Patents of eye tracking system- a survey Feng Li Center for Imaging Science Rochester Institute of Technology, Rochester, NY 14623 Email: Fxl5575@cis.rit.edu Vision is perhaps the most important of the human senses. It provides us, seemingly effortlessly, with a detailed three-dimensional (3-D) description of a complex and rapidly changing world. Eye tracking is a technique used to determine where a person is looking. The concepts underlying eye tracking are deceptively simple: track the movements of the user's eyes and note what the pupils are doing while the user is looking at a particular feature. In practice, however, these measures are difficult to achieve and require high-precision instruments as well as sophisticated data analysis and interpretation. Equipment which is used to do this are called eye trackers. The purpose of this paper is to survey the patents of eye tracking system in U.S.A. 1. United States Patent: 6,542,081-- System and method for monitoring eye movement The system includes a frame that is worn on a person's head, an array of emitters on the frame for directing light towards the person's eye, and an array of sensors on the 1
frame for detecting light from the array of emitters. The sensors detect light that is reflected off of respective portions of the eye or its eyelid, thereby producing output signals indicating when the respective portions of the eye is covered by the eyelid. The emitters project a reference frame towards the eye, and a camera on the frame monitors movement of the eye relative to the reference frame. 2. United States Patent : 6,433,760--Head mounted display with eyetracking capability The eye-tracking system is based on the reflection of four light emitting diodes (LED)s at the cornea of user's eve. The whole eye is illuminated by near infrared light and the contrast between the dark pupil and the bright iris on the CCD sensor allows knowledge of the location of the center of the entrance pupil. 3. United States Patent: 6,334,683 -- Eye illumination system and method The main body is constructed and arranged to be mounted in spaced relation to an eye to be tracked. An infrared light source is carried by the main body on at least a significant portion of its inner circumferential surface to direct infrared light toward the eye being treated at an angle from about 20 to 45 degrees with respect to an iris base plane of the eye being tracked. 4. United States Patent: 6,283,954 -- Linear array eye tracker Linear photodetectors extend across the pupil, optionally also extending across the iris to the sclera. A pair of such linear photodetectors can accurately sense and measure one-dimensional positioning error and provide feedback to a one-dimensional positioning apparatus, resulting in a simple, highly linear system capable of accurate position 2
tracking. 5. United States Patent:5,583,335 -- Method of making an eye tracking system having an active matrix display An eye tracking system is disclosed which is comprised of an eye tracking module formed of a display joined to a photodetector array. Each pixel in the display is aligned with a corresponding photodetector. An image generated by the display is projected onto a viewing screen or toward a viewer. Axial light rays from the display pixels are reflected by the eye and detected by a respective photodetector which generates an electrical signal indicative of eye position. 6. United States Patent: 5,231,674-- Eye tracking method and apparatus It provided a method and apparatus for precise location of image features such as edge coordinates between the pupil and iris of the eye and of the center coordinates of light reflections off the cornea of the eye. 7. United States Patent: 6,134,339-- Method and apparatus for determining the position of eyes and for correcting eye-defects in a captured frame The illumination source is located adjacent to the optical lens or close to the optical axis of the camera. Next the illumination level of the images is compensated to make them equal in illumination. Following that an analysis of the images is performed to determine the difference between the illumination compensated images. After the 3
illumination compensation the difference has to be caused by eye-defects or specular reflections from glasses. The pixel coordinates of the transitory eye-defect regions are recorded and analyzed to determine the spacing of the potential eye locations and/or the spatial structure of the eyes for plausibility. Once confirmed the coordinates are output and recorded. 8. United States Patent: 6,634,749 -- Eye tracking system The eye sensor includes a light source for outputting light through the eyepiece towards the user's eye, a lens for causing the light from the source to be collimated when it exits the eyepiece, an imaging transducer for imaging the user's eye through the eyepiece and for generating an electrical image signal, and processing means for processing the image signal to determine the location of the user's pupil center and the location of a reflection of the light source to determine the gaze direction information. 9. United States Patent 6,578,962-- Calibration-free eye gaze tracking The preferred embodiment includes two synchronized interlaced cameras, each viewing the user's eye and having on-axis lighting that is alternately modulated. An image difference between lighted and unlighted images of the eye is used to identify a user's pupil. A plane containing the gaze vector is defined by rotating a base plane through the angle in a camera image plane between a pupil center, a first glint, and a second glint. The intersection of two such planes (one from each camera), defines the gaze vector. The gaze position is the intersection of the gaze vector with the object being viewed by the user. Alternate embodiments are also described. 4
10. United States Patent 6,568,808-- Eye tracker control system and method A system and method for controlling an eye movement tracker includes monitoring a plurality of eye positions by following a feature using the tracker. An optical beam is sent into the eye, and an intensity of a reflected beam from the eye is sensed at each position. If the intensity of the reflected beam fluctuates from a predetermined acceptable intensity range, the tracker is returned to a frozen position. The frozen position comprises a most recent position at which the intensity lay within the intensity range. 5