CN1060722A - A kind of rotary scanning interferometer - Google Patents

Abstract

A kind of optical path scanning device of interferometer, adopt the rotation of intersecting Double sided mirror to replace common moving of plane mirror to realize optical path scanning, simplify the gear train of instrument, saved the required precise guide rail device of motion scan, increased the stability of instrument; Compare with existing rotary scanning mode, its optical path difference and corner have good linear relationship, have kept the flux superiority of motion scan Michelson interferometer.In addition, this interferometer has characteristics simple in structure, that volume is little, can realize several centimetres optical path scanning easily, is applicable to the Fourier transform spectrometer of various spectrum workspace.

Description

A kind of rotary scanning interferometer

The invention belongs to spectrometric instrument, relate to interferometer rotary scanning Design of device technology.

Fourier transform spectrometer is one of best instrument of spectral measurement, it is a mathematical relation of utilizing interferogram and spectrogram, convert the interferogram of measuring to spectrogram by fourier transform and realize spectral measurement, so it can be regarded as by interferometer and fourier transform unit and forms.In order to measure interferogram, must realize steadily and accurate optical path scanning that as seen, the optical path scanning device is the key of the core interferometer design of Fourier transform spectrometer.

Be explanation interferometer optical path scanning Design of device scheme, at first introduce the multiple path difference scan mode of interferometer.The optical path scanning mode of interferometer can be divided into rotation and move two kinds by the forms of motion of scanned copy; Can be divided into two kinds of reflection and transmissions by the optical characteristics of scanned copy.Use the catoptrics part to move back and forth the interferometer of scanning at present in the Fourier transform spectrometer mostly.For example, classical Michelson interferometer, focus type double-sided reflecting mirror interferometer and two opal constructive interference instrument are that the motion scan mode of scanned copy also has certain application with the transmission wedge.Because domestic still do not have high-precision linear electric motors, adopt the interferometer of motion scan form all to need to change into the rotation of motor mobile, make transmission link complicated, and the motion scan mode requires scanned copy can only minimum inclination be arranged the relative standard position in motion process, in order to satisfy this requirement, interferometer usually is furnished with air guide rail, needs the investigation of superprecision, increased instrument cost, and annexes such as air tank, tensimeter make troubles also for the use of instrument.For transmission motion scan mode, the pass of its path difference change amount P and wedge displacement x is

P＝sinβ（n-1）x （1）

Wherein β is the wedge angle of wedge, and n is the wedge refractive index, because refractive index n is the function of wavelength X and temperature t, therefore different wavelength X will obtain different path difference P in scanning process, and this will make the interferogram distortion, therefore must proofread and correct the spectrum that obtains.The inclination that this interferometer moves wedge requires to decrease, and has increased stability of instrument, but because wedge displacement is about 10 times of scan light path difference, so the larger-size wedge of interferometer needs, this device is difficult to realize.

Because the shortcoming of motion scan interferometer, the exploitation of rotary scanning interferometer obtains people's attention.The optical element that can be used for rotary scanning has: parallel flat, prism of corner cube and Double sided mirror.

Interferometer shown in Figure 1 utilizes the rotation of parallel flat to realize optical path scanning.Because light is with any direction incident parallel flat, its emergent ray direct of travel is constant.When parallel flat 8 tilted, incident ray and emergent ray be keeping parallelism still, can eliminate droop error automatically.If parallel flat thickness is d, the scan start point angle of incidence of light is i, and the parallel flat refractive index is n, and then the pass of optical path difference P and rotational angle theta is:

$p=\frac{\mathrm{nd}}{\sqrt{n^2-{\sin }^2(i+\mathrm{\θ})}}-\frac{\mathrm{nd}}{\sqrt{n^2-{\sin }^2(i-\mathrm{\θ})}}----\left(2\right)$

By the visible this interferometer of formula (2) following shortcoming is arranged: 1 optical path difference P is relevant with refractive index n, needs the interferogram of measuring is proofreaied and correct; 2 optical path difference P and rotational angle theta are nonlinear relationship.In addition, the scanned copy parallel flat of this interferometer requires very high, processing difficulties.

