Interferometry in Green

Well, it turns out that one of the problems I was having with my green laser and the VRP-M film is my shutter.

image

When it opened it set the table to ringing for at least a full second.  My 2-4 second exposures were incredibly dim because they were getting fogged for the first second.  I found this out after setting up an interferometer (shown above, click for a larger picture) opening and closing the shutter while it was going.  The fringes really moved when the shutter closed but as no light would have been reaching the film, I didn’t care about that.  Have it shake the table when opening was a problem though.

I tried all sorts of things to improve the isolation of the shutter and damp the vibrations it was putting out but in the end I had to give up and make a shutter from scratch.

I took a panel meter and attached a multi-layered piece of aluminum foil and used that reflect the incoming beam and create a beam dump on the inner surface of the meter housing.  Painting the whole thing black created a nice little box to keep the beam in.

After putting a couple of beads of silicone where the meter arm rests against the coil I ended up with a nice quiet shutter that didn’t disturb the fringes at all.

It’s being put through its first hologram-making test right now.

Using holograms to diagnose astigmatism

image This is pretty cool and something that even hobbyist holographers could make.

Laser Focus World is reporting that researchers at New South Wales University have developed a holographic astigmatism test that’s faster to use than the lens-flipping "how does the chart look now?" test we’ve all endured when having our eyes checked.

The current method of looking at a distant object through a number of lenses to prescribe corrective glasses is at best cumbersome. In an alternate approach, the researchers recorded the wavefront emanating from various sunburst patterns located at different distances from the eye in a hologram. When a subject views through this hologram (illuminated by a plane wave), he or she will see the images of various sunburst patterns located at different distances from the eye.

Unfortunately there’s no additional information at the university site.  Perhaps they’ll put something up soon.

Optics.org has a bit more information and a few extra photos available.

Let there be green

After several days of tests I’ve gotten a couple of decent transmission holograms on VRP-M using a Coherent 315m.

GreenShot1

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Back in the lab

You ever look back at something you did months ago and wonder, "why did I do that?"

I did that this evening with the controller that I’ve got in my lab.

I’m starting work on another hologram for a professor at A&M and needed to do a bit of maintenance on the table. Strange, but every time a new hologram request from her comes in, there’s something that needs doing in the lab before I can get started.

This time the HEPA fan wasn’t shutting off during an exposure and the table light sensor wasn’t working.

It turned out with the HEPA fan that somehow I’d wired up the relay connection with an additional 5v going to it. I have no idea why I did that. Fortunately it just caused the controller chip on that port to heat up (and not work) but didn’t blow anything. Odd that it was working for a while and then just stopped.

The light sensor just turned out to be a loose connection at the junction between the table wiring and the controller wiring. Gremlins.

I also found a problem with the holocontroller software not always shutting off the fan and fixed that.

Now I just need to straighten up the lab, prep some film, paint the subject and shoot. All tomorrow morning.

Dolmen work III

The dolmen work is proceeding. Things have been slow this week but since the last update I’ve made masters for the main dolmen and the lit interior.

Here are two thumbnail views of the transmission masters.

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Dolmen work II

The dolmen is moving along (slowly, but moving) and last night I did a reflection color test to find out what concentration of TEA (triethanolamine) to use to get some interesting colors in the final hologram.

As a test I prepared some 2, 3, and 4% solutions of TEA and cut up a 4×6" piece of film into three sections.

the TEA was fleshly prepared and still warm and each piece of film was soaked for about a minute, squeegeed and left to dry for 30 minutes in my drying box.

The subject was a simple background that I could use to easily judge the differences in color.

After a 10s exposure the strips were developed in JD2 and bleached with EDTA and dried.

I ended up with a range of colors from yellow-red to gold that should work well in the final hologram.

At the moment I’m thinking of using a subtle range of colors rather than the more easily made red/green/orange I was thinking of. Something more along the lines of orange for the moon, golden for the terrain and a fire red for the inside of the dolmen where a fire might be.

With luck I’ll do the masters this weekend

Dolmen work

It’s been a while since I’ve really been in the lab. After the first of the year I got really caught up in the Irish dancing events that Susan and I are involved with, did some travelling for work and then got sucked into the Irish dance St. Patrick’s "season."

Finally there’s a lull and I can get back to working on a dolmen hologram that I’ve had on the back-burner for three years.

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How to make a hologram

This is a pretty cool video of how basic holograms are made. The only part I don’t like (other than the music) is when the person making the hologram puts his unprotected hand in the developer. Don’t do that!

Green transmission test 4

hologram test 4 preview
Yeah, I didn’t post the results of test 3, get over it :-).

The third test on the floor, using the PVC breadboard was passable but nothing to write home about compared to test 2.

Test 4 though came out very nice.

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December lab update

It’s been a busy year in a number of way which is why I haven’t been posting too many lab updates and tutorials.

I’ve got a number of tutorials in the pipeline and pictures that need taking but the next two weeks promise to be just as full so I’m not sure how much I’ll be able to get to while I’ve got the time off my "day job." We’ll see though.

Click through for some pictures and descriptions of what I’ve been up to.

Continue reading “December lab update”