Measuring Heat, Seeing IR, Bubbles

[David Horn <dh@xxxxxxxxxxxxx>]

Enjoyed Wayde Allen's posts on IR. You have to get down to the basic
physics!
Re. measuring temperature using IR, I looked up The Omega "Handbook &
Encyclopedia" Vol. E section J: Infrared Temperature Measurement.
Infrared Pyrometers are used for the remote measuring of temperature
down to ambient. For example, the Omega OS522 "Handheld Infrared
Thermometer" is claimed to cover the range of -18 to 870 degrees C, with
a resolution of 1 degree. It looks at the IR spectrum between 8 and 14
microns (i.e. 8000nm to 14000nm). Response time is 250ms. The Handbook
gives more background info. and discusses emissitivity issues. Check out
 http://www.omega.com
A low cost pyro-electric sensor is used in the "people sensors" you see
everywhere. I have one in my office, that turns down the lights when I
go out. I have one outside my house to turn on the light when someone
approaches. They are recognizable by the multifaceted freznel lens used
to cover the sensor. The sensor normally has several large "pixels",
which are used to discriminate a moving hot object from the static
background. I had a data sheet from a company selling the sensors. They
are dirt cheap.

>A question for experts:  Is it physically possible for humans, at least
>some humans, (mutants?) to see infrared?

I have a 830nm laser, that I can definitely see. I think is is just a
question of sensitivity. (Before enyone goes looking at IR lasers, be
very careful! You can easily damage your retina!)

>I just got a film back from the lab and there are lots of undeveloped spots
>on the film, about 1mm in diameter.  These are clear on the negative, and
>some have a tiny developed spot in the centre.

Probably air bubbles. Try a different lab or develop yourself. Fixes
include:
1) pour the developer into the tank first, and slowly lower in the film.
2) Prewash in warm water first (I wonder if a drop of Photoflow might
help?
3) As soon as you pour in the developer, bang the tank on the table top
a few times to dislodge any bubbles. Then agitate hard.
Good Luck!
-- 
David Horn,  Bell Labs Multimedia Communications Research Laboratory
Room 2A-308, 600 Mountain Avenue, Murray Hill, NJ 07974, USA
phone +1 908 582 5533,   Fax +1 908 582 6344, e-mail dh@xxxxxxxxxxxxx

------------------------------

Topic No. 7