1243887 玖、發明說明： 【發明所屬之技術領域】 本發明係關於-種非線性位移校正裝置，尤指—種利用光學 方式提供壓電致動器之非線性位移誤差之校正裝置。 【先前技術】 精岔儀器中的位移驅動器，定位精確度是影響量測結果關鍵 ，子。壓電致動器多使用於精密儀器中作為精妓位的位移驅動 益’具有高解析度的定位精度優點，但由於屋電致動器的非線性 磁滞現象’施加同-電壓會有不同位移量的變化，影響^位的精 確度，因此需利用校正裝置量測該位移驅動器的非線性曲線，並 補f貝非線性駐的t彡響。而精密儀器巾的機構設計，可用於量測 位移驅動器的空間十分有限，因此需開發—可用於有限空間的高 解析度位移校正裝置，校正精密儀器中的位移驅動器。 *光纖式感測器在許多產業均有不同的應用目的及方法，如美 商奇異（General Electric company)於1撕年有兩篇關於光纖感測 器作為定位之用的專利，其卜篇為购8伽，其制用將兩 先纖端面各作一切角’第一光纖因機構轉動而帶動轉動切面第 二光纖的鄰接切面因不同切角而有不同的受光面積由光強产的 變化達成轉動角度定位裝置；另—篇us侧152則是在—伸缩又套 筒纏繞單層多圈的光纖…連動機構依附—或多個咖光源，當 伸細套筒移動’光源照射在不同位置的光纖表面可由接收器 收的光強度判斷伸縮套筒的位移量。 ^ 美商波音公司（Boeing company)1995年申請之咖術942乙 案中揭露利用光纖感測器架設於直昇機的螺㈣及機鼻上用於 監控溫度，化，其_用因光纖受祕，造錢^位的變、 化’利用光學式Mach-Zender干涉術，建立光學相位的變化量與 溫度變化線性關係，作為溫度監控的感測器。 1243887 美商維克威公司（Rockwell International corp·)於1986年揭露 US4572670乙案，其係利用光纖位移感測器量測壓電致動器的微 振動’利用Michelson干涉術量測壓電致動器一表面上的兩位置 點的相對位移變化，作為振動的監控感測器。 美國史丹福大學於1987年揭露US4652744乙案，其係利用 光纖位移感測器量測試片表面的聲波振動，該聲波振動是利用壓 電致動裔激發表面聲波，使試片表面產生微小位移的變化，光纖 位移感測器加上利用Mach-Zender干涉術量測表面聲波訊號移動 時間’作為表面小位移量測感測器。 美商國際商業機器公司（International Business Machine，IBM) 於1991年揭露US5017010乙案，其係利用光纖位移感測器作為 原子力顯微鏡的微定位裝置，將光纖位移感測器置放於原子力顯 微探針的懸臂樑上方，量測懸臂樑的軸向位移變化。 由前述諸案技術的揭露，可知光纖位移感測器的多面向功 能，並對於微小位移的量測有高解析度的能力。然而，前述諸案 並未提供利用光纖位移感測器校正精密儀器的位移驅動器之技 術及解決位移驅動器之非線性位移誤差。 【發明内容】 本發明之目的在提供一種非線性位移校正裝置，可於有限空 間的精密儀器中，提供量測壓電致動器的微位移變化，並就非線 性位移量測結果作曲線擬合補償其非線性誤差，降低精密儀器因 非線性所造成量測結果的干擾。 達到上述目的之非線性位移校正裝置，包含：雷射光源、第 一至弟二光纖耗合器及兩個光偵測器，前述雷射光源經一光纖連 接至前述第一光纖耦合器之入射端，前述兩光偵測器係分別經由 一光纖連接至前述第二光纖耦合器及第三光纖耦合器之反射 1243887 端，前述第一光纖耦合器之射出端亦分別以一光纖連接至前述第 二光纖耦合器及第三光纖耦合器之入射端，前述第二光纖耦合器 及第三光纖耦合器之射出端則分別連接一光纖且此兩光纖以彼 此光學相差90度並列平行鄰近於待測物。 本發明之另一目的在提供一種非線性位移校正方法，可校正 待測物如壓電致動器之非線性誤差。 達到上述目的之非線性位移校正方法，包含：提供一非線性 位移校正裝置；量測移動之待測物；將前述校正裝置中之兩光積 測器之光學相差90度的兩干涉訊號轉為相差90度的電子弦波訊 號；將前述電子弦波訊號輸入至電子分割電路，以得到待測物 之位移值；將前述位移值轉換為非線性線圖及非線性誤差值；及 估算非線性函數，並修正待測物之非線性誤差。 本發明之前述目的或特徵，將依據後附圖式加以詳細說明， 惟需明瞭的是，後附圖式及所舉之例，祇是做為說明而非在限制 或縮限本發明。 【實施方式】 如第一圖所示，本發明非線性位移校正裝置100包含：以雷 射半導體激發光源之雷射光源卜一個1x2型式（第二型式）之具有 一入射端及兩射出端之光纖耦合器2A、兩個2x1型式（第一型式） 之具有兩入射端及一射出端之光纖耦合器2B、兩個光偵測器5、 及連接前述元件之複數條光纖3。前述雷射光源1經一光纖3連 接至光纖耦合器2A(第一光纖耦合器）之入射端，兩光偵測器5係 分別經由一光纖3連接至各光纖耦合器2B(第二光纖耦合器及（第 三光纖耦合器）)之入射端，前述光纖耦合器2A之射出端亦分別以 光纖3連接至前述光纖耦合器2B之入射端，該兩光纖耦合器2B 之射出端則分別連接一光纖3且各該光纖3自由端之端面30以 彼此光學相差90度0())=90°)並列平行鄰近於待測物4。 1243887 請續參看第二圖，顯示出第一圖令之光纖3之端面 端面3 0所鄰近之待測物4間之光路，圖中之端面3 〇與 = 隔—距離卜如第二圖所示，雷射光源！之雷射光波在^ =纖3之端面30射出一光^，該光^在前述光纖3之端面3〇 形成反射光上’且傳播至待測物4表面後反射回前述端面3〇構成 反射光ι3，^述光ι2與光l3兩道光波於光纖麵合器2b中形 學干涉現象，並傳遞於光_!! 5中，由該光侧器5將^ 號轉換為電子訊號輸出。 前述光學干涉訊號丨經由下列公式可得知： l = l2+l3+2^^C〇S~，其中Φ為干涉訊號的相位角。 ^若待測物4軸向往返運動，非線性位移校正裝置可量測位移 變化如第三圖弦波函數所示，由邁克森(Michels〇n)光學干涉術可 知，干涉tfi號在波峰形成歧性干涉（)，及波谷形成相消姓 干涉（暗紋），位移值D = (mA)/2，其中m為計數條紋數目的計 數值，λ為波峰至波峰的週期值（亦為雷射波長值）。舉例而言，第 三圖弦波函數約4.5週期值，雷射波長為！ 3 μιη，可計數得° 物位移值為2.95 μπι。 由於計數週期的方式無法判斷待測物4軸向移動的方向，故 將雷射光源分光為兩組，參考第一圖，兩光纖麵合器2β的端面 3〇光程相位差90度設為初始相差，同時量測待測物4的軸向運 動，由兩訊號的相位差資訊，判讀待測物4的位移運動方向。 由於電子細分割（Electric interpolation)的技術發展成熟，利 用Heidenhain公司的細分割電子訊號卡，將第一圖中之通道a及 通道B兩通道的相差9〇度的干涉訊號輸入該卡，可獲得相位-位 移的線性函數關係式。 利用本發明之非線性位移校正裝置100量測一壓電致動器推 1243887 二二=’得到該壓電致動器的非線性位移曲線如第四圖所 二=Γ圖中：x輪為驅動壓電致動器帽值，γ軸為本 ^ I生位移权正t置⑽量顯電致動器的 γ圖之㈣結果’顯示㈣致動器的非線性誤差需被校正及補 辟ftr Α(如干涉顯微鏡、原子力顯微鏡、奈米虔痕 夕以選擇壓電致動时為位移驅動器，藉以產生微小 塑科^立^一由於麼電致動器自身材料特性所造成非線性影 利用位移感測器（如電容位移感測器、光纖位移感測器…） 4疋位之用。如應用干涉顯微鏡進行的掃描白光干涉術或相 :干涉術等’係利用壓電致動器帶動鏡頭位移，並在數個特定位 點以c C D感測ϋ擷取待測試片上的干涉條紋影像，再進行影像 處理繪製待測物的表面形貌。 …以下’接著祝明本發明之非線性位移校正裝置⑽應用於干 涉喊微鏡系統2GG之實例，藉以量測干涉顯微鏡的塵電致動器的 位移。 如第五圖所示，干涉顯微鏡系統2〇〇包含··樣品載台2〇1、 Muau干涉鏡組202、壓電致動器2〇3、驅動台2〇4、白光源2〇5、 光束調整系統2G6及陣列強度彳貞測器2G7。於第五圖中，符號m 表:驅動台2G4軸向的移動。依據前述，本發明之非線性位移校 正I置100之兩光纖3之端面3〇以彼此光學相差9〇度並列平行 鄰近於壓電致動器203。 月ij述壓電致動益2〇3上附有一電容位移感測器（圖未示），當驅 動壓電致動器使其軸向運動例如1GG _，同步紀錄電容感測器及 非線性位移校正裝置100的讀值，如第六圖所示；並估算其非線 性誤差小於0.12%，及利用曲線擬合的方式得出非線性函數，如 第七圖所示，可修正壓電致動器2〇3的非線性誤差。有關壓電致 1243887 動:203的非線性块差，進—步藉由第八圖及第九 施加及施加後非線性補償函數的試片掃描圖形。 