radiance; sterance; radiant sterance
Technical term in optics and radiometry. Refers to the radiant flux emitted, reflected, transmitted, or received by a surface, per unit solid angle per unit projected area. The term 'radiance' is the most common English equivalent; 'sterance' and 'radiant sterance' are less common alternatives.
Radiance is a fundamental quantity in radiometry.
Compound of 立体角 (solid angle) + 密度 (density), reflecting the physical definition as flux per unit solid angle per unit area.