Patent Publication Number: US-9848134-B2

Title: Infrared imager with integrated metal layers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/730,435 filed Nov. 27, 2012, entitled “INFRARED IMAGER WITH INTEGRATED METAL LAYERS” which is hereby incorporated by reference in its entirety. 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/748,018 filed Dec. 31, 2012 and entitled “COMPACT MULTI-SPECTRUM IMAGING WITH FUSION” which is hereby incorporated by reference in its entirety. 
     This patent application is a continuation-in-part of U.S. patent application Ser. No. 13/437,645 filed Apr. 2, 2012 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     U.S. patent application Ser. No. 13/437,645 is a continuation-in-part of U.S. patent application Ser. No. 13/105,765 filed May 11, 2011 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     U.S. patent application Ser. No. 13/437,645 also claims the benefit of U.S. Provisional Patent Application No. 61/473,207 filed Apr. 8, 2011 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     U.S. patent application Ser. No. 13/437,645 is also a continuation-in-part of U.S. patent application Ser. No. 12/766,739 filed Apr. 23, 2010 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     U.S. patent application Ser. No. 13/105,765 is a continuation of International Patent Application No. PCT/EP2011/056432 filed Apr. 21, 2011 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     U.S. patent application Ser. No. 13/105,765 is also a continuation-in-part of U.S. patent application Ser. No. 12/766,739 filed Apr. 23, 2010 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/EP2011/056432 is a continuation-in-part of U.S. patent application Ser. No. 12/766,739 filed Apr. 23, 2010 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/EP2011/056432 also claims the benefit of U.S. Provisional Patent Application No. 61/473,207 filed Apr. 8, 2011 and entitled “INFRARED RESOLUTION AND CONTRAST ENHANCEMENT WITH FUSION” which is hereby incorporated by reference in its entirety. 
     This application is a continuation-in-part of International Patent Application No. PCT/US2012/041744 filed Jun. 8, 2012 and entitled “LOW POWER AND SMALL FORM FACTOR INFRARED IMAGING” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041744 claims the benefit of U.S. Provisional Patent Application No. 61/656,889 filed Jun. 7, 2012 and entitled “LOW POWER AND SMALL FORM FACTOR INFRARED IMAGING” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041744 claims the benefit of U.S. Provisional Patent Application No. 61/545,056 filed Oct. 7, 2011 and entitled “NON-UNIFORMITY CORRECTION TECHNIQUES FOR INFRARED IMAGING DEVICES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041744 claims the benefit of U.S. Provisional Patent Application No. 61/495,873 filed Jun. 10, 2011 and entitled “INFRARED CAMERA PACKAGING SYSTEMS AND METHODS” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041744 claims the benefit of U.S. Provisional Patent Application No. 61/495,879 filed Jun. 10, 2011 and entitled “INFRARED CAMERA SYSTEM ARCHITECTURES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041744 claims the benefit of U.S. Provisional Patent Application No. 61/495,888 filed Jun. 10, 2011 and entitled “INFRARED CAMERA CALIBRATION TECHNIQUES” which is hereby incorporated by reference in its entirety. 
     This application is a continuation-in-part of International Patent Application No. PCT/US2012/041749 filed Jun. 8, 2012 and entitled “NON-UNIFORMITY CORRECTION TECHNIQUES FOR INFRARED IMAGING DEVICES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041749 claims the benefit of U.S. Provisional Patent Application No. 61/545,056 filed Oct. 7, 2011 and entitled “NON-UNIFORMITY CORRECTION TECHNIQUES FOR INFRARED IMAGING DEVICES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041749 claims the benefit of U.S. Provisional Patent Application No. 61/495,873 filed Jun. 10, 2011 and entitled “INFRARED CAMERA PACKAGING SYSTEMS AND METHODS” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041749 claims the benefit of U.S. Provisional Patent Application No. 61/495,879 filed Jun. 10, 2011 and entitled “INFRARED CAMERA SYSTEM ARCHITECTURES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041749 claims the benefit of U.S. Provisional Patent Application No. 61/495,888 filed Jun. 10, 2011 and entitled “INFRARED CAMERA CALIBRATION TECHNIQUES” which is hereby incorporated by reference in its entirety. 
     This application is a continuation-in-part of International Patent Application No. PCT/US2012/041739 filed Jun. 8, 2012 and entitled “INFRARED CAMERA SYSTEM ARCHITECTURES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041739 claims the benefit of U.S. Provisional Patent Application No. 61/495,873 filed Jun. 10, 2011 and entitled “INFRARED CAMERA PACKAGING SYSTEMS AND METHODS” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041739 claims the benefit of U.S. Provisional Patent Application No. 61/495,879 filed Jun. 10, 2011 and entitled “INFRARED CAMERA SYSTEM ARCHITECTURES” which is hereby incorporated by reference in its entirety. 
     International Patent Application No. PCT/US2012/041739 claims the benefit of U.S. Provisional Patent Application No. 61/495,888 filed Jun. 10, 2011 and entitled “INFRARED CAMERA CALIBRATION TECHNIQUES” which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     One or more embodiments of the invention relate generally to thermal imaging devices and more particularly, for example, to integrated circuits used to implement such devices. 
     BACKGROUND 
     Infrared imaging devices, such as infrared cameras or other devices, are typically implemented with an array of infrared sensors. Such devices are often implemented as integrated circuits with interconnections provided between the infrared sensors and related circuitry. For example, such interconnections may be provided between the infrared sensors and various components of a read out integrated circuit (ROIC). 
     Many existing infrared imaging devices are implemented with relatively large arrays of infrared sensors. Unfortunately, as the number of infrared sensors increases, greater numbers of interconnected metal layers are typically required to provide signal paths between the infrared sensors and ROIC components. This complicates the design of integrated circuits and increases their associated manufacturing costs. 
     SUMMARY 
     Various techniques are provided for implementing, operating, and manufacturing infrared imaging devices using integrated circuits. In one embodiment, a system includes a focal plane array (FPA) integrated circuit comprising: an array of infrared sensors adapted to image a scene; a plurality of active circuit components; a first metal layer disposed above and connected to the circuit components; a second metal layer disposed above the first metal layer and connected to the first metal layer; a third metal layer disposed above the second metal layer and below the infrared sensors, wherein the third metal layer is connected to the second metal layer and the infrared sensors; wherein the first, second, and third metal layers are the only metal layers of the FPA between the infrared sensors and the circuit components; and wherein the first, second, and third metal layers are adapted to route signals between the circuit components and the infrared sensors. 
     In another embodiment, a method includes imaging a scene using a focal plane array (FPA) integrated circuit comprising: an array of infrared sensors adapted to image the scene, a plurality of active circuit components, a first metal layer disposed above and connected to the circuit components, a second metal layer disposed above the first metal layer and connected to the first metal layer, a third metal layer disposed above the second metal layer and below the infrared sensors, wherein the third metal layer is connected to the second metal layer and the infrared sensors, and wherein the first, second, and third metal layers are the only metal layers of the FPA between the infrared sensors and the circuit components; and routing signals between the circuit components and the infrared sensors through the first, second, and third metal layers. 
     In another embodiment, a method of manufacturing a focal plane array (FPA) integrated circuit includes forming a plurality of active circuit components; forming a plurality of insulating layers above the active circuit components; forming first, second, and third metal layers above the active circuit components; forming a plurality of infrared sensors above the metal layers and the insulating layers; wherein the circuit components, the first metal layer, the second metal layer, the third metal layer, and the infrared sensors are separated by corresponding ones of the insulating layers; wherein the first, second, and third metal layers are the only metal layers of the FPA between the infrared sensors and the circuit components; and wherein the first, second, and third metal layers are adapted to route signals between the circuit components and the infrared sensors. 
     The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an infrared imaging module configured to be implemented in a host device in accordance with an embodiment of the disclosure. 
         FIG. 2  illustrates an assembled infrared imaging module in accordance with an embodiment of the disclosure. 
         FIG. 3  illustrates an exploded view of an infrared imaging module juxtaposed over a socket in accordance with an embodiment of the disclosure. 
         FIG. 4  illustrates a block diagram of an infrared sensor assembly including an array of infrared sensors in accordance with an embodiment of the disclosure. 
         FIG. 5  illustrates a flow diagram of various operations to determine non-uniformity correction (NUC) terms in accordance with an embodiment of the disclosure. 
         FIG. 6  illustrates differences between neighboring pixels in accordance with an embodiment of the disclosure. 
         FIG. 7  illustrates a flat field correction technique in accordance with an embodiment of the disclosure. 
         FIG. 8  illustrates various image processing techniques of  FIG. 5  and other operations applied in an image processing pipeline in accordance with an embodiment of the disclosure. 
         FIG. 9  illustrates a temporal noise reduction process in accordance with an embodiment of the disclosure. 
         FIG. 10  illustrates particular implementation details of several processes of the image processing pipeline of  FIG. 6  in accordance with an embodiment of the disclosure. 
         FIG. 11  illustrates spatially correlated fixed pattern noise (FPN) in a neighborhood of pixels in accordance with an embodiment of the disclosure. 
         FIG. 12  illustrates a block diagram of another implementation of an infrared sensor assembly including an array of infrared sensors and a low-dropout regulator in accordance with an embodiment of the disclosure. 
         FIG. 13  illustrates a circuit diagram of a portion of the infrared sensor assembly of  FIG. 12  in accordance with an embodiment of the disclosure. 
         FIG. 14  illustrates a cross-sectional view of a portion of an infrared sensor assembly in accordance with an embodiment of the disclosure. 
         FIG. 15  illustrates a process of manufacturing an infrared sensor assembly in accordance with an embodiment of the disclosure. 
     
    
    
     Embodiments of the invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an infrared imaging module  100  (e.g., an infrared camera or an infrared imaging device) configured to be implemented in a host device  102  in accordance with an embodiment of the disclosure. Infrared imaging module  100  may be implemented, for one or more embodiments, with a small form factor and in accordance with wafer level packaging techniques or other packaging techniques. 
     In one embodiment, infrared imaging module  100  may be configured to be implemented in a small portable host device  102 , such as a mobile telephone, a tablet computing device, a laptop computing device, a personal digital assistant, a visible light camera, a music player, or any other appropriate mobile device. In this regard, infrared imaging module  100  may be used to provide infrared imaging features to host device  102 . For example, infrared imaging module  100  may be configured to capture, process, and/or otherwise manage infrared images and provide such infrared images to host device  102  for use in any desired fashion (e.g., for further processing, to store in memory, to display, to use by various applications running on host device  102 , to export to other devices, or other uses). 
     In various embodiments, infrared imaging module  100  may be configured to operate at low voltage levels and over a wide temperature range. For example, in one embodiment, infrared imaging module  100  may operate using a power supply of approximately 2.4 volts, 2.5 volts, 2.8 volts, or lower voltages, and operate over a temperature range of approximately −20 degrees C. to approximately +60 degrees C. (e.g., providing a suitable dynamic range and performance over an environmental temperature range of approximately 80 degrees C.). In one embodiment, by operating infrared imaging module  100  at low voltage levels, infrared imaging module  100  may experience reduced amounts of self heating in comparison with other types of infrared imaging devices. As a result, infrared imaging module  100  may be operated with reduced measures to compensate for such self heating. 
