Obtaining the information of the target object through an opaque scattering medium is one of the important research topics in the field of optical imaging.The concept of optical memory effect has provided strong support for the research of scattering medium imaging,and has promoted the development of various practical scattering imaging technologies.However,the concept of optical memory effect is mainly proposed on the basis of incident light rotation or spatial translation,and the scattered imaging methods developed on this basis have many limitations such as small imaging range.In this paper,the physical meaning of the concept of optical memory effect is introduced,and the development of the concept is reviewed since it was first proposed from the perspective of spatial translation,and then gradually developed to cover the spatial domain and spectral domain.A prediction is made that the concept will further develop to the spatio-temporal range and becomes an important index helpful to comprehensively describe the spatio-temporal characteristics of point spread function.And the concept of generalized optical memory effect is put forward to provide a new idea for the in-depth study of correlation scattering imaging technology.