Abstract

The construction and results obtained with a scanning heterodyne differential microscope capable of simultaneously imaging in differential phase and differential intensity modes are described. Interfering the two signal beams with a common reference beam (indirect interference) permits an optimum differential phase and intensity performance to be obtained simultaneously. The considerations that ensure satisfactory performance are discussed. Results that demonstrate the ability to alter electronically the imaging mode and the optical transfer function within each imaging mode are presented. This permits the system performance to be matched to the requirements of each sample.

© 1995 Optical Society of America

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References

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  1. T. Wilson, C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, New York, 1984).
  2. M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
    [CrossRef]
  3. M. J. Offside, M. G. Somekh, “Interferometric scanning optical microscope for surface characterization,” Appl. Opt. 31, 6772–6782 (1992).
    [CrossRef] [PubMed]
  4. R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
    [CrossRef]
  5. C. W. See, M. Vaez Iravani, “Linear imaging in scanning polarisation/interference contrast optical microscope,” Electron. Lett. 22, 1079–1081 (1986).
    [CrossRef]
  6. M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
    [CrossRef]
  7. C. W. See, M. Vaez Iravani, H. K. Wickramasinghe, “Scanning differential phase-contrast optical microscope-application to surface studies,” Appl. Opt. 24, 2373–2379 (1985).
    [CrossRef] [PubMed]
  8. C. W. See, M. Vaez Iravani, “Differential amplitude scanning optical microscope—theory and practice,” Appl. Opt. 27, 2786–2792 (1988).
    [CrossRef] [PubMed]
  9. C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
    [CrossRef]
  10. M. G. Somekh, “Depth discrimination in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 168, 131–151 (1992).
    [CrossRef]
  11. R. D. Holmes, M. G. Somekh, “Extended focus phase imaging with an interferometric confocal microscope,” Appl. Opt. 33, 654–661 (1994).
    [CrossRef] [PubMed]
  12. R. K. Appel, M. G. Somekh, C. W. See, “A scanning heterodyne interferometer with immunity from microphonics,” in Surface Characterization and Testing II, J. E. Greivenkamp, M. Young, eds., Proc. Soc. Photo-Opt. Instrum. Eng.1164, 250–261 (1989).
  13. R. T. Smith, F. S. Welsh, “Temperature dependence of the elastic, piezoelectric and dielectric constants of lithium tantalate and lithium niobate,” J. Appl. Phys. 42, 2219–2230 (1971).
    [CrossRef]
  14. T. E. Parker, M. B. Shulz, “SiO2 film overlays for temperature-stable surface wave devices,” Appl. Phys. Lett. 26, 75–77 (1975).
    [CrossRef]
  15. J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.
  16. D. K. Hamilton, C. J. R. Sheppard, “Differential phase contrast in scanning optical microscopy,” J. Microsc. (Oxford) 133, 27–39 (1984).
    [CrossRef]
  17. M. G. Somekh, “Image formation in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 160, 225–243 (1990).
    [CrossRef]

1994 (1)

1992 (2)

M. G. Somekh, “Depth discrimination in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 168, 131–151 (1992).
[CrossRef]

M. J. Offside, M. G. Somekh, “Interferometric scanning optical microscope for surface characterization,” Appl. Opt. 31, 6772–6782 (1992).
[CrossRef] [PubMed]

1991 (1)

M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
[CrossRef]

1990 (1)

M. G. Somekh, “Image formation in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 160, 225–243 (1990).
[CrossRef]

1988 (2)

C. W. See, M. Vaez Iravani, “Differential amplitude scanning optical microscope—theory and practice,” Appl. Opt. 27, 2786–2792 (1988).
[CrossRef] [PubMed]

C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
[CrossRef]

1986 (1)

C. W. See, M. Vaez Iravani, “Linear imaging in scanning polarisation/interference contrast optical microscope,” Electron. Lett. 22, 1079–1081 (1986).
[CrossRef]

1985 (2)

M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
[CrossRef]

C. W. See, M. Vaez Iravani, H. K. Wickramasinghe, “Scanning differential phase-contrast optical microscope-application to surface studies,” Appl. Opt. 24, 2373–2379 (1985).
[CrossRef] [PubMed]

1984 (2)

R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
[CrossRef]

