JP4382781B2 - Optical recording medium - Google Patents

Description

  The present invention relates to an optical recording medium capable of recording information data on a user side.

  Currently, write-once DVDs (Digital Versatile Discs) -R and rewritable DVD-RWs have been commercialized as such optical recording media. FIG. 1 is a perspective view showing the structure of a recording surface and a cross section of a DVD-R or DVD-RW (hereinafter simply referred to as a DVD). FIG. 1 shows a form before information data (audio data, video data, and computer data) is recorded by the information recording / reproducing apparatus.

  As shown in FIG. 1, on the recording layer R of the DVD before recording information data, a groove track GV and a concave shape (similarly from the viewpoint of the figure) and a concave shape (similarly from the viewpoint of the figure) are preliminarily formed. ) Land tracks LD are alternately formed spirally or concentrically. As shown in FIG. 1, the DVD has a transparent substrate B, and the transparent substrate is attached on the recording layer R with the surface having the grooves and land tracks.

  Further, on the land track LD, an address indicating a position on the groove track GV and a plurality of land pre-pits LPP for recording timing are formed in advance. Each of the land pre-pits LPP is formed so as to connect between the adjacent groove tracks GV, and the bottom surface (surface shown by hatching) is the bottom surface of the groove track GV (also shown by hatching). It is connected.

  Here, an information recording / reproducing apparatus for recording information data on such a DVD recognizes a position on the groove track GV by reading the land prepit LPP from the DVD, and records a beam corresponding to the information data. Light is irradiated onto the groove track GV. At this time, heat is transmitted to the area irradiated with the recording beam light, and information pits PT as shown in FIG. 2 are formed in the area.

However, when such a recording beam light is applied to a position over the land pre-pit LPP, deformed information pits PT such as information pits PT ₁ and PT ₂ shown in FIG. 2 are formed. This is because the heat when the recording beam light is irradiated is also conducted to a part of the land prepit LPP. Accordingly, when information data is reproduced from a DVD in a recording state as shown in FIG. 2, waveform distortion may occur in the read signal when the information pits PT ₁ and PT ₂ deformed as described above are read. There was a problem of high read error rate.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide an optical recording medium capable of obtaining a read signal without waveform distortion at the time of reproducing the information.

  The optical recording medium according to claim 1 is an optical recording medium including a groove information track on which information pits for carrying information data are to be formed and a land pre-pit track. Pre-pits are formed in advance, groove information tracks and land pre-pit tracks are alternately formed, the land pre-pits are coupled to the groove information tracks, and the track width of the groove information tracks is In at least a part of each of the land prepit existing sections, the track width is narrower than the land prepit nonexisting section, and the land prepits are adjacent to the two grooves on both sides. It is characterized by being coupled to both information tracks.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 is a perspective view showing the structure of a recording surface of a DVD that can be additionally written or rewritten as an optical recording medium according to the present invention. FIG. 3 shows a form before information data is recorded by an information recording / reproducing apparatus to be described later.

  As shown in FIG. 3, on the recording layer R of the DVD according to the present invention, a groove track GV having a convex shape (viewed from the viewpoint of the figure) and a land having a concave shape (also viewed from the viewpoint of the figure) are previously formed. The tracks LD are alternately formed in a spiral shape or a concentric shape. As shown in FIG. 3, the DVD has a transparent substrate B, and the transparent substrate B is attached to the recording layer R on the surface having the groove and land track.

  On the land track LD, an address for the information recording / reproducing apparatus to recognize the position on the groove track GV and a land prepit LPP for recording timing are formed in advance when information data is recorded. Further, the section of the groove track GV connected to the land prepit LPP is narrowed by a groove track recess GVK as shown in FIG.

  FIG. 4 is a diagram showing the configuration of an information recording / reproducing apparatus that records and reproduces information data on such a DVD. In FIG. 4, a recording / reproducing head 2 has a recording beam light generator (FIG. 3) for recording information data on a DVD 1 as a write-once or rewritable optical recording medium having the form shown in FIG. (Not shown), a reading beam light generation device (not shown) for reading recorded information (including information data) from the DVD 1, and a four-divided photodetector.

