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Proceedings Paper

Visual inspection system with flexible illumination and autofocusing
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Paper Abstract

The visual information obtained from CCD camera is vulnerable to external illumination and the surface reflection properties of object images. Thus, the success of extracting aimed features from images depends mostly on the appropriate design of illumination. This paper presents a visual inspection system that is equipped with a flexible illumination and an auto-focusing unit. The proposed illumination system consists of a three-layered LED illumination device and the controllable diffusers. Each layer is composed of LEDs arranged in a ring type, and a controllable diffuser unit is located in front of each layer. The diffuser plays a role of diffusing lights emitted from the LEDs so that the characteristics of illumination is made varied. This combined configuration of the LED light sources and the adjustable diffuser creates the various lighting conditions. In addition to this flexible illumination function, the vision system is equipped with an auto-focusing unit composed of a pattern projector and a working distance adjustable zoom camera. For the auto-focusing, hill climbing algorithm is used here based on a reliable focus measure that is defined as the variance of high frequency terms in an image. Through a series of experiments, the influence of the illumination system on image quality is analyzed for various objects that have different reflective properties and shapes. As an example study, the electrical parts inspection is investigated. In this study, several types of chips with different sizes and heights are segmented and focused automatically, and then analyzed for part inspection. The results obtained from a series of experiments confirm the usefulness of the proposed system and the effectiveness of the illumination and focusing method.

Paper Details

Date Published: 18 October 2002
PDF: 13 pages
Proc. SPIE 4902, Optomechatronic Systems III, (18 October 2002); doi: 10.1117/12.467381
Show Author Affiliations
Young Jun Roh, Korea Advanced Institute of Science and Technology (South Korea)
Duk-Young Lee, Korea Advanced Institute of Science and Technology (South Korea)
Min-Young Kim, Korea Advanced Institute of Science and Technology (South Korea)
Hyungsuck Cho, Korea Advanced Institute of Science and Technology (South Korea)

Published in SPIE Proceedings Vol. 4902:
Optomechatronic Systems III
Toru Yoshizawa, Editor(s)

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