CN107024430A - Many light path air absorbing cavities and its measuring system - Google Patents

Many light path air absorbing cavities and its measuring system Download PDF

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CN107024430A
CN107024430A CN201610066377.6A CN201610066377A CN107024430A CN 107024430 A CN107024430 A CN 107024430A CN 201610066377 A CN201610066377 A CN 201610066377A CN 107024430 A CN107024430 A CN 107024430A
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lens
light path
mirror
field lens
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CN107024430B (en
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杨铮
郭崟
孙利群
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Tsinghua University
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
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Abstract

The invention discloses a kind of many light path air absorbing cavities of even state, by the curvature center for the two of which object lens for changing the object lens multi-optical path absorption chambers of tradition Chernin types MMS tetra-, realize that (m 1) row (n 1) row facula position on the mirror of home court in addition to the row corresponding to incidence point and eye point is multiplexed four times, a line facula position multiplexing in incidence point respective column and auxiliary field lens is twice, so that cavity total number of pass times is increased to (4m 2) (2n 1), the structure proposed compared to traditional Chernin, light path increases one times or so, light path is effectively absorbed so as to be greatly promoted in the case of absorbing cavity constancy of volume, the detection limit of lowering apparatus.The invention also discloses a kind of many light path air absorbing cavities of odd state.The invention also discloses corresponding measuring system.

Description

Many light path air absorbing cavities and its measuring system
Technical field
The present invention relates to gas absorption spectra quantitative analysis tech field, more particularly to a kind of many light path air absorbing cavities and Its measuring system.
Background technology
Many light path air absorbing cavities are a kind of important devices being widely used in trace gas quantitative analytical instrument.Based on bright Bobi's that absorption law, increases detection light absorbs light path using the principle of light multiple reflections in the limited bulk of gas cell, So as to reduce the detection limit (can reach ppbv magnitudes) of the concentration detected to trace gas.
The method that increase conventional at present absorbs light path mainly has two kinds：1st, long light path Differential Optical Absorption Spectroscopy (LP- DOAS), absorption light path is lifted by directly detecting the distance between the R-T unit and cooperative target of light in space increase, received Transmitting apparatus is launched the emergent light of wideband light source using Cassegrain's formula telescope relatively above (can reach hundreds of at a distance into space Rice arrive several kms) cooperative target (such as:Prism of corner cube), then receive the echo-signal of reflection, the detection light of specific wavelength Absorbed in two-way process by under test gas, the absorption spectrum of gas can be constructed by differential optical absorption spectrum algorithm, So as to the gas mean concentration in inverting trip path.This instrument is aligned for light path, meteorology, screening in the range of measurement space The requirement of the conditions such as gear is strict；And can only obtain the mean concentration of under test gas in longer path, it is impossible to draw gas in space Exact concentrations distribution；And not readily portable, transfer and deployment.2nd, many light path air absorbing cavity methods, are carrying out gas absorption During spectral measurement, object gas is filled with multi-optical path absorption chamber first, then by the outgoing optical coupling of laser or white light source Into intracavitary carry out multiple reflections, experience one compared with after long light path from intracavitary outgoing, by measuring the light of different wave length in intracavitary Absorbed intensity, obtains the absorption spectrum of object gas, so that the information such as gas concentration at inverting.Certain in cavity size In the case of, light is more in the order of reflection that multi-optical path absorption intracavitary is passed through, and light path is longer, the target gas levels that can be realized Detection limit it is lower.
Chernin types MMS (multipass matrix system) is a kind of White Cell improvement in the prior art System, is a kind of multi-optical path absorption chamber that Chernin was proposed in 1991, it is broadly divided into two kinds of three object lens chambers and four object lens chambers Structure, wherein four object lens chambers meet four object lens M of eccentric conjugate relation using position1~M4Respectively with home court mirror F1The two of composition Individual PBWC structures, the light that laser or wideband light source are sent from auxiliary field lens F2The incident intracavitary in side, in wherein one PBWC Complete to shine auxiliary field lens F after coming and going2On, then switch in another PBWC and continue roundtrip, until from auxiliary field Mirror F2Opposite side outgoing, the overall structure of chamber is as shown in Figure 1.Field lens F of the incident light in the object lens chamber of Chernin types fouri、F2On The flare of the distributed rectangular of m rows (m can be any positive integer) n row (n can be any positive odd number) can be sequentially formed, (m=5, n=7 are taken in Fig. 2) as shown in Figure 2, the same facula position of wherein (m-1) row (n-2) row in home court mirror center is answered With (having reflected light twice to fall same facula position in a matrix) twice, therefore light is in total number of pass times of intracavitary (4m-2)·(n-1)。
It can thus be seen that above-mentioned multi-optical path absorption chamber is in field lens F1、F2The matrix type hot spot of upper formation can only be odd number Row, and even column can not be designed.Moreover, it is to have key issue to be solved in the industry that further increase, which absorbs light path,.
The content of the invention
In view of this, goal of the invention of the invention is：Lifted in the case of absorbing cavity constancy of volume and effectively absorb light path.
To reach above-mentioned purpose, what technical scheme was specifically realized in：
The invention provides a kind of many light path air absorbing cavities of even state, the two ends point of many light path air absorbing cavities of even state Field lens group and four objective lens are not relatively set with, and the field lens group includes the home court mirror and auxiliary of sphere apex coordinate vertical distribution Field lens；Four objective lens include the first object lens to the 4th object lens；The side of auxiliary field lens is provided with the light source incidence point of coincidence And eye point, respective coordinates are (X, y, 0), and light source enters from incidence point absorbs cavity, by between field lens group and four objective lens Multiple reflections, the matrix type hot spot distribution of m rows × n row is formed during eye point outgoing, in microscope group on the scene, line space is dr=4c, column pitch is dc=2w, m are natural number, and n is even number；
Three-dimensional cartesian coordinate system is set up using the sphere apex coordinate of home court mirror as coordinate origin；
The center of curvature coordinate of first object lens is CM1(w, c, 0)；
The center of curvature coordinate of second object lens is CM2(w ,-c, 0)；
The center of curvature coordinate of 3rd object lens is CM3(0, c, 0)；
The center of curvature coordinate of 4th object lens is CM4(0 ,-c, 0)；
The center of curvature coordinate of the home court mirror is (0,0, R)；
The center of curvature coordinate of the auxiliary field lens is (0, (2m-1) c, R).
Present invention also offers a kind of many light path air absorbing cavities of odd state, the two ends of many light path air absorbing cavities of odd state It is relatively set with field lens group and four objective lens respectively, the field lens group includes the home court mirror of sphere apex coordinate vertical distribution and auxiliary Help field lens；Four objective lens include the first object lens to the 4th object lens；The side of auxiliary field lens is provided with the light source incidence of coincidence Point and eye point, respective coordinates are (X, y, 0), and light source enters from incidence point absorbs cavity, by field lens group and four objective lens it Between multiple reflections, the matrix type hot spot distribution of m rows × n row, line space are formed during eye point outgoing, in microscope group on the scene For dr=4c, column pitch is dc=2w, m are natural number, and n is odd number；
Three-dimensional cartesian coordinate system is set up using the sphere apex coordinate of home court mirror as coordinate origin；
The center of curvature coordinate of first object lens is CM1(0, c, 0)；
The center of curvature coordinate of second object lens is CM2(0 ,-c, 0)；
The center of curvature coordinate of 3rd object lens is CM3(- w, c, 0)；
The center of curvature coordinate of 4th object lens is CM4(- w ,-c, 0)；
The center of curvature coordinate of the home court mirror is (0,0, R)；
The center of curvature coordinate of the auxiliary field lens is (0, (2m-1) c, R).
