Abstract: An imaging system incorporating a scanned array of infrared detectors for a presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing equality between the magnitude of an average value of a detector signal and a reference signal. The imaging system comprises a set of channels connecting with respective ones of the detectors, each channel having adaptive gain control circuitry. A common value of the reference signal is applied to each channel for uniformity in a displayed image. The averaging time is several times greater than the duration of a single scan in the scanning of the detector array so that the display is relatively free of nonuniformities associated with differing responsivities of the detectors to infrared radiation.

Abstract: An optical receiving system for thermal radiation is useable, with slight modification, for the simultaneous, low-loss reception of laser radiation and is nevertheless still composed of standard, common modules. To this end, a geometrical out-coupling of the laser radiation out of the shared receiving channel following a scanner and the geometrical separation of the thermal and laser radiations is provided, whereby the out-coupled laser radiation, separated from the thermal radiation, is directed via a simple optical assembly onto a preferably shared sensor. For the utilization of the common reception channel and, thus, of the reception optics as well for the emission of the laser radiation, the transmission radiation can be coupled into the separated laser reception channel via a polarization separating filter. By so doing, the transmission optics is eliminated, whereby good optical conditions for the transmission radiation are established without deterioration of the common reception channel.

Abstract: An imaging system incorporating a scanned array of infrared detectors for presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing euality between the magnitude of an average value of a detector signal and a reference signal. The imaging system comprises a set of channels connecting with respective ones of the detectors, each channel having adaptive gain control circuitry. A common value of the reference signal is applied to each channel for uniformity in a displayed image. The averaging time is several times greater than the duration of a single scan in the scanning of the detector array so as the display is relatively free of nonuniformities associated with differing responsivities of the detectors to infrared radiation. A nonlinear gain function is produced by connection of multipliers and/or logarithmic circuitry in a forward branch of the loop.

Abstract: In an opto-mechanical scanner with associated scanning and ranging functions the scanning beam, obtained by line-scanning means and frame-scanning means, and the ranging beam converge on a scanning detector array and on a ranging detector, respectively. According the invention, the scanning and ranging beams traverse an arrangement of fixed optical elements which are arranged to ensure that the beams follow two different optical paths in such a way that the ranging beam traverses the line-scanning means two times. This ensures that the ranging beam has a fixed orientation which is independent of the line-scanning means.

Abstract: A self-alignment device is provided for an optical infrared image observation system having essentially an input optical system, and infrared reading system, as well as a return mirror in a given position situated in the field of the optical input system so that the infrared reading system may see its own image in this mirror. Deviation measuring and slaving systems allow centering of the image to adjusted with respect to the position of the return mirror.

Abstract: The cooled infrared detector of an infrared microscope is scanned over a target specimen at ambient temperature, the signal is stored, inverted and added to subsequent radiance signals derived from subsequent scans of the target to provide a continuous correction for the "Narcissus Effect".

Abstract: In an opto-mechanical scanner combining scanning and ranging functions the scanning beam, obtained from line-scanning means and frame-scanning means, and the ranging beam converge on a scanning detector array and a ranging detector, respectively. In accordance with the invention, the scanning beams and the ranging beams traverse an arrangement of fixed optical elements which are arranged to ensure that the beam each follow two different optical paths such that the ranging beam bypasses the line-scanning means. This ensures that the ranging beam has a fixed spatial orientation which is independent of the line-scanning means.

Abstract: a ratating sensor responsive to infrared or electro-optic radiation has a nearly hemispherical field of view. The sensor comprises a rotating platform (3) supporting a planar multidetector focal plane array (1). The array (1) has three or four sides. Two of the sides are straight lines. One or two sides are portions of conic sections. Individual detectors (2) within the array (1) can be continuous or discrete, and are organized into rows generally following the shape of the conic section(s). In either embodiment, time delay integration is performed row by row within the array (1) so as to equalize the sensitivity and resolution for each portion of the viewed scene. Several arrays (1) can be mounted within the carrier vehicle (8), mounted at different field angles. In this embodiment, the shape of the arrays (1) vary from a sector of a circle to rectangular.

