asymmetry detection unit 42 incorporated in the DSP 30. The asymmetry detector 42 detects the asymmetry (Ipk + Ibm-2Iavg) / (Ipk-Ibm) of the reflected light from the peak level Ipk, the bottom level Ibm, and the average level Iavg of the reflected light, and indicates the asymmetry of the reflected light Is output to the power adjustment unit 43.

  The power adjustment unit 43 searches for an optimum value of the laser light power so that the asymmetry of the reflected light becomes a desired value (for example, 0).

  Next, with reference to FIG. 13, the procedure of the laser light power adjustment method will be described.

  Power adjustment is performed on the recording film of the optical disc 1 (S1). In such power adjustment, for example, the power control unit 32 controls the laser element 12 to irradiate the optical disc 1 with laser light having power according to a predetermined control target level, and the power adjustment unit 43 This is achieved by adjusting the control target level so that the asymmetry of the reflected light from the optical disc 1 becomes a desired value (for example, 0). Thus, the control target level adjusted by the power adjustment unit 43 is set in the power control unit 32.

  The power adjustment unit 43 updates the table value corresponding to the current temperature to the control target level adjusted by the power adjustment unit 43 (S2).

  It is determined whether or not the temperature has changed (S3). The output of the temperature detector 17 is AD converted by an AD converter 45 built in the DSP 30, and the output of the AD converter 45 is supplied to the power adjustment unit 43. For example, the power adjustment unit 43 determines whether the temperature has changed by monitoring the output of the AD converter 45.

  If it is determined that the temperature has changed, it is determined whether or not the control target level has been adjusted with respect to the current temperature (S4). For example, the power adjustment unit 43 searches the RAM 44 to determine whether or not the control target level has been adjusted.

  When it is determined that the control target level has been adjusted, the power adjustment unit 43 reads the control target level corresponding to the current temperature from the table stored in the RAM 44 (S5), and the read control target. The level is set in the power control unit 32 (S6).

  If it is determined that the control target level has not been adjusted, the process returns to step S1.

According to the method for adjusting the power of the laser beam described above, even if the power of the laser beam emitted from the laser element fluctuates due to the use environment temperature of the optical disk device or the influence of temperature variation due to heat generated by the operation of the device, Recording can be performed in which a reproduction signal is obtained such that the asymmetry of the reflected light becomes a desired value (for example, 0).
Japanese Patent Laid-Open No. 1-112551

  However, in the conventional recording method, when the information recording film of the optical disc has two layers, for example, if recording is performed on the other layer after the environmental temperature has changed, it is not possible to record with the optimum laser power. More specifically, even if a data table is created and stored in one layer according to a temperature change, the data table in the other layer cannot be created. In order to create the data table of the other layer, it is necessary to adjust the power to perform recording and reproduction by moving to the other layer after adjusting the power in one layer according to the temperature change. At this time, it takes time to move back to the other layer and time to adjust the power by recording and reproducing in the other layer, and the power adjustment time is doubled or more. Here, in order to continuously record a moving image on an optical disk, it is necessary to record at a predetermined transfer speed. However, while the recording is temporarily interrupted and power adjustment is performed, moving image data is stored in the DRAM. The fact that the power adjustment time is more than doubled has to double the storage capacity of the DRAM, leading to an increase in the cost of the device.

  A laser power control apparatus according to the present invention is a laser power control apparatus used in an optical disc apparatus that records information on an optical disc having at least a first layer and a second layer, and the power of the laser beam is set to a control target level. A power control unit that controls the laser element so as to approach, a fluctuation detection unit that detects that a recording condition for the optical disc has fluctuated, and a recording film of the first layer according to an output from the fluctuation detection unit A power adjusting unit that adjusts the power of the laser beam, and the power adjusting unit is configured to record the second layer of the recording film based on the power of the laser beam adjusted to the recording layer of the first layer. The power of the laser beam with respect to is determined.

  The optical disk device includes an optical pickup that irradiates the optical disk with laser light, and a drive circuit that drives the optical pickup, and the optical pickup receives the laser element and the laser light emitted from the laser element. An output light detector for detecting, wherein the power control unit generates a laser drive value so that the power of the laser light detected by the output light detector approaches a control target level, and according to the laser drive value And controlling the laser element, and the power adjusting unit detects the level of the laser beam detected by the emitted light detector, the control target level, and the level of the laser driving value according to the output from the fluctuation detecting unit. The power of the laser beam for the recording film of the first layer may be adjusted by adjusting at least one of the above.

  The power adjustment unit may determine the control target level for the recording film of the second layer as a function of the control target level for the recording film of the first layer.

  The function may be a ratio of the control target level for the recording film of the second layer to the control target level for the recording film of the first layer.

  The function may be a linear function or a quadratic function.

  The function may be recorded in a predetermined area of the optical disc.

  The optical disc further includes a third layer, and the power adjustment unit further sets the control target level for the recording film of the third layer as a function of the control target level for the recording film of the first layer. And the function used in determining the control target level for the recording film of the second layer is different from the function used in determining the control target level for the recording film of the third layer. May be different.

  The fluctuation detection unit includes a temperature detection unit that detects a temperature, a tilt detection unit that detects a tilt between a normal direction of an information surface of the optical disc and an optical axis direction of the laser light applied to the optical disc, And a spherical aberration detector that detects a spherical aberration of the laser beam due to a base material thickness of the optical disc, and the power adjustment unit includes an output from the temperature detector and a tilt detector. The power of the laser beam for the recording film of the first layer may be adjusted based on at least one of the output from the spherical aberration detector and the output from the spherical aberration detector.

  The laser power control device further includes an asymmetric detection unit that detects asymmetry of reflected light from the optical disc, and the power adjustment unit is configured so that the output from the asymmetric detection unit becomes a desired value. You may adjust the power of the laser beam with respect to the recording film of one layer.

  The laser power control apparatus further includes a modulation degree detection unit that detects a modulation degree of reflected light from the optical disc, and the power adjustment unit is configured so that an output from the modulation degree detection unit becomes a desired value. The power of the laser beam for the recording film of the first layer may be adjusted.

  In the initial adjustment of the power of the laser light, the power control unit controls the laser element so that the power of the laser light approaches a control target level Pw2 ′ set in advance for the recording film of the second layer. The control target level Pw2 ′ is controlled with respect to the control target level Pw1 adjusted for the recording film of the first layer, the level of the reference power Pw1 ″ for the recording film of the first layer, and the first level And the reference power Pw1 ″ is recorded in a predetermined area of the optical disc, and the reference power Pw2 ″ is a predetermined level of the optical disc. It may be recorded in this area.

  The control target level Pw2 'may be defined by the equation Pw2' = Pw1 * Pw2 "/ Pw1".

  The laser power control method of the present invention is a laser power control method used in an optical disc apparatus for recording information on an optical disc having at least a first layer and a second layer, and the power of the laser beam is set to a control target level. The step of controlling the laser element so as to approach, the step of detecting that the recording condition for the optical disk has changed, and the power of the laser beam for the recording film of the first layer are adjusted according to the change of the recording condition And determining the laser beam power for the second layer recording film based on the laser beam power adjusted for the first layer recording film.

