CN101049232B - Method and device for scanning optical fault image - Google Patents

Abstract

An optical laminagraphic image-scanning method for testing a medium includes such steps as providing the low-homology light beams with frequency associated photon pair, focusing said light beams at different positions with different depths in the medium, reflecting by said medium to obtain the lift beam of signal, and analyzing the signal by a signal processing unit to obtain the laminagraphic image of said medium. Its apparatus is also disclosed.

Description

Optical fault image scan method and device thereof

[technical field]

The present invention relates to a kind of fault image scanning means and method thereof, particularly relate to a kind of optical fault image scan method and device thereof.

[background technology]

Optics people having the same aspiration and interest fault image scanning means (Optical CoherenceTomography, OCT) be to use at present at ophthalmology, department of dermatologry, cardiovascular and the quite useful fault image scanning means of other relevant medical diagnosis, because it can provide the diagnosis various diseases required clear fault image (sectionalimage), and compared with the medical science of other non-intrusion types according to the shadow technology, for example the computer fault image scans (Computer Tomography, CT), magnetic radiography (the Magnetic Resonance Imaging that shakes, MRI) with ultrasound (ultrasound) etc., OCT can provide better spatial resolution.

Basically, OCT is to use the McKesson interferometer of low same tone (low coherence) light source.The optical path difference (optical path difference) of McKesson interferometer between signal beams and reference beam interfered less than people having the same aspiration and interest length (coherence length) Shi Caihui of light source, again because OCT uses low same tone light source, so people having the same aspiration and interest length is very short, therefore signal beams and the optical path difference between reference beam of OCT must just can interfere forr a short time, with the reflected image in the acquisition people having the same aspiration and interest length, so the shorter then longitudinal resolution of people having the same aspiration and interest length better.

Consult Fig. 1, existing OCT is applicable to and measures a medium 11, and comprises a light source 12, a beam splitter (beam splitter) 13, one reflecting mirror 14, a condenser lens 15, a photodetector 161 and a signal processing unit 162.

Light source 12 is launched the light beam of a low same tone.Beam splitter 13 is disposed on the bang path of light beam, in order to being received from the light beam that light source 12 penetrates, and divides light component not advance through a signal beams 101 and a reference beam 102 of different bang paths light beam.

Reflecting mirror 14 is disposed on the bang path of reference beam 102, and can be driven and move around, and the reference beam 102 that penetrates from beam splitter 13 in order to reflection.And condenser lens 15 is disposed on the bang path of signal beams 101, in order to being received from the signal beams 101 that beam splitter 13 penetrates, and signal beams 101 is focused on the surface or the inner a certain fixed point of medium 11.

Signal processing unit 162 is electrically connected with photodetector 161, be reflected after mirror 14 reflection reference beam 102 and passed through beam splitter 13 once more by the signal beams 101 after medium 11 reflections, incide photodetector 161 then, transform the light beam into electronic signal by photodetector 161, signal processing unit 162 then is to obtain the fault image of medium 11 in order to the analytical electron signal.

From the signal beams 101 of medium 11 reflection is a plurality of depth locations reflections from medium 11, so change the light path (optical path) of reference beam 102 by mobile mirror 14, can obtain the interference signal of different depth, obtain the fault image of medium 11 whereby.That is to say, when reference light beam 102 and from the optical path difference of 101 of the signal beams of a certain degree of depth reflection of medium 11 during less than the people having the same aspiration and interest length of light source 12, just produce the interference signal of interfering and obtaining, analyzing behind the signal that each degree of depth obtains, just can piece together out the three-dimension disclocation image of medium 11.

Therefore, the longitudinal resolution of fault image is the people having the same aspiration and interest length decision by light source 12, just the shorter then longitudinal resolution of people having the same aspiration and interest length better, lateral resolution then is the numerical aperture (NumericalAperture by condenser lens 15, NA) decision, the light beam that uses numerical aperture to heal after 15 focusing of high condenser lens is littler, and lateral resolution just better.

Consult Fig. 2, but because the depth of field (depth of field) of the higher condenser lens 15 of numerical aperture is shorter, then depart from the obvious variation of lateral resolution of the fault image that focus obtained of condenser lens 15 a little.So as Fig. 3, general OCT still is to use the condenser lens 15 of the about 20 times low numerical aperture of enlargement ratio, makes the depth of field enough long, can remain in the depth of field to guarantee people having the same aspiration and interest lock (coherencegate) always.

General normal use super brightness diode (Super LuminescentDiode, SLD) as light source 12, then longitudinal resolution is approximately 10～15 μ m, such resolution can only be distinguished the variation on the kenel that kenel and disease caused of biological tissue's level, but as if the optical section of desiring to reach real (optical biopsy), just want to diagnose pathological changes, then need the resolution of 1 μ m grade (order) just can reach at least as biological cell levels such as cancers.

In order to improve longitudinal resolution, the most direct method just is to use the wideer light source of frequency range 12, the shorter light source 12 of people having the same aspiration and interest length just, for example use the locked mode titanium sapphire laser, then its vertically and lateral resolution can reach 1.5 μ m and 3 μ m respectively, yet this laser system optical required precision height is not suitable for being used in medical clinic applications.

Another method then is to use the condenser lens 15 of high-NA to improve lateral resolution, and cooperate a pin hole (pinhole), so-called optical people having the same aspiration and interest microscopy (optical coherence microscopy just, OCM), when people having the same aspiration and interest lock and by condenser lens 15 and the formed confocal lock of pin hole (confocal gate) when same depth location is overlapping, have only from medium 11 and can pass through pin hole at the light of the focus place of condenser lens 15 reflection, the reflected light of other positions in medium 11 then can't pass through because of the formed spatial filtering lock of pin hole (spatial filtering gate), therefore can reach the longitudinal resolution of 1 μ m grade.And because use white light, so can in the darker high scattering medium of the degree of depth, obtain high-resolution fault image than general confocal microscope.

