Fig. 1. Optical schematic of the calibration source system. The cavity, which is made of a highly reflective material, is filled with a scattering medium.

Fig. 2. Values of transmittance (solid line), cavity absorption (dashed line) and medium absorption (dashed–dotted line) as predicted by the Monte Carlo simulation at varying cavity widths. Each curve corresponds to (a) different cavity reflectivities R=0.90 (○), 0.95 (▽), 0.98 (□), and 1.00 (⋄), respectively, in the case of L=0.5  cm, and l*=100  μm; (b) different transport mean free paths l*=50 (○), 100 (▽), and 200 μm (□), respectively, in the case of R=0.98. The values of L in graph (b) meet the condition L/l*=const in order to maintain the correlation time for each curve.

Fig. 3. Values of transmittance (solid line), cavity absorption (dashed line), and medium absorption (dashed–dotted line) versus the cavity length t. Each curve corresponds to different cavity reflectivities. R=0.90 (○), 0.95 (▽), 0.98 (□), and 1.00 (⋄), respectively, at two different transport mean free paths (a) l*=100  μm and (b) l*=25  μm. The values of L=5  mm and W=3  cm are used here.

Fig. 4. Flatness of the far field for different extended source sizes W and distances z. An extremely low non-uniformity is obtained around the central region.

Fig. 5. Measure of non-uniformity after averaging multiple measurements with the use of our detector.