JP2009043360A - Optical disk device and optical disk device control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device capable of preventing collision of an objective lens with an optical disk even when-wobbling of an optical disk occurs. <P>SOLUTION: Focus control is carried out on a trial basis by using an optical beam having the longest focal distance among optical beams emitted from a laser diode. An actuator driving voltage when the level of a focus error signal decreases below a predetermined value or when it becomes the lowest, is obtained as a measuring voltage. The obtained measuring voltage is supplied to a reference voltage calculation circuit. The reference voltage calculation circuit calculates a reference voltage used for focus control during reproducing the optical disk for each of a plurality of optical beams of different focal distances. The focus control circuit performs various controls by using the reference voltage as a default value of a voltage applied to an actuator when focus control of the objective lens is carried out during reproducing the optical disk. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc device for reading information recorded on an optical disc and an optical disc device control method, and in particular, a collision between an optical disc and an objective lens caused by vertical deflection (hereinafter referred to as “surface deflection”) of the optical disc. The present invention relates to an optical disc apparatus for preventing the occurrence of the trouble and an optical disc apparatus control method.

  In recent years, optical discs such as compact discs (hereinafter referred to as “CD”) and digital versatile discs (hereinafter referred to as “DVD”) have become widespread and are generally used. As an apparatus for reading out and reproducing information recorded on the optical disk, for example, audio information and video information, there is an optical disk apparatus. As a widely known optical disk device, for example, a CD player, a DVD player, a CD-ROM drive connected to a personal computer, and the like can be cited.

  An optical disk device is provided with an optical pickup for reading information by irradiating an optical disk with a light beam. The optical pickup irradiates a light beam onto the information recording surface of the optical disk fixed on the turntable and rotating. Then, the reflected light from the optical disk is received by a light receiving element, for example, a photodiode, provided in the optical pickup. Then, light is converted into an electric signal by the light receiving element, and information recorded on the optical disk is output based on the obtained electric signal.

  An actuator for driving the objective lens in a direction perpendicular or horizontal to the information recording surface is provided in the optical pickup. Further, a focus servo mechanism is provided for driving the actuator so as to keep the distance between the objective lens and the information recording surface constant.

  However, the information recording surface of the optical disc may be warped due to various factors. Further, when fixed on the turntable, the vicinity of the outer periphery hangs down due to its own weight, and the information recording surface of the disc may not be able to be rotated within one plane. When these warps or sags are slight, the optical axis of the light beam and the information recording surface can maintain a substantially vertical relationship. Therefore, information can be read by driving the objective lens in a direction perpendicular to the information recording surface by the actuator provided in the optical pickup described above.

  However, if the information recording surface is warped or drooped greatly, or if the rotation axis of the disk is tilted, the correction by the servo mechanism alone cannot provide a sufficient response, and the information recording surface collides with the objective lens of the optical pickup. There was a problem that they could be damaged.

  In relation to the above problem, in Patent Document 1, it is possible to control so that the tilt (= tilt) of the disc is automatically reduced, and it is possible to suitably control the gap even if the disc is shaken. An optical disc device that can be used is disclosed. This optical disk apparatus includes means for detecting the angle between the head and the information recording surface, and estimates the amount of periodic blurring of the distance between the head and the rotating disk based on the detected angle. Based on the estimated amount of shake, the separation / contact mechanism is controlled so that the distance between the head and the rotating information recording surface is a constant distance. Further, the variable mechanism is controlled based on the detected angle so as to reduce the tilt of the head with respect to the information recording surface.

  In relation to the above problem, Patent Document 2 discloses an analyzer that can obtain an accurate measurement value that is not affected by the amount of surface deflection. This analyzer includes a light receiving means for receiving the light reflected from the disk, and the amount of light received by the light receiving means is calculated based on an amount based on a difference between a surface perpendicular to the rotation axis of the disk and a point on the disk. to correct. Furthermore, a conversion means for converting the amount of received light into an electric signal is provided, and the conversion means corrects the amount of received light by changing the potential level of the electric signal.

In relation to the above problem, Patent Document 3 discloses an optical disc apparatus for reducing the processing load for obtaining the surface shake amount. This optical disk apparatus acquires in advance the correspondence between the position of the objective lens in the radial direction of the optical disk and the amount of surface deflection of the optical disk at the lens position. As a result, the lens moving distance at the time of refocusing is shortened, the redrawing time is shortened, and the calculation amount of the surface shake amount is reduced.
JP 2005-209318 A JP 2007-003362 A JP 2005-158139 A

  However, in the devices disclosed in Patent Documents 1 to 3, it is possible to efficiently correct the tilt, correct the amount of received light, increase the efficiency of focus pull-in, etc., but the surface shake is extremely large. In some cases, there is a problem that it is insufficient to avoid collision between the optical disk and the objective lens. Therefore, there is a risk that both the objective lens and the optical disk are damaged.

  In view of the above points, the object of the present invention is to prevent the collision between the optical disk and the objective lens even when an extreme tilt occurs in the optical disk, and to adjust the objective lens in accordance with the tilt occurring in the optical disk. An object of the present invention is to provide an optical disc apparatus capable of efficiently performing focus control.

