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Gloss meter in action. A glossmeter (also gloss meter) is an instrument which is used to measure specular reflection gloss of a surface. Gloss is determined by projecting a beam of light at a fixed intensity and angle onto a surface and measuring the amount of reflected light at an equal but opposite angle.
When reflection occurs from thin layers of material, internal reflection effects can cause the reflectance to vary with surface thickness. Reflectivity is the limit value of reflectance as the sample becomes thick; it is the intrinsic reflectance of the surface, hence irrespective of other parameters such as the reflectance of the rear surface.
Surface roughness influences the specular reflectance levels; in the visible frequencies, the surface finish in the micrometre range is most relevant. The diagram on the right depicts the reflection at an angle on a rough surface with a characteristic roughness height variation . The path difference between rays reflected from the top and ...
In architecture, light reflectance value (LRV), is a measure of visible and usable light that is reflected from a surface when illuminated by a light source. [1] The measurement is most commonly used by design professionals, such as architectural color consultants , architects , environmental graphic designers and interior designers .
The CU value should be obtained by the manufacturer of the luminaire which is to be evaluated. In order to determine the CU on the manufacturer's table, a room cavity ratio (RCR) must be used. Also, the reflectance of the ceiling, walls and floor must be known. RCR = 5 x (room height) x (room width + room length) / [(room width) x (room length ...
An integrating sphere can be used to measure the diffuse reflectance of surfaces, providing an average over all angles of illumination and observation. A number of methods exist to measure the absolute reflectance of a test object mounted on an integrating sphere. In 1916, E. B. Rosa and A. H. Taylor published the first such method. [7]
Diagram showing vectors used to define the BRDF. All vectors are unit length. points toward the light source. points toward the viewer (camera). is the surface normal.. The bidirectional reflectance distribution function (BRDF), symbol (,), is a function of four real variables that defines how light from a source is reflected off an opaque surface. It is employed in the optics of real-world ...
Ellipsometry measures the change of polarization upon reflection or transmission and compares it to a model. It can be used to characterize composition, roughness, thickness (depth), crystalline nature, doping concentration, electrical conductivity and other material properties. It is very sensitive to the change in the optical response of ...