JP3556394B2 - Digital disk player and disk identification method thereof - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital disk player and a method for identifying the disk, and more particularly to a digital disk player for reading and reproducing recorded data from a dual layer disk having two signal recording layers or a single layer disk having only one signal recording layer, and a digital disk player therefor. It relates to a disk identification method.
[0002]
[Prior art]
Digital video disc players (DVD players) include a single layer disc having only one signal recording layer and a dual layer disc having two signal recording layers. FIG. 4A is a structural diagram of a single-layer disc, in which RL is a signal recording layer, SR is a transparent plastic layer (base), and PL is a protection layer for protecting the signal layer. FIG. 4B is a structural diagram of a dual-layer disc, in which two discs having signal recording layers RL1 and RL2 and transparent plastic layers (bases) SR1 and SR2, respectively, are laminated via a space layer SPL. It has a structure. Note that LS is an objective lens.
Conventional discs such as CDs do not have a dual-layer disc, and thus have been used only for reproducing a single-layer disc (such as a CD).
[0003]
[Problems to be solved by the invention]
From the viewpoint of compatibility, it is convenient for the user if the DVD player can reproduce both a single-layer disc and a dual-layer disc. However, in order to be able to reproduce both discs, it is necessary to identify whether the disc loaded in the player is a single-layer disc or a dual-layer disc because the standards are different.
Accordingly, an object of the present invention is to provide a digital disc player and a disc identification method for discriminating whether a disc loaded in a player is a single-layer disc or a dual-layer disc.
[0004]
[Means for Solving the Problems]
According to the present invention, the above object is achieved by a means for performing a focus search, and a means for determining whether a disc is a dual-layer disc or a single-layer disc based on the amplitude of a focus error signal generated during the focus search. .
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
(A) Schematic of the present invention In a DVD player, a focus servo control device is provided to focus a laser beam on a signal recording surface of a disk. The focus servo control device generates a focus error signal having a voltage value corresponding to a distance between an objective lens position and a focal point position (the position of the objective lens when the focus of the objective lens coincides with the signal recording surface), The position of the objective lens with respect to the disk is controlled so that the error signal becomes zero.
In order for the focus servo controller to be able to perform servo control, the distance between the objective lens and the signal surface of the disk must be close to a certain depth of focus. Therefore, when the disc is mounted on the player, it is necessary to move the objective lens to a position where focus servo can be performed. For this reason, a focus search signal which is a triangular wave signal of about 1/2 Hz is generated, and the objective lens is moved to a position where focus servo can be performed, for example, to a focus position (focus search control). Focus servo control is performed by a signal.
[0006]
In the focus search, if the disc is a single layer disc, as shown in FIG. 1A, only one S curve of the focus error signal FE can be observed during the half cycle A of the focus search signal FS. However, in the case of a dual layer disc, two S curves can be observed as shown in FIG. Therefore, in the first disc identification method of the present invention, when there is one S curve that can be observed during the focus search, the disc is determined as a single layer disc, and when there are two S curves, it is determined as a dual layer disc.
[0007]
The reflectivity of the single-layer disc is different from that of the dual-layer disc. The reflectivity of the single-layer disc is 70%, and the reflectivity of the dual-layer disc is 25 to 45%. Therefore, the amplitude P ₁ of S curve detected during focus search single layer disc, the larger amplitude P ₂ S-curve detected during focus search of the dual layer disc. Therefore, in the second disc identification method of the present invention, when the amplitude of the S curve observed during the focus search is large, the disc is determined to be a single layer disc, and when the amplitude of the S curve is small, the disc is determined to be a dual layer disc.
[0008]
(B) First Embodiment of the Present Invention FIG. 1 is a configuration diagram of a main part of a DVD player according to a first embodiment of the present invention.
Reference numeral 11 denotes a disk, which is a single layer disk or a dual layer disk. An optical pickup 12 includes an objective lens 12a, a focus actuator 12b for moving the position of the objective lens, a photodiode (not shown), and the like. Reference numeral 13 denotes an RF amplifier, 14 denotes an error signal generation unit that outputs a focus error signal FE from a signal output from the optical pickup, and 15 denotes a gain control unit (attenuator or gain) that controls a focus servo gain based on a servo coefficient described later. Variable amplifier), 16 is a phase compensation circuit, 17 is a focus search signal generation circuit for generating a focus search signal FS, and 18 is a signal switch for selecting and outputting the focus search signal FS and the focus error signal FE. A circuit 19 for driving the focus actuator 12b based on the focus error signal FE or the focus search signal FS to control the distance between the objective lens 12a and the signal recording surface of the disk, and 20 a thread motor , 21 are spindle motors.
[0009]
Numeral 22 detects the level (peak value) of the focus error signal FE when the objective lens 12a passes near the focal point of the signal recording layer by the focus search signal FS during the focus search control. An error signal level detection circuit; 23, an AD converter (ADC) for converting the detected focus error signal level into a digital value; 24, a system controller for executing focus servo control, control for determining a servo gain coefficient, disc identification control, and the like. It is.
A comparison circuit 25 compares the level Lf of the focus error signal FE output from the error signal generation circuit 14 during the focus search control with the set level Ls, and outputs a high-level signal when Lf> Ls. The counter counts the number of high-level signals output from the circuit 25.
