CN103267494B - A kind of method of surface appearance interference measurement and device - Google Patents

Abstract

The present invention relates to measuring surface form field, disclose a kind of method and device of the surface appearance interference measurement combined with phase-shifted sweep based on multi-wavelength rotation.Method of the present invention comprises the following steps: 1: start light source; 2: carry out image acquisition; 3: toggle lights; 4: judge that light source switches and whether complete, if not, then perform step 2; If so, then change the position of reference mirror, and gather the interference signal of different wave length laser under different reference mirror positions; 5: judge whether collection completes, if not, then perform step 1; If so, then picture signal process, the calculating of sample topography parameter and display is carried out.The inventive system comprises: light source cell, interference micrometering unit, image acquisition units, multi-wavelength switch unit, piezoelectric ceramics PZT driver element, image procossing and control module; The present invention takes full advantage of the advantage of length scanning and phase-shifted sweep two kinds of measuring methods, achieves the high precision absolute measurement of surface topography.

Description

A kind of method of surface appearance interference measurement and device

Technical field

The present invention relates to measuring surface form field, disclose a kind of method and device of the surface appearance interference measurement combined with phase-shifted sweep based on multi-wavelength rotation.

Background technology

Measuring surface form has extremely important effect in ultraprecise detects, particularly in semiconductor industry, and optical device manufacture field.Current ultra-precision surface measuring method mainly divides non-optical measurement and optical measurement two kinds, and wherein non-optical measuring method mainly comprises: contact pilotage technology of profiling, scanning electron microscopy (SEM), Scanning Probe Microscopy (SPM) etc.; Optical interferometry method mainly comprises: white light phase shift interference, multi-wavelength interference and length scanning etc.

In non-optical measuring method, contact pilotage technology of profiling is a kind of contact measurement method, and probably scratch surface of the work when measuring optical surface, contact pilotage technology of profiling is a kind of point-to-point measurement method, and measuring period is long, and efficiency is low; SEM measuring method Sample Preparation Procedure is complicated, measures sample type also limited, and can not provide real three-dimensional data; SPM measuring method is also that areas imaging is in micron order based on the point by point scanning to measured surface, and efficiency is low.

Measuring method has noncontact, and operating process is simple, and measuring speed is fast, precision advantages of higher.White light phase shift interference technology is driven by phase shift, finds the zero optical path difference position of measured point one by one, and therefore, white light micro-interference measurement range determines by the driving scope of vertical scanning platform.Dual wavelength or multi-wavelength measuring method utilize the difference of dual wavelength and multi-wavelength measurement result to obtain order of interference, thus obtain the real depth of measured point, do not need wavelength to switch, but interference pattern fineness is low, the monochromatic light light intensity of wave plate is too weak after filtration, and interference pattern signal to noise ratio (S/N ratio) is low.Based on the optical interferometry technology of length scanning, it is the frequency shift wavelength by constantly changing radio driver, cause changing relative phase difference when absolute light path difference is constant, do not need corresponding drive unit, but the short transverse of surface topography cannot be judged, because wavelength scanning range and resolution affect, identification range is difficult to improve.

Summary of the invention

The invention provides a kind of method and device of the surface appearance interference measurement combined with phase-shifted sweep based on multi-wavelength rotation, take full advantage of the advantage of length scanning and phase-shifted sweep two kinds of measuring methods, achieve the high precision absolute measurement of surface topography.The present invention can carry out nano level interferometry to object surface appearance, and measurement range is tens microns.

The technical solution used in the present invention is:

A method for surface appearance interference measurement, is characterized in that, comprises the following steps:

Step 1: start light source;

Step 2: carry out image acquisition;

Step 3: toggle lights;

Step 4: judge that light source switches and whether complete, if not, then perform described step 2; If so, then change the position of reference mirror, and gather the interference signal of different wave length laser under different reference mirror positions;

Step 5: judge whether collection completes, and if not, then performs described step 1; If so, then picture signal process, the calculating of sample topography parameter and display is carried out.

As preferably, described picture signal process, respectively pointwise phase bit arithmetic is frame by frame carried out to the interference two field picture of the interference signal of described different wave length laser, the phase differential of application two nearly wavelength is established surface topography and is estimated pattern point height relative within the scope of the direction of virtual reference plane and large scale within the scope of large scale, by the error of two wavelength phase difference far away further contract measurement result in small scale, finally in conjunction with Single wavelength phase calculation final measurement.