D. K. Hamilton, C. J. R. Sheppard, “Differential phase contrast in scanning optical microscopy,” J. Microsc. (Oxford) 133, 27–39 (1984).
[CrossRef]

1975 (1)

T. E. Parker, M. B. Shulz, “SiO2 film overlays for temperature-stable surface wave devices,” Appl. Phys. Lett. 26, 75–77 (1975).
[CrossRef]

1971 (1)

R. T. Smith, F. S. Welsh, “Temperature dependence of the elastic, piezoelectric and dielectric constants of lithium tantalate and lithium niobate,” J. Appl. Phys. 42, 2219–2230 (1971).
[CrossRef]

Appel, R. K.

M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
[CrossRef]

C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
[CrossRef]

R. K. Appel, M. G. Somekh, C. W. See, “A scanning heterodyne interferometer with immunity from microphonics,” in Surface Characterization and Testing II, J. E. Greivenkamp, M. Young, eds., Proc. Soc. Photo-Opt. Instrum. Eng.1164, 250–261 (1989).

Downs, M. J.

M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
[CrossRef]

Ferguson, H. J.

M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
[CrossRef]

Hamilton, D. K.

D. K. Hamilton, C. J. R. Sheppard, “Differential phase contrast in scanning optical microscopy,” J. Microsc. (Oxford) 133, 27–39 (1984).
[CrossRef]

Hobbs, P. C.

R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
[CrossRef]

Holmes, R. D.

Jungerman, R. L.

R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
[CrossRef]

Kino, G. S.

R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
[CrossRef]

McGivern, W. H.

M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
[CrossRef]

Offside, M. J.

Parker, T. E.

T. E. Parker, M. B. Shulz, “SiO2 film overlays for temperature-stable surface wave devices,” Appl. Phys. Lett. 26, 75–77 (1975).
[CrossRef]

See, C. W.

C. W. See, M. Vaez Iravani, “Differential amplitude scanning optical microscope—theory and practice,” Appl. Opt. 27, 2786–2792 (1988).
[CrossRef] [PubMed]

C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
[CrossRef]

C. W. See, M. Vaez Iravani, “Linear imaging in scanning polarisation/interference contrast optical microscope,” Electron. Lett. 22, 1079–1081 (1986).
[CrossRef]

C. W. See, M. Vaez Iravani, H. K. Wickramasinghe, “Scanning differential phase-contrast optical microscope-application to surface studies,” Appl. Opt. 24, 2373–2379 (1985).
[CrossRef] [PubMed]

R. K. Appel, M. G. Somekh, C. W. See, “A scanning heterodyne interferometer with immunity from microphonics,” in Surface Characterization and Testing II, J. E. Greivenkamp, M. Young, eds., Proc. Soc. Photo-Opt. Instrum. Eng.1164, 250–261 (1989).

Sheppard, C. J. R.

D. K. Hamilton, C. J. R. Sheppard, “Differential phase contrast in scanning optical microscopy,” J. Microsc. (Oxford) 133, 27–39 (1984).
[CrossRef]

T. Wilson, C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, New York, 1984).

Shui, Y. A.

J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.

Shulz, M. B.

T. E. Parker, M. B. Shulz, “SiO2 film overlays for temperature-stable surface wave devices,” Appl. Phys. Lett. 26, 75–77 (1975).
[CrossRef]

Smith, R. T.

R. T. Smith, F. S. Welsh, “Temperature dependence of the elastic, piezoelectric and dielectric constants of lithium tantalate and lithium niobate,” J. Appl. Phys. 42, 2219–2230 (1971).
[CrossRef]

Somekh, M. G.

R. D. Holmes, M. G. Somekh, “Extended focus phase imaging with an interferometric confocal microscope,” Appl. Opt. 33, 654–661 (1994).
[CrossRef] [PubMed]

M. G. Somekh, “Depth discrimination in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 168, 131–151 (1992).
[CrossRef]

M. J. Offside, M. G. Somekh, “Interferometric scanning optical microscope for surface characterization,” Appl. Opt. 31, 6772–6782 (1992).
[CrossRef] [PubMed]

M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
[CrossRef]

M. G. Somekh, “Image formation in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 160, 225–243 (1990).
[CrossRef]

C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
[CrossRef]

R. K. Appel, M. G. Somekh, C. W. See, “A scanning heterodyne interferometer with immunity from microphonics,” in Surface Characterization and Testing II, J. E. Greivenkamp, M. Young, eds., Proc. Soc. Photo-Opt. Instrum. Eng.1164, 250–261 (1989).

