JP4290142B2 - Photothermal conversion measuring apparatus and method - Google Patents

Description

The present invention is used when analyzing the content material, etc. of the sample, the excitation light relates photothermal conversion measuring instrument and a measuring method thereof for measuring a refractive index change occurring sample by photothermal effect when irradiated to the sample is there.

In the analysis of substances contained in various samples, improvement of analysis sensitivity is important in order to reduce the amount of reagents, simplify the sample concentration process, increase the efficiency of analysis, and reduce costs. On the other hand, when the sample is irradiated with excitation light, the irradiated portion generates heat by absorbing the excitation light, which is called a photothermal effect. Measuring this heat generation is called photothermal conversion measurement.
Conventionally, a method using a thermal lens effect formed on a sample by a photothermal effect (hereinafter referred to as a thermal lens method) is known as a high-sensitivity analysis method for a sample by this photothermal conversion measurement.
An analysis apparatus (photothermal conversion spectroscopic analysis apparatus) using a thermal lens method is disclosed in Patent Document 1, for example. In this analyzer using the thermal lens method, the detection light (measurement light) irradiated to the sample is condensed and passed through a pinhole, and the light intensity of the detection light after passing through the pinhole is detected to detect excitation light. The change in the refractive index due to the heat generation of the sample irradiated with is detected as a change in the condensing state of the detection light.

On the other hand, Patent Document 2 discloses a technique in which a change in refractive index due to the photothermal effect of a sample is regarded as a phase change in measurement light that has passed (transmitted) through the sample and measured using optical interferometry. .
Thus, for example, even if the position of the photodetector (photoelectric conversion means), the intensity of the measurement light, and its intensity distribution differ from device to device, if it does not change during measurement, it is stable without depending on these. In addition, it is possible to measure the refractive index change of the sample optically with high accuracy and high sensitivity.
Furthermore, Patent Document 1 and Patent Document 2 use excitation light that is periodically intensity-modulated, and measure the measurement light (detection light) with respect to the same period component as the intensity modulation period of the excitation light. Improvements are shown.
Japanese Patent Laid-Open No. 10-232210 JP 2004-301520 A

By the way, when evaluating the absorption spectral characteristics of a sample, a white light source is used as a light source of excitation light. Generally, since a white light source has a wide light emitting portion, the light is condensed with high accuracy and irradiated onto the sample. It is difficult to let
However, in the measurement by the thermal lens method disclosed in Patent Document 1, it is necessary to collect the excitation light with high accuracy and irradiate the sample in order to generate the thermal lens effect, and a white light source cannot be used. For this reason, there is a problem that a laser oscillator whose wavelength band is specified must be used as a light source, and the absorption spectral characteristics of the sample cannot be evaluated.
Furthermore, in the measurement by the thermal lens method disclosed in Patent Document 1, in order to increase the measurement sensitivity, it is necessary to increase the intensity of the excitation light or to reduce the diameter of the pinhole that allows the measurement light after passing through the sample to pass. However, increasing the excitation light intensity increases power consumption and costs, and reducing the pinhole diameter reduces the S / N ratio due to the decrease in the amount of light received by the detector and increases the measurement time. There was a problem of inviting.
In both Patent Document 1 and Patent Document 2, a refractive index change caused by heating by excitation light, such as a cell containing a sample and a solvent accommodated together with the sample in the optical path of measurement light and excitation light. In the case where there is a substance (hereinafter referred to as “disturbing substance”) that causes turbulence, this becomes a disturbance and there is a problem that the S / N ratio is deteriorated.
Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to measure the refractive index change due to the photothermal effect in the sample with a simple configuration including the measurement of the absorption spectral characteristics of the sample. An object of the present invention is to provide a photothermal conversion measuring apparatus and method capable of measuring with high sensitivity and low noise.

In order to achieve the above object, the present invention relates to the change in the refractive index of the sample caused by the photothermal effect of the excitation part of the sample irradiated with excitation light, into the measurement light that is irradiated to the excitation part and transmitted through the sample. The present invention is applied to a photothermal conversion measuring device or a measuring method used for measurement based on the above, and splits light from a predetermined light source and outputs it as two excitation light beams having different wavelength bands from each other. The two excitation lights having different wavelength bands and different wavelength bands from each other (for example, before irradiation of the sample) are subjected to intensity modulation in opposite phases, and the two excitation lights in the sample are irradiated. One measurement light transmitted through the one excitation unit is detected, and a component having the same period as the intensity modulation period of the excitation light is extracted from the detection signal.
Then, the refractive index change caused by the photothermal effect of the sample is measured based on the extracted signal for the intensity modulation period from the detection signal of the measurement light.
Thus, when the two types of excitation light having different wavelength bands are irradiated, the intensity balance of each of the excitation light is set in advance so that the amount of light absorption does not change in each state. Because the intensity modulation of the two excitation lights is in opposite phase, the temperature of the disturbing substance does not change during any of the excitation light irradiations, while the photothermal effect of the sample is irradiated with the excitation light having different wavelength bands. It changes every time. For this reason, the measurement sensitivity (detection sensitivity) of the signal processing system can be increased without considering the saturation of the dynamic range (measurement range) of the excitation light measurement signal due to the temperature change of the disturbance substance (amplification). It is possible to prevent the S / N ratio from being deteriorated due to a temperature change (refractive index change) of the disturbance substance when the measurement light is detected.
In addition, each time the wavelength band of the excitation light is changed, the measurement of the absorption spectral characteristic of the sample can be easily performed by detecting the measurement light.

