Shape from Shading. Surface Inspection for Challenging Surfaces

Shape from Shading Surface Inspection for Challenging Surfaces

SHAPE FROM SHADING Function Directional illumination

SHAPE FROM SHADING Function Diffuse illumination

trevista Structured and diffuse dome illumination

Algorithm Algorithm with 4 input images 4 + 1 result images Slope image x direction Slope image y direction Curvature image Integration image (optional) Texture image

Result images Slope x direction Slope y direction Curvature Texture

Sequence Structured dome illumination Result images show slope and texture Test program identifies defects

Benefit Defects starting from few microns in height or depth can be identified Inspection of different materials (metal, ceramics, plastic ) Compensation for texture features and gloss (different material batches, lubrication ) Minimum number of pseudo defects

Benefit Inspection of curved surfaces Maximum part output Software algorithm optimized for multicore CPUs Calibrated system, no illumination tests required Easy Integration

trevista component Structured dome illumination Integrated camera mounting LED controller unit Software DLL with dongle

Field of view Field of view 20mm Field of view 50mm Field of view 200mm

Models trevista SURFACE Inspection of static parts trevista CYLINDER Inspection of cylindrical parts trevista MULTILINE Inspection of moving parts

trevista SURFACE Inspection of static parts Area scan camera Image capture typ. 15-100ms/MPixel

trevista CYLINDER Inspection of cylindrical parts Rotation of part Line scan camera 2k or 4k Line frequency (4 illuminations) up to 15kHz/4

trevista MULTILINE Inspection of moving parts Linear movement or rotation Line length 2k Line frequency up to 10kHz

trevista MULTILINE Used for rotary table sorting device Simultaneous inspection of front side and back side

Inspection features Inspection of grooves, dents, scratches Difficult surfaces with turning marks and along edges

Inspection features Inspection of sealing areas Reading of stamped codes

Inspection features Short-wave defects visible in curvature image (non directional) Medium-wave defects visible in slope image (directional) Long-wave defects visible in integration image (non directional) Differences in brightness visible in texture image

Materials Metal parts of any kind and production technology (turned, milled, grinded, rolled, stamped with diffuse up to glossy reflection) Plastic, rubber Ceramic Printed circuit boars, bonding contacts

Parts Turned parts, rotationally symmetric parts Screws Sleeves Stamping parts Profile bars

SHAPE FROM SHADING Turned part Texture Slope x direction

SHAPE FROM SHADING Turned part Slope y direction Curvature

SHAPE FROM SHADING Turned part Integration Slope radial direction

SHAPE FROM SHADING Turned part Result images can be used in parallel (e. g. texture image is used for part tracking) Slope image in tangential direction suppresses turning marks and shows defects Slope image in tangential direction is suitable for inspection of edges Slope tangential direction Easy and reliable detection of finest defects

Profile bar Conventional illumination Curvature image

Metal sleeve Conventional illumination Curvature image

Summary Shape from Shading is an established technology for detecting finest defects even on challenging surfaces, in particular metal surfaces The inspection of difficult surfaces and along edges is possible using the result images which are best suited for the specific task