{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:00:59Z","timestamp":1760241659982,"version":"build-2065373602"},"reference-count":37,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2018,7,15]],"date-time":"2018-07-15T00:00:00Z","timestamp":1531612800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51575388"],"award-info":[{"award-number":["51575388"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this paper, a novel 3D gaze estimation method for a wearable gaze tracking device is proposed. This method is based on the pupillary accommodation reflex of human vision. Firstly, a 3D gaze measurement model is built. By uniting the line-of-sight convergence point and the size of the pupil, this model can be used to measure the 3D Point-of-Regard in free space. Secondly, a gaze tracking device is described. By using four cameras and semi-transparent mirrors, the gaze tracking device can accurately extract the spatial coordinates of the pupil and eye corner of the human eye from images. Thirdly, a simple calibration process of the measuring system is proposed. This method can be sketched as follows: (1) each eye is imaged by a pair of binocular stereo cameras, and the setting of semi-transparent mirrors can support a better field of view; (2) the spatial coordinates of the pupil center and the inner corner of the eye in the images of the stereo cameras are extracted, and the pupil size is calculated with the features of the gaze estimation method; (3) the pupil size and the line-of-sight convergence point when watching the calibration target at different distances are computed, and the parameters of the gaze estimation model are determined. Fourthly, an algorithm for searching the line-of-sight convergence point is proposed, and the 3D Point-of-Regard is estimated by using the obtained line-of-sight measurement model. Three groups of experiments were conducted to prove the effectiveness of the proposed method. This approach enables people to obtain the spatial coordinates of the Point-of-Regard in free space, which has great potential in the application of wearable devices.<\/jats:p>","DOI":"10.3390\/s18072292","type":"journal-article","created":{"date-parts":[[2018,7,16]],"date-time":"2018-07-16T04:05:33Z","timestamp":1531713933000},"page":"2292","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["A Novel Method for Estimating Free Space 3D Point-of-Regard Using Pupillary Reflex and Line-of-Sight Convergence Points"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3158-8746","authenticated-orcid":false,"given":"Zijing","family":"Wan","sequence":"first","affiliation":[{"name":"State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"},{"name":"MOEMS Education Ministry Key Laboratory, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6199-1632","authenticated-orcid":false,"given":"Xiangjun","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"},{"name":"MOEMS Education Ministry Key Laboratory, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kai","family":"Zhou","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaoyun","family":"Chen","sequence":"additional","affiliation":[{"name":"MOEMS Education Ministry Key Laboratory, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3965-5728","authenticated-orcid":false,"given":"Xiaoqing","family":"Wang","sequence":"additional","affiliation":[{"name":"MOEMS Education Ministry Key Laboratory, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2018,7,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1109\/MC.1993.274943","article-title":"Hot topics-eye-gaze computer interfaces: What you look at is what you get","volume":"26","author":"Jacob","year":"1993","journal-title":"Computer"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"799","DOI":"10.1016\/S0923-5965(98)00044-7","article-title":"Eye and gaze tracking for visually controlled interactive stereoscopic displays","volume":"14","author":"Talmi","year":"1999","journal-title":"Signal Process. Image Commun."},{"key":"ref_3","unstructured":"D\u2019Orazio, T., Leo, M., and Distante, A. (2004, January 14\u201317). Eye detection in face images for a driver vigilance system. Proceedings of the IEEE Intelligent Vehicles Symposium, Parma, Italy."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"801","DOI":"10.1682\/JRRD.2007.05.0075","article-title":"Adaptive eye-gaze tracking using neural-network-based user profiles to assist people with motor disability","volume":"45","author":"Sesin","year":"2008","journal-title":"J. Rehabil. Res. Dev."