As preferably, the Single wavelength interference signal of described different wave length laser certain any light intensity in interference region is:

$I(\mathrm{\δ},\mathrm{\λ})=I_1+I_2+2\sqrt{I_1{I}_2}\cos \left(\frac{2\mathrm{\π\δ}}{\mathrm{\λ}}\right),$

Described Single wavelength phase place is:

Wherein, δ is optical path difference, and λ is coherent light wavelength, I ₁, I ₂be the light intensity of two coherent lights at this point;

Due to described phase place identification can only between (-π, π), therefore for Single wavelength, determine that the scope of described measuring surface form height h can only within half wavelength, that is:

The dual-wavelength measurement of two described different wave lengths, under same optical path difference, its phase differential meets:

Wherein, be the phase place of two different wave length laser, λ _i, λ _jbe the wavelength of two different wave length laser, i=1,2,3, j=1,2,3;

Visible, wavelength difference is less, and phase differential becomes less with optical path difference change, thus between the optical path difference cog region determining described dual wavelength is:

$-\mathrm{\&pi;}<{\mathrm{\&phi;}}_{\mathrm{ij}}=\frac{2\mathrm{\&pi;\&delta;}({\mathrm{\&lambda;}}_j-{\mathrm{\&lambda;}}_i)}{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_j}<\mathrm{\&pi;},$

Described dual-wavelength measurement scope is:

$-\frac{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_i}{4({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_j)}<h=\frac{\mathrm{\&delta;}}{2}<\frac{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_i}{4({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_j)},$

From the measurement range of described dual wavelength, λ _i-λ _jless, measurement range enlarges markedly.

Technical scheme of the present invention also comprises a kind of device of surface appearance interference measurement, it is characterized in that, comprising: light source cell, interference micrometering unit, image acquisition units, multi-wavelength switch unit, piezoelectric ceramics PZT driver element, image procossing and control module;

Described light source cell is for generation of the same light path laser without wavelength;

Described interference micrometering unit is for generation of interference image;

Described image acquisition units is used for carrying out image acquisition;

Described multi-wavelength switch unit is used for toggle lights;

Described piezoelectric ceramics PZT driver element for driving piezoelectric ceramic actuator, thus changes the position of reference mirror;

Described image procossing and control module are used for picture signal process, sample topography parameter calculates and shows.

As preferably, described light source cell also comprises: the first light source, secondary light source, the 3rd light source, fiber coupler;

Described interference micrometering unit also comprises: optical fiber, laser collimation system, Amici prism, the first object lens, reference mirror, piezoelectric ceramics PZT driver, as mirror, the second object lens;

Described image acquisition units is also comprising: high-speed CCD, image pick-up card;

Described multi-wavelength switch unit also comprises: I/O switches delivery outlet, light source constant current source driving circuit;

Described piezoelectric ceramics PZT driver element also comprises: D/A change-over circuit, PZT driving circuit;

Described image procossing and control module also comprise: computing machine, FPGA circuit;

The first described light source, secondary light source, the 3rd light source are the semiconductor laser of three different wave lengths;

The laser beam of three kinds of different wave lengths that described light source cell exports enters described optical fiber same light path transmission after described fiber coupler, export through described laser collimation system collimation again, two bundles are divided into through described Amici prism, light beam is through the first described object lens and described reference mirror, described reference mirror is mounted on described piezoelectric ceramics PZT driver, another bundle is through the second described object lens and testee, two-beam eventually passes through described interfering as mirror, and this interference signal is received by described high-speed CCD;

Described image pick-up card input end is connected with described high-speed CCD, output terminal is connected with described computing machine, and described image pick-up card comprises A/D conversion and multi-channel data acquisition function;

The image that described image procossing and control module gather for the treatment of described image pick-up card with control described in multi-wavelength switch unit and piezoelectric ceramics PZT driver element; Described fanout is connected with the input end of described FPGA circuit and described D/A change-over circuit respectively, and described FPGA circuit output end switches delivery outlet with described I/O respectively and described image pick-up card input end is connected;

Described I/O switches delivery outlet by described FPGA control circui, the light source constant current source driving circuit described in the access of its output terminal, and described light source constant current source driving circuit is for controlling the first described light source, secondary light source, the 3rd light source;

The described computing machine described in the access of D/A change-over circuit input end, the PZT driving circuit described in output terminal access, the described piezoelectric ceramics PZT driver described in the access of PZT driving circuit output terminal.

