JP2738860B2 - Spectrum synthesis method and spectrum synthesis apparatus used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for synthesizing two spectra whose wavelength regions partially overlap with each other, and a spectrum synthesizing apparatus used therefor.

<Conventional technology> In order to obtain the spectrum of a light source or the spectrum of light transmitted or reflected by a sample, light is dispersed using a dispersive element such as a diffraction grating, and a photodiode array is arranged on the focal plane of the dispersed light. Then, a method of electrically processing the one-dimensional output signal of the photodiode array is adopted.

By the way, a diffraction grating has a large number of grooves with a small interval on a plane or a concave surface, and thus the diffraction angle range is wider than that of a prism spectroscope. Therefore, 1
One photodiode array may not be able to accommodate the desired wavelength range, so the photodiode array or diffraction grating is moved to perform multiple measurements while changing the wavelength range. After the measurement, the end and end of each spectrum are measured. Are superimposed to obtain one broad spectrum.

<Problems to be Solved by the Invention> However, when imaging is performed a plurality of times by changing the wavelength range as described above, the following problem occurs.

First, when the photodiode array or the diffraction grating is moved, the diffraction angle (the angle between the diffraction grating and the dispersed light emitted from the diffraction grating) changes, and the amount of wavelength change per unit length Δl on the photodiode array (Δλ / Δl) changes. For this reason, when the ends of the spectra overlap each other, the waveforms of the spectra do not match exactly, and this mismatch appears as an error in the spectrum waveform.

In addition, since a screw or a cam mechanism is used when moving the photodiode array or the diffraction grating, backlash occurs depending on the screw feed direction or the cam rotation direction, and a shift (Δλ) may occur in the measurement wavelength. .

In addition, errors in the surface shape of the diffraction grating, errors in groove spacing,
When a collimator is used, it is difficult to superimpose the spectra due to the aberration of the collimator, the difference in the wavelength sensitivity characteristics of each element constituting the photodiode array, and the like.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a spectrum synthesis method and a spectrum synthesis apparatus capable of accurately overlapping spectra by processing a spectrum signal. I do.

<Means and Actions for Solving the Problems> The spectrum synthesizing method of the present invention for achieving the above-described object is such that both waveforms are most similar in a wavelength overlapping region, and one or both spectrum end points are determined. In this method, two spectra are synthesized by shifting in the wavelength direction, distributing the amount of shift at the above-mentioned end point based on the wavelength calibration point of the spectrum, and expanding and contracting the entire spectrum in the wavelength direction.

Further, the spectrum synthesizing apparatus of the present invention is a spectroscope for dispersing light from a sample, a light receiving detection means for detecting a light beam dispersed by the spectroscope, and a sample light, a spectroscope, and a relative positional relationship between the light receiving detecting means. By shifting, the moving means for acquiring at least two spectra partially overlapping the wavelength range for the same sample light, and the waveforms of both are most similar in the overlapping area of the wavelengths of the plurality of spectra obtained by the light receiving and detecting means. In this way, the amount of shift of one or both spectrum end points in the wavelength direction is determined, and the shift amount at the end point is distributed with respect to the wavelength calibration point of the spectrum to expand or contract the entire spectrum in the wavelength direction. Wavelength compensating means, and combining two spectra based on the spectrum corrected by the wavelength compensating means. Those having a stage.

According to the above-described spectrum synthesizing method and the spectrum synthesizing apparatus, the wavelength shift is eliminated by shifting one or both end points of the spectrum in the wavelength direction so that the waveforms of the two are most similar in the wavelength overlapping region. By using the wavelength calibration point as a reference, the amount of shift at the above-mentioned end point can be distributed to expand and contract the entire spectrum. As a result, the wavelength difference between the two spectra (Δ
λ) and the difference in scale (Δλ / Δl) can be matched.

<Example> Hereinafter, an example will be described in detail with reference to the accompanying drawings.

