{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T07:01:53Z","timestamp":1784530913710,"version":"3.55.0"},"reference-count":46,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,17]],"date-time":"2026-07-17T00:00:00Z","timestamp":1784246400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Advances in microelectronics have driven the miniaturization of endoscopic systems, leading to increasingly compact devices with enhanced optical and electronic performance. However, the current state-of-the-art commercial endoscopes\u2014typically ranging from several millimeters to over 1 cm in diameter\u2014still face significant limitations when accessing delicate anatomical structures such as the Fallopian tubes, urethra, and other narrow cavities. In this paper, we introduce an ultracompact endoscope based on the use of a CMOS image sensor from ams OSRAM (NanEyeM) and a single micro-LED (LTW-FC03DCD5). We achieved a total diameter of 1.8 mm, compatible with ultra-narrow cavities of the human body. Optically, a minimal correlated color temperature of 10,343 K and a maximal color rendering index of 73.6 were achieved. These values allow for the detection of structures of small dimensions by morphological and vascular contrast. The optical system demonstrated the ability to resolve up to 83 lp\/mm, with a diagonal field-of-view of 115.0\u00b0 \u00b1 2.4\u00b0, measured at different working distances, suitable for working distances encountered in narrow anatomical cavities. This work represents a first prototype for direct visual imaging in human organs not previously accessible by endoscopy, assisting healthcare professionals in clinical assessment and supporting the diagnosis of diseases.<\/jats:p>","DOI":"10.3390\/s26144544","type":"journal-article","created":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T06:09:09Z","timestamp":1784527749000},"page":"4544","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A 1.8 mm-Diameter Chip-on-Tip Endoscope with Integrated \u00b5LED Illumination for Narrow-Cavity Imaging"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-3094-7624","authenticated-orcid":false,"given":"Manuela P.","family":"S\u00e1","sequence":"first","affiliation":[{"name":"CMEMS-UMinho, University of Minho, 4800-058 Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bernardo S.","family":"Dores","sequence":"additional","affiliation":[{"name":"CMEMS-UMinho, University of Minho, 4800-058 Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2527-5006","authenticated-orcid":false,"given":"Jos\u00e9 A.","family":"Rodrigues","sequence":"additional","affiliation":[{"name":"CMEMS-UMinho, University of Minho, 4800-058 Guimar\u00e3es, Portugal"},{"name":"LABBELS\u2014Associate Laboratory, Braga\/Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5991-1069","authenticated-orcid":false,"given":"Jos\u00e9 H.","family":"Correia","sequence":"additional","affiliation":[{"name":"CMEMS-UMinho, University of Minho, 4800-058 Guimar\u00e3es, Portugal"},{"name":"LABBELS\u2014Associate Laboratory, Braga\/Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1752-2687","authenticated-orcid":false,"given":"Marino J.","family":"Maciel","sequence":"additional","affiliation":[{"name":"CMEMS-UMinho, University of Minho, 4800-058 Guimar\u00e3es, Portugal"},{"name":"LABBELS\u2014Associate Laboratory, Braga\/Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,17]]},"reference":[{"key":"ref_1","first-page":"54","article-title":"Advances in the Design of Miniature Single-Use Medical Endoscopy CMOS Image Sensors","volume":"62","author":"Sami","year":"2023","journal-title":"Proc. Univ. RUSE"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"0289","DOI":"10.34133\/cbsystems.0289","article-title":"Development of a Bioinspired Soft Robotic System for Teleoperated Endoscopic Surgery","volume":"6","author":"Zhu","year":"2025","journal-title":"Cyborg Bionic Syst."