The inherent danger in laser safety eyewear

I have designed an experiment which explained why the filter in a laser protective eyewear could crack under prolonged contact to a laser beam. My hypothesis stated that the nonlinearity of absorption of light played an important role in the failure of the filter. Using a xeon-arc lamp, a photoconductive cell, a multimeter and filters that consisted of 0 to 15 blue transparency(ies), I indirectly measured the amount of light that these filter absorbed. From the data I affirmed my hypothesis. If a laser beam hit an actual protective filter, because of the nonlinearity of absorption, the front surfaces of the filters would absorb much more laser light than the back surfaces. thus the front would heat up and expand more quickly than the back causing the filter to crack. Because future optometrists will need to learn the practical significance of the nonlinear process of absorption, I have also incorporated my experimental procedure into a physical optics experiment

Evaluation of flash and fluorescent sources with respect to recommended ocular exposure thresholds

A system was established for the evaluation of sources of optical radiation with respect to recommended ocular exposure limits. This system consists of a diode array radiometer calibrated for absolute radiometric measurements and software for the application of the currently accepted threshold limits for exposure to the various wavelengths of radiation. Absolute calibration of the array radiometer was accomplished to within 3 percent of values obtained by a conventional instrument. Day-to-day repeatability of the instrument indicates the possiblility of absolute calibration of the detector array responsivity for everyday use in the measurement of continuous sources to an accuracy of plus-or-minus 2.8 percent. It was also determined that the output of several optical sources used in copying machines and photography can exceed the retinal thermal Threshold Limit Value. One typical 35 mm photographic flash exceeded the threshold at a range of 3 meters. Other threshold expressions were not exceeded at significant distances or exposure durations for these sources

LASER SYSTEMS SAFETY CLASSIFICATION ACCORDING TO HEALTH HAZARD LEVEL

The importance of work safety in laser and optoelectronic technology professional activity is discussed in the paper. The principles defined are considered when forming the professional competence of the field, as working with laser technology is connected with exposure to complex hazardous and harmful factors, the number and intensity of which depends on laser emission. Hence, ensuring safety is essential and failure to comply with working conditions requirements could result in injuries or fatalities.Key words: safety recuirements, laser safety classes, biological hazards, non-beam laser hazards.кандидат педагогічних наук, Дембіцька С. В., Краснощока А. К. Класифікація безпеки лазерних систем за ступенем загрози здоров’ю / Вінницький національний технічний університет, Україна, Вінниця. В статті висвітлено важливість охорони праці в професійній діяльності спеціаліста з лазерної та оптоелектронної техніки. Визначені принципи, які необхідно враховувати під час формування професійної компетентності майбутніх фахівців в галузі, тому що при роботі із лазерною технікою  працівник піддається впливу комплексу небезпечних і шкідливих факторів, кількість і інтенсивність яких залежать від лазерного випромінювання. Відповідно, у професії оптотехніка є надзвичайно важливим забезпечення безпеки праці, оскільки недотримання нормативних вимог щодо умов праці можуть спричинити травмування або летальні випадки .Ключеві слова: класи лазерної безпеки, біологічні загрози, безпроменеві лазерні загрози.кандидат педагогических наук, Дембицкая С.В., Краснощека А.К .. Классификация безопасности лазерных систем по степени угрозы здоровью. / Винницкий наиональний технический университет, Украина, Винница. В статье освещены важность охраны труда в профессиональной деятельности специалиста по лазерной и оптоэлектронной технику. Определены принципы, которые необходимо учитывать при формировании профессиональной компетентности будущих специалистов в данной области, так как при работе с лазерной техникой работник подвергается воздействию опасных и вредных факторов, количество и интенсивность которых зависят от лазерного излучения. Соответственно, в профессии оптотехника чрезвычайно важным является обеспечение безопасности труда, поскольку несоблюдение нормативных требований по условиям труда могут привести к травмированию или летальным случаям.Ключевые слова: классы лазерной безопасности, биологические угрозы, безлучевые лазерные угрозы

Real-Time Gaze Tracking with a Consumer-Grade Video Camera

Eye gaze can be a rich source of information to identify particular interests of human users. Eye gaze tracking has been largely used in different research areas in the last years, as for example in psychology, visual system design and to leverage the user interaction with computer systems. In this paper, we present an IR-based gaze tracking framework that can be easily coupled to common user applications and allows for real-time gaze estimation. Compared to other gaze tracking systems, our system uses only affordable consumer-grade hardware and still achieves fair accuracy. To evaluate the usability of our gaze tracking system, we performed a user study with persons of different genders and ethnicities

