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Journal ArticleDOI

Refractive index profilometry using the total internally reflected light field.

20 Nov 2017-Applied Optics (Optical Society of America)-Vol. 56, Iss: 33, pp 9241-9246
TL;DR: A full-field polarization-based technique is presented for quantitative evaluation of the spatial distribution of the refractive index in macro and micro samples, and one of the salient features of the proposed technique is that the depth of measurement is dependent on the penetration depth of the sample's evanescent field, thereby facilitatingrefractive index measurements along a thin section of the samples.
Abstract: A full-field polarization-based technique is presented for quantitative evaluation of the spatial distribution of the refractive index in macro and micro samples. The sample is mounted on a glass–air interface of a prism, illuminated by a linearly polarized collimated light beam, and two intensity frames are digitally recorded with specific orientations of an analyzer. The pair of intensity data frames captured with this simple setup is combined through an algorithm specially developed for the purpose, to yield the phase difference between the transverse electric and transverse magnetic components of the total internally reflected light field. The phase difference is then related to the refractive index of the sample. Experimental results for refractive index variations in a laser-etched glass plate and red blood corpuscles are presented. One of the salient features of the proposed technique is that the depth of measurement is dependent on the penetration depth of the sample’s evanescent field, which is typically of the order of a few hundred nanometers, thereby facilitating refractive index measurements along a thin section of the sample.
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Journal ArticleDOI
TL;DR: In this article, the authors provide an up-to-date review on the resolution enhancement approaches in QPM, discussing the pros and cons of each technique as well as the confusion on resolution definition claims.
Abstract: Quantitative phase microscopy (QPM), a technique combining phase imaging and microscopy, enables visualization of the 3D topography in reflective samples, as well as the inner structure or refractive index distribution of transparent and translucent samples. Similar to other imaging modalities, QPM is constrained by the conflict between numerical aperture (NA) and field of view (FOV): an imaging system with a low NA has to be employed to maintain a large FOV. This fact severely limits the resolution in QPM up to 0.82λ/NA, λ being the illumination wavelength. Consequently, finer structures of samples cannot be resolved by using modest NA objectives in QPM. Aimed to that, many approaches, such as oblique illumination, structured illumination, and speckle illumination (just to cite a few), have been proposed to improve the spatial resolution (or the space–bandwidth product) in phase microscopy by restricting other degrees of freedom (mostly time). This paper aims to provide an up-to-date review on the resolution enhancement approaches in QPM, discussing the pros and cons of each technique as well as the confusion on resolution definition claims on QPM and other coherent microscopy methods. Through this survey, we will review the most appealing and useful techniques for superresolution in coherent microscopy, working with and without lenses and with special attention to QPM. Note that, throughout this review, with the term “superresolution” we denote enhancing the resolution to surpass the limit imposed by diffraction and proportional to λ/NA, rather than the physics limit λ/(2n med ), with n med being the refractive index value of the immersion medium.

60 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D laser profilometer developed at the Department of Design and Technical Systems Monitoring at MIT was used in roughness measurement of various materials produced by water jet cutting.
Abstract: The paper is an evaluation of the surface roughness of various materials produced by water jet cutting (AWJ, abrasive water jet). A 3D laser profilometer developed at the Department of Design and Technical Systems Monitoring at our University was used in roughness measurement. To verify the values measured by the laser profilometer, another measurement was performed using a 2D contact roughness meter. The tests were done on aluminum and stainless-steel materials, respectively. Six samples were produced; three made of stainless steel and three made of aluminum. All samples were produced at a different feed rate of the cutting head. This was adapted to the different roughness required, per the manufacturer’s material data sheets. Varying rates of separation translated into different qualities of the surfaces under evaluation. The evaluated roughness parameters were Ra and Rz. Dependencies were plotted in the chart based on the values measured, which were then compared and evaluated.

15 citations

Journal ArticleDOI
01 Oct 2021-Optik
TL;DR: In this article, a linearly polarized light beam is used to illuminate the sample surface and two intensity data frames are recorded with specific orientations of an analyzer to determine surface roughness of metal surfaces.

3 citations

Journal ArticleDOI
TL;DR: In this article , the application conditions of the Leeb hardness test in rock engineering are investigated. And the effect of physical properties on the leeb method, including scale effect, temperature effect, surface roughness effect, and the effect effect on physical properties have been studied.

2 citations