Development of Lateral Scanning Confocal Profilometry for Automatic Optical Inspection

• Main Authors: Sheng-Han Chen, 陳聖涵
• Other Authors: Liang-Chia Chen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/2r5vg9

碩士 === 國立臺北科技大學 === 自動化科技研究所 === 97 === Confocal microscopy used as a surface profilometer has its advantages in possessing high longitudinal depth resolution and non-contact scanning property. A confocal microscope works by geometrically matching two conjugate focal points in image space. As a tested surface is scanned through the focal point, peak intensity can be detected only when the focal point lies directly on the surface of the sample. A lateral scanning confocal 3-D surface profilometer for on-line automatic optical inspection (AOI) using digital structured fringe projection is presented in the thesis. Different from the traditional Vertical Scanning Confocal 3-D surface profilometers, it is designed to scan the tested object by one inclined angle with the lateral scanning plane and the optical focus plane. With this apparatus, the acquiring image can include confocal focusing and defocusing signals of the scanned point. By forming the above signals laterally, one can construct a focus-to-depth curve. By further identifying the peak of the focus-to-depth curve, the height can be determined for reconstruction of 3D map. A standard step height has been measured to attest the measurement accuracy and feasibility of the developed approach. This technology is suitable for inspection in Roll to Roll manufacturing process. From the experimental tests of some measurement examples, it was verified that the depth measurement resolution can reach up to 0.1 µm. The measurement efficiency can be significantly improved for on-line automatic optical inspection (AOI).