JP2022035080A - Spectroscopy measuring device - Google Patents

Abstract

To make it less susceptible to changes in environmental conditions and structural disturbances so that highly reliable arbitrary wavelength selective spectroscopic measurement can be stably performed.SOLUTION: Supercontinuum light emitted from a light source 1 that emits light in a band including a plurality of selectable wavelengths is wavelength-divided by a waveguide type wavelength dividing element 2, and light having a specific wavelength is modulated by an electro-optical modulator as a modulation element 3 and is selectively irradiated to an object S. The light transmitted through the object S is received by a light receiver 7, and its output is processed by a data processing unit 8 to obtain a spectroscopic measurement result.SELECTED DRAWING: Figure 1

Description

The invention of this application relates to a technique of spectroscopic measurement for measuring the optical characteristics of an object at a specific wavelength.

A spectroscopic measurement technique in which an object is irradiated with light and the transmitted light or reflected light from the object is separated by a spectroscope to measure the spectrum is one of the typical methods for material analysis. A typical spectroscopic measurement method is a method using a diffraction grating. The light to be measured incident from the incident slit is converted into parallel light by a concave mirror and irradiated to the diffraction grating, the dispersed light from the diffraction grating is similarly condensed by the concave mirror, and a light receiver is placed at the condensing position for detection. By changing (scanning) the attitude of the diffraction grating, light of different wavelengths is sequentially incident on the light receiver, and the output of the light receiver becomes a spectral spectrum.

In the technical field of such spectroscopic measurement, a device that selectively receives only light of a specific wavelength with a light receiver is known. Patent Document 1 and Patent Document 2 disclose this type of device.
If you want to selectively receive only light of a specific wavelength, you can either receive it through a filter such as a bandpass filter, or use a light source such as a laser that emits only light of a specific wavelength to light the object. A configuration is conceivable in which light is received from the object by irradiating it. However, with such a method, it is difficult to change the selected wavelength. It is conceivable to prepare a large number of filters and replace them, but this is expensive and structurally complicated. It is also unrealistic in terms of cost and structure to irradiate light while preparing a large number of light sources having different wavelengths and exchanging them. Therefore, the devices of Patent Document 1 and Patent Document 2 have been proposed.

The devices proposed in these patent documents spatially disperse the light from a light source that emits light in a wavelength band that is wide to some extent (a band that includes wavelengths that may be selected) by a dispersion element such as a diffraction grating. A spatial optical modulator such as a digital mirror device (DMD) is configured to selectively extract and use only light of a specific wavelength. The wavelength to be selected is changed by controlling the spatial light modulator.
In addition to the above patent documents, those using a prism as a dispersion element (Non-Patent Document 1) and those using an LCOS (Liquid Crystal on Silicon) type spatial light modulator (Non-Patent Document 2) are known. ..

U.S. Pat. No. 8,406,859 Japanese Unexamined Patent Publication No. 2004-361201

Applied Optics, Vol. 56, No. 8 / March 10 2017 / 2359-2367 NATURE PHOTONICS | VOL 10 | AUGUST 2016 534-541 J. Plasma Fusion Res. Vol.92, No.12 (2016) 917-921

In the devices disclosed in the above-mentioned patent documents and non-patent documents, a space dispersion element such as a diffraction grating or a prism is used, and light is selected by wavelength division in free space. Therefore, there is a problem that it is easily affected by environmental conditions such as temperature and disturbance such as vibration, and highly reliable measurement cannot be performed stably.

For example, in a dispersion element such as a diffraction grating or a prism, the refractive index changes depending on the temperature, and the position where the dispersed light of each wavelength travels slightly changes. For this reason, the position when the light reaches the spatial light modulator such as DMD also changes slightly, and the selected wavelength also deviates from the planned one. Spatial light modulators may also have temperature dependence, and the reproducibility of wavelength selection may decrease due to temperature changes. The reduced reproducibility of the selected wavelength is also caused by mechanical disturbances such as vibration. The dispersion position of each wavelength by the dispersion element is spatially displaced by vibration, and in the case of a mechanical spatial light modulator such as DMD, it is easily affected by mechanical disturbance. In particular, in the devices disclosed in the above-mentioned patent documents and non-patent documents, since the dispersive element and the spatial light modulator are connected via free space, the dispersive element and the spatial light are connected due to temperature changes and mechanical disturbances. Relative displacement of the modulator occurs and the selected wavelength is liable to change.
The present invention has been made to solve the above-mentioned problems in the technique of arbitrary wavelength selective spectroscopic measurement, and is less susceptible to changes in environmental conditions and mechanical disturbances, and has high reliability of arbitrary wavelengths. The purpose is to enable stable selective spectroscopic measurement.

