Patent Application
20230266239
One reason that fog is difficult to see through is that light does penetrate in, but the various water droplets act as a type of lens and scatter the light so that the fogged items don't make visual sense, and they are unrecognizable. This means the light is not useful for illuminating shapes and outlines, and instead doesn't illuminate anything.
An example earlier mechanism that attempts to resolve this issue using a water-absorption band of 940 nm is disclosed in U.S. Pat. No. 9,077,868, issued Jul. 7, 2015. That earlier mechanism was limited by the fact that the water absorption band is only about 10 nm wide and that VIS/NIR (visible/nearInfraRed) detector sensitivity is very low in the NIR spectrum. Consequently, an improved mechanism for overcoming problems such as scattering effect, and other problems, is desired.
The spectral absorption properties of water can be exploited to improve SWIR sensor performance in the presence of clouds. Limiting the spectral passband of a sensor to a water absorption band can improve SNR (Signal to Noise Ratio). Higher SNR permits improved CSO resolution. Further, higher SNR reduces the uncertainty in matching observations in one sensor to the epipolar lines of another sensor, thus reducing the time needed to achieve unambiguous matches.
The embodiments herein overcome scattering of light that is caused by fog, thereby increasing visibility. The light is still scattered, but viewing fog through the embodiments herein can strip out some of the scattered light. What remains is a more exact illustration, where boundaries, shapes, and maybe even colors become more recognizable.
However, there exists a much deeper water absorption band in the SWIR spectral region (e.g. 1400 nm with a bandwidth of e.g. 70 nm). This SWIR spectral region also includes absorption bands for related phenomena such as oil fogs, sand/dust reflection, and CO2/H2O band ratios for reducing background clutter.
To take advantage of these conditions,
An embodiment comprises the SWIR camera 102 being fitted with the filter 104 tuned to 1400 nm. Using the 1400 nm water absorption band, the system 100 collects and then using the processing module 108 produces high-end videos showing for example the fog penetration performance of the specialized SWIR camera compared to visible, NIR and unmodified SWIR passbands.
The processing module 108 can be implemented in a variety of configurations, including both software, firmware, customized hardware, and other ways of fabricating sophisticated electronic and digital signal processing components.
Meanwhile, in sharp contrast, the system 100 operates at 1400 nm (1.4 micron) which is in the high detectivity region of HgCdTe (Mercury Cadmium Tellerium) detector arrays used for detecting IR and focal planes. The depth of the water absorption band is much stronger at 1400 nm and SWIR naturally provides a better fog penetration than Visible/NearInfraRed (VIS/NIR). Further, the water absorption band is around 70 nm wide so the SWIR camera 102 within the system 100 can be operated with a much wider field-of-view and still take advantage of the improved fog viewing capability.
Next, the embodiments herein contemplate either/any of software, or a toolkit, or a GUI which enables users to vary alpha (a), using perhaps a slider-bar mechanism. Further, an end-customer\purchaser of the system 100 might create his own alpha “slider bar” for consistency with their own preferred visual flow. Either way, the embodiments herein can achieve an end-user package where a customer can pick their own mechanism for representing and varying alpha (a). This in turn means the customer has options for “tuning” or adjusting alpha (a) and then visually observing which setting of alpha achieves the best visual image.
A point source object is when an object's image is just a blurry spot on a focal plane. Within
Within the interpolation step 1008 of
The process at the bottom of
To the extent not already discussed herein, further embodiments are contemplated. These include, but are not limited to: oil fog obscurant penetration; penetration for brownout; multi-band effects including SNR enhancement and clutter reduction; and multi-frame image enhancement for stationary scenes.
The 1400 nm spectral region is a niche area having numerous opportunities for commercial exploitation. Potential sales channels include but are not limited to transportation-related organizations which are tasked with monitoring for accidents in fog prone areas. This may include US Coast Guard for port monitoring, but also the Army Corp of Engineers for dam/lock monitoring.
Further embodiments include oil fog penetration, sand/dust penetration, water/carbon dioxide band ratio SNR enhancement, and background clutter reduction. Additionally, technologies exploiting optical properties of materials is the SWIR spectral region. Some components may include the processing module 108 being in the format of a tablet/laptop having customized software loaded therein.
There exist numerous ways of testing and affirming proper performance of the system 100. These can include an oil fog generator, various filters, and a field reflectance spectrometer. Such test kits for the system 100 can be shown to and/or loaned to potential customers, and be made part of the purchase. The oil-fog generator could be used for simulating/testing related to the system 100 can include testing on oil fogs and sand/dust (haboob) visibility.
Another embodiment of the system 100 features a candidate sensor for a weather tracking mesonet for a traffic corridor along a highway, e.g. an I-65 traffic corridor. This application uses both the filter (1400 nm) and various software components including but not limited to the processing module 108 for image enhancement. The improved imagery provided by the system 100 permits detection and identification of traffic accidents and obstacles on a highway in all weather conditions. These data-points could be embedded within traffic alerts found in e.g. Google Maps.
The system 100 can also be configured to provide upgrades to an Enhanced Regional Situation Awareness (ERSA) visual warning system. That embodiment of the system 100 could include a telephoto lens systems, i.e. narrow field-of-view lens suited to the multilayer bandpass filter since its passbands shifts with changing angle-of-incidence.
The system 100 also can be used to increase Signal to Noise Ratio (SNR) and reduce background clutter for e.g. satellite surveillance and tracking of hypersonic missiles. The Tranche 1 and Tranche 2 layers for detecting and tracking of hypersonic missiles is well matched to the 1400 nm and 2.8 micron water absorption bands. In addition, a CO2 absorption band adjacent to the H2O absorption band can be exploited to enhance SNR and reduce clutter/noise viewing against the hard earth background. In this embodiment, a 2.8 micron absorption band for water is used, and narrower still is a co CO2 absorption band. In the narrower bandit becomes possible to penetrate the cloud by turning the fog off. It is also possible to simplify background clutter by assessing CO2 as a curtain to eliminate anything coming up from the ground. Doing so reduces more background than the sought-after target being viewed, thus increasing SNR.
As a way of testing/verifying the system 100 in such a hypersonic missile scenario, it is possible to view a target looking in and out of the spectral band mentioned earlier. To determine when missiles are going into the atmosphere, a viewer can hop back and forth between the two bands, and thereby obtain an estimate of the altitude of that object as it's burning in. The deeper a missile goes, the more CO2 will be blocked going down, dropping altitude, thus detecting something as it's burning In reentry.
While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations, or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations, or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.
