200813393 九、發明說明： 【發明所屬之技術領域】 本發明係爲了測定作用於液晶板或電漿顯示板 透過性之測定對象物的應力或應變等之光彈性測定 其裝置，尤其是欲精確地測定作用於隔着微小間隙 2片互相貼合基板的各個基板之應力的技術。 【先前技術】 作爲欲求作用於像玻璃基板等具有透過性之測 物的應力之方法，習知有如下的方法。作爲第1方 將光照射於平坦之桌上並保持平面的測定對象物， 測定對象物之表面及背面反射回來的反射光，而從 光的變化求取作用於測定對象物之主應力的差和 又，作爲第2方法，係朝向測定對象物照射之光當 透過測定對象物之透過光的變化求取作用於測定對 主應力的差和角度。 專利文獻1: 曰本非專利文獻1 : 最新應力/應變測定/評估技術（第49頁-頁）監修：河田幸三發行：股份有限公司總合技 【發明內容】 〔發明所欲解決之課題〕 然而，習知的方法有其次的問題。 第1及第2的方法，對於具有1片透過性之測 物的基板都可有效地發揮機能，但欲測定光學特性 等具有 方法及 配備之 定對象 法，係 量測從 其反射 角度。 中，從 象物之 -第66 術中心 定對象 '尤其 200813393 是折射率不同之複數原料所堆疊的基板，特別是隔着微小 間隙配備的2片互相貼合基板之主應力的差和角度時，有 或無法精準地求取作用於2片基板的何一基板，及雙方基 板之主應力的差和角度的問題。 即，關於上述貼合基板，當應用第1方法爲了測定作 用於2片基板的任一基板，或雙方基板之主應力的差和角 度時，從貼合基板反射回來的反射光，係將從各基板的表 面及背面返回者全部被合成。因此，即使爲了求知主應力 的差和角度有必要僅取得從各個基板之背面的反射光，但 也不容易將各個分離。又，適用第2方法時，透過貼合基 板之透過光係全部被合成，無法將透過每一基板之透過光 各個分離。 本發明係著眼於如此實情而開發者，以提供一種光彈 性測定方法及其裝置爲主要目的，其係作爲光學特性折射 率不同之複數原料所堆疊的基板，尤其是關於隔着微小間 隙堆疊的貼合基板，正確地分辨應力所作用的基板，同時 可精度良好地求取由於作用於其基板之應力而發生雙折射 的變化量及主應力的差和角度。 〔用以解決課題之手段〕 本發明爲了達成如此目的，採取其次的構成。 即，第1發明之特徵，係將具有以中心波長爲準的既 定範圍之波長分布的照射光，照射於由複數層構成之具有 透過性的測定對象物與參考面時，至少對測定對象物照射 第1方向的直線偏光， 200813393 使從該測定對象物之既定層的測定對象面反射回來的 反射光當中的依偏光狀態变化而產生之與該第1方向正交 之第2方向的偏光成分，以與從參考面返回之反射光能通 過同一光路的方式使之匯集並發生干涉， 並取得基於該相互重疊之兩反射光的同一偏光成分彼 此之干涉光的光強度而取得基於雙折射之偏光的變化量資 訊。 根據有關第1發明之光彈性測定方法，第1方向的直 線偏光朝向測定對象物照射之同時，另一方的偏光照射於 參考面。被照射於測定對象物之直線偏光透過複數的層， 而從各層的表面或背面反射回來。此時，應力作用於測定 對象之既定層時，反射回來之第1方向的直線偏光的偏光 狀態會變化。將與此偏光狀態變化之第1方向的直線偏光 正交之第2方向的直線偏光，從測定對象物反射之全部的 反射光之中抽出。而此抽出之第2方向的直線偏光與從參 考面反射之反射光能通過同一光路的方式使之匯集並發生 干涉。 從重疊之兩反射光，更取得基於同一偏光成分彼此之 千涉光的光強度。從此取得之光強度的變化可取得在測定 對象物藉由雙折射而受到變化之偏光的變化資訊。此時利 用求取主應力之差的演算式之雙折射的變化量資訊=主應 力的差X測定對象物的厚度X光彈性係數。若在此演算式內 的3個參數已知，則可求出剩餘的未知參數。一般，測定 對象物的厚度、光彈性係數用其他方法即可容易求得，所 200813393 以作爲未知參數藉由求取雙折射量可求得複數層中之既定 層的主應力的差。 此時，藉由使測定對象物或參考面之至少一方朝向光 之進行方向的前後移動一面取得干涉光的光強度，也可同 時算出測定對象物的厚度。即，測定對象物之各層與參考 面光強度的波形，係基於測定對象物之層間的光學上距離 大略一致時，基於干涉之光強度會發生變動。此時，例如， 若於橫軸作爲測定對象物或參考面的移動距離，縱軸作爲 光強度而將光強度的變化標在圖上的位置以取得光強度之 絕對値的包絡線，此包絡線之頂點間的距離將與測定對象 物之層間的光學上距離一致。因此，從此頂點間的距離亦 可同時算出測定對象物的厚度。 此外，若根據此方法發明，理想上使參考面或測定對 象面之任一面對照射光的進行方向前後移動，取得干涉光 之光強度成爲最大的光強度資訊（申請專利範圍第2項）。 又，從此時之光強度資訊可求出正確的雙折射變化 量，進而可精度良好地求出既定層之主應力的差。 又，若根據此方法發明，理想上以構成干涉光之兩反 射光的各相位可錯開半波長的方式大致分離成一半，取分 離後兩相位的差分，除去干涉光之光強度中的直流成分（申 請專利範圍第3項）。 此時，藉由產生千涉之兩反射光的相位錯開半波長’ 兩相位成爲反轉1 8 0 °狀態。即，在此狀態藉由取兩相位的 差分，可除去從參考面反射之偏光狀態中無變化的直流成 200813393 分’而僅可抽出產生偏光狀態變化的偏光成分。即，可精 度良好地求出在僅應力作用之既定層雙折射時之偏光的變 化量。 又，若根據此方法發明，理想上從使參考面或測定對 象面之任一面移動的移動量與干涉光之光強度的關係求出 周期性關係’而將此周期性關係的實相位與預先決定的基 準相位作比較，根據其結果判斷作用於測定對象物的既定 層之主應力的差是拉力或壓縮力（申請專利範圍第4項）。 此時，預先利用與測定對象物同樣試料進行實驗、理 論演算、及模擬，在此試料上特定作爲應力而作用之拉力 或壓縮力的條件而決定基準相位。藉由此基準相位與測定 測定對象物之既定層時的實相位作比較，而判斷所作用之 主應力的差是拉力抑或壓縮力。 又，若根據此方法發明，理想上使照射於測定對象面 之直線偏光與該測定對象面在直線偏光的光軸周圍相對地 旋轉，依各旋轉角度求取基於雙折射之偏光的變化量資 訊，從此等複數個偏光的變化量資訊與旋轉角度的兩種資 訊求取作用於測定對象物之主應力的差和角度（申請專利 範圍第5項）。例如，理想上使旋轉角度至少爲2個角度， 使從各角度照射之光的直線偏光方向不同而求取主應力之 差的角度（申請專利範圍第6項）。 此時，將依各旋轉角度（例如2個角度）求得之干涉 光的光強度之値轉換爲向量，而使兩旋轉角度的向量合 成，並從藉由其向量合成所顯示的角度可特定主應力之差 200813393 的角度。 其次，第7的發明其特徵在於：在將具有以中心波長 爲準的既定範圍之波長分布的照射光’照射於由複數層構 成之具有透過性的測定對象物與參考面時’至少對測定對 象物照射略圓偏光，該略圓偏光係將既定的第1方向直線 偏光與第1方向相差45。之第2方向成分錯開1/4波長之 略圓偏光， 使從該測定對象物之既定層的測定對象面反射回來的 ® 反射光，與從參考面返回之反射光的光路長一致，同時對 於來自測定對象面之反射光，係將該第2方向成分錯開- 1 / 4波長而返回略直線偏光，將其中依偏光狀態变化而產 生之與該第1方向正交之第3方向的偏光成分抽出，並以 此第3方向的偏光成分與從參考面返回之反射光能通過同 一光路的方式使之匯集並發生干涉， 取得基於該相互重疊之兩反射光的同一偏光成分彼此 之干涉光的光強度而取得基於雙折射之偏光的變化資 訊。 若根據有關第7之發明的光彈性測定方法，照射光會 照射於測定對象物與參考面的雙方。此時，至少對於測定 對象面’第1方向之直線偏光會變換成略圓偏光而照射。 被照射於測定對象物之略圓偏光透過複數之層，並在各層 的表面或背面反射。此時，若應力作用於測定對象物之既 定層時’反射回來之略圓偏光的偏光狀態會變化，即變化 成橢圓偏光。照此偏光狀態的原狀，抽出原來之第i方向 -10- 200813393 的偏光成分。而將與第1方向的直線偏光正交之第3方向 的直線偏光，從在測定對象物反射之所有反射光中抽出。 將此第3方向的直線偏光與反射自參考面的反射光能通過 同一光路的方式使之匯集並發生干涉。 從重疊之兩反射光，更取得基於同一偏光成分彼此之 干涉光的光強度。從取得之光強度的變化可取得受到在測 定對象物藉由雙折射變化之偏光的變化資訊。作爲此偏光 的變化資訊，可取得作用於測定對象之既定層的應力的影 響而產生之雙折射的變化量、測定對象物的厚度、及光彈 性係數之中的未知參數。例如，利用雙折射的變化量二主 應力的差X測定對象物的厚度X光彈性係數之演算式來求得 主應力的差，至少若已知2個參數，則可容易地求得剩餘 的未知參數。更，各參數若齊備，則作用於既定層之主應 力的差也可容易且精度良好地求出，進而也可分辨複數層 之中那一層有應力作用。 此外，若根據此方法發明，理想上使參考面或測定對 象面之任一面對照射光的進行方向前後移動，取得干涉光 之光強度成爲最大的光強度資訊（申請專利範圍第8項）。 此時，藉由取得干涉光之光強度成爲最大的光強度資 訊，可容易地分辨在測定對象的既定層有應力作用。又， 此時，可從光強度資訊求出正確之雙折射的變化量，進而 也可精度良好地求出既定層之主應力的差。 又，若根據此方法發明，理想上以構成干涉光之兩反 射光的各相位能錯開半波長般地大致分離成一半，取得分 200813393 離後之兩相位的差分’除去干涉光之光強度中的直流成分 (申請專利範圍第9項）。 此時，藉由使兩反射光的移送錯開半波長，則兩相位 成爲反轉1 8 0 °的狀態。即，在此狀態藉由取兩相位的差分， 可除去在參考面反射之偏光狀態中無變化的直流成分，而 僅可抽出產生偏光狀態變化的偏光成分。因此，可精度良 好地求出僅在應力作用之既定層雙折射時之偏光的變化 量。’ ^ 又，若根據此方法發明，理想上以與被照射的圓偏光 之傳播方向正交的測定對象面能在垂直平面上移動的方式 使圓偏光與測定對象物相對地移動，在其過程取得基於複 數處雙折射之偏光的變化量資訊，從其分佈狀態而推測作 用於測定對象物之既定層的應力方向（申請專利範圍第1〇 項）。此時，用以推測利用略圓偏光時之主應力的角度可 有效地發揮機能。 其次，第1 1之發明其特徵在於具備： 照射手段，係輸出具有以中心波長爲準既定範圍之波 長分布的照射光； 分離手段，係將來自該照射手段之照射光分離成2束 直線偏光，而將被分離之第1方向的直線偏光輸出於由複 數層構成之具有透過性的測定對象物，另一方之第2方向 的直線偏光則輸出於參考面； 抽出手段，係從該既定層之測定對象面的反射光中將 第2方向成分抽出； -12- 200813393 結合手段，係使從該測定對象物之既定層的測定對象 面反射回來之藉由抽出手段抽出的反射光，與從參考面返 回之反射光能通過同一光路的方式使之匯集並發生干涉； 移動手段，係使該測定對象物或該參考面之至少一方 於直線偏光行進方向的前後移動，使從該既定層的測定對 象面返回結合手段的反射光，與從該參考面返回結合手段 之反射光的光路長能一致； 檢測手段，係檢測該相互重疊之兩反射光的同一偏光 0 成分的光強度變化；以及 演算手段，係根據該檢測手段的檢測結果，求取基於 雙折射的偏光變化量資訊。 若依據有關第11之發明的光彈性測定裝置，因分離手 段分離成2束直線偏光的照射光之中，第1方向的直線偏 光朝向由複數層形成的測定對象物輸出，另一方之第2方 向的直線偏光則朝向參考面輸出。各個直線偏光到達輸出 $ 端即會反射。尤其是，具有透過性的測定對象物，透過之 直線偏光在各層的表面及背面即會反射。在此等複數面反 射之反射;7½ ’右有應力作用於既定層時，在往復透過其層 的過程中偏光狀態即會變化。從此偏光狀態變化的直線偏 光’藉由抽出手段僅將與第1方向正交之第2方向的偏光 成分抽出。而因結合手段，使被抽出的偏光成分與來自參 考面的反射光能通過同一光路的方式使之匯集並發生干 涉。 將此兩反射光匯集到結合手段之前，藉由移動手段， -13- 200813393 將測定對象物或參考面之至少一方於直線偏光之行進方向 的前後移動，使返回結合手段之複數層的背面反射之第2 方向的直線偏光之任一方，與從參考面至結合手段的光路 長能一致。此時，當兩光路長一致時，可藉由抽出手段僅 抽出往復透過具有背面之既定層返回的反射光，並藉由檢 測手段檢測此抽出之偏光成分與來自參考面的反射光之中 同一偏光成分的光強度變化。而，根據此檢測結果，演算 手段基於在測定對象物之雙折射求取偏光的變化資訊。 即，可以適當地實現第1的方法發明。 此外，若根據此裝置發明，理想上具備旋轉驅動手段， 用以使由照射手段、參考面、分離手段、抽出手段、結合 手段及檢測手段構成之光學系與測定對象物，在從光學系 輸出於測定對象物之直線偏光的光軸周圍相對地旋轉（申 請專利範圍第1 2項）。 若根據此構成，可將不同角度的直線偏光照射於測定 對象物。即，可求取各旋轉角度基於雙折射之偏光的變化 量資訊。利用此等複數個偏光的變化量資訊之干涉的光強 度變換爲向量之値與旋轉角度資訊的雙方，可將向量合成 特定主應力的角度。即，可以適當地實現第5、第6的方 法發明。 又，若根據此裝置發明，理想上更具備記憶手段，係 預先藉由移動手段使參考面或與測定對象物同樣之試料任 一個移動時的移動量與該干涉光之光強度的關係所求取實 驗的周期性關係，記憶此周期性關係之基準相位，演算手 -14- 200813393 段，係將基於測定對象物之實測的周期性關係的實相位與 從記憶手段讀出的基準相位作比較，根據其結果而判斷作 用於測定對象物之既定層的主應力之差爲拉力抑或壓縮力 (申請專利範圍第1 3項）。 若根據此構成，利用與測定對象物同樣試料進行實 驗、理論演算、及模擬，在此試料上特定作爲應力而作用 之拉力或壓縮力的條件而決定基準相位記憶於記憶手 段。而，藉由此基準相位與測定測定對象物之既定層的實 相位作比較，可判斷作用之主應力的差爲拉力抑或壓縮 力。即，可以適當地實現第4的方法發明。 其次，第14的發明其特徵在於具備： 照射手段，係輸出具有以中心波長爲準既定範圍之波 長分布的照射光； 分離手段，係使來自該照射手段之照射光分離成2束 直線偏光，而將該被分離之第1方向的直線偏光輸出於由 複數層構成之具有透過性的測定對象物，另一方之第2方 向的直線偏光則輸出於參考面； 第1變換手段，係使在該分離手段分離而朝向該測定 對象物的直線偏光與第1方向相差45°之第3方向成分錯開 1 / 4波長而變換成略圓偏光， 第2變換手段，係使在該既定層的測定對象面反射回 來的反射光，與該第3方向成分錯開- 1 / 4波長而變換成 略直線偏光； 抽出手段，係將在該第2變換手段大致成爲直線偏光 -15- 200813393 之反射光當中之依偏光狀態变化而產生之與該第1方向正 交之第3方向的偏光成分抽出； 結合手段，係使該第3方向的偏光成分與從參考面返 回之反射光能通過同一光路的方式使之匯集並發生干涉； 移動手段，係使該測定對象物或該參考面之至少一方 於直線偏光之行進方向的前後移動，使從該既定層的測定 kf象面返回結合手段的反射光，與從該參考面返回結合手 段之反射光的光路長能一致； w 檢測手段，係檢測該相互重疊之兩反射光的同一偏光 成分的光強度變化；以及 演算手段，係根據該檢測手段的檢測結果，求取基於 雙折射的偏光變化量資訊。 若依據有關第1 4之發明的光彈性測定裝置，藉由分離 手段分離成2束直線偏光的照射光中，將第1方向之直線 偏光輸出朝向於由複數層構成的測定對象物，另一方之第 2方向的直線偏光則朝向參考面輸出。朝向此測定對象物 之第1方向的直線偏光，藉由第1變換手段，變換成略圓 偏光。各個直線偏光到達輸出端即會反射。尤.其是，具有 透過性之測定對象物，透過之略圓偏光在各層的表面及背 面反射。在此等複數面反射的反射光，若於既定層有應力 作用時，在往復透過其層的過程中偏光狀態即會變化。即， 從略圓偏光變化成橢圓偏光。更將此橢圓偏光，藉由第2 變換手段變回到第1方向的略直線偏光。而藉由抽出手段 僅將與第1方向正交之第3方向的偏光成分抽出。而藉由 -16- 200813393 結合手段’使被抽出的偏光成分與來自參考面的反射光能 通過同一光路的方式使之匯集並發生干涉。 將此兩反射光匯集到結合手段之前，藉由移動手段， 將測定對象物或參考面之至少一方於偏光之行進方向的前 後移動’使返回結合手段之複數層的背面反射之第1方向 的略圓偏光之任一方，與從參考面至結合手段的光路長能 一致。此時，若使兩光路長一致的狀態下產生干涉時，想 要測定之任意層的干涉光強度成爲最大。此光強度成爲最 大時來自測定對象物的反射光與來自參考面之反射光中同 一偏光成分的光強度變化藉由檢測手段檢測。而，根據此 檢測結果，演算手段基於在測定對象物之雙折射求取偏光 的變化資訊。即，可以適當地實現第7的方法發明。 在上述.第1 1至第1 4之發明，理想上移動手段，係使 測定對象物或參考面之至少一方對於光的行進方向平行的 前後移動；檢測手段，係逐次檢測在移動過程中之干涉光 的光強度；演算手段，係根據檢測手段的檢測結果，求取 干涉光之光強度的最大値，而從所求之結果求取基於雙折 射之偏光的變化量資訊（申請專利範圍第1 5項）。即， 若根據此構成，可以適當地實現第2及第8的方法發明。 又，在上述第11至第15之發明，理想上具備：光學 手段，係使得構成依結合手段而發生干涉的干涉光之兩反 射光的各相位能錯開半波長大致分離成一半；演算手段， 係藉由分離後該反射光之兩相位的差分，除去干涉光之光 強度中的直流成分而求取基於雙折射之偏光的變化量資訊 -17- 200813393 (申請專利範圍第1 6項）。即，若根據此構成，可以適 當地實現第3及第9的發明。 〔發明效果〕 有關本發明之光彈性測定方法及其裝置，係將光照射 於測定對象物及參考面，而僅抽出來自測定對象物之反射 光中偏光狀態變化的偏光成分，藉由因來自此偏光成分與 參考面之反射光產生干涉，而可抽出由於作用於任意層之 應力的影響而產生之雙折射的變化量。又，可從此雙折射 ® 的變化量精度良好地求得作用於任意層之主應力的差，進 而可分辨應力作用之層。 【實施方式】 〔實施例1〕 以下，參考圖式說.明本發明之實施例。此外，在本實 施例係採取利用直線偏光的情況爲例加以說明。 第1圖係顯示利用本發明之光彈性測定方法之裝置的 槪略構成之圖。 本實施例裝置係由以下所構成：將2片液晶板或電漿 顯示板般具有透過性的玻璃基板W 1，W2，隔着微小間隙保 持於平坦之載置台60的測定對象物W，以具有以中心波長 爲準的既定範圍之波長分布的光照射的光學系組件1，及 控制光學系組件1的控制系組件2，和利用從光學系組件1 輸出的反射光，藉由往復透過測定對象物，將作用於既定 層之應力的影響使偏光狀態變化的偏光成分抽出，利用此 偏光成分檢測產生之干涉光的光強度之偏極計3。又，在 -18- 200813393 控制系組件2中包含根據偏極計3檢測之光強度，求取偏 光之變化量資訊的演算處理部1 5。以下，詳述有關各構成。 光學系組件1，係從光源4朝向測定對象物W照射的 光路上，依視準儀透鏡5、偏光板6、第1分光器7、物透 鏡8、第2分光器9之順序配備。又，在第1分光器7所 分離而朝向與測定對象物W不同方向前進之光的光路上配 備集光1¾ 10及光電二極體11。更在第2分光器9所分離 而朝向與測定對象物W不同方向前進之光的光路上配備有 ® 偏光板1 2及參考鏡1 3。以下，具體說明有關各構成。 光源4係發生比較寬頻帶區的光。例如，在本實施例 的情況，可利用具有790± 20 nm之帶區的超發光二極體。 從此光源4發生的光，藉由視準儀透鏡5變成平行光而朝 向偏光板6。此外，光源4相當於本發明之照射手段。 偏光板6，係被配置成45 °，從光源4照射之隨意偏光 之中，抽出偏光面爲4 5。之初期的直線偏光，並使此直線偏 光朝向第1分光器7。 第1分光器7,係使偏光面爲45。的直線偏光通過。即， 通過偏光板6之偏光面爲45。的直線偏光，係照原樣通過。 又，第1分光器7，係使從第2分光器9返回之偏光成分 朝向光電二極體1 1。即，測定對象物W之各玻璃基板W 1， W 2的表面和背面及在參考鏡1 3反射回到第2分光器9的 直線偏光之中，偏光面不旋轉而維持原來初期的偏光狀態 回來的偏光成分從第2分光器9回到第1分光器7，而此 第1分光器7,係將已回來之偏光成分朝向光電二極體11。 -19- 200813393 光電二極體1 1，係檢測從第2分光器9返回之偏光成 分的光，並將檢測信號送信到後述之控制系2的演算處理 部15。 物透鏡8，係將射進來的直線偏光朝向下游側之測定 對象物W及參考鏡1 3集光的透鏡。藉由此物透鏡8集光 的直線偏光係到達第2分光器9。 第2分光器9，係將在集光透鏡8集光的光分離成正 交的1組直線偏光。即，分離成朝向測定對象物W之第1 ^ 方向的測定光與朝向參考鏡1 3之第2方向的參考光。又， 第2分光器9，係將分別在測定對象物W及參考鏡1 3反射 而返回同一光路之參考光和測定光再度匯集。此時，僅分 別從測定光及參考光之中將偏光狀態有變化的偏光成分抽 出，使此偏光成分朝向與初期光路不同之偏極計3，而偏 光狀態無變化的偏光成分，則通過初期光路回到第1分光 器7。此外，第2分光器9，係作爲本發明的分離手段、抽 出手段、及結合手段而發揮功能。 偏光板1 2，係配備在從第2分光器9朝向參考鏡1 3 之參考光的光路上，而將來自第2分光器9之直線偏光透 過內部改變成偏光面傾斜4 5。的直線偏光，使此偏光狀態變 化的參考光在參考鏡1 3反射而回到第2分光器9。 參考鏡13，係對於參考光的行進方向垂直地安裝。以 此參考鏡1 3反射的參考光，係通過同一光路回到第2偏光 分光器9。又，參考鏡13之構成，係藉由壓電元件14的 作動而可相對於參考光的行進方向前後移動微小距離。此 -20- 200813393 外，參考鏡1 3，係相當於本發明的參考面，壓電 係相當於本發明的移動手段。 集光透鏡1 0，係將來自第2分光器9之直線 光電二極體11集光的透鏡。 其次’偏極計3係由以下所構成：分別把在 器1 9及第3分光器1 9所分離之直線偏光集光的 2 0，2 1，及接受來自集光透鏡2 0，2 1之直線偏光的 二極體22,和第2光電二極體23。兹將有關各構 #說明如下。 物透鏡1 8，係將來自第2分光器9之直線偏 平行光朝向第3分光器19的透鏡。 第3分光器19，係配置成45°，使在第2分 抽出之返回同一光路的測定光及參考光的各相位 波長而分離成一半，此等被分離之直線偏光在各 20，21被集光並使朝向能到達各光電二極體22, 本實施例的情況，構成上被分離使彼此一致成爲 ® 之測定光和參考光而成之直線偏光，朝向第1光 22，而彼此一致成爲一45°成分之由測定光和參考 直線偏光，則朝向第2光電二極體2 3。 第1及第2光電二極體22,23，係將檢測之直 光強度信號位準分別輸出到演算器24。此外，莞 光電二極體22,23，係相當於本發明的檢測手段。 由兩光電二極體22,23檢測之光強度的信號成爲 及第3圖所示之千涉波形’而各個的相位係反轉 元件1 4， 偏光朝向 第3分光 集光透鏡 第1光電 成具體地 光使成爲 光器9所 能錯開半 集光透鏡 23 ° 即， + 4 5 °成分 電二極體 光而成之 線偏光的 ;1及第2 此時，藉 如第2圖 1 80〇 ° -21 - 200813393 演算器24，係採取適應兩光電二極體22,23檢 強度値之信號位準的差分而合成。此種情況下，如: 及第3圖所示，因爲以兩光電二極體22，23檢測之 形的兩相位反轉1 80。，所以採取兩光強度値之差分 而合成。結果，如第4圖所示，干涉波形的直流成 除’僅基於從測定對象物W反射回來之雙折射變化 的干涉光可被抽出。 其次，控制系組件2，係包含演算處理部1 5、 制部1 6、及操作部1 7等。兹將有關各構成具體地 下。 演算處理部1 5，作爲第1處理係執行千涉光的 準’作爲第2處理係求取藉由作用於測定對象物w 的玻離基板W 1或W2的主應力之差而發生雙折射 量、光彈性係數、及玻離基板的厚度之中的未知參 作用於既定之玻離基板的應力。此外，演算處理部 相當於本發明的演算手段。 作爲第1處理，例如，光電二極體1 1係從測定 W及參考鏡1 3的反射光之中，檢測在測定對象物 考鏡1 3中偏光狀態無變化而返回之反射光彼此千 涉光強度。此時，將命令信號送信到驅動控制部Η 作動控制壓電元件1 4，一面以光電二極體1 1逐次 測之光強度値而算出干涉光強度成爲最大之參考鏡 位置。即，此參考鏡1 3的位置，也係藉由偏’極計3 涉光之光強度値成爲最大的位置。 測之光 第2圖 千涉波 的方式 分被去 量成分 驅動控 說明如 焦點對 之既定 的變化 數，和 15，係 對象物 W及參 涉的干 ►，一面 檢測檢 13的 檢測干 -22- 200813393 射入光電二極體1 1的光強度，比射入偏極計的光強度 更大。因此’若以偏極計3無法檢測出干涉光時，可判斷 係因爲雙折射的變化量過小，或光學系之光軸的偏位，尤 其是因爲測定對象物W的煽動不吻合之光軸的偏位以致無 法檢測光。 作爲第2處理，係以演算器2 4從檢測之干涉光的光強 度値，取得在測定對象物W變化之雙折射的變化量資訊。 又’作用於既定測定對象物之主應力的差，係藉由雙折射 的變化量資訊=主應力的差X測定對象物的厚度><光彈性係 數的式子來求取。即，若求得雙折射的變化量資訊，可從 已知的測定對象物的厚度與光彈性係數，容易地求得作用 於其測定對象物之主應力的差。例如測定對象物爲既定的 玻璃基板時’作用在既定玻璃基板之主應力的差，可藉由 雙折射的變化量資訊二主應力的差X玻璃基板的厚度X光彈 性係數的式子來求得。即，若求得雙折射的變化量資訊， φ 可從已知之玻璃基板的厚度及光彈性係數，容易地求得作 用於此玻璃基板之主應力的差。 驅動控制部1 6，係依照從操作部1 7輸入被設定的條 件，而使光學系組件1從光源4朝向測定對象物W之直線 偏光的行進方向前後僅移動既定的距離。即，驅動控制未 圖示之脈衝電動機等的移動手段，從第2分光器9到玻璃 基板W1之背面的距離L1與從第2分光器9到參考鏡13 的距離L2，及從第2分光器9到玻璃基板W2之背面的距 離L3和從第2分光器9到參考鏡1 3的距離L4之各個組的 -23- 200813393 距離彼此能大略一致的方式使光學系組件1移動。 又，驅動控制部1 6，係依照來自演算處理部1 5的命 令信號，作動控制壓電元件1 4使干涉光的光強度能成爲最 大的方式微調參考鏡1 3的位置。 操作部1 7，係設定輸入玻璃基板W1、W2的厚度、各 玻璃基板的光彈性係數、材料、折射率、各構成部彼此的 距離L 1〜L4等各種測定條件者。 其次，用上述實施例裝置，說明關於測定作用於測定 ® 對象物W之主應力的差之一巡的動作。此外，取應力作用 於構成測定對象物W之玻璃基板w 1、W2雙方的情況爲例 加以說明。 從操作部1 7輸入測定條件，並開始測定。首先，驅動 控制使從第2分光器9到玻璃基板W1之背面的距離L1， 與從第2分光器9到參考鏡13的距離L2相同，即，驅動 控制部1 6作動控制未圖示之脈衝電動機等的移動手段使 兩光路長略一致的方式，移動光學系組件1。 ® 光學系組件1到達兩光路長略一致之位置時，從光源 4照射光。被照射之光以視準儀透鏡5成爲平行光之後， 藉由偏光板6使變成偏光面4 5 °的直線偏光，通過在後段之 被配置45°的第1分光器7朝向第2分光器9。 以被配備在第2分光器9之前段的物透鏡8集光的直 線偏光，到達第2分光器9時，被分離成2束正交的直線 偏光。被分離之第1方向（水平方向）的直線偏光（測定 光），係朝向測定對象物W而在玻璃基板W1、W2往復透 -24- 200813393 過的過程中，在玻璃基板w 1、W 2的表面及背面反射，而 返回第2分光器9。另一方之第2方向（垂直方向）的直 線偏光（參考光），係在參考鏡13反射而返回第2分光器 9的過程中，以偏光板1 2成爲傾斜4 5。的直線偏光，而返 回第2分光器9。 第2分光器9，係在測定對象物W的各面反射回來的 測定光之中，僅將基於偏光狀態的變化而產生與第1方向 直行之第2方向的偏光成分的測定光抽出，而使之朝向偏 極計3。此時，使抽出之第2方向的測定光及從參考鏡1 3 返回之參考光能通過同一光路的方式再度使之匯集並發生 干涉。 此外，從測定對象物W反射回來之偏光狀態無變化之 直線偏光，係經由上游側之第1分光器7而藉由光電二極 體1 1檢測。 