丁“未 如▲第十圖所示’轉明進—步提供_種非線純移校正方法 300，δ亥方法300包含：步驟te 裝置刚·句彻θ 4供如前述之非線性位移校正 衣置100，步私302，1測移動之待測 之壓電致動器203 ;步驟303，將前乂 τ ^待測物為例如前述 / M ，將刖述校正裝置1〇〇 測器5之光學㈣90度的兩干涉訊號轉為相差9 訊號;步驟3。4,將前述電子弦波訊號輸入至電子二=波 以得到待測物（逐電致動器2〇3)之位移值；# 3〇6 Ιί；；； ϋ函數，並修正待測物之非線性誤差。 、’· 達太 之優點在於：運用邁克森光學干涉術量測解析度可 二、寺、.及’具南Α竑度及南解析度；且為—非接觸式位移校正 j，不會破壞待測物表面；並藉由光纖的可撓性及光纖的微小 動哭的I㈣架設於精密儀㈣部有限”巾及提供量測壓電致 =錢移變化，並就非線性位移量測結果作曲線擬合補償其 非、、泉生决差，降低精密儀器因非線性所造成量測結果的干柃。 1243887 【圖式簡單說明】 第一圖係顯示本發明之非線性位移校正裝置之具體實施例。 第二圖係顯示第一圖之具體實施例之光路圖。 第三圖係顯示依據第一圖之具體實施例量測位移之干涉訊 號波形圖。 第四圖係顯示依據第一圖之具體實施例量測壓電致動器推 動待測物所得到該壓電致動器的非線性位移曲線圖。 第五圖係顯示依據第一圖之具體實施例應用於干涉顯微鏡 系統之配置圖，藉以量測干涉顯微鏡中的壓電致動器位移變化。 第六圖係顯示同步記錄第五圖之壓電致動器所附著之電容 感測器與本發明之非線性位移校正裝置之位移讀值比對圖。 第七圖係顯示第六圖之電容感測器與本發明之非線性位移 校正裝置之位值差值及曲線擬合函數圖。 第八圖之（a)及（b)係分別顯示第五圖應用例之未補償非線性 誤差函數前的干涉顯微鏡試片掃描之3D影像圖及干涉條紋圖。 第九圖之（a)及（b)係分別顯示第五圖應用例之施加補償非線 性誤差函數後的干涉顯微鏡試片掃描之3D影像圖及干涉條紋圖。 第十圖係本發明之非線性位移校正方法之方塊圖。 [主要元件符號對照說明] 100…非線性位移校正裝置 1···雷射光源 2A、2B…光纖麵合器 3…光纖 4…待測物 5···光偵測器 A…通道 1243887 B…通道 300…非線性位移校正方法1243887 发明 Description of the invention: [Technical field to which the invention belongs] The present invention relates to a kind of non-linear displacement correction device, in particular to a kind of non-linear displacement error correction device that uses a piezoelectric actuator to optically provide a piezoelectric actuator. [Previous technology] The displacement driver in the precision fork instrument, the positioning accuracy is the key to affect the measurement results. Piezoelectric actuators are mostly used in precision instruments as displacement drive benefits for fine prostitutes. They have the advantage of high-resolution positioning accuracy, but due to the non-linear hysteresis phenomenon of electric actuators, there will be differences when applying the same voltage. The change of the displacement amount affects the accuracy of the position. Therefore, it is necessary to use a correction device to measure the nonlinear curve of the displacement driver, and to compensate for the non-stationary noise. However, the mechanism design of precision instrument towels can be used to measure the space of displacement actuators. Therefore, it is necessary to develop a high-resolution displacement correction device that can be used in limited spaces to calibrate displacement actuators in precision instruments. * Fiber optic sensors have different application purposes and methods in many industries. For example, General Electric company has two patents on fiber optic sensors for positioning in 1 year. Purchase 8-ga, its system uses the two fiber end faces to make all angles. The first optical fiber drives the rotating cutting plane due to the mechanism rotation. The adjacent cutting plane of the second optical fiber has different light receiving areas due to different cutting angles. Rotation angle positioning device; the other part of the us side 152 is-telescoping and the sleeve is wound with a single layer of multi-circle optical fiber ... the linkage mechanism is attached-or multiple light sources, when the thin sleeve moves, the light source is illuminated at different positions The displacement of the telescopic sleeve can be judged by the light intensity received by the receiver on the surface of the optical fiber. ^ The Boeing company ’s 1995 application of Kashu 942B disclosed that the use of fiber-optic sensors installed on the screw and nose of the helicopter for monitoring temperature and temperature. Make money change, use optical Mach-Zender interferometry to establish a linear relationship between the change in optical phase and temperature change, as a sensor for temperature monitoring. 