A visible near infrared spectroscopy scanner optical system

Abstract

The application discloses a visible near-infrared spectrum scanner optical system, which comprises a front objective lens assembly, a slit and a spectrometer assembly; the front objective lens assembly comprises a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a first turning mirror, a ninth lens and a tenth lens in sequence in the direction from an object plane to an image plane; the spectrometer assembly comprises a second turning mirror, a first reflector, a diffraction grating and a second reflector in sequence in the direction from the object plane to the image plane; the application is provided with two groups of complex achromatic double cemented lenses, and the diaphragm is arranged at the middle position of the front optical system, so that the light incident from the object plane is sequentially converged by the front lens group, passes through the diaphragm, and then enters the subsequent double cemented lens group and other lenses for imaging processing; the angle of the outgoing light is regulated, the image far-infrared light path is formed, the pupil matching effect is improved, and the spectrum imaging quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of imaging optics technology, and specifically relates to an optical system for a visible and near-infrared spectral scanner. Background Technology

[0002] In existing technologies, the demand for refined inspection of paper documents, tickets, and printed media is increasing in fields such as cultural relic protection, forensic identification, digital archival storage, and anti-counterfeiting identification. In particular, when performing spectral scanning analysis on the surface fiber structure, ink overprinting relationships, hidden marks, and minute defects of documents under macro conditions, higher requirements are placed on the spatial resolution and imaging area of ​​the imaging system.

[0003] Existing imaging systems used for document inspection or spectral scanning often face a difficult technical contradiction between spatial resolution and scanning area: high-resolution systems typically have a limited imaging range, require multiple stitching scans, are inefficient and prone to introducing errors; while large-format scanning systems are limited by optical structure and image quality control capabilities, making it difficult to maintain uniform and clear imaging quality across the entire field of view under macro conditions, and thus failing to meet the needs for detailed analysis of the fine structure and spectral features of documents. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides an optical system for a visible and near-infrared spectral scanner, which solves the technical problems of existing high-resolution systems, such as limited imaging range, the need for multiple stitching scans, low efficiency and easy introduction of errors, and the difficulty of maintaining the full field of view in large-format scanning systems under macro conditions.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows: An optical system for a visible-near-infrared spectroscopy scanner includes a front objective lens assembly, a slit, and a spectrometer assembly. The front objective lens assembly, in the direction from the object plane to the image plane, sequentially includes a first lens, a second lens, a third lens, a fourth lens, an aperture, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a first folding mirror, a ninth lens, and a tenth lens.

[0006] The spectrometer assembly includes, in sequence, a second folding mirror, a first reflecting mirror, a diffraction grating, and a second reflecting mirror in the direction from the object plane to the image plane.

[0007] The first lens is aspherical on the side near the image plane, the third lens is aspherical on the side near the image plane, the fourth lens is aspherical on the side near the object plane, the sixth lens is aspherical on the side near the image plane, the eighth lens is aspherical on the side near the image plane, the ninth lens is aspherical on the side near the object plane, the tenth lens is aspherical on the side near the image plane, and the first and second reflecting mirrors are aspherical mirrors. The second lens, the fifth lens, and the seventh lens are all spherical mirrors. The fifth lens and the sixth lens, as well as the seventh lens and the eighth lens, are all cemented doublet lenses.

[0008] Furthermore, the radius of curvature R1 of the first lens on the side closest to the object surface satisfies -255 mm ≤ R1 ≤ -250 mm; The radius of curvature R2 of the first lens on the side closer to the image plane satisfies 25 mm ≤ R2 ≤ 30 mm; The radius of curvature R3 of the second lens on the side closer to the object surface satisfies -310 mm ≤ R3 ≤ -305 mm; The radius of curvature R4 of the second lens on the side closer to the image plane satisfies -100 mm ≤ R4 ≤ -95 mm; The radius of curvature R5 of the third lens on the side closest to the object surface satisfies -55 mm ≤ R5 ≤ -50 mm; The radius of curvature R6 of the third lens on the side closer to the image plane satisfies -135 mm ≤ R6 ≤ -130 mm; The radius of curvature R7 of the fourth lens on the side closest to the object surface satisfies -205 mm ≤ R7 ≤ -200 mm; The radius of curvature R8 of the fourth lens on the side closest to the image plane satisfies -55 mm ≤ R8 ≤ -50 mm; The radius of curvature R9 of the fifth lens on the side closest to the object surface satisfies 45 mm ≤ R9 ≤ 50 mm; The radius of curvature R10 of the fifth lens on the side closer to the sixth lens is the same as the radius of curvature of the sixth lens on the side closer to the fifth lens, and satisfies 50 mm ≤ R10 ≤ 55 mm. The radius of curvature R11 of the sixth lens on the side closest to the image plane satisfies -55 mm ≤ R11 ≤ -50 mm; The radius of curvature R12 of the seventh lens on the side closest to the object surface satisfies -80 mm ≤ R12 ≤ -75 mm; The radius of curvature R13 of the seventh lens on the side closer to the eighth lens is the same as the radius of curvature of the eighth lens on the side closer to the seventh lens, and satisfies 30 mm ≤ R13 ≤ 35 mm. The radius of curvature R14 of the eighth lens on the side near the image plane satisfies -90 mm ≤ R14 ≤ -85 mm; The radius of curvature R15 of the ninth lens on the side closest to the object surface satisfies -80 mm ≤ R15 ≤ -75 mm; The radius of curvature R16 of the ninth lens on the side near the image plane satisfies -110 mm ≤ R16 ≤ -105 mm; The radius of curvature R17 of the tenth lens on the side closest to the object surface satisfies 135 mm ≤ R17 ≤ 140 mm; The radius of curvature R18 of the tenth lens on the side near the image plane satisfies -150 mm ≤ R18 ≤ -145 mm; The radius of curvature R19 of the first reflecting mirror satisfies -195 mm ≤ R19 ≤ -190 mm; The radius of curvature R20 of the diffraction grating satisfies -100 mm ≤ R20 ≤ -95 mm; The radius of curvature R21 of the second reflector satisfies -195 mm ≤ R21 ≤ -190 mm Furthermore, the center thickness d1 of the first lens satisfies 5 mm ≤ d1 ≤ 10 mm; The center thickness d2 of the second lens satisfies 8 mm ≤ d2 ≤ 12 mm; The center thickness d3 of the third lens satisfies 8 mm ≤ d3 ≤ 12 mm; The center thickness d4 of the fourth lens satisfies 8 mm ≤ d4 ≤ 12 mm; The center thickness d5 of the fifth lens satisfies 5 mm ≤ d5 ≤ 10 mm; The center thickness d6 of the sixth lens satisfies 8 mm ≤ d6 ≤ 12 mm; The center thickness d7 of the seventh lens satisfies 8 mm ≤ d7 ≤ 12 mm; The center thickness d8 of the eighth lens satisfies 8 mm ≤ d8 ≤ 12 mm; The center thickness d9 of the ninth lens satisfies 5 mm ≤ d9 ≤ 10 mm; The center thickness d10 of the tenth lens satisfies 8 mm ≤ d10 ≤ 12 mm.