Present invention also offers a kind of direct absorption process measuring system, including described many light path air absorbing cavities, also wrap Include：Preposition Optical devices, rearmounted Optical devices, and detector；Preposition Optical devices include the first speculum and composite prism Part I, rearmounted Optical devices include the Part II of the second speculum and composite prism；
The Part I of composite prism is plane or sphere, and the Part II of composite prism is plane or sphere, institute The angle for stating Part I and Part II is 90 °；First speculum is parallel with the Part I of composite prism, the second speculum It is parallel with the Part II of composite prism；
First speculum is used to turn back incident light 90 ° to incide the Part I of composite prism；The of composite prism A part is used to imported into enter at the incidence point of many light path air absorbing cavities by incident light to absorb cavity；The second of composite prism Part is used to that the second speculum will to be imported into from the emergent light of the eye point outgoing of many light path air absorbing cavities；Second speculum For emergent light to be turned back 90 °, it is sent on detector.
Absorbed present invention also offers a kind of off-axis many light path cavity-type BPM measuring systems, including described many light path gases Chamber, in addition to：Preposition Optical devices, rearmounted Optical devices, and the first linear array detector and the second linear array detector；
Preposition Optical devices include optoisolator, for receiving the light of light source, and prevent emergent light feedback into light source；
Rearmounted Optical devices include condenser lens, for focusing on the transmitted light beam on auxiliary field lens in the spy of linear array detector On survey face；
Linear array detector, for detecting transmitted light intensity.
Absorbed present invention also offers a kind of off-axis many light path cavity-type BPM measuring systems, including described many light path gases Chamber, in addition to：Preposition Optical devices and discrete detector；
Preposition Optical devices include optoisolator, for receiving the light of light source, and prevent emergent light feedback into light source；
Discrete detector, the light intensity for detecting the transmitted light beam on auxiliary field lens.
As seen from the above technical solutions, the present invention is by changing the object lens multi-optical path absorption chambers of tradition Chernin types MMS tetra- Two of which object lens the curvature center, realize (the m- in addition to the row corresponding to incidence point and eye point on the mirror of home court 1) row (n-1) row facula position is multiplexed four times, a line facula position multiplexing in incidence point respective column and auxiliary field lens twice, from And cavity total number of pass times is increased to (4m-2) (2n-1), the structure proposed compared to traditional Chernin, light path is increased One times or so, light path, the detection limit of lowering apparatus are effectively absorbed so as to be greatly promoted in the case of absorbing cavity constancy of volume.
Brief description of the drawings
Fig. 1 is many light path air absorbing cavity structural representations of prior art Chernin types.
Fig. 2 is the matrix type that m rows × n row are formed in many light path air absorbing cavity microscope groups on the scene of prior art Chernin types Hot spot distribution schematic diagram.
Fig. 3 is the test system composition frame chart based on many light path air absorbing cavities.
Fig. 4 is many light path air absorbing cavity structural representations of the even state of the embodiment of the present invention one.
Fig. 5 is hot spot reflected order schematic diagram on many light path air absorbing cavity field lenses of the even state of the embodiment of the present invention one.
Fig. 6 is each minute surface scale diagrams of many light path air absorbing cavities of the even state of the embodiment of the present invention one.
Fig. 7 is many light path air absorbing cavity structural representations of the odd state of the embodiment of the present invention two.
Fig. 8 is hot spot reflected order schematic diagram on many light path air absorbing cavity field lenses of the odd state of the embodiment of the present invention two.
Fig. 9 is each minute surface scale diagrams of many light path air absorbing cavities of the odd state of the embodiment of the present invention two.
Figure 10 (a) is direct absorption process measuring system side view knot of the embodiment of the present invention three based on many light path air absorbing cavities Structure schematic diagram.
Figure 10 (b) is that the direct absorption process measuring system of the embodiment of the present invention three is imitative in TracePro ray-tracing softwares True result.
Figure 11 (a) is off-axis many light path chambers for detecting after focusing of the embodiment of the present invention four based on many light path air absorbing cavities Decline and swing measuring system overlooking the structure diagram.
Figure 11 (b) is the off-axis many light path cavity-type BPM measuring systems detected after the embodiment of the present invention four is focused in TracePro Simulation result in Optics trace software.
Figure 12 (a) declines for off-axis many light path chambers of discrete detection of the embodiment of the present invention four based on many light path air absorbing cavities Swing measuring system overlooking the structure diagram.
Figure 12 (b) is off-axis many light path cavity-type BPM measuring systems of the discrete detection of the embodiment of the present invention four in TracePro light Learn the simulation result in tracing software.
Embodiment
For the purpose of the present invention, technical scheme and advantage is more clearly understood, develop simultaneously embodiment referring to the drawings, The present invention is described in more detail.
Fig. 3 is the test system composition frame chart based on many light path air absorbing cavities.Including light source 301, preposition Optical devices 302nd, many light path air absorbing cavities 303, rearmounted Optical devices 304, detection device 305.In measurement process, sealing many first Under test gas is full of in light path air absorbing cavity room, after after gas equalization, by light source 301 by preposition Optical devices 302 from Entrance window is coupled into many light path air absorbing cavities 303, completes to enter cavity to during exit window outgoing from entrance window (4m-2) (2n-1) secondary reflection, be coupled into detection device by rearmounted Optical devices afterwards, obtain the suction of under test gas Receive spectral signal.
Wherein, many light path air absorbing cavities 303 proposed by the present invention are identical anti-for R 6 spheres by radius of curvature Microscope group is penetrated into wherein one end is main field lens F1With auxiliary field lens F2The field lens group of composition, the other end is object lens M1~M4The thing of composition Microscope group, the distance between field lens group and objective lens are about radius of curvature R, F1The center of curvature in objective lens M1~M4Aperture in In the symmetrical centre of the heart, F2The center of curvature in object lens M1And M3Aperture center line midpoint on, object lens M1~M4Curvature Center is in F1Near minute surface, its specific coordinate position can be divided into two kinds according to the difference of the flare matrix columns n of generation Situation：1st, n is even number, now referred to as many light path air absorbing cavities of even state；2nd, n is odd number, now referred to as many light path gases of odd state Absorbing cavity.It is introduced individually below.
The present invention is in auxiliary field lens F2Side be provided with the light source incidence point and eye point of coincidence, light source is clicked through from incidence Enter to absorb cavity, by the multiple reflections between field lens group and four objective lens, during eye point outgoing, shape in microscope group on the scene Into the matrix type hot spot distribution of m rows × n row, line space is dr=4c, column pitch is dc=2w, m are natural number, n be even number or Odd number.Therefore, many light path air absorbing cavities, by parameter group (R, m, n, dr, dc) characterize, wherein R be used field lens, The radius of curvature of the spherical reflectors such as object lens, m is by the line number of the matrix type spot array formed on field lens, and n is shape on field lens Into matrix type spot array columns, drFor the line space of matrix type spot array, dcFor the column pitch of matrix type hot spot.
Embodiment one
For many light path air absorbing cavities of even state, line number m is any positive integer (m=1,2,3......), and columns n is to appoint During meaning even number (n=2,4,6......), in order to make full use of field lens minute surface space, typically require that generation hot spot is overlapping on field lens, Require m >=2, n >=2.Object lens M1~M4The curvature center as shown in figure 4, Fig. 4 midpoints O be main field lens F1Sphere top Point, three-dimensional cartesian coordinate system is set up by the origin of coordinates of point O, then F2Sphere apex coordinate be ((0, (2m-1) c, 0), home court The sphere summit vertical distribution of mirror and auxiliary field lens；The center of curvature coordinate of each object lens is respectively：CM1(w, G, 0), CM2(w ,- C, 0), CM3(0,G, 0), CM4(0 ,-c, 0)；The center of curvature coordinate of two field lenses is respectively：F1(0,0,R),F2(0,(2m-1) c,R).Incident light is coupled into intracavitary from entrance window, and the wherein centre coordinate of entrance window is I (nw, (2m-1) c, 0).Light is each Continuous reflection in individual hysteroscope, in field lens F1And F2Upper formation m row n row hot spots, finally the position still near entrance window go out from intracavitary Penetrate, as shown in Figure 5 (with m=5 in Fig. 5, exemplified by n=6), light is the order that hot spot is produced on field lens in the number of times that intracavitary passes through (4m-2) (2n-1) (in Fig. 5 light intracavitary carried out 99 times come and go, number of pass times be 198 times).Between adjacent rows hot spot At intervals of drInterval d between=4c, adjacent two rowc=2w.In spot diameter d of the setting incident light source at entrance window0And light The corresponding numerical aperture of the source angle of divergence (NA), is so assured that in necessarily input light source (d0, NA) under the conditions of absorbing cavity Structural parameters group (R, m, n, dr, dc), wherein R is curvature radius of spherical reflector, and m is line number, and n is columns, drFor line space, dcFor column pitch.
