Infrared spectrum measuring device and method based on microsphere lens

Abstract

The invention belongs to the technical field of infrared spectrum measurement, and particularly relates to an infrared spectrum measurement device and method based on a microsphere lens. The device comprises a microscope objective, a microsphere lens, piezoelectric ceramics, a stepping moving platform and a sample surface measuring system, a microscope objective located on an output light path of the sample surface measuring system is arranged above the piezoelectric ceramic and stepping mobile platform, and a microsphere lens is arranged between the piezoelectric ceramic and stepping mobile platform and the microscope objective; and a sample is arranged on the piezoelectric ceramic and the stepping moving platform. Incident light is subjected to ultra-strong focusing through the photon nano jet flow effect of the microsphere lens, and a measurement light beam is focused in a sub-wavelength size area; the surface displacement change caused by the absorption of the infrared light by the sample is measured, so that the infrared absorption spectrum measurement of the sample is realized; the method overcomes the defects that in an existing infrared absorption spectrum measurement technology, a sample is prone to being damaged, and the large-range imaging efficiency is low, and pure optical and lossless super-resolution infrared spectrum imaging of the submicron area of the sample is achieved.

Description

Technical Field

[0001] This invention belongs to the field of infrared spectroscopy measurement technology, and specifically relates to an infrared spectroscopy measurement device and method based on a microsphere lens. Background Technology

[0002] Infrared spectroscopy is one of the most widely used chemical analysis techniques. The amount of infrared light absorbed by a sample is related to the wavelength of the infrared light; therefore, the chemical properties of a substance can be characterized by measuring its infrared absorption spectrum. The position, intensity, and shape of the absorption peaks can be used to infer and identify the chemical bonds and composition of the substance. However, Fourier transform infrared (FTIR) microscopes commonly used in laboratories often require high brightness of the infrared light source for infrared absorption spectroscopy imaging, and their spatial resolution is limited by the optical diffraction limit corresponding to the infrared wavelength (~). Due to the inherent optical quality of microscopes, the spatial resolution is often limited to tens of micrometers, making it difficult to achieve super-resolution local spatial spectral imaging. To improve spatial resolution, scientists have attempted to couple high-brightness infrared synchrotron radiation sources into FTIR microscopes. By optimizing optical components and using arrayed detectors, the spatial resolution of FTIR microscopes has reached 1 micrometer. However, the relatively low spatial resolution restricts most traditional infrared microscopy applications to research and industrial characterization at length scales of several micrometers and above.

[0003] In recent years, with the increasing demand for high spatial resolution infrared spectroscopy in polymer applications, scientists have gradually combined nanotechnology with infrared spectrometers to develop nanoscale spectrometers and submicron-scale infrared imaging technologies. Among these, three main types have attracted the most attention: AFM-based infrared spectroscopy (AFM-IR), scanning near-field optical microscopy (s-SNOM), and tip-enhanced Raman spectroscopy (TERS). AFM-IR primarily uses AFM technology to detect the surface deformation of the sample caused by infrared absorption for spectral absorption measurement, while the other two methods mainly detect the spectrum scattered from the sample surface. To enhance detection sensitivity, TERS technology utilizes tip detection to detect the Raman frequency shift caused by scattering in small regions. This makes the production of commercially available probes with sufficiently large and reproducible enhancement factors a major limiting factor for this technology. s-SNOM technology requires calculation and simulation of the optical properties of the sample and substrate, making it highly sensitive to peak shifts caused by sample thickness and substrate, which greatly limits its widespread application. In contrast, AFM-IR can probe deeper sample information, and commercially available AFM probes do not require large enhancement factors, making them more favored for infrared spectroscopy applications. However, AFM-IR detection technology requires the AFM probe to contact the sample surface for detection, which can easily damage the sample surface and greatly limit its application in the life sciences. In summary, existing nanoscale and submicron-scale infrared spectroscopy imaging techniques struggle to achieve high-sensitivity, high signal-to-noise ratio, and non-destructive infrared super-resolution measurements. Developing a purely optical infrared super-resolution measurement and imaging technology and device that meets these requirements has become a hot topic in this field. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide an infrared spectroscopy measurement system and method based on a microsphere lens. This system utilizes the photonic nanojet effect of the microsphere lens to overcome the Abbe diffraction limit in infrared spectroscopy measurement, enabling purely optical, non-contact super-resolution infrared spectroscopy measurement in the subwavelength region of the sample.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] The present invention provides an infrared spectroscopy measurement device based on a microsphere lens, including a microscope objective, a microsphere lens, piezoelectric ceramics, a stepping moving platform, and a sample surface measurement system;

[0007] A microscope objective is provided above the piezoelectric ceramic and the stepping platform, and the microscope objective is located on the output optical path of the sample surface measurement system; a microsphere lens is provided between the piezoelectric ceramic and the stepping platform and the microscope objective; a sample is placed on the piezoelectric ceramic and the stepping platform.

