Abstract: A method of marking a thermoplastic article can comprise: combining a thermoplastic with a light-marking additive to form a composition, forming the composition into an article having a maximum optical absorption wavelength; and illuminating, at a marking wavelength, at least a portion of the article with a device having a power of less than or equal to about 200 mW, to form a light-mark. The light-mark can have a size, as measured along a major axis, of greater than or equal to about 10 micrometers. The light-mark can also have a mark absorption wavelength that is greater than or equal to about ±100 nm of the maximum optical absorption wavelength, and can have a spectral absorption curve.

Abstract: Disclosed herein is a method comprising illuminating a microstructured prism, or linear array of prisms of a prism sheet with an incident beam. The method further comprises making measurements of the refracted image of the beam on a measuring device to measure the distance disposed on an opposing side of the prism sheet from the side that the light beam is incident upon. Measurement of two angles of the refracted images of the beam on the ruled scale, measured twice, illuminating the sample at different angles are used in an equation to simultaneously provide the apex angle, the skew angle and the refractive index of the prism sheet.

Abstract: An authentication system may comprise: a first light source, a second light source, and at least three optically filtered light sensing devices. The first light source can have a first light source spectral distribution and can be capable of providing sufficient excitation to produce a photoluminescent emission from a medium comprising a luminescent tag and a color. The second light source can have a visible multi-wavelength spectral distribution and can be capable of providing sufficient visible multi-wavelength illumination of the medium to generate a second analog response. Each light sensing device can have a different device spectral sensitivity range.