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Present Sunday, June 15, 2003 It's been almost two months since I've made anything of note. Susan and I went to Ireland for two weeks in late April/May and then I had a major milestone due at work in early June which left me with little time to mess with anything holographic. I've been trying to put my laser diode(s) back in the setup so that I'll have more power and coherence length to play with. Unfortunately four out of the last five holograms I've made have all had the bands which are typical of a diode that has changed frequency during the exposure. I've just finished assembling my second driver (it had been on a breadboard) and I'm going to try that one today.
The new driver under construction.
On the left is the spec sheet for the old diode and the right is the latest diode. Notice the difference in wavelength.
And the new aluminum case with the switch and light at one end and the power input and laser output at the other. Wednesday, June 18, 2003 So far I've made two holograms with the new driver and both have come out ok, though not as bright as I'd like. The first was a single-beam reflection of Snoopy and the second was a two-beam reflection. The first was a bit dim but the second is fairly bright. So far, that's two decent holograms out of two with the new driver. I'm keeping my fingers crossed that the new driver is the key. I purchased four small inner tubes today with the intention of replacing the two larger tubes so that I'd have more lateral stability. Once I jacked up the table and put them in, they weren't a whole lot better than the ones I'd had before except that the table was less likely to rotate along the long axis. While pondering how to gain more stability I decided to make a radical change and use the huge roll of bubble-wrap that I had left over from the last time I'd "rebuilt" my table.
Each column is composed of 24 layers of bubble-wrap and is 3.5" thick when the table is down. The results are very good. The table settles faster than it did when I was using inner tubes, regardless of how I had them inflated and the table top is less prone to movement than before. Tuesday, June 24, 2003 This evening I set up an interferometer to double-check the new support and found a few things. Some good, some not so good (except that I found them). 1) I can walk around most of my office and not disturb the fringes. The only exception is along the same floor supports that the table rests on. The latter was true when using the inner tubes except that I couldn't get very close to the same supports without seeing fringe movement. In fact, I could barely enter the office before I would see the fringes move. Now, if I'm walking carefully, I can get fairly close to the table before the fringes start moving. 2) Given that the table moves so little when I'm working with it (almost none), if I have to go back to using a HeNe I should be able to put the laser on my developing station and free up some space on the table. 2) I've some slow component creep going on. There isn't much, but there's enough that I'm sure it's affecting my holograms. I'm going to have to tweak my lens and mirror mounts until that creep goes away. 4) I've also discovered that the canopy is both helping me and hurting me. It's preventing air currents from washing across the table but is actually causing slight movements of the table itself when strong air currents are present. This is rare, but there have been a few times when I've forgotten to turn the AC off and that's probably contributed to a loss of image quality. The canopy is going to have to change. Sunday, June 29, 2003
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