how to reduce background reflection?

We are trying to measure a surface temperature of a body accurately. The body is put in an enclosure to reduce reflection on the body from background objects with a different temperature. Should this enclosure have a high or low emissivity to further reduce reflection effects from the enclosure (which will have a different temperature from the body) itself on the body?

 

[PSE]

If you are trying to measure the surface temperature of the complete body, then you would wish for your enclosure to have an emissivity as close to 1.0 as possible (perfect blackbody). If you can get away with measuring a smaller area background reflections become less of a concern as the field of view narrows. If the temperature of the body under test remains relatively constant with time, you may be able to "zoom" in and scan the body rather than taking a whole image including background.

 

[IRstuff]

Having the cavity emissivity at 1 only works if your object is the the dominate heat source, which means that you need to have truckloads of insulation around the cavity.

Is your object's emissivity reasonably high?, otherwise, you'll still have problems will seeing the correct radiance.

Why IR? The accuracy is somewhat limited for objects with complicated spectral characteristics.

How accurate are you trying to get? A well calibrated PRT or even a thermistor will achieve better than 0.1 deg C, which is difficult to achieve radiometrically.

TTFN