參考鏡13的位置一旦決定，從第2分光器9朝向偏極 計3之第2方向的直線偏光，藉由集光透鏡18所集光之 後，到達構成偏極計3之第3分光器1 9。 第3分光器1 9，係將到達之由水平成分構成的直線偏 光，使相位錯開半波長的方式，大致分離成一半。此時， 匯集成測定光與參考光之彼此+ 45°成分，及彼此- 45。成 分’而一致成爲相同方向的彼此直線偏光。此等方向一致 之各組的直線偏光之中，由水平成分構成的直線偏光被集 光在集光透鏡20而以第1光電二極體22檢測。由垂直成 分形成的直線偏光被集光在集光透鏡21而以第2光電二極 -25- 200813393 體23檢測。 以各光電二極體22，23接受光的兩直線偏光，係以演 算器24變換成分別之光強度値，而被減算。此時，兩直線 偏光的相位因爲反轉1 8 0 °，所以從參考鏡1 3反射回來之參 考光的直流成分被除去，而僅獲得測定光的干涉成分。 此千涉成分的光強度値，輸入於演算處理部1 5，而由 演算處理部1 5求取雙折射的變化量資訊及主應力的差。 以上，結束了求取玻璃基板W 1之雙折射的變化量資 訊和主應力之差的處理，其次，驅動控制部1 6作動控制移 動手段使光學系組件1移動，同時作動控制壓電元件1 4使 從玻璃基板W2的背面到第2分光器9的距離L3，與從參 考鏡1 3到第2分光器9之光學距離L4的光學距離大略一 致般地調整之後，藉由與上述玻璃基板W 1執行同樣處理 求取玻璃基板W2之雙折射的變化量資訊及主應力的差。 如上所述，將光學系組件1移動使從第2分光器9到 參考鏡1 3的距離與到玻璃基板W 1、W2之背面的光路長大 略一致，利用在各玻璃基板 Wl、W2之背面與參考鏡13 反射回來的測定光與參考光時，可正確地求取測定對象之 任意層的雙折射的變化量資訊與主應力的差。即，從應力 作用之測定對象物返回之測定光因爲偏光面發生變化，所 以僅與第1方向正交之第2方向的偏光成分可藉由第2分 光器9抽出，此偏光成分與從參考面13返回之參考光能通 過同一光路的方式使之匯集並發生干涉，可使此干涉光朝 向偏極計3反射輸出。由此參考光與測定光形成之第2方 -26- 200813393 向之直線偏光的相位，更錯開半波長而分離，藉由將偏光 成分與相同成分彼此一致，可以作用於玻璃基板之主應力 的差僅雙折射之偏光成分作爲干涉光的光強度而檢測。 因此，藉由利用此干涉光的光強度，可求取作用於由 複數層所形成之具有透過性的測定對象物.，之藉由任意層 之主應力的差而產生之雙折射的變化量，進而，藉由利用 此雙折射的變化量，亦可求取作用於任意層之主應力的差 和主應力之差的角度。即，藉由主應力之差的角度求向量 ® 成分可正確地分辨作用各複數層的應力。又，亦可藉由主 應力之差的角度及其所求之向量成分而正確地判斷作用於 各複數層之應力的大小及方向。 〔實施例2〕 在上述實施例1，係利用來自光源4照射之光變換成 直線偏光，但在本實施則採取利用圓偏光朝向測定對象物 W輸出偏光的情況爲例加以說明。此外，在本實施例，關 於與上述實施例相同之構成僅止於附上同一符號，而具體 地說明關於不同的構成。 第5圖係顯示利用本發明之圓偏光時的光彈性測定裝 置的槪略構成圖。係由本實施例裝置之光學系組件1、控 制系組件2、及第1偏極計3所構成。 光學系組件1，係由光源3 0之超發光二極體朝向測定 對象物W照射的光路上，依視準儀透鏡3丨、偏光板32、 第1分光器33、及配置成45。的1/4波長板35的順序配 備。又，從第1分光器3 3朝向測定對象物W輸出，在測 -27- 200813393 定對象物W反射朝向偏極計3之測定光的光路上，依反射 鏡3 6、配置成一 4 5 °的1 / 4波長板3 7、反射鏡3 8、偏光板 39、及第2分光器40之順序配備。又，在第1分光器33 所分離而朝向與測定對象物W不同方向行進之光的光路 上，配備有參考鏡4 1，更在此參考鏡4 1反射而朝向偏極 計3之參考光的光路上，依反射鏡42、43、偏光板44、及 第2分光器40之順序配備。以下，對各構成具體地加以說 明。 ^ 偏光板32，係配置成45。，將來自視準儀透鏡31之平 行光改變成偏光面45°的初期的直線偏光，使此直線偏光對 向第1分光器33。 第1分光器3 3，係將自偏光板3 2到達之直線偏光， 即，分離成對向測定對象物W之第1方向的測定光，與朝 向參考鏡13之第2方向的參考光。此外，第1分光器33, 係相當於本發明的分離手段。 配置成45°之1/ 4波長板35 ’係藉由通過第3方向之 直線偏光的測定光，將直線偏光改變成略圓偏光。此外， 配置成一 45°之1/4波長板37，係相當於本發明的第1變 換手段。 其次，反射鏡3 6，係將在構成測定對象物W之玻璃g 板W 1、W2的各面反射之反射光，更加以反射導引至配備 在與射入光路不同的光路上配置成—45。的1/4波長丰反 37。 配置成一 45。之1/ 4波長板37，係藉由從測定對象物 -28- 200813393 w之各面反射回來的反射光使通過其內部，回到略直線偏 光。即，若應力作用於測定對象物W之玻璃基板w 1或W2 時，圓偏光的偏光面會微小旋轉使變化成橢圓偏光。使此 橢圓偏光通過，變換成含有雙折射變化量的直線偏光。此 外，配置成—4 5 °之1 / 4波長板3 7，係相當於本發明的第 2變換手段。 反射鏡3 8，係使藉由配置成—4 5。之1/4波長板37 而改變成略直線偏光的測定光，通過偏光板3 9而對向第2 • 分光器4 0。 第2分光器4 0，係配備在來自測定對象物w反射之測 定光，與來自參考鏡41反射之參考光相交叉的位置。而第 2分光器4 0，係分別在各測定對象物W與參考鏡1 3反射 回到同一光路之參考光及測定光再度匯集。此時，反射回 來之測定光之中僅抽出偏光狀態有變化的偏光成分，將此 偏光成分對向偏極計3側，偏光狀態無變化之偏光成分， 則對向後段的第2偏極計45。此外，第2分光器40 ,係作 ® 爲本發明之抽出手段及結合手段而發揮機能。 參考鏡41，係反射與射入時之參考光不同方向的參考 光。此反射之參考光更以2個反射鏡42、43，對向於後段 的偏光板44。又，參考鏡41的構成，係藉由壓電元件14 的作動相對於參考光的進行方向可前後移動微小距離。此 外，參考鏡41相當於本發明的參考面。 偏光板44，係配置成45。，將透過內部之參考光變成 45°的直線偏光。即，參考光，藉由前段的偏光板32與該 -29- 200813393 偏光板4 4的作用變成相差9 0 °的直線偏光，而到達 光器40。 其次，第1偏極計3，如第6圖所示，係由第 器46、接受在此第3分光器46所分離之各個直線 第1光電二極體22、第2光電二極體23、及演算器 構成。以下，對各構成具體地說明。 第3分光器46,係配置成45°，使在第2分光署 抽出而返回同一光路的測定光與參考光的各相位可 ^ 波長的方式分離成一半，此等被分離之直線偏光在 透鏡20、21被集光而朝向可到達各光電二極體22 即，本實施例的情況，其構成係被分離成爲水平成 整齊的測定光與參考光而成的直線偏光，係朝向第 二極體22，彼此整齊成垂直成分的測定光與參考光 直線偏光，係朝向第2光電二極體23。 第1及第2光電二極體22、23，將檢測之偏光 度値信號分別輸出演算器24。 演算器24，係如第2圖及第3圖所示，拾取適 電二極體22、23檢測之光強度値的信號位準之差分 而合成。此時，如第2圖及第3圖所示，以兩光電 22、23檢測之干涉波形的兩相位因爲反轉180°，所 取兩光強度値之差分的方式而合成。結果，如第4匱 干涉波形的直流成分被除去，而僅基於來自測定對 反射之雙折射的變化量成分的干涉光會被抽出。 第2偏極計4 5的構成，與第1偏極計3相同， 第2分 3分光 偏光的 ^ 24所 I 40所 錯開半 各集光 、23 ° 分彼此 1光電 而成的 的光強 應兩光 的方式 二極體 以依拾 I所示， 象物w 係由第 -30- 200813393 3分光器46與第1及第2光電二極體22、23所構成。即， 第2偏極計4 5，係利用以第3分光器4 0所分離的偏光， 從測定對象物W及參考鏡4 1的反射光之中，檢測在測定 對象物W及參考鏡4 1之中，偏光狀態無變化即返回之反 射光彼此干涉的干涉光強度。並將此信號送到演算處理部 15 〇 控制系組件2的構成係與實施例1相同，包含演算處 理部1 5、驅動控制部1 6、及操作部1 7等。 其次，使用上述實施例裝置，說明關於測定作用於測 定對象物W之主應力的差之一巡的動作。此外，取應力作 用於構成測定對象物W之玻璃基板W 1、W2的雙方之情況 爲例加以說明。 從操作部1 7輸入測定條件，並開始測定。首先，驅動 控制使從第1分光器3 3到玻璃基板W1之背面的距離，與 從第1分光器3 3到參考鏡4 1的距離相同，即，使兩光路 長可一致的方式，驅動控制部1 6作動控制未圖示之脈衝電 動機等的移動手段使光學系組件1移動。 光學系組件1到達光路長略一致時，從光源30照射 光。被照射之光以視準儀透鏡3 1成爲平行光之後，藉由偏 光板32使變成偏光面4 5°的直線偏光，而到達第1分光器 33 - 此直線偏光，藉由第1分光器3 3分離成正交的2束直 線偏光，被分離之第1方向（水平方向）的直線偏光，係 朝向測定對象物W。另一方之第2方向（垂直方向）的直 200813393 線偏光係朝向參考鏡41。 在此，朝向測定對象物W的直線偏光，係透過配置成 4 5°的1/ 4波長板35 ’此時，直線偏光之測定光，可改變 成略圓偏光的測定光。 此測定光’朝向測定對象物W而在透過玻璃基板W 1、 W2的過程中，在各測定對象物wi、W2的表面及背面反 射。此時，因爲應力作用於玻璃基板W 1，所以測定光在往 復透過的過程中從圓偏光變化爲橢圓偏光。成爲此橢圓偏 W 光的測定光，由於測定對象物W以傾斜姿勢配備，所以傾 斜地被反射而朝向反射鏡4 2。到達反射鏡3 6的測定光， 係朝向配置成一45°的1/ 4波長板37。到達配置成一 45。 之1 / 4波長板3 7的測定光，透過其內部返回到含有雙折 射變化量的直線偏光。透過配置成-4 5。之1 / 4波長板3 7 而返回到直線偏光的測定光，藉由反射鏡3 8被反射，而到 達第2分光器40。 0 另一方在第1分光器3 3所分離之第2方向之直線偏光 的參考光，係在以傾斜姿勢被配備之參考鏡4 1以與射入方 向不同的斜方向被反射。而，此參考光係依反射鏡42、43 之順序被反射，並透過偏光板44而到達第2分光器40。 第2分光器40，係抽出將在測定對象物W的各面反射 回來的測定光之中藉由偏光狀態的變化而產生之第2方向 的偏光成分，與來自在參考鏡4丨反射之後通過偏光板44 的參考光之中的第丨方向的偏光成分，使能通過同一光路 的方式到達第1偏極計3匯集而產生千涉。 -3 2 - 200813393 又，第2分光器4 0，抽出在測定對象物W的各面反射 回來的測定光之中偏光狀態無變化之成分的第1方向的偏 光成分，與來自在參考鏡41反射之後通過偏光板44的參 考光中之第2方向的偏光成分，使能通過同一光路的方式 到達第2偏極計45匯集而產生干涉。 第1偏極計3的第3分光器46，係將到達之測定光與 梦考光的水平成分彼此所形成的直線偏光，使相位可錯開 半波長的方式，略分離成一半。此時，匯集測定光與參'考 光彼此成爲水平成分，及彼此成爲垂直成分，整齊成同方 向的彼此直線偏光。此等方向整齊之各組直線偏光當中， 由水平成分形成之直線偏光，在集光透鏡20被集光而以第 1光電二極體2 2檢測。由垂直、成分形成之直線偏光，在集 光透鏡2 1被集光而藉由第2光電二極體23檢測。 採取適應各光電二極體22、23檢測之光強度値的信號 位準的差分的方式而合成。此種情況，如第2圖及第3圖 0 所示，因爲以兩光電二極體22、23檢測之干涉波形的兩相 位反轉1 8 0 °，所以採取兩光強度値之差分的方式而合成， 如第4圖所示除去干涉波形的直流成分。 此干涉成分的光強度値輸入演算處理部1 5、而由演算 處理部1 5求取雙折射之變化量資訊及主應力的差。 第2偏極計4 5之第4分光器4 6，係將到達之測定光 與參考光之由水平成分彼此所形成的直線偏光，使相位可 錯開半波長的方式，略分離成一半。此時，匯集成測定光 與參考光之水平成分彼此，及垂直成分彼此，整齊成爲相 -33 - 200813393 同方向的彼此直線偏光。此等方向整齊之各組的直線偏光 之中，由水平成分形成之直線偏光被集光透鏡2 0集光而以 第3光電二極體22檢測。由垂直成分形成之直線偏光被集 光透鏡21集光而以第4光電二極體23檢測。據此測定光 與參考光之中由水平成分所形成的直線偏光部分的干涉波 形可被檢測。此波形的相位可利用作爲判斷作用於測定對 象物之既定層的主應力的差是拉力或壓縮力的基準相位。 此外，所謂基準相位係意味著，使參考鏡4 1或測定對 象物W之任一方移動時，從其移動量與干涉光之光強度的 關係求出周期性的關係，再從此周期性的關係求取相位。 由以上，結束了處理求取玻璃基板W 1之雙折射的變 化量資訊與主應力的差，其次，驅動控制部1 6，作動控制 未圖示之移動手段使光學系組件1移動，同時作動控制壓 電元件1 4調整使從玻璃基板W2的背面至第1分光器3 3 的距離，與從參考鏡41至第1分光器3 3的距離能一致之 後’藉由執行與上述玻璃基板W 1的同樣處理求取玻璃基 板W2之雙折射的變化量資訊和主應力的差。 根據上述之構成，與利用直線偏光的情況同樣，藉由 利用干涉光的光強度，可求取作用於由複數層構成之具有 透Μ性的測定對象物之任意層主應力的差而產生之雙折射 的變化量’進而，藉由利用此雙折射的變化量，亦可求取 作用於任意層之主應力的差。即，可正確地分辨作用於複 數之各層的應力。 又’在本實施例，藉由利用圓偏光，不論應力的方向 -34- 200813393 如何都以1次的測.定即可確實地辨別有無應力。 此外，本發明並不限於上述實施例，亦可如下變形實 施。[Technical Field] The present invention is a device for measuring photoelasticity of stress or strain of a measuring object acting on a liquid crystal panel or a plasma display panel, in particular, to accurately A technique of measuring the stress acting on each of the substrates on which the substrates are bonded to each other with a small gap therebetween was measured. [Prior Art] As a method for applying stress to a transparent sample such as a glass substrate, the following method is known. The object to be measured, which is irradiated with light on a flat table and held in a flat surface, is used to measure the reflected light reflected from the surface and the back surface of the object, and the difference in the principal stress acting on the object to be measured is obtained from the change in light. In addition, as a second method, the light that is irradiated toward the object to be measured is determined by the change in the transmitted light transmitted through the object to be measured, and the difference and angle acting on the measured principal stress are obtained. Patent Document 1: Nippon Non-Patent Document 1: Latest Stress/Strain Measurement/Evaluation Technology (page 49-page) Supervision: Kawada Kosei Distribution: General Co., Ltd. [Invention] [The problem to be solved by the invention] However, the conventional method has the next problem. The first and second methods can effectively exhibit the function of a substrate having a single permeability test, but the method of measuring the optical characteristics, such as the method of measuring the optical characteristics, is measured from the angle of reflection. In the case of the image-center 66, the object is 'in particular, 200813393 is a substrate on which a plurality of materials having different refractive indices are stacked, in particular, the difference in the principal stress of the two mutually bonded substrates provided with a small gap, and the angle There is or can not accurately determine which substrate acts on the two substrates, and the difference in the principal stress between the two substrates and the angle. In other words, when the first method is applied to measure the difference between the principal stresses applied to the two substrates or the principal stress of the two substrates, the reflected light reflected from the bonded substrate will be applied to the bonded substrate. The surface and back return of each substrate were all synthesized. Therefore, even if it is necessary to obtain only the reflected light from the back surface of each substrate in order to find the difference and angle of the principal stress, it is not easy to separate each. Further, when the second method is applied, all of the transmitted light transmitted through the bonded substrate is combined, and the transmitted light transmitted through each of the substrates cannot be separated. The present invention is directed to the developer to provide a photoelastic measurement method and apparatus thereof as a main object, which is a substrate on which a plurality of raw materials having different refractive indices of optical characteristics are stacked, in particular, stacked with a small gap interposed therebetween. When the substrate is bonded, the substrate on which the stress acts is accurately resolved, and the amount of change in the birefringence and the difference in the principal stress and the angle due to the stress acting on the substrate can be accurately obtained. [Means for Solving the Problem] In order to achieve such an object, the present invention adopts the second configuration. In other words, in the first aspect of the invention, when the irradiation light having a wavelength distribution of a predetermined range, which is a predetermined value of the center wavelength, is irradiated onto the measurement object and the reference surface which are formed of a plurality of layers, at least the object to be measured The linearly polarized light in the first direction is irradiated, and the polarized light component in the second direction orthogonal to the first direction, which is generated by the change in the polarization state of the reflected light reflected from the measurement target surface of the predetermined layer of the measurement target, is transmitted. And collecting and interfering with the reflected light returning from the reference surface through the same optical path, and obtaining the light intensity based on the interference light of the same polarized component of the mutually overlapping two reflected light to obtain the birefringence based Information on the amount of change in polarization. According to the photoelastic measurement method of the first aspect of the invention, the linearly polarized light in the first direction is irradiated toward the object to be measured, and the other polarized light is irradiated on the reference surface. The linearly polarized light that is irradiated onto the object to be measured passes through a plurality of layers, and is reflected back from the surface or the back surface of each layer. At this time, when a stress acts on a predetermined layer of the measurement target, the polarization state of the linearly polarized light in the first direction reflected back changes. The linearly polarized light in the second direction orthogonal to the linearly polarized light in the first direction in which the polarization state is changed is extracted from all of the reflected light reflected from the object to be measured. On the other hand, the extracted linear polarized light in the second direction and the reflected light reflected from the reference surface can be collected and interfered by the same optical path. From the two reflected light beams, the light intensity based on the light of the same polarization component is obtained. The change in the light intensity obtained from this can be obtained by changing the polarization of the object to be measured by the birefringence. At this time, the amount of change in the birefringence of the calculation formula for obtaining the difference in the principal