JP2008108369A - Optical disk device and discriminating method of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device which can perform accurately and stably discrimination of a kind of an optical disk of which the thickness of a protection layer protecting a recording plane is different. <P>SOLUTION: In a discriminating means (system control part 12) possessed by an optical disk device 1, a kind of the optical disk is discriminated based on that in respective cases in which a tilt angle prescribed by an angle formed by a recording plane of the optical disk 20 and an optical axis of a light beam converged by an objective lens (not illustrated) is a first tilt angle or a second tilt angle, a whole light quantity obtained by a photodetecting means when the objective lens is positioned at the prescribed position is obtained, a rate of variation of the whole light quantity caused by difference of the tilt angles is different depending on the thickness of the protection layer protecting the recording plane of the optical disk 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that performs recording and reproduction of an optical disc. The present invention also relates to an optical disc discrimination method for discriminating the type of optical disc.

  Optical disks such as compact disks (hereinafter referred to as CDs) and digital versatile disks (hereinafter referred to as DVDs) are in widespread use. Recently, in order to further increase the amount of information on an optical disk, research on increasing the density of the optical disk has been advanced, and optical disks with higher density such as a Blu-ray disk (hereinafter referred to as BD) have been put into practical use.

  Recording and reproduction of information on the optical disc is performed in the optical disc apparatus. Since there are a plurality of types of optical discs as described above, an optical disc that can be compatible with a plurality of types of optical discs in one device in consideration of its convenience and the like. The device has become widespread. In such an optical disk device, generally, when an optical disk is inserted into the apparatus, first, the type of the optical disk is determined, and the apparatus is set to a condition suitable for the corresponding optical disk based on the determination result, and recording or reproduction of the optical disk is performed. I do.

  For example, Patent Document 1 introduces a method for determining the type of an optical disc by detecting the color of the recording surface of the optical disc. Patent Document 2 discloses a method of discriminating the type of an optical disk using an S-shaped waveform of a focus error signal obtained when the objective lens is moved in a direction approaching the optical disk in a state where a light beam is emitted from a light source. Has been introduced.

The method introduced in Patent Document 2 will be further described. When the objective lens (held by the optical pickup) is moved in the direction approaching the optical disk, it is derived from the S-shaped waveform derived from the surface of the optical disk and the recording surface of the optical disk. S-shaped waveform can be obtained. The thickness of the transparent cover that protects the recording surface of the optical disc differs depending on the type of the optical disc (for example, BD is 0.1 mm, DVD is 0.6 mm, and CD is 1.2 mm). The time interval at which the waveform is obtained varies depending on the type of the optical disc. For this reason, the type of the optical disk is determined by measuring the time interval at which two S-shaped waveforms are obtained.
JP 2006-179087 A Japanese Patent Laid-Open No. 2002-92872

  However, in the case of the method introduced in Patent Document 1, since a separate light source and detector are provided to detect the color of the optical disk, the number of parts increases and the cost for manufacturing the optical disk apparatus increases. There is a problem of rising.

  In the case of the method introduced in Patent Document 2, the S-shaped waveform derived from the surface of the optical disk is derived from the surface of the optical disk because the signal is smaller than the S-shaped waveform derived from the recording surface of the optical disk. There is a problem in that the detection of the S-shaped waveform to be performed fails, the optical disk determination fails, or the time required for optical disk determination becomes longer than the re-determination.

  In this regard, in Patent Document 2, for example, the optical pickup (including the objective lens) is brought close to the optical disc, and the time for driving the optical pickup is started at the approach limit position, and the optical pickup is started from the approach limit position. Is driven in a direction away from the optical disc, and the time of the drive time of the optical pickup is stopped based on the output based on the reflection of the recording surface of the optical pickup, and the difference in position in the thickness direction of the recording surface of the optical disc medium A method for discriminating the type of the optical disk medium by determining the difference in the driving time based on the above has been proposed. According to this method, even if the power of the surface reflected light is weak (the S-shaped waveform derived from the surface of the optical disk). Even if the signal is small, the type of the optical disk medium can be accurately determined.

  However, in the case of this method, since it is necessary to accurately measure the time by moving the optical pickup as a starting point, there is a problem that the burden at the time of assembling and adjusting the apparatus is large and the manufacturing cost is increased.