  The reading beam light generator irradiates the DVD 1 rotated by the spindle motor 11 with reading beam light, and forms an information reading spot on the recording surface. As shown in FIG. 5, the four-divided photodetector has light receiving surfaces 20a to 20d that are divided into four by a direction along the recording track (groove track GV) of the DVD 1 and a direction orthogonal to the recording track. It consists of a photoelectric conversion element. Such a photoelectric conversion element receives the reflected light from the DVD 1 by the information reading spot by each of the four light receiving surfaces 20a to 20d, and outputs the signals individually converted into electric signals as read signals Ra to Rd.

  The servo control device 4 generates a focus error signal, a tracking error signal, and a slider drive signal based on the read signals Ra to Rd. The servo control device 4 controls a focusing actuator (not shown) mounted on the recording / reproducing head 2 based on the focus error signal. At this time, the focusing actuator adjusts the focus of the information reading spot based on the focus error signal. The servo control device 4 controls a tracking actuator (not shown) mounted on the recording / reproducing head 2 based on the tracking error signal. At this time, the tracking actuator biases the formation position of the information reading spot in the radial direction of the disk based on the tracking error signal. Further, the servo control device 4 controls the slider 100 based on the slider drive signal. At this time, the slider 100 moves the recording / reproducing head 2 in the disk radial direction at a speed corresponding to the slider driving signal.

Prepit detecting circuit 5, based on the read signal Ra to Rd, as shown in FIG. 1, it detects and records the pre-pit detection signal PP _D the land prepits LPP formed on the land tracks LD in DVD1 This is supplied to the processing circuit 7. FIG. 5 shows an internal configuration of the prepit detection circuit 5. In FIG. 5, an adder 51 adds the read signals Ra and Rd received by the light receiving surfaces 20a and 20d of the four-divided photodetector and converted into electrical signals, and adds the added read signal Ra _{+ d} . This is obtained and supplied to the subtractor 52. On the other hand, the adder 53 adds the read signals Rb and Rc received by the light receiving surfaces 20b and 20c of the four-divided photodetector and converted into electric signals to obtain an added read signal R _{b + c} , Is supplied to the subtractor 52. The subtractor 52 obtains a value obtained by subtracting the added read signal R _{b + c} from the added read signal R _{a + d} as a difference signal SB, and supplies this to the binarization circuit 54. Binarizing circuit 54, such differential signal SB is binarized with a predetermined threshold value, and outputs it as the pre-pit detection signal PP _D.

FIG. 6 shows waveforms of the addition read signal R _{a + d} , the addition read signal R _{b + c} , and the difference signal SB obtained when the information reading spot SP traces on the groove track GV before information data recording on the DVD 1. FIG. As shown in FIG. 6, each of the addition reading signal R _{a + d} and the addition reading signal R _{b + c} obtained when the information reading spot SP is tracing on the groove track GV of the DVD 1 is “0”. It is. However, when the information reading spot SP is placed over the land pre-pit LPP, the amount of light received at each of the light-receiving surfaces 20a and 20d of the quadrant photodetector decreases due to the influence of diffraction by the land pre-pit LPP. On the other hand, since the diffracted light diffracted by the land prepits LPP is incident on each of the light receiving surfaces 20b and 20c, the amount of received light increases. Therefore, at this time, as shown in FIG. 6, the addition read signal R _{a + d} gradually decreases from the “0” state to the minimum value L ₁ , and the addition read signal R _{b + c} is “0”. gradually increases from the state to continue to transition to the maximum value L _2. Then, the information as the reading spot SP moves away from the land prepit LPP, the addition read signal R _{a + d} went remained to the state of gradual increase to "0" from the state of the minimum value L _1, the addition read signal R _{b + c} gradually decreases from the state of the maximum value L ₂ and transitions to the state of “0”. Therefore, the difference signal SB obtained by subtracting the addition read signal R _{b + c} from the addition read signal R _{a + d} is shown in FIG. 6 obtained by subtracting the maximum value L ₂ from the minimum value L ₁ . As shown, the waveform has a minimum value L ₃ . Therefore, if binarized by a predetermined threshold value Th such differential signal SB by the binarization circuit 54 is the pre-pit detection signal PP _D indicating the tracing point of the land prepits LPP can be obtained.

In addition, when the land pre-pit LPP is detected from the conventional DVD as shown in FIG. 1, the addition read signal R _{a + d} and the addition read signal R _{b + c} having the waveform form as shown in FIG. Each is obtained, but the absolute value of each of the minimum value L ₁ and the maximum value L ₂ is larger than that obtained from the DVD according to the present invention as shown in FIG. This is because, in the DVD according to the present invention, as shown in FIG. 3, the track width in the section connecting with the land prepit LPP on the groove track GV is narrowed by the groove track concave portion GV _K. That is, by reducing the track width of the groove track GV in the section connecting with the land prepit LPP on the groove track GV, the minimum value L ₁ and the maximum value of each of the addition read signal R _{a + d} and the addition read signal R _{b + c} absolute value L ₂ is to increase.

Therefore, according to the DVD according to the present invention as shown in FIG. 3, the absolute value of the minimum value L ₃ of the difference signal SB obtained when tracing the land prepit LPP is as shown in FIG. This is larger than that obtained when the land prepit LPP is traced from the DVD. Accordingly, it is shown are wider dynamic range when performing binarization by but such a predetermined threshold value Th in FIG 6, is the increased accuracy of detecting the land pre-pit detection signal PP _D.

Recording processing circuit 7, on the basis of the pre-pit detection signal PP _D, the position where the recording and reproducing head 2 recording is performed at the present time, i.e., to recognize the position on the groove tracks GV, the desired recording position from the recording position A control signal for causing the recording / reproducing head 2 to make a track jump is supplied to the servo controller 4. Further, the recording processing circuit 7 performs a desired recording modulation process on the information data to be recorded to generate a recording modulation data signal, and supplies it to the recording / reproducing head 2. The recording beam light generator mounted on the recording / reproducing head 2 generates recording beam light corresponding to the recording modulation data signal and irradiates the recording beam light on the groove track GV on the DVD 1. At this time, heat is transmitted to a region on the groove track GV irradiated with the recording beam, and information pits PT as shown in FIG. 7 are formed in the region.

Incidentally, when the recording beam light is irradiated to the position over the land prepit LPP on the groove track GV, deformed information pits PT ₁ and PT ₂ as shown in FIG. 7 are formed. At this time, in each of these information pits PT ₁ and PT ₂ , the information pit area extends to a part of the land pre-pit LPP to increase the pit area. However, the amount of increase in the pit area, narrowing the track width of the groove track GV by the groove track recess GV _K, have been offset by having a small pit area. That is, although the information pits PT ₁ and PT ₂ have their pit shapes deformed, the ratio of the pit area to the pit length is the same as the information pit PT having a normal shape.

  Here, when reproducing information data from the DVD 1 on which the information data is recorded as shown in FIG. 7, the head amplifier 3 in FIG. 4 is supplied from the quadrant photodetector of the recording / reproducing head 2. The sum of the read signals Ra to Rd is obtained, and the information read signal RF obtained by amplifying it is supplied to the information data reproducing circuit 30. The information data reproduction circuit 30 binarizes the information read signal RF, and then sequentially performs demodulation processing, error correction processing, and various information decoding processing, thereby performing information data (video data, video data, (Audio data, computer data) is reproduced and output.

At this time, information pits PT ₁ and PT _{2 which} are deformed as shown in FIG. 7 may exist at positions over the land pre-pits LPP on the groove track GV of the DVD 1. However, as described above, the ratio of the pit area to the pit length of each of the information pits PT ₁ and PT ₂ is the same as that of the information pit PT having a normal shape. This is the same as when the reading beam light is irradiated to the information pit PT having.

Therefore, according to the DVD of the present invention, a good read signal without waveform distortion can be obtained. Incidentally, in the embodiment shown in Figure 3, it has a groove track GV each of the track width of both sides of the land prepit LPP to reduce the groove track recess GV _K. However, as shown in FIG. 8, only one of the groove tracks GV may be provided with a groove track concave portion GV _K in the connecting section with the land prepit LPP to narrow the track width.

  The land pre-pits LPP in the above embodiment are coupled to the groove tracks GV on both sides of the land pre-pits LPP, but may be formed apart from any one of the groove tracks GV. FIG. 9 is a perspective view showing another structure of the recording surface of the DVD according to the present invention made in view of the above points.

On the land track LD in the DVD shown in FIG. 9, an address for recognizing the position on the groove track GV and a plurality of land pre-pits LPP ′ for recording timing are formed in advance. The land prepit LPP ′ is formed so as to be coupled to only one of the two groove tracks GV sandwiching the land prepit LPP ′, and is formed apart from the other groove track GV. Further, the groove tracks GV of who the land prepits LPP 'is attached, be provided with a groove track recess GV _K.

FIG. 10 is a diagram showing an example of a recording form when information data is recorded on the DVD shown in FIG. As is shown in Figure 10, also in the DVD shown in FIG. 9, when the recording beam light is irradiated to a position across the land prepits LPP 'on the groove track GV, the information pit PT ₂ deformed is formed . At this time, although the pit shape of the information pit PT ₂ is deformed, as described above, the ratio of the pit area to the pit length is the same as the information pit PT having a normal shape.

  Therefore, even if the structure shown in FIG. 9 is adopted, a good read signal without waveform distortion can be obtained when reproducing the information data, as in the case shown in FIG. In order to manufacture a DVD having such a form as shown in FIG. 9, it is necessary to create a disc master having groove grooves GV and land prepits LPP 'formed in a concave shape. In creating this master disc, first, a mask pattern having the form of each of the groove track GV and the land prepit LPP 'is created by laser cutting.

FIG. 11 is a diagram for explaining the laser cutting operation. In FIG. 11, the cutting beam generator CBG masks one of the cutting beam for the groove track GV and the cutting beam for the land prepit LPP while moving in the direction of the white arrow as shown in the figure. Irradiate on the sheet. That is, as shown in FIG. 11, only the cutting beam for the groove track GV is irradiated in the section A on the mask sheet, and only the cutting beam for the land prepit LPP is irradiated in the section B. At this time, the cutting beam for the groove track GV is irradiated by tracing a virtual line J _GV on the mask sheet as shown in FIG. 11, and the cutting beam for the land prepit LPP traces the virtual line J _LP. Is irradiated. By these cutting beams, the beam spot SP _GV having the central axis is irradiated on the virtual line J _GV in the section A, while the beam spot SP _LP having the central axis is irradiated on the virtual line J _{LP in the} section B. The Therefore, on the mask sheet, a cutting pattern CP as shown by the hatched portion is formed in the area irradiated with the beam spot SP _GV and the beam spot SP _LP . At this time, as shown in FIG. 11, the cutting pattern for the groove track GV is formed on the mask sheet by the operation in the sections A and B, and the cutting pattern for the land pre-pit LPP ′ is formed by the operation in the section B. Is formed on the mask sheet.

FIGS. 12A to 12C are diagrams showing another embodiment of the present invention. According to this embodiment, as illustrated, the land prepit LPP is with biases the cutting beam SP _GV for the groove GV in the disk radial direction, is formed by raising the cutting beam SP predetermined period laser power _GV The The position of the cutting beam SP _GV is controlled based on the tracking offset signal shown in FIG. 12B, and as indicated by the chain line J _GV in FIG. After being gradually biased, it is gradually returned to its starting position. Further, as shown in FIG. 12A, the laser power of the cutting beam SPGV is increased from time t1 to time t2. As a result, the beam diameter of the cutting beam SP _GV increases within a certain period after the time t1, and decreases within a certain period after the time t2 to the original beam diameter. As a result, the center of the as shown in the shaded portion, the curve in the period A1 (the period from time t1 t3) by increasing the beam diameter of the cutting beam SP bias and the cutting beam SP _GV position _GV shown in FIG. 12 (c) In the same way, the track width of the groove track (excluding the portion where the land prepit LPP is formed) is reduced in the period A2 (between the time between t1 and t2 and t3). The The upper and lower hatched portions in FIG. 12 (c) indicate adjacent groove tracks GV.

