Thiết kế chế tạo ma trận thấu kính biên dạng tự do nhằm tăng hiệu suất trong chiếu sáng cây trồng

BỘ GIÁO DỤC VÀ ĐÀO TẠO VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ - Kiều Ngọc Minh THIẾT KẾ CHẾ TẠO MA TRẬN THẤU KÍNH BIÊN DẠNG TỰ DO NHẰM TĂNG HIỆU SUẤT TRONG CHIẾU SÁNG CÂY TRỒNG LUẬN VĂN THẠC SĨ NGÀNH VẬT LÝ Hà Nội – Tháng năm 2021 BỘ GIÁO DỤC VÀ ĐÀO TẠO VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ - Kiều Ngọc Minh THIẾT KẾ CHẾ TẠO MA TRẬN THẤU KÍNH BIÊN DẠNG TỰ DO NHẰM TĂNG HIỆU SUẤT TRONG CHIẾU SÁNG CÂY TRỒNG Chuyên ngành: Mã số: Vật lý kỹ thuật 8520401 LUẬN VĂN THẠC SĨ NGÀNH VẬT LÝ CÁN BỘ HƯỚNG DẪN KHOA HỌC: TS Tống Quang Công Hà Nội – Tháng năm 2021 LỜI CAM ĐOAN Tôi xin cam đoan đề tài nghiên cứu luận văn cơng trình nghiên cứu dựa tài liệu, số liệu tơi tự tìm hiểu nghiên cứu Chính vậy, kết nghiên cứu đảm bảo trung thực khách quan Đồng thời, kết chưa xuất nghiên cứu Các số liệu, kết nêu luận văn trung thực sai tơi hồn chịu trách nhiệm Người làm luận văn Kiều Ngọc Minh LỜI CẢM ƠN Luận văn thực Phòng Laser bán dẫn – Viện Khoa học vật liệu – Viện Hàn lâm Khoa học & Công nghệ Việt Nam Trước tiên, xin gửi lời cảm ơn tới Tiến Sĩ Tống Quang Công, PGS TS Trần Quốc Tiến người thầy hướng dẫn, giúp đỡ cho không gian làm việc chuyên nghiệp suốt trình thực luận văn Tơi xin bày tỏ lịng biết ơn đến TS Vũ Ngọc Hải, NCS Vũ Hoàng cán nhân viên Phòng Laser bán dẫn – Viện Khoa học vật liệu tận tình bảo hỗ trợ tơi q trình nghiên cứu thực đề tài Tôi xin bày tỏ lời cảm ơn sâu sắc đến thầy cô giáo giảng dạy năm qua ban Lãnh đạo, phòng Đào tạo, phòng chức Học viện Khoa học Công nghệ giúp đỡ, bảo thời gian học tập Học viện Khoa học Công nghệ - Viện Hàn lâm Khoa học & Công nghệ Việt Nam Cuối xin gửi lời cảm ơn đến gia đình, bạn bè người thân hỗtrợ giúp đỡ suốt trình học tập thời gian thực khóa luận Tơi xin chân thành cảm ơn! Hà Nội, tháng năm 2021 Kiều Ngọc Minh MỤC LỤC DANH MỤC VIẾT TẮT DANH MỤC BẢNG BIỂU DANH MỤC HÌNH ẢNH MỞ ĐẦU CHƯƠNG TỔNG QUAN 1.1 Nguồn sáng LED cho chiếu sáng trồng 1.1.1 Nguồn sáng dải 1.1.2 Nguồn sáng điểm (LED Spotlight) 1.2 Các thông số nguồn đèn điểm chiếu sáng trồng 10 1.2.1 Cường độ chiếu sáng 10 1.2.2 Bước sóng ánh sáng 11 1.2.3 Phân bố ánh sáng 13 1.2.4 Cường độ xạ 14 1.3 Tối ưu phân bố quang nguồn sáng điểm sử dụng kỹ thuật quang học không tạo ảnh 15 1.3.1 Khái niệm quang học không tạo ảnh 15 1.3.2 Linh kiện quang học quang học không tạo ảnh 17 1.3.3 Ứng dụng kỹ thuật quang học không tạo ảnh 18 1.3.4 Cơng cụ tính tốn mơ (Mathlab, Light tools) 19 CHƯƠNG KỸ THUẬT THỰC NGHIỆM 24 2.1 Tính tốn, mơ nguồn sáng, linh kiện quang học 24 2.1.1 Tính tốn, thiết kế biên dạng thấu kính 24 2.1.2 Mơ hình dạng quang trình thấu kính biên dạng tự 30 2.2 Chế tạo mẫu thấu kính biên dạng tự 32 2.2.1 Phương pháp chế tạo thấu kính 32 2.2.2 Gia cơng hồn thiện mẫu thấu kính biên dạng tự 36 2.3 Kỹ thuật đo đạc 37 2.3.1 Xây dựng hệ đo phân bố ánh sáng 37 2.3.2 Lắp ráp hoàn thiện hệ đo 38 2.3.3 Xây dựng hệ đo thông số truyền qua thấu kính biên dạng tự 40 2.4 Lắp ráp đèn LED điểm hoàn chỉnh 42 CHƯƠNG KẾT QUẢ VÀ THẢO LUẬN 44 3.1 Kết đo thông số nguồn sáng điểm (chip LED) 44 3.1.1 Kết đo thông số quang điện chip LED 44 3.1.2 Kết đo phổ chip LED 44 3.2 Kết chế tạo mô phân bố quang lối hệ thấu kính biên dạng tự 45 3.2.1 Kết mơ phỏng, chế tạo thấu kính dạng kép 45 3.2.2 Kết mô phỏng, chế tạo thấu kính dạng ma trận 47 3.2.3 Kết mô khác 48 3.3 Kết đo thơng số thấu kính 50 3.3.1 Kết đo độ truyền qua thấu kính 50 3.3.2 Kết đo phân bố ánh sáng tạo nguồn sáng hệ thấu kính biên dạng tự 51 3.3.3 Phân bố ánh sáng phụ thuộc vào góc nghiêng thấu kính biên dạng tự thấu kính chuẩn trực 54 3.3.4 Phân bố ánh sáng phụ thuộc vào vị trí đặt chip LED 56 KẾT LUẬN VÀ KIẾN NGHỊ 58 TÀI LIỆU THAM KHẢO 59 CƠNG TRÌNH ĐÃ CƠNG BỐ 61 DANH MỤC VIẾT TẮT COB: Chips On Board CNC: Computer Numerical Control CRI: Color Rendering Index LASER: Light Amplification by Stimulated Emission of Radiation LCD: Liquid-crystal Display LED: Light-Emitting Diode PAR: Photosynthetically Active Radiation PE: Photon Efficacy PMMA: Poly Methyl Methacrylate PPF: Photosynthetic Photon Flux PPFD: Photosynthetic Photon Flux Density SMD: Surface-Mount Device DANH MỤC BẢNG BIỂU Bảng 2.1: Thông số thiết kế thấu kính dạng kép Bảng 2.2: Thơng số thiết kế thấu kính dạng ma trận Bảng 2.3: Thơng số phép đo phân bố ánh sáng DANH MỤC HÌNH ẢNH Trang Hình 1.1: Đèn LED dạng ứng dụng chiếu sáng trồng Hình 1.2: Đèn LED sử dụng chiếu sáng điều khiển hoa hoa cúc 10 Hình 1.3: Sự khác Lux lumen 11 Hình 1.4: Hình ảnh thể định nghĩa bước sóng 12 Hình 1.5: Sự khác quang học tạo ảnh quang học không tạo ảnh 17 Hình 1.6: Tính tốn, mơ vẽ đồ thị phần mềm matlab 20 Hình 1.7: Mơ hình thiết kế phần mềm Light Tools 22 Hình 2.1: Sơ đồ khối thiết kế đèn LED tăng độ đồng phân bố 24 Hình 2.2: Thấu kính chuẩn trực sử dụng chế tạo đèn 25 Hình 2.3: Ngun tắc thiết kế thấu kính dựa quang hình tự do[3] 25 Hình 2.4: Quy trình tính tốn thấu kính biên dạng tự dạng kép 27 Hình 2.5: Quy trình thiết kế thấu kính biên dạng tự dạng kép 28 Hình 2.6: Quy trình thiết kế thấu kính biên dạng tự dạng ma trận 30 Hình 2.7: Cấu hình chiếu sáng đèn LED với hệ thấu kính 31 Hình 2.8: Cấu trúc phân tích mát phân tích tia 32 Hình 2.9: Máy CNC 3004001000mm dùng chế tạo biên dạng 33 thấu kính Hình 2.10: Mũi V-bit mũi phay 3mm sử dụng chế tạo thấu kính 33 Hình 2.11: Thiết kế thấu kính phần mềm Auto CAD 34 Hình 2.12: Mơ đường mũi khoan cơng đoạn tạo biên dạng bề mặt thấu kính 34 Hình 2.13: Máy CNC chế tạo thấu kính biên dạng tự dạng kép 35 Hình 2.14: Máy CNC chế tạo thấu kính biên dạng tự dạng ma trận 35 Hình 2.15: Các cơng cụ xử lý bề mặt thấu kính 36 Hình 2.16: Sơ đồ hệ đo phân bố quang cho thấu kính 37 Hình 2.17: Hình ảnh hệ dịch chuyển hai chiều 38 Hình 2.18: Nguồn Thorlabs ITC 4005 39 Hình 2.19: Arduino R3 photodiode sử dụng phép đo 39 Hình 2.20: Sơ đồ hệ đo độ truyền qua thấu kính 40 Hình 2.21: Thiết bị đo cơng suất quang MELLES GRIOT 41 Hình 2.22: Laser diode 650nm cơng suất 200mW 41 Hình 2.23: Thấu kính biên dạng tự thấu kính chuẩn trực sau ghép nối 42 Hình 2.24: Linh kiện đèn LED lắp ráp 42 Hình 3.1: Đồ thị đáp ứng cơng suất phụ thuộc vào dịng ni LED 635nm 44 Hình 3.2: Kết đo phổ ánh sáng đèn LED sử dụng thiết kế phép đo 45 Hình 3.3: Thấu kính biên dạng tự dạng kép 45 Hình 3.4: Kết mơ phân bố chiếu sáng thấu kính biên dạng tự dạng kép 46 Hình 3.5: Mơ phỏng, thiết kế thấu kính biên dạng tự dạng ma trận 47 Hình 3.6: Thấu kính biên dạng tự a) trước b) sau xử lý bề mặt 47 Hình 3.7: Kết mơ phân bố chiếu sáng thấu kính biên dạng tự dạng ma trận 48 Hình 3.8: Phân bố ánh sáng mặt thu có (a) d = °; (b) d = 49 °; (c) d = °; (d) Hiệu suất độ đồng phụ thuộc vào góc lệch chuẩn trực Hình 3.9: Đồ thị đo hiệu suất truyền qua dạng thấu kính trước xử lý bề mặt 50 Hình 3.10: Đồ thị đo hiệu suất truyền qua dạng thấu kính sau xử lý bề mặt 51 Hình 3.11: Phân bố ánh sáng thấu kính biên dạng tự dạng kép a) Kết đo phân bố ánh sáng; b) Hình ảnh thực tế phân bố; c) Mặt cắt phân bố ánh sáng 52 Hình 3.12: Phân bố cường độ ánh sáng thấu kính biên dạng tự dạng ma trận bề mặt cách nguồn sáng 70cm a) Kết đo phân bố ánh sáng; b) Hình ảnh thực tế phân bố; c) Mặt cắt phân bố ánh sáng 53 Hình 3.13: Phân bố ánh sáng góc lệch khác thấu kính chuẩn trực thấu kính biên dạng tự 55 Hình 3.14: Phân bố ánh sáng giá trị góc mở thấu kính chuẩn trực.a) 14O; b) 30O; c) 43O; d) 54O 56 Mathematical Science of Optics in the 17th Century”, Kluwer Academic Publishers, 2004, ISBN 1-4020-2697-8 60 CƠNG TRÌNH ĐÃ CÔNG BỐ [1] Hoang Vu, Ngoc Minh Kieu, Do Thi Gam, Seoyong Shin, Tran Quoc Tien, Ngoc Hai Vu “Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel lenses” Applsci-774614 (2020) 61 applied sciences Article Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel Lenses Hoang