Abstract: A photoelectric receiver for picture recording equipment, particularly for thermal-image equipment having local brightness adaptation, comprises at least one first detector element for providing point-by-point scanning of the image generated by an optical receiving system, as well as at least one second detector element associated with one or several of the first detector element(s) having a larger radiation-sensitive area for picking up at least part of the surroundings of a picture point picked up by a first detector element. The second detector element determines the gain, with which the signals of the first detector element(s) are amplified for the formation of video signals.

Abstract: In a system for imaging radiation of a subject (14), particularly infrared radiation, the radiation scanned past a set of detectors (12), each of which produces an output signal amplified by an individual amplifying channel. Each amplifying channel includes a forward amplifier (38) and a feedback amplifier (50), the latter driving a diode (46) to limit excursion of a detector signal to an amplitude which is sufficiently small to avoid saturation of the forward amplifier. The forward amplifier (38) is AC coupled between a detector (12) and an output display (18), the limiting action of the diode (46) preventing the buildup of excessive charge on the coupling capacitors (40, 42), thereby to permit a viewing of fine detail superposed on coarse detail of the subject being viewed. A low-pass filter (48) in the feedback branch provides a delayed response to the limiting action which permits the passage of high-frequency detail to be imaged on the display (18).

Abstract: An infra red photo detector system comprises a piece of detector material, such as Cd.sub.x Hg.sub.1-x Te, InSb, InAs, etc, carrying at least a pair of spaced electrodes. An optical arrangement directs a small spot of radiation onto the detector. The position of the small spot on the much larger detector is found by applying an electrical bias between the electrodes causing a drift of photo carriers. The bias may be of alternating polarity and the detector output measured at each polarity. Alteratively a high frequency bias may be applied and the A.C. offset from the detector used to indicate spot position. Alternatively the spot position may be modulated or swept along the detector by a mirror moving in a sawtooth scanning action.

Abstract: An optical and mechanical scanner including a device for scanning a field of vision to detect and recognize with high resolution distant objects in the field of vision. Scanning is accomplished in two directions including a direction x for line scanning and a direction y for raster or image scanning. One embodiment of the scanning device includes, in order along the direction of a path of a mean incident beam from the field of vision, an objective, a raster scanning mirror for scanning in the y direction, a field mirror which delimits the field of the objective in the x direction, a rotating drum and an image transport system for line scanning in the x direction, the field mirror deflecting the beams towards the drum, and a detector sensitive to the radiation contained in the beams, the scanning device ensuring convergence of the beams at the detector.

Abstract: A system and method are disclosed for initiating target crossover recovery in a pyroelectric camera by electronically detecting crossover and automatically initiating recovery in response thereto. The video signal appearing at the output of the video amplifier during readout of the vidicon tube is coupled to a level detector to detect crossover by sensing a positive signal having an amplitude greater than any such signal producible during readout arising from an optical input to the video amplifier, with reliability of detection being enhanced by use of an automatic balancing circuit providing a stable reference.

Abstract: A scanning infrared display system capable of variable magnification and high spatial resolution measures the emitted infrared radiation caused by the scanning of a highly collimated energy source beam on the surface to be imaged. The resulting infrared emissions are collected with a high sensivity stationary detector. The display image is formed on a CRT by scanning the object with a raster pattern in synchronization with the CRT and modulating the Z axis CRT potential (brightness) with the infrared detection signal.

Abstract: A stereoscopic infrared imager includes optics for producing infrared images of two different views of an infrared scene. A scanning mirror alternately scans the two infrared images across a single infrared detector array. The detector array modulates a light source array to produce a visible image of the scanned part of the infrared scene. Optics are provided for producing visible images of the light source array at the positions of the eyes of the observer. A second scanning mirror alternately scans the image of the light source array across the two eyes of the observer in order to construct full visible images of the scene.