[0009] Furthermore, the distance p1 between the side of the first lens near the image plane and the side of the second lens near the object plane satisfies 30 mm ≤ p1 ≤ 35 mm; The distance p2 between the second lens near the image plane and the third lens near the object plane satisfies 5 mm ≤ p2 ≤ 10 mm; The distance p3 between the third lens near the image plane and the fourth lens near the object plane satisfies 2 mm ≤ p3 ≤ 5 mm; The distance p4 between the fourth lens and the aperture stop on the side closer to the image plane satisfies 60 mm ≤ p4 ≤ 65 mm; The distance p5 between the aperture and the fifth lens on the side closest to the object surface satisfies 10 mm ≤ p5 ≤ 15 mm; The distance p6 between the side of the sixth lens near the image plane and the side of the seventh lens near the object plane satisfies 1 mm ≤ p6 ≤ 5 mm; The distance p7 between the eighth lens and the first folding mirror on the side closest to the image plane satisfies 45 mm ≤ p7 ≤ 50 mm; The distance p8 between the first folding mirror and the ninth lens on the side closest to the object surface satisfies 48 mm ≤ p8 ≤ 53 mm; The distance p9 between the ninth lens near the image plane and the tenth lens near the object plane satisfies 12 mm ≤ p9 ≤ 17 mm; The distance p10 of the tenth lens from the slit on the side closest to the image plane satisfies 5 mm ≤ p10 ≤ 10 mm; The distance p11 between the slit and the second folding mirror satisfies 40 mm ≤ p11 ≤ 45 mm; The distance p12 between the second folding mirror and the first reflecting mirror satisfies 145 mm ≤ p12 ≤ 150 mm; The distance p13 between the first reflecting mirror and the diffraction grating satisfies 95 mm ≤ p13 ≤ 100 mm; The distance p14 between the diffraction grating and the second reflecting mirror satisfies 95 mm ≤ p14 ≤ 100 mm; The distance p15 between the second reflecting mirror and the image plane satisfies 190 mm ≤ p15 ≤ 195 mm.

[0010] Furthermore, the focal length f1 of the first lens satisfies -45 mm ≤ f1 ≤ -40 mm; The focal length f2 of the second lens satisfies 225 mm ≤ f2 ≤ 230 mm; The focal length f3 of the third lens satisfies -110 mm ≤ f3 ≤ -105 mm; The focal length f4 of the fourth lens satisfies 95 mm ≤ f4 ≤ 100 mm; The focal length f5 of the fifth lens satisfies 430 mm ≤ f5 ≤ 435 mm; The focal length f6 of the sixth lens satisfies 60 mm ≤ f6 ≤ 65 mm; The focal length f7 of the seventh lens satisfies -30 mm ≤ f7 ≤ -25 mm; The focal length f8 of the eighth lens satisfies 40 mm ≤ f8 ≤ 45 mm; The focal length f9 of the ninth lens satisfies -440 mm ≤ f9 ≤ -435 mm; The focal length f10 of the tenth lens satisfies 125 mm ≤ f10 ≤ 130 mm.

[0011] Furthermore, the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, eighth lens, ninth lens and tenth lens are all made of optical glass.

[0012] Furthermore, the conic coefficient k1 of the first lens on the side closer to the image plane is -0.697; The conic coefficient k3 of the third lens on the side closest to the image plane is -2.307; The conic coefficient k4 of the fourth lens on the side closest to the object surface is 10; The conic coefficient k6 of the sixth lens on the side closest to the image plane is -2.539; The conic coefficient k8 of the eighth lens on the side closest to the image plane is -0.987; The conic coefficient k9 of the ninth lens on the side closest to the object surface is 1.62; The conic coefficient k10 of the tenth lens on the side closest to the image plane is -3.646.

[0013] Furthermore, the aspherical surface shapes of both the first and second reflectors conform to Formula 1:

[0014] Where Z is the sag, c is the curvature, r is the radial distance from a point on the lens to the optical axis, k is the conic coefficient, and A and B are both aspherical coefficients; The first reflector satisfies: A = -3.871E-8, B = -5.564E-14, k = -2.191; The second reflector satisfies: A=-3.871E-8, B=-5.564E-14, k=-2.191.

