A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus
Technical field
The application relates to a kind of imaging Fourier trasform spectroscopy measurement scanning interferometer instrument apparatus.
Background technology
Imaging Fourier transform spectrometer, adopts planar array detector to replace single-point detector, expand the spatial resolving power of common Fourier transform spectrometer,, can obtain the two-dimensional space image information of target to be measured and one dimension spectral information simultaneously, realize imaging spectral (or claiming light spectrum image-forming) and measure.Under appropriate design, imaging Fourier transform spectrometer, can be good at inheriting some spectral measurement advantages of general Fourier transformation spectrometer, as consistent in: 1 hyperchannel, 2 high light fluxes, 3 hyperspectral measurement precision, 4 wide measurement wave bands, 5 height/tunable optical spectral resolution, 6 all band resolution.Abundant space and spectral information acquisition capability make imaging Fourier transform spectrometer, have important using value in multiple fields such as physics, biology, chemistry, medical science, pharmacy, food, environmental protection, remote sensing, space flight.
The core of typical case's imaging Fourier transform spectrometer, is Michelson interferometer, and its basic structure and principle of work are as shown in Figure 1.Imaging Fourier transform spectrometer, system also comprises the parts such as light source, light collecting system, planar array detector and main control computer.The light that target to be measured is sent enters Michelson interferometer after the light collecting system of spectrometer front end is collected collimation, the beam splitter (semi-transparent semi-reflecting lens) of interferometer is divided equally for transmission and two light beams of reflection, a branch of directive index glass, another beam is to horizontal glass; Two-beam is got back to beam splitter after horizontal glass and index glass reflection respectively and is again met, through beam splitter beam splitting again; Two-way coincidence light beam light path difference in interferometer outgoing is less than under the coherence length of laser condition, and the two produces interference; Outgoing interfering beam through cylinder mirror focal imaging to planar array detector; In the time that index glass is done linear reciprocation scanning near interferometer two arm zero optical path differences, computer control detector records a series of interference images, and the numerical value of this series digit image same pixel position forms the discrete interference pattern of this place's light signal; According to Fourier Transform Spectroscopy principle, computing machine carries out the processing of fast discrete Fourier transform to the interference pattern of all location of pixels of target image, can obtain the digital picture of target to be measured and the spectrum at picture upper all pixels place, realizes image-forming spectral measurement.
Typical Michelson interferometer is a kind of scanning interferometer, and its index glass is plane mirror, in the time of work, is driven and is done the linear reciprocation scanning motion that is parallel to optical axis by mechanical actuator.But any Mechanical Driven mechanism all cannot guarantee the absolute rectilinear scanning of index glass, therefore level crossing can produce in surface sweeping process, the light beam that flat mirror reflects is returned is produced larger inclination by this, so that cannot keep optical parallel with another road reference beam, also cannot with its beam splitter again can with time overlap.Because the spectral resolution of Fourier transform spectrometer, is directly proportional (the longer spectral resolution of scanning distance is higher) to index glass scanning light path, therefore, in the time that needs are realized high spectral resolution, the lengthening of scanning distance can cause this inclination more serious.Index glass tilts not only to affect two-way light beam to become on detector the coincidence of image, causes picture element to decline, and can reduce the interference contrast at each pixel place, even cannot form interference, thereby cannot realize spectral measurement.
Hollow pyramid retroreflector is made up of three orthogonal reflectings surface, is characterized in that incident beam produces retroeflection therein after triple reflection, and retroeflection light beam keeps highly parallel with incident beam, therefore has the parallel self compensation mechanism of the incident beam of going out.Utilize hollow pyramid retroreflector as Michelson interferometer index glass, even if produce small inclination in scanning process, due to its self compensation mechanism, can effectively overcome index glass folded light beam.But, although hollow pyramid retroreflector can guarantee that incidence reflection light beam is parallel, can introduce the traversing of the relative incident beam of folded light beam.Imperfect due to cylinder mirror, this traversing meeting causes the image quality of two light beams after it focuses on to decline even interfering and disappear, affect image-forming spectral measurement.And, because light beam is in the triple reflection of pyramid retroreflector inside, interferometer swing arm light path is lengthened greatly; According to Fourier Transform Spectroscopy principle, for guaranteeing that index glass sweep limit can cover interferometer zero optical path difference position, the corresponding prolongation of also having to of reference arm light path.So greatly increase the shared space of scanning interferometer take it as index glass, be unfavorable for miniaturization and the densification of the imaging Fourier transform spectrometer, building accordingly.
