WO2017037871A1

WO2017037871A1 - Measurement device

Info

Publication number: WO2017037871A1
Application number: PCT/JP2015/074859
Authority: WO
Inventors: 育也菊池; 敦也伊藤
Original assignee: パイオニア株式会社; 日機装株式会社
Priority date: 2015-09-01
Filing date: 2015-09-01
Publication date: 2017-03-09

Abstract

This measurement device comprises: a laser light source (110) that emits a laser light toward an object (500) to be measured, said object exhibiting wavelength-dependent transmittance such that the transmittance varies according to the wavelength of the laser light; and a detection unit (120) that detects the laser light transmitted through or reflected off the object to be measured, and exhibits wavelength-dependent sensitivity such that the detection sensitivity varies according to the wavelength of the laser light. The wavelength dependence of the sensitivity of the detection unit is set so that, within the range of wavelengths of the laser light, the product of the wavelength dependence of the sensitivity of the detection unit and the wavelength dependence of the transmittance of the object to be measured is smaller than the wavelength dependence of the transmittance of the object to be measured. As a result, discrepancies in the measurement results caused by fluctuations of the laser light wavelength can be minimized.

Description

measuring device

The present invention relates to a technical field of a measuring apparatus that acquires information on information to be measured using laser light.

As this type of device, for example, a device that irradiates light to be measured and detects information transmitted or reflected to acquire information on the measured object is known. For example, Patent Document 1 discloses an apparatus that irradiates blood with light and measures blood concentration from the amount of transmitted light.

Japanese Patent Laid-Open No. 11-226119

However, blood has a transmission wavelength dependency in which the transmission amount changes depending on the wavelength of light. For this reason, if the wavelength of the light to irradiate changes, the amount of transmitted light also changes. Therefore, in the technique such as Patent Document 1 that measures the blood concentration from the amount of transmitted light, there is a technical problem that the accurate blood concentration cannot be measured if the wavelength of the irradiated light changes. Arise.

It should be noted that if a light source whose wavelength does not change is used, a change in the amount of transmitted light can be suppressed, but in that case, a new technical problem such as an increase in cost may occur.

Examples of problems to be solved by the present invention include the above. An object of the present invention is to provide a measuring apparatus that can suitably realize measurement using laser light.

A measuring apparatus for solving the above problems includes a laser light source that emits laser light toward a measurement target having a transmittance wavelength dependency in which the transmittance changes according to the wavelength of the laser light, and the wavelength of the laser light. The detection wavelength has a sensitivity wavelength dependency that changes in response, and includes a detection unit that detects the laser light transmitted or reflected by the measurement target, and the sensitivity wavelength dependency of the detection unit is In the wavelength range of the laser beam, the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the measurement target is smaller than the transmittance wavelength dependency of the measurement target. Is set.

It is a schematic block diagram which shows the whole structure of the measuring apparatus which concerns on an Example. It is a graph which shows the wavelength dependence of the light absorbency of blood. It is a graph (the 1) which shows the sensitivity wavelength dependence of a detector. It is a graph which shows the wavelength dependence of a water-soluble processing oil agent. It is a graph (the 2) which shows the sensitivity wavelength dependence of a detector. It is a graph which shows the wavelength dependence of the standardized detection light quantity. It is a graph which shows the sensitivity wavelength dependence of a detector with the wavelength range of a laser beam. It is a graph which shows the synthetic transmittance and the sensitivity wavelength dependence of a detector. It is a graph which shows the wavelength dependence of the standardized detection light quantity for every detector. It is a schematic block diagram which shows the whole structure of the measuring apparatus which concerns on a 1st modification. It is a schematic block diagram which shows the whole structure of the measuring apparatus which concerns on a 2nd modification. It is a schematic block diagram which shows the whole structure of the measuring apparatus which concerns on a 3rd modification. It is a schematic block diagram which shows the whole structure of the measuring apparatus which concerns on a 4th modification. It is a graph which shows the wavelength dependence of a to-be-measured object, a detector, and an optical element. It is a graph which shows the wavelength dependence of the standardized detection light quantity separately according to the presence or absence of an optical element.

<1>
The measurement apparatus according to the present embodiment includes a laser light source that emits laser light toward a measurement target having a transmittance wavelength dependency in which the transmittance changes according to the wavelength of the laser light, and the wavelength of the laser light. A detection unit that detects the laser beam transmitted or reflected on the object to be measured, and the sensitivity wavelength dependency of the detection unit In the light wavelength range, the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the measurement target is set to be smaller than the transmittance wavelength dependency of the measurement target. ing.

