CN1563917A - Moire filtering synthetic process for digital moire phase shifting interference tech - Google Patents
Moire filtering synthetic process for digital moire phase shifting interference tech Download PDFInfo
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Abstract
The invention includes following procedures: removing background (DC component) of virtual interference fringe and actual interference fringe respectively; carrying out morie synthetic method including digital multiplication and superposition; removing background interference fringe from morie fringe; extending bandwidth of morie fringe; simplified lowpass filtering process for saving time of filtering process in order to obtain morie interference fringe in sine distribution in real time through hardware.
Description
Affiliated technical field
The present invention is a kind of More's filtering synthetic method that is used for digital More's movable phase interfere art, belongs to optical measurement and Flame Image Process
Technical field.
Background technology
Numeral More interferometry is the interference technique that a kind of new development is got up, its principle is to utilize computing machine to calculate interferogram (virtual interfere figure) according to the light path and the complicated tested corrugated of standard of actual interferometer, when actual detected, gather the interferogram (actual interferogram) of the actual tested corrugated formation of actual interferometer in real time, with the synthetic Moire fringe that obtains of this two width of cloth interferogram More, thereby realize the directly relevant of complicated corrugated, and can Real Time Observation and employing digital phase shift method fast processing Moire fringe.This digital More's movable phase interfere art is mainly used in directly and complicated standard corrugated occasion relatively.As: aspheric surface detects, and optical system is debug, the detection of aspects such as profile measurement and structural mechanics, fluid mechanics, thermodynamics.
Numeral More interferometry requires the energy Real Time Observation and handles Moire fringe, and therefore requiring More's Moire fringe intensity distributions synthetic and that filtering speed is quick and filtering is later is cosine distribution, and Moire fringe density is enough big, to increase the measurement range on corrugated.The numeral synthetic method is actual interference fringe numeral to be gathered become digital quantity, and the More is synthetic with the digital computation realization, specifically is divided into two kinds of methods of hardware and software digital processing again, synthesizes because speed limit is made numeral with hardware usually.Moire fringe after synthetic also will be made Filtering Processing, can do digital phase shift and calculate.
The virtual interfere striped:
I
R(x，y)＝a+bcos[2πf+
R(x，y)] (1)
Actual interference fringe:
I
0(x，y)＝c(x，y)+d(x，y)cos[2πf+
0(x，y)] (2)
Usually the synthetic Moire fringe that two stripeds directly multiplied each other, its light distribution is
I
m(x，y)＝A(x，y)+B(x，y)cos[2πf+
R(x，y)]+C(x，y)cos[2πf+
0(x，y)]+
(3)
D(x，y)cos[
R(x，y)-
0(x，y)]+D(x，y)cos[4πf+
R(x，y)+
0(x，y)]
(3) in the formula, the 4th D (x, y) cos[
R(x, y)-
0(x, y)] be Moire fringe, be Useful Information, other several need filtering to remove.Second and the 3rd is the background interference striped, and its bandwidth and the 4th differ not very big, makes to be difficult to leach the 4th fast simply, perhaps will limit the bandwidth of the 4th Moire fringe, thus the measurement range of dwindling the corrugated.Therefore, its wavefront measurement scope of existing More's synthetic method is still waiting to improve.
More's filtering synthetic method that the present invention proposes, its purpose are directly to remove second and the 3rd in (3) formula when synthesizing Moire fringe, promptly remove the background interference striped that is superimposed upon in the Moire fringe, measure the corrugated bandwidth to increase, and are convenient to digital filtering; Revise first and improved the signal to noise ratio (S/N ratio) of signal, thereby improve the precision that Moire fringe is handled in phase shift to improve the contrast of Moire fringe.
Summary of the invention
Adopt virtual interfere striped and actual interference fringe to go background (DC component) respectively, and then More's synthetic method of digital multiply stack, remove the background interference striped in the Moire fringe, the bandwidth of expansion Moire fringe, simplify low-pass filtering treatment, save the Filtering Processing time, make the hardware real-time Moire fringe that obtains Sine distribution fast.
More's filtering synthetic method principle is for to remove the background (DC component) in virtual interfere striped and the actual interference fringe respectively, thereby removes cross term in the Moire fringe after synthetic, to reach the purpose of removing the background interference striped.
The present invention is achieved in that
The digital picture formula (1) of virtual interfere striped is deducted a to be become:
I′
R(x，y)＝bcos[2πf+
R(x，y)] (4)
With the digital picture formula (2) of actual interference fringe deduct c (x y) becomes:
I′
0(x，y)＝d(x，y)cos[2πf+
0(x，y)] (5)
To remove two width of cloth image digitizations after the background multiplies each other and obtains Moire fringe
Following formula has negative intensity level, can not more can't directly show as the light distribution expression formula of Moire fringe, need fill suitable DC component (or background), to increase the contrast of Moire fringe as far as possible.In the ideal case, the amplitude factor of Moire fringe is 1/2 of a direct current background, thus DC component numerical value should be bd (x, y).Moire fringe I ' then
mFor
(7) formula is reduced to
I '
m(x, y)=A ' (x, y)+D ' (x, y) cos[
R(x, y)-
0(x, y)]+D ' (x, y) cos[4 π f+
R(x, y)+
0(x, y)] (8) have removed second and the 3rd background striped in (3) formula in (8) formula, (8) second (Moire fringe) is bigger with the 3rd band separation in the formula, cutoff frequency that can corresponding raising low-pass filtering, thereby the bandwidth of corresponding increase Moire fringe has also promptly increased the measurement range on tested corrugated.Improved simultaneously the effect of filtering again and shortened the filtering time, be convenient to real-time Moire fringe demonstration and phase shift Moire fringe and handle.
