CN1598504A - Separating method of high-grade secondary superimposition spectrum of raster spectrograph - Google Patents

Abstract

The invention relates to a separation method for higher order superposition spectrum of the grating spectroscope. At first, it measures the heterograde spectrum signal ratio gamma2/1(gamma I) based on grating and spectroscope structure; then carries on interpolation to the first order spectrum signal data, acquires the spectrum signal I1; multiplies the heterograde spectrum signal and the short wave first order spectrum signal, and acquires the short wave second spectrum signal I2 (gamma i); then measures the compound spectrum signal I 1+2(gamma I), and subtracts out the I2 (gamma i), and acquires the long wave first order spectrum I1(gamma j). Thus the separation can be accomplished; the other superposed high order spectrum also can be separated in order. The method can separate high order spectrum in any spectrum range, it does not depend on the cut-off light filter of the high order spectrum separation, and it can reduce the complexity of structure design of the grating spectrum device structure.

Description

The separation method of senior stack of grating spectrum instrument spectrum

Technical field: the invention belongs to spectral instrument and spectral measurement field, relate to the separation method of senior shortwave spectrum of stack in grating spectrum instrument longwave optical spectrum.

Background technology: (spectrophotometer, monochromator, spectral radiometer utilize the multi-channel spectrometer based of linear array detector to all kinds of grating spectrum instruments ... Deng) all there is a problem of stack shortwave senior sub-spectrum signal in the longwave optical spectrum signal of its operation wavelength.If do not take measures at spectrometer and in measuring, the spectral signal that obtains in this long wave stack district is a mixed spectra.Must from this mixed spectra, separate the shortwave senior sub-spectrum and could obtain long wave spectrum.Common solution all is the stack that adds cutoff filter prevention senior sub-spectrum before at these stack spectral region now.

To use the diffraction grating primary spectrum, operation wavelength is an example at the spectrometer of 340nm～1100nm, and it is at the second order spectrum of 680nm～1100nm spectral coverage with regard to the 340nm～550nm that superposeed successively.Therefore, cutoff filter before these stack spectral region just add a 550nm, the spectral signal of prevention 340nm～550nm obtains the spectral signal of 680nm～1100nm.

In the length scanning type spectral instrument, in order not make the senior sub-spectrum stack, length scanning just stops the shortwave senior sub-spectrum to add by cutoff filter before the rotating disk insertion and enters in the longwave optical spectrum signal to spectrum stack district.Use in the spectral instrument of detector array, the method for solution is to add optical filter on the corresponding pixel in array device spectrum stack district.These methods have all increased the complicacy of apparatus structure, and concerning some was used, these structures were complicated more.For example, use the imaging spectrometer of planar array detector, optical filter accurately being installed on the pixel of definite spectrum stack wavelength of planar array detector photosurface is suitable difficulty.

Detailed content of the present invention:

The present invention is directed to above-mentioned background technology cutoff filter before the stack spectral region add and stop the senior sub-spectrum stack, make problems such as apparatus structure complexity, the objective of the invention is to provide the separation method of senior stack of a kind of grating spectrum instrument spectrum.

Separating step of the present invention is as follows: to the free spectral range short wavelength light spectrum signal I (λ that records _j)=I ₁(λ _j) (j=0,1,2 ..., n) and the stack spectral region mixed spectra signal I ₁₊₂(λ _i)=I ₁(λ _j)+I ₂(λ _i) (i=0,1,2 ..., 2n; J=m, m+1 ..., spectroscopic data m+2n) carries out computing, just can be from I ₁₊₂(λ _i) separate shortwave second order spectrum signal I in the mixed spectra signal ₂(λ _i), thereby obtain long wave primary spectrum signal I ₁(λ _j).

A. at first measure based on the shortwave second order spectrum signal of grating and spectrometer architecture and the ratio of shortwave primary spectrum signal, obtain different level spectral signal and compare γ _2/1(λ _i):

$\frac{I_2\left({\mathrm{\λ}}_i\right)}{I_1\left({\mathrm{\λ}}_i\right)}=\frac{E\left({\mathrm{\λ}}_i\right){\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_i\right)R\left({\mathrm{\λ}}_i\right)}{E\left({\mathrm{\λ}}_i\right){\mathrm{\η}}_1\left({\mathrm{\λ}}_i\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_i\right)R\left({\mathrm{\λ}}_i\right)}=\frac{{\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right)}{{\mathrm{\η}}_1\left({\mathrm{\λ}}_i\right)}={\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right)---i=\mathrm{0,1,2},\·\·\·,2n---\left[8\right]$

