{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T17:38:55Z","timestamp":1779903535605,"version":"3.53.1"},"reference-count":34,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2023,8,29]],"date-time":"2023-08-29T00:00:00Z","timestamp":1693267200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"MCIN\/AEI\/10.13039\/501100011033 and European Union NextGenerationEU\/PRTR","award":["CPP2021-008931"],"award-info":[{"award-number":["CPP2021-008931"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and European Union NextGenerationEU\/PRTR","award":["PDC2022-133597-C42"],"award-info":[{"award-number":["PDC2022-133597-C42"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and European Union NextGenerationEU\/PRTR","award":["TED2021-131739B-C21"],"award-info":[{"award-number":["TED2021-131739B-C21"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and European Union NextGenerationEU\/PRTR","award":["PID2022-137344OB-C32"],"award-info":[{"award-number":["PID2022-137344OB-C32"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and \u201cERDF A way of making Europe\u201d","award":["CPP2021-008931"],"award-info":[{"award-number":["CPP2021-008931"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and \u201cERDF A way of making Europe\u201d","award":["PDC2022-133597-C42"],"award-info":[{"award-number":["PDC2022-133597-C42"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and \u201cERDF A way of making Europe\u201d","award":["TED2021-131739B-C21"],"award-info":[{"award-number":["TED2021-131739B-C21"]}]},{"name":"MCIN\/AEI\/10.13039\/501100011033 and \u201cERDF A way of making Europe\u201d","award":["PID2022-137344OB-C32"],"award-info":[{"award-number":["PID2022-137344OB-C32"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>One of the main challenges faced by iris recognition systems is to be able to work with people in motion, where the sensor is at an increasing distance (more than 1 m) from the person. The ultimate goal is to make the system less and less intrusive and require less cooperation from the person. When this scenario is implemented using a single static sensor, it will be necessary for the sensor to have a wide field of view and for the system to process a large number of frames per second (fps). In such a scenario, many of the captured eye images will not have adequate quality (contrast or resolution). This paper describes the implementation in an MPSoC (multiprocessor system-on-chip) of an eye image detection system that integrates, in the programmable logic (PL) part, a functional block to evaluate the level of defocus blur of the captured images. In this way, the system will be able to discard images that do not have the required focus quality in the subsequent processing steps. The proposals were successfully designed using Vitis High Level Synthesis (VHLS) and integrated into an eye detection framework capable of processing over 57 fps working with a 16 Mpixel sensor. Using, for validation, an extended version of the CASIA-Iris-distance V4 database, the experimental evaluation shows that the proposed framework is able to successfully discard unfocused eye images. But what is more relevant is that, in a real implementation, this proposal allows discarding up to 97% of out-of-focus eye images, which will not have to be processed by the segmentation and normalised iris pattern extraction blocks.<\/jats:p>","DOI":"10.3390\/s23177491","type":"journal-article","created":{"date-parts":[[2023,8,29]],"date-time":"2023-08-29T08:59:05Z","timestamp":1693299545000},"page":"7491","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Real-Time Embedded Eye Image Defocus Estimation for Iris Biometrics"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8270-2062","authenticated-orcid":false,"given":"Camilo A.","family":"Ruiz-Beltr\u00e1n","sequence":"first","affiliation":[{"name":"Departamento Tecnologia Electronica, ETSI Telecomunicacion, University of M\u00e1laga, 29071 M\u00e1laga, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6570-5859","authenticated-orcid":false,"given":"Adri\u00e1n","family":"Romero-Garc\u00e9s","sequence":"additional","affiliation":[{"name":"Departamento Tecnologia Electronica, ETSI Telecomunicacion, University of M\u00e1laga, 29071 M\u00e1laga, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9216-0372","authenticated-orcid":false,"given":"Mart\u00edn","family":"Gonz\u00e1lez-Garc\u00eda","sequence":"additional","affiliation":[{"name":"Departamento Tecnologia Electronica, ETSI Telecomunicacion, University of M\u00e1laga, 29071 M\u00e1laga, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1573-5096","authenticated-orcid":false,"given":"Rebeca","family":"Marfil","sequence":"additional","affiliation":[{"name":"Departamento Tecnologia Electronica, ETSI Telecomunicacion, University of M\u00e1laga, 29071 M\u00e1laga, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3147-0307","authenticated-orcid":false,"given":"Antonio","family":"Bandera","sequence":"additional","affiliation":[{"name":"Departamento Tecnologia Electronica, ETSI Telecomunicacion, University of M\u00e1laga, 29071 M\u00e1laga, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1016\/j.patcog.2017.05.021","article-title":"Long range iris recognition: A survey","volume":"72","author":"Nguyen","year":"2017","journal-title":"Pattern Recognit."