Abstract:
A method for reproducing information on a dual layer disc which has two recording layers including layer  0  and layer  1  reproducible from one side of the disk, wherein each layer has a plurality of sectors. The method includes the steps of emanating an optical beam from a laser source, concentrating the optical beam on a recording layer with an objective lens, moving the objective lens in the direction of the thickness of the disk so that a focal point of the objective lens is focused on one layer of the two recording layers, obtaining a present layer information of a sector of the recording layer being reproduced from the reflected light from the disk, confirming a target layer information of a target recording layer of a target information, and moving the objective lens in a direction of the thickness of the disk until the focal point of the objective lens is focused on layer  1  when the present layer information is layer  0  and the target layer information is layer  1.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation of U.S. application Ser. No. 09/394,601, filed Sep. 13, 1999, which is a continuation of U.S. application Ser. No. 08/888,469, filed Jul. 7, 1997, now U.S. Pat. No. 6,002,655 and relates to copending application U.S. application Ser. No. 09/394,600, filed Sep. 13, 1999, now U.S. Pat. No. 6,108,291, the subject matter of which is incorporated by reference herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to an optical disc apparatus accessing method and system therefor capable of reproducing an optical disc on one surface of which are provided plural layers of information recording surfaces.  
           [0004]    2. Description of the Prior Art  
           [0005]    In the optical disc as a recording medium, laser discs (LD) have been extensively popularized as media in which plural layers of information recording surfaces are provided. In these recording media, each layer of information recording surface is present on both surfaces of the media in terms of physical construction. Therefore, in the case where information recording layers to be reproduced need be switched, it is general that the disc is inverted or changed.  
           [0006]    With the recent trend of larger capacity of data for a computer and practical use of recording and reproducing of digital moving picture information, it has been demanded to make the optical disc higher recording density. The specification of a large capacity optical disc such as DVD (Digital Versatile Disc) has been proposed, and an optical disc such as a dual-layer disc has been standardized in addition to a conventional information recording of a one-side single layer. Since these optical discs have a dual-layer information recording layer on one side, there is necessary a reproducing method different from the conventional reproduction of single layer disc depending  6 n switching of an information recording layer to be reproduced, and the form of information recorded and how to use it. One method is an accessing method and the other is a pausing (temporary stop) method.  
           [0007]    In the optical disc, in the case where an optical pickup is accessed to a recording position of read target information of the same information recording layer in order to realize the high speed access, normally, present position information recorded in the disc is first read to obtain the present position of the optical pickup. Then, a target position is obtained from a logic or physical address of read target information. These two positions are converted from an information recording format of the disc into physical position information, the distance on a disc plane between the two points is obtained, and the optical pickup is accessed to the target position by means for controlling a slider on which the optical pickup is loaded.  
           [0008]    However, in the case of the optical disc having a plurality of information recording layers on one side, there is taken the procedure such that in the case where read target information is present on the other information recording layer, the track positions between the information recording layers are not always coincided, and the optical pickup is moved to the target position on the basis of position information of the information recording layer now being reproduced, after which the optical pickup is moved to the target information recording layer. This procedure has a problem in that accessing cannot be made to the target position at high speeds and accurately.  
           [0009]    In addition, the one-side dual-layer disc of DVD includes two kinds, one being a parallel track path (hereinafter referred to as OTP) in which the recording path of the first layer is the same as that of the second layer as shown in FIG. 3( 1 ), and the other being an opposite track path (hereinafter referred to as OTP) in which the recording path of the first layer is reversed to that of the second layer as shown in FIG. 3 ( 2 ). In case of the OTP, the physical address of the second layer is provided without direct relation with that of the first layer, and therefore, accessing to the other information layer is impossible on the basis of the position information of the information recording layer now being reproduced.  
           [0010]    Also, with respect to the pausing (temporary stop) operation, there is a problem in that the pausing is not obtained in the second layer of the disc of OTP in the state of the operation of the conventional reproduction of one-side single disc.  
