Off-axis paraboloid mirror image difference correction high-resolution spectrum detection method and device

Abstract

The invention discloses an off-axis paraboloid mirror image difference correction high-resolution C-T type spectrum detection method and device, and belongs to the technical field of spectrum imaging and detection. The collimating mirror and the convergent mirror are off-axis parabolic mirrors. The off-axis parabolic mirror is used for correcting the spherical aberration of the spectrometer; suppressing and correcting coma of the spectrometer by using the off-axis angles of the collimating mirror and the convergent mirror and focal length symmetric structure parameters; the field curvature of the spectrograph is corrected by calculating the optimal grating position; performing linear array integral detection on the convergent light by using a small-pixel deep refrigeration array detector; by combining high and low density gratings, the gratings are switched under the application requirements of different wave band ranges, resolving power and scanning speed, and rapid light splitting detection from ultraviolet to infrared broadband is realized; high-precision grating rotary scanning and angle monitoring are utilized, and large-range spectral broadband and high-resolution detection is realized through spectral line splicing. According to the invention, wide-spectrum, high-resolution and high-sensitivity rapid detection of Raman, infrared, emission, absorption and other spectral signals can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral imaging and detection, and relates to an off-axis parabolic mirror aberration correction high-resolution spectral detection method and device, which are used to correct aberrations such as spherical aberration, coma, field curvature, and astigmatism of a spectral detection device to improve spectral resolution. Background Technique

[0002] Spectral detection technology is widely used in fields such as biomedicine, materials science, deep space exploration, and environmental monitoring. As an important tool for spectral detection, spectrometers are widely used in detection fields such as Raman, infrared, and fluorescence. Among many spectrometer structures, the Czerny-Turner (C-T) structure is simple and easy to assemble and align, and is the most suitable spectrometer structure for high-resolution spectral detection.

[0003] Traditional high-resolution C-T spectrometers use off-axis spherical mirrors, resulting in aberrations such as spherical aberration, coma, field curvature, and astigmatism in the system. These aberrations will increase with the increase of the spectrometer focal length and are difficult to correct, seriously affecting spectral resolution and imaging quality, and restricting their further application. At the same time, since spectral signals are usually weak and carry rich information, how to suppress the aberrations of the spectrometer to detect spectral signals in a wide spectral range with high resolution and high sensitivity is the key prerequisite for extracting and characterizing sample information.

[0004] At present, many researchers have studied how to suppress the aberrations of spectrometers. The team of the Radio Propagation Laboratory of the National Institute of Standards and Technology in the United States proposed a method to correct coma for a specific wavelength by setting the geometric parameters of a spherical collimator and a converging mirror. This method still uses spherical mirrors and will introduce other aberrations such as spherical aberration and field curvature. In terms of suppressing astigmatism, the team of the National Institute of Advanced Industrial Science and Technology in Japan uses toroidal mirrors or free-form mirrors to replace spherical converging mirrors to achieve astigmatism correction. However, this method has extremely high requirements for the mechanical dimension accuracy of the system, and the toroidal mirror is extremely expensive. In addition, the focal length of the toroidal mirror in the sagittal direction depends on the central wavelength of the incident light, which results in poor astigmatism correction performance for this method in a wide spectral range. Institutions such as Beijing Institute of Technology, Zhejiang University, and Changchun Institute of Optics and Fine Mechanics proposed methods such as adding cylindrical mirrors or cylindrical mirrors in the system. This method will increase the optical elements and alignment difficulty of the system, which is unacceptable for long-focus spectrometers that already have great alignment difficulty. The above methods all correct the current aberrations of spectrometers to a certain extent, but there is currently no method suitable for correcting multiple aberrations of long-focus and wide-spectral-range high-resolution spectrometers.

