Apparatus for eye examination

Details Apparatus for eye examination Apparatus for eye examination

1985-05-20

1987-07-14

Bovernick, Rodney B.

Optics: eye examining, vision testing and correcting

Eye examining or testing instrument

Subjective type

351205, 351211, 351241, A61B 302, A61B 310

Patent

active

046799214

ABSTRACT:
An eye-examining apparatus comprises a first positive lens unit, a negative lens unit, a second positive lens unit, a third positive lens unit and a target mark arranged in the named order from the side of the examined eye. The third positive lens unit is mounted movably along the optical axis. Between the first and second positive lens units there is interposed on astigmatic system rotatable about the optical axis. The negative lens unit, the second positive lens unit and the third positive lens unit are so arranged as to form an image of the mark at a position near the focal point on the target mark side of the first lens unit. The focal point on the examined eye of the composite system composed of the negative lens unit, the second positive lens unit and the third positive lens unit is approximately coincident with the position conjugate with the pupil of the examined eye relative to the first positive lens unit. The diopter of the apparatus is changed by moving the third positive lens unit and the change of the axis and degree of astigmatism are achieved by rotating the astigmatism system.

REFERENCES:
patent: 3664631 (1972-05-01), Guyton
patent: 4185896 (1980-01-01), Buhler
patent: 4248506 (1981-02-01), Takahashi

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