Angle-adjustable monochromator type concave holographic grating, spectrometer and method

Abstract

The invention belongs to the technical field of ICP spectral analysis, and particularly relates to an angle-adjustable monochromator type concave holographic grating, a spectrometer and a method. A servo motor in the holographic grating is connected with a lead screw mechanism and can drive a lead screw of the lead screw mechanism to rotate, a polished rod bearing is connected to a connecting block, the connecting block is fixed to the movable end of the lead screw mechanism, a monochromator type concave holographic grating body is connected to a movable base, one end of a polished rod makes contact with the monochromator type concave holographic grating body, and the other end of the polished rod makes contact with the movable base. The other end is matched in the polish rod bearing; according to the invention, two DMDs and a monochromator type concave holographic grating are adopted to realize spatial imaging spectral analysis, the first DMD realizes spatial position selection of an ICP plasma torch, the monochromator type holographic grating realizes high-efficiency and simple-structure rotating grating type light splitting, and the second DMD is selected as an exit slit with adjustable width to carry out fine light splitting on a selected wave band, so that the light splitting efficiency of the ICP plasma torch is improved. Therefore, the spatial imaging spectrum analysis of the ICP plasma torch by the system is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of ICP spectrum analysis, and in particular relates to an angle-adjustable monochromator-type concave holographic grating, a spectrometer and a method. Background Art

[0002] An imaging spectrometer is an optical instrument that combines imaging technology with spectral technology. It can simultaneously collect the spatial information and spectral information of the target to form a data cube that integrates the spectrum and image. It has important application value in the fields of cell membrane fluidity determination, three-dimensional image reconstruction, pathology and clinical applications, precise positioning observation of biochemical components, and quantitative positioning analysis of fluorescence. In the late 1970s and early 1980s, the Jet Propulsion Laboratory of the California Institute of Technology, with the support of NASA, took the lead in starting the research on imaging spectroscopy technology. With the extensive research and investment of relevant technicians at home and abroad in this field in recent years, imaging spectroscopy technology and its performance have made great progress and have been significantly improved. At present, it has been widely used in many fields such as target detection and recognition, remote sensing imaging, food testing, and biomedicine.

[0003] Digital micromirrors (DMDs) are flexible, programmable, and independently addressable spatial light modulation devices. In the field of spectral imaging, DMDs can finely and controllably modulate the imaging field of view, thereby replacing traditional mechanical masks and mechanical scanning structures. In 1982, DMDs were born as spatial light modulation devices at Texas Instruments Laboratories and were mainly used in the field of projection display in the early days. Through continuous exploration and research by scientific researchers, the application areas of DMDs have also expanded from traditional projection display fields to maskless lithography, beam shaping, holographic imaging, and confocal measurement.

[0004] The concave holographic grating adopts a monochromator type holographic grating, which is an important spectroscopic element. The monochromator type concave grating disperses the light from the entrance slit and refocuses it on the exit slit. The wavelength scan is obtained by simply rotating the grating. As a spectral spectroscopic element, compared with the traditional ruled grating, it has the following advantages: no ghost lines in the spectrum, less stray light, high resolution, large effective aperture, high production efficiency, low price, etc. It has been widely used in various grating spectrometers. Compared with the Czerny-Turner monochromator (equipped with a plane grating, a collimator and a focusing mirror), the monochromator grating provides better light collection efficiency and signal-to-noise ratio.

[0005] ICP spectrometer technology began in the 1970s. After nearly 30 years of rapid development, the instrument and technology have become mature and have been widely used in agriculture, chemical industry, petroleum, geology, environment, materials and other fields, and have achieved many important technological achievements. It is currently one of the most widely used analytical tools in the field of elemental analysis. However, the spectral interference of ICP spectrometers limits the improvement of detection limits and accuracy. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an adjustable-angle monochromator-type concave holographic grating, a spectrometer and a method, which are applied to environmental pollution analysis, medicine and health, food safety and other fields, and can effectively reduce the influence of spectral interference and improve the signal-to-noise ratio and resolution.

