A low-distortion macro lens

Abstract

The application relates to the technical field of industrial lens, and discloses a low-distortion macro lens, which comprises a mechanical device and an optical module installed in the mechanical device; the optical module is sequentially provided with a first lens group T1, a diaphragm, a second lens group T2 and a third lens group T3 from an object side to an image side; the first lens group T1 has positive refractive power, the focal length of the first lens group T1 is f T1 ; the second lens group T2 has negative refractive power, the focal length of the second lens group T2 is f T2 ; the third lens group T3 has positive refractive power, the focal length of the third lens group T3 is f T3 ; the total focal length of the optical module is f, 0.50<|f T1 / f|<0.85, 3.00<|f T2 / f|<4.00, 1.60<|f T3 / f|<2.50. The low-distortion macro lens realizes an optical system of a high-resolution low-distortion macro lens with a focal length of 50 mm, the maximum optical distortion of a full field of view is lower than 0.14%, and the problem of poor close-range imaging effect of an industrial macro lens is solved.

Description

Technical Field

[0001] This application relates to the field of industrial lens technology, specifically a low-distortion macro lens. Background Technology

[0002] Industrial macro lenses are specialized lenses used for macro photography, primarily for inspecting the appearance quality of products moving at high speeds on manufacturing production lines and detecting minute defects that are difficult to see with the naked eye. Industrial macro lenses are widely used in machine vision-based production automation, such as for the inspection of plastic parts, the appearance inspection of springs, and barcode recognition. By acquiring images of parts and products using industrial macro lenses and magnifying them several times, defect detection and dimensional measurement can be completed clearly and quickly, allowing for the rejection of defective products and ensuring product quality.

[0003] With the continuous upgrading of modern industrial automation and intelligence, the requirements for industrial macro lenses are also constantly deepening. Especially in the precision manufacturing process, where workpiece positioning and inspection are required, the lens resolution must be as high as possible, while distortion must be as low as possible to reduce image deformation. Traditional industrial lenses mostly have a working distance in the meter range, resulting in poor imaging or even inability to focus at close range, affecting the accuracy of back-end inspection and failing to meet the application needs of precision manufacturing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a low-distortion macro lens, which solves the problem of poor close-range imaging performance of industrial macro lenses.

[0005] To achieve the above objectives, this application provides the following technical solution: a low-distortion macro lens, characterized in that it includes a mechanical device and an optical module installed inside the mechanical device, wherein the optical module is provided with a first lens group T1, an aperture, a second lens group T2 and a third lens group T3 in sequence from the object side to the image side;

[0006] The first lens group T1 has positive optical power, and the focal length of the first lens group T1 is f. T1 ;

[0007] The second lens group T2 has negative optical power, and the focal length of the second lens group T2 is f. T2 ;

[0008] The third lens group T3 has positive optical power, and the focal length of the third lens group T3 is f. T3 ;

[0009] The total focal length of the optical module is f, 0.50 < |f T1 / f|<0.85, 3.00<|f T2 / f|<4.00, 1.60<|f T3 / f|<2.50.

[0010] Preferably, the first lens group T1 comprises the following components arranged sequentially:

[0011] A first lens G1 has positive optical power and a focal length of f. G1 , 0.65 < |f G1 / f|<1.30;

[0012] The second lens G2 has positive optical power, a meniscus structure, and a focal length of f. G2 , 1.15 < |f G2 / f|<1.80;

[0013] A first fixed lens group U1, having negative optical power, has a focal length of f. U1 , 0.65 < |f U1 / f|<1.30.

[0014] Preferably, the first fixed lens group U1 includes:

[0015] The third lens G3 has positive optical power and is a biconvex structure;

[0016] The fourth lens G4 has negative optical power and is a biconcave structure.

[0017] The third lens G3 abuts against the fourth lens G4, and the third lens G3 and the fourth lens G4 are fixedly connected.

[0018] Preferably, the second lens group T2 comprises the following components arranged sequentially:

[0019] The second fixed lens group U2 has positive optical power and a focal length of f. U2 , 0.65 < |f U2 / f|<1.30;

[0020] The seventh lens G7 has negative optical power, a meniscus structure, and a focal length of f. G7 , 0.55 < |f G7 / f|<1.10.

