1) The relative cell-to-lens distance for the full-glass lens is defined as zero where the efficiency shown in the bottom right of Fig. 3 dips during the plateau.
2) For the SoG Fresnel lens, a relative cell-to-lens distance of zero is defined at the highest measured efficiency. Since the SoG Fresnel lens investigated here has been designed for and molded at ambient temperature, temperature effects due to the difference of mold temperature to operation temperature [4] can be neglected. Due to the large pitch of the Fresnel lens, diffraction effects are very small and may be neglected as well so that all effects in the focal volume of the SoG Fresnel lens can mainly be associated with the chromatic aberration of the lens.