Multiple-angle retroreflectometer
First Claim
1. A portable handheld instrument for measuring the retroreflectivity of a surface such as a highway sign or marker configured to be illuminated by vehicle headlights, comprising:
- a housing;
an optical system supported by the housing, the optical system configured to illuminate the retroreflective surface and to focus a retroreflected light, comprising light reflected from the retroreflected surface, into at least two annular zones; and
an electronic system supported by the housing for measuring and processing signals representing an intensity of the retroreflected light in the several annular zones.
1 Assignment
0 Petitions
Accused Products
Abstract
A system and method for measuring the photometric retroreflectivity of materials. The system comprises a light source and a first optical pathway along which an illumination light beam travels originating from the light source, and ending at a retroreflective surface to be measured. A second optical pathway is provided along which a retroreflected beam travels back from the retroreflective surface to an aperture array that selects multiple annular areas to be further directed to multiple detectors, one detector for each annular area selected by the aperture. Each detector has a filter for the determination of photometric retroreflectivity. The retroreflected light reaching the detectors produces currents proportion to the intensity of the light. A high-gain current-to-voltage amplifier is used to provide voltage signal to an analog-to-digital converter that converts a voltage to a digital number. A processor is electrically coupled to the analog-to-digital converter with an accompanying memory on which is stored operating logic adapted to determine the photometric intensity of a predetermined pattern of the retroreflected beam incident to the array of apertures and detectors which defines the retroreflected light which propagates from the retroreflective surface at a predetermined observation angle.
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Citations
19 Claims
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1. A portable handheld instrument for measuring the retroreflectivity of a surface such as a highway sign or marker configured to be illuminated by vehicle headlights, comprising:
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a housing; an optical system supported by the housing, the optical system configured to illuminate the retroreflective surface and to focus a retroreflected light, comprising light reflected from the retroreflected surface, into at least two annular zones; and an electronic system supported by the housing for measuring and processing signals representing an intensity of the retroreflected light in the several annular zones. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification