Abstract
A method for the depth-resolved detection of fluorescent radiation based on imaging of an interference pattern of two intersecting beams and shearing interferometry is presented. The illumination setup provides the local addressing of the excitation of fluorescence and a coarse confinement of the excitation volume in axial and lateral directions. The reconstruction of the depth relies on the measurement of the phase of the fluorescent wave fronts. Their curvature is directly related to the distance of a source to the focus of the imaging system. Access to the phase information is enabled by a lateral shearing interferometer based on a Michelson setup. This allows the evaluation of interference signals even for spatially and temporally incoherent light such as emitted by fluorophors. An analytical signal model is presented and the relations for obtaining the depth information are derived. Measurements of reference samples with different concentrations and spatial distributions of fluorophors and scatterers prove the experimental feasibility of the method. In a setup optimized for flexibility and operating in the visible range, sufficiently large interference signals are recorded for scatterers placed in depths in the range of hundred micrometers below the surface in a material with scattering properties comparable to dental enamel.
Highlights
Microscopy methods for noninvasive diagnostics are limited by the strong scattering encountered in biological materials
Single crystals of rhodamine 6G with sizes in the range of a few microns are placed on a sample holder. This sample offers the advantage that fluorescent wave fronts arising from well-defined lateral and axial positions are obtained, where the axial position can be precisely set by means of the stage of the microscope
The reconstruction of the axial position relies on the knowledge of the phase of the fluorescent wave fronts
Summary
Microscopy methods for noninvasive diagnostics are limited by the strong scattering encountered in biological materials. This leads to disturbing background signals, weak signal-to-noise ratio, and image degradation. Some sort of discrimination between the desired signal and contributions arising from scattering in the rest of the sample is needed. Many diagnostic applications require such dimensional measurements: in the classification of skin cancer, the extent of a tumor in the vertical direction is directly linked to its development over time.[1] threedimensional (3-D) data about the location of certain structures, in particular along the z-axis, could contribute to a better classification of images, the recognition of features, and the automated segmentation of malign and benign areas. In applications where optical methods aid in the determination of tumor margins or even serve as feedback during surgery,[2] dimensional information is obviously of crucial importance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
