Long-working-distance fixed-magnification lens and optical system thereof
By designing the optical system of a fixed-magnification lens with a long working distance, and using a specific lens combination and high refractive index materials, the problem of low imaging magnification at long distances in fixed-focus industrial lenses has been solved, achieving higher imaging accuracy and magnification, making it suitable for high-precision inspection.
Patent Information
- Application Number
- CN202520578140.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2035-03-28
AI Technical Summary
Existing fixed-focus industrial lenses have low magnification at long working distances, resulting in insufficient accuracy and failing to meet the requirements of high-precision inspection.
Design an optical system for a fixed-magnification lens with a long working distance, including a front group A and a rear group B. The lens combination satisfies a specific focal length relationship, and high-refractive-index glass and a novel achromatic cemented lens are used. The lens materials and structure are optimized to improve image quality.
It achieves greater magnification and higher imaging accuracy when shooting at long distances, making it suitable for high-precision detection at long distances.
Smart Images
Figure CN223897702U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of optical device technology, and in particular to a long working distance fixed magnification lens and its optical system. Background Technology
[0002] With the development of industrial automation, industrial lenses are widely used in machine vision inspection, such as product measurement and defect detection in semiconductors, 3C electronics, new energy, packaging and printing, intelligent logistics, automobile manufacturing, and pharmaceuticals. The ever-increasing demands for inspection accuracy and the widespread application of high-resolution cameras are placing new requirements on the imaging quality and performance of industrial lenses.
[0003] Currently, most fixed-focus industrial lenses on the market have focal lengths below 75mm, resulting in low magnification and insufficient accuracy when shooting at long working distances. Therefore, it is necessary to improve existing industrial lenses to meet the special application requirements of high-precision imaging at long working distances.
[0004] The above information is provided as background information only to aid in understanding this disclosure and does not constitute an assertion or admission that any of the above content can be used as prior art relative to this disclosure. Utility Model Content
[0005] The purpose of this invention is to provide a long working distance fixed magnification lens and its optical system to solve or at least partially solve the technical problems existing in the prior art.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, this utility model provides an optical system for a fixed-magnification lens with a long working distance, comprising a front group A and a rear group B arranged sequentially from the object side to the image side;
[0008] The front group A includes a first lens G1 with positive optical power; a second lens G2 with positive optical power; and a third lens G3 with negative optical power.
[0009] The rear group B includes a fourth lens G4 with positive optical power; a fifth lens G5 with negative optical power; and a sixth lens G6 with positive optical power.
[0010] An aperture S is provided between the third lens G3 and the fourth lens G4;
[0011] The combined focal length of the first group A is f A The combined focal length f of the latter group B B f A and f B The relation is satisfied: 0.75 < |f A / f B|<1.25.
[0012] Optionally, the focal length of the first lens G1 is f1, and the combined focal length with the front group A is f1. A The following relationship must be satisfied: 0.3 < |f1 / f A |<0.8;
[0013] The second lens G2 and the third lens G3 are cemented together to form a first cemented lens U1 with negative optical power; the focal length of the first cemented lens U1 is f. U1 f U1 with f A The relation is satisfied: 0.37 < |f U1 / f A |<0.87;
[0014] Optionally, the fourth lens G4 and the fifth lens G5 form a second cemented lens U2 with negative optical power; the focal length of the second cemented lens U2 is f. U2 f U2 with f B Satisfies the relation: 0.6 < |f U2 / f B |<1.0;
[0015] The focal length of the sixth lens G6 is f6, and f6 is the same as f B The relation is satisfied: 0.25 < |f6 / f B |<0.75.
[0016] Optionally, the sixth lens G6 has a refractive index of n6 and an Abbe number of v6, satisfying the relation: 1.47 <n6<1.55;70<v6<85。
[0017] Optionally, in the front group A, the first lens G1 and the second lens G2 are both biconvex lenses, and the third lens G3 is a biconcave lens.
[0018] In the rear group B, the fourth lens G4 is a meniscus lens, the fifth lens G5 is a biconcave lens or a plano-concave lens, and the sixth lens G6 is a biconvex lens.
[0019] Optionally, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all glass spherical lenses.
