In order to inspecting stripes error of code-bar grade rod

a method of visual collimation and double-frequency laser interferometry is discussed. Precise measurement system of code-bar grade rod is designed and the method of collimation and measurement is investigated. When image of code-bar edge presents on collimation area

the image and the data of laser interferometer are collected rapidly

needing not move worktable carried grade rod tardily. Then collimation and measurement are completed by software program. Image detection of code-bar edge is discussed. First

the algorithm of maximal square deviation is used to image segmentation. Then a way named image edge-tracking is presented to obtain code-bar edge directly

avoiding the difficulty of noise filter. Finally

a fine division method based on probability and statistics theory is applied to locate code-bar edge

improving the resolution of visual collimation. In the practice

the criterion deviation of vision collimation is 0.23μm and the criterion deviation of system stability is below 0.5μm. The method of collimation and measurement improves measurement efficiency and measurement precision is 4 times high than the requirement

it ensures credibility of code-bar grade rod measurement. The measurement system has been used in the stripes error inspection of code-bar grade rod successfully.