[0008] The sample surface measurement system includes a visible measurement laser, a collimating beam expander, a polarizing beam splitter, a quarter-wave plate, a first dichroic mirror, a first infrared tunable laser, a collimating optical component, and a first reflecting mirror.

[0009] The output optical path of the visible measurement laser is sequentially provided with a collimating beam expander, a polarizing beam splitter, a quarter-wave plate, and a first dichroic mirror; the output optical path of the infrared tunable laser is provided with a first reflecting mirror, and the reflected optical path of the first reflecting mirror passes sequentially through the first dichroic mirror and a microscope objective.

[0010] The polarization beam splitter has an astigmatic lens and a first photodetector arranged sequentially on its reflected optical path.

[0011] The sample surface measurement system includes a first visible light laser, a first beam splitter, a second beam splitter, a third beam splitter, a second reflector, a second photodetector, a second infrared tunable laser, and a second dichroic mirror.

[0012] The output optical path of the first visible light laser is provided with a first beam splitter, a second beam splitter, and a second dichroic mirror in sequence; a second reflector is provided on the beam-splitting optical path of the first beam splitter, and a third beam splitter and a second photodetector are provided on the reflected optical path of the second reflector in sequence; the third beam splitter is provided on the beam-splitting optical path of the second beam splitter; the second dichroic mirror is provided on the output optical path of the second infrared tunable laser; the output optical path of the second dichroic mirror is incident on the microscope objective.

[0013] A Bragg box is provided between the second reflector and the third beam splitter.

[0014] Another aspect of the present invention provides an infrared spectroscopy measurement method based on a microsphere lens, comprising the following steps: a microscope objective converges the incident infrared spectrum and the visible light measurement spectrum; the infrared light is focused onto the sample surface by the microsphere lens; the sample surface absorbs the infrared spectrum and produces fluctuations; the data is collected by the sample surface measurement system and processed to obtain the infrared absorption spectrum of the sample.

[0015] The fluctuations generated by the sample surface absorbing infrared spectra are collected and processed by the sample surface measurement system, including the following steps:

[0016] The light emitted by the visible measurement laser is collimated and expanded sequentially by the collimating and expanding assembly, then converted into p-type linearly polarized light by the polarization beam splitter, and then becomes clockwise elliptically polarized light after passing through a quarter-wave plate. It is then reflected by the first dichroic mirror to the microscope objective for primary focusing. The focused beam is then refocused by the microsphere lens, which breaks through the diffraction limit and focuses the light spot on the sample surface. The infrared spectrum emitted by the first infrared tunable laser is collimated by the collimating optical assembly, reflected by the first mirror, and then incident on the microscope objective after passing through the first dichroic mirror. It is focused on the sample surface, and the absorption of the infrared spectrum in this region causes a change in the distance between the photon nanojet generated by the microsphere lens and the sample surface.

[0017] The microsphere lens collects visible light reflected from the sample surface within the range of the photon nanojet. The originally clockwise elliptically polarized light becomes counterclockwise elliptically polarized light, which is reflected by the first dichroic mirror onto the quarter-wave plate. At this point, the counterclockwise elliptically polarized light becomes S-shaped polarized light, which is reflected by the polarization beam splitter onto the astigmatic lens for convergence. The shape and size of the light spot are detected by the first photodetector.

[0018] After the first photodetector detects the shape and size of the light spot, it obtains the absorption spectrum curve based on the detection information, including the following steps:

[0019] Based on the shape, direction, and size of the light spot on the first photodetector, the change in distance between the microsphere lens and the sample surface and the direction of deviation from the initial position are obtained. Based on the relationship between the sample's absorbed infrared spectrum and the sample's photothermally induced surface undulation, the data spectrum of the sample's absorption intensity at the specified absorption spectrum is obtained. The infrared absorption spectrum curve of the sample within the specified range is obtained through continuous spectral scanning.

[0020] The fluctuations generated by the sample surface absorbing infrared spectra are collected and processed by the sample surface measurement system, including the following steps:

[0021] The measurement laser emitted by the first visible light laser is split into two beams by the first beam splitter, namely the reference beam and the object beam. The object beam is then focused once by the second beam splitter and the second dichroic mirror. The focused beam is then focused a second time by the microsphere lens. The photonic nanojet effect of the microsphere lens is used to make the size of the focused spot break through the diffraction limit and focus on the area on the sample surface.

