JPH09229883A - Dark field type photothermal transduction spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dark field photothermal transduction spectrometer in a simple constitution with high sensitivity and a good S/N ratio. SOLUTION: A pump beam A output from a pump beam source 50 is condensed and cast on an object 70 to be measured. A heat lens is formed in the vicinity of a position where the object 70 is illuminated. A probe light B output from a probe light source 60 is also projected to the position where the heat lens is formed. The probe light B is diverged and output with an angle corresponding to focal length and diameter of the heat lens. A luminous flux in the vicinity of an optical axis of the probe light B diverged by the heat lens is shut at a shielding area 82a of a shielding plate 82. However, a luminous flux separated a predetermined distance or more from the optical axis is not shut by the shielding plate 82 and detected by a photodetector 86. Since the luminous flux corresponds to a concentration of the object 70 to be measured at the position of the heat lens, the concentration of the object 70 can be detected based on an output signal of the photodetector 86.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention changes the refractive index of an object to be measured in accordance with a change in temperature distribution generated by the heat generated by irradiating the object to be measured with light and diffusing to the surrounding medium. The present invention relates to a dark-field type photothermal conversion spectroscopic analysis technique utilizing a phenomenon, that is, a photothermal lens effect.

[0002]

2. Description of the Related Art When an object to be measured is irradiated with light, the temperature in the vicinity of the irradiated position rises and the refractive index changes accordingly. The change in the refractive index depends on the temperature distribution of the measured object, and the temperature distribution includes the light absorption coefficient of the measured object, the luminous flux diameter and intensity of the irradiation light, the thermal conductivity of the solvent, the refractive index of the solvent. It depends on the change and the concentration of the measured object. Then, this refractive index distribution acts as a lens. This is called a thermal lens. In general, for many substances, the refractive index becomes smaller as the temperature rises, so the thermal lens is a concave lens. Spectroscopic analysis of the object to be measured is performed by utilizing such a photothermal lens effect.

Conventionally, a spectroscopic analyzer utilizing the photothermal lens effect has the following configuration. FIG. 4 is a block diagram of a conventional spectroscopic analyzer.

In this apparatus, the pump light A output from the pump light source 10 is modulated by the optical chopper 30 for transmission / blocking, and then reflected by the dichroic mirror 14.
The light enters the lens 32 and is condensed and irradiated to the DUT 34.
When the object to be measured 34 is irradiated with the pump light A, the refractive index changes due to the temperature rise and a thermal lens is formed.

On the other hand, the probe light B output from the probe light source 20 is reflected by the reflecting mirror 24, transmitted through the dichroic mirror 14, output on the same optical axis as the pump light A, and enters the lens 32. The object to be measured 34 is focused and irradiated.

The probe light B transmitted through the object to be measured 34 is
The light flux is limited by the pinhole 35, condensed by the lens 36, reflected by the reflecting mirror 38, transmitted through the pump light absorption filter 40, and detected by the photodetector 42. Pump light A
Is also condensed by the lens 36 and pumped by the pump light absorption filter 40.
However, since the light is absorbed by the pump light absorption filter 40, it is not detected by the photodetector 42.

The amount of the probe light B condensed by the lens 36 and detected by the photodetector 42 depends on the optical characteristics of the thermal lens formed on the object 34 to be measured. , Depends on the concentration of the DUT 34. Therefore, by using the lock-in amplifier 44 to synchronously detect the light amount of the probe light B detected by the photodetector 42 at the modulation cycle of the optical chopper 30, the concentration of the DUT 34 can be known.

[0008]

However, the above conventional example has the following problems. The probe light B of the light beam condensed by the lens 36 passes near the optical axis of the thermal lens formed on the DUT 34. Therefore, when the thermal lens is formed on the DUT 34 (when the pump light A is being irradiated or immediately thereafter), the light amount of the probe light B reaching the photodetector 42 and the thermal lens are formed. The difference from the light amount of the probe light B that reaches the photodetector 42 when the pump light A is not irradiated (after a certain time has elapsed after the irradiation of the pump light A is completed) is small.

