1336391 九、發明說明： 【發明所屬之技術領域】 本發明有關於對測定被檢面的傾斜角度的干涉儀的角 度靈敏度進行校準的方法。1336391 IX. Description of the Invention: [Technical Field of the Invention] The present invention relates to a method of calibrating the angular sensitivity of an interferometer for measuring the inclination angle of a surface to be inspected.
10 15 【先前技術】 目則，爲了能夠測定被檢面的傾斜角度而構成的干涉 儀，習知的是用於光纖連接器部的傾斜研磨型套圈的前端 面測定用的干涉儀（參照下述專利前案丨）。 傾斜研磨型套圈的前端面的傾斜角度（相對於與套圈 的軸線垂直的面的角度）已由JIS標準化爲8度。另一方面， 在套圈測定用的干涉儀中，可測定的傾斜角度範圍有時被 限制在5度左右，在這樣的套圈測定用的干涉儀中，使用進 行保持的專用的保持器具，以使套圈的前端面相對於測定 光軸的垂直面的傾斜角度爲4度左右，從而進行測定（參照 下述專利前案2)。10 15 [Prior Art] An interferometer for measuring the tip end surface of an inclined polishing type ferrule for an optical fiber connector portion is known as an interferometer configured to measure the tilt angle of the surface to be inspected (see The following patent case 丨). The inclination angle of the front end face of the inclined grinding type ferrule (angle with respect to the plane perpendicular to the axis of the ferrule) has been standardized to 8 degrees by JIS. On the other hand, in the interferometer for measuring the ferrule, the range of the tilt angle that can be measured is limited to about 5 degrees, and in such an interferometer for measuring the ferrule, a dedicated holder for holding is used. The measurement was performed so that the inclination angle of the front end surface of the ferrule with respect to the vertical plane of the measurement optical axis was about 4 degrees (refer to Patent Reference 2 below).
20 但是，在這種傾斜角度測定用的干涉儀中，表示所觀 察的條紋條數與傾斜角度之間的對應關係的角度靈敏度已 被預先設定，由於因干涉儀的設置誤差及常年使用產生的 誤差等，有時需要校準暫且設定的角度靈敏度。 目前，作爲進行這樣校準的方法，公知的是，將由成 爲校準物件的干涉儀測量的被檢面的傾斜，和由自動準直 儀等基準角度儀測定相同被檢面而得的傾斜進行比較來校 準的方法’但疋’由於需要高精度地進行成爲校準物件的 5 1436391 儀及基準肖度儀的各校準，並且需要改變被檢面的傾 斜進行多次測定，所以存在校準所需要的程式繁雜，需要 报多時間的問題》 另方面本發明申請人提出了使用具有相互所呈的 5角度已知的兩個反射面的校準用夫具的校準方法，並已經 對專利局公開（參照下述專利前案3)。該校準方法，由於 能夠基於由成爲校準物件的干涉儀拍攝的一個條紋圖像進 行校準，因此可容易地進行角度靈敏度的校準。 專利前案1:曰本特開2〇〇4— 37167號公報。 1〇 專利前案2 :曰本特開2004- 286595號公報。 專利前案3:日本特願2〇〇5_1〇2934號說明書。 但是，所述專利前案3所記載的校準方法存在難以適用 於套圈測定用的干涉儀這一問題。即在該校準方法中，前 提是使用具有兩個反射面的校準用夾具，而由於在套圈測 15定用的干涉儀的場合，需要使校準用的夾具相當小地形 成’所以難以咼精度地製作兩個反射面（尤其是相互的邊 界部分）。 另外’該校準方法在干涉儀的角度靈敏度相對於測定 角度的大小具有線性（相對於被檢面的傾斜角度的變化 2〇 的、觀察到的干涉條紋的條數變化的比例爲一定）時是有 效的，但是，在角度靈敏度具有非線性時，恐怕不能進行 高精度的校準。 由於套圈測定用干涉儀所測定的傾斜角度限定在夾著 基準角度（例如4度）的規定的狭小範圍（例如，±0」度左 6 1336391 右的角度範圍），所以對於在該角度範圍内的角度靈敏度 如果能容易且高精度地校準，是極其有益的。 【發明内容】 本發月目的在於提供一種干涉儀的角度靈敏度校準方 法’其可容易且高精度地校準所測定的傾斜角度限定在規 定的角度範圍内的傾斜角度測定用的干涉儀的角度靈敏 度。 本發明提供-種干涉儀的角度靈敏度校準方法，所述 ίο干涉儀拍攝承載有被檢面的傾斜資訊的干涉條纹圖像，並 基於該干涉條紋圖像測定所述被檢面的傾斜角度，所述干 涉儀的角度靈敏度校準方法對所述干涉儀的角度靈敏度進 行校準’係依次進行以下步驟： 角度靈敏度算式設定步驟，其在與所述被檢面的傾斜 15角度對應的規定的被測定角度範圍内，視爲在所述被檢面 的每單位長度的干涉條紋的條數p和所述傾斜角度Θ之 間，使用了規定的比例係數]<;的比例關係成立，設定下式〇) 所示的角度靈敏度算式。 測定步驟’其用所述干涉儀測定以呈所述被測定角度 20範圍内的基準傾斜角度α的方式設定的基準傾斜面，求出該 基準傾斜面的每單位長度的條紋條數”，並且基於該條紋 條數Pi和下式（1)計算所述基準傾斜角度α的測定臨時值（仮 値）αι，從而得到下式（2)的關係。 以及’校準步驟，其基於所述條紋條數以和所述基準 傾斜角度α且通過下式（3)求出已校準的比例係數匕，將該已 7 25 丄336391 ίο 1520 However, in the interferometer for measuring the inclination angle, the angular sensitivity indicating the correspondence between the number of stripes to be observed and the inclination angle has been set in advance, due to the setting error of the interferometer and the use of the perennial use. Errors, etc., sometimes need to be calibrated for the temporarily set angle sensitivity. At present, as a method of performing such calibration, it is known that the inclination of the surface to be inspected measured by the interferometer serving as the calibration object is compared with the inclination obtained by measuring the same surface to be inspected by a reference angle meter such as an automatic collimator. The calibration method 'but 疋' requires a high-precision calibration of the 5 1436391 instrument and the reference oscilloscope to be used as a calibration object, and it is necessary to change the inclination of the surface to be examined for multiple measurements. Therefore, there is a program required for calibration. It is complicated and requires a lot of time to report. In addition, the applicant of the present invention has proposed a calibration method using a calibration tool having two reflection surfaces having a mutual known angle of 5, and has been disclosed to the patent office (refer to Said patent case 3). This calibration method can be easily calibrated based on a stripe image taken by an interferometer that becomes a calibration object. Patent Proceedings 1: 曰本特开2〇〇4—37167. 