Abstract: An optical system of an under-display camera (UDC) includes: a display comprising pixels having a first periodic structure; an image sensor disposed under a screen of the display; one or more optical elements disposed between the display and the image sensor and configured to form an image of an external scene on the image sensor; and an additional diffraction member comprising an array of elements having a second periodic structure and configured such that the second periodic structure overlaps the first periodic structure by an offset of the elements to redirect a second light which is a portion of a first light corresponding to the external scene transmitted to the image sensor through the display.