Abstract

Differential phase detection or differential time detection has been adopted as the method for deriving an optical tracking-error signal for the new generation of optical disks with increased density (DVD system). An overview is given of the various methods in the analog and the binary signal domains and of their properties with respect to optical disk structure, mechanical tolerances, and disk defocus.

© 1998 Optical Society of America

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References

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  1. G. Bouwhuis, J. Braat, “Video disk player optics,” Appl. Opt. 17, 1993–2000 (1978).
    [CrossRef] [PubMed]
  2. J. Braat, “Read-out of optical discs,” in Principles of Optical Disc Systems, G. Bouwhuis, J. Braat, J. Pasman, G. van Rosmalen, K. S. Immink, A. Huijser, eds. (Hilger, Bristol, UK, 1985), pp. 7–87.
  3. J. Isailovic, Videodisc and Optical Memory Systems (Prentice-Hall, Englewood Cliffs, N.J., 1985).
  4. A. Marchant, Optical Recording: A Technical Overview (Addison-Wesley, Reading, Mass., 1990).
  5. G. Thomas, “Optical recording,” in Imaging and Information Storage Technology, W. Gerhartz, ed. (VCH, Weinheim, Germany, 1992), pp. 203–282.
  6. J. Braat, “Centering detection system for an apparatus for playing optically readable record carriers,” U.S. patent4,057,833 (8November1977).
  7. J. Braat, G. Bouwhuis, “Position sensing in video disk readout,” Appl. Opt. 17, 2013–2021 (1978).
    [CrossRef] [PubMed]
  8. J. Braat, G. Bouwhuis, “Optical video disks with undulating tracks,” Appl. Opt. 17, 2022–2028 (1978).
    [CrossRef] [PubMed]
  9. H. Hopkins, “Diffraction theory of laser read-out systems for optical video discs,” J. Opt. Soc. Am. 69, 4–24 (1979).
    [CrossRef]
  10. K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).
  11. Toshiba Corporation, Physical Specifications, Part I of DVD System (Toshiba, Tokyo, 1996), p. 48.
  12. M. Hiragawa, Victor Company of Japan (JVC), Tokyo (personal communication, 1996).

1979 (1)

1978 (3)

Bouwhuis, G.

Braat, J.

J. Braat, G. Bouwhuis, “Position sensing in video disk readout,” Appl. Opt. 17, 2013–2021 (1978).
[CrossRef] [PubMed]

G. Bouwhuis, J. Braat, “Video disk player optics,” Appl. Opt. 17, 1993–2000 (1978).
[CrossRef] [PubMed]

J. Braat, G. Bouwhuis, “Optical video disks with undulating tracks,” Appl. Opt. 17, 2022–2028 (1978).
[CrossRef] [PubMed]

J. Braat, “Centering detection system for an apparatus for playing optically readable record carriers,” U.S. patent4,057,833 (8November1977).

J. Braat, “Read-out of optical discs,” in Principles of Optical Disc Systems, G. Bouwhuis, J. Braat, J. Pasman, G. van Rosmalen, K. S. Immink, A. Huijser, eds. (Hilger, Bristol, UK, 1985), pp. 7–87.

Hiragawa, M.

M. Hiragawa, Victor Company of Japan (JVC), Tokyo (personal communication, 1996).

Hopkins, H.

Immink, K.

K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).

Isailovic, J.

J. Isailovic, Videodisc and Optical Memory Systems (Prentice-Hall, Englewood Cliffs, N.J., 1985).

Marchant, A.

A. Marchant, Optical Recording: A Technical Overview (Addison-Wesley, Reading, Mass., 1990).

Nijboer, J.

K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).

Odaka, K.

K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).

Ogawa, H.

K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).

Thomas, G.

G. Thomas, “Optical recording,” in Imaging and Information Storage Technology, W. Gerhartz, ed. (VCH, Weinheim, Germany, 1992), pp. 203–282.

Appl. Opt. (3)

J. Opt. Soc. Am. (1)

Other (8)

J. Braat, “Read-out of optical discs,” in Principles of Optical Disc Systems, G. Bouwhuis, J. Braat, J. Pasman, G. van Rosmalen, K. S. Immink, A. Huijser, eds. (Hilger, Bristol, UK, 1985), pp. 7–87.

J. Isailovic, Videodisc and Optical Memory Systems (Prentice-Hall, Englewood Cliffs, N.J., 1985).

A. Marchant, Optical Recording: A Technical Overview (Addison-Wesley, Reading, Mass., 1990).

G. Thomas, “Optical recording,” in Imaging and Information Storage Technology, W. Gerhartz, ed. (VCH, Weinheim, Germany, 1992), pp. 203–282.

J. Braat, “Centering detection system for an apparatus for playing optically readable record carriers,” U.S. patent4,057,833 (8November1977).