  In order to achieve the above object, an optical disc apparatus according to the present invention includes a light source capable of emitting a plurality of light beams having different focal lengths, and irradiating the recording surface of the optical disc with the light beam emitted from the light source, thereby An objective lens that receives light, an actuator that moves the objective lens in the vertical direction of the optical disc, a photodetector that converts reflected light reflected by the optical disc into an electrical signal, and an electrical signal obtained by the photodetector In an optical disc apparatus comprising a focus control means for controlling the drive of the actuator based on a focus error signal included in the light beam, the light beam having the longest focal length among the light beams that can be emitted by the light source is used. Focus control is performed by the focus control means, and an action is taken when the focus error signal falls below a predetermined level. Measurement voltage acquisition means for acquiring a rotor drive voltage as a measurement voltage, and reference voltage calculation means for calculating, for each type of light beam, a reference voltage that is a reference value of an actuator drive voltage at the time of reproducing an optical disk from the measurement voltage. And the focus control means performs focus control using the reference voltage corresponding to the type of light beam to be used.

  The optical disc apparatus of the present invention further includes a rotation angle acquisition unit that acquires the rotation angle of the optical disc, and the measurement voltage acquisition unit generates related information that associates the measurement voltage with the rotation angle at the time of measurement voltage acquisition. The reference voltage calculation means calculates a reference voltage for each rotation angle based on the related information.

  The optical disc apparatus of the present invention further includes a recording unit, wherein the measurement voltage acquisition unit records the generated related information in the recording unit, and the reference voltage calculation unit adds the related information read from the recording unit to the related information. The reference voltage calculated based on the recording unit is recorded in the recording unit, and the focus control unit reads the reference voltage from the recording unit and performs focus control.

  In the optical disc apparatus of the present invention, the reference voltage calculation unit calculates a difference between a focal length of the light beam used by the measurement voltage acquisition unit and a focal length of the reproduction light beam, and the difference is calculated as a drive voltage. The reference voltage is calculated by dividing the focus sensitivity, which is a ratio with the driving distance, and adding the value obtained by the division to the measurement voltage.

  In the optical disk apparatus of the present invention, the reference voltage calculation unit determines a voltage within a predetermined range above and below the reference voltage as a limit voltage, and the focus control unit determines that the driving voltage of the objective lens is an upper limit value of the limit voltage. The objective lens is moved away from the optical disk when the value exceeds or below the lower limit value of the limit voltage.

  In the optical disk apparatus of the present invention, the reference voltage calculation unit divides the working distance of the objective lens by the focus sensitivity, and adds a value obtained by the division to the reference voltage as an upper limit value of the limit voltage. In addition, a value obtained by subtracting the value obtained by the division from the reference voltage is set as a lower limit value of the limit voltage.

  The optical disc apparatus control method of the present invention also receives a reflected light from the optical disc by irradiating a recording surface of the optical disc with a light source capable of emitting a plurality of light beams having different focal lengths, and a light beam emitted from the light source. An objective lens, an actuator for moving the objective lens in the vertical direction of the optical disc, a photodetector for converting the reflected light reflected by the optical disc into an electrical signal, and a focus included in the electrical signal obtained by the photodetector In a control method of an optical disc apparatus including a focus control unit that controls driving of the actuator based on an error signal, the focus is obtained by using a light beam having the longest focal length among light beams that can be emitted by the light source. The focus is controlled by the control means, and the action when the focus error signal falls below the predetermined level A measurement voltage acquisition step for acquiring an eta drive voltage as a measurement voltage, and a reference voltage calculation step for calculating, for each type of light beam, a reference voltage that is a reference value of an actuator drive voltage at the time of reproducing an optical disc from the measurement voltage. And the focus control means performs focus control using the reference voltage corresponding to the type of light beam to be used.

  The optical disc apparatus control method of the present invention includes a rotation angle acquisition step for acquiring the rotation angle of the optical disc, a related information generation step for generating related information in which the measurement voltage and the rotation angle at the time of measurement voltage acquisition are associated, And a reference voltage calculation step of calculating a reference voltage for each rotation angle based on the related information.

  In the optical disk apparatus control method of the present invention, in the reference voltage calculation step, the difference between the focal length of the measurement-voltage acquiring light beam and the reproduction light beam is calculated, and the difference is calculated as a drive voltage. The reference voltage is calculated by dividing by the focus sensitivity, which is a ratio to the driving distance, and adding the value obtained by the division to the measurement voltage.

  The optical disc apparatus control method of the present invention includes a limit setting step for determining a voltage within a predetermined range above and below the reference voltage as a limit voltage, and the driving voltage of the objective lens exceeds the upper limit value of the limit voltage, or the limit The objective lens is separated from the optical disk when the voltage is below the lower limit value.

  In the optical disc apparatus control method of the present invention, in the limit setting step, the working distance of the objective lens is divided by focus sensitivity, and a value obtained by adding the value obtained by the division to the reference voltage is an upper limit value of the limit voltage. And a value obtained by subtracting the value obtained by the division from the reference voltage is set as a lower limit value of the limit voltage.

  According to the present invention, the photodetector extracts the focus error signal from the electrical signal obtained by photoelectrically converting the reflected light from the optical disk recording surface. The focus control circuit determines the drive voltage of the actuator based on the focus error signal and performs focus control of the objective lens. The measurement voltage acquisition circuit (= measurement voltage acquisition means) experimentally performs focus control using a light beam having the longest focal length among light beams that can be emitted from the laser diode.

