JP4826821B2 - Optical disk apparatus, medium type discrimination method, and program - Google Patents

Description

  The present invention relates to an optical disk device, a medium type determination method, and a medium type determination program, and in particular, an optical disk device, a medium type determination method, and a medium type determination for determining the type of an optical disk from reflected light from an optical disk during focus search. Regarding the program.

  2. Description of the Related Art Conventionally, in an optical disc apparatus that performs recording / reproduction corresponding to a plurality of types of optical discs having different recording densities such as CD, DVD, HD DVD, etc., an LD (laser) used for recording / reproduction according to the type of the set optical disc. Diode) and the generation method of the focus error signal and the track error signal according to the recording method of the optical disk such as ROM, R, RW, RAM, etc. must be switched. Prior to the start of execution, it was necessary to determine the type of the optical disk.

  As a medium discriminating method for discriminating the type of the optical disc, the objective lens is moved up and down at a constant speed in the optical axis direction while condensing and irradiating the optical disc with the laser beam through the objective lens, and the focal position of the beam is changed to the optical disc light. During a focus search operation in which a signal is detected from reflected light from an optical disk controlled within a range including the incident surface and the recording layer, a focus S signal or a data signal (in a focus error signal generated on the surface of the optical disk and the recording layer) Alternatively, the thickness of the transparent substrate is measured using the appearance interval of the pulse waveform in the sum signal) to determine whether the substrate is a CD having a substrate thickness of 1.2 mm or a DVD having a substrate thickness of 0.6 mm. Japanese Patent Application Laid-Open No. H10-228707 discloses a method for determining the number of recording layers based on the number of times a focus S-shaped signal is generated during a focus search operation.

  Patent Document 2 discloses a technique for determining the number of recording layers of an optical disc and whether it is read-only or recordable. The method disclosed in Patent Document 2 uses a stray light detection unit that detects stray light that is reflected from a recording layer other than the recording layer to be focused, and changes the level of stray light during focus search. Based on the detected level change, the number of recording layers and the type of recording layer of the optical disc are discriminated.

Japanese Patent Laid-Open No. 9-259435 JP 2006-155791 A

  However, in the method disclosed in Patent Document 2, when the stray light signal is binarized using a threshold during the focus search, the stray light signal decreases when the focal position of the irradiation light is in the recording layer, and high → low → high. A medium (Blu-ray Disc-SL-RE) that becomes a changing tooth loss signal appears. Such a stray light signal cannot be used as a signal indicating the presence of the recording layer. Further, it is not described which of the light reception signals A to J is generated from the sum signal SUM, and there is an inconvenience that an extra cost is required because a dedicated light detection unit is used to obtain a stray light signal. It was.

  In the method disclosed in Patent Document 1, the surface of the optical disc and the recording layer are detected using either the focus S-shaped signal or the data signal (or the sum signal), but in order to reduce false detection. Has a problem of which one of the focus S-shaped signal and the data signal (or the sum signal) is optimal. Furthermore, the method disclosed in Patent Document 1 sets a threshold (threshold) to a constant level of the sum signal or focus S-shaped signal, and sets the position where the sum signal or focus S-shaped signal shows a value equal to or higher than the threshold to the surface of the optical disc. However, when the medium is discriminated for various optical discs having different reflectivities, there is a problem of what value the threshold can be set for optimal detection.

  Further, in an optical disc apparatus configured to perform track servo by the three-beam method, a main beam and a sub beam can be obtained, so there is a problem of which beam is optimal for detecting the surface of the optical disc and the recording layer. there were.

  Further, in the case of ordinary optical disk medium discrimination, focus search is executed, servo parameters such as focus S-shaped signal amplitude and offset, track error signal gain and offset, focus servo and track servo band setting gain, RF signal This is the area where the session information is recorded after adjusting the recording / playback parameters such as the offset of the focus error signal that maximizes the RF signal amplitude to improve the recording / playback performance after turning on the focus servo. The medium type was determined from the medium identification information in the lead-in, but the L0 recording layer, which is a single-sided dual-layer hybrid optical disk and closer to the light incident surface, is a DVD- Twin fo with ROM and the other L1 recording layer is HD DVD-ROM If the disc is determined to be mat disc (hereinafter referred to as TWIN), then it is necessary for the user to select whether to play the L1 recording layer of the HD DVD or the L0 recording layer of the DVD. There was a problem that it took.

[the purpose]
Accordingly, an object of the present invention is to solve the above-described problems of the related art and more accurately determine the medium type for various types of optical disks.

  In order to achieve the above object, an optical disc apparatus according to the present invention includes a beam generating means for generating a main beam and at least one sub beam having a light quantity smaller than that of the main beam, and an objective lens for condensing and irradiating the plurality of beams onto the optical disc. And a focus search means for performing a focus search by controlling the focal position of each beam by moving the objective lens in the optical axis direction, and the reflected light from the optical disk at a position conjugate with the focal point of the objective lens of each beam. A plurality of photodetectors for receiving each light, and a sub-sum signal generating means for generating a sub-sum signal based on the amount of light received by at least one photodetector relating to the sub-beams, and the focus of the sub-beams during the focus search. It detects the level change of the subsum signal when it passes through the light incident surface of the optical disk and when it passes through the recording layer. Sub-sum signal change detecting means for measuring the time interval of the detection time of the optical disk, substrate thickness calculating means for calculating the thickness of the substrate or cover layer of the optical disk based on the measured time interval, and the calculated substrate or cover Medium discriminating means for discriminating the type of the optical disk based on the thickness of the layer, and the photodetector for generating the sub-sum signal is arranged on the imaging surface of the reflected light of the main beam. In addition, the photodetector related to the sub beam receives the reflected light of the sub beam from the optical disc by overlapping a part of the spread component of the reflected light of the main beam.

  Next, the medium type discriminating method of the present invention includes a beam emitting step for emitting a main beam and a sub beam having a light quantity smaller than that of the main beam, and condensing and irradiating the plurality of beams onto an optical disc through an objective lens. A focus search step that performs focus search by controlling the focal position of each beam by moving the lens in the optical axis direction, and the reflected light from the sub-beam optical disk partially overlaps the reflected light of the main beam Sub-sum signal generation step for generating a sub-sum signal based on the amount of received light, and a sub-sum signal when the focal point of the sub beam passes through the light incident surface of the optical disk and the recording layer during the focus search. A sub-sum signal change detection step for detecting a level change of the signal and measuring a time interval of the detection time, and an optical signal based on the time interval. A substrate thickness calculating step for calculating the thickness of the substrate or cover layer of the disc and a medium determining step for determining the type of the optical disk based on the calculated value of the thickness of the substrate or cover layer. .

  Next, the medium type discriminating program of the present invention condenses and irradiates the main beam and a sub beam having a light quantity smaller than that of the main beam onto the optical disc through the objective lens, and applies the objective lens based on the reflected light from the optical disc. A photodetector for receiving reflected light of a sub beam arranged in advance in a main beam imaging plane in an optical disc apparatus for executing a focus search for controlling a focal position of each beam by moving in an optical axis direction Sum signal input processing for inputting a sub-sum signal generated based on the received light amount of the sub-signal, and a sub-sum signal when the focal point of the sub beam passes through the light incident surface of the optical disc and the recording layer during the focus search. Sub-sum signal change detection process that detects level change and measures the time interval of the detection time, and the light incident surface of the optical disc based on this time interval The computer executes a substrate thickness calculation process for calculating the thickness of the substrate or cover layer up to the recording layer and a medium determination process for determining the type of the optical disk based on the calculated value of the thickness of the substrate or cover layer. It is characterized by making it.

  Since the present invention is configured and functions as described above, the sub sum signal is affected by the leakage of reflected light of the main beam during the focus search, and thus has a pulse width larger than that of the main sum signal. Generate a waveform. By using the sub-sum signal to detect the light incident surface and the recording layer of the optical disc, it is possible to detect even at a lower sampling period, reducing false detection, and the thickness from the light incident surface of the optical disc to the recording layer. The accuracy of medium discrimination based on the height is improved.

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

  FIG. 1 is a diagram showing a schematic configuration of an optical disc apparatus 100 of the present embodiment. As shown in FIG. 1, the optical disc apparatus 100 includes an optical head 113 including an objective lens 21, an objective lens actuator 109, a beam splitter 110, an LD (laser diode) 111, and a photodetector 112. A sled motor 108 that drives the optical disk 101 in the radial direction, a spindle drive system 102 that rotationally drives the set optical disk 101, and a servo drive that controls the sled motor 108 and the objective lens actuator 109 to move the objective lens 21. A system 103, a servo controller 104 that controls the spindle drive system 102 and the servo drive system 103 to perform focus servo and tracking servo, a system controller 105 that controls the operation of the entire optical disc apparatus 100, An RF signal (reproduction signal) is output based on the output from the LD driving unit 106 that controls the light emission of D111 and the photodetector 112, and a servo error signal (focus error signal and track error signal), a sum signal, and the like are output. An RF circuit unit 107 that generates and outputs is configured.

  The optical disc apparatus 100 according to the present embodiment records, as the optical disc 101, a CD that uses infrared light with a wavelength of 780 nm, a DVD that uses red light with a wavelength of 650 nm, and an HD DVD that uses blue light with a wavelength of 405 nm. As an object to be reproduced, the LD 111 is configured to output any one of three-wavelength laser light beams of blue light having a wavelength of 405 nm, red light having a wavelength of 650 nm, and infrared light having a wavelength of 780 nm.