  An optical disk apparatus according to the present invention is an optical disk apparatus for recording information on an optical disk having at least a first layer and a second layer, and an optical pickup for irradiating the optical disk with laser light, and driving the optical pickup A drive circuit; and a laser power control device that controls the power of the laser light, the laser power control device controlling a laser element so that the power of the laser light approaches a control target level; and A fluctuation detecting unit for detecting that the recording condition for the optical disc has fluctuated; and a power adjusting unit for adjusting the power of the laser beam with respect to the recording film of the first layer according to an output from the fluctuation detecting unit. The power adjusting unit applies the second layer recording film based on the power of the laser light adjusted for the first layer recording film. To determine the power of the laser light.

  The recording method of the present invention is a recording method for recording information on an optical disc having at least a first layer and a second layer, the step of irradiating the optical disc with laser light, and controlling the power of the laser light The step of controlling the power of the laser light includes the step of controlling the laser element so that the power of the laser light approaches a control target level, and detecting that the recording conditions for the optical disk have changed. Adjusting the power of the laser light for the recording film of the first layer according to the change in the recording conditions, and adjusting the power of the laser light adjusted for the recording film of the first layer And determining the power of the laser beam with respect to the recording film of the second layer.

  According to the method for adjusting the power of laser light according to the present invention, even an optical disc having a plurality of recording layers can be adjusted without increasing the power adjustment time associated with a temperature change. Even when continuously recording moving images, the apparatus can be configured without increasing costs by increasing the storage capacity of a DRAM that stores moving image data for interrupting recording.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus 100 that records information on an optical disc 101.

  The optical disc apparatus 100 includes an optical pickup 10 that irradiates an optical disc 101 with laser light, and a DSP (Digital Signal Processor) 130. The DSP 130 functions as a laser power control device that controls the power of laser light.

  The optical disc 101 includes a first layer 101a and a second layer 101b. Each of the first layer 101a and the second layer 101b is provided with a recording film. The optical disc 101 may include a plurality of layers of three or more layers. One of the plurality of layers is used as a reference layer.

  Hereinafter, the operation of the optical disc apparatus 100 will be described.

  The optical pickup 10 converges the laser light on the recording film of the first layer 101a, or converges the laser light on the recording film of the second layer 101b. A part of the laser light emitted from the laser element 12 passes through the reflection plate 15 and is detected by the emitted light detector 13. The laser light emitted from the laser element 12 is reflected by the reflecting plate 15, passes through the deflection hologram 16, and is recorded by the converging lens 11 on the recording film (the recording film of the first layer 101a or the second layer). 101b). The laser light (reflected light) reflected by the recording film of the optical disc 101 passes through the converging lens 11, is deflected by the deflection hologram 16, passes through the reflecting plate 15, and is detected by the reflected light detector 14.

  The laser light detected by the emitted light detector 13 is AD converted by the AD conversion unit 31 built in the DSP 130. An output from the AD conversion unit 31 is supplied to a power control unit 32 built in the DSP 130. The power control unit 32 generates a laser drive value so that the power of the laser light detected by the emitted light detector 13 approaches the control target level, and controls the laser element 12 according to the laser drive value. For example, the laser drive value generated by the power control unit 32 is DA-converted by the DA conversion unit 33 incorporated in the DSP 130, and the output from the DA conversion unit 33 is supplied to the drive circuit 2. Achieved. The control target level is determined by the power adjustment unit 143 and set in the power control unit 32. The drive circuit 2 drives the laser element 12 according to the output from the DA converter 33.

  The laser light (reflected light) detected by the reflected light detector 14 is AD converted by the AD conversion unit 41 built in the DSP 130. An output from the AD conversion unit 41 is supplied to an asymmetry detection unit 42 incorporated in the DSP 130. The asymmetry detector 42 detects the asymmetry (Ipk + Ibm-2Iavg) / (Ipk-Ibm) of the reflected light from the peak level Ipk, the bottom level Ibm, and the average level Iavg of the reflected light, and indicates the asymmetry of the reflected light Is output to the power adjustment unit 143.

  FIG. 2 is a characteristic diagram showing the relationship between the power of laser light and the asymmetry of reflected light. In FIG. 2, the horizontal axis indicates the power of the laser light, and the vertical axis indicates the asymmetry of the reflected light.

  The power adjustment unit 143 searches for an optimum value of the power of the laser light so that the asymmetry of the reflected light becomes a desired value (for example, 0) as indicated by a point A shown in FIG. Such a search is performed, for example, by irradiating the optical disc 101 with laser light having appropriate two powers, detecting the asymmetry of the reflected light from the reflected light from the optical disc 101, and determining the asymmetry of the reflected light. This is achieved by calculating the power of the laser beam by which the asymmetry of the reflected light becomes a desired value (for example, 0) by linear approximation. The power adjustment unit 143 outputs the optimum value of the laser beam power to the power control unit 32 as a control target level.

  Further, the power adjusting unit 143 adjusts the power of the laser beam with respect to the recording film of the first layer 101a (reference layer) according to the output from the temperature detector 17.

  Hereinafter, the procedure of the laser light power adjustment method will be described. This method is executed by operating the optical disc apparatus 100, for example.

  First, with reference to FIG. 3A, the procedure of the laser light power adjustment method when adjusting the laser light power before starting the recording of data on the optical disc 101 (ie, in the case of initial adjustment) will be described. .

  Power adjustment is performed on the first layer 101a of the optical disc 101 (S101). In such power adjustment, for example, the power control unit 32 irradiates the optical disc 101 with laser light having power according to a predetermined control target level Pw1 ′ for the recording film of the first layer 101a. Then, the power adjustment unit 143 adjusts the control target level for the recording film of the first layer 101a so that the asymmetry of the reflected light from the optical disk 101 becomes a desired value (for example, 0). Is achieved by doing The control target level adjusted by the power adjustment unit 143 in this way is set in the power control unit 32 as the control target level Pw1 for the recording film of the first layer 101a.

  The control target level Pw1 ′ preset for the recording film of the first layer 101a is the reference power level Pw1 ″ for the recording film of the first layer 101a set in the firmware executed by the DSP 130. Alternatively, it may be the reference power level Pw1 ″ for the recording film of the first layer 101a recorded in a predetermined area of the optical disc 101 (for example, a predetermined area in the lead-in area).

  The recording film on which data is to be recorded is moved from the recording film of the first layer 101a to the recording film of the second layer 101b (S102).

  Power adjustment is performed on the second layer 101b of the optical disc 101 (S103). In such power adjustment, for example, the power control unit 32 irradiates the optical disc 101 with laser light having power according to a predetermined control target level Pw2 ′ for the recording film of the second layer 101b. And the power adjustment unit 143 adjusts the control target level for the recording film of the second layer 101b so that the asymmetry of the reflected light from the optical disc 101 becomes a desired value (for example, 0). Is achieved by doing The control target level adjusted by the power adjustment unit 143 in this way is set in the power control unit 32 as the control target level Pw2 for the recording film of the second layer 101b.

