Automated optical inspection for holograms with mixed patterns

作者：Kwon Hyuk Joong; Park Tae Hyoung^*

来源：International Journal of Advanced Manufacturing Technology, 2011, 54(1-4): 215-221.

DOI：10.1007/s00170-010-2915-9

• Automated optical inspection
• Hologram inspection
• Computer-generated hologram
• Pattern matching

This paper proposes an automated optical inspection system for holograms with mixed patterns. The hardware system consists of LED illuminator, CCD camera, and vision processor. The LEDs of illuminator emit alternatively and change the incident angle to acquire each pattern from hologram. The software system consists of the stages of pattern generation and pattern matching. The acquired images of hologram are compared with their reference images by template matching. Since several patterns are mixed in one hologram, the reference image should be changed if the hologram is rotated. To compensate for the positioning error of hologram, reference images should be generated online. The frequency transformation-based computer-generated hologram method is applied to generate the reference image. The pattern is also matched in the frequency domain to reduce the computational time. The holograms attached to a Korean currency are used to evaluate the performance of the proposed system.

• 出版日期2011-4