JP4372114B2 - Optical disc apparatus, optical disc, focus servo method and program - Google Patents

Description

  The present invention relates to an optical disc apparatus, an optical disc, a focus servo method, and a program, and more particularly to an automatic focusing technique based on reflected light from an optical disc.

  An optical disc apparatus moves an optical pickup (optical head) in a radial direction of an optical disc and a focal direction of a lens in order to access a desired track of the optical disc on which recording / reproducing tracks are formed in a spiral shape or a circumferential shape. Read and write. A technique for correcting a focus shift by providing a focus servo adjustment area (calibration area) in a part of an optical disk for the purpose of lens alignment during movement in the focal direction is known (Patent Documents 1 and 2). reference).

  The optical disk device described in Patent Document 1 applies a linearly polarized laser beam having a single wavelength to an optical disk medium, separates the reflected light, inputs it to a two-part photosensor, extracts the difference signal and the sum signal, Auto focus using the signal. A high-pass filter that passes a high-frequency signal of the sum signal, an integrator that integrates the signal that has passed through the high-pass filter, an AD converter that converts the signal into a digital signal, and converted calibration level data A microprocessor for comparing with previous calibration level data, a DA converter for converting the objective lens into an analog signal based on the calculation result, and an electric power for driving the electromagnetic coil by inputting the analog signal And a power amplifier that outputs. In addition, the optical disk medium is formed with a radial groove having a certain width in a certain region in the vicinity of the inner periphery of the optical disk medium, separately from the groove of the track formed concentrically.

  The optical disc apparatus described in Patent Document 2 performs focus servo on an optical disc including a focus servo adjustment region in which concave and convex shapes are arranged in the radial direction. An optical pickup including an objective lens that condenses and irradiates an optical disk with laser light beyond the diffraction limit of a single lens is moved to the focus servo adjustment area, and focus pull-in is performed in the focus servo adjustment area. Then, the objective lens is moved in the radial direction of the optical disc, the peak of the reproduced signal detected due to the uneven shape is detected, and the offset of the focus servo is adjusted so that the peak of the reproduced signal is maximized.

  According to such an optical disk device, a focus servo adjustment area (calibration area) is provided on the optical disk, and a correction value for defocus is obtained by accessing this area, and the defocus is corrected by this correction value. Accurate focusing can be performed.

JP-A-6-60407 JP 2001-93163 A

  Incidentally, in recent years, the recording density of optical discs has been increased, and there are optical discs provided with a plurality of recording layers. In the focus control of the conventional optical disc apparatus, when the reflectance is within a certain range (within the standard), it is possible to perform focusing normally. However, in an optical disc having a plurality of recording layers, since the reflectivity is different, focusing cannot be performed reliably. When the data is used only for data reproduction, if the lens is near the focal point, the data reproduction process may not be affected much. On the other hand, in the data recording process, there is an increased possibility that normal recording cannot be performed because the energy density with respect to the recording surface is dispersed or the size and shape of the data pits are changed.

  An object of the present invention is to provide a focusing technique for surely focusing on a multi-layered optical disk having a plurality of recording / reproducing layers.

  An optical disc apparatus according to one aspect of the present invention includes a recording / reproducing area having grooves formed concentrically, and a calibration area in which a radial groove having a constant width is formed in a predetermined area. Is an optical disc apparatus for accessing an optical disc having a plurality of recording layers corresponding to laser beams having different wavelengths, and irradiating the optical discs with laser beams having different wavelengths corresponding to the plurality of recording layers in the calibration region. Laser light generator, optical sensor that converts the reflected light from the recording layer of the optical disk into an electrical signal, and reflected light obtained by sequentially irradiating the calibration area with laser light of different wavelengths in initialization of disk access Holds the correction bias value of the focus servo corresponding to each position where becomes in-focus, and when accessing the recording / playback area A focusing control circuit that outputs a drive signal based on a correction bias value corresponding to the laser light of a predetermined wavelength in focusing of the reflected light obtained by irradiating the recording / reproducing area with the laser light of a predetermined wavelength; A focus direction drive coil that positions the focal point of the lens with respect to the recording layer of the optical disc according to the drive signal.

