Rubber, particularly carbon black-filled rubber used in tires, plays a critical role in a world of mobility. Tires are exposed to various influences, including temperature fluctuations, dynamic mechanical loads, and exposure to solar-origin UV radiation, which can affect their durability. To investigate the effects of UV radiation on tire aging, this study aimed to identify spectral absorption ranges in specifically aged tire samples providing information about their aging condition. The study utilized samples of different rubber compounds and exposed them to UV radiation for varying durations from 48 h up to 1000 h. ATR (attenuated total reflection) spectroscopy was used to analyze the aged samples and evaluate changes in their chemical structure. The results showed consistent aging behavior across all samples, with a decrease in the intensity of the double peak at approximately 2900 cm-1, corresponding to the C-H bond. Another aging-relevant range from 1500 cm-1 to 1450 cm-1, characteristic of C-H groups as well, exhibited a declining absorption trend with UV aging. The impacts on the absorption spectrum resulting from the different rubber mixtures' compositions led to a reduction in the intensity of characteristic peaks. For evaluating the aging state of used tires, the CH related peaks can be utilized.
In Germany there are millions of people in retirement age which are living alone. Approx. 30% of them come into emergency situation because of a fall once a year. If the fall leads to bone fracture, the person isn’t able to stand off by itself and if there is nobody recognizing the situation, the fall can lead to death. Therefore a detector is developed, which can detect a person lying on the ground and send a signal to a family member in case of emergency. The system is built optically, which makes it insensitive to outer factors like humidity or thermal drifts. Vice versa it won’t apply any electromagnetic radiation onto medical devices situated in the room. The whole system consists of a laser, a material which shows birefringence, two polarizers and a detector. The material covers a big area in the apartment, which needs to be watched by a senor. If the senor is under strain, the polarization of the light will change its direction while passing the material and the system will measure an increase of light intensity after the 2nd polarizer. To discriminate an emergency from normal everyday situation, an algorithm is implemented, which asks for three steps to be positive ere the system triggers a signal. If the system has access to an already existing smart home-system, a signal can be activated to inform the person’s next relatives or even an emergency service. The systems works best, if the apartment is built newly
The perception of a display’s content can be negatively influenced due to surface properties and variable ambient light conditions. Conventional measurement methods, such as DIN EN ISO 2813, provide limited information on the relationship between gloss values and gloss perception. Generally, there are no further statements about scattering or disturbing reflections and their correlation to perception. This work presents the development of a display measuring device which can measure several optical parameters simultaneously as well as in a spatially resolved manner. The measuring principle was oriented on the DIN EN ISO 2813 standard with measuring reflection geometries of 20° and 60° relative to the normal. The determined objective properties were correlated with the subjective perception of the end user using a laboratory study. In this study, subjects assessed the reflections from the displays in terms of gloss and scatter on a scale of 1 (minimal) to 5(maximal). The influence of different settings of viewing positions, ambient brightness and display brightness was investigated. For the comparison between objective and subjective data, the subjective scale was related to the objective measured value for gloss and dispersion. A correlation between objectively measured data and the subjective perception of optical properties of displays was observed. This correlation occurs mainly in extremely glossy and matt displays.
Modern surfaces are often used as technical design elements. The high-quality appearance of these surfaces is crucial. Depending on the application, different requirements such as colour, reflectivity and resistance have to be met by the surfaces. Surface defects in highly transparent materials such as cover glasses, windows and displays affect long-term stability and distract the user. This paper shows the development of a camera-based measurement system for the investigation of structural defects in highly transparent materials. The requirements for a system like the one presented here are comparable to solution qualities of the human eye. The system is particularly suitable for the detection of surface imperfections with depths in the single µm range and widths below 50 μm as well as lengths in the mm range. At the same time, however, it can also be used to evaluate the gloss, scatter and contrast of the surface for rating the appearance quality of those. For this purpose, the setup was designed in which a sample in darkfield configuration is illuminated with an angled, multispectral LED array that can be individually switched sectorally and also uses the usual reflection approaches.
