Wide-spectrum high-resolution Czerny-Turner light splitting system for handheld Raman

Abstract

The utility model belongs to the technical field of Raman spectrometers, and particularly discloses a beam splitting system of a wide-spectrum high-resolution Czerny-Turner structure spectrograph, which comprises a collimation system, a dispersion system, a focusing system and a signal collection system, the collimation system comprises a slit and a spherical collimating lens, the dispersion system comprises a plane diffraction grating, and the focusing system comprises a focusing lens and a focusing lens. The focusing system comprises a focusing mirror and a cylindrical mirror, and the signal collection system comprises a linear array sensor; the slit is arranged between incident light and the spherical collimating mirror, the plane diffraction grating is arranged on the upper left portion of the spherical collimating mirror, the focusing mirror is arranged on the lower right portion of the plane diffraction grating, the cylindrical mirror is arranged on the upper left portion of the focusing mirror, and the linear array sensor is arranged on the upper left portion of the cylindrical mirror and inclines towards the Y direction. According to the utility model, the cylindrical mirror is added, the aberration and astigmatism are improved, the focusing capability is improved, the cylindrical mirror is attached to the front window of the CMOS detector, the installation process is simplified, and the resolution and the detection precision of the system are improved at the same time.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of Raman spectrometer, specifically relates to a kind of spectrometer's spectrometer system of wide spectral range high resolution Czerny-Turner structure. BACKGROUND

[0002] Raman spectrum as a very promising analysis technique has been widely used in many fields, including polymer, petrochemical industry, health and safety, national security, biomedical, jewelry identification and environmental monitoring. This technique can provide material structure information and component analysis by measuring molecular vibration spectrum, with the advantages of rapid, non-destructive and high sensitivity. In order to meet the needs of real-time monitoring and field application, miniaturization and portability of Raman spectrometer is an important trend of current technology development. In this direction, the development of handheld Raman spectrometer has become one of the key directions of market demand.

[0003] The core component of handheld Raman spectrometer is the spectrometer system, which directly affects the performance indicators of the whole device, such as resolution, spectral range and volume. At present, most of the spectrometer systems use plane diffraction grating spectrometer method, and the optical path structure often adopts Czerny-Turner structure, which has the characteristics of compact structure, small volume and easy debugging.

[0004] However, there is a complex relationship between resolution, spectral range and volume in the design process. It is a challenge to optimize the design of the three performance indicators at the same time, because improving one indicator may sacrifice the other indicators. The current spectrometer structure and relatively large volume limit the practical application and promotion of handheld Raman spectrometer, so it is necessary to seek innovative technical solutions to overcome these obstacles and promote the development and market application of handheld Raman spectrometer technology. UTILITY MODEL CONTENT

[0005] The utility model aims at overcoming the shortcomings of large volume, difficult to install and low resolution in the prior art, and provides a spectrometer system of wide spectral range high resolution Czerny-Turner structure, which can not only improve the resolution by using Czerny-Turner structure to constrain the change of wavelength of the diffraction grating and the beam expansion, but also plays a crucial role in beam focusing and collimation.

[0006] The utility model discloses a kind of wide-band high-resolution Czerny-Turner spectroscopy systems for handheld Raman, including collimating system, dispersion system, focusing system and signal collection system, the collimating system includes slit, spherical collimating mirror, the dispersion system includes plane diffraction grating, the focusing system includes focusing mirror and cylindrical mirror, the signal collection system includes linear array sensor;The slit is arranged between incident light and spherical collimating mirror, the plane diffraction grating is arranged in the left upper side of spherical collimating mirror, the focusing mirror is arranged in the right lower side of plane diffraction grating, the cylindrical mirror is arranged in the left upper side of focusing mirror, the linear array sensor is arranged in the left upper side of cylindrical mirror and is inclined to Y direction.

[0007] Wide-band high-resolution Czerny-Turner spectroscopy system is designed according to the dispersion structure of handheld Raman spectrometer, the focal length of the whole lens and the reflection angle range are limited; a mathematical model is established; the wavelength range is determined according to the spectral working band, and the evaluation index is used to evaluate the effect of cylindrical mirror on aberration correction, and the specific focal length of the cylindrical mirror is determined; and a suitable linear array sensor is selected. The working principle is as follows: the outgoing light passes through the exit slit to reach the spherical collimating mirror, and then is collimated by the spherical collimating mirror and projected onto the plane diffraction grating surface for light splitting; light rays of different wavelengths are emitted to the focusing mirror according to different diffraction angles; the focusing mirror focuses light beams of the same wavelength; the cylindrical mirror eliminates astigmatism aberration; the light beams are further focused and collimated; and finally, the light beams with the same wavelength are collected by the linear array sensor CMOS in different light-sensitive areas.

