WO2019049250A1

WO2019049250A1 - Spectrometry device

Info

Publication number: WO2019049250A1
Application number: PCT/JP2017/032204
Authority: WO
Inventors: 茉佑子高井; 啓太山口
Original assignee: 株式会社日立ハイテクノロジーズ; 茉佑子高井; 啓太山口
Priority date: 2017-09-07
Filing date: 2017-09-07
Publication date: 2019-03-14
Also published as: JPWO2019049250A1; JP6782849B2

Abstract

The objective of the present invention is to reduce or eliminate the influence on spectrometry of scattering by particles composing an object of measurement. This objective is achieved by a spectrometry device comprising an electromagnetic wave irradiation unit for irradiating electromagnetic waves, a light reception unit for receiving electromagnetic waves, a probe light irradiation unit for irradiating probe light, a probe light detection unit for detecting probe light and outputting a detection signal, a calculation unit for calculating the detected intensity of the electromagnetic waves from the detection signal, and a beam diameter control unit for controlling the beam diameter of the probe light, said spectrometry device being characterized in that the electromagnetic wave irradiation unit irradiates electromagnetic waves onto an object of measurement, the light reception unit receives the electromagnetic waves irradiated onto the object of measurement, the probe light irradiation unit irradiates the probe light onto the light reception unit, the probe light detection unit detects the probe light irradiated onto the light reception unit and outputs a detection signal, the calculation unit calculates the detected intensity on the basis of the detection signal and the beam diameter of the probe light, and the beam diameter control unit controls the beam diameter of the probe light on the basis of the calculated detected intensity.

Description

Spectrometer

The present invention relates to a spectrometer which reduces or eliminates the influence of scattering of an object to be measured.

In recent years, medical product spectroscopy by electromagnetic waves such as terahertz waves has attracted attention. For example, there are many absorption peaks due to intermolecular vibration and intramolecular vibration in the terahertz frequency band where the frequency is 100 GHz or more and 30 THz or less, and it is necessary to identify not only the type of substance but also the difference in binding state by analysis of these peaks. It is also possible to quantitatively measure the concentration of each molecule in the drug.
As background art of this technical field, there exists Unexamined-Japanese-Patent No. 2014-173967, for example. Patent Document 1 states that "a sample inspection apparatus capable of suppressing a decrease in detection accuracy due to scattering of terahertz waves is provided" as a problem, and a solution means "a sample inspection apparatus according to the present invention is a terahertz wave A transport unit configured to transport the sample in the in-plane direction of the transport surface, the transport unit configured to transport the specimen in the in-plane direction of the transport surface; An irradiation direction changing unit that changes the irradiation direction of the terahertz wave that is emitted from the generation unit and is irradiated to the sample placed on the transport surface, and the sample placed on the transport surface is irradiated or transmitted A terahertz wave detection unit that detects the reflected terahertz wave, and the irradiation direction changing unit changes the irradiation direction by changing the position of the terahertz wave generation unit. It has been.
In the method of Patent Document 1, only the scattering of the electromagnetic wave due to the shape and arrangement of the measurement object is dealt with, and the removal of the scattering by the particles constituting the measurement object is not considered. Furthermore, the number of measurement points is increased, and although random scattered components can be removed, scattered components proportional to the frequency may not be removed.

Japanese Patent Application Laid-Open No. 2014-173967

An object of the present invention is to provide a technique for reducing or eliminating the influence of scattering by particles constituting an object to be measured in spectrometry.

The above problems include, for example, an electromagnetic wave irradiation unit that emits an electromagnetic wave, a light reception unit that receives an electromagnetic wave, a probe light irradiation unit that emits a probe light, and a probe light detection unit that detects the probe light and outputs a detection signal. The arithmetic unit for calculating the detection intensity of the electromagnetic wave from the detection signal, and the beam diameter control unit for adjusting the beam diameter of the probe light, the electromagnetic wave irradiation unit irradiates the electromagnetic wave to the object to be measured, and the light reception The unit receives the electromagnetic wave emitted to the object to be measured, the probe light irradiating unit irradiates the probe light to the light receiving unit, and the probe light detecting unit irradiates the probe light irradiated to the light receiving unit. The detection unit outputs a detection signal, and the calculation unit calculates the detection intensity based on the detection signal and the beam diameter of the probe light, and the beam is calculated based on the calculated detection intensity. Adjusting portion is solved by the spectral measurement device and controls the beam diameter of the probe light.