  Specifically, the level change of the focus error signal acquired by the photodetector is confirmed while changing the drive voltage applied to the actuator. Then, when the level of the focus error signal falls below a predetermined value or when it becomes the lowest, the actuator drive voltage is acquired as the measurement voltage.

  The acquired measurement voltage is given to a reference voltage calculation circuit (= reference voltage calculation means). The reference voltage calculation circuit calculates a reference voltage used for focus control during reproduction of the optical disc for each of a plurality of light beams having different focal lengths. The reference voltage is a driving voltage for moving the objective lens to a position of the objective lens (hereinafter referred to as “reference position”) in a state where correction by various servo mechanisms such as tilt servo and tracking servo is not applied to the objective lens. It is. Since the reference position is different if the focal length of the light beam is different, the reference voltage calculation circuit calculates the reference voltage for each type of light beam.

  The calculated reference voltage is given to the focus control circuit. The focus control circuit uses the reference voltage as the default value of the voltage applied to the actuator when performing focus control of the objective lens during playback of an optical disc, and uses various controls such as tilt control and tracking control based on the reference voltage. Do it.

  For this reason, it is possible to reduce the amount of correction required in various correction processes such as focus control and tilt control, compared to a case where a predetermined constant value is used as the reference voltage. As a result, it is possible to improve the efficiency of various controls and improve the processing accuracy. Further, since the measurement voltage is acquired using the light beam having the longest focal length, it is possible to prevent the objective lens from contacting the optical disk during the measurement voltage acquisition.

  Further, according to the present invention, there is provided a rotation angle acquisition circuit (= rotation angle acquisition means) for acquiring a rotation angle when the optical disk is viewed from the vertical direction when the light beam is collided on the optical disk recording surface by the laser diode. ing. The rotation angle is an angle at which a straight line connecting the reference point and the rotation axis of the optical disc with a point on the information recording surface of the optical disc intersects with a straight line connecting the light beam irradiation point and the rotation axis of the optical disc. It is shown.

  In other words, the reference point is 0 degree, 180 degrees when the optical disk makes a half turn, and 360 degrees (= 0 degree) when the optical disk makes a full turn. When the measurement voltage acquisition circuit acquires the measurement voltage, the measurement voltage acquisition circuit acquires the rotation angle at the acquired point using the rotation angle acquisition circuit. Then, related information that associates the measurement voltage with the rotation angle is given to the reference voltage calculation circuit. Thereby, the reference voltage calculation circuit can calculate the reference voltage every predetermined rotation angle, for example, every 30 degrees.

  If the reference voltage is calculated every 30 degrees, the reference voltage is calculated at a total of 12 points on the optical disc. How many times the reference voltage is calculated depends on the relationship with the design items and the like. It can be changed as appropriate. For this reason, even when the surface shake accompanying the rotation of the optical disk occurs periodically, the reference voltage corresponding to the rotation angle can be acquired, so that focus control with higher accuracy can be performed.

  In addition, according to the present invention, a recording unit such as a memory is provided, and the measurement voltage acquisition circuit records the acquired measurement voltage and related information in the memory. The reference voltage calculation circuit calculates a reference voltage corresponding to the rotation angle based on the measured voltage read from the memory and related information, and records the calculated reference voltage in the memory. The focus control circuit reads the reference voltage from the memory and performs focus control.

  For this reason, as long as the optical disk is not exchanged, focus control can be performed using the same reference voltage. For this reason, as long as the optical disk is not exchanged, focus control can be performed using the same reference voltage. Therefore, since it is not necessary to calculate the measurement voltage and the reference voltage every time focus control is performed, the processing can be made efficient.

  According to the invention, the reference voltage calculation circuit calculates a difference between the focal length of the light beam used by the measurement voltage acquisition circuit and the focal length of the light beam emitted from the light source according to the type of the optical disc when the optical disc is reproduced. . Then, the difference is divided by the focus sensitivity, and the obtained value is added to the measurement voltage. Thereby, the reference voltage at the time of reproducing the optical disk is calculated. Therefore, the reference voltage for each light beam can be easily calculated from the difference between the focal length of the measurement light beam and the focal length of the reproduction light beam. Moreover, since the present invention can be applied regardless of the number of types of light beams used for reproduction, versatility is enhanced.

  According to the invention, the reference voltage calculation circuit calculates a limit voltage having an upper limit value obtained by adding a predetermined voltage to the reference voltage and a lower limit value obtained by subtracting the predetermined voltage. When performing focus control of the objective lens, the focus control circuit performs normal focus control if it is within the limit voltage range, but if the limit voltage exceeds the upper limit value or falls below the lower limit value, the focus control is interrupted. Then, the objective lens is moved away from the optical disk. This prevents the objective lens from contacting the optical disc. For this reason, damage to the objective lens and the optical disk can be prevented even when a larger surface shake than usual occurs due to impact or the like.

  According to the present invention, the reference voltage calculation circuit divides the working distance of the objective lens when the reproduction light beam is used by the focus sensitivity as a method for the reference voltage calculation circuit to calculate the limit voltage. Then, the upper limit value of the limit voltage is determined by adding the value obtained by the division to the reference voltage for each light beam. Further, the lower limit value of the limit voltage is determined by subtracting the value obtained by the division from the reference voltage. Thereby, the objective lens can be prevented from coming into contact with the optical disk, and the limit voltage can be calculated easily and reliably, so that the processing efficiency can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, embodiment shown here is an example and this invention is not limited to embodiment shown here.

