CN102538714A - Detection device for high precision and parallel degree of plane - Google Patents

Abstract

The invention discloses a detection device for high precision and parallel degree of a plane. The detection device comprises a plane interference measuring device and a phase-shifting device, wherein the plane interference measuring device can perform laser plane interference measurement on the parallel degree between a first plane to be measured and a second plane to be measured; the phase-shifting device can move the second plane to be measured in the direction of a light path; the first plane to be measured is a semi-reflective and semi-transparent plane to be measured; the second plane to be measured is a fully-reflective plane to be measured; and on the light path, the first plane to be measured is positioned in front of the second plane to be measured. The laser plane interference measurement technology and the phase-shifting interference technology are combined in the device, so the precision of the laser plane interference measurement technology is greatly improved, and the high precision and parallel degree of the plane can be detected.

Description

The pick-up unit of a kind of plane high precision depth of parallelism

Technical field

The invention belongs to the optical detective technology field, relate to the pick-up unit of a kind of plane high precision depth of parallelism.

Background technology

The measurement of plane parallel degree has important effect in optical detection and processing.The laser plane interfere measurement technique is can be very ripe is used for detecting parallelism of two planes, and it has untouchable characteristics, and measuring accuracy can reach 1/2nd wavelength, can be good at satisfying requirement generally speaking.

About the laser plane interfere measurement technique, be that example is specifically introduced with the plane fizeau interferometer below.The plane fizeau interferometer is made up of laser instrument, beam splitter, collimator objective, test plane and standard flat.Homogeneous beam incides on the standard flat, the partial reflection light beam as a reference of returning; The part transmission is also returned as detecting light beam through the test plane reflection.Detect light beam and overlap, form equal thick interference fringe with reference beam.Can detect the surface shape and the homogeneity thereof of flat board or prism, about 1 micron of measuring accuracy with striking cable plane interferometer.

But; Mention the laser plane interfere measurement technique above,, can't further improve measuring accuracy because receive the restriction of visual field intra-striate interpretation; So can't be applied under some environment that need the high precision depth of parallelism (nanometer scale), for example technical field such as nano impression and nano-photoetching.

In addition on the one hand, movable phase interfere technical development in recent years is very ripe, and it can reach the measuring accuracy of one of percentage wavelength.Specifically, in the interferometry, if one of them plane is moved by the piezoelectric crystal driving and generating or vibrated, its immediate movement is l _t, the face shape on seized surface is that (x y), then does w with reference to the corrugated

w ₁＝a·exp[i2k(s+l _t)]

Seized light path corrugated does

w ₂＝b·exp{[i2k[s+w(x，y)]}

In the formula, a, b are two corrugated amplitudes; S is the initial light path of two optical interference circuits; W (x y) is the face shape function on seized surface, it with the position on seized surface mutually 2k w (x y) only differs from a constant, so often (x y) just is used as the position phase on seized corrugated w.So the light distribution of interference fringe does

I(x，y，l _t)＝|w ₁+w ₂| ²

I(x，y，l _i)＝a ²+b ²+2ab?cos?2k[ω(x，y)-l _t]

＝(a ²+b ²){1+r?cos?2k[w(x，y)-l _t]} (1)

In the formula,

is the contrast of interference fringe.

Following formula explanation, in the interference field arbitrarily the light intensity of any all be l _tCosine function because l _tChange in time; Therefore following formula has the time cycle function property; This just can use Communication Theory is extracted signal from the information that has noise correlation detection technology or Synchronous Detection, so that from the interference fringe of band noise, extract needed corrugated phase information.

