CN100464172C - Digitalized intervention phase difference magnification method - Google Patents

Abstract

This invention relates to digital interference phase difference amplifying method, which comprises the following steps: putting one mach to Chender interferometer; shooting one interference sample with carrier wave strips with general cameral by the interferometer; putting one phase difference sample in one arm of the interferometer and then shooting the interferometer sample of the carrier wave modulated by the sample; then putting two pieces of interference samples into the computer to process the Fourier conversion and filter and then line athwart conversion to get two phase difference information of the two interference samples; the two information are subtracted by each other and are amplified with N times.

Description

Digitalized intervention phase difference magnification method

Technical field

The present invention relates to phasic difference and amplify, particularly a kind of digitalized intervention phase difference magnification method, it has practical application widely in high-accuracy, large-aperture optical engineering detecting.

Background technology

It is a kind of means that improve phase discrimination rate and interferometry precision that phasic difference is amplified, and can be used to the distortion and because the system bits phase change that the change of thing field causes etc. of detection optical element or optical system.It mainly is to interfere mutually by the high order diffraction item of non-linear hologram to realize that traditional phasic difference is amplified, and is applied to fields such as optical holography, electronic holographic.In recent years, the digital holography fast development with photoelectric detector recorded holograms such as CCD, is used the computer realization Digital Reconstruction of Hologram, and whole process has more dirigibility, is more convenient for analyzing and detecting.

" the digital hologram double exposure phase difference amplification " of Chen Jianwen, Gao Hongyi, Xu Zhizhan invention, number of patent application 03129607.6 has been used for the detection optical corrugated effectively.Ordinary optical holographic phase difference amplifying technique, promptly use the phase information of object under the photographic plate recording, utilize diffraction principle to reconstruct the diffracted wave of their different diffraction level time then, allow their the overlapping interference of conjugate wave again, circulation so repeatedly obtains the high power phasic difference and amplifies.The digital hologram phase difference amplification has been inherited the basic thought of ordinary optical holographic phase difference amplifying technique, but different means have been adopted in record, storage and reconstruct to hologram, the first has replaced holographic dry plate as recording medium with the CCD charge-coupled device, the hologram that records is stored in the computing machine after digitized processing.It two is handle to replace optical diffraction with digital fourier transformation to finish the reconstruct of the thing field of being write down, by the hologram intensity distributions that is write down is made fast Fourier transformation operation, obtaining its spatial frequency spectrum distributes, therefrom separate and extract the frequency spectrum of thing light wave, through the inverse Fourier transform computing, just obtain thing multiplexed optical wave distribution of amplitudes again.

The COMPLEX AMPLITUDE of supposing the thing light wave is:

O(x，y)＝O ₀(x，y)exp[jφ ₀(x，y)]

In the formula, O ₀(x, y) and φ ₀(x, y) being respectively the amplitude of thing light wave on the record plane distributes mutually with the position, if certain reason: the distortion of optical system, electromagnetic field, thermal effect, gravity etc. cause object the position change mutually into φ ' (x, y), so new thing multiplexed optical wave distribution of amplitudes is:

O′(x，y)＝O ₀(x，y)exp[jφ ₀′(x，y)]

Two states before and after changing is done digital addition with double exposing to be recorded on the hologram, and then carry out digital fourier transformation and Filtering Processing, its superimposed light intensity distributions expression formula is:

$I(x,y)={|O(x,y)+O\′(x,y)|}^2=4O_0^2(x,y){\cos }^2\left[\frac{\mathrm{\φ}\′(x,y)-{\mathrm{\φ}}_0(x,y)}{2}\right]$

The numeral phase difference amplification, just the PHASE DISTRIBUTION function in the COMPLEX AMPLITUDE of thing field is multiplied by an integer factor, N for example, just phasic difference can be amplified N doubly, at this moment, fringe spacing representative be 2 π/N phase change, we can obtain more, abundant variation details more from stripe pattern like this.

The weak point of this method is to need reconstruction software and high-resolution ccd detector of a hologram, when enlargement factor is higher, the noise of CCD has also been amplified.

Summary of the invention

The technical problem to be solved in the present invention is to overcome above-mentioned the deficiencies in the prior art, and a kind of digitalized intervention phase difference magnification method is provided, and method is simple for this, surveys the corrugated shape with sensitivity, and its precision can be better than 1/500 wavelength.

Essence of the present invention is to utilize two interferograms, and from interferogram the fetch bit phase information, amplify then.This method is very easy, can be undertaken by following 5 steps:

1) builds a Mach-Chen Deer interferometer, i.e. M-Z interferometer;

2) on the M-Z interferometer, take an interference pattern that has carrier fringe with a common digital camera;

3) in an arm of M-Z interferometer, put into a position phase sample to be measured, take a carrier fringe of being modulated by sample again;

4) two interference patterns are input in the computing machine go, carry out Fourier transform filtering, carry out inverse transformation then, take out the phase information of two kinds of interference patterns;

Multiply by positive integer N again after two phase informations that 5) will take out subtract each other and amplify, the span of this N is 1～1000.

