Abstract

This paper describes a moiré technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects. A grid pattern is generated on the object by illuminating it with a laser interference pattern, and a master negative is made by photographing the illuminated object with a view camera. With the negative occupying its original position, the moiré pattern corresponding to changes in the object can be observed in real time by viewing the image of the deformed or second object through the negative. The technique is noncontacting and quantitative. It is useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.

© 1969 Optical Society of America

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References

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  1. G. Oster, Y. Nishijima, Sci. Amer. 208, 54 (May1963).
    [CrossRef]
  2. W. F. Riley, Exper. Mech. 7, 19A (1967).
    [CrossRef]
  3. A. J. Durelli, Applied Stress Analysis (Prentice-Hall, Inc., Princeton, 1967), pp. 60–65.
  4. L. I. Goldfischer, J. Opt. Soc. Amer. 55, 247 (1965).
    [CrossRef]
  5. R. S. Longhurst, Geometrical and Physical Optics (John Wiley & Sons, Inc., New York, 1967), p. 307.
  6. J. Strong, Concepts of Classical Optics (W. H. Freeman and Co., San Francisco, 1958), p. 348.

1967 (1)

W. F. Riley, Exper. Mech. 7, 19A (1967).
[CrossRef]

1965 (1)

L. I. Goldfischer, J. Opt. Soc. Amer. 55, 247 (1965).
[CrossRef]

1963 (1)

G. Oster, Y. Nishijima, Sci. Amer. 208, 54 (May1963).
[CrossRef]

Durelli, A. J.

A. J. Durelli, Applied Stress Analysis (Prentice-Hall, Inc., Princeton, 1967), pp. 60–65.

Goldfischer, L. I.

L. I. Goldfischer, J. Opt. Soc. Amer. 55, 247 (1965).
[CrossRef]

Longhurst, R. S.

R. S. Longhurst, Geometrical and Physical Optics (John Wiley & Sons, Inc., New York, 1967), p. 307.

Nishijima, Y.

G. Oster, Y. Nishijima, Sci. Amer. 208, 54 (May1963).
[CrossRef]

Oster, G.

G. Oster, Y. Nishijima, Sci. Amer. 208, 54 (May1963).
[CrossRef]

Riley, W. F.

W. F. Riley, Exper. Mech. 7, 19A (1967).
[CrossRef]

Strong, J.

J. Strong, Concepts of Classical Optics (W. H. Freeman and Co., San Francisco, 1958), p. 348.

Exper. Mech. (1)

W. F. Riley, Exper. Mech. 7, 19A (1967).
[CrossRef]

J. Opt. Soc. Amer. (1)

L. I. Goldfischer, J. Opt. Soc. Amer. 55, 247 (1965).
[CrossRef]

Sci. Amer. (1)

G. Oster, Y. Nishijima, Sci. Amer. 208, 54 (May1963).
[CrossRef]

Other (3)

R. S. Longhurst, Geometrical and Physical Optics (John Wiley & Sons, Inc., New York, 1967), p. 307.

J. Strong, Concepts of Classical Optics (W. H. Freeman and Co., San Francisco, 1958), p. 348.

A. J. Durelli, Applied Stress Analysis (Prentice-Hall, Inc., Princeton, 1967), pp. 60–65.

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Figures (7)

Fig. 1
Fig. 1

Contour stripes projected upon a telephone using a Lloyd's mirror arrangement for generating the two light beams. The 6-mm spacing between the light sheets is much greater than normally would be employed for moiré gauging.

Fig. 2
Fig. 2

Projection of light sheets upon a curved surface. For simplicity, only two sheets are shown with dotted lines lying behind sheet B.

Fig. 3
Fig. 3

Ray optic focal depth.

Fig. 4
Fig. 4

Master negative of a turbine blade, d = 0.33 mm, ϕ = 40°. (Ignore the coarse, spurious moiré fringe pattern caused by the halftone screen.)

Fig. 5
Fig. 5

Diagram of the optical arrangement used for real-time moiré gauging.

Fig. 6
Fig. 6

Photograph of a master turbine blade compared with itself (upper) and with a replica blade (lower). The jig used to position the blades in place is seen just below the blades.

Fig. 7
Fig. 7

Moiré fringes from a turbine blade undergoing torsion. From top to bottom, the blades are twisted (right end) with angular increments of 5°.

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

d = λ / 2 sin 1 2 θ .
δ = d / cos ϕ ,
Δ = d ( cos ψ / cos ϕ ) ,
δ = d / ( v 1 ) , and Δ = d ( v n ) / ( v 1 ) .
L / D = S / N λ .
Δ L 2 ( S 2 / N λ ) .
S = d [ v n / | v × ( l × n ) | ] .

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