[0020] Optionally, the optical axes of the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all on a predetermined optical axis;
[0021] Optionally, the aperture of the stop S is a circular hole, and the center of the circular hole is on the predetermined optical axis.
[0022] Secondly, this utility model provides a long working distance fixed magnification lens, including the optical system of a long working distance fixed magnification lens as described above.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] This utility model provides a long working distance fixed magnification lens with a focal length much greater than that of ordinary fixed focal length industrial lenses. When shooting at long distances, it has a greater magnification and higher precision than ordinary fixed focal length industrial lenses, making it more suitable for long-distance, high-precision detection applications.
[0025] This invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of this invention. Attached Figure Description
[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0027] Figure 1 This is a schematic diagram of the optical system of a fixed-magnification lens with a long working distance provided in Embodiment 1 of this utility model.
[0028] Figure 2 The MTF curve of an optical system for a fixed-magnification lens with a long working distance provided in Embodiment 1 of this utility model.
[0029] Figure 3 The distortion diagram is provided for an optical system of a fixed-magnification lens with a long working distance according to Embodiment 2 of this utility model.
[0030] Figure 4 MTF curve of an optical system for a fixed-magnification lens with a long working distance provided in Embodiment 2 of this utility model. Detailed Implementation
[0031] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.
[0032] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.
[0033] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.
[0034] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.
[0035] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.
[0036] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.
[0037] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.
[0038] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.
[0039] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.
[0040] Example 1:
[0041] Please see Figure 1 , Figure 1 This is a schematic diagram of the optical system of a fixed-magnification lens with a long working distance provided in Embodiment 1 of this utility model.
[0042] like Figure 1 As shown, the optical system includes:
[0043] This includes setting up a front group A and a rear group B sequentially from the object side to the image side;
[0044] The front group A includes a first lens G1 with positive optical power; a second lens G2 with positive optical power; and a third lens G3 with negative optical power.
[0045] The rear group B includes a fourth lens G4 with positive optical power; a fifth lens G5 with negative optical power; and a sixth lens G6 with positive optical power.
[0046] An aperture S is provided between the third lens G3 and the fourth lens G4;
[0047] The combined focal length of the first group A is f A The combined focal length f of the rear group B B f A and f BSatisfy the relational expression: 0.75 < |f A / f B | < 1.25.
[0048] Specifically, the focal length of the first lens G1 is f1, and the combined focal length f of the first lens G1 and the front group A A Satisfy the following relational expression: 0.3 < |f1 / f A | < 0.8;
[0049] The second lens G2 and the third lens G3 are cemented to form a first cemented lens U1 with a negative optical power; the focal length of the first cemented lens U1 is f U1 f U1 and f A Satisfy the relational expression: 0.37 < |f U1 / f A | < 0.87;
[0050] It should be noted that in this embodiment, the first lens G1 is made of a high refractive index glass material; the first lens G1 with a high refractive index can reduce the curvature of the lens, thereby reducing the high-order aberration and the tolerance sensitivity;
[0051] The cemented lens U1 has a relatively large central thickness, which can correct the chromatic aberration of the system and is beneficial to correcting the field curvature and astigmatism of the system.
[0052] Specifically, the fourth lens G4 and the fifth lens G5 form a second cemented lens U2 with a negative optical power; the focal length of the second cemented lens U2 is f U2 f U2 and f B Satisfy the relational expression: 0.6 < |f U2 / f B | < 1.0;
[0053] The focal length of the sixth lens G6 is f6, and f6 and f B Satisfy the relational expression: 0.25 < |f6 / f B | < 0.75.
[0054] It should be noted that in this embodiment, the second cemented lens U2 is a new type of achromatic cemented lens. On the one hand, this lens is beneficial to balancing the field curvature of the system. On the other hand, it can also use the residual spherical aberration to balance the high-order aberration, achieving a good imaging effect with a smaller number of lenses.
[0055] Furthermore, the refractive index of the sixth lens G6 is n6, and the Abbe number is v6, which satisfy the relational expression: 1.47 < n6 < 1.55; 70 < v6 < 85. By satisfying the above refractive index and dispersion, it is beneficial to balance spherical aberration, coma, and distortion.
