Transmission Hologram

Simple answers are here! For Theory look in General Holography.
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LawrenceM

Transmission Hologram

Post by LawrenceM »

Hello all
lm a new Holographer and recently purchased the holography kit from integraf.
1st thing l made was the reflection hologram which came out perfect 1st time and l was very impressed by it.
l then moved on to try and make a transmission hologram but have run into a roadblock.
Every attempt l make results in a very dim hologram.
l am using the single beam setup with the laser lens off to utilise the wide beam.
Tried using some chess pieces as object with plate and object 90 degrees to each
with the beam coming in plane.
got very very dim results with bout 2 inches depth
then l changed my setup. now with some coins and keys as object (as they are more shiny)
and with the laser above the plate and object pointing down towards them.
(sorry if my descriptions are not very clear but basically iv done both the transmission setups
on this page http://www.holokits.com/a-make_transmis ... gram_2.htm )

On the second setup got brighter results, but however only a depth of about half a inch!
far from the six inch depth l was promised.

l just dont understand where lm going wrong. l lv tried extending exposure time
20 - 40 - 60 seconds, but cannot seem to get optimum results.

lm using the PFG-03M plates (2.5"x2.5") and JD-4 processing kit.

l would greatly appreciate any hints or tips you guys can give me as to
where l am going wrong as l really dont want to keep wasting plates on failed
attempts.
Tom B.

Transmission Hologram

Post by Tom B. »

Diagnostics:

- bad laser, film, or chemistry - probably not, obtained good results with reflection which is much more fussy.

- bad setup - maybe. The diagrams show the plate vertical relative to object and ground plane. Any movement of the plate (or object during exposure will screw things up. Is your plate holder absolutely rigid relative to the objects? Do you get an image with stripes (contour lines) ? This would indicate movement during exposure.

I must confess my transmission results with PFG and BB plates with rehalogenating bleach chemistry have always been disappointing. I have been more interested in reflection than transmission so this has not bothered me much. Maybe someone out there that has had good transmission results can straighten us out.
jnhong

Transmission Hologram

Post by jnhong »

I've had pretty similar results from single-beam setups. The likeliest cause is vibration or movement. I've shot the same exact setups multiple times and only a few plates will show expected results. Some of the failed shoots I attribute to noise coming from outside the room or outside the house. One time I forgot to turn off the heater which then started blowing during my 20 second recording period. The longer you shoot, the more things happen.

Another issue that may be a factor is the light intensity coming from the farther objects. If the foreground items are bright enough, they could swamp out the other objects in the background. Point the diverging beam such that the brightest area (mostly the center area) shines on the objects, and only a weaker portion of the beam shines on the plate.

One way I've improved this setup is to reflect some extra light onto the objects. I used a small mirror, placed it into a portion of the beam that would have been wasted anyway, and reflected the light back onto the coins or keys. Make sure the mirror does not cast a shadow onto the plate. The extra lighting always helps.

Joe
dave battin

Transmission Hologram

Post by dave battin »

these are good words from joe, ive included a video of a one beam transmission,there is a mirror just out of view off the left side (in the hologram),bouncing some of that wasted light back on the skull.......

LawrenceM

Transmission Hologram

Post by LawrenceM »

Thank you for the replys, they have really helped me find where l was going wrong.
l do indeed get contour lines in the hologram, so it is a movement problem, l will endeavour to improve
my setup to rectify this, as well as the tip about using a mirror to utilise some of the lost light.
l will let you know how l get along.
cheers all
:)
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