Abstract

A lens made of a birefringent material shows two focal points. If the polarization of incident light is switched periodically and a detector is placed between the two focal points, this property can be utilized to detect a focus error signal equivalent to that of a dual detection optics. The proposed system offers the possibility to achieve amplitude detection for the focus error. It results in a compact optical pickup with reduced adjustment requirements. A second possible pickup uses a birefringent lens and a Wollaston prism. In this case, a compact dual detection method is achieved.

© 1990 Optical Society of America

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References

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  1. Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).
  2. S. Yonezawa et al., “Method and Apparatus for Recording and Reproducing a Video-Disk with an Oscillated Track,” U.S. Patent4,223,187.
  3. G. Bouwhuis et al., Principles of Optical Disc Systems (Adam Hilger, Bristol, 1985), p. 75.
  4. Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).
  5. M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.
  6. S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).
  7. D. Malacara, Optical Shop Testing (Wiley, New York, 1978).
  8. M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1970) Chap. 14.
  9. We assume in the following a crystal which shows positive birefringence, i.e., ne > no (and therefore also fe < fo). If a crystal showing negative birefringence is used, indices e and o have to be exchanged in all the formulas to find the correct results.
  10. M. Ojima, N. Ohta, “Erasable Optical Disk Technologies,” Hitachi Rev. 37 (1988).
  11. Because a birefringent material has two refractive indices, a lens made of a birefringent material shows two spherical aberrations. Similarly, because a birefringent material has two dispersion relations, a lens made of a birefringent material shows two different chromatic aberrations. In general, it is impossible to correct the aberrations for both indices; only a correction of the mean value is possible.
  12. Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
    [CrossRef]

1988 (1)

M. Ojima, N. Ohta, “Erasable Optical Disk Technologies,” Hitachi Rev. 37 (1988).

1986 (1)

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

1983 (1)

Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).

1976 (1)

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1970) Chap. 14.

Bouwhuis, G.

G. Bouwhuis et al., Principles of Optical Disc Systems (Adam Hilger, Bristol, 1985), p. 75.

Fukumoto, A.

M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.

Horigome, S.

Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).

Kaku, T.

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

Kato, T.

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

Kubota, S.

M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.

Maeda, T.

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

Malacara, D.

D. Malacara, Optical Shop Testing (Wiley, New York, 1978).

Matsuhashi, Y.

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Mizuishi, K.

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

Morikawa, T.

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Nakamura, S.

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

Nakao, T.

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

Ohta, N.

M. Ojima, N. Ohta, “Erasable Optical Disk Technologies,” Hitachi Rev. 37 (1988).

Ojima, M.

M. Ojima, N. Ohta, “Erasable Optical Disk Technologies,” Hitachi Rev. 37 (1988).

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

Oka, M.

M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.

Osato, K.

M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.

Sakurai, K.

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Seko, A.

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Shimada, J.

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Tsunoda, Y.

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).

Tsutsumi, Z.

Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1970) Chap. 14.

Yonezawa, S.

S. Yonezawa et al., “Method and Apparatus for Recording and Reproducing a Video-Disk with an Oscillated Track,” U.S. Patent4,223,187.

Hitachi Rev. (1)

M. Ojima, N. Ohta, “Erasable Optical Disk Technologies,” Hitachi Rev. 37 (1988).

Opt. Commun. (1)

Y. Matsuhashi, T. Morikawa, A. Seko, K. Sakurai, J. Shimada, “Self Coupled Optical Pick-Up,” Opt. Commun. 17, 95 (1976).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (2)

Y. Tsunoda, T. Kaku, S. Nakamura, T. Maeda, “On-Land Composite Pregroove Method for High Track Density Recording,” Proc. Soc. Photo-Opt. Instrum. Eng. 695, 224–229 (1986).

Y. Tsunoda, S. Horigome, Z. Tsutsumi, “Optical Digital Data Storage Technologies with Semiconductor Laser Head,” Proc. Soc. Photo-Opt. Instrum. Eng. 382, 252 (1983).

Other (8)

M. Oka, A. Fukumoto, K. Osato, S. Kubota, “A New Focus Servo Method for Magneto-Optical Disk Systems,” in Proceedings, International Symposium on Optical Memory (1987), pp. 187–190.

