標題: | Generation of Two-Dimensional Optical Reference Signals Based on Parametric Minimum Cross Entropy |
作者: | Su, Yi-Sheng Wu, Tsung-Cheng Wang, Chung-Hsuan Chang, Min-Kuan 電機工程學系 Department of Electrical and Computer Engineering |
關鍵字: | Autocorrelation function;combinatorial optimization;optical position measurement;optimization method;parametric minimum cross entropy (PMCE);two-dimensional (2-D) optical zero reference signal (ZRS);two-dimensional (2-D) zero reference code (ZRC) |
公開日期: | 15-Jun-2011 |
摘要: | In this letter, a novel design of two-dimensional (2-D) zero reference codes (ZRCs) based on parametric minimum cross entropy (PMCE) is proposed to generate 2-D optical zero reference signals (ZRSs) with low second maximum for grating alignment systems. An optical ZRS is necessary to obtain an absolute measurement in grating alignment systems. A method to acquire an optical ZRS is by means of illuminating two identical superimposed ZRCs. Because the movement between the two ZRCs is in two-axis, 2-D ZRCs are required. However, they are hard to design due to the high computational complexity, especially for large codes. The proposed PMCE method not only reduces the second maximum of 2-D optical ZRSs, but also decreases the computational complexity. Simulation results indicate that there are 8.33%similar to 22.22% reductions in the second maximum of several 2-D optical ZRSs, as compared with those of the recently proposed cross-entropy (CE) method. The PMCE method proves to be a powerful tool for the design of 2-D ZRCs. |
URI: | http://dx.doi.org/10.1109/LPT.2011.2140368 http://hdl.handle.net/11536/22627 |
ISSN: | 1041-1135 |
DOI: | 10.1109/LPT.2011.2140368 |
期刊: | IEEE PHOTONICS TECHNOLOGY LETTERS |
Volume: | 23 |
Issue: | 12 |
起始頁: | 813 |
結束頁: | 815 |
Appears in Collections: | Articles |
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