Image Detecting Technology For Code Bar Grade Rod

Since the introduction of the first digital level by Leica in 1990, this type of equipment has rapidly gained acceptance because it has many advantages such as high precision, fast measurement speed and simple operation. Digital levels had taken the place of optical levels in many fields of precision leveling, deformation monitoring and appropriate industrial surveying. As compared with optical level, digital level has novel reading principle. The code combination of bar includes the altitude information corresponding to level axis of water level and its precision influences the measurement result of veracity and stability directly. So the periodic function checking of code bar is the base of ensuring veracity and stability of the measurement result of digital level. Although different manufactures have their own model of digital level and the code-bar grade rods cannot be exchanged during measurement, they both work by estimating the unequal width and interval. So it is the main task of code-bar grade rod checking to detect the code bar nicely according to coding character, based on the analysis the code principle.The traditional methods used for leveling rod inspection employ the visual-reading microscope and the double-frequency laser interferometer to measure in static state or dynamic state. For code-bar grade rod's unequal width and interval, the method of using photoelectric microscope to measure it in dynamic state is under research. Up to the present, no successful reports have issued.Based on the analyses of the precision index of code-bar grade rod, this paper put forward an inspecting scheme using image collimation and the double-frequency laser interferometer, and developed an image collimation system for inspecting code-bar grade rod stripes error, which employed image technology, computer technology and data processing technology. Technical analysis and experimental verification was done for the key techniques of image segment and edge detection. The error factors of the inspection system were analyzed. The feasibility of the image collimation inspection scheme was validated by experiments, and it provided theory base for drawing the inspecting methods for code-bar grade rod. Furthermore, the image collimation method has a practical value and can be referred to in the field of untouched industry inspection.