A method to determine the aliasing effects of infrared focal plane arrays was proposed, and specifically the aliasing value in each direction was determined based on the angular dependence of both sample transfer function and aliasing equation. The mean value as the aliasing value of the array was defined. Further, this model was used to calculate the aliasing value of the rectangular and hexagonal lattices of the same pixel, showing that the hexagonal lattice′s aliasing value is higher by 4%. The equivalent bandwidth in each direction of the staring array was corrected allowing for the degradation caused by the aliasing effects. The image quality of rectangular and hexagonal lattices with aliasing effects was quantified, showing that the rectangular lattice in the sense of image-quality is superior to the hexagonal lattice by 11%.