Visible and near-infrared optical system in small-stroke inner focusing form

Abstract

The invention provides a visible and near-infrared optical system in a small-stroke inner focusing form, which is suitable for the wavelength of 400-1100nm and the object distance from infinity to 50mm, can keep the focal length basically unchanged, realizes small focusing stroke, effectively solves the problem of chromatic aberration, improves the imaging quality, and meets the application requirements of spectral analysis, high-precision imaging, detection and the like.

Description

Technical Field

[0001] The invention relates to the technical field of optical lenses, and in particular to a visible near-infrared optical system in a small-stroke focusing form. Background Art

[0002] In current optical lens technology, there are many types of lens designs for different wavelength ranges and specific object distances. However, for application scenarios with wavelengths of 400nm - 1100nm and object distances from infinity to 50mm, traditional lenses have some limitations. Existing lenses often cannot effectively focus on light of different wavelengths at the same time, and there are chromatic aberration problems. Especially in the short wavelength (around 400nm) and long wavelength (around 1100nm) regions, chromatic aberration causes blurred imaging, affecting image quality and subsequent analysis and processing. Although the internal focusing lens has solved some of the focusing problems to a certain extent, the existing technology still has shortcomings for the design requirements of basically unchanged focal length and small focusing stroke under this specific wavelength range and object distance conditions. When the object distance changes from infinity to 50mm, it is difficult for existing lenses to keep the focal length basically unchanged. This makes the imaging plane unstable when shooting or observing at close range, resulting in a decrease in imaging quality and failure to meet the needs of high-precision observation. In order to achieve the focusing function within the range of object distance variation, the focusing stroke of some lenses is designed to be relatively large, which not only makes the lens structure complex and increases the volume, but also makes it unsuitable for some application scenarios with strict space requirements, and also increases the difficulty of lens manufacturing and assembly. Therefore, it is of great practical significance to develop a visible near-infrared optical system with a small focusing stroke by combining existing focusing technology and material selection. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a visible near-infrared optical system with a small-stroke focusing form.

[0004] The technical solution adopted by the present invention is as follows: a visible near-infrared optical system with a small stroke internal focusing form, which is provided with a front fixed lens group, a front moving lens group, an intermediate fixed lens group, a rear compensation lens group, a rear fixed lens group and a diaphragm in sequence from the object plane to the image plane, The front fixed lens group comprises: A first lens having positive refractive power, wherein both the object side surface and the image side surface are convex; The second lens has a negative optical power, the object side surface is convex, and the image side surface is concave; The front movable lens group comprises: The third lens has positive power, the object side surface is concave, and the image side surface is convex; The fourth lens element has a negative optical power, the object side surface is concave, and the image side surface is convex; The intermediate fixed lens group comprises: A fifth lens having positive refractive power, wherein both the object side surface and the image side surface are convex; The rear compensation lens group comprises: The sixth lens element has a negative optical power, and its object side surface is convex and its image side surface is concave; The seventh lens has positive refractive power, and both the object side surface and the image side surface are convex; The eighth lens has positive refractive power, and both the object side surface and the image side surface are convex; The rear fixed lens group comprises: The ninth lens element has negative optical power, and its object side surface is concave and its image side surface is convex.

[0005] Preferably, the front movable lens group and the rear compensation lens group are movable groups. During the focusing process, the air gap D1 between the front fixed lens group and the front movable lens group changes in the range of 3.9mm≤D1≤5.6mm, and the air gap D2 between the front movable lens group and the middle fixed lens group changes in the range of 0.3mm≤D2≤2.0mm. The air interval D3 between the intermediate fixed lens group and the rear compensation lens group varies in a range of 3.5 mm ≤ D3 ≤ 4.6 mm, and the air interval D4 between the rear compensation lens group and the rear fixed lens group varies in a range of 1.4 mm ≤ D4 ≤ 2.5 mm.

[0006] Preferably, in the front fixed lens group, the air gap between the first lens and the second lens is 0.7-0.8 mm. In the front moving lens group, the air gap between the third lens and the fourth lens is 1.6-1.8mm. In the rear compensation lens group, the air gap between the sixth lens and the seventh lens is 0.7-0.8 mm, and the air gap between the seventh lens and the eighth lens is 0.2-0.4 mm. The air gap between the rear fixed lens group and the aperture is 11.5-12.0 mm.