<1. Internal configuration>
FIG. 1 is a block diagram showing a disc player 100 according to an embodiment of the present invention. The disc player 100 includes an optical pickup 1, an RF amplifier 31, a DSP (Digital Signal Processor) 32, a reproduction processing circuit 33, an output circuit 34, a system controller 41, a driver 42, a display unit 43, an operation unit 44, a feed motor 51, and A spindle motor 52 is provided.

  The optical pickup 1 irradiates the optical disc 2 with a light beam, and reads various information such as audio information and video information recorded on the optical disc 2 (CD, DVD, or BD). The optical pickup 1 is provided with a CD light beam, a DVD light beam, and a BD (Blu-lay) light beam. Details of the inside of the optical pickup 1 will be described later.

  Audio information and video information obtained by the optical pickup 1 are converted into audio and video by the RF amplifier 31 to the output circuit 34 and output from a speaker and a monitor (not shown), respectively. The RF amplifier 31 amplifies an audio signal, a video signal, etc. from the optical pickup 1. The DSP 32 and the reproduction processing circuit 33 perform various information processing (for example, video processing) for reproduction on the signal from the RF amplifier 31. The output circuit 34 performs D / A conversion processing and the like in order to output the signal from the reproduction processing circuit 33 to a speaker and a monitor (not shown).

  The system controller 41 and the driver 42 control the operations of the optical pickup 1 and the driving device (= feed motor 51 and spindle motor 52). The system controller 41 receives information from the operation unit 44 and transmits it to the DSP 32, and transmits information from the DSP 32 to the display unit 43. The driver 42 controls operations of the optical pickup 1 and the driving device based on an instruction from the DSP 32.

  The feed motor 51 is driven by a driver 42 that operates based on an instruction from the DSP 32. As a result, the optical pickup 1 moves in the radial direction of the optical disc 2. The spindle motor 52 drives the optical disc 2 in the rotation direction by the driver 42. The driver 42 performs focus control of the objective lens 17 (FIG. 2) of the pickup device 1 based on the instruction from the DPS 32.

<2. About optical pickup configuration>
FIG. 2 is a schematic diagram showing an optical system of the optical pickup 1 according to the embodiment of the present invention. The optical pickup 1 reads information recorded on the recording surface of the optical disc 2 by irradiating the optical disc 2 such as a CD with a light beam and receiving reflected light. The type and number of optical discs 2 that can be read with the optical pickup 1 are not limited to the type and number shown in the present embodiment, and various changes can be made without departing from the scope of the present invention.

  The optical pickup 1 includes a first light source 11a, a second light source 11b, a dichroic prism 12, a collimator lens 13, a beam splitter 14, a rising mirror 15, a liquid crystal element 16, an objective lens 17, and a detection. A lens 18, a photodetector 19, and an actuator 21 are provided.

  Further, as a processing circuit for performing the objective lens control processing of the present invention, a measurement voltage acquisition circuit 22 (= measurement voltage acquisition means), a rotation angle acquisition circuit 23 (= rotation angle acquisition means), and a focus control circuit 24 (= focus) Control means) and a reference voltage calculation circuit 25 (= reference voltage calculation circuit). In addition, these processing circuits include a memory 26 (= recording unit) as a recording medium for recording various information. Each processing circuit described above does not need to be included in the pickup 1 and may be electrically connected outside the pickup 1.

  The first light source 11a is a laser diode that can emit a light beam of 650 nm band corresponding to DVD and a light beam of 780 nm band corresponding to CD. The second light source 11b is a laser diode capable of emitting a 405 nm band light beam corresponding to BD. In the present embodiment, a two-wavelength integrated laser diode having two light emitting points capable of emitting light beams of two types of wavelengths is used as the first light source 11a. However, the present invention is not limited to this. For example, a laser diode that emits only a light beam having a single wavelength may be used.

  The dichroic prism 12 transmits the light beam emitted from the first light source 11a that emits the DVD light beam, and reflects the light beam emitted from the second light source 11b that emits the BD light beam. Then, the optical axes of the light beams emitted from the first light source 11a and the second light source 11b are matched. The light beam transmitted or reflected by the dichroic prism 12 is sent to the collimating lens 13.

  The collimating lens 13 converts the light beam transmitted through the dichroic prism 12 into parallel light. Here, the parallel light means light in which all optical paths of the light beams emitted from the first light source 11a and the second light source 11b are substantially parallel to the optical axis. The light beam converted into parallel light by the collimator lens 13 is sent to the beam splitter 14.

  The beam splitter 14 functions as a light separation element that separates an incident light beam, transmits the light beam transmitted from the collimating lens 13, guides it to the optical disk 2 side, and reflects the reflected light reflected by the optical disk 2. Is reflected and guided to the photodetector 19 side. The light beam that has passed through the beam splitter 14 is sent to the rising mirror 15.

