A wide-spectrum optical lens from ultraviolet to short-wave infrared

Abstract

The application discloses the technical field of optical imaging lenses and relates to a wide-spectrum optical lens from ultraviolet to short-wave infrared, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along an optical axis from an object side to an image side, wherein the first lens is a meniscus lens with negative optical power, the second lens is an asymmetric biconvex lens with positive optical power, the third lens is a meniscus lens with negative optical power, the fourth lens is a meniscus lens with positive optical power, the fifth lens is a meniscus lens with positive optical power, the sixth lens is an asymmetric biconvex lens with positive optical power, and the seventh lens is an asymmetric biconcave lens with negative optical power. The application realizes excellent achromatism and high-order aberration balance in a 240-2500 nm super-wide waveband through the alternative distribution of optical power of the seven lenses and material matching, and is suitable for wide-spectrum high-performance optical imaging applications.

Description

Technical Field

[0001] This invention relates to a broadband optical lens that extends from the ultraviolet to the shortwave infrared, belonging to the field of optical imaging lens technology. Background Technology

[0002] With advancements in optical imaging technology, the value of broadband imaging in numerous applications continues to rise. Currently, most broadband lenses on the market can only achieve high-quality imaging within a limited wavelength range (e.g., 400-1100 nm). Once the spectral range is broadened to the deep ultraviolet to short-wave infrared region (e.g., 240-2500 nm), the image quality significantly deteriorates. This is primarily due to the limitations of traditional lens designs in addressing chromatic aberration and transmittance across a wide spectrum: different wavelengths of light exhibit dispersion due to differences in refractive index, impairing image sharpness; simultaneously, conventional optical materials have poor transmittance in the ultraviolet and infrared bands, resulting in reduced image brightness, making it difficult to maintain stable high-resolution performance across such a broad spectral range.

[0003] Broadband imaging technology, by acquiring rich spectral information, provides crucial evidence for the high-precision identification and classification of substances. Within the 240-2500 nm broad spectral range, imaging spectrometers can simultaneously acquire spectral information from the ultraviolet to the short-wave infrared. In industrial inspection, it can simultaneously perform the identification of surface micro-defects and non-destructive analysis of internal components; in medical diagnostics, imaging information at different wavelengths can more comprehensively reveal the structure and state of biological tissues, providing more sufficient evidence for disease diagnosis; and in remote sensing observation, it significantly improves the classification accuracy of complex ground features and the ability to monitor environmental dynamics.

[0004] Patent publication number "120143415A" discloses "An Imaging Lens Applicable to a Wide Spectral Range," which designs a lightweight and compact lens with an operating wavelength of 400-2500 nm and uses eight lenses. However, it cannot correct various aberrations and achieve clear imaging in the ultraviolet band. Patent publication number "107976785A" discloses "A Short Focal Length Wide-Spectral Ultraviolet Optical Lens," which designs a wide field of view, compact structure, and low distortion lens with an operating wavelength of 240-1000 nm and uses nine lenses. However, it cannot achieve clear imaging in the wider infrared band.

[0005] None of the above-mentioned solutions can operate within the wavelength range from ultraviolet to short-wave infrared, resulting in low efficiency. Furthermore, the availability of optical materials in the 240-2500 nm band is currently limited, and most glasses cannot effectively correct chromatic aberration across such a wide band, often hindering image quality improvement. Therefore, most lenses employ cemented lens groups to correct chromatic aberration; however, the cementing process itself introduces light absorption loss in the ultraviolet band, thus relying primarily on the distribution of optical power to achieve chromatic aberration balance. How to achieve high-quality imaging across a wide spectral range while ensuring controlled chromatic aberration is a key technical challenge that lenses currently need to overcome. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a broadband optical lens that extends from the ultraviolet to the short-wave infrared, thereby solving the problems of narrow wavelength range, large weight, and large size of the prior art.