Vaez Iravani, M.

Valera, M. S.

M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
[CrossRef]

Welsh, F. S.

R. T. Smith, F. S. Welsh, “Temperature dependence of the elastic, piezoelectric and dielectric constants of lithium tantalate and lithium niobate,” J. Appl. Phys. 42, 2219–2230 (1971).
[CrossRef]

Wickramasinghe, H. K.

Wilson, T.

T. Wilson, C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, New York, 1984).

Wu, W. Q.

J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.

Yin, J. H.

J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.

Zhang, D.

J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.

Appl. Opt. (4)

Appl. Phys. Lett. (3)

T. E. Parker, M. B. Shulz, “SiO2 film overlays for temperature-stable surface wave devices,” Appl. Phys. Lett. 26, 75–77 (1975).
[CrossRef]

C. W. See, R. K. Appel, M. G. Somekh, “Differential optical profilometer for simultaneous measurement of amplitude and phase variation,” Appl. Phys. Lett. 53, 10–12 (1988).
[CrossRef]

R. L. Jungerman, P. C. Hobbs, G. S. Kino, “Phase sensitive scanning optical microscope,” Appl. Phys. Lett. 45, 845–848 (1984).
[CrossRef]

Electron. Lett. (2)

C. W. See, M. Vaez Iravani, “Linear imaging in scanning polarisation/interference contrast optical microscope,” Electron. Lett. 22, 1079–1081 (1986).
[CrossRef]

M. S. Valera, M. G. Somekh, R. K. Appel, “Common path differential intensity profilometry using time division multiplexing,” Electron. Lett. 27, 719–720 (1991).
[CrossRef]

J. Appl. Phys. (1)

R. T. Smith, F. S. Welsh, “Temperature dependence of the elastic, piezoelectric and dielectric constants of lithium tantalate and lithium niobate,” J. Appl. Phys. 42, 2219–2230 (1971).
[CrossRef]

J. Microsc. (Oxford) (3)

M. G. Somekh, “Depth discrimination in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 168, 131–151 (1992).
[CrossRef]

D. K. Hamilton, C. J. R. Sheppard, “Differential phase contrast in scanning optical microscopy,” J. Microsc. (Oxford) 133, 27–39 (1984).
[CrossRef]

M. G. Somekh, “Image formation in scanned heterodyne microscope systems,” J. Microsc. (Oxford) 160, 225–243 (1990).
[CrossRef]

Precision Eng. (1)

M. J. Downs, W. H. McGivern, H. J. Ferguson, “A system for measuring the profiles of supersmooth surfaces,” Precision Eng. 7, 211–215 (1985).
[CrossRef]

Other (3)

T. Wilson, C. J. R. Sheppard, Theory and Practice of Scanning Optical Microscopy (Academic, New York, 1984).

R. K. Appel, M. G. Somekh, C. W. See, “A scanning heterodyne interferometer with immunity from microphonics,” in Surface Characterization and Testing II, J. E. Greivenkamp, M. Young, eds., Proc. Soc. Photo-Opt. Instrum. Eng.1164, 250–261 (1989).

J. H. Yin, W. Q. Wu, D. Zhang, Y. A. Shui, “Temperature characteristics of Rayleigh waves in SiO2 Y-X LiNbO3 structure,” in Proceedings of the Ultrasonics Symposium, B. R. McAroy, ed. (Institute of Electrical and Electronic Engineers, New York, 1987), pp. 237–240.

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Figures (12)

Fig. 1
Fig. 1

Schematic diagram of differential intensity and phase scanning optical microscope: BS, beam splitter; CCA, current-controlled attenuator.

Fig. 2
Fig. 2

Schematic that shows the principle of the differential intensity system.

Fig. 3
Fig. 3

Schematic diagram that shows the modulation scheme possible for simultaneous differential intensity and phase operation. Regions 1 and 3 give the differential intensity response, and region 2 gives the differential phase response.

