CN203744933U

CN203744933U - Two-dimensional displacement measuring device based on variable-spacing grating diffraction

Info

Publication number: CN203744933U
Application number: CN201420122234.9U
Authority: CN
Inventors: 楼俊; 李本冲; 许宏志; 谭耀成; 徐贲; 黄杰; 沈为民
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2014-03-14
Filing date: 2014-03-14
Publication date: 2014-07-30
Anticipated expiration: 2024-03-14

Abstract

The utility model discloses a two-dimensional displacement measurement device based on variable-pitch grating diffraction, which solves the problems of large volume of the measurement system and complex mathematical processing methods in the existing two-dimensional displacement measurement, including: a light source, a reflector, a focusing A lens, an aperture, a collimating lens, a two-dimensional measuring grating, a two-dimensional displacement platform, a first detector, a second detector and a spectrometer. When the broadband light emitted by the light source passes through the reflector, it is parallel incident on the focusing lens, and the focused light is vertically incident on the two-dimensional measuring grating through the diaphragm and the collimating lens, and the light beam diffracts on the two-dimensional measuring grating, and the detector The diffracted light is received at a fixed angle, and the detected signal is analyzed and processed by a spectrometer. The device described in the utility model is accurate and convenient in the measurement process, and the volume of the device is reduced.

Description

Two-dimensional Displacement Measuring Device Based on Variable Pitch Grating Diffraction

技术领域technical field

本发明涉及一种位移测量装置，尤其涉及一种二维位移测量装置。The invention relates to a displacement measuring device, in particular to a two-dimensional displacement measuring device.

背景技术Background technique

用于位移测量的装置，在机械加工业中有广泛的应用。目前，精密位移测量装置大多是一维的，公知的用来精密测量物体的移动的工具包括光栅尺、磁栅尺、球栅尺等，这些都是测量一个方向上位移的，而在实际应用中被测点的位移大多产生在两个方向上，利用它们也可以构成测量平面位置的系统。但是，在某些比较特殊的领域，比如半导体工业测量，测量显微镜，要求测量系统体积相对较小，移动方便等。公知的一种二维位移测量装置所用测量光栅为等宽、等间隔光栅，其衍射光分析相对复杂，信号处理过程繁琐，不易于实验分析与测量。Devices for displacement measurement are widely used in the machining industry. At present, most of the precision displacement measurement devices are one-dimensional. The known tools used to precisely measure the movement of objects include grating scales, magnetic scales, ball scales, etc., all of which measure displacement in one direction, but in practical applications Most of the displacements of the measured points are generated in two directions, and they can also be used to form a system for measuring the position of the plane. However, in some special fields, such as semiconductor industry measurement and measuring microscope, the measurement system is required to be relatively small in size and easy to move. A known two-dimensional displacement measuring device uses a measuring grating of equal width and equal interval, and its diffracted light analysis is relatively complicated, and the signal processing process is cumbersome, making it difficult for experimental analysis and measurement.

发明内容Contents of the invention

本发明的目的是提供一种基于变间距光栅衍射的二维位移测量装置，该装置具有抗干扰性强的优点，它能够准确测量物体微小位移，而且数学表达式简单。The object of the present invention is to provide a two-dimensional displacement measurement device based on variable-pitch grating diffraction, which has the advantages of strong anti-interference, can accurately measure small displacements of objects, and has simple mathematical expressions.

基于变间距光栅衍射的二维位移测量装置，该装置包括光源、反射镜、聚焦透镜、光阑、准直透镜、二维测量光栅、二维位移平台、第一探测器、第二探测器和光谱仪。光源发出的宽带光经反射镜入射到聚焦透镜上，聚焦后的光通过光阑和准直透镜垂直入射到二维测量光栅上，光束在二维测量光栅上发生衍射，衍射光以固定角度被第一探测器、第二探测器接收，探测的信号通过光谱仪分析处理。A two-dimensional displacement measurement device based on variable-pitch grating diffraction, the device includes a light source, a mirror, a focusing lens, an aperture, a collimator lens, a two-dimensional measurement grating, a two-dimensional displacement platform, a first detector, a second detector and spectrometer. The broadband light emitted by the light source is incident on the focusing lens through the reflector, and the focused light is vertically incident on the two-dimensional measuring grating through the diaphragm and the collimating lens. The first detector and the second detector receive, and the detected signal is analyzed and processed by a spectrometer.

