M.Sc Thesis


M.Sc StudentGordon Racheli
SubjectMicroscopic Scan-Free Surface Profiling over Extended
Axial Ranges by Point-Spread-Function Engineering
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Yoav Shechtman
Full Thesis textFull thesis text - English Version


Abstract

The shape of a surface, i.e., its topography, influences many functional properties of a material; hence, surface characterization is critical in a wide variety of applications. Surface profiling techniques are mainly divided into contact and noncontact methods. While contact methods are based on a cantilever-mounted tip, in direct contact (or close proximity) with the specimen, noncontact methods are typically based on electron microscopy or optical imaging. Optical imaging techniques have been widely applied to microsurface profiling and benefit from being nondestructive (for samples that are not light sensitive). Two notable challenges of optical microsurface profiling techniques are profiling temporally changing structures, which requires high-speed acquisition, and capturing geometries with large axial steps.

Here, we develop a scan-free, dynamic, optical microsurface profiling method, based on point-spread-function engineering - a technique that enables three-dimensional imaging, by modifying the shape of the image detected when observing a light point source (i.e., the point spread function of a microscope), to encode depth information. The presented method is robust to axial steps and acquires full fields of view at camera-limited framerates. Furthermore, it can be implemented as an add-on to existing light microscopes. We present two approaches for surface profiling implementation: fluorescence-based, using fluorescent emitters scattered on a surface, and label-free, using reflected light from a projected pattern of illumination spots, demonstrating the applicability to a variety of sample geometries and surface types.