The a pair of cubic prism of humans such as V.Tank of Germany replaces index glass and the horizontal glass in the former Michelson interferometer, and a prism of corner cube is fixed, and another piece prism of corner cube rotates the realization optical path scanning continuously, (see figure 2), and the pass of its optical path difference P and rotational angle theta is

P＝a+b·sin（θ+c） （3）

In the formula

$a=\frac{2(2\mathrm{\&beta;}+2\sqrt{3}\mathrm{Lx}+4\mathrm{dz}-2\sin \mathrm{\&beta;}(x\cos \mathrm{\&beta;}+z\sin \mathrm{\&beta;}))}{\sqrt{3(x^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="91111050X\_DRIMG1.png,91111050X\_DRIMG4.png"\; state="\{\{state\}\}">y</figure-callout>}}^2+z^2)}}$ $b=\frac{2(4d\sin \mathrm{\&beta;}-2\sqrt{3}(1+\sin \mathrm{\&beta;})\sqrt{(x^2+z^2){\sin }^2(\mathrm{\&beta;}+p)+y^2})}{\sqrt{3(x^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="91111050X\_DRIMG1.png,91111050X\_DRIMG4.png"\; state="\{\{state\}\}">y</figure-callout>}}^2+z^2)}}$ $c=\mathrm{arctg}\frac{\sqrt{x^2+{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="91111050X\_DRIMG1.png,91111050X\_DRIMG4.png"\; state="\{\{state\}\}">z</figure-callout>}}^2}\sin (\mathrm{\&beta;}+\mathrm{arctg}\frac{x}{z})}{y}$

See that easily a, b, c are by rotating shaft position (β, l), the constant of incident ray direction vector (x, y, z) and the decision of prism of corner cube size, optical path difference P is the sine function of rotational angle theta.If interferometer is made scanned copy with the solid axle cone prism, path difference is just relevant with refractive index, and the material cost of this piece prism of corner cube is very high, if adopt hollow prism to make scanned copy, the processing of hollow prism is very difficult.In addition, this interferometer beam bore is small-sized with respect to prism of corner cube, and the utilization factor of optical element is very low.

Fig. 3 is a pinacoid mirror rotary scanning interferometer, and two plane mirrors distance of establishing Double sided mirror is H, and the incident angle of optical path scanning starting point light is 45 °, and then the pass of optical path difference P and rotational angle theta is

$P=\sqrt{2}H(\cos \mathrm{\&theta;}+\sin \mathrm{\&theta;}-1)----\left(4\right)$

Because the sampling delay time of circuit is inevitable, so if optical path scanning speed (dP)/(dt) instability, then the sample interval is no longer equal, and this will cause the distortion of interferogram.Therefore, Fourier transform spectrometer requires in the optical path scanning process, and the fluctuation △ V of optical path scanning speed satisfies inequality with the ratio of optical path scanning speed V

$\frac{\mathrm{\&Delta;V}}{V}\&le;\frac{{8W}_{\mathrm{\&beta;}}}{\mathrm{\&tau;}\&CenterDot;V\&CenterDot;{\mathrm{\&sigma;}}_o\&CenterDot;\sqrt{R}}----\left(5\right)$

τ, V, σ in the formula ₀, R is respectively the maximum wave number and the instrument resolving power of circuit delay time, optical path scanning speed, apparatus measures spectral range, W _β" satellite line " that causes for interferogram distortion and the ratio of true line strength.

In the rotary scanning mode, the sweep velocity of optical path difference is

V＝ (dP)/(dt) ＝ (dP)/(dθ) × (dθ)/(dt) （6）

For above-mentioned three kinds of rotary scanning modes, because path difference p and rotational angle theta are nonlinear relationship, i.e. (dP)/(d θ) is not constant, and for satisfying (5) formula, motor speed (d θ)/(dt) needs constantly to change, and this has improved the requirement to speed control system.