According to the present invention, it is possible to perform spectroscopic measurement in which the influence of scattering of the measurement object is reduced or eliminated.
Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the 1st Example of a spectrometry apparatus. A schematic view of the spatial distribution of the electric field or intensity of the terahertz wave on the detection crystal and the beam spot of the probe light. FIG. 2 is a schematic view showing an example of a beam diameter adjustment unit 20. (A) First adjustment flow of probe light beam diameter in the first embodiment. (B) Detailed flow of the first adjustment flow S2 of the probe light beam diameter in the first embodiment. FIG. 6 is a diagram showing the relationship between a probe light beam diameter and a calculated value in Embodiment 1. List of known parameters used to adjust probe light beam diameter (A) Second adjustment flow of probe light beam diameter in the first embodiment. (B) Detailed flow of the second adjustment flow S22 of the probe light beam diameter in the first embodiment. Diagram showing the correspondence between probe light beam diameter and difference value The block diagram which shows the 2nd Example of a spectrometry apparatus. Adjustment flow of probe light beam diameter in the second embodiment. FIG. 14 is a configuration diagram showing a case where the position of the detection nonlinear optical crystal 102 is controlled in the second embodiment of the spectrometry device. The block diagram which shows the 3rd Example of a spectrometry apparatus. The block diagram which shows the 4th Example of a spectrometry apparatus. FIG. 14 is a block diagram of an image sensor in a fourth embodiment. The block diagram which shows the 5th Example of a spectrometry apparatus. Adjustment flow of probe light in the sixth embodiment.

The following description will be given taking a terahertz wave as an example of the electromagnetic wave.

FIG. 1 is a block diagram schematically showing a first embodiment of the terahertz spectrometer of the present invention. The terahertz spectrometry apparatus according to the present embodiment is configured as an apparatus for irradiating the terahertz wave T1 to the measurement object 101 and measuring the amplitude of the transmitted terahertz wave T2 absorbed or scattered by the substance constituting the measurement object 101. There is.
The terahertz wave T <b> 1 emitted from the terahertz wave generation unit 1 is focused on the measurement target object 101 by the focusing element 111. The transmitted terahertz wave T2 absorbed or scattered by the substance constituting the measurement object 101 is incident on the non-linear optical crystal 102 for detection.

The probe light source 2 of FIG. 1 emits a probe light L1 for detecting a terahertz wave. The probe light L1 enters the beam diameter adjustment unit 20, and the beam diameter is expanded or reduced to become probe light L2 having a beam diameter B. Thereafter, the probe light L2 is polarized by the polarizer 301, is reflected by the beam splitter 311, and is incident on the non-linear optical crystal 102 for detection. A wavelength selection mirror may be inserted between the measurement object 101 and the detection nonlinear optical crystal 102, and the probe light L2 may be incident from the surface of the detection nonlinear optical crystal 102. Here, the wavelength selection mirror is an optical element that transmits the terahertz wave T2 and reflects the probe light L2, and includes, for example, a pellicle or a silicon plate.

When the terahertz wave T2 is incident on the detecting nonlinear optical crystal 102, an electro-optical effect is generated, and the birefringence of the detecting nonlinear optical crystal 102 changes according to the amplitude of the incident terahertz wave T2. The probe light transmitted or reflected by the detection nonlinear optical crystal 102 changes its polarization state in accordance with the change in birefringence. The probe light L2 transmitted from the beam splitter 311 among the probe light L2 reflected from the detection nonlinear optical crystal 102 and whose polarization state has changed is analyzed by the compensator 302 and the polarizer 303 to detect the change in polarization state, and the detector 304 The intensity of the probe light L2 is detected by The component of the probe light incident on the detector 304 is converted into, for example, a voltage, and is input to the measurement unit 321 of the processing unit 3. The signal input to the measurement unit 321 is proportional to the electric field or the intensity of the terahertz wave T2 incident on the detection nonlinear optical crystal 102. Here, when measuring the intensity, it is possible to use, for example, a method of making the transmission axes of the polarizer 301 and the polarizer 303 orthogonal and making the fast axis or the slow axis of the compensator 302 coincide with the transmission axis of the polarizer 303. When the electric field is measured, for example, the transmission axes of the

polarizers

301 and 303 can be orthogonal to each other, and the fast or slow axis of the compensator 302 can be obtained by making the transmission axis of the polarizer 303 an angle larger than 0 degrees. . A Wollaston prism is disposed instead of the polarizer 303, the probe light is divided into two paths, the detector 304 is a balance detector, and the detection efficiency is improved by detecting the intensity difference of the probe light of each optical path. Also good.

By the above procedure, a signal proportional to the intensity or the amplitude of the terahertz wave of the portion on the detection nonlinear optical crystal 102 irradiated with the probe light L2 is obtained. In the present invention, adjustment control of the beam diameter B of the probe light L2 is performed by the beam diameter adjustment unit 20 so that the terahertz wave T2 widely distributed on the detection crystal can be measured by the scattering by the measurement object 101. FIG. 2 shows a schematic view of a beam spot L3 of probe light distributed on the detection nonlinear optical crystal 102 and a spatial distribution T3 of the terahertz wave T2 spread by the scattering on the measurement object.

