Volumetric imaging efficiency: the fundamental limit to compactness of imaging systems

A new metric for imaging systems, the volumetric imaging efficiency (VIE), is introduced. It compares the compactness and capacity of an imager against fundamental limits imposed by diffraction. Two models are proposed for this fundamental limit based on an idealized thin-lens and the optical volume required to form diffraction-limited images. The VIE is computed for 2,871 lens designs and plotted as a function of FOV; this quantifies the challenge of creating compact, wide FOV lenses. We identify an empirical limit to the VIE given by VIE < 0.920 × 10^-0.582×FOV when using conventional bulk optics imaging onto a flat sensor. We evaluate VIE for lenses employing curved image surfaces and planar, monochromatic metasurfaces to show that these new optical technologies can surpass the limit of conventional lenses and yield >100x increase in VIE.