TECHNICAL FIELD

The present invention generally relates to information recording media, recording layer discriminating methods, recording layer discriminating apparatuses and optical disk apparatuses, and more particularly to an information recording medium having a plurality of recording layers, and a recording layer discriminating method and a recording layer discriminating apparatus for discriminating a recording layer that is an access target in such an information recording medium, and an optical disk apparatus having such a recording layer discriminating apparatus.

In addition, the present invention also relates more particularly to an information recording medium forming apparatus, an information recording medium forming method, an information detecting method, an information detecting apparatus, and an information recording medium apparatus.

BACKGROUND ART

Recently, due to progresses made in digital techniques and improvements made in data compression techniques, there is much attention on optical disks for storing information (hereinafter also referred to as â€œcontentsâ€ ) such as music, movies, photographs and computer software. The optical disks include compact disks (CDs), digital versatile disks (DVDs) capable of recording approximately 7 times the amount of data recordable on a CD having the same diameter as the DVD. Optical disk apparatuses which use the optical disks as the information recording medium have become popular as the optical disks have become less inexpensive.

The optical disk apparatus records information on or erases information from a spiral track or concentric tracks on the optical disk by irradiating laser light on a recording layer of the optical disk, and reproduces information from the spiral track or concentric tracks based on a reflected light (returned beam) from the recording layer. Hence, the optical disk apparatus is provided with an optical pickup unit that emits the laser light and receives the returned beam.

Generally, the optical pickup unit includes an objective lens, an optical system that guides the laser light emitted from a light source to the recording layer and guides the returned beam to a predetermined light receiving position, and a photodetector that is arranged at the light receiving position. The photodetector outputs signals including not only reproduced information of data recorded in the recording layer, but also information (servo information) necessary to control the position of the objective lens.

The amount of information of the contents is increasing every year, and there are demands to further increase the recording capacity of the optical disk. As one means of increasing the recording capacity of the optical disk, information recording media having a plurality of recording layers and apparatuses which use such information recording media as the access target have been developed. For example, such information recording media and apparatuses which use such information recording media as the access target are proposed in Japanese Laid-Open Patent Applications No. 2001-52342, No. 2002-74679, No. 2003-91874, No. 8-147762, No. 11-96568 and No. 2002-334448.

In order to control the position of the objective lens with respect to the information recording medium having a plurality of recording layers so that a light spot is accurately formed at a target position, it is necessary to accurately discriminate the recording layer on which the light spot is formed. In addition, in order to achieve a high-speed access, the position of the objective lens must be controlled at a high speed. However, according to the information recording media and the apparatuses proposed in the Japanese Laid-Open Patent Applications No. 2001-52342, No. 2002-74679, No. 2003-91874, No. 8-147762, No. 11-96568 and No. 2002-334448 referred above, it sometimes takes time to discriminate the recording layer on which the light spot is formed, and the access time may become long.

DISCLOSURE OF THE INVENTION

It is a general object of the present invention to provide a novel and useful information recording medium, recording layer discriminating method, recording layer discriminating apparatus and optical disk apparatus, in which the problem described above are suppressed.

A first object of the present invention is to provide an information recording medium that enables information for discriminating a recording layer to be acquired quickly and accurately.

A second object of the present invention is to provide a recording layer discriminating method and a recording layer discriminating apparatus that can quickly and accurately discriminate a recording layer on which a light spot is formed of a plurality of recording layers of an information recording medium.

A third object of the present invention is to provide an optical disk apparatus that can make a quick access to an information recording medium having a plurality of recording layers.

A more specific object of the present invention is to provide an information recording medium characterized by a plurality of information recordable recording layers, wherein a spiral or concentric tracks are formed on each of the plurality of recording layers, and at least a portion of each track has wobbles corresponding to a wobble signal that includes layer information for discriminating a recording layer on which the track is formed. According to the information recording medium of the present invention, it is possible to discriminate the recording layer on which a light spot is formed when accessing the information recording medium, by detecting the wobble signal based on reflected light from the wobbles and extracting the layer information from the wobble signal. In other words, it is possible to quickly and accurately acquire the information for discriminating the recording layer.

In this case, at least a portion of each track may have the wobbles corresponding to the wobble signal in which a layer information part including the layer information is modulated according to a predetermined modulation technique.

In this case, at least a portion of each track may have the wobbles corresponding to the wobble signal that further includes a carrier wave part for use in generating a reference clock.

In this case, the layer information part may be arranged between 2 carrier wave parts.

In the above information recording medium, predetermined synchronizing information may be recorded on each track at a predetermined synchronization period.

In this case, at least a portion of each track may have the wobbles corresponding to the wobble signal in which the layer information part is arranged at a period that is an integer multiple of the synchronization period.

In the above information recording medium, the layer information and the synchronizing information may be recorded on the track with mutually different formats.

In this case, the synchronizing information may be recorded on the track as formation of pits.

In the above information recording medium, at least a portion of each track may have the wobbles corresponding to the wobble signal that further includes the synchronizing information modulated according to a modulation technique different from that of the layer information part.

In this case, the layer information part and the synchronizing information part may have mutually different signal waveforms.

In the above information recording medium, the modulation technique may be a phase modulation technique.