In order to solve the above problems, the spectroscopic measuring apparatus of the present invention has a light source that emits light in a band containing a plurality of different wavelengths that can be selected, and a waveguide type wavelength dividing element that divides the light emitted from the light source into wavelengths. A modulation element that modulates the light so that the light of a specific wavelength is selectively irradiated to the object among the light of each wavelength divided by the wavelength dividing element, and the light modulated by the modulation element are irradiated. It is equipped with a light receiver that receives light from the object and a data processing unit that obtains the optical characteristics of the object with respect to the wavelength of the light selectively irradiated by the modulation element by processing the output from the light receiver. ing.
Further, in order to solve the above problems, in this spectroscopic measuring device, the waveguide type wavelength dividing element may be an array waveguide diffraction grating.
Further, in order to solve the above problems, in this spectroscopic measuring device, the modulation element may be an electro-optical modulator, a thermo-optical modulator, an acousto-optic modulator, or a mechanical fiber switch.
Further, in order to solve the above problems, the light source may be a fiber light source in this spectroscopic measuring device.
Further, in order to solve the above problems, the light source may be a supercontinuum light source in this spectroscopic measuring device.
Further, in order to solve the above problems, the spectroscopic measuring device may have a configuration in which the emission end of each wavelength in the waveguide type wavelength dividing element and the modulation element are connected by a relay fiber.
Further, in order to solve the above problems, this spectroscopic measuring device is provided with a modulation control unit that controls the modulation element so as to correspond to the replacement of the Hadamard mask, and the data processing unit processes the output from the receiver. Then, it may have a configuration that it is a unit that performs Hadamard spectroscopy.
Further, in order to solve the above problems, in this spectroscopic measuring device, the light receiver may be a two-dimensional array light receiver that receives light from an object in two dimensions.
Further, in order to solve the above problems, this spectroscopic measurement device is provided with a spectroscopic optical system that further disperses the light from the object irradiated with the light modulated by the modulation element, and the photoreceiver is spectroscopic optics. It may have a configuration in which the system is a light receiver that receives the dispersed light.
Further, in order to solve the above-mentioned problems, in this spectroscopic measurement device, the light source is a pulse light source, and a dividing element that divides the light modulated by the modulation element and irradiates one of the objects is provided, and receives light. The vessel is a fluorescence receiver that receives the fluorescence generated in the object irradiated with one of the divided lights, and is placed at a position where the other light divided by the dividing element is incident without passing through the object. The synchronous light receiver is provided, and the data processing unit may include a module that performs a time-correlated single photon counting method according to the output of the synchronous light source and the output of the fluorescent light source. ..

As described below, according to the spectroscopic measurement apparatus of the present invention, in the arbitrary wavelength selection type spectroscopic measurement apparatus, an array waveguide diffraction grating which is a waveguide type is used as a wavelength division element, and each wavelength divided is used. Since the light is modulated by a modulation element and is not configured for wavelength division and wavelength selection in free space, it is not easily affected by the usage environment and disturbance. Therefore, the accuracy of wavelength selection is high, and spectroscopic measurement of arbitrary wavelength selection can be performed accurately and stably.
Further, in a configuration in which the wavelength dividing element is an arrayed waveguide diffraction grating, it is easy to increase the number of divisions, which is preferable in this respect.
Further, in the configuration where the light source is a fiber light source, the connection with the wavelength dividing element can be performed without passing through a free space, which is more preferable in this respect.
Further, in the configuration where the light source is a supercontinuum light source, the selectable wavelength band can be widened while obtaining the above effect, which is more preferable in this respect.
Further, in the configuration in which the emission end of each wavelength and the modulation element of the wavelength dividing element are connected by a relay fiber, the existing wavelength dividing element can be used, which is practical in this respect.
Further, it is extremely simple if the data processing unit is a unit that processes the output from the receiver to perform Hadamard spectroscopy by providing a modulation control unit that controls the modulation element so as to correspond to the replacement of the Hadamard mask. Hadamard spectroscopy can be performed in the configuration, and it is not easily affected by the usage environment and disturbance. Since the light energy instantaneously given to the object is small, it is possible to suitably analyze the object having low heat resistance and light resistance by Hadamard spectroscopy.
Further, in a configuration in which the photoreceiver is a two-dimensional array photoreceiver that receives light from an object in two dimensions, it is possible to perform arbitrary wavelength selective irradiation type spectroscopic measurement in two dimensions, and in particular, hyperspectral images can be easily obtained. Obtainable.
Further, it is said that a spectroscopic optical system is provided that further disperses the light from the object irradiated with the light modulated by the modulation element, and the light receiver is a light receiver that receives the light dispersed by the spectroscopic optical system. The result of further spectroscopy of the light from the object can be obtained as the measurement result, which is a useful device especially in the application of fluorescence observation.
Further, the light source is a pulse light source, and the fluorescence receiver captures the fluorescence generated in the object to which one of the lights divided by the dividing element is incident, and the synchronization receiver is provided at the position where the other light is incident. In the configuration where the time-correlated single photon counting method is performed according to the input from the fluorescence receiver and the synchronization receiver, the relationship between the wavelength of the excitation light and the fluorescence lifetime can be investigated in an extremely short time. can.

It is a schematic diagram of the spectroscopic measuring apparatus which concerns on 1st Embodiment. It is a plane schematic diagram of the array waveguide grating used as a wavelength dividing element. It is a schematic diagram of the spectroscopic measuring apparatus of the 2nd Embodiment. It is a schematic diagram of the spectroscopic measurement apparatus of the 3rd Embodiment which performs the time correlation single photon counting method.