使用的光栅是变间距光栅，光栅的栅格呈等比数列变化，可以得到移动位移与光栅周期之间的关系。由光栅方程可知，在衍射情况下测得的衍射波长与该位置处的光栅周期具有一一对应的关系，在变间距光栅表面不同点所测得的衍射波长不同。第一探测器位于y-z平面，与x轴方向平行的光栅刻槽所衍射的光线被第一探测器接收，可得x方向上一级衍射光与光栅周期的关系；第二探测器位于x-z平面，与y轴方向平行的光栅刻槽所衍射的光线被第二探测器接收，可得y方向一级衍射光与光栅周期的关系。The grating used is a variable-pitch grating, and the grid of the grating changes in a geometric sequence, and the relationship between the displacement and the period of the grating can be obtained. It can be seen from the grating equation that the diffraction wavelength measured in the case of diffraction has a one-to-one correspondence with the grating period at the position, and the diffraction wavelength measured at different points on the surface of the variable-pitch grating is different. The first detector is located on the y-z plane, and the light diffracted by the grating groove parallel to the x-axis direction is received by the first detector, and the relationship between the first-order diffracted light in the x-direction and the grating period can be obtained; the second detector is located on the x-z plane , the light diffracted by the grating grooves parallel to the y-axis direction is received by the second detector, and the relationship between the first-order diffracted light in the y-direction and the period of the grating can be obtained.

进一步，通过光谱仪得到衍射光的衍射光谱，分析出光强最大值所对应的波长，一级衍射光光谱的光强度峰值对应的中心波长与传感器的位移一一对应，这样就精确地测出了平面二维位移。Further, the diffraction spectrum of the diffracted light is obtained by the spectrometer, and the wavelength corresponding to the maximum value of the light intensity is analyzed, and the center wavelength corresponding to the peak value of the light intensity of the first-order diffraction light spectrum corresponds to the displacement of the sensor one by one, thus accurately measuring Two-dimensional displacement of the plane.

本发明的有益效果：二维测量光栅和二维位移平台粘合在一起，测量过程中只需要移动二维位移平台，操作简单方便。The invention has beneficial effects: the two-dimensional measuring grating and the two-dimensional displacement platform are glued together, and only the two-dimensional displacement platform needs to be moved during the measurement process, and the operation is simple and convenient.

再者，本发明装置中二维测量光栅采用变间距光栅，通过测量光的波长可直接得到平台移动位移，而波长是光的本质属性之一，不受压力、温度等外界环境的影响，测量精确度大大提高。Furthermore, the two-dimensional measurement grating in the device of the present invention adopts a variable-pitch grating, and the displacement of the platform can be directly obtained by measuring the wavelength of the light, and the wavelength is one of the essential properties of light, which is not affected by external environments such as pressure and temperature. Accuracy is greatly improved.

附图说明Description of drawings

图1二维测量装置结构示意图；Figure 1 Schematic diagram of the structure of the two-dimensional measuring device;

图2二维测量光栅元件局部放大示意图；Figure 2 is a partial enlarged schematic diagram of two-dimensional measuring grating components;

图3变间距光栅衍射在θ位置的合成光强度I和波长λ的关系曲线。Fig. 3 is the relationship curve between the synthetic light intensity I and the wavelength λ at the θ position of the variable-pitch grating diffraction.

具体实施方式Detailed ways

如图1所示，二维位移测量的装置，包括：光源1、反射镜2、聚焦透镜3、光阑4、准直透镜5、二维测量光栅6、二维位移平台7、第一探测器8、第二探测器9、光谱仪10。光源1发出的宽带光经反射镜2入射到聚焦透镜3上，聚焦后的光通过光阑4和准直透镜5垂直入射到二维测量光栅6上，光束在二维测量光栅上发生衍射，第一探测器8和第二探测器9以固定角度接收衍射光，探测的信号经光谱仪分析处理。As shown in Figure 1, the device for two-dimensional displacement measurement includes: light source 1, reflector 2, focusing lens 3, aperture 4, collimator lens 5, two-dimensional measurement grating 6, two-dimensional displacement platform 7, first detection Device 8, second detector 9, spectrometer 10. The broadband light emitted by the light source 1 is incident on the focusing lens 3 through the reflector 2, and the focused light is vertically incident on the two-dimensional measuring grating 6 through the diaphragm 4 and the collimating lens 5, and the light beam is diffracted on the two-dimensional measuring grating. The first detector 8 and the second detector 9 receive diffracted light at a fixed angle, and the detected signals are analyzed and processed by a spectrometer.

