1. An image sensor, comprising: a plurality of pixels, each comprising: an optical element; and at least a dummy metal segment, disposed above the optical element, wherein the dummy metal segment is not directly above the optical element; wherein the image sensor includes a dummy metal segment with a size different from a size of another dummy metal segment included in the image sensor, the pixels include a first pixel, a second pixel at a left side of the first pixel, and a third pixel between the first pixel and the second pixel; a first optical element included in the first pixel is disposed at an optical center of the image sensor; a third dummy metal segment included in the third pixel is smaller than a first dummy metal segment included in the first pixel; and a second dummy metal segment included in the second pixel is smaller than the third dummy metal segment included in the third pixel.