Interferogram to SpectrumΒΆ

Fast Fourier Transform interferograms, including zero filling, apodization and phase correction.

Inputs

  • Interferogram: input interferogram

  • Stored Phase: Previously calculated phase data

Outputs

  • Spectra: dataset with spectra

  • Phases: calulated phases

The Interferogram to Spectrum widgets calculates real or complex FFT for interferograms.

../_images/FFT.png

  1. Info: Information about number and type of interferograms and metadata available.

  2. Input Data:

    • Datapoint spacing: The pathlength step size used to calculate the output frequencies. "Auto" will use values from metadata or a default HeNe fallback.

    • Sweep direction: For datasets containing 2 full interferograms that were collected with forward and backward mirror motion.

    • ZPD Peak Search: Zero-point difference peak search algorithm. Disable search to manually enter value for entire dataset. The second entry is for double interferograms.

  3. FFT Options:

    • Complex FFT: Calculate the complex FFT from Amplitude and Phase data. Data can be interleaved or amplitude on first input and phase on the second.

    • Apodization Function: Windowing function to apply before FFT

    • Zero Filling Factor: Pad dataset with zeros to 2**zff

    • Phase Correction: Calculate phase using Mertz, or use a stored phase. "None" outputs both real/imaginary values.

  4. Output:

    • Limit spectral region: Cut the output to the specified range.