An optical imaging system with a variable light field for a biometrics application includes: a central processing unit (CPU); a display, which is electrically connected to the CPU, displays information to a user or interacts with the user, and provides a digital light signal to an object placed upon the display, the object covers a cover region of the display, and the cover region has at least an outer region and an inner region from outside to inside; and an optical imaging device electrically connected to the CPU and disposed in or under the display, the optical imaging device receives a digital light signal reflected from the object and obtains an optical image of biometrics characteristics of the object to obtain an image sensing signal. The digital light signal has the variable light field varying from the outer region to the inner region.