Achromatic Transmission Holograms

This is a forum to share experiences and ideas about holography.
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John Klayer

Achromatic Transmission Holograms

Post by John Klayer »

I'm thinking of giving achromatic holograms a try. Anybody have luck with them? Any tips you can give? Thanks
Ed Wesly

Achromatic Transmission Holograms

Post by Ed Wesly »

The main thing to think about is having the master angled at the so-called Benton or tip or alpha angle, not parallel to the H2, to get the deepest achromatic zone. Which takes some getting used to.
Justin W

Achromatic Transmission Holograms

Post by Justin W »

Hi John!

I've been experimenting with some achromacity and/or custom additive colors.
The method I've been going with has been just like Ed mentioned - master at "tip angle".
I originally started with a regular transmission master parallel to my H2 film, with different color channels being lit in stripes on the master. The red channel, seperated by several more degrees from the green channel than the blue is, often wouldn't replay simultaneously with the green and blue channel especially.

And that's to say nothing of trying to get the images to replay in register! That's what the tip angle is supposed to do - orient your master so that the red channel it plays from the top of the film is lined up with green and blue images (middle and bottom of your film). The tip angle at which you burn your master is supposed to coordinate with your H2 reference angle for best results. Different tip angles require different H2 ref angles. I've been working with masters at 41deg tip angle for transferring into 60deg H2s. As pointed out by folks a time ago regarding the 41deg tip angle - this is a nice plate angle to work with as the fringes will likely be standing almost straight upright out of the film and emulsion shrinkage should have minimal effect.

The tip angle thing isn't magic though. When I first tried, I thought it would work perfect right out of the box. Nah.
The images are closer to being registered than ever before, but there's still lots of trimming to do.
Hopefully you can make some headway on this! I'm looking forward to hearing how things go as you work in this direction.
Justin W

Achromatic Transmission Holograms

Post by Justin W »

Hi again John

Just had another thought.
Now, bear in mind that I have not tried this and cannot confirm any part of this for myself, but I have been told that (and someone please correct me if I'm full of bull) an open-aperture transfer from a master to an image-planed transmission H2 will replay an achromatic image with white light. If memory serves, you will have something like 3cm of depth at the film plane where what you would think would be a laser transmission will replay with white light. I would assume that any part of the image outside this zone will do the standard thing and play back as a rainbow-ey blur with white light, just as all laser trannys do.

The most I can say from my personal experience is that I may have accidentally done this once; I can recall many moons ago shining a white LED through a transmission holo I had just made and seeing a fantastically clear, sharp image of some clothespins holding a mirror near the plate. It was startling. The clothespins were... well, clothespin-colored :shock:

I'd love to do this again except maybe next time on purpose. The image quality was rather impressive.
Vidar

Achromatic Transmission Holograms

Post by Vidar »

Hi Justin,
I have tried this several times with resonable results. It is actually easier to make the open app type than any other hologam type, the low stability and resolution requirement are probably the main reason, as well as the short exposure time. Have a look at the gun hologram at the intro page of this forum, or read the story at www.holografi.no. The sharpness is resonable OK over 20-30 mm. If you restrict the master vertically the sharpness and brightness increase quite a lot. Not that you have to do that if your object is not deeper than say 40 mm. The brightness is usually quite high even when not restricting the master.

I noticed that using pyro dev on open apperture holograms, the image comes out in a "golden" color.

It's a long time since I posted here, and a long time since I made a hologam. I hope however to be able to shoot some holograms again soon. I still have a big stock of 8E75 left, as well as some BB640. Even if have have not been active i my lab for a while, I still visit this forum several times each week.
Vidar

Achromatic Transmission Holograms

Post by Vidar »

Forgot to mention that I did not have any luck with the master at the tip angle. Could have been the cohorence lenght or my skills at the time of testing, but I would love to try the tip angle again.
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