[0021] Preferably, the second fixed lens group U2 includes:

[0022] The fifth lens G5 has negative optical power and is a biconcave structure;

[0023] The sixth lens G6 has positive optical power and is a biconvex structure;

[0024] The fifth lens G5 abuts against the sixth lens G6, and the fifth lens G5 and the sixth lens G6 are fixedly connected.

[0025] Preferably, the third lens group T3 includes an eighth lens G8, which has positive optical power and is a meniscus structure.

[0026] The distance between the third lens group T3 and the second lens group T2 is D. S ,|D S / f|<0.65.

[0027] Preferably, the length of the optical system is L, and |L / f|>1.00.

[0028] Preferably, the optical back intercept of the optical system is BFL, and |BFL / f| < 0.40.

[0029] Preferably, the half-image height of the optical system is y',|y' / f|<0.25.

[0030] Preferably, the aperture of the aperture is a circular hole, and the aperture of the aperture (1) is adjustable in the range of F2.8 to F16.

[0031] This application provides a low-distortion macro lens, which has the following beneficial effects:

[0032] This low-distortion macro lens, through the setting of a first lens group T1, a second lens group T2, and a third lens group T3, achieves an optical system for a high-resolution, low-distortion macro lens with a focal length of 50mm. It has an image-side F-number of 2.8, a maximum imaging surface of φ19.4mm, and a resolution of 145 l p / mm. This corresponds to a maximum imaging chip size of 15 million pixels, with a maximum optical distortion of less than 0.14% across the entire field of view. The use of a floating focus mechanism enables the lens to achieve clear imaging at working distances of 98-132mm, solving the problem of poor close-range imaging performance in industrial macro lenses. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application 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 application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the optical structure of the lens optical module in the embodiments of this application.

[0035] Figure 2 This is the optical distortion curve of the lens optical module in the embodiments of this application.

[0036] In the diagram: 1. Grating; 2. Image plane; T1. First lens group; T2. Second lens group; T3. Third lens group; G1. First lens; G2. Second lens; G3. Third lens; G4. Fourth lens; G5. Fifth lens; G6. Sixth lens; G7. Seventh lens; G8. Eighth lens; T1. First lens group; T2. Second lens group. Detailed Implementation

[0037] To make the purpose, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] In the description of this application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0039] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] Please see Figure 1 This application provides a technical solution: a low-distortion macro lens, including a mechanical device and an optical module installed inside the mechanical device. The optical module is provided with a first lens group T1, an aperture 1, a second lens group T2 and a third lens group T3 in sequence from the object side to the image side. The total focal length of the optical module is f.

[0041] The first lens group T1 has positive optical power, and the focal length of the first lens group T1 is f. T1 , 0.50<|f T1 / f|<0.85. Specifically, the first lens group T1 includes a first lens G1, a second lens G2, and a first fixed lens group U1 arranged sequentially. The first lens G1 has positive optical power, and its focal length is fG1, 0.65 < |fG1 / f| < 1.30. The second lens G2 has positive optical power, is a meniscus structure, and its focal length is f G2 , 1.15 < |f G2 / f|<1.80.

[0042] The first fixed lens group U1 has negative optical power, and the focal length of the first fixed lens group U1 is f. U1 , 0.65 < |f U1 / f|<1.30. The first fixed lens group U1 includes a third lens G3 and a fourth lens G4. The third lens G3 has positive optical power and is a biconvex structure. The fourth lens G4 has negative optical power and is a biconcave structure. The third lens G3 and the fourth lens G4 abut against each other and are glued and fixedly connected.

[0043] The second lens group T2 has negative optical power, and the focal length of the second lens group T2 is f. T2 , 3.00<|f T2 / f|<4.00. The second lens group T2 includes a second fixed lens group U2 and a seventh lens G7 arranged sequentially. The second fixed lens group U2 has positive optical power, and the focal length of the second fixed lens group U2 is f. U2 , 0.65 < |f U2 / f|<1.30. The second fixed lens group U2 includes a fifth lens G5 and a sixth lens G6. The fifth lens G5 has negative optical power and is biconcave. The sixth lens G6 has positive optical power and is biconvex. The fifth lens G5 and the sixth lens G6 abut against each other and are cemented together for fixation. The seventh lens G7 has negative optical power, is meniscus, and has a focal length of f. G7 , 0.55 < |f G7 / f|<1.10.