Here, as a means for detecting the measurement light, as disclosed in Patent Document 2, light for detecting the intensity of interference light by causing predetermined reference light to interfere with the measurement light transmitted through the excitation unit in the sample . An interferometric method (hereinafter referred to as first measuring light detection means) is conceivable.
In this way, the refractive index change due to the photothermal effect of the sample is regarded as the phase change of the measurement light and detected by the optical interferometry (relative optical technique), for example, a photodetector (photoelectric conversion means) for each device. ) And the intensity of the measurement light and its intensity distribution, etc., if they do not change during measurement, they are highly reproducible (stable), optically accurate and The sample can be analyzed with sensitivity.
When this first measurement light detection means is used, after the back surface side light reflection means is provided on the opposite side of the measurement light irradiation surface of the sample and reflected by this, the sample passes back and forth through the excitation section. The reference light is made to interfere with the measurement light, or the back surface side light reflecting means and the opposite surface side light reflecting means are provided, and after being subjected to multiple reflection and passing through the excitation part in the sample The detection sensitivity can be further improved by causing the reference light to interfere with the measurement light.

Further, as another means for detecting the measurement light, the sample is formed by two light reflecting means arranged to face both sides of the sample so as to reflect the incident light and transmit at least one part of the incident light. While passing through the sample, the predetermined measurement light applied to the excitation part in the light is reflected multiple times along one axis between the light reflecting means, and is transmitted through the light reflecting means on the side that transmits a part of the incident light. It is also conceivable to detect the light intensity of the measurement light by means of light intensity detection means (hereinafter referred to as second measurement light detection means).
As a result, the measurement light reaching the light intensity detection means is superimposed with measurement light having different numbers of round trips between the two light reflection means, but the photothermal effect (refractive index change) in the sample is superimposed. ), The phase of the measurement light with a larger number of reciprocations shifts more greatly. As a result, the light intensity can be detected even with a slight change in refractive index (change in optical path length). The detection signal (light intensity detection signal) of the means changes greatly. As a result, the refraction index changes arising by photothermal effect of the sample, it is possible to measure more sensitive than with the thermal lens method or an optical interference method described above. Moreover, such high-sensitivity measurement can be realized with a very simple configuration of two light reflecting means and light intensity detecting means arranged opposite to each other.
In the second measurement light detection means, the large change in the light intensity detection signal with respect to the change in the optical path length of the measurement light means that the influence of disturbance noise such as vibration is large, while the excited state of the sample is If stable, the light intensity detection signal that should be detected should not fluctuate.
Therefore, if a mirror interval adjusting means for adjusting the interval between the two light reflecting means is provided in a direction to suppress the fluctuation of the detection signal of the light intensity detecting means, the influence of disturbance noise such as vibration can be suppressed and the sample can be obtained with high accuracy. refractive index change can be measured.
Further, in each of the first measurement light detection means and the second measurement light detection means, the light from a predetermined light source such as a white light source is dispersed and output as the two excitation lights, and their wavelengths. If variable spectral means for changing the band is provided, the measurement light is detected by the first or second measurement light detection means or the like each time the wavelength band of the excitation light is changed by the variable spectral means. Accordingly, the absorption spectral characteristics of the sample can be easily measured.

According to the present invention, the two excitation lights having different wavelength bands are subjected to intensity modulation in opposite phases before the sample is irradiated, and the two excitation lights in the sample are irradiated. While detecting one said measurement light which permeate | transmitted the said excitation part , since the same period component as the intensity | strength modulation period of the said excitation light is extracted from the detection signal, the intensity balance of two said excitation lights is adjusted beforehand Accordingly, the temperature of the disturbance substance can be prevented from changing during any excitation light irradiation, while the photothermal effect of the sample changes each time the excitation light having a different wavelength band is irradiated. Can be prevented from deteriorating the S / N ratio due to a temperature change (refractive index change) of the disturbance substance.
Further, if the measurement light is detected based on an optical interferometry method in which a predetermined reference light is made to interfere with the measurement light transmitted through the excitation unit in the sample and the intensity of the interference light is detected, a relative optical technique is used. Since the measurement light is detected by this, the sample can be analyzed stably with high accuracy and high sensitivity.
On the other hand, a predetermined measurement light irradiated on the excitation part of the sample is applied to the sample by two light reflecting means (at least one of which transmits a part of incident light) arranged opposite to both sides of the sample. If the light intensity of the measurement light transmitted through at least one of the two light reflecting means is detected while detecting multiple light reflections between the light reflecting means while passing through one axis, a slight refractive index of the sample is obtained. also becomes the light intensity detection signal changes greatly changes, the refraction index changes arising by photothermal effect of the sample, can be measured with high accuracy and high sensitivity. Moreover, such highly sensitive measurement can be realized with a very simple configuration.
In addition, the light from a predetermined light source (white light source, etc.) is dispersed and output as the two excitation lights, their wavelength bands are made variable, and the measurement light is detected each time the excitation light wavelength band is changed. Thus, the absorption spectral characteristics of the sample can be easily measured.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
Here, FIG. 1 is a schematic configuration diagram of the photothermal conversion measurement device X1 according to the first embodiment of the present invention, FIG. 2 is a schematic diagram showing an application example of a part of the configuration of the photothermal conversion measurement device X1, and FIG. 4 is a schematic configuration diagram of a photothermal conversion measurement device X2 according to a second embodiment of the invention, FIG. 4 is a schematic configuration diagram of a photothermal conversion measurement device X3 according to a third embodiment of the present invention, and FIG. It is a figure showing the relationship between the optical path length of the measurement light which advances between two high reflection mirrors, and the intensity | strength of the measurement light reflected and permeate | transmitted to the high reflection mirror.