Laser ablation of thin membranes for industrial applications such as Micro-Electrical-Meachanical Systems has high demands regarding the process stability, alignment, surface shape and surface roughness. In the production of laser structured membranes with thicknesses in the single-digit μm-range ablation monitoring is therefore desired at every stage of the manufacturing process. This works presents a shape-from-shading approach where the surface of microstructured circular steel membranes is illuminated by two different light sources in order to generate sufficient surface reflection data from which a three-dimensional depth profile is reconstructed. By rotational scanning of the sample under examination, data is gathered from different angles and wavelengths at the same time. The advantage of this novel approach is the gain in acquisition speed as the spectrally encoded angle information can be acquired within one camera frame. Data processing is performed on the R, G, and B channels of the recorded image in parallel. In experiments, steel membranes with thickness of 2:1 μm and ablated structures with approximately 1:5 μm depth were examined during the structuring process. In order to compare the results of the in-line metrology approach, the surface topography of the laser-ablated samples were characterized on a confocal laser microscope. A discussion of the implications of the results regarding the usability of the metrology approach in industrial use cases concludes the work.
Microphone membranes tthat have theeir frequency response uniiquely tailoreed to specificc applications are typicallyy produced in an unautomated and expensive manuufacturing prrocess. A combination off holographic stroboscopyy, numerical simulation and laser structuriing is appliedd to shift the resonant frequencies of thee membrane too their desired values given an unknown tension across the microphone membrane due to manuufacturing tollerances. Thee uncharacterized microphone membrane is driven thrrough physical contact withh a piezo. Thhe piezo is swept through a range of frequencies and the full surface profile oscillations are recorded using stroboscopic digitaal holographyy techniques. These resonant displacemennt maps will bee used, in combination with finite differeence eigenvaluue simulationss and perturbattion theory, to determine the preloadedd tension profile across the membrane. Given a desired responsee function of the membrane,, a new membrane mass-density profile can be tailoreed to match the current meembrane to thee requirements of the micropphone. A 20 WW ns Q-switchhed laser steerred by galvanometer mirrorrs will be usedd to restructuree the mass density of the membrane to meeet the design requirements of the micropphone.
The aim of the presented work is to investigate the angle-resolved scattering characteristics of biological nano- and micro-scaled cell structures. The scattering results of cellular structures were compared to measurements of ideal spherical nano- and micro-particles. A monolayer of mouse fibroblasts L929 cells was cultivated in a Dulbecco's Modified Eagle Medium (DMEM) in a standard 24 well cell culture plate. The system allows an in situ measurement directly in the standard cell culture plate and a contaminant-free investigation of the viability of the cell cultures. Of particular interest was whether changes in the tumor characteristics occur in apoptosis or other cell-harming effects. Because of the size ratios between wavelength and the scattering particles, all observations were investigated using Mie scattering theory. A setup for reliable measurements was developed and the scattered angle dependent intensity obtained was compared with simulated scattering characteristics. A homemade supercontinuum (SC) light source was filtered by an optical bandpass filter with a central wavelength of 500 nm. The scattered portion of the pulsed SC light behind the sample was recorded in a time-resolved manner at defined angles. A specimen holder adapted to standard cell culture plates allows detection of scattered radiation at angles between ±80° without angle-dependent Fresnel reflection losses and a Snell’s law bending of the propagation direction. Finally, the system was tested to detect structural changes of mouse fibroblast L929 cells before and after poisoning the cells with the cell detergent Triton X100 and the data clearly shows changes in the scattering characteristics when the cells were destroyed.
