Case Study – High Precision Sphere Measurements

  • High-precision sphere measurements
  • Small, fast sphere (Zygo reference sphere)

ssiApp2 fig1

 

 


 

Repeatability results

  • Mean = 5.60 nm rms
  • Range = 0.025 nm
  • Std Dev: 0.007 nm rms

ssiApp2 fig2

 


 

 

Cross-test results

  • Mean = 5.69 nm rms
  • Difference from repeats = 0.09 nm


TS#2 - 6” F/0.8 (similar lattice)

ssiApp2 fig3

 


 

Pixel-by-pixel subtractions

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  • Performed pixel-by-pixel subtraction on average of 10 measurements
  • Slightly different lattice (different level of overlap) used for the two sets of 10 measurements
  • Pixel-by-pixel comparisons will give higher results than comparing rms numbers, so sub-nm results are excellent

ssiApp2 fig4