Stereogram
A
stereogram is a type of hologram which is an optical illusion of depth
that is created from flat, two-dimensional image or images. Infact
stereograms are considered to be hybrids of holography and photography.
These holograms have the qualities of both media, but each add something
of their own. These stereograms are a series of holograms consisting of
strips of hundreds of the same images, which are multiplexed into a
single hologram. This unique and pioneering type of hologram is a
breakthrough, as it allows reproduction of living subjects, computer
graphics, and virtually anything that can be photographed to become a
3-D hologram with motion. In other words, this type of hologram is
created from hundreds of horizontal images which are taken of the
original object in motion. When light falls on the hologram, it is
reflected and scattered. This creates a 3-D image of the original
object. The final stereogram is created using laser light and high
technology optics.|
Process of Making Holographic Stereogram |
A stereogram is formed if we take several photographs of an image from different angles. Each of the pictures taken are then to be exposed onto a little area of the holographic filmplate.
The figure above shows us the principle of a stereogram with 3 pictures. These three pictures are multiplexed into one hologram. However, the stereogram formed is of low resolution because the number of pictures is less. Therefore it is important to use a large number of pictures to obtain a good resolution in the hologram. The more the number of pictures, the greater is the resolution. It is advisable to expose about 1 to 2 mm of the holographic film plate for each picture of the object.
Source:
http://www.fou.uib.no/fd/
1996/h/404001/kap10.htm
|
Types of Stereogram |
The various types of stereogram are as follows:
- Stereoscopic imaging: It uses stereoscope to present a
slightly different image to each eye. If the images are narrow and
placed side by side, the stereo pair can be viewed with the naked
eye.
- Anaglyph images: They combine two stereo images from
slightly different viewpoints into a single image and are recognized
as "red/green" or "magenta/cyan" images. The
images viewed using "anaglyph glasses", which use color
filters to moderate the light reaching each eye. This in turn
creates the illusion of a three dimensional image.
- Random dot stereograms: These employ either one anaglyph
or two stereoscopic images. The input image (or images) consist of
random dots with no discernible shapes. A hidden 3D scene emerges
from these random dots when the proper viewing device is used.
- Autostereograms: Using only a single image, they produce
an illusion of depth. By repeating a narrow pattern from left to
right, the image is usually generated by computer.
- Single Image Random Dot Stereogram (SIRDS): They are a form of autostereogram where each repeated pattern is altered slightly. This in turn creates a hidden image which is not discernible unless the right viewing method is used.
|
Levels of Reality |
A holographic stereogram has two levels of reality:
- There is the surface level. This level appears chaotic and often
disorganized with its variety of colors and patterns.
- There is also the deeper and hidden level of reality. This is the hidden image, which actually contains the real meaning of the stereogram. Infact, the hidden image is the real reality image.
|
How to view a stereogram ? |
The steps involved are as follows:
- Put your face near to the screen. You pretend that you are looking through the monitor.
- Next, move away very slowly from the screen.
- After making several attempts, as you move back the image will come into view.
|
Applications of Stereograms |
Stereograms are widely used in variety of applications such as:
|
|
