Abstract:
A small and compact infrared scene projector allows for projection of infrared images from a variety of sources. The unit utilizes an external power supply to reduce the weight of the unit and has several input pathways such as an integrated RS-232 serial port and a video port for receiving RS-170 formatted video signals. The projector uses a digital signal processor to control its internal electronics and for on-board generation of pre-programmed infrared images. A processor electronics card and a scene generator electronics card communicate internally to generate images and to control a thermoelectric cooling device mounted to a semiconductor infrared emitter array to project flicker free, high resolution infrared images. Optics in the form of an interchangeable lens or a mirrored collimator allow for projection of a generated image onto a test object. Internal high speed memory and electrically erasable firmware, both externally programmable, allow for on-the-fly programming and self-sustaining and continued operation after disconnection from a separate programming computer. An external, user programmable interface allows for the download of commands and images into the scene projector. Once programmed by an external computer, such as a personal notebook computer, the scene projector can be placed in the field for live, self test of military electronics that rely on infrared sensors to make decisions.

Description:
This application claims the benefit of filing priority under 35 U.S.C. §119 and 37 C.F.R. §1.78 of the co-pending U.S. Provisional Application Ser. No. 60/351,566 filed Jan. 24, 2002, for a COMPACT INTEGRATED INFRARED IMAGE SCENE PROJECTOR. All information disclosed in that prior pending provisional application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to image projectors. In particular, the present invention relates to military type image scene projectors. In greater particularity, the present invention relates infrared image scene projectors. 
     BACKGROUND OF THE INVENTION 
     A good deal of military and communications weaponry today relies upon infrared imaging and acquisition techniques. For example, missile targeting systems rely upon templated infrared signatures to lock onto aircraft exhaust signatures, helicopter gun ships use tank heat signatures to lock onto targeted vehicles, and military aircraft navigation aids use infrared sensors to assist in auto-navigating through rough terrain and inclement weather. In more complex systems, such as satellite imaging, navigation element tracking, and forward looking infrared (FLIR) navigation systems, recorded infrared scenes are compared to live sensory data for real-time decision making. In general, infrared image sensing signatures of geography, buildings, and even people will likely become a major component in target acquisition and locking systems; and it is expected that various sorts of weaponry—missiles, artillery, navigation, and rifle targeting systems—will utilize infrared imaging in some form or fashion in the future. 
     Infrared image sensors detect electromagnetic radiation from a scene and output electrical or optical information extracted from the scene. Lenses associated with a selected imaging system focus infrared radiation upon one or more sensors so that acceptable signal capture is obtained. However, while image detection has been advanced due to improvements in infrared focal plane arrays (FPAs) and advanced optics design, a great deal of attention is now being drawn to the design of software for image recognition and decision making based upon received images. Sophisticated software analyzes received images and makes logical determinations based upon pre-established criteria, such as object templates, spectrum signatures (e.g. frequency signatures), and intensity to analysis. 
     Testing of infrared imaging systems can be as complex as the imaging design itself. Most production testing methods inject an electrical test signal for a sensor system to process and compare system component responses based upon an expected result. However, signal injection is not an optimum test method because the image detector with its related electronics and associated gimbals and optics are not tested. The optics and detector of the system are usually tested separately using a very simple static scene or test pattern, or with a very slow moving, but somewhat more complex series of synthetic scenes. This two-part test methodology does not perform an end-to-end test of the entire system and is inferior to providing live scene image testing data. Hence, as the quantity and complexity of such systems has increased the need for generating and projecting synthetic images for input into image sensors has also grown. 
     Several systems are now available capable of presenting realistic, detailed infrared images or “scenes” into the field of view of the sensors being tested for a selected system. For example, Kenyon U.S. Pat. No. 6,123,288, has developed a system to provide flicker-less projection of infrared scenes using a non-volatile electron beam addressed light-valve output. Leddy, U.S. Pat. No. 5,457,493, has developed a micro-mirror based image simulation system in which a digital micro-mirror reflects infrared energy from a separate infrared source onto a testing subject. And, Billingsley, U.S. Pat. No. 4,530,010, has designed a dynamic infrared scene projector using thin films of vanadium dioxide which are excited to produce infrared images. 
     However, each of these designs and others currently available in the industry suffer from several drawbacks, namely: (1) none of the currently available systems allow for easy mobile transport of a scene generator; (2) none allow for solid state generation of scene images on location and at reduced atmospheric pressures; and (3) none provide a self-contained, compact design that is capable of self-generation of images without external stimulus. Hence, military systems utilizing infrared sensory electronics cannot be easily tested in the field and do not include the ability for continuous live testing in airborne vehicles. 
     Moreover, one of the most desired testing methods for testing defense armaments and navigation systems is “built-in-self test (BIT). However, BIT is most useful if the testing hardware can be utilized in the field in the typical environment of the system. For example, if a scene projector could be integrated into a FLIR system, live pre-flight or in flight testing could be accomplished to ensure the integrity of the system&#39;s operation. BIT could also allow relatively easy refinements to existing imaging systems and allow the enhancement of on-board software recognition systems, thereby increasing the effectiveness of the current infrared sensory electronics. 
     Therefore, what is needed is a compact, self-contained infrared scene projector that can be configured to test infrared imaging systems in the field and during live operations. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a solid state, self-contained infrared scene projector. 
     It is another object of the present invention to provide an infrared scene projector that can internally create infrared scene images for projection onto a target testing object. 
     It is still another object of the current invention to provide an infrared scene projector that can receive image commands from an external computer for projection. 
     It is yet another object of the current invention to provide an infrared scene projector that can receive external video source imagery and project such source imagery. 
     It is still another object of the current invention to provide an infrared scene projector that can provide internal cooling for an infrared pixel array and thereby properly regulate infrared background temperatures of projected solid objects. 
     It is still another object of the current invention to provide an infrared scene projector that allows for interchangeable optics. 
     It is still another object of the current invention to provide an infrared scene projector that can be integrated with a mirrored collimator for multi-spectral projection of scene imagery. 
     In summary, the present invention is a relatively small and compact infrared scene projector. An external power supply powers the projector unit and an integrated RS-232 serial port on the projector allows for reception of commands from a connected personal computer. The projector utilizes a digital signal processor to control the internal electronics and for generation of preprogrammed infrared objects. A processor assembly card and a scene projector assembly card communicate internally to control a thermoelectric cooling (TEC) device and an electronic infrared projector array to project flicker free, high resolution infrared images onto a targeted sensor for testing. Optics in the form of interchangeable lens or a mirrored collimator allow for projection of an array generated image onto a live test object. Internal high speed memory and electrically erasable firmware, both externally programmable, allow for on-the-fly programming and self-contained operation. The projector can be co-located with military electronics that utilize infrared sensory imagery to provide field located built in self test (BIT). 
    
