Optical lens system and spectrometer

Abstract

An optical lens system and a spectrometer. The optical lens system comprises a dispersion element (20) arranged on a beam propagation path. The dispersion element (20) comprises at least one grism, and the grism includes a prism and a metasurface grating. The prism includes an incident surface, a reflective surface, and an exit surface, which are sequentially arranged on a beam propagation path. The grating is arranged on the incident surface or the exit surface. By combining the prism with the metasurface grating, the grating diffraction efficiency is increased, excellent dispersion performance is achieved, and the volume of an optical lens system can also be reduced.

Description

Optical lens system and spectrometer

[0001] The present application is based on and claims priority to Chinese patent application No. 202411104793.1, filed on August 13, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of spectral testing and spectral analysis, and in particular to an optical lens system and a spectrometer. BACKGROUND

[0003] A spectrometer, also known as a spectroscope, is widely known as a direct-reading spectrometer. A spectrometer is a device that measures the intensity of different wavelengths of a spectrum using a photodetector such as a photomultiplier tube. It is composed of an entrance slit, a dispersion system, an imaging system, and one or more exit slits.

[0004] A narrow-band spectrometer needs to separate the light as much as possible in space so that the detector can distinguish different wavelengths. On this basis, the smaller the focal spot of the spectrometer, the higher the resolution. However, under the premise of fixed focal length, high resolution will make the aperture of the spectrometer larger. Therefore, in the prior art, the wider the width of the collimated light source required by the spectrometer, the larger the volume of the spectrometer, and it is difficult to realize the miniaturization of the spectrometer.

[0005] Any prior art mentioned in the specification does not mean that it is recognized or suggested that the prior art constitutes part of the common general knowledge in any jurisdiction, or that the prior art can be reasonably expected to be understood, considered relevant, and / or combined with other prior art by a person skilled in the art. SUMMARY

[0006] The purpose of the present application is to provide an optical lens system and a spectrometer to solve the problems in the prior art.

[0007] In order to achieve one of the above purposes, the present application provides an optical lens system, comprising a dispersion element arranged on a light beam transmission path, the dispersion element comprising at least one grating, the grating comprising a prism and a metasurface grating, the prism comprising an incident surface, a reflecting surface and an exit surface arranged in sequence on the light beam transmission path, and the metasurface grating being arranged on the incident surface or the exit surface.

[0008] As a further improvement of an embodiment of the present application, the prism comprises a first right-angle prism and a second right-angle prism which are arranged in axial symmetry with respect to the metasurface grating.

[0009] The first and second right-angle prisms each comprise an inclined surface, a right-angle side surface and a right-angle bottom surface, the right-angle bottom surface being the reflecting surface, the inclined surface of one of the first and second right-angle prisms being the incident surface and the right-angle side surface being the exit surface, the right-angle side surface of the other being the incident surface and the inclined surface being the exit surface.

[0010] As a further improvement of an embodiment of the present application, the optical lens system further comprises a collimating element located on the side of the grating incident light, the center of the collimating element in the vertical direction and the center of the grating in the vertical direction are located on the same horizontal plane.

[0011] As a further improvement of an embodiment of the present application, the included angle α between the inclined surface and the right-angle side surface is ≥45°.

[0012] As a further improvement of an embodiment of the present application, the metasurface grating is formed on the right-angle side surface of the first right-angle prism, and the right-angle side surface of the second right-angle prism is connected to the side wall of the metasurface grating away from the first right-angle prism.

[0013] As a further improvement of an embodiment of the present application, the metasurface grating is located between the right-angle side surface of the first right-angle prism and the right-angle side surface of the second right-angle prism, and the metasurface grating has an extension protruding from the first right-angle prism and the second right-angle prism.

[0014] As a further improvement of an embodiment of the present application, the extension comprises a first extension protruding from the right-angle bottom surface, the end surface of the first extension in the extension direction is a first reflecting surface, and the side opposite to the microstructure in the metasurface grating is a second reflecting surface.

[0015] As a further improvement of an embodiment of the present application, the optical lens system has a size range of 15mm-22mm in the axial direction, and a size range of 3.5mm-7.5mm in the radial direction.

[0016] As a further improvement of an embodiment of the present application, the prism is an isosceles right-angle prism, the prism has a third right-angle side surface, a fourth right-angle side surface and an inclined side surface, the third right-angle side surface is the incident surface, the fourth right-angle side surface is the reflecting surface, and the inclined side surface is the exit surface, and the metasurface grating is located on the third right-angle side surface.

[0017] As a further improvement of an embodiment of the present application, the grating is provided with at least two, and a plurality of the gratings are arranged along the beam transmission path.

