!258598 坎、發明說明： 【發明所屬之技術領域】 本發㈣關於—種共焦顯微量_統，尤指_種以光學干涉 ==縱向反應曲線的斜率’從而提高共焦顯微鏡在縱向的量測 角午析度之干涉式差動共焦顯微量測系統。 【先前技術】 光學絲員微鏡是現代精密的量測儀哭库 料,士德“_ 山7里列儀為’廣泛應用於材質的表面 、生物樣本的表面微小特徵及動態料、或生物薄膜、膠 原史白、細胞運動、液體界m氣體界面特料研究上。至於 =業應用方面’數位多用途光碟(DVD)與薄膜電晶體(tft)等產品 :程的檢測上，也都需使用光學顯微鏡。光學顯微鏡在先天上且 2破壞檢測㈣性’同時具有不必對待測樣本作特殊處理料 優勢。然而，由於光波的繞射現象，使其解析力受限 於+波長的寺級（一般稱為繞射極限）。 共焦顯微鏡（C〇nfocal microsc〇pe )利用針孔進行空間遽波， 使影像解析度稱加優絲絲顯微鏡，同時又具有縱向檢測的能 力，因此廣泛使用在半導體薄膜厚度檢測、生物活體切面 析的研究上。 共焦顯微鏡可以作三維的影像掃聪，亦即，除了可以得到二 維的表面形貌之外，也可以解析試片内部的層狀結構。由於妓隹 顯微鏡不需使用探針，因此可以很快的速度作掃猫動作，且^有、 較大的掃瞒範圍。然而，共焦顯微鏡縱向解析度僅約為·麵， 換言之’當試片内的層狀結構小於5〇〇nm日夺，其無法將之解析 出來。這樣的解析度，對於半導體薄膜厚度量測或生物細胞切片 分析等的應用是不夠的。 共焦掃描顯微的原理，一般咸認在1957年時由Marvin Minsky提出的US3013467乙案所揭露。由於當時缺乏適當的光 !258598 源與數據處理的能力，使得這一原理仍停留在純理論之階段，共 焦掃描顯微技術能真正成為一個實用的顯微技術則是等到雷射 與個人電腦發明以後。 在 1969 年，Paul Davidovits 和 Μ· David Egger 利用雷射發展 了第一台共焦掃描顯微鏡，而第一台商業化的共焦掃描顯微鏡則 是到1987年才問世。近十餘年來，無論是雷射技術或者是個人 電腦都有著驚人的發展，使得共焦顯微技術更形完備。單光子共 焦頒微鏡的光學理論首由時在英國牛津大學的Colin Sheppard和 Tony Wilson提出。美國康乃爾大學的Watt W. Webb等人則於 1989年實驗上證實了雙光子共焦顯微鏡的獨特性。 美商AT&A Bell實驗室於1992年以US5078482乙案揭露將 共焦顯微鏡技術用於半導體線寬控制的加工程序，該發明提供一 較短的焦距深度，及較一般共焦顯微鏡高的有效解析度。 曰商Nikon公司於1994年以US5296700乙案揭露以螢光共 焦顯微鏡搭載掃描式鏡組及光學物鏡提供測向解晰度，利用上述 系統進行待測物影像重建及光學色差補償，可有效提高螢光標定 技術的量化結果。 德國Siemens公司於1999年以US5991040乙案揭露以三角 量測法提升共焦顯微技術量測三維表面影像的解晰度，其利用一 角隅菱鏡的轉動，可分別量出待測物的上表面及鄰近左右表面的 形貌，且利用陣列式光偵測器可快速將掃描點的資訊結果描繪出 來。 美商 Digital Optical Image 公司於 2002 年以 US6388809 乙案 揭露以離焦平面的資訊，繪製與焦平面高低差的資訊，例如量測 待測物鄰近三點（A、B、C)資訊，其中B點位於焦平面設為零點， A、C兩點位於離焦平面，比較與焦平面高低差的資訊，即可繪 Ϊ258598 出待測物表面形貌。 ::rYr達 rr ㈣二二二== ^本馬達驅動平台的的位置掃描資訊，該技術主要針對大範 圍的表面檢測，例如LCD或晶圓的表面均勾度。 日商Olympus 0pticai公司於2〇〇2年以仍⑷7㈣乙 =使mr整合2向位移裝置於共焦顯微鏡頭上位移 反射回細器的光強—直維持於焦點上，由z 得掃描^ 彳向位置點(Z) ’ Χ _ Υ二維掃描機構亦可由控制器 旦,L，（x，y)’由座標點（x，y，z)的資訊可得待測物三維形貌 =:貌=控制器的掃描線性圖經電子細分割後可得高解析 ^ ChieagG大學於则年以US65488iq乙案揭露整合掃 田式、焦顯微鏡及掃描式電子束顯微鏡，其量測8]〇_厚戶的 試片時’解析度能仍低於100nm，該整合型顯微鏡具節省空^優 點，適合一般實驗室使用。 明 有關傳統共焦顯微鏡的架構及原理’將藉由第六圖詳加說_ 如第六圖所示，傳統共焦顯微鏡1G包含：分光鏡u、物鏡 12、集光鏡13、針孔14及光_器15。—試片16(待測物）係設 於載台（圖未示）上且位於物鏡12之後方。—準直的雷射光束17 經由物鏡12聚焦於試片16之表面後，由該試片16之表面反射， 再經由分光鏡u、集光鏡η及針孔14到達先偵測器15。由於 武片16之表面在物鏡12的焦平面上，且針孔14亦位於集光鏡 13的焦平面上，因此所有的光線都會通過針孔14而被光偵測器 !258598 15所接收，請參考圖中之實線部分，使光偵測器15輸出最大的 汛號。當試片16依Z方向移動時，該試片16之表面將離開物鏡 U的焦平面（如虛線所示之試片16)，先前由試片16反射的光將 破阻擋而無法穿過針孔14，從而無法到達光偵測器丨5，請參考 圖中之虛線部分，因此輸出的訊號較弱。 如第七圖所不，根據繞射理論，通過針孔14的光強度與試 片Μ離焦的距離（z縱向位移）成sinc2函數的關係。在橫向掃瞄試 片16表面時，微調試片16載台的高度，使光強度保持在極大值 的位置，再根據載台高度的移動量，就可得知試片16纟面形貌。 设睛麥照第七圖 丨寻、，、尤，、焦顯微鏡从尤强独穴值馮量測 可得到最大的信號強度，但是該處的信號強度對試片位 靈敏度）為零’因此縱向解析度僅約為0.一;至 處的斜率最大，也就是向反應曲線的山腰位置，此 腰處的钭m/ 變極為敏感。假設曲線山 ===::=了:時，，光強度會有1%的 為0.1%時，縱向解析度就可以達ίιΜ 右先強度^虎比 :微鏡之縱向解析度比傳統共焦顯微鏡高二ί可知，差動共焦 【發明内容】 反應曲線的斜率，以獲的較高二::=: 達到上述目的之共焦顯微量測系 集光鏡、針孔、光偵測器及干ϋέ :分光鏡、物鏡 述物鏡及待測物之間，含Φ “㈤述干涉儀係設置於 述干涉儀分成兩道光，束經由前述物鏡聚焦時，係由 涉儀’且此兩道光被反射^ :別入射於前述待側物表面與 者原路傻經前述分光鏡來到集光鏡」 1258598 Γ⑽，瞻㈣她穿她谢_器所接 經由前述物鏡二含*考面鏡及分光鏡，前述雷射光束 及該兩道先=於:前述干涉儀之分光鏡分成兩道光線， 尤刀別入射於所述待側#表面與干 較佳者’前述共焦顯微量測系統係 日兄 測系統。 勺丁 ν式差勳共焦顯微量 較佳者，前述待測物係位於物鏡的焦平面/ 於丽述集光鏡的焦平面上，由 "处針孔係位 針孔而被前述光偵測器接收。、丨的光束均通過前述 :佳者，通過前述針孔的光強度與待測物 成縱向反應曲線，該曲線成sine2函數關係。 ’、、、的㈣構 較佳者’前料 縱向反應曲線的山腰位置，此虚似％ +_切條紋的 _。 f此處斜率取大，縱向高度的改變最為 微二=二:共焦顯微量測系統經由橫向掃描待測物表面、 =測，台的縱向高度、載台高度位移量及橫向掃描的平面 4置，可得待測物三維表面形貌。 本：明之前述目的或特徵’細康後附圖式加以詳細說明， 後附圖式及所舉之例，祇一 【實施方式】 如第-圖所示’本發明之共焦顯微量測系統卜包含 ，、1卜物鏡12、集光鏡13、針孔14、光偵測器15及干涉儀^。 剛返分光鏡11、物鏡12、集光鏡13、針孔14及光债測哭15， 即係第六圖所示之傳統共焦顯微鏡1〇。一試 於載台(圖未示)上且位於物鏡12之後方，即光束穿過物:二置 1258598 16之間，該 之側。’前述干涉儀20係設置於前述物鏡i2及試片 干涉儀20包含參考面鏡21及分光鏡2?。 工 當雷射光束17經由物鏡12聚隹沾、a 2〇之八t 的過程中，係《述干涉儀 L二 線，此兩道光分別聚焦於試片μ之表 面與=儀2G之參考面鏡21。接著這兩道光被反射= =鏡11來到集光鏡13與針孔14的位 ; 用並穿過針孔丨4而為光偵測器15所接收。 十"作 根據光干涉原理，可以推墓Φ产乂 j以推V出在針孔14位置的光強度盥 :二離焦距離⑺的關係為：Μι+·_。