一種基于帶有特別的過濾和偏移調制的光柵投影的位移傳感器畢業(yè)論文外文翻譯.doc

1、.附 錄附錄1一種基于帶有特別的過濾和偏移調制的光柵投影的位移傳感器胡建明，曾愛軍，王向朝，中國摘要由美國A-B公司生產的ControlLogix系列可編程序邏輯控制器(PLC)提供了多種接口類型：如以太網、ControlNet、DeviceNet、RS-232等等。ControlLogix以太網連接模塊“1756-ENET”使用了EtherNet/IP、ControlNet等協(xié)議，并采用了專業(yè)的服務代碼封裝于以太網協(xié)議包中。針對“實驗性物理和工業(yè)控制系統(tǒng)”(EPICS)開發(fā)的驅動程序使用了EtherNet/IP協(xié)議，從而使得控制器可以運行vxWorks RTOS、Win32和Unix/Lin

2、ux的測試程序。現(xiàn)在來分析一下這個接口的特點和使用場合。1 正文一種基于石油光柵空間濾波和偏振調制的位置傳感器被提出。它是一種光柵投射到被測物體上要通過4倍的空間濾波器光學系統(tǒng)。經被測物體反射的光柵投影通過另一個4倍光學系統(tǒng)成像形成莫爾條紋。莫爾極化信號獲取被測物體的位置信息。在位置傳感器，不同的莫爾正弦信號對應不同的對象的位置。測量是用獨立的光柵投影強度和對象的反射率來衡量。在實驗中，位置傳感器的效力得到證明，并且均方根（RMS）的每個測量位置誤差小于13納米。位置的測量已在許多領域發(fā)揮了重要作用，例如制造，生物物理學，和自動控制領域。在位置的測量方法，光學方法讓人更有興趣，因為它具有高度的

3、準確性并且是非接觸式測量。在普通光學方法，諸如圖像測量，干涉儀，使用位置靈敏探測器（PDS）的直線位移測量，測量光束方向是垂直于被測物體表面的。當有物體阻擋在對象的垂直方向時，普通光學方法就不在適用。要解決這個問題,本文提出一種新的基于臨界入射的位移光柵傳感器。這種位置傳感器是如圖-1所示。一個投射光柵被平行激光束照亮,投置到前面的焦面鏡L1。焦距透鏡組L1和L2組成4倍焦系統(tǒng)1。在這個4倍焦系統(tǒng)中，頻率平面有一個孔徑。投影光柵被投射到被測物體投影光柵通過這個臨界入射的4倍焦系統(tǒng)1 被檢測。由鏡頭L3和L4組成的4倍焦系統(tǒng)2同系統(tǒng)1有相同的光學參數(shù)。這個傳感光柵呈現(xiàn)在L4的背面焦點平面。經物體

4、反射后,這個投影光柵的影像通過4倍焦系統(tǒng)2 投影到傳感光柵上。由于檢測光柵和投影光柵的影像重疊產生莫爾條紋。莫爾條紋輸出信號隨物體的方位變化由一個探測器通過透鏡L5探測到。一個起偏鏡和鍍板在L4和檢測光柵之間。形成投影光柵圖像的光線通過偏光系統(tǒng)成為線性偏振光。通過鍍板，線性偏振光被分成兩個垂直極化相互交叉的光線。一個分析儀安置在檢測光柵和L5之間。當分析儀是圍繞在4倍焦系統(tǒng)2的光軸線周圍，偏光器板和分析形成偏振調制器。隨著極化調制，莫爾信號對在光柵投影上光的強度的變化是不敏感的。因此，該被測物體的位置，通過檢測調制能夠準確的測量。圖-1位置傳感器示意圖在圖-1中，位于4倍焦系統(tǒng)中的光軸定義為z

