In a 3D profilometer by the fringe projection, the shadow will be produced inevitably, thus the fringes cannot be detected
in the region of the shadow. In addition, a smooth surface or a metal surface produces the specular reflection, and then,
no projection fringe can be recorded in the region of oversaturation on CCD. This paper reveals a proposed system for
improved these defects and shows some preliminary improved 3D profiles by the proposed dual fringe projection.
To obtain the profile of sample hided in the shadow and the oversaturation, this study used the dual-projection system by
two projectors. This system adopted two different directions of fringe projection and illuminates them alternately,
therefore, the shadow and the oversaturation produced in their corresponding locations. Two raw 3D profiles obtained
from taking the dual-projection by the four-step phase-shift. A set of algorithms used to identify the pixels of the shadow
and the oversaturation, and create an error-map. According to the error-map to compensate, two 3D profiles merged into
an error-reduced 3D profile. We used the solder paste as a testing sample. After comparatively analyzing the 3D images
obtained by our measurement system and by a contact stylus profilometer, the result shows that our measurement system
can effectively reduce the error caused by shadows and oversaturation.
Fringe projection system by using a projector is a non-contact, full field and quickly measuring system. The proposed
dual-projection by dual-projectors can effectively reduce the shadow and the oversaturation errors and enhance the scope
of application of the 3D contour detection, especially in the detection of precision structure parts with specular reflection.
An extremely sensitive fluorescent sensor based on a phenylboronic acid monolayer was developed for detecting
saccharide molecules. The fluorescent sensor was prepared by assembling a monolayer of 4-mercaptophenylboronic
acid (4-MPBA) onto a gold-coated compact disk. The change in the fluorescence of the 4-MPBA monolayer was
extremely obvious in basic methanolic buffer containing monosaccharides down to the picomolar level. The
fluorescence spectra demonstrated that the 4-MPBA monolayer was sensitive to monosaccharides and disaccharides, and
the affinity of the monolayer toward saccharides was in the order of glucose < fructose < mannose < galactose < maltose > lactose > sucrose. Additionally, the fluorescence intensity of 4-MPBA monolayer was restorable after cleaning with weak acid, indicating that the reported fluorescent sensor with the detection limit of glucose down to the picomolar level is reusable for sensing saccharides.
This study utilizes a surface-enhanced Raman spectroscopy (SERS) based on the attenuated-total-reflection (ATR)
method to investigate that the structural information of the biomolecular monolayer on sensing surface can be
dynamically observed with a higher signal-to-noise ratio signal. The secondary structures of long oligonucleotides and
their influence on the DNA hybridization on the sensing surface are investigated. The SERS spectrum provides the
structural information of the oligonucleotides with the help of a silver colloidal nanoparticle monolayer by control of
the size and distribution of the nanoparticles adapted as a Raman active substrate. It is found that the ring-breathing
modes of adenine, thymine, guanine, and cytosine in Raman fingerprint associated with three 60mer oligonucleotides
with prominent secondary structures are lower than those observed for the two oligonucleotides with no obvious
secondary structures. It is also determined that increasing the DNA hybridization temperature from 35°C to 45°C
reduces secondary structure effects. The ATR-SERS biosensing technique will be used to provide valuable structural
information regarding the short-term reversible interactions and long-term polymerization events in the A&bgr; aggregates
on the sensing surface.
This paper proposes a technique of realizing sub-wavelength focusing spot on surface by modifying the spatial phase in far-field. This focusing spot will use to detect the spectrum of the monolayer biomolecules on the planar surface. Taking the advantage of modifying spatial phase and polarization of incident laser beam, the field distribution in near-field (near focal point) can be changed and can achieve to the smallest spot size of sub-wavelength under the reasonable adjustment of the phase and polarization of incident beam in far-field. Although nano-scale light sources can produce by labelling dye on nanoparticles, quantum dots etc., but technically it is not easy to finely manipulate nanoparticles. On the contrary, using the planar thin film of matured, reliable fabrication processes, not only the near-field twisted electromagnetic of nanostructure can be eliminated, but also fixing the biomolecules on planar surface makes its arrangement to have the consistent direction, thereupon the overall behavior of molecular vibration is simple, pure, and advantageous to detect the vibrational spectra of the monolayer molecules on surface.
