The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 30, 1976
Filed:
Mar. 17, 1975
Bradford Howland, Cambridge, MA (US);
Other;
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. Ideally, he sees an undistorted pattern of vertical and horizontal lines; but depending on the nature of his refractive defect, various distortions of the grid pattern are seen which the subject may then sketch, or identify, with the aid of an atlas of variously distorted patterns.