CN106092514A - Optical heterogeneity measurement apparatus and method based on dual wavelength fizeau interferometer - Google Patents

Abstract

The invention discloses a kind of optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer and method, by in dual wavelength Fizeau interference instrument apparatus, successively gather the interference pattern of reference light wave and the reflecting light of level crossing front surface to be measured, obtain wavelength X by first step phase shift measurement₁And λ₂Corresponding wavefront aberration data Δ W₁₁(x, y), Δ W₂₁(x, y)；Gather the interference pattern of reference light wave and the light wave through level crossing to be measured and by level crossing rear surface to be measured reflection, obtain wavelength X by phase shift measurement₁And λ₂Corresponding wavefront aberration data Δ W₁₂(x, y), Δ W₂₂(x, y).Seek difference by the corresponding wavelength wavefront aberration data that two pacings measure, it is thus achieved that level crossing optical heterogeneity to be measured.The present invention does not needs to introduce standard reflection mirror, completely eliminates the impact on measurement result of the face shape of standard reflection mirror, and measuring process is simple, compensate for tradition absolute method of measurement complex steps, easily by the shortcoming of air agitation.

Description

Optical heterogeneity measurement apparatus and method based on dual wavelength fizeau interferometer

Technical field

The invention belongs to field of optical measuring technologies, particularly a kind of optical heterogeneity based on dual wavelength fizeau interferometer Measurement apparatus and method.

Background technology

Optical transmission material is the important component part of optical material, and whole optical system is had important by its optical property Effect.Generally evaluate the index of optical transmission material property have dispersion, surface face shape, optical heterogeneity, radius of curvature, Stress birfringence, striped and bubble etc..Wherein, optical heterogeneity reflection is same optical material inner refractive index Inconsistency.If optical material inner refractive index is inconsistent, it will cause the change of transmission wavefront, change optical system The wave aberration of system, and then affect the performance of optical system.The optical heterogeneity of magnitude, can bring the ripple of wavelength magnitude Aberration, thus the high-precision detection of optical heterogeneity to optical material, be very urgent and necessary.

The optical heterogeneity of optical material can directly result in the change of transmission wavefront, thus can be by measurement transmitted wave prewave The knots modification of aberration, obtains the optical heterogeneity distribution of optical material.In current detection means, interferometric method conduct Contactless high precision test means, have a wide range of applications.Currently, measuring the heteropical method of optical element has A variety of.2003, Guo Peiji et al. proposed three kinds in absolute measurement techniques one literary composition of optical glass optical homogeneity For measuring the heteropical absolute method of measurement of optical glass, and have developed a high-precision optical glass material optics Nonuniform measurement instrument, achieves high-acruracy survey, but instrument price is expensive to optical glass heterogeneity, it is impossible to real Now extensively apply.2008, Wang Jun et al. was in optical homogeneity one literary composition with short-coherence light source measurement parallel plate glass Propose a kind of new method, utilize the coherence of short-coherence light source, it is achieved that be high to the optical heterogeneity of parallel flat The detection of precision, but due to the short coherence of short-coherence light source, it is necessary to make reference light and test light be in zero optical path difference Position, adjusts to experiment light path and brings very big difficulty.

Content of the invention

It is an object of the invention to provide a kind of optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer and method, Solve tradition absolute method of measurement complex steps, the easy problem by air agitation.

The technical solution realizing the object of the invention is: a kind of optical heterogeneity based on dual wavelength fizeau interferometer is surveyed Amount device include the first laser instrument, second laser, refluxing reflection mirror, switched mirror, beam expanding lens, Amici prism, Refluxing reflection mirror, collimator objective, reference planes mirror, aperture diaphragm, imaging lens group, ccd detector, to be measured flat Face mirror；Common optical axis sets gradually refluxing reflection mirror, collimator objective, reference planes mirror, level crossing to be measured, and above-mentioned parts Residing optical axis is primary optic axis；Common optical axis sets gradually Amici prism, aperture diaphragm, imaging lens group, CCD spy Surveying device, and the optical axis residing for above-mentioned parts being the second optical axis, primary optic axis is parallel with the second optical axis；Common optical axis sets gradually Refluxing reflection mirror, switched mirror, beam expanding lens, Amici prism, refluxing reflection mirror, and the optical axis residing for above-mentioned parts is 3rd optical axis, the 3rd optical axis is vertical with primary optic axis, and switched mirror edge is parallel to primary optic axis direction and moves；All light Learn element coaxially contour relative to substrate, i.e. coaxially contour relative to optical table or instrument base.

Wherein, refluxing reflection mirror, collimator objective, reference planes mirror, level crossing to be measured set gradually along optical path direction, structure Become optical system for testing；Refluxing reflection mirror, collimator objective, reference planes mirror set gradually along optical path direction, constitute reference path； The wavelength of the first laser instrument is λ₁, the wavelength of second laser is λ₂。

Switched mirror is removed the 3rd optical axis, and the laser of the first laser emitting, through refluxing reflection mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Level crossing is transmitted into level crossing to be measured, is reflected as test beams through level crossing to be measured, and reflexes to reference planes mirror； Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, through refluxing reflection mirror Reflex to Amici prism, focus at aperture diaphragm through Amici prism reflection, then through imaging lens group, be imaged on CCD On the target surface of detector, it is thus achieved that wavelength X₁Corresponding interference image.

Switched mirror is moved into the 3rd optical axis, and the laser of second laser outgoing, through switched mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Level crossing is transmitted into level crossing to be measured, is reflected as test beams through level crossing to be measured, and reflexes to reference planes mirror； Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, through refluxing reflection mirror Reflex to Amici prism, focus at aperture diaphragm through Amici prism reflection, then through imaging lens group, be imaged on CCD On the target surface of detector, obtain wavelength X₂Corresponding interference image.

The described optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, reference planes mirror is connected with PZT, Realize that phase shift is measured.

The described optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, the centre wavelength of the first laser instrument is λ₁, the centre wavelength of second laser is λ₂, and λ₁≠λ₂。。

The measuring method of the described optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, step is as follows:

Step 1, build the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer:

Based on the optical heterogeneity measurement apparatus of dual wavelength fizeau interferometer, including the first laser instrument, second laser, Refluxing reflection mirror, switched mirror, beam expanding lens, Amici prism, refluxing reflection mirror, collimator objective, reference planes mirror, Aperture diaphragm, imaging lens group, ccd detector, level crossing to be measured；Common optical axis sets gradually refluxing reflection mirror, standard Straight object lens, reference planes mirror, level crossing to be measured, and the optical axis residing for above-mentioned parts is primary optic axis；Common optical axis sets successively Put Amici prism, aperture diaphragm, imaging lens group, ccd detector, and the optical axis residing for above-mentioned parts is the second light Axle, primary optic axis is parallel with the second optical axis；Common optical axis sets gradually refluxing reflection mirror, switched mirror, beam expanding lens, divides Light prism, refluxing reflection mirror, and the optical axis residing for above-mentioned parts is the 3rd optical axis, the 3rd optical axis is vertical with primary optic axis, Switched mirror edge is parallel to primary optic axis direction and moves；All optical elements are coaxially contour relative to substrate, i.e. relative to Optical table or instrument base are coaxially contour.