As preferably, the first described light source, secondary light source, the 3rd light source are semiconductor laser.

As preferably, described computing machine is connected with described FPGA circuit by USB interface, and described FPGA circuit switches delivery outlet and image pick-up card for controlling described I/O.

The high precision absolute measurement of surface topography of algorithm realization that this large small scale provided by the invention combines, breach the bottleneck that Single wavelength cannot surmount half-wavelength measurement range on the one hand, both remain the precision that Single wavelength is measured, also widen overall measurement range; On the other hand, high to the accuracy requirement under often kind of yardstick, for strong noise or on-line measurement have prepared condition, the in-site measurement level of significant increase instrument and practical value.

Accompanying drawing explanation

Fig. 1: be the method flow diagram of surface appearance interference measurement of the present invention.

Fig. 2: be the system architecture schematic diagram of the device of surface appearance interference measurement of the present invention.

Fig. 3: for removing the graph of relation of the relative height of its light intensity gray scale and surface topography after DC component in the embodiment of the present invention.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with the drawings and specific embodiments, the structure of device of the present invention and measuring principle are described in further detail.

The invention provides a kind of surface appearance interference measurement method of combining with phase-shifted sweep based on multi-wavelength rotation and measurement mechanism, take full advantage of the advantage of length scanning and phase-shifted sweep two kinds of measuring methods, achieve the high precision absolute measurement of surface topography.The present invention can carry out nano level interferometry to object surface appearance, and measurement range is tens microns.

Ask for an interview Fig. 1, a kind of method of surface appearance interference measurement, comprises the following steps:

Step 1: start light source;

Step 2: carry out image acquisition;

Step 3: toggle lights;

Step 4: judge that light source switches and whether complete, if not, then perform step 2; If so, then change the position of reference mirror, and gather the interference signal of different wave length laser under different reference mirror positions;

Step 5: judge whether collection completes, if not, then performs step 1; If so, then picture signal process, the calculating of sample topography parameter and display is carried out.

Picture signal process, respectively pointwise phase bit arithmetic is frame by frame carried out to the interference two field picture of the interference signal of different wave length laser, the phase differential of application two nearly wavelength is established surface topography and is estimated pattern point height relative within the scope of the direction of virtual reference plane and large scale within the scope of large scale, by the error of two wavelength phase difference far away further contract measurement result in small scale, finally in conjunction with Single wavelength phase calculation final measurement.

The Single wavelength interference signal of different wave length laser certain any light intensity in interference region is:

$I(\mathrm{\&delta;},\mathrm{\&lambda;})=I_1+I_2+2\sqrt{I_1{I}_2}\cos \left(\frac{2\mathrm{\&pi;\&delta;}}{\mathrm{\&lambda;}}\right),$

Single wavelength phase place is:

Wherein, δ is optical path difference, and λ is coherent light wavelength, I ₁, I ₂be the light intensity of two coherent lights at this point;

Due to phase place identification can only between (-π, π), therefore for Single wavelength, determine that the scope of described measuring surface form height h can only within half wavelength, that is:

The dual-wavelength measurement of two different wave lengths, under same optical path difference, its phase differential meets:

Wherein, be the phase place of two different wave length laser, λ _i, λ _jbe the wavelength of two different wave length laser, i=1,2,3, j=1,2,3;

Visible, wavelength difference is less, and phase differential becomes less with optical path difference change, thus between the optical path difference cog region determining dual wavelength is:

$-\mathrm{\&pi;}<{\mathrm{\&phi;}}_{\mathrm{ij}}=\frac{2\mathrm{\&pi;\&delta;}({\mathrm{\&lambda;}}_j-{\mathrm{\&lambda;}}_i)}{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_j}<\mathrm{\&pi;},$

Dual-wavelength measurement scope is:

$-\frac{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_i}{4({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_j)}<h=\frac{\mathrm{\&delta;}}{2}<\frac{{\mathrm{\&lambda;}}_i{\mathrm{\&lambda;}}_i}{4({\mathrm{\&lambda;}}_i-{\mathrm{\&lambda;}}_j)},$

From the measurement range of dual wavelength, λ _i-λ _jless, measurement range enlarges markedly.

Present invention employs there is narrow band bandwidth cosine and sinusoidal operator to the smoothing filtering of data and differential convolution algorithm, and combine least square fitting algorithm high precision identification carried out to difference.

