The reflected light path is decoupled by a beam splitter. The cylindrical lens splits the focus into a horizontal and a vertical focal line. The detector is positioned midway between the nominal position of the two focal lines. A circle appears on the detector if the surface is exactly in focus. Deviation from the focus position results in an ellipse on the detector. The orientation and eccentricity of the ellipse depends on the magnitude and direction of the defocus.
The shape deviation is evaluated by the different current distributions in the four quadrants of a photodiode and is fed to a control loop (objective lens control). By adjusting the movable objective lens, the control loop causes a tracking movement of the lens on the surface. The track movement of the movable objective is determined by a glass scale and displayed as a measured value.
Wipo Publishes Patent of Universidad De Murcia for "Optometer and Method for Determining the Diopters Necessary for Enhancing Night Vision" (Spanish Inventors)
Apr 12, 2013; GENEVA, April 12 -- Publication No. WO/2013/050638 was published on April 11.Title of the invention: "optometer AND METHOD...