It uses technology of analyse of layer of optical be concerned with the fundamental of smooth interferometer of weak be concerned with, detect the back that biology organizes different deepness layer to face light of incident weak be concerned with to reflection or signal of a few scattering, pass scanning, attainable biology organizes 2 dimension or three-dimensional structure image.

 

Compare other a few into like the technology, exceed acoustic imaging, nuclear magnetic resonance to become for example picture (fault of computer of ray of MRI) , X- (CT) , OCT technology is had compare high resolution to it () of class of a few micron, in the meantime, with copolymerization Jiao Xianwei (, much photon is microscopical the photograph of freeboard resolution technology such as the technology is compared, OCT technology is had again compare great layer analyse ability to it. Can say OCT technology fill these two kinds are become like the blank between the technology.

 

Analyse of layer of optical be concerned with becomes the structure that resemble and rationale

 

 

Analyse of layer of optical be concerned with is become resemble be based on interferometer principle, use illumination of close infra-red weak be concerned with to be shot wait for measure an organization, generate interference according to smooth coherence, use superheterodyne to explore a technology, the light intensity that measures reflection to come back, use at organizing shallow surface layer to become to resemble. OCT system is by Er of illuminant of low be concerned with, fiber-optic Michael abdicate interferometer is mixed photoelectricity exploration system form.

 

 

The core of OCT is interferometer of abdicate of fiber-optic Michael Er. Illuminant of low be concerned with exceeds radiation glow diode (Superluminescence Diode, the smooth coupling that SLD) gives out enters single standard fiber-optic, by 2×2 fiber-optic coupler is equational it is two, it is the referenced light that returns from planar illuminator via lenticular collimation all the way; is classics lens focusing another the sampling beam of light to the sample that be measured.

 

The referenced light that returns by illuminator and be measured of sample backward scattering light is confluent on detector, when both the optical path difference between is in length of illuminant be concerned with when produce interference, what detector outputs signal to mirror medium is backward scattering intensity.

 

Scanning illuminator records its space position, make consult light and come from what deepness differs inside medium is backward scattering light produces interference. According to illuminator position and corresponding interference signal intensity namely Ding obtains sample different deepness (Z direction) measure data. The scanning of recombine sampling beam of light inside X-y plane, computer of earnings result classics is handled, can obtain the three-dimensional structure information of sample.

 

OCT becomes the evolution that resembles a technology

 

Check the wide application in ophthalmic domain as ultrasonic, people hopes to develop a kind of higher resolution detect method. Supersonic biology microscope (this one requirement was satisfied on the certain piece now level of UBM) , it is passed use more high-frequency sound wave, can of high resolution of travel of the Duan Jin before cross-eye into picture. But because tall frequency sound wave is inside biology organization rapid attenuation, the exploration deepness that it is in is restricted certainly. If use light-wave to replace sound wave, whether can its blemish get compensating?

 

1987, the interference of Takada low be concerned with that excogitates optics measures a way, it is the development below the support in fibre optics and photoelectricity component becomes the methodological;Youngquist that undertakes high resolution optics is measured to wait to excogitate reflectometer of optical be concerned with, its illuminant is direct the super glow diode with fiber-optic Ou couplet, an arm that referenced lens scale contains in the instrument is located in interior, and in another arm fiber-optic join with the equipment that is similar to camera. These occurrence that are OCT laid theory and technical basis.

 

 

1991, the David Huang of scientist of foreign citizen of Chinese origin of Masschusetts Institute of Technology OCT that will develop is used at measuring the retina from body and coronary artery. Because OCT has unprecedented high resolution, be similar to optical work check, because this is used very quickly at biology by development,organize measure and become picture.

 

As a result of the optical characteristic of eye ministry, OCT technology develops the most quickly in ophthalmic and clinical application. Before 1995, the organization such as film of Ji Hong of the retina that the scientist such as Huang applies OCT to reach key point of live body person to leaving put oneself in another’s position, corneal, anteroom undertakes measure and be becominged resembling, perfect OCT technology ceaselessly. Through improvement of a few years, OCT system is perfected further, develop become a kind clinical and practical detect tool, made commercial instrument, decided it becomes the advantage that resembles a respect in eye ground and retina finally. OCT began to be used formally at ophthalmology 1995 clinical.

 

1997, OCT is applied at the examination of dermatological department, enteron, urology and cardiovascular respect gradually. OCT of department of make water of bowel of esophagus, stomach, secrete and cardiovascular OCT all are invade sexual examination, be similar to endoscope and conduit, but its resolution is higher, considerable examine exceeds small structure. Skin OCT is checked to contact a gender, considerable also examine exceeds small structure.