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0008] In a first aspect, the present invention provides a broadband optical lens extending from the ultraviolet to the shortwave infrared, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object side to the image side, wherein:

[0009] The first lens is a meniscus lens with negative optical power, the second lens is an asymmetric biconvex lens with positive optical power, the third lens is a meniscus lens with negative optical power, the fourth lens is a meniscus lens with positive optical power, the fifth lens is a meniscus lens with positive optical power, the sixth lens is an asymmetric biconvex lens with positive optical power, and the seventh lens is an asymmetric biconcave lens with negative optical power.

[0010] An aperture is provided between the third lens and the fourth lens;

[0011] The first lens, the second lens, and the third lens constitute the front lens group, and the fourth lens, the fifth lens, the sixth lens, and the seventh lens constitute the rear lens group.

[0012] Furthermore, the rear surface of the sixth lens is an even-order aspherical surface made of magnesium fluoride, while the optical surfaces of the remaining lenses are all spherical.

[0013] Furthermore, the first, third, and seventh lenses are made of fused silica, the fourth, fifth, and sixth lenses are made of magnesium fluoride, and the second lens is made of lithium fluoride.

[0014] Furthermore, the combined focal length Fa of the first to third lenses and the combined focal length Fb of the fourth to seventh lenses satisfy the following condition: -4 <Fa / Fb<-3。

[0015] Furthermore, the focal length F1 of the first lens and the combined focal length Fa of the first to third lenses satisfy the following condition: 0 <F1 / Fa<1。

[0016] Furthermore, the back focal length FL of the broadband optical lens and the focal length f of the entire system satisfy the following condition: 0 <FL / f<0.7。

[0017] Furthermore, the refractive indices of the first to the seventh lenses are nd1, nd2, nd3, nd4, nd5, nd6, and nd7, respectively, and nd1>nd2>1.40, nd3>nd4>1.40, nd7>nd5>1.40, and nd7>nd6>1.40.

[0018] Furthermore, the Abbe coefficients of the first to the seventh lenses are vd1, vd2, vd3, vd4, vd5, vd6, and vd7, respectively, and vd2>vd1>65, vd3>vd4>100, vd5>vd7>100, and vd6>vd7>100.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] I. This invention features a rationally designed lens system, with three lenses in the front group and four lenses in the rear group. The first lens, with its concave surface facing the image side, effectively controls incident beam divergence and suppresses spherical aberration. The second lens provides the system's principal optical power, achieving initial focusing. The third lens, together with the first two lenses, forms a positive-negative-positive combination, collaboratively correcting primary chromatic aberration and coma. In the rear group, the fourth and fifth lenses are both positive optical power meniscus lenses to balance field curvature and magnification chromatic aberration. The sixth lens is a positive optical power asymmetric biconvex lens, further enhancing imaging convergence. The seventh lens is a negative optical power asymmetric biconcave lens, used for fine correction of axial chromatic aberration and residual higher-order aberrations. The entire system does not employ a cemented structure. Through the alternating distribution of optical power and material matching of the seven lenses, excellent apochromatic performance and balance of higher-order aberrations are achieved within the ultra-wide 240–2500 nm wavelength range, making it suitable for wide-spectrum, high-performance optical imaging applications.

[0021] Second, the lens of the present invention has a wide field of view, compact structure, light weight, small size, low distortion, high imaging quality, and is non-cemented, making it suitable for broadband optical systems. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1This is a schematic diagram of the structure of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the light path of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0025] Figure 3 This is a dot plot of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0026] Figure 4 This is an MTF chart of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0027] Figure 5 This is a distortion F-Tan (Theta) curve of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0028] Figure 6 This is a field curvature curve of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0029] Figure 7 This is a relative illumination diagram of a broadband optical lens from ultraviolet to short-wave infrared provided in an embodiment of the present invention;

[0030] In the diagram: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Image plane; 9. Aperture stop. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0032] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0033] Example:

[0034] Please see Figures 1 to 2, this embodiment provides a wide-spectrum optical lens from ultraviolet to short-wave infrared. Along an optical axis from the object side to the image side, it sequentially includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh lens 7. An aperture stop 9 is provided between the third lens 3 and the fourth lens 4. Among them: The first lens 1 is a meniscus lens with a negative focal power, its object side is convex, and its image side is concave; the second lens 2 is an asymmetric biconvex lens with a positive focal power; the third lens 3 is a meniscus lens with a negative focal power, its object side is concave, and its image side is convex; the fourth lens 4 is a meniscus lens with a positive focal power, its object side is concave, and its image side is convex; the fifth lens 5 is a meniscus lens with a positive focal power, its object side is concave, and its image side is convex; the sixth lens 6 is an asymmetric biconvex lens with a positive focal power; the seventh lens 7 is an asymmetric biconcave lens with a negative focal power. In this embodiment, the first lens 1, the second lens 2, and the third lens 3 constitute the front lens group, and the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 constitute the rear lens group.

[0035] It should be noted that in this embodiment, the rear surface of the sixth lens 6 is an even aspherical surface, and the material is magnesium fluoride, and the optical surfaces of the other lenses are spherical surfaces. The materials of the first lens 1, the third lens 3, and the seventh lens 7 are fused silica, the material of the second lens 2 is lithium fluoride, and the materials of the fourth lens 4, the fifth lens 5, and the sixth lens 6 are magnesium fluoride.

[0036] In addition, in this embodiment, the combined focal length Fa of the first lens 1 to the third lens 3 and the combined focal length Fb of the fourth lens to the seventh lens satisfy: -4 < Fa / Fb < -3. The focal length F1 of the first lens 1 and the combined focal length Fa of the first lens 1 to the third lens 3 satisfy: 0 < F1 / Fa < 1. The back focal length FL of this wide-spectrum optical lens and the total focal length f of the imaging lens satisfy the following condition: 0 < FL / f < 0.7. The refractive indices of the first lens to the seventh lens are nd1, nd2, nd3, nd4, nd5, nd6, and nd7 respectively. And nd1 > nd2 > 1.40, nd3 > nd4 > 1.40, nd7 > nd5 > 1.40, nd7 > nd6 > 1.40. The Abbe numbers of the first lens to the seventh lens are: vd1, vd2, vd3, vd4, vd5, vd6, and vd7 respectively, and vd2 > vd1 > 65, vd3 > vd4 > 100, vd5 > vd7 > 100, vd6 > vd7 > 100.

[0037] In actual assembly, the total length of the wide-spectrum optical lens, that is, the distance between the center of the object-side optical surface of the first lens 1 and the image plane 8 can be selected as: 40 mm < TTHI < 55 mm; 10 mm < BFL < 18 mm, where TTHI is the total length of the optical imaging lens, and BFL is the optical back focal length of the optical imaging lens. The lens aperture number F satisfies: 2 < F < 3, and it is defined that F = f / D, where D is the entrance pupil diameter. 5 mm < f < 15 mm, where f is the total focal length of the imaging lens.

[0038] The following gives specific embodiments of the present invention. The specific parameters of each lens in the embodiments are shown in Table 1:

[0039]

[0040] Table 1 Specific parameters of each lens

[0041] In this embodiment, the aspheric parameters of the lens are shown in Table 2:

[0042]

[0043] Table 2 Aspheric parameters of the lens

[0044] In Table 2, K is the conic coefficient, A4 is the 4th-order aspheric coefficient, A6 is the 6th-order aspheric coefficient, and A8 is the 8th-order aspheric coefficient.

[0045] This solution takes the aberration co-correction as the core, adjusts the surface parameters, material combination and focal power distribution according to requirements, and finally realizes high-resolution imaging in the wide wavelength range of 240 - 2500 nm. The wide-spectrum imaging lens provided by this solution has an effective focal length of 25 mm, the combined focal length of the first lens 1 to the third lens 3 is 58.094 mm, and the combined focal length of the fourth lens 4 to the seventh lens 7 is 17.269 mm. In this embodiment, the aperture number F of the wide-spectrum imaging lens is 2.5, and it is defined that F = f / D, and the entrance pupil diameter D = 10 mm; the field angle of the wide-spectrum imaging lens is 26°, the back working intercept is 17.526 mm, the size of the image plane diameter is 11.5 mm, and the total length of the lens is 43 mm.

