CN103376072B - Digital hologram is interfered and Frequency projected fringe duplex measurement system and method - Google Patents

Abstract

The invention discloses a kind of digital hologram to interfere and Frequency projected fringe duplex measurement system and method, belong to technical field of electro-optical measurement, comprise a set of continuous variable-angle digital holographic metrology device or become wavelength numeral holographic interference and a set of multistep Frequency projecting fringe measurement device, multistep Frequency projecting fringe measurement method measuring targets is first utilized to carry out bigness scale, obtain altitude range roughly, recycle continuous variable-angle digital holographic metrology device or become wavelength numeral holographic interference measuring targets and carry out accurate measurement, just can obtain the elevation information of object each point, the present invention treats the independent measurement of object each point in measuring process, without the need to the step of Carrier-smoothed code, can measure complex-shaped, there is the face shape parameter of the object of interruption, interfere with independent multistep Frequency projecting fringe measurement and continuous varied angle digital hologram or become wavelength numeral holographic interference and compare, simultaneously advantage to reach the requirement that measuring accuracy is high and measuring height variation range is large.

Description

Digital hologram is interfered and Frequency projected fringe duplex measurement system and method

Technical field

The invention belongs to technical field of electro-optical measurement, be specifically related to comprehensive measurement device and method that a kind of varied angle digital hologram continuously interferes (or becoming wavelength numeral holographic interference) and multistep Frequency projecting fringe measurement compound.

Background technology

Digital hologram interferometry is one and utilizes laser interference method to carry out the technology of measuring, have noncontact, measurement of full field, precision high, highly sensitive, measure the advantage such as easy rapidly, may be used for the measurement of the face shape parameters such as flatness, coplane degree, thickness, have broad application prospects in the field such as precision optical machinery, Aero-Space.

In existing digital hologram interferometry, digital hologram demodulates information method is divided into two kinds, and the first is phase shift demodulation method, phase-shifter is utilized to introduce known phase shift, obtaining the wrapped phase figure that object treats measurement information, then through removing parcel process mutually, obtaining the whole audience information of object.But when object complex-shaped, Carrier-smoothed code cannot carry out, institute in this way can only be applicable to simple shape object.The method of the phase demodulating that the paper " holographic phase-shifting technique is used for the three dimension profile measurement of object " delivered in " laser technology " as Lv Xiaoxu adopts.Second method is that JosephC.Marron is at United States Patent (USP) 5,926,277, " Methodandapparatusforthree-dimensionalimagingusinglaseri lluminationinterferometry " and MaterMichaelJ are at United States Patent (USP) 7, the multi-wavelength holographic interferometry method that 317,541 " Interferometrymethodbasedonthewavelengthdriftofanillumin ationsource " propose.This method utilizes tunable laser to produce the laser of multiple wavelength, using the known quantity of wavelength as interference information demodulation, by processing the interferogram under multiple wavelength illumination, obtains the face type information of object.Because holographic interference methods measurement range is little, the measurement requirement with discontinuous objects on a large scale cannot be met.

Projected fringe formula optical 3-dimensional topography measurement method has noncontact, measuring speed is fast, efficiency is high and the advantage such as non-destructive, but because its measuring basis is the periodic width of the striped be projected on object, so compare with optical interferometry, its measuring accuracy is lower.According to the different disposal method to projected fringe in existing projected fringe optical 3-dimensional topography measurement method, the methods such as Moire topography art, phase measuring profilometer (PMP), Fourier transform profilometry (FTP), Hilbert transform technology of profiling, wavelet transform profilometry can be categorized as.These methods are all the wrapped phase values obtaining object, then obtain the continuous phase place value corresponding with object height information by Phase-un-wrapping process, all need Phase-un-wrapping process.

