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Fast signature preserving LWIR detail uncovering and image enhancement with dedicated color tables

: Müller, Thomas


Holst, Gerald C. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXII : 12-16 April 2021, Online Only, United States
Bellingham, WA: SPIE, 2021 (Proceedings of SPIE 11740)
ISBN: 978-1-5106-4317-8
ISBN: 978-1-5106-4318-5
Paper 117400E, 19 pp.
Conference "Infrared Imaging Systems - Design, Analysis, Modeling, and Testing" <32, 2021, Online>
Conference Paper
Fraunhofer IOSB ()
image enhancement; signature preservation; detail uncovering; LWIR / MWIR image; thermal image

There are powerful image enhancement methods using, e.g., contrast stretching or retinex to compute enhanced LWIR or MWIR gray value images. But some methods have considerable computation times. Additionally, some applications demand object signatures to remain structurally unchanged for further evaluations. Furthermore, since humans can distinguish only far less than 100 gray values, but numerous different colors, gray value visualization of thermal images is considerably suboptimal anyway. So, there are several reasons to use pre-defined, fast color tables. But this pseudo-coloring method is often limited in practice, especially when structures with small thermal differences need to be examined. As a solution, this paper explores different possibilities to reach a maximum benefit for detail uncovering by generating high dynamics in color, saturation, and/or brightness. The challenge is to balance detail uncovering with local as well as global image understandability and to find a long discrete 1D path in 3D color space without visible ambiguities. On the one hand, neighboring colors on this path need to have distances in color space big enough for good detail uncovering. On the other hand, non-neighbor parts of the path need to have even bigger color distances to distinguish high temperature differences. Different color tables are generated and compared. The given results show the reached benefit.