Abstract: A two-dimensional focal plane array (FPA) is divided into sub-arrays of rows and columns of pixels, each sub-array being responsive to light energy from a target object which has been separated by a spectral filter or other spectrum dividing element into a predetermined number of spectral bands. There is preferably one sub-array on the FPA for each predetermined spectral band. Each sub-array has its own read out channel to allow parallel and simultaneous readout of all sub-arrays of the array. The scene is scanned onto the array for simultaneous imaging of the terrain in many spectral bands. Time Delay and Integrate (TDI) techniques are used as a clocking mechanism within the sub-arrays to increase the signal to noise ratio (SNR) of the detected image. Additionally, the TDI length (i.e., number of rows of integration during the exposure) within each sub-array is adjustable to optimize and normalize the response of the photosensitive substrate to each spectral band.

Abstract: A dual band hyperspectral framing aerial reconnaissance camera includes an objective optical subassembly for receiving incident radiation from a scene external of the vehicle, and a dividing element receiving radiation from the objective optical subassembly. The dividing element directs radiation into a first optical path for imaging in a first band of the spectrum and a separate second optical path for imaging in a second band. A first two-dimensional electro-optical detector in the first path generates a first series of images and a second two-dimensional electro-optical detector in the second optical path generates a second set of imagery. At least one of the first and second electro-optical detectors comprises a hyperspectral imager.

Abstract: A reconnaissance camera is described which has a Cassegrain optical system forming an objective lens that directs radiation to a spectrum-dividing prism. The prism directs radiation in a portion of the electromagnetic spectrum (e.g., visible) into a first optical path having a two-dimensional image-recording medium. Radiation in a second band of the spectrum (e.g., IR or UV) is directed to a second optical path, which has a two-dimensional image-recording medium. A motor system is coupled to a camera housing that encloses the optical elements of the camera and the image recording media. The motor steps the entire camera housing about the roll axis while the image recording media are exposed to generate frames of imagery.

Abstract: An electro-optical roll-framing camera is described in which successive overlapping frames of scene imagery are generated by an electro-optical imaging array. Image motion compensation is performed electronically to stop or freeze image motion caused by the roll motion. The image motion compensation is performed by the array during the generation of the frames of imagery. The successive frames of imagery are made during a continuous roll motion of the entire camera (including the array). The image motion due to roll is stopped or frozen without mechanically stopping the roll motion, such as found in prior art step frame cameras. The roll framing cycles of the camera generate sweeping coverage of the terrain of interest. The roll rate for a given electro-optical array is a function of the frame size and the framing rate, and is controllable by a master camera control computer.

Abstract: A two-dimensional focal plane array (FPA) is divided into sub-arrays of rows and columns of pixels, each sub-array being responsive to light energy from a target object which has been separated by a spectral filter or other spectrum dividing element into a predetermined number of spectral bands. There is preferably one sub-array on the FPA for each predetermined spectral band. Each sub-array has its own read out channel to allow parallel and simultaneous readout of all sub-arrays of the array. The scene is scanned onto the array for simultaneous imaging of the terrain in many spectral bands. Time Delay and Integrate (TDI) techniques are used as a clocking mechanism within the sub-arrays to increase the signal to noise ratio (SNR) of the detected image. Additionally, the TDI length (i.e., number of rows of integration during the exposure) within each sub-array is adjustable to optimize and normalize the response of the photosensitive substrate to each spectral band.

Abstract: 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.

Abstract: 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 al generate a series of two-dimensional frames of imagery.

Abstract: A framing aerial reconnaissance camera is described which has a 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 framing CCD array. Radiation in the infrared (IR) band of the spectrum is directed to a second optical path, which has a two-dimensional framing IR-sensitive image-recording medium. The entire camera can be either rotated about the aircraft roll axis in a continuous fashion or stepped in a series of steps to generate frames of imagery, providing panoramic coverage of the scene across the line of flight in two bands of the spectrum simultaneously.

