| 摘要 |
<p>The problem is that available automatic objective visual acuity measuring devices are not practical for mass vision testing since they are complex in nature, having considerable electronics and lens systems, and, therefore, expensive. The present invention by eliminating complex lens systems, complicated mechanics and extensive electronics is simple to operate and inexpensive. A visual acuity device measures the visual acuity of a patient"s eye (12) by directing a pulsating beam of light (10) on the eye and detecting the resulting reflection. A primary pattern (22) having a pattern formed by transparent and non-transparent portions is positioned in the optical path of the pulsating beam of light. A fixed pair of analyzer or secondary patterns (34 and 36) is positioned in the optical path of the beam of light reflected from the patient"s eye. One (34) of these analyzer or secondary patterns has a pattern which substantially corresponds to the pattern of the primary fixation pattern and the other (36) has a pattern which is negative mirror image of the pattern of the first analyzer or secondary pattern. The beam of light reflected from the patient"s eye is divided by a beam splitter (32) so that each of the analyzer patterns receives the reflected image of the primary pattern from the patient"s eye. A photoelectric device (42 and 44) is associated with each of the analyzer patterns for detecting the reflected beam of light passing through each of these analyzer patterns to generate an electrical output signal. The photoelectric devices are connected to a difference amplifier (58) for eliminating any glare and generating a signal which is determinative of the visual acuity of the patient"s eye. Far visual acuity can be measured by using infrared light adding a collimating (52) and compensating (54) lens. Thus, the visual acuity device objectively measures both far and near visual acuity. </p> |
