CN114235746A - Device and method for measuring absolute reflectivity spectrum - Google Patents
Device and method for measuring absolute reflectivity spectrum Download PDFInfo
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Abstract
The invention discloses a device and a method for measuring an absolute reflectivity spectrum, and belongs to the technical field of material absolute reflectivity spectrum measurement. The invention utilizes a diffuse reflection cubic integral cavity to measure the absolute diffuse reflectance spectrum of a material, the cubic cavity comprises a cavity body and a movable and detachable top cover plate, and the side wall of the cavity body is provided with a light inlet hole and a light outlet hole; light emitted by the light source is converged by the biconvex lens and enters the cubic cavity through the light inlet, then is emitted from the light outlet, is received by the optical fiber probe and is transmitted to the spectrometer, and spectral data split by the spectrometer is transmitted to the computer for recording. And different emergent spectra are obtained by adjusting the sizes of different top cover openings, and the absolute diffuse reflectance spectrum of the diffuse reflection cubic cavity is obtained after data processing. According to the invention, the absolute diffuse reflectance spectrum of the material of the wall in the cavity is accurately calculated by measuring the emergent spectra of the cubic cavity under the conditions of different additional aperture ratios, so that the accurate measurement of the absolute diffuse reflectance spectrum of the material is realized.
Description
Technical Field
The invention relates to a device and a method for measuring an absolute reflectivity spectrum, belonging to the technical field of material absolute reflectivity spectrum measurement.
Background
The reflection of an object to light can be divided into specular reflection and diffuse reflection, and the specular reflection means that when light is incident on an object with a smooth surface, an included angle between the reflected light and the incident light meets the reflection law of the light in geometric optics, and the reflected light is still parallel light. Diffuse reflection refers to a phenomenon in which, when light is incident on a rough object surface, the reflected light propagates in various directions. The reflectivity of a material is one of the important parameters characterizing the optical properties of the material. Different materials have different internal structures and components, so that the absorption of light is different, and therefore, by measuring the diffuse reflectance spectrum of the material, relevant information about the chemical components of the material can be obtained, for example, by measuring and comparing the diffuse reflectance spectra of natural jade and artificial jade, the authenticity of jade can be identified very accurately. In addition, the X-ray is incident on the surface of the material, and important parameters such as the density, the roughness, the thickness and the like of the material to be measured can be obtained by measuring the incident angle of the X-ray when the total reflection occurs. The substances contacted in the actual production life are more rough surfaces, so that the method has important practical value and significance for measuring the diffuse reflectance of various materials.
At present, diffuse reflectance measurement of materials can be generally divided into absolute measurement methods and relative measurement methods according to whether a standard white board is required or not, the absolute measurement methods are mostly measurement methods based on an integrating sphere at present, and common methods include an auxiliary integrating sphere method, a Kott method and a Sharp-Lite method. The improved absolute diffuse reflectance spectrum measurement method based on the auxiliary integrating sphere is a standard for measuring and tracing the absolute diffuse reflectance spectrum in China, which is proposed by the national measurement science research institute. The method comprises the steps of measuring an auxiliary integrating sphere and a measured sample, and respectively preventing a signal ratio relative to a reference plate at an integrating sphere sample port of an instrument and determining an absolute diffuse reflectance spectrum of the inner wall coating according to a parameter aperture ratio of the integrating sphere. But since the aperture ratio in this method is measured by directly measuring the diameter of each aperture of the integrating sphere to calculate the aperture area and dividing by the desired total internal surface area of the integrating sphere. In the actual processing and production process of the integrating sphere, the processing of the sphere cavity is more difficult than that of a plane plate. Therefore, not only is the processing cost high, but also the processed integrating sphere tends to generate an error deviating from an ideal spherical surface, and the error further causes a larger error between the real aperture ratio of the integrating sphere and the aperture ratio obtained by measuring the aperture diameter, thereby finally causing an increase of the absolute diffuse reflectance spectrum measurement error.
Another method for measuring the diffuse reflectance of a material is relative measurement, which generally requires a standard white plate made of Polytetrafluoroethylene (PTFE) as a reference standard and a diffuse-reflectance integrating sphere as a main measurement device. The relative diffuse reflectance of the material to be measured is determined by measuring the ratio of the diffuse reflectance spectrum of the standard white board to the diffuse reflectance spectrum of the material to be measured, and the diffuse reflectance of the material is measured by using a relative method which is relatively simple compared with an absolute measurement method in the world at present. However, this method determines the relative value of the diffuse reflectance of the standard whiteboard rather than the absolute diffuse reflectance of the material, so although this method is commonly used, the diffuse reflectance measured by this method is still not accurate due to the error caused by the measurement of the absolute diffuse reflectance of the standard whiteboard. Therefore, a method capable of measuring the absolute diffuse reflectance spectrum of the material more accurately becomes a problem to be solved.