In this case, the 1 period of a reference clock generated from the carrier wave part may amount to 1 wobble, the synchronization period may amount to 93 wobbles, and the layer information part may exist between a 12th wobble and an 88th wobble when the synchronizing information part starts from a 0th wobble.

In the above information recording medium, at least a portion of each track may have the wobbles corresponding to the wobble signal that further includes address information.

A further object of the present invention is to provide a recording layer discriminating method for discriminating a recording layer on which a light spot is formed when accessing the information recording medium described above, characterized in that the method comprises a first step acquiring the layer information from the wobble signal that is detected based on reflected light from the information recording medium; and a second step discriminating the recording layer on which the light spot is formed based on the layer information. According to the recording layer discriminating method of the present invention, the layer information is acquired solely from the wobble signal, and the layer information can be acquired more accurately and within a shorter time compared to the conventional method. As a result, with respect to the information recording medium having the plurality of recording layers, it is possible to quickly and accurately discriminate the recording layer on which the light spot is formed.

Another object of the present invention is to provide a recording layer discriminating method for discriminating a recording layer on which a light spot is formed when accessing the information recording medium described above, characterized in that the method comprises a first step acquiring the layer information and the address information based on reflected light from the information recording medium; and a second step discriminating the recording layer on which the light spot is formed based on the layer information and the address information. According to the recording layer discriminating method of the present invention, the layer information and the address information are acquired solely from the wobble signal, and the recording layer is discriminated based on the layer information and the address information. Hence, the recording layer can be discriminated more accurately and within a shorter time compared to the conventional method. In other words, with respect to the information recording medium having the plurality of recording layers, it is possible to quickly and accurately discriminate the recording layer on which the light spot is formed.

Still another object of the present invention is to provide a recording layer discriminating apparatus for discriminating a recording layer on which a light spot is formed when accessing the information recording medium described above, characterized in that the apparatus comprises demodulating means for demodulating the wobble signal that is detected based on reflected light from the information recording medium; and layer information detection means for detecting the layer information from the wobble signal that is demodulated. According to the recording layer discriminating apparatus of the present invention, the layer information is acquired solely from the wobble signal, and the layer information can be acquired more accurately and within a shorter time compared to the conventional method. As a result, with respect to the information recording medium having the plurality of recording layers, it is possible to quickly and accurately discriminate the recording layer on which the light spot is formed.

A further object of the present invention is to provide a recording layer discriminating apparatus for discriminating a recording layer on which a light spot is formed when accessing the information recording medium described above, characterized in that the apparatus comprises demodulating means for demodulating the wobble signal that is detected based on reflected light from the information recording medium; layer information detection means for detecting the layer information from the wobble signal that is demodulated; address information detection means for detecting the address information from the wobble signal that is demodulated; and discriminating means for discriminating the recording layer on which the light spot is formed based on the layer information and the address information. According to the recording layer discriminating apparatus of the present invention, the layer information and the address information are acquired solely from the wobble signal, and the recording layer is discriminated based on the layer information and the address information. Hence, the recording layer can be discriminated more accurately and within a shorter time compared to the conventional method. In other words, with respect to the information recording medium having the plurality of recording layers, it is possible to quickly and accurately discriminate the recording layer on which the light spot is formed.

In the above recording layer discriminating apparatus, the demodulating means may comprise a clock generating circuit generating a reference clock from the wobble signal; and a demodulating circuit demodulating the wobble signal based on the reference clock, and the layer information detection means may comprise a synchronizing information detection circuit detecting the synchronizing information; a counter counting a number of reference clocks using the synchronizing information as a starting point; and a layer information detection circuit detecting the layer information based on a counted value of the counter.

Another object of the present invention is to provide an optical disk apparatus for carrying out at least one of recording, reproduction and erasure of information with respect to an information recording medium, characterized in that the apparatus comprises a optical pickup unit forming a light spot on one of a plurality of recording layers via an objective lens, and receiving reflected light from said one of the plurality of recording layers; a recording layer discriminating apparatus described above, discriminating the recording layer on which the light spot is formed, based on the wobble signal that is detected from an output signal of the optical pickup unit; a servo control unit controlling a position of the objective lens based on the output signal of the optical pickup unit and an output signal of the recording layer discriminating apparatus; and a processing unit carrying out at least one of recording, reproduction and erasure of information via the optical pickup unit. According to the optical disk apparatus of the present invention, it is possible to accurately discriminate within a short time the recording layer on which the light spot is formed by the recording layer discriminating apparatus, and thus, it is possible to quickly and accurately control the position of the objective lens by the servo control unit. Consequently, the access, including at least reproduction, of the recording, reproduction and erasure of information with respect to the information recording medium having the plurality of recording layers, can be carried out at a high speed.

It is also a general object of the present invention to provide an information recording medium forming apparatus, information recording medium forming method, information detecting method, information detecting apparatus and information recording medium apparatus, which are suited for the information recording medium described above.