Compare with traditional grating spectrograph, Fourier transform spectrometer has the flux superiority, and this is crucial characteristics of Fourier transform spectrometer.Because what spectrometer used all is the area source with certain size, so light part behind collimating mirror is parallel to optical axis, and all the other then favour optical axis.For the Fourier transform spectrometer that adopts motion scan, the light maximum inclination angle alpha that it allowed is by the maximum wave number σ of instrument resolving power δ σ and work spectral region _MaxDecision

$\cos \mathrm{\&alpha;}\&GreaterEqual;1-\frac{\mathrm{\&delta;\&sigma;}}{{\mathrm{\&sigma;}}_{\max }}----\left(7\right)$

In whole scanning process, the maximum differential of oblique light ray and parallel optical axis light optical path difference is

P-Pcosα= 1/(σ _max) =λ _min（8）

The rotary scanning Fourier transform spectrometer also must guarantee in overall optical path difference scanning process, and the maximum differential of all light optical path differences that is incident in interferometer is less than λ _MinOn the plane of vertical rotation axis, establish P ₀Be the optical path difference of parallel optical axis light, P _αFor the optical path difference of α angle light, P being arranged with optical axis _-αFor having with optical axis-optical path difference of α angle light.For parallel flat rotary scanning mode and parallel Double sided mirror rotary scanning mode, scanned copy forwards θ to by 0 ° and realizes optical path scanning, P ₀, P _α, P _-αBe respectively

P ₀＝P _（θ）-P _（0）

P _α＝P _（θ+α）-P _（α）

P _-α＝P _（θ-α）-P _（-α）

Obviously, P ₀, P _α, P _-αDifference depend on P and θ degree near linear relationship, α should satisfy inequality

Max（｜P ₀-P _α｜，｜P ₀-P _-α｜，｜P _α-P _-α｜）≤λ _min（9）

Because the optical path difference and the corner of parallel flat rotary scanning and parallel Double sided mirror rotary scanning are nonlinear relationship, the α value all very little (being about one of percentage of motion scan) that they allow.The light flux values that this path difference scan mode allows is about the per mille of translation scanning, the flux superiority forfeiture of Fourier transform spectrometer.

In prism of corner cube rotary scanning mode shown in Figure 2, light tilts will change direction vector X, Y, the Z of incident ray.If the plane of incidence of light, is established light and optical axis included angle α on the XOZ plane, then prism of corner cube rotates the maximum optical path difference scan values of realization continuously and is

P _max＝8〔l-（γ- 2/3 d）sinβ〕sin（β+α）

If angle β=10 of the geometirc symmetry axis of prism of corner cube and its rotating shaft °, P _Max=1.00cm ^-1, λ _Min=2.5 μ, α＜0.0025 ° then, this α value (1.28 °) much smaller than the motion scan interferometer.The flux superiority of fourier transform spectral light has also been lost.

The purpose of the invention is the defective that overcomes motion scan mode and existing rotary scanning mode, a kind of crossing Double sided mirror rotary scanning interferometer is provided for this reason, do the defective that scanned copy overcomes transmission scan with the catoptrics part, and its optical path difference and corner have extraordinary linear relationship, can keep the flux superiority of motion scan Fourier transform spectrometer.

