Make a hologram with mirrors to learn about light refraction and photography. Holograms are used on everything from passports to cereal boxes. Although the theory behind the holographic image is simple, in truth, capturing the hologram can be very tricky. Using only mirrors (no beam splitter or other lenses) you can create a simple hologram. In addition to the mirrors other supplies are required to make a hologram.
Set up your optical table in a room with no air or vibration interference. Use any sturdy table and add sides to it with lumber, and then fill the enclosed area of the table with sand to buffer any potential vibration.
Set up holographic assembly. Turn on safe (darkroom) light. Set the concave mirror on a stand so the centre of the mirror is at the same elevation as the laser beam (laser is set behind the object). Set the flat transfer mirror so the beam, directed from the concave mirror hits the flat mirror behind the object. Place a holographic plate so it is completely cast in light from the reflection of the beam from the flat mirror. Place the white card in front of the laser to block the beam.
Expose the image. Being exceedingly careful to not cause any vibrations, or let anything (including clothing) brush against your set-up, you are ready to expose the holograph. Leave the green lights on, but turn off all the other lights and be certain that the sticky (emulsion) side of the holographic plate is facing your subject (between the flat mirror reflection and the object). Gently lift the card (blocking the beam) off its support, still blocking the beam, hold it still for 30 to 60 seconds. Lift the card to uncover the beam and hold it in position, with the laser beam exposed, for 6 to 10 seconds.
Develop hologram. Label each tray (developer, bleach or overflow). Fill trays according to label. Developer is 50ml (a) + 50ml (b) + 50ml-distilled water; mix well. Place exposed holograph plate into developer tray, agitate the fluid by lifting one end of the tray every two minutes. The exposed plate will become very dark. In the sink, place the developed plate inside a container that is deep and narrow enough that the plate does not sit horizontally. Run water over plate for three minutes.
Bleach developed hologram. With about 150ml of bleach in the next tray, place developed plate and agitate as in Step 4. Agitate until all dark (silver) is washed off. Continue agitating for additional 30 seconds. Wash in sink as in Step 4. Use a third tray for Photo-Flow, and following directions on the bottle, dip developed, bleached and washed hologram in the tray. Drain the plate and blot with lint-free rag. In a quick, sweeping motion use a hair dryer, on a warm setting, to completely dry the plate.
Label developing trays. Use concrete blocks as sturdy bases for mirrors and object.
Even the slightest vibration from air or sound waves will cause the holographic image to be dirty.
Tips and warnings
- Label developing trays.
- Use concrete blocks as sturdy bases for mirrors and object.
- Even the slightest vibration from air or sound waves will cause the holographic image to be dirty.
Things you need
- Helium-neon laser (1 to 10 mw) with sturdy mount
- 1 concave FS (front side) mirror (about 15mm focal length) with sturdy mount
- 1 flat transfer FS mirror with sturdy mount
- 1 holographic plate with sturdy mount
- White card (shutter)
- Subject (any small object) with sturdy mount
- Optical table
- 'Safe' green light
- Three 5x7 trays
- Developer (for developing the holographic image)
- Distilled Water
- Rubber gloves
- Hair dryer