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Phase contrast microscopy with oblique back-illumination

WO 2013148360 A1. Filed on March 15, 2013, published on Oct. 3, 2013. view in google patents

A method of creating a phase contrast image is provided. In some embodiments the method comprises illuminating the target region of a sample with a first light source to provide a first oblique back illumination of the target region of the sample, and detecting a first phase contrast image from light originating from the first light source and back illuminating the target region of the sample. In some embodiments the method further comprises illuminating the sample with a second light source to provide a second oblique back illumination of the target region of the sample, and detecting a second phase contrast image from light originating from the second light source and back illuminating the target region of the sample. In some embodiments a difference image of the target region of the sample is created by subtracting the second phase contrast image of the target region of the sample from the first phase contrast image of the target region of the sample. Apparatus for carrying out the methods are also provided. The methods and apparatus find use, for example, in endoscopy.

An offset fiber produces oblique illumination

Monte Carlo simulation of "photon banana" (i.e. density of photons in scattering sample that are injected by an off-axis fiber and detected by an on-axis contact-mode endomicroscope objective. Note that illumination through focal plane (dashed line) is oblique, leading to phase-gradient contrast.