Yet the condenser lens 15 that uses high-NA needs people having the same aspiration and interest lock and confocal lock overlapping always, and best signal is just arranged, so will make the mode that longitudinal scanning just need the use dynamic focusing, people having the same aspiration and interest lock can be moved with confocal lock.

When condenser lens 15 is moved around, the also same moved further of reflecting mirror 14, but during as if the refractive index heterogeneity in the medium 11, not only move the light path that changes signal beams 101 because of condenser lens 15, condenser lens 15 focuses on the light path that different refractivity place in the medium 11 also can change signal beams 101 with signal beams 101, then reflecting mirror 14 is not only wanted same moved further, on the bang path of reference beam 102, also need to place the refractive index compensator (compensator) identical, so that the optical path difference between two light beams can be less than the people having the same aspiration and interest length of light source 12 with the refractive index of medium 11.But the change of refractive of medium 11 because can't know for sure can only be with proximate refractive index refractive index as compensation.

No matter be because use the condenser lens 15 of high-NA, or because signal beams 101 enters the aberration (aberration) and dispersion differences (dispersion) that medium 11 causes than the depths, the capital causes signal beams 101 asymmetric with the light path of reference beam 102, and make the ripple bag (wave packet) of interference signal widen, cause the resolution variation.

Moreover, because medium 11 can scattered signal light beams 101, especially when medium 11 is high scattering thing, can cause the reflected light of other depth locations in medium 11 also can pass through pin hole, cause the signal to noise ratio (snr) of interference signal to descend, thereby reduce the quality of fault image.

[summary of the invention]

The object of the present invention is to provide and a kind ofly reduce scattering effect and reduce aberration simultaneously and dispersion differences and can improve the optical fault image scan method and the device thereof of the vertical and horizontal resolution fault image of imaging in higher scattering medium

Another object of the present invention is to provide a kind of optical fault image scan method and the device thereof that can offset aberration and dispersion differences automatically.

Another purpose of the present invention is to provide a kind of optical fault image scan method and device thereof that system sets up degree of difficulty that reduce.

So optical fault image scanning means of the present invention is applicable to measuring media, it is characterized in that:

This device comprises a double frequency light beam generation unit, a relaying beam splitter, a condenser lens and a signal processing unit.

This double frequency light beam generation unit is launched the interrelated photon of bifrequency to light beam, and comprises that one receives and reflect the reflecting mirror of the light beam that penetrates from this beam splitter in order to the light source of launching low same tone light beam, respectively in order to the beam splitter and two that is received from the light beam beam split that polarizer that this light beam that this light source penetrates and modulation become line polarization light beam, will be by polarizer.To after two light beams of described mirror reflects pass through this beam splitter once more, two light beam bang paths be overlapped respectively.Wherein a reflecting mirror is to be driven and with fixed frequency vibration, and the position of this two-mirror is to make optical path difference between described light beam less than the people having the same aspiration and interest length of this light source.

This relaying beam splitter is in order to being received from the interrelated photon of bifrequency that this double frequency light beam produces to light beam, and with the light beam beam split.

This condenser lens can be driven and move, be the bifrequency photon that penetrates from this relaying beam splitter in order to receiving unit to light beam, and described light beam focused on this medium.Described light beam by this dieletric reflection after and become signal beams, and incide this condenser lens and this relaying beam splitter again.

This signal processing unit receives also analyzes the described signal beams that penetrates from this relaying beam splitter, obtaining the fault image of this medium, and comprises that one is positioned at pin hole on the focus of these lens in order to the lens and that focus on described signal beams.

So optical fault image scan method of the present invention is applicable to measuring media, it is characterized in that:

The method includes the steps of:

(A) provide the interrelated photon of bifrequency to low same tone light beam, and the optical path difference between described light beam is less than the people having the same aspiration and interest length of described light source, and wherein the frequency of a light beam is that reflecting mirror by a vibration changes because of Doppler effect.

(B) described light beam is focused on different depth position in this medium with the optics co-route, then described light beam by this dieletric reflection after and become the signal beams of difference interference, and can reduce scattering effect, dispersion differences and aberration to improve the fault image quality.

(C) by the described signal beams that comprises after signal processing unit analysis that lens and are positioned at the pin hole on the focus of these lens is by this dieletric reflection, to obtain the high spatial resolution fault image of this medium.

The present invention adopts difference interference (heterodyne interference) principle, the aberration and the dispersion differences of the identical light beam of bang path are cancelled out each other automatically, and see through mobile focusing lens and make longitudinal scanning, the reduction system sets up degree of difficulty, and the condenser lens that can use high-NA solves problem vertical in the past, that lateral resolution can't be taken into account whereby to obtain the fault image of high lateral resolution.In addition, the present invention is applicable especially to measure high scattering medium, on the one hand because the interrelated low same tone photon of bifrequency to depolarisation effect in scattering medium; And because of using low same tone light beam, then the low people having the same aspiration and interest bifrequency photon through scattering can't produce interference to light beam, reduces scattering effect whereby.On the one hand signal beams is filtered the signal beams of the out of focus plane reflection of condenser lens again through lens focus by pin hole again, also can reduce scattering effect and obtain the fault image of high longitudinal resolution.

[description of drawings]

Below in conjunction with drawings and Examples optical fault image scan method of the present invention and device thereof are elaborated:

Fig. 1 is a sketch map, and existing optics people having the same aspiration and interest fault image scanning means is described.

