JP2014163741A - Spectrum measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a clear spectrum with uniform noises in a measurement wavelength range extending from UV/visible light region to a near-infrared region.SOLUTION: A control processing part 10 includes: calculation means (a signal processing part 11) for determining the optimum number of times of integration of a photometric value integrated in each measuring point in a measurement wavelength range before starting a spectrum measurement for a specimen; and storage means (a storage part 13) for storing the number of times of integration allotted to each measuring point determined by the calculation means. A photometric value is obtained at each measuring point to execute a baseline correction according to the number of times of integration allotted to each measuring point, and a spectrum measurement for the specimen is performed at each measuring point with the same number of times of integration.

Description

  The present invention relates to a spectrum measuring apparatus such as a spectrophotometer, and more particularly to a spectrum measuring apparatus capable of measuring a spectrum over a wide measurement wavelength range from an ultraviolet / visible region to a near infrared region.

  The spectrophotometer has a very wide range of applications, and is used for various purposes from routine analysis to research in fields such as materials, chemistry, electricity / electronics, energy, food / agriculture, and bio / pharmaceuticals. In particular, ultraviolet / visible / near-infrared spectrophotometers capable of performing spectrum measurement over a wide wavelength range from the ultraviolet / visible region to the near-infrared region have become widespread as being capable of supporting spectroscopic measurements in a wide range of fields.

  Ultraviolet / visible / near-infrared spectrophotometers measure a spectrum in a wide measurement wavelength range from the ultraviolet / visible region to the near-infrared region, so a single light source cannot be used as the light source for irradiating the sample with measurement light. . Usually, a plurality of light sources having different emission spectra, for example, a deuterium lamp having a continuous spectrum in the ultraviolet region and a halogen lamp having a continuous spectrum in the visible region and the near infrared region are used in combination (Patent Document 1). In switching between the plurality of light sources, light from any one of the plurality of light sources is selectively reflected by a reflecting mirror whose reflection direction can be changed and guided to the spectroscope (Patent Document 2).

Further, in the ultraviolet / visible / near infrared spectrophotometer, it is impossible to detect all wavelengths from the ultraviolet / visible region to the near infrared region with a single photodetector. Therefore, usually, a plurality of types of photodetectors such as a photomultiplier tube (PMT), a PbS (lead sulfide) detector, and an InGaAs detector are switched at a predetermined wavelength (Patent Document 1).
Furthermore, many reflection-type diffraction gratings (spectrometers) are used as spectroscopic measurement optical systems. However, since a single diffraction grating cannot diffract with high efficiency in a wide wavelength range, a wavelength range in which diffraction can be performed efficiently. In some cases, a plurality of diffraction gratings different from each other are mounted and mechanically switched according to the measurement wavelength range (Patent Document 2).

In the ultraviolet / visible / near-infrared spectrophotometer, since a plurality of light sources, a plurality of types of photodetectors, a plurality of diffraction gratings and the like are switched as described above, for example, as shown in FIG. Steps and shocking noise are inevitable at the time of (310 nm), the diffraction grating switching wavelength (720 nm), and the photodetector switching wavelength (870 nm, 1650 nm).
The switching wavelength point is an area where sensitivity is weak, and noise is inevitably increased as compared with the sensitivity of other areas. Therefore, instead of erasing the step and shock noise at the time of switching, the light source and photodetector on the graph in the data display section so that the analyst does not mistake the step or shock noise as the peak derived from the sample component. It is also proposed to display the position of the switching wavelength such as (see Patent Document 1 and FIG. 3).

JP 2009-250787 A JP 2005-201680 A

However, even if the position of the switching wavelength of the light source, the light detector, etc. is displayed on the data graph, it does not erase the step or shocking noise at the time of switching, so there is still a possibility that the analyst will misunderstand. .
In addition, it is possible to reduce the shocking noise by slowing down the wavelength scanning speed to increase the number of times the photometric value data is integrated at each measurement point, but it takes time to scan the wavelength required for measurement. Originally, such steps and shock-like noise are locally generated, and it is not necessary to apply equalization at each measurement point in the measurement wavelength range from the ultraviolet / visible region to the near infrared region. .

