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ANALYTICAL HAZE SIMULATION OF OPTICAL FILMS WITH 2D PARABOLOIDAL MICROLENS ARRAY Jeng-Feng Lin, Chin-Chieh Kang, and Shih-Fu Tseng Department of Electro-Optical Engineering, Southern Taiwan University, Tainan, Taiwan E-mail:jengfeng@mail.stut.edu.tw, 97-EC-17-A-05-S1-114 ABSTRACT This paper describes haze simulation of optical films with 2D paraboloidal microlens array by analytical formulae and optical simulation software ASAP, respectively. Derivation of the analytical formulae assumes every paraboloidal lens is independent, i.e., we ignore the situation that outgoing rays from a paraboloidal microlens can hit nearby paraboloidal microlenses. Comparison between formulae calculation and ASAP simulation shows that they are close. INRODUCTION Under the pressure of cost down, multifunctional optical films, which combine light diffusion and luminance gain, have become key components in LCD backlight units. Most of multifunctional optical films are composed of regularly or randomly distributed conic microlenses [1, 2, 3, 4]. In this paper, first the behavior of normally incident rays inside the optical film is examined. Then formulae for haze calculation and haze simulation by ASAP are presented. The schematic diagram of the optical film with 2D paraboloidal microlens array is shown in Fig. 1. The substrate is PET with thickness of 180 mm and refractive index of 1.49. Above the PET there are a thin layer with thickness of 20 mm and microlens array, and both are made of cured UV resin with refractive index of 1.56. RAY TRACING For haze measurement light is essentially normally incident to the sample. Therefore, as shown in Fig. 2, we assume the light is normally incident to the left half of the paraboloidal microlens. Since the microlens is rotationally symmetric and the light is normally incident, we only need to do the ray tracing on a plane which contains the optical axis (z axis). We can express the parabola in Fig. 2 as z = x 2 /2r, where r is radius of curvature and is negative. Let R b denote the radius of the circular bottom of the microlens and define shape factor k as k = R b /|r|. As shown in Fig. 2, the incident ray is normally reflected back to the substrate after consecutive reflections at points A and B. Therefore, reflection at A and B can have three cases: (a) when x 2c

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