During the operation of the measuring apparatus according to the present embodiment, laser light is emitted from the laser light source toward the measurement target. Specific examples of the laser light source include a Fabry-Perot (FP) laser light source and a distributed feedback (DFB) laser light source, but the type of the light source is not particularly limited in this embodiment. Further, examples of the measurement target include blood and the like, but are not limited to those related to a living body, and may be gas, liquid, or solid.

The laser light emitted from the laser light source is detected or detected by the detection unit after being transmitted or reflected by the measurement target. The detection unit is configured as a photodiode, for example, and configured to be able to detect the intensity of the laser beam. Here, the intensity of the laser light transmitted or reflected by the measurement target changes in accordance with the transmittance or reflectance of the measurement target. Therefore, if the intensity of the laser beam detected by the detection unit is used, information (for example, concentration) about the measurement target can be acquired.

In the present embodiment, in particular, the detection unit described above has a sensitivity wavelength dependency in which the detection sensitivity changes according to the wavelength of the laser light. In particular, the sensitivity wavelength dependency of the detection unit is the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the measurement target in the wavelength range of the laser light. It is set to be smaller. That is, the detection unit has a sensitivity wavelength dependency that at least partially cancels the transmittance wavelength dependency of the measurement target.

The “transmission wavelength dependency” is a value indicating how much the ratio of the intensity of the laser beam incident on the object to be measured and the intensity of the emitted laser beam changes depending on the wavelength. This is a concept that also includes reflectance wavelength dependency in which the reflectance changes in accordance with the wavelength of. The product of the sensitivity wavelength dependency and the transmittance wavelength dependency of the object to be measured is a value indicating the wavelength dependency obtained by combining the sensitivity wavelength dependency and the transmittance wavelength dependency. It shows how much the intensity of the emitted laser light changes depending on the wavelength in the measurement target and the detection unit. For this reason, the “product” here is not limited to a value obtained by simple multiplication.

When the object to be measured has transmittance wavelength dependency, if the wavelength of the laser light emitted from the laser light source fluctuates, the intensity of the laser light emitted from the object to be measured changes. Also, when there is a difference in the wavelength of the laser light emitted due to individual differences in the laser light source, even when the same type of laser light source is used, the laser light emitted from the measurement target due to the difference in wavelength There is a change in strength. Therefore, if the detection unit does not have sensitivity wavelength dependency, the intensity of the laser beam detected by the detection unit varies depending on the wavelength. That is, even for the same object to be measured, different measurement results are obtained due to the transmittance wavelength dependency of the object to be measured.

However, in this embodiment, as described above, the transmittance wavelength dependency of the measurement target is reduced due to the sensitivity wavelength dependency of the detection unit. As a result, the change in the intensity of the detection light due to the difference in the wavelength of the laser light can be reduced. Therefore, the deviation of the measurement result due to the difference in the wavelength of the laser beam can be reduced. Therefore, accurate measurement can be performed even when the wavelength of the laser light source fluctuates or even when the laser light source has individual differences. In order to effectively suppress the deviation of the measurement result, the product of the sensitivity wavelength dependency and the transmittance wavelength dependency of the object to be measured is as small as possible (that is, a value close to a state having no wavelength dependency). ).

As described above, according to the measuring apparatus according to the present embodiment, it is possible to accurately measure even when the measurement target has transmittance wavelength dependency.

<2>
In one aspect of the measuring apparatus according to this embodiment, the laser light source is a Fabry-Perot laser light source.

Fabry-Perot laser light sources are considered to be inexpensive and highly reliable compared to different types of laser light sources such as distributed feedback laser light sources. For this reason, if a Fabry-Perot type laser light source is used, cost reduction and reliability improvement can be realized.

On the other hand, it is known that the Fabry-Perot type laser light source varies the wavelength of the laser beam to be irradiated due to temperature characteristics. However, in this aspect, the transmittance wavelength dependency of the measurement target is at least partially offset by the sensitivity wavelength dependency of the detection unit. Therefore, even if the wavelength fluctuates, the deviation of the measurement result can be effectively suppressed.

<3>
In another aspect of the measuring apparatus according to the present embodiment, the laser light source emits laser light in a wavelength range in which the transmittance wavelength dependency of the measurement target is linear.

According to this aspect, even if the transmittance wavelength dependence of the measurement target is not linear when viewed in the entire wavelength range, it is linear when viewed only in the wavelength range of the laser light source. Can be considered. Therefore, it is possible to effectively cancel out the transmittance wavelength dependency of the object to be measured by using the detection unit whose sensitivity wavelength dependency is linear. Specifically, for example, when the wavelength of the laser light emitted from the measurement target decreases as the wavelength of the laser light incident on the measurement target increases, the greater the wavelength of the incident laser light, A detection unit that increases the intensity of the laser beam to be detected may be used.

As described above, if the transmittance wavelength dependency of the measurement target can be regarded as linear, it is easy to select an appropriate detection unit, and the influence of the transmittance wavelength dependency of the measurement target is suitably reduced. be able to.

<4>
In another aspect of the measuring apparatus according to this embodiment, the laser light source emits laser light in a wavelength range that does not include a wavelength at which the detection sensitivity of the detection unit is maximized.

The detection sensitivity of the detection unit typically increases linearly until the detection sensitivity reaches a maximum according to the wavelength, and then decreases linearly. That is, the detection sensitivity increases or decreases linearly except for the wavelength vicinity where the detection sensitivity is maximum. Therefore, if the wavelength range of the laser light does not include a wavelength that maximizes the detection sensitivity of the detection unit, it can be considered that the detection sensitivity of the detection unit increases or decreases linearly. Therefore, it is possible to suitably cancel out the transmittance wavelength dependency of the measurement target using the sensitivity wavelength dependency of the detection unit.

<5>
In another aspect of the measuring apparatus according to the present embodiment, the optical device further includes an optical element that is disposed on the optical path of the laser light and has the transmittance wavelength dependency, and the transmittance wavelength dependency of the optical element is In the wavelength range of the laser beam, the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the optical element and the measurement target is the sensitivity wavelength dependency of the detection unit and the It is set to be smaller than the product of the transmittance wavelength dependency of the object to be measured.

According to this aspect, the optical element is arranged on the optical path of the laser beam. For this reason, the laser light emitted from the laser light source enters the detection unit via the measurement target and the optical element. The optical element may be disposed between the laser light source and the measurement target, or may be disposed between the measurement target and the detection unit. A plurality of optical elements may be arranged on the optical path of the laser beam.

The optical element described above has a transmittance wavelength dependency in which the transmittance changes in accordance with the wavelength of the laser light, similarly to the object to be measured. In particular, the transmittance wavelength dependency of the optical element is the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the optical element and the object to be measured in the wavelength range of the laser light. It is set to be smaller than the product of the sensitivity wavelength dependency and the transmittance wavelength dependency of the object to be measured. That is, the optical element has a transmittance wavelength dependency that at least partially cancels the wavelength dependency of the object to be measured and the detection unit.

If the optical element is arranged, the influence of the wavelength dependency of the optical element on the wavelength of the optical element cannot be reduced sufficiently by the sensitivity wavelength dependency of the detector alone. Thus, the influence of wavelength dependency on the entire apparatus can be further reduced. Therefore,
It is possible to more effectively suppress the deviation in the measurement result due to the difference in the wavelength of the laser light.

The operation and other gains of the measuring apparatus according to this embodiment will be described in more detail in the following examples.

Hereinafter, embodiments of the measuring apparatus will be described in detail with reference to the drawings.

<Device configuration>
First, the configuration of the measurement apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram illustrating the overall configuration of the measurement apparatus according to the embodiment.

In FIG. 1, the measuring apparatus according to the present embodiment includes a laser light source 110 and a detector 120.

The laser light source 110 is configured as a Fabry-Perot laser light source, for example, and irradiates blood 500 flowing through the tube 510 with laser light in a predetermined wavelength range. Blood 500 is a specific example of “object to be measured”.

The detector 120 is configured as a photodiode, for example, and detects laser light emitted from the laser light source 110 and transmitted through the optical element 200 and the blood 500. The detector 120 is configured to output a detection signal corresponding to the intensity of the detected laser beam, for example, to an analysis device (not shown). The detector 120 has a sensitivity wavelength dependency in which the detection sensitivity changes according to the wavelength of the incident laser light. The detector 120 is a specific example of “detection unit”.