5、軸。投影光柵平面上,垂直、平行于投影光柵槽的方向分別被定義為x0和y0軸。同樣，定義x2，y2軸和x3，y3軸。在4倍焦系統(tǒng)1的頻平面上的x1，y1軸分別平行于光柵投影平面x0，y0軸。光柵投影中心放置在x0軸的起點。該光柵投影空間的比例為1:1。光柵投影的周期和寬度分別為D和B。通過光柵投影振幅分布表示為：（-1）公式（-1）中I1是在光柵投影強度。隨著透鏡L1傅立葉變換，在4焦距系統(tǒng)的頻平面上的頻率分布情況為：（-2）式中是激光波長和f是L1的焦距。在頻平面上，孔徑作為空間濾波器，其過濾的功能如下所示：（-3）因此，只有0，± 1衍射角的光能通過孔徑，通過孔徑的頻率分布寫為：（-

6、4）經L2傅里葉變換，在L2的回焦平面上振幅E(x2) 分布如下式：（-5）因此，在光柵投影圖像的光強分布表示為：（-6）被測物放在靠近L2 的背焦點的地方。L3的前焦點與L2的背焦點是重疊，4倍焦系統(tǒng)的1和2在縱向是對稱的。經過對象反射，投影通過4倍焦系統(tǒng)成像與檢測光柵上。L3的前焦點所在水平面被定義為位移傳感器的零平面。如果在被測物與傳感器的零平面之間存在一距離x，檢測光柵投影光柵在檢測光柵上的圖像將隨著位置的改變而變化：（-7）式中是入射光角度。關于檢測光柵投影光柵在檢測光柵上的圖像的光強分布表示為：（-8）式中R表示被測物的反射率。起偏器的傳播軸線與檢測光柵槽間的夾角為45 °

7、;。鍍板包括兩塊相互正交的雙折射板。它將形成投影光柵的圖像光線分成正交極化、相互交叉的兩條線，即常規(guī)的和特殊的光射線。因此，投影光柵的被稱作常和特殊的兩個圖像在檢測光柵上成像。兩圖像間的距離是d/2。常規(guī)和特殊的圖像強度分布表示為：（-9）（-10）兩式中，B/2x32x sinB/2。檢測光柵有同投影光柵一樣的周期和占空比，而且有平行的槽。檢測光柵放在距離軸X3的起點d/4的地方。兩個莫爾信號表示如下：（-11）（-12）如果檢偏鏡透線與檢測光柵槽間的角度是，那么這兩個通過檢偏鏡的莫爾信號表示如下：，（-13）（-14）檢測器通過檢偏鏡檢測光通量，探測器上的光強度由下式給出：（-15）當檢偏

8、鏡繞4倍焦系統(tǒng)2的光軸轉動角度為時，莫爾信號的極化調制得以實現(xiàn)，它在檢測器上表示為：（-16）此時，光強度信號被檢測器轉化為包含直流分量IDC和交變電流分量IAC的電信號。電力信號由放大器放大，其直流和交流成分被濾波電路分開。被測物的位移表示如下：（-17）x的范圍：（-18）在(17)中，IAC和IDC有相同的因子I1和R，因此，位移x與初始強度I1和反射率R無關。那么，激光輸出強度和不同被測物的反射率將不會影響位移傳感器。按光路圖-1所示，進行了實驗。用一束波長為785nm的平行激光照射投影光柵。投影光柵的周長為0.1mm，占空比為1:1。透鏡L1的焦距為120 mm。4倍焦系統(tǒng)1的頻率板

9、上的孔徑為3.5 mm。被測物放在一個能提供做上下線性運動的地方。4倍焦系統(tǒng)1的光軸線與正規(guī)物體間的夾角為84.5°。4倍焦系統(tǒng)2和4倍焦系統(tǒng)1有相同的光學參數(shù)，檢測光柵和投影光柵有相同的光學參數(shù)。起偏器和檢偏器是格倫泰勒棱鏡。鍍板由兩個相同的光束位移差0.05 mm的石英棱鏡組成。檢偏鏡放置在一移動的裝置上，通過旋轉調制莫爾信號。 圖-2 當垂直移動對象時IAC/IDC（a）和均方根誤差（b）測量結果試驗中，通過移動裝置在50um的范圍內按2.5um的步進一步步移動被測物。在每個位置對被測物高度測量100次。實驗結果顯示在圖-2。圖-2(a)顯示IACIDC與被測物高度的關系。IA

