High-density packaged element positioning method based on speeded up robust features (SURFs)

Abstract

The invention discloses a high-density packaged element positioning method based on speeded up robust features (SURFs), which comprises the following steps: (1), coarse positioning: coarse transformation parameters (m, n and Beta) are obtained by adopting a SURF registration method; (2) fine positioning: an image I (x, y) to be registered is inversely transformed by utilizing the coarse transformation parameters (m, n and Beta) to obtain an image g (x and y), the minimum energy equation E of the image g (x and y) and a template image f (x and y) is calculated, each partial derivative of the E is solved and enabled to be zero, and transformation parameters (a, b and Theta) are solved; m' is enabled to be equal to m plus a, n' is enabled to be equal to n plus b, and Beta' is enabled to be equal to Beta plus Theta; the energy equation E under a transformation relation (m', n' and Beta') is calculated; whether the E is smaller than a set value or not is judged, and if no, next iteration is conducted; and if yes, the iteration process is finished, m' is taken as the final translation parameter in an x direction, n' is taken as the final translation parameter in a y direction, and Beta' is taken as the final rotation angle. Compared with the prior art, the high-density packaged element positioning method realizes high-precision sub-pixel positioning and has great robustness on illumination transformation and noise.

Description

technical field [0001] The invention relates to the field of identification and positioning in precision electronic assembly, in particular to a high-density packaging component positioning method based on SURF (Speeded up robust features, accelerated robust features). Background technique [0002] SMT has entered a fully mature stage after 50 years of development since the 1960s. At present, SMT has not only become the mainstream of contemporary circuit assembly technology and the pillar manufacturing technology of the electronics industry, but also continues to develop in depth to maximize the use efficiency of equipment and meet the rapidly growing production needs. Visual inspection is a necessary process for surface mounting. It separates components of various shapes and specifications from the background. Accurate position and angle compensation information. Therefore, the accuracy of visual inspection determines the quality of surface mount. At present, the placeme...

AI Technical Summary

Problems solved by technology

[0004] Although SURF is superior to SIFT in terms of calculation speed, the accuracy of key point positioning will decrease due to the use of a simplified Hessian matrix to detect key points.

The error of simply using the SURF algorithm is relatively large, and it cannot meet the actual production requirements. Therefore, based on the SURF detection results, a minimum energy sub-pixel method is proposed to further accurately position the two images to be registered.

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