JP2005327422A - Recording/reproducing device and recording/reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording/reproducing device and a recording/reproducing method for realizing a sure focus control discrimination operation while preventing damage to a recording medium due to a scratch, etc., with respect to the recording medium, the kind of which is unknown (e.g. CD, DVD or BD). <P>SOLUTION: Since the focus discrimination operation is carried out by using first the light source of the CD (optical system 20 for the CD), which has a longest wavelength among those of BD/DVD/CD, a collision of an objective lens 12 with an optical disk medium 11 at the focus discrimination operation is prevented, then possibility of damaging the optical disk medium 11 can be evaded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording / reproducing apparatus capable of recording and reproducing a plurality of types of recording media such as a BD (Blu-ray Disc), a DVD (Digital Versatile Disc), and a CD (Compact Disc), and the recording / reproducing thereof. Regarding the method.

  An optical disk using a blue-violet semiconductor laser (wavelength: about 405 nm) and a high numerical aperture objective lens (numerical aperture: 0.85) for the purpose of increasing the recording density (recording capacity per medium) of an optical recording medium typified by an optical disk The device BD (Blu-ray Disc) was proposed. Although this apparatus can realize a large capacity recording that is approximately five times as large as a DVD (Digital Versatile Disc) apparatus, it has one aspect in which the lens working distance is reduced.

  BD was initially commercialized using a dedicated objective lens with a lens operating distance of about 0.15 mm, but later advances in lens design and processing technology, as well as subordinate to conventional optical discs (DVD, CD: Compact Disc) In order to ensure compatibility, a method of sharing the same objective lens has been proposed.

  For example, Non-Patent Document 1 reports a design example in which three methods, BD / DVD / CD, are realized with a single lens and a wavelength-selective aperture limiting element. The aperture limiting element plays a role of realizing an objective lens numerical aperture different from 0.85 / 0.6 / 0.45 by the above-described methods by disposing a wavelength selective filter in the optical path. In this example, the operating distance of 0.5 mm ensured for BD is reduced to 0.21 mm for CD.

In Non-Patent Document 2, a similar method is used to realize an objective lens that shares the two BD / DVD methods. In this case, the lens operating distance secured by BD is 0.53 mm. It is reduced to 0.3mm on DVD.
R. Katayama, "Blue / DVD / CD Compatible Optical Head Technologies," Technical Digest of International Symposium on Optical Memory, Nara, pp.216-217 (2003) K. Takada, J. Hashimura, Y. Ori, N. Mushiake, "Blu-ray Disc / DVD Compatible Objective Lens Assembly," Technical Digest of International Symposium on Optical Memory, Nara, pp. 230-231 (2003)

  The basic relationship between the lens numerical aperture and the operating distance will be described. FIG. 9 shows a design example in which the lens operating distance (distance from the upper surface of the objective lens 12 to the surface of the optical disk medium 11a) is 0.5 mm in BD, and FIG. 10 shows the application of the lens to a CD (optical disk medium 11b). This is shown in the figure.

  When a plurality of numerical apertures are realized with a single lens, as shown in Non-Patent Documents 1 and 2, generally, the lens operating distance is shortened under a long wavelength condition. In this example, the lens operation is performed with a CD. The distance is 0.3mm. The optical element 13 corresponds to a wavelength selection filter that limits the numerical aperture, and achieves an objective lens numerical aperture of 0.85 for BD and 0.45 for CD.

  As is clear from comparison between FIG. 9 and FIG. 10, the distance from the upper surface of the objective lens to the optical disc medium signal surface is clearly longer in FIG. This is because the light transmission protective layer (cover layer) is 0.1 mm in the BD, whereas the signal is read through the 1.2 mm cover layer in the CD.

  Here, consider a case where an unknown disk medium is loaded in the optical disk recording / reproducing apparatus. In an optical disc apparatus, the focus control pull-in operation is usually performed with the optical disc medium rotated. However, when the pull-in operation to the CD is performed under the BD setting conditions shown in FIG. The objective lens 12 and the optical disk medium come into contact with each other before reaching.

  In most cases, a protective material (protector) is added on the objective lens 12 side in preparation for contact with the optical disc, but the possibility of damaging the optical disc by contact cannot be denied. In particular, in an existing CD device, since the possibility of contact with the objective lens is extremely low, the surface hard coat is usually not applied to the medium for the purpose of protection at the time of contact. For this reason, there is a problem that the optical disk is damaged and data cannot be reproduced or recorded.