1〇 Patent Proceedings 2: 曰本特开2004-286595. Patent Pre-Case 3: Japanese Special Purpose 2〇〇5_1〇2934 specification. However, the calibration method described in the third patent document has a problem that it is difficult to apply to an interferometer for measuring a ferrule. That is, in the calibration method, it is premised that a calibration jig having two reflecting surfaces is used, and in the case of an interferometer for measuring the ferrule 15, it is necessary to make the jig for calibration relatively small. Two reflective surfaces (especially the boundary portions of each other) are produced. In addition, the calibration method is linear when the angular sensitivity of the interferometer is linear with respect to the magnitude of the measurement angle (the ratio of the change in the inclination angle of the observed surface to the detected surface is 2 为). Effective, however, when the angular sensitivity is nonlinear, it may not be possible to perform high-precision calibration. Since the tilt angle measured by the interferometer for the ferrule measurement is limited to a predetermined narrow range (for example, ±0° degrees left 6 1336391 right angle range) sandwiching the reference angle (for example, 4 degrees), for the angle range The internal angular sensitivity is extremely beneficial if it can be easily and accurately calibrated. SUMMARY OF THE INVENTION The purpose of the present invention is to provide an angular sensitivity calibration method for an interferometer that can easily and accurately calibrate the angular sensitivity of an interferometer for measuring an inclination angle in which a measured inclination angle is limited within a predetermined angle range. . The present invention provides an angle sensitivity calibration method for an interferometer that captures an interference fringe image carrying tilt information of a detected surface, and determines an inclination angle of the detected surface based on the interference fringe image The angle sensitivity calibration method of the interferometer calibrates the angular sensitivity of the interferometer. The following steps are sequentially performed: an angle sensitivity calculation formula setting step of specifying a predetermined angle corresponding to the tilt angle 15 of the detected surface In the measurement angle range, it is considered that a proportional relationship using a predetermined proportional coefficient]<; is established between the number p of interference fringes per unit length of the examined surface and the tilt angle ,, and is set Equation 〇) The angle sensitivity formula shown. a measurement step of measuring a reference inclined surface set such that the reference inclination angle α in the range of the measured angle 20 is measured by the interferometer, and determining the number of stripes per unit length of the reference inclined surface, and The measured temporary value (仮値) αι of the reference tilt angle α is calculated based on the stripe number Pi and the following formula (1), thereby obtaining a relationship of the following formula (2). And a 'calibration step based on the stripe strip Counting the angle α with the reference and obtaining the calibrated scale factor 下 by the following equation (3), the 7 25 丄 336391 ίο 15
校準的比例係、數ki和下式（1).的比例係數k置*，從而得到下 式（4)所不的已校準的角度靈敏度算式。The calibrated proportional system, the number ki, and the proportional coefficient k of the following equation (1) are set to *, thereby obtaining a calibrated angular sensitivity formula of the following equation (4).