    
     Other features and objects and advantages of the present invention will become apparent from a reading of the following description as well as a study of the appended drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A scene projector incorporating the features of the invention is depicted in the attached drawings which form a portion of the disclosure and wherein: 
     FIG. 1 is an exploded perspective view of the bottom side (access panel side) of scene projector showing the primary physical components of the system; 
     FIG. 2 is a front perspective view of an assembled scene projector; 
     FIG. 3 a  is a perspective view of another embodiment of the assembled scene projector showing an attached tower and reflective fold mirror assembly in place of an optical lens; 
     FIG. 3 b  is a diagrammatic view of the scene projector including the tower and reflective fold mirror with an adjacent collimator; 
     FIG. 4 is a front elevational view of the assembled scene projector; 
     FIG. 5 is a side elevational view of the left side of FIG. 6; 
     FIG. 6 is a plan view of the top of the scene projector; 
     FIG. 7 is a side elevational view of the right side of FIG. 6; 
     FIG. 8 is a plan view of the bottom of the assembled scene projector; 
     FIG. 9 is an end view of the assembled scene projector; 
     FIG. 10 is a perspective cutaway view of the assembled scene projector showing the relative positions of the projector&#39;s housing, the DSP CCA, the Scene Projector CCA, a passive heat sink and TEC cooling device, the array CCA, and the optical subassembly; 
     FIG. 11 is a functional system diagram showing the primary functional subsystems of the scene projector and their inter-communication data paths; 
     FIG. 12 is a system component diagram showing functional communication paths between the primary electrical elements of the scene projector CCA; 
     FIG. 13 is a system component diagram showing functional communication paths between the primary electrical elements of the DSP CCA; and, 
     FIG. 14 is an optical element diagram of the optical subassembly used in the scene projector. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings for a better understanding of the function and structure of the invention, FIG. 1 shows an exploded view of the primary components of one embodiment of the infrared scene projector  10 . A primary housing or case  11  acts as a protective enclosure and support for the primary electronics assembly  12  which is mated to an infrared array assembly  13 . As shown in the Figure, screws affix the combined electronics assembly  12  and infrared array assembly  13  into housing  11  along an outer circumferential margin of the array assembly board  13  seated on an inner circumferential flange of the housing  11 . A lens mounting plate  14  is aligned onto dowels extending forward from the primary housing  11  with additional screws securing the plate  14  against the housing as shown, enclosing the electronics assembly  12  and the array assembly  13  within the housing  11 . Aperture  15  is located at the center of the lens mounting plate  14  to allow passage of the infrared emissions emanating from the seated infrared emitter array. The aperture  15  also serves as a receptor for lens assembly  16  which includes a threaded or smooth extension from its body for mounting onto the plate  14 . As shown in FIG. 2, the to assembled scene projector  10  occupies a rather compact and unobtrusive shape, having a typical thickness of approximately 3 inches and a total length measured from the foremost point on the lens assembly to the rearmost portion of the housing of only about 8 inches. 
     FIGS. 3 a-b  shows another embodiment of the scene projector  10  in which the enclosed electronics ( 12 ,  13 ) and housing components ( 11 ) are outfitted with a tower and fold mirror in lieu of a refractive lens assembly  14 ,  16 , and placed adjacent to a collimator assembly. In certain applications it is advantageous that the scene-projector  10  be positioned in front of a large aperture enclosed within a weather resistant housing. In such applications, a fold mirror and collimator assembly allows for testing structures to be positioned within an aircraft or vehicle for the purposes of mission readiness and target acquisition refinements. As shown in FIG. 3 a , an angled collimator mounting plate  17  supports a tower assembly  18  of multiple leg extensions  18   a-h , and a fold mirror  19  is held by a suitable bracket  21  that allows for positioning of the mirror in an angle for reflecting a projected infrared image into an adjacent collimator. As shown in FIG. 3 b , a typical collimator assembly  22  might include, two curved mirrors, one convex and one concave, both suitably shaped to focus a projected infrared image onto a proximally located infrared sensor objective. As will be understood in the industry, various types of collimator lens and shapes can be manufactured to address various types of targeting sensor sizes and other physical configurations of infrared sensor electronics. It will also be noticed that the collimator mounting plate  17  is angled at approximately 12.32°. However offset angles of various ranges are anticipated to address various types of collimator and fold mirror configurations and sizes. The figure shows a Ritchey-Chretien type of collimator, although various configurations and types will be utilized. In the shown example configuration, both mirror surfaces are off-axis aspheric sections with an 8-inch clear aperture having a 36-inch focal length. An interface plate engages alignment pins to allow for positioning of the infrared array at the tilted image plane of the collimator. 
