JP4119411B2 - Photothermal conversion measuring apparatus and method - Google Patents

Description

  The present invention relates to a photothermal conversion measuring apparatus and method for measuring a characteristic change based on a refractive index change generated in a sample due to a photothermal effect when the sample is irradiated with a sample and the like and irradiated with excitation light. Is.

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.
By the way, 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.
FIG. 5 is a configuration diagram of a sample analyzer using the thermal lens method disclosed in Patent Document 1 (see FIG. 1 of Patent Document 1). Note that some of the reference numerals in FIG. 5 may overlap with reference numerals in FIGS. 1 to 4 described later, but these indicate different objects.
As shown in FIG. 5, the excitation light A from the excitation light source 10 is converted into intermittent light (that is, intensity modulated periodically) by the chopper 11, and the beam expander 12, the position control mirrors 31 and 32, and the lens 34. The sample 40 is irradiated through the microscope 35. Thereby, the sample 40 absorbs excitation light and generates heat, and its refractive index changes.
This change in refractive index is detected by the detection light B (measurement light) from the detection light source 20.
The detection light B from the detection light source 20 becomes a coaxial path with the excitation light A via the beam expander 22 and is reflected by the position control mirrors 31 and 32, and further irradiated to the sample 40 via the lens 34 and the microscope 35. The Then, the detection light B that has passed through the sample 40 is condensed by the condenser lens 50, passes through the opening 51A (pinhole), and is received by the detector 53, and its light intensity is detected. Here, since the condensing state of the detection light B in the sample 40 changes due to the change in the refractive index of the sample 40, the intensity of the detection light obtained through the pinhole is a change in the refractive index of the sample (that is, the sample The amount of light absorption varies according to the contained material and the like. By measuring the intensity change of the detection light B, the change in the refractive index of the sample can be measured, and the amount of the substance contained in the sample can be evaluated based on the measurement result.
In Patent Document 1, in order to detect an intensity change of the detection light B with a high S / N ratio (signal-to-noise ratio), an intermittent frequency component (frequency component of the intensity modulation period) of the excitation light A by the chopper by the lock-in amplifier 61 is used. ) Only detected.
Japanese Patent Laid-Open No. 10-232210

However, the analysis of a sample by the thermal lens method detects a change in refractive index due to heat generation of the sample by a change in light intensity (intensity of detection signal) due to a change in the focusing state of measurement light (detection light). The change in the light intensity (detection signal intensity) depends not only on the change in the refractive index of the sample but also on the light receiving position of the detector 53 (photoelectric conversion means), the intensity of the measurement light, its intensity distribution, and the like. For this reason, there is a problem that it is difficult to analyze the sample (measure the refractive index change) with good reproducibility (stable).
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 through which the measurement light after passing through the sample is passed. The increase in the cost and the increase in the cost of the pinhole have also caused problems such as a decrease in the S / N ratio due to a decrease in the amount of light received by the detector and a longer measurement time.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to be able to stably and accurately measure changes in characteristics due to the photothermal effect of a sample, and to increase power consumption and cost. An object of the present invention is to provide a photothermal conversion measuring apparatus and method capable of performing high-sensitivity measurement while preventing the increase in the measurement time, the decrease in the S / N ratio, and the increase in the measurement time.

To accomplish the above object, which the excitation light is applied to the photothermal conversion measuring instrument or photothermal conversion measuring method for measuring the refractive index change of the sample caused by the photothermal effect of the sample is irradiated, the container The measurement light is irradiated to the stored sample from a first direction by a predetermined measurement light irradiation means to pass the measurement light through the measurement unit of the sample, and the sample stored in the container is By irradiating excitation light whose intensity is periodically modulated by a predetermined excitation light irradiation means from a second direction different from the first direction, the excitation light is different from the measurement light passing portion in the container. The phase change of the same period component as the intensity modulation period of the excitation light in the measurement light after passing through the measurement part of the sample and passing through the measurement part of the sample. Law Is a device or method to more measured.
In this way, the change in the refractive index due to the photothermal effect of the sample (the change in the refractive index caused by the temperature rise of the sample) is detected, and the phase change in the measurement light that has passed (transmitted) through the measurement part of the sample using optical interferometry. If the measurement is performed by measuring (the phase change due to the irradiation of the excitation light), that is, by measuring the phase difference between the reference light and the measurement light, the sample can be analyzed with high accuracy.
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 does not depend on them and is highly reproducible (stable In addition, it is possible to measure the refractive index change (characteristic change) of the sample optically with high accuracy.
In addition, since the irradiation directions of the measurement light and the excitation light to the measurement unit are different, the excitation light generates a change in characteristics such as heat generation by the excitation light before reaching the measurement unit of the sample ( Even when passing through a wall of the container ( hereinafter referred to as a passing material), the measurement light can be configured not to pass through a portion where the characteristic change of the passing material occurs. It is possible to prevent measurement accuracy from deteriorating due to noise .