Therefore, an expensive lock-in amplifier 44 must be used to detect the amplitude of the component of the change in the light quantity of the probe light B which is synchronized with the modulation cycle of the optical chopper 30.

Further, in order to block the pump light A of the light flux condensed by the lens 36, a pump light absorption filter 40 is provided.
However, the pump light A is not completely blocked by the pump light absorption filter 40, but a part of the pump light A passes through to reach the photodetector 42 although it is slight.

Of the light quantity of the light flux reaching the photodetector 42, the light quantity that changes in synchronization with the modulation cycle of the optical chopper 30 is very small. Therefore, the signal received by the photodetector 42 and input to the lock-in amplifier 44 is a small-amplitude periodic signal buried in a relatively large bias signal. / N
There is a problem that the ratio is poor.

Further, even when the density of the object to be measured 34, that is, the optical characteristics of the formed thermal lens greatly differ, the light passes through the vicinity of the optical axis of the thermal lens and is focused on the lens 36 to detect the photodetector. The difference in the amount of probe light A reaching 42 is small. Therefore, there is also a problem that the measurement sensitivity is poor.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a dark-field photothermal conversion spectroscopic analyzer having a simple structure with high sensitivity and good S / N ratio. To do.

[0014]

A dark-field type photothermal conversion spectroscopic analysis apparatus according to the present invention makes probe light incident on a thermal lens formed on an object to be measured upon irradiation with pump light, and outputs the probe light. A dark-field photothermal conversion spectroscopic analyzer that performs spectroscopic analysis of an object to be measured based on probe light
(1) Pump light source unit that outputs pump light, (2) Probe light source unit that outputs probe light, (3) Pump light and probe light are input, and pump light is input to a predetermined position of the DUT. An irradiation optical system that irradiates the probe with focused light to form a thermal lens and irradiates the probe light at a predetermined position, and (4) Pump light output from the DUT when the thermal lens is not formed at the predetermined position. And a shielding means for shielding the probe light,
A light receiving optical system that inputs the pump light and the probe light output from the predetermined position of the DUT and outputs a light beam other than the light beam blocked by the shielding means, and (5) the light beam output from the light receiving optical system. And a photodetector for detecting.

This dark-field type photothermal conversion spectroscopic analyzer operates as follows. The pump light output from the pump light source unit is focused and irradiated by the irradiation optical system at a predetermined position of the object to be measured, and a temperature distribution is generated in the vicinity of the predetermined position. A lens is formed. The probe light output from the probe light source unit is also applied by the irradiation optical system to a predetermined position where the thermal lens is formed. This probe light is diverged and output at a divergence angle according to the focal length of the thermal lens and the lens diameter. And
In the probe light diverged by the thermal lens, a light beam near the optical axis is blocked by the blocking means by the light receiving optical system, but a light beam separated by a certain distance or more from the optical axis is not blocked by the blocking means and is a photodetector. To reach. The amount of light flux detected by the photodetector depends on the thermal lens formed on the object to be measured, and the optical characteristics of the thermal lens depend on the density of the object to be measured. The concentration of the object to be measured is detected based on the output signal from the photodetector.

The pump light source unit may be provided with pump light modulating means for modulating the pump light in a pulsed form and outputting it. In this case, since a thermal lens having a small lens diameter is formed, a high position is provided. Resolution is obtained.

The irradiation optical system adjusts the luminous flux diameter of the pump light and adjusts the luminous flux diameter so that the entire luminous flux of the pump light output from the object to be measured is incident on the shielding means when the thermal lens is not formed at a predetermined position. Means may be provided. In this case, when the thermal lens is not formed on the object to be measured, the entire luminous flux of the pump light is blocked by the blocking means and is not detected by the photodetector, so that a high S / N ratio can be obtained.