},{"key":"ref_3","first-page":"0616","article-title":"A Bionic Multichannel Whisker System for Assisting Endoluminal Intervention","volume":"69","author":"Wang","year":"2026","journal-title":"Cyborg Bionic Syst."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"055024","DOI":"10.1088\/2057-1976\/ac1d88","article-title":"Design, Simulation, and Fabrication of an Ingestible Capsule with Gastric Balloon for Obesity Treatment","volume":"7","author":"Freitas","year":"2021","journal-title":"Biomed. Phys. Eng. Express"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1111\/den.14111","article-title":"History of Endoscopes: Contribution of the Japan Gastroenterological Endoscopy Society","volume":"34","author":"Fujishiro","year":"2022","journal-title":"Dig. Endosc."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"684","DOI":"10.1016\/j.cgh.2023.11.030","article-title":"From Hirschowitz to 2023: Modern Endoscopy and Beyond","volume":"22","author":"Schulman","year":"2024","journal-title":"Clin. Gastroenterol. Hepatol."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Boese, A., Wex, C., Croner, R., Liehr, U.B., Wendler, J.J., Weigt, J., Walles, T., Vorwerk, U., Lohmann, C.H., and Friebe, M. (2022). Endoscopic Imaging Technology Today. Diagnostics, 12.","DOI":"10.3390\/diagnostics12051262"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"(2021). Pentax Colonoscopes and Gastroscopes. Biomed. Saf. Stand., 51, 167\u2013168.","DOI":"10.1097\/01.BMSAS.0000802948.37104.10"},{"key":"ref_9","unstructured":"Omnivision (2026, May 06). The Future of Endoscopy Is CMOS\u2014It\u2019s Time to Transition from CCD. Available online: https:\/\/www.ovt.com\/blog\/the-future-of-endoscopy-is-cmos\/."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"3921","DOI":"10.1073\/pnas.1117135109","article-title":"High-Grade Serous Ovarian Cancer Arises from Fallopian Tube in a Mouse Model","volume":"109","author":"Kim","year":"2012","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"339","DOI":"10.1158\/1940-6207.CAPR-15-0072","article-title":"The Fallopian Tube: From Back Stage to Center Stage","volume":"8","author":"Greene","year":"2015","journal-title":"Cancer Prev. Res."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Jiang, B. (2025). Correction: Analysis of Global Ovarian Cancer Disease Burden and Its Changing Trend from 1990 to 2021. BMC Womens Health, 25.","DOI":"10.1186\/s12905-025-04188-y"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"15","DOI":"10.14311\/1109","article-title":"Technical Evolution of Medical Endoscopy","volume":"49","author":"Gross","year":"2009","journal-title":"Acta Polytech."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Gounella, R., Ferreira, G.M., Amorim, M.L.M., Soares, J.N., and Carmo, J.P. (2024). A Review of Optical Sensors in CMOS. Electronics, 13.","DOI":"10.3390\/electronics13040691"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1401","DOI":"10.1016\/j.sse.2008.04.012","article-title":"CMOS Image Sensors: State-of-the-Art","volume":"52","author":"Theuwissen","year":"2008","journal-title":"Solid-State Electron."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.sna.2019.04.026","article-title":"Development of a Small-Diameter and High-Resolution Industrial Endoscope with CMOS Image Sensor","volume":"296","author":"Yang","year":"2019","journal-title":"Sens. Actuators A Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2136","DOI":"10.30574\/wjaets.2025.15.2.0763","article-title":"Rise of Flexible Endoscopy Camera in Diagnosis and Treatment: A Minimally Invasive Approach","volume":"15","author":"Suresh","year":"2025","journal-title":"World J. Adv. Eng. Technol. Sci."},{"key":"ref_18","first-page":"1","article-title":"Coherent Narrow-Band Light Source for Miniature Endoscopes","volume":"25","author":"Chen","year":"2019","journal-title":"IEEE J. Sel. Top. Quantum Electron."},{"key":"ref_19","unstructured":"(2026, May 05). Myriad Fiber Imaging Visualization Systems \u201cChip on Tip\u201d. Available online: https:\/\/myriadfiber.com\/cmos-endoscopes-manufacturing\/."