  The control target level Pw2 ′ preset for the recording film of the second layer 101b may be the control target level Pw1 that has been adjusted in step S101, or may be a predetermined area (for example, lead-in) of the optical disc 101. The reference power level Pw2 ″ for the recording film of the second layer 101b recorded in a predetermined area) may be used. Alternatively, Pw2 ′ = Pw1 × Pw2 ″ / Pw1 ″. The ratio Pw2 ″ / Pw1 ″ may be recorded in a predetermined area of the optical disc 101 (for example, a predetermined area in the lead-in area).

  Alternatively, Pw2 ′ (= Pw1 × Pw2 ″ / Pw1 ″) is set as Pw2 in the power control unit 32 without adjusting the control target level for the recording film of the second layer 101b by the power adjustment unit 143. May be.

  Information (for example, a table) stored in the RAM 44 is updated (S104). Such an update is performed by, for example, the control target level Pw1 for the recording film of the first layer 101a and the control target level Pw2 for the recording film of the second layer 101b with respect to the control target level Pw1 for the recording film of the first layer 101a. The ratio (ie, Pw2 / Pw1) is written to the RAM 44. An arbitrary rewritable memory can be used instead of the RAM 44.

  Instead of writing the ratio Pw2 / Pw1 into the RAM 44, a function of Pw1 may be written into the RAM 44. As the function of Pw1, for example, a linear function of Pw1 or a quadratic function of Pw1 can be used. The power adjustment unit 143 may determine the control target level Pw2 for the recording film of the second layer 101b as a function of the control target level Pw1 for the recording film of the first layer 101a. The function of Pw1 can be stored in the interlayer correction table of the RAM 44, for example.

  FIG. 3B shows an example of an interlayer correction table. In this example, the function F2 (Pw1) is used when determining the control target level Pw2 for the second-layer recording film, and the function F3 (Pw3) is used when determining the control target level Pw3 for the third-layer recording film. Pw1) is used. The function F2 (Pw1) and the function F3 (Pw1) may be the same function or different functions.

  Next, referring to FIG. 4A, after the initial adjustment, the laser beam power is adjusted when the power of the laser beam is adjusted during recording of data onto the optical disc 101 due to factors such as temperature fluctuations (ie, readjustment). The procedure of the power adjustment method will be described.

  It is determined whether or not the recording film on which data is to be recorded has moved from the recording film of the first layer 101a (reference layer) to the recording film of the second layer 101b (layer other than the reference layer) (S111). .

  When it is determined that the recording film on which data is to be recorded has moved from the recording film of the first layer 101 a to the recording film of the second layer 101 b, the power adjustment unit 143 performs control from the table stored in the RAM 44. The target level ratio Pw2 / Pw1 and the current control target level Pw1t for the recording film of the first layer 101a are read (S121), and the current control target level Pw2t for the recording film of the second layer 101b is Pw2t = Pw1t × The current control target level Pw2t for the recording film of the second layer 101b calculated in this way is set in the power control unit 32 (S123).

  When the function of Pw1 (for example, F2 (Pw1)) is stored in the RAM 44 instead of the ratio Pw2 / Pw1, the power adjustment unit 143 receives the function F2 (Pw1) and the first layer 101a from the RAM 44. The current control target level Pw1t for the recording film of the second layer 101b may be read (S121), and the current control target level Pw2t for the recording film of the second layer 101b may be calculated according to the formula Pw2t = F2 (Pw1t) ( S122).

Here, the current control target level Pw1t for the recording film of the first layer 101a is intended to compensate for fluctuations in the control target level Pw1 due to temperature fluctuations. For example, the control target level Pw1 is the control target level at the reference temperature X0 ° C., the temperature changes from X0 ° C. to X1 ° C., and the temperature correction coefficient K _T (X1 ° C.) for the current temperature X1 ° C. is 1.01 ( 101%). In this case, the current control target level Pw1t is calculated according to the formula: Pw1t = Pw1 × K _T (X1 ° C.) = 1.01 · Pw1. Temperature correction coefficient K _T is, for example, may be stored in the temperature correction table RAM44 as the power ratio with respect to the reference temperature of the reference layer.

FIG. 4B shows an example of the temperature correction table. In this example, K _T (X1 ° C.) = 1.01 (101%) and K _T (X2 ° C.) = 0.97 (97%) with respect to the reference temperature X0 ° C.

  The power adjustment unit 143 reads the control target level ratio Pw2 / Pw1 from the table stored in the RAM 44, and instead of reading the control target level ratio Pw2 / Pw1 from the table stored in the RAM 44, the power target unit 143 Pw2 / Pw1 may be read out. Alternatively, the power adjustment unit 143 reads the function of Pw1 (for example, F2 (Pw1)) from the table stored in the RAM 44, instead of reading the function of Pw1 recorded in a predetermined area (for example, the lead-in area) of the optical disc 101. You may make it read a function.

  In this way, the power adjustment unit 143 determines the power of the laser light for the recording film of the second layer 101b based on the power of the laser light adjusted for the recording film of the first layer 101a.

  It is determined whether or not the temperature has changed (S112). The output of the temperature detector 17 is AD converted by the AD converter 45 built in the DSP 130, and the output of the AD converter 45 is supplied to the power adjustment unit 143. For example, the power adjustment unit 143 determines whether or not the temperature has changed by monitoring the output of the AD converter 45.

If it is determined that the temperature has changed, it is determined whether or not the power of the laser beam for the recording film of the first layer 101a has been adjusted with respect to the current temperature (S114). Such a determination is made, for example, whether or not the control target level Pw1 for the recording film of the first layer 101a has been adjusted with respect to the current temperature (that is, the current control target level Pwlt for the current temperature or the current temperature). This is done by determining whether or not the temperature correction coefficient _KT is stored in the RAM 44. For example, the power adjustment unit 143 searches the RAM 44 to determine whether or not the control target level Pw1 has been adjusted.

  When it is determined that the power of the laser beam with respect to the recording film of the first layer 101a has been adjusted, steps S121, S122, and S123 are executed. Steps S121, S122, and S123 are as described above.

When it is determined that the power of the laser beam for the recording film of the first layer 101a has not been adjusted, the power adjustment for the first layer 101a is performed in the same manner as in step S101 shown in FIG. 3A (S131). ). In such power adjustment, for example, the power control unit 32 irradiates the optical disc 101 with laser light having power according to a predetermined control target level Pw1 ′ for the recording film of the first layer 101a. Then, the power adjustment unit 143 adjusts the control target level for the recording film of the first layer 101a so that the asymmetry of the reflected light from the optical disk 101 becomes a desired value (for example, 0). Is achieved by doing The power adjustment unit 143 calculates a value to be stored in the table of the RAM 44 (S132), and updates the table of the RAM 44 using the calculated value (S133). For example, the power adjustment unit 143 may store the set of the current temperature and the control target level adjusted by the power adjustment unit 143 (control target level with respect to the current temperature) in the RAM 44, or the reference temperature control target level and calculates a temperature correction coefficient K _T for the current temperature from the control target level adjusted by the power adjusting section 143 (control target level of the current with respect to temperature), the current temperature and the temperature correction coefficient K _T in May be stored in the RAM 44.