  The present invention solves the above-described problems of the prior art, and reduces steps and shock noise when switching between a plurality of light sources, a plurality of types of photodetectors, a plurality of diffraction gratings, and the like in the ultraviolet / visible region. An object of the present invention is to provide a spectrum measuring apparatus capable of obtaining a clean spectrum with uniform noise in a measurement wavelength range extending from 1 to the near infrared region.

In order to solve the above-described problems, a spectrum measuring apparatus according to the present invention includes a light source, a spectroscope, a sample chamber in which a sample is installed, a measuring unit including a photodetector, and a control processing unit. A spectrum measurement device that performs spectrum measurement at each measurement point while scanning a wavelength at a predetermined measurement interval in a measurement wavelength range from a region to a near infrared region,
1) a calculation means for determining an optimum number of times of photometric value data to be integrated at each measurement point in the measurement wavelength range before starting spectrum measurement on the sample;
2) storage means for storing the number of integrations determined by the calculation means and assigned to each measurement point, and obtaining a photometric value data at each measurement point according to the number of integrations assigned to each measurement point Correction is performed and spectrum measurement is performed on the sample at each measurement point with the same number of integrations.
Here, the photometric value data is a raw value, and the number of integration corresponds to the number of samplings of the acquired photometric value.
Therefore, in the spectrum measuring apparatus of the present invention, since the optimum number of times of photometric value data is determined at each measurement point in the measurement wavelength range from the ultraviolet / visible region to the near infrared region, the wavelength scanning speed is measured. The scanning speed of the wavelength does not become a fixed scanning speed within the wavelength range, but the scanning speed of the wavelength fluctuates according to the number of integrations at each measurement point in the measurement wavelength range.

Further, the spectrum measuring apparatus according to the present invention described in claim 2 is the spectrum measuring apparatus according to claim 1, wherein the calculating means for determining the number of times the photometric value data is integrated at each measurement point includes:
1) means for acquiring a predetermined number of photometric value data at each measurement point in the measurement wavelength range and converting it into a predetermined number of 100% spectral data before starting spectrum measurement on the sample;
2) means for obtaining a standard deviation value of a predetermined number of 100% spectrum data at each measurement point;
3) Means for obtaining an average standard deviation value of a predetermined number of standard deviation values falling within a preset range among standard deviation values at each measurement point in the measurement wavelength range;
4) means for dividing the individual standard deviation values at each measurement point by the average standard deviation value;
And the number of times the photometric value data is integrated at each measurement point is determined based on the individual values obtained by the dividing means.
Here, the 100% spectral data can be obtained by sequentially dividing the acquired photometric value data immediately before by the immediately subsequent photometric value data (only a predetermined number of the last photometric value data is divided by the first photometric value data. ). In addition, each standard deviation value (SD value) at each measurement point in the measurement wavelength range indicates the “fluctuation” of the value at each measurement point.
In addition, the average standard deviation value (excellent SD value) means that when the individual SD values at the respective measurement points in the entire measurement wavelength range are arranged in order from the smallest to the largest, the higher one is counted from the smallest, for example, 20%. The average of SD values within the range is obtained. Based on a value (SD value / excellent SD value) obtained by dividing each SD value at each measurement point by this excellent SD value, the number of integrations is assigned to each measurement point based on a preset reference.

