An optical system and a long-focus industrial lens for high-resolution close-range imaging

Abstract

The present invention relates to the technical field of optical devices, and specifically discloses an optical system and a long-focus industrial lens for high-resolution close-range imaging. The optical system is sequentially provided with a fixed group S1 and a focusing group S2 from the object side to the image side. The focusing group S2 can move closer to or away from the fixed group S1 along the optical axis to achieve focusing. The fixed group S1 includes a first lens G1 with a positive optical power, a second lens G2 with a negative optical power, a third lens G3 with a positive optical power, a fourth lens G4 with a positive optical power, a fifth lens G5 with a negative optical power, a sixth lens G6 with a negative optical power, and a seventh lens G7 with a positive optical power. Among them, a diaphragm S is provided between the fifth lens G5 and the sixth lens G6. The focusing group S2 has a positive optical power. The combined focal length of the fixed group S1 is fS1, and the combined focal length of the focusing group S2 is fS2, where 0.4 < |fS1 / fS2| < 1.4. The optical system and the long-focus industrial lens for high-resolution close-range imaging provided by the present invention can effectively meet the application requirements of high-resolution close-range imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and in particular to an optical system and a long - focal - length industrial lens for high - resolution close - range imaging. Background Art

[0002] With the development of industrial automation, industrial lenses are widely used in the field of machine vision inspection, such as workpiece measurement and judgment, defect detection, food packaging, intelligent logistics, medical diagnosis, etc. The continuously increasing demand for detection accuracy and the wide application of high - resolution cameras have put forward new requirements for the imaging quality and performance of industrial lenses.

[0003] Industrial lenses are often used in close - range imaging projects. At present, most long - focal - length industrial lenses on the market can only achieve good imaging when shooting at a long distance, lacking in close - range imaging effect and having insufficient resolution.

[0004] Therefore, it is necessary to improve the existing industrial lenses to meet the application requirements of close - range high - resolution imaging.

[0005] The above information disclosed in this background section is only included to enhance the understanding of the background of the present disclosure, and thus may include information that does not form the prior art already known to those of ordinary skill in the art at present. Summary of the Invention

[0006] An object of the present invention is to provide an optical system and a long - focal - length industrial lens for high - resolution close - range imaging, which can effectively meet the application requirements of close - range high - resolution imaging.

[0007] To achieve the above object, on the one hand, the present invention provides an optical system, which is sequentially provided with a fixed group S1 and a focusing group S2 from the object side to the image side. The focusing group S2 can move closer to or away from the fixed group S1 along the optical axis to achieve focusing.

[0008] The fixed group S1 includes a first lens G1 with positive optical power, a second lens G2 with negative optical power, a third lens G3 with positive optical power, a fourth lens G4 with positive optical power, a fifth lens G5 with negative optical power, a sixth lens G6 with negative optical power, and a seventh lens G7 with positive optical power.

[0009] Wherein, a diaphragm S is provided between the fifth lens G5 and the sixth lens G6.

[0010] The focusing group S2 has positive optical power.

[0011] The combined focal length of the fixed group S1 is f S1 , and the combined focal length of the focusing group S2 is f S2 , wherein, 0.4 < |f S1 / f S2 |<1.4

[0012] The first lens G1 is a biconvex lens, the second lens G2 is a meniscus lens convex toward the image side, the third lens G3 is a biconvex lens or a plano-convex lens convex toward the object side, the fourth lens G4 is a biconvex lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconcave lens, and the seventh lens G7 is a biconvex lens.

[0013] Optionally, the first lens G1 and the second lens G2 are cemented to form a first cemented lens U1, and the fourth lens G4 and the fifth lens G5 are cemented to form a second cemented lens U2.

[0014] Optionally, the dispersions of the first lens G1 and the third lens G3 are both lower than that of the second lens G2.

[0015] Optionally,

[0016] The focal length of the first cemented lens U1 is f U1 , and the focal length of the third lens is f3, where: 0 < |f S1 / f U1 |<1.5, 0.5 < |f3 / f S1 |<1.5;

[0017] The focal length of the sixth lens G6 is f6, and the focal length of the seventh lens G7 is f7, where: 0.10 < |f6 / f S1 |<0.30, 0.25 < |f7 / f S1 |<0.50.

[0018] Optionally,

[0019] The refractive index of the fourth lens G4 is n4, and the refractive index of the fifth lens G5 is n5, where: 1.85 < n4 < 2.1, 1.6 < n5 < 1.85.

[0020] Optionally, the focusing group S2 is a single lens or a cemented lens.

[0021] Optionally, the semi-image height y of the optical system and the focal length f of the optical system satisfy the relation: |y / f| < 0.15.

[0022] On the other hand, a long-focus industrial lens for high-resolution close-range imaging is provided, which includes a mechanical system and any one of the optical systems described above. The mechanical system is used to drive the focusing group S2 of the optical system to approach or move away from the fixed group S1 of the optical system along the optical axis to achieve focusing.