B. will handle based on the shortwave primary spectrum signal data adjacency intermediate interpolated of the free spectral range of grating and spectrometer architecture again, obtain interpolation shortwave primary spectrum signal I ₁(λ _i):

I ₁(λ ₁)＝E(λ _i)η ₁(λ _i)τ ₀(λ _i)R(λ _i) i＝0，1，2，…，2n [7]

C. different level spectral signal is compared γ _2/1(λ _i) and interpolation shortwave primary spectrum signal I ₁(λ _i) multiply each other the shortwave second order spectrum signal I of the spectral region that obtain superposeing ₂(λ _i):

I ₂(λ _i)＝E(λ _i)η ₂(λ _i)τ ₀(λ _i)R(λ _i) i＝0，1，2，…，2n [6]

D. measure the mixed spectra signal I of stack spectral region ₁₊₂(λ _i):

I ₁₊₂(λ _i)＝I ₁(λ _j)+I ₂(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n [4]

E. from superimposed light spectrum signal I ₁₊₂(λ _i) in deduct I ₂(λ _i), just obtained long wave primary spectrum signal I ₁(λ _j):

I ₁(λ _j)＝I ₁₊₂(λ _i)-γ _2/1(λ _i)I ₁(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n[10]

Like this, just finished the separation of the second order spectrum of grating spectrum instrument stack, other senior sub-spectrum of stack can separate by above-mentioned steps.

Calculate the advantage of separation method

The calculating separation method of senior stack of grating spectrum instrument of the present invention spectrum without any need for hardware measure, can separate the senior sub-spectrum of grating in ultraviolet, visible light, infrared any spectral range.Just broken away from of the dependence of separation senior sub-spectrum by the present invention to cutoff filter, only recording the spectral signal data computing through spectral instrument handles, just can from stack spectral region mixed spectra, separate senior sub-spectrum and obtain the longwave optical spectrum signal, and can reduce the complicacy of grating spectrum instrument structural design.For the grating spectrum instrument that uses planar array detector, its structural design is more prone to especially.

Description of drawings:

Fig. 1 is a cutoff filter spectral transmittance before the background technology

Fig. 2 is one-level of the present invention, second order spectrum and mixed spectra signal distributions synoptic diagram

Embodiment:

As shown in Figure 2, the present invention is to carrying out on the based measurement based on the instrument parameter of the second order spectrum efficient of grating and spectrometer architecture and one-level time spectrum efficiency ratio, and the primary spectrum signal of free spectral range measured, determine the second order spectrum signal of stack spectral region thus, and then from the mixed signal of stack spectral region, isolate the second order spectrum signal and obtain long wave primary spectrum signal.

Now the situation with second order spectrum stack primary spectrum in the grating spectrum instrument (abbreviation spectrometer) of 340nm～1100nm wavelength work is an example, with typical spectral analysis and the explanation of measurement situation, from the long wave primary spectrum, separate second order spectrum in the mixed spectra signal of stack shortwave second order spectrum, thereby obtain the spectral signal of long wave itself.340nm～1100nm wavelength region may is divided into order has only primary spectrum by spectral region: 340nm～680nm scope; The superposeed second order spectrum of 340nm～550nm of stack spectral region: 680nm～1100nm scope.

If the luminous flux of importing on the spectrometer is E (λ),

τ ₀(λ)---the spectrometer system transmitance; I ₁(λ)---the output of primary spectrum detector signal;

R (λ)---detector spectral response degree; I ₂(λ)---the output of second order spectrum detector signal;

η ₁(λ)---the primary spectrum grating efficiency; I ₁₊₂(λ)---the output of mixed spectra detector signal;

η ₂(λ)---the second order spectrum grating efficiency; γ _2/1(λ _i)---different level spectral signal ratio

α---free spectral range; β---stack spectral region;

Primary spectrum: λ ₀, λ ₁..., λ _n..., λ _m, λ _M+1, λ _M+2..., λ _M+2n,

j＝0，…，n，…，m，…，m+2n，m＞n；

Shortwave primary spectrum: λ ₀～λ _n: the adjacency intermediate interpolated obtains 2n+1 item number certificate altogether;

Be λ ₀, λ _1/2, λ ₁..., λ _N-1/2, λ _nPerhaps be expressed as: λ ₀, λ ₁, λ ₂...,

λ _2n-1，λ _2n，i＝0，1，2，…，2n；

Long wave primary spectrum: λ _m=2 λ ₀, λ _M+1=2 λ ₁..., λ _M+2n=2 λ _2n,

j＝m，m+1，…，m+2n；

Shortwave second order spectrum: λ ₀, λ ₁, λ ₂..., λ _2n-1, λ _2n, i=0,1,2 ..., 2n.

