Method for optical characterization and evaluation of optically variable devices and media
AssigneeApplied Extrusion Technologies, Inc.
InventorsRobert K. Grygier, Kelan Wieloch
Life of this patent
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Abstract
Methods for evaluating an optically variable device (“OVD”) or optically variable media (“OVM”) are disclosed. The methods include the steps of applying light of a single wavelength from a calibrated light source to the OVD or OVM; measuring the light diffracted by the OVD or OVM with an integrating sphere; measuring the total incident light on the OVD or OVM; and calculating a diffraction efficiency for the OVD or OVM at the single wavelength based on the measurement of light diffracted and the measurement of total incident light.
Claims29
A method of evaluating an Optically Variable Device (OVD) or Optically Variable Media (OVM), comprising the steps of:
- a) applying light of a single wavelength from a calibrated light source to the OVD or OVM;
- b) measuring light diffracted by the OVD or OVM with an integrating sphere;
- c) measuring total incident light on the OVD or OVM;
- and
- d) calculating a diffraction efficiency for the OVD or OVM at said single wavelength based on said measurement of light diffracted and said measurement of total incident light.
A method of evaluating optical characteristics of an Optical Variable Device (OVD) or Optically Variable Media (OVM), comprising the steps of:
- a) measuring a diffraction efficiency the OVD or OVM for a plurality of wavelengths;
- b) establishing a desired optical characteristic for a particular OVD or OVM design;
- and
- c) evaluating a plurality of OVDs or OVMs having said particular design by performing step “a” for each one of said plurality and comparing the result of step “a” with said desired optical characteristic.
A method for evaluating an Optically Variable Device or Optically Variable Media under test having a grating depth and period, comprising the steps of:
- a) applying light of a single wavelength to the OVD or OVM under test with a calibrated light source;
- b) collecting and measuring light diffracted by said OVD or OVM under test with an integrating sphere;
- c) calculating a wavelength dependent diffraction efficiency of the OVD or OVM under test using said measured diffracted light;
- d) applying light of a single wavelength to the OVD or OVM under test with a calibrated light source;
- e) collecting and measuring light reflected by said OVD or OVM under test with an integrating sphere;
- f) calculating a wavelength dependent reflectivity for the OVD or OVM under test;
- g) Normalizing said diffraction efficiency relative to said reflectivity;
- h) Repeating steps “a”-“g” for a plurality of wavelengths;
- i) selecting an exemplary OVD or OVM target having a known normalized diffraction efficiency;
- and
- j) Evaluating the OVD or OVM under test by comparing said normalized diffraction efficiency with said known normalized diffraction efficiency of said exemplary OVD or OVM.
Dependencies are inferred from the claim text.