CN103033141A - Two-dimensional displacement measurement device - Google Patents

Abstract

The invention discloses a device of two-dimensional displacement measurement, and relates to a two-dimensional displacement measurement device based on a micro-optics member. The two-dimensional displacement measurement device aims to solve the problem that in an existing two-dimensional displacement measurement process, two sets of independent measurement systems are needed so that a bigger size is resulted in. The two-dimensional displacement measurement device comprises an optical maser, a beam-expanding mirror, a reflecting mirror, a semi-reflecting semi-permeable mirror, a two-dimensional measurement optical grating, a two-dimensional displacement platform, focusing lenses and a two-dimensional surface array detector. Laser light sent out by the optical maser passes through the beam-expanding mirror and the reflecting mirror and then shoot the semi-reflecting semi-permeable mirror in parallel. Transmission light focuses on the two-dimensional measurement optical grating through the focusing lenses. A light beam generates diffraction on the two-dimensional measurement optical grating, and diffraction light passes through the semi-reflecting semi-permeable mirror and the reflecting mirror and then shoots on the focusing lenses in parallel, and finally an image is formed on the two-dimensional surface array detector. According the two-dimensional displacement measurement device, measuring is accurate and convenient in the process of measurement, and size of the two-dimensional displacement measurement device is reduced.

Description

The device that two-dimension displacement is measured

Technical field

The present invention relates to a kind of two-dimensional displacement measurer.

Background technology

The device that is used for displacement measurement has in mechanical industry very widely and uses.At present, the instrument of the known moving displacement that is used for the precision measurement object comprises grating scale, magnetic railings ruler, and ball bar ruler etc., these all are to measure a direction top offset, utilize them, also can consist of the system of measurement plane location.But, in some more special field, measure measuring microscope such as semi-conductor industry, require measuring system volume less, displacement is convenient etc., as the system that adopts two one-dimensional grating chis to consist of, read head is two, and data line is two covers also, is unfavorable for reducing system bulk.

Summary of the invention

The present invention has now in two-dimension displacement is measured for solving, and needs two cover independent measurement systems, causes the larger problem of volume, provides a kind of and can carry out the device that two-dimension displacement is measured.

The device that two-dimension displacement is measured, this device comprises laser instrument, beam expanding lens, the first catoptron, half-reflecting half mirror, the first condenser lens, the two-dimensional measurement grating, the two-dimension displacement platform, the second catoptron, the second condenser lens and two-dimensional array detector, it is characterized in that: the laser beam that laser instrument sends is the parallel half-reflecting half mirror that incides behind beam expanding lens and the first catoptron, transmitted light beam focuses on concurrent the gaining interest of two-dimensional measurement grating through poly-the first focus lens and penetrates, diffracted beam is parallel inciding on the second condenser lens behind half-reflecting half mirror and the second catoptron, finally imaging on the two-dimensional array detector, image display system shows the imaging on the two-dimensional array detector.

Beneficial effect of the present invention: the present invention adopts two dimension to carry out two-dimensional measurement with reference to micro optics array device and two-dimensional measurement micro optics array device, only need mobile two-dimensional measurement micro optics array device in the measuring process, receive image and get final product accurate completion bit shift measurement according to later stage signal processing by the two-dimensional array detector, device of the present invention is measured accurately convenient in measuring process, and has reduced the volume of device.

Description of drawings

Fig. 1 two-dimentional measuring device structural representation;

Fig. 2 two-dimensional measurement optical grating element structural representation;

Fig. 3 order of diffraction secondary ring synoptic diagram;

The irradiance that Fig. 4 focused beam scan amplitude type grating pair is answered.

Embodiment

Embodiment one, as shown in Figure 1, the device that two-dimension displacement is measured comprises: laser instrument 1, beam expanding lens 2, catoptron 3, half-reflecting half mirror 4, condenser lens 5, two-dimensional measurement grating 6, two-dimension displacement platform 7, catoptron 8, condenser lens 9, two-dimensional array detector 10 and image display system 11.The laser that laser instrument 1 sends is by beam expanding lens 2 and catoptron 3 later on parallel inciding on the half-reflecting half mirror 4, transmitted light focuses on the two-dimensional measurement grating 6 through condenser lens 5, diffraction occurs at two-dimensional measurement grating 6 in light beam, diffraction light is by half-reflecting half mirror 4 and catoptron 8 later parallel inciding on the condenser lens 9, finally imaging on two-dimensional array detector 10 is by image display system 11 observationss.

