Vibrometer Displacement
Convert interferometric fringe count to out-of-plane vibrometer displacement.
Description
Reflection interferometry gives two optical path changes per normal surface displacement.
Reflection interferometry gives two optical path changes per normal surface displacement. Oblique incidence introduces a cosine projection.1
Convert interferometric fringe count to out-of-plane vibrometer displacement.
When to use Vibrometer Displacement
Use this tool to convert interferometric fringe count to out-of-plane vibrometer displacement.
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 Vibrometer 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, 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 | Interferometric fringe count | number | Required |
| wavelengthMeters | Wavelength (m) | number; minimum: 0 | Required |
| incidenceAngleDegrees | Incidence angle (°) | number | Required |
Enter finite signed fringe count, positive wavelength and finite incidence angle in degrees. Reject |cosθ|<1e−12 and return signed displacement in meters.
displacement=fringes×λ/(2 cosθ) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| displacementMeters | Out-of-plane displacement (m) | number |
{
"input": {
"fringeCount": 100,
"wavelengthMeters": 6.33e-7,
"incidenceAngleDegrees": 0
},
"output": {
"displacementMeters": 0.000031650000000000004
}
}Limitations and assumptions
Angles are not restricted to a physical incidence interval. No fringe counting, phase unwrapping or vibration spectrum is performed.
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 Interferometer Displacement: Convert reflected-path fringe count to displacement with refractive-index and angle correction. For a complementary task, use Heterodyne Displacement: Convert heterodyne Doppler frequency integrated over time into displacement.
References
-
Vibrometer Displacement — tool.io
Similar or alternative tools
- Interferometer Displacement
Convert reflected-path fringe count to displacement with refractive-index and angle correction.
- Heterodyne Displacement
Convert heterodyne Doppler frequency integrated over time into displacement.