Quantitative Measurement and Reconstruction of 3D Density Field by CGBOS (Colored Grid Background Oriented Schlieren) Technique

Introduction

The Background Oriented Schlieren (BOS) technique was proposed by Meier [1], and it enables us to have the quantitative density measurement with computer-aided image analysis. In the past several years, BOS technique had applied to various experiments [2],[3]. The principle of BOS is similar to conventional Schlieren technique, it exploit the bending of light caused by refractive index change corresponding to density change in the medium and both techniques are sensitive to density gradient. Conventional Schlieren technique employs many optical elements - pinhole, concave mirror, knife edge or color filter, camera...etc, however it is difficult to realize quantitative measurement and this technique is commonly used for qualitative measurement like flow visualization. On the other hand BOS requires only a background and a digital still camera and it can realize the quantitative measurement of density.