Liu Changgeng, Pazzucconi Beatrice, Liu Juan, Liu Lei, Yao Xincheng
Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, 60607, USA.
Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optoelectronics, Beijing Institute of Technology, Beijing, 100081, China.
Proc SPIE Int Soc Opt Eng. 2018 Jan-Feb;10474. doi: 10.1117/12.2290065. Epub 2018 Feb 19.
We demonstrated the feasibility of using holographic waveguide for eye tracking. A custom-built holographic waveguide, a 20 mm x 60 mm x 3 mm flat glass substrate with integrated in- and out-couplers, was used for the prototype development. The in- and out-couplers, photopolymer films with holographic fringes, induced total internal reflection in the glass substrate. Diffractive optical elements were integrated into the in-coupler to serve as an optical collimator. The waveguide captured images of the anterior segment of the eye right in front of it and guided the images to a processing unit distant from the eye. The vector connecting the pupil center (PC) and the corneal reflex (CR) of the eye was used to compute eye position in the socket. An eye model, made of a high quality prosthetic eye, was used prototype validation. The benchtop prototype demonstrated a linear relationship between the angular eye position and the PC/CR vector over a range of 60 horizontal degrees and 30 vertical degrees at a resolution of 0.64-0.69 degrees/pixel by simple pixel count. The uncertainties of the measurements at different angular positions were within 1.2 pixels, which indicated that the prototype exhibited a high level of repeatability. These results confirmed that the holographic waveguide technology could be a feasible platform for developing a wearable eye tracker. Further development can lead to a compact, see-through eye tracker, which allows continuous monitoring of eye movement during real life tasks, and thus benefits diagnosis of oculomotor disorders.
我们展示了使用全息波导进行眼动追踪的可行性。一个定制的全息波导，即一块20毫米×60毫米×3毫米的带有集成输入和输出耦合器的平板玻璃基板，被用于原型开发。输入和输出耦合器是带有全息条纹的光聚合物薄膜，在玻璃基板中引发全内反射。衍射光学元件被集成到输入耦合器中以用作光学准直器。该波导捕捉其正前方眼睛前段的图像，并将这些图像引导至远离眼睛的处理单元。连接眼睛瞳孔中心（PC）和角膜反射（CR）的向量被用于计算眼睛在眼窝中的位置。一个由高质量假眼制成的眼睛模型被用于原型验证。通过简单的像素计数，台式原型在60度水平和30度垂直的范围内，以0.64 - 0.69度/像素的分辨率展示了眼睛角度位置与PC/CR向量之间的线性关系。不同角度位置测量的不确定性在1.2像素以内，这表明该原型具有高度的可重复性。这些结果证实，全息波导技术可能是开发可穿戴眼动追踪器的一个可行平台。进一步的发展可以带来一个紧凑、透视的眼动追踪器，它能够在现实生活任务中持续监测眼睛运动，从而有益于动眼神经障碍的诊断。