The fringe contrast of actual interferogram is often less than 1, just d (x, y)＜c (x, y).(3) in the formula
A(x，y)＝ac(x，y) (9)
D(x，y)＝1/2bd(x，y) (10)
D (x, y)/(x, y)＜1/2, contrast is lower than theoretical value to A.
In the formula (8)
A′(x，y)＝bd(x，y) (11)
D′(x，y)＝1/2bd(x，y) (12)
D ' (x, y)/(x, y)=1/2, contrast reaches theoretical value to A ', so the Moire fringe contrast in (8) formula will be higher than the represented Moire fringe of (3) formula.Thereby increased signal intensity, helped improving phase shift More processing accuracy.
When stating principle on the implementation, a, b, c (x, y) and d (x, numerical value y) determine very crucial, because the virtual interfere striped is the interferogram that a numerical evaluation goes out, a and b can be that available constant is represented uniformly.And the c in the actual interferogram (x, y) and d (x, y) with regard to complexity how, (x y) is influenced by the inhomogeneous and system's veiling glare of illuminating bundle mainly to c.D (x, y) main with two to restraint the coherence of the beam intensity ratio of coherent lights and laser instrument relevant.In addition, c (x, y) and d (x, numerical stability y) is relevant with the power stability of laser instrument, if adopt frequency stabilization power stabilize laser instrument, then c (x, y) and d (x, numerical stability y) still is higher, can think constant substantially.If (x y) can be used as constant and handles the even c of illumination, and (x y) also can think a constant to d.Because actual interferogram striped is very close, (x y) can adopt the method that the each point light intensity is averaged on the interferogram to try to achieve to c.
(x y) is calculated by formula (4) d
I wherein
0maxAnd I
OminBe light path maximal value and the minimum value in the actual interferogram.If illumination unevenness is similar to actual interference field light distribution because of the reference path light distribution, gather the light distribution I that the interferometer reference path is returned in advance
r(x y), and obtains correction factor as normalized
I in the formula
RmaxBe maximal value in the reference light distribution.Light intensity value I with actual interferogram
0(x, y) divided by K (x y) then obtains the uniform interferogram of a width of cloth, the computing method formula during then with even illumination obtain c (x, y) and d (x, y).
After c and d determine, just can realize that the digital filtering of Moire fringe is synthetic.
Virtual interfere figure goes DC terms a to finish in advance, as long as optical interference circuit is determined, (x y) also determines with regard to corresponding K, also can measure in advance, c (x, y) and d (x y) can calculate by the actual interferogram of first pilot production one width of cloth, also is constant to tested corrugated c and the d that determines, they can be existed in the internal memory, when actual measurement, c be deducted from actual interferogram in real time.
For improving processing speed, remove c, the More is synthetic, mend A ' (x, y) and process such as spatial domain smothing filtering to realize with hardware.
Effective benefit of the present invention is:
1, is simple and easy to realize.More's filtering synthetic method is simple and easy to realize, goes the background interference stripe effect remarkable.
2, expanded the measurement range of Moire measuring method.Improve the cutoff frequency of low-pass filtering, simplified filtering method, can expand the measurement range of Moire measuring method simultaneously.
Description of drawings
Fig. 1 is the digital filtering synthetic schemes of Moire fringe of the present invention
Fig. 2 is actual interference fringe pretreatment process figure.
The present invention is further described below in conjunction with the drawings and specific embodiments:
The More's filtering synthetic method that is used for digital More's movable phase interfere art, realize in the following manner:
Synthetic for ease of More's filtering in real time, in advance pre-service is done in actual interference fringe collection, obtaining the correlation parameter of actual interference fringe, and then gather the correlation parameter that actual interference fringe utilization measures in advance, it is synthetic to carry out More's filtering.
Actual interference fringe often light intensity is inhomogeneous, needs that actual interference fringe is made homogenising and handles.With reference to light intensity, it is similar to the interference field light distribution in elder generation's collection interferometer, can it calculate the uneven correction factor of correction light intensity,
I
r(x y) is the reference path light distribution, I
Rmax(x y) is the light intensity maximal value.Actual interference fringe light intensity I with this collection
0(x, y) (x y) just obtains the actual interference fringe I ' of light intensity homogenising divided by K
0(x, y).Its background (DC component) c (x, y) and amplitude d (x y) all can think constant c and d, and c is I '
0(x, mean value y),
A ' (x, y)=bd, with c, d, A ' stores as the stand-by parameter that the More synthesizes, and the preprocessing process of actual interference fringe is finished.
