<title>Determining 3D shapes of hybrid surfaces by laser rangefinder</title>

Abstract

This paper describes a new triangulation-based laser rangefinder for measuring the 3D shapes of objects with hybrid reflectance, which combines Lambertian reflectance and specular reflectance. To date, ordinary laser range finding techniques have rarely been used to measure objects with hybrid reflectance. Like ordinary rangefinders, the proposed rangefinder consists of a light-stripe generator, a lens system, and an image sensor. The core of the scheme of our rangefinder is the lens system, which consists of a field stop, a lens, and shield masks. The basic concept of the proposed rangefinder is to maintain a constant incident angle of a light-stripe upon the image sensor by using a shield masks, resulting in the ability to play a triangulation system to the measurement of objects with specular reflectance. We designed and built a prototype rangefinder. The experimental results demonstrate that the proposed rangefinder allows the measurement of hybrid objects with almost the same level of accuracy as that of Lambertian objects and specular objects. The proposed rangefinder is especially valuable for industrial purposes, since consistent accuracy and high reliability are assured even for objects with unknown reflectance properties.