As shown in Figure 2, grating is to be made of a large amount of wide, equally spaced slit.Measure grating for two and be of a size of 100mm * 100mm, the x direction grating cycle is 50 μ m, and the y direction grating cycle is 50 μ m.Be that the microstructure amount of monomer is N on the x direction _x=D/ Λ _xThe microstructure amount of monomer is N on=2000, the y direction _y=D/ Λ _y=2000.

Shown in Figure 3, during for two-dimensional measurement, order of diffraction secondary ring synoptic diagram.Be that+1 grade of light is identical with the variation of zero order light interference field striped with zero order light and-1 grade of light at the emergent pupil place, so in measuring process, only need the variation of+1 grade of light of observation and zero order light interference field striped to get final product.Laser instrument Output of laser wavelength is 0.5 μ m, and the condenser lens focal length is 10mm.

When $\frac{n}{20}<x_s<\frac{(n+1)}{20}$ The time,

$\begin{array}{c}{x}_s=\frac{{\mathrm{\&Lambda;}}_x}{2\mathrm{\&pi;}}\arccos \left[\frac{\mathrm{\&pi;}}{\left|c_{+}{c}_{-}^{*}\right|}(I_{+1}-\frac{{\left|c_{+}\right|}^2}{4}-\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2})\right]+{\mathrm{n\&Lambda;}}_x-x_{\mathrm{\&phi;}}\\ =\frac{1}{40\mathrm{\&pi;}}\arccos (4.7461I_{+1}-1.4428)+0.1682+\frac{n}{20}\end{array}$ ，（n=0,1,2…，2000）

Same, on the y direction,

When $\frac{n}{20}<y_s<\frac{(n+1)}{20}$ The time,

$\begin{array}{c}{y}_s=\frac{{\mathrm{\&Lambda;}}_{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002673260500011.png"\; state="\{\{state\}\}">y</figure-callout>}}}{2\mathrm{\&pi;}}\arccos \left[\frac{\mathrm{\&pi;}}{\left|c_{+}{c}_{-}^{*}\right|}(I_{+1}-\frac{{\left|c_{+}\right|}^2}{4}-\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2})\right]+{\mathrm{n\&Lambda;}}_y-y_{\mathrm{\&phi;}}\\ =\frac{1}{40\mathrm{\&pi;}}\arccos (4.7461I_{+1}-1.4428)+0.1682+\frac{n}{20}\end{array}$ ，（n=0,1,2…，2000）

Shown in Figure 4, during for two-dimensional measurement, take the x-z plane surveying as example.To calculate at two-dimensional measurement grating range of movement be the grating during cycle according to above-mentioned, and ccd signal is processed the relative irradiance of gained and the relation curve between the grating movement locus.Transverse axis represents displacement and the ratio in grating cycle of grating, and the longitudinal axis represents the relative irradiance on the CCD.The corresponding dependent variable of independent variable, but corresponding two independents variable of dependent variable.Supposed by the data handling system counter records n=1 cycle, then had:

I +1	x s1	x s2	I +1	x s1	x s2
						0.5116	0.000	1.000	0.30	0.280	0.774
0.50	0.086	0.967	0.25	0.318	0.736
						0.45	0.155	0.899	0.20	0.359	0.695
0.40	0.201	0.852	0.15	0.407	0.646
						0.35	0.242	0.812	0.10	0.486	0.567

If recorded n=10, in n=100 cycle, the displacement of then describing in above table adds n Λ _x=0.5, n Λ _x=5, be the displacement of displacement platform on the x direction of principal axis.

