Optimisation of the light transmission and irradiance distribution of an aspherical lens for 3-D time-of-flight sensors

The irradiance distribution and power transmission in a 3-D sensor, which i s based on the principle of time-of-flight (TOF) and uses modulated active illumination, should be optimised because of a large light energy damper an d low signal-noise ratio at the receiver detector an ay. A numerical design of a spherical-aspherical lens with large numerical aperture has been pres ented to generate a homogeneous irradiance on a measure object from an LED source. Based on the design and analysis of reflection loss, optimisations have been taken to maximise the optical transmittance of the lens. The resu lts show that thr total transmittance can be improved by optimising the sha pe and material of the lens. (C) 2000 Elsevier Science Ltd. All rights rese rved.