碟片晃動對光碟機讀取資料之影響分析與補償

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研究生：	黃仕臣
論文名稱：	碟片晃動對光碟機讀取資料之影響分析與補償
指導教授：	陳文良
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 動力機械工程學系 Department of Power Mechanical Engineering
論文出版年：	2004
畢業學年度：	92
論文頁數：	72
中文關鍵詞：	光碟機、讀取資料、像差
相關次數：	點閱：1 下載：0
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當光碟在讀取碟片資料時，高速旋轉的碟片往往會因為輕微的晃動，因此造成碟片傾斜，這樣的情況是像差產生的主要原因。由於像差會對光學頭在碟片上的聚焦強度有所影響，進而造成光碟機由碟片讀出的訊號品質劣化、甚至錯誤的情況產生。以現今 DVD 的規格來說，碟片傾斜所造成的影響還在可以容許的程度。但隨著資料儲存密度的要求提高，對於讀取訊號正確率的要求勢必會提高，因此像差對讀取訊號的影響必須有更進一步的認識。
這篇論文主要探討在DVD的規格下，光碟片晃動對於從碟片上讀取HF (high-frequency) 資料訊號的影響。首先用來分析這些影響以及建立數學模型的光學理論將會被一一描述。最後建立整個光碟機讀取碟片訊號的數學模型。不同傾斜角度對於由碟片讀取的3T~11T與14T的訊號的影響將被模擬、檢驗。最後利用改變光源之光強度的方式進行補償，以降低碟片晃動對HF訊號的影響。在本論文中，所有的模擬都是根據精確的數學模型所建立，而透過MATLAB這個軟體來加以實現。

High-speed rotation of the disk in optical driver always causes disk tilt, and then produces aberration. Aberration due to disk tilt would affect the intensity of the laser beam on the disk, and reduce the quality of the readout signal. From the specification of the DVD, the effect of small disk tilt still could be endured. However, as the storage density increases, this effect should be taken into consideration in order to improve the signal quality.
This thesis will concentrate on the influences due to disk tilt on the high-frequency readout signal in DVD optical driver. Several optical theories used to analyze such deviations and to establish the mathematical model of the optical pickup will be studied. Then the model of the overall optical driver system in reading the data from the disk would be constructed. The variation of HF signal with period from 3T to 11T and 14T is simulated and examined under different disk tilt angles. Finally, the HF signal affected by disk tilt will be compensated by modifying the power of the laser diode. All simulations within this thesis are based on the mathematical model and the MATLAB software.

Contents

Contents    Ⅰ
List of Figures    Ⅲ
List of Tables     Ⅵ

Chapter1 Preface    1
1.1 Introduction     1
1.2 Framework    2

Chapter2 Optics Theories    3
2.1 Ray optics    3
2.1.1 Postulates of ray optics    3
2.1.2 Properties of ray optics    4
2.2 Wave optics    7
2.2.1 Postulates of wave optics    7
2.2.2 Elementary waves    9
2.2.3 Effect of thin lens on incident light wave    11
2.3 Fourier optics    13
2.3.1 Transfer function of free space    13
2.3.2 Fresnel and Fraunhofer approximation of free space 15

Chapter3 Mathematical Model of the Optical Pickup    19
3.1 The ideal mathematical model of the optical pickup    19
3.1.1 System overview and free space approx. verification 20
3.1.2 Ideal mathematical model construction    23
3.2 Aberration theory    26
3.3 Expressions for aberration coefficients due to disk tilt    26

Chapter4 Influence of Disk Tilt on High-Frequency Readout Signal    32
4.1 The optical pickup    32
4.2 The simulation construction of DVD-ROM    34
4.3 Aberration coefficient due to disk tilt    36
4.4 Disk tilt effect on high-frequency readout signal    45

Chapter5 Compensating the Effect of Disk Tilt    52
5.1 Intensity compensation of optical pickup    52
5.2 Simulation result after compensation    61
5.2.1 Dynamics of disk oscillation    62
5.2.2 Simulation results    63

Chapter6 Conclusions and Research Prospects    66
6.1 Conclusions    66
6.2 Research Prospects    66