  The raising mirror 15 reflects the light beam transmitted through the beam splitter 14 and guides it to the optical disc 2. The rising mirror 15 is inclined by 45 ° with respect to the optical axis of the light beam from the beam splitter 14, and the optical axis of the light beam reflected by the rising mirror 15 is the same as the recording surface of the optical disc 2. It is almost orthogonal. The light beam reflected by the rising mirror 15 is sent to the liquid crystal element 16.

  The liquid crystal element 16 controls the change in the refractive index by applying a voltage to a liquid crystal (neither of which is shown) sandwiched between transparent electrodes, utilizing the property that the liquid crystal molecules change the orientation direction thereof, and the liquid crystal element 16 This element enables control of the phase of the light beam that passes through the element 6. By disposing the liquid crystal element 16, it is possible to correct spherical aberration caused by a difference in the thickness of the protective layer that protects the recording surface of the optical disc 2. The light beam that has passed through the liquid crystal element 16 is sent to the objective lens 17.

  The objective lens 17 focuses the light beam transmitted through the liquid crystal element 16 on the recording surface of the optical disc 2. The objective lens 17 can be moved, for example, in the vertical and horizontal directions in FIG. 2 by an actuator 21 to be described later, and its position is controlled based on the focus servo signal and the tracking servo signal.

  In the present embodiment, the liquid crystal element 16 is also mounted on the actuator 21 so that it can move together with the objective lens 17. However, the liquid crystal element 16 does not necessarily need to be mounted on the actuator 21, and the configuration can be changed according to the configuration of the optical system.

  The reflected light reflected by the optical disk 2 passes through the objective lens 17 and the liquid crystal element 16 in this order, is reflected by the rising mirror 15, is further reflected by the beam splitter 14, and is reflected on the photodetector 19 by the detection lens 18. The light is condensed to a light receiving element provided in the.

  The photodetector 19 converts optical information received using a light receiving element such as a photodiode into an electrical signal, and outputs the electrical signal to, for example, an RF amplifier (not shown). This electric signal is used as a reproduction signal for data recorded on the recording surface, and further as a servo signal for performing focus control and tracking control.

  The actuator 21 moves the objective lens 17 in the radial direction of the optical disc 2 in accordance with the objective lens drive signal generated and output by the driver 42. The actuator 21 is not limited thereto, but here the actuator 21 can drive the objective lens 17 with Lorentz force by passing a drive current through a coil (not shown) in a magnetic field formed by a permanent magnet (not shown). It may be.

  In addition to the tracking operation that moves the objective lens 17 in the direction along the recording surface of the optical disc 2, the actuator 21 tilts the objective lens 17 so that the optical axis of the light beam emitted from the objective lens 17 swings. Alternatively, a focusing operation for moving the objective lens 17 toward and away from the optical disc 2 can also be performed.

  The measurement voltage acquisition circuit 22 uses the rotation angle acquisition circuit 23 and the focus control circuit 24 to perform focus control at a plurality of predetermined measurement points on the optical disc, thereby focusing the objective lens at each measurement point. Therefore, the drive voltage necessary for this is acquired as the measurement voltage.

  The measurement voltage acquisition circuit 22 gives an instruction to the focus control circuit 24 so that each measurement is performed using the light beam having the longest focal length among the plurality of light beams that can be emitted from the first light source 11a and the second light source 11b. Performs focus control at a point. The focal length is the distance from when the light beam passes through the objective lens until it is focused on the recording surface of the optical disc.

  The focal length will be described with reference to FIG. FIG. 5 is a cross-sectional view of the optical disc 2 and the objective lens 17 as viewed from the side, and the optical disc 2 is configured to include at least a recording layer 2a (= recording surface) and a protective layer 2b. Irregularities called pits are formed in the recording layer, and information is acquired from the recording surface 2a by irradiating the recording layer with a light beam. The protective layer 2b is a transparent member for protecting the recording surface 2a. For example, plastic or the like is used.

  FIG. 5A shows a light beam for BD reproduction, where L1 is a focal length and D1 is a working distance. FIG. 5B shows a light beam for CD reproduction, where L2 is a focal length and D2 is a working distance. As shown in FIG. 5A, the BD has a thinner protective layer than the CD shown in FIG. Further, the focal length of the BD reproducing light beam is shorter than that of the CD reproducing light beam. As described above, in the present embodiment, the CD reproduction light beam has the longest focal length, and thus the measurement voltage acquisition circuit 22 acquires the measurement voltage using the CD reproduction light beam.

  Upon receiving the measurement voltage acquisition instruction from the measurement voltage acquisition circuit 22, the focus control circuit 24 acquires the focus error signal by the photodetector 19 while changing the drive voltage applied to the actuator 21. Then, the drive voltage applied to the actuator 21 when the focus error signal falls below a predetermined level is returned to the measurement voltage acquisition circuit 22 as a measurement voltage.

  The measurement voltage acquisition circuit 22 that has received the measurement voltage acquires the rotation angle of the measurement point at which the measurement voltage is measured using the rotation angle acquisition circuit 23, and stores related information that associates the measurement voltage with the rotation angle in the memory 26. To record.

  The rotation angle is a point where the optical disk is viewed from the vertical direction as a reference point, and the relationship between the reference point and the measurement point of the measurement voltage is represented by the rotation angle of the optical disk. For example, in the example shown in FIG. 6, the point a is the reference point. Also. There are seven measurement points from point b to point h concentrically with point a. A straight line connecting the reference point point a and the optical disk rotation axis is a straight line t1. Further, a straight line connecting a predetermined measurement point and the optical disc rotation axis is a straight line t2.