Abstract: The invention relates to an apparatus for obtaining an enlarged image of a part of the field of view of an IR camera. A device (4,6) for horizontal deflection and a device (5,17) for vertical deflection deflect IR rays (7) incident on the camera towards detector elements (8). These sense the field of view along parallel scanning lines costituting bands, and generate video signals so that the lines can be presented on a display screen (3). In accordance with the invention the device (5,17) for vertical deflection forms a smaller portion in height of the field of view than normal height thereof. The bands partially overlap each other so that the scanning lines in one band fall in the space between scanning lines in a preceding band. The bands are individually noted in the reading order in separate memory (C, D, E). The data for the lines falling in the space will be noted at addresses which do not correspond to their true position in the field of view.

Abstract: The invention relates to a device for optically scanning a field of vision divided into different regions and for displaying the field, scanning being done in two perpendicular directions, i.e. "line" scanning in a direction x and "raster" or "image" scanning in a direction y, the device scanning along beams coming from different regions of the field and causing the beams to converge on to an element sensitive to the radiation in the beams, the present invention being concerned particularly with the line-scanning means, which is designed so that the device can operate with smaller apertures without affecting its resolution. The line-scanning system comprises a rotating drum having reflecting surfaces but the detector image is conveyed outside the drum axis.

Abstract: A photodetector sensing system is disclosed which combines staring and scanning features. By providing both temporal and spatial filtering, many system benefits are obtained. Each pixel in the viewed scene has a "dedicated" filter, which receives signals only from that pixel. By integrating time spaced signals from the same pixel, the filter maintains the staring effect of a two-dimensional detector array. A single detector may view a plurality of pixels, thereby improving resolution. A single pixel may be viewed by a plurality of detectors, thereby providing redundancy to correct for detector failures. The signal from each detector, after amplification, is first sent through a spatial, high frequency filter, and then is set to one of a plurality of parallel temporal, low frequency filters, which time share the detector. Synchronizing means are provided for ensuring that each temporal filter always receives its time spaced signals from the same source. Any suitable scanning mechanism may be used.

Abstract: A wavefront sensor apparatus for a large optical system, such as a telescope, having a reticle with at least one slit therein to provide image signatures for various portions of the aperture to an array of infrared sensor cells. The time differences between the image signatures represents relative image displacement caused by the wavefront slope variation in the actual wavefront.

Abstract: A radiant energy interlace system comprises an electromagnetic radiant energy reflector means having a magnetic core which includes a reed mirror portion and a body portion. The reed mirror portion is either a polished plate or frame of magnetic material holding a mirror and the body portion is of magnetic material having a center section with a centrally disposed ridge from which downwardly sloping surfaces extend to solid bar reel sections surrounded by coils of conductive wire. End sections of magnetic material having sloping surfaces for continuing the sloping surface of the center section complete the body section. A circuit is connected to the coils for alternately energizing the coils to magnetize alternate portions of the reed mirror portion to rotate the reed mirror portion about the fulcrum ridge of the center section. The slope of the body portion surfaces is equal to one half of the desired interlace angle.

Abstract: An infrared scanner includes an infrared energy reflecting surface rigidly fixed to a supporting shaft. The shaft is supported by jewel bearings for rotation by a motor controlled by a control circuit for imparting a scanning motion to the reflecting surface. A collar interconnects the shaft to an electrical coil which is energized by a two-directional source of power. A magnetic means includes a pair of "U" shaped members forming a housing of electromagnetic material for containing a pair of opposing magnets. The legs of the "U" shaped members support a coil pole in an air gap forming relationship with respect to the magnets.

Abstract: In the present invention, the temperatures of cooling passages in a gas turbine engine blade are changed, as by forcing a heated gas through them. The infrared signatures of the channels are measured during the initial temperature transient of the channels and the signatures are compared with a reference. The reference may be the signature of other channels on the same blade.