[0015] Furthermore, it can be applied to visible and near-infrared spectral imaging in the 400nm~1000nm band.

[0016] Furthermore, the front objective lens assembly is an image-side telecentric optical path.

[0017] Compared with the prior art, the present invention has the following advantages: 1. This invention sets up two sets of apochromatic cemented doublet lenses and places the aperture stop in the middle of the front optical system. This allows light rays incident from the object surface to be converged by the front lens group and then pass through the aperture stop before entering the subsequent cemented doublet lens group and other lenses for imaging processing. The angle of the outgoing light is controlled to form a telecentric optical path on the image side, thereby improving the pupil matching effect and thus improving the spectral imaging quality.

[0018] 2. In this invention, the front objective lens assembly forms a telecentric optical path on the image side, which makes the light beam emitted from the slit maintain a relatively stable emission angle distribution on the image side. This is beneficial to improving the matching stability between the system and the subsequent spectral splitting unit, reducing the impact of changes in the incident angle of light on the spectral imaging quality, thereby effectively reducing aberrations, improving imaging consistency, and improving the overall optical performance of the visible and near-infrared spectral imaging system. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the first lens, the second lens, the third lens, and the fourth lens in this invention; Figure 3 This is a schematic diagram of the structure of the first cemented doublet lens and the second cemented doublet lens in this invention; Figure 4 This is a schematic diagram of the spectrometer assembly in this invention; Figure 5 Modulation transfer function (MTF) of the visible and near-infrared spectral scanning system provided in this embodiment of the invention at a wavelength of 400 nm. Figure 6 Modulation transfer function (MTF) of the visible and near-infrared spectroscopy scanning system provided in this embodiment of the invention at a wavelength of 600 nm. Figure 7 Modulation transfer function (MTF) of the visible and near-infrared spectroscopy scanning system provided in the embodiments of the present invention at a wavelength of 900 nm. Figure 8 The modulation transfer function (MTF) of the visible and near-infrared spectroscopy scanning system provided in this embodiment of the invention at a wavelength of 1000 nm. Figure 9 This is a schematic diagram of Smile distortion in a visible and near-infrared spectral scanning system provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of Keystone distortion in a visible and near-infrared spectral scanning system provided in an embodiment of the present invention.

[0020] Reference numerals: 101, First lens; 102, Second lens; 103, Third lens; 104, Fourth lens; 106, Fifth lens; 107, Sixth lens; 108, Seventh lens; 109, Eighth lens; 111, Ninth lens; 112, Tenth lens; 1, First spherical surface; 2, Second aspherical surface; 3, Third spherical surface; 4, Fourth spherical surface; 5, Fifth spherical surface; 6, Sixth aspherical surface; 7, Seventh aspherical surface; 8, Eighth... 9. Aperture; 10. Tenth spherical surface; 11. Eleventh spherical surface; 12. Twelfth aspherical surface; 13. Thirteenth spherical surface; 14. Fourteenth spherical surface; 15. Fifteenth aspherical surface; 16. First folding mirror; 17. Seventeenth aspherical surface; 18. Eighteenth spherical surface; 19. Nineteenth spherical surface; 20. Twentieth aspherical surface; 21. Slit; 22. Second folding mirror; 23. First reflecting mirror; 24. Diffraction grating; 25. Second reflecting mirror. Detailed Implementation

[0021] In the description of this invention, it should be understood that the terms "one end", "the other end", "outer side", "upper side", "inner side", "horizontal", "coaxial", "center", "end", "length", "outer end", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] like Figure 1 and 2 As shown, an optical system for a visible-near-infrared spectroscopy scanner includes, in sequence from the object plane to the image plane, a front objective lens assembly, a slit, and a spectrometer assembly. The front objective lens assembly, in sequence from the object plane to the image plane, includes a first lens, a second lens, a third lens, a fourth lens, an aperture, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a first folding mirror, a ninth lens, and a tenth lens. The spectrometer assembly, in sequence from the object plane to the image plane, includes a second folding mirror, a first reflecting mirror, a diffraction grating, and a second reflecting mirror.

[0024] The first lens, located at the very front of the optical system, serves as the incident light-receiving element, receiving the incident beam across a large field of view and providing initial control over the light rays at the edges of the field of view. The second lens, together with the first lens, forms the front group of optical power distribution, used to further adjust the aperture angle and beam height of the incident beam. For close-range, large-format scanning systems, the front group of lenses not only needs to achieve a certain converging effect but also needs to control astigmatism, field curvature, and distortion at the edges of the field of view. The second lens, with its relatively gentle front surface and strong rear curvature, can compensate for the diverging or converging tendencies of the light rays introduced by the first lens, allowing the beam to enter the subsequent correction group in a more suitable state.

[0025] The third lens in the front objective lens assembly plays a role in aberration correction, controlling spherical aberration, coma, and residual chromatic aberration under wide spectral conditions. The fourth lens, located before the aperture stop, further refines the beam after passing through the first, second, and third lenses, ensuring the light enters the aperture stop at a specified aperture height and angle. Since the aperture stop directly affects the system's aperture aberration, vignetting, and principal ray distribution, placing the fourth lens before the aperture stop allows it to participate in wide-field aberration correction and also influences the beam symmetry and telecentric design conditions of subsequent systems.

[0026] An aperture stop is used to define the effective aperture of an optical system and control the incident beam aperture angle.