[0022] The reference light is reflected by the second mirror into the Bragg cell for acousto-optic modulation, and then incident on the second photodetector after passing through the third beam splitter. The infrared spectrum emitted by the second infrared tunable laser is incident on the microscope objective after passing through the second dichroic mirror and is focused onto the sample surface area. The absorption of the infrared spectrum in this area causes a change in the distance between the microsphere lens and the sample surface.

[0023] The microsphere lens collects the visible light reflected from the sample surface within the range of the photon nanojet, returns along the original optical path, and after being reflected by the second and third beam splitters, it is simultaneously incident on the second photodetector with the reference light, causing interference for data acquisition.

[0024] After acquiring the interference data of the two beams, and combining it with the Doppler frequency shift principle, the infrared absorption spectrum curve of the sample is obtained through data processing, including the following steps:

[0025] The change in distance between the microsphere lens and the sample is detected. The direction of the distance change between the microsphere lens and the sample surface is obtained by the Doppler frequency shift generated by the Bragg cell. The amount of surface undulation change is obtained by the interference data, thereby obtaining the amount and direction of the undulation change in the infrared spectrum of the sample surface. By the relationship between the amount of light-induced surface undulation change and the infrared spectral intensity, and the corresponding wavelength of the infrared spectrum, an infrared absorption spectrum curve of the sample is established.

[0026] The present invention has the following beneficial effects and advantages:

[0027] This invention utilizes a rapidly tunable infrared laser to excite photothermal effects at different wavelengths, while simultaneously using a visible laser beam as a probe to detect the photothermal effects on the sample surface, effectively reducing the Abbe diffraction limit's limitation on the size of infrared spectral measurements.

[0028] This invention utilizes the photonic nanojet effect of a microsphere lens to achieve ultra-strong focusing of visible measurement lasers, overcoming the Abbe diffraction limit and focusing the measurement laser on a region of less than half the wavelength on the sample surface, thereby further improving the spatial resolution of infrared spectroscopy measurements.

[0029] This invention proposes three super-resolution infrared spectroscopy measurement systems combining microlenses, which combine microsphere lenses with laser astigmatism, heterodyne interferometry, and null interference methods, respectively, greatly improving the resolution of infrared spectroscopy measurements.

[0030] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 This is a schematic diagram of the infrared spectroscopy measurement device based on a microsphere lens according to the present invention;

[0034] Figure 2 This is a schematic diagram of the laser astigmatism method system for measuring the infrared absorption spectrum of a sample in measurement system one of this invention;

[0035] Figure 3 This is a schematic diagram of the heterodyne method system for measuring the infrared absorption spectrum of a sample in measurement system two of this invention;

[0036] Figure 4 This is a schematic diagram of the zero-difference method for measuring the infrared absorption spectrum of a sample in measurement system three of this invention.

[0037] In the figure: 1. Microscope objective; 2. Microsphere lens; 3. Sample; 4. Piezoelectric ceramic and stepping platform; 5. Sample surface measurement system; 6. Host computer; 201. Visible measurement laser; 202. Collimating and beam expanding assembly; 203. Polarizing beam splitter; 204. Quarter-wave plate; 205. First dichroic mirror; 206. Astigmatic lens; 207. First photodetector; 208. First infrared tunable laser; 209. Collimating optical assembly; 210. First reflecting mirror; 301. First visible laser. 302, First beam splitter; 303, Second beam splitter; 304, Second reflector; 305, Bragg box; 306, Third beam splitter; 307, Second photodetector; 308, Second infrared tunable laser; 309, Second dichroic mirror; 401, Second visible laser; 402, Fourth beam splitter; 403, Fifth beam splitter; 404, Third reflector; 405, Sixth beam splitter; 406, Third photodetector; 407, Third infrared tunable laser; 408, Third dichroic mirror. Detailed Implementation

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0040] See Figure 1 As shown, this invention provides an infrared spectroscopy measurement device based on a microsphere lens, including a microscope objective 1, a microsphere lens 2, a piezoelectric ceramic and a stepping platform 4, and a sample surface measurement system 5. The microscope objective 1 is positioned above the piezoelectric ceramic and stepping platform 4 and is located in the output optical path of the sample surface measurement system 5. The microsphere lens 2 is positioned between the piezoelectric ceramic and stepping platform 4 and the microscope objective 1. A sample 3 is placed on the piezoelectric ceramic and stepping platform 4. The incident light is highly focused using the photonic nanojet effect of the microsphere lens 2, concentrating the measurement beam within a subwavelength region. The surface displacement change caused by the sample's absorption of infrared light is measured, thus achieving infrared absorption spectroscopy measurement of the sample. This invention overcomes the shortcomings of existing infrared absorption spectroscopy measurement techniques, which easily damage samples and have low imaging efficiency over large areas, achieving pure optical, non-destructive, super-resolution infrared spectroscopy imaging of the sample in the submicron region.