Adjusting mirror position to be measured, the front surface making level crossing to be measured is vertical with primary optic axis, it is achieved before level crossing to be measured Surface reflection ripple and the interference of reference planes mirror reflecting light.

Step 2, respectively acquisition wavelength X₁And λ₂Corresponding first time phase-shift interference image:

Switched mirror is removed the 3rd optical axis, and the laser of the first laser emitting, through refluxing reflection mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Level crossing is transmitted into level crossing to be measured, becomes test beams through level crossing front surface reflection to be measured, and it is flat to reflex to reference Face mirror；Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, through turning back Speculum reflexes to Amici prism, focuses at aperture diaphragm through Amici prism reflection, then through imaging lens group, imaging On the target surface of ccd detector, it is thus achieved that wavelength X₁Corresponding interference image, PZT drives reference planes mirror to carry out phase shift, Obtain wavelength X₁Under level crossing front surface to be measured and reference planes mirror rear surface interfere the phase-shift interference being formed.

Switched mirror is moved into the 3rd optical axis, and the laser of second laser outgoing, through switched mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Level crossing is transmitted into level crossing to be measured, becomes test beams through level crossing front surface reflection to be measured, and it is flat to reflex to reference Face mirror；Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, through turning back Speculum reflexes to Amici prism, focuses at aperture diaphragm through Amici prism reflection, then through imaging lens group, imaging On the target surface of ccd detector, obtain wavelength X₂Corresponding interference image, PZT drives reference planes mirror to carry out phase shift, Obtain wavelength X₂Under level crossing front surface to be measured and reference planes mirror rear surface interfere the phase-shift interference being formed.

Step 3, according to wavelength X₁And λ₂Corresponding first time phase shifting interference₅Use corresponding Phase-shifting algorithm, obtain ripple Long λ₁And λ₂Respectively corresponding phase information, and the constant term that carries out to the phase information under two wavelength disappearing, disappear inclination item process, Obtain wavelength X₁And λ₂Wave front aberration at corresponding level crossing front surface any point to be measured

ΔW₁₁(x, y)=2n_aA (x, y)+2S (x, y)

ΔW₂₁(x, y)=2n_aA (x, y)+2S (x, y)

Δ W in formula₁₁(x, y) for measurement wavelength X for the first time₁Corresponding wave front aberration, Δ W₂₁(x, y) for measurement ripple for the first time Long λ₂(x, y) be the surface form deviation of level crossing front surface to be measured, (x y) is interferometer measuration system to S for corresponding wave front aberration, A Systematic error, n_aFor air refraction.

Step 4, respectively acquisition wavelength X₁And λ₂Corresponding second time phase-shift interference image:

Adjusting pitching and the inclination of level crossing to be measured, the rear surface making level crossing to be measured is vertical with primary optic axis, it is achieved pass through Level crossing to be measured the light wave by level crossing rear surface to be measured reflection are interferenceed with reference planes mirror reflecting light；

Switched mirror is removed the 3rd optical axis, and the laser of the first laser emitting, through refluxing reflection mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Level crossing is transmitted into level crossing to be measured, is reflected as test beams through level crossing rear surface to be measured, and it is flat to reflex to reference Face mirror；Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, through turning back Speculum reflexes to Amici prism, focuses at aperture diaphragm through Amici prism reflection, then through imaging lens group, imaging On the target surface of ccd detector, it is thus achieved that wavelength X₁Corresponding interference image, PZT drives reference planes mirror to carry out phase shift, Obtain wavelength X₁Under level crossing rear surface to be measured and reference planes mirror rear surface interfere the phase-shift interference being formed.

Switched mirror is moved into the 3rd optical axis, and the laser of second laser outgoing, through switched mirror, reflexes to expand Mirror, it is achieved expanding of light beam, after Amici prism transmission, then reflexes to collimator objective through refluxing reflection mirror, and one-tenth is as the criterion Straight angle pencil of ray, part collimated light beam becomes reference beam after reflecting through the rear surface of reference planes mirror, and another part is through reference Plane transmission enters level crossing to be measured, is reflected as test beams through level crossing rear surface to be measured, and reflexes to reference planes Mirror；Reference beam and test beams close bundle in reference planes mirror rear surface, return refluxing reflection mirror along light path, anti-through turning back Penetrate mirror and reflex to Amici prism, focus at aperture diaphragm through Amici prism reflection, then through imaging lens group, be imaged on On the target surface of ccd detector, obtain wavelength X₂Corresponding interference image, PZT drives reference planes mirror to carry out phase shift, Obtain wavelength X₂Under level crossing rear surface to be measured and reference planes mirror rear surface interfere the phase-shift interference being formed.

Step 5, according to wavelength X₁And λ₂Corresponding second time phase shifting interference, uses corresponding Phase-shifting algorithm, obtains ripple Long λ₁And λ₂Respectively corresponding phase information, and the phase information to two wavelength carry out disappearing constant term, disappear inclination item process, Obtain wavelength X₁Wave front aberration Δ W at corresponding level crossing front surface any point to be measured₁₂(x, y), And λ₂Wave front aberration Δ W at corresponding level crossing front surface any point to be measured₂₂(x, y):

ΔW₁₂(x, y)=2 (n_a-n₁₀) A (x, y)+2n₁₀B (x, y)+2 Δs (x, y)+2S (x, y)

ΔW₂₂(x, y)=2 (n_a-n₂₀) A (x, y)+2n₂₀B (x, y)+2 Δs (x, y)+2S (x, y)

In formula, Δ W₁₂(x y) is second step measurement wavelength X₁Corresponding wave front aberration, Δ W₂₂(x y) is second step measurement wavelength X₂ Corresponding wave front aberration, (x y) is the surface form deviation of level crossing rear surface to be measured, n to B₁₀And n₂₀It is respectively level crossing to be measured In wavelength X₁And λ₂Under mean refractive index, (x, y) for due to the introduced wavefront of the optical heterogeneity of level crossing to be measured for Δ Deviation.

Wherein,

Δ (x, y)=d₀Δ n (x, y)

In formula, d₀For the average thickness of level crossing to be measured, (x, y) for optical heterogeneity to be measured for Δ n.