According to the spectrum measuring apparatus of the present invention, since the optimum number of times of photometric value data integration at each measurement point is determined before the spectrum measurement on the sample is started, the sensitivity is weak (large fluctuation) at the time of spectrum measurement. The number of integrations is increased by concentrating only the measurement points, and there is no longer any significant noise that occurs when the light source or photodetector is switched over the measurement wavelength range from the ultraviolet / visible region to the near infrared region. It is possible to obtain a clean spectrum with the same number.
Further, at other measurement points with high sensitivity, the number of integrations can be reduced to increase the wavelength scanning speed and the time required for spectrum measurement can be minimized, so that the best spectrum can be obtained in the minimum time.

  Further, according to the spectrum measurement of the present invention, the photometric value data acquired for determining the number of integrations is a raw value, for example, data obtained by applying data processing such as smoothing after the spectrum measurement, that is, artificial processing. Compared to the above, the reliability of the spectrum measurement according to the present invention is high.

It is a schematic block diagram which shows the outline | summary of the whole structure of the spectrum measuring apparatus of one Example of this invention. It is a flowchart which shows operation | movement of the spectrum measuring apparatus of one Example of this invention. It is a figure which shows the noise state (A) of the spectrum measuring apparatus of one Example of this invention, and the noise state (B) of a conventional apparatus.

Hereinafter, an example of an embodiment of a spectrum measuring apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing the overall configuration of a spectrum measuring apparatus according to an embodiment of the present invention. Hereinafter, a deuterium lamp and a halogen lamp are used as a light source and range from the ultraviolet / visible region to the near infrared region. An ultraviolet, visible, and near-infrared spectrophotometer that performs spectrum measurement in a wide measurement wavelength range will be described.

In FIG. 1, a measurement unit 1 includes a deuterium lamp 2 having a continuous spectrum in the ultraviolet region as a light source, a halogen lamp 3 having a continuous spectrum in the visible region and the near infrared region, a deuterium lamp 2, and a halogen lamp 3. A light source switching mirror 4 is arranged. The light source switching mirror 4 can be rotated in an arrow R direction (rotation direction of the light source switching mirror 4) about an axis perpendicular to the paper surface by a mirror driving unit (not shown) including a motor, and the reflection direction is switched. . The deuterium lamp 2 and the halogen lamp 3 are normally switched around a wavelength of 310 nm.
Light from either the deuterium lamp 2 or the halogen lamp 3 is selectively reflected and collected by the light source switching mirror 4 and guided to a spectroscope 5 such as a reflective diffraction grating.
The light emitted from the deuterium lamp 2 or the halogen lamp 3 includes a wide continuous spectrum (multiple wavelengths), and one wavelength used for measurement is selected by the diffraction grating of the spectroscope 5 and is extracted as monochromatic light. It is. The monochromatic light extracted by the spectroscope 5 is irradiated to the sample cell 7 disposed in the sample chamber 6, and the light transmitted through the sample cell 7 is detected by the photodetector 8.

In spectrum measurement, a spectroscope 5 such as a diffraction grating is driven at a constant speed by a driving means (not shown), and wavelength scanning is performed at a measurement interval set in advance in the measurement wavelength range, for example, a measurement interval of 1 nm. A spectrum is measured at each measurement point.
In spectrum measurement, the photometric value data sampled at each measurement point in the measurement wavelength range is normally multiplied a predetermined number of times equally. In the present invention, as described later, an optimum value is obtained for each measurement point. Total number of times is allocated.

  The photodetector 8 performs spectrum measurement in a wide measurement wavelength range from the ultraviolet / visible region to the near-infrared region, so that a plurality of types of photodetectors such as a photomultiplier tube (PMT) and PbS (lead sulfide) are used. The detector and the InGaAs detector are switched at a predetermined wavelength and used. The switching wavelength of the photodetector 8 depends on the characteristics of the photodetector 8, for example, the PMT detector and the PbS detector are switched between 800 nm and 900 nm (for example, 870 nm), and the PbS detector and the InGaAs detector are switched at 1650 nm. It is done.

