Flat field correction for infrared cameras

Various techniques are provided to perform flat field correction for infrared cameras. In one example, a method of calibrating an infrared camera includes calibrating a focal plane array (FPA) of the infrared camera to an external scene to determine a set of flat field correction values associated with a first optical path from the external scene to the FPA. The method also includes calibrating the FPA to a shutter of the infrared camera to determine a set of flat field correction values associated with a second optical path from the shutter to the FPA. The method also includes using the flat field correction values associated with the first and second optical paths to calculate a set of supplemental flat field correction values to apply to thermal image data obtained with the infrared camera. The method also includes storing the supplemental flat field correction values.

TECHNICAL FIELD

The invention relates generally to thermal imaging systems and, more particularly, to systems and methods for calibrating thermal imaging devices, such as focal plane arrays.

BACKGROUND

Focal plane arrays (FPAs) which detect infrared radiation are well known in the art and are used by infrared cameras to provide thermal images. For example, infrared radiation passing through an optical path of the infrared camera is received by infrared detectors of the FPA, which provide thermal image data for pixels of a two-dimensional image.

The quality of thermal images provided by FPAs may be degraded due to non-uniform responses among the individual infrared detectors to incident infrared radiation. Factors contributing to the performance degradation may include, for example, variations in the physical characteristics (i.e., dimensions and locations), infrared radiation absorption coefficient, resistance, temperature coefficient of resistance (TCR), heat capacity, and/or thermal conductivity of the individual infrared detectors. FPA performance may also be degraded by non-uniform out-of-field infrared radiation from surrounding mechanical components. Because the magnitude of the non-uniformity may be large in comparison to the magnitude of the actual response due to the incident infrared radiation, various techniques are typically used to compensate for the non-uniformity and obtain a desirable signal-to-noise ratio.

For example, the FPA may be calibrated over one or more levels of photon flux by inserting a shutter (i.e., an optical obscuration also referred to as a calibration flag) into the optical path of the infrared camera. The temperature of the shutter may be adjusted to emulate a thermal black body detected by the FPA. The FPA takes one or more data frames or snapshots of the shutter to calibrate its response, and the collected data may then be used to calibrate the FPA to provide a more uniform response. The shutter location is often chosen to be as close as possible to the FPA (i.e., between the FPA and the lens) to reduce the shutter size and thus provide a more compact infrared camera.

Although the above-described shutter calibration technique permits calibration of the FPA for the portion of the optical path between the shutter and the FPA, it does not calibrate the FPA to correct for the thermal non-uniformity of the shutter's paddle and the out-of-field infrared radiation caused by other portions of the optical path including, for example, lenses, windows, mounting hardware, or other components of the infrared camera which may be implemented in front of the shutter (i.e., not between the shutter and the FPA). Such non-uniformities may further degrade FPA performance by radiometrically distorting the thermal image data detected by the FPA. Accordingly, there is a need for an improved approach to the calibration of an FPA within an infrared camera.

SUMMARY

One or more embodiments may be used to provide flat field correction for infrared cameras. For example, infrared detectors of an infrared camera may be calibrated to determine flat field correction values, which may be used to correct for non-uniformities associated with optical paths of the infrared camera. Supplemental flat field correction values may also be determined and applied to thermal image data to further correct for such non-uniformities.

In one embodiment, a method of calibrating an infrared camera includes calibrating a focal plane array (FPA) of the infrared camera to an external scene to determine a set of flat field correction values associated with a first optical path from the external scene to the FPA; calibrating the FPA to a shutter of the infrared camera to determine a set of flat field correction values associated with a second optical path from the shutter to the FPA; using the flat field correction values associated with the first and second optical paths to calculate a set of supplemental flat field correction values to apply to thermal image data obtained with the infrared camera; and storing the supplemental flat field correction values.

In another embodiment, an infrared camera includes a focal plane array (FPA) adapted to capture thermal image data in response to infrared radiation received by the FPA; a shutter; a memory adapted to store a set of supplemental flat field correction values based on a first optical path from an external scene to the FPA; and a processor adapted to: calibrate the FPA to the shutter to determine a set of flat field correction values associated with a second optical path from the shutter to the FPA, and apply the supplemental flat field correction values to the thermal image data to adjust for non-uniformities associated with the first optical path.

In another embodiment, a method of processing thermal image data captured by an infrared camera includes capturing thermal image data at a focal plane array (FPA) of the infrared camera; and applying a set of supplemental flat field correction values to the thermal image data to adjust for non-uniformities associated with the infrared camera, wherein the supplemental flat field correction values are based on differences between a set of flat field correction values obtained from a calibration of the FPA to an external scene and a set of flat field correction values obtained from a calibration of the FPA to a shutter of the infrared camera.

