近年來，全球暖化問題已成為人類的重大問題。因此，再生能源廣泛被應用，減少化石燃料耗損和節約能源已成發展趨勢。其中，太陽能源為地球上最重要且取之不盡的資源之一。若將太陽能源直接導引至室內，有效提供建築用電或室內照明所需，不只可以節約能源，更可以提供舒適且健康的照明環境。因此我們研究團隊發展了自然光照明系統，為了於室內發展高品質的日照光源，提高系統效率為首要的目的。於自然光照明系統中利用集光子系統收集陽光，並藉由傳光子系統，例如，導光管或光纖導引至室內。然而，由於光線在介質中傳遞造成的偏折，容易使光線從集光子系統傳遞到傳光子系統時發生能量損耗，無法傳到較遠的距離。因此，我們研究一光準直器，將之應用於集光子系統出口端，將出口端偏折較大角度的光線收斂成近平行光，讓在遠處都能達到應有的照度。
我們提出一種以自由曲面設計之準直透鏡，而此準直透鏡是由多個不同曲率之微透鏡所組成。就由網格分析法，我們找出光磚出口上的光線出光角度的位置分佈，以此出不同的自由曲面。結果顯示我們不但縮小準直器的體積，以不同單元網格大小所設計的準直器，單元網格越小。光線發散角度1°內的光通量總和與所有光線光通量總和之比，最高的是單元網格大小為 0.2 × 0.2 mm2所設計之準直器，達79%。且其耦合效率也是最高，達64%。並且在60mm的位置耦合效率仍有51%，且在300mm以後效率已不再降低。

Nowadays, global warming has become a major issue. Reducing the consumption of fossil fuel and saving energy were the top priorities. In response to the energy crisis, renewable energy has been widely taken as other energy options. Solar energy is one of the most essential and abundant energy. If we can collect and transmit natural light into buildings without opto-electronic conversion, that will save energy and provide healthier light into our daily life. Therefore, our team designed a series of products known as Natural Light Illumination System (NLIS). In developing the high-quality NLIS, our primary concern was to increase the efficiency of the system. When the concentrators in daylight system collects sunlight, the light transmits through light pipe or fiber to any room you want. However, the efficiency decreases dramatically as the number of concentrator increases, due to the interconnection parts which encounter huge loss.
In this paper, we present a free-form collimator applied to the outputs of LightBricks. The collimator is composed of different microlenses, which are derived from geometric optics, and include free-form refractive surfaces and total internal reflective surfaces. By mesh generation method, we successfully compress the collimator’s volume and the computer simulation results show that a ratio of luminous flux within ±25° and the total flux within ±90° on the collimator's output has a dramatically decrease, and the collimator with the best performance has a ratio of luminous flux within ±1° and the total flux within ±90° at 79%. Also it has an optical efficiency of 64%.

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