Graphene nanoplatelets exhibit high potential for current engineering applications, particularly in context of conductive inks for organic and flexible electronic. Electrodes for organic displays are expected to be transparent in the visible part of electromagnetic spectrum.
Thus this study aimed at full-field transmission measurements in the visible wavelength range. The paper presents transmission characteristics of different graphene samples. Samples, prepared using spray coating methods contained 3 types of deposited inks. Each of them was based on different concentration and size of graphene nanoplatelets. Moreover, they had various numbers of layers. Such materials were characterized by different parameters, like distribution of deposited carbon nanoparticles which is influencing layers homogeneity, resulting in different optical properties.
Further, this research tries to establish a robust indicators characterizing examined samples. Authors built in Institute novel scanning optical system with fiber-based, compact spectrometer instead of other expensive techniques used for material characteristic in nanosciences i.e. high-resolution scanning electron microscopy. An optical scheme, design of system and technical parameters are described.
Performed examinations show, that number of parameters derived from our measurements, strongly correlate with physical properties of deposited inks. Authors estimated surface roughness, homogeneity and distribution of nanoparticles agglomerates within the deposited layers.
Presented results suggest, that this novel cost-effective, simple optical method of materials characterization especially in production of graphene nanoplates coatings can be promising in concern of repeatability assessment and optical properties.
Optical coherence tomography (OCT) is noncontact and nondestructive interferometric method which allows visualization of internal structure of an investigated sample. Till now it has found many applications in measurements of biological tissues, technical materials and conservation of art. Optical coherence tomography in full-field configuration is a great technique for visualization of subsurface structures of measured sample with high resolution. In this technique, en-face data acquisition is applied, which allows application of microscope objectives with high numerical aperture while the depth of field is not a problem. These objectives allow obtaining ultra high transverse resolution like in traditional microscopy. Additionally, light sources with broad spectrum, like low cost incandescent lamps (i.e. halogen lamp), allow measurements with micrometer scaleaxial resolution. In this paper the authors present application of full-field optical coherence tomography with a Linnik microscope for the thickness measurement of layers in flexible display with electrodes made of graphene and carbone nanotubes. Thicknesses of layer have a huge impact on the display parameters. There is a correlation between the thickness of the graphene layer and its electrical resistance. Graphene is a new and very promising material which is durable, flexible and has a good adhesion to diverse substrates. It gives a theoretical possibility to create flexible electronics, such as graphene bendable screens. Using OCT we can evaluate the quality of printed layers and detect subsurface defects.
An algorithm for interpolation of central fringe position in low-coherence interferometry measurements is presented. The algorithm is based on a polynomial curve fitting. Fast calculation of interpolation is possible due to the use of an NVIDIA Compute Unified Device Architecture (CUDA) technology, which allows independent analysis of different points of a high-resolution detector matrix on separate cores of a graphics processing unit (GPU). The dependency of the method’s accuracy on the spectral width of the light source is checked. The computation times on a GPU are compared with those achieved with a multicore central processing unit, showing nearly 30 times faster calculations when using CUDA technology. The algorithm accuracy is tested by measuring a flat glass surface with two different cameras—an ordinary CCD camera and a cooled EMCCD camera. Finally, the algorithm is applied to measurements of a populated optical fiber connector array prototyped using deep proton writing technology.
The most suited techniques for quantitative and accurate determination of the phase distribution in a phase photonic
microstructures are based on the interferometry, especially the digital holography (DH) in microscopic configuration.
However there is well known limitation of the coherent full- field interferometric measurements: the phase difference
between the neighboring samples cannot be larger than 2π, or objects shape have to generate light that can be collected
by used optical system. This limitation might be overcame by use of a well-known technique called low-coherence
interferometry (LCI) which allows for absolute shape measurements with a nanometer resolution and does not have 2π
limitation of coherent interferometric techniques. In this work a dual channel measurement system for characterization of
a high numerical aperture objects is presented. The system combines functionalities of the LCI system based on
Twyman-Green configuration and the DHM system based on Mach-Zehnder configuration. The DHM allows to measure
sample in transmission while LCI setup provides reflective measurement data and, therefore, provides a more complete
tool for topography characterization. In presented paper we focus on the measurement of high gradient objects were both methods fail if applied independently: the LCI gives measurement only in the object area of low NA while the DHM cannot provide absolute shape characterization due to limited NA of imaging system. The dual channel system extends
capabilities of both methods. In our paper we present experimental results for topography measurement of high NA
microlenses. The accuracy of the development method is discussed and both simulation and experimental data are
provided.