This programme adopts and intersects the Double sided mirror rotary scanning, this interferometer is the same with interferometer in all Fourier transform spectrometers, be double beam interferometer, form by light source, collimating mirror, beam splitter, catoptron, convergent mirror and detector based on Michelson interferometer.But the scanned copy of this interferometer is reflecting surface angle β satisfies the crossing Double sided mirror of 0 °＜β＜180 °, and its basic characteristics are to replace common plane mirror to move or other optical element rotates and realizes optical path scanning with the rotation of intersecting Double sided mirror.Result of calculation shows, intersects the position (this shaft parallel is in crossing Double sided mirror two reflecting surface intersections) that Double sided mirror rotary scanning optical path difference is decided by Double sided mirror rotational angle and the relative Double sided mirror of rotating shaft.Therefore adopt the device of this path difference scan mode will guarantee that not only Double sided mirror can rotate reposefully, and will guarantee accurately to adjust the position of rotating shaft with respect to Double sided mirror.Figure 4 shows that a kind of organization plan figure that intersects Double sided mirror rotary scanning device, intersect Double sided mirror 16(as shown in A-A analyses and observe among Fig. 4) be fixed on the upper mounting plate 24, separable also glue-bondable being integral, its workplace OX, OY are coated with outer reflective membrane.Rotor 28 links to each other with axle 26 among the figure, and axle links to each other with platform support 21 again, and motor drives upper and lower platform by axle, platform support and is fixed on crossing Double sided mirror rotation on the upper mounting plate.Because the rotating shaft of axle, platform support, upper and lower platform and crossing Double sided mirror all overlaps with machine shaft, and stationkeeping, therefore have only by changing the position of intersecting Double sided mirror and regulate the position of the relative Double sided mirror of rotating shaft.Scheme guarantees that upper mounting plate can freely rotate with respect to lower platform 23 together with crossing Double sided mirror, and lower platform 23 can move relative to platform support 21 with crossing Double sided mirror together with upper mounting plate 24.Guarantee the crossing relatively Double sided mirror adjustable positions of rotating shaft thus, this regulated quantity can utilize graticule 25 to observe.By result of calculation and consider light path design, the vertical Double sided mirror rotary scanning mode effect that the reflecting surface angle is 90 ° is best, therefore introduce vertical Double sided mirror rotary scanning below, and at the relation of vertical Double sided mirror derivation optical path difference and rotating shaft position and rotational angle.

If two planes of reflection of Double sided mirror are all vertical with paper, and be X-axis with the level crossing at light first reflection place, the level crossing that reflects the place for the second time is a Y-axis, and the rib of two mirrors is that initial point is set up rectangular coordinate system, shown in A-A analyses and observe among Fig. 4.Rotational angle theta is 0 when establishing light with 45 ° of incident angle incident Double sided mirrors again, and θ was for just when Double sided mirror turned to X-axis by Y-axis.As shown in Figure 5 incidence point A coordinate be (X, O).If establish Double sided mirror AOC is rotating shaft R(x, y around vertical paper) rotate, when forward rotation θ angle arrives BO ' E, then opticpath becomes WABE by WACD, obviously because Double sided mirror rotates the optical path difference P that causes is

P＝｜AB｜+｜BE｜-｜AC｜-｜CD｜

Because the incident ray and the emergent ray of Double sided mirror are parallel rays,, the path difference of an available illustrated light changes so changing the optical path difference that replaces whole light beam.In order to derive conveniently, make boost line AA ' G, it is that Double sided mirror XOY is the position that a forward rotation θ angle arrives with the A point.By geometry as can be known, line segment rotates around arbitrary axis, and corresponding line segment equates, and the angle of line segment equals rotation angle before and after the rotation, so have

AA′‖O′X′，A′G‖O′Y′

And R(x, y) coordinate in coordinate system X ' O ' Y ' still is (x, y), so

｜FI｜＝y-y cosθ＝2y sin ²(θ)/2

｜BO′｜＝｜O′F｜+｜BF｜＝x+y sinθ-2y sin ²(θ)/2 tg（45°-θ）

Again because | OA|=X

So | CA|=

Again | CD|=|TE|cos(45 °-θ)=(| O ' E|-(| O ' T|) cos(45 °-θ)

And | O ' E|=|BO ' | tg(45 °+θ)

＝〔x+y sinθ-2y sin ²(θ)/2 tg（45°-θ）〕tg（45°+θ）

｜O′T｜＝｜TH｜+｜O′H｜＝〔｜AI｜+｜IH｜〕tg（45°-θ）

+2y sin ²(θ)/2

＝（x+y sinθ）tg（45°-θ）+2y sin ²(θ)/2

Therefore | CD|={ (x+y sin θ-2y sin ²(θ)/2 tg(45 °-θ)) tg(45 °+θ)

-（x+y sinθ）tg（45°-θ）-2y sin ²(θ)/2 ｝cos（45°-θ）

So optical path difference P is

P＝｜AB｜+｜BE｜-｜AC｜-｜CD｜

-｛〔x+ysinθ-2ysin ²(θ)/2 tg(45°-θ)〕tg(45°+θ)

