Utility model content
Technical problem to be solved in the utility model is to overcome the technical matterss such as the existing cost of prior art is higher, making difficulty, not high to vibration sensing, resolution, wavelength measurement scope is narrower, and a kind of spectral measurement device based on magneto-optic modulation is provided.
Spectral measurement device based on magneto-optic modulation of the present utility model, comprises the first polaroid, magneto-optic modulation device, the second polaroid, the photo-detector that set gradually along incident light direction.
Further, the described spectral measurement device based on magneto-optic modulation also comprises the optical collimator being arranged at before the first polaroid.
Further, the described spectral measurement device based on magneto-optic modulation also comprises the calculation processing unit being connected with described photodetector signal.
Further, described calculation processing unit is connected with the control end of described magneto-optic modulation device, can control the magnetic field intensity of magneto-optic modulation device.
The spectral measurement method of the utility model based on magneto-optic modulation, the spectral measurement device based on magneto-optic modulation described in arbitrary technical scheme more than using, comprises the following steps:
Step 1, the frequency range that described photo-detector can be surveyed are divided into
nindividual frequency range is Δ
ffrequency band,
nfor being greater than 10 integer, the centre frequency of each frequency band is
f 1 ,
f 2 ,
f n ;
Step 2, make incident light to be measured successively by the first polaroid, magneto-optic modulation device, the second polaroid, and undertaken by described magneto-optic modulation device
nthe magneto-optic modulation of individual different magnetic field intensity, uses this
nthe value that under individual magnetic field intensity, described photo-detector detects deducts respectively after neighbourhood noise, obtains one group of numerical value, is designated as
p 1 ,
p 2 ,
p n ;
Step 3, obtain each frequency component in incident light to be measured by solving following system of equations
f 1 ,
f 2 ,
f n size
p(
f 1 ),
p(
f 2 ) ...,
p(
f n ):
In formula,
c ij (
i=1,2 ... n) (
j=1,2 ... n) be illustrated in
junder individual magnetic field intensity, frequency is
f i light through with in the first polaroid, magneto-optic modulation device, the second polaroid situation, the value that photo-detector detects deducts respectively both ratio after neighbourhood noise, records in advance by experiment;
Step 4, right
p(
f 1 ),
p(
f 2 ),
p(
f n ) carry out linear fit, and through spectral calibration, obtain the spectrum of incident light to be measured.
Compared to existing technology, the technical solution of the utility model has following beneficial effect:
1, spectral measurement device anti-vibration ability of the present utility model is strong, while carrying out spectral measurement, without mobile optical device, therefore vibrates its impact littlely, and stable performance, can be used for the real-time measurement in complex environment.
2, spectral measurement device of the present utility model is easy to make, with low cost: its needed magnet-optical medium, polaroid, photo-detector etc. are all very ripe products, need the equipment of complexity, costliness than making other spectrometers, make more easily simple.
3, spectral measurement device resolution of the present utility model is high, and spectral measurement ranges is wide.
4, spectral measurement device of the present utility model can be eliminated distortion, realizes spectrum and measures in real time: the method that adopts Tikhonov regularization to solve large linear systems is restored spectrum, can eliminate distortion, realizes quick real time spectrum and restores.Meanwhile, the invalid data that the photo-detector causing due to a variety of causes collects, can, by casting out the method solving equation group of these invalid datas, make new system of equations full rank and meet solving condition, avoids the larger distortion of spectrum recovering.
Embodiment
Below in conjunction with accompanying drawing, the technical solution of the utility model is elaborated:
Thinking of the present utility model is to utilize magneto-optic modulation device to treat survey incident light to carry out magneto-optic modulation, is changed and in magnet-optical medium, is propagated polarisation of light state, thereby reach the object that changes light intensity by magneto-optic effect.By measuring one group of modulation light intensity under different magnetic field intensity, and obtain the frequency spectrum of incident light to be measured by solving system of linear equations.
Magneto-optic effect refers to the various optical phenomenas that occur to interact between material in magnetized state and light and cause, comprise Faraday effect, Kerr magnetooptical effect, Zeeman effect, Cotton-Mouton effet etc., wherein, Faraday effect refers to: in the time of the Cucumber of linearly polarized light by under magnetic fields, its plane of polarization is subject to being proportional to externally-applied magnetic field and is parallel to the effect of direction of propagation component and deflects; Also can be called Faraday rotation effect or magnetic circular birefringence effect.And common said magneto-optic modulation is exactly the light modulation techniques of utilizing Faraday effect.
For incident light is carried out to optical shaping, in this example, first make incident light pass through an optical collimator, the structure of this optical collimator as shown in Figure 1, comprise confocal lens 2 and lens 4, the common focus place of lens 2 and lens 4 is provided with aperture 3, and the light that incident light source 1 sends can change directional light into after by this optical collimator.So not only make to only have directional light just can incide magneto-optic modulation spectrometer, and define the width of light beam of incident light, be conducive to improve the accuracy of measuring.