[0056] Specifically, in this embodiment, in the front group A, the first lens G1 and the second lens G2 are both biconvex lenses, and the third lens G3 is a biconcave lens.
[0057] In the rear group B, the fourth lens G4 is a meniscus lens, the fifth lens G5 is a biconcave lens or a plano-concave lens, and the sixth lens G6 is a biconvex lens.
[0058] More specifically, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all glass spherical lenses.
[0059] In this embodiment, the optical axes of the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all on a predetermined optical axis.
[0060] The aperture of stop S is a circular hole, and the center of the circular hole is on the predetermined optical axis.
[0061] Understandably, the aperture value of stop S needs to be adjusted according to the specific application scenario.
[0062] To verify whether the optical system described above meets the design objectives, the following is a specific test example based on the above settings in this embodiment:
[0063] In this test example, the lens data of the optical system are shown in Table 1 below:
[0064] Table 1
[0065]
[0066]
[0067] It should be noted that in Table 1, "front surface" corresponds to... Figure 1 The left surface of the lens or lens group corresponds to the middle surface, while the rear surface corresponds to the left surface. Figure 1 The right side surface of the corresponding lens or lens group; or it can be understood as: the object surface in Figure 1 On the left, the image plane (or image surface) is... Figure 1 On the right side, the surface closer to the object is called the "front surface", and the surface closer to the image is called the "back surface".
[0068] In this test example, the combined focal length of the first group A is f. A =304mm; the combined focal length of the rear group B is f B =275mm; the focal length of the first lens G1 is f1 = 158mm; the focal length of the first cemented lens U1 is f U1 = -172mm; the focal length of the second cemented lens U2 is f U2= -223mm; the focal length of the sixth lens G6 is f6 = 129mm.
[0069] Substituting the above values into the respective relations, we obtain:
[0070] |f A / f B |=1.105,|f1 / f A |=0.520,|f U1 / f A |=0.566,|f U2 / f B |=0.811,|f6 / f B |=0.469.
[0071] Therefore, the relevant relational expression in this embodiment is satisfied, namely:
[0072] 0.75<|f A / f B |<1.25, 0.3<|f1 / f A |<0.8, 0.37<|f U1 / f A |<0.87, 0.6<|f U2 / f B |<1.0, 0.25<|f6 / f B |<0.75.
[0073] Please refer to Figure 2 Figure 2 The MTF (Modulation Transfer Function) curve of the optical system of a fixed-magnification lens with a long working distance provided in Embodiment 1 of this utility model.
[0074] The lens optical system shown in this test example has a focal length f' of 194mm and a magnification of 0.4X at a working distance of 700mm.
[0075] In summary, the optical system of the long working distance fixed-magnification lens provided in this embodiment has a focal length much greater than that of ordinary fixed-focus industrial lenses. When shooting at long distances, it has a greater magnification and higher precision than ordinary fixed-focus industrial lenses, making it more suitable for long-distance, high-precision detection applications.
[0076] Example 2:
[0077] Please see Figure 3 , Figure 3 This is a schematic diagram of the optical system of a fixed-magnification lens with a long working distance provided in Embodiment 2 of this utility model.
[0078] like Figure 3 As shown, the optical system includes:
[0079] This includes setting up a front group A and a rear group B sequentially from the object side to the image side;
[0080] The front group A includes a first lens G1 with positive optical power; a second lens G2 with positive optical power; and a third lens G3 with negative optical power.
[0081] The rear group B includes a fourth lens G4 with positive optical power; a fifth lens G5 with negative optical power; and a sixth lens G6 with positive optical power.
[0082] An aperture S is provided between the third lens G3 and the fourth lens G4;
[0083] The combined focal length of the first group A is f A The combined focal length f of the rear group B B f A and f B The relation is satisfied: 0.75 < |f A / f B |<1.25.
[0084] Specifically, the focal length of the first lens G1 is f1, and the combined focal length with the front group A is f1. A The following relationship must be satisfied: 0.3 < |f1 / f A |<0.8;
[0085] The second lens G2 and the third lens G3 are cemented together to form a first cemented lens U1 with negative optical power; the focal length of the first cemented lens U1 is f. U1 f U1 with f A The relation is satisfied: 0.37 < |f U1 / f A |<0.87;
[0086] It should be noted that in this embodiment, the first lens G1 is made of high refractive index glass; the high refractive index of the first lens G1 can reduce the curvature of the lens, thereby reducing higher-order aberrations and lowering tolerance sensitivity.