[0018] As a further improvement of an embodiment of the present application, the centers of a plurality of the prisms along the center line in the direction of the beam transmission path are located on the same plane.

[0019] As a further improvement of the embodiment of the present application, the size of the grating of the prisms close to the collimating element is smaller than the size of the grating of the prisms away from the collimating element.

[0020] As a further improvement of the embodiment of the present application, the super surface grating and the prism are connected by chemical bonding or gluing.

[0021] As a further improvement of the embodiment of the present application, the third straight side of the adjacent prisms are staggered up and down.

[0022] In order to achieve one of the above-mentioned purposes, the present application also provides an optical lens system comprising the above-mentioned optical lens system.

[0023] Compared with the prior art, the present application adopts the combination of the prism and the super surface grating, the super surface grating has nanoscale manufacturing precision, improves the efficiency of grating diffraction in the formed grating structure, and has excellent dispersion performance. Under the premise of fixed focal length, the wide collimated light source can form a wide dispersion light beam through the diffraction and refraction of the super surface grating and the prism, so that the combination structure of the super surface grating and the prism can reduce the volume of the optical lens system without affecting the dispersion width, thereby realizing the miniaturization of the optical spectrum. At the same time, the light beam enters the prism from the incident surface, and under the action of the reflecting surface, the light beam can be transmitted again in the prism, so that the space of the entire prism can be fully utilized, and the volume of the optical lens system is further reduced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 is a structural schematic diagram of an optical spectrum in the embodiment.

[0025] Fig. 2 is a surface structure schematic diagram of a super surface grating.

[0026] Fig. 3 is a structural schematic diagram of an optical lens system in the first embodiment.

[0027] Fig. 4 is a structural schematic diagram of a dispersion element in Fig. 3.

[0028] Fig. 5 is a structural schematic diagram of an optical lens system in the second embodiment.

[0029] Fig. 6 is a structural schematic diagram of a dispersion element in Fig. 5.

[0030] Fig. 7 is an enlarged structural schematic diagram of part A in Fig. 6.

[0031] Fig. 8 is a structural schematic diagram of an optical lens system in the third embodiment.

[0032] Fig. 9 is a structural schematic diagram of a dispersion element in the optional embodiment of the third embodiment.

[0033] Reference signs:

[0034] 10 collimating element; 20 dispersing element; 21 first right-angle prism; 211 first bevel; 212 first right-angle side; 213 first right-angle base; 22 first grating; 221 first reflecting surface; 222 second reflecting surface; 223 first extension; 224 second extension; 23 second right-angle prism; 231 second bevel; 232 second right-angle side; 233 second right-angle base; 24 third prism; 241 third right-angle side; 242 fourth right-angle side; 243 bevel side; 25 second grating; 30 focusing element; 40 detector. DETAILED DESCRIPTION

[0035] The embodiments described below are exemplary only, and are not to be construed as limiting the present application.

[0036] The terms such as "upper", "lower", etc. used in the present embodiments for the purpose of description of spatial relative positions of one unit or feature with respect to another unit or feature as shown in the drawings. The terms of spatial relative positions can be intended to include different orientations of the device in use or operation in addition to the orientation shown in the drawings. For example, "upper", "lower", "horizontal", "vertical" in the present embodiments are spatial relative positions of the spectrometer or optical lens system in the normal use state.

[0037] The terms first, second, third, etc. in the present application are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated; in addition, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, the connection can be direct connection or indirect connection through intermediate medium, and can be fixed connection or movable connection or detachable connection or integral connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings 1 to 9 in the embodiments of the present application. Wherein, Fig. 1 is a structural schematic diagram of a spectrometer in the embodiments of the present application; Figs. 2 to 9 are structural schematic diagrams of optical lens systems in the preferred embodiments of the present application.

[0039] An embodiment of the present application provides a spectrometer, referring to Fig. 1, the spectrometer comprises an optical lens system, a detector 40. The optical lens system comprises a collimating element 10, a dispersing element 20, a focusing element 30.

[0040] In the embodiment, the collimating element 10, the dispersing element 20, the focusing element 30 and the detector 40 are arranged along the light beam transmission path in sequence. The incident light passes through the collimating element 10, the dispersing element 20 and the focusing element 30 in sequence and then enters the detector 40 to realize spectral detection.

[0041] The collimating element 10 is used to collimate the incident light into a parallel light beam, which helps to improve the accuracy and efficiency of spectral measurement.

[0042] The dispersing element 20 is used to realize beam splitting of light of different wavebands. In the embodiment, the parallel light beam collimated by the collimating element 10 is split into light of different wavebands after passing through the dispersing element 20.