  FIG. 2 is a diagram showing a configuration of the optical head 113 including the optical system in the present embodiment.

  In FIG. 2, the optical head 113 divides the light beam from the LD 111, the collimator lens 22 that converts the light beam from the LD 111 into parallel light, and the light beam from the LD 111 into three light beams. A diffraction grating 23 having a function as a beam generating means for generating a sub beam and a function as a phase adding means for giving a phase difference of about 180 degrees to substantially half faces of the two sub beams, and the three light beams as an optical disk The objective lens 21 for condensing and irradiating the light beam 101, the objective lens actuator 109 for moving the objective lens 21 in the focus direction and the track direction, and the reflected light of the three beams from the optical disk 101 are optically combined with the focus of each beam. Main beam quadrant photodetector 26 receiving light at a conjugate position and sub beam quadrant photodetector 5 and 27, a beam splitter 110 that guides the three light beams from the diffraction grating 23 to the objective lens 21 and allows the reflected light from the optical disc 101 to pass toward the photodetector 112, and the optical disc 101. And a focusing lens 24 that irradiates the reflected light from the light onto the photodetector 112 and narrows it down to a spot of an appropriate size.

  As shown in FIG. 2, the optical disc apparatus 100 according to the present embodiment is configured to execute track servo by the three-beam method, and the three light beams generated by the diffraction grating 23 are spirally formed on the recording layer of the optical disc 101. Three focused spots 28, 29, and 30 are formed on the track 20 formed in (1). Then, the reflected light from the three condensing spots 28, 29, and 30 is narrowed down by the focusing lens 24 and received by the corresponding quadrant photodetectors 26, 27, and 25, respectively.

  FIG. 3 is a functional block diagram showing the configuration of the RF circuit unit 107 in the present embodiment.

  As shown in FIG. 3, the RF circuit unit 107 includes reproduction signal output means 107A that outputs an RF signal (reproduction signal) that is an electric signal output from the main beam quadrant photodetector 26, and three four signals. Servo error signal generation means 107B for generating a focus error signal and a track error signal from the outputs of the divided light detectors 25, 26, and 27, and a main sum signal based on the amount of light detected by the light detector 26 for the main beam. Main sum signal generating means 107E to be generated, sub sum signal generating means 107C for generating a sub sum signal based on the amount of light detected by the sub beam photodetectors 25 and 27, and identification information unique to the optical disc 101 are recorded. Signal obtained by drawing the focus servo into the burst cutting area (hereinafter referred to as BCA) BCA signal extracting means 107D for extracting the BCA signal from the signal). The BCA is an area in a specific part of the optical disc, and is an area where a signal is engraved with a barcode-shaped uneven pattern.

  Here, the sum signal is a signal obtained by removing the data component from the RF signal, and the main sum signal generated by the main sum signal generation means 107E is data from the RF signal (reproduction signal) output from the photodetector 26. The sub-sum signal generated by the sub-sum signal generation unit 107C is a signal obtained by removing data components from the RF signals output from the photodetectors 25 and 27.

  FIG. 4 is a functional block diagram showing the configuration of the servo controller 104 in the present embodiment.

  As shown in FIG. 4, the servo controller 104 controls the servo drive system 103 by performing phase compensation on the focus error signal and the track error signal from the RF circuit unit 107 and transmitting a focusing control signal and a tracking control signal. Servo control means 122 for performing focus servo and tracking servo is provided.

  Servo control means 122 adjusts servo parameters such as focus error signal amplitude and offset, track error signal gain and offset, focus servo and track servo band setting gains, etc. to servo drive system 103 for focusing control signal and track king. Send a control signal.

  The servo drive system 103 shown in FIG. 1 and FIG. 2 drives the objective lens actuator 109 based on the focusing control signal from the servo controller 104 to move the objective lens 21 in the optical axis direction and finely adjust the servo controller 103. The objective lens actuator 109 is driven based on the track king control signal from 104, and the objective lens 21 is moved in the track direction (y direction in FIG. 2) and finely adjusted. Here, the Y direction in FIG. 2 is a direction that is in a plane parallel to the light incident surface of the optical disc 101 and is perpendicular to the track 20.

  Further, the servo control means 122 described above moves the objective lens 21 in the optical axis direction to move the focal points of the main beam and the sub beam within a range including the light incident surface and the recording layer of the optical disc 101 before performing the focus servo. The servo drive system 103 is controlled to perform a focus search. The objective lens actuator 109 is driven by the servo drive system 103 and the objective lens 21 is moved in the optical axis direction, thereby realizing a function as a focus search means for executing a focus search. In the present embodiment, the LD 111 is configured to emit blue light during a focus search.

  As shown in FIG. 4, the servo controller 104 further regulates the level change of the sub-sum signal when the focal point of the sub beam passes through the light incident surface of the optical disc 101 and the recording layer during the focus search with a threshold. The sub-sum signal change detecting means 119 for detecting and measuring the time interval of the detection time and the number of times of detection, and the substrate or cover layer of the optical disc 101 based on the time interval measured by the sub-sum signal change detecting means 119 A substrate thickness calculating means 121 for calculating the thickness; a medium determining means 115 for determining the type of the optical disc 101 based on the calculated value of the thickness of the substrate or cover layer or the number of times measured by the sub-sum signal change detecting means 119; The focus S-character signal generated in the focus error signal from the RF circuit unit 107 is detected and the number of occurrences is detected. A focus S-shaped signal detecting unit 114 for measuring, and a recording layer number determining unit 116 for determining the number of recording layers of the optical disc 101 based on the number of appearances of the focus S-shaped signal measured by the focus S-shaped signal detecting unit 114. ing.

  The sub sum signal change detection means 119 receives the sub sum signal from the RF circuit unit 107 during the focus search, determines whether the signal level is equal to or higher than the threshold (first threshold), and determines the sub sum signal level. Has a function of measuring a time interval from a timing when the voltage becomes equal to or higher than the threshold to a timing when the voltage becomes equal to or higher than the threshold again by a timer (not shown) and the number of times of the timing.

  The substrate thickness calculating means 121 calculates the moving distance of the objective lens from the time interval measured by the sub-sum signal change detecting means 119, and calculates the thickness of the transparent substrate from the light incident surface of the optical disc 101 to the recording layer from the calculated value. Has a function to calculate. Since the substrate thickness of the optical disk 101 is 1.2 mm for CD and 0.6 mm for DVD and HD DVD, the recording layer number determination means 116 presets 1.2 mm and 0.6 mm as determination values, If the value calculated by the substrate thickness calculating means 121 is 1.2 mm, the optical disk 101 is determined as a CD, and if it is 0.6 mm, it is one of DVD, HD DVD, and hybrid SACD (Hybrid Super Audio CD). Determine.

  The focus S-shaped signal detection means 114 receives a focus error signal from the main beam from the RF circuit unit 107, decreases after the signal level exceeds the + (positive) threshold (second threshold), and then decreases. , The focus S-shaped signal is detected by observing that it exceeds the negative (negative) threshold (third threshold) and then has a function of measuring the number of appearances of the focus S-shaped signal. When the polarity of the focus error signal is reversed, the focus S signal is detected by exceeding after falling below the minus threshold and then falling after exceeding the plus threshold.

  Further, when the recording layer number determination unit 116 determines the number of recording layers of the optical disc 101, the servo control unit 122 described above receives a command from the system controller 105 and immediately determines a predetermined recording layer of the optical disc 101. It has a function of controlling the servo drive system 103 so that the focus servo is pulled into the BCA in a specific part. The sled motor 108 and the objective lens actuator 109 are driven by the drive control of the servo drive system 103 to move the objective lens 21, thereby realizing the function as the BCA read means for bringing the focus servo into the BCA.

  Here, the sub-sum signal change detecting means 119, the substrate thickness calculating means 121, the recording layer number determining means 116, the focus S-shaped signal detecting means 114, and the recording layer number determining means 116 described above are programmed. It may be configured to be executed by a computer.

  The system controller 105 shown in FIGS. 1 and 2 controls the entire optical disc apparatus 100 and is connected to the host controller 201 of the host computer 200 via the interface unit 120. The system controller 105 receives the RF signal (reproduction signal) from the RF circuit unit 107, and the focus error that maximizes the amplitude and offset of the RF signal and the RF signal amplitude for improving the recording / reproduction performance when the focus servo is turned on. It has a function of adjusting recording / reproducing parameters such as signal offset and transmitting reproduction data obtained from an RF signal (reproduction signal) to the host controller 201 and a function of receiving a reproduction command and a recording command from the host controller 201. .

  Further, the system controller 105 determines the presence / absence of medium identification information from the BCA signal based on the reflected light from the BCA when the focus servo is drawn into the BCA at the specified position of the optical disc 101 by the servo controller 122. An identification information determination unit 117 and a medium identification unit 118 that identifies the presence or absence of the medium identification information in the BCA or the type of the optical disc 101 according to the medium identification information.

  The host computer 200 is equipped with a host controller 201, a display unit 202, and an input unit 203. The input unit 203 of the host computer 200 receives, for example, type information of a medium to be recorded / reproduced from a user by a remote controller or a keyboard, and then transmits type information of a medium to be recorded / reproduced to the system controller 105 via the host controller 201. To do. The display unit 202 is, for example, a liquid crystal or a CRT, and displays reproduction data from the system controller 105 and a request.

  In the optical disc apparatus 100 of the present embodiment, the servo control unit 122 immediately brings the focus servo into the BCA after the recording layer number determination unit 116 determines the number of recording layers. The time until media type determination is shortened.