The waveform (S1) shown in FIG. 1 shows a spectrum extending from λ11 to λ13 around the wavelength λ10, and the waveform (S2) shows a spectrum extending from λ21 to λ23 around the wavelength λ20. Wavelength λ at the end of the spectrum (S1)
13 is equal to the wavelength λ22 of the spectrum (S2), and the wavelength λ21 at the end of the spectrum (S2) is the wavelength λ22 of the spectrum (S1).
Equal to 12, the two spectra (S1) and (S2) overlap in the end wavelength regions (λ12 to λ13 and λ21 to λ22) (hereinafter, this region is referred to as “overlapping region W”). The wavelength λ10 of S1) is calibrated (referred to as a wavelength calibration point), but the other wavelengths deviate from the actual wavelength as the distance from the wavelength calibration point increases. The spectrum (S2) is also calibrated at the wavelength λ20, but the other wavelengths deviate from the actual wavelength as the distance from the wavelength calibration point increases.

Therefore, the waveform at λ12 is not always equal to the waveform at λ21, and the waveform at λ22 does not always match the waveform at λ13.

Therefore, in the present embodiment, in the overlap region W, both spectra are compared, and one or both wavelengths are shifted so that the waveforms are most similar, and the intensities are matched.

First, to shift the wavelength, as shown in the following equation, the intensity S2 (λ) of the spectrum (S2) is shifted by Δλ with respect to the intensity S1 (λ) of the spectrum (S1), and the difference between the two is minimized over the overlapping region. The amount of deviation Δλmin is determined.

Then, the end λ22 of the spectrum (S2) is shifted by Δλmin, and Δλmin is proportionally distributed based on the wavelength calibration point λ20 to expand and contract the entire spectrum (S2) horizontally. The stretched spectrum is defined as (S2 ′).

Note that instead of the above equation, the shift amount Δλmin at which the product of the spectral intensities becomes the maximum may be obtained using the following equation.

Next, to correct the intensity of the spectrum, the intensity of the spectrum (S1) in the overlapped regions λ21 to λ13 in FIG.
Sum of S1 (λ) and intensity S2 ′ of spectrum (S2 ′)
(Λ) is multiplied by a coefficient α to match the sum of αS2 ′ (λ). That is, Is determined so as to coincide with the coefficient .alpha., And the coefficient .alpha. Is multiplied by the entire spectrum intensity S2 '(. Lamda.). The product obtained by multiplying this α is defined as a spectrum (S2 ″).

As a result, as shown in FIG.
The spectrum (S1) and the spectrum (S
2 ″) matches in both wavelength and intensity.

In the above procedure, the spectrum (S1) (S
At the stage when 2) is obtained, if the intensity correction has already been performed using the reference sample or the like, there is no need to perform the intensity correction of the equation (2) again.

Number of spectra to be overlapped is 3 or more (S1) (S2)
(S3) (S4)... In some cases, as shown in FIG. 3, the superposition means (A) of the spectrum (S1) and the spectrum (S2) is executed, and the result is superimposed on the spectrum (S3). Procedures such as matching and superimposing the result on the spectrum (S4) may be sequentially repeated.

FIG. 4 shows a spectrum synthesizing apparatus for implementing the above-described method of superimposing spectra. Light from the sample (11), which is a spectrum measurement target (the measurement target may be a light source, or may be transmitted light or reflected light of the sample) passes through a collimator lens (12) and a slit (13). And a photodiode array (1) dispersed by a concave diffraction grating (14) and arranged on a Rowland circle (R).
5). The photodiode array (15) includes, for example, 512 light receiving elements, and an output signal of each light receiving element is amplified by an amplifier (16). Then, it is stored in a memory (31) built in the controller (17) and displayed on a display (18) as required.

Since the above-mentioned photodiode array (15) can obtain only a spectrum in a limited wavelength range at a time, an optical system including a collimator lens (12), a slit (13), and a concave diffraction grating (14) is illustrated. A moving means (for example, a rotary table or a feed screw) is provided so as to be able to move as shown by the middle arrow to obtain a spectrum in a plurality of wavelength ranges.

The controller (17) has means (32) for taking out data from the memory (31) in which each spectrum data is stored and performing wavelength superposition according to the procedure described above, and means (33) for performing intensity correction. ing. Each means (32) (33)
Is specifically realized by calculation software of a computer.