The control processing unit 10 includes a signal processing unit 11, a control unit 12, and a storage unit 13, and photometric value data obtained by the photodetector 8 is input to the signal processing unit 11. The signal processing unit 11 processes the photometric value data and executes various arithmetic processes for calculating transmittance and absorbance, for example.
The control unit 12 includes an operation unit 20 for an analyst to set various parameters related to spectrum measurement and give instructions for various measurements and processes, and a display unit 30 for displaying information for operation and spectra of measurement results. Is connected. The control unit 12 also switches the signal processing unit 11, the light source switching mirror 4 of the measurement unit 1, the wavelength scanning of the spectroscope 5, the switching of the photodetector 8, and the storage unit 13 that temporarily stores photometric value data. Control the operation.
The control processing unit 10 is generally configured around a general-purpose personal computer (not shown), and various controls and signal processing are executed by mounting a predetermined control program on the personal computer.

Next, the calculation means for determining the number of integrations in the spectrum measuring apparatus of one embodiment of the present invention will be described with reference to Table 1.
As shown in Table 1, for convenience of explanation, the measurement wavelength range is 200 nm to 1000 nm, the measurement interval is 1 nm, and the wavelength scan is performed at a slow speed, for example, 10 times (No. 1 to No. 10). An example of performing baseline correction will be described.
Such baseline correction is performed before the start of spectrum measurement. That is, in the case of transmittance measurement, wavelength correction is performed by performing wavelength scanning with no sample in the sample cell 7 of the sample chamber 6 or in the case of reflectance measurement with a reference plate disposed.

  1) Ten photometric value data are acquired by the photodetector 8 at each measurement point in the measurement wavelength range of 200 nm, 201 nm, 203 nm and sequentially up to 1000 nm, for example, ten photometric value data acquired at a measurement point of 200 nm, for example. 1st photometric value data / 2nd photometric value data 2nd photometric value data / 3rd photometric value data 3rd photometric value data / 4th photometric value data 10th photometric value Like the value data / first photometric value data, the previously acquired photometric value data is divided by the next photometric value data (only the 10th last photometric value data is divided by the first photometric value data. Converted into 10 pieces of 100% spectral data (100.15 nm, 98.86, 99.37... 100.48), and noise at each measurement point. Examine the size. This operation is called “learning baseline correction”. That is, the learning baseline correction is for information collection.

  2) For example, in Table 1, since 10 100% spectrum data are obtained at a measurement point of 200 nm, the standard deviation value at the measurement point of 200 nm is defined as the “fluctuation” of the value of the 100% spectrum data at the measurement point of 200 nm. Calculated as (SD value). Therefore, 801 SD values are obtained in the measurement wavelength range of 200 nm to 1000 nm. Since the 801 SD values are different in wavelength energy and sensitivity of the photodetector 8 at each measurement point, each 801 SD value is different. It is not accurate to determine the number of integrations at each measurement point based on these 801 SD values. Therefore, in this embodiment, the number of integration is determined according to the following criteria and assigned to each measurement point.

  3) When 801 SD values are arranged in order from the smallest to the largest, the average of the SD values within a predetermined range, for example, the upper 20%, is calculated from the smallest. This average SD value is referred to as “excellent SD value”.

4) A value obtained by dividing the 801 SD values of each measurement point in the measurement wavelength range of the learning baseline correction by the excellent SD value (SD value / excellent SD value) is obtained and integrated with respect to each measurement point according to the following criteria. The number of times is allocated and stored in the storage unit 13.
(SD value / excellent SD value) is less than 0 to 2 ... number of integrations once (uses one photometric value data)
(SD value / excellent SD value) is less than 2 to 4 ... 10 times of integration (SD value / excellent SD value) is less than 4 to 6 ... 25 times of integration (SD value / excellent SD value) is 6 More than 50 times

