人脸识别是一项非常具有挑战性的技术，在计算机科学、视觉和模式识别技术领域有着非常重要的研究课题。这是因为面部识别会受到姿态、光照和面部表情的影响。从执法到商业，从娱乐到社交媒体，有许多新兴的应用和要求。人脸识别是行业最重要的需求(Wang et al.， 2014)。人脸识别的自动化和高效是当今世界的主要需求。在人脸识别方面已经做了大量的研究。一些研究人员已经在努力解决这些问题，但在人脸识别技术中仍有许多需要解决的挑战。在人脸识别过程中遇到的一些重要问题是姿态的变化、人脸的表情、场景的照明和方向(Wang et al.， 2014)。随着人脸数据库规模的增大，人脸识别时间成为一个大问题。
Face recognition is a very challenging technology that has very significant topic of research in the area of computer science, vision and pattern recognition techniques. This is because face recognition can be affected by the pose, illumination and facial expression. There are many emerging applications and requirements from law enforcement to commercial requirement and from entertainment to social media. Face recognition is the most important demand of the industry (Wang et al., 2014). The automated and efficient face recognition is the major demand in the contemporary world. There has been significant research done on the face recognition. Several researchers have worked to solve the problems, yet there are many challenges in the face recognition technology that are required to be resolved. Some of the significant issues that are aced during face recognition are change of the pose, expressions of face, illumination of the scene and orientation (Wang et al., 2014). It has been noticed that when size of the face database increases, the face recognition time becomes a big problem.