Make Machine Vision Lighting Work for You

Transcription

1 Make Machine Vision Lighting Work for You Lighting is our passion Flexibility is our model Daryl Martin Technical Sales and Product Specialist Advanced illumination

2 Who is Advanced illumination? Ai is a Machine Vision lighting solutions company based in Rochester, Vermont 1 st Vision LED Lighting Company in the USA Full line of LED lighting & drive electronics (100K BTO products in 1-3 weeks) 50 Employees; 26 th year in Business Long History of Technology Innovation Complete In-house Custom Design & Prototyping Long-time Vision Partner to OEMs & Mfrs. Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

3 Topics Objectives of Vision Lighting Review of Light Cornerstones 1-4 (Geometry/Structure, Color & Wavelength, Filters) UV and IR Imaging Vision Lighting Design Method 9 Guidelines for Applying MV Lighting Otherwise known as: Vision Lighting Best Practices

4 Primary Objective of Vision Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Lighting What we really require is control of the lighting environment! Why? - Create Feature-appropriate lighting on the Part of Interest - Standardize components, techniques, deployment & operation - Generate Reproducible inspection results - Demonstrate Robustness for sample variations of all types

5 Lighting Contrast It s All About (creating) Contrast Contrast!! Have we? 1) Maximize contrast features of interest (Signal) No 2) Minimize contrast features of no interest (Noise) 3) Minimize sensitivity to normal variations minor part differences presence of, or change in ambient lighting sample handling / presentation differences Yes! Points 1 & 2 might solve some apps; # 3 can be critical!

6 Review of Light for Vision Illumination

7 Visible Light Properties UV Incident Illumination Near IR Absorb 400 nm 500 nm 600 nm 700 nm Human Visible Range Reflect Light Interacting with objects: Emit (fluorescence) Transmit Reflection Diffusion (Absorb) Refraction Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

8 4 Lighting Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Cornerstones Change Light / Object / Camera Geometry 3-D spatial relationship Change Light Pattern (Structure) How do we change (create) contrast? Warm Cool Light Head Type: Spot, Line, Dome, Array Illumination Type: B.F. D.F. Diffuse B.L. Change Spectrum (Color / Wavelength) Monochrome / White vs. Object and Camera Response Warm vs. Cool color families Object vs. Background Change Light Character (Filtering) Affecting the wavelength / direction of light to the camera Important: impact of incident light on the part and its immediate O R Y V G B Filter Image Courtesy Midwest Optical Systems Palatine, IL

9 Cornerstones 1&2: Lighting Geometry/Structure Techniques

10 Basic Lighting Techniques 1 - Partial Bright Field 2 - Dark Field 3 - Back Lighting

11 Advanced Lighting Techniques 4- Co-Axial Diffuse* 5 - Diffuse 6 - Flat Dome Diffuse Collimated Co-axial Back Lighting Multi-Axis / Combo Dome + Dark Field Bright and Dark Field Addressable Rows Full Bright Field Structured Laser/LED grids, lines Focused Linears * It should be noted that strictly defined, Co-axial Diffuse lighting is a partial bright field Technique. Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

12 Bright Field vs. Dark Field Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Typical On-Axis Ring Light Sample Geometry Bright Field Dark Field

13 Bright Field vs. Dark Field Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Classic W Pattern Partial Bright Field Lights in White Area (Inside the W ) Dark Field Lights in Grey Areas (Outside the W ) 45 Mirrored Surface Scratch

14 Dark Field Example - Angled light 45 degrees or less - Used on highly reflective surfaces - OCR or surface defect applications

15 Back Lighting - Edge or hole detection Q 1 - Useful on translucent materials Liquid fill levels Glass/plastic cracks High-accuracy gauging: - Use monochrome light - Shorter wavelengths better Use collimation parallel rays Longer l light may penetrate some objects better - Part P/A - Vision-Guided Robotics: Pick & Place Red 660 nm Back Light - Gauging: Including high-accuracy measurements IR 880 nm Back Light Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

16 Back Lighting Example Small Bottle Determine Fill Level Consider colors and materials properties also. Longer wavelength isn t always best for penetration! 660 nm Red Backlight 880 nm IR Backlight 470 nm Blue Backlight

17 Diffuse Dome - Similar to the light on an overcast day. - Creates minimal glare.

18 Co-Axial Diffuse Illumination - Light directed at beam splitter - Used on non-curved, reflective objects

19 Flat Diffuse - Diffuse sheet directed downward - Long WD and larger FOV - Hybrid diffuse (dome and Co- BF Axial) Diffuse On-Axis Diffuse Flat Diffuse Co-Axial DF Dome Ring

20 Technique vs. Object Surface Flat Matt e Surface Reflectivity Mixed Mirror Specular Axial Diffuse Geometry Independe nt Area Bright Field Surface Texture / Shape Uneven Topography Dark Field Flat Diffuse Curved Diffuse Dome / Cylinder

21 Inspection Environment Physical Constraints - Access for camera, lens & lighting in 3-D (working volume) - The size and shape of the working volume - Min and max camera, lighting working distance and FOV Part Characteristics - Is the part presented consistently in orientation & position? - Any potential for ambient light contamination? - Object stationary, moving, or indexed? - If moving or indexed: speeds, feeds & expected cycle time? - Strobing? Expected pulse rate, on-time & duty cycle? Ergonomics and Safety - Man-in-the-loop for operator interaction? - Safety related to strobing or intense lighting applications?

