An absorption spectrometer, direct measurement method of absorption light intensity

Abstract

The present application relates to the field of spectral analysis, and relates to an absorption spectrometer and a direct measurement method of absorption light intensity. The present application provides an absorption spectrometer which can directly measure absorption light intensity. The absorption spectrometer comprises a light source assembly, a sample cell, a semi-transparent mirror and a light detector. The absorption spectrometer also provides a direct measurement method of absorption light intensity. In the front light path of two coherent lights, a same sample cell is placed in each light path. The optical path of one light is adjusted until the output of the light detector included in the absorption spectrometer is minimum. Then, a sample to be measured is added to one sample cell, and a blank solution is added to the other sample cell. At this time, the light detector measures the intensity of the remaining light which is not completely cancelled after the convergence of the two lights, i.e. the intensity of the light absorbed by the sample to be measured, i.e. the absorption light intensity. The absorption spectrometer provided by the present application detects absorption light intensity, while the traditional absorption spectrometer detects absorbance. Changing the detection of absorbance to the detection of absorption light intensity can avoid the quantum noise of a large signal from drowning out a weak signal, thereby greatly improving the detection sensitivity of the absorption spectrometer.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral analysis, and in particular to an absorption spectrometer and a direct measurement method for absorption light intensity. Background Art

[0002] The ultraviolet-visible spectrophotometer came out in 1935 and is still the most commonly used chemical analysis instrument so far. It is almost indispensable in any analysis laboratory and is mainly used to test the absorption spectrum of substances. By measuring the change in the absorption light intensity, the composition and concentration of the sample are analyzed. The quantitative basis of the absorption spectrum is the Lambert-Beer law A = abc, that is, the absorbance (A) is the product of the extinction coefficient (a), the optical path length (b) of the incident light passing through the sample, and the concentration (c) of the analyte. The absorbance itself is defined as A = –log(I t / I0), where I0 is the incident light and I t is the transmitted light.

[0003] That is to say, what the absorption spectrum measures is not the amount of light absorbed by molecules or atoms, but the ratio of the intensity of the incident light to the transmitted light. For the detection of ultraviolet and visible light, irradiation noise detectors such as photomultiplier tubes, photodiodes, and photodiode arrays are necessarily used. These detectors can all generate current under the irradiation of light and are very sensitive. However, the amount of noise is also proportional to the intensity of the measured light. Therefore, the measurement sensitivity of the absorbance A is actually I a / (I a is the absorption light intensity, is the I0 noise intensity, that is, the signal-to-noise ratio), not I a / ( is the intensity of the quantum noise caused by I a ). When approaching the detection limit, the absorption is weak, I a <<I0, that is, << , at this time the absorption signal is easily submerged, which is the ultimate limitation of the sensitivity of the existing spectrophotometer. If the absorption light can be directly detected, the detection sensitivity is I a / instead of I a / , therefore, directly measuring I a will necessarily greatly improve the detection sensitivity.

[0004] Because absorption spectroscopy is directly related to the electronic energy levels of atoms and molecules, the quantum effect of electronic transitions produced by the absorption of light by each atom or molecule is fixed. Therefore, their absorption spectra are vectors and naturally stable. Moreover, all molecules of matter necessarily have electronic transition energy levels, so they can necessarily be measured by absorption spectroscopy. In addition, the instruments for absorption spectroscopy are inexpensive, easy to operate, and have very low analytical costs. If its sensitivity can be improved to a level close to that of mass spectrometry, then it will have huge advantages in terms of stability, accuracy, analytical cost, portability, and so on.

[0005] Direct measurement of absorbance I a Just like emission spectroscopy, the only molecular emission spectra that can represent molecular properties are fluorescence and Raman scattering. Fluorescent substances are few in number, so the application range of fluorescence detection is very limited. All substances exhibit Raman scattering, but its quantum efficiency is less than 10^6. -5 In other words, only a few photons will produce Raman scattering after absorbing more than 100,000 photons. Most of the absorbed photon energy is released as elastic scattering or heat. Therefore, the sensitivity of Raman spectroscopy should be more than 100,000 times lower than that of absorption spectroscopy. However, in reality, the sensitivity of a Raman spectrometer is close to that of a spectrophotometer, at most about 10 times lower. This is because Raman spectroscopy is an emission spectroscopy, and its sensitivity is I... r / , where I r The Raman signal intensity, This refers to the noise generated by the Raman light illuminating the photometric element. In other words, measuring the absorption spectrum by absorbance (A) could potentially reduce the sensitivity of the absorption spectrum by 10,000 times! Therefore, if we could measure the absorption light (IA) like we measure the emitted light... a The sensitivity of the absorption spectrometer is thousands or even tens of thousands of times higher than that of the existing spectrophotometer, and it is basically on par with the detection sensitivity of the mass spectrometer. This is of great significance for the characterization of absorption spectra and the analysis of sample component concentrations. Summary of the Invention

[0006] Currently, ultraviolet-visible absorption spectral signals must be detected using photoelectric conversion devices. These devices inevitably contain quantum noise proportional to the intensity of the measured light, and the absorbance A = log(I0 / I... t That is, the absorbance (A) is proportional to the logarithm of the incident light intensity (I0), but after absorption by the sample, the transmitted light intensity (I0) is reduced. t Since the absorbance is always less than I0, the absorbance always contains noise caused by I0, and weak absorption signals are drowned out by the noise of I0. Therefore, the detection sensitivity (i.e., signal-to-noise ratio) of absorption spectroscopy is limited by the quantum noise of the incident light. Compared to absorption spectroscopy, although emission spectroscopy uses the same photometric element, the quantum noise generated when the emission signal is weak is also weak. Therefore, the detection sensitivity of emission spectroscopy is much higher than that of absorption spectroscopy.

[0007] This invention aims to transform absorption spectroscopy detection into emission spectroscopy detection, thereby improving the sensitivity of absorption spectrometers. This invention provides an absorption spectrometer for directly measuring absorbed light intensity, comprising a light source assembly, a double-beam interferometer, a sample cell, and a photometer. This invention also provides a direct method for measuring absorbed light intensity. This involves adding equal amounts of blank solution to two sample cells placed in two separate beams, adjusting the optical path lengths of the two beams until the output of the photometer in the absorption spectrometer is minimized; then replacing the blank solution in one of the sample cells with an equal amount of the sample to be tested. At this point, the photometer measures the intensity of the residual light after the two beams converge and interfere, which is entirely equal to the light absorbed by the sample. Therefore, this invention enables direct measurement of absorbed intensity rather than absorbance, significantly improving the sensitivity of absorption spectroscopy measurements.