Fig. 2 is a sketch map, illustrates that the depth of field of condenser lens of a high-NA of existing optics people having the same aspiration and interest fault image scanning means is shorter.

Fig. 3 is a sketch map, illustrates that the depth of field of condenser lens of a low numerical aperture of existing optics people having the same aspiration and interest fault image scanning means is longer.

Fig. 4 is a sketch map, and first preferred embodiment of optical fault image scan method of the present invention and device thereof is described.

Fig. 5 is a sketch map, but the fault image of the Phase delay of this first preferred embodiment slotted line polarization birefringent medium is described.

Fig. 6 is a sketch map, and second preferred embodiment of optical fault image scan method of the present invention and device thereof is described.

Fig. 7 is a sketch map, and the 3rd preferred embodiment of optical fault image scan method of the present invention and device thereof is described.

Fig. 8 is a sketch map, the 4th preferred embodiment of bright optical fault image scan method of the present invention and device thereof.

Fig. 9 is a sketch map, and the condenser lens depth of field of high-NA that optical fault image scan method of the present invention and device thereof be described is short but people having the same aspiration and interest lock is longer.

[specific embodiment]

About aforementioned and other technology contents, characteristics and effect of the present invention, in the detailed description of following cooperation four embodiment with reference to the accompanying drawings, can clearly present.

For convenience of description, in following embodiment, components identical is represented with identical label.

Consult Fig. 4, first preferred embodiment of optical fault image scan method of the present invention and device thereof comprises a double frequency light beam generation unit 3, a relaying beam splitter 41, a condenser lens 42 and a signal processing unit 5.

Double frequency light beam generation unit 3 comprises for example super brightness diode (SLD) of a low same tone light source 31, can adjust the polarizer (polarizer) 32 of polarizing angle to produce 45 ° of line polarization light beams by one, by a polarization light beam splitter (Polarizing Beam Splitter, PBS) 33 ' ' line polarization light beam is divided into parallel polarization (p-polarization) light beam and vertical polarization (s-polarization) light beam, hereinafter to be referred as P ripple and S ripple, the S ripple is through quarter-wave plate (the Quarter Wave Plate of azimuth (azimuth angle) 45 °, QWP) become round polarization light beam after 36, reflecting mirror 341 via the vibration back and forth because of piezo-activator (PieZo-electric Transduceractuator, PZT actuator) reflects and generation Doppler (Doppler) frequency shift (FS) Δ ω again _DAnd can pass polarization light beam splitter 33 ' by becoming the P ripple behind the quarter-wave plate 36 once more ', at this moment, the P wave frequency has become ω ₁=ω ₀+ Δ ω _D, ω ₀Mid frequency for light source 31, originally by polarization light beam splitter 33 ' ' become round polarization light beam behind the then same quarter-wave plate 36 of the P ripple that penetrates through 45 ° at azimuth, reflected by fixed reflecting mirror 342 again, and become the S ripple through behind the quarter-wave plate 36 once more, because of not having Doppler effect, then S wave frequency ω ₂=ω ₀, and at polarization light beam splitter 33 ' ' reflection, overlap with the P ripple and form bifrequency (ω ₁, ω ₂) interrelated and orthogonal line polarization photon is to low same tone light beam.But not as limit, the light beam that penetrates from double frequency light beam generation unit 3 also can be oval polarization light beam or circle polarization light beam, or the non-polarization light beam.

Moreover the position of reflecting mirror 341,342 must make optical path difference between light beam less than the people having the same aspiration and interest length of light source 31.And in the present embodiment, reflecting mirror 341 is to see through piezo-activator and produce vibration, and piezo-activator is again that the function generator of more vairable (function generator) that sent fixed frequency signal drives and makes Δ ω _DImmobilize, but, also can use additive method to make reflecting mirror 341 vibrations cause same effect not as limit.

In the present embodiment, for measuring high scattering medium 2, therefore the superhigh brightness LED that uses low same tone to obtain high-resolution fault image, still not as limit, also can be other low same tone light sources as light source 31.And if non-scattering medium 2, then can use high same tone light source.

In the present embodiment, the polarised direction of polarizer 32 all differs 45 degree with X-axis as shown in Figure 4 and Y-axis, and polarization light beam splitter 33 ' ' can penetrate and vertical polarization beam reflection for parallel polarization light beam.But the polarised direction of polarizer 32 also can be other directions, and polarization light beam splitter 33 ' ' also can be to penetrate and parallel polarization beam reflection for vertical polarization light beam.

Then, the bifrequency photon moves around through relaying beam splitter 41 with respect to medium 2 to light beam and focuses on the imaging plane in the scattering medium 2 with the condenser lens 42 that carries out longitudinal scanning and tool high-NA and reflection, and the signal beams of reflection is again via condenser lens 42 and relaying beam splitter 41 reflection and incident signal processing units 5.By the polarization visual analysor 57 that can adjust polarised direction angle θ s, lens 51 and pin hole 52, again by a difference interference electronic signal that photodetector 53 receives and produces.

The definition of polarizing angle θ s is that the polarised direction of polarization visual analysor 57 and X-axis as shown in Figure 4 differ θ s degree, and differs (90-θ s) degree with Y-axis.

Lens 51 can focus on signal beams, and pin hole 52 then is positioned on the focus of lens 51, to filter out in medium 2 and to be positioned at the signal beams of the out of focus plane reflection of condenser lens 42.