[0087] The cemented lens U1 has a large center thickness, which can help correct system chromatic aberration, as well as system field curvature and astigmatism.
[0088] Specifically, the fourth lens G4 and the fifth lens G5 form a second cemented lens U2 with negative optical power; the focal length of the second cemented lens U2 is f. U2 f U2 with f B Satisfies the relation: 0.6 < |f U2 / f B< 1.0;
[0089] The focal length of the sixth lens G6 is f6, and f6 and f B Satisfy the relational expression: 0.25 < |f6 / f B | < 0.75.
[0090] It should be noted that in this embodiment, the second cemented lens U2 uses a new type of achromatic cemented lens. On the one hand, this kind of lens is beneficial to balance the field curvature of the system. On the other hand, it can also use the residual spherical aberration to balance the higher-order aberrations, so as to achieve good imaging effects with fewer lenses.
[0091] Furthermore, the refractive index of the sixth lens G6 is n6, and the Abbe number is v6, which satisfy the relational expression: 1.47 < n6 < 1.55; 70 < v6 < 85. By satisfying the above refractive index and dispersion, it is beneficial to balance spherical aberration, coma and distortion.
[0092] Specifically, in this embodiment, in the front group A, the first lens G1 and the second lens G2 are both biconvex lenses, and the third lens G3 is a biconcave lens;
[0093] In the rear group B, the fourth lens G4 is a meniscus lens, the fifth lens G5 is a biconcave lens or a plano-concave lens, and the sixth lens G6 is a biconvex lens.
[0094] More specifically, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5 and the sixth lens G6 are all glass spherical lenses.
[0095] In this embodiment, the optical axes of the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5 and the sixth lens G6 are all on the predetermined optical axis;
[0096] The aperture of the aperture stop S is a circular hole, and the center of the circular hole is on the predetermined optical axis.
[0097] It can be understood that the aperture value of the aperture stop S needs to be adjusted correspondingly according to the specific application scenario.
[0098] To verify whether the above optical system meets the design purpose, the following is a specific test example given according to the above settings of this embodiment:
[0099] In this test example, the data of each lens of the optical system are shown in Table 2 below:
[0100] Table 2
[0101] surface Radius (mm) Thickness (mm) Refractive index Abbe number G1 front surface 418.2 8.0 1.85 - G1 rear surface -212.2 16.1 G2 front surface 44.3 12.4 1.5 80 G2 and G3 adhesive surfaces -130.6 18.0 1.75 - G3 rear surface 40.0 11.8 Aperture S ∞ 3.5 G4 front surface -118.1 10.0 1.80 - G4 and G5 adhesive surfaces -24.9 2.4 1.75 - G5 rear surface ∞ 12.1 G6 front surface 396.5 5.0 1.5 80 G6 rear surface -89.7 226 Image / <000039The left surface of the lens or lens group corresponds to the middle surface, while the rear surface corresponds to the left surface. Figure 3 The right side surface of the corresponding lens or lens group; or it can be understood as: the object surface in Figure 3 On the left, the image plane (or image surface) is... Figure 3 On the right side, the surface closer to the object is called the "front surface", and the surface closer to the image is called the "back surface".
[0103] In this test example, the combined focal length of the first group A is f. A =318mm; the combined focal length of the rear group B is f B =338mm; the focal length of the first lens G1 is f1 = 165mm; the focal length of the first cemented lens U1 is f U1 = -174mm; the focal length of the second cemented lens U2 is f U2 = -215mm; the focal length of the sixth lens G6 is f6 = 146mm.
[0104] Substituting the above values into the respective relations, we obtain:
[0105] |f A / f B |=0.941,|f1 / f A |=0.519,|f U1 / f A |=0.547,|f U2 / f B |=0.636,|f6 / f B |=0.432.