  In view of this problem, the present invention realizes a reliable focus control pull-in operation while preventing damage to the recording medium due to scratches on a recording medium of unknown type (for example, CD, DVD, or BD). It is an object of the present invention to provide a recording / reproducing apparatus and a recording / reproducing method that can be used.

(1) In order to solve such a problem, a recording / reproducing apparatus according to the present invention includes a first light source for irradiating a recording medium with laser light having a first wavelength, and the recording medium having the first wavelength. A second light source for irradiating a laser beam having a second wavelength shorter than the first light source, the first light source, the second light source, and the recording medium interposed between the recording medium and the recording medium. An objective lens common to the first light source and the second light source provided so as to be movable back and forth, a light receiving means for receiving laser light reflected from the recording medium, for example, through the objective lens, and Before the second light source, the recording medium is irradiated with laser light having a first wavelength from the first light source, and the objective lens is applied to the recording medium based on the laser light received by the light receiving means. The recording medium is in the first position. Characterized by comprising a control means for determining whether it is possible to record / reproducing with a laser beam of a wavelength.

  The recording / reproducing method according to another aspect of the present invention is the first of the laser light having the first wavelength for irradiating the recording medium and the laser light having the second wavelength shorter than the first wavelength. A laser beam having a wavelength of 1 is selected, the recording medium is irradiated with the laser beam having the first wavelength via an objective lens commonly used for the laser beams having the first and second wavelengths, and the recording medium is reflected. For example, the received laser beam is received through an objective lens, and the objective lens is moved forward and backward with respect to the recording medium based on the received laser beam, and the recording medium is focused by the laser beam having the first wavelength. It is characterized by determining whether recording / reproduction is possible.

  Here, “/” in “recording / reproduction” means three cases of recording and reproduction, reproduction only, and recording only.

In the present invention, the laser light of the first wavelength is irradiated to the recording medium prior to the laser light of the second wavelength shorter than the first wavelength, and the objective lens is advanced and retracted relative to the recording medium. Therefore, the lens operating distance (the operating distance between the objective lens and the recording medium) becomes small.
Therefore, it is possible to prevent the objective lens and the recording medium from colliding with each other at the time of focusing, and avoid the risk of damaging the recording medium.

When the apparatus according to the present invention performs recording / reproduction compatible with CD, DVD and BD, for example, the light source of the CD having the longest wavelength is used first to perform the focus pulling operation.
(2) In the apparatus according to the present invention, when the previous recording medium cannot be recorded / reproduced by the laser beam having the first wavelength, the control means controls the recording medium from the second light source to the recording medium. The laser beam of the second wavelength is irradiated, and the objective lens is moved forward and backward with respect to the recording medium based on the laser beam received by the light receiving means, and the recording medium is focused by the laser beam of the second wavelength. It may be configured to determine whether recording / reproduction is possible.

  In the method according to the present invention, when recording / reproduction is not possible with the laser beam with the first wavelength, the laser beam with the second wavelength is selected next, and the laser with the second wavelength is passed through the objective lens. The recording medium is irradiated with light, and the laser beam reflected from the recording medium is received through, for example, an objective lens, and the objective lens is moved forward and backward with respect to the recording medium based on the received laser beam, and focused. You may comprise so that the said recording medium may discriminate | determine whether recording / reproducing is possible with the laser beam of the said 2nd wavelength.

  In the present invention, when the focus control pull-in operation by the laser beam of the first wavelength is impossible, the focus control pull-in operation is performed by the laser beam of the second wavelength, so that a more reliable focus control pull-in operation is realized. Can do.

These focus pulling operations may be repeated a plurality of times. Thereby, a more reliable focus control pull-in operation can be realized.
(3) As one form of the focus pull-in operation (determination as to whether the recording medium is recordable / reproducible) according to the present invention, it is performed based on the servo error signal obtained from the reflected light intensity of the received laser beam. Good. As a result, more rapid discrimination is possible.

  As another form of the focus pull-in operation according to the present invention, it may be performed based on a reproduction signal of a recording medium obtained from received laser light. Thereby, more reliable discrimination is possible.