10、CIDC隨高度做正弦變化。至此，該位置傳感器測量原理得以驗證。圖-2（b）顯示了均方根（RMS）21位置測量誤差的均方根（RMS），其值小于13 nm。因此，被測物象的高度被位移傳感器高精度測量。最后，我們提出了一種基于帶有特別的過濾和偏移調制的光柵投影的位移傳感器。這種位移傳感器適用于垂直被測物方向有障礙物的測量。莫爾信號隨物體位移變化而產生的正弦曲線由位移傳感器得到。這種位置傳感器是基于不敏感的光源和物體極化調制反射率的差異而在輸出發(fā)生變化。試驗中，該方法的可行性得以驗證。 附錄2A position sensor based on grating projection with spat

11、ial filtering and polarization modulationJianmlng Hu(胡建明)12，Aijun Zeng(曾愛軍)1，and Xiangzhao Wang(王向朝)Shanghai Institute of Optics and Fine Mechanics，Chinese Academy of Sciences，Shanghai 201800 Graduate School of the Chinese Academy of Sciences, Beijing 100039Received April 262005A position sensor bas

12、ed oil grating projection with spatial filtering and polarization modulation is presentedA grating is projected onto the object to be measured through a 4f optical system with a spatial filterAfter reflected by the object the grating projection is imaged on a detection grating through another 4f opt

13、ical system to form moiré fringes. The polarization modulated moire signal is detected to obtain the position information of the objectIn the position sensor，the moire signal varies sinusoidally with the position of object. The measurement is independent of the incident intensity on the project

14、ion grating and the reflectivity of the object to be measuredIn experiments，the effectiveness of the position sensor is proved，and the root mean square(RMS) error at each measurement position is less than 13 nmPosition measurements have been playing an important role in many fields such as fabricati

15、on, biophysics, and auto controlIn methods of position measurement，optical method holds more interest because of its high accuracy and non-contact measurement. In the common optical methods such as image measurement, interferometer ,and direct position detection using position sensitive detector (PD

16、S),the measuring beam is in the direction perpendicular to the surface of the object to be measured. When there exists a block in the direction perpendicular to the object，the common optical methods cannot be applied. To solve the problem，a new position sensor based on grating projection with grazin

17、g incidence is presented in this paper.The position sensor is schematically shown in Fig. -1.A proiection grating is illuminated by a collimated laser beam and placed in the front focal plane of lens L1Lenses L1 and L2 form 4f system 1In this 4f system，an aperture is placed in the frequency planeThe

18、 projection grating is projected onto the object to be measured through the 4f system 1 with grazing incidenceThe 4f system 2 composed of lenses L3 and L4 Jams the same optical parameters with 4f system 1The detection grating is placed in the back focal plane of L4After reflected by the object，the i

19、mage of the projection grating is imaged onto the detection grating through the 4f system 2Due to tile overlapping of the detection grating and the image of the projection grating, the moire fringes are produced. The moiré signal varying with tile position of the object is detected by a detecto

20、r through lens L5A polarizer and a Savant plate are plated between L4 and the detection gratingThe rays forming the image of the projection grating become linearly polarized light through the polarizerPassing the Savant plate, the linearly polarized light is split into two orthogonally polarized and

21、 mutually sheared beamsAn analyzer is placed between the detection grating and L5When the analyzer is rotated around the optical axis of 4f system 2，the polarizer Savant plate and analyzer form a polarization modulatorWith the polarization modulation，the moiré signal is insensitive to the chang

22、e of light intensity on the projection gratingThus the position of the object can be measured accurately by detecting the modulated signalFig. -1.Schematic diagram of the position sensorIn Fig -1the optical axes of the 4f systems are defined as z axisIn the projection grating plane，the directions pe

23、rpendicular and parallel to the groove of the projection grating are defined as directions of x0 mid y0 axes respectivelySimilarly, x2 ,y2 axes and x3，y3 axes are defined on the image planes of the projection gratingIn the frequency plane of the 4f system 1，x1，y1 axes are parallel to x0, y0 axes in

