Enhanced field-of-view LiDAR

Small, low power, yet highly capable lidar that can fit on a space-limited platform

Photonics Electronics
A helicopter creates a dust cloud.

A MEDEVAC helicopter in Iraq creates a dust storm causing poor visibility. (Army file photo)

LiDAR (light/laser detection and ranging) systems use light to determine the distance to an object. Since the speed of light is well known, lidar can use a short pulsed laser to illuminate a target and then time how long it takes the light to return.

The advantage of lidar over radar (radio detection and ranging) is that lidar can also image the target at the same time as it determines the distance. This allows a 3-D view of the object in question.

Lidar receiver performance is directly related to the effective aperture of the input optical system. A larger aperture increases the amount of light energy collected and increases the effective range of the system. However, the field-of-view (FOV) of the optical system is inversely proportional to the effective aperture, practically limiting the size of the effective aperture for a given FOV.

Army researchers have solved this dilemma by dividing the overall FOV into smaller pieces, with each smaller piece covered by a separate receiver element that can have a larger effective aperture due to its smaller FOV. When properly combined, the small FOV receivers increase the overall system performance over that which can be achieved with a single, wide FOV receiver.

One application of the enhanced capability is the Rotorcraft Advanced Surveillance and Collision Avoidance Lidar, or Rascal. The imaging lidar provides a 3-D picture of the landing zone along with object size and distance from the aircraft as an aid for a rotary aircraft pilot landing in difficult situations. The lidar device is small and can easily be re-packaged into an existing internal compartment on the rotorcraft. An external pod mount is unnecessary.

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