The present invention have chosen wavelength 650nm, 635nm, 550nm tri-kinds of semiconductor laser wavelengths, ask for an interview Fig. 3, for removing the relation curve of the relative height of its light intensity gray scale and surface topography after DC component, the difference symbol of three kinds of wavelength is symmetrical about y-axis, and this is establish surface topography to lay a good foundation relative to the direction of virtual reference plane.

For each wavelength, each pixel corresponding obtains one group of data, and therefore for three wavelength, a pixel can obtain three groups of light intensity datas, and wherein Single wavelength interference signal certain any light intensity in interference region is:

$I(\mathrm{\&delta;}+\mathrm{k\&Delta;},{\mathrm{\&lambda;}}_i)=I_1+I_2+2\sqrt{I_1{I}_2}\cos \left(\frac{2\mathrm{\&pi;}(\mathrm{\&delta;}+\mathrm{k\&Delta;})}{{\mathrm{\&lambda;}}_i}\right),$

Wherein δ is optical path difference, and △ is PZT step-length, k=0,1 ..., m-1, m for drive step number, λ _i, i=1,2,3, corresponding different wave length, I ₁, I ₂for two coherent lights of this wavelength are in the light intensity of this point;

Cosine and the sinusoidal operator of application narrow band bandwidth process often organizing the smoothing filtering of light intensity data and differentiating, and result is respectively c (k, λ _i) and s (k, λ _i), following formula can be drawn by convolution theory:

$\left\{\begin{array}{c}{x}_{\mathrm{ik}}=c(k,{\mathrm{\&lambda;}}_i)=A_i\cos \left(\frac{2\mathrm{\&pi;}(\mathrm{\&delta;}+\mathrm{k\&Delta;})}{{\mathrm{\&lambda;}}_i}\right)\\ y_{\mathrm{ik}}=s(k,{\mathrm{\&lambda;}}_i)=B_i\cos (\frac{2\mathrm{\&pi;}(\mathrm{\&delta;}+\mathrm{k\&Delta;})}{{\mathrm{\&lambda;}}_i}+\frac{\mathrm{\&pi;}}{2})\end{array}\right.,$

Wherein A _i, B _ifor the signal amplitude after convolution, x _ikthe result after light intensity data and cosine operator convolution algorithm, y _ikit is the result after light intensity data and sinusoidal operator convolution algorithm;

According to the coordinate figure of each pixel collected, the known phase place of further ellipse fitting meets following formula:

Wherein n _ifor integer undetermined;

Relatively λ ₁, λ ₂for nearly wavelength, λ ₃for wavelength far away, so n in measurement range ₁=n ₂, phase differential meets following relation:

Obtained phase differential can be obtained the optical path difference of surface topography by least square fitting:

$\mathrm{\&delta;}=\frac{1}{m}(\underset{k=0}{\overset{m-1}{\mathrm{\&Sigma;}}}\frac{{\mathrm{\&lambda;}}_1{\mathrm{\&lambda;}}_2{\mathrm{\&phi;}}_{12k}}{2\mathrm{\&pi;}({\mathrm{\&lambda;}}_2-{\mathrm{\&lambda;}}_1)}-\frac{m(m-1)}{2}\mathrm{\&Delta;}).$

Because the optical path difference range scale now calculated is large, error is also larger.Utilize the phase differential between wavelength far away to carry out correcting and refinement calculating: the result of calculation δ of optical path difference, deducts λ for this reason ₁λ ₃/ (λ ₃-λ ₁) m ₁after integral multiple light path, between the correction zone determining the phase differential between wavelength far away, with this Scaling interval for reference, adopt and use the same method, computation interval optical path difference δ _district; The method utilizing Single wavelength to correct is: interval optical path difference δ _districtdeduct λ ₁m ₂direct application of formula after integral multiple optical path difference least square fitting obtains the optical path difference δ that Single wavelength phase place obtains _single; Last overall light path difference result of calculation is:

The device of a kind of surface appearance interference measurement of the present invention, comprising: light source cell, interference micrometering unit, image acquisition units, multi-wavelength switch unit, piezoelectric ceramics PZT driver element, image procossing and control module; Described light source cell is for generation of the same light path laser without wavelength; Described interference micrometering unit is for generation of interference image; Described image acquisition units is used for carrying out image acquisition; Described multi-wavelength switch unit is used for toggle lights; Described piezoelectric ceramics PZT driver element for driving piezoelectric ceramic actuator, thus changes the position of reference mirror; Described image procossing and control module are used for picture signal process, sample topography parameter calculates and shows.Light source cell also comprises: the first light source 1, secondary light source 2, the 3rd light source 3, fiber coupler 4; Micrometering unit is interfered also to comprise: optical fiber 5, laser collimation system 6, Amici prism 7, first object lens 8, reference mirror 9, piezoelectric ceramics PZT driver 10, as mirror 12, second object lens 13; Image acquisition units is also comprising: high-speed CCD 11, image pick-up card 15; Multi-wavelength switch unit also comprises: I/O switches delivery outlet 17, light source constant current source driving circuit 16; Piezoelectric ceramics PZT driver element also comprises: D/A change-over circuit 19, PZT driving circuit 18; Image procossing and control module also comprise: computing machine 20, FPGA circuit 21; First light source 1, secondary light source 2, the 3rd light source 3 are the semiconductor laser of three different wave lengths.

Light source cell export three kinds of different wave lengths laser beam through fiber coupler 4 laggard enter optical fiber 5 same light path transmission, collimate through laser collimation system 6 again and export, two bundles are divided into through Amici prism 7, light beam is through the first object lens 8 and reference mirror 9, reference mirror 9 is mounted on piezoelectric ceramics PZT driver 10, another bundle is through the second object lens 13 and testee 14, and two-beam eventually passes through and interferes as mirror 12, and this interference signal is received by high-speed CCD 11; Image pick-up card 15 input end is connected with high-speed CCD 11, output terminal is connected with computing machine 20, and image pick-up card 15 comprises A/D conversion and multi-channel data acquisition function; The image that image procossing and control module gather for the treatment of image pick-up card 15 with control multi-wavelength switch unit and piezoelectric ceramics PZT driver element; Computing machine 20 output terminal is connected with the input end of FPGA circuit 21 and D/A change-over circuit 19 respectively, and FPGA circuit 21 output terminal switches delivery outlet 17 with I/O respectively and image pick-up card 15 input end is connected; I/O switches delivery outlet 17 and is controlled by FPGA circuit 21, its output terminal access light source constant current source driving circuit 16, and light source constant current source driving circuit 16 is for controlling the first light source 1, secondary light source 2, the 3rd light source 3; D/A change-over circuit 19 input end access computing machine 20, output terminal access PZT driving circuit 18, PZT driving circuit 18 output terminal access piezoelectric ceramics PZT driver 10.

First light source 1, secondary light source 2, the 3rd light source 3 are semiconductor laser.Computing machine 20 is connected with FPGA circuit 21 by USB interface, and FPGA circuit 21 switches delivery outlet 17 and image pick-up card 15 for controlling described I/O.

The high precision absolute measurement of surface topography of algorithm realization that this large small scale provided by the invention combines, breach the bottleneck that Single wavelength cannot surmount half-wavelength measurement range on the one hand, both remain the precision that Single wavelength is measured, also widen overall measurement range; On the other hand, high to the accuracy requirement under often kind of yardstick, for strong noise or on-line measurement have prepared condition, the in-site measurement level of significant increase instrument and practical value.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Claims (5)

1. a device for surface appearance interference measurement, is characterized in that, comprising: light source cell, interference micrometering unit, image acquisition units, multi-wavelength switch unit, piezoelectric ceramics PZT driver element, image procossing and control module;

Described light source cell is for generation of the same light path laser without wavelength;

Described interference micrometering unit is for generation of interference image;

Described image acquisition units is used for carrying out image acquisition;

Described multi-wavelength switch unit is used for toggle lights;

Described piezoelectric ceramics PZT driver element for driving piezoelectric ceramic actuator, thus changes the position of reference mirror;

Described image procossing and control module are used for picture signal process, sample topography parameter calculates and shows;

Described light source cell also comprises: the first light source (1), secondary light source (2), the 3rd light source (3), fiber coupler (4);

Described interference micrometering unit also comprises: optical fiber (5), laser collimation system (6), Amici prism (7), the first object lens (8), reference mirror (9), piezoelectric ceramics PZT driver (10), as mirror (12), the second object lens (13);

Described image acquisition units also comprises: high-speed CCD (11), image pick-up card (15);

