Well, it turns out that one of the problems I was having with my green laser and the VRP-M film is my shutter.
When it opened it set the table to ringing for at least a full second.Â My 2-4 second exposures were incredibly dim because they were getting fogged for the first second.Â 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.Â The fringes really moved when the shutter closed but as no light would have been reaching the film, I didn’t care about that.Â 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.Â 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.
It’s taken way to long to get the new Coherent 315M integrated in my lab (insert excuses here) but that’s now been completed.
The power and shutter controls have been wired up, the software has been updated to control a third laser and it’s been tested and is ready for use.Â One thing I seriously need to do is refactor the HoloController source so that it’s simpler to control an arbitrary number of lasers.
The layout shown above is the one I used to create a transmission master for a professor at A&M.Â I was surprised to see that theÂ beads which I’d painted fluorescent orange show up yellow under green light.Â It’ll be interesting to see how they come out when shot with green-sensitive film.Â
The red in the background is from my copy layout which uses a HeNe.Â The red dot in the middle-right is the beam from my red mastering laser.Â Ordinarily it would be shining on the subject in the foreground but it’s being blocked by the transfer mirror used to "inject" the green beam into the mastering path.
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.
I spent some time on Thursday night finishing up the platform for the new laser.
I’ve got a Kee-Klamp scaffold over my table that holds the big red laser and nothing else. I had planned to hang optics off the scaffold but that didn’t quite work out. Fortunately it made a great place to put the SP-907 laser box.
Now it’s got another rider in the green laser, telescope and shutter.
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.
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.