It is assumed that the beam diameter B of the probe light L2 adjustable by the beam diameter adjusting unit 20 can change the range from the minimum value 602 to the maximum value 604.
Here, one of the specific examples of the method of changing the probe light beam diameter B by the beam diameter adjustment unit 20 will be described. FIG. 3 shows a schematic view of the probe light beam diameter adjusting unit 20 in the present embodiment. In this embodiment, the case where the probe light beam diameter adjustment unit 20 includes the concave lens 201 and the

convex lenses

202 and 203 forming the focus variable optical system is shown. Besides, any combination of lenses and optical elements may be used as long as the ratio of the beam diameters A and B is variable. These lenses are disposed on the rails 211, are driven by the controller 212, and are movable in parallel on the optical axis of the probe lights L1 and L2. In this embodiment, when the refractive index of the lens 202 is f ₁ , the refractive index of the lens 203 is f ₂ , and the distance between the lenses is d ₂ , when the

lenses

202 and 203 are combined, it can be regarded as a convex lens of the focal distance f. . The focal length f can be expressed as equation 1.

(Formula 1) f = f ₁ f ₂ / (f ₁ + f ₂ -d ₂ )
Here, the focal length F is the distance from the principal point P of the

compound lenses

202 and 203 to the focal point. The principal point P is at a distance h ₁ from the lens 202 and a distance h ₂ from the lens 203. The ratio of h ₁ to h ₂ is expressed by Equation 2.

(Expression 2) h ₁ / h ₂ = f ₁ / f ₂
Further, assuming that the focal length of the concave lens 201 is f ₃ , the distance d ₁ from the principal point p of the

compound lenses

202 and 203 to the concave lens 201 is a position represented by Formula 3.

(Expression 3) d ₁ = f−f ₃
As a result, the ratio A / B of the beam diameters of the probe lights L1 and L2 can be expressed as Expression 3.

(Expression 4) A / B = f ₃ / f
In summary, the value of f is determined so that the ratio A / B of the beam diameters of the probe lights L1 and L2 becomes a desired value, and a control signal is sent to the controller 212 so that the value of F can be obtained. The positions of the lenses 201 to 203 are adjusted to change D _2, and D ₁ is further changed to satisfy Formula 3.

Further, the controller 212 holds the position information of the

complex lenses

202 and 203 and the concave lens 201, and has a function of calculating the probe beam diameter B from the position information and the value of the probe beam diameter A determined by the probe light source 2. The method of calculating the probe beam diameter B is not limited to the above. For example, the controller 212 holds only the position information of the

compound lenses

202 and 203 and the concave lens 201, and the calculation of the probe light beam diameter B is performed by the calculation unit 322 of FIG. You may

The method of changing the beam diameter ratio A / B of the probe lights L1 and L2 by changing the position of the lens whose focal length is fixed has been described as a method of changing the beam diameter B by the beam diameter adjusting unit 20 as described above. Is an example and is not limited thereto. Besides, for example, instead of the

compound lenses

202 and 203, convex lenses of different focal lengths are set in an exchangeable holder to make the focal length and the lens position variable, and the distance of the concave lens 201 corresponds to the focal length of the convex lens. To change the beam diameter.

The following shows the flow of adjusting the probe light in the present embodiment. This adjustment is performed, for example, when the apparatus is started. First, FIG. 4A shows a flowchart of probe light adjustment in the present embodiment.
In this embodiment, the detection intensity proportional to the electric field or intensity of the terahertz wave T2 is calculated from the signal inputted to the measurement unit 321, and the probe light beam diameter B is adjusted to the beam diameter adjustment unit so that the terahertz wave detection intensity becomes large. Adjust by 20. In S21, the correspondence between the probe light beam diameter B and the detected intensity (calculated value) of the tera-hertz wave is determined. A curve 601 in FIG. 5 is a curve showing the correspondence between the probe light beam diameter B and the tera-hertz wave detection intensity (calculated value). The details of the procedure S22 will be described later.
In step S22, the probe light beam diameter 603 in FIG. 5 is determined from the correspondence relationship determined in step S21 so that the calculated value calculated by the calculation unit 322 is maximum and the beam diameter is reduced. Here, for example, in consideration of the control accuracy of the beam diameter adjusting unit 20 that controls the probe light beam diameter B, the calculated value may have a width such as ± 20% variation with respect to the maximum value.
In step S23, a control signal is output from the control unit 323 to the probe light beam shape adjustment unit 20 so as to be close to the probe light beam diameter 603 obtained in step S22, and the probe light beam system is changed. By performing the measurement after adjusting the probe light beam diameter according to the above-described procedure, it is possible to perform the spectral measurement in which the influence of the scattering generated by the substance constituting the object to be measured 101 is reduced or eliminated.

