Abstract: The present invention comprises various embodiments of a retroreflectometer capable of measuring the retroreflectance of a material. The retroreflectometer comprises an illumination path and a retroreflection path. The illumination path comprises focusing optics, a source aperture, a beamsplitter and a collimating lens. The retroreflection path comprises a focusing lens, a beamsplitter, a receiver aperture and a receiver. The source aperture shapes the transverse profile of the light to make it appropriate to the measurement. Focusing optics, such as a biconvex lens, may be placed between the light source and the source aperture. After the beam is reflected by the object under test, it enters the retroreflection path of the instrument. The focusing lens focuses the light through the beamsplitter and onto the receiver aperture. The receiver aperture may be the input slit for a spectrometer, or there may be optics, such as a lens or an optical fiber, that transfer the light from the aperture to the receiver.

Abstract: The present invention comprises various embodiments of a retroreflectometer capable of measuring the retroreflectance of a material. The retroreflectometer comprises an illumination path and a retroreflection path. The illumination path comprises focusing optics, a source aperture, a beamsplitter and a collimating lens. The retroreflection path comprises a focusing lens, a beamsplitter, a receiver aperture and a receiver. The source aperture shapes the transverse profile of the light to make it appropriate to the measurement. Focusing optics, such as a biconvex lens, may be placed between the light source and the source aperture. After the beam is reflected by the object under test, it enters the retroreflection path of the instrument. The focusing lens focuses the light through the beamsplitter and onto the receiver aperture. The receiver aperture may be the input slit for a spectrometer, or there may be optics, such as a lens or an optical fiber, that transfer the light from the aperture to the receiver.

Abstract: A reflective article has a structured surface which includes geometric structures each having at least three specularly reflecting faces which converge at an apex or other extremity. The article is marked with a plurality of spots located between the extremities, the spots having different reflectivity characteristics than the specularly reflecting faces. The geometric structures can comprise cube corner elements. The spots can be diffusely reflecting and distributed uniformly on the structured surface or distributed to define a particular pattern. The article can have a plurality of first active areas at a first illumination geometry, and the spots can be sized and positioned such that they avoid the first active areas. The article can have first inactive areas adjacent the first active areas, and each spot can cover a majority of one inactive area.

Abstract: a retroluminometer for measuring retroreflectivity of signs or markings at their actual point of use comprises (1) a source of alternating light; (2) optical means for both directing the alternating light onto a sign or marking that is to be tested and for transmitting light retroreflected by the sign or marking onto a panel within the retroluminometer; (3) a matrix of light-transmitting means arranged on the face of the panel; (4) photosensing means optically connected to the light-transmitting means and adjustable to sense and measure the light from different ones of the light-transmitting means, thereby measuring retroreflection at different angles of deviation from the axis of the light beam incident on the sign or marking; and (5) electric circuitry for presenting the photosensed light as a visually-readable measurement.