     As shown in  FIG. 1 , host device  102  may include a socket  104 , a shutter  105 , motion sensors  194 , a processor  195 , a memory  196 , a display  197 , and/or other components  198 . Socket  104  may be configured to receive infrared imaging module  100  as identified by arrow  101 . In this regard,  FIG. 2  illustrates infrared imaging module  100  assembled in socket  104  in accordance with an embodiment of the disclosure. 
     Motion sensors  194  may be implemented by one or more accelerometers, gyroscopes, or other appropriate devices that may be used to detect movement of host device  102 . Motion sensors  194  may be monitored by and provide information to processing module  160  or processor  195  to detect motion. In various embodiments, motion sensors  194  may be implemented as part of host device  102  (as shown in  FIG. 1 ), infrared imaging module  100 , or other devices attached to or otherwise interfaced with host device  102 . 
     Processor  195  may be implemented as any appropriate processing device (e.g., logic device, microcontroller, processor, application specific integrated circuit (ASIC), or other device) that may be used by host device  102  to execute appropriate instructions, such as software instructions provided in memory  196 . Display  197  may be used to display captured and/or processed infrared images and/or other images, data, and information. Other components  198  may be used to implement any features of host device  102  as may be desired for various applications (e.g., clocks, temperature sensors, a visible light camera, or other components). In addition, a machine readable medium  193  may be provided for storing non-transitory instructions for loading into memory  196  and execution by processor  195 . 
     In various embodiments, infrared imaging module  100  and socket  104  may be implemented for mass production to facilitate high volume applications, such as for implementation in mobile telephones or other devices (e.g., requiring small form factors). In one embodiment, the combination of infrared imaging module  100  and socket  104  may exhibit overall dimensions of approximately 8.5 mm by 8.5 mm by 5.9 mm while infrared imaging module  100  is installed in socket  104 . 
       FIG. 3  illustrates an exploded view of infrared imaging module  100  juxtaposed over socket  104  in accordance with an embodiment of the disclosure. Infrared imaging module  100  may include a lens barrel  110 , a housing  120 , an infrared sensor assembly  128 , a circuit board  170 , a base  150 , and a processing module  160 . 
     Lens barrel  110  may at least partially enclose an optical element  180  (e.g., a lens) which is partially visible in  FIG. 3  through an aperture  112  in lens barrel  110 . Lens barrel  110  may include a substantially cylindrical extension  114  which may be used to interface lens barrel  110  with an aperture  122  in housing  120 . 
     Infrared sensor assembly  128  may be implemented, for example, with a cap  130  (e.g., a lid) mounted on a substrate  140 . Infrared sensor assembly  128  may include a plurality of infrared sensors  132  (e.g., infrared detectors) implemented in an array or other fashion on substrate  140  and covered by cap  130 . For example, in one embodiment, infrared sensor assembly  128  may be implemented as a focal plane array (FPA). Such a focal plane array may be implemented, for example, as a vacuum package assembly (e.g., sealed by cap  130  and substrate  140 ). In one embodiment, infrared sensor assembly  128  may be implemented as a wafer level package (e.g., infrared sensor assembly  128  may be singulated from a set of vacuum package assemblies provided on a wafer). In one embodiment, infrared sensor assembly  128  may be implemented to operate using a power supply of approximately 2.4 volts, 2.5 volts, 2.8 volts, or similar voltages. 
     Infrared sensors  132  may be configured to detect infrared radiation (e.g., infrared energy) from a target scene including, for example, mid wave infrared wave bands (MWIR), long wave infrared wave bands (LWIR), and/or other thermal imaging bands as may be desired in particular implementations. In one embodiment, infrared sensor assembly  128  may be provided in accordance with wafer level packaging techniques. 
     Infrared sensors  132  may be implemented, for example, as microbolometers or other types of thermal imaging infrared sensors arranged in any desired array pattern to provide a plurality of pixels. In one embodiment, infrared sensors  132  may be implemented as vanadium oxide (VOx) detectors with a 17 μm pixel pitch. In various embodiments, arrays of approximately 32 by 32 infrared sensors  132 , approximately 64 by 64 infrared sensors  132 , approximately 80 by 64 infrared sensors  132 , or other array sizes may be used. 
     Substrate  140  may include various circuitry including, for example, a read out integrated circuit (ROIC) with dimensions less than approximately 5.5 mm by 5.5 mm in one embodiment. Substrate  140  may also include bond pads  142  that may be used to contact complementary connections positioned on inside surfaces of housing  120  when infrared imaging module  100  is assembled as shown in  FIG. 3 . In one embodiment, the ROIC may be implemented with low-dropout regulators (LDO) to perform voltage regulation to reduce power supply noise introduced to infrared sensor assembly  128  and thus provide an improved power supply rejection ratio (PSRR). Moreover, by implementing the LDO with the ROIC (e.g., within a wafer level package), less die area may be consumed and fewer discrete die (or chips) are needed. 
       FIG. 4  illustrates a block diagram of infrared sensor assembly  128  including an array of infrared sensors  132  in accordance with an embodiment of the disclosure. In the illustrated embodiment, infrared sensors  132  are provided as part of a unit cell array of a ROIC  402 . ROIC  402  includes bias generation and timing control circuitry  404 , column amplifiers  405 , a column multiplexer  406 , a row multiplexer  408 , and an output amplifier  410 . Image frames (e.g., thermal images) captured by infrared sensors  132  may be provided by output amplifier  410  to processing module  160 , processor  195 , and/or any other appropriate components to perform various processing techniques described herein. Although an 8 by 8 array is shown in  FIG. 4 , any desired array configuration may be used in other embodiments. Further descriptions of ROICs and infrared sensors (e.g., microbolometer circuits) may be found in U.S. Pat. No. 6,028,309 issued Feb. 22, 2000, which is incorporated herein by reference in its entirety. 
     Infrared sensor assembly  128  may capture images (e.g., image frames) and provide such images from its ROIC at various rates. Processing module  160  may be used to perform appropriate processing of captured infrared images and may be implemented in accordance with any appropriate architecture. In one embodiment, processing module  160  may be implemented as an ASIC. In this regard, such an ASIC may be configured to perform image processing with high performance and/or high efficiency. In another embodiment, processing module  160  may be implemented with a general purpose central processing unit (CPU) which may be configured to execute appropriate software instructions to perform image processing, coordinate and perform image processing with various image processing blocks, coordinate interfacing between processing module  160  and host device  102 , and/or other operations. In yet another embodiment, processing module  160  may be implemented with a field programmable gate array (FPGA). Processing module  160  may be implemented with other types of processing and/or logic circuits in other embodiments as would be understood by one skilled in the art. 
     In these and other embodiments, processing module  160  may also be implemented with other components where appropriate, such as, volatile memory, non-volatile memory, and/or one or more interfaces (e.g., infrared detector interfaces, inter-integrated circuit (I2C) interfaces, mobile industry processor interfaces (MIPI), joint test action group (JTAG) interfaces (e.g., IEEE 1149.1 standard test access port and boundary-scan architecture), and/or other interfaces). 
     In some embodiments, infrared imaging module  100  may further include one or more actuators  199  which may be used to adjust the focus of infrared image frames captured by infrared sensor assembly  128 . For example, actuators  199  may be used to move optical element  180 , infrared sensors  132 , and/or other components relative to each other to selectively focus and defocus infrared image frames in accordance with techniques described herein. Actuators  199  may be implemented in accordance with any type of motion-inducing apparatus or mechanism, and may positioned at any location within or external to infrared imaging module  100  as appropriate for different applications. 
     When infrared imaging module  100  is assembled, housing  120  may substantially enclose infrared sensor assembly  128 , base  150 , and processing module  160 . Housing  120  may facilitate connection of various components of infrared imaging module  100 . For example, in one embodiment, housing  120  may provide electrical connections  126  to connect various components as further described. 
     Electrical connections  126  (e.g., conductive electrical paths, traces, or other types of connections) may be electrically connected with bond pads  142  when infrared imaging module  100  is assembled. In various embodiments, electrical connections  126  may be embedded in housing  120 , provided on inside surfaces of housing  120 , and/or otherwise provided by housing  120 . Electrical connections  126  may terminate in connections  124  protruding from the bottom surface of housing  120  as shown in  FIG. 3 . Connections  124  may connect with circuit board  170  when infrared imaging module  100  is assembled (e.g., housing  120  may rest atop circuit board  170  in various embodiments). Processing module  160  may be electrically connected with circuit board  170  through appropriate electrical connections. As a result, infrared sensor assembly  128  may be electrically connected with processing module  160  through, for example, conductive electrical paths provided by: bond pads  142 , complementary connections on inside surfaces of housing  120 , electrical connections  126  of housing  120 , connections  124 , and circuit board  170 . Advantageously, such an arrangement may be implemented without requiring wire bonds to be provided between infrared sensor assembly  128  and processing module  160 . 
     In various embodiments, electrical connections  126  in housing  120  may be made from any desired material (e.g., copper or any other appropriate conductive material). In one embodiment, electrical connections  126  may aid in dissipating heat from infrared imaging module  100 . 
     Other connections may be used in other embodiments. For example, in one embodiment, sensor assembly  128  may be attached to processing module  160  through a ceramic board that connects to sensor assembly  128  by wire bonds and to processing module  160  by a ball grid array (BGA). In another embodiment, sensor assembly  128  may be mounted directly on a rigid flexible board and electrically connected with wire bonds, and processing module  160  may be mounted and connected to the rigid flexible board with wire bonds or a BGA. 
     The various implementations of infrared imaging module  100  and host device  102  set forth herein are provided for purposes of example, rather than limitation. In this regard, any of the various techniques described herein may be applied to any infrared camera system, infrared imager, or other device for performing infrared/thermal imaging. 
     Substrate  140  of infrared sensor assembly  128  may be mounted on base  150 . In various embodiments, base  150  (e.g., a pedestal) may be made, for example, of copper formed by metal injection molding (MIM) and provided with a black oxide or nickel-coated finish. In various embodiments, base  150  may be made of any desired material, such as for example zinc, aluminum, or magnesium, as desired for a given application and may be formed by any desired applicable process, such as for example aluminum casting, MIM, or zinc rapid casting, as may be desired for particular applications. 
     In various embodiments, base  150  may be implemented to provide structural support, various circuit paths, thermal heat sink properties, and other features where appropriate. In one embodiment, base  150  may be a multi-layer structure implemented at least in part using ceramic material. 
     In various embodiments, circuit board  170  may receive housing  120  and thus may physically support the various components of infrared imaging module  100 . In various embodiments, circuit board  170  may be implemented as a printed circuit board (e.g., an FR4 circuit board or other types of circuit boards), a rigid or flexible interconnect (e.g., tape or other type of interconnects), a flexible circuit substrate, a flexible plastic substrate, or other appropriate structures. In various embodiments, base  150  may be implemented with the various features and attributes described for circuit board  170 , and vice versa. 