Vu , Ngoc Minh Kieu 2,3 , Do Thi Gam , Seoyong Shin 1, * , Tran Quoc Tien 2,3, * and Ngoc Hai Vu 5, * * Department of Information and Communication Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin, Gyeonggi-do 17058, Korea; vuhoangims@gmail.com Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 1000, Vietnam; minhkn@ims.vast.ac.vn Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 11307, Vietnam Vietnam Academy of Science and Technology, Center for High Technology Development, Hanoi 11307, Vietnam; honggam@htd.vast.vn Faculty of Electrical and Electronics Engineering and Phenikaa Institute for Advanced Study, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 12116, Vietnam Correspondence: sshin@mju.ac.kr (S.S.); tientq@ims.vast.ac.vn (T.Q.T.); hai.vungoc@phenikaa-uni.edu.vn (N.H.V.) Received: 31 March 2020; Accepted: May 2020; Published: May 2020 Abstract: Redistribution of LED radiation in lighting is necessary in many applications In this article, we propose a new optical component design for LED lighting to achieve a higher performance The design consists of a commercial collimator and two linear Fresnel lenses The LED radiation is collimated by a collimator and redistributed by double linear Fresnel lenses to create a square-shaped, uniform distribution The linear Fresnel lenses design is based on Snell’s law and the “edge-ray principle” The optical devices are made from poly methyl methacrylate (PMMA) using a high-speed computer numerical control (CNC) machine The LED prototypes with complementary optics were measured, and the optical intensity distribution was evaluated The numerical results showed we obtained a free-form lens that produced an illumination uniformity of 78% with an efficiency of 77% We used the developed LED light sources for field experiments in agricultural lighting The figures of these tests showed positive effects with control flowering criteria and advantages of harvested products in comparison with the conventional LED sources This allows our approach in this paper to be considered as an alternative candidate for highly efficient and energy-saving LED lighting applications Keywords: geometric optical design; illumination design; light-emitting diodes; non-imaging optics Introduction In recent years, LEDs have been used in many different fields With the highlight of energy savings, long life, and safety for users [1,2], LEDs are replacing other traditional lamps However, LEDs have disadvantages of a wide beam angle (from 120◦ to 150◦ ) depending on the type of LEDs [3] and have Lambertian distributions Illumination should be redistributed using an integrated primary optical system or secondary optical system to control distribution shape and uniformity [4] Utilizing free-form optics is a new trend to design secondary optical components for LEDs The advantages of free-form optics are their unique design, compact size, and precise irradiation control [5] In order to design a free-form lens, various methods have been proposed For example, the Miñano group developed the simultaneous multiple-surface method (SMS method) [6] to design Appl Sci 2020, 10, 3257; doi:10.3390/app10093257 www.mdpi.com/journal/applsci Appl Sci 2020, 10, 3257 of 13 Appl Sci 2020, 10, x FOR PEER REVIEW of 13 a collimator for LEDs [7] This method redistributes light from the source to the reflective surface ◦ This produce a parallel beam with a beam angle of of ± 1.5° method also uses a wave-front theory of to produce a parallel beam with a beam angle ±1.5This method also uses a wave-front theory geometrical optics [8] to design a Fresnel lens with combined functions of LED collimation and of geometrical optics [8] to design a Fresnel lens with combined functions of LED collimation and redistribution for for uniform uniform illumination illumination Wang al used redistribution Wang et et al used aa light light energy energy mapping mapping method method to to make make aa compact freeform freeformlens lenscreate create even distribution in many different [5] In addition, the compact anan even distribution in many different shapesshapes [5] In addition, the optimal optimal numerical method can also be used to design free surfaces for LED arrays, such as in Yu et numerical method can also be used to design free surfaces for LED arrays, such as in Yu et al [9] All of al [9] All methods of the above work very well the in controlling distribution shape and producing the above workmethods very well in controlling distributionthe shape and producing a uniform light a uniform light distribution, but they are not flexible in different types of LEDs Equations for lens distribution, but they are not flexible in different types of LEDs Equations for lens surface calculations surface calculations have parameters dependent on the light source Therefore, the lens structure have parameters dependent on the light source Therefore, the lens structure must be recalculated must be recalculated whentypes applied to different types of LEDs when applied to different of LEDs In this paper, we present a method to fabricate an optical component for a single LED, which In this paper, we present a method to fabricate an optical component for a single LED, which can be can be applied to many types of LEDs with different beam angles to make a uniform distribution applied to many types of LEDs with different beam angles to make a uniform distribution The single The single can be aLED high-power LED or LED chip-on-board LED LED) collimator The commercial LED can be LED a high-power or chip-on-board (COB LED) The(COB commercial lens is collimator lens is placed on top of the single LED to collect and collimate the light output from the placed on top of the single LED to collect and collimate the light output from the LED The collimated LED is The collimated by beam redistributed by two Fresnel lenses [10] to create a uniform beam redistributed two is linear Fresnel lenses [10] linear to create a uniform distribution on the receiver, distribution on the receiver, as shown in Figure The surface of the linear Fresnel lens is designed as shown in Figure The surface of the linear Fresnel lens is designed by using the edge-ray by using the principle [11] and Snell’s The parameters ofare thenot linear Fresnel lens areLED not principle [11]edge-ray and Snell’s law The parameters oflaw the linear Fresnel lens dependent on the dependent on collimators, the LED chips and poly the collimators, where poly(PMMA) methyl methacrylate (PMMA) material chips and the where methyl methacrylate material is used to produce the is used to produce the lens The results include the simulation of uniformity and efficiency of the lens The results include the simulation of uniformity and efficiency of the system, comparison of system, comparison of simulations, and experimental Finally, anwas experiment simulations, and experimental results Finally, an experimentresults on chrysanthemum conductedon to chrysanthemum was conducted to control flowering Other experiments on flowering control not control flowering Other experiments on flowering control not present how the uniformity of the present how has the uniformity the light source an effect onhave plantfocused growth,on and studies have light source an effect onofplant growth, andhas most studies themost wavelength and focusedofon thesources wavelength and power of study light sources Therefore, study will bequality a useful power light [12] Therefore, this will be a[12] useful referencethis to achieve better of reference to achieve better quality of agricultural products by improving lighting uniformity agricultural products by improving lighting uniformity Figure The principle of our proposed uniform LED