[0043] The focusing element 30 is configured to converge light of different wavebands at different positions of the detector 40. The light beam is Fourier-transformed by the focusing element 30, which facilitates sensing of the detector 40.

[0044] The detector 40 is used to sense the convergent light emitted by the focusing element 30. In the embodiment, the sensing surface of the detector 40 is arranged on the image plane of the spectrometer system. The focusing element 30 converges light of different wavebands at different positions of the sensing surface of the detector 40, which facilitates the detector 40 to sense the intensity of light beams of different wavebands, thereby forming a spectral image or data.

[0045] In the embodiment, the direction of the incident light incident on the dispersing element 20 is the same as the direction of the emergent light from the dispersing element 20, which simplifies the difficulty of assembling the spectrometer, compresses the size of the spectrometer in the height direction, and is more suitable for packaging in a narrow space.

[0046] One end of the incident light source is accessed by an optical fiber, and a standard FC / APC optical fiber interface can be used for the joint. An infrared detector can be directly placed at the system image plane behind the optical lens system to directly image the spectrum. In addition, a white screen sensing surface can also be arranged behind the optical lens system, and a high-speed camera is additionally provided to take a photo of the dispersed spectrum for subsequent image processing.

[0047] The optical lens system in the embodiment includes the collimating element 10, the dispersing element 20 and the focusing element 30 arranged along the light beam transmission path in sequence. The dispersing element 20 includes at least one grating, and the grating includes a grating and a prism. The prism includes an incident surface, a reflection surface and an emergent surface arranged along the light beam transmission path in sequence. The grating is arranged on the incident surface or the emergent surface.

[0048] The light beam enters the prism from the incident surface, and under the action of the reflecting surface, the light beam can be transmitted in the prism again, so that the light beam increases at least one transmission path in the echelle, and the space of the entire prism can be fully utilized. In order to improve the spectral resolution of the spectrometer, after increasing the top angle a of the prism, even if the light beam trend becomes steep, the light beam can reach the grating after being reflected without increasing the height size of the echelle, thereby improving the diffraction efficiency of the grating. Therefore, the optical lens system in the embodiment can reduce the size while ensuring the dispersion width and improving the spectral resolution, thereby realizing the miniaturization of the spectrometer.

[0049] Referring to FIG. 2, the gratings in the present application are all super surface gratings, which include a plurality of arrayed nanostructures. The super surface grating can reduce reflection, effectively avoiding the problem of light beam diffusion, while increasing the dispersion width and improving the precision of the spectrometer detection.

[0050] In an optional embodiment, the grating can be a traditional grating structure.

[0051] The collimating element 10 is a collimating lens. In an optional embodiment, the collimating element 10 can be a collimating lens group composed of a plurality of collimating lenses.

[0052] The focusing element 30 is a focusing lens. In an optional embodiment, the focusing element 30 can be a focusing lens group composed of a plurality of focusing lenses.

[0053] The optical lens system described above is divided into three different embodiments according to the dispersion element 20 provided with different structures.

[0054] Please refer to FIGS. 3-4, which show the optical lens system in the first embodiment of the present application.

[0055] The optical lens system includes a collimating element 10, a dispersion element 20, and a focusing element 30. The dispersion element 20 includes a symmetric echelle, which includes a first right-angle prism 21, a first grating 22, and a second right-angle prism 23 along the light beam transmission path.

[0056] Referring to FIG. 4, the first right-angle prism 21 and the second right-angle prism 23 have the same structure. The first right-angle prism 21 has a first inclined surface 211, a first right-angle side surface 212, and a first right-angle bottom surface 213. The second right-angle prism 23 has a second inclined surface 231, a second right-angle side surface 232, and a second right-angle bottom surface 233.

[0057] The first right-angle side surface 212 of the first right-angle prism 21 and the second right-angle side surface 232 of the second right-angle prism 23 are oppositely arranged. The first grating 22 is connected between the first right-angle side surface 212 and the second right-angle side surface 232, and the first right-angle prism 21 and the second right-angle prism 23 are symmetrically arranged about the first grating 22.

[0058] The first inclined surface 211 is an incident surface of the first right-angle prism 21, and the first right-angle side surface 212 is an exit surface of the first right-angle prism 21. After the light beam is refracted by the first right-angle prism 21, the light beam is diffracted by the first grating 22 for color dispersion, and then enters the second right-angle prism 23. The second right-angle side surface 232 is an incident surface of the second right-angle prism 23, and the second inclined surface 231 is an exit surface of the second right-angle prism 23. Under the action of the second right-angle prism 23, the light beams of different wave bands are dispersed, and at the same time, the exit direction of the central wavelength is kept consistent with the incident direction.