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.cviu.2004.07.006","article-title":"Special issue: Eye detection and tracking","volume":"98","author":"Ji","year":"2005","journal-title":"Comput. Vis. Image Underst."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"478","DOI":"10.1109\/TPAMI.2009.30","article-title":"In the Eye of the Beholder: A Survey of Models for Eyes and Gaze","volume":"32","author":"Hansen","year":"2010","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_7","unstructured":"Beymer, D., and Flickner, M. (2003, January 18\u201320). Eye gaze tracking using an active stereo head. Proceedings of the 2003 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, Madison, WI, USA."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1119","DOI":"10.1109\/TCE.2012.6414976","article-title":"Long range eye gaze tracking system for a large screen","volume":"58","author":"Cho","year":"2012","journal-title":"IEEE Trans. Consum. Electron."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"542","DOI":"10.4218\/etrij.12.0111.0193","article-title":"Gaze Detection by Wearable Eye-Tracking and NIR LED-Based Head-Tracking Device Based on SVR","volume":"34","author":"Cho","year":"2012","journal-title":"ETRI J."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1123","DOI":"10.1109\/TSMCB.2008.926606","article-title":"A novel gaze estimation system with one calibration point","volume":"38","author":"Villanueva","year":"2008","journal-title":"IEEE Trans. Syst. Man Cybern. Part B"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1109\/TBME.2009.2039351","article-title":"An Automatic Personal Calibration Procedure for Advanced Gaze Estimation Systems","volume":"57","author":"Dmitri","year":"2010","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Chen, J., and Ji, Q. (2011, January 20\u201325). Probabilistic gaze estimation without active personal calibration. Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, Providence, RI, USA.","DOI":"10.1109\/CVPR.2011.5995675"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1536","DOI":"10.1364\/AO.56.001536","article-title":"Calibration method for 3D gaze tracking systems","volume":"56","author":"Chi","year":"2017","journal-title":"Appl. Opt."},{"key":"ref_14","unstructured":"Baluja, S., and Pomerleau, D. (1994). Non-Intrusive Gaze Tracking Using Artificial Neural Networks, Carnegie Mellon University."},{"key":"ref_15","unstructured":"Ishikawa, T. (2004). Passive Driver Gaze Tracking with Active Appearance Models, Robotics Institute."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Zhang, X., Sugano, Y., Fritz, M., and Bulling, A. (2015, January 7\u201312). Appearance-based gaze estimation in the wild. Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, Boston, MA, USA.","DOI":"10.1109\/CVPR.2015.7299081"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Sugano, Y., Matsushita, Y., and Sato, Y. (2014, January 23\u201328). Learning-by-synthesis for appearance-based 3d gaze estimation. Proceedings of the Computer Vision and Pattern Recognition, Columbus, OH, USA.","DOI":"10.1109\/CVPR.2014.235"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Wood, E., Baltru\u0161aitis, T., Morency, L.P., Robinson, P., and Bulling, A. (2016, January 14\u201317). Learning an appearance-based gaze estimator from one million synthesised images. Proceedings of the Biennial ACM Symposium on Eye Tracking Research & Applications, Charleston, SC, USA.","DOI":"10.1145\/2857491.2857492"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Sugano, Y., Matsushita, Y., Sato, Y., and Koike, H. (2008, January 12\u201318). An Incremental Learning Method for Unconstrained Gaze Estimation. Proceedings of the 10th European Conference on Computer Vision: Part III, Marseille, France.","DOI":"10.1007\/978-3-540-88690-7_49"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2033","DOI":"10.1109\/TPAMI.2014.2313123","article-title":"Adaptive Linear Regression for Appearance-Based Gaze Estimation","volume":"36","author":"Lu","year":"2014","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"660","DOI":"10.1049\/iet-cvi.2015.0316","article-title":"Fast and accurate algorithm for eye localisation for gaze tracking in low-resolution images","volume":"10","author":"George","year":"2016","journal-title":"IET Comput. Vis."