The irradiation optical system is provided between (a) a combining means for combining the pump light and the probe light on the same optical axis, and (b) between the combining means and the probe light source section. Is provided between the first lens for condensing the light at the first position, and (c) the combining means and the object to be measured, so that the pump light is condensed and irradiated at a predetermined position, and at the same time, it is condensed at the first position. A second lens that irradiates a predetermined position with the emitted probe light as a parallel light flux may be provided. Alternatively, it is provided between (a) a combining means for combining the pump light and the probe light on the same optical axis, and (b) between the combining means and the pump light source section, and collects the pump light on the DUT. A condensing lens that emits light may be provided. In either case, the object to be measured is irradiated with condensed pump light to form a thermal lens, and the region where the thermal lens is formed is irradiated with the probe light.

When the object scanning means for scanning the object relatively in the direction perpendicular to the optical axis of the pump light incident on the object is further provided, the two-dimensional concentration distribution of the object is measured. To be done.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. FIG. 1 is a configuration diagram of a dark-field photothermal conversion spectroscopic analyzer according to this embodiment.

The pump light source 50 outputs the pump light A as a parallel light flux, and an Ar laser light source is used, for example, and its output is about 100 mW. The optical chopper (pump light modulator) 52 receives the pump light A output from the pump light source 50, and performs transmission / blocking modulation at a modulation cycle of 1 kHz, for example. If the pump light source 50 oscillates in pulses, the optical chopper 52 is unnecessary.

The pump light A modulated and output by the optical chopper 52 passes through a dichroic mirror (combining means) 54 and reaches a pinhole plate (beam diameter adjusting means) 56. The pinhole plate 56 is provided with an opening 56a, and of the pump light A that has reached the pinhole plate 56, only the light beam portion irradiated on the opening 56a is passed.

The pump light A that has passed through the opening 56a reaches the lens 58. The lens 58 condenses and irradiates the object 70 to be measured placed at the focal position with the pump light A.
The DUT 70 is put in a transparent cell container or dropped on a transparent slide glass. Alternatively, if the DUT 70 has a fixed shape, it may be left as it is.

As described above, when the object 70 is condensed and irradiated with the pump light A, a thermal lens is formed around the position where the condensed light is irradiated. FIG. 2 is an explanatory diagram of a thermal lens formed on the DUT 70. When the pump light A is focused and irradiated, the object to be measured 70 rises in temperature at the irradiated position. However, in the region where the temperature rises, not only the position where the pump light A is condensed and irradiated, but also the heat diffuses to the surroundings, so the temperature of the surrounding region also rises. As for the temperature profile, the temperature is higher as it is closer to the position where the pump light A is condensed and irradiated. Then, the DUT 70 has a refractive index distribution according to the temperature distribution. In general, the higher the temperature is, the smaller the refractive index is. Therefore, the closer the position is to the position where the pump light A is focused and irradiated, the smaller the refractive index is. That is, the thermal lens 72 is formed around the position where the pump light A is condensed and emitted.

The focal length and the lens diameter of the thermal lens 72 thus formed are the intensity of the pump light A, the light absorption coefficient and the heat diffusion coefficient of the pump light A at the position where the pump light A is irradiated, and It depends on the elapsed time from the time when the pump light A is irradiated. That is, the higher the intensity of the pump light A, the larger the light absorption coefficient of the pump light A at the position where the pump light A is irradiated, and the smaller the thermal diffusion coefficient, the larger the temperature gradient, that is, the refractive index gradient. , The focal length becomes shorter. However, as time elapses from the irradiation time of the pump light A, heat diffuses and the temperature gradient decreases, so that the focal length gradually increases and the lens diameter increases.

