In keeping with this principle, any enclosed space can be made into a "pinhole camera" by piercing a small hole in it. Rays of light passing through the pinhole cause a vertically and laterally inverted real image of the object in view to fall onto the surface opposite it, as illustrated in the diagram above.
應用這個原理，就是在任何密閉的空間上鑽個小孔即可成「針孔相機」，光線透過針孔，使得目標物呈上下左右顛倒的實像於其相對的表面上，如右圖：