Theoretical model for optical coherence tomography imaging and its application to volumetric differential contrast imaging.

A new formulation of the lateral imaging process of point-scanning optical coherence tomography (OCT) and a new differential contrast method designed by using this formulation are presented. The formulation is based on a mathematical sample model called the dispersed scatterer model (DSM), in which the sample is represented as a material with a spatially slowly varying refractive index and randomly distributed scatterers embedded in the material. It is shown that the formulation represents a meaningful OCT image and speckle as two independent mathematical quantities.

A general theory of far-field optical microscopy image formation and resolution limit using double-sided Feynman diagrams.

Optical resolution of far-field optical microscopy is limited by the diffraction of light, while diverse light-matter interactions are used to push the limit. The image resolution limit depends on the type of optical microscopy; however, the current theoretical frameworks provide oversimplified pictures of image formation and resolution that only address individual types of microscopy and light-matter interactions. To compare the fundamental optical resolutions of all types of microscopy and to codify a unified image-formation theory, a new method that describes the influence of light-matter interactions on the resolution limit is required.

Phase-shift effect of amplitude spread function on spectrum and image formation in coherent Raman scattering microspectroscopy.

Coherent Raman scattering microspectroscopy, which includes coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microspectroscopy, permits label-free hyperspectral imaging. We report the theoretical study of the phase-shift effect of the impulse response function on the spectral and image-forming properties of coherent Raman scattering microspectroscopy. We show that the spectrum and image are influenced by not only the NA of objective for excitation (NA(ex)) but also that for signal collection (NA(col)), in association with the phase-shift effect.

Electronically resonant third-order sum frequency generation spectroscopy using a nanosecond white-light supercontinuum.

Third-order sum frequency generation (TSFG) is one of the third-order nonlinear optical processes, and has the generation mechanism analogous to third harmonic generation (THG). By using a white-light supercontinuum, we can obtain broadband multiplex TSFG spectra. In the present study, we developed an electronically resonant TSFG spectrometer, and applied it to obtain TSFG spectra of hemoproteins.

Coherent transfer function of Fourier transform spectral interferometric coherent anti-Stokes Raman scattering microscopy.

We analyze the optical resolution of Fourier transform spectral interferometric-coherent anti-Stokes Raman scattering microscopy, which extracts the complex amplitude of an image by using a spectral interferometric effect. Image-formation formulas are presented that describe the properties of the image observed by the apparatus. The image-formation properties represented by the coherent transfer function are different depending on the mode (transmission, reflection, etc.

Resolution properties of nonlinear optical microscopy.

We analyze the resolution properties of nonlinear optical microscopy systems that use nonlinear optical effects, such as multiphoton-excited fluorescence, second- and third-harmonic generation, coherent anti-Stokes Raman scattering, and stimulated-emission depletion. Image formation formulas are presented that unitedly describe the properties of the image observed, wherein coherent, incoherent, or mixed-coherent phenomena are utilized. We develop the formalism for the optical resolution of all types of nonlinear systems.

Proposal of three-dimensional phase contrast holographic microscopy.

We propose a three-dimensional phase contrast digital holographic microscopy. The object to be observed is a low-contrast transparent refractive index distribution sample, such as biological tissue. Low contrast phase objects are converted to high contrast images through the microscopy we propose.