[0007] A monochromator type concave holographic grating with a rotatable angle comprises a monochromator type concave holographic grating body 1, an optical rod bearing 2, an optical rod 3, a movable base 5, a servo motor 6 and a screw mechanism, wherein the servo motor 6 is connected to the screw mechanism and can drive the screw of the screw mechanism to rotate, the optical rod bearing 2 is movably connected to a connecting block 11, the connecting block 11 is fixed to the movable end of the screw mechanism, the monochromator type concave holographic grating body 1 is connected to the movable base 5, one end of the optical rod 3 is in contact with the rear end of the monochromator type concave holographic grating body 1, and the other end is fitted and connected in the optical rod bearing 2.

[0008] The screw mechanism includes a screw 4, a right screw bearing 7, a left screw bearing 8, and a screw moving block 10, wherein the transmission shaft of the servo motor 6 is connected to the left side of the screw 4 through the plum blossom shaft 9 and the left screw bearing 8, and can drive the screw 4 to rotate. The right side of the screw 4 is connected to the right screw bearing 7, the screw moving block 10 is sleeved outside the screw 4, and the connecting block 11 is fixed on the screw moving block 10.

[0009] The transmission shaft of the servo motor 6 is connected to one end of the plum blossom shaft 9 , and the left side of the screw rod 4 is matched and connected in the left screw rod bearing 8 , and passes through the left screw rod bearing 8 to be connected to the other end of the plum blossom shaft 9 .

[0010] The left screw bearing 8 is a plum blossom coupling.

[0011] An imaging spectrometer based on a double DMD and a holographic grating comprises a concave reflector, a focusing lens, a DMD, a monochromator type concave holographic grating and a photomultiplier tube, wherein an ICP plasma torch to be measured is focused and imaged by the concave reflector and then incident on a first DMD, wherein the first DMD performs spatial light modulation to form a slit as an incident slit of the monochromator type concave holographic grating, and reflects light to the monochromator type concave holographic grating, and the remaining light is reflected by the first DMD to a set light trap, and the monochromator type concave holographic grating realizes light splitting, and the spectrum lines after being split by the monochromator type concave holographic grating body 1 are incident on a second DMD, and the second DMD performs fine selection on the spectrum lines after being split, and the selected spectrum lines are incident on a focusing mirror, and the light rays converged by the focusing mirror are incident on a photomultiplier tube and received by the photomultiplier tube.

[0012] A method for realizing spatial imaging spectrum analysis by an imaging spectrometer based on a dual DMD and a holographic grating comprises the following steps:

[0013] Step 1: Focusing and imaging the ICP plasma torch to be tested: The ICP plasma torch to be tested is used as an incident light source and is reflected by a concave reflector; a reduced image is formed at the first DMD, so that the image of the ICP plasma torch is completely contained within the entire reflection surface of the first DMD;

[0014] Step 2, spatial modulation: according to the known spatial distribution of the ICP plasma torch to be tested, the first DMD is used as the incident slit of the monochromator type concave holographic grating, wherein different areas of the plasma torch to be tested are selected, and a local area consisting of one or several micromirrors on the first DMD is selected according to the position and area of ​​the incident spectrum line, and the micromirrors corresponding to the local area on the first DMD are flipped to form a slit as the incident slit of the monochromator type concave holographic grating, and the light is reflected to the monochromator type concave holographic grating, and the remaining light is reflected to the set light trap through the first DMD;

[0015] Step 3, grating spectrometry: spectrometry is realized by a monochromator type concave holographic grating, wherein the servo motor 6 of the monochromator type concave holographic grating controls the lead screw 4 to drive the optical rod 3 to control the monochromator type concave holographic grating body 1 to rotate to a corresponding angle, so that the light diffracted by the first DMD can be incident on the monochromator type concave holographic grating body 1, and the spectrum line after the spectrometry by the monochromator type concave holographic grating body 1 is incident on the second DMD;