[0005] As described above, the existing methods have insufficient aberration correction ability for C-T spectrometers. Among them, the astigmatism correction effect is insufficient, and the field curvature and spherical aberration are not corrected, which restricts the beam focusing and compression ability of the condenser lens and limits the spectral imaging detection resolution. Therefore, effective aberration correction of C-T spectrometers is the only way to improve the spectral detection resolution. Summary of the Invention

[0006] To solve the problem that it is difficult to improve the spectral detection resolution and imaging quality caused by the aberration of the C-T grating spectral detection system, the purpose of the present invention is to provide an off-axis parabolic mirror aberration correction high-resolution C-T spectral detection method and device, which can achieve the overall correction of the aberration of the spectral detection system, ensure the precise focusing of beams with different diffraction angles, and improve the spectral resolution and imaging quality of spectral signals.

[0007] The purpose of the present invention is achieved by the following technical solutions.

[0008] An off-axis parabolic mirror aberration correction high-resolution spectral detection method disclosed by the present invention uses off-axis parabolic mirrors for the collimator and condenser lens in the C-T structure. By utilizing the characteristic that the off-axis parabolic mirror has no primary spherical aberration, the spherical aberration of the spectrometer is effectively corrected; the coma of the spectrometer is suppressed and corrected by using the symmetric structural parameters of the off-axis angles and focal lengths of the collimator and condenser lens; the effective correction of the field curvature of the spectrometer is achieved by calculating the optimal grating position; the astigmatism of the convergent beam of the spectrometer is corrected by using the characteristic that the primary astigmatism at the focus of two off-axis parabolic mirrors with the same parameters is zero. A small pixel deep-cooled array detector is used for linear array integration detection of the convergent light, significantly improving the detection sensitivity and signal-to-noise ratio; by combining high-density gratings and low-density gratings, the gratings are switched under the application requirements of different wavelength ranges, resolutions, and scanning speeds to achieve fast spectroscopic detection in the wide wavelength range from ultraviolet to infrared; high-precision grating rotation scanning and angle monitoring are used to achieve high-stability scanning of spectral signals in specific spectral segments under a specific grating, and wide-range spectral wide-band and high-resolution detection are achieved through spectral line splicing; the above four methods are combined to take into account the range, resolution, scanning speed, and sensitivity of spectral detection, and achieve wide-spectrum, high-resolution, and high-sensitivity fast detection of spectral signals such as Raman, infrared, emission, and absorption.

[0009] An off-axis parabolic mirror aberration correction high-resolution spectral detection method disclosed by the present invention includes the following steps:

[0010] Step 1: The measured polychromatic light beam containing different spectral information is converged and focused onto the entrance slit to form an incident emission beam. The incident divergent beam passing through the entrance slit is collimated into a polychromatic parallel light by an off-axis parabolic collimator. The polychromatic parallel light is incident on the diffraction grating at the same incident angle and is scattered and spectroscopically analyzed by the reflective diffraction grating to form diffracted parallel light at different exit angles. The diffracted parallel light contains monochromatic light beams with different diffraction angles, which are incident on the off-axis parabolic focusing mirror and are converged by the parabolic focusing mirror to form a converging beam, which is focused on the detection surface to form a series of laterally distributed focused spots.

[0011] Among them, the parabolic mirror is used as the collimator and focusing mirror in the C-T type structure, and both work in an off-axis state. The reflection by the parabolic mirror itself will generate aberrations, including spherical aberration, coma, field curvature, and astigmatism, resulting in the beam emitted through the slit not being an ideal point but becoming a diffused spot after passing through the optical system, and the foci of the focusing meridian plane and the sagittal plane do not coincide, seriously affecting the resolution and imaging quality of the spectrometer. The primary aberration coefficients of the parabolic mirror are:

[0012]

[0013] Among them, S1, S2, S3, S4, and S5 are the distribution coefficients of spherical aberration, coma, astigmatism, field curvature, and distortion respectively. j is the Lagrange-Helmholtz invariant, h is the ray height, l is the off-axis height, and x is the distance from the image plane to the vertex of the parabola. The main primary aberrations in the spectrometer are spherical aberration, coma, and astigmatism. From the above formula, it can be seen that the spherical aberration coefficient in the primary aberration of the parabolic mirror is zero. Therefore, in the present invention, an off-axis parabolic mirror is used as the collimator and focusing mirror to correct spherical aberration.