The combined spectrum obtained by the means for performing intensity correction (33) is stored in the memory (31) and displayed on the display (18) as necessary.

The present invention is not limited to the above embodiment. For example, in a spectrum synthesizing method, both spectra can be shifted and overlapped. At this time, the shift amount Δλ1min of the spectrum (S1) and the shift amount Δλ2min of the spectrum (S2) are obtained (for example, −
Δλ1min = Δλ2min = Δλmin / 2. ), On the basis of the wavelength calibration points λ10 and λ20 of the spectra (S1) and (S2) based on the amounts of these shifts, the entire spectra (S1) and (S2) expand and contract horizontally.

In addition, the number of spectra to be overlapped is three or more (S1) (S
2) (S3) (S4) ... In some cases, superimpose spectrum (S1) and spectrum (S2), superimpose spectrum (S3) and spectrum (S4), and superimpose each result. You may do so.

The collimator lens (12), the slit (13), the concave diffraction grating (14) and the like in the spectrum superimposing device shown in FIG. 4 are examples from a known example. It is possible to make changes.

<Effects of the Invention> As described above, according to the spectrum synthesizing method and the spectrum synthesizing apparatus of the present invention, the wavelength is shifted so that the spectral waveform is most similar in the overlapping region of the wavelength, and the entire spectrum is shifted by the wavelength. Since expansion and contraction can be performed according to the amount of the shift, the shift between the wavelengths of both spectra can be eliminated, the wavelength scale can be adjusted, and an accurate spectrum without waveform distortion can be obtained over a wide wavelength range.

[Brief description of the drawings]

FIG. 1 is a diagram showing two spectrum waveforms to be synthesized, FIG. 2 is a diagram showing a waveform of a synthesized spectrum, FIG. 3 is a diagram illustrating a method of synthesizing three or more spectra, FIG. FIG. 3 is a block diagram of a spectrum synthesis device. (S1) (S2): spectrum, W: wavelength overlapping region, λ10, λ20: wavelength calibration point of spectrum, Δλmin
… Amount of shift (14)… Diffraction grating spectroscope, (15)… Photodiode array, (32)… Wavelength correction means, (33)… Spectrum intensity correction means

Continuation of the front page (56) References JP-A-62-228123 (JP, A) JP-A-53-85483 (JP, A) JP-A-61-111425 (JP, A) JP-A-60-7330 (JP , A)

Claims (4)

(57) [Claims] 1. A method for synthesizing two spectra having partially overlapped wavelength regions, wherein one end of one or both spectra is shifted in the wavelength direction so that both waveforms are most similar in the overlap region of the wavelengths. A spectrum synthesizing method for synthesizing two spectra by distributing an amount of shift at the end point with reference to a wavelength calibration point and expanding and contracting the entire spectrum along a wavelength direction. 2. A spectroscope for dispersing light from a sample,
At least two spectra that partially overlap in the wavelength range for the same sample light by displacing the relative positions of the sample light, the spectroscope, and the light reception detection means with the light receiving detection means for detecting the light flux dispersed by the spectroscope. The moving means for acquiring the and the amount of shifting the end point of one or both spectra in the wavelength direction so that both waveforms are most similar in the overlapping region of the wavelengths of the plurality of spectra obtained by the light receiving detection means, Based on the wavelength calibration point of the spectrum, the amount of deviation at the above-mentioned end point is distributed, and two wavelength correcting means for expanding and contracting the entire spectrum in the wavelength direction, and two based on the spectrum corrected by the wavelength correcting means are provided. A spectrum synthesizing device, comprising: synthesizing means for synthesizing a spectrum. 3. Synthesizing a spectrum for expanding and contracting the entire spectrum along the wavelength direction according to the procedure described in claim 1, and correcting the intensity of the spectrum so that the integrated value of each spectrum becomes the same in a common wavelength region. Method. 4. The apparatus according to claim 2, further comprising spectrum intensity correction means for correcting the intensity of the spectrum corrected by the wavelength correction means so that the integrated value of each spectrum becomes the same.
The spectrum synthesizing apparatus according to the above.