DETAILED DESCRIPTION

FIG. 1illustrates an infrared camera100in accordance with an embodiment of the invention. Infrared camera100includes an infrared detector package106, a motor108, a shutter110, a power block114, an optics block116, a processing and control block120, a temperature sensor128, and an optional window170.

In one example, infrared camera100may represent any type of infrared camera or thermal imaging system, is not limited to any specific embodiment disclosed herein, and may be implemented as desired for particular applications. Accordingly, in one embodiment, the components illustrated inFIG. 1may be implemented as a standalone infrared camera. In another embodiment, the components ofFIG. 1may be distributed between a plurality of different devices. For example, processing and control block120may be implemented by one or more external computer systems that interface with infrared camera100(e.g., over a network or other appropriate communication medium). In another embodiment, infrared camera100may be implemented with greater, fewer, and/or different components than those illustrated inFIG. 1as appropriate for particular applications.

Infrared energy received from a scene180in front of infrared camera100passes along an optical path150through optics block116(e.g., athermalized optics including one or more lenses for focusing infrared radiation on infrared detector package106) to infrared detector package106(e.g., a vacuum package assembly). In one embodiment, infrared detector package106and optics block116may be sealed inside a chamber (not shown) including window170(e.g., a heated or temperature controlled protective window) positioned between optics block116and scene180.

In another embodiment, one or more lenses of optics block116may be selectively inserted into optical path150. Accordingly, infrared camera110may be operated with various lenses (e.g., 25 mm, 35 mm, 50 mm, 140 mm, or others) as may be desired for particular applications. The different types of lenses may contribute to different non-uniformities in the propagation of infrared radiation along optical path150.

Infrared detector package106includes a focal plane array (FPA)104to detect infrared radiation passing through a window105and provide thermal image data in response thereto. FPA104may be implemented using various types of infrared detectors (e.g., quantum wells, microbolometers, or other types) as may be desired for particular implementations.

In order to calibrate FPA104, a thermal black body126may be positioned in scene180such that thermal black body126fully subtends the lens field of view (FOV) of infrared camera100. By operating infrared camera100in a thermally stable environment (e.g., corresponding to a thermal steady state condition such as room temperature) and capturing thermal images of thermal black body126, flat field correction values may be determined which may be applied to thermal image data received from FPA104to correct for non-uniformities (e.g., thermal loading or optical irregularities) present in optical path150.

Shutter110may be selectively inserted into optical path150through the operation of motor108to facilitate calibration of FPA104. For example, in the embodiment illustrated inFIG. 1, shutter110is shown inserted into optical path150. While inserted into optical path150, shutter110substantially blocks infrared radiation from passing to FPA104from scene180. In this case, FPA104instead detects infrared radiation received from shutter110along an optical path140, to the exclusion of infrared radiation received along an optical path160. In one embodiment, shutter110may be implemented to approximate a thermal black body in front of infrared detector package106. By calibrating FPA104to shutter110, flat field correction values may be determined which may be applied to infrared detectors of FPA104in order to correct for non-uniformities present in optical path140, as discussed further herein.

Power block114may include a circuit board power subsystem (e.g., a power board) for infrared camera100. For example, power block114may provide various power conversion operations and desired power supply voltages, power on-off switching, and various other operations (e.g., a shutter driver for motor108), including an interface to a battery or external power supply, as would be understood by one skilled in the art.

Processing and control block120includes a processor122and a memory124. Processor122may be configured with appropriate software (e.g., one or more computer programs for execution by processor122) stored on a machine readable medium130(e.g., a CD-ROM or other appropriate medium) and/or in memory124to instruct processor122to perform one or more of the operations described herein. Processor122and memory124may be implemented in accordance with any desired combination of one or more processors and/or one or more memories as desired for particular implementations.

Processing and control block120receives thermal image data captured by infrared detectors of FPA104and processes the thermal image data to perform a flat field correction on the data to account for non-uniformities associated with the infrared detectors of FPA104and other non-uniformities associated with other portions of optical path150(e.g., non-uniformities associated with optics block116or other portions of infrared camera100). The corrected thermal image data may be used to provide corrected thermal images which account for aberrations in optical path150.

