Patent Publication Number: US-6704254-B1

Title: Optical disk device, control method of optical system, medium, and information aggregate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, for example, to an optical disk device used for recording a signal in an optical disk or for reproducing a signal of an optical disk, a control method of an optical system, a medium, and an information aggregate. 
     2. Description of the Related Art 
     The configuration and action of a conventional optical disk device will be described on the basis of FIG.  1 (A) to FIG.  1 (C) and FIGS. 2,  7 . FIG.  1 (A), FIG.  1 (B), and FIG.  1 (C) are a cross-sectional configuration figure of a conventional optical head, a typical figure of optical detecting means  9 , and a partial enlarged view showing grooves and pits formed on an optical disk signal surface and the position of an optical spot, respectively. Herein, the position of a pit  14   c  in FIG.  1 (C) is on the inner peripheral side of an optical disk  8  from the positions of pits  14   a,    14   b.    
     In FIG.  1 (A), light  2  emitted from a radiating light source  1  such as a semiconductor laser penetrates a beam splitter  3 , and is converted into parallel light  5  by a collimate lens  4 . This light  5  is reflected on a reflecting mirror  6  and is condensed on a signal surface  8 S formed on the rear surface of an optical disk  8  by an objective lens  7 . In the objective lens  7 , the focusing and tracking, and the tilt in the radial direction are controlled by an actuator. The light reflected on the signal surface  8 S is condensed by the objective lens  7  and reflected on the reflecting mirror  6 , and passing through the collimate lens  4 , it is reflected on the beam splitter  3 , and becomes light  10  to be condensed on optical detecting means  9 . 
     The optical detecting means  9  is divided by a dividing line  9 L corresponding to the rotational direction (direction Y at right angles to the paper surface of FIG.  1 (A)) of the optical disk  8 , and as shown in FIG.  1 (B), this dividing line  9 L approximately equally divides an optical spot  10 S on the optical detecting means into two, and each difference signal  10 S is detected by a subtracter  10 , and a summation signal  11 S is detected by an adder  11 . 
     As shown in FIG.  1 (C), on the signal surface  8 S of the optical disk, uneven groves  13 G and inter-groove spaces  13 L, pit lines  14   a  and pit lines  14   b  with a fixed length are formed in cycles at a pitch p in the radial direction  12  of the optical disk  8 . On the groove  13 G and inter-groove space  13 L, signal marks  15  having a reflection factor different from that out of the own area are formed, and the difference of those reflection factors is read as a reproduction signal by an optical spot  16  scanning along the groove and inter-groove space. The positions of the pit lines  14   a,    14   b  are in synchronization with each other in the adjacent tracks, and they are also in cycles at a pitch q in the rotational direction of the optical disk. Furthermore, the center of the pit line  14   a  deviates from the center of the groove  13 G by s along the radial direction, and the pit line  14   b  deviates by s in the opposite direction thereof. Accordingly, when the optical spot  16  that has been tracking-position-controlled on the groove  13 G and the inter-groove space  13 L scans on the pit lines  14   a,    14   b,  each goes on a position deviating from the center of the pit by s. 
     On the other hand, on the inner peripheral side of the optical disk, pit lines  14   c  are formed in cycles at a pitch P′ in the radial direction  12 . It is possible that the positions of the pit lines  14   c  are not in synchronization with each other in the adjacent ones, and it is also possible that there is no periodicity in the rotational direction of the optical disk and the length is random. Naturally, when the tracking-position-controlled optical spot  16  scans on the pit line  14   c,  it goes on the center position of the pit. 
     FIG. 2 shows a signal waveform of a summation signal  11 S at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b.  Herein, in FIG. 2, the time-axis is shown in the horizontal axis, and it expresses the fact that the signal waveform of the pit line  14   b  is detected after the signal waveform of the pit line  14   a  has been detected. When the optical spot  16  is positioned at places  101   a,    101   b  just beside the pits (refer to FIG.  1 (c)), the scattering effect by the pit is large and the detected light quantity is lowered, but when it is positioned at places  102   a,    102   b  just beside the inter-pit spaces (spaces between a pit and a next pit) (refer to FIG.  1 (C)), the detected light quantity is restored. Accordingly, by scanning beside the pit line  14   a,  the reproduction signal vibrates between an envelope  17   a  (corresponding to the reproduction signal at the position  101   a ) and an envelope  18   a  (corresponding to the reproduction signal at the position  102   a ) (letting the output differences from a level  19  of a detected light quantity of zero to the respective envelopes be A 1 , A 2 ). Similarly, by the scanning of the optical spot  16  beside the pit line  14   b,  the reproduction signal also vibrates between an envelope  17   b  (corresponding to the reproduction signal at the position  101   b ) and an envelope  18   b  (corresponding to the reproduction signal at the position  102   b ) (letting the output differences from a level  19  of a detected light quantity of zero to the respective envelopes be B 1 , B 2 ). 
     FIG. 7 shows a flow of the control signal process in the movable tilting means of a conventional optical disk device. In FIG. 7, a summation signal  11 S created in the adder  11  is a signal at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b,  and it shows a signal waveform shown in FIG.  2 . These signals whose detecting times are different are introduced into an arithmetic circuit  20 , and the delaying process is applied, and a signal B defined by the relation of B=(A 2 −A 1 )−(B 2 −B 1 ) is created, and a signal  23  in which the high frequencies are cut by a low-pass filter  22  is made. 