         SUMMARY OF THE INVENTION  
         [0011]    It is an object of the present invention to provide, in the reproduction of these discs having a plurality of recording layers, a method for carrying out an access control of an optical pickup accurately, at high speeds and easily, a method for carrying out a pausing operation accurately irrespective of kinds of discs and a system therefor.  
           [0012]    For achieving the aforementioned object, according to the present invention, there is provided an accessing method for an optical disc apparatus for recording/reproducing an optical disc on one side of which are provided plural layers of information recording surfaces and system therefor, the method comprising:  
           [0013]    recording/reproducing information on at least one information recording layer among said plural layers of information recording layers, and  
           [0014]    switching the information recording layer for information to be recorded/reproduced during the information recording/reproducing.  
           [0015]    More specifically, according to the present invention, in starting the access control of an optical pickup over a plurality of recording layers, first, a beam focal point of the optical pickup is moved by using a moving means to a recording layer in which target information is recorded to switch information recording layers during reproduction, and after this, the distance on a disc plane between two points is obtained from a present position of the optical pickup on the information recording layer after movement and a target position of read information, using a control processing means similar to the access between the same recording layers to perform the access control of the optical pickup. Further, according to the present invention, with respect to the pausing operation, whether or not a disc during reproduction is one-side dual-disc is stored in advance by an optical disc reproducing apparatus, and when instructions for pausing operation are given at the time of reproduction of the second layer of the OTP disc, the track jump direction of the pickup is reversed to that of the first layer. 
       
    
    
       [0016]    The foregoing and other objects, advantages, manner of operation and novel features of the present invention will be understood from the following detailed description when read in connection with the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a block diagram of an optical disc apparatus forming the constitutional requirement of the present invention according to a first embodiment of the present invention;  
         [0018]    [0018]FIG. 2 is view schematically showing the construction of a DVD dual-layer disc used in the present embodiment;  
         [0019]    FIGS.  3 ( a ) and  3 ( b ) are respectively views schematically showing a physical sector layout of DVD dual-layer disc and address information construction used in the present embodiment;  
         [0020]    [0020]FIG. 4 is a flowchart showing the flow of a switching process of reproducing information recording layer in one embodiment of the present invention;  
         [0021]    [0021]FIG. 5 is a flowchart showing the flow of an access controlling process of an optical pickup in one embodiment of the present invention;  
         [0022]    [0022]FIG. 6 is a flowchart showing the flow of conventional pausing operation; and  
         [0023]    [0023]FIG. 7 is a flowchart showing the flow of conventional pausing operation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    The present invention will be explained hereinafter with reference to one embodiment shown in the drawings.  
         [0025]    [0025]FIG. 1 is a block diagram of an optical disc apparatus forming the constitutional requirement of the present invention according to a first embodiment of the present invention. The present optical disc reproducing apparatus is composed of, other than those shown here, a decoder block for reproducing, demodulating, error-correcting signals for decoding reproduced data, a system control block for controlling the entire optical disc apparatus, an interface block for the interface with external information processing equipment, an encoder block for modulation and error-correction for recording data, etc. The blocks not directly relating to the present invention out of the above-described blocks will be omitted in their explanation and drawings.  
         [0026]    First, the functions of the blocks shown will be roughly explained below.  
         [0027]    An optical disc  1  is an optically readable information storage medium such as a compact disc (CD), a digital versatile disc (DVD), etc. Information is recorded in a signal recording surface at a concave portion called a pit.  
         [0028]    An optical pickup  2  is to reproduce information from the optical disc  1  and comprises a semiconductor laser is not shown, a focus actuator  3 , a tracking and optical part actuator  4 , and a light detector  5 . Light departed from the semiconductor laser is focused at a signal recording surface of the optical disc  1  to form an optical spot. Since the quantity of light reflected from the optical spot changes due to the presence or absence of pit, the change of the quantity of light can be detected as a signal to reproduce the signal.  
         [0029]    The light detector  5  is to convert the change in the quantity of light reflected from the optical disc  1  into a current signal. An output of the light detector  5  is converted into a voltage signal by a current-voltage converter circuit  6 , which voltage signal is transmitted to a focus error detection circuit  7  and a tracking servo circuit  8 . A focus error signal  71  detected by the focus error detection circuit  7  is applied to the focus actuator  3  via a phase compensation circuit  9 , a switch  10  and a drive circuit  11  to form a focus servo loop for controlling an objective lens  12  in a focusing direction.  
