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Abstract
Este trabalho apresenta a metodologia utilizada para calcular o bloco óptico de um sistema de triagem visual utilizando sistema digital com tela LCD. Inicialmente, apresenta os fundamentos da medida da acuidade visual, em especial o padrão definido por Snellen em 1862, baseado na distância e no ângulo de resolução de um optótipo, sendo, até o momento, um dos principais padrões. Define algumas características das telas LCD, principalmente o tamanho do pixel, que, em conjunto com o padrão de Snellen, é uma das variáveis de entrada para o cálculo do bloco óptico. Além do tamanho do pixel, utilizado para calcular o tamanho do optótipo, também é necessário definir as lentes e a distância entre elas, tendo como resultado a ampliação, o tamanho e a distância da imagem formada. Esta metodologia foi aplicada na produção de três protótipos e no estudo de atualização da tecnologia desenvolvida, sendo empregada para diminuir o tamanho do equipamento ou para alterar a potência das lentes para outras encontradas no mercado.
Palavras-chave: Acuidade visual. Bloco óptico. Snellen. LCD.
Methodology to calculate the optical unit of a visual acuity screening system by using a lcd screen
Abstract
This paper describes the methodology used to calculate the optical unit of a visual acuity screening system by using a LCD screen. It begins with the fundamentals of visual acuity, especially the standard defined by Snellen in 1862, based on distance and angle resolution of an optotype, and, so far, one of the main standards. The fundamentals of visual acuity and some characteristics of LCD screen are presented. Beyond the pixel size used to calculate the size of the optotype, it is also necessary to define the lenses and the distance between them, resulting in magnification, size and distance of the formed image. Three prototypes were produced using this methodology. Furthermore, it has been used to decrease the size of the equipment and/or to change the power of the lenses to others found in the market.
Keywords: Visual Acuity, Optical Layout, Snellen, LCD.
References
BICAS, H. E. A. Acuidade visual: medidas e notações. Arquivos Brasileiros de Oftalmologia, v. 65, p. 375 – 384, 2002.
EVANS, J. M. Standards for visual acuity. Gaithersburg (USA): NIST, 2006.
FRIENDLY, D. S. Preschool visual acuity screening tests. Transactions of the American Ophthamological Society, v. 76. 1978.
KOLB, H. et al. (Ed.). Webvision: the organization of the retina and visual system. [Bethesda, Md.]: [National Library of Medicine]: [National Center for Biotechnology Information], 2007. Disponível em: . Acesso em: 15 mar. 2010.
SMITH, W. J. Pratical optical system layout and use of stock lenses. New York: McGraw-Hill Companies, 1997.
SNELLEN, H. Probebuchstaben zur Bestimmung der Sehschärfe. Utrecht: P.W. van de Weijer, 1862.
SOARES, F. C. et al. Equipamento binocular digital para a verificação da acuidade visual e do limiar auditivo. BR Pat. 1003231-2, 15 de março de 2010, 25 p.
SOARES, F. C. Sistema de triagem visual e auditiva de crianças em idade escolar, conectado a um banco de dados. 2009. 140 f. Tese (Doutorado em Engenharia Mecânica) – Universidade Federal de Minas Gerais, Escola de Engenharia, Belo Horizonte, 2009.
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