stress is used = the difference X of the main stress is measured by the thickness X photoelastic coefficient of the object. If the three parameters in this formula are known, the remaining unknown parameters can be found. In general, the thickness and the photoelastic coefficient of the object to be measured can be easily obtained by other methods. In 200813393, the difference in the principal stress of a predetermined layer in the plurality of layers can be obtained by obtaining the amount of birefringence as an unknown parameter. In this case, the light intensity of the interference light can be obtained by moving at least one of the measurement target or the reference surface in the direction in which the light travels, and the thickness of the measurement object can be simultaneously calculated. In other words, when the waveform of the light intensity of each layer of the measurement object and the reference surface is substantially equal to the optical distance between the layers of the measurement object, the intensity of the light based on the interference fluctuates. In this case, for example, if the horizontal axis is the moving distance of the measurement target or the reference surface, the vertical axis indicates the change in the light intensity as the light intensity at the position on the map to obtain the envelope of the absolute 光 of the light intensity. The distance between the vertices of the lines will coincide with the optical distance between the layers of the object to be measured. Therefore, the thickness of the object to be measured can be simultaneously calculated from the distance between the vertices. In addition, according to the method of the present invention, it is preferable to move the reference light or the measurement target surface to the direction in which the irradiation light is moved forward and backward, and to obtain the light intensity information in which the light intensity of the interference light is maximum (the second item of the patent application) . Further, from the light intensity information at this time, the correct birefringence variation can be obtained, and the difference in the principal stress of the predetermined layer can be accurately obtained. Further, according to the method of the present invention, it is preferable that the phases of the two reflected lights constituting the interference light are substantially separated into half by a half-wavelength, and the difference between the two phases after the separation is taken to remove the DC component in the light intensity of the interference light. (Applicant's patent scope item 3). At this time, the two phases of the two reflected light beams are shifted by a half wavelength ', and the two phases are inverted by 180 degrees. In other words, in this state, by taking the difference between the two phases, it is possible to remove the DC component which does not change from the polarization state reflected from the reference surface to 200813393 minutes, and only the polarization component which changes the polarization state can be extracted. In other words, the amount of change in polarization when the birefringence of a predetermined layer is applied only by stress can be accurately obtained. Further, according to the method of the present invention, it is preferable to obtain a periodic relationship from the relationship between the amount of movement of the reference surface or the measurement target surface and the light intensity of the interference light, and to obtain the real phase of the periodic relationship with The determined reference phase is compared, and based on the result, it is judged that the difference in the principal stress of the predetermined layer acting on the object to be measured is the tensile force or the compressive force (item 4 of the patent application). In this case, experiments, theoretical calculations, and simulations are carried out in advance using the same sample as the object to be measured, and the reference phase is determined by specifying the conditions of the tensile force or the compressive force acting as stress on the sample. By comparing the reference phase with the real phase when measuring the predetermined layer of the object to be measured, it is judged whether the difference in the principal stress acting is the tensile force or the compressive force. According to the method of the present invention, it is preferable that the linearly polarized light irradiated on the measurement target surface is relatively rotated around the optical axis of the measurement target surface in the linearly polarized light, and the amount of change in the polarization of the birefringence based on the respective rotation angles is obtained. From the information of the plurality of polarization changes and the rotation angle, the difference between the principal stress of the object to be measured and the angle (the fifth item of the patent application) is obtained. For example, it is desirable to obtain an angle at which the rotation angle is at least two angles and to obtain a difference in principal stress between the linearly polarized directions of the light irradiated from the respective angles (article 6 of the patent application). At this time, the 光 of the light intensity of the interference light obtained by each rotation angle (for example, two angles) is converted into a vector, and the vectors of the two rotation angles are combined, and can be specified from the angle displayed by the vector synthesis thereof. The difference in principal stress is the angle of 200813393. According to a seventh aspect of the invention, in the case where the irradiation light having a wavelength distribution of a predetermined range, which is a predetermined wavelength range, is irradiated onto the transparent measurement object and the reference surface composed of a plurality of layers, at least the measurement is performed. The object is irradiated with a slightly circularly polarized light which is different from the first direction by 45 in a predetermined first direction linear polarization. The second direction component is shifted by a slight circularly polarized light of 1/4 wavelength, and the reflected light reflected from the measurement target surface of the predetermined layer of the measurement target coincides with the optical path length of the reflected light returned from the reference surface, and The reflected light from the surface to be measured is a linearly polarized light which is shifted by a wavelength of -1 / 4 from the second direction component, and a polarized component in a third direction which is orthogonal to the first direction due to a change in the polarization state. The light-receiving component in the third direction and the reflected light returning from the reference surface are collected and interfered by the same optical path, and the interference light of the same polarization component based on the mutually overlapping two reflected light is obtained. The change in the polarization of the birefringence based on the light intensity. According to the photoelastic measurement method of the seventh aspect of the invention, the irradiation light is applied to both the measurement target and the reference surface. At this time, at least the linearly polarized light in the first direction of the measurement target surface is converted into a slightly circularly polarized light and irradiated. The slightly circularly polarized light that is irradiated onto the object to be measured passes through a plurality of layers and is reflected on the surface or the back surface of each layer. At this time, when stress acts on a predetermined layer of the object to be measured, the polarization state of the slightly circularly polarized light reflected back changes, that is, changes to elliptically polarized light. According to the original state of the polarized state, the polarized component of the original i-th direction -10- 200813393 is extracted. On the other hand, the linearly polarized light in the third direction orthogonal to the linearly polarized light in the first direction is extracted from all the reflected light reflected by the object to be measured. The linearly polarized light in the third direction and the reflected light reflected from the reference surface are collected and interfered by the same optical path. From the two reflected light beams, the light intensity based on the interference light of the same polarization component is obtained. From the change in the intensity of the light obtained, information on the change in the polarization of the object to be measured by the birefringence can be obtained. As the change information of the polarized light, an unknown parameter among the amount of change in birefringence, the thickness of the object to be measured, and the photoelastic coefficient, which are caused by the influence of the stress of the predetermined layer of the measurement target, can be obtained. For example, the difference between the two principal stresses of the birefringence is measured by the difference X of the principal stress, and the difference between the principal stresses is obtained. At least two parameters are known, and the remaining unknowns can be easily obtained. parameter. Further, if the parameters are all available, the difference in the principal stress acting on the predetermined layer can be easily and accurately determined, and the layer in the plurality of layers can be distinguished from the stress. In addition, according to the method of the present invention, it is preferable to move the reference light or the measurement target surface to face the direction in which the illumination light is moved forward and backward, and to obtain the light intensity information in which the light intensity of the interference light is maximized (article 8 of the patent application) . At this time, by obtaining the light intensity information in which the light intensity of the interference light becomes maximum, it is possible to easily distinguish the stress acting on the predetermined layer of the measurement target. Further, in this case, the amount of change in the correct birefringence can be obtained from the light intensity information, and the difference in the principal stress of the predetermined layer can be accurately obtained. Further, according to the method of the present invention, it is preferable that the phases of the two reflected lights constituting the interference light are substantially separated into half by a half wavelength, and the difference between the two phases after the separation of 200813393 is obtained. DC component (No. 9 in the scope of patent application). At this time, by shifting the two reflected light by a half wavelength, the two phases are in a state of being inverted by 180 °. In other words, in this state, by taking the difference between the two phases, the DC component which does not change in the polarization state reflected by the reference surface can be removed, and only the polarization component which changes the polarization state can be extracted. Therefore, the amount of change in polarization of the predetermined layer birefringence only under stress can be accurately obtained. In addition, according to the invention, it is preferable to move the circularly polarized light relative to the object to be measured so that the surface to be measured orthogonal to the direction of propagation of the circularly polarized light can move in a vertical plane. The information on the amount of change in the polarization of the birefringence at the complex point is obtained, and the stress direction acting on the predetermined layer of the object to be measured is estimated from the distribution state (the first aspect of the patent application). At this time, it is estimated that the angle of the principal stress