Advances in spatial frequency modulation imaging: spatio-spectral encoding

Abstract

In the following thesis I present my work advancing the state of the art in spatial frequency modulation imaging (SPIFI). There are many imaging scenarios in which traditional segmented detectors are impractical. Segmented detectors become prohibitively expensive outside of commonly used wavelength ranges and are susceptible to scattering. In such cases, single element detectors provide access to a larger range of wavelengths and may remove scattering ambiguity; however, they require a method for coupling spatial information into temporal signals. SPIFI couples spatial information into temporal signals from a single element detector by modulating the spatial intensity distribution of light illuminating the sample. This work extends the utility of SPIFI by developing simple optimization algorithms for the modulation pattern, developing a fiber deliverable SPIFI system, two multi-dimensional SPIFI systems, and a single shot SPIFI system. The thesis is organized into six chapters. I begin with an introduction to single element imaging and SPIFI. In chapter two I describe how to optimize the SPIFI modulation pattern for various constraints such as the manufacturing resolution or the numeric aperture of an optical system. Chapter 3 describes the technique I developed for fiber deliverable SPIFI imaging: wavelength domain SPIFI. By modulating the spectrum of the illumination beam, wavelength domain SPIFI facilitates remote delivery via optical fiber or free space transmission. I provide theoretical analysis of wavelength domain SPIFI along with experimental validation of the technique and its compatibility with fiber delivery. Wavelength domain SPIFI can be combined with SPIFI along the perpendicular transverse dimension. In chapter 4 I present experimental realization of a two dimensional SPIFI system with spatial and wavelength modulation. I also demonstrate a scan free SPIFI system where the wavelength encoded axis is sampled with a linear CMOS detector. Chapter 5 presents initial results from wavelength multiplexed single shot SPIFI. This technique provides a valuable illumination scheme for phenomena that occur faster than the scan time of traditional SPIFI. I end the thesis by describing future work related to these techniques and presenting some concluding statements.