When if interference fringe photoelectricity receives, because vibration, air turbulence, the influences such as noise of light source and photo-translating system make not only to comprise seized phase information in the signal, but also include noise item n (t).If cosine signal and seized signal with a same carrier frequencies carry out related operation.Then

$<I_1>=\underset{T\&RightArrow;\&infin;}{\lim }\frac{1}{T}{\&Integral;}_o^T[I(x,y,l_t)+n\left(t\right)]\cos 2k{l}_t$

(1) formula substitution following formula, and establish n (t) for random noise, then its correlation product another arena does

<I ₁>＝r?cos?2kw(x，y) (2)

So related function<i ₁>Reflected wavefront w (x, size y), for can obtain w (x, y), with seized signal simultaneously and sin 2kl _tRelevant, in like manner can obtain

<I ₂>＝r?sin?2kw(x，y) (3)

By (2), (3) two formulas can obtain needed corrugated phase information and do

$w(x,y)=\frac{1}{2k}{\tan }^{-1}\frac{<I_2>}{<I_1>}$

Wherein $k=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}.$

To reach the result identical in order utilizing to interfere to detect, to be launched into (1) formula the form of Fourier series with above-mentioned correlation detection technology:

I(x，y?，l _t)＝a ₀+a ₁?cos?2kl _t+b ₁?sin?2kl _t

A in the formula ₀=a ²+ b ², a ₁=2ab cos 2kw (x, y), b ₁=2ab sin 2kw (x, y) (4)

To a plurality of data point samplings in the interference field, make 1 to make discrete stepped for ease.Because 1 every variation λ/2, the bright dark variation one-period of striped, the stepped change number of establishing one-period interior 1 is n, and promptly 1 changes a fringe period to each sampled point sampling n time, and its sampled value does

I(x，y，l _i)＝a ₀+a ₁?cos?2kl _i+b ₁?sin?2kl _i

$l_i=\frac{\mathrm{\&lambda;}}{2n}\&CenterDot;i,i=\mathrm{0,1,2,3}\mathrm{LLn}-1$

According to the orthogonality of trigonometric function relation, can obtain each coefficient of Fourier series, promptly

$a_0=\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}I(x,y,l_i)$

$a_1=\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}I(x,y,l_i)\cos 2k{l}_i---\left(5\right)$

$b_1=\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}I(x,y,l_i)\sin 2k{l}_i$

The Fourier series expression formula that formula (4) and formula (5) provide is to the best-fit of interference field brightness period of change function on least squares sense.Therefore the position of the last sampled point of interference field can be provided by the ratio of two weighted mean values mutually:

$w(x,y)=\frac{1}{2k}{\tan }^{-1}\frac{b_1}{a_1}=\frac{1}{2k}{\tan }^{-1}\frac{\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}I(x,y,l_i)\sin 2k{l}_i}{\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}I(x,y,l_i)\cos 2k{l}_i}$

For further reducing noise effect, improve measuring accuracy, can further do progressive mean, promptly to the measurement data in P cycle $w(x,y)=\frac{1}{2k}{\mathrm{Tan}}^{-1}\frac{\frac{2}{n}\underset{i=1}{\overset{n\&CenterDot;p}{\mathrm{\&Sigma;}}}I(x,y,l_i)\mathrm{Sin}2k{l}_i}{\frac{2}{n}\underset{i=1}{\overset{n\&CenterDot;p}{\mathrm{\&Sigma;}}}I(x,y,l_i)\mathrm{Cos}2k{l}_i}$

Therefore, in the aperture arbitrarily the position of any can try to achieve by n * p luminosity sampling value calculating this aspect on mutually, calculate the position phase of each point on the aperture one by one, just can obtain whole seized phase or face shape.And since cancellation the dc terms in the interference light intensity, so the dc shift that the light intensity disturbance produces also has been eliminated.

Adopt four step algorithms calculate w (x, y), can be so that the measuring accuracy of movable phase interfere technology reaches one of percentage wavelength, i.e. nanometer scale.Specifically

Can make 2kl _i=0, pi/2, π, 3 pi/2s, i=1,2,3,4

Then $\mathrm{\&omega;}(x,y)=\frac{1}{2k}\mathrm{Arctan}\frac{I_4-I_2}{I_1-I_3}---\left(6\right)$

By ω (x, y) distribution curve we can obtain the tilt quantity on two planes in the visual field

Δω＝ω _max-ω _min

The depth of parallelism

wherein, D is the interference field bore.The unit of the depth of parallelism is radian (rad).

