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LIF Image Processing Software

Quantitative LIF imaging relies on accurately mapping the florescence light-intensity collected by a camera into physical units, such as concentration or temperature. Towards that end, two dedicated software modules are available in LaVision DaVis: the LIF software base module (1-color) and the add-on LIF ratiometric software module (2-color). The complex workflow of quantitative scalar-imaging includes noise-filtering and masking, background, laser-sheet and flat-field corrections, and finally a calibration which converts the processed signal intensity to the desired physical unit. The new LIF Image Processing module streamlines this workflow by introducing a fully integrated processing-dialog that incorporates all required processing steps in a single operation.

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       Raw                  Background-corrected

                                       and Filtered

                         

Image Pre-Processing

The accurate quantification of LIF signals requires the application of numerous processing steps prior to calibration. These are seamlessly integrated in an interactive dialog which includes:

  • geometric masking to restrict the calculation to the user’s area of interest
  • background subtraction and flat-field correction routines to account for cameras dark current, inhomogeneities, vignetting and image distortion effects
  • intensity corrections to compensate for laser energy fluctuations
  • masking filters to reject areas with low intensity and poor SNR
  • noise filtering routines using spatial (Gaussian) smoothing
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LIF Signal Calibration

LIF images at specified calibration conditions must be recorded and processed in order to quantify the relationship between the photo-emission response of the tracer and the quantity of interest. The new LIF Image Processing allows the user to:

  • generate calibration curves for a wide range of scalars including pH values, dye and species concentration, soot concentration via LII and gas/liquid temperature
  • select suitable fit models
  • use pre-defined sequences for automated calibration
  • achieve sub-pixel mapping for high fidelity 2-color ratiometric LIF
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        Raw                              SNR

SNR Analysis

The final 2D map of the measured scalar contains additional signal-to-noise (SNR) and measurement-uncertainty distributions. This allows the user to:

  • quickly and intuitively gauge the fidelity of the measurement on a per-image basis and in a space-resolved manner
  • identify and isolate areas with reliable content based on locally high SNR
  • optimize pre-processing operations to boost the SNR of the measurement in conjunction with the desired spatial resolution
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    Temperature               Uncertainty

Uncertainty Analysis

Measurement uncertainties from photon and camera noise, and uncertainties during the calibration and data-processing are considered in the analysis:

  • independent treatment of random and systematic uncertainties
  • uncertainty quantification and propagation at each processing step
  • visualization of the individual and total uncertainties of the intermediate and final measurement results
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Interactive Live Processing

The LIF software features fast processing with live-preview updated at any change of the processing-parameters. Consequently, the user interface updates the result in real time, allowing the user to seamlessly experiment with the parameters of the workflow, thus facilitating the optimization of data processing.