},{"key":"ref_20","unstructured":"(2026, May 06). ams-OSRAM Ams NanEyeM Miniature Camera Modules. Available online: https:\/\/ams-osram.com\/products\/sensor-solutions\/cmos-image-sensors\/ams-naneyem-miniature-camera-modules."},{"key":"ref_21","unstructured":"(2026, May 06). Mouser Electronics LTW-FC03DCD5. Available online: https:\/\/pt.mouser.com\/ProductDetail\/LITEON\/LTW-FC03DCD5?qs=Y0Uzf4wQF3mWfyLMUAv4qg%3D%3D&utm_id=22436684098&utm_source=google&utm_medium=cpc&utm_marketing_tactic=emeacorp&gad_source=1&gad_campaignid=22433190671&gbraid=0AAAAADn_wf2res9XJNp-PmbWHs9nnDQkt&gcl."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1080\/15502724.2018.1518717","article-title":"Tutorial: The LuxPy Python Toolbox for Lighting and Color Science","volume":"16","author":"Smet","year":"2020","journal-title":"LEUKOS"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1080\/15502724.2014.989802","article-title":"Tutorial: Color Rendering and Its Applications in Lighting","volume":"12","author":"Houser","year":"2016","journal-title":"LEUKOS"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1080\/15502724.2014.839020","article-title":"Practical Use and Calculation of CCT and Duv","volume":"10","author":"Ohno","year":"2014","journal-title":"LEUKOS"},{"key":"ref_25","first-page":"137","article-title":"New Technologies for Reproductive Medicine: Laparoscopy, Endoscopy, Robotic Surgery and Gynecology. A Review of the Literature","volume":"62","author":"Cho","year":"2010","journal-title":"Minerva Ginecol."},{"key":"ref_26","unstructured":"Eppeldauer, G.P., Cooksey, C.C., Yoon, H.W., Hanssen, L.M., Podobedov, V.B., Vest, R.E., Arp, U., and Miller, C.C. (September, January 28). Broadband Radiometric LED Measurements. Proceedings of the SPIE Optics + Photonics: Optical Engineering + Applications Symposium, San Diego, CA, USA."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Wang, Q., Tran, C., Burns, P., and Namazi, N.M. (2024). Best Practices for Measuring the Modulation Transfer Function of Video Endoscopes. Sensors, 24.","DOI":"10.3390\/s24155075"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Sawyer, T.W., Luthman, A.S., and Bohndiek, S.E. (2017, January 16). Evaluation of Illumination Systems for Wide-Field Hyperspectral Imaging in Biomedical Applications. Proceedings of the SPIE 10068 Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XV, San Francisco, CA, USA.","DOI":"10.1117\/12.2250633"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"e2396","DOI":"10.1002\/rcs.2396","article-title":"Endoscopic Image Luminance Enhancement Based on the Inverse Square Law for Illuminance and Retinex","volume":"18","author":"Wang","year":"2022","journal-title":"Int. J. Med. Robot. Comput. Assist. Surg."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1186\/s43593-023-00044-4","article-title":"Real Time Full-Color Imaging in a Meta-Optical Fiber Endoscope","volume":"3","author":"Huang","year":"2023","journal-title":"eLight"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1441","DOI":"10.1364\/BOE.8.001441","article-title":"Endoscope Field of View Measurement","volume":"8","author":"Wang","year":"2017","journal-title":"Biomed. Opt. Express"},{"key":"ref_32","unstructured":"(2024). Digital Cameras\u2014Resolution and Spatial Frequency Responses (Standard No. ISO 12233:2024)."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Zhang, S., Wang, F., Wu, X., and Gao, K. (2023). MTF Measurement by Slanted-Edge Method Based on Improved Zernike Moments. Sensors, 23.","DOI":"10.3390\/s23010509"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Bianchi, L., Asadi, S., De Landro, M., Korganbayev, S., and Saccomandi, P. (2022, January 22\u201324). Measurement of Thermal Properties of Biological Tissues and Tissue-Mimicking Phantom with a Dual-Needle Sensor. Proceedings of the 2022 IEEE International Symposium on Medical Measurements and Applications (MeMeA), Messina, Italy.","DOI":"10.1109\/MeMeA54994.2022.9856408"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"076001","DOI":"10.1117\/1.JBO.26.7.076001","article-title":"Sub-Millimeter Endoscope Demonstrates Feasibility of in Vivo Reflectance Imaging, Fluorescence Imaging, and Cell Collection in the Fallopian Tubes","volume":"26","author":"Cordova","year":"2021","journal-title":"J. Biomed. Opt."