Abstract

We propose and experimentally demonstrate an acousto-optic cylindrical lens with a very fast (400-kHz) focal scanning. The lens is realized by use of two adjacent acousto-optic scanners with counterpropagating acoustic waves that have the same frequency modulation but a π phase difference. This scheme completely suppresses the lateral scan but adds the linear chirp of the two waves and thus functions as a fast focal-scan lens. We also demonstrate the use of this scanning lens in a very fast confocal profilometer.

© 2001 Optical Society of America

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References

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  1. L. Zhu, P. C. Sun, and Y. Fainman, Appl. Opt. 38, 5350 (1999).
    [CrossRef]
  2. S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
    [CrossRef]
  3. Y. Takaki and H. Ohzu, Opt. Commun. 126, 123 (1996).
    [CrossRef]
  4. T. Shibaguchi and H. Funato, Jpn. J. Appl. Phys. 31, 3196 (1992).
    [CrossRef]
  5. A. VanderLugt, Optical Signal Processing (Wiley, New York, 1992).
  6. A. VanderLugt and A. M. Bardos, Appl. Opt. 31, 4058 (1992).
    [CrossRef] [PubMed]
  7. One- and two-dimensional focal scans can also be obtained with two and four acoustic transducers, respectively, attached to a single crystal.
  8. N. Freidman, A. Kaplan, and N. Davidson, Opt. Lett. 25, 1762 (2000).
    [CrossRef]
  9. Such a realization causes difficulties, first, because of the jumps in the chirp at the end of every cycle and, second, because of the higher harmonics that are needed, which limit the available scan speed.
  10. Our analysis is readily adapted for other laser beam shapes, such as a Gaussian beam, with small changes of numerical constants.
  11. Brimrose Model TEF-110-60.
  12. A diffraction efficiency >70% for the entire Δf is achievable in commercial AOSs, resulting in >25% power efficiency for the spherical lens configuration.

2000 (1)

1999 (1)

1996 (1)

Y. Takaki and H. Ohzu, Opt. Commun. 126, 123 (1996).
[CrossRef]

1992 (2)

T. Shibaguchi and H. Funato, Jpn. J. Appl. Phys. 31, 3196 (1992).
[CrossRef]

A. VanderLugt and A. M. Bardos, Appl. Opt. 31, 4058 (1992).
[CrossRef] [PubMed]

1985 (1)

S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
[CrossRef]

Bardos, A. M.

Davidson, N.

Fainman, Y.

Freidman, N.

Funato, H.

T. Shibaguchi and H. Funato, Jpn. J. Appl. Phys. 31, 3196 (1992).
[CrossRef]

Kaplan, A.

Ohzu, H.

Y. Takaki and H. Ohzu, Opt. Commun. 126, 123 (1996).
[CrossRef]

Sato, R.

S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
[CrossRef]

Sato, S.

S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
[CrossRef]

Shibaguchi, T.

T. Shibaguchi and H. Funato, Jpn. J. Appl. Phys. 31, 3196 (1992).
[CrossRef]

Sugiyama, A.

S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
[CrossRef]

Sun, P. C.

Takaki, Y.

Y. Takaki and H. Ohzu, Opt. Commun. 126, 123 (1996).
[CrossRef]

VanderLugt, A.

A. VanderLugt and A. M. Bardos, Appl. Opt. 31, 4058 (1992).
[CrossRef] [PubMed]

A. VanderLugt, Optical Signal Processing (Wiley, New York, 1992).

Zhu, L.

Appl. Opt. (2)

Jpn. J. Appl. Phys. (2)

S. Sato, A. Sugiyama, and R. Sato, Jpn. J. Appl. Phys. 24, L626 (1985).
[CrossRef]

T. Shibaguchi and H. Funato, Jpn. J. Appl. Phys. 31, 3196 (1992).
[CrossRef]

Opt. Commun. (1)

Y. Takaki and H. Ohzu, Opt. Commun. 126, 123 (1996).
[CrossRef]

Opt. Lett. (1)

Other (6)

A. VanderLugt, Optical Signal Processing (Wiley, New York, 1992).

Such a realization causes difficulties, first, because of the jumps in the chirp at the end of every cycle and, second, because of the higher harmonics that are needed, which limit the available scan speed.

Our analysis is readily adapted for other laser beam shapes, such as a Gaussian beam, with small changes of numerical constants.

Brimrose Model TEF-110-60.

A diffraction efficiency >70% for the entire Δf is achievable in commercial AOSs, resulting in >25% power efficiency for the spherical lens configuration.

One- and two-dimensional focal scans can also be obtained with two and four acoustic transducers, respectively, attached to a single crystal.

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Figures (4)

Fig. 1
Fig. 1

Schematic experimental setup. A laser beam passes two AOSs with counterpropagating sound waves, with a 180° phase shift between their frequency-modulating signals. The light is focused on a CCD camera that is mounted on a translation stage and used to measure the focal distance. For this measurement, an acousto-optic modulator (AOM) is used to pulse the beam synchronously with the scan, and the focus position changes with the pulse delay time.

Fig. 2
Fig. 2

Measured position of the focal plane as a function of the pulse delay +, around the focus of the AOS lens combined with a 150-mm lens. The solid curve is a sinusoidal fit with a frequency of 400  kHz and a span of 60  mm.

Fig. 3
Fig. 3

Setup for ultrafast confocal profilometer. The AOS fast focal-scan lens is used to scan the focus of the combined lens. A photomultiplier tube is used to measure the intensity of the light that passes the slit in the conjugate focal plane.

Fig. 4
Fig. 4

Calibration of the profilometer: measured times of the peaks in the PMT signal as a function of the position of the mirror . The data are fitted with a sinusoidal scan at a rate of 400  kHz and a span of 100 μm. The inset shows a typical scan of the PMT signal over two scan periods. The time of the peaks is a measure of the position of the reflecting object along the z direction.

Equations (6)

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αx,t=λvf1t+x/v+f2t-x/v,
αlinearx,t=λv2fcenter+2ax/v=αoffaxis+x/F,
F=v22aλ=v2Tscan2 λΔf.
αcosinex,t=λv2fcenter-Δfsin2πt/Tscan×sin2πx/vTscan.
Ft=FAOSsin2πt/Tscan=v2Tscan2πλΔfsin2πt/Tscan.
NRP=4πηTaccess2ΔfTscan,

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