Robust and objective automatic optical surface inspection using modulated dark field phasing illumination

Heejoo Choi, John Kam, Joel D. Berkson, Logan R. Graves, Huang Lei, Dae Wook Kim

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Dark field illumination (DFI) is an elegant inspection technique sometimes used to detect particles on a specular surface. However, traditional DFI struggles with repeatability, limiting its applications in automated inspection. We present an improvement to DFI by introducing a modulated dark field illumination (MDFI) that utilizes the phase rather than the intensity in the detection of defects. For modulated dark field illumination (MDFI), the phase-based information is independent from the reflectance of the surface, but has a higher sensitivity to the light scattered from a defect than DFI. As a result, we obtain a robust computational image process method that is insensitive to the environment and provides clearly defined defect information. In order to extend the application to industry, the instantaneous MDFI systems were developed and validated.

Original languageEnglish (US)
Title of host publicationApplied Optical Metrology III
EditorsErik Novak, James D. Trolinger
ISBN (Electronic)9781510628977
StatePublished - 2019
EventApplied Optical Metrology III 2019 - San Diego, United States
Duration: Aug 13 2019Aug 15 2019

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceApplied Optical Metrology III 2019
Country/TerritoryUnited States
CitySan Diego


  • Automatic optical inspection
  • Dark field
  • Particle detection
  • Phase measurement

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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