[0016] Step 4, gating modulation: the second DMD is used as an exit slit with adjustable width. The second DMD is used as an exit slit with adjustable width. According to the position of the spectrum line after splitting and the target spectrum line wavelength of the grating splitting at the second DMD, a local area composed of one or more micromirrors on the second DMD is selected, and the micromirrors corresponding to the local area on the second DMD are flipped to form an exit slit, so as to make a fine selection of the spectrum line after splitting. The spectrum line after gating is incident on the focusing mirror, and the light converged by the focusing mirror is incident on the photomultiplier tube and received by the photomultiplier tube;

[0017] Step 5. Receiving and detecting: The photomultiplier tube converts the optical signal into an electrical signal, which is converted into a digital signal after passing through the A / D conversion circuit. The digital signal enters the FPGA microcontroller to form spectral data. Based on the spectral data, a high-resolution spatial imaging spectrum of the light source to be tested is drawn with the wavelength as the horizontal axis and the spectral response as the vertical axis.

[0018] Beneficial effects of the present invention:

[0019] The present invention adopts two DMDs and a monochromator-type concave holographic grating to realize spatial imaging spectral analysis. The first DMD realizes the spatial position selection of the ICP plasma torch, and the monochromator-type holographic grating realizes high-efficiency, simple-structure rotating grating type spectrometry. The second DMD is selected as an output slit with adjustable width to perform fine spectrometry on the selected band, thereby realizing the system's spatial imaging spectral analysis of the ICP plasma torch. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without creative work.

[0021] Figure 1 It is a schematic diagram of the monochromator type concave holographic grating structure of the present invention.

[0022] Figure 2 It is a light path diagram of the spectrometer of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0024] Example 1

[0025] A rotatable monochromator type concave holographic grating, such as Figure 1 As shown, it includes a monochromator type concave holographic grating body 1, an optical rod bearing 2, an optical rod 3, a movable base 5, a servo motor 6 and a screw mechanism, wherein the servo motor 6 is connected to the screw mechanism and can drive the screw of the screw mechanism to rotate, the optical rod bearing 2 is movably connected to a connecting block 11, the connecting block 11 is fixed to the movable end of the screw mechanism, the monochromator type concave holographic grating body 1 is movably connected to the movable base 5, one end of the optical rod 3 is in contact with the rear end of the monochromator type concave holographic grating body 1, and the other end is fitted and connected in the optical rod bearing 2.

[0026] The screw mechanism includes a screw 4, a right screw bearing 7, a left screw bearing 8, and a screw moving block 10, wherein the transmission shaft of the servo motor 6 is connected to the left side of the screw 4 through the plum blossom shaft 9 and the left screw bearing 8, and can drive the screw 4 to rotate. The right side of the screw 4 is connected to the right screw bearing 7, the screw moving block 10 is sleeved outside the screw 4, and the connecting block 11 is fixed on the screw moving block 10.

[0027] The transmission shaft of the servo motor 6 is connected to one end of the plum blossom shaft 9 , and the left side of the screw rod 4 is matched and connected in the left screw rod bearing 8 , and passes through the left screw rod bearing 8 to be connected to the other end of the plum blossom shaft 9 .

[0028] The left screw bearing 8 is a plum blossom coupling.