Abstract: The present invention is an improvement on the thermal imaging detector of Elliott (U.S. Pat. No. 3,995,195). This detector, which has come to be called the SPRITE detector (Signal PRocessing In The Element), is being applied in serially scanned thermal imaging systems for the 8-12 micrometer infrared spectral band. All such SPRITE detectors to date have been three terminal devices, including two bias contacts at either end of the detector, and one additional readout electrode which, together with the nearby bias contact, define the readout zone across which the integrated photoconductive signal voltage is measured. The present invention recognizes that using a bias contact as one of the two readout electrodes can substantially reduce the spatial frequency response of the SPRITE detector. Thus, the present invention utilizes a four-terminal SPRITE detector configuration in which readout is achieved in a differential manner across two voltage probes.

Abstract: A thermal imaging device uses a scanning mirror (2) to guide incident radiation to a detector array (4) which, after optoelectronic conversion, drives a light-emitting diode array (6) synchronously; this image is represented via the back of the scanning mirror on the imaging optical system (9). On the visual collimator side of the scanning mirror, a scan position sensor (12) including a light source (12a) is provided in addition to a detector (12b), a beam splitter (12d), and a collimator objective (12c). A plane plate (7) which operates as a dichroic beam splitter is shown between the scanning mirror (2) and the light-emitting diode array (6). Another dichroic beam splitter (8) is shown between the scanning mirror (2) and the scan position sensor (12). Autocollimation is obtained since both beam splitters reflect the radiation from the light source in the direction of the scanning mirror.

Abstract: An arrangement for the multispectral imaging of objects, preferably targets, including an optical system for imaging the object dots of the objects on at least one charge-coupled semiconductor element, with each charge-coupled semiconductor element including a plurality of light sensitive individual detectors and a charge-transfer circuit arrangement connected to said detectors. The plurality of individual detectors includes at least two groups of detectors with each group being sensitive to light energy of a different wavelength or wavelength range. The groups of detectors are disposed on the surface of the semiconductor element such that the optical system, due to its scatter circle, images each object dot on at least one detector of each group, and the output signals of each individual detector are fed to the charge-transfer circuit arrangement of the semiconductor element.

Abstract: A radiation scan system (10) incorporates a scanning device (13) which transfers radiation between transmitting station (12) and receiving station (11) with simultaneous mapping of a point (14) in station (11) into a line (15) in station (12). Station (12) is in the form of a distant plane. Scanning device (13) has at least one mirror (16) mounted on a carrier (17) movable about an axis (18) which lies in the plane of the angular offset between the radiation beams at scan device (13) incoming from and outgoing to the stations (11,12). A refractive prism corrector (26) is located in the path of the radiation beam between scan device (13) and station (12) whereat line (15) exists, the vertex edge (27) of the prism corrector (26) being perpendicular to axis (18) and the parameter values of the prism corrector (26) are such that at least the line (15) in station ( 12) is straight.

Abstract: A thermal wave imaging apparatus generates a real time image of the surface and subsurface of an opaque solid object. A.C. electrical signals indicative of the configuration of the surface and subsurface of the object which are generated during a thermal wave scan of the object by a first heating beam which generates a localized temperature gradient on the object and a deflectable second probe beam heating beam, which deflection is detected by a detection device mounted adjacent to the object, are stored in an image memory under the control of a central processor. A refresh counter generates sequential, incremental signals used to control the X and Y axis deflection of a display monitor. Such signals also address the image memory and generate output data controlling the intensity of the display point at each generated X and Y axis deflection point.

Abstract: An aiming apparatus, for example, for aiming at a target, has an aiming h (11), an ocular unit (13) and a display section (22) between the aiming head and the ocular unit. The display section (22) has, for example, a thermal imager (24) and a cathode ray tube (26, 27) operated by the thermal imager for displaying a thermal image received through a beam splitter. The aiming head (11) and the ocular unit include the required optical elements and an ocular (19). Each section has its respective housing. The housing of the aiming head (11') is rotably interconnected for rotation about its normally vertical axis (30) at least with the thermal imager (24) rotatable about its horizontal axis (23) in a corresponding synchronous rotation, whereby the screen (27) and any image on the screen of the cathode ray tube (26) retain their relationship unchanged even if the aiming head is rotated by a pointer through an azimuth angle. This is so because the aiming head and the thermal imager rotate with the same angles.