Step 6, the optical heterogeneity distribution obtaining level crossing to be measured

6-1) solve and measure wavelength X with second time for the first time₁Corresponding wave front aberration difference DELTA W₁(x, y)

$\begin{array}{c}\mathrm{\Δ}{W}_1(x,y)=\frac{(\mathrm{\Δ}{W}_{12}(x,y)-\mathrm{\Δ}{W}_{11}(x,y))}{2}\\ =n_{10}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{10}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

6-2) solve and measure wavelength X with second time for the first time₂Corresponding wave front aberration difference DELTA W₂(x, y)

$\begin{array}{c}\mathrm{\Δ}{W}_2(x,y)=\frac{(\mathrm{\Δ}{W}_{22}(x,y)-\mathrm{\Δ}{W}_{21}(x,y))}{2}\\ =n_{20}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{20}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

Wherein,

Δ d (x, y)=B (x, y)-A (x, y)

The thickness d of level crossing to be measured (x, y) is represented by:

D (x, y)=d₀+ Δ d (x, y)

In formula, d₀For the average thickness of level crossing to be measured, Δ d (x, y) thickness for being caused by flat mirror deformation to be measured Variable quantity.

Level crossing to be measured is for wavelength X₁Refractive index n₁(x, y) with for wavelength X₂Refractive index n₂(x y) can represent For:

n₁(x, y)=n₁₀+Δn₁(x, y)=n₁₀+ Δ n (x, y)

n₂(x, y)=n₂₀+Δn₂(x, y)=n₂₀+ Δ n (x, y)

In formula, Δ n₁(x y) represents level crossing to be measured in wavelength X₁Under optical heterogeneity, Δ n₂(x, y) level crossing to be measured In wavelength X₂Under optical heterogeneity.

Obtain Lorentz-Lorenz equations according to the dispersive model of Lorentz:

$\frac{n^2-1}{n^2+2}=\frac{4\mathrm{\π}}{3}\mathrm{N\α}$

In formula, n is Refractive Index of Material；N is material internal molecule or atomicity density；α is Mean static polarizabilities, it with enter The angular frequency penetrating light wave is relevant.

Above formula can be obtained the relation between Refractive Index of Material n and heterogeneity Δ n and N thereof with analysis and arrangement:

$n^2=\frac{8\mathrm{N\α\π}+3}{3-4\mathrm{N\α\π}}$

Can obtain after derivation:

$\mathrm{\Δn}=\frac{36\mathrm{N\α\π}+3}{2n{(3-4\mathrm{N\α\π})}^2}\frac{\mathrm{\ΔN}}{N}$

Arrange further and can obtain:

$\mathrm{\Δn}=\frac{(n^2-1)(n^2+2)}{6n}\frac{\mathrm{\ΔN}}{N}$

So:

$\frac{\mathrm{\Δ}{n}_1}{\mathrm{\Δ}{n}_2}=\frac{({n_1}^2-1)({n_1}^2+2)}{({n_2}^2-1)({n_2}^2+2)}\frac{n_2}{n_1}$

Thus can obtain, the difference of the optical heterogeneity in a wavelength range is much smaller than optical heterogeneity itself, one Can be approximately considered during the optical heterogeneity using the light wave measurement optical material of different wave length or element in wavelength range Δ n=Δ n₁=Δ n₂。

So Δ n (x y) is the optical heterogeneity of level crossing to be measured to be measured.

6-3) determine level crossing to be measured optical heterogeneity Δ n (x, y):

$\mathrm{\Δn}(x,y)=\frac{n_{20}\·\mathrm{\Δ}{W}_1(x,y)-n_{10}\·\mathrm{\Δ}{W}_2(x,y)}{d_0(n_{10}-n_{20})}.$

Compared with prior art, it is an advantage of the current invention that: (1) uses dual wavelength phase-shifting interferometer two pacing amount The optical heterogeneity of method detection level crossing to be measured, it is not necessary to introduce standard reflection mirror, completely eliminate standard anti- Penetrate the impact on measurement result of the face shape of mirror；(2) measuring process is simple, compensate for tradition absolute method of measurement step Suddenly loaded down with trivial details, easily by the shortcoming of air agitation；The advantage also simultaneously with traditional absolute measurement, thus reduce right Tested level crossing to be measured and the required precision of interferometer system face shape.

Brief description

Fig. 1 is the optical heterogeneity measurement apparatus schematic diagram based on dual wavelength fizeau interferometer.

Fig. 2 is the measuring method flow chart of the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer.

Fig. 3 is corresponding wavefront picture under two wavelength of level crossing front surface to be measured recording in the embodiment of the present invention Difference figure, wherein (a) is wavelength X₁Under the wave front aberration figure of corresponding level crossing front surface to be measured, (b) is ripple Long λ₂Under the wave front aberration figure of corresponding level crossing front surface to be measured.

Fig. 4 is corresponding wavefront picture under two, the level crossing rear surface to be measured wavelength recording in the embodiment of the present invention Difference figure, wherein (a) is wavelength X₁Under the wave front aberration figure of corresponding level crossing rear surface to be measured, (b) is ripple Long λ₂Under the wave front aberration figure of corresponding level crossing rear surface to be measured.

Fig. 5 is the optical heterogeneity distribution of the level crossing to be measured recording in the embodiment of the present invention.

Fig. 6 is that the optical heterogeneity that in the embodiment of the present invention, level crossing to be measured uses ZYGO interferometer to record is divided Cloth.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is described in further detail.

In conjunction with Fig. 1, a kind of optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer includes that first swashs Light device the 1st, second laser the 2nd, refluxing reflection mirror the 3rd, switched mirror the 4th, beam expanding lens the 5th, Amici prism is the 6th, Refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror the 9th, aperture diaphragm the 10th, imaging lens group the 11st, CCD Detector the 12nd, level crossing 13 to be measured；It is flat that common optical axis sets gradually the 8th, the reference of refluxing reflection mirror the 7th, collimator objective Face mirror the 9th, level crossing 13 to be measured, and the optical axis residing for above-mentioned parts is primary optic axis；Common optical axis sets gradually point Light prism the 6th, aperture diaphragm the 10th, imaging lens group the 11st, ccd detector 12, and the light residing for above-mentioned parts Axle is the second optical axis, and primary optic axis is parallel with the second optical axis；Common optical axis sets gradually refluxing reflection mirror and the 3rd, switches Speculum the 4th, beam expanding lens the 5th, Amici prism the 6th, refluxing reflection mirror 7, and the optical axis residing for above-mentioned parts is the 3rd Optical axis, the 3rd optical axis is vertical with primary optic axis, and switched mirror 4 moves along being parallel to primary optic axis direction；Institute There is optical element coaxially contour relative to substrate, i.e. coaxially contour relative to optical table or instrument base.

Wherein, refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror the 9th, level crossing to be measured 13 is along light path side To setting gradually, constitute optical system for testing；Refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror 9 is along light path Direction sets gradually, and constitutes reference path；The wavelength of the first laser instrument 1 is λ₁, the wavelength of second laser 2 For λ₂。

Switched mirror 4 is removed the 3rd optical axis, the laser of the first laser instrument 1 outgoing through refluxing reflection mirror 3, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 is reflected as test beams, and reflexes to reference planes mirror 9；Reference beam and test beams exist Bundle is closed in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, reflexes to point through refluxing reflection mirror 7 Light prism 6, focuses at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, becomes As on the target surface of ccd detector 12, it is thus achieved that wavelength X₁Corresponding interference image.