Optical Safety Assessment of a Near-Infrared Brain-Computer Interface

This paper describes a safety assessment study of near-infrared sources used in an optical brain-computer interface (BCI). The measurement elements of an optical BCI consist of sets of optical sources and detectors. Our current system utilises sources which comprise of dual wavelength light emitting diodes (LED) at 760nm and 880nm. An optical analysis demonstrated that NIR radiation is a negligible source of heating in this case. LED heat conduction however is a major source of heating, and LEDs, though much safer than laser diodes, have been known to cause burns if improperly used. We describe a procedure by which we measure the heat conduction effect of LEDs. We show that the LED systems used in our current generation BCI produce safe levels of thermal energy and are within published safety levels

Optical Safety Assessment of a Near-Infrared Brain-Computer Interface

This paper describes a safety assessment study of near-infrared sources used in an optical brain-computer interface (BCI). The measurement elements of an optical BCI consist of sets of optical sources and detectors. Our current system utilises sources which comprise of dual wavelength light emitting diodes (LED) at 760nm and 880nm. An optical analysis demonstrated that NIR radiation is a negligible source of heating in this case. LED heat conduction however is a major source of heating, and LEDs, though much safer than laser diodes, have been known to cause burns if improperly used. We describe a procedure by which we measure the heat conduction effect of LEDs. We show that the LED systems used in our current generation BCI produce safe levels of thermal energy and are within published safety levels

A Mechanical Mounting System for Functional Near-Infrared Spectroscopy Brain Imaging Studies

In this work a mechanical optode mounting system for functional brain imaging with light is presented. The particular application here is a non-invasive optical brain computer interface (BCI) working in the near-infrared range. A BCI is a device that allows a user to interact with their environment through thought processes alone. Their most common use is as a communication aid for the severely disabled. We have recently pioneered the use of optical techniques for such BCI systems rather than the usual electrical modality [1]. Our optical BCI detects characteristic changes in the cerebral haemodynamic responses that occur during motor imagery tasks. On detection of features of the optical response, resulting from localised haemodynamic changes, the BCI translates such responses and provides visual feedback to the user. While signal processing has a large part to play in terms of optimising performance we have found that it is the mechanical mounting of the optical sources and detectors (optodes) that has the greatest bearing on the performance of the system and indeed presents many interesting and novel challenges with regard to sensor placement, depth of penetration, signal intensity, artifact reduction and robustness of measurement. Here a solution is presented that accommodates the range of experimental parameters required for the application as well as meeting many of the challenges outlined above. This is the first time that a concerted study on optode mounting systems for optical BCIs has been attempted and it is hoped this paper may stimulate further research in this area

Safety assessment of near infrared light emitting diodes for diffuse optical measurements

BACKGROUND: Near infrared (NIR) light has been used widely to monitor important hemodynamic parameters in tissue non-invasively. Pulse oximetry, near infrared spectroscopy, and diffuse optical tomography are examples of such NIR light-based applications. These and other similar applications employ either lasers or light emitting diodes (LED) as the source of the NIR light. Although the hazards of laser sources have been addressed in regulations, the risk of LED sources in such applications is still unknown. METHODS: Temperature increase of the human skin caused by near infrared LED has been measured by means of in-vivo and in-vitro experiments. Effects of the conducted and radiated heat in the temperature increase have been analyzed separately. RESULTS: Elevations in skin temperature up to 10°C have been observed. The effect of radiated heat due to NIR absorption is low – less than 0.5°C – since emitted light power is comparable to the NIR part of sunlight. The conducted heat due to semiconductor junction of the LED can cause temperature increases up to 9°C. It has been shown that adjusting operational parameters by amplitude modulating or time multiplexing the LED decreases the temperature increase of the skin significantly. CONCLUSION: In this study, we demonstrate that the major risk source of the LED in direct contact with skin is the conducted heat of the LED semiconductor junction, which may cause serious skin burns. Adjusting operational parameters by amplitude modulating or time multiplexing the LED can keep the LED within safe temperature ranges