[0007] Preferably, the curvature radius R1 of the object side surface of the first lens satisfies 355mm≤R1≤405mm, and the curvature radius R2 of the image side surface of the first lens satisfies -45mm≤R2≤-35mm; The curvature radius R3 of the object side surface of the second lens satisfies 55mm≤R3≤65mm, and the curvature radius R4 of the image side surface of the second lens satisfies 5mm≤R4≤15mm; The curvature radius R5 of the object side surface of the third lens satisfies -25mm≤R5≤-15mm, and the curvature radius R6 of the image side surface of the third lens satisfies -20mm≤R6≤-10mm; The radius of curvature R7 of the object side of the fourth lens satisfies -15 mm ≤ R7 ≤ -5 mm, and the radius of curvature R8 of the image side of the fourth lens satisfies -20 mm ≤ R8 ≤ -10 mm; The radius of curvature R9 of the object side of the fifth lens satisfies 15 mm ≤ R9 ≤ 25 mm, and the radius of curvature R10 of the image side of the fifth lens satisfies -25 mm ≤ R10 ≤ -15 mm; The radius of curvature R11 of the object side of the sixth lens satisfies 30 mm ≤ R11 ≤ 40 mm, and the radius of curvature R12 of the image side of the sixth lens 6 satisfies 5 mm ≤ R12 ≤ 15 mm; The radius of curvature R13 of the object side of the seventh lens satisfies 5 mm ≤ R13 ≤ 15 mm, and the radius of curvature R14 of the image side of the seventh lens 7 satisfies -45 mm ≤ R14 ≤ -35 mm; The radius of curvature R15 of the object side of the eighth lens satisfies 35 mm ≤ R15 ≤ 45 mm, and the radius of curvature R16 of the image side of the eighth lens 8 satisfies -15 mm ≤ R16 ≤ -5 mm; The radius of curvature R17 of the object side of the ninth lens satisfies -15 mm ≤ R17 ≤ -5 mm, and the radius of curvature R18 of the image side of the ninth lens 9 satisfies -15 mm ≤ R18 ≤ -5 mm.

[0008] Preferably, the central thickness of the first lens is 3 - 4 mm; The central thickness of the second lens is 2 - 3 mm; The central thickness of the third lens is 3 - 5 mm; The central thickness of the fourth lens is 3 - 4 mm; The central thickness of the fifth lens is 2 - 4 mm; The central thickness of the sixth lens is 1 - 2 mm; The central thickness of the seventh lens is 2 - 3 mm; The central thickness of the eighth lens is 1 - 3 mm; The central thickness of the ninth lens is 1 - 2 mm.

[0009] Preferably, both the object side and the image side of the first lens are aspherical surfaces.

[0010] Preferably, the material of the first lens is HQK3L_CDGM.

[0011] Preferably, the object sides and the image sides of the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all spherical surfaces.

[0012] Preferably, the dispersion coefficients of the first lens and the second lens are greater than 70.

[0013] The beneficial effects of the present invention are as follows: 1. The present invention is applicable to wavelengths of 400nm-1100nm and object distances from infinity to 50mm. It can keep the focal length basically unchanged and achieve a small focusing stroke. At the same time, it can effectively solve the chromatic aberration problem and improve the imaging quality to meet the application requirements of spectral analysis, high-precision imaging and detection.

[0014] 2. In order to adapt to the wide wavelength range, the front fixed lens group adopts special optical materials and aspherical design. It uses materials with high Abbe number (Abbe number is greater than 70. Generally speaking, Abbe number above 50 is usually considered to be high Abbe number. Among optical materials, the Abbe number of common optical glass materials is mostly between 30-60. Among them, materials with Abbe number above 50 have relatively small dispersion and better imaging quality.) and low dispersion characteristics to reduce the chromatic aberration of short-wavelength and long-wavelength light. Its aspherical shape helps to correct spherical aberration and improve the convergence efficiency of light.