Further, the second direction is, if the direction substantially perpendicular to the surface of the container, said container refractive index is heated is changed by the excitation light, the irradiation of the excitation light to the measurement of the sample This is still preferable because it can prevent the angle (irradiation direction) from changing slightly and the measurement accuracy from deteriorating.
In general, since a cell (container) for storing a sample often forms a rectangular parallelepiped, if the first direction and the second direction are substantially orthogonal, the measurement light and the Each of the excitation light can be perpendicularly incident on the surface of the cell wall, and there is no need to consider the refractive index when the measurement light or the excitation light passes through the cell wall . Therefore, it is preferable that the cell wall is heated by the excitation light to prevent the refractive index from changing and the measurement accuracy from deteriorating.

Further, a back surface side light reflecting means for reflecting the measurement light is provided on the opposite side of the measurement light irradiation surface of the sample, and the measurement light is reflected by the back surface side light reflecting means so that the measurement portion of the sample is If the phase change of the measurement light after reciprocating is to be measured, the measurement light passes through the excitation part of the sample a plurality of times, without increasing the output of the excitation light and decreasing the S / N ratio. It becomes possible to measure the refractive index change with high sensitivity.
To measure the phase variation of the previous SL measuring light for intensity modulation period and the periodic component of the excitation light, measuring only the refractive index change of the sample while eliminating the influence of no noise frequency components of the excitation light it can. Thereby, the S / N ratio in the measurement of the phase change is improved.
Further, the excitation light is a multiplexed light of intensity-modulated light with a different period for each wavelength, and the phase change of the measurement light is measured for each of the same period components as the intensity modulation period of each wavelength of the excitation light. Conceivable.
The change in the refractive index of the measurement light due to the photothermal effect also varies depending on the wavelength of the excitation light, and the photothermal effect for the excitation light of each wavelength and the change in the refractive index of the sample due to the photothermal effect also differ depending on the type of substance contained in the sample.
Accordingly, if the multiplexed light is used, the change in the refractive index of the sample with respect to the measurement light of a plurality of wavelengths can be measured by one measurement. In addition, efficient measurement is possible in terms of time and effort.

Further, as the means for measuring the phase change, the measurement light and the measurement light are obtained by the photoelectric conversion means for photoelectrically converting the intensity of interference light between the measurement light and a predetermined reference light having a different optical frequency, and the photoelectric conversion means. Further, it may be possible to include a phase change calculating means for calculating the phase change of the measurement light based on the intensity signal of the interference light.
The electric signal (interference light intensity signal) obtained in this way becomes a signal whose optical frequency is converted into an electric signal, and its phase component can be extracted by FM demodulation or the like. The extracted phase component includes a signal of refractive index change due to heat generation of the sample. In addition, since the phase change between the reference beam and the measurement beam is measured, it is highly reproducible (stable) without depending on the position of the photodetector (photoelectric conversion means), the intensity of the measurement beam, its intensity distribution, etc. In addition, it is possible to measure the refractive index change of the sample optically with high accuracy.

According to the present invention, the change in the refractive index due to the photothermal effect of the sample is detected by the phase change in the measurement light that has passed (transmitted) through the measurement part of the sample using the optical interferometry (the phase change due to the irradiation of excitation light). Is measured, that is, by measuring the phase difference between the reference light and the measurement light. For example, the position of the photodetector (photoelectric conversion means), the intensity of the measurement light, and the intensity distribution thereof for each apparatus. Even if they are different, it is possible to measure the change in the refractive index of the sample stably and optically with high accuracy without depending on these as long as they do not change during measurement.
In addition, since the irradiation directions of the measurement light and the excitation light are different, the excitation light passes through an object that undergoes a characteristic change such as heat generated by the excitation light before reaching the measurement portion of the sample. Even so, it can be configured so that the measurement light does not pass through the portion where the characteristic change of the passing material occurs, and it can be prevented that the characteristic change of the excitation light passing material becomes noise with respect to the measurement light and the measurement accuracy deteriorates. .
Furthermore, the output of the excitation light (that is, increased power consumption and cost) can be increased by passing the measurement light back and forth through the sample with a simple configuration in which the measurement light is reflected by a light reflecting means (mirror, etc.). The change in the refractive index of the sample can be measured with high sensitivity without causing a decrease in the S / N ratio.
As a result, stable and highly sensitive sample analysis can be performed.

Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. It should be noted that the following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention.
Here, FIG. 1 is a schematic configuration diagram of the photothermal conversion measuring device X according to the embodiment of the present invention, and FIG. 2 is a diagram showing three patterns in which measurement light and excitation light are incident on a measurement unit of a sample accommodated in a cell. FIG. 3 is a diagram illustrating an example of the structure of a cell that accommodates a sample, and FIG. 4 is a diagram illustrating the measurement light in the photothermal conversion measuring device according to the embodiment of the present invention between the front surface and the back surface of the sample. FIG. 5 is a schematic sectional view of a conventional photothermal conversion measuring device (photothermal conversion spectroscopic analyzer).

Hereinafter, the photothermal conversion measuring apparatus X according to the embodiment of the present invention will be described with reference to FIG. This photothermal conversion measuring device X is a device that measures a change in characteristics of a sample caused by the photothermal effect of the sample irradiated with excitation light.
The pumping light P3 output from a predetermined pumping light source 1 (for example, a laser having a wavelength of 533 nm and an output of 100 mW (YAG double wave)) is converted into intermittent light (intermittent frequency: f) by the chopper 2 (that is, periodicity). The intensity of the sample 5 is applied to the sample 5 through the lens 3. Thereby, the sample 5 absorbs the excitation light P3 and generates heat (photothermal effect), and the refractive index of the sample 5 changes due to the temperature change (rise).
On the other hand, the measurement light output from a laser light source 7 (for example, a He—Ne laser having an output of 1 mW) that outputs measurement light for measuring the refractive index change of the sample 5 is a half-wave plate 8 and has a plane of polarization. Then, the light is further split into two polarized waves (P1, P2) orthogonal to each other by a polarization beam splitter (PBS) 9.
The polarizations P1 and P2 are shifted in frequency (frequency conversion) by the acousto-optic modulators (AOM) 10 and 11, reflected by the mirrors 12 and 13, and then synthesized by the polarization beam splitter 14. . Frequency difference f _b of 2 to these orthogonal polarization P1, P2, for example, a 30MHz or the like.
One polarization P2 of the synthesized measurement light passes (transmits) through the polarization beam splitter 15 and is reflected by the mirror 18, thereby returning to the polarization beam splitter 15 again. Here, the polarization P2 that has returned to the polarization beam splitter 15 reciprocally passes through the quarter-wave plate 16 disposed between the polarization beam splitter 15 and the mirror 18, so that the polarization plane is 90 °. Since it is rotating, it is reflected by the polarization beam splitter 15 and directed toward the photodetector 20.

On the other hand, the other polarization P1 of the combined measurement light is reflected by the polarization beam splitter 15, passes through the quarter-wave plate 17 and the lens 4, and enters the measurement unit 5a of the sample 5. . Further, the excitation light P3 is also configured to be applied to the measurement unit 5a of the sample 5.
Further, the polarization P1 (measurement light) incident on the sample 5 passes through the measurement unit 5a of the sample 5 and is provided on the back side of the sample 5 (on the opposite side of the irradiation surface of the measurement light (polarization P1)). The light is reflected by the reflecting mirror 6, passes again through the measurement unit 5 a of the sample 5 (ie, reciprocates), passes through the lens 4 and the quarter-wave plate 17, and returns to the polarizing beam splitter 15. Here, since the polarization plane of the polarization P1 (measurement light) is rotated 90 ° by reciprocating through the quarter-wave plate 17, this time, the polarization P1 (measurement light) passes through the polarization beam splitter 15 and passes through the polarization beam splitter 15. It merges with the wave P <b> 2 and travels toward the photodetector 20.
A polarizing plate 19 is disposed between the polarizing beam splitter 15 and the photodetector 20, and in this polarizing plate 19, the polarization P 1 and the polarization P 2 having a different optical frequency from the polarization P 1 are Each of them interferes as observation light (measurement light) and reference light, and the light intensity of the interference light is converted into an electric signal (hereinafter, the signal value of the electric signal is referred to as interference light intensity) by the photodetector 20 (photoelectric conversion means). Converted. This electric signal (that is, interference light intensity) is input and stored in a signal processing device 21 composed of a computer or the like, and the signal processing device 21 calculates (calculates) a phase change of the polarization P1 (measurement light). That is, phase change is measured by optical interferometry. Here, an optical device that guides the polarizations P1 and P2 in a predetermined direction, the polarizing plate 19 that forms interference light of the polarizations P1 and P2 (measurement light and reference light), and the photodetector 20 respectively. And the signal processing device 21 constitute an example of the phase change measuring means.

