Color display modes for a thermal imaging system

Abstract

Systems and methods for allocating display colors to thermal image intensity data acquired by thermal band photodetectors are described. The intensity data from the photodetectors, which corresponds to the scene temperature, is usually converted to a digital value falling within the range of the analog to digital conversion (ADC). The full ADC range may be divided into two or more sub-ranges. In at least one sub-range intensity values within that sub-range may be assigned display colors from a first color table utilizing one or more Histogram Equalization (HE) techniques. In at least one other sub-range, specific display values from a color table different from the first may be assigned to specific intensity values. In some embodiments, the HE assigned sub-range may be lower in intensity than the specific assigned sub-range. For a thermal imaging system including thermography, the sub-ranges may correspond to scene temperature ranges, where lower temperatures are assigned colors using HE and higher temperatures are assigned specific colors corresponding to specific temperatures. Such an arrangement is particularly applicable to thermal imaging use by firefighters because the arrangement allows them to determine temperature directly from displayed color for potentially dangerous temperatures. In some cases the sub-range may be applied to certain pixels within desired temperature ranges, and those chosen pixels may be assigned to all or part of a second color table, and in some cases the second color table may be applied to the sub-range pixels by histogram equalization. This arrangement is applicable to highlighting temperatures corresponding to objects, such as humans or animals to make these objects high contrast for search applications.

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