Abstract

Noise sources in the readback signal for phase-change and magneto-optical disks at red, green, and blue wavelengths are examined, and a simple model is presented to explain the observed noise spectra. For phase-change disks the media noise, which corresponds to ∼0.4% fluctuation in the disk’s amplitude reflection coefficient, is the limiting performance factor for the conventional detection scheme. In magneto-optical media the depolarization noise, whose fluctuations are ∼0.05% of the disk’s reflection coefficient, is the major contributor to the media noise in the differential detection scheme. In phase-change optical disks the main sources of noise are the roughness of the groove profiles and the graininess of the polycrystalline recording layer. In nongrooved regions of the disk the media noise measured with green light is found to be nearly the same as that obtained with the red light. In magneto-optical disks the scattering of light from the rough groove profiles, as well as media inhomogeneities, gives rise to depolarization. Measurements on nongrooved regions of a magneto-optical disk indicate that the media noise obtained with the green light is somewhat higher than that obtained with the red light.

© 1998 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef]
  4. F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
    [CrossRef]
  5. A. G. Dewey, “Measurement and modeling of optical disk noise,” in Optical Mass Data Storage II, R. P. Freese, A. A. Jamberdino, M. de Haan, eds., Proc. SPIE695, 72–78 (1986).
    [CrossRef]
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    [CrossRef]
  7. B. I. Finkelstein, W. C. Williams, “Noise sources in magnetooptic recording,” Appl. Opt. 27, 703–709 (1988).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef]
  13. C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088 (1997).
    [CrossRef]
  14. E. Bahar, S. Chakrabarti, “Scattering and depolarization by large conducting spheres with rough surfaces,” Appl. Opt. 24, 1820–1825 (1985).
    [CrossRef] [PubMed]
  15. Y. Honguh, “Diffraction analysis of groove noise in optical disk readout signal,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 258–266 (1995).
    [CrossRef]

1997 (2)

1994 (1)

1988 (1)

1986 (1)

D. Treves, D. S. Bloomberg, “Signal, noise, and codes in optical memories,” Opt. Eng. 25, 881–891 (1986).
[CrossRef]

1985 (2)

E. Bahar, S. Chakrabarti, “Scattering and depolarization by large conducting spheres with rough surfaces,” Appl. Opt. 24, 1820–1825 (1985).
[CrossRef] [PubMed]

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

1982 (1)

M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Signal and noise in magneto-optical readout,” J. Appl. Phys. 53, 4485–4494 (1982).
[CrossRef]

1978 (1)

Akiyama, T.

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

Bahar, E.

Bartlett, C.

Bates, K.

Bennett, J. M.

Bletscher, W.

Bloomberg, D. S.

D. Treves, D. S. Bloomberg, “Signal, noise, and codes in optical memories,” Opt. Eng. 25, 881–891 (1986).
[CrossRef]

Chakrabarti, S.

Cheng, L.

Chung, C. S.

Connell, G. A. N.

M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Signal and noise in magneto-optical readout,” J. Appl. Phys. 53, 4485–4494 (1982).
[CrossRef]

Dewey, A. G.

A. G. Dewey, “Measurement and modeling of optical disk noise,” in Optical Mass Data Storage II, R. P. Freese, A. A. Jamberdino, M. de Haan, eds., Proc. SPIE695, 72–78 (1986).
[CrossRef]

A. G. Dewey, “Optimizing the noise performance of a magneto-optic read channel,” in Optical Data Storage Topical Meeting, G. R. Knight, C. N. Kurtz, eds., Proc. SPIE1078, 279–286 (1989).
[CrossRef]

Erwin, J. K.

Finkelstein, B. I.

Gerber, R. E.

Goodman, J. W.

M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Signal and noise in magneto-optical readout,” J. Appl. Phys. 53, 4485–4494 (1982).
[CrossRef]

Goodman, T. D.

Heemskerk, J. P. J.

Honguh, Y.

Y. Honguh, “Diffraction analysis of groove noise in optical disk readout signal,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 258–266 (1995).
[CrossRef]

Imanaka, R.

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

Ingers, J.

Inoue, F.

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

Isomura, H.

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

Itoh, A.

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

Kawanishi, K.

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

Kim, S. G.

Kim, T.

Kim, W. M.

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088 (1997).
[CrossRef]

Lee, S. K.

Maeda, A.

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

Mansuripur, M.

M. Mansuripur, C. Peng, J. K. Erwin, W. Bletscher, S. G. Kim, S. K. Lee, R. E. Gerber, C. Bartlett, T. D. Goodman, L. Cheng, C. S. Chung, T. Kim, K. Bates, “Versatile, polychromatic dynamic testbed for optical disks,” Appl. Opt. 36, 9296–9303 (1997).
[CrossRef]

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088 (1997).
[CrossRef]

M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Signal and noise in magneto-optical readout,” J. Appl. Phys. 53, 4485–4494 (1982).
[CrossRef]

M. Mansuripur, The Physical Principles of Magneto-Optical Recording (Cambridge U. Press, London, 1995), Chap. 9.
[CrossRef]

Marchant, A. B.

A. B. Marchant, Optical Recording: A Technical Overview (Addison-Wesley, Reading, Mass., 1990), Chap. 6.

Mattsson, L.

Ohta, T.

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

Peng, C.

Treves, D.

D. Treves, D. S. Bloomberg, “Signal, noise, and codes in optical memories,” Opt. Eng. 25, 881–891 (1986).
[CrossRef]

Williams, W. C.

Yoshioka, K.

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

Appl. Opt. (5)

Appl. Phys. Lett. (1)

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088 (1997).
[CrossRef]

IEEE Trans. Magn. (1)

F. Inoue, A. Maeda, A. Itoh, K. Kawanishi, “The medium noise reduction by intensity dividing readout in magneto-optical memories,” IEEE Trans. Magn. 21, 1629–1631 (1985).
[CrossRef]

J. Appl. Phys. (1)

M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Signal and noise in magneto-optical readout,” J. Appl. Phys. 53, 4485–4494 (1982).
[CrossRef]

Opt. Eng. (1)

D. Treves, D. S. Bloomberg, “Signal, noise, and codes in optical memories,” Opt. Eng. 25, 881–891 (1986).
[CrossRef]

Other (6)

M. Mansuripur, The Physical Principles of Magneto-Optical Recording (Cambridge U. Press, London, 1995), Chap. 9.
[CrossRef]

T. Ohta, K. Yoshioka, H. Isomura, T. Akiyama, R. Imanaka, “High sensitivity overwritable phase-change optical disk for PD systems,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 302–311 (1995).
[CrossRef]

A. B. Marchant, Optical Recording: A Technical Overview (Addison-Wesley, Reading, Mass., 1990), Chap. 6.

A. G. Dewey, “Measurement and modeling of optical disk noise,” in Optical Mass Data Storage II, R. P. Freese, A. A. Jamberdino, M. de Haan, eds., Proc. SPIE695, 72–78 (1986).
[CrossRef]

A. G. Dewey, “Optimizing the noise performance of a magneto-optic read channel,” in Optical Data Storage Topical Meeting, G. R. Knight, C. N. Kurtz, eds., Proc. SPIE1078, 279–286 (1989).
[CrossRef]

Y. Honguh, “Diffraction analysis of groove noise in optical disk readout signal,” in Optical Data Storage ’95, G. R. Knight, H. Ooki, Y. Tyan, eds., Proc. SPIE2514, 258–266 (1995).
[CrossRef]

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Figures (11)

Fig. 1
Fig. 1

Spectra of various noise components at the output of a PC readout system. The traces were obtained, a, with light blocked from reaching the detector; b, with the disk stationary and the light allowed to reach the detector; c, with the disk spinning and the focused spot reading an erased track; d, with the disk spinning and the focused spot reading a written track. The laser had a wavelength of 690 nm. During both writing and readout the disk was spinning at 2400 rpm, and the linear velocity of the track was ∼11.3 m/s.

Fig. 2
Fig. 2

Spectra of various noise components at the output of a PC readout system. The traces were obtained, a, with light blocked from reaching the detector; b, with the disk stationary and the light allowed to reach the detector; c, with the disk spinning and the focused spot reading an erased track; d, with the disk spinning and the focused spot reading a written track. The laser had a wavelength of 514 nm. During both writing and readout the disk was spinning at 2400 rpm, and the linear velocity of the track was ∼11.3 m/s.

Fig. 3
Fig. 3

Spectra of various noise components at the differential output of a MO readout system. (a) The traces were obtained, a, with the light blocked from both detectors; b, with the disk stationary and the light allowed to reach the detectors; c, with the disk spinning and the focused spot reading a written track. The dots overlapping trace c correspond to the noise spectrum obtained from an erased track. (b) The spectra were obtained in a similar fashion, but one of the detectors was blocked. The light for these measurements had a wavelength of 690 nm. During both writing and readout the disk was spinning at 2400 rpm, and the linear velocity of the track was ∼11.3 m/s.

