System schematic and calibration data. (a) 20% of the laser source was relayed to a free-space Michelson interferometer with 0.23 image space NA (S1). The back-coupled signal was detected using a custom-built spectrometer. (b) Representative cross-sections of a ceramic reference sphere surface sampled out to ±1.5 mm (Rdecenter) showing loss of specular reflection signal with decenter. (c) Segmented lens surface converted from pixels to physical units and fit using a best-fit sphere. (d) Percent deviation between measured and manufacturer specification for reference sphere radius at different sampling densities (number of samples per cross-section). Data points and shaded regions represent mean percent error and standard deviation, respectively, (n = 5). BS, cube beamsplitter; CMOS, line-scan camera; f, lenses; SLD, super luminescent diode; VPHG, volume phase holographic grating.