[0014] The coma of the spectrometer system is closely related to the off-axis angle. By adjusting ε 1、 ε2 reduces the influence of coma on the spectral detection resolution. When the coma of the system is zero, the structural parameters of the collimator and focusing mirror are calculated according to the following formula:

[0015]

[0016] Among them, ε 1， ε2 are the off-axis angles of the collimating parabolic mirror and the focusing parabolic mirror respectively, f1 and f2 are their focal lengths respectively. In the present invention, parabolic mirrors with the same focal length are used as the collimator and focusing mirror. The incident angle and reflection angle of the grating can be obtained according to the designed central wavelength of the spectrometer. Therefore, on the premise of meeting the spatial position, ε 1， ε2 satisfying a certain relationship can effectively correct the coma of the system.

[0017] The existence of field curvature causes the actual image plane of the system not to coincide with the Gaussian image plane, but a cylindrical surface with a certain distance from the Gaussian image plane. The radius of the imaging cylindrical surface can be calculated according to the following formula:

[0018]

[0019] Therefore, there is:

[0020] x = 0.8452r2 / 2 (4)

[0021] where x is the horizontal distance from the diffraction grating to the parabolic converging mirror.

[0022] Meanwhile, the angle between the ideal image plane and the tangential direction of the meridian plane can be calculated according to formula (6):

[0023]

[0024] Through equations (4) and (5), by setting appropriate grating positions and the tilt angle of the detector, effective correction of the system field curvature is achieved.

[0025] The present invention uses two off-axis parabolic mirrors with the same parameters for collimation and focusing. According to the calculation formula of the parabolic mirror aberration coefficient, when the distance between the detector and the parabolic converging mirror is the focal length of the parabolic mirror, the primary aberration of the parabolic mirror is zero. Therefore, in the present invention, using off-axis parabolic mirrors as collimating mirrors and converging mirrors can effectively correct the system astigmatism.

[0026] Step 2: The two off-axis parabolic mirrors correct the on-axis aberrations such as spherical aberration generated by the spectrometer, and off-axis aberrations such as coma, field curvature, astigmatism, etc., so as to compress the focused light spot and make it closer to the ideal optical imaging. Compared with the aberration light spot image of the traditional spherical converging mirror, the aberration-corrected light spot image of the off-axis parabolic mirror;

[0027] Step 3: The light spot after aberration correction converges to the detector target surface located at the focus of the off-axis parabolic converging mirror. The longitudinal distribution of the detector light spot represents the light intensity data corresponding to a specific wavelength, and its transverse distribution is the wavelength distribution corresponding to the grating rotation angle. Longitudinal cumulative summation is performed on the light intensity of each column of pixels to obtain the spectral curve of the wavelength–light intensity distribution on the detector;

[0028] Step 4: Use a motor to drive the grating turntable to drive the diffraction grating to rotate step by step, repeat Steps 1 to 3, and sequentially obtain the spectral curves of each end-to-end connected spectral segment. The spectral curves of the spectral segments are spliced to obtain the wide-spectrum spectral curve, that is, off-axis parabolic mirror aberration correction high-resolution spectral detection is achieved.

[0029] As a preferred solution: The diffraction grating includes gratings with different line densities and blaze wavelengths to adapt to different spectral detection ranges, spectral resolutions, and scanning speeds, and a precision rotating shaft rotary drive is adopted..

[0030] As a preferred solution: The diffraction grating adopts an ion-etched holographic blazed grating to avoid the occurrence of "ghost lines".

[0031] As a preferred solution: Before detection, adjust the width of the incident slit to change the size of the light spot dispersion direction. On the premise of ensuring that most of the energy of the light spot is not lost, reduce the lateral size of the incident light spot on the detector, so as to improve the detection resolution while ensuring the detection light flux.