1243887 Rockwell International Corp. disclosed US4572670 case B in 1986, which used optical fiber displacement sensors to measure the micro-vibrations of piezoelectric actuators, and used Michelson interferometry to measure piezoelectric actuation. The relative displacement change of two position points on one surface of the device is used as a vibration monitoring sensor. Stanford University in the United States disclosed US4652744 Case B in 1987, which used a fiber-optic displacement sensor to measure the acoustic wave vibration on the surface of the test piece. The acoustic wave vibration uses piezoelectric actuators to excite the surface acoustic wave and cause small displacement changes on the surface of the test piece. A fiber-optic displacement sensor coupled with Mach-Zender interferometry to measure the surface acoustic wave signal movement time 'is used as a surface small displacement measurement sensor. International Business Machine (IBM) disclosed US5017010 Case B in 1991, which used a fiber-optic displacement sensor as a micro-positioning device of an atomic force microscope, and placed the fiber-optic displacement sensor on an atomic force microscope. Above the cantilever of the needle, measure the change in axial displacement of the cantilever. According to the technical disclosures of the aforementioned cases, it can be known that the multi-faceted function of the optical fiber displacement sensor and the high-resolution capability for the measurement of small displacements. However, the aforementioned cases do not provide a technique for calibrating a displacement driver of a precision instrument using a fiber-optic displacement sensor and solving a nonlinear displacement error of the displacement driver. SUMMARY OF THE INVENTION The object of the present invention is to provide a non-linear displacement correction device that can measure the micro-displacement change of a piezoelectric actuator in a precision instrument with limited space, and make a curve simulation of the non-linear displacement measurement result. It can compensate its non-linear error and reduce the interference of measurement results caused by non-linear precision instruments. The non-linear displacement correction device for achieving the above-mentioned purpose includes a laser light source, first to second optical fiber couplers, and two light detectors. The laser light source is connected to the incident of the first optical fiber coupler through an optical fiber. The two optical detectors are respectively connected to the reflection 1243887 of the second optical fiber coupler and the third optical fiber coupler through an optical fiber, and the emitting ends of the first optical fiber coupler are also connected to the first optical fiber coupler respectively through an optical fiber. The incident ends of the two fiber couplers and the third fiber coupler, and the exit ends of the aforementioned second fiber coupler and the third fiber coupler are respectively connected to an optical fiber, and the two fibers are parallel to each other at an angle of 90 degrees from each other in parallel and adjacent to the test object. Thing. Another object of the present invention is to provide a non-linear displacement correction method capable of correcting non-linear errors of a test object such as a piezoelectric actuator. A non-linear displacement correction method for achieving the above-mentioned purpose includes: providing a non-linear displacement correction device; measuring a moving object to be measured; and converting two interference signals with 90 degrees optical difference between two optical integrators in the aforementioned correction