Browsing by Subject "vision"

The study examines various uses of computer technology in acquisition of information for visually impaired people. For this study 29 visually impaired persons took part in a survey about their experiences concerning acquisition of infomation and use of computers, especially with a screen magnification program, a speech synthesizer and a braille display. According to the responses, the evolution of computer technology offers an important possibility for visually impaired people to cope with everyday activities and interacting with the environment. Nevertheless, the functionality of assistive technology needs further development to become more usable and versatile. Since the challenges of independent observation of environment were emphasized in the survey, the study led into developing a portable text vision system called Tekstinäkö. Contrary to typical stand-alone applications, Tekstinäkö system was constructed by combining devices and programs that are readily available on consumer market. As the system operates, pictures are taken by a digital camera and instantly transmitted to a text recognition program in a laptop computer that talks out loud the text using a speech synthesizer. Visually impaired test users described that even unsure interpretations of the texts in the environment given by Tekstinäkö system are at least a welcome addition to complete perception of the environment. It became clear that even with a modest development work it is possible to bring new, useful and valuable methods to everyday life of disabled people. Unconventional production process of the system appeared to be efficient as well. Achieved results and the proposed working model offer one suggestion for giving enough attention to easily overlooked needs of the people with special abilities. ACM Computing Classification System (1998): K.4.2 Social Issues: Assistive technologies for persons with disabilities I.4.9 Image processing and computer vision: Applications

At visual threshold, the vision relies on catching incident photons. The ultimate limitation of visual sensitivity arises from the quantal nature of light. At night, the uncertainty of photon arrivals differs fundamentally from daylight conditions, where photon flow can be considered continuous, and sets an absolute physical limitation to visual sensitivity. Visual sensitivity has been postulated to be affected by circadian physiological changes. Here, we have shown, that absolute visual sensitivity is under circadian control in light decrement, or quantal shadow, detection in mice. A behavioural visual task of finding a dark stimulus spot was conducted in a white water maze across several background light intensities leading gradually from clearly visible light to darkness. The percentage of correct choices in the task as a function of light intensity was used to measure visual sensitivity, which was remarkably higher nocturnally. Another parameter affecting visual sensitivity was shown to be the decrement size. Mice were more successful in finding the bigger decrements of the three spatial scales used, as well as succeeding in the task better at night. This finding suggests that visual sensitivity is affected by the absolute number of photons, or more precisely, the absolute number of missing photons in contrast to photons of the background illumination.