  As still another form of the focus pull-in operation according to the present invention, it may be performed based on a time interval between two changing points of the reflected light intensity of the laser beam received at the time of focusing. Thereby, a quicker and more reliable determination becomes possible.

  In the present invention, these multiple types of focus pull-in operations may be combined. For example, when performing the focus pull-in operation using the light source of the CD first and when performing the focus pull-in operation using the light source of the DVD next, it is performed on the basis of the servo error signal to obtain the next speed. When performing the focus pull-in operation on the BD, the certainty may be obtained based on the reproduction signal of the recording medium.

  Further, when the focus pull-in operation is repeated a plurality of times as described above, for example, it may be performed first based on the servo error signal and then based on the reproduction signal of the recording medium. Furthermore, it is of course possible to carry out these various combinations.

  As described above, according to the present invention, it is possible to prevent the objective lens and the recording medium from colliding with each other at the time of focusing, and avoid the risk of damaging the recording medium. The present invention is extremely effective for a CD or the like that is not subjected to surface protection treatment of the recording medium, and can be easily applied to the front / back determination of the recording medium.

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

  In this embodiment, signals are transmitted via the same objective lens to three types of optical disc media, BD / DVD / CD, which are examples of a plurality of types of optical disc media having different thicknesses of light transmission protective layers (cover layers). A recording / reproducing apparatus capable of recording / reproducing data will be described as an example.

  FIG. 1 is a diagram for explaining a recording / reproducing apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 11 denotes an optical disc medium of BD / DVD / CD as a recording medium. An objective lens 12 is provided so as to be movable back and forth with respect to the optical disk medium 11 and has an effective lens numerical aperture (NA) different for each wavelength. An optical element 13 corresponds to a wavelength selection filter for limiting the numerical aperture. , 14 is a quarter-wave plate that plays the role of converting linearly polarized light of the semiconductor laser into circularly polarized light, and 15 is a spherical aberration correcting element mainly required for BD. The spherical aberration correction element 15 can be constituted by a liquid crystal element, for example. The liquid crystal element (spherical aberration correction element 15) has, for example, a concentric electrode pattern, and corrects spherical aberration caused by the thickness error of the cover layer in accordance with the voltage applied to each electrode. Fulfill.

  Reference numerals 16 and 17 denote combining prisms, and 20, 30 and 40 denote optical systems for CD, DVD and BD, respectively. Reference numeral 18 denotes an actuator for driving the objective lens 11 forward and backward, and 19 denotes a control unit for controlling the actuator 18 and the like based on detection signals from the optical systems 20, 30 and 40 for CD, DVD and BD.

  In the figure, a light beam for BD having a wavelength of 405 nm (solid line) and a light beam for CD having a wavelength of 780 nm (dotted line) are shown. In the case of a CD, the spot is condensed on the b surface through a 1.2 mm cover layer.

  FIG. 2 is a diagram showing a configuration example of the optical system 40 for BD shown in FIG.

  Light emitted from the blue-violet semiconductor laser 41 having a wavelength of 405 nm is converted into parallel light by the collimator lens 42 (infinite optical system), and is used to generate a side spot (± first-order diffracted light) that is used to generate a track control error signal. After passing through the diffraction grating 44, it passes through the polarization beam splitter 45 and is guided to the combining prism 17 (see FIG. 1).

  A part of the emitted light is reflected by the polarizing beam splitter 45 and then guided to the light receiving element 47 for detecting the light output by the condenser lens 46, and used for the purpose of controlling the laser output to a constant value. The amount of light incident on the light receiving element 47 can be adjusted by rotating the half-wave plate 43, and the actual laser output can be arbitrarily set by, for example, an automatic output control (APC) circuit (not shown). The light emission output value is controlled.

  On the other hand, the reflected light from the optical disk medium 11 passes through all of the combining prisms 16 and 17 shown in FIG. 1, and then is reflected by the beam splitter 45 and guided to the detection optical path. In this embodiment, the astigmatism method is used as an example of the focus control error signal, and the differential push-pull method is used as an example of the track control error signal, and the convergent light passing through the condenser lens 48 and the multi lens 49 is used. Enters the light receiving element 50 for detecting a servo error signal and RF signal, and is subjected to photoelectric conversion.

  FIG. 3 is a diagram showing a configuration of the light receiving element 50 for detecting a servo error signal and RF signal.

