1. A display device comprising: a display panel having a photosensor; and an image processing circuit operationally connected to the display panel, wherein the photosensor is configured to capture a black image, a white image and an image of an object, wherein the image processing circuit is configured to produce an image having data represented by a formula: MAX×(Z−X)/(Y−X), wherein MAX represents a maximum value of a gray scale, wherein X represents data of the black image, wherein Y represents data of the white image, and wherein Z represents data of the image of the object.