CN104483022A - Fourier conversion spectrum instrument based on Michelson interferometer of equivalent intersecting mirror - Google Patents

Abstract

The invention relates to a Fourier conversion spectrum instrument based on a Michelson interferometer of an equivalent intersecting mirror, and belongs to the technical field of spectrum measuring instruments. The Fourier conversion spectrum instrument comprises a Michelson interference optical path part and a circuit part, wherein the circuit part comprises a CCD (charge coupled device) signal collector (12), an amplifier (13), an AD (analog to digital) converter (14), an embedded processor (15) and a display device (16), the display device (16) is related with the embedded processor, the CCD signal collector (12) is used for collecting interference fringe signals generated by the Michelson interference optical path, and the CCD signal collector (12), the amplifier (13), the AD converter (14), the embedded processor (15) and the display device (16) related with the embedded processor are sequentially connected. The Fourier conversion spectrum instrument has the advantages that by adopting an embedded computer, the measuring is more intelligent, the accuracy is greatly improved, the liquid crystal screen can simultaneously display the optical frequency corresponding to the spectral line peak, and a simple and intelligent light wavelength and frequency measuring system is formed.

Description

The Fourier transform spectrometer, of the Michelson interferometer of mirror is intersected based on equivalence

Technical field

The present invention is a kind of Fourier transform spectrometer, based on Michelson interferometer, belongs to spectrum measurement instruments technical field, comprises the aspects such as computer measurement, photoelectron technology and interferometer system.The present invention can be used for the luminous or reflective spectral distribution of object, and can carry out accurate Calculation to the wavelength of characteristic feature spectral line, in spectral investigation and species analysis field extensive application.

Background technology

Spectrometer at vague generalization Epidemiological Analysis, DNA sequencing, biology and chemical noxious material and other application more and more important.Fourier transform spectrometer, (FTS) has attracted a large amount of notices in the past ten years, because their specific characteristic, as high accuracy, high sensitivity and high spectral resolution.

In traditional Fourier transform spectrometer, the intensity of output beam is measured by scanning interferometer, and the optical path difference (OPD) of interferometer determines the resolution of Fourier transform spectrometer.Recently, some multi-form Fourier transform spectrometer,s are found out.The Fourier transform spectrometer, in a ultra-short pulse laser source by using micromicrowatt magnitude is developed, and it accurately can measure the performance of compound.In addition, be also developed out based on fibre optic interferometer Non-scanning mode Fourier transform spectrometer, it has high resolving power and low cost.In addition, the Fourier transform spectrometer, utilizing birefringent prism, a pair polarizer and linear CCD array is also had.This design improves conventional Fourier transform spectrometer by eliminating optical path difference (OPD) space in moving part and communication process, makes system less, more reliable, greatly reduces Measuring Time.But these methods always need complicated assembly, are not suitable at Practical Project.

Summary of the invention

The present invention proposes a kind of michelson interferometer optical path Fourier transform spectrometer, intersecting mirror based on equivalence.11 virtual images formed by catoptron V 10 pairs of catoptron IV 9 minute surfaces, mirror is intersected in equivalence be catoptron IV 9 with 11 crossing, as shown in Figure 1.All incided in Michelson interferometer by light-metering and reference light, and collect the Fourier trasform spectroscopy of interference fringe by charge coupled cell (CCD) and flush bonding processor.The peak point of reference light spectrum, for calibrating by the peak point of light-metering, can be calculated by reference to light with by the Fourier trasform spectroscopy of light-metering by light-metering spectrum.Form because Michelson interferometer intersects mirror by equivalence, Fourier transform spectrometer, realizes without any mechanical motion, by two-beam common irradiation to be improve the precision of spectrometer to the light path at same Michelson interferometer, improves the light path of propagation.The method has high-performance, high reliability and low cost.

Concrete scheme of the present invention is as follows:

Fourier transform spectrometer, in the present invention comprises michelson interferometer optical path part and circuit part, described circuit part comprises ccd signal collector 12, amplifier 13, AD converter 14, display 16 that flush bonding processor 15 is relevant with flush bonding processor, wherein ccd signal collector 12 gathers the interferometric fringe signal that michelson interferometer optical path produces, and the display 16 that ccd signal collector 12, amplifier 13, AD converter 14, flush bonding processor 15, flush bonding processor are relevant is connected successively.