     On the other hand, a signal A of the difference created in the subtracter  10  is a signal at the time when the optical spot  16  scans on the groove  13 G or the inter-groove space  13 L. A difference signal  24  of this signal A and the signal  23  is introduced into a driving circuit  25 , and a tracking drive signal  26  is created. By this drive signal  26 , the objective lens  7  is moved in the radial direction of the optical disk  8 , and according to the control formula B=0, the tracking center control of the optical spot  16  is performed. 
     Furthermore, under the condition where this tracking control is applied, the signal A becomes a signal  28  in which the high frequencies are cut by a low-pass filter  27  and is introduced into a driving circuit  29 , and a lens tilt drive signal  30  is created. By this drive signal  30 , the objective lens  7  is tilted in the radial direction of the optical disk  8  (state of the objective lens  7 ′ in FIG.  1 (A)), and according to the control formula A=0, the lens tilt control is performed. 
     By such a control, it has been intended to reduce the off-track quantity of the optical spot  16  and to cancel the aberration (especially, third order coma aberration) of the optical spot  16  created by the tilt of the optical disk  8  (state of the optical disk  8 ′ in FIG.  1 (A)). 
     However, actually, there has been such a problem that the off-track quantity cannot be made zero by a conventional method like this, and that the third order coma aberration also cannot be cancelled. Furthermore, it has been impossible to well understand the reason. 
     When the off-track quantity deviates from zero, there is such a problem that the optical spot  16  eliminates part of the adjacent signal mark  15  at the time of recording and that the cross-talk increases at the time of reproduction to degrade the jitter or the like. Furthermore, when the third order coma aberration cannot be cancelled, there are problems such as the power shortage at the time of recording or the degradation of the jitter at the time of reproduction. 
     BRIEF SUMMARY OF THE INVENTION 
     Considering such problems, it is an object of the present invention to provide, for example, an optical disk device in which the off-track or the third order coma aberration created by the relative tilt of the disk can be suppressed to an extremely small degree, a control method of an optical system, a program recording medium, and an information aggregate. 
     One aspect of the present invention is an optical disk device comprising: 
     optical condensing means for condensing radiated light from a light source on an optical disk; 
     optical detecting means for detecting reflected light from said optical disk; and 
     control means for performing tracking control and/or tilt control of said optical condensing means by utilizing output from said optical detecting means, wherein said control means uses an off-track quantity and/or a tilt quantity of said optical condensing means, when said control is performed. 
     Another aspect of the present invention is an optical disk device comprising: 
     a radiating light source for performing radiation of a radiated light; 
     an objective lens for condensing said radiated light on a signal surface of an optical disk as an optical spot, and for condensing returning light from said optical disk; 
     movable tilting means for controlling movement of said objective lens in the radial direction of said optical disk, and tilt in said radial direction of said objective lens; and 
     optical detecting means for detecting a light quantity of said returning light, wherein 
     a signal A and a signal B that are detected when said optical spot scans near cyclic grooves or cyclic pits formed on a signal surface of said optical disk are compensated by using quantities 
     β·LT and γ·LT proportional to a tilt quantity LT of said objective lens to be a compensated signal (A-β·LT) and a compensated signal (B-γ·LT), and letting said compensated signal (A-β·LT) be a tilt control signal for controlling tilt of said objective lens, and letting said compensated signal (B-γ·LT) be a tracking control signal for controlling an alignment to said cyclic grooves or said cyclic inter-groove spaces of said optical spot, said movable tilting means controls said movement of said objective lens and said tilt of said objective lens so that said tilt control signal and said tracking control signal may substantially be zero. 
     Still another aspect of the present invention is the optical disk device, further comprising optical distributing means for distributing said radiated light and said returning light, wherein said returning light is bent in a direction different from that on the approach route side of said radiated light by said optical distributing means and condensed on said optical detecting means. 
     Yet another aspect of the present invention is the optical disk device, wherein 
     said cyclic grooves and said cyclic pits are formed along the radial direction of said optical disk by a pitch P, and 
     in said cyclic pits, there are cyclic pits a arranged such that the positions thereof are shifted to the inner peripheral side along the radial direction from the positions of cyclic grooves by s in cycles in the rotational direction of the optical disk, and cyclic pits b arranged to be inversely shifted to the outer peripheral side by s in cycles in the rotational direction of said optical disk, and 
     said optical spot scans on said cyclic grooves or on said cyclic inter-groove spaces. 
     Still yet another aspect of the present invention is the optical disk device, wherein a positional shift s of said cyclic pits is equal to P/4 or P/2. 
     A further aspect of the present invention is the optical disk device, wherein a tilt quantity LT of said objective lens is estimated by using driving current on the tilt side of said movable tilting means or driving voltage on the tilt side of said movable tilting means. 
     A still further aspect of the present invention is the optical disk device, wherein set values of said coefficient β and said coefficient γ are changed depending on whether said optical spot scans on said cyclic grooves or on said cyclic inter-groove spaces. 