[0008] In a first aspect, the present invention provides an absorption spectrometer, which is an absorption spectrometer capable of directly measuring the intensity of absorbed light.

[0009] As one possible implementation, a sample cell is placed in the optical path of two coherent beams of equal intensity. Both sample cells are filled with blank solution. The optical path difference between the two coherent beams is adjusted until the output of the photometer included in the absorption spectrometer is minimized. The blank solution in one of the sample cells is replaced with the sample to be tested. At this time, the photometer measures the intensity of the remaining light after the two beams converge and interfere, which is not completely canceled out. That is, the intensity of the light absorbed by the sample to be tested, or the intensity of the absorbed light.

[0010] One possible approach is to adjust the optical path difference between the two coherent beams until the output of the photometer included in the absorption spectrometer is minimized. Specifically, this involves adjusting the optical path difference between one beam and the other to an odd multiple of half the wavelength. ,in, It is a positive integer. λ is the wavelength.

[0011] As one possible implementation, the absorption spectrometer is a single-wavelength absorption spectrometer, which includes: A light source assembly for providing monochromatic light with a preset wavelength; A two-beam interferometer splits the monochromatic light input from the light source component into two coherent beams of equal intensity and introduces them into two optical paths with an optical path difference of an odd multiple of half the wavelength. The beams then converge and interfere with each other to cancel each other out. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. The first sample cell is set at any position in one of the optical paths of the two-beam interferometer; The second sample cell, serving as a reference cell, is positioned at any point in the other optical path of the two-beam interferometer. A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal.

[0012] When directly measuring the absorbed light intensity of the sample solution, the sample solution to be tested is added to the first sample cell, and a blank sample solution is added to the second sample cell. At this time, the output of the photometer is the electrical signal corresponding to the absorbed light intensity of the sample solution to be tested.

[0013] As one possible implementation, the light source component is a laser or a filter light source; When the light source component is a filter light source, the filter light source includes, in sequence along the light transmission direction, a white light source, a lens or a reflecting focusing mirror, and a color filter. Before the sample is measured, both sample cells are emptied, and then monochromatic light of different preset wavelengths is obtained by changing the laser or switching the color filter. Then, the two beams of the two-beam interferometer are adjusted to cancel each other out through the optical path adjustment mechanism, and the photometer reading reaches the minimum value. During the sample measurement, as long as the sample solution is added to the sample cell and the blank sample solution is added to the reference cell, the output of the photometer is the light absorption intensity signal of the sample.

[0014] As one possible implementation, the absorption spectrometer is a multi-wavelength absorption spectrometer, which includes: A beam splitter is used to provide monochromatic light output. The beam splitter includes a combined light source capable of emitting light from ultraviolet to infrared, a beam splitting element, and a mechanical rotating device. The beam splitting element is a grating or a beam splitting prism. In use, continuous white light is emitted from the combined light source and converted into parallel light before shining on the beam splitting element. The beam splitting element outputs the incident light at different angles according to the wavelength. If the output light is not parallel, the beam splitter also includes a reflecting focusing mirror to convert the output light of the beam splitting element into parallel light output. The mechanical rotating device drives the beam splitting element or the reflecting focusing mirror to rotate. Different rotation angles correspond to monochromatic light output of different wavelengths. A two-beam interferometer receives monochromatic light output from a beam splitter, splits it into two beams of equal intensity, and introduces them into two different optical paths. The beams are then converged to interfere with each other and produce bright and dark patterns. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Sample cells are respectively set in two optical paths in a two-beam interferometer; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. The positioning laser and laser detector, set at the photometer end or the incident light end, will show a laser interference pattern when the optical path adjustment mechanism is continuously adjusted. At the same time, the reading of the laser detector corresponding to the first lowest point measured on the photometer for a given absorption wavelength is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point.

[0015] As one possible implementation, the absorption spectrometer is an atomic absorption spectrometer, which includes: Element lamps emit characteristic spectral lines of specific elements; A two-beam interferometer splits the monochromatic parallel light output from an element lamp into two beams of equal intensity. The two beams are then introduced into two different optical paths, and then converged to interfere with each other to produce bright and dark patterns. The two-beam interferometer contains an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Two sample cells are respectively set in the two optical paths of the two-beam interferometer, and the sample cells can be graphite furnaces or atomized flames; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. A positioning laser and a laser detector are set at the photometer end or the incident light end. The output signal of the laser detector is presented as a laser interference pattern by continuously adjusting the optical path adjustment mechanism. At the same time, given an absorption wavelength, the reading of the laser detector corresponding to the first lowest point measured on the photometer is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point. During sample absorbance detection, the corresponding element lamp needs to be replaced for each element determination. Each time the element lamp is switched, the two sample cells need to be emptied and the optical path of the dual-beam interferometer needs to be adjusted to minimize the output of the photometer. Then, the sample solution and blank sample solution are input into the two sample cells respectively. At this time, the output of the photometer is the absorbance intensity signal of the corresponding element in the sample.

[0016] As one possible implementation, a pre-calibrated absorption spectrometer is used. The calibration method is as follows: empty both sample cells, control the mechanical rotation device in the spectrometer to rotate to select the wavelength output by the spectrometer, and then drive the optical path adjustment mechanism of the two-beam interferometer to minimize the output of the two-beam interferometer. Repeat this process until all measurable wavelengths are swept, record each wavelength, the corresponding rotation angle of the mechanical rotation device, and the laser detector reading at the corresponding time to obtain a wavelength-rotation angle-laser value list, i.e., a calibration table, which can be stored as system control parameters. During sample testing, the test sample solution and blank sample solution are added to two sample cells respectively. After setting a wavelength, the absorption spectrometer is adjusted to the state given by the calibration table. At this time, the output of the photometer is the absorption signal of the test sample solution at the given wavelength. According to the parameters contained in the calibration table, the absorption spectrometer can be controlled to perform multi-wavelength or full-scan detection.

[0017] As one possible implementation, the two-beam interferometer is the Michelson interferometer.

[0018] Secondly, the present invention provides a method for directly measuring the intensity of absorbed light, comprising the following steps: A sample cell is placed in the optical path of two coherent beams of equal intensity; Both sample cells are filled with blank solution. The optical path difference between the two coherent beams is adjusted until the output of the photometer included in the absorption spectrometer is minimized. When the blank solution in one of the sample cells is replaced with the sample to be tested, the photometer measures the intensity of the remaining light after the two beams converge and interfere, which is the intensity of the light absorbed by the sample to be tested, or the intensity of the absorbed light.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The absorption spectrometer provided by this invention can directly measure the intensity of absorbed light of a substance, and can improve the sensitivity of the absorption spectrum by more than 1,000 times compared with the traditional spectrophotometer. 2. The absorption spectrometer provided by this invention can directly measure the intensity of absorbed light in one operation without the need to test the incident light and transmitted light separately. It can effectively eliminate signal interference from matrix substances in the sample, and is simple to operate, efficient and accurate. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the single-wavelength absorption spectrometer provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a multi-wavelength absorption spectrometer provided in an embodiment of the present invention.

