現今綠建築在利用太陽光照明時有幾種方式，其中一種是利用天井直接照明，另一種為使用自然光照明系統，將自然光進行傳導作為照明應用。然而，採用天井照明會使得綠建築的結構受到限制；而自然光照明系統係會由於陽光受到建築物遮蔽抑或陽光隨著時間移動而無法垂直入射於集光元件而導到整體系統效能無法發會到極大的作用。

因此本文提出一應用於自然光照明系統的定日鏡裝置，該裝置系統為反射鏡組成的結構，其可進行雙軸的轉動。本文計算其定日鏡安裝地點之太陽運行軌跡，再藉由反射定律運算定日鏡單元反射鏡之雙軸轉動角度，我們利用光學反射鏡特性，引導太陽光垂直入射於集光元件，以提升自然光在傳導中之效率。
而且，此設計可將定日鏡裝置模組化，達到適用於各式建築設計應用。陣列式定日鏡模組可使整體系統日均效率達到原本的3.32倍。

The daylighting system is designed to guide sunlight into buildings for illumination. It has highest illumination performance when sunlight vertically impinges on the collector of daylighting system. Due to the Earth is revolving about the sun, the daylighting system has low performance when sunlight is incident obliquely on the collector. To overcome the problem, this paper investigates the design of a heliostat which reflect sun light vertically into daylighting system. In order to enhance the performance when sunlight is incident obliquely on the collector. This study proposes a 3x3 mirror array of heliostat which is different from the traditional heliostat with single mirror. With the heliostat, the performance of systems increase as high as 3.32 times.

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