Parallelized multichannel BSDF measurements

Theoretical derivation and application of empirical Harvey scatter model

Starting from the Rayleigh-Rice perturbation theory, this paper derives the empirical Harvey scatter model and ABg scatter model applied extensively in optical analysis software packages and verifies the shift-invariant behavior of the scattered radiance in direction cosine space. Using data obtained from multi-wavelength laser scatterometer on carbon nanotube black coating and pineblack coating, we establish the polynomial model based on the sine of the scattering angle plus the sine of the specular reflection angle, i.e., sin θs+sin θ0 and the dual-Harvey model based on sin θs-sin θ0 , respectively. The models are in good accordance with the experimental data and further extend the valid range of empirical models.

Immediate and one-point roughness measurements using spectrally shaped light

Capitalizing on a previous theoretical paper, we propose a novel approach, to our knowledge, that is different from the usual scattering measurements, one that is free of any mechanical movement or scanning. Scattering is measured along a single direction. Wide-band illumination with a properly chosen wavelength spectrum makes the signal proportional to the sample roughness, or to the higher-order roughness moments. Spectral shaping is carried out with gratings and a spatial light modulator. We validate the technique by cross-checking with a classical angle-resolved scattering set-up. Though the bandwidth is reduced, this white light technique may be of key interest for on-line measurements, large components that cannot be displaced, or other parts that do not allow mechanical movement around them.

Synchronous measurement method of a multi-angle scattered light field

A synchronous multi-angle scattered light field measurement system is constructed in this study to overcome issues with current systems in the field of multi-angle remote sensing. A mathematical model of the scattered light field measurement was established. An off-axis catadioptric optical system was designed to satisfy hemispheric spatial scattered light field measurements in a zenith angle range of 68°. The off-axis calibration model was established, and the spatial relationship was calibrated. The measurement accuracy was calibrated via an integrating sphere light source, and the maximum measurement relative error was -3.71%. The scattered light field of the reference diffuse reflective target plate Labsphere Permaflect-50 and 304 stainless steel was simulated under an incident light irradiation range within the zenith angle of -23.5^∘ to +23.5^∘, and synchronous measurement of the multi-angle scattered light field of the sample was realized. The measurement system could provide technical support for building the complex model of multi-angle reflection/radiation from the earth's surface, multi-angle sensor radiation calibration, and improvement of the physical parameter inversion accuracy of observation targets.

Instantaneous one-angle white-light scatterometer

We present a white light scatterometer operating at a unique scattering direction. Mechanical motions and wavelength scans are removed. The technique provides an immediate flexible characterization of roughness with no loss of resolution.