The present invention compares the advantage that is had with technology formerly:

1) though what adopt is interference technique fetch bit phase information, do not have specific (special) requirements, promptly possess the characteristics of hologram-interferometer, just can obtain the detection of very high degree of precision with common interferometer for the optical element in the M-Z interferometer.

2) owing to do not adopt conventional holography method to carry out the phasic difference amplification, therefore do not need special software, and test corrugated bore can be very big, for example bore can be up to more than the 500mm.

3) can test various optical devices in this way, between integrated mill and compact car, can reequip any interferometer and implement, application prospect is infinitely wide.

Embodiment

The invention will be further described below in conjunction with embodiment, but should not limit protection scope of the present invention with this.

The present invention is undertaken by following 5 steps:

1) builds a M-Z interferometer;

2) on this M-Z interferometer, take an interference pattern that has carrier fringe with a common digital camera;

3) in an arm of M-Z interferometer, put into a position phase sample to be measured, take the interference pattern of a carrier fringe of being modulated by sample again;

4) two interference patterns are input in the computing machine go, carry out Fourier transform filtering, carry out inverse transformation then, take out the phase information of two kinds of interference patterns;

5) amplify after computing machine two phase informations that will take out subtract each other, enlargement factor can reach 100～1000 times again, the phase information that just can obtain to amplify.

Set forth its principle of work below:

According to the interference strength formula, the intensity distributions of interference figure can be write as:

I(x，y)＝a(x，y)+b(x，y)cos(2πf ₀x+φ(x，y)) (1)

Wherein, we suppose that carrier fringe is parallel to the y axle.So-called carrier fringe is not exactly when placing testing sample, by the interference fringe that interferometer directly obtains, f ₀Be carrier frequency, f ₀=1/d, d are the spacing of carrier fringe.(x is that (x y) is bias light intensity to a, and (x y) is the contrast of image to b because testing sample makes the phase migration of incident X-rays ripple generation y) to φ.By following formula as can be known, interference figure is that the position of object distributes mutually to be superimposed upon on the carrier fringe and forms, and corresponding to the circle of equal altitudes that the object position distributes mutually, promptly the position of object distributes mutually and makes carrier fringe generation deviation.

Interference figure is that the position of sample distributes and the carrier fringe formation that is superimposed mutually.The position that obtains sample distributes mutually, needs to eliminate earlier the carrier fringe on the interference figure.Below we provide a kind of Fourier transformation method and achieve this end, this method only is applicable to phase migration φ, and (x is y) less than the situation of 2 π.

We are rewritten into following exponential form with (1) formula:

I(x，y)＝a(x，y)+c(x，y)exp(i2πf ₀x)+c ^*(x，y)exp(-i2πf ₀x)

Wherein

$c(x,y)=\frac{1}{2}b(x,y)\exp \left(\mathrm{i\φ}(x,y)\right)---\left(2\right)$

(1) formula is carried out one-dimensional Fourier transform to be obtained:

$I_F(f,y)=a_F(f,y)+c_F(f-f_0,y)+c_F^{*}(f+f_0,y)---\left(3\right)$

From following formula as can be known, the sharp-pointed crest of three apart from each others can appear in interference field in Fourier's frequency domain, and their distances each other are f ₀That crest of the left side and that crest of the right correspond respectively to the 3rd and second of (2) formula, have only these two crests to include the position phase distributed intelligence of object under test.We can take out that crest on the right separately, and to the inverse Fourier transform that it makes one dimension obtain c (x, y), the position that just can obtain object according to (2) formula distributes mutually again, with the position multiplication by constants factor N that distributes mutually, the position is amplified N times mutually so, N is a positive integer.

Claims (1)

1. digitalized intervention phase difference magnification method is characterized in that this method comprises following 5 steps:

1) builds a Mach-Chen Deer interferometer;

2) on this Mach-Chen Deer interferometer, take an interference pattern that has carrier fringe with a common digital camera;

3) in an arm of this Mach-Chen Deer interferometer, put into a position phase sample to be measured, take the interference pattern of a carrier fringe of being modulated by sample again;

4) two interference patterns are input in the computing machine go, carry out Fourier transform and filtering, carry out inverse transformation then, promptly obtain the phase information of two interference patterns;

5) multiply by positive integer N again after computing machine two phase informations that will take out subtract each other and amplify, just obtained to have amplified N phasic difference information doubly.