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Zengzhuo Li, Guoqiang Li; Eye Tracker with Distance Measurement for Autofocus Eyeglass. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3129.
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© 2017 Association for Research in Vision and Ophthalmology.
Eye trackers have shown potential in several areas. However, commercially available eye trackers only provide 2D lateral location of the gazing points on a monitor screen instead of 3D location in real world. The depth information is necessary for the development of autofocus eyeglass. Our purpose is to develop a compact eye tracker which can measure the distance between the viewer and the objects. It can be used to automatically adjust the focusing power of an electro-optic eyeglass to provide sharp vision adaptively for dynamic vision tasks without manual operation. This can be very useful in correction of presbyopia, especially for people with disabilities.
We used one near-infrared LED and one mini-camera for each eye that were mounted on the frame of the eyeglass and obtained the distance information by analyzing the eye movement when the viewer gazed at different points. The gazing angle is assumed to be linear as a function of the lateral separation between the center of the pupil and the glint (the reflected image of the LED from the cornea). Specifically, there were two steps in the procedure of the distance measurement: (1) Calibration; (2) Estimation. In the first step, the user wears the eye tracker and keeps the head stable in the chin rest, while looking at the targets located at far distance, e.g., 400 cm from the subject. Images corresponding to 5×5 lateral locations were taken, and then the coefficients for the linear fitting were calibrated. Next, a set of images for near (40cm)- and intermediate (70cm)-vision were taken separately while the user looked at the targets at these distances. The gazing angle for each target can be calculated based on the linear fitting and the viewing distance can be estimated.
The average values of the estimated distances for far (400 cm)-, intermediate (70cm)-, and near (40 cm)-vision are 431.3cm, 79.02cm, and 36.97cm, respectively. This result is accurate enough for the adaptive control of the autofocus eyeglasses so that the power needed for each vision task can be provided.
All estimations for near-, intermediate-, far-vision are decent. This technique is reliable for the measurement of eye gazing distance, and the eye tracker can be integrated with the adaptive electro-optic lenses as an autofocus eyeglass. This work is of great value in vision care for normal subjects and for subjects with disabilities.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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