retroreflectometer

A retroreflectometer is an optical instrument used to measure retroreflection. Retroreflection is a property of surfaces that reflect light directly back to the source of the light, regardless of the angle of incidence. This phenomenon is commonly seen in reflective materials like those used on road signs, safety clothing, and bicycle reflectors.

Retroreflectometers work by emitting a beam of light and then measuring the intensity of the light that is reflected back. The instrument typically contains a light source, such as an LED or a lamp, and a detector, such as a photodiode or a CCD sensor. The light source is positioned at a fixed angle relative to the detector, mimicking the typical viewing conditions of a retroreflective surface. The measurement is usually expressed in terms of the retroreflective coefficient, often denoted as R', which quantifies how effectively a surface returns light to its origin. Higher R' values indicate better retroreflective performance.

These instruments are crucial for quality control and performance verification of retroreflective materials. For example, they are used to ensure that traffic signs meet regulatory standards for visibility, or that safety vests are sufficiently reflective to be seen by drivers in low-light conditions. Different types of retroreflectometers exist, varying in their measurement geometry, light sources, and measurement units, to suit specific applications and international standards.