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Automatic Focus Control for Assembly Alignment in a Lens Module Process  

Kim, Hyung-Tae (Korea Institute of Industrial Technology)
Kang, Sung-Bok (Korea Institute of Industrial Technology)
Kang, Heui-Seok (Korea Institute of Industrial Technology)
Cho, Young-Joon (Korea Institute of Industrial Technology)
Park, Nam-Gue (Robots and Design)
Kim, Jin-Oh (Dept. of Information and Control Engineering, Kwangwon Univ.)
Publication Information
Journal of the Korean Society for Precision Engineering / v.27, no.2, 2010 , pp. 70-77 More about this Journal
Abstract
This study proposed an auto focusing method for a multi-focus image in assembling lens modules in digital camera phones. A camera module in a camera phone is composed of a lens barrel, an IR glass, a lens mount, a PCB board and aspheric lenses. Alignment among the components is one of the important factors in product quality. Auto-focus is essential to adjust image quality of an IR glass in a lens holder, but there are two focal points in the captured image due to thickness of IR glass. So, sharpness, probability and a scale factor are defined to find desired focus from a multi-focus image. The sharpness is defined as clarity of an image. Probability and a scale factors are calculated using pattern matching with a registered image. The presented algorithm was applied to a lens assembly machine which has 5 axes, two vacuum chucks and an inspection system. The desired focus can be determined on the local maximum of the sharpness, the probability and the scale factor in the experiment.
Keywords
IR Glass Filter; Lens Module Assembly; Digital Camera Phone; Auto-focus Control; Sharpness; Automatic Alignment;
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