     Socket  104  may include a cavity  106  configured to receive infrared imaging module  100  (e.g., as shown in the assembled view of  FIG. 2 ). Infrared imaging module  100  and/or socket  104  may include appropriate tabs, arms, pins, fasteners, or any other appropriate engagement members which may be used to secure infrared imaging module  100  to or within socket  104  using friction, tension, adhesion, and/or any other appropriate manner. Socket  104  may include engagement members  107  that may engage surfaces  109  of housing  120  when infrared imaging module  100  is inserted into a cavity  106  of socket  104 . Other types of engagement members may be used in other embodiments. 
     Infrared imaging module  100  may be electrically connected with socket  104  through appropriate electrical connections (e.g., contacts, pins, wires, or any other appropriate connections). For example, socket  104  may include electrical connections  108  which may contact corresponding electrical connections of infrared imaging module  100  (e.g., interconnect pads, contacts, or other electrical connections on side or bottom surfaces of circuit board  170 , bond pads  142  or other electrical connections on base  150 , or other connections). Electrical connections  108  may be made from any desired material (e.g., copper or any other appropriate conductive material). In one embodiment, electrical connections  108  may be mechanically biased to press against electrical connections of infrared imaging module  100  when infrared imaging module  100  is inserted into cavity  106  of socket  104 . In one embodiment, electrical connections  108  may at least partially secure infrared imaging module  100  in socket  104 . Other types of electrical connections may be used in other embodiments. 
     Socket  104  may be electrically connected with host device  102  through similar types of electrical connections. For example, in one embodiment, host device  102  may include electrical connections (e.g., soldered connections, snap-in connections, or other connections) that connect with electrical connections  108  passing through apertures  190 . In various embodiments, such electrical connections may be made to the sides and/or bottom of socket  104 . 
     Various components of infrared imaging module  100  may be implemented with flip chip technology which may be used to mount components directly to circuit boards without the additional clearances typically needed for wire bond connections. Flip chip connections may be used, as an example, to reduce the overall size of infrared imaging module  100  for use in compact small form factor applications. For example, in one embodiment, processing module  160  may be mounted to circuit board  170  using flip chip connections. For example, infrared imaging module  100  may be implemented with such flip chip configurations. 
     In various embodiments, infrared imaging module  100  and/or associated components may be implemented in accordance with various techniques (e.g., wafer level packaging techniques) as set forth in U.S. patent application Ser. No. 12/844,124 filed Jul. 27, 2010, and U.S. Provisional Patent Application No. 61/469,651 filed Mar. 30, 2011, which are incorporated herein by reference in their entirety. Furthermore, in accordance with one or more embodiments, infrared imaging module  100  and/or associated components may be implemented, calibrated, tested, and/or used in accordance with various techniques, such as for example as set forth in U.S. Pat. No. 7,470,902 issued Dec. 30, 2008, U.S. Pat. No. 6,028,309 issued Feb. 22, 2000, U.S. Pat. No. 6,812,465 issued Nov. 2, 2004, U.S. Pat. No. 7,034,301 issued Apr. 25, 2006, U.S. Pat. No. 7,679,048 issued Mar. 16, 2010, U.S. Pat. No. 7,470,904 issued Dec. 30, 2008, U.S. patent application Ser. No. 12/202,880 filed Sep. 2, 2008, and U.S. patent application Ser. No. 12/202,896 filed Sep. 2, 2008, which are incorporated herein by reference in their entirety. 
     As discussed, in some embodiments, host device  102  may include other components  198  such as a non-thermal camera (e.g., visible light camera). The non-thermal camera may be a small form factor imaging module or imaging device, and may be implemented in a similar manner as various embodiments of infrared imaging module  100  disclosed herein, but with one or more sensors responsive to radiation in the non-thermal spectrum (e.g., radiation in visible light wavelengths, ultraviolet wavelengths, or other non-thermal wavelengths). For example, in some embodiments, the non-thermal camera may be implemented with a charge-coupled device (CCD) sensor, an electron multiplying CCD (EMCCD) sensor, a complementary metal-oxide-semiconductor (CMOS) sensor, a scientific CMOS (sCMOS) sensor, or other sensors. 
     In some embodiments, the non-thermal camera may be co-located with infrared imaging module  100  and oriented such that a field-of-view (FOV) of the non-thermal camera at least partially overlaps a FOV of infrared imaging module  100 . In one example, infrared imaging module  100  and the non-thermal camera may be implemented as a dual sensor module sharing a common substrate according to various techniques described in U.S. Provisional Patent Application No. 61/748,018 incorporated by reference herein. 
     For embodiments of host device  102  having such a non-thermal light camera, various components (e.g., processor  195 , processing module  160 , and/or other processing component) may be configured to superimpose, fuse, blend, or otherwise combine infrared images (e.g., including thermal images) captured by infrared imaging module  100  and non-thermal images (e.g., including visible light images) captured by the non-thermal camera, in accordance with various techniques disclosed in, for example, U.S. patent application Ser. No. 61/473,207, 12/766,739, 13/105,765, or 13/437,645, or International Patent Application No. PCT/EP2011/056432, all incorporated by reference herein. 
     Referring again to  FIG. 1 , in various embodiments, host device  102  may include shutter  105 . In this regard, shutter  105  may be selectively positioned over socket  104  (e.g., as identified by arrows  103 ) while infrared imaging module  100  is installed therein. In this regard, shutter  105  may be used, for example, to protect infrared imaging module  100  when not in use. Shutter  105  may also be used as a temperature reference as part of a calibration process (e.g., a NUC process or other calibration processes) for infrared imaging module  100  as would be understood by one skilled in the art. 
     In various embodiments, shutter  105  may be made from various materials such as, for example, polymers, glass, aluminum (e.g., painted or anodized) or other materials. In various embodiments, shutter  105  may include one or more coatings to selectively filter electromagnetic radiation and/or adjust various optical properties of shutter  105  (e.g., a uniform blackbody coating or a reflective gold coating). 
     In another embodiment, shutter  105  may be fixed in place to protect infrared imaging module  100  at all times. In this case, shutter  105  or a portion of shutter  105  may be made from appropriate materials (e.g., polymers or infrared transmitting materials such as silicon, germanium, zinc selenide, or chalcogenide glasses) that do not substantially filter desired infrared wavelengths. In another embodiment, a shutter may be implemented as part of infrared imaging module  100  (e.g., within or as part of a lens barrel or other components of infrared imaging module  100 ), as would be understood by one skilled in the art. 
     Alternatively, in another embodiment, a shutter (e.g., shutter  105  or other type of external or internal shutter) need not be provided, but rather a NUC process or other type of calibration may be performed using shutterless techniques. In another embodiment, a NUC process or other type of calibration using shutterless techniques may be performed in combination with shutter-based techniques. 
     Infrared imaging module  100  and host device  102  may be implemented in accordance with any of the various techniques set forth in U.S. Provisional Patent Application No. 61/495,873 filed Jun. 10, 2011, U.S. Provisional Patent Application No. 61/495,879 filed Jun. 10, 2011, and U.S. Provisional Patent Application No. 61/495,888 filed Jun. 10, 2011, which are incorporated herein by reference in their entirety. 
     In various embodiments, the components of host device  102  and/or infrared imaging module  100  may be implemented as a local or distributed system with components in communication with each other over wired and/or wireless networks. Accordingly, the various operations identified in this disclosure may be performed by local and/or remote components as may be desired in particular implementations. 
       FIG. 5  illustrates a flow diagram of various operations to determine NUC terms in accordance with an embodiment of the disclosure. In some embodiments, the operations of  FIG. 5  may be performed by processing module  160  or processor  195  (both also generally referred to as a processor) operating on image frames captured by infrared sensors  132 . 
     In block  505 , infrared sensors  132  begin capturing image frames of a scene. Typically, the scene will be the real world environment in which host device  102  is currently located. In this regard, shutter  105  (if optionally provided) may be opened to permit infrared imaging module to receive infrared radiation from the scene. Infrared sensors  132  may continue capturing image frames during all operations shown in  FIG. 5 . In this regard, the continuously captured image frames may be used for various operations as further discussed. In one embodiment, the captured image frames may be temporally filtered (e.g., in accordance with the process of block  826  further described herein with regard to  FIG. 8 ) and be processed by other terms (e.g., factory gain terms  812 , factory offset terms  816 , previously determined NUC terms  817 , column FPN terms  820 , and row FPN terms  824  as further described herein with regard to  FIG. 8 ) before they are used in the operations shown in  FIG. 5 . 
     In block  510 , a NUC process initiating event is detected. In one embodiment, the NUC process may be initiated in response to physical movement of host device  102 . Such movement may be detected, for example, by motion sensors  194  which may be polled by a processor. In one example, a user may move host device  102  in a particular manner, such as by intentionally waving host device  102  back and forth in an “erase” or “swipe” movement. In this regard, the user may move host device  102  in accordance with a predetermined speed and direction (velocity), such as in an up and down, side to side, or other pattern to initiate the NUC process. In this example, the use of such movements may permit the user to intuitively operate host device  102  to simulate the “erasing” of noise in captured image frames. 
     In another example, a NUC process may be initiated by host device  102  if motion exceeding a threshold value is detected (e.g., motion greater than expected for ordinary use). It is contemplated that any desired type of spatial translation of host device  102  may be used to initiate the NUC process. 
     In yet another example, a NUC process may be initiated by host device  102  if a minimum time has elapsed since a previously performed NUC process. In a further example, a NUC process may be initiated by host device  102  if infrared imaging module  100  has experienced a minimum temperature change since a previously performed NUC process. In a still further example, a NUC process may be continuously initiated and repeated. 
     In block  515 , after a NUC process initiating event is detected, it is determined whether the NUC process should actually be performed. In this regard, the NUC process may be selectively initiated based on whether one or more additional conditions are met. For example, in one embodiment, the NUC process may not be performed unless a minimum time has elapsed since a previously performed NUC process. In another embodiment, the NUC process may not be performed unless infrared imaging module  100  has experienced a minimum temperature change since a previously performed NUC process. Other criteria or conditions may be used in other embodiments. If appropriate criteria or conditions have been met, then the flow diagram continues to block  520 . Otherwise, the flow diagram returns to block  505 . 
     In the NUC process, blurred image frames may be used to determine NUC terms which may be applied to captured image frames to correct for FPN. As discussed, in one embodiment, the blurred image frames may be obtained by accumulating multiple image frames of a moving scene (e.g., captured while the scene and/or the thermal imager is in motion). In another embodiment, the blurred image frames may be obtained by defocusing an optical element or other component of the thermal imager. 
     Accordingly, in block  520  a choice of either approach is provided. If the motion-based approach is used, then the flow diagram continues to block  525 . If the defocus-based approach is used, then the flow diagram continues to block  530 . 
