MWIR lens system for wide area motion imagery

A MidWave InfraRed (MWIR) Wide Area Motion Imagery (WAMI) system comprising, in order, from an object to an image plane:

• a fast scanning mirror providing scanning about two axes to scan the object;
• a first optical group having a positive optical power configured to receive MWIR radiation from the object and provide a converged MWIR radiation, wherein first optical group comprises a first optical element having a positive optical power, a second optical element having a negative optical power and a third optical element having a positive optical power;
• a first fold mirror and a second fold mirror configured to bend an optical axis of the converged MWIR radiation;
• a second optical group having a positive optical power and configured to receive the converged MWIR radiation from the first fold mirror and focus the converged MWIR radiation, wherein the second optical group comprises a fourth optical element having a positive optical power, a fifth optical element having a positive optical power, a sixth optical element having a negative optical power, and a seventh optical element having a positive optical power;
• A Dewar window;
• An aperture stop;
• a cold filter;
• and
• a Focal Plane Array (FPA), wherein the focused converged MWIR radiation travels through the Dewar window, aperture stop, cold filter and forms an image on the FPA;
• wherein the MidWave InfraRed (MWIR) system has a spectral waveband of 3.3 μm-5.1 μm.

An airborne Mid-Wave Infrared (MWIR) Wide Area Motion Imagery (WAMI) remote sensor comprising, in order, from an object to an image plane:

• a fast scanning mirror providing scanning about two axes to scan the object;
• a first optical group having a positive optical power;
• a first fold mirror;
• a second fold mirror;
• a second optical group having a positive optical power;
• a Dewar window;
• an aperture stop;
• a cold filter;
• and
• a Focal Plane Array;
• wherein the first optical group is configured to receive MWIR radiation from the object and to direct a converged light onto the second optical group;
• the first optical group comprising three optical elements having, in order from the object to the image plane, positive, negative and positive optical powers correspondingly;
• the first fold mirror located between the first optical group and the second fold mirror;
• the second fold mirror located between the first fold mirror and the second optical group, wherein the first and second fold mirror are configured to bend an optical axis of the converged light;
• the second optical group is configured to re-image the converged light from the first optical group, and to focus the re-imaged light through the Dewar window, the aperture stop, and the cold filter onto the focal plane array in corresponding order;
• the second optical group consists of four optical elements having, in order from the object to the image plane, positive, positive, negative and positive optical powers correspondingly;
• wherein the optical elements of first and second optical groups consist of two optical materials;
• and
• wherein the sensor operates in a spectral waveband of 3.31 μm-5.1 μm and forms an MWIR image on the focal plane array.