  In a conventional optical disc apparatus, focus search is executed, servo parameters such as focus S-signal amplitude and offset, track error signal gain and offset, focus servo and track servo band setting gain, and RF signal amplitude and After adjusting the recording / playback parameters such as the offset of the focus error signal that maximizes the RF signal amplitude to improve the recording / playback performance after turning on the offset and focus servo, read the lead-in that is the area where the session information is recorded. In this case, the medium type is determined from the medium identification information in the lead-in. The L0 recording layer, which is a single-sided dual-layer hybrid optical disk and is closer to the light incident surface, is already a DVD-ROM. Twin form with one L1 recording layer being HD DVD-ROM If it is determined as t disc (hereinafter referred to as “TWIN”), it is necessary for the user to select whether to play the L1 recording layer of the HD DVD or the L0 recording layer of the DVD. It took time.

  In this embodiment, when the number of recording layers of the optical disc 101 is determined, the focus servo is drawn into the BCA only by adjusting the focus servo parameter, and only the reproduction parameter adjustment for reading the BCA code is performed. There is no need to perform servo pull-in, and the time until medium discrimination based on the medium discrimination information recorded in the BCA is shortened. If it is determined to be TWIN, the servo parameter and the recording / reproducing parameter are adjusted in the HD DVD layer (L1 layer) assuming that the user plays a selection request and returns a response until the response is returned. Since preparation for reproduction is performed, the time from when the optical disc 101 is set and the medium type is completed and the reproduction of the HD DVD layer on the TWIN medium is started is greatly shortened compared to the conventional case.

  Furthermore, in the present embodiment, as shown in FIG. 2, quadrant photodetectors 25 and 27 that mainly receive the sub-beams are arranged in the image plane of the reflected light of the main beam. If the quadrant light detectors 25 and 27 are arranged in the image plane of the reflected light of the main beam, a part of the reflected light of the main beam leaks into the quadrant light detectors 25 and 27 at the time of defocusing. In the focus search, the broad waveform can be detected in the sub-sum signal that is the sum signal of the four-divided photodetectors 25 and 27, and the light incident surface and the recording layer of the optical disc 101 can be detected stably.

  FIG. 5 is a diagram showing the positions of the focused spots 28, 29, 30 on the optical disc 101 and the corresponding four-split photodetectors 25, 26, 27 in this embodiment. The X and Y directions shown in FIG. 3 correspond to the X and Y directions shown in FIG.

  As shown in FIG. 5, light spots 37, 38, and 39 are formed on the four-divided photodetectors 25, 26, and 27 by reflected light from the focused spots 30, 28, and 29 formed on the optical disc 101. Is done. Since the light beam that generates the condensing spot 28 is the main beam and the light beam that generates the condensing spots 30 and 29 is the sub-beam, the quadrant photodetector 26 mainly reflects the reflected light from the optical disc 101 of the main beam. Then, the four-divided photodetectors 25 and 27 mainly detect the reflected light from the optical disk 101 of the sub beam.

  In this embodiment, the diffraction grating 23 divides the beam from the LD 111 to realize a function as a beam generation unit that generates a main beam and a sub beam. However, the light amount ratio of the sub beam to the main beam is set to 1/5. A diffraction grating 23 having the following configuration is employed. This is because the RF signal (reproduction signal) obtained from the pits on the optical disc 101 is obtained from the main beam, and the light amount of the main beam is not sufficient unless the light amount ratio of the sub beam to the main beam is 1/5 or less. This is because the signal quality deteriorates.

  As shown in FIG. 5, each of the four-divided photodetectors 25, 26, and 27 has a light receiving region composed of four divided regions, and the photodetector 25 has light receiving regions 31, 32, 70, and 71. The photodetector 26 has light receiving areas 33, 34, 72 and 73, and the photodetector 27 has light receiving areas 35, 36, 74 and 75. Here, the output levels from the four light receiving areas of the photodetectors 25, 26, and 27 are represented by E, F, G, H, A, B, C, D, I, J, K, and L shown in FIG. And

The focus error signal (MFE) by the main beam generated by the servo error signal generation means 107B in the RF circuit unit 107 is expressed as (MFE) = A + C− (B + D). The focus error signal (SFE) by the sub beam is expressed as (SFE) = E + G + I + K− (F + H + J + L). The focus error signal (DFE) using the differential astigmatism method is expressed as (DFE) = (MFE) −k ₁ × (SFE), where k ₁ is a constant.

The track error signal (MTE) by the main beam is expressed as (MTE) = A + D− (B + C). The track error signal (STE) by the sub beam is expressed as (STE) = E + H + I + L− (F + G + J + K). The track error signal (DPP) using the differential push-pull method is expressed as (DPP) = (MTE) −k ₂ × (STE), where k ₂ is a constant. The main sum signal generated by the main sum signal generation means 107E is represented as A + B + C + D. The sub sum signal generated by the sub sum signal generation means 107C is expressed as E + F + G + H + I + J + K + L.

  FIG. 6 is a diagram illustrating changes in the focus error signal and the sum signal during a focus search performed while moving the objective lens 21 at a constant speed in the focus direction in the present embodiment.

  As shown in FIG. 6A15, the objective lens 21 is driven from the position where the focal point of the laser does not reach the substrate surface of the optical disc 101 in the direction approaching the optical disc 101.

  As shown in FIG. 6A, when the optical disc 101 is a CD, first, when the focal points of the main beam and the sub beam pass through the surface of the optical disc 101 (A5 in FIG. 6), the focus error signal has a focus. An S-shaped signal appears (A4 in FIG. 6), and a pulse waveform exceeding the threshold appears in the main sum signal and the sub sum signal.

  The sub-sum signal level detection means 119 detects that the sub-sum signal level has exceeded the threshold (A8 in FIG. 6). The sub-sum signal reference potential (the sub-sum before the focused position of the sub-beam reaches the optical disc 101) is detected. The first threshold (A11 in FIG. 6), which is the sub sum signal change point detection threshold, is set from the potential of the signal to the potential of +, and after the potential level of the sub sum signal exceeds the threshold, it again falls below the threshold. It is determined by.

  The detection of the focus S-shaped signal by the focus S-shaped signal detection means 114 is performed when the sum signal level exceeds the threshold before the reference potential of the focus error signal (before the focused positions of the main beam and the sub beam reach the optical disc 101). The threshold (+ threshold is smaller than the maximum value of the focus error signal and -threshold is larger than the minimum value of the focus error signal) is set to a potential level of ± from the potential of the focus error signal of FIG. A12), it is determined to be lower after exceeding the + threshold (second threshold), and thereafter exceeding after falling below the −threshold (third threshold). Here, when the polarity of the focus error signal is reversed, it is determined by exceeding after falling below the minus threshold and then falling after exceeding the plus threshold.

  In this way, by executing the detection of the focus S-shaped signal using the two threshold values, it is possible to prevent erroneous recognition of the noise waveform of the peaks or valleys not showing the S shape as the focus S-shaped signal.

  Thereafter, also when the focal points of the main beam and the sub beam pass through the recording layer of the optical disc 101, a focus S-shaped signal appears (A4 in FIG. 6), and a pulse waveform appears in the main sum signal and the sub sum signal.

  When the optical disc 101 is a DVD or HD DVD, as shown in FIGS. 6A and 6C, as in the case of a CD, the focus S-shaped signal, the main sum signal, and the sub sum on the light incident surface of the optical disc 101 are used. Then, when the focus of the main beam and the sub beam comes to the recording layer, the focus S-shaped signal and the pulse waveform of the main sum signal and the sub sum signal appear.

  Further, when the optical disc 101 is a DVD or HD DVD double-layer medium, as shown in FIG. 6C, after the focus S-shaped signal appears in the first recording layer (A6 in FIG. 6). When the focus of the main beam and the sub beam passes through the second recording layer (A7 in FIG. 6), a focus S-shaped signal further appears. Unlike the focus S-shaped signal, the main sum signal and the sub sum signal do not decrease to a value below the threshold between the first recording layer (L0 layer) and the second recording layer (L1 layer). The number of recording layers cannot be determined from the number of times the sum signal rises above the threshold. Therefore, the recording layer number determination means 116 in this embodiment determines the number of recording layers based on the number of appearances of the focus S-shaped signal.

  As shown in FIG. 6C, a period in which the level of the sub sum signal exceeds the threshold for the second time counted from the surface of the optical disc 101 indicates the recording layer. At this time, the sub sum signal has the threshold. The number of appearances of the focus S-shaped signal within the exceeding period indicates the number of recording layers of the optical disc 101.

  For example, in FIG. 6A, since one focus S-shaped signal is detected in the period indicating the presence of the recording layer, it can be determined that the medium is a single-layer medium. In FIG. 6C, since two focus S-shaped signals are detected in the period indicating the recording layer, it can be determined that the medium is a two-layer medium. Thus, when the focus S-shaped signal is detected a total of n (n is a natural number) times following the focus S-shaped signal of the L0 layer, which is the recording layer on the side closer to the light incident surface, the recording layer is the n layer. Can be determined.

  The distance between the surface of the optical disc 101 and the L0 layer corresponds to the substrate thickness of the optical disc 101 calculated by the substrate thickness calculating means 121, and this calculated value indicates that the sub-sum signal level has a threshold on the surface of the optical disc 101. It is calculated from the movement amount (movement time) of the objective lens 21 from when the sub sum signal change detecting means 119 detects that the sub sum signal has been exceeded until it is detected that the sub sum signal has exceeded the threshold in the recording layer.

