Gu-In Jung

Laser-induced thermoelastic effects can evoke tactile sensations

Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli.

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.

Evaluation of the possibility and response characteristics of laser-induced tactile sensation

In this study, we examined the possibility and perceptual response characteristics of tactile sense induced by laser stimulation to the finger with different laser energy densities through human response experiments. 15 healthy adult males and 4 healthy adult females with an age of 22.6±2.2 years were tested. A frequency-doubled Q-switched laser was used with a wavelength of 532 nm and a 5 ns pulse width. The experimental trial spanned a total of 30 s and included a rest phase (19 s), a stimulation phase (7 s), and a response phase (4 s). During the rest phase, subjects kept their fingers comfortable. During the stimulation phase, one of three types of laser energy density (13.5, 16.6, 19.8 mJ/cm(2)) or a sham stimulation was used to irradiate the distal phalanx on the right index finger. During the response phase, the cognitive response to the laser stimulation was recorded by a PC by pressing the response button. The confusion matrix was configured to evaluate the possibility that the tactile sense was caused by the laser. In addition, changes in the response characteristics were observed according to three types of laser energy densities. From the analysis of the confusion matrix, the accuracy and sensitivity were not high. In contrast, precision and specificity were found to be high. Furthermore, there was a strong positive correlation between the laser irradiation and tactile perception, indicating that tactile sense can be induced using a laser in a mid-air manner. In addition, it was found that as the laser energy density increased, the tactile perception possibility also increased.

Simple LED spectrophotometer for analysis of color information.

A spectrophotometer is the basic measuring equipment essential to most research activity fields requiring samples to be measured, such as physics, biotechnology and food engineering. This paper proposes a system that is able to detect sample concentration and color information by using LED and color sensor. Purity and wavelength information can be detected by CIE diagram, and the concentration can be estimated with purity information. This method is more economical and efficient than existing spectrophotometry, and can also be used by ordinary persons. This contribution is applicable to a number of fields because it can be used as a colorimeter to detect the wavelength and purity of samples.

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.

Photomechanical effect on Type I collagen using pulsed diode laser.

BACKGROUND As the most abundant protein in human tissues, the use of collagen is essential in the fields of biological science and medicine. OBJECTIVE The aim of this study is to investigate the mechanical effect of pulsed laser irradiation on collagen tissue. METHODS With various laser parameters such as peak power, pulse width, and repetition rate, the induced stresses on samples were measured and analyzed. Monte Carlo simulation was performed to investigate the effect of laser parameters on the collagen sample. RESULTS The results indicated that the magnitude of mechanical stress could be controlled by various laser parameters. CONCLUSIONS This study can be used in biostimulation for therapy and mechanoreceptor stimulation for tactile application.

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.

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.