Thickening agents are commonly used to prevent aspiration, a condition that can prove fatal in the elderly. However, no established indicators exist that show the extent to which sticky food reduces the risk of aspiration. VideoEndoscopy (VE) and VideoFluorography (VF) are the classic inspection methods used for evaluating the function of swallowing, but they are both have limited utility in that they are invasive. In this study, we propose a non-invasive method that exploits esophagus ultrasound videos to estimate the internal flow characteristics of foods, and facilitates quantitative evaluation of the swallowing function. The method combines optical flow with Maximally Stable Extremal Regions (MSER) to extract the movement velocity and position of the esophagus and bolus. The results suggest that movement velocity could be used as an indicator to quantify the internal flow characteristics of foods. The displacement of the esophagus indicates the esophageal opening and could be used as an indicator to evaluate swallowing.
In this study, we develop a plastic optical fiber (POF) sensor with a double-layer structure cladding consisting of a swelling polymer lower layer and a dye-doped swelling polymer upper layer. Both cladding layers swell and decrease their refractive indices when exposed to alkane vapor. Then, the structure of the POF sensor changes from leaky to waveguide mode. Therefore, the intensity of transmitted light changes remarkably, depending on the presence of alkane. The absorption of light due to the dye in the upper cladding layer increases the change in transmitted light intensity. In this study, we fabricated a POF sensor by using the electrospray deposition method and examined its response to alkane vapor. The results indicate an improvement in the sensitivity of the POF alkane sensor due to the effect of the double-clad layer.
We have developed plastic optical fiber (POF)-type humidity sensors, which consist of swelling polymer cladding.
The proposed sensor consists of a polyvinylpyrrolidone (PVP) cladding layer that surrounds a poly(methyl methacrylate)
core. The operation of the sensor is based on the POF structure changing from a leaky-POF to a guided-POFbecause of
the changes in the refractive index caused by swelling of the cladding layer in high humidity. Therefore, the clad
transparency condition before swelling affects the sensitivity of the sensor.
In this study, to investigate the effect of the clad transparency condition, we fabricated three types of POF humidity
sensors, which have different transparent cladding. The results indicate that the sensitivity of the sensor was improved by
using the dye-doped swelling polymer clad.
We have developed and tested plastic optical fiber (POF)-type humidity sensors, which consist of a dye-doped
swelling polymer cladding. POF-type humidity sensors consist of a hydroxyethyl cellulose or polyvinylpyrrolidone
(PVP) cladding layer that surrounds a poly(methyl methacrylate) core. The operation of these sensors is based on the
change in refractive index caused by swelling of the cladding layer. To improve the sensitivity of the humidity sensor,
we have investigated the effect of doping the cladding polymer with phthalocyanine dye. The results indicate that the
POF-type humidity sensor using PVP is three times more sensitive for relative humidities above 80% when the dyedoped
swelling-polymer cladding is used.
Combustible gases, such as propane and methane-based city gas, are widely used in many homes and factories.
However, accidents caused by gas leakage have become a menace to everyday life. Therefore, we have developed a
simple and safe optical sensor for detecting leaking gas, which consists of plastic optical fiber (POF) coated with
swelling polymer as a sensitive cladding layer. In experiments, a gas concentration below 3% was detected for both
propane and methane gas. However, it was also confirmed that this system is influenced by humidity. Therefore, further
improvement of the POF gas-sensing system with a POF humidity calibrator is proposed and discussed in this paper.
A novel plastic-optical-fiber (POF) microphone for discerning devoiced breath, which is based on the detection of
moisture pattern depending on the shape of mouth, have been studied. In the experiment coupled with this microphone
and Dynamic Programming (DP) matching method, recognition rate over 90% was obtained against five devoiced
vowels in Japanese. Therefore, using this system, verbally handicapped people will create sounds with a small effort.
Combustible gases such as propane gas and methane gas are widely used in many homes and factories. However,
accidents caused by gas leakage become a menace to everyday life. Therefore, development of quick and highly
sensitive gas leakage sensor is required strongly. From these backgrounds, we have studied about plastic optical fiber
(POF) gas leakage sensor because the POF have many advantages such as low-cost, light weight, immunity to electromagnetic noise. In this paper, the POF sensing system for multi-point gas leakages and its long term stability have been studied. In the experiment, gas concentration below 1% was detected for both propane gas and methane gas. This operation does not depend on a light wavelength. So, using several LED light sources with different wavelength, the POF sensing
system for multi-point gas leakages was constructed. In the experiment using blue-, green- and red-LED, sensing of
three-point gas leakages could successfully be obtained. Further more, considering its system for real application, long
term stability of the sensor head was also checked and it was confirmed that the sensitivity does not change over 15 days.