如图2所示，光栅是由大量变栅距的狭缝构成。二维测量光栅的尺寸为20mm×20mm。As shown in Figure 2, the grating is composed of a large number of slits with variable pitch. The size of the two-dimensional measuring grating is 20mm×20mm.

当宽带光垂直入射到光栅表面，以y-z平面测量为例，由光栅方程可知(取一级衍射光)：When the broadband light is vertically incident on the surface of the grating, taking the y-z plane measurement as an example, it can be known from the grating equation (take the first-order diffracted light):

d_nsinθ=λ_n (1)d _n sinθ=λ _n (1)

变间距光栅的栅距d按等比数列变化，狭缝距离a不变。设变间距光栅栅距方程为The pitch d of the variable-pitch grating changes according to the geometric sequence, and the slit distance a does not change. Let the grating pitch equation of the variable pitch grating be

d_k=d₀(1-q)^k (2)d _k = d ₀ (1-q) ^k (2)

k为栅距序号，1-q为栅距公比。设d₀处对应位移X₀=0，该点对应一级衍射光中心波长λ₀。d_n处对应的位移为X_n，根据等比数列前n项和求和公式得：k is the serial number of the grid pitch, and 1-q is the common ratio of the grid pitch. Assuming that d ₀ corresponds to displacement X ₀ =0, this point corresponds to the central wavelength λ ₀ of the first-order diffracted light. The corresponding displacement at d _n is X _n , according to the first n items of the geometric sequence and the summation formula:

${X x}_{n no} = = {Σ Σ}_{k k = = 00}^{n no - - 11} {d d}_{k k} = = \frac{{d d}_{00} [[11 - - {((11 - - q q))}^{n no}]]}{q q} ((k k = = 0,1,2 0,1,2,, . . . . . . n no - - 11)) - - - - - - ((33))$

d₀sinθ=λ₀ (4)d ₀ sinθ=λ ₀ (4)

${d d}_{n no} = = \frac{{λ λ}_{n no} {d d}_{00}}{{λ λ}_{00}} - - - - - - ((55))$

得：have to:

${X x}_{n no} = = \frac{{d d}_{00}}{q q} - - \frac{{λ λ}_{n no}}{q q sin sin θ θ} - - - - - - ((66))$

同理可得：In the same way:

${Y Y}_{n no} = = \frac{{d d}_{00}}{q q} - - \frac{{λ λ}_{n no}}{q q sin sin θ θ} - - - - - - ((77))$

即得到了二维位移与一级衍射光中心波长的关系，可以看出X_n、Y_n与λ_n成简单的线性关系。只要测出一级衍射中心波长就可以得出二维位移值。通过探测器得到衍射光谱，分析出光强最大值所对应的波长，一级衍射光光谱的光强度峰值对应的中心波长与二维位移平台移动的位移一一对应，这样就精确地测出了平面二维位移。That is, the relationship between the two-dimensional displacement and the central wavelength of the first-order diffracted light is obtained. It can be seen that X _n , Y _n and λ _n form a simple linear relationship. As long as the center wavelength of the first-order diffraction is measured, the two-dimensional displacement value can be obtained. The diffraction spectrum is obtained by the detector, and the wavelength corresponding to the maximum light intensity is analyzed. The central wavelength corresponding to the light intensity peak value of the first-order diffraction light spectrum corresponds to the displacement of the two-dimensional displacement platform one by one, so that the precise measurement is made. Two-dimensional displacement of the plane.

