Vision Lighting Training Seminar

1. Vision Lighting Training Seminar

2. Today’s Objectives • Machine Vision Illumination Principles & Techniques • Sample Applications • Imaging Beyond the “Visible” – Near IR & UV • “Pass” Filters and Polarization

3. Sources • LED - Light Emitting Diode • Quartz Halogen – W/ Fiber Optics • Fluorescent • Metal Halide (Microscopy) • Xenon • High Pressure Sodium • Ultraviolet (Black Light) • Infrared • Electro-luminescent

4. Source Comparisons ** Until Recently

5. Lighting – Intensity vs. Spectrum Quartz Halogen / Tungsten Mercury (Purple) 100 Daytime Sunlight Relative Intensity (%) 80 Fluorescent 60 White LED Xenon 40 20 Red LED 0 300 400 500 600 700 Wavelength (nm)

6. Optical Characteristics of an LED Mechanical Axis Optical Axis

7. Broad Area Linear Arrays (BALA) AL4424-660

8. RGB Lights • Red, Green, Blue light heads offer flexibility • Equal parts RGB creates white light • Color mixing capabilities

9. The right light helps the vision system do its job • Lighting is one of the least expensive, most flexible components in any machine vision inspection system. • Sample-appropriate Lighting is critical to a successful inspection.

10. Brief Review of Light and Optics for Vision Illumination

11. The Visible Light Spectrum IR UV 390 735 400 nm 500 nm 600 nm 700 nm Human Visible Range Decreasing Frequency Increasing Wavelength Decreasing Photon Energy Increasing Photometric Output Increasing Penetration Depth

12. The Visible Light Spectrum • Light is Seen Differently by film, humans and CCDs IR UV 390 455 470 505 520 595 625 660 695 735 400 nm 500 nm 600 nm 700 nm Human Visible Range

13. Reflection on Specular Surfaces • Light reflects at the angle of incidence • Just like a pool ball off the bumper F1 = F2 1 2 • Surface Angle determines where light comes from in order to illuminate the surface

14. Divergence and Intensity • Intensity falls with the inverse square of the divergence radius • I = 1/r2 • Use collimation and short working distances when possible

15. Lighting Environment and the Part • Ring Light • Small Solid Angle Note: The solid angle of any light source may be increased by placing it closer to the object of interest. • Continuous Dome • Large Solid Angle

16. OK, so where do we start?

17. The Optimized Image • It’s All About Contrast! • Feature Separation or Segmentation • Maximum contrast • features of interest • Minimum contrast • features of no interest (noise) • Minimum sensitivity to normal variations • minor part differences • presence of, or change in ambient lighting • sample handling / presentation differences

18. Creating Contrast – Lighting Cornerstones • Change Light Direction w/ Respect to Sample and Camera (Geometry) - 3-D spatial relationship - sample, light & camera • Change Light Pattern (Structure) - Light Head Type: Spot, Line, Dome, Sheet - Illumination Type: B.F. - D.F. - Diffuse - B.L. • Change Spectrum (Color / Wavelength) -Monochrome, white vs. sample / camera response - Warm vs. cool color families – object vs. background Need to understand the impact of incident light on both the part of interest and its immediate background!

19. General Sequence for Lighting Analysis • Analyze Part Access / Presentation - Clear or obstructed - Min / Max WD range - Moving / stationary - Sweet Spot FOV • Analyze Surface Characteristics - Texture - Reflectivity / Specularity - Effective Contrast – Object vs. background - Surface flat, curved, combination • Light Types and Applications Techniques Awareness - Rings, Domes, Bars, ADIs, Spots, Controllers - Bright Field, Diffuse, Dark Field, Back Lighting • Determine Cornerstone Issues - 3-D Geometry, Structure, Color • Ambient Light Effects / Environmental Issues

20. Using Color to our Advantage

21. Using Color Use Colored Light to Create Contrast Warm Cool • Use Like Colors or Families to Lighten(yellow light makes yellow features brighter) • Use Opposite Colors or Families to Darken(red light makes green features darker) R V O B Y G

