Hidenobu Arimoto

Retrieval of the cross-spectral density propagating in free space

A technique for retrieving the cross-spectral density propagating in free space across an arbitrary plane is proposed. Theoretical descriptions are based on the propagation law of the cross-spectral density described in the Fourier domain. Results of an experiment demonstrating retrieval of the cross-spectral density across an arbitrary reference plane are also reported. The cross-spectral density in the observation area is measured by use of a wave-front-folded interferometer, and the retrieved cross-spectral densities and the intensity distribution agree well with the theoretical expectations.

Coherence-Based 3-D and Spectral Imaging and Laser-Scanning Microscopy

The basics of three-dimensional (3-D) and spectral imaging techniques that are based on the detection of coherence functions and other related techniques are reviewed. The principle of the 3-D source retrieval is based on understanding the propagation law of optical random field through the free space. The 3-D and spectral information are retrieved from the cross-spectral density function of optical random field or numerical calculation of the inverse propagation of the cross-spectral density. We will first introduce the coherence-based spectral tomography techniques with low-coherence light sources. These techniques limit their scheme of coherence detection only along the optical axis and some of them achieve simultaneously the high resolution and high speed of detection taking advantage of an imaging lens. We then provided explanations of the principle of 3-D source retrieval that is based on the propagation law of optical random field through the free space along with the introduction of the numerical holography and computed tomography techniques. We will lastly show 3-D spectral imaging schemes with the concurrent laser-scanning cross-sectioning techniques: one is the confocal laser scanning microscopy and the other is the two-photon laser-scanning fluorescence microscopy.

Passive interferometric 3-D imaging and incoherence gating

This paper proposes interferometric 3-D imaging based on retrieving the space variant cross-spectral density. The cross-spectral density across an arbitrary transverse plane can be retrieved by using the propagation law described in the Fourier domain. The 3-D intensity distribution is reconstructed from a series of the cross-spectral densities across planes within the slab geometry considered. Results of an experiment conducted by incorporating two point sources are also reported. The point spread function of the proposed interferometric imaging system, and its similarity to an ordinary imaging system are discussed. To detect spatially incoherent sources, we also propose an incoherence gating method based on the present interferometric imaging technique. The second-order differential of the series of retrieved cross-spectral densities with respect to a two-point separation enable us to estimate field correlations over the 3-D field, and locations of primary sources are clearly determined.

Implementation of a Raspberry-Pi-based LED array microscope for multi-contrast images

The light emitting diode (LED) array microscope enables various multi-contrast imaging such as bright-field, darkfield and differential phase-contrast by various illumination patterns without any expensive optical components. We build an LED array microscopic system operated with Raspberry Pi. Illumination patterns are controlled with Raspberry Pi and images are obtained with a Raspberry Pi camera module. We demonstrate acquisition of bright-field, dark-field, and differential phase-contrast of cells.

Reconstruction of complex amplitude by lensless phase-shift digital holography through an opaque glass plate

Optical imaging through diffusive or scattering media has attracted much attention. Digital holographic microscopy provides quantitative phase imaging thorough diffusive media. We experimentally reconstruct intensity and phase images of an object through an opaque ground glass screen by means of digital holography. A clear image of the object is acquired by wavefield back propagation algorithm for the object with an information of a quantitative phase distribution of the diffusive screen measured in advance with the principle of the lensless digital holography.

Computed three-dimensional display based on integral imaging

A computed three-dimensional (3-D) displaying system based on integral imaging is presented. The 3-D image is reconstructed by numerical processing of an optically observed image array formed by a micro-lens array. The algorithm to reconstruct 3-D images is simple, and it enables us to obtain the images viewed from arbitrary directions. The computer-based image retrieval makes it possible to improve quality of the image such as contrast, brightness, and resolution. In this presentation, we show the experimental results of the 3-D image reconstruction to test and verify the performance of the algorithms.

Propagation of angular cross-spectral density and 3D imaging

Interferometric 3D imaging based on measuring the space- variant cross-spectral density propagated in free space is reviewed. The spatial coherence function such as the cross- spectral density or the mutual intensity conserves the total 3D information as propagating in free space. The present method is on the basis of the propagation law of the cross- spectral density described in the Fourier domain. By using this law, the cross-spectral density across an arbitrary transverse plane is retrieved from the cross-spectral density measured on the observation plane. A series of retrieved cross-spectral densities composes the 3D intensity distribution. An experimental retrieval of the intensity distribution is demonstrated by using uncorrelated two point sources. A similarity of a point spread function of the present interferometric imaging system to an ordinary image forming system is also discussed.

Interferometric imaging by inverse propagation of cross-spectral density

New imaging method based on measuring the spatial coherence function across an observation area is presented. The propagation law of the cross-spectral density described in the Fourier domain allows us to retrieve the cross-spectral density at arbitrary reference planes. The method can be applied to a source of any state of coherence. Results of the experimental demonstration are also shown.

Passive interferometric 3D imaging based on the propagation law of cross-spectral density

A new method for retrieving the three-dimensional image is proposed. The method is on the basis of the propagation law of the cross-spectral density and the relationship between the cross-spectral density and the generalized radiance. The image is obtained in terms of the spatial distribution of the generalized radiance. Results of numerically calculated examples are also shown.