illumination system Figure The principle of our proposed uniform LED illumination system Module Design and Simulation Module Design and Simulation 2.1 Module Design 2.1 Module Design In this section we present the theory of designing a uniform illumination system for single LEDs We propose a novelwe uniform consisting of three parts: LED, collimator, and two In this section presentillumination the theory ofsystem designing a uniform illumination system for single LEDs perpendicular linearuniform Fresnel illumination lenses, as shown as consisting in Figure 2.ofThe collimator was used to collimate We propose a novel system three parts: LED, collimator, and two all light from the LEDFresnel source.lenses, The collimated from the collimator lenswas wasused redistributed using perpendicular linear as shown beam as in Figure The collimator to collimate all double linear lenses to provide uniform light distribution over the light from theFresnel LED source The collimated beam from the collimator lensgiven was target redistributed using double linear Fresnel lenses to provide uniform light distribution over the given target Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci Appl Sci 2020, 10, 3257 Appl Sci Sci 2020, 2020, 10, 10, xx FOR FOR PEER PEER REVIEW REVIEW Appl of 13 of 13 13 33 of Figure 2 Structure Structureofof ofLED LED illumination system composed ofLED an LED LED chip, collimator, and double double illumination system composed of an chip,chip, collimator, and double linear Figure Structure LED illumination system composed of an collimator, and Fresnel lenses.lenses linear Fresnel Fresnel lenses linear Commercial We collimator from Led-link Optics Inc [8] Commercial collimators collimators are are cone-like cone-like lenses lenses We We chose chose aaa collimator collimator from from Led-link Led-link Optics Optics Inc Inc [8] [8] Commercial collimators are cone-like lenses chose for The image of the collimator lens for our our experiment experiment The The image image of of the the commercial commercial collimator collimator lens lens is is shown shown in in Figure Figure 3 Collimators Collimators for our experiment commercial is shown in Figure Collimators are often designed for point sources and fixed to create ideal collimated while are often often designed designed for for point point sources sources and and aaa fixed fixed wavelength wavelength to to create create ideal ideal collimated collimated beams, beams, while while are wavelength beams, LED chips are usually × mm or larger Therefore, the output beams from the collimator are slightly LED chips chips are are usually usually 11 ××1 mm mm or or larger larger Therefore, Therefore, the output beams from the collimator are slightly LED divergent Details will be presented in the simulation part divergent Details Details will will be be presented presented in in the the simulation simulation part part divergent Figure Illustration of collimator using in this research: (a) Principles of Total Internal Reflection (TIR) Figure 3.AIllustration Illustration ofcollimator collimator using in in this this research: research: (a) (a) Principles Principles of of Total Total Internal Internal Reflection Reflection Figure collimator using lens; (b)3 commercialof lens (TIR) lens; lens; (b) (b) A A commercial commercial collimator collimator lens lens (TIR) The collimated beam needs to be distributed to create uniform illumination We used the double collimated beam needs to to be be distributed distributed to create create uniform illumination We used4 the double The collimated needs uniform illumination used the linearThe Fresnel lensesbeam as a redistribution module, to the design method as shown inWe Figure Adouble single linear Fresnel Fresnellens lenses as redistribution module,beam the design design method asin shown in Figure Figure 4.as Ashown single linear Fresnel lenses aa redistribution module, the as shown in A single canas redistribute the collimated in onemethod direction the receiver area,4 linear Fresnel lens can can redistribute redistribute the collimated collimated beamain in one direction direction in the the the receiver area, asconsists shown linear Fresnel lens one in receiver area, as shown in Figure 4a Although the incident the beam does not beam have uniform distribution, Fresnel lens in many Figuresmall 4a Although Although the incident incident beam does does not have have uniform distribution, the Fresnel lens in Figure 4a beam not aa uniform distribution, lens of grooves, the where each groove is similar to a linear convex lens Whenthe theFresnel collimated consists of many many small grooves, where lens, each these groove is similar similar to linear convexbeam lens (a When the consists of small where each groove is aa linear convex lens When the beam passes through thegrooves, linear Fresnel grooves will to split the incident divided collimated beam passesto through the linear lineardistribution) Fresnel lens, lens,and these grooves will split the incident incident beam (a (a collimated passes through Fresnel these grooves will split the beam beam can bebeam considered have a the uniform spread it over the receiver in one direction divided beam can be considered to have a uniform distribution) and spread it over the receiver in divided beam can be considered have a uniform distribution) it over the receiver When two linear Fresnel lenses areto perpendicular to each other, theyand willspread direct the collimated beam in to one direction direction When two linear linear Fresnel lenses are are perpendicular perpendicular to to each each other, other, they they will will direct direct the the one When two lenses spread across the receiver in twoFresnel directions collimated beamthe to spread spread across the receiver receiver in two two path directions collimated beam to across the in directions We applied “edge-ray principle” and optical length conservation to calculate the curves We applied applied the “edge-ray “edge-ray principle” and optical path length length conservation to calculate calculate the curves curves We the principle” optical path to of Fresnel lens grooves The calculation isand shown in Figure 4b andconservation consists of three steps the of Fresnel Fresnel lens grooves The calculation is shown shown in Figure Figure 4b and and consists ofsuch threeas steps of lens grooves calculation is in 4b consists of three steps Step 1: Some initialThe conditions of light source (collimated light beam) left edge AL BL , Step 1:ASome Some initial conditions of light light source (collimated (collimated light beam) beam) such as as left leftspace: edge 𝐴𝐴 𝐵𝐿𝐿‘),, conditions of source light such edge rightStep edge1: BR ofinitial the segment, position of Fresnel lens, and receiver size (illumination RR 𝐿𝐿𝐵 R right edge 𝐴𝐴𝑅𝑅𝐵𝐵𝑅𝑅 of of the the segment, segment, position position of of Fresnel Fresnel lens, lens, and and receiver receiver size size (illumination (illumination space: space: RR RR ‘)‘) right edge are selected are selected selected are Step 2: The ray to the left edge of AL BL passes through a linear Fresnel lens groove and refracts to Stepside 2: The The rayreceiver to the the left left edgeRof of 𝐴𝐿𝐿𝐵𝐵𝐿𝐿ray passes through linear Fresnel lens grooveaand and refracts Step 2: ray to edge passes aa linear lens groove refracts the right of the (point ‘) 𝐴The to thethrough right edge of ARFresnel BR passes through groove and to the the right right side ofside the receiver receiver (point R R(point ‘) The TheR) rayThese to the thetwo right edge of 𝐴𝐴𝑅𝑅𝐵𝐵𝑅at passes through groove to side of the (point ‘) ray to right edge of through aa groove refracts to the left of the receiver rays intersect the focal line Similarly, 𝑅 