22. Using RGB View with color camera under white light View with B&W camera under white light

23. Using Monochrome LED Illumination Red LED Green LED White Light Blue LED

24. Using Geometry and Structure

25. Common Lighting Techniques Partial Bright Field Dark Field Back Lighting Diffuse Dome Axial Diffuse Full Bright Field

26. Bright Field vs. Dark Field Camera Bright Field Image Bright Field Ring Light Mirrored Surface

27. Bright Field vs. Dark Field Dark Field Image Camera Scratch Dark Field Ring Light Mirrored Surface

28. Dark Field • Angled light • Used on highly reflective surfaces • OCR or surface defect applications

29. Result of Dark-Field Light • Emphasize Height Changes • Diffuse Surfaces are Bright • Flat Polished Surfaces are Dark • Shape and Contour are Enhanced

30. Axial Diffuse • Light directed at beam splitter • Used on reflective objects

31. Result of Axial Diffuse Illumination • Surface Texture Is Emphasized • Angled Elevation Changes Are Darkened

32. Diffuse Dome • Similar to the light on an overcast day. • Creates minimal glare.

33. Wavelength vs. Composition Checklist Monochrome

34. Sample Applications

35. Bright field spot light Dark Field ring light Line light Bright field ring light Stamped Date Code • Recessed metal part • Reflective, textured, flat or curved surface

36. Standard Dome Dark Field Ring Light Broad Area Linear Array Bright Field Ring Light Data Matrix • Peened data matrix • Flat, shiny surface

37. Bright Field Ring Light Dark Field Ring Light Broad Area Linear Array Axial Diffuse Illuminator UPC Bar Code • Printing beneath cellophane wrapped package

38. Bar Code under Clear Wrap Broad Area Linear Array

39. Dark Field Ring Light Bright Field Spot Light Bright Field Ring Light Diffuse Dome Axial Diffuse Illuminator Ink Jet OCR • Purple Ink • Concave, reflective surface

40. Using Near IR and Near UV Light

41. Imaging Beyond “Visible” – Near IR • Infra-red (IR) light interacts with sample material properties, often negating color differences. Black Red White Yellow White light – B&W Camera IR light – B&W Camera

42. Imaging Beyond “Visible” – Near IR • Near IR light can penetrate materials more easily because of the longer wavelength. Red 660 nm Back Light IR 880 nm Back Light

43. Imaging Beyond “Visible” – Near IR • Red 660 nm light reveals the blue dot matrix printed bottle date & lot codes. IR 880nm Back Light Red 660nm Back Light

44. Imaging Beyond “Visible” – Near UV • Near UV light when used w/ a matched UV excitation dye, illuminates codes and structural fibers. • Top Image Set: Diaper • Lower Image Set: Motor Oil Bottle

45. Imaging Beyond “Visible” – Near UV • Near UV light fluoresces many polymers, including nylon. • Top Image: UV Light, B&W CCD • Lower Image: UV Light, Color CCD

46. Designing Vision Lighting • When designing a vision system and parts handling / presentation, optimize the lighting solution early in the process, if possible. • Remember like colors (or color family) lighten and opposite colors darken. • If using monochrome LED light, let a band pass filter control ambient light. • Think Geometry – the 3-D spatial relationship among sample, light, and camera. • Consider how the light pattern and color will potentially interact with the sample and background surfaces.

47. Light Application Tips

48. Filters are useful too!

49. Pass Filters in Machine Vision 715 nm Long Pass • Pass filters exclude light based on wavelength. • Sunlight and mercury vapor light are reduced by 4X • Fluorescent light is reduced by 35X 510 nm Short Pass 660 nm Band Pass

50. Pass Filters • Top Image: UV light w/ strong Red 660 nm “ambient” light. • Bottom Image: Same UV and Red 660 nm “ambient” light, with 510 nm Short Pass filter applied.