     FIGS. 4-9 show different elevational views of the refractive lens embodiment of the infrared projector  10 . FIG. 8 additionally shows an access plate  26  that allows for access to the internal wiring harness (not shown) connecting the internal electronics assembly boards to the projector&#39;s external port connectors. FIG. 9 shows external connectors, namely, a standard RS-232 9 pin serial port connector  28 , a 10 pin recessed pin grid connector  29  which provides power and grounding for the projector, and a video input jack  30  that provides a port for receiving RS-170 video signals. 
     FIG. 10 shows a perspective cut away view of the assembled scene projector showing relative positions of various critical components for the scene projector  10 . The projector housing  11  holds the passive heat sink  32  via screws protruding through each heat sink cooling fin, allowing for isolation of the heat conducted away from the array emitter  51  from the primary electronics assembly  12 . Bracket  31  holding electronic assemblies  34  and  36  (not visible) is secured into array emitter CCA  13  with  4  screws extending through the emitter CCA  13  and into the bracket  31 . The assemblies  34  and  36  are secured to the bracket with flat pan screws. A TEC (Thermoelectric Cooler) device  33  is positioned between heat sink  32  and infrared array assembly board  13  and affixed to a flat portion of the heat sink  32  with thermally conducting pads and to the bottom of the actual array emitter. As can be seen in the figure, connectors are suitably positioned to engage each of the boards electronic internal connectors and provide for electrical communications between the boards over prescribed lines. A rectangular aperture in the printed circuit board holding the infrared array emitter  51  allows the TEC cooling device to be mounted directly onto the ventral surface of the ceramic semiconductor package of the emitter array  51 , which is affixed thereto with suitable heat conducting pads. The heat sink  32  is also adhesively affixed to the heat transference side of the TEC to promote transfer heat emissions generated by the infrared emitter away from the emitter and against the inner surface of the housing  11  Heat is therefore conducted away from the emitter  51  and the primary electronic assembly  12  through the housing  11  top and bottom surfaces. As those skilled in the art will appreciate, establishing proper controls for background infrared emissions is an important component in proper infrared scene generation. The disclosed arrangement of the TEC cooler and suitably sized heat sink allows for sufficient dissipation of heat energy from the infrared array emitter such that, under proper electrical control as will be discussed, background energy emissions are controlled. 
     Thermoelectric cooling devices such as the TEC cooler disclosed herein  33  are primarily electric heat pumps used for the removal of heat from one side of a TEC device to another side. Each side is sometimes referred to as the hot and cold sides of the TEC device. In the disclosed embodiment, the cold or cooling side of the TEC device is affixed to the rear or underside portion of the infrared emitter array and the hot or heat dissipation side is located on a side opposite from the cooling side and against a forward-most, flat portion of the passive heat sink 32. A suitable TEC cooler utilized in the disclosed design is a FRIGICHIP FC series type available from Melcor, Inc. The passive heat sink  32  is made from suitably conductive metal alloys such as conductive aluminum which satisfactorily dissipates heat transferred by the TEC cooler. As infrared emitter technology advances, it is anticipated that a passive heat sink design may, in and of itself, provide sufficient cooling, thereby obviating the need for thermoelectric cooling. 
     The infrared array emitter  51  can be comprised of any industry standard matrix addressable infrared emitter (albeit with some electronics reconfiguration for each model). The current preferred embodiment utilizes analog generated input signals to address image pixel intensity requirements, although the inventors contemplate that a purely digital based infrared emitter will be available in the future. A suitable emitter for the current design is offered by Honeywell, Inc. under the brand name Brite 128-512 Infrared Emitters. These types of emitters directly radiate energy from underlying pixel addressable points on a silicon wafer. A matrix of 128×128 pixels form a matrix of gray body emitters with an infrared radiance that varies as a function of an applied voltage. These types of Honeywell emitters generate infrared radiance at individual pixel locations by passing current through a thin film resistor suspended above a polarized substrate. The current through the emitter resistor is a function of the gate voltage stored in the hold capacitor connected to the gate allowing for very low power operation by which pixel emissions vary within a wide dynamic range. Moreover, these types of infrared emitters have high vacuum integrity because the pixels are fabricated using low vapor pressure materials, such as nitride and oxides, with bulk properties having melting temperatures in the 1500-2000 k temperature range. Hence, each pixel emits a high contrast infrared point with very high thermal stability that performs over a range of atmospheric pressures, such as may be experienced in airborne applications. 