[0059] The first right-angle bottom surface 213 and the second right-angle bottom surface 233 are reflective surfaces. After polishing, the first right-angle bottom surface 213 and the second right-angle bottom surface 233 naturally satisfy the total reflection condition. Of course, in an alternative embodiment, the first right-angle bottom surface 213 and the second right-angle bottom surface 233 can be coated to meet the reflection requirement (for example, the total reflection requirement). The light beam refracted by the first inclined surface 211 reaches the first right-angle bottom surface 213, the first right-angle bottom surface 213 reflects the light beam to the first grating 22, the light beam diffracted by the first grating 22 enters the second right-angle bottom surface 233, the second right-angle bottom surface 233 reflects the light beam to the second inclined surface 231, and the light beam exits along a direction substantially the same as the incident direction after passing through the second inclined surface 231. Such an arrangement can fully utilize the space of the entire first right-angle prism 21, and reduce the volume of the dispersion element 20 while keeping the resolution unchanged.

[0060] In order to enable the light beam to smoothly reach the first right-angle bottom surface 213, the height of the collimating element 10 and the grating in the vertical direction needs to meet certain requirements. In this embodiment, the center of the collimating element 10 in the vertical direction and the center of the grating in the vertical direction are located on the same horizontal plane. The light beam calibrated by the collimating element 10 is divided into an upper light beam and a lower light beam. The upper light beam is directly refracted to the first grating 22 under the action of the first right-angle prism 21, and the lower light beam is refracted to the first right-angle bottom surface 213 under the action of the first right-angle prism 21, and then reflected to the first grating 22 under the action of the first right-angle bottom surface 213.

[0061] The second right-angle prism 23 has the same height as the first right-angle prism 21. The lower light beam is refracted to the second right-angle bottom surface 233 after being diffracted by the first grating 22, and then exits after being reflected to the second inclined surface 231 by the second right-angle bottom surface 233. The exit direction of the exiting light beam is the same as the incident direction of the incident light beam.

[0062] The angle a is formed between the first inclined surface 211 and the first right-angle side surface 212, and the angle a' is formed between the second inclined surface 231 and the second right-angle side surface 232, a = a', and a ≥ 45°. In the case of a fixed refractive index, the line pair number of the grating is naturally increased to improve the spectral resolution in order to satisfy the Littrow structure after the angle a is increased. In the present application, the reflective surface (the first right-angle bottom surface 213 and the second right-angle bottom surface 233) is added, the light beam refracted by the incident surface of the first right-angle prism 21 reaches the reflective surface, the light beam can be totally reflected to the grating for diffraction, the diffracted light beam is refracted to the reflective surface in the second right-angle prism 23, and then is emitted to the focusing element 30 in the same direction as the incident light. Therefore, the total reflection of the collimated light beam can be ensured without increasing the size of the prism in the vertical direction after the angle a is increased, the dispersion width of the optical lens system is increased, and the volume of the spectrometer is reduced.

[0063] As an example, the wavelength of 1550 nm ± 15 nm is used in a specific embodiment, wherein the focal length of the collimating lens is between 5 mm and 10 mm, and the focal length of the focusing lens is between 30 mm and 60 mm. The first right-angle prism 21 and the second right-angle prism 23 are glass prisms, the refractive index is 1.95, and the glass material is H-ZLAF90. The first grating 22 is based on a 0.5 mm thick silicon wafer. The structure satisfies the same direction of the incident light and the emitted light, and at the same time, the 30 nm bandwidth of the wavelength is separated by 9 mm at the image plane. The single wavelength focusing spot size is 150 um, and the spectral resolution is 0.25 nm. In terms of size, the total length of the structure of the spectrometer composed of the optical lens system in the embodiment is 15 mm to 22 mm, and the diameter including the external structural member can be compressed to Φ 3.5 mm to 7.5 mm. The volume of the spectrometer is small, and the production requirements of the miniaturization of the spectrometer can be met.

[0064] The height dimension of the first grating 22 is equal to the height dimension of the first right-angle prism 21 and the second right-angle prism 23. Specifically, the first grating 22 is formed on the first right-angle side surface 212 of the first right-angle prism 21. In the embodiment, the first right-angle prism 21 and the first grating 22 are arranged on the same substrate, and the second right-angle prism 23 is arranged on a separate substrate. The two-piece structure is relatively simple to assemble, and the accuracy of the prism can be improved.

