There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

Measurement of intraocular distances by backscattering spectral interferometry

PROBLEM TO BE SOLVED: To provide an optical element for multiple-scene imaging with simple constitution and to provide a line-of-sight detecting input device which is constituted including the same and can detect an object being gazed at more directly and shows the direction of the line of sight in a real space. SOLUTION: The optical element 1 for multiple-scene imaging guides a plurality of scenes (m, e, etc.) in different directions to one imaging surface (s) at the same time and comprises a single holographic optical element configured to image respective lights of the plurality of scenes on the one imaging surface (s). COPYRIGHT: (C)2007,JPO&INPIT

Optical element for multiple-scene imaging and line-of-sight detecting input device

For the reconstruction of absorber embedded in a homogeneous scattering medium, a backprojection method using intensity ratio is evaluated numerically. The proposed method uses the intensity ratio between an object medium and a reference medium.

Assessment of reconstruction method of absorber in scattering medium using intensity ratio

We have proposed a new configuration of the single-shot, dual-wavelength, common-path, off-axis DHM system. The proposed system is used for decoupling the refractive index and thickness of a biological specimen.

Decoupling the refractive index and thickness by dual-wavelength digital holographic microscopy

An optical method to improve the system for modulo exponentiation is proposed. In this method, modulation patterns are modified in comparison with that of our original system. The proposed method is numerically analyzed and effectiveness of the method is verified.

http://ieeexplore.ieee.org/iel5/6097354/6110253/06110365.pdf

Improvement of modulation patterns in a method for parallel modulo exponentiation with optical amplitude modulation

To see through a random light field in real-time, single-shot generalized Hanbury Brown–Twiss experiments using a polarization camera are proposed. The target intensity distribution is obtained from a complex coherence function which is calculated from auto-correlation and cross correlation functions of phase-shifted speckle intensity distributions. The phase-shifted speckle intensity distributions are simultaneously obtained through a strategy of parallel phase-shifting digital holography. Experimental results show that the proposed method can image a moving object in a random light field using a measured complex coherence function through the van Cittert–Zernike theorem. 

Osamu Matoba

Papers

Optical element for multiple-scene imaging and line-of-sight detecting input device

Assessment of reconstruction method of absorber in scattering medium using intensity ratio

Decoupling the refractive index and thickness by dual-wavelength digital holographic microscopy

Improvement of modulation patterns in a method for parallel modulo exponentiation with optical amplitude modulation

Single-shot generalized intensity interferometry