The ultra broadband spectrum detection system of ultrahigh resolution spectral coverage OCT
Technical field
This utility model relates to Optical Coherence Tomography Imaging Technology, relates in particular to a kind of ultra broadband spectrum detection system of ultrahigh resolution spectral coverage OCT.
Background technology
Optical coherent chromatographic imaging (Optical Coherence Tomography, be called for short OCT) be a kind of emerging optical image technology, can realize the organizational structure and the physiological function of live body inside are carried out noncontact, not damaged, high-resolution imaging, in the earlier detection of disease with in body biopsy field extensive application.
Present spectral coverage OCT system comes the spectral components of parallel acquisition interference signal by high speed linear array CCD, need not the depth information that axial scan just can obtain sample, has quick and highly sensitive characteristics, and its system core is the quick grating spectrograph of feeler arm.In the OCT system, the axial resolution of system is inversely proportional to the light source bandwidth, and the light source bandwidth is wide more, and corresponding coherence length is just short more, and axial resolution is just high more.In subjects such as ophthalmology, skin, tumor, the medical image image of ultrahigh resolution (2-3um) has great significance to clinical disease diagnosis.Therefore, spectral coverage OCT must adopt the more light source of wide spectral range, and the grating spectrograph of feeler arm must be surveyed wideer spectral component simultaneously, could improve the axial resolution of system.External a lot of scientific research institution has all carried out the research of this respect, N.A.Nassif group as U.S. Harvard Medical School has made up the centre wavelength based on 890nm, the ultrahigh resolution spectral coverage OCT system of the SLD of bandwidth 150nm (super luminescence diode) light source, axial resolution is 2.9um; The J.G.Fujimoto group of masschusetts, u.s.a science and engineering has made up the centre wavelength based on 850nm, the super spectral coverage OCT of the ultrahigh resolution of the femto-second laser of bandwidth 144nm system, and axial resolution is 2.1um.Feeler arm part in ultrahigh resolution spectral coverage OCT system, traditional method is to adopt the line array CCD of more pixel counts to survey more spectral components, perhaps survey wideer spectral region based on the line array CCD of limited pixel count, but the spectral resolution of sacrificial light spectrometer.Because the increase of line array CCD pixel count means the increase of visual field, unless the optical imaging system that design is complicated more, otherwise serious curvature of field phenomenon inevitably can appear in (CCD photosurface) on image planes, simultaneously because spectral region is too wide, dispersion phenomenon is serious, causes the focal position difference of different color light, makes spectrogrph to separate various coloured light fully and introduces crosstalk (cross-talk), survey signal to noise ratio and descend then that system axial resolution descends, finally reduced image quality.And the spectral resolution that reduces spectrogrph means the reduction of the spectral coverage OCT imaging degree of depth.Therefore, how making grating spectrograph high-resolution ground measure broader spectral region under the situation of limited imaging viewing field is big technological difficulties of ultrahigh resolution spectral coverage OCT system development.
Summary of the invention
The purpose of this utility model is to provide a kind of optical spectrum detecting method and system of ultrahigh resolution spectral coverage OCT.Feeler arm part in the spectral coverage OCT system of ultrahigh resolution, adopt the structure of double grating to realize cross dispersion, reduce imaging viewing field by DMD (abbreviation of DMD Digital Micromirror Device) simultaneously, can under the situation of little imaging viewing field, survey more spectral components.
The purpose of this utility model is achieved by the following technical solution:
A kind of spectrum investigating system of ultrahigh resolution spectral coverage OCT:
The low-coherent light that comes out from wideband light source, incide broadband optical fiber coupler through first Polarization Controller, optoisolator, one the tunnel enters scanheads through second Polarization Controller after beam split, another Lu Jingdi three Polarization Controllers enter reference arm, after the light that returns is interfered in broadband optical fiber coupler, through the 4th Polarization Controller, enter feeler arm interference signal is resolved into different spectrum, last these spectral signals import computer into, handle at computer, by the inverse Fourier transform reconstructed image.
Described scanheads: form by collimating lens, scanning galvanometer and condenser lens; Behind collimating lens, scanning galvanometer and condenser lens, shine sample through the light after the beam split, return through second Polarization Controller to broadband optical fiber coupler by former road.
