I. Introduction
Human facial expressions contain rich emotional information, and the ability to recognize these expressions has many potential applications. Facial Expression Recognition (FER) plays an essential role in pattern recognition in artificial intelligence. FER has made substantial contributions to the medical field by facilitating the exploration and interpretation of patients' emotional behavior [1]. The study of emotion detection also opens up broad opportunities in entertainment technology, such as games and animations that are more responsive and attractive to users. In addition, its application in audience analysis in marketing, human-computer interaction systems such as smartphones, behavioral studies of emotion recognition, security, robotics, and other fields also involves aspects of the study of emotion detection.