Be operated under the situation of primary spectrum

I ₁(λ)＝E(λ)η ₁(λ)τ ₀(λ)R(λ) [1]

And corresponding second order spectrum, because its chromatic dispersion doubles also many one times of hits than primary spectrum.

I ₂(λ)＝E(λ)η ₂(λ)τ ₀(λ)R(λ) [2]

In the free spectral range, has only primary spectrum.Therefore, record total spectral signal output I (λ)=I ₁(λ), that is:

Free Spectral Range at 340nm～680nm

I(λ)＝I ₁(λ _j)＝E(λ _j)η ₁(λ _j)τ ₀(λ _j)R(λ _j) j＝0，1，…，n，…，m [3]

At 680nm～1100nm spectral region that superpose, primary spectrum I is arranged then ₁(λ _j) (j=m, m+1 ..., m+2n) and the second order spectrum I of 340nm～550nm ₂(λ _i) (i=0,1,2 ..., 2n) superimposed mixed spectra I ₁₊₂(λ _i).

I ₁₊₂(λ _i)＝I ₁(λ _j)+I ₂(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n [4]

I wherein ₁(λ _j) and I ₂(λ _i) be

I ₁(λ _j)＝E(λ _j)η ₁(λ _j)τ ₀(λ _j)R(λ _j) j＝m，m+1，…，m+2n [5]

I ₂(λ _i)＝E(λ _i)η ₂(λ _i)τ ₀(λ _i)R(λ _i) i＝0，1，2，…，2n [6]

Like this, at free spectral range λ ₀～λ _nSample range has n+1 data.The stack spectral region are because the chromatic dispersion of shortwave second order spectrum is the twice of primary spectrum.So stack spectral region shortwave second order spectrum has 2n+1 data.The long wave primary spectrum also has 2n+1 data.So, with free spectral range λ ₀～λ _nN+1 data adjacency intermediate interpolated of scope sampling, it is corresponding one by one with stack spectral region sampled data to obtain 2n+1 data.

Therefore, with shortwave primary spectrum I ₁(λ _j) just the spectroscopic data hits with second order spectrum is identical later on for the processing of sampled data adjacency intermediate interpolated, obtains interpolation shortwave primary spectrum I ₁(λ _i):

I ₁(λ _i)＝E(λ _i)η ₁(λ _i)τ ₀(λ _i)R(λ _i) i＝0，1，2，…，2n [7]

If do not take some measure in the spectral instrument, we are [3] formula and [4] formula from the spectral signal output that detector records.The spectral signal that records in the free spectral range is [3] formula, has only I (λ)=I ₁(λ _j) (j=0,1 ..., n ..., the m) spectrum of wavelength zone.But what recorded by [4] formula at the stack spectral region is the mixed spectra of shortwave second order spectrum of having superposeed on the long wave primary spectrum, promptly

I ₁₊₂(λ _i)＝I ₁(λ _j)+I ₂(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n [4]

Must be from the mixed spectra I that records ₁₊₂(λ _i) the middle I that separates ₂(λ _i), could obtain the longwave optical spectrum signal of desired stack spectral region.Common way is the preceding cutoff filter (as shown in Figure 1) that adds a 550nm at the stack spectral region now.

At the stack spectral region, the second order spectrum that wavelength is shorter than 550nm just can not pass through spectrometer, i.e. I so ₂(λ _i)=0 has just obtained longwave optical spectrum signal I with optical filter like this ₁(λ _j).

Optical grating construction and characteristic (blazing angle, efficient, chromatic dispersion ... Deng) determine after.Primary spectrum is only relevant with grating and spectrometer architecture with second order spectrum signal distributions ratio in the spectral instrument.Promptly as can be known from [6] formula and [7] formula

$\frac{I_2\left({\mathrm{\λ}}_i\right)}{I_1\left({\mathrm{\λ}}_i\right)}=\frac{E\left({\mathrm{\λ}}_i\right){\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_i\right)R\left({\mathrm{\λ}}_i\right)}{E\left({\mathrm{\λ}}_i\right){\mathrm{\η}}_1\left({\mathrm{\λ}}_i\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_i\right)R\left({\mathrm{\λ}}_i\right)}=\frac{{\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right)}{{\mathrm{\η}}_1\left({\mathrm{\λ}}_i\right)}={\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right)---i=\mathrm{0,1,2},\·\·\·,2n---\left[8\right]$