又由於前述來 :面鏡2卜試片16之表面與針孔14同在共軛焦的位置 Γ因針此孔:的錢度與試片16離焦的距離亦成‘函數的關 子、、二、心15接收到的光訊號形式同時受到光干涉與sinc2 =數的規範。由於前述光干涉訊號對縱向位移極為敏感，因此本 二^之:㈣‘里測系統1之縱向反應曲線斜率將會提高許多， 4考弟„圖所示之曲線示。假設光源波長為㈣麵，第〇階反 f、曲線的斜率約為12/_，亦即，當將量測基準鎖定在第0階縱 -反應曲、、泉的山腰位置時，縱向解析度將比非干涉式的差動共隹 顯微鏡高出10倍以上。 巷本考X月之干涉式差動共焦顯微量測系統1量測20nm的階高 杌準片里’則結果如第三圖影像所示，由該第三圖的中心位置可 明顯^出斷差（如圖中箭頭所指之處）。 請筝看第四圖及第五圖，其中第四圖係顯示第三圖中線1位 ^ 構里測結果；第五圖係顯示第三圖中線Η位置的光拇 、、、°構里’則結果。線1為第三圖左側的光柵波谷位置，量測結果為 5〇’6nm’如第四圖所示；線II為第三圖右側光栅波谷位置，量 、、σ果為70.2 nm，如第五圖所示。線^及線η兩位置差值為να 1258598 _ ’該Μ結果與2〇_階高標準片高低差十分一致。 本^明之0賴非朗 的表面或内部微έ士氆，十4仏4兰丄 a m材貝 膜、穋原蛋白、：胞運i r=g行為’亦可提供生物薄 究上的支援。本發明之二面或液體/氣體界面特性等研 相同功n Γ 為Miehel議、Linik或等 待、、則物=4路°本發明之共㈣微量測系統經由橫向掃描 ==微調待測物载台的縱向高度、載台高度位移量及橫 ^田的千面位置點，可得待測物三維表面形貌。 本1 B月之優點在於：縱向解析率高、非接觸性檢測及高靈敏 L則^。現代的喊微知作技術、螢光標定技術等都相容，適合 硯測彳政小而快速的動態變化。 1258598 【圖式簡單說明】 第二圖係顯示柄'明共焦顯微量測系統之架構圖。 ::圖係顯不第一圖中之試片之縱向位移反應曲線圖。 弟二圖係顯不以本發明共焦顯微量測系統量測2〇nm階高標 準片之結果。 第四圖係顯示第三圖中線〗位置的光柵結構量測結果。 第五圖係顯示第三圖中線π位置的光柵結構量測結果。 第六圖係顯示傳統共焦顯微鏡之架構圖。 第七圖係顯示第六圖中之試片之縱向位移反應曲綠。 [主要元件符號對照說明] ’回 1…共焦顯微量測系統 11…分光鏡 12…物鏡 13…集光鏡 14…針孔 15…光偵測器 16…試片（待測物） 17…雷射光束 20…干涉儀 21…參考面鏡 22…分光鏡 Ζ···縱向位移 12!258598 坎, invention description: [Technical field of invention] The present invention (4) relates to a kind of confocal microscopy, especially the optical interference == slope of the longitudinal reaction curve, thereby increasing the amount of the confocal microscope in the longitudinal direction Interferometric differential confocal microscopy measurement system for angle measurement. [Prior Art] Optical wire micromirror is a modern precision measuring instrument crying material, Shide "_山7里列仪" is widely used on the surface of materials, surface microscopic features of biological samples and dynamic materials, or biological Film, collagen history, cell movement, liquid gas m gas interface special materials research. As for the application of 'digital multi-purpose optical disc (DVD) and thin film transistor (tft) and other products: the test of the process, also need The use of optical microscopy. Optical microscopy in the congenital and 2 damage detection (four) sex 'has the advantage of not having to treat the sample as a special treatment material. However, due to the diffraction phenomenon of light waves, its resolution is limited to the + wavelength of the temple level ( It is generally called the diffraction limit.) Confocal microscopy (C〇nfocal microsc〇pe) uses pinholes for spatial chopping, which makes the image resolution a plus-filament microscope and has the ability to detect longitudinally. Confocal microscopy can be used for three-dimensional image scavenging, that is, in addition to the two-dimensional surface topography, It can analyze the layered structure inside the test piece. Since the microscope does not need to use the probe, it can scan the cat at a very fast speed, and has a large broom range. However, the confocal microscope longitudinal resolution Only about the surface, in other words, 'When the layered structure in the test piece is less than 5〇〇nm, it cannot be resolved. Such resolution is applied to semiconductor film thickness measurement or biological cell slice analysis. It is not enough. The principle of confocal scanning microscopy is generally disclosed in US Patent No. 3,013,467 filed by Marvin Minsky in 1957. Due to the lack of proper light at the time! 258598 source and data processing capabilities, this principle is still Staying at the stage of pure theory, confocal scanning