Fig. 4
Fig. 4

Schematic diagram of the electronic systems used to extract the differential phase signal: (a) filter-based system, (b) SAW-delay-line-based system. R. F., radio frequency; M’s, mixers; S’s, signal generators.

Fig. 5
Fig. 5

Electronic system used to equalize the power in beams A and B; CCA, current-controlled attenuator.

Fig. 6
Fig. 6

Micrographs of periodic samples: (a) differential intensity response, frequency difference 1 MHz, corresponding to a beam separation of 0.7 μm; (b) differential phase response, frequency difference 1 MHz; (c) differential intensity response, frequency difference 10 MHz, corresponding to a beam separation of 7 μm; (d) differential phase response, frequency difference 10 MHz. Samples have 20-nm-deep etched tracks and were imaged with a 0.25-NA objective. Full width across the image is 480 μm.

Fig. 7
Fig. 7

Micrographs of a partially implanted silicon wafer: (a) differential intensity response, frequency difference 1 MHz, corresponding to a beam separation of 0.3 μm; (b) differential intensity response, frequency difference 10 MHz, corresponding to a beam separation of 3.0 μm. The sample was imaged with a 0.65-NA objective. The full width across the image is 200 μm.

Fig. 8
Fig. 8

Micrographs of onion skin: (a) differential intensity response, frequency difference 1 MHz, corresponding to a beam separation of 0.3 μm; (b) differential phase response, frequency difference 1 MHz; (c) differential intensity response, frequency difference 10 MHz, corresponding to a beam separation of 3 μm; (d) differential phase response, frequency difference 10 MHz. The sample was imaged with a 0.65-NA objective. The full width across the image is 200 μm.

Fig. 9
Fig. 9

Real part of the weak object transfer function (solid curve), and the imaginary part of the corresponding differential intensity transfer function for normalized beam separations of 0.62π (dashed curve), π (dotted curve), and 6.2π (dotted–dashed curve).

Fig. 10
Fig. 10

Theoretical response of differential intensity system to a point scatterer for normalized beam separations of 0.62π (solid curve), π (dashed curve), and 6.2π (dotted curve). Because the response is odd, only the response for positive normalized positions is shown.

Fig. 11
Fig. 11

Schematic diagram that shows the leakage of microphonics into the detection band of the microscope: (a) conventional absolute phase interferometer; (b) indirect interference differential phase system. Infinitely sharp filters are shown for clarity.

Fig. 12
Fig. 12

CPF versus Bragg cell modulation frequency for a Butterworth filter with a cut-off frequency of 1.5 kHz (solid curve, fourth-order filter; dashed curve, second-order filter).

Equations (9)

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Δ θ = ( λ opt 2 v ac ) ( f 1 - f 2 ) ,
O A ( t ) = ½ R A [ 1 + S ( t ) ] cos [ 4 π f 1 t + θ 1 + m 1 ( t ) ] ,
O B ( t ) = ½ R B [ 1 - S ( t ) ] cos [ 4 π f 2 t + θ 2 + m 2 ( t ) ] ,
i ( x s ) = - - C part ( m ; p ) T ( m ) T * ( p ) × exp 2 π j ( m - p ) x s d m d p ,
C DI ( m ; p ) = j C part ( m ; p ) sin 2 π ( m - p ) ɛ ,
CPF = 1 - N diff N conv ,
O A ( t ) ½ [ cos ( 2 π f 1 t + θ 1 ) - m ( t ) sin ( 2 π f 1 t + θ 1 ) + m ( t ) S ( t ) sin ( 2 π f 1 t + θ 1 ) ] + ½ S ( t ) cos ( 2 π f 1 t + θ 1 ) ,
O B ( t ) ½ [ cos ( 2 π f 2 t + θ 2 ) - m ( t ) sin ( 2 π f 2 t + θ 2 ) - m ( t ) S ( t ) sin ( 2 π f 2 t + θ 2 ) ] - ½ S ( t ) cos ( 2 π f 2 t + θ 2 ) .
O ( t ) = A { cos [ 2 π ( f 1 - f 2 ) t + θ 1 - θ 2 ] - 2 S ( t ) m f ( t ) sin [ 2 π ( f 1 - f 2 ) t + θ 1 - θ 2 ] } ,

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