Interferogram to Spectrum

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.

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.