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a block diagram showing a structure of a first embodiment of an optical disk apparatus according to the present invention;

FIGS. 2A and 2B

respectively are diagrams for explaining recording layers of the optical disk shown in

FIG. 1

;

FIG. 3

is a diagram for explaining an information frame format of a wobble signal of the optical disk shown in

FIG. 2

;

FIG. 4

is a diagram for explaining a number of wobbles in the information frame shown in

FIG. 3

and at each part of the information frame;

FIGS. 5A and 5B

respectively are diagrams for explaining signal waveforms at a layer information part;

FIGS. 6A and 6B

respectively are diagrams for explaining signal waveforms at an address information part;

FIGS. 7A and 7B

respectively are diagrams for explaining signal waveforms at a synchronizing information part;

FIG. 8

is a diagram for explaining data bits of an address information part;

FIG. 9

is a diagram for explaining a structure of an optical pickup unit shown in

FIG. 1

;

FIG. 10

is a diagram for explaining a light receiver for a returned beam shown in

FIG. 9

;

FIG. 11

is a block diagram for explaining a structure of a reproduced signal processing circuit shown in

FIG. 1

;

FIG. 12

is a block diagram for explaining a structure of a wobble signal analyzing circuit shown in

FIG. 11

;

FIG. 13

is a timing chart for explaining functions of the wobble signal analyzing circuit;

FIG. 14

is a flow chart for explaining a recording process of the optical disk apparatus that is carried out in response to a recording request command from a host unit;

FIG. 15

is a flow chart for explaining a reproduction process of the optical disk apparatus that is carried out in response to a reproduction request command from the host unit;

FIG. 16

is a diagram for explaining a modulation technique for a wobble signal;

FIG. 17

is a diagram for explaining a modification of the wobble signal information format shown in

FIG. 3

;

FIG. 18

is a block diagram for explaining a modification of the wobble signal analyzing circuit shown in

FIG. 11

;

FIGS. 19A and 19B

respectively are diagrams for explaining an optical disk recorded with synchronizing information by formation of pits;

FIG. 20

is a block diagram for explaining a structure of the wobble signal analyzing circuit corresponding to the optical disk shown in

FIG. 19A

or 19B;

FIG. 21

is a diagram for explaining a structure of an optical disk recordable with information and to which a second embodiment of the present invention is applicable;

FIGS. 22A through 22C

respectively are diagrams for explaining a structure of the recordable optical disk;

FIG. 23

is a diagram for explaining a light receiving element and a signal processing circuit that detect various signals from recorded information on the optical disk;

FIG. 24

is a diagram for explaining an example of a wobble signal waveform employing a general wobble modulation technique;

FIGS. 25A through 25C

respectively are diagrams showing an example of the entire format when recording position information by wobble modulation;

FIG. 26

is a diagram for explaining particular wobble waveforms employing PSK, FSK and FSK+PSK modulations for the wobble waveform;

FIG. 27

is a diagram showing the wobble waveforms shown in

FIG. 26

in relation to the entire format;

FIG. 28

is a diagram showing an example of a structure of a signal detecting unit;

FIG. 29

is a diagram for explaining another example of the structure of the signal detecting unit;

FIG. 30

is a block diagram showing an example of a particular circuit structure of a clock generating means;

FIG. 31

is a diagram for explaining a signal distortion of a filtered output of the wobble signal at a modulating part;

FIGS. 32A and 32B

respectively are block diagrams showing an example of a particular circuit structure of first and second modulating means;

FIG. 33

is a timing chart showing various signals for a case where the wobble signal employing the FSK modulation is demodulated with respect to a second embodiment of a disk;

FIG. 34

is a timing chart showing various signals for a case where the wobble signal employing the FSK+PSK modulation is demodulated for the second embodiment of the disk;

FIG. 35

is a block diagram showing electrical connections of a second embodiment of an optical disk forming apparatus;

FIG. 36

is a flow chart for explaining an information recording medium forming method that is carried out by the optical disk forming apparatus;

FIG. 37

is a block diagram showing electrical connections of a second embodiment of the optical disk apparatus; and

FIG. 38

is a flow chart for explaining an information detecting method that is carried out by the optical disk apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of various embodiments of the present invention, by referring to the drawings.

First Embodiment

First, a description will be given of an embodiment of the information recording medium, the recording layer discriminating method, the recording layer discriminating apparatus and the optical disk apparatus according to the present invention, by referring to

FIGS. 1 through 15

FIG. 1

shows a general structure of an optical disk apparatus 20 as an embodiment of the present invention.

The optical disk apparatus 20 shown in

FIG. 1

includes a spindle motor 22 for driving and rotating an optical disk 15 that is used as an information recording medium in this embodiment, an optical pickup unit 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduced signal processing circuit 28, a servo controller 33, a buffer RAM 34, a buffer manager 37, an interface 38, a flash memory 39, a CPU 40, a RAM 41 and the like. Connection lines connecting the blocks in

FIG. 1

are merely shown to indicate the flow of representative signals and information, and not all connection relationships of the blocks are shown in

FIG. 1

For example, the optical disk 15 includes 2 recording layers (M1 and M2) on which information is recordable, as shown in

FIGS. 2A and 2B

, for example, and a spiral track or concentric tracks made up of a spiral or concentric grooves G and lands L are formed on each recording layer. At least a portion of each track has wobbles corresponding to a wobble signal that includes synchronizing information, address information and layer information.