     As partially shown in FIG. 10, connectors on the infrared emitter array assembly board  13  provide for electrical signal connections between various electronic assembly boards, and wiring harness  38  provides electrical signal connectivity from external connectors  28 - 30  to the various boards. 
     Referring now to FIG. 11, the system consists of four functional components: (1) a DSP circuit card assembly (“CCA”)  36 ; (2) a scene generator circuit card assembly  34 ; (3) an infrared emitter array CCA  13 ; and, (4) an optical assembly  53 . The scene generator CCA  34  provides power  41  to other functional elements in the system. A RS-232 port  43  provides serial information input into the DSP CCA  36  to receive computer commands from a graphical user interface running on a separate personal computer (not shown) and also provides for reprogramming of internal firmware and downloading of DSP operational commands. A connector  30  (see FIG. 9) allows for RS-170 signals  42  to be received by the scene generator CCA  34 , which are then separated into digital video data  64  and video synchronization information  67 . A digital signal processor or “DSP” integrated semiconductor  46  provides video data  47  for conversion through a digital analog converter  48  into analog signals  49  received by infrared emitter array  51  for infrared image generation  52 . The DSP  46  provides direct video feed from the RS-170 signal into the digital analog converter  48  or, alternatively, the DSP can generate its own infrared images through algorithm computations stored in FLASH memory and in association with logic stored in firmware FPGA  56  (Field Programmable Gate Array). Also, an RS-232 source  43  can provide a bit mapped scene image to be held in high speed memory on the DSP CCA  36  such that it can then be transferred directly to the infrared image emitter array  51 . A TEC cooler  58  provides cooling to the array emitter  51  as already discussed and thermistor  99  outputs a feedback signal to analog digital converter  54  that is read by DSP integrated circuit  46 . In response, the DSP outputs commands through the FPGA interface  56  to control the TEC cooling rate through TEC control signals  57 . 
     FIG. 12 shows more specific details regarding the function and operation of individual components located on the scene generator CCA  34 . A buffer  71  normalizes voltages compatible with the CCA&#39;s voltage levels from the inputted RS-170 signal  42 , and a video sink separator  72  separates the video synchronization signal from the RS-170 buffered signal to establish a timing indicator signal for use by pixel clock generator  73 . The pixel clock generator includes logic to send appropriate clock signals via a pixel clock input line to a 12-bit analog to digital converter  74 . “Backporch” signal  76  from separator  72  is used to offset-normalize the video information  78  via DC restorer  77  to allow for proper digital conversion. Video information  78  is then converted from analog to digital via 12-bit video analog to digital converter  74  and saved in a 256K×18 FIFO  79  memory for interim storage of individual interlaced signal fields. The pixel clock generator  73  generates a field storage signal at approximately a 60 Hz rate so that interlaced fields can be combined into a non-interlaced frame by the DSP CCA  36 . The pixel clock generator  73  utilizes external phase loop logic  81  in conjunction with the pixel clock generator logic  73  contained within the FPGA  56  to produce the appropriate clock signals. The combination of these video and logic elements  82  allows for the continual conversion of RS-170 source signals, either in color or black and white, to be continually digitized and processed by the DSP CCA  36 . As will be explained in more detail, the DSP CCA  36  has available one field of video stored in the FIFO  79  for processing in accordance with prior downloaded instructions from a separate user software package or prior loaded internal processing instructions. Due to the speed of the DSP processor, processing of individual video fields stored in the FIFO  79  occurs well prior to the availability of the next interlaced video field presented by the external RS-170 signal source, thereby permitting the combining of interlaced fields into a non-interlaced image and the timely transference of the image to the emitter array  51 . 
     FIFO interface  83  provides a signal to the DSP CCA  36  signaling whether or not the FIFO  79  contains a complete field and is available for transference to the DSP CCA. FIFO interface  83  also sends control signals to the FIFO  79  instructing the FIFO to load digital video from the 12-bit video analog-to-digital converter  74 . Core interface logic  84  provides interface logic to accept control signals from the DSP CCA  36  via multiplexed buses  86 - 88 . Bus lines  86 - 88  are physically identical on the scene generator CCA  34  and on the DSP CCA  36 . However, the digital signal processor  46  utilizes chip selects to multiplex values on the bus  86 - 88  to present data and receive data from appropriate integrated circuits such as, for example, the FIFO video frame information  79  and transference of core logic instructions to core interface  84  on FPGA  56 . Bus  86 - 88  is utilized to transfer 32 bit data information to data buffer  91  and matrix addressing array buffer  92 . FPGA  56  also includes digital to analog conversion interface logic  95  that provides control signals to the 32 bit digital analog converter  93 . Those skilled in the art will understand, therefore, that the 20 bit address bus, the 32 bit data bus, and the control bus  86 - 88  are a multiplex set of lines circumscribing paths on both the scene generator CCA  34  and the DSP CCA  36 . By using a chip select function, the DSP CCA  36  can receive interlaced video field data from FIFO  79  and combine it with a second interlaced field to produce a non-interlaced display image frame for writing to the 32 16-bit DAC  93  in preparation for display. 