Switched mirror 4 is moved into the 3rd optical axis, the laser of second laser 2 outgoing through switched mirror 4, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 is reflected as test beams, and reflexes to reference planes mirror 9；Reference beam and test beams exist Bundle is closed in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, reflexes to point through refluxing reflection mirror 7 Light prism 6, focuses at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, becomes As, on the target surface of ccd detector 12, obtaining wavelength X₂Corresponding interference image.

Based on the optical heterogeneity measurement apparatus of dual wavelength fizeau interferometer, reference planes mirror 9 is with PZT even Connect, it is achieved phase shift is measured.

Based on the optical heterogeneity measurement apparatus of dual wavelength fizeau interferometer, the centre wavelength of the first laser instrument 1 For λ₁, the centre wavelength of second laser 2 is λ₂, and λ₁≠λ₂。

A kind of measuring method of the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, step is as follows:

Step 1, build the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer:

Based on the optical heterogeneity measurement apparatus of dual wavelength fizeau interferometer, including the first laser instrument the 1st, second Laser instrument the 2nd, refluxing reflection mirror the 3rd, switched mirror the 4th, beam expanding lens the 5th, Amici prism the 6th, refluxing reflection mirror is the 7th, The 12nd, collimator objective the 8th, reference planes mirror the 9th, aperture diaphragm the 10th, imaging lens group the 11st, ccd detector is treated Survey level crossing 13；Common optical axis sets gradually refluxing reflection mirror 7), collimator objective the 8th, reference planes mirror the 9th, to be measured Level crossing 13, and the optical axis residing for above-mentioned parts is primary optic axis；Common optical axis sets gradually Amici prism the 6th, hole Footpath diaphragm the 10th, imaging lens group the 11st, ccd detector 12, and the optical axis residing for above-mentioned parts is the second optical axis, Primary optic axis is parallel with the second optical axis；Common optical axis sets gradually refluxing reflection mirror the 3rd, switched mirror and the 4th, expands Mirror the 5th, Amici prism the 6th, refluxing reflection mirror 7, and the optical axis residing for above-mentioned parts is the 3rd optical axis, the 3rd light Axle is vertical with primary optic axis, and switched mirror 4 moves along being parallel to primary optic axis direction；All optical element phases Coaxially contour for substrate, i.e. coaxially contour relative to optical table or instrument base；

Adjusting level crossing 13 position to be measured, the front surface making level crossing 13 to be measured is vertical with primary optic axis, it is achieved Level crossing 13 front surface reflection light wave to be measured and the interference of reference planes mirror 9 reflecting light；

Step 2, respectively acquisition wavelength X₁And λ₂Corresponding first time phase-shift interference image:

Switched mirror 4 is removed the 3rd optical axis, the laser of the first laser instrument 1 outgoing through refluxing reflection mirror 3, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 front surface reflection becomes test beams, and reflexes to reference planes mirror 9；Reference beam and test Light beam closes bundle in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, anti-through refluxing reflection mirror 7 It is mapped to Amici prism 6, focus at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, it is imaged on the target surface of ccd detector 12, it is thus achieved that wavelength X₁Corresponding interference image, PZT drives Reference planes mirror 9 carries out phase shift, it is thus achieved that wavelength X₁Under after level crossing 13 front surface to be measured and reference planes mirror 9 The phase-shift interference that Surface Interference is formed；

Switched mirror 4 is moved into the 3rd optical axis, the laser of second laser 2 outgoing through switched mirror 4, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 front surface reflection becomes test beams, and reflexes to reference planes mirror 9；Reference beam and test Light beam closes bundle in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, anti-through refluxing reflection mirror 7 It is mapped to Amici prism 6, focus at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, it is imaged on the target surface of ccd detector 12, obtain wavelength X₂Corresponding interference image, PZT drives Reference planes mirror 9 carries out phase shift, it is thus achieved that wavelength X₂Under after level crossing 13 front surface to be measured and reference planes mirror 9 The phase-shift interference that Surface Interference is formed；

Step 3, according to wavelength X₁And λ₂Corresponding first time phase shifting interference, uses corresponding Phase-shifting algorithm, Obtain wavelength X₁And λ₂Respectively corresponding phase information, and the constant term that carries out to the phase information under two wavelength disappearing, Disappear inclination item process, obtains wavelength X₁And λ₂Wavefront at corresponding level crossing to be measured 13 front surface any point Aberration

ΔW₁₁(x, y)=2n_aA (x, y)+2S (x, y)

ΔW₂₁(x, y)=2n_aA (x, y)+2S (x, y)

Δ W in formula₁₁(x, y) for measurement wavelength X for the first time₁Corresponding wave front aberration, Δ W₂₁(x, y) for for the first time Measurement wavelength X₂Corresponding wave front aberration, A (x, y) be the surface form deviation of level crossing 13 front surface to be measured, S (x, y) Systematic error, n for interferometer measuration system_aFor air refraction；

Step 4, respectively acquisition wavelength X₁And λ₂Corresponding second time phase-shift interference image:

Adjusting the angle of level crossing 13 to be measured, the rear surface making level crossing 13 to be measured is vertical with primary optic axis, real Now pass through level crossing 13 to be measured and the light wave by level crossing 13 rear surface to be measured reflection reflects with reference planes mirror 9 Light wave interference；

Switched mirror 4 is removed the 3rd optical axis, the laser of the first laser instrument 1 outgoing through refluxing reflection mirror 3, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 rear surface is reflected as test beams, and reflexes to reference planes mirror 9；Reference beam and test Light beam closes bundle in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, anti-through refluxing reflection mirror 7 It is mapped to Amici prism 6, focus at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, it is imaged on the target surface of ccd detector 12, it is thus achieved that wavelength X₁Corresponding interference image, PZT drives Reference planes mirror 9 carries out phase shift, it is thus achieved that wavelength X₁Under after level crossing 13 rear surface to be measured and reference planes mirror 9 The phase-shift interference that Surface Interference is formed；

Switched mirror 4 is moved into the 3rd optical axis, the laser of second laser 2 outgoing through switched mirror 4, Reflex to beam expanding lens 5, it is achieved expanding of light beam, after Amici prism 6 transmission, then through refluxing reflection mirror 7 Reflexing to collimator objective 8, becoming collimation angle pencil of ray, part collimated light beam is anti-through the rear surface of reference planes mirror 9 Becoming reference beam after penetrating, another part is transmitted into level crossing 13 to be measured through reference planes mirror 9, through to be measured Level crossing 13 rear surface is reflected as test beams, and reflexes to reference planes mirror 9；Reference beam and test Light beam closes bundle in reference planes mirror 9 rear surface, returns refluxing reflection mirror 7 along light path, anti-through refluxing reflection mirror 7 It is mapped to Amici prism 6, focus at aperture diaphragm 10 through Amici prism 6 reflection, then through imaging lens group 11, it is imaged on the target surface of ccd detector 12, obtain wavelength X₂Corresponding interference image, PZT drives Reference planes mirror 9 carries out phase shift, it is thus achieved that wavelength X₂Under after level crossing 13 rear surface to be measured and reference planes mirror 9 The phase-shift interference that Surface Interference is formed；

