{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:17:10Z","timestamp":1760235430463,"version":"build-2065373602"},"reference-count":35,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2021,8,21]],"date-time":"2021-08-21T00:00:00Z","timestamp":1629504000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2017M3A9E2056461","2020R1A2C4001606"],"award-info":[{"award-number":["2017M3A9E2056461","2020R1A2C4001606"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Ministry of Science and ICT, the Ministry of Trade, Industry and Energy, the Ministry of Health &amp; Welfare, the Ministry of Food and Drug Safety","award":["202017D01"],"award-info":[{"award-number":["202017D01"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper introduces an ambient light rejection (ALR) circuit for the autonomous adaptation of a subretinal implant system. The sub-retinal implants, located beneath a bipolar cell layer, are known to have a significant advantage in spatial resolution by integrating more than a thousand pixels, compared to epi-retinal implants. However, challenges remain regarding current dispersion in high-density retinal implants, and ambient light induces pixel saturation. Thus, the technical issues of ambient light associated with a conventional image processing technique, which lead to high power consumption and area occupation, are still unresolved. Thus, it is necessary to develop a novel image-processing unit to handle ambient light, considering constraints related to power and area. In this paper, we present an ALR circuit as an image-processing unit for sub-retinal implants. We first introduced an ALR algorithm to reduce the ambient light in conventional retinal implants; next, we implemented the ALR algorithm as an application-specific integrated chip (ASIC). The ALR circuit was fabricated using a standard 0.35-\u03bcm CMOS process along with an image-sensor-based stimulator, a sensor pixel, and digital blocks. As experimental results, the ALR circuit occupies an area of 190 \u00b5m2, consumes a power of 3.2 mW and shows a maximum response time of 1.6 s at a light intensity of 20,000 lux. The proposed ALR circuit also has a pixel loss rate of 0.3%. The experimental results show that the ALR circuit leads to a sensor pixel (SP) being autonomously adjusted, depending on the light intensity.<\/jats:p>","DOI":"10.3390\/s21165638","type":"journal-article","created":{"date-parts":[[2021,8,22]],"date-time":"2021-08-22T22:59:27Z","timestamp":1629673167000},"page":"5638","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Ambient Light Rejection Integrated Circuit for Autonomous Adaptation on a Sub-Retinal Prosthetic System"],"prefix":"10.3390","volume":"21","author":[{"given":"Hosung","family":"Kang","sequence":"first","affiliation":[{"name":"Department of Medical Science, Korea University, Seoul 02841, Korea"}]},{"given":"Hojong","family":"Choi","sequence":"additional","affiliation":[{"name":"Department of Medical IT Convergence Engineering, Kumoh National Institute of Technology, 350-27 Gumi-Daero, Gumi 39253, Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5866-465X","authenticated-orcid":false,"given":"Jungsuk","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Gachon Univesity, Hambakmoe-ro 191, Incheon 21936, Korea"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1383","DOI":"10.1016\/j.clinph.2019.11.029","article-title":"An update on retinal prostheses","volume":"131","author":"Ayton","year":"2020","journal-title":"Clin. Neurophysiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2569","DOI":"10.1016\/S0042-6989(99)00052-8","article-title":"Pattern electrical stimulation of the human retina","volume":"39","author":"Humayun","year":"1999","journal-title":"Vision Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"334","DOI":"10.1080\/02713683.2016.1270326","article-title":"Advances in retinal prosthetic research: A systematic review of engineering and clinical characteristics of current prosthetic initiatives","volume":"42","author":"Cheng","year":"2017","journal-title":"Curr. Eye Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"432","DOI":"10.1016\/j.ophtha.2017.09.019","article-title":"Assessment of the electronic retinal implant alpha AMS in restoring vision to blind patients with end-stage retinitis pigmentosa","volume":"125","author":"Edwards","year":"2018","journal-title":"Ophthalmology"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2946","DOI":"10.1109\/JSSC.2007.908693","article-title":"A 232-channel epiretinal stimulator ASIC","volume":"42","author":"Ortmanns","year":"2007","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1946","DOI":"10.1109\/JSSC.2010.2055371","article-title":"An integrated 256-channel epiretinal prosthesis","volume":"45","author":"Chen","year":"2010","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1230","DOI":"10.1109\/TBCAS.2020.3036091","article-title":"1225-channel neuromorphic retinal-prosthesis SoC with localized temperature-regulation","volume":"14","author":"Park","year":"2020","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"036015","DOI":"10.1088\/1741-2552\/abe6b8","article-title":"Vertical-junction photodiodes for smaller pixels in retinal prostheses","volume":"18","author":"Huang","year":"2021","journal-title":"J. Neural Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"529","DOI":"10.1109\/TED.2019.2960295","article-title":"Retinal Prosthesis Using Thin-Film Devices on a Transparent Substrate and Wireless Power Transfer","volume":"67","author":"Tomioka","year":"2020","journal-title":"IEEE Trans. Electron Devices"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"5035","DOI":"10.1167\/iovs.03-0341","article-title":"Facial recognition using simulated prosthetic pixelized vision","volume":"44","author":"Thompson","year":"2003","journal-title":"Invest. Ophthalmol. Visual Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1547","DOI":"10.1016\/j.ophtha.2015.04.032","article-title":"Long-term results from an epiretinal prosthesis to restore sight to the blind","volume":"122","author":"Ho","year":"2015","journal-title":"Ophthalmology"},{"key":"ref_12","first-page":"179","article-title":"Functionality and performance of the subretinal implant chip Alpha AMS","volume":"30","author":"Daschner","year":"2018","journal-title":"Sens. Mater."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1167\/iovs.15-18400","article-title":"The effect of electric cross-talk in retinal neurostimulation","volume":"57","author":"Matteucci","year":"2016","journal-title":"Invest. Ophthalmol. Visual Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.preteyeres.2016.05.002","article-title":"Retinal stimulation strategies to restore vision: Fundamentals and systems","volume":"53","author":"Yue","year":"2016","journal-title":"Prog. Retin. Eye Res."