Once the probe light beam diameter B is adjusted, measurement may be performed continuously without performing adjustment. In the case where the correspondence between the probe light beam diameter B and the calculation value calculated by the calculation unit 322 is once acquired under the same measurement conditions and stored in the storage unit 324 of FIG. You may omit it. If the beam diameter 603 in FIG. 5 is known, the value of the beam diameter 603 in FIG. 5 may be directly input from the input unit 325 to the calculation unit 322, and the process may proceed to S24 without performing S22 and S23.

FIG. 4B shows the details of step S22. The number of times of measurement is set in S201. In S202, the measurement unit 321 determines the intensity of the probe light incident on the detector 304 as a measurement value, and in S203 the measurement value of the probe light obtained by the calculation unit 322 and the beam diameter B of the probe light obtained from the beam diameter adjustment unit 20 Calculate the product of Here, this operation is not limited to a product, but may be division. A curve 601 in FIG. 5 is a curve showing the correspondence between the probe light beam diameter B and the calculation value calculated by the calculation unit 322. The probe light beam diameter B starts to change from the small beam diameter 602 or the large beam diameter 604, and measurement is performed, and the result is stored in the storage unit 324. In S205, it is determined whether or not the number set in S201 has been reached, and the beam diameter B is changed by the beam diameter adjustment unit 20 in S206 until the set number is reached, the procedure of S202 to S204 is repeated, and the number of measurements is If the number of times set in S201 is reached, the process proceeds to S207 and the curve 601 is obtained.

It is also possible to use the result calculated using known parameters for adjusting the probe light beam diameter. For example, when the average particle diameter and refractive index of particles contained in the measurement object and the constituent substance of the measurement object are known, it is not necessary to perform multiple measurements for adjusting the probe light beam diameter, and S21 This can be shortened, and high-speed probe light beam diameter adjustment becomes possible. The flowchart of the probe light adjustment in this case is as follows. First, as parameters to be input to the input unit 325 of FIG. 1 in S21, for example, there are the average particle diameter and the refractive index of the particles that constitute the object to be measured. The input parameter is acquired by the calculation unit 322 and stored in the storage unit 324. In addition, the wavelength or frequency of the terahertz wave T1 emitted from the terahertz wave irradiation unit 1 is acquired by the calculation unit 322, and is similarly recorded in the storage unit 324.

In S22, based on the parameters stored in the storage unit 324 in S21 and the distance between the object to be measured 101 and the nonlinear optical crystal for detection 102, the magnitude of scattering of terahertz waves on the surface of the nonlinear optical crystal for detection 102 is calculated. For example, when the average particle diameter and average refractive index of the object to be measured and the wavelength of the incident terahertz wave T1 are known, the scattering angle range of the terahertz wave T2 is estimated according to the theoretical formula of Mie scattering, and the determined scattering angle range and measurement From the distance between the object 101 and the detection nonlinear optical crystal 102, the magnitude of the spread angle T3 of the spatial distribution of the terahertz wave on the detection nonlinear optical crystal 102 may be determined using a trigonometric function. The target probe beam diameter is determined so that the spatial distribution T3 of the terahertz wave can be widely acquired. Finally, the control unit 323 outputs a control signal so as to approach the probe beam diameter 603, and the probe light beam diameter adjustment unit 20 changes the probe light beam diameter B. According to the above-described procedure, after the adjustment of the probe light beam diameter B is performed, by starting the measurement, it is possible to perform the spectral measurement in which the influence of the scattering generated in the substance constituting the measurement object 101 is reduced or eliminated.

Also, known parameters used to adjust the probe light beam diameter may be stored in the storage unit 324 as a list, and may be called by the control unit 323 as needed. FIG. 6 shows a schematic view of the list. The parameters shown in this schematic diagram are not limited to this. In addition, the optimum probe light beam diameter may be automatically learned from the measurement result and the name of the measurement object input to the input unit 325, and a list may be generated and stored. Known parameters used to adjust the probe light beam diameter include, for example, the probe light beam diameter and the position of the optical element included in the beam diameter adjustment unit 20.
Furthermore, measurement conditions (for example, measurement object name, probe light beam diameter, etc.) are input to the calculation unit 322 by the input unit 325, and the calculation unit searches past measurement results based on the list, and measurement conditions (past measurement conditions) For example, the lens position or the like included in the beam diameter adjustment unit 20 may be applied to this measurement.

In addition, a distance measurement unit that acquires the distance between the detection nonlinear optical crystal 102 and the measurement object 101 and a distance adjustment unit that adjusts the distance are added, and control signals are transmitted from the control unit 323 to the distance adjustment unit. By doing this, the distance between the detection nonlinear optical crystal 102 and the measurement object 101 may be reduced, and the spread angle of the scattered light by the measurement object may be suppressed.
Furthermore, an example of performing measurement for probe light beam diameter adjustment will be shown below. According to this configuration, it is possible to perform the spectroscopic measurement after confirming the reduction of the influence of the scattering.
In the present embodiment, a measurement target (reference sample) to be a reference, which is a component similar to the original measurement target (target sample) and has less scattering, is separately prepared as the measurement target object 101. For example, the same tablet as the target sample is ground in a mortar, sieved to a sufficiently small particle size, and compressed again.