[0065] In an optional embodiment, the first grating 22 can be arranged on a separate substrate, that is, the first right-angle prism 21, the first grating 22, and the second right-angle prism 23 are in a three-piece structure, and the first grating 22 is connected between the first right-angle side surface 212 and the second right-angle side surface 232.

[0066] Please refer to FIGS. 5-7, which show the optical lens system in the second embodiment of the present application.

[0067] Different from the first embodiment, the first grating 22 is an independent structure, that is, the first grating 22, the first right-angle prism 21 and the second right-angle prism 23 are a three-piece grating structure, and the height dimension of the first grating 22 is greater than the maximum height dimension of the first right-angle prism 21 and the second right-angle prism 23. In this way, when the first grating 22, the first right-angle prism 21 and the second right-angle prism 23 are connected, the area protruding from the first grating 22 is convenient for positioning, and the alignment and connection of the structure are facilitated.

[0068] Referring to FIGS. 6 and 7, the first grating 22 has an extension section, which includes a first extension section 223 protruding from the first right-angle bottom surface 213 and the second right-angle bottom surface 233, and a second extension section 224 protruding from the top of the first right-angle prism 21 and the second right-angle prism 23.

[0069] The first extension section 223 has a first reflection surface 221 and a second reflection surface 222 facing the side of the first right-angle prism 21 (the side opposite to the microstructure in the super surface grating). The end surface of the first extension section 223 along the extension direction thereof is the first reflection surface 221.

[0070] The first reflection surface 221 and the second reflection surface 222 are both reflection surfaces formed after polishing, and of course, the first reflection surface 221 and the second reflection surface 222 can also be coated to meet the reflection requirements (for example, to meet the total reflection requirements).

[0071] The normal light ray trend is shown by the light ray λ1, and the partial light ray trend is shown by λ2. The light ray will enter the protruding area of the first grating 22 that is not connected with the first right-angle prism 21, that is, the first extension section 223, and the first reflection surface 221 and the second reflection surface 222 will return to the first grating 22 and the second right-angle prism 23 after total reflection, and finally the light beam will reach the system image surface according to the normal trend, avoiding the light beam from being emitted from the bottom surface or the side surface of the silicon substrate in the first grating 22, thereby reducing the loss of light energy.

[0072] The second embodiment in the present application is the same as the first embodiment except for the above-mentioned differences; therefore, no further description is given herein.

[0073] The preparation method of the optical lens system provided by the embodiment of the present application is used for preparing a three-piece grating structure, and includes the following steps.

[0074] The first substrate and the second substrate are provided. The materials of the first substrate and the second substrate include but are not limited to quartz glass, crystalline silicon, amorphous silicon, aluminum oxide, silicon nitride, calcium fluoride, titanium oxide, tantalum oxide, hafnium oxide, photoresist, gallium nitride, crystalline germanium, selenium sulfide, chalcogenide glass, or a polymer, a polymer composition or the like material with a refractive index greater than 1.8.

[0075] The nano-microstructure is made on the first substrate to form the metasurface grating. The microstructure can be formed by electron beam lithography or nano-imprinting.

[0076] A protective layer is arranged on the side of the metasurface grating away from the first substrate, that is, the protective layer is arranged on the surface of the metasurface grating. The protective layer can be formed by coating a polymer or a metal material.

[0077] The first substrate is cut to form the first right-angle prism 21.

[0078] The protective layer is removed.

[0079] The second substrate is cut to form the second right-angle prism 23.

[0080] The metasurface grating is located on one of the right-angle faces of the first right-angle prism 21. After the first right-angle prism 21 is cut, the right-angle face of the first right-angle prism 21 on which the metasurface grating is not located needs to be polished or coated to form a reflective face. After the second right-angle prism 23 is cut, one of the right-angle faces of the second right-angle prism 23 needs to be polished or coated to form a reflective face.

[0081] The right-angle face of the second right-angle prism 23 on which no reflective face is arranged is connected to the side of the first right-angle prism 21 on which the metasurface grating is arranged. If the first substrate and the second substrate are both silicon substrates, the connection method of the first right-angle prism 21 and the second right-angle prism 23 can be chemical bonding such as surface oxygen ion activation and / or high-temperature bonding to form a silicon-silicon covalent bond between the metasurface grating and the second right-angle prism 23. If the first substrate and the second substrate are both glass substrates with a refractive index greater than 1.8, the connection method of the first right-angle prism 21 and the second right-angle prism 23 can be gluing. The glue used for gluing needs to have a refractive index matched with that of the glass substrate, and the glue must completely fill into the nanostructure when gluing, so that there is no air gap in the form of bubbles or the like between the glue and the nanostructure to avoid affecting the light transmittance.