[0021] Figure label: 1-Light source assembly, 2-Double beam interferometer, 3-Filter, 4-Sample cell, 5-Reference cell, 6-Photometer, 7-Positioning laser, 8-One-way transmission mirror, 9-Laser detector; 20-Collecting lens; 21-Slit; 22-Parallel light lens; 23-Semi-transparent mirror; 24-Reflecting mirror; 25-Condenser lens; 26-Beam splitter; 240 - Fixed reflector, 241 - Moving reflector. Detailed Implementation

[0022] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0023] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Currently, ultraviolet-visible absorption spectral signals must be detected using photoelectric conversion devices. These devices inevitably contain quantum noise proportional to the intensity of the measured light, and the absorbance A = log(I0 / I... t That is, the absorbance (A) is proportional to the logarithm of the incident light intensity (I0), but after absorption by the sample, the transmitted light intensity (I0) is reduced. tThe absorbance is always less than I0, and the maximum noise caused by I0 is always included in the absorbance. Weak absorption signals are drowned out by the noise of I0. Therefore, the detection sensitivity (i.e., signal-to-noise ratio) of absorption spectroscopy is limited by the quantum noise of the incident light. Compared to absorption spectroscopy, although emission spectroscopy uses the same photometric element, the quantum noise generated when the emission signal is weak is also weak. Therefore, the detection sensitivity of emission spectroscopy is much higher than that of absorption spectroscopy.

[0028] This invention aims to transform absorption spectroscopy detection into emission spectroscopy detection, thereby improving the sensitivity of ultraviolet-visible absorption spectrometers. This invention provides an absorption spectrometer capable of directly measuring absorption spectral intensity. The spectrometer includes a light source assembly, a sample cell, a semi-transparent mirror, and a photometer. This invention also provides a direct method for measuring absorption intensity: equal volumes of blank solution are placed in two sample cells, and the optical path of one beam is adjusted until the output of the photometer in the absorption spectrometer is minimized. Then, the blank solution in one of the sample cells is replaced with an equal volume of the sample to be tested. At this point, the photometer measures the intensity of the residual light after the two beams converge and interfere, which is the intensity of the light absorbed by the sample, i.e., the absorption intensity. This spectrometer transforms the absorbance signal received by the photometer element into an absorption intensity signal, reducing the influence of noise on the received signal and greatly improving the detection sensitivity of the absorption spectrometer.

[0029] In a first aspect, embodiments of the present invention provide an absorption spectrometer, which is an absorption spectrometer capable of directly measuring the intensity of absorbed light.

[0030] An absorption spectrometer is a spectrometer that analyzes the composition and concentration of a sample by measuring changes in the intensity of absorbed light, based on the absorption characteristics of atoms or molecules to light of a specific wavelength.

[0031] Absorbed light intensity refers to the absolute energy or intensity of light absorbed after passing through a solution or substance. It is related to the properties of the substance, its concentration, the wavelength of the light, and fixed properties such as the material and structure of the sample cell.

[0032] Specifically, the absorption spectrometer provided in this embodiment of the invention uses the intensity of absorbed light of a substance as a detection signal to form the substance's absorption spectrum. Compared with the prior art, traditional absorption spectrometers use absorbance as a detection signal to form the substance's absorption spectrum, but absorbance is the base-10 logarithm of the ratio of incident light intensity to transmitted light intensity, i.e., A = –lg(I t / I0), where I0 is the incident light, I t This is transmitted light. Absorbance A is directly proportional to the concentration of the absorbing substance and the optical path length, and is also related to the absorption coefficient (which is related to the solution properties and the wavelength of the incident light). In addition, absorbance is also related to temperature, the intensity of the incident light, etc.

[0033] Traditional absorption spectroscopy measures absorbance. The photometric detector used is very sensitive, but the amount of noise is also proportional to the intensity of the light being measured. Therefore, the measurement sensitivity of absorbance A is actually I a / (i.e., the signal-to-noise ratio, I a is the intensity of the absorbed light, and is the noise intensity of I0), rather than I a / ( is the intensity of the quantum noise caused by I a ). When the absorption is weak near the detection limit, I a <<I0, that is, << , and at this time, the absorption signal is easily overwhelmed by .

[0034] When directly detecting the absorbed light, the detection sensitivity is I a / instead of I a / , so directly measuring I a will surely greatly improve the detection sensitivity.

[0035] Through the above technical solution, the embodiment of the present invention provides an absorption spectrometer, which improves the detection sensitivity of the absorption spectrometer by changing the detection of absorbance to the detection of the intensity of the absorbed light.

[0036] As a possible implementation, a sample cell is placed on the optical paths of two coherent light beams with equal intensity; blank solutions are filled in both sample cells, and the optical path difference between the two coherent light beams is adjusted until the output of the photometric detector included in the absorption spectrometer is minimized; the blank solution in one of the sample cells is replaced with the待测 sample. At this time, the photometric detector measures the intensity of the remaining light that is not completely canceled after the two light beams converge and interfere, that is, the intensity of the light absorbed by the待测 sample, which is also the intensity of the absorbed light.

[0037] Specifically, first, the monochromatic light incident on the interferometer (a semi-transparent and semi-reflective mirror in this embodiment) is divided into two coherent light beams with equal intensity. The two coherent light beams enter the blank sample cell as incident light and then pass through the blank sample cell. The optical path difference between the two coherent light beams is adjusted so that interference cancellation can occur after passing through the blank sample cell, and finally, the light intensity received by the photometric detector is minimized to minimize the influence of factors such as background noise that interfere with the test results; as an example, the optical path of one of the light beams can be adjusted so that the difference in optical path between it and the other light beam can cause the two coherent light beams to interfere and cancel each other after convergence and make the output of the photometric detector minimum.