FIG. 7A shows a flowchart of the probe light adjustment in this case. First, in step S21, the terahertz wave detection intensity (calculation value) of the reference sample is measured and stored in the storage unit 324. Thereafter, in S22, the calculated value of the target sample is repeatedly measured while changing the size of the probe light beam diameter B. Details will be described later. The result is stored in the storage unit 324. In the reference measurement S21 and the adjustment measurement S22, the measurement may be performed not at a plurality of frequencies but at a single frequency. In S23, from the result of the adjustment measurement stored in S22 (a difference value to be described later), the operation unit 322 in FIG. In S24, the control unit 323 outputs a control signal so as to approach the probe beam diameter 803 obtained in S23, and the probe light beam diameter adjustment unit 20 changes the probe light beam diameter B.

FIG. 7B shows the details of step S22. The number of times of measurement is set in S201. In S202, the measurement unit 321 acquires the intensity of the probe light incident on the detector 304 as a measurement value, and in S203, the calculation unit 322 obtains terahertz wave detection intensities (calculation values) at a plurality of or single frequencies. Further, a difference value is calculated by subtracting the calculated value of the reference sample stored in S21 from the calculated value of the target sample. In S204, the difference value obtained in S213 is stored. A curve 801 in FIG. 8 is a curve showing the correspondence between the probe light beam diameter B and the difference value calculated by the calculation unit 322. The probe light beam diameter B starts to change from the small beam diameter 602 or the large beam diameter 604, the measurement is performed, and the result is stored in the storage unit 324 as described above. In S205, it is determined whether or not the number set in S201 has been reached, and the beam diameter B is changed by the beam diameter adjusting unit 20 in S206 to repeat the procedure of S202 to S204 until the set number is reached. When the number of times of measurement reaches the number of times set in S201, the process proceeds to S207 and the curve 801 is obtained. Thereafter, the beam diameter 803 in which the difference value of the difference values stored in S23 is the smallest is calculated and acquired in S21.

By determining and applying the probe light beam diameter 803 by which the difference between the result of adjustment measurement and the result of reference measurement is reduced by the above-described procedure, the influence of scattering generated in the substance constituting the object to be measured 101 can be reduced or eliminated more accurately. Spectral measurement is possible.

FIG. 9 is a block diagram schematically showing a second embodiment of the terahertz spectrometer of the present invention. The present embodiment differs from the first embodiment in that the imaging result of the spatial distribution of the terahertz wave is used to adjust the probe light beam diameter B. According to this configuration, since the beam diameter of the probe light can be controlled while observing the actual spatial distribution of the terahertz wave, it is not necessary to perform a plurality of measurements and accurate adjustment becomes possible.
In this embodiment, the difference from the first embodiment will be described.

An imaging lens 312 is disposed behind the non-linear optical crystal 102 for detection, a beam is divided by a half mirror 313, one is incident on an image sensor 305, and the other is incident on a detector 304. The probe light L3 including the information of the spatial distribution T3 of the terahertz wave on the detection nonlinear optical crystal 102 as shown in FIG. Here, for example, without arranging the half mirror 313 and the detector 304, both imaging and intensity measurement of the spatial distribution T3 of the terahertz wave on the detection crystal may be performed by the image sensor 305.

FIG. 10 shows a flowchart of probe light adjustment in the present embodiment. The probe light beam diameter B is set to the maximum value 604 in S11. When the terahertz wave imaging to be described next can not be performed due to insufficient probe light intensity or the like at the maximum value 604, the probe light beam diameter B is changed to a diameter at which imaging is possible. At this time, when the size of the terahertz wave irradiation portion T3 on the detection crystal becomes larger than the probe light beam diameter B, the distance between the measurement object and the detection nonlinear optical crystal 102 is adjusted using the method described in the seventh embodiment. And the size of T3 may be reduced.
When the terahertz wave T2 is incident on the detecting nonlinear optical crystal 102, an electro-optical effect is generated, and the birefringence of the detecting nonlinear optical crystal 102 changes according to the amplitude of the incident terahertz wave T2. The probe light transmitted or reflected by the detection nonlinear optical crystal 102 changes its polarization state in accordance with the change in birefringence.
In S12, the probe light incident on the image sensor 305 is imaged by the measurement unit 321 of the processing unit 3 and is output as a detection image. Similar to the method described in the first embodiment, the calculation unit 322 calculates the spatial distribution T3 on the nonlinear optical crystal 102 for detection of the electric field or intensity of the terahertz wave from the detection image.

In S13, the difference between the size of the spatial distribution of the terahertz wave irradiated to the light receiving unit and the beam diameter of the probe light obtained from the beam diameter adjusting unit is calculated by the calculation unit 322 from the detected image, and the difference becomes smaller The probe light beam diameter B is determined as follows.