[0082] Further, an antireflection film can be coated on the inclined face of the first right-angle prism 21. The antireflection film can reduce or eliminate the reflected light on the surface of the first right-angle prism 21, thereby increasing the light transmittance and reducing or eliminating the stray light of the optical lens system.

[0083] In an optional embodiment, the first substrate can be cut first to form the first right-angle prism 21, the first right-angle prism 21 being a right-angle prism. Then, the metasurface grating is formed on one of the right-angle faces of the first right-angle prism 21. Finally, the second right-angle prism 23 is connected to the right-angle face of the first right-angle prism 21 on which the metasurface grating is located.

[0084] In an optional embodiment, the nano-microstructure can be formed by etching. Specifically, a high-refractive material such as silicon nitride is coated on the surface of the first substrate / first right-angle prism 21 as a barrier layer / transmittance layer, and then a-Si material is coated on the surface and etched to form the nano-microstructure. This method can better control the thickness of the metasurface formed, and the grating structure produced is more accurate.

[0085] An embodiment of the present application provides a preparation method of an optical lens system, which is used for preparing a three-piece grating structure. The method comprises the following steps:

[0086] A first substrate, a second substrate and a third substrate are provided. The material of the first substrate and the second substrate includes but is not limited to quartz glass, crystalline silicon, aluminum oxide, silicon nitride and calcium fluoride. The material of the third substrate includes but is not limited to titanium oxide, tantalum oxide, hafnium oxide, silicon nitride, photoresist, quartz glass, aluminum oxide, crystalline silicon, gallium nitride, crystalline germanium, selenium sulfide, selenium sulfide and chalcogenide glass.

[0087] The first substrate is cut to form a first right-angle prism 21. After the first right-angle prism 21 is cut, a right-angle surface of the first right-angle prism 21 needs to be polished or coated to form a reflecting surface.

[0088] The second substrate is cut to form a second right-angle prism 23. After the second right-angle prism 23 is cut, a right-angle surface of the second right-angle prism 23 needs to be polished or coated to form a reflecting surface.

[0089] A nano-microstructure is made on the surface of the third substrate to form a metasurface grating. The microstructure can be formed by electron beam lithography, nano-imprinting or etching. Then the third substrate is cut to form a first grating 22, and one side surface of the first grating 22 is the nano-microstructure. Alternatively, the third substrate is cut into a thin piece with a thickness of about 0.4 mm to 1.4 mm, and then a nano-microstructure is made on one side surface of the thin piece to form a metasurface grating. It should be noted that after the nano-microstructure is made, a flat protective layer needs to be formed on the surface of the nano-microstructure, and the protective layer can be formed by coating a polymer or a metal material.

[0090] The right-angle surface of the first right-angle prism 21 without a reflecting surface is connected to the side of the first grating 22 away from the metasurface grating, and the right-angle surface of the second right-angle prism 23 without a reflecting surface is connected to the side of the second grating 25 where the metasurface grating is located.

[0091] In an optional embodiment, the height dimension of the first grating 22 is greater than the height dimension of the first right-angle prism 21 and the second right-angle prism 23. The top and bottom of the first grating 22 protrude from the first right-angle prism 21 and the second right-angle prism 23, the area where the bottom of the first grating 22 protrudes forms a first extension area 223, and the area where the top of the first grating 22 protrudes forms a second extension area 224. When the first right-angle prism 21, the first grating 22, and the second right-angle prism 23 are connected, the protruding first grating 22 facilitates fixed positioning and facilitates alignment of the connection position.

[0092] After the first right-angle prism 21, the first grating 22, and the second right-angle prism 23 are connected into a symmetrical grating structure, a protective layer needs to be formed on the reflecting surfaces of the first right-angle prism 21 and the second right-angle prism 23. The two sides of the non-hypersurface microstructure of the first extension area 223 of the first grating 22 (i.e., the two sides that are not provided with hypersurface structures) are polished again, so that the two sides form a first reflecting surface 221 and a second reflecting surface 222, respectively. After polishing, the protective layer on the reflecting surfaces of the first right-angle prism 21 and the second right-angle prism 23 is removed. This allows the light beam refracted into the interior of the first grating 22 to be ultimately refracted into the second right-angle prism 23 under the action of the refracting bottom surface and the refracting side surface, thereby reducing the loss of light energy.

[0093] Please refer to FIGS. 8-9 for the optical lens system in the third embodiment of the present application.

[0094] The optical lens system includes a collimating element 10, a dispersion element 20, and a focusing element 30. The dispersion element 20 includes at least two gratings, and a plurality of the gratings are arranged along the light beam transmission path.

