Reflective Intensity Modulation Research Articles

Optical sensor response towards hydrogen peroxide in low fat and full cream milk

Fiber Optic Displacement Sensor (FODS) categorized as one of the optical sensor based reflective intensity modulation. An intensity based sensor have been widely used in detecting various substances due to their simplicity structures. Generally for sensing principle, a pair of fiber is used to construct FODS which one of optical fiber is the transmitting fiber and another one is receiving fiber. The objective of this current work is to introduce FODS to evaluate the optical response in terms of voltage reading at different concentration of hydrogen peroxide in two different types of milk. A real-time measurement, low cost, stability, high sensitivity and simplicity of design promote a well-developed sensor in providing useful parameters in detecting hydrogen peroxide in milk. Hydrogen peroxide is an adulterated agent added in milk that can harm the consumers. Transmitive optical sensor as a function of displacement technique was developed to study the hydrogen peroxide concentrations in the range of 0 %-10 % as consuming more than 3-10 % of hydrogen peroxide can cause mild allergies reactions, stomach upset and vomiting. The output from the receiving fiber in this designated system was measured in terms of voltage reading through multimeter. The sensor shows outstanding performances of delivering 0.0007 V/% sensitivity for low fat milk and with linearity of >98 %. Whereas, the sensitivity achieved for full cream milk was 0.0005 V/% with a good linearity >97 %. The simplicity and credibility of this system offer a good opportunity in this project and also foods industry applications.

Optical Response Analysis at Various Pb2+ Concentration by Using Fiber Optic Displacement Sensor

A simple and low-cost Fiber Optic Displacement Sensor (FODS) using reflective intensity modulation technique was developed to analyze various concentrations of Pb2+, a compound classified under heavy metal ions. Lead is harmful to the environment including to human but is used in the cosmetic field for beauty without realizing and considering the hazardousness of lead as it would cause a long-term effect. Therefore, a feasible way has been identified in this study to demonstrate the level of Pb2+ concentration in cosmetics field by employing the theory of modulation of intensity as a function of displacement sensor. The permissible limit according to Malaysian Cosmetics Guidelines and ASEAN Cosmetic Directive was 20 ppm. The concentration sensor’s system exhibits 0.0018 V/ppm sensitivity with a linearity of 96% and 94% respectively, for both peaks. Meanwhile, the sensitivity was 0.034 V/ppm for the first peak and 27.72 V/ppm for the second peak, with slope linearity of more than 96% for surface tension parameter. The credibility of these optical response curves data might be useful, especially in the cosmetic’s industrial application.

A Differential Light Intensity-Modulation Optical Fiber Bundles Designed for Milling Tool Vibration Measurement

Tool vibration occurs widely in various machining operations and is one of the main factors affecting machining quality and stability. Light intensity-modulation optical fiber displacement sensor has distinctive advantages and greatly potential in tool vibration measurement. In order to overcome the shortages of conventional reflective light intensity modulation fiber bundle in small measurement range or low sensitivity, a novel differential light-intensity optical fiber bundles were proposed for measuring the high-speed milling tool vibration displacement. The mathematical model was demonstrated based on differential light-intensity modulation principle for sensing characteristics analyzing in this paper, firstly; then, the static calibration platform and the dynamic experiment platform were established to verify the differential light intensity-modulation characteristic of the fiber bundles; in the end, the static calibration experiment results shown that the measurement range of the differential light-intensity fiber bundles is more than 2mm, which expanded the measurement range of conventional fiber bundle by two times while improving the sensitivity obviously. The dynamic experimental results confirm the operating principle of differential light-intensity optical fiber bundles well. It has greatly availability applied for on-line precision measurement of tool vibration in milling machines.

A wearable fiber-optic sensor for monitoring human elbow and wrist joint motion

This article describes a wearable sensor for monitoring the motion of human elbow and wrist joints. The sensor converts the joint motion angle into a displacement, which is monitored using a fiber-optic sensor based on reflective light intensity modulation. A mathematical model is established, and the potential influencing factors of the sensor are investigated. Two prototypes for elbow and wrist joint angle monitoring are fabricated and validated. The experimental results indicate that the proposed sensor has a measurement range of 0–60° (0–120°), with a resolution of 0.338° (3.6°) for monitoring the wrist joint palm flexion (elbow joint flexion). The proposed sensor has the potential to be used for rehabilitation purposes and monitoring of joint angles while performing reaching tasks, which are the most common upper-limb gestures.

Determination of Hydrocarbon Level in Distilled Water via Fiber Optic Displacement Sensor

Fiber optic displacement sensor offers a feasible way to detect hydrocarbon level in water. A reflective light intensity modulation technique is accomplished to detect hydrocarbon concentration in the ranges of 0%–20%. The reflective configuration technique enables the sensor to collect output voltage at a different displacement. The output voltage decreases linearly with hydrocarbon level at a corresponding optimized displacement of 1.5 mm. Linearity index close to one indicates that a high confident degree the sensor. Simple in design and low cost, makes this system as a promising sensor for determination of hydrocarbon level in water.

