This thesis studies the design and optical performance of collimating lenses for modulating the UV lights from an ultraviolet light emitting diode (UV LED). The lens design is based on freeform surfaces and total internal reflection (TIR) surfaces for collimating the UV light which might have a relatively large diverging angle when emitting from the LED. The advantages of this kind of lens design are higher optical efficiency, lower fabrication cost, and compact lens size. A systematic approach for the lens design is developed based on geometrical optics by assuming a point source for the LED. However, since LEDs are finite area light sources in reality, the optical performance and characteristics of the obtained lens profile along with its corresponding UV LED are simulated and analyzed by a commercial ray tracing software (Zemax).
The designed lens/LED units are used for two different applications: (1) to illuminate a fly’s eyes homogenizer system and therefore project the UV light into an area with uniform intensity distribution; and (2) to collectively form an array of UV light sources for UV exposure. For the first purpose and when working with a high power (13.4 Watt) UV-LED with a 3×3 mm2 emitting area size and a divergent angle of 120°, a freeform/TIR collimating lens can achieve a high optical efficiency of 67.6 % and a collimation angle of ±4.5°. For the second applications, a conventional double convex lens with both aspheric surfaces is designed for two kinds of UV-LEDs of 60o and 120o divergent angles, and the optical efficiency is 42.62 % and 30.70 %, respectively, with and collimation angle of ±3.94° and ±2.55°, respectively. Finally, to further improve the optical performance, a freeform/TIR collimating lens is designed for a low power UV-LED with a 1.25×1.25 mm2 emitting area size and a divergent angle of 120°. The optical efficiency is 45.8 % with the collimation angle of ±2°. Experimental measurements have been carried out on the conventional double convex lens along with two UV LEDs, and the measured data are analyzed and compared with their theoretical counterparts.

1. H. Ries and J. Muschaweck,”Tailored freeform optical surfaces,” J. Opt. Soc. Am. A., vol. 19, pp. 590-595 (2002).
2. A. Pawlak and K. Zaremba,”Reflector luminaire with high power light-emitting diodes for general lighting,” Appl. Opt., vol. 47, pp. 467-473 (2008).
3. Domhardt A., , Rohlfing U., , Weingaertner S., , Klinger K., , Koob D., , Manz K., , and Lemmer U., “ New design tools for LED headlamps. ,” Proc. SPIE. 0277-786X 7003, , 70032C (2008).
4. Domhardt A., , Weingaertner S., , Rohlfing U., , and Lemmer U., “ TIR optics for non-rotationally symmetric illumination design. ,” Proc. SPIE. 0277-786X 7103, , 710304 (2008).
5. Hao X., , Zheng Z., , Liu X., , and Gu P., “ Freeform surface lens design for uniform illumination. ,” J. Opt. A, Pure Appl, Opt., vol. 39, pp.1464-4258 (2008).
6. Ding Y., , Liu X., , Zheng Z., , and Gu P., “ Freeform LED lens for uniform illumination. ,” Opt. Express, vol. 17, pp. 12958–12966 (2008).
7. P. Benítez, J. C. Miñano, J. Blen, R. Mohedano, J. Chaves, O. Dross, M. Hernández, and W. Falicoff,“Simultaneous multiple surface optical design method in three dimensions,” Opt. Eng., vol. 43, pp. 1489–1502 (2004).
8. Y. Ding, X. Liu, Z. R. Zheng, and P. F. Gu, “Freeform LED lens for uniform illumination,” Opt. Express, vol. 16, pp. 12958–12966 (2008).
9. L. Sun, S. Jin, and S. Cen, “Free-form microlens for illumination applications,” Appl. Opt., vol. 48, pp. 5520–5527 (2009).
10. F. R. Fournier, W. J. Cassarly, and J. P. Rolland, “Fast freeform reflector generation using source-target maps,” Opt. Express, vol. 18, pp. 5295–5304 (2010).
11. W. Zhang, Q. Liu, H. Gao, and F. Yu, “Free-form reflector optimization for general lighting,” Opt. Eng., vol. 49, pp. 929-936 (2010).
12. G. Wang, L. Wang, L. Li, D. Wang, and Y. Zhang, “Secondary optical lens designed in the method of sourcetarget mapping,” Appl. Opt., vol. 50, pp. 4031–4036 (2011).
13. J.-J. Chen and C.-T. Lin, “Freeform surface design for a light-emitting diode–based collimating lens,” Opt. Eng., vol. 49, pp. 093-101 (2010).
14. C-Y Tsai,” “Free-form surface design method for collimator TIR lens," J. Opt. Soc. Am. A., vol. 33, pp. 785-792 (2016).
15. Y. X. Tao, Yang Jian-feng, X Bin, Zhang G-Q, and B. U. Fan,” Design of a novel LED collimating element based on freeform surface” Optoelectron. Lett., vol. 9, pp. 1673-1685 (2013).
16. J. J Chen, Chin-Tang Lin,” Freeform surface design for a light-emitting diode–based collimating lens” Opt. Eng., vol. 49, pp. 9301-9318 (2010).
17. Zemax fly’s eye homogenizer. http://www.zemax.com/os/resources/learn/knowledgebase/flys-eye-arrays-for-uniform-illumination-in-digita.
18. Maik Zimmermann, Norbert Lindleinb, Reinhard Voelkelc, Kenneth J.Weiblec “Microlens Laser Beam Homogenizer – From Theory to Application”. Proc. SPIE 6663, Laser Beam Shaping VIII, 666302 (September 12, 2007).
19. Data sheet for the UV-LED used for the LG 60° 3535 series 365 nm UV-LED. https://www.lasercomponents.com/de/?embedded=1&file=fileadmin/user_upload/home/Datasheets/lg/lg_uv_led_overview.pdf&no_cache=1.
20. Data sheet for the UV-LED used for the printed circuit board exposure system CUN66A1B.http://www.neumueller.com/datenblatt/seoulviosys/CUN66A1B_R10.pdf.
21. Data sheet for the UV-LED used for fly’s eye homogenizer application. http://www.luminus.com/products/Luminus_CBT90UV_Datasheet.pdf
22. Data sheet for power meter used to measure the light intensity and collimation angle. http://www.ophiropt.com/laser--measurement/sites/default/files/IS-1_3A-IS_3A-IS-IRG_1.pdf.
23. Pinhole mounted on the power meter.www.edmundoptics.com/optomechanics/irises-apertures/pinholes-slits/100mum-aperture-diameter-mounted-precision-pinhole/.
24. Power meter reader used to measure the light intensity and collimation angle. . http://www.ophiropt.com/laser--measurement/laser-power-energy-meters/products/smart-displays/nova2?r=drp
25. Sigma Koki stage. http://www.global-optosigma.com/en_jp/Catalogs/gno/? from=page&pnoname=SGSP20%28XY%29&ccode=W9012&dcode=&gnoname=SGSP20-85%28XY%29.
26. UV- LED application. http://www.ledsmagazine.com/articles/print/volume-12/issue-11/features/strategically-speaking/emerging-applications-for-uv-leds-drive-broad-interest.html.