microscopy can truly become a practical microscopy after waiting for laser and personal computer invention. In 1969, Paul Davidovits and David David Egger developed the first use of lasers. A confocal scanning microscope, and the first commercial confocal scanning microscope was introduced in 1987. For nearly a decade, either laser technology or Personal computers have made amazing developments, making confocal microscopy more complete. The optical theory of single-photon confocal micromirrors was first proposed by Colin Sheppard and Tony Wilson of Oxford University in the United Kingdom. Watt W. Webb of Cornell University, USA In 1989, the experiment confirmed the uniqueness of the two-photon confocal microscope. The American AT&A A Bell Laboratory disclosed the processing procedure of confocal microscopy for semiconductor linewidth control in 1992, US5078482. The invention provides a shorter focal depth and a higher effective resolution than a general confocal microscope. The Nikon company disclosed in U.S. Patent 5,296,700 in 1994, which is equipped with a scanning confocal microscope and an optical objective lens. To solve the problem, the above system can be used to reconstruct the image of the object to be tested and the optical color difference compensation, which can effectively improve the quantified result of the technology of the cursor. In 1999, the German company Siemens published the US5991040 case to reveal the resolution of the three-dimensional surface image by the triangulation method. The rotation of the corner mirror can be used to measure the upper surface of the object to be tested. The appearance of the left and right surfaces is adjacent, and the information of the scanning points can be quickly drawn out by using the array photodetector. In 2002, Digital Optical Image Company disclosed the information on the defocus plane in 2002, and plotted the information about the height difference between the focal planes, such as measuring the three points (A, B, C) of the object under test, where B The point is located at the focal plane set to zero, and the two points A and C are located on the off-focus plane. Comparing the difference between the height and the focal plane, the surface morphology of the object to be tested can be drawn 258598. ::rYr rr (4) 2 22 == ^ The position scan information of this motor drive platform, this technology is mainly for a wide range of surface inspection, such as the surface of the LCD or wafer. Japanese business Olympus 0pticai company in 2 2 years to still (4) 7 (four) B = mr integrated 2 displacement device on the confocal microscope head displacement reflected back to the light intensity - directly in focus, from z to scan ^ 彳Position point (Z) ' Χ _ Υ 2D scanning mechanism can also be obtained by the controller Dan, L, (x, y)' from the coordinate point (x, y, z) information can obtain the three-dimensional shape of the object to be tested =: appearance =The scanning linear graph of the controller can be highly resolved after fine division by electrons ^ChieagG University in the United States in the US65488iq case revealed the integration of sweeping field, focal microscope and scanning electron beam microscope, its measurement 8] 〇 _ thick household The resolution of the test piece is still less than 100nm. The integrated microscope has the advantage of saving space and is suitable for general laboratory use. The structure and