Here, the interference light intensity S1 is expressed by the following equation (1).
S1 = C1 + C2 · cos (2π · f _b · t + φ) (1)
In this equation (1), C1 and C2 are constants determined by the transmittance of an optical system such as a polarizing beam splitter and the sample 5, φ is a phase difference due to the optical path length difference between the polarizations P1 and P2, and f _b is a two-polarization P1. , P2 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).
Further, in the measurement unit 5a of the sample 5, the endothermic amount (heat generation amount) changes in accordance with the amount of the predetermined contained substance that absorbs the excitation light P3, and the refractive index of the measurement unit 5a changes in accordance with the amount of heat generation. The phase difference φ (the optical path length of the polarization P1 in the sample 5) changes according to the refractive index. That is, the greater the amount of the substance that absorbs the excitation light P3, the greater the change in the phase difference φ with respect to the change in the excitation light P3 (that is, the phase change in the polarization P1). Therefore, if the phase difference φ is measured, the change in the refractive index caused by the temperature change of the sample 5 can be obtained, and as a result, the amount (concentration) of the substance contained in the sample can be analyzed.
For example, the photothermal conversion measuring device X is used to measure the change of the phase difference φ for a plurality of types of sample samples whose amounts (concentrations) of a predetermined content are known in advance, and the result and the amount of the content 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. .
In this way, the change in refractive index due to the photothermal effect of the sample 5 is caused by the phase change (excitation light P3) in the measurement light (the polarization P1) that has passed (transmitted) through the measurement unit 5a of the sample 5 using optical interferometry. Is detected (measured) by measuring the relative phase (phase difference) between the reference light (the polarization P2) and the measurement light (the polarization P1). As a result, for example, even if the position of the photodetector 20, the intensity of the measurement light P1 and its intensity distribution, etc. differ from device to device, as long as they do not change during the measurement, they are stable and optically independent. Therefore, it is possible to measure the refractive index change of the sample with high accuracy.

In this photothermal conversion measuring apparatus X, the measurement light (polarized wave P1) is reflected on the sample by reflecting the measurement light (polarized wave P1) on the reflection mirror 6 on the back side (an example of the back side light reflecting means). Since the phase change measurement is performed on the measurement light after being reciprocated to 5 and passing through the reciprocating passage, the change in the phase difference φ can be measured with twice the sensitivity 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.
Furthermore, since the excitation light is intensity-modulated at the frequency f, the refractive index of the sample 5 also changes at the frequency f, and the optical path length of the polarization P1 also changes at the frequency f (the optical path length of the polarization P2 is constant). The phase difference φ also changes with the frequency f. Therefore, if the change in the phase difference φ is measured (calculated) with respect to the component of the frequency f (the same period component as the intensity modulation period of the excitation signal), the influence of noise having no component of the frequency f is removed. Only a refractive index change of 5 can be measured.
Thereby, the S / N ratio in the measurement of the phase difference φ is improved.

