Understanding Optical Path Difference in Optics | OPD Explained

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SUMMARY

The discussion focuses on the calculation of Optical Path Difference (OPD) in optics, specifically the formula OPD = n2(AB + BC) - n1(AD). Participants clarify the significance of the refractive indices 'n1' and 'n2' and the path lengths involved. The negative sign in the formula indicates a subtraction of optical path lengths from different media. The geometric relationship between points C and D, which lie on the same wavefront, is emphasized to aid understanding of the OPD calculation.

PREREQUISITES
  • Understanding of refractive indices in optics
  • Familiarity with wavefront concepts
  • Basic knowledge of geometric optics
  • Ability to interpret optical path length calculations
NEXT STEPS
  • Study the principles of wavefronts in optics
  • Learn about the significance of refractive indices in optical calculations
  • Explore examples of Optical Path Difference in different media
  • Investigate the impact of geometric configurations on OPD calculations
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Students and professionals in optics, physicists, and engineers involved in optical design and analysis will benefit from this discussion.

moatasim23
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SOme one help me with the OPD.
How is here the OPD=n2(AB + BC) -n1(AD)?
I am not confused with the introduction of 'n'..Rather the path length is confusing me..Why is there a negative sign?
 

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They are computing a path difference ...
 
Just to elaborate a little on Simon's response.

Notice that the line connecting C and D is perpendicular to the rays. This indicates the C and D lie on the same wavefront.

Ergo, the OPD is calculated as the difference in optical path lengths from A-C and from A-D.

Claude.
 

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