     A 32-bit data buffer  91  is used for signal fan out to the 32 16-bit DACs  93 . Pixel intensity information is retained in the 32 16-bit DAC  93  and presented to the infrared emitter array  51  via eight analog input lines  77 . These analog input values are held and the DSP CCA  36  energizes the appropriate address lines. A TTL-to-CMOS buffer  92  is used to convert the DSP CCA  36  3.3V TTL logic levels to 5V CMOS logic required by the infrared emitter array  51 . Additional address strobes are replicated until all of the pixels in the array  51  have been loaded with analog intensity information. Although a 128×128 pixel configuration is shown, those skilled in the art will understand that a scalable addressing scheme may be utilized to address larger arrays such as a 256×256 or 512×512 pixel arrays. 
     The TEC cooler  58  is mounted to the underside of the array  51  to provide cooling as previously discussed. A TEC cooler drive  96  receives constant frequency signal from a pulse width modulator  97  which varies its duty cycle in accordance with modulation logic in the FPGA  56  to control the rate of cooling by the TEC cooler  58 , and which in turn is controlled by command signals provided by the DSP CCA  36  through the core interface logic  84 . A thermistor measurement circuit  98  receives sensory information from a temperature sensitive thermistor  99  which is then converted into digital information through analog to digital converter  54  on the DSP CCA  36 . Digital signal processor  46  then interprets digital values of the thermistor measurement circuit  98  and sends appropriate control signals to the FPGA  56  to control the modulator  97 . Hence, through this feedback communication strategy, the TEC cooler  58  can be controlled with a high level of granularity that allows for control of the background infrared emissions of the infrared emitter array  51 , thereby enhancing infrared image generation integrity. 
     Module interface  101  comprises an external connector  29  and wiring harness (not shown) providing appropriate +5V, +12V, and −12V input voltages and returns. The module interface  101  also comprises the RS-232 pin connector  28  that allows for direct connection into the DSP CCA  36 . In order to minimize feedback noise potential, a separate pixel power line  102  provides +5V direct input and return into the infrared emitter array  51 . If common +5V lines were utilized to power the infrared emitter array  51 , a possibility of switching noise generated by the DSP CCA  36  could be propagated through power lines into the array CCA  13  and provide undesirable interference with the infrared emitter&#39;s operation. 
     Referring now to FIG. 13 for a better understanding of the operation of the DSP CCA  36 , a TMS320C6211 digital signal processor  46  provides the primary processing functions of the DSP CCA  36 . Texas Instruments is the manufacturer of the TMS320 series of digital processors two of which, the TMS320C62211 (non-floating point) and the TMS320C6711 (floating point) digital signal processors, may be utilized in the instant described design. However, those skilled in the art will understand that any type of processor having the capability of executing instructions and algorithmic processes at sufficient speeds may be utilized. For example, the inventors anticipate that a general purpose microprocessor such as Intel&#39;s 386 16-bit line of microprocessors could be utilized in place of herein described digital signal processor. The DSP CCA 36 is a fairly self-contained CCA and may be utilized in various other systems. The actual DSP operates at 150 MHz and uses an internal 100 MHz system bus, and the speed of the DSP CCA  36  is approximately 1200 MIPS or 600 MFLOPS. The DSP CCA includes 256K×16 bit FLASH memory  111  and 64K×32 bit asynchronous static memory (ASRAM)  112  for DSP program store and image calculations. The CCA  36  also utilizes several high speed and low speed (100 MSPS, 100 KSPS) analog to digital converters (not shown) controlled by a XLINX FPGA through control lines  114 . 
     The procedures by which the TMS32ODSP, or an alternative microprocessor, are programmed will not be discussed in as much as programming kits and code compilers are readily available and well understood in the industry. For example, Texas Instruments offers a software developer&#39;s kit called a “Code Composer Studio Development Environment” for the TMS320 line of DSPs and Intel sells similar developer kits for its line of microprocessors allowing for DSP code assembly and compilation. 