[0015] 3. The front moving lens group and the rear compensating lens group are the key parts to realize the internal focusing function. By adopting a movable lens unit design, it moves on the high-precision rail inside the lens barrel. The material and curvature design of the front moving lens group and the rear compensating lens group are optimized so that when they move within a small range, they can effectively compensate for the light propagation difference caused by the change of object distance, while keeping the focal length basically unchanged.

[0016] 4. The rear fixed lens is responsible for accurately focusing the light adjusted by the front moving lens group and the rear compensation lens group onto the imaging plane. Its design takes into account the light propagation characteristics of the entire wavelength range to ensure that a clear image can be obtained within 400nm - 1100nm.

[0017] 5. The system aperture is placed at the rear, so that after the light passes through the front lens group, it can be filtered by the aperture, so that the light at different heights can be better converged on the image plane. The design of the rear position can optimize the light propagation path, so that the image in the entire field of view can be imaged more flatly on the detector plane, reduce the blur of the edge field of view, make the distant image clearer and more symmetrical, and improve the clarity of the image. The aperture can be placed at the rear to reasonably select the range of the light beam entering the system according to the parameters such as the size of the detector and the focal length of the optical system, avoid too much stray light from entering the system, and thus improve the utilization rate of light energy on the detector. In the visible and near-infrared bands, the refractive index of some optical materials will change with temperature, thus affecting the performance of the optical system. The aperture can reduce this effect to a certain extent, because it can make the light propagation path of the optical system relatively more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0019] Figure 1 is a schematic diagram of the optical system of the present invention when it is at an infinite object distance; Figure 2 A schematic diagram of the optical system of the present invention when the object distance is 50 mm; Figure 3 The figure shows a transfer function curve schematic diagram of the system of this embodiment when the object distance is infinite; Figure 4 The figure shows the transfer function curve of the system of this embodiment when the object distance is 50mm; Figure 5 The figure is a schematic diagram of field curvature aberration when the object distance is infinite in the system of this embodiment; Figure 6 The figure shows the field curvature aberration schematic diagram of the system of this embodiment when the object distance is 50mm; In the figure, 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, 6-sixth lens, 7-seventh lens, 8-eighth lens, 9-ninth lens, 10-aperture. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1-2 The figure shows a visible near-infrared optical system of a small-stroke internal focusing type, in which a front fixed lens group, a front moving lens group, an intermediate fixed lens group, a rear compensation lens group, a rear fixed lens group and a stop 10 are arranged in sequence from the object plane to the image plane. The front fixed lens group comprises: A first lens 1 having positive refractive power, wherein both the object side surface and the image side surface are convex; A second lens 2 with negative optical power, having a convex object-side surface and a concave image-side surface; The front movable lens group comprises: The third lens 3 has positive refractive power, the object side surface is concave, and the image side surface is convex; The fourth lens 4 has a negative optical power, the object side surface is concave, and the image side surface is convex; The intermediate fixed lens group comprises: A fifth lens 5 having positive refractive power, wherein both the object side surface and the image side surface are convex; The rear compensation lens group comprises: A sixth lens element 6 having negative optical power, wherein the object side surface is convex and the image side surface is concave; A seventh lens element 7 having positive refractive power, wherein both the object side surface and the image side surface are convex; An eighth lens 8 with positive refractive power, both the object side surface and the image side surface are convex; The rear fixed lens group comprises: The ninth lens element 9 with negative refractive power has a concave object-side surface and a convex image-side surface.

[0022] The front movable lens group and the rear compensation lens group are movable groups. During the focusing process, the air gap D1 between the front fixed lens group and the front movable lens group changes in the range of 3.9mm≤D1≤5.6mm, and the air gap D2 between the front movable lens group and the middle fixed lens group changes in the range of 0.3mm≤D2≤2.0mm. The air interval D3 between the intermediate fixed lens group and the rear compensation lens group varies in a range of 3.5 mm ≤ D3 ≤ 4.6 mm, and the air interval D4 between the rear compensation lens group and the rear fixed lens group varies in a range of 1.4 mm ≤ D4 ≤ 2.5 mm.

