accurate 3D inspection Marcel Krist, CEO What kind of applications - PowerPoint PPT Presentation

Photonfocus AG Comparison of 3D Algorithms to ensure accurate 3D inspection Marcel Krist, CEO

What kind of applications are using the 3D laser triangulation approach? Different applications need different methods and different 3D hardware and software Titelmasterformat durch Klicken bearbeiten Source Marexi Marine Techn. ▪ Dark areas vs. surface defects Titelmasterformat durch Klicken ▪ Measurements in different planes ▪ Quality control of complex shapes ▪ Volumetric measurements Source LAP Laser 2

Many 3D camera manufacturers provide a sub-pixel accuracy Principle of 3D laser triangulation and accuracy drivers Titelmasterformat durch Klicken bearbeiten Accuracy aspects/drivers Titelmasterformat durch Klicken ▪ CMOS Sensor (Pixel size, resolution, Noise, etc.) ▪ Top quality lens ▪ Bandpass filter ▪ Speckle-reduced laser ▪ Ideal illumination (LED or Laser in “ right ” color) ▪ No or very low vibrations on object to be scanned ( “ perfect ” conveyor belts) ▪ Calibrated system ▪ Set-up of camera and laser ▪ Working distance of camera ▪ Auto exposure ▪ Perfect 3D algorithm 3

Solutions for laser triangulation – compact scanners Pros and Cons of compact or portable 3D scanners using laser triangulation Titelmasterformat durch Klicken bearbeiten Generic compact 3D laser scanner Titelmasterformat durch Klicken Pros Cons Laser Diode ▪ Fast set-up ▪ Fixed angels, reflection and CMOS Detector ▪ Calibrated sensor artefacts (disruptions) ▪ Dedicated software ▪ Different compact scanners Lens Lens ▪ Standard feature set needed for different applications ▪ Space is limited for Working distance multisensory systems (stand-off) ▪ Price increases due to Measurement Range complexity ▪ Algorithm changes are almost impossible and algorithm often is unknown 4

Solutions for laser triangulation – free 3D construction Typical triangulation setup in a free configruable system Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken Camera with one Line Finder Two cameras to cope with occlusions Camera with two Line Finders Cons of Adaptive configuration Pros of Adaptive configuration ▪ Working distance is variable ▪ Deep 3D knowledge required ▪ Components research is needed ▪ Flexible angles of camera/s and laser/s ▪ Variable lens selection ▪ Calibration as ongoing task, if set-up change ▪ Multiple laser options, fast changes ▪ Algorithm can be adapted to application needs 5

Characteristics of surfaces determine the inspection quality Characteristics of specular, Lambertian and Translucid-Lambertian surfaces Titelmasterformat durch Klicken bearbeiten Cone of light as viewed Titelmasterformat durch Klicken by the camera Arrow lengths indicate the power of the FOV reflected light rays in every Specular surface (Mirror, …) Lamb. – Spec. surface (Metal, …) direction. These light rays are also visible by the camera!!! Lamb. surface (Opaque plastic, … ) Translucid-Lambertian surface 6

Laser stripe recognition (reflection) on different surfaces Laser stripe on Lambertian and Translucid-Lambertian surfaces Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken Translucid-Lambertian surface Lambertian Surface Intensity profile of the The maximum The maximum Intensity profile of the stripe stripe intensity is NOT in the intensity is in the Image image middle of the stripe middle of the stripe 95% of all analysed objects! image image. 7

Line Finder algorithm versus Centre of Gravity (COG) What kind of accuracy can be achieved with the COG method? Titelmasterformat durch Klicken bearbeiten ▪ COG = Centre of gravity Titelmasterformat durch Klicken ▪ Grey values of pixels above threshold ▪ Calculate weighted COG out of grey values of every pixel COG = Le + ∑(P i ∙x i )/ ∑(P i ) Sum of grey values P i Left Edge above threshold First moment of grey values above threshold Threshold Le th of a pixel “ Real ” resolutions around 1 / 10 8

Line Finder algorithm versus Centre of Gravity (COG) What accuracy can be achieved with the Line Finder? Titelmasterformat durch Klicken bearbeiten ▪ Digital filtering of noise Titelmasterformat durch Klicken ▪ Non linear interpolation ▪ Maximum intensity value detector for non-gaussian curves Resolutions of up to 1/64 th of a pixel!!! 9