Recently, alcohols such as methanol and ethanol have a wide attention as important fuel in next generation. However, As
is known, many alcohols have a toxic and explosive nature. To prevent accidents caused by alcohol, development of a
safety and highly sensitive sensor is required strongly. In addition, it is desired to be simple and low-cost. So, in this
paper, polymer waveguide-type optical alcohol sensors such as fiber-type and channel waveguide-type have been
studied. In these sensor head, refractive index n2 of cladding layer was set at slightly larger value than that of core (n1). Therefore, in the state without alcohol, the sensor head operate as a leaky waveguide. On the other hand in the state with
alcohol, cladding polymer causes swelling and its refractive index becomes lower than n1 in core. Based on this principle,
large change in output light intensity occurs and detection of alcohol concentration becomes possible even for vapor
phase alcohol. In the experiment using a fiber-type sensor with a core size of 0.25 mm, detection of 1% methanol
vapor could easily be obtained. Furthermore, using a channel waveguide-type sensor head with a core size of about
50μm×40μm, large increase in sensitivity was observed.
Conversation is the most practical and common form in communication. However, people with a verbal handicap feel a
difficulty to produce words due to variations in vocal chords. This research leads to develop a new devoiced microphone
system based on distinguishes between the moisture patterns for each devoiced breaths, using a plastic optical fiber
(POF) moisture sensor. In the experiment, five POF-type moisture sensors with fast response were fabricated by coating
swell polymer with a slightly larger refractive index than that of fiber core and were set in front of mouth. When these
sensors are exposed into humid air produced by devoiced breath, refractive index in cladding layer decreases by swelling
and then the POF sensor heads change to guided type.
Based on the above operation principle, the output light intensities from the five sensors set in front of mouth change
each other. Using above mentioned output light intensity patterns, discernment of devoiced vowels in Japanese (a,i,u,e,o)
was tried by means of DynamicProgramming-Matching (DP-matching) method. As the result, distinction rate over 90%
was obtained to Japanese devoiced vowels. Therefore, using this system and a voice synthesizer, development of new
microphone for the person with a functional disorder in the vocal chords seems to be possible.
This paper deals with experimental results on detection of toluene dispersed in water by means of a new and simple
plastic optical fiber (POF) sensor. Its sensing part consists of swelling polymer cladding layer such as high density
polyethylene (HDPE) with slightly larger refractive index n2 than that of poly(methyl methacrylate) (PMMA) core with
n1. When is exposed to toluene dispersed in water, HDPE cladding layer causes swelling and the value of n2 decreases quickly. Then the POF structure in the sensing part changes from leaky-type to guided-one and the output light intensity
increases dramatically. By measuring this light intensity change, it becomes possible to detect toluene concentration. In
addition, as compared with the popular evanescent-wave detection principle type, this sensor operation does not depend
on the wavelength of light source. Therefore, we can use an inexpensive LED or LD in visible region. In experiment,
detection of less than 1 wt% toluene in water was easily obtained with fast response about only 1 s. Furthermore, this
sensor can detect pure toluene even for a small amount below 1 ml.
In order to develop a simple system for sensing taste substances, an optical method using polymer/lipid films doped with a voltage-sensitive dye and plastic optical fibers (POFs) has been studied experimentally. The several kinds of polymer/lipid blended membranes doped with rhodamine-B dye with a long hydrocarbon chain were used after transferring on to the glass substrate glued on the end surface of POF. Its fluorescence intensity around 600 nm showed different patterns for the taste substance solutions such as bitter, salty and "umami". These results and a principal component analysis gave the possibility of an optical fiber taste substance sensor.
Novel plastic fiber optic sensors, which is based on the refractive index change in the novolac polymer cladding layer on the norbornene polymer core, have been developed to detect vapor phase methanol and ethanol.