[0023] In the front fixed lens group, the air gap between the first lens 1 and the second lens 2 is 0.7-0.8 mm. In the front moving lens group, the air interval between the third lens 3 and the fourth lens 4 is 1.6-1.8 mm. In the rear compensation lens group, the air gap between the sixth lens 6 and the seventh lens 7 is 0.7-0.8 mm, and the air gap between the seventh lens 7 and the eighth lens 8 is 0.2-0.4 mm. The air gap between the rear fixed lens group and the aperture 10 is 11.5-12.0 mm.

[0024] The curvature radius R1 of the object side surface of the first lens 1 satisfies 355 mm ≤ R1 ≤ 405 mm, and the curvature radius R2 of the image side surface of the first lens 1 satisfies -45 mm ≤ R2 ≤ -35 ​​mm; The curvature radius R3 of the object side surface of the second lens 2 satisfies 55 mm ≤ R3 ≤ 65 mm, and the curvature radius R4 of the image side surface of the second lens 2 satisfies 5 mm ≤ R4 ≤ 15 mm; The curvature radius R5 of the object side surface of the third lens 3 satisfies -25mm≤R5≤-15mm, and the curvature radius R6 of the image side surface of the third lens 3 satisfies -20mm≤R6≤-10mm; The curvature radius R7 of the object side surface of the fourth lens 4 satisfies -15mm≤R7≤-5mm, and the curvature radius R8 of the image side surface of the fourth lens 4 satisfies -20mm≤R8≤-10mm; The curvature radius R9 of the object side surface of the fifth lens 5 satisfies 15 mm ≤ R9 ≤ 25 mm, and the curvature radius R10 of the image side surface of the fifth lens 5 satisfies -25 mm ≤ R10 ≤ -15 mm; The curvature radius R11 of the object side surface of the sixth lens 6 satisfies 30 mm≤R11≤40 mm, and the curvature radius R12 of the image side surface of the sixth lens 6 satisfies 5 mm≤R12≤15 mm; The curvature radius R13 of the object side surface of the seventh lens 7 satisfies 5mm≤R13≤15mm, and the curvature radius R14 of the image side surface of the seventh lens 7 satisfies -45mm≤R14≤-35mm; The curvature radius R15 of the object side surface of the eighth lens 8 satisfies 35 mm ≤ R15 ≤ 45 mm, and the curvature radius R16 of the image side surface of the eighth lens 8 satisfies -15 mm ≤ R16 ≤ -5 mm; The curvature radius R17 of the object side surface of the ninth lens 9 satisfies -15 mm ≤ R17 ≤ -5 mm, and the curvature radius R18 of the image side surface of the ninth lens 9 satisfies -15 mm ≤ R18 ≤ -5 mm.

[0025] The center thickness of the first lens 1 is 3-4 mm; The center thickness of the second lens 2 is 2-3 mm; The central thickness of the third lens 3 is 3-5 mm; The center thickness of the fourth lens 4 is 3-4 mm; The center thickness of the fifth lens 5 is 2-4 mm; The center thickness of the sixth lens 6 is 1-2 mm; The center thickness of the seventh lens 7 is 2-3 mm; The center thickness of the eighth lens 8 is 1-3 mm; The center thickness of the ninth lens 9 is 1-2 mm.

[0026] The object-side surface and the image-side surface of the first lens 1 are both aspherical surfaces.

[0027] The material of the first lens 1 is HQK3L_CDGM.

[0028] The object-side surface and the image-side surface of the second lens 2 , the third lens 3 , the fourth lens 4 , the fifth lens 5 , the sixth lens 6 , the seventh lens 7 , the eighth lens 8 , and the ninth lens 9 are all spherical surfaces.

[0029] The Abbe coefficients of the first lens 1 and the second lens 2 are greater than 70.

[0030] Example 1 This embodiment provides a visible near-infrared optical system with a small range of focus. The system parameters are as follows: Image-side F-number: 4; field of view: 48.6°-53.5°; working band: 400nm-1100nm, high-definition imaging is achieved through internal focusing; total optical length: 50mm; resolution: 1920×1080, 3.45μm pixel, compatible with high-definition detectors.