[0044] The third lens group T3 has positive optical power, and the focal length of the third lens group T3 is f. T3 , 1.60<|f T3 / f|<2.50, the third lens group T3 includes an eighth lens G8, the eighth lens G8 has positive optical power, and the eighth lens G8 has a meniscus structure.

[0045] By designing a mechanical mechanism, the distance between the third lens group T3 and the image plane 2 is kept unchanged, and the relative positions and distances of the first lens group T1, the aperture stop, and the second lens group T2 are kept constant. This allows the distance D between the third lens group T3 and the second lens group T2 to be changed. S This method achieves the lens's imaging needs at different focal lengths. Specifically, the distance between the vertex of the curved surface of the seventh lens G7 near the eighth lens G8 and the vertex of the curved surface of the eighth lens G8 near the seventh lens G7 is the distance D between the third lens group T3 and the second lens group T2. S ,|D S / f|<0.65.

[0046] Furthermore, the length of the optical system is L. Specifically, the distance between the vertex of the curved surface of the first lens G1 away from the eighth lens G8 and the vertex of the curved surface of the eighth lens G8 away from the first lens G1 is the length of the optical system, L, and |L / f|>1.00.

[0047] Furthermore, the optical back intercept of the optical system is BFL, and |BFL / f| < 0.40.

[0048] Furthermore, the half-image height of the optical system is y', |y' / f| < 0.25.

[0049] Furthermore, the aperture of stop 1 is a circular aperture, and the aperture of stop 1 is adjustable in the range of F2.8 to F16.

[0050] It should be noted that a meniscus lens is a lens that is concave on one side and convex on the other, a biconvex lens is a lens that is convex on both sides, and a biconcave lens is a lens that is concave on both sides. In this embodiment, all lenses in the first lens group T1, the second lens group T2, and the third lens group T3 are spherical mirrors.

[0051] In this embodiment, the preferred values ​​for the optical system parameters are as follows:

[0052]

[0053]

[0054] The focusing data of the optical module in this embodiment is as follows:

[0055]

[0056] It should be noted that the object distance is the distance between the lens and the subject being photographed.

[0057] In this embodiment, the preferred values ​​for the optical system are: a focal length f of 50mm, a maximum aperture of F# = 2.8, and a focal length f of the first lens group T1. T1= 36.61mm, the focal length f of the second lens group T2 T2＝ -170.10mm, the focal length f of the third lens group T3 T3 = 95.84mm, optical back intercept BFL = 14.60mm, half image height y' = 9.7mm, focal length f of the first lens G1 G1 = 45.04mm, the focal length f of the second lens G2 G2 =71.91mm, the focal length f of the first cemented lens group U1 = -45.56mm, focal length f of the second cemented lens group U2 = 45.81mm, the focal length f of the seventh lens G7 G7 = -40.86mm.

[0058] Various relational expressions:

[0059] |f T1 / f|=0.73;|f T2 / f|=3.40;|f T3 / f|=1.92; |L / f|=1.28~1.71;

[0060] |B FL / f|=0.29;|y' / f|=0.19;|f G1 / f|=0.90;|f G2 / f|=1.44;

[0061] |f U1 / f|=0.91;|f U2 / f|=0.92;|f G7 / f|=0.82;

[0062] |D S / f|=0.03~0.46.

[0063] Satisfying the relation:

[0064] 0.50<|f T1 / f|<0.85; 3.00<|f T2 / f|<4.00; 1.60<|f T3 / f|<2.50;

[0065] |L / f|>1.00; |BFL / f|<0.40; |y' / f|<0.25;

[0066] 0.65 < |f G1 / f| < 1.30; 1.15 < |f G2 / f|<1.80;

[0067] 0.65 < |f U1 / f| < 1.30; 0.65 < |f U2 / f|<1.30;

[0068] 0.55 < |f G7 / f|<1.10;|D S / f|<0.65.

