Processes and devices for measuring stresses within a transparent body for electromagnetic waves

Claim 1

A photoelasticity-measuring apparatus comprising a supporting frame, nonpolarized light source means, a first optical system mounted onto said supporting frame and containing said light source means, said optical system focusing said nonpolarized light from said source means onto a predetermined point along a lighting axis, supporting means mounted onto said frame being adjustable in three mutually perpendicular directions for supporting a three-dimensional photoelastic model so as to expose predetermined points of said model to said image of said source means, controlling means for rotating said model about an observation axis perpendicular to said lighting axis and forming a a horizontal plane with said lighting axis, said two axes intersecting at said predetermined point of said model, a constantly rotating analyzer centrally located about said observation axis, a photomultiplier positioned along said observation axis, a second optical system mounted onto said supporting frame and containing said analyzer and said photomultiplier and electronic circuit means for separating and simultaneously measuring the DC and AC components of the voltage output of said photomultiplier.

Claim 5

An apparatus for measuring the mechanical stresses in any point of a three-dimensional light-transparent model, comprising a controlled and stabilized source of nonpolarized light, an optical system focusing a sharp image of said source onto a selected point of said model, means for adjusting the position of said model in space such that said sharp image can be focused onto a number of points within said model, two diaphragms which define an observation axis along which there is provided a constantly rotating analyzer for use with elliptically polarized waves, the polarized light scattered by said point passing through said two diaphragms; a photomultiplier adapted to receive said scattered light after it has traversed said analyzer, electronic means for measuring the magnitude of the AC voltage output from said photomultiplier, whereby the position of the axis and their bisectors as well as the flattening of the ellipse of polarized light coming from the birefringence of said point can be determined and computing means for deriving from said determined values, by mathematical formulas, the mechanical stress at said point.

Claim 6

An apparatus for measuring the mechanical stresses in any point of a three-dimensional light-transparent model, comprising a controlled and stabilized source of nonpolarized light, an optical system focusing a sharp image of said source onto a selected point of said model, means for adjusting the position of said model in space such that said sharp image can be focused onto a number of points within said model, two diaphragms which define an observation axis along which there is provided a constantly rotating analyzer for use with elliptically polarized waves, the polarized light scattered by said point passing through said two diaphragms; a photomultiplier adapted to receive said scattered light after it has traversed said analyzer, electronic means for measuring the magnitude of the AC voltage output from said photomultiplier, whereby the position of the axis and their bisectors as well as the flattening of the ellipse of polarized light coming from the birefringence of said point can be determined and computing means for deriving from said determined values, by mathematical formulas, the mechanical stress at said point.

Claim 7

A method for measuring the ratio of the long and short axes (flattening) of the ellipse of polarized light in any point of a flat, two-dimensional model of polarizing material using an optical system, an analyzer, a photomultiplier and a measuring system, comprising the steps of: a. focusing an image of nonpolarized light source means onto a predetermined point of said flat model along an optical axis by means of said optical system; b. constantly rotating said analyzer about an observation axis perpendicular to said optical axis; c. positioning said photomultiplier along said observation axis to receive the output of said analyzer; d. measuring the R.M.S. of the AC current output from the photomultiplier wherein the maximum and minimum values correspond to the positions of the axis and the minimum value with respect to the normalized maximum value is a function of the flattening of the ellipse of polarized light in the direction of the observation axis; and e. repeating the process after displacing the model along the observation axis by a distance dx, the two measurements permitting the determination of the thickness dx of the birefringent, which is perpendicular to the axis of observation.

Claim 8

A method for measuring the ratio of the long and short axes (flattening) of the ellipse of polarized light in any point of a flat, two-dimensional model of polarizing material using an optical system, an analyzer, a photomultiplier and a measuring system, comprising the steps of: a. focusing an image of nonpolarized light source means onto a predetermined point of said flat model along an optical axis by means of said optical system; b. constantly rotating said analyzer about an observation axis perpendicular to said optical axis; c. positioning said photomultiplier along said observation axis to receive the output of said analyzer; d. measuring the R.M.S. of the AC current output from the photomultiplier wherein the maximum and minimum values correspond to the positions of the axis and the minimum value with respect to the normalized maximum value is a function of the flattening of the ellipse of polarized light in the direction of the observation axis; and e. repeating the process after displacing the model along the observation axis by a distance dx, the two measurements permitting the determination of the thickness dx of the birefringent, which is perpendicular to the axis of observation.