Use above-mentioned spectrometer measurement by the frequency of light-metering, its step is as follows:

1), in michelson interferometer optical path, light source I1 and light source II 2 can respectively as reference light light source and tested radiants.Light source I1 produces light beam I, and light beam I incides semi-transparent semi-reflecting lens 4 by catoptron I3.Light source II 2 produces light beam II, and light beam II is by inciding semi-transparent semi-reflecting lens 4 after catoptron II 5, III 6.Light beam I reflects and light beam II transmission by semi-transparent semi-reflecting lens 4, and pools light beam III.Light beam III is incided in polarization beam apparatus 8 by collimation lens set 7 again.Light beam incides in catoptron IV 9, V 10 through polarization beam apparatus 8 respectively, after reflection by being received by ccd signal collector 12 after polarization beam apparatus 8, and converts thereof into analog signal output and processes to circuit part;

2) ccd signal collector 12 outputs signal by inputing to AD converter 14 sampled signal input end after amplifier 13;

3) AD converter 14 converts simulating signal to digital signal, digital signal is sent to flush bonding processor 15, and signal is carried out Fourier transform by flush bonding processor 15, and is shown on display 16 by Fourier trasform spectroscopy.

4) two coordinate diagram of Fourier trasform spectroscopy are demonstrated by display 16.Horizontal ordinate is Frequency point, also represent frequency values.Ordinate represents spectral intensity.Reference light and be respectively Nr and Nm by the crest frequency point that light-metering is corresponding.Abscissa value Nr corresponding to the peak value of light-metering and reference light is read respectively and Nm, Nr represent that, by the abscissa value of light-metering, Nm represents the abscissa value of reference light, according to formula from the Fourier trasform spectroscopy of display tested light frequency can be calculated, f _mrepresent tested light frequency, f _rrepresent reference light frequency.

Spectral measuring method in the present invention is relevant with michelson interferometer optical path, is described below to its principle:

The optical path that the present invention uses adopts interfere type, based on Michelson Interference Principle: two-beam superposes mutually, produce interference fringe, the contrast reference laser of given frequency and unknown frequency by the waveform of the interference signal of light-metering, flush bonding processor is utilized to gather the simulating signal of fringe intensity, simultaneously and do the spectrum that Fourier transform obtains interference fringe, thus accurately calculate tested light frequency.

Distance between michelson interferometer optical path accompanying drawing 1. catoptron IV 9 and polarization beam apparatus 8 and the distance between catoptron V 10 and polarization beam apparatus 8 are all identical, catoptron IV 9 and catoptron V 10 minute surface angle in 90 °.11 virtual images formed by catoptron V 10 pairs of catoptron IV 9 minute surfaces, catoptron IV 9 carries out small angle rotation relative to 11.Therefore, the optical path difference when michelson interference light path is different and produce with the angle of 11 by catoptron IV 9.

In fig 2, suppose that θ angle is angle between catoptron IV 9 and 11, O point is the point of crossing between two mirrors, and O' point is the corresponding point of O point at CCD.Optical path difference can be expressed as

d＝2xtanθ (1)

Wherein d is optical path difference, and x is the absolute value of the distance in CCD between pixel and O' point.

Therefore, can be expressed as by the interference fringe of light-metering and reference light

$I_m=I_{b1}+I_{c1}\cos \left(\frac{2\mathrm{\π}}{{\mathrm{\λ}}_m}d\right)---\left(2\right)$

$I_r=I_{b2}+I_{c2}\cos \left(\frac{2\mathrm{\π}}{{\mathrm{\λ}}_r}d\right)---\left(3\right)$

Wherein I _mand I _rrespectively by the intensity of light-metering and reference light, I _b1and I _b2the bias light of instrument place environment, I _c1and I _c2respectively by light-metering and reference light, λ _mand λ _rby the wavelength of light-metering and reference light.

Then converted to electric signal by the interference fringe of light-metering and reference light by CCD, calculated the Fourier trasform spectroscopy of interference fringe by embedded computer.The Fourier trasform spectroscopy G of interference fringe _mand G _r, can be expressed as

$G_m\left(f\right)=A_{b1}+B_{c1}(f+f_m)+B_{c1}^{*}(f-f_m)---\left(4\right)$

$G_r\left(f\right)=A_{b2}+B_{c2}(f+f_r)+B_{c2}^{*}(f-f_r)---\left(5\right)$

Wherein A _b1and A _b2position be the Fourier transform of bias light, B _c1and B _c2be the Fourier transform of contrast light, f is the frequency of spectral distribution, and * represents a complex conjugate, f _mand f _rbe the frequency of interference fringe, and provide

$f_m=\frac{2\tan \mathrm{\θ}}{{\mathrm{\λ}}_m}---\left(6\right)$

$f_r=\frac{2\tan \mathrm{\θ}}{{\mathrm{\λ}}_r}---\left(7\right)$

Therefore, tested optical wavelength can by comparing by the frequency computation part of the Fourier transform of light-metering and reference light interference fringe out, namely