In the photothermal conversion measuring apparatus X, the measurement light (polarized wave) P1 is applied to the measurement unit 5a of the sample 5 by the laser light source 7 and the various optical systems 9, 12, 14, 15, 4 (an example of measurement light irradiation means). And the direction in which the excitation light P3 is irradiated to the measuring part 5a of the sample 5 by the excitation light source 1, the chopper 2, etc. (an example of excitation light irradiation means) (hereinafter referred to as the first direction) Hereinafter, the second direction is different. That is, in the measurement part 5a of the sample 5, the measurement light P1 and the excitation light P3 intersect each other.
As shown in FIG. 1, in the present embodiment, the first direction and the second direction are configured to be substantially orthogonal to each other.
The sample 5 is held by a cell S that is a container for containing the sample 5, and the measurement light P <b> 1 and the excitation light P <b> 3 pass (transmit) through the wall (an example of a holding member) of the cell S. The measurement unit 5a is irradiated. Here, the cell S (the wall) is made of a material such as quartz that allows the measurement light P1 and the excitation light P3 to pass (transmit).
The wall of the cell S is formed in a rectangular parallelepiped shape, and the first direction (irradiation direction of the measurement light P1) and the second direction (irradiation direction of the excitation light P3) orthogonal to each other are respectively The cell S is configured (arranged) in a direction substantially perpendicular to the wall surface (an example of the surface of the holding member).

FIG. 2 is a diagram illustrating a state in which the measurement light P1 and the excitation light P3 are incident on the measurement unit 5a of the sample 5 accommodated in the cell S with respect to three patterns of incident states.
Here, FIG. 2A shows a state in which the measurement light P1 and the excitation light P3 are incident (irradiated) on the measurement unit 5a of the sample 5 from directions orthogonal to each other as shown in FIG. 2 (b) shows a state where the incident direction of the measurement light P1 and the incident direction of the excitation light P3 form an acute angle (hereinafter referred to as pattern b), and FIG. 2 (c) shows the measurement light P1 and the excitation light P3. Represents an incident state (hereinafter referred to as a pattern c) in the same direction (from the same direction).
Further, the wall of the cell S shown in FIG. 2 is formed in a rectangular parallelepiped shape, and the pattern a has an incident direction (first direction) of the orthogonal measuring light P1 and an incident direction (second) of the excitation light P3. Are directions that are different from each other and are substantially perpendicular to the wall surface of the cell S (an example of the surface of the holding member).
In the pattern c, the portion S3 through which the measurement light P1 passes in the cell S and the portion S4 through which the excitation light P3 pass overlap or are close to each other. For this reason, when the passage portion S4 of the excitation light P3 is excited and a characteristic change occurs, the measurement light P1 passes through the portion S3 that overlaps or is close to the excitation portion S4. Depending on the size, the measurement accuracy may deteriorate due to noise in the measurement light P1.
On the other hand, in the pattern a, the portion S1 through which the measurement light P1 passes in the cell S and the portion S2 through which the excitation light P3 pass are completely different (not overlapping and not in the vicinity). For this reason, even if a characteristic change occurs such that a part S2 of the cell S generates heat due to the excitation light P3, the measurement light P1 does not pass through the excitation part S2 (passage part (heat generation part) of the excitation light P3). Therefore, the characteristic change of the excitation unit S2 does not become noise in the measurement light P1, and the measurement accuracy does not deteriorate.
Similarly, in the pattern b, the portion S1 ′ through which the measurement light P1 passes in the cell S and the portion S2 ′ through which the excitation light P3 pass are completely different, so that the characteristic change of the excitation portion S2 ′ in the cell S changes. The measurement accuracy does not deteriorate due to noise in the measurement light P1.
In this way, by making the irradiation directions of the measurement light P1 and the excitation light P3 to the measurement unit 5a different, the excitation light P3 passes through the object excited by the excitation light P3 before reaching the measurement unit 5a. Even in this case, it can be easily configured so that the measurement light P1 does not pass through the excited portion, and it is possible to prevent the change in characteristics of the excitation portion from becoming noise with respect to the measurement light P1 and degrading the measurement accuracy.
However, in the pattern b, since the excitation light P3 is not perpendicularly incident on the wall surface of the cell S, the excitation light P3 is refracted at the passing portion S2 ′ (excitation portion) in the cell S, and its refractive index. Changes according to the change in the excitation state (heat generation state) of the passage S2 ′. Due to this change in refractive index, the incident angle (irradiation direction) of the excitation light P3 with respect to the measurement unit 5a of the sample 5 may be slightly changed, and the measurement accuracy may be slightly deteriorated.
On the other hand, in the pattern a, since the excitation light P3 is substantially perpendicularly incident on the wall surface of the cell S, the excitation light P3 is related to the excitation (heating) state in the passage portion S2 in the cell S. No refraction. Therefore, the change in the excitation state of the excitation light P3 in the passage part S2 does not affect the change in the incident angle (irradiation direction) of the excitation light P3 with respect to the measurement part 5a of the sample 5 and the measurement accuracy does not deteriorate slightly. .