     Referring now to the motion-based approach, in block  525  motion is detected. For example, in one embodiment, motion may be detected based on the image frames captured by infrared sensors  132 . In this regard, an appropriate motion detection process (e.g., an image registration process, a frame-to-frame difference calculation, or other appropriate process) may be applied to captured image frames to determine whether motion is present (e.g., whether static or moving image frames have been captured). For example, in one embodiment, it can be determined whether pixels or regions around the pixels of consecutive image frames have changed more than a user defined amount (e.g., a percentage and/or threshold value). If at least a given percentage of pixels have changed by at least the user defined amount, then motion will be detected with sufficient certainty to proceed to block  535 . 
     In another embodiment, motion may be determined on a per pixel basis, wherein only pixels that exhibit significant changes are accumulated to provide the blurred image frame. For example, counters may be provided for each pixel and used to ensure that the same number of pixel values are accumulated for each pixel, or used to average the pixel values based on the number of pixel values actually accumulated for each pixel. Other types of image-based motion detection may be performed such as performing a Radon transform. 
     In another embodiment, motion may be detected based on data provided by motion sensors  194 . In one embodiment, such motion detection may include detecting whether host device  102  is moving along a relatively straight trajectory through space. For example, if host device  102  is moving along a relatively straight trajectory, then it is possible that certain objects appearing in the imaged scene may not be sufficiently blurred (e.g., objects in the scene that may be aligned with or moving substantially parallel to the straight trajectory). Thus, in such an embodiment, the motion detected by motion sensors  194  may be conditioned on host device  102  exhibiting, or not exhibiting, particular trajectories. 
     In yet another embodiment, both a motion detection process and motion sensors  194  may be used. Thus, using any of these various embodiments, a determination can be made as to whether or not each image frame was captured while at least a portion of the scene and host device  102  were in motion relative to each other (e.g., which may be caused by host device  102  moving relative to the scene, at least a portion of the scene moving relative to host device  102 , or both). 
     It is expected that the image frames for which motion was detected may exhibit some secondary blurring of the captured scene (e.g., blurred thermal image data associated with the scene) due to the thermal time constants of infrared sensors  132  (e.g., microbolometer thermal time constants) interacting with the scene movement. 
     In block  535 , image frames for which motion was detected are accumulated. For example, if motion is detected for a continuous series of image frames, then the image frames of the series may be accumulated. As another example, if motion is detected for only some image frames, then the non-moving image frames may be skipped and not included in the accumulation. Thus, a continuous or discontinuous set of image frames may be selected to be accumulated based on the detected motion. 
     In block  540 , the accumulated image frames are averaged to provide a blurred image frame. Because the accumulated image frames were captured during motion, it is expected that actual scene information will vary between the image frames and thus cause the scene information to be further blurred in the resulting blurred image frame (block  545 ). 
     In contrast, FPN (e.g., caused by one or more components of infrared imaging module  100 ) will remain fixed over at least short periods of time and over at least limited changes in scene irradiance during motion. As a result, image frames captured in close proximity in time and space during motion will suffer from identical or at least very similar FPN. Thus, although scene information may change in consecutive image frames, the FPN will stay essentially constant. By averaging, multiple image frames captured during motion will blur the scene information, but will not blur the FPN. As a result, FPN will remain more clearly defined in the blurred image frame provided in block  545  than the scene information. 
     In one embodiment, 32 or more image frames are accumulated and averaged in blocks  535  and  540 . However, any desired number of image frames may be used in other embodiments, but with generally decreasing correction accuracy as frame count is decreased. 
     Referring now to the defocus-based approach, in block  530 , a defocus operation may be performed to intentionally defocus the image frames captured by infrared sensors  132 . For example, in one embodiment, one or more actuators  199  may be used to adjust, move, or otherwise translate optical element  180 , infrared sensor assembly  128 , and/or other components of infrared imaging module  100  to cause infrared sensors  132  to capture a blurred (e.g., unfocused) image frame of the scene. Other non-actuator based techniques are also contemplated for intentionally defocusing infrared image frames such as, for example, manual (e.g., user-initiated) defocusing. 
     Although the scene may appear blurred in the image frame, FPN (e.g., caused by one or more components of infrared imaging module  100 ) will remain unaffected by the defocusing operation. As a result, a blurred image frame of the scene will be provided (block  545 ) with FPN remaining more clearly defined in the blurred image than the scene information. 
     In the above discussion, the defocus-based approach has been described with regard to a single captured image frame. In another embodiment, the defocus-based approach may include accumulating multiple image frames while the infrared imaging module  100  has been defocused and averaging the defocused image frames to remove the effects of temporal noise and provide a blurred image frame in block  545 . 
     Thus, it will be appreciated that a blurred image frame may be provided in block  545  by either the motion-based approach or the defocus-based approach. Because much of the scene information will be blurred by either motion, defocusing, or both, the blurred image frame may be effectively considered a low pass filtered version of the original captured image frames with respect to scene information. 
     In block  550 , the blurred image frame is processed to determine updated row and column FPN terms (e.g., if row and column FPN terms have not been previously determined then the updated row and column FPN terms may be new row and column FPN terms in the first iteration of block  550 ). As used in this disclosure, the terms row and column may be used interchangeably depending on the orientation of infrared sensors  132  and/or other components of infrared imaging module  100 . 
     In one embodiment, block  550  includes determining a spatial FPN correction term for each row of the blurred image frame (e.g., each row may have its own spatial FPN correction term), and also determining a spatial FPN correction term for each column of the blurred image frame (e.g., each column may have its own spatial FPN correction term). Such processing may be used to reduce the spatial and slowly varying (1/f) row and column FPN inherent in thermal imagers caused by, for example, 1/f noise characteristics of amplifiers in ROIC  402  which may manifest as vertical and horizontal stripes in image frames. 
     Advantageously, by determining spatial row and column FPN terms using the blurred image frame, there will be a reduced risk of vertical and horizontal objects in the actual imaged scene from being mistaken for row and column noise (e.g., real scene content will be blurred while FPN remains unblurred). 
     In one embodiment, row and column FPN terms may be determined by considering differences between neighboring pixels of the blurred image frame. For example,  FIG. 6  illustrates differences between neighboring pixels in accordance with an embodiment of the disclosure. Specifically, in  FIG. 6  a pixel  610  is compared to its 8 nearest horizontal neighbors: d0-d3 on one side and d4-d7 on the other side. Differences between the neighbor pixels can be averaged to obtain an estimate of the offset error of the illustrated group of pixels. An offset error may be calculated for each pixel in a row or column and the average result may be used to correct the entire row or column. 
     To prevent real scene data from being interpreted as noise, upper and lower threshold values may be used (thPix and −thPix). Pixel values falling outside these threshold values (pixels d1 and d4 in this example) are not used to obtain the offset error. In addition, the maximum amount of row and column FPN correction may be limited by these threshold values. 
     Further techniques for performing spatial row and column FPN correction processing are set forth in U.S. patent application Ser. No. 12/396,340 filed Mar. 2, 2009 which is incorporated herein by reference in its entirety. 
     Referring again to  FIG. 5 , the updated row and column FPN terms determined in block  550  are stored (block  552 ) and applied (block  555 ) to the blurred image frame provided in block  545 . After these terms are applied, some of the spatial row and column FPN in the blurred image frame may be reduced. However, because such terms are applied generally to rows and columns, additional FPN may remain such as spatially uncorrelated FPN associated with pixel to pixel drift or other causes. Neighborhoods of spatially correlated FPN may also remain which may not be directly associated with individual rows and columns. Accordingly, further processing may be performed as discussed below to determine NUC terms. 
     In block  560 , local contrast values (e.g., edges or absolute values of gradients between adjacent or small groups of pixels) in the blurred image frame are determined. If scene information in the blurred image frame includes contrasting areas that have not been significantly blurred (e.g., high contrast edges in the original scene data), then such features may be identified by a contrast determination process in block  560 . 
     For example, local contrast values in the blurred image frame may be calculated, or any other desired type of edge detection process may be applied to identify certain pixels in the blurred image as being part of an area of local contrast. Pixels that are marked in this manner may be considered as containing excessive high spatial frequency scene information that would be interpreted as FPN (e.g., such regions may correspond to portions of the scene that have not been sufficiently blurred). As such, these pixels may be excluded from being used in the further determination of NUC terms. In one embodiment, such contrast detection processing may rely on a threshold that is higher than the expected contrast value associated with FPN (e.g., pixels exhibiting a contrast value higher than the threshold may be considered to be scene information, and those lower than the threshold may be considered to be exhibiting FPN). 
     In one embodiment, the contrast determination of block  560  may be performed on the blurred image frame after row and column FPN terms have been applied to the blurred image frame (e.g., as shown in  FIG. 5 ). In another embodiment, block  560  may be performed prior to block  550  to determine contrast before row and column FPN terms are determined (e.g., to prevent scene based contrast from contributing to the determination of such terms). 
     Following block  560 , it is expected that any high spatial frequency content remaining in the blurred image frame may be generally attributed to spatially uncorrelated FPN. In this regard, following block  560 , much of the other noise or actual desired scene based information has been removed or excluded from the blurred image frame due to: intentional blurring of the image frame (e.g., by motion or defocusing in blocks  520  through  545 ), application of row and column FPN terms (block  555 ), and contrast determination (block  560 ). 
     Thus, it can be expected that following block  560 , any remaining high spatial frequency content (e.g., exhibited as areas of contrast or differences in the blurred image frame) may be attributed to spatially uncorrelated FPN. Accordingly, in block  565 , the blurred image frame is high pass filtered. In one embodiment, this may include applying a high pass filter to extract the high spatial frequency content from the blurred image frame. In another embodiment, this may include applying a low pass filter to the blurred image frame and taking a difference between the low pass filtered image frame and the unfiltered blurred image frame to obtain the high spatial frequency content. In accordance with various embodiments of the present disclosure, a high pass filter may be implemented by calculating a mean difference between a sensor signal (e.g., a pixel value) and its neighbors. 
     In block  570 , a flat field correction process is performed on the high pass filtered blurred image frame to determine updated NUC terms (e.g., if a NUC process has not previously been performed then the updated NUC terms may be new NUC terms in the first iteration of block  570 ). 
     For example,  FIG. 7  illustrates a flat field correction technique  700  in accordance with an embodiment of the disclosure. In  FIG. 7 , a NUC term may be determined for each pixel  710  of the blurred image frame using the values of its neighboring pixels  712  to  726 . For each pixel  710 , several gradients may be determined based on the absolute difference between the values of various adjacent pixels. For example, absolute value differences may be determined between: pixels  712  and  714  (a left to right diagonal gradient), pixels  716  and  718  (a top to bottom vertical gradient), pixels  720  and  722  (a right to left diagonal gradient), and pixels  724  and  726  (a left to right horizontal gradient). 