The specific works flow process of embodiment two, present embodiment is: measure grating for two and be of a size of D * D, the x direction grating cycle is Λ _x, the y direction grating cycle is Λ _yBe that x direction glazing grid cycle quantity is N _x=D/ Λ _x, y direction glazing grid cycle quantity is N _y=D/ Λ _y

Grating is placed on the displacement plane, when planar movement, cause optical system focus point raster, the phase place of ± 1 grade of light changes with respect to zero order light, can observe catoptrical instantaneous modulation at the emergent pupil place of optical system, this instantaneous modulation is reflected in the emergent pupil place reaches-1 grade of light and zero order light interference field striped for+1 grade of light and zero order light variation.By observing the variation of striped generation, finally obtain the movement locus of two-dimension displacement platform.

Select suitable grating periods lambda make optical grating reflection ± 1 order diffraction light is not overlapping at the emergent pupil place of system, and zero order light interferes, thereby obtain simple interference pattern.When the vertical grid line scanning direction grating in focal spot edge, the light field distribution of amplitudes of establishing the focal plane is U _i(x ₀, y ₀), it can be obtained by the two-dimension fourier transform of pupil place light field amplitude:

$U_i(x_0,y_0)=F{\left\{P(x,y)\right\}}_{{\mathrm{\&xi;}}_0=x_0/\mathrm{\&lambda;z},{\mathrm{\&eta;}}_0={\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00002673260500022.png"\; state="\{\{state\}\}">y</figure-callout>}}_0/\mathrm{\&lambda;z}}---\left(1\right)$

Here, x, y are the coordinates on the emergent pupil face, x ₀, y ₀The coordinate of grating planar, ξ ₀, η ₀Be the frequency variable of Fourier transform, λ is wavelength, the z focal length of lens, and P (x, y) is the light field complex amplitude.

If displacement platform edge

Direction vector moves, because the x axle is uncorrelated mutually with the y axle, the two dimensional motion of displacement platform can be approximately the stack of motion in one dimension on x, y axle.Therefore, can be write the displacement of two-dimensional movement platform as the component form.Wherein, vector Component on the x axle is x _s, vector

Component on the y axle is y _sIt is pointed out that in moving process to produce a minute optical phenomenon, as long as process by the signal of CCD, separate, filtering, draw displacement platform respectively along the motion track of x and y direction.

The light field amplitude direct representation of optical grating reflection is:

$U_r(x_0,y_0)=\hat{f}(x_0-x_s,y_0-y_s)U_i(x_0,y_0)---\left(2\right)$

Here,

The diffraction of expression square wave amplitude grating.

The light field amplitude that reflects at the emergent pupil place is provided by the two-dimentional inverse Fourier transform of formula (2), and it is and U _a(x, y) is proportional, U _a(x, y) is defined as:

$\begin{array}{c}{U}_a(x,y)=\frac{c+}{2}P(x,y)\\ +\frac{c_{-}}{\mathrm{\&pi;}}[P(x-\frac{\mathrm{\&lambda;z}}{{\mathrm{\&Lambda;}}_x},y)\exp \left(\frac{-2\mathrm{\&pi;i}{x}_s}{{\mathrm{\&Lambda;}}_x}\right)+P(x+\frac{\mathrm{\&lambda;z}}{{\mathrm{\&Lambda;}}_x},y)\exp \left(\frac{2\mathrm{\&pi;i}{x}_s}{{\mathrm{\&Lambda;}}_x}\right)]\\ +\frac{c_{-}}{\mathrm{\&pi;}}[P(x,y-\frac{\mathrm{\&lambda;z}}{{\mathrm{\&Lambda;}}_y})\exp \left(\frac{-2\mathrm{\&pi;i}{y}_s}{{\mathrm{\&Lambda;}}_y}\right)+P(x,y+\frac{\mathrm{\&lambda;z}}{{\mathrm{\&Lambda;}}_y})\exp \left(\frac{2\mathrm{\&pi;i}{y}_s}{{\mathrm{\&Lambda;}}_y}\right)]\end{array}---\left(3\right)$