The difference interference electronic signal is passed through one with difference frequency (beatfrequency) Δ ω then _DFor the band filter of mid frequency (Band PassFilter, BPF) 54, the difference interference electronic signal that is produced can be write as

I _sig(Δωt)＝γA _pA _ssin2θ _scos(Δωt+δ _p-δ _s)，

Difference frequency $\mathrm{\Δ}{\mathrm{\ω}}_D={\mathrm{\ω}}_0\·\frac{v}{c},$ The Homological Algebra of light source 31 (coherencefunction) $\mathrm{\γ}=\exp [-{\left(\frac{2\mathrm{\Δl}\sqrt{\ln 2}}{l_{\mathrm{\ω}}}\right)}^2],$ The speed of the reflecting mirror 341 of vibration $v=\frac{\∂\left(\mathrm{\Δl}\right)}{\∂t},$

Δ l is the displacement of the reflecting mirror 341 of vibration, and Δ l also is the optical path difference of bifrequency photon to light beam simultaneously, l _wBe the people having the same aspiration and interest length of light source 31, A _pWith A _sThen be respectively the amplitude of parallel and vertical polarization signal beams, ω ₀The mid frequency of the light beam of being launched for light source 31, c is the light velocity, δ _pWith δ _sBe respectively the phase place of parallel and vertical polarization signal beams, again because the bang path of parallel and vertical polarization signal beams is identical, so δ _p=δ _s, then

Then with filtered electronic signal after a linear amplifier (linearamplifier) 55 amplifies, the amplitude and the phase contrast of reuse demodulator (demodulator) 56 picked up signal light beams, or utilize Xi Baite conversion (Hilbert transform) to be presented in the two-dimentional display with the demodulation of difference interference electronic signal and with amplitude size and phase signal with the computer software method.

In the present embodiment, demodulator 56 is lock-in amplifier (lock-inamplifier), but also can replace with other electronic installations.

When medium 2 is made tomoscan, can be by horizontal move media 2 so that light beam focus on a certain position of medium 2, mobile focusing lens 42 just carries out longitudinal scanning with the signal beams of the different depth that obtains same lateral attitude then.Utilize signal processing unit 5 to analyze the signal beams of the different longitudinal position reflection in medium 2 again, with the amplitude and the phase contrast of the signal beams that obtains each position, again the information of each position is pieced together vertical (X-Z) fault image that can obtain medium 2 at last.In like manner also can fix same lengthwise position to do lateral attitude scanning and obtain laterally (X-Y) tomography and sweep image.

Because the bifrequency polarized photon is to by scattering medium 2 time, by difference interference efficient (heterodyne efficiency) to the sensitivity of direction of beam propagation and the depolarization phenomenons such as (depolarization) of 2 pairs of polarized lights of scattering medium, produce difference interference because of the existence of polarization visual analysor 57, can significantly reduce scattering effect, therefore it is right to utilize polarization visual analysor 57 to filter the polarized photon of large angle scatterings, and can form polarization screening lock (polarization gating) and people having the same aspiration and interest lock (coherencegating) with generation difference interference signal.Effectively collect more weak scattering photon to (weak scattering photon-pair), can improve signal signal to noise ratio (Signal to Noise Ratio, SNR) and promote the quality of scan-image.

Therefore, compare with general OCT or OCM imaging in scattering medium, this first preferred embodiment imaging in scattering medium 2 has the ability of higher oppressive multiple scattering photon to (multiple scattering photon-pairs), have simultaneously and collect the ability of weak scattering photon preferably (weak scatteringphoton-pairs), and can obtain SNR preferably, this all is to propagating with co-route in scattering medium 2, so produce the edge of difference interference signal because of the bifrequency polarized photon.

In addition, dispersion differences, aberration etc. do not match the wavefront that causes problem on deformation also because of the bifrequency polarized photon to simultaneously in medium 2, propagating and can significantly offset with co-route, therefore this first preferred embodiment can imaging in high scattering medium 2, and preferable image quality arranged, particularly can have concurrently simultaneously and vertically reach lateral resolution, can have scanning lateral fault image (sectioningimage simultaneously, x-y scan) and the fault image ability of longitudinal tomography image (tomography, x-z scan).And the P ripple of other light paths such as scattering and S ripple are all because of the restriction of hanging down same tone light source 31, make that the polarized photon in people having the same aspiration and interest regional extent can not utilize band filter 54 to remove to all can't effectively producing the difference interference signal, to reach the purpose of fault image.

Consult Fig. 5, when having the optical characteristics of line polarization birefringence (birefringence), can again utilize a reference beam 74 more to obtain Phase delay (phase retardation) δ=δ of medium 2 as if medium 2 _P1-δ _S1Fault image.The light beam that part is penetrated from relaying beam splitter 41 is as reference light beam 74, and reference beam 74 to pass an azimuth be θ _rPolarization visual analysor 43 back difference interferences take place, and then incident one photodetector 44 and be converted into electronic signal I _r(Δ ω t) ≈ A _pA _sCos (Δ ω t).And signal beams 76 also passes an azimuth is θ _sPolarization visual analysor 81 incident one photodetector 82 again.Then,, just can obtain the fault image of the Phase delay of medium 2 to analyze the phase contrast between signal beams by the electronic signal of a signal processing unit 83 analytic signal light beams 76 with reference beam 74.Signal processing unit 83 can be lock-in amplifier or differential amplifier (Differential Amplifier, DA).Advantage with differential amplifier is, its SNR height and speed are fast, and reference beam 74 can be expressed as I _r≈ A _P2A _S2Sin2 θ rcos (Δ ω t), signal beams 76 can be expressed as Is ≈ A _P1A _S1Sin2 θ scos (Δ ω t+ δ _P1+ δ _S1), by adjusting θ _rAnd θ _sAngle can make K=A _P1A _S1Sin2 θ s=A _P2A _S2Sin2 θ r, the electronic signal after then handling via differential amplifier can be expressed as

$\mathrm{\&Delta;I}=I_s-I_r=2K\sin (\frac{{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">p</figure-callout>}1}}{2}-\frac{{\mathrm{\&delta;}}_{s1}}{2})\sin \left(\mathrm{\&Delta;\&omega;t}\right)\&ap;K({\mathrm{\&delta;}}_{p1}-{\mathrm{\&delta;}}_{s1})\sin \left(\mathrm{\&Delta;\&omega;t}\right)$

Then by the amplitude K (δ of electronic signal _P1-δ _S1) can obtain Phase delay δ=δ _P1-δ _S1, the detailed technology means see also applicant's No. 89104991 patent application case in Taiwan and the patent case of U.S.'s certificate number 7006562.