[0008] In a preferred embodiment of the utility model, the lenses of the spherical collimating mirror, the focusing mirror and the cylindrical mirror are all simple concave mirrors, which can eliminate astigmatism aberration. Since spherical reflection can cause astigmatism aberration, a vertical-axis parabolic mirror or a wheel mirror can be used to eliminate astigmatism aberration, but the processing cost of such lenses is high.

[0009] In a preferred embodiment of the utility model, the plane diffraction grating can solve the problem of wide spectral band and poor wavelength resolution of monochromatic light in the optical filter spectrometer.

[0010] In a preferred embodiment of the utility model, the slit is a rectangular aperture with a size of (0.05-0.06) mm x (0.2-0.5) mm and a distance of 0.8-1.5 mm from the object plane.

[0011] In a preferred embodiment of the utility model, the curvature of the spherical collimating mirror, i.e., the first concave mirror, is -48, and the included angle between the incident light and the outgoing light is α=12.49°.

[0012] In a preferred embodiment of the utility model, the diffraction angle i of the plane diffraction grating is 32°, the light exit angle is θ=-13°, the ruling density of the plane diffraction grating is 830 lp / mm, and the diffraction order is +1.

[0013] In a preferred embodiment of the utility model, the focusing mirror is a concave mirror, the curvature is-52, and the included angle between the incident light and the exit light is β=9.35°.

[0014] In a preferred embodiment of the utility model, the cylindrical mirror is mainly used for collimating and focusing and correcting aberration, and the curvature radius is-2.

[0015] In a preferred embodiment of the utility model, the cylindrical mirror is initially tilted by 2-3° around the Y axis in the direction of the CMOS linear array sensor in the initial state perpendicular to the Z axis.

[0016] In a preferred embodiment of the utility model, the distance from the slit to the spherical collimating mirror is 24mm, the distance from the collimating mirror to the plane diffraction grating is-24mm, the distance from the plane diffraction grating to the focusing mirror is 22mm, the distance from the focusing mirror to the cylindrical mirror is-23mm, and the distance from the cylindrical mirror to the linear array sensor is-1.6mm.

[0017] In a preferred embodiment of the utility model, the image plane is the Y axis according to the size of the detector pixel and the optical axis direction, and after the detector is rotated by a corresponding angle, the Y axis size of the light spot is maximized to 7μm and minimized to 2μm, which completely meets the Y axis width of 14μm of the detector pixel.

[0018] In a preferred embodiment of the utility model, the detection unit receives diffraction light of the diffraction order +1, the number of detector pixels is 2048, the pixel size is 14*200μm, and the corresponding spectral range is 400-1000nm.

[0019] In a preferred embodiment of the utility model, the resolution of the overall optical system is as low as 5cm -1 , the RMS radius at 790nm wavelength is 5.031, the RMS radius at 920nm wavelength is 6.324, the RMS radius at 1048nm wavelength is 8.651, and the structure size of the optical path part is 2.4*2.8*1.5cm.

[0020] Compared with the background art, the technical scheme has the following advantages:

[0021] 1. The utility model discloses a combination of off-axis optical system and Czerny-Turner type spectrometer system, adopts plane diffraction grating as dispersion element, and effectively utilizes the aperture change and beam broadening problem of different wavelength beams caused by grating diffraction of Czerny-Turner structure constraint.

[0022] 2. The utility model discloses the optical system optimization of introducing cylindrical lens, on the basis of eliminating astigmatism difference, installs directly in COMS detector front end window position, utilizes the collimation focusing ability of cylindrical lens to ensure signal intensity, improves resolution, and facilitates mechanical assembly.

[0023] 3. The utility model discloses the optical structure parameter of cylindrical lens, collimating mirror, focusing mirror and the like through reasonable optimization design, makes resolution reach 5cm -1 , and greatly compresses the volume of spectrometer simultaneously.

[0024] 4. The utility model discloses the plane diffraction grating of optical system adopts the finished product grating template customization size, reduces the manufacturing cost significantly, provides technical basis for realizing the commercial application of high-performance handheld Raman spectrometer. DRAWINGS

[0025] The application is further described below in combination with the drawings and examples.

[0026] Figure 1 It is the optical system principle diagram of the utility model;

[0027] Figure 2 It is the optical system light path simulation diagram of the utility model, and the blue line is the light of imaging channel, and the spectrum light path is formed after the light of spectrum channel passes through plane diffraction grating;

[0028] Figure 3 It is the dispersion point array diagram of the utility model;

[0029] Figure 4 It is the center wavelength RMS radius size diagram of the utility model;

[0030] Figure 5 It is the center wavelength MTF distribution of the utility model;

[0031] In the drawing: 1-slits, 2-spherical collimating mirror, 3-plane diffraction grating, 4-focusing mirror, 5-cylindrical lens and 6-linear array sensor. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be further described below in conjunction with the accompanying drawings and embodiments. These embodiments may take different forms and should not be construed as limited to the description herein. Throughout the document, the same reference numerals always represent the same elements, and similar reference numerals represent similar elements.