Development of Robust LineFinders Robustness Analysis of LineFinders in Presence of Reflections with Uncalibrated 3D Profiles Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 10

Development of Robust LineFinders Generation of Calibrated 3D Profiles with Structured-light 3D Scanners and Tactile Probes Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 11

Development of Robust LineFinders Comparison of Robustness and Sub-Pixel Resolution with Calibrated 3D Profiles Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 12

Development of Robust LineFinders Simulations of Sub-Pixel Resolution vs SNR – Gauss Profile with Speckle Noise Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 13

Development of Robust LineFinders Simulations of Sub-Pixel Resolution vs SNR – Weibull Profile with Speckle Noise Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 14

Solutions for laser triangulation Mix cameras to complete the 3D Titelmasterformat durch Klicken bearbeiten Camera B Camera A Titelmasterformat durch Klicken This area is not visible by camera A Rane Map Camera B Rane Map Camera A Rane Map Camera A and B 15

Line Finder – Surfaces of 3D objects COG delivers 3D scans with rough surfaces – Line Finder has better accuracy Titelmasterformat durch Klicken bearbeiten COG Line Finder Titelmasterformat durch Klicken 8x to 10x better detection accuracy 16

Modes of Photonfocus 3D cameras Photonfocus 3D camera operating modes Titelmasterformat durch Klicken bearbeiten 2D only Titelmasterformat durch Klicken Laser line detection is turned off and the camera behaves as a normal area scan camera. This mode serves as a preview mode in the setup and debugging phase of the vision system. 2D & 3D Laser line detection is turned on. The sensor image (2D image) is transmitted together with the 3D data. In the PF 3D Suite, the detected laser line is shown as a coloured line in the 2D image. This mode serves as a preview mode in the setup and debugging phase of the triangulation system. 3D only Laser line detection is turned on and only 3D data plus an additional image row for line scan applications is transmitted. The scan rate of this mode is considerably faster than the 2D&3D mode. This is the real working mode of the standard cameras. Moving ROI This feature enables at small ROI’s high frame rates due to the automatic tracking of the laser line. 17

Moving ROI – Camera based line tracking Automatic Tracking of Laser Lines in Small ROI ‘ s Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken 18

Summary Benefits of creating your “own” 3D algorithm Titelmasterformat durch Klicken bearbeiten Build your own 3D algorithm and…. Titelmasterformat durch Klicken ▪ .....you get a flexible, robust and accuract 3D inspection tool ▪ …..you get better detection results and smaller details will be visible ▪ .....you are able to take into consideration your customer feedback and expert knowledge ▪ .....you can improve your line stripe saturation and sub-pixel resolution ▪ .....you know exactly the behaviour of your 3D algorithm and you can control it! 19

Thank you very much for your attention Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken Photonfocus AG Bahnhofplatz 10 CH-8853 Lachen SZ Switzerland Phone: +41 55 451 00 00 www.photonfocus.com info@photonfocus.com sales@photonfocus.com Date: March 2018 Produced by: Marcel Krist, CEO 20

3D laser triangulation can uncover the non visible (non-descript) Dark areas vs. surface defects Titelmasterformat durch Klicken bearbeiten Dark areas and holes can be Titelmasterformat durch Klicken mixed or holes can be not well seen Grey image of a wood block In a depth map, holes can be easily distinguished from the base material Pseudo-color depth image of the wood block 21

3D laser triangulation used for volume measurement and sorting Volume measurement Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken ▪ Determination of volumes ▪ Determination of dimensions ▪ Sorting into quality classes Source: Baixcat Vision S.L. Source Marexi Marine Technology. 22

3D laser triangulation used for quality inspection Inspection system for quality control in railway Titelmasterformat durch Klicken bearbeiten Titelmasterformat durch Klicken Inspection system for quality control of rails, using 2 laser lines (3 and 4) and 2 cameras (1 and 2). [A]: Light-section image from the top camera [1], used to inspect the running surface (triangulation angle of 60 ° to the laser line generator [3]). [B]: Light-section image from the side- mounted camera [2], used to inspect the rail flank. 23

Line Finder vs. COG Comparison of COG and Line Finder without noise Titelmasterformat durch Klicken bearbeiten COG & Line Finder ▪ Lambertian surface Titelmasterformat durch Klicken ▪ Translucid-Lambertian surface Line Finder COG 24