device into An electronic sine wave signal with a 90 degree difference; input the aforementioned electronic sine wave signal to an electronic division circuit to obtain the displacement value of the object to be measured; convert the foregoing displacement value into a non-linear line graph and a non-linear error value; and estimate the non-linearity Function and correct the non-linear error of the object under test. The foregoing objects or features of the present invention will be described in detail with reference to the following drawings, but it should be understood that the following drawings and examples are for illustration only and are not intended to limit or limit the present invention. [Embodiment] As shown in the first figure, the non-linear displacement correction device 100 of the present invention includes a laser light source using a laser semiconductor excitation light source and a 1x2 type (second type) having one incident end and two outgoing ends. Fiber coupler 2A, two 2x1 type (first type) fiber couplers 2B with two incidence ends and one emission end, two light detectors 5, and a plurality of optical fibers 3 connected to the aforementioned components. The aforementioned laser light source 1 is connected to the incident end of the optical fiber coupler 2A (the first optical fiber coupler) through an optical fiber 3, and the two photodetectors 5 are connected to each optical fiber coupler 2B (the second optical fiber coupling) through an optical fiber 3 respectively. And (the third optical fiber coupler)), the emitting end of the aforementioned optical fiber coupler 2A is also connected to the incident end of the aforementioned optical fiber coupler 2B by the optical fiber 3, and the outgoing ends of the two optical fiber couplers 2B are respectively connected An optical fiber 3 and the end surfaces 30 of the free ends of each of the optical fibers 3 are adjacent to each other 4 in parallel by being optically different from each other by 90 degrees (0 ()) = 90 °). 1243887 Please continue to refer to the second figure, which shows the optical path between the end of the optical fiber 3 and the test object 4 adjacent to the end of the optical fiber 3 in the first figure, and the end face 3 in the figure is separated by a distance-as shown in the second figure Show, laser light source! The laser light wave emits a light ^ at the end face 30 of the fiber 3, and the light ^ forms reflected light on the end face 30 of the optical fiber 3, and propagates to the surface of the object 4 to be reflected and reflects back to the end face 30. The optical interference phenomenon of light 3, light 2 and light 13 is transmitted in the optical fiber coupler 2b and transmitted to the light _ !! 5. The light side device 5 converts the ^ number into an electronic signal output. The aforementioned optical interference signal can be obtained by the following formula: l = l2 + l3 + 2 ^^ CoS ~, where Φ is the phase angle of the interference signal. ^ If the object to be measured 4 moves back and forth in an axial direction, the non-linear displacement correction device can measure the change in displacement as shown by the sine wave function in the third figure. It can be known from Michels ’optical interferometry that the interference tfi is formed at the peak. Ambiguity interference (), and trough formation destructive interference (darkness), displacement value D = (mA) / 2, where m is the count value of the number of fringe counts, and λ is the period value from the peak to the peak (also the thunder Emission wavelength value). For example, the sine wave function in the third figure is