July 12, 2004
I've been watching Frank's work with LCD panels over the last several months and even bought a couple with plans to do my own experiments. Because of work I've had little time to pursue those plans but that changed somewhat this morning.
I never found any information on removing the polarizer on an LCD panel so I
decided to experiment on my own.
I started working on what I'm calling a "light box" for my large laser today. This is a simple wooden box with a hinged door and fans added that will house the laser and allow me to mount it on the wall and shield the table from the incredible amount of light it emits. Up to this point I've had the laser sitting on the table, elevated using some marble tiles and covered with cardboard to keep the light away from the rest of the table.
The box is a simple 48" x 7" x 7" affair with an open back and hinged front. I left the back open since it will be up against the wall
I've cut holes for the fans, one will pull air into the box and the other will pull it out so that the laser doesn't overheat and drilled an exit hole just below the mirror shown above. The metal bar is the same bar I've used for many of my other mounts and holds a mirror which is attached to a strong rectangular magnet.
Later this evening I'll mount the box on the wall, put the laser inside and give it a good holographic testing.
I finished up the box last night and after putting a back on it (I decided not to take the chance that light would leak out the back) I hauled it upstairs and mounted it on the wall.
Shots of the box closed (the tape is temporary until I can purchase some magnetic cabinet catches) and open. I'll also be purchasing some tubing so air can be brought in from outside the canopy, vented through the box and back outside the canopy.
Here's the shutter and beam steering mirror. Having the shutter inside the box is nice because with it closed the entire box acts as a beam dump and I don't have to card off the shutter anymore.
Along with some good old relaxation time, I spent a bit of time today trying to get a hologram with the new Polygrama photopolymer.
After setting up my table for a two-beam transmission image of R2D2 and making a successful test shot on PFG-01 I gathered together the following materials:
For the first exposure I left the plate in the holder and shone the 75W light on it while still in the holder. Here you can see the sandwich in the plate holder after the polymer has been bleached out.
Unfortunately that first attempt yielded no image at all. Not even a flash of light from any angle.
I double-checked the exposure times and realized that even though the sensitivity given for the polymer is approximately half of PFG-01 I was exposing somewhat short. So I increased my exposure time to 20 seconds to get closer to the bottom range of 200uj. In this case, I was giving the polymer a total exposure of 230uj.
That was a dud as well. Still no flashes of light or sign of an image. I also noticed that prior to the halogen post-exposure treatment that that polymer was still a blue of approximately this color:
After corresponding with Polygrama one possibility was that the polymer layer was too thin. With that in mind I switched to the only other spacing material I had handy. Scotch tape.
Following the same general procedures I created my polymer sandwich and exposed for 20 seconds. Nothing. Not even a flash of light.
According to the information on the polymer, "The emulsion will bleach as receive the laser power, autobleaching feature will indicate end of exposure." Since it appeared that the auto-bleaching wasn't happening, I doubled the exposure time.
Same general procedures for sandwich making and exposed for 40 seconds. Still nothing.
It still looks like I'm not exposing long enough although according to the given sensitivity my last exposure should have been at the upper end of the range for the polymer.
[Editors note, Jul26: I hate it when a conversion error bites me. In this case I was converting from uj to mj by simply dividing by 10. Stupid. I should have been dividing by 1000. Rather than a 20 second exposure I should have been exposing for 30 minutes.]
More testing of the polymer. For this round I'm using the scotch tape again but I've changed two variables:
I'm measuring 26uW at the plate so according to the data given with the polymer I should expose for 12 minutes minimum and 32 maximum. The longest exposure I've done to date has been about two minutes, 12 should be interesting to say the least.
8:30am: First attempt was using manual control of the shutter. Unfortunately the sleep time on the RCX was set to 10 minutes and the shutter closed early meaning that this attempt was another dud. After this I set about re-programming the shutter control to allow exposures of up to 45 minutes.
9:00am: Second attempt today involved changing the table setup for a single-beam Denisyuk of a british coin. This is a particularly good subject because it is composed of a central circle of nickel surrounded by a copper donut with a variety of designs that are easy to see. Why a single-beam setup? Power. I needed to get the exposure times down as far as possible. I decided on a 6 minute exposure after attempting to measure the beam strength with my home-made meter. Unfortunately my 30mW laser easily overpowers my meter and I had to guess at the exposure based on the distance from the plate where the meter could measure the power (good ole inverse square law). The coin was taped to the back of the glass.