-(x+ysinθ)tg(45°-θ)-2ysin ²(θ)/2 ｝cos(45°-θ)-

Behind the abbreviation

$p=\sqrt{2}x(\cos \mathrm{\&theta;}-\sin \mathrm{\&theta;}-1)+\sqrt{2}y(\cos \mathrm{\&theta;}+\sin \mathrm{\&theta;}-1)----\left(10\right)$

As seen, path difference variable P is by position coordinates (x, the y) decision of Double sided mirror rotational angle theta and rotating shaft R, and this is an important conclusion of the present invention.Suitably select rotating shaft position coordinate (x, y) can make optical path difference P and rotational angle theta that fabulous linear relationship is arranged, this is the key issue that the present invention seeks to solve.Obviously, as (d ²P)/(d θ ²) time, the linear relationship of optical path difference P and rotational angle theta is best, to formula (10) differentiate,

$\frac{\mathrm{dp}}{\mathrm{d\&theta;}}=-\sqrt{2}(\sin \mathrm{\&theta;}+\cos \mathrm{\&theta;})x+\sqrt{2}(\cos \mathrm{\&theta;}-\sin \mathrm{\&theta;})y$ $\frac{d^{2}p}{{\mathrm{d\&theta;}}^2}=\sqrt{2}(\sin \mathrm{\&theta;}-\cos \mathrm{\&theta;})x-\sqrt{2}(\sin \mathrm{\&theta;}+\cos \mathrm{\&theta;})y=0$

I.e. (y+x)/(y-x)=-tg θ

So, at sweep limit θ ₁～θ ₂, should select (x, y) to make

$\frac{y+x}{y-x}=\frac{{\&Integral;}_{{\mathrm{\&theta;}}_1}^{{\mathrm{\&theta;}}_2}-\mathrm{tg\&theta;d\&theta;}}{{\mathrm{\&theta;}}_2-{\mathrm{\&theta;}}_1}=\frac{\ln \left|{\cos \mathrm{\&theta;}}_2\right|-\ln \left|{\cos \mathrm{\&theta;}}_1\right|}{{\mathrm{\&theta;}}_2-{\mathrm{\&theta;}}_1}----\left(11\right)$

Adopt this rotary scanning mode to require decision optical path difference P by instrumental resolution according to the convenient rotational angle theta of selecting of circuit and Machine Design.Right back-pushed-type (10), formula (11) is obtained the coordinate (x, y) of rotating shaft R.According to solving coordinate (x, y), utilize the method for above-mentioned adjusting platform just can obtain the optimum position of vertical Double sided mirror, make path difference P and rotational angle theta that fabulous linear relationship be arranged.Easily see, rotate so vertical Double sided mirror, can realize several centimetres optical path scanning easily.

The traversing usable floor area that can increase follow-up light path optical element of light, it is traversing therefore to wish to reduce light generally speaking, and the traversing amount of light is in this scanister

D＝｜DE｜＝｜TE｜sin（45°-θ）-｜CT｜

And | CT|=|AC|-|AT|=|AC|-(| AI|+|IH|)/cos(45 °-θ)=

X-(x+ysin θ)/(cos(45 °-θ))

So

D=｛〔x+y sinθ- 2y sin ²(θ)/2 tg(45°-θ)〕tg(45°+θ)

-〔x+ysinθ)tg(45°-θ)-2ysin ²(θ)/2 ｝sin(45°-θ)

-

+(x+ysinθ)/cos(45°-θ)

Behind the abbreviation

$D=\sqrt{2}x(\sin \mathrm{\&theta;}+\cos \mathrm{\&theta;}-1)+\sqrt{2}y(1+\sin \mathrm{\&theta;}-\cos \mathrm{\&theta;})----\left(12\right)$

Can obtain the traversing D of light easily by formula (12).

