1. A method for reliable wide range depth acquisition in a synthesis system of time-of-flight (ToF) camera and stereo camera, the method comprising: receiving a depth image of a scene taken with a ToF camera and a left color image and a right color image of the scene taken with a stereo camera; estimating an error per pixel of the depth image; calculating a value of a maximum distance multiple per pixel of the depth image based on a difference between points projected onto the left color image and the right color image, the points being within an error range corresponding to the error per pixel, the value of the maximum distance multiple being indicative of a distance of an object in the scene with respect to a maximum acquirable distance of the ToF camera; and generating a reconstructed depth image by conducting phase unwrapping on the depth image using the value of the maximum distance multiple per pixel of the depth image, wherein the estimating of the error per pixel of the depth image includes estimating, to be the error, a smallest standard deviation among standard deviations calculated using depths of pixels included in windows of a desired size.