S. Nakamura, M. Ojima, T. Nakao, T. Kato, K. Mizuishi, “Compact Two-Beam Head with a Hybrid Two-Wavelength Laser Array for Magneto-Optic Recording,” in Proceedings, International Symposium on Optical Memory (1987), pp. 117–120; Jpn. J. Appl. Phys. Suppl.26-4 (1987).

D. Malacara, Optical Shop Testing (Wiley, New York, 1978).

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1970) Chap. 14.

We assume in the following a crystal which shows positive birefringence, i.e., ne > no (and therefore also fe < fo). If a crystal showing negative birefringence is used, indices e and o have to be exchanged in all the formulas to find the correct results.

S. Yonezawa et al., “Method and Apparatus for Recording and Reproducing a Video-Disk with an Oscillated Track,” U.S. Patent4,223,187.

G. Bouwhuis et al., Principles of Optical Disc Systems (Adam Hilger, Bristol, 1985), p. 75.

Because a birefringent material has two refractive indices, a lens made of a birefringent material shows two spherical aberrations. Similarly, because a birefringent material has two dispersion relations, a lens made of a birefringent material shows two different chromatic aberrations. In general, it is impossible to correct the aberrations for both indices; only a correction of the mean value is possible.

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Figures (7)

Fig. 1
Fig. 1

Pickup of an optical disk using a focus error detection optics consisting of a birefringent lens and a switchable halfwave plate.

Fig. 2
Fig. 2

Experimental setup for measuring the focus error signal furnished by a focus error detection optics consisting of a birefringent lens and a Wollaston prism.

Fig. 3
Fig. 3

Geometric properties of the birefringent lens and the correcting dispersive lens.

Fig. 4
Fig. 4

Calculated results of the relative intensities detected in the two branches of the focus error detection optics and their difference.

Fig. 5
Fig. 5

Measured intensities in the two branches of the focus error detection optics without focus error correction.

Fig. 6
Fig. 6

Measured focus error signal and the SCOOP signal without focus error correction. The full width of the SCOOP signal is ~8 μm.

Fig. 7
Fig. 7

Measured focus error signal with focus error correction.

Equations (28)

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f o = R n o - 1 ,             f e = R n e - 1 ,
z = 2 f o · f e f o + f e ,
d 1 = d 0 f o - f e f o + f e ,
α = f o - f e f o + f e = n e - n o n e + n o - 2
d 0 o = d 0 e = d 0 · D / d 1 = D / α .
d 0 o = min [ D α · 1 1 - α o β , d 0 ] ,
d 0 e = min [ D α · 1 1 - α e β , d 0 ] ,
α o = 2 f 1 2 [ 2 f o f e f o - f e + ( a 1 - f 1 ) ] ,
α e = 2 f 1 2 [ 2 f o f e f o - f e - ( a 1 - f 1 ) ] ,
β = b - f 1 .
S = β d 0 o 2 - d 0 e 2 d 0 2 = 2 D 2 α 2 d 0 2 ( α o + α e ) .
z = f 3 2 f o f e - a 2 ( f o + f e ) 2 f o f e + ( f 3 - a 2 ) ( f o + f e ) ,
d 1 = d 0 f 3 ( f o - f e ) 2 f o f e + ( f 3 - a 2 ) ( f o + f e ) ,
α = f 3 ( f o - f e ) 2 f o f e + ( f 3 - a 2 ) ( f o + f e ) ,
z o = f 3 f o - a 2 f o + f 3 - a 2 ,
z e = f 3 f e - a 2 f e + f 3 - a 2 .
f o = 11.834 mm ,
f e = 11.642 mm ,
f 3 = - 20.628 mm ,
a 2 = - 0.782 mm ,
z = 31.850 mm ,
z o = 32.484 mm ,
z e = 31.240 mm ,
α = 2.08 × 10 - 2 .
f 1 = 4.54 mm ,
d 1 = α · d 0 = 94.4 μ m ,
α o = 0.156 / μ m , α e = 0.123 / μ m .
δ = n e - n o n e + n o - 2

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