     The DSP  46  communicates to the scene generator CCA  34  via external memory interface EMIF  121  and via connectors  116  and  117 . Other communication links such as the RS-232 link  43 , a controlled area network link (not shown), and a host port interface (HPI)  130  can also be invoked for other types of communication and controls. Currently the EMIF is a little endian format, but other suitable formats may be utilized. Flash memory  111  includes FPGA reprogramming code  119  to allow for reprogramming of the XLINX FPGA  113  and includes a protective portion of flash memory for boot up code  125 . The DSP  46  and the XLINX FPGA  113  communicate with the scene generator CCA  34  through the external memory interface  121 . The DSP  46  utilizes four external address spaces in its external memory interface  121 , namely; CE 0 , CE 1 , CE 2 , and CE 3 . CE 0  is used to access static RAM  112  and CE 1  is used to access FLASH memory  111 , registers on a separate PLD (not shown), and registers on the XLINX FPGA  113 . The XLINX FPGA  113  decodes each of these address spaces into four sub address spaces to allow a total of eight addressable spaces. Therefore, the XLINX FPGA may utilize one of its sub-address enables using the top two address bits (ADR 21  and ADR 20 ) from which chip enables CE 2  or CE 3  may be activated by the DSP  46  via the EMIF  121 . The scene projector CCA  34  generally utilizes 5 of the 8 sub addresses to decode logic signals. 
     The XLINX FPGA  113  includes all the necessary logic to decode and control various peripherals on the DSP CCA  36 . This includes the Analog to Digital Converter (ADC)  54  for receiving thermistor measurement signals  98 , DSP external interrupt control registers, such as interrupt pole, mask, and status registers, and an optional fast ADC, other optional fast and slow Analog to Digital Converters (DAC), LED control registers, clock control registers, and FPGA configuration status registers. 
     Communications between the DSP CCA  36  and the scene generator CCA  34  occur through CE decodes over the address bus, the data bus of the EMIF, and the read/write control signals of the EMIF bus. The CE lines (see Figure) decode whether the EMIF bus lines are being utilized for communication between the DSP  46  and the scene generator FPGA  56 , the DSP and the scene generator CCA digital analog converters, or the FIFO  79 . Transceivers  122  and  123  insure error free communications across connectors  116  and  117  between the DSP CCA  36  and the scene generator CCA  34 . Also, a separate programmable logic (PLD) device on the DSP CCA (not shown) controls the FLASH memory  111 , sets the timing input for and enables reprogramming of the XLINX FPGA  113 , contains XLINX FPGA  113  read back signals, and generates a 10 MHz clock for the use of an optional controlled area network controller. 
     FIG. 14 shows an optical element configuration suitable for the herein described scene projector. Various types of optical assemblies and optical elements may be utilized to project an image emitted by the infrared emitter  51  onto various objectives. The shown optical assembly is optimized to project an image into a selected FLIR objective lens. It will be understood that varying optical assemblies could utilize threaded or bayonet type mounts to facilitate the interchangeability of lens on mounting plate  14  to allow for rapid reconfiguration of the infrared projector  10  to suit different situations. 
     Inasmuch as optical assemblies and techniques for combining various optical elements to produce suitable focal lengths and fields of view are well known and understood in the industry, a detailed description of individual optical elements will not be provided. Nonetheless, an example configuration is shown in FIG. 14 which has been used by the inventors and is suitable for the herein described types of applications. As shown, individual pixel elements of the infrared emitter array  51  emanate from plane position  131  and are refracted by zinc selenide optical element  132 . Element  132  has shaped properties pursuant to the values shown and is suitable for infrared refraction. Infrared image rays strike a second germanium optical element  133  and are again refracted to project an infrared image into a test article objective. Element  133  has optical properties as shown in the Figure. A typical distance of the optical element  132  and infrared source  131  is 16.4562 mm and the distance between Element  132  and Element  133  is 79.0 mm. 
     In operation, the scene projector  10  can produce infrared images through three primary methods: (1) it can project a received RS-170 video signal which is refreshed at television video rates; (2) it can project a preloaded bit-map image received via the RS-232 communications link; or (3) it can construct synthetic images from parameters received from a separate user interface running on a serially connected personal computer or other computing device. Preloaded images, either through parameter description or as a bit-mapped image, can also be saved in memory ( 111  or  112 ) and projected on demand. In fact, a demonstration program using stored images or a preloaded test program can be created by storing such images or parameters and accessing them through an iterative display loop program. 
     Creation of synthetic objects are accomplished by transferring inputs from an operator via a host interface to the scene projector  10 , and executing algorithms stored in memory using transferred variable values to create images. A separate application program running on a personal computer allows a user to send command functions to the scene projector instructing it to, for example, be ready to receive a bit mapped image for display, prepare for firmware programming, start displaying RS-170 images, begin receiving object descriptor information to calculate and display synthetic image objects, etc. Selected functions are communicated to the DSP in a binary string of digits as a packet in a form as shown in Table 1: 
     