${\mathrm{\λ}}_m={\mathrm{\λ}}_r\frac{f_r}{f_m}---\left(8\right)$

Reference light and be respectively N by the crest frequency point that light-metering is corresponding _rand N _m.By formula (6) and (7), tested photopeak value Frequency point N _mand frequency f _m, wavelength X _mbetween relation can be expressed as

$N_m=f_m\×\frac{N}{F_s}=\frac{2N\tan \mathrm{\θ}}{{\mathrm{\λ}}_m{F}_s}---\left(9\right)$

Reference light crest frequency point N _rand frequency f _r, wavelength X _rbetween relation can be expressed as

$N_r=f_r\×\frac{N}{F_s}=\frac{2N\tan \mathrm{\θ}}{{\mathrm{\λ}}_r{F}_s}---\left(10\right)$

Wherein N is the half of sampled data, F _sit is sample frequency.

Bring formula 10 into formula 9 to draw

$\frac{N_r}{N_m}=\frac{f_r}{f_m}=\frac{{\mathrm{\λ}}_m}{{\mathrm{\λ}}_r}$

Therefore, can be calculated from reference light with by the crest frequency point that light-metering is corresponding by the wavelength of light-metering, can be expressed as

${\mathrm{\λ}}_m=\frac{N_r}{N_m}{\mathrm{\λ}}_r---\left(12\right)$

$f_m=\frac{N_m}{N_r}{f}_r---\left(13\right)$

For (12) (13) formula, N _rand N _mdirectly read in liquid crystal display images by output, and f _rand λ _rfor reference light frequency and wavelength known, see the wavelength X obtained respectively by light-metering when bringing (12) (13) respectively into _mand frequency f _m.

The research field of spectral analysis and measurement and the high-accuracy measurement of laser or calculating field need the spectral measurement method of more high precision, wider measurement range.Meanwhile, in traditional Fourier spectrometer, the optical path difference of michelson interferometer optical path is the distance between two mirrors, therefore needs a mobile mirror to change optical path difference.What adopt in the present invention is the optical path difference being produced michelson interferometer optical path by two mirror angle differences, and Fourier transform spectrometer, is overall without any mechanical motion.Fourier spectrometer can be made into less size, and the impact that can bring except mechanical motion, improve the precision of spectrometer.The present invention adopts embedded computer, and make measurement more intelligent, precision also improves a lot, and shows light frequency corresponding to optic spectrum line peak value with liquid crystal display simultaneously, constitutes the optical wavelength of an easy intelligence and the measuring system of frequency.

1. the present invention adopts embedded computer, precisely controls ccd signal collector 12 and AD converter 14, convert the simulating signal of collection to digital signal and be input in flush bonding processor 15 by flush bonding processor 15.After flush bonding processor 15 carries out Fourier transform to the interference fringe numeral signal collected, and the Fourier transform of interference fringe is shown by display 16.Complete collection by flush bonding processor 15, calculate and Presentation Function, such that the system bulk of spectrometer is little, cost is low, speed is fast, stable, precision is high.

2. for ensureing that measuring accuracy is 10 ^?9above.The present invention adopts Michelson interference method, solves the problem that resolution is low, and measurement range has been expanded to infrared and visible-range.In addition, adopt equivalence to intersect mirror and produce the michelson interferometer optical path of interference fringe, make reference light and synchronous by light signal, and avoid the error that mechanical motion brings.Meanwhile, each ccd signal collector 12 sampling pixel points is 2 ⁿpoint, wherein N is integer.AD converter 14 selects more than 8 resolution, and flush bonding processor 15 adopts FFT module to calculate Fourier transform frequency spectrum fast, and shows.

3. according to the wavelength of reference light and frequency known, reference light also adopts Frequency Stabilized Lasers light source, then by the measurement result of liquid crystal display display in the present invention, reads N _rand N _mpositional value, can accurately calculate by the wavelength of light-metering and frequency by (12) (13) formula.

Accompanying drawing illustrates:

Fig. 1: michelson interferometer optical path;

Fig. 2: the optical interference circuit figure between catoptron 10 and 11;

Fig. 3: interference fringe Fourier transform frequency spectrum;

Fig. 4: spectrometer signal acquisition process block scheme;