After actual interference fringe pre-service work was finished, the actual interference fringe parameter that available pre-service obtains was done the synthetic calculating of More's filtering.Respectively with virtual interfere striped subtracting background a and actual interference fringe subtracting background c, the result that the two is subtracted each other multiplies each other and does More's stack then, fill direct current background A ' again, obtain removing the Moire fringe of background interference striped, by the low-pass filtering treatment in spatial domain, just obtain having only the Moire fringe of cosine light distribution.
The advantage that the present invention has is: More's filtering synthetic method is simple and easy to realize, goes the background interference stripe effect remarkable. Improve The cut-off frequency of LPF, simplify filtering method, can expand the measurement category of Moire measuring method simultaneously. For hardware is realized In real time Moire fringe filtering is laid a good foundation.
Claims (3)
1. More's filtering synthetic method that is used for digital More's movable phase interfere art, it is characterized in that: adopt virtual interfere striped and actual interference fringe to go background (DC component) respectively, and then More's synthetic method of digital multiply stack, remove the background interference striped in the Moire fringe, the bandwidth of expansion Moire fringe, simplify low-pass filtering treatment and save the Filtering Processing time, make the hardware real-time Moire fringe that obtains Sine distribution fast.
2. a kind of More's filtering synthetic method that is used for digital More's movable phase interfere art as claimed in claim 1, it is characterized in that: this method realizes by following concrete computing method step: gather in the interferometer earlier with reference to light intensity, it is similar to the interference field light distribution, can it calculate the uneven correction factor of correction light intensity
I
r(x y) is the reference path light distribution, I
Rmax(x y) is the light intensity maximal value.Actual interference fringe light intensity I with this collection
0(x, y) (x y) just obtains the actual interference fringe I ' of light intensity homogenising divided by K
0(x, y).Its background (DC component) c (x, y) and amplitude d (x y) all can think constant c and d, and c is I '
0(x, mean value y),
A ' (x, y)=bd, with c, d, A ' stores as the stand-by parameter that the More synthesizes, and the preprocessing process of actual interference fringe is finished.
3. a kind of More's filtering synthetic method that is used for digital More's movable phase interfere art as claimed in claim 1 is characterized in that: the actual interference fringe parameter of utilizing pre-service to obtain, do the synthetic calculating of More's filtering.Respectively with virtual interfere striped subtracting background a and actual interference fringe subtracting background c, the result that the two is subtracted each other multiplies each other and does More's stack then, fill direct current background A ' again, obtain removing the Moire fringe of background interference striped, by the low-pass filtering treatment in spatial domain, just obtain having only the Moire fringe of cosine light distribution.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106931905A (en) * | 2017-03-09 | 2017-07-07 | 北京理工大学 | A kind of digital Moiré patterns phase extraction method based on nonlinear optimization |
| CN107388963A (en) * | 2017-07-13 | 2017-11-24 | 北京理工大学 | The digital Moiré patterns phase extraction method that wavelet analysis and LPF are combined |
| CN108562240A (en) * | 2018-01-24 | 2018-09-21 | 北京理工大学 | Splice the digital Moire phase-shifting interference measuring method of method based on two step carrier waves |
| CN109186497A (en) * | 2018-10-30 | 2019-01-11 | 北京理工大学 | Spectrum aliasing noise minimizing technology in the digital Moire phase shift interferometry of Newton iteration |
| CN111238397A (en) * | 2020-02-10 | 2020-06-05 | 北京理工大学 | Transient digital Moire phase-shifting interferometry device and method for optical element surface shape |
-
2004
- 2004-04-22 CN CNB2004100339873A patent/CN100491938C/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106931905A (en) * | 2017-03-09 | 2017-07-07 | 北京理工大学 | A kind of digital Moiré patterns phase extraction method based on nonlinear optimization |
| CN106931905B (en) * | 2017-03-09 | 2019-02-05 | 北京理工大学 | A kind of digital Moiré patterns phase extraction method based on nonlinear optimization |
| CN107388963A (en) * | 2017-07-13 | 2017-11-24 | 北京理工大学 | The digital Moiré patterns phase extraction method that wavelet analysis and LPF are combined |
| CN108562240A (en) * | 2018-01-24 | 2018-09-21 | 北京理工大学 | Splice the digital Moire phase-shifting interference measuring method of method based on two step carrier waves |
| CN108562240B (en) * | 2018-01-24 | 2019-08-23 | 北京理工大学 | Digital Moire phase-shifting interference measuring method based on two step carrier waves splicing method |
| CN109186497A (en) * | 2018-10-30 | 2019-01-11 | 北京理工大学 | Spectrum aliasing noise minimizing technology in the digital Moire phase shift interferometry of Newton iteration |
| CN109186497B (en) * | 2018-10-30 | 2019-11-26 | 北京理工大学 | Spectrum aliasing noise minimizing technology in the digital Moire phase shift interferometry of Newton iteration |
| CN111238397A (en) * | 2020-02-10 | 2020-06-05 | 北京理工大学 | Transient digital Moire phase-shifting interferometry device and method for optical element surface shape |
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