Infrared reflection spectrum testing device based on confocal curved mirror design

Abstract

The present application relates to a kind of adaptation to commercial Fourier transform infrared spectrometer, based on the material (including solid, powder, coating and liquid phase in-situ reaction) infrared reflection spectrum measuring device of off-axis ellipsoidal mirror and off-axis parabolic mirror of confocal point.This application is mainly composed of sample cell, two pieces of plane mirror, and two pieces of off-axis parabolic mirror and a piece of off-axis ellipsoidal mirror arranged in confocal point.By precise slide rail and screw fine adjuster, positioning and fine adjustment are realized.Compared with existing butterfly light path infrared diffuse reflection accessory, by the coplanar design of the optical axis of each mirror and the detection beam of infrared spectrometer, not only the size of the device is effectively reduced, but also it is adapted to all commercial infrared spectrometer models.Furthermore, by the confocal design of off-axis ellipsoidal mirror and parabolic mirror, the integral collection angle and intensity of sample diffuse reflection light are expanded, and the accuracy of emittance test by reflectance optical method is improved.

Description

Technical Field

[0001] This invention pertains to an infrared reflectance spectroscopy testing device. More specifically, it is a material infrared reflectance (or emission) spectroscopy testing device adapted to commercial Fourier transform infrared spectrometers, based on confocal off-axis ellipsoidal mirrors and off-axis parabolic mirrors. Background Technology

[0002] Emissivity, the ratio of an object's radiative exitance to that of a blackbody under the same temperature and wavelength conditions, characterizes the thermal radiation capability of a real object and is a crucial factor affecting its temperature through radiative heat transfer. With the demands of technological advancements and the increasing emphasis on energy conservation and emission reduction, thermal management materials play an increasingly important role in fields such as infrared camouflage, infrared stealth, infrared heat exchange, and radiative cooling. Beyond the single emissivity value obtained from traditional calorimetry, researchers increasingly seek to obtain the emissivity spectrum of materials at corresponding wavelengths. This allows for more targeted research on material modification and facilitates the evaluation of materials' practical applications. Therefore, using reflectometer optical methods to test material emission spectra has become an indispensable option: the sample is placed in a sample cell, and the infrared reflectance spectrum is measured using a Fourier transform infrared spectrometer. According to Kirchhoff's thermodynamic laws, for opaque materials, the spectral emissivity ε(λ) and reflectance R(λ) at the same wavenumber have the following relationship: ε(λ) = 1 - R(λ). Thus, the emissivity spectrum of the material in the infrared band can be derived from the relative intensity information of the infrared reflectance spectrum.

[0003] Compared to transmission spectroscopy, the reflectance testing mode of Fourier transform infrared (FTIR) spectrometers collects reflected light and some scattered light from the sample, resulting in a relatively weaker signal. Therefore, when using diffuse reflectance spectroscopy to detect sample emissivity, it is crucial to minimize the loss of diffuse reflectance signal during optical path propagation. Common commercial FTIR diffuse reflectance accessories typically employ a "butterfly-shaped optical path": a design using a plane mirror—plane mirror—off-axis ellipsoidal mirror—sample cell—off-axis ellipsoidal mirror—plane mirror—plane mirror. This symmetrical design is adapted to infrared spectrometers with different light source orientations. However, current commercial devices have several shortcomings in using reflectometer optical methods to test material emission spectra: 1. When incident light is irradiated onto the sample surface via a plane mirror—ellipsoidal mirror, most of the parallel light exits through a non-ellipsoidal focal point and cannot be focused onto the sample by the ellipsoidal mirror. This means the spectrometer cannot fully utilize the incident light, leading to a decrease in light signal intensity. 2. To ensure optical path compatibility with different spectrometer models, common commercial solutions employ two symmetrical ellipsoidal mirrors. The diffuse infrared light reflected from the sample may return via the incident light path, causing coherent destructive interference with the spectrometer's incident light, thus interfering with the test results. 3. The off-axis ellipsoidal mirror's profile forms a 120° conical angle with the sample cell center, which is only the minimum required value for testing. Furthermore, it is only installed on one side of the sample cell, resulting in very limited collection of diffuse infrared light emitted from the sample. Consequently, the obtained emission spectrum deviates significantly from the true value. 4. During the multiple reflections of the sample's reflected light into the spectrometer's signal collection device via ellipsoidal mirror-plane mirror-plane mirror, the diffuse infrared scattering angle, containing sample information, continuously increases, further reducing the proportion of infrared light reaching the signal collection point. In other words, significant light signal loss occurs during the multiple reflections before reaching the signal collection device. Since the infrared reflected signal is typically weaker than the transmitted signal, and the collection angle and orientation are limited, these factors are all detrimental to accurately determining the sample's emissivity spectrum and other optical properties using infrared reflectance spectroscopy. Summary of the Invention