<Detector wavelength dependence>
Next, the transmittance wavelength dependency of the optical element 200 described above will be described in detail with reference to FIGS. FIG. 2 is a graph showing the wavelength dependency of the absorbance of blood, and FIG. 3 is a graph (part 1) showing the sensitivity wavelength dependency of the detector. FIG. 4 is a graph showing the wavelength dependency of the water-soluble processing oil, and FIG. 5 is a graph (No. 2) showing the sensitivity wavelength dependency of the detector.

In FIG. 2, the absorbance (transmittance) of blood 500 varies according to the wavelength of the incident laser light. Although the figure shows the absorbance of HbO ₂ and Hb, it will be described here HbO _2, measured as blood concentration in the example dialysis.

The absorbance of HbO ₂ varies while repeatedly increasing and decreasing in the wavelength range of 650 nm to 1200 nm. Therefore, when the wavelength of the laser light varies, the intensity of the laser light emitted from the blood 500 changes. Further, when there is a difference in the wavelength of the laser light emitted due to individual differences in the laser light source 110, even when the same type of laser light source 110 is used, the laser light emitted from the blood 500 due to the difference in wavelength. Changes in the strength. Therefore, if the detector 120 does not have sensitivity wavelength dependency, the intensity of the detected laser light varies according to the wavelength. That is, even if the same object to be measured is used, different measurement results are obtained due to the different wavelengths of the laser light.

The present embodiment aims to reduce the above-described transmittance wavelength dependency by making the detector 120 have sensitivity wavelength dependency. Specifically, the transmittance wavelength dependency of blood 500 is at least partially offset by the sensitivity wavelength dependency of detector 120. At that time, in order to effectively cancel the transmittance wavelength dependency, the transmittance wavelength dependency of HbO ₂ is preferably linear with respect to the wavelength. Therefore, in this embodiment, the wavelength range of the laser light emitted by the laser light source 110 is set to a specific wavelength range so that the transmittance wavelength dependency of HbO ₂ can be regarded as substantially linear. Specifically, the laser light source 110 according to the present embodiment irradiates laser light having a wavelength range of 750 nm to 900 nm in which the absorbance of HbO ₂ increases linearly with an increase in wavelength.

In FIG. 3, in order to reduce the transmittance wavelength dependency of HbO ₂ described above, a detector 120 whose sensitivity increases as the wavelength becomes longer may be used. In this way, when the wavelength of the laser beam is increased, the intensity of the laser beam that passes through the blood 500 is decreased, whereas the detection sensitivity of the detector 120 is increased (that is, the detected light amount is increased). ). Therefore, fluctuations in the intensity of the laser light according to the wavelength can be reduced, and deviations in measurement results can be suppressed.

In FIG. 4, the object to be measured is not limited to blood 500, and may be, for example, a water-soluble processing oil used in industrial applications. In this case, if the wavelength range of the laser light emitted by the laser light source 110 is 630 nm to 680 nm, the transmittance wavelength dependency of the water-soluble processing oil can be regarded as linear. Examples of the laser light source 110 that can irradiate a laser beam in the wavelength range of 630 nm to 680 nm include a laser light source used for reading a DVD. For this reason, when utilizing the said wavelength range, the cheap component generally spread can be utilized and cost reduction can be aimed at.

In FIG. 5, in order to reduce the transmittance wavelength dependency of the water-soluble processing oil described above, a detector 120 whose detection sensitivity decreases as the wavelength becomes longer may be used. In this way, when the wavelength of the laser beam becomes longer, the intensity of the laser beam that passes through the water-soluble processing oil increases, whereas the detection sensitivity of the detector 120 decreases (that is, the detected light amount decreases). Smaller). Therefore, fluctuations in the intensity of the laser light according to the wavelength can be reduced, and deviations in measurement results can be suppressed.

Next, the effect obtained by the sensitivity wavelength dependency of the detector 120 will be described in detail with reference to FIG. FIG. 6 is a graph showing the wavelength dependence of the normalized transmitted light amount.

In FIG. 6, when the detector 120 whose detection sensitivity decreases as the wavelength increases is applied to the blood 500 whose transmitted light amount increases as the wavelength increases, the detected light amount becomes substantially constant regardless of the wavelength. (Note that the detected light amount here is normalized with the light amount at the shortest wavelength being “1”). As a result, even if the wavelength of the laser beam fluctuates during use due to, for example, the temperature characteristics of the laser light source 110, the intensity of the detected laser beam is constant. Further, even when there is a variation in the wavelength range of the laser light due to individual differences of the laser light sources 110, the intensity of the detected laser light is constant. As described above, if the detector 120 that cancels the transmittance wavelength dependency of the object to be measured is used, the deviation of the measurement result due to the wavelength of the laser light can be effectively suppressed.