  The angle formed by the intersection of t1 and t2 is θ. As shown in FIG. 6, when the point b is a measurement point, θ is 45 degrees. Further, the reference point point a is 0 degrees, the optical disk half-rounded point e is 180 degrees, and the rounded point a is 360 degrees (= 0 degrees).

The reference voltage calculation circuit 25 reads the related information in which the measurement voltage and the rotation angle are associated from the memory 26, thereby calculating the reference voltage for each type of light beam at each measurement point from the measurement voltage at each measurement point. . Specifically, the reference voltage is calculated using the following formula.
B [V] = P [V] + (fa [mm] −fb [mm]) ÷ S [mm / V]
In addition, the content of the symbol used for the said numerical formula is as follows.
B [V]: Reference voltage. The unit is bolts.
P [V]: A measurement voltage obtained by the measurement voltage acquisition circuit 22. The unit is bolts.
fa [mm]: Focal length of the measurement light beam. The unit is millimeter.
fb [mm]: focal length of the reproducing light beam. The unit is millimeter.
S [mm / V]: focus sensitivity (= ratio between applied drive voltage and objective lens drive distance). The unit is millimeter / volt.

  As described above, the reference voltage for each type of light beam is calculated at a plurality of measurement points from the difference between the focal length of the measurement light beam and the focal length of the reproduction light beam. Then, a reference voltage corresponding to the rotation angle is calculated from the calculated reference voltage by approximation interpolation. For example, in FIG. 7, reference voltages measured at eight points from measurement point a to measurement point h are connected by an approximate curve. The curve ΔV obtained in this way becomes a reference voltage corresponding to the rotation angle. The reference voltage corresponding to the rotation angle may be calculated using a straight line, a pseudo curve, or the like instead of a curve.

Further, the reference voltage calculation circuit 25 calculates the limit voltage based on the reference voltage. Specifically, the limit voltage is calculated using the following formula.
R [V] = B [V] ± (D [mm] ÷ S [mm / V])
In addition, the content of the symbol used for the said numerical formula is as follows.
R [V]: Limit voltage. The unit is bolts.
B [V]: Reference voltage. The unit is bolts.
D [mm]: Objective lens working distance when using a reproducing light beam. The unit is millimeter.
S [mm / V]: Focus sensitivity. The unit is millimeter / volt.

  As described above, the limit voltage corresponding to the rotation angle is calculated from the reference voltage of the measurement light beam and the objective lens working distance. For example, in FIG. 7, a dashed curve ΔR1 and a dashed curve ΔR2 that exist in parallel above and below the reference voltage ΔV are limit voltages according to the rotation angle. The limit voltage calculation method may be such that the limit voltage is calculated for each measurement point and approximate value interpolation is performed, or (D [mm] ÷ S [mm / V]) is directly applied to the curve ΔV. A form in which the broken line curve ΔR1 and the broken line curve ΔR2 are generated by addition and subtraction may be employed.

<3. Reference voltage acquisition process>
Here, reference voltage calculation processing by the optical pickup 1 according to the embodiment of the present invention will be described with reference to the block diagrams of FIGS. 1 and 2 and the flowchart of FIG.

  FIG. 3 is a flowchart showing a process flow of the reference voltage calculation process according to the embodiment of the present invention. This process shown in FIG. 3 is started when a spin-up process for enabling reading of the optical disk 2 is detected when the optical disk 2 is inserted into the disk player 100.

  After this processing is started, the measurement voltage acquisition circuit 22 acquires the measurement voltage in step S110 using the measurement light beam, that is, the light beam for CD reproduction with the longest focal length. Specifically, the focus error signal is acquired by the photodetector 19 while changing the drive voltage applied to the actuator 21 using the focus control circuit 24. Then, the drive voltage when the light beam is focused is obtained as a measurement voltage.

  Next, in step S120, the measurement voltage acquisition circuit 22 uses the rotation angle acquisition circuit to acquire the rotation angle of the optical disc 2 when the measurement voltage is acquired. In step S <b> 130, related information that associates the acquired measurement voltage with the rotation angle is recorded in the memory 26.

  Next, in step S140, the measurement voltage acquisition circuit 22 determines whether the measurement voltage acquisition process completion condition is satisfied. In addition, as a completion condition, the form made into completion by performing the acquisition process of predetermined times, for example, 10 times in the measurement point determined at random may be sufficient, for example. Alternatively, it may be configured to be completed by performing at least one acquisition process at a predetermined measurement point, for example, each of the measurement points a to h shown in FIG.

  If it is determined in step S140 that the completion condition is not satisfied, the measurement voltage acquisition circuit 22 proceeds to step S110 again and continues to acquire the measurement voltage. On the contrary, if it is determined that the completion condition is satisfied, the reference voltage calculation circuit 25 calculates the reference voltage for each reproduction light beam from the measurement voltage for each measurement point recorded in the memory 26 in step S150. To do.

  Specifically, for example, the reference voltage of the CD reproduction light beam, the reference voltage of the DVD reproduction light beam, and the reference voltage of the BD reproduction light beam are measured at the respective measurement points a to h in FIG. Calculated from the measured voltage. Therefore, in this embodiment, a reference voltage of 3 (= type of light beam) × 8 (= number of measurement points) = 24 is calculated. Note that the reference voltage is calculated using the above-described mathematical formula.