Simple optic sensors for detecting fuel gases, which consist of plastic optical fibers (POFs), have been studied. The sensing mechanism is based on the swelling phenomena in the rubber-type polymers. The POF-type sensor head was fabricated by coating the swelling polymer on the plastic fiber core and was connected to the normal POFs. When this system was exposed to fuel gases such as gasoline and propane, the light intensity passing through the sensor head changed remarkably depending on the pressure of fuel gases. The sensor response was also found to be fast, stable and reproducible.
Optical fiber sensors for detecting leakage of gasoline have been studied. When exposed to gasoline vapor, certain rubber-type polymers such as polyisoprene cause swelling and their refractive indexes decrease depending on the vapor pressure of gasoline. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. This sensor head changes its fiber structure from leaky to guided, and then, change in the transmitted light intensity by leakage of gasoline can be observed. The improvement of sensitivity in a wide range of gasoline vapor pressure was attempted.
A new technique for the optical sensing of dissolved oxygen (DO) is proposed here. It is based on the enhancement in fluorescence yield of TPP dye at (lambda) equals 656 nm, when excited by He-Cd blue laser of (lambda) equals 441 nm in the presence of dissolved oxygen. The sensor head was fabricated by cladding the ARTON fiber core with the poly-4-methyl-1- pentene polymer matrix suitably doped with Tetraphenylporphine dye. This sensor head, when placed in a test chamber and end-pumped by He-Cd laser, generates the intense fluorescence at 656 nm. Its intensity was noticed to increase with increasing the amount of DO. A theoretical model of the sensor response was designed and is also discussed.
New optical fiber sensors for detecting leakage of vapor phase alkanes and gasoline have been studied. When exposed to these vapors, certain rubber-type polymers such as polyisoprene and polyisobutylene cause swelling and their refractive indexes decease depending on the vapor pressure of these substances. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. When was exposed to vapor phase substances, the sensor head changed its fiber structure from leaky to guided one, and then a large change in the transmitted light intensity was observed in a wide range of the vapor pressure. The response was also found to be reversible and reproducible.
In order to develop a simple sensing system for taste substances, an optical method using an LB film doped with a voltage-sensitive dye was studied experimentally. The blended LB film of arachidic acid and rhodamine B (RBC18) dye with a long hydrocarbon chain, which as a mixture ratio of 75:1, was transferred on to the ITO substrate and was used to measure both the fluorescence intensity around (lambda) f equals 600 nm and the membrane potential of the RBC18-LB film in various taste substance solutions. As a result, for example, it was found that the fluorescence intensity increased as the NaCl concentration increased but on the other hand the membrane potential decreased. The different patterns were obtained for the different taste substance solutions. These experimental results show the possibility of an optical fiber taste substance sensor using blended LB film of arachidic acid and RBC18.
An attempt has been made to improve the sensitivity and stability of optical fiber sensor used for the continuous monitoring of gaseous oxygen. It utilizes the quenching phenomena of cladding fluorescence. Two polymers viz. poly cyclohexyl methylacrylate (PCMA) and poly (4-methyl-1-pentene) (PMP) were selected which were doped with 9,10-diphenyl anthracene (DPA) and sensor head was prepared by dipcoating the polymer on a 4.2 cms length of an especially designed ARTONTM plastic fiber with 1 mm core diameter. For dipcoating, polymer matrix containing 3% wt of fluorescent dye was used. The sensor head thus prepared was tested for various oxygen concentrations varied by mixing nitrogen. D2lamp was used for UV side pumping and thus the fluorescence generated in the cladding was coupled to another plastic optical fiber at the output end. The change in fluorescence due to oxygen content was recorded using a photo-multiplier at the (lambda) equals 430 nm. The results obtained have been tabulated in the form of comparative studies. The response was found to be fast, reversible and reproducible with recovery time of the order of few seconds in both the cases. The sensors were found to detect a wide range of oxygen concentration ranging from 0.5% to 100% of O2. In the case of PCMA, better stability in long-term was observed. The effect of cladding thickness on the sensor performance was also explored.
Improvement of the optical fiber oxygen sensor based on the fluorescence quenching by oxygen gas was studied. Using the newly synthesized poly-l-methylmethacrylate (PMtMA) and its blend of the PMtMA/PMP as the cladding layer, in which sensing dye was doped, the plastic optical fiber (POF) O2 sensor with high sensitivity and a fast response time could be realized. In addition this sensor didn't receive any affect by humidity.
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.