  According to the laser light power adjustment method described above, table data indicating the laser light power adjusted for each temperature is stored in the RAM 44 built in the DSP 130, and thereafter, even if the temperature fluctuates, the temperature is changed. If there is table data stored in the past, the control target level of the power control unit 32 can be set based on the table data stored in the RAM 44 without recording and reproducing. Further, even in an optical disc including a plurality of layers, recording of each layer other than the reference layer is performed based on a ratio between the control target level for the recording film of one reference layer and the control target level for the recording film of each layer other than the reference layer. A control target level for the membrane can be set. Alternatively, instead of the ratio, a function of a control target level for the recording film of the reference layer may be used. The function may be, for example, a linear function or a quadratic function. As a result, even if the power of the laser beam emitted from the laser element fluctuates due to the influence of the temperature fluctuation caused by the operating environment temperature of the optical disc apparatus or the heat generated by the operation of the optical disc apparatus, the optical disc having a plurality of layers The adjustment of the power of the laser beam for recording to obtain a reproduction signal in which the asymmetry of the reflected light becomes a desired value (for example, 0) can be realized in substantially the same time as a single-layer optical disc.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration of an optical disc apparatus 200 that records information on the optical disc 101.

  The optical disc apparatus 200 includes an optical pickup 210 that irradiates the optical disc 101 with laser light, and a DSP (Digital Signal Processor) 230. The DSP 230 functions as a laser power control device that controls the power of laser light.

  Since the optical disk 101 is deformed so as to bend with temperature change, the optical line 101 has a normal direction of the information surface of the optical disk 101 and an optical axis direction of the laser beam irradiated to the optical disk 101 at different positions along the radial direction of the optical disk 101. The tilt between them fluctuates, and the effective power of the laser light fluctuates. In the second embodiment, the effective power of the laser beam is adjusted with respect to the tilt variation.

  Hereinafter, the operation of the optical disc apparatus 200 will be described.

  The optical pickup 210 converges the laser light on the recording film of the first layer 101a, or converges the laser light on the recording film of the second layer 101b. A part of the laser light emitted from the laser element 12 passes through the reflection plate 15 and is detected by the emitted light detector 13. The laser light emitted from the laser element 12 is reflected by the reflecting plate 15, passes through the deflection hologram 16, and is recorded by the converging lens 11 on the recording film (the recording film of the first layer 101a or the second layer). 101b). The laser light (reflected light) reflected by the recording film of the optical disc 101 passes through the converging lens 11, is deflected by the deflection hologram 16, passes through the reflecting plate 15, and is detected by the reflected light detector 14.

  Further, the optical pickup 210 includes a tilt detector 217 that detects a tilt from the distribution of reflected light detected by the reflected light detector 14.

  The laser beam detected by the emitted light detector 13 is AD converted by the AD converter 31 built in the DSP 230. An output from the AD conversion unit 31 is supplied to a power control unit 32 built in the DSP 230. The power control unit 32 generates a laser drive value so that the power of the laser light detected by the emitted light detector 13 approaches the control target level, and controls the laser element 12 according to the laser drive value. For example, the laser drive value generated by the power control unit 32 is DA-converted by the DA conversion unit 33 built in the DSP 230 and the output from the DA conversion unit 33 is supplied to the drive circuit 2. Achieved. The control target level is determined by the power adjustment unit 243 and set in the power control unit 32. The laser drive circuit 2 drives the laser element 12 according to the output from the DA converter 33.

  The laser light (reflected light) detected by the reflected light detector 14 is AD-converted by the AD conversion unit 41 built in the DSP 230. An output from the AD conversion unit 41 is supplied to an asymmetry detection unit 42 incorporated in the DSP 230. The asymmetry detector 42 detects the asymmetry (Ipk + Ibm-2Iavg) / (Ipk-Ibm) of the reflected light from the peak level Ipk, the bottom level Ibm, and the average level Iavg of the reflected light, and indicates the asymmetry of the reflected light Is output to the power adjustment unit 243.

  The power adjustment unit 243 searches for an optimum value of the laser light power so that the asymmetry of the reflected light becomes a desired value (for example, 0). The procedure of this search method is as already described in the first embodiment with reference to FIG. Therefore, the description is omitted here. The power adjustment unit 243 outputs the optimum value of the laser beam power to the power control unit 32 as a control target level.

  Further, the power adjustment unit 243 adjusts the power of the laser beam with respect to the recording film of the first layer 101a (reference layer) in accordance with the output from the tilt detector 217.

  FIG. 6 is a characteristic diagram showing the relationship between tilt and laser beam power. In FIG. 6, the horizontal axis indicates the tilt, and the vertical axis indicates the power of the laser beam. As shown in FIG. 6, the optimum power of the laser light varies depending on the tilt. The power adjustment unit 243 adjusts the power of the laser light according to the tilt. For example, when it is detected that the tilt has changed in the order of point A, point B, point C, point D, and point E shown in FIG. 6, the power adjustment unit 243 sets each point shown in FIG. In contrast, the power of the laser beam is adjusted. As a result, the control target level adjusted by the power adjustment unit 243 is stored in the table of the RAM 44.

  Hereinafter, the procedure of the laser light power adjustment method will be described. This method is executed by operating the optical disc apparatus 200, for example.

  With reference to FIG. 3A, the procedure of the laser light power adjustment method in the case where the laser light power is adjusted before starting the recording of data on the optical disc 101 (that is, in the case of initial adjustment) is described in the first embodiment. As already explained. Therefore, the description is omitted here.

  Referring to FIG. 7A, after the initial adjustment, the laser beam in the case of adjusting the power of the laser beam during recording of data on the optical disc 101 due to factors such as the tilt variation of the optical disc 101 (that is, in the case of readjustment). The procedure of the power adjustment method will be described.

  It is determined whether or not the recording film on which data is to be recorded has moved from the recording film of the first layer 101a (reference layer) to the recording film of the second layer 101b (layer other than the reference layer) (S211). .

  When it is determined that the recording film on which data is to be recorded has moved from the recording film of the first layer 101 a to the recording film of the second layer 101 b, the power adjustment unit 243 controls from the table stored in the RAM 44. The target level ratio Pw2 / Pw1 and the current control target level Pw1t for the recording film of the first layer 101a are read (S221), and the current control target level Pw2t for the recording film of the second layer 101b is Pw2t = Pw1t × The current control target level Pw2t for the recording film of the second layer 101b calculated in this way is set in the power control unit 32 (S223).

  When the function of Pw1 (for example, F2 (Pw1)) is stored in the RAM 44 instead of the ratio Pw2 / Pw1, the power adjustment unit 243 receives the function F2 (Pw1) and the first layer 101a from the RAM 44. The current control target level Pw1t for the recording film of the second layer 101b may be read (S221), and the current control target level Pw2t for the recording film of the second layer 101b may be calculated according to the equation Pw2t = F2 (Pw1t) ( S222).

Here, the current control target level Pw1t for the recording film of the first layer 101a is intended to compensate for fluctuations in the control target level Pw1 due to tilt fluctuations. For example, the control target level Pw1 is the control target level at the reference tilt Y0 °, the tilt changes from Y0 ° to Y1 °, and the tilt correction coefficient K _C (Y1 °) for the current tilt Y1 ° is 1.03 ( 103%). In this case, the current control target level Pw1t is calculated according to the formula: Pw1t = Pw1 × K _C (Y1 °) = 1.03 · Pw1. The tilt correction coefficient K _C can be stored, for example, in the tilt correction table of the RAM 44 as a power ratio with respect to the reference tilt of the reference layer.