[0069] Figure 2 The figure shown is an optical distortion curve of this embodiment, with the maximum optical distortion being less than 0.14% across the entire field of view.

[0070] In summary, the above structure realizes an optical system for a high-resolution, low-distortion macro lens with a focal length of 50mm, an image-side F-number of 2.8, a maximum imaging surface of φ19.4mm, and a resolution of 145 l p / mm. This corresponds to a maximum imaging chip with 15 million pixels and a maximum optical distortion of less than 0.14% across the entire field of view. The floating focus method enables the lens to achieve clear imaging at working distances of 98-132mm, and its aperture can also be flexibly adjusted.

[0071] It should be noted that, in this document, relational 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 such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0072] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0073] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 application.

Claims

1. A low-distortion macro lens, characterized in that, It includes a mechanical device and an optical module installed inside the mechanical device. The optical module consists of a first lens group T1, an aperture (1), a second lens group T2 and a third lens group T3 arranged sequentially from the object side to the image side. The first lens group T1 has positive optical power, and the focal length of the first lens group T1 is f. T1 ; The second lens group T2 has negative optical power, and the focal length of the second lens group T2 is f. T2 ; The third lens group T3 has positive optical power, and the focal length of the third lens group T3 is f. T3 ; The total focal length of the optical module is f, 0.50 < |f T1 / f|<0.85, 3.00<|f T2 / f|<4.00, 1.60<|f T3 / f|<2.50; The first lens group T1 is composed of a first lens G1, a second lens G2 and a first fixed lens group U1 arranged in sequence. The first lens G1 has positive optical power and is a plano-convex structure with the convex surface facing the object. The second lens G2 has positive optical power and is a meniscus structure with the convex surface facing the object. The first fixed lens group U1 has negative optical power. The first fixed lens group U1 is composed of a third lens G3 and a fourth lens G4. The third lens G3 has positive optical power and is a biconvex structure. The fourth lens G4 has negative optical power and is a biconcave structure. The third lens G3 abuts against the fourth lens G4, and the third lens G3 and the fourth lens G4 are fixedly connected. The second lens group T2 consists of a second fixed lens group U2 and a seventh lens G7 arranged sequentially. The second fixed lens group U2 has positive optical power, and the seventh lens G7 has negative optical power. The seventh lens G7 is a meniscus structure with its convex surface facing the image side. The second fixed lens group U2 is composed of a fifth lens G5 and a sixth lens G6. The fifth lens G5 has negative optical power and is a biconcave structure. The sixth lens G6 has positive optical power and is a biconvex structure. The fifth lens G5 and the sixth lens G6 abut against each other and are fixedly connected. The third lens group T3 is composed of an eighth lens G8, which has positive optical power and is a meniscus structure with its convex surface facing the object.

2. The low-distortion macro lens according to claim 1, characterized in that, The focal length of the first lens G1 is f G1 , 0.65 < |f G1 / f|<1.30; the focal length of the second lens G2 is f G2 , 1.15 < |f G2 / f|<1.80; the focal length of the first fixed lens group U1 is f U1 , 0.65 < |f U1 / f|<1.

30.

3. A low-distortion macro lens according to claim 1, characterized in that, The focal length of the second fixed lens group U2 is f U2 , 0.65 < |f U2 / f|<1.30; the focal length of the seventh lens G7 is f G7 , 0.55 < |f G7 / f|<1.

10.

4. A low-distortion macro lens according to claim 1, characterized in that, The distance between the third lens group T3 and the second lens group T2 is D. S ,|D S / f|<0.

65.

5. A low-distortion macro lens according to claim 1, characterized in that, The length of the lens is L, and |L / f|>1.

00.

6. A low-distortion macro lens according to claim 1, characterized in that, The optical back focal length of the lens is BFL, and |BFL / f| < 0.

40.

7. A low-distortion macro lens according to claim 1, characterized in that, The half-image height of the lens is y', |y' / f| < 0.

25.

8. A low-distortion macro lens according to claim 1, characterized in that, The aperture of the aperture (1) is a circular hole, and the aperture of the aperture (1) is adjustable in the range of F2.8 to F16.

Images