Compact long-working-distance fixed-magnification lens and optical system thereof

Abstract

The invention relates to the technical field of optical imaging, and discloses a compact long-working-distance fixed-magnification lens and an optical system thereof. The optical system comprises a front group with positive focal power, a middle group with negative focal power, a diaphragm and a rear group with positive focal power, the focal length f of the optical system, the optical back focal length BFL, the focal length fS1 of the front group, the focal length fS2 of the middle group and the focal length fS3 of the back group respectively meet the relational expression of 0.4 lt; fS1 / flt; 0.75, 1.1 lt, 0.75, 1.1 lt; fS2 / flt; 1.7, 1.50 lt, 1.7, 1.50 lt; fS3 / flt; 8.00, 0.05 lt, 0.00, 0.00, 0.00; bFL / flt; and 0.35. The long-working-distance fixed-magnification lens with high resolution is realized, the amplification factor of the lens is 0.94 X, the highest resolution can reach 100lp / mm, the lens can be matched with a 5-micron pixel chip, the maximum target surface size is 1.2 '', and meanwhile, the lens has low distortion performance.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a compact long-working-distance fixed-magnification lens and an optical system thereof. Background Art

[0002] With the rapid development of industrial inspection, machine vision, and precision instrumentation, long working distance lenses are widely used in high-precision imaging optical systems because they can achieve long-distance, high-precision imaging without interfering with the object being measured or avoiding environmental interference. Fixed-magnification lenses have significant advantages in standardized inspection scenarios due to their simple structure and stable imaging. However, the lack of compatibility between long working distance and compact design in existing technologies has become a key bottleneck restricting the widespread application of such lenses. Especially at high magnifications (≥0.9X), the long working distance often restricts the numerical aperture and resolution of the lens, making it difficult to meet micron-level inspection requirements.

[0003] Existing industrial fixed-magnification lenses on the market face three core challenges: the spatial conflict between long working distance and compact size, the difficulty of correcting aberrations within the constraints of fixed magnification, and the dilemma of balancing high resolution and low distortion. These issues severely restrict device integration and inspection accuracy. Therefore, the development of fixed-magnification optical lenses with long working distance, high resolution, and low distortion is even more urgent.

[0004] The above information is presented as background information only to assist with an understanding of the present disclosure and is not a determination or admission that any of the above may be applicable as prior art with respect to the present disclosure. Summary of the Invention

[0005] The object of the present invention is to provide a compact long-working-distance fixed-magnification lens and an optical system thereof, so as to solve or at least partially solve the technical problems existing in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an optical system of a compact long-working-distance fixed-magnification lens, comprising a front lens group with positive optical power, a middle lens group with negative optical power, an aperture, and a rear lens group with positive optical power, which are arranged in sequence from the object side to the image side;

[0008] The focal length of the optical system is f, the optical back focus of the optical system is BFL, and the focal length of the front group is f S1 , the focal length of the middle group is f S2 , the focal length of the rear group is f S3 , respectively satisfying the relationship:

[0009] 0.4<|f S1 / f|<0.75, 1.1<|f S2 / f|<1.7, 1.50<|f S3 / f|<8.00, 0.05<|BFL / f|<0.35.

[0010] Optionally, the front group includes a first lens having positive optical power, and the first lens is a biconvex lens;

[0011] A distance between a front surface vertex of the first lens and a rear surface vertex of the rear lens group is L, and L and f satisfy the relationship: 0.7<|L / f|<1.50.

[0012] Optionally, the middle lens group includes a second lens having negative power, a third lens having positive power, a fourth lens having negative power, a fifth lens having positive power, and a sixth lens having negative power; the second lens, the third lens, and the fourth lens are cemented into a first cemented lens group having negative power, and the fifth lens and the sixth lens are cemented into a second cemented lens group having positive power;

[0013] The focal length of the first cemented lens group is f U1 , f U1 and f satisfy the relationship: 0.65<|f U1 / f|<1.15;

[0014] The focal length of the second cemented lens group is f U2 , f U2 and f satisfy the relationship: 1.8<|f U2 / f|<3.80.

[0015] Optionally, the second lens is a meniscus lens, the third lens and the fifth lens are both biconvex lenses, the fourth lens is a meniscus lens or a biconcave lens, and the sixth lens is a biconcave lens.

