Dual band framing reconnaissance camera

A framing aerial reconnaissance camera is described which has a catoptric Cassegrain optical system forming an objective lens that directs radiation to a spectrum-dividing prism. The prism directs radiation in the visible portion of the electromagnetic spectrum into a first optical path having a two-dimensional image-recording medium, such as a charge-coupled device. Radiation in the infrared (IR) band of the spectrum is directed to a second optical path, which has a two-dimensional IR-sensitive image-recording medium, such as an electro-optical IR imaging array. The entire camera is rotated about the aircraft roll axis in a continuous fashion to generate frames of imagery providing panoramic coverage of the scene across the line of flight. While the camera is being rotated about the roll axis, the arrays are exposed to the scene repeatedly to generate a series of two-dimensional frames of imagery. Forward motion compensation is accomplished by rotation of the Cassegrain optical system in the direction of flight. Image motion due to the camera roll is canceled out in the array by moving pixel information through the arrays as the same rate as the image rotation due to roll. The combination of roll motion compensation and forward motion compensation freezes the image relative to the image recording media, allowing high resolution images to be obtained of the terrain of interest in two different bands of the electromagnetic spectrum simultaneously.