JP3597188B1 - optical disk - Google Patents

Abstract

An optical disk capable of acquiring information required for recording and reproduction with high accuracy is provided.
A spiral recording track has a recording surface formed to meander including a predetermined phase modulation wave portion and a carrier wave portion, and the carrier wave portion is moved in a direction orthogonal to a tangential direction of the track. is formed so as to periodically portion _{(R 2 1, R 2 2} ) adjacent to the phase modulated wave part is smaller than the amplitude of the portion not adjacent to the phase modulated wave part. Thus, in the optical disk device using this optical disk as an access target medium, when reproducing the phase-modulated wave portion, the signal from the carrier wave portion adjacent in the direction orthogonal to the tangential direction of the track is converted from the signal from the phase-modulated wave portion. Is suppressed, it is possible to accurately demodulate the signal from the phase modulation wave part, it is possible to correctly obtain the information necessary for recording and reproduction included in the phase modulation wave part Become.
[Selection diagram] FIG.

Description

  The present invention relates to an optical disc, and more particularly, to an optical disc having a recording surface on which spiral or concentric information recording tracks are formed.

  2. Description of the Related Art In recent years, with the advance of digital technology and improvement of data compression technology, CDs (compact discs) and CDs have been used as media for recording information (hereinafter, also referred to as “contents”) such as music, movies, photographs, and computer software. Optical disks, such as DVDs (digital versatile discs), capable of recording data equivalent to about seven times the size of data on a disk having the same diameter as a CD, have attracted attention. The optical disk device which performs is becoming widespread.

  So-called write-once optical discs such as CD-R (CD-recordable), DVD-R (DVD-recordable) and DVD + R (DVD + recordable), CD-RW (CD-rewritable), DVD-RW (DVD-rewritable) and DVD + RW ( On a recording surface of a so-called rewritable optical disk such as a DVD + rewritable), guide grooves called grooves are formed to meander. In the optical disk device, the recording surface of the optical disk is irradiated with laser light via an objective lens, and the laser light reflected on the recording surface is received by a photodetector, and the output signal of the photodetector corresponds to the meandering shape of the groove. A wobble signal is detected.

  However, the optical disc has a high recording density and a small interval (track pitch) between adjacent tracks. For example, when the wavefront aberration increases, an optical spot formed on the recording surface is referred to as a target track (hereinafter simply referred to as a “target track”). ), It is difficult to narrow down to only the adjacent track (hereinafter, abbreviated as “adjacent track”) in some cases. In this case, crosstalk from the adjacent track (unnecessary signal leakage: crosstalk) occurs, and the detected wobble signal is a signal in which the wobble signal of the adjacent track is superimposed on the wobble signal of the target track. Therefore, when the phase of the wobble signal of the target track and the phase of the wobble signal of the adjacent track are substantially the same, the amplitude of the detected wobble signal increases, while the phase of the wobble signal of the target track and the phase of the adjacent track are different. When the phases of the wobble signals are substantially opposite to each other, the amplitude of the detected wobble signal becomes small. Normally, adjacent tracks have different distances from the center of rotation, and as shown in FIG. 10 as an example, the relationship between the phase of the wobble signal of the target track and the phase of the wobble signal of the adjacent track fluctuates almost periodically. I do.

  For example, when the wobble signal has a carrier for generating a reference clock signal and a phase modulation wave including ADIP (Address in Pregroove) information, such as a DVD + R or DVD + RW, the carrier of the wobble signal of the target track is FIG. 11 shows an example in which the phase (hereinafter also referred to as “target track carrier” for convenience) and the phase of the carrier in the wobble signal of the adjacent track (hereinafter also referred to as “adjacent track carrier”) are substantially the same. As described above, the detected wobble signal (signal B) has a larger amplitude of the carrier wave portion and a smaller amplitude of the phase modulation wave portion than the wobble signal (signal A) of the target track. Usually, a circuit for detecting the wobble signal is provided with an AGC amplifier circuit for keeping the signal level of the carrier wave section constant. A signal (signal C) output from the AGC amplifier circuit is a phase modulated wave. The amplitude of the part is even smaller. Therefore, it is difficult to accurately demodulate the phase modulated wave. That is, the detection accuracy of the ADIP information is reduced, which may adversely affect recording and reproduction.

  Therefore, various methods and devices have been devised for reducing the influence of crosstalk in a wobble signal (for example, see Patent Documents 1 to 4).