The synchronizing information is the information that is used to detect recorded positions of the address information and the layer information. The address information is the information related to a physical address of the track. The layer information is the information that distinguishes whether the track is a track on the recording layer M1 or a track on the recording layer M2. For example, the optical disk 15 in this embodiment is adapted to laser light having a wavelength of approximately 660 nm.

For example, the wobble signal in this embodiment has a format in which 1 information frame is formed by a synchronizing information part that includes the synchronizing information, an address information part that includes the address information, a carrier wave part for reference clock formation, a layer information part that includes the layer information, and a carrier wave part for reference clock formation, as shown in

FIG. 3

. If 1 period of the reference clock generated from the carrier wave is regarded as 1 wobble, the information frame has a size amounting to 93 wobbles (wobble numbers 0 through 92) as shown in

FIG. 4

, for example. In other words, a synchronization period of the synchronizing information part amounts to 93 wobbles. The wobble numbers 0 through 3 correspond to the synchronizing information part, the wobble numbers 4 through 7 correspond to the address information part, the wobble numbers 8 through 25 correspond to the carrier wave part, the wobble number 26 corresponds to the layer information part, and the wobble numbers 27 through 92 correspond to the carrier wave part. That is, the synchronizing information part amounts to 4 wobbles, the address information part amounts to 4 wobbles, the layer information part amounts to 1 wobble, and the carrier wave part is provided before and after the layer information part. Each of the information parts described above is modulated according to a phase modulation technique (PSK: Phase Shift Keying). Since the synchronizing information part must be clearly distinguished from the other information parts, the synchronizing information part has a signal waveform having an appearing frequency that is extremely low in the other information parts.

For example, the layer information part in this embodiment has a phase that is the same as that of the carrier wave part in the recording layer M1 as shown in

FIG. 5A

, and has a phase that is inverted with respect to that of the carrier wave part in the recording layer M2 as shown in

FIG. 5B

For example, the address information part represents 1 bit of data by 4 wobbles, similarly as in the case of the DVD. If the bit data is â€œ0â€ , for example, the preceding 2 wobbles are made to be the same phase as the carrier wave part and the subsequent 2 wobbles are made to be the inverted phase of the carrier wave part as shown in

FIG. 6A

. On the other hand, if the bit data is â€œ1â€ , the preceding 2 wobbles are made to be the inverted phase of the carrier wave part and the subsequent 2 wobbles are made to be the same phase as the carrier wave part as shown in

FIG. 6B

. 51 bits are required as address data.

In the synchronizing information part, if the address information part of the next information frame is the starting bit of the address data, a word synchronizing signal, that is, all 4 wobbles are made to be the inverted phase of the carrier wave part as shown in

FIG. 7A

, for example. In addition, if the address information part includes the bit data, a bit synchronizing signal, that is, 1 starting wobble is made to be the inverted phase of the carrier wave part and the remaining 3 wobbles are made to be the same phase as the carrier wave part.

Accordingly, in this embodiment, 1 address information is obtained from 52 information frames, as shown in

FIG. 8

. As one example, the address following the last address of the track on the recording layer M1 is the first address of the track on the recording layer M2 in this embodiment. More particularly, addresses 00000H through 10000H are allocated to the tracks of the recording layer M1, and addresses 10001H through 20000H are allocated to the tracks of the recording layer M2.

The optical pickup unit 23 irradiates laser light on a recording surface of the optical disk 51 having the spiral or concentric tracks formed thereon, and receives reflected light from the recording surface. As shown in

FIG. 9

, for example, the optical pickup unit 23 includes a light source unit 51, a collimator lens 52, a beam splitter 54, an objective lens 60, 2 detection lenses 58 and 72, 2 light receivers 59 and 73, a reflecting mirror 71, a driving system (not shown) and the like. The driving system includes a focusing actuator, a tracking actuator and a seek motor.

The light source unit 51 includes a semiconductor laser 51a that is used as a light source and emits the laser light having a wavelength of 660 nm. In this embodiment, a maximum intensity emission direction of a bundle of rays of the laser light (hereinafter simply referred to as a â€œbeamâ€ ) emitted from the light source unit 51 is regarded as being a +X direction. The collimator lens 52 is arranged on the +X side of the light source unit 51, and forms the laser beam from the light source unit 51 into approximately parallel light. The reflecting mirror 71 is arranged in a vicinity of the collimator lens 52, and reflects a portion of the laser beam emitted from the light source unit 51 in a âˆ’Z direction as a monitoring beam.

The beam splitter 54 is arranged on the +X side of the collimator lens 52, and transmits as it is the beam that is formed into the approximate parallel light by the collimator lens 52. In addition, the beam splitter 54 deflects the beam (return beam) that is reflected by the optical disk 15 and is received via the objective lens 60 in the âˆ’Z direction. The objective lens 60 is arranged on the +X side of the beam splitter 54, and converges the beam transmitted through the beam splitter 54 on the recording surface of the optical disk 15. The detection lens 58 is arranged on the âˆ’Z side of the beam splitter 54, and converges the return beam that is deflected in the âˆ’Z direction by the beam splitter 54 on a light receiving surface of the light receiver 59.