Fig. 4
Fig. 4

Spectra of various noise components at the differential output of a MO readout system. The traces were obtained, a, with the light blocked from both detectors; b, with the disk stationary and the light allowed to reach the detectors; c, with the disk spinning and the focused spot reading a written track. The dots overlapping trace c correspond to the noise spectrum obtained from an erased track. The light for these measurements had a wavelength of 514 nm. During both writing and readout the disk was spinning at 2400 rpm, and the linear velocity of the track was ∼11.3 m/s.

Fig. 5
Fig. 5

Media-noise spectra of the PC disk obtained at 690 nm. During readout the disk was spinning at 3000 rpm, and the linear velocities of the measured tracks were 8.2 m/s. The effective incident laser powers at the disk during reading of the erased (crystalline) track and the amorphized track were 1.36 and 1.92 mW, respectively. The reflected power at the detector was ∼52 μW in both cases.

Fig. 6
Fig. 6

Media-noise spectra of a PC optical disk obtained by reading of an erased track at 690, 514, and 488 nm. The disk was spinning at 2400 rpm, and the linear velocity of the measured track was 11.3 m/s. The incident laser power at the disk for all these wavelengths was ∼1.36 mW, and the reflected powers at the detector were 70, 92, and 70 μW.

Fig. 7
Fig. 7

Media-noise spectra of a 4× MO disk obtained by reading of an erased track at 690 and 514 nm. The disk was spinning at 2400 rpm, and the linear velocity of the measured track was 11.3 m/s. The incident laser power at the disk was 1.28 mW for the red light and 2 mW for the green light; the reflected power at the detector was 18 μW for both red and green lights.

Fig. 8
Fig. 8

Plots of measured MTF’s at the indicated wavelengths for the readout system used in the experiments. During both writing and readout the disk was spinning at 2400 rpm, and the linear velocities of the tracks under consideration were 11.3 m/s.

Fig. 9
Fig. 9

Media-noise spectra of the PC disk obtained by reading of an erased track with the red light and by reading of an erased flat region (i.e., an ungrooved region) with the red and the green wavelengths. The disk was spinning at 3000 rpm, and the linear velocity under the focused spot was 8.2 m/s. The reflected optical power reaching the detector was 114 μW with the red light and 160 μW with the green light.

Fig. 10
Fig. 10

Media-noise spectra of a 4× MO disk obtained by reading of an erased track with the red light and by reading of an erased flat region (i.e., ungrooved) with the red and the green wavelengths. The disk was spinning at 1800 rpm, and the linear velocity under the focused spot was 11.3 m/s. The reflected optical power reaching each detector was ∼20 μW with the red light and ∼27 μW with the green light.

Fig. 11
Fig. 11

Media-noise spectra of the 1× and 4× MO disks obtained with the red light at the output of the differential channel (a) with both detectors active and (b) with one of the detectors blocked. The disks were spinning at 2400 rpm, and the linear velocities of the tracks under consideration were 11.3 m/s. In all cases the optical reflected power reaching each detector was ∼18 μW.

Tables (2)

Tables Icon

Table 1 Measured Fluctuations for MO and PC Media at 690 nm within the 12-MHz Bandwidth of Interest

Tables Icon

Table 2 Normalized Fluctuating Parameters Inferred from the Readout Channel Outputa

Equations (14)

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r t = r 0 1 + δ r t ,
P = P 0 η | 1 + δ e t r 0 1 + δ r t | 2 .
S = η s P 0 η r 0 2 1 + 2   Re δ e + δ r .
i shot = ( 2 eP 0 η η s r 0 2 ) 1 / 2 ,
i laser = 2 P 0 η η s r 0 2 Δ e ,
i disk = 2 P 0 η η s r 0 2 Δ r ,
Δ e = Re 2 δ e t 1 / 2 ,
Δ r = Re 2 δ r t 1 / 2 .
i noise 2 = i th 2 + i shot 2 B + i laser 2 + i disk 2 .
SNR = P 0 η η s Δ R / 2 2 i th 2 + 2 eP 0 η η s R B + 2 P 0 η η s R 2 Δ e 2 + Δ r 2 ,
SNR Δ R R 2 1 16 Δ e 2 + Δ r 2 .
i disk = 0 12 P m f R G 2 B d f 1 / 2 0.26   μ A .
i signal 2 = ( 2 η η s P 0 γ | r x 0 | | r y 0 | ) 2 ,
( i noise ) 2 = [ 2 i th 2 + 2 e η η s P 0 γ 2 | r x 0 | 2 ( 1 + | r y 0 / γ r x 0 | 2 ) ] B + ( 2 η η s P 0 γ | r x 0 r y 0 | ) 2 ( 4 Δ e 2 + Δ x 2 + Δ y 2 + | r x 0 / r y 0 | 2 Δ xy 2 ) .

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