In aircraft structures

there are a lot of standard connection holes. In order to ensure the assembly quality

it is necessary to detect the quality of the countersink holes. The visual inspection equipment based on robot or machine tool has the problems of low positioning accuracy

difficult to reach local position and easy to be affected by ambient light. In this study

a hand-held visual detection method for checking the quality of the countersink holes is proposed. The sub-pixel detection algorithm for the diameter and depth of the countersink is developed

and a hand-held visual detection device is designed. The mechanical structure

hardware system and software system are described in detail. The diameter and the countersink depth measured by this method are compared with the test results of the third party certification. The results show that the accuracy of diameter measurement is better than 0.01 mm

and the accuracy of depth is better than 0.1 mm. The hand-held vision detection equipment designed in this study has high detection accuracy

wide application and is not affected by ambient light.