指纹识别技术是方便、可靠、非侵害和价格低廉的生物识别技术。为提高图像的质量,根据表面等离子体共振(SPR)的原理,提出采用表面等离子体共振成像(SPRI)采集指纹图像的方法。介绍了表面等离子体共振成像采集指纹图像的原理、自行组建的表面等离子体共振成像指纹采集系统的结构。采用Kretschmann型棱镜耦合结构激励表面等离子体共振,偏振的平面光经棱镜投射到传感片,发生表面等离子体共振现象。由CCD摄像机采集反射光指纹图像。分别用表面等离子体共振成像方法和传统光学方法采集了同一指纹的图像。两图中主要区域指纹脊和谷的对比度分别为0.2014和0.0516。表面等离子体共振成像方法采集的指纹图像的对比度和清晰度显著提高。

The technology of fingerprint identification is a convenient, reliable, noninvasive and cheap scheme for biometrics. A method that adopts surface plasmon resonance imaging (SPRI) to collect fingerprints utilizing surface plasmon resonance (SPR) phenomenon is put forward to improve the quality of images in this paper. The principles and the structure of SPRI system are introduced. SPR is stimulated by a Kretschmann prism couple configuration. The cover glass coated with a 50 nm gold film serves as a sensor chip. The fingerprint is then imprinted on the gold film. Polarized monochromatic light is projected on the sensor through the prism, where the SPR phenomenon occurs. The reflected fingerprint image is collected by CCD. The images are collected by SPRI and conventional optic method for the same fingerprint, two different contrast gradients in which the fingerprint ridges are compared with the valleys of the main parts of the two images are 0.2014 and 0.0516 respectively. The contrast and clarity of the image collected by SPRI are much improved.