In S14, the control unit 323 outputs a control signal so as to approach the probe beam diameter obtained in S13, and changes the probe light beam diameter B. According to the above-described procedure, after the adjustment of the probe light beam diameter B is performed, by starting the measurement, it is possible to perform the spectral measurement in which the influence of the scattering generated in the substance constituting the measurement object 101 is reduced or eliminated.
Here, for example, in S13 of FIG. 10, the spatial distribution T3 of the terahertz wave is photographed, and as a result, it is estimated that the size of the spatial distribution T3 of the terahertz wave is larger than the maximum value 604 of the beam diameter B of the probe light In this case, adjustment is made to bring the non-linear optical crystal for detection 102 closer to the measurement object 101 to reduce the size of the spatial distribution T3 of the terahertz wave. FIG. 11 schematically shows the terahertz spectrometer in this example. FIG. A different point from FIG. 9 is that the position of the detection nonlinear optical crystal 102 is controlled in addition to the beam diameter adjustment unit 20 by the control signal from the control unit 323. The non-linear optical crystal 102 for detection is driven by a motor 1021, and the position information is held by the motor 1021.

As a method of reducing the distance between the non-linear optical crystal for detection 102 and the measurement object 101, for example, the thickness of the measurement object 101 is input to the input unit 325 of FIG. There is a method of controlling the motor 1021 by a control signal of the control unit 323 so that the distance between the crystal 102 and the measurement object 101 is larger than the thickness of the measurement object 101 and closer to the original position. By the above method, the size of the spatial distribution T3 of the terahertz wave can be reduced.

FIG. 12 is a block diagram schematically showing a third embodiment of the terahertz spectrometer of the present invention. The present embodiment differs from the first embodiment in that an interference optical system is combined as a detector. According to this configuration, when the amplitude of the terahertz wave T2 to be detected is weak, the signal can be amplified and measured, and the sensitivity of the measurement can be improved.
In this embodiment, the difference from the first embodiment will be described.

Interferometric optics 306 of FIG. 12 includes a detector. The interference optical system 306 receives the probe light transmitted or reflected by the detection nonlinear optical crystal 102 and the reference light L4 for causing the probe light to interfere. The detector included in the interference optical system 306 detects interference light in which the probe light and the reference light L4 interfere with each other. An independent laser may be used as the reference light source 4, or light may be branched from a laser included in a probe light source or a terahertz wave light source using a beam splitter or the like to be the reference light L4. As a method of selecting the frequency of the reference light L4, for example, there is a heterodyne method not matched with the frequency of the probe light or a homodyne method matched with the frequency of the probe light. In the case of the homodyne method, there is a method of separating and measuring the phase and amplitude of the interference light by, for example, a four-phase simultaneous detection method or a phase shift method. According to the above-described method, it is possible to perform the spectral measurement and the sensitivity improvement in which the influence of the scattering generated in the substance constituting the measuring object 101 is reduced or eliminated.

FIG. 13 is a configuration diagram schematically showing a fourth example of the terahertz spectrometry apparatus of the present invention. The present embodiment differs from the first embodiment in that the detector is replaced by an image sensor. Moreover, what is to be measured is an electric field of terahertz wave (terahertz electric field). When measuring the terahertz electric field, when the phase is not uniform in the beam spot T3, the spatial distribution of the terahertz electric field is integrated in the measurement of the single detector, so that the positive and negative electric fields cancel each other and the measurement is performed. The signal proportional to the terahertz electric field may be small. According to this configuration, the influence can be eliminated from the result of the spectroscopic measurement.
In this embodiment, the difference from the first embodiment will be described.

A schematic view of the image sensor 305 is shown in FIG. The probe light beam spot L3 on the detection crystal is imaged on the image sensor 305, and a signal proportional to the terahertz wave electric field spatial distribution T3 is measured at each pixel. The result of each pixel is converted to an intensity and then the average value of the intensity at the required pixel is obtained. For example, assuming that the terahertz electric field detected by the pixel 321 is E ₁ and the terahertz electric field detected by the pixel 322 is E ₂ ..., The detection intensity I is I = (| E ₁ | ² + | E ₂ | ² + ·· It may be calculated as: · · · / (number of pixels added).
When performing phase measurement, that is, measuring the time waveform of the electric field, such as terahertz time domain spectroscopy, measure the time waveform E ₁ (t), E ₂ (t) ... of the electric field at each pixel and then at each pixel. Each is subjected to time-wise Fourier transformation to obtain an intensity for each wavelength and then integration is performed.

According to the above-described method, it is possible to perform the spectral measurement and the sensitivity improvement in which the influence of the scattering generated in the substance constituting the measuring object 101 is reduced or eliminated.