[0095] The grating includes a third prism 24 and a second grating 25 connected to the third prism 24. The second grating 25 is a hypersurface grating, which includes a plurality of arrayed nanometer structures. The hypersurface grating can reduce reflection and effectively avoid the problem of light beam diffusion, thereby improving the precision of the spectrometer detection.

[0096] The third prism 24 is an isosceles right-angle prism, which includes a third right-angle side 241, a fourth right-angle side 242, and an oblique side 243. The third right-angle side 241 and the fourth right-angle side 242 are the faces where the two isosceles right-angle sides of the third prism 24 are located, and the oblique side 243 is the face where the oblique side / base side of the third prism 24 is located.

[0097] In the embodiment, three prisms are provided, which are prism a, prism b and prism c. The three prisms are arranged along the light beam transmission path, and the three prisms are attached to each other or arranged at intervals. The third right-angled side 241 and the fourth right-angled side 242 of the third prism 24 are both directed to one side of the incident light beam, and the inclined side 243 is directed to one side of the emergent light beam. The plane where the two equal sides of the right angle of the third prism 24 are located is the incident plane or the reflection plane, and the plane where the inclined side / bottom side of the third prism 24 is located is the emergent plane. In the optical path design, the incident plane is the third right-angled side 241, the reflection plane is the fourth right-angled side 242, the emergent plane is the inclined side 243, and the second grating 25 is connected to the third right-angled side 241. According to the direction of the optical path refraction, in the adjacent third prisms 24, the third right-angled sides 241 are arranged in an up-down staggered manner, and similarly, the second gratings 25 are arranged in an up-down staggered manner.

[0098] The center lines of the three third prisms 24 along the direction of the light beam transmission path are located on the same plane, so that the emergent plane of the previous third prism 24 and the incident plane of the next third prism 24 are located in the same range, so that the light beam is smoothly transmitted from the previous third prism 24 to the next third prism 24, and the maximum dispersion effect of the light beam in a limited space is ensured.

[0099] As shown in FIG. 8, the incident light beam is parallelly incident to the upper half of the prism a after passing through the collimating lens, and the light beam is emergent from the lower half of the prism a to the air after diffraction and refraction. The light beam is incident to the lower half of the prism b from the air, and the light beam is emergent from the upper half of the prism b to the air after diffraction and refraction. Further, the light beam is incident to the upper half of the prism c from the air, and the light beam is emergent from the lower half of the prism c to the air after diffraction and refraction, and finally transmitted to the focusing lens from the air. The collimating lens is arranged in the range corresponding to the upper half of the prism a, and the focusing lens is arranged in the range corresponding to the lower half of the prism c, that is, the position of the collimating lens matches the position of the incident light beam, and the position of the focusing lens matches the position of the emergent light beam.

[0100] The dispersion angle of the light beam after multiple diffraction and refraction is continuously increased, which greatly improves the dispersion ability, ensures the dispersion width, and improves the resolution of the spectrometer.

[0101] In the optional embodiment, the size of the prism close to the collimating element 10 among the two adjacent prisms is smaller than the size of the prism away from the collimating element 10. That is, the size of the prism can be gradually increased along the direction from the incident light beam to the emergent light beam, that is, the size of the prism a is the smallest, and the size of the prism c is the largest. The size of the prism on the side of the incident light beam can be reduced while ensuring the smooth transmission of the light beam in the upper and lower two sections, so that the size of the optical lens system is reduced while ensuring the wide dispersion.

[0102] In an optional embodiment, the second grating 25 can be directly formed on the side surface of the third prism 24, or can be connected to the side surface of the third prism 24 as an independent structure.

[0103] An embodiment of the present application provides a preparation method of an optical lens system, comprising the following steps:

[0104] A first substrate and a second substrate are provided.

[0105] The first substrate is cut to form a third prism 24, which is an isosceles right prism.

[0106] A nano microstructure is made on the second substrate to form a super surface grating, and then the second substrate is cut to form a second grating 25, one side surface of the second grating 25 being the nano microstructure. Alternatively, the second substrate is cut into a thin sheet with a thickness of about 0.4mm to 1.4mm, and then a nano microstructure is made on one side surface of the thin sheet to form a super surface grating.

[0107] One right surface of the third prism 24 is connected to the side of the second grating 25 having the microstructure.

[0108] In an optional embodiment, a preparation method of an optical lens system comprises the following steps: providing a substrate, cutting the substrate to form a third prism 24, which is an isosceles right prism, and making a nano microstructure on one right surface of the third prism 24 to form a super surface grating. Alternatively, a super surface grating is formed on the surface of the substrate, and then the substrate is cut to form a third prism 24, the super surface grating being located on one right surface of the third prism 24.