about 4.5 cycles, and the laser wavelength is! 3 μιη, can be counted ° object displacement value of 2.95 μπι. Because the counting cycle method cannot determine the direction of the axial movement of the DUT 4, the laser light source is divided into two groups. Referring to the first figure, the end faces of the two optical fiber couplers 2β and the optical path phase difference of 90 degrees are set to 90 degrees. The initial phase difference is measured at the same time as the axial movement of the object 4 to be measured, and the direction of displacement and movement of the object 4 is determined from the phase difference information of the two signals. As the technology of electronic fine interpolation (Electric interpolation) is mature, using the fine-dividing electronic signal card of Heidenhain Company, input the interference signal with a difference of 90 degrees between the two channels of channel a and channel B in the first picture, and obtain Phase-shift linear function. Use the non-linear displacement correction device 100 of the present invention to measure a piezoelectric actuator. Push 1243887 22 == to get the nonlinear displacement curve of the piezoelectric actuator. Driving the piezo actuator cap value, the γ axis is based on the displacement weight positive t, and the result of the γ diagram of the electric actuator is shown. The non-linear error of the actuator needs to be corrected and repaired. ftr Α (such as interference microscopes, atomic force microscopes, nanometers, and piezo actuators are selected as displacement actuators to generate micro plastics ^ ^ ^ due to the non-linear effects of the electric actuator's own material characteristics Displacement sensors (such as capacitive displacement sensors, fiber-optic displacement sensors, etc.) are used for 4 positions. For example, scanning white light interferometry or phase: interferometry using an interference microscope is driven by a piezoelectric actuator. The lens shifts, and captures the interference fringe image on the test piece with c CD sensing at several specific points, and then performs image processing to draw the surface topography of the test object.… The following is to wish the non-linearity of the present invention Displacement correction device An example of the system 2GG is used to measure the displacement of the electrostatic actuator of the interference microscope. As shown in the fifth figure, the interference microscope system 2000 includes a sample stage 201, a Muau interferometer group 202, a piezoelectric Actuator 203, driving table 204, white light source 205, beam adjustment system 2G6, and array intensity sensor 2G7. In the fifth figure, the symbol m indicates the axial movement of the driving table 2G4. According to the foregoing, the end faces 30 of the two optical fibers 3 of the non-linear displacement correction device 100 of the present invention are optically different from each other by 90 degrees in parallel and adjacent to the piezoelectric actuator 203. The piezoelectric actuation benefit 203 Attached is a capacitive displacement sensor (not shown). When the piezoelectric actuator is driven to move axially, such as 1GG _, the readings of the capacitive sensor and the non-linear displacement correction device 100 are recorded synchronously, such as the sixth It is estimated that the nonlinear error is less than 0.12%, and the nonlinear function is obtained by curve fitting. As shown in the seventh figure, the nonlinear error of the piezoelectric actuator 20 can be corrected. Related Piezo-induced 1243887 motion: 203 non-linear block difference, further by applying