Principle Types of Measurments

Interaction

Information

Probes & Tools

Emission/ Irradiance

Light is emitted by surface or bulk of matter, sources are radiant recombination due to electrical, thermal, chemical, or optical excitation of energy levels within atoms or molecules

Brightness and spectral distribution of light sources, fluorescence / lifetime of excitation states

Fiber with or without optics, as an option with diffusor

Transmission/ Absorption

Light travels through matter, interaction of photons with individual atoms or molecules causes absorption or scatter, the amount of passing light is reduced

Concentration, filter characteristics

Immersion probes for liquids,gas cell, 2x collimating otpics on combined optical axis

Diffuse Reflection

Light hits the rough surface or surface near area of matter, light is reflected in all directions due to the surface roughness

Color, texture, surface conditions

Integration sphere (for solids), diffusor disk or bare fiber

Direct Reflection (special case of diff. refl.)

Ditto, except the surface is smooth, therefore, light is reflected in a well defined direction (angle of incidence = angle of reflection

Refractive index, reflectivity

Colimating optics, goniometer or ellipsometer set-up

White Light Interference (special case of direct refl.)

Ditto, the surface consists of one or more thin (semi-)transparent layers, light reflected from individual layer surfaces interfere in accordance with optical path length difference

Layer thickness

Colimating optics typically under normal incidence

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