JP7129694B2 - Optical measuring instrument - Google Patents

Description

The present invention is an optical measurement that combines a detector with a light source with a wide wavelength band, such as a spectrophotometer or a laser with equivalent functions (especially a tunable laser), a cascade laser, or a swept source (wavelength swept light source). The present invention relates to an instrument, and more particularly to an optical measuring instrument that performs stable measurements outdoors.

When performing measurement using an optical measuring instrument such as a spectrophotometer, it is necessary to eliminate as much as possible or maintain a constant influence other than the target sample. For example, when measuring the degree of maturity of fruit, the measurement results change due to factors such as atmospheric humidity and carbon dioxide concentration that affect the measurement wavelength of the sample, making it impossible to obtain highly accurate measurement results.
Fig. 1 shows an example of measurement results in the case of using a spectrophotometer in the atmosphere, showing the results of measuring wavelengths in the range of 2.5 µm to 20 µm from an infrared spectrometer in the atmosphere. .
As is clear from Fig. 1, carbon dioxide, which has a strong absorption characteristic for the measurement wavelength around 4.1-4.4 μm, and water vapor, which has a strong absorption characteristic for the measurement wavelength around 2.0-2.9 μm and 5.0-7.7 μm. It can be seen that this has a great influence on the spectroscopic measurement results.

In this way, when spectroscopic measurement is performed in the atmosphere, it is greatly affected by the carbon dioxide and water vapor contained in the atmosphere. If the wavelength at which λ is obtained intersects with these absorption characteristics, the reliability of the measurement accuracy is greatly impaired.
Therefore, as disclosed in Patent Document 1, nitrogen gas is introduced into the sample chamber to completely replace the inside with nitrogen to eliminate the influence of other gas components and humidity fluctuations.
Further, Patent Document 2 and Non-Patent Document 1 disclose spectrophotometers in which only the sample installation surface of a total reflection prism (ATR prism) is exposed to the outside so that air or the like does not enter the device.

JP 2005-207838 A Japanese Patent No. 3830571

N.J. Harrick, “Internal Reflection Spectroscopy: theory and applications,” Interscience Publisher (1967)

However, such a spectrophotometer requires a sample chamber having a space capable of completely enclosing the sample to be measured, which causes the spectrophotometer to become large. In addition, after the sample is set in the sample chamber, the sample chamber must be closed and replaced with nitrogen gas.
Furthermore, for example, when measuring the degree of ripeness of fruit before harvesting with a spectrophotometer, the work is carried out outdoors, and moreover, without affecting the surface of the fruit, a large number of fruits can be measured simply and in a short time. The use of spectrophotometers with sample chambers is practically impossible due to the need to make measurements.

In addition, with a total reflection prism, the interaction distance between the sample and the measurement light must be about one wavelength of the light from the prism surface. However, it cannot be used for samples with irregularities, round samples, and easily damaged samples such as fruits.

Accordingly, an object of the present invention is to prepare a space including at least part of the optical path of the incident light from the optical measuring instrument and the optical path of the reflected light from the measurement object in advance when performing measurement with an optical measuring instrument such as a spectrophotometer. By filling the chamber with a known gas, it is possible to perform stable, high-precision measurements even outdoors without using a sample chamber. To efficiently perform a large number of measurements simply and in a short time without directly contacting a device.

In order to solve this problem, the optical measuring instrument of the present invention injects a gas having known components toward a space that includes at least part of the optical path of the incident light and the optical path of the reflected light in the open air space. Therefore, a gas injection device for replacing the outside air with this gas is provided.

According to the present invention, since the space that includes the optical path through which the light used for measurement, such as incident light and reflected light, passes is filled with a gas whose composition is known, outdoor measurement can be performed without using a sample chamber. In addition, it is possible to obtain accurate measurement results that are not affected by the environment. Moreover, since it is not necessary to directly contact the sample, it is possible to perform high-precision measurement simply and in a short period of time even if the measurement target has unevenness or a surface that is easily damaged.

FIG. 1 is a diagram showing an example of measurement results when a spectrophotometer is used in the air. FIG. 2 shows an embodiment applied to a spectrophotometer. FIG. 3 is a diagram showing an example of comparison of measurement results obtained using an infrared spectrometer in the atmosphere before and after nitrogen gas injection. FIG. 4 shows absorbance spectra of material removed by nitrogen blowing.

This embodiment is applied to a spectrophotometer.
Spectroscopic analysis is used for analysis using light such as emission, fluorescence, and absorption. In particular, infrared spectroscopy is mainly used for absorbance spectrum analysis, and is used for quantitative analysis of organic substances contained in substances. For example, when analyzing the absorbance spectrum of strawberries, quantitative analysis is performed based on the absorption of sugars such as glucose and fructose and the absorption of acids such as citric acid.