  The substrate thickness calculation unit 121 of the servo controller 104 detects that the sub-sum signal has exceeded the threshold in the recording layer after the sub-sum signal change detection unit 119 detects that the sub-sum signal has exceeded the threshold on the surface of the optical disc 101. The movement time of the objective lens 21 until it is detected is measured by a timer (not shown), and the transparent substrate thickness of the optical disc 101 is calculated from the measured movement time. Then, the medium discriminating means 115 determines whether or not the transparent substrate thickness is 0.6 mm. If the transparent substrate thickness is not 0.6 mm, it is determined that the optical disc 101 is a CD, and if it is 0.6 mm, it is a DVD or HD DVD. It is determined that

  Since HD DVD and DVD have a transparent substrate thickness of 0.6 mm, it is impossible to distinguish HD DVD or DVD from the amount of movement of the objective lens 21. Therefore, BCA is used to distinguish between HD DVD and DVD in this embodiment. Since the HD DVD has a BCA and the medium type identification information is recorded on the BCA, the identification information determination unit 117 of the system controller 105 reads the BCA signal to read from the medium type identification information to the HD DVD. And the type of the HD DVD (ROM, R, RW, RAM, TWIN). On the other hand, since a BCA does not necessarily exist in a DVD, when the medium information in the BCA does not indicate an HD DVD, or when the BCA cannot be read, it is determined that the DVD is a DVD.

  Next, the reason for detecting the surface of the optical disc 101 and the recording layer using the sum signal instead of the focus S-shaped signal in this embodiment will be described.

  FIG. 7 is a diagram showing the waveforms of the focus S-shaped signal and the sum signal on the recording layer and the surface of the optical disc 101, and the reflected light spot shape on the main beam photodetector 26. FIG.

  (2) in FIG. 7 shows a sum signal and a focus S-shaped signal when the focus of the beam passes through the recording layer or the surface of the optical disc 101 during the focus search. FIG. 7A shows a reflected light spot shape on the photodetector 26 when the focus of the beam passes through the recording layer and the surface when performing a focus search by the astigmatism method in this embodiment. Is shown.

  In (1) of FIG. 7, A, B, C, and D indicate the light receiving levels of the respective areas when the light receiving area of the photodetector 26 is divided into four, and the focus error signal is A + C− (B + D), the sum signal. Is represented by A + B + C + D.

  In (1) and (2) of FIG. 7, a and d are cases where the focal point of the beam is located on the recording layer or the surface of the optical disc 101, and the reflected light spot shape on the photodetector 26 is the photodetector 26. Since the center of the light receiving region is a circle and A = B = C = D, the focus S signal (focus error signal) is zero. Further, since the focal point of the beam reaches the recording layer or the substrate surface, the amount of reflected light is the largest and the sum signal level has a peak value.

  B and e in FIGS. 7A and 7B are cases where the focus S-shaped signal peaks in the positive direction, and the reflected light spot shape on the photodetector 26 is longer in the A and C directions. . In FIGS. 7 (1) and (2), c and f are cases where the focus S-shaped signal peaks in the negative direction, and the reflected light spot shape on the photodetector 26 is longer in the B and D directions. .

  Here, the focus error signal is represented as A + C- (B + D), the sum signal is represented as A + B + C + D, and the spherical aberration is set to be minimum in the recording layer in order to ensure recording / reproducing performance. Therefore, as shown in FIG. 7A, the spot shape on the photodetector 26 is different between the recording layer and the surface, and the common area on the photodetector 26 is increased on the surface as compared with the recording layer. As a result, the amplitude peak level (e to f in FIG. 7) is smaller in the focus S-shaped signal that is different from A + C− (B + D), compared to the sum signal that is summed with A + B + C + D. Although the main beam photodetector 26 has been described in FIG. 7, the same applies to the serve beam photodetectors 25 and 27.

  Therefore, the sum signal has a higher level indicating the disk surface or the recording layer than the focus S-shaped signal due to the influence of spherical aberration, and the sum signal can detect the surface and the recording layer more stably. The position of the surface of the optical disc 101 and the recording layer is detected using the signal.

  Next, the reason for detecting the surface of the optical disc 101 and the position of the recording layer using the sub sum signal instead of the main sum signal in this embodiment will be described with reference to FIG.

  In the configuration of the optical head 113 described above, the light amount ratio of the sub beam to the main beam is 1/5 or less. Further, the sub-beam detection quadrant light detectors 25 and 27 are arranged in the image plane of the reflected light of the main beam, and the sub-beam quadrant light detection is performed from the center of the main beam quadrant photodetector 26. The distances to the respective centers of the detectors 25 and 27 are such that the reflected light of the main beam does not reach the sub-beam photodetectors 25 and 27 at the time of focusing, and the reflected light of the main beam at the time of defocusing is the sub-beam photodetector 25. And a distance significantly extending to 27.

  FIG. 8 is a diagram showing reflected light spots of the sub beam and the main beam on the photodetectors 25 and 26, the main sum signal, and the sub sum signal waveform.

  (1) of FIG. 8 shows the time change of the reflected light spot shape with respect to the main beam photodetector 26 and the sub beam photodetector 25. Here, the sub-beam photodetector 27 is omitted.

  (3) in FIG. 8 shows the time response of the main sum signal at the time of focus search, and (2) in FIG. 8 shows the main sum signal shown in (3) in FIG. 8 with 2 as a reference based on the main sum signal threshold. It is a binarized signal that has been digitized. (4) in FIG. 8 is a time response of the sub-sum signal at the time of focus search, and (5) in FIG. 8 is a sub-sum signal shown in (4) of FIG. 8 based on the sub-sum signal threshold. It is a binarized signal that has been digitized.

  M1, M2, M2 ′, M3, M3 ′, M4, M4 ′, S1, S2, S2 ′, S3, S3 ′, S4, and S4 ′ in (1) of FIG. 8 are represented by (3) and ( 4) corresponding to M1, M2, M2 ′, M3, M3 ′, M4, M4 ′, S1, S2, S2 ′, S3, S3 ′, S4, S4 ′.

  M1 and S1 in FIG. 8 indicate when the focal points of the main beam and the sub beam are located on the surface of the optical disc 101. As shown in FIG. 8A, the reflected light spot is the smallest, and FIGS. ), The main sum signal level and the sub sum signal level are maximized.

  (2) to (5) in FIG. 8 show a case where the focus of the main beam and the sub beam approaches the optical disc 101 during the focus search operation, and moves away from the recording layer direction after focusing on the disc surface with M1 and S1. .

  First, when the focal points of the main beam and the sub beam approach the optical disc 101 and become the state of M4 and S4 in FIG. 8, the main beam and the sub beam shown in FIG. It becomes M4 and S4 of the spot. In this case, the reflected light of the main beam and the sub beam is applied to both the sub beam photodetector 25 and the main beam photodetector 26, but since the amount of received light is small, the main beam photodetector. 26 and the sub-beam photodetector 25 are M4 and S4 in FIGS. 8 (3) and 8 (4).

  When the focus of the main beam and the sub beam approaches the optical disc 101 and enters the state of M3 and S3 in FIG. 8, spots M3 and S3 in which the focus of the main beam and the sub beam shown in FIG. It becomes. In this case, the reflected light of the main beam is detected by the main beam photodetector 26 and also leaks into the sub beam photodetector 25. On the other hand, the reflected light of the sub-beam is detected by the sub-beam photodetector 25. However, since the light amount ratio of the sub-beam to the main beam is sufficiently small as 1/5 or less, it is not detected significantly by the main-beam photodetector 26. Therefore, the main sum signal is M3 in FIG. 8 (3), but the sub sum signal has a level larger than M3 in FIG. 8 (4) and S3 generated only by the reflected light of the sub-beam, and exceeds the threshold.

  When the focus of the main beam and the sub beam approaches the optical disc 101 from the state of M3 and S3 in FIG. 8 to the state of M2 and S2 in FIG. 8, the reflected light spots of the main beam and the sub beam in FIG. M3 and S3 are smaller and not blurred spots. In this case, since the reflected light spot of the main beam and the sub beam has a small amount of light with respect to each other's photodetector, the reflected light of the main beam and the sub beam is detected by the main beam photodetector 26 and the sub beam photodetector 25, respectively. Only M2 and S2 in FIGS. 8 (3) and 8 (4) are detected.

  After the focal points of the main beam and the sub beam are located on the surface of the optical disc 101, when they are separated in the recording layer direction and become the states of M2 ′ and S2 ′ in FIG. 8, the reflected light spots of the main beam and the sub beam in FIG. This is the same as the case of M2 and S2 in FIG. In this case, the reflected light of the main beam and the sub beam is detected only by the main beam photodetector 26 and the sub beam photodetector 25, respectively, and becomes M2 ′ and S2 ′ in FIGS. 8 (3) and 8 (4). .

  When the focal points of the main beam and the sub beam move in the direction of the recording layer and become the states of M3 ′ and S3 ′ in FIG. 8A, the reflected light spots of the main beam and the sub beam in FIG. , S3. In this case, the reflected light of the main beam is detected by the main beam photodetector 26 and also leaks into the sub beam photodetector 25 and is detected. On the other hand, the reflected light of the sub beam is detected by the sub beam photodetector 25. Therefore, the main sum signal becomes M3 ′ in FIG. 8 (3), and the sub sum signal becomes M3 ′ in FIG. 8 (4), and the level becomes larger than S3 ′ generated only by the reflected light of the sub beam.

