diffusereflectance

Diffuse reflectance refers to the portion of incident electromagnetic radiation that is scattered in many directions after striking a surface, rather than being reflected in a single specular direction. The phenomenon is governed by the microscopic structure of the material, surface roughness, and the wavelength of light. In optical science, it is distinguished from specular reflectance, which is produced by smooth surfaces that obey the law of reflection, and from absorption, in which the energy is converted to other forms such as heat.

The quantitative description of diffuse reflectance is provided by the diffuse reflectance factor, the ratio of diffusely reflected light to incident light under defined illumination and detection conditions. It is often measured using integrating sphere instruments that capture light scattered into all angles, and can also be obtained with goniophotometers that record angular distributions. Spectral diffuse reflectance curves are widely used to characterize pigments, coatings, and natural materials, enabling the identification of composition and condition. In the field of remote sensing, diffuse reflectance data are essential for interpreting satellite albedo measurements, assessing vegetation health, and mapping mineral deposits.

Diffuse reflectance modeling requires assumptions about surface roughness and scattering mechanisms. The Bidirectional Reflectance Distribution Function (BRDF) extends this concept to angle-dependent reflectance, describing both diffuse and specular components for arbitrary illumination and observation geometries. In practice, diffuse reflectance is utilized in industries such as automotive paint, architectural coatings, and biomedical imaging, where surface texture and color need to be quantified accurately. The term is synonymous with “diffuse scattering” in many scientific contexts, and it remains a fundamental concept in photometry and material science.