Described reference arm: form by collimating lens, dispersion compensator, neutral colour filter and plane mirror; Light after beam split is returned through the 3rd Polarization Controller to broadband optical fiber coupler by former road through collimating lens, dispersion compensator, neutral colour filter and plane mirror.
Described feeler arm: form by optical fiber, collimating lens, first diffraction grating, two gummed condenser lens, second diffraction grating, two gummed condenser lens, DMD, two gummed condenser lens and area array CCD; After the light that is returned by scanheads and reference arm is interfered in broadband optical fiber coupler, enter optical fiber, collimating lens, first diffraction grating, two gummed condenser lens, second diffraction grating, two gummed condenser lens, DMD, two gummed condenser lens and area array CCD successively through the 4th Polarization Controller, interference signal is resolved into different spectrum, last these spectral signals import computer into, handle at computer, by the inverse Fourier transform reconstructed image.
The groove direction of first diffraction grating in the described feeler arm and the groove direction of second diffraction grating are orthogonal, wherein the demand pairs of diffraction grating are the 1/M of the demand pairs of second diffraction grating, M is the integer greater than 1, on the front focal plane of the two gummed of first diffraction grating condenser lens, DMD is positioned on the back focal plane of two gummed condenser lenses (18), and DMD and area array CCD satisfy the object-image conjugate relation, and the picture that DMD becomes to dwindle is on area array CCD, scaling is N: 1, and N is the integer greater than 1.
A kind of optical spectrum detecting method of ultrahigh resolution spectral coverage OCT:
Feeler arm in ultrahigh resolution spectral coverage OCT system adopts the double grating structure, uses DMD and area array CCD to realize the detection of small field of view and ultra broadband spectrum simultaneously; Its concrete steps are as follows:
1) in the feeler arm of ultrahigh resolution spectral coverage OCT system, use two orthogonal diffraction gratings of groove direction to come coming the interference spectrum signal to carry out beam split, thereby the two-dimension spectrum that obtains the interference spectrum signal distribute;
2) feeler arm in ultrahigh resolution spectral coverage OCT system partly adds DMD, simultaneously by imaging len, makes its and two-dimensional array CCD satisfy the object-image conjugate relation, makes picture that DMD one-tenth dwindles on the CCD face, and scaling is N: 1, and N is the integer greater than 1;
3) the two-dimension spectrum component that separates of double grating images on the DMD, and DMD is again with these spectral components reflections and be imaged on the area array CCD once more and measure.Because DMD and CCD satisfy object-image relation, and scaling is N: 1, N is the integer greater than 1, can form a dummy unit to the N on the DMD pixel, when light spectrum image-forming is measured, allow a DMD pixel cell in the dummy unit image on the area array CCD successively, can obtain N by N measurement and doubly measure to the spectral components of CCD number of picture elements.
Compare with background technology, the beneficial effect that the utlity model has is:
1, by two orthogonal diffraction gratings of groove direction the interference spectrum signal is carried out beam split, the spectral signal that can obtain two dimension distributes.Compare traditional monochromatic light grating spectrograph, spectral signal distributes from one dimension and has become Two dimensional Distribution, reduced the visual field of light spectrum image-forming, because diminishing of imaging viewing field, the curvature of field that can eliminate that spectrum that the spectrogrph of traditional spectral coverage OCT system exists is crosstalked and exist during big visual field when big spectral region is surveyed, distortion and the out of focus phenomenon that causes of chromatic dispersion can significantly improve the signal to noise ratio of spectral measurement.
2, by DMD spectral components is imaged on the CCD, improved the multiplexing capacity of the spectral measurement of limited yardstick and limited pixel count CCD, not only enlarged the scope of spectrographic detection, can also improve the resolution of spectral measurement, can realize the super-resolution detection of ultra broadband spectrum simultaneously, thereby guarantee the spectral coverage OCT imaging of high s/n ratio and ultrahigh resolution.
3, ultra-wide spectrum measuring method that the utility model proposes and system also can be applied to all multispectral surveies field such as astronomy except being applied to the spectral coverage OCT system of ultrahigh resolution, elementary analysis, and in other spectrum bio-imaging methods.