  The servo error signal / RF signal detection light receiving element 50 includes one quadrant light detection element 51 and two two-part detection elements 52 and 53, which are divided into three beams by the diffraction grating 44 shown in FIG. Of the illumination light, the reflected light of the 0th order light is the elements from A to D in the 4-split light detection element 51, and the reflected light of the ± 1st order light is the elements from E to H in the 2-split detection elements 52 and 53 Will be received. A focus error signal (FE) and a track error signal (TE) are calculated based on the outputs of these elements.

  FIG. 4 is a diagram showing a configuration example of the optical system 20 for CD shown in FIG.

  The light emitted from the infrared semiconductor laser 21 having a wavelength of 780 nm passes through a side spot generating diffraction grating 22 for generating a track control error signal, and then has a transmittance and a reflectance of 50%. And is guided to the combining prism 16 shown in FIG.

  The objective lens output power in this embodiment is controlled to an arbitrary output value by an APC circuit (not shown) based on, for example, a signal output from a monitor terminal of a semiconductor laser. Further, in the optical system 20 for CD, the spherical aberration generated due to the difference in the thickness of the light transmission protective layer can be corrected by adopting a configuration in which the illumination to the objective lens 12 is a diffuse spherical wave (finite optical system). Has the function of facilitating.

  The reflected light from the optical disk medium 11 is reflected by the combining prism 16 shown in FIG. 1, then reflected by the beam splitter 23, and then guided to the detection optical path. In the present embodiment, the astigmatism method is used as an example of the focus control error signal, and the three-spot method is used as an example of the track control error signal. The convergent light passing through the condenser lens 24 and the multi-lens 25 is The light enters the light receiving element 26 for detecting a servo error signal and RF signal, and is subjected to photoelectric conversion.

  The servo error signal / RF signal detection light receiving element 26 has the same dividing elements as in FIG. 3, and a focus error signal (FE) and a track error signal (TE) are calculated based on the output of each element. The Further, similarly to the BD optical system 40 shown in FIG. 2, it is easy to configure an optical system capable of signal recording by providing a light-receiving output detection element for monitoring the laser output.

  The DVD optical system 30 has an infinite optical path configuration having a configuration substantially equivalent to the BD optical system 40. A red semiconductor laser having a wavelength of 650 nm is used as the light source, and signal detection is performed by a divided light receiving element similar to that shown in FIG. Therefore, illustration and description thereof are omitted here.

  Next, error signals detected by the optical systems 20, 30, and 40 for BD / DVD / CD are shown below.

  The focus error signal (FE) is obtained by performing the calculation shown in Expression (1) for each detection light receiving element. In the illustrated astigmatism focus error signal, the multi-lens 25, 49 shows a circular intensity distribution on the light receiving elements 26, 50 on the light receiving elements 26, 50, as shown in FIG. The calculation result generates an output (commonly known as an S-shaped error signal) that becomes zero level when focused.

      FE = (A + C) − (B + D) (1)

  As a track error signal in the optical system 20 for CD, for the read-only disc in which the information pit row is formed in advance, the reflected light of the two side spots generated by the diffraction grating is used to calculate the formula (2). This method is called the 3-spot method.

      3TE−CD = (E + F) − (G + H) (2)

  On the other hand, as a track error signal in the optical systems 30 and 40 for BD and DVD, a phase difference method (DPD) is mainly used for a read-only disc in which an information pit row is formed in advance. This method is a method of detecting the phase difference between the sum signal of the light receiving elements A and C and the sum signal of B and D, and is expressed by Expression (3).

      DPD = φ (A + C) −φ (B + D) (3)

  Further, in any of the optical systems 20, 30, and 40 of BD / DVD / CD, when performing track control on a recordable medium in which a groove shape is formed in advance, a differential push-pull detection method (DPP, For example, see JP-A 61-94246. Specifically, as shown in Equation (4), the sum of the sub push-pull signals detected by the two sub beams is multiplied by the coefficient (k) and subtracted from the main push pull signal detected from the main beam. Thus, an error signal is calculated. Further, the reproduction signal (RF) signal can be detected by calculating the sum of the light receiving elements A to D as shown in the equation (5).

      DPP = (A + D) − (B + C) −k · {(E + F) − (G + H)} (4)

      RF = A + B + C + D (5)

  Next, an operation when an unknown disk medium is loaded in the recording / reproducing apparatus according to the present embodiment will be described. FIG. 6 is a flowchart showing the operation, which is executed under the control of the control unit 19.