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3962","DOI":"10.1109\/TIP.2014.2337714","article-title":"Accurate Iris Recognition at a Distance Using Stabilized Iris Encoding and Zernike Moments Phase Features","volume":"23","author":"Tan","year":"2014","journal-title":"IEEE Trans. Image Process."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"116505","DOI":"10.1016\/j.eswa.2022.116505","article-title":"Real-time embedded eye detection system","volume":"194","author":"Pedraza","year":"2022","journal-title":"Expert Syst. Appl."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2107","DOI":"10.1109\/TIP.2018.2881830","article-title":"A Local Metric for Defocus Blur Detection Based on CNN Feature Learning","volume":"28","author":"Zeng","year":"2019","journal-title":"IEEE Trans. Image Process."},{"key":"ref_5","first-page":"3143","article-title":"An FPGA-Based Energy-Efficient Reconfigurable Convolutional Neural Network Accelerator for Object Recognition Applications","volume":"68","author":"Li","year":"2021","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"83224","DOI":"10.1109\/ACCESS.2020.2988311","article-title":"An Efficient Task Assignment Framework to Accelerate DPU-Based Convolutional Neural Network Inference on FPGAs","volume":"8","author":"Zhu","year":"2020","journal-title":"IEEE Access"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"83664","DOI":"10.1109\/ACCESS.2019.2924330","article-title":"FPGA Design of Real-Time MDFD System Using High Level Synthesis","volume":"7","author":"Wei","year":"2019","journal-title":"IEEE Access"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"10054","DOI":"10.1109\/JSEN.2023.3259150","article-title":"Implementing Hand Gesture Recognition Using EMG on the Zynq Circuit","volume":"23","author":"Kerdjidj","year":"2023","journal-title":"IEEE Sens. J."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.sysarc.2012.06.002","article-title":"FPGA-based architecture for the real-time computation of 2-D convolution with large kernel size","volume":"58","year":"2012","journal-title":"J. Syst. Archit."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1126","DOI":"10.1109\/TIP.2017.2771563","article-title":"Edge-Based Defocus Blur Estimation with Adaptive Scale Selection","volume":"27","author":"Karaali","year":"2018","journal-title":"IEEE Trans. Image Process."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Zhang, D., and Jain, A.K. (2005). Advances in Biometrics, Springer.","DOI":"10.1007\/11608288"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"572","DOI":"10.1109\/TIFS.2008.924606","article-title":"A Selective Feature Information Approach for Iris Image-Quality Measure","volume":"3","author":"Belcher","year":"2008","journal-title":"IEEE Trans. Inf. Forensics Secur."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Li, X., Sun, Z., and Tan, T. (2011, January 11\u201314). Comprehensive assessment of iris image quality. Proceedings of the 2011 18th IEEE International Conference on Image Processing, Brussels, Belgium.","DOI":"10.1109\/ICIP.2011.6116326"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Batyrshin, I., and Sidorov, G. (2011). Advances in Soft Computing, Springer.","DOI":"10.1007\/978-3-642-25330-0"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1852","DOI":"10.1016\/j.patcog.2011.03.009","article-title":"Defocus map estimation from a single image","volume":"44","author":"Zhuo","year":"2011","journal-title":"Pattern Recognit."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Chen, D.J., Chen, H.T., and Chang, L.W. (2016, January 25\u201328). Fast defocus map estimation. Proceedings of the 2016 IEEE International Conference on Image Processing (ICIP), Phoenix, AZ, USA.","DOI":"10.1109\/ICIP.2016.7533103"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1109\/TIP.2021.3127850","article-title":"Defocus Image Deblurring Network with Defocus Map Estimation as Auxiliary Task","volume":"31","author":"Ma","year":"2022","journal-title":"IEEE Trans. Image Process."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"5943","DOI":"10.1109\/TIP.2016.2617460","article-title":"Defocus Map Estimation From a Single Image Based on Two-Parameter Defocus Model","volume":"25","author":"Liu","year":"2016","journal-title":"IEEE Trans. Image Process."