[0004] In view of this, in order to solve the problem of significant loss in the collection of diffuse reflection light signals by traditional infrared diffuse reflection accessories, the present invention provides an infrared reflection spectroscopy testing device based on a confocal curved mirror design.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An infrared emission spectroscopy measurement device for materials (including solids, powders, coatings, and in-situ liquid reactions) is disclosed using a commercial Fourier transform infrared spectrometer, based on a confocal off-axis ellipsoidal mirror and an off-axis parabolic mirror. The invention comprises a plane mirror, an off-axis parabolic mirror, an off-axis ellipsoidal mirror, and a sample cell, positioned and fixed using precision slide rails and a screw fine-tuning device. Two plane mirrors, two off-axis parabolic mirrors, and one off-axis ellipsoidal mirror (which can also be composed of two pieces joined together, depending on manufacturing capabilities) are used. The optical axes of each mirror are coplanar with the detection beam of the Fourier transform infrared spectrometer, thereby reducing the size of the device and making it compatible with all commercial Fourier transform infrared spectrometer models.

[0007] The optical axes of each reflector are coplanar with the detection beam of the Fourier transform infrared spectrometer, thereby reducing the size of the device and making it compatible with all commercial Fourier transform infrared spectrometer models.

[0008] Among them, the two plane mirrors are divided into the first plane mirror and the second plane mirror, and the two off-axis parabolic mirrors are divided into the first off-axis parabolic mirror and the second off-axis parabolic mirror.

[0009] After the detection light is emitted from the light outlet of the infrared spectrometer, it passes sequentially through the first plane mirror, the first off-axis parabolic mirror, the sample cell, the off-axis ellipsoidal mirror, the second off-axis parabolic mirror, and the second plane mirror, and finally enters the light outlet, where the spectrometer collects infrared test data.

[0010] In this invention, the parallel detection beam emitted from the light output port of the spectrometer is reflected by the first plane mirror to the first off-axis parabolic mirror. The first off-axis parabolic mirror focuses the parallel detection beam off-axis to its common focal point with the off-axis ellipsoidal mirror, which is the position of the sample cell, denoted as F1.

[0011] The detection light reflected by the diffuse (or specular) reflection sample in the sample cell is integrated by the off-axis ellipsoidal mirror and reflected and converged to the second focus of the off-axis ellipsoidal mirror, denoted as F2;

[0012] The light is then converted into parallel light by a second off-axis parabolic mirror that shares a focal point (F2) with the off-axis ellipsoidal mirror. The light is then reflected by a second plane mirror and enters the light output aperture of the spectrometer. The spectrometer collects the data to measure the infrared emission spectrum of the material.

[0013] F1 and F2 are the two focal points of the off-axis ellipsoidal mirror. Point F1 is the common focal point of the off-axis ellipsoidal mirror and the first off-axis parabolic mirror; point F2 is the common focal point of the off-axis ellipsoidal mirror and the second off-axis parabolic mirror.

[0014] Preferably, the infrared reflection spectroscopy testing device based on a confocal curved mirror design includes five infrared high-reflectivity mirrors in its infrared optical path design, which reduces the number of mirrors and decreases the loss of light signals in the propagation path.

[0015] Preferably, the off-axis ellipsoidal reflector has a single-piece or spliced ​​structure, and its maximum forward collection angle is 180°, maximum backward collection angle is 145°, maximum dual lateral collection angle is 180°, and its overall shape is basically equivalent to three-eighths of a complete ellipsoidal surface reflector.

[0016] Preferably, the off-axis ellipsoidal reflector is fixed in position, and a light-transmitting circular hole with a diameter of 10 mm is opened in the direction of the line connecting its first focal point F1 and the first off-axis parabolic reflector to facilitate the detection of light incident.

[0017] Preferably, the line connecting the center of the first off-axis parabolic reflector and point F1 forms a 45° angle with the horizontal plane to ensure that the incident light beam on the sample surface is within the range of 35 to 45° to obtain the strongest infrared light reflection signal.

[0018] Preferably, the reflection angles of the first and second planar reflectors can be finely adjusted to ensure unobstructed optical paths and maximized signal strength.

[0019] Preferably, the position and reflection angle of the first off-axis parabolic mirror can be finely adjusted to facilitate the adjustment of the incident light spot size for samples with different shapes and sizes.

