Non-Contact Retroreflectometer With Synchronized Mirror Scanning
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Solution Overview
Problem
Conventional methods for measuring the retroreflectivity of road signs and safety markers require physical proximity, which is impractical for elevated signs, and dedicated vehicle-based systems are costly and inefficient.
Innovation Solution
A portable retroreflectometer that performs non-contact measurements using synchronized moving mirror assemblies to maintain concentricity and adjust observation angles, incorporating a light source, collimating lens, imaging lens, and processor for determining optical characteristics from a distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If handheld devices are used to measure retroreflectivity, then measurement precision can be achieved, but the device requires physical proximity to the object which is impractical for elevated signs
Solution Approach 1:
The patent replaces the mechanical contact-based measurement system with an optical system using light sources, lenses, and detectors to perform non-contact measurements of retroreflectivity from a distance, eliminating the need for physical proximity to elevated signs
Solution Approach 2:
The patent introduces optical intermediaries including collimating lenses, imaging lenses, and light collectors that enable the measurement system to interact with the retroreflective surface remotely through optical paths rather than direct physical contact
2Ease of operation
If fixed light sources and cameras mounted on vehicles are used, then non-contact measurement is achieved, but the system requires a dedicated vehicle and is cost prohibitive
Solution Approach 1:
The patent divides the measurement system into separate portable components (light source assembly, optical components, detector, and processing unit) that can be independently configured and deployed without requiring a dedicated vehicle platform, reducing overall system complexity and cost
Solution Approach 2:
The patent designs a universal measurement system that can be adapted to measure various retroreflective objects at different distances and angles using adjustable optical paths and movable components, eliminating the need for specialized vehicle-mounted systems
3Measurement precision
If the observation angle is adjusted to meet ASTM standards, then measurement accuracy is improved, but the alignment of illumination spot and observation point becomes difficult to maintain
Solution Approach 1:
The patent implements feedback control where the detector position and illumination angle are continuously adjusted based on real-time detection of the retroreflected light intensity, automatically maintaining the correct observation angle without complex manual alignment procedures
Solution Approach 2:
The patent uses dynamic adjustment mechanisms that allow the optical components to move and adapt their positions during measurement, enabling automatic maintenance of the illumination spot concentricity with the observation point across varying distances and angles
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient, non-contact measurement of retroreflective materials from various distances, ensuring nighttime visibility of road signs and markers, and providing accurate data on retroreflectivity and degradation.
Implementation Method 1
a light source for emitting a light beam; a first moving mirror assembly for scanning the light beam
Implementation Method 2
a collimating lens for collimating the scanning light on an illumination spot on the surface of the DUT
Implementation Method 3
a retroreflectometer for non-contact measurements of optical characteristics of retroreflective materials
Implementation Method 4
an imaging lens for receiving a reflected scanning light comprised of the collimated scanning light reflected from the surface of the DUT
Implementation Method 5
a light collector for collecting the reflected light from the second moving mirror assembly
Data Source
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AI summary
A retroreflectometer for non-contact measurements of optical characteristics of retroreflective materials from a range of distances includes a light source for emitting a light beam; a first moving mirror assembly for scanning the light beam; a collimating lens for collimating the scanning light on an illumination spot on the surface of the DUT; an imaging lens for receiving a reflected scanning light comprised of the collimated scanning light reflected from the surface of the DUT; a second moving mirror assembly for controlling a predetermined observation angle, wherein the first moving mirror assembly and the second moving mirror assembly moved in synchronization to maintain concentricity of the illumination spot on the surface of the DUT; a light collector for collecting the reflected light from the second moving mirror assembly; a processor including a memory for determining the optical characteristics of the surface of the DUT responsive to the collected reflected light.