Heterodyne Displacement
Convert heterodyne Doppler frequency integrated over time into displacement.
Description
Heterodyne displacement integrates a constant Doppler frequency over a measurement interval.
Heterodyne displacement integrates a constant Doppler frequency over a measurement interval. A reflected-path conversion then divides by two.1
Convert heterodyne Doppler frequency integrated over time into displacement.
When to use Heterodyne Displacement
Use this tool to convert heterodyne Doppler frequency integrated over time into 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 Heterodyne 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 dopplerFrequencyHertz, measurementSeconds, wavelengthMeters using the field table and calculation rules, then run the tool.
- Read fringeCount, 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 |
|---|---|---|---|
| dopplerFrequencyHertz | Measured Doppler frequency (Hz) | number | Required |
| measurementSeconds | Measurement duration (s) | number; minimum: 0 | Required |
| wavelengthMeters | Wavelength (m) | number; minimum: 0 | Required |
Enter finite signed Doppler frequency and nonnegative time/wavelength. Return signed fringe count and meters.
fringes=frequency×time; displacement=fringes×λ/2 Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| fringeCount | Accumulated fringe count | number |
| displacementMeters | Reflector displacement (m) | number |
{
"input": {
"dopplerFrequencyHertz": 1000,
"measurementSeconds": 2,
"wavelengthMeters": 5e-7
},
"output": {
"fringeCount": 2000,
"displacementMeters": 0.0005
}
}Limitations and assumptions
No time-varying integration, medium index or angle 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 Interferometer Displacement: Convert reflected-path fringe count to displacement with refractive-index and angle correction. For a complementary task, use Doppler Lidar Frequency Shift: Calculate monostatic lidar Doppler frequency shift from radial velocity and wavelength.
References
-
Heterodyne Displacement — tool.io
Similar or alternative tools
- Interferometer Displacement
Convert reflected-path fringe count to displacement with refractive-index and angle correction.
- Doppler Lidar Frequency Shift
Calculate monostatic lidar Doppler frequency shift from radial velocity and wavelength.