ABSTRACT
Laser transmission holograms: e image appears in a single hue and shows laser speckle (Figure 2.6). e illumination is usually from the side and behind the hologram. In this type of hologram, the image resolution is high, and it can be deep too, as much as a meter or more. You have to use a laser to illuminate the hologram. If it is a large image, you will need a powerful laser, and apart from the initial hire fee, you will need to pay someone to look after it. Local authorities often seem to regard a laser beam as some sort of death ray, and it is sometimes dicult to persuade them to let you display laser-lit holograms in exhibitions. If this is the case, you will have to resort to a ltered mercury arc source, which will sacrice some denition, though the speckle will also be largely suppressed. is problem is to some extent
receding, as the widespread use of small diode lasers for pointers and alignment checking has not only made the public more familiar with them but has made the display of laser transmission holograms much less of a headache. In addition, laser video projectors are becoming more and more available. ey employ three laser beams, namely, red, green, and blue; if you illuminate your laser transmission hologram with all three lasers, you will get three images. So choose just the one beam and dim the others.