Requirement according to table 1 just can determine that the size and position coordinates of each object lens and field lens.Table 1 is many light path gas of even state Body absorbing cavity dimensional parameters set up tables of data, unit：mm.
Table 2
Wherein, DxRepresent object lens in x-axis to maximum length, DyRepresent object lens in y-axis to maximum length, w1And h1Difference table Show home court mirror F1In x, y-axis to size, w2And h2Auxiliary field lens F is represented respectively2In x, y-axis to size, DrFor F1Sphere Summit (i.e. the origin of coordinates (0,0,0)) and the distance of top edge, DcRepresent F1Sphere summit and left hand edge distance, each mirror The size in face is as shown in Figure 6.
When (w, c) in each object lens coordinate is determined, ranks interval is also identified as dr=4c, dc=2w.Light is in chamber Interior roundtrip formation m row n row hot spots.Wherein in home court mirror F1Upper formation (m-1) row n row hot spots, order is often gone, each column outermost Hot spot apart from the half that mirror edges are row, column spacing, then F1The size of mirror is：
w1=2w (n-1)+w+w=2nw
h1=4c (m-1-1)+2c+2c=4 (m-1) c
Aid in field lens F2On can form 1 row (n-1) row hot spot, therefore, F2The size of mirror is：
w2=2 (n-1-1) w+w+w=2 (n-1) w
h2=2c+2c=4c
Although for many light path chambers of odd, even state, F1Mirror and F2The calculation formula of mirror size is identical, but mirror edges With mirror sphere summit (F1Mirror sphere summit is in (0,0,0), F2Mirror sphere summit is in (0, Y, 0)) distance it is different, meanwhile, enter The calculation formula of exit point coordinate is also differed, and situation analysis is divided below：
For many light path air absorbing cavities of even state, F1There is a row hot spot on x=0 axles where mirror sphere summit, its Right side (x>0) formedRow hot spot, left side (x<0) formedRow hot spot, therefore its left and right sides mirror edges is relative to sphere Summit is asymmetric, the distance between left hand edge and sphere summit：
F1Distance is to have a line hot spot on the y=c axles at c above mirror sphere summit, above it (y>C) have onRow Hot spot, and lower section (y<C) then haveRow.Therefore F1Two edges are asymmetric relative to sphere summit above and below mirror, top edge and ball The distance of vertex of surface is：
F2Mirror only has a row hot spot, so minute surface lower edges are symmetrical relative to its sphere summit；In its sphere summit institute X=0 axles on have a line hot spot, (x on the right side of it>0) with left side (x<0) haveRow hot spot, therefore F2The mirror left and right sides Edge is also symmetrical relative to sphere summit.
(xi,yi,zi) be each object lens (i takes 1,2,3,4) aperture center coordinate.In order to ensure the whole quilts of incident light Object lens are received, it is desirable to NA and d0Meet formula NA≤(D-d0)/2R, D represent the axial full-size of each object lens.And then, according to Formula d0+2RNA<Dx<2x, d0+2RNA<Dy<2y, determines D1xTo D4x、D1yTo D4y, the first objective aperture centre coordinate M1(x1, y1), the second objective aperture centre coordinate M2(-x2,-y2), the 3rd objective aperture centre coordinate M3(-x3,y3), the 4th objective aperture Centre coordinate M4(x4,-y4)；Wherein, d0Entrance pupil spot diameter is represented, NA represents numerical aperture, and R represents the song of spherical reflector Rate radius, Dx represents object lens in x-axis to maximum length, DyRepresent object lens in y-axis to maximum length.
(X, Y, 0) is the incidence/exit window centre coordinate, wherein X=nw, Y=(2m-1) c of Theoretical Design.In even state In the case of many light path air absorbing cavities, incidence point and the origin of coordinates (i.e. F1Mirror sphere summit) distance in the X direction isRow, Distance in the Y direction adds for cOK, therefore its transverse and longitudinal coordinate is respectively：
As first object lens M1Coordinate meet x1=X or yiThe angle of a dimension is adjusted merely by during=Y it is ensured that Incident light is beaten in M1Aperture center and ensure will not light leak.For convenience of explanation, x is taken here1=X, yi=Y, i.e. incident light are only Incident along z-axis, needing not move through any regulation just can incidence M1Aperture center.Object lens M1~M4Z coordinate z1~z4Meet ball Face speculum condition：Culminating point and center of curvature line are R.In order that adjacent rows and two row hot spots not aliasing on field lens, It is required that the row, column interval of hot spot is met on field lens：
dr=4c>d0
dc=2w>d0
So far just complete for (d under the conditions of known incident light source optical0, NA), for certain hot spot be distributed (m, n, 2w, 4c) mirror size adaptation because if the design of table size is minimum appearance and size, as long as therefore meet it is incident/go out In the case that exit point coordinate is constant, for meeting desired smaller m, n, corresponding optical texture can also be realized.
Embodiment under one group of special parameter of many light path air absorbing cavities of even state described herein：Assuming that launching spot diameter 10mm, NA=0.03, during radius of curvature R=600mm, selection (m, n, 2w, 4c) is respectively (5,6,15,15), the following ginseng of selection Number just completes the design of N=(4m-2) (2n-1)=198 new four object lens absorbing cavity, and ensure that approximate with launching spot 1:1 imaging outgoing.Table 3 is the parameter of the structure many light path air absorbing cavities of even state in example, unit：mm
Table 2
Embodiment two
For many light path air absorbing cavities of odd state, when line number m takes any positive integer (m=1,2,3......), columns n is During any odd number (n=1,3,5......), also require that generation hot spot is overlapping on field lens, that is, requires m >=2, n >=3.Object lens M1 ~M4The curvature center as shown in fig. 7, still with home court mirror F1Sphere summit O set up three-dimensional rectangular coordinate for the origin of coordinates It is, then F2Sphere apex coordinate for ((0, (2m-1) c, 0), home court mirror and auxiliary field lens sphere summit vertical distribution；Each The center of curvature coordinate of object lens is respectively：CM1(0, c, 0), CM2(0 ,-c, 0), CM3(- w, c, 0), CM4(- w ,-c, 0)；Two fields The center of curvature coordinate of mirror is still：F1(0,0, R), F2(0, (2m-1) c, R).The centre coordinate of entrance window is I ((n-1) w, (2m- 1) c, 0).Light is still in field lens F1And F2Upper formation m row n row hot spots, finally the position near entrance window is from intracavitary outgoing, field As shown in Figure 8 (with m=5 in Fig. 8, exemplified by n=7), the number of times passed through is (4m-2) (2n-1) (figure to the order that hot spot is produced on mirror In 8 light intracavitary carried out 117 times come and go, number of pass times be 234 times).The row, column interval of adjacent spots is respectively dr=4c, dc =2w.It can equally determine in necessarily input light source (d0, NA) under the conditions of absorbing cavity structural parameters group (R, m, n, dr, dc).Press Requirement according to table 3 just can determine that the size and position coordinates of each object lens and field lens.Table 3 is many light path air absorbing cavity chis of odd state Very little parameter sets up tables of data, unit：mm.