Disclosure of Invention
The invention provides a device and a method for measuring an absolute reflectivity spectrum, which aim to solve the problem of large measurement error of the conventional diffuse reflectivity measurement method.
The technical scheme of the invention is as follows:
an apparatus for measuring an absolute reflectance spectrum, the apparatus comprising: the device comprises a light source 1, a biconvex lens 2, a rectangular cavity, a fiber probe 8, a spectrometer 9 and a computer 10; the cubic cavity comprises a cavity body 6 and a top cover plate 5, two adjacent side walls of the cavity body 6 are respectively provided with a light inlet hole 3 and a light outlet hole 7, and the top cover plate 5 is movable and detachable;
light emitted by the light source 1 is converged by the biconvex lens 2 and then enters the cavity 6 of the cubic cavity through the light inlet 3, the light is emitted from the light outlet 7 through diffuse reflection in the cavity 6, emergent light is received by the optical fiber probe 8 after being emitted and then transmitted to the spectrometer 9, and spectral data after being split by the spectrometer 9 is transmitted to the computer 10.
Further, the light source 1 is an incoherent broadband light source, and the power range of the light source 1 is 100-150W.
More particularly, the light source 1 is a tungsten halogen lamp.
Further defined, the lenticular lens 2 is made of quartz of JGS 1.
The method for measuring the absolute reflectivity spectrum by using the device comprises the following steps:
the method comprises the following steps that firstly, light emitted by a light source 1 is converged by a biconvex lens 2 and then enters a cavity 6 of a cubic cavity through a light inlet 3;
step two, light is emitted from the light outlet 7 through diffuse reflection in the cavity 6, emergent light is received by the optical fiber probe 8 after being emitted, then is transmitted to the spectrometer 9, and spectral data split by the spectrometer 9 is transmitted to the computer 10;
step three, moving the openings of the top cover plate 5 and the cavity 6, and changing the additional opening ratio fxRepeating the operation of the first step and the operation of the second step, and recording a plurality of groups of spectral data;
and step four, calculating the diffuse reflectance rho (lambda) at the wavelength lambda.
Further defined, the calculation formula of the diffuse reflectance ρ (λ) at the wavelength λ in the fourth step:
in the formula fxI (lambda) is the intensity of light exiting the exit aperture when the additional aperture ratio is 0; i' (λ) is an additional aperture ratio of fxThe intensity of light emerging from the exit aperture; f. of0The original opening ratio of the diffuse reflection cubic cavity is the opening ratio of the cavity when the top cover plate is completely covered tightly;
wherein the additional opening ratio fxThe calculation formula of (a) is as follows:
in the formula, x is the opening length of the movable top cover plate 5 and the cavity 6, and L is the side length of the cavity 6.
Further limiting, L is 6-12 cm.
Is further defined as f x0 to 0.0833.
The invention has the beneficial effects that:
the invention utilizes the diffuse reflection cubic integral cavity to measure the absolute diffuse reflectance spectrum of the material, takes broadband incoherent light as a light source, obtains emergent spectra of cavities under different aperture ratio conditions by changing the size of an opening of a top cover of the cubic cavity, and obtains the absolute diffuse reflectance spectrum of the diffuse reflection cubic cavity by further calculation. Compared with the prior art, the invention has the following advantages:
(1) according to the method, a standard white board or an auxiliary integrating sphere is not required to be used as a reference, the absolute diffuse reflectance value of the cavity is obtained by changing the additional aperture ratio for multiple times to obtain the relative change of the emergent light intensity of the cavity, and the complex steps of a reference material or a baffle and the like in the conventional diffuse reflectance measuring method are effectively solved, so that the error is smaller, and the precision is higher;
(2) compared with the conventional diffuse reflection integrating sphere for measuring the diffuse reflectivity, the diffuse reflection cubic cavity has the obvious advantages of simple structure, easiness in processing and low cost.
Drawings
FIG. 1 is an experimental schematic diagram of the absolute diffuse reflectance spectroscopy measurement method of the present invention;
FIG. 2 shows the emission spectra of the diffuse reflection cubic cavity obtained under different conditions of additional aperture ratio;
FIG. 3 shows the wavelength at a specific wavelength
The variation curve of the opening ratio is attached;
FIG. 4 is the absolute diffuse reflectance spectrum of the diffuse reflection cubic cavity in the 450-900nm band calculated by the method;
in the figure, 1-a light source, 2-a biconvex lens, 3-a light inlet, 5-a top cover plate, 6-a cavity, 7-a light outlet, 8-a fiber-optic probe, 9-a spectrometer and 10-a computer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.