[0020] Preferably, the position and reflection angle of the second off-axis parabolic reflector can be finely adjusted to facilitate the adjustment of the emitted beam in order to obtain the maximum signal strength;

[0021] Preferably, the sample container can be flexibly designed according to the characteristics and size of the sample, with a minimum diameter of 2 mm (or 2 × 2 mm). 2 Maximum diameter 10mm (or 10×10mm) 2 The sample surface can be finely adjusted within a range of up to 10° in both horizontal and tilted towards the incident beam direction to meet the testing requirements.

[0022] Preferably, the size and shape of the sample cell can be changed according to different usage requirements such as powder / sheet / block testing, in-situ reaction, and temperature variation testing. The usable space dimensions include: a height of 70 mm, a length of 50 mm, and a width of 50 mm.

[0023] Preferably, the sample cell has a precision slide rail positioning structure to facilitate the handling and positioning of samples and other auxiliary devices (such as constant temperature and variable temperature testing mechanisms).

[0024] The precision slide rail positioning structure includes a sample cell placement platform and a precision slide rail; the sample cell is connected to the precision slide rail via the sample cell placement platform.

[0025] The precision slide rail is fixed to the bottom of the device housing.

[0026] Preferably, the device is equipped with a retractable light-shielding tube on the side wall of the outer shell, which can be adjusted according to different spectrometer signals to avoid external light interference with the test.

[0027] Preferably, an angle regulator is installed below the sample cell to control the angle of the sample cell.

[0028] The positioning pins allow for flexible design and adjustment of the device base plate according to different matching spectrometers, and can be used with most models of Fourier transform infrared spectrometers.

[0029] Preferably, the reflective film is an infrared high reflectivity gold film, which can reduce the loss of infrared light in the optical path. Other optional infrared high reflectivity coating materials include aluminum and silver (a protective layer is required).

[0030] Preferably, the accessory dimensions include a height of 140mm, a length of 140mm, and a width of 100mm, which can fit into most Fourier transform infrared spectrometers.

[0031] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0032] Traditional infrared diffuse reflection accessory designs often employ a combination of a plane mirror—a plane mirror—an ellipsoidal mirror—a sample cell—a plane mirror—a plane mirror. This invention, however, uses a combination of a plane mirror—an off-axis parabolic mirror—a sample cell—an off-axis ellipsoidal mirror—an off-axis parabolic mirror—a plane mirror. This reduces the number of mirrors and decreases the loss of infrared light signals due to mirror reflection. It also expands the sample's infrared light collection angle, with a maximum forward collection angle of 180°, a maximum backward collection angle of 145°, and a maximum dual-lateral collection angle of 180°, thus maximizing the acquisition of optical information from the sample. It closely approximates the integrating sphere; the infrared beam is incident on the sample surface at 35-45°, which is the range for obtaining the strongest infrared light reflection spectrum signal from the sample; it expands the range of test objects for the accessory, and can collect infrared spectral information from diffuse reflection, specular reflection, and specular reflection samples; the combination of a confocal off-axis ellipsoidal reflector and an off-axis parabolic reflector solves the problem that the plane reflector further deflects the converging infrared light reflected by the ellipsoidal reflector, resulting in a small proportion of infrared light reaching the infrared spectrometer signal collection device after diffuse reflection of the sample, incomplete spectral information collection, and a large deviation between the emission spectrum and the true value.

[0033] Compared to traditional infrared diffuse reflectance accessories, this invention can collect infrared spectral information over a wider range, improving the accuracy of emissivity testing using reflectometer optical methods. It also controls the overall device design dimensions and can be applied to most Fourier transform infrared spectrometers. It is particularly useful for testing samples with weak infrared reflectance signals and for observing the optical properties of samples at corresponding wavenumbers across a wide infrared band. This allows researchers to study the infrared radiation characteristics of samples using inverse design optics methods. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This is a side view schematic diagram of the infrared reflecting device of the present invention;

[0036] Figure 2 This is a schematic diagram of the installation of the infrared reflection device of the present invention in conjunction with a Fourier transform infrared spectrometer;

[0037] Figure 3 This is a schematic diagram of the optical path design of the infrared reflection device of the present invention;

[0038] In the figure:

[0039] 1-First plane mirror; 2-First off-axis parabolic mirror; 3-Sample cell; 4-Off-axis ellipsoidal mirror; 5-Second off-axis parabolic mirror; 6-Second plane mirror; 7-Sample cell placement platform; 8-Precision slide rail; 9-Retractable light shield; 10-Angle adjuster. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides an infrared reflectance spectroscopy testing device based on a confocal curved mirror design. The infrared reflectance testing accessory is designed using the FITR-650S Fourier transform infrared spectrometer as an example. Under the condition of meeting the sample chamber size of the infrared spectrometer, it can theoretically be used with most types of infrared spectrometers.