 

First application is OCT1 at clinical OCT, comprise by console and dynamical station respectively. Console includes monitor of OCT computer, OCT, control plate and station of power of surveillant screen; to include eye ground to observe system, interference controls a system solely. Because console and dynamical station are relatively independent unit, both between be linked together by lead, instrument volume is so larger, what occupy a space bigger.

 

The analytic program cent of OCT1 is measured for image processing and image. Image processing includes gauss of image calibration, image calibration and image standardization, standardization, image to make the same score median of slippery, image flowing; image measures an order less, only retinal ply is measured measure with ply of layer of retinal nerve fiber. But the scanning program as a result of OCT1 and analytic program all less, be replaced very quickly by OCT2 place consequently.

 

OCT2 is in the foundation of OCT1 aspirant travel software upgrades form. Also having a few instruments is console and motive force the stage joins 2 for one, form the instrument of OCT2, this kind of instrument reduced image monitor, be in same the scanning place situation of an image of OCT of the observation on computer screen and surveillant patient, but operation and OCT1 likeness, it is in control plate begin moves an operation.

 

2002 the occurrence of OCT3, indicate the technology enters an OCT a new level. OCT3 divides an operation the interface is more friendly, outside operating usable mouse to be finished on computer entirely, its scan and analyse a program to be perfected with each passing day. More important is, the resolution of OCT3 is higher, ≤10 μm of its axial resolution, transverse resolution is 20μm. The axial sample book that OCT3 gets increases 768 from 128 when an original A scans, the integral because of this OCT3 the 131 072 from before increase 786 432, the hierarchy of the image of scanning organization cross section that compose builds is clearer.

 

OCT becomes the technical sort that resemble

 

Respect of OCT technology measure, differ according to exploring the type of signal, OCT basically has medium of two kinds of technologies: Time domain OCT(Time Domain OCT, TD-OCT) and frequency domain OCT(Fourier Domain OCT, FD-OCT) .

 

Technology of time domain OCT

 

Principle of technology of time domain OCT pursues as follows:

 

 

Layer analyse became optical be concerned with to combine low be concerned with like the system interference and in all the characteristic that Jiao Xianwei measures. The illuminant that the system chooses is broadband illuminant, commonly used is to exceed radiation glow diode (SLD) . The coupler of smooth classics 2×2 that illuminant gives out passes sample arm and referenced arm illuminate to arrive respectively sample and referenced lens, the reflex in two smooth roads is confluent in coupler, and two arms optical path difference is only inside length of a be concerned with ability happening interferes signal. At the same time the sample arm as a result of the system is in all anxious microscope system, focus of exploration beam of light is in returned beam of light to have the strongest signal, can exclude the effect of the sample scattering light outside the focus, this is OCT can high-powered into one of accounts that resemble. Output interference signal to detector, the reflection intensity of the intensity correspondence sample of signal, through the processing of demodulation circuit, finally by collect card to collect the computer to undertake gray scale is become picture.

 

 

OCT wants the reflectivity of differ to sample deepness to distributing namely into the major idea that resemble. If the reflectivity of referenced lens place is certain, so the inhomogenous sex as a result of sample structure, differ from sample deepness scattering the smooth intensity that come back is different, the interference that generates when two arms light encounters so contains sample in signal the reflection of different deepness leads information. By the low coherence of broadband illuminant knowable, OCT interferometer can be obtained narrower length of be concerned with, assure what axial scans to become be in like resolution micron class. To tape illuminant, if graph A place is shown, because length of its be concerned with is very long, can output interference stripe change inside range of quite big optical path difference. Such interference stripe contrast and the change of optical path difference of two arms have nothing to do almost, cannot determine the position of 0 class stripe, cannot find wait for light path dot, lost the function of exact location. And to broadband illuminant character, if graph B place is shown, when only the optical path difference when two arms is in in length of this very short be concerned with, detector ability detects the contrast that interferes stripe changes. And, in contrast the light path such as the move nods the biggest place correspondence, as the addition of optical path difference, rapid acute decreases contrast, because this has precision of very good layer analyse fixed position. Then the reflex of portable referenced arm scans lens, will seek the balance site after change, the change of the fiber-optic sensor length that can measure accordingly through measuring the displacement of the metabolic around that reflexes scanning lens.

 

 

Because illuminant is illuminant of broadband of low be concerned with, reason length of its be concerned with is extremely short. And mix when referenced arm only when measuring brachial optical path difference to be in the length of a be concerned with of illuminant, the back just is met to scattering light and referenced light generation interference, and be close to zero hour to just have strength of the biggest be concerned with when optical path difference. Accordingly, move as the axial of referenced lens, in optional choose sample to it the layer with equal light path will undertake resembling, and the information of other layer will be dropped by filter, realized layer analyse to become thereby picture.