Hereinafter, embodiments (embodiments) for carrying out the invention of this application will be described.
FIG. 1 is a schematic view of a spectroscopic measuring device according to the first embodiment. This spectroscopic measuring device arbitrarily selects one or a plurality of wavelengths from a plurality of different wavelengths, irradiates the object S with light of the wavelength, and receives the light from the irradiated object S as a receiver. It is a device that receives light at 7.
The wavelength here is a wavelength band in a strict sense. That is, for example, light having a wavelength of 1100 nm means light having a wavelength of 1095 nm to 1104 nm in a strict sense, and is strictly expressed as a “wavelength band”. Strictly speaking, it is a wavelength band, but since it is complicated, it is simply referred to as "wavelength" in the following description. Therefore, the band including a certain wavelength is a band wider than the band in the strict sense of the wavelength.

As shown in FIG. 1, the spectroscopic measuring device of the embodiment includes a light source 1, a wavelength dividing element 2, and a modulation element 3.
The light source 1 is a light source that emits light in a band (hereinafter referred to as a measurable wavelength band) including a wavelength for which it is necessary to irradiate an object S to know its optical characteristics. Therefore, it is selected according to the type of the object S and the optical characteristics to be known. In this embodiment, a fiber light source is used as the light source 1, and in particular, a supercontinuum light source that emits supercontinuum light (hereinafter referred to as SC light) is used. In this specification, a light source whose emission unit is a fiber is broadly referred to as a fiber light source. A fiber laser is a typical fiber light source, but an SC light source is used as the light source 1 in this embodiment because it is necessary to emit light in a wide wavelength band called a measurable wavelength band.

Specifically, the light source 1 includes an ultrashort pulse laser source 11 and a non-linear element 12. As the ultrashort pulse laser source 11, a gain switch laser, a microchip laser, a fiber laser, or the like can be used. A fiber is used as the non-linear element 12. For example, a photonic crystal fiber or other non-linear fiber can be used as the non-linear element 12. The fiber mode is often a single mode, but it can be used as a non-linear element 12 as long as it exhibits sufficient non-linearity even in a multi-mode.

SC light is light obtained by passing light from an ultrashort pulse laser source through a non-linear element such as a fiber and widening the wavelength by a non-linear optical effect such as self-phase modulation or induced Raman scattering. By selecting an appropriate ultrashort pulse laser source or non-linear element, it is possible to obtain light spread over an arbitrary wavelength band. In this embodiment, since spectroscopic analysis in the near infrared region is assumed, one that emits SC light having a continuous spectrum over a wavelength band of, for example, about 1100 to 1200 nm is used. However, a light source that emits SC light in a wider band such as about 1000 to 1300 nm may be used as the light source 1.

The wavelength dividing element 2 largely characterizes the device of this embodiment. In this embodiment, unlike the conventional case, the waveguide type wavelength dividing element 2 is used. The waveguide type wavelength dividing element refers to an element that divides the wavelength of light when propagating light through an optical path (wavelength path) formed of a solid material, not in free space. Specifically, in this embodiment, an arrayed waveguide grating (AWG) is used as the wavelength dividing element 2.

FIG. 2 is a schematic plan view of an array waveguide grating used as the wavelength dividing element 2.
The arrayed waveguide grating is an element developed for optical communication, and its use for optical measurement is not known. As shown in FIG. 2, the array waveguide diffraction grating is configured by forming each functional waveguide 22 to 26 on the substrate 21. Each functional waveguide includes a large number of grating waveguides 22 having slightly different optical path lengths, slab waveguides 23 and 24 connected to both ends (incident side and emission side) of the grating waveguide 22, and incident side slab waveguides. The incident side waveguide 25 for incidenting light on the 23 and the respective emitting side waveguide 26 for extracting light of each wavelength from the emitting side slab waveguide 24.

The light incident on the incident side waveguide 25 spreads on the incident side slab waveguide 23 and is incident on each grating waveguide 22. Since the lengths of the grating waveguides 22 are slightly different, the light reaching the end of each grating waveguide 22 is out of phase (shifted) by this difference. Light is diffracted and emitted from each grating waveguide 22, but the diffracted light passes through the emitting side slab waveguide 24 while interfering with each other and reaches the incident end of the emitting side waveguide 26. At this time, due to the phase shift, the interference light has the highest intensity at the position corresponding to the wavelength. That is, light having different wavelengths is sequentially incident on each emission end waveguide 26, and the light is spatially divided into wavelengths. Strictly speaking, each emitting side waveguide 26 is formed so that each incident end is located at such a divided position.

The arrayed waveguide diffraction grating as shown in FIG. 2 was developed for wavelength division multiplexing (WDM) in the field of optical communication, but the inventor described it as an embodiment, although the application and the wavelength range are significantly different. It has been found that the spectroscopic measuring apparatus can be used as a wavelength dividing element 2 for selecting an arbitrary wavelength.
Such an arrayed waveguide diffraction grating can be produced, for example, by surface-treating a silicon substrate 21. Specifically, a clad layer (SiO ₂ layer) is formed on the surface of the silicon substrate 21 by a flame deposition method, and a SiO ₂ -GeO ₂ layer for a core is similarly formed by a flame deposition method, and then photolithography. This is produced by patterning the SiO ₂ -GeO ₂ layers to form the waveguides 22 to 26, and further forming an overclad layer (SiO ₂ layer). The line width of each grating waveguide 22 is, for example, about 5 to 6 μm.
The number of grating waveguides 22 to be formed depends on the number of wavelength divisions, but for example, when dividing into 10 to 100 wavelength bands over a wavelength bandwidth of about 1000 to 1300 nm, the number of grating waveguides is 30. The number is about 300, and the light is divided into different wavelengths by 3 to 30 nm and emitted.