Pl = k.ai ……(2) kl=Pi/a ……(3) P=kr ^ ……(4) 在所述測定步驟中，使所述基準傾斜面相對於所述干 涉儀自轉規定角度，在該自轉操作前後的兩個旋轉位置分 別進行測定，基於這兩個測定結果，使用規定的運算式， 汁算所述基準傾斜角度a的測定臨時值a厂 根據本發明干涉儀的角度靈敏度校準方法，在與被檢 面的傾斜角度對應的規定的被測定角度範圍内，視爲在被 檢面的每單位長度的干涉條紋的條數和傾斜角度之間比例 關係成立而設定規定的角度靈敏度算式，基於以呈被測定 角度範圍内的基準傾斜角度的方式設定的基準傾斜面的測 定結果，校準該設定的角度靈敏度算式的比例係數，所以， 起到如下的效果。 即，因爲其與現有方法不同，不需要使用具有兩個反 射面的校準用夾具，所以對於套圈測定用的干涉儀也可適 用0 另外，如套圈測定用的干涉儀所述，在所測定的傾斜 角度限定在規定的狹小角度範圍内的干涉儀中，即使角度 靈敏度在寬範圍具有非線性時，也可以通過將所述基準傾 斜角度設疋爲該狹小角度範圍内的角度，來容易並且高精 20 1336391 度地校準用於該角度範圍内的測定解析的角度靈敏度。 【實施方式】 下面’參照附圖對本發明的實施方式進行詳細說明。 5圖1是表示應用本發明一實施方式的干涉儀的結構示意 圖，圖2是表不具有基準傾斜面的校準用夾具的結構的立體 圖。 圖1所不的干涉儀是基於所拍攝的千涉條紋圖像測定 # 被檢面的傾斜角度的干涉儀，其具有拍攝干涉條紋圖像的 10菲索型的干涉儀主體1、和對拍攝的干涉條紋圖像進行解析 的解析部2。 所述干涉儀主體丨具有：輸出高可干涉性的光束的光源 部11、將從該光源部u射出的發散光束變成平行光束的準 15Pl = k.ai (2) kl=Pi/a (3) P=kr ^ (4) In the measuring step, the reference inclined surface is rotated at a predetermined angle with respect to the interferometer The measurement is performed at two rotation positions before and after the rotation operation, and based on the two measurement results, the measurement temporary value a of the reference inclination angle a is calculated using a predetermined calculation formula, and the angular sensitivity of the interferometer according to the present invention is used. In the calibration method, the proportional relationship between the number of interference fringes per unit length of the surface to be inspected and the tilt angle is established in the predetermined measured angle range corresponding to the tilt angle of the surface to be inspected, and a predetermined angle is set. The sensitivity calculation formula calibrates the proportional coefficient of the set angle sensitivity formula based on the measurement result of the reference inclined surface set so as to be the reference tilt angle in the range of the measured angle, and therefore has the following effects. In other words, since it is different from the conventional method, it is not necessary to use a calibration jig having two reflecting surfaces. Therefore, it is also applicable to an interferometer for measuring the ferrule. Further, as described in the interferometer for measuring the ferrule, The measured tilt angle is limited to an interferometer within a predetermined narrow angle range, and even if the angle sensitivity has a nonlinearity over a wide range, it is easy to set the reference tilt angle to an angle within the narrow angle range. And the high precision 20 1336391 degree is used to calibrate the angular sensitivity for the analysis of the angle range. [Embodiment] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a schematic view showing the configuration of an interferometer to which an embodiment of the present invention is applied, and Fig. 2 is a perspective view showing a configuration of a jig for calibration having a reference inclined surface. The interferometer shown in FIG. 1 is an interferometer that measures the tilt angle of the detected surface based on the photographed thousand-streaked image, and has a 10 phenotype-type interferometer main body 1 that captures an interference fringe image, and a pair of photographs. The analysis unit 2 that analyzes the interference fringe image. The interferometer main body 丨 has a light source portion 11 that outputs a high-interference light beam, and a divergent light beam emitted from the light source portion u becomes a parallel light beam.