Sensing in harsh environments, such as in high magnetic fields like those found within MRI machines or in high-voltage conditions like those found within power transformers lends itself well for the use of fiber optic sensors. Where conventional electronic sensors fail for obvious reasons, specially designed fiber optic sensors can fill in these gaps. The aim of this research was to investigate the feasibility and technical parameters necessary to design a flexure sensor based on evanescent coupling between the modes of a two- (or more) core fiber. The design parameters are discussed and the sensitivity of the sensor is shown to be tunable by modifying variables which the coupling constant is sensitive to. The physical model used to simulate this system is derived from an effective index change due to a combination of strain and an effective path difference which is induced by bending the fiber. The result of this model is a coupled-mode equation that can be systematically solved using an eigenvector approach to mode coupling. With proper fiber drawing techniques, this model predicts measurement sensitivities of curvature down to km-1. Furthermore, this technique can be extended based on simulated long-wavelength measurements to make predictions about where along the length of the fiber the flexing took place. This system has the potential to be used as a competing system for Rayleigh backscattering based flexure measurements.
Nutrient and oxygen transport, as well as the removal of metabolic waste are essential processes to support and maintain viable tissue. Current bioreactor technology used to grow tissue cultures in vitro has a fundamental limit to the thickness of tissues. Based on the low diffusion limit of oxygen a maximum tissue thickness of 200 μm is possible. The efficiency of those systems is currently under investigation. During the cultivation process of the artificial tissue in bioreactors, which lasts 28 days or longer, there are no possibilities to investigate the viability of cells. This work is designed to determine the influence of a non-disruptive cell viability measuring system on cellular activity. The measuring system uses a natural cellular marker produced during normal metabolic activity.
Nicotinamide adenine dinucleotide (NADH) is a coenzyme naturally consumed and produced during cellular metabolic processes and has thoroughly been studied to determine the metabolic state of a cell. Measuring the fluorescence of NADH within the cell represents a non-disruptive marker for cell viability. Since the measurement process is optical in nature, NADH fluorescence also provides a pathway for sampling at different measurement depths within a given tissue sample. The measurement system we are using utilizes a special UV light source, to excite the NADH fluorescence state. However, the high energy potentially alters or harms the cells. To investigate the influence of the excitation signal, the cells were irradiated with a laser operating at a wavelength of 355 nm and examined for cytotoxic effects. The aim of this study was to develop a non-cytotoxic system that is applicable for large-scale operations during drug-tissue interaction testing.
Online process control systems often only detecting temperatures at a local area of the machining point and determining an integrated value. In order to determine the proper welding quality and the absence of defects, such as temperature induced stress cracks, it is necessary to do time and space resolved measurements before, during and after the production process. The system under development consists of a beam splitting unit which divides the electromagnetic radiation of the heated component on two different sensor types. For high temperatures, a sensor is used which is sensitive in the visible spectrum and has a dynamic range of 120dB.1 Thus, very high intensity differences can be displayed and a direct analysis of the temperature profile of the weld spots is possible.2 A second sensor is operating in the wavelength range from 1 micron to 5 microns and allows the determination of temperatures from approximately 200°C.3
At the beginning of a welding process, the heat-up phase of the metal is critical to the resultant weld quality. If a defined temperature range exceeded too fast, the risk of cracking is significantly increased.4 During the welding process the thermal supervision of the central processing location is decisive for a high secure weld. In the border areas as well as in connection of the welding process especially cooling processes are crucial for the homogeneity of the results. In order to obtain sufficiently accurate resolution of the dynamic heating- and cooling-processes, the system can carry out up to 500 frames per second.