Consult Fig. 6, the different polarization directions of the light beam that this double frequency light beam generation unit 30 is launched that are with this first preferred embodiment of second preferred embodiment of optical fault image scan method of the present invention and device thereof are parallel to each other.

The relative X-axis in azimuth that makes polarizer 32 is 0 ° and produces parallel polarization light beam P ripple, reflects with the reflecting mirror 341 of PZT vibration and the reflecting mirror 342 of fixed position via beam splitter 33 beam split and process, and produces the P ripple that bifrequency is parallel to each other, (P ₁(ω ₁) and P ₂(ω ₂)), incide in the medium 2.Again via relaying beam splitter 41 reflection, incide in the photodetector 53 through lens 51 and pin hole 52 again and produce the difference interference electronic signal.

In the present embodiment, the polarised direction of polarizer 32 is identical with X-axis as shown in Figure 5, so light beam 71 is parallel polarization light beam, but also can be other line polarization light beams.

Consult Fig. 7, the different light beams of launching from this double frequency light beam generation unit 3 ' that are with this first preferred embodiment of the 3rd preferred embodiment of optical fault image scan method of the present invention and device thereof are the line polarization (P that is parallel to each other ₁(ω ₁)+P ₂(ω ₂)).

The quarter-wave plate 35 that the azimuth is 45 ° becomes two dextrorotation polarization light beams with the P ripple modulation that is parallel to each other, but also the line polarization light beam modulation that is parallel to each other can be become two left-handed polarization light beams, incide then in the medium 2, by quarter-wave plate 35 two dextrorotation polarization light beams are changed into the S ripple that is parallel to each other again through reflection, and at the 41 ' reflection of polarization light beam splitter and scioptics 51 and pin hole 52 arrival photodetectors 53 generation difference interference signals.

In the present embodiment, the polarised direction of polarizer 32 is identical with X-axis as shown in Figure 6, so light beam is parallel polarization light beam, and polarization light beam splitter 41 ' can penetrate and vertical polarization beam reflection for parallel polarization light beam, and quarter-wave plate 35 can become dextrorotation polarization light beam with parallel polarization light beam modulation.But the polarised direction of polarizer 32 also can be other directions, and polarization light beam splitter 41 ' also can be to penetrate and parallel polarization beam reflection for vertical polarization light beam.41 ' also can replace with the non-polarization beam splitter.

Consult Fig. 8, be different with this first preferred embodiment of the 4th preferred embodiment of optical fault image scan method of the present invention and device thereof is respectively a dextrorotation polarization light beam and a left-handed polarization light beam from the light beam that this double frequency light beam generation unit 30 ' is launched, and adds that differential amplifier 65 promotes sensitivity to reach the raising signal to noise ratio.

With SLD is light source 31, is in order to reach the purpose of line polarization in conjunction with a polarizer 32.Light beam is via a polarization light beam splitter 33 ' ' beam split, principle with first preferred embodiment forms bifrequency and the low same tone light beam of orthogonal line polarization, be to become a double-frequency dextrorotation polarization and a left-handed polarization light beam behind 45 ° the quarter-wave plate 37 through the azimuth together, be called for short R ripple and L ripple, via a condenser lens that can scan 42 R ripple and L ripple focused on medium 2 and reflection again.Then dextrorotation and left-handed signal beams can be expressed as respectively

$A_R\left(\begin{array}{c}1\\ -i\end{array}\right)e^{{\mathrm{i\&delta;}}_R}{e}^{{\mathrm{i\&omega;}}_{0}t}=[A_R{e}^{{\mathrm{i\&delta;}}_{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">R</figure-callout>}}}\left(\begin{array}{c}1\\ 0\end{array}\right)-i{A}_R{e}^{{\mathrm{i\&delta;}}_R}\left(\begin{array}{c}0\\ 1\end{array}\right)]e^{{\mathrm{i\&omega;}}_{0}t}$ With

$A_L\left(\begin{array}{c}1\\ i\end{array}\right)e^{{\mathrm{i\&delta;}}_L}{e^{\mathrm{i\&Delta;\&omega;t}}e}^{{\mathrm{i\&omega;}}_{0}t}=[A_L{e}^{i(\mathrm{\&Delta;\&omega;t}+{\mathrm{\&delta;}}_L)}\left(\begin{array}{c}1\\ 0\end{array}\right)+i{A}_L{e}^{i(\mathrm{\&Delta;\&omega;t}+{\mathrm{\&delta;}}_L)}\left(\begin{array}{c}0\\ 1\end{array}\right)]e^{i({\mathrm{\&omega;}}_0+\mathrm{\&Delta;}{\mathrm{\&omega;}}_D)t}$

A _RWith A _LBe respectively the amplitude of dextrorotation and left-handed signal beams, δ _RWith δ _LThen be respectively the phase place of dextrorotation and left-handed signal beams, ω ₀The mid frequency of the light beam of being launched for this light source 31, Δ ω _DIt then is difference frequency.

The signal beams of reflection is being received and is producing difference interference by relaying beam splitter 41 and polarized light beam splitter 61 backs by two photodetectors 62, by polarized light beam splitter 61 R is involved P wave component (P in the L ripple ₁+ P ₂) and S wave component (S ₁+ S ₂) be input to two photodetectors 62 respectively and form the difference interference signal magnitude and be

${\mathrm{<figure-callout\; id="1"\; label="I\; P"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">I</figure-callout>}}_{P_{}}\left(\mathrm{\&Delta;\&omega;t}\right)={|A_R{e}^{{\mathrm{i\&delta;}}_R}{e}^{{\mathrm{i\&omega;}}_{0}t}+A_L{e}^{{\mathrm{i\&delta;}}_L}{e}^{i({\mathrm{\&omega;}}_0+\mathrm{\&Delta;}{\mathrm{\&omega;}}_D)t}|}^2={A_{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">R</figure-callout>}}}^2+{A_{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">L</figure-callout>}}}^2+2A_R{A}_L\cos (\mathrm{\&Delta;\&omega;t}+\mathrm{\&delta;})$

$I_{S_1+S_2}\left(\mathrm{\&Delta;\&omega;t}\right)={|A_R{e}^{{\mathrm{i\&delta;}}_R}{e}^{{\mathrm{i\&omega;}}_{0}t}-A_L{e}^{{\mathrm{i\&delta;}}_L}{e}^{i({\mathrm{\&omega;}}_0+\mathrm{\&Delta;}{\mathrm{\&omega;}}_D)t}|}^2={A_{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="S06174677520060515E000022.png,S06174677520060515E000031.png"\; state="\{\{state\}\}">R</figure-callout>}}}^2+{A_L}^2-2A_R{A}_L\cos (\mathrm{\&Delta;\&omega;t}+\mathrm{\&delta;})$

δ=δ _R-δ _L, again because dextrorotation is identical with the bang path of left-handed signal beams, so δ _R=δ _L, then δ ≌ 0.

In the present embodiment, polarized light beam splitter 61 can penetrate and vertical polarization beam reflection for parallel polarization light beam, but also can be to penetrate and parallel polarization beam reflection for vertical polarization light beam.

The difference interference signal passes through with Doppler frequency shifted by delta ω respectively again _DTwo band filters 63 for mid frequency.Then other light path comprises that the R ripple of scattering and L ripple all can't effectively produce the difference interference signal because of SLD for low same tone light source 31, therefore can utilize band filter 63 filtration difference interference signals and improve signal to noise ratio.

Then amplify the difference interference signal respectively by two linear amplifiers 64, again the difference interference signal is input to differential amplifier 65 and subtracts each other and amplify twice, because system satisfies the condition of balanced detector (balance detector), so can significantly reduce background noise, increase signal intensity simultaneously, the SNR of elevator system, then the signal of differential amplifier 65 outputs can be expressed as I _Out(Δ ω t)=4A _RA _LCos (Δ ω t+ δ) again via amplitude demodulator 66, will vertically reach the transversal scanning fault image and be presented on the two dimensional display.

In like manner, if medium 2 is when having the optical characteristics of round polarization birefringence (circularbirefringence), δ=δ then _R-δ _LTherefore can be expressed as the Phase delay that round polarization is produced in medium 2, can add to analyze a reference beam 75 again, it is 0 ° polarization visual analysor 43 by the azimuth and connects photodetector 44, and can produce difference interference reference beam I _r(Δ ω t) ≈ A _RA _LCos (Δ ω t).By phase demodulator 66, the electronic signal of analytic signal light beam and reference beam 75 just can obtain the fault image of the round polarization birefringent phase delay δ of medium 2 equally.

Conclude above-mentioned, optical fault image scan method of the present invention and device thereof use the interrelated low same tone photon of bifrequency right, and the right frequency of photon has certain difference frequency to exist, and can obtain to improve simultaneously in scattering medium 2 fault image of the depth resolution and the lateral resolution of three-dimension disclocation image.In addition, because of the twice light beam simultaneously with path incident medium 2 altogether, then dispersion differences and aberration problem nature such as do not match is cancelled each other because of difference interference, therefore when doing tomoscan, does not need to know in advance dispersion differences that medium 2 causes and aberration and can compensate automatically.Screen the existence of lock, space people having the same aspiration and interest lock (spatialcoherence gating), time people having the same aspiration and interest lock (temporal coherencegating) and pin hole 52 formed spatial filtering locks (spatialfiltering gating) simultaneously because of polarization, and can significantly reduce scattering effect, improve vertically and transverse spatial resolution.Again because be to make longitudinal scanning by condenser lens 42, with decision longitudinal scanning position, just confocal lock (confocalgating) is always in time people having the same aspiration and interest lock interscan (as Fig. 9), and the degree of difficulty that can the reduction system sets up, the system that makes does not need to adopt the mode of dynamic focusing, obtains the vertically fault image of (axial direction) scanning easily.And the present invention also can be parallel to each other or orthogonal bifrequency polarization photon to Phase delay carry out fault image scanning, and then obtain for example Phase delay fault image of birefringence optics characteristic, and Doppler's fault image, can reach purpose of the present invention really.

Claims (30)

1. an optical fault image scan method is applicable to measuring media, it is characterized in that:

The method includes the steps of:

A, provide two light beams of the interrelated photon of bifrequency, and the optical path difference between described light beam is less than the people having the same aspiration and interest length of light source, and wherein a light beam produces frequency change by the reflecting mirror of a vibration to low same tone;

B, described light beam is focused on different depth position in this medium with the optics co-route, then described light beam by this dieletric reflection after and become the signal beams of difference interference, and can reduce scattering effect, dispersion differences and aberration to improve the fault image quality; And

C, by the described signal beams of a signal processing unit analysis after, to obtain the high spatial resolution fault image of this medium by this dieletric reflection.