Since the pump light A is transmitted near the center of the thermal lens 72 formed on the object 70 to be measured, it is emitted almost in the same direction as the incident direction. That is, the emission direction of the pump light A from the thermal lens 72 hardly depends on the focal length of the thermal lens 72, and has little relation to the presence or absence of the thermal lens 72. However, since the pump light A has a finite light flux diameter even though it is condensed and irradiated to the center of the thermal lens 72, the thermal lens 72
The light is slightly spread and emitted.

The pump light A transmitted through the object 70 to be measured is condensed by the lens 80 and reaches the shielding area 82a of the shielding plate (shielding means) 82. The shield plate 82 is composed of a shield region 82a made of a material such as a metal material or a ceramic material that does not transmit any light flux at the center, and a transmissive region 82b made of a material such as a glass material that allows the light flux to pass therethrough. It is a thing. The pump light A is shielded by the shield area 82a of the shield plate 82, does not proceed further than this, and does not reach the photodetector 86. It should be noted that a part of the pump light A slightly expanded by the thermal lens 72 and emitted is transmitted through the transmission region 82b of the shield plate 82, but is absorbed by the pump light absorption filter 84. Never reach.

On the other hand, the probe light source 60 outputs the probe light B as a parallel light beam, for example, He-
A Ne laser light source is used, and its output is, for example, about 5 mW. The probe light B output from the probe light source 60 passes through the lens 62, is reflected by the dichroic mirror 54, and is condensed at a predetermined position. As described above, the dichroic mirror 54 transmits the pump light A, reflects the probe light B, and outputs the both on the same optical axis.

The probe light B passes through the opening 56a of the pinhole plate 56 and reaches the lens 58. The lens 58 and the lens 62 are arranged with an optical path length equal to the sum of their focal lengths. Therefore, the probe light B is output from the lens 58 as a parallel light flux. Then, as shown in FIG. 2, the probe light B formed into a parallel light beam is condensed and irradiated with the pump light A, and the object to be measured 70 is irradiated.
Is input to the area of the thermal lens 72 formed in. In addition,
When the probe light B is formed into a parallel light flux having a light flux diameter larger than the lens diameter of the thermal lens 72 and is applied to the entire area where the thermal lens 72 is formed, it is suitable for adjusting the optical axis.

When the object 70 to be measured is irradiated with the probe light B in this manner, the object 70 to be measured is condensed and irradiated with the pump light A to form the thermal lens 72, and when the thermal lens 72 is not formed. The divergence angle of the probe light B output from the DUT 70 is different. That is, the pump light A is applied to the DUT 70.
After a lapse of a certain time from the point where the light is focused and emitted, that is, when the thermal lens 72 is not formed, the probe light B1 output from the DUT 70 remains a parallel light flux. Then, the lens 80 inputs the probe light B1 and irradiates the shielding plate 82. The shielding area 82a of the shielding plate 82 is formed wider than the irradiation area of the probe light B1. Therefore, when the thermal lens 72 is not formed, the probe light B1 is not detected by the photodetector 86.

However, when the pump light A is focused on the object to be measured 70 and the thermal lens 72 is formed, the probe light B2 output from the object to be measured 70 is the thermal lens 7.
The divergence angle diverges according to the focal length of 2 and is output. Therefore, in this case, although the probe light B2 is partially shielded by the shield region 82a of the shield plate 82, the remaining portion thereof transmits the transmission region 82b, further transmits the pump light absorption filter 84, and the photodetector 86. Detected in.

Here, the quantity of the probe light B2 detected by the photodetector 86 depends on the focal length of the thermal lens 72 formed on the object 70 to be measured, that is, the density of the object 70 to be measured. Based on the amount of light received by the photodetector 86, the concentration of the DUT 70 can be measured.

Next, the operation of the dark-field type photothermal conversion spectroscopic analyzer according to this embodiment will be described. FIG. 3 is a light quantity change diagram for each of the pump light and the probe light in the dark-field photothermal conversion spectroscopic analysis device according to the present embodiment.