Similarly to a normal optical disk apparatus, a 4-part light receiving element shown in

FIG. 10

made up of 4 light detecting parts 59a, 59b, 59c and 59d may be used as the light receiver 59. In this case, a Y direction approximately matches a tangential direction to the track on the optical disk 15. Each of the light detecting parts 59a, 59b, 59c and 59d generates a current signal according to an amount of light received by making a photoelectric conversion, and outputs the generated current signal to the reproduced signal processing circuit 28.

The detection lens 72 is arranged on the âˆ’Z side of the reflecting mirror 71, and converges the monitoring beam that is reflected in the âˆ’Z direction by the reflecting mirror 71 on a light receiving surface of the light receiver 73. The light receiver 73 generates a current signal depending on an amount of light received by making a photoelectric conversion, and outputs the generated current signal to the laser control circuit 24 as a power monitor signal.

The reproduced signal processing circuit 28 includes an I/V amplifier 28a, a servo and wobble signal detection circuit 28b, a wobble signal analyzing circuit 28c, an RF signal detection circuit 28d, a decoder 28e and the like, as shown in

FIG. 11

The I/V amplifier 28a includes an amplifier a1 for converting the current signal from the light receiving part 59a into a voltage signal Sa, an amplifier a2 for converting the current signal from the light receiving part 59b into a voltage signal Sb, an amplifier a3 for converting the current signal from the light receiving part 59c into a voltage signal Sc, and an amplifier a4 for converting the current signal from the light receiving part 59d into a voltage signal Sd.

The servo and wobble signal detection circuit 28b includes 5 adders ad1, ad2, ad3, ad4 and ad5, 2 subtractors sb1 and sb2, 3 lowpass filters lp1, lp2 and lp3, and a highpass filter hp.

The adder ad1 adds the signals Sa and Sd, and the adder ad2 adds the signals Sb and Sc. The adder ad3 ads the signals Sa and Sc, and the adder ad4 adds the signals Sb and Sd. In other words, an output signal Sa+Sd is obtained from the adder ad1, and an output signal Sb+Sc is obtained from the adder ad2. In addition, an output signal Sa+Sc is obtained from the adder ad3, and an output signal Sb+Sd is obtained from the adder ad4.

The adder ad5 adds the output signal of the adder ad1 and the output signal of the adder ad2. In other words, an output signal Sa+Sb+Sc+Sd is obtained from the adder ad5. This output signal of the adder ad5 is supplied to the lowpass filter lp1.

The subtractor sb1 subtracts the output signal of the adder ad2 from the output signal of the adder ad1. In other words, an output signal {(Sa+Sd)âˆ’(Sb+Sc)} is obtained from the subtractor sb1. This output signal of the subtractor sb1 is supplied to the wobble signal analyzing circuit 28c, the lowpass filter lp2 and the highpass filter hp.

The subtractor sb2 subtracts the output signal of the adder ad4 from the output signal of the adder ad3. In other words, an output signal {(Sa+Sc)âˆ’(Sb+Sd)} is obtained from the subtractor sb2. This output signal of the subtractor sb2 is supplied to the lowpass filter lp3.

The lowpass filter lp1 is arranged in a stage subsequent to the adder ad5, and eliminates a high-frequency component that is included in the output signal of the adder ad5. An output signal of the lowpass filter lp1 is supplied to the servo controller 33 as a track cross signal Stc.

The lowpass filter lp2 is arranged in a stage subsequent to the subtractor sb1, and eliminates a high-frequency component that is included in the output signal of the subtractor sb1. An output signal of the lowpass filter lp2 is supplied to the servo controller 33 as a track error signal Ste.

The highpass filter hp is arranged in a stage subsequent to the subtractor sb1, and eliminates a low-frequency component that is included in the output signal of the subtractor sb1. An output signal of the highpass filter hp is supplied to the wobble signal analyzing circuit 28c as a wobble signal Swb.

The lowpass filter lp3 is arranged in a stage subsequent to the subtractor sb2, and eliminates a high-frequency component that is included in the output signal of the subtractor sb2. An output signal of the lowpass filter lp3 is supplied to the servo controller 33 as a focus error signal Sfe.

The RF signal detection circuit 28d is a high band circuit, and detects an RF signal Srf by adding the signals Sa, Sb, Sc and Sd. The detected RF signal Srf is supplied to the decoder 28e and the wobble signal analyzing circuit 28c.

The decoder 28e carries out a decoding process, an error detection process and the like with respect to the RF signal Srf, and stores the processed data in the buffer RAM 34 via the buffer manager 37 as reproduced data. The decoder 28e also carries out a predetermined error correction process when an error is detected by the error detection process.

The wobble signal analyzing circuit 28c includes a clock generating circuit c1, a demodulating circuit c2, a synchronization detection circuit c3, a counter c4, an address detection circuit c5, a layer information detection circuit c6 and the like, as shown in

FIG. 12

The clock generating circuit c1 includes a bandpass filter c11 for extracting a carrier wave component that is included in the wobble signal Swb, a binarization circuit c12 for binarizing an output signal of the bandpass filter c11, a phase locked loop (PLL) circuit c13 for stabilizing the period of an output signal of the binarization circuit c12 and the like. An output signal of the PLL circuit c13 is supplied to the encoder 25, the demodulating circuit c2 and the like as a reference clock signal Wck shown in

FIG. 13

The demodulating circuit c2 includes a highpass filter c21, a lowpass filter c22, a sinusoidal wave generating circuit c23, a multiplier c24, an integration circuit c25, a sample and hold (S/H) circuit c26, a timing signal generating circuit c27 and the like.

