CLICK HERE TO VIEW BROWNOUT SAMPLE VIDEO
FIGURE A - Click to Expand
FIGURE B - Click to Expand
FIGURE C - Click to Expand
FIGURE D - Click to Expand
DEGRADED VISUAL ENVIRONMENTS
3D Flash LIDAR Degraded Visual Environmental Tests
ASC 3D Flash LIDAR cameras can operate in either (a) the 1st return (“Trigger”) mode where all pixels operate capture and profile the 1st return to the camera providing time-of-flight range and co-register intensity data, (b) a Delay-trigger mode where the Trigger mode is made operational only after a specified range and (c) the Continuous Sample Mode (CSM) where the pulse sampling is captured on all pixels over the entire specified range (Figure A). This latter mode is appropriate for penetrating obscuration where the return from the obscuration surface could “trigger” all the pixels. The CSM mode can be utilized during landing for dust, smoke or fog penetration. Notice the 10° diffuser being used with a 45° lens and the ability of the camera to image completely through 10 meters of dense fog. The distance from the camera to the back wall was 17.3 meters.
For the test in Figure A, artificial fog was generated using vaporized water and a glycerin-based fluid injected into a heated block. It produced about ~3um sized vapor particles. The rolling door was closed completely and the fog machine was used for 15 minutes to create maximum saturation of the air. The test was begun by starting the 3D Flash LIDAR in CSM and then the door opened. The resulting visibility for the initial 2 minutes was reduced to less than 15cm inside the room. During the test, the wind was blowing from the right side of the picture across the front of the room at approximately 5kts per hour). In a separate test, a 4 meters x 8 meters (narrow across the front opening) tent was used as shown in Figure B. The test used “corn starch” to simulate large dust particles (~15um) and inserted a “dummy” into the tent as the target. This test was potentially hazardous because of the a fine, flammable material (the corn starch dust) suspended in air. There was little wind for the Corn Starch Test. In both cases, the terminal settling velocity of an aerosol or "artificial smoke" particle increases rapidly with particle size. The settling velocity is proportional to the square of the particle diameter. The settling velocity for the 3um artificial fog due to gravity is about 1000mm per hour. For the 15um cornstarch dust, it is about 33,000mm (33cm) per hour.
In a separate test, ASC captured data in Yuma, Arizona, USA for helicopter brownout testing. These tests (shown in Figure third sample video on the left from the top) were difficult because the various particle sizes ranging from submicron (0.2um) to 80um for the small particles to small “pebbles” and “rocks” that were kicked up by the helicopter’s rotor blades. In addition, the albedo (reflectivity) of the material was quite high, resulting in some saturation. The ASC 3D Flash LIDAR cameras in CSM penetrated 50 meters to the requested targets (see insets in Figure C & D) and captured both range and intensity of the targets in real-time. It is possible to see the surface of the dust cloud developing in 3D as well as imaging into and through both the front and back walls of the cloud.
Using Continuous Sample Mode in Degraded Visual Environments, including looking directly at the sun, is of use for a wide range of applications such as automotive, aerial landing, fire-fighting, mapping through foliage, surveillance, surveying and the like.
Dust Penetration Testing at Yuma Proving Grounds
- Directed to monitor a target at 150 feet
- Used a TigerEye camera with external laser
- Camera imaged horizontally across dust clouds
- ASC 3D Flash LIDAR never lost sight of the target
- The TigerEye monitored the front of the dust cloud, as well as the target
- ASC 3D Flash LIDAR and software hold promise for brownout conditions
- Additional testing and exploitation recommended to create a deployment solution