In addition, the interference peaks light intensity that the bright pixel of traditional imaging Fourier transform spectrometer, target image in measurement and dark pixel place form may be crossed over great scope, and this dynamic range to planar array detector has proposed very harsh requirement.If the pixel dynamic range of planar array detector is large not, very easily cause the saturated or dark pixel place that bright pixel place interference signal is measured to interfere consequence too faint to survey.Thereby the spectral measurement of deteriorated spectrometer.
In view of the above problems, the imaging Fourier trasform spectroscopy of narrating in the present invention is measured the dynamic and static arm configuration of interferometer that adopts a kind of light path folding with scanning interferometer instrument apparatus, the light beam that can effectively overcome in the scanning of Michelson interferometer index glass tilts and traversing problem, be reduced to as the overall volume of Fourier transform spectrometer, and make its more small compact, can also be lowered into picture Fourier trasform spectroscopy and measure the high request to planar array detector dynamic range.
The present invention proposes a kind of novel imaging Fourier trasform spectroscopy measurement scanning interferometer instrument apparatus, comprise a beam splitter, swing arm and a quiet arm (reference arm), it is characterized in that described swing arm and quiet arm share same fixing two-sided planar catoptron, two reflectings surface of this plane mirror respectively incident beam of vertical reflection swing arm and quiet arm are back to beam splitter; Described quiet arm light path is inserted with compensating plate, to compensate optical path difference between two arms.Its swing arm forms light path folding structure by a hollow pyramid retroreflector and a fixing two-sided planar catoptron, hollow pyramid retroreflector wherein realizes linear reciprocation light path by a rectilinear translation platform driving and scans, and its quiet arm forms light path folding structure by same two-sided planar catoptron, an optical path compensation plate and 45 ° of catoptrons.The light beam that the foldable structure of swing arm light path can overcome in the scanning of Michelson interferometer index glass well tilts and traversing problem, in quiet arm light path, insert compensating plate can be lowered into picture Fourier trasform spectroscopy measure the high request to planar array detector dynamic range, folding and the shared same two-sided planar catoptron of two arm light paths can reduce the volume of scanning interferometer, makes the more small compact of imaging Fourier transform spectrometer, according to its structure.
Summary of the invention
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, by a beam splitter, a swing arm and a quiet arm composition, quiet arm also claims reference arm, it is characterized in that described swing arm and quiet arm share same fixing two-sided planar catoptron, two reflectings surface of this plane mirror respectively incident beam of vertical reflection swing arm and quiet arm are back to beam splitter; Described quiet arm light path is inserted with compensating plate, to compensate optical path difference between two arms.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that described beam splitter is unpolarized 50: 50 splitting ratio type beam splitters, described beam splitter is positioned on the collimated light path of imaging Fourier transform spectrometer, light collecting system generation, transmission and folded light beam through beam splitter beam splitting are orthogonal, and incident beam and the outgoing beam of interferometer are orthogonal; Described beam splitter is conventional cube splitter, or a kind of 45 ° of parallel four limit body beam splitters.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that described swing arm is made up of a hollow pyramid retroreflector, a rectilinear translation platform and a fixing two-sided planar catoptron, described hollow pyramid retroreflector is positioned on the transmitted light path of described beam splitter, and cone angle is described three-dimensional beam splitter dorsad, the linear reciprocation scanning motion of described hollow pyramid retroreflector is driven by its residing rectilinear translation platform, and the reflecting surface of described fixing two-sided planar catoptron is perpendicular to the retroeflection light path of described pyramid retroreflector.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that described quiet arm is made up of same two-sided planar catoptron, an optical path difference compensating plate and 45 ° of catoptrons; Described 45 ° of catoptrons are positioned in quiet arm light path, its reflecting surface and its input path angle at 45 °; The incident of described compensating plate and exit facet are perpendicular to the reflected light path of described 45 ° of catoptrons, and described fixing two-sided planar mirror reflection surface is perpendicular to the reflected light path of described 45 ° of catoptrons.