[0016] Optionally, the rear lens group includes a seventh lens having negative focal power, an eighth lens having positive focal power, a ninth lens having negative focal power, and a tenth lens having positive focal power; the seventh lens and the eighth lens are cemented into a third cemented lens having positive focal power;

[0017] The focal length of the third cemented lens group is f U3 , f U3 and f satisfy the relationship: 1.00<|f U3 / f|<2.50;

[0018] The focal length of the ninth lens is f G9 , f G9 Satisfies the relationship with f: 0.18<|f G9 / f|<0.40;

[0019] The focal length of the tenth lens is f G10 , fG10 Satisfies the relationship with f: 0.25<|f G10 / f|<0.60.

[0020] Optionally, the seventh lens and the seventh lens are both biconcave lenses, the eighth lens is a biconvex lens; and the tenth lens is a meniscus lens or a plano-convex lens.

[0021] Optionally, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens and the tenth lens are all spherical lenses, and the optical axes of all the spherical lenses coincide with the predetermined optical axis.

[0022] Optionally, the half-image height of the optical system is y';

[0023] y' and f satisfy the relationship: |y' / f|<0.12.

[0024] Optionally, the aperture of the diaphragm is a circular hole, the center of the circular hole is on the predetermined optical axis; the adjustment range of the aperture value of the diaphragm is F2.8 to F16.

[0025] In a second aspect, the present invention provides a compact long working distance fixed magnification lens, comprising an optical system of the compact long working distance fixed magnification lens as described above;

[0026] The compact long working distance fixed magnification lens has a magnification of 0.94X.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The optical system of the long working distance fixed magnification lens provided by the present invention has a lens magnification of 0.94X, a maximum imaging surface of φ19.2mm, a maximum resolution of up to 100lp / mm, can match a 5-micron pixel chip, and when the corresponding maximum chip size is reached, its pixels can reach 7 million pixels. The maximum optical distortion of the full field of view can be less than 0.10%, and the working distance can reach 264mm.

[0029] The present invention has other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain certain principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 The present invention is a schematic structural diagram of an optical system of a compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention.

[0032] Figure 2 The optical distortion curve of the optical system of a compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention is shown.

[0033] Figure 3 The diagram is a structural diagram of an optical system of another compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention.

[0034] Figure 4 This is an optical distortion curve of an optical system of another compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to explain in detail the possible application scenarios, technical principles, specific solutions that can be implemented, and the purpose and effects of this application, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0036] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0037] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0038] In the description of this application, the term "and / or" is used to describe a logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and both A and B exist. In addition, the character " / " in this document generally indicates that the objects before and after are in a logical "or" relationship.

[0039] In this application, terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, priority or sequence relationship between these entities or operations.

[0040] Without further limitations, in this application, the words "include", "comprise", "have" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those defined elements, but also other elements not explicitly listed, or elements inherent to such process, method or product.

[0041] Consistent with the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceed" are understood to exclude the number itself; expressions such as "above," "below," and "within" are understood to include the number itself. Furthermore, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this manner, such as "multiple groups," "multiple times," etc., unless otherwise specifically defined.

[0042] In the description of the embodiments of the present application, the space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating 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, it should not be understood as a limitation on the embodiments of the present application.

[0043] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms "installed", "connected", "connected", "fixed", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated 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 elements or the interaction relationship between two elements. For those skilled in the art of the present application, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] Example 1:

[0045] See also Figure 1 , Figure 1 1 is a schematic structural diagram of an optical system of a compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention;

[0046] like Figure 1 As shown, the optical system includes a front group S1 with positive optical power, a middle group S2 with negative optical power, an aperture A0, and a rear group S3 with positive optical power, which are arranged in sequence from the object side to the image side;

[0047] The focal length of the optical system is f, the optical back focus of the optical system is BFL, and the focal length of the front group S1 is f S1 , the focal length of the middle group S2 is f S2 , the focal length of the rear group S3 is f S3 , respectively satisfying the relationship:

[0048] 0.4<|f S1 / f|<0.75, 1.1<|f S2 / f|<1.7, 1.50<|f S3 / f|<8.00, 0.05<|BFL / f|<0.35.

[0049] Furthermore, the half-image height of the optical system is y';

[0050] y' and f satisfy the relationship: |y' / f|<0.12.

[0051] Specifically, the front group S1 includes a first lens G1 having positive refractive power, and the first lens G1 is a biconvex lens;

[0052] For the sake of convenience, in this embodiment, the front surface of a lens or lens group refers to the surface of the lens or lens group close to the object side, that is, Figure 1 The left side surface of the middle lens or lens group; correspondingly, the rear surface of the lens or lens group refers to the side surface of the lens or lens group close to the image side, that is, Figure 1 The right side surface of the middle lens or lens group.