At the end of the exposure I noticed that the polymer was a much lighter blue than with the previous attempts. Not clear but definitely much lighter.
So, did it work? Yes, this time I ended up with a very dim red hologram of a coin. It's brighter in laser light but still not the brightness that I was hoping for.
9:30am: Tried another single-beam attempt with a 10 minute exposure. After settling for 20 minutes the bot ran the shutter for 10. The polymer was much lighter this time, almost clear. After the post treatment I was rewarded with a slightly brighter red coin hologram. Unfortunately both are dim enough that there's no way I could get a decent photo although I may try later.
Well, that's it for this morning. Time to get some chores done (although the settling and exposure times this morning have allowed for a lot of that already).
6:45pm: Moved the plate holder closer so that the only light hitting
the plate is right around the coin. There's almost no wasted light.
Using an OD 1 filter and my light meter I calculated the intensity at 654uW at
the plate. I'm going to give it a 45 second exposure which should apply
30mJ of energy to the polymer.
After exposure I could clearly see a difference between the area that had been exposed and the area that hadn't. The former was almost completely clear and the latter still had a noticeable blue tinge.
Unfortunately this one was largely a dud. While I can get a partial image in laser light, the polymer was still spreading out through the glass as the exposure was made and so most of the coin is invisible. I know the polymer was still spreading because the "spot" was quite a bit larger when I took the plate out of the holder vs when I put it in.
My last day at Paradigm Entertainment. On August 9th I start with Multigen-Paradigm, a CA company. Woot!
It's going to be another polymer morning. I've cut an old plate into small 2"x2" squares and I'm attempting a transmission as I've been told that this polymer is optimized for transmissions.
For the first plate I've moved the setup even closer to the spatial filter (note to self, take some more pictures) and calculated the exposure at approximately 30 seconds. Total dud. The polymer began to move after the plate had been clamped into the plate holder.
The second plate I've zapped with a white light for two seconds from 1 foot away prior to exposure. Partial dud. The polymer still moved some when placed into the plate holder. There's a fairly bright flash of a sliver of subject though.
Third, horizontal arrangement 90s exposure, partial image but the polymer was still moving perhaps because I ran into the room while the exposure was still going.
Switched to a horizontal reflection layout at this point and changed the object to a flat off-white Celtic magnet.
Fourth, horizontal, prelatens 3s 1 foot 50W, 90s exp. Bright in an odd way under laser light.
Fifth, horizontal, no prelatens, 120s exp. Bright under laser light but shows clear movement of the polymer.
Summary of the latest results:
For all of these tests I used 2mil glass, scotch tape as the plate separator and small binder clips to hold the plates together.
8:30pm: Prepared a new plate using backup tape as the separator and three binder clips to form a tripod. Prepared the plate and put it in a light-tight box to settle. I've modified the table layout for a horizontal single-beam transmission setup using the same Celtic magnet as the subject. Two minute exposure and the polymer was completely clear. Image isn't very bright but is visible and very mirror like where the image shows through.
I only had time for one polymer test today and that consisted of a transmission test using 2" glass and backup tape. Ended up with a transflection hologram and is dim but you can see the object in transmission mode and the base the plate was sitting on as reflection. Pictures are going to be near impossible to get but I'll try soon.
Asked by TomB on the Holography Forum
Done. I don't have a
good UV source but do have a 75W blacklight spot. Placing it 6" above the
sandwich for 5 minutes resulted in hardening of the polymer. I tested the
sandwich periodically by trying to slide the plates against each other and was
able to do so until the last 30 seconds.
So, did I get a hologram? Yes. Is it any better than the last dozen? A little, but it still requires a lot of light to see the image. So far, the polymer isn't worth the effort compared to silver. It's promising to see a new polymer becoming available but it's still at such an early stage in its development that it's more of a science project at this point than a product. I may continue to experiment next week but for the moment I'm going back to silver. I've had some specific holograms on my mind and it's time to make them. If anyone else is working or going to work with the Polygrama polymer I'd be very interested in hearing how your experiments came out.
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