Abstract: An infrared viewing apparatus is described which comprises an infrared objective, a pivotal mirror, a linear infrared detection array, an amplifier arrangement connected to this array, and a display array which is driven by the amplifier arrangement and is imaged onto a plane of observation via the back of the pivotal mirror. By arranging a beam splitter in the radiation path between the display array and the pivotal mirror, which beam splitter transmits a part of the visible radiation to a line sensor, and by controlling the read-out of this sensor by synchronizing device which detects the movement of the pivotal mirror, an electric signal for remote display purposes can be obtained.

Abstract: A dual field of view sensor, particularly adapted for use as a forward-looking infrared night vision detector, includes a single detector (24) for receiving a light signal and developing an output electrical signal therefrom. A rotating polygon scanner (16) having a plurality of reflective facet (14) thereon receives light (12, 34) from two separate optical systems (10, 32) and directs the light onto the facets (14) of the scanner (16) at positions offset by one-half the facet angle such that the light beams alternately strike a facet and the juncture between two facets. The reflected light is then directed through a beam splitter 40 onto the detector in an alternating, interleaved sweeping motion. The beam splitter permits only one at a time of the light (12, 34) from entering the detector. In one embodiment, both optical systems include a steerable dual field of view telescope.

Abstract: A forward looking infrared (FLIR) energy imaging device has been found to include components which are required by the receiver portion of a long-wavelength rangefinder. For example, the FLIR collecting lens system which focuses energy from a scene onto a sensitive, cooled detector array duplicates the function which must be performed by the laser rangefinder receiver. Thus an integrated laser/FLIR rangefinder comprises a laser transmitter for illuminating a target, and an IR energy optic channel having a FLIR for receiving IR energy and producing a visible image representative thereof, said FLIR including an afocal lens system for collecting and focusing energy from the target and energy from the laser return having a wavelength compatible with the band pass of the IR optics and detector onto a cooled sensitive detector.

Abstract: The method and apparatus for scanning for radiated energy employs a scanning mirror (1) pivoting azimuthally about a vertical scanning axis (2) and capable of being pivoted also about a pivotal axis (3) that makes an angle with the scanning axis. The mirror reflects the incident IR energy onto a vertically disposed field composed on n individual IR detector elements (22) having (n-1) spacings of equal magnitude. The horizontal motion of the mirror takes place in customary manner but the pivotal motion is smaller than the individual detector elements and their separations. Therefore, the same thermal image requires several pivotal processes and, hence, also several mutually parallel horizontal scanning motions, resulting in achieving greater resolution of the image.

Abstract: A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

Abstract: In an integrated laser/FLIR rangefinder a scanner position sensor comprising an LED of the array of LEDs of a forward looking infrared (FLIR) system, a reticle grating located at the image plane of LED optical path, and a silicon detector positioned to receive the light passing through the reticle grating for producing a plurality of signals in response to light passing through each grating slot. One of the signals is selected for the synchronization logic for controlling the charging and firing of the laser. If there is no range return a second signal is selected for adjusting the position of the timing pulse.

Abstract: An optical processing system for processing infrared information prior to detection. In one embodiment, optical information from an infrared scene is focused by optics (10) onto a thermoptic modulator (12) which contains an optical structure (16) disposed on the faceplace of a cathode ray tube. The modulator is normally nonreflective of infrared energy from the scene incident thereon. Reflecting spots (22) written on the modulator by an electron beam reflect a portion of the scene to a detector (52) which generates a signal representative of the radiance of the scene element sampled. A series of first and second reflecting spots of different size are written at selected coordinates on the modulator. The respective signals generated by the detector for each spot of the pair are subtracted to provide a spatial band pass filtered signal for each sampling coordinate on the modulator.