References    68
Appendix    70

List of Figures
Figure 2.1    Reflection and refraction at the  boundary of two different media    4
Figure 2.2    Image formation by thin lens    6
Figure 2.3    Transition from spherical wave to plane wave    10
Figure 2.4    Plano-convex lens    11
Figure 2.5    Double convex lens    12
Figure 2.6    Arbitrary wave as a superposition of plane waves    13
Figure 2.7    An arbitrary wavevector in space    14
Figure 2.8    Transmission of an optical wave between two planes    15
Figure 3.1    Optical layout while CD inserted    19
Figure 3.2    Optical layout while DVD inserted    20
Figure 3.3    Principal components employed in the mathematical model    20
Figure 3.4    Illustration of the effect of disk tilt    27
Figure 3.5    Limiting cycle defined by the marginal rays    29
Figure 4.1    The optical configuration employed    32
Figure 4.2    Track structure of DVD-ROM    35
Figure 4.3    Disk distribution on disk    36
Figure 4.4    Variation of the spherical aberration coefficients    37
Figure 4.5    Variation of the linear coma coefficients    38
Figure 4.6    Variation of the astigmatism coefficients    39
Figure 4.7    Variation of the cubic coma coefficient    40
Figure 4.8    Comparison of major aberration terms    41
Figure 4.9    Comparison of minor aberration terms    41
Figure 4.10    Variation of the spherical aberration coefficients with lens compensation    43
Figure 4.11    Comparison of major aberration coefficients with lens compensation    44
Figure 4.12    Comparison of minor aberration coefficients with lens compensation    44
Figure 4.13    Illustration of radial tilt    45
Figure 4.14    Example of HF signal while aberration free    46
Figure 4.15    Processes of signal transformation    47
Figure 4.16    HF signal in various situations    48
Figure 4.17    Jitter caused by disk tilt    50
Figure 5.1    Change of jitter with compensation as tilt angle =  degree
52
Figure 5.2    Change of jitter with compensation as tilt angle =  degree
53
Figure 5.3    Change of jitter with compensation as tilt angle =  degree
54
Figure 5.4    Change of jitter with compensation as tilt angle =  degree
55
Figure 5.5    Change of jitter with compensation as tilt angle =  degree
56
Figure 5.6    Change of jitter with compensation as tilt angle =  degree
57
Figure 5.7    Change of jitter with compensation as tilt angle =  degree
58
Figure 5.8    Diagram of overall system    60
Figure 5.9    The angular variation of disk tilt    61
Figure 5.10    Comparison of HF signal without compensation    62
Figure 5.11    Comparison of HF signal with compensation    63
Figure 5.12    Power variation    63
Figure 5.13    Comparison of total jitter    64

List of Tables
Table 3.1    Description of each symbol in Figure 3.3    21
Table 3.2    Dimension measurement of the optical pickup    21
Table 3.3    Examination of conditions for each approximation    22
Table 4.1    Simulation parameters and optical specifications for the optical pickup    33
Table 4.2    Physical parameters of DVD-ROM    35
Table 4.3    Signal period corresponding to the pit length    46
Table 5.1    Optimal value of   to each tilt angle
59
Table 5.2    Optimal value of   to range of tile angle
60
Table 5.3    Parameter of disk oscillation    61

                                

References

[1]
徐桂香, “光碟讀取頭光路之數學模型”, 清華大學動力機械工程學系碩士論文, 民國90年6月.

[2]
陳信豪, “光碟機讀取頭光路系統像差對聚焦偵測之影響”, 清華大學動力機械工程學系碩士論文, 民國91年6月.

[3]
黃仁澤, “碟片晃動對光碟機讀取頭光強度及聚焦控制之影響分析”, 清華大學動力機械工程學系碩士論文, 民國92年6月.

[4]
B.E.A.Saleh, M.C.Teich, “Fundamentals of Photonics”, New York: Wiley, 1991.

[5]
“Optical Pick-Up Specifications for DVD/CD: HOP-1000”, Hitachi. Ltd., 1998.

[6]
Miles V.Klein, Thomas E.Furtak, “Optics”, New York: Wiley, 1986.

[7]
Frank L., Leno S., “Introduction to Optics”, Prentice Hall, Englewood Cliffs, 1993.

[8]
Eugene Hecht, “Optics”, Addison Wesley Longman, third edition, 1998.

[9]
Joseph Braat, “Analytical expressions for the aberration coefficients of a tilted plane parallel plate”, Applied Optics, Vol. 36, No. 32, pp. 8459-8466, 1997.

[10]
“DVD specifications for Read-Only Disc”, Hitachi, Matsushita, Mitsubishi, Philips, Pioneer, Sony, Thomson, Toshiba, TimeWarner, JVC, August 1996.

[11]
R.E. Gerber, M. Mansuripur, “Tilt correction in an optical disk system”, Applied Optics, Vol. 35, pp. 7000-7007, 1996.

[12]
Doh, T.-Y. Ma B.I., Choi B.H., Park I.S., Chung C.S., Lee Y.-H., Kim S.J., Shin D.H., “Radial tilt detection using one beam and its compensation in a high-density read only memory” Jpn. J. Appl Phys. Part 1, No.3B pp.1680-1683, Mar 2001

[13]
Shin-inchi Yamada, Seiji Nishiwaki, Atsushi Nakamura, Takashi Ishida, Hiroyuki Yamaguchi, “Track center servo and radial tilt servo system for digital versatile rewritable disk (dvd-ram)” Jpn. J. Appl Phys. Part 1, No.2B pp.867-870, Feb 2000

[14]
C. Bartlett, D. Kay, M. Mansuripur, “Computer simulations of effects of disk tilt and lens tilt on push-pull tracking error signal in an optical disk drive”, Applied Optics, Vol. 36, pp. 8467-8473, 1997.

[15]
“CD-ROM Learning Kit”, 太和科技, 初版, 民國87年1月

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