The highpass filter c21 eliminates low-frequency noise that is included in the wobble signal Swb. The lowpass filter c22 eliminates high-frequency noise that is included in an output signal of the highpass filter c21. As shown in

FIG. 13

, for example, the sinusoidal wave generating circuit c23 generates a sinusoidal wave Ssin having the reference clock frequency based on the reference clock signal Wck from the clock generating circuit c1. The multiplier c24 multiplies an output signal of the lowpass filter c22 and the sinusoidal wave Ssin that is generated by the sinusoidal wave generating circuit c23. Hence, a phase-modulated wave component is extracted.

As shown in

FIG. 13

, for example, the integration circuit c25 integrates an output signal Smul of the multiplier c24 for every period of the reference clock signal Wck. This integration circuit c25 is reset by a reset signal Srst from the timing signal generating circuit c27. As shown in

FIG. 13

, for example, the S/H circuit c26 performs a sample and hold with respect to an output signal Sintg of the integration circuit c25 in synchronism with a timing signal Ssh from the timing signal generating circuit c27. In this particular case, the signal Sintg is sampled at a rise timing of the reference clock signal Wck. An output signal of the S/H circuit c26 is supplied to the synchronization detection circuit c3, the address detection circuit c5 and the layer information detection circuit c6 as a demodulated signal Sdm.

The synchronization detection circuit c3 judges whether or not the demodulated signal Sdm corresponds to the synchronizing information part. If the demodulated signal Sdm corresponds to the starting part of the synchronizing information part, the synchronization detection circuit c3 sets â€œ0â€ to a counted value of the counter c4. In addition, if the demodulated signal Sdm does not correspond to the starting part of the synchronizing information part, the synchronization detection circuit c3 increments the counted value of the counter c4 by +1. In other words, a value that indicates the place or position of the demodulated signal Sdm in terms of the period of the reference clock signal Wck (for example, nth period of the reference clock signal Wck) using the starting part of the synchronizing information part as a starting point.

The address detection circuit c5 refers to the counted value of the counter c4, and extracts the demodulated signal Sdm when the address detection circuit c5 judges that the demodulated signal Sdm corresponds to the address information part. In this particular case, the demodulated signal Sdm is extracted when the counted value of the counter c4 is â€œ4â€ to â€œ7â€ . When the demodulated signal Sdm extracted by the address detection circuit c5 reaches a predetermined amount (that is, amounts to 52 data bits in this particular case), the address detection circuit c5 acquires address data from the extracted demodulated signal Sdm. The acquired address data is output to the CPU 40 as an address signal Sad.

The layer information detection circuit c6 refers to the counted value of the counter c4, and extracts the demodulated signal Sdm when the layer information detection circuit c6 judges that the demodulated signal Sdm corresponds to the layer information part. In this particular case, the demodulated signal Sdm is extracted when the counted value of the counter c4 is â€œ26â€ . The layer information detection circuit c6 generates a layer signal Slay based on the extracted demodulated signal Sdm, and outputs this layer signal Slay to the servo controller 33. In this particular case, the layer signal Slay indicates the recording layer M1 when the extracted demodulated signal Sdm has a high level, and indicates the recording layer M2 when the extracted demodulated signal Sdm has a low level.

Returning now to the description of

FIG. 1

, the servo controller 33 generates a focus control signal for correcting the focus error, based on the focus error signal Sfe from the servo and wobble signal detection circuit 28b and the layer signal Slay from the wobble signal analyzing circuit 28c. In addition, the servo controller 33 generates a tracking control signal for correcting the tracking error, based on the track error signal Ste from the servo and wobble signal detection circuit 28b. The control signals generated by the servo controller 33 are output to the motor driver 27 when the servo is ON, and is not output when the servo is OFF. The servo ON state and the servo OFF state are set by the CPU 40.

The motor driver 27 outputs a driving signal for the focusing actuator to the optical pickup unit 23 based on the focus control signal described above, and outputs a driving signal for the tracking actuator to the optical pickup unit 23 based on the tracking control signal described above. In other words, the tracking control and the focus control are carried out by the servo and wobble signal detection circuit 28b, the servo controller 33 and the motor driver 27. In addition, the motor driver 27 outputs driving signals for the spindle motor 22 and the seek motor based on the control signals from the CPU 40.

The buffer RAM 34 includes a buffer region and a variable region. The buffer region temporarily stores the data to be recorded on the optical disk 15 (recording data), the data reproduced from the optical disk 15 (reproduced data) and the like. The variable region stores various program variables and the like. The buffer manager 37 manages the data input to and the data output from the buffer RAM 34, and notifies the CPU 40 when the amount of data stored in the buffer region reaches a predetermined amount.