Step 5, according to wavelength X₁And λ₂Corresponding second time phase shifting interference, uses corresponding Phase-shifting algorithm, Obtain wavelength X₁And λ₂Respectively corresponding phase information, and the phase information to two wavelength carry out disappearing constant term, disappear Tilt item process, obtain wavelength X₁And λ₂Wavefront picture at corresponding level crossing to be measured 13 front surface any point Difference:

ΔW₁₂(x, y)=2 (n_a-n₁₀) A (x, y)+2n₁₀B (x, y)+2 Δs (x, y)+2S (x, y)

ΔW₂₂(x, y)=2 (n_a-n₂₀) A (x, y)+2n₂₀B (x, y)+2 Δs (x, y)+2S (x, y)

In formula, Δ W₁₂(x y) is second step measurement wavelength X₁Corresponding wave front aberration, Δ W₂₂(x y) is the second pacing Amount wavelength X₂Corresponding wave front aberration, (x y) is the surface form deviation of level crossing 13 rear surface to be measured, n to B₁₀And n₂₀ It is respectively level crossing to be measured 13 in wavelength X₁And λ₂Under mean refractive index, (x, y) for due to level crossing to be measured for Δ The introduced wavefront deviation of the optical heterogeneity of 13.

Wherein,

Δ (x, y)=d₀Δ n (x, y)

In formula, d₀For the average thickness of level crossing 13 to be measured, (x, y) for optical heterogeneity to be measured for Δ n.

Step 6, the optical heterogeneity distribution obtaining level crossing 13 to be measured:

6-1) solve and measure wavelength X with second time for the first time₁Corresponding wave front aberration difference DELTA W₁(x, y)

$\begin{array}{c}\mathrm{\Δ}{W}_1(x,y)=\frac{(\mathrm{\Δ}{W}_{12}(x,y)-\mathrm{\Δ}{W}_{11}(x,y))}{2}\\ =n_{10}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\end{array}$

$=n_{10}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)$

6-2) solve and measure wavelength X with second time for the first time₂Corresponding wave front aberration difference DELTA W₂(x, y)

$\begin{array}{c}\mathrm{\Δ}{W}_2(x,y)=\frac{(\mathrm{\Δ}{W}_{22}(x,y)-\mathrm{\Δ}{W}_{21}(x,y))}{2}\\ =n_{20}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{20}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

Wherein,

Δ d (x, y)=B (x, y)-A (x, y)

The thickness d of level crossing 13 to be measured (x, y) is represented by:

D (x, y)=d₀+ Δ d (x, y)

In formula, d₀For the average thickness of level crossing 13 to be measured, (x, y) for by level crossing 13 face deformation to be measured for Δ d Change the amounts of thickness variation causing.

Level crossing to be measured 13 is for wavelength X₁Refractive index n₁(x, y) with for wavelength X₂Refractive index n₂(x, y) It is expressed as:

n₁(x, y)=n₁₀+Δn₁(x, y)=n₁₀+ Δ n (x, y)

n₂(x, y)=n₂₀+Δn₂(x, y)=n₂₀+ Δ n (x, y)

In formula, Δ n₁(x y) represents level crossing to be measured 13 in wavelength X₁Under optical heterogeneity, Δ n₂(x y) treats Survey level crossing 13 in wavelength X₂Under optical heterogeneity.

Obtain Lorentz-Lorenz equations according to the dispersive model of Lorentz:

$\frac{n^2-1}{n^2+2}=\frac{4\mathrm{\π}}{3}\mathrm{N\α}$

In formula, n is Refractive Index of Material；N is material internal molecule or atomicity density；α is Mean static polarizabilities, It is relevant with the angular frequency of incident light wave；

Above formula can be obtained the relation between Refractive Index of Material n and heterogeneity Δ n and N thereof with analysis and arrangement:

$n^2=\frac{8\mathrm{N\α\π}+3}{3-4\mathrm{N\α\π}}$

Can obtain after derivation:

$\mathrm{\Δn}=\frac{36\mathrm{N\α\π}+3}{2n{(3-4\mathrm{N\α\π})}^2}\frac{\mathrm{\ΔN}}{N}$

Arrange further and can obtain:

$\mathrm{\Δn}=\frac{(n^2-1)(n^2+2)}{6n}\frac{\mathrm{\ΔN}}{N}$

So:

$\frac{\mathrm{\Δ}{n}_1}{\mathrm{\Δ}{n}_2}=\frac{({n_1}^2-1)({n_1}^2+2)}{({n_2}^2-1)({n_2}^2+2)}\frac{n_2}{n_1}$

Thus can obtain, the difference of the optical heterogeneity in a wavelength range is much smaller than optical heterogeneity itself, When using the optical heterogeneity of the light wave measurement optical material of different wave length or element in a wavelength range Δ n=Δ n can be approximately considered₁=Δ n₂；So Δ n (x y) is the optics of level crossing to be measured 13 to be measured Heterogeneity.

6-3) determine level crossing 13 to be measured optical heterogeneity Δ n (x, y):

$\mathrm{\Δn}(x,y)=\frac{n_{20}\·\mathrm{\Δ}{W}_1(x,y)-n_{10}\·\mathrm{\Δ}{W}_2(x,y)}{d_0(n_{10}-n_{20})}.$

Embodiment one

A kind of optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, uses the first laser instrument 1 Centre wavelength be λ₁The frequency stabilization polarization He-Ne laser of=632.8nm, power output 1.5mw, output facula Bore is φ 1mm；The centre wavelength of second laser 2 is λ₂=532nm frequency stabilization polarizes semiconductor laser, Power 1.5mw, output facula bore is φ 1mm.Level crossing 13 to be measured is quartz crystal, the mouth of quartz crystal Footpath is D=110mm, thickness d=21.70mm, the angle of wedge be 11 ' 49 ' '.This level crossing to be measured 13 is at wavelength λ₁Refractive index under=632.8nm is n₁=1.4570, in wavelength X₂Refractive index under=532nm is n₂=1.4607.Light beam is through the reflection of refluxing reflection mirror 3, and after laser beam expanding lens 5, hot spot bore is φ 8mm, Reflection through refluxing reflection mirror 7 again, forms a branch of directional light after collimator objective 8 collimation, flat through reference Face mirror 9 reflection obtains reference planes wavefront；Reference light wave is respectively by surface before and after test level crossing 13 to be measured Reflection obtains test wavefront data.After reference beam and test beams interfere, through refluxing reflection mirror 7 Again semi-transparent semi-reflecting lens 6 reflection is converged at pin hole 10 after reflection, be imaged on CCD via image-forming objective lens 11 On detector 12, obtain interference pattern.

