A screen printing machine includes a supporting member, a printing mechanism, and a spraying mechanism. The chain has an inner link in which both end portions of a pair of front and rear bushings are press-fitted into bushing holes of a pair of right and left inner plates, and an outer link in which both end portions of a pair of front and rear pins are press-fitted into pin holes of a pair of right and left outer plates. The method may also include processing the image, using the computer system, to determine whether a viewer is present in the viewing area.