[0027] The fifth lens is made of ZF7LGT, and the sixth lens is made of H-FK95N, bonded together with optical adhesive to form the first cemented doublet. Located behind the aperture stop, the first cemented doublet utilizes the combination of glass materials with different dispersion characteristics of the fifth and sixth lenses to compensate for the focal shifts of different wavelengths of light, thereby reducing axial chromatic aberration and magnification chromatic aberration. For the 400–1000nm visible-near-infrared system, the first cemented doublet effectively improves focal consistency over a wide spectral range. Simultaneously, the side of the sixth lens closest to the image plane is set as an aspherical surface, allowing the first cemented doublet to not only correct chromatic aberration but also spherical aberration and advanced aberrations. It can be understood as the first core apochromatic and image quality correction group in the front objective lens.

[0028] The seventh and eighth lenses are bonded together with optical adhesive to form a second cemented doublet. Located after the first cemented doublet, this second doublet further corrects residual broadband chromatic aberration, field curvature, astigmatism, and magnification chromatic aberration after the first doublet. Magnification chromatic aberration is particularly important for hyperspectral document scanning systems because differences in imaging magnification across different wavelengths can lead to spatial misalignment between different spectral bands, affecting subsequent spectral analysis and multi-band fusion. By making the side of the eighth lens closest to the image plane as aspherical, the second cemented doublet can perform advanced aberration correction, further compressing residual chromatic aberration while improving image plane consistency and the basis for spatial registration between spectral bands across a wide field of view.

[0029] The first folding mirror alters the direction of light propagation, folding the beam output from the second cemented doublet onto the ninth lens, thereby compressing the overall size of the optical system. The ninth lens is a fine-tuning element for image quality, used to correct residual aberrations, improve edge field-of-view imaging, and create conditions for image-side telecentricity and pupil matching. The tenth lens completes the final convergence of light rays, ensuring that the one-dimensional spatial image of the document target (referring to the document sample or its surface area to be tested, placed on the scanning platform and subjected to hyperspectral scanning, including but not limited to paper substrates, handwriting, printed text, seals, correction marks, and obscuring information) accurately falls at the slit position. Simultaneously, the tenth lens participates in controlling the image-side principal ray angle, enabling better pupil matching between the front objective lens assembly and the subsequent spectrometer assembly.

[0030] The slit serves as the interface between the front objective lens assembly and the spectrometer assembly. The front objective lens assembly images a spatial line from the document target onto the slit. The slit defines the field of view of the light, allowing light from that field to enter the subsequent spectrometer. For pushbroom hyperspectral imaging, the slit determines the instantaneous spatial sampling position, while the subsequent scanning motion completes the spatial sampling of the two-dimensional image. The slit width and the dispersive capability of the spectrometer assembly together determine the system's spectral resolution, and also affect the light transmission and signal-to-noise ratio. Therefore, the slit in the system is both the entry point for spatial information and a crucial constraint on the formation of spectral resolution.

[0031] The second folding mirror is used to change the direction of light propagation, and can fold the light beam output from the slit onto the first reflecting mirror.

[0032] The first reflecting mirror serves as the incident reflecting surface of the Offner spectrometer, used to receive the diverging beam emitted from the slit and reflect it onto the diffraction grating.

[0033] A diffraction grating is used to diffract and disperse a received light beam, meaning that different wavelengths satisfy different diffraction angles. Specifically, after passing through the diffraction grating, the light beam in the range of 400–1000 nm will be dispersed along the spectral dimension. In other words, a light beam incident on the same spatial position on the diffraction grating will be decomposed into different positions on the detector according to its wavelength, thus forming continuous spectral sampling.

[0034] The second mirror is used to re-image the dispersed beam, ensuring that the imaging position on the detector is stable for different wavelengths and different fields of view.

[0035] In this embodiment, the two sides of the first lens are a first spherical surface near the object plane and a second aspherical surface near the image plane. The radius of curvature R1 of the first spherical surface satisfies -255 mm ≤ R1 ≤ -250 mm, preferably -254.37 mm; the radius of curvature R2 of the second aspherical surface satisfies 25 mm ≤ R2 ≤ 30 mm, preferably 27.210 mm.

[0036] The second lens has a third spherical surface near the object plane and a fourth spherical surface near the image plane. The radius of curvature R3 of the third spherical surface satisfies -310 mm ≤ R3 ≤ -305 mm; preferably -309.678 mm. The radius of curvature R4 of the fourth spherical surface satisfies -100 mm ≤ R4 ≤ -95 mm; preferably -95.688 mm.

[0037] The third lens has a fifth spherical surface near the object plane and a sixth aspherical surface near the image plane on its two sides. The radius of curvature R5 of the fifth spherical surface satisfies -55 mm ≤ R5 ≤ -50 mm; preferably -52.148 mm. The radius of curvature R6 of the sixth aspherical surface satisfies -135 mm ≤ R6 ≤ -130 mm; preferably -134.740 mm.

[0038] The fourth lens has a seventh aspherical surface near the object plane and an eighth spherical surface near the image plane on its two sides. The radius of curvature R7 of the seventh aspherical surface satisfies -205 mm ≤ R7 ≤ -200 mm, preferably -204.727 mm; the radius of curvature R8 of the eighth spherical surface satisfies -55 mm ≤ R8 ≤ -50 mm, preferably -54.726 mm.

[0039] There are three surfaces between the fifth and sixth lenses: the tenth spherical surface of the fifth lens near the object plane; the eleventh spherical surface at the bonding point between the fifth and sixth lenses; and the twelfth aspherical surface of the sixth lens near the image plane. The radius of curvature R9 of the tenth spherical surface satisfies 45 mm ≤ R9 ≤ 50 mm, preferably 46.738 mm. The radius of curvature R10 of the eleventh spherical surface satisfies 50 mm ≤ R10 ≤ 55 mm, preferably 50.418 mm. The radius of curvature R11 of the twelfth aspherical surface satisfies -55 mm ≤ R11 ≤ -50 mm, preferably -51.682 mm.