The photothermal conversion measurement devices X1 to X3 according to the embodiment of the present invention measure changes in the characteristics of the sample caused by the photothermal effect of the sample irradiated with excitation light based on the measurement light that is irradiated to the sample and transmitted therethrough. The two excitation lights with different wavelength bands are subjected to intensity modulation with opposite phases before irradiating the sample, and the measurement light irradiated to the sample and transmitted through it is detected. In addition, a component having the same period as the intensity modulation period of the excitation light is extracted from the detection signal.
<First Embodiment>
First, the photothermal conversion measuring device X1 according to the first embodiment of the present invention will be described using the schematic configuration diagram shown in FIG.
The photothermal conversion measurement device X1 includes a spectral excitation light source unit Z including an excitation light source 1, a reflection mirror 3a, two variable spectrometers 1a and 1b, and a chopper 2, and two pulsed excitation lights B3a output therefrom. , B3b is irradiated to the sample 5.
In the spectral excitation light source unit Z, excitation light (white light) output from a predetermined excitation light source 1 (for example, a white light source such as a halogen lamp) that emits white light is reflected by the reflection mirror 3a and branched into two. , Each split light is split by the two variable spectrometers 1a and 1b, respectively, and is output as two excitation lights B3a and B3b having different wavelength bands.
Each of the variable spectrometers 1a and 1b outputs light obtained by separating the white light from the excitation light source 1 with a diffraction grating or the like as two excitation lights B3a and B3b, and the wavelength bands of the excitation lights B3a and B3b. Is arbitrarily adjusted or selected from a plurality of wavelength band candidates (variable spectroscopic means).
Two excitation lights B3a and B3b having different wavelength bands output from the variable spectrometers 1a and 1b are irradiated to the sample 5 via the reflection mirror 18 and the lens 4, but before the sample 5 is irradiated. Then, it is converted (periodically intensity modulated) into intermittent light (intermittent frequency: f) having a predetermined period by the chopper 2 (an example of the antiphase intensity modulation means). At this time, the two excitation lights B3a and B3b are subjected to intensity modulation with opposite phases. That is, while the one excitation light B3a is being irradiated to the sample 5, the irradiation of the other excitation light B3b to the sample 5 is blocked, and the irradiation of the one excitation light B3a to the sample 5 is blocked. During the process, the process of irradiating the sample 5 with the other excitation light B3b is performed at a constant period.
Thereby, the sample 5 absorbs excitation light and generates heat (photothermal effect), and the refractive index of the sample 5 changes due to the temperature change (rise).
On the other hand, it was output from a laser light source 7 (for example, a He-Ne laser having an output of 1 mW) that is used as both a light source for measuring light for measuring the refractive index change of the sample 5 and a reference light that interferes therewith. The plane of polarization of the laser light is adjusted by the half-wave plate 8 and further split into two polarized waves (B1, B2) orthogonal to each other by a polarizing beam splitter (hereinafter referred to as PBS) 9. Thereafter, one B1 functions as measurement light and the other B2 functions as reference light.
The polarization frequencies B1 and B2 are shifted in frequency (frequency conversion) by acousto-optic modulators (AOM) 10 and 11, reflected by mirrors 12 and 13, and guided to PBS. Frequency difference f _b of the second polarization B1, B2 of these orthogonal, for example, a 30MHz or the like.