The structure of spectral measurement device of the present utility model as shown in Figure 2, comprises the polaroid 5, magneto-optic modulation device, polaroid 9, the photo-detector 10 that set gradually along incident light direction.In the utility model, photo-detector 10 is to be irradiated to its surperficial luminous power for measuring, and can adopt existing various photo-detector, for example modal silicon detector.In order automatically to realize numerical value collection and the calculating in spectrum recovering process, in the present embodiment, also comprise the calculation processing unit (not shown in Fig. 2) being connected with photo-detector 10 signals.
Magneto-optic modulation device contains magnet-optical medium 6, can adopt cerous fluoride crystal, YIG or mix the materials such as the YIG of Ga; Spiral winding 7, it is looped around on magnet-optical medium 6; Driving power 8.When work, the electric current that driving power 8 changes will induce magnetic field by spiral winding 7.Utilize Faraday rotation effect, in the time of the Propagation of a branch of linearly polarized light by under externally-applied magnetic field effect, its polarization direction can rotate, the anglec of rotation
size with along the magnetic field intensity of beam direction
hwith the length of light at Propagation
llong-pending being directly proportional, that is:
In formula,
vfor Theresa Weld constant, determined by medium and frequency of light wave, under the unit's of being illustrated in magnetic field intensity, linearly polarized light is by the angle of the magnet-optical medium rear polarizer direction rotation of unit length.
Particularly, as shown in Figure 2, in the time being parallel to magnetic direction by the linearly polarized light of polaroid 5 and inciding magnet-optical medium 6 in magneto-optic modulation device surperficial, polarized light can resolve into dextrorotation and left-handed two bundle polarized lights, and corresponding electric vector is
e r with
e l , both sense of rotation are contrary.Here dextrorotation and left-handed be for magnetic direction.Under the effect in magnetic field, because magnet-optical medium 6 has different refractive indexes to both
n r with
n l , the velocity of propagation of right-circularly polarized light
c/n r velocity of propagation with left circularly polarized light
c/n l not etc., then when they by thickness be
dmagnet-optical medium 6 after, produced different phase delays:
In formula,
λfor the wavelength in vacuum.
When they are from magnet-optical medium 6 outgoing, the synthetic electric vector of two circularly polarized lights
evibration plane rotated an angle with respect to original vibration plane
θ:
Cause
So
When the angle of polaroid 5 and polaroid 9 is
α, according to Marlu's principle, incident light by the output intensity after polaroid 5, magneto-optic modulation device, polaroid 9 is successively when at the angle:
In formula,
i ofor incident light is by the output intensity after polaroid 5,
n r -
n l be proportional to the magnetic field intensity along beam direction
h.
From above formula, at the angle of polaroid 5 and polaroid 9
αone timing, is placed in light intensity and incident light wavelength that polaroid 9 photo-detector 10 afterwards detects
and magnetic field intensity
hrelevant.Therefore under identical magnetic field intensity, the incident light of different frequency passes through after polaroid 5, magneto-optic modulation device, polaroid 9, and photo-detector 10 will detect different light intensities; And the incident light of same frequency by the magneto-optic modulation device under polaroid 5, different magnetic field intensity, polaroid 9 after, the light intensity that photo-detector 10 detects is also different.Treating survey incident ray polarized light at magneto-optic modulation device carries out
nwhen the magneto-optic modulation of individual different magnetic field intensity, photo-detector 10 just can record a series of data, and the data that photo-detector 10 is detected are removed respectively a series of values that obtain after neighbourhood noise as augmented matrix; 10 frequency ranges that can survey of photo-detector are evenly divided into
npart, the size of the centre frequency of every portion in incident light spectrum is as unknown number; Record in advance photo-detector 10 in magneto-optic modulation device
nplant the detectivity to each frequency component under different magnetic field intensitys, and using this detectivity as matrix of coefficients.By solving this matrix equation, and the spectrum that acquired results is carried out to linear fit, spectral calibration and just can obtain treating photometry.Can obtain spectral measurement of the present utility model (spectrum recovering) method based on this principle, specific as follows:
Step 1,10 frequency ranges that can survey of described photo-detector are divided into
nindividual frequency range is Δ
ffrequency band,
nfor being greater than 10 integer, the centre frequency of each frequency band is
f 1 ,
f 2 ,
f n .
As shown in Figure 3, within the scope of the survey frequency of photo-detector 10, the curve of spectrum is evenly divided into
nsection.Whole spectrum area is just divided into multiple elongated rectangles by approximate, supposes that the centre frequency of every portion is
f 1 , f 2 ... f n , frequency range is Δ
f,
p (f i )for frequency
f i corresponding watt level (
i=1,2 ... n), in incident light, the corresponding power of each frequency band is the area of each little rectangle, according to infinitesimal analysis principle, and the general power of incident light
p 0 can be approximated to be in figure the summation of each little rectangular area, the i.e. superposition of each frequency component power below curve.If represent with mathematical formulae, can be expressed as:
P 0 = P(
f 1 )
Δf + P(
f 2 )
Δf + …
+ P(
f n )
Δf
Step 2, make incident light to be measured successively by polaroid 5, magneto-optic modulation device, polaroid 9, by magneto-optic modulation device, the incident light to be measured through polaroid 5 is carried out
nthe magneto-optic modulation of individual different magnetic field intensity, uses this
nthe value that under individual magnetic field intensity, described photo-detector detects deducts respectively after neighbourhood noise, obtains one group of numerical value, is designated as
p 1 ,
p 2 ,
p n .