  When the focal points of the main beam and the sub beam are in the state of M4 ′ and S4 ′ in FIG. 8, the reflected light spots of the main beam and the sub beam in FIG. 8 (1) are the same as those in M4 and S4 in FIG. In this case, the light reception levels of the main beam photodetector 26 and the sub beam photodetector 25 are M4 ′ and S4 ′ in FIGS.

  Here, with reference to FIG. 8, the case where the focus of the main beam and the sub beam passes through the surface of the optical disc 101 during the focus search operation has been described, but the same applies when the focus passes through the recording layer.

  Therefore, as shown in FIG. 8 (4), the sub-sum signal generated in this embodiment has a peak at the position where the focal point of the main beam and the sub-beam passes through the surface of the optical disc 101 and the recording layer. In addition, the focal point of the sub beam decreases monotonously as it moves away from the position passing through the surface or the recording layer, and then the waveform has a peak again due to the reflected light of the main beam. For example, if the half values of M1 and S1 in FIGS. 8 (3) and 8 (4) are binarized, the main sum signal binarized signal in FIG. 8 (2) and the sub sum signal binary in FIG. A signal is obtained.

  As described above, in the configuration of the present embodiment, the sub-sum signal is affected by the leakage of the main beam. Therefore, the binarized signal of the sub-sum signal has a broader pulse waveform than the binarized signal of the main sum signal. Appear. When the servo controller 104 is a digital servo, a broad signal can be detected stably even at a lower sampling period, and can be detected even if a large fluctuation occurs. From the above, in this embodiment, the sub sum signal is used to detect the surface of the optical disc 101 and the recording layer.

  As in the present embodiment, when the four-divided photodetectors 25 and 27 that mainly receive the sub-beams are arranged in the image plane of the reflected light of the main beam, the reflected light of the main beam is divided into the four-divided photodetector at the time of defocusing. 25 and 27, it becomes possible to detect a broad waveform in the sub-sum signal that is the sum signal of the four-divided photodetectors 25 and 27 during focus search, so that the surface of the optical disc 101 and the recording layer can be detected. It becomes easy to do.

  Here, the distance from the center of each of the four-split photodetectors 25 and 27 to the center of the four-split photodetector 26 that mainly receives the main beam is that the reflected light of the main beam at the time of focusing is the four-split photodetector 25, The reflected light of the main beam may be in a range that significantly extends to the four-split photodetectors 25 and 27 during defocusing, but is practically 100 to 200 μm.

  Next, the focus S-shaped signal detection threshold shown in (A12) of FIG. 6, the main sum signal detection threshold shown in (A10) of FIG. 6, and the sub sum signal change point detection threshold shown in (A11) of FIG. 6 will be described. .

  In this embodiment, the optical disc 101 is an HD DVD (HD DVD-ROM 1 layer, HD DVD-R 1 layer, HD DVD-RW 1 layer, HD DVD-ROM 2 layer, HD DVD-R 2 layer, HD DVD-RW 2 layer, TWIN). DVD (DVD-ROM 1 layer, DVD ± R 1 layer, DVD ± RW 1 layer, DVD-RAM, DVD-ROM 2 layer, DVD ± R 2 layer, DVD ± RW 2 layer), CD (CD-ROM, CD-R, CD- RW, hybrid SACD).

  Considering that the focus search is performed in the data region using the blue light LD, the effective reflectivity of the recording layer with respect to the blue light LD is the CD layer of the hybrid SACD, and the reflectivity is 0.25. % (0.225% to 0.275% considering variation of ± 10%). The effective reflectance refers to the ratio of the amount of light returning to the optical head 113 as reflected light from the recording layer with respect to the amount of light irradiated on the surface of the optical disc 101. In addition, in the case of HD DVD or DVD with a substrate thickness of 0.6 mm other than hybrid SACD, the distance from the light incident surface of the disc to the recording layer is 0.6 mm, and the label surface on the opposite side of the light incident surface from the recording layer Is also 0.6 mm. At the time of focus search operation using blue light, the reflectance on the label surface is less than 0.20% at maximum.

  Therefore, the main sum signal detection threshold and the sub sum signal change point detection threshold set to detect the surface and the recording layer of the optical disc 101 are less than the lower limit of the reflectance of the CD layer of the hybrid SACD and the label of the HD DVD or DVD. More than the reflectance on the surface. If the reflectance is set within the range of 0.20% or more and less than 0.225%, it is possible to detect the disk surface and the recording layer for all of the above-mentioned types by one focus search, and medium discrimination. Can be speeded up.

  In discriminating the number of recording layers (detection of a focus S-shaped signal), only one layer of CD is excluded from the discriminating object, and considering that the focus search is performed in the data area using the blue light LD, the blue light LD On the other hand, the disc other than the CD having the lowest effective reflectance of the recording layer is the HD DVD-R2 layer, and the reflectance is about 1.00% (in consideration of the variation of ± 10%, 0.90% to 1. 10%). Therefore, the focus S-shaped signal detection threshold set for determining the number of recording layers (detection of the focus S-shaped signal) is less than 0.90% which is the lower limit of the reflectivity of the HD DVD-R2 layer, and If it is set to fall within the reflectance range of 0.225% or more, which is 1/4 of 90%, the number of recording layers for all types other than the above-mentioned CD is determined (focus S-character) by one focus search. Signal detection).

  As described above with reference to FIGS. 4, 5, and 6, in this embodiment, the sub sum signal is used for determining the substrate thickness of the optical disc 101, and the focus S-shaped signal is used for determining the number of recording layers. Thus, more stable medium discrimination is realized.

  Next, a sequence showing the operation of the present embodiment will be described with reference to FIGS. Here, since the following description of the operation is an embodiment of the medium determination method, each step of the medium determination method is shown along with a description of the corresponding operation.

  In FIG. 9, the optical disk 101 is set to the spindle motor of the spindle drive system 102 after the optical disk apparatus 100 is turned on, or the optical disk apparatus 100 is turned on with the optical disk 101 set in advance to the spindle motor. (Step S11 in FIG. 9), the spindle drive system 102 rotates the optical disc 101. Further, the optical head 113 is moved to the data area of the optical disc 101 by the thread motor 108 (step S12 in FIG. 9).

  Subsequently, when the LD driving unit 106 turns on the blue light LD in the LD 111 (step S13 in FIG. 9) and irradiates the optical disk 101 with the blue light, the blue light is divided by the diffraction grating 23 and the main beam and the sub beam are emitted. (Beam extraction step). At that time, the servo drive system 103 drives the objective lens actuator 109, thereby moving the objective lens 21 up and down in the focus direction at a constant speed to execute a focus search (step S14 in FIG. 9, focus search step). .

  During this focus search, a servo error signal is generated by the servo error signal generation means 107B of the RF circuit unit 107, and a sub sum signal is generated by the sub sum signal generation means 107C (sub sum signal generation step). The sub sum signal change detecting means 119 of the servo controller 104 detects the timing when the level of the sub sum signal is equal to or higher than the threshold and measures the time interval and the number of times between the timings (sub sum signal change detecting step), and the focus S-shape. The signal detection means 114 detects the focus S-shaped signal in the focus error signal and measures the number of appearances (focus S-shaped signal detection step). This focus error signal can be generated from the main beam, from the sub beam, or from both the main beam and the sub beam as in the differential astigmatism method. May be.

  During the focus search, the substrate thickness calculating means 121 of the servo controller 104 calculates the substrate thickness of the optical disc 101 from the time interval from when the sub sum signal level exceeds the threshold on the disc surface until it exceeds the threshold on the recording layer (substrate). (Thickness calculation step), the medium determination means 115 determines whether or not the substrate thickness is 0.6 mm, and if it is determined that it is equivalent to 1.2 mm instead of 0.6 mm, it is determined as a CD. (Step S14-1 in FIG. 9, medium discrimination step). When the CD is determined as described above, the blue light LD is turned off and the infrared light LD is turned on to start the information recording or reproducing operation.

  When it is determined that the sub sum signal exceeds the threshold when the CD is not CD, the number of times that the sub sum signal exceeds the threshold is 3, and the time interval when the sub sum signal exceeds the threshold between the surface and the L0 layer is equivalent to 0.6 mm, and When the time interval when the sub sum signal exceeds the threshold in the L0 layer and the L1 layer is equivalent to 0.6 mm, the hybrid SACD (the hybrid SACD is the SA0 in the L0 layer and the CD in the L1 layer, and the disc surface and the L0 layer It is determined that the distance is 0.6 mm and the distance between the L0 layer and the L1 layer is 0.6 mm (step S14-2 in FIG. 9, medium determining step).

  If the substrate thickness is 0.6 mm and it is determined that the substrate is not a hybrid SACD, the optical disc 101 is determined to be a DVD or an HD DVD. In this case, the recording layer number determining means 116 determines whether the optical disc 101 is a single-layer medium or a double-layer medium from the number of appearances of the focus S-shaped signal (step S14-3 in FIG. 9, recording layer number). Judgment step).

  Thus, in this embodiment, a focus search is performed using a blue light beam. This is because if the HD DVD double-layer medium is irradiated with red light, the L-layer focus S-shaped signal cannot be almost detected, and the HD DVD double-layer medium is erroneously determined as the single-layer medium. This is because the two recording layers can be reliably recognized by irradiating with blue light.