Abstract: Analog signals representing infrared radiation from an object are generated by a scanner. These signals are digitized and one frame of data is stored in a computer. The computer and a display generator process the data, and supply one frame to a TV monitor which displays an image of the object. A grey scale is also displayed alongside the image to provide calibrated quantitative information related to the temperature at different places of the object. A tape recorder may be used to record the analog signals, for later digitizing and displaying the images.

Abstract: An optical system produces sensor data from at least two fields of view (which may be centered differently) in a sequence selected to satisfy two simultaneous functions of the sensor.

Abstract: In a thermal-radiation imaging device a detector element comprises a semiconductor strip, e.g. of n-type cadmium mercury telluride, on which biasing-electrode means are spaced for causing a bias current predominantly of majority charge carriers to flow along each strip. The bias current supports an ambipolar drift of radiation-generated charge carriers in the opposite direction. A readout area is present in a part of the drift path between a pair of spaced electrodes. At least one space extends locally across the width of strip in-between the spaced readout electrodes from at least one side of the readout area to narrow at least locally the drift path in the readout area and to increase the electric field. A detector having increased responsivity results, particularly when at least two spaces extend from opposite sides to form a meandering drift path in the read-out area. Close spacing of the readout electrodes permits good image resolution even with a long meandering drift path.

Abstract: A signal processing system is disclosed for a pyroelectric camera having a mechanical chopper in the optical path for causing information sensed by the camera to appear as dynamic information. The pyroelectric camera includes a pyroelectric vidicon tube which senses thermal energy emitted by a target and provides an electrical output signal indicative of the received thermal information. The output signal developed by the pyroelectric vidicon tube includes a relatively large pedestal signal component that is established during flyback due to secondary electron generation and a slightly wider but relatively small pedestal signal that is established due to differences in temperature sensed by the pyroelectric vidicon tube, which pedestal signal is timewise aligned with the relatively large pedestal signal generated due to secondary electron generation.

Abstract: A scan conversion circuit for a thermal imager device in which a field is scanned by a parallel-series array of infra-red detectors swept broadside over the field to produce a band of parallel I.R. signals. The signals from the array of detectors are sampled at high speed in a pattern which traces each parallel line of detectors in turn. A C.R.T. is scanned in a similar pattern, the pattern being repeated at high speed with successive lateral displacements corresponding to the rate at which the I.R. array sweeps the field.

Abstract: An apparatus known as a common module for converting a thermal scene into a visible image. The apparatus comprises an infrared objective, a pivotal mirror which can be pivoted back and forth about an axis, an infrared detection array comprising a plurality of detectors, and a linear display array which is connected to the infrared detection array via an amplifier arrangement. The radiation emitted by the display array is imaged in a plane of observation, preferably via the back of the pivotal mirror and via at least one diverting mirror. For omnidirectional viewing in the horizontal and the vertical direction the infrared objective, the pivotal mirror, the detector array and the display array are combined to form a constructional unit, which is arranged to be pivotable about a horizontal and about a vertical axis. Between the diverting mirror and the eyepiece an erecting prism is arranged. The erecting prism is rotated in conformity with the rotation of the constructional unit.

Abstract: The present invention provides a thermal imaging method to evaluate the surface and subsurface properties of a material and is based on techniques of optical beam deflection thermal imaging. The invention uses a localized excitation source, such as an optical beam, to provide localized heating of the sample surface. A surface thermal gradient is induced on the sample surface as heat flows, in three dimensions, from the area of localized excitation into the test material. The surface temperature gradient causes a thermal refractive lens to be generated in the fluid (gas or liquid) adjacent to the sample surface. An optical probe beam is directed through the thermal lens and is deflected by changes in a refractive index of the thermal lens. Changes in the refractive index are induced by variations of the surface temperature. In this manner, a detailed surface temperature profile can be generated which reveals surface and subsurface properties of the material tested.