The modulation element 3 also largely characterizes the spectroscopic measuring device of this embodiment. As the modulation element 3, an electro-optical modulator (EOM) is used in this embodiment. The electro-optical modulator is an element that utilizes the fact that the refractive index changes when a voltage is applied to the electro-optical crystal, and for example, lithium niobate is used as the electro-optical crystal.
The modulation performed by the modulation element 3 is amplitude modulation, which is on / off (transmission, cutoff). As shown in FIG. 1, the wavelength dividing element 2 and each modulation element 3 are connected by a relay fiber 4. As shown in FIG. 2, the incident end of each relay fiber 4 is connected to each emitting side waveguide 26 of the array waveguide diffraction grating as the wavelength dividing element 2. Each modulation element 3 is attached to the emission end of each relay fiber 4.

As shown in FIG. 1, the apparatus includes a modulation control unit 30 that controls the modulation element 3. The modulation control unit 30 is a control unit that transmits a control signal to each modulation element 3. Specifically, the modulation control unit 30 selectively operates each modulation element 3, transmits light to the selected modulation element 3, and blocks light to the unselected modulation element 3. Is.
As shown in FIG. 1, the emission fiber 5 is connected to the emission side of each modulation element 3. The end of the emission fiber 5 is bundled into one, and the emission end element 51 is provided there. As the emission end element 51, for example, an array waveguide diffraction grating is used. That is, by injecting light in the direction opposite to the case where the arrayed waveguide diffraction grating is used as the wavelength dividing element, the light from each emission fiber 5 can be combined with one waveguide. Further, as the emission end element 51, a bundle fiber or a fan-in / fan-out device may be used.
Although it has been described that the modulation element turns on and off the light, the off state may take a different mode depending on the configuration of the modulation element 3. The light may be attenuated there and the intensity may be substantially zero, or it may be reflected in a direction different from the normal direction so that it does not enter the emitting fiber 5 (is not transmitted).

In this embodiment, an irradiation optical system 50 for irradiating the object S with the light emitted from the emission end element 51 is provided. The irradiation optical system 50 includes a collimating lens 52. The collimating lens 52 is an element for collimating and irradiating a beam according to the size of the object S.
In this example, the object S is placed on the receiving plate 6, and the irradiation optical system 50 is an optical system for irradiating the object S on the receiving plate 6. In this example, a mirror is used, but a light guide fiber may be used. When a light guide fiber is used, a configuration may be adopted in which the light guide fiber is connected to the emission end element 51 and the collimating lens 52 is attached to the end thereof.

The device of the embodiment is a device for analyzing the transmission characteristics of the object S, and therefore, the light receiver 7 is arranged at a position where the transmitted light of the object S is received. The light receiver 7 has sensitivity over the entire measurable wavelength band, and one using a semiconductor light receiving cell such as Si or InGaAs is used. Two different photoreceivers may be used interchangeably.

As shown in FIG. 1, the spectroscopic measuring device of the embodiment includes a data processing unit 8 for processing measurement data. The data processing unit 8 is composed of a general-purpose computer such as a PC in this example.
The data processing unit 8 includes a processor 81 and a storage unit (hard disk, memory, etc.) 82. A data processing program 83 for processing data from the receiver 7 to obtain a measurement result and other necessary programs are installed in the storage unit 82. An AD converter 80 is provided between the photoreceiver 7 and the data processing unit 8, and the output of the photoreceiver 7 is digitized and input to the data processing unit 8.

In this example, the data processing unit 8 is also used as a control unit and a data input unit that control the entire apparatus. That is, the data processing unit 8 is equipped with a measurement sequence control program 84 that controls each unit in a predetermined sequence, a wavelength selection input program 85 that inputs an input for arbitrary wavelength selection, and the like.
As shown in FIG. 1, the data processing unit 8 includes a display unit 801 and an input unit 802. The wavelength selection input program 85 is a program in which a screen for selecting an arbitrary wavelength is displayed on the display unit 801 and input by the input unit 802. Information on the wavelength selected by input (selected wavelength information) is temporarily stored in the storage unit 82, and is passed as an argument when the data processing program 83 is executed.

The wavelength selection by the wavelength selection input program 85 is performed in units of wavelength division in the wavelength division element 2. When the wavelength dividing element 2 is configured to select n wavelengths from λ ₁ to λ _n , n modulation elements 3 are also provided and each is connected by a relay fiber 4. In this case, in the wavelength selection program, it is possible to select a specific one of n wavelengths, and it is also possible to select a plurality of continuous wavelengths such as λ ₁ to λ ₅ . Furthermore, it is possible to select a plurality of wavelengths that are not continuous (split), and it is also possible to select all wavelengths.