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Command Function and Argument Communication Format 
               
             
          
           
               
                 Names of Binary 
                   
               
               
                 Fields of Each 
               
               
                 Packet in sequence 
                 Description 
               
               
                   
               
               
                 Byte Count 
                 First 16 bits indicating the length in bits 
               
               
                   
                 of the packet. 
               
               
                 Command Op. Code 
                 Next 8 bits defining the current function. 
               
               
                 Data 
                 Argument for Command op. code function 
               
               
                   
                 having a variable length depending upon selected 
               
               
                   
                 op. code function. 
               
               
                 CRC 
                 Fixed length of 32 bits allowing for cyclical 
               
               
                   
                 redundancy checking. 
               
               
                 Sequence 
                 Unique 8 bit number identifying each transferred 
               
               
                   
                 packet of information to allow for matching of 
               
               
                   
                 acknowledgement responses from DSP. 
               
               
                   
               
             
          
         
       
     
     In the situation in which a command function calling for an object to be synthesized and displayed by the scene projector is transferred to the DSP, the data argument would consist of image creation parameters called “object descriptors.” The PC application program includes a graphical user interface or “GUI” that allows for easy input of the object descriptors via predefined fields. These defined object descriptors are then grouped into the argument of the command function packet as part of the Data Field and transferred to the DSP CCA  36  via the serial RS-232 connection. The format and parameters of the object descriptor data portion is as shown in Table 2 below. The inventors envision a multitude of types and quantities of description elements, but  13  pre-defined parameters seem to satisfactorily describe most synthetic images. Since the type and operation of a graphical user interface is not essential for a complete understanding of the operation of the scene projector  10 , and since combining a list of input object parameters into a binary data packet and transferring it to the memory of a computing device is well understood in the industry and may be accomplished in a variety of ways, further description of such interfaces will not be described. The essential capability of the remote user interface is that it be able to transfer binary files and bit mapped images via the RS-232 link, and that the creation of the object descriptors be created and transferred into memory elements  111  or  112 . Object descriptors shown in Table 2 below are satisfactory for most synthetic images: 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 A Suitable Object Descriptor Packet 
               
             
          
           
               
                 Descriptor Variable 
                   
               
               
                 Name 
                 Description 
               
               
                   
               
               
                 1. X Offset 
                 No. of array pixels in X (±) direction by which 
               
               
                   
                 the object is offset from center of the emitter 
               
               
                   
                 array. 
               
               
                 2. Y Offset 
                 No. of array pixels in Y (±) direction by which 
               
               
                   
                 the object is offset from center of the emitter 
               
               
                   
                 array. 
               
               
                 3. X Sweep Rate 
                 Rate at which the object is moved from right to 
               
               
                   
                 left or left to right. Rate is based upon an internal 
               
               
                   
                 clock frequency. 
               
               
                 4. Y Sweep Rate 
                 Rate at which the object is moved from top to 
               
               
                   
                 bottom or bottom to top. Rate is based upon an 
               
               
                   
                 internal clock frequency. 
               
               
                 5. X Sweep Range 
                 Limit or bounds of a sweeping range in X 
               
               
                   
                 direction measured in no. of array pixels. 
               