principle of the conventional confocal microscope will be described in detail in the sixth figure. As shown in the sixth figure, the conventional confocal microscope 1G includes: a beam splitter u, an objective lens 12, a collecting mirror 13, and a pinhole 14 And light _ device 15. - The test piece 16 (object to be tested) is placed on a stage (not shown) and located behind the objective lens 12. The collimated laser beam 17 is focused on the surface of the test piece 16 via the objective lens 12, reflected by the surface of the test piece 16, and then reaches the first detector 15 via the beam splitter u, the collecting mirror η and the pinhole 14. Since the surface of the cymbal 16 is on the focal plane of the objective lens 12, and the pinhole 14 is also located on the focal plane of the concentrating mirror 13, all of the light is received by the photodetector! 258598 15 through the pinhole 14. Please refer to the solid line part in the figure to make the photo detector 15 output the largest nickname. When the test piece 16 is moved in the Z direction, the surface of the test piece 16 will leave the focal plane of the objective lens U (such as the test piece 16 shown by the broken line), and the light previously reflected by the test piece 16 will be broken and cannot pass through the needle. The hole 14 is unable to reach the photodetector 丨5. Please refer to the dotted line in the figure, so the output signal is weak. As shown in the seventh figure, according to the diffraction theory, the distance between the light intensity passing through the pinhole 14 and the defocus of the test piece (z longitudinal displacement) becomes a function of the sinc2 function. When the surface of the test piece 16 is laterally scanned, the height of the stage 16 is micro-tuned to maintain the light intensity at the maximum value, and the shape of the test piece 16 can be known based on the amount of movement of the stage height. The seventh picture of the eye is taken, and the special microscope intensity is obtained from the Youqiang single point value von measurement, but the signal intensity of the test piece is zero for the test piece position. The resolution is only about 0.1. The slope is everywhere, that is, the position of the mountainside to the reaction curve, and the 钭m/ at the waist is extremely sensitive. Suppose curve mountain ===::=: When the light intensity will be 1% of 0.1%, the vertical resolution can reach ίιΜ right first intensity ^ tiger ratio: the longitudinal resolution of the micro mirror is better than the traditional confocal Microscope high, we can know, differential confocal [invention content] The slope of the reaction curve, to obtain the higher two::=: Confocal microscopy system for the above purpose, collection lens, pinhole, photodetector and cognac : Between the spectroscope, the objective lens and the object to be tested, including Φ "(5) The interferometer is installed in the interferometer and is divided into two lights. When the beam is focused by the objective lens, it is caused by the instrument' and the two lights are reflected ^ : Don't be incident on the surface of the object to be side-by-side and the original road is stupid through the aforementioned beam splitter to the concentrator. 