Description of drawings
Fig. 1 is the system schematic of specific embodiment of the optical spectrum detecting method of ultrahigh resolution spectral coverage OCT described in the utility model.
Fig. 2 is the structural representation of the spectrum investigating system of ultrahigh resolution spectral coverage OCT described in the utility model.
Fig. 3 is that DMD goes up the distribution of micro mirror on off state and CCD goes up the pixel distribution sketch map.
Fig. 4 is the synchronous control signal sequential sketch map of DMD and CCD.
Among the figure: 1, wideband light source, 2, optoisolator, 3, broadband optical fiber coupler, 4, Polarization Controller, 5, collimating lens, 6, scanning galvanometer, 7, condenser lens, 8, sample, 9, collimating lens, 10, dispersion compensator, 11, neutral colour filter, 12, plane mirror, 13, optical fiber, 14, collimating lens, 15, diffraction grating, 16, two gummed condenser lens, 17, diffraction grating, 18, two gummed condenser lenses, 19, DMD, 20, two gummed condenser lens, 21, area array CCD, 22, feeler arm, 23, scanheads, 24, reference arm.
The specific embodiment
Below in conjunction with drawings and Examples this utility model is further described:
As shown in Figure 1, the low-coherent light that this utility model comes out from wideband light source 1, incide broadband optical fiber coupler 3 through first Polarization Controller 4, optoisolator 2, one the tunnel enters scanheads 23 through second Polarization Controller 4 after beam split, another Lu Jingdi three Polarization Controllers 4 enter reference arm 24, after the light that returns is interfered in broadband optical fiber coupler 3, through the 4th Polarization Controller 4, enter feeler arm 22 interference signal is resolved into different spectrum, last these spectral signals import computer into, handle at computer, by the inverse Fourier transform reconstructed image.
Described scanheads 23: form by collimating lens 5, scanning galvanometer 6 and condenser lens 7; Behind collimating lens 5, scanning galvanometer 6 and condenser lens 7, shine sample 8 through the light after the beam split, return through second Polarization Controller 4 to broadband optical fiber coupler 3 by former road.
Described reference arm 24: form by collimating lens 9, dispersion compensator 10, neutral colour filter 11 and plane mirror 12; Light after beam split is returned through the 3rd Polarization Controller 4 to broadband optical fiber coupler 3 by former road through collimating lens 9, dispersion compensator 10, neutral colour filter (11) and plane mirror 12.
As shown in Figure 2, described feeler arm 22: form by optical fiber 13, collimating lens 14, first diffraction grating 15, two gummed condenser lens 16, second diffraction grating 17, two gummed condenser lens 18, DMD19, two gummed condenser lens 20 and area array CCD 21; After the light that is returned by scanheads 23 and reference arm 24 is interfered in broadband optical fiber coupler 3, enter optical fiber 13, collimating lens 14, first diffraction grating 15, two gummed condenser lens 16, second diffraction grating 17, two gummed condenser lens 18, DMD 19, two gummed condenser lens 20 and area array CCD 21 successively through the 4th Polarization Controller 4, interference signal is resolved into different spectrum, last these spectral signals import computer into, handle at computer, by the inverse Fourier transform reconstructed image.
The groove direction of the groove direction of 22 first diffraction grating 15 and second diffraction grating 17 is orthogonal in the described feeler arm, wherein the demand pairs of diffraction grating 15 are the 1/M of the demand pairs of second diffraction grating 17, M is the integer greater than 1, on the front focal plane of 15 pairs of gummeds of first diffraction grating condenser lens 16, DMD19 is positioned on the back focal plane of two gummed condenser lenses 18, DMD 19 satisfies the object-image conjugate relation with area array CCD 21, and 19 one-tenth pictures that dwindle of DMD are on area array CCD 21, scaling is N: 1, and N is the integer greater than 1.
