The most evident limitation of a two-dimensional vision system is its ability to move and rotate only in the X-Y plane. This has led to a demand for high qualityCONTROL ENGINEERING China版权所有, three-dimensional (3D) processing technologyCONTROL ENGINEERING China版权所有, the use of which is increasing. For engineers exploring the use of 3D inspectionwww.cechina.cn, there are now many different technologies available for creating 3D images.
        The most important task for engineers to successfully create such an application for industrial use is to achieve a high measurement resolution in all (xCONTROL ENGINEERING China版权所有, y, z) directions. Depending on the shape and size of the object and the distance between the object and the vision sensor, different methods of three-dimensional measurement, and different types of active vision systems, can be used.

        A 3D object model

        3D image acquisition

        The vision system consists of a set of devices, which convert light and measurement data into informationCONTROL ENGINEERING China版权所有, with spatial and material attributes of the scene. These devices have photosensitive sensors (a camera with a lens which focuses images on a photosensitive element or the eye) and computational mechanisms (a computer) allowing information to be collected from the sensors.
        Humans can easily distinguish objects they see and are also able to recognize them in various light conditions and from different frames of reference. However, in the case of vision systems, the proper interpretation of a pixel value is a very difficult task. Additionally, the brightness of pixels (and thus of the image received) depends on several factors:
        •Scene geometry - the shape and position of the object in the field of vision (when the shape or the position is cha