Interferometric scattering microscopy methods and systems
A method comprising the steps of: measuring a first series of interferometric scattering microscopy (iSCAT) signals and a second series of iSCAT signals of a sample on a sample holder, the sample comprising a particle dissolved in solution; deriving an illumination heterogeneity for the first series of iSCAT signals; deriving a reflectance profile for the first series of iSCAT signals based on the illumination heterogeneity and/or the second series of iSCAT signals; measuring a third series of iSCAT signals of the sample on the sample holder; and normalizing an interferometric contrast for the third series of iSCAT signals with the reflectance profile.
1. A method comprising:
measuring a first series of interferometric scattering microscopy (iSCAT) signals and a second series of iSCAT signals of a sample on a sample holder, the sample comprising a particle dissolved in solution;
deriving an illumination heterogeneity for the first series of iSCAT signals;
deriving a reflectance profile for the first series of iSCAT signals based on the illumination heterogeneity and/or the second series of iSCAT signals;
measuring a third series of iSCAT signals of the sample on the sample holder;
normalizing an interferometric contrast for the third series of iSCAT signals with the reflectance profile.
2. The method of claim 1 , wherein the first series of iSCAT signals is from different locations along the sample holder, wherein deriving the illumination heterogeneity comprises:
calculating a median image from the first series of iSCAT signals; and
blurring the median image by a kernel larger than a dimension of a point spread function to produce the illumination heterogeneity.
3. The method of claim 1 , wherein the first series of iSCAT signals is from a single location along the sample holder, wherein deriving the illumination heterogeneity comprises:
calculating a median image from the first series of iSCAT signals; and
blurring the median image by a kernel larger than a dimension of a roughness feature on the sample holder to produce the illumination heterogeneity.
4. The method of claim 1 , wherein deriving a reflectance profile comprises:
measuring local differences in reflectance at a sample-sample holder interface;
calculating a median of the local differences in reflectance; and
dividing the median of the local differences in reflectance by the illumination heterogeneity.
5. The method of claim 1 , wherein normalizing the interferometric contrast comprises:
multiplying each of the third series of iSCAT signals times a square root of the reflectance profile.
6. The method of claim 1 , further comprising:
quantifying the mass of the particle, wherein quantifying the mass of said particle is based on the normalized third series of iSCAT signals.
7. A system comprising:
a processor;
a non-transitory machine readable medium that stores machine-readable instructions for execution by the processor, the machine-readable instructions comprising:
measure a first series of interferometric scattering microscopy (iSCAT) signals and a second series of iSCAT signals of a sample on a sample holder, the sample comprising a particle dissolved in solution;
derive an illumination heterogeneity for the first series of iSCAT signals;
derive a reflectance profile for the first series of iSCAT signals based on the illumination heterogeneity and the second series of iSCAT signals;
measure a third series of iSCAT signals of the sample on the sample holder;
normalize an interferometric contrast for the third series of iSCAT signals with the reflectance profile.
8. The system of claim 7 , wherein the first series of iSCAT signals is from different locations along the sample holder, wherein the step of derive the illumination heterogeneity comprises:
calculate a median image from the first series of iSCAT signals; and
blur the median image by a kernel larger than a dimension of a point spread function to produce the illumination heterogeneity.
9. The system of claim 8 , wherein the first series of iSCAT signals is from a single location along the sample holder, wherein the step of derive the illumination heterogeneity comprises:
calculate a median image from the first series of iSCAT signals; and
blur the median image by a kernel larger than a dimension of a roughness feature on the sample holder to produce the illumination heterogeneity.
10. The system of claim 8 , wherein the step of derive the reflectance profile comprises:
measure local differences in reflectance at a sample-sample holder interface;
calculate a median of the local differences in reflectance; and
divide the median of the local differences in reflectance by the illumination heterogeneity.
11. The system of claim 8 , wherein normalizing the interferometric contrast comprises:
multiplying each of the third series of iSCAT signals times a square root of the reflectance profile.
12. The system of claim 8 , wherein the machine-readable instructions further comprise:
quantifying the mass of the particle, wherein quantifying the mass of said particle is based on the normalized third series of iSCAT signals.