An obvious application of holography is in displays. With the availability of suitable photographic emulsions coated on glass plates in sizes up to 1.5 m × 1.0 m, as well as film in rolls up to 1 m wide, several striking displays have been made using holograms. Some of the problems involved and techniques used to solve them have been described by Fournier, Tribillon and Vienot [1977] as well as by Bjelkhagen [1977a]. Even larger displays are possible with projection techniques using a reflecting lenticular screen (see, for example, Okoshi [1977]).

However, conventional holograms have several drawbacks [Benton, 1975], such as the limited angle over which the image can be viewed, low image luminance, and the need to use a monochromatic source to illuminate the hologram, as well as the necessity to illuminate the subject with laser light when recording the hologram. This chapter discusses some of the techniques developed for holographic displays that have overcome these limitations (see also Benton [1980]).

360° holograms

Holograms that give a 360° view of the object can be recorded using either four or more plates [Jeong, Rudolf & Luckett, 1966; Chau, 1970] or a cylinder of film to surround the object [Hioki & Suzuki, 1965; Jeong, 1967; Stirn, 1975; Upatnieks & Embach, 1980].

A very simple optical system for this purpose [Jeong, 1967] is shown in fig. 8.1. In this arrangement, the object is placed at the centre of a glass cylinder which has a strip of holographic film taped to its inner surface with the emulsion side facing inwards.