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Proceedings Paper

Field depth extension of 2D barcode scanner based on wavefront coding and projection algorithm
Author(s): Tingyu Zhao; Zi Ye; Wenzi Zhang; Weiwei Huang; Feihong Yu
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Paper Abstract

Wavefront coding (WFC) used in 2D barcode scanners can extend the depth of field into a great extent with simpler structure compared to the autofocus microscope system. With a cubic phase mask (CPM) employed in the STOP, blurred images will be obtained in charge coupled device (CCD), which can be restored by digital filters. Direct methods are used widely in real-time restoration with good computational efficiency but with details smoothed. Here, the results of direct method are firstly filtered by hard-threshold function. The positions of the steps can be detected by simple differential operators. With the positions corrected by projection algorithm, the exact barcode information is restored. A wavefront coding system with 7mm effective focal length and 6 F-number is designed as an example. Although with the different magnification, images of different object distances can be restored by one point spread function (PSF) with 200mm object distance. A QR code (Quickly Response Code) of 31mm X 27mm is used as a target object. The simulation results showed that the sharp imaging objective distance is from 80mm to 355mm. The 2D barcode scanner with wavefront coding extends field depth with simple structure, low cost and large manufacture tolerance. This combination of the direct filter and projection algorithm proposed here could get the exact 2D barcode information with good computational efficiency.

Paper Details

Date Published: 4 January 2008
PDF: 8 pages
Proc. SPIE 6837, Information Optics and Photonics Technologies II, 683711 (4 January 2008); doi: 10.1117/12.756077
Show Author Affiliations
Tingyu Zhao, Zhejiang Univ. (China)
Zi Ye, Zhejiang Univ. (China)
Wenzi Zhang, Zhejiang Univ. (China)
Weiwei Huang, Zhejiang Univ. (China)
Feihong Yu, Zhejiang Univ. (China)

Published in SPIE Proceedings Vol. 6837:
Information Optics and Photonics Technologies II
Guoguang Mu; Feijun Song; Francis T. S. Yu; Suganda Jutamulia, Editor(s)

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