  In the optical disk apparatus of the first development form, the focusing control circuit is configured to obtain a maximum value of a high-frequency component that separates and outputs a focus control signal included in the electrical signal, and a high-frequency component of the focus control signal separated by the high-pass filter. A level determination circuit that originally obtains a correction bias value, a correction bias generator that holds correction bias values corresponding to each of a plurality of recording layers, and outputs the correction bias values upon request, and while receiving correction bias values, A focus level generator that outputs a voltage value required for alignment, and a focus direction drive amplifier that outputs a drive signal to the focus direction drive coil in accordance with the voltage value output from the focus level generator. Good.

  In the optical disk apparatus of the second development form, the level determination circuit includes a peak hold circuit that stores the maximum value of the high-frequency component of the separated focus control signal component, and an AD converter that converts the output of the peak hold circuit into a digital value The correction bias generator includes a plurality of correction bias generation circuits that store the output data of the AD converter in association with each of the plurality of recording layers, and is an access target when accessing the recording / reproducing area. One of a plurality of correction bias generation circuits may be selected corresponding to the recording layer, and the output value to be output may be supplied to the focus level generator.

  An optical disc according to one aspect of the present invention includes a recording / reproducing area having grooves formed concentrically, and a calibration area in which a radial groove having a constant width is formed in a predetermined area. A plurality of recording layers corresponding to laser beams having different wavelengths.

  In the optical disk of the first development form, recording layers corresponding to a plurality of recording layers may be provided in the recording / reproducing area.

  A focus servo method according to one aspect of the present invention includes a recording / reproducing area having grooves formed concentrically and a calibration area in which a radial groove having a constant width is formed in a predetermined area. The area is a method in which the optical disk apparatus performs focus servo by accessing an optical disk having a plurality of recording layers corresponding to laser beams each having a different wavelength. In initialization of disk access, each wavelength is set in the calibration area. A step of holding a correction bias value of each focus servo corresponding to each position where reflected light obtained by sequentially irradiating different laser beams is focused, and a laser having a predetermined wavelength when accessing the recording / reproducing area The correction bias corresponding to the laser beam of a predetermined wavelength is used for focusing the reflected light obtained by irradiating the recording / reproducing area with light. Including a step of performing, based on the.

  In the focus servo method of the first development mode, in the step of holding the correction bias value, the position where the reflected light is in focus is determined from the amplitude of the sensor signal obtained by converting the reflected light into the electrical signal, and the electrical signal The correction bias value may be obtained based on the level of the sensor signal at the time when the amplitude of the high-frequency component becomes the maximum value.

  A program according to one aspect of the present invention includes a recording / reproducing area having grooves formed concentrically, and a calibration area in which a radial groove having a constant width is formed in a predetermined area. The reflected light obtained by sequentially irradiating the calibration area with laser beams having different wavelengths on a computer that constitutes an optical disc apparatus that accesses an optical disc having a plurality of recording layers corresponding to laser beams having different wavelengths respectively. A disk access initialization process that holds the correction bias value of each focus servo corresponding to each focus position, and focusing of reflected light obtained by irradiating the recording / reproducing area with laser light of a predetermined wavelength A recording / reproducing area access process for generating a servo signal for generating a servo signal based on a correction bias value corresponding to a laser beam of a predetermined wavelength; To be executed.

  In the program of the first development form, in the disk access initialization process, the position where the reflected light is in focus is determined from the amplitude of the sensor signal obtained by converting the reflected light into the electrical signal, and the high frequency component of the electrical signal is determined. The correction bias value may be obtained based on the level of the sensor signal when the amplitude reaches the maximum value.

