Aberration measurement from confocal axial intensity response using neural network.

We propose a high-speed, parallel system for lens aberration measurement employing a confocal optical setup. This method uses a non-interferometric, conventional confocal axial response to determine the spherical aberration coefficient of a confocal objective. The aberration coefficients are successfully calculated from the intensity axial response by employing a neural network. It is estimated that the system can find out the aberration coefficients of 10,000 microlenses in 20 seconds of measurement and 1 second of calculation time. Our experimental results also demonstrate the practicality of this system.

Melanin and blood concentration in human skin studied by multiple regression analysis: experiments.

Knowledge of the mechanism of human skin colour and measurement of melanin and blood concentration in human skin are needed in the medical and cosmetic fields. The absorbance spectrum from reflectance at the visible wavelength of human skin increases under several conditions such as a sunburn or scalding. The change of the absorbance spectrum from reflectance including the scattering effect does not correspond to the molar absorption spectrum of melanin and blood. The modified Beer-Lambert law is applied to the change in the absorbance spectrum from reflectance of human skin as the change in melanin and blood is assumed to be small. The concentration of melanin and blood was estimated from the absorbance spectrum reflectance of human skin using multiple regression analysis. Estimated concentrations were compared with the measured one in a phantom experiment and this method was applied to in vivo skin.

Melanin and blood concentration in a human skin model studied by multiple regression analysis: assessment by Monte Carlo simulation.

Measurement of melanin and blood concentration in human skin is needed in the medical and the cosmetic fields because human skin colour is mainly determined by the colours of melanin and blood. It is difficult to measure these concentrations in human skin because skin has a multi-layered structure and scatters light strongly throughout the visible spectrum. The Monte Carlo simulation currently used for the analysis of skin colour requires long calculation times and knowledge of the specific optical properties of each skin layer. A regression analysis based on the modified Beer-Lambert law is presented as a method of measuring melanin and blood concentration in human skin in a shorter period of time and with fewer calculations. The accuracy of this method is assessed using Monte Carlo simulations.

Experimental and numerical study of the colour appearance of tattoo models.

The colour of tattooed skin has been predicted by a Monte Carlo method based on the optical coefficient spectra of the skin and tattoo dyes. Slices of pig skin, a tattoo phantom and skin phantoms with different thickness were prepared, and their reflectance and transmittance spectra were measured using an integrating sphere at wavelengths varying from 400nm to 700nm. The absorption and scattering coefficient spectra of skin phantoms, pig skins and the tattoo phantom were each calculated using the inverse Monte Carlo method. The skin phantoms and pig skins were overlaid on the tattoo phantom, and the reflectance spectra of the two-layered structures were measured. The reflectance spectra of the two-layered structures were calculated from the optical coefficient spectra using the Monte Carlo method. They agreed well with the measured spectra. The colour differences between the calculated and measured spectra were also evaluated by the L*a*b* colour space distances and showed good agreement, with 3.49 for the skin phantoms and 8.27 for the pig skins.

[Relation between temporomandibular joint disorder and subjective symptoms of fatigue].

An investigation was performed for the purpose of guaging the relation between temporomandibular joint disorder on the one hand and occupational category and subjective symptoms of fatigue on the other. Subjects were 2,414 workers (1,598 male, 816 female) in small and medium size enterprises at 67 workplaces in Hiroshima Prefecture. A comparison of cases with and without temporomandibular joint disorder showed that there were more complaints of fatigue among those with the disorder. Given these indications that temporomandibular joint disorder was related to occupation, it is possible that temporomandibular joint disease may be a work-related disease.

[The relation of dental examination results at corporation offices to occupation, subjective symptoms of fatigue and daily lifestyle--an investigation based on the number of missing teeth].

