Field tester gaze tracking using content addressable memories to improve image data analysis speed
US5491757A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1993 |
| Grant date | Feb 13, 1996 |
| Priority date | — |
| Expiry date | Dec 22, 2013 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61F2009/0035
- WIPO fieldMedical technology
- WIPO sectorInstruments
Abstract
A field test apparatus and method is disclosed in which gradual movement of the head supporting chin cup is used to maintain a centered relation between the eye being tested and the trial lens frame holding the required prescription for optimum vision of the patient. During the test, alternating illumination is provided in the infrared between a central corneal reflection and an iris illuminating source which imparts a high contrast bright circular iris image surrounding a central dark pupil. Content addressable memories are used to delineate areas of contrast change for rapid and abbreviated microprocessor analysis of conventional RAM images. Both the corneal reflection image--which is a brightly illuminated spot on an otherwise dark background--and the pupillary image--which is a dark pupil surrounded by a brightly illuminated high contrast image of the iris are approximately located at their boundaries using content addressable memory. Thereafter, conventionally stored video data is processed at locations restricted to the high contrast boundaries. For location of the pupil center, special techniques are disclosed for examining the image's first and second derivatives to establi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.