[0032] The present invention also discloses an off-axis paraboloid mirror aberration correction high-resolution spectral detection device, including an incident slit, a diaphragm, a paraboloid collimating mirror, a grating assembly, a paraboloid converging mirror, a detector, and a grating turntable; the incident slit is located at the focus of the paraboloid collimating mirror; the diaphragm is located in the light beam propagation direction behind the slit; the grating assembly is located in the reflection direction of the collimating mirror, which includes multiple diffraction gratings with different grating pitches, and the reflecting surface of the grating is located on the center of rotation of the turntable; the paraboloid converging mirror is located in the diffraction direction of the grating; the detector target surface is located on the focal plane of the converging mirror; the grating turntable includes a motor and a driver for driving the grating to rotate and a circular grating encoder for feedback of the grating rotation angle.

[0033] As a preferred solution: The grating assembly includes a diffraction grating combination and a grating switching motor. The diffraction grating is composed of a combination of multiple high-density diffraction gratings and low-density diffraction gratings; the grating switching motor is used to switch gratings with different line densities and rotate the reflecting surface of the diffraction grating to the center of the axis of rotation of the grating turntable.

[0034] As a preferred solution: The detection surface is a matrix detector, and the detection surface adopts a high-sensitivity CCD detector; or, the detection surface is a linear array detector, and the detection surface is constructed by a high-speed linear array CMOS detector with an electronic shutter function.

[0035] As a preferred solution: The grating turntable is composed of a bearing, a coupling, a stepping motor, and a circular grating encoder.

[0036] As a preferred solution: The circular grating encoder of the grating turntable can be adapted to electronic subdivision boxes with different subdivision multiples to meet the stability and accuracy requirements of different light wavelengths.

[0037] As a preferred solution: Before detection, the diameter of the variable diaphragm can be adjusted to match it according to the numerical aperture NA of the incident light, ensuring that the light beam can just pass through the incident diaphragm, avoiding light scattering and interference, and thus obtaining better focusing ability and spectral resolution.

[0038] As a preferred solution: The diaphragm is an electric variable diaphragm, which meets the requirements of light flux, numerical aperture, and resolution.

[0039] Beneficial effects:

[0040] 1. The off-axis parabolic mirror aberration correction high-resolution C-T type spectral detection method and device disclosed by the present invention use an off-axis parabolic mirror to correct and compensate for the off-axis astigmatism of the spectrometer, achieving the correction of spherical aberration, coma, field curvature, and astigmatism of the high-resolution C-T spectral detection structure, improving the convergence ability of light beams with different diffraction angles, and solving the problem that it is difficult to precisely converge light beams affected by aberration. In addition, using an off-axis parabolic mirror to correct and compensate for the off-axis astigmatism of the spectrometer eliminates the need to add extra optical elements and does not change the overall structure of the spectrometer, enabling the inheritance of the high diffraction efficiency of the C-T type spectrometer and significantly improving the detection resolution. By compensating for aberration with an off-axis parabolic mirror, the present invention can transform the existing spectrometer structure, with low cost and high efficiency;

[0041] 2. The off-axis parabolic mirror aberration correction high-resolution C-T type spectral detection method and device disclosed by the present invention use a small pixel high-sensitivity area array detector combined with longitudinal column pixel accumulation detection to improve the detection light intensity without changing the optical path structure, significantly improving the detection sensitivity of the spectrometer to spectra, especially low-flux spectra, that is, the present invention can achieve high-resolution and high-sensitivity detection of spectral signals.

[0042] 3. The off-axis parabolic mirror aberration correction high-resolution C-T type spectral detection method and device disclosed by the present invention use multi-grating coaxial rotary scanning detection, using grating step scanning and spectral segment detection stitching to form a map, taking into account both the spectral detection resolution and the detection range, and can achieve high-resolution spectral detection in a wide spectral range through grating scanning, taking into account both the detection range and the resolution.

