Risto Myllylä

Laser ranging : a critical review of usual techniques for distance measurement

We review some usual laser range finding techniques for in- dustrial applications. After outlining the basic principles of triangulation and time of flight (pulsed, phase-shift and frequency modulated continu- ous wave (FMCW)), we discuss their respective fundamental limitations. Selected examples of traditional and new applications are also briefly presented.

Wireless sensor and data transmission needs and technologies for patient monitoring in the operating room and intensive care unit

In the intensive care unit, or during anesthesia, patients are attached to monitors by cables. These cables obstruct nursing staff and hinder the patients from moving freely in the hospital. However, rapidly developing wireless technologies are expected to solve these problems. To this end, this study revealed problem areas in current patient monitoring and established the most important medical parameters to monitor. In addition, usable wireless techniques for short-range data transmission were explored and currently employed wireless applications in the hospital environment were studied. The most important parameters measured of the patient include blood pressures, electrocardiography, respiration rate, heart rate and temperature. Currently used wireless techniques in hospitals are based on the WMTS and WLAN standards. There are no viable solutions for short-range data transmission from patient sensors to patient monitors, but potentially usable techniques in the future are based on the WPAN standards. These techniques include Bluetooth, ZigBee and UWB. Other suitable techniques might be based on capacitive or inductive coupling. The establishing of wireless techniques depends on ensuring the reliability of data transmission, eliminating disturbance by other wireless devices, ensuring patient data security and patient safety, and lowering the power consumption and price

TiO2 nanoparticles as an effective UV-B radiation skin-protective compound in sunscreens

Protecting human skin against harmful UV-B radiation coming from the sun is currently a problem. Due to the decreased thickness of the ozone layer, a more dangerous amount of UV-B light reaches the surface of our planet. This causes increased frequency of skin diseases. Titanium dioxide (TiO2) fine particles are embedded with sunscreens into the skin to effectively attenuate UV-B radiation. This study evaluates the most appropriate size of such particles assuming they are spheres. The distribution of TiO2 particles within the skin, achieved with topically applied sunscreens, is determined experimentally by the tape-stripping technique. Computer code implementing the Monte Carlo method is used to simulate photon migration within the plain 20??m thick horny layer matrix partially filled with nano-sized TiO2 particles. Dependences of harmful UV-B radiation of 307?311?nm absorbed by, backscattered from and transmitted through the horny layer on the concentration of TiO2 particles are obtained and analysed. As a result, particles of 62?nm are found to be the most effective in protecting skin against UV-B light.

Profiling of hot surfaces by pulsed time-of-flight laser range finder techniques.

The possibilities for using the pulsed time-of-flight (TOF) laser radar technique for hot refractory lining measurements are examined, and formulas are presented for calculating the background radiation collected, the achievable signal-to-noise ratio (SNR), and the measurement resolution. An experimental laser radar device is presented based on the use of a laser diode as a transmitter. Results obtained under real industrial conditions show that a SNR of 10 can be achieved at measurement distances of up to 15-20 m if the temperature of the converter is 1400 °C and the peak power of the laser diode used is 10 W. The single-shot resolution is about 60 mm (sigma value), but it can be improved to millimeter range by averaging techniques over a measurement time of 0.5 s. A commercial laser radar profiler based on the experimental laser radar device is also presented, and results obtained with it in real measurement situations are shown. These measurements indicate that it is possible to use the pulsed TOF laser radar technique in demanding measurement applications of this kind to obtain reliable data on the lining wear rate of a hot converter in a steel works.

Effect of size of TiO2 nanoparticles embedded into stratum corneum on ultraviolet-A and ultraviolet-B sun-blocking properties of the skin

Recently there has been a strong demand to protect human skin against negative effects of the UV solar light. This problem is interesting due to the increased frequency of human diseases caused by such radiation. We aim to evaluate how the optical properties of the horny layer of skin can be effectively changed by imbedding TiO2 fine particles to achieve the maximal attenuation of the UV solar radiation. In-depth distribution of TiO2 particles embedded into the skin by multiple administration of sunscreens is determined experimentally using the tape-stripping technique. A computer code implementing the Monte Carlo method is developed to simulate photon migration within the 20-microm-thick horny layer filled with nanosized TiO2 spheres, 25 to 200 nm in diameter. Dependencies of the UV radiation of two wavelengths (310 and 400 nm) absorbed by and totally reflected from, as well as transmitted through the horny layer on the size of TiO2 particles are obtained and analyzed. The most attenuating particles are found to be 62 and 122 nm in diameter for 310- and 400-nm light, respectively. The former could be suggested as the main fraction to be used in sunscreens to prevent erythema.