Vertical Double sided mirror is in each position in scanning process path difference scanning situation can be obtained in important relationship formula (10), (11), (12) that derivation obtains above utilizing, and these computational datas can illustrate the effect of this path difference scanning.Computational data when table 1 has been listed among the embodiment 1 vertical Double sided mirror and realized the optical path scanning of 1cm with 1 ° to 30 ° corner respectively, in the table, x, y are rotating shaft R(x, y) position coordinates, D _MaxBe the maximum sideslip of light in whole scanning process, R is the linearly dependent coefficient of optical path difference P and rotational angle theta, (△ V/V) _MaxBe when scanned copy (vertical Double sided mirror) when being driven by desirable uniform speed electric motor, the maximum fluctuation value of optical path scanning speed and the ratio of optical path scanning speed, α is that the maximum wave number of instrument work spectral region is

σ _Max=4000cm ^-1, resolution is δ σ=1cm ^-1The time oblique light ray that allowed and the angle of optical axis.From the data of table 1 as can be seen, in 90 ° of angle Double sided mirror rotary scanning processes, light traversing very little this be very favourable to interferometer design example shown in Figure 6.In addition, optical path difference P and rotational angle theta have fabulous linear relationship, and with the increase of scanning angle θ, the linearly dependent coefficient R of P and θ slightly reduces, but still near 1.Because optical path difference P and rotational angle theta have good linear relationship, (dP)/(d θ) near constant, as using (d θ)/(dt) is uniform speed electric motor's driven sweep part of constant, then the fluctuation of optical path scanning speed (dP)/(dt) is caused by the fluctuation of (dP)/(d θ) fully, (seeing formula 6), by table 1 as seen, (△ V/V) _MaxVery little, so in bigger rotary scanning scope, all available uniform speed electric motor's driven sweep part.

For resolution is 1cm ^-1, the maximum wave number of work spectral region is 4000cm ^-1The motion scan Fourier transform spectrometer, it can be got by formula (7) the restriction of light inclination alpha

α≤arc cos（1- 1/4000 ）＝1.2812°

Listed in the table 1 when adopting vertical Double sided mirror rotary scanning, to the restriction of light inclination alpha, seen easily that under equal conditions vertical Double sided mirror is suitable with the motion scan mode to the restriction of α when realizing optical path scanning with little rotational angle with sampling instrument.Along with the increase of scanning angle θ, the linear relationship variation of optical path difference and corner, so the value of α also will reduce, but still be higher than the α value of other three kinds of rotary scanning modes far away.This shows that vertical Double sided mirror rotary scanning has kept the flux superiority of motion scan Fourier transform spectrometer.

For the ease of comparing, table 2 has been listed the pinacoid mirror respectively with the calculated value of 0 ° to 30 ° corner realization 1cm optical path scanning, and H is the distance of two plane mirrors in the Double sided mirror in the table, R, (△ V/V) _MaxThe implication of α is with table 1, from computational data as can be known, pinacoid mirror rotary scanning can only keep optical path difference and corner that good linear relationship is arranged in less angle range, optical path difference P is lower than vertical Double sided mirror rotary scanning with the linearly dependent coefficient of rotational angle theta, the fluctuation of optical path scanning speed is more much bigger than the vertical Double sided mirror scanning of identical corner, and the oblique light ray inclination alpha that interferometer allowed is 1/tens of a vertical Double sided mirror rotary scanning, the luminous flux that is received is about the per mille of vertical Double sided mirror rotary scanning, in a word, the performance of this rotation optical path scanning mode is lower than vertical Double sided mirror rotary scanning.

Description of drawings:

Fig. 1 is the index path of parallel flat rotary scanning interferometer.Wherein 1 is that light source, 2 is that collimation lens, 3 is beam splitter, and 4,5,6,7 is that plane mirror, 8 is that parallel flat, 9 is that convergent lens, 10 is detector.

Fig. 2 is the index path of prism of corner cube rotary scanning interferometer.Wherein 1 is that light source, 2 is that collimating mirror, 3 is that beam splitter, 11 is that fixed angles cone prism, 12 is that reflection right-angle prism, 13 is the angle of rotation cone prism.

