臺灣國際科展

利用雙雷射精密測定準靜物的極微小變位

科展類別
臺灣國際科展
屆次
2004年
科別
工程學
學校名稱
高雄縣立鳳西國民中學
指導老師
劉百清
作者
郭倍綸
關鍵字
雙雷射 準靜物

摘要或動機

To-be static objects, such as bridges, volcanoes, seldom move ordinarily but have mini displacement only under special conditions, like flood or earthquakes. Therefore, how to measure their mini displacement has never become fully popular with scientists’ research. Then, beginning with “ Optical Lever Theorem”, through a series of speculation and discussion, I decide to use laser ray as light source to perform an experiment ------- trying to find objects with mini displacement in our daily lives, such as revolving electric fans, engine-opening motorcycles, shaken trees, testing their magnifying effect first. Next, I try to use the control-experiment method to find out the magnifying relation and formula of the rotation angle of the plane mirror and the displacement quantity of light focus. As to the measure of mini displacement on objects, I utilize the pillar mirror as a reflection plane to research the magnifying relation of reflection light focus and original displacement quantity. The image made from the light focus of pillar mirror’s reflection, however, isn’t so perfect that I have to use a special plastic-made light-concentrating mirror, which is also called “ Fresnel Lens ”, to focalize the light for easy observation. Besides, I find out the “ function graph ” of the mini displacement quantity on to-be static objects and the displacement quantity of reflection light focus. At last, I try to build up a “ Bridge Alarm System ” of Optical Lever Theorem. 準靜物如橋樑、火山,由於平常不輕易移動,只有在特殊情況下(如洪水、地震)時,才會發生位移的現象。因此,其微小變位如何測量,一向是科學界較少探討的題目。於是,先由光學槓桿原理著手,經過一番思考、探討,決定採用雷射光作為光源,並作了第一個實驗--找生活中具極微小變位的東西,如轉動中的電扇、引擎發動的摩托車、被搖動的樹木等,先測試其放大效果。接著就試圖用控制變因的方法,找出平面鏡旋轉角度和光點平移量的放大關係和公式。至於物體微小的平移量之測量,則是利用柱面鏡作為反射面,來探討反射光點的位移與本來的平移量之放大關係。然而,柱面鏡的反射光點成像並不理想,於是用一種特製的塑膠集光鏡,又稱Fresnel Lens,將光點集中以利觀測,並且找出準靜物之微小平移量及反射光點的位移量的函數圖形。最後,嘗試建立一套光學槓桿式的「橋樑預警系統」。


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