 

 

The place on the graph shows the result of fore-and-aft scanning when organize simply for. This sample organization is formed by two, refractive index is N1 and N2 respectively, differ with N of airy refractive index. In sample arm, the place of face of have a common boundary in medium of two kinds of different refractive index can produce reflection. When the illuminator of referenced arm scans, the output end of detector can see two interference signal. Among them signal of the first interference is corresponding air and constituent layer the face of have a common boundary of 1, signal of the 2nd interference is corresponding organization layer 1 with constituent layer the face of have a common boundary of 2. Demodulation is in in carrier wave frequency, can get the primitive light intensity that interferes signal. Move through direction of X of edge sample surface and Y direction the three-dimensional image that sample arm can acquire sample.

 

Technology of frequency domain OCT

 

 

Frequency domain OCT is in replaced time domain OCT gradually in recent years, its are important the reason depends on his need not undertaking in referenced arm light path scans, direct one-time get fore-and-aft scanning. Such, of system of frequency domain OCT into will get like speed great rise. What time domain OCT collects is the intensity signal that changes along with referenced arm light path, each its fore-and-aft sweep time is equal to referenced arm light path to change a periodic time. The referenced arm of frequency domain OCT need not scan, it collects some one-timely the interference spectrum signal of the deepness direction of transverse position, namely frequency domain signal. The time domain signal of deepness direction is with respect to encode in this spectrum. Each fore-and-aft scanning interferes spectrum actually with respect to correspondence, do Fourier commutation to be able to restore to give time domain signal to spectrum. Leave out of frequency domain OCT the time that deepness scans among OCT of traditional time domain, great rose to become resemble gathering speed.

 

Obtain interference spectrum to basically have two kinds of methods at present, one kind is to be based on spectrometer, another kind is to be based on sweep illuminant. Former we say for OCT(SD-OCT) of spectral frequency domain, we weigh latter for sweep OCT(SS-OCT) .

 

 

SD-OCT is the spectrometer that is based on grating and lens through, will interfere signal prismatic again focusing arrives line blast Harge-Coupled Device of charge coupling component, interference spectrum obtains on CCD) .

 

 

SS-OCT is the sweep illuminant that follows scanning of time high speed through using an output wavelengh, the signal of below repass detector record each wavelengh gets interfering spectrum then.

 

The application of technology of analyse of layer of optical be concerned with

 

Inchoate OCT applies at ophthalmology mostly, because the eye is opposite for belong to pervious to light the medium with better sex. As the ceaseless development of OCT technology, to pervious to light quality the other organization with so not good, stronger scattering, OCT also had a lot of application gradually. In the past in ten years, OCT and fiber-optic technology and inside peep technical union, application expanded a lot of domain such as gastric bowel path, skin, lung, kidney, heart and vessels.

 

In the application of ophthalmic respect

 

Domain of the first of OCT technology clinical application is ophthalmology. Because used the low coherence of broadband illuminant, OCT has outstanding optical section capacity, the layer analyse that can implement high to second surface resolution is become picture, its explore deepness Yuan Chao to cross a tradition in all anxious microscope, suit what the eye organizes to become especially like research, the retinal fault that can offer traditional and ophthalmic nondestructive to diagnose a technology to cannot be offerred writtens guarantee composition of a picture resembles, show retinal fine structure and pathology change can clearly not only, still can have observation at the same time and make quantitative analysis, one of key direction that the research that its diagnose a respect in ophthalmology is development of application of OCT biology medicine, cross-eye division disease is diagnosed make significant contribution, already made the diagnostic tool with retinal disease and strong glaucoma at present.

 

As OCT function rise, can forecast OCT cross-eye division to will produce more far-reaching effect, can raise a disease thereby inchoate diagnostic sensitivity and particularity, the change monitors disease evolutional ability. The structure with retinal to understanding OCT and function, the hair interpretation of the cause that explains retinal disease manages, define new-style treatment program, the disease that monitor treats the respect such as the effect to having mainer and mainer effect. Be in at present clinical on OCT basically uses Yuqingguang of blood-vessel of the new student below disease of retina of pathological changes of eye, yellow spot, vitreous body, retina inchoate diagnose examine is followed after reaching art.

 

In the application of dermatological department respect

 

OCT technology has achieved human body skin to become the end that resemble. The OCT of high resolution can detect cutaneous of human body health is cuticular layer, dermal layer, accessary implement with blood-vessel. The Welzel human body skin that implemented OCT system is become picture, it is 830nm into the wavelengh in resembling a system, deepness resolution is 15μm, exploration deepness is 0.5~1.5mm, into it is 10~40s like time. The Wang in skin of body small rat and bowel of human body stomach OCT that still can depict an axial resolution <10μm is become picture, glycerine and third 2 mellow besmear are become at OCT of surface of small rat skin picture, see layer of cuticular, cuticular base, dermal tit layer, dermal network layer, subcutaneous tissue, muscle film, muscle and wool bursa.