[0043] 4. The off-axis parabolic mirror aberration correction high-resolution C-T type spectral detection method and device disclosed by the present invention use a grating switching motor to switch each grating, ensuring that the reflecting surface of each grating is always at the center of the rotation axis; using a circular grating encoder combined with an electronic subdivision box to detect and feedback the rotation angle of the turntable to ensure the rotation angle accuracy, thereby improving the accuracy and stability of the spectral detection wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the drawings and embodiments:

[0045] Figure 1 is a schematic diagram of the off-axis parabolic mirror aberration correction high-resolution spectral detection method of the present invention;

[0046] Figure 2 is a schematic diagram of the geometric parameters of the off-axis parabolic mirror of the present invention;

[0047] Figure 3 is a schematic diagram of the comparison of the converging light spots between a traditional spherical mirror and the off-axis parabolic mirror of the present invention;

[0048] Figure 4 is a schematic structural diagram of the off-axis paraboloid mirror aberration correction high-resolution spectral detection device of the present invention;

[0049] Figure 5 is a schematic structural diagram of the worm and worm gear type rotating shaft of the present invention;

[0050] Figure 6 is a schematic structural diagram of the grating switching turntable of the present invention;

[0051] In the figure: 1 - incident slit, 2 - paraboloid collimating mirror, 3 - grating turntable, 4 - diffraction grating, 5 - paraboloid converging mirror, 6 - detector, 7 - incident divergent light beam, 8 - collimated polychromatic light, 9 - diffracted parallel light, 10 - converging light beam, 11 - off-axis paraboloid mirror, 12 - spherical mirror converging spot image, 13 - off-axis paraboloid mirror converging spot image, 14 - adjustable aperture, 15 - shutter, 16 - folding mirror, 17 - low-density diffraction grating, 18 - high-density diffraction grating, 19 - first motor driver, 20 - first motor, 21 - first coupling, 22 - worm, 23 - worm wheel, 24 - first circular grating encoder, 25 - second motor driver, 26 - second motor, 27 - second coupling, 28 - flange, 29 - second circular grating encoder, 30 - grating fixing frame. Specific embodiments

[0052] In order to better illustrate the purpose and advantages of the present invention, the following further describes the content of the invention with reference to the drawings and examples.

[0053] An embodiment of the off-axis paraboloid mirror aberration correction high-resolution spectral detection method of the present invention is as Figure 1 shown. The entire system consists of an incident slit, a collimating mirror, a grating turntable, a converging mirror, and a detector. The aberration of the off-axis light beam of the spectrometer is corrected by using the unique aberration correction characteristic of the off-axis paraboloid mirror, so that the focused spot is close to the ideal optical imaging; the grating rotation scanning is used to perform sub-band scanning on the measured spectral signals in a wide band range, and the wide-range and high-resolution detection of the spectral signals is realized through spectral line splicing; the high-sensitivity small pixel area array detector is used to perform integral detection on the converging spot, so as to realize the high-resolution and high-sensitivity detection of the spectral signals.

[0054] An embodiment of the off-axis paraboloid mirror aberration correction high-resolution spectral detection method of the present invention is as Figure 1As shown: An off-axis parabolic mirror is used as the collimating mirror and the converging mirror in a Czerny-Turner type spectrometer. By taking advantage of the fact that the off-axis parabolic mirror has no primary spherical aberration, the spherical aberration of the spectrometer is effectively corrected. The coma of the spectrometer is suppressed and corrected by using the symmetric structural parameters of the off-axis angles and focal lengths of the collimating mirror and the converging mirror, and their off-axis angles are 3.96° and 2.54° respectively. The field curvature of the spectrometer is effectively corrected by placing the grating at the optimal position (the horizontal distance between the grating and the converging mirror is 633.9 mm). The astigmatism of the converging beam of the spectrometer is corrected by taking advantage of the fact that the primary astigmatism at the focal points of two off-axis parabolic mirrors with the same parameters of a focal length of 750 mm and an aperture of 100 mm is zero. A small-pixel deep-cooled array detector is used to perform linear array integration detection on the converging light, significantly improving the detection sensitivity and signal-to-noise ratio. By combining high- and low-density gratings and switching the gratings according to the application requirements in different wavelength ranges, resolutions, and scanning speeds, rapid spectroscopic detection in a wide wavelength range from ultraviolet to infrared is achieved. By using high-precision grating rotation scanning and angle monitoring techniques, highly stable scanning of spectral signals in sub-bands under a specific grating is achieved, and wide-band, high-resolution detection of a large range of spectra is achieved through spectral line stitching. Finally, rapid detection of spectral signals such as Raman, infrared, emission, and absorption with wide spectral bands, high resolution, and high sensitivity is realized.

