为进一步缩小光学相关器体积,设计了一种折反式2f系统光学相关器,光路采用折叠反射式结构,用数字微透镜取代传统相关器中的实体透镜,缩减了结构体积,提升了系统集成度。利用等效光路法对其进行理论分析,给出了折反式2f相关器的结构设计条件及结构参数。针对该相关器,设计了与之匹配的综合鉴别函数滤波器,利用自编程序进行模拟仿真分析。结果显示,当待识别目标发生缩放与旋转畸变时, 该相关器仍具有较好的畸变不变识别性能。

实验研究了混沌激光通过脂肪乳液的时间点扩展函数(TPSF)的特性。采用混沌光作为光源，利用混沌信号的相关函数具有delta函数特性的特点，将探测到的信号与原始信号作互相关运算，提取出测量系统的TPSF。实验中通过增加脂肪乳液的浓度,使其散射系数增大，保持吸收系数不变,得到混沌光穿过不同浓度脂肪乳液的TPSF,从获得的TPSF中提取出差分路径长度因子(DPF)，定性地分析脂肪乳液的光学特性。实验结果表明，随着脂肪乳液浓度的不断增大，两路信号的相关度不断减小，DPF与脂肪乳液的散射系数呈正相关。

能否输出相关峰是相关器判定目标真伪的主要方式，但其元件调节精准度不高时，容易对相关峰产生误判。基于匹配滤波相关识别器，从理论上分析了相关峰产生误判的3种可能，重点对相关信号的强度判别进行了理论和实验研究，针对这3种可能产生误判的情况，分别从实验结果的相关峰阈值强度、形态、输入图像旋转方面探讨真伪相关峰的判别，为相关峰的判别提供实验参考。

In this paper, an overview of author’s research is presented, commencing at the University of Kent under Prof. David A. Jackson. Early research in short optical pulses and fiber-optic delay-line digital correlators led to optical communications research in code-division multiple access networking. This research was based on broadband incoherent light, and this theme continued with research into spectrum-sliced wavelength-division multiplexing. In shifting from photonics research to biomedical optics and biophotonics in the late 1990s, the emphasis on exploiting broadband light continued with research in optical coherence tomography, amongst other topics. In addition to the research outcomes, how these outcomes were attained is described, including mention of the exceptional contributions of many of my colleagues.

A novel fully phase color image encryption/decryption scheme based on joint fractional Fourier transform correlator (JFRTC) and phase retrieval algorithm (PRA) is proposed. The security of the system is enhanced by the fractional order as a new added key. This method takes full advantage of the parallel processing features of the optical system and could optically realize single-channel color image encryption. The system and operation procedures are simplified. The simulation results of a color image indicate that the new method provides efficient solutions with a strong sense of security.

A lensless Vanderlugt optical correlator using two phase-only spatial light modulators (SLMs) is proposed. The SLMs are used for displaying input and filter patterns respectively. The SLMs are also used as programmable lenses in order to realize the lensless construction. This lensless system is simple and its alignment adjustment is easy. The performance of the SLMs as programmable lenses is also described.

An image encryption method combining the joint transform correlator (JTC) architecture with phase-shifting interferometry to realize double random-phase encoding is proposed. The encrypted field and the decrypting key are registered as holograms by phase-shifting interferometry. This method can encrypt two images simultaneously to improve the encryption efficiency of the methods based on JTC architecture, and eliminate the system alignment constraint of the methods based on Mach-Zehnder interferometer (MZI) architecture. Its feasibility and validity are verified by computer simulations. Moreover, image encryption and decryption can be achieved at high speed optically or digitally. The encrypted data are suitable for Internet transmission.

A new system of multi-channel single-output joint fractional Fourier transform correlator (JFRTC) for color pattern recognition is proposed based on the conventional system of multi-channel single-output joint transform correlator (JTC). The theoretical analysis and optical experiments are performed. With this method, one can obtain three correlation peaks at the output plane which show a pair of desired cross-correlation peaks and one auto-correlation peak. In comparison, the conventional system leads to more correlation peaks playing a noise role in color pattern recognition.

A novel communication technique is proposed, which utilizes a set of mutually distinguishable optical patterns instead of convergent facula to transmit information. Then the capacity is increased by exploiting the optical spatial bandwidth resources. At last, we experimentally demonstrate the proposed communication technique based on four 8*8 spatial pattern signals by using lenslet array processor.

This paper suggests that the linear interferometric correlation (LFC) can be used to measure pulse duration of a few cycles, single cycle or even sub-cycle light pulse. The relations between pulsewidth and LFC curve are derived for Gaussian- and hyperbolic secant-shaped pules. This new method abandons focusing, frequency doubling and filtering in the traditional second order correlation method, meanwhile the signal-to-noise ratio (SNR) is improved.