the eighth figure and the ninth Scanning pattern of the test piece of the non-linear compensation function after application. Ding "Not as shown in ▲ Tenth picture 'turn bright forward-step provided _ a kind of non-linear pure shift correction method 300, δ Hai method 300 includes: step te device just · Sentence θ 4 is for the above-mentioned non-linear displacement correction clothing 100, step 302, 1 to measure the piezoelectric actuator 203 to be measured; step 303, the former 乂 τ ^ the object to be tested is, for example, / M , The two interference signals of the 90 ° optical ㈣ of the calibration device 100 tester 5 are converted into signals with a phase difference of 9; step 3.4, the aforementioned electronic sine wave signal is input to the electronic two = wave to obtain the object to be measured (by electricity The displacement value of the actuator 203); # 3〇6 Ιί ;; ϋ function, and correct the non-linear error of the test object. The advantage of Dat is that the measurement resolution using Michelson optical interferometry can be two, temple,. And 'with South A 竑 and South resolution; and-non-contact displacement correction j, will not destroy The surface of the object to be measured; and the optical fiber's flexibility and the tiny movement of the optical fiber are installed on the precision instrument's limited area and provide measurement of piezoelectricity = change in money movement, and the measurement results of nonlinear displacement The curve fitting is used to compensate the difference between the non-linear and non-linear dynamics, and to reduce the dryness of the measurement results caused by the non-linearity of the precision instrument. Specific embodiment. The second diagram is a light path diagram showing the specific embodiment of the first diagram. The third diagram is a waveform diagram of the interference signal for measuring displacement according to the specific embodiment of the first diagram. The fourth diagram is based on the first embodiment. The specific embodiment of the figure measures the non-linear displacement curve of the piezoelectric actuator obtained by measuring the piezoelectric actuator to push the object to be measured. The fifth figure shows the application of the specific embodiment according to the first figure to the interference microscope system. Configuration diagram The displacement change of the piezoelectric actuator in the interference microscope is measured. The sixth figure shows the displacement reading ratio of the capacitive sensor attached to the piezoelectric actuator of the fifth figure and the non-linear displacement correction device of the present invention. Contrast. The seventh diagram is a diagram showing the difference in position and curve fitting function of the capacitance sensor of the sixth diagram and the non-linear displacement correction device of the present invention. (A) and (b) of the eighth diagram are respectively The 3D image and interference fringes of the interference microscope test strip before the non-compensated nonlinear error function are shown in the fifth application example. (A) and (b) of the ninth illustration show the application of the fifth application example, respectively. The 3D image and interference fringes of the interference microscope scan after compensating for the non-linear error function. The tenth figure is a block diagram of the non-linear displacement correction method of the invention. Device 1 ... Laser source 2A, 2B ... Fiber optic coupler 3 ... Fiber 4 ... DUT 5 ... Light detector A ... Channel 1243887 B ... Channel 300 ... Non-linear displacement correction method