As shown in Figure 2, by the interference light signal of optical fiber 13 outgoing, behind collimating lens 14, become directional light and be radiated on the diffraction grating 15, the groove direction of diffraction grating 15 is a vertical direction, so interference signal chromatic dispersion in the horizontal direction.Because the groove direction of diffraction grating 17 is vertical mutually with the groove direction of diffraction grating 15, when these different color lights through a chromatic dispersion project diffraction grating 17 by two gummed condenser lenses 16 again, meeting chromatic dispersion once more, dispersion direction is with dispersion direction is vertical for the first time, in the vertical direction chromatic dispersion, therefore after process diffraction grating 17, can obtain the interference spectrum component of two dimension, wherein diffraction grating 15 is positioned on the back focal plane of two gummed condenser lenses 16, effect is the coloured light through the different directions of diffraction after the diffraction grating 15 to be become directional light once more be radiated on the diffraction grating 17, thereby has guaranteed that these coloured light have identical angle of incidence once more during diffraction; These two-dimension spectrum components focus on the DMD19 by two gummed condenser lenses 18; By the groove number of change diffraction grating 15 and diffraction grating 17, and the distance between diffraction grating 17 and the two gummed condenser lens 18, can on DMD19, obtain difform two-dimension spectrum and distribute.Typical dmd chip, constitute by 1024*768 micro-reflector as DMD3000, the size of each micro-reflector is 13.68um*13.68um, have+12 degree, 0 degree, three kinds of reflective conditions of-12 degree, concrete parameter and index can be referring to the website of Texas ,Usa instrument company (TI) about the DMD technology:
Http:// www.dlp.com.cn/dlp technology/default.asp, the corner that changes the last micro-reflector of DMD just can be controlled the reflection direction of micro-reflector; And DMD19 and area array CCD 20 satisfy object-image conjugate relation, and the picture that DMD19 becomes to dwindle is on area array CCD 21, and scaling is N: 1 (N for greater than 1 integer).
Fig. 3 a is depicted as DMD19 and goes up the distribution of micro mirror on off state; Fig. 3 b is depicted as CCD21 and goes up the pixel distribution sketch map, and as the specific embodiment, the micro mirror number of DMD19 is 16*16, and the pixel count of CCD21 is 8*8, and the scaling of DMD19 and CCD21 is 4: 1,1 pixel on last per 4 micro mirrors correspondence CCD21 of DMD19; And the last micro mirror of DMD19 is in+12 be " opening " state when spending, and this moment, micro mirror spectrum of reflected light component can image on the area array CCD 21 by two gummed condenser lenses 20; Be in-12 and be " passs " state when spending, micro mirror spectrum of reflected light component can not image on the area array CCD 21 by two gummed condenser lenses 20 at this moment; By computer DMD19 is achieved as follows division: per 4 micro mirrors in the micro mirror array are divided into a sub-piece, 4 micro mirrors in sub-piece label respectively are 1,2,3,4, the micro mirror of same position is given identical numbering in the different sub-pieces, thereby all micro mirrors are divided into 4 classes by the locus: micro mirror 1, micro mirror 2, micro mirror 3, micro mirror 4; Control all micro mirror 1 synchronization actions by synchronous circuit, when being in " opening " state, all the other micro mirrors all are in " pass " state, the rest may be inferred, make micro mirror 1-2-3-4 be in "open" state according to this, CCD21 just can realize 4 times of super-resolution spectral measurements to the CCD pixel count through successive 4 spectral measurements.
Fig. 4 is a synchronizing signal sequential sketch map, wherein micro mirror is in high level interval scale "open" state, in low level interval scale "off" state, in the time of integration of CCD21, guarantee to have only a micro mirror to be in " opening " state in the micro mirror 1,2,3,4 by synchronous circuit, all the other micro mirrors all are in " pass " state; According to the order of micro mirror 1-2-3-4, make micro mirror be in "open" state according to this, by successive four exposures, just can finish once complete spectra collection.
The effect of Polarization Controller 4 is polarization modes of being convenient to adjust each passage in the system, drops to minimumly with the influence with polarization mode dispersion, improves image quality.
The optical spectrum detecting method and the system of the disclosed a kind of ultrahigh resolution spectral coverage OCT of this utility model, can be under the situation of limited visual field, ultra-wide spectrum is carried out super-resolution to be measured, thereby can realize the superelevation axial resolution of spectral coverage OCT, can improve simultaneously in traditional spectral coverage OCT system spectrum measurement by the curvature of field, the spectrum degradation problem under the signal to noise ratio introduced and the axial resolution of crosstalking, significant in the spectrographic detection of ultrahigh resolution spectral coverage OCT.