 

OCT can be used at injuring repair to monitor. Yeh with microscope of OCT, much photon (Multiphoton Microscope, MPM) monitors laser fire damage and subsequently scathing rehabilitate in skin organization emulation model. From the skin of body the organization emulates a model by contain 1 model the cuticular composition with the derma of cell of collagen albumen, fiber and different role enzymatic albumen. Be not the series that invades sexual light to become the matrix injury that is used as to follow time to change like the technology and rehabilitate to measure, check result contrast with constituent pathology.

 

In the application of cardiovascular system

 

OCT serves as blame invade a gender to detect the technology is used at live body blood to become picture, study in biology medicine and clinical very great value is had in diagnosing. Layer analyse becomes optical Duopule picture (Optical Doppler Tomography, ODT) is laser much general forces flowmeter and OCT photograph union, also call chromatic much general to strap analyse of layer of be concerned with to become picture (Color Doppler Optical Coherence Tomography, CDOCT) , the high resolution that can reach human body blood stream is become resemble and detect in real time. Obtained the analyse of layer of live body blood stream in chorion of body chicken embryo and rodent animal mesentery Chen with ODT speed is become picture, the change with the kinetic blood stream after the interpose that monitors active to blood-vessel medicaments and smooth kinetic cure reachs the change of hemal structure.

 

In the application that crosses family operation territory

 

In cross family operation respect, OCT can have in the analysis in the operation process of purify tumour without cancer cell. Generally speaking, the surgeon is taken out when be being organized all round tumor, always hope to be able to keep clear of all cancer cell. And the tumour that is kept clear of and the analysis that the organization all round can send to pathology lab to have a week, in order to make the written report after the operation. Because OCT is video in histology / pathology application all is same resolution, accordingly the OCT system in surgery can let a surgeon know accurately to need to keep clear of to more or less be organized, leave share of how many safe brim at the same time, use such methods the organization that won’t wrong purify did not contract cancer, consequently the charge of operation of dispense with follow-up reachs anguish. OCT technology can let a doctor the resolution level with histology, real time sees video, so that the surgical department of purify tumour has in first time,better decision is made when the operation.

 

In the future can more uses the medical treatment application of OCT technology. For example, OCT can match the small tumor that puncture section excises inchoate phase. The disease that contracts lacteal cancer to meet with suffers from, OCT can match vision and technology of processing of signal of “ intelligence ” , guide fine needle to insert exact tumor position, in order to find out the organization that doubt is like infection, reduce an operation as far as possible invade a gender. To cardiovascular disease patient, OCT can match minimum tracheal bracket, find out the bracket inside blood-vessel well and truly or check spot piece deposit. In the application of these types, advanced digital signal handles a technology to be able to achieve superexcellent video picture to pledge not only, and can undertake constituent classified.

 

Be not the application of medical domain

 

The original intent that OCT studies is the layer analyse that is biology medicine into picture, and medical application still continues take dominant place. Besides the application in medical domain, as the development of OCT technology, OCT technology is being advanced to other sphere, especially industry measures a domain, the ply that is like displacement sensor, small photographic plate measures what can be changed into displacement with etc to be measured of content measure.

 

Recently, technology of low be concerned with already occupied the crucial technology of memory as high density degree. The integrality of construction of the leftover small opening that OCT technology still can use at measuring element of tall scattering polymer, fiber and structure. Return the film that can be used at measuring material. OCT technology still can be used at material science, the person such as J.P.Dunkers used OCT technology to undertake to composite material scatheless detects. The person such as M.Bashkansky used OCT system to undertake detecting to material of pottery and porcelain, extended the applied range of OCT technology. The S.R.Chinn application in returning pair of OCT to occupy memory in high density degree undertook study, implementation is multilayer and optical memory and tall exploration sensitivity.

 

The future of OCT technology develops a tendency

 

The development trend of prospective OCT can consider as roughly form from pure form become functional OCT integratedly to develop to function and structure like OCT. Normally biology organization is in before producing pathological change, its function parameter already began to produce change, accordingly, functional parameter is inchoate to the disease diagnosing is very useful. These functional parameter include blood stream rate normally, contain property of change of structure of oxygen pressing, organization, birefraction to wait, function OCT resembles providing more information through exploring these change to undertake the function is become. The function that gets rapid development in recent years OCT technology includes: Much general straps OCT, polarized light sensitive OCT, spectrum OCT and double light OCT.

 

Analyse of layer of optical be concerned with is become resemble be being become novelly as a kind like the technology, can internal to live body organization tiny composition has real time, become in fault of body, high resolution picture, become with the tradition compare like diagnostic method photograph, show huge advantage, in medical disease very large latent capacity is had in diagnosing.

 

The article is reprinted from sensor technology.