22 Cornerstone 3: Using Color and Wavelength

23 Create Contrast with Color Use Monochrome Light to Create Contrast 1 - Use Like Colors or Families to Lighten: Warm R V Cool (red light makes red features brighter) O B 2 - Use Opposite Colors or Families to Darken: Y G (red light makes green features darker)

24 Create Contrast with Color Warm Cool R V Red Green O B Y G Blue White 1 - red light makes red features brighter 2 - red light makes green features darker White light will contrast all colors; may be a compromise. 3 - Color affects both the object and its background! 4 - Hint: You are creating more contrast in this case Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

25 Cornerstone 4: Using Pass and Polarization Filters

26 Control it with pass filters Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Ambient Light Any light other than the vision-specific lighting that the camera collects. Controlling and Negating Ambient Light Turn off the ambient contribution Most effective... Least Likely! Build a shroud Very effective, but time-consuming, bulky and expensive Overwhelm the ambient contribution w/ high-power lighting (Continuous-on or Strobe over-drive) Effective, but requires more cost and complexity

27 Pass Filters in Machine Vision Pass filters exclude light based on wavelength. Reduce sunlight and mercury vapor light 4X Reduce fluorescent light 35X Graphics courtesy of Midwest Optical, Palatine, IL 715 nm Long Pass 510 nm Short Pass 660 nm Band Pass

28 Avoiding Surface Glare Change Geometry 3D spatial arrangement of Light, Sample, and Camera (preferred) Strobe to overwhelm glare from ambient sources Use polarization filters (least preferred) Courtesy Wikimedia Commons

29 Polarizing Filters in Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Vision On-axis Light w/o Polarizers w/o Polarizers On-axis Light w/ Polarizers Off-axis Light w/o Polarizers Up to 2 ½ f/stops opened! w/ Polarizers

30 Avoiding Surface Glare 3-D Reflection Geometry: Light - Sample - Camera

31 Avoiding Surface Glare - Bar Code Printing beneath cellophane wrapped package On-Axis Off-Axis Co-Axial Dark Bright Broad Diffuse Field Area Illuminator Ring Linear Light

32 Imaging with UV & Near IR Light Cornerstones 3 & 4

33 Vision Lighting Spectrum Typical CCD Sensor Human Visual System Graphics courtesy of Midwest Optical, Palatine, IL

34 Imaging with UV Light - Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Fluorescence Colors (wavelengths) and filters work together Fluorescing Printing Caveats: Fluorescing Polymers (nylon) 1) UV light is not always needed part dependent 2) Use band pass filters to enhance feature contrast 3) Goal is collecting emitted light from part, NOT excitation source light (unlike visible) 4) Emitted (fluorescent yield) light from part is always: - longer wavelength, thus less energy and less radiant power than source

35 Imaging with UV Light - Fluorescenc Under 355 nm UV and Strong Ambient Application of a Band Pass Filter Graphics courtesy of Midwest Optical, Palatine, IL Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT

36 Imaging with Near IR (NIR) Infra-red (IR) light interacts with sample material properties, often negating color differences. White light B&W Camera IR light B&W Camera

37 Vision Lighting Design Precision Lighting for Vision and Imaging 440 State Garage Road, Rochester, VT Method 1) Determine the Exact Features of Interest 2) Analyze Part Access / Presentation Clear or obstructed, Moving / Stationary Min / Max WD range, Sweet Spot FOV, etc. 3) Analyze Surface Characteristics Texture Reflectivity / Specularity Effective Contrast Object vs. background Surface flat, curved, combination 4) Understand Light Types and Applications Techniques Rings, Domes, Bars, Spots, Controllers, etc Bright Field, Diffuse, Dark Field, Back Lighting 5) Determine Cornerstone Issues 3-D Geometry, Structure, Color & Filters 6) Eliminate Ambient Light Effects / Environmental Issues

38 MV Lighting Best Practices 1) Coordinated Lighting & Optics are crucial when properly selected, they provide the foundation for the MV system. 2) Develop the lighting solution early in the vision system design process on the bench first, if necessary. 3) Dedicated Lighting = Control of the Lighting Environment. 4) Make the lighting solution robust AND reproducible. 5) Develop Object Feature-Appropriate Lighting. 6) Apply the 4 Cornerstones for enhancing contrast of features. 7) Be aware of and block ambient light. 8) Consider that light MAY interact differently w/ respect to surface texture, color, composition and incident wavelength. 9) Understand the Inspection Environment w/ respect to Physical Constraints, Object Characteristics and Ergonomic / Safety aspects.

39 Ai Company Contacts General Sales, International Sales, OEM Contacts Paul Kling (VP Sales and Marketing) , Regional Sales/Product Manager Midwest USA, Canada Daryl Martin , Regional Sales Western USA (excl AZ) Tyler Pence , Inside Sales and Customer Support Rob Kyle x 277, rkyle@advill.com Factory Apps Support Mike Romano x 227, mromano@advill.com Communications, Advertising

40 Questions? Light per unit Solid Angle (Projected at a sphere) Luminous, Radiant Intensity Lumens (lm /Sr); Watts (W / Sr) r Solid Angle Ω = A/r 2 Light Power (From an infinitely small sphere) Luminous, Radiant Flux A Lumens (lm); Watts (W) Light Available (At a Surface) Illuminance, Irradiance Lumens / m 2 (LUX); W / m 2 Light (Through an area) Luminance, Radiance Lumens / m 2 / Sr or cd / m 2 ; W / m 2 / Sr Light Reflected (From a Surface) Illuminance, Irradiance Lumens / m 2 (LUX); W / m 2 Transmitted or Emitted Light (Through or From a Surface) Luminous, Radiant Emittance Lumens / m 2 (LUX); W / m 2 Daryl Martin Technical Sales & Product Specialist Advanced illumination, Inc. 440 State Garage Road Rochester, Vermont USA Phone: Cell: dmartin@advill.com