Table 3
The radius of curvature of wherein all spherical reflectors is R, DxRepresent object lens in x-axis to maximum length, DyRepresent that object lens exist Y-axis is to maximum length, w1And h1Home court mirror F is represented respectively1In x, y-axis to size, w2And h2Auxiliary field lens F is represented respectively2 X, y-axis to size, DrFor F1Sphere summit (i.e. the origin of coordinates (0,0,0)) and top edge distance, DcRepresent F2Sphere Summit and the distance of left hand edge, the size of each minute surface are as shown in Figure 9.
For many light path air absorbing cavities of odd state, F1There is a row hot spot on x=0 axles where mirror sphere summit, its Right side (x>0) with left side (x<0) it is each to be formedRow hot spot, therefore its left and right sides mirror edges is pair relative to sphere summit Claim；F1Distance is to have a line hot spot on the y=c axles at c above mirror sphere summit, above it (y>C) have onRow light Spot, and lower section (y<C) then haveRow.Therefore F1Two edges are asymmetric relative to sphere summit above and below mirror, top edge and sphere The distance on summit is：
F2Mirror only has a row hot spot, so minute surface lower edges are symmetrical relative to its sphere summit；And on its sphere summit There is a line hot spot on the x=0 axles at place, have on the right side of itRow hot spot, left side hasRow hot spot, therefore F2Mirror or so two Lateral edges are asymmetric relative to sphere summit, and left hand edge is with sphere vertex distance：
(xi,yi,zi) be each object lens (i takes 1,2,3,4) aperture center coordinate.In order to ensure the whole quilts of incident light Object lens are received, it is desirable to NA and d0Meet formula NA≤(D-d0)/2R, D represent the axial full-size of each object lens.And then, according to Formula d0+2RNA<Dx<2x, d0+2RNA<Dy<2y, determines D1xTo D4x、D1yTo D4y, the first objective aperture centre coordinate M1(x1, y1), the second objective aperture centre coordinate M2(-x2,-y2), the 3rd objective aperture centre coordinate M3(-x3,y3), the 4th objective aperture Centre coordinate M4(x4,-y4)；Wherein, d0Entrance pupil spot diameter is represented, NA represents numerical aperture, and R represents the song of spherical reflector Rate radius, Dx represents object lens in x-axis to maximum length, DyRepresent object lens in y-axis to maximum length.
(X, Y, 0) is incidence/exit window centre coordinate of Theoretical Design, wherein, X=(n-1) w, Y=(2m-1) c. In the case of many light path air absorbing cavities of odd state, incidence point and the origin of coordinates (i.e. F1Mirror sphere summit) distance in the x direction isRow, distance in y-direction adds for cOK, therefore its transverse and longitudinal coordinate is respectively：
As first object lens M1Coordinate meet x1=X or yiThe angle of a dimension is adjusted merely by during=Y it is ensured that Incident light is beaten in M1Aperture center and ensure will not light leak.For convenience of explanation, x is still taken1=X is while yi=Y, i.e. incident light As long as incident along z-axis, needing not move through any regulation just can incidence M1Aperture center.Object lens M1~M4Z coordinate z1~z4Meet Spherical reflector condition：Culminating point and the center of curvature line distance be R.In order that adjacent rows and two row hot spots are not on field lens Aliasing, it is desirable to which the row, column interval of hot spot still needs to meet on field lens：
dr=4c>d0
dc=2w>d0
So far just complete for (d under the conditions of known incident light source opticalo, NA), for certain hot spot be distributed (m, n, 2w, 4c) mirror size adaptation because if the design of table size is minimum appearance and size, as long as therefore meet it is incident/go out In the case that exit point coordinate is constant, for meeting desired smaller m, n, corresponding optical texture can also be realized.
Embodiment under one group of special parameter of many light path air absorbing cavities of odd state described herein：It will again be assumed that launching spot is straight Footpath 10mm, NA=0.03, radius of curvature R=600mm now select (m, n, 2w, 4c) to be respectively (5,7,15,15), and selection is such as Lower parameter just completes the design of N=(4m-2) (2n-1)=234 new four object lens absorbing cavity, and ensure that and launching spot Approximate 1:1 imaging outgoing.Table 4 is the parameter of the structure many light path air absorbing cavities of odd state in example, unit：mm
Table 4
To sum up, in many light path air absorbing cavities of even state, or many light path air absorbing cavities of odd state, by changing tradition The curvature center of the two of which object lens of the object lens multi-optical path absorption chambers of Chernin types MMS tetra-, is realized on the mirror of home court except incidence (m-1) row (n-1) row facula position outside row corresponding to point and eye point is multiplexed four times, incidence point respective column and auxiliary field A line facula position on mirror is multiplexed twice, so that cavity total number of pass times is increased to (4m-2) (2n-1), compared to biography The structure that the Chernin that unites is proposed, light path increases one times or so, so as to greatly promoted in the case of absorbing cavity constancy of volume Effect absorbs light path, the detection limit of lowering apparatus.
For above-mentioned many light path air absorbing cavities, present invention also offers directly absorb and off-axis many light path cavity-type BPMs two Plant in the measuring system of absorption spectrum metering system, the system, many light path air absorbing cavities of even state, or many light path gases of odd state Absorbing cavity is all suitable for.It is described in detail below by embodiment three and example IV.
Embodiment three
The principle of direct absorption process measuring system gas absorption spectra is to be based on Lambert-Beer's law, i.e., when a branch of parallel Light is by (trace gas such as to be measured) during a certain uniform non-scatter extinction material, and its absorbance A is dense with extinction material to be measured Degree C and absorber thickness l is directly proportional：
A (λ)=ln [I0(λ)/I (λ)]=ln [1/T (λ)]=σ (λ) Cl
Wherein I0(λ) and I (λ) be respectively the incident light intensity absorbed before sample on certain specific wavelength λ and by sample after Transmitted light intensity, A (λ) is referred to as absorbance (or optical density), T (λ) be the transmittance of testing sample, i.e. transmitted intensity with it is incident The ratio between luminous intensity, C is the concentration of testing sample, and l is the optical path length that light passes through in the sample, and σ (λ) is referred to as absorbing sample in spy The absorption cross-section data for determining various trace gas in the absorption cross-section in wavelength X, air can be by inquiring about the standards such as HITRAN Gas data storehouse is obtained, and in the case of absorbing known to light path l, is absorbed by measuring light intensity by the change before and after sample A (λ) is spent, the concentration of under test gas is finally inversed by according to above formula, here it is the directly principle of absorption process measurement.As can be seen that in energy The minimal absorption degree enough measured is certain, in the case of absorption cross-section σ (λ) is known, and the Cmin that can be finally inversed by is with absorbing light Journey is inversely proportional, i.e., the absorption light path l in air absorbing cavity is longer, and the gas Cmin that instrument can be measured is lower, detection Limit is lower.
Because the incidence point and eye point distance of many light path air absorbing cavities proposed by the present invention are too near, be unfavorable for light source and The placement of detector.The present invention proposes a kind of direct absorption process measuring system, come overcome because entrance and exit too close to Drawback.This system is all suitable for even state and many light path air absorbing cavities of odd state.
The system also includes in addition to many light path air absorbing cavities：Preposition Optical devices, rearmounted Optical devices, and detection Device；Preposition Optical devices include the Part I of the first speculum and composite prism, and rearmounted Optical devices include the second speculum With the Part II of composite prism；
The Part I of composite prism is plane or sphere, and the Part II of composite prism is plane or sphere, institute The angle for stating Part I and Part II is 90 °；First speculum is parallel with the Part I of composite prism, the second speculum It is parallel with the Part II of composite prism；
First speculum is used to turn back incident light 90 ° to incide the Part I of composite prism；The of composite prism A part is used to imported into enter at the incidence point of many light path air absorbing cavities by incident light to absorb cavity；The second of composite prism Part is used to that the second speculum will to be imported into from the emergent light of the eye point outgoing of many light path air absorbing cavities；Second speculum For emergent light to be turned back 90 °, it is sent on detector.