  In view of the above points, an object of the present invention is to provide an optical disc apparatus capable of accurately and stably discriminating types of optical discs having different protective layer thicknesses for protecting a recording surface. Another object of the present invention is to provide an optical disc apparatus capable of suppressing an increase in cost when the type discrimination of the optical disc can be accurately and stably performed. Furthermore, another object of the present invention is to provide an optical disc discriminating method capable of accurately and stably discriminating types of optical discs having different protective layer thicknesses for protecting the recording surface.

  In order to achieve the above object, the present invention provides a plurality of light sources having different wavelengths, an objective lens for condensing a light beam emitted from the light source on a recording surface of an optical disc, and reflected light reflected by the optical disc. Light detecting means for receiving light, tilt angle adjusting means capable of changing a tilt angle defined by an angle formed by a recording surface of the optical disc and an optical axis of a light beam condensed by the objective lens, and a type of the optical disc A discriminating means for discriminating between the optical disc apparatus and the optical disc apparatus compatible with a plurality of types of optical discs having different thicknesses for protecting the recording surface, wherein the discriminating means has the first tilt angle. For each of the case and the case of the second tilt angle, the total amount of light obtained by the light detection means when the objective lens is located at a predetermined position is obtained and obtained. The type of the optical disk having a different thickness of the protective layer is discriminated based on the ratio of the two total light amounts, and the first tilt angle is obtained by changing the tilt angle to at least three angles and obtaining the respective cases. The tilt angle when the total light quantity of the quadratic curve is maximized when the relation between the tilt angle and the total light quantity is approximated by a quadratic curve by the least square method based on the total light quantity. The tilt angle of 2 is an angle inclined by a predetermined amount with respect to the first tilt angle, and the reflected light is received by the light detection means when the objective lens is located at the predetermined position. The angle at which light is received in a state where at least part of the light leaks from the area, and the predetermined position is a maximum of the total light amount of the reflected light when the objective lens is moved in a direction in contact with or away from the optical disk. Where The total amount of light in each case and the second tilt angle between said first tilt angle is characterized in that it is determined from the quadratic curve.

  In order to achieve the above object, the present invention provides a plurality of light sources having different wavelengths, an objective lens for condensing a light beam emitted from the light source on a recording surface of the optical disc, and a reflection reflected by the optical disc. Light detecting means for receiving light, tilt angle adjusting means capable of changing a tilt angle defined by an angle formed by a recording surface of the optical disc and an optical axis of a light beam condensed by the objective lens, and the optical disc A discriminating means for discriminating the type of the optical disc apparatus, wherein the discriminating means has a first tilt angle that is compatible with a plurality of types of optical discs having different protective layer thicknesses for protecting the recording surface. And the second tilt angle, the total amount of light obtained by the light detection means when the objective lens is located at a predetermined position, and The rate of change in the total light quantity caused by a difference in belt angle is characterized by determining the type of the optical disc based on different depending on the thickness of the protective layer.

  In the optical disc apparatus having the above-described configuration, the first tilt angle may be such that the reflected light does not leak from the light receiving area of the light detecting means when the objective lens is located at the predetermined position. The second tilt angle is an angle at which the reflected light is received in a state where at least part of the reflected light leaks from the light receiving region of the light detecting means when the objective lens is located at the predetermined position. It is characterized by being.

  Further, the present invention provides the optical disc apparatus having the above-described configuration, wherein the first tilt angle is obtained by changing the tilt angle to at least three angles, and using the least square method based on the total amount of light obtained in each case. When the relationship between the tilt angle and the total light amount is approximated by a quadratic curve, the tilt angle is obtained when the total light amount of the quadratic curve is maximized, and the second tilt angle is the first tilt angle. The total light quantity in each case of the first tilt angle and the second tilt angle is obtained from the quadratic curve. It is said.

  Further, the present invention is the optical disc apparatus having the above-described configuration, wherein the predetermined position is a position where the total amount of the reflected light is maximum when the objective lens is moved in a direction in which the objective lens is moved toward and away from the optical disc. It is characterized by being.