Described multi-wavelength switch unit also comprises: I/O switches delivery outlet (17), light source constant current source driving circuit (16);

Described piezoelectric ceramics PZT driver element also comprises: D/A change-over circuit (19), PZT driving circuit (18);

Described image procossing and control module also comprise: computing machine (20), FPGA circuit (21);

Described the first light source (1), secondary light source (2), the 3rd light source (3) are the semiconductor laser of three different wave lengths;

The laser beam of three kinds of different wave lengths that described light source cell exports enters described optical fiber (5) same light path transmission after described fiber coupler (4), export through described laser collimation system (6) collimation again, two bundles are divided into through described Amici prism (7), light beam is through described the first object lens (8) and described reference mirror (9), described reference mirror (9) is mounted on described piezoelectric ceramics PZT driver (10), another bundle is through described the second object lens (13) and testee (14), two-beam eventually passes through described picture mirror (12) and interferes, this interference signal is received by described high-speed CCD (11),

Described image pick-up card (15) input end is connected with described high-speed CCD (11), output terminal is connected with described computing machine (20), and described image pick-up card (15) comprises A/D conversion and multi-channel data acquisition function;

The image that described image procossing and control module gather for the treatment of described image pick-up card (15) with control described in multi-wavelength switch unit and piezoelectric ceramics PZT driver element; Described computing machine (20) output terminal is connected with the input end of described FPGA circuit (21) and described D/A change-over circuit (19) respectively, and described FPGA circuit (21) output terminal switches delivery outlet (17) with described I/O respectively and described image pick-up card (15) input end is connected;

Described I/O switches delivery outlet (17) and is controlled by described FPGA circuit (21), light source constant current source driving circuit (16) described in the access of its output terminal, described light source constant current source driving circuit (16) is for controlling described the first light source (1), secondary light source (2), the 3rd light source (3);

The described computing machine (20) described in the access of D/A change-over circuit (19) input end, PZT driving circuit (18) described in output terminal access, the described piezoelectric ceramics PZT driver (10) described in the access of PZT driving circuit (18) output terminal.

2. the device of surface appearance interference measurement according to claim 1, is characterized in that: described the first light source (1), secondary light source (2), the 3rd light source (3) are semiconductor laser.

3. the device of surface appearance interference measurement according to claim 1, it is characterized in that: described computing machine (20) is connected with described FPGA circuit (21) by USB interface, described FPGA circuit (21) switches delivery outlet (17) and image pick-up card (15) for controlling described I/O.

4. utilize the device of the surface appearance interference measurement described in claim 1 to carry out a method for surface appearance interference measurement, it is characterized in that, comprise the following steps:

Step 1: start light source;

Step 2: carry out image acquisition;

Step 3: toggle lights;

Step 4: judge that light source switches and whether complete, if not, then perform described step 2; If so, then change the position of reference mirror, and gather the interference signal of different wave length laser under different reference mirror positions;

Step 5: judge whether collection completes, and if not, then performs described step 1; If so, then picture signal process, the calculating of sample topography parameter and display is carried out;

Described picture signal process, respectively pointwise phase bit arithmetic is frame by frame carried out to the interference two field picture of the interference signal of described different wave length laser, the phase differential of application two nearly wavelength is established surface topography and is estimated pattern point height relative within the scope of the direction of virtual reference plane and large scale within the scope of large scale, by the error of two wavelength phase difference far away further contract measurement result in small scale, finally in conjunction with Single wavelength phase calculation final measurement.

5. method according to claim 4, is characterized in that:

The Single wavelength interference signal of described different wave length laser certain any light intensity in interference region is:

Described Single wavelength phase place is:

Wherein, δ is optical path difference, and λ is coherent light wavelength, I ₁, I ₂be the light intensity of two coherent lights at this point;

Due to described phase place identification can only between (-π, π), therefore for Single wavelength, determine that the scope of described measuring surface form height h can only within half wavelength, that is:

The dual-wavelength measurement of two different wave lengths, under same optical path difference, its phase differential meets:

Wherein, be the phase place of two different wave length laser, λ _i, λ _jbe the wavelength of two different wave length laser, i=1,2,3, j=1,2,3;

Visible, wavelength difference is less, and phase differential becomes less with optical path difference change, thus between the optical path difference cog region determining described dual wavelength is:

Described dual-wavelength measurement scope is:

From the measurement range of described dual wavelength, λ _i-λ _jless, measurement range enlarges markedly.