Reference numeral 27 denotes a signal processing unit which demodulates MPEG data based on a signal input from an RF amplifier, and performs digital signal processing such as error correction processing, separation processing of MPEG video data and MPEG audio data, and extraction processing of address information. Is an MPEG video decoder for decoding image data from MPEG video data, and 29 is an MPEG audio decoder for decoding PCM audio data from MPEG audio data.
[0010]
When the disc 11 is loaded into the player, the system controller 24 controls the focus search signal generating circuit 17 to control the focus sensor as a triangular wave of (1/2) Hz as shown in FIGS. 1 (a) and 1 (b). A focus signal FS, and the objective lens 12a is moved toward and away from the disk surface by the focus search signal FS. Error signal level detecting circuit 22, peak of the focus error signal FE when the objective lens 12a is passing through the focus position near the signal recording layers - Kleber P ₁ or P _{2 (FIG.} 1 (a), (b) see) detects, system controller 24 the detected peak - based on Kleber P ₁ or P _2, the servo gain factor g determined as the gain of the servo loop is to the optimal value, the gain control unit 15 Set.
[0011]
In parallel with the gain determination control, the comparison circuit 25 compares the focus error signal level Lf with the set level Ls, outputs a high-level signal when Lf> Ls, and the counter 26 counts the number of high-level signals. I do. When the disc 11 is a single-layer disc, as shown in FIG. 1A, the count value of the counter 26 becomes 1 because Lf> Ls is satisfied only once during the half cycle A of the focus search signal FS. On the other hand, when the disc is a dual-layer disc, as shown in FIG. 1B, Lf> Ls is satisfied twice during the half cycle A of the focus search signal FS, so that the count value of the counter 26 is 2. The system controller 24 reads the value counted by the counter 26 during the half cycle A of the focus search signal FS. If the count value is 1, the disc is a single layer disc, and if the count value is 2, the disc is a dual layer disc. It is determined and stored, and thereafter, control relating to the type of disk is performed.
[0012]
After the above gain control and disc discrimination control are completed, the objective lens 12a is further moved by the focus search signal FS. When the focus error signal FE becomes zero, the system controller 24 controls the signal switching circuit 18 to control the focus switch. Input the focus error signal FE to the actuator driver 19 instead of the switch signal FS. Thereby, the focus servo control is performed thereafter.
[0013]
(C) Second Embodiment FIG. 3 is a configuration diagram of a main part of a DVD player according to a second embodiment of the present invention, and the same parts as those in the first embodiment of FIG. The second embodiment is different from the first embodiment in that a single / dual discriminator for discriminating a disc type based on a peak value of a focus error signal FE is used instead of the comparison circuit 25 and the counter 26 in the first embodiment. 30 is provided.
[0014]
As described with reference to FIG. 1, the reflectance is different between the single-layer disc and the dual-layer disc. The reflectivity of the single-layer disc is 70%, and the reflectivity of the dual-layer disc is 25 to 45%. Therefore, the amplitude P ₁ of S curve detected during focus search single layer disc, the larger amplitude P ₂ S-curve detected during focus search of the dual layer disc. Therefore, the single / dual discriminating unit 30 compares the amplitude value of the S curve detected by the error signal level detection circuit 22 during the focus search with the set level L. It is determined that the disc is a layer disc. If the disc is below the set level, it is decided that the disc is a dual layer disc, and the result of the decision is input to the system controller 24. The system controller 24 stores the disk identification information and performs control relating to the type of the disk.
According to the second embodiment, it is not necessary to largely move the objective lens at the time of the focus search as in the first embodiment, and the servo can be turned on at the time of the first S curve, so that the search time can be reduced.
[0015]
As described above, in the second embodiment, the disc type is determined by providing the single / dual identification unit 30. However, the system controller 24 determines the servo gain coefficient g based on the amplitude value input from the error signal level detection circuit 22 at the same time. It can also be configured to identify the type.
As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.
[0017]
【The invention's effect】
According to the present invention, since the disc is determined to be a dual-layer disc or a single-layer disc based on the amplitude of a focus error signal generated at the time of a focus search, the disc type can be determined with a simple configuration. The disc can be identified and can be reproduced regardless of whether the disc is a single-layer disc or a dual-layer disc. In addition, since the disc type is identified in parallel with the focus search, the time until the start of reproduction can be reduced. Further, since it is not necessary to move the objective lens greatly during the focus search, the search time can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of the present invention.
FIG. 2 is a main part configuration diagram of a DVD player according to the first embodiment of the present invention.
FIG. 3 is a main part configuration diagram of a DVD player according to a second embodiment of the present invention.
FIG. 4 is an explanatory diagram of a disk structure.
[Explanation of symbols]
11 disk 14 error signal generation unit 17 focus search signal generation circuit 22 error signal level detection circuit 24 system controller 25 comparison circuit 26 counter 30 single / dual identification unit

Claims (2)

In a digital disc player for reading and reproducing recorded data from a dual layer disc having two signal recording layers or a single layer disc having only one signal recording layer,
A disc identification method comprising: determining whether a disc is a dual-layer disc or a single-layer disc based on the amplitude of a focus error signal generated during a focus search. In a digital disc player for reading and reproducing recorded data from a dual layer disc having two signal recording layers or a single layer disc having only one signal recording layer,
An amplitude detector that detects the amplitude of a focus error signal generated during a focus search,
A disk type determination unit that determines whether the disk is a dual layer disk or a single layer disk based on the amplitude,
A digital disc player comprising:

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