passes and refracts refracts to to the the left left side sideof of the the receiver receiver (point (point R) R) These These two two rays rays intersect intersect at at the the focal focal line line Similarly, Similarly, and Appl Sci Sci 2020, 2020, 10, 10, x; x; doi: doi: FOR FOR PEER PEER REVIEW REVIEW Appl www.mdpi.com/journal/applsci www.mdpi.com/journal/applsci Appl Sci Sci 2020, 2020, 10, 10, 3257 x FOR PEER REVIEW Appl Appl Sci 2020, 10, x FOR PEER REVIEW of13 13 44of of 13 the 𝐴𝑛 𝐵𝑛 rays between the 𝐴𝐿 𝐵𝐿 and 𝐴𝑅 𝐵𝑅 rays must also intersect at the focal line Based on the law the A 𝐴𝑛B𝐵𝑛 rays rays betweenthe theA𝐴𝐿B𝐵𝐿and and A𝐴𝑅B𝐵𝑅 rays raysmust mustalso alsointersect intersectat atthe thefocal focal line line Based Based on on the the the law law n n pathbetween Lconservation, L R R we have of optical length (OPL) Equation (1): of optical path length (OPL) conservation, we have Equation (1): of optical path length (OPL) conservation, we have Equation (1): 𝑛1 |𝐴 + 𝑛 = 𝑛1 |𝐴 𝐵𝑅 || + + n𝑛0 |B |𝐵𝑅F𝐹| |𝐴𝑛B𝐵𝑛||++ n𝑛0|B |𝐵𝑛F|𝐹| |𝐵 B𝐿L||| ++ F𝐹| B |A𝐿𝐿L𝐵𝐵 |BL𝐿𝐿𝐹| |= |A𝑅R𝑅𝐵 | == n𝑛11|𝐴 |A n n n R| + 𝑛 𝑛n11|𝐴 𝑛n00|𝐵 = 𝑛n11|𝐴 𝐿 𝑅 00|𝐵R 𝑅 𝐹| = 𝑛1 𝑛 𝐵𝑛 | + 𝑛00 |𝐵𝑛 𝐹| (1) (1) (1) where 𝑛0 , 𝑛1 are refractive indices of air and materials of Fresnel lens, respectively Based on the where refractive indices of air materials of Fresnel lens, lens, respectively BasedBased on theon above where n𝑛00, ,n1𝑛1are are refractive indices of and air and materials of Fresnel respectively the above equation, all coordinates of the segment surface curves are calculated equation, all coordinates of the segment surfacesurface curves curves are calculated above equation, all coordinates of the segment are calculated Step3:3:Repeat Repeatthe the calculation process, and allother the other grooves of linear lens Fresnel lens are Step calculation process, and all the grooves of linear are obtained Step 3: Repeat the calculation process, and all the other grooves ofFresnel linear Fresnel lens are obtained by procedure the same procedure by the same obtained by the same procedure Figure Design method of linear Fresnel lens (a) A single linear Fresnel lens redistributes light to a Figure Design method of linear Fresnel lens (a) A single linear Fresnel lens redistributes light to a receiver (b) Design for a segment of a linear Fresnel lens (c) The lights were spread in two dimensions receiver The lights lights were were spread spread in two dimensions dimensions receiver (b) Design for a segment of a linear Fresnel lens (c) The by double Fresnel lenses by double Fresnel lenses Because a linear linear Fresnel Fresnel lens lens distributes distributes light light in in only only one one direction, direction, we we placed placed two two linear linear Fresnel Fresnel Because Because aa linear Fresnel lens distributes light in only one direction, we placed two linear Fresnel lenses perpendicularly to propagate light in two directions over the lighting area, as shown in Figure lenses the lighting area, as as shown in Figure 4c lenses perpendicularly perpendicularlyto topropagate propagatelight lightinintwo twodirections directionsover over the lighting area, shown in Figure 4c So, a two-dimensional redistribution will create a square shape on the receiver So, a two-dimensional redistribution willwill create a square shape on the receiver 4c So, a two-dimensional redistribution create a square shape on the receiver The focal focal line is important in this linear Fresnel lens The LED light was focused on the focalfocal line The line is important in this linear Fresnel lens The LED light focused on focal the The focal line is important in this linear Fresnel lens The LED light waswas focused on the line and was spread across the receiver RR’ Figure shows the design process of the novel lens in Matlab line and spread was spread across the receiver RR’ Figure shows the design of thelens novel lens in and was across the receiver RR’ Figure shows the design processprocess of the novel in Matlab Some initial conditions of the light source such as Fresnel lens radius (r), number of grooves (a), Matlab Some initial conditions of the light source such as Fresnel lens radius (r), number of grooves Some initial conditions of the light source such as Fresnel lens radius (r), number of grooves (a), distance from the light source to the receiver (d), refractive index (n), receiver size (RR’), and so forth (a), distance the light source toreceiver the receiver (d), refractive (n), receiver size (RR’), and so distance fromfrom the light source to the (d), refractive indexindex (n), receiver size (RR’), and so forth were selected Based on these initial conditions, the coordinates of the Fresnel lens surface in one forth selected on these initial conditions, coordinates theFresnel Fresnellens lenssurface surface in in one one were were selected BasedBased on these initial conditions, thethe coordinates of of the directionwas was designed designed direction direction was designed Figure The flowchart of the design process of the linear Fresnel lens We designed aFigure linear5.Fresnel lensesofsystem for aprocess 5W power whose The flowchart the design of the COB linear LED, Fresnel lens wavelength was Figure The flowchart of the design process of the linear Fresnel lens 630 nm and had a collimator lens diameter of 100 mm The lighting distance was m, and the lighting area was m × m The number of grooves of a linear Fresnel lens affects uniformity and efficiency [10] Appl Sci 2020, 10, x; doi: FOR PEER REVIEW Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci www.mdpi.com/journal/applsci Appl Sci 2020, 10, x FOR PEER REVIEW of 13 We designed a linear Fresnel lenses system for a 5W power COB LED, whose wavelength was 630 a collimator lens diameter of 100 mm The lighting distance was m, and the lighting Appl.nm Sci and 2020,had 10, 3257 of 13 area was m × m The number of grooves of a linear Fresnel lens affects uniformity and efficiency [10] Based on the previous results in [10], we selected a linear Fresnel lens with a groove number of Based on 1the previous resultssystem in [10],specifications we selected a linear Fresnel lens with a groove number of 20 20 Table shows the optical Table shows the optical system specifications Table The double Fresnel lenses design parameters Table The double Fresnel lenses design parameters Design Parameters Design Parameters Type of LED COB Type of collimator TIR Type of LED COB Refractive index of the Fresnel lens 1.49 Type of collimator TIR Thickness of the Fresnel lens mm Refractive index of the Fresnel lens 1.49 Thickness of theofFresnel lens lens 520 mm Number of grooves the Fresnel Number of grooves ofFresnel the Fresnel Diameter of the lens lens 100 20 mm Diameter of the Fresnel lens 100 mm 2.2 Simulation: Illumination Performance and Tolerance Analyses 2.2 Simulation: TM Illumination Performance and Tolerance Analyses LightTools optical simulation software was used to simulate the structure of the proposed TM optical simulation software was used to simulate the structure of the proposed LED LED LightTools lighting system The structure of the simulation system is shown in Figure A square lighting lighting system The structure of the simulation the system is shown of in Figure A square lighting shape shape was chosen as an example to investigate performance the designed lighting system As was chosenabove, as an example investigate the performance the designed system As described described the LEDtolighting system consisted of of a single LED, alighting commercial collimator lens, above, theofLED lighting a single LED, commercial collimator lens, a set of and a set double linearsystem Fresnelconsisted lenses to of redistribute