The basis for the number of integrations at each measurement point allocated based on the above criteria will be described.
The magnitude of the noise is considered to be substantially equal to the magnitude of the SD value, and it is known that the noise becomes smaller in the route 1 / n where the number of integrations is n. The number of integrations is determined based on the route 1 / n.
That is, when “(SD value / excellent SD value) is less than 2 to 4 ... the number of integrations is 10 times”, if (SD value / excellent SD value) is about 3, the route 1/10 is obtained when the number of integrations is 10 times. Since it is about か ら, the size of (SD value / excellent SD value) can be made almost 1 when measuring a sample. That is, noise can be reduced. The same applies to other cumulative counts.
When spectrum measurement is performed with such integration times, as shown in FIG. 3A, the magnitude of noise can be made substantially the same in a wide measurement wavelength range from the ultraviolet / visible region to the near infrared region.

Prior to the start of spectrum measurement, the baseline correction is performed by integrating the photometric value data at each measurement point in the entire measurement wavelength range according to the number of integrations based on the reference. That is, instead of performing the integration evenly at each measurement point, the baseline correction of 100% spectrum data is executed by intensively increasing the number of integrations of only the measurement points with low sensitivity. This is called “standard baseline correction”.
The series of signal processing / calculation is executed in the control processing unit 10.

Next, the operation of the spectrum measuring apparatus according to the embodiment of the present invention will be described with reference to the flowchart of FIG.
Before starting the spectrum measurement for the sample in the sample cell 7 arranged in the sample chamber 6, the control processing unit 10 corrects the learning baseline to identify the sensitive and bad areas at each measurement point in the measurement wavelength range. Then, the optimum number of integrations is assigned to each measurement point (step S1).
The standard baseline correction is performed at each measurement point in the measurement wavelength range according to the allocated number of times (step S2).
After the standard baseline correction, the spectroscope 5 is driven to perform wavelength scanning, and the spectrum measurement of the sample is started in accordance with the same conditions as the standard baseline correction, that is, the optimum number of integrations assigned to each measurement point ( Step S3).
The above operation is repeated until all spectrum measurements at each measurement point in the measurement wavelength range are completed (step S4).

DESCRIPTION OF SYMBOLS 1 Measurement part 2 Deuterium lamp 3 Halogen lamp 4 Light source switching mirror 5 Spectrometer 6 Sample chamber 7 Sample cell 8 Photodetector 10 Control processing part 11 Signal processing part 12 Control part 13 Storage part 20 Operation part 30 Display part R Light source switching Mirror rotation direction

Claims (2)

It has a light source, a spectroscope, a sample chamber where the sample is installed, a measurement unit including a photodetector, and a control processing unit, and scans the wavelength at a predetermined measurement interval in the measurement wavelength range from the ultraviolet / visible region to the near infrared region. However, the spectrum measurement device that performs spectrum measurement at each measurement point, the control processing unit,
1) a calculation means for determining an optimal number of times of photometric value data to be integrated at each measurement point in the measurement wavelength range before starting spectrum measurement for the sample;
2) storage means for storing the number of integrations determined by the calculation means and assigned to each measurement point;
And integrating the photometric value data at each measurement point according to the number of times assigned to each measurement point, converting it to 100% spectrum data, and performing baseline correction, A spectrum measuring apparatus that performs spectrum measurement on the sample at a measurement point. The spectrum measuring apparatus according to claim 1, wherein the calculation means for determining the number of times of integration of photometric value data at each measurement point is
1) means for obtaining a predetermined number of photometric value data at each measurement point in the measurement wavelength range and converting it into a predetermined number of 100% spectral data before starting spectrum measurement on the sample;
2) means for obtaining a standard deviation value of the predetermined number of 100% spectrum data at each measurement point;
3) Means for obtaining an average standard deviation value of a predetermined number of the standard deviation values falling within a preset range among the standard deviation values of the measurement points in the measurement wavelength range;
4) means for dividing the individual standard deviation value at each measurement point by the mean standard deviation value;
And measuring the number of integrations of photometric value data at each measurement point based on the individual values obtained by the dividing means.

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