[0040] There are three surfaces between the seventh and eighth lenses: the thirteenth spherical surface of the seventh lens near the object plane; the fourteenth spherical surface at the joint between the seventh and eighth lenses; and the fifteenth aspherical surface of the eighth lens near the image plane.

[0041] The radius of curvature R12 of the thirteenth sphere satisfies -80 mm ≤ R12 ≤ -75 mm, preferably -77.273 mm. The radius of curvature R13 of the fourteenth sphere satisfies 30 mm ≤ R13 ≤ 35 mm, preferably 33.654 mm. The radius of curvature R14 of the fifteenth aspherical surface satisfies -90 mm ≤ R14 ≤ -85 mm, preferably -89.479 mm.

[0042] The ninth lens has two side surfaces: a seventeenth aspherical surface near the object plane and an eighteenth spherical surface near the image plane. The radius of curvature R15 of the seventeenth aspherical surface satisfies -80 mm ≤ R15 ≤ -75 mm, preferably -79.803 mm; the radius of curvature R16 of the eighteenth spherical surface satisfies -110 mm ≤ R16 ≤ -105 mm, preferably -107.447 mm.

[0043] The tenth lens has two side surfaces: a nineteenth spherical surface near the object plane and a twentieth aspherical surface near the image plane. The radius of curvature R17 of the nineteenth spherical surface satisfies 135 mm ≤ R17 ≤ 140 mm, preferably 137.981 mm. The radius of curvature R18 of the twentieth aspherical surface satisfies -150 mm ≤ R18 ≤ -145 mm, preferably -149.496 mm.

[0044] The surface 23 of the first reflecting mirror is aspherical, and its radius of curvature R19 satisfies -195 mm ≤ R19 ≤ -190 mm, preferably -191.651 mm. The radius of curvature R20 of the surface 24 in the diffraction grating used for diffraction dispersion satisfies -100 mm ≤ R20 ≤ -95 mm, preferably -97.540 mm. The surface 25 of the second reflecting mirror is aspherical, and its radius of curvature R21 satisfies -195 mm ≤ R21 ≤ -190 mm, preferably -191.651 mm.

[0045] According to the visible and near-infrared spectroscopy scanner optical system provided by the present invention, the center thickness d1 of the first lens satisfies 5 mm ≤ d1 ≤ 10 mm, preferably 5.50 mm.

[0046] The center thickness d2 of the second lens satisfies 8 mm ≤ d2 ≤ 12 mm, and is preferably 9.999 mm.

[0047] The center thickness d3 of the third lens satisfies 8 mm ≤ d3 ≤ 12 mm, and is preferably 9.993 mm.

[0048] The center thickness d4 of the fourth lens satisfies 8 mm ≤ d4 ≤ 12 mm, preferably 9.990 mm.

[0049] The center thickness d5 of the fifth lens satisfies 5 mm ≤ d5 ≤ 10 mm, preferably 7.492 mm.

[0050] The center thickness d6 of the sixth lens satisfies 8 mm ≤ d6 ≤ 12 mm, preferably 9.016 mm.

[0051] The center thickness d7 of the seventh lens satisfies 8 mm ≤ d7 ≤ 12 mm, preferably 9.999 mm.

[0052] The center thickness d8 of the eighth lens satisfies 8 mm ≤ d8 ≤ 12 mm, preferably 9.970 mm.

[0053] The center thickness d9 of the ninth lens satisfies 5 mm ≤ d9 ≤ 10 mm, preferably 5.500 mm.

[0054] The center thickness d10 of the tenth lens satisfies 8 mm ≤ d10 ≤ 12 mm, preferably 10.002 mm.

[0055] Furthermore, in the visible and near-infrared spectroscopy scanner optical system provided by the present invention, the distance p1 between the side of the first lens near the image plane and the side of the second lens near the object plane satisfies 30 mm ≤ p1 ≤ 35 mm, preferably 33.255 mm.

[0056] The distance p2 between the second lens near the image plane and the third lens near the object plane satisfies 5 mm ≤ p2 ≤ 10 mm, preferably 6.973 mm.

[0057] The distance p3 between the third lens near the image plane and the fourth lens near the object plane satisfies 2 mm ≤ p3 ≤ 5 mm, preferably 2.402 mm.

[0058] The distance p4 of the fourth lens from the aperture stop on the side closest to the image plane satisfies 60 mm ≤ p4 ≤ 65 mm, preferably 62.028 mm.

[0059] The distance p5 between the aperture and the fifth lens on the side closest to the object surface satisfies 10 mm ≤ p5 ≤ 15 mm, preferably 11.891 mm.

[0060] The distance p6 between the sixth lens near the image plane and the seventh lens near the object plane satisfies 1 mm ≤ p6 ≤ 5 mm, preferably 1.500 mm.

[0061] The distance p7 between the eighth lens and the first folding mirror on the side closest to the image plane satisfies 45 mm ≤ p7 ≤ 50 mm, preferably 49.385 mm.

[0062] The distance p8 between the first folding mirror and the ninth lens on the side closest to the object surface satisfies 48 mm ≤ p8 ≤ 53 mm, preferably 50.00 mm.

[0063] The distance p9 between the ninth lens near the image plane and the tenth lens near the object plane satisfies 12 mm ≤ p9 ≤ 17 mm, preferably 15.097 mm.

[0064] The distance p10 of the tenth lens from the slit on the side closest to the image plane satisfies 5 mm ≤ p10 ≤ 10 mm, preferably 5.594 mm.

[0065] The distance p11 between the slit and the second folding mirror satisfies 40 mm ≤ p11 ≤ 45 mm, preferably 43.751 mm.