Common optical axis sets gradually refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror the 9th, level crossing 13 to be measured, And the optical axis residing for above-mentioned parts is primary optic axis；The 10th, common optical axis sets gradually Amici prism the 6th, aperture diaphragm Imaging lens group the 11st, ccd detector 12, and the optical axis residing for above-mentioned parts is the second optical axis, primary optic axis Parallel with the second optical axis；Common optical axis sets gradually refluxing reflection mirror the 3rd, switched mirror the 4th, beam expanding lens and the 5th, divides Light prism the 6th, refluxing reflection mirror 7, and the optical axis residing for above-mentioned parts is the 3rd optical axis, the 3rd optical axis and first Optical axis is vertical, and switched mirror 4 moves along being parallel to primary optic axis direction；All optical elements are relative to substrate Coaxially contour, i.e. coaxially contour relative to optical table or instrument base.

Wherein, refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror the 9th, level crossing to be measured 13 is along light path side To setting gradually, constitute optical system for testing；Refluxing reflection mirror the 7th, collimator objective the 8th, reference planes mirror 9 is along light path Direction sets gradually, and constitutes reference path；The wavelength of the first laser instrument 1 is λ₁, the wavelength of second laser 2 For λ₂。

In conjunction with Fig. 2, the measuring method of a kind of optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, Step is as follows:

Step 1, build the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer.

Step 2, respectively acquisition wavelength X₁And λ₂Corresponding first time phase-shift interference image:

Put into level crossing 13 to be measured, adjust level crossing 13 to be measured, make the front surface and first of level crossing 13 to be measured Optical axis is vertical, it is achieved the interference of level crossing 13 front surface reflection light wave to be measured and reference planes reflecting light.Will Switched mirror 4 moves into the 3rd optical axis, drives reference planes displacement to realize eight step phase shift measurements by control PZT, Record wavelength X₂The corresponding phase shifting interference of=532nm；Switched mirror 4 is removed the 3rd optical axis, passes through Control PZT drives reference planes displacement to realize eight step phase shift measurements, records wavelength X₁The corresponding shifting of=632.8nm Interference figure.

Step 3, take eight step Phase-shifting algorithm and phase unwrapping technology, and the constant term that carries out to phase information disappearing, Disappear inclination item process, thus obtains wavelength X₁Corresponding corrugated information Δ W₁₁(x, y) and wavelength X₂Corresponding corrugated Information Δ W₂₁(x, y).Face shape information and system that this corrugated information comprises level crossing 13 front surface to be measured are missed Difference.Wherein λ₁Corresponding corrugated information Δ W₁₁(x, y), λ₂Corresponding corrugated information Δ W₂₁(x, y) such as figure Shown in 3.

Step 4, respectively acquisition wavelength X₁And λ₂Corresponding second time phase-shift interference image:

Adjusting level crossing 13 to be measured, the rear surface making level crossing 13 to be measured is vertical with primary optic axis, it is achieved to be measured Level crossing 13 rear surface reflecting light and the interference of reference planes reflecting light.Switched mirror 4 is moved into Three optical axises, drive reference planes displacement to realize eight step phase shift measurements by control PZT, record wavelength λ₂The corresponding phase shifting interference of=532nm；Switched mirror 4 is removed the 3rd optical axis, by control PZT Drive reference planes displacement to realize eight step phase shift measurements, record wavelength X₁The corresponding phase shifting interference of=632.8nm.

Step 5, take eight step Phase-shifting algorithm and phase unwrapping technology, and the constant term that carries out to phase information disappearing, Disappear inclination item process, thus obtains wavelength X₁Corresponding corrugated information Δ W₁₂(x, y) and wavelength X₂Corresponding corrugated Information Δ W₂₂(x, y).This corrugated information comprises the face shape information of level crossing 13 rear surface to be measured, and inside is non-all The distribution of even property and systematic error.Wherein λ₁Corresponding corrugated information Δ W₁₂(x, y), λ₂Corresponding corrugated Information Δ W₂₂(x, y) as shown in Figure 4.

Step 6: the optical heterogeneity obtaining level crossing to be measured is distributed:

6-1) by measurement for the first time and second time measurement wavelength X₁Corresponding wave front aberration asks difference to obtain:

ΔW₁(x, y)=(Δ W₁₂(x, y)-Δ W₁₁(x, y)) ÷ 2

=n₁₀[B (and x, y)-A (x, y)]+d₀Δ n (x, y)

=n₁₀Δ d (x, y)+d₀Δ n (x, y)

6-2) by measurement for the first time and second time measurement wavelength X₂Corresponding wave front aberration asks difference to obtain:

$\begin{array}{c}\mathrm{\Δ}{W}_2(x,y)=\frac{(\mathrm{\Δ}{W}_{22}(x,y)-\mathrm{\Δ}{W}_{21}(x,y))}{2}\\ =n_{20}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{20}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

Wherein,

Δ d (x, y)=B (x, y)-A (x, y)

Then level crossing 13 to be measured thickness d (x, y) is represented by:

D (x, y)=d₀+ Δ d (x, y)

In formula, d₀For the average thickness of level crossing 13 to be measured, (x, y) for by level crossing 13 face deformation to be measured for Δ d The thickness change causing.

Obtain Lorentz-Lorenz equations according to the dispersive model of Lorentz:

$\frac{n^2-1}{n^2+2}=\frac{4\mathrm{\π}}{3}\mathrm{N\α}$

In formula, n is Refractive Index of Material；N is material internal molecule or atomicity density；α is Mean static polarizabilities, It is relevant with the angular frequency of incident light wave；

Above formula can be obtained the relation between Refractive Index of Material n and heterogeneity Δ n and N thereof with analysis and arrangement:

$n^2=\frac{8\mathrm{N\α\π}+3}{3-4\mathrm{N\α\π}}$

Can obtain after derivation:

$\mathrm{\Δn}=\frac{36\mathrm{N\α\π}+3}{2n{(3-4\mathrm{N\α\π})}^2}\frac{\mathrm{\ΔN}}{N}$

Arrange further and can obtain:

$\mathrm{\Δn}=\frac{(n^2-1)(n^2+2)}{6n}\frac{\mathrm{\ΔN}}{N}$

So:

$\frac{\mathrm{\Δ}{n}_1}{\mathrm{\Δ}{n}_2}=\frac{({n_1}^2-1)({n_1}^2+2)}{({n_2}^2-1)({n_2}^2+2)}\frac{n_2}{n_1}$

Thus can obtain, the difference of the optical heterogeneity in a wavelength range is much smaller than optical heterogeneity itself, When using the optical heterogeneity of the light wave measurement optical material of different wave length or element in a wavelength range Δ n=Δ n can be approximately considered₁=Δ n₂；So Δ n (x y) is the optics of level crossing to be measured 13 to be measured Heterogeneity.

