Study On Vision Measurement Method In Thermal Vacuum Environment

With the development of computer vision theory and image processing technology, vision measurement technology has become more widely used. Vision measurement has many advantages such as direct-viewing, high accuracy, non-contact and strong environmental adaptability; however, its accuracy can be greatly affected by ambient temperature, pressure, vibration and other conditions. If it works in special environment including high/low temperature and vacuum for long hours, performance of some key components will be severely affected and even be damaged and so measurement results will be unreliable. Therefore, it is necessary to study vision measurement method used in special environment.Vision measurement system is a complex system including optics, electronics, computer and mechanics, and its various aspects may be affected by environment. Taking parts’dual dimensions gap size high accuracy measurement method in thermal vacuum environment as main study contents, impacts of ambient temperature, press- ure and vibration on measurement system is analyzed theoretically, corresponding solutions is proposed and a set of vision measurement system is designed.In the hardware design of the system, it uses computer as processing platform, industrial CCD camera in high resolution, telecentric lens, LED light, digital voltage regulator and reduces environmental impacts by using temperature controller and isolation platform, and in this way it can ensure the measurement system’s stable performance under special environment.Measurement software is developed by using modular design to make it conveni- ent for function expansion. Image denoising, threshold segmentation, edge detection, sub-pixel algorithm and other image processing algorithm are used to obtain a satisfactory processing effect. An exposure compensation algorithm based on local average gray value of feature area in picture is designed to eliminate light intensity changes’impacts on measurement. A real-time simplified calibration method based on pixel equivalent is designed to reduce measurement error of environment changes.The measurement system is tested in thermal vacuum environment and testing results show that this system can work stably for a long time in thermal vacuum environment. Various features dual dimensions gap size measurement experiments of parts’are done in thermal vacuum environment. Experiment results show that this system can work stable in special environment for long hours with high accuracy.