FIG. 7B shows an example of a tilt correction table. In this example, K _C (Y1 °) = 1.03 (103%) and K _C (Y2 °) = 0.99 (99%) with respect to the reference tilt Y0 °.

  The power adjusting unit 243 reads the control target level ratio Pw2 / Pw1 from the table stored in the RAM 44, instead of reading the control target level ratio Pw2 / Pw1 in a predetermined area (for example, the lead-in area) of the optical disc 101. Pw2 / Pw1 may be read out. Alternatively, instead of reading the Pw1 function (for example, F2 (Pw1)) from the table stored in the RAM 44, the power adjustment unit 243 reads the Pw1 recorded in a predetermined area (for example, the lead-in area) of the optical disc 101. You may make it read a function.

  In this way, the power adjustment unit 243 determines the power of the laser light for the recording film of the second layer 101b based on the power of the laser light adjusted for the recording film of the first layer 101a.

  It is determined whether or not the tilt has changed (S212). The output of the tilt detector 217 is AD converted by the AD converter 45 built in the DSP 230, and the output of the AD converter 45 is supplied to the power adjustment unit 243. For example, the power adjustment unit 243 determines whether the tilt has changed by monitoring the output of the AD converter 45.

If it is determined that the tilt has changed, it is determined whether or not the power of the laser beam for the recording film of the first layer 101a has been adjusted with respect to the current tilt (S214). Such a determination is made, for example, whether or not the control target level Pw1 for the recording film of the first layer 101a has been adjusted with respect to the current tilt (that is, the current control target level Pwlt for the current tilt or the current tilt correction coefficient K _C of relative tilt is made by determining whether) is stored in the RAM 44. For example, the power adjustment unit 243 searches the RAM 44 to determine whether or not the control target level Pw1 has been adjusted.

  When it is determined that the power of the laser beam with respect to the recording film of the first layer 101a has been adjusted, steps S221, S222, and S223 are executed. Steps S221, S222, and S223 are as described above.

If it is determined that the power of the laser beam for the recording film of the first layer 101a has not been adjusted, the power adjustment for the first layer 101a is performed in the same manner as in step S101 shown in FIG. 3A (S231). ). In such power adjustment, for example, the power control unit 32 irradiates the optical disc 101 with laser light having power according to a predetermined control target level Pw1 ′ for the recording film of the first layer 101a. Then, the power adjustment unit 243 adjusts the control target level for the recording film of the first layer 101a so that the asymmetry of the reflected light from the optical disk 101 becomes a desired value (for example, 0). Is achieved by doing The power adjustment unit 243 calculates a value to be stored in the table of the RAM 44 (S232), and updates the table of the RAM 44 using the calculated value (S233). For example, the power adjustment unit 243 may store the set of the current tilt and the control target level adjusted by the power adjustment unit 243 (control target level with respect to the current tilt) in the RAM 44, or the reference tilt calculating a tilt compensation coefficient K _C, the current tilt the tilt correction coefficient for controlling a target level and a control target level adjusted by the power adjusting section 243 of the current from the (control target level for the current tilt) tilt in K _C May be stored in the RAM 44.

  According to the laser light power adjustment method described above, table data indicating the laser light power adjusted for each tilt is stored in the RAM 44 built in the DSP 230, and thereafter, even if there is a tilt variation, If there is table data stored in the past for tilt, the control target level of the power control unit 32 can be set based on the table data stored in the RAM 44 without recording and reproducing. Further, even in an optical disc including a plurality of layers, recording of each layer other than the reference layer is performed based on a ratio between the control target level for the recording film of one reference layer and the control target level for the recording film of each layer other than the reference layer. A control target level for the membrane can be set. Alternatively, instead of the ratio, a function of a control target level with respect to the recording film of the reference layer may be used. The function may be, for example, a linear function or a quadratic function. Thus, for an optical disc having a plurality of layers, the asymmetry of the reflected light is a desired value even if the optical disc is deformed and the tilt changes due to a change in the operating environment temperature of the optical disc device or a temperature change due to heat generation of the optical disc device. Adjustment of the power of the laser beam for recording to obtain a reproduction signal (for example, 0) can be realized in substantially the same time as a single-layer optical disc.

(Embodiment 3)
FIG. 8 is a block diagram showing a configuration of an optical disc apparatus 300 that records information on the optical disc 101.

  The optical disc apparatus 300 includes an optical pickup 310 that irradiates the optical disc 101 with laser light, and a DSP (Digital Signal Processor) 330. The DSP 330 functions as a laser power control device that controls the power of laser light.

  The optical disc 101 has spherical aberration due to uneven thickness of the base material. The effective power of the laser beam varies due to the influence of spherical aberration. In the third embodiment, the effective power of the laser light is adjusted with respect to the variation in spherical aberration accompanying the uneven thickness of the base material.

  Hereinafter, the operation of the optical disc apparatus 300 will be described.

  The optical pickup 310 converges the laser light on the recording film of the first layer 101a, or converges the laser light on the recording film of the second layer 101b. A part of the laser light emitted from the laser element 12 passes through the reflection plate 15 and is detected by the emitted light detector 13. The laser light emitted from the laser element 12 is reflected by the reflecting plate 15, passes through the deflection hologram 16, and is recorded by the converging lens 11 on the recording film (the recording film of the first layer 101a or the second layer). 101b). The laser light (reflected light) reflected by the recording film of the optical disc 101 passes through the converging lens 11, is deflected by the deflection hologram 16, passes through the reflecting plate 15, and is detected by the reflected light detector 14.

  The optical pickup 310 further includes a spherical aberration detector 317 that detects spherical aberration from the distribution of reflected light detected by the reflected light detector 14.

  The laser light detected by the emitted light detector 13 is AD converted by the AD conversion unit 31 built in the DSP 330. An output from the AD conversion unit 31 is supplied to a power control unit 32 built in the DSP 330. The power control unit 32 generates a laser drive value so that the power of the laser light detected by the emitted light detector 13 approaches the control target level, and controls the laser element 12 according to the laser drive value. For example, the laser drive value generated by the power control unit 32 is DA-converted by the DA conversion unit 33 built in the DSP 330 and the output from the DA conversion unit 33 is supplied to the drive circuit 2. Achieved. The control target level is determined by the power adjustment unit 343 and set in the power control unit 32. The drive circuit 2 drives the laser element 12 according to the output from the DA converter 33.

  The laser light (reflected light) detected by the reflected light detector 14 is AD converted by the AD conversion unit 41 built in the DSP 330. An output from the AD conversion unit 41 is supplied to an asymmetry detection unit 42 incorporated in the DSP 330. The asymmetry detector 42 detects the asymmetry (Ipk + Ibm-2Iavg) / (Ipk-Ibm) of the reflected light from the peak level Ipk, the bottom level Ibm, and the average level Iavg of the reflected light, and indicates the asymmetry of the reflected light Is output to the power adjustment unit 343.

