ABSTRACT
There are quite a number of different types of hologram, and you will find details of all of them in this chapter; the subsequent chapters will explain how to make them. There are two main categories of hologram: transmission and reflection. Transmission holograms, as you have seen, are made with the object and reference beams incident on the holographic emulsion from the same side; reflection holograms are made with the object and reference beams incident from opposite sides. For the purpose of displaying holographic images, there are also two broad categories of hologram: those giving images that can be displayed only by light from a laser or some form of quasi-monochromatic light source, and those that can be displayed using white light. The former are usually confined to scientific and technological applications, whereas the latter have their main uses in the world of display holography. However, display holograms have to be made initially from laser-lit originals, so it is appropriate to begin with this type.