20 直透鏡12、配置於來自該準直透鏡12的平行光束的光路上 的分光器13及基準板14。 另外’該干涉儀主體1利用從被檢面反射的光束和從所 述基準板14的基準面14a反射的基準光的干涉，得到承載有 被檢面的形狀及傾斜資訊的干涉肢，其除所述構成外還 具有：使所得到的干涉條紋成像的成像透_、和拍攝該 干涉條紋的攝影機16。 另一方面’所述解析部2具有：進行圖像處理和條紋解 析的條紋解析裝置2卜鍵盤等輸入裝置22、和顯示裝置U 所述條紋解析裝置21由電腦等構成，具有：存儲用 圖像處理及條紋解析的程式的存儲部、和進行程式的執行 及各種運异的運算部等’基於被所述攝影機16攝入的干涉 9 25 1336391 條紋，可求出被檢面的傾斜角度。 另外，在圖1所示的干涉儀中，表示所觀察到的條紋 條數和傾斜角度之間的對應關係的角度靈敏度被預先設 定，所設定的角度靈敏度存儲於所述條紋解析裝置21的記 5 憶體等中。 ° 進而，圖1所示的干涉儀設計爲，測定的傾斜角度被限 定於炎著基準角度（例如4度）的規定的狹小角度範圍（例 如’ ±0.1度的角度範圍）。作爲這樣的干涉儀例如可例舉 所述的專利前案1、2記載的傾斜研磨型套圈測定用的干涉 10 儀作爲其具體的形態。 圖2所不的校準用失具3是實施後述的干涉儀角度靈敏 度校準方法時使用的夾具，其在圓柱狀的構件的前端具有 基準傾斜面31。該基準傾斜面3丨的構成爲：具有與圖丨所示 的干涉儀作爲測定物件的被檢面的傾斜角度相對應的、規 15定的被測定角度範圍内（例如，夾著4度的±0」度的角度範 圍内）的基準傾斜角度α(在圓2中，作爲校準用夾具3的中 心軸線S和基準傾斜面31的法線τ所成的角度來表示）。 下面對有關本發明的一實施方式的干涉儀角度靈敏度 校準方法的實施順序進行說明。 2〇 <1>首先，在所述被測定角度範圍内，視爲在被檢面的 每單位長度的干涉條紋的條數1)和所述傾斜角度0之間，使 用了規定的比例係數k的比例關係成立，設定下式（丨）所示的 角度靈敏度算式（角度靈敏度算式設定步驟）。 P=k· 0 ......⑴ 10 <2>其-人’如圖i所不’在干涉儀上設置校準用夾具3 並進行測定，求出基準傾斜面31的每單位長度的條紋條數 Pi〜並且基於該條紋條數Ρι和上式⑴計算基準傾斜角 度α的 二疋時值αι ( ai_pi/k),從而得到下式⑺的關係（測定 步驟）。 P1 = k*«i ......(2) <3>其次，基於求出的條紋條數？1和基準傾斜角度a, 用下式(3)求出已校準的比例係數&，將該已校準的比例係 私和上式⑴的比例係數k置換，得到下式⑷所示的已校 準的角度靈敏度算式（校準步驟）^ ki= Pi/a ......(3) P~ ^! · θ ......(4) 通過以上的順序’角度靈敏度的校準結束。也就是說， 使用通過所述順序得到的角度靈敏度算式⑷，計算被檢面 的傾斜角度即可。 另外，在干涉儀上設置所述校準用夾具3時，例如，可 以使用所述的專利職卜2記载的Μ裝置及其保持器具。 而且，在所述順序（2)令，是以設置後的校準用夾具3 的中心轴線S (參照圖2)和干涉儀的測定光軸R (參照圖i ) 相互一致爲前提的。但是，在實際的設置狀況中也可能 産生在校準用夾具3的中心軸線S相對於干涉儀的測定光軸 R傾斜的狀態下進行設置的情況。 考慮到這一點，在所述順序（2)的測定步驟中，可使用 所述的專利前案1記載的被稱爲反轉法的方法。該反轉法是 1336391 如下所述的方法：在柱狀構件保持於夾緊裝置的狀態下， 使柱狀構件相對於干涉儀自轉規定角度，在兩個旋轉位置 i ’分別檢測出干涉儀的基準面和柱狀構件前端面之間的 相對角度，基於該檢測出的兩個角度，使用規定的運算式 5 測疋該柱狀構件的轴的傾斜，所述規定角度爲180度的情況 下’作爲所述運算式，例如使用下式所示的算式。 ai=(m1-m2+ 180)/2 ......(5) 其中’ 1111表示在第一旋轉位置檢測出的、干涉儀的基 準面和柱狀構件前端面之間的相對角度，m2表示在第二旋 10轉位置檢測出的、干涉儀的基準面和柱狀構件前端面之間 的相對角度。 15The straight lens 12 and the spectroscope 13 and the reference plate 14 disposed on the optical path of the parallel beam from the collimator lens 12. Further, the interferometer main body 1 obtains an interference limb that carries the shape of the surface to be inspected and the tilt information by the interference of the light beam reflected from the surface to be inspected and the reference light reflected from the reference surface 14a of the reference plate 14 In addition to the configuration, there is an imaging through which the obtained interference fringes are imaged, and a camera 16 that captures the interference fringes. On the other hand, the analysis unit 2 includes a stripe analysis device 2 for performing image processing and stripe analysis, an input device 22 such as a keyboard, and a display device U. The stripe analysis device 21 is composed of a computer or the like, and has a map for storage. The storage unit of the program such as the processing and the stripe analysis, and the execution of the program and various arithmetic calculation units, etc., can obtain the inclination angle of the surface to be inspected based on the interference 9 25 1336391 stripe taken by the camera 16. Further, in the interferometer shown in FIG. 1, the angular sensitivity indicating the correspondence relationship between the number of stripes to be observed and the inclination angle is set in advance, and the set angle sensitivity is stored in the note of the stripe analyzing device 21. 