  The power adjustment unit 343 searches for an optimum value of the laser light power so that the asymmetry of the reflected light becomes a desired value (for example, 0). The procedure of this search method is as already described in the first embodiment with reference to FIG. Therefore, the description is omitted here. The power adjustment unit 343 outputs the optimum value of the laser beam power to the power control unit 32 as a control target level.

  Further, the power adjustment unit 343 adjusts the power of the laser beam with respect to the recording film of the first layer 101a (reference layer) in accordance with the output from the spherical aberration detector 317.

  FIG. 9 is a characteristic diagram showing the relationship between spherical aberration and the power of laser light. In FIG. 9, the horizontal axis indicates spherical aberration, and the vertical axis indicates the power of laser light. As shown in FIG. 9, the optimum power of the laser light varies depending on the spherical aberration. The power adjustment unit 343 adjusts the power of the laser light according to the spherical aberration. For example, when it is detected that the spherical aberration has changed in the order of point A, point B, point C, point D, and point E shown in FIG. 9, the power adjustment unit 343 determines each point shown in FIG. The power of the laser beam is adjusted with respect to. As a result, the control target level adjusted by the power adjustment unit 343 is stored in the table of the RAM 44.

  Hereinafter, the procedure of the laser light power adjustment method will be described. This method is executed by operating the optical disc apparatus 300, for example.

  With reference to FIG. 3A, the procedure of the laser light power adjustment method in the case where the laser light power is adjusted before starting the recording of data on the optical disc 101 (that is, in the case of initial adjustment) is described in the first embodiment. As already explained. Therefore, the description is omitted here.

  Referring to FIG. 10A, after the initial adjustment, the laser in the case where the power of the laser beam is adjusted during recording of data on the optical disc 101 due to factors such as fluctuations in spherical aberration of the optical disc 101 (that is, in the case of readjustment). The procedure of the light power adjustment method will be described.

  It is determined whether the recording film on which data is to be recorded has moved from the recording film of the first layer 101a (reference layer) to the recording film of the second layer 101b (layer other than the reference layer) (S311). .

  When it is determined that the recording film on which data is to be recorded has moved from the recording film of the first layer 101 a to the recording film of the second layer 101 b, the power adjustment unit 343 controls from the table stored in the RAM 44. The target level ratio Pw2 / Pw1 and the current control target level Pw1t for the recording film of the first layer 101a are read (S321), and the current control target level Pw2t for the recording film of the second layer 101b is Pw2t = Pw1t × The current control target level Pw2t for the recording film of the second layer 101b calculated in this way is set in the power control unit 32 (S323).

  When the function of Pw1 (for example, F2 (Pw1)) is stored in the RAM 44 instead of the ratio Pw2 / Pw1, the power adjustment unit 343 receives the function F2 (Pw1) and the first layer 101a from the RAM 44. The current control target level Pw1t for the recording film of the second layer 101b may be read (S321), and the current control target level Pw2t for the recording film of the second layer 101b may be calculated according to the formula Pw2t = F2 (Pw1t) ( S322).

Here, the current control target level Pw1t for the recording film of the first layer 101a is intended to compensate for the fluctuation of the control target level Pw1 due to the spherical aberration fluctuation. For example, the control target level Pw1 is the control target level at the reference spherical aberration Z0 μm (base material conversion), the spherical aberration changes from Z0 μm to Z1 μm, and the spherical aberration correction coefficient K _S (Z1 μm) for the current spherical aberration Z1 μm. Is 1.02 (102%). In this case, the current control target level Pw1t is calculated according to the formula: Pw1t = Pw1 × K _S (Z1 μm) = 1.02 · Pw1. The spherical aberration correction coefficient K _S can be stored, for example, in the spherical aberration correction table of the RAM 44 as a power factor with respect to the reference spherical aberration of the reference layer.

FIG. 10B shows an example of a spherical aberration correction table. In this example, K _S (Z1 μm) = 1.02 (102%) and K _S (Z2 μm) = 0.98 (98%) with respect to the reference spherical aberration Z0 μm.

  The power adjustment unit 343 does not read out the control target level ratio Pw2 / Pw1 from the table stored in the RAM 44, but instead controls the control target level ratio recorded in a predetermined area (for example, the lead-in area) of the optical disc 101. Pw2 / Pw1 may be read out. Alternatively, instead of reading the Pw1 function (eg, F2 (Pw1)) from the table stored in the RAM 44, the power adjustment unit 343 reads the Pw1 recorded in a predetermined area (eg, the lead-in area) of the optical disc 101. You may make it read a function.

  In this way, the power adjustment unit 343 determines the power of the laser light for the recording film of the second layer 101b based on the power of the laser light adjusted for the recording film of the first layer 101a.

  It is determined whether or not the spherical aberration has changed (S312). The output of the spherical aberration detector 317 is AD converted by the AD converter 45 built in the DSP 330, and the output of the AD converter 45 is supplied to the power adjustment unit 343. The power adjustment unit 343 determines, for example, whether the spherical aberration has changed by monitoring the output of the AD converter 45.

If it is determined that the spherical aberration has changed, it is determined whether or not the power of the laser beam with respect to the recording film of the first layer 101a has been adjusted with respect to the current spherical aberration (S314). Such a determination is made, for example, whether or not the control target level Pw1 for the recording film of the first layer 101a has been adjusted with respect to the current spherical aberration (that is, the current control target level Pwlt for the current spherical aberration). Alternatively, it is determined by determining whether or not the spherical aberration correction coefficient K _S for the current spherical aberration is stored in the RAM 44. For example, the power adjustment unit 343 searches the RAM 44 to determine whether or not the control target level Pw1 has been adjusted.

  If it is determined that the power of the laser beam with respect to the recording film of the first layer 101a has been adjusted, steps S321, S322, and S323 are executed. Steps S321, S322, and S323 are as described above.

When it is determined that the laser beam power for the recording film of the first layer 101a has not been adjusted, the power adjustment for the first layer 101a is performed in the same manner as in step S101 shown in FIG. 3A (S331). ). In such power adjustment, for example, the power control unit 32 irradiates the optical disc 101 with laser light having power according to a predetermined control target level Pw1 ′ for the recording film of the first layer 101a. Then, the laser element 12 is controlled, and the power adjustment unit 343 adjusts the control target level for the recording film of the first layer 101a so that the asymmetry of the reflected light from the optical disc 101 becomes a desired value (for example, 0). Is achieved by doing The power adjustment unit 343 calculates a value to be stored in the table of the RAM 44 (S332), and updates the table of the RAM 44 using the calculated value (S333). For example, the power adjustment unit 343 may store a set of the current spherical aberration and the control target level adjusted by the power adjustment unit 343 (control target level for the current spherical aberration) in the RAM 44, A spherical aberration correction coefficient K _S for the current spherical aberration is calculated from the control target level for the reference spherical aberration and the control target level (the control target level for the current spherical aberration) adjusted by the power adjustment unit 343, and the current spherical surface is calculated. A set of aberration and spherical aberration correction coefficient K _S may be stored in the RAM 44.