[0041] During operation, the microscope objective 1 focuses the incident infrared spectrum and visible measurement laser, while the microsphere lens 2 focuses the visible measurement laser after it has been focused by the microscope objective 1, forming a photon nanojet within the sub-diffraction limit. Using this principle, the infrared absorption spectrum of the sample 3 within the sub-diffraction limit can be detected by the sample surface measurement system 5.

[0042] See Figure 2 As shown, in one embodiment of the present invention, when using the laser astigmatic infrared spectroscopy measurement method, the sample surface measurement system 5 includes a visible measurement laser 201, a collimating beam expander 202, a polarizing beam splitter 203, a quarter-wave plate 204, a first dichroic mirror 205, a first infrared tunable laser 208, a collimating optical component 209, and a first reflecting mirror 210; the collimating beam expander 202, the polarizing beam splitter 203, the quarter-wave plate 204, and the first dichroic mirror 205 are sequentially arranged on the output optical path of the visible measurement laser 201; the first reflecting mirror 210 is arranged on the output optical path of the infrared tunable laser 208, and the reflected optical path of the first reflecting mirror 210 passes sequentially through the first dichroic mirror 205 and the microscope objective 1.

[0043] Furthermore, an astigmatic lens 206 and a first photodetector 207 are sequentially arranged on the reflected light path of the polarization beam splitter 203. By utilizing the shape, direction, and size of the elliptical spot of the visible measurement laser 201 on the photodetector 207, the distance and deviation direction between the microsphere lens 2 and the sample 3 are measured, and then the infrared absorption spectrum of the sample 3 is measured.

[0044] See Figure 3 As shown, in another embodiment of the present invention, when using the heterodyne infrared spectroscopy measurement method, the sample surface measurement system 5 includes a first visible light laser 301, a first beam splitter 302, a second beam splitter 303, a third beam splitter 306, a second reflector 304, a second photodetector 307, a second infrared tunable laser 308, and a second dichroic mirror 309; the first visible light laser 301 has the first beam splitter 302, the second beam splitter 303, and the second dichroic mirror 309 arranged sequentially on its output optical path; the second reflector 304 is arranged on the beam splitting optical path of the first beam splitter 302, and the third beam splitter 306 and the second photodetector 307 are arranged sequentially on the reflected optical path of the second reflector 304; the third beam splitter 306 is arranged on the beam splitting optical path of the second beam splitter 303; the second dichroic mirror 309 is arranged on the output optical path of the second infrared tunable laser 308; the output optical path of the second dichroic mirror 309 enters the microscope objective 1.

[0045] Furthermore, a Bragg cell 305 is provided between the second reflecting mirror 304 and the third beam splitter 306. The reference beam and object beam split by the first visible light laser 301 are reflected back by the sample after passing through the microsphere lens 2 and finally reach the second photodetector 307. The reference beam is acousto-optic modulated by the Bragg cell 305 and finally reaches the second photodetector 307. Based on the principles of optical interference and Doppler frequency shift, the distance and deviation direction between the microsphere lens 2 and the sample 3 are measured, and then the infrared absorption spectrum of the sample 3 is measured.

[0046] See Figure 4 As shown, in another embodiment of the present invention, when using the zero-difference infrared spectroscopy measurement method, the sample surface measurement system 5 includes a second visible light laser 401, a fourth beam splitter 402, a fifth beam splitter 403, a third reflecting mirror 404, a sixth beam splitter 405, a third photodetector 406, a third infrared tunable laser 407, and a third dichroic mirror 408. The output light path of the second visible light laser 401 is sequentially provided with the fourth beam splitter 402, the fifth beam splitter 403, and the third dichroic mirror 408. The beam splitter 402 has the third reflecting mirror 404 on its beam-splitting path, and the third reflecting mirror 404 has the sixth beam splitter 405 and the third photodetector 406 sequentially on its reflected light path. The sixth beam splitter 405 is located on the beam-splitting path of the fifth beam splitter 403. The third dichroic mirror 408 is located on the output light path of the third infrared tunable laser 407, and the output light path of the third dichroic mirror 408 enters the microscope objective 1. The visible laser emitted by the second visible laser 401 is divided into a reference light and an object light. The object light is reflected back by the sample after passing through the microsphere lens 2 and finally reaches the third photodetector 406. The reference light is reflected and finally reaches the third photodetector 406. According to the principle of optical interference, the distance between the microsphere lens 2 and the sample 3 is measured, and then the infrared absorption spectrum of the sample 3 is measured.

