An Improved Shape from Focus Method for Measurement of Three-Dimensional Features of Fuel Nozzles

Abstract

The precise three-dimensional measurement of fuel nozzles is of great significance to assess the manufacturing accuracy and improve the spray and atomization performance. This paper proposes an improved fast shape from focus (SFF) method for three-dimensional measurement of key features of fuel nozzles. In order to ensure the measurement accuracy and efficiency of the SFF, the dispersion of the measured points from a standard flat plane was used to select the optimal combination of the focus measure operator, window size and sampling step size. In addition, an approximate method for the focus measure interval is proposed to improve the measurement efficiency, which uses the peak region of the central pixel to replace the peak region of other pixels. The results show that the proposed method decreased the average computation time of the focus measure by 79.19% for the cone section and by 38.30% for the swirl slot. Compared with a reference laser scanning microscope, the measurement error in length is within 10 μm and the error in angle is within a maximum 0.15°.

Edge Bleeding Artifact Reduction for Shape from Focus in Microscopic 3D Sensing

“…Second, the object texture intensity affects the FM value v u (x, y) of the object, as shown in Figure 5a. An edge bleeding artifact occurs when the FM value v u a (x, y) by edge blur is greater than the FM value v u (x, y) of the object, as expressed in Equation (10). Therefore, the less the object texture, the smaller the FM value of the object, resulting in more edge bleeding artifacts.…”

“…Stereoscopy is a method of estimating depth using the shape difference between the images captured by two cameras at different positions [6][7][8]. SFF estimates depth using the degree to which each image is in the focus of the image sequences captured with different focal distances with a single camera [9][10][11]. The focal distance means the distance between the lens and the focus position in the object plane.…”

An image fusion-based method for recovering the 3D shape of roll surface defects

“…Based on the above analysis, the focusing method will be used for the 3D reconstruction of defects due to its relative cost-effectiveness and ease of measurement. Hou et al [26] proposed an improved fast-focusing shape method for 3D measurement of key features of fuel nozzles. Zhang et al [27] proposed a focal shape-based method.…”