Kenichi Kameyama

Virtual clay modeling system

This paper describes a CAD system in which a user can directly manipulate the shape of a virtual object like a clay model and can produce its solid model data. The key component of its hardware is a special input device with a 3D position tracker and a tactile sensor. In this system, the movement of a virtual object is directly corresponding to the movement of the input device, and its surface is deformed when a user pushes somewhere on the tactile sensor. This makes a user feel as if he/she can manipulate a virtual object in a real world since he/she actually holds and touches the device. The software consists of a graphical viewer for displaying an object in 3-D, a data translator with a solid modeler for producing solid model data from polygonal data. Connecting this system with a manufacturing system, a virtually created shape can be easily actualized in a very short time. A preliminary prototype environment for a nonspherical lens-like object design is mentioned as an example.

A shape modeling system with a volume scanning display and multisensory input device

This paper describes a newly developed 3-D shape modeling system, in which a user can design a free-form surface as if he or she actually manipulates a flexible object made from rubber or clay. Such reality can be realized in the system without any encumbering devices like goggles, glasses, or gloves, which is impossible in conventional virtual reality systems. The system is composed of a volume scanning display for presenting a surface image in a real 3-D space, a multisensory input device for detecting the force for deformation, and a half-silvered mirror for spatial superposition of the image onto the input device. A user can directly manipulate a free-form surface by virtually pushing the image, actually pushing the input device, and at the same time, he or she can feel the input device resist its actual deformation as the resisting force of the virtual surface. The system has several types of deforming models, and two types of free-form surfaces that have different curvatures have been experimentally created.

Comparison of reflected green light and infrared photoplethysmography

We evaluated the accuracy of pulse rate measurements obtained by reflected green light photoplethysmography (PPG) compared to reflected infrared light photoplethysmography and ECG. The wavelengths of the green and infrared light were 525 and 880 nm, respectively, and experiments were performed at 25°C and at a skin temperature below 15°C. The pulse rate obtained from reflected green light PPG was compared with the ECG RR interval and the pulse rate from reflected infrared PPG. The results indicated a stronger correlation between green PPG and ECG results at both temperatures. These results suggested that reflected green light PPG had an advantage over reflected infrared PPG, especially at temperatures below 15°C.

Measuring Photoplethysmogram-Based Stress-Induced Vascular Response Index to Assess Cognitive Load and Stress

Quantitative assessment for cognitive load and mental stress is very important in optimizing human-computer system designs to improve performance and efficiency. Traditional physiological measures, such as heart rate variation (HRV), blood pressure and electrodermal activity (EDA), are widely used but still have limitations in sensitivity, reliability and usability. In this study, we propose a novel photoplethysmogram-based stress induced vascular index (sVRI) to measure cognitive load and stress. We also provide the basic methodology and detailed algorithm framework. We employed a classic experiment with three levels of task difficulty and three stages of testing period to verify the new measure. Compared with the blood pressure, heart rate and HRV components recorded simultaneously, the sVRI reached the same level of significance on the effect of task difficulty/period as the most significant other measure. Our findings showed sVRIs potential as a sensitive, reliable and usable parameter.

A direct 3-D shape modeling system

A newly developed 3-D shape modeling system based on constructive solid geometry (CSG) is described, in which a direct and interactive shape modeling process is supported. This feature is realized by a voxel model for real-time set operations, and a volume scanning display for the direct visualization of the voxel model, besides the CSG model for data structure management. The set operations on the voxel model can be executed as simple bit calculations, and therefore, the voxel data for the set object can be created in real time. The volume scanning display is a suitable device for presenting the voxel data. There is not need for intensive calculations to display the set objects. The volume scanning display can provide exact 3-D images without goggles or glasses. The concept should be useful in an actual modeling environment.<<ETX>>

Development of the irregular pulse detection method in daily life using wearable photoplethysmographic sensor

We developed an arrhythmic pulse detection algorithm from photoplethysmography (PPG) measured in daily life using a wearable PPG sensor, in order to provide a simpler device than a Holter electrocardiograph (ECG). However, PPG is very sensitive to artifacts in daily life, e.g. body movement. First, we analyzed the correlation between the ECG and the PPG measured at the same time when the arrhythmic heartbeat occurred in daily life. Using the correlation characteristics, we developed a detection algorithm of the arrhythmic pulse to distinguish the artifacts ascribable to body movement and evaluated its accuracy. The algorithm detects pulse-to-pulse interval (PPI) and pulse amplitude by a beat to distinguish between irregular PPI by arrhythmic pulse and that by the artifact.

Estimation of thermal sensation using human peripheral skin temperature

Control of indoor thermal environments in accordance with peoples preferences, makes an important contribution to comfort. To keep a suitably temperate environment, we tried to estimate a subjects thermal sensation using biologic signals. We focused on peripheral skin temperature to estimate individual thermal sensation. First we carried out an experiment involving an alteration of environmental temperatures to reveal the relationship between peripheral skin temperature and thermal sensation votes. Next we made an algorithm of estimating thermal sensation and assessed the algorithm. When thermal sensation indices estimated by our algorithm were compared with the subjects votes, error of mean squares was 1 or less in most cases. As a result, the possibility of thermal sensation measurement using peripheral skin temperatures is confirmed. Furthermore, we implemented the temperature control system using a household air conditioner and a thermal sensor.

Development of a sleep apnea event detection method using photoplethysmography

We studied the possibility of detection of sleep apnea or hypopnea events from photoplethysmography (PPG) wave variation patterns during sleep. In three patients with suspected sleep apnea syndrome, polysomnography (PSG) and the PPG wave were measured simultaneously during sleep. The characteristics of the PPG wave variation patterns in apnea or hypopnea events detected by PSG were investigated. It was found that pulse rate increases and pulse wave amplitude decreases during apnea or hypopnea events, and the respiratory component of heart rate variability has a tendency to decrease before the apnea or hypopnea events. Also, compared to hypopnea, the ratio of the pulse rate is higher, the reduction of the pulse amplitude is more significant, and the decrease of the degree of respiratory variation component in the apnea event is greater. We devised the apnea / hypopnea detection algorithm using these characteristics and evaluated its effectiveness.

Virtual surgical operation system using volume scanning display

This paper describes an interactive 3-D display system for supporting image-guided surgery. Different from conventional CRT-based medical display systems, this one can provide true 3- D images of the patients anatomical structures in a physical 3-D space. Furthermore, various tools for view control, target definition, and simple treatment simulation, have been developed and can be used for directly manipulating these images. This feature is very useful for a surgeon to intuitively recognize the precise position of a lesion and other structures and to plan a more accurate treatment. The hardware system is composed of a volume scanning 3-D display for 3-D real image presentation, a 3-D wireless mouse for direct manipulation in a 3-D space, and a workstation for the data control of these devices. The software is for analyzing X-CT, MRI, or SPECT images and for organizing the tools for treatment planning. The system is currently aimed at being used for stereotactic neurosurgical operations.

The Development of a System for Sleep Care and Its Applications

This paper describes a new sleep monitoring system for home use. The basic system consists of a wearable physiological sensor and the PC software for analyzing sleep quality from users wrist motion and heart rate variability. Different from a conventional sleep monitoring device used in a hospital, the sensor is so small and easy-to-use that a normal person can use It at home. This means that the system is useful not only for a sleep specialist who wants to check his/her patients daily sleep pattern, but also is useful for self-care. The concepts of the tele-care system and the real-time control of electric appliances for creating better sleep environment are also mentioned.