5 Recalling the body and so on. Further, the interferometer shown in Fig. 1 is designed such that the measured tilt angle is limited to a predetermined narrow angle range (e.g., an angular range of ± 0.1 degrees) of the inflammatory reference angle (e.g., 4 degrees). As such an interferometer, for example, the interference meter for measuring the inclined polishing type ferrule described in the above-mentioned Patent Nos. 1 and 2 can be exemplified as a specific embodiment. The calibration loss device 3 shown in Fig. 2 is a jig used in the method of performing an interferometer angle sensitivity calibration method to be described later, and has a reference inclined surface 31 at the tip end of the columnar member. The reference inclined surface 3 is configured to have a range of measured angles corresponding to the inclination angle of the surface to be inspected of the interferometer as the measurement object shown in FIG. The reference inclination angle α (in the circle 2) is expressed as an angle formed by the central axis S of the calibration jig 3 and the normal τ of the reference inclined surface 31. Next, an implementation procedure of the interferometer angle sensitivity calibration method according to an embodiment of the present invention will be described. 2〇<1> First, within the range of the measured angles, a predetermined proportional coefficient is used between the number of interference fringes per unit length of the examined surface 1) and the tilt angle 0. The proportional relationship of k is established, and the angle sensitivity formula (the angle sensitivity calculation formula setting step) shown by the following formula (丨) is set. P=k· 0 (1) 10 <2> The human-like 'impossible as shown in Fig. i' is provided with a calibration jig 3 on the interferometer and measured, and the unit length of the reference inclined surface 31 is obtained. The stripe number Pi to the second stripe value αι (ai_pi/k) of the reference tilt angle α is calculated based on the stripe number Ρι and the above formula (1), thereby obtaining the relationship of the following formula (7) (measurement step). P1 = k*«i ......(2) <3> Secondly, based on the number of stripes obtained? 1 and the reference tilt angle a, the calibrated scale factor & is obtained by the following equation (3), and the calibrated scale system is replaced with the scale factor k of the above formula (1) to obtain the calibrated equation represented by the following formula (4). Angle sensitivity formula (calibration step) ^ ki = Pi / a ...... (3) P~ ^! · θ (4) By the above sequence, the calibration of the angle sensitivity ends. That is to say, the angle of inclination of the surface to be inspected can be calculated using the angle sensitivity formula (4) obtained by the above procedure. Further, when the calibration jig 3 is provided on the interferometer, for example, the crucible device described in the above-mentioned Patent Application 2 and its holder can be used. Further, in the above-described sequence (2), it is assumed that the center axis S (see FIG. 2) of the set calibration jig 3 and the measurement optical axis R (see FIG. i) of the interferometer coincide with each other. However, in the actual installation state, the center axis S of the calibration jig 3 may be set in a state where it is inclined with respect to the measurement optical axis R of the interferometer. In view of this, in the measurement step of the above-described sequence (2), the method referred to as the inversion method described in the above Patent