Processing and control block120also interfaces with motor108to control the insertion and removal of shutter110from optical path150. Advantageously, processing and control block120may receive thermal image data captured by FPA104either while shutter110is inserted into optical path150or while shutter110is removed from optical path150. As a result, processing and control block120may selectively calibrate FPA104along either optical path140(e.g., while shutter110is inserted in optical path150) or optical path150(e.g., while shutter110is removed from optical path150). For example, in one embodiment, processing and control block120may determine flat field correction values (e.g., gain and offset values) associated with individual infrared detectors of FPA104to correct for non-uniformities associated with the infrared detectors for either optical path140or optical path150. As further described herein, the flat field correction values may be further processed to determine supplemental flat field correction values to correct for non-uniformities associated with the infrared detectors for optical path160.

Processing and control block120also interfaces with temperature sensor128to determine a temperature and a rate of temperature change of the ambient environment in which infrared camera100is positioned and/or one or more components of infrared camera100(e.g., FPA104, infrared detector package106, motor108, shutter110, power block114, optics block116, processing and control block120, window170, and/or other components). Processing and control block120may be configured to scale the supplemental flat field correction values based on temperature readings obtained from temperature sensor128.

Temperature sensor128may be positioned in any desired location of infrared camera100(e.g., optics block116, FPA104, mechanical components near optical path150such as shutter110and/or window170, and/or other locations of infrared camera100) and/or in the ambient environment in which infrared camera100is positioned. For example, in one embodiment, temperature sensor128is positioned on FPA104and window170.

FIG. 2illustrates a process of determining supplemental flat field correction values in accordance with an embodiment of the invention. In one example, the process ofFIG. 2may be performed by a provider of infrared camera100(e.g., a manufacturer, designer, or other party providing infrared camera100). In this example, supplemental flat field correction values may be prepared by the provider and stored by infrared camera100to be subsequently used during operation of infrared camera100by a user. In another example, the process ofFIG. 2may be performed by a user of infrared camera100. In yet another example, performance of the process ofFIG. 2may be distributed between a provider of infrared camera100and a user of infrared camera100.

In steps202through210, flat field correction values are determined for the infrared detectors of FPA104to correct for non-uniformities in optical path150. In steps212through220, flat field correction values are determined for the infrared detectors of FPA104to correct for non-uniformities in optical path140. In steps222through232, the flat field correction values associated with optical path140are subtracted from those associated with optical path150and the resulting supplemental flat field correction values are further processed. These supplemental flat field correction values may be applied to thermal image data obtained during subsequent operation of infrared camera100.

Advantageously, the supplemental flat field correction values may be used to correct for non-uniformities associated with optical path160(e.g., the portion of optical path150external to shutter110and infrared detector package106) that would not otherwise be correctable using only flat field correction values associated with optical path140. Such non-uniformities may be attributable to, for example, window170, optics block116, mounting hardware of infrared camera100, or other components of infrared camera100. Also, the use of supplemental flat field correction values may reduce the effects of imperfections in window105(e.g., crop circles), FPA104(e.g., botches or tilted pixels), or shutter110(e.g., imperfections in the thermal black body presented by shutter110to FPA104(e.g., due to non-uniform temperature or heating of shutter110)).

In one embodiment, the process ofFIG. 2may be performed while infrared camera100and the surrounding ambient environment are under thermally stable conditions at room temperature (e.g., in a temperature-controlled chamber) while infrared camera100is in a final configuration to be used for capturing thermal image data during normal operation of infrared camera100. For example, in this embodiment, all mechanical and thermal components of infrared camera100(e.g., lenses of optics block116, mounting hardware, and other components of infrared camera100) may be mounted and powered on for at least ten minutes or until temperature sensor128indicates insignificant changes in temperature before the process ofFIG. 2is performed.

In another embodiment, the process ofFIG. 2may be repeated for different temperatures of the surrounding ambient environment and/or components of infrared camera100. As a result, different supplemental flat field correction values may be determined for different temperatures.

In another embodiment, the process ofFIG. 2may be repeated for different configurations of infrared camera100. For example, in different iterations of the process ofFIG. 2, infrared camera100may be powered on and configured for capturing thermal images with different lenses in optics block116(e.g., different sizes of lenses or lenses provided by different manufacturers), different mounting hardware, and/or other components. As a result, different supplemental flat field correction values may be determined for different configurations of infrared camera100, or different types of infrared cameras100.