     A still yet further aspect of the present invention is the optical disk device, wherein 
     tilt to an optical axis of said objective lens converging as a result of control agrees with the tilting direction of a base plate of said optical disk, and 
     a third order coma aberration component of an optical spot on said signal surface is substantially suppressed by setting of said coefficient β with each tilt. 
     An additional aspect of the present invention is the optical disk device, wherein an alignment error to cyclic grooves or cyclic inter-groove spaces of said optical spot converging as a result of control is substantially suppressed by setting of said coefficient γ. 
     A still additional aspect of the present invention is the optical disk device, wherein 
     said optical detecting means is divided into two by a straight line corresponding to the rotational direction of said optical disk, and can detect a difference signal from the divided areas, and 
     either said signal A or said signal B is said difference signal at the time when said optical spot scans on said cyclic grooves or said cyclic inter-groove spaces. 
     A yet additional aspect of the present invention is the optical disk device, wherein 
     when letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be A 1 , and a detecting level of an envelope drawn by a side with a larger detected light quantity be A 2  between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits a, and 
     letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be B 1 , and a detecting level of an envelope drawn by a side with a larger detected light quantity be B 2  between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits b, 
     said signal A is expressed by any one of A=A 1 −B 1 , A=A 2 −B 2 , and A=(A 2 −A 1 )−(B 2 −B 1 ). 
     A still yet additional aspect of the present invention is the optical disk device, wherein 
     when letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be A 1 , and a detecting level of an envelope drawn by a side with a larger detected light quantity be A 2  between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits a, and 
     letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be B 1 , and a detecting level of an envelope drawn by a side with a larger detected light quantity be B 2  between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits b, 
     said signal B is expressed by any one of B=A 1 −B 1 , B=A 2 −B 2 , and B=(A 2 −A 1 )−(B 2 −B 1 ). 
     A supplementary aspect of the present invention is the optical disk device, wherein 
     said signal A is said difference signal, and 
     a pit along the rotational direction of said optical disk is formed on the inner peripheral side of said optical disk, and 
     said movable tilting means tilts said objective lens so that a detected signal amplitude at the time when said optical spot scans on said pit may be maximum, and moves said optical spot onto said cyclic grooves or said cyclic inter-groove spaces while keeping tilt of said objective lens, and detects an output level of said signal A when said compensated signal (B-γ·LT) becomes zero, and uses a value made by subtracting an offset quantity because of an adjusting error from an output level of said detected signal A, instead of said signal A. 
     A still supplementary of the present invention is a control method of an optical system, comprising the steps of: 
     condensing radiated light from a light source on an optical information recording medium by using a given optical system; 
     detecting reflected light from said optical information recording medium; and 
     performing tracking control and/or tilting control of said optical system on the basis of said detected light, wherein said control is performed by using an off-track quantity and/or a tilt quantity of said optical system. 
     A yet supplementary aspect of the present invention is a medium that carries a program and/or data for executing by a computer all or part of functions of all or part of means of the present invention, wherein said medium can be processed by a computer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 (A) is a conventional cross-sectional configuration figure of an optical head; 
     FIG.  1 (B) is a conventional typical figure of optical detecting means of the optical head; 
     FIG.  1 (C) is a conventional partial enlarged view showing grooves and pits formed on an optical disk signal surface, and the position of an optical spot scanning thereon; 
     FIG. 2 is a conventional signal waveform figure of a summation signal at the time when the optical spot scans near pit lines  14   a  and  14   b;    
     FIG. 3 is an explanation figure showing a flow of the control signal process in an optical disk device of embodiment  1 ; 
     FIG. 4 is an explanation figure showing a flow of the control procedure in the optical disk device of embodiment  1 ; 
     FIG. 5 is an explanation figure showing a flow of the control signal process in an optical disk device of embodiment  2 ; 
     FIG. 6 is an explanation figure showing a flow of the control signal process in an optical disk device of embodiment  3 ; and 
     FIG. 7 is an explanation figure showing a flow of the control signal process in an optical disk device of a conventional example. 
    
    
     DESCRIPTION OF SYMBOLS 
       7  . . . objective lens 
       8  . . . optical disk 
       10  . . . subtracter 
     A . . . difference signal 
       11  . . . adder 
       11 S . . . summation signal 
     B . . . arithmetic signal 
       20  . . . arithmetic circuit 
       22 ,  27  . . . low-pass filter 
       25 ,  29  . . . driving circuit 
       26  . . . tracking drive signal 
       30  . . . lens tilt drive signal 
       32 ,  35  . . . compensation signal 
       31 ,  34  . . . amplifier 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described below on the basis of FIG.  1 (A) to FIG.  6 . FIG.  1 (A) to FIG.  1 (C) and FIG. 2 are explanation views common to all of embodiment 1 to embodiment 3 to be described below. FIG. 1 (A) to FIG.  1 (C) show the configuration of the cross section of an optical head of the present invention, the state of an optical spot on the optical disk signal surface, or the like, and the description will be omitted since they are similar to those in the case of the previously described conventional example. FIG. 2 shows a signal waveform of a summation signal  11 S at the time when an optical spot  16  scans near pit lines  14   a  and  14   b,  and the description will also be omitted since this is similar to that in the case of the above described conventional example. 