Abstract: In a thermal-radiation imaging device a plurality of photoconductive detector elements are present on a common substrate. Each detector element comprises a semiconductor strip on which biasing-electrode means are spaced for causing a bias current predominantly of majority charge carriers to flow along each strip. The bias current supports an ambipolar drift of radiation-generated charge carriers in the opposite direction. Readout means for detecting these carriers comprises a connection protruding from one side of the strip. A recess extends across part of the width of the strip at the side opposite the readout connection. The readout connection of one strip extends into the recess of an adjacent strip so that a compact, closely-spaced and substantially aligned arrangement of the parallel detector elements can be obtained.

Abstract: Apparatus is described for scanning a scene in bands of lines and reconstructing the scene in visible light. Use is made of a prism having mirrors which subtend a sequence of various tilt angles with an axis of rotation. According to the invention, all but one of the mirrors are used for scanning and reconstruction. To achieve this, the angular spacing between the scanning and reconstruction locations around the prism is an integral multiple of the angular spacing between adjacent mirrors, which multiple is not a sub-multiple of the total number of mirrors. For all but one of the mirrors, the tilt angle of a mirror at a scanning location differs from the tilt angle of the mirror simultaneously present at a reconstruction location by the same amount and in the same direction.

Abstract: A scanning mechanism for a fast framing thermal imaging system such as a FLIR is disclosed. The scanning mechanism comprises two prisms which are canted with respect to one another and positioned in front of the final image forming lens of the FLIR. The two prisms are precisely counter-rotated with respect to one another by a drive train assembly and motor means. An annular timing disc is positioned about one of the prisms to enable an optically sensitive transducer to sense the rotational position of the prisms. The counter-rotating prisms function to enable the detector array of the FLIR to dissect the thermal image in a 2:1 interlacing technique.

Abstract: The "narcissus" effect in a thermal imaging apparatus employing scanned arrays of cooled infrared radiation detectors is produced, in part, by the detectors seeing themselves by reflection in the surfaces of the optical elements during the middle part of the scan. The narcissus effect results in a darkened center in the displayed picture. To compensate for this effect, a signal is formed of the sum of the detector outputs. This signal is applied in negative feedback to each detector output. Extended bright or dark areas are suppressed but picture detail special to individual detectors is largely unaffected.

Abstract: A shield for limiting the radiation received by electromagnetic energy radiation detectors to the radiation provided to the detectors by the optics of an electromagnetic energy detection system. The shield comprises a member transparent to a predetermined spectrum of radiation. An opaque thin film is deposited on a surface of the member, the thin film having apertures defined therein, the detectors viewing the optics through the member and the apertures. The thin film shields the detectors from electromagnetic radiation generated outside the field of view of the optics, thereby improving the sensitivity of the detection system. Virtually any desired thickness for the member may be used, thus allowing very close placement of the shield to the detectors and permitting use of very high density arrays.

Abstract: A pyroelectric vidicon has an improved signal-to-noise ratio by essentially eliminating pedestal noise and using signal gain to overcome preamplifier noise. Pedestal noise is substantially eliminated by charging the target, during the flyback read period, down to a small fixed value above the quiescent value. This is accomplished by setting the cathode potential, during the flyback read period, at a value below the reference value. The time duration of the flyback read period is such that the target is charged down to a value which is still above the quiescent value.

Abstract: The optoelectronic device comprises an optical element for producing an image scan and an optical element for focusing on an array of detectors. The detected signals are processed by amplifying circuits and a thermal-drift correcting unit comprising an occultation device having two states. A correction loop of the unit includes a memory for storing the values of amplifying circuit signals in the first state of the occultation device, a first circuit for subtracting the stored values from the amplifying circuit outputs in order to compensate for thermal drift, a measuring circuit for obtaining the mean value of the amplified videofrequency signals, and a second circuit for subtracting the mean value from the signal of each detector.

Abstract: The present invention is a method of referencing and operating an infrared imaging system that may be used with virtually any system. A preferred embodiment of the invention is disclosed using a mechanical scanning mirror that minimizes spatial scan distortion.