  The reason is that there is no resolution that can detect the intermediate layer thickness of HD DVD dual-layer media with red light, so the thinner the intermediate layer thickness, the less the focus S-shaped signal is generated in each recording layer. It is not possible. The intermediate layer thickness of the HD DVD two-layer medium is determined so that the L0 layer and the L1 layer can be separated by an optical system with NA of 0.65 and a wavelength of 405 nm (in this case, the intermediate layer thickness is 15 μm to 25 μm) The intermediate layer thickness of the DVD dual-layer medium is determined so that the L0 layer and the L1 layer can be separated at an NA of 0.60 and a wavelength of 650 nm (in this case, the intermediate layer thickness is 40 μm to 70 μm). Therefore, when a focus search is performed on a two-layer medium of HD DVD with an optical system using NA of 0.60 and red light having a wavelength of 650 nm on the premise of DVD recording / reproduction, the intermediate layer is thinner than the assumed intermediate layer thickness. As the thickness is closer to 15 μm, the focus S-shaped signal is not separately generated in the L0 layer and the L1 layer, and the two layers cannot be separated and detected.

  Another reason is that regarding the double layer medium of HD DVD, the L0 layer has a transmittance of 50% or more for blue light, but the L0 layer has a transmittance of about 30% for red light. This is because, even if the HD DVD two layers can be separated and detected with red light, the reflectance of the L1 layer is lowered and it becomes difficult to detect the focus S-shaped signal of the L1 layer. Since the irradiation light to the L1 layer passes through the L0 layer twice at the time of irradiation and reflection, the effective reflectance of the L1 layer detected by the optical head 113, that is, the amount of light irradiated on the surface of the optical disc 101 The ratio of the amount of light returning to the optical head 113 as reflected light from the L1 layer is reduced to 50% for each pass of the L0 layer, even when the reflectance of the L1 layer itself is 100%, and when it is blue light. Although it is 25%, red light is reduced to 30% for each passage of the L0 layer, so the amount of reflected light in the L1 layer is only about 9%. Further, in the case of infrared light used for CD recording / reproduction, the transmittance of the L0 layer is less than 30%, and it becomes more difficult to detect the focus S-shaped signal of the L1 layer than when red light is used.

  Here, HD DVD is specified to form BCA in the L1 layer when there are two recording layers. When the recording layer number determination means 116 determines that the optical disk 101 is a two-layer medium, the servo control means 122 of the servo controller 104 immediately controls the servo drive system 103 and turns the sled motor 108 while the blue light LD is lit. The optical head 113 is moved to a position where the BCA on the inner periphery of the optical disk 101 can exist (step S15 in FIG. 9), and then the focus servo is drawn into the L1 layer where the BCA is formed (step S16 in FIG. 9). , BCA lead step).

  In a state where the focus servo is pulled into the BCA, the BCA signal extraction means 107D of the RF circuit unit 107 regulates the RF signal output from the photodetector 112 with a threshold set to an intermediate level between the peak and bottom of the RF signal. To binarize and extract the BCA signal. Thereafter, the identification information determination unit 117 of the system controller 105 determines whether or not the BCA signal can be read (step S17 in FIG. 9, identification information determination step). When the BCA signal can be read, the medium identification unit 118 sets the type of the optical disc 101 to HD DVD-ROM two layers, HD DVD-R two layers, HD DVD-RW according to the medium identification information recorded in the BCA. The two layers are identified as TWIN (step S17-1, medium identification step in FIG. 9). If the medium identification information does not indicate HD DVD, or if the BCA signal cannot be read, it is determined that the medium is a DVD (step S17-2 in FIG. 9, medium identification step).

  When it is determined that the number of recording layers of the optical disc 101 is a single-layer medium, the servo control means 122 of the servo controller 104 ends the focus search and the parameter adjustment for data reproduction is performed with the blue light LD turned on. Only, the servo drive system 103 is immediately controlled to move the sled motor 108, and the optical head 113 is moved to a place where the BCA on the inner periphery of the optical disk 101 can exist (step S15 in FIG. 9), and the focus servo Only the parameters are adjusted, and the focus servo is drawn into the L0 layer (step S16 in FIG. 9, BCA read step).

  Then, only parameter adjustment for data reproduction is performed, and the BCA signal extraction unit 107D of the RF circuit unit 107 sets the RF signal output from the photodetector 112 to an intermediate level between the peak and bottom of the RF signal. The BCA signal is extracted by binarizing by regulating with the threshold. Thereafter, the identification information determination unit 117 of the system controller 105 determines whether or not data can be read from the BCA signal (step S17 in FIG. 9, identification information determination step). When data can be read from the BCA signal, the medium identification unit 118 determines that the optical disc 101 is one layer of HD DVD-ROM, one layer of HD DVD-R, and HD DVD- according to the medium identification information recorded in the BCA. It is identified as the first layer of RW (step S17-1, FIG. 9 medium identification step). If the medium identification information does not indicate HD DVD, or if the BCA signal cannot be read, it is determined that the medium is a DVD (step S17-2 in FIG. 9, medium identification step).

  Before the focus servo is pulled into the BCA, it is necessary to adjust the focus S-shaped signal amplitude and offset, and to adjust the amplitude and offset of the main sum signal or sub sum signal. This is because, as described above, the recording layer position is specified from the sum signal, and the focus servo is drawn into the desired recording layer using the focus S-shaped signal in the recording layer. Further, after the focus servo is pulled into the BCA, it is necessary to set a threshold for BCA detection at an intermediate level between the amplitude of the RF signal and the peak and bottom of the RF signal. Since the track servo is not drawn from the focus search (step S14 in FIG. 9) to the BCA read (step S17 in FIG. 9), it is not necessary to adjust the track servo parameters.

  The amplitude setting gain and applied offset of the focus S-shaped signal, the amplitude setting gain and applied offset of the main sum signal or sub-sum signal, the amplitude setting gain of the RF signal, and the BCA detection threshold are obtained in advance as parameters for acquiring medium identification information. Alternatively, it may be configured to set immediately before the focus servo pull-in for BCA detection (step S16 in FIG. 9). In this way, parameter adjustment when the focus servo is pulled into the BCA can be omitted.

  When the optical disk 101 is determined to be TWIN, the sequence of FIG. 10 is executed.

  Information that the optical disk 101 set on the spindle is TWIN is transmitted from the system controller 105 to the host controller 201 of the host computer 200 via the interface unit 120.

  When the host controller 201 recognizes that the optical disk 101 is TWIN, the host controller 201 displays a screen for inquiring whether to reproduce HD DVD or DVD on the display unit 202 (for example, 1 = HD DVD, 2 = DVD), and HD DVD. Or the DVD to be played back, the user is prompted to input information indicating this to the input unit 203 (step T11 in FIG. 10).

  The host computer 200 waits for input until information indicating whether it is an HD DVD or a DVD is input to the input unit 203. As soon as input is received, the host computer 200 generates an interrupt to the system controller 105 of the optical disc apparatus 100, and the user selects it. Type information (HD DVD or DVD) is sent. Further, when receiving the recording / reproduction command acceptance state from the system controller 105 of the optical disc apparatus 100 together with the interruption, the reproduction command is transmitted to the system controller 105 of the optical disc apparatus 100 after transmitting the type information of the medium selected by the user.

  The system controller 105 of the optical disc apparatus 100 turns on the blue light LD when the type information of the medium selected by the user transmitted with the interruption from the host computer 200 is HD DVD or when the user does not select the type of medium. The sled motor 108 is driven while the focus servo is pulled into the L1 HD DVD layer, and the optical head 113 is moved to the data area of the optical disc 101 (step T12 in FIG. 10). Then, servo parameters and recording / reproducing parameters are automatically adjusted (step T13 in FIG. 10).

  After the automatic adjustment is completed, the track servo is turned off, the sled motor 108 is driven, the optical head 113 is moved to the system lead-in in the recording area of the optical disc 101, the track servo is pulled in, and the system lead-in is read (see FIG. 10). Step T14) is performed to acquire information necessary for recording / reproduction of the optical disc 101.

  After reading the system lead-in, the track servo is turned off, the sled motor 108 moves the optical head 113 to the data area of the optical disk 101, the track servo is pulled in, and the servo is moved to a specific radial position by track jump. The recording / reproducing command from the host computer 200 is kept waiting (step T15 in FIG. 10), and the host computer 200 is notified of the recording / reproducing command receiving state together with an interruption. When the system controller 105 receives a playback command from the host computer 200 together with an interrupt, it turns off the track servo and drives the sled motor 108 to move the optical head 113 to the playback start position in the data area of the optical disc 101 to pull in the track servo. The reproduction of the stored information is started.

  When the type information of the medium selected by the user is DVD, the system controller 105 immediately turns off the servo operation, turns off the blue light LD (step T16 in FIG. 10), drives the sled motor 108, and drives the optical head 113. Is moved to the data area of the optical disc 101 (step T17 in FIG. 10). Then, the red light LD is turned on (step T18 in FIG. 10), and the servo parameters and recording / reproducing parameters of the L0 layer (DVD) are automatically adjusted (step T19 in FIG. 10). Thereafter, the track servo is turned off, the sled motor 108 is driven, the optical head 113 is moved to the lead-in of the optical disc 101, the track servo is pulled in, and the lead-in is read to read out information necessary for recording / reproducing of the optical disc ( Step T20 in FIG.