6-3) by measurement for the first time and second time measurement wavelength X₁、λ₂Corresponding wave front aberration difference can calculate to be asked Level crossing 13 to be measured optical heterogeneity Δ n (x, y) be:

$\mathrm{\Δn}(x,y)=\frac{n_{20}\·\mathrm{\Δ}{W}_1(x,y)-n_{10}\·\mathrm{\Δ}{W}_2(x,y)}{d_0(n_{10}-n_{20})}$

The optical heterogeneity of the level crossing to be measured 13 recovering is distributed such as Fig. 5.

What the result of the optical heterogeneity of this quartz crystal that the method records and ZYGO interferometer recovered should Optical heterogeneity result (such as Fig. 6) contrast of quartz crystal, optical heterogeneity distribution is basically identical, tests Correctness and the feasibility of algorithm are demonstrate,proved.

The present invention uses the optical heterogeneity of dual wavelength phase-shifting interferometer two step mensuration detection level crossing to be measured, Do not need to introduce standard reflection mirror, completely eliminate the impact on measurement result of the face shape of standard reflection mirror；Measurement Step is simple, compensate for tradition absolute method of measurement complex steps, easily by the shortcoming of air agitation；Also have simultaneously The advantage having traditional absolute measurement, thus reduce the precision to tested level crossing to be measured and interferometer system face shape Require.

Claims (4)

1. the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer, it is characterised in that bag Include the first laser instrument (1), second laser (2), refluxing reflection mirror (3), switched mirror (4), expand Mirror (5), Amici prism (6), refluxing reflection mirror (7), collimator objective (8), reference planes mirror (9), hole Footpath diaphragm (10), imaging lens group (11), ccd detector (12) and level crossing to be measured (13)；Light altogether Axle sets gradually refluxing reflection mirror (7), collimator objective (8), reference planes mirror (9), level crossing to be measured (13), Optical axis residing for above-mentioned parts is primary optic axis；Common optical axis set gradually Amici prism (6), aperture diaphragm (10), Imaging lens group (11), ccd detector (12), the optical axis residing for above-mentioned parts is the second optical axis, first Optical axis is parallel with the second optical axis；Common optical axis sets gradually refluxing reflection mirror (3), switched mirror (4), expands Mirror (5), Amici prism (6), refluxing reflection mirror (7), the optical axis residing for above-mentioned parts is the 3rd optical axis, the Three optical axises are vertical with primary optic axis, and switched mirror (4) edge is parallel to primary optic axis direction and moves；All light Learn element coaxially contour relative to substrate, i.e. coaxially contour relative to optical table or instrument base；

Wherein, refluxing reflection mirror (7), collimator objective (8), reference planes mirror (9), level crossing to be measured (13) Set gradually along optical path direction, constitute optical system for testing；Refluxing reflection mirror (7), collimator objective (8), reference are flat Face mirror (9) sets gradually along optical path direction, constitutes reference path；

Switched mirror (4) is removed the 3rd optical axis, and the laser of the first laser instrument (1) outgoing is anti-through turning back Penetrate mirror (3), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), be reflected as test beams through level crossing to be measured (13), and reflex to ginseng Examine level crossing (9)；Reference beam and test beams close bundle in reference planes mirror (9) rear surface, return along light path Return refluxing reflection mirror (7), reflex to Amici prism (6) through refluxing reflection mirror (7), through Amici prism (6) Reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on ccd detector (12) Target surface on, it is thus achieved that wavelength X₁Corresponding interference image；

Switched mirror (4) is moved into the 3rd optical axis, and the laser of second laser (2) outgoing is anti-through switching Penetrate mirror (4), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), be reflected as test beams through level crossing to be measured (13), and reflex to ginseng Examine level crossing (9)；Reference beam and test beams close bundle in reference planes mirror (9) rear surface, return along light path Return refluxing reflection mirror (7), reflex to Amici prism (6) through refluxing reflection mirror (7), through Amici prism (6) Reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on ccd detector (12) Target surface on, obtain wavelength X₂Corresponding interference image.

2. the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer according to claim 1, It is characterized in that: above-mentioned reference planes mirror (9) is connected with PZT, it is achieved phase shift is measured.

3. according to the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer described in claim 1, It is characterized in that: the centre wavelength of the first laser instrument (1) is λ₁, the centre wavelength of second laser (2) is λ₂, and λ₁≠λ₂。

4. based on the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer described in claim 1 Measuring method, it is characterised in that step is as follows:

Step 1, build the optical heterogeneity measurement apparatus based on dual wavelength fizeau interferometer:

Based on the optical heterogeneity measurement apparatus of dual wavelength fizeau interferometer, including the first laser instrument (1), Dual-laser device (2), refluxing reflection mirror (3), switched mirror (4), beam expanding lens (5), Amici prism (6), Refluxing reflection mirror (7), collimator objective (8), reference planes mirror (9), aperture diaphragm (10), imaging len Group (11), ccd detector (12), level crossing to be measured (13)；Common optical axis set gradually refluxing reflection mirror (7), Collimator objective (8), reference planes mirror (9), level crossing to be measured (13), the optical axis residing for above-mentioned parts is One optical axis；Common optical axis set gradually Amici prism (6), aperture diaphragm (10), imaging lens group (11), Ccd detector (12), the optical axis residing for above-mentioned parts is the second optical axis, and primary optic axis is parallel with the second optical axis； Common optical axis set gradually refluxing reflection mirror (3), switched mirror (4), beam expanding lens (5), Amici prism (6), Refluxing reflection mirror (7), the optical axis residing for above-mentioned parts is the 3rd optical axis, and the 3rd optical axis is vertical with primary optic axis, Switched mirror (4) edge is parallel to primary optic axis direction and moves；All optical elements are coaxial relative to substrate Height, i.e. coaxially contour relative to optical table or instrument base；

Adjusting level crossing to be measured (13) position, the front surface making level crossing to be measured (13) is vertical with primary optic axis, Realize the interference of level crossing to be measured (13) front surface reflection light wave and reference planes mirror (9) reflecting light；

Step 2, respectively acquisition wavelength X₁And λ₂Corresponding first time phase-shift interference image:

Switched mirror (4) is removed the 3rd optical axis, and the laser of the first laser instrument (1) outgoing is anti-through turning back Penetrate mirror (3), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), become test beams through level crossing to be measured (13) front surface reflection, and instead It is mapped to reference planes mirror (9)；Reference beam and test beams close bundle, edge in reference planes mirror (9) rear surface Light path returns refluxing reflection mirror (7), reflexes to Amici prism (6) through refluxing reflection mirror (7), through light splitting rib Mirror (6) reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on CCD On the target surface of detector (12), it is thus achieved that wavelength X₁Corresponding interference image, PZT drives reference planes mirror (9) Carry out phase shift, it is thus achieved that wavelength X₁Under level crossing to be measured (13) front surface and reference planes mirror (9) rear surface do Relate to the phase-shift interference of formation；