[0029] like Figure 2As shown, an imaging spectrometer based on a dual DMD and a holographic grating includes a concave reflector, a focusing lens, a DMD, a monochromator-type concave holographic grating, a photomultiplier tube, and a signal processing circuit (the purpose is to amplify and rectify the signal collected by the photomultiplier tube and transmit it to a host computer), wherein the ICP plasma torch to be measured is focused and imaged by the concave reflector and then incident on the first DMD, wherein the first DMD performs spatial light modulation, and since different areas of the plasma excited by the light source have different temperature distributions, the entire analysis channel is divided into: an atomization area (lower temperature), an atomic emission area (temperature The method comprises the following steps: selecting different areas of the plasma torch to be measured, selecting a local area composed of one or several micromirrors on the first DMD according to the position and area of ​​the incident spectrum line, flipping the micromirrors corresponding to the local area on the first DMD to form a slit, which serves as the incident slit of the monochromator type concave holographic grating, reflecting the light to the monochromator type concave holographic grating, and reflecting the remaining light to the set light trap through the micromirrors at -12 degrees (all micromirrors except those receiving the spectrum line to be measured are set to -12 degrees) on the first DMD, and the monochromator type concave holographic grating realizes spectral separation. The servo motor 6 of the grating controls the lead screw 4 to drive the optical rod 3 to control the monochromator type concave holographic grating body 1 to rotate to the required angle that can make the light to be measured incident (the monochromator type concave holographic grating is a rotating grating type spectroscopic device, and one wavelength corresponds to an angle between the incident light and the outgoing light) to realize wavelength scanning. The spectrum line after the splitting by the monochromator type concave holographic grating body 1 is incident on the second DMD. The second DMD is used as an exit slit with adjustable width. According to the position of the spectrum line after the splitting and the target spectrum line wavelength of the grating splitting at the second DMD, a local area composed of one or more micromirrors on the second DMD is selected. , flip the micromirror corresponding to the local area on the second DMD to form an exit slit, so as to finely select the spectral lines after splitting, and the selected spectral lines are incident on the focusing mirror. The light converged by the focusing mirror is incident on the photomultiplier tube and received by the photomultiplier tube. The photomultiplier tube converts the optical signal into an electrical signal, which is converted into a digital signal after passing through the A / D conversion circuit. The digital signal enters the FPGA microcontroller (later field programmable gate array embedded system) to form spectral data. According to the spectral data, a high-resolution spatial imaging spectrum of the light source to be tested is drawn with wavelength as the horizontal axis and spectral response as the vertical axis.

[0030] A method for realizing spatial imaging spectrum analysis by an imaging spectrometer based on a dual DMD and a holographic grating comprises the following steps:

[0031] Step 1: Focusing and imaging the ICP plasma torch to be tested: The ICP plasma torch to be tested is used as an incident light source and is reflected by a concave reflector; a reduced image is formed at the first DMD, so that the image of the ICP plasma torch is completely contained within the entire reflection surface of the first DMD;

[0032] Step 2, spatial modulation: according to the known spatial distribution of the ICP plasma torch to be tested, the first DMD is used as the incident slit of the monochromator type concave holographic grating, wherein different areas of the plasma torch to be tested are selected, and a local area consisting of one or several micromirrors on the first DMD is selected according to the position and area of ​​the incident spectrum line, and the micromirrors corresponding to the local area on the first DMD are flipped to form a slit as the incident slit of the monochromator type concave holographic grating, and the light is reflected to the monochromator type concave holographic grating, and the remaining light is reflected to the set light trap through the micromirrors of -12 degrees (all micromirrors except those receiving the spectrum line to be tested are set to -12 degrees) on the first DMD;

[0033] Step 3, grating spectrometry: spectrometry is realized by a monochromator type concave holographic grating, wherein the servo motor 6 of the monochromator type concave holographic grating controls the lead screw 4 to drive the optical rod 3 to control the monochromator type concave holographic grating body 1 to rotate to a corresponding angle, so that the light diffracted by the first DMD can be incident on the monochromator type concave holographic grating body 1, and the spectrum line after the spectrometry by the monochromator type concave holographic grating body 1 is incident on the second DMD;

[0034] Step 4, gating modulation: the second DMD is used as an exit slit with adjustable width. The second DMD is used as an exit slit with adjustable width. According to the position of the spectrum line after splitting and the target spectrum line wavelength of the grating splitting at the second DMD, a local area composed of one or more micromirrors on the second DMD is selected, and the micromirrors corresponding to the local area on the second DMD are flipped to form an exit slit, so as to make a fine selection of the spectrum line after splitting. The spectrum line after gating is incident on the focusing mirror, and the light converged by the focusing mirror is incident on the photomultiplier tube and received by the photomultiplier tube;

[0035] Step 5. Receiving and detecting: The photomultiplier tube converts the optical signal into an electrical signal, which is converted into a digital signal after passing through the A / D conversion circuit. The digital signal enters the FPGA microcontroller (later field programmable gate array embedded system) to form spectral data. Based on the spectral data, a high-resolution spatial imaging spectrum of the light source to be tested is drawn with the wavelength as the horizontal axis and the spectral response as the vertical axis.