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"107485","DOI":"10.1016\/j.patcog.2020.107485","article-title":"Defocus map estimation from a single image using improved likelihood feature and edge-based basis","volume":"107","author":"Liu","year":"2020","journal-title":"Pattern Recognit."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Bertero, M., and Boccacci, P. (1998). Introduction to Inverse Problems in Imaging, IOP Publishing.","DOI":"10.1887\/0750304359"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1109\/TIP.2013.2286328","article-title":"Parametric Blur Estimation for Blind Restoration of Natural Images: Linear Motion and Out-of-Focus","volume":"23","author":"Oliveira","year":"2014","journal-title":"IEEE Trans. Image Process."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"4879","DOI":"10.1109\/TIP.2013.2279316","article-title":"Estimating Spatially Varying Defocus Blur from A Single Image","volume":"22","author":"Zhu","year":"2013","journal-title":"IEEE Trans. Image Process."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1519","DOI":"10.1109\/TPAMI.2003.1251145","article-title":"Personal identification based on iris texture analysis","volume":"25","author":"Ma","year":"2003","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_24","first-page":"1910","article-title":"Blind Image Blur Estimation via Deep Learning","volume":"25","author":"Yan","year":"2016","journal-title":"IEEE Trans. Image Process."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1109\/TCSVT.2003.818350","article-title":"How iris recognition works","volume":"14","author":"Daugman","year":"2004","journal-title":"IEEE Trans. Circuits Syst. Video Technol."},{"key":"ref_26","first-page":"62020D","article-title":"Image quality assessment for iris biometric","volume":"6202","author":"Flynn","year":"2006","journal-title":"Biometric Technology for Human Identification III, Proceedings of the Defense and Security Symposium, Orlando, FL, USA, 17\u201321 April 2006"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Mohammad, K., and Agaian, S. (2009, January 11\u201314). Efficient FPGA implementation of convolution. Proceedings of the 2009 IEEE International Conference on Systems, Man and Cybernetics, San Antonio, TX, USA.","DOI":"10.1109\/ICSMC.2009.5346737"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Sreenivasulu, M., and Meenpal, T. (2019, January 20\u201322). Efficient Hardware Implementation of 2D Convolution on FPGA for Image Processing Application. Proceedings of the 2019 IEEE International Conference on Electrical, Computer and Communication Technologies (ICECCT), Coimbatore, India.","DOI":"10.1109\/ICECCT.2019.8869347"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Kanade, T., Jain, A., and Ratha, N.K. (2005). Audio- and Video-Based Biometric Person Authentication, Springer.","DOI":"10.1007\/978-3-540-31638-1"},{"key":"ref_30","unstructured":"Wan, J., He, X., and Shi, P. (2007, January 16\u201318). An Iris Image Quality Assessment Method Based on Laplacian of Gaussian Operation. Proceedings of the IAPR International Workshop on Machine Vision Applications, Tokyo, Japan."},{"key":"ref_31","unstructured":"Viola, P., and Jones, M. (2001, January 8\u201314). Rapid object detection using a boosted cascade of simple features. Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001, Kauai, HI, USA."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Lienhart, R., Liang, L., and Kuranov, A. (2003, January 6\u20139). A detector tree of boosted classifiers for real-time object detection and tracking. Proceedings of the 2003 International Conference on Multimedia and Expo. ICME \u201903. Proceedings (Cat. No.03TH8698), Baltimore, MD, USA.","DOI":"10.1109\/ICME.2003.1221607"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Dong, W., Sun, Z., and Tan, T. (2009, January 4\u20136). A Design of Iris Recognition System at a Distance. Proceedings of the 2009 Chinese Conference on Pattern Recognition, Nanjing, China.","DOI":"10.1109\/CCPR.2009.5344030"},{"key":"ref_34","unstructured":"Yambay, D., Doyle, J.S., Bowyer, K.W., Czajka, A., and Schuckers, S. (October, January 29). LivDet-iris 2013\u2014Iris Liveness Detection Competition 2013. Proceedings of the IEEE International Joint Conference on Biometrics, Clearwater, FL, USA."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/17\/7491\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:41:34Z","timestamp":1760128894000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/17\/7491"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,8,29]]},"references-count":34,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2023,9]]}},"alternative-id":["s23177491"],"URL":"https:\/\/doi.org\/10.3390\/s23177491","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,8,29]]}}}