Improvement on theoretical model for thin-wire and slot measurement by optical diffraction

Tang, Wing Man; Zhou, Yanxin; Zhang, J

doi:10.1088/0957-0233/10/11/401

Cited by 22 publications

(10 citation statements)

References 2 publications

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“…But none of them could give a quantitative interpretation [2][3][4]. Some other papers discuss a lot about diffraction [5][6][7][8], which totally deviates the principle of the laser ring phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Research on a Laser Ring Induced by a Metal Wire

Feng¹

2017

AJPA

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Abstract:When the metal wire is irradiated with a beam of laser, a light ring will appear on the screen. The formation mechanism of the light ring is discussed in this article. It is also discussed how various parameters, including the shape of the laser beam, the laser diameter, the wire diameter, the wire roughness, and the incidence angle, influence the ring through computational simulation and experiments simultaneously. Our calculation is in good agreement with experimental results.

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Section: Introductionmentioning

confidence: 99%

Research on a Laser Ring Induced by a Metal Wire

Feng¹

2017

AJPA

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“…The currently known noncontact method of wave optics for diameter measurement is through diffraction [4][5][6][7]. The diffraction method works well for small solid disks.…”

Section: Introductionmentioning

confidence: 99%

Far-field interference from a sphere and its applications

Tian

2012

Appl. Opt.

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A theoretical model of far-field interference from a sphere has been established, and its applications have been investigated. When two coherent parallel laser beams shine on a smooth sphere surface from opposite directions, the reflected lights form interference fringes at far field. The fringes have hyperbolic shapes and are not uniformly distributed. This paper derives a method for calculating the path-length difference between two parallel reflected lights, analyzes the interference field, and discusses reasons that cause the fringe density variations. A formula for calculating the highest orders of interference fringes is also provided. A method for using a spectrometer, CCD camera, and computer to measure the sphere diameter is demonstrated. The results agree with those from an Abbe comparator. The theory and methods are also suitable for measuring diameters of smooth cylinders.

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“…Most of these optical methods, for measuring the diameters of thin opaque wires and fibers with high accuracy, are usually based on principles of optical diffraction 1-7 , polarization 8 , interferometry 9-10 , Optical microscopy 11 and laser beam scanning 12 . In past few decades optical diffractometry under Fraunhofer approximation has been widely used as an automated industrial inspection technique for dimension estimation [1][2][3][4][5][6][7] . In this methodology a CCD camera is used to record the Fraunhofer diffraction pattern of the wire and diameter is estimated from separation between successive diffraction minima.…”

Section: Introductionmentioning

confidence: 99%

“…As a result several methods to increase the resolution of diameter estimation under Conventional Fraunhofer diffraction using modified fringe spacing algorithms, wide-angular range of measurements, consideration of 3-D model of the object etc have been proposed in recent years 2,4,5,7,8 . However for most of the methods the diameters of wires under inspection range from 100-it is observed that errors in measurement through these methods increase greatly as diameter approaches the wavelength of light.…”

Section: Introductionmentioning

confidence: 99%

A novel method for diameter estimation of small opaque objects using Fraunhofer diffraction

Vyas

Lolla

2010

Reflection, Scattering, and Diffraction From Surfaces II

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A novel optical method is proposed and demonstrated, for real-time dimension estimation of thin opaque cylindrical objects. The methodology relies on free-space Fraunhofer diffraction principle. The central region, of such tailored diffraction pattern obtained under suitable choice of illumination conditions, comprises of a pair of 'equal intensity maxima', whose separation remains constant and independent of the diameter of the diffracting object. An analysis of 'the intensity distribution in this region' reveals the following. At a point symmetrically located between the said maxima, the light intensity varies characteristically with diameter of the diffracting object, exhibiting a relatively stronger intensity modulation under spherical wave illumination than under a plane wave illumination. The analysis reveals further, that the said intensity variation with diameter is controllable by the illumination conditions. Exploiting these 'hitherto unexplored' features, the present communication reports for the first time, a reliable method of estimating diameter of thin opaque cylindrical objects in real-time, with nanometer resolution from single point intensity measurement. Based on the proposed methodology, results of few simulation and experimental investigations carried-out on metall is well-suited for high resolution on-line monitoring of ultrathin wire diameters, extensively used in micro-mechanics and semiconductor industries, where the conventional diffraction-based methods fail to produce accurate results.

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Improvement on theoretical model for thin-wire and slot measurement by optical diffraction

Cited by 22 publications

References 2 publications

Research on a Laser Ring Induced by a Metal Wire

Research on a Laser Ring Induced by a Metal Wire

Far-field interference from a sphere and its applications

A novel method for diameter estimation of small opaque objects using Fraunhofer diffraction

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