The operation of the spectroscopic measuring device of such an embodiment will be described below.
The measurer places the object S on the receiving plate 6 and inputs the measurement wavelength at the input unit 802. Then, when a measurement start command is input from the input unit 802, the measurement sequence control program 84 installed in the data processing unit 8 is executed.
The measurement sequence control program 84 operates the light source 1 to emit SC light. The emitted SC light is wavelength-divided by the wavelength-dividing element 2, modulated by the modulation element 3, and emitted. Then, the beam is collimated by the collimating lens 52 and irradiated to the object S. At this time, the measurement sequence control program 84 sends a control signal to the modulation control unit 30. This control signal is a signal that operates the modulation element 3 corresponding to the selected wavelength and prevents the other modulation elements 3 from operating. The modulation control unit 30 controls each modulation control unit 30 according to this control signal, and turns on only the modulation element 3 having the selected wavelength.

As a result, the object S is irradiated with only the light having the selected wavelength. The light incident on the object S and transmitted reaches the light receiver 7, its intensity is detected, and the data is input to the data processing unit 8 via the AD converter 80.
The data processing program 83 executed by the data processing unit 8 performs necessary data processing and displays the result on the display unit 801. In the case of measuring the absorption rate, the necessary data processing is to compare the absorption rate with the reference value of the wavelength (selected wavelength) among the reference values measured in the state where the object S is not arranged on the receiving plate 6. It is a process to calculate.
When all wavelengths are sequentially selected, all wavelengths are applied to the object S, and the transmitted light is received by the light receiver 7, which is compared with each reference value, so that the measurement result is in the measurable wavelength band. It is an absorption spectrum for the entire range of.

According to the spectroscopic measurement apparatus of the embodiment, in the arbitrary wavelength selection type spectroscopic measurement apparatus, an array waveguide diffraction grating which is a waveguide type is used as the wavelength division element 2, and the divided light of each wavelength is modulated by the modulation element 3. Since it is turned on and off with, and is not configured for wavelength division and wavelength selection in free space, it is not easily affected by the usage environment and disturbance. Therefore, the accuracy of wavelength selection is high, and spectroscopic measurement of arbitrary wavelength selection can be performed accurately and stably.

Further, in this embodiment, since the wavelength dividing element 2 and the modulation element 3 are connected by the relay fiber 4, the configuration is more practical. When the relay fiber 4 is not used, it is conceivable that each modulation element 3 is directly provided at each emission end of the wavelength dividing element 2 (each end where light of each divided wavelength is emitted). However, in the case of the arrayed waveguide diffraction grating adopted as the wavelength dividing element 2, since such a thing is not commercially available, it is necessary to make it by oneself. The configuration using the relay fiber 4 is practical in that there is no such trouble.
Since the output of the arrayed waveguide diffraction grating as the dividing element 2 is in single mode and the modulation element 3 is often operated in single mode, it is desirable that the relay fiber 4 is a single mode fiber.

The spectroscopic measurement device of such an embodiment can also be configured as a device that performs so-called Hadamard spectroscopy (Hadamard transform spectroscopy). This point will be described below.
As described in Patent Document 2 and Non-Patent Document 3, when Hadamard spectroscopy is performed, an Hadamard mask is created and used based on the Hadamard matrix. For example, as described in Non-Patent Document 3, an n-1st-order S-matrix is created from an n-th-order Hadamard matrix (H matrix), and a Hadamard mask corresponding to this S-row example is created. Then, each Hadamard mask is sequentially replaced to perform measurement. In Patent Document 2, a programmable mirror is used to control light corresponding to the replacement of the Hadamard mask.

On the other hand, when Hadamard spectroscopy is performed using the spectroscopic measuring device of the embodiment, the sequence for controlling each modulation element 3 corresponds to the replacement of the Hadamard mask. That is, the light is turned on and off in a form corresponding to the n-1th-order S-matrix. In this case, since n is an integer of 2 ^m , for example, the modulation element 3 can be controlled by using 15 modulation elements 3 in a sequence corresponding to the replacement of the 15th-order Hadamard mask. That is, the first time, each modulation element 3 is turned on and off so that the first (first row in the S-matrix) Hadamard mask is reproduced. The second time, each modulation element 3 is turned on and off so that the second (second line) Hadamard mask is reproduced. This is repeated, and in the 15th time, each modulation element 3 is turned on and off so that the 15th (15th line) Hadamard mask is reproduced.

The data processing program 83 is programmed so that each modulation element 3 obtains a spectrum from each measured value obtained by sequence control as described above. Taking the above 15th-order Adamal mask as an example, each measured value in 15 measurements is multiplied by the inverse matrix of the S-matrix to obtain a spectrum calculation result.
When performing Hadamard spectroscopy using the spectroscopic measuring device of the embodiment (in the case of the Hadamard spectroscopic measuring device), the configurations of the modulation control unit 30 and the data processing program 83 are changed as described above. Since the replacement of the Hadamard mask is realized by the control sequence of each modulation element 3, it becomes extremely simple. Further, since it is not necessary to use a programmable mirror as in Cited Document 2, it is not easily affected by the usage environment and disturbance.

Further, in the above method, instead of irradiating the object S with light and applying the adamar mask to the light from the object S, the wavelength is selected in the sequence corresponding to the adamar mask and the object S is irradiated with the light. , The light energy instantaneously given to the object S is small. Therefore, even an object S having low heat resistance and light resistance can be suitably analyzed by Hadamard spectroscopy.