2. optical fault image scan method as claimed in claim 1, it is characterized in that: among this step C, if this medium has line polarization or circle polarization birefringent characteristic,, can obtain the fault image of the Phase delay of medium by the phase contrast between a differential amplifier analytic signal light beam.

3. optical fault image scan method as claimed in claim 1, it is characterized in that: among this step C, can obtain the phase contrast of described signal beams by this signal processing unit, then if this medium has a flow velocity, just can be via the phase contrast time differential of calculating described signal beams, to obtain the flow velocity fault image of this medium.

4. optical fault image scan method as claimed in claim 1 is characterized in that: this step B focuses on described light beam with respect to the condenser lens that this medium moves around being driven.

5. optical fault image scan method as claimed in claim 1 is characterized in that: in this steps A, described light beam is the non-polarization light beam.

6. optical fault image scan method as claimed in claim 1 is characterized in that: in this steps A, the polarization direction of described light beam is parallel to each other.

7. optical fault image scan method as claimed in claim 6 is characterized in that: this steps A comprises: steps A 1 becomes line polarization light beam with a light beam modulation; Steps A 2 becomes two wires polarization light beam with this line polarization light beam beam split; Steps A 3 reflects described line polarization light beam respectively by two-mirror, one of them of described reflecting mirror is to be driven and with fixed frequency vibration, and the position of described reflecting mirror is to make optical path difference between described line polarization light beam less than the people having the same aspiration and interest length of this light beam; And steps A 4 overlaps the bang path of described line polarization light beam.

8. optical fault image scan method as claimed in claim 1 is characterized in that: in this steps A, described light beam is two circle polarization light beams.

9. optical fault image scan method as claimed in claim 8 is characterized in that: this steps A comprises: steps A 1 becomes line polarization light beam with a light beam modulation; Steps A 2 becomes two wires polarization light beam with this line polarization light beam beam split; Steps A 3 reflects described line polarization light beam respectively by two-mirror, one of them of described reflecting mirror is to be driven and with fixed frequency vibration, and the position of described reflecting mirror is to make optical path difference between described line polarization light beam less than the people having the same aspiration and interest length of this light beam; Steps A 4 becomes circle polarization light beam with described line polarization light beam modulation, and this step B comprises: the described round polarization light beam of step B1 focuses on this medium; The described round polarization light beam of step B2 by this dieletric reflection after and become signal beams; The described signal beams of step B3 is become line polarization signal beams by modulation.

10. as claim 6 or 8 described optical fault image scan methods, it is characterized in that: this step C comprises: step C1 GRIN Lens focuses on described signal beams, after the described signal beams that filters from the out of focus plane reflection of this condenser lens; Step C2 converts described signal beams to electronic signal; Step C3 only allows the difference frequency of described light beam pass through to this electronic signal filtering; Step C4 amplifies this electronic signal; And amplitude and the phase contrast of this electronic signal of step C5 demodulation to obtain described signal beams.

11. optical fault image scan method as claimed in claim 1 is characterized in that: in this steps A, the polarization direction of described light beam is vertical mutually.

12. optical fault image scan method as claimed in claim 11 is characterized in that: this steps A comprises: steps A 1 becomes line polarization light beam with a light beam modulation; Steps A 2 becomes a vertical polarization light beam and a parallel polarization light beam with this line polarization light beam beam split; Steps A 3 should become circle polarization light beam by the parallel polarization light beam with this of vertical polarization light beam modulation respectively; Steps A 4 reflects described round polarization light beam respectively by two-mirror, one of them of described reflecting mirror is to be driven and with fixed frequency vibration, and the position of described reflecting mirror is to make optical path difference between described round polarization light beam less than the people having the same aspiration and interest length of this light beam; Reach steps A 5 and make described round polarization light beam be become parallel polarization light beam and vertical polarization light beam, and bang path overlaps by modulation.

13. optical fault image scan method as claimed in claim 11 is characterized in that: this step C comprises: step C1 makes described signal beams produce difference interference; Step C2 GRIN Lens focuses on described signal beams, after the described signal beams that filters from the out of focus plane reflection of this condenser lens; Step C3 converts described signal beams to electronic signal; Step C4 only allows the difference frequency of described light beam pass through to this electronic signal filtering; Step C5 amplifies this electronic signal; And amplitude and the phase contrast of this electronic signal of step C6 demodulation to obtain described signal beams.

14. optical fault image scan method as claimed in claim 1 is characterized in that: in this steps A, described light beam is respectively a dextrorotation polarization light beam and a left-handed polarization light beam.

15. optical fault image scan method as claimed in claim 14 is characterized in that: this steps A comprises: steps A 1 becomes line polarization light beam with a light beam modulation; Steps A 2 becomes a vertical polarization light beam and a parallel polarization light beam with this line polarization light beam beam split; Steps A 3 should become circle polarization light beam by the parallel polarization light beam with this of vertical polarization light beam modulation respectively; Steps A 4 reflects described round polarization light beam respectively by two-mirror, one of them of described reflecting mirror is to be driven and with fixed frequency vibration, and the position of described reflecting mirror is to make optical path difference between described round polarization light beam less than the people having the same aspiration and interest length of this light beam; Steps A 5 makes described round polarization light beam be become parallel polarization light beam and vertical polarization light beam by modulation respectively, and bang path overlaps; Reach steps A 6 this parallel polarization light beam is become dextrorotation polarization light beam with one of them modulation of this vertical polarization light beam, and another modulation becomes left-handed polarization light beam.