Fiber optic displacement sensor using fiber coupler probe and real objects

PurposeThe purpose of this paper is to demonstrate a simple design of a fiber optic displacement sensor using a multimode plastic fiber coupler based on reflective intensity modulation technique.Design/methodology/approachThe performances of this sensor are investigated by correlating the detector output with different light sources, coupling ratios and various real objects with different reflectivity properties namely aluminum, brass and copper. In contrast to the output profile produced by probes with multiple fibers placed adjacently together, this sensor uses only one fiber for sending and receiving the light and therefore only the back slope exists.FindingsAluminum exhibit the highest performance among the real objects when coupled with a red He‐Ne laser and a coupling ratio of 50:50 with a sensitivity, linear range, resolution and dynamic range of 1.7 mV/mm, 1.5 mm, 16 μm, and 5.0 mm, respectively.Originality/valueThis is the first demonstration of a fiber optic displacement sensor using fiber coupler probe with successful examination of the correlation between the detector output, variation in coupling ratios and reflectivity properties of the tested real objects.

Non-Contact Vibration Sensor Using Bifurcated Bundle Fiber for Real Time Monitoring of Diesel Engine

A non-contact vibration sensor is demonstrated using bifurcated bundle fiber based on the principle of extrinsic reflective intensity modulation for monitoring the health condition of the diesel engine. An IR-source is used along with glass fibers to avoid the effect of stray light in sensing. The encapsulation of the sensor enables easy alignment, flexible handling and usage in harsh environments. The sensor is capable of measuring the frequencies up to 650Hz with vibration amplitude resolution of 10µm, enough to monitor the vibrations generated in heavy machines like diesel engine.

FIBER OPTIC SENSOR FOR THE MEASUREMENT OF CONCENTRATION AND REFRACTIVE INDEX OF LIQUIDS BASED ON INTENSITY MODULATION

This paper reports the use of fiber optic sensor consists of two-fiber probe and reflector for the measurement of concentration and refractive index of liquids based on the reflective intensity modulation. Conventionally such a sensor is used for measuring micro-displacement of fiber tip with reference to the reflector. In one of the previously reported work we have established that if the separation between fiber tips and reflector is maintained constant the same arrangement can be directly used for sensing refractive index changes of medium. The liquid under test fills the gap between probe and reflector. Depending upon the refractive index of liquid, angle of emittance will change which will decide the received output power by receiving fiber. Apart from pure solvents which have different refractive indices, there are mixtures of various types which also alter the refractive index of a given medium. The developed sensor is used to detect the concentration of the alcohols like methanol & ethylene glycol in mixture with water.

Negative backside thermoreflectance modulation of microscale metal interconnects

The variation of backside reflectance modulation effects on metal line samples at different electrical bias and silicon backside thicknesses is investigated. Negative reflected intensity modulations are observed and are one to two orders of magnitude larger than the values from published results. It was found that the negative reflected intensity modulation with electrical bias depends on the temperature variation of the absorption coefficient while observed positive reflectance intensity modulation is due to temperature variation of the reflectance.

Influence of membrane surface shape change on the performance characteristics of a fiber optic microphone

At a reflective intensity modulated fiber optic microphone (RIM-FOM), the acoustic signal makes a membrane vibrate and modulate the reflected intensity. In the existing models of the RIM-FOM, the offset of all points of the membrane, due to the vibration, is assumed to be equal. However, this assumption does not represent the actual vibration of the membrane, which follows a continuous surface shape change caused by the acoustic signal. We establish a revised theoretical model in which the influence of the actual membrane surface shape change on the reflective intensity modulation is considered. Experiments show that there is a discrepancy between the experimental optimum operating distance and the analytical result from the existing model, while our new model gives a better agreement with the experimental results. In particular, our analysis shows that, in using the existing model, the other microphone performance characteristics are misestimated, while our revised model can provide a closer solution.

Fiber-optic dipping liquid analyzer: theoretical and experimental study of light transmission

A fiber-optic dipping liquid analyzer (FDLA) is developed for measuring liquid properties such as concentration, refractive index, surface tension, and viscosity. An important feature of the FDLA is that a liquid drop is introduced on the end face of a fiber probe, and the drop can be regarded as a planar-convex lens. The light transmitting path and receiving power are affected by the refractive index of the liquid drop. We present a theoretical and experimental analysis of the light transmission. A mathematical model of receiving power is established based on paraxial refraction imaging and fiber reflective intensity modulation methods. Sucrose-water solutions were tested with the FDLA. The experimental results agree well with the theoretical analysis.