[0109] In the present application, the prism is preferably made of optical glass, quartz glass, alkali metal halide (such as sodium bromide) crystal, or the like, and the prism and the super surface grating are connected by gluing, and a protective layer needs to be provided on the microstructure surface of the super surface grating before gluing. In an optional embodiment, the prism can be made of a silicon substrate, and the prism and the super surface grating are connected by chemical bonding.

[0110] The above embodiments shown in the drawings illustrate the structure, features and effects of the present application, and the above description is only a preferred embodiment of the present application, but the present application is not limited to the embodiments shown in the drawings, and any changes or modifications made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, are still within the scope of the present application.

Claims

1. An optical lens system comprising a dispersive element (20) disposed in the path of a light beam, characterised in that: The dispersion element (20) comprises at least one prism, the prism comprises a prism and a metasurface grating, the prism comprises an incident surface, a reflection surface and an exit surface arranged in sequence on the light beam transmission path, and the metasurface grating is arranged on the incident surface or the exit surface.

2. The optical lens system according to claim 1, wherein: The prism comprises a same first right-angle prism (21) and a second right-angle prism (23), the first right-angle prism (21) and the second right-angle prism (23) are arranged in axial symmetry with respect to the metasurface grating. The first right-angle prism (21) and the second right-angle prism (23) each comprise an inclined surface, a right-angle side surface and a right-angle bottom surface, the right-angle bottom surface is the reflection surface, the inclined surface of one of the first right-angle prism (21) and the second right-angle prism (23) is the incident surface, and the right-angle side surface is the exit surface, and the right-angle side surface of the other is the incident surface, and the inclined surface is the exit surface.

3. The optical lens system according to claim 2, wherein: The optical lens system further comprises a collimating element (10) located on one side of the prism incident light, the center of the collimating element (10) in the vertical direction and the center of the prism in the vertical direction are located on the same horizontal plane.

4. The optical lens system according to claim 2, wherein: The included angle α between the inclined surface and the right-angle side surface is greater than or equal to 45°.

5. The optical lens system according to claim 2, wherein: The metasurface grating is formed on the right-angle side surface of the first right-angle prism (21), and the right-angle side surface of the second right-angle prism (23) is connected to the side wall of the metasurface grating away from the first right-angle prism (21).

6. The optical lens system according to claim 2, wherein: The metasurface grating is located between the right-angle side surface of the first right-angle prism (21) and the right-angle side surface of the second right-angle prism (23), and has an extension segment protruding from the first right-angle prism (21) and the second right-angle prism (23).

7. The optical lens system according to claim 6, wherein: The extension segment comprises a first extension segment (223) protruding from the right-angle bottom surface, an end surface of the first extension segment (223) along the extension direction thereof is a first reflection surface (221), and a side of the first extension segment (223) opposite to the microstructure in the metasurface grating is a second reflection surface (222).

8. The optical lens system according to claim 2, wherein: The optical lens system has a size range of 15mm to 22mm in the axial direction, and a size range of 3.5mm to 7.5mm in the radial direction.

9. The optical lens system according to claim 1, wherein: The prism is an isosceles right-angle prism, the prism has a third right-angle side surface (241), a fourth right-angle side surface (242) and an inclined side surface (243), the third right-angle side surface (241) is the incident surface, the fourth right-angle side surface (242) is the reflection surface, the inclined side surface (243) is the exit surface, and the metasurface grating is located on the third right-angle side surface (241).

10. The optical lens system according to claim 9, wherein: The prism is an isosceles right-angle prism, the prism has a third right-angle side surface (241), a fourth right-angle side surface (242) and an inclined side surface (243), the third right-angle side surface (241) is the incident surface, the fourth right-angle side surface (242) is the reflection surface, the inclined side surface (243) is the exit surface, and the metasurface grating is located on the third right-angle side surface (241).

11. The optical lens system according to claim 10, wherein: The prism is arranged in at least two, and a plurality of prisms are arranged along the center line of the light beam transmission path.

12. The optical lens system according to claim 10, wherein: The centers of a plurality of prisms along the center line of the light beam transmission path are located on the same plane.

13. The optical lens system according to claim 10, wherein: The size of a prism of two adjacent prisms close to the collimating element is smaller than the size of a prism away from the collimating element.

14. The optical lens system according to claim 1, characterized in that: In adjacent prisms, the third right-angle side surfaces (241) are arranged alternately up and down.

15. A spectrometer, characterized by: The metasurface grating and the prism are connected by chemical bonding or gluing. The optical lens system comprises the optical lens system according to any one of claims 1 to 14.

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