Automated segmentation of the macula by optical coherence tomography

This paper presents optical coherence tomography (OCT) signal intensity variation based segmentation algorithms for retinal layer identification. Its main ambition is to reduce the calculation time required by layer identification algorithms. Two algorithms, one for the identification of the internal limiting membrane (ILM) and the other for retinal pigment epithelium (RPE) identification are implemented to evaluate structural features of the retina. Using a 830 nm spectral domain OCT device, this paper demonstrates a segmentation method for the study of healthy and diseased eyes.

A Cell Phone Based Health Monitoring System with Self Analysis Processor using Wireless Sensor Network Technology

This paper describes the integrated wireless CDMA-based ubiquitous healthcare monitoring system for disease and chronic management and better patient care in the hospital, home or travel environments with extended standalone simple electrocardiogram (ECG) diagnosis algorithm at cell phone. This system utilizes a wireless dongles prototype as the intermediary devices to remotely monitor the physiological signs of patients from a tiny wireless sensor to transmit directly to medical center monitoring/PDA wirelessly within 802.15.4 wireless LAN or using cell phone to relay the medical data through CDMA network when outside the coverage LAN. The external standalone ECG diagnosis was implemented to enable continuous monitoring and evaluation of the ECG signal locally before any medical data could be sent to the medical center.

Simulation of optical coherence tomography images by Monte Carlo modeling based on polarization vector approach.

Monte Carlo method is applied for simulation of 2D optical coherence tomography (OCT) images of skin-like model. Layer boundaries in skin model feature curved shape which agrees with physiological structure of human skin. The effect of coherence properties of probing radiation on OCT image formation and speckles in the detected OCT signal is considered. The developed model is employed for image simulation both for conventional and polarization dependent time-domain OCT modalities. Simulation of polarized OCT signal is performed using vector approach developed previously for modeling of electromagnetic field transfer in turbid media.

Tracking laser radar for 3-D shape measurements of large industrial objects based on time-of-flight laser rangefinding and position-sensitive detection techniques

A tracking laser radar device is proposed for the 3-D measurement of the shapes of large industrial objects. The measuring system includes a servo-controlled measuring head and small reflectors attached to the object. The sensor consists of a tracking sensor, a pulsed time-of-flight rangefinder and angle encoders. The implementation of the tracking sensor and its test results are explained in detail. Tracking is accomplished by illuminating the reflectors of the target object and focusing the reflected light on the surface of a four-quadrant (4Q) position-sensitive detector, the signals of which are used to drive the servo motors of the measuring head. The test results show a tracking sensor resolution of about 0.003 mm (/spl sigma/ value) and bias of about /spl plusmn/0.1 mm when the distance and angle of the target reflector vary in the ranges 2-5 m and /spl plusmn/45/spl deg/, respectively. The pointing accuracy of the tracking system was better than /spl plusmn/0.3 mm. >

Time‐to‐digital converter with an analog interpolation circuit

The construction and capability of a time‐to‐digital converter (TDC) is presented. The TDC consists of a 100‐MHz clock and an analog interpolation circuit composed of two time‐to‐amplitude converters for the time fractions between the start pulse and the next clock pulse but one and the stop pulse and the next clock pulse but one, respectively. The difference between the time fractions is digitized with an analog‐to‐digital converter, and the output of this plus the main counters roughly digitizing the time interval to be measured are then summed to give the final result. The channel width, single‐shot accuracy, and measurement range of the TDC are about 40 ps, 80 ps (FWHM), and 2.5 μs, respectively. The effects of the averaging of the measurement results on the resolution and accuracy of the device are measured and discussed. The temperature stability of the interpolation circuit is better than 3 ps/°C. The TDC combines the good single‐shot accuracy of time‐to‐amplitude conversion with the long measureme...