Gallery, Projects and General > The Design Shop
Making IR optics.
S. Heslop:
Been looking at this a bit more and found this great video.
This style of old video are always great to watch. More info and less 'mercial.
One thing it doesn't say though is how youre supposed to clean out the embedded grits. Maybe a disposable pitch lap would work well for the lapping plate with optical parts.
I'm keen to try this stuff out but i'm really jumping the gun, as always, and i've got a couple other projects I need to finish first.
awemawson:
Years ago when I worked for Mullards, we were lapping Yttrium Iron Garnet into fine wafers for use as IR detectors, and the thinner you could get the wafer the less back ground boltzmann noise was produced improving the signal to noise ratio of the detectors (these things were cooled with liquid nitrogen, and sometime liquid air again to reduce the thermal noise). One day my colleague managed to sneeze on a wafer, and something in his outpouring managed to dissolve some of the YIG producing an area significantly thinner than the rest of the area around it. It went undetected and the wafer was used.
When I did the testing of the bucket brigade 256 element array that was laid on that particular bit, all of a sudden I found a far higher signal than expected :clap: It took a long time to repeat the experiment and find something more reliable than a sneeze to produce the same effect
These things were used in early spy satellites - a bit un-nerving having armed guards on the lab :bugeye:
Joules:
Love the video :D 3D printed lapping machine coming right up.... :thumbup:
S. Heslop:
--- Quote from: awemawson on June 26, 2016, 12:57:31 PM ---These things were used in early spy satellites - a bit un-nerving having armed guards on the lab :bugeye:
--- End quote ---
It sounds like a job like that would pay you well enough to make up for it though!
I had this arrive yesterday. It's a UV-VIS spectrometer, but an old and somewhat weird one.
(i've given it another scrub to remove some of the stains since taking these photos. and i'm making sure to wash my hands every time i touch it)
I didn't expect it to work, but it was listed fairly cheaply on ebay so I figured i'd have a punt at it and maybe at least get a diffraction grating and some mirrors out of it, and maybe a deuterium lamp if I was lucky. But it powered on fine. I couldn't find much information about it online so I emailed Biochrom asking about it and they sent me the manual almost immediately, which was very kind of them. The manual suggests it was made in about 1987.
Got some thermal paper for it today and was at first a bit disappointed by the stepped chart. But reading the manual carefully I found out that 'calibration' isnt the same as recording a baseline.
I'm really thrilled it works. I'll need to think of something interesting to do with it though. My big dream for a while has been to try making chemistry videos, but i'm still not sure exactly what i'm going to go for. I'd like to at least avoid using stuff that isn't so easy to get ahold of.
S. Heslop:
Also got a balance, a Sartorius LA230S. It didn't have a power supply with it and i'm not sure exactly what it requires. The back says 12 and 30 volts DC but its some weird custom 4 pin connector. I might be able to figure it out from the circuit board but I'll try emailing the company that makes it first.
There's not alot of information on these things online, and photos of their innner workings are as rare and low resolution as photos of bigfoot. I've attached a bunch of higher resolution photos just in case anyone interested finds this via google.
I'm probably mucking up the calibration by taking this cover off.
From what little i've been able to find online, they work on balancing the weight in the pan against an electromagnetic coil (the big round bit in the middle-right), sensing it's position via an optical position sensor (I assume to be that gold package on the far right) and adjusting the current to get it balanced. Then measuring the current to deduce the weight. The lever itself is a parallelogram flexure so the weight's position on the pan doesnt affect the reading. There might be some extra lever to amplify the travel of the coil too, but i'm going cross-eyed looking at this thing to make anything out.
There's one other electronic device on the flexure too that i'm not so sure about. It might be a temperature sensor to correct for things expanding.
I think this has something to do with automatically calibrating itself. My best guess is that it lowers those weights onto those brackets screwed onto the pan to use as a reference.
While I had the cover off I took Andrew's advise and made sure to sneeze on it to boost it's performance. I also made sure to touch all the chips without grounding myself and poked everything possible with a sharp screwdriver.
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