  According to the laser beam power adjustment method described above, the table data indicating the laser beam power adjusted for each spherical aberration is stored in the RAM 44 built in the DSP 330. When there is table data stored in the past for the spherical aberration, the control target level of the power control unit 32 can be set based on the table data stored in the RAM 44 without recording and reproducing. Further, even in an optical disc including a plurality of layers, recording of each layer other than the reference layer is performed based on a ratio between the control target level for the recording film of one reference layer and the control target level for the recording film of each layer other than the reference layer. A control target level for the membrane can be set. Alternatively, instead of the ratio, a function of a control target level with respect to the recording film of the reference layer may be used. The function may be, for example, a linear function or a quadratic function. As a result, with respect to an optical disc having a plurality of layers, a reproduction signal is obtained in which the asymmetry of the reflected light becomes a desired value (for example, 0) even if the spherical aberration fluctuates due to the uneven thickness of the base material of the optical disc. Adjustment of the power of the laser beam for recording to be obtained can be realized in substantially the same time as a single-layer optical disc.

  The asymmetry detector 42 is used for detecting the optimum power of the laser light. The asymmetry detector 42 may be replaced with an arbitrary detector that detects the optimum power of the laser beam. For example, the asymmetry detection unit 42 can be replaced with a modulation degree detection unit that detects the modulation degree of reflected light from the optical disc. For example, the modulation degree detection unit detects the modulation degree (Ipk−Ibm) / Ipk of the reflected light from the peak level Ipk and the bottom level Ibm of the reflected light, and outputs a signal indicating the modulation degree of the reflected light to the power adjustment unit. To do. The power adjusting unit adjusts the control target level of the power of the laser light so that the modulation degree of the reflected light becomes a desired value.

  When information is recorded on an optical disc by the CAV method in which the angular velocity of the optical disc is constant, the linear velocity of the optical disc is proportional to the position along the radial direction of the optical disc.

  FIG. 11 is a characteristic diagram showing the relationship between the position along the radial direction of the optical disc and the power of the laser beam. In FIG. 11, the horizontal axis indicates the position along the radial direction of the optical disc, and the vertical axis indicates the power of the laser beam. As shown in FIG. 11, since the optimum power of the laser beam varies depending on the position along the radial direction of the optical disk, the power of the laser beam is adjusted at two or more positions along the radial direction. Must be stored in the RAM along with the radial position. For example, the power of the laser beam may be adjusted at the positions along two radial directions, point A and point B shown in FIG. 11, and the characteristics obtained by linear approximation of the two points may be stored in the RAM. In the case of a two-layer optical disk, the optimum value of the laser beam power corresponding to the position along the radial direction is stored for only one reference layer, and the power ratio of the laser beam is used for layers other than the reference layer. It may be configured to calculate using such as. By adjusting the power of the laser beam performed at each position along the radial direction of the optical disc for only one reference layer, the time for adjusting the power of the laser beam can be shortened. In this case, the power characteristic of the laser beam with respect to the linear velocity may be used instead of the power characteristic of the laser beam with respect to the position along the radial direction of the optical disk.

  In the first to third embodiments described above, the example in which the control target level of the laser light power is adjusted in accordance with each of the temperature variation, tilt variation, and spherical aberration variation has been described. It is also within the scope of the present invention to adjust the control target level of the laser light power in accordance with a combination of at least two of temperature variation, tilt variation and spherical aberration variation.

  For example, the DSP 130 (or the like) may be provided with a fluctuation detector including at least one of the temperature detector 17 (FIG. 1), the tilt detector 217 (FIG. 5), and the spherical aberration detector 317 (FIG. 8). 230, 330). In this case, the power adjustment unit 143 (or 243, 343) is based on at least one of the output from the temperature detection unit 17, the output from the tilt detection unit 217, and the output from the spherical aberration detector 317. The control target level for the recording film of the reference layer is adjusted.

For example, the control target level for the recording film of the reference layer (for example, the first layer 101a) at the reference temperature X0 ° C., the reference tilt Y0 °, and the reference spherical aberration Z0 μm is Pw1, and the temperature correction coefficient K for the current temperature X1 ° C. _T (X1 ° C.) is 1.01 (101%), the tilt correction coefficient K _C (Y1 °) for the current tilt Y1 ° C. is 1.03 (103%), and the spherical aberration correction coefficient for the current spherical aberration Z1 μm. K _S (Z1 μm) is set to 1.02 (102%). In this case, the control target level Pw1t for the recording film of the reference layer at the current temperature X1 ° C., the current tilt Y1 °, and the current spherical aberration Z1 μm is Pw1t = Pw1 × K _T (X1 ° C.) × K _C (Y1 ° ) × K _S (Z1 μm) = Pw1 × 1.01 × 1.03 × 1.02

Further, the control target level Pw2t for the recording film other than the reference layer (for example, the second layer 101b) at the current temperature X1 ° C., the current tilt Y1 °, and the current spherical aberration Z1 μm is Pw2t = F2 (Pw1 ) × K _T (X1 ° C.) × K _C (Y1 °) × K _S (Z1 μm) = F2 (Pw1) × 1.01 × 1.03 × 1.02 Here, F2 (Pw1) is a function of Pw1 used to determine a control target level for the recording film of a layer other than the reference layer (for example, the second layer 101b). In this way, at least one correction coefficient (K _T , K _C , K _S, etc.) for the reference layer and an interlayer correction coefficient (F2 (Pw1), etc.) between the reference layer and a layer other than the reference layer are combined. By using these, the control target level for the recording film of the layer other than the reference layer can be calculated. These correction coefficients are stored in a memory such as a RAM in the form of a table, for example.

  In the first to third embodiments described above, the example in which the power of the laser beam for the recording film of the first layer 101a is adjusted by adjusting the control target level for the recording film of the first layer 101a has been described. However, the present invention is not limited to this. For example, the power of the laser light with respect to the recording film of the first layer 101a may be adjusted by adjusting the level of the laser light detected by the emission light detector 13, or the level of the laser driving value may be adjusted. Thus, the power of the laser beam for the recording film of the first layer 101a may be adjusted. Alternatively, the power of the laser beam with respect to the recording film of the first layer 101a is adjusted by adjusting at least one of the level of the laser beam detected by the emission light detector 13, the control target level, and the level of the laser driving value. You may adjust. Such adjustment is performed by, for example, a power adjustment unit, and the adjustment result is set in the power control unit.

  In the first to third embodiments described above, the optical disk apparatus of the type that irradiates laser light from one side of the optical disk has been described, but the present invention is not limited to this. For example, the present invention can be applied to an optical disc apparatus that irradiates laser light from both sides of the optical disc.

  In the first to third embodiments described above, the optical disk having a plurality of layers has been described. However, the present invention is not limited to this. For example, the present invention can be applied to a disk changer that performs recording or reproduction on a single-layer optical disk selected from a plurality of single-layer optical disks.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful as a laser power control apparatus and method used in an optical disc apparatus that records information on an optical disc having a plurality of layers, an optical disc apparatus that records information on the optical disc, a recording method that records information on the optical disc, and the like. is there.