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1145\/2897824.2925947","article-title":"Realtime 3D eye gaze animation using a single RGB camera","volume":"35","author":"Wang","year":"2016","journal-title":"ACM Trans. Graph."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"531","DOI":"10.1109\/THMS.2014.2318324","article-title":"Estimating 3-D Point-of-Regard in a Real Environment Using a Head-Mounted Eye-Tracking System","volume":"44","author":"Takemura","year":"2014","journal-title":"IEEE Trans. Hum. Mach. Syst."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Su, D., and Li, Y.F. (2017, January 5\u20138). Toward flexible calibration of head-mounted gaze trackers with parallax error compensation. Proceedings of the IEEE International Conference on Robotics and Biomimetics, Macau, China.","DOI":"10.1109\/ROBIO.2016.7866370"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Li, B., Fu, H., Wen, D., and LO, W. (2018). Etracker: A Mobile Gaze-Tracking System with Near-Eye Display Based on a Combined Gaze-Tracking Algorithm. Sensors, 18.","DOI":"10.3390\/s18051626"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1016\/j.ins.2015.02.004","article-title":"Real time gaze estimation with a consumer depth camera","volume":"320","author":"Li","year":"2015","journal-title":"Inf. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"414","DOI":"10.1109\/THMS.2015.2477507","article-title":"Gaze Estimation from Color Image Based on the Eye Model with Known Head Pose","volume":"46","author":"Li","year":"2016","journal-title":"IEEE Trans. Hum.-Mach. Syst."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"8363","DOI":"10.3390\/s140508363","article-title":"An Investigation on the Feasibility of Uncalibrated and Unconstrained Gaze Tracking for Human Assistive Applications by Using Head Pose Estimation","volume":"14","author":"Cazzato","year":"2014","journal-title":"Sensors"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2824","DOI":"10.1109\/TBME.2017.2677902","article-title":"3D-Gaze-based Robotic Grasping through Mimicking Human Visuomotor Function for People with Motion Impairments","volume":"64","author":"Li","year":"2017","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Pirri, F., Pizzoli, M., and Rudi, A. (2011, January 20\u201325). A general method for the point of regard estimation in 3D space. Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, Providence, RI, USA.","DOI":"10.1109\/CVPR.2011.5995634"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"8680541","DOI":"10.1155\/2016\/8680541","article-title":"Low Cost Eye Tracking: The Current Panorama","volume":"2016","author":"Ferhat","year":"2016","journal-title":"Comput. Intell. Neurosci."},{"key":"ref_32","unstructured":"Loewenfeld, I.E., and Lowenstein, O. (1993). The Pupil: Anatomy, Physiology, and Clinical Applications, Wayne State University Press."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1097\/00006324-200205000-00013","article-title":"Kappa and Hirschberg ratio measured with an automated video gaze tracker","volume":"79","author":"Schaeffel","year":"2002","journal-title":"Optom. Vis. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1275","DOI":"10.1007\/s00138-016-0776-4","article-title":"Pupil detection for head-mounted eye tracking in the wild: An evaluation of the state of the art","volume":"27","author":"Fuhl","year":"2016","journal-title":"Mach. Vis. Appl."},{"key":"ref_35","first-page":"1735","article-title":"A novel harris multi-scale corner detection algorithm","volume":"29","author":"Zhang","year":"2007","journal-title":"J. Electron. Inf. Technol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"828","DOI":"10.1152\/physrev.1972.52.4.828","article-title":"Accommodation function of the human eye","volume":"52","author":"Toates","year":"1972","journal-title":"Physiol. Rev."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1082","DOI":"10.1364\/JOSA.57.001082","article-title":"Spatiotemporal modulation transfer in the human eye","volume":"57","author":"Koenderink","year":"1967","journal-title":"J. Opt. Soc. Am."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/7\/2292\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:12:16Z","timestamp":1760195536000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/7\/2292"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,7,15]]},"references-count":37,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2018,7]]}},"alternative-id":["s18072292"],"URL":"https:\/\/doi.org\/10.3390\/s18072292","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2018,7,15]]}}}