Next, the spectroscopic measuring device of the second embodiment will be described. FIG. 3 is a schematic view of the spectroscopic measuring device of the second embodiment.
Similar to the first embodiment, the spectroscopic measuring device of the second embodiment is a device that irradiates the object S with light having an arbitrarily selected wavelength. Then, unlike the first embodiment, the second embodiment is a device for measuring the reflected light from the object S irradiated with light.

Also in the second embodiment, a configuration is adopted in which the light from the light source 1 is divided by the wavelength dividing element 2 and turned on and off by the modulation element 3 to irradiate the object S. As shown in FIG. 3, in the second embodiment, the irradiation optical system 50 includes a light guide fiber 53. The light guide fiber 53 is connected to the emission end element 51, and a collimating lens 52 is provided at the end thereof.
The collimating lens 52 is attached in a posture of irradiating the object S placed on the receiving plate 6 with light from diagonally above, and the light receiver 7 is provided via the lens 71 at a position where the reflected light is received. Has been done. The light receiver 7 is similarly connected to the data processing unit 8 via the AD converter 80.

In this embodiment, the light receiver 7 is a two-dimensional array light receiver in which light receiving cells are arranged two-dimensionally. The two-dimensional array receiver 7 can be an image sensor (camera) such as an area image sensor. In this case, the lens 71 may form an image of the surface of the object S on the light receiving surface.
The data processing program 83 mounted on the data processing unit 8 is a program for processing two-dimensional data from the receiver 7. The data processing program 83 takes the result of the two-dimensional data processing as the result of the two-dimensional spectroscopic measurement of the surface of the object S for the selected wavelength. In this case, if the selected wavelength is a single wavelength, it is a measurement result of how the reflectance of the wavelength is distributed on the surface of the object S. When multiple wavelengths are sequentially selected, the measurement result is a so-called hyperspectral image. When all wavelengths are sequentially selected, a hyperspectral image over the entire measurable wavelength band is obtained as the measurement result.
Since a reference value is required when calculating the reflectance, a standard reflector is used to obtain the reflectance in advance. The standard reflector is a reflector whose reflectance at each wavelength is known. The reflectance of the surface of the object S is calculated based on the ratio to the measured value when the standard reflector is used.

According to the spectroscopic measuring device of the second embodiment, since the photoreceiver 7 is a two-dimensional array photoreceiver, the spectroscopic characteristics of the object S can be obtained as two-dimensional data, and the distribution of the spectroscopic characteristics in the plane can be obtained. It is particularly suitable when it is necessary to know such things as. It is also possible to obtain a hyperspectral image by selecting a plurality of wavelengths, which is particularly suitable when it is necessary to analyze the two-dimensional optical characteristics of the object S in more detail.

As a conventional method for obtaining a hyperspectral image, a line scan method and a snapshot method are known. In the line scan method, the light that has passed through the slit is separated by a diffraction grating or the like, and the light is scanned while scanning, so that there is a drawback that the measurement is structurally complicated and takes time. It is also susceptible to changes in the measurement environment and disturbances. In the snapshot method, a configuration is known in which a spectroscopic filter using a liquid crystal element or the like is incorporated on the incident side of the photoreceiver, or an image sensor incorporating a spectroscopic filter different for each pixel is used as the photoreceiver. However, there is a problem that the structure of the camera becomes large and the cost becomes high. Further, in the method using the filter built-in image sensor, there is a problem that the spatial resolution tends to decrease because the spectral data is not exactly the same point. When the hyperspectral image is obtained by the apparatus of the embodiment, these problems do not exist.

In the conventional method for obtaining a hyperspectral image, the object S is irradiated with light of all wavelengths, the irradiated object S is received in two dimensions, and the spectrum is dispersed at that time. It is a method to do. On the other hand, the apparatus of this embodiment is a method in which light is irradiated to the object S one wavelength at a time and integrated in the data processing from the receiver 7 to form a two-dimensional spectral spectrum, which is a basic idea. Is different. According to the apparatus of the embodiment, since the energy of the light instantaneously applied to the object S is reduced, it is particularly suitable for an object having low heat resistance or an object having low light resistance.

In the second embodiment, the reflected light is received by the two-dimensional array receiver 7 to obtain two-dimensional data (reflectance data), but the transmitted light is received by the two-dimensional array receiver 7 to obtain two-dimensional data. Transparency data may be obtained. However, if the receiver 7 is provided at a position where the transmitted light is received, the amount of scattered light contained in the light incident on the receiver 7 tends to increase, so that the reflected light is two-dimensional data. It is preferable to obtain the configuration.

In the configuration using the two-dimensional array receiver 7 as in the second embodiment, it is also possible to perform the above-mentioned Hadamard spectroscopy. That is, as described above, the two-dimensional array photoreceiver 7 receives light while controlling each modulation element 3 in a sequence corresponding to the replacement of the Adamal mask, and the output sequence (output data of each time) in each light receiving cell (pixel) is reversed. Multiply the matrices to obtain the spectral spectrum of each point (in the above example, the spectral reflectance distribution).

According to this configuration, the replacement of the Hadamard mask is realized by the control sequence of each modulation element 3, which is extremely simple. Further, since it is not necessary to use a programmable mirror as in Cited Document 2, it is not easily affected by the usage environment and disturbance.
Further, in the above method, instead of irradiating the object S with light and applying the adamar mask to the light from the object S, the wavelength is selected in the sequence corresponding to the adamar mask and the object S is irradiated with the light. , The light energy instantaneously given to the object S is small. Therefore, even an object S having low heat resistance and light resistance can be suitably analyzed by Hadamard spectroscopy.