That is to say, at the second order spectrum signal I of stack spectral region ₂(λ _i) and primary spectrum signal I ₁(λ _i) ratio be the second order spectrum of grating and the ratio of primary spectrum efficient ${\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right)/{\mathrm{\η}}_1\left({\mathrm{\λ}}_i\right)={\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right),$ With incident light radiation intensity E (λ _i), spectrometer system transmitance τ ₀(λ _i), detector spectral response degree R (λ _i) wait all and have nothing to do; Be instrument parameter γ _2/1(λ _i) (co-wavelength is relevant).γ in the actual spectrum instrument _2/1(λ _i) mainly by η ₂(λ _i) and η ₁(λ _i) ratio decision, be subjected to the influence of parasitic light etc. in addition.But,, can measure in advance as instrument parameter.

The γ that (measured and obtained) known in the spectrometer _2/1(λ _i), just can be from stack spectral region mixed spectra signal I ₁₊₂(λ _i) in isolate shortwave second order spectrum I ₂(λ _i), and then obtain longwave optical spectrum signal I ₁(λ _j).

According to [4] formula, stack spectral region mixed spectra signal

I ₁₊₂(λ _i)＝I ₁(λ _j)+I ₂(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n [4]

According to [8] formula

$I_2\left({\mathrm{\λ}}_i\right)/I_1\left({\mathrm{\λ}}_i\right)={\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right)---i=\mathrm{0,1,2},\·\·\·,2n---\left[8\right]$

So

I ₁₊₂(λ _i)＝I ₁(λ _j)+γ _2/1(λ _i)I ₁(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n[9]

I ₁(λ _j)＝I ₁₊₂(λ _i)-γ _2/1(λ _i)I ₁(λ _i) i＝0，1，2，…，2n；j＝m，m+1，…，m+2n[10]

Because the spectral signal I of free spectral range in each spectral measurement ₁(λ _j) directly record, and can draw 2n+1 item spectroscopic data as [7] formula with interpolation method, so can calculate I by [8] formula ₂(λ _i)=γ _2/1(λ _i) I ₁(λ _i).Thereby, can be from I ₁₊₂(λ _i) the middle I that separates ₂(λ _i) and obtain I ₁(λ _j) ([10] formula).Use the situation of other senior sub-spectrum, can according to said method separate.

γ among the present invention _2/1(λ _i) measuring method:

Use the light illumination entrance slit on the spectrometer, export with the detector received signal at exit slit.

Measure for the first time: do not add preceding cutoff filter.(the spectral signal that 340nm～680nm) obtains in the free spectral range so

I(λ)＝I ₁(λ _j)＝E(λ _j)η ₁(λ _j)τ ₀(λ _j)R(λ _j) j＝0，1，2，…，n，…，m [3]

At stack spectral region (the mixed spectra signal that 680nm～1100nm) obtains

I ₁₊₂(λ _i)＝I ₁(λ _j)+I ₂(λ _i)

＝E(λ _j)η ₁(λ _j)τ ₀(λ _j)R(λ _j) i＝0，1，2，…，2n [9]

+E(λ _i)η ₂(λ _i)τ ₀(λ _i)R(λ _i) j＝m，m+1，…，m+2n

Measure for the second time: still measurement for the first time is the same together in the free spectral range, does not add optical filter, with measurement for the first time, and with I ₁(λ _j) processing of sampled data adjacency intermediate interpolated, identical with the spectroscopic data hits of corresponding second order spectrum.Be I ₁' (λ _i)

I ₁′(λ _i)＝I ₁(λ _i)＝E(λ _i)η ₁(λ _i)τ ₀(λ _i)R(λ _i) i＝0，1，2，…，2n [11]

(680nm～1100nm) add a spectral transmittance is τ at the stack spectral region _FPreceding cutoff filter (as shown in Figure 1) (λ).So, eliminated shortwave second order spectrum I in the spectral signal that in the stack spectral region are measured for the second time, obtains ₂(λ _i)=0, and have only long wave primary spectrum I ₁(λ _j), promptly