[0033] A broadband, high-resolution Czerny-Turner spectroscopic system for handheld Raman spectroscopy, comprising a collimation system, a dispersion system, a focusing system, and a signal collection system, such as... Figure 1 As shown, it consists of a slit (1), a spherical collimating lens (2), a plane diffraction grating (3), a focusing lens (4), a cylindrical lens (5), and a linear array sensor (6); the collimation system includes the slit (1) and the spherical collimating lens (2), the dispersion system includes the plane diffraction grating (3), the focusing system includes the focusing lens (4) and the cylindrical lens (5), and the signal collection system includes the linear array sensor (6); the slit is located behind the incident light beam, 1 mm away from the incident light beam; the spherical collimating lens is located directly behind the slit. The distance between the slit and the collimating lens is 24mm; the distance between the plane diffraction grating and the collimating lens is -24mm, located to the upper left of the collimating lens; the distance between the focusing lens and the plane diffraction grating is 22mm, located to the lower right of the plane engraved diffraction grating; the cylindrical lens is located to the upper left of the focusing lens, at a distance of -23mm; the linear array sensor is located to the upper left of the cylindrical lens and tilted 2° in the Y direction. Due to the presence of the cylindrical lens, the Y-axis is fixed as the optical axis, and the corresponding image plane setting should also rotate 90° with the cylindrical lens.

[0034] like Figure 2 As shown, a wide-spectrum high-resolution Czerny-Turner spectrometer system for handheld Raman spectroscopy works as follows: The light propagation direction is that the outgoing light passes through the outgoing slit (1) to the spherical collimating mirror (2), and is then collimated by the spherical collimating mirror (2) and projected onto the surface of the planar diffraction grating (3) for spectral dispersion. Light of different wavelengths is emitted to the focusing mirror (4) according to different diffraction angles, and then focused by the focusing mirror (4) onto the cylindrical mirror (5) to eliminate astigmatism and aberration, and further focused and collimated. Finally, the light beams that have passed through resolution limitation and double focusing collimation hit different photosensitive areas of the linear array sensor CMOS (6) with the same wavelength for signal collection.

[0035] The slit (1) is 0.5mm*0.3mm in size, which restricts the direction and width of light propagation and is used to select light of a specific wavelength for spectral analysis.

[0036] The purpose of setting the spherical collimating mirror behind the slit (1) is to convert the converging light incident at the slit (1) into collimated parallel light, so that the light rays can keep stable direction when propagating in the system, and the accuracy and stability of the optical path are improved. The parallel light emitted by the spherical collimating mirror (2) forms a spectral light path after passing through the plane diffraction grating (3).

[0037] The diffraction grating (3) can disperse the incident light by wavelength through its periodic structure, so that the light rays of different wavelengths are diffracted at different angles to realize the light splitting effect.

[0038] The focusing mirror (4) focuses and reflects the light beams after splitting

[0039] The cylindrical mirror (5) further focuses and collimates the light beams, so that the final light beam accurately falls on the photosensitive surface of the detector.

[0040] The lenses all adopt simple processing concave mirrors made of K9 material. In order to eliminate the influence of astigmatism, a cylindrical mirror made of BK7 material is installed behind the focusing mirror. The use of the cylindrical mirror can further improve the focusing accuracy of the light beam, reduce aberration and astigmatism, and enable monochromatic light of the same wavelength to be accurately collected on the detector, thereby significantly improving the resolution and detection accuracy of the system. Through the synergistic effect of the cylindrical mirror and the focusing mirror, the optical path system of the present application not only realizes compact structure, but also ensures the stability and high resolution of the system, and is particularly suitable for use in miniature and portable Raman spectrometers.

[0041] In the present optical system, the distance from the slit to the spherical collimating mirror is 16mm, the curvature radius is -33.678, the included angle between the incident light and the emitted light is 12.49°, the distance from the collimating mirror to the plane diffraction grating is -18mm, the incident angle and the diffraction angle are 32.41° and -13.27° respectively, and the ruling is 830lp / mm. A ready-made grating template is selected to customize, which can reduce the cost. The distance from the plane diffraction grating to the focusing mirror is 16mm, the distance from the focusing mirror to the cylindrical mirror is -16.763mm, the curvature radius of the focusing mirror is -52, the included angle between the incident light and the emitted light is 18.6°, the distance from the cylindrical mirror to the linear array sensor is -0.559mm, the cylindrical mirror is a 1mm cylindrical lens made of BK7 material, the curvature radius is -2, and it is located below the linear array sensor and directly installed at the front window position of the COMS detector. Due to the existence of the cylindrical lens, the Y-axis is fixed as the optical axis direction, and the corresponding image surface should also be rotated 90° with the cylindrical lens.