     These absolute differences may be summed to provide a summed gradient for pixel  710 . A weight value may be determined for pixel  710  that is inversely proportional to the summed gradient. This process may be performed for all pixels  710  of the blurred image frame until a weight value is provided for each pixel  710 . For areas with low gradients (e.g., areas that are blurry or have low contrast), the weight value will be close to one. Conversely, for areas with high gradients, the weight value will be zero or close to zero. The update to the NUC term as estimated by the high pass filter is multiplied with the weight value. 
     In one embodiment, the risk of introducing scene information into the NUC terms can be further reduced by applying some amount of temporal damping to the NUC term determination process. For example, a temporal damping factor λ between 0 and 1 may be chosen such that the new NUC term (NUC NEW ) stored is a weighted average of the old NUC term (NUC OLD ) and the estimated updated NUC term (NUC UPDATE ). In one embodiment, this can be expressed as NUC NEW =λ·NUC OLD +(1−λ)·(NUC OLD +NUC UPDATE ). 
     Although the determination of NUC terms has been described with regard to gradients, local contrast values may be used instead where appropriate. Other techniques may also be used such as, for example, standard deviation calculations. Other types flat field correction processes may be performed to determine NUC terms including, for example, various processes identified in U.S. Pat. No. 6,028,309 issued Feb. 22, 2000, U.S. Pat. No. 6,812,465 issued Nov. 2, 2004, and U.S. patent application Ser. No. 12/114,865 filed May 5, 2008, which are incorporated herein by reference in their entirety. 
     Referring again to  FIG. 5 , block  570  may include additional processing of the NUC terms. For example, in one embodiment, to preserve the scene signal mean, the sum of all NUC terms may be normalized to zero by subtracting the NUC term mean from each NUC term. Also in block  570 , to avoid row and column noise from affecting the NUC terms, the mean value of each row and column may be subtracted from the NUC terms for each row and column. As a result, row and column FPN filters using the row and column FPN terms determined in block  550  may be better able to filter out row and column noise in further iterations (e.g., as further shown in  FIG. 8 ) after the NUC terms are applied to captured images (e.g., in block  580  further discussed herein). In this regard, the row and column FPN filters may in general use more data to calculate the per row and per column offset coefficients (e.g., row and column FPN terms) and may thus provide a more robust alternative for reducing spatially correlated FPN than the NUC terms which are based on high pass filtering to capture spatially uncorrelated noise. 
     In blocks  571 - 573 , additional high pass filtering and further determinations of updated NUC terms may be optionally performed to remove spatially correlated FPN with lower spatial frequency than previously removed by row and column FPN terms. In this regard, some variability in infrared sensors  132  or other components of infrared imaging module  100  may result in spatially correlated FPN noise that cannot be easily modeled as row or column noise. Such spatially correlated FPN may include, for example, window defects on a sensor package or a cluster of infrared sensors  132  that respond differently to irradiance than neighboring infrared sensors  132 . In one embodiment, such spatially correlated FPN may be mitigated with an offset correction. If the amount of such spatially correlated FPN is significant, then the noise may also be detectable in the blurred image frame. Since this type of noise may affect a neighborhood of pixels, a high pass filter with a small kernel may not detect the FPN in the neighborhood (e.g., all values used in high pass filter may be taken from the neighborhood of affected pixels and thus may be affected by the same offset error). For example, if the high pass filtering of block  565  is performed with a small kernel (e.g., considering only immediately adjacent pixels that fall within a neighborhood of pixels affected by spatially correlated FPN), then broadly distributed spatially correlated FPN may not be detected. 
     For example,  FIG. 11  illustrates spatially correlated FPN in a neighborhood of pixels in accordance with an embodiment of the disclosure. As shown in a sample image frame  1100 , a neighborhood of pixels  1110  may exhibit spatially correlated FPN that is not precisely correlated to individual rows and columns and is distributed over a neighborhood of several pixels (e.g., a neighborhood of approximately 4 by 4 pixels in this example). Sample image frame  1100  also includes a set of pixels  1120  exhibiting substantially uniform response that are not used in filtering calculations, and a set of pixels  1130  that are used to estimate a low pass value for the neighborhood of pixels  1110 . In one embodiment, pixels  1130  may be a number of pixels divisible by two in order to facilitate efficient hardware or software calculations. 
     Referring again to  FIG. 5 , in blocks  571 - 573 , additional high pass filtering and further determinations of updated NUC terms may be optionally performed to remove spatially correlated FPN such as exhibited by pixels  1110 . In block  571 , the updated NUC terms determined in block  570  are applied to the blurred image frame. Thus, at this time, the blurred image frame will have been initially corrected for spatially correlated FPN (e.g., by application of the updated row and column FPN terms in block  555 ), and also initially corrected for spatially uncorrelated FPN (e.g., by application of the updated NUC terms applied in block  571 ). 
     In block  572 , a further high pass filter is applied with a larger kernel than was used in block  565 , and further updated NUC terms may be determined in block  573 . For example, to detect the spatially correlated FPN present in pixels  1110 , the high pass filter applied in block  572  may include data from a sufficiently large enough neighborhood of pixels such that differences can be determined between unaffected pixels (e.g., pixels  1120 ) and affected pixels (e.g., pixels  1110 ). For example, a low pass filter with a large kernel can be used (e.g., an N by N kernel that is much greater than 3 by 3 pixels) and the results may be subtracted to perform appropriate high pass filtering. 
     In one embodiment, for computational efficiency, a sparse kernel may be used such that only a small number of neighboring pixels inside an N by N neighborhood are used. For any given high pass filter operation using distant neighbors (e.g., a large kernel), there is a risk of modeling actual (potentially blurred) scene information as spatially correlated FPN. Accordingly, in one embodiment, the temporal damping factor λ may be set close to 1 for updated NUC terms determined in block  573 . 
     In various embodiments, blocks  571 - 573  may be repeated (e.g., cascaded) to iteratively perform high pass filtering with increasing kernel sizes to provide further updated NUC terms further correct for spatially correlated FPN of desired neighborhood sizes. In one embodiment, the decision to perform such iterations may be determined by whether spatially correlated FPN has actually been removed by the updated NUC terms of the previous performance of blocks  571 - 573 . 
     After blocks  571 - 573  are finished, a decision is made regarding whether to apply the updated NUC terms to captured image frames (block  574 ). For example, if an average of the absolute value of the NUC terms for the entire image frame is less than a minimum threshold value, or greater than a maximum threshold value, the NUC terms may be deemed spurious or unlikely to provide meaningful correction. Alternatively, thresholding criteria may be applied to individual pixels to determine which pixels receive updated NUC terms. In one embodiment, the threshold values may correspond to differences between the newly calculated NUC terms and previously calculated NUC terms. In another embodiment, the threshold values may be independent of previously calculated NUC terms. Other tests may be applied (e.g., spatial correlation tests) to determine whether the NUC terms should be applied. 
     If the NUC terms are deemed spurious or unlikely to provide meaningful correction, then the flow diagram returns to block  505 . Otherwise, the newly determined NUC terms are stored (block  575 ) to replace previous NUC terms (e.g., determined by a previously performed iteration of  FIG. 5 ) and applied (block  580 ) to captured image frames. 
       FIG. 8  illustrates various image processing techniques of  FIG. 5  and other operations applied in an image processing pipeline  800  in accordance with an embodiment of the disclosure. In this regard, pipeline  800  identifies various operations of  FIG. 5  in the context of an overall iterative image processing scheme for correcting image frames provided by infrared imaging module  100 . In some embodiments, pipeline  800  may be provided by processing module  160  or processor  195  (both also generally referred to as a processor) operating on image frames captured by infrared sensors  132 . 
     Image frames captured by infrared sensors  132  may be provided to a frame averager  804  that integrates multiple image frames to provide image frames  802  with an improved signal to noise ratio. Frame averager  804  may be effectively provided by infrared sensors  132 , ROIC  402 , and other components of infrared sensor assembly  128  that are implemented to support high image capture rates. For example, in one embodiment, infrared sensor assembly  128  may capture infrared image frames at a frame rate of 240 Hz (e.g., 240 images per second). In this embodiment, such a high frame rate may be implemented, for example, by operating infrared sensor assembly  128  at relatively low voltages (e.g., compatible with mobile telephone voltages) and by using a relatively small array of infrared sensors  132  (e.g., an array of 64 by 64 infrared sensors in one embodiment). 
     In one embodiment, such infrared image frames may be provided from infrared sensor assembly  128  to processing module  160  at a high frame rate (e.g., 240 Hz or other frame rates). In another embodiment, infrared sensor assembly  128  may integrate over longer time periods, or multiple time periods, to provide integrated (e.g., averaged) infrared image frames to processing module  160  at a lower frame rate (e.g., 30 Hz, 9 Hz, or other frame rates). Further information regarding implementations that may be used to provide high image capture rates may be found in U.S. Provisional Patent Application No. 61/495,879 previously referenced herein. 
     Image frames  802  proceed through pipeline  800  where they are adjusted by various terms, temporally filtered, used to determine the various adjustment terms, and gain compensated. 
     In blocks  810  and  814 , factory gain terms  812  and factory offset terms  816  are applied to image frames  802  to compensate for gain and offset differences, respectively, between the various infrared sensors  132  and/or other components of infrared imaging module  100  determined during manufacturing and testing. 
     In block  580 , NUC terms  817  are applied to image frames  802  to correct for FPN as discussed. In one embodiment, if NUC terms  817  have not yet been determined (e.g., before a NUC process has been initiated), then block  580  may not be performed or initialization values may be used for NUC terms  817  that result in no alteration to the image data (e.g., offsets for every pixel would be equal to zero). 
     In blocks  818  and  822 , column FPN terms  820  and row FPN terms  824 , respectively, are applied to image frames  802 . Column FPN terms  820  and row FPN terms  824  may be determined in accordance with block  550  as discussed. In one embodiment, if the column FPN terms  820  and row FPN terms  824  have not yet been determined (e.g., before a NUC process has been initiated), then blocks  818  and  822  may not be performed or initialization values may be used for the column FPN terms  820  and row FPN terms  824  that result in no alteration to the image data (e.g., offsets for every pixel would be equal to zero). 
     In block  826 , temporal filtering is performed on image frames  802  in accordance with a temporal noise reduction (TNR) process.  FIG. 9  illustrates a TNR process in accordance with an embodiment of the disclosure. In  FIG. 9 , a presently received image frame  802   a  and a previously temporally filtered image frame  802   b  are processed to determine a new temporally filtered image frame  802   e . Image frames  802   a  and  802   b  include local neighborhoods of pixels  803   a  and  803   b  centered around pixels  805   a  and  805   b , respectively. Neighborhoods  803   a  and  803   b  correspond to the same locations within image frames  802   a  and  802   b  and are subsets of the total pixels in image frames  802   a  and  802   b . In the illustrated embodiment, neighborhoods  803   a  and  803   b  include areas of 5 by 5 pixels. Other neighborhood sizes may be used in other embodiments. 
     Differences between corresponding pixels of neighborhoods  803   a  and  803   b  are determined and averaged to provide an averaged delta value  805   c  for the location corresponding to pixels  805   a  and  805   b . Averaged delta value  805   c  may be used to determine weight values in block  807  to be applied to pixels  805   a  and  805   b  of image frames  802   a  and  802   b.    
