Abstract: A lens meter is disclosed in which continuously variable spherical and astigmatic corrective optics are manipulated to measure the prescription of a suspect optical system. A target including a straight line is focused for maximum clarity, the target being arbitrarily aligned without respect to the axis of the suspect optical system. Continuously variable spherical and first astigmatic optics are juxtaposed to the suspect optics and the image of the target projected through both the suspect optics and the continuously variable optics. Spherical and first astigmatic corrections along at least one axis diagonal to the line target is made until maximum sharpness of a projected image of the line results. A first component of astigmatic correction results. A second target, again consisting of a straight line, is introduced; this target is angularly inclined with respect to the first target preferably at 45.degree..

Abstract: A stabilizer is disclosed which can alone, or in combination with other optics of known magnification, produce stabilized images where ambient instrument vibration occurs. An optically transparent liquid of known index of refraction is confined to a chamber having at least one freely movable transparent wall. A light path is defined into or out of the chamber substantially normal to the neutral position of the freely movable transparent wall. When the chamber is subjected to accidental angular motion, the fluid within the chamber inertially acts upon the freely movable transparent wall to move the wall and thereby create a transparent fluid wedge. This transparent fluid wedge, either alone or in conjunction with other optics of known magnification, produces apparent image movement equal and opposite to the image movement produced by ambient accidental vibration. Optical stabilization results.