Fig. 3 is the index path of pinacoid mirror rotary scanning interferometer.Wherein 1 is that light source, 2 is that collimating mirror, 3 is that beam splitter, 4 is that plane mirror, 14 is that pinacoid mirror, 6 is that plane mirror, 9 is that convergent mirror, 10 is a detector.

Fig. 4 is the schematic structure diagram of vertical Double sided mirror rotary scanning device, wherein 18 be the motor stator fixed mount, 19 for bearing bridge, 20 for axle sleeve, 21 for platform support, 22 for the flexible adjustment screw, 23 for lower platform, 16 for vertical Double sided mirror assembly, 24 for upper mounting plate, 25 for graticule, 26 for axle, 27 for the rotor fixed mount, 28 for rotor, 29 for motor stator.

Fig. 5 is vertical Double sided mirror rotary scanning schematic diagram.Wherein OX, OY are respectively two plane mirrors, R(x, the y of Double sided mirror) be the position of Double sided mirror after the θ angle is rotated in its rotating shaft for the rotating shaft position of vertical bimirror assembly, X ' O ' Y '.

Fig. 6 is the index path of vertical Double sided mirror rotary scanning interferometer embodiment 1.Wherein 1 is that light source, 2 is detector for throw face mirror, 9 from axle for assembling spherical mirror, 10 for rotary scanning Double sided mirror, 17 for fixed double-sided mirror, 16 for beam splitter, 15 for collimating mirror, 3.

Fig. 7 is the index path of vertical Double sided mirror rotary scanning interferometer embodiment 2.Wherein 1 is that light source, 2 is detector for throw face mirror, 9 from axle for assembling spherical mirror, 10 for plane mirror, 17 for plane mirror, 6 for vertical Double sided mirror, 5 for beam splitter, 16 for collimating mirror, 3.

Fig. 8 is the index path of vertical Double sided mirror rotary scanning interferometer embodiment 3.Wherein 1 is that light source, 2 for from axle throw face mirror, 9 for assemble spherical mirror, 10 is detector for plane mirror, 17 for rotating Double sided mirror, 15 for fixed double-sided mirror, 6 for beam splitter, 16 for collimating mirror, 3.

Fig. 9 is non-perpendicular crossing Double sided mirror rotary scanning interferometer index path.Wherein 1 is light source, 2 be collimating mirror, 3 for beam splitter, 30 for Double sided mirror (0＜β＜180 °, β ≠ 90 °), 11 be the fixed angles cone prism, 6 for plane mirror, 17 be detector for throw face mirror, 9 from axle for assembling spherical mirror, 10.

Accompanying drawings embodiment is described further the organization plan that intersects the Double sided mirror rotary scanning interferometer.

Vertical Double sided mirror as shown in Figure 6 is the gummed all-in-one-piece, and this path difference scan mode light is traversing little.(seeing Table 1), the rib of Double sided mirror 15,16 all is in the center of light beam, because light is traversing very little, can think that light beam returns by former road, and laser interferometer can be total to the road with illustrated main interference instrument.Utilize the rotation of vertical Double sided mirror 16 can realize required optical path scanning.Characteristics simple in structure, that volume is little, cost is low that this interferometer has are applicable to the infrared Fourier transform spectrometer of intermediate resolution.

Interferometer shown in Figure 7 is similar to Fig. 6, but two catoptrons of vertical Double sided mirror separate, the vertical Double sided mirror 16 of light beam twice process scanned copy in this interferometer, compare with interferometer shown in Figure 6 and can realize bigger optical path scanning, therefore can be used for the higher infrared Fourier transform spectrometer of resolution.

Interferometer shown in Figure 8 is that the plane mirror in Fig. 7 interferometer 5 is changed into fixed vertical Double sided mirror 15, the rib of Double sided mirror 16 is vertical mutually with the mirror of Double sided mirror 15, Double sided mirror 16 is if any inclination in scanning process, Double sided mirror 15 can compensate this droop error automatically, similar with Fig. 7, its optical path scanning value also is the twice of interferometer shown in Figure 6 under the equal conditions, therefore this interferometer can be used for the higher visible or infrared Fourier transform spectrometer of resolution, or the ultraviolet Fourier transform spectrometer of medium accuracy.

