Absolute phase retrieval methods for digital fringe projection profilometry: A review

We propose a high-speed projection system that is able to project statistical speckle patterns at a rate of 500Hz. Its purpose is to generate structured light for a real-time photogrammetry stereo vision setup. As conventional digital light projector (DLP) projection setups are limited in their maximum projection rate to 250Hz for gray-value patterns, stripe projection systems are usually applied for real-time three-dimensional (3D) measurements. However, these techniques can only be used on steady surfaces as phase unwrapping has to be done. In contrast, the proposed setup is able to measure the shape of multiple spatially separated objects at once. We compare the speckle setup with a system using a DLP projector and with other fast 3D shape measurement setups, like the widely used stripe projection methods, qualitatively and quantitatively.

High-speed pattern projection for three-dimensional shape measurement using laser speckles

A stereo-phase-based absolute three-dimensional (3D) shape measurement method is provided that requires neither phase unwrapping nor projector calibration. This proposed method can be divided into two steps: (1) obtain a coarse disparity map from the quality map; and (2) refine the disparity map using local phase information. Experiments demonstrated that the proposed method could achieve high-quality 3D measurement even with extremely low-quality fringe patterns. The method is particular well-suited for a number of different applications including in mobile devices such as phones.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1076&context=me_pubs

Absolute three-dimensional shape measurement using coded fringe patterns without phase unwrapping or projector calibration

Here we propose a method for 3D shape measurement by means of phase correlation based fringe projection in a
stereo arrangement. The novelty in the approach is characterized by following features. Correlation between phase
values of the images of two cameras is used for the co-ordinate calculation. This work stands in contrast to the sole
usage of phase values (phasogrammetry) or classical triangulation (phase values and image co-ordinates - camera
raster values) for the determination of the co-ordinates. The method's main advantage is the insensitivity of the 3D-coordinates
from the absolute phase values. Thus it prevents errors in the determination of the co-ordinates and
improves robustness in areas with interreflections artefacts and inhomogeneous regions of intensity. A technical
advantage is the fact that the accuracy of the 3D co-ordinates does not depend on the projection resolution. Thus the
achievable quality of the 3D co-ordinates can be selectively improved by the use of high quality camera lenses and
can participate in improvements in modern camera technologies.
The presented new solution of the stereo based fringe projection with phase correlation makes a flexible, errortolerant
realization of measuring systems within different applications like quality control, rapid prototyping, design
and CAD/CAM possible. In the paper the phase correlation method will be described in detail. Furthermore, different
realizations will be shown, i.e. a mobile system for the measurement of large objects and an endoscopic like system
for CAD/CAM in dental industry.

3D shape measurement with phase correlation based fringe projection

Three-dimensional (3-D) measurement systems based on coded-light techniques are conventionally limited by the projection speed, which is typically in the range of a few 100 Hz, resulting in 3-D frame rates of 1 to 60 Hz. We propose to use an array projector for 3-D shape measurements, which enables much higher projection frame rates of up to the 100-kHz range. In contrast to previous setups, it does not project well-known phase-shifted sinusoidal fringes and Gray code patterns, but aperiodic sinusoidal fringes. This new technique, based on sine-shaped fringes with spatially and temporally varying offset, amplitude, period length, and phase shift, allows accurate 3-D measurement of objects, even with sharp edges, high slope, or varying surface properties, at high speed up to the kilohertz range. This paper explains the 3-D measurement principle and the basic design of an array projector that projects aperiodic sinusoidal fringes. It verifies the consistency between specified and projected patterns and points out the results of the setup’s characterization, e.g., of its high-speed capability. Furthermore, first 3-D shape measurements at a projection frame rate of 3 kHz resulting in a 3-D frame rate of >330  Hz are presented and evaluated.

Array projection of aperiodic sinusoidal fringes for high-speed three-dimensional shape measurement

This article presents a fast and accurate method to measure human faces for medical applications To encode an object point, several random patterns are projected A correlation technique, which takes only the area of one pixel into account, is used to locate the homologous points It could be shown that band limited random patterns are helpful for noise reduction The comparison of the point cloud of a measured plane with an ideal one showed a standard deviation less then 50μm Furthermore a depth difference of 20μm is detectable

Human face measurement by projecting bandlimited random patterns

In this article a rapid and self-calibrating stereophotogrammetry based method for 3D measurements is described. The approach uses a series of statistical generated illumination patterns to encode the surface under test. The allocation of homologous points, which is necessary for 3D reconstruction by triangulation, is done by an adapted correlation technique.

/pdf/3d-measurement-of-human-face-by-stereophotogrammetry-317sxferj0.pdf

Holger Wagner

Papers

Human face measurement by projecting bandlimited random patterns

3D measurement of human face by stereophotogrammetry