The temporal change in the intensity of the pump light A output from the pump light source 50 and modulated by the optical chopper 52 and output is pulse-shaped as shown in FIG. 3 (a). The pulsed pump light A passes through the dichroic mirror 54, passes through the opening of the pinhole plate 56 to have a predetermined light beam diameter, and is focused and irradiated on the object 70 to be measured by the lens 58.

While the object 40 to be measured is irradiated with the pump light A, the thermal lens 72 grows on the object 70 to be measured, and gradually approaches a certain thermal equilibrium state. During this time, the pump light A that has entered the thermal lens 72 is gradually expanded as the thermal lens 72 grows, but is emitted. However, when the irradiation of the pump light A is finished, the thermal lens 72 is gradually eliminated, so that the divergence angle of the probe light A output from the thermal lens 72 gradually decreases.

Therefore, the transparent region 82b of the shielding plate 82
The intensity of the pump light A that is incident on and transmitted to the laser light gradually increases with time from the irradiation start time of the pump light A, and gradually decreases with time from the irradiation end time of the pump light A. . FIG. 3B shows the change over time in the intensity of the pump light A transmitted through the shield plate 82. However, the pump light A passing through the shield plate 82 has a weak intensity because it has passed through the vicinity of the center of the thermal lens 72 as described above, and is absorbed by the pump light absorption filter 84. Never reach.

On the other hand, the probe light B output from the probe light source 60 is once condensed by the lens 62, reflected by the dichroic mirror 54, made into a parallel light flux by the lens 58, and then the thermal lens 72 of the object 70 to be measured. Is irradiated to the area where the is formed. Like the pump light A, the probe light B also
As the thermal lens 72 grows and disappears, the divergence angle when it is output from the thermal lens 72 changes, and the light amount of the probe light B transmitted through the transmission region 82b of the shield plate 82 changes.

That is, the intensity of the probe light B which is incident on and transmitted through the transmission region 82b of the shield plate 82 gradually increases with the passage of time from the irradiation start time of the pump light A, and the irradiation end time of the pump light A. It gradually decreases from time to time. FIG. 3C shows the time change of the intensity of the probe light B transmitted through the shield plate 82.
The probe light B transmitted through the shield plate 82 is transmitted through the pump light absorption filter 84 and detected by the photodetector 86.

Therefore, when the output signal from the photodetector 86 is observed with, for example, an oscilloscope (not shown), a waveform as shown in FIG. 3C is obtained, and the amplitude of the waveform shows the measured object 70. The concentration can be measured. Alternatively, the output signal from the photodetector 86 can be smoothed by a smoothing circuit (not shown), and the concentration of the DUT 70 can be measured from the level of the smoothed signal.

As described above, the cycle of the light amount change detected by the photodetector 86 is the cycle of growth and elimination of the thermal lens 72 formed by irradiating the object 70 with the pulsed pump light A, that is, the cycle. , Pump light A by the optical chopper 52
Is the same as the modulation period of. Further, the amplitude of the light amount detected by the photodetector 86 is determined by the intensity of the pump light A that irradiates the DUT 70, the intensity of the probe light B that irradiates the area where the thermal lens 72 is formed, and the pump. It depends on the light absorption coefficient and the thermal diffusion coefficient at the position of the DUT 70 irradiated with the light A. Here, if the output intensity of each of the pump light source 50 and the probe light source 60 is constant,
The amount of light detected by the photodetector 86 depends on the light absorption coefficient and the thermal diffusion coefficient at the position of the DUT 70 irradiated with the pump light A, that is, the concentration of the DUT 70.