Calculations described herein with regard to the process ofFIG. 2may be performed in a localized or distributed manner as may be desired in particular applications. For example, in one embodiment, the calculations may be performed locally by infrared camera100(e.g., where processing and control block120is implemented as part of infrared camera100). In another embodiment, the calculations may be performed by one or more external computer systems that interface with infrared camera100(e.g., where processing and control block120is implemented by such computer systems). In yet another embodiment, the calculations may be performed locally by infrared camera100and one or more external computer systems that interface with infrared camera100(e.g., where processing and control block120is implemented as part of infrared camera100and is also implemented by such computer systems).

Referring now to the particular steps in the process ofFIG. 2, in step202, infrared camera100begins performing a flat field correction (FFC) process for FPA104using thermal black body (TBB)126which is external to infrared camera100. Accordingly, during step202, processing and control block120controls motor108to remove shutter110from optical path150.

In step204, FPA104captures (e.g., acquires) two or more frames of thermal image data corresponding to infrared radiation received along optical path150. For example, in one embodiment, FPA104captures eight frames of thermal image data which is passed to processing and control block120.

In step206, processing and control block120averages the thermal image data over the two or more frames received from FPA104to average out differences in the captured image values from frame to frame. In one embodiment, the value of each pixel is averaged for all values of the same pixel in the frame sequence captured in previous step204. For example, if eight frames of thermal image data are captured in previous step204, then the average value of each pixel is determined based on the eight values for the pixel captured in the eight frames of thermal image data.

Also in step206, when determining the average value of each pixel, processing and control block120may chose to ignore one or more pixel values from one or more frames that fall outside a selected range when compared to the same pixels of the other captured frames. For example, if eight frames are captured in step204, and if a particular pixel of one of the frames has a value that significantly differs from values associated with corresponding pixels of the remaining seven frames, then the pixel value of the one frame may skew the average pixel value determined for the eight frames. Accordingly, processing and control block120may choose to ignore the pixel value of the one frame and instead determine an average pixel value over the remaining seven frames. As a result, the accuracy of the thermal image data provided in step206can be improved.

In optional step208, the pixel values are multiplied by a factor of two for convenient computation by processing and control block120. In optional step210, processing and control block120applies row and column spatial noise suppression to the multiplied average pixel values based on conventional processing techniques as would be understood by one skilled in the art.

Following the completion of step210, flat field correction values will have been determined for all infrared detectors of FPA104. In this embodiment, any infrared radiation detected by FPA during steps202to210includes non-uniformities associated with infrared detectors of FPA104, optics block116, or other components of infrared camera100which may contribute infrared radiation along optical path150. Accordingly, differences in thermal data obtained during steps202to210correspond to the composite effect of all non-uniformities along optical path150. Processing and control block120uses these data values to determine a flat field correction value for each pixel that results in a thermally calibrated data value for the pixel when the flat field correction value is applied to a thermal image captured along optical path150while thermal black body126is in place and shutter110is removed from optical path150(e.g., for a given calibrated temperature).

In step212, infrared camera100begins performing a flat field correction of FPA104using shutter110as a thermal black body which is internal to infrared camera100. Accordingly, during step212, processing and control block120controls motor108to insert shutter110into optical path150. As a result, FPA104is configured to receive infrared radiation along only optical path140(i.e., not the entire optical path150).

Steps214through220are performed for optical path140in substantially the same manner as described above for steps204through210for optical path150. Accordingly, following the completion of step220, another set of flat field correction values will have been determined for all infrared detectors of FPA104. In this embodiment, any infrared radiation detected by FPA during steps212to220includes non-uniformities associated with shutter110, infrared detectors of FPA104, and/or other components of infrared camera100which may contribute infrared radiation along optical path140. Accordingly, any differences in thermal data obtained during steps212to220correspond to the composite effect of all non-uniformities along optical path140. Processing and control block120uses these data values to determine a flat field correction value for each pixel that results in a thermally calibrated data value for the pixel when the flat field correction value is applied to a thermal image captured along optical path140while shutter110is inserted into optical path150.

In step222, processing and control block120subtracts flat field correction values associated with optical path140from those associated with optical path150to obtain a supplemental flat field correction value for each pixel (i.e., infrared detector) of FPA104.

In steps224through232, processing and control block120further processes the supplemental flat field correction values. For example, in step224, processing and control block120applies kernel smoothing to the supplemental flat field correction values to minimize high-frequency noise in the previously acquired image data. The kernel smoothing of step224may be applied using any desired density (e.g., 3 by 3 pixels or other densities). This kernel smoothing may be repeated any desired number of times (step226). In one embodiment, step224may be performed in accordance with the process ofFIG. 3or may be performed using conventional techniques as would be understood by one skilled in the art.