     In one embodiment, as shown in graph  809 , the weight values determined in block  807  may be inversely proportional to averaged delta value  805   c  such that weight values drop rapidly towards zero when there are large differences between neighborhoods  803   a  and  803   b . In this regard, large differences between neighborhoods  803   a  and  803   b  may indicate that changes have occurred within the scene (e.g., due to motion) and pixels  802   a  and  802   b  may be appropriately weighted, in one embodiment, to avoid introducing blur across frame-to-frame scene changes. Other associations between weight values and averaged delta value  805   c  may be used in various embodiments. 
     The weight values determined in block  807  may be applied to pixels  805   a  and  805   b  to determine a value for corresponding pixel  805   e  of image frame  802   e  (block  811 ). In this regard, pixel  805   e  may have a value that is a weighted average (or other combination) of pixels  805   a  and  805   b , depending on averaged delta value  805   c  and the weight values determined in block  807 . 
     For example, pixel  805   e  of temporally filtered image frame  802   e  may be a weighted sum of pixels  805   a  and  805   b  of image frames  802   a  and  802   b . If the average difference between pixels  805   a  and  805   b  is due to noise, then it may be expected that the average change between neighborhoods  805   a  and  805   b  will be close to zero (e.g., corresponding to the average of uncorrelated changes). Under such circumstances, it may be expected that the sum of the differences between neighborhoods  805   a  and  805   b  will be close to zero. In this case, pixel  805   a  of image frame  802   a  may both be appropriately weighted so as to contribute to the value of pixel  805   e.    
     However, if the sum of such differences is not zero (e.g., even differing from zero by a small amount in one embodiment), then the changes may be interpreted as being attributed to motion instead of noise. Thus, motion may be detected based on the average change exhibited by neighborhoods  805   a  and  805   b . Under these circumstances, pixel  805   a  of image frame  802   a  may be weighted heavily, while pixel  805   b  of image frame  802   b  may be weighted lightly. 
     Other embodiments are also contemplated. For example, although averaged delta value  805   c  has been described as being determined based on neighborhoods  805   a  and  805   b , in other embodiments averaged delta value  805   c  may be determined based on any desired criteria (e.g., based on individual pixels or other types of groups of sets of pixels). 
     In the above embodiments, image frame  802   a  has been described as a presently received image frame and image frame  802   b  has been described as a previously temporally filtered image frame. In another embodiment, image frames  802   a  and  802   b  may be first and second image frames captured by infrared imaging module  100  that have not been temporally filtered. 
       FIG. 10  illustrates further implementation details in relation to the TNR process of block  826 . As shown in  FIG. 10 , image frames  802   a  and  802   b  may be read into line buffers  1010   a  and  1010   b , respectively, and image frame  802   b  (e.g., the previous image frame) may be stored in a frame buffer  1020  before being read into line buffer  1010   b . In one embodiment, line buffers  1010   a - b  and frame buffer  1020  may be implemented by a block of random access memory (RAM) provided by any appropriate component of infrared imaging module  100  and/or host device  102 . 
     Referring again to  FIG. 8 , image frame  802   e  may be passed to an automatic gain compensation block  828  for further processing to provide a result image frame  830  that may be used by host device  102  as desired. 
       FIG. 8  further illustrates various operations that may be performed to determine row and column FPN terms and NUC terms as discussed. In one embodiment, these operations may use image frames  802   e  as shown in  FIG. 8 . Because image frames  802   e  have already been temporally filtered, at least some temporal noise may be removed and thus will not inadvertently affect the determination of row and column FPN terms  824  and  820  and NUC terms  817 . In another embodiment, non-temporally filtered image frames  802  may be used. 
     In  FIG. 8 , blocks  510 ,  515 , and  520  of  FIG. 5  are collectively represented together. As discussed, a NUC process may be selectively initiated and performed in response to various NUC process initiating events and based on various criteria or conditions. As also discussed, the NUC process may be performed in accordance with a motion-based approach (blocks  525 ,  535 , and  540 ) or a defocus-based approach (block  530 ) to provide a blurred image frame (block  545 ).  FIG. 8  further illustrates various additional blocks  550 ,  552 ,  555 ,  560 ,  565 ,  570 ,  571 ,  572 ,  573 , and  575  previously discussed with regard to  FIG. 5 . 
     As shown in  FIG. 8 , row and column FPN terms  824  and  820  and NUC terms  817  may be determined and applied in an iterative fashion such that updated terms are determined using image frames  802  to which previous terms have already been applied. As a result, the overall process of  FIG. 8  may repeatedly update and apply such terms to continuously reduce the noise in image frames  830  to be used by host device  102 . 
     Referring again to  FIG. 10 , further implementation details are illustrated for various blocks of  FIGS. 5 and 8  in relation to pipeline  800 . For example, blocks  525 ,  535 , and  540  are shown as operating at the normal frame rate of image frames  802  received by pipeline  800 . In the embodiment shown in  FIG. 10 , the determination made in block  525  is represented as a decision diamond used to determine whether a given image frame  802  has sufficiently changed such that it may be considered an image frame that will enhance the blur if added to other image frames and is therefore accumulated (block  535  is represented by an arrow in this embodiment) and averaged (block  540 ). 
     Also in  FIG. 10 , the determination of column FPN terms  820  (block  550 ) is shown as operating at an update rate that in this example is 1/32 of the sensor frame rate (e.g., normal frame rate) due to the averaging performed in block  540 . Other update rates may be used in other embodiments. Although only column FPN terms  820  are identified in  FIG. 10 , row FPN terms  824  may be implemented in a similar fashion at the reduced frame rate. 
       FIG. 10  also illustrates further implementation details in relation to the NUC determination process of block  570 . In this regard, the blurred image frame may be read to a line buffer  1030  (e.g., implemented by a block of RAM provided by any appropriate component of infrared imaging module  100  and/or host device  102 ). The flat field correction technique  700  of  FIG. 7  may be performed on the blurred image frame. 
     In view of the present disclosure, it will be appreciated that techniques described herein may be used to remove various types of FPN (e.g., including very high amplitude FPN) such as spatially correlated row and column FPN and spatially uncorrelated FPN. 
     Other embodiments are also contemplated. For example, in one embodiment, the rate at which row and column FPN terms and/or NUC terms are updated can be inversely proportional to the estimated amount of blur in the blurred image frame and/or inversely proportional to the magnitude of local contrast values (e.g., determined in block  560 ). 
     In various embodiments, the described techniques may provide advantages over conventional shutter-based noise correction techniques. For example, by using a shutterless process, a shutter (e.g., such as shutter  105 ) need not be provided, thus permitting reductions in size, weight, cost, and mechanical complexity. Power and maximum voltage supplied to, or generated by, infrared imaging module  100  may also be reduced if a shutter does not need to be mechanically operated. Reliability will be improved by removing the shutter as a potential point of failure. A shutterless process also eliminates potential image interruption caused by the temporary blockage of the imaged scene by a shutter. 
     Also, by correcting for noise using intentionally blurred image frames captured from a real world scene (not a uniform scene provided by a shutter), noise correction may be performed on image frames that have irradiance levels similar to those of the actual scene desired to be imaged. This can improve the accuracy and effectiveness of noise correction terms determined in accordance with the various described techniques. 
     As discussed, in various embodiments, infrared imaging module  100  may be configured to operate at low voltage levels. In particular, infrared imaging module  100  may be implemented with circuitry configured to operate at low power and/or in accordance with other parameters that permit infrared imaging module  100  to be conveniently and effectively implemented in various types of host devices  102 , such as mobile devices and other devices. 
     For example,  FIG. 12  illustrates a block diagram of another implementation of infrared sensor assembly  128  including infrared sensors  132  and an LDO  1220  in accordance with an embodiment of the disclosure. As shown,  FIG. 12  also illustrates various components  1202 ,  1204 ,  1205 ,  1206 ,  1208 , and  1210  which may implemented in the same or similar manner as corresponding components previously described with regard to  FIG. 4 .  FIG. 12  also illustrates bias correction circuitry  1212  which may be used to adjust one or more bias voltages provided to infrared sensors  132  (e.g., to compensate for temperature changes, self-heating, and/or other factors). 
     In some embodiments, LDO  1220  may be provided as part of infrared sensor assembly  128  (e.g., on the same chip and/or wafer level package as the ROIC). For example, LDO  1220  may be provided as part of an FPA with infrared sensor assembly  128 . As discussed, such implementations may reduce power supply noise introduced to infrared sensor assembly  128  and thus provide an improved PSRR. In addition, by implementing the LDO with the ROIC, less die area may be consumed and fewer discrete die (or chips) are needed. 
     LDO  1220  receives an input voltage provided by a power source  1230  over a supply line  1232 . LDO  1220  provides an output voltage to various components of infrared sensor assembly  128  over supply lines  1222 . In this regard, LDO  1220  may provide substantially identical regulated output voltages to various components of infrared sensor assembly  128  in response to a single input voltage received from power source  1230 . 
     For example, in some embodiments, power source  1230  may provide an input voltage in a range of approximately 2.8 volts to approximately 11 volts (e.g., approximately 2.8 volts in one embodiment), and LDO  1220  may provide an output voltage in a range of approximately 1.5 volts to approximately 2.8 volts (e.g., approximately 2.5 volts in one embodiment). In this regard, LDO  1220  may be used to provide a consistent regulated output voltage, regardless of whether power source  1230  is implemented with a conventional voltage range of approximately 9 volts to approximately 11 volts, or a low voltage such as approximately 2.8 volts. As such, although various voltage ranges are provided for the input and output voltages, it is contemplated that the output voltage of LDO  1220  will remain fixed despite changes in the input voltage. 
     The implementation of LDO  1220  as part of infrared sensor assembly  128  provides various advantages over conventional power implementations for FPAs. For example, conventional FPAs typically rely on multiple power sources, each of which may be provided separately to the FPA, and separately distributed to the various components of the FPA. By regulating a single power source  1230  by LDO  1220 , appropriate voltages may be separately provided (e.g., to reduce possible noise) to all components of infrared sensor assembly  128  with reduced complexity. The use of LDO  1220  also allows infrared sensor assembly  128  to operate in a consistent manner, even if the input voltage from power source  1230  changes (e.g., if the input voltage increases or decreases as a result of charging or discharging a battery or other type of device used for power source  1230 ). 
     The various components of infrared sensor assembly  128  shown in  FIG. 12  may also be implemented to operate at lower voltages than conventional devices. For example, as discussed, LDO  1220  may be implemented to provide a low voltage (e.g., approximately 2.5 volts). This contrasts with the multiple higher voltages typically used to power conventional. FPAs, such as: approximately 3.3 volts to approximately 5 volts used to power digital circuitry; approximately 3.3 volts used to power analog circuitry; and approximately 9 volts to approximately 11 volts used to power loads. Also, in some embodiments, the use of LDO  1220  may reduce or eliminate the need for a separate negative reference voltage to be provided to infrared sensor assembly  128 . 