     (Embodiment 1) 
     The configuration and action of an optical disk device of the present embodiment will be described below while referring to FIG.  3  and FIG. 4, and at the same time, one embodiment of a control method of an optical system of the present invention will also be described. Here, FIG. 3 shows a flow of the control signal process in an optical disk device of the present embodiment 1. 
     First, in FIG. 3, the summation signal  11 S created in an adder  11  is a signal at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b,  and it shows a signal waveform shown in FIG.  2 . By introducing this signal into an arithmetic circuit  20 , a signal B defined by the relation of B=(A 2 −A 1 )−(B 2 −B 1 ) is created, and from the signal B, a compensation signal  35  to be described later is subtracted to create a signal  36 , and the high frequencies are cut by a low-pass filter  22 , and a signal  123  is made. 
     On the other hand, a signal A of the difference created in the subtracter  10  is a signal at the time when the optical spot  16  scans on the groove  13 G or the inter-groove space  13 L. A difference signal  124  of this signal A and the signal  123  is introduced into a driving circuit  25 , and a tracking drive signal  126  is created. By this drive signal  126 , the objective lens  7  is moved in the radial direction of the optical disk  8 , and the tracking center control of the optical spot  16  is performed. 
     Furthermore, under the condition where this tracking control is applied, a compensation signal  32  to be described later is subtracted from the signal A to create a signal  33 , and the high frequencies are cut by a low-pass filter  27 , and a signal  128  is made. 
     Herein, a lens tilt drive signal  130  to be described later is proportional to the above described signal  128 , and is a driving current or a driving voltage of an actuator (omitted in the figure) for keeping the tilt angle of the objective lens  7 . This driving current is proportional to the tilt quantity from the reference position of the objective lens  7 . Accordingly, it can be said that the signal  128  is a signal corresponding to the tilt quantity LT of the lens in the radial direction. 
     This signal  128  is amplified by β times in an amplifier  31  to be the above described compensation signal  32 , and on the other hand, it is amplified by γ times in an amplifier  34  to be the above described compensation signal  35  (determination of the values of coefficients β, γ will be described later). The signal  128  is introduced into a driving circuit  29 , and a lens tilt drive signal  130  is created. Then, as mentioned above, by this drive signal  130 , the objective lens  7  is tilted in the radial direction of the optical disk  8  (state of the objective lens  7 ′ in FIG.  1 (A)), and the lens tilt control is performed. 
     Here, the description of the action of an optical disk device of the present embodiment using FIG. 3 is once finished, and the reason why the off-track quantity has not been made zero and the third order coma aberration has not been cancelled by the conventional method will be described. Herein, the description of the action of the optical disk device of the present embodiment using FIG. 4 will be given later. 
     First, the present inventor has thought that the signal A and signal B are functions of an off-track quantity OT (deviation quantity of the position in the radial direction between the light intensity peak point of the optical spot  16  and the center of the groove  13 G or the inter-groove space  13 L), the disk tilt quantity DT in the radial direction (component in the radial direction of the angle between the normal of the disk surface and the incident optical axis), and the lens tilt quantity LT in the radial direction (component in the radial direction of the angle between the lens center axis and the incident optical axis), and these are approximately given by the following expressions: 
     
       
           B=a·OT+b·DT−c·LT   (Expression 1) 
       
     
     
       
           A=a′·OT+b′·DT−c′·LT   (Expression 2) 
       
     
     Here, the values of coefficients a, b, c and a′, b′, c′ can theoretically be calculated, but they are different depending on whether the optical spot  16  scans on the groove  13 G or on the inter-groove space  13 L. Furthermore, the coefficient c or c′ is not zero, and it is important in the present invention that the inventor has thought out of this fact. 
     In the present embodiment, as the values of the respective coefficients, a=214 (1/μm), b=16 (1/deg), c=24 (1/deg), a′=212 (1/μm), b′=36 (1/deg), and c′=40 (1/deg) have been used. 
     Herein, as for the method for determining the values of the above described coefficients, it is also possible to obtain suitable values by a method in which the configuration of the circuit shown in FIG. 3 is used and the respective coefficients are determined by the trial and error technique. 
     Furthermore, the condition for canceling the third order coma aberration is given by the following expression using a coefficient k determined by the designing condition of a lens (aspheric surface coefficient or the like). 
     
       
           LT=k·DT   (Expression 3) 
       
     
     Then, as mentioned above, the control formula of the tracking center in a conventional optical disk is B=0, and the control formula of the lens tilt is A=0, and therefore, when making these relations coexist with (Expression 1) and (Expression 2), the following expressions hold: 
     
       
           OT=DT· ( b′c−bc′ )/( ac′−a′c )  (Expression 4) 
       
     
       LT=DT· ( ab′−a′b )/( ac′−a′c )  (Expression 5) 
     In (Expression 4), usually, b′c−bc′=0 is not made, and therefore, such a result that the off-track quantity is zero (OT=0) is not made. Furthermore, in (Expression 5) usually, (ab′−a′b)/(ac′−a′c)=k is not made, and therefore, the third order coma aberration is not cancelled. Thus, it has been understood that the reason why the above describe problems are caused can theoretically be explained by using the above described approximate expressions thought out by the present inventor. 