A spectrophotometer consists of a light source, a spectrometer, a spectroscopic probe, an optical fiber that guides the light from the light source to the spectroscopic probe, and the light emitted from the spectroscopic probe toward the sample surface and reflected from the sample surface. It is composed of an input optical fiber that collects the reflected light and guides it to the spectroscope. A spectroscope measures the sugar content of a sample by spectrally analyzing the intensity of light reflected from the surface of the sample.

Specifically, as shown in FIG. 2, the optical measuring instrument 1 of the present embodiment includes a light source 1a, a spectroscope 1b, a spectroscope probe main body 1c, and a light beam that guides the incident light irradiated to the sample 2 from the light source 1a. It is composed of a fiber 1d, an optical fiber 1e for guiding the sample reflected light reflected from the sample 2 to the spectroscope 1b, and the like. The spectroscope 1b analyzes the spectrum of the intensity of the incident light with which the sample 2 is irradiated and the intensity of the reflected light from the sample 2 to analyze the sample.

The spectroscopic probe main body 1c is provided with a grip portion 1f extending downward from the end thereof, and a gas cylinder 3 filled with nitrogen is housed inside the grip portion 1f.
An injection port 3a for injecting nitrogen gas stored in a gas cylinder 3 toward the sample 2 is arranged around the measurement light emitting portion 1g for irradiating the sample 2 with the light from the light source 1a.
The ejection port 3a is composed of, for example, a circular slit arranged so as to surround the optical path, or a plurality of small holes arranged on a circle coaxial with the optical path.

The gas cylinder 3 and the spout 3a provided at the tip of the spectrometer probe main body 1c are communicated through a pipe inside the main body, and this pipe is connected to the spout 3a to turn on and off the injection of nitrogen gas. A valve is provided.
A trigger 1h is provided at the boundary between the spectroscopic probe main body 1c and the grip portion 1f. By pulling the trigger 1h, light irradiation from the light source 1a and operation of the spectroscope 1b are started. These actions can be stopped by releasing .
This trigger 1h and the valve provided in the pipe connecting the gas cylinder 3 and the jet port 3a are interlocked. Prior to the start of operation, the valve is opened to start blowing nitrogen from the blowing port 3a.

Spectroscopic measurement by the spectroscope 1b is performed in a state in which the outside air in the spectroscopic measurement region through which the incident light and the reflected light pass is completely filled with nitrogen by the nitrogen jetted from the jet port 3a. The amount of nitrogen gas to be ejected should be at least as long as it fills the volume of the space defined by the diameter of the injection port and the optical path length between the spectroscope probe main body 1c and the sample 2 .
Also, the distance between the sample and the spectroscope probe main body 1c can be applied from a close position to a distant position as long as the ejected gas is within the reachable range. A certain degree of effect can be obtained by substituting a part of the incident light path or the reflected light path with nitrogen gas even for a sample placed farther than the reachable range of the ejected gas.
In order to minimize the influence of carbon dioxide and water vapor in the atmosphere, it is conceivable to bring the measurement light irradiation part of the spectroscopic probe main body 1c as close as possible to the sample 2, but even if the spectroscopic probe main body 1c Even though it appears to be adhered to the sample 2, there are slight gaps due to the irregularities on the surface of the sample 2, and it is possible to replace the air in these small spaces with nitrogen by blowing out nitrogen gas. Become.

In order to fill the optical path with the spouted nitrogen in a short period of time, a plurality of spouts 3a are arranged so as to cover the distance from the far side to the near side according to the distance, and the spouts are spouted in various directions. preferably set. Further, in order to change the reaching distance of each of the ejection ports 3a, the hole diameters of the plurality of holes may be different or a pressure gradient may be generated inside the device, or may be performed at the same time.

In addition, the gas to be ejected is not limited to nitrogen, but if it is a gas with known components, including air with a constant humidity and carbon dioxide concentration, etc., it can be accurately calibrated based on the measurement results using a reference sample. can be obtained. The optimum gas can be selected according to the target sample, measurement items, required measurement accuracy, and so on.
In order to eject such gas, it is easy and convenient to use a small gas cylinder, but it is also possible to use a large cylinder, a compression device, or the like. Combining a compression device with various gas absorbent materials/air filters can also be considered for permanent use while taking in gas from the surrounding environment.

If the spectroscopic measurement cannot be completed in a short period of time, such as when a relatively long period of integration is required, it may be possible to reduce the amount of gas ejection to a minimum. That is, since it is only necessary to replenish the amount that is lost due to gas diffusion, etc., once the desired gas replacement is completed, the ejection amount is reduced to the minimum required to maintain this state, or intermittently. You may make it inject.