Few-mode fiber (FMF) has become very popular for use in multiplexing telecommunications data over fiber optics. The
simplicity of producing FMF and the relative robustness of the optical modes, coupled with the simplicity of reading out
the information make this fiber a natural choice for communications. However, little work has been done to take
advantage of this type of fiber for sensors. Here, we demonstrate the feasibility of using FMF properties as a mechanism
for detecting flexure by exploiting mode coupling between modes when the cylindrical symmetry of the fiber is
perturbed. The theoretical calculations shown here are used to understand the coupling between the lowest order linearly
polarized mode (LP01) and the next higher mode (LP11x or LP11y) under the action of bending. Twisting is also
evaluated as a means to detect flexure and was determined to be the most reliable and effective method when observing
the LP21 mode. Experimental results of twisted fiber and observations of the LP21 mode are presented here. These types
of fiber flexure sensors are practical in high voltage, high magnetic field, or high temperature medical or industrial
environments where typical electronic flexure sensors would normally fail. Other types of flexure measurement systems
that utilize fiber, such as Rayleigh back-scattering [1], are complicated and expensive and often provide a higher-than
necessary sensitivity for the task at hand.
The importance of fluorescence lifetime measurement as an optical analysis tool is growing. Many applications already exist in order to determine the fluorescence lifetime, but the majority of these require the addition of fluorescence-active substances to enable measurements. Every usage of such foreign materials has an associated risk. This paper investigates the use of auto-fluorescing substances in Saccharomyces cerevisiae (Baker’s yeast) as a risk free alternative to fluorescence-active substance enabled measurements. The experimental setup uses a nitrogen laser with a pulse length of 350 ps and a wavelength of 337 nm. The excited sample emits light due to fluorescence of NADH/NADPH and collagen. A fast photodiode collects the light at the output of an appropriate high-pass edge-filter at 400 nm. Fluorescence lifetimes can be determined from the decay of the measurement signals, which in turn characterizes the individual materials and their surrounding environment. Information about the quantity of the fluorescence active substances can also be measured based on the received signal intensity. The correlation between the fluorescence lifetime and the metabolic state of Saccharomyces cerevisiae was investigated and is presented here.
With 332,000 operations carried out every year, the implantation of an artificial hip joint is one of the most common
surgical operations performed in the US. According to prognosis which takes the demographical change into account, the
number of these operations will increase in the coming years.
One of the essential requirements is the perfect reconstruction of the biomechanical functions, especially the knowledge
about the center of the hip rotation and the length of the leg. Based on this information it is possible to ensure the right
position of the newly set leg during surgery.
The aim of this work is to present and evaluate an optical measurement method in order to gather information about the
center of the hip joint and the leg length. An appropriate laboratory setup has been designed and implemented in order to
evaluate two different approaches: a structured light-method consisting of a DLP-Beamer or a laser source which
projects defined patterns onto the patient and a marker-based system. Together with this both methods are combined
with custom software to determine the hip joint center and the leg length with an accuracy of around +/- 0.2 inches. The
clinical use of the tested approaches would give the surgeon the opportunity to reset the implant-parameters in the course
of the surgery. In this way subsequent illnesses such as scoliotic pelvis can be prevented.
The production of complex titanium components for various industries using laser welding processes has received growing attention in recent years. It is important to know whether the result of the cohesive joint meets the quality requirements of standardization and ultimately the customer requirements. Erroneous weld seams can have fatal consequences especially in the field of car manufacturing and medicine technology. To meet these requirements, a real-time process control system has been developed which determines the welding quality through a locally resolved temperature profile. By analyzing the resulting weld plasma received data is used to verify the stability of the laser welding process. The determination of the temperature profile is done by the detection of the emitted electromagnetic radiation from the material in a range of 500 nm to 1100 nm. As detectors, special high dynamic range CMOS cameras are used. As the emissivity of titanium depends on the wavelength, the surface and the angle of radiation, measuring the temperature is a problem. To solve these a special pyrometer setting with two cameras is used. That enables the compensation of these effects by calculating the difference between the respective pixels on simultaneously recorded images. Two spectral regions with the same emissivity are detected. Therefore the degree of emission and surface effects are compensated and canceled out of the calculation. Using the spatially resolved temperature distribution the weld geometry can be determined and the laser process can be controlled. The active readjustment of parameters such as laser power, feed rate and inert gas injection increases the quality of the welding process and decreases the number of defective goods.
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 or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.