Validity and correctness test verification of the measuring software has been a thorny issue hindering the development of Gear Measuring Instrument (GMI). The main reason is that the software itself is difficult to separate from the rest of the measurement system for independent evaluation. This paper presents a Virtual Gear Measuring Instrument (VGMI) to independently validate the measuring software. The triangular patch model with accurately controlled precision was taken as the virtual workpiece and a universal collision detection model was established. The whole process simulation of workpiece measurement is implemented by VGMI replacing GMI and the measuring software is tested in the proposed virtual environment. Taking involute profile measurement procedure as an example, the validity of the software is evaluated based on the simulation results; meanwhile, experiments using the same measuring software are carried out on the involute master in a GMI. The experiment results indicate a consistency of tooth profile deviation and calibration results, thus verifying the accuracy of gear measuring system which includes the measurement procedures. It is shown that the VGMI presented can be applied in the validation of measuring software, providing a new ideal platform for testing of complex workpiece-measuring software without calibrated artifacts.

When the metal surface profile is measured by the linear structured light method, the extraction error of stripe center is often large due to the influence of optical properties and speckle noise of metal surface. Therefore, a profile measurement method that used incoherent linear structured light was proposed, which could avoid the influence of speckle noise. A corresponding method for extracting the center of incoherent linear structured light stripe was proposed by analyzing the characteristics of metal surface profile stripe images. Firstly, the original stripe image was segmented using adaptive threshold segmentation algorithm combined with integral image principle. Then, the center coordinates of original stripe were roughly extracted by gray centroid method. The regions of interest and background of stripe image after threshold segmentation were determined by extending the roughly center to stripe width direction, and the noise in the background region was removed. Finally, the stripe center was extracted by geometric center method after median filtering. The experimental results show that the average error of incoherent light stripe center of roughness specimen surface extracted by proposed method was 1.5 μm and that of involute gear was 0.9 μm, which are both smaller than those of line laser stripes. The proposed method can accurately extract the center of incoherent linear structured light stripe on metal surface.

To achieve high-precision 3D measurement of surface profile of the object, a telecentric optical path measurement system with large field of view (FOV), object distance and measuring range was proposed. The composition of the system and the principle of optical triangulation were introduced, the construction of the optical path with the angle of 45 ° between the projection and double optical path and the normal line of the measured surface could reduce the requirement of depth of field of the imaging objective lens for large depth measurement range. The theoretical model of system depth calibration was established, and the theoretical value of CCD unit pixel depth was 0.554 4 μm. The magnification, numerical apertures and other optical parameters were calculated and the optical path was constructed. The resolution, measuring range, minimum width of light stripe and edge quality of the system were analyzed by experiments. The experimental results show that the longest projection stripe is 2 mm, the minimum line width is 8.96 μm, and the stripe edge is clear and smooth. The imaging distortion of the system is small, and the optical resolution of 1.62 µm and the depth pixel resolution of 0.54 µm can be achieved. The object distance is 65 mm, the depth measurement range is no less than 140 µm. The system has good measurement performances.