Our investigation was intended to find a relationship between the dental health of labourers and, their jobs, subjective symptoms of fatigue and daily lifestyle. Dentists checked the dental health of 2,565 corporation employees (790 male and 775 female) of small to medium-sized enterprises in Hiroshima prefecture. At the same time they examined the employees' occupation, subjective symptoms of fatigue and their health maintenance behavior according to Breslow's criteria. The data were divided into age groups spanning 10 years. Among males in their 30s, those engaged in transport/driving and engineering/production had more missing teeth than others. We found a relationship between the number of missing teeth and subjective symptoms of fatigue among men in their 30s. This suggests that the greater the number of missing teeth, the greater their subjective symptoms of fatigue. The results suggest that missing teeth cause malocclusion which leads to subjective symptoms of fatigue.

Stereoscopic approach to 3-D display using computer-generated holograms.

A composite hologram to reconstruct a three-dimensional object is synthesized with a computer using the technique of holographic stereogram. In the first step of the method, a sequence of perspective projections of the three-dimensional object is calculated, and their Fourier transform holograms are also generated with a computer. These holograms are assembled into a final hologram in the second step. This method requires a computation time far less than the conventional method of producing a computer-generated hologram and makes it possible to reconstruct an image with a wide view angle. Some characteristics of the reconstructed image are described, and optimum parameters for the synthesis and reconstruction process are discussed. Finally, an experimental example is presented.

Phase optimization of a kinoform by simulated annealing.

The design of a kinoform by the use of simulated annealing is discussed. The simulated annealing process is applied to decrease the reconstruction noise and to adjust the phase distribution of the kinoform to the configuration of the recording device. A liquid-crystal spatial light modulator is used to display the kinoform. The reconstructed image of the optimized kinoform is found to be in good agreement with the computed image. Some experimental results obtained with a liquid-crystal spatial light modulator are presented. The phase quantization effect of the kinoform is discussed.

Use of the fast Fourier transform method for analyzing linear and equispaced Fizeau fringes.

The Fourier transform method is applied to analyze the initial phase of linear and equispaced Fizeau fringes. We develop an algorithm for high-precision phase measurement by using the Fourier coefficient that corresponds to the spatial frequency of the Fizeau fringes, and we describe methods for determining the fringe carrier frequency. Errors caused by carrier frequency fluctuation and data truncation are studied theoretically and by computer simulation. To demonstrate the method we apply it to the real-time calibration of a piezoelectric transducer mirror in a Twyman-Green interferometer.

Interferometric testing with computer-generated holograms: aberration balancing method and error analysis.

When testing aspheric surfaces with a computer-generated hologram, some problems should be considered. In this paper, first, we compare two types of hologram: Lohmann and interference. The phase error in the Lohmann type hologram is estimated, and a method of compensating the error is described. Second, we discuss the relation between the shape of the required wavefront and the number of resolution cells of the hologram. Since testing smaller f number optical elements increases the required number of resolution cells of the hologram, we propose the aberration balancing method to reduce the number of resolution cells. The optimum values of the defocus aberration are calculated. Especially, it is shown that the number of resolution cells in the hologram is capable of being reduced to 25%. Third, we discuss the error due to incorrect hologram size and due to misalignment of the optical system when the aberration balancing method is applied. Finally, an experimental example for testing an aspheric mirror 150 mm in diameter and 300 mm in focal length is given.

Fringe pattern correlator for three-dimensional object recognition.

We propose a novel three-dimensional (3-D) object-recognition method based on a Fourier-transform profilometry technique and a two-dimensional (2-D) correlation technique. Height information on 3-D objects is transformed to phase information on 2-D complex amplitude by use of the Fourier-transform profilometry technique. 3-D objects are recognized using correlation by use of the transformed complex amplitude.

Phase measuring Ronchi test.

Use of synchronous phase detection in the conventional Ronchi test is discussed to measure a large amount of wavefront aberration or an aspheric wavefront. This method provides a simple but powerful tool for aspheric surface evaluation. By moving the Ronchi grating sideways, a periodic phase shift in the Ronchigram is introduced for synchronous phase detection. A theoretical interpretation of the Ronchigram and the procedure for an analysis are presented, and experimental results are shown.