In each of the above-described embodiments, a WDM coupler can also be used as the wavelength dividing element 2. The number of wavelengths that can be selected is about two or three, but if the selection is sufficient, the cost of the device can be reduced by using a WDM coupler. However, when the arrayed waveguide diffraction grating is used as the wavelength dividing element 2, it is easy to increase the number of divisions and the number of selectable wavelengths, which is preferable in this respect.

Further, as the modulation element 3, a thermo-optical modulator can be used in addition to the electro-optical modulator. For example, the Mach-Zehnder interferometer type PLC optical switch has a structure in which one of the waveguides provided in the middle of the branch portion and the combine portion is heated by a thin film heater to delay the phase, thereby turning off the light at the combine portion. .. Such a thermo-optical modulator can be used as the modulation element 3.
Further, as the modulation element 3, an acoustic-optical modulator can also be used. In the acoustic-optical modulator, a piezoelectric converter is attached to one side of the acoustic-optical crystal, and by applying a high-frequency signal to the piezoelectric converter, an acoustic progressive wave is generated in the crystal, and a specific wavelength is generated by the photoelastic effect. It is an element designed to operate as a modulator for. Such an acoustic-optical modulator can be used as the modulation element 3.

Further, although the modulation element 3 in each embodiment can be called an optical switch because it is intended to turn light on and off, a mechanical optical fiber switch can be used. In particular, among the mechanical optical fiber switches that have been put into practical use, the MEMS type optical fiber switch can be preferably used. The MEMS type optical fiber switch is an element that drives a micromirror manufactured by microfabrication to turn light on and off. When used as the modulation element 3 in each embodiment, it is possible to incorporate all the modulation elements 3 into one element by microfabrication as each switch, which can contribute to the compactification of the entire device. In addition, as the mechanical fiber switch, an element that operates as a switch by displacing the prism mirror, an element that operates as a switch by displacing the fiber itself, and the like can also be used.
Since the modulation element 3 is an element provided after the wavelength dividing element 2 of the waveguide type, a PLC (Planar Lightwave Circuit) type or fiber type modulator including each of the above modulators has a general affinity. It is expensive and can be suitably used.

In each of the above embodiments, the modulation element 3 turns on and off the light, but a modulation element that does not completely block the light but weakens it to some extent (reduces the amplitude) may be adopted. .. For example, a device that blocks the intensity so as to be 10% or less or 5% or less of the intensity when emitted from the wavelength dividing element 2 may be used as the modulation element 3. Depending on the application and purpose of the spectroscopic measurement, it may be sufficient to reduce the intensity of the light of the non-selected wavelength, and if the intensity of the non-selected wavelength can be negligibly reduced with respect to the intensity of the selected wavelength. Such a modulation element may be used. As an example, a VOA array (Variable Optical Attenuator Array) using a MEMS type optical fiber switch as an intensity modulation element can be used.

Further, in each of the above embodiments, a configuration in which the reference value is acquired in real time may be adopted. For example, in the case of the first embodiment, a beam splitter is provided on the exit side of the collimating lens 52 to split the light, one of which is an irradiation optical system for irradiating the object S with light, and the other is a reference optical system. In the reference optical system, light is received by the reference light receiver 7 through the receiving plate 6 on which the object S is not arranged, and the output thereof is used as a reference value. In the case of the second embodiment, the reference optical system is configured to irradiate the standard reflector with light and receive the reflected light by the reference receiver. In either case, the real-time reference value is acquired, so that the reliability of the measurement result is further improved.

The SC light source used as the light source 1 is an example of a fiber light source, but the use of a fiber light source also takes into consideration the affinity with the waveguide type wavelength selection element 2. Since the emitting portion of the fiber light source is a fiber, the fiber light source can be connected to the waveguide type wavelength selection element 2 without passing through a free space. Therefore, it is also less susceptible to the usage environment and disturbances.
As the light source 1, an ASE (Amplified Spontaneous Emission) light source, an SLD (Superluminescent diode) light source, or the like can also be used. Furthermore, it does not have to be a laser-based light source, and LEDs or other incoherent light sources may be used. As for these light sources, if a fiber light source having a fiber provided at the emitting portion is used, the effect of being less susceptible to the usage environment and disturbance can be obtained.

The object S is not particularly limited as long as it is necessary to know the optical characteristics. Not limited to solids, liquids and gases may be objects S. For example, a liquid or gas may be encapsulated as an object S in a translucent cell, and the transmission spectrum may be measured.
Further, the light from the object S is not limited to transmitted light and reflected light, but may be scattered light or fluorescence. In either case, a spectroscopic optical system that further disperses the light from the object S may be provided. Specifically, the light from the object S is focused by a lens, and a slit is provided at the focused position. Then, the light that has passed through the slit is made into parallel light by a collimator lens, dispersed by a diffraction grating, and received by a one-dimensional array type light receiver (polychromator). Such a configuration is particularly effective in observing fluorescence. That is, by spectroscopically analyzing the generated fluorescence while scanning the light irradiating the object S under the control of each modulation element 3 (while changing sequentially), the relationship between the wavelength of the excitation light and the spectrum of the generated fluorescence is extremely short. Can be investigated.