In one embodiment, processing and control block120may be configured to process only positive (e.g., zero or greater) supplemental flat field correction values during the kernel smoothing of step224. In this embodiment, the supplemental flat field correction values may be offset by a desired positive number (e.g., an offset value of 1000) before step224is performed, which is then subtracted from the kernel smoothed field correction values after steps224and226are performed.

Although steps224and226have been described with regard to kernel smoothing techniques, other techniques may be used to smooth or otherwise reduce the differences between individual pixel values of the supplemental flat field correction values. Such techniques may include, for example, high frequency noise suppression techniques, pixel value blurring techniques, and/or other appropriate techniques as will be appreciated by one skilled in the art.

In optional step228, processing and control block120divides the supplemental flat field correction values by a factor of two (e.g., if optional steps208and218were previously performed).

In step230, processing and control block120scales the supplemental flat field correction values to an eight bit resolution corresponding to a range from −127 to 128 (e.g., using seven data bits and one sign bit). In this regard, an eight bit resolution may permit efficient usage of memory124during the processing of the supplemental flat field correction values while still providing sufficient resolution to adjust for non-uniformities present in thermal image data. In one embodiment, the flat field correction values associated with optical paths140and150determined in steps202to220, as well as the supplemental flat field correction values determined in step222, may have a fourteen bit resolution (e.g., corresponding to the resolution of individual infrared detectors of FPA104). In this embodiment, the supplemental flat field correction values are scaled to a resolution of eight bits in step230as would be understood by one skilled in the art. In other embodiments, such as where larger adjustments are desired, higher bit resolutions may be used for the supplemental flat field correction values.

In step232, the smoothed, scaled supplemental flat field correction values are stored as a supplemental flat field correction map which may be applied to thermal image data obtained during subsequent operation of infrared camera100to adjust for non-uniformities in optical path160(e.g., corresponding to the difference between optical path150and optical path140).

FIG. 3illustrates a process of adjusting supplemental flat field correction values in accordance with an embodiment of the invention. For example, in one embodiment, the process ofFIG. 3may be performed by processing and control block120during step224ofFIG. 2.

In step304, processing and control block120performs a kernel smoothing on three by three pixel groups of the supplemental flat field correction values that were stored in step232ofFIG. 2. A threshold value used to perform the kernel smoothing of step304is selected from a range of 0 to 127 (identified in step306). As similarly discussed above with regard to steps224and226, other techniques may be used in step304to smooth or otherwise reduce the differences between individual pixel values of the supplemental flat field correction values.

In step308, processing and control block120performs a kernel smoothing on five by five pixel groups of the previously-smoothed supplemental flat field correction values. A threshold value used to perform the kernel smoothing of step308is selected from a range of 0 to 127 (identified in step310). As similarly discussed above with regard to steps224,226, and304, other techniques may be used in step308to smooth or otherwise reduce the differences between individual pixel values of the supplemental flat field correction values.

In step312, the twice-smoothed supplemental flat field correction values determined in step308are subtracted from the once-smoothed supplemental flat field correction values determined in step304. In step314, a gain factor (identified in step316) is applied to the difference values determined in step312. In step318, the gain-adjusted difference values (determined in step314) are added to the twice-smoothed supplemental flat field correction values (determined in step308) to provide adjusted supplemental flat field correction values.

FIG. 4illustrates a process of performing flat field correction in accordance with an embodiment of the invention. For example, in one embodiment, the process ofFIG. 4may be performed by processing and control block120following the process ofFIG. 2.

In step402, processing and control block120monitors temperature sensor128and obtains temperature data for the components of infrared camera100and/or the ambient environment in which infrared camera100is positioned. In step404, processing and control block120processes the temperature data to determine a rate of temperature change. For example, in one embodiment, the rate of temperature change may be integrated over a five second period of time to smooth out high frequency noise.

In step406, processing and control block120determines a scale factor associated with the rate of temperature change determined in step404. The scale factors may be used to adjust the amount of supplemental flat field correction applied to thermal image data in realtime during operation of infrared camera100. For example, the following Table 1 identifies various scale factors which may be applied to the supplemental flat field correction values for different rates of temperature change:

TABLE 1Scale factor applied tosupplemental flat fieldTemperature rate of change in degreescorrection valuesCelsius for five second period0.0029 < temperature rate of change0.2523 < temperature rate of change ≦ 290.5015 < temperature rate of change ≦ 230.755 < temperature rate of change ≦ 151.00temperature rate of change ≦ 5

In step408, appropriate supplemental flat field correction values are provided from memory124. In one embodiment, the supplemental flat field correction values provided in step408are selected from a plurality of different sets of supplemental flat field correction values corresponding to different configurations of infrared camera100. For example, as previously described, the process ofFIG. 2may be repeated for different infrared cameras100or different configurations of infrared camera100to store different sets of supplemental flat field correction values corresponding to various configurations of optics block116, mounting hardware, and/or other components of infrared camera100. Accordingly, in step408, the supplemental flat field correction values corresponding to the current infrared camera100or current configuration of infrared camera100are selected.