I′(λ _j)＝I ₁′(λ _j)＝E(λ _j)η ₁(λ _j)τ ₀(λ _j)τ _F(λ _j)R(λ _j)＝τ _F(λ _j)I ₁(λ _j)

j＝m，m+1，…，m+2n

$I_1\left({\mathrm{\λ}}_j\right)=I_1^{\′}\left({\mathrm{\λ}}_j\right)/{\mathrm{\τ}}_F{\left({\mathrm{\λ}}_J\right)-}_{}--j=m,m+1,\·\·\·,m+2n---\left[12\right]$

[12] formula is brought into [9] formula, put in order

$I_2\left({\mathrm{\λ}}_j\right)=I_{1+2}\left({\mathrm{\λ}}_i\right)-I_1\left({\mathrm{\λ}}_j\right)---i=\mathrm{0,1,2},\·\·\·,2n$

$=I_{1+2}\left({\mathrm{\λ}}_i\right)-I_1^{\′}\left({\mathrm{\λ}}_j\right)/{\mathrm{\τ}}_F\left({\mathrm{\λ}}_j\right)---j=m,m+1,\·\·\·,m+2n---\left[13\right]$

Formula [13] ÷ [11] is just drawn γ _2/1(λ _i)

${\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right)=\frac{I_2\left({\mathrm{\λ}}_i\right)}{I_1^{\′}\left({\mathrm{\λ}}_i\right)}$

$=[I_{1+2}\left({\mathrm{\λ}}_i\right)-I_1^{\′}\left({\mathrm{\λ}}_j\right)/{\mathrm{\τ}}_F\left({\mathrm{\λ}}_j\right)]/I_1^{\′}\left({\mathrm{\λ}}_i\right)---i=\mathrm{0,1,2},\·\·\·,2n;j=m,m+1,\·\·\·,m+2n---\left[14\right]$

Can measure γ like this _2/1(λ _i).

Claims (1)

1, the separation method of the senior time stack of grating spectrum instrument spectrum is characterized in that separating step: the free spectral range short wavelength light spectrum signal I (λ to recording only _j)=I ₁(λ _j) and the stack spectral region mixed spectra signal I ₁₊₂(λ _i)=I ₁(λ _j)+I ₂(λ _i) spectroscopic data carry out computing, just can be from I ₁₊₂(λ _i) separate shortwave second order spectrum signal I in the mixed spectra signal ₂(λ _i), thereby obtain long wave primary spectrum signal I ₁(λ _j):

A. at first measure based on the shortwave second order spectrum signal of grating and spectrometer architecture and the ratio of shortwave primary spectrum signal, different level spectral signal compares γ _2/1(λ _i):

$\frac{I_2\left({\mathrm{\λ}}_i\right)}{I_1\left({\mathrm{\λ}}_i\right)}=\frac{E\left({\mathrm{\λ}}_i\right){\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_i\right)R\left({\mathrm{\λ}}_i\right)}{E\left({\mathrm{\λ}}_j\right){\mathrm{\η}}_1\left({\mathrm{\λ}}_j\right){\mathrm{\τ}}_0\left({\mathrm{\λ}}_j\right)R\left({\mathrm{\λ}}_j\right)}=\frac{{\mathrm{\η}}_2\left({\mathrm{\λ}}_i\right)}{{\mathrm{\η}}_1\left({\mathrm{\λ}}_j\right)}={\mathrm{\γ}}_{2/1}\left({\mathrm{\λ}}_i\right)$

B. will handle based on the shortwave primary spectrum signal data adjacency intermediate interpolated of the free spectral range of grating and spectrometer architecture again, obtain interpolation shortwave primary spectrum signal I ₁(λ _i):

I ₁(λ _i)＝E(λ _i)η ₁(λ _i)τ ₀(λ _i)R(λ _i)

C. different level spectral signal is compared γ _2/1(λ _i) and interpolation shortwave primary spectrum signal I ₁(λ _i) multiply each other the shortwave second order spectrum signal I of the spectral region that obtain superposeing ₂(λ _i): I ₂(λ _i)=E (λ _i) η ₂(λ _i) τ ₀(λ _i) R (λ _i)

D. measure the mixed spectra signal I of stack spectral region ₁₊₂(λ _i): I ₁₊₂(λ _i)=I ₁(λ _j)+I ₂(λ _i)

E. from superimposed light spectrum signal I ₁₊₂(λ _i) in deduct I ₂(λ _i), just obtained long wave primary spectrum signal I ₁(λ _j): I ₁(λ _j)=I ₁₊₂(λ _i)-γ _2/1(λ _i) I ₁(λ _i)

This has just finished the separation of grating spectrum instrument stack second order spectrum, and other senior sub-spectrum that superposes can separate by above-mentioned steps.