Transmission hologram is a master or copy hologram in which the image can be viewed when a light source passes through the recording medium, somewhat like a slide. When a transmission hologram is a master hologram, it is reconstructed using laser light. Copy transmission holograms, however, are illuminated with white light, and in some cases, can be viewed with a mercury or a sodium lamp.

Transmission holograms are lit from behind, bending the light as it passes through the hologram to the eyes producing a virtual image. An other characteristic of transmission holograms is that the object beam and the reference beam come in from the same side of the holographic film plate during the exposure.

When the developed film is illuminated, diffraction and interference gives rise to a new wavefront quite similar to the original wavefront. The result is that, it is difficult to see the difference between the object and the image. The image appears to us as though it is formed at a distance behind the filmplate. The plane of the image is called the holographic window. This image is the virtual image.

Types of Transmission Hologram

• Laser Transmission Holograms - These are made with lasers and also lit with lasers. The image produced appear in the color of the laser used in illuminating them for viewing.
• White light transmission holograms - These are illuminated with incandescent light or white light and produce images that contain the rainbow spectrum of colors. The color changes as the viewer moves up and down.

Transmission Holograms can also be classified as:

• A single beam transmission hologram is a very simple optical arrangement and requires less system stability. This hologram is called a transmission hologram because during the viewing of the hologram the light source is on the opposite side of the hologram from the viewer and the reconstructing light is "transmitted" through the hologram.
• A multi beam transmission hologram create two or more beams with a beamsplitter. The design helps to control the placement and illumination of the object scene separately from the reference beam and provides the proper placement of the real image for use in making a white light reflection display hologram.

Applications of Transmission Hologram

• For security ID and labelling
• Commercial display
• On packaging
• For identification purpose
• For printing jobs
• Food and drug packaging
• Brouchers and catalogs