     Then, the present inventor has paid attention to LT of the above described approximate expression, which can be estimated by the tilt side driving current or tilt side driving voltage of the movable tilting means, and has thought out of performing the compensation of the control formula using this. That is, the inventor has discovered that the above described problems can be solved by letting the control formula of the tracking center in an optical disk device in the present embodiment 1 be B−γ·LT=0, and letting the control formula of the lens tilt be A−β·LT=0. 
     Next, the effectiveness of the above described control formulas that are the essential point of the present invention will be described in detail. That is, these control formulas are made to coexist with (Expression 1) and (Expressing 2) (values of the coefficients a, b, c and a′, b′, c′ are equal to those in the above described case), and when solved on the condition that the relations of OT=0 and LT=k·DT are satisfied, the following expressions are determined: 
     
       
           γ=b/k−c   (Expression 6) 
       
     
     
       
           β=b′/k−c′   (Expression 7) 
       
     
     Conversely speaking, when (Expression 6) and (Expression 7) hold, even if the disk tilt exists, the relations of OT =0 and LT=k·DT hold, and the off-track quantity is zero (OT=0), and the third order coma aberration is cancelled (LT=k·DT). However, as mentioned above, the values of the coefficients a, b, c and a′, b′, c′ are different depending on whether the optical spot  16  scans on the groove  13 G or on the inter-groove space  13 L, and therefore, the values of β, γ should also be switched to the respective optimum values depending on the scanning places. 
     Next, by using FIG. 4, the description of the action of the present embodiment 1 will further be performed. FIG. 4 shows a flow of the control procedure in an optical disk device of the present embodiment 1. At the time of initial learning, the optical spot  16  scans on the pit line  14   c  formed in the inner peripheral part of the optical disk, and the lens tilt quantity LT in the radial direction is adjusted so that the signal amplitude thereof (RF amplitude) may be maximum (S 1  to S 3 ). 
     After the adjustment, the optical spot  16  moves to the part of the groove  13 G or inter-groove space  13 L of the optical disk, and the off-track quantity OT is adjusted so that B−γ·LT =0 may be satisfied while LT is fixed, and the output level (AO+β·LT) of the signal A is read (S 4  to S 7 ). Originally, AO is zero, but the signal A is a difference signal, and therefore, it has an offset quantity AO because of the relative positional error of the optical spot  10 S and the detector  9 , and in order to eliminate this influence, the value A′ made by subtracting AO from the signal A is treated as the true value of the signal A (S 8 ). 
     Next, the action moves to the control loop, and repeats the control process of adjusting LT so that (1) A′−β·LT=0 may be satisfied and of adjusting OT so that (2) B−γ·LT=0 may be satisfied (S 9  to S 12 ). By the above described procedure, the influence because of the adjusting error of the detector can be eliminated. 
     Herein, in the present embodiment, it is possible for the signal B to be a signal defined by the relation of B=A 1 −B 1 , and it is also possible to be a signal defined by the relation of B=A 2 −B 2 . At these moment, the coefficients a, b, c have values different from those in the present embodiment 1, but similarly to the present embodiment 1, by using new coefficient values and adopting β and γ that makes (Expression 6) and (Expression 7) hold, the off-track quantity can be made zero to cancel the third order coma aberration even when the disk tilt exists. 
     (Embodiment 2) 
     In the following, while referring to FIG. 5, the configuration and action of an optical disk device of the present embodiment will be described, and at the same time, one embodiment of a control method of an optical system of the present invention will also be described. Here, FIG. 5 shows a flow of the control signal process in an optical disk device of the present embodiment 2 of the present invention. 
     In FIG. 5, the difference signal B created in the subtracter  10  is a signal at the time when the optical spot  16  scans on the groove  13 G or the inter-groove space  13 L. From this signal, a compensation signal  35  to be described later is subtracted to create a signal  36 , and the high frequencies are cut by a low-pass filter and a signal  123  is made. 
     On the other hand, the summation signal  11 S created in the adder  11  is a signal at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b,  and it shows a signal waveform shown in FIG.  2 . By introducing this signal into the arithmetic circuit  20 , the signal A defined by the relation of A=(A 2 −A 1 )−(B 2 −B 1 ) is created, and the difference signal  124  of this signal A and the signal  123  is introduced into a driving circuit  25  to create a tracking drive signal  126 . By this drive signal  126 , the objective lens  7  is moved in the radial direction of the optical disk  8  to perform the tracking center control of the optical spot  16 . 
     Furthermore, under the condition where this tracking control is applied, a compensation signal  32  to be described later is subtracted from the signal A to create a signal  33 , and by a low-pass filter  27 , the high frequencies are cut to create a signal  128 . The signal  128  is a signal corresponding to the lens tilt quantity LT in the radial direction, and this signal  128  is amplified by β times in an amplifier  31  to be the above described compensation signal  32 , and on the other hand, it is amplified by γ times in an amplifier  34  to be the above described compensation signal  35 . The signal  128  is introduced into a driving circuit  29  to create a lens tilt drive signal  130 . By this drive signal  130 , the objective lens  7  is tilted in the radial direction of the optical disk  8  (state of the objective lens  7 ′ in FIG.  1 (A)) to perform the lens tilt control. 