For the most frequently used phase measuring profilometer, phase measuring profilometer relies on phase-shift method to obtain the wrapped phase figure of object, and recycling unwrapping algorithm obtains continuous print PHASE DISTRIBUTION figure.C.AllanHobson, explanation in the paper " TheapplicationofDigitalFilteringtoPhaseRecoverywhenSurfa ceContouringusingFringeProjectionTechniques " that JohnT.Atkinson and FrancisLilley delivers at periodical Opticsandlasersinengineering, if object under test is discontinuous or in the wrapped phase figure that obtains noise too many, be impossible obtain correct solution parcel result.Su Xianyu is published in the paper " Reliability-guidedPhaseunwrappingAlgorithm:Areview " of Opticsandlasersinengineering and mentions, and shade, modulation of fringes are too low, striped fracture, lack sampling etc. all can cause Phase-un-wrapping process to produce mistake.Most unwrapping algorithm all depends on path, and the Quality Map utilizing degree of modulation function to generate such as mentioned in Soviet Union aobvious Chongqing paper " Reliability-guidedPhaseunwrappingAlgorithm:Areview " carries out the Quality Map guiding method solution encapsulation process of separating parcel.So parcel figure cannot obtain good solution parcel result under comprising the situations such as shade, striped fracture and object discontinuous (there is sudden change).And current projected fringe face type measuring method mostly needs Carrier-smoothed code process, thus these methods are caused to be difficult to be applied to modal in engineering, to have isolated discrete regions object measurement.And its measuring accuracy is lower relative to holographic interferometry, but measurement range is large.

Summary of the invention

A kind of digital hologram is the object of the present invention is to provide to interfere and Frequency projected fringe duplex measurement system and method.

For achieving the above object, present invention employs following technical scheme.

A kind of digital hologram is interfered and Frequency projected fringe duplex measurement system, this duplex measurement system comprises digital hologram interferometric measuring means and striped produces optical devices, described digital hologram interferometric measuring means is continuous variable-angle digital holographic metrology device or becomes wavelength numeral holographic interference measuring device, striped produces optical devices and is connected with the computing machine of digital hologram interferometric measuring means, utilizes ccd video camera and the described computing machine composition multistep Frequency projecting fringe measurement device of striped generation optical devices, digital hologram interferometric measuring means.

It is projector that described striped produces optical devices.

Described duplex measurement system also comprises photoswitch, between the laser instrument that photoswitch is arranged at digital hologram interferometric measuring means and fiber optic splitter (whether photoswitch accesses light path to laser switches, without the need to Q-swith laser Q frequent because of measuring).

The measuring method of above-mentioned digital hologram interference and Frequency projected fringe duplex measurement system, comprises the following steps:

1) bigness scale amount: utilize multistep Frequency projecting fringe measurement device measuring targets to carry out measuring (concrete grammar is disclosed in application for a patent for invention 201210251114.4), obtains the face type information (the height distribution of low precision) of the low precision of object under test;

2) after step 1), utilize continuous variable-angle digital holographic metrology device or become wavelength numeral holographic interference measuring device, obtain the wrapped phase value of object under test under each angle or wavelength, the cosine of the wrapped phase value of certain point under each angle or wavelength on object under test is added the peak function of searching obtaining corresponding point, and (concrete grammar is disclosed in application for a patent for invention 201210006821.7, and CarlC.Aleksoff. " Multi-Wavelengthdigitalholographicmetrology. " Proc.SPIE6311, 6311D1-6311D7 (2006) .),

3) accurate measurement amount: carry out peak of function search to searching peak function according to step 1) gained face type information, after peak value searching process terminates, just obtains high-precision the type information (high-precision height distribution) of object under test.

The concrete steps of described step 3) are: a) according to the height value corresponding to object under test peak in the type information of step 1) gained face, determine certain some D on object under test ₁peak of function hunting zone, then calculate and put D in peak of function hunting zone ₁the value of searching independent variable corresponding when peak function obtains maximum value, calculate respectively in the value of these independents variable and step 1) gained face type information and correspond to a some D ₁the absolute error of height, the value of independent variable corresponding when absolute error is minimum is on object under test puts D ₁precise height; B) on measuring targets, every bit obtains corresponding precise height according to step a).

Or the concrete steps of described step 3) are: a) according to corresponding to certain some D on object under test in the type information of step 1) gained face ₁height, determine a D ₁peak of function hunting zone, then in peak of function hunting zone to a D ₁peak function of searching carry out peak of function search, obtain on object under test and put D ₁precise height; B) on measuring targets, every bit obtains corresponding precise height according to step a).

Described peak of function hunting zone is (H-x, H+x), and wherein x is for searching peak threshold value, and x value is for searching peak period of a function half-breadth, and H represents in the type information of step 1) gained face corresponding to a some D ₁height.

Search peak process for above-mentioned two kinds, the first needs the maximum point position in Continuous plus multiple cycle, and the second is then only search within the scope of one-period, and by contrast, it is long that the first searches peak method comparatively second method consuming time.Search in peak precision, two kinds of methods are completely the same.