16. optical fault image scan method as claimed in claim 14 is characterized in that: this step C comprises: step C1 becomes one to have two kinds of frequencies and the vertical polarization light beam and of difference interference has two kinds of frequencies and the parallel polarization light beam of difference interference described signal beams beam split; Step C2 becomes electronic signal with described vertical polarization light beam with described parallel polarization Beam Transformation respectively; Step C3 only allows the difference frequency of described light beam pass through to this electronic signal filtering; Step C4 amplifies described electronic signal respectively; Step C5 subtracts each other described electronic signal, to increase signal to noise ratio; And amplitude and the phase contrast of this electronic signal of step C6 demodulation to obtain described signal beams.

17. an optical fault image scanning means is applicable to measuring media, it is characterized in that: this device comprises:

One double frequency light beam generation unit, launch the interrelated photon of bifrequency to light beam, and the polarizer, that the light source, that comprises an emission light beam becomes line polarization light beam with this light beam modulation is the beam splitter of this light beam beam split and two reflecting mirror of folded light beams respectively, and then described light beam overlaps through the bang path behind this beam splitter once more; Wherein a reflecting mirror is to be driven and with fixed frequency vibration, and the position of this two-mirror is to make optical path difference between described light beam less than the people having the same aspiration and interest length of this light source;

One relaying beam splitter is received from the described light beam that the beam splitter of this double frequency light beam generation unit penetrates, and with each light beam beam split;

One condenser lens can be driven and moves, and will focus on this medium from the described light beam that this relaying beam splitter penetrates; Described light beam by this dieletric reflection after and become signal beams, and this condenser lens of incident and this relaying beam splitter again; And

One signal processing unit is analyzed the described signal beams that penetrates from this relaying beam splitter, to obtain the fault image of this medium.

18. optical fault image scanning means as claimed in claim 17, it is characterized in that: this double frequency light beam generation unit comprises that also one is disposed at the quarter-wave plate between this relaying beam splitter and this condenser lens, and this relaying beam splitter is a polarization light beam splitter, and this quarter-wave plate is that the described light beam modulation that this relaying beam splitter certainly penetrates is become dextrorotation polarization light beam or left-handed polarization light beam.

19. optical fault image scanning means as claimed in claim 17 is characterized in that: this signal processing unit comprises that lens, that one on the bang path that is disposed at described signal beams in regular turn focuses on described signal beams are positioned at the pin hole and a photodetector, a band filter that is electrically connected with this photodetector, a linear amplifier that is electrically connected with this band filter and a demodulator that is electrically connected with this linear amplifier on the focus of these lens.

20. optical fault image scanning means as claimed in claim 17, it is characterized in that: this double frequency light beam generation unit also comprises the quarter-wave plate of the two described light beams that penetrate in order to the beam splitter that is received from this double frequency light beam generation unit respectively, and the beam splitter of this double frequency light beam generation unit is a polarization light beam splitter, the beam splitter of this double frequency light beam generation unit matches this light beam beam split is become a vertical polarization light beam and a parallel polarization light beam with polarizer, and described quarter-wave plate should become circle polarization light beam by the parallel polarization light beam with this of vertical polarization light beam modulation respectively.

21. optical fault image scanning means as claimed in claim 20 is characterized in that: this signal processing unit comprises that one on the bang path that is disposed at described signal beams in regular turn can adjust the pin hole and a photodetector, a band filter that is electrically connected with this photodetector, a linear amplifier that is electrically connected with this band filter and a demodulator that is electrically connected with this linear amplifier on the focus that lens, that the polarization visual analysor of polarizing angle, focuses on described signal beams are positioned at these lens.

22. optical fault image scanning means as claimed in claim 17, it is characterized in that: this double frequency light beam generation unit also comprises the quarter-wave plate of a vertical polarization light beam with this of this parallel polarization light beam that penetrates in order to the beam splitter that is received from this double frequency light beam generation unit, this parallel polarization light beam is become dextrorotation polarization light beam with one of them of this vertical polarization light beam by this quarter-wave plate modulation, and another person's modulation becomes left-handed polarization light beam.

23. optical fault image scanning means as claimed in claim 22, it is characterized in that: this signal processing unit comprises a polarized light beam splitter and two photodetectors on the bang path that is disposed at described signal beams, two band filters that are electrically connected with described photodetector respectively, two linear amplifiers that are electrically connected with described band filter respectively, one differential amplifier that is electrically connected with described linear amplifier and a demodulator that is electrically connected with this differential amplifier, this polarized light beam splitter becomes a vertical polarization light beam and a parallel polarization light beam with each signal beams beam split.

24. as claim 21 or 23 described optical fault image scanning means, it is characterized in that: this optical fault image scanning means also comprises a polarization visual analysor and a photodetector that is electrically connected with this signal processing unit, and part is this photodetector of incident after the described light beam that this relaying beam splitter penetrates passes this polarization visual analysor.

25. as claim 17 or 18 or 20 or 22 described optical fault image scanning means, it is characterized in that: this light source is high same tone light source.

26. as claim 17 or 18 or 20 or 22 described optical fault image scanning means, it is characterized in that: this light source is low same tone light source.

27. optical fault image scanning means as claimed in claim 26 is characterized in that: this light source is a superhigh brightness LED.

28. as claim 17 or 18 or 20 or 22 described optical fault image scanning means, it is characterized in that: this condenser lens can be driven and move around with respect to this medium.

29. as claim 17 or 18 or 20 or 22 described optical fault image scanning means, it is characterized in that: this double frequency light beam generation unit comprises that also one of them a piezo-activator and that drives described reflecting mirror drives the function generator of more vairable of this piezo-activator.

30. as claim 19 or 21 or 23 described optical fault image scanning means, it is characterized in that: this demodulator is a lock-in amplifier.

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