  When any one of the BD / DVD / CD optical disc media 11 is loaded in the recording / reproducing apparatus according to the present embodiment (step 601), first, the CD optical system 20 is operated, and another optical system is operated. 30 and 40 are stopped (step 602), and a focus pull-in operation is performed under the conditions of a light source wavelength of 780 nm corresponding to the CD optical system 20 and an objective lens numerical aperture of 0.45 (step 603). Specifically, as the focus pull-in operation, first, the objective lens 12 is moved back and forth in the optical axis direction to determine the focus of the focused spot. Thereafter, when the loaded optical disk medium 11 is a CD, a track error signal by a three-spot or DPP detection method is obtained as a prescribed signal level, and track control and signal reproduction are possible. If focus pull-in is achieved (step 604), the focus pull-in operation is terminated (step 605), and a normal reproduction operation using the CD optical system 20 is performed (step 606).

  Note that, as the focus pull-in operation, it may be determined that the focus pull-in has been performed when the track error signal is obtained at the specified signal level, or it may be determined that the focus pull-in has been performed when reproduction is possible. Good.

  On the other hand, when the focus pull-in cannot be performed by the CD optical system 20, or when the focus pull-in is possible but a specified error signal level or reproduction signal cannot be obtained (step 604), Attempt to pull in the optical system 30 for DVD by shortening the light source wavelength by one step. That is, when a focus pulling operation is attempted with respect to a BD or DVD optical disk medium by the CD optical system 20 (step 603), the focus pulling can be performed from the viewpoint of the lens operating distance, but the light transmission protective layer There is a possibility that a large spherical aberration occurs due to the difference in thickness (CD: 1.2 mm, DVD: 0.6 mm, BD: 0.1 mm) and a sufficient focus error signal (S-shaped signal) cannot be obtained. Therefore, the DVD optical system 30 is operated, and the other optical systems 20 and 40 are stopped (step 607), the light source wavelength corresponding to the DVD optical system 30 is 650 nm, and the lens numerical aperture is 0.6 (partially, The focus pull-in operation is performed under the condition of 0.65 (step 608). When the loaded optical disk medium 11 is a DVD, a track error signal by a DPD or DPP detection method is obtained as a prescribed signal level, and track control and signal reproduction are possible. If focus pull-in has been achieved (step 608), the focus pull-in operation is terminated (step 605), and a normal reproduction operation using the DVD optical system 30 is performed (step 606).

  On the other hand, when both the optical system 20 and 30 for CD and DVD cannot perform focus pull-in, or when focus pull-in is possible but a specified error signal level or reproduction signal cannot be obtained. (Step 608), the light source wavelength is shortened by one more step, and the pull-in operation in the BD optical system 40 is attempted. That is, the BD optical system 40 is operated, and the other optical systems 20 and 30 are stopped (step 609), and the focal point is obtained under the condition that the light source wavelength corresponding to the BD optical system 40 is 405 nm and the lens numerical aperture is 0.85. A pull-in operation is performed (step 610). When the loaded optical disk medium 11 is a BD, a track error signal by a DPD or DPP detection method is obtained as a prescribed signal level, and track control and signal reproduction are possible. If the focus can be pulled in (step 610), the focus pulling operation is terminated (step 605), and a normal reproduction operation using the BD optical system 40 is performed (step 606).

  Normally, the optical disk medium 11 in which the focus pull-in operation has not been completed in the operation sequence so far is considered to be BD. Therefore, by using the optical system 40 for BD having a light source wavelength of 405 nm and a lens numerical aperture of 0.85, S of a prescribed level is used. The character signal is detected and the focus control is completed, and a track error signal obtained by the DPD or DPP detection method is obtained as a prescribed signal level, thereby enabling track control and signal reproduction.

  However, even when the optical system 40 for BD is used, for example, when the optical disk medium 11 is loaded upside down, a predetermined error signal cannot be finally obtained, and the focus pull-in operation is not completed. Is done.

  Therefore, in the present embodiment, the series of pull-in operations is performed a plurality of times (step 611).

  If focus control is not completed even after a series of pull-in operations, the focus pull-in operation is terminated and the disk medium is ejected (step 612), and a process of notifying with an error display is performed (step 613). ). Thus, for example, when a BD is loaded upside down, the apparent cover layer thickness is close to that of a CD, so it can also be used for front / back determination by determining the presence or absence of a signal.