(Example)
FIG. 3 is a diagram showing an example of the structure of the cell S ′ containing the liquid sample 5, and is a cross-sectional view (a), a plan view (b), a bottom view (c), and a side direction as seen from the front direction. Sectional drawing (d) and the enlarged view (e) of the measurement part 5a of the sample 5 are represented.
The cell S ′ has a structure in which two plate-like members Sa and Sb (hereinafter referred to as a base material Sb and a lid material Sa) made of a quartz material are bonded to each other, and the bottom surface (the lid material Sa) of the base material Sb. The reflection mirror 6 that reflects the measurement light P1 is provided on the surface opposite to the surface facing the surface.
Further, a groove Sg extending in a band shape when viewed from above is formed on the upper surface of the base material Sb (the surface facing the lid material Sa). The groove Sg is a groove for storing the liquid sample 5.
On the other hand, the cover material Sa is provided with a through hole Sh, and the liquid sample 5 is poured into the groove Sg on the substrate Sb side through the through hole Sh in a state where the cover material Sa and the substrate Sb are bonded together. It has a structure that can.
In the cell S ′ shown in FIG. 3, in order to reduce the sample 5 and increase the measurement sensitivity, the groove Sg for storing (holding) the sample 5 is fine (for example, a depth of 100 μm, a width of 200 μm, and a length of about 30 mm). It is. As the processing method, for example, it is conceivable to dissolve the base material Sg with a solvent, and in this case, the groove Sg has a slightly rounded shape.

In the above embodiment, the sensitivity is improved by reciprocating the measurement light (the polarization P1) through the sample 5, but this reciprocation is further multiplexed, that is, the measurement light is It is also possible to further improve sensitivity by making multiple passes through the sample 5.
FIG. 4 is a schematic cross-sectional view of a configuration in which measurement light is subjected to multiple reflection between the front surface and the back surface of the sample.
As shown in FIG. 4, reflection mirrors 31 and 32 (high reflection mirror, front surface side light reflecting means and rear surface side light are respectively provided on the front surface side (the measurement light irradiation surface side) and the back surface side of the sample 5. An example of a reflecting means) can be arranged, and the measurement light (the polarization P1) can be subjected to multiple reflection between the reflecting mirrors 31 and 32. Here, in order to schematically show multiple reflection, FIG. 4 shows that the measurement light is obliquely incident on the reflection mirrors 31 and 32 for the sake of convenience. The reflected light should be coaxial. As a result, the measurement light (the polarized wave P1) is reflected by the reflection mirrors 31 and 32, and a part of the measurement light is transmitted through the reflection mirror 31 on the surface side of the sample 5, and the photodetector 20 is transmitted. Head in the direction of Accordingly, since the measurement light that has passed through the sample 5 is superimposed and input to the photodetector 20, it is possible to perform phase difference measurement with high sensitivity, that is, measurement of refractive index change.
In this case, a drive mechanism 30 (mirror drive mechanism) for controlling the position of one of the reflection mirrors may be provided in order to finely adjust the distance between the reflection mirrors 31 and 32 so as to synchronize the phase of the multiple reflected measurement light. desirable.

By the way, the change in the refractive index of the measurement light due to the photothermal effect differs depending on the wavelength of the excitation light, and the photothermal effect on the excitation light of each wavelength and the change in the refractive index of the sample due to the photothermal effect also differ depending on the type of substance contained in the sample.
Therefore, by irradiating a plurality of excitation light beams having different wavelengths and measuring the change of the phase difference φ for each of them, the type and amount of the substance contained in the sample can be specified (evaluated) from the distribution. However, measuring with irradiation of excitation light at different wavelengths is inefficient in terms of time and labor.
Therefore, the excitation light is a multiplexed light of intensity-modulated light with different periods for each wavelength, and the signal processor 21 changes the phase φ of the measurement light to the intensity modulation period of each wavelength of the excitation light. If each of the same periodic components is measured, the change in the refractive index of the sample with respect to the measurement light of a plurality of wavelengths can be measured by one measurement, and efficient measurement becomes possible.
As a light source (irradiation means) of such excitation light, light from a white light source (for example, a tungsten lamp) is dispersed with a spectroscope, and the intensity is modulated via a chopper having a different frequency for each of the dispersed light. It is conceivable that the above-described excitation light is collected (combined) light.
Also, the light from the white light source is split in two directions by the beam splitter, reflected by the fixed mirror and the moving mirror, returned to the beam splitter and merged, and the well-known Fourier spectroscopy using this as the excitation light was used. An excitation light output unit may be considered.