Below by taking many light path air absorbing cavities of odd state as an example, side view structure such as Figure 10 of its direct absorption process measuring system (a) shown in.Figure 10 (b) is simulation result of the direct absorption process measuring system in TracePro ray-tracing softwares.Compound rib Mirror is by plane P that angle is 90 °1And Spherical Surface S1Composition, preposition Optical devices include the first speculum Pa and plane P1, rearmounted light Learning device includes the second speculum Pb and Spherical Surface S1, the first speculum Pa, which turns back incident light 90 °, incides the flat of composite prism Face P1On, at the incidence window for directing light into many light path air absorbing cavities, after light beam reflex behavior described above, go out The Spherical Surface S of composite prism will be passed through in incidence window neighbouring position outgoing by penetrating light1It imported on the second speculum Pb, second is anti- Penetrate mirror Pb emergent light is turned back 90 °, be sent on detector.According to the similitude of incident light and emergent light, if adjustment is compound The position of prism so that incident beam compared to the incidence window position (X, Y) of design offset downward a certain distance Δ y or To the right after offset distance Δ x, the symmetric position of such outgoing beam and incident beam on the incidence point (X, Y) of design is realized The separation of incident light and outgoing optical position, a little all beats on field lens to ensure, it is desirable to which the distance of skew meets following want Ask：
0<Δx≤1/4min(dr,dc)
Or 0<Δy≤1/4min(dr,dc)
Composite prism S1Effect be to focus on outgoing beam on detector, it is assumed that many light path air absorbing cavities are all anti- The radius of curvature for penetrating mirror is R, and composite prism is d apart from the distance of exit window1, by S1, it is necessary to propagation distance d after reflection2 Detection target surface can be entered, according to object-image relation, meet prism S1Radius of curvature R1Should be
So far to parameter (m, n, dr, dc) one for the present invention many light path chambers front and rear integration optics set Meter, it is equally applicable to even state and many light path chambers of odd state.
Specific embodiment can take set below parameter：X=45mm, Y=33.75mm, m=5, n=7, dr=15mm, dc=15mm, R=600mm, Δ y=2mm set composite prism to be located at apart from incidence window d1At=100mm positions, it is assumed that multiple The reflected light for closing prism passes through d2=400mm enters the entrance of spectrometer or Photodetection system, therefore, according to formulaThe Spherical Surface S of composite prism1Radius of curvature R1=400mm.
In order to which many light path air absorbing cavities for describing the present invention are used for the measuring system that direct absorption process is measured, system Light source can select laser or broadband radiation light source (xenon lamp, tungsten lamp etc.), and detection device is according to being to be directed to narrow-band spectrum scope Detection and broadband spectral range detection, can be respectively adopted photodiode detector or grating spectrograph/Fourier's infrared light Spectrometer is detected.
Example IV
Off-axis many light path cavity-type BPM measuring systems are transmitted by the hysteroscope diverse location measured in multi-optical path absorption chamber Light, fitting emitting cavity swings curve with declining of decaying of light path, so as to build the measuring method of absorption spectrum.Traditional cavity ring-down spectroscopy (Cavity Ring-Down Spectroscopy) is coupled into identical two sides using pulse or continuous laser along axis In the optical stabilization resonator of high reflectance spherical reflector composition, fast optical detectors detection arteries and veins is utilized in the other end of chamber The situation that laser intensity is decayed with the time is rushed, or is closed using fast optical switch after incoming continuous wave laser, the continuous glistening light of waves is measured The strong decay with the time, fits the exponential curve of decay, obtains the time τ required for light intensity decays to 1/e from initial value, i.e., Ring-down time, then obtains loss of the light in intracavitary according to following formula：
Wherein R (λ) is the reflectivity of high reflectance spherical reflector, is the function of wavelength X, d is between the hysteroscope of two sides Distance, L is the length of intracavitary sample cell, and c is the light velocity.Equation right-hand member Section 1 represents what is brought by the reflectivity of hysteroscope less than 1 Cavity loss, Section 2 is then represented due to the loss that intracavity gas absorption band comes.Measurement is not put into the cavity of absorption cell first Ring-down time τ0(λ), now equation right-hand member Section 2 is 0, even if also saying τ0(λ) only characterizes the loss of cavity；Then measurement is put into Cavity-type BPM time τ (λ) of gas absorption cell, now τ (λ) characterize the superposition for the loss that cavity and gas absorption band come, pass through Following formula can be finally inversed by the concentration of under test gas：
Although tradition CRDS methods have effective optical length, detection limit is low, the advantage such as insensitive to intensity noise, needs The photodetector to be exceedingly fast rise time, and need pulsed laser source or high-speed switch or intensity tune are carried out to continuous laser source System, causes detection cost higher；It is that the event of swinging that declines many times is detected in certain detection time actually to decline and swing measurement, then will Obtained result is averaged, it is assumed that declining for being detected within the unit interval swings event times for N, then the detection obtained after being averaged Limit withIt is directly proportional, i.e., declining of being detected in the unit interval swings that event times are more, and the detection limit that can be realized is lower.And The repetition rate of traditional CRDS measurements is limited to single ring-down time τ (λ), if τ (λ) is smaller, single, which declines, swings the detection of realization Limit is just relatively low, if τ (λ) is larger, the number of times for the event of swinging that declines that can be measured in the unit interval will be reduced.I.V.Nikolaev Off-axis many light path chamber diode ring-down spectroscopies Deng proposition are just improved for problem above, utilize off-axis multi-optical path absorption Chamber and the detector being spatially separated realize cavity ring-down spectroscopy, that is, utilize the detector detection relevant position on hysteroscope diverse location Output intensity, because the light path that the corresponding light of hysteroscope diverse location passes through in intracavitary is different, therefore corresponding light intensity is just suitable Emergent light light intensity in the traditional CRDS event of swinging that declines not in the same time.The photodetection that this method need not be exceedingly fast the rise time Device, carries out high-speed switch or modulation, while when also substantially increasing unit without using light-pulse generator or to continuous radiant The quantity of the interior event of swinging that declines that can be measured, but because its off-axis many light path chamber used is Herriott die cavities, to minute surface Utilization rate is relatively low, and the hot spot possible position of the different light paths of correspondence is overlapping.And many light path gases proposed in the present invention are inhaled Larger separation can be realized by design in position and direction between emergent light of the receipts chamber on auxiliary field lens, ensured simultaneously Longer light path, therefore had the advantage that in off-axis many light path cavity-type BPM measurements.
Off-axis many light path cavity-type BPM measuring systems of the present invention are divided into two kinds, and a kind of is to use linear array detector after focusing on Off-axis many light path cavity-type BPM measuring systems, will aid in the secondary transmitted light beams of 2 (n-1) on field lens to enter after focusing on using linear array detector Row detection, obtains off-axis many light paths and declines to swing signal, so as to build the absorption spectrum of under test gas.One kind is to use discrete detector Off-axis many light path cavity-type BPM measuring systems, will aid in field lens on 2 (n-1) secondary transmitted light beams visited using discrete detector Survey, obtain off-axis many light paths and decline to swing signal, so as to build the absorption spectrum of under test gas.Illustrate separately below.
Detected after focusing：
Off-axis many light path cavity-type BPM measuring systems that the present invention is detected after focusing on, in addition to many light path air absorbing cavities, are also wrapped Include：Preposition Optical devices, rearmounted Optical devices, and the first linear array detector and the second linear array detector；Preposition Optical devices Including optoisolator, for receiving the light of light source, and emergent light feedback into light source is prevented；Rearmounted Optical devices include focusing on thoroughly Mirror, for focusing on the transmitted light beam on auxiliary field lens in the test surface of linear array detector；Linear array detector, for detecting transmission Light intensity.
