Single-shot three-dimensional sensing with improved data density

Abstract

We introduce a novel concept for motion robust optical 3D sensing. The concept is based on multiline triangulation. The aim is to evaluate a large number of projected lines (high data density), in a large measurement volume, with high precision. Implementing all those attributes at the same time principally allows for the "perfect" single-shot 3D movie camera (our long-term goal). The key problem toward this goal is ambiguous line indexing: we will demonstrate that the necessary information for unique line indexing can be acquired by two synchronized cameras and a back projection scheme. The introduced concept preserves high lateral resolution, since the lines are as narrow as the sampling theorem allows. No spatial bandwidth is consumed by encoding of the lines. In principle, the distance uncertainty is only limited by shot noise and coherent noise. The concept can be also advantageously implemented as a hand-guided sensor with real-time registration, for a complete and dense 3D acquisition of complicated scenes.

Single-shot 3D motion picture camera with a dense point cloud

“…How to manage the necessary "indexing" of that many lines? The corresponding ambiguity problem is discussed in a previous paper [15]. As the novel solution is an extension of the earlier results, these are briefly summarized:…”

“…This second sensor delivers more precise data, but with ambiguity. As both sensors look at the same projected lines, the first sensor can "tell" the second sensor the correct index of each line, via the same back-projection mechanism as described in [15]. With the proper choice of the triangulation angles, there is no accidental overlap of false and correct data.…”

“…4(e)). Reference [15] explains how these outliers can be detected and corrected by exploiting the data of a second camera, positioned at a second angle of triangulation. The basic idea is to (virtually) project the data of the first camera back onto the camera chip of the second camera.…”

Reflections about holographic and non-holographic acquisition of surface topography

“…Typically, single-shot sensors display point cloud densities much lower than 1/3 [18] as the available space bandwidth additionally needs to account for the solution of the indexing problem. The "single-shot 3D movie camera" [12,18,19] solves this problem with a trick that (from a systems-theoretical side) shows strong similarities to twowavelength holography or -interferometry: Instead of a sequence of images taken at different wavelengths (or fringefrequencies), two cameras simultaneously capture two images of the fringe-encoded surface from two different viewing angles. This is noteworthy, as the mathematical structure of the deocding algorithms strongly resemble those used in dual-wavelength interferometry [18,20,21].…”

Exploiting wavelength diversity for high resolution time-of-flight 3D imaging

“…Recent years have witnessed an explosion of interest in threedimensional (3D) imaging and sensing technologies [1][2][3][4][5][6][7][8]. Common applications include medical 3D imaging [9][10][11][12], precision engineering, industrial inspection [13][14][15], absolute distance metrology [16][17][18], autonomous navigation [1,19], documentation of cultural heritage [20,21], and virtual/augmented reality [22][23][24].…”