| 摘要 |
An objective refractor for the eye is disclosed in which knife-edge optics are utilized. The knife-edge optics cause characteristic illumination of the retina so that components of sphere and astigmatism can be identified. Provision for remote reading of the characteristic images is provided with the result that two orthogonally disposed knife-edge images can identify the sphere, cylinder and axis required for prescriptive patterns giving the direction and magnitude of required prescriptive change. A system of at least two orthogonally disposed, (and preferably four), knife edges with weighted lighting is disclosed for detection. Utilization of the knife-edge images is made possible by the detection of the low light level images at a detector having low noise level. A photo-sensitive element divided into a plurality of photo-discrete segments has light from the images proportionally dispersed over its surface. Such dispersion occurs through a matrix of wedge-shaped segments or alternately in the form of optical elements having cylindrical components. This dispersion of the light when used in combination with push-pull knife-edge patterns herein disclosed produces detectable low level refractive signal. An embodiment using an optic having a plurality of side by side optic elements, each element having the effect of crossed cylinders, is disclosed with the detector. Separate independent and non-interactive positional information on one hand, and refractive information on the other hand, is provided. Consequently the disclosed refractor is insensitive to adjustment and can accommodate a large range of pupil configuration with insensitivity to local retinal variations in light emission.
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