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changgeng liu, Beatrice Pazzucconi, juan liu, Lei Liu, Xincheng Yao; A holographic waveguide based eye tracking device. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2162.
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© ARVO (1962-2015); The Authors (2016-present)
This study is to test the potential of using a planar holographic waveguide for constructing a wearable, see-through eye tracker. The planar holographic waveguide can significantly reduce the physical dimension of the device in front of the eye, promising a powerful tool to diagnose oculomotor disorders outside of laboratories.
A custom-built holographic waveguide, which is a 20 mm x 60 mm x 3 mm flat glass substrate with integrated in- and out-couplers, was used to image the eye in a prototype eye tracker. A prosthetic eye model, mounted on a 3D gimbal and illuminated with an LED light source, was used to test this prototype. The image of the eye was captured by the waveguide in front of the eye and was guided away from the eye to a camera (Fig. 1A). A custom Matlab program was used to compute the locations of pupil center (PC) and the corneal reflection (CR). The offset between PC and CR was used to register eye rotation.
Figure 1B is a representative anterior segment image taken through the holographic waveguide imager, when the eye model was rotated horizontally -15 degrees (to the left). Also shown in Fig. 1B are the pupil border (dotted ellipse), the PC (small white star) and the center of CR (small red cross). The horizontal offset between PC and CR in pixels is linearly related to horizontal eye position between -30 and +30 degrees (Fig. 1C, slope=1.05 pixels/deg; r=0.99). The vertical offset fluctuation was very small (SD=1.07 pixels). Similarly, the vertical PC/CR offset was linearly related to vertical eye position between -25 and +25 degrees (slope=1.25 pixels/deg; r=0.99) with small horizontal fluctuation (SD=1.48 pixels). The root mean square error of repeated measures of PC/CR offsets at -10, -5, 0, 5, and 10 deg horizontal eye positions ranged from 0.1 to 0.7 pixels.
The benchtop prototype of the holographic waveguide imager demonstrated a linear relationship between the angular eye position and the PC/CR vector over a range of 60 horizontal degrees and 50 vertical degrees. These preliminary results confirmed that the holographic waveguide technology can be a feasible platform for developing a wearable eye tracker.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1 Schematic diagram of the prototype holographic waveguide based eye tracker and experimental results.
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