     Additional aspects of the low voltage operation of infrared sensor assembly  128  may be further understood with reference to  FIG. 13 .  FIG. 13  illustrates a circuit diagram of a portion of infrared sensor assembly  128  of  FIG. 12  in accordance with an embodiment of the disclosure. In particular,  FIG. 13  illustrates additional components of bias correction circuitry  1212  (e.g., components  1326 ,  1330 ,  1332 ,  1334 ,  1336 ,  1338 , and  1341 ) connected to LDO  1220  and infrared sensors  132 . For example, bias correction circuitry  1212  may be used to compensate for temperature-dependent changes in bias voltages in accordance with an embodiment of the present disclosure. The operation of such additional components may be further understood with reference to similar components identified in U.S. Pat. No. 7,679,048 issued Mar. 16, 2010 which is hereby incorporated by reference in its entirety. Infrared sensor assembly  128  may also be implemented in accordance with the various components identified in U.S. Pat. No. 6,812,465 issued Nov. 2, 2004 which is hereby incorporated by reference in its entirety. 
     In various embodiments, some or all of the bias correction circuitry  1212  may be implemented on a global array basis as shown in  FIG. 13  (e.g., used for all infrared sensors  132  collectively in an array). In other embodiments, some or all of the bias correction circuitry  1212  may be implemented an individual sensor basis (e.g., entirely or partially duplicated for each infrared sensor  132 ). In some embodiments, bias correction circuitry  1212  and other components of  FIG. 13  may be implemented as part of ROIC  1202 . 
     As shown in  FIG. 13 , LDO  1220  provides a load voltage Vload to bias correction circuitry  1212  along one of supply lines  1222 . As discussed, in some embodiments, Vload may be approximately 2.5 volts which contrasts with larger voltages of approximately 9 volts to approximately 11 volts that may be used as load voltages in conventional infrared imaging devices. 
     Based on Vload, bias correction circuitry  1212  provides a sensor bias voltage Vbolo at a node  1360 . Vbolo may be distributed to one or more infrared sensors  132  through appropriate switching circuitry  1370  (e.g., represented by broken lines in  FIG. 13 ). In some examples, switching circuitry  1370  may be implemented in accordance with appropriate components identified in U.S. Pat. Nos. 6,812,465 and 7,679,048 previously referenced herein. 
     Each infrared sensor  132  includes a node  1350  which receives Vbolo through switching circuitry  1370 , and another node  1352  which may be connected to ground, a substrate, and/or a negative reference voltage. In some embodiments, the voltage at node  1360  may be substantially the same as Vbolo provided at nodes  1350 . In other embodiments, the voltage at node  1360  may be adjusted to compensate for possible voltage drops associated with switching circuitry  1370  and/or other factors. 
     Vbolo may be implemented with lower voltages than are typically used for conventional infrared sensor biasing. In one embodiment, Vbolo may be in a range of approximately 0.2 volts to approximately 0.7 volts. In another embodiment, Vbolo may be in a range of approximately 0.4 volts to approximately 0.6 volts. In another embodiment, Vbolo may be approximately 0.5 volts. In contrast, conventional infrared sensors typically use bias voltages of approximately 1 volt. 
     The use of a lower bias voltage for infrared sensors  132  in accordance with the present disclosure permits infrared sensor assembly  128  to exhibit significantly reduced power consumption in comparison with conventional infrared imaging devices. In particular, the power consumption of each infrared sensor  132  is reduced by the square of the bias voltage. As a result, a reduction from, for example, 1.0 volt to 0.5 volts provides a significant reduction in power, especially when applied to many infrared sensors  132  in an infrared sensor array. This reduction in power may also result in reduced self-heating of infrared sensor assembly  128 . 
     In accordance with additional embodiments of the present disclosure, various techniques are provided for reducing the effects of noise in image frames provided by infrared imaging devices operating at low voltages. In this regard, when infrared sensor assembly  128  is operated with low voltages as described, noise, self-heating, and/or other phenomena may, if uncorrected, become more pronounced in image frames provided by infrared sensor assembly  128 . 
     For example, referring to  FIG. 13 , when LDO  1220  maintains Vload at a low voltage in the manner described herein, Vbolo will also be maintained at its corresponding low voltage and the relative size of its output signals may be reduced. As a result, noise, self-heating, and/or other phenomena may have a greater effect on the smaller output signals read out from infrared sensors  132 , resulting in variations (e.g., errors) in the output signals. If uncorrected, these variations may be exhibited as noise in the image frames. Moreover, although low voltage operation may reduce the overall amount of certain phenomena (e.g., self-heating), the smaller output signals may permit the remaining error sources (e.g., residual self-heating) to have a disproportionate effect on the output signals during low voltage operation. 
     To compensate for such phenomena, infrared sensor assembly  128 , infrared imaging module  100 , and/or host device  102  may be implemented with various array sizes, frame rates, and/or frame averaging techniques. For example, as discussed, a variety of different array sizes are contemplated for infrared sensors  132 . In some embodiments, infrared sensors  132  may be implemented with array sizes ranging from 32 by 32 to 160 by 120 infrared sensors  132 . Other example array sizes include 80 by 64, 80 by 60, 64 by 64, and 64 by 32. Any desired array size may be used. 
     Advantageously, when implemented with such relatively small array sizes, infrared sensor assembly  128  may provide image frames at relatively high frame rates without requiring significant changes to ROTC and related circuitry. For example, in some embodiments, frame rates may range from approximately 120 Hz to approximately 480 Hz. 
     In some embodiments, the array size and the frame rate may be scaled relative to each other (e.g., in an inversely proportional manner or otherwise) such that larger arrays are implemented with lower frame rates, and smaller arrays are implemented with higher frame rates. For example, in one embodiment, an array of 160 by 120 may provide a frame rate of approximately 120 Hz. In another embodiment, an array of 80 by 60 may provide a correspondingly higher frame rate of approximately 240 Hz. Other frame rates are also contemplated. 
     By scaling the array size and the frame rate relative to each other, the particular readout timing of rows and/or columns of the FPA may remain consistent, regardless of the actual FPA size or frame rate. In one embodiment, the readout timing may be approximately 63 microseconds per row or column. 
     As previously discussed with regard to  FIG. 8 , the image frames captured by infrared sensors  132  may be provided to a frame averager  804  that integrates multiple image frames to provide image frames  802  (e.g., processed image frames) with a lower frame rate (e.g., approximately 30 Hz, approximately 60 Hz, or other frame rates) and with an improved signal to noise ratio. In particular, by averaging the high frame rate image frames provided by a relatively small FPA, image noise attributable to low voltage operation may be effectively averaged out and/or substantially reduced in image frames  802 . Accordingly, infrared sensor assembly  128  may be operated at relatively low voltages provided by LDO  1220  as discussed without experiencing additional noise and related side effects in the resulting image frames  802  after processing by frame averager  804 . 
     Other embodiments are also contemplated. For example, although a single array of infrared sensors  132  is illustrated, it is contemplated that multiple such arrays may be used together to provide higher resolution image frames (e.g., a scene may be imaged across multiple such arrays). Such arrays may be provided in multiple infrared sensor assemblies  128  and/or provided in the same infrared sensor assembly  128 . Each such array may be operated at low voltages as described, and also may be provided with associated ROIC circuitry such that each array may still be operated at a relatively high frame rate. The high frame rate image frames provided by such arrays may be averaged by shared or dedicated frame averagers  804  to reduce and/or eliminate noise associated with low voltage operation. As a result, high resolution infrared images may be obtained while still operating at low voltages. 
     In various embodiments, infrared sensor assembly  128  may be implemented with appropriate dimensions to permit infrared imaging module  100  to be used with a small form factor socket  104 , such as a socket used for mobile devices. For example, in some embodiments, infrared sensor assembly  128  may be implemented with a chip size in a range of approximately 4.0 mm by approximately 4.0 mm to approximately 5.5 mm by approximately 5.5 mm (e.g., approximately 4.0 mm by approximately 5.5 mm in one example). Infrared sensor assembly  128  may be implemented with such sizes or other appropriate sizes to permit use with socket  104  implemented with various sizes such as: 8.5 mm by 8.5 mm, 8.5 mm by 5.9 mm, 6.0 mm by 6.0 mm, 5.5 mm by 5.5 mm, 4.5 mm by 4.5 mm, and/or other socket sizes such as, for example, those identified in Table 1 of U.S. Provisional Patent Application No. 61/495,873 previously referenced herein. 
     In various embodiments, infrared sensor assembly  128  may be implemented by an integrated circuit. Such an integrated circuit may be provided in a compact manner with a reduced number of layers and interconnections in comparison with conventional infrared imaging devices. In particular, a limited number of metal layers (e.g., no more than three in some embodiments) may be provided between active circuit components and infrared sensors  132  of infrared sensor assembly  128 . 
     For example,  FIG. 14  illustrates a cross-sectional view of a portion of infrared sensor assembly  128  in accordance with an embodiment of the disclosure. In particular,  FIG. 14  illustrates a cross-sectional view of infrared sensor assembly  128  taken through a single infrared sensor  132  of an FPA and showing various integrated circuit layers underneath. 
     Infrared sensor assembly  128  may be implemented with infrared sensors  132  disposed on top of various layers  1401 . Layers  1401  may be represented, for example, by substrate  140  of infrared sensor assembly  128  previously described herein. Layers  1401  include an epitaxial layer  1402 , active circuit components  1408 , insulating layers  1404  and  1406 A-D, and metal layers  1410 A-C. Vias  1460 A-D, additional layers, and/or additional components may be provided within layers  1401  as appropriate. 
     As shown in  FIG. 14 , active circuit components  1408  may be provided on and/or in epitaxial layer  1402  (e.g., a silicon layer). In some embodiments, active circuit components  1408  may be any of the components of ROICs  402 / 1202  such as, for example, bias generation and timing control circuitry  404 / 1204 , column amplifiers  405 / 1205 , column multiplexers  406 / 1206 , row multiplexers  408 / 1208 , output amplifiers  410 / 1210 , bias correction circuitry  1212 , LDO  1220 , switching circuitry  1370 , and/or various components as appropriate. 
     In  FIG. 14 , active circuit components  1408  are represented by metal-oxide-semiconductor field-effect transistors (MOSFETs)  1420  and  1440  which are provided only for purposes of example. In this regard, active circuit components  1408  may include many additional and/or other types of circuit components (e.g., distributed under other infrared sensors  132  and/or elsewhere in ROICs  402 / 1202  and/or other portions of infrared sensor assembly  128 ). For example, in some embodiments, many active circuit components  1408  may be provided substantially in a single tier of components (e.g., shown in  FIG. 14 ) which may be across infrared sensor assembly  128 . 
     Transistor  1420  is implemented as a PMOS transistor including source/drain regions  1422  and  1424 , a gate  1425  (e.g., including an oxide layer  1426  and a polysilicon layer  1428 ), a channel region  1430 , and an N-well  1432 . Transistor  1440  is implemented as an NMOS transistor including source/drain regions  1442  and  1444 , a gate  1445  (e.g., including an oxide layer  1446  and a polysilicon layer  1448 ), and a channel region  1450 . Other implementations of active circuit components  1408  are also contemplated. 