lightaon the receiver A 5W, 630 nmand COB LED double linear Fresnel lenses to redistribute light on the receiver A 5W, 630 nm COB LED was used in was used in simulations with a luminous flux of 200 lm Fresnel lenses and the collimator lens were simulations with a luminous flux of 200 lm Fresnel lenses and the collimator lens were made of poly made of poly methyl methacrylate (PMMA) material Double Fresnel lenses produced a uniform methyl methacrylate (PMMA) Fresnel lenses was produced a 2uniform of distribution of illumination on amaterial m × mDouble receiver The receiver located m awaydistribution from the light illumination on a m × m receiver The receiver was located m away from the light source source Figure The simulation parameters using LighttoolsTM software Figure The simulation parameters using LighttoolsTM software The simulation results of ray tracing of the collimator lens are shown in Figure Figure 7a shows The simulation results of in raythe tracing of the collimator lensdistance are shown inm, Figure Figure 7a shows the illumination distribution receiver With a lighting of the distribution on the the illumination incm the Figure receiver a the lighting distance of m, the distribution on the receiver area has distribution a radius of 15 7b With shows intensity distribution of the far-field receiver receiver radius of 15 Figure 7b shows the intensity distribution theflux far-field receiver It showsarea thathas theafull width at cm half-maximum intensity angle was 1.2◦ The of total was 198.4 lm It shows the fulldisplays width atthe half-maximum intensitythe angle was 1.2° The total flux was 198.4 lm Figure 7cthat intuitively rays passing through collimator lens Figure 7c intuitively displays the rays passing through the collimator lens Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci Appl Sci 2020, 10, x FOR PEER REVIEW of 13 Appl Sci 2020, 10, 3257 Appl Sci 2020, 10, x FOR PEER REVIEW of 13 of 13 Figure Simulation performance of collimator lens: (a) light distribution of output beam; (b) viewing angle of7.LED with collimator at 1.2°; and (c) raylens: tracing of LED with collimator Figure Simulation performance of collimator (a) light distribution of output beam; (b) viewing ◦ ; and Figure Simulation performance collimator (a) of light distribution of output beam; (b) viewing angle of7.LED with collimator at 1.2of (c) raylens: tracing LED with collimator Simulation results of the optical of theof COB LEDcollimator with the collimator and double angle of LED with collimator at 1.2°; distribution and (c) ray tracing LED with Fresnel lenses are shown Figure It shows the of illumination withwith a size × m square on the Simulation results ofin the optical distribution the COB LED theofcollimator and double targetSimulation surface distribution formed ashows squarethe radiation withwith size ofcollimator m× m at double height ×2 m1.8 square on the Fresnel lenses The areresults shown Figure Itdistribution illumination with aasize of 21.8 ofinthe optical of the pattern COB LED the and of m, which was in agreement with the expected shape The uniformity of illumination on the target target surface The distribution formed a square radiation pattern with a size of 1.8 m× 1.8 m at height Fresnel lenses are shown in Figure It shows the illumination size of × m square on the surface was 78% with a minimum intensity of 28radiation lux and The maximum intensity is 48 The of m, surface which was indistribution agreement with theaexpected shape uniformity of illumination onmefficiency the target target The formed square pattern with a size of 1.8lux m× 1.8 at height was Illumination is calculated Equation surface was 78% with auniformity minimum intensity of 28bylux and maximum intensity is 48 lux The of 77% m, which was in agreement with the expected shape The(2): uniformity of illumination on efficiency the target was 77%.was Illumination calculated bylux Equation (2): surface 78% with auniformity minimum is intensity of 28 and maximum intensity is 48 lux The efficiency was 77% Illumination uniformity is calculated by 𝐼Equation (2): 𝑚𝑖𝑛 = Imin (2) u𝑢= (2) 𝑎𝑣𝑔 I𝐼avg 𝐼𝑚𝑖𝑛 𝑢 = is the averaged intensity value of all the pixels.(2) where I is the minimum intensity value and I avg 𝐼𝑎𝑣𝑔 where 𝐼min is the averaged intensity value of all the pixels 𝑚𝑖𝑛 is the minimum intensity value and 𝐼𝑎𝑣𝑔 where 𝐼𝑚𝑖𝑛 is the minimum intensity value and 𝐼𝑎𝑣𝑔 is the averaged intensity value of all the pixels Figure Light distribution distribution on on an an LED LED receiver receiver using using aa collimator Figure Light collimator and and double double linear linear Fresnel Fresnel lenses lenses To evaluate the losses system, we two optical surface receivers in simulation To evaluate thedistribution losses in in the the we inserted inserted optical and surface receivers in the the lenses simulation Figure Light on system, an LED receiver usingtwo a collimator double linear Fresnel process, as shown in Figure The system losses were from the loss of the collimator and process, as shown in Figure The system losses were from the loss of the collimator and the the loss loss of of the double Fresnel lenses The loss of the collimator was from the material absorption and the Fresnel the double Fresnelthe lenses The of the collimator wastwo from the material Fresnel To evaluate losses in loss the system, we inserted optical surface absorption receivers inand thethe simulation losses The loss of the the collimator wassystem 1.56 Lux, Lux, as show show in Figure 7b The collimator losses arethe denoted losses The of was 1.56 as Figure losses are denoted process, asloss shown in collimator Figure The losses werein from the7b lossThe of collimator the collimator and loss of by L Using LightTools™ software, L can be calculated by Equation (3): 1 by 𝐿 Using LightTools™ software, 𝐿 can be calculated by Equation (3): the double Fresnel lenses The loss of the collimator was from the material absorption and the Fresnel 1 losses The loss of the collimator was Lux, source as show in Figure 7b The1 collimator losses are denoted Flux1.56 o f LED − Flux on Receiver L1 =𝐹𝑙𝑢𝑥 𝑜𝑓 (3) by 𝐿1 Using LightTools™ software, 𝐿1 𝐿𝐸𝐷 canFlux be calculated by Equation (3): 𝑠𝑜𝑢𝑟𝑐𝑒 − 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 o f LED source 𝐿1 = (3) 𝐹𝑙𝑢𝑥 𝑜𝑓 𝐿𝐸𝐷 𝑠𝑜𝑢𝑟𝑐𝑒 𝐹𝑙𝑢𝑥 𝑜𝑓 𝐿𝐸𝐷 𝑠𝑜𝑢𝑟𝑐𝑒 − 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 𝐿1 = (3) 𝐹𝑙𝑢𝑥 𝑜𝑓 𝐿𝐸𝐷 𝑠𝑜𝑢𝑟𝑐𝑒 Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci LighTools™ software, 𝐿2 can be calculated by Equation (4): 𝐿2 = 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 − 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 Appl Sci 2020, 10, 3257 (4) of 13 Figure Illustration of the simulation structure for loss analysis and ray-tracing analysis Figure Illustration of the simulation structure for loss analysis and ray-tracing analysis The loss of double Fresnel lenses was from the material absorption, the Fresnel losses, and the By calculating andGeometrical (4), respectively, wethe found L1 =lens 0.7%occurred and L2 =when 22.3% The total geometrical loss of Equations the Fresnel(3) lens loss of Fresnel a non-ideal loss is the sum of was 𝐿1 and 𝐿2 and can be calculated by Equation (5): collimated beam applied to this design Although the theoretical design was optimized for an ideal parallel beam, this design still worked with a highly collimated beam, with a slight reduction in optical efficiency and uniformity In𝑜𝑓 this research, selected collimator 𝐹𝑙𝑢𝑥 𝐿𝐸𝐷 𝑠𝑜𝑢𝑟𝑐𝑒 the − 𝐹𝑙𝑢𝑥 𝑜𝑛 𝑅𝑒𝑐𝑒𝑖𝑣𝑒𝑟 provided a beam with a 𝐿total divergence of 1.2◦ , so there were=some staggered that𝑠𝑜𝑢𝑟𝑐𝑒 could not reach the receiver The loss of(5) the 𝐹𝑙𝑢𝑥rays 𝑜𝑓 𝐿𝐸𝐷 double Fresnel lenses was 44.26 Lux The double