[0031] Table 1 below shows the parameters of each optical element in this embodiment: Table 1 Parameters of optical components in Example 1 The focus interval variation of the optical system of this embodiment is shown in Table 2 below: Table 2 Focus interval variation table of Example 1 The aspheric coefficients of the first lens in the optical system of this embodiment are shown in Table 3 below: Table 3 Aspheric coefficients of the first lens in Example 1 Among them, surface 1 and surface 2 in the above table may represent the object plane side and the image plane side of the first lens, surface 3 and surface 4 may represent the object plane side and the image plane side of the second lens, surface 5 and surface 6 may represent the object plane side and the image plane side of the third lens, surface 7 and surface 8 may represent the object plane side and the image plane side of the fourth lens, surface 9 and surface 10 may represent the object plane side and the image plane side of the fifth lens, surface 11 and surface 12 may represent the object plane side and the image plane side of the sixth lens, surface 13 and surface 14 may represent the object plane side and the image plane side of the seventh lens, surface 15 and surface 16 may represent the object plane side and the image plane side of the eighth lens, and surface 17 and surface 18 may represent the object plane side and the image plane side of the ninth lens.

[0032] The thickness of surface 1 can represent the center thickness of the first lens, and the thickness of surface 2 can represent the vertical distance between the image side of the first lens and the object side of the second lens, and the same applies to surfaces 3-18.

[0033] like Figure 3-4The figures show the transfer function curves of the system of this embodiment at infinite object distance and 50mm object distance respectively. The MTF curve represents the comprehensive resolution level of an optical system. This system works in the visible and near-infrared bands. After balancing the performance and aberrations of different object distances, the four-frequency MTF is greater than 0.6@36Lp / mm and the two-frequency MTF is greater than 0.3@72Lp / mm, which makes the system have high resolution characteristics.

[0034] like Figure 5-6 The figures are schematic diagrams of field curvature aberration at infinite object distance and 50mm object distance of the system of this embodiment, respectively. The figure shows that the axial chromatic aberration and astigmatism field curvature are both within ±0.05mm, and the distortion is within -2%. The aberration is well corrected, which is conducive to high-quality imaging.

[0035] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A visible near-infrared optical system with a small-stroke focusing form, characterized in that: A front fixed lens group, a front movable lens group, an intermediate fixed lens group, a rear compensation lens group, a rear fixed lens group and an aperture (10) are sequentially arranged from the object plane to the image plane. The front fixed lens group comprises: A first lens (1) having positive refractive power, wherein both the object side surface and the image side surface are convex; A second lens (2) having negative optical power, wherein the object side surface is convex and the image side surface is concave; The front movable lens group comprises: A third lens (3) having positive refractive power, a concave object-side surface and a convex image-side surface; A fourth lens (4) having negative optical power, wherein the object side surface is concave and the image side surface is convex; The intermediate fixed lens group comprises: A fifth lens (5) having positive refractive power, wherein both the object side surface and the image side surface are convex; The rear compensation lens group comprises: A sixth lens (6) having negative optical power, wherein the object side surface is convex and the image side surface is concave; A seventh lens (7) having positive refractive power, wherein both the object side surface and the image side surface are convex; An eighth lens (8) having positive refractive power, wherein both the object side surface and the image side surface are convex; The rear fixed lens group comprises: The ninth lens (9) has negative optical power, and its object side surface is concave and its image side surface is convex.

2. A visible near-infrared optical system with a small-stroke focusing form according to claim 1, characterized in that: The front movable lens group and the rear compensation lens group are movable groups. During the focusing process, the air gap D1 between the front fixed lens group and the front movable lens group changes in the range of 3.9mm≤D1≤5.6mm, and the air gap D2 between the front movable lens group and the middle fixed lens group changes in the range of 0.3mm≤D2≤2.0mm. The air interval D3 between the intermediate fixed lens group and the rear compensation lens group varies in a range of 3.5 mm ≤ D3 ≤ 4.6 mm, and the air interval D4 between the rear compensation lens group and the rear fixed lens group varies in a range of 1.4 mm ≤ D4 ≤ 2.5 mm.