[0038] Then, the blank solution in one of the blank sample cells is replaced with the sample to be tested. The incident light enters the sample cell, is absorbed by the sample, and then transmitted out. This means the sample absorbs specific light waves due to its chemical structure (selective absorption). The unabsorbed light is transmitted from the sample cell and interferes destructively with the light transmitted from the blank sample cell. Because some light is absorbed, the symmetry of the original coherent light is broken, causing the amplitudes of the two original coherent beams to no longer be equal, and they can no longer interfere destructively. Only the light transmitted from the sample cell (i.e., the unabsorbed light) interferes destructively with the original coherent light. After the original coherent light interferes destructively with the transmitted light, a portion of the original coherent light remains unaffected. This unaffected portion has the same intensity as the light absorbed by the sample. This remaining light signal is received by a photometer, which then converts it into an output (absorption intensity), forming the absorption spectrum of the substance. As an example, the remaining light intensity I... res The formula for calculating the intensity of light that is not completely canceled out after interference is: Where E1 is the reference light amplitude passing through the blank sample, and E2 is the probe light amplitude passing through the sample.

[0039] The formula for calculating absorbed light intensity is: Where I0 is the theoretical minimum interference of the two beams when there is no absorption (ideally close to zero), and in practice it is the background baseline intensity.

[0040] Compared to existing technologies, traditional absorption spectroscopy measurement methods use absorbance A as the received signal of the photometer. Absorbance A contains the ratio of incident light intensity to transmitted light intensity. Since the incident light intensity is always greater than the transmitted light intensity, the absorbance always contains the maximum noise caused by I0, and weak absorption signals are drowned out by the noise of I0. This invention uses the absorption intensity of the extinct interference light with the same intensity as the absorbed light as the received signal of the photometer. The extinct interference state itself greatly reduces system noise, thus significantly improving the signal-to-noise ratio of the absorption signal. It directly obtains the light intensity change caused by the sample, eliminating the need to separately measure the reference light intensity and eliminating the influence of light source fluctuations.

[0041] Through the above technical solution, the embodiments of the present invention replace the absorbance signal in the absorption spectrometer with the absorption intensity signal, which more directly reflects the light absorption characteristics of the substance and is minimally affected by noise. It is the core technology for achieving high-precision quantitative analysis.

[0042] One possible approach is to adjust the optical path difference between the two coherent beams until the output of the photometer included in the absorption spectrometer is minimized. Specifically, this involves adjusting the optical path difference between one beam and the other to half a wavelength. ,in, It is a positive integer. λ is the wavelength.

[0043] Wherein is the actual distance that light travels through the sample, measured in centimeters (cm) or millimeters (mm). The detection sensitivity can be optimized by adjusting the optical path length; for example, a short optical path length is suitable for high-concentration samples, while a long optical path length is suitable for low-concentration samples.

[0044] Among them, the light meter refers to the illumination noise detector, such as photomultiplier tube, photodiode, photodiode array, etc., which is a type of highly sensitive detector that can convert weak light signals into electrical signals.

[0045] Specifically, when two coherent beams meet, the optical path difference they experience is an odd multiple of half the wavelength, resulting in optical interference cancellation. After optical interference cancellation occurs, dark fringes are formed. Essentially, when the phase difference of the coherent beams is an odd multiple of π, the electric field vectors are out of phase and superimposed, leading to a reduction in amplitude. At this time, the photometer's ability to receive signals is the weakest, resulting in the minimum output.

[0046] The formula for calculating optical path difference is: in, It is a positive integer. λ is the wavelength.

[0047] The core of achieving destructive optical interference in absorption spectrometers is to reduce background noise and improve measurement accuracy by precisely controlling the optical path difference.

[0048] The above technical solution utilizes optical interference cancellation to ensure minimal background noise and maximum testing accuracy in absorption spectrum testing.

[0049] As one possible implementation, the absorption spectrometer is a single-wavelength absorption spectrometer, which includes: A light source assembly for providing monochromatic light with a preset wavelength; A two-beam interferometer splits the monochromatic light input from the light source into two coherent beams of equal intensity and introduces them into two optical paths with an optical path difference of an odd multiple of half the wavelength. The beams then converge and interfere with each other to cancel each other out. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. The first sample cell is set at any position in one of the optical paths of the two-beam interferometer; The second sample cell, serving as a reference cell, is positioned at any point in the other optical path of the two-beam interferometer. A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal.

[0050] When directly measuring the absorbed light intensity of the sample solution, the sample solution to be tested is added to the first sample cell, and a blank sample solution is added to the second sample cell. At this time, the output of the photometer is the electrical signal corresponding to the absorbed light intensity of the sample solution to be tested.

[0051] Specifically, the absorption spectrometer uses monochromatic light of a preset wavelength as the incident light to ensure the transferability and stability of the measurement wavelength; after receiving the incident light, the two-beam interferometer splits it into two coherent beams of equal intensity, forming the basis of dual-path interference.

[0052] The first sample cell is placed in one optical path of the two-beam interferometer to hold the sample to be tested. The mirrors included in this optical path of the two-beam interferometer reflect the light passing through the sample cell back to the optical path. The second sample cell is placed in the other optical path of the two-beam interferometer to hold the reference solution (or blank medium). The other mirror included in the two-beam interferometer realizes the reflection of the optical path. By strictly controlling the optical path difference between the two beams to be an odd multiple of half the wavelength, it is ensured that the output of the incident light in the direction of the photometer before the sample is introduced is coherently canceled to the maximum extent, thereby establishing a detection baseline close to zero. The photometer is used to receive light that is reflected back and reconverged by two mirrors. Specifically, it receives the outgoing light in the direction of first-order interference. When the incident light is interfered and canceled before the sample is introduced, the photometer reading is the lowest. After the sample is introduced, the light beam passing through the sample is partially absorbed and its intensity is weakened. The two beams cannot completely cancel each other after coherence. The remaining light, which is equal to the absorbed light, is incident on the photometer and generates a signal.

[0053] During sample absorbance measurement, simply add the sample solution to the first sample cell and the blank sample solution to the second sample cell, ensuring the optical path difference between the two optical paths in the two-beam interferometer is an odd multiple of half the wavelength. The final output of the photometer is the absorbed light intensity signal of the sample. The thickness and material of both sample cells are the same.

[0054] Through the above technical solution, this embodiment is based on the principle of two-beam interference. By synchronously comparing the reference optical path and the measurement optical path, it effectively eliminates systematic errors such as light source fluctuations, environmental disturbances, and matrix absorption, thereby improving the accuracy and reproducibility of light absorption detection. Moreover, after configuring the positioning laser accessory, the wavelength and interference adjustment can be precisely adjusted without frequent calibration, making it suitable for high-sensitivity and high-accuracy analytical detection applications.

