In this tutorial, we will try to follow Einstein’s dictum so that you can easily make holograms.
“everything should be made as simple as possible, but not simpler.” — Albert Einstein
The procedures we propose here are as simple as physically possible. In the process, we make holography not only as simple as possible, but also safer, less expensive, and more accessible to young people.
Most of the essential items described in this article can be found in our holokittm hologram kits or are available separately. the kits allow you to make many types of holograms, including the reflection hologram (visible with white light) and the transmission hologram (visible and projectable with laser light) described in this tutorial.
2. summary on how to make a hologram
Before we dive into the details, here’s a very quick overview of how a hologram is made. making a hologram involves recording the interference pattern that occurs when light from a stabilized laser meets its own light that bounces off the object it is illuminating. the key is to set up the laser, the object, and the recording film or plate so that it captures the interference pattern. once this is done, we simply need to expose the object and the film plate with the laser light and then develop the exposed film plate. once you get the hang of it, the whole process can be completed in 3 minutes.
Our holograms kits include everything you need to make holograms, including step-by-step instructions and tips.
Since we need to capture the microscopic interference pattern exactly as it is at any given time, you can imagine how the movement of the object, the film plate, or the laser can mess things up. in fact, the movement of any element by more than 1 millionth of a meter is enough to ruin your hologram. so we have to make sure our setup is super stable i.e. no movement, no vibrations, no noise, no drafts, etc.
3. holography supplies
you will need the diode laser discussed below, a supply of 2.5 x 2.5 inch (63mm x 63mm) pfg-03m film plates, and a jd-4 processing kit (or alternatively , pfg-01 plates with jd-2) . all these elements are included in the holokit hologram kits or are available separately in our catalog.
Although slightly more complicated and therefore not recommended for first time holographers, sheets of pfg-01 holographic film can also be used sandwiched and trimmed between two glass plates instead of using holographic plates. develop with jd-2. For the instructions below, replace the holographic glass plates with the correctly sandwiched film sheet. see our article on how to use holographic film sheets for important details.
3.1 the laser
To make holograms, we take off the collimating lens of the laser to shine its pure, naturally spread beam right on to the holographic plate and object.
The following figure shows a Class IIIA diode laser with an output of 3 to 4 mW when operating on 3.0 V DC. if the power is supplied by batteries, its 650nm wavelength red light reaches a coherence length greater than 1m after a warm-up period of a few minutes. the traditional helium-neon laser, on the other hand, operates at dangerously high voltages, is prone to breakage, has a shorter lifespan, and has a coherence length of about 30 cm.
Unlike many laser diodes and laser pointers, the laser shown below and in our catalog has a stabilized frequency output (a must for holography), good coherence length (also a must) and a collimating lens removable. With the spring-loaded collimating lens mounted on the laser, the output beam can be adjusted to focus at any arbitrary distance.
To make holograms, we will remove the collimator lens. without the lens, the direct laser output spreads out with a highly eccentric elliptical profile. since the beam encounters no external optical elements, the light has no speckled patterns caused by interference and diffraction, and appears perfectly clean. in other words, we will project this pure beam directly onto the holographic plate and the object.
The responsible parent or teacher is advised to remove the lens and small tension spring before allowing the student to use the laser. in this way, the power density received by human eyes will not exceed that received by looking at an ordinary grocery store laser scanner. When the laser is not in use, replace the collimating lens (with or without the tension spring). this helps ensure you won’t lose the lens, and more importantly, it will help keep dust out of the laser.
If you are using your own “laser pointer” to make holograms, be aware that many laser pointers and diodes do not have frequency stabilizer circuitry (like the one above), which is required for holography. Also, since most laser pointers do not have a removable collimation lens, you must purchase a special optical lens to spread the beam. With two lenses (four-lens surfaces) through which the laser beam must shine, there can be many objectionable patterns in the resulting beam due to the four lens surfaces and dirt on them.
3.2 stable laser support
An excellent support for such a small laser is a wooden clothespin, as shown below. for mechanical stability and maneuverability, the clothespin that holds the laser is stuck into a cup of sand, salt, or sugar (not pepper!). on the other hand, for schools with available lab hardware, the clothespin can be glued to a bar and mounted to a lab stand with a right-angle clamp.
The wooden clothespin offers another advantage. Being a thermal insulator, the laser will reach thermal, electrical, and frequency stability within minutes of being turned on, assuming batteries are used as the power source. an alternative mount would be a rubber tipped thermometer mount.
4.0 make a hologram by the “contact copy” method
The “white light reflection hologram” is the simplest to make. we recommend the “contact copy” method, whereby the holographic plate (holoplate) is held directly against the object during exposure. As long as there is no relative motion between the object and the plate, no separate vibration isolation is needed.
4.1 choose your object
The choice and preparation of the object is crucial: (1) it must be made of a solid material, such as a quarter or dime (no hair or cloth); (2) It should appear bright when illuminated with the red laser light; and (3) must not move or warp.
If this is your first time making a hologram, try to avoid choosing objects that are fabric or furry (eg teddy bears) because these objects are easily deformed. Also avoid large plastic objects, as they tend to expand and contract with the slightest change in temperature (even from the heat of your fingers!). For best results, try metal or porcelain objects that can be easily illuminated with laser light and are no larger than the size of the holoplate, such as coins.
if there is any doubt about the possible movement, you can glue the object to a stable wooden or metal platform where the hologram will be made. Another way to dampen movement or vibration is by placing the object on your computer mouse pad or, better yet, in a tray of sand, salt, sugar (or even kitty litter).
4.2 prepare your developer solutions
Prepare chemical processing solutions and place processing trays as instructed in the instructions accompanying the jd-4 (or jd-2) kits. Although the chemical solutions are called non-volatile, the chemicals evaporate over time and can cause nose and throat irritation. use chemicals in a ventilated area.
It is not necessary to have a completely dark room. however, the room must be dark enough that it cannot be read in. use a standard night light if necessary so you can move around safely. block any direct light from reaching the holography system, i.e. place the night light under the table.
5. make your reflection hologram
Now it’s time to do the holgoram! carefully follow these steps to align and expose the hologram to the laser:
- adjust the laser on its mount so that the beam spreads out horizontally.
- place the object 35 to 40 cm away from the laser.
- place a white card behind the object and adjust the laser while observing the shadow on the card. adjust the laser position until the object is optimally illuminated. then remove the white card.
6. seeing your hologram
After the hologram has completely dried, it can be viewed with a point source of incandescent light such as from a projector, flashlight, or the sun. you can not use diffuse light sources such as frosted bulbs and fluorescent lamps. For best results, spray the emulsion (sticky) side with a diffuse black paint. this protects the emulsion and provides a dark background to improve image visibility.
Now, read on to see how to make a panoramic transmission hologram.