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"066027","DOI":"10.1088\/1741-2552\/ab34b3","article-title":"Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays","volume":"16","author":"Ho","year":"2019","journal-title":"J. Neural Eng."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"290","DOI":"10.1109\/JSSC.2008.2007436","article-title":"A CMOS chip with active pixel array and specific test features for subretinal implantation","volume":"44","author":"Rothermel","year":"2008","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1016\/j.mejo.2005.07.002","article-title":"Review of CMOS image sensors","volume":"37","author":"Bigas","year":"2006","journal-title":"Microelectron. J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"897","DOI":"10.1109\/JSEN.2007.894897","article-title":"A wide-dynamic-range compression image sensor with negative-feedback resetting","volume":"7","author":"Ikebe","year":"2007","journal-title":"IEEE Sens. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2590","DOI":"10.1109\/TED.2008.2003023","article-title":"A dual-capture wide dynamic range CMOS image sensor using floating-diffusion capacitor","volume":"55","author":"Kim","year":"2008","journal-title":"IEEE Trans. Electron Devices"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1672","DOI":"10.1109\/JSSC.2011.2144130","article-title":"A 160 \u00d7 120-Pixels Range Camera with In-Pixel Correlated Double Sampling and Fixed-Pattern Noise Correction","volume":"46","author":"Perenzoni","year":"2011","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_21","first-page":"70","article-title":"Light-controlled biphasic current stimulator IC using CMOS image sensors for high-resolution retinal prosthesis and in vitro experimental results with rd1 mouse","volume":"62","author":"Oh","year":"2014","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Kang, H., Abbasi, W.H., Kim, S.-W., and Kim, J. (2019). Fully Integrated Light-Sensing Stimulator Design for Subretinal Implants. Sensors, 19.","DOI":"10.3390\/s19030536"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1097\/ICU.0000000000000467","article-title":"Implantation, removal and replacement of subretinal electronic implants for restoration of vision in patients with retinitis pigmentosa","volume":"29","author":"Katrin","year":"2018","journal-title":"Curr. Opin. Ophthalmol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1383","DOI":"10.1016\/j.clinph.2019.11.029","article-title":"An update on retinal prostheses","volume":"131","author":"Lauren","year":"2020","journal-title":"Clin. Neurophysiol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/j.jneumeth.2004.10.020","article-title":"Electrical stimulation of excitable tissue: Design of efficacious and safe protocols","volume":"141","author":"Merrill","year":"2005","journal-title":"J. Neurosci. Methods"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2998","DOI":"10.1109\/JSSC.2006.884868","article-title":"A 1\/1.8-inch 6.4 MPixel 60 frames\/s CMOS image sensor with seamless mode change","volume":"41","author":"Yoshihara","year":"2006","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Nitta, Y., Muramatsu, Y., Amano, K., Toyama, T., Mishina, K., Suzuki, A., Taura, T., Kato, A., Kikuchi, M., and Yasui, Y. (2006, January 6\u20139). High-speed digital double sampling with analog CDS on column parallel ADC architecture for low-noise active pixel sensor. Proceedings of the 2006 IEEE International Solid State Circuits Conference-Digest of Technical Papers, San Francisco, CA, USA.","DOI":"10.1109\/ISSCC.2006.1696261"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1109\/4.68134","article-title":"Two novel fully complementary self-biased CMOS differential amplifiers","volume":"26","author":"Bazes","year":"1991","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1591","DOI":"10.1109\/TCSI.2011.2150910","article-title":"A two-stage fully differential inverter-based self-biased CMOS amplifier with high efficiency","volume":"58","author":"Figueiredo","year":"2011","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_30","first-page":"1295","article-title":"Impedance characterization and modeling of electrodes for biomedical applications","volume":"52","author":"Franks","year":"2005","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_31","first-page":"675","article-title":"In vivo impedance characterization of cortical recording electrodes shows dependence on electrode location and size","volume":"66","author":"John","year":"2018","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_32","first-page":"045003","article-title":"Electrode-size dependent thresholds in subretinal neuroprosthetic stimulation","volume":"15","author":"Andrea","year":"2021","journal-title":"J. Neural Eng."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1097","DOI":"10.1016\/j.ophtha.2020.02.024","article-title":"Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration","volume":"127","author":"Daniel","year":"2020","journal-title":"Ophthalmology"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Rothermel, A., Kaim, H., Gambach, S., Schuetz, H., Moll, S., Steinhoff, R., Herrmann, T., and Zeck, G. (2020, January 20\u201324). Subretinal Stimulation Chip Set with 3025 Electrodes, Spatial Peaking Filter, Illumination Adaptation and Implant Lifetime Optimization. Proceedings of the 2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), Montreal, QC, Canada.","DOI":"10.1109\/EMBC44109.2020.9175722"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Moll, S., Gambach, S., Sch\u00fctz, H., Steinhoff, R., Kaim, H., and Rothermel, A. (2020, January 20\u201324). System design of a physiological ambient illumination adaptation for subretinal stimulator. Proceedings of the 2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), Montreal, QC, Canada.","DOI":"10.1109\/EMBC44109.2020.9175818"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5638\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:48:39Z","timestamp":1760165319000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5638"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,21]]},"references-count":35,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["s21165638"],"URL":"https:\/\/doi.org\/10.3390\/s21165638","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2021,8,21]]}}}