[0066] The distance p12 between the second folding mirror and the first reflecting mirror satisfies 145 mm ≤ p12 ≤ 150 mm, and is preferably 145.825 mm.

[0067] The distance p13 between the first reflecting mirror and the diffraction grating satisfies 95 mm ≤ p13 ≤ 100 mm, preferably 95.825 mm.

[0068] The distance p14 between the diffraction grating and the second reflecting mirror satisfies 95 mm ≤ p14 ≤ 100 mm, preferably 95.828 mm.

[0069] The distance p15 between the second reflecting mirror and the image plane satisfies 190 mm ≤ p15 ≤ 195 mm, and is preferably 194.519 mm.

[0070] According to the visible and near-infrared spectroscopy scanner optical system provided by the present invention, the focal length f1 of the first lens satisfies -45 mm ≤ f1 ≤ -40 mm, preferably -43.452 mm.

[0071] The focal length f2 of the second lens satisfies 225 mm ≤ f2 ≤ 230 mm, and is preferably 225.49 mm.

[0072] The focal length f3 of the third lens satisfies -110 mm ≤ f3 ≤ -105 mm, preferably -108.72 mm.

[0073] The focal length f4 of the fourth lens satisfies 95 mm ≤ f4 ≤ 100 mm, preferably 99.604 mm.

[0074] The focal length f5 of the fifth lens satisfies 430 mm ≤ f5 ≤ 435 mm, preferably 434.25 mm.

[0075] The focal length f6 of the sixth lens satisfies 60 mm ≤ f6 ≤ 65 mm, preferably 60.503 mm.

[0076] The focal length f7 of the seventh lens satisfies -30 mm ≤ f7 ≤ -25 mm, preferably -29.185 mm.

[0077] The focal length f8 of the eighth lens satisfies 40 mm ≤ f8 ≤ 45 mm, and is preferably 44.841 mm.

[0078] The focal length f9 of the ninth lens satisfies -440 mm ≤ f9 ≤ -435 mm, preferably -435.97 mm.

[0079] The focal length f10 of the tenth lens satisfies 125 mm ≤ f10 ≤ 130 mm, and is preferably 129.47 mm.

[0080] Furthermore, in the visible and near-infrared spectroscopy scanner optical system provided by the present invention, the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, eighth lens, ninth lens, and tenth lens are all made of optical glass. Specifically, the conic coefficient k1 of the first lens near the image plane is -0.697, the conic coefficient k3 of the third lens near the image plane is -2.307, the conic coefficient k4 of the fourth lens near the object plane is 10, the conic coefficient k6 of the sixth lens near the image plane is -2.539, the conic coefficient k8 of the eighth lens near the image plane is -0.987, the conic coefficient k9 of the ninth lens near the object plane is 1.62, and the conic coefficient k10 of the tenth lens near the image plane is -3.646.

[0081] The aspherical surfaces of both the first and second reflecting mirrors conform to the formula shown in Formula 1:

[0082] Where Z is the sag, c is the curvature, r is the radial distance from a point on the lens to the optical axis, k is the conic coefficient, and A and B are both aspherical coefficients.

[0083] In this invention, the first reflector satisfies: A=-3.871E-8, B=-5.564E-14, k=-2.191; the second reflector satisfies: A=-3.871E-8, B=-5.564E-14, k=-2.191.

[0084] Table 1 below illustrates the radius of curvature, thickness, and material parameters of various optical components in the visible and near-infrared spectral imaging lens provided in this application:

[0085] The working principle of this invention is as follows: The visible and near-infrared spectral scanner optical system provided by this invention is applied to visible and near-infrared spectral imaging in the 400nm~1000nm wavelength range. The front objective lens assembly is an image-side telecentric optical path.

[0086] Operating wavelength range: 0.4μm-1.0μm, focal length: 50mm, F number: 5, object-side field of view: 210mm, telecentricity <0.1°, dispersion width 2.4mm, can be matched with a 6144×6144 detector with a pixel size of 10 μm.

[0087] When the optical system of this invention performs visible and near-infrared spectral imaging, the front objective lens assembly receives visible and near-infrared light from the object surface under test. This light first reaches the first lens. The first lens receives the incident beam emitted from the wide-angle object surface and performs preliminary control on the edge rays of the large field of view, ensuring that the height and angle of the light entering the subsequent optical path are within a correctable range. Subsequently, the light enters the second lens, which compensates for the divergence or convergence tendency of the beam after the preliminary control by the first lens and improves the propagation state of the edge field of view rays.

[0088] Subsequently, the light beam passes through the third and fourth lenses in sequence. The third lens adjusts the spherical aberration, coma, astigmatism, and residual chromatic aberration across a wide spectral range. The fourth lens further refines the beam, ensuring it reaches the aperture stop at a suitable aperture height and angle of incidence. As the light beam passes through the fourth lens and enters the aperture stop, the stop limits the aperture of the entire optical system and controls the angle of the principal ray, maintaining a relatively stable exit direction for subsequent beams on the image side.

[0089] Light passing through the aperture enters the first cemented doublet, which consists of a fifth lens and a sixth lens. The fifth and sixth lenses, made of glass materials with different dispersion properties, compensate for chromatic aberration within a broad spectral range of 400nm-1000nm, while further correcting spherical aberration and higher-order aberrations using aspherical structures. Subsequently, the light enters the second cemented doublet, which consists of a seventh lens and an eighth lens. The second cemented doublet continues to compress residual chromatic aberration based on the corrections made by the first cemented doublet.