Wherein, the common intersection and the z-axis direction distance of condenser lens of outgoing beam on field lens are aided in
The distance of outgoing beam focus point and condenser lens in z-axis direction
The abscissa of the common intersection of each bar light beam sent on first object lens
The abscissa of the common intersection of each article of light beam sent on 3rd object lens
The top edge abscissa x of first linear array detector1, n-1Meet：
The lower edge abscissa x of first linear array detector1,1Meet：
The top edge abscissa x of second linear array detector3, n-1Meet：
The lower edge abscissa x of second linear array detector3,1Meet：
The minimum widith H of first linear array detector test surface1Meet：x1,1-x1, n-1≤H1；
The minimum widith H of second linear array detector test surface2Meet：x3,1-x3, n-1≤H2；
Wherein, R represents the radius of curvature of spherical reflector, and the columns of n representing matrix types hot spot distribution, f represents to focus on thoroughly The focal length of mirror, d represents condenser lens with aiding in the distance between field lens.
To detect the NO near 662nm wavelength3Exemplified by absworption peak.During using the scheme detected after focusing, light source can make With the semiconductor laser near 662nm wavelength, the IQu2C types diode of such as Power Technology Inc. companies swashs Light device, its centre wavelength is in 661.85nm, close to 662nmNO3Absworption peak, angle of divergence ＜ 1mrad (numerical aperture NA ＜ 0.0005) directional light can, be considered as.The light that light source is sent first passes around an optoisolator, because finally going out from intracavitary The light penetrated, in order to prevent emergent light from feeding back to laser, influences the normal work of laser, optoisolator almost along backtracking The IO-3D-660-VLP types of Thorlabs companies can be used.Subsequent light enters intracavitary roundtrip, some specific reflection number of times Light from auxiliary field lens F2Upper outgoing, might as well be so that columns is many light path air absorbing cavity of odd number as an example：Assuming that line number is m (m= 1,2,3......）, columns is n（N=1,3,5......), then it is respectively 1 (4m-2), 3 (4m- in intracavitary number of pass times 2), 5 (4m-2), (2n-3) (4m-2) light beam are from the first object lens M1Aperture center is nearby sent, incremental according to x coordinate Sequentially from F2Upper outgoing, the light beam as shown in each solid arrow in Figure 11 (a)；It is respectively 2 (4m- in intracavitary number of pass times 2), 4 (4m-2), 6 (4m-2), (2n-2) (4m-2) light beam are from the 3rd object lens M3Aperture center is nearby sent, according to x The order that coordinate successively decreases is from F2Upper outgoing, the light beam as shown in each overstriking solid arrow in Figure 11 (a).In F2One is placed afterwards The larger condenser lens of bore (such as customization focal length and the Fresnel Lenses of bore), then from M1And M3The light beam of upper reflection will be respectively Converge at two common intersections；Simultaneously when the incident intracavitary of directional light, each light beam is converged in the midpoint of chamber, then divergently From F2Locate on outgoing, the test surface for two linear array detectors for focusing on Figure 11 (a) respectively after condenser lens, linear array detection Device can use the S11156-2048-01 back lighting type CCD line array sensors of Bin Song companies, and it is about in 662nm quantum efficiency 75%, photosensitive area is 28.672mm × 1.000mm, and pixel count is 2048, and most fast reading speed is 10MHz.When each in figure The radius of curvature R of individual spherical reflector, M3And M4Center of curvature abscissa-w, columns n (odd number), the focal length f of condenser lens, And lens and auxiliary field lens F2The distance between after the parameter such as d determines, in the case where paraxial optics is approximate, we can just count respectively Calculate F2The common intersection of upper outgoing beam and the z-axis direction of condenser lens are apart from L, and each outgoing beam focus point is with focusing on Lens z-axis direction apart from l, and two linear array detector test surfaces minimum widith H, it is final by changing parameter d and f Obtain meeting the design of actual detector size and instrument overall dimension.
First, M1And M3The light beam sent respectively on mirror is in F2The middle point coordinates of upper emergent light spot is (- w, Y, 0), therefore is gathered The optical axis of focus lens can be along x=-w, and this straight line of y=Y is placed, because each light beam can all be considered as from M1And M3Hole Footpath center is sent, and convergence of such condenser lens to these light beams can be considered as the point thing progress paraxial imagery for R+d to object distance, So as to obtain the distance of each common intersection and condenser lens in z-axis direction：
And when the incident many light path air absorbing cavities of directional light, it is believed that from M1And M3Each bar light beam of upper reflection is focused on On the midpoint of cavity axis, that is,Place, so effect of the lens to each bar light beam can be considered as is to object distance Point thing into paraxial picture, therefore distance of each outgoing beam focus point with condenser lens in z-axis direction is met：
Next two respective abscissas of common intersection are calculatedM first1(can be with the line of lens centre Be considered as one virtual " chief ray ", as shown in dotted line in Figure 11 (a)) and lens axis angle theta1Meet
M3With the line (one virtual " chief ray " equally being can be considered, as shown in dotted line in Figure 11 (a)) of lens centre With the angle theta of lens axis3Meet
So as to theoretical, the M according to paraxial optics1On each bar light beam common intersection (common intersection 1 in Figure 11 (a)) that sends Abscissa is
M3On the abscissa of each bar light beam common intersection (common intersection 2 in Figure 11 (a)) that sends be
Based on common intersection and abscissa X1And X3, the upper and lower edge focusing point of two linear array detectors can be calculated respectively Coordinate, so as to be compared with the test surface width H of detector, so that it is determined that whether design reasonable.M first1Sent on mirror Top edge light beam in F2Abscissa is-(n-1) w on minute surface, and abscissa on the focusing lens is-(n-1) w- (d/R) (2n- 4) w, light beam focuses on the lower edge of linear array detector 1, the abscissa x of its focus point1,2Meet：
M1The lower edge light beam sent on mirror is in F2Abscissa is (n-3) w, abscissa on the focusing lens on minute surface For (n-3) w, light beam focuses on the top edge of linear array detector 1, the abscissa x of its focus point1, n-1Meet：
In order that all light beam focus points can be received by detector photosurface, lower edges focus point and detector Width H1Need to meet：
x1,1-x1, n-1≤H1
M3The top edge light beam sent on mirror is in F2Abscissa is-(n-1) w, abscissa on the focusing lens on minute surface For-(n-1) w, light beam focuses on the lower edge of linear array detector 2, the abscissa x of its focus point3,1Meet：
M3The lower edge light beam sent on mirror is in F2Abscissa is (n-3) w, abscissa on the focusing lens on minute surface For (n-3) w+ (d/R) (2n-4) w, light beam focuses on the top edge of linear array detector 2, the abscissa x of its focus point3, n-1Meet
Same lower edges focus point and detector width H2Need to meet：
x3,1-x3, n-1≤H2
And in order that the position of linear array detector 1,2 is not interfered, it is necessary to make this two groups of focus points spatially divide Open, so that the lower edge focus point of linear array detector 1 should be higher than the top edge focus point of linear array detector 2, i.e.,
x3, n-1＞ x1,1
Using more design method, using following parameter：Between radius of curvature R=600mm, line number m=5, columns n=7, row Away from dC=15mm, condenser lens uses focal length f=150mm Fresnel Lenses, focus lamp and auxiliary field lens F2The distance between be 50mm.Calculating obtained parameter is respectively：Common intersection is apart from L=195mm；Each light beam focus point is apart from l=262.5mm； The lower edges coordinate of linear array detector 1 is respectively X1,1=-13.558mm, x1, n-1=-41.683mm；Linear array detector 1 it is upper Lower edge coordinate is respectively x3,1=20.625mm, x3, n-1=-7.5mm；The minimum photosurface width of the detector that needs is 28.125mm, less than the 28.672mm of shore pine S11156-2048-01 back lighting type CCD line array sensors, therefore can be realized.Root According to this shown in the simulation result such as Figure 11 (b) for the TracePro Optics trace softwares that upper parameter is carried out.
