Kim Byungwook, Choi Minseok, Kim Hokwan, Lim Jiseok, Kang Shinill
Department of Mechanical Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749, Korea.
Opt Express. 2009 Sep 28;17(20):17916-27. doi: 10.1364/OE.17.017916.
A Fresnel lens is an optical component that can be used to create systems more compact, cost-effective, and lightweight than those using conventional continuous surface optics. However, Fresnel lenses can usually cause a loss of flux efficiency and non-uniform distribution of illuminance due to secondary refraction by surface discontinuities, especially along the groove facet. We therefore proposed to modify a groove angle in the Fresnel lens and analyzed interrelation between the groove angle and multiple optical performances, such as flux efficiency and the uniformity of illuminance and color. The groove angle was optimized to maximize the uniformity and efficiency in the target viewing angle considering various weights of merit functions. Specifically, in our study, when the uniformity of illuminance had a little more weight than the flux efficiency (ratio of 0.6:0.4), final optimum groove angles of 24.7 degrees , 29.4 degrees , and 31.3 degrees were obtained at target viewing angles of 20 degrees , 30 degrees , and 40 degrees , respectively. We also fabricated a modified Fresnel lens with a groove angle of 29.4 degrees using UV-imprinting. The real optical performance of the fabricated Fresnel lens was then compared to that of a spherical lens.
菲涅耳透镜是一种光学元件，与使用传统连续表面光学器件的系统相比，它可用于制造更紧凑、更具成本效益且更轻的系统。然而，由于表面不连续性引起的二次折射，尤其是沿着凹槽小平面，菲涅耳透镜通常会导致光通量效率损失和照度分布不均匀。因此，我们提议修改菲涅耳透镜中的凹槽角度，并分析凹槽角度与多种光学性能之间的相互关系，如光通量效率、照度均匀性和颜色均匀性。考虑到品质因数的各种权重，对凹槽角度进行了优化，以在目标视角下最大化均匀性和效率。具体而言，在我们的研究中，当照度均匀性的权重比光通量效率略高（比例为0.6:0.4）时，在20度、30度和40度的目标视角下，最终获得的最佳凹槽角度分别为24.7度、29.4度和31.3度。我们还使用紫外压印制造了一种凹槽角度为29.4度的改进型菲涅耳透镜。然后将制造的菲涅耳透镜的实际光学性能与球面透镜的光学性能进行了比较。