Document 1 can be used. The inversion method is 1336391. The method is as follows: in a state where the columnar member is held by the clamp device, the columnar member is rotated at a predetermined angle with respect to the interferometer, and the interferometer is respectively detected at the two rotational positions i' The relative angle between the reference surface and the front end surface of the columnar member is measured based on the detected two angles, and the inclination of the axis of the columnar member is measured using a predetermined arithmetic expression 5, and the predetermined angle is 180 degrees. 'As the arithmetic expression, for example, an equation shown by the following formula is used. Ai=(m1-m2+ 180)/2 (5) where '1111 denotes the relative angle between the reference plane of the interferometer and the front end face of the columnar member detected at the first rotational position, m2 The relative angle between the reference surface of the interferometer and the front end surface of the columnar member detected at the second rotation 10 rotation position is indicated. 15
20 即，在使用該反轉法時，使所述基準傾斜面相對於干 β儀”堯中心轴線3自轉⑽度，並在兩個旋轉位置分別進行 測定，基於兩個測定結果使用所述運算式（5)計算出基準傾 斜角度α的測定臨時值αι。另外，在用於所述說明的各算式 中，將傾斜角度作爲向量來處理。 以上說明了本發明的一個實施方式，不過本發明不限 於所述的實施方式。例如，在所述實施方式中，使用了圓 柱狀的校準用夾具’但也可以使㈣成爲棱柱狀的校準用 另外’在所述實施方式中，示出了將本發明應用於 斜研磨型套_定㈣干涉儀的例子，但是，本發明也 以合適地應用於對測定的傾斜角度限定於規 的各㈣斜角度測定用的干涉儀，進行其角度靈敏度的 12 1336391 準的情況。 · 【圖式簡單說明】 圖1是表示應用本發明一實施方式的干涉儀的結構示意圖。 5 圓2是表示具有基準傾斜面的校準用夾具的結構的立體圖。 【主要元件符號說明】 干涉儀主體1 解析部2 夾具3 準直透鏡12 基準板14 成像透鏡15 條紋解析裝置21 顯示裝置2 3 光柏R 法線T 光源部11 分光器13 基準面14a 攝影機16 輸入裝置22 基準傾斜面31 中心軸線S 基準傾斜角度α 13In other words, when the inversion method is used, the reference inclined surface is rotated (10) degrees with respect to the center axis 3 of the dry beta meter, and measured at two rotational positions, and the operation is performed based on the two measurement results. The measurement temporary value α1 of the reference inclination angle α is calculated in the equation (5). Further, in each of the equations used for the description, the inclination angle is treated as a vector. One embodiment of the present invention has been described above, but the present invention The embodiment is not limited to the above-described embodiment. For example, in the above-described embodiment, a cylindrical calibration jig is used, but (4) may be used as a prismatic calibration. In the above embodiment, The present invention is applied to an example of an oblique-grinding type-fourth interferometer. However, the present invention is also suitably applied to an interferometer for measuring each of the four (four) oblique angles for which the measured tilt angle is limited to the gauge, and the angular sensitivity thereof is performed. 12 1336391 The case of the first embodiment of the present invention is shown in Fig. 1. Fig. 1 is a schematic view showing the structure of an interferometer according to an embodiment of the present invention. A perspective view of the structure of the calibration jig. [Explanation of main component symbols] Interferometer main body 1 Analysis unit 2 Clamp 3 Collimating lens 12 Reference plate 14 Imaging lens 15 Stripe analysis device 21 Display device 2 Optical cymbal R Normal line T Light source unit 11 Beam splitter 13 Reference plane 14a Camera 16 Input device 22 Reference inclined surface 31 Center axis S Reference tilt angle α 13