  Thereafter, the track servo is turned off, the sled motor 108 is driven, the optical head 113 is moved to the data area of the optical disc 101, the track servo is pulled in, and the servo is continuously applied in the vicinity of a specific radial position by track jump. While waiting for a recording / reproducing command from 200 (step T21 in FIG. 10), the host computer 200 is notified of the recording / reproducing command accepting state together with an interrupt.

  Thereafter, when the system controller 105 receives a reproduction command together with an interrupt from the host computer 200, the system controller 105 turns off the track servo and drives the sled motor 108 to move the optical head 113 to a predetermined reproduction start position in the data area of the optical disc 101. The track servo is pulled in, and the reproduction of stored information is started.

  In the conventional optical disc apparatus, when playing TWIN, since it is left to the user to select which of the HD DVD layer and the DVD layer is played, the time until the start of playback is longer than in the case of other media types. However, by determining the type of the optical disk 101 by immediately reading the BCA after determining the number of recording layers during the focus search as in the present embodiment, the time until determining the type of the optical disk 101 is shortened. Assuming playback, parameter adjustment for data playback of the HD DVD layer (L1 layer) is performed after a selection request is output to the user until a response is returned, so that playback of the HD DVD layer on a TWIN medium is performed. The time to start can be greatly reduced.

  Further, by performing a focus search using the blue light LD, the number of recording layers can be reliably determined. When the optical disc 101 is TWIN, the BCA signal of the L1 layer can be read immediately after determining the number of recording layers.

  In this embodiment, after reading the BCA signal (step S17 in FIG. 9), the optical head 113 is moved to the data area of the optical disc 101 while the focus servo is kept on. However, after reading the BCA signal (step S17 in FIG. 9), the focus servo may be temporarily turned off, the optical head 113 may be moved to the data area of the optical disc 101, and the focus servo may be turned on again in the data area. In this case, adjustment of the amplitude and offset of the focus S-shaped signal and adjustment of the amplitude and offset of the main sum signal or sub-sum signal are performed before the focus servo is drawn in the data area.

  In this embodiment, the data area of the recording layer of the optical disc 101 is irradiated with a beam to determine the number of recording layers, and then the objective lens 21 is moved to the BCA area of the optical disc 101, and focus servo is performed in the BCA area. I'm pulling in. However, the focus servo may be pulled in the data area, and the objective lens 21 may be moved to the BCA area while the focus servo is pulled.

  In the above description, while the user is thinking about the selection (step T1 in FIG. 10), the HD DVD automatic adjustment, the system lead-in reading, the command waiting from the host computer 200, and the process proceeded. While waiting for selection by the user as to whether to play back HD DVD or DVD as shown in FIG. 4, the optical disc apparatus 100 does not proceed to the next processing, and after the user's selection is completed, such as automatic adjustment of HD DVD or DVD Processing may be executed. In the case of advancing the process, if the user selects a DVD while executing a process such as HD DVD automatic adjustment, the HD DVD process is forcibly terminated and the process proceeds to the DVD process. Power consumption is as much as executed. If the process cannot be advanced, the next process is not performed until the user selects the DVD, so that useless power consumption can be avoided.

  Here, in the above-described contents, the substrate thickness of the optical disc 101 is calculated using the main beam and the sub beam for executing the conventional three beam method. The light beam is generated from one of a plurality of photodetectors mainly detecting a plurality of light beams having a smaller light amount than the light beam having the largest light amount and existing in the imaging plane of the reflected light of the light beam having a large light amount. Even when the sum signal is used, the pulse waveform of the sum signal becomes broader as shown in FIG. 8 (4), and the surface of the optical disc 101 and the recording layer can be easily detected. Further, since it is sufficient if the sum signal can be detected from the received light amounts of the sub-beam photodetectors 25 and 27, if the sub-beam is used only for medium discrimination, the light-receiving areas of the sub-beam photodetectors 25 and 27 are divided. It does not have to be.

  Further, although the case where the blue light LD is used has been described, regarding the calculation of the substrate thickness, in addition to the blue light LD, various wavelength light such as red light LD and infrared light LD may be used. Furthermore, in this embodiment, the focus error signal is generated from the differential astigmatism method, but may be generated from the knife edge method.

  Further, HD DVD, DVD, CD, and hybrid SACD are targeted for discrimination as the type of optical disc 101, and the media discrimination means 115 discriminates the CD from the difference in thickness of the disc substrate or cover layer. Not limited to this, if the thickness of the substrate or cover layer is a unique type, it can be determined.

  The sum signal is a signal obtained by removing the data component from the RF signal. However, the sum signal is a signal that exhibits a level change when the focus position passes through the light incident surface of the optical disc 101 and the recording layer. Since it is good, the RF signal itself may be sufficient. Therefore, the main sum signal and the sub sum signal generated by the main sum signal generation unit 107E and the sub sum signal generation unit 107C are RF signals (reproduction signals) output from the photodetectors 25, 26, and 27 themselves. Also good.

  As described above, in this embodiment, the number of recording layers can be easily detected by using the focus S-shaped signal. Also, the type of the optical disc to be discriminated is different between the sub sum signal and the focus S-shaped signal, and the sub disc is based on the reflectivity of the optical disc having the lowest reflectivity with respect to blue light among a plurality of types of optical discs to be discriminated. A threshold for detecting the sum signal and a threshold for detecting the focus S-shaped signal are set. As a result, high-speed and stable medium discrimination can be realized in many types of optical disks.

  The present embodiment can be widely applied to an optical disc apparatus configured to detect a difference signal and a sum signal generated from a plurality of beams, and the application improves the accuracy of medium identification and is required for medium identification. Time can be significantly reduced.

  Next, the above-described medium identification by BCA will be described in detail.

  In the present embodiment, first, the light beam emitted from the LD 111 is condensed and irradiated onto the optical disc 101 through the objective lens 21, and the servo drive system 103 drives the objective lens actuator 109, thereby causing the objective lens 21 to emit light. A focus search is performed by moving in the axial direction and controlling the focal position of the light beam.

  The focus S-shaped signal detecting means 114 detects the focus S-shaped signal generated in the focus error signal during the focus search and measures the number of times of detection, and the recording layer number determining means 116 counts the number of appearance of the focus S-shaped signal. Based on the above, the number of recording layers of the optical disc 101 is determined.

  When the number of recording layers of the optical disc 101 is determined, the system controller 105 identifies the recording layer in which the BCA exists, and the servo control unit 122 of the servo controller 104 receives a command from the system controller 105 and receives the focus servo from the BCA. The servo drive system 103 is controlled to draw

  Then, the BCA signal extraction means 107D extracts the BCA signal from the reproduction signal based on the reflected light of the beam light from the BCA, the identification information determination unit determines the presence / absence of the medium identification information from the BCA signal, and the medium identification step identifies The type of the optical disc 101 is identified based on the presence or absence of information or the content of identification information.

  As described above, in this embodiment, when the recording layer number determination unit 116 determines the number of recording layers of the optical disc 101, the servo control unit 122 of the servo controller 104 immediately starts the servo so that the focus servo is drawn into the BCA. The drive system 103 is controlled. As a result, the time until medium discrimination by BCA reading is shortened as compared with the prior art.

  The BCA is an area where a signal is engraved with a concavo-convex pattern that is sufficiently wider than the normal pit width. To read the signal (BCA code), the track servo is not necessary and only the focus servo needs to be performed. Therefore, in this embodiment, when the number of recording layers of the optical disk 101 is determined, the servo parameter is not adjusted, only the reproduction parameter is adjusted, and the focus servo is immediately drawn into the BCA, so that the medium recorded in the BCA is recorded. The time until the medium discrimination based on the discrimination information is significantly shortened compared to the conventional case.

  When the optical disc 101 is determined to be TWIN, the determination result is transmitted to the host computer 200 and a selection request is sent to the user. The time until presenting is shortened. Therefore, for the user, the time from insertion of the TWIN disc until it can be selected is shortened, and the troublesomeness is reduced.

  In addition, during the selection process by the user, assuming the playback of the HD DVD, the servo parameters and the recording / playback parameters are adjusted in the HD DVD layer (L1 layer), the system lead-in reading is completed, and the recording / playback preparation is completed. As a result, the time until the optical disc 101 is set and the medium type is completed and the playback of the HD DVD layer on the TWIN medium is started is greatly shortened compared to the conventional case.

  For example, conventionally, the focus search is started, the number of recording layers is determined, the RF signal and the servo error signal are adjusted, the servo is drawn into the data recording area, the system lead-in is read, and the BCA signal is read. If it takes 15 seconds to identify a TWIN, in this embodiment, when the number of recording layers is determined, the BCA signal is read immediately. Therefore, it takes about 5 seconds to identify the TWIN. In the present embodiment, after identifying the TWIN and before making a selection request to the user and receiving a response, the HD DVD layer (L1 layer) assumes an RF DVD playback and an RF signal and a servo error signal. Since the system lead-in is read and preparation for playback is performed, if the user considers whether to play back HD DVD or DVD is 10 seconds, playback is performed when the user selects HD DVD. The time until this is 25 seconds in the past, but is reduced to 15 seconds in the present embodiment. That is, by changing the conventional sequence and determining the number of recording layers, the focus search is terminated and BCA reading is immediately performed, so that the time until the start of playback of the HD DVD layer on the TWIN medium can be shortened.

  Also, assuming that DVD playback is performed after the user has made a selection request and received a response after identifying TWIN, servo parameters and recording / playback parameters are adjusted in the DVD layer (L0 layer). Since the reading of the system lead-in is completed and preparation for playback is made, the time until the optical disk 101 is set and the medium type is completed and the playback of the DVD layer on the TWIN medium is started is significantly larger than in the past. It can be shortened.