Discrete detection：
Off-axis many light path cavity-type BPM measuring systems of the discrete detection of the present invention, in addition to many light path air absorbing cavities, in addition to： Preposition Optical devices and discrete detector；Preposition Optical devices include optoisolator, for receiving the light of light source, and prevent outgoing Light feedback into light source；Discrete detector, the light intensity for detecting the transmitted light beam on auxiliary field lens.
Wherein, existed respectively by the two-beam of the 3rd object lens and the first objective lens exit at same facula position i on auxiliary field lens X-axis on test surface is to distance：
Respectively by M at two neighboring hot spot i and i+1 on auxiliary field lens3And M1X-axis of the light beam of mirror outgoing on test surface It is to distance：
And xI, 2-xI, 1=xI+1,1-xI, 2；
Plane where discrete detector and auxiliary field lens z-axis to distance
Wherein, R represents the radius of curvature of spherical reflector, the columns of n representing matrix types hot spot distribution；
I=1,2 ... (n-1)；J=1,2.
To detect the NO near 662nm wavelength3Exemplified by absworption peak.Using discrete photodiode after auxiliary field lens it is straight Tap into the basic phase of scheme detected after the scheme (such as Figure 12 (a) is shown) of row detection, its light source and coupling importation and focusing Together, the IQu2C type diode lasers of Power Technology Inc. companies, the IO- of Thorlabs companies can still be used The devices such as 3D-660-VLP type optoisolators.Its rearmounted probe portion is detected using (2n-2) individual photodiode of small volume Device is detected, can use Bin Song companies S-2386-18L type silicon photoelectric diodes, its photosensitive area size be 1.1mm × 1.1mm, front end carries Pyrex lens, is easy to be focused detection light, and photosensitive sensitive on the 662nm wavelength of detection ＞ 40% is spent, dark current is low (2pA), and the linearity and reliability are preferable.When being detected using discrete detector, it is thus necessary to determine that Plane where detector and auxiliary field lens F2Z-axis to apart from d and each detector x-axis to coordinate xI, jWherein footmark i (i= 1,2 ..., n-1) represent to aid in the two-beam of outgoing at the hot spot that i-th overlaps on field lens along x-axis positive direction, and j (j=1,2) then represents this two-beam 1 beam therein respectively, is represented during wherein J=1 from M1The light beam of upper reflection is (in Figure 12 (a) Light beam shown in solid arrow), and represented during J=2 from M3Light beam (the light shown in overstriking solid arrow in Figure 12 (a) of upper reflection Beam).It is to allow the corresponding x of each detector as far as possible that d calibrates standard reallyI, JSpatially equably separate, be easy to the reality of detector Put on border.
When d values are determined, M1Coordinate x after the beam exit of upper reflection in detection planeI, 1Meet：
And M3Coordinate x after the beam exit of upper reflection in detection planeI, 2Meet：
It can then calculate in F2X-axis of the two-beam of outgoing on test surface is to distance at upper same facula position i：
Respectively by M at two neighboring hot spot i and i+13And M1X-axis of the light beam of mirror outgoing on test surface be to distance：
Cause the corresponding x of each detectorI, jSpatially equably separate, it is necessary to meet：
xI, 2-xI, 1=xI+1,1-xI, 2
So as to solve
Wherein, i=1,2 ... (n-1)；J=1,2.That is, in auxiliary field lens F2On can produce n-1 hot spot, institute With i=1,2 ... (n-1).
Example still takes following parameter：Radius of curvature R=600mm, line number m=5, columns n=7, column pitch dr= 15mm.Plane where calculating obtained discrete detector and auxiliary field lens F2Z-axis to apart from d=54.5455mm.According to Upper parameter is emulated in Optics trace software TracePro, shown in obtained result such as Figure 12 (b).
The beneficial effects of the invention are as follows：
1. the center of curvature of the two of which object lens by changing the object lens multi-optical path absorption chambers of tradition Chernin types MMS tetra- Position, realizes (m-1) row (n-1) row facula position multiplexing four in addition to the row corresponding to incidence point and eye point on the mirror of home court Secondary, a line facula position in incidence point respective column and auxiliary field lens is multiplexed twice, so that cavity total number of pass times is increased to (4m-2) (2n-1), the structure proposed compared to traditional Chernin, light path increases one times or so, so as to absorb cavity Greatly promoted in the case that product is constant and effectively absorb light path, the detection limit of lowering apparatus.
2. by setting speculum and composite prism, realize that direct absorption process is surveyed based on above-mentioned many light path air absorbing cavities Amount.
3. by setting condenser lens and linear array detector, off-axis many light paths are realized based on above-mentioned many light path air absorbing cavities Cavity-type BPM is measured.
4th, by setting discrete detector, realize that off-axis many light path cavity-type BPMs are surveyed based on above-mentioned many light path air absorbing cavities Amount.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the scope of the present invention.It is all Within the spirit and principles in the present invention, any modification, equivalent substitution and improvement for being made etc. should be included in the guarantor of the present invention Within the scope of shield.

Claims (15)

1. a kind of many light path air absorbing cavities of even state, the two ends of many light path air absorbing cavities of even state are relatively set with field respectively Microscope group and four objective lens, the field lens group include the home court mirror and auxiliary field lens of sphere apex coordinate vertical distribution；Four thing Microscope group includes the first object lens to the 4th object lens；The side of auxiliary field lens is provided with the light source incidence point and eye point of coincidence, correspondence Coordinate is (X, Y, 0), and light source enters from incidence point absorbs cavity, by the multiple reflections between field lens group and four objective lens, from The matrix type hot spot distribution of m rows × n row is formed during eye point outgoing, in microscope group on the scene, line space is dr=4c, column pitch For dc=2w, m are natural number, and n is even number；
Three-dimensional cartesian coordinate system is set up using the sphere apex coordinate of home court mirror as coordinate origin；
The center of curvature coordinate of first object lens is CM1(w, c, 0)；
The center of curvature coordinate of second object lens is CM2(w ,-c, 0)；
The center of curvature coordinate of 3rd object lens is CM3(0, c, 0)；
The center of curvature coordinate of 4th object lens is CM4(0 ,-c, 0)；
The center of curvature coordinate of the home court mirror is (0,0, R)；
The center of curvature coordinate of the auxiliary field lens is (0, (2m-1) c, R).
2. many light path air absorbing cavities of even state as claimed in claim 1, it is characterised in that according to formula d0+2RNA<Dx<2x, d0+2RNA<Dy<2y, determines D1xTo D4x、D1yTo D4y, the first objective aperture centre coordinate M1(x1,y1), in the second objective aperture Heart coordinate M2(-x2,-y2), the 3rd objective aperture centre coordinate M3(-x3,y3), the 4th objective aperture centre coordinate M4(x4,-y4)； Wherein, d0Entrance pupil spot diameter is represented, NA represents numerical aperture, and R represents the radius of curvature of spherical reflector, and Dx represents that object lens exist X-axis is to maximum length, DyRepresent object lens in y-axis to maximum length.
3. many light path air absorbing cavities of even state as claimed in claim 1, it is characterised in that
(X, Y, 0), X=nw, Y=(2m-1) C；
Home court mirror aperture center coordinate is (w ,-c, 0), size w of the home court mirror in X-direction1=2nw, home court mirror is in Y direction Size h1=4 (m-1) c, home court mirror sphere summit and top edge apart from Dr=(2m-3) c, home court mirror sphere summit and the left side Edge apart from Dc=(n-1) w；It is (0, (2m-1) c, 0), chi of the auxiliary field lens in X-direction to aid in field lens aperture center coordinate Very little w2=2 (n-1) w, size h of the auxiliary field lens in Y direction2=4c.
