Automatic refraction apparatus and method
Patent 3969020 Issued on July 13, 1976. Estimated Expiration Date: 
July 13, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
July 13, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3172404 3486813 3602580 3718386 3822932 InventorsAssigneeApplicationNo. 429143 filed on 12/28/1973US Classes:351/237, Including target image projection351/222, Subjective type351/234, Mounted on rotatable disc351/238Tachistoscope typeExaminersPrimary: Sacher, Paul A.Attorney, Agent or FirmAbstractApparatus and method provide for automatically measuring the refractive error of the human eye and thus the prescription for lens or eye glasses for correcting this error. Test symbols are alternately presented at two different locations on a test screen under control of a programmed automatic data processing system. The symbols are viewed by a subject through a lens system whose power may be continuously varied also under control of the data processing system. The data processing system also varies the size of the symbols presented to compensate for the power of the lens system so that a given symbol will appear to the subject to be of constant size. In one illustrative embodiment of the present invention, the subject communicates with the data processing equipment via a subject response device to indicate his preference for one or the other of the symbols presented at the two locations. The data processing system interprets the responses to alter the presentation of symbols and elicit another response from the subject. | |
