Real-time slope mapping and defect detection in bent plates using Talbot interferometry

Trivedi, Satya Prakash; Prakash, Shashi; Rana, Santosh; Sasaki, Osami

doi:10.1364/ao.49.000897

Cited by 10 publications

(3 citation statements)

References 25 publications

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“…Laser based optical techniques have been extensively used in industries and laboratories for non-destructive testing, inspection and evaluation [1,2]. Optical techniques are simple, non-contact, and highly sensitive.…”

Section: Introductionmentioning

confidence: 99%

Histogram error based algorithm for efficient collimation testing

Dhanotia

Bande

Bhatia

et al. 2019

J. Opt.

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This communication reports an investigation undertaken towards setting collimation of an optical beam using a self-imaging technique and histogram error (HE) based approach. The beam under test illuminates an amplitude type Ronchi grating. After the grating, a beam splitter is placed such that the grating’s self-images are formed in two perpendicular directions, at the different Talbot planes. The images are then recorded using two identical CCD cameras. Towards implementing a HE based algorithm, first, element-by-element subtraction of the normalized histogram of both self-images is computed. Next, the sum of the elements of the resultant image matrix is determined. Finally, the square of the sum yields the HE. HE provides an estimate of the collimation errors in the beam. For an incident collimated beam, the self-images recorded at different Talbot planes have identical unit magnification with respect to the grating; however, when the beam diverges or converges, the size and fringe width of self-images are differentially magnified or demagnified. Hence, when the beam is collimated, the HE is minimum. For the decollimated beam, the value of HE is higher, and increases as the decollimation errors increase. Using the proposed method, we could set the collimation position to a resolution of 1 μm, which relates to ±0.22 μ radians in terms of collimation angle (for a lens of focal length 300 mm and diameter 40 mm). Experimental results conclusively establish the viability of the technique. Good accuracy and precision in the measurement have been achieved.

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Section: Introductionmentioning

confidence: 99%

Histogram error based algorithm for efficient collimation testing

Dhanotia

Bande

Bhatia

et al. 2019

J. Opt.

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“…For example, Talbot interferometry allows to study the surface profile of transparent objects [3], the slope contours of bent plates [4] and also was used for collimation testing [5]. Additionally, the selfimaging properties of the Talbot effect are also suitable for sub-wavelength focusing of light [6] and offer new solutions for spectroscopy [7,8].…”

Section: Introductionmentioning

confidence: 99%

Effective and flexible modeling approach to investigate various 3D Talbot carpets from a spatial finite mask

Maaß

Sandfuchs

Thomae

et al. 2013

J. Eur. Opt. Soc.-Rapid Publ.

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We present an effective modeling approach for a fast calculation of the Talbot carpet from an initially 2-dimensional mask pattern. The introduced numerical algorithm is based on a modified angular-spectrum method, in which it is possible to consider the border effects of the Talbot region from a mask with a finite aperture. The Bluestein's fast Fourier transform (FFT) algorithm is applied to speed up the calculation. This approach allows as well to decouple the sampling points in the real space and the spatial frequency domain so that both parameters can be chosen independently. As a result an extended three-dimensional Talbot-carpet can be calculated with a minimized number of numerical steps and computation time, but still with high accuracy. The algorithm was applied to various 2-dimensional mask patterns and illumination setups. The influence of specific mask patterns to the resulting field intensity distribution is discussed.

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“…These effects have been used in many applications, which include periodic pattern projection [12][13][14], optical shearing interferometry [15][16][17][18][19], array illuminators [20,21], X-ray interferometry [22][23][24], and matter-wave interferometry [25]. These applications will become more important because fabrication techniques of micro-elements including gratings are making much progress.…”

Section: Introductionmentioning

confidence: 99%

Relaxation of the Talbot condition in generalized grating imaging

Iwata¹,

Satoh

Moriwaki

2012

Appl. Opt.

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We can form a grating image with two gratings having different pitches with an extended light source. It is called generalized grating imaging or the Talbot-Lau effect. When we want to obtain high contrast image with pure absorption gratings or pure phase gratings, the separation between the two gratings is restricted. This corresponds to the Talbot condition. In this paper, we propose to use a combination of absorption grating and phase grating to relax the separation restriction. The theory of generalized grating imaging is applied to the system with this kind of grating. Simulations are performed for calculating contrast variation and show that the proposed system practically relaxes the Talbot condition. An experiment verifies the result of the simulation.

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Real-time slope mapping and defect detection in bent plates using Talbot interferometry

Cited by 10 publications

References 25 publications

Histogram error based algorithm for efficient collimation testing

Histogram error based algorithm for efficient collimation testing

Effective and flexible modeling approach to investigate various 3D Talbot carpets from a spatial finite mask

Relaxation of the Talbot condition in generalized grating imaging

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