Reflection Holography

Tracy Singh and Elizabeth Roberts
WISE 187 Course
Stony Brook University

May 2003



Background Information:

Holography is a process in which a 3-dimensional picture is taken of an object. What sets a hologram apart from a photograph is that with a hologram, the amplitude and phase of the light that originally illuminated the object is recreated perfectly. Because of this, the image looks 3-dimensional. The interference of the light reflecting off of the object forms a pattern on the holographic plate. When light is reflected off this pattern, the original information is reproduced and the human eye percieves the object as being "real". Laser light is used to make a hologram because it is coherent, (the light waves are in phase), and it is all one color. This makes it easier for an exact "picture" of the image to be taken.

There are different types of holograms that can be created, but the type that we chose to work with was a reflection hologram. In this case the object to be viewed is placed behind the plate and the hologram is created by reflecting light. This is as opposed to a transmission hologram, which is created with the object on the same side of the plate as the light source, where the light passes through the plate to create the hologram.

As a reflection hologram, the ones we created can be viewed under normal light, but they seem to show up somewhat better under the laser they were created with.


Preparation

Before beginning, we had to mix the chemicals for the developer and
the bleach solution.  When handling these chemicals, gloves should
always be worn.  
 The chemicals we used were:

DEVELOPER PART A- 
Distilled Water 700ml
Metol 4 g 
Ascorbic Acid 25 g 
add Distilled Water total 1000 ml

DEVELOPER PART B-
Distilled Water 700ml
Sodium Carbonate 70 g
Sodium Hydroxide 15 g
add Distilled Water to total 1000 ml

BLEACH SOLUTION-
Distilled Water 700ml
Copper Sulfate  35 g
Potassium Bromide 100 g
Sodium Bisulfate  5 g
add Distilled Water to total 1000 ml 


Setup

Once chemicals are mixed, mix equal parts of Developer A and Developer B in one dish, bleach solution in another dish, and fill two beakers with distilled water, one mixed with a capful of wetting agent. The room in which this is done must be completely dark and quiet, as light and sound waves will interfere with the wave interference. Also, no movements should be made that could create vibrations, because this will also interfere.

Procedure

The first step is to expose the hologram. This is done by placing the object 40 cm away from the laser, with the holographic plate standing vertically against the object (see picture). Make sure the emulsion side is against the object.

Shine the laser on the object for 5-10 seconds, and then shut off the laser immediately and using tongs, quickly place the plate in the developer for 10 seconds. Then rinse the plate in the pure distilled water for 20 seconds with agitation. Then place the plate in the bleach solution, agitating it for 1 minute or until it appears clear. Lastly, place the plate in the water/wetting agent solution for 20 seconds. Place the plate standing vertically to completely dry. This may take up to a full day.

Discussion:

There was a considerate amount of error in our results, as we developed three holographic plates and only one showed an image. There are many factors that could have caused this, including vibrations from us moving around the room or talking, plus my cell phone ringing. The one factor that probably had the greatest effect though was the fact that the object was touching the plate in the last try as opposed to the other two, and this was the one that worked.

Our Hologram

Examples of Other Holograms

The photograph is from Doug Broege's website on his holography experiments.

Links:

The company where we obtained the supplies and directions for procedure.

Background information about holography.