The polarized light B1 serving as the reference light passes (transmits) through the PBS 14 and travels toward the polarizing plate 19.
On the other hand, the other polarization B1 which becomes the measurement light passes through the PBS 14, passes through the quarter-wave plate 17, the mirror 18 and the lens 4, and is irradiated with the excitation lights B3a and B3b on the sample 5. A portion (that is, one excitation portion as shown in FIG. 1 ) is configured to be irradiated from substantially the same direction as the excitation lights B3a and B3b.
Further, one measurement light B1 incident on the sample 5 passes through the sample 5, is reflected by the reflection mirror 6 provided on the back surface side of the sample 5 (on the opposite side to the irradiation surface of the measurement light B1), and again the sample. 5 (ie, reciprocating), passes through the lens 4, the mirror 18, and the quarter-wave plate 17 and returns to the PBS 14.
Here, since the polarization plane of the measurement light B1 is rotated 90 ° by reciprocating through the ¼ wavelength plate 17, this time, the measurement light B1 is reflected by the PBS 14 and the polarization B2 (reference light). Heading to the polarizing plate 19.
In the polarizing plate 19, the measurement light B1 and the reference light B2 having a different optical frequency interfere with each other, and the light intensity of the interference light B1 + B2 is detected by the photodetector 20 (photoelectric conversion means). The signal value of the signal is converted into interference light intensity). This electric signal (that is, the interference light intensity) is input and stored in a signal processing device 21 such as a computer, and the signal processing device 21 calculates the phase change of the measurement light B1 (measures the phase change by the optical interference method). Is made.
As described above, the photothermal conversion measuring device X1 guides the measurement light B1 irradiated to and transmitted through the sample 5 and the reference light B2 by the optical system device in the direction of the polarizing plate 19, and the measuring light is transmitted by the polarizing plate 19. Each apparatus includes an apparatus for detecting the measurement light B1 by optical interferometry by forming interference light between B1 and the reference light B2 and detecting the interference light intensity by the photodetector 20 (measurement light detection means and optical interference means). Example).
Here, the sample 5 is accommodated in a cell 15 which is a transparent container such as quartz glass. In some cases, the sample 5 is accommodated in the cell 15 together with a predetermined solvent. Therefore, the measurement light B1 and the excitation light B3a and B3b are irradiated to the sample 5, and the cell 15 and, in some cases, the solvent also pass (transmit).

In the measurement using this photothermal conversion measuring device X1, the chopper 2 applies intensity modulation of opposite phases to the two excitation lights B3a and B3b with different wavelength bands irradiated on the sample 5 (reverse phase). An example of the intensity modulation step), the measurement light B1 transmitted through the sample 5 during execution of such intensity modulation is detected by the photodetector 20 and the signal processing device 21 (an example of the measurement light detection step), and the detection thereof. The signal processing device 21 extracts the same periodic component as the intensity modulation period of the excitation light B3a, B3b from the signal (an example of the same period component extracting step), and the characteristic change caused by the photothermal effect of the sample 5 based on the extracted signal ( (Refractive index change) is measured (an example of a characteristic change measurement step).
In addition, the spectral excitation light source unit Z changes the wavelength bands of the excitation light B3a and B3b (an example of the wavelength band changing process), and the measurement light B1 is detected at each change, thereby changing the absorption spectral characteristics of the sample. Measurement can also be performed easily.
Here, the interference light intensity S1 acquired by the signal processing device 21 is expressed by the following equation (1).
S1 = C1 + C2 · cos (2π · f _b · t + φ) (1)
C1 and C2 are constants determined by the optical system such as PBS and the transmittance of the sample 5, φ is a phase difference due to an optical path length difference between the measurement light B1 and the reference light B2, and f _b is between the measurement light B1 and the reference light B2. Is the frequency difference. From the equation (1), the change in the phase difference φ can be obtained from the change in the interference light intensity S1 (difference between when the excitation light is not irradiated or when the light intensity is low and when the light intensity is high). Recognize. The signal processing device 21 calculates the change in the phase difference φ based on the equation (1).
By the way, if the amplitudes (intensity changes) of the interference light when irradiating the excitation lights B3a and B3b are Ka and Kb, respectively, the phase difference φ due to the optical path length difference between the measurement light B1 and the reference light B2 depends on the excitation light B3a. It is expressed by the following equation (2) that represents the superposition of the state change and the state change by the excitation light B3b.
φ = Ka · sin (ωt) −Kb · sin (ωt) (2)
If the intensity and wavelength of each of the excitation lights B3a and B3b are adjusted in advance so that Ka≈Kb in the state where the sample 5 does not exist, φ≈0 can be obtained. As a result, in the state where the sample 5 exists, Ka> Kb or Ka <Kb is satisfied, so that a phase difference signal resulting from a change in the excited state of the sample 5 is detected.
In addition, using the photothermal conversion measuring device X1, the change in the phase difference φ is measured for a plurality of types of sample samples whose amounts (concentrations) of the predetermined contained substances are known in advance, and the result and the amount of the contained substances Is stored in the signal processing device 21 as a data table. Then, the signal processing device 21 may execute a process of specifying the amount of the contained substance by, for example, performing an interpolation process on the measurement result of the phase difference φ of the sample to be measured based on the data table. .
Thus, the refractive index change due to the photothermal effect of the sample 5 is measured by measuring the phase change caused by the excitation light irradiation in the measurement light B1 that has passed (transmitted) through the sample 5 using the optical interferometry, that is, the measurement. Since measurement is performed by relative evaluation (phase difference) of the phase between the light B1 and the reference light B2, for example, even if the position of the photodetector 20, the intensity of the measurement light, its intensity distribution, and the like vary from device to device, it changes during measurement. If not, it is possible to measure the refractive index change of the sample stably and optically with high accuracy without depending on these.