[0055] The specific implementation steps of the off-axis parabolic mirror aberration correction high-resolution spectroscopic detection method are as follows: Step 1: The measured signal forms an incident divergent beam 7 through the incident slit 1. The incident divergent beam 7 is collimated into a collimated polychromatic light 8 by the parabolic collimating mirror 2. After being dispersed and spectroscopically analyzed by the diffraction grating 4, the collimated polychromatic light forms a diffracted parallel light 9, which is composed of monochromatic parallel lights with different diffraction angles and is finally focused on the detector 6 by the parabolic converging mirror 5 to form a series of focused spots.

[0056] Among them, the parabolic mirror is used as the collimating mirror and the converging mirror in the Czerny-Turner type structure, and as Figure 2 shown, both work in an off-axis state. Among them, the spherical aberration coefficient of the parabolic mirror is zero; two parabolic mirrors with the same geometric structure parameters are selected to correct the coma of the system; the appropriate grating position and the tilt angle of the detector are set to correct the field curvature of the system; the detector is placed at the focal plane of the object surface converging mirror to correct the astigmatism of the system. Therefore, in the present invention, an off-axis parabolic mirror is used as the collimating mirror and the converging mirror, which can effectively correct aberrations such as spherical aberration, coma, field curvature, and astigmatism of the system;

[0057] Step 2: The off-axis parabolic mirror effectively corrects the aberrations generated by the spectrometer, thereby compressing the focused spots to form Figure 3 the off-axis parabolic mirror focused spots 13 shown. Compared with Figure 3 the aberration spot image 12 of the traditional spherical converging mirror shown, the aberration-corrected spot image of the off-axis parabolic mirror is closer to the ideal optical imaging.

[0058] Step 3: The spot after aberration correction falls on the target surface of the detector 6, and the light intensities of each column of pixels are longitudinally accumulated and summed, and the spectral detection curve is reconstructed according to the transverse distribution.

[0059] Step 4: Drive the stepping motor 20 to drive the grating turntable 3 to rotate step by step, repeat Steps 1 to 3, and sequentially obtain the spectral curves of each end-to-end spectral segment, and splicing can obtain the wide-spectrum spectral curve.

[0060] The first embodiment of the off-axis parabolic mirror aberration correction high-resolution spectral detection device of the present invention is as Figure 4 shown: It includes an incident slit 1, a parabolic collimating mirror 2, a grating assembly, a parabolic focusing mirror 5, and a detector 6. The incident slit 1 is located at the focal plane of the parabolic collimating mirror 2. The grating assembly is arranged in the reflection direction of the parabolic collimating mirror 2 and is arranged on the grating turntable 3. The parabolic focusing mirror is placed in the reflection direction of the diffraction grating 4, and the detector 6 is arranged at the focal plane of the parabolic focusing mirror 5.

[0061] The grating assembly consists of three gratings: a diffraction grating 4 (1200 l / mm), a low-density diffraction grating 17 (600 l / mm), and a high-density diffraction grating 18 (2400 l / mm). The three gratings are circumferentially symmetrically distributed with respect to the axis of the grating switching turntable. By switching the three gratings, different measurement ranges and measurement resolutions can be adopted according to different application scenarios.

[0062] The grating turntable 3 mainly consists of a worm and gear rotary shaft and a grating switching turntable. As Figure 5 shown, the worm and gear type grating rotary shaft consists of a first motor driver 19, a first motor 20, a first coupling 21, a worm 22, a worm gear 23, and a first circular grating encoder 24. As Figure 6 shown, the grating switching turntable consists of a second motor driver 25, a second motor 26, a second coupling 27, a flange 28, a second circular grating encoder 29, and a grating fixing bracket 30.

