Effect of image curvatures in digital holographic microscopy

Hsieh, Wang-Ta; Huang, Ji-Lu; Yau, Hon–Fai; Shiu, Min-Tzung; Wang, Je-Chung; Chang, Chi-Ching

doi:10.1007/3dres.02(2011)1

Cited by 3 publications

(1 citation statement)

References 32 publications

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“…Liebling et al proposed a metric for the reconstruction of digital Fresnel holograms based on the computation of the sparsity of a Fresnelet decomposition [21]. Furthermore, Fan et al and Fonseca et al discussed many sparsity metrics for autofocusing in digital holographic microscopy and in-line phase-shifting holography [22][23][24]. The performance of those sharpness metric-based methods is highly dependent on the features of the samples, so they are very limited in practice.…”

Section: Introductionmentioning

confidence: 99%

Autofocusing based on cosine similarity in dual-wavelength digital holographic microscopy

Yu¹,

Jia²,

Liu³

et al. 2021

Meas. Sci. Technol.

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An autofocusing method based on cosine similarity in dual-wavelength digital holographic microscopy is proposed. In our experiments, red and green lasers are employed for illumination and the generated holograms are recorded by a color camera. During the refocusing process, the reconstructed optical field near the focus plane contains more regular features than the one on the defocus plane. Moreover, due to the wavelength dependency of the diffraction process, the further away from the focus plane, the greater the difference in the reconstructed optical fields from the two wavelengths. Therefore, the focus plane can be determined by finding the maximum value of the cosine similarity between the amplitude vectors from the reconstructed optical fields of the two wavelengths. Simulation and experimental results demonstrate the effectiveness of the proposed method in off-axis dual-wavelength digital holographic microscopy for shape measurement.

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Section: Introductionmentioning

confidence: 99%

Autofocusing based on cosine similarity in dual-wavelength digital holographic microscopy

Yu¹,

Jia²,

Liu³

et al. 2021

Meas. Sci. Technol.

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Range Sensing

Konolige¹,

Nüchter²

2016

Springer Handbook of Robotics

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Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

Tengen

2011

Nanoscale Res Lett

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Grain shapes are acknowledged to impact nanomaterials' overall properties. Research works on this issue include grain-elongation and grain-strain measurements and their impacts on nanomaterials' mechanical properties. This paper proposes a stochastic model for grain strain undergoing severe plastic deformation. Most models deal with equivalent radii assuming that nanomaterials' grains are spherical. These models neglect true grain shapes. This paper also proposes a theoretical approach of extending existing models by considering grain shape distribution during stochastic design and modelling of nanomaterials' constituent structures and mechanical properties. This is achieved by introducing grain 'form'. Example 'forms' for 2-D and 3-D grains are proposed. From the definitions of form, strain and Hall-Petch-Relationship to Reversed-Hall-Petch-Relationship, data obtained for nanomaterials' grain size and conventional materials' properties are sufficient for analysis. Proposed extended models are solved simultaneously and tested with grain growth data. It is shown that the nature of form evolution depends on form choice and dimensional space. Long-run results reveal that grain boundary migration process causes grains to become spherical, grain rotation coalescence makes them deviate away from becoming spherical and they initially deviate away from becoming spherical before converging into spherical ones due to the TOTAL process. Percentage deviations from spherical grains depend on dimensional space and form: 0% minimum and 100% maximum deviations were observed. It is shown that the plots for grain shape functions lie above the spherical (control) value of 1 in 2-D grains for all considered grain growth mechanisms. Some plots lie above the spherical value, and others approach the spherical value before deviating below it when dealing with 3-D grains. The physical interpretations of these variations are explained from elementary principles about the different grain growth mechanisms. It is observed that materials whose grains deviate further away from the spherical ones have more enhanced properties, while materials with spherical grains have lesser properties. It is observed that there exist critical states beyond which Hall-Petch Relationship changes to Reversed Hall-Petch Relationship. It can be concluded that if grain shapes in nanomaterials are constrained in the way they evolve, then nanomaterials with desired properties can be designed.

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Effect of image curvatures in digital holographic microscopy

Cited by 3 publications

References 32 publications

Autofocusing based on cosine similarity in dual-wavelength digital holographic microscopy

Autofocusing based on cosine similarity in dual-wavelength digital holographic microscopy

Range Sensing

Designing nanomaterials with desired mechanical properties by constraining the evolution of their grain shapes

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