Fresnel lenses are denoted by L2 Using LighTools™ software, be calculated byabove, Equation With Lthe parameters given the(4): efficiency was found to be 77%, including the material can absorption, the Fresnel losses, and the geometrical loss of the Fresnel lens Fluxfor on Receiver −lenses Flux onInReceiver Tolerance is an important issue free-form this study, the effects of the angle L2 = (4) Flux on Receiver between the collimator lens and double linear Fresnel lens were analyzed in terms of uniformity and efficiency as shown Equations in Figure 10 shows the line and distributions along X By calculating (3) Figure and (4),10a–c respectively, weeffects found of L1the = 0.7% L2 = 22.3% Thethe total axis axis of across theL2center of be thecalculated illuminated for dT angles of 2°, 3°, and 4° Figure 10d loss and is theYsum L1 and and can by area Equation (5): shows the results of simulations of the efficiency and the uniformity as a function of angle tolerance Flux o f LED source − Flux on Receiver When the deflection angle dT of the Ltotal = elements increased from 0° to 4°, the efficiency and the uniformity (5) Flux o f LED source optical devices changes the incident were reduced accordingly Because the change in angle between angle of the collimated light beam to the linear Fresnel lens, the distribution will be skewed to the With the parameters given above, the efficiency was found to be 77%, including the material corresponding angle, reducing uniformity The permissible deviation of dT is 1.8° as long as the absorption, the Fresnel losses, and the geometrical loss of the Fresnel lens uniformity and the efficiency are kept at 90% Tolerance is an important issue for free-form lenses In this study, the effects of the angle between the collimator lens and double linear Fresnel lens were analyzed in terms of uniformity and efficiency as shown in Figure 10 Figure 10a–c shows the effects of the line distributions along the X axis and Y axis across the center of the illuminated area for dT angles of 2◦ , 3◦ , and 4◦ Figure 10d shows the results of simulations of the efficiency and the uniformity as a function of angle tolerance When the deflection angle dT of the elements increased from 0◦ to 4◦ , the efficiency and the uniformity were reduced accordingly Because the change in angle between optical devices changes the incident angle of the collimated light beam to the linear Fresnel lens, the distribution will be skewed to the corresponding Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci angle, reducing uniformity The permissible deviation of dT is 1.8◦ as long as the uniformity and the efficiency are kept at 90% Appl Sci 2020, 10, x FOR PEER REVIEW Appl Sci 2020, 10, 3257 Appl Sci 2020, 10, x FOR PEER REVIEW of 13 of 13 of 13 Figure 10 Light distribution on a receiver with (a) dT = 2°; (b) dT=3°; and (c) dT=4° (d) Efficiency and Figure 10 Light distribution on a receiver with (a) dT = 2◦ ; (b) dT=3◦ ; and (c) dT=4◦ (d) Efficiency and uniformity depend on deflection angle dT Figure 10 depend Light distribution on aangle receiver uniformity on deflection dT with (a) dT = 2°; (b) dT=3°; and (c) dT=4° (d) Efficiency and uniformity depend on deflection angle dT In addition, addition,another another tolerance considered this which study,iswhich is the angle of the In tolerance waswas alsoalso considered in thisinstudy, the angle of the collimated collimated beam The simulation results of the efficiency and the uniformity as a function of beam addition, another tolerance was alsoand considered in thisasstudy, whichofisbeam the angle of of the the beam.InThe simulation results of the efficiency the uniformity a function angle of the collimated beam dθ of 2°, 4°, and 6° are shown in Figure 11a–c When the beam angle collimatedbeam beam.dθ The of the efficiency and theWhen uniformity as a angle function beam collimated of simulation 2◦ , 4◦ , and results 6◦ are shown in Figure 11a–c the beam wasofwider, was wider, the square shape illumination shape changed more, the efficiency uniformity and efficiency also angle of the collimated beamchanged dθ of 2°, 4°, and areuniformity shownand inand Figure 11a–c also When the beamThis angle the square illumination more, and6° the decreased is decreased This is explained by the beam angle related to incident angle of the light to the Fresnel was wider, squareangle illumination changed more, and to the andWhen efficiency also explained by the the beam related toshape incident angle of the light theuniformity Fresnel lens the beam lens When the beam anglelight is wider, output light does focus the focal line, so it to is impossible decreased This isoutput explained by thethe beam angle related to incident of the the angle is wider, the does not focus on the focalnot line, so iton is angle impossible tolight control theFresnel shape to control the shape of distribution in two directions The maximum beam angle was 3°, and 90% ◦ lens When theinbeam angle is wider, output beam light does focus on the focal line, soand it isuniformity impossible of distribution two directions The the maximum anglenot was , and 90% efficiency efficiency and was obtained to control the uniformity shape of distribution in two directions The maximum beam angle was 3°, and 90% was obtained efficiency and uniformity was obtained Figure 11 Light distribution on a receiver with (a) dθ = 2◦ ; (b) dθ = 4◦ ; and (c) dθ = 6◦ (d) Efficiency and uniformity depend on the angle of the collimated beam Appl Sci 2020, 10, x; doi: FOR PEER REVIEW Appl Sci 2020, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci www.mdpi.com/journal/applsci Appl Sci 2020, 10, x FOR PEER REVIEW of 13 Figure Appl Sci 2020,11 10, Light 3257 distribution on a receiver with (a) dθ = 2°; (b) dθ = 4°; and (c) dθ = 6° (d) Efficiency9 of 13 and uniformity depend on the angle of the collimated beam Experiment 3.1 3.1 Manufacturing Manufacturing Process Process of of Double Double Fresnel Fresnel Lenses Lenses We We used used aa commercial commercial collimator collimator lens lens from from Led-link Led-link Optics Optics Inc Inc [13] [13] to to collimate collimate all all light light from from the LED A 5W COB LED with 630 nm wavelength was selected Redistribution module consisted the LED A 5W COB LED with 630 nm wavelength was selected Redistribution module consisted of of two two linear linear Fresnel Fresnel lenses lenses perpendicular perpendicular to to each each other other Optical Optical elements elements were were made made of of poly poly methyl methyl methacrylate methacrylate (PMMA) (PMMA) The The module module size size was was determined determined by by aa commercial commercial collimator collimator lens lens with with aa diameter of 100 mm Based on this, the two linear Fresnel lenses had 100 mm diameters, respectively diameter of 100 mm Based on this, the two linear Fresnel lenses had 100 mm diameters, respectively The The lens lens system system was was designed designed for for aa lighting lighting area area of of 22 ×× 22 m, m, and and the the distance distance from from the the light light source source to to the target was m the target was m The made based on the FresnelFresnel lens structure We changed simulation The prototype prototypewas was made based onsimulated the simulated lens structure Wethe changed the file into a CAD G-code, and processed theprocessed lens by high-speed CNC milling CNC simulation filefile, intogenerated a CAD file, generated G-code, and the lens by high-speed CNCProxxon milling MF70 was usedMF70 to realize the prototype The basic[14] information this method presented CNC Proxxon was used to realize [14] the prototype The basicofinformation ofisthis methodin is reference [15] We used an acrylic