  Such a medium identification processing sequence can be executed as long as it is configured to irradiate an optical disk with one beam of light. Therefore, the sequence is not limited to the optical disk apparatus 100 using the three-beam method as in the present embodiment. It can be applied to an optical disk device.

1 is a diagram showing a schematic configuration of an optical disc apparatus according to an embodiment of the present invention. It is a figure which shows the structure of the optical system in embodiment disclosed in FIG. It is a functional block diagram which shows the structure of the RF circuit part in embodiment disclosed in FIG. It is a functional block diagram which shows the structure of the servo controller in embodiment disclosed in FIG. It is a figure which shows the relationship between the position of the light spot formed on an optical disk in the embodiment disclosed in FIG. 1, and a photodetector. It is a figure which shows the waveform of the focus S character signal and sum signal which are produced | generated at the time of a focus search in embodiment disclosed in FIG. 1 for every medium type. It is a figure which shows the relationship between the light spot shape on the photodetector in FIG. 1 disclosed in FIG. 1, and a sum signal / focus S signal. It is a figure which shows the relationship between the light spot on the photodetector in embodiment disclosed in FIG. 1, and a main sum signal / sub sum signal. 3 is a sequence showing a part of the operation of the optical disc apparatus according to the embodiment disclosed in FIG. 1. 3 is a sequence showing a part of the operation of the optical disc apparatus according to the embodiment disclosed in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Objective lens 22 Collimator lens 23 Diffraction grating 24 Focusing lens 25, 27 4-part photodetector for sub-beam 26 Quad-segment photodetector for main beam 100 Optical disc device 101 Optical disc 103 Servo drive system 104 Servo controller 105 System controller 106 LD Drive unit 107 RF circuit unit 107A reproduction signal generation unit 107B servo error signal generation unit 107C sub-sum signal generation unit 107D BCA signal extraction unit 108 thread motor 109 objective lens actuator 110 beam splitter 111 laser diode 112 photodetector group 113 optical head 114 focus S-curve signal detecting means 115 medium discrimination means 116 recording layer number determination unit 117 identifying information determining section 118 medium identification section 119 sub-sum signal changes Detecting means 121 substrate thickness calculating means 122 the servo control unit 200 the host computer 201 the host controller 202 display unit 203 input unit

Claims (17)

Beam generating means for generating a main beam and at least one sub beam having a light quantity smaller than the main beam, an objective lens for condensing and irradiating the plurality of beams onto the optical disc, and moving the objective lens in the optical axis direction to Focus search means for controlling the focal position of each beam to perform a focus search, and a plurality of photodetectors that receive reflected light from the optical disc at positions optically conjugate with the focal point of each beam by the objective lens. As well as
Sub-sum signal generating means for generating a sub-sum signal based on the amount of light received by at least one photodetector relating to the sub-beam, and when the focus of the sub-beam passes through the light incident surface of the optical disc during the focus search; Sub-sum signal change detection means for detecting a level change of the sub-sum signal when passing through the recording layer and measuring a time interval of the detection time, and on the substrate or cover layer of the optical disc based on the measured time interval Substrate thickness calculating means for calculating the thickness, and medium determining means for determining the type of the optical disk based on the calculated thickness of the substrate or cover layer,
An optical disc apparatus, wherein a photodetector for generating the sub-sum signal is disposed on an image plane of reflected light of the main beam. In the optical disk device according to claim 1,
An optical disc apparatus, wherein the photodetector for generating the sub-sum signal receives light by superimposing a partial leak of a spread component of the reflected light of the main beam on the reflected light of the sub beam from the optical disc. In the optical disk device according to claim 1 or 2,
An optical disc apparatus, wherein the sub-sum signal change detecting means has a function of detecting, as the level change, a timing at which the signal level of the sub-sum signal rises beyond a preset first threshold value. In the optical disk device according to claim 3,
The first threshold employed in the sub-sum signal change detecting means is based on the light reflectance of the lowest optical reflectance among the types of optical disks to be calculated for the thickness of the substrate or cover layer. An optical disc apparatus having a set value. In the optical disc apparatus according to any one of claims 1 to 4,
The sub-sum signal change detecting means detects a level change of the sub-sum signal when the focus of the sub beam passes through the light incident surface of the optical disc and the recording layer during the focus search, and the number of times of detection. An optical disc apparatus comprising: a function of measuring the optical disc, and a function of discriminating the type of the optical disc based on the number of times the medium discriminating unit measures the sub sum signal change detecting unit. In the optical disc apparatus according to any one of claims 1 to 5,
A focus error signal generating means for generating a focus error signal based on a difference in light quantity between light receiving regions divided into a plurality of photodetectors for at least a main beam among the plurality of photodetectors; Focus S-character signal detecting means for detecting a focus S-character signal generated in the focus error signal and measuring the number of detections thereof, and recording for determining the number of recording layers of the optical disk based on the number of appearances of the focus S-character signal An optical disc apparatus comprising: a layer number determination unit. The optical disc apparatus according to claim 6, wherein
The focus S-shaped signal detecting means is configured to detect the focus S-shaped signal based on the second and third threshold values set in advance to a level for detecting one and the other protruding area. An optical disc apparatus characterized by the above. The optical disk apparatus according to claim 7, wherein
The second and third threshold values employed in the focus S-shaped signal detection means are values set based on the light reflectivity of the lowest optical reflectivity among the types of optical discs for which the number of recording layers is to be determined. An optical disc apparatus characterized by the above. A beam emitting step for emitting a main beam and a sub beam having a light quantity smaller than that of the main beam, and converging and irradiating the plurality of beams onto an optical disc through the objective lens, and moving the objective lens in the optical axis direction to thereby each of the beams. A focus search step for controlling the focal position of the lens and performing a focus search,
A sub-sum signal generating step of receiving light in which the reflected light of the main beam partially overlaps the reflected light of the sub-beam from the optical disc and generating the sub-sum signal based on the received light amount;
A sub-sum signal for detecting the level change of the sub-sum signal when the focus of the sub-beam passes through the light incident surface of the optical disc and the recording layer during the focus search and measures the time interval of the detection time A change detection step;
A substrate thickness calculating step for calculating the thickness of the substrate or cover layer of the optical disk based on this time interval;
A medium type discriminating method comprising: a medium discriminating step for discriminating the type of the optical disk based on the calculated value of the thickness of the substrate or cover layer. In the medium type discrimination method according to claim 9 ,
In the sub-sum signal change detecting step, a timing at which the signal level of the sub-sum signal rises above a preset first threshold is detected as the level change, and a time interval between the timings is measured. To determine media type. In the medium type determination method according to claim 9 or 10 ,
In the sub-sum signal change detecting step, the level change of the sub-sum signal is detected when the focus of the sub-beam passes through the light incident surface of the optical disc and the recording layer during the focus search, and the number of times And determining the type of the optical disc based on the number of times measured in the sub-sum signal change detecting step. The medium type determination method according to any one of claims 9 to 11 ,
A focus S-curve signal detection step for detecting a focus S-curve signal generated in the focus error signal during the focus search and measuring the number of times, and the number of recording layers of the optical disc based on the number of appearances of the focus S-curve signal. And a recording layer number determination step for determining the medium type. A focus search is performed to control the focal position of each beam by focusing and irradiating the main beam and a sub beam having a light quantity smaller than that of the main beam onto the optical disc through the objective lens and moving the objective lens in the optical axis direction. An optical disk device that
During the focus search, a sum signal input process for inputting a sub sum signal generated based on a received light quantity of a photodetector that receives the reflected light of the sub beam arranged in advance in the imaging plane of the main beam, and during the focus search A sub-sum signal change detection process for detecting a level change of the sub-sum signal when the focal point of the sub-beam passes through the light incident surface of the optical disc and a recording layer, and measuring a time interval of the detection time; Based on the time interval, a substrate thickness calculation process for calculating the thickness of the substrate or cover layer from the light incident surface of the optical disk to the recording layer, and the type of the optical disk based on the calculated value of the thickness of the substrate or cover layer A medium type determination program for causing a computer to execute a medium determination process for determining a medium. In the medium type determination program according to claim 13 ,
The sub-sum signal change detection process is specified to determine whether or not the signal level of the sub-sum signal is equal to or higher than a first threshold and to measure the time interval between timings determined to be equal to or higher than the threshold. A medium type discrimination program characterized by the above. In the medium type determination program according to claim 14 ,
The first threshold value used in the sub-sum signal change detection process is based on the light reflectance of the lowest optical reflectance among the types of optical discs for which the thickness of the substrate or cover layer is calculated. A medium type discrimination program characterized by a set value. In the medium type determination program according to any one of claims 13 to 15 ,
The sub-sum signal change detection process detects the level change of the sub-sum signal when the focus of the sub beam passes through the light incident surface of the optical disc and the recording layer during the focus search, and the number of times And determining the type of the optical disc based on the number of times measured in the sub-sum signal change detection process. . The medium type determination program according to any one of claims 13 to 16 ,
A focus error signal input process for inputting a focus error signal generated based on a difference in light quantity between a plurality of light receiving areas of the photodetector for receiving reflected light of the main beam; and during the focus search A focus S-character signal detection process for detecting a focus S-character signal generated in the focus error signal and measuring the number of times, and a recording layer for determining the number of recording layers of the optical disk based on the number of appearances of the focus S-character signal A medium type determination program for causing a computer to execute a number determination process.

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