Here, since both the pumping lights B3a and B3b are subjected to intensity modulation of a fixed period by the chopper 2, the interference light intensity S1 also fluctuates in synchronization therewith. Therefore, the signal processing device 21 extracts the same period component as the intensity modulation period of each of the excitation lights B3a and B3b from the detection signal of the photodetector 20 that detects the measurement light B1 that has passed through the sample 5, and the extraction thereof. Based on the signal, the phase change of the measurement light B1 (characteristic change caused by the photothermal effect of the sample 5) is measured (an example of the same period component extraction means).
At that time, the excitation light B3a, B3b absorbs not only the sample 5 but also the surrounding cells 15 and solvent, and the temperature rises, and the refractive index changes.
However, when two types of excitation light B3a and B3b having different wavelength bands are irradiated in the state where the sample 5 does not exist, excitation is performed so that the amount of light absorbed by the cell 15 or the like does not change in each state. If the intensity balance of each of the lights B3a and B3b is set in advance, the intensity modulation of the two excitation lights B3a and B3b is in reverse phase, so that any substance other than the sample 5 (cell 15 or solvent) can be used during any excitation light irradiation. Etc.) can be prevented from changing in temperature.
On the other hand, since the photothermal effect of the sample 5 changes every time the excitation lights B3a and B3b having different wavelength bands are switched and irradiated, the temperature change (refractive index change) of the cell 15 or the like is detected when the measurement light B1 is detected. It is possible to prevent the deterioration of the S / N ratio due to.
Further, since the influence of noise having no frequency f component is removed, the S / N ratio is improved.

Further, in this photothermal conversion measuring device X1, the measurement light B1 is reflected back and forth on the reflection mirror 6 on the back side (an example of the back surface side light reflection means), so that the measurement light B1 after reciprocating through the sample 5 is reflected. Since the optical interference measurement is performed by interfering with the reference light B2, the change in the phase difference φ can be measured with a sensitivity twice that in the case of one-way passage. In addition, there is no increase in the output of pumping light or a decrease in the S / N ratio.
Here, the configuration of an application example in which the sensitivity is further improved in the photothermal conversion measurement device X1 will be described using the schematic diagram shown in FIG.
In the configuration shown in FIG. 2, the high-reflection mirrors 6a and 6b (the front-side light reflecting means and the back-side light reflecting means are provided on the front side of the sample 5 (the measurement light irradiation surface side) and the back side thereof, respectively. An example) is arranged, and the measurement light B1 is subjected to multiple reflection between the high reflection mirrors 6a and 6b.
As a result, the measurement light B1 passes through the high reflection mirror 6a on the surface side of the sample 5 and is directed toward the photodetector 20 while being subjected to multiple reflection between the high reflection mirrors 6a and 6b. Therefore, since the interference light between the reference light B2 and the measurement light B1 on which the light that has passed through the sample 5 is superimposed is input to the detector 20, the phase difference can be measured with higher sensitivity, that is, the refractive index. Changes can be measured.
In this case, in order to finely adjust the interval between the two high reflection mirrors 6a and 6b so as to synchronize the phase of the multiple reflected measurement light, it is desirable to provide a drive mechanism for controlling the position of one of the reflection mirrors.

Second Embodiment
Next, a photothermal conversion measuring device X2 according to a second embodiment of the present invention will be described using the schematic configuration diagram shown in FIG.
This photothermal conversion measurement device X2 is an application example of the photothermal conversion measurement device X1, and the portion for detecting the measurement light B1 by optical interferometry is the same as the photothermal conversion measurement device X1 and is not shown. (In the figure, the part indicated as “measurement system”).
In the first embodiment described above, an example in which the intensities of the two excitation lights B3a and B3b are set in advance according to the endothermic characteristics of the cell 15 or a solvent has been described.
On the other hand, in the photothermal conversion measuring device X2 shown in FIG. 3, a sample channel 15a into which the sample is poured into the cell 15 is provided.
In the measurement using the photothermal conversion measurement device X2, the cell 15 is irradiated with two excitation lights B3a and B3b whose intensity is modulated before the sample 5 is injected into the sample channel 15a. The intensity of the excitation light B3a and B3b is adjusted by the output intensity adjustment function of the excitation light source 1 so that the signal value detected by the photodetector 20 (see FIG. 1) is constant (does not vary).
Next, the sample 5 is injected into the sample flow path 15a, and in this state, the measurement light is detected by the photodetector 20 and the signal processing device 21.
Accordingly, the intensity of the two excitation lights B3a and B3b can be appropriately adjusted even for the cell 15 and the like whose heat absorption characteristics are unknown.
Further, as shown in FIG. 3, the light guiding means for guiding the excitation light B3a, B3b to the sample 5 is not limited to the reflection mirror, but the excitation light B3a, B3b is guided by the optical fiber 60, etc. It may be configured to irradiate.