at the time of using a slightly circular polarized light can effectively exhibit the function. According to a first aspect of the invention, there is provided an apparatus for: illuminating means for outputting an illumination light having a wavelength distribution within a predetermined range of a central wavelength; and separating means for separating the illumination light from the illumination means into two linearly polarized lights And the linearly polarized light in the first direction to be separated is outputted to the measurement object having a permeability formed by the plurality of layers, and the linearly polarized light in the second direction is outputted to the reference surface; and the extraction means is from the predetermined layer The second direction component is extracted from the reflected light of the measurement target surface. -12- 200813393 The means for combining is the reflected light extracted by the extraction means reflected from the measurement target surface of the predetermined layer of the measurement target. The reflected light returned from the reference surface can be collected and interfered by the same optical path. The moving means moves at least one of the measurement target or the reference surface in the forward direction of the linear polarization, so as to be moved from the predetermined layer. The reflected light of the measurement target surface return bonding means is consistent with the optical path length of the reflected light returned from the reference surface by the bonding means; Segment, two reflected light detecting system overlaps the same change in light intensity of each polarized component is 0; and means for calculating, based the detection result of the detecting means, the polarization change amount is obtained based on information birefringence. According to the photoelasticity measuring apparatus according to the eleventh aspect of the invention, the linearly polarized light in the first direction is output toward the object to be measured formed by the plurality of layers, and the other is the second one. The linear polarization of the direction is output toward the reference plane. Each linear polarized light will reflect when it reaches the output $ end. In particular, the measurement object having permeability is reflected by the linearly polarized light transmitted through the surface and the back surface of each layer. The reflection of these complex plane reflections; 71⁄2 ′ when the right stress acts on a given layer, the polarization state changes during the process of reciprocating through the layer. The linearly polarized light from which the polarization state changes is extracted by the extraction means only the polarized component in the second direction orthogonal to the first direction. By means of the combination, the extracted polarized component and the reflected light from the reference surface can be collected and interfered by the same optical path. Before the two reflected lights are collected before the combining means, at least one of the measuring object or the reference surface is moved back and forth in the traveling direction of the linearly polarized light by the moving means, -13-200813393, and the back surface of the plurality of layers of the return bonding means is reflected. Either one of the linear polarizations in the second direction coincides with the optical path length from the reference surface to the bonding means. At this time, when the lengths of the two optical paths are the same, only the reflected light that is reciprocally transmitted through the predetermined layer having the back surface can be extracted by the extraction means, and the detected polarized light component and the reflected light from the reference surface can be detected by the detecting means. The light intensity of the polarizing component changes. Further, based on the detection result, the calculation means obtains information on the change of the polarization based on the birefringence of the object to be measured. That is, the first method invention can be suitably realized. Further, according to the device of the present invention, it is preferable to provide a rotation driving means for outputting an optical system and an object to be measured, which are composed of an irradiation means, a reference surface, a separating means, a drawing means, a coupling means, and a detecting means, from the optical system. The object is relatively rotated around the optical axis of the linearly polarized light of the object to be measured (Patent No. 12 of the patent application). According to this configuration, linear polarized light of different angles can be irradiated onto the object to be measured. That is, information on the amount of change in polarization of each rotation angle based on birefringence can be obtained. The light intensity of the interference of the information of the plurality of polarizations is transformed into the vector of the vector and the rotation angle information, and the vector can be combined to the angle of the specific principal stress. That is, the fifth and sixth method inventions can be suitably realized. Further, according to the invention of the device, it is preferable to further provide a memory means by using a moving means to change the relationship between the amount of movement of the reference surface or the sample corresponding to the object to be measured and the light intensity of the interference light by a moving means. Taking the periodic relationship of the experiment and memorizing the reference phase of the periodic relationship, the calculation hand-14-200813393 segment compares the real phase of the measured periodic relationship based on the measured object with the reference phase read from the memory means. According to the result, it is judged that the difference of the principal stress acting on the predetermined layer of the object to be measured is the tensile force or the compressive force (article 13 of the patent application). According to this configuration, experiments, theoretical calculations, and simulations are performed using the same sample as the object to be measured, and the conditions of the tensile force or the compressive force acting as stress are specified on the sample to determine the reference phase to be stored in the memory means. Further, by comparing the reference phase with the actual phase of the predetermined layer of the measurement object, it is possible to determine whether the difference in the principal stress of the action is the tensile force or the compressive force. That is, the fourth method invention can be suitably realized. According to a fourth aspect of the invention, there is provided an apparatus for: illuminating means for outputting an irradiation light having a wavelength distribution within a predetermined range of a center wavelength; and separating means for separating the irradiation light from the irradiation means into two linearly polarized lights, The linearly polarized light in the first direction to be separated is outputted to the measurement object having a permeability composed of a plurality of layers, and the linearly polarized light in the second direction is outputted to the reference surface. The first conversion means is The separation means separates the linearly polarized light that is directed toward the object to be measured, and the third direction component that is different from the first direction by 45 degrees is shifted by 1/4 wavelength to be converted into a slightly circularly polarized light, and the second conversion means measures the predetermined layer. The reflected light reflected from the target surface is converted into a slightly linearly polarized light by shifting the third direction component by -1 / 4 wavelength; and the extraction means is substantially reflected by the second conversion means as linearly polarized light -15-200813393 The polarization component in the third direction orthogonal to the first direction generated by the change in the polarization state is extracted; and the coupling means is such that the polarization component in the third direction is derived from the reference The reflected light returning from the surface can be collected and interfered by the same optical path. The moving means moves at least one of the measurement target or the reference surface in the forward direction of the linearly polarized light to make the predetermined layer The reflected light of the kf image surface return bonding means is measured to have the same optical path length as the reflected light from the reference surface returning means; and the detecting means detects the light intensity change of the same polarized light component of the mutually overlapping reflected light; And the calculation means is based on the detection result of the detection means to obtain the polarization change amount information based on birefringence. According to the photoelasticity measuring apparatus according to the first aspect of the invention, the linearly polarized light of the first direction is outputted toward the measurement light composed of the plurality of layers by the separating means, and the other is The linearly polarized light in the second direction is output toward the reference surface. The linearly polarized light in the first direction of the object to be measured is converted into a slightly circularly polarized light by the first conversion means. Each linear polarized light will reflect when it reaches the output. In particular, the object to be measured having permeability is reflected by the slightly circularly polarized light transmitted through the surface and the back surface of each layer. When the reflected light reflected by the complex surface has a stress in a predetermined layer, the polarized state changes during the process of reciprocating through the layer. That is, it changes from a slightly circularly polarized light to an elliptically polarized light. Further, the ellipses are polarized, and the second conversion means is returned to the slightly linearly polarized light in the first direction. On the other hand, only the polarization component in the third direction orthogonal to the first direction is extracted by the extraction means. On the other hand, by means of -16-200813393, the extracted polarized light component and the reflected light from the reference surface can be collected and interfered by the same optical path. Before the two reflected lights are collected before the bonding means, at least one of the measurement object or the reference surface is moved back and forth in the traveling direction of the polarized light by the moving means to return the back surface of the plurality of layers of the return bonding means in the first direction. Any one of the slightly circularly polarized light can be consistent with the optical path length from the reference surface to the bonding means. At this time, if interference occurs in a state in which the two optical path lengths match, the intensity of the interference light of any layer to be measured is maximized. When the light intensity is maximum, the change in light intensity of the same polarized component from the reflected light from the object to be measured and the reflected light from the reference surface is detected by the detecting means. On the basis of this detection result, the calculation means obtains information on the change of the polarization based on the birefringence of the object to be measured. That is, the method invention of the seventh aspect can be suitably realized. In the invention of the first to the first aspect, the moving means is preferably such that at least one of the measurement target or the reference surface moves back and forth in parallel with the traveling direction of the light, and the detecting means sequentially