One of the popular peculiarities of the Denisyuk hologram is the replay of the real image, where the object behind the holo plate during recording appears in front of the plate during replay. This is accomplished by flipping the holoplate top to bottom with respect to the overhead reference beam.
However, this image is pseudoscopic; if a face is holographed, and its virtual image behind the plate looks correct, or orthoscopic, then its reconstructed real image looks like the inside of an upside down mask made from the face. (Click here to see an interesting article about starting with a "mask" to make an orthoscopic image in front of the holo plate plane. Below is the most famous hologram made with this technique, " The Russian Lion" . And here is an image of the author putting his finger in the eye of the Lion.)
Flipping the plate between exposures and replay can give rise to various images floating in space in front and behind the holo plate simultaneously. But this project produces a hologram where the image pierces, or straddles the holographic plate! Something no real obect can do, but light, being immaterial, can do this!
The optical definintion of a real image is that it can be focused onto a viewing screen. (This aspect of the real image of a transmission hologram is investigated in Project 4 and Bonus Project 2.) It is easy to see the image on a screen with a transmission hologram, but is rather awkward in the reflection hologram case. The real image of a reflection hologram is easy to see by eye, but when a groundglass or waxed paper is introduced into the setup, it usually casts a shadow into the works.
The key to success in this project is first producing not only a bright first generation hologram, the master, or H1, but ensuring that it is bright at the color of the laser that made it, and will make the second generation, the transfer, or H2. It is recommended to bone up on the non-wavelength shifting processing schemes for silver halide recording materials with these pages on this site:
If you are using something like the Bayer Photopolymer either from either the current source or Liti, you are lucky, as one of the wonders of this material is the ability to barely change its fringe spacing, maintaining its replay color. If you are working with dichromated gelatin, you need to figure out a narrow bandwidth, non -shrinking, non-expanding processing scheme.
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<Introduction> <Equipment> <The Big Beam> <Project 1a: In-line "Gabor" type Holograms> < Project 1b: Off-Axis Holograms> < Project 2: Single Beam Transmission Deep Scene Hologram> <Project 3: Division of Amplitude Hologram> <Project 4: Pseudo-Achromat Transfer Hologram> <Project 5: Cylindrical Hologram> <Project 6: Single Beam Reflection Hologram> <Project 7: Image Plane Reflection Hologram> <Bonus Project 1: Diffraction Gratings> <Bonus Project 2: Holoroids>