[0036] Example 2

[0037] A method for realizing spatial imaging spectrum analysis based on an imaging spectrometer with dual DMD and holographic grating comprises the following steps:

[0038] Step 1: Focusing and imaging the ICP plasma torch to be tested: The ICP plasma torch to be tested is focused and reflected by a concave reflector; a reduced image is formed at the first DMD, so that the image of the ICP plasma torch is completely contained within the entire reflection surface of the first DMD;

[0039] Specifically, the spectral line to be measured passes through the concave reflector to form a reduced real image at the first DMD, and is reflected by the DMD to serve as the incident light of the grating.

[0040] Step 2, spatial modulation: According to the known spatial distribution of the ICP plasma torch to be tested, the first DMD is used as the incident slit of the holographic grating in step 3. Due to the different temperature distributions in different areas of the plasma, the entire analysis channel is divided into: atomization area (low temperature), atomic emission area (high temperature) and ion emission area (high temperature). Different areas of the plasma torch are selected, and a local area composed of one or more micromirrors is selected according to the position of the incident spectrum line. The micromirror of the first DMD is flipped to form a slit, which is used as the incident slit of the monochromator type concave holographic grating to reflect the light to the monochromator type concave holographic grating; specifically, the surface of the DMD chip is composed of thousands of aluminum micromirrors. After the light source is incident on the concave reflector and irradiates the DMD working surface, the computer generates data and transmits it to the DMD device through the driving circuit and controls the flipping of the micromirror. During operation, the DMD controller loads a "1" or a "0" for each basic storage unit. Next, a mirror reset pulse is applied, which causes each micromirror to electrostatically deviate by about one hinge, thereby reaching the corresponding + / -12° state. The two valid states are repeatable in their deflection angles due to the physical stop caused by the resistance of two spring-loaded pins. In a projection system, the +12° state corresponds to an "on" pixel and the -12° state corresponds to an "off" pixel. Grayscale patterns are created by programming the on / off duty cycle of each mirror, and multiple light sources can be multiplexed to create RGB full-color images.

[0041] The micromirrors in most DMD chips flip with the diagonal of the micromirror as the axis of symmetry. Here we can regard the micromirror array flipped along the diagonal as a two-dimensional blazed grating in the x and y directions, so the DMD can be used as a programmable two-dimensional blazed grating to modulate the light beam to achieve tunable wavelength. Taking the DMD with a 1024*768 matrix array as an example, it has 1024 columns and 768 rows. The specific control parameters of the DMD include the flip start column, the number of columns flipped simultaneously, the number of columns flipped interval, the number of flips, the number of repetitions, the residence time, and the integration time. The selection and setting of the above parameters can realize the DMD flip state and timing control of the entire detection process. According to the known wavelength of the spectral line to be measured, the corresponding number of DMD flip columns is determined; through the host computer software, instructions are sent to the DMD according to the known wavelength, and the DMD micromirrors at the corresponding wavelength will flip;

[0042] Step 3, grating spectrometry: by controlling the servo motor, the monochromator type concave holographic grating body 1 is rotated to a corresponding angle, so that the light diffracted by the DMD can be incident on the position of the monochromator type concave holographic grating body 1, and the spectrum line to be measured is dispersed to obtain a one-dimensional spectrum line;

[0043] Specifically, a type IV aberration-corrected monochromator grating is used, and a single concave grating disperses and collimates the light incident through the DMD in step two and refocuses it onto the second DMD in step four. A servo motor is used to link a lead screw to drive an optical rod to control the monochromator-type concave holographic grating to rotate to a desired angle (the monochromator-type concave holographic grating is a rotating grating-type spectroscopic device, and one wavelength corresponds to an angle between an incident light and an outgoing light) to achieve wavelength scanning. MATLAB is used to send instructions to the servo motor through serial communication to control its rotation speed and rotation angle. The grating rotation angle is determined according to the wavelength of the incident light from the DMD in step two, so that the grating is rotated to a position where the incident spectral line can be received, so that the holographic grating is simply rotated to obtain wavelength scanning, and the spectra after spectrometry are incident on the second DMD.