         [0030]    A search signal generation circuit  13  is a circuit for generating a search signal  15  according to a focus search control signal  14 . The search signal  15  is transmitted to the drive circuit  11  and applied to the focus generator  3  whereby the objective lens  12  can be moved in the focusing direction separately from the focus servo loop.  
         [0031]    The switch  10  is switched according to the state of a focus switching signal  16  to switch the switch  10  so that an output of the phase compensation circuit  9  is transmitted to the drive circuit  11  whereby the operation of the focus servo loop can start.  
         [0032]    The tracking servo circuit  8  comprises a tracking error-detection circuit, a phase compensation circuit and the like, and an output signal is applied to the tracking actuator  4  via a drive circuit  17  to form a tracking servo loop for controlling the objective lens  12  in a tracking direction.  
         [0033]    In the switch  18 , the tracking servo loop is opened by a tracking control switching signal  19 , and the objective lens  12  can be moved in the tracking direction by an output signal of a tracking actuator motion signal generation circuit  20 .  
         [0034]    A slide motor  21  is to move the optical pickup  2 . Normally, an output signal of the tracking servo circuit  8  is transmitted to a drive circuit  23  via a slide motor servo circuit  22  to form a slide motor servo loop. In the case where the optical pickup is moved for the access operation or the like, a switch  25  is switched by a slide motor control switching signal  24 , and a controller  27  outputs a slide motor control signal  28  to a slide motor motion signal generation circuit  29  according to speed and position information obtained by an output signal of a rotary encoder  26  to drive a slide motor  21  via the drive circuit  23 .  
         [0035]    Next, one example of an optical disc on one side of which are provided two layers of information recording layers will be explained. The present optical disc apparatus reproduces CD, DVD single layer, and DVD dual layer discs. The dual disc of DVD will be explained below as an example.  
         [0036]    [0036]FIG. 2 shows the construction of a DVD dual-layer disc.  
         [0037]    The DVD dual-layer disc bas two information recording layers arranged on one side of the disc at intervals of approximately 55 μm thickness-wise of the disc. These information recording layers are normally formed separately and mechanically pasted together.  
         [0038]    In FIG. 2, a first layer {circle over ( 1 )} is a translucent recording film, and a second layer {circle over ( 2 )} is a reflecting film formed of aluminum vapor deposition or the like. The reproduction of the dual-layer disc is carried out, as shown in FIG. 2, by irradiating a laser beam from the first layer {circle over ( 1 )} side and having the objective lens  12  in the direction at right angles to the disc to form a focal point to the first layer {circle over ( 1 )} and the second layer {circle over ( 2 )}.  
         [0039]    FIGS.  3 ( a ) and  3 ( b ) are respectively views schematically showing a physical sector layout of DVD dual-player disc and address information construction.  
         [0040]    [0040]FIG. 3( a ) shows a parallel track path (PTP). A physical sector of the same address, which is not related to address information and incremented from the inner circumference to the outer circumference of the disc, is present in each information recording layer between a physical sector on the layer  0  (first layer) and a physical sector on the layer  1  (second layer).  
         [0041]    [0041]FIG. 3( b ) shows an opposite track path (OTP). Address information of a start physical sector on the layer  1  (second layer) is represented by address information whose each bit being inverted of address information of a final physical sector on the layer  0  (first layer), and the address information of the layer  1  (second layer) is incremented from the outer circumference to the inner circumference of the disc and recorded. That is, the address information of the layer  0  (first layer) is incremented from the inner circumference to the outer circumference of the disc whereas the address information of the layer  1  (second layer) is incremented from the outer circumference to the inner circumference of the disc.  
         [0042]    In the DVD disc, information of one side single-layer disc, one side dual-layer disc, disc of PTP or disc of OTP is recorded as index information of disc in a control data area of the disc, and information of the layer  0  (first layer) of the layer  1  (second layer) is recorded in the sector address.  
