Polarization-grating moire

Claim 2

Apparatus for the formation of moire-fringe patterns comprising a first grating structure having a periodic variation of polarization, at leat a second grating structure having a periodic variation of polarization positioned in superposition with said first grating structure in a defined optical path, and means for illuminating said grating structures whereby a moirefringe pattern is formed.

Claim 3

The apparatus as defined in claim 1 wherein is further included in said optical path between said first and second grating structures a one-half wave plate for controlling the modulation of the moire-pattern in accordance with the angular position of said plate.

Claim 6

The apparatus as defined in claim 3 wherein is further included low-pass filtering means for eliminating disturbing frequency components.

Claim 7

The apparatus as defined in claim 1 wherein said grating structures are formed of strips cut in different directions from linearly dichroic polarizer sheets.

Claim 8

The apparatus as defined in claim 5 wherein said grating structures are formed such that between successive strips a substantially constant rotation of the transmittance axes of said gratings occur.

Claim 9

The apparatus as defined in claim 1 wherein said grating structures are linear polarizers and wherein is further included two quarter-wave ( lambda /4) plates disposed in said optical path between said first and second grating structures for rotating the direction of polarization of said polarizers.

Claim 10

The apparatus as defined in claim 7 wherein said plates are attached to said polarizers such that the fast axes bisect the two orthogonal directions of said polarizers.

Claim 11

The apparatus as defined in claim 1 wherein said grating structures are binary polarizers.

Claim 12

The apparatus as defined in claim 1 wherein said grating structures are superposed such that the polarization states of the respective structures are orthogonal whereby maximum contrast in the moire pattern is obtained.

Claim 13

Apparatus for producing interferograms in an image plane from an illuminated object comprising: means for illuminating said object, means for polarizing the illumination from said object positioned in the optical path between said object and said image plane, said polarizing means having a periodic variation of polarization, means for splitting said illumination into at least two beams of radiation directed toward said image plane, means for imaging said illumination such that said beams interfere with one another to produce an interferogram in said image plane, and means for compensating said illumination prior to the formation of said interferogram such that the positional restraints of said polarizing means are substantially removed.

Claim 14

Apparatus for producing interferograms in an image plane from an illuminated object comprising: means for illuminating said object, means for polarizing the illumination from said object positioned in the optical path between said object and said image plane, said polarizing means having a periodic variation of polarization, means for splitting said illumination into at least two beams of radiation directed toward said image plane, means for imaging said illumination such that said beams interfere with one another to produce an interferogram in said image plane, and means for compensating said illumination prior to the formation of said interferogram such that the positional restraints of said polarizing means are substantially removed.

Claim 15

The apparatus as defined in claim 11 wherein said compensating means is a quarter-wave plate.

Claim 16

The apparatus as defined in claim 12 wherein said polarizing means comprises at least two polarizers, one of which is disposed in the optical path to function as a structured analyzer.

Claim 19

ThE method of claim 14 wherein said compensating step comprises positioning a compensator in the optical path between said object and said image plane.

Claim 20

The method of claim 15 wherein said compensator is a quarter-wave plate.