sheet (PMMA) with a thickness of mm to create the grooves in the presented in reference [15] We used an acrylic sheet (PMMA) with a thickness of mm to create the linear Fresnel The CNC milling has an accuracy µm, so we polishing grooves in the lenses linear Fresnel lenses The machine CNC milling machine hasof an2accuracy of 2applied µ m, so awe applied process to make the lenses clearer Figure 12 shows the two Fresnel lenses after polishing Efficiency a polishing process to make the lenses clearer Figure 12 shows the two Fresnel lenses after polishing measurement results showed that the linear Fresnel lenses afterFresnel polishing had aafter transmission efficiency Efficiency measurement results showed that the linear lenses polishing had a up to 95% with a 650 nm laser transmission efficiency up to 95% with a 650 nm laser lenses Figure 12 Photograph of the fabricated linear Fresnel lenses 3.2 3.2 Prototype Prototype Test Test We We made made the the optical optical distribution distribution measurement measurement system system shown shown in in Figure Figure 13 13 Osram Osram bpw21 bpw21 photodiode [16] was used to collect optical energy from the light source, and this photodiode photodiode [16] was used to collect optical energy from the light source, and this photodiode was was located and controlled byby computer WeWe made a program for located along alongthe theXY XYaxis, axis,which whichcould couldbebemoved moved and controlled computer made a program the to sample at consecutive locations cm apart The measurement systemsystem had an had area an of for photodiode the photodiode to sample at consecutive locations cm apart The measurement 2area m ×of2 2m.mSo, the square detector system had 50 × 50 pixels The value of the pixel ranged from to × m So, the square detector system had 50 × 50 pixels The value of the pixel ranged Appl.(8Sci 2020, 10, x FOR PEER REVIEW 10 of 13 255 analog to analog digital converter (ADC)), which quantitatively representsrepresents the intensity light from 0bits to 255 (8 bits to digital converter (ADC)), which quantitatively theof intensity of light Appl Sci 2020, 10, x; doi: Figure FOR PEER www.mdpi.com/journal/applsci 13 REVIEW Experimental setup of light distribution measurements Figure 13 Experimental setup of light distribution measurements The simulated intensity and the measured intensity were normalized to compare simulation and test results Figure 14 shown the Experiment results of the distribution measuring system Figure 14a shows the measured optical distribution, and Figure 14b shows a comparison of the line distributions along the X axis across the center of the illuminated area Appl Sci 2020, 10, 3257 Figure 13 Experimental setup of light distribution measurements 10 of 13 Thesimulated simulatedintensity intensityand and the the measured measured intensity intensity were were normalized normalizedto to compare compare simulation simulationand and The testresults results Figure Figure 14 14 shown shown the the Experiment Experiment results resultsof ofthe the distribution distributionmeasuring measuringsystem system Figure Figure14a 14a test shows the measured optical distribution, and Figure 14b shows a comparison of the line distributions shows the measured optical distribution, and Figure 14b shows a comparison of the line distributions along the the XXaxis axisacross acrossthe thecenter centerof ofthe theilluminated illuminatedarea area along Figure Figure 14 14 Experiment Experiment results results of of the the distribution distribution measuring measuring system system (a) (a) Distribution Distribution on on the the target target surface (b) Comparison of the simulation and experiment distribution along the X axis across the surface (b) Comparison of the simulation and experiment distribution along the X axis across the center of the target surface center of the target surface Most of the linear distributions along the X axis for simulation and experiment results were Most of the linear distributions along the X axis for simulation and experiment results were consistent with each other The experiment achieved a uniformity of 75% with a minimum value of 110 consistent with each other The experiment achieved a uniformity of 75% with a minimum value of and maximum value of 243, where uniformity was calculated by Equation (2) The difference between 110 and maximum value of 243, where uniformity was calculated by Equation (2) The difference simulation and test results can be explained by many factors Firstly, the exact value of the PMMA between simulation and test results can be explained by many factors Firstly, the exact value of the refractive index could be different from the simulation In addition, the size of the engraving tools may PMMA refractive index could be different from the simulation In addition, the size of the engraving cause quality degradation Creating lens morphologies may not entirely be accurate with this design tools may cause quality degradation Creating lens morphologies may not entirely be accurate with Increasing the accuracy of engraving tools helps to achieve a more precise morphology However, this design Increasing the accuracy of engraving tools helps to achieve a more precise morphology studies have also shown that if an engraving tool is too small, it can deteriorate the quality of the work However, studies have also shown that if an engraving tool is too small, it can deteriorate the quality surface [11] of the work surface [11] 3.3 Outdoor Test 3.3 Outdoor Test An LED with an optical component in this study was applied to control chrysanthemum flowering An LED with optical plant, component this study was the applied to control chrysanthemum Chrysanthemum is aan short-day which in flowers only when provided photoperiod is shorter flowering Chrysanthemum a short-day plant, which flowers only the in provided photoperiod than the “critical period” [17].is We used night break phenomenon [12]when as show Figure 15 to control is shorter than the “critical We period” Weflash usedof night asso show in Figure 15 chrysanthemum flowering made[17] a short lightbreak in thephenomenon middle of the [12] night the plant would to control chrysanthemum flowering We made a short flash of light in the middle of the night so the behave as if it had been exposed to a long day The differences of chrysanthemum growth between plant would behaveand as uncontrolled if it had been exposedare to shown a longinday The 15b differences chrysanthemum controlled flowering flowering Figures and 15c, of respectively When growth between controlled flowering and uncontrolled flowering are shown in Figure 15b and Figure chrysanthemums were under uncontrolled flowering, it flowered at a time of no demand Flower sizes were small, and the quality was also low Chrysanthemums under controlled flowering had a longer Appl Sci 2020, 10, x; doi: FOR PEER REVIEW vegetative process, resulting in taller chrysanthemums With time-controlledwww.mdpi.com/journal/applsci flowering, the quality of the product improved Appl Sci.Sci 2020, 10,10, x FOR PEER REVIEW Appl 2020, x FOR PEER REVIEW 11 11 of 13 of 13 15c, respectively When chrysanthemums were under uncontrolled flowering, it flowered at at a time 15c, respectively When chrysanthemums were under uncontrolled flowering, it flowered a time of of nono demand Flower sizes were small, and thethe quality was also low Chrysanthemums under demand Flower sizes were small, and quality was also low Chrysanthemums under controlled flowering had a longer vegetative process, resulting in taller chrysanthemums With timecontrolled flowering had a longer vegetative process, resulting in taller chrysanthemums With Appl Sci 2020, 10, 3257 11 