[0044] Seya-Namioka type monochromator grating, with very small astigmatism and coma, its coating material is aluminum or gold, the spectral range is 190 to 10000nm, with a line density of 100 to 2000gr / mm, and a wide spectral range from violet to red. In addition, the holographic master grating can be blazed by ion beam etching to improve efficiency, suitable for sturdy, compact and low stray light monochromators, and can provide a wide range of dispersion. Using the aberration-corrected monochromator grating independently, the dispersion, collimation and focusing functions of the grating can be completed. When the position points of the entrance slit and the exit slit are fixed, the wavelength scanning process is completed by controlling the rotation of the grating.

[0045] Step 4: Gating modulation: The second DMD acts as an output slit with adjustable width to finely select the spectrum lines after splitting, and controls the reflection state of each micromirror unit on the digital micromirror through the host computer.

[0046] Specifically, the flipping area of ​​the second DMD micromirror is determined according to the position of the spectrum line after the splitting, and the second digital micromirror DMD is used as an output slit with adjustable width. The spectral line width of the output light can be calculated according to the position of the spectrum line after the splitting, the linear dispersion rate of the grating splitting at the second DMD, and the width of the slit. Assuming that the focal length of the spectrometer is f, the linear dispersion rate is dl / dλ, according to the definition of resolution R=λ / Δλ, and R=mN (where m is the diffraction order, and N is the total number of grating lines), the slit width w=Δλ / (dl / dλ), so that the spectrum line after the splitting is finely selected, and the selected spectrum line is converged to the photomultiplier tube through a concave reflector;

[0047] Step 5, receiving and detecting: The focused light is received by a photomultiplier tube (PMT), and the optical signal is converted into an electrical signal. Finally, the obtained data is transmitted to the host computer via Ethernet to obtain the corresponding spectrum, the spatially resolved spectrum, and the 3D imaging spectrum cube diagram including spatial resolution and spectral resolution.

[0048] Reception and detection use photomultiplier tubes as receiving devices. When selecting PMT, considering that the PMT working mode is a combination of single photon counting mode and current / voltage conversion mode, and the signal to be measured is a weak light signal, the selected photomultiplier tube needs to have sufficient sensitivity at a wavelength of 400nm, that is, it can respond to weak light signals; it needs to have a sufficiently large dynamic range. After comprehensive consideration, R955 from Beijing Hamamatsu Company was selected in this design.

[0049] The weak current signal collected by the photomultiplier tube is first converted into a digital signal through the A / D conversion circuit, and then the embedded system counts the converted digital signal and transmits the obtained data to the host computer. The spectral resolution diagram is obtained with the wavelength as the horizontal axis and the spectral response as the vertical axis to complete the detection purpose.

[0050] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the protection scope of the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention. These simple variations all belong to the protection scope of the present invention.

Claims

1. A rotatable monochromator type concave holographic grating, characterized in that: The invention comprises a monochromator type concave holographic grating body (1), an optical rod bearing (2), an optical rod (3), a movable base (5), a servo motor (6) and a screw mechanism, wherein the servo motor (6) is connected to the screw mechanism and can drive the screw of the screw mechanism to rotate, the optical rod bearing (2) is movably connected to a connecting block (11), the connecting block (11) is fixed to the movable end of the screw mechanism, the monochromator type concave holographic grating body (1) is connected to the movable base (5), one end of the optical rod (3) is in contact with the rear end of the monochromator type concave holographic grating body (1), and the other end is matched and connected in the optical rod bearing (2).

2. The rotatable monochromator type concave holographic grating according to claim 1, characterized in that: The screw mechanism comprises a screw (4), a right screw bearing (7), a left screw bearing (8), and a screw moving block (10), wherein the transmission shaft of the servo motor (6) is connected to the left side of the screw (4) through a plum blossom shaft (9) and a left screw bearing (8), and can drive the screw (4) to rotate, the right side of the screw (4) is connected to the right screw bearing (7), the screw moving block (10) is sleeved outside the screw (4), and the connecting block (11) is fixed on the screw moving block (10).