  Next, in step S160, the reference voltage calculation circuit 25 calculates a reference voltage corresponding to the rotation angle for each type of reproduction light beam by approximation interpolation. Specifically, as shown in FIG. 7, the reference voltage corresponding to the rotation angle is calculated by connecting the reference voltage at each measurement point with an approximate curve. The calculated reference voltage value is recorded in the memory 26 for each type of reproduction light beam.

  Next, in step S170, the reference voltage calculation circuit 25 calculates a limit voltage from the reference voltage corresponding to the rotation angle. Specifically, as shown in FIG. 7, a value obtained by adding a predetermined value to a reference voltage corresponding to the rotation angle is set as an upper limit value of the limit voltage, and a value obtained by subtracting the predetermined value is set as a lower limit value of the limit voltage. Determine the voltage range. The upper limit value and the lower limit value are calculated using the above-described mathematical expressions. In step S180, the calculated limit voltage is recorded in the memory 26, and then the present process is terminated.

<4. About optical disc playback processing>
Here, the optical disk reproduction processing by the optical pickup 1 according to the embodiment of the present invention will be described with reference to the block diagrams of FIGS. 1 and 2 and the flowchart of FIG.

  FIG. 4 is a flowchart showing a processing flow of the optical disc reproduction processing according to the embodiment of the present invention. The process shown in FIG. 4 is started when a playback instruction for the optical disc 2 inserted in the disc player 100 is detected. The reproduction instruction is issued when the user presses a reproduction start button included in the operation unit 44, for example.

  After this processing is started, in step S210, the optical pickup 1 selects and switches the light source to be used in order to emit a reproduction light beam corresponding to the reproduction target optical disc. For example, when reproducing a BD, switching to the second light source 11b that emits a 405 nm band light beam corresponding to the BD is performed.

  Next, the focus control circuit 24 reads the reference voltage and limit voltage corresponding to the type of the light beam to be used from the memory 26 in step S220. Then, the actuator 21 is driven using the read reference voltage as a reference value, and focus control is performed by moving the objective lens toward and away from the optical disk in the vertical direction according to the rotation angle.

  Next, in step 230, the focus control circuit 24 determines whether or not the drive voltage applied to the actuator 21 exceeds the limit voltage. If it is determined that the voltage exceeds the limit voltage, the focus control circuit 24 interrupts the focus control process and moves the objective lens 17 away from the optical disc 2 in step 235. In addition, although it does not specifically limit about the distance to separate, It is desirable to separate to the limit of the drive area | region of the objective lens 17. FIG.

  If it is determined in step S230 that the limit voltage has not been exceeded, the focus control circuit 24 determines in step 240 whether or not an instruction to stop the optical disc playback process has been detected. The stop instruction is issued, for example, when a playback stop button included in the operation unit 44 is pressed by the user, or when the disc player 100 is powered off.

  When the reproduction stop instruction is detected in step S240, the focus control is stopped and this process is terminated. On the other hand, when the reproduction stop instruction is not detected, the process proceeds to step S220, and the focus control using the reference voltage is continued again.

[Other embodiments]
The present invention has been described with reference to the preferred embodiments and examples. However, the present invention is not necessarily limited to the above embodiments and examples, and various modifications may be made within the scope of the technical idea. Can be implemented.

Therefore, the present invention can also be applied to the following embodiments.
(A) In the present embodiment, the disc player 100 is described as an example of the optical disc device provided with the optical pickup 1, but other optical disc devices provided with the optical pickup 1, for example, an optical disc recording device such as a CD-R drive, The present invention can also be implemented in a personal computer or the like equipped with these optical disk recording devices.

  (B) In the present embodiment, calculation of the reference voltage and focus control using the calculated reference voltage are performed using the measurement voltage acquisition circuit 22, the rotation angle acquisition circuit 23, the focus control circuit 24, and the reference voltage calculation circuit 25. However, the focus control processing of the present invention may be realized by executing a program having functions equivalent to those of the plurality of circuits on a processing device such as a microprocessor.

These are the block diagrams which show the disc player which concerns on one Embodiment of this invention. These are the block diagrams which show the optical pick-up which concerns on one Embodiment of this invention. These are the flowcharts which showed the processing flow of the reference voltage calculation process which concerns on one Embodiment of this invention. These are the flowcharts which showed the processing flow of the optical disk reproduction | regeneration processing based on one Embodiment of this invention. These are side surface sectional drawings which showed the positional relationship of the optical disk and objective lens which concern on one Embodiment of this invention. These are the schematic diagrams which showed the reference voltage measurement point of the optical disk based on one Embodiment of this invention. These are the graphs which showed an example of the relationship between the reference voltage and limit voltage which concern on one Embodiment of this invention, and a rotation angle.