如图3所示，为二维测量时变间距光栅衍射在θ位置的合成光强度I和波长λ的关系曲线，以y-z平面测量为例。对于等狭缝变间距光栅，每一种确定的波长λ_m，可按光强公式计算出它们在θ方向的合成光强度I_m。用积分法求得通过第n个单缝的衍射光在焦平面上的合成振动公式为：As shown in Figure 3, it is the relationship curve between the synthetic light intensity I and the wavelength λ at the θ position of the time-varying pitch grating diffraction in two-dimensional measurement, taking the yz plane measurement as an example. For equal-slit variable-pitch gratings, for each determined wavelength λ _m , their combined light intensity I _m in the θ direction can be calculated according to the light intensity formula. Using the integral method to obtain the synthetic vibration formula of the diffracted light passing through the nth single slit on the focal plane is:

$E E. = = {E E.}_{00} a a \frac{sin sin \frac{22 π π a a sin sin θ θ}{{λ λ}_{m m}}}{\frac{22 π π a a sin sin θ θ}{{λ λ}_{m m}}} = = {E E.}_{00} β β - - - - - - ((88))$

式中E₀-光波振幅；a-光缝宽度；λ_m-单色平行光波长；In the formula, E ₀ -light wave amplitude; a-light slit width; λ _m -monochromatic parallel light wavelength;

β-第n条狭缝衍射光合成振幅系数；β-the nth slit diffraction photosynthetic amplitude coefficient;

$β β = = a a \frac{sin sin \frac{22 π π a a sin sin θ θ}{{λ λ}_{m m}}}{\frac{22 π π a a sin sin θ θ}{{λ λ}_{m m}}} - - - - - - ((99))$

θ-出射角；θ - exit angle;

θ=arcsin(λ_m／d₀) (10)θ=arcsin(λ _m ／d ₀ ) (10)

d₀-起始栅距。d ₀ - initial grid pitch.

通过N条光缝的N束衍射平行光，其相位均不相同，则通过第n条光缝的衍射光，其光波的向量表达式为：The phases of N beams of diffracted parallel light passing through N optical slits are all different, so the vector expression of the light wave of the diffracted light passing through the nth optical slit is:

M_n=βE₀e^{i(ωt-cr+δn)}(n＝0，1，2，……，N-1) (11)M _n =βE ₀ e ^{i(ωt-cr+δn)} (n=0, 1, 2,..., N-1) (11)

式中，ω-圆频率，常数；t-时间；r-初相位；c-常数；d_n-第n个栅距；δ_n-第n条狭缝衍射光相位角In the formula, ω—circular frequency, constant; t—time; r—initial phase; c—constant; d _n —the nth grating pitch; δ _n —the nth slit diffracted light phase angle

${δ δ}_{n no} = = \frac{44 π π sin sin θ θ}{{λ λ}_{m m}} {Σ Σ}_{k k = = 00}^{n no} {d d}_{k k},, ((n no = = 0,1,2 0,1,2,, . . . . . . . . . . . .,, N N - - 11)) - - - - - - ((1212))$

求解N束相干光的合成问题是向量求和问题，它们合成向量的表达式为：Solving the synthesis problem of N beams of coherent light is a vector summation problem, and the expression of their synthesis vector is:

$M m = = {Σ Σ}_{k k = = 00}^{N N - - 11} β β {E E.}_{00} {e e}^{i i ((ωt ωt - - cr cr + + δn δn))} = = {E E.}_{00} {e e}^{i i ((ωt ωt - - cr cr))} {Σ Σ}_{k k = = 00}^{N N - - 11} β β {e e}^{iδn iδn} - - - - - - ((1313))$

适当的选择单位，可将合成光强度I用合成光向量M振幅的平方表示为：With proper selection of units, the synthetic light intensity I can be expressed by the square of the amplitude of the synthetic light vector M as:

$I I = = {E E.}_{00}^{22} {| | {Σ Σ}_{k k = = 00}^{N N - - 11} β β {e e}^{iδn iδn} | |}^{22} = = {I I}_{00} [[{(({Σ Σ}_{k k = = 00}^{N N - - 11} β β cos cos {δ δ}_{n no}))}^{22} + + {(({Σ Σ}_{k k = = 00}^{N N - - 11} β β sin sin {δ δ}_{n no}))}^{22}]] - - - - - - ((1414))$

式中，I₀-入射光强，I₀=E₀ ²。In the formula, I ₀ -incident light intensity, I ₀ =E ₀ ² .