     The control formula of the tracking center in the present embodiment 2 is B−γ·LT=0, and the control formula of the lens tilt is A−β·LT=0, and therefore, when these relations are made to coexist with (Expression 1) and (Expression 2) (values of the coefficients a, b, c and a′, b′, c′ are different from those in the embodiment 1) and they are solved under the condition where the relations of OT=0 and LT=k·DT are satisfied, (Expression 6) and (Expression 7) are determined. Accordingly, similarly to embodiment 1, by adopting β and γ that can make (Expression 6) and (Expression 7) hold, the off-track quantity can be made zero to cancel the third order coma aberration even when the disk tilt exists. As mentioned above, the values of the coefficients a, b, c and a′, b′, c′ are different depending on whether the optical spot  16  scans on the groove  13 G or scans on the inter-groove space  13 L, and therefore, it is necessary to switch the values of β and γ to the respective optimum values depending on the scanning places. 
     Herein, in the present embodiment 2, the signal A may be a signal defined by the relation of A=A 1 −B 1 , and it may also be a signal defined by the relation of A=A 2 −B 2 . At these moments, the coefficients a′, b′, c′ have values different from those in the present embodiment 2, but similarly to the present embodiment 2, by using new coefficient values and adopting and y that makes (Expression 6) and (Expression 7) hold, the off-track quantity can be made zero to cancel the third order coma aberration even when the disk tilt exists. 
     (Embodiment 3) 
     In the following, while referring to FIG. 6, the configuration and action of an optical disk device of the present embodiment will be described, and at the same time, one embodiment of a control method of an optical system of the present invention will also be described. Here, FIG. 6 shows a flow of the control signal process in an optical disk device of the present embodiment  3 . In FIG. 6, the summation signal  11 S created in the adder  11  is a signal at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b,  and it shows a signal waveform shown in FIG.  2 . By introducing this signal into the arithmetic circuit  20 , the signal B defined by the relation of B=(A 2 −A 1 )−(B 2 −B 1 ) is created, and from this signal, a compensation signal  35  to be described later is subtracted to create a signal  36 , and by a low-pass filter  22 , the high frequencies are cut to create a signal  123 . 
     On the other hand, the summation signal  11 S′ created in the adder  11 ′ is also a signal at the time when the optical spot  16  scans near the pit lines  14   a  and  14   b,  and it shows a signal waveform shown in FIG.  2 . By introducing this signal into the arithmetic circuit  20 ′, the signal A defined by the relation of A=A 1 −B 1  is created, and the difference signal  124  of this signal A and the signal  123  is introduced into the driving circuit  25 , and the tracking drive signal  126  is created. By this drive signal  126 , the objective lens  7  is moved in the radial direction of the optical disk  8 , and the tracking center control of the optical spot  16  is performed. 
     Furthermore, under the condition where this tracking control is applied, a compensation signal  32  to be described later is subtracted from the signal A to create a signal  33 , and by the low-pass filter  27 , the high frequencies are cut to create a signal  128 . The signal  128  is a signal corresponding to the lens tilt quantity LT in the radial direction, and this signal  128  is amplified by β times in the amplifier  31  to be the above described compensation signal  32 , and on the other hand, it is amplified by γ times in the amplifier  34  to be the above described compensation signal  35 . The signal  128  is introduced into the driving circuit  29  and the lens tilt drive signal  130  is created. By this drive signal  130 , the objective lens  7  is tilted in the radial direction of the optical disk  8  (state of the objective lens  7 ′ in FIG.  1 (A)), and the lens tilt control is performed. 
     The control formula of the tracking center in the present embodiment  3  is B−γ·LT=0, and the control formula of the lens tilt is A−β·LT=0, and therefore, when these relations are made to coexist with (Expression 1) and (Expression 2) (values of the coefficients a, b, c and a′, b′, c′ are different from those in the embodiment 1) and they are solved under the condition where the relations of OT=0 and LT=k·DT are satisfied, (Expression 6) and (Expression 7) are determined. Accordingly, similarly to embodiment 1, by adopting β and γ that can make (Expression 6) and (Expression 7) hold, the off-track quantity can be made zero to cancel the third order coma aberration even when the disk tilt exists. As mentioned above, the values of the coefficients a, b, c and a′, b′, c′ are different depending on whether the optical spot  16  scans on the groove  13 G or scans on the inter-groove space  13 L, and therefore, it is also necessary to switch the values of β and γ to the respective optimum values depending on the scanning places. 
     Herein, in the present embodiment 3, the signal A may be a signal defined by the relation of A=(A 2 −A 1 )−(B 2  −B 1 ), and it may also be a signal defined by the relation of A=A 2 −B 2 . 
     Furthermore, the signal B may be a signal defined by the relation of B=A 2 −B 2 , and it may also be a signal defined by the relation of B=A 1 −B 1 . At these moments, the coefficients a, b, c and a′, b′, c′ have values different from those in the present embodiment 3, but similarly to the present embodiment 3, by using new coefficient values and adopting β and γ that can make (Expression 6) and (Expression 7) hold, the off-track quantity can be made zero to cancel the third order coma aberration even when the disk tilt exists. 
     Herein, the objective lens  7  in embodiments 1, 2, 3 corresponds to the optical condensing means of the present invention. 