FIG. 15 is a block diagram schematically showing a fifth embodiment of the terahertz spectrometer of the present invention. The present embodiment is different from the first embodiment in that a condensing element 112 is inserted between the measuring object 101 and the non-linear optical crystal 102 for detection. According to this configuration, it is possible to separate and measure the distance between the light collecting element 112 and the object to be measured 101.
In this embodiment, the difference from the first embodiment will be described.

The numerical aperture (NA) of the focusing element 112 is designed as large as possible so as to sufficiently collect the scattered light of the object to be measured. For example, a combination of two plano-convex lenses or parabolic mirrors as the focusing element 112 or a single biconvex lens such that the distance between the object to be measured 101 and the nonlinear optical crystal 102 for detection is twice the focal length There is one placed in In the present embodiment, the beam diameter B of the probe light has a difference with the size of the terahertz wave spatial distribution T3 including the scattering component focused on the detection nonlinear optical crystal 102 by the focusing element 112 according to the first and second embodiments. It is controlled to be smaller. When the target probe light beam diameter is obtained by calculation in the calculation unit 322 according to the first embodiment, the measurement object 101 is obtained in order to obtain the terahertz wave spatial distribution T3 including the scattered component collected on the detection nonlinear optical crystal 102. In addition to the light scattering, the effect of light collection by the light collection element 112 may be determined by ray tracing. Alternatively, the size of the spatial distribution T3 may be calculated as follows. When the thickness of the measurement object and D _SAMPLE, the scattering angle range ± theta obtained from the parameters and the incident terahertz wavelength of the particles contained in the measurement object in accordance with the theory of Mie scattering as described in Example 1, from D _SAMPLE, condenser The approximate size 2D _SAMPLE tanθ of the spatial distribution T3 of the terahertz wave formed on the detection nonlinear optical crystal 102 by the element 112 is determined.

By the above method, since the distance between the object to be measured 101 and the light collecting element 112 can be separated, it is possible to cope with the case where the thickness of the object to be measured 101 is thick. Spectroscopic measurement with reduced or eliminated influence is possible.

In this embodiment, an optical axis adjustment unit for adjusting the optical axis of the probe light and an intensity distribution adjustment unit are provided in the probe light beam diameter adjustment unit 20 and adjustment is performed. This configuration can increase the detection efficiency of the signal detected by the detector 304.
In this embodiment, the difference from the first embodiment will be described.

FIG. 16 shows a flowchart of probe light adjustment in the present embodiment. First, at F5, the probe light diameter B is set to the minimum value 302, and at S31, the central portion of the spatial distribution T3 of the electric field or intensity of the terahertz wave, that is, the detection intensity of the terahertz wave detected by the detector 304 is maximized Control the adjustment unit. Thereafter, in step S32, the probe light beam diameter B is adjusted by the control of the beam diameter adjusting unit 20 according to the first to third embodiments. Finally, in S33, the intensity distribution adjustment unit makes the intensity distribution of the probe light uniform in the plane. As a method of adjusting the intensity distribution, for example, there is a method of cutting out only the center portion of the probe light beam with an iris.
The adjustment result of the optical axis or the intensity distribution of the probe light may be confirmed by imaging the beam spot T2 of the probe light on the crystal 102 using the image sensor 305 in the same configuration as that of the second embodiment or the fourth embodiment. . At that time, for example, when the probe light is attenuated by the direction of the compensator 302 or the

polarizers

301 and 303 and the entire probe light beam spot L3 is not reflected on the image sensor, the compensator 302 or the

polarizer

301 or 303 is Or manually rotate it so that the entire probe light beam spot L3 is captured and then imaged.

By the above method, the detection efficiency of the signal detected by the detector 304 can be increased. Furthermore, it is possible to perform spectroscopic measurement with reduced or eliminated the influence of scattering generated by the substance constituting the measurement object 101.
The present invention can be applied to measurements other than spectrometry. Applications include, for example, measurements that are affected by scattered light, such as terahertz CT scanning and imaging with absorptivity and reflectivity. Furthermore, as described earlier, the wavelength of incident light used for measurement is not limited to terahertz waves, and may be infrared rays or electromagnetic waves having a wavelength shorter than infrared rays, for example, or wavelengths longer than millimeter waves or millimeter waves Even electromagnetic waves of In this case, if the terahertz wave is replaced with an electromagnetic wave in the above description, the above description is applied as it is. Therefore, the description of electromagnetic waves other than terahertz waves is omitted here.

