1. An apparatus for increasing resolution of a cryogenically cooled and vacuum-sealed infrared imaging detector, comprising: a two-dimensional detector array of photosensitive pixels arranged in a matrix, said detector array having a fill factor value, said detector array successively exposed to an image scene to acquire multiple infrared imaging samples of said image scene, said detector array being operative within a wavelength range of 1-15 micrometers (μm); a masking filter, having a single pattern, integrated with said detector array and disposed between said detector array and said image scene, said masking filter operative to mask part of an active region of each of said photosensitive pixels, thereby reducing said fill factor value of said detector array by a fill factor reduction amount, such that only a sub-region of a pixel region of said image scene is imaged onto a corresponding masked pixel of said detector array; an optical element disposed between said masking filter and said image scene, said optical element positioned to direct said image scene onto said detector array through said masking filter; a directional angle shifter for shifting an angle at which said imaging samples are directed onto said two-dimensional detector array to thereby successively shift said image scene relative to said detector array between each of said imaging samples by a shifting increment corresponding to said fill factor reduction amount and smaller than an unmasked active region of a masked photosensitive pixel, wherein each masked photosensitive pixel of said detector array receives partially overlapping sub-regions in said imaging samples; and a processor, operative for reconstructing an image frame from said acquired imaging samples, the reconstructed image frame having a resolution greater than an intrinsic resolution of said infrared imaging detector by a factor defined by said fill factor reduction amount; wherein said fill factor reduction amount is less than half of said pixel region thereby increasing said resolution above a Nyquist frequency of said two dimensional detector array; wherein said masking filter reduces a sensitivity of said two dimensional detector array due to said fill factor reduction amount; and wherein an f number of said optical element is reduced in accordance with said fill factor reduction amount to compensate for said reduction in sensitivity of said two dimensional detector array.