[0043] The device of the present invention includes: a plane mirror, an off-axis parabolic mirror, an off-axis ellipsoidal mirror, and a sample cell, wherein there are two plane mirrors and two off-axis parabolic mirrors, and one off-axis ellipsoidal mirror, all placed on a vertical plane with the line connecting the light output aperture and the light input aperture of the spectrometer passing through it;

[0044] Among them, the plane mirror includes a first plane mirror 1 and a second plane mirror 6, the off-axis parabolic mirror includes a first off-axis parabolic mirror 2 and a second off-axis parabolic mirror 5, the off-axis ellipsoidal mirror is an off-axis ellipsoidal mirror 4, and the sample cell is a sample cell 3.

[0045] The first plane mirror 1 reflects the parallel detection beam emitted from the light output port of the spectrometer to the first off-axis parabolic mirror 2. The size of the mirror should be larger than that of the infrared light source, and the installation position should be such that the infrared light emitted by the infrared light source is completely reflected to the first off-axis parabolic mirror 2.

[0046] The parallel detection light is focused off-axis by the first off-axis parabolic reflector 2 to the common focal point of the parabolic reflector 2 and the off-axis ellipsoidal reflector, i.e., the center F1 position of the sample cell 3. The off-axis angle of the first off-axis parabolic reflector 2 can be designed according to the sample chamber space of the infrared spectrometer. The mirror size should be able to fully accept the infrared light reflected by the plane reflector 1.

[0047] The detection light reflected by the diffuse (or specular) reflection sample in the sample cell 3 is integrated and reflected by the off-axis ellipsoidal mirror 4 and converged to the second focus F2 position of the off-axis ellipsoidal mirror 4.

[0048] The light is then converted into parallel light by the second off-axis parabolic mirror 5, which shares a focal point (F2) with the off-axis ellipsoidal mirror 4. The light is then reflected by the second plane mirror 6 and enters the light output aperture of the spectrometer. The spectrometer collects the data and realizes the measurement of the infrared emission spectrum of the material.

[0049] Point F1 is both the major axis focus of the off-axis ellipsoidal reflector 4 and the parabolic focus of the first off-axis parabolic reflector 2. Point F2 is both the major axis focus of the off-axis ellipsoidal reflector 4 and the parabolic focus of the second off-axis parabolic reflector 5.

[0050] The line connecting the center of the first off-axis parabolic reflector 2 and point F1 forms a 45° angle with the horizontal plane to ensure that the incident light beam on the sample surface is within the range of 35-45° to obtain the strongest infrared light reflection signal.

[0051] The off-axis ellipsoidal reflector 4 is fixed in position, and a light-transmitting circular hole with a diameter of 10mm is opened in the direction of the line connecting its first focal point F1 and the first off-axis parabolic reflector to facilitate the detection of light incident.

[0052] The position and reflection angle of the first off-axis parabolic mirror 2 can be finely adjusted to facilitate the adjustment of the incident light spot size for samples with different shapes and sizes.

[0053] The position and reflection angle of the second off-axis parabolic reflector 5 can be finely adjusted to facilitate the adjustment of the emitted beam and obtain the maximum signal strength.

[0054] The off-axis ellipsoidal reflector 4 has a single or spliced ​​structure, and its maximum forward collection angle is 180°, maximum backward collection angle is 145°, and maximum bilateral collection angle is 180°. Its overall shape is basically equivalent to three-eighths of an ellipsoidal reflector.

[0055] The base layer of the plane mirror, off-axis parabolic mirror, and off-axis ellipsoidal mirror is made of 6061 aluminum, and the reflective film is an infrared high-reflectivity gold film.

[0056] The size and shape of sample cell 3 can be changed according to different usage requirements such as powder / tablet / block testing, in-situ reaction, and temperature variation testing. The usable space dimensions include: height of 70mm, length of 50mm, and width of 50mm.

[0057] In this embodiment, the sample cell is equipped with a precision slide rail positioning structure to facilitate the placement and positioning of samples and other auxiliary devices (such as constant temperature and variable temperature testing mechanisms).

[0058] The precision slide rail positioning structure includes a sample cell placement platform 7 and a precision slide rail 8; the sample cell 3 is connected to the precision slide rail 8 through the sample cell placement platform 7.

[0059] The precision slide rail 8 is fixed to the bottom of the device housing. The device is equipped with a retractable light shield 9 on the side wall of the housing, which can be adjusted according to different spectrometer signals to avoid external light interference with the test.