4. many light path air absorbing cavities of even state as claimed in claim 1, it is characterised in that incidence point and outgoing are removed on the mirror of home court (m-1) row (n-1) row facula position outside the corresponding row of point is multiplexed four times, and one in incidence point respective column and auxiliary field lens Row facula position is multiplexed twice, light order of reflection N=(4m-2) (2n-1) total in many light path air absorbing cavities of the even state.
5. a kind of many light path air absorbing cavities of odd state, the two ends of many light path air absorbing cavities of odd state are relatively set with field respectively Microscope group and four objective lens, the field lens group include the home court mirror and auxiliary field lens of sphere apex coordinate vertical distribution；Four thing Microscope group includes the first object lens to the 4th object lens；The side of auxiliary field lens is provided with the light source incidence point and eye point of coincidence, correspondence Coordinate is (X, Y, 0), and light source enters from incidence point absorbs cavity, by the multiple reflections between field lens group and four objective lens, from The matrix type hot spot distribution of m rows × n row is formed during eye point outgoing, in microscope group on the scene, line space is dr=4c, column pitch For dc=2w, m are natural number, and n is odd number；
Three-dimensional cartesian coordinate system is set up using the sphere apex coordinate of home court mirror as coordinate origin；
The center of curvature coordinate of first object lens is CM1(0, c, 0)；
The center of curvature coordinate of second object lens is CM2(0 ,-c, 0)；
The center of curvature coordinate of 3rd object lens is CM3(- w, c, 0)；
The center of curvature coordinate of 4th object lens is CM4(- w ,-c, 0)；
The center of curvature coordinate of the home court mirror is (0,0, R)；
The center of curvature coordinate of the auxiliary field lens is (0, (2m-1) c, R).
6. many light path air absorbing cavities of odd state as claimed in claim 5, it is characterised in that according to formula d0+2RNA<Dx<2x, d0+2RNA<Dy<2y, determines D1xTo D4x、D1yTo D4y, the first objective aperture centre coordinate M1(x1,y1), in the second objective aperture Heart coordinate M2(-x2,-y2), the 3rd objective aperture centre coordinate M3(-x3,y3), the 4th objective aperture centre coordinate M4(x4,-y4)； Wherein, d0Entrance pupil spot diameter is represented, NA represents numerical aperture, and R represents the radius of curvature of spherical reflector, and Dx represents that object lens exist X-axis is to maximum length, DyRepresent object lens in y-axis to maximum length.
7. many light path air absorbing cavities of odd state as claimed in claim 5, it is characterised in that
(X, Y, 0), X=(n-1) w, Y=(2m-1) C；
Home court mirror aperture center coordinate is (0 ,-c, 0), size w of the home court mirror in X-direction1=2nw, home court mirror is in Y direction Size h1=4 (m-1) c, home court mirror sphere summit and top edge apart from Dr=(2m-3) c；Aid in field lens aperture center coordinate For (- w, (2m-1) c, 0), size w of the auxiliary field lens in X-direction2=2 (n-1) w, size h of the auxiliary field lens in Y direction2 =4c, auxiliary field lens sphere summit and left hand edge apart from Dc=nw.
8. many light path air absorbing cavities of odd state as claimed in claim 5, it is characterised in that incidence point and outgoing are removed on the mirror of home court (m-1) row (n-1) row facula position outside the corresponding row of point is multiplexed four times, and one in incidence point respective column and auxiliary field lens Row facula position is multiplexed twice, light order of reflection N=(4m-2) (2n-1) total in many light path air absorbing cavities of the even state.
9. a kind of direct absorption process measuring system, including many light path air absorbing cavities as described in any one of claim 1 to 8, Also include：Preposition Optical devices, rearmounted Optical devices, and detector；Preposition Optical devices include the first speculum and compound The Part I of prism, rearmounted Optical devices include the Part II of the second speculum and composite prism；
The Part I of composite prism is plane or sphere, and the Part II of composite prism is plane or sphere, described the The angle of a part and Part II is 90 °；First speculum is parallel with the Part I of composite prism, and the second speculum is with answering The Part II for closing prism is parallel；
First speculum is used to turn back incident light 90 ° to incide the Part I of composite prism；First of composite prism Dividing is used to imported into enter at the incidence point of many light path air absorbing cavities by incident light to absorb cavity；The Part II of composite prism For the second speculum will to be imported into from the emergent light of the eye point outgoing of many light path air absorbing cavities；Second speculum is used for Emergent light is turned back 90 °, is sent on detector.
10. system as claimed in claim 9, it is characterised in that the composite prism is additionally operable to, by adjusting self-position, Incidence point and eye point position are separated；
Wherein, incidence point is compared to the distance, delta that X is moved to rightx, or the distance, delta moved down compared to YyMeet respectively：
0<△x≤1/4min(dr,dc)
Or 0<△y≤1/4min(dr,dc)。
11. system as claimed in claim 9, it is characterised in that the sphere curvature radius of the Part II of the composite prismWherein, d1 is the distance between composite prism and eye point, and d2 is on composite prism Part II Distance of the reflected light travels to detector entrance.
12. a kind of off-axis many light path cavity-type BPM measuring systems, including many light path gases as described in any one of claim 1 to 8 Absorbing cavity, in addition to：Preposition Optical devices, rearmounted Optical devices, and the first linear array detector and the second linear array detector；
Preposition Optical devices include optoisolator, for receiving the light of light source, and prevent emergent light feedback into light source；
Rearmounted Optical devices include condenser lens, for focusing on the transmitted light beam on auxiliary field lens in the test surface of linear array detector On；
Linear array detector, for detecting transmitted light intensity.
13. system as claimed in claim 12, it is characterised in that
Aid in the common intersection and the z-axis direction distance of condenser lens of outgoing beam on field lens
The distance of outgoing beam focus point and condenser lens in z-axis direction
The abscissa of the common intersection of each bar light beam sent on first object lens
The abscissa of the common intersection of each article of light beam sent on 3rd object lens
The top edge abscissa x of first linear array detector1,n-1Meet：
The lower edge abscissa x of first linear array detector1,1Meet：
The top edge abscissa x of second linear array detector3,n-1Meet：
The lower edge abscissa x of second linear array detector3,1Meet：
The minimum widith H of first linear array detector test surface1Meet：x1,1-x1,n-1≤H1；
The minimum widith H of second linear array detector test surface2Meet：x3,1-x3,n-1≤H2；
Wherein, R represents the radius of curvature of spherical reflector, and the columns of n representing matrix types hot spot distribution, f represents condenser lens Focal length, d represents condenser lens with aiding in the distance between field lens.
14. a kind of off-axis many light path cavity-type BPM measuring systems, including many light path gases as described in any one of claim 1 to 8 Absorbing cavity, in addition to：Preposition Optical devices and discrete detector；
Preposition Optical devices include optoisolator, for receiving the light of light source, and prevent emergent light feedback into light source；
Discrete detector, the light intensity for detecting the transmitted light beam on auxiliary field lens.
15. such as the system of claim 14, it is characterised in that
Respectively by the two-beam of the 3rd object lens and the first objective lens exit on test surface at same facula position i on auxiliary field lens X-axis is to distance：
Respectively by M at two neighboring hot spot i and i+1 on auxiliary field lens3And M1X-axis of the light beam of mirror outgoing on test surface to away from From for：31
And xi,2-xi,1=xi+1,1-xi,2；
Plane where discrete detector and auxiliary field lens z-axis to distance
Wherein, R represents the radius of curvature of spherical reflector, the columns of n representing matrix types hot spot distribution；
I=1,2 ... (n-1)；J=1,2.
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