Abstract: A dual band optical system for a framing aerial reconnaissance camera is described. The camera including at least two two-dimensional image recording media for generating frames of imagery of a scene external of an aerial reconnaissance vehicle carrying the camera. The camera includes a Cassegrain optical system forming an objective lens for the optical system, including a a primary mirror having a central aperture and a secondary mirror. The primary and secondary mirrors are aligned along an objective optical axis. The optical system also includes an azimuth mirror receiving radiation from the secondary mirror. The azimuth mirror is placed between the primary and secondary mirrors. A spectrum-dividing element in the form of a prism receives radiation from the azimuth mirror.

Abstract: Forward motion compensation techniques are described for an aerial reconnaissance camera having a Cassegrain objective optical subassembly consisting of a primary mirror, a secondary mirror and a flat azimuth mirror located between the secondary mirror and the Cassegrain image plane. The camera includes a camera housing oriented such that the camera housing is substantially parallel to the roll axis of the aircraft. The primary and secondary mirror are rotated about an axis orthogonal to the roll axis in the direction of flight of the aircraft, while maintaining the image recording medium in a fixed condition relative to the camera housing. While the primary and secondary mirror are rotating, the azimuth mirror is rotated in the direction of flight at a rate one half the rate of rotation of the primary and secondary mirror.

Abstract: An aerial reconnaissance system generates imagery of a scene that meets resolution or field of view objectives automatically and autonomously. In one embodiment, a passive method of automatically calculating range to the target from a sequence of airborne reconnaissance camera images is used. Range information is use for controlling the adjustment of a zoom lens to yield frame-to-frame target imagery that has a desired, e.g., constant, ground resolution or field of view at the center of the image despite rapid and significant aircraft altitude and attitude changes. Image to image digital correlation is used to determine the displacement of the target at the focal plane. Camera frame rate and aircraft INS/GPS information is used to accurately determine the frame to frame distance (baseline). The calculated range to target is then used to drive a zoom lens servo mechanism to the proper focal length to yield the desired resolution or field of view for the next image.

Abstract: An electro-optical imaging array having pixels arranged in rows and columns electronically compensates for image motion in the plane of the array regardless of whether the motion vector is in the row direction, the column direction, or in a diagonal direction, i.e., in some vector combination of row and column directions. In an aerial reconnaissance application, the image motion may be due to rotation of the aircraft about roll, pitch and/or yaw angles in addition to forward velocity of the aircraft. The image motion compensation is achieved with no moving parts and does not require a stabilized platform.A camera control computer determines the magnitude and direction of the image motion from inertial navigation system inputs, including velocity, flight, and aircraft rotation information, and calculates pixel information transfer rates in the row and column directions. The pixel information transfer rates are supplied to a counter and clock driver circuit for the array.

Abstract: An electro-optical step-frame camera system in which successive overlapping frames of scene imagery are generated by an electro-optical imaging array, and in which electronic image motion compensation is performed by the array during the generation of at least some of the frames of imagery. The successive frames of imagery are made in a stepping pattern that is repeated in a series of cycles of steps, each step separated by a framing interval in which a frame of imagery is obtained. The stepping cycles of the camera generate sweeping coverage of the terrain of interest. As the velocity to height ratio of the reconnaissance aircraft changes, the stepping cycle and electronic image motion compensation are continually adjusted, so as to ensure maximum scene coverage and preservation of image resolution.

Abstract: An electro-optical area array reconnaissance detector is disclosed which accomplishes forward motion compensation electronically and without moving parts. The array is made of photo-sensitive cells arranged in rows and columns, the columns being organized into one or more column groups. Charge packets collected in the cells representing scene information are transferred down the columns at the same rate as the image motion in the plane of the array. In a side oblique reconnaissance scenario, the columns may be organized into 16 column groups, each column group having its own charge transfer rate corresponding to the image motion rate in that column group.