[0060] An angle regulator 10, which controls the angle of the sample cell, is installed below the sample cell.

[0061] The positioning pins allow for flexible design and adjustment of the device base plate according to different matching spectrometers, and can be used with most models of Fourier transform infrared spectrometers.

[0062] The accessory dimensions are: height 140mm, length 140mm, and width 100mm.

[0063] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0064] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An infrared reflectance spectroscopy testing device based on a confocal curved mirror design, characterized in that, The device includes: two plane mirrors, two off-axis parabolic mirrors, one off-axis ellipsoidal mirror, and a sample cell; The optical axes of the plane mirror, off-axis parabolic mirror, and off-axis ellipsoidal mirror are designed to be coplanar with the detection beam of the spectrometer, and this plane is perpendicular to the plane. The two planar reflectors are divided into a first planar reflector and a second planar reflector, and the two off-axis parabolic reflectors are divided into a first off-axis parabolic reflector and a second off-axis parabolic reflector. After the detection light is emitted from the light outlet of the infrared spectrometer, it passes sequentially through the first plane mirror, the first off-axis parabolic mirror, the sample cell, the off-axis ellipsoidal mirror, the second off-axis parabolic mirror, and the second plane mirror, and finally enters the light outlet, where the spectrometer collects infrared test data.

2. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 1, characterized in that, The parallel detection beam emitted from the spectrometer's output port is reflected by the first plane mirror to the first off-axis parabolic mirror. The first off-axis parabolic mirror focuses the parallel detection beam off-axis to its common focal point with the off-axis ellipsoidal mirror, which is the position of the sample cell, denoted as F1. The detection light reflected by the diffuse or specular reflection sample in the sample cell is integrated by the off-axis ellipsoidal mirror and reflected and converged to the second focus of the off-axis ellipsoidal mirror, denoted as F2; The light is then converted into parallel light by the second off-axis parabolic mirror, which shares the same focal point F2 with the off-axis ellipsoidal mirror. The light is then reflected by the second plane mirror and enters the light output aperture of the spectrometer. The spectrometer collects the data and realizes the measurement of the infrared emission spectrum of the material. F1 and F2 are the two focal points of the off-axis ellipsoidal mirror.

3. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 2, characterized in that, The off-axis ellipsoidal reflector is fixed in position, and a light-transmitting circular hole with a diameter of 10 mm is opened in the direction of the line connecting its first focal point F1 and the first off-axis parabolic reflector to facilitate the detection of light incident. The reflection angles of the first and second planar reflectors can be finely adjusted to ensure unobstructed optical paths and maximized signal strength. The position and reflection angle of the first off-axis parabolic mirror can be finely adjusted to facilitate the adjustment of the incident light spot size for samples with different shapes and sizes. The position and reflection angle of the second off-axis parabolic reflector can be finely adjusted to facilitate the adjustment of the emitted beam in order to obtain the maximum signal strength; The sample container is flexibly designed according to the characteristics and size of the sample, with a minimum diameter of 2 mm or a minimum area of ​​2×2 mm. 2 Maximum diameter 10 mm or maximum area 10×10 mm 2 The sample surface can be tilted up to 10 degrees horizontally and towards the incident beam direction. o Fine-tuning within a certain range to meet testing requirements.

4. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 2, characterized in that, Location point F1 is the common focal point of the off-axis ellipsoidal mirror and the first off-axis parabolic mirror; Location point F2 is the common focal point of the off-axis ellipsoidal mirror and the second off-axis parabolic mirror.

5. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 2, characterized in that, The off-axis ellipsoidal reflector has a single-piece or modular structure, and its maximum forward collection angle is 180°. o The maximum backward collection angle is 145 degrees. o Maximum collection angle of 180 degrees from both sides o Its overall shape is roughly equivalent to three-eighths of an ellipsoidal reflector; The line connecting the center of the first off-axis parabolic mirror and position point F1 forms a 45° angle with the horizontal plane to ensure that the incident light beam on the sample surface is within the 35-45° range. o The range from which the strongest infrared reflected light signal is obtained.

6. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 1, characterized in that: The bottom of the sample cell is equipped with a precision slide rail positioning structure; The precision slide rail positioning structure includes a sample cell placement platform and a precision slide rail; the sample cell is connected to the precision slide rail through the sample cell placement platform.

7. The infrared reflectance spectroscopy testing device based on a confocal curved mirror design according to claim 1, characterized in that, The planar reflector, off-axis parabolic reflector, and off-axis ellipsoidal reflector all include a base layer and an infrared high-reflectivity gold-plated film on the surface.

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