[0063] The above is only the preferred embodiment of the present application and is not used to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application. Other structures and principles are the same as those of the prior art and will not be described in detail here.

Claims

1. An off-axis paraboloid mirror aberration correction method, characterized in that: In the C-T structure, the collimating mirror and the converging mirror adopt off-axis parabolic mirrors. By taking advantage of the fact that off-axis parabolic mirrors have no primary spherical aberration, the spherical aberration of the spectrometer is corrected. The coma of the spectrometer is suppressed and corrected by using the symmetric structural parameters of the off-axis angles and focal lengths of the collimating mirror and the converging mirror. The field curvature of the spectrometer is effectively corrected by calculating the optimal grating position. By taking advantage of the fact that the primary astigmatism at the foci of two off-axis parabolic mirrors with the same parameters is zero, the astigmatism of the converging beam of the spectrometer is corrected. A small-pixel deep-cooling array detector is used to perform linear array integration detection on the converging light, significantly improving the detection sensitivity and signal-to-noise ratio. By combining a high-density grating and a low-density grating, the gratings are switched under the application requirements of different wavelength ranges, resolutions, and scanning speeds to achieve fast spectroscopic detection in the wide wavelength range from ultraviolet to infrared. By using high-precision grating rotation scanning and angle monitoring, high-stability scanning of spectral signals in sub-spectral bands under a specific grating is achieved, and wide-band, high-resolution detection of a large range of spectra is achieved through spectral line splicing.

2. The off-axis parabolic mirror aberration correction high-resolution spectral detection method according to claim 1, characterized in that: It includes the following steps: Step 1: The measured signal forms an incident divergent beam (7) through the incident slit (1). The incident divergent beam (7) is collimated by the parabolic collimating mirror (2) into a collimated polychromatic light (8). The collimated polychromatic light (8) is dispersed and spectroscopically analyzed by the diffraction grating (4) to form a diffracted parallel light (9). The diffracted parallel light (9) consists of monochromatic parallel lights with different diffraction angles and is focused on the detector (6) by the parabolic converging mirror (5) to form a series of focused spots. Among them, the collimating mirror (2) and the converging mirror (5) in the C-T structure adopt parabolic mirrors and both operate in an off-axis state. As can be seen from formula (1), the spherical aberration coefficient of the parabolic mirror is zero. Two parabolic mirrors with the same geometric structure parameters are selected, and the off-axis angles are set through formula (2) to correct the coma of the system. The field curvature of the system is corrected by setting the appropriate grating position and the tilt angle of the detector according to formula (3). The detector is placed at the focal plane of the object surface converging mirror to correct the astigmatism of the system. Off-axis parabolic mirrors are used as the collimating mirror and the converging mirror to correct the system aberrations. The aberrations include spherical aberration, coma, field curvature, and astigmatism. Among them, S1, S2, S3, S4, and S5 are the distribution coefficients of spherical aberration, coma, astigmatism, field curvature, and distortion respectively. j is the Lagrange-Helmholtz invariant. h is the ray height. l is the off-axis height. x is the distance from the image plane to the vertex of the paraboloid. In the spectrometer, there are mainly primary aberrations such as spherical aberration, coma, and astigmatism. where ε 1、 ε2 are the off-axis angles of the collimating paraboloid mirror and the converging paraboloid mirror respectively, f1 and f2 are their focal lengths respectively. In the present invention, paraboloid mirrors with the same focal length are used as the collimating mirror and the converging mirror, and the incident angle and the reflection angle of the grating can be obtained according to the central wavelength of the designed spectrometer; on the premise of satisfying the spatial position, ε 1， ε2 satisfy a certain relationship to effectively correct the coma of the system; Among them, x is the horizontal distance from the diffraction grating to the parabolic converging mirror. β is the tilt angle of the detector. By setting the appropriate grating position and the tilt angle of the detector, the effective correction of the system field curvature is achieved. Step 2: The off-axis parabolic mirror (11) effectively corrects the aberrations generated by the spectrometer, thereby compressing the focused spots to form off-axis parabolic mirror focused spots (13). The aberration-corrected spot image of the off-axis parabolic mirror is closer to the ideal optical imaging. Step 3: The spots after aberration correction fall on the detector target surface, and the light intensities of each column of pixels are longitudinally accumulated and summed, and the spectral detection curve is reconstructed according to the transverse distribution. Step 4: Drive the stepping motor to drive the grating turntable (3) to rotate step by step. Repeat Steps 1 to 3 to obtain spectral curves of each spectrum segment connected end to end in sequence. Stitch the spectral curves of the spectrum segments to obtain a wide-spectrum segment spectral curve, that is, realize off-axis parabolic mirror aberration correction high-resolution spectral detection.

