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 shutter for reconnaissance cameras includes a digital signal processor (DSP) system which provides for control of motors moving two curtains. The curtains each define an edge, the gap between the edges of the curtains defines an exposure slit. The shutter replaces the prior art DC curtain motors and potentiometer curtain position sensing devices with AC motors having integral resolvers that provide motor shaft position feedback information. Furthermore, a mechanical clutch coupling the curtains together, which has been standard practice in the prior art, has been eliminated, with the precise movement of the curtains governed by the motors under control by the DSP. The marriage of DSP control with the AC motors and resolvers provides a direct coupling to the curtains, with built-in motor shaft position feedback via the resolvers.

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: A method and retainer assembly for securely retaining a lens in a cell or other holding structure so that the lens does not become displaced when the cell is subject to mechanical shock and vibration. The invention is particularly useful for use in retaining large, heavy optical elements, such as can be found in long focal length aerial reconnaissance camera systems. The method involves the step of seating and centering the lens into the cell. The lens has a peripheral surface having a beveled feature. A first rigid, e.g., metallic, ring having a complementary beveled surface is installed over the peripheral beveled surface of the lens. A second rigid, e.g., metallic, ring is installed over the first ring. A retaining ring is threaded onto the cells such that the retaining ring abuts against the second ring. The retaining ring is tightening onto the cell such that the second ring conforms to the retaining ring while maintaining the alignment of the lens in the cell.

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 optical sight for a weapon system is upgraded with a retrofit module that provides both gunner sighting at the eyepiece and video transmission of the image the gunner sees to a remote location such as, for example, the helmet display of the commander for the weapon system. The video image may be used for both fire control as well as training of the gunner. The retrofit module is adaptable to most types of sighting systems.

Abstract: A camera system is described which is based on an electro-optical imaging array performs electronic image motion compensation without moving parts during a reconnaissance maneuver in which the aircraft is experiencing a non-zero rate of change in the pitch axis, such as in a dive bomb maneuver when the pilot is pulling out of the dive. The camera system has a camera control computer that calculates a pixel information transfer rate for the array based on parameters supplied by the aircraft's navigation system and pre-mission known parameters, including the aircraft's velocity, height above ground, attach angle, pitch angle, and rate of change in pitch during the period in which the array is taking successive exposures of the scene. The camera control computer supplies information to the drive and control electronics that control the transfer of pixel information in the array.

Abstract: A camera system is described which is based on an electro-optical imaging array performs electronic image motion compensation without moving parts during a reconnaissance maneuver in which the aircraft is experiencing a non-zero rate of change in the pitch axis, such as in a dive bomb maneuver when the pilot is pulling out of the dive. The camera system has a camera control computer that calculates a pixel information transfer rate for the array based on parameters supplied by the aircraft's navigation system and pre-mission known parameters, including the aircraft's velocity, height above ground, attach angle, pitch angle, and rate of change in pitch during the period in which the array is taking successive exposures of the scene. The camera control computer supplies information to the drive and control electronics that control the transfer of pixel information in the array.

Abstract: A multi-spectral decentered catadioptric-type optical system suitable for use with long range oblique aerial reconnaissance camera systems, spectrum analyzers, astronomical imagers, remote sensing, and other applications is described. The optical system includes an aspheric primary mirror receiving incident radiation and defining a central aperture. An aspheric secondary mirror is provided for receiving the radiation from the primary mirror. The primary and secondary mirrors are positioned and constructed such that entrance aperture of the system is displaced or decentered relative to the optical axis of the system, so as to thereby increase the modulation transfer function of the optical system as compared to a centrally obscured system.The aspheric secondary mirror directs the incident radiation onto a means for splitting the radiation to a first optical path and a second optical path.

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: A system for measuring the attitude of the platform that is movable relative to a fixed frame. The system comprises at least three platform mounting assemblies, each of the three mounting assemblies comprising (a) an isolation mount interconnecting the platform to the frame, the isolation mount permitting the platform to move relative to the frame, and (b) a means for measuring the movement of a point on the platform relative to the frame along three orthogonal axes. For each of the three mounting assemblies, the means for measuring, in the preferred embodiment, comprise a set of three linear position sensors having a known fixed attachment point to the frame and an end portion that terminates at or about the point on the platform. The linear position sensors or potentiometers generate measurement signals corresponding to the measurements of platform movement.

Abstract: An electro-optical imaging array provides compensation for image motion due to variations in scene terrain electronically and with no moving parts. Pixel information representing scene information is transferred through the array in column groups. Each column group has its own charge transfer rate U. Successive images of the scene are generated by the imaging array, and the images are correlated by electronic signal processing circuitry to determine the image displacement of a fixed point in the scene between successive images. The image displacement is used to calculate a residual image velocity U.sub..delta. in each column group. As successive images of the scene are generated, the charge transfer rates U for each column group are updated, whereby U=U.sub.0 -U.sub..delta., where U.sub.0 is the charge transfer rate for the previous exposure, and U.sub..delta. is the residual image velocity in each column group.

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: Apparatus and methods for stabilizing a line of sight of an optical system without the use of gimbals. The apparatus includes a fixed plano-concave lens element mounted in a frame and a moveable plano-convex lens element mounted in a carriage. The frame mounts onto a preexisting optical system such that the lens elements are nominally aligned with the line of sight of the preexisting optical system. A motor driving unit is provided in the frame which moves the plano-convex lens element back and forth relative to the fixed plano-concave lens element about two orthogonal movement axes in response to small amplitude disturbances imparted to the optical system. The line of sight stabilization apparatus is suitable for retrofit installation onto preexisting optical systems, and in particular, to missile tracking guidance and sighting systems which were originally manufactured or installed without line of sight stabilization capability.

Abstract: The present invention is a method and an apparatus for automatically tuning a plant. The method includes the steps of applying a plurality of sinusoidal signals to the plant, and measuring the frequency response of the plant to the plurality of sinusoidal signals to detect frequencies at which the plant is resonant. The coefficients of at least one digital filter are calculated such that the at least one filter when combined with the plant suppresses the detected resonances. The method further includes applying at least one sinusoidal signal having a frequency substantially equal to a crossover frequency of the system to the at least one filter and plant, and measuring the frequency response to calculate the magnitude and phase response of the filters and plant at that frequency. The coefficients of the compensator are calculated such that when combined with the plant and the at least one filter the combination provides a response which yields said predetermined system response.

Abstract: Improved apparatus and methods of image information processing are disclosed which extend the operational coverage of an image system to higher velocity to height ratio scenarios while optimizing image resolution. The invention typically is implemented by a time delay and integrate charge-coupled device. In conjunction with an image variable row scan rate, a novel method of clocking the device is used to adjust the number of cycles of clocking performed in one row read out time, and to simultaneously transfer pixel information located in a plurality of rows of an imaging array having a predetermined row relationship. The relationship between the variable row scan rate, the predetermined row relationship and the number of cycles of clocking is adjusted so that the scan rate can increase above a maximum base scan rate by a factor of (AB)/(B-1), where A is the number of cycles of clocking performed and B is an integer corresponding to the predetermined row relationship.

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.