A method for forming a retroreflective prism in a substrate includes inserting and retracting a single point diamond tool through a surface of the substrate while moving the single point diamond tool, the substrate, or both the single point diamond tool and the substrate in a direction of travel along at least one axis to generate a facet in the substrate having a facet face parallel to the direction of travel of at least one of the single diamond point tool or the substrate. The facet face has an angle defined by a chiseling edge of the single point diamond tool. The inserting and retracting is repeated at a plurality of locations on the substrate to form an array of retroreflective microstructures on the surface of the substrate. At least one of the array of retroreflective microstructures is a retroreflective prism having a polygonal projected aperture.

Disclosed is a retro-reflective thread 100 including an internal section 10; a plurality of fibers 12, each fiber comprising a respective longitudinal axis and a respective surface and each fiber comprising a first material that is at least partially optically transmissive, and wherein said plurality of fibers are configured with their respective longitudinal axes substantially co-linearly aligned with one another and said plurality of fibers are interconnected in series around said internal section and wherein a first part 12b of said respective surface of each of said plurality of fibers faces into said internal section; and a reflective material 14 provided on said first part of said respective surface of each of said plurality of fibers.

A method of making an array (18) of aberrated optical elements (20). The method comprises the steps of providing a substrate having a first surface with forming elements thereon, and controlled working a localized region on the first surface of the substrate. The controlled working is of a magnitude sufficient to aberrate one or more of the forming elements in an affected site surrounding the localized region.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

The disclosed structured retroreflective article includes a symbol aligned with raised regions of the structured retroreflective article through an orientation mark which aligns the symbol to the raised region. In one embodiment, the retroreflective article comprises a substrate comprising a background surface and a raised region, a retroreflective film comprising a first symbol and an orientation mark, wherein the retroreflective film is applied to the substrate and the orientation mark aligns the first symbol to the raised region.

Provided is a processing method for a single-column and multi-row equivalent negative refractive flat lens, including: processing an optical material into parallel plates including upper and lower surfaces each being a polished surface; cutting the parallel plates into strip-shaped optical waveguides; plating each polished surface with an aluminum film; attaching and gluing the surfaces together to form a single-column and multi-row strip-shaped optical waveguide array; curing the strip-shaped optical waveguide array through heating treatment; cutting the plate of the strip-shaped optical waveguide array into two sets of plates of strip-shaped optical waveguide array arranged in a direction of 45 degrees; and gluing the two sets of plates in such a manner that arrangement directions of the two sets of plates are perpendicular to each other, and then adding protective window sheets on both sides of the glued plates.

The present disclosure is directed to lamina(e) comprising cube corner elements, a tool comprising an assembly of laminae and replicas thereof. The disclosure further relates to retroreflective sheeting.

Techniques are disclosed to enable manufacture of open-air corner-cube retroreflectors having a corner-cube cavity. The techniques involve additively forming a substrate by way of additive manufacturing technologies such as three-dimensional printing technologies. The techniques further involve optionally machining the additively formed surface of the substrate and replicating a reflective surface in the corner-cube cavity using a master that is coated with a reflective material. An adhesive is applied to the corner-cube cavity so that when the adhesive cures and the master is withdrawn from the corner-cube cavity, the reflective surface adheres to the adhesive and remains an integral part of the retroreflector.

One embodiment of the present disclosure provides a black microprismatic retroreflective film. The black microprismatic retroreflective film comprises a body layer and a black color layer. The body layer includes microprismatic optical elements. The black color layer gives the black microprismatic retroreflective film a daytime color of black. The black microprismatic retroreflective film has a coefficient of retroreflectivity greater than 50 cd/lx/m2 at a 4 degree entrance angle and 0.2 degree observation angle.

Provided are a reflective sheet having selective reflection in a wide wavelength range and a small change in tint depending on angles at which light is visually recognized, a decorative sheet, and a method of manufacturing a reflective sheet, the reflective sheet including a pitch gradient layer in which a helical pitch changes in a thickness direction of the layer. The reflective sheet includes at least one cholesteric liquid crystal layer having wavelength selective reflection properties, in which at least one of the cholesteric liquid crystal layers is a pitch gradient layer in which a helical pitch changes in a thickness direction, a half-width of an integral reflection spectrum of the reflective sheet is 100 nm or longer, and in a case where a wavelength on a short wavelength side that defines the half-width is represented by , a wavelength on a long wavelength side that defines the half-width is represented by , a center wavelength that defines the half-width is represented by .sub.C, .sub.1=(+.sub.C/2, and .sub.2=(.sub.C+)/2, the following Expressions (1) and (2) are satisfied.
IR(.sub.1)>IR(.sub.2) Expression (1)
SCE(.sub.1)/IR(.sub.1)>SCE(.sub.2)/IR(.sub.2) Expression (2)