And then, adopt the four step methods of average can reduce the phase calculation error that the phase-shifted error causes in the movable phase interfere, concrete grammar is following:

In (6) formula, get 2kl _i=0, pi/2, π, 3 pi/2s, 2 π make 0, pi/2, π, 3 pi/2s are measured combination as one, miss an interferogram after, get pi/2, π, 3 pi/2s, 2 π measure combination as one, wherein, 0, pi/2, π, 3 pi/2s, 2 π are corresponding i=1 respectively, 2,3,4,5.Obtain ω respectively in being based on four step phase-shifting methods ₁And ω ₂, average these two results at last, promptly

$\mathrm{\&omega;}(x,y)=\frac{1}{2}\left\{\frac{1}{2k}\right[\arctan \frac{I_4-I_2}{I_1-I_3}+\arctan \frac{I_5-I_3}{I_2-I_4}\left]\right\}---\left(7\right)$

At present, also have no talent the movable phase interfere technology of top detailed description, and data processing methods such as corresponding four step algorithms, the four step methods of average, specifically be applied in the aspect that the plane high precision depth of parallelism detects.

Summary of the invention

Not high in order to solve existing plane parallel degree pick-up unit measuring accuracy; Can't be useful in the technical matters that the plane high precision depth of parallelism detects; A kind of laser plane interfere measurement technique and movable phase interfere technology of having combined is proposed, the pick-up unit of the plane high precision depth of parallelism.

The technical scheme that technical solution problem of the present invention is adopted is following:

The pick-up unit of a kind of plane high precision depth of parallelism comprises:

The plane interference measurement mechanism, it can carry out the laser plane interferometry to the depth of parallelism between first to be measured and second to be measured;

Phase shifting equipment, it can move on optical path direction said second to be measured;

Said first to be measured is to be measured of half-reflection and half-transmission, and said second to be measured is to be measured of total reflection, and on light path, said first face to be measured was positioned at before said second to be measured.

In technique scheme, said plane interference measurement mechanism is the plane fizeau interferometer.

In technique scheme, said phase shifting equipment comprises:

The PZT piezoelectric ceramics, it links to each other with said second to be measured, is used for adjusting said second to be measured position on light path;

Driving circuit, it is used for controlling the work of said PZT piezoelectric ceramics;

Control circuit, it is used for controlling the work of said driving circuit;

Testing circuit, it is used for detecting the position of said PZT piezoelectric ceramics;

Power circuit, it is used for to driving circuit, control circuit, testing circuit is supplied power.

In technique scheme, also comprise the information acquisition treating apparatus in the said pick-up unit, it comprises:

Detector, it is used for receiving the interference information that the laser plane interferometry obtains;

Information acquisition card, it is used for gathering the information that said detector detects;

PC, it is used for the information that the process information capture card collects.

The invention has the beneficial effects as follows:

The pick-up unit of the plane of the present invention high precision depth of parallelism utilizes the laser plane interfere measurement technique is combined with the movable phase interfere technology, significantly improves the degree of accuracy of laser plane interfere measurement technique, thereby can detect the plane high precision depth of parallelism.

Description of drawings

Fig. 1 is a kind of light path principle synoptic diagram of embodiment of the pick-up unit of the plane of the present invention high precision depth of parallelism.

Reference numeral among the figure is expressed as:

1. laser instrument; 2. beam-expanding collimation device; 3. the polarizer; 4. beam splitter; 5.1/4 wave plate; 6-7. to be measured; 8.PZT; 9.CCD.

Embodiment

Below in conjunction with accompanying drawing the present invention is done and to describe in further detail.

As shown in Figure 1, in the pick-up unit of the plane of the present invention high precision depth of parallelism, comprise plane interference measurement mechanism and phase shifting equipment.On optical path direction, be respectively equipped with: be used to provide the laser instrument 1 of coherent source, beam-expanding collimation device 2, the polarizer 3, beam splitter 4, quarter wave plate 5, to be measured 6 with to be measured 7, and with said to be measured 7 phase shifting equipment that is connected.Said to be measured 6 is to be measured of half-reflection and half-transmission, and said to be measured 7 is to be measured of total reflection.Light will produce reference beam respectively and detect light beam, and can return through original optical path after reflecting through to be measured 6 and to be measured 7, reflex among the CCD9 through beam splitter 4 and gather, and realize interference.The polarizer 3 wherein and the effect of quarter wave plate 5 are to be used for the interference of inhibitory reflex light to laser.