The encoder 25 obtains the recording data recorded in the buffer RAM 34 via the buffer manager 37 based on an instruction from the CPU 40, carries out a data modulation, addition of an error correction code and the like, to generate a write signal that is to be written on the optical disk 15. The generated write signal is output to the laser control circuit 24 together with the reference clock signal described above.

The laser control circuit 24 generates a driving signal for the semiconductor laser 51a based on a light emission characteristic of the semiconductor laser 51a, the power monitor signal described above, the write signal from the encoder 25, the reference clock signal and the like. The interface 38 forms a bidirectional or two-way communication interface between the optical disk apparatus 20 and a host unit. For example, the interface 38 is in conformance with the AT Attachment Packet Interface (ATAPI) standards.

The flash memory 39 includes a program region and a data region. The program region stores programs that are written in codes decodable by the CPU 40. The data region stores information related to the light emission characteristic of the semiconductor laser 51a, information related to a seek operation (hereinafter referred to as â€œseek informationâ€ ), recording strategy information and the like.

The CPU 40 controls the operation of various parts of the optical disk apparatus 20 according to the programs stored in the program region of the flash memory 39. In addition, the CPU 40 stores data necessary for the control and the like to the variable region of the buffer RAM 34 and the RAM 41.

Next, a description will be given of a process (recording process) of the optical disk apparatus 20 when a recording request command is received from the host unit, by referring to

FIG. 14

. A flow chart shown in

FIG. 14

corresponds to a series of processing algorithms executed by the CPU 40. When the recording request command is received from the host unit, a starting address of the program corresponding to the flow chart shown in

FIG. 14

is set in a program counter of the CPU 40, and the recording process starts.

In a first step 501, a control signal for rotating the spindle motor 22 is output to the motor driver 27 based on a recording velocity, and a notification indicating that the recording request command was received from the host unit is made to the reproduced signal processing circuit 28. In addition, the buffer manager 37 is instructed to store the data (recording data) received from the host unit into the buffer RAM 34.

In a step 503, the servo ON state is set with respect to the servo controller 33 when it is confirmed that the rotation of the optical disk 15 has reached a predetermined linear velocity. As a result, the tracking control and the focus control are carried out as described above. The tracking control and the focus control are carried out at all times until the recording process ends.

In a step 505, an optimum power control (OPC) is carried out based on the recording velocity, so as to acquire an optimum recording power. In other words, the recording power is varied in steps, while a test write of predetermined data is made in a test write region that is referred to as a power calibration area (PCA), and the data is successively reproduced. For example, in a case where an asymmetry value detected from the RF signal approximately matches a target value that is obtained in advance by experiments or the like, it is judged that the recording quality is the highest in this case, and the recording power for this case is regarded as the optimum recording power.

In a step 507, a present address is acquired based on the address signal Sad. In a next step 509, a difference (address difference) between the present address and a target address that is extracted from the recording request command is calculated. In a step 511, a judgement is made based on the address difference to determine whether or not a seek is necessary. In this particular case, a reference is made to a threshold value that is stored in the flash memory 39, as the seek information described above, and the judgement result in the step 511 becomes YES and the process advances to a step 513 if the address difference exceeds the threshold value.

In the step 513, a control signal for the seek motor, according to the address difference, is output to the motor driver 27. Accordingly, the seek motor is driven, the seek operation is carried out, and the process returns to the step 507.

If the address difference does not exceed the threshold value and the judgement result in the step 511 is NO, the process advances to a step 515.

In the step 515, a judgement is made to determine whether or not the present address matches the target address. If the present address and the target address do not match and the judgment result in the step 515 is NO, the process advances to a step 517. In the step 517, the present address is acquired based on the address signal Sad, and the process returns to the step 515.

The processes of the steps 515 through 517 are repeated until the judgement result in the step 515 becomes YES.

If the present address and the target address match and the judgement result in the step 515 is YES, the process advances to a step 519. In the step 519, the encoder 25 is permitted to write. Hence, the recording data is written on the optical disk 15 via the encoder 25, the laser control circuit 24 and the optical pickup unit 23. When all of the recording data are written, the recording process ends after carrying out a predetermined ending process.

A description will be given of a process (reproduction process) of the optical disk apparatus 20 when a reproduction request command is received from the host unit, by referring to

FIG. 15

. A flow chart shown in

FIG. 15

corresponds to a series of processing algorithms executed by the CPU 40. When the reproduction request command is received from the host unit, a starting address of the program corresponding to the flow chart shown in

FIG. 15

is set in a program counter of the CPU 40, and the reproduction process starts.

In a first step 701, a control signal for rotating the spindle motor 22 is output to the motor driver 27 based on a reproducing velocity, and a notification indicating that the reproduction request command was received from the host unit is made to the reproduced signal processing circuit 28.

In a step 703, the servo ON state is set with respect to the servo controller 33 when it is confirmed that the rotation of the optical disk 15 has reached a predetermined linear velocity. As a result, the tracking control and the focus control are carried out as described above. The tracking control and the focus control are carried out at all times until the reproduction process ends.