A kind of 45 ° of parallel four limit body beam splitters, it is characterized in that described parallel four limit body beam splitters are solid glass, the folded acute angle of two Adjacent Working Faces is 45 °, and a pair of relative parallel workplace is light splitting surface and reflective surface, and another is that light beam goes out the plane of incidence to relative parallel workplace; Light splitting workplace adds plating multilayer dielectric film, and reflective workplace adds metal-coated membrane, and two straight flanges go out incident working surface and add plating anti-reflection film.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that described 45 ° of catoptrons are plane mirrors, or 45 ° of glass right-angle prisms of inclined-plane metal-coated membrane; Adopting glass right-angle prism can play compensating plate as 45 ° of catoptrons increases the effect of light path, and it goes out incident working surface and adds plating anti-reflection film.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that two workplaces of described two-sided planar catoptron are parallel, is the glass plate of two-sided metal-coated membrane, or the solid glass flat board of one side metal-coated membrane; The glass plate that adopts one side metal-coated membrane is during as catoptron, and metal coating is facing to hollow corner cube reflector, and another side adds plating anti-reflection film, and glass substrate can play compensating plate increases the effect of light path.
A kind of imaging Fourier trasform spectroscopy is measured and is used scanning interferometer instrument apparatus, it is characterized in that circular bore has been divided into equal-sized 6 sector regions by symmetry from entering perpendicular to described hollow pyramid retroreflector bore face; Described hollow pyramid retroreflector is adjusted in rotation, makes its incident beam and outgoing beam in described 6 sector regions in a pair of symmetrically relative sector region.
Beneficial effect of the present invention is: the light beam 1) effectively overcoming in the scanning of Michelson interferometer index glass tilts and traversing problem, 2) reduce the overall volume of scanning interferometer, 3) be lowered into picture Fourier trasform spectroscopy and measure the dynamic range high request to planar array detector.The present invention is extremely beneficial to miniaturization, densification and the cost of imaging Fourier transform spectrometer.The imaging Fourier transform spectrometer, of realizing accordingly can be at good application benefits of multi-field generation such as physics, biology, chemistry, medical science, pharmacy, food, environmental protection, remote sensing, space flight.
Accompanying drawing explanation
Fig. 1 is imaging Fourier transform spectrometer, structure and the principle of work schematic diagram in background technology of the present invention
Fig. 2, Fig. 3, Fig. 4, Fig. 5 are imaging Fourier trasform spectroscopy in the specific embodiment of the invention and measure the structural representation with scanning interferometer instrument apparatus
Fig. 6 be in Fig. 2, Fig. 3, Fig. 4, Fig. 53 P to structural representation
Description of reference numerals:
1, incident beam; 2, cube splitter; 3, hollow pyramid retroreflector; 4, rectilinear translation platform; 5,45 ° of plane mirrors; 6, compensating plate; 7, two-sided planar catoptron; 8, outgoing beam; 9, one side metal coating compensating plate; 10,45 ° of reflection right-angle prisms; 11,45 ° of parallel four limit body beam splitters; 12, retroreflector incident beam; 13, retroreflector retroeflection light beam.
Embodiment
For clearly demonstrating the technical characterstic of this programme, below in conjunction with accompanying drawing and embodiment, this programme is set forth.
Figure 2 shows that a kind of imaging Fourier trasform spectroscopy of the present invention measures the vertical view with scanning interferometer instrument apparatus: the light that target to be measured is sent is imaged that the light collecting system of Fourier transform spectrometer, front end is collected, collimation is that incident beam 1,1 enters directive cube splitter 2 after spectrometer; There are 90 ° of folding directive compensating plates 6 in the light path after 5 reflections of 45 ° of plane mirrors of the folded light beam through 2, light beam is transmitted through a lateral reflection face of vertical incidence two-sided planar catoptron 7 after 6, the 7 motionless vertical reflections that are finally fixed, are back to 2 along the former road of input path; The quiet arm of interferometer forms by 2,5,6,7.
Described incident beam 1 is through 2 the hollow pyramid retroreflector 3 of transmitted light beam directive, the light beam of incident 3 is with certain traversing by 3 folding retroeflection, along with the opposite side reflecting surface of the direction directive 7 of 180 ° of incident beams, finally by 7 vertical reflections, be back to 2 along the former road of input path; Wherein, 3 can drive and do linear reciprocation scanning motion by rectilinear translation platform 4 along incident beam parallel direction; The swing arm of interferometer forms by 2,3 and 7.
Two light beams that are reflected back along described swing arm and Jing Beibeiyuan road can merge by beam splitting again again at described beam splitter 2; Wherein two bundles overlap and return along the former road of incident beam 1, and other two bundles overlap and form the outgoing beam 8 of interferometer along the direction perpendicular to incident beam 1; Be less than under the coherent length condition of light source in composition 8 two light beams optical path difference, the two produces interference, can be by a mirror focal imaging of imaging Fourier transform spectrometer, to planar array detector, and recorded the interference image of target to be measured by planar array detector.
