AIM TSC DPM Ad Hoc

1
AIM TSCDPM Ad Hoc

• A Revised Quality Measurement Method for DPM
• Presentation to MH-10
• Jan 13, 2005

2
Agenda

• Review problem and approach
• Status of new specification
• Summary of changes
• Application Guidance
• Next Steps - Ad hoc meeting in Feb.

3
Background the problem

• Good DPM marks got failing grades under todays
  ISO/IEC 15415 method
• Good as determined by visual inspection and
  reader performance
• Typical failure modes
• Symbol Contrast
• Unconnected Dots in the L
• Sub-optimal illumination

4
Status of new specification

• Draft specification has been distributed and
  comments reviewed
• Most open questions have been resolved
• Grading parameters contrast, mod, etc.
• Lighting Angles
• Some questions remain
• Algorithm for dot peened symbols
• Specular image calibration

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Summary of Changes

• Many types of lighting
• Algorithm to connect the dots for finding the
  L pattern in dot peened symbols
• Specular and non-specular reflection
• Modified calculations and reporting methods of
• Symbol Contrast (Cell Contrast)
• Modulation (Cell Modulation)

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Lighting - 30 Low Angle
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Lighting - 30T Two Sides
Needed for brushed textures Parts are
directionally sensitive
30Q
30T
30T
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Algorithm to Connect Dots
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Algorithm to Connect Dots
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Algorithm to Connect Dots
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Algorithm to Connect Dots
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Algorithm for Thresholding

• Optimum Threshold
• Improves Modulation Grade
• New Name -gt Cell Modulation

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A Failing Symbol
Peen with Dull Pin
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Optimized Thresholding

• Otsus algorithm for bimodal histograms
• Finds a threshold that gives smallest variance of
  two resulting sub-histograms
• T1 - on initial 20X circle
• T2 - on area of symbol
• T3 - only at module centers

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SC -gt CC (Cell Contrast)

• CC Cell Contrast
• For images that reflect more than a 100 diffuse
  target, first set 100 to upper end of histogram
• Measure from (Mean of dark - sigma of dark) to
  (Mean of light sigma of light)
• Grade boundaries are reduced
• 35
  lt 4
• 30 lt 3 lt 35
• 25 lt 2 lt 30
• 20 lt 1 lt 25

16
MOD -gt CM(Cell Modulation)

• Normalized for 0 at threshold and 100 at mean
  of each sub-distribution
• UEC Overlay only uses A, B, F levels. C D
  merged into B.

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Modification to FPD

• AG (average grade)
• modified to DDG (distributed damage grade)
• Modulation overlay restricted to only use D/F
  level for DDG segments

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Guidance to Applications

• Category 0 Package Labels, that non-specialized
  readers need to read

• Symbols that pass this criteria are easy to
  read and not really direct part marks
• Use Existing IEC/ISO 15415

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Guidance to Applications

• Category 1 parts to be scanned in field service
  using Hand-held DPM scanners

• These symbols are the source of most of the
  disconnect between readers and verification (as
  it stands with existing IEC/ISO 15415)
• This is the Category of typical symbols that are
  failing IEC/ISO 15415
• These symbols are readable by many hand held
  readers (although somewhat specialized for DPM)
• These symbols may be a little hard to read,
  require some orientation, and generally will
  require somewhat specialized DPM enabled readers

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Guidance to Applications

• Category 2 small internal parts, need fixed
  cameras and specialized lighting angle
• These symbols are being read today mainly by
  specialized setups
• Are difficult to read even by specialized hand
  held readers because orientation is critical
• Symbols that pass this criteria may be hard to
  scan with un-oriented hand held scanners

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Next Steps

• There are still some open issues
• Low angle lighting for dot peen symbols
• Calibrating specular images
• Handling bright spots in specular images
• Adding process control measurements
• Dot ovality, size,
• Informative document
• Comparison to AS9132

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Conclusions

• The DPM verification technology issues have been
  addressed
• Guidance to Applications is included
• Draft Specification summarized here
• Comments on Draft are welcome
• Testing is needed on a broad range of parts

23
AIM TSCDPM Ad Hoc

• A Revised Quality Measurement Method for DPM
• Presentation to MH-10 SC 8
• Jan 13, 2006