[0047] Specifically, the microscope objective 1 is a Nikon TU Plan ELWD 50X model; the microsphere lens 2 is a barium titanate microsphere with a diameter of 30~60μm.

[0048] The photodetector, piezoelectric ceramic, and stepping platform 4 in the sample surface measurement system 5 are all connected to the host computer 6. Combined with the host computer 6 for controlling platform movement and image processing, the sample surface measurement system 5 can achieve pure optical, non-destructive infrared spectroscopy measurement and three-dimensional imaging of sample surface morphology in three ways.

[0049] The present invention provides an infrared spectroscopy measurement device based on a microsphere lens, the working principle of which is as follows:

[0050] A method combining a high-magnification microscope objective 1 with a microsphere lens 2 is employed. The incident light is highly focused through the photonic nanojet effect of the microsphere lens 2, concentrating the measurement beam within a subwavelength region. Three optical measurement systems based on different principles are introduced to measure the surface displacement changes caused by infrared absorption of the sample: laser astigmatism, heterodyne interferometry, and null interference. A numerical relationship between the sample's infrared absorption wavelength, absorption amount, and sample surface displacement is established. Through data processing, the infrared absorption spectrum of the sample is measured. With the three-dimensional movement of piezoelectric ceramics and a stepping platform 4, the infrared absorption spectrum of different regions of the sample is measured, and the sample surface morphology is imaged simultaneously. This method overcomes the shortcomings of existing infrared absorption spectroscopy measurement techniques, which are prone to damaging the sample and have low efficiency in large-area imaging, and achieves pure optical, non-destructive, super-resolution infrared spectroscopy imaging of the sample in the submicron region.

[0051] See Figure 1As shown, another aspect of the present invention provides an infrared spectroscopy measurement method based on a microsphere lens, comprising the following steps: a high-magnification microscope objective 1 is simultaneously connected to the incident infrared spectrum and the visible light measurement spectrum. The infrared light is focused by the microscope objective 1 onto a large region on the sample surface that exceeds the diffraction limit. The photothermal effect of the sample surface causes corresponding fluctuations in the sample surface after absorbing the infrared spectrum in this large region. The visible light measurement spectrum, after being focused by the high-magnification microscope objective 1, is again focused by the microsphere lens 2. Due to the photon nanojet effect generated by the ultra-strong beam focusing effect of the microsphere lens 2, the sample surface changes within the visible light optical diffraction limit range are collected by the microsphere lens 2 and then detected by the subsequent sample surface measurement system 5. Data processing is performed through the mathematical relationship between the changes in the light spot / optical interference fringes, the changes in surface morphology fluctuations, and the intensity of the sample's absorbed infrared spectrum to reconstruct the sample's infrared absorption spectrum. By using the cyclic reciprocating motion of piezoelectric ceramics and stepping moving platform 4, a large-scale infrared spectral image of the surface of sample 3 is detected. Then, through data processing, the morphology of each sampling point before deformation is stitched together to obtain the surface morphology information of sample 3.

[0052] Example 1

[0053] See Figure 2 As shown, the fluctuations in the surface of sample 3 after absorbing infrared spectra are collected by the sample surface measurement system 5 and the data processing includes the following steps:

[0054] The light emitted by the visible measurement laser 201 is collimated and expanded sequentially by the collimating and expanding assembly 202, becomes p-type linearly polarized light by the polarization beam splitter 203, and becomes clockwise elliptically polarized light after passing through the quarter-wave plate 204. It is then reflected by the first dichroic mirror 205 to the microscope objective 1 for primary focusing. The focused beam is then refocused by the microsphere lens 2, so that the light spot breaks through the diffraction limit and is focused on the region on the surface of the sample 3. The infrared spectrum emitted by the first infrared tunable laser 208 is collimated by the collimating optical assembly 209, reflected by the first reflecting mirror 210, and then incident on the microscope objective 1 after passing through the first dichroic mirror 205. It is focused on the region on the surface of the sample 3. The absorption of the infrared spectrum in this region causes a change in the distance between the photon nanojet generated by the microsphere lens 2 and the surface of the sample 3.