In step410, the supplemental flat field correction values (e.g., provided from memory124in step408) are scaled (e.g., multiplied) by the scale factor determined in step406. For example, as shown in Table 1, if the temperature rate of change is relatively stable (e.g., changing between zero and five degrees within a five second period), then a scale factor of 1.0 will be determined in step406and applied in step410.

In contrast, if the temperature rate of change is relatively unstable (e.g., changing more than 29 degrees within a five second period), then a scale factor of zero will be determined in step406and applied in step410. In this case, the supplemental flat field correction values will not be applied to thermal image data.

Other scale factors (e.g., 0.25, 0.50, or 0.75) may be determined and applied for other temperature rates of change as set forth in Table 1. Moreover, although particular scale factors and temperature rates of change are identified in Table 1, other scale factors and temperature rates of change are contemplated. In particular, the scale factors and temperature rates of change identified in Table 1 are dependant on the particular optical path150of infrared camera100and the desired amount of supplemental flat field correction that may be desired in particular applications. For example, in another embodiment, scale factors having increments of 0.1 may be used.

In step412, processing and control block120applies the flat field correction values determined by steps212to220ofFIG. 2(e.g., determined for optical path140with shutter110inserted into optical path150) to infrared detectors of FPA104to provide thermal image data that accounts for non-uniformities in optical path140.

In step414, processing and control block120also applies the scaled supplemental flat field correction values determined in step410to the thermal image data to account for non-uniformities in optical path160. As a result, processing and control block120provides corrected thermal image data in step416which has been processed to account for non-uniformities along the full optical path150(e.g., corresponding to optical paths140and160together). Thus, by using supplemental flat field correction values determined for particular configurations of infrared camera100, non-uniformities attributable to such configurations may be corrected.

Although only a single set of supplemental flat field correction values are identified inFIG. 4, it is contemplated that different sets of supplemental flat field correction values may be used depending on the particular infrared camera100used, the configuration of infrared camera100, and/or detected temperatures or rates of temperature change. For example, in one embodiment, processing and control block120may be configured to extrapolate a single set of supplemental flat field correction values depending on detected temperatures or rates of temperature changes. In another embodiment, processing and control block120may be configured to select different sets of supplemental flat field correction values, or extrapolate between such values, depending on detected temperatures or rates of temperature changes. In yet another embodiment, such selections or extrapolations may be performed based on the particular infrared camera100used or the configuration of infrared camera100.

Advantageously, the supplemental flat field correction values as described herein can be applied to thermal image data captured by FPA104to compensate for non-uniformities that may otherwise remain uncorrected by conventional shutter-based infrared detector calibrations. Such non-uniformities include, for example, image artifacts of infrared detectors of FPA104(e.g., botches or tilted pixels), image artifacts of window105(e.g., crop circles), and non-uniformities in the thermal black body provided by shutter110(e.g., caused by non-uniform internal heating).

Also, the use of supplemental flat field correction values can provide more accurate thermal image data which consequently reduces the frequency at which FPA104is recalibrated to the thermal black body provided by shutter110. As a result, shutter110and motor108may be used less frequently which may improve their reliability.

In one embodiment, the use of supplemental flat field correction values may be selectively enabled or disabled as may be desired in particular applications. For example, in one embodiment, a user may selectively enable or disable the use of supplemental flat field correction values by interacting with a graphic user interface provided by infrared camera100or specifying a dynamic header of a graphical user interface (GUI) as will be understood by those skilled in the art. In another example, a provider of infrared camera100may specify default conditions to enable or disable the use of supplemental flat field correction values.

Where applicable, the various described embodiments may 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 may be combined into composite components comprising software, hardware, and/or both without departing from the spirit of the disclosure. Where applicable, the various hardware components and/or software components set forth herein may be separated into sub-components comprising software, hardware, or both without departing from the spirit of the disclosure. In addition, where applicable, it is contemplated that software components may be implemented as hardware components, and vice-versa.