[0055] As one possible implementation, the light source component is a laser or a filter light source; When the light source component is a filter light source, the filter light source includes, in sequence along the light transmission direction, a white light source, a collecting lens, a slit, a parallel light lens or a reflector, and a color filter. Before the sample is measured, the two sample cells are emptied, and then monochromatic light of different preset wavelengths is obtained by changing the laser or switching the color filter. Then, the two beams of the two-beam interferometer are adjusted to interference cancellation through the optical path adjustment mechanism, and the photometer reading reaches the minimum value. During the sample measurement, as long as the sample solution is added to the sample cell and the blank sample solution is added to the reference cell, the output of the photometer is the light absorption intensity signal of the sample.

[0056] Specifically, the light source component can be a monochromatic light source such as a laser or a continuous light source (such as white light) with a color filter. The laser, as the core light source, provides high-brightness, monochromatic, and parallel incident light. As an example, by changing the operating parameters of the tunable laser (such as current or temperature) or switching between different single-wavelength lasers, different wavelengths of output light can be obtained, allowing different samples to be selected with wavelengths close to their maximum absorption. A white light source with a color filter is a combination of a white light source, a lens (in sequence: collecting lens, first condenser lens, slit, and second condenser lens) or a reflecting focusing lens, and a color filter, arranged sequentially along the light transmission direction. An ideal white light source might cover the ultraviolet to infrared spectrum with continuously tunable wavelengths and uniform intensity. A combination of a deuterium lamp and an incandescent lamp is relatively close to an ideal white light source. The color filter is a key component for wavelength selection, selectively transmitting light of specific wavelengths through physical or chemical methods while blocking other wavelengths. As an example, switching color filters can directly obtain output light of different preset wavelengths.

[0057] Before testing, the absorption spectrometer must be calibrated to ensure that the photometer reading is at its minimum, thus ensuring that the influence of the environment (such as the sample cell itself on the absorbed light) is fully eliminated.

[0058] As one possible implementation, the absorption spectrometer is a multi-wavelength absorption spectrometer, which includes: A beam splitter is used to provide monochromatic light output. The beam splitter includes a combined light source capable of emitting light from ultraviolet to infrared, a beam splitting element, and a mechanical rotating device. The beam splitting element is a grating or a beam splitting prism. In use, continuous white light is emitted from the combined light source and converted into parallel light before shining on the beam splitting element. The beam splitting element outputs the incident light at different angles according to the wavelength. If the output light is not parallel, the beam splitter also includes a reflecting focusing mirror to convert the output light of the beam splitting element into parallel light output. The mechanical rotating device drives the beam splitting element or the reflecting focusing mirror to rotate. Different rotation angles correspond to monochromatic light output of different wavelengths. A two-beam interferometer receives monochromatic light output from a beam splitter, splits it into two beams of equal intensity, and introduces them into two different optical paths. The beams are then converged to interfere with each other and produce bright and dark patterns. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Sample cells are respectively set in two optical paths in a two-beam interferometer; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. The positioning laser and laser detector, set at the photometer end or the incident light end, will show a laser interference pattern when the optical path adjustment mechanism is continuously adjusted. At the same time, the reading of the laser detector corresponding to the first lowest point measured on the photometer for a given absorption wavelength is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point.

[0059] Specifically, the light source assembly of this absorption spectrometer provides parallel monochromatic light as incident light for the test, and a spectrometer can be used as its light source assembly. The spectrometer includes a combined light source capable of emitting light from ultraviolet to infrared, a spectroscopic element, a reflecting focusing mirror, and a mechanical rotation device. The spectroscopic element is either a grating or a spectroscopic prism. In operation, continuous white light is emitted from the combined light source and converted into parallel light before illuminating the spectroscopic element. The spectroscopic element then outputs the incident light at different angles according to its wavelength. If the spectroscopic element is a concave grating, the output light must be converted into parallel light by the reflecting focusing mirror before being output. The mechanical rotation device drives the spectroscopic element or the reflecting focusing mirror to rotate, with different rotation angles corresponding to different wavelengths of monochromatic light output.

[0060] By adjusting the moving distance of the moving mirror in the two-beam interferometer, the optical path difference between the two coherent beams can reach an odd multiple of half the wavelength, so that the coherent beams can undergo destructive interference (dark fringes appear during destructive interference). At this time, when both the sample cell and the reference cell contain blank samples (the thickness and material of the sample cell and the reference cell are the same), the light intensity signal received by the photometer is the minimum, and thus the photometer has the minimum output. This step is to eliminate the influence of background noise and improve the test accuracy.

[0061] Because the error of mechanical positioning is much greater than the wavelength difference, the XYZ coordinate record of the position is insufficient to accurately position the device to the predetermined location. Interferometers typically add a laser beam to the photometer or incident end. The reading on the laser detector corresponding to the first lowest point measured on the photometer for a given absorption wavelength is the marker point for determining the absorption at that wavelength. Positioning lasers generally use mature red laser pointers, but any small micro-laser of other colors with stable output can also be used. Furthermore, using multiple laser beams of different wavelengths can make positioning more accurate.

[0062] Through the above technical solution, this embodiment is based on the principle of two-beam interference. By synchronously comparing the reference optical path and the measurement optical path, it effectively eliminates systematic errors such as light source fluctuations, matrix absorption, and environmental disturbances, thereby improving the accuracy and reproducibility of light absorption intensity measurement.

[0063] As one possible implementation, the absorption spectrometer is an atomic absorption spectrometer, which includes: Element lamps emit characteristic spectral lines of specific elements; A two-beam interferometer splits the monochromatic characteristic light output by an element lamp into two beams of equal intensity. The two beams are then introduced into two different optical paths, and then converged to interfere with each other to produce bright and dark patterns. The two-beam interferometer contains an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Two sample cells are respectively arranged in the two optical paths of the two-beam interferometer, and the sample cells can be graphite furnaces or atomized flames; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. A positioning laser and a laser detector are set at the photometer end or the incident light end. The output signal of the laser detector is presented as a laser interference pattern by continuously adjusting the optical path adjustment mechanism. At the same time, given an absorption wavelength, the reading of the laser detector corresponding to the first lowest point measured on the photometer is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point. During sample absorbance detection, the corresponding element lamp needs to be replaced for each element determination. Each time the element lamp is switched, the two sample cells need to be emptied and the optical path of the dual-beam interferometer needs to be adjusted to minimize the output of the photometer. Then, the sample solution and blank sample solution are input into the two sample cells respectively. At this time, the output of the photometer is the absorbance intensity signal of the corresponding element in the sample.

