An infrared sensor and infrared imaging system, wherein said infrared sensor comprises: a first film structure, a second film structure, a gap between said first film structure and said second film structure. Reference light is incident from one of said first film structure and said second film structure. When said gap distance changes, the intensity of transmitted reference light changes, and the intensity of reflected reference light changes. When infrared light is incident, at least one of the said first and second film structures absorbs infrared light and the temperature changes, causing said gap distance to change. By detecting the intensity of said transmitted reference light or reflected reference light, the incident infrared light can be measured.