         [0043]    Accordingly, in the optical disc reproducing apparatus, it is possible to know what disc is contained by reading the index information, and it is possible to carry out the special reproduction conveniently by storing whether the disc being reproduced is the disc of PTP or the disc of OTP in the optical disc reproducing apparatus.  
         [0044]    In what disc of PTP shown in FIG. 3( a ) and of OTP shown in FIG. 3( b ), in the case where accessing between and over information recording layers so that the optical pickup is moved from the physical sector A present on the layer  0  (first layer) to the physical sector B present on the layer  1  (second layer), the movement of the optical pickup in a direction of thickness of the disc for switching the information recording layer in which the optical-spot forms a focal point is necessary in addition to the movement of the optical pickup in a radial direction of the disc in the prior art.  
         [0045]    The procedure for switching an information recording layer to be reproduced in the present optical disc apparatus will be explained below. In the ensuing procedure, an example will be explained in which the processing of CPU which functions as a system controller is accomplished by soft-ware.  
         [0046]    [0046]FIG. 4 is a flowchart showing the flow of a switching process of reproducing information recording layer.  
         [0047]    In  401 , confirmation is made by information in the sector address whether or not the information recording layer being now reproduced while the objective lens of the optical pickup forms a focal point is the first layer or the second layer. In  402 , confirmation is made of the recording layer of the target information.  
         [0048]    As a result of the processing in  401  and  402 , if judgement is made that the target recording layer is another layer, the servo loop such as the focus servo, tracking servo, etc. for maintaining a focal point of the optical spot in an intended position of the information recording layer of the disc is set to off, in  404 .  
         [0049]    After this, in  405 , a focus search control signal for driving the objective lens toward the focusing direction of the target information recording layer starts to be delivered. As a result, a focus error signal starts to be output as the focal point of the optical spot gradually moves close to the adjacent information recording layer.  
         [0050]    In  406 , the focus search control signal is continued to deliver till exceeding a preset judging level while monitoring the focus error signal.  
         [0051]    After exceeding the judging level, in  407 , a signal reverse in phase to the drive signal applied in  405  is output to the focus search control signal for the drawing stabilization of the thereafter focus servo loop to apply a brake to the focus actuator.  
         [0052]    In  408 , the zero cross point of the focus error signal is detected to thereby judge to be reached to the adjacent information recording layer.  
         [0053]    Thereafter, in  409 , the switch is switched to set the focus servo loop to on, and to set other servo loops to on sequentially.  
         [0054]    Now, in the optical disc in which two information recording layers are actually provided on one side, accessing over the information recording layers will be explained.  
         [0055]    Generally, in the optical discs such as CD and DVD, the procedure is employed in which the logical present position and target position at the start of accessing are converted into the physical position on the disc, the difference thereof is obtained to calculate the distance on the disc plane between relative two points, and the optical pickup is moved to the target position at high speeds without reading the position information recorded in the moving disc using control means for the slider on which the optical pickup is loaded.  
         [0056]    One example of the method for converting the present position and the target position into the physical position will be explained. Let R 0  (m) be the radius from the center of the disc of the sector number S 0  as a reference on the disc, CLV (m/s) be the linear speed when the information of disc is recorded, TP (m) be the track pitch, and To be the time required to reproduce  1  sector. Then, the relation with the radius R 1  (m) from the disc center of the sector number S 1  present on the same information recording layer can be expressed by 
         R 12 =( CLV·TP· T 0 (S 1 −S 0 )/π)+R 02   
         [0057]    In the case of the dual-disc, the information recording layers are different in the linear speed and the track pitch in terms of forming the disc, it is therefore necessary to use the above-described formula every information recording layer in which sector is recorded.  
         [0058]    In the case where accessing is carried out over the information recording layers, in the disc of PTP, the physical sector is provided from the inner circumference to the outer circumference of the disc in both the layer  0  (first layer) and the layer  1  (second layer). So, there is a method comprising: moving the target distance on the basis of the information of the information recording layer now being reproduced, approaching to the target sector while reading the present position information recorded in the information recording layer being reproduced, and after this, accessing to the target sector over the information recording layers. However, since the layer  0  and the layer  1  are not always coincided in the track pitch and the linear speed, the wasteful access time to the final target sector occurs.  