Here, x _s, y _sRespectively the displacement on raster x and the y direction, Λ _x, Λ _yRespectively the grating cycle on x and the y direction, d/ Λ _x, d/ Λ _yBe dutycycle, c ₁, c ₂Complex amplitude reflection coefficient for two different pieces of grating.c ₊=c ₁+c ₂，c _-=c ₁-c ₂。

The below considers that take the x-z plane as example displacement platform is along the motion in one dimension rule of x axle.Square wave amplitude grating along x axle direction of scanning can be described by the delta functional symbol:

$\begin{array}{c}f(x_0-x_s)=\left\{{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA00002673260500021.png,HDA00002673260500022.png"\; state="\{\{state\}\}">c</figure-callout>}}_1\mathrm{rect}(\frac{x_0}{d}\&CircleTimes;\underset{n=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}[(x_0-x_s)-n{\mathrm{\&Lambda;}}_x\left]\right)\right\}\\ +\{{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00002673260500011.png"\; state="\{\{state\}\}">c</figure-callout>}}_2\mathrm{rect}\left(\frac{x_0}{{\mathrm{\&Lambda;}}_x-d}\right)\&CircleTimes;\underset{n=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}[(x_0-x_s)-n{\mathrm{\&Lambda;}}_x-\frac{{\mathrm{\&Lambda;}}_x}{x}\left]\right\}\end{array}---\left(4\right)$

Formula (4) further is decomposed into fourier series and represents the different order of diffraction of grating time.Here only considering ± 1 grade and zero order light, so only preserve front two, is the equivalence of the grating of rectangle square wave sinusoidal grating so just, and selecting the dutycycle of grating is 50%, d=Λ _x/ 2, then have:

$\begin{array}{c}f(x_0-x_s)\&ap;\hat{f}(x_0-x_s)=\frac{{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA00002673260500021.png,HDA00002673260500022.png"\; state="\{\{state\}\}">c</figure-callout>}}_1}{2}+\frac{2{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA00002673260500021.png,HDA00002673260500022.png"\; state="\{\{state\}\}">c</figure-callout>}}_1}{\mathrm{\&pi;}}\cos \left[\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_x}(x_0-x_s)\right]\\ +\frac{{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00002673260500011.png"\; state="\{\{state\}\}">c</figure-callout>}}_2}{2}+\frac{2{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00002673260500011.png"\; state="\{\{state\}\}">c</figure-callout>}}_2}{\mathrm{\&pi;}}\sin \left\{\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_x}\right[(x_0-x_s)-\left]\frac{{\mathrm{\&Lambda;}}_x}{2}\right\}\end{array}---\left(5\right)$

Corresponding with overlapping region (± 1 grade and zero order light) so light intensity a constant multiple take interior as:

$I_{\&PlusMinus;1}=\frac{{\left|c_{+}\right|}^2}{4}+\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2}+\frac{1}{\mathrm{\&pi;}}\left|c_{+}{c}_{-}^{*}\right|\cos \left[\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_x}(x_s\&PlusMinus;x_{\mathrm{\&phi;}})\right]---\left(6\right)$

Here, , φ is

Phase angle.I _{± 1}Reflected optical grating reflection ± light distribution situation that 1 order diffraction light and zero order diffracted light interfere.c ₁, c ₂Be the complex amplitude reflection coefficient of grating, as:

, wherein, N ₁Be c ₁The complex index of refraction of material.When wavelength is 0.5 μ m, N is arranged for chromium ₁=2.5+4.5i.c ₂Get the refractive index N of conventional optical glass ₂=1.5 calculate.

Suppose that mobile platform displacement on the x direction is x _s, displacement is y on the y direction _sThe condenser lens focal length is f.In the platform movement process, as 0＜x _s＜Λ _xThe time,

$I_{\&PlusMinus;1}=\frac{{\left|c_{+}\right|}^2}{4}+\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2}+\frac{1}{\mathrm{\&pi;}}\left|c_{+}{c}_{-}^{*}\right|\cos \left[\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_x}(x_s\&PlusMinus;x_{\mathrm{\&phi;}})\right]$

This just in time finishes one-period, works as x _sContinue to increase, come back to initial point and begin to repeat above-mentioned motion.By counting, obtain x _sOscillation cycle can the completion bit shift measurement.

