The efficiency of airborne search and rescue, situational awareness and navigation tasks is predicated based on the availability of high-resolution imagery that provides pilots with the widest possible field of view and a clear picture. While the human eye has exceptionally high resolution with an unmatched ability to identify high-spatial-frequency (HSF) objects across a wide field of regard, human vision can easily get exhausted, is subject to environmental conditions and is vastly degraded at night.
Multi-megapixel visible imaging cameras, like human vision, provide the best platform for the above-mentioned tasks during daylight hours but rapidly drop in sensitivity and become ineffective as night approaches. Due to this, thermal infrared (IR) imaging has developed as an effective 24/7 imaging technology for these applications.
The Need for Automation
Airborne search and rescue operations can materially benefit from the development and use of high-resolution sensors during both the day and night (Figure 1). When Malaysia Airlines Flight #370 disappeared in the Indian Ocean, in March 2014, the primary tools of the search and rescue efforts were fixed-wing, human-piloted and rotary aircraft, which scoured the ocean while crew members searched with the help of binoculars. Even with the highest level of training for rescue pilots and crew members, the search operations were still delayed by the human condition, including poor vision at night and fatigue.
Figure 1. Search and rescue helicopter over water during daylight operation.
In this tragic, but obvious example, one must wonder if more automated, effective imaging technologies had been utilized, would it have been of any benefit for these search efforts? Almost every organization involved in these types of search applications would like to carry out more effective operations at night; to attain this goal, imaging technology will have to perform a lot better than the human eye.
Algorithmic data processing can drastically enhance the efficiency of the cameras by employing automated search and detection algorithms. The detection task uses particular algorithms to sift through thousands of false-alarm events that can happen over water — wave breaks or whitecaps, cloud artifacts, reflection artifacts, sun glint, etc. Programmers have spent considerable time and effort particularly on this task of sifting through the data and discovering highly-positively correlating events that offer predictive-value-detection of objects in the water.
This has been scaled to systems that are actively on aircraft today in order to validate the use-case during daytime with high-resolution visible-imaging sensors; the results have been effective and encouraging. Simultaneously, high-magnification queued sensors are being employed for the inspection of detection events. This technology, in the visible spectrum, is almost ready for deployment on small tactical unmanned aircraft systems or STUAS-class robotic aircraft.
While automation technology can enhance the effectiveness of search operations, IR imaging technology can extend the operational use in bad weather conditions, through the night and can further provide a wide field of view (FOV) for monitoring huge areas of the ocean. Camera technology utilizing IR energy far beyond what the human eye can see will offer important benefits over visible-imaging cameras.
At night, visible-imaging cameras would need active illumination that offers a narrow field of view, which is contrary to the application of wide-area surveillance. Passive technology using midwave infrared (MWIR), shortwave infrared (SWIR), and longwave infrared (LWIR) imaging are perfect for wide-area surveillance as they do not depend on external illumination. Of these, LWIR is considered to be the most prevalent detector technology because of its lower cost, high sensitivity, ease of export, high resolution and independence from atmospheric nightglow.
A Brief History of Thermal Imaging
Historically, IR imaging has been restricted by low resolution in comparison to visible imaging, but today, the IR industry is on the edge of a mini-revolution with the development and also the commercialization of high definition (HD) sensors. This evolution is composed to advance the efficiency of navigation, airborne search and rescue and situational awareness operations at night.
In the last 25 years, the technological capability of IR technology has followed two varied tracks — that which was developed and exclusively used by the military and that which was available for commercial use. The immense majority of commercially available IR sensors presently sold were developed in the early 1990s and offer standard definition (SD) 640 x 512 resolution or less. In the late 2000s, higher resolution technology was developed but these were research-grade, cooled MWIR sensors for military use.
Within the last five years, cooled MWIR 1280 x 1024 and 1920 x 1576 cameras and 1024 x 768 resolution LWIR have also moved from the military arena into the commercial space. Today, while higher resolution technology continues to be constrained to use within military programs, January 2017 marked the next evolution in thermal IR camera technology with the launch of the first commercially-available 1920 x 1200 uncooled LWIR camera.
Figure 2. Vayu HD LWIR thermal imager provides true HD resolution for a variety of surveillance and search & rescue operations.
As part of an effort to increase the use of improved infrared imaging, primarily for airborne search and rescue, situational awareness and navigation applications, Sierra Olympic (Hood River, Oregon) lately developed the Vayu HD uncooled LWIR thermal camera (Figure 2). The imager offers true HD resolution at 1920 x 1200 with a 12 µm pixel pitch and, most essentially, is now available commercially.
The new high-resolution thermal imager employs an uncooled vanadium oxide (VOx) detector, offers 1080p video output via HD-SDI or H.264-IP compression over Ethernet, and has an IP67-rated environmental enclosure for extreme, rugged outdoor conditions (Figure 3). Full HD resolution IR sensors with a wide FOV are presently available in order to provide the greatest degree of situational awareness and visual navigation at night. Furthermore, these new sensors are uncooled, which affords extended life and lower expense while maintaining extremely high thermal imaging performance.
Figure 3. High definition, LWIR thermal imagery from Sierra-Olympic’s Vayu HD camera provides clear details of sailboats.
Early deployment of test systems for navigation, search and rescue and situational awareness operations is presently underway, which will help decide the full value of HD resolution sensors in the search and rescue application area.
This information has been sourced, reviewed and adapted from materials provided by Sierra-Olympic Technologies Inc.
For more information on this source, please visit Sierra-Olympic Technologies Inc.