oftime13 controlled flowering, the quality of the product improved controlled flowering, the quality of the product improved Figure 15 Night break phenomenon (a) Principle; (b) Chrysanthemum with controlled flowering by Figure 15.15 Night break phenomenon (a)(a) Principle; (b)(b) Chrysanthemum with controlled flowering byby Figure Night break phenomenon Principle; Chrysanthemum with controlled flowering LED (c) Chrysanthemum without controlled flowering LED (c) Chrysanthemum without controlled flowering LED (c) Chrysanthemum without controlled flowering The flowering process takes 20 to 30 days after stopping the night break phenomenon The flowering process takes 2020 to to 3030 days after stopping thethe night break phenomenon The The flowering days stopping night break phenomenon The The wavelength that isprocess suitabletakes for illumination is after 630 nm [18] In this experiment, we used two wavelength that is issuitable forforillumination is is630 nm [18] In Inthis experiment, weweused two wavelength that suitable illumination 630 nm [18] this experiment, used two flowerbeds of chrysanthemums The first flowerbed was under a 5W COB LED with 630 nm wavelength flowerbeds of ofchrysanthemums The flowerbed was a 5W LED flowerbeds chrysanthemums Thefirst firstthe flowerbed wasunder under 5WCOB COB LEDwith with630 630nm with optical components we designed, and second flowerbed wasa under the same LED with anm wavelength with optical components wewe designed, and thethe second flowerbed was under thethe same wavelength with optical components designed, and second flowerbed was under same traditional parabolic reflector Chrysanthemums were illuminated at night with a projection time of LED with parabolic reflector Chrysanthemums were illuminated at atnight with a2 a witha and atraditional traditional parabolic Chrysanthemums illuminated night hLED per day, the distance betweenreflector stems was 10 × 16 cm Thewere area of the flowerbed was 4with m projection time of h per day, and the distance between stems was 10 × 16cm The area of of the projection time of h per day, and the distance between stems was 10 × 16cm The area (2 × m) Thus, 250 flowers were planted in each flowerbed After two months, the results are shownthe 2 flowerbed was m (2 × m) Thus, 250 flowers were planted in each flowerbed After two months, in flowerbed Figure 16 was m (2 × m) Thus, 250 flowers were planted in each flowerbed After two months, thethe results areare shown in in Figure 16.16 results shown Figure Figure 16 Chrysanthemums under controlled flowering (a) By LED with a parabolic reflector (b) By Figure 16.16 Chrysanthemums under controlled flowering (a)(a) ByBy LED with a parabolic reflector (b)(b) ByBy Figure Chrysanthemums under controlled flowering LED with a parabolic reflector LED with our optical component LED with ourour optical component LED with optical component As shown in Figure 16a, chrysanthemums under LED with parabolic reflectors had non-uniform AsAs shown in in Figure chrysanthemums under LED with parabolic reflectors had non-uniform heights; the plants on the16a, edge of the area were shorter than the plants at the center, which results in a shown Figure 16a, chrysanthemums under LED with parabolic reflectors had non-uniform heights; the plants on the edge of the area were shorter than the plants at the center, which results in in lower-quality product chrysanthemums with our results optical heights; the commercial plants on the edge ofOn thethe areaother werehand, shorter than the plantsunder at the LED center, which a lower-quality commercial product OnOn thethe other chrysanthemums under LED with our components showed quite uniform heights, which ishand, important in the market Specific numerical a lower-quality commercial product other hand, chrysanthemums under LED with our optical components showed quite uniform heights, which is important in the market Specific results are shown in Table optical components showed quite uniform heights, which is important in the market Specific numerical results areare shown in in Table 2 numerical results shown Table Table Results of chrysanthemums after months of testing Results of of chrysanthemums after months ofLED testing Table Results chrysanthemums after months of testing Parameter Table LED with Double Fresnel Lenses with Parabolic Reflector LED with double lenses with parabolic Number ofParameter stems surveyed 216 Fresnel 207 reflector Parameter LED with double Fresnel lenses LED LED with parabolic reflector Rate of early flowering 4.2% 5.9% Number of of stems surveyed 216216 207 Number stems surveyed 207 Lowest height of the stems 75 cm 58 cm Rate of of early flowering 4.2% 5.9% Rate early flowering 4.2% 5.9% Highest height of the stems 84 cm 80 Lowest height of of thethe stems 75 75 cmcm 58 58 cmcm Lowest height stems cm Average height of the stems 82 cm 72 cm Average diameter of the flower 7.8 cm 7.3 cm Appl Sci.Sci 2020, 10,10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci Appl 2020, x; doi: FOR PEER REVIEW www.mdpi.com/journal/applsci Based on the data in Table 2, we can see that both samples had good results in controlled flowering; more than 94% of plants had no flowers before stopping the night break illumination The LED with Appl Sci 2020, 10, 3257 12 of 13 our optical components was better than the LED with a parabolic reflector for controlling the flowering effect in terms of uniformity in height Also, the overall height of flowers under our light source was higher than those under the conventional LED source by 12% The flower size was also 6% larger in our case A uniform light distribution on the cultivated area using our proposed design is a very promising solution in the field of high-value-added agriculture Our method can be applied to many types of LEDs, reducing costs and achieving high efficiency Conclusions In this paper, double linear Fresnel lenses made of PMMA with 20 grooves each were fabricated using high-speed CNC milling The method of making the lenses demonstrated its capability for high-volume-based manufacturing Design, simulation, fabrication, and measurement of double linear Fresnel lenses were discussed The achieved uniformity of the redistributed irradiation was about 75%, which is consistent with the simulation result An outdoor test of the performance of our design for agricultural lighting and a comparison between our light source and a conventional light source were conducted It shows our proposed design exhibits great potential for commercialization Author Contributions: S.S.; T.Q.T., and N.H.V proposed the ideas and designed the simulation and experiments H.V and N.M.K performed simulations and experiments and analyzed the data D.T.G collected agricultural experiment results All authors have read and agreed to the published version of the manuscript Funding: This research was funded by Vietnam Academy of Science & Technology under Grant Number QTKR01.01/18-19, National Science & Technology Program for Development of Center Highlands (Vietnam) under Grant Number TN18/C08 and Ministry of Science and Technology of Vietnam 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kép Chế tạo thấu kính biên dạng tự dạng ma trận Hình 2.14: Máy CNC chế tạo thấu kính biên dạng tự dạng ma trận 35 Hình 2.14 cho thấy máy CNC thực thao tác chế tạo. .. kính 75mm Thơng số thiết kế thấu kính biên dạng tự dạng kép thể bảng 2.2 Hình 2.6 mơ tả quy trình thiết kế thấu kính biên dạng tự dạng ma trận 29 Hình 2.6: Quy trình thiết kế thấu kính biên dạng. .. dụng thiết kế phép đo 3.2 Kết chế tạo mô phân bố quang lối hệ thấu kính biên dạng tự 3.2.1 Kết mơ phỏng, chế tạo thấu kính dạng kép Hình 3.3: Thấu kính biên dạng tự dạng kép a) Một mảng thấu kính