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"3335","DOI":"10.1364\/BOE.7.003335","article-title":"Supercontinuum as a Light Source for Miniaturized Endoscopes","volume":"7","author":"Lu","year":"2016","journal-title":"Biomed. Opt. Express"},{"key":"ref_37","unstructured":"(2026, May 25). International Electrotechnical Comission IEC 60601-2-41:2021. Available online: https:\/\/webstore.iec.ch\/en\/publication\/62677."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1138","DOI":"10.21037\/qims-22-728","article-title":"A Narrative Review: Narrow-Band Imaging Endoscopic Classifications","volume":"13","author":"Yang","year":"2023","journal-title":"Quant. Imaging Med. Surg."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Slomka, B., Duan, S., Knapp, T.G., Lima, N., Sontz, R., Merchant, J.L., and Sawyer, T.W. (2023). Design, Fabrication, and Preclinical Testing of a Miniaturized, Multispectral, Chip-on-Tip, Imaging Probe for Intraluminal Fluorescence Imaging of the Gastrointestinal Tract. Front. Photonics, 3.","DOI":"10.3389\/fphot.2022.1067651"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1476","DOI":"10.1016\/j.ultras.2014.04.018","article-title":"Influence of Subcutaneous Fat in Surface Heating of Ultrasonic Diagnostic Transducers","volume":"54","author":"Petrella","year":"2014","journal-title":"Ultrasonics"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1080\/01478885.2021.1972250","article-title":"Study of Fallopian Tube Anatomy and Mechanical Properties to Determine Pressure Limits for Endoscopic Exploration","volume":"45","author":"Howard","year":"2022","journal-title":"J. Histotechnol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"e202000011","DOI":"10.1002\/tbio.202000011","article-title":"Reengineering a Falloposcope Imaging System for Clinical Use","volume":"2","author":"Kiekens","year":"2020","journal-title":"Transl. Biophotonics"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1002\/lsm.23877","article-title":"First Clinical Feasibility and Safety Study of a Novel Multimodality Fallopian Tube Imaging Endoscope","volume":"57","author":"Rocha","year":"2025","journal-title":"Lasers Surg. Med."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"032005","DOI":"10.1117\/1.JBO.25.3.032005","article-title":"Submillimeter Diameter Rotary-Pullback Fiber-Optic Endoscope for Narrowband Red-Green-Blue Reflectance, Optical Coherence Tomography, and Autofluorescence In Vivo Imaging","volume":"25","author":"Buenconsejo","year":"2019","journal-title":"J. Biomed. Opt."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"288","DOI":"10.1515\/cdbme-2020-3073","article-title":"Novel Flexible Endoscope Concept with Swiveling Camera Tip","volume":"6","author":"Boese","year":"2020","journal-title":"Curr. Dir. Biomed. Eng."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Cheng, S.-H., Lin, Y.-T., Lu, H.-T., Tsuei, Y.-C., Chu, W., and Chu, W.-C. (2024). The Evolution of Spinal Endoscopy: Design and Image Analysis of a Single-Use Digital Endoscope Versus Traditional Optic Endoscope. Bioengineering, 11.","DOI":"10.3390\/bioengineering11010099"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/14\/4544\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T06:10:17Z","timestamp":1784527817000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/14\/4544"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,17]]},"references-count":46,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["s26144544"],"URL":"https:\/\/doi.org\/10.3390\/s26144544","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,17]]}}}