In addition, the fluorescence lifetime from the object S may be measured. In this case, a time-correlated single photon counting method (TCSPC) can also be performed. An embodiment in which TCSPC is performed will be described below as a third embodiment. FIG. 4 is a schematic diagram of a spectroscopic measuring device according to a third embodiment for performing TCSPC.
As shown in FIG. 4, when performing TCSPC, the data processing unit 8 is configured to include the TCSPC module 86, and is provided with a synchronization signal generation unit synchronized with the pulse emitted from the light source 1. There are several possible configurations for the synchronization signal generation unit, but here, a configuration is adopted in which a part of the light is divided and received by a light receiver, and the output thereof is used as a synchronization signal. That is, as shown in FIG. 4, the irradiation optical system 50 includes a splitting element 54 such as a beam splitter on the exit side of the collimating lens 52. Then, a synchronization receiver 70 such as a high-speed photodiode is arranged at a position where one of the divided lights is incident, and an object S is arranged at a position where the other light is incident via a lens 61.

An avalanche photodiode or the like is arranged via the lens 701 as a fluorescence receiver 700 that captures the fluorescence generated in the object S. Each output of the synchronous receiver 70 and the fluorescent receiver 700 is input to the data processing unit 8 including the TCSPC module 86. An ND filter 55 is appropriately arranged on each optical path. As the TCSPC module 86, for example, a module manufactured by Becker & Hickl can be used. The TCSPC module 86 obtains the delay time of the input pulse from the two receivers 70 and 700 by a time to Amplitude Convertor (TAC), and obtains histogram data of the number of fluorescent photons at each delay time.

According to the spectroscopic measuring device of the third embodiment as described above, the TCS PC can be separated and performed. That is, the relationship between the wavelength of the excitation light and the fluorescence lifetime is investigated in an extremely short time by measuring the fluorescence lifetime while scanning (sequentially changing) the pulsed light irradiating the object S under the control of each modulation element 3. be able to.
The position where the dividing element 54 is provided may be another position, or may be on the incident side of the wavelength dividing element 2 or inside the light source 1. Further, the light may be divided in the ultrashort pulse laser source 11 and received for synchronization to generate a synchronization signal, or a drive signal in the ultrashort pulse laser source 11 (for example, a drive signal of an excitation laser). ) May be taken out and used as a synchronization signal.

1 Light source 2 Wavelength dividing element 3 Modulation element 30 Modulation control unit 4 Relay fiber 5 Emission fiber 51 Emission end element 52 Beam expander 53 Light guide fiber 6 Receiver plate 7 Receiver 700 Fluorescence receiver 8 Data processing unit 80 AD converter 86 TCSPC Module S Object

Claims (10)

A light source that emits light in a band containing multiple different wavelengths that can be selected,
A waveguide-type wavelength dividing element that divides the wavelength of light emitted from a light source,
A modulation element that modulates the light so that the light of a specific wavelength is selectively irradiated to the object among the light of each wavelength divided by the wavelength dividing element.
A receiver that receives light from an object irradiated with light modulated by a modulation element, and a receiver.
A spectroscopic measuring device including a data processing unit that obtains the optical characteristics of an object with respect to the wavelength of light selectively irradiated by a modulation element by processing an output from a light receiver. The spectroscopic measuring device according to claim 1, wherein the waveguide type wavelength dividing element is an array waveguide diffraction grating. The spectroscopic measuring apparatus according to claim 1 or 2, wherein the modulation element is an electro-optical modulator, a thermo-optical modulator, an acousto-optic modulator, or a mechanical fiber switch. The spectroscopic measuring device according to any one of claims 1 to 3, wherein the light source is a fiber light source. The spectroscopic measuring device according to claim 4, wherein the fiber light source is a supercontinuum light source. The spectroscopic measuring apparatus according to any one of claims 1 to 5, wherein the emission end of each wavelength in the waveguide type wavelength dividing element and the modulation element are connected by a relay fiber. A modulation control unit that controls the modulation element is provided so as to correspond to the replacement of the Hadamard mask.
The spectroscopic measurement device according to any one of claims 1 to 6, wherein the data processing unit is a unit that processes an output from the photoreceiver to perform Hadamard spectroscopy. The spectroscopic measuring device according to any one of claims 1 to 7, wherein the photoreceiver is a two-dimensional array photoreceiver that receives light from an object in two dimensions. A spectroscopic optical system that further disperses the light from the object irradiated with the light modulated by the modulation element is provided, and the light receiver is a light receiver that receives the light dispersed by the spectroscopic optical system. The spectroscopic measuring apparatus according to any one of claims 1 to 7. The light source is a pulse light source.
A synchronization signal generation unit that generates a synchronization signal synchronized with the pulsed light emitted by the light source is provided.
The receiver is a fluorescence receiver that receives fluorescence generated in an object irradiated with pulsed light modulated by the modulation element.
Any of claims 1 to 6, wherein the data processing unit includes a module that performs a time-correlated single photon counting method according to a synchronization signal generated by a synchronization signal generator and an output of a fluorescence receiver. The spectroscopic measuring device described in the above.

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