DOSI (Double integrating sphere Optical Scattering Instrument) is a new facility for measuring hemispherical reflectance, hemispherical transmittance under direct and diffuse illumination of materials in the visible range (400 nm to 800 nm). The measured quantities are used to investigate the diffuse optical properties of materials; these parameters are critical for understanding the interaction of light with optically diffusive materials.
DOSI will provide calibrations reference materials, solid and liquid tissue mimicking phantoms, measurements of scattering, absorption, reflectance and transmittance of materials such as tissues, plant leaves, suspended solids and plankton for databases, model validation, and scales (e.g., turbidity).
DOSI is designed to be NIST’s national reference instrument dedicated to the measurement of the diffuse optical properties of samples at room temperature. Three laser lines and laser-driven broadband light source can be alternatively used to illuminate a sample set between two integrating spheres to measure the hemispherical reflectance and transmittance. A custom model-based analysis program has been developed to determine the optical coefficients and the associated uncertainties. The sample can either be solid or liquid (contained in a dedicated liquid cell).