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

Although the off-road mobility characteristics of wheeled or tracked vehicles are generally recognized as being inferior to those of man and cursorial animals, the complexity of the joint-coordination control problem has thus far frustrated attempts to achieve improved vehicular terrain adaptability through the application of legged locomotion concepts. Nevertheless, the evident superiority of biological systems in this regard has motivated a number of theoretical studies over the past decade which have now reached a state of maturity sufficient to permit the construction of experimental computer-controlled adaptive walking machines. At least two such vehicles are known to have recently demonstrated legged locomotion over smooth hard-surfaced terrain. This paper is concerned with an extension of the present theory of limb coordination for such machines to the case in which the terrain includes regions not suitable for weight-bearing and which must consequently be avoided by the control computer in deciding when and where to successively place the feet of the vehicle. The paper includes a complete problem formalization, a heuristic algorithm for solution of the problem thus posed, and a preliminary evaluation of the proposed algorithm in terms of a computer simulation study.

Adaptive Locomition of a Multilegged Robot over Rough Terrain

Roughness determines many functional properties of surfaces, such as adhesion, friction, and (thermal and electrical) contact conductance. Recent analytical models and simulations enable quantitative prediction of these properties from knowledge of the power spectral density (PSD) of the surface topography. The utility of the PSD is that it contains statistical information that is unbiased by the particular scan size and pixel resolution chosen by the researcher. In this article, we first review the mathematical definition of the PSD, including the one- and two-dimensional cases, and common variations of each. We then discuss strategies for reconstructing an accurate PSD of a surface using topography measurements at different size scales. Finally, we discuss detecting and mitigating artifacts at the smallest scales, and computing upper/lower bounds on functional properties obtained from models. We accompany our discussion with virtual measurements on computer-generated surfaces. This discussion summarizes how to analyze topography measurements to reconstruct a reliable PSD. Analytical models demonstrate the potential for tuning functional properties by rationally tailoring surface topography - however, this potential can only be achieved through the accurate, quantitative reconstruction of the power spectral density of real-world surfaces.

/pdf/quantitative-characterization-of-surface-topography-using-1di6n32wn5.pdf

Quantitative characterization of surface topography using spectral analysis

Roughness determines many functional properties of surfaces, such as adhesion, friction, and (thermal and electrical) contact conductance. Recent analytical models and simulations enable quantitative prediction of these properties from knowledge of the power spectral density (PSD) of the surface topography. The utility of the PSD is that it contains statistical information that is unbiased by the particular scan size and pixel resolution chosen by the researcher. In this article, we first review the mathematical definition of the PSD, including the one- and two-dimensional cases, and common variations of each. We then discuss strategies for reconstructing an accurate PSD of a surface using topography measurements at different size scales. Finally, we discuss detecting and mitigating artifacts at the smallest scales, and computing upper/lower bounds on functional properties obtained from models. We accompany our discussion with virtual measurements on computer-generated surfaces. This discussion summarizes how to analyze topography measurements to reconstruct a reliable PSD. Analytical models demonstrate the potential for tuning functional properties by rationally tailoring surface topography—however, this potential can only be achieved through the accurate, quantitative reconstruction of the PSDs of real-world surfaces.

/pdf/quantitative-characterization-of-surface-topography-using-45kh8tzr33.pdf

Quantitative Characterisation of Surface Texture

Calculation of the fractal dimensions of machined surface profiles

Study on the gaits of an inchworm robot through a narrow path

In this research, an inchworm-type robot is being developed for the purpose of rescue missions. This robot has the ability to traverse obstacles such as stairs with fewer joints than legged robots. A self-standing inchworm robot, which has five links and four joints, is produced for trial purposes. In order for this robot to be able to climb up stairs, the kinematical analysis and the development of the program were investigated. As a result, the effectiveness of this robot is confirmed experimentally.

An investigation of climbing up stairs for an inchworm robot

A new method for profile measurement using phase-shifting technique is proposed and verified by experiments. The method realizes the measurement by projecting an interferometric fringe pattern as a grating pattern on the object surface and by observing the deformed fringe pattern at the direction different from the projection. The fringe pattern is shifted in four steps by means of a mirror mounted on a piezoelectric translator. Path difference at each point on the object surface is calculated precisely from the four intensity data. From the path difference data, we can calculate the object profile. This technique needs no fine fringe pattern to improve lateral resolving power as it gives height distribution at all the picture elements over the object image. Furthermore, the technique has the advantage that it can measure the object with spatially varying reflectivity. This paper also estimates the measuring errors caused by A/D converter.

Grating projection method for profile measurement using phase-shifting technique.

Being buried to death under eollasped houses without being found became a big issue during a major calamity. The developnaent of a robot which finds life in the suffering district is needed as soon as possible. In this research, the method of lnoving the inchworm-type robot is being developed for the purpose of the rescue. This robot has the ability to traverse obstacles such as the stairs with fewer joints than the wheel type and the legged type. The selfstanding inchworm robot which has five links and four joints is made for trial purposes. In order to achieve climbing stairs for this robot, the kinematical analysis and the development of the program was researched. As a result, the effectiveness of this robot is confirmed by the experiment.

Motoyoshi Hasegawa

Papers

Calculation of the fractal dimensions of machined surface profiles

Study on the gaits of an inchworm robot through a narrow path

An investigation of climbing up stairs for an inchworm robot

Grating projection method for profile measurement using phase-shifting technique.

An Investigation of Climbing up Stairs for Inchworm Robot.