Abstract: Lens testing charts using a vernier pattern, a sawtooth pattern, and a sinusoidally varying reflectance pattern are described and are used in conjunction with a lens under test to be focussed by said lens onto suitable high contrast film to provide an image from which the quality of the lens may be determined.

Abstract: An eye chart having a plurality of rows of letters where each letter is composed of a line-stroke having a plurality of adjoining black and white segments to provide an average reflectance which is the same as the reflectance of the gray background of the chart. Each row of the letters utilizes a different width line stroke (the line segments thereof are proportioned correspondingly). The sizes of the letters of each row are geometrically decreasing and are preferably in proportion to the width of the line stroke.

Abstract: A process for making a new type of diffuser is described wherein an electric field is applied to a liquid containing a suspension of transparent platelets having a refractive index higher than that of the fluid and a different dielectric constant. The field causes the planes of the platelets to be aligned substantially parallel to that of the field but to have random angular orientation with respect to the direction of the field. While the platelets are thus aligned, the liquid is hardened to permanently retain the platelets in the aligned position even in the absence of the electric field. The resulting structure produces good diffusion of light with a high ratio of transmitted to reflected light.

Abstract: The invention is a test lens made to fit a standard optometrist's trial-lens frame. The lens is a crossed-cylinder astigmator of about .+-. 5 diopter strength, preferably formed by cementing together a first planoconvex cylinder lens of about 5 diopter strength and a second equal-strength plano-concave cylinder lens with a parallelogram grid sandwiched between them, the grid lines being about one millimeter apart in each of the parallel sets, and inclined one set to the other at an angle of about 73 degrees, the axes of principal curvature of the lens elements being perpendicular one to the other, and respectively parallel one to each of the diagonals of the grid elements. The subject under test views monocularly a spectrally pure point source through the test lens.

Abstract: Fiber optic displacement/position measuring apparatus having increased working distance and measuring range capability is provided by combining an optical extending sensing head in fixed relationship with the common end of a bifurcated fiber optic bundle. The sensing head includes a lens system which is operative to focus the image of the end face of the fiber optic bundle onto the surface of an object whose displacement is to be determined and to refocus that image back onto the end in an upright relationship.