In a step 705, a present address is acquired based on the address signal Sad. In a step 707, a difference (address difference) between the present address and a target address that is extracted from the reproduction request command is calculated. In a step 709, a judgement is made based on the address difference to determine whether or not a seek is necessary, similarly to the step 511. The judgement result in the step 709 becomes YES and the process advances to a step 711 if the seek is necessary. In the step 711, a control signal for the seek motor, according to the address difference, is output to the motor driver 27, and the process returns to the step 705. On the other hand, the judgement result in the step 709 becomes NO and the process advances to a step 713 if the seek is not necessary.

In the step 713, a judgement is made to determine whether or not the present address matches the target address. If the present address and the target address do not match and the judgment result in the step 713 is NO, the process advances to a step 715. In the step 715, the present address is acquired based on the address signal Sad, and the process returns to the step 713.

The processes of the steps 713 through 715 are repeated until the judgement result in the step 713 becomes YES.

If the present address and the target address match and the judgement result in the step 713 is YES, the process advances to a step 717. In the step 717, the reproduced signal processing circuit 28 is instructed to read. Hence, the reproduced data is acquired by the reproduced signal processing circuit 28 and stored in the buffer RAM 34. The reproduced data is transferred to the host unit via the buffer manager 37 and the interface 38 in units of sectors. When the reproduction of all of the data instructed from the host unit ends, the reproduction process ends after carrying out a predetermined ending process.

As may be seen from the description above, in the optical disk apparatus 20 according to this embodiment, the recording layer discriminating apparatus is formed by the wobble signal analyzing circuit 28c, and the servo control apparatus is formed by the servo controller 33 and the motor driver 27.

In addition, the processing apparatus is realized by the CPU 40 and the program executed by the CPU 40. However, the present invention is of course not limited to such. In other words, the embodiment described above is only one example, and at least a portion of the processing apparatus that is realized by the CPU 40 and the program executed by the CPU 40 may be formed by hardware or, the processing apparatus in its entirety may be formed by hardware.

The recording layer discriminating method according to this embodiment is realized by the processing operation of the wobble signal analyzing circuit 28c.

As described above, according to the optical disk 15 according to this embodiment, 2 information recordable recording layers are provided, and the spiral or concentric tracks are formed on each of the recording layers. In addition, at least a portion of each track has wobbles corresponding to the wobble signal that includes the layer information for discriminating the recording layer on which the track is formed. Hence, when accessing the optical disk 15, the wobble signal is detected based on the reflected light from the wobble portion, and the recording layer on which the light spot is formed can be discriminated by extracting the layer information from the wobble signal. In other words, it is possible to quickly and accurately acquire the information for discriminating the recording layer.

Since the wobble signal includes the carrier wave part for the reference clock generation, it is easy to demodulate the wobble signal.

Because the layer information part and the synchronizing information part have mutually different signal waveforms, the synchronizing information part can be detected accurately.

The wobble signal includes the carrier wave part before and after the layer information part. For this reason, it is possible to prevent the generating accuracy from deteriorating when generating the reference clock signal.

If 1 period of the reference clock generated from the carrier wave part corresponds to 1 wobble, the synchronizing period is 93 wobbles. If the starting part of the synchronizing information part is regarded as the 0th wobble, the layer information part exists between the 12th wobble and the 88th wobble, and it is possible to prevent the generating accuracy from deteriorating when generating the reference clock signal.

According to the wobble signal analyzing circuit 28c of this embodiment, the wobble signal that is detected based on the reflected light from the optical disk 15 is demodulated in the clock generating circuit c1 and the demodulating circuit c2, and the layer information is detected from the demodulated wobble signal in the synchronization detection circuit c3, the counter c4 and the layer information detection circuit c6. In other words, because the layer information is acquired solely from the wobble signal, it is possible to more accurately acquire the layer information within a shorter time compared to the conventional method. As a result, in the information recording medium having a plurality of recording layers, it is possible to quickly and accurately discriminate the recording layer on which the light spot is formed.

According to the optical disk apparatus 20 of this embodiment, it is possible to quickly and accurately control the position of the objective lens because the recording layer on which the light spot is formed can be discriminated by the wobble signal analyzing circuit 28c within a short time. As a result, it is possible to quickly access the information recording medium having the plurality of recording layers, at least for the reproduction of the information from the information recording medium, of the recording of information on, reproduction of the information from and erasure of the information from the information recording medium.

In the embodiment described above, each information part of the wobble signal is phase-modulated, but the present invention is not limited to such. For example, it is possible to employ the Frequency Shift Keying (FSK) modulation, the sawtooth modulation, Minimum Shift Keying (MSK) modulation, ON-OFF modulation or the like as shown in

FIG. 16

. In this case, the wobble signal analyzing circuit 28c must employ a detection method suited for the modulation technique that is employed. In addition, from the point of view of the stability of the reference clock signal, it is preferable also in this case to provide the carrier wave part between the address information part and the layer information part.

In the embodiment described above, the modulation technique used for the synchronizing information part and the modulation technique used for the layer information part are the same. However, the present invention is not limited to such, and the modulation technique used for the synchronizing information part and the modulation technique used for the layer information part may be different.

Moreover, in the embodiment described above, the layer information part and the synchronizing information part have mutually different signal waveforms. However, the layer information part and the synchronizing information part may have the same signal waveform provided that it is possible to positively separate th