Explanation of symbols

100 disc player (optical disc device)
1 Optical pickup 2 Optical disc 2a Recording layer (recording surface)
11a First light source (light source)
11b Second light source (light source)
17 Objective Lens 19 Photodetector 21 Actuator 22 Measurement Voltage Acquisition Circuit (Measurement Voltage Acquisition Unit)
23 Rotation angle acquisition circuit (rotation angle acquisition means)
24 Focus control circuit (focus control means)
25 Reference voltage calculation circuit (reference voltage calculation means)
26 Memory (Recording part)
D1 Working distance D2 Working distance L1 Focal length L2 Focal length ΔV Reference voltage ΔR1 Limit voltage upper limit ΔR2 Limit voltage lower limit

Claims (11)

A light source capable of emitting a plurality of light beams having different focal lengths;
An objective lens for irradiating a recording surface of an optical disc with a light beam emitted from the light source and receiving reflected light from the optical disc;
An actuator for moving the objective lens in the vertical direction of the optical disc;
A photodetector that converts the reflected light reflected by the optical disc into an electrical signal;
A focus control means for controlling the driving of the actuator based on a focus error signal included in an electrical signal obtained by the photodetector;
In an optical disc device comprising:
Using the light beam having the longest focal length among the light beams that can be emitted from the light source, focus control is performed by the focus control means, and the actuator drive voltage when the focus error signal falls below a predetermined level is used as the measurement voltage. A measurement voltage acquisition means for acquiring;
A reference voltage calculating means for calculating, for each type of light beam, a reference voltage that is a reference value of an actuator driving voltage at the time of reproducing an optical disc from the measured voltage;
With
An optical disc apparatus characterized in that the focus control means performs focus control using the reference voltage corresponding to the type of light beam to be used. A rotation angle acquisition means for acquiring the rotation angle of the optical disc;
The measurement voltage acquisition means generates related information associating the measurement voltage with the rotation angle at the time of measurement voltage acquisition,
The optical disc apparatus according to claim 1, wherein the reference voltage calculation unit calculates a reference voltage for each rotation angle based on the related information. With a recording unit,
The measurement voltage acquisition unit records the generated related information in the recording unit,
The reference voltage calculation means records the reference voltage calculated based on the related information read from the recording unit in the recording unit,
The optical disc apparatus according to claim 2, wherein the focus control unit performs focus control by reading the reference voltage from the recording unit. The reference voltage calculation means calculates a difference between the focal length of the light beam used by the measurement voltage acquisition means and the focal length of the reproduction light beam;
2. The reference voltage is calculated by dividing the difference by a focus sensitivity that is a ratio between a drive voltage and a drive distance, and adding a value obtained by the division to a measurement voltage. The optical disk device according to claim 3. The reference voltage calculation means determines a voltage within a predetermined range above and below the reference voltage as a limit voltage,
The focus control unit causes the objective lens to move away from the optical disc when the driving voltage of the objective lens exceeds an upper limit value of the limit voltage or falls below a lower limit value of the limit voltage. The optical disk device according to claim 4. The reference voltage calculation means divides the working distance of the objective lens by the focus sensitivity, and sets a value obtained by the division to the reference voltage as an upper limit value of the limit voltage, and is obtained by the division. 6. The optical disc apparatus according to claim 5, wherein a value obtained by subtracting the calculated value from the reference voltage is set as a lower limit value of the limit voltage. A light source capable of emitting a plurality of light beams having different focal lengths;
An objective lens for irradiating a recording surface of an optical disc with a light beam emitted from the light source and receiving reflected light from the optical disc;
An actuator for moving the objective lens in the vertical direction of the optical disc;
A photodetector that converts the reflected light reflected by the optical disc into an electrical signal;
A focus control means for controlling the driving of the actuator based on a focus error signal included in an electrical signal obtained by the photodetector;
In a method for controlling an optical disc device comprising:
Using the light beam with the longest focal length among the light beams that can be emitted from the light source, focus control is performed by the focus control means, and the actuator drive voltage when the focus error signal falls below a predetermined level is used as the measurement voltage. A measurement voltage acquisition step to acquire;
A reference voltage calculating step for calculating a reference voltage, which is a reference value of an actuator driving voltage at the time of reproducing an optical disc, for each type of light beam from the measured voltage;
Including
An optical disc apparatus control method, wherein the focus control means performs focus control using the reference voltage corresponding to the type of light beam to be used. A rotation angle acquisition step of acquiring the rotation angle of the optical disc;
A related information generating step for generating related information associating the measured voltage with the rotation angle at the time of acquiring the measured voltage;
A reference voltage calculating step for calculating a reference voltage for each rotation angle based on the related information;
The optical disk apparatus control method according to claim 7, further comprising: In the reference voltage calculation step, a difference between the focal length of the measurement-voltage-acquisition light beam and the reproduction-light beam is calculated, and the difference is expressed by a focus sensitivity that is a ratio of the drive voltage and the drive distance. The optical disk apparatus control method according to claim 7 or 8, wherein the reference voltage is calculated by dividing and adding a value obtained by the division to a measurement voltage. A limit setting step for defining a voltage within a predetermined range from the reference voltage as a limit voltage,
The objective lens is moved away from the optical disc when the driving voltage of the objective lens exceeds the upper limit value of the limit voltage or falls below the lower limit value of the limit voltage. An optical disk device control method according to claim 1. In the limit setting step, the working distance of the objective lens is divided by the focus sensitivity, and the value obtained by the division is added to the reference voltage as an upper limit value of the limit voltage, and obtained by the division. The optical disk apparatus control method according to claim 10, wherein a value obtained by subtracting a value from the reference voltage is set as a lower limit value of the limit voltage.

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