Reflection hologram is the most common type of hologram, viewed with the light source on the same side as the viewer. Such hologram features a truly three-dimensional image near its surface. The reflection hologram is illuminated by a ray of white incandescent light that are held at a specific angle and are located on the viewer’s side of the hologram. So, finally the image, formed by this process consist of light reflected by the hologram.
Importance of Reflection hologram
Different holograms are differentiated by the way in which they are lighted or illuminated. The reasons for using reflection holograms are as follows.
The reflection hologram better known as monochromatic hologram features shorter exposure time that leads to less stringent condition on the required mechanical steadiness.
Such holograms can be viewed easily with a point source of white light or the Sun, which is not applicable with other holograms.
These types of holograms are used widely as they are viewed with reflected light. The colors of reflection hologram can be shifted by expanding the recording material.
Reflection hologram and its source of illumination
The reflection hologram selects appropriate bands of wavelengths to reconstruct the image, if the highly directed beam of white light illuminates it. Such hologram reflects light within a narrow band of wavelength. In case of reflection hologram there are different film emulsions that make images with different characteristics. Lets have a look at different film emulsions.
Silver Halide – These glass plates are used to get the highest quality images. It is considered as the most common emulsion of choice for most artists and holographers.
Dichromated Gelatin – This is a type of chemical gelatin mix, where the images formed using DCG have the least range of depth and are easily viewable at normal room light without the help of any spot light.
Photo polymer – Photo polymers with plastic backing are suitable for long production runs. Although its image depth is less but they look brighter with a wider angle view.