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Proceedings ArticleDOI

Optical Sensing And Engineering Metrology

10 Aug 1983-Vol. 0376, pp 2-7
TL;DR: In this article, the International Society for Optical Engineering (ISME) presented a survey of optical measurement techniques for metrology applications in the field of engineering metrology, focusing on the benefits of improved metrology accrue from assured compliance with specifications, lower failure rates and better performance.
Abstract: Techniques of optical sensing are not new to engineering metrology and optical instruments have a long history of successful application in this field. Recent advances in the application of lasers, the development of detectors and the use of computers have produced many new optical techniques for making fast, accurate measurements of engineering parameters. The benefits of improved metrology accrue from assured compliance with specifications, lower failure rates and better performance. The application of new optical techniques reduces measurement time and shortens the calibration chain.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
References
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Journal ArticleDOI
Bengt Edlén1
TL;DR: In this article, the authors presented an improved dispersion formula for standard air, (n − 1)s × 108 = 8342, where σ is the vacuum wave-number in μm-1.
Abstract: Present knowledge of the refractive index of air is reviewed. Regarding the absolute values there are as yet no definite indications that the standard adopted in 1953 on the basis of Barrell and Sears' measurements should be changed, but new experiments aiming at reducing the present uncertainty of about ± 5 × 10-8 would be desirable. Several recent investigations have contributed important new information on the dispersion of air, which has made it possible to derive an improved dispersion formula for standard air, (n − 1)s × 108 = 8342.13 + 2406030 (130 − σ2)-1 + 15997 (38.9 − σ2)−1, where σ is the vacuum wave-number in μm-1. The deviations from the 1953 formula are small and practically negligible in most spectroscopic work. An equation for the dependence of refractivity on temperature and pressure based on theoretical considerations has been derived. For the range of atmospheric conditions normally found in a laboratory the equation can be approximated by the formula (n − 1)tp = (n − 1)s × 0.00138823 p/(1 + 0.003671 t), with p in torr, t in °C, and (n − 1)s given by the dispersion formula for standard air. The effect of carbon dioxide and water vapour is discussed. From Erickson's dispersion data for water vapour, combined with Barrell and Sears' absolute measurements, one obtains the equation ntpf – ntp = −f (5.722 − 0.0457 σ2) × 10-8 for the difference in refractive index of moist air, containing f torr of water vapour, and dry air at equal temperature and total pressure. The equation is valid for visible radiations and normal atmospheric conditions.

1,229 citations

Journal ArticleDOI
TL;DR: In this paper, surface displacement can be measured by recording a double-exposure photograph of the laser-illuminated object, followed by optical processing of the recorded speckle-pattern image.
Abstract: Surface displacement can be measured by recording a double-exposure photograph of the laser-illuminated object, followed by optical processing of the recorded speckle-pattern image. The analysis can either be on a point-by-point basis, or by a spatial filtering technique which resolves the motion in any desired direction orthogonal to the line of sight. The limits within which the technique may be used to measure lateral translations and rotations of the surface are examined theoretically and experimentally, and the effect of lens aberrations and surface scattering properties are discussed. Surface tilt may also be measured by recording a defocused double exposure image and analysing its optical transform. The photographic techniques described can be extended to measuring surface vibration, by recording a single ‘time-averaged’ exposure and examining the modified optical transform fringe pattern.

294 citations

Journal ArticleDOI
TL;DR: A moiré technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects, useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.
Abstract: This paper describes a moire technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects. A grid pattern is generated on the object by illuminating it with a laser interference pattern, and a master negative is made by photographing the illuminated object with a view camera. With the negative occupying its original position, the moire pattern corresponding to changes in the object can be observed in real time by viewing the image of the deformed or second object through the negative. The technique is noncontacting and quantitative. It is useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.

105 citations

PatentDOI
TL;DR: In this paper, a method of producing a multiplehologram of an object communicating with other objects is described. But the method is not applicable to the case of a single person communicating with multiple people.

94 citations

Journal ArticleDOI
TL;DR: The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique, and the technique is compared to laser speckle photography.
Abstract: If a camera is to be used for the special purpose of recording periodic grid-like patterns, the range of spatial frequencies which it must handle is limited, and its imaging performance for a given range can be optimized by installing a suitably slotted mask inside the lens aperture. With this modification, a standard 35 mm single lens reflex camera has been found to resolve up to 600 lines/mm in both vertical and horizontal directions across the full format. The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique. Some preliminary results are described, and the technique is compared to laser speckle photography.

67 citations