detects the movement during the movement. The light intensity of the interference light is calculated according to the detection result of the detection means, and the maximum intensity of the light intensity of the interference light is obtained, and the information of the change amount of the polarization based on the birefringence is obtained from the obtained result (patent application scope) 1 5 items). That is, according to this configuration, the second and eighth method inventions can be appropriately realized. Further, in the eleventh to fifteenth aspects of the invention, it is preferable that the optical means is such that each phase of the two reflected lights constituting the interference light that interferes with the combining means can be substantially separated by a half wavelength by a half wavelength; The amount of change in the polarization of the birefringence is obtained by removing the DC component of the light intensity of the interference light by the difference between the two phases of the reflected light after separation (Related Patent Application No. 16). That is, according to this configuration, the third and ninth inventions can be suitably realized. [Effect of the Invention] The photoelastic measurement method and apparatus according to the present invention emit light to the object to be measured and the reference surface, and extract only the polarization component of the reflected light in the reflected light from the object to be measured, This polarizing component interferes with the reflected light of the reference surface, and extracts the amount of change in birefringence due to the influence of the stress acting on any layer. Further, from the change amount of the birefringence ®, the difference in the principal stress acting on any layer can be accurately obtained, and the layer in which the stress acts can be resolved. [Embodiment] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Further, in the present embodiment, a case where linear polarization is employed will be described as an example. Fig. 1 is a view showing a schematic configuration of a device using the photoelastic measurement method of the present invention. The apparatus of the present embodiment is configured such that the glass substrate W 1, W2 having transparency as in the case of two liquid crystal panels or a plasma display panel is held by the measurement target W of the flat mounting table 60 with a small gap therebetween. An optical system component 1 having light having a wavelength distribution of a predetermined range as a center wavelength, and a control system component 2 for controlling the optical system component 1, and a reflected light output from the optical system component 1 by reciprocating transmission The target object extracts a polarizing component that changes the polarization state by the influence of the stress acting on the predetermined layer, and detects the light intensity of the interference light generated by the polarizing component. Further, in the control system unit 2 of -18-200813393, the arithmetic processing unit 15 for obtaining the information on the amount of change in the polarization based on the light intensity detected by the polarometer 3 is included. Hereinafter, each configuration will be described in detail. The optical system unit 1 is provided in the order of the light source 4 toward the measurement target W, in the order of the collimator lens 5, the polarizing plate 6, the first beam splitter 7, the objective lens 8, and the second beam splitter 9. In addition, the light collecting unit 126 and the photodiode 11 are disposed on the optical path separated by the first spectroscope 7 and moving toward the direction different from the object W to be measured. Further, the polarizing plate 1 2 and the reference mirror 13 are provided on the optical path separated by the second spectroscope 9 and directed toward the direction different from the object W to be measured. Hereinafter, each configuration will be specifically described. The light source 4 generates light in a relatively wide band region. For example, in the case of the present embodiment, a superluminescent diode having a band of 790 ± 20 nm can be utilized. The light generated from the light source 4 is directed toward the polarizing plate 6 by the collimator lens 5 becoming parallel light. Further, the light source 4 corresponds to the irradiation means of the present invention. The polarizing plate 6 is arranged at 45 °, and the polarizing surface is extracted from the random polarized light irradiated from the light source 4 by 45. In the initial stage, the linearly polarized light is directed toward the first beam splitter 7. The first spectroscope 7 has a polarizing surface of 45. The linear polarization passes through. That is, the polarizing surface passing through the polarizing plate 6 is 45. The linear polarization is passed as it is. Further, in the first spectroscope 7, the polarization component returned from the second spectroscope 9 is directed toward the photodiode 1 1. In other words, the surface and the back surface of each of the glass substrates W1, W2 of the measurement object W and the linearly polarized light reflected back to the second spectroscope 9 by the reference mirror 13 are not rotated, and the original polarization state is maintained. The returned polarized component returns from the second spectroscope 9 to the first spectroscope 7, and the first spectroscope 7 directs the returned polarized component toward the photodiode 11. -19- 200813393 The photodiode 1 1 detects the light of the polarization component returned from the second spectroscope 9, and transmits a detection signal to the arithmetic processing unit 15 of the control system 2 to be described later. The objective lens 8 is a lens that directs the incident linearly polarized light toward the measurement object W and the reference mirror 13 on the downstream side. The linear polarization system that collects light by the object lens 8 reaches the second beam splitter 9. The second beam splitter 9 separates the light collected by the collecting lens 8 into a pair of linear polarized lights which are orthogonal. In other words, the measurement light that is directed toward the first ^ direction of the measurement target W and the reference light that faces the second direction of the reference mirror 13 are separated. Further, the second spectroscope 9 recollects the reference light and the measurement light which are reflected by the measurement object W and the reference mirror 13 and return to the same optical path. At this time, only the polarization component having the polarization state changed from the measurement light and the reference light is extracted, and the polarization component is shifted toward the polarization meter 3 different from the initial optical path, and the polarization component having no change in the polarization state passes through the initial stage. The optical path returns to the first beam splitter 7. Further, the second spectroscope 9 functions as a separation means, an extraction means, and a coupling means of the present invention. The polarizing plate 12 is provided on the optical path of the reference light from the second spectroscope 9 toward the reference mirror 13, and the linearly polarized light from the second spectroscope 9 is internally changed to the polarizing surface by 45. The linearly polarized light causes the reference light whose orientation state is changed to be reflected by the reference mirror 13 and returned to the second beam splitter 9. The reference mirror 13 is mounted vertically for the direction of travel of the reference light. The reference light reflected by the reference mirror 13 is returned to the second polarization beam splitter 9 through the same optical path. Further, the configuration of the reference mirror 13 is movable forward and backward by a slight distance with respect to the traveling direction of the reference light by the operation of the piezoelectric element 14. This -20-200813393, reference mirror 13 is equivalent to the reference surface of the present invention, and the piezoelectric system corresponds to the moving means of the present invention. The collecting lens 10 is a lens that collects light from the linear photodiode 11 of the second spectroscope 9. Next, the 'polar pole meter 3' is composed of 20 0, 2 1 which respectively collects the linearly polarized light separated by the device 19 and the third beam splitter 19, and receives the light from the collecting lens 2 0, 2 1 . The linearly polarized diode 22 and the second photodiode 23 are provided. The relevant structure # is explained below. The objective lens 18 is a lens that directs the linearly parallel light from the second spectroscope 9 toward the third beam splitter 19. The third spectroscope 19 is arranged at 45°, and is separated into half by the phase wavelengths of the measurement light and the reference light which are returned to the same optical path at the second minute, and the separated linear polarized lights are respectively at 20, 21 In the case of the present embodiment, the linear light is separated from the measurement light and the reference light which are separated from each other, and is directed toward the first light 22, and is aligned with each other. When the measurement light and the reference linear polarization become a 45° component, the second photodiode 23 is directed. The first and second photodiodes 22, 23 output the detected direct light intensity signal levels to the calculator 24, respectively. Further, the photoelectric photodiodes 22, 23 correspond to the detecting means of the present invention. The signal of the light intensity detected by the two photodiodes 22, 23 becomes the phase-inverting element 14 of each of the thousands of waveforms shown in Fig. 3, and the polarized light is directed toward the third optical splitting lens. Specifically, the light is polarized by the optical illuminator 9 which can be shifted by the semi-collector lens 23 °, that is, the + 4 5 ° component electric diode light; 1 and 2, at this time, by the second figure 1 80 〇° -21 - 200813393 The calculator 24 is synthesized by taking the difference between the signal levels of the two photodiodes 22, 23 and the intensity of the detection. In this case, as shown in Fig. 3, the two phases of the shape detected by the two photodiodes 22, 23 are inverted by 180. Therefore, it is synthesized by taking the difference between the two light intensities. As a result, as shown in Fig. 4, the DC division of the interference waveform can be extracted only by the interference light which changes based on the birefringence reflected from the measurement object W. Next, the control system unit 2 includes an arithmetic processing unit 15 , a system 16 , an operation unit 17 , and the like. The relevant components are specifically described below. The calculation processing unit 15 performs the birefringence as the second processing system to obtain the difference between the principal stresses of the glass substrate W 1 or W2 acting on the measurement object w as the second processing system. The unknown parameter among the amount, the photoelastic coefficient, and the thickness of the glass-base substrate acts on the stress of the predetermined glass-base substrate. Further, the arithmetic processing unit corresponds to the arithmetic means of the present invention. As the first processing, for example, the photodiode 1 1 detects that the reflected light returned from the measurement target object 13 does not change from the measurement target W and the reflected light returned from the reference mirror 13 brightness. At this time, the command signal is sent to the drive control unit Η to control the piezoelectric element 14 to calculate the reference beam position at which the intensity of the interference light