Focal length measurement based on Fresnel diffraction from a phase plate

Dashtdar, Masoomeh; Hosseini-Saber, S. Mohammad-Ali

doi:10.1364/ao.55.007434

Cited by 20 publications

(5 citation statements)

References 24 publications

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“…Finally, we should mention that the researchers have applied the Fresnel diffraction from a phase step to the measurements of the refractive index in X-ray region [23], film thickness [24][25][26], etching rate [27], simultaneous measurement of film thickness and refractive index [26], focal lengths of the lenses [28], specification of the spectral line profile [29], and modulation of phase function [30], Applications are increasing, particularly, in quantitative imaging of the phase objects in different scales [13,[31][32].…”

Section: Measurement Of Diffusion Coefficientmentioning

confidence: 99%

Fresnel Diffraction from Phase Steps and Its Applications

Tavassoly

Salvdari

2020

IJOP

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The well-established Fresnel diffraction occurs as an opaque object partially obstructs the passage of a coherent beam of light. In this process, the amplitude of the optical wave experiences a discontinuous change that leads to peculiar bright and dark fringes near the ray optics border of the beam. The fringe pattern varies very slowly by distance from the object and away from the beam border the diffraction effect is negligible. These behaviors have limited the applications of the conventional Fresnel diffraction very severely. In this article, we introduce a new kind of Fresnel diffraction that occurs due to discontinuous change in phase or phase gradient, in a part of a coherent beam of light. The change splits the beam into two diffracting wavefronts with common border that interfere with each other. In this kind of diffraction, the fringes may appear in the central part of the beam and their locations and visibilities are very sensitive to the phase change. Therefore, the researchers have utilized the effect in the measurements of different physical quantities, with high accuracy, using modest equipment. In this article, we use the Fresnel diffraction from the semi-infinite opaque screen (knife-edge) as the building block to describe the introduced effect, diffraction from the phase steps, and discuss its different aspects. We simulate the implied diffraction patterns, investigate the patterns by experiments, elaborate on the unique features of the effect, and present some interesting applications.

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Section: Measurement Of Diffusion Coefficientmentioning

confidence: 99%

Fresnel Diffraction from Phase Steps and Its Applications

Tavassoly

Salvdari

2020

IJOP

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“…In the case of negative lenses, an auxiliary positive lens is used to achieve the convergence of the rays and take an "indirect" measurement of the focal length by means of the experimental determination of the "back focal length." This process can be performed using different techniques or physical approaches, such as Fresnel diffraction, which, unlike the method proposed in this study, considers an angle of incidence [31]. Thus, the method proposed here produces better measurable results.…”

Section: Introductionmentioning

confidence: 99%

Method for determining uncertainty and error in the process of ophthalmic lens calibration

Salgar-Marín

Vargas

Ramírez-Barrera

2021

TecnoL.

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In the present investigation, a scientific procedure was developed, and a mathematical model was proposed, with the objective of determining, under standard conditions, the uncertainty, and the measurement of dioptric power in ophthalmic lenses. The methodology of the scientific procedure is based on the fundamentals of geometric optics, this process guarantees and establishes a standardized uncertainty measure in repeatable and reproducible processes. The methodology is complemented with a proposed mathematical model based on the guide for the expression of uncertainty in measurement - GUM. This model can be applied to lenses used for calibrating eye care equipment (such as lensometers, which are used to diagnose myopia and farsightedness) by evaluating the lenses without having direct contact with patients. When the proposed mathematical model was applied, its experimental result was a maximum expanded uncertainty of ± 0.0079 diopters in a 0.5-diopter lens. This is optimal compared to the result of other authors this article, who reported a maximum expanded uncertainty of ± 0.0086 diopters. In conclusion, the application of this scientific procedure provides manufacturers and users of this type of lenses with a reliable measurement thanks to a calibration process based on geometrical optics and centered on patient safety.

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“…Thus far, Fresnel diffraction from a phase step is studied [27][28][29] and widely considered in the context of different metrological applications, e.g., the measurement of refractive indices of solids and liquids [30][31][32], thickness of films and plates [33], focal length of an imaging system [34], etching rate of glass steps [35], and determination of the off-axis angle and the wavelength of light [36].…”

Section: Introductionmentioning

confidence: 99%

Quantitative phase imaging based on Fresnel diffraction from a phase plate

Ebrahimi

Dashtdar

2019

Applied Physics Letters

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The structural complexity and instability of many interference phase microscopy methods are the major obstacles toward high-precision phase measurement. In this vein, improving more efficient configurations as well as proposing new methods are the subjects of growing interest. Here we introduce Fresnel diffraction from a phase step to the realm of quantitative phase imaging. By employing Fresnel diffraction of a divergent (or convergent) beam of light from a plane-parallel phase plate, we provide a viable, simple and compact platform for three-dimensional imaging of micron-sized specimens. The recorded diffraction pattern of the outgoing light from an imaging system in the vicinity of the plate edge can be served as a hologram, which would be analyzed via Fourier transform method to measure the sample phase information. The period of diffraction fringes is adjustable simply by rotating the plate without the reduction of both field of view and fringe contrast. The high stability of the presented method is affirmatively confirmed through comparison the result with that of conventional Mach-Zehnder based digital holographic method. Quantitative phase measurements on silica microspheres, onion skin and red blood cells ensure the validity of the method and its ability for monitoring nanometer-scale fluctuations of living cells, particularly in real-time.

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Focal length measurement based on Fresnel diffraction from a phase plate

Cited by 20 publications

References 24 publications

Fresnel Diffraction from Phase Steps and Its Applications

Fresnel Diffraction from Phase Steps and Its Applications

Method for determining uncertainty and error in the process of ophthalmic lens calibration

Quantitative phase imaging based on Fresnel diffraction from a phase plate

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