Described peak function representation of searching is:

For continuous variable-angle digital holographic metrology device, search peak function as the formula (1):

$S\left(h\right)=\left|\frac{1}{K_1}\underset{k=1}{\overset{K_1}{\mathrm{\Σ}}}\exp \right\{[\frac{2\mathrm{\π}(h-h\cos {\mathrm{\θ}}_k)}{\mathrm{\λ}}+\mathrm{\Φ}\left({\mathrm{\θ}}_k\right)-\mathrm{\Θ}\left({\mathrm{\θ}}_k\right)]\×i\left\}\right|---\left(1\right)$

In formula (1), S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, and λ is laser wavelength, θ _kfor the angle of a kth change, Φ (θ _k) and Θ (θ _k) being respectively base plate interferogram corresponding under a kth angle and object interferogram, i represents complex unit, adopts K altogether ₁individual angle;

For change wavelength numeral holographic interference measuring device, search peak function as the formula (2):

$S\left(h\right)=\left|\frac{1}{K_2}\underset{k=1}{\overset{K_2}{\mathrm{\Σ}}}\exp \right[\frac{4\mathrm{\πh}}{{\mathrm{\λ}}_k}-\mathrm{\Θ}\left(k\right)]\·i|---\left(2\right)$

In formula (2), S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, λ _kfor a kth wavelength of laser instrument change, Θ (k) is object interferogram corresponding under a kth wavelength, and i represents complex unit, adopts K altogether ₂individual wavelength.

Beneficial effect of the present invention is embodied in:

The deficiency of (or becoming wavelength numeral holographic interference) measuring technique is interfered for existing projected fringe face type measuring technique and continuous varied angle digital hologram, the present invention proposes the method and apparatus that a kind of varied angle digital hologram continuously interferes the composite measurement of (or becoming wavelength numeral holographic interference) and multistep Frequency projecting fringe measurement phase compound, in measuring process, first utilize multistep Frequency projecting fringe measurement technology measuring targets to carry out bigness scale, obtain the general height scope of object each point, recycling bigness scale data interfere the peak step of searching of (or becoming wavelength numeral holographic interference) to instruct to continuous varied angle digital hologram, thus obtain the measuring accuracy of object height submicron order, the invention enables measurement range and measuring accuracy to be improved simultaneously.

Accompanying drawing explanation

Fig. 1 is one of present system structural drawing;

Fig. 2 is present system structural drawing two;

Fig. 3 is measurement procedure figure of the present invention;

Fig. 4 is that when utilizing continuous varied angle digital image holographic interferometry to measure, on object, certain puts the change curve of the composograph light intensity height utilizing formula (1) to obtain;

In figure: 1 is laser instrument, 2 is optical fiber, and 3 is fiber optic splitter, 4 is off axis paraboloid mirror calibration mirror, and 5 is optical fiber phase-shifter, and 6 is collimation lens set, 7 is fine angle inflector assembly, 8 is light-combining prism, and 9 is imaging len, and 10 is ccd video camera, 11 is computing machine, 12 is projector, and 13 is fixing plane mirror, and 14 is photoswitch.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

The invention provides the comprehensive measurement device that a kind of varied angle digital hologram continuously interferes (or becoming wavelength numeral holographic interference) and multistep Frequency projecting fringe measurement compound, comprise a set of continuous variable-angle digital holographic metrology subsystem (or becoming wavelength numeral holographic interference subsystem) and a set of multistep Frequency projecting fringe measurement subsystem, by computing machine, ccd video camera, projector, laser instrument (becoming in wavelength numeral holographic interference system is tunable laser), fiber optic splitter, optical fiber phase-shifter, fine angle inflector assembly (becoming in wavelength numeral holographic interference system is fixing plane mirror), collimation lens set, light-combining prism, imaging len, composition such as off axis paraboloid mirror calibration mirror and optical fiber etc.

