RESUMO
We present a novel optical method, to our knowledge, to measure the refractive index of liquids by means of the images produced by an optofluidic lens. In addition we propose a new method to make optofluidic lenses.
Assuntos
Lentes , Microfluídica/instrumentação , Refratometria/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Espalhamento de RadiaçãoRESUMO
Plateau's experiment, in which the bisection method was introduced, is recognized as the first psychophysical experiment ever done. That experiment was replicated and extended using modem imaging devices. First, participants with professional training in visual arts painted grayscales with no control on illumination. Then, the trained participants and the nontrained participants generated grayscales using a personal computer in three different conditions: a white background of a linearized monitor, a black background of that monitor, and a white background but without linearizing the monitor. Analyses showed that with artificial illumination, scales with steps more evenly spread were produced than with natural illumination. Humans do not seem to have a natural ability to use the bisection method properly. Experts seem to be able to judge the reflectance of distal stimuli, and perceptual learning played an important role in the perception of achromatic colors as found in prior literature.
Assuntos
Percepção de Cores , Sensibilidades de Contraste , Aprendizagem por Discriminação , Iluminação , Ilusões Ópticas , Software , Adolescente , Adulto , Limiar Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pinturas , Prática Psicológica , Psicofísica , Adulto JovemRESUMO
Here we present a new method to make liquid lenses. It is based on the microfluidics method and involves the preparation of emulsions one drop at a time. Tests of lenses by image formation are presented. Experimental results are compared with results of an optical design program. We also present a new type of lens that we call a Compound Lens which consists of two spherical lenses, one inside the other.
Assuntos
Lentes , Microfluídica/instrumentação , Óptica e Fotônica , Coloides/química , Dimetilpolisiloxanos/química , Emulsões , Desenho de Equipamento , Micelas , Microesferas , Oscilometria/métodos , Silício/química , Temperatura , TermodinâmicaRESUMO
Simple reaction times (SRT) to visual stimuli were investigated through reactions to computer simulations of changes of traffic lights. The performance in the detection of visual stimuli, implying decision processes, was also assessed using the two alternative forced choice (2AFC) method. Subjects were patients affected by diabetes type 2, and observers without diabetes. Results indicated that mean SRT was longer in the group of diabetic patients but was not correlated with age, diabetes duration or fasting glucose. The performance index (d') was correlated with age and with diabetes duration. Unexpectedly, the correlation between fasting glucose and d' was not negative.
Assuntos
Diabetes Mellitus/fisiopatologia , Estimulação Luminosa/métodos , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Adulto , Fatores Etários , Algoritmos , Glicemia , Humanos , Modelos Lineares , Pessoa de Meia-IdadeRESUMO
Here we propose a new optical method, to our knowledge, to measure the pressure in liquids or gases by means of a flexible lens. Images of an object given by the dynamical lens are analyzed, and through the visibility of those images pressure is inferred.
Assuntos
Algoritmos , Interpretação de Imagem Assistida por Computador/instrumentação , Interpretação de Imagem Assistida por Computador/métodos , Lentes , Manometria/instrumentação , Manometria/métodos , Desenho Assistido por Computador , Elasticidade , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
To study the radiation emitted by the human skin, the emissivity of its surface must be known. We present a new approach to measure the emissivity of the human skin in vivo. Our method is based on the calculation of the difference of two infrared images: one acquired before projecting a CO(2) laser beam on the surface of the skin and the other after such projection. The difference image contains the radiation reflected by the skin, which is used to calculate the emissivity, making use of Kirchhoff's law and the Helmholtz reciprocity relation. With our method, noncontact measurements are achieved, and the determination of the skin temperature is not needed, which has been an inconvenience for other methods. We show that it is possible to make determinations of the emissivity at specific wavelengths. Last, our results confirm that the human skin obeys Lambert's law of diffuse reflection and that it behaves almost like a blackbody at a wavelength of 10.6 microm.
Assuntos
Algoritmos , Temperatura Cutânea/fisiologia , Pele/efeitos da radiação , Espectrofotometria Infravermelho/métodos , Termografia/métodos , Relação Dose-Resposta à Radiação , Raios Infravermelhos , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Here we propose optofluidic spherical microlenses that can change their focal distance by varying the refractive index of the liquid that composes them. These lenses are fabricated in the bulk of a polymeric mixture. Results of a characterization study of the profile of the lenses, the image forming capability, and the behavior of the focal distance as a function of the refractive index are presented. Ionic liquids are suggested as a source of liquids useful for fabricating this type of lens.
RESUMO
We present a new kind of compact, simple, and low cost optical pressure sensor. The physical principle on which the sensor is based, components, layout of the system, and characterization are described. The range of pressures in which the sensor works is from about 0.5 to 3 psi (1 psi=6.895 kPa).
RESUMO
Signal detection psychophysical experiments were conducted to investigate the visual path of children with autism. Computer generated images with Gaussian noise were used. Simple signals, still and in motion were embedded in the background noise. The computer monitor was linearized to properly display the contrast changes. To our knowledge, this is the first time that experiments of this type have been done with observers with autism. Our results show that the visual capabilities of typically developed children were superior to those of the children with autism, and that the related problems of children with autism are sensation related only in a reduced proportion. There is no evidence that they are disabled in detecting simple visual stimuli, still and in motion.
Assuntos
Transtorno Autístico/fisiopatologia , Área de Dependência-Independência , Reconhecimento Visual de Modelos/fisiologia , Detecção de Sinal Psicológico/fisiologia , Vias Visuais/fisiopatologia , Transtorno Autístico/diagnóstico , Transtorno Autístico/psicologia , Criança , Aprendizagem por Discriminação/fisiologia , Feminino , Humanos , Masculino , Percepção de Movimento/fisiologia , Mascaramento Perceptivo/fisiologia , Desempenho Psicomotor/fisiologia , PsicofísicaRESUMO
OBJECTIVE: To describe a simple and quick procedure for modeling samples of tissue with Voronoi diagrams. STUDY DESIGN: Instead of calculating the centers of the so-called Dirichlet domains (i.e., the polygonal areas occupied by individual cells), the centroid of such areas is used to generate Voronoi diagrams. The coordinates of the centroids are calculated by simply averaging the coordinates of the points of the cell contours; that is much simpler and faster than any geometric procedure for locating the Dirichlet centers. Using the centroids as centers, circles are allowed to grow until no space on the surface is available. With this procedure it is easy to control the rate of growth of individual cells or groups of cells according to any rule or rules. It is also possible to simulate the effects of removing > or = 1 cells from the sample. CONCLUSION: The procedure was successfully applied to modeling some of the changes that can occur in a real sample of human corneal endothelium. The procedure is simple, completely automated, efficient and flexible and can be easily implemented on a personal computer. It can be used to test growth or communication strategies among cells.