We present detection of inhomogeneities in amorphous corundum layers by optical coherence tomography system with
CMOS matrix detector. The presented setup is based on modified Twyman-Green interferometer with specially designed
scanning module. The module consists of two beam directing mirrors, a beam splitter, an objective lens and it's
illuminated by a high-power pig-tailed light emitting diode. The system is calibrated that the objective gives image of
zero optical path difference plane in infinity. Due to this and because the matrix detector is placed in the focal plane of
an imaging lens, therefore even if distance between the objective and the imaging lens changes during scanning process,
the zero optical path difference plane is always in-focus. Hence the system focuses itself on imaged layers and there is no
drop in transverse resolution coming from defocusing. In the paper we present, the idea of self-focusing tomographic
system, its theoretical analysis and design aspects. Calibration of proposed system and its application for measurement of
amorphous corundum layers are also presented. The measurements results show occurrences of the inhomogeneities in
the investigated samples.
Although low coherence interferometers are commercially available (e.g., white light interferometers), they are generally
quite bulky, expensive, and offer limited flexibility. In the paper the new portable profilometer based on low coherence
interferometry is presented. In the device the white light diode with controlled spectrum shape is used in order to
increase the zero order fringe contrast, what allows for its better and quicker localization. For image analysis the special
type of CMOS matrix (called smart pixel camera), synchronized with reference mirror transducer, is applied. Due to
hardware realization of the fringe contrast analysis, independently in each pixel, the time of measurement decreases
significantly. High speed processing together with compact design allows that profilometer to be used as the portable
device for both in and out door measurements. The capabilities of the designed profilometer are well illustrated by a few
application examples.
This paper presents novel application of Low Coherence Interferometry (LCI) in measurements of characteristic
parameters as circular pitch, foot diameter, heads diameter, in extremely small cogged wheels (cogged wheel diameter
lower than θ=3 mm and module m = 0.15) produced from metal and ceramics. The most interesting issue concerning
small diameter cogged wheels occurs during their production. The characteristic parameters of the wheel depend strongly
on the manufacturing process and while inspecting small diameter wheels the shrinkage during the cast varies with the
slight change of fabrication process.
In the paper the LCI interferometric Twyman - Green setup with pigtailed high power light emitting diode,
for cogged wheels measurement, is described. Due to its relatively big field of view the whole wheel can be examined
in one measurement, without the necessity of numerical stitching. For purposes of small cogged wheel's characteristic
parameters measurement the special binarization algorithm was developed and successfully applied.
At the end the results of measurement of heads and foot diameters of two cogged wheels obtained by proposed
LCI setup are presented and compared with the results obtained by the commercial optical profiler. The results
of examination of injection moulds used for fabrication of measured cogged wheels are also presented. Additionally,
the value of cogged wheels shrinkage is calculated as a conclusion for obtained results.
Proposed method is suitable for complex measurements of small diameter cogged wheels with low module
especially when there are no measurements standards for such objects.
One of the most important challenges in multiple-fiber connectors is to achieve accurate fiber positioning, i.e. to
ensure that the fiber end facets coincide with the front facet of the connector plate. Therefore, it is crucial
to increase the accuracy of the assembly process of fiber connectors. We present the population of a plastic
multi-fiber connector designed for optical interconnect applications with silica fiber, with a good uniformity of
fiber protrusion across the array of ±2.5-μm. To this end, an interferometric setup for in situ monitoring of
fiber tip positions during the insertion phase was developed. It ensures an accurate fiber tip position at the
fiber connector's front facet and across the fiber array in cases where post-insertion polishing is not possible.
Furhermore, our setup can provide us with insight into the influence of the curing process (e.g. shrinkage) on
the tip position during the fiber fixation step and allows us to assess the fiber facet quality. We compare the
fiber tip position measured in situ using our setup with the position measured off-line using a commercial white
light interferometer, showing a deviation smaller than 5%.
Deep Proton Writing (DPW) is a rapid prototyping technology allowing for the fabrication of micro-optical and micro-mechanical
components in PMMA, which are compatible with low-cost replication technologies. Using DPW, a high-precision
2D fiber connector featuring conically-shaped micro-holes for easy fiber insertion, was realized. When
populating these fiber connectors by fiber insertion and fixation, a critical issue is the accurate control of the fiber
protrusion. The use of laser interferometry to measure the fiber's facet position with respect to the connector surface to
within a few micrometers, is inconvenient in view of the measurement range as compared to the fiber dimensions. In this
paper, we propose an interferometric method for in-situ monitoring of the fiber insertion depth, based on the
phenomenon of low temporal coherence light interference in a Twyman - Green setup. In addition, achieving a few
micrometers measurement range with low coherence light requires vertical scanning of the sample under test. The design
of the experimental setup and the achieved measurement results are shown and discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print format on
SPIE.org.