A holographic method for viewing a stereo photo pair without any apparatus has been proposed. In this paper, two techniques, the transparency contact method and 2-step method, are presented and tried to realize wide observation area. By these methods, easy and natural stereoscopic viewing has been achieved when the hologram is seen right in front.
In the transparency contact method, the optical system for making the hologram is very simple, but the density deviation of the transparencies must be small. Contrary, in the 2-stepmethod, 3-D image of high quality can be observed when the original pictures are high contrast.