1. A blood vessel locating system comprising: an image capture device configured to capture a first image of a region of skin of a subject when the region is illuminated by a first light and to capture a second image of the region of skin when the region is illuminated by a second light; and an image processing module configured to calculate the difference between the first image and the second image to obtain a differential image, the image processing module further configured to enhance the differential image to obtain an enhanced image of blood vessels located under the surface of the skin of the subject and to superimpose the enhanced image of the blood vessels on the first image to obtain a final image.