Example 1:
specifically describing the embodiment with reference to fig. 1, the method for measuring the absolute reflectance spectrum in the embodiment is implemented based on a device that includes a light source 1, a lenticular lens 2, a rectangular cavity, a fiber probe 8, a spectrometer 9, and a computer 10; the cubic cavity comprises a cavity body 6 and a top cover plate 5, two adjacent side walls of the cavity body 6 are respectively provided with a light inlet hole 3 and a light outlet hole 7, and the top cover plate 5 is movable and detachable;
light emitted by the light source 1 is converged by the biconvex lens 2 and then enters the cavity 6 of the cubic cavity through the light inlet 3, the light is emitted from the light outlet 7 through diffuse reflection in the cavity 6, emergent light is received by the optical fiber probe 8 after being emitted and then transmitted to the spectrometer 9, and spectral data after being split by the spectrometer 9 is transmitted to the computer 10.
The measuring method comprises the following steps:
the method comprises the following steps that firstly, light emitted by a light source 1 is converged by a biconvex lens 2 and then enters a cavity 6 of a cubic cavity through a light inlet 3;
step two, light is emitted from the light outlet 7 through diffuse reflection in the cavity 6, emergent light is received by the optical fiber probe 8 after being emitted, then is transmitted to the spectrometer 9, and spectral data split by the spectrometer 9 is transmitted to the computer 10;
step three, moving the openings of the top cover plate 5 and the cavity 6, and changing the additional opening ratio fxRepeating the operation of the first step and the operation of the second step, and recording a plurality of groups of spectral data;
and step four, calculating the diffuse reflectance rho (lambda) at the wavelength lambda.
Calculation formula of diffuse reflectance ρ (λ) at wavelength λ:
in the formula fxI (lambda) is the intensity of light exiting the exit aperture when the additional aperture ratio is 0; i' (λ) is an additional aperture ratio of fxThe intensity of light emerging from the exit aperture; f. of0The original aperture ratio of the diffuse reflection cubic cavity, namely the aperture ratio of the cavity when the top cover plate is completely covered tightly (the aperture ratio of the diffuse reflection cubic cavity consists of two parts, one part is the original aperture ratio f0The opening ratio of the cavity is the opening ratio when the top cover of the cavity is completely covered, and the additional opening ratio is the opening ratio which is additionally increased due to the movement of the top cover when the top cover is completely closed relative to the top cover after the top cover is opened to a certain size; the total cavity opening ratio is composed of the original opening ratio and the additional opening ratio together);
wherein the additional opening ratio fxThe calculation formula of (a) is as follows:
in the formula, x is the opening length of the movable top cover plate 5 and the cavity 6, and L is the side length of the cavity 6.
The following specific description of the absolute reflectance spectrum measurement and calculation process using a tungsten halogen lamp as a light source and data processing at a wavelength of 613nm as an example includes the following specific processes:
(1) a plurality of groups of emission spectrum data are obtained by changing the additional aperture ratio, as shown in fig. 2, data with a wavelength of 613nm are extracted, and the obtained data are shown in table 1 (when the diffuse reflectance spectrum is calculated, experimental data with an emission intensity less than 15% of the maximum emission intensity is regarded as invalid data with poor signal-to-noise ratio, and is discarded without processing):
(2) according to different additional opening ratios
The values of (a) are shown in Table 1;
TABLE 1
(3) With additional opening ratio fxAs the independent variable, there is a variable,
the value of (d) is fitted to the dependent variable by the equation y — kx, and the slope k of the fitted straight line is obtained as 18.919, as shown in fig. 3.
(4) The original aperture ratio f of the diffuse reflection cubic cavity0The formula (1) was substituted with 0.02, and the diffuse reflectance ρ was obtained as 0.95.
The absolute diffuse reflectance spectrum of the diffuse reflection cubic cavity at the 450-900nm waveband calculated by the method is shown in fig. 4, wherein the inner wall material of the cavity is an Avian-D coating developed by Avian Technologies, and the main component of the coating is two-component water-based ethane.
The above embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments, and modifications and changes thereof may be made by those skilled in the art within the scope of the claims of the present invention.
