Optical Setup
Measurement design utilizes a reflective dome to collect light scattered from a fabric surface to evaluate color. This sphere geometry is used in high-precision spectrophotometers to measure color without being affected by fabric texture or gloss. The interior of the sphere is coated with a highly reflective white material that diffuses the light evenly.
This provides a uniform illumination of the test sample.
Specular Component
Standard measurements can either include or exclude the gloss component of the fabric surface. By using sphere geometry, the spectrophotometer can include the specular component to measure the actual pigment color, or exclude it to match the human eye’s perception. This choice is critical when measuring shiny synthetic fabrics like satin or polished cotton because the surface reflection can alter the perceived color.
The laboratory must specify the mode used.
Texture Exclusion
Woven and knitted structures create shadows that can distort color readings in standard instruments. This is where sphere geometry offers an advantage by illuminating the sample from all directions simultaneously. The diffused light eliminates surface shadows to give a more accurate reading of the dye concentration.
This leads to more reliable recipe formulation.
Device Calibration
Daily calibration of the spectrophotometer is required to maintain accuracy. The instrument is calibrated using a black trap and a white tile. This ensures that the sphere geometry measurements remain stable.
