Navy

Adaptable illumination LiDAR camera

Device uses a spatial light modulator for masking illumination of an undesirable feature and selectively illuminating a target of interest in a field of view

Photonics

Active imaging systems, such as a LiDAR system, contain an illumination source as well as an imaging detector- the former component being a major contributor to the size, weight and power draw of the overall system.

For efficiency gains, the illumination of the scene should be optimized to avoid wasting laser power. Illumination control for lidar systems has been implemented through a variety of beam reshaping approaches. These have required additional optics or computation.

LiDAR image shows road contour, elevation, and roadside vegetation. (Oregon Transportation Department/Wikimedia)

Navy researchers have developed an alternative approach using a spatial light modulator that specifically illuminates targets or specific voids in the imaging scene. The process is applicable in areas such as foliage penetration, cloud avoidance, or bathymetry LiDAR. In more common LiDAR vegetation mapping, the heights and surfaces of the foliage are desired.

However, some applications require the maximization of the light through the foliage, to the ground targets below. The new Navy technology concentrates the laser illumination power between the leaves of the foliage so the majority of light reaches the ground level.

Complementing this, the technology masks out areas of intermediate clouds, thus reducing the noise caused by these scattering returns and redirecting the light to areas in the scene of interest. If used for bathymetry applications, reflections from the water surface which cause high-intensity glints are masked out which improves collection from other non-masked parts of the field of view.

In addition to increasing laser power to specific areas of the scene to aid in the increased signal return from those regions, directed laser power can be used as an active warning signal to people and/or objects within the scene. Re-illuminating the scene at directed targets at a wavelength sensitive to detection by a person in the scene may alert them that their presence is being monitored. For example, such an alert would indicate to the targets that their presence was being monitored by unfriendly parties and as such their safety was possibly at risk.

The initial illumination beam used to detect the LiDAR returns is optionally invisible to the targets, while a shaped illumination beam is optionally at a wavelength visible to the targets.

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