  The present invention can be applied to a photothermal conversion measuring device that measures a change in the characteristics of the sample caused by the photothermal effect of the sample irradiated with excitation light.

The schematic block diagram of the photothermal conversion measuring apparatus X which concerns on embodiment of this invention. The figure showing the state in which measurement light and excitation light inject into the measurement part of the sample accommodated in the cell about the incident state of three patterns. The figure showing an example of the structure of the cell which accommodates a sample. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a configuration in which measurement light in a photothermal conversion measurement device according to an embodiment of the present invention is subjected to multiple reflection between a front surface and a back surface of a sample. The schematic block diagram of the conventional photothermal conversion measuring apparatus (photothermal conversion spectroscopy analyzer).

1 ... Excitation light source (excitation light irradiation means)
2 ... Chopper 3, 4 ... Lens 5 ... Sample 6, 32 ... Reflection mirror (back side light reflecting means)
7. Laser light source (measurement light irradiation means)
10, 11 ... Acousto-optic modulator (AOM)
20: Photodetector (photoelectric conversion means)
21 ... Signal processing device (phase change measuring means)
31 ... Reflection mirror (surface side light reflection means)
S, S '... cell (sample holding member)
P1: Polarization (measurement light)
P2: Polarization (reference light)
P3 ... Excitation light

Claims (7)

A photothermal conversion measuring device for measuring a change in refractive index of a sample caused by a photothermal effect of a sample irradiated with excitation light,
A measuring light irradiation means for passing the measurement light to the measurement of the sample to the sample contained in the container is irradiated with measurement light from a first direction,
By irradiating a periodically intensity-modulated excitation light from a second direction different from said first direction to said sample contained in the container, passage of the measuring light excitation light in said container Excitation light irradiating means that passes through the measurement part of the sample through which the measurement light passes while passing through a different part from
Phase change measuring means for measuring the phase change of the same period component as the intensity modulation period of the excitation light in the measurement light after passing through the measurement unit of the sample by optical interferometry;
A photothermal conversion measuring device comprising: The photothermal conversion measuring apparatus according to claim 1 , wherein the second direction is a direction substantially perpendicular to a surface of the container in which the sample is accommodated . Photothermal conversion measuring instrument according to claim 1 or 2 to the first direction and the second direction is a direction substantially orthogonal. Comprising a back side light reflecting means provided on the opposite side of the measurement light irradiation surface of the sample and reflecting the measurement light;
The phase change measuring means, one said measurement light according to claim 1 to 3 obtained by measuring the phase shift of the measuring light after reciprocally passes through the measurement portion of the sample is reflected on the rear surface side light reflecting means The photothermal conversion measuring device according to claim 1. The excitation light is multiplexed light of intensity-modulated light with different periods for each wavelength,
The phase change measuring means, the measurement light photothermal conversion measuring instrument according to a phase change to any one of claims 1 to 4 made by measuring for each intensity modulation period and the periodic component of the wavelength of the excitation light. The phase change measuring means comprises:
Photoelectric conversion means for photoelectrically converting the intensity of the interference light between the measurement light and the predetermined reference light having a different optical frequency from the measurement light;
Phase change calculation means for calculating a phase change of the measurement light based on an intensity signal of the interference light obtained by the photoelectric conversion means;
The photothermal conversion measuring device according to any one of claims 1 to 5 . A photothermal conversion measurement method for measuring a change in refractive index of a sample caused by a photothermal effect of a sample irradiated with excitation light,
To the sample contained in the container is irradiated with the measurement light by a predetermined measuring light irradiation means from the first direction together with passing the measurement light to the measurement of the sample, the sample contained in the container On the other hand, by irradiating excitation light whose intensity is periodically modulated by a predetermined excitation light irradiating means from a second direction different from the first direction , the excitation light is passed through the measurement light in the container. Passing through the measurement part of the sample through which the measurement light passes while passing through different parts ,
A photothermal conversion measurement method comprising measuring, by optical interferometry, a phase change of the same period component as the intensity modulation period of the excitation light in the measurement light after passing through the measurement unit of the sample.

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