1258598 Γ(10), Zhan (4) She wears her Xie _ device and passes through the above-mentioned objective lens II with a face mask and a beam splitter. The laser beam and the two channels are first: the splitter of the interferometer is divided into two light rays, and the special knife is incident on the surface of the to-be-side #surface and the dry one is better than the aforementioned confocal microscopy system. system. The spoon-shaped ν-type differential confocal microscopy is better, the object to be tested is located in the focal plane of the objective lens / on the focal plane of the Lizhao collecting mirror, and is subjected to the aforementioned optical detection by the pinhole of the pinhole The detector receives. The beam of 丨 is passed through the foregoing: preferably, the light intensity of the pinhole is longitudinally reflected with the object to be tested, and the curve is in a sine2 function relationship. ',,, (4) The preferred one is the front side of the longitudinal response curve, which is imaginary % _ _ stripe _. f where the slope is large, the longitudinal height changes the most two = two: the confocal microscopy system scans the surface of the object to be tested laterally, = measurement, the longitudinal height of the table, the displacement of the stage height and the plane of the lateral scanning The three-dimensional surface topography of the object to be tested can be obtained. The foregoing objects or features of the present invention are described in detail below, and the following figures and examples are only one embodiment. [Embodiment] As shown in the figure - the confocal microscopy system of the present invention Including, 1 objective lens 12, collecting mirror 13, pinhole 14, photodetector 15 and interferometer ^. Just return to the beam splitter 11, the objective lens 12, the collecting mirror 13, the pinhole 14 and the optical debt measurement crying 15, which is the conventional confocal microscope shown in the sixth figure. One try on the stage (not shown) and behind the objective lens 12, that is, the beam passing through: two between 1258598 16 and the side. The interferometer 20 is provided in the objective lens i2 and the test piece interferometer 20 includes a reference mirror 21 and a beam splitter 2?. When the laser beam 17 is condensed by the objective lens 12 and is a 2 〇 8 t, it is the second line of the interferometer L, and the two lights are respectively focused on the surface of the test piece μ and the reference surface of the instrument 2G. Mirror 21. Then the two lights are reflected = = the mirror 11 comes to the position of the collecting mirror 13 and the pinhole 14; it is received by the photodetector 15 through the pinhole 丨4. According to the principle of light interference, it is possible to push the tomb Φ to produce 乂 j to push the light intensity at the pinhole 14 position: the relationship between the two defocus distances (7) is: Μι+·_. Because of the foregoing, the surface of the mask 2 and the pinhole 14 are at the position of the conjugate focal point, and the distance between the money of the hole and the distance of the test piece 16 is also a function of the function. Second, the form of the optical signal received by the heart 15 is subject to both optical interference and sinc2 = number specification. Since the above-mentioned optical interference signal is extremely sensitive to the longitudinal displacement, the slope of the longitudinal response curve of the system is improved by a lot. 4 The tester shows the curve shown in the figure. It is assumed that the wavelength of