     Furthermore, the part including the objective lens  7  in embodiments 1, 2, 3 corresponds to the optical system of the present invention. 
     Furthermore, the part including the driving circuit  25  and driving circuit  29  in embodiments 1, 2, 3 corresponds to the control means of the present invention. 
     Furthermore, the part including the driving circuit  25  and driving circuit  29  in embodiments 1, 2, 3 corresponds to the movable tilting means of the present invention. 
     Furthermore, in the case where the signal mark  15  is formed on the groove  13 G and the inter-groove space  13 L, one pit can be used for the groove and the inter-groove space when making s=P/4. Furthermore, it is also possible that the signal mark  15  is formed only on the groove  13 G (or on the inter-groove space  13 L), and at this moment, when making s=P/2, one pit can be used for the adjacent grooves (or for the adjacent inter-groove spaces). 
     Furthermore, there is a method other than the beam splitter for branching the returning light, and this may be the hologram or polarization hologram, and the mounting position thereof may be a space between the objective lens  7  and the reflecting mirror  6 , or a space between the reflecting mirror  6  and the collimate lens  4 . 
     Furthermore, it is unnecessary to perform the control in the present invention by using only the tilt quantity of the optical system like that in the above described embodiment, and it may be performed by using the off-track quantity and/or the tilt quantity of the optical system. However, in the case where the off-track quantity is used, it is sufficient to have means for directly measuring the off-track quantity, or for indirectly calculating that from the tracking drive current or the like. 
     Furthermore, in the present invention, to use the off-track quantity and/or the tilt quantity of the optical condensing means is, as mentioned above, for example, as shown in FIG. 3, to perform the control for satisfying the control formula (A−β·LT=0) by multiplying the value of the lens tilt quantity LT in the radial direction by β times and feeding back that to the signal A as the tilt quantity of the optical condensing means. Furthermore, in the case of FIG. 3, similarly to this, by multiplying the lens tilt quantity LT in the radial direction by γ times and feeding back that to the signal B as the tilt quantity of the optical condensing means, the control for satisfying the control formula (B−γ·LT=0) is also together performed. Furthermore, for example, in the cases of the configurations shown in FIG.  5  and FIG. 6, the control similar to that in the above description is also performed, which is mentioned above. 
     Furthermore, in the control in the present invention, it is unnecessary to perform both the tracking control and the tilt control of the optical system similar to that in the above described embodiment, and it is also possible to perform only either of these. That is, in the above described embodiment, the description has been given as for the case where the tilt quantity of the optical system of the present invention is used as the compensation quantity in both controls of the tracking control and the tilt control of the optical system, but it is not limited to this, and for example, it is also possible to use the tilt quantity of the optical system only for either control as the compensation quantity. In that case, for the other control, it is sufficient to perform a control similar to the conventional one. Furthermore, in the case where the off-track quantity is used as the compensation quantity, the fact similar to the above description can be said. 
     Furthermore, it is possible to realize the function of each component of an optical disk device of the present invention with a special hardware, and it is also possible to realize that in the manner of software by using a computer program. 
     Furthermore, it is possible to execute an action similar to that in the above description by preparing and utilizing a program recording medium such as an optical disk or a magneto-optical disk, wherein programs for executing all or part of actions of all or part of steps of each of the above described embodiments by a computer are recorded. 
     An optical disk device of the present invention presents, for example, the following effect. That is, it is an optical disk device comprising a radiating light source, an objective lens, optical distributing means, and optical detecting means, in which the light emitted from the radiating light source passes through the optical distributing means and is condensed on a signal surface formed on the rear surface of a base material of an optical disk by the objective lens, and the returning light reflected on this and condensed by the objective lens advances in a direction different from that on the approach route side by the optical distributing means and is condensed on the optical detecting means so that the light quantity may be detected, wherein the objective lens can be moved and tilted in the radial direction of the optical disk by a movable tilting means supporting this, and cyclic grooves and cyclic pits are formed on the signal surface of the optical disk, and the signals A−β·LT and B−γ·LT made by compensating two types of signals A and B detected when the optical spot condensed on the signal surface scans near the cyclic grooves or the cyclic pits with the quantities β·LT and γ·LT proportional to the tilt quantity LT of the objective lens are made to be the tilt control signal of the movable tilting means and the tracking control signal (that is, the alignment control signal to the cyclic grooves or cyclic inter-groove spaces) respectively, and the control is performed so that each signal may be zero. 
     Herein, the cyclic grooves and the cyclic pits are formed along the radial direction of the optical disk by a pitch P, and in the cyclic pits, there are cyclic pits (cyclic pits a) whose positions are shifted to the inner peripheral side by s along the radial direction from the cyclic groove positions and are also arranged in cycles in the rotational direction of the optical disk, and cyclic pits (cyclic pits b) whose positions are shifted inversely to the peripheral side by s and are also arranged in cycles in the rotational direction of the optical disk, and the optical spot scans on the cyclic grooves or the cyclic inter-groove spaces. The tilt quantity LT of the objective lens is estimated by the tilt side driving current or the tilt side driving voltage of the movable tilting means, and the set values of the coefficients β and γ are changed depending on whether the optical spot scans on the cyclic grooves or on the cyclic inter-groove spaces. 