3. The rotatable monochromator type concave holographic grating according to claim 2, characterized in that: The transmission shaft of the servo motor (6) is connected to one end of the plum blossom shaft (9), and the left side of the screw rod (4) is matched and connected in the left screw rod bearing (8), and passes through the left screw rod bearing (8) to be connected to the other end of the plum blossom shaft (9).

4. The rotatable monochromator type concave holographic grating according to claim 3, characterized in that: The left screw bearing (8) is a plum blossom coupling.

5. An imaging spectrometer based on a dual DMD and a holographic grating according to any one of claims 1 to 4, characterized in that: The invention comprises a concave reflector, a focusing lens, a DMD, a monochromator type concave holographic grating and a photomultiplier tube, wherein an ICP plasma torch to be tested is focused and imaged by the concave reflector and then incident on a first DMD, wherein the first DMD performs spatial light modulation to form a slit as an incident slit of the monochromator type concave holographic grating, and reflects light to the monochromator type concave holographic grating; the remaining light is reflected by the first DMD to a set light trap, and the monochromator type concave holographic grating realizes light splitting; the spectrum lines after light splitting by the monochromator type concave holographic grating body (1) are incident on a second DMD, the second DMD performs fine selection on the spectrum lines after light splitting; the selected spectrum lines are incident on a focusing mirror; the light rays converged by the focusing mirror are incident on a photomultiplier tube and received by the photomultiplier tube.

6. A method for realizing spatial imaging spectrum analysis by using the imaging spectrometer based on dual DMD and holographic grating as claimed in claim 5, characterized in that: The following steps are involved: Step 1: Focusing and imaging the ICP plasma torch to be tested: The ICP plasma torch to be tested is used as an incident light source and is reflected by a concave reflector; a reduced image is formed at the first DMD, so that the image of the ICP plasma torch is completely contained within the entire reflection surface of the first DMD; Step 2, spatial modulation: according to the known spatial distribution of the ICP plasma torch to be tested, the first DMD is used as the incident slit of the monochromator type concave holographic grating, wherein different areas of the plasma torch to be tested are selected, and a local area consisting of one or several micromirrors on the first DMD is selected according to the position and area of ​​the incident spectrum line, and the micromirrors corresponding to the local area on the first DMD are flipped to form a slit as the incident slit of the monochromator type concave holographic grating, and the light is reflected to the monochromator type concave holographic grating, and the remaining light is reflected to the set light trap through the first DMD; Step 3, grating spectrometry: spectrometry is achieved by a monochromator type concave holographic grating, wherein a servo motor (6) of the monochromator type concave holographic grating controls a lead screw (4) to drive an optical rod (3) to control the monochromator type concave holographic grating body (1) to rotate to a corresponding angle, so that the light diffracted by the first DMD can be incident on the monochromator type concave holographic grating body (1), and the spectrum after the spectrometry by the monochromator type concave holographic grating body (1) is incident on the second DMD; Step 4, gating modulation: the second DMD is used as an exit slit with adjustable width. The second DMD is used as an exit slit with adjustable width. According to the position of the spectrum line after splitting and the target spectrum line wavelength of the grating splitting at the second DMD, a local area composed of one or more micromirrors on the second DMD is selected, and the micromirrors corresponding to the local area on the second DMD are flipped to form an exit slit, so as to make a fine selection of the spectrum line after splitting. The spectrum line after gating is incident on the focusing mirror, and the light converged by the focusing mirror is incident on the photomultiplier tube and received by the photomultiplier tube; Step 5. Receiving and detecting: The photomultiplier tube converts the optical signal into an electrical signal, which is converted into a digital signal after passing through the A / D conversion circuit. The digital signal enters the FPGA microcontroller to form spectral data. Based on the spectral data, a high-resolution spatial imaging spectrum of the light source to be tested is drawn with the wavelength as the horizontal axis and the spectral response as the vertical axis.

Images