Ju-Hyeon Choi

Development of an optical fiber sensor for angular displacement measurements.

For diagnostic and therapeutic purposes, the joint angle measurement of a patient after an accident or a surgical operation is significant for monitoring and evaluating the recovering process. This paper proposed an optical fiber sensor for the measurement of angular displacement. The effect of beveled fiber angle on the detected light signal was investigated to find an appropriate mathematical model. Beveled fiber tips redirected the light over a range of angles away from the fiber axis. Inverse polynomial models were applied to directly obtain and display the joint angle change in real time with the Lab-VIEW program. The actual joint angle correlated well with the calculated LabVIEW output angle over the test range. The proposed optical sensor is simple, cost effective, small in size, and can evaluate the joint angle in real time. This method is expected to be useful in the field of rehabilitation and sport science.

Study of an Optical Goniometer Using a Multi-Photodiode Sensor

The monitoring and measurement of the motion of a human joint is very important in screening for degenerative brain diseases and tracking the rehabilitation process. Since there are various medical fields to benefit from angular motion measurement, the necessity for monitoring of human joint movement is increasing. In this study, the optical sensor is composed of a light emission unit with a red LED and an optical fiber, and a reception unit with an arrangement of three photodiodes. The angular detection range was widened with the use of multiple photodiodes and the developed algorithm. The result will be useful for designing an effective angular sensor with low cost and small size.

Development of multi-colored LED system for therapeutic application.

BACKGROUND The evaluation and control of lighting is crucial in physiological, biomedical, and industrial fields. Many kinds of lighting techniques based on LED have been developed due to its advantages. OBJECTIVE The aim of this study is to develop the multi-colored LED system for healing purposes. METHODS Light source with three-color chip LEDs was investigated to detect the dominant wavelength. RESULTS The results show that the additive principle by three-color LEDs can be successfully applied to lighting system by generating a variety of colors. CONCLUSIONS The results are expected to be useful in the field of light therapy and medicine. Applications of the developed light system are lighting therapies such as stimulating blood circulation and digestive processes, and controlling inflammation.

An Array-Type RGB Sensor for Precision Measurement of pH

As pH is a widely used index in chemical, medical, and environmental applications, research on pH sensors has been active in recent years. This study obtained RGB values by measuring the reflected light from a liquid sample to detect fine changes in pH, and performed mathematical modeling to investigate the relationship between the detected optical signal and pH value. Also, the trends in pH changes were easily identified by analyzing RGB values and displaying them in the color coordinate for easy visualization of data. This method implemented a user-friendly system that can measure and analyze in real time. This system can be used in many fields such as genetic engineering, environmental engineering, and clinical engineering, because it not only can measure pH but also replaces a colorimeter or turbidimeter.

An Optical Technique for Concentration Measurement by Color Analysis

Many studies have been done to measure and analyze color for various purposes. Visual assessment has lack of objectivity and the equipment for color measurement is very expensive. In this study, we developed a device for quantitative analysis of the color using optical elements. With the color sensor, the ratio of RGB was calculated by measuring the light intensity that is reflected from an object. Inverse transformation of optical signal was performed to detect the color density. The suggested color analyzer can detect color information as well as sample concentration. Results of this study are expected to be used in various medical fields such as pH indicator and urine analysis.

A Study on Angle Measurements Using an Optical Fiber

The measurement and analysis of angular change have been stu died in many fields. This s tudy developed an angle measurement technique with opticl fiber and photodiode. The po sition and attached angle of pho todiode were investigated to find the proper combination of p arameter. The results showed th at the increased measuring range was achieved when the position of detector was away from the center of rotation. Inve rse mathematical model was us ed to obtain angular changes with an optical fiber. The appli cations of this study include i n optical sensor, joint angle measurement, and sport science.

Design of Infrared Angular Sensor for Human Joint Angle

Joint angle generally can be measured to check the recovery process in rehabilitation field. This paper suggests to measure joint angle with Infrared sensor based on triangulation principle. We performed various experiments to find the optimal condition of the sensor’s attached distance, height, and angle. The results were compared with commercial goniometer for accuracy. The proposed infrared joint angle sensor can be effectively used in rehabilitation and sport science fields.

Detection of Color Information Using Optical Method

Color is distinguished due to the light in which natural light is reflected by object and made with combination of RGB(red, green, blue; three colors). This study proposes color analysis system with optical method to be used conveniently. Color information of sample is determined with the optical sensor. By using the CIE diagram in particular, it detects purity value and wavelength. The method to distinguish color is very economical, simple, and convenient. The result can be used to confirm accurate information of color for various applications.

A new optical technique to monitor joint motion using position sensitive detector

BACKGROUND Evaluation of joint movements is essential to choose an appropriate rehabilitation protocol for a patient. OBJECTIVE The aim of this study is to suggest an alternative optical technique for measurement of joint angle which is convenient, inexpensive, and can be operated in real time. METHODS According to the principle of the triangulation method, position sensitive detector (PSD) converts reflected light signals into distance-related voltages. Various parameters were investigated to increase detection range and resolution of joint angle measurements. RESULTS The accuracy of the suggested optical sensor was verified by comparing with a commercial goniometer and 3D motion capture system. CONCLUSIONS This method can be applied to monitor recovery progress for the patient in rehabilitation and sport science.

Optical Method to Determine Gait Parameters Using Position Sensitive Detector

This study suggests an optical method to measure cardinal of gait (step width, step length, and stride length) with position sensitive detector (PSD). The effect of reflector’s shape (flat and cylinder) on the PSD output voltage was examined for the application of the suggested system to real situations with a curved shape reflector (e.g. shoes). Various mathematical models were evaluated to find the optimal equation for the distance measurement. Considering the effect of shape on detected signal, the inverse polynomial model was developed. The suggested method is simple to operate, low in cost, small in size, and can evaluate gait parameters in real time. This method is expected to be useful in the field of rehabilitation and sport science.