Patent ID: 8824055

Claim:
A multi-band refractive optical imaging system comprising: a plurality of lenses configured to receive and propagate electromagnetic radiation in at least the visible spectral band and the longwave infrared (LWIR) spectral band, the plurality of lenses including a first group of lenses of a first crown material, at least one lens of a first flint material, and at least one lens of a second material, different than the first crown material and the first flint material, the plurality of lenses including at least one crown-flint pair configured as an achromat to provide color correction in at least one of the visible spectral band and the LWIR spectral band; a first beamsplitter configured to receive the electromagnetic radiation from the plurality of lenses, to separate the electromagnetic radiation into the visible spectral band and the LWIR spectral band; and a rear external aperture stop positioned between the plurality of lenses and the first beamsplitter.