Interferometer shown in Figure 9 adopts the Double sided mirror of 0 °＜β of reflecting surface angle＜90 ° or 90 °＜β＜180 ° to make scanned copy, points out once above that these Double sided mirrors also can realize optical path scanning.But it has compared its deficiency with vertical Double sided mirror, and at first result of calculation shows the increase along with the relative 90 ° of deviation values of β, and the desirable rotating shaft position of Double sided mirror will more and more depart from the geometric center of Double sided mirror, brings difficulty for the meter tool design of scanister.Secondly along with the increase of β with respect to 90 ° of deviation values, the design of interferometer light path system is also all the more difficult.And the inclination of the Double sided mirror countershaft of non-90 ° of angles without compensation, in order to compensate the droop error in the turntable scanning process, will place expensive prism of corner cube thereafter.But also there is the rotating shaft position that makes optical path difference and the sexual intercourse of corner retention wire in this Double sided mirror, has equally also overcome the defective that has mobile or rotary scanning mode now, the scanned copy of the scanning interferometer that therefore also can rotate.

According to the technical characterictic that intersects the Double sided mirror rotary scanning interferometer, this interferometer has following advantages:

1. can the driven sweep part have been saved the accurate transmission mechanism of translation scanning with the uniform rotation motor straight.

2. can be low with cost, rolling bearing that volume is little replaces complex structure, expensive air bearing or air guide rail in the motion scan interferometer, reduced the instrument volume, reduced instrument cost.

3. can take into account circuit and Machine Design and select in the larger context scanning angle, reduce the requirement of machinery and circuit design.

4. compare with existing rotary scanning interferometer, this interferometer has kept the flux superiority of motion scan interferometer, and it also decreases to the requirement of speed control system.

5. can automatically eliminate the scanned copy heeling error, be applicable to visible so that the ultraviolet Fourier transform spectrometer.

In sum, intersect the defective that the Double sided mirror rotary scanning interferometer has overcome motion scan interferometer and existing rotary scanning interferometer, be applicable to the Fourier transform spectrometer of various spectrum workspace and various resolution ratio.

Claims (4)

1, a kind of rotary scanning interferometer, mainly form by light source, collimating mirror, beam splitter, catoptron, convergent mirror and detector, it is characterized in that utilizing the rotation of crossing Double sided mirror [16] to change the optical path difference of two phase Zhi Xianggan light paths, the workplace of this Double sided mirror is that angle is the reflecting surface of two catoptrons of β (0 °＜β＜180 °), it rotates around parallel axle with two reflecting surface intersections, realizes optical path scanning.

2, interferometer according to claim 1, it is characterized in that intersecting Double sided mirror is fixed on the rotatable platform, motor drives the platform smooth rotation by gearing, and the position of the relative Double sided mirror of rotating shaft (16) can be regulated, to select the optimum position of the relative Double sided mirror of rotating shaft.

3, interferometer according to claim 1, it is characterized in that intersecting Double sided mirror (16) can be separated from each other, also glue-bondable being integral, its workplace is coated with outer reflective membrane.

4, interferometer according to claim 1 is characterized in that intersecting Double sided mirror angle β is 90 °, and according to the variation range of given path difference P with the scanning rotational angle theta, presses following two formula:

$\left(1\right)p=\sqrt{2}x(\cos \mathrm{\&theta;}-\sin \mathrm{\&theta;}-1)+\sqrt{2}y(\cos \mathrm{\&theta;}+\sin \mathrm{\&theta;}-1);$ $\left(2\right)\frac{y+x}{y-x}=\frac{\ln \left|{\cos \mathrm{\&theta;}}_2\right|-\ln \left|{\cos \mathrm{\&theta;}}_1\right|}{{\mathrm{\&theta;}}_2-{\mathrm{\&theta;}}_1}.$

Determine rotating shaft R(x, y) position coordinates x, the y of vertical relatively Double sided mirror.

Images