Single-Frame Direct Reflectance Estimation With Indirect Time-of-Flight Cameras

Abstract

Computer vision algorithms are influenced by variations in lighting conditions. Images, independent of lighting conditions have the potential to improve tasks such as material and object classification. For Time-of-Flight (ToF) cameras the largest variation in lighting condition is caused by the distance between the camera and the object. ToF cameras are intended for 3D distance measurement. However, the features which enable distance measurement can be used to realize methods to record distance normalised grey images.In this paper, we explore methods to extract direct reflectance estimates from ToF measurements. We propose two novel methods relying on coded modulation (CM) and compare them to a method that can convert data from the state-of-the-art continuous wave (CW) measurement method. With the invention of the CM based methods, we can realize the normalization in a single frame measurement, compared to the four frames recorded by the CW method.All three methods are evaluated based on simulation results and in-laboratory measurements. We are able to demonstrate that our novel methods, relying on CM, can achieve the desired measurement behaviour.