[0053] In this embodiment, the front surface of the first lens G1 ( Figure 1 From the vertex of the left side of the first lens G1 to the rear surface of the rear group S3 ( Figure 1 The distance between the vertex of the ninth lens element G9 and the right side surface of the ninth lens element G9 is L, and L and f satisfy the relationship: 0.7<|L / f|<1.50.

[0054] Specifically, the middle lens group S2 includes a second lens group G2 with negative focal power, a third lens group G3 with positive focal power, a fourth lens group G4 with negative focal power, a fifth lens group G5 with positive focal power, and a sixth lens group G6 with negative focal power. The second lens G2, the third lens G3, and the fourth lens G4 are cemented to form a first cemented lens group U1 with negative focal power, and the fifth lens G5 and the sixth lens G6 are cemented to form a second cemented lens group U2 with positive focal power.

[0055] The focal length of the first cemented lens group U1 is f U1 , f U1 and f satisfy the relationship: 0.65<|f U1 / f|<1.15;

[0056] The focal length of the second cemented lens group U2 is f U2 , f U2 and f satisfy the relationship: 1.8<|f U2 / f|<3.80.

[0057] Specifically, the second lens G2 is a meniscus lens, the third lens G3 and the fifth lens G5 are both biconvex lenses, the fourth lens G4 is a meniscus lens or a biconcave lens, and the sixth lens G6 is a biconcave lens.

[0058] Specifically, the rear group S3 includes a seventh lens element G7 having negative refractive power, an eighth lens element G8 having positive refractive power, a ninth lens element G9 having negative refractive power, and a tenth lens element G10 having positive refractive power. The seventh lens G7 and the eighth lens G8 are cemented together to form a third cemented lens U3 having positive refractive power.

[0059] The focal length of the third cemented lens group U3 is f U3 , f U3 and f satisfy the relationship: 1.00<|f U3 / f|<2.50;

[0060] The focal length of the ninth lens G9 is f G9 , f G9 Satisfies the relationship with f: 0.18<|f G9 / f|<0.40;

[0061] The focal length of the tenth lens G10 is f G10 , fG10 Satisfies the relationship with f: 0.25<|f G10 / f|<0.60.

[0062] Specifically, the seventh lens G7 and the seventh lens G9 are both biconcave lenses, the eighth lens G8 is a biconvex lens, and the tenth lens G10 is a meniscus lens or a plano-convex lens.

[0063] Specifically, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9 and the tenth lens G10 are all spherical lenses, and the optical axes of all the spherical lenses coincide with the predetermined optical axis.

[0064] Specifically, the aperture of the diaphragm A0 is a circular hole, the center of which is on a predetermined optical axis; the adjustment range of the aperture value of the diaphragm A0 is F2.8 to F16.

[0065] More specifically, the aperture of the aperture A0 is set as a circular hole, the center of which is on the predetermined optical axis;

[0066] In this embodiment, the aperture value of the aperture A0 can be adjusted, and the adjustment range of the aperture value is F2.8 to F16.

[0067] The following are specific application examples of optical systems using the above structure:

[0068] Example 1:

[0069] In this example, the relevant data of the optical system are shown in Table 1;

[0070] Table 1

[0071]

[0072]

[0073] It should be noted that in Table 1, the “front surface” corresponds to Figure 1 The left side surface of the lens or lens group corresponds to the "back surface" Figure 1 The center corresponds to the right side surface of the lens or lens group; that is, the "front" corresponds to Figure 1 On the left side, "back" corresponds to Figure 1 on the right side.

[0074] In this example, the focal length f of the optical system is 152.27 mm, the object side numerical aperture NA = 0.06, and the focal length f of the front group S1 is S1 =80.18mm, focal length f of center group S2 S2 =-209.60mm, focal length f of rear group S3 S3=1010.07mm, the distance L from the front vertex of the first lens G1 to the imaging plane = 171.84mm, the optical back focus BFL = 23.12mm, the half-image height y' = 9.66mm, the focal length f of the first cemented lens group U1 =-155.00mm, the focal length of the second cemented lens group f U2 =457.64mm, the focal length of the third cemented lens group f U3 =252.89mm, the focal length of the ninth lens G9 is f G9 =-40.00mm, the focal length f of the tenth lens G10 G10 =75.06mm.