[0106] Therefore, the relevant relational expression in this embodiment is satisfied, namely:
[0107] 0.75<|f A / f B |<1.25, 0.3<|f1 / f A |<0.8, 0.37<|f U1 / f A |<0.87, 0.6<|f U2 / f B |<1.0, 0.25<|f6 / f B |<0.75.
[0108] Please refer to Figure 4 , Figure 4 MTF curve of an optical system for a fixed-magnification lens with a long working distance provided in Embodiment 2 of this utility model;
[0109] The lens optical system shown in this embodiment has a focal length f' of 232mm, which is much larger than the focal length of commonly used fixed-focus industrial lenses. At a working distance of 800mm, the magnification reaches 0.42X, making it suitable for long-distance, high-precision inspection applications.
[0110] Example 3:
[0111] This embodiment provides a fixed-magnification lens with a long working distance, including the optical system of a fixed-magnification lens with a long working distance as described in Embodiment 1 or Embodiment 2.
[0112] Since the optical system has been described in detail in the above embodiments, it will not be repeated in this embodiment.
[0113] In summary, the long working distance fixed-magnification lens provided in this embodiment has a focal length much greater than that of ordinary fixed-focus industrial lenses. When shooting at long distances, it has a greater magnification and higher precision than ordinary fixed-focus industrial lenses, making it more suitable for long-distance, high-precision detection applications.
[0114] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. An optical system for a fixed-magnification lens with a long working distance, characterized in that, This includes setting up a front group A and a rear group B sequentially from the object side to the image side; The front group A includes a first lens G1 with positive optical power; a second lens G2 with positive optical power; and a third lens G3 with negative optical power. The rear group B includes a fourth lens G4 with positive optical power; a fifth lens G5 with negative optical power; and a sixth lens G6 with positive optical power. An aperture S is provided between the third lens G3 and the fourth lens G4; The combined focal length of the first group A is f A The combined focal length f of the rear group B B f A and f B The relation is satisfied: 0.75 < |f A / f B |<1.
25.
2. The optical system of a long working distance fixed-magnification lens according to claim 1, characterized in that, The focal length of the first lens G1 is f1, and the combined focal length with the front group A is f1. A The following relationship must be satisfied: 0.3 < |f1 / f A |<0.8; The second lens G2 and the third lens G3 are cemented together to form a first cemented lens U1 with negative optical power; the focal length of the first cemented lens U1 is f. U1 f U1 with f A The relation is satisfied: 0.37 < |f U1 / f A |<0.
87.
3. The optical system of a long working distance fixed-magnification lens according to claim 2, characterized in that, The fourth lens G4 and the fifth lens G5 together form a second cemented lens U2 with negative optical power; the focal length of the second cemented lens U2 is f. U2 f U2 with f B Satisfies the relation: 0.6 < |f U2 / f B |<1.0; The focal length of the sixth lens G6 is f6, and f6 is the same as f B The relation is satisfied: 0.25 < |f6 / f B |<0.
75.
4. The optical system of a fixed-magnification lens with a long working distance according to claim 3, characterized in that, The sixth lens G6 has a refractive index of n6 and an Abbe number of v6, satisfying the relation: 1.47 <n6<1.55;70<v6<85。 5. The optical system of a fixed-magnification lens with a long working distance according to claim 3, characterized in that, In the first group A, the first lens G1 and the second lens G2 are both biconvex lenses, and the third lens G3 is a biconcave lens. In the rear group B, the fourth lens G4 is a meniscus lens, the fifth lens G5 is a biconcave lens or a plano-concave lens, and the sixth lens G6 is a biconvex lens.
6. The optical system of a long working distance fixed-magnification lens according to claim 5, characterized in that, The first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all glass spherical lenses.
7. The optical system of a fixed-magnification lens with a long working distance according to claim 1, characterized in that, The optical axes of the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, and the sixth lens G6 are all on a predetermined optical axis.
8. The optical system of a fixed-magnification lens with a long working distance according to claim 7, characterized in that, The aperture of the stop S is a circular hole, and the center of the circular hole is on the predetermined optical axis.
9. A fixed-magnification lens with a long working distance, characterized in that, The optical system includes a fixed-magnification lens with a long working distance as described in any one of claims 1-8.