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RGBD cameras provide images of depth and 3D information of physical objects. These cameras, which are usually based on Time of Flight techniques, have become an alternative for detecting superficial defects in industrial production. Traditionally, the measurement of changes in thickness of a transparent flat glass has been carried out by means of point like techniques. Thus, for the measurement of an extended surface of the glass a scanning process is necessary. This drawback can be improved using cameras RGBD like the Kinect V2. In this article, a novel method for detecting the change in thickness of an area of interest of a glass is described. This proposal is based on the refraction of the light when it goes from air to glass, i.e., it is based on the change of direction and velocity of the light due to the change of refraction index between the media. This phenomenon is evident in the RGBD images of a known scene when a transparent flat glass is put before its background. The changes in the RGBD images of the scene with and without glass are caused by the increment in time of flight by the refraction in the glass. We obtained a correlation between the thicknesses of different glasses and the depth measurements for a controlled scene, by using an experimental setup with a Kinect V2 as RGBD camera. We processed the data using a K-means algorithm to determine the change of thickness in transparent flat glasses.
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