<Third Embodiment>
Next, the photothermal conversion measuring device X3 according to the second embodiment of the present invention will be described using the schematic configuration diagram shown in FIG.
The photothermal conversion measurement device X3 irradiates the sample 5 with two excitation light beams B3a and B3b having different wavelength bands, which are subjected to intensity modulation having opposite phases to each other, and the sample 5 is irradiated and transmitted through the sample 5. In the point which detects light, it has the structure similar to the said photothermal conversion measuring apparatus X1.
However, the photothermal conversion measurement device X3 is different from the photothermal conversion measurement device X1 in the configuration of means for irradiating and detecting the measurement light B1.
As shown in FIG. 4, the photothermal conversion measurement device X3 also includes the spectral excitation light source unit Z, whereby two excitation lights B3a and B3b having different wavelength bands can be intensity-modulated so as to have opposite phases to each other. Then, the sample 5 is irradiated.
In addition to the spectral excitation light source Z, the photothermal conversion measurement device X3 includes the laser light source 7 for measurement light, the lens 20, the beam splitter 54, the high reflection mirrors 52 and 53, the photodetectors 20a and 20b, and a mirror displacement mechanism. 50, a displacement control device 51, a signal processing device 21 ', and the like.
By irradiating the excitation light B3a and B3b from the spectral excitation light source Z, the sample 5 absorbs the excitation light and generates heat (photothermal effect), and the refractive index of the sample 5 changes due to its temperature change (rise). To do.

On the other hand, the measurement light B1 output from the laser light source 7 that outputs the measurement light for irradiating the sample 5 and measuring the change in the refractive index thereof passes through the beam splitter 54 and passes through both sides of the sample 5 (front). One of the two high reflection mirrors 52 and 53 (an example of the light reflecting means) disposed opposite to each other in parallel to the surface side and the back surface side (hereinafter referred to as the first high reflection mirror 52). Most of the light is reflected, but only a small part of the measurement light passes through the first high-reflection mirror 52 and is irradiated onto the sample 5. The measurement light applied to the sample 5 is between a high-reflection mirror 53 on the back side (hereinafter referred to as a second high-reflection mirror) and the first high-reflection mirror 52 disposed opposite to each other with the sample 5 interposed therebetween. Multiple reflection is performed along one axis while transmitting through the sample 5. Then, a part of the measurement light B1 that is transmitted through the sample 5 and multiple-reflected between the two high reflection mirrors 52 and 53 is transmitted each time the measurement light B1 reaches each of the high reflection mirrors 52 and 53.
Thereby, the high reflection mirrors 52 and 53 are used as measurement light (hereinafter referred to as reflection side measurement light) that reflects the first high reflection mirror 52 on the side opposite to the side where the sample 5 exists (upper side in FIG. 1). Measurement beams having different numbers of reciprocations between them are transmitted and superimposed from the side where the sample 5 exists. In addition, the high reflection mirrors 52 and 53 are also connected to measurement light (hereinafter referred to as transmission side measurement light) transmitted through the second high reflection mirror 53 on the side opposite to the side where the sample exists (the lower side in FIG. 1). Measurement light having different numbers of reciprocations between them is transmitted and superimposed from the side where the sample 5 exists.

The reflection-side measurement light that reflects the first high reflection mirror 52 to the side opposite to the side where the sample 5 is present is deflected by the beam splitter 54 to be one of the photodetectors 20a (hereinafter referred to as a first photodetector). , An example of the light intensity detecting means), and a signal (light intensity signal) representing the light intensity of the reflection-side measurement light detected by this is taken into the signal processing device 21 ′ composed of a computer or the like.
The signal processing device 21 ′ is a computer or the like having an input interface for a light intensity signal detected by the first light detector 20a, and the intensity modulation of the excitation lights B3a and B3b by the chopper 2 is performed on the light intensity signal. The same period component as the period is extracted and output as a photothermal conversion signal to another measurement processing device (an example of the same period component extracting means).
As a result, as in the case of the photothermal conversion measuring device X1, the temperature of the cell 15 or the like can be prevented from changing during either irradiation of the two excitation lights B3a and B3b, while the photothermal effect of the sample 5 is in the wavelength band. Since the excitation light B3a and B3b having different values change each time they are switched and irradiated, the S / N ratio is deteriorated due to temperature change (refractive index change) of the cell 15 or the like when the measurement light B1 is detected. Can be prevented.
Further, since the influence of noise having no frequency f component is removed, the S / N ratio is improved.
On the other hand, the transmission side measurement light transmitted through the second high reflection mirror 53 to the side opposite to the side where the sample 5 exists is transmitted to the other light detector 20b (hereinafter referred to as a second light detector). The light intensity signal detected and received by this is taken into the displacement control device 51.
The displacement control device 51 supports the second high reflection mirror 53 based on the detection signal of the second light detector 20b (light intensity detection means) and sets the support position in the optical axis direction of the measurement light. By controlling the mirror displacement mechanism 50 that automatically displaces, the interval between the two high reflection mirrors 52 and 53 is automatically adjusted in a direction that suppresses fluctuations in the detection signal of the second photodetector 20b (light intensity detection means). (An example of mirror interval adjusting means).