  As the use of optical discs becomes more general, there is an increasing demand from users for higher access speeds. However, when the access speed is further increased, the crosstalk in the wobble signal increases with the access speed, and the method disclosed in Patent Documents 1 to 4 below may not be able to sufficiently reduce the influence of the crosstalk. .

  Recently, an optical disk device using a semiconductor laser (blue laser) having an oscillation wavelength of about 405 nm has been vigorously developed. The track pitch of an optical disk corresponding to this optical disk device is less than half that of a conventional DVD, and it is expected that the methods disclosed in Patent Literatures 1 to 4 below cannot cope with the problem.

JP-A-2002-190116 JP 2000-357344 A JP-A-2003-123321 JP 2002269975 A

  The present invention has been made under such circumstances, and an object of the present invention is to provide an optical disc capable of accurately acquiring information necessary for recording and reproduction.

  According to the first aspect of the present invention, a spiral or concentric information recording track is formed in a meandering manner including a phase modulation wave portion containing predetermined information and a carrier wave portion for generating a clock signal. Wherein the amplitude of a portion adjacent to the phase modulation wave portion is smaller than the amplitude of a portion not adjacent to the phase modulation wave portion in a direction orthogonal to a tangential direction of the track in the carrier wave portion. It is an optical disk.

  According to this, the optical disc of the present invention has a recording surface in which a spiral or concentric recording track is formed to meander including a phase modulation wave portion and a carrier wave portion, and the carrier wave portion is formed of a track. In the direction orthogonal to the tangential direction, the amplitude of a portion adjacent to the phase modulation wave portion is smaller than the amplitude of a portion not adjacent to the phase modulation wave portion. Therefore, in an optical disc apparatus using this optical disc as an access target medium, when reproducing the phase-modulated wave portion, a signal from a carrier wave portion adjacent in a direction orthogonal to the tangential direction of the track is converted into a signal from the phase-modulated wave portion. Superposition can be suppressed. Thereby, it is possible to accurately demodulate the signal from the phase modulation wave unit, and to correctly acquire information included in the phase modulation wave unit. Therefore, information necessary for recording and reproduction can be obtained with high accuracy.

  In this case, as in the optical disk according to claim 2, the phase modulation wave portion and the carrier wave portion each have a fixed length, and the track meandering includes a plurality of pairs of the phase modulation wave portion and the carrier wave portion. It may be configured to include a set.

  In this case, as in the optical disk according to the third aspect, the track is spiral, and the track is divided by a length corresponding to one rotation starting from a meandering start position on the inner peripheral side of the track. When the first partial track, the second partial track,..., And the Y-th partial track are sequentially arranged from the inner peripheral side, each of the partial tracks may include at least one set of the above-described sets.

  In this case, as in the optical disc according to claim 4, the carrier wave portion in the Xth (2 ≦ X <Y) partial track of the track is a portion adjacent to the phase modulation wave portion included in the (X + 1) th partial track. And a second region including a portion adjacent to the phase modulation wave portion included in the X-1 partial track.

  In this case, as in the optical disk according to claim 5, the length n of the phase modulation wave portion, the length m of the carrier wave portion, and the length of the first partial track are set in units of the length of one cycle of the carrier wave. Using the length k, the difference L between the lengths of the adjacent partial tracks, and the remainder j of k ÷ (n + m), starting from the leading position of the phase-modulated wave portion in the X-th partial track, the first region is ｛ j− (X−2) · L} to {j− (X−2) · L + n}, and the second region is {n + m + 1−j + (X−2) · L} to {2n + m + 1−j + (X -2) · L}.

  In this case, as in the optical disk according to claim 6, the carrier wave portion in the first partial track has a region including a portion adjacent to a phase modulation wave portion included in a second partial track. Are represented by (j + L) to (j + L + n) starting from the head position of the phase-modulated wave part in the first partial track, and the carrier wave part in the Y-th partial track is the phase included in the Y-1 partial track. It has a region including a portion adjacent to the modulation wave portion, and this region starts from the leading position of the phase modulation wave portion in the Yth partial track and starts from {n + m + 1-j + (Y-2) .L} to {2n + m + 1}. −j + (Y−2) · L}.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 schematically shows a cross-sectional shape of an optical disk 15 according to an embodiment of the present invention. In the present embodiment, it is assumed that the optical disk 15 conforms to the DVD + R standard as an example.