K. Immink, J. Nijboer, H. Ogawa, K. Odaka, “Method of coding binary data,” U.S. patent4,501,000 (19February1985).

Toshiba Corporation, Physical Specifications, Part I of DVD System (Toshiba, Tokyo, 1996), p. 48.

M. Hiragawa, Victor Company of Japan (JVC), Tokyo (personal communication, 1996).

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Figures (12)

Fig. 1
Fig. 1

Propagation of the focused light beam from the objective toward the disk (shown in transmission) and then toward the detector, which preferably is located in the exit pupil of the objective (far-field region). The diffraction of the impinging light beam by a periodic disk structure gives rise to the specific pattern shown in Fig. 2.

Fig. 2
Fig. 2

Schematic drawing illustrating the far-field pattern generated by an optical disk with a regular information pattern. The centers of the diffracted orders are offset by distances ±X 0 and ±Y 0 in the X and Y directions, respectively, where X 0 = λ/(pN) and Y 0 = λ/(qN); N is the numerical aperture of the scanning laser beam with wavelength λ. The detection region is the inner part of the zeroth order (thick circle); the four quadrants are denoted AD. The track direction is parallel to the X axis; the radial direction is parallel to the Y direction.

Fig. 3
Fig. 3

Phasor diagram representing the contributions of the interfering terms in a quadrant to the total signal at frequency ν. The signal components in quadrants A and B are depicted, where the main difference is caused by the change in sign of the main frequency ν in shifting from the upper-right to the upper-left quadrant. The tracking-dependent phase shifts of components 3 and 4 are denoted by pluses and minuses.

Fig. 4
Fig. 4

Schematically drawn focused spot (circle with midpoint M) is scanning an optical pit with a tracking error v 0. Positions 1 and 3 mark the front and the end of the pit as they are detected by the detector pair (A, C); positions 2 and 4 correspond to the beginning and the end of the pit when they are detected by the diagonal detector pair (B + D).

Fig. 5
Fig. 5

Phase changes that are present in the two diagonal signals, illustrated with the aid of phasor diagrams. Each quadrant signal (A through D) with its tracking-error-dependent phase is shown, and the phase difference between signals (A + C) and (B + D) is used as an error signal to reduce to zero the off-track distance of the scanning spot.

Fig. 6
Fig. 6

Phase change δ that is present in the signal from quadrants A + C as a result of a beam-landing error ∊. The quadrant combination B + D shows an opposite phase shift, and the total error is 2δ.

Fig. 7
Fig. 7

Phase difference Δϕ in the overlapping regions on, e.g., quadrants A or D and B or C in the presence of a certain amount of defocusing. The tangential frequency on the optical disk is one quarter of the cutoff frequency (left). On detector A the average phase of the signal at frequency ν that is due to the interference of the orders 0 and +1 has increased with respect to its original value ψ, whereas the signal resulting from the interference between the orders 0 and -1 (frequency ν) on detector A has decreased in phase. Identical phase shifts are detected by detector D. On detectors B and C the same phase shifts also arise, but they are related to temporal frequencies with opposite sign. Of course, the phase shifts change sign when the defocusing is reversed.

Fig. 8
Fig. 8

Phasor diagram showing the phase change of the reference signal that is due to defocusing. In quadrant A or D the frequency +ν has obtained a total phase of ψ + Δϕ+1, whereas the contribution from the smaller frequency component -ν has a phase -ψ - Δϕ-1. In quadrants B and C the phases have opposite sign. The dashed phasors represent the in-focus position; the solid phasors correspond to a defocused readout setting.

Fig. 9
Fig. 9

Radial tracking signals DTD2 and DTD4 with different amounts of defocus. The defocus parameter DW20 is expressed in wave-front aberration at the pupil rim in units of the wavelength λ of the light. A value of 0.25 corresponds to a defocusing of one focal depth (typically 0.8 μm for a DVD system). The tracking-error signal was numerically computed by use of a long sequence of pits that obey the EFM modulation scheme. The disk layout and the reading conditions are those encountered in the DVD system, but the depth of the information pits has been reduced to 60 nm instead of the common 100 nm.

Fig. 10
Fig. 10

Phasor diagrams for the interfering signals on quadrant A. The signals are generated by a rewritable disk with a phase-change material as the recording medium. The diagrams apply to three situations that differ with respect to phase change ϕ e imparted to the reflected light by the written domains.

Fig. 11
Fig. 11

Radial tracking signals DTD2 and DTD4 obtained from a rewritable disk with an induced phase change ϕ e of -30°. The tracking-error signal was numerically computed with a long sequence of pits that obey the EFM modulation scheme.

Fig. 12
Fig. 12

Layout of an elementary cell of a rewritable disk. The land area is denoted A. A continuous groove with a certain depth for tracking purposes (region B) is present, and in this groove an effect (region C) has been recorded that introduces an extra change in amplitude and phase to the reflected light.