[0064] Specifically, this absorption spectrometer is used to test atomic absorption spectra. Its structure is similar to the aforementioned single-wavelength absorption spectrometer, except that the light source component is replaced with an element lamp. The element lamp (hollow cathode lamp) excites a cathode made of the element to be measured through glow discharge, emitting light of a specific wavelength. The elements in the sample absorb the radiation of the corresponding element lamp, and the resulting absorption signal can be used to accurately determine the element content. The advantages of this light source are obvious: the emitted spectral lines are narrow and the intensity is high, which can effectively avoid interference from other elements.

[0065] Meanwhile, the sample cell is replaced with a graphite furnace or an atomizing flame. During testing, the sample is placed in the graphite furnace or introduced into a high-temperature flame for heating to achieve atomization. The absorption of characteristic wavelength light by ground-state atoms is then quantitatively analyzed.

[0066] When measuring the absorbance of a sample, the corresponding element lamp needs to be replaced for each element measurement. Each time the element lamp is switched, the two sample cells need to be emptied and the optical path of the double-beam interferometer needs to be adjusted to minimize the output of the dynamometer. Then, the sample solution and blank sample solution are input into the two sample cells respectively. At this time, the output of the photometer is the absorbance signal of the corresponding element in the sample.

[0067] Through the above technical solutions, the embodiments of the present invention provide an atomic absorption spectrometer, which is based on an absorption spectrometer and becomes an atomic absorption spectrometer by replacing the sample cell with an atomization device.

[0068] As one possible implementation, a pre-calibrated absorption spectrometer is used. The calibration method is as follows: empty both sample cells, control the mechanical rotation device in the spectrometer to rotate to select the wavelength output by the spectrometer, and then drive the optical path adjustment mechanism of the two-beam interferometer to minimize the output of the two-beam interferometer. Repeat this process until all measurable wavelengths are swept, record each wavelength, the corresponding rotation angle of the mechanical rotation device, and the laser detector reading at the corresponding time, and obtain a wavelength-rotation angle-laser value list, i.e., a calibration table, which can be built into the system control parameters.

[0069] During sample testing, the sample solution to be tested and the blank sample solution are added to the two sample cells respectively. After setting a wavelength, the absorption spectrometer is adjusted to the state given by the calibration table. At this time, the output of the photometer is the absorption signal of the sample solution to be tested at the given wavelength. The absorption spectrometer is adjusted according to the parameters listed in the calibration table in sequence and the absorption signal in each state is read. The resulting set of absorption signals is the full scan absorption spectrum.

[0070] Specifically, multi-wavelength absorption spectrometers and atomic absorption spectrometers need to be calibrated before use. The calibration process is as follows: Empty both sample cells, use the control system to control the rotation of the precision mechanical rotating device in the beam splitter to select the output wavelength of the beam splitter, and then drive the optical path adjustment mechanism of the two-beam interferometer to minimize the interferometer output. Repeat this process for each selected wavelength, and record the wavelength, the corresponding rotation angle of the precision mechanical rotating device, and the laser detector reading at the corresponding time to obtain a wavelength-rotation angle-laser value list, i.e., a calibration table, which can be stored as fixed parameters in the software.

[0071] During sample testing, the sample solution to be tested and the blank sample solution are added to two sample cells respectively. After a wavelength is given, the control system adjusts the absorption spectrometer to the state given by the calibration table. At this time, the output of the photometer is the absorption signal of the sample at the given wavelength.

[0072] Based on the parameters contained in the calibration table, the control system can control the absorption spectrometer to perform multi-wavelength or full-scan detection.

[0073] Through the above technical solution, the control system organically combines mechanical control, optical adjustment, and data acquisition to form a complete automated measurement process. It transforms manually adjusted and optimized parameter relationships into pre-configured parameters in the system's memory, enabling intelligent operation of the spectrometer through an electronic control system. This design retains the accuracy of manual adjustments while improving the ease of use of the equipment, making it suitable for scientific research and industrial applications requiring multi-wavelength measurements.

[0074] As one possible implementation, the two-beam interferometer is the Michelson interferometer.

[0075] Specifically, the Michelson interferometer is used as a two-beam interferometer in single-wavelength absorption spectrometers, multi-wavelength absorption spectrometers, and atomic absorption spectrometers.

[0076] The Michelson interferometer is a core piece of equipment in optical experiments. It achieves precise measurements through the interference of light and its applications span multiple fields, from fundamental physics to cutting-edge technology.

[0077] (1) Working principle: Beam splitting and interference: Incident light is split into two beams by a semi-transparent and semi-reflective mirror, and after being reflected by a plane mirror, they rejoin. Interference occurs because the frequency, direction, and phase difference are constant.

[0078] Fringe shifting: By adjusting the length of the interference arm or the refractive index of the medium, the optical path difference is changed to form a trajectory with equal optical path difference. During fringe shifting, the moving mirror's shift distance d and the number of fringe shifts N satisfy d=Nλ / 2 (λ is the wavelength), meaning the optical path difference can be adjusted to an odd or even multiple of half the wavelength as needed.

[0079] (2) Structural composition: The core components of a Michelson interferometer include a beam splitter, a compensating plate, and two plane mirrors. The beam splitter divides the incident light into two beams, the compensating plate ensures that the optical path lengths of the two beams are equal, one plane mirror is fixed, and the other is movable; the optical path difference can be changed by adjusting the movable mirror. In addition, the instrument includes a base, guide rails, a slide, a reading system, and accessory support rods.

[0080] Adjustment mechanism: The moving mirror moves via a fine-tuning drive wheel, with a minimum reading of 10. -4 mm, combined with the coarse adjustment drive wheel to achieve precise control.

[0081] Through the above technical solution, the embodiments of the present invention realize the optical path difference adjustment mechanism, which is suitable for scientific research and industrial applications that require precise measurement.

[0082] Secondly, the present invention provides a method for directly measuring the intensity of absorbed light, comprising the following steps: Place an identical sample cell in the optical path of two coherent beams of equal intensity; Adjust the optical path difference between the two coherent beams until the output of the photometer included in the absorption spectrometer is minimized; A blank solution is added to one of the sample cells, and the sample to be tested is added to the other. At this time, the photometer measures the intensity of the remaining light after the two beams of light converge and interfere, which is not completely canceled out. That is, the intensity of the light absorbed by the sample to be tested, or the intensity of the absorbed light.

[0083] Specifically, the core of this method is based on the principle of dual-path interference and optical path self-calibration, which enables direct measurement of light absorption intensity.