  In the recording layer M of the optical disk 15 shown in FIG. 1, a groove G as a spiral guide groove is formed. Generally, in an optical disk, when viewed from the incident direction of laser light, a convex portion is called a groove G, and a concave portion is called a land L. Here, the groove G is a track for recording information, and data is recorded in the groove G. The groove G is wobbling with respect to the center of the track as shown in FIG. 2 as an example. The track pitch is 0.74 μm. Further, as shown in FIG. 3, the position where the distance Nr from the rotation center of the optical disk 15 is 22.000 mm is the meandering start position.

  According to the DVD + R standard, the meandering shape of the track includes a plurality of sets of a phase modulation wave part and a carrier wave part, as shown in FIG. 4 as an example. This phase modulation wave section contains various information. The carrier part is used to form a reference clock signal. In the present embodiment, each of the phase modulation wave part and the carrier wave part has a fixed length, and a set of the phase modulation wave part and the carrier wave part is called an information frame.

  Assuming that the size of one information frame is one wobble, assuming that the size of one cycle (also referred to as a wobble cycle) of a meandering shape (hereinafter also referred to as a “carrier shape” for convenience) in a carrier part is one wobble. 93 wobbles (wobble numbers 0 to 92). Wobble numbers 0 to 7 are phase modulation wave parts, and wobble numbers 8 to 92 are carrier wave parts. That is, the length of the phase modulation wave part is 8 wobbles, and the length of the carrier wave part is 85 wobbles.

  As an example, as shown in FIG. 6, the optical disk 15 starts a meandering start position on the inner circumference side of the track, that is, a position where the distance Nr from the center of rotation is 22.000 mm. The track is divided for each corresponding length, and a first partial track, a second partial track,... Therefore, the length of the first partial track is the shortest, and the length of the Yth partial track is the longest. The meandering shape of each partial track includes a plurality of information frames.

  In the carrier wave part, the amplitude of the carrier wave shape is not constant, and the amplitude of the part adjacent to the phase modulation wave part in the direction orthogonal to the tangential direction of the track is adjusted to be smaller than the amplitude of the part not adjacent to the phase modulation wave part Have been.

  A region including a portion adjacent to the phase modulation wave portion in the direction orthogonal to the track tangent direction in the carrier wave portion (hereinafter also referred to as “adjustment carrier wave region” for convenience) differs for each track, and the length of the phase modulation wave portion It can be calculated from the difference between the length of the carrier wave portion, the length of the first partial track, and the length of the adjacent partial track. Note that the length of the adjusted carrier wave area is the same as the length of the phase modulation wave part. Therefore, next, a calculation formula for calculating the head position of the adjusted carrier wave area in each track will be described. Here, the length of the phase modulation wave part is n wobbles, the length of the carrier wave part is m wobbles, the length of the first partial track is k wobbles, the difference between the lengths of adjacent partial tracks is L wobbles, k ÷ ( The remainder of (n + m) is j wobbles. Also, the head position of the adjusted carrier area is indicated by a distance (unit: wobble) from the head position of the information frame.

The first partial track is the first part track has an adjustment carrier region adjacent to the phase modulated wave part included in the second partial track (and R _1). The head position P ₁ of the region R ₁ is represented by the following equation (1).
P ₁ = j + L (1)

Each of the second partial track to the (Y-1) th partial track has two adjusted carrier wave areas. For example, the X-th (2 ≦ X <Y) partial track includes an adjusted carrier wave area (first area R _X1 ) adjacent to the phase modulation wave part included in the X + 1-th partial track, and an X−1 partial track. And an adjusted carrier wave region (referred to as a second region R _X2 ) adjacent to the phase-modulated wave portion included in. The head position P _{X1 of} the first area R _X1 is represented by the following equation (2a).
P _X 1 = j− (X−2) · L (2a)

The head position P _{X2 of} the second region R _X2 is represented by the following equation (2b).
P _X 2 = n + m + 1−P _X 1 (2b)

In other words, the head position P ₂ 1 of the first region R ₂ 1 in the second partial track, and the head position P ₂ 2 of the second region R ₂ 2 are each represented by the following equation (3).
_{P 2 1 = j, P 2} 2 = n + m + 1-P 2 1 ...... (3)

Similarly, the head position P ₃ 1 of the first region R ₃ 1 in the third partial track, and the head position P ₃ 2 of the second region R ₃ 2 are each represented by the following equation (4).
_{P 3 1 = j-L,} P 3 2 = n + m + 1-P 3 1 ...... (4)

