Scheiner-Principle Vernier Optometer.
Patent, Filed 23 Jun 89, patented 24 Jul 90,
DEPARTMENT OF THE NAVY WASHINGTON DC
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The optometer apparatus includes a pinhole aperture plate having first and second horizontally positioned apertures disposed on opposite sides of a first optical axis first and second orthogonally-oriented polarizing filters respectively covering the first and second horizontally positioned apertures a positive lens having an optical axis on the fist optical axis and being positioned at a distance of approximately one focal length from the pinhole aperture plate a lens system having an optical axis third and fourth vertically positioned polarizing filters selectively disposed adjacent to the slit aperture plate, the third and fourth polarizing filters being respectively oriented parallel to the first and second polarizing filters a monochromatic light source for propagating light along the first optical axis through the lens system, through portions of the third and fourth polarizing filters covering the slit, through the positive lens and through the first and second apertures to form first and second images on the retina of a persons eye and movable means attached to the slit aperture plate, the lens system and the monochromatic light source together in a fixed relationship along the first optical axis to enable the person to align the first and second images. Patents. jhd