Based on above-mentioned comprehensive measurement device, the present invention also provides a kind of varied angle digital hologram continuously to interfere the comprehensive measuring method of (or becoming wavelength numeral holographic interference) and multistep Frequency projecting fringe measurement compound, utilize multistep Frequency projected fringe method to carry out bigness scale amount to object, obtain general height distributed data.Compared with measuring method that multistep Frequency projecting fringe measurement method is interfered with continuous varied angle digital hologram (or becoming wavelength numeral holographic interference), multistep Frequency projecting fringe measurement method measurement range is large, but measuring accuracy is low.Continuous varied angle digital hologram is interfered (or becoming wavelength numeral holographic interference), and measurement range is little, but measuring accuracy is high.To search the algorithm at peak in continuous variable-angle digital holographic metrology method, the measurement range of continuous variable-angle digital holographic metrology method determines (as shown in Figure 4) by the distance between two tops, if certain point of object under test is highly more than the distance between two tops, when namely exceeding measurement range, search in peak process can find two or more top simultaneously, cannot determine that the real height of object is just reflected in the position at which top actually.So, the present invention proposes to carry out bigness scale with multistep Frequency projecting fringe measurement method measuring targets, thus obtain the general height distribution of object, the data that before then can utilizing in the search peak process of follow-up continuous varied angle digital hologram interference technique, bigness scale obtains to determine the height of the current measured point of object reflects (in as Fig. 4 A, B, C scope) by which peak value actually, thus obtain accurate measurement result.The method overcomes the not high problem of measuring accuracy in multistep Frequency projecting fringe measurement technology, also solve the problem that continuous varied angle digital hologram interferes the measurement range of (or becoming wavelength numeral holographic interference) measuring method too small simultaneously, measurement range and measuring accuracy are improved simultaneously.

After carrying out bigness scale to object height, the height distribution obtaining object general is designated as O ₁(x, y), continuous variable-angle digital holographic metrology needs utilization to search peak function, as the formula (1), to highly searching for, finally obtains the true altitude of object.

$S\left(h\right)=\left|\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\exp \right\{[\frac{2\mathrm{\π}(h-h\cos {\mathrm{\θ}}_k)}{\mathrm{\λ}}+\mathrm{\Φ}\left({\mathrm{\θ}}_k\right)-\mathrm{\Θ}\left({\mathrm{\θ}}_k\right)]\×i\left\}\right|---\left(1\right)$

Wherein, S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, and λ is laser wavelength, θ _kfor the angle of a kth change, Φ (θ _k) and Θ (θ _k) being respectively base plate interferogram corresponding under a kth angle and object interferogram, i represents complex unit, adopts K angle altogether.

Utilizing change wavelength numeral holographic interferometry to need utilization to search peak function, as the formula (2), to highly searching for, thus obtaining the true altitude of object.

$S\left(h\right)=\left|\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\exp \right[\frac{4\mathrm{\πh}}{{\mathrm{\λ}}_k}-\mathrm{\Θ}\left(k\right)]\·i|---\left(2\right)$

For formula (2), S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, λ _kfor a kth wavelength of laser instrument change, Θ (k) is object interferogram corresponding under a kth wavelength, and i represents complex unit, adopts K angle altogether.

All there will be phenomenon as shown in Figure 4 when being undertaken searching peak by formula (1) or formula (2), because formula (1) and formula (2) are one-period functions, periodically occur so top becomes.By the height value of measurement point corresponding to peak value in computerized algorithm search graph, the height to be measured of every bit just can be obtained.But, because top periodically occurs, cannot determine which peak value place to be actually only on object the true altitude of a bit, this just must limit to object height to be measured, cause when utilizing separately continuous varied angle digital hologram to interfere (or becoming wavelength numeral holographic interference) to measure, the problem that measurement range is less.

The idiographic flow of measuring method of the present invention is as follows:

1) utilize multistep Frequency projecting fringe measurement method to carry out bigness scale amount to object, obtain height distribution (concrete grammar is disclosed in application for a patent for invention 201210251114.4) that object is general;

2) utilize continuous variable-angle digital holographic metrology method (concrete grammar is disclosed in application for a patent for invention 201210006821.7) or change wavelength numeral holographic interferometry method and step 1) gained bigness scale data to carry out precision measurement to object, utilize bigness scale data to instruct continuous varied angle digital hologram interference or the peak value searching become in wavelength numeral holographic interference methods;

Due to used in step 1 and step 2 be same ccd video camera, so the image resolution ratio collected in two steps is identical, namely the picture point obtained in two kinds of measuring methods is one to one, utilize face type information of certain point on the object that obtains in step 1), correspond to step 2) in certain point after, a) according to the height value corresponding to object under test peak in the type information of step 1) gained face, certain some D on object under test is determined ₁peak of function hunting zone, then calculate and put D in peak of function hunting zone ₁the value of searching independent variable corresponding when peak function obtains maximum value, calculate respectively in the value of these independents variable and step 1) gained face type information and correspond to a some D ₁the absolute error of height, the value of independent variable corresponding when absolute error is minimum is on object under test puts D ₁precise height; B) on measuring targets, every bit obtains corresponding precise height according to step a).

