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.
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