is maximized by the light intensity 逐 measured by the photodiode 1 1 successively. That is, the position of the reference mirror 13 is also the position at which the light intensity 涉 of the light ray is the largest. The light of the second picture of the measured light is divided into the component-driven control to indicate the number of changes to the focus, and 15, the object W and the dryness of the reference, and the detection of the test 13 - 22- 200813393 The light intensity incident on the photodiode 1 1 is greater than the intensity of light incident on the polarimeter. Therefore, if the interference light cannot be detected by the polarization meter 3, it can be judged that the amount of change in birefringence is too small, or the optical axis of the optical system is deviated, especially because the tilt of the measurement object W does not match. The bias is such that light cannot be detected. In the second processing, the calculator 24 obtains the amount of change in the birefringence of the change in the measurement target W from the intensity of the detected interference light. Further, the difference in the principal stress acting on the predetermined measurement object is measured by the amount of change in birefringence = the difference X of the principal stress, and the thickness of the object is measured. <The formula of the photoelastic coefficient is obtained. In other words, when the information on the amount of change in birefringence is obtained, the difference between the principal stress acting on the object to be measured can be easily obtained from the thickness and the photoelastic coefficient of the known object to be measured. For example, when the measurement object is a predetermined glass substrate, the difference in the principal stress acting on a predetermined glass substrate can be determined by the difference between the amount of change in birefringence information and the difference in the principal stress of the glass substrate X, the thickness of the glass substrate, and the photoelastic coefficient. Got it. Namely, when the information on the amount of change in birefringence is obtained, φ can be easily obtained from the thickness of the known glass substrate and the photoelastic coefficient, and the difference in the principal stress applied to the glass substrate can be easily obtained. In response to the input of the set condition from the operation unit 17, the drive control unit 16 moves the optical system unit 1 by a predetermined distance from the light source 4 toward the traveling direction of the linearly polarized light of the measurement target W. In other words, the driving means such as a pulse motor (not shown) is driven to control the distance L1 from the second spectroscope 9 to the back surface of the glass substrate W1, the distance L2 from the second spectroscope 9 to the reference mirror 13, and the second splitting light. The optical system unit 1 is moved in such a manner that the distance L3 between the device 9 and the back surface of the glass substrate W2 and the distance -23-200813393 of each of the distances L4 from the second beam splitter 9 to the reference mirror 13 are substantially identical to each other. Further, the drive control unit 16 fine-tunes the position of the reference mirror 13 in accordance with the command signal from the arithmetic processing unit 15 to control the piezoelectric element 14 to maximize the light intensity of the interference light. The operation unit 17 sets various measurement conditions such as the thickness of the input glass substrates W1 and W2, the photoelastic coefficient of each glass substrate, the material, the refractive index, and the distances L 1 to L4 between the respective components. Next, the operation of measuring the difference in the principal stress acting on the measurement object W by the above-described embodiment will be described. Further, a case where stress is applied to both of the glass substrates w 1 and W 2 constituting the object to be measured W will be described as an example. The measurement conditions are input from the operation unit 17 and measurement is started. First, the drive control causes the distance L1 from the second spectroscope 9 to the back surface of the glass substrate W1 to be the same as the distance L2 from the second spectroscope 9 to the reference mirror 13, that is, the drive control unit 16 is operated and not shown. The moving means such as a pulse motor moves the optical system unit 1 such that the lengths of the two optical paths are slightly coincident. ® When the optical system component 1 reaches a position where the two optical paths are slightly coincident, the light is radiated from the light source 4. After the collimated light is collimated with the collimator lens 5, the polarizing plate 6 linearly polarizes the polarizing surface by 45°, and passes through the first spectroscope 7 disposed at 45° in the subsequent stage toward the second spectroscope. 9. The linearly polarized light collected by the objective lens 8 provided in the preceding stage of the second spectroscope 9 reaches the second spectroscope 9, and is separated into two orthogonal linear polarized lights. The linearly polarized light (measurement light) in the first direction (horizontal direction) to be separated is directed toward the object to be measured W, and the glass substrates W1 and W2 are reciprocated through the period of -24-13,393, and the glass substrates w1 and W2 are in the process. The surface and back surface are reflected and returned to the second beam splitter 9. The linearly polarized light (reference light) in the second direction (vertical direction) of the other side is reflected by the reference mirror 13 and returned to the second beam splitter 9, and the polarizing plate 12 is inclined by 45. The linear light is polarized and returned to the second beam splitter 9. Among the measurement lights reflected by the respective surfaces of the measurement object W, the second spectroscope 9 extracts only the measurement light of the polarization component in the second direction that is straight in the first direction based on the change in the polarization state. Orient it toward the pole meter 3. At this time, the extracted measurement light in the second direction and the reference light returned from the reference mirror 13 are again collected and interfered by the same optical path. Further, the linearly polarized light having no change in the polarization state reflected from the object to be measured W is detected by the photodiode 1 1 via the first spectroscope 7 on the upstream side. When the position of the reference mirror 13 is determined, the linearly polarized light from the second spectroscope 9 toward the second direction of the polarimeter 3 is collected by the collecting lens 18, and then reaches the third spectroscope 1 constituting the polarimeter 3. 9. The third spectroscope 19 is substantially separated into half by a linear polarization of the horizontal component which is reached by shifting the phase by a half wavelength. At this time, the components of the measurement light and the reference light are +45°, and each other is -45. The components are linearly polarized with each other in the same direction. Among the linearly polarized light of each of the groups in which the directions are aligned, the linearly polarized light composed of the horizontal components is collected by the collecting lens 20 and detected by the first photodiode 22. The linearly polarized light formed by the vertical component is collected by the collecting lens 21 and detected by the second photodiode -25 - 200813393 body 23. The two linearly polarized light that receives the light by each of the photodiodes 22, 23 is converted into a respective light intensity 以 by the calculator 24, and is subtracted. At this time, since the phase of the two linear polarizations is reversed by 180 °, the DC component of the reference light reflected from the reference mirror 13 is removed, and only the interference component of the measurement light is obtained. The light intensity 値 of the thousands of components is input to the arithmetic processing unit 15 , and the arithmetic processing unit 15 obtains the difference between the amount of change in birefringence information and the principal stress. As described above, the process of obtaining the difference between the amount of change in the birefringence of the glass substrate W1 and the principal stress is completed. Next, the drive control unit 16 operates the control means to move the optical system unit 1 while operating the piezoelectric element 1 4, after adjusting the distance L3 from the back surface of the glass substrate W2 to the second spectroscope 9 to be substantially the same as the optical distance from the optical distance L4 of the reference mirror 13 to the second spectroscope 9, by using the above-mentioned glass substrate W 1 performs the same processing to obtain the difference information of the birefringence of the glass substrate W2 and the difference in the principal stress. As described above, the optical system unit 1 is moved such that the distance from the second spectroscope 9 to the reference mirror 13 slightly matches the optical path length to the back surfaces of the glass substrates W1 and W2, and is used on the back surface of each of the glass substrates W1 and W2. When the measurement light and the reference light reflected by the reference mirror 13 are used, the difference between the change amount information of the birefringence and the principal stress of any layer of the measurement target can be accurately obtained. In other words, since the measurement light returned from the object to be measured by the stress changes due to the polarization plane, only the polarization component in the second direction orthogonal to the first direction can be extracted by the second spectroscope 9, and the polarization component and the reference are obtained from the reference. The reference light returned from the surface 13 is collected and interfered by the same optical path, and the interference light can be reflected and output toward the polarization meter 3. Therefore, the phase of the linear polarization of the reference light and the second light formed by the measurement light is separated by a half wavelength, and the polarization component and the same component are aligned with each other to act on the principal stress of the glass substrate. The polarization component of the difference only birefringence is detected as the light intensity of the interference light. Therefore, by using the light intensity of the interference light, the amount of change in birefringence which is caused by the difference in the principal stress of any layer can be obtained by the measurement object which is formed by the plurality of layers. Further, by utilizing the amount of change in the birefringence, the angle of the difference between the principal stress acting on any layer and the principal stress can be obtained. That is, the vector ® component is obtained from the angle of the difference of the principal stresses to correctly resolve the stress acting on each of the plurality of layers. Further, the magnitude and direction of the stress acting on each of the plurality of layers can be accurately determined by the angle of the difference between the principal stresses and the vector component obtained. [Embodiment 2] In the first embodiment, the light emitted from the light source 4 is converted into linearly polarized light. However, in the present embodiment, a case where the polarized light is output toward the object to be measured W by the circularly polarized light is taken as an example. Further, in the present embodiment, the same configurations as those of the above-described embodiment are merely given the same reference numerals, and