3) instruct after peak value searching process terminates, just can obtain the accurate face type information of whole object.

The present invention can also adopt measurement procedure as described below: 1) first utilize multistep Frequency projecting fringe measurement method to carry out bigness scale (concrete grammar is disclosed in application for a patent for invention 201210251114.4) to object, obtain the approximate range (a certain scope in A, B, C as shown in Figure 4) of object point, 2) and then utilize continuous varied angle digital hologram to interfere (concrete grammar is disclosed in application for a patent for invention 201210006821.7) or change wavelength numeral holographic interferometry method to carry out peak value searching within the scope of this.

Be one-period function owing to searching peak function, so must determine which object point highly fall within, in this cycle, then search precise height that peak just can obtain this point of object in cycle.Due to step 1) and step 2) in used be same ccd video camera, so the image resolution ratio collected in two steps is identical, namely the picture point obtained in two kinds of measuring methods is one to one, utilize primary face type information H(height of certain point on the object that obtains in step 1)), correspond to step 2) in certain point after, at (H-x, H+x) in scope, object height is searched for, uniquely can obtain the precise height of this point of object, after this process is all done to object every bit, the final face type information of object can be obtained.Wherein x is for searching peak threshold value, and be used for determining to search the upper and lower bound at peak, x value is for searching peak period of a function half-breadth.

Combined measurement method of the present invention, overcome the low and continuous varied angle digital hologram of multistep Frequency projecting fringe measurement precision and interfere (or becoming wavelength numeral holographic interference) deficiency that measurement range is little, not only can realize the measuring accuracy of sub-micron, and large measurement range can be realized.And do not need Carrier-smoothed code, the compound system of formation can measure the object of complicated shape.

When adopting continuous varied angle digital hologram to interfere in system, laser instrument 1 is connected with fiber optic splitter 3 by optical fiber 2, optical fiber is divided into object light and reference light two-way light by fiber optic splitter 3, off axis paraboloid mirror calibration mirror 4 is set in the port of object light optical fiber, object light reflexes on testee through off axis paraboloid mirror calibration mirror 4, connecting fiber phase-shifter 5 on reference light optical fiber, collimation lens set 6 is connected at reference light fiber port place, reference light after expanding is radiated on the plane mirror that is connected with fine angle inflector assembly 7 of one side, the directional light of plane mirror reflection is through light-combining prism 8 and enter ccd video camera 10 after the object light of imaging len 9 is interfered, ccd video camera 10 is connected with computing machine 11, increase in addition and projector 12(striped generation optical devices are set), form one of duplex measurement system of the present invention as shown in Figure 1.

When adopting change wavelength numeral holographic interference in systems in which, the laser instrument in Fig. 1 is needed to become wavelength variable laser (tunable laser), the fixing plane mirror 13 of the plane mirror be connected with fine angle inflector assembly replaces, and namely forms the duplex measurement system two of the present invention shown in Fig. 2.

See Fig. 3, first object under test is placed, close photoswitch, open projector, first allow multistep Frequency projecting fringe measurement subsystem carry out bigness scale to object; Then open photoswitch, close projector, allow continuous variable-angle digital holographic metrology subsystem (or becoming wavelength numeral holographic interferometry subsystem) carry out accurate measurement; Then by composite algorism (utilizing the search peak step of bigness scale data to continuous varied angle digital hologram interference or change wavelength numeral holographic interference to instruct), carry out the compound of two kinds of method measurement results, obtain final measurement result.

