Lighting Techniques

I produce white light reflection display holograms because the images are monochromatic (gold in color) and lend themselves to a more realistic representation of the original object or scene. Because of the diffractive nature of holograms (diffraction lenses), keeping the image close to the plate plane enhances the image's monochromatic effect (single color reconstruction) and resolution (sharpness). As the image is moved away from the plane of H2, factors come into play that decrease monochromaticity and resolution. This can cause the image to no longer be gold in color and start showing multiple rainbow colors. These multiple colors are actually multiple colored images of the object scene being created as the white light starts to spread into a rainbow the further the reconstructing light moves past the plate. The actual term for this phenomenon is called white light dispersion.

My normal method of illuminating display reflection holograms is by hanging the hologram on a wall and using track lighting on the ceiling to illuminate the hologram (overhead lighting or overhead reconstruction) as shown in Figure 22a. Figure 21a would be the appropriate optical setup for this. Figure 21c would be the appropriate optical setup to illuminate the hologram with the light source on a desktop (underneath lighting or underneath reconstruction) as shown in Figure 22b. The reconstructing angle for both types will be the recording angle which is 56 degrees.

In the following two photographs, both the skull and the human brain are projected 3 inches out in front of the plate. You'll notice that you can project fairly far out in front of the plate without getting any dispersion.

I use Halo or Hampton Bay brand halogen lamps. Specifically, I use the L2710 MBX lamp holder or equivalent. The lamps that plug into the holder should be at least 65 watts and have a narrow beam designation [ (Sylvania brand 65MR16Q/NSP(FPA) ]. All lamps should have a clear, glass envelope, not frosted. You can see these lamps and their holders in Figures 22a and 22b.

As a final note, don't hesitate to contact me via email if you have any questions, comments, or suggestions regarding anything on this web site. I built it as a teaching tool and your feedback is welcome.