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The spectral hemispherical reflectance in frequency and spectral hemispherical reflectance in wavelength of a surface, denoted R ν and R λ respectively, are defined as [1] =,,, =,,, where Φ e, ν r is the spectral radiant flux in frequency reflected by that surface;
Values of spectral parameters like reflectance can then be directly extracted from all pixels in the imagery, aggregated and averaged to produce a reflectance curve for spectral analysis. [ 6 ] [ 8 ] In terms of non-imaging spectroradiometry, data collection and sampling are usually conducted through direct scanning with spectroradiometers in ...
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
Making metameric matches using reflective materials is more complex. The appearance of surface colors is defined by the product of the spectral reflectance curve of the material and the spectral emittance curve of the light source shining on it. As a result, the color of surfaces depends on the light source used to illuminate them.
The reflectance for s-polarized light is = ... Fresnel equations calculator; FreeSnell – Free software computes the optical properties of multilayer materials.
When the measurement involves two or more films in a stack of films, the theoretical expression for reflectance must be expanded to include the n(λ) and k(λ) spectra, plus thickness, t, of each film. However, the regression may not converge to unique values of the parameters, due to the non-linear nature of the expression for reflectance.
Coplanar condition of specular reflection, in which = Reflections on still water are an example of specular reflection.. Specular reflection, or regular reflection, is the mirror-like reflection of waves, such as light, from a surface.
Diffuse reflectance spectroscopy can be used to determine the absorption spectra of powdered samples in cases where transmission spectroscopy is not feasible. This applies to UV-Vis-NIR spectroscopy or mid-infrared spectroscopy .