The first region R _Y-1 1 of the head position P _Y-1 1 in the Y-1 partial track, and the head position P _Y-1 2 of the second region R _Y-1 2 is the following, respectively (5 ) Expression.
P _Y−11 = j− (Y−3) · L, P _Y−12 = n + m + 1−P _Y−11 (5)

The Yth partial track, which is the last partial track, has an adjusted carrier wave area (referred to as _RY ) adjacent to the phase modulation wave part included in the (Y-1) th partial track, and the start position _PY of this area _RY Is expressed by the following equation (6).
P _Y = n + m + 1−j + (Y−2) · L (6)

  In this embodiment, the length n of the phase modulation wave part is 8 wobbles, and the length m of the carrier wave part is 85 wobbles. In addition, the length k of the first partial track can be calculated based on the distance Nr from the rotation center of each of the start position and the end position of the first partial track, and here is 10581.2 wobbles. Therefore, the remainder j of k ÷ (n + m) is 72.2 wobbles. Further, since the track pitch is 0.74 μm, the difference L between the lengths of the adjacent partial tracks is 1.09 wobbles.

Therefore, when each value is substituted into the above equation (1), P ₁ = 73.29. That is, in the first part track, as shown in FIG. 7 as an example, adjusting the carrier region R ₁ is a until 81.29 wobbles from 73.29 wobble. Thus, in a first partial track is adjusted so that the amplitude of the carrier wave shapes included in the adjustment carrier region R ₁ is reduced.

Further, by substituting each value into the equation (3), P ₂ 1 = 72.2, a P _{2 2} = 21.8. That is, in the second partial track, as shown in FIG. 8 as an example, the first region R ₂ 1 is be between 80.2 wobbles from 72.2 wobbles, the second region R ₂ 2 is 21.8 Between wobble and 29.8 wobbles. Therefore, in the second partial track, the amplitude of the carrier wave shapes included in the first region R ₂ 1 and the second region R ₂ 2 is adjusted so that each smaller.

Further, by substituting each value into the equation (4), P ₃ 1 = 71.1, a P ₃ 2 = 22.9. That is, in the third partial track, the first region R ₃ 1 is be between 79.1 wobbles from 71.1 wobbles, the second region R ₃ 2 is a between 30.9 wobbles from 22.9 wobbles . Accordingly, in the third partial track, the amplitude of the carrier wave shapes included in the first region R ₃ 1 and the second region R ₃ 2 is adjusted so that each smaller.

In the above equation (2a), the head position P _{X1 of} the first region R _X1 may have a negative value. In such a case, correction is performed using the following equation (7), and a new start position P _X 1 ′ is obtained.
P _X 1 ′ = n + m + P _X 1 (7)

For example, in the first 115 part track, since the _{P 115 1 = -50.97, 42.03 (} = 93-50.97) becomes the new head position. If P _X 1 ′ calculated in the above (7) is a negative value, the P _X 1 ′ is substituted for P _X 1 in the above (7), and a new head position P _X 1 ′ is further substituted. Ask.

In the above equation (2b), the value of P _X 2 may exceed the value of (n + m). In such a case, correction is performed using the following equation (8), and a new start position P _X 2 ′ is obtained.
P _X 2 ′ = P _X 2− (n + m) (8)

For example, in the 120th partial track, since the _{P 120 2 = 150.42, 57.42 (} = 150.42-93) becomes the new head position. If the value of P _X 2 ′ calculated in the above (8) exceeds the value of (n + m), that P _X 2 ′ is substituted for P _X 2 in the above (8), and a new head Find the position P _X 2 '.

  As described above, according to the optical disc 15 according to the present embodiment, the spiral recording track is formed to meander including the phase modulation wave portion including the predetermined information and the carrier wave portion for generating the clock signal. The carrier wave portion is formed such that the amplitude of a portion adjacent to the phase modulation wave portion is smaller than the amplitude of a portion not adjacent to the phase modulation wave portion in a direction orthogonal to the tangential direction of the track. ing. Therefore, in an optical disk device using this optical disk as an access target medium, for example, as shown in FIG. 9, when reproducing the phase modulated wave portion of the X-th partial track, the phase of the carrier wave of the X-th partial track and the adjacent track Even if the phases of the carrier waves of the (X-1) th partial track and the (X + 1) th partial track are substantially the same, the signal amplitude of the phase modulation wave portion of the Xth partial track in the wobble signal (signal Xa) becomes small. Even if an AGC amplifier circuit is provided for keeping the signal level of the carrier wave section constant, the signal amplitude of the phase modulation wave section in the output signal (signal Xb) of the AGC amplifier circuit becomes higher than before. . This makes it possible to accurately demodulate the signal from the phase modulation wave section. Therefore, it is possible to correctly obtain information included in the phase modulation wave part, and as a result, it is possible to obtain information necessary for recording and reproduction with high accuracy.

