Abstract

In optical interferometry diffuse reflectivity of the surface under study should be high and homogeneous. Application of a white reflective coating can strongly improve measurement results. The optical properties of bronze powder, TiO2 powder, white Chinese ink, and MgO coatings are discussed. Measurements of reflected intensity distribution show that white Chinese ink and MgO have superior optical characteristics, and electron microscopy shows that these coatings cause thickness artifacts of less than 7.5 and 17 µm, respectively. The effect on deformation measurements is demonstrated by moiré topography on a thin membrane that is deformed under small static pressures. The membrane center displacement varies from 15 to 100 µm, and within a measuring precision of 2.5 µm no artifacts on this deformation are found.

© 1997 Optical Society of America

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References

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  1. J. Tonndorf, S. M. Khanna, “Tympanic membrane vibrations in human cadaver ears studied by time-averaged holography,” J. Acoust. Soc. Am. 52, 1221–1233 (1972).
    [CrossRef] [PubMed]
  2. S. M. Khanna, Fowler Memorial Laboratory, Columbia University, New York, N.Y. 10032 (personal communication, 1996).
  3. J. J. J. Dirckx, W. F. Decraemer, “Human tympanic membrane deformation under static pressure,” Hear. Res. 51, 93–106 (1991).
    [CrossRef] [PubMed]
  4. J. J. J. Dirckx, W. F. Decraemer, G. Dielis, “Phase shift method based on object translation for full field automatic 3-D surface reconstruction from moire topograms,” Appl. Opt. 27, 1164–1169 (1988).
    [CrossRef] [PubMed]
  5. K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
    [CrossRef] [PubMed]

1991 (1)

J. J. J. Dirckx, W. F. Decraemer, “Human tympanic membrane deformation under static pressure,” Hear. Res. 51, 93–106 (1991).
[CrossRef] [PubMed]

1988 (1)

1987 (1)

K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
[CrossRef] [PubMed]

1972 (1)

J. Tonndorf, S. M. Khanna, “Tympanic membrane vibrations in human cadaver ears studied by time-averaged holography,” J. Acoust. Soc. Am. 52, 1221–1233 (1972).
[CrossRef] [PubMed]

Bank, G.

K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
[CrossRef] [PubMed]

Decraemer, W. F.

Dielis, G.

Dirckx, J. J. J.

Ivarsson, A.

K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
[CrossRef] [PubMed]

Khanna, S. M.

J. Tonndorf, S. M. Khanna, “Tympanic membrane vibrations in human cadaver ears studied by time-averaged holography,” J. Acoust. Soc. Am. 52, 1221–1233 (1972).
[CrossRef] [PubMed]

S. M. Khanna, Fowler Memorial Laboratory, Columbia University, New York, N.Y. 10032 (personal communication, 1996).

Konradsson, K. S.

K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
[CrossRef] [PubMed]

Tonndorf, J.

J. Tonndorf, S. M. Khanna, “Tympanic membrane vibrations in human cadaver ears studied by time-averaged holography,” J. Acoust. Soc. Am. 52, 1221–1233 (1972).
[CrossRef] [PubMed]

Appl. Opt. (1)

Hear. Res. (1)

J. J. J. Dirckx, W. F. Decraemer, “Human tympanic membrane deformation under static pressure,” Hear. Res. 51, 93–106 (1991).
[CrossRef] [PubMed]

J. Acoust. Soc. Am. (1)

J. Tonndorf, S. M. Khanna, “Tympanic membrane vibrations in human cadaver ears studied by time-averaged holography,” J. Acoust. Soc. Am. 52, 1221–1233 (1972).
[CrossRef] [PubMed]

Scand. Audiol. (1)

K. S. Konradsson, A. Ivarsson, G. Bank, “Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane,” Scand. Audiol. 16, 159–166 (1987).
[CrossRef] [PubMed]

Other (1)

S. M. Khanna, Fowler Memorial Laboratory, Columbia University, New York, N.Y. 10032 (personal communication, 1996).

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Figures (4)

Fig. 1
Fig. 1

Histograms of the intensity distribution of the light reflected by a coin, recorded on 200 × 200 pixels with a CCD camera with 256 gray values. The horizontal axis indicates the center of 25 bins in arbitrary units with 0 for CCD dark current and 255 for CCD saturation. Histograms are shown for (a) the uncoated coin, (b) the same coin coated with bronze powder, (c) the coin coated with TiO2 powder, (d) the coin coated by the MgO smoke of burning magnesium wire, and (e) the coin coated with Chinese ink.

Fig. 2
Fig. 2

Scanning electron micrograph of an aluminum substrate coated with Chinese ink. The thickness of the coating (micrometers) was calculated as the projection of the distance between the upper and the lower edge under 45°.

Fig. 3
Fig. 3

Moiré interferometric measurement of the displacement along the center horizontal section of a 50-µm-thick polyethylene membrane under a static pressure of 2500 Pa. The lowest thick curve shows the displacement of the uncoated membrane. The second and third thick curves show the displacement after we coated the membrane with, respectively, MgO and Chinese ink. The differences between the displacement curve of the uncoated membrane and the displacement curves of the membrane coated with ink and MgO are indicated in a thin line, with offsets of 20 and 40 µm.

Fig. 4
Fig. 4

Moiré interferometric measurement of the center displacement of the polyethylene membrane under static pressures between 500 and 2500 Pa. Displacements for the uncoated membrane and for the membrane coated with Chinese ink and MgO are indicated with circles, squares, and triangles, respectively.

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