Next, a method for selecting the detector 120 will be described in detail with reference to FIGS. FIG. 7 is a graph showing the sensitivity wavelength dependency of the detector together with the wavelength range of the laser beam. FIG. 8 is a graph showing the combined transmitted light rate and the sensitivity wavelength dependency of the detector, and FIG. 9 is a graph showing the wavelength dependency of the normalized detected light amount for each detector.

In FIG. 7, when the wavelength range of the laser light source 110 is 850 ± 15 nm, consider an example in which a detector A and a detector B having different sensitivity wavelength dependencies are used. In the detector A, the wavelength with the maximum detection sensitivity is included in the wavelength range of 850 ± 15 nm of the laser light source 110. On the other hand, in the detector B, the wavelength range of the laser light source 110 that is 850 ± 15 nm does not include the wavelength that maximizes the detection sensitivity. If only the detection sensitivity is taken into consideration, the detector A having a high detection sensitivity in the wavelength range of the laser light source 110 may be used. In order to reduce the transmittance wavelength dependency of the measurement target, the sensitivity Trends in wavelength dependence should also be considered.

In FIG. 8, the detector A has a wavelength dependence on the sensitivity wavelength because the wavelength range of the laser light source 110 includes the wavelength with the maximum detection sensitivity. On the other hand, since the detector B does not include the wavelength at which the detection sensitivity is maximized in the wavelength range of the laser light source 110, the sensitivity wavelength dependency is linear. Further, the sensitivity wavelength dependency of the detector B has a tendency that is almost opposite to the transmittance wavelength dependency of the measurement target.

In FIG. 9, when the detector A is used, the wavelength dependency of the transmittance of the linear object to be measured cannot be offset appropriately because the sensitivity wavelength dependency is piled up. As a result, the amount of light detected when the detector A is used varies depending on the wavelength of the laser light. Specifically, when the detector A is used, the detected light quantity decreases as the wavelength of the laser light increases. On the other hand, when the detector B is used, since the sensitivity wavelength dependency is linear, the wavelength dependency of the transmittance of the measurement target can be offset appropriately. As a result, the amount of light detected when the detector B is used hardly changes even if the wavelength of the laser light changes. Here, the detected light amount is standardized with the maximum value being “1”.

As a result, when trying to cancel the wavelength dependency of the combined transmittance using the sensitivity wavelength dependency of the detector 120, the wavelength range of the laser light source 110 includes the wavelength with the maximum detection sensitivity. The one that is not (ie detector B) should be used.

<Modification>
Next, a measuring apparatus according to a modification will be described with reference to FIGS.

<Device configuration>
First, with reference to FIGS. 10 to 13, a configuration of a measuring apparatus according to a modification will be described. FIGS. 10 to 13 are schematic configuration diagrams showing the overall configuration of the measuring apparatus according to the first to fourth modifications, respectively.

In FIG. 10, in the measuring apparatus according to the first modification, an optical element 200 is disposed between the laser light source 110 and the blood 500. The optical element 200 has a transmittance wavelength dependency in which the transmittance changes according to the wavelength of the laser light. The optical element 200 is configured, for example, as an optical filter using a dielectric multilayer film, or a resin or the like mixed with a specific wavelength light absorbing material such as an infrared blocking film and an ultraviolet blocking film.

In FIG. 11, in the measuring apparatus according to the second modification, the optical element 200 is disposed between the blood 500 and the detector 120. For this reason, the laser beam after passing through the blood 500 is incident on the optical element 200 according to the second modification. Thus, even when the optical element 200 is arranged on the detector 120 side when viewed from the object to be measured, the effect obtained by the measuring apparatus according to the modified example described later does not change. That is, as long as the optical element 200 is disposed on the optical path between the laser light source 110 and the detector 120, the position of the optical element 200 is not particularly limited.

12, in the measurement apparatus according to the third modification, a collimator lens 150 for making laser light parallel light is disposed between the laser light source 110 and the blood 500. The collimator lens 150 is coated to give wavelength dependency. Therefore, in the second modification, the collimator lens 150 functions as the optical element 200. In this manner, an existing member can be made to function as the optical element 200 without providing the optical element 200 separately.