         [0059]    Further, in the disc of OTP, the layer  0  is totally different in the physical sector from that of the layer  1 , and it is impossible to access to the target sector of the other information recording layers on the basis of the information of the information recording layer now being reproduced.  
         [0060]    In the present embodiment, the aforementioned problems are solved by the following processing.  
         [0061]    [0061]FIG. 5 is a flowchart showing the flow of an access controlling process of an optical pickup according to the present invention.  
         [0062]    In the present embodiment, first, in  501 , confirmation is made of the position of the optical pickup by reading the present position information recorded in the optical disc.  
         [0063]    Then, in  502 , judgement is made whether or not the recording position of the target information subjected to accessing is the same as the present information recording layer.  
         [0064]    When the information recording layer is not the same, in  503 , the beam focal point of the optical pickup is moved to the target information recording layer by the focus moving means previously explained with reference to FIG. 4.  
         [0065]    After movement, in  504 , confirmation is made of the present position of the optical pickup on the information recording layer after movement by the processing similar to that of  501 .  
         [0066]    In  505  and  506 , the present position and the target position are converted to the physical position on the disc.  
         [0067]    In  507 , the distance on the disc plane between the relative two points is calculated from the physical positions of the present position and the target position obtained by the above described methods. In  508 , the optical pickup is moved to the target position at high speeds, without reading the position information recorded in the moving disc, using the control means of the slider on which the optical pickup is loaded.  
         [0068]    After movement, in  509 , the optical pickup is accessed to the target information recording position while confirming the position information recorded in the disc.  
         [0069]    In the above-described series of processings, also in the case of accessing over the information recording layers, accessing is carried out merely adding the processings of  502 ,  503  and  504 , so that the processing means similar to the conventional accessing processing in the same information recording layer after  505  can be used, thus enabling the high speed accessing and enabling processing easily.  
         [0070]    The pausing operation according to the present invention will be explained hereinafter with reference to FIGS. 6 and 7. FIG. 6 is a flowchart of the pausing operation heretofore used in CD and LD. FIG. 7 is a flowchart of the pausing operation according to the present invention. In both CD and LD, information is recorded along the spiral signal track from the inner circumference to the outer circumference of the disc. In FIG. 6, upon command of the pausing operation, in  601 , “Jump by one track toward the inner circumference, at the pause designated position.” whereby the pausing is realized. In  602 , this operation is repeated till receipt of the end of pause command. Also in the single-layer disc of DVD and the PTP disc, pausing can be realized in FIG. 6. However, in the layer  1  (second layer) of the OTP disc, the FIG. 6 method rapidly progresses, failing to provide the pausing operation.  
         [0071]    In FIG. 7, in the optical disc reproducing apparatus, the presence of the OTP disc is read from the index information. Upon receipt of command of pausing operation, first, in  703 , “OTP disc ?” is checked, and in  704 , “Layer  1  (second layer) ?” is checked from the sector address being reproduced. Only at the time of the layer  1  (second layer) in the OTP disc, “Jump by one track toward the outer circumference, at the pause designated position” in  705  whereby the pausing operation is realized.  
         [0072]    While in the embodiments according to the present invention, a description has been made of the case of the dual-layer disc, it is to be noted that needless to say, the accessing method and the pausing method according to the present invention can be applied to the disc reproducing apparatus having a plurality of information recording layers such as three layers, four layers, etc.  
         [0073]    According to the present invention, in the optical disc apparatus having a plurality of information recording surfaced to be reproduced on one side of the optical disc and which is necessary to switch these information recording layers to be reproduced during the operation, even in the case where the recording position of intended information is provided other than the information recording layer now being reproduced, it is possible to carry out the access control of the optical pickup using the control processing means similar to the access between the same recording layers accurately, at high speeds and relatively easily, and further in both PTP disc and OTP disc, the pausing operation can be realized.