A--Viewing Holograms

Viewing Your First Hologram

I failed to make a hologram . . . or did I?

By Alec Jeong

1. SUMMARY

If you can't see a holographic image after you've exposed and developed your film or plate, don't automatically think it's because you failed to make a hologram. It may be just the way you're viewing it.

2. INTRODUCTION

When my father Dr. Tung Jeong taught me how to make my first hologram 25 years ago for a science fair project, he also taught me not to jump to conclusions based on faulty assumptions (sounds like a scientist talking, eh?).

I had just completed all the steps to making a hologram per my father's expert guidance. I had chosen a solid object (a few coins), placed the object, laser, and film plate relatively safe from vibration, exposed the plate for about 10 seconds, and developed the plate under safelight. All said and done, when I went to view the plate I still could not find a 3-D image, let alone any image at all! The only thing I saw was one disappointing translucent piece of glass with some greenish tint on it. Crestfallen, I sighed, "Dad, I think I've failed. I must have messed up something in the process."

My father then took the plate into his hand. He tilted the plate a little bit the to left and right, then up and down, until he finally settled at a certain position. He then looked at me and said, "The image is right here!" To my amazement, there suspended in air before my eyes was a holographic 3-D image of my coins and quarters. So, I had not failed after all. Somehow, it was the way we viewed the hologram that made all the difference.

3. HOW TO OBSERVE THE IMAGE

Viewing Reflection Holograms

To view your hologram, you need an appropriate viewing angle and light source. With the appropriate light source, view the image by shining the spot light at the hologram from approximately the same angle you had the laser shoot when you were first exposing plate. You might need to tilt the plate left and right or forward and back to maximize the brightness of the image. It may take some practice.

As for the light source, ideally, you want a bright spot light. Spot lights concentrate the light using a built-in reflector so that all the light is confined to the correct angle. Spot light are available at any K-Mart, Wal-Mart, and most other retail store. As a cheap substitute, you could also use a $1.98 (batteries included!) Rayovac pin light from K-Mart. In general, you cannot view a reflection hologram with a laser, fluorescent light, or light from a frosted bulb.

Viewing Transmission Holograms

For transmission holograms, the image is viewed using the laser light that exposed it. Reposition the hologram at the same location (and orientation) as that used during exposure. Allow the laser light to illuminate the hologram. Look through the hologram toward the location where the object was placed. The image you see should be exactly the same as the object. This is called the virtual image.

Beginners should also try viewing the image by exposing the hologram with the laser beam head-on onto the plate. At this exposure angle, the viewing angle will shift minimally even if the emulsion shrinks during processing. After you get good at it, try a 45 degree angle; this is better for exhibition purposes when you can hang the hologram on a wall and illuminate it at 45 degrees with track-lighting from above.

You can also project the “real image” (you can read about this in any high school physics textbook) onto the white screen. Simply replace the collimating lens onto the laser and adjust it until the laser becomes a “pointer”, i.e., focused into the smallest spot far away. Now shine the laser beams through the finished hologram in exactly the backward direction. Place a white card at the original location of the object and you will see the “real image."