应用光栅衍射强度分布的一般公式计算该传感器焦平面处各种波长的合成光强度。传感器入射光为宽带光(设波长下限位λ_z，波长上线为λ_t)，但各种波长是不相干的。按上式计算光栅衍射强度分布，以起始栅距d₀为基准栅距，λ_m=λ₀为基准波长，则出射角θ由下式确定：The general formula for grating diffraction intensity distribution is applied to calculate the resultant light intensity at various wavelengths at the focal plane of the sensor. The incident light of the sensor is broadband light (set the lower limit of wavelength λ _z , and the upper limit of wavelength is λ _t ), but various wavelengths are irrelevant. Calculate the grating diffraction intensity distribution according to the above formula, take the initial grating pitch d ₀ as the reference grating pitch, and λ _m = λ ₀ as the reference wavelength, then the exit angle θ is determined by the following formula:

θ＝arcsin(λ₀／d₀) (15)θ＝arcsin(λ ₀ ／d ₀ ) (15)

对每一种确定的波长λ_m，可按光强公式计算出它们在θ方向的合成光强度I_m。分别计算出对应λ_z～λ_t每种波长的合成光强度I_z～I_t，则可得变栅距光栅在θ方向的合成衍射光强度I与波长λ的关系曲线I=f(λ)。找到合成光强峰值点对应的波长λ_n，从而得出x方向的位移X_n。同理可得y方向的位移Y_n。For each determined wavelength λ _m , their combined light intensity I _m in the θ direction can be calculated according to the light intensity formula. Calculate the synthetic light intensity I _z ～I _t corresponding to each wavelength of λ _z ～λ _t respectively, then the relationship curve I=f(λ) of the synthetic diffracted light intensity I and wavelength λ of the variable pitch grating in the θ direction can be obtained . Find the wavelength λ _n corresponding to the peak point of the synthetic light intensity, so as to obtain the displacement X _n in the x direction. Similarly, the displacement Y _n in the y direction can be obtained.

计算表明，当光斑照射该变间距光栅不同位置时，其一级衍射光均为窄带光，但带宽随栅线密度增加而减小；并且，合成光强度最大值对应的波长，均近似等于相应窄带光中心波长。Calculation shows that when the light spot irradiates different positions of the variable-pitch grating, the first-order diffracted light is narrow-band light, but the bandwidth decreases with the increase of the grating line density; moreover, the wavelength corresponding to the maximum value of the synthetic light intensity is approximately equal to the corresponding The central wavelength of narrowband light.

当平面移动时，引起光学系统聚焦点扫描光栅，一级衍射光合成光强最大值对应的中心波长发生变化，通过中心波长的变化，最终得到二维位移平台的运动轨迹。所以在测量过程中，只需要找到合成光强度最大值对应的波长，即可得光域中心栅距相对应的位移。When the plane moves, the focal point of the optical system is caused to scan the grating, and the central wavelength corresponding to the maximum intensity of the first-order diffraction light synthesis changes. Through the change of the central wavelength, the motion track of the two-dimensional displacement platform is finally obtained. Therefore, in the measurement process, it is only necessary to find the wavelength corresponding to the maximum value of the synthetic light intensity to obtain the corresponding displacement of the center pitch of the optical domain.

Claims

1. the two-dimensional displacement measurer based on becoming spacing optical grating diffraction, this device comprises light source, catoptron, condenser lens, diaphragm, collimation lens, two-dimensional measurement grating, two-dimension displacement platform, the first detector, the second detector and spectrometer, the broadband light that light source sends incides on condenser lens through catoptron, light after focusing impinges perpendicularly on two-dimensional measurement grating by diaphragm and collimation lens, on two-dimensional measurement grating, there is diffraction in light beam, diffraction light with fixed angle by the first detector, the second detector receives, the signal of surveying is processed by spectrometer analysis.

2. the two-dimensional displacement measurer based on becoming spacing optical grating diffraction according to claim 1, it is characterized in that: the first detector is positioned at y-z plane, the light of the grating cutting institute diffraction parallel with x direction of principal axis is received by the first detector, the second detector is positioned at x-z plane, and the light of the grating cutting institute diffraction parallel with y direction of principal axis is received by the second detector.

3. the two-dimensional displacement measurer based on becoming spacing optical grating diffraction according to claim 1, it is characterized in that: the two-dimensional measurement grating of use is to become spacing grating, the grid of grating is Geometric Sequence to be changed, and obtains moving displacement and the relation of grating between the cycle.