  According to the present invention, when accessing an optical disc having a plurality of recording layers, a correction value is obtained for each recording layer using an optical disc provided with a defocus calibration area for each recording layer, and the defocus is calculated using this correction value. Correcting enables accurate focusing.

  FIG. 1 is a diagram schematically showing the structure of an optical disc according to an embodiment of the present invention. In FIG. 1, an optical disk 10 has a recording / reproducing area 11 having grooves in a track direction formed concentrically or spirally, and a radial groove having a constant width in a predetermined area of the optical disk, for example, a constant area near the inner periphery. And a formed calibration region 12. Further, the optical disc 10 includes a plurality of recording layers, for example, a recording layer A for wavelength λa, a recording layer B for wavelength λb, and a recording layer C for wavelength λc.

  The calibration region 12 is formed, for example, in a section having a width of 3 mm in the vicinity of the inner periphery so that the depth of the groove in the radial direction is 1/4 of the wavelength λ of the laser beam irradiated corresponding to each recording layer. Further, the grooves are formed at intervals equal to or close to the wavelength λ of the laser beam. With such a structure, the phase difference between the reflected light from the partial concave portion of the groove of the optical disk recording surface and the reflected light from the convex portion of the irradiated laser light is λ / 4 × 2 = λ / 2. An addition effect is produced at the boundary between the concave and convex portions, and reflected light for focus control is obtained.

  FIG. 2 is a block diagram showing a configuration of the optical disc apparatus according to the embodiment of the present invention. In FIG. 2, the optical disk apparatus includes an optical head 20, a preamplifier 30, a focusing control circuit 40, and a track control circuit 60. The optical head 20 includes a laser light generator 21, a diffraction grating 22, a half mirror 23, a collimator lens 24, an objective lens 25, an optical sensor 26, a focal direction drive coil 27, and a track direction drive coil 28.

  The laser beam generator 21 selectively outputs laser beams A, B, and C having a plurality of wavelengths. The diffraction grating 22 functions so as not to pass the polarization plane of the laser light irradiated by the laser light generator 21 or to return the reflected light to the laser light generator 21. The half mirror 23 irradiates the optical disk surface with laser light and transmits the reflected light to the optical sensor 26. The collimator lens 24 converts the diffused light into parallel light. The objective lens 25 is movable in the focal direction or in the radial direction of the optical disk 10, and makes the focal point of the irradiation light coincide with the recording surface of the optical disk 10 or aligns the irradiation light with the track orbit. The optical sensor 26 receives reflected light from the recording surface of the optical disc 10 and converts it into an electrical signal. Further, the preamplifier 30 amplifies the signal converted into the electric signal by the optical sensor 26 and outputs the optical sensor signal Vs to the focusing control circuit 40. The focus control circuit 40 generates a drive signal based on the optical sensor signal Vs and operates the focus direction drive coil 27. The focal direction drive coil 27 drives the objective lens 25 based on the drive signal. Further, the track control circuit 60 drives the track direction drive coil 28 based on the optical sensor signal Vs to move the objective lens 25 in the radial direction of the optical disc.

  FIG. 3 is a block diagram illustrating the configuration of the focusing control circuit 40. The focusing control circuit 40 includes a low-pass filter 41, a high-pass filter 42, a reflected light peak level determination unit 43, a focus position correction bias generator 44, a focus level generator 45, a lens position determination circuit 46, a microcomputer 47, and an initial stage. A focusing circuit 48, an analog switch 49, and a focus direction drive amplifier 50 are provided.

  The focus control circuit 40 corrects the bias bias value of the focus servo corresponding to each position where the reflected light obtained by sequentially irradiating the calibration region 12 with laser beams having different wavelengths in the initialization of disk access. Are held in the focal position correction bias generator 44, respectively. In this initial position control state, the focus direction drive coil 27 is driven by drive signals generated by the path of the lens position determination circuit 46, the microcomputer 47, the initial focus adjustment circuit 48, the analog switch 49, and the focus direction drive amplifier 50. .