[0084] The light emitted from the light source is split into two coherent beams of equal intensity. These two beams are incident on a blank sample cell and then transmitted through it. The optical path lengths of the two beams are adjusted so that they interfere destructively after passing through the blank sample cell, resulting in the minimum intensity of light received by the photometer, thus minimizing the impact of background noise on the test results. Next, the blank solution in one of the blank sample cells is replaced with the sample to be tested. The incident light then enters the sample cell, is absorbed by the sample, and exits. Due to its chemical structure, the sample absorbs specific light waves (selective absorption), while the unabsorbed light is transmitted through the sample cell. This transmitted light then interferes destructively with the light transmitted from the blank sample cell. Because some specific light waves transmitted through the sample are absorbed, the amplitudes of the two original coherent beams are no longer equal. A portion of the light remains after coherence. This un-destructively interfered light has the same intensity as the light absorbed by the sample. This remaining light is received by the photometer and converted into an electrical signal output, forming the absorption spectrum of the substance.

[0085] Through the above technical solution, the embodiments of the present invention provide a method for directly measuring the intensity of absorbed light by dual-path interference and optical path self-calibration. Its core value lies in eliminating the interference of incident light quantum noise and improving measurement accuracy and sensitivity.

[0086] To facilitate understanding of the technical solution of this application, further explanation is provided below with reference to specific embodiments.

[0087] Example 1 See Figure 1 The simplest structure of this invention is a single-wavelength fixed-wavelength absorption spectrometer, comprising a light source assembly 1 (monochromatic light source), a two-beam interferometer 2, a sample cell 4, a reference cell 5, and a photometer 6. The light source assembly is a monochromatic light source, consisting of a point light source, a collecting lens 20, and a filter 3. The point light source is located at the focal point of the collecting lens 20. The emitted light is collected by the collecting lens 20 and converted into parallel light, which is then filtered to obtain monochromatic light before entering the two-beam interferometer 2. Figure 1The two-beam interferometer 2 is a Michelson interferometer, including a semi-transparent mirror 23 and two plane mirrors 24, each fixed at a distance from the center of the semi-transparent mirror 23 that is an odd multiple of half the wavelength of the monochromatic light entering the interferometer. The sample cell 4 is placed in one optical path of the two-beam interferometer 2, and the reference cell 5 is placed in the other, equally important optical path. During detection, simply replace the blank sample in the sample cell with the sample to be tested. This single-wavelength absorption spectrometer can be very small, suitable for dedicated applications. In such applications, the light source and two mirrors can be fixed after adjusting the interferometer to its minimum signal output using a blank sample, and the blank liquid in the reference cell can also be sealed and placed in a fixed position. Such an absorption spectrometer is easily made into a small, lightweight, handheld or pocket-sized detection tool.

[0088] Example 2 See Figure 2 The present invention can also be used as a multi-wavelength absorption spectrometer, comprising a light source assembly 1; a collecting lens 20; a slit 21; a parallel light lens 22 that converts incident light into parallel light; a rotatable beam splitter grating 26; and a two-beam interferometer 2 (Michelson interferometer) including a semi-transparent mirror 23, two reflecting mirrors 24 (a fixed reflecting mirror 240 and a moving reflecting mirror 241); a sample cell 4 placed in one of the two beam paths of the two-beam interferometer, a reference cell 5 placed in the other beam path, a photometer 6 placed at the detection end of the two-beam interferometer 2, a positioning laser 7, a one-way transparent reflecting mirror 8, and a laser detector 9.

[0089] In summary, this absorption spectrometer requires only one light source component, such as a laser source, a color filter source, or a spectrometer; a two-beam interferometer; a sample cell; a reference cell; and a photometer. The spectrometer has a precision mechanical rotating device for selecting the output wavelength, used to rotate the spectroscopic element or the exiting optical mirror after spectrometry. The two-beam interferometer is equipped with an optical path adjustment mechanism to lower the output light intensity of the interferometer to a minimum when the sample cell is empty, establishing a baseline value for absorbance detection. At this point, simply adding the sample solution to the sample cell and the blank sample solution to the reference cell will allow the photometer reading to represent the intensity of the absorbed light from the sample. The full UV-Vis absorption spectrum can be visualized by linking the spectrometer's rotating device and the interferometer's optical path adjustment mechanism. By controlling their coordinated movement to scan all wavelengths, the photometer will simultaneously output a series of signals. When both the sample and reference cells are empty, this series of signals constitutes the correction function; when the sample cell contains the sample solution and the reference cell contains the blank sample solution, this series of signals represents the sample's absorption spectrum.

[0090] Because the error in mechanical positioning is much greater than the wavelength difference, recording the position of the optical path adjuster using XYZ coordinates is insufficient for precise repeatability. Interferometers typically add a positioning laser and a dedicated laser detector at the metering or incident end. The interference cancellation position obtained by the spectrometer is marked with the laser detector reading at the same moment, thus solving the coordinate positioning error problem. To further ensure accurate positioning, the position of the optical path adjuster can be marked with the normalized value of the laser reading. Normalization is achieved by dividing the reading at a specific point by the sum of the readings at all points along the cross-section of the laser interference fringe where that point lies. The positioning laser is generally a well-established red laser pointer, but any small micro-laser of other colors with stable output can also be used.

[0091] Example 3 This invention relates to an atomic absorption spectrometer for element analysis, comprising a double-beam interferometer, an element lamp, two sample cells, a photometer, a laser, and a laser detector. The double-beam interferometer is equipped with an optical path adjustment mechanism; the sample cell is a graphite furnace or an acetylene flame. During setup, the optical path difference is adjusted to an odd multiple of half the wavelength of the element lamp using the optical path adjustment mechanism, targeting either a blank graphite furnace or an acetylene flame. At this point, the photometer output is at its minimum. The name of the element to be measured and the laser detector reading at this time are recorded as built-in parameters for instrument control. In use, the element name is input, and the sample solution and blank sample solution are input into the two sample cells respectively. The control system automatically adjusts the spectrometer to the detection state for that element, and the photometer output is the atomic absorption signal of the sample.

[0092] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0093] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. An absorption spectrometer, characterized in that, An absorption spectrometer is an absorption spectrometer that can directly measure the intensity of absorbed light.

2. The absorption spectrometer according to claim 1, characterized in that, A sample cell is placed in the optical path of two coherent beams of equal intensity. Both sample cells are filled with blank solution. The optical path difference between the two coherent beams is adjusted until the output of the photometer included in the absorption spectrometer is minimized. The blank solution in one of the sample cells is replaced with the sample to be tested. At this time, the photometer measures the intensity of the remaining light after the two beams converge and interfere, which is not completely canceled out. That is, the intensity of the light absorbed by the sample to be tested, or the intensity of the absorbed light.

