So everybody knows about those sticker thermometers you stick to the side of a fish tank or slap across your forehead and read the temperature in colors on a black background right? Mood rings? Remember? How about a FLIR-like system based on that thermal response?
This post is inspired by frankd20's blogpost:
"The Build Your Own Thermal Camera for Under $50 Challenge"
http://cr4.globalspec.com/blogentry/7423
But since my idea is significantly different from that original idea, I thought it might be time to start a new thread and get a few new eyes looking at the idea of using liquid crystals for thermal camera guts.
About 5 years ago I tried to pull the materials for this together after thinking about it for 15, and if someone would take the last step where I dropped the ball it might bare fruit.
An outline of the ideal:
2 small "drums" stretched with ultra thin plastic or other material (Mylar from low-voltage capacitors? see below for other materials/suppliers). These materials have extremely low thermal mass (mass that would otherwise slow the response of the thing).
With the 2 drum faces almost or nearly touching, introduce a small droplet of liquid crystals to the edge of the gap. Capillary action fills the gap and produces a target 'screen'. Seal or otherwise protect the edge.
Either a lens or a paraboloid can be used to focus on the liquid crystal screen. Using plastic infrared Fresnel lenses might push down the cost some as compared with a germanium lens (with a resolution loss, but "Minimal Absorption Loss in the 8-14 micron Region", see below).
And I think that a silicon wafer (polished or not) (instead of germanium) might block out much or all of the visible light whatever you use for focus optics (available on Ebay).
Making a little cold box with Peltier devices should be cheap though. I bought a stack of 11 for cheap on Ebay. Could also use one to keep things dry in there since you can get frost to condense and then flash it off by reversing the current (teensy air-lock?). You could even have the main ones cycle the temp of the chamber in response to the contrast of the image (blah-blah-blah).
Depending on the optical effects in the target, reflectance or transmission should get you something to point a cheap vid cam at. (I think there is a polarization effect in there somewhere, maybe even more sensitive than the reflectance effect per degree) Though might have to silver, lampblack, and/or otherwise change one half of the drum-set if light transmission turns out not to be the right sort of thing for reading the screen.
"Are we there yet?"
RR

Thermal Liquid Crystal Paints
(capsules seemed too massive for what I wanted)
As low as: 68 - 77°F (20 - 25°C)
http://scientificsonline.com/product.asp_Q_pn_E_3053484
"Water soluble paints contain microencapsulated nontoxic cholesteryl ester-based liquid crystals"

Liquid Crystal Sheets
(I think some of the cheapo "fish tank" thermometers can just be cut and squeezed-out, not these. and too much thermal mass here for anything but stand-in)
http://scientificsonline.com/product.asp_Q_pn_E_3072374
"3 to 5 micron sized crystals dispersed within a polymer matrix"

silicon wafers on ebay:
http://shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=silicon+wafer&_sacat=See-All-Categories

ultralight films:
(used for indoor model planes... click "Links" at left for suppliers)
http://www.indoorduration.com/IndoorDurationFrame.htm

Infrared Fresnel Lenses
(should never have sold my set...)
http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2042