Optical scanning holography (OSH) has been researched as one of single pixel holography. Although incoherent holograms can be obtained with a bucket detector, OSH requires sequentially scanning an illumination pattern on an object with a moving stage and a phase shifter. This fact imposes disadvantages of unstable and bulky setup on OSH. To solve the problem, we have proposed the OSH technique without mechanical scanning by using a polarization property of a spatial light modulator. The proposed technique makes its setup inline and simple due to absence of moving parts. In this presentation, a basic principle of the proposed technique and its improvement based on parallel phase shifting and compressive sensing are introduced.
Two phase imaging methods with transport of intensity equation (TIE) under a low signal to noise ratio (SNR) are introduced. One is a TIE phase imaging with deep learning. It is useful for parallel TIE using a diffractive optics to produce defocus images simultaneously. The defocus images are obtained by an optical convolution integral by the calculated blurred point spread functions. However the point spread functions are different from the ideals due to the limited extent and/or limited resolution of the diffractive optics. This means that an SNR of the through-focus images is low. Therefore, deep learning compensates the error. Another is transport-of- intensity computational ghost imaging (TI-CGI). It is a combination of TIE and a computational ghost imaging (CGI). It is useful for noninvasive imaging for the biomedical field because most cells are photo-sensitive and often suffer from phototoxicity. However, CGI can obtain only amplitude information. In the biomedical field, a phase information is important to know the physical parameters. To achieve, under weak illumination, it is difficult to obtain through-focus images with high SNRs. Therefore, combination of TIE and CGI is useful.
Quantitative phase imaging is widely studied for such as bio-imaging and industrial inspection. Quantitative phase imaging is divided into interferometric approach and non-interferometric intensity-based one. Interferometry often uses object and reference arms, rendering an optical setup complicated. The transport of intensity equation has been used for non-interferometric quantitative phase imaging. It allows to retrieve a phase distribution from through-focus series of an object. To obtain through-focus series, mechanical scanning of the object or a camera is required. This is not suitable for the quantitative phase imaging of dynamic phenomena. In this presentation, some of our proposed scan-less methods are presented. Numerical and/or experimental results are also shown.
Wavefront sensing techniques are mainly needed in an adaptive optics system for high resolution imaging. One of them is a Shack-Hartmann method which is composed of very simple structure. Although the method is widely utilized, it also has the limitation for the measurable magnitude of wavefront aberrations. To overcome the problem, the improved Shack-Hartmann method for larger aberrated wavefronts has been proposed. In this paper, the principle of the proposed method and the numerical evaluation of the performance of the proposed method are presented.
A Shack-Hartmann wavefront sensor (SHWFS) which consists of a microlens array and an image sensor has been
used to measure the wavefront aberrations in various fields owing to its advantages such as simple configuration.
However, a conventional SHWFS has the finite dynamic range. The dynamic range cannot be expanded without
sacrificing the spatial resolution and the sensitivity in a conventional SHWFS. In this study, the SHWFS using
a dual microlens array to solve the problem is proposed. In the proposed method, an astigmatic microlens is
arranged at the center of a group of 2 x 2 spherical microlenses. A pattern image including spots and linear
patterns is obtained at the focal plane by the dual microlens array. The pattern image can be separated into two
images as if two microlens array with different diameter were used by discriminating spots from linear patterns
with the pattern matching technique. The proposed method enables to expand the dynamic range of an SHWFS
by using the separated two images. The performance of the proposed method is confirmed by the numerical
simulation for measuring a spherical wave.
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