Towards shot noise limited triangulation

We design a system-level architecture for approaching the shot noise limit for passive triangulation of a quasi-monochromatic point source. Our emphasis is not in the novelty of the basic physics, but that existing systems lose fundamental information in the measurement pipeline. We preserve that information through maintaining analog signals combined with common-mode noise rejection in the layers of signal processing. We review the Cramer-Rao bound of angle sensing as applied to the field of triangulation. Using a monolithic camera/balanced detector system and a doubly-layered analog voltage differential system, we experimentally achieve nanometer-scale depth precision at 1.42 meter standoff with a baseline of only 10 centimeters. While still roughly two orders of magnitude above the shot noise limit, the results represent several orders of magnitude improvement over current camera-only or other position-sensitive detector systems. The system can be further improved with vibration and turbulence mitigation.