  In the above embodiment, the case where the meandering shape of the groove G conforms to the DVD + R standard has been described, but the present invention is not limited to this. In short, it is only necessary that the track meander including the phase modulation section.

  In the above embodiment, the case where the track is formed in a spiral shape has been described. However, the present invention is not limited to this. For example, the track may be formed in a concentric shape.

  In the above embodiment, the case where the groove G is a track for recording information is described. However, the present invention is not limited to this, and a land may be a track for recording information. Further, both the groove and the land may be information recording tracks.

  Further, in the above-described embodiment, the case where each of the phase modulation wave unit and the carrier wave unit has a fixed length has been described. However, the invention is not limited thereto, and at least one of the phase modulation wave unit and the carrier wave unit may have a variable length.

FIG. 1 is a cross-sectional view for explaining a configuration of an optical disc according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a meandering shape of a track in the optical disc of FIG. 1. FIG. 2 is a diagram for explaining a meandering area of a track on the optical disc of FIG. 1. FIG. 3 is a diagram for explaining an information frame. FIG. 3 is a diagram for explaining the length of a phase modulation wave part and a carrier wave part in an information frame. It is a figure for explaining a partial track. FIG. 4 is a diagram for explaining a carrier wave part in a first partial track. FIG. 9 is a diagram for explaining a carrier wave part in a second partial track. FIG. 9 is a waveform diagram for explaining a wobble signal of a phase modulation wave part in an X-th partial track. FIG. 4 is a waveform diagram for explaining a wobble signal when there is crosstalk. FIG. 4 is a waveform diagram for explaining waveform adjustment of a wobble signal.

Explanation of reference numerals

15 ... optical disc, G ... groove (track), R ₁ ... adjusting carrier region, R ₂ 1 ... first region, R 2 ₂ ... second region.

Claims (6)

A spiral or concentric information recording track is an optical disc having a recording surface formed to meander including a phase modulation wave portion containing predetermined information and a carrier wave portion for generating a clock signal.
The optical disc according to claim 1, wherein in the carrier wave section, in a direction orthogonal to a tangential direction of the track, an amplitude of a portion adjacent to the phase modulation wave portion is smaller than an amplitude of a portion not adjacent to the phase modulation wave portion.   The said phase modulation wave part and the said carrier wave part are each fixed length, The meander of the said track is formed including the several sets of the said phase modulation wave part and the said carrier wave part, The characterized by the above-mentioned. 2. The optical disc according to 1.   The track has a spiral shape, and the track is divided by a length corresponding to one rotation starting from the meandering start position on the inner peripheral side of the track, and the first partial track and the second partial track are sequentially arranged from the inner peripheral side. 3. The optical disk according to claim 2, wherein each of the partial tracks includes at least one of the sets when the partial tracks are defined as a Y-th partial track.   The carrier wave portion in the Xth (2 ≦ X <Y) partial track of the track includes a first region including a portion adjacent to the phase modulation wave portion included in the X + 1 partial track, and an X−1 partial track 4. The optical disk according to claim 3, further comprising: a second region including a portion adjacent to the phase modulation wave portion included in the second region.   The length n of the phase modulation wave portion, the length m of the carrier wave portion, the length k of the first partial track, and the difference L between the lengths of the adjacent partial tracks are set in units of the length of one cycle of the carrier wave. , And the remainder j of k ÷ (n + m), and the first region is {j− (X−2) · L}｝ {j−, starting from the start position of the phase modulation wave part in the Xth partial track. (X-2) · L + n}, and the second region is represented by {n + m + 1−j + (X−2) · L} to {2n + m + 1−j + (X−2) · L}. The optical disc according to claim 4. The carrier wave portion in the first partial track has a region including a portion adjacent to the phase modulation wave portion included in the second partial track, and the region is a head position of the phase modulation wave portion in the first partial track. Are represented by (j + L) to (j + L + n),
The carrier wave portion in the Yth partial track has a region including a portion adjacent to the phase modulation wave portion included in the Y-1 partial track, and the region includes a region of the phase modulation wave portion in the Yth partial track. 6. The optical disk according to claim 5, wherein the start position is represented by {n + m + 1-j + (Y-2) .L} to {2n + m + 1-j + (Y-2) .L}.

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