3. The off-axis parabolic mirror aberration correction high-resolution spectral detection method according to claim 2, characterized in that: The diffraction grating includes gratings (4), (17), (18) with different grating line densities and blazing wavelengths to adapt to different spectral detection ranges, spectral resolutions, and scanning speeds, and a precision rotary shaft rotation drive is adopted.

4. The off-axis parabolic mirror aberration correction high-resolution spectral detection method according to claim 2, wherein: The diffraction gratings (4), (17), (18) adopt ion-etched holographic blazing gratings to avoid the occurrence of "ghost lines".

5. The off-axis parabolic mirror aberration correction high-resolution spectral detection method according to claim 2, characterized in that: Before detection, adjust the width of the incident slit to change the size of the light spot dispersion direction. On the premise of ensuring that most of the energy of the light spot is not lost, reduce the lateral size of the incident light spot on the detector, so as to improve the detection resolution while ensuring the detection light flux.

6. An off-axis parabolic mirror aberration correction high-resolution spectral detection device, characterized in that: Incident slit (1), aperture (14), parabolic collimating mirror (2), grating assembly (4), parabolic focusing mirror (5), detector (6), grating turntable (3); the incident slit (1) is located at the focus of the parabolic collimating mirror (2); the aperture (15) is located in the beam propagation direction behind the slit; the grating assembly (4) is located in the reflection direction of the collimating mirror, including multiple diffraction gratings with different grating pitches, and the reflecting surface of the grating is located on the rotation center of the turntable; the parabolic focusing mirror (5) is located in the diffraction direction of the grating (4); the target surface of the detector (6) is located at the focal plane of the focusing mirror (5); the grating turntable (3) includes a motor (20) and a driver (19) for driving the grating to rotate, and a circular grating encoder (24) for grating rotation angle feedback.

7. The off-axis parabolic mirror aberration correction high-resolution spectral detection device according to claim 6, characterized in that: The grating assembly includes a diffraction grating combination (4), (17), (18), and a grating switching motor (26). The diffraction grating is composed of a combination of multiple high-density diffraction gratings and low-density diffraction gratings; the grating switching motor (26) is used to switch gratings with different grating line densities and rotate the reflecting surface of the diffraction grating to the rotation axis center of the grating turntable.

8. The off-axis parabolic mirror aberration correction high-resolution spectral detection device according to claim 6, wherein: The detection surface (6) is a area array detector, and the detection surface (6) adopts a high-sensitivity CCD detector; alternatively, the detection surface (6) is a linear array detector, and the detection surface (6) is constructed by a high-speed linear array CMOS detector with an electronic shutter function.

9. The off-axis parabolic mirror aberration correction high-resolution spectral detection device according to claim 6, wherein: The grating turntable is composed of a coupling (21), a stepping motor (20), and a circular grating encoder (24); The circular grating encoder of the grating turntable can be adapted to electronic subdivision boxes with different subdivision multiples to meet different optical wavelength stabilities and accuracies.

10. The off-axis parabolic mirror aberration correction high-resolution spectral detection device according to claim 5, characterized in that: Before detection, adjust the diameter of the variable aperture (14) to match it according to the numerical aperture NA of the incident light to ensure that the beam can just pass through the incident aperture, avoid light scattering and interference, and thus obtain better focusing ability and spectral resolution; The aperture (14) is an electrically variable aperture, which meets the requirements of light flux, numerical aperture, and resolution.

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