Above-mentioned by laser instrument 1, beam-expanding collimation device 2, beam splitter 4, to be measured 6 with to be measured 7, and the measurement mechanism formed of CCD9 is the plane fizeau interferometer.

Said phase shifting equipment comprises: PZT piezoelectric ceramics 8, driving circuit, control circuit, testing circuit and power circuit.The PZT piezoelectric ceramics 8 that links to each other with said second to be measured is to be used for adjusting to be measured 7 position on light path; Driving circuit is the work that is used for controlling said PZT piezoelectric ceramics 8; Control circuit is the work that is used for controlling said driving circuit; Testing circuit is the position that is used for detecting said PZT piezoelectric ceramics 8; And power circuit is to be used for to driving circuit, control circuit, and testing circuit is supplied power.

Go back the information acquisition treating apparatus in the pick-up unit of the plane of the present invention high precision depth of parallelism, it comprises: detector, information acquisition card, and PC.Detector is to be used for receiving the interference information that the laser plane interferometry obtains; Information acquisition card is used for gathering the information that said detector detects; PC is used for the information that the process information capture card collects.

The principle of work of pick-up unit of the present invention is: laser instrument 1 emission light beam is through beam-expanding collimation device 2 collimator and extenders; Through the polarizer 3; Incide on the beam splitter 4; Behind the quarter wave plate 5 through beam splitter 4 back, incide to be measured 6 with to be measured 7 on (to be measured 6 be respectively half-reflection and half-transmission and be all-trans parallel flat with to be measured 7).Carry out phase shift through phase shifting equipment to be measured 7 then and handle, make to be measured the 7 position change amount mutually on optical path direction be respectively 0, pi/2, π, 3 pi/2s, 2 π.Detect the interferogram of above-mentioned 5 positions respectively.Adopt the four step methods of average that detected data are handled then, obtain the information of the depth of parallelism between to be measured 6 and to be measured 7, the measuring accuracy of the depth of parallelism can reach microradian (microradian, magnitude mrad).

The driving frequency of PZT8 in the said phase shifting equipment and CCD9 sampling are complementary, and satisfy the requirement of phase shift measurement and four step average data disposal routes.Interference image is gathered by CCD9.The information acquisition treating apparatus is through detector, surveys from CCD9 and obtains interference information, collect in the information acquisition card then, and then the information that collects by PC process information capture card, and export the result.

Obviously, the foregoing description only be for explanation clearly done for example, and be not qualification to embodiment.For the those of ordinary skill in affiliated field, can also make other multi-form variation or change on the basis of the above description.Here need not also can't give exhaustive to all embodiments.And conspicuous variation of being extended out thus or change still are among the protection domain of the invention.

Claims (4)

1. the pick-up unit of a plane high precision depth of parallelism is characterized in that, comprising:

The plane interference measurement mechanism, it can carry out the laser plane interferometry to the depth of parallelism between first to be measured and second to be measured;

Phase shifting equipment, it can move on optical path direction said second to be measured;

Said first to be measured is to be measured of half-reflection and half-transmission, and said second to be measured is to be measured of total reflection, and on light path, said first face to be measured was positioned at before said second to be measured.

2. pick-up unit as claimed in claim 1 is characterized in that, said plane interference measurement mechanism is the plane fizeau interferometer.

3. pick-up unit as claimed in claim 1 is characterized in that, said phase shifting equipment comprises:

The PZT piezoelectric ceramics, it links to each other with said second to be measured, is used for adjusting said second to be measured position on light path;

Driving circuit, it is used for controlling the work of said PZT piezoelectric ceramics;

Control circuit, it is used for controlling the work of said driving circuit;

Testing circuit, it is used for detecting the position of said PZT piezoelectric ceramics;

Power circuit, it is used for to driving circuit, control circuit, testing circuit is supplied power.

4. like the arbitrary described pick-up unit of claim 1-3, it is characterized in that also comprise the information acquisition treating apparatus in the said pick-up unit, it comprises:

Detector, it is used for receiving the interference information that the laser plane interferometry obtains;

Information acquisition card, it is used for gathering the information that said detector detects;

PC, it is used for the information that the process information capture card collects.