Image sensor having a variable aperture and mono-color focal plane array for dual color detection

An image sensor is provided that includes a focal plane array; a cold shield having a top wall disposed over the focal plane array and defining an aperture operatively configured to be selectively switched between a first diameter and a second diameter that is larger than the first diameter; and a filter element disposed between the cold shield aperture and the focal plane array. The filter element includes a first band-pass filter and a second band-pass filter. The first band-pass filter is disposed directly beneath the cold shield aperture when the cold shield aperture is switched to the first diameter or the second diameter. The second band-pass filter is covered by the top wall of the cold shield when the cold shield aperture is switched to the first diameter and is disposed directly beneath the cold shield aperture when the cold shield aperture is switched to the second diameter.