3. The absorption spectrometer according to claim 2, characterized in that, Adjust the optical path difference between the two coherent beams until the output of the photometer included in the absorption spectrometer is minimized. Specifically, adjust the optical path difference between one beam and the other beam to an odd multiple of half the wavelength. ,in, It is a positive integer. λ is the wavelength.

4. The absorption spectrometer according to claim 1, characterized in that, The absorption spectrometer is a single-wavelength absorption spectrometer, which includes: A light source assembly for providing monochromatic light with a preset wavelength; A two-beam interferometer splits the monochromatic light input from the light source into two coherent beams of equal intensity and introduces them into two optical paths with an optical path difference of an odd multiple of half the wavelength. The beams then converge and interfere with each other to cancel each other out. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. The first sample cell is set at any position in one of the optical paths of the two-beam interferometer; The second sample cell, serving as a reference cell, is positioned at any point in the other optical path of the two-beam interferometer. A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal. When measuring the absorbed light intensity of the sample solution, the sample solution is added to the first sample cell and a blank sample solution is added to the second sample cell. At this time, the output of the photometer is the electrical signal corresponding to the absorbed light intensity of the sample solution.

5. The absorption spectrometer according to claim 4, characterized in that, The light source component is a laser or a filter light source; When the light source component is a filter light source, the filter light source includes, in sequence along the light transmission direction, a white light source, a lens or a reflecting focusing mirror, and a color filter. Before the sample is measured, both sample cells are emptied, and then monochromatic light of different preset wavelengths is obtained by changing the laser or switching the color filter. Then, the two beams of the two-beam interferometer are adjusted to cancel each other out through the optical path adjustment mechanism, and the photometer reading reaches the minimum value. During the sample measurement, as long as the sample solution is added to the sample cell and the blank sample solution is added to the reference cell, the output of the photometer is the light absorption intensity signal of the sample.

6. The absorption spectrometer according to claim 1, characterized in that, The absorption spectrometer is a multi-wavelength absorption spectrometer, which includes: A beam splitter is used to provide monochromatic light output. The beam splitter includes a combined light source capable of emitting light from ultraviolet to infrared, a beam splitting element, and a mechanical rotating device. The beam splitting element is a grating or a beam splitting prism. In use, continuous white light is emitted from the combined light source and converted into parallel light before shining on the beam splitting element. The beam splitting element outputs the incident light at different angles according to the wavelength. If the output light is not parallel, the beam splitter also includes a reflecting focusing mirror to convert the output light of the beam splitting element into parallel light output. The mechanical rotating device drives the beam splitting element or the reflecting focusing mirror to rotate. Different rotation angles correspond to monochromatic light output of different wavelengths. A two-beam interferometer receives monochromatic light output from a beam splitter, splits it into two beams of equal intensity, and introduces them into two different optical paths. The beams are then converged to interfere with each other and produce bright and dark patterns. The two-beam interferometer is equipped with an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Sample cells are respectively set in two optical paths in a two-beam interferometer; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. The positioning laser and laser detector, set at the photometer end or the incident light end, will show a laser interference pattern when the optical path adjustment mechanism is continuously adjusted. At the same time, the reading of the laser detector corresponding to the first lowest point measured on the photometer for a given absorption wavelength is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point.

7. The absorption spectrometer according to claim 1, characterized in that, The absorption spectrometer is an atomic absorption spectrometer, which includes: A beam splitter is used to provide monochromatic light output; Element lamps emit characteristic spectral lines of specific elements; A two-beam interferometer splits the monochromatic parallel light output from an element lamp into two beams of equal intensity. The two beams are then introduced into two different optical paths, and then converged to interfere with each other to produce bright and dark patterns. The two-beam interferometer contains an optical path adjustment mechanism that can adjust the optical path length of at least one of the two optical paths. Two sample cells are respectively set in the two optical paths of the two-beam interferometer, and the sample cells can be graphite furnaces or atomized flames; A photometer is used to receive the outgoing light after passing through a two-beam interferometer and convert it into an electrical signal output. A positioning laser and a laser detector are set at the photometer end or the incident light end. The optical path adjustment mechanism is continuously adjusted until the output signal of the laser detector presents a laser interference pattern. At the same time, the reading of the laser detector corresponding to the first lowest point measured on the photometer for a given absorption wavelength is the marker point for measuring the absorption of that wavelength. The absorption of the sample at that wavelength must be tested after the optical path adjustment mechanism is adjusted to the marker point. During sample absorbance detection, the corresponding element lamp needs to be replaced for each element determination. Each time the element lamp is switched, the two sample cells need to be emptied and the optical path of the dual-beam interferometer needs to be adjusted to minimize the output of the photometer. Then, the sample solution and blank sample solution are input into the two sample cells respectively. At this time, the output of the photometer is the absorbance intensity signal of the corresponding element in the sample.

8. The absorption spectrometer according to claim 6 or 7, characterized in that, The calibration method for using a pre-calibrated absorption spectrometer is as follows: Empty both sample cells, control the mechanical rotation device in the spectrometer to rotate to select the wavelength output by the spectrometer, and then drive the optical path adjustment mechanism of the two-beam interferometer to minimize the output of the two-beam interferometer. Repeat this process until all measurable wavelengths are swept, and record each wavelength, the corresponding rotation angle of the mechanical rotation device, and the laser detector reading at the corresponding time to obtain a wavelength-rotation angle-laser value list, which is the calibration table. This calibration table can be stored as system control parameters. During sample testing, the sample solution to be tested and the blank sample solution are added to the two sample cells respectively. After setting a wavelength, the absorption spectrometer is adjusted to the state given by the calibration table. At this time, the output of the photometer is the absorption signal of the sample solution to be tested at the given wavelength. The absorption spectrometer is adjusted according to the parameters listed in the calibration table in sequence and the absorption signal in each state is read. The resulting set of absorption signals is the full scan absorption spectrum.

9. The absorption spectrometer according to claim 4, 6, or 7, characterized in that, The two-beam interferometer is a Michelson interferometer.

10. A method for directly measuring the intensity of absorbed light, characterized in that, Includes the following steps: A sample cell is placed in the optical path of two coherent beams of equal intensity; Both sample cells are filled with blank solution. The optical path difference between the two coherent beams is adjusted until the output of the photometer included in the absorption spectrometer is minimized. When the blank solution in one of the sample cells is replaced with the sample to be tested, the photometer measures the intensity of the remaining light after the two beams converge and interfere, which is the intensity of the light absorbed by the sample to be tested, or the intensity of the absorbed light.

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