101: measurement object, 102: nonlinear optical crystal for detection, 111: focusing element, 20: probe light beam diameter control unit, 3: beam control signal generation unit, 301. Polarizer 302 Compensator 303 Polarizer 304 Detector T1 Incident terahertz wave T2 Emitted terahertz wave L1 Probe light L2・ Adjusted probe light

Claims

An electromagnetic wave irradiation unit that irradiates an electromagnetic wave;
A light receiving unit that receives an electromagnetic wave;
A probe light irradiator for irradiating a probe light;
A probe light detection unit that detects the probe light and outputs a detection signal;
An arithmetic unit that calculates detection strength of an electromagnetic wave from the detection signal;
A beam diameter control unit that adjusts a beam diameter of the probe light;
The electromagnetic wave irradiation unit irradiates the object to be measured with the electromagnetic wave,
The light receiving unit receives the electromagnetic wave emitted to the measurement object,
The probe light irradiation unit irradiates the probe light to the light receiving unit,
The probe light detection unit detects the probe light irradiated to the light receiving unit, and outputs a detection signal.
The calculation unit calculates the detection intensity based on the detection signal and the beam diameter of the probe light.
The beam diameter adjusting unit controls the beam diameter of the probe light based on the calculated detected intensity.
The spectrometer according to claim 1, wherein
The said probe light detection part outputs the detection signal corresponded to the polarization state or intensity | strength change of the probe light irradiated to the said light-receiving part.
The spectrometer according to claim 2, wherein
A storage unit that stores data related to measurement;
And an input unit for inputting measurement parameters to the arithmetic unit;
The calculation unit selects the measurement condition corresponding to the measurement parameter based on the measurement condition information stored in the storage unit input to the calculation unit;
A spectrometric apparatus characterized in that the selected measurement condition is applied to this measurement.
The spectrometer according to claim 2, wherein
And an image sensor that outputs a detection image of a spatial distribution of changes in polarization state or intensity of the probe light,
The calculation unit calculates the difference between the spread width of the spatial distribution of the electromagnetic wave irradiated to the light receiving unit from the detection image and the beam diameter of the probe light obtained from the beam diameter adjusting unit,
The spectrometer according to claim 1, wherein the beam diameter adjusting unit controls a beam diameter of the probe light based on the difference.
The spectrometer according to claim 2, wherein
The said light receiving part is a nonlinear optical crystal, The spectroscopy measuring apparatus characterized by the above-mentioned.
The spectrometer according to claim 2, wherein
The probe light irradiation unit includes an intensity distribution adjustment unit that adjusts an in-plane intensity distribution of the probe light, and an optical axis adjustment unit that changes an optical axis of the probe light.
The intensity distribution adjusting unit controls the intensity distribution in a direction in which the in-plane intensity distribution of the probe light becomes uniform,
The optical axis adjustment unit controls the optical axis of the probe light based on the detection signal output from the probe light detection unit.
The spectrometer according to claim 3, wherein
The measurement parameters include the particle size and the refractive index of the particles contained in the measurement object,
The calculation unit is characterized in that the detection intensity of the electromagnetic wave is calculated based on the spread width of the spatial distribution of the electric field or intensity of the electromagnetic wave in the light receiving unit, and the measurement condition is updated based on the calculated detection intensity. Spectroscopic measuring device.
The spectrometer according to claim 2, wherein
A storage unit for recording the first result of spectral measurement of the first measurement object;
The difference between the second result spectrally measured by the second measurement object and the first result stored in the storage unit is calculated by the calculation unit, and the beam diameter adjustment is performed based on the calculation result of the calculation unit A control unit for controlling a unit, wherein the beam diameter adjusting unit is controlled so that the difference between the calculation results becomes small.
The spectrometer according to claim 2, wherein
A reference light generation unit that generates reference light;
An interference optical system that causes the probe light and the reference light to interfere with each other;
A spectrometric measurement apparatus characterized in that an interference optical system causes interference between reference light generated from a reference light generation unit and probe light incident on the probe light detection unit to amplify the detection signal.
The spectrometer according to claim 2, wherein
A distance measuring unit that acquires a distance between the measurement object and the light receiving unit;
A distance adjustment unit that adjusts the distance between the measurement object and the light receiving unit;
Equipped with
The spread width of the spatial distribution of the electric field or intensity of the electromagnetic wave in the light receiving portion is reduced to increase the detection signal,
A spectrometer according to claim 1, wherein the distance adjusting unit controls the distance between the object to be measured and the light receiving unit to be smaller based on an output from the distance measuring unit.
The spectrometer according to claim 2, wherein
It includes a light-collecting element that irradiates the object to be measured and condenses an electromagnetic wave transmitted or reflected by the object to be measured on the light receiving unit,
The said light collection element is arrange | positioned so that the said electromagnetic wave which spread by scattering may be condensed, and the said detection signal may become large.
The spectrometer according to claim 2, wherein
The probe light detection unit includes an image sensor that outputs a detection image of a spatial distribution of changes in polarization state or intensity of probe light transmitted through or transmitted and reflected by the light reception unit,
The arithmetic unit calculates the electric field of the electromagnetic wave at each pixel of the image sensor, calculates the intensity from the electric field at each pixel, integrates the intensity at the pixel where information of the electromagnetic field at least exists, A spectrometry apparatus characterized by performing measurement so that detection intensity goes up.