Second harmonic generation based joint transform correlator for human face and QR code recognitions

Abstract

We propose a nonlinear joint transform correlator (JTC) based on a joint power spectrum via second-harmonic generation (SHG) in the Fourier domain. The fundamental waves of 1064 nm infrared light illuminate the images displayed by a single spatial light modulator. After SHG in a type-II potassium titanyl phosphate crystal in the Fourier domain, the second-harmonic wave of 532 nm visible light yields the correlation signal. We demonstrate the performance of our SHG-based JTC for human face recognition and quick response code recognition. Our work has the potential in various optical information processing applications such as infrared pattern recognition and remote sensing, security verification, target tracking, and optical computing.

Nonlinear optics with structured light

“…Even complex images can be handled in this manner, with the benefit of noise reduction (squaring a signal will amplify the strong and the decrease weak). For this reason, this has been an emerging application of SHG, with demonstrations including augmented edge contrast 77,78 and contrast enhancement to improve recognition of human faces and QR codes 79 .…”

Structured light based optical pattern recognition:Principle and technical progress

“…2000年Banerjee等人 [29] 使 用新型的光折变聚合物材料实现了边缘增强的JTC, 将非线性效应引入到光学信息处理, 使得全光的相关 器进入新的发展阶段, 除了光折变效应这种弱光非线 性效应以外还可以通过强光作用的非线性效应实现光 学模式识别. 本课题组最近基于傅里叶频域内的非线 性上转换过程分别实现了轨道角动量模式识别 [30] , 以 及人脸识别和二维码识别 [31] . 对于非线性频率下转换 过程, 即自发参量下转换(Spontaneous Parametric Down-Conversion, SPDC), 本课题组对泵浦光进行空 间光场调控, 同时结合傅里叶空间中的量子关联成像 过程, 构建一个量子版本的Vander Lugt匹配滤波相关 器 [32,33] , 实现了非定域的人脸识别.…”

“…图 7 (网络版彩图)基于二次谐波产生实现的联合变换相关器实验方案. (a1)和(b1)分别为输入的两个相同和不同人脸的联合 图像; (a2)和(b2)分别表示图(a1)和(b1)的相关输出信号(转载来自文献 [31], 获得了© AIP 出版社的许可) Figure 7 (Color online) Experimental setup for performing SHG-based JTC. Insets (a1) and (b1) show the input joint images of two identical faces and two different faces, respectively; insets (a2) and (b2) show the output correlation planes of insets (a1) and (b1), respectively (reprinted with permission from ref.…”

“…Insets (a1) and (b1) show the input joint images of two identical faces and two different faces, respectively; insets (a2) and (b2) show the output correlation planes of insets (a1) and (b1), respectively (reprinted with permission from ref. [31] © AIP Publishing).…”

Highly efficient second harmonic generation of thin film lithium niobate nanograting near bound states in the continuum

“…Second harmonic generation(SHG) is an essential technology, doubling the frequency of light by interaction with nonlinear material [15], which enjoys widespread applications including holographic imaging [16], human face and QR code recognitions [17] and harmonic optical tomography [18], etc. However, since the nonlinear optical response is intrinsically weak, advances in artificial nanostructured plasmonic and all-dielectric metasurfaces have enabled nonlinear optical processes that do not satisfy phase matching condition strictly [19][20][21].…”