A Fundamental Study of a Backward Emission Method to Detect an Unknown Light Source Position by Monte Carlo Simulation

Abstract

An advanced method to detect the position of an unknown light source is proposed. In this method, photon bundles received at light receiving sensors are backward emitted to a light room according to the illuminance distribution at the light receiving sensors. A tentative position in subdivided cubic elements is first determined by the backward emission of photon bundles from sensors. Next, photon bundles are forward emitted from subdivided cubic elements, including cubic elements within a spatial range around the coordinates of the tentative cubic element. Photon bundles transmitted by photon emissions from the unknown light source and from the tentative light source are detected by light sensors and compared. When both illuminance values agree, the tentative light source is determined to be at the position of the unknown light source. Monte Carlo simulations are used to solve this kind of inverse problem in a light room calculation. To express the performance of the simulation method, the rate of spatial reduction of the light room is newly introduced. Monte Carlo simulation demonstrated that the advanced method of backward emission of photon bundles is very useful for detection of an unknown light source in a shorter computing time compared to the conventional method.