In FIG. 13, in the measuring apparatus according to the fourth modification, a mold member 125 for protecting the detector 120 is provided on the surface of the detector 120 (more specifically, the surface on which the laser light is incident). ing. The mold member 125 is mixed with a material that absorbs laser light having a specific wavelength (for example, glass powder doped with an organic dye substance or a wavelength selective substance (CdS or the like)). Therefore, in the fourth modification, the mold member 125 of the detector 120 functions as the optical element 200.

In the fourth modification, the collimator lens 150 may function as the optical element 200 in addition to the mold member 125. Thus, a plurality of optical elements 200 may be arranged on the optical path of the laser light.

<Transmission wavelength dependency of optical element>
Next, the transmittance wavelength dependency of the optical element will be described in detail with reference to FIGS. FIG. 14 is a graph showing the wavelength dependence of the object to be measured, the detector, and the optical element. FIG. 15 is a graph showing the wavelength dependence of the standardized detected light amount divided by the presence or absence of an optical element. In the example shown in FIGS. 14 and 15, the detector B is used among the detectors described with reference to FIGS.

When the transmittance wavelength dependency of the measurement target is large, the transmission wavelength dependency of the measurement target may not be sufficiently reduced only by the detection sensitivity of the detector 120. In this case, the sensitivity wavelength dependency of the detector 120 may be changed to a larger one, but it can be dealt with by using the optical element 200 in combination.

In the example shown in FIG. 14, the object to be measured has a transmittance wavelength dependency in which the transmittance decreases relatively rapidly as the wavelength increases. On the other hand, the detector B has a sensitivity wavelength dependency in which the detection sensitivity increases relatively gradually as the wavelength increases. The optical element 200 also has a sensitivity wavelength dependency that the detection sensitivity increases as the wavelength increases.

In FIG. 15, if it is attempted to cancel out the transmittance wavelength dependency of the object to be measured using only the detector B, the detected light amount changes according to the wavelength because the sensitivity wavelength dependency of the detector B is small. Specifically, the detected light amount decreases as the wavelength increases. On the other hand, when the optical element 200 is added, the transmittance wavelength dependency of the object to be measured can be canceled by both the detector B and the optical element 200, so that the detected light amount hardly changes even if the wavelength varies. . As described above, by adding the optical element 200, it is possible to more suitably reduce the transmittance wavelength dependency of the measurement target.

Incidentally, in the case of using a plurality of optical elements 200, it is sufficient that a value obtained by synthesizing the transmittance wavelength dependency of each of the plurality of optical elements 200 has a value as shown in FIG.

As described above, according to the measuring apparatus according to the present embodiment, it is possible to reduce the transmittance wavelength dependency of the measurement target, and therefore it is possible to realize a suitable measurement independent of the wavelength of the laser beam. .

The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 110 Laser light source 120 Detector 125 Mold 150 Collimator lens 200 Optical element 500 Blood 510 Tube

Claims

A laser light source that emits laser light toward a measurement target having a transmittance wavelength dependency in which the transmittance changes according to the wavelength of the laser light;
It has a sensitivity wavelength dependency in which detection sensitivity changes according to the wavelength of the laser light, and includes a detection unit that detects the laser light transmitted or reflected on the measurement target.
The sensitivity wavelength dependency of the detection unit is the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the measurement target in the wavelength range of the laser light. A measuring apparatus that is set to be smaller than the transmittance wavelength dependency.
2. The measuring apparatus according to claim 1, wherein the laser light source is a Fabry-Perot laser light source.
3. The measuring apparatus according to claim 1, wherein the laser light source emits a laser beam in a wavelength range in which the transmittance wavelength dependency of the object to be measured is linear.
The measurement apparatus according to any one of claims 1 to 3, wherein the laser light source emits laser light in a wavelength range that does not include a wavelength at which the detection sensitivity of the detection unit is maximum.
An optical element that is disposed on the optical path of the laser light and has the transmittance wavelength dependency;
The transmittance wavelength dependency of the optical element is the product of the sensitivity wavelength dependency of the detection unit and the transmittance wavelength dependency of the optical element and the object to be measured in the wavelength range of the laser beam. 5. It is set so that it may become smaller than the product of the sensitivity wavelength dependence of the said detection part, and the said transmittance | permeability wavelength dependence of the said to-be-measured object. The measuring device described.