[0090] After passing through the first and second cemented doublet lenses, the light reaches the first folding mirror. The first folding mirror changes the direction of light propagation, thereby compressing the system's structural dimensions and facilitating subsequent optomechanical layout. The folded light then enters the ninth lens, which serves as a subsequent correction element, responsible for compensating for residual aberrations in the system and further modulating the beam height and propagation angle.

[0091] Subsequently, the light enters the tenth lens, which completes the final convergence, so that the one-dimensional spatial line image on the object under test is accurately imaged onto the slit. At the same time, the angle of the principal ray in front of the slit is controlled to ensure that the line image at the slit is clear and the position is stable.

[0092] The slit only allows light rays from that line of view to enter the subsequent beam splitting system, thus determining the instantaneous spatial sampling position. Through scanning motion, the optical system obtains another dimension of spatial information; through subsequent spectral splitting, the system obtains spectral information.

[0093] The light rays passing through the slit reach the second folding mirror, which again changes the direction of the light path, directing the beam into the reflective spectrometer section. Subsequently, the light reaches the first reflecting mirror, which receives the beam exiting the slit and reflects it to the diffraction grating, causing the light to illuminate the grating surface at a suitable angle. The diffraction grating disperses the incident polychromatic light, with different wavelengths spreading out at different diffraction angles, thus separating spectral information from the same spatial location into different propagation directions. Finally, the dispersed light is refocused by the second reflecting mirror and imaged onto the detector's image plane, forming a two-dimensional spectral image with one direction representing the spatial dimension and the other the spectral dimension. As the system scans, the spatial-spectral data of the target object can be obtained.

[0094] Figure 2 - Figure 5 The values ​​represent the modulation transfer function (MTF) of the optical system operating at the Nyquist frequency of 50 lp / mm. The MTF is greater than 0.55 across the entire field of view in the 400 nm–1000 nm spectral range. Figure 6 - Figure 7 The results show the Smile distortion and Keystone distortion of the system, respectively. The maximum Smile distortion of the system is 1.72 μm, and the maximum Keystone distortion is 1.88 μm. Both are less than 1 / 5 of a pixel, indicating that the system has good spectral stability and spatial registration accuracy in the visible hyperspectral imaging range.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical system for a visible and near-infrared spectroscopy scanner, characterized in that: It includes a front objective lens assembly, a slit, and a spectrometer assembly; the front objective lens assembly includes, in sequence from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, an aperture, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a first folding mirror, a ninth lens, and a tenth lens; The spectrometer assembly includes, in sequence from the object plane to the image plane, a second folding mirror, a first reflecting mirror, a diffraction grating, and a second reflecting mirror; The first lens is aspherical on the side near the image plane, the third lens is aspherical on the side near the image plane, the fourth lens is aspherical on the side near the object plane, the sixth lens is aspherical on the side near the image plane, the eighth lens is aspherical on the side near the image plane, the ninth lens is aspherical on the side near the object plane, the tenth lens is aspherical on the side near the image plane, and the first and second reflecting mirrors are aspherical mirrors. The second lens, the fifth lens, and the seventh lens are all spherical mirrors. The fifth lens and the sixth lens, as well as the seventh lens and the eighth lens, are all cemented doublet lenses.

2. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The radius of curvature R1 of the first lens on the side closest to the object surface satisfies -255 mm ≤ R1 ≤ -250 mm; The radius of curvature R2 of the first lens on the side closer to the image plane satisfies 25 mm ≤ R2 ≤ 30 mm; The radius of curvature R3 of the second lens on the side closer to the object surface satisfies -310 mm ≤ R3 ≤ -305 mm; The radius of curvature R4 of the second lens on the side closer to the image plane satisfies -100 mm ≤ R4 ≤ -95 mm; The radius of curvature R5 of the third lens on the side closest to the object surface satisfies -55 mm ≤ R5 ≤ -50 mm; The radius of curvature R6 of the third lens on the side closer to the image plane satisfies -135 mm ≤ R6 ≤ -130 mm; The radius of curvature R7 of the fourth lens on the side closest to the object surface satisfies -205 mm ≤ R7 ≤ -200 mm; The radius of curvature R8 of the fourth lens on the side closest to the image plane satisfies -55 mm ≤ R8 ≤ -50 mm; The radius of curvature R9 of the fifth lens on the side closest to the object surface satisfies 45 mm ≤ R9 ≤ 50 mm; The radius of curvature R10 of the fifth lens on the side closer to the sixth lens is the same as the radius of curvature of the sixth lens on the side closer to the fifth lens, and satisfies 50 mm ≤ R10 ≤ 55 mm. The radius of curvature R11 of the sixth lens on the side closest to the image plane satisfies -55 mm ≤ R11 ≤ -50 mm; The radius of curvature R12 of the seventh lens on the side closest to the object surface satisfies -80 mm ≤ R12 ≤ -75 mm; The radius of curvature R13 of the seventh lens on the side closer to the eighth lens is the same as the radius of curvature of the eighth lens on the side closer to the seventh lens, and satisfies 30 mm ≤ R13 ≤ 35 mm. The radius of curvature R14 of the eighth lens on the side near the image plane satisfies -90 mm ≤ R14 ≤ -85 mm; The radius of curvature R15 of the ninth lens on the side closest to the object surface satisfies -80 mm ≤ R15 ≤ -75 mm; The radius of curvature R16 of the ninth lens on the side near the image plane satisfies -110 mm ≤ R16 ≤ -105 mm; The radius of curvature R17 of the tenth lens on the side closest to the object surface satisfies 135 mm ≤ R17 ≤ 140 mm; The radius of curvature R18 of the tenth lens on the side near the image plane satisfies -150 mm ≤ R18 ≤ -145 mm; The radius of curvature R19 of the first reflecting mirror satisfies -195 mm ≤ R19 ≤ -190 mm; The radius of curvature R20 of the diffraction grating satisfies -100 mm ≤ R20 ≤ -95 mm; The radius of curvature R21 of the second reflector satisfies -195 mm ≤ R21 ≤ -190 mm.

3. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The center thickness d1 of the first lens satisfies 5 mm ≤ d1 ≤ 10 mm; The center thickness d2 of the second lens satisfies 8 mm ≤ d2 ≤ 12 mm; The center thickness d3 of the third lens satisfies 8 mm ≤ d3 ≤ 12 mm; The center thickness d4 of the fourth lens satisfies 8 mm ≤ d4 ≤ 12 mm; The center thickness d5 of the fifth lens satisfies 5 mm ≤ d5 ≤ 10 mm; The center thickness d6 of the sixth lens satisfies 8 mm ≤ d6 ≤ 12 mm; The center thickness d7 of the seventh lens satisfies 8 mm ≤ d7 ≤ 12 mm; The center thickness d8 of the eighth lens satisfies 8 mm ≤ d8 ≤ 12 mm; The center thickness d9 of the ninth lens satisfies 5 mm ≤ d9 ≤ 10 mm; The center thickness d10 of the tenth lens satisfies 8 mm ≤ d10 ≤ 12 mm.

4. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The distance p1 between the side of the first lens near the image plane and the side of the second lens near the object plane satisfies 30 mm ≤ p1 ≤ 35 mm; The distance p2 between the second lens near the image plane and the third lens near the object plane satisfies 5 mm ≤ p2 ≤ 10 mm; The distance p3 between the third lens near the image plane and the fourth lens near the object plane satisfies 2 mm ≤ p3 ≤ 5 mm; The distance p4 between the fourth lens and the aperture stop on the side closer to the image plane satisfies 60 mm ≤ p4 ≤ 65 mm; The distance p5 between the aperture and the fifth lens on the side closest to the object surface satisfies 10 mm ≤ p5 ≤ 15 mm; The distance p6 between the side of the sixth lens near the image plane and the side of the seventh lens near the object plane satisfies 1 mm ≤ p6 ≤ 5 mm; The distance p7 between the eighth lens and the first folding mirror on the side closest to the image plane satisfies 45 mm ≤ p7 ≤ 50 mm; The distance p8 between the first folding mirror and the ninth lens on the side closest to the object surface satisfies 48 mm ≤ p8 ≤ 53 mm; The distance p9 between the ninth lens near the image plane and the tenth lens near the object plane satisfies 12 mm ≤ p9 ≤ 17 mm; The distance p10 of the tenth lens from the slit on the side closest to the image plane satisfies 5 mm ≤ p10 ≤ 10 mm; The distance p11 between the slit and the second folding mirror satisfies 40 mm ≤ p11 ≤ 45 mm; The distance p12 between the second folding mirror and the first reflecting mirror satisfies 145 mm ≤ p12 ≤ 150 mm; The distance p13 between the first reflecting mirror and the diffraction grating satisfies 95 mm ≤ p13 ≤ 100 mm; The distance p14 between the diffraction grating and the second reflecting mirror satisfies 95 mm ≤ p14 ≤ 100 mm; The distance p15 between the second reflecting mirror and the image plane satisfies 190 mm ≤ p15 ≤ 195 mm.

5. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The focal length f1 of the first lens satisfies -45 mm ≤ f1 ≤ -40 mm; The focal length f2 of the second lens satisfies 225 mm ≤ f2 ≤ 230 mm; The focal length f3 of the third lens satisfies -110 mm ≤ f3 ≤ -105 mm; The focal length f4 of the fourth lens satisfies 95 mm ≤ f4 ≤ 100 mm; The focal length f5 of the fifth lens satisfies 430 mm ≤ f5 ≤ 435 mm; The focal length f6 of the sixth lens satisfies 60 mm ≤ f6 ≤ 65 mm; The focal length f7 of the seventh lens satisfies -30 mm ≤ f7 ≤ -25 mm; The focal length f8 of the eighth lens satisfies 40 mm ≤ f8 ≤ 45 mm; The focal length f9 of the ninth lens satisfies -440 mm ≤ f9 ≤ -435 mm; The focal length f10 of the tenth lens satisfies 125 mm ≤ f10 ≤ 130 mm.

6. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, eighth lens, ninth lens and tenth lens are all made of optical glass.

7. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The conic coefficient k1 of the first lens on the side closer to the image plane is -0.697; The conic coefficient k3 of the third lens on the side closest to the image plane is -2.307; The conic coefficient k4 of the fourth lens on the side closest to the object surface is 10; The conic coefficient k6 of the sixth lens on the side closest to the image plane is -2.539; The conic coefficient k8 of the eighth lens on the side closest to the image plane is -0.987; The conic coefficient k9 of the ninth lens on the side closest to the object surface is 1.62; The conic coefficient k10 of the tenth lens on the side closest to the image plane is -3.

646.

8. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The aspherical surface shapes of both the first and second reflectors conform to Formula 1:

9. Among them, Z is the sag, c is the curvature, r is the radial distance from a point on the lens to the optical axis, k is the conic coefficient, and A and B are both aspherical coefficients. The first reflector satisfies: A = -3.871E-8, B = -5.564E-14, k = -2.191; The second reflector satisfies: A=-3.871E-8, B=-5.564E-14, k=-2.

191.

10. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: It is applied to visible and near-infrared spectral imaging in the 400nm~1000nm band.

11. The optical system for a visible and near-infrared spectroscopy scanner according to claim 1, characterized in that: The front objective lens assembly is an image-side telecentric optical path.

Images