  As described above, in the recording / reproducing apparatus according to the present embodiment, the focus light-in operation is performed by first using the light source of CD (optical system 20 for CD) which is the light source having the longest wavelength among BD / DVD / CD. As a result, the operating distance between the objective lens 12 and the optical disk medium 11 is reduced, and the collision between the objective lens 12 and the optical disk medium 11 at the time of focusing is prevented in advance, and the risk of damaging the optical disk medium 11 is avoided. It becomes possible to do.

  That is, normally, the focus control pull-in operation is performed with the optical disk medium 11 rotated, but when the pull-in operation to the CD is performed under the BD setting conditions shown in FIG. 9, the focused spot reaches the signal surface. Prior to this, the objective lens 12 and the optical disk medium 11 come into contact with each other. In a device capable of recording / reproducing BD, a protective material (protector) is usually provided on the objective lens 12 side in preparation for contact with the optical disk medium 11, but the optical disk medium 11 may be damaged by contact. Cannot be denied. In particular, an existing device capable of recording / reproducing a CD is based on the premise that the lens operating distance is long. Therefore, in conventional CDs, it is rare that a surface hard coat is applied to a medium for the purpose of protection upon contact. Therefore, in the present embodiment, when performing a focusing spot focusing operation using a BD / DVD / CD light source, first, among the plurality of laser light sources, a CD light source (objective lens 12 and optical disc) having the longest wavelength. The focus pull-in operation is performed using the smallest operating distance to the medium 11.

  In the present invention, various methods other than the above method can be considered as the focus pull-in operation. For example, it is possible to use a method of determining the distance between the surface of the cover layer of the optical disk medium and the information recording layer based on a time interval of a plurality of reflected light intensities detected during the pull-in operation. FIG. 7 shows a focus error signal (FE) and a reflected light intensity signal (SUM, equation (5) obtained when the objective lens is moved forward and backward in the optical axis direction (corresponding to Forward and Backward in the figure) during the focus pull-in operation. As an example, (a) and (b) are the signals obtained in BD, and (c) and (d) are obtained in CD. It represents a signal. As is apparent from FIG. 7, the difference in the intensity of the reflected light detected on both the cover layer surface and the information recording layer is different due to the difference in the cover layer thickness in BD / DVD / CD, and a certain level. The disc can be discriminated with the probability of.

  In the above embodiment, as shown in step 611 of the flowchart of FIG. 6, when the focus pull-in of the series of BD / DVD / CD is NG, the focus pull-in of the series of BD / DVD / CD is tried again. However, as shown in FIG. 8, when the focus pull-in is NG for each BD / DVD / CD focus pull-in, the focus pull-in of the BD / DVD / CD may be performed again (step 611a). ~ 611c). Thereby, it becomes possible to perform the focus pull-in in a shorter time.

  Further, in the above embodiment, for example, each optical system shown in FIG. 2 and FIG. 4 is an optical pickup configured with discrete components. However, for example, in Japanese Patent Laid-Open No. 2000-303430 and Japanese Patent Laid-Open No. 2003-32335. As illustrated, each can be an integrated optical element formed by integrating a semiconductor laser, a detection element, and an optical component. In addition, for the detection method of each servo error signal, a spot size method or knife edge detection method is used as the focus error signal, and a single spot push-pull detection method is used as the track error signal. It is possible to use.

  Furthermore, in the above-described embodiment, the case of performing signal reproduction and recording / reproduction using the same objective lens for the three optical disc formats of BD / DVD / CD has been illustrated, but only two of these formats are used. This is also effective when an optical system is configured for focusing. The same technique can also be applied when sharing the same objective lens for other optical disc formats.

It is a figure for demonstrating the recording / reproducing apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structural example of the optical system 40 for BD shown in FIG. FIG. 3 is a diagram showing a configuration of a servo error signal / RF signal detection light receiving element 50 shown in FIG. 2. It is a figure which shows the structural example of the optical system 20 for CD shown in FIG. It is a figure which shows intensity distribution on a light receiving element in an astigmatism focus error signal. 6 is a flowchart showing an operation when an unknown disk medium is loaded in the recording / reproducing apparatus according to the embodiment. It is a figure for demonstrating the other example of the focus drawing-in operation | movement which concerns on this invention. It is a flowchart which shows operation | movement when an unknown disc medium is loaded in the recording / reproducing apparatus which concerns on other embodiment. It is a figure for demonstrating the basic relationship between a lens numerical aperture and an operating distance (in the case of BD). It is a figure for demonstrating the basic relationship between a lens numerical aperture and an operating distance (in the case of CD).