the different configurations are specifically described. Fig. 5 is a schematic view showing the configuration of a photoelasticity measuring apparatus when circularly polarized light of the present invention is used. The optical system unit 1, the control unit unit 2, and the first polarization meter 3 of the apparatus of the present embodiment are constructed. The optical system unit 1 is disposed on the optical path of the super-light-emitting diode of the light source 30 toward the object to be measured W, by the collimator lens 3, the polarizing plate 32, the first beam splitter 33, and 45. The order of the quarter-wavelength plates 35 is provided. In addition, the first spectroscope 3 3 is outputted toward the object to be measured W, and the object W reflected on the measuring light of the polarimeter 3 is measured at -27-200813393, and is arranged at a mirror angle of 36°. The 1/4 wavelength plate 3, the mirror 38, the polarizing plate 39, and the second beam splitter 40 are provided in this order. Further, the reference beam 4 1 is disposed on the optical path separated by the first spectroscope 33 and directed toward the direction different from the object W to be measured, and the reference mirror 4 1 is reflected toward the reference beam of the polarizer 3 The optical path is provided in the order of the mirrors 42, 43, the polarizing plate 44, and the second beam splitter 40. Hereinafter, each configuration will be specifically described. ^ The polarizing plate 32 is configured as 45. The parallel light from the collimator lens 31 is changed to the initial linearly polarized light of the polarizing surface of 45°, and the linearly polarized light is directed to the first spectroscope 33. The first spectroscope 3 3 is linearly polarized from the polarizing plate 32, i.e., separated into measurement light in the first direction facing the object to be measured W and reference light in the second direction toward the reference mirror 13. Further, the first spectroscope 33 corresponds to the separation means of the present invention. The 1/4 wavelength plate 35' disposed at 45° changes the linearly polarized light to a slightly circularly polarized light by the measurement light of the linearly polarized light passing through the third direction. Further, the 1⁄4 wavelength plate 37 disposed at 45° corresponds to the first conversion means of the present invention. Next, the mirrors 63 are reflected by the respective surfaces of the glass plates W1 and W2 constituting the object W to be measured, and are further guided by reflection to be disposed on an optical path different from the incident light path. 45. The 1/4 wavelength is reversed 37. Configured as a 45. The 1/4 wavelength plate 37 passes through the inside of the measurement object -28-200813393 w, and returns to the slightly linear polarization. In other words, when stress acts on the glass substrate w 1 or W 2 of the measurement target W, the polarized surface of the circularly polarized light is slightly rotated to be changed into elliptically polarized light. This elliptically polarized light is passed through and converted into a linearly polarized light containing a birefringence variation. Further, the 1/4 wavelength plate 37 disposed at -45 ° is equivalent to the second conversion means of the present invention. The mirror 3 8 is configured to be -45. The quarter-wavelength plate 37 is changed to a slightly linearly polarized measurement light, and is opposed to the second light splitter 40 by the polarizing plate 39. The second spectroscope 40 is provided at a position where the measurement light reflected from the measurement object w intersects with the reference light reflected from the reference mirror 41. On the other hand, the second spectroscope 40 recollects the reference light and the measurement light, which are reflected back to the same optical path by the respective measurement object W and the reference mirror 13. At this time, among the measurement lights reflected back, only the polarization component having a changed polarization state is extracted, and the polarization component that is opposite to the polarization meter 3 side and the polarization state is not changed, and the second polarization meter of the backward stage 45. Further, the second spectroscope 40 is used as a means for extracting and combining means for the present invention. The reference mirror 41 reflects the reference light in a different direction from the reference light when it is incident. The reflected reference light is further directed by the two mirrors 42, 43 to the polarizing plate 44 of the rear stage. Further, the reference mirror 41 is configured such that the operation of the piezoelectric element 14 can be moved back and forth by a slight distance with respect to the direction in which the reference light is made. Further, the reference mirror 41 corresponds to the reference surface of the present invention. The polarizing plate 44 is arranged at 45. It will become 45° linear polarized light through the internal reference light. Namely, the reference light is incident on the optical device 40 by the polarizing plate 32 of the preceding stage and the linear polarizing plate of the -29-200813393 polarizing plate 4 4 which are different from each other by 90 °. Next, as shown in FIG. 6, the first polarization meter 3 receives the first linear photodiode 22 and the second photodiode 23 separated by the third spectroscope 46. And the composition of the calculator. Hereinafter, each configuration will be specifically described. The third spectroscope 46 is arranged at 45°, and the measurement light that is extracted by the second spectroscopic unit and returned to the same optical path is separated from the phase of the reference light by a wavelength, and the separated linear polarized light is in the lens. 20 and 21 are collected and can be directed to each of the photodiodes 22, that is, in the case of the present embodiment, the configuration is separated into horizontally polarized beams of reference light and reference light, which are oriented toward the second pole. The body 22 is linearly polarized with the reference light and is linearly directed toward the reference light, and is directed toward the second photodiode 23. The first and second photodiodes 22 and 23 respectively output the detected polarization 値 signals to the calculator 24. The calculator 24 is synthesized by picking up the difference between the signal levels of the light intensity 检测 detected by the suitable diodes 22 and 23 as shown in Figs. 2 and 3. At this time, as shown in Fig. 2 and Fig. 3, the two phases of the interference waveform detected by the two photoelectrics 22, 23 are combined by inverting 180° and taking the difference between the two light intensities 値. As a result, the DC component of the interference waveform of the fourth 被 is removed, and only the interference light from the component of the change amount measuring the birefringence of the reflection is extracted. The second polarization meter 4 5 has the same configuration as that of the first polarization meter 3, and the light intensity of the second minute 3 splitting polarized light I 40 is shifted by half of each collected light and 23 ° is divided into two. In the two-light mode, the diode is shown by the pick-up I, and the image w is composed of the -30-200813393 3 spectroscope 46 and the first and second photodiodes 22 and 23. In other words, the second polarization meter 4 5 detects the measurement object W and the reference mirror 4 from the reflected light of the measurement object W and the reference mirror 4 1 by the polarization separated by the third spectroscope 40. Among them, the intensity of the interference light in which the reflected light returns to each other without change in the polarization state. This signal is sent to the arithmetic processing unit 15 . The configuration of the control system unit 2 is the same as that of the first embodiment, and includes an arithmetic processing unit 15 , a drive control unit 16 , an operation unit 17 , and the like. Next, an operation for measuring one of the differences in the principal stress acting on the measurement target W will be described using the apparatus of the above-described embodiment. In addition, the case where the stress is applied to both of the glass substrates W1 and W2 constituting the object to be measured W will be described as an example. The measurement conditions are input from the operation unit 17 and measurement is started. First, the drive control causes the distance from the first spectroscope 3 3 to the back surface of the glass substrate W1 to be the same as the distance from the first spectroscope 3 3 to the reference mirror 41, that is, the two optical paths can be made to match each other. The control unit 16 operates to move the optical system unit 1 by a moving means such as a pulse motor (not shown). When the optical system unit 1 reaches the optical path length slightly, the light is emitted from the light source 30. After the collimated light is collimated by the collimator lens 31, the polarized light is polarized by the polarizing plate 32, and reaches the first spectroscope 33. This linear polarized light is transmitted by the first spectroscope. 3 3 is divided into two orthogonal linear polarizations, and the linearly polarized light in the first direction (horizontal direction) to be separated is directed toward the measurement object W. The other straight line of the second direction (vertical direction) of the 200813393 line is directed toward the reference mirror 41. Here, the linearly polarized light toward the measurement target W is transmitted through the 1/4 wavelength plate 35' disposed at 45°, and the measurement light of the linearly polarized light can be changed to the measurement light of the slightly circularly polarized light. The measurement light is directed toward the measurement target W and is reflected on the front and back surfaces of the respective measurement objects wi and W2 while passing through the glass substrates W1 and W2. At this time, since the stress acts on the glass substrate W1, the measurement light changes from circularly polarized light to elliptically polarized light in the course of repeated transmission. The measurement light that is the ellipsometric W light is reflected in an inclined posture, and is reflected obliquely toward the mirror 42. The measurement light reaching the mirror 36 is directed toward the 1/4 wavelength plate 37 which is arranged at a 45° angle. Arrival is configured as a 45. The measurement light of the 1/4 wavelength plate 37 is returned to the linearly polarized light having a birefringence variation through the inside thereof. Through configuration to -4 5. The measurement light that returns to the linearly polarized light of the 1/4 wavelength plate 3 7 is reflected by the mirror 38 and reaches the second beam splitter 40. The reference light of the linearly polarized light in the second direction separated by the first spectroscope 3 3 is reflected in an oblique direction different from the incident direction by the reference mirror 41 provided in the inclined posture. However, the reference light is reflected in the order of the mirrors 42, 43 and passes through the polarizing plate 44 to reach the second beam splitter 40. The second spectroscope 40 extracts a polarization component in the second direction which is generated by a change in the polarization state among the measurement lights reflected by the respective surfaces of the measurement object W, and passes through the reflection from the reference mirror 4丨. The polarization component in the second direction of the reference light of the polarizing plate 44 is caused to reach the first polarization meter 3 by the same optical path, and is generated. -3 2 - 200813393 In addition, the second beam splitter 40 extracts the