Owing to more or less can there is noise effect in measurement environment, the utility model, in order to improve the accuracy of results of spectral measurements, obtains light intensity data by actual measurement and calibrates, and deducts neighbourhood noise.For specific measurement environment, neighbourhood noise is well-determined definite value, there is no under incident light condition to be measured light intensity data in the measurement environment that photo-detector 10 detects.
Magnetic field intensity in magneto-optic modulation device gets
jin the situation of individual value, the luminous power that photo-detector 10 measures should be after deducting noise power:
P j = C 1j P(
f 1 )
Δf + C 2j P(
f 2 )
Δf + …
+ C nj P(
f n )
Δf
Wherein,
c 1j , C 2j ... C nj be respectively
junder individual magnetic field intensity, frequency is
f i light through with without polaroid 5, magneto-optic modulation device, polaroid 9 in the situation that, the value that photo-detector 10 detects deducts respectively both ratio after neighbourhood noise, records in advance by experiment.
When the magnetic field intensity in magneto-optic modulation device is got
nwhen individual different value, photo-detector 10 just can record a series of power data, and these power are expressed as to system of linear equations:
P 1 = C 11 P(f 1 )Δf +C 21 P(f 2 )Δf + … + C n1 P(f n )Δf ,
P 2 = C 12 P(f 1 )Δf +C 22 P(f 2 )Δf + … + C n2 P(f n )Δf ,
…
P n = C 1n P(f 1 )Δf +C 2n P(f 2 )Δf + … + C nn P(f n )Δf ,
Wherein,
c ij (
i=1,2 ... n) (
j=1,2 ... n) be illustrated in
junder individual magnetic field intensity, frequency is
f i light through with without polaroid 5, magneto-optic modulation device, polaroid 9 in the situation that, the value that photo-detector 10 detects deducts respectively both ratio after neighbourhood noise.After spectral measurement device is made,
c ij be one group of definite value, can record in advance by experiment, for example, can adopt with the following method: in darkroom, first utilize monochromator to produce different frequency
f 1 , f 2 ... f n incident light, survey the luminous power of different frequency incident light with photo-detector 10, suppose to be designated as
; Then before photo-detector 10, place successively polaroid 5, magneto-optic modulation device, polaroid 9, the magnetic field intensity in magneto-optic modulation device is got a certain value, measures the different frequency being obtained by monochromator
f 1 , f 2 ... f n incident light after polaroid 5, magneto-optic modulation device, polaroid 9, the luminous power that photo-detector 10 detects, supposes to be designated as
.
, be frequency
f 1 , f 2 ... f n incident light under this magnetic field intensity for the detectivity of photo-detector 10, wherein
for neighbourhood noise, there is no under incident light condition to be measured luminous power in the measurement environment that photo-detector 10 detects.Change magnetic field intensity, repeat above-mentioned steps, can obtain one group of detectivity data
c ij (i=1,2 ... n) (j=1,2 ... n).These group data can form matrix of coefficients
c :
Matrix of coefficients
c be the intrinsic parameter of spectral measurement device, for each specific spectral measurement device, this matrix of coefficients is well-determined.
Step 3, obtain each frequency component in incident light to be measured by solving following system of equations
f 1 ,
f 2 ,
f n luminous power
p(
f 1 ),
p(
f 2 ) ...,
p(
f n ):
If use matrix form
y=Cx represent, establish
x the size of the normalized power of the centre frequency that represents every portion in incident light,
c represent the matrix of coefficients of detectivity composition, and the received corresponding luminous power of photo-detector 10 deducts after noise power as augmented matrix
y , system of linear equations can be expressed as above matrix form.Solving above-mentioned system of linear equations obtains
x , and further calculate according to following formula:
Just can be in the hope of the corresponding power of each frequency component in incident light spectrum
p(
f i ) size.
Step 4, right
p(
f 1 ),
p(
f 2 ),
p(
f n ) carry out linear fit, and through spectral calibration, obtain the spectrum of incident light to be measured.
In practical devices manufacturing process, the size of device, shape, material behavior etc. may have certain deviation with initial designing requirement, but after device is carried out, photo-detector 10 is for the incident light of magnetic field intensity certain in magneto-optic modulation device and certain wavelength, and its detectivity is a fixed value.As long as for the incident light of different magnetic field intensitys and different wavelength, the detectivity difference of photo-detector 10, just can solving equations.In solving equation group process, the luminous power that photo-detector 10 collects and be all measured value to the detectivity of different frequency light.Due to reasons such as measuring error, this system of equations is real is ill-condition equation group, add in system of equations the quantity of equation more, solve with commonsense method is more difficult, and the method that adopts Tikhonov regularization solves, this system of linear equations can be eliminated obvious distortion and the speed that solves is fast, after this solving equations, get final product to obtain normalization spectral power corresponding to the each frequency of incident light, finally carry out spectral calibration and just obtained the recovery spectrum of incident light.