Tables (2)

Tables Icon

Table 1 Different Combinations of Quadrant Signalsa

Tables Icon

Table 2 Amplitudes and Phases of Diffracted Orders from a Rewritable Disk

Equations (24)

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A u ,   v = f x ,   y ,
A u ,   v = A u ,   v R u ,   v ,
A X ,   Y = - 1 A u ,   v R u ,   v = f X ,   Y r X ,   Y .
ϕ m ,   n = ψ m ,   n + 2 π m ν t + 2 π n   v 0 q ,
S A t = W 0 ,   0 ;   + 1 ,   0 cos ψ + 1 , 0 - ψ 0 , 0 + 2 π ν t + W 0 ,   + 1 ;   + 1 ,   + 1 cos ψ + 1 , + 1 - ψ 0 , + 1 + 2 π ν t + W 0 ,   0 ;   + 1 ,   + 1 cos ψ + 1 , + 1 - ψ 0 , 0 + 2 π ν t + ϕ r + W 0 ,   + 1 ;   + 1 ,   0 cos ψ + 1 , 0 - ψ 0 , + 1 + 2 π ν t - ϕ r ,
S A t ,   ϕ r = cos 2 π ν t + ψ + α   cos 2 π ν t + ϕ r + ψ , S B t ,   ϕ r = cos 2 π ν t - ψ + α   cos 2 π ν t - ϕ r - ψ , S C t ,   ϕ r = cos 2 π ν t - ψ + α   cos 2 π ν t + ϕ r + ψ , S D t ,   ϕ r = cos 2 π ν t + ψ + α   cos 2 π ν t - ϕ r + ψ ,
S CA t ,   ϕ r   + 1 + α   cos   ϕ r cos   ψ   cos 2 π ν t , S t PP t ,   ϕ r   - 1 + α   cos   ϕ r sin   ψ   sin 2 π ν t , S r PP t ,   ϕ r   - α   sin   ϕ r sin   ψ   cos 2 π ν t , S d PP t ,   ϕ r   - α   sin   ϕ r cos   ψ   sin 2 π ν t .
S 1 ϕ r     - α   cos 2   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r .
S 2 ϕ r     α   sin   ψ   cos   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r .
S 3 ϕ r     - α   sin   ψ   cos   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r .
S 4 ϕ r     α   sin 2   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r .
τ n = 2   0.1 1 / 4 0.74 0.50 2 π   10 0.85 ,
S A t ,   ϕ r = 1 + cos 2 π ν t + ψ + α   cos 2 π ν t + ϕ r + ψ , S B t ,   ϕ r = 1 + cos 2 π ν t - ψ + α   cos 2 π ν t - ϕ r - ψ , S C t ,   ϕ r = 1 - cos 2 π ν t - ψ + α   cos 2 π ν t + ϕ r - ψ , S D t ,   ϕ r = 1 - cos 2 π ν t + ψ + α   cos 2 π ν t - ϕ r + ψ .
S r PP t ,   ϕ r     - α   sin   ϕ r sin   ψ   cos 2 π ν t -   cos   ψ   cos 2 π ν t , S d PP t ,   ϕ r     - α   sin   ϕ r cos   ψ   sin 2 π ν t +   sin   ψ   sin 2 π ν t .
S 1 ϕ r     - α   cos 2   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r +   sin   ψ   cos   ψ 1 + α   cos   ϕ r , S 2 ϕ r     α   sin   ψ   cos   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r -   sin 2   ψ 1 + α   cos   ϕ r , S 3 ϕ r     - α   sin   ψ   cos   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r -   cos 2   ψ 1 + α   cos   ϕ r , S 4 ϕ r     α   sin 2   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r +   sin   ψ   cos   ψ 1 + α   cos   ϕ r .
S 5 ϕ r = S 1 ϕ r - S 4 ϕ r     sin   ϕ r + 1 / 2 α   sin   2 ϕ r .
S 5 ϕ r = A - D B + C 90 ° - B - C A + D 90 ° .
S 6 ϕ r = S 2 ϕ r - 1 + p S 3 ϕ r   1 + p / 2 sin   ψ × cos   ψ sin   ϕ r + 1 / 2 α   sin   2 ϕ r + / 2 sin 2   ψ - 1 + p cos 2   ψ 1 + α   cos   ϕ r .
p = tan 2   ψ   -   1 .
S 6 ϕ r = CD - AB + p / 4 C + D ) 2 - A + B 2 .
A m ,   n = 1 pq - p / 2 + p / 2 - q / 2 + q / 2   R u ,   v exp 2 π i u m / p + v n / q d u d v .
R A = 1 , R B = exp i ϕ 2 , R C = α   exp i ϕ 2 + ϕ 1 ,
A m ,   n = sinc π m sinc π n + exp i ϕ 2 - 1 × γ 2 q sinc π n γ 2 q sinc π m + α   exp i ϕ 1 + ϕ 2 - exp i ϕ 2 β γ 1 pq × sinc π m β p sinc π n γ 1 q ,
ψ = π - arctan cos ϕ 1 / 2 1 - 2 β γ 1 / pq .

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