Switched mirror (4) is moved into the 3rd optical axis, and the laser of second laser (2) outgoing is anti-through switching Penetrate mirror (4), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), become test beams through level crossing to be measured (13) front surface reflection, and instead It is mapped to reference planes mirror (9)；Reference beam and test beams close bundle, edge in reference planes mirror (9) rear surface Light path returns refluxing reflection mirror (7), reflexes to Amici prism (6) through refluxing reflection mirror (7), through light splitting rib Mirror (6) reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on CCD On the target surface of detector (12), obtain wavelength X₂Corresponding interference image, PZT drives reference planes mirror (9) Carry out phase shift, it is thus achieved that wavelength X₂Under level crossing to be measured (13) front surface and reference planes mirror (9) rear surface do Relate to the phase-shift interference of formation；

Step 3, according to wavelength X₁And λ₂Corresponding first time phase shifting interference, uses corresponding Phase-shifting algorithm, Obtain wavelength X₁And λ₂Corresponding phase information, and the constant that carries out disappearing respectively to the phase information under two wavelength respectively , disappear inclination item process, obtain wavelength X₁And λ₂At corresponding level crossing to be measured (13) front surface any point Wave front aberration

ΔW₁₁(x, y)=2n_aA(x,y)+2S(x,y)

ΔW₂₁(x, y)=2n_aA(x,y)+2S(x,y)

Δ W in formula₁₁(x, y) for measurement wavelength X for the first time₁Corresponding wave front aberration, Δ W₂₁(x, y) for for the first time Measurement wavelength X₂Corresponding wave front aberration, A (x, y) is the surface form deviation of level crossing to be measured (13) front surface, (x y) is systematic error, the n of interferometer measuration system to S_aFor air refraction, (x y) is level crossing to be measured (13) The coordinate of front surface any point；

Step 4, respectively acquisition wavelength X₁And λ₂Corresponding second time phase-shift interference image:

Adjust the angle of level crossing to be measured (13), make the rear surface of level crossing to be measured (13) and primary optic axis hang down Directly, it is achieved pass through level crossing to be measured (13) the light wave being reflected by level crossing to be measured (13) rear surface and reference Level crossing (9) reflecting light interference；

Switched mirror (4) is removed the 3rd optical axis, and the laser of the first laser instrument (1) outgoing is anti-through turning back Penetrate mirror (3), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), be reflected as test beams through level crossing to be measured (13) rear surface, and instead It is mapped to reference planes mirror (9)；Reference beam and test beams close bundle, edge in reference planes mirror (9) rear surface Light path returns refluxing reflection mirror (7), reflexes to Amici prism (6) through refluxing reflection mirror (7), through light splitting rib Mirror (6) reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on CCD On the target surface of detector (12), it is thus achieved that wavelength X₁Corresponding interference image, PZT drives reference planes mirror (9) Carry out phase shift, it is thus achieved that wavelength X₁Under level crossing to be measured (13) rear surface and reference planes mirror (9) rear surface do Relate to the phase-shift interference of formation；

Switched mirror (4) is moved into the 3rd optical axis, and the laser of second laser (2) outgoing is anti-through switching Penetrate mirror (4), reflex to beam expanding lens (5), it is achieved expanding of light beam, after Amici prism (6) transmission, then Reflex to collimator objective (8) through refluxing reflection mirror (7), become collimation angle pencil of ray, part collimated light beam warp Becoming reference beam after the rear surface reflection of reference planes mirror (9), another part is saturating through reference planes mirror (9) Inject level crossing to be measured (13), be reflected as test beams through level crossing to be measured (13) rear surface, and instead It is mapped to reference planes mirror (9)；Reference beam and test beams close bundle, edge in reference planes mirror (9) rear surface Light path returns refluxing reflection mirror (7), reflexes to Amici prism (6) through refluxing reflection mirror (7), through light splitting rib Mirror (6) reflection focuses on aperture diaphragm (10) place, then through imaging lens group (11), is imaged on CCD On the target surface of detector (12), obtain wavelength X₂Corresponding interference image, PZT drives reference planes mirror (9) Carry out phase shift, it is thus achieved that wavelength X₂Under level crossing to be measured (13) rear surface and reference planes mirror (9) rear surface do Relate to the phase-shift interference of formation；

Step 5, according to wavelength X₁And λ₂Corresponding second time phase shifting interference, uses corresponding Phase-shifting algorithm, Obtain wavelength X₁And λ₂Respectively corresponding phase information, and the phase information to two wavelength carry out disappearing constant term, disappear Tilt item process, obtain wavelength X₁And λ₂Wavefront at corresponding level crossing to be measured (13) front surface any point Aberration:

ΔW₁₂(x, y)=2 (n_a-n₁₀)A(x,y)+2n₁₀B(x,y)+2Δ(x,y)+2S(x,y)

ΔW₂₂(x, y)=2 (n_a-n₂₀)A(x,y)+2n₂₀B(x,y)+2Δ(x,y)+2S(x,y)

In formula, Δ W₁₂(x y) is second step measurement wavelength X₁Corresponding wave front aberration, Δ W₂₂(x is y) second Pacing amount wavelength X₂Corresponding wave front aberration, B (x, y) is the surface form deviation of level crossing to be measured (13) rear surface, n₁₀For level crossing to be measured (13) in wavelength X₁Under mean refractive index, n₂₀For level crossing to be measured (13) at ripple Long λ₂Under mean refractive index, Δ (x, y) for due to the optical heterogeneity of level crossing to be measured (13) introduced Wavefront deviation；

Wherein,

Δ (x, y)=d₀·Δn(x,y)

In formula, d₀For the average thickness of level crossing to be measured (13), and Δ n (x, y) non-all for optics to be measured Even property；

Step 6, the optical heterogeneity distribution obtaining level crossing to be measured (13):

6-1) determine and measure wavelength X with second time for the first time₁Corresponding wave front aberration difference DELTA W₁(x,y)

$\begin{array}{c}{\mathrm{\ΔW}}_1(x,y)=\frac{({\mathrm{\ΔW}}_{12}(x,y)-{\mathrm{\ΔW}}_{11}(x,y))}{2}\\ =n_{10}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{10}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

6-2) determine and measure wavelength X with second time for the first time₂Corresponding wave front aberration difference DELTA W₂(x,y)

$\begin{array}{c}{\mathrm{\ΔW}}_2(x,y)=\frac{{\mathrm{\ΔW}}_{22}(x,y)-{\mathrm{\ΔW}}_{21}(x,y)}{2}\\ =n_{20}[B(x,y)-A(x,y)]+d_0\·\mathrm{\Δn}(x,y)\\ =n_{20}\mathrm{\Δd}(x,y)+d_0\·\mathrm{\Δn}(x,y)\end{array}$

Wherein,

Δ d (x, y)=B (x, y)-A (x, y)

△ d (x, y) amounts of thickness variation for being caused by flat mirror to be measured (13) deformation；

6-3) determine level crossing to be measured (13) optical heterogeneity Δ n (x, y):

$\mathrm{\Δn}(x,y)=\frac{n_{20}\·{\mathrm{\ΔW}}_1(x,y)-n_{10}\·{\mathrm{\ΔW}}_2(x,y)}{d_0(n_{10}-n_{20})}.$