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

We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, data postprocessing and analysis methods and advantages and limitations are presented. Several industrial application examples are presented. Important areas requiring further R&D are discussed. Finally, a comprehensive bibliography on 3-D shape measurement is included, although it is not intended to be exhaustive. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00101-X)

Overview of three-dimensional shape measurement using optical methods

Active, optical range imaging systems collect three-dimensional coordinate data from object surfaces. These systems can be useful in a wide variety of automation applications, including shape acquisition, bin picking, assembly, inspection, gauging, robot navigation, medical diagnosis, cartography, and military tasks. The range-imaging sensors in such systems are unique imaging devices in that the image data points explicitly represent scene surface geometry in a sampled form. At least six different optical principles have been used to actively obtain range images: (1) radar, (2) triangulation, (3) moire, (4) holographic interferometry, (5) lens focusing, and (6) diffraction. The relative capabilities of different sensors and sensing methods are evaluated using a figure of merit based on range accuracy, depth of field, and image acquisition time.

Active optical range imaging sensors

Stress concentration factor due to a circular hole in functionally graded panels under uniaxial tension

The fast development in the fields of integrated circuits, photovoltaics, the automobile industry, advanced manufacturing, and astronomy have led to the importance and necessity of quickly and accurately obtaining three-dimensional (3D) shape data of specular surfaces for quality control and function evaluation. Owing to the advantages of a large dynamic range, non-contact operation, full-field and fast acquisition, high accuracy, and automatic data processing, phase-measuring deflectometry (PMD, also called fringe reflection profilometry) has been widely studied and applied in many fields. Phase information coded in the reflected fringe patterns relates to the local slope and height of the measured specular objects. The 3D shape is obtained by integrating the local gradient data or directly calculating the depth data from the phase information. We present a review of the relevant techniques regarding classical PMD. The improved PMD technique is then used to measure specular objects having discontinuous and/or isolated surfaces. Some influential factors on the measured results are presented. The challenges and future research directions are discussed to further advance PMD techniques. Finally, the application fields of PMD are briefly introduced.

Three-Dimensional Shape Measurements of Specular Objects Using Phase-Measuring Deflectometry.

Dynamic stress concentrations for an axially loaded strut at discontinuities due to an elliptical hole or double circular notches

An efficient system for retroreflective grating generation andanalysis has been constructed to measure the derivative and the contourof specular surfaces. In this system, a new optical configurationhas been provided to generate and capture a grating image with aretroreflective screen. Tests show that the system can detectindents and outdents with a maximum depth of less than 10mum. The method can be developed for automated industrialinspection and machine vision.

Retroreflective grating generation and analysis for surface measurement.

Retroreflective grating analysis versus physical measurements of surface contour

This is the first of a two-part paper on measurement of displacement and profile using changes in the far-field diffraction patterns of a slit aperture formed between a test and reference object. When applied to displacement measurement the method is very accurate over a considerable range, noncontacting, linear, and easy to use. In addition to the measurement considerations involved in this diffractographic technique, three unique applications are discussed. These are: simultaneous deflection measurement along a line, deflection measurement of a surface relative to an edge, and vibration amplitude measurement using time-averaged fringes.

Diffractographic dimensional measurement. Part 1: displacement measurement.

Retroreflective metrology has been used to measure the 3-D surface waviness on standard artifacts. An optical configuration was constructed for the measurement, in which the grating image is produced by projection. The three-step algorithm of phase-shifting technology was applied to analyze the image. Two standard artifacts with 8.0- and 16.0-µm peak-to-peak wave amplitudes were tested. The experiments show that retroreflective metrology can successfully recover the contour and amplitude of the surface waviness on the standard artifacts. Â© 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)02101-2]

Walter P. T. North

Papers

Dynamic stress concentrations for an axially loaded strut at discontinuities due to an elliptical hole or double circular notches

Retroreflective grating generation and analysis for surface measurement.

Retroreflective grating analysis versus physical measurements of surface contour

Diffractographic dimensional measurement. Part 1: displacement measurement.

Analysis of 3-D surface waviness on standard artifacts by retroreflective metrology