Dual-reference holographic interferometry with a double pulsed laser.

Dual-reference holographic interferometry is applied to transient deformation phenomena with a double pulsed laser. Automated interpretation of the interfering pattern of two reconstructed images produced by the double exposure hologram is achieved with a precision of lambda/35. The lateral motion which causes the reduction of fringe visibility is compensated by varying the reference angle in reconstruction. Two switching methods to synchronize the two pulses as two reference beams are shown. Its use in measuring the displacement and deformation of a solid diffusely scattering object is demonstrated.

Changes in microvascular structure of the fibrotic pancreas and their influence on pancreatic endocrine function.

The objectives of this study were to clarify the microvascular structure in and around the Langerhans' islands of the normal pancreas, elucidate how the structure changes with advance of pancreatic fibrosis owing to stagnation of pancreatic juice, and how these changes influence the endocrine function of the pancreas. For these purposes, the changes in microvascular structure of the fibrotic pancreas, produced by ligation of the pancreatic duct in mongrel adult dogs, were investigated by microangiography and injection replica scanning electron microscopic methods. In addition, the endocrine function of the pancreas was studied by the intravenous (iv) glucose tolerance test. The results revealed that the basic blood vessel structure of the Langerhans' islands, and its insulin secretory function, were maintained relatively well in the long-term, duct-ligated pancreas though the capillary network spreading in the pancreatic exocrine part could hardly be observed.

Computer-aided speckle pattern interferometry.

An on-line computer system for measuring the deformation of a diffuse object with a speckle interferometer is presented. Methods for evaluating a speckle interferogram using digital image processing techniques are also discussed. The system consists of an interferometric optical setup and a computer-TV image processing facility. A speckle interferogram is generated arithmetically between two digitized speckle patterns before and after deformation of the object. The information about the deformation is extracted by two procedures in analyzing the interferogram: (a) automatic analysis using digital image processing techniques such as gray scale modification, linear spatial filtering, thresholding, and skeletoning; (b) man-machine interactive method for simple high-speed processing of the interferogram using a light pen. The determined fringe order numbers are interpolated and differentiated spatially to give strain, slope, and bending moment of the deformed object. Some examples of processed patterns are presented.

Modified signed-digit arithmetic based on redundant bit representation.

Fully parallel modified signed-digit arithmetic operations are realized based on redundant bit representation of the digits proposed. A new truth-table minimizing technique is presented based on redundant-bitrepresentation coding. It is shown that only 34 minterms are enough for implementing one-step modified signed-digit addition and subtraction with this new representation. Two optical implementation schemes, correlation and matrix multiplication, are described. Experimental demonstrations of the correlation architecture are presented. Both architectures use fixed minterm masks for arbitrary-length operands, taking full advantage of the parallelism of the modified signed-digit number system and optics.

Quantized phase optimization of two-dimensional Fourier kinoforms by a genetic algorithm.

We have developed a phase optimization method of a quantized kinoform by a genetic algorithm. Because the genetic algorithm inherently deals with discrete values, the quantized phase of the kinoform can be easily estimated. The two-dimensional Fourier kinoform can utilize effectively the periodicity of the discrete Fourier transform in the genetic algorithm. This condition enables us to perform the crossover process that is one of the processes in genetic algorithm without a spatial bandwidth of the kinoform. The optimization has been performed successfully in computer simulation. The optically reconstructed image agrees well with the theoretical one.

Simple algorithm for large-grid phase reconstruction of lateral-shearing interferometry.

A simple zonal approach is proposed for estimating phase distribution on large grids. The estimation is based on phase differences that are precisely measured in two orthogonal directions by a lateral-shearing interferometer. It requires only O(N(2)) operations for reconstructing a phase distribution on an N × N grid. Computer simulation and experimental results are demonstrated to show the effectiveness of the new algorithm.