24、the projection grating plane，respectivelyThe center of the projection grating is placed at the origin of x0 axes. The line-to-space ratio of the projection grating is 1:1The period and width of the projection grating are represented by D and B, respectivelyThe amplitude distribution through the proj

25、ection grating is expressed as（-1）Where I1 is the intensity on the projection gratingWith Fourier transform of lens L1, the frequency distribution in the frequency plane of the 4f system 1 is given as （-2）where is the wavelength of the laser and f is the focal length of L1In the frequency plane，the

26、aperture is used as a spatial filter and its filtering function is written as （-3）Hence only 0, ±1 diffraction orders pass the aperture and the frequency distribution through the aperture is written as （-4） With Fourier transform of L2，the amplitude distribution E(x2) in the back focal plane of

27、 L2 is given by（-5）Thus the intensity distribution I(x2) of the image of projection grating is expressed as（-6）The object to be measured is placed near the back focus of L2The front focus of L3 is superposed with the back focus of L2 and 4f systems 1 and 2 are laid symmetrically relative to tile ver

28、tical. After reflected by the object，the projection is imaged on the detection grating through the 4f system 2The horizontal plane where the front focus of L3 is placed is defined as the zero plane of the position sensorIf there exists a distance x between the object and the sensors zero plane, the

29、image of the projection grating on the detection grating will be moved with displacement（-7）whereis the angle of grazing incidenceThe intensity distribution of the image of the projection grating on the detection grating is expressed as （-8） where R is the reflectivity of the object to be measured.

30、The angle between the polarizers transmission axis and the groove direction of the detection grating is 45°The Savant plate comprises two birefringence plates whose optic axes are orthogonal mutuallyIt splits the rays that form the image of the projection grating into two orthogonally polarized

31、 and mutually sheared rays，namely ordinary and extraordinary rays. Thus two images of the projection grating called ordinary and extraordinary images are formed on the detection grating. The distance between the two images is d2The intensity distribution of the ordinary and extraordinary images are

32、expressed as（-9） （-10）respectively，where B2x32x sinB2The detection grating has the same period and line-to-space ratio as the projection grating and its groove is parallel to the groove of the projection gratingThe detection grating is placed with d4 offset relative to the origin of axis x3The two m

33、oiré signals are written as（-11）（-12）If the angle between the analyzers transmission axis and groove direction of the detection grating is ，the two moiré signals through the analyzer are written as（-13）（-14）The detector detects the light flux through the analyzer，and the intensity on the d

34、etector is given by（-15）When the analyzer is rotated with angle (t) around the optical axis of the 4f system 2，polarization modulation of the moiré signal is realize and the modulated intensity on the detector is expressed as（-16）The intensity is converted by the detector into electric signal w

35、hich includes a direct current component IDC and an alternating current component IACThe electric signal is amplified by an amplifier and its direct and alternating current components are separated by a filter circuitThe position of the object is given by（-17）with the variation range（-18）In Eq(17)，I

36、AC and IDC have common factors I1 and R，so the distance is independent of the initial intensity I1 and the reflectivity RThe influence of the output variation of the laser and the reflectivity difference in different objects to be measured can be eliminated in the position sensorUsing the light path

37、 shown in Fig. -1, the experiment was carried outA projection grating was illuminated by a collimated laser beam whose wavelength was 785nmThe period of projection grating was 0.1 mmThe fine-to-space ratio of projection grating is 1：1The focal length of lens L1 was 120 mmThe diameter of the aperture

38、 in the frequency plane of the 4f system 1 was 3.5 mm. The object to be measured was placed on a manual linear stage supplying updown movementThe angle between the axis of 4 f system 1 and the normal of the object was 84.5°The 4f system 2 and the detection grating had same optical parameter as the 4f system 1 and the projection grating，respectivelyThe polarizer and the analyzer were Glen-Taylor prismsThe Savant plate Was made of two same quartz prisms whose beam displacement was 0.05 mmThe analyzer was placed in a rotation mount and was rotated to modulate the