Pietro Craighero Laboratory of Optoelectronics, University of Brescia 2D Vision Course Telecentric Measurement System

Pietro Craighero Problem definition  Measurement of the inner and outer radius Set up for inner radius Set up for outer radius

Pietro Craighero System Engineers vision have to face these problems: 1.Alteration of the magnification (due to object displacement) 2.Image distortion 3.Perspective errors 4.Low image resolution 5.Uncertainty of the position of the boundary (due to lighting geometry)

Pietro Craighero Hardware available  Telecentric technology addresses the need to have high- contrast images and almost no distortion  Telecentric lenses reduce or even cancel most of these problem, and for this reason have become a key component for any high accuracy gauging applications

Pietro Craighero Alteration of the magnification (telecentric lenses) dH = ds * theta = 1 * mm = 0,0017 mm With telecentric lenses the image size is left unchanged with object displacement, provided the object stays within a certain range often referred to as “depth of field” or “telecentric range”  In a telecentric lens the magnification change is determined by the “telecentric slope”  theta = 0,0017 rad  ds = 1 mm

Pietro Craighero Perspective errors  Telecentric lenses eliminate the perspective effect This effect is due to the specific path of the rays Non telecentric lens Telecentric lens

Pietro Craighero Good image resolution The resolution provided by telecentric lenses is compatible with very small pixel sizes and high resolution cameras thus increasing the measurement resolution. Frame rate : 11.2 fps Sensor type : CMOS Pixel size : 3.2 um Optical size : x mm Resolution : 2048 x 1536 Optical class : ½” Resolution class : 3.15 Mpix RSx = FOVx/(#pixel) = 46.5 mm / 2048 pixel = mm/pixel RSy = FOVy/(#pixel) = 34.9 mm / 1536 pixel = mm/pixel

Pietro Craighero Imaging system set up  Working Distance : 182,3 (+/-) 5 [mm]  Field of View (with ½” detector) : 46,5 x 34,9 [mm] WDWD 46.5 mm 34.9mm

Pietro Craighero Software structure  State machine  User choises Init / Idle /Calibrazione offline /Calibrazione online / Acquisizione online / Acquisizione offline / Misura Raggi Interni Misura Raggi Esterni Calibration & Acquisition

Pietro Craighero Inner radius  ROI selection? Default mode Manual mode ROI Cluster  Compute inner radius and display

Pietro Craighero Outer radius While(stop == false){.. If(new ROI drawn == false) {.. }

Pietro Craighero Outer radius While(stop == false){.. If(new ROI drawn == false) {.. } 30,33 mm

Pietro Craighero Conclusion set and choose the right hardware friendly interface design Thank you for your attention