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Photometric Stereo 3D Inspection

Euresys SARequest Info
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Among the numerous techniques used for extracting 3D information from scenes, Euresys' Photometric Stereo is a function estimating the orientation and albedo of each point of a surface by acquiring several images taken from a single viewpoint under illumination from different directions. Requiring only one camera, different images are acquired in synchronization with the lighting, it is suitable for the detection of details present on the object’s surface.

The Photometric Stereo algorithm is available in Euresys' Open eVision Easy3D library. It can be used as a preprocessing phase before other Euresys libraries such as code reading, optical character recognition, alignment, measurement, or defect detection.

How does it work?
For a given vision set-up (positions and angles of the inspected object, lights (typically 3 or 4), and camera), calibrated on a reference object, image capture of the inspected objects is performed in multiple steps for each lighting angle.

Euresys - Photometric Stereo 3D Inspection 1

At user's request, Photometric Stereo individually extracts surface normals, albedo, X & Y gradients, mean and Gaussian curvatures and use them for the reconstruction of the 3D information in the 2D domain making it ready for further processing.

Euresys - Photometric Stereo 3D Inspection 2

In above Figure :
  • Object captured under four lighting conditions (1 to 4)
  • Reconstructed image (A)
  • Isolated subset of data (B), here Gaussian curvature information.
  • Inspection results (C) Open eVision EasySegment Deep Learning library identifies two puncture points (B).

Identifying and tuning the most appropriate parameters to the actual application results and significant speed improvement, e.g. specific linear detections, detection of sharp edges, specification of a specific Region of Interest (ROI).

One can see how originally not detectable information can be captured by Photometric Stereo to be effectively exploited by a standard eVision library (EasySegment in this instance). The Photometric Stereo Imager functionality is available in Euresys' Open eVision Easy3D Library.

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ProductsEuresysEasy3DPhotometric StereoOpen eVisionsurface inspectionlightingcomputer visionvisionVision Spectra

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