Showing papers by "Satoshi Kawata published in 1986"

Optimal Wavelength Selection for Quantitative Analysis

Abstract: A new computer algorithm has been developed for selecting the optimal set of wavelengths for spectroscopic quantitative analysis of mixture samples. The method is based on the criterion of the minimum mean square error between concentrations of the mixture components and their estimates. The branch and bound algorithm finds the optimal set from all possible combinations of wavelengths. This algorithm saves computation time significantly, compared with the enumerative method. The mathematical formulation of the lower bound of the mean square errors for the combinations in a given subset is derived as a recurrence inequality. Experimental results of wavelength selection for infrared absorption spectra of xylene-isomer mixtures are shown to demonstrate the effectiveness of the algorithm in terms of computation complexity and accuracy in quantitative analysis for the fixed measurement time.

A Photodiode Array Fourier Transform Spectrometer Based on a Birefringent Interferometer

Abstract: A new version of the photodiode array Fourier transform spectrometer for visible spectroscopy is described. In this version, a birefringent interferometer with a Wollaston prism produces a spatial interferogram the of the radiation, which is detected by a linear photodiode array. In addition to the merit of having no mechanical moving parts, this spectrometer has the beneficial advantage of the simple and rugged optical setup and alignment due to its common-path and in-line interferometer formation. These advantages lend this spectrometer to field-use applications. Emission spectra of a low-pressure mercury lamp and a light-emitting diode and an absorption spectrum of a didymium glass filter measured by the developed spectrometer are presented.

The principle and applications of optical microscope tomography

Abstract: A new principle to obtain sectional images of a thick specimen by a conventional optical microscope without physically slicing is developed. An optical microscope with an off-axis pupil is used to project a three-dimensional (3-D) distribution of a specimen in various directions within the numerical aperture of the objective lens onto a fixed TV camera position. The obtained images of the thick sample are combined to reconstruct its 3-D density distribution. Since the system is strictly angularly-limited, a strong constraint is needed to form the 3-D structure with a moderate spatial resolution from the projections. The conjugate gradient method with the object boundary constraint which is a priori known solves this problem. Experimental results with a biological sample verify the capability of the proposed method as a promising instrumentation of optical tomography in microscopic size.

Superresolving deconvolution by Nonnegative Least Squares Method.

Abstract: A new nonnegative-constrained decon volution method is proposed to restore the original spectrum from its observation blurred by the slit-function of a spectrophotometer. The developed method is based on the Nonnegative Least Squares Method incorporating with the Minimum Mean Squared Error Estimation. Using a priori knowledge about the longi tudinal axis of the spectrum as a constraint, the method may expand the band limit of the system or the resolution limit determined by the conventional Wiener-Helstrom filter due to the existence of noise. Experimental results by the proposed method for the spectra of emission lines of a hollow cathod lamp and infrared absorption of amnmonia gas demonstrate the effectiveness of the method.

Heterodyne Interferometric Temperature Sensor Using a Transverse Zeeman Laser and a Polarization Maintaining Fiber

Abstract: A new fiber-optic temperature sesnor using a polarization maintaining fiber and a transverse Zeeman laser based on heterodyne interferometry has been developed. The temperature variation is detected by coupling two orthogonal linear polirization components of a laser beam, each differently phase-modulated during transmitting a birefringent single-mode polarization maintaining fiber. A transverse He-Ne Zeeman laser was developed to achieve heterodyning demodulation of the phase-shift caused by the temperature of the fiber. Experimental result demonstrates that this sensor has the temperature resolution of 0.0032°C with a very wide dynamic range. Besides, this fiber sensor has the advantages of simple construction and ruggedness against pressure turbulence.© (1986) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.