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Optical disk medium 12 Objective lens 13 Optical element 14 1/4 wavelength plate 15 Spherical aberration correction element 16, 17 Synthetic prism 18 Actuator 19 Control unit 20 Optical system 30 for CD 30 Optical system for DVD 40 Optical system for BD

Claims (12)

A first light source for irradiating the recording medium with laser light having a first wavelength;
A second light source for irradiating the recording medium with laser light having a second wavelength shorter than the first wavelength;
An objective common to the first light source and the second light source, which is interposed between the first light source, the second light source, and the recording medium and is provided so as to be movable forward and backward with respect to the recording medium. A lens,
A light receiving means for receiving laser light reflected from the recording medium;
Prior to the second light source, the recording medium is irradiated with laser light having a first wavelength from the first light source, and the objective is applied to the recording medium based on the laser light received by the light receiving means. A recording / reproducing apparatus comprising: a control unit configured to determine whether the recording medium can be recorded / reproduced by the laser beam having the first wavelength; The recording / reproducing apparatus according to claim 1,
The control means irradiates the recording medium with a laser beam having a second wavelength from the second light source when the recording medium is not capable of recording / reproducing with the laser beam having the first wavelength, Based on the laser beam received by the light receiving means, the objective lens is advanced and retracted with respect to the recording medium to focus, and it is determined whether the recording medium can be recorded / reproduced by the laser beam of the second wavelength. Characteristic recording / reproducing apparatus. The recording / reproducing apparatus according to claim 1,
The recording / reproducing apparatus, wherein the control unit determines whether the recording / reproducing is possible based on a servo error signal obtained from a reflected light intensity of the laser beam received by the light receiving unit. The recording / reproducing apparatus according to claim 1,
The recording / reproducing apparatus, wherein the control unit determines whether the recording / reproducing is possible based on a reproduction signal of the recording medium obtained from the laser beam received by the light receiving unit. The recording / reproducing apparatus according to claim 1,
The control means determines whether the recording / reproduction is possible based on a time interval between two change points of the reflected light intensity of the laser beam received by the light receiving means at the time of focusing. Recording / playback device. The recording / reproducing apparatus according to claim 1,
The recording / reproducing apparatus, wherein the control means repeatedly determines whether the recording / reproduction is possible a plurality of times. Selecting a laser beam having a first wavelength from among a laser beam having a first wavelength for irradiating a recording medium and a laser beam having a second wavelength shorter than the first wavelength;
Irradiating the recording medium with the laser light of the first wavelength via an objective lens commonly used for the laser light of the first and second wavelengths;
Receiving the laser beam reflected from the recording medium;
Based on the received laser light, the objective lens is advanced and retracted with respect to the recording medium to focus,
It is determined whether the recording medium can be recorded / reproduced by the laser beam having the first wavelength. The recording / reproducing method according to claim 7,
When recording / reproduction is not possible with the laser beam of the first wavelength, the laser beam of the second wavelength is then selected,
Irradiating the recording medium with the laser light of the second wavelength through the objective lens,
Receiving the laser beam reflected from the recording medium;
Based on the received laser light, the objective lens is advanced and retracted with respect to the recording medium to focus,
It is determined whether the recording medium can be recorded / reproduced by the laser beam having the second wavelength. The recording / reproducing method according to claim 7,
The recording / reproducing method characterized by repeatedly determining whether the recording / reproducing is possible a plurality of times. The recording / reproducing method according to claim 7,
The recording / reproducing method is characterized by determining whether recording / reproducing is possible based on a servo error signal obtained from a reflected light intensity of the received laser beam. The recording / reproducing method according to claim 7,
The recording / reproducing method is characterized by determining whether the recording / reproducing is possible based on a reproduction signal of the recording medium obtained from the received laser beam. The recording / reproducing method according to claim 7,
The determination as to whether the recording / reproducing is possible is performed based on a time interval between two changing points of the reflected light intensity of the received laser beam at the time of focusing.

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