An imaging device comprising: an IR source; a collimator positioned downstream of the IR source; an interferometer positioned downstream of the collimator; a sample compartment positioned downstream of the interferometer; a detector positioned downstream of the sample compartment; and an aperture controlling assembly positioned between the sample compartment and the detector and comprising: a first plate having a first plurality of circular plate apertures extending therethrough; a second plate having a second plurality of rectangular plate apertures extending therethrough, wherein the second plurality of rectangular plate apertures includes four groups of rectangular plate apertures (42, 44, 46, 48), wherein each group of rectangular plate apertures comprises a plurality of rectangular plate apertures of the same length, wherein each group has rectangular plate apertures of a different width from the other groups, wherein the plurality of rectangular plate apertures in the same group are of the same size; a first motor operably connected to the first plate; and a second motor operably connected to the second plate, the first and second motors (26, 20) configured to move the first plate and the second plate with respect to one another so as to align any one of the first plurality of circular plate apertures with any one of the second plurality of rectangular plate apertures to define a plurality of light beam apertures, wherein for each group of rectangular plate apertures, the rectangular plate apertures are positioned on the second plate such that each rectangular plate aperture of the group of rectangular plate apertures is configured to align with any one of the circular plate apertures in a different orientation. an IR source; a collimator positioned downstream of the IR source; an interferometer positioned downstream of the collimator; a sample compartment positioned downstream of the interferometer; a detector positioned downstream of the sample compartment; and an aperture controlling assembly positioned between the sample compartment and the detector and comprising: a first plate having a first plurality of circular plate apertures extending therethrough; a second plate having a second plurality of rectangular plate apertures extending therethrough, wherein the second plurality of rectangular plate apertures includes four groups of rectangular plate apertures (42, 44, 46, 48), wherein each group of rectangular plate apertures comprises a plurality of rectangular plate apertures of the same length, wherein each group has rectangular plate apertures of a different width from the other groups, wherein the plurality of rectangular plate apertures in the same group are of the same size; a first motor operably connected to the first plate; and a second motor operably connected to the second plate, the first and second motors (26, 20) configured to move the first plate and the second plate with respect to one another so as to align any one of the first plurality of circular plate apertures with any one of the second plurality of rectangular plate apertures to define a plurality of light beam apertures, wherein for each group of rectangular plate apertures, the rectangular plate apertures are positioned on the second plate such that each rectangular plate aperture of the group of rectangular plate apertures is configured to align with any one of the circular plate apertures in a different orientation. a first plate having a first plurality of circular plate apertures extending therethrough; a second plate having a second plurality of rectangular plate apertures extending therethrough, wherein the second plurality of rectangular plate apertures includes four groups of rectangular plate apertures (42, 44, 46, 48), wherein each group of rectangular plate apertures comprises a plurality of rectangular plate apertures of the same length, wherein each group has rectangular plate apertures of a different width from the other groups, wherein the plurality of rectangular plate apertures in the same group are of the same size; a first motor operably connected to the first plate; and a second motor operably connected to the second plate, the first and second motors (26, 20) configured to move the first plate and the second plate with respect to one another so as to align any one of the first plurality of circular plate apertures with any one of the second plurality of rectangular plate apertures to define a plurality of light beam apertures, wherein for each group of rectangular plate apertures, the rectangular plate apertures are positioned on the second plate such that each rectangular plate aperture of the group of rectangular plate apertures is configured to align with any one of the circular plate apertures in a different orientation.