1. An image system comprising: a light source configured to illuminate an object comprising at least one portion; an image sensing device configured to generate a picture comprising an image produced by the object, wherein the image comprises at least one part corresponding to the at least one portion of the object; and a computing apparatus configured to determine an intensity value representing the at least one part of the image and to determine at least one distance between the at least one portion of the object and the image sensing device using the intensity value and a dimension of the at least one part of the image.