               
                 6. Y Sweep Range 
                 Limit or bounds of a sweeping range in Y 
               
               
                   
                 direction measured in no. of array pixels. 
               
               
                 7. Rotation Angular 
                 Speed at which object rotates about center of 
               
               
                 Rate 
                 array from vertical (as altered by X and Y 
               
               
                   
                 Offsets) in radians/sec. 
               
               
                 8. Rotation Angle 
                 Set angle in radians by which an object is to be 
               
               
                   
                 rotated. 
               
               
                 9. Object Type 
                 Selection of a predefined and preprogrammed 
               
               
                   
                 object shape. 
               
               
                 10. Object Size 
                 Size of object in no. of array pixels. 
               
               
                 11. Orbit Angular 
                 Rotation rate about center of array (as altered by 
               
               
                 Rate 
                 X and Y Offsets) in radians/sec. 
               
               
                 12. Orbit Radius 
                 Radius dimension from center of array (as altered 
               
               
                   
                 by X and Y Offsets) in array pixels. 
               
               
                 13. Temp. Difference 
                 Temperature of emitted object in Degrees Celsius 
               
               
                   
                 above ambient temperature. 
               
               
                   
               
             
          
         
       
     
     Upon transmission of a command function packet calling for the creation of a defined image, the DSP  46  uses the received descriptors to set the initial conditions of the image and to set a rate timer that regulates the motion of the object, if any. The DSP then calculates the location of the object origin in terms of two dimensional Cartesian coordinates. After calculating the sweep position and orbit angle from the sweep rate and orbit angular rates respectively, the origin is computed utilizing the specified sweep position, sweep range, orbit angle, and orbit radius. Once the origin of the object is determined, the object is drawn in static memory  112  as a matrix representing individual pixel elements of the array  51 . 
     Various predefined objects are preprogrammed into the DSP&#39;s memory  112  for execution upon receiving a recognized object type in the descriptor data (see parameter  9 ). The selected object type at the required size and specified delta temperature is then drawn using a combination of three basic drawing functions (not to be confused with operation command functions). The primary drawing functions and their associated arguments are a “plotline” (x 0 ,y 0 ,x 1 ,y 1 , width), a “plot circle” (radius), and a “fill” (color). Each object is drawn using a combination of these primary drawing functions calculated by the DSP in association with other user supplied inputs from the scene projector&#39;s GUI. Each drawing function has an initial configuration and is scaled using the descriptor parameters to form the selected object. For example, a bar object might be invoked, a 4-bar object, a circle object, a triangle object, or an alignment object. Solid objects such as the triangle and circle are filled with a color that is based on a user inputted temperature differential. If rotation of an object is required then the rotation angle and rotation angular rate are provided in the object descriptor data, which are used to compute the next required image in a movement sequence. This is done using a polar coordinate system in which the coordinates of key features of the object are first computed and then the object is drawn in the same manner as in the original object position. After an object image is drawn by the DSP and saved in memory, the object image information is written to the infrared array. In the event that the drawn image moves beyond the 128×128 array pixel matrix bounds, the portion of the object still within the boundary of the pixel matrix is displayed. This display strategy allows for the replacement or upgrading of the 128×128 array to larger arrays such as 256 or 512 pixels without rewriting the DSP instructions. Below, a description of how each primary object is drawn by the DSP is given in terms of the primary drawing functions. Obviously, as new objects are added over time, new functions may also be created to efficiently draw each object. 
     The bar object is essentially a 7:1 aspect ratio bar constructed from the line and fill functions. Based on the user specified size described in terms of number of pixel elements, two horizontal lines are drawn and two connecting vertical lines having a length 7 times that of the bar width are inserted between their endpoints. The resulting rectangle is then filled with the fill level or “color” based on the received delta temperature parameter. 
     The 4-bar object is created using a four 7:1 aspect ratio bar equally spaced by an equidistant amount. The perimeter of the resulting pattern is a square which is then centered in the array and each bar is then constructed as with the single bar method, but with lines added and a fill color drawn. 
     The circle object uses the size specified by the operator in parameter No. 10 as the radius of a circle where the units of the radius is in number of pixel emitters of the array. The circle function is used to draw the circle object and then the fill function is applied. 
     A triangle is created using three line functions and applying the fill function. The size of the triangle is specified by the user and determines the distance in emitters from the center of the array to the vertices of an isosceles triangle. 
     Lastly, the alignment object is generated by combining four concentric circle functions and two orthogonal lines through the center point of the circles. The temperature level of the lines are based on the temperature delta selected by the operator. 
     While the above four objects have been developed using the described three primary drawing line functions, it will be understood that additional drawing functions and objects will likely be developed depending upon the evolution of testing applications and additional testing refinements. 
     While we have shown our invention in one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof.