JP2004110934A - Optical disk recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk recording and reproducing device having a photo-detector which can detect highly accurately an LPP signal. <P>SOLUTION: A light shielding plate for shielding a reflected light from both ends of the vertical direction for a tangent of a groove of an optical disk is placed on a photo-detector of an optical disk recording and reproducing device. And by forming a light receiving spot shielding one part of the reflected light from both ends of the vertical direction for a tangent of the groove, difference of luminosity of left and right for a tangent of a groove in a light receiving spot in which a diffraction angle of the reflected light is varied by LPP is improved. <P>COPYRIGHT: (C)2004,JPO

Description

表１に示すように、遮光板を設けることによりＡＲが向上し、また、変調度が高い領域においてもＬＰＰ信号を検出することが可能となる。
【００４０】
ここで、本実施の形態では、ピット状のＬＰＰを高精度に検出しているが、図５に示すように、グルーブを蛇行させて形成したＬＰＰを高精度に検出することも可能であり、第２の実施の形態として、グルーブを蛇行させて形成したＬＰＰについて説明する。
【００４１】
なお、本実施の形態では、図５に示すように、記録トラックの進行方向に対して右側にグルーブを蛇行させて形成したＬＰＰを検出する。
【００４２】
グルーブを蛇行させて形成したＬＰＰにレーザービームを照射すると、図６（ａ）に示すように、フォトディテクタ上に形成される受光スポットは、蛇行の方向に応じて移動する。
【００４３】
そして、図６（ｂ）は、遮光板を設けたフォトディテクタ上に形成される受光スポットであり、遮光板により遮光される領域を斜線で示している。
【００４４】
遮光板は、グルーブの蛇行により形成されたＬＰＰにより形成された、領域Ａ、Ｃにおいて比較的明度の高い領域Ｈを遮光すると共に、領域Ｂ、Ｄにおいて比較的明度の低い領域Ｌを遮光しており、グルーブの接線方向に対して左右の明度の差が増加した受光スポットがフォトディテクタ上に形成される。
【００４５】
このため、グルーブの接線方向に対して左右の出力信号の差が増加し、ＬＰＰ信号を高精度に検出することが可能となる。
【００４６】
なお、本実施の形態では４分割フォトディテクタを用いているが、２分割フォトディテクタなど、グルーブの接線方向に対して平行に分割したフォトディテクタに用いることができる。
【００４７】
【発明の効果】
本発明では、ＬＰＰ信号を高精度に検出することができる。
【図面の簡単な説明】
【図１】本発明に係る光ディスク記録再生装置の構成の一例を示す概略ブロック図
【図２】本発明に係る光ディスク記録再生装置のピックアップの構成の一例を示す概略ブロック図
【図３】本発明に係る遮光板を設けたフォトディテクタの構成の一例を示す概略図
【図４】第１の実施の形態においてフォトディテクタ上に形成される受光スポットを示す概略図
【図５】グルーブを蛇行させてＬＰＰを形成した光ディスクの記録層の構成を示す概略図
【図６】第２の実施の形態においてフォトディテクタ上に形成される受光スポットを示す概略図
【図７】光ディスクの記録層の構成を示す概略図
【図８】フォトディテクタ上に形成される受光スポットを示す概略図
【図９】４分割フォトディテクタの構成を示す概略図
【符号の説明】
１…光ピックアップ
２…信号補正回路
３…信号補正回路
４…信号抽出回路
５…光ディスク
１１…フォトディテクタ
１２…信号算出部
１３…遮光板
２０…グルーブ
２１…ピット
２２…ランド
Ｓ１、Ｓ２、Ｓ３、Ｓ４…ビームスポット[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photodetector of an optical disk recording / reproducing apparatus, and more particularly to an optical disk recording / reproducing apparatus having a photodetector capable of correcting a diffraction intensity distribution and improving LPP characteristics.
[0002]
[Prior art]
In general, a DVD-R (Digital Versatile Disc-Recordable) disk is formed by forming layers such as a recording layer (dye film), a reflective layer (metal film), and a protective layer on a transparent resin substrate by sputtering or spin coating. It has a multilayer structure.
[0003]
Then, as shown in FIG. 7, a guide groove for a laser beam called a groove 20 is formed on the surface of the transparent resin substrate, and pits 21 (recording pits) based on a recording signal are formed in this groove to thereby store data. Records are being made.
[0004]
A region between the grooves is called a land 22, and an LPP 103 (Land Pre-Pit) including address information and the like is arranged on the land according to a predetermined rule.
[0005]
Now, since the spot diameter of the beam spot S formed when the recording surface of the DVD-R is irradiated with the laser beam is larger than the groove width, a part of the beam spot leaks to the land adjacent to the groove.
[0006]
Therefore, the reflected light of the laser beam irradiated on the DVD-R includes an information component (RF signal) from the groove and an information component (LPP signal) from the LPP formed on a land adjacent to the groove.
[0007]
Here, as shown in spots S1 and S2 in FIG. 7, the light receiving spot formed on the photodetector by the reflected light from the area where the LPP is arranged is, as shown in FIGS. 8B and 8D, Since the diffraction angle of the reflected light changes due to the LPP, the brightness differs between the left and right regions (A + D and B + C) divided in parallel to the tangential direction of the groove.
[0008]
8A, 8B, 8C, and 8D correspond to the light receiving spots formed on the photodetector by the reflected lights of the beam spots S1, S2, S3, and S4 in FIG. The arrows indicate the scanning direction of the laser beam (X-axis direction: track direction of the optical disk).
[0009]
In the photodetector that receives the reflected light, for example, as shown in FIG. 9, the quadrant is divided into two parts corresponding to the tangential direction of the groove (X-axis direction) and the radial direction of the optical disc (Y-axis direction). The reflected light of each area (A, B, C, D) is received by the light receiving element, and the output signal of each area in the direction perpendicular to the groove (Y-axis direction) The difference is calculated, and the difference signal (push-pull signal) is binarized by a predetermined threshold to detect the LPP signal.
[0010]
LPP signal = (B + C)-(A + D)
Further, the RF signal is detected based on the sum of output signals from the respective regions of the light receiving element.
[0011]
[Problems to be solved by the invention]
However, in FIG. 7, as shown by the spots S3 and S4, the reflected light from the area where the recording pit exists has a reduced lightness of the entire light receiving spot as shown in FIGS. 8C and 8D. , The difference between the left and right output signals with respect to the tangential direction of the groove decreases, and the LPP signal amplitude decreases.
[0012]
For this reason, AR (Aperture Ratio) indicating the range in which the LPP signal can be detected is reduced, and it may be difficult to detect the LPP signal with high accuracy.
[0013]
Also, since the AR decreases as the degree of modulation of the RF signal increases, it has become more difficult to detect the LPP signal as the degree of modulation of the RF signal increases.
[0014]
In addition, conventionally, good LPP characteristics have been maintained by using a recording medium or a circuit. However, with the increase in recording speed and the like, it has been difficult to cope with only the conventional technology.
[0015]
Accordingly, an object of the present invention is to provide an optical disk recording / reproducing apparatus having a photodetector capable of detecting an LPP signal with high accuracy.
[0016]
[Means for Solving the Problems]
An optical disk recording / reproducing apparatus according to the present invention is an optical disk recording / reproducing apparatus having a photodetector for detecting a reflected light of a laser beam applied to an optical disk having an LPP. Characterized in that a light-shielding plate for shielding a part of the light-emitting element is provided.
[0017]
With this configuration, the difference between the left and right brightness with respect to the tangential direction of the groove increases in the light receiving spot formed by the reflected light whose diffraction angle has been changed by the LPP, so that the LPP signal can be detected with high accuracy.
[0018]
In addition, since the light shielding plate is curved toward the center of the photodetector, it is possible to improve the difference in lightness of the light receiving spots whose lightness balance has been changed by the LPP, while suppressing a decrease in the lightness of the entire light receiving spot.
[0019]
This is because when the recording pit and the LPP are adjacent to each other, the diffraction effect is large and a stable LPP signal cannot be obtained. However, by bending the photo disc, only the diffraction effect from the adjacent LPP is reduced. It is because it can be made to.
[0020]
Such a configuration is particularly effective when the recording pit is a short signal such as a 3T signal.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an optical disk recording / reproducing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
[0022]
FIG. 1 is a schematic block diagram showing a configuration of an optical disk recording / reproducing apparatus.
[0023]
In FIG. 1, the optical disc recording / reproducing apparatus includes an optical pickup 1, an LPP signal correction circuit 2, an RF signal correction circuit 3, and a signal extraction circuit 4.
[0024]
As shown in FIG. 2, the optical pickup 1 has a four-divided photodetector 11 divided into two parts corresponding to the tangential direction of the groove (X-axis direction) and the radial direction of the optical disc (Y-axis direction). A signal calculating unit 12 is provided for calculating a push-pull signal (PP signal) by calculating a difference between signals output from the respective light receiving regions, and calculating an RF signal by calculating a sum of signals output from the respective light receiving regions. Have been.
[0025]
Then, the optical pickup 1 irradiates the recording surface of the optical disk 5 that has been rotationally driven with a reproduction laser beam, and receives the reflected light of the irradiated reproduction laser beam from the recording surface with the photodetector 11. The signal calculation unit 12 calculates the PP signal and the RF signal from the amount of the reflected light thus obtained.
[0026]
The PP signal and the RF signal output from the optical pickup 1 are input to the LPP signal correction circuit 2, and the amplitude of the LPP signal carried by the PP signal is corrected by the RF signal RF.
[0027]
The signal output from the LPP signal correction circuit 2 is input to the signal extraction circuit 4, where the LPP signal LPP is extracted.
[0028]
The LPP signal output from the signal extraction circuit 4 is input to an arithmetic circuit such as a CPU (not shown) and used for reproducing address information and the like, and is also input to the RF signal correction circuit 3.
[0029]
In the RF signal correction circuit 3, the amplitude of the input RF signal is corrected by the LPP signal, and a reproduction signal of desired information recorded on the optical disk 5 is output.
[0030]
FIG. 3 is a schematic diagram showing the configuration of the photodetector according to the present invention. The light-shielding plate 13 is arranged in parallel with the tangential direction (X-axis direction) of the groove to the light receiving surface (surface on which reflected light is incident) 14 of the photodetector 11. It is provided on the side.
[0031]
Here, the light shielding plate 13 is provided so as to shield an arbitrary distance from an end of the photodetector in parallel with a tangential direction of a groove in which recording pits are formed (a tangential direction of a track of an optical disc).
[0032]
Preferably, as shown in FIG. 3B or 3C, the shape of the light shielded on the photodetector is rectangular or elliptical.
[0033]
FIG. 4A is a light receiving spot formed on a photodetector by reflected light of a region where a recording pit is formed at a position adjacent to the LPP, as indicated by a spot S4 in FIG.
[0034]
FIG. 4B shows a light receiving spot formed on a photodetector provided with a light shielding plate, and a region shielded by the light shielding plate is indicated by oblique lines.
[0035]
The light-shielding plate shields the relatively high brightness area H in the areas B and D and the relatively low brightness area L in the areas A and C formed by the change in the diffraction angle due to the LPP. A light receiving spot in which the difference in brightness between left and right with respect to the tangential direction of the groove is increased is formed on the photodetector.
[0036]
For this reason, the difference between the left and right output signals with respect to the tangential direction of the groove increases, and the LPP signal can be detected with high accuracy.
[0037]
Here, AR was measured using a photodetector using the light-shielding plate according to the present invention and a conventionally used photodetector without a light-shielding plate while changing the modulation factor.
[0038]
Table 1 shows the measurement results.
[0039]
[Table 1]

As shown in Table 1, the AR is improved by providing the light shielding plate, and the LPP signal can be detected even in a region where the degree of modulation is high.
[0040]
Here, in the present embodiment, the pit-shaped LPP is detected with high accuracy. However, as shown in FIG. 5, it is also possible to detect the LPP formed by meandering the groove with high accuracy. As a second embodiment, an LPP formed by meandering a groove will be described.
[0041]
In this embodiment, as shown in FIG. 5, an LPP formed by meandering a groove to the right with respect to the traveling direction of a recording track is detected.
[0042]
When an LPP formed by meandering the groove is irradiated with a laser beam, the light receiving spot formed on the photodetector moves according to the meandering direction, as shown in FIG.
[0043]
FIG. 6B shows a light receiving spot formed on a photodetector provided with a light shielding plate, and a region shielded by the light shielding plate is indicated by oblique lines.
[0044]
The light-shielding plate shields a relatively high brightness area H in the areas A and C and a relatively low brightness area L in the areas B and D formed by the LPP formed by the groove meandering. Thus, a light receiving spot in which the difference in brightness between the left and right with respect to the tangential direction of the groove is increased is formed on the photodetector.
[0045]
For this reason, the difference between the left and right output signals with respect to the tangential direction of the groove increases, and the LPP signal can be detected with high accuracy.
[0046]
In the present embodiment, a four-segment photodetector is used, but the invention can be applied to a photodetector that is split in parallel to the tangential direction of the groove, such as a two-segment photodetector.
[0047]
【The invention's effect】
According to the present invention, an LPP signal can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram illustrating an example of a configuration of an optical disk recording / reproducing apparatus according to the present invention; FIG. 2 is a schematic block diagram illustrating an example of a pickup configuration of the optical disk recording / reproducing apparatus according to the present invention; FIG. 4 is a schematic diagram showing an example of the configuration of a photodetector provided with a light-shielding plate according to the present invention. FIG. 4 is a schematic diagram showing a light receiving spot formed on the photodetector in the first embodiment. FIG. FIG. 6 is a schematic diagram showing a configuration of a recording layer of the formed optical disc. FIG. 6 is a schematic diagram showing a light receiving spot formed on a photodetector in the second embodiment. FIG. 7 is a schematic diagram showing a configuration of a recording layer of the optical disc. FIG. 8 is a schematic diagram showing a light receiving spot formed on a photodetector. FIG. 9 is a schematic diagram showing a configuration of a four-division photodetector.
DESCRIPTION OF SYMBOLS 1 ... Optical pick-up 2 ... Signal correction circuit 3 ... Signal correction circuit 4 ... Signal extraction circuit 5 ... Optical disk 11 ... Photodetector 12 ... Signal calculation unit 13 ... Light shielding plate 20 ... Groove 21 ... Pit 22 ... Lands S1, S2, S3, S4 … Beam spot

Claims (2)

An optical disc recording / reproducing apparatus having a photodetector for detecting reflected light of a laser beam applied to an optical disc having an LPP,
An optical disc recording / reproducing apparatus, wherein light-shielding plates are provided at both ends of the photodetector to block a part of reflected light from both sides of a recording track of the optical disc. The light shielding plate,
2. The optical disk recording / reproducing apparatus according to claim 1, wherein the optical disk is curved toward a center of the photodetector.

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