Optical Review

, Volume 4, Issue 4, pp 507–515 | Cite as

Simultaneous Measurement of Refractive Index and Thickness of Transparent Plates by Low Coherence Interferometry

  • Masato Ohmi
  • Takehisa Shiraishi
  • Hideyuki Tajiri
  • Masamitsu Haruna


We demonstrate a novel low coherence Michelson interferometer which can provide simultaneous measurement of the refractive index and thickness of transparent plates used as a measured object. Unlike the existing low coherence interferometers reported so far, either an object or a focusing lens aligned on the signal arm is scanned repeatedly by a precise translation stage in synchronization with movement of a reflection mirror on the reference arm. The so-called object or lens scanning method gives us two measured quantities a movement distance of the stage between two light focusing states on the front and rear planes of an object and the corresponding optical path difference. These two measured quantities, result in desirable values of the index and thickness of the object with a short calculation. The measurement accuracy of ≤0.1% is expected for a thickness of more than 1 mm. In the experiment using the object scanning method, the accuracy of 0.3% or less was successfully attained for nearly 1-mm thick plates of fused quartz, sapphire, LiTaO3 and slide glass.

Key words

low coherence light source interferometry simultaneous measurement of index and thickness opto-electronics precise mechanics 


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Copyright information

© The Optical Society of Japan 1997

Authors and Affiliations

  • Masato Ohmi
    • 1
  • Takehisa Shiraishi
    • 2
  • Hideyuki Tajiri
    • 2
  • Masamitsu Haruna
    • 1
    • 2
  1. 1.School and Allied Health Sciences, Faculty of MedicineOsaka UniversityOsakaJapan
  2. 2.Course of Electronic Engineering, Graduate School of EngineeringOsaka UniversityOsakaJapan

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