the light source is (four) , the first step inverse f, the slope of the curve is about 12 / _, that is, when the measurement reference is locked in the 0th-order longitudinal-reaction, spring, the mountain waist position, the longitudinal resolution will be more than non-interferometric The differential conjugate microscope is more than 10 times higher. The X-ray interferometric differential confocal microscopy system 1 measures the 20nm step height 杌 ' 片 片 ” The center position of the third figure can clearly show the difference (as indicated by the arrow in the figure). Please look at the fourth and fifth pictures, and the fourth picture shows the line in the third figure. The fifth graph shows the results of the optical thumb, and the structure of the line in the third figure. Line 1 is the grating trough position on the left side of the third figure, and the measurement result is 5〇'6nm'. The fourth graph is shown; line II is the raster trough position on the right side of the third graph, and the quantity, σ fruit is 70.2 nm, as shown in the fifth figure. The difference between the two positions of the line ^ and the line η is να 1258598 _ 'The result of the Μ is very consistent with the height difference of the standard 〇 阶 。 。 。 。 。 。 。 。 。 。 本 本 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 十 十 十 十 十 十 十Lancome ah material shell film, prion protein,: cell transport ir = g behavior 'can also provide support for biological thinning. The two sides of the present invention or liquid / gas interface characteristics and other research work n Γ for Miehel, Linik or waiting, then the object = 4 channels. The total (four) micro-measurement system of the present invention passes the horizontal scanning == fine-tuning the longitudinal height of the test object stage, the displacement height of the stage, and the thousand-dimensional position of the horizontal field. The three-dimensional surface topography of the object to be tested can be obtained. The advantages of this 1st B month are: high vertical resolution, non-contact detection and high sensitivity L. ^ Modern shouting micro-knowledge technology, fluorescent cursor technology, etc. are compatible It is suitable for measuring the small and rapid dynamic changes of the government. 1258598 [Simple diagram of the diagram] The second diagram shows the architecture diagram of the handle 'Ming Confocal Microscopic Measurement System. :: The diagram shows the test piece in the first picture The longitudinal displacement response curve diagram. The second diagram is not measured by the confocal microscopy system of the present invention. The result of the nm-order high standard film. The fourth figure shows the measurement result of the grating structure in the position of the line in the third figure. The fifth figure shows the measurement result of the grating structure in the position of the line π in the third figure. The structural diagram of the conventional confocal microscope is shown. The seventh figure shows the longitudinal displacement response of the test piece in the sixth figure. [Main component symbol comparison description] 'Back 1... Confocal microscopic measurement system 11... Beam splitter 12... Objective lens 13... Collecting mirror 14...Pinhole 15...Photodetector 16...Test piece (object to be tested) 17...Laser beam 20...Interferometer 21...Reference mirror 22...Spectrum mirror Ζ···Longitudinal displacement 12