thermal imagers maximum resolution

Hi,

I'm trying to calculate the maximum resolution of CCDs in thermal
imagers. These device can detect pure thermal heat in the 7-13
micrometers. The wavelenth is much bigger than light which is 380-740
nanometer. How do the calculate the maximum resolution where more
resolution would just waste pixels without giving more details?

First let's talk about visible light and 1X magnification in digital
camera. The airy disc size is thus (for a wavelength of 560
nanometer):

airy disc size = 1.22 wavelength / aperture = 1.22 (0.000000560) /
0.020 = 34 micrometer

Is this correct?

For a thermal wavelength of say 8 micrometer.

airy disc size = 1.22 (0.000008) / 0.020 = 488 micrometer

Now for each of the above. How do you calculate the maximum resolution
of ccd where more MPs won't give more details?

Note that current thermal imagers have resolution of 320x240 in the
$8000 range and 640x480 in the $20,000 range. Because thermal
wavelength is bigger than that of visible light. It can max out at
lower resolution. So what resolution is that... 1MP? 2MP? where more
pixels won't produce more details.
Thanks.