polarization component in the first direction of the component in which the polarization state is not changed among the measurement lights reflected by the respective surfaces of the measurement object W, and the reference beam 41 from the reference mirror 41 After the reflection, the polarization component in the second direction of the reference light passing through the polarizing plate 44 is allowed to reach the second polarization meter 45 by the same optical path, and interference occurs. The third spectroscope 46 of the first polarization meter 3 is a linearly polarized light which is formed by the horizontal components of the measured light and the dream light, and is slightly separated into half by a half-wavelength. At this time, the collected measurement light and the reference light are horizontal components, and are perpendicular to each other, and are linearly polarized in the same direction. Among the linear polarizations of the respective groups in which the directions are aligned, the linearly polarized light formed by the horizontal components is collected by the collecting lens 20 and detected by the first photodiode 22. The linearly polarized light formed by the vertical and the components is collected by the collecting lens 21 and detected by the second photodiode 23. The difference is made so as to adapt to the difference in the signal level of the light intensity 检测 detected by each of the photodiodes 22 and 23. In this case, as shown in FIG. 2 and FIG. 3, since the two phases of the interference waveform detected by the two photodiodes 22 and 23 are reversed by 180°, the difference between the two light intensities is adopted. The synthesis, as shown in Fig. 4, removes the DC component of the interference waveform. The light intensity 値 of the interference component is input to the calculation processing unit 15 , and the arithmetic processing unit 15 obtains the difference between the amount of change in birefringence information and the principal stress. The fourth spectroscope 4 6 of the second polarization meter 4 5 is a linearly polarized light which is formed by the horizontal components of the measurement light and the reference light which are reached, and is slightly separated into half by a phase which can be shifted by a half wavelength. At this time, the horizontal components of the measurement light and the reference light are collected, and the vertical components are aligned with each other to become linearly polarized in the same direction as the phase -33 - 200813393. Among the linear polarizations of the respective groups in which the directions are aligned, the linearly polarized light formed by the horizontal components is collected by the collecting lens 20 and detected by the third photodiode 22. The linearly polarized light formed by the vertical component is collected by the collecting lens 21 and detected by the fourth photodiode 23. According to this, the interference waveform of the linearly polarized portion formed by the horizontal component among the light and the reference light can be detected. The phase of this waveform can be utilized as a reference phase for determining whether the difference in principal stress acting on a given layer of the object is a tensile or compressive force. In addition, the reference phase system means that when either the reference mirror 41 or the measurement object W is moved, a periodic relationship is obtained from the relationship between the amount of movement and the light intensity of the interference light, and then the periodic relationship is obtained. Find the phase. As described above, the difference between the change amount information of the birefringence of the glass substrate W1 and the principal stress is obtained by the processing. Next, the drive control unit 16 is operated by a moving means (not shown) to move the optical system unit 1 while being actuated. The piezoelectric element 14 is controlled so that the distance from the back surface of the glass substrate W2 to the first beam splitter 3 3 is equal to the distance from the reference mirror 41 to the first beam splitter 33, by performing the above-described glass substrate W The same treatment of 1 is performed to obtain the difference between the amount of change in the birefringence of the glass substrate W2 and the principal stress. According to the configuration described above, by using the light intensity of the interference light, it is possible to obtain a difference in the principal stress of any layer of the measurement target having the transparency which is formed of a plurality of layers. The amount of change in birefringence' Further, by using the amount of change in birefringence, the difference in principal stress acting on any layer can also be obtained. That is, the stress acting on each of the plural layers can be correctly distinguished. Further, in the present embodiment, by using the circularly polarized light, the stress can be surely discriminated regardless of the direction of the stress -34-200813393. Further, the present invention is not limited to the above embodiment, and may be modified as follows.
(1) 利用上述實施例1之直線偏光的情況，亦可如下 變形。例如，構成亦可如第7圖所示，在從光源4朝向測 定對象物W照射的光路上，替代實施例1之第1分光器7 及第2分光器9依順序配備半鏡5 0與分光器5 1，從測定 對象物W及參考鏡1 3返回的偏光之中，從測定對象物W ^ 反射回來之偏光面的旋轉測定光，與從參考鏡1 3反射藉由 複數之反射鏡42、43而被誘導的參考光匯集而輸出偏極計 3。此外，半鏡5 0係相當於本發明之分離手段，分光器5 1 係作爲本發明之抽出手段及結合手段而發揮機能。 (2) 在上述各實施例中，使測定對象物及光學系組件 在其光軸周圍相對地旋轉，求取複數方向之主應力的差和 角度，亦可藉由在各旋轉角度的方向使在演算處理部i 5合 φ 成，求取作用於測定對象物W之應力的大小及其方向。 在此’利用實施例1及變形裝置求取主'應力之差的大 小及其方向時，亦可使光學系組件1本身繞着光軸周圍旋 轉，亦可旋轉測定對象物W或載置台6 0。 (3 )在上述各實施例中，爲了求取干涉光的最大値其 構成雖具備有光電二極體11或第2偏極計45，但當從各 分光器9、3 3到測定對象物w的距離，與從各分光器9、 3 3到參考鏡1 3、4 1的距離可預先精度良好地調合時，亦 可不需具備此構成。 -35 - 200813393 (4) 在上述各實施例中，雖利用於玻璃基板配備之測 定對象物W，但測定對象物W並不限定於此形態，亦可將 具有透過性之複數片的測定對象物密接堆疊。例如，有玻 璃基板彼此、玻璃基板與薄膜等折射率不同之測定對象物 的組合等。尤其是，測定組合背面反射率低之測定對象物 可有效地發揮機能。 (5) 在上述各實施例中，雖使從測定對象物W及參考 鏡1 3反射回來之反射光的光路長一致，但不一致的構成亦 響可。 例如，不使壓電元件1 4作動而將參考鏡1 3、4 1固定 的狀態下，從測定對象物W及參考鏡1 3返回之兩反射光 通過繞射光柵，改變成與第2方向正交的單色光之後，檢 測各波長的干涉強度，藉由傅立葉變換（F 〇 u r i e r Transformation)使壓電元件14作動時藉由演算求得所求 之最大干涉強度亦可。 (6) 在上述各實施例中，作爲光源4雖利用超發光二 極體， 但不限定於此，只要可產生既定頻率帶區的光即可。 例如，亦可將來自鹵素燈之光藉由帶通濾波器（band pass filter)限制於既定頻率帶區般的構成。 (7) 本發明之裝置，並不限定於上述實施形態，藉由 變更光學元件之鏡的種類或個數，可變形成複數種類的設 計。 〔產業上之利用可能性〕 -36- 200813393 如以上’本發明係適合求取作用於由具有透過性之複 數層所形成之工件的各層之主應力的差及其方向。 【圖式簡單說明】 第1圖係顯示實現有關實施例1之光彈性測定方法的 裝置之槪略構成的圖。 第2圖係顯示干涉光之光強度之檢測狀態的圖。 第3圖係顯示干涉光之光強度之檢測狀態的圖。 第4圖係顯示干涉光之光強度之檢測狀態的圖。 第5圖係顯示實現有關實施例2之光彈性測定方法的 裝置之槪略構成的圖。 第6圖係顯示實施例2之裝置的第1及第2偏極計的 構成之圖。 第7圖係顯示變形例裝置的構成之圖。 【主要元件符號說明】 1 光 學 系 組 件 2 控 制 系 組 件 3 偏 極 計 4 光 源 5 視 準 儀 透 鏡 6 偏 光 板 9 第 2 分 光 器 12 偏 光 板 13 參 考 鏡 14 壓 電 元 件 -37- 200813393 19 第 3分光器 22 第 1光電二極體 23 第 2光電二極體 24 演算器(1) In the case of the linearly polarized light of the above-described first embodiment, it may be modified as follows. For example, as shown in FIG. 7, the first beam splitter 7 and the second beam splitter 9 of the first embodiment may be provided with a half mirror 50 in an optical path irradiated from the light source 4 toward the object to be measured W. Among the polarized light returned from the measurement object W and the reference mirror 13, the spectroscope 51 receives the rotation measurement light of the polarization surface reflected from the measurement object W^, and reflects it from the reference mirror 13 by a plurality of mirrors. The reference light induced by 42 and 43 is collected and output to the polarimeter 3. Further, the half mirror 50 corresponds to the separating means of the present invention, and the spectroscope 5 1 functions as the extracting means and the joining means of the present invention. (2) In each of the above embodiments, the measurement target and the optical component are relatively rotated around the optical axis, and the difference and angle of the principal stress in the plural direction are obtained, and the direction of each rotation angle can be made. The calculation processing unit i 5 combines φ to determine the magnitude and direction of the stress acting on the measurement target W. Here, when the magnitude and the difference of the main stress difference are obtained by the first embodiment and the deforming device, the optical system unit 1 itself may be rotated around the optical axis, or the measuring object W or the mounting table 6 may be rotated. 0. (3) In the above-described respective embodiments, the photodiode 11 or the second polarization meter 45 is provided in order to obtain the maximum 干涉 of the interference light, but the measurement object is obtained from each of the spectroscopes 9 and 3 3 . The distance of w and the distance from each of the spectroscopes 9, 3 to the reference mirrors 13 and 4 1 can be precisely adjusted in advance, and it is not necessary to have such a configuration. -35 - 200813393 (4) In the above-described embodiments, the measurement target W is used in the glass substrate, but the measurement target W is not limited to this embodiment, and the measurement target of the plurality of transparent sheets may be used. The objects are connected to the stack. For example, there are combinations of measurement objects such as glass substrates, glass substrates, and films having different refractive indices. In particular, it is possible to effectively measure the function of the measurement object having a low combined back reflectance. (5) In the above embodiments, the optical paths of the reflected light reflected from the measurement object W and the reference mirror 13 are identical, but the configuration is not uniform. For example, in a state where the reference mirrors 1 3 and 4 1 are fixed without the piezoelectric element 14 being actuated, the two reflected light returned from the measurement object W and the reference mirror 13 are passed through the diffraction grating to be changed to the second direction. After the orthogonal monochromatic light, the interference intensity of each wavelength is detected, and the maximum interference intensity obtained by the calculation of the piezoelectric element 14 when the piezoelectric element 14 is actuated by Fourier transform is used. (6) In the above embodiments, the super light-emitting diode is used as the light source 4. However, the present invention is not limited thereto, as long as light of a predetermined frequency band can be generated. For example, the light from the halogen lamp can also be limited to a predetermined frequency band by a band pass filter. (7) The apparatus of the present invention is not limited to the above embodiment, and a plurality of types of designs can be formed by changing the type or number of mirrors of the optical elements. [Industrial Applicability] -36- 200813393 As described above, the present invention is suitable for obtaining a difference in principal stress of each layer acting on a workpiece formed of a plurality of layers having permeability and a direction thereof. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a schematic configuration of a device for realizing the photoelastic measurement method of the first embodiment. Fig. 2 is a view showing a detection state of light intensity of interference light. Fig. 3 is a view showing a detection state of the light intensity of the interference light. Fig. 4 is a view showing a detection state of the light intensity of the interference light. Fig. 5 is a view showing a schematic configuration of a device for realizing the photoelasticity measuring method of the second embodiment. Fig. 6 is a view showing the configuration of the first and second polarization meters of the apparatus of the second embodiment. Fig. 7 is a view showing the configuration of a modification device. [Main component symbol description] 1 Optical system component 2 Control system component 3 Polaroid meter 4 Light source 5 Sight lens 6 Polarizer 9 Second beam splitter 12 Polarizer 13 Reference mirror 14 Piezoelectric element -37- 200813393 19 3 Beam splitter 22 first photodiode 23 second photodiode 24 calculator