[0046] The wide-spectrum imaging lens of the embodiment is tested, and the results are as follows:

[0047] See Figure 3 , it can be seen that the spot radii of different fields of view are all small, apochromatism is performed within the wide-spectrum range, chromatic aberration and aberration are corrected well, the imaging quality is high, and the spot diagram presents regular circular and symmetric distributions, and there is no significant astigmatism or asymmetric aberration in the imaging lens.

[0048] See Figure 4It can be seen that under the condition of 36 lp / mm, the MTF value of the transfer function of the entire field of view is greater than 0.3, which has high resolution, can distinguish image details, and aberrations are also effectively controlled.

[0049] See Figure 5 Imaging lenses require distortion F-Tan (Theta) of less than 1% within half the field of view.

[0050] See Figure 6 It can be seen that the performance was controlled in Between them, the solid line represents the meridional field curve within the half-field angle of each wavelength, and the dashed line represents the sagittal field curve within the half-field angle of each wavelength.

[0051] See Figure 7 It can be seen that the relative illumination is high and well controlled, ensuring uniform relative illumination across the field of view and uniform image stitching and overlay. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention, although the invention has been described in detail with reference to the foregoing embodiments. As is known from common technical knowledge, the present invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments are merely illustrative in all respects and are not the only ones. All modifications within the scope of the present invention or equivalent to the scope of the present invention are included in the present invention.

[0052] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A broadband optical lens that extends from the ultraviolet to the shortwave infrared, characterized in that, include: The first lens (1), the second lens (2), the third lens (3), the fourth lens (4), the fifth lens (5), the sixth lens (6), and the seventh lens (7) are arranged sequentially along the optical axis from the object side to the image side, wherein: The first lens (1) is a meniscus lens with negative optical power, the second lens (2) is an asymmetric biconvex lens with positive optical power, the third lens (3) is a meniscus lens with negative optical power, the fourth lens (4) is a meniscus lens with positive optical power, the fifth lens (5) is a meniscus lens with positive optical power, the sixth lens (6) is an asymmetric biconvex lens with positive optical power, and the seventh lens (7) is an asymmetric biconcave lens with negative optical power. An aperture stop (9) is provided between the third lens (3) and the fourth lens (4). The first lens (1), the second lens (2) and the third lens (3) constitute the front lens group, and the fourth lens (4), the fifth lens (5), the sixth lens (6) and the seventh lens (7) constitute the rear lens group.

2. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The rear surface of the sixth lens (6) is an even-order aspherical surface made of magnesium fluoride, while the optical surfaces of the other lenses are spherical.

3. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The first lens (1), the third lens (3) and the seventh lens (7) are made of fused silica, the fourth lens (4), the fifth lens (5) and the sixth lens (6) are made of magnesium fluoride, and the second lens (2) is made of lithium fluoride.

4. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The combined focal length Fa of the first lens (1) to the third lens (3) and the combined focal length Fb of the fourth lens (4) to the seventh lens (7) satisfy the following condition: -4 <Fa / Fb<-3。 5. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The focal length F1 of the first lens (1) and the combined focal length Fa of the first lens (1) to the third lens (3) satisfy the following condition: 0 <F1 / Fa<1。 6. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The back focal length FL of the broadband optical lens and the focal length f of the entire system satisfy the following condition: 0 <FL / f<0.7。 7. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, The refractive indices of the first lens (1) to the seventh lens (7) are nd1, nd2, nd3, nd4, nd5, nd6, and nd7, respectively, and nd1>nd2>1.40, nd3>nd4>1.40, nd7>nd5>1.40, and nd7>nd6>1.

40.

8. The broadband optical lens from ultraviolet to shortwave infrared according to claim 1, characterized in that, in, The Abbe coefficients of the first lens (1) to the seventh lens (7) are vd1, vd2, vd3, vd4, vd5, vd6, and vd7, respectively, and vd2>vd1>65, vd3>vd4>100, vd5>vd7>100, and vd6>vd7>100.

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