[0042] The CMOS linear array image sensor has an effective photosensitive length of 1024 pixels, a pixel size of 7x200μm, and a spectral range of 400-1000nm. The signal processing adopts a microcomputer system which completes data acquisition, storage and transmission functions.

[0043] As shown in Figure 3 , after the calculation of the full-waveband 5 wave number resolution, the corresponding wavelength is set, the adjacent resolution light spots corresponding to the adjacent resolution light spots on the image plane are completely separated, and according to Figure 1 the scale, the overall volume is 2.4*2.8*1.5cm.

[0044] As shown in Figure 4 , according to the size of the detector pixel and the optical axis direction is Y elbow, after the detector rotates the corresponding angle, the Y axis size of the light spot is 9um at most and 2um at least, which completely meets the Y axis width of the detector pixel 14um.

[0045] As shown in Figure 5 , the MTF (modulation transfer function) result shows that when the spatial frequency is 20lp / mm, the overall MTF efficiency is better than 70%.

[0046] The example of the application is that the full-waveband spectral resolution is better than 5cm -1 , the spectral wave number range is 790-1048nm, the object space spatial NA aperture value is 0.06, and the optical path part structure size is 2.4*2.8*1.5cm.

[0047] The RMS radius of the application at 790nm wavelength is 5.031, the RMS radius at 920nm wavelength is 6.324, and the RMS radius at 1048nm wavelength is 8.651.

[0048] The cylindrical lens is added in the wide-spectrum high-resolution Czerny-Turner spectral system, which can not only improve the aberration and coma and improve the focusing ability, but also simplify the installation process by directly attaching the cylindrical lens to the front window of the CMOS detector. Meanwhile, the resolution and detection accuracy of the system are significantly improved. In this optical system, the cylindrical lens and the focusing lens cooperate with each other, so that the system structure is compact, and high stability and resolution are maintained. It opens up a new possibility for the application and promotion of handheld Raman spectrometer, and provides a solid foundation for future development.

[0049] The above examples are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A Czerny-Turner spectrometer system for handheld Raman, comprising a collimating system, a dispersing system, a focusing system and a signal collecting system, the collimating system comprising a slit and a spherical collimating mirror, the dispersing system comprising a plane diffraction grating, the focusing system comprising a focusing mirror and a cylindrical mirror, and the signal collecting system comprising a linear array sensor; the slit is arranged between the incident light and the spherical collimating mirror, the plane diffraction grating is arranged above the left of the spherical collimating mirror, the focusing mirror is arranged below the right of the plane diffraction grating, the cylindrical mirror is arranged above the left of the focusing mirror, and the linear array sensor is arranged above the left of the cylindrical mirror and is tilted towards the Y direction.

2. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The spherical collimating mirror, the focusing mirror and the cylindrical mirror are concave mirrors.

3. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The slit is a rectangular aperture with a size of (0.05-0.06) mm x (0.2-0.5) mm and a distance of 0.8-1.5 mm from the object plane.

4. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The spherical collimating mirror, i.e. the first concave mirror, has a curvature of -48 and an included angle between the incident light and the outgoing light of α = 12.49°.

5. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The plane diffraction grating has a diffraction angle i = 32°, an outgoing light angle of θ = -13°, a ruling density of 830 lp / mm and a diffraction order of +1.

6. The Czerny-Turner spectroscopic system for handheld Raman as claimed in claim 1, wherein, The focusing mirror has a curvature of -52 and an included angle between the incident light and the outgoing light of β = 9.35°, and the cylindrical mirror has a curvature radius of -2.

7. The Czerny-Turner spectroscopic system for handheld Raman as claimed in claim 1, wherein, The cylindrical mirror is initially perpendicular to the Z axis and is tilted by 2-3° around the Y axis towards the CMOS linear array sensor.

8. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The distance from the slit to the spherical collimating mirror is 24 mm, the distance from the collimating mirror to the plane diffraction grating is -24 mm, the distance from the plane diffraction grating to the focusing mirror is 22 mm, the distance from the focusing mirror to the cylindrical mirror is -23 mm, and the distance from the cylindrical mirror to the linear array sensor is -1.6 mm.

9. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The linear array sensor receives diffraction light of the +1 order, has 2048 pixels, a pixel size of 14*200 μm and a corresponding spectral range of 400-1000 nm.

10. The Czerny-Turner spectroscopic system for handheld Raman according to claim 1, wherein, The structure size of the optical path part of the spectrometer system is 2.4 x 2.8 x 1.5 cm.

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