FIG. 3 shows an example of comparison of measurement results obtained using an infrared spectrometer in the atmosphere before and after nitrogen gas injection. FIG. 4 also shows the absorbance spectrum of material removed by nitrogen blowing.
In this example, fluctuations were observed especially in the wavenumber range of 2300 to 2400 cm ^-1 in atmospheric conditions before nitrogen gas injection, but after nitrogen gas injection, these fluctuations almost disappeared and stable measurements were made. The results were obtained. As a result, it was confirmed that the effect of CO ₂ whose concentration changes depending on the environment can be almost eliminated by replacing the CO ₂ contained in the atmosphere with nitrogen gas.

The spectroscope is not limited to the infrared spectroscope, and spectroscopes of various wavelength ranges can be used in the same way.
In many cases, it is not necessary to completely replace the outside air in the space through which the incident light and the reflected light pass with a gas whose composition is known in advance, and the amount of substances to be removed in the outside air should be kept below a certain amount. Just do it. For this reason, it is possible to stop or reduce the gas ejection by controlling the gas ejection time, flow rate, etc., or by detecting that the amount has fallen below a certain level by spectroscopic monitoring, etc., and start the target sample measurement. be.

The ATR method has been proposed as a method for placing the sample to be measured outside the main body. When it is difficult to contact the ATR prism for reasons such as the above, the measurement is difficult. In the present invention, even a sample placed at a distance from the measurement probe can be measured, so the sample can be measured without using an ATR prism.

In an environment where temporal change is gradual, it may be possible to measure even if the sample is distant from the spectroscope. This is when a reference surface such as a diffuse reflector is placed at the same position as the sample as a reference measurement and compared with the result of the sample measurement. Since the reference measurement includes the influence of interfering substances, it can be subtracted from the result of the sample measurement.
However, in this case, it is necessary to install a reference plane, and to adjust the distance between the reference measurement and the sample to the reference plane every time, which is complicated. According to the present invention, even in such a case, it is possible to greatly save labor.

An optical instrument for which the present invention is effective is a device to which spectroscopy is applied in which carbon dioxide and moisture in the atmosphere pose a problem. Spectroscopic methods mainly include those that perform spectroscopy on the detection side and those that perform spectroscopy on the light source side. The former is a conventional spectrometer, and the latter is a tunable light source (a combination of a broadband light source and a wavelength selection device, a supercontinuum light source, a wavelength-swept laser, a quantum cascade laser, and a combination of multiple single-wavelength light sources). etc.). The present invention is applicable to any of these spectroscopic methods.

Moreover, even if the light source is not placed in nearly the same optical path as the path to the temporarily purged spectrometer, the effects of the present invention can be achieved even if the detection path is only stabilized with a temporary purge. demonstrated.
If a cylinder having the same diameter as the probe is arranged on the front side of the spectroscopic probe and a hood is attached, the straightness and convergence of nitrogen can be improved, and the necessary ejection amount can be reduced.

As described above, according to the present invention, there is no need to use a sample chamber for purging with nitrogen gas or the like, and even for a measurement object with unevenness or a surface that is easily damaged, the measurement object can be exposed to the outside air. Moreover, since high-precision measurement can be performed in a short period of time without touching the object to be measured, it can be expected to be widely used, for example, when FT-IR saccharimeters are used outdoors.

1: optical measuring instrument 1a: light source 1b: spectroscope 1
1c: spectrometer probe main body 1f: grip portion 1g: measurement light emitting portion 1h: trigger 2: sample 3: gas cylinder 3a: injection port

Claims (4)

An optical measuring instrument for spectroscopic analysis that enables field measurements including a spectroscopic probe connected to a device main body having a spectroscope,
The spectroscopic probe includes a measurement light emitting part that irradiates a sample with light from a light source as incident light, and a collector that collects reflected light generated by being reflected by the sample and guides it to the spectroscope. and a light part at one end, and an ejection port for ejecting a gas of known components toward the sample is provided around the measurement light emitting part at the one end,
1. An optical measuring instrument, wherein outside air in a space open to outside air, which includes at least part of the optical path of the incident light and the optical path of the reflected light, is replaced with the gas. 2. The apparatus according to claim 1, wherein said ejection port comprises a circular slit arranged so as to surround said optical path, or a plurality of small holes arranged on a circle coaxial with said optical path. an optical instrument. A grip portion at the other end of the spectroscope probe is provided with a trigger for starting and stopping the emission of the incident light, and the injection of the gas is started and stopped in conjunction with the operation of the trigger. 3. An optical measuring instrument according to claim 1 or 2, characterized in that it is adapted to perform. 3. The optical measuring instrument according to claim 1, wherein the injection time of said gas is determined based on a predetermined time or a measurement result of said spectrometer.

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