Described scanning interferometer instrument apparatus is when for imaging Fourier trasform spectroscopy surveying work, drive hollow pyramid retroreflector 3 by described rectilinear translation platform 4, make 3 near the sound arm zero optical path difference of interferometer, to do linear reciprocation scanning motion along incident beam parallel direction, can constantly continuously change the optical path difference between two arms.Now recorded a series of interference images of target to be measured by computer control planar array detector, the numerical value of this series digit image same pixel position forms the discrete interference pattern of this place's light signal.Identical with the principle of general imaging Fourier transform spectrometer, afterwards, utilize computing machine to carry out the processing of fast discrete Fourier transform to the interference pattern of all location of pixels of this series target interference image, can obtain the digital picture of target to be measured and the spectrum at picture upper all pixels place, realize image-forming spectral measurement.
As shown in Figure 6, described hollow pyramid retroreflector has three orthogonal reflectings surface, in three faces, the seam of any two faces can be imaged on the 3rd face, therefore, from entering perpendicular to described large pyramid retroreflector bore face, circular bore has been divided into equal-sized 6 sector regions by symmetry.In enforcement of the present invention, described hollow pyramid retroreflector 3 is adjusted in rotation, make retroreflector incident beam 12 its circular bore center of circle symmetry relative to retroreflector outgoing beam 13 in 6 sector regions in a pair of relative sector region, can avoid so described 12,13 light beams to beat the seam crossing at any two reflectings surface of retroreflector, thereby cause light loss and reduce folded light beam quality.
The realization of described scanning interferometer swing arm has utilized the reflective feature of pyramid retroreflector: any incident beam is not as long as its incidence point overlaps with the retroreflector bore center of circle, folded light beam all can be with certain transversal displacement by retroeflection, and outgoing beam and incident beam keeping parallelism; On incidence point and the eye point same diameter line in the circular incident bore of corner cube reflector, and the incidence point center of circle relative to eye point symmetry.In the time that described hollow pyramid retroreflector 3 scans, its self compensation mechanism can guarantee that any small skew being produced by rectilinear translation platform 4 can not affect the depth of parallelism of its outgoing beam 13 and incident beam 12; And the small traversing reflecting surface due to two-sided planar catoptron 7 of retroeflection light beam 13 that 3 inclination produces remains with the vertical of retroeflection light beam 13 and is compensated.Therefore, the boom structure of described light path folding can avoid the light beam in Michelson interferometer index glass scanning process to tilt and traversing problem dexterously.
Described fixing two-sided planar catoptron 7 can be substrate by circular glass material, two reflectings surface can select to add the metal film realization of plating different materials according to the spectrum working range of imaging Fourier transform spectrometer,, also can be realized by the block substrate polishing both surfaces of metal material.The quiet arm of swing arm in described scanning interferometer instrument apparatus, owing to all having adopted the structure of light path folding, is shared same two-sided planar catoptron 7 and is completed as two arms the device that the former road of light beam is reflected.This design proposal makes the structure of whole interferometer very compact, the miniaturization of the imaging Fourier transform spectrometer, that is very beneficial for building accordingly.In reality is implemented, under the prerequisite that meets requirement of mechanical strength, calculate according to how much that the thickness of known double mirrors 7 is more thin more easily makes whole interferometer volume-diminished.
Calculate according to how much known, if in described scanning interferometer instrument apparatus without described compensating plate 6, swing arm light path will be greater than quiet arm light path all the time; According to Fourier transform spectrometer, principle of work, the swash width of hollow pyramid retroreflector 3 must cover the zero optical path difference position of two arms, therefore needs to insert higher than the compensating plate of air refraction material to increase the light path of quiet arm light path.Described compensating plate 6 can be substrate by circular glass material, and two parallel planes of incidence can be selected to add the different anti-reflection film of plating according to the spectrum working range of imaging Fourier transform spectrometer, and realize.Calculate knownly according to geometrical optics, the refractive index of making described compensating plate 6 glass materials used is more high is more of value to reducing of described scanning interferometer volume.
