Interferometer Displacement
Convert reflected-path fringe count to displacement with refractive-index and angle correction.
Description
Reflected-path interferometry converts fringe count into displacement with medium index and incidence projection.
Reflected-path interferometry converts fringe count into displacement with medium index and incidence projection. Vacuum wavelength is divided by the supplied index.1
Convert reflected-path fringe count to displacement with refractive-index and angle correction.
When to use Interferometer Displacement
Use this tool to convert reflected-path fringe count to displacement with refractive-index and angle correction.
Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
How to use Interferometer Displacement and understand its results
- Prepare the optical measurements, geometry, fitted coefficients or caller-selected thresholds requested. Confirm wavelength, radius/diameter, pulse-width, angle and unit conventions before running the calculation.
- Enter fringeCount, wavelengthMeters, refractiveIndex, incidenceAngleDegrees using the field table and calculation rules, then run the tool.
- Read displacementMeters. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| fringeCount | Fringe count | number | Required |
| wavelengthMeters | Wavelength (m) | number; minimum: 0 | Required |
| refractiveIndex | Path refractive index | number; minimum: 0 | Required |
| incidenceAngleDegrees | Incidence angle (°) | number | Required |
Enter finite signed fringe count/angle, positive wavelength/index and reject |cosθ|<1e−12. Return signed meters.
displacement=fringes×λ/(2n cosθ) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| displacementMeters | Reflector displacement (m) | number |
{
"input": {
"fringeCount": 20,
"wavelengthMeters": 5e-7,
"refractiveIndex": 1,
"incidenceAngleDegrees": 0
},
"output": {
"displacementMeters": 0.0000049999999999999996
}
}Limitations and assumptions
Angle is not restricted to physical incidence bounds. No fringe extraction, phase unwrapping or environmental correction is supplied.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Vibrometer Displacement: Convert interferometric fringe count to out-of-plane vibrometer displacement. For a complementary task, use Heterodyne Displacement: Convert heterodyne Doppler frequency integrated over time into displacement.
References
-
Interferometer Displacement — tool.io
Similar or alternative tools
- Vibrometer Displacement
Convert interferometric fringe count to out-of-plane vibrometer displacement.
- Heterodyne Displacement
Convert heterodyne Doppler frequency integrated over time into displacement.