Fig. 5: interference fringe Fourier transform spectrum example figure

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

According to Michelson Interference Principle, light path of optical spectrometer presses accompanying drawing 1 layout.Reference light selects frequency stabilized laser as standard sources, and the degree of stability of the frequency of reference light determines the measuring accuracy of spectrometer.Light source I 1 is as reference optical output beam I, and mirror catoptron I 3 enters semi-transparent semi-reflecting lens 4, and incident beam I part reflects by semi-transparent semi-reflecting lens 4.Meanwhile, light source II 2, as tested optical output beam II, enters semi-transparent semi-reflecting lens 4 after catoptron II 5 and catoptron III 6 reflect.Light beam II some light transmission is crossed semi-transparent semi-reflecting lens 4 and II and is formed light beam III through the reflected light of semi-transparent semi-reflecting lens 4.Light beam III is mapped in polarization beam apparatus 8 after collimation lens set 7, and light beam will be irradiated to catoptron IV 9 and catoptron V 10 respectively through polarization beam apparatus 8.Catoptron IV 9 and catoptron V 10 are gathered after reflected incident light by ccd signal collector 12 after polarization beam apparatus 8.

Light signal is converted to analog electrical signal after collecting the simulating signal of spectrum by ccd signal collector 12, signal is input to AD converter 14 by analog electrical signal after amplifier 13 amplifies, analog electrical signal is converted to digital electric signal and is transferred to flush bonding processor 15 by AD converter 14, and the digital electric signal of input is carried out Treatment Analysis and demonstrates accompanying drawing 5 image by display 16 by flush bonding processor 15.

Practical measuring examples

In circuit part, flush bonding processor 15 selects FPGA, and ccd signal collector 12 sampling pixel points is 2 ¹¹point, selects the AD converter 14 of resolution 12.And using 531.5nm solid state laser as reference radiant I 1, tested radiant II 2 uses 632.8nm solid state laser.Wherein θ angle is 1.90 °.After measuring through using the present invention, the Fourier trasform spectroscopy of display display interference fringe, as shown in Figure 5.Reference light and be respectively 917 and 769 by the crest frequency point that light-metering is corresponding.Tested light wavelength lambda can be calculated by formula 12 _m=633.79nm.

Meanwhile, select 471.5nm solid state laser as tested radiant, θ angle is 1.71 °, and after measuring, result is 470.41nm.Select 648.7nm solid state laser as tested radiant, θ angle is 1.90 °, and after measuring, result is 649.85nm.Whole measurement result and error are as table 1.

Table 1. example measurement result and error

Claims (2)

1. the Fourier transform spectrometer, of the Michelson interferometer of mirror is intersected based on equivalence, it is characterized in that: comprise michelson interferometer optical path part and circuit part, described circuit part comprises ccd signal collector (12), amplifier (13), AD converter (14), the display (16) that flush bonding processor (15) is relevant with flush bonding processor, wherein ccd signal collector (12) gathers the interferometric fringe signal that michelson interferometer optical path produces, ccd signal collector (12), amplifier (13), AD converter (14), flush bonding processor (15), the display (16) that flush bonding processor is relevant is connected successively.

2. the Fourier transform spectrometer, intersecting the Michelson interferometer of mirror based on equivalence according to claim 1, is characterized in that:

Use described spectrometer measurement by the frequency of light-metering, concrete steps are as follows:

1), in michelson interferometer optical path, light source I (1) and light source II (2) are respectively as reference light light source and tested radiant; Light source I (1) produces light beam I, and light beam I incides semi-transparent semi-reflecting lens (4) by catoptron I (3); Light source II (2) produces light beam II, and light beam II is by inciding semi-transparent semi-reflecting lens (4) after catoptron II (5), catoptron III (6); Light beam I reflects and light beam II transmission by semi-transparent semi-reflecting lens (4), and pools light beam III; Light beam III incides in polarization beam apparatus (8) by collimation lens set (7) again; Light beam incides in catoptron IV (9), V (10) through polarization beam apparatus (8) respectively, after reflection by being received by ccd signal collector (12) after polarization beam apparatus (8), and convert thereof into analog signal output and process to circuit part;

2) ccd signal collector (12) output signal is by inputing to AD converter (14) sampled signal input end after amplifier (13);

3) AD converter (14) converts simulating signal to digital signal, digital signal is sent to flush bonding processor (15), signal is carried out Fourier transform by flush bonding processor (15), and is shown to by Fourier trasform spectroscopy on display (16);

4) two coordinate diagram of Fourier trasform spectroscopy are demonstrated by display (16); Horizontal ordinate is Frequency point, also represent frequency values; Ordinate represents spectral intensity.Reference light and be respectively Nr and Nm by the crest frequency point that light-metering is corresponding; Abscissa value Nr corresponding to the peak value of light-metering and reference light is read respectively and Nm, Nr represent by the abscissa value of light-metering from the Fourier trasform spectroscopy of display; Nm represents the abscissa value of reference light; According to formula tested light frequency can be calculated, f _mrepresent tested light frequency, f _rrepresent reference light frequency.