This study develops a coupled waveguide-surface plasmon resonance (CWSPR) biosensor with a sub-wavelength grating structure for the real-time analysis of biomolecular interactions. In the proposed optical metrology system, normally incident white light is coupled into the waveguide layer through the sub-wavelength grating structure thereby enhancing the wave vector which excites the surface plasmons on the metal sensing surface. The proposed CWSPR biosensor not only retains the same sensing sensitivity as that of a conventional surface plasmon resonance device, but also yields a sharper dip in the reflectivity spectrum and therefore provides an improved measurement precision. Moreover, the metrology setup overcomes the limitations of the conventional Kretschmann attenuated total reflection approach and is less sensitive to slight variations in the angle of the incident light. The experimental results confirm that the current CWSPR biosensor provides a straightforward yet powerful technique for real-time biomolecular interaction analysis.
A coupled waveguide-surface plasmon resonance (CWSPR) biosensor constructed with sub-wavelength grating structure is developed and used to analyze biomolecular interaction in real time. The normal incident white light is coupled into the waveguide layer through the sub-wavelength grating, and hence it has an enhanced wave vector to excite the localized surface plasmons on the metal grating surface. The CWSPR biosensor with the surface plasmon resonance (SPR) mode and the waveguide mode not only retains the same sensing sensitivity as that of a conventional SPR device, but also yields sharper dips in the reflectivity spectrum and therefore provides an improved measurement precision. Moreover, without the limitation of a conventional attenuated total reflection coupler and with the help of
normal incidence, the system is more flexible and feasible for protein microarray and imaging applications.
In this paper, the reflection resonance spectrum of a sub-wavelength diffraction grating-coupled waveguide is used to analyze biomolecular interactions in real time. When the diffraction grating waveguide structure is destroyed by external factors such as slight refractive index changes of the buffer or molecule adsorption on the grating surface, the optical path of the light coupled through the grating into the waveguide is changed and a resonance wavelength shift is induced as a result. By detecting this resonance wavelength shift, the optical waveguide biosensor provides the ability to identify the kinetics of the biomolecular interaction on an on-line basis without the need for the extrinsic labeling of the biomolecules. A theoretical analysis of the sub-wavelength optical waveguide biosensor is performed. A biosensor with a narrow reflection resonance spectrum, and hence an enhanced detection resolution, is then designed and fabricated. Currently, the detection limit of the optical waveguide sensor is found to be approximately 10-5 refractive index units. The developed biosensor is successfully applied to study the kinetics of an antibody interaction with protein G adsorbed on the sensing surface.
The ability to recognize the conformational changes and structural variations of a protein when immobilized in a solid surface is of great importance in a variety of applications. Surface plasmon resonance (SPR) sensing is an appropriate technique for investigating interfacial phenomena, and enables the conformational changes of proteins to be monitored through the variation in the SPR angle shift. Meanwhile, the surface-enhanced Raman scattering (SERS) system can also assist in clarifying the changes in protein structure. The present study utilizes a 1 mM CrO3 phosphate buffer solution (PBS) to induce conformational changes of human serum albumin (HSA). Monitoring the corresponding SPR angle shifts and the SPR reflectivity spectrum enables the relationships between the conformational changes of the surface-immobilized protein and the thickness and dielectric constants of the protein layer to be estimated. The experimental SPR results indicate that the Cr6+ ions cause significant conformational change of the protein. It is established that the ions are not merely absorbed into the protein as a result of electrostatic forces, but that complex protein refolding events also take place. Furthermore, the data acquired from the SERS system yield valuable information regarding the changes which take place in the protein structure.
This paper presents an optical device capable of the simultaneous measurement of the surface plasmon resonance (SPR) spectrum, which provides information regarding the change in the dielectric constant of the binding analytes, and the surface-enhanced Raman scattering (SERS) spectrum, which yields analytical data regarding the structural changes of the analytes. SPR sensing is an established technology in the field of direct real-time analysis of biomolecular interactions such as antibodies/antigens, DNA hybridization, receptors/ligands, etc. Meanwhile, SERS sensing techniques represent a powerful means of acquiring and diagnosing structural information relating to analyte binding. This study adopts the attenuated total reflection (ATR) method and an Au nanocluster-embedded dielectric sensing film in developing a biosensor which integrates the SPR and SERS sensing techniques. The results confirm the effectiveness of the proposed multi-functional device in developing a detailed understanding of the mechanisms of biomolecular recognition.
The angular distribution of the photon pairs of a Zeeman laser scanning confocal microscope (ZLSCM) is measured in turbid media. By scanning the pinhole at different locations on a focal plane, the angular distribution of the snake photon pairs that is contributed by the object plane in the scattering medium is measured. The narrower width of the angular distribution of the snake photon pairs implies the better performance of the depth resolution of ZLSCM in turbid media. In this study, the dependence between depth resolutions of ZLSCM with respect to different vol. % concentrations of the scattering medium is observed. In addition, the correlation between angular distribution and depth resolution in different concentrations is also demonstrated and discussed.
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