  By the above operation, the land pre-pits LPP are formed in the section A1, and the groove track GV is formed narrow in the section A2 where the groove track GV is narrower than the section A1. In FIG. 12C, the section A1 where the land pre-pits LPP are formed and the section A2 where the groove track GV is formed with a narrow track width are both shown to end at time t3. The time relationship between A1 and section A2 is not limited to this. For example, the laser power-up signal and the tracking offset signal may be controlled so that the section A2 where the track width is narrowed ends before the section A1.

  In the DVD shown in the above embodiment, the groove track GV is convex and the land track LD is concave, but the concave and convex shapes are opposite, that is, the groove track GV is concave and the land track LD is convex. It does not matter.

(The invention's effect)
As described above, according to the optical recording medium of the present invention, since the irradiation heat of the recording beam is conducted to the land pre-pit through the groove track, the deformed information pit is formed on the groove track. However, a read signal without waveform distortion can be obtained.

It is a perspective view which shows the structure of the recording surface of the conventional write-once or rewritable DVD. It is a figure which shows an example of the form of the recording surface when an information pit is formed in DVD shown in FIG. It is a perspective view which shows the structure of the recording surface of DVD which can be additionally recorded or rewritten as an optical recording medium by this invention. It is a figure which shows the structure of the information recording / reproducing apparatus which records and reproduces | regenerates information data with respect to DVD by this invention. FIG. 3 is a diagram showing an internal configuration of a quadrant photodetector and pre-pit detection circuit 5; FIG. 6 is a diagram showing internal operation waveforms of the prepit detection circuit 5. FIG. 4 is a diagram illustrating an example of a form of a recording surface when information pits are formed on the DVD illustrated in FIG. 3. It is a perspective view which shows the other structure of the recording surface of DVD by this invention. It is a perspective view which shows the other structure of the recording surface of DVD by this invention. FIG. 10 is a diagram showing an example of a form of a recording surface when information pits are formed on the DVD shown in FIG. 9. It is a figure for demonstrating the cutting operation of the mask pattern used when manufacturing DVD shown in FIG. FIG. 12A is a diagram showing another example according to the present invention, FIG. 12A shows a laser power-up control signal, FIG. 12B shows a tracking offset control signal, and FIG. 12C shows a recording surface of a DVD. The shape of the groove track is shown.

Explanation of main part codes

GV Groove Track LD Land Track GV _K Groove Track Recess LPP Land Prepit

Claims (2)

An optical recording medium including a groove information track on which information pits for carrying information data are to be formed, and a land pre-pit track,
A plurality of land pre-pits are formed in advance in the land pre-pit track, groove information tracks and land pre-pit tracks are alternately formed, and the land pre-pits are coupled to the groove information tracks, The track width of the groove information track is narrower than the track width in the non-existing section of the land prepits in at least a part of each of the existing sections of the land prepits.
The notch width of the groove information track in a direction perpendicular to the tangential direction of the groove information track in the section where the land prepit exists is greater than the width of the land prepit coupled to the groove information track in the vertical direction. Is small, and
The land pre-pit is coupled to one of the two groove information tracks adjacent on both sides, and is formed apart from the other groove information track. recoding media. An optical system including a groove information track on which information pits for carrying information data are to be formed, and a land pre-pit track coupled to the groove information track, and a plurality of land pre-pits formed in advance on the land pre-pit track A manufacturing method of a recording medium,
Forming the groove information track having a track width narrower than the track width in the non-existing section of the land prepit in at least a part of each of the existing sections of the land prepit;
In the direction perpendicular to the tangential direction of the groove information track, the width of the land prepit coupled to the groove information track is larger than the notch width of the groove information track in the section where the land prepit exists. Forming the land pre-pits as follows :
The land pre-pit is coupled to one of the two groove information tracks adjacent on both sides, and is formed apart from the other groove information track.

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