New computational hybrid three-wavelength-based approach of phase shifting for analyzing the stress field in photoelasticity studies

Restrepo-Martínez, Alejandro; Toro, Hermes A. Fandiño; León, Juan Diego

doi:10.1117/12.2594296

Cited by 2 publications

(2 citation statements)

References 30 publications

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“…With the last set of images and equations, a hybrid wavelength step technique (HWST) method was developed [16][17] . It needs only the bright field image because the dark field images are generated computationally based on the one proposed by Briñez in reference 18 .…”

Section: Light Intensitymentioning

confidence: 99%

“…All these facts limit a wide use of this phase-shifting method. This paper has as contribution the development of an algorithm that uses the structure of a standard load-stepping method [14][15][16][17] but incorporates digital processing for generating a special color image that allows to produce phase shifting, avoiding the problems associated with the limitations of the load, the number of images, movement, or deformation of the sample. Thus, this article proposes a new three-wavelength chromatic-corrected image hybrid phase shift method that works for single-camera digital photoelasticity applications.…”

Section: Introductionmentioning

confidence: 99%

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A new three-wavelength chromatic-corrected hybrid phase shifting method for single-camera digital photoelasticity

Restrepo-Martínez

2023

Modeling Aspects in Optical Metrology IX

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Digital photoelasticity is a non-contact inspection technique, that requires new strategies to unwrap the stresses map based on color images. Therefore, this paper presents a new three-wavelength chromatic-corrected hybrid phase-shift method for single-camera digital photoelasticity applications. For the experiments, the intensities of isochromatic images are simulated considering a birefringent sample compressed and a circular polariscope configured to produce a bright field image that avoids the effects caused by isoclinics. To increase the range of the fringe order, three LEDs with peaks of close wavelengths were used. Additionality, for each LED a RGB color image is simulated. The red channel of each image is used to generate a new synthetic chromatic-corrected image (CCI) thereby: the red channel of λ3 is the red channel of the new CCI, and the green and blue channels of the CCI use the respective red channels of λ2 and λ1; additionally, the wavelengths must satisfy the following condition (λ3 > λ2 >λ1). An inverted image of the CCI is computed. Thus, with the CCI and its inverted image, six images are stored, and with these images and some trigonometric relations proposed by Ekman and Nurse a wrapped phase map is extracted. Finally, an unwrapping algorithm is applied to reconstruct the stresses map. The results show that the method improves the detected maximum order and reduces stress map distortions compared to similar color phase shifting approaches. Furthermore, since the algorithm requires only a camera and a circular polariscope setup, it can be implemented in dynamic experimental applications.

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Section: Light Intensitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A new three-wavelength chromatic-corrected hybrid phase shifting method for single-camera digital photoelasticity

Restrepo-Martínez

2023

Modeling Aspects in Optical Metrology IX

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Fringe pattern analysis to evaluate light sources and sensors in digital photoelasticity

Fandiño¹,

Aristizábal-López²,

Restrepo-Martínez

et al. 2023

Appl. Opt.

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When experimental photoelasticity images are acquired, the spectral interaction between the light source and the sensor used affect the visual information of the fringe patterns in the produced images. Such interaction can lead to fringe patterns with an overall high quality, but also can lead to images with indistinguishable fringes, and bad stress field reconstruction. We introduce a strategy to evaluate such interaction that relies on measuring the value of four handcrafted descriptors: contrast, an image descriptor that accounts simultaneously for blur and noise, a Fourier-based descriptor to measure image quality, and image entropy. The utility of the proposed strategy was validated by measuring the selected descriptors on computational photoelasticity images, and the fringe orders achieved when evaluating the stress field, from 240 spectral configurations: 24 light sources and 10 sensors. We found that high values of the selected descriptors can be related to spectral configurations that lead to better stress field reconstruction. Overall, the results show that the selected descriptors can be useful to identify bad and good spectral interactions, which could help to design better protocols for acquiring photoelasticity images.

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New computational hybrid three-wavelength-based approach of phase shifting for analyzing the stress field in photoelasticity studies

Cited by 2 publications

References 30 publications

A new three-wavelength chromatic-corrected hybrid phase shifting method for single-camera digital photoelasticity

A new three-wavelength chromatic-corrected hybrid phase shifting method for single-camera digital photoelasticity

Fringe pattern analysis to evaluate light sources and sensors in digital photoelasticity

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