3. A visible near-infrared optical system with a short-range focusing form according to claim 1 or 2, characterized in that: In the front fixed lens group, the air gap between the first lens (1) and the second lens (2) is 0.7-0.8 mm. In the front moving lens group, the air gap between the third lens (3) and the fourth lens (4) is 1.6-1.8 mm. In the rear compensation lens group, the air gap between the sixth lens (6) and the seventh lens (7) is 0.7-0.8 mm, and the air gap between the seventh lens (7) and the eighth lens (8) is 0.2-0.4 mm. The air gap between the rear fixed lens group and the diaphragm (10) is 11.5-12.0 mm.

4. The visible near-infrared optical system with a small-stroke focusing form according to claim 1, characterized in that: The radius of curvature R1 of the object side surface of the first lens (1) satisfies 355 mm ≤ R1 ≤ 405 mm, and the radius of curvature R2 of the image side surface of the first lens (1) satisfies -45 mm ≤ R2 ≤ -35 ​​mm; The curvature radius R3 of the object side surface of the second lens (2) satisfies 55 mm ≤ R3 ≤ 65 mm, and the curvature radius R4 of the image side surface of the second lens (2) satisfies 5 mm ≤ R4 ≤ 15 mm; The radius of curvature R5 of the object side surface of the third lens (3) satisfies -25 mm ≤ R5 ≤ -15 mm, and the radius of curvature R6 of the image side surface of the third lens (3) satisfies -20 mm ≤ R6 ≤ -10 mm; The curvature radius R7 of the object side surface of the fourth lens (4) satisfies -15 mm ≤ R7 ≤ -5 mm, and the curvature radius R8 of the image side surface of the fourth lens (4) satisfies -20 mm ≤ R8 ≤ -10 mm; The curvature radius R9 of the object side surface of the fifth lens (5) satisfies 15 mm ≤ R9 ≤ 25 mm, and the curvature radius R10 of the image side surface of the fifth lens (5) satisfies -25 mm ≤ R10 ≤ -15 mm; The curvature radius R11 of the object side surface of the sixth lens (6) satisfies 30 mm ≤ R11 ≤ 40 mm, and the curvature radius R12 of the image side surface of the sixth lens (6) satisfies 5 mm ≤ R12 ≤ 15 mm; The curvature radius R13 of the object side surface of the seventh lens (7) satisfies 5 mm ≤ R13 ≤ 15 mm, and the curvature radius R14 of the image side surface of the seventh lens (7) satisfies -45 mm ≤ R14 ≤ -35 ​​mm; The curvature radius R15 of the object side surface of the eighth lens (8) satisfies 35 mm ≤ R15 ≤ 45 mm, and the curvature radius R16 of the image side surface of the eighth lens (8) satisfies -15 mm ≤ R16 ≤ -5 mm; The curvature radius R17 of the object side surface of the ninth lens (9) satisfies -15 mm ≤ R17 ≤ -5 mm, and the curvature radius R18 of the image side surface of the ninth lens (9) satisfies -15 mm ≤ R18 ≤ -5 mm.

5. The visible near-infrared optical system with a small-stroke focusing form according to claim 1, characterized in that: The center thickness of the first lens (1) is 3-4 mm; The center thickness of the second lens (2) is 2-3 mm; The central thickness of the third lens (3) is 3-5 mm; The center thickness of the fourth lens (4) is 3-4 mm; The central thickness of the fifth lens (5) is 2-4 mm; The central thickness of the sixth lens (6) is 1-2 mm; The center thickness of the seventh lens (7) is 2-3 mm; The central thickness of the eighth lens (8) is 1-3 mm; The center thickness of the ninth lens (9) is 1-2 mm.

6. The visible near-infrared optical system with a small-stroke focusing form according to claim 1, characterized in that: The object side surface and the image side surface of the first lens (1) are both aspherical surfaces.

7. The visible near-infrared optical system with a short-range focusing form according to claim 1, characterized in that: The material of the first lens (1) is HQK3L_CDGM.

8. The visible near-infrared optical system with a short-range focusing form according to claim 1, characterized in that: The object side surfaces and image side surfaces of the second lens (2), the third lens (3), the fourth lens (4), the fifth lens (5), the sixth lens (6), the seventh lens (7), the eighth lens (8) and the ninth lens (9) are all spherical surfaces.

9. The visible near-infrared optical system with a short-range focusing form according to claim 1, characterized in that: The dispersion coefficients of the first lens (1) and the second lens (2) are greater than 70.

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