As n Λ _x＜x _s＜(n+1) Λ _xThe time,

$I_{\&PlusMinus;1}=\frac{{\left|c_{+}\right|}^2}{4}+\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2}+\frac{1}{\mathrm{\&pi;}}\left|c_{+}{c}_{-}^{*}\right|\cos \left[\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_x}(x_s\&PlusMinus;x_{\mathrm{\&phi;}}-n{\mathrm{\&Lambda;}}_x)\right]$ ，（n=0,1,2…，N _x）

$x_s=\frac{{\mathrm{\&Lambda;}}_x}{2\mathrm{\&pi;}}\arccos \left[\frac{\mathrm{\&pi;}}{\left|c_{+}{c}_{-}^{*}\right|}(I_{\&PlusMinus;1}-\frac{{\left|c_{+}\right|}^2}{4}-\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2})\right]+n{\mathrm{\&Lambda;}}_x\stackrel{\&OverBar;}{+}{x}_{\mathrm{\&phi;}}$ ，（n=0,1,2…，N _x）

Same, on the y direction,

As n Λ _y＜y _s＜(n+1) Λ _yThe time,

$I_{\&PlusMinus;1}=\frac{{\left|c_{+}\right|}^2}{4}+\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2}+\frac{1}{\mathrm{\&pi;}}\left|c_{+}{c}_{-}^{*}\right|\cos \left[\frac{2\mathrm{\&pi;}}{{\mathrm{\&Lambda;}}_y}(y_s\&PlusMinus;y_{\mathrm{\&phi;}}-n{\mathrm{\&Lambda;}}_y)\right]$ ，（n=0,1,2…，N _y）

$y_s=\frac{{\mathrm{\&Lambda;}}_{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002673260500011.png"\; state="\{\{state\}\}">y</figure-callout>}}}{2\mathrm{\&pi;}}\arccos \left[\frac{\mathrm{\&pi;}}{\left|c_{+}{c}_{-}^{*}\right|}(I_{\&PlusMinus;1}-\frac{{\left|c_{+}\right|}^2}{4}-\frac{{\left|c_{-}\right|}^2}{{\mathrm{\&pi;}}^2})\right]+n{\mathrm{\&Lambda;}}_y\stackrel{\&OverBar;}{+}{y}_{\mathrm{\&phi;}}$ ，（n=0,1,2…，N _y）

Grating is classified by its modulating action to incident light can be divided into amplitude grating and phase grating.The grating type of introducing previously is amplitude type, and in like manner, the phase-type grating is equally applicable in the above-mentioned two-dimension displacement measuring system.

When planar movement, cause optical system focus point raster, the phase place of ± 1 grade of light changes with respect to zero order light, by observing the variation of striped generation, finally obtains the movement locus of two-dimension displacement platform.Be that+1 grade of light is identical with the variation of zero order light interference field striped with zero order light and-1 grade of light at the emergent pupil place, so in measuring process, only need the variation of+1 grade of light of observation and zero order light interference field striped to get final product.

Claims (2)

1. the device measured of two-dimension displacement, this device comprises laser instrument (1), beam expanding lens (2), the first catoptron (3), half-reflecting half mirror (4), the first condenser lens (5), two-dimensional measurement grating (6), two-dimension displacement platform (7), the second catoptron (8), the second condenser lens (9) and two-dimensional array detector (10), it is characterized in that: the laser beam that laser instrument (1) sends is the parallel half-reflecting half mirror (4) that incides behind beam expanding lens (2) and the first catoptron (3), transmitted light beam focuses on concurrent the gaining interest of two-dimensional measurement grating (6) through poly-the first focus lens (5) and penetrates, diffracted beam is parallel inciding on the second condenser lens (9) behind half-reflecting half mirror (4) and the second catoptron (8), finally in the upper imaging of two-dimensional array detector (10).

2. the device of two-dimension displacement measurement according to claim 1 is characterized in that also comprise image display system (11), described image display system (11) shows the imaging on the two-dimensional array detector (10).

Images