1 is a block diagram showing a configuration of an optical disc device according to Embodiment 1. FIG. Characteristic diagram showing the relationship between laser beam power and reflected light asymmetry 7 is a flowchart showing a procedure of an initial adjustment method of laser beam power in the first embodiment. The figure which shows an example of an interlayer correction table 7 is a flowchart showing a procedure of a laser beam power readjustment method according to the first embodiment. The figure which shows an example of a temperature correction table FIG. 3 is a block diagram showing a configuration of an optical disc device according to a second embodiment. Characteristic diagram showing the relationship between tilt and laser beam power 7 is a flowchart showing the procedure of the laser light power readjustment method according to the second embodiment. The figure which shows an example of a tilt correction table FIG. 7 is a block diagram showing a configuration of an optical disc device according to a third embodiment. Characteristic chart showing the relationship between spherical aberration and laser beam power Flowchart showing the procedure of the laser light power readjustment method in the third embodiment The figure which shows an example of a spherical aberration correction table Characteristic diagram showing the relationship between the position along the radial direction of the optical disk and the power of the laser beam The block diagram which shows the structure of the optical disk apparatus in a prior art The flowchart which shows the procedure of the adjustment method of the power of the laser beam in a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Drive circuit 10 Optical pick-up 11 Converging lens 12 Laser element 13 Outgoing light detector 14 Reflected light detector 15 Reflecting plate 16 Deflection hologram 17 Temperature detector 30 DSP (Digital Signal Processor)
31 AD conversion unit 32 Power control unit 33 DA conversion unit 41 AD conversion unit 42 Asymmetry detection unit 43 Power adjustment unit 44 RAM
45 AD converter 101 Optical disc 130 DSP
143 Power adjustment unit

Claims (15)

A laser power control device used in an optical disc apparatus for recording information on an optical disc having at least a first layer and a second layer,
A power control unit for controlling the laser element so that the power of the laser beam approaches the control target level;
A fluctuation detecting unit for detecting that a recording condition for the optical disc has fluctuated;
A power adjusting unit that adjusts the power of the laser beam with respect to the recording film of the first layer in accordance with the output from the fluctuation detecting unit,
The laser power control device, wherein the power adjustment unit determines the power of the laser beam with respect to the recording film of the second layer based on the power of the laser beam adjusted with respect to the recording film of the first layer. The optical disc apparatus includes an optical pickup that irradiates the optical disc with laser light, and a drive circuit that drives the optical pickup,
The optical pickup includes the laser element, and an emitted light detector that detects the laser light emitted from the laser element,
The power control unit generates a laser drive value so that the power of the laser light detected by the emitted light detector approaches a control target level, and controls the laser element according to the laser drive value,
The power adjustment unit is configured to output at least one of a laser light level detected by the emission light detector, the control target level, and the laser drive value level according to an output from the fluctuation detection unit. The laser power control apparatus according to claim 1, wherein the power of the laser beam with respect to the recording film of the first layer is adjusted by adjusting.   2. The laser power control apparatus according to claim 1, wherein the power adjustment unit determines the control target level for the recording film of the second layer as a function of the control target level for the recording film of the first layer. .   4. The laser power control apparatus according to claim 3, wherein the function is a ratio of the control target level for the recording film of the second layer to the control target level for the recording film of the first layer.   The laser power control apparatus according to claim 3, wherein the function is a linear function or a quadratic function.   The laser power control apparatus according to claim 3, wherein the function is recorded in a predetermined area of the optical disc. The optical disc further includes a third layer,
The power adjustment unit further determines the control target level for the recording film of the third layer as a function of the control target level for the recording film of the first layer;
The function used when determining the control target level for the recording film of the second layer is different from the function used when determining the control target level for the recording film of the third layer. The laser power control apparatus according to claim 1. The fluctuation detection unit includes a temperature detection unit that detects a temperature, a tilt detection unit that detects a tilt between a normal direction of an information surface of the optical disc and an optical axis direction of the laser light applied to the optical disc, And at least one of a spherical aberration detector for detecting a spherical aberration of the laser beam due to a substrate thickness of the optical disc,
The power adjusting unit applies to the recording film of the first layer based on at least one of an output from the temperature detecting unit, an output from the tilt detecting unit, and an output from the spherical aberration detecting unit. The laser power control apparatus according to claim 1, wherein the laser power is adjusted. The laser power control device further includes an asymmetric detector that detects asymmetry of reflected light from the optical disc,
2. The laser power control apparatus according to claim 1, wherein the power adjustment unit adjusts the power of the laser beam with respect to the recording film of the first layer so that an output from the asymmetric detection unit becomes a desired value. The laser power control device further includes a modulation degree detection unit that detects a modulation degree of reflected light from the optical disc,
2. The laser power control apparatus according to claim 1, wherein the power adjustment unit adjusts the power of the laser beam with respect to the recording film of the first layer so that an output from the modulation degree detection unit becomes a desired value. . In the initial adjustment of the power of the laser light, the power control unit controls the laser element so that the power of the laser light approaches a control target level Pw2 ′ set in advance for the recording film of the second layer. Control
The control target level Pw2 ′ includes the control target level Pw1 adjusted for the recording film of the first layer, the level of the reference power Pw1 ″ for the recording film of the first layer, and the second layer And the reference power Pw1 ″ is recorded in a predetermined area of the optical disc, and the reference power Pw2 ″ is applied to a predetermined area of the optical disc. The laser power control device according to claim 1, wherein the laser power control device is recorded.   The laser power control apparatus according to claim 11, wherein the control target level Pw2 ′ is defined by an expression Pw2 ′ = Pw1 × Pw2 ″ / Pw1 ″. A laser power control method used in an optical disc apparatus for recording information on an optical disc having at least a first layer and a second layer,
Controlling the laser element so that the power of the laser beam approaches the control target level;
Detecting that the recording conditions for the optical disc have changed,
Adjusting the power of the laser beam with respect to the recording film of the first layer according to the change in the recording condition;
Determining the power of the laser beam for the recording film of the second layer based on the power of the laser beam adjusted for the recording film of the first layer. An optical disc apparatus for recording information on an optical disc having at least a first layer and a second layer,
An optical pickup for irradiating the optical disc with laser light;
A drive circuit for driving the optical pickup;
A laser power control device for controlling the power of the laser beam,
The laser power control device
A power control unit for controlling the laser element so that the power of the laser beam approaches a control target level;
A fluctuation detecting unit for detecting that a recording condition for the optical disc has fluctuated;
A power adjusting unit that adjusts the power of the laser beam with respect to the recording film of the first layer in accordance with the output from the fluctuation detecting unit,
The power adjusting unit is an optical disc apparatus that determines the power of the laser light with respect to the recording film of the second layer based on the power of the laser light adjusted with respect to the recording film of the first layer. A recording method for recording information on an optical disc having at least a first layer and a second layer,
Irradiating the optical disc with laser light;
Controlling the power of the laser beam,
The step of controlling the power of the laser beam includes:
Controlling the laser element such that the power of the laser light approaches a control target level;
Detecting that the recording conditions for the optical disc have changed,
Adjusting the power of the laser beam with respect to the recording film of the first layer according to the change in the recording condition;
Determining the power of the laser beam for the recording film of the second layer based on the power of the laser beam adjusted for the recording film of the first layer.

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