Multi-image mosaic with SIFT and vision measurement for microscale structures processed by femtosecond laser

作者：Wang, Fu-Bin; Tu, Paul^*; Wu, Chen; Chen, Lei; Feng, Ding

来源：Optics and Lasers in Engineering, 2018, 100: 124-130.

DOI：10.1016/j.optlaseng.2017.08.004

• Femtosecond laser
• Silicon wafer microgroove
• SIFT image mosaic
• Image calibration
• Image measurement

In femtosecond laser processing, the field of view of each image frame of the microscale structure is extremely small. In order to obtain the morphology of the whole microstructure, a multi-image mosaic with partially overlapped regions is required. In the present work, the SIFT algorithm for mosaic images was analyzed theoretically, and by using multiple images of a microgroove structure processed by femtosecond laser, a stitched image of the whole groove structure could be studied experimentally and realized. The object of our research concerned a silicon wafer with a microgroove structure ablated by femtosecond laser. First, we obtained microgrooves at a width of 380 mu m at different depths. Second, based on the gray image of the microgroove, a multi-image mosaic with slot width and slot depth was realized. In order to improve the image contrast between the target and the background, and taking the slot depth image as an example, a multi-image mosaic was then realized using pseudo color enhancement. Third, in order to measure the structural size of the microgroove with the image, a known width streak ablated by femtosecond laser at 20 mW was used as a calibration sample. Through edge detection, corner extraction, and image correction for the streak images, we calculated the pixel width of the streak image and found the measurement ratio constant K-w, in the width direction, and then obtained the proportional relationship between a pixel and a micrometer. Finally, circular spot marks ablated by femtosecond laser at 2 mW and 15 mW were used as test images, and proving that the value K-w was correct, the measurement ratio constant K-h in the height direction was obtained, and the image measurements for a microgroove of 380 x 117 mu m was realized based on a measurement ratio constant K-w and K-h. The research and experimental results show that the image mosaic, image calibration, and geometric image parameter measurements for the microstructural image ablated by femtosecond laser were realized effectively.

• 出版日期2018-1
• 单位长江大学; 北京科技大学; 中国科学技术大学; 上海海事大学