  In order to achieve the above object, the present invention provides an optical disc discriminating method for discriminating types of optical discs having different thicknesses of protective layers for protecting the recording surface, wherein the optical disc is focused on the recording surface of the optical disc and the objective lens. When the angle between the optical axis and the optical axis of the light beam is defined as the tilt angle, the tilt angle is the first tilt angle and the second tilt angle. When the objective lens is located at a predetermined position, the total amount of light obtained by the light detecting means for receiving the reflected light from the optical disk is acquired, and the ratio of the change in the total amount of light caused by the difference in the tilt angle is the protection The type of the optical disc is discriminated based on the difference depending on the thickness of the layer.

  According to the first configuration of the present invention, since the optical disc is discriminated using the total amount of light obtained by the light detecting means, there is a possibility that the disc detection may fail due to insufficient signal detection. Low. Accordingly, it is possible to accurately and stably discriminate the optical disc. In addition, since it is not necessary to add a new part for discriminating the type of the optical disc, an increase in manufacturing cost can be suppressed. Further, it is possible to determine the optical disc stably without being influenced by the type of the optical disc inserted into the optical disc apparatus. Further, the total amount of light is obtained for at least three tilt angles, an approximate curve is calculated for the relationship between the tilt angle and the total amount of light, and the total amount of light for the predetermined two tilt angles is obtained from the approximate curve. Therefore, it is unlikely that the type of the optical disc is erroneously determined due to the influence of distortion or the like of the optical disc. Furthermore, when discriminating the type of optical disc by using the difference in the total amount of light caused by the difference in tilt angle for each type of optical disc, a configuration in which the total amount of light does not change due to factors other than the change in tilt angle is realized. Easy to do.

  Further, according to the second configuration of the present invention, since the optical disc is discriminated using the total amount of light obtained by the photodetecting means, the signal detection is insufficient and the disc discrimination may fail. The nature is low. Accordingly, it is possible to accurately and stably discriminate the optical disc. In addition, since it is not necessary to add a new part for discriminating the type of the optical disc, an increase in manufacturing cost can be suppressed. Furthermore, it is possible to determine the optical disc stably without being affected by the type of the optical disc inserted into the optical disc apparatus.

  Further, according to the third configuration of the present invention, in the optical disc device having the second configuration, it is accurately determined that the rate of change in the total light amount caused by the difference in tilt angle varies depending on the thickness of the protective layer protecting the recording surface. Therefore, the optical disc can be discriminated more accurately.

  Further, according to the fourth configuration of the present invention, in the optical disc apparatus having the third configuration, the total amount of light is acquired for at least three tilt angles, and an approximate curve is calculated for the relationship between the tilt angle and the total amount of light. In addition, since the total light amount in the case of two predetermined tilt angles is obtained from the approximate curve and the rate of change in the total light amount is determined, there is a possibility that the type of the optical disk is erroneously determined due to the influence of the distortion etc. of the optical disk. Is low.

  Further, according to the fifth configuration of the present invention, in the optical disc apparatus having any one of the second to fourth configurations, the rate of change in the total light amount caused by the difference in tilt angle is different for each type of optical disc. When discriminating the type of optical disk by using it, it is easy to realize a configuration in which the total amount of light does not change due to factors other than the change in tilt angle.

  In addition, according to the sixth configuration of the present invention, since the optical disc is discriminated using the total amount of light obtained by the light detecting means, the signal detection is insufficient and the disc discrimination may fail. The nature is low. Accordingly, it is possible to accurately and stably discriminate the optical disc. Further, this optical disc discrimination method is useful because it can be realized without adding new parts. Furthermore, it is possible to determine the optical disc stably without being affected by the type of the optical disc inserted into the optical disc apparatus.

  The content of the present invention will be described in detail below, but the embodiment shown here is an example, and the present invention is not limited to the embodiment shown here.

  FIG. 1 is a block diagram showing a configuration of an optical disc apparatus 1 according to the present embodiment. The optical disc apparatus 1 is provided so as to be able to reproduce information on the optical disc 20 and record information on the optical disc 20. The optical disc apparatus 1 is compatible with three types of optical discs of BD, DVD, and CD.

  Reference numeral 2 denotes a spindle motor, and the optical disc 20 is detachably held by a chuck portion (not shown) provided on the upper portion of the spindle motor 2. The spindle motor 2 continuously rotates the optical disc 20 when recording / reproducing information on the optical disc 20. The rotation control of the spindle motor 2 is performed by the spindle motor drive circuit 3.