The present invention treats the independent measurement of object each point in measuring process, without the need to the step of Carrier-smoothed code, can measure the face shape parameter of object that is complex-shaped, that have interruption.This method had both overcome the low shortcoming of projecting fringe measurement precision.Overcome again continuous varied angle digital hologram interfere or become the little shortcoming of wavelength numeral holographic interferometry height change scope.This method utilizes projecting fringe measurement device to carry out bigness scale, and measurement range can be made to expand; Utilizing projecting fringe measurement result to instruct the measuring process of digital hologram interferometry simultaneously, ultimate measurement accuracy can being made to carry out higher than only using projected fringe the result measured.This method is interfered with independent multistep Frequency projecting fringe measurement, continuously varied angle digital hologram or change wavelength numeral holographic interference is compared, and simultaneously advantage to reach the requirement that measuring accuracy is high and measuring height variation range is large.In mechanical measurement, if think acquisition high-precision measurement data, measurement range is inevitable very little, if think the measurement range that acquisition one is large, measuring accuracy just must be too high.And the present invention utilizes two kinds of method composite measurements, measurement range and measuring accuracy are all improved.

Claims (4)

1. a measuring method for digital hologram interference and Frequency projected fringe duplex measurement system, is characterized in that: comprise the following steps:

1) bigness scale amount: utilize multistep Frequency projecting fringe measurement device measuring targets to measure, obtain the face type information of the low precision of object under test;

2) through step 1) after, utilize continuous variable-angle digital holographic metrology device or become wavelength numeral holographic interference measuring device, obtain the wrapped phase value of object under test, the cosine of wrapped phase value is added and obtains searching peak function;

3) accurate measurement amount: according to step 1) gained face type information carries out peak of function search to searching peak function, obtains high-precision type information of object under test;

Described peak function representation of searching is:

For continuous variable-angle digital holographic metrology device, search peak function such as formula shown in (1):

$S\left(h\right)\left|\frac{1}{K_1}\underset{k=1}{\overset{K_1}{\Σ}}\exp \right\{\[\frac{2\mathrm{\π}(h-{\mathrm{hcos\θ}}_k)}{\mathrm{\λ}}+\mathrm{\Φ}\left({\mathrm{\θ}}_k\right)-\mathrm{\Θ}\left({\mathrm{\θ}}_k\right)\]\×i\left\}\right|---\left(1\right)$

In formula (1), S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, and λ is laser wavelength, θ _kfor the angle of a kth change, Φ (θ _k) and Θ (θ _k) being respectively base plate interferogram corresponding under a kth angle and object interferogram, i represents complex unit, adopts K altogether ₁individual angle;

For change wavelength numeral holographic interference measuring device, search peak function such as formula shown in (2):

$S\left(h\right)=|\frac{1}{K_2}\underset{k=1}{\overset{K_2}{\Σ}}\exp \[\frac{4\mathrm{\π}h}{{\mathrm{\λ}}_k}-\mathrm{\Θ}\left(k\right)\]\·i|---\left(2\right)$

In formula (2), S (h) is the relative intensity of certain some multi-frame interferometry figure synthesis on object, and h is the height of object, λ _kfor a kth wavelength of laser instrument change, Θ (k) is object interferogram corresponding under a kth wavelength, adopts K altogether ₂individual wavelength.

2. a kind of digital hologram is interfered and the measuring method of Frequency projected fringe duplex measurement system according to claim 1, it is characterized in that: described step 3) concrete steps be: a) according to step 1) correspond to the height value of object under test peak in the type information of gained face, determine object under test puts D ₁peak of function hunting zone, then calculate and put D in peak of function hunting zone ₁the value of searching independent variable corresponding when peak function obtains maximum value, calculate value and the step 1 of independent variable respectively) correspond to a some D in the type information of gained face ₁the absolute error of height, the value of independent variable corresponding when absolute error is minimum is on object under test puts D ₁precise height; B) on measuring targets, every bit a) obtains corresponding precise height according to step.

3. a kind of digital hologram is interfered and the measuring method of Frequency projected fringe duplex measurement system according to claim 1, it is characterized in that: described step 3) concrete steps be: a) according to step 1) put D corresponding on object under test in the type information of gained face ₁height, determine a D ₁peak of function hunting zone, then in peak of function hunting zone to a D ₁peak function of searching carry out peak of function search, obtain on object under test and put D ₁precise height; B) on measuring targets, every bit a) obtains corresponding precise height according to step.

4. a kind of digital hologram is interfered and the measuring method of Frequency projected fringe duplex measurement system according to claim 3, it is characterized in that: described peak of function hunting zone is (H-x, H+x), wherein x is for searching peak threshold value, x value is for searching peak period of a function half-breadth, and H represents step 1) correspond to a some D in the type information of gained face ₁height.