[0055] The microsphere lens 2 collects the visible light reflected from the surface of the sample 3 within the range of the photon nanojet. The originally clockwise elliptically polarized light becomes counterclockwise elliptically polarized light, which is reflected by the first dichroic mirror 205 onto the quarter-wave plate 204. At this time, the counterclockwise elliptically polarized light becomes S-shaped polarized light, which is reflected by the polarization beam splitter 203 onto the astigmatic lens 206 for convergence. The shape and size of the light spot are detected by the first photodetector 207.

[0056] After the first photodetector 207 detects the shape and size of the light spot, it obtains the absorption spectrum curve based on the detection information, including the following steps:

[0057] Based on the shape, direction and size of the light spot on the first photodetector 207, the change in distance between the microsphere lens 2 and the surface of the sample 3 and the direction of deviation from the initial position are obtained. Based on the relationship between the sample's absorbed infrared spectrum and the sample's photothermal induced surface undulation, the data spectrum of the sample's absorption intensity at the specified absorption spectrum is obtained. The infrared absorption spectrum curve of the sample within the specified range is obtained by continuous spectral scanning.

[0058] Example 2

[0059] See Figure 3 As shown, the fluctuations in the surface of sample 3 after absorbing infrared spectra are collected by the sample surface measurement system 5 and the data processing includes the following steps:

[0060] The measurement laser emitted by the first visible light laser 301 is split into two beams by the first beam splitter 302, namely the reference beam and the object beam. The object beam is then focused once by the second beam splitter 303 and the second dichroic mirror 309. The focused beam is then focused a second time by the microsphere lens 2. The photonic nanojet effect of the microsphere lens 2 is used to make the size of the focused spot break through the diffraction limit and focus on the area on the surface of the sample 3.

[0061] The reference light is reflected by the second mirror 304 into the Bragg cell 305 for acousto-optic modulation, and then incident on the second photodetector 307 after passing through the third beam splitter 306. The infrared spectrum emitted by the second infrared tunable laser 308 is incident on the microscope objective 1 after passing through the second dichroic mirror 309 and is focused onto the surface region of the sample 3. The absorption of the infrared spectrum in this region causes a change in the distance between the microsphere lens 2 and the surface of the sample 3.

[0062] After collecting the visible light reflected from the surface of the sample 3 within the range of the photon nanojet, the microsphere lens 2 returns along the original optical path. After being reflected by the second beam splitter 303 and the third beam splitter 306, it is simultaneously incident on the second photodetector 307 with the reference light, and then interferes to collect data.

[0063] After acquiring the interference data of the two beams, and combining it with the Doppler frequency shift principle, the infrared absorption spectrum curve of the sample is obtained through data processing, including the following steps:

[0064] The distance change between the microsphere lens 2 and the sample 3 is detected. The direction of the distance change between the microsphere lens 2 and the sample 3 surface is obtained by the Doppler frequency shift generated by the Bragg cell 305. The amount of surface undulation change of the sample is obtained by the interference data, thereby obtaining the amount and direction of the undulation change of the infrared spectrum of the sample surface. By the relationship between the amount of light-induced surface undulation change of the sample and the infrared spectral intensity, and the corresponding wavelength of the infrared spectrum, an infrared absorption spectrum curve of the sample is established.

[0065] Example 3

[0066] See Figure 4 As shown, the main principle of the sample surface measurement system 5 is the zero-difference interferometry method based on the Michelson interferometry principle. The measurement laser emitted by the second visible laser 401 is split into two beams by the fourth beam splitter 402, namely the reference beam and the object beam. The object beam is then focused once by the high-magnification microscope objective 1 after passing through the fifth beam splitter 403 and the third dichroic mirror 408. The beam, after being focused by the microsphere lens 2, is then focused a second time by the microsphere lens 2, so that the light spot breaks through the diffraction limit and is focused on a very small area on the sample surface 3. The reference beam is reflected by the third reflecting mirror 404 to the sixth beam splitter 405 and then enters the third photodetector 406. At the same time, the infrared spectrum emitted by the third infrared tunable laser 407 is entered by the microscope objective 1 after passing through the third dichroic mirror 408 and is focused on a larger area on the sample surface 3. The absorption of the infrared spectrum in this larger area causes a slight change in the distance between the microsphere lens 3 and the sample surface 3. The microsphere lens 2 collects the visible light reflected from the surface of sample 3 within the range of the photon nanojet. The light then returns along the original optical path, is reflected by the fifth beam splitter 403 and the sixth beam splitter 405, and simultaneously incident on the third photodetector 406 along with the reference light. Interference occurs, and the detector collects the data. Using the principle of optical interference, the change in distance between the microsphere lens 2 and the surface of sample 3 is calculated, yielding the fluctuation in the infrared spectrum of the sample surface. By establishing the relationship between the light-induced fluctuation in the sample surface and the infrared spectral intensity, along with the corresponding wavelength of the infrared spectrum, an infrared absorption spectrum curve of the sample is constructed.