Claims (8)
1. An apparatus for measuring absolute reflectance spectra, the apparatus comprising: the device comprises a light source (1), a biconvex lens (2), a rectangular cavity, an optical fiber probe (8), a spectrometer (9) and a computer (10); the cubic cavity comprises a cavity body (6) and a top cover plate (5), two adjacent side walls of the cavity body (6) are respectively provided with a light inlet hole (3) and a light outlet hole (7), and the top cover plate (5) is movable and detachable;
light emitted by the light source (1) is converged by the double-convex lens (2) and then enters the cavity (6) of the cubic cavity through the light inlet hole (3), the light is emitted from the light outlet hole (7) through diffuse reflection in the cavity (6), emergent light is received by the optical fiber probe (8) after being emitted, then the emergent light is transmitted to the spectrometer (9), and spectral data after being split by the spectrometer (9) is transmitted to the computer (10).
2. The device for measuring absolute reflectivity according to claim 1, wherein the light source (1) is an incoherent broadband light source, and the power range of the light source (1) is 100-150W.
3. The apparatus for measuring absolute reflectivity according to claim 2, wherein the light source (1) is a tungsten halogen lamp.
4. The apparatus for measuring absolute reflectivity of claim 1, wherein the lenticular lens (2) is made of quartz of JGS 1.
5. A method of measuring absolute reflectance spectra using the apparatus of any one of claims 1 to 4, the method comprising the steps of:
the method comprises the following steps that firstly, light emitted by a light source (1) is converged by a biconvex lens (2) and then enters a cavity (6) of a cubic cavity through a light inlet (3);
step two, light is emitted from a light outlet hole (7) through diffuse reflection in a cavity (6), emergent light is received by an optical fiber probe (8) after being emitted, then is transmitted to a spectrometer (9), and spectral data split by the spectrometer (9) is transmitted to a computer (10);
thirdly, moving the openings of the top cover plate (5) and the cavity (6) and changing the additional opening ratio fxRepeating the operation of the first step and the operation of the second step, and recording a plurality of groups of spectral data;
and step four, calculating the diffuse reflectance rho (lambda) at the wavelength lambda.
6. The method for measuring absolute reflectance spectrum according to claim 5, wherein the calculation formula of diffuse reflectance p (λ) at wavelength λ in the fourth step is:
in the formula fxI (lambda) is the intensity of light exiting the exit aperture when the additional aperture ratio is 0; i' (λ) is an additional aperture ratio of fxIntensity of light emitted from the exit aperture；f0The original aperture ratio of the diffuse reflection cubic cavity is obtained;
wherein the additional opening ratio fxThe calculation formula of (a) is as follows:
in the formula, x is the opening length of the movable top cover plate (5) and the cavity (6), and L is the side length of the cavity (6).
7. The method for measuring absolute reflectance spectrum according to claim 6, wherein L is 6-12 cm.
8. The method of claim 5, wherein f isx0 to 0.0833.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999014578A1 (en) * | 1997-09-16 | 1999-03-25 | Labsphere Inc. | Ultraviolet transmittance analyzing method and instrument |
| CN103353440A (en) * | 2013-07-16 | 2013-10-16 | 哈尔滨工业大学 | Device and method for measuring material diffuse reflectance by adopting gas absorption spectrum |
| CN108827918A (en) * | 2018-05-29 | 2018-11-16 | 天津九光科技发展有限责任公司 | Diffuse reflection spectrum measuring device based on integrating sphere, measuring method and correcting method |
| CN109444082A (en) * | 2018-12-21 | 2019-03-08 | 天津九光科技发展有限责任公司 | diffuse reflection spectrum measuring device and measuring method |
| CN109632717A (en) * | 2018-12-29 | 2019-04-16 | 深圳奥比中光科技有限公司 | Diffusing reflection rate detection device and method |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999014578A1 (en) * | 1997-09-16 | 1999-03-25 | Labsphere Inc. | Ultraviolet transmittance analyzing method and instrument |
| CN103353440A (en) * | 2013-07-16 | 2013-10-16 | 哈尔滨工业大学 | Device and method for measuring material diffuse reflectance by adopting gas absorption spectrum |
| CN108827918A (en) * | 2018-05-29 | 2018-11-16 | 天津九光科技发展有限责任公司 | Diffuse reflection spectrum measuring device based on integrating sphere, measuring method and correcting method |
| CN109444082A (en) * | 2018-12-21 | 2019-03-08 | 天津九光科技发展有限责任公司 | diffuse reflection spectrum measuring device and measuring method |
| CN109632717A (en) * | 2018-12-29 | 2019-04-16 | 深圳奥比中光科技有限公司 | Diffusing reflection rate detection device and method |
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