  Further, the focusing control circuit 40 corresponds to laser light having a predetermined wavelength in focusing of reflected light obtained by irradiating the recording / reproducing area 11 with laser light having a predetermined wavelength when the recording / reproducing area 11 is accessed. A drive signal is output based on the correction bias value. In this automatic focusing state, the focus direction drive coil 27 is driven by a drive signal generated by the path of the low-pass filter 41, the focus level generator 45, the analog switch 49, and the focus direction drive amplifier 50.

  The high-pass filter 42 passes the high-frequency component voltage Vac of the optical sensor signal Vs and outputs it to the reflected light peak level determiner 43. The reflected light peak level determination unit 43 holds the maximum level value (peak value) of the high-frequency component voltage Vac of the optical sensor signal Vs, performs AD conversion, and outputs it to the focal position correction bias generator 44. The focal position correction bias generator 44 uses the data of the reflected light peak level determination unit 43 reflecting the difference in reflectance of the optical disc 10 with respect to the focal level generator 45 for controlling the in-focus position of the objective lens 25. A correction bias is supplied to the focus level generator 45.

  Next, the operation of the optical disc apparatus will be described. FIG. 4 is a flowchart showing the operation of the optical disc apparatus according to the embodiment of the present invention.

  When the power of the optical disk apparatus is turned on (step S1), the initial state of the apparatus is recognized by the control programmed in the microcomputer 47 (step S2), and the optical disk 10 is waited for loading (step S3).

  When the optical disk 10 is loaded, the optical disk 10 is rotated (step S4), and a focus pull-in operation is executed (step S5). In this focus pull-in operation, the focus control circuit 40 performs the following focus adjustment.

  FIG. 5 is a diagram showing the relationship between the position of the objective lens 25 and the potential of the optical sensor signal Vs. The focus position potential is Vsj, the focus pull-in position potential (automatic focus start potential) is Vsp, the far-position potential is Vsf, the near-position potential is Vsx, Vsy, and near the focus position. The potential at the position on the lens side is Vsz. Each potential has a relationship of Vsf> Vsp> Vsx> Vsj> Vsy> Vsz. The optical sensor signal Vs is an addition voltage of the high-frequency component voltage Vac of the recording data and the voltage Vdc indicating the defocus amount, and has a relationship of Vs = Vac + Vdc.

  The output of the initial focusing circuit 48 is controlled by the microcomputer 47 to output a potential for driving the objective lens 25 gradually from the far position to the near position to the focus direction driving amplifier 50 via the analog switch 49 to drive the focus direction. The amplifier 50 moves the objective lens 25 in the focal direction. Along with this, as shown in FIG. 5, the optical sensor signal Vs changes according to the position of the objective lens 25. In the vicinity of the focal point, in particular, the unevenness of the data track that crosses the laser beam spot due to the eccentricity is largely captured by the high-pass filter 42 as the voltage Vac of the high-frequency component of the optical sensor signal Vs.

  If the focus pull-in is successful, the track control circuit 60 for placing the laser beam spot on the data track trajectory is then activated (step S6). Further, the objective lens 25 is controlled through the track direction drive coil 28 so that the laser beam spot is maintained on the data track trajectory.

  Next, it moves to the target track for recording or reproducing data (step S7), performs data recording / reproducing processing (step S8), and ends recording / reproducing data on the same optical disk (step S9). Steps S7 to S9 are repeated.

  After the data recording / reproduction is completed, it is confirmed whether or not the optical disk has been taken out (step S10), and a new optical disk is awaited (step S3).

  Next, the focusing operation will be described in detail. FIG. 6 is a flowchart showing details of step S5 for performing defocus calibration and focus pull-in.

  Data Df at which the position of the objective lens 25 becomes the far position Vsf shown in FIG. 5 is input to the initial focusing circuit 48 (step S51). The analog switch 49 is switched so that the output of the initial focusing circuit 48 is input to the focal direction driving amplifier 50 (step S52).