[0067] The infrared spectroscopy measurement device and method based on a microsphere lens provided by this invention achieves ultra-high focusing of incident light through the photonic nanojet effect of the microsphere lens 2, focusing the measurement beam into a subwavelength region. The surface displacement changes caused by the absorption of infrared light by the sample are measured to realize the infrared absorption spectrum measurement of the sample. This invention overcomes the shortcomings of existing infrared absorption spectroscopy measurement techniques, such as easy damage to the sample and low imaging efficiency over a large area, achieving pure optical, non-destructive super-resolution infrared spectroscopy imaging of the sample in the submicron region. This invention can be applied to infrared absorption spectroscopy measurement and material composition identification of various polymer materials, including biodegradable polymers, polymer blends, composite materials, multilayer films, polymer nanostructures, thin films / coatings, fibers, fuel cell membranes, biomedical materials and drugs, etc., achieving non-contact and non-destructive spatial submicron scale infrared absorption spectroscopy imaging and spatial distribution analysis of chemical functional groups.

[0068] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An infrared spectroscopy measurement device based on a microsphere lens, characterized in that, It includes a microscope objective (1), a microsphere lens (2), a piezoelectric ceramic and a stepping moving platform (4), and a sample surface measurement system (5). A microscope objective (1) is provided above the piezoelectric ceramic and stepping platform (4), and the microscope objective (1) is located on the output optical path of the sample surface measurement system (5); a microsphere lens (2) is provided between the piezoelectric ceramic and stepping platform (4) and the microscope objective (1); a sample (3) is provided on the piezoelectric ceramic and stepping platform (4).

2. The infrared spectroscopy measuring device based on a microsphere lens according to claim 1, characterized in that, The sample surface measurement system (5) includes a visible measurement laser (201), a collimating beam expander (202), a polarizing beam splitter (203), a quarter-wave plate (204), a first dichroic mirror (205), a first infrared tunable laser (208), a collimating optical component (209), and a first reflecting mirror (210). The output optical path of the visible measurement laser (201) is sequentially provided with a collimating beam expander (202), a polarizing beam splitter (203), a quarter-wave plate (204), and a first dichroic mirror (205); the output optical path of the infrared tunable laser (208) is provided with a first reflecting mirror (210), and the reflected optical path of the first reflecting mirror (210) passes sequentially through the first dichroic mirror (205) and the microscope objective (1).

3. The infrared spectroscopy measuring device based on a microsphere lens according to claim 2, characterized in that, The polarization beam splitter (203) has an astigmatic lens (206) and a first photodetector (207) arranged sequentially on its reflected light path.

4. The infrared spectroscopy measuring device based on a microsphere lens according to claim 1, characterized in that, The sample surface measurement system (5) includes a first visible light laser (301), a first beam splitter (302), a second beam splitter (303), a third beam splitter (306), a second reflector (304), a second photodetector (307), a second infrared tunable laser (308), and a second dichroic mirror (309). The output optical path of the first visible light laser (301) is provided with a first beam splitter (302), a second beam splitter (303), and a second dichroic mirror (309) in sequence; a second reflector (304) is provided on the beam splitting optical path of the first beam splitter (302), and a third beam splitter (306) and a second photodetector (307) are provided on the reflected optical path of the second reflector (304) in sequence; the third beam splitter (306) is provided on the beam splitting optical path of the second beam splitter (303); the second dichroic mirror (309) is provided on the output optical path of the second infrared tunable laser (308); the output optical path of the second dichroic mirror (309) is incident on the microscope objective (1).

5. The infrared spectroscopy measuring device based on a microsphere lens according to claim 4, characterized in that, A Bragg box (305) is provided between the second reflector (304) and the third beam splitter (306).

6. An infrared spectroscopy measurement method based on a microsphere lens, characterized in that, Includes the following steps: The microscope objective (1) converges the incident infrared spectrum and the visible light measurement spectrum. The infrared light is focused onto the surface of the sample (3) by the microsphere lens (2). The surface of the sample (3) absorbs the infrared spectrum and produces fluctuations. The data is collected by the sample surface measurement system (5) and processed to obtain the infrared absorption spectrum of the sample.