Further, by providing an object scanning means (not shown) for relatively two-dimensionally scanning the object 70 in a direction perpendicular to the optical axis of the pump light A, the object 70 to be measured is provided.
It is possible to obtain a two-dimensional concentration distribution of

The position resolution of the object to be measured 70 is the degree of the diameter of the thermal lens 72 formed by condensing and irradiating the object to be measured 70 with the pump light A. Therefore, the DUT 70
Is smaller in the optical axis direction of the pump light A, and the aberration of the lens 58 is smaller and the pump light A with which the DUT 70 is irradiated is narrowed to the diffraction limit, the area of the region irradiated with the pump light A becomes smaller. Since it is small, it is possible to perform measurement with excellent position resolution. Furthermore, the shorter the pulse width of the pump light A focused and irradiated onto the object 70 to be measured, and the larger the intensity thereof, the smaller the expansion of the thermal lens diameter due to thermal diffusion, and thus the positional resolution of the measurement is excellent.

The present invention is not limited to the above embodiment, but can be variously modified. For example, the optical chopper 52 is not always necessary. In the above-described embodiment, the pump light A is applied to the object to be measured 70 in pulses by using the optical chopper 52. Therefore, the object to be measured 70 does not reach a thermal equilibrium state, and therefore the thermal lens 72 having a small diameter is used. Can be formed, and measurement with high position resolution is possible. However, the pump light A is emitted as continuous light to the DUT 70 without using the optical chopper 52, and the pump light A is reached even when the DUT 70 reaches thermal equilibrium.
A thermal lens is formed near the irradiation position. The focal length and the lens diameter of the thermal lens correspond to the density of the DUT 70 in the area where the thermal lens is formed. Therefore, similarly, the concentration of the DUT 70 can be measured by making the probe light B enter the thermal lens and detecting the light amount of the probe light B diverged by the thermal lens.

Further, the pump light absorption filter 84 is not always necessary. Because the pump light A is also diverged by the thermal lens 72 formed on the DUT 70, the degree of divergence, that is, the amount of the diverged light flux of the pump light A incident on the thermal lens 72 is also affected. This is because it depends on the concentration of the measurement object 70.

Instead of providing the lenses 62 and 58, a lens is provided between the pump light source 50 and the dichroic mirror 54, and the pump light A is provided by this lens.
The object 70 to be measured may be focused and irradiated. Also in this case, similarly, the pump light A is focused and irradiated on the object 70 to be measured, and the probe light B is incident on the thermal lens 72 formed on the object 70 to be measured as a parallel light flux. To be

Further, the pump light A incident on the object 70 to be measured.
The probe light B and the probe light B do not necessarily have to have the same optical axis.
The point is that the probe light B is incident on the thermal lens 72 formed on the object to be measured 70 by condensing and irradiating the pump light A, and the light amount of the probe light B diverged by the thermal lens 72 is measured.

Further, the shape and arrangement of the shielding plate are not limited to those shown in FIG. 1, and for example, they may be arranged inclined with respect to the optical axis. The light incident on may be guided to the beam damper.

When the object to be measured has a higher refractive index as the temperature rises, the thermal lens formed by irradiation with the pump light is a convex lens, but even in this case,
The present invention is applicable. That is, for example, the probe light that is once condensed by the thermal lens and then diverges from the condensing point may be detected by the same optical system as in the above-described embodiment.

[0049]

As described above in detail, according to the present invention, the pump light output from the pump light source is focused and irradiated on a predetermined position of the object to be measured, and a temperature distribution is generated in the vicinity of the predetermined position. A refractive index distribution is generated according to this temperature distribution to form a thermal lens. The probe light output from the probe light source is also applied to a predetermined position where the thermal lens is formed. This probe light is diverged and output at a divergence angle according to the focal length of the thermal lens and the lens diameter. Then, of the probe light diverged by the thermal lens, the light flux near the optical axis is blocked by the blocking means, but the light flux distant from the optical axis by a certain distance or more is detected by the photodetector without being blocked by the blocking means. To be done. The amount of light flux detected by this photodetector depends on the thermal lens formed on the object to be measured, and the optical characteristics of this thermal lens depend on the density of the object to be measured. The concentration of the object to be measured is detected based on the output signal from the photodetector.

With such a configuration, the photodetector detects only the light flux of the pump light and the probe light near the optical axis, and detects only the light flux of the probe light diverged by the thermal lens. It is possible to perform measurement with high sensitivity and S / N ratio with a simple device configuration without using.

When the pump light is focused and irradiated on the object to be measured in a pulsed manner, a thermal lens having a small lens diameter is formed, so that measurement with high position resolution is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a dark-field photothermal conversion spectroscopic analyzer according to the present invention.

FIG. 2 is an explanatory diagram of a concave lens formed on an object to be measured in the dark-field photothermal conversion spectroscopic analyzer according to the present invention.

FIG. 3 is a light quantity change diagram for each of pump light and probe light in the dark-field photothermal conversion spectroscopic analyzer according to the present invention.

FIG. 4 is a configuration diagram of a conventional photothermal conversion spectrometer.

[Explanation of symbols]

50 ... Pump light source, 52 ... Optical chopper, 54 ... Dichroic mirror, 56 ... Pinhole plate, 56a ... Opening part, 58 ... Lens, 60 ... Probe light source, 62 ... Lens, 70 ... Object to be measured, 72 ... Thermal lens , 80 ... lens,
82 ... Shielding plate, 82a ... Shielding region, 82b ... Transmissive region,
84 ... Pump light absorption filter, 86 ... Photodetector, A ... Pump light, B, B1, B2 ... Probe light.

Claims (6)

[Claims] 1. A probe light is incident on a thermal lens formed on an object to be measured by being irradiated with pump light, and spectral analysis of the object to be measured is performed based on the probe light output from the thermal lens. A dark-field photothermal conversion spectroscopic analysis device, wherein a pump light source unit that outputs the pump light, a probe light source unit that outputs the probe light, the pump light and the probe light are input, and the pump An irradiation optical system that irradiates light at a predetermined position on the object to be measured to form the thermal lens, and irradiates the probe light at the predetermined position, and the thermal lens is not formed at the predetermined position. When the pump light and the probe light that are output from the object to be measured are provided with a shielding unit that shields the pump light and the probe light that are output from the predetermined position of the object to be measured, A dark-field type photothermometer comprising: a light receiving optical system that inputs and outputs a light beam other than the light beam blocked by the shielding unit; and a photodetector that detects the light beam output from the light receiving optical system. Conversion spectroscopic analyzer. 2. The dark-field photothermal conversion spectroscopic analyzer according to claim 1, wherein the pump light source unit includes a pump light modulator that modulates and outputs the pump light in a pulse shape. 3. The irradiation optical system adjusts the luminous flux diameter of the pump light to determine the total luminous flux of the pump light output from the DUT when the thermal lens is not formed at the predetermined position. The dark field type photothermal conversion spectroscopic analysis apparatus according to claim 1, further comprising: a light beam diameter adjusting unit that enters the shielding unit. 4. The irradiation optical system is provided between a combining means for combining the pump light and the probe light on the same optical axis, and between the combining means and the probe light source section. A first lens that focuses probe light on a first position, and a pump lens that is provided between the combining unit and the object to be measured to focus and irradiate the pump light on the predetermined position, and The second-field photothermal conversion spectroscopic analysis apparatus according to claim 1, further comprising: a second lens that irradiates the predetermined position with the probe light condensed at the position as a parallel light beam. 5. The irradiation optical system is provided between a combining means for combining the pump light and the probe light on the same optical axis, and between the combining means and the pump light source section,
The dark-field type photothermal conversion spectroscopic analyzer according to claim 1, further comprising: a condenser lens that condenses the pump light on the object to be measured. 6. An object scanning unit for relatively scanning the object to be measured in a direction perpendicular to an optical axis of the pump light incident on the object to be measured.
The dark-field photothermal conversion spectroscopic analyzer described.