Vision testing system

Details Vision testing system Vision testing system

1982-05-07

1984-05-08

Corbin, John K.

Optics: eye examining, vision testing and correcting

Eye examining or testing instrument

Subjective type

351243, 351211, A61B 302

Patent

active

044471416

ABSTRACT:
A vision testing system is disclosed in which a collimated beam of coherent light waves is passed through a transparency of an object such as a grating, a Snellen letter or a portrait to produce the diffraction pattern of the object. Then the light waves forming the diffraction pattern pass through a lens to produce the Fourier transform (the diffraction pattern) at the focal plane of the lens. A variable spatial frequency filter is positioned at the focal plane. Then the spatially filtered light waves are passed through a second lens to produce the inverse of the Fourier transform at the image plane of the second lens. That image is the spatially filtered object. By varying the degree and type of spatial filtering the resultant image can be used to test for contrast sensitivity or character (object) recognition.

REFERENCES:
patent: 4293200 (1981-10-01), Dobson et al.

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