7. The infrared spectroscopy measurement method based on a microsphere lens according to claim 6, characterized in that, The fluctuations that occur when the surface of the sample (3) absorbs infrared spectra are collected by the sample surface measurement system (5) and the data is processed, including the following steps: The light emitted by the visible measurement laser (201) is collimated and expanded sequentially by the collimating and expanding assembly (202), and then converted into p-type linearly polarized light by the polarization beam splitter (203). After passing through the quarter-wave plate (204), it becomes elliptically polarized light in the clockwise direction. It is reflected by the first dichroic mirror (205) to the microscope objective (1) for a first focusing. The focused beam is then refocused by the microsphere lens (2) so that the light spot breaks through the diffraction limit and is focused on the area on the surface of the sample (3). The infrared spectrum emitted by the first infrared tunable laser (208) is collimated by the collimating optical assembly (209), reflected by the first reflecting mirror (210), and then incident on the microscope objective (1) after passing through the first dichroic mirror (205). It is focused on the area on the surface of the sample (3). The absorption of the infrared spectrum in this area causes the distance of the photon nanojet generated by the microsphere lens (2) relative to the surface of the sample (3) to change. The microsphere lens (2) collects the visible light reflected from the surface of the sample (3) within the range of the photon nanojet. The originally clockwise elliptically polarized light becomes counterclockwise elliptically polarized light and is reflected by the first dichroic mirror (205) onto the quarter-wave plate (204). At this time, the counterclockwise elliptically polarized light becomes S-shaped polarized light and is reflected by the polarization beam splitter (203) onto the astigmatic lens (206) for convergence. The first photodetector (207) detects the shape and size of the light spot.

8. The infrared spectroscopy measurement method based on a microsphere lens according to claim 7, characterized in that, After the first photodetector (207) detects the shape and size of the light spot, it obtains the absorption spectrum curve based on the detection information, including the following steps: Based on the shape, direction and size of the light spot on the first photodetector (207), the change in distance between the microsphere lens (2) and the sample (3) surface and the direction of deviation from the initial position are obtained. Based on the relationship between the sample's absorbed infrared spectrum and the sample's photothermal induced surface undulation, the data spectrum of the sample's absorption intensity at the specified absorption spectrum is obtained. The infrared absorption spectrum curve of the sample within the specified range is obtained by continuous spectral scanning.

9. The infrared spectroscopy measurement method based on a microsphere lens according to claim 6, characterized in that, The fluctuations that occur when the surface of the sample (3) absorbs infrared spectra are collected by the sample surface measurement system (5) and the data is processed, including the following steps: The measurement laser emitted by the first visible light laser (301) is split into two beams by the first beam splitter (302), namely the reference beam and the object beam. After the object beam passes through the second beam splitter (303) and the second dichroic mirror (309), it is incident on the microscope objective (1) for a first focusing. The focused beam then passes through the microsphere lens (2) for a second focusing. The photon nanojet effect of the microsphere lens (2) is used to make the size of the focused spot break through the diffraction limit and focus on the area on the surface of the sample (3). The reference light is reflected by the second mirror (304) into the Bragg cell (305) for acousto-optic modulation, and then incident on the second photodetector (307) after passing through the third beam splitter (306); the infrared spectrum emitted by the second infrared tunable laser (308) is incident on the microscope objective (1) after passing through the second dichroic mirror (309), and is focused onto the surface area of ​​the sample (3). The absorption of the infrared spectrum in this area causes the distance of the microsphere lens (2) relative to the surface of the sample (3) to change; After collecting the visible light reflected from the surface of the sample (3) within the range of the photon nanojet, the microsphere lens (2) returns along the original optical path. After being reflected by the second beam splitter (303) and the third beam splitter (306), it is simultaneously incident on the second photodetector (307) with the reference light and interferes to collect data.

10. The infrared spectroscopy measurement method based on a microsphere lens according to claim 9, characterized in that, After acquiring the interference data of the two beams, and combining it with the Doppler frequency shift principle, the infrared absorption spectrum curve of the sample is obtained through data processing, including the following steps: The distance change between the microsphere lens (2) and the sample (3) is detected. The direction of the distance change between the microsphere lens (2) and the sample (3) surface is obtained by the Doppler frequency shift generated by the Bragg cell (305). The amount of surface undulation change of the sample is obtained by the interference data, thereby obtaining the amount and direction of the undulation change of the infrared spectrum of the sample surface. The infrared absorption spectrum curve of the sample is established by the relationship between the amount of surface undulation change induced by light and the intensity of the infrared spectrum, and the wavelength of the corresponding infrared spectrum.

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