     In the case where the optical detecting means is divided into two by a straight line corresponding to the rotational direction of the optical disk, a difference signal can be detected from these divided areas, and either the signal A or signal B can be a difference signal at the time when the optical spot scans on the cyclic grooves or the cyclic inter-groove spaces. Furthermore, when between the signal waveforms detected by the optical detecting means at the time when the optical spot scans near the cyclic pits a, the detection level of an envelope drawn by a signal waveform having a smaller detected light quantity is A 1  and the detection level of an envelope drawn by a signal waveform having a larger detected light quantity is A 2 , and between the signal waveforms detected by the optical detecting means at the time when the optical spot scans near the cyclic pits b, the detection level of an envelope drawn by a waveform having a smaller detected light quantity is B 1 , and the detection level of an envelope drawn by a waveform having a larger detected light quantity is B 2 , the signals A, B may be any one of A 1 −B 1 , A 2 −B 2 , and (A 2  −A 1 )−(B 2 −B 1 ). 
     Furthermore, in the case where the signal A is a difference signal, pits along the rotational direction of the optical disk are formed on the inner peripheral side of the optical disk, and the objective lens is tilted so that the detected signal amplitude at the time when the optical spot scans on these pits may be maximum, and moving to the groove part (or the inter-groove space part) while keeping this tilt, the output level (AO+β·LT) of the signal A at the time when b −γ·LT=0 is made is recorded, and after that, the signal A is replaced by (A−AO) and the control is performed. Herein, reference symbol AO denotes the offset quantity because of the relative positional error of the optical spot  10 S and the detector  9 . 
     According to the above described configuration, the tilt to the optical axis of the objective lens converging as a result of the control agrees with the tilting direction of the base material of the optical disk, and by each tilt, the third order coma aberration component of the optical spot on the signal surface is approximately cancelled by setting of the coefficient β. Furthermore, the alignment error to the cyclic grooves (or the cyclic inter-groove spaces) of the optical spot converging as a result of the control can be made approximately zero by setting of the coefficient γ. 
     Herein, concretely, if the tilt to the optical axis of the objective lens converging as a result of the control agrees with the tilting direction of the base material of the optical disk and by each tilt, the third order coma aberration component of the optical spot on the signal surface is suppressed to an aberration quantity of {fraction (1/10)} or less by setting of the coefficient β, the shortage of power at the time of recording, the degradation of the jitter at the time of reproduction, or the like is not a substantial problem. 
     Furthermore, concretely, if the alignment error to the cyclic grooves (or the cyclic inter-groove spaces) of the optical spot converging as a result of the control is suppressed to {fraction (1/20)} or less of the wavelength of the light source by setting of the coefficient γ, the partial elimination by the optical spot  16  of the adjacent signal marks at the time of recording, the increase of the cross-talk at the time of reproduction, the degradation of the jitter, or the like is not a substantial problem. 
     According to the above described present invention, for example, the tilt of the objective lens can accurately be controlled to have an angle at which the third order coma aberration can be cancelled even when there is a tilt in the optical disk, and in addition to that, the off-track quantity of the optical spot on the signal surface can be made zero. Accordingly, it is possible to solve the various problems created in the case where there is a tilt in the optical disk (elimination of the adjacent signal marks at the time of recording, degradation of the jitter because of the increasing of the cross-talk at the time of reproduction, or the like) and therefore, there is a large effect in realizing recording and reproduction of a signal with a high density. 
     Herein, the tilt of the objective lens in the present invention may be a relative tilt to the optical disk. 
     Herein, the present invention is a medium that holds a program and/or data for executing all or part of the functions of all or part of the above described means of the present invention by a computer, wherein the reading by a computer is possible, and the above described read program and/or data executes the above described functions working together with the above described computer. 
     Furthermore, the present invention is a medium that holds a program and/or data for executing all or part of the actions of all or part of the above described steps of the present invention by a computer, wherein the reading by a computer is possible, and the above described read program and/or data executes the above described actions working together with the above described computer. 
     Furthermore, the present invention is an information aggregate that is a program and/or data for executing all or part of the functions (or actions) of all or part of the above described means (or steps) of the present invention by a computer, wherein the reading by a computer is possible, and the above described read program and/or data executes the above described functions (or actions) working together with the above described computer. 
     Furthermore, the above described data includes the data structure, data format, types of data, or the like. 
     Furthermore, the above described medium includes a recording medium such as a ROM, a transmitting medium such as the internet, and a transmitting medium such as light, radio-wave, or sound-wave. 
     Furthermore, the above described holding medium includes, for example, a recording medium for recording a program and/or data, a transmitting medium for transmitting a program and/or data, or the like. 
     Furthermore, the possibility of being processed by a computer is, for example, the possibility of being read by a computer in the case of a recording medium such as a ROM, and it includes the fact that a program and/or data to be the object of transmission can be treated by a computer, as a result of the transmission in the case of a transmitting medium. 
     Furthermore, the above described information aggregate includes, for example, a software such as a program and/or data. 
     It is clear from the above description that the present invention has such an advantage that the off-track quantity or the occurrence of the third order coma aberration can be suppressed to a smaller one when compared with that of the prior art.