Thermal Imaging Camera?

[Grunff]

On a cold day, when she's been outside for a while, you push back the fur and it's over 25C.

[Huge]

Make a cheese sandwich and give it to a friendly physicist?

[Tony Williams]

I think the old Land Pyrometer used a germanium lens. A reflector focussing system can have a much wider optical bandwidth than lenses.

[Willy Eckerslyke]

Cheaper than that. You don't measure light itself but something that travels at the same(ish) speed. Or rather you don't, you measure its effect on something else. That gives you the wavelength, which you multiply by the frequency (which is written on the label of your common item of kitchen equipment) to get the speed of light. Approximately.

[Andy Turner]

Cheers for everyone's ideas/suggestions on this. It sounds like the technology isn't quite at the level I was thinking (well they have those night vision goggles in the Gadget Shop for a tenner!!). Looks like I'll just have to go and drop a feather next to the windows. If it's good enough for Ted Moult, it's good enough for me!!

andyt

[G&M]

As an interesting question, how much would people be prepared to pay for a fairly simpish device - shows the hot spots on TV or PC but probably not too accurate on temperature ?

Regards

Mike

[Dave Plowman]

Hmm. Look what happened to him.

[John Rumm]

Many manual lenses have an IR focus mark slightly offset from the main focus mark. The intention is you focus visually as normal - but then shift the focus from the normal position to the IR position marked on the lense to allow for the slight difference in refractive power at that wavelength.

[John Rumm]

Unrelated to IR specifically - but films do keep better colour accuracy if you keep them cool. This is more true of the "pro" films rather than the more consumer oriented versions.

In our local camera shop they have a display fridge for all of the better films.

[Andy Turner]

Personally I'd go up to £100 or so, but then I'm a gadget freak. I bought a gadget that tells me how fast my car does 0-60, I bought a gadget that tells me how many watts are being pulled through a plug (so I know how much each device costs me in electricity bills!).

andyt

[John Rumm]

In the past I have done work on avionics spec thermal imaging kit (i.e. the good stuff - not just the images they let you see on telly!)

Looking round the lab with a steerable thermal imager with built in thermal telescope was "educational"!

Needless to say, you could get into serious trouble if any of the ladies in the lab even thought you were pointing it in their direction!

(although this is where video autotrackers have uses - you can be well away from the controls and leave it to follow the "hot body").

That's right, machined from germanium, totally opaque to normal light. The telescope fitted to the setup I was using cost about 100K on its own. Ordinary glass looks black, opaque and a little reflective on a thermal image - no use at all for lenses.

As you say, IR film is a world away from real thermal imaging. The best high resolution kit, is sensitive enough to see the thermal impression of foot prints left after someone has just walked normally over a bit of floor (in shoes)!

[David]

You could try this

[geoff]

In message , John Rumm writes

When I worked on a contract in Germany once, a germanium lens which had been ordered arrived in QA

They measured it - yes it was 24mm in diameter - PASS

[all mail refused]

Good thing you weren't anywhere else - a californium lens for instance wouldn't have worked.

[geoff]

In message , David writes

I've got one of those (from RS) at about the same price. I'm sure I've seen them quite a bit cheaper elsewhere

[geoff]

Hey, I missed that one, didn't I

I must be growing old

[Steve Firth]

Yeh, but where the hell is Thalia?

[Dave Plowman]

Next to Sylvia.

[geoff]

Right, and all of this is easy for manufacturers to implement at low cost.

At 80 degrees possibly, but at 40?

I don't think that that would fly somehow. Until the appearance and colour temperature of these can be made to match tungsten lighting or at least be in the area, and be dimmable people, I don't think that they will become that popular.

I don't mind having fluorescent lamps in a workshop or even for outside lights but not for living areas. They are too cold.

.andy

To email, substitute .nospam with .gl

[Will]

I bought one of these 12 or so months ago. They have one huge drawback, in that the infra-red emitted by a body is influenced by the surface finish of said body as well as its temperature.

For example, last week I was checking the temperature of the external surface of a twin walled flue pipe, which is galvanised, the thermometer showed about 22°C. I taped a piece of black paper to the flue, it then measured about 140°C, which was somewhat nearer to the mark.

The thermometers are calibrated to read accurately on a "neutral" background, similar to the grey cards that are used for accurate photographic exposures. Different surfaces emit different levels of infra-red at the same temperature, so allowances (and care) have to be made...