
It
is essentially essentially a hologram of a hologram, in which the
first-generation hologram is masked with a narrow slit. The rainbow
hologram separates out components wavelengths of white light and sends
them in different directions, so that the viewer sees the image by light
of only one wavelength, the actual wavelength being determined by the
viewpoint.
They are made by a double holographic process where an ordinary
hologram such as a transmission hologram is used as the object and a
second hologram is made through a slit. During image reconstruction, the
slit operates and it removes the coherence requirement on the viewing
light. This makes it possible to maintain the 3 dimensional character of
an image while the viewer moves horizontally. This also maintains the
brightness of the image. If the viewers eye is moved vertically, no
parallax is seen and the image color sweeps through the rainbow spectrum
from blue to red, hence rainbow hologram.
Applications of Rainbow Hologram
- Decorative and product packaging
- Promotional labels
- Gift wraps
- Stickers
- Displays
- Image processing