Simple design of optical fiber displacement sensor using a multimode fiber coupler

A simple design sensor is demonstrated using a fabricated multimode plastic fiber coupler in conjunction with reflective intensity modulation technique. The performances of this sensor are investigated for different light sources. This sensor uses only one fiber for sending and receiving the light and therefore only the back slope exists. The sensor shows the highest performance with the use of yellow light source, which has the highest intensity and the smallest beam divergence. The sensitivity, linear range, resolution and dynamic range of the sensor are obtained at 0.0001 mV/μm, 1500 μm, 70 μm, and 5.0 mm, respectively. The simplicity of the design, high degree of sensitivity, dynamic range and the low cost of the fabrication make it suitable for real field applications.

Simulation of Spin-Axis Position Measurement of Superconducting Sphere Rotor by Fiber Optic Sensor

The reflective intensity modulated (RIM) fiber optic sensor is introduced for the measurement of superconducting sphere rotor spin-axis position in cryogenic instrument. A diffuse reflective rectangle pattern scribed on the circular flat surface at one end of the spin axis was used to modulate the reflective optical intensity on which the deviation value and direction of the spin-axis was determined. The relationship between the deviation of spin axis and the reflective optical intensity modulation is presented and some related factors are analyzed.

Multi-wavelength optical fiber liquid refractometry based on intensity modulation

A novel approach of development of fiber optic sensor for measurement of refractive index of liquids is presented. This sensor uses two fibers, mirror as reflector and liquid as medium. The light is carried by the illuminating fiber up to modulation zone where the properties of incident light is modulated by modulator. The modulated light is carried by receiving fiber to the detector. The measurement principle is based on reflective intensity modulation. A novel sensing probe is designed with outer ring of fibers acting as illuminating fibers and center fiber acting as read fiber. Using this probe, effect of wavelength on refractive index is studied.

Measurement of Porous Silicon Dielectric Constant by VUV Laser Harmonic Radiation

By combining the use of laser harmonic radiation as vacuum ultraviolet (VUV) light source with that of a standard NIR–VIS–UV spectrometer, the reflectance of porous silicon over a wide energy spectral range from 1 to 16 eV was measured. Reflected intensity modulation due to interference effects arising from the finite thickness of the porous layer in the visible range was also taken into account and reduced by fringe fitting. Porous silicon dielectric constant was then deduced from reflectance measurements by Kramers-Kronig analysis. Data are found to be in good agreement with those reported in literature, thus showing that laser harmonics represent a new alternative and suitable VUV source for optical characterisation of materials.

A simple optical displacement sensor utilizing dual-channel angle-limited integrated scattering measurements

Abstract A dual-channel optical displacement sensor based on the reflective intensity modulation is constructed. The sensor collects light scattered from the surface of a sample at a limited solid angle. This value of the angle-limited integrated scattering (ALIS) depends on the proximity between the sensor and the sample. The ALIS signals from both channels are used to check alignment of samples. The sensor is capable of measuring displacement with an accuracy about 0.5% over proximity ranging from 70 to 90 mm.

A simple optical displacement sensor utilizing dual-channel angle-limited integrated scattering measurements

A dual-channel optical displacement sensor based on the reflective intensity modulation is constructed. The sensor collects light scattered from the surface of a sample at a limited solid angle. This value of the angle-limited integrated scattering (ALIS) depends on the proximity between the sensor and the sample. The ALIS signals from both channels are used to check alignment of samples. The sensor is capable of measuring displacement with an accuracy about 0.5% over proximity ranging from 70 to 90 mm.

Effects of fibre geometry on the modulation function of a reflective intensity modulation sensor

Abstract Effects of fibre diameter and numerical aperture (NA) on the modulation function of a fibre optic displacement sensor are studied. The sensing is based on the principle of reflective intensity modulation. The deviation of fibre diameter and NA from their nominal values, therefore, will modify the peak position as well as the shape of the modulation function curves.

Reflective fibre optical displacement sensors for the inspection of tilted objects

Modulation functions of fibre optical displacement sensors, based on the principle of reflective intensity modulation, are calculated. Effects of surface features, such as reflectivity slope and inclination of samples, on the sensor response are studied. These studies have been carried out for two types of samples: perfectly smooth ones, that only reflect a probe beam specularly; and samples considered as Lambertian objects, that diffuse the probe beam in all directions. Applications of both theoretical models for practical measurements are discussed, particularly for a dual-channel sensor, using two receiving fibres, that is able to compensate for the effects of sample surface features on the modulation functions.

Effects of fibre geometry on the modulation function of a reflective intensity modulation sensor

Abstract Effects of fibre diameter and numerical aperture (NA) on the modulation function of a fibre optic displacement sensor are studied. The sensing is based on the principle of reflective intensity modulation. The deviation of fibre diameter and NA from their nominal values, therefore, will modify the peak position as well as the shape of the modulation function curves.