Kubelka–Munk theory

A two-flux radiative transfer model from 1931 describing how light is absorbed and scattered in turbid layers such as paint films and paper.

Two-flux approximation: Simplifying radiative transfer by collapsing all light into a forward beam and a backward diffuse flux. Kubelka–Munk is the classic two-flux model, and this names the assumption behind its equations.
Paul Kubelka: Austrian chemist who co-published the two-flux theory in 1931 while working on paint films. First author of the 1931 paper that gave the theory its name.
Color matching: Computing pigment recipes that reproduce a target color in a given medium. Textile, paint and plastics plants use Kubelka–Munk equations to solve recipes numerically.
Bouguer–Lambert law: Exponential attenuation of light through an absorbing, non-scattering medium. The no-scattering limit Kubelka–Munk reduces to; the contrast clarifies what scattering adds.
Diffuse reflectance: The fraction of incident diffuse light a surface scatters back, the quantity the theory predicts. The measured R in the equations; understanding its definition precedes the mathematics.
Kubelka–Munk function: The ratio of absorption to scattering coefficients, (1−R)²/2R, used to quantify color strength from reflectance. The practical formula pigment analysts derive directly from the theory's equations.
Franz Munk: Austrian physicist, co-author of the 1931 Kubelka–Munk paper on the optics of paint layers. Co-formulator of the equations; his name completes the theory's title.
Paper opacity: A paper's ability to hide printing on its reverse, measured against black and white backing. TAPPI opacity standards are built directly on Kubelka–Munk hiding-power formulas.
Mie scattering: Exact electromagnetic scattering theory for spheres comparable in size to the wavelength. Mie theory predicts scattering coefficients from particle physics; Kubelka–Munk takes them as measured inputs.
Saunderson correction: A correction converting measured instrument reflectance to the mathematical reflectance Kubelka–Munk assumes. Without it, measured reflectance fed into the equations gives systematic errors.

Linked from 11 pages