  Data Df + 1 for driving the objective lens 25 from the far position to the near position is input to the initial focusing circuit 48 (step S53), and it is monitored whether or not “optical sensor signal Vs ≧ automatic focusing start potential Vsp”. (Steps S54 and S55). If “Vs <Vsp”, steps S53 and S54 are repeated until “Vs ≧ Vsp”.

  The peak hold data Pd is monitored by the reflected light peak level determination unit 43 from the time when “Vs ≧ Vsp” is satisfied (steps S56 to S60), and the output voltage Vf of the initial focusing circuit 48 at the time when Pd does not change. Is stored (step S61).

  The peak hold data Pd is taken into one circuit of the focus position correction bias generator 44, for example, the correction bias circuit 44a, and the bias voltage is output to the focus level generator 45 (step S62). = The output voltage Vf of the initial focusing circuit 48 is confirmed (step S63).

  When “Vo = Vf”, the analog switch 49 is switched to connect the focus level generator 45 and the focus direction drive amplifier 50 (step S64).

  By the operation of the focusing control circuit 40 operating as described above, the objective lens 25 → the optical sensor 26 → the preamplifier 30 → the low pass filter 41 → the focus level generator 45 → the analog switch 49 → the focus direction drive amplifier 50 → the focus. A closed circuit composed of the direction drive coil 27 and the objective lens 25 is formed, and is controlled so as to maintain the potential Vsj at the in-focus position with respect to a desired recording layer.

  In step S60, if the peak hold data Pd does not change or approximate data cannot be obtained, an error indicating an abnormality of the optical disk carrier or the optical disk apparatus is displayed (step S65), and the process ends.

  As described above, when accessing an optical disc having a plurality of recording layers with different media, the optical disc apparatus obtains a correction value using an optical disc provided with a defocus calibration area for each recording layer, and based on the stored correction value. Operates to focus. Therefore, even when accessing an optical disc having a plurality of recording layers, more accurate focusing can be performed.

It is a figure which shows typically the structure of the optical disk which concerns on embodiment of this invention. 1 is a block diagram illustrating a configuration of an optical disc device according to an embodiment of the present invention. It is a block diagram showing the structure of a focusing control circuit. 5 is a flowchart showing the operation of the optical disc apparatus according to the embodiment of the present invention. It is a figure which shows the relationship between the position of an objective lens, and the electric potential of an optical sensor signal. It is a flowchart which shows the detail of the step which performs a focus shift calibration and focus drawing-in.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical disk 11 Recording / reproducing area 12 Calibration area 20 Optical head 21 Laser light generator 22 Diffraction grating 23 Half mirror 24 Collimator lens 25 Objective lens 26 Optical sensor 27 Focus direction drive coil 28 Track direction drive coil 30 Preamplifier 40 Focusing Control circuit 41 Low-pass filter 42 High-pass filter 43 Reflected light peak level determination unit 44 Focus position correction bias generators 44a to 44c Correction bias circuit 45 Focus level generator 46 Lens position determination circuit 47 Microcomputer 48 Initial focusing circuit 49 Analog Switch 50 Focus direction drive amplifier 60 Track control circuit

Claims (9)

It has a recording / reproducing area having grooves formed concentrically and a calibration area in which a radial groove having a constant width is formed in a predetermined area, and the calibration area corresponds to at least laser beams having different wavelengths. An optical disk device for accessing an optical disk having a plurality of recording layers,
A laser beam generator for irradiating the optical disc with laser beams having different wavelengths corresponding to a plurality of recording layers in the calibration region;
An optical sensor that converts reflected light from the recording layer of the optical disc into an electrical signal;
In initialization of disk access, the correction bias value of the focus servo corresponding to each position where the reflected light obtained by sequentially irradiating the calibration area with laser beams of different wavelengths is in focus is recorded and reproduced. When the area is accessed, a driving signal is output based on the correction bias value corresponding to the laser light of the predetermined wavelength in focusing of the reflected light obtained by irradiating the recording / reproducing area with the laser light of the predetermined wavelength. A focusing control circuit;
A focal direction drive coil for positioning the focal point of the lens with respect to the recording layer of the optical disc by the drive signal;
An optical disc apparatus comprising: The focusing control circuit includes:
A high-pass filter that separates and outputs a focus control signal included in the electrical signal;
A level determination circuit for obtaining the correction bias value based on the maximum value of the high-frequency component of the focus control signal separated by the high-pass filter;
A correction bias generator that holds the correction bias value corresponding to each of the plurality of recording layers and outputs the correction bias value upon request;
A focus level generator that outputs a voltage value required for focusing while receiving the correction bias value;
A focus direction drive amplifier that outputs a drive signal to the focus direction drive coil in accordance with a voltage value output by the focus level generator;
The optical disk apparatus according to claim 1, further comprising: The level determination circuit includes:
A peak hold circuit for storing a maximum value of a high frequency component of the separated focus control signal component;
An AD converter for converting the output of the peak hold circuit into a digital numerical value;
The correction bias generator is
A plurality of correction bias generation circuits for storing the output data of the AD converter corresponding to each of the plurality of recording layers,
When accessing the recording / reproducing area, one of the plurality of correction bias generation circuits is selected corresponding to a recording layer to be accessed, and an output value to be output is supplied to the focus level generator. The optical disk apparatus according to claim 2. A recording / reproducing area having grooves formed concentrically;
A calibration region having a radial groove having a constant width in a predetermined region,
An optical disc comprising a plurality of recording layers corresponding to at least laser beams having different wavelengths in the calibration region.   5. The optical disc according to claim 4, further comprising a recording layer corresponding to each of the plurality of recording layers in the recording / reproducing area. It has a recording / reproducing area having grooves formed concentrically and a calibration area in which a radial groove having a constant width is formed in a predetermined area, and the calibration area corresponds to at least laser beams having different wavelengths. An optical disc apparatus accesses an optical disc having a plurality of recording layers to perform focus servo,
In initialization of disk access, a step of holding a correction bias value of each focus servo corresponding to each position where reflected light obtained by sequentially irradiating laser beams having different wavelengths to the calibration area is in focus; and ,
A step of performing focusing of reflected light obtained by irradiating the recording / reproducing area with laser light having a predetermined wavelength based on the correction bias value corresponding to the laser light having the predetermined wavelength when the recording / reproducing area is accessed. When,
A focus servo method comprising:   In the step of holding the correction bias value, the position where the reflected light is focused is determined from the amplitude of the sensor signal obtained by converting the reflected light into the electrical signal, and the amplitude of the high frequency component of the electrical signal is the maximum value. 7. The focus servo method according to claim 6, wherein the correction bias value is obtained based on a sensor signal level at a certain point in time. It has a recording / reproducing area having grooves formed concentrically and a calibration area in which a radial groove having a constant width is formed in a predetermined area, and the calibration area corresponds to at least laser beams having different wavelengths. A computer constituting an optical disk device for accessing an optical disk having a plurality of recording layers,
A disk access initialization process for holding a correction bias value of each focus servo corresponding to each position at which reflected light obtained by sequentially irradiating laser light having different wavelengths to the calibration area is in focus;
Recording / reproducing area for generating a servo signal for focusing reflected light obtained by irradiating the recording / reproducing area with laser light of a predetermined wavelength based on the correction bias value corresponding to the laser light of the predetermined wavelength Access processing,
A program that executes   In the disk access initialization process, the position at which the reflected light is focused is determined from the amplitude of the sensor signal obtained by converting the reflected light into the electrical signal, and the amplitude of the high-frequency component of the electrical signal becomes the maximum value 9. The program according to claim 8, wherein the correction bias value is obtained based on the level of the sensor signal.

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