APPARATUS FOR MEASURING THE VISUAL ACUITY OF A PERSON

摘要

An apparatus for measuring the visual acuity of a patient comprising: - a front display surface; - at least one liquid crystal screen comprising a plurality of liquid crystal cells arranged adjacent to one another in order to provide a matrix, the cells having electric contacts for applying an electric field to the liquid crystal; - a control circuit for operating singularly the cells; - a light source adapted to backlight the screen opposite to the surface. The control circuit produces a first group of images at a first portion of the surface and a second group of images at a second portion of the surface. Furthermore, at least one polarized film is arranged between the screen and the surface only at the second portion, whereby the second group of images appears on the display surface at the second portion in polarized conditions for visual acuity tests. This way, it is possible to have high performances of the liquid crystal screen for first portion, obtaining the same quality of image achieved in case of optometric examinations not involving polarized images, reaching in the meantime a maximum quality also for the second portion that in case of optometric examinations involves polarized images. The apparatus is thus highly flexible for carrying out a wide variety of optometric examinations.