[0075] Substituting the above values ​​into the corresponding equations, we can obtain:

[0076] |f S1 / f|=0.53;|f S2 / f|=1.38;|f S3 / f|=6.63;|L / f|=1.13;|BFL / f|=0.15;|y' / f|=0.06;|f U1 / f|=1.02;|f U2 / f|=3.01;|f U3 / f|=1.66;|f G9 / f|=0.26;|f G10 / f|=0.49.

[0077] The obtained values ​​satisfy the respective relationships, as shown below:

[0078] 0.4<|f S1 / f|<0.75; 1.1<|f S2 / f|<1.7; 1.50<|f S3 / f|<8.00; 0.7<|L / f|<1.50; 0.05<|BFL / f|<0.60; |y' / f|<0.12; 0.65<|f U1 / f|<1.15;1.8<|f U2 / f|<3.80;

[0079] 1.00<|f U3 / f|<2.50;0.18<|f G9 / f|<0.40;0.25<|f G10 / f|<0.60.

[0080] Please continue to refer to Figure 2 , Figure 2is an optical distortion curve of an optical system of a compact long working distance fixed magnification lens provided by an embodiment of the present invention, such as Figure 2 As shown, the maximum optical distortion within the entire field of view is less than 0.10%.

[0081] Example 2:

[0082] Please refer to Figure 3 , Figure 3 The diagram is a structural diagram of an optical system of another compact long-working-distance fixed-magnification lens provided by an embodiment of the present invention.

[0083] In this example, the relevant data of the optical system are shown in Table II;

[0084] Table 2

[0085]

[0086]

[0087] It should be noted that in Table 2, the “front surface” corresponds to Figure 3 The left side surface of the lens or lens group corresponds to the "back surface" Figure 3 The center corresponds to the right side surface of the lens or lens group; that is, the "front" corresponds to Figure 3 On the left side, "back" corresponds to Figure 3 on the right side.

[0088] In this example, the focal length f of the optical system is 168.09 mm, the object side numerical aperture NA = 0.06, and the focal length f of the front group S1 is S1 =89.99mm, focal length f of center group S2 S2 =-219.11mm, focal length f of rear group S3 S3 =369.06mm, the distance from the front surface vertex of the first lens G1 to the imaging plane L = 181.30mm, the optical back focus BFL = 13.060mm, the half-image height y' = 9.66mm, the focal length f of the first cemented lens group U1 =-155.06mm, the focal length of the second cemented lens group f U2 =401.56mm, the focal length of the third cemented lens group f U3 =213.11mm, the focal length of the ninth lens G9 is f G9 =-40.00mm, the focal length f of the tenth lens G10 G10 =67.92mm.

[0089] Substituting the above values ​​into the corresponding equations, we can obtain:

[0090] |f S1 / f|=0.54;|f S2 / f|=1.30;|f S3 / f|=2.20;|L / f|=1.08;|BFL / f|=0.08;|y' / f|=0.06;|f U1 / f|=0.92;|f U2 / f|=2.39;|f U3 / f|=1.27;|f G9 / f|=0.24;|f G10 / f|=0.40.

[0091] The obtained values ​​satisfy the respective relationships, as shown below:

[0092] 0.4<|f S1 / f|<0.75; 1.1<|f S2 / f|<1.7; 1.50<|f S3 / f|<8.00; 0.7<|L / f|<1.50; 0.05<|BFL / f|<0.60; |y' / f|<0.12; 0.65<|f U1 / f|<1.15;1.8<|f U2 / f|<3.80;

[0093] 1.00<|f U3 / f|<2.50;0.18<|f G9 / f|<0.40;0.25<|f G10 / f|<0.60.

[0094] Please continue to refer to Figure 4 , Figure 4 is an optical distortion curve of another optical system of a compact long working distance fixed magnification lens provided by an embodiment of the present invention, such as Figure 4 As shown, the maximum optical distortion within the entire field of view is less than 0.12%.

[0095] This embodiment uses the above-mentioned structure to realize an optical system of a fixed-magnification lens with low distortion and high resolution. The object-side NA number is 0.06, the lens magnification is 0.94X, the maximum imaging surface is φ19.2mm, the maximum resolution can reach 100lp / mm, and it can match a 5-micron pixel chip. At the corresponding maximum chip size, its pixels can reach 7 million pixels, and the maximum optical distortion of the entire field of view can be minimized to less than 0.10%; its working distance can reach 264mm, and its light aperture can also be flexibly adjusted.