In the time that the spectrum of target to be measured covers very wide wave band, the interference peaks light intensity that common interferometer forms at zero optical path difference place may cover great scope, therefore the dynamic range of detector is required harsh.And described compensating plate 6 is made for glass material, the light signal of different wave length is had to different refractive indexes, therefore there is certain dispersion; According to Fourier Transform Spectroscopy principle, the insertion of described compensating plate 6, make the light signal zero optical path difference position difference of described scanning interferometer to different wave length, therefore can greatly reduce the range of light intensity of the interference signal of described scanning interferometer generation, weaken the imaging Fourier trasform spectroscopy carrying out according to it and measure the high request to planar array detector dynamic range, thereby reduce the imaging Fourier transform spectrometer, system cost according to its structure.
Embodiment shown in Fig. 2 has been illustrated central principle of the present invention, and thought can also provide several improved embodiment accordingly, as shown in Fig. 3,4,5:
As shown in Figure 3, the two-sided planar catoptron 7 in the quiet arm of Fig. 2 and compensating plate 6 can be merged into an one side metal coating compensating plate 9.Described 9 can be substrate by circular glass material, one side towards 3 is perpendicular to its outgoing beam, after this mirror polish, according to the spectrum working range of imaging Fourier transform spectrometer,, select to add the metal film that plates certain thickness different materials as the shared catoptron of index glass two arms; Described 9 another side is parallel with metal-plated face, can add plating anti-reflection film.Described 9 use has merged two elements 6 and 7, has not only reduced component number, has reduced the complicacy that in cost and reality, element is installed, known according to how much calculating, also helps the volume that further reduces whole described scanning interferometer than scheme shown in Fig. 2.
As shown in Figure 4,45 ° of plane mirrors 5 in the quiet arm of Fig. 3 can be substituted by 45 ° of reflection right-angle prisms 10.Described 10 make for solid glass material, its hypotenuse reflecting surface selects to add the metal film realization of plating different materials according to the spectrum working range of imaging Fourier transform spectrometer,, its straight flange two planes can add plating anti-reflection film according to the spectrum working range of imaging Fourier transform spectrometer.Described 10 introducing is equivalent to the merging of compensating plate 6 and plane mirror 5, but still needs to use 9 light paths with balance two arms.Calculate knownly according to how much, with described 10 alternative 5, can reduce 9 thickness, thereby further dwindle the volume of interferometer as shown in Figure 3.
As shown in Figure 5, the described cube splitter 2 in Fig. 3 can be merged into one 45 ° parallel four limit body beam splitters 11 with 45 ° of plane mirrors 5.Described 11 can be made up of solid glass material, and the folded acute angle of two Adjacent Working Faces is 45 °; A pair of relative parallel workplace is light splitting surface and reflective surface, and another is that light beam goes out the plane of incidence to relative parallel workplace; Described light splitting workplace selects to add plating multilayer dielectric film according to the spectrum working range of imaging Fourier transform spectrometer,, described reflective workplace selects to add metal-coated membrane according to the spectrum working range of imaging Fourier transform spectrometer,, and described two go out incident working surface and can select add plating anti-reflection film according to the spectrum working range of imaging Fourier transform spectrometer.In actual enforcement, described in incident beam 1 vertical incidence after 11 a plane of incidence to its light splitting workplace, through the light beam directive interferometer swing arm of described light splitting workplace transmission; Through 45 ° of reflective surfaces of 11 described in the light beam directive of light splitting workplace reflection, after 45 ° of reflective surfaces reflections along the direction parallel with described incident beam 1, the exit facet transmission through described 11 and going out, the quiet arm of scanning interferometer described in directive; Sound two arm incident beams are back to described 11 light splitting surface and again meet along the former road of above-mentioned light path after being reflected by described one side metal coating compensating plate 9, after beam splitting again, the light beam that two beams go out described scanning interferometer overlaps and forms described outgoing beam 8.Described 11 use merged shown in Fig. 3 two elements 2 in scheme and 5 or Fig. 4 shown in 2 and 10 in scheme; This scheme has not only reduced component number, reduce the complicacy that in reality, element is installed, known according to how much calculating, use this scheme can reduce 9 thickness, also help the volume that further reduces whole described scanning interferometer than scheme shown in Fig. 2, Fig. 3 and Fig. 4.
The present invention can pass through or adopt existing techniques in realizing without the technical characterictic of describing; do not repeat them here; certainly; above-mentioned explanation is not limitation of the present invention; the present invention is also not limited in above-mentioned giving an example; variation, remodeling, interpolation or replacement that those skilled in the art make in essential scope of the present invention, also should belong to protection scope of the present invention.