     Insulating layer  1404  is provided on epitaxial layer  1402  and may be implemented, for example, as a silicon layer or a silicon dioxide layer. Active circuit components  1408  may be provided on and/or in insulating layer  1404 . 
     Additional insulating layers  1406 A-D are provided above insulating layer  1404  and may be implemented, for example, as silicon layers and/or silicon dioxide layers. As shown, active circuit components  1408  may be provided on and/or in insulating layer  1406 A. 
     Metal layers  1410 A-C are disposed between the various insulating layers  1406 A-D. For example, in some embodiments, metal layer  1410 A may be disposed between insulating layers  1406 A and  1406 B, metal layer  1410 B may be disposed between insulating layers  1406 B and  1406 C, and metal layer  1410 C may be disposed between insulating layers  1406 C and  1406 D. 
     Infrared sensors  132  are disposed on top of insulating layer  1406 D. Active circuit components  1408 , metal layer  1410 A, metal layer  1410 B, metal layer  1410 C, and infrared sensors  132  are separated by corresponding ones of insulating layers  1406 A-D, and are interconnected by various vias  1460 A-D (e.g., metal connections) passing through insulating layers  14606 A-D. 
     For example, a set of vias  1460 A connect metal layer  1410 A with active circuit components  1408 , a set of vias  1460 B connect metal layer  1410 B with metal layer  1410 A, a set of vias  14600  connect metal layer  1410 C with metal layer  1410 B, and a set of vias  1460 D connect infrared sensor  132  with metal layer  1410 C. Although particular vias  1460 A-D are shown, greater or fewer numbers of vias may be used. For example, although vias  1460 A are illustrated as connecting metal layer  1410 A to various source/drain regions  1422 ,  1424 ,  1442 , and  1444  of active circuit components  1408 , additional vias may be provided to connect gates  1425  and  1445  to metal layer  1410 A (e.g., not present in the particular cross-section taken in  FIG. 14 ). 
     Although vias  1460 A-D are shown connecting adjacently stacked active circuit components  1408 , metal layers  1410 A-C, and infrared sensors  132 , additional vias may be provided to interconnect various portions of infrared sensor assembly  128  together. For example, in some embodiments, other vias may be provided to directly connect any of active circuit components  1408 , metal layers  1410 A-C, and/or infrared sensors  132  together without requiring other intermediate connections by other metal layers  1410 A-C or other vias  1460 A-D. 
     Signals may be routed (e.g., passed) between active circuit components  1408  and infrared sensors  132  through various connections provided by metal layers  1410 A-C and vias  1460 A-D (e.g., up and down the various layers  1401  generally in the directions identified by arrows  1403  and  1405 , respectively). Such signals (e.g., currents or voltages) may include, for example, bias signals (e.g., to bias infrared sensors  132  and/or various active circuit components  1408 ), signals corresponding to image frames captured by infrared sensors  132 , and/or other signals. 
     In some embodiments, metal layer  1410 A may be used to provide local connections between adjacent or nearby active circuit components  1408  to route signals therebetween. For example, as shown in  FIG. 14 , each of transistors  1420  and  1440  are connected to metal layer  1410 A through vias  1460 A. Metal layer  1410 A may be implemented with appropriate signal paths (e.g., not present in the particular cross-section taken in  FIG. 14 ) to connect together the various portions of metal layer  1410 A residing above transistors  1420  and  1440 . 
     In some embodiments, metal layer  1410 B may be used to provide regional connections between various active circuit components  1408 , such as blocks or groups of active circuit components  1408  that reside in different regions of infrared sensor assembly  128  (e.g., various active circuit components  1408  that are substantially horizontally disposed relative to each other substantially in a single tier). For example, metal layer  1410 B may be connected to different portions of metal layer  1410 A (e.g., through vias  1460 B) at different areas of infrared sensor assembly  128 . Signals may be routed from local active circuit components  1408  (e.g., transistors  1420  and/or  1440  in some embodiments) through vias  1460 A up to metal layer  1410 A, and through vias  1460 B up to metal layer  1410 B. Metal layer  1410 B may route such signals to a remote region of infrared sensor assembly  128 . In the remote region, the signals may be routed to remote active circuit components  1408  from metal layer  1410 B through vias  1460 E down to metal layer  1410 A, and through vias  1460 A down to the remote active circuit components  1408 . 
     In some embodiments, metal layer  1410 C may be used to provide regional connections between various active circuit components  1408 , such as blocks or groups of active circuit components  1408  that reside in different regions of infrared sensor assembly  128  (e.g., various active circuit components  1408  that are substantially horizontally disposed relative to each other substantially in a single tier and/or vertically disposed relative to each other in multiple tiers). For example, metal layer  1410 C may be connected to different portions of metal layer  1410 B (e.g., through vias  14600 ) at different areas of infrared sensor assembly  128 , and signals may be routed between metal layers  1410 B and  1410 C through vias  1460 C. 
     In some embodiments, metal layer  1410 C may be used to provide connections between infrared sensors  132  and other portions of infrared imaging module  128  (e.g., active circuit components  1408  and/or other portions). For example, infrared sensors  132  may be connected to different portions of metal layer  1410 C (e.g., through vias  1460 D) at different areas of infrared sensor assembly  128 , and signals may be routed between infrared sensors  132  and metal layer  1410 C through vias  1460 D. 
     Thus, metal layers  1410 A-C and vias  1460 A-D provide a flexible and compact interconnected network of conductive paths to route various signals between any desired combination of active circuit components  1408 , infrared sensors  132 , and/or other portions of infrared sensor assembly  128 . 
     As discussed, infrared imaging module  100  may be configured to operate at low voltage levels and may be implemented with circuitry configured to operate at low power and/or in accordance with other parameters that permit infrared imaging module  100  to be conveniently and effectively implemented in various types of host devices  102 , such as mobile devices and other devices. Implementing infrared sensor assembly  128  as an FPA with a maximum of only three metal layers (e.g., metal layers  1410 A,  1410 B, and  1410 C) between active circuit components  1408  and infrared sensors  132  provides these and various other advantages over conventional implementations. 
     For example, because signals may be passed between active circuit components  1408  and infrared sensors  132  through a maximum of three metal layers  1410 A-C and associated vias  1460 A-D, the overall length of circuit connections are reduced. In addition, by using a relatively small array of infrared sensors  132  running at low voltages, the effects of resistance exhibited by substantially horizontal connections (e.g., metal layers  1410 A-C) may be reduced. In this regard, with a small array of infrared sensors  132  running at low voltages, the currents sent substantially horizontally (e.g., through metal layers  1410 A-C) from the array to bond pads (e.g., bond pads  142 ) may be reduced. Due to this decrease in current, substantially horizontal signal paths may be implemented with larger resistances, and infrared sensor assembly  128  may be implemented with fewer numbers of metal layers (e.g., three metal layers  1410 A-C). This contrasts with conventional implementations where large numbers of metal layers may be stacked on top of each other and used to route current horizontally in order to reduce horizontal resistances. 
     Moreover, implementing infrared sensor assembly  128  as an FPA with a maximum of only three metal layers between active circuit components  1408  and infrared sensors  132  reduces the complexity of infrared sensor assembly  128  which reduces manufacturing costs and improves manufacturing yields. 
     Infrared sensor assembly  128  may be manufactured in accordance with various techniques. Although layers  1401  of infrared sensor assembly  128  are described herein as being manufactured according to various processes, other processes may be used as appropriate. 
       FIG. 15  illustrates a process of manufacturing infrared sensor assembly  128  in accordance with an embodiment of the disclosure. In operation  1510 , epitaxial layer  1402  is formed. In operation  1520 , active circuit components  1408  are formed (e.g., formed on and/or in epitaxial layer  1402  and/or insulating layers  1404  and  1406 A). For example, in various embodiments, one or more N-wells  1432  and/or P-wells may be formed in epitaxial layer, and various other structures (e.g., remaining portions of transistors  1420  and  1440 ) may be formed on top of epitaxial layer  1402 . Although several example structures are shown in  FIG. 14 , any integrated circuit components may be formed as desired. In some embodiments, insulating layers  1404  and/or  1406 A may be formed as part of operation  1520 . 
     In operation  1530 , insulating layers  1406 A-D, metal layers  1410 A-C, and vias  1460 A-D are formed. In some embodiments, insulating layer  1404  may also be formed as part of operation  1530 . In some embodiments, operation  1530  may be implemented as an iterative process as the various metal layers  1410 A-C and their associated insulating layers  1406 A-D and vias  1460 A-D are formed. For example, after insulating layer  1406 A, vias  1460 A, and metal layer  1410 A are formed, remaining sets of layers may be formed above them in an iterative process. Thereafter, in operation  1540 , infrared sensors  132  are formed on top of insulating layer  1406 D. In operation  1550 , additional structures (not shown in  FIG. 14 ) may be formed as may be desired for particular implementations of infrared sensor assembly  128 . 
     Although particular structures of infrared sensor assembly  128  have been described with regard to  FIGS. 14 and 15 , other implementations are contemplated. For example, additional layers may be provided above, below, and/or between the various layers  1401  illustrated in  FIG. 14  as may be desired in various implementations. 
     Although three metal layers  1410 A-C have been described, the principles of the present disclosure may be applied to other embodiments using different numbers of metal layers. For example, in some embodiments, infrared sensor assembly  128  may be implemented with one, two, three, four, five, six, or greater numbers of metal layers as may be desired for various implementations. Where applicable, various associated vias may also be provided in such implementations to interconnect one or more of such metal layers, active circuit components  1408 , and/or infrared sensors  132 . 
     Moreover, the particular circuitry illustrated in  FIG. 14  is only provided for purposes of example. As such, various other types of circuit components (e.g., active or non-active) may be implemented in accordance with the present disclosure. 
     Where applicable, various embodiments provided by the present disclosure can be implemented using hardware, software, or combinations of hardware and software. Also where applicable, the various hardware components and/or software components set forth herein can be combined into composite components comprising software, hardware, and/or both without departing from the spirit of the present disclosure. Where applicable, the various hardware components and/or software components set forth herein can be separated into sub-components comprising software, hardware, or both without departing from the spirit of the present disclosure. In addition, where applicable, it is contemplated that software components can be implemented as hardware components, and vice-versa. 
     Software in accordance with the present disclosure, such as non-transitory instructions, program code, and/or data, can be stored on one or more non-transitory machine readable mediums. It is also contemplated that software identified herein can be implemented using one or more general purpose or specific purpose computers and/or computer systems, networked and/or otherwise. Where applicable, the ordering of various steps described herein can be changed, combined into composite steps, and/or separated into sub-steps to provide features described herein. 
     Embodiments described above illustrate but do not limit the invention. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the invention. Accordingly, the scope of the invention is defined only by the following claims.