[0096] Example 2:

[0097] This embodiment provides a compact long working distance fixed magnification lens, comprising a focusing structure and an optical system of a compact long working distance fixed magnification lens as in the first embodiment;

[0098] The focusing structure is used to drive the first lens group S1, the aperture A0 and the second lens group S2 as a whole along a predetermined optical axis to move closer to or away from the third lens group S3 to achieve focusing.

[0099] Since the optical system has been described in detail in the first embodiment, it will not be described again in this embodiment.

[0100] In summary, the present embodiment realizes a long working distance fixed magnification lens with high resolution. The lens magnification is 0.94X, the maximum resolution can reach 100lp / mm, it can match 5-micron pixel chips, the maximum target surface size is 1.2", and it has low distortion performance.

[0101] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact optical system with a long working distance fixed magnification lens, characterized in that: The optical system comprises a front optical group with positive optical power, a middle optical group with negative optical power, an aperture, and a rear optical group with positive optical power, which are sequentially arranged from the object side to the image side; The focal length of the optical system is f, the optical back focus of the optical system is BFL, and the focal length of the front group is f S1 , the focal length of the middle group is f S2 , the focal length of the rear group is f S3 , respectively satisfying the relationship: 0.4<|f S1 / f|<0.75,1.1<|f S2 / f|<1.7,1.50<|f S3 / f|<8.00,0.05<|BFL / f|<0.35。 2. The optical system of a compact long working distance fixed magnification lens according to claim 1, characterized in that: The front group includes a first lens with positive optical power, and the first lens is a biconvex lens; A distance between a front surface vertex of the first lens and a rear surface vertex of the rear lens group is L, and L and f satisfy the relationship: 0.7<|L / f|<1.

50.

3. The optical system of a compact long working distance fixed magnification lens according to claim 2, characterized in that: The middle lens group includes a second lens having negative power, a third lens having positive power, a fourth lens having negative power, a fifth lens having positive power, and a sixth lens having negative power; the second lens, the third lens, and the fourth lens are cemented into a first cemented lens group having negative power, and the fifth lens and the sixth lens are cemented into a second cemented lens group having positive power; The focal length of the first cemented lens group is f U1 , f U1 and f satisfy the relationship: 0.65<|f U1 / f|<1.15; The focal length of the second cemented lens group is f U2 , f U2 and f satisfy the relationship: 1.8<|f U2 / f|<3.

80.

4. The optical system of a compact long working distance fixed magnification lens according to claim 3, characterized in that: The second lens is a meniscus lens, the third lens and the fifth lens are both biconvex lenses, the fourth lens is a meniscus lens or a biconcave lens, and the sixth lens is a biconcave lens.

5. The optical system of a compact long working distance fixed magnification lens according to claim 3, characterized in that: The rear lens group includes a seventh lens having negative power, an eighth lens having positive power, a ninth lens having negative power, and a tenth lens having positive power; the seventh lens and the eighth lens are cemented into a third cemented lens having positive power; The focal length of the third cemented lens group is f U3 , f U3 and f satisfy the relationship: 1.00<|f U3 / f|<2.50; The focal length of the ninth lens is f G9 , f G9 Satisfies the relationship with f: 0.18<|f G9 / f|<0.40; The focal length of the tenth lens is f G10 , f G10 Satisfies the relationship with f: 0.25<|f G10 / f|<0.

60.

6. The optical system of a compact long working distance fixed magnification lens according to claim 5, characterized in that: The seventh lens and the seventh lens are both biconcave lenses, the eighth lens is a biconvex lens, and the tenth lens is a meniscus lens or a plano-convex lens.

7. The optical system of a compact long working distance fixed magnification lens according to claim 5, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens and the tenth lens are all spherical lenses, and the optical axes of all the spherical lenses coincide with the predetermined optical axis.

8. The optical system of a compact long working distance fixed magnification lens according to claim 1, characterized in that: The half image height of the optical system is y'; y' and f satisfy the relationship: |y' / f|<0.

12.

9. The optical system of a compact long working distance fixed magnification lens according to claim 7, characterized in that: The aperture of the diaphragm is a circular hole, the center of the circular hole is on the predetermined optical axis; the adjustment range of the aperture value of the diaphragm is F2.8 to F16.

10. A compact long working distance fixed magnification lens, characterized in that: An optical system comprising a compact long working distance fixed magnification lens according to any one of claims 1 to 9; The compact long working distance fixed magnification lens has a magnification of 0.94X.

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