  Reference numeral 4 denotes an optical pickup that irradiates the optical disc 20 with laser light emitted from a light source, thereby enabling writing of information on the optical disc 20 and reading of information recorded on the optical disc 20. FIG. 2 is a schematic diagram showing an optical system of the optical pickup 4. As shown in FIG. 2, the optical pickup 4 includes a first light source 21, a second light source 22, a dichroic prism 23, a collimator lens 24, a beam splitter 25, an objective lens 26, a condenser lens 27, A photodetector 28. The configuration of the optical system that constitutes the optical pickup is not limited to this, and various changes can be made.

  The first light source 21 is a laser diode that emits a laser beam having a single wavelength, and emits a laser beam having a wavelength of 405 nm used for BD. The second light source 22 is a two-wavelength compatible laser diode capable of emitting two-wavelength laser light. The second light source 22 is a laser light having a wavelength of 650 nm used for a DVD, and a laser light having a wavelength of 780 nm used for a CD. , Is emitted.

  In the optical pickup 4, the laser beams emitted from the light sources 21 and 22 have the same optical axis by the color synthesis prism 23, become parallel light by the collimator lens 24, pass through the beam splitter 25, and pass through the beam splitter 25. Is collected on the recording surface 20a on which the information is recorded. The reflected light reflected by the recording surface 20 a of the optical disk 20 passes through the objective lens 26, is reflected by the beam splitter 25, and is collected by the condenser lens 27 on the light receiving portion of the photodetector 28. The photodetector 28 converts optical information contained in the received light beam into an electrical signal.

  FIG. 3 is a schematic front view of the optical detector 28 provided in the optical disc apparatus 1 as viewed from the light receiving surface side. The optical detector 28 has light receiving areas A to D divided into four. Then, the optical information obtained in each of the light receiving areas A to D is converted into an electric signal and supplied to an RF amplifier 6 (see FIG. 1) described later. Needless to say, the photodetector 28 is not limited to the configuration of the present embodiment, and various modifications can be made without departing from the object of the present invention.

  Returning to FIG. 1, the laser drive circuit 5 switches between the first light source 21 and the second light source 22 in accordance with the type of the optical disc 20 inserted in the optical disc apparatus 1, or receives a light receiving element for front monitoring. Based on information from (not shown), output control of laser light emitted from the light sources 21 and 22 is performed.

  The RF amplifier 6 is supplied with an electrical signal from the photodetector 28 that receives the reflected light from the optical disc 20 and calculates the supplied electrical signal. Specifically, the electrical signals from the four light receiving areas A to D of the photodetector 28 are added (A + B + C + D) to generate an RF signal indicating the total amount of light that is the total amount of reflected light, A focus error signal (FE signal), which is a signal that detects the defocus of the irradiation laser of the pickup 4, is generated by the astigmatism method ((A + C) − (B + D)), and further, the track shift of the irradiation laser of the optical pickup 4 is detected. A tracking error signal (TE signal) that is a detected signal is generated by a push-pull method ((A + B) − (C + D)).

  The information detection circuit 7 performs processing such as waveform equalization on the RF signal supplied from the RF amplifier 6 and reads information recorded on the optical disc 20. The information read out by the information detection circuit 7 is demodulated by the decoder 8, and the demodulated reproduction signal is output to an external device such as a personal computer via the interface 11.

  The servo circuit 9 generates a focus drive signal and a tracking drive signal based on the FE signal and the TE signal generated by the RF amplifier 6. Further, the optical pickup 4 is provided with a tilt sensor (not shown) so that the tilt angle (angle of the optical axis of the laser beam with respect to the recording surface 20a of the optical disk 20) can be measured. Tilt servo control is also performed based on the output signal of the sensor.

  The actuator drive circuit 10 controls the drive of an actuator 29 (see FIG. 2) on which the objective lens 26 is mounted based on signals such as a focus drive signal and a tracking drive signal supplied from the servo circuit 9. Since the detailed configuration of the actuator 29 is known, the description is omitted, but the objective lens 26 is mounted on the objective lens holder supported by the wire, and the objective lens holder is moved in the focus direction and the tracking direction by electromagnetic force. Further, it is configured to be able to rotate around the axis parallel to the tracking direction. Accordingly, the actuator 29 moves the objective lens 26 in the focus direction and the tracking direction to perform focus control and tracking control, and further rotates the objective lens 26 around the axis parallel to the tracking direction to tilt. Adjust the corners.

  The system control unit 12 includes a microcomputer and appropriately executes control processing according to required operations to be performed by each unit constituting the optical disc apparatus 1. Further, the system control unit 12 also functions as a determination unit that determines the type of the optical disk 20 described later.

  The system control unit 12 includes a ROM (Read Only Memory) 13 and a RAM (Random Access Memory) 14. The ROM 13 stores various parameters and operation programs necessary for the system control unit 12 to perform various processes. The RAM 14 is used as a work area by the system control unit 12 and is a storage area for various necessary information.

  Next, a method for discriminating the type of the optical disc 20 inserted into the apparatus by the system control unit 12 functioning as discriminating means for the optical disc 20 in the optical disc apparatus 1 configured as described above will be described. First, a discrimination principle for discriminating the type of the optical disc 20 in the optical disc apparatus 1 will be described with reference to FIG.

  FIG. 4 shows the positional relationship between the beam spot formed by the reflected light from the optical disc 20 and the light receiving areas A to D of the photodetector 28 when two types of laser beams having different tilt angles are incident on the optical disc 20. FIGS. 4A to 4C are diagrams schematically illustrating the case where the optical disc 20 is a BD, a DVD, and a CD in order.

  In the optical disc apparatus 1, the light detector 28 forms reflected light from the optical disc 20 when laser light having a tilt angle of 90 ° is incident on the optical disc 20 (corresponding to the laser beam indicated by the dashed arrow in FIG. 4). A beam spot (a beam spot indicated by a broken line S on the photodetector 28 in FIG. 4 corresponds) is received without leaking from the light receiving region of the photodetector 28. On the other hand, when a laser beam having a tilt angle θ tilted by a certain value or more from a tilt angle of 90 ° is incident on the optical disc 20 (the laser beam indicated by the solid line arrow in FIG. 4 corresponds), reflected light from the optical disc 20 is formed. The beam spot (corresponding to the beam spot indicated by the broken line T on the photodetector 28 in FIG. 4) is received in a state where it partially leaks from the light receiving region of the photodetector 28.

  The recording surface 20a of the optical disc 20 is covered with a transparent protective layer 20b. The thickness of the protective layer 20b is different from 0.1 mm for BD, 0.6 mm for DVD, and 1.2 mm for CD. ing. For this reason, as shown in FIGS. 4A to 4C, when a laser beam having a tilt angle θ is incident, the amount of light leaking from the light receiving region of the photodetector 28 differs due to the difference in the optical path length. . Therefore, when the laser beam having a tilt angle of 90 ° is incident on the optical disc 20 and the laser beam having the tilt angle θ is changed to be incident on the optical disc, the total amount of light (light receiving region) obtained by the photodetector 28 is changed. The rate at which the sum of (A to D) changes differs for BD, DVD, and CD.

That is, the total amount of light detected by the photodetector 28 when the tilt angle is 90 ° is AS _BD1 , AS _DVD1 and AS _CD1 for each optical disk, and the total amount of light detected by the photodetector 28 when the tilt angle θ is Is AS _BD2 , AS _DVD2 , AS _CD2 for each optical disk, for example, the following relational expression is obtained.
(AS _BD2 / AS _BD1 )> (AS _DVD2 / AS _DVD1 )> (AS _CD2 / AS _CD1 )
Therefore, if two set threshold values X and Y are determined in advance, two types of laser beams having different tilt angles are irradiated on the optical disc to obtain the total amount of light in each case, thereby obtaining the BD, DVD and CD. The type of optical disc can be determined.

  In the above description, the case where the laser beam having the tilt angle 90 ° and the tilt angle θ inclined by a certain value or more from the tilt angle 90 ° is described as an example, but the present invention is not necessarily limited to this. That is, by making the tilt angle of the laser light incident on the optical disc 20 different, if the ratio of the change in the total amount of light caused by the difference in tilt angle is different in each case of BD, DVD, CD, Two other types of tilt angles may be selected.

Further, in the above description, in determining the type of the optical disk using the fact that the rate of change in the total light amount caused by the difference in the tilt angle differs depending on the type of the optical disk, the following calculation (1) is performed to determine the type of the optical disk. For example, as another configuration, the following calculation (2) may be performed to determine the optical disc.
AS (tilt angle θ) / AS (tilt angle 90 °) (1)
(AS (tilt angle 90 °) −AS (tilt angle θ)) / AS (tilt angle 90 °) (2)
In (1) and (2), AS (tilt angle) indicates the total amount of light in the case of the tilt angle shown in parentheses.

  Next, the procedure for discriminating the type of the optical disc 20 in the optical disc apparatus 1 will be described with reference to the flowcharts shown in FIGS. When the optical disk 20 is inserted into the optical disk device 1 or when the power is turned on, the type of the optical disk 20 is determined. When the discrimination of the optical disk 20 is started, the objective lens 26 is moved in the lens down direction, which is the direction away from the optical disk 20, and set to the initial position (step S1).

  Next, the objective lens 26 is rotated by the actuator 29 (see FIG. 2), and the tilt angle of the laser light incident on the optical disk is set to the first tilt angle (step S2). After setting to the first tilt angle, the light sources 21 and 22 emit light, and laser light having any wavelength for BD, DVD, or CD is emitted (step S3). When the laser light is emitted, the lens 29 is started to move in the direction in which the objective lens 26 is brought closer to the optical disc 20 by the actuator 29 (step S4).

  Simultaneously with the start of lens up, measurement of the total light quantity is started (step S5). Here, measurement of the total amount of light means measurement of an RF signal, and an RF signal obtained by the RF amplifier 6 is supplied to the system control unit 12. Thereafter, it is confirmed whether or not the lens-up for which the movement amount has been determined in advance is to be ended (step S6). If not, the lens-up and the measurement of the total light quantity are continued. On the other hand, when the lens up is finished, the measurement of the total light quantity is also finished at the same time as the lens up is finished (step S7). When the measurement of the total light amount is completed, the maximum value AS1 of the total light amount obtained when the lens is raised is acquired (step S8).

  In the present embodiment, in step S8, the maximum value AS1 is acquired from the total amount of light obtained when the lens is raised. This is a state where the focal point of the objective lens 26 is on the recording surface 20a. This is because the total amount of light is acquired. However, it is only necessary to obtain a state in which the total amount of light does not change due to factors other than the change in the tilt angle, and the configuration for acquiring the maximum value AS1 of the total amount of light is not necessarily required. In addition, what was described here is the same when acquiring the maximum values AS2 and AS3 of the total light quantity, which will be described later.

  Next, the objective lens 26 is rotated by the actuator 29, and the tilt angle of the laser light incident on the optical disk is changed to a second tilt angle having an angle different from the first tilt angle (step S9). When the second tilt angle is changed, lens down is started (step S10). Simultaneously with the start of lens down, measurement of the total light quantity is started by the photodetector 28 (step S11). Thereafter, it is confirmed whether or not the lens down for which the movement amount is determined in advance is to be ended (step S12). If not, the lens down and the measurement of the total light quantity are continued. On the other hand, when the lens down is ended, the measurement of the total light quantity is also ended together with the end of the lens down (step S13). When the measurement of the total light quantity is completed, the maximum value AS2 of the total light quantity obtained when the lens is down is acquired (step S14).

  Next, the objective lens 26 is rotated by the actuator 29, and the tilt angle of the laser light incident on the optical disk is changed to a third tilt angle having an angle different from the first and second tilt angles (step S15). When the angle is changed to the third tilt angle, lens up is started (step S16). Simultaneously with the start of lens up, measurement of the total light quantity is started by the photodetector 28 (step S17). Thereafter, it is confirmed whether or not the lens-up for which the movement amount has been determined in advance is to be ended (step S18). If not, the lens-up and the measurement of the total light quantity are continued. On the other hand, when the lens up is finished, the measurement of the total light quantity is also finished together with the end of the lens up (step S19). When the measurement of the total light quantity is completed, the maximum value AS3 of the total light quantity obtained when the lens is raised is acquired (step S20).

  When AS1, AS2, and AS3 are obtained, using these values and the first to third tilt angles, as shown in FIG. 7, a secondary order indicating the relationship between the tilt angle and the total light quantity (AS) is obtained. An approximate curve is calculated by the least square method (step S21). When the quadratic approximate curve is obtained, the maximum AS value a is calculated from the obtained quadratic approximate curve (step S22). Note that the tilt angle θa (see FIG. 7) when the maximum value a is obtained is approximately 90 °.

Next, the AS value b in the case of θb (see FIG. 7) tilted by a predetermined amount from the tilt angle θa is calculated using a quadratic approximate curve (step S23). Here, θb is a tilt angle at which at least a part of the reflected light from the optical disk 20 is received in a state of leaking from the light receiving region of the photodetector 28. When the AS value b in the case of the maximum AS value a and the predetermined tilt angle θb is obtained from the quadratic approximate curve, AS _R = b / a is calculated (step S24).

When AS _R is calculated, it is confirmed whether AS _R is smaller than the design threshold value X (step S25). If AS _R is smaller than the design threshold X, it is determined that the AS change rate belongs to the region having the largest AS change rate, and the optical disc 20 is determined to be a CD (step S26). On the other hand, if AS _R is greater than or equal to the design threshold X, it is confirmed whether AS _R is greater than or equal to the design threshold and less than or equal to the design threshold Y (step S27). If AS _R is greater than or equal to the design threshold X and less than or equal to the design threshold Y, it is determined that the AS change rate belongs to the second largest region, and the optical disc 20 is determined to be a DVD (step S28). ). On the other hand, when AS _R is not less than the design threshold X and not more than the design threshold Y, it is determined that AS _R is greater than the design threshold Y, it is determined that the AS change rate belongs to the smallest region, and the optical disc 20 is It is determined that it is a BD (step S29).

  As described above, in the optical disc apparatus 1, the optical discs 20 having different thicknesses of the protective layer 20b can be stably used by using laser light having one wavelength regardless of the type of the optical disc 20 inserted in the apparatus. It is possible to accurately determine the type.

  In the embodiment described above, in order to obtain an approximate curve indicating the relationship between the tilt angle and the total light amount, the total light amount is measured for three different tilt angles. However, the approximate curve is more accurate. In order to achieve this, the total light quantity may be measured for four or more tilt angles.

  In the present embodiment, a quadratic approximate curve is calculated, and the total light quantity in the case of two predetermined tilt angles is used to determine the type of optical disc using this. However, the present invention is not necessarily limited to this configuration. That is, for example, for a predetermined two tilt angles, the total amount of light may be obtained directly from the photodetector 28 and used to determine the type of the optical disc.

  Furthermore, in the present embodiment, the actuator 29 that can rotate the objective lens 26 around a predetermined axis is used as the tilt angle adjusting means for changing the tilt angle. However, the present invention is not limited to this. The whole 4 may be configured to use a tilt angle adjusting means that rotates around a predetermined axis.

  In addition, in the present embodiment, the type of the optical disc is determined for the three types of BD, DVD, and CD. However, the present invention is not limited to this, and the present invention is not limited to this type of optical disc with a different protective layer thickness for protecting the recording surface. Needless to say, it can be widely applied to discrimination.

  The method for discriminating an optical disc according to the present invention can be widely applied to discriminating types of optical discs having different thicknesses in the protective layer for protecting the recording surface, and thus can be widely applied to optical disc apparatuses compatible with a plurality of types of optical discs.

These are block diagrams which show the structure of the optical disk apparatus of this embodiment. These are the schematic which shows the structure of the optical system of the optical pick-up with which the optical disk apparatus of this embodiment is provided. These are the schematic front views which looked at the photodetector with which the optical disk device of this embodiment is provided from the light-receiving surface side. These are the schematic diagrams for demonstrating the discrimination principle which discriminate | determines the kind of optical disc in the optical disc apparatus of this embodiment. These are the flowcharts which show the discriminating procedure of the optical disc in the optical disc apparatus of this embodiment. These are the flowcharts which show the discriminating procedure of the optical disc in the optical disc apparatus of this embodiment. These are figures which show the quadratic approximated curve obtained from the relationship between a tilt angle and total light quantity (AS).

Explanation of symbols

1 Optical disk device 12 System control unit (discriminating means)
DESCRIPTION OF SYMBOLS 20 Optical disk 20a Recording surface 20b Protective layer 21 1st light source 22 2nd light source 26 Objective lens 28 Light detector (light detection means)
29 Actuator (Tilt angle adjustment means)

Claims (6)

A plurality of light sources having different wavelengths;
An objective lens for condensing the light beam emitted from the light source on the recording surface of the optical disc;
Light detecting means for receiving reflected light reflected by the optical disc;
A tilt angle adjusting means capable of changing a tilt angle defined by an angle formed by a recording surface of the optical disc and an optical axis of a light beam condensed by the objective lens;
Discriminating means for discriminating the type of the optical disc;
In an optical disc apparatus compatible with a plurality of types of optical discs having different thicknesses of protective layers for protecting the recording surface,
The discriminating means is configured to detect the light detection means when the objective lens is positioned at a predetermined position for each of the case where the tilt angle is the first tilt angle and the case where the tilt angle is the second tilt angle. Obtain the total amount of light obtained, determine the type of optical disc with a different thickness of the protective layer based on the ratio of the two obtained total light amounts,
The first tilt angle is obtained by changing the tilt angle to at least three angles, and the relationship between the tilt angle and the total light amount is a quadratic curve by the least square method based on the total light amount obtained in each case. Is a tilt angle when the total light quantity of the quadratic curve is maximized when approximated by
The second tilt angle is an angle inclined by a predetermined amount with respect to the first tilt angle, and when the objective lens is located at the predetermined position, the reflected light is detected by the light detection means. Is an angle at which light is received in a state where at least part of the light receiving area leaks,
The predetermined position is a position where the total light amount of the reflected light is maximum when the objective lens is moved in a direction in which the objective lens is moved toward and away from the optical disk.
An optical disc apparatus characterized in that the total light quantity in each case of the first tilt angle and the second tilt angle is obtained from the quadratic curve. A plurality of light sources having different wavelengths;
An objective lens for condensing the light beam emitted from the light source on the recording surface of the optical disc;
Light detecting means for receiving reflected light reflected by the optical disc;
A tilt angle adjusting means capable of changing a tilt angle defined by an angle formed by a recording surface of the optical disc and an optical axis of a light beam condensed by the objective lens;
Discriminating means for discriminating the type of the optical disc;
In an optical disc apparatus compatible with a plurality of types of optical discs having different thicknesses of protective layers for protecting the recording surface,
The discriminating means is configured to detect the light detection means when the objective lens is positioned at a predetermined position for each of the case where the tilt angle is the first tilt angle and the case where the tilt angle is the second tilt angle. An optical disc apparatus, wherein the total amount of light obtained is obtained, and the type of the optical disc is determined based on a change rate of the total amount of light caused by a difference in the tilt angle depending on a thickness of the protective layer. The first tilt angle is an angle at which the reflected light is received without leaking from a light receiving region of the light detecting means when the objective lens is located at the predetermined position,
The second tilt angle is an angle at which the reflected light is received at least partially leaking from a light receiving region of the light detection means when the objective lens is located at the predetermined position. The optical disc apparatus according to claim 2. The first tilt angle is obtained by changing the tilt angle to at least three angles, and the relationship between the tilt angle and the total light amount is a quadratic curve by the least square method based on the total light amount obtained in each case. Is a tilt angle when the total light quantity of the quadratic curve is maximized when approximated by
The second tilt angle is an angle inclined by a predetermined amount with respect to the first tilt angle,
4. The optical disc apparatus according to claim 3, wherein the total amount of light in each case of the first tilt angle and the second tilt angle is obtained from the quadratic curve.   5. The predetermined position is a position where the total light amount of the reflected light becomes maximum when the objective lens is moved in a direction in which the objective lens is moved toward and away from the optical disk. An optical disc device according to any one of the above. A method of discriminating optical discs for discriminating types of optical discs having different protective layer thicknesses for protecting the recording surface,
When the angle between the recording surface of the optical disc and the optical axis of the light beam collected by the objective lens is defined as a tilt angle,
In each case where the tilt angle is the first tilt angle and the second tilt angle, the reflected light from the optical disc is received when the objective lens is located at a predetermined position. Obtain the total amount of light obtained by the light detection means,
A method of discriminating an optical disc, wherein the type of the optical disc is discriminated based on a change rate of the total light quantity caused by a difference in tilt angle depending on a thickness of the protective layer.

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