Speckle Structured Light

Projecting a random infrared speckle pattern onto a scene and computing depth from how it deforms or matches.

Speckle structured light is a form of structured light: an infrared laser, passed through a diffractive element, projects a pseudo-random pattern of speckles; a camera photographs where the speckles land on the object’s surface, and comparing this against a pre-calibrated reference pattern gives the depth of every point via triangulation. Because each small patch of the speckle pattern is unique, matching can be done from a single frame, which makes it well suited to dynamic scenes. The original Kinect (using PrimeSense’s design) and many phone face-recognition modules use this approach. Active stereo cameras (such as the RealSense D400 series) also project a speckle pattern, but there it serves to “add texture” to an otherwise texture-less surface, with depth still computed through stereo matching. Its drawback is that the speckle pattern is easily washed out in strong outdoor sunlight, and accuracy drops at longer range.

ExampleThe original Microsoft Kinect outputs a depth map using infrared speckle projection combined with a single infrared camera.

Also called

Laser Speckle Pattern, Speckle Projection

Related

Structured Light · Active Stereo · Depth Camera · Triangulation · Time of Flight

Sources

Structured-light 3D scanner - Wikipedia