Multi-spectrum imaging systems and methods are provided to imaging in multiple spectrums, e.g., thermal IR (infrared) at 4 μm and 10 μm wavelengths, near-IR, and visible light, all on a same optical centerline. For example, an imaging system includes a first imager and a second imager. The first imager includes an array of thermal IR detectors, wherein the first imager is configured to receive incident photonic radiation and generate a thermal IR image, wherein each thermal IR detector comprises a photon absorber member that is configured to absorb thermal IR photonic radiation from the incident photonic radiation, and reflect remaining photonic radiation in the incident photonic radiation along an optical path of the imaging system. The second imager is disposed in said optical path of the imaging system, wherein the second imager is configured to receive the remaining photonic radiation reflected from the first imager and generate a second image.