Next, referring to FIG. 5, the optical path length L (hereinafter referred to as the inter-mirror optical path length L) of the one-way (outward path or return path) of the measurement light traveling between the two high reflection mirrors 52 and 53 and the first A relationship between the intensity P1 of the reflection side measurement light reflected by the high reflection mirror 52 and the intensity P2 of the transmission side measurement light transmitted through the second high reflection mirror 53 will be described.
As described above, measurement light (hereinafter referred to as multiple reflection measurement light) having different numbers of reciprocations between the high reflection mirrors 52 and 53 is superimposed on the transmission side measurement light. Therefore, as shown in FIG. 5, when the optical path length L between the mirrors satisfies L = n · λ / 2 (n is a positive integer and λ is the wavelength of the measurement light between the two mirrors). , The phases of the multiple reflection measurement lights are synchronized and emphasized (resonate), and the light intensity P2 becomes the maximum intensity P2max. If the optical path length L between the mirrors is slightly deviated from the relationship L = n · λ / 2, the phase of the multiple reflection measurement light having a large number of reciprocations between the mirrors will be greatly shifted, resulting in a slight optical path length. Even if L changes, the intensity of the transmission side measurement light is greatly reduced. Here, when the reflectivity of each of the high reflection mirrors 52 and 53 is R (0 to 1) and the optical path length between the mirrors satisfying the relationship of L = n · λ / 2 is Ln (= n · λ / 2). , When the optical path length between mirrors L = Ln, the optical path length range ΔL (hereinafter referred to as “P2max−P2max / 2”) is generated in the intensity P2 of the transmission side measurement light around the optical path length Ln. , Referred to as the optical path length range) is expressed by the following equation (3).
ΔL = Ln · π · R ^1/2 / (1-R) (3)
That is, as the reflectivity R of the high reflection mirrors 52 and 53 is larger and the optical path length Ln between the mirrors is shorter, the optical path length range ΔL can be reduced, and a slight change in optical path length can be measured with high sensitivity.
On the other hand, the intensity P1 of the reflection side measurement light is obtained by subtracting the intensity P2 of the transmission side measurement light from the intensity P1max substantially equal to the original intensity of the measurement light or an intensity close thereto (P1≈P1max). −P2).
This photothermal conversion measuring device X3 utilizes the characteristics shown in FIG.
If the photothermal conversion measuring device X3 changes the irradiation state of the excitation light B3a, B3b to the sample 5 every time the sample 5 is detected by the signal processing device 21 ′ through the first photodetector 20a, the excitation light Since the refractive index of the sample 5 is changed by the photothermal effect due to the irradiation of B3a and B3b, the optical path length L between the mirrors is changed. As a result, the intensity of the reflection-side measurement light is changed by the change in the irradiation state of the excitation light. Even a slight change in refractive index changes relatively.
Therefore, it is possible to measure with high sensitivity the refractive index change (characteristic change) caused by the photothermal effect of the sample 5 based on the intensity of the reflection side measurement light detected in this way. Moreover, such high-sensitivity measurement can be realized with a very simple configuration as shown in FIG.
In addition, by changing the wavelength bands of the excitation light B3a and B3b by the spectral excitation light source unit Z and detecting the light intensity at each change, the absorption spectral characteristics of the sample can be easily measured.

In the above-described measurement, the example in which the photothermal conversion characteristic of the sample 5 is measured based on the light intensity P1 of the reflection-side measurement light reflected by the first high reflection mirror 52 has been described. The light intensity P1 and the intensity P2 of the transmission side measurement light have a relationship in which the sum thereof is constant (≈P1max). Therefore, the transmission that transmits through the second high reflection mirror 53 is taken into consideration. A configuration may be adopted in which the photothermal conversion characteristic of the sample 5 is measured based on the light intensity P2 of the side measurement light. That is, the light intensity of the measurement light reflected or transmitted from at least one of the two high reflection mirrors 52 and 53 to the side opposite to the side where the sample 5 exists is detected, and the characteristics of the sample 5 are determined based on the detected intensity. What is necessary is just to evaluate.
When the light intensity is detected only on one of the two high reflection mirrors 52 and 53, the reflection mirror on the side opposite to the side where the light intensity is detected is theoretically completely reflected ( (Reflectance = 100%).

    The present invention can be used for photothermal conversion measurement.

The schematic block diagram of the photothermal conversion measuring apparatus X1 which concerns on 1st Embodiment of this invention. Schematic showing the example of a part of application of the structure of the photothermal conversion measuring apparatus X1. The schematic block diagram of the photothermal conversion measuring apparatus X2 which concerns on 2nd Embodiment of this invention. The schematic block diagram of the photothermal conversion measuring apparatus X3 which concerns on 3rd Embodiment of this invention. The figure showing the relationship between the optical path length of the measurement light which advances between two highly reflective mirrors in the photothermal conversion measuring apparatus X3, and the intensity | strength of the measured light reflected and permeate | transmitted to the highly reflective mirror.

Explanation of symbols

X1, X2, X3 ... Photothermal conversion measuring device Z ... Spectral excitation light source unit 1 ... Excitation light source 1a, 1b ... Variable spectroscope 2 ... Chopper 4 ... Lens 5 ... Sample 6 ... Reflection mirror 6a, 6b ... High reflection mirror 7 ... Laser Light source 8 ... 1/2 wavelength plates 9, 14 ... Polarizing beam splitters 10,11 ... Acousto-optic modulator 15 ... Cell 15a ... Sample channel 17 ... ¼ wavelength plate 19 ... Polarizing plates 20, 20a, 20b ... Light detection (Light intensity detection means)
21, 21 '... signal processing device 50 ... mirror displacement mechanism 51 ... displacement control devices 52, 53 ... high reflection mirror 54 ... beam splitter 60 ... optical fiber

Claims (8)

Photothermal conversion measurement device used for measuring the refractive index change of the sample caused by the photothermal effect of the excitation portion of the sample irradiated with excitation light, based on the measurement light irradiated on and transmitted through the excitation portion of the sample Because
Variable spectroscopic means for splitting light from a predetermined light source and outputting it as two excitation light beams having different wavelength bands, and making the wavelength bands variable;
Anti-phase intensity modulation means for performing intensity modulation of opposite phases on two pumping lights having mutually different wavelength bands;
Measuring light detecting means for detecting one measuring light transmitted through the one excitation part irradiated with the two exciting lights in the sample;
Same period component extracting means for extracting the same period component as the intensity modulation period of the excitation light from the detection signal of the measurement light detecting means;
A photothermal conversion measuring device comprising: The measuring light detection means is
The photothermal conversion measuring apparatus according to claim 1, further comprising: a light interference unit configured to cause a predetermined reference light to interfere with the measurement light transmitted through the excitation part in the sample and detect the intensity of the interference light. The measuring light detection means is
A back surface side light reflecting means provided on the opposite side of the measurement light irradiation surface of the sample; and the measurement light reflected by the back surface side light reflecting means and reciprocated through the excitation portion of the sample. The photothermal conversion measurement apparatus according to claim 2, wherein the reference light is caused to interfere with the later measurement light. The measuring light detection means is
Back side light reflecting means provided on the opposite side of the measurement light irradiation surface of the sample;
A surface-side light reflecting means provided on the excitation light irradiation surface side of the sample, and the measurement light is multiple-reflected between the back-side light reflecting means and the surface-side light reflecting means, and The photothermal conversion measurement apparatus according to claim 2, wherein the reference light is made to interfere with the measurement light after passing through the excitation part in a sample. The measuring light detection means is
Oppositely arranged on both sides of the sample, the predetermined measurement light irradiated on the excitation part in the sample is transmitted through the sample and is reflected multiple times along one axis and at least one of the measurement light is Two light reflecting means that partially transmit,
A light intensity detection means for detecting the light intensity of the measurement light reflected or transmitted to the side opposite to the side where the sample is present through the light reflection means for transmitting a part of the measurement light;
The photothermal conversion measuring apparatus according to claim 1, comprising:   6. The photothermal conversion measuring device according to claim 5, further comprising a mirror interval adjusting unit that adjusts an interval between the two light reflecting units in a direction that suppresses a variation in a detection signal of the light intensity detecting unit. A photothermal conversion measurement method for measuring a change in the refractive index of the sample caused by a photothermal effect of an excitation part of a sample irradiated with excitation light based on measurement light irradiated on and transmitted through the excitation part of the sample. ,
A wavelength band changing step of splitting light from a predetermined light source and outputting the two excitation light beams having different wavelength bands, and changing the wavelength band of the excitation light by a variable spectroscopic means for changing the wavelength band; ,
An anti-phase intensity modulation step of applying intensity modulation in opposite phases to the two excitation lights having different wavelength bands irradiated to the sample;
Each time the wavelength band of the excitation light is changed by the wavelength band changing step, 1 is transmitted through the one excitation part irradiated with the two excitation lights in the sample during the execution of the antiphase intensity modulation step. A measuring light detecting step for detecting two measuring lights by a measuring light detecting means;
The same period component extracting step of extracting the same period component as the intensity modulation period of the excitation light from the detection signal by the measurement light detecting step;
A characteristic change measuring step for measuring a refractive index change caused by the photothermal effect of the sample based on an extraction signal obtained by the same period component extracting step;
A photothermal conversion measurement method characterized by comprising: The photothermal conversion measurement method according to claim 7 , wherein the two excitation lights are excitation lights from which substantially the same detection result is obtained by the measurement light detection means in the absence of the sample.

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