[0023] The beneficial effects of the present invention are as follows: It provides an optical system and a long-focus industrial lens for high-resolution close-range imaging, which are applicable to the application scenarios of machine vision inspection. Through reasonable lens combination and focal length matching, the application requirements of high-resolution imaging at close range can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of the optical system provided in Embodiment 1;

[0026] Figure 2 It is an MTF (Modulation Transfer Function) diagram of the optical system provided in Embodiment 1;

[0027] Figure 3 It is a schematic structural diagram of the optical system provided in Embodiment 2;

[0028] Figure 4 It is an MTF (Modulation Transfer Function) diagram of the optical system provided in Embodiment 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] In the description of the present invention, it should be understood that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component.

[0031] In addition, terms such as "long", "short", "inner", "outer", etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or component referred to must have this specific orientation and be constructed and operated in this specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0032] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included within the protection scope of the present invention.

[0033] Embodiment 1

[0034] This embodiment provides a high-resolution close-range imaging long-focus industrial lens, which includes an optical system and a mechanical system for focusing the optical system. The high-resolution close-range imaging long-focus industrial lens is applicable to the application scenario of machine vision inspection, and through reasonable lens combination and focal length matching, the application requirements of high-resolution imaging at close range are achieved.

[0035] See Figure 1 , the optical system provided in this embodiment is sequentially provided with a fixed group S1 and a focusing group S2 from the object side to the image side. Among them, the mechanical system is connected to the focusing group S2 and is used to drive the focusing group S2 to approach or move away from the fixed group S1 along the optical axis to achieve focusing.

[0036] The fixed group S1 includes a first lens G1 with positive optical power, a second lens G2 with negative optical power, a third lens G3 with positive optical power, a fourth lens G4 with positive optical power, a fifth lens G5 with negative optical power, a sixth lens G6 with negative optical power, and a seventh lens G7 with positive optical power;

[0037] Among them, a diaphragm S is provided between the fifth lens G5 and the sixth lens G6;

[0038] The focusing group S2 has positive optical power; in this embodiment, the focusing group S2 is an eighth lens G8 with a single-lens structure. Optionally, the eighth lens G8 is a meniscus lens convex toward the object side.

[0039] The combined focal length of the fixed group S1 is f S1 , the combined focal length of the focusing group S2 is f S2 , where 0.4 < |f S1 / f S2 | < 1.4.

[0040] In this embodiment, the first lens G1 is a biconvex lens, the second lens G2 is a meniscus lens convex toward the image side, the third lens G3 is a biconvex lens or a plano-convex lens convex toward the object side, the fourth lens G4 is a biconvex lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconcave lens, and the seventh lens G7 is a biconvex lens.

[0041] Optionally, the first lens G1 and the second lens G2 are cemented to form a first cemented lens U1, and the fourth lens G4 and the fifth lens G5 are cemented to form a second cemented lens U2. Among them, the first lens G1 and the third lens G3 are made of low-dispersion materials, and the second lens G2 is made of high-dispersion materials. That is, the dispersions of the first lens G1 and the third lens G3 are both lower than that of the second lens G2. Then, the combination of the first lens G1, the second lens G2, and the third lens G3 can effectively reduce the secondary spectrum existing in the optical system and improve the resolution.

[0042] Optionally, when each lens satisfies the following parameter restrictions, the imaging effect is better:

[0043] The focal length of the first cemented lens U1 is f U1 , and the focal length of the third lens is f3, where: 0 < |f S1 / f U1 | < 1.5, 0.5 < |f3 / f S1 | < 1.5;

[0044] The focal length of the sixth lens G6 is f6, and the focal length of the seventh lens G7 is f7, where: 0.10 < |f6 / f S1 | < 0.30, 0.25 < |f7 / f S1 | < 0.50;

[0045] The refractive index of the fourth lens G4 is n4, and the refractive index of the fifth lens G5 is n5, where: 1.85 < n4 < 2.1, 1.6 < n5 < 1.85;

[0046] The semi-image height y of the optical system and the focal length f of the optical system satisfy the relationship: |y / f| < 0.15.

[0047] The following gives specific examples according to the above settings of the present invention for explanation.

[0048] The data of each lens of the exemplary optical system are shown in Table 1 below, and the corresponding MTF diagram is as Figure 2 shown.

[0049] Table 1 Summary of parameters of each lens of the optical system with single-lens focusing

[0050]

[0051] In the optical system shown in Table 1 above, the variation range of the focal length f of the optical system is 69 mm - 79.2 mm; the working distance range is 250 mm to 700 mm; the semi-image height y = 5.50 mm; the maximum aperture is F2.8; the focal length of the fixed group S1 is f S1= 74.48 mm; the focal length f of the focusing group S2 S2 = 112.54 mm; the focal length of the first cemented lens U1 is f U1 = 198.06 mm; the focal length of the third lens is f3 = 77.27 mm; the focal length f6 of the sixth lens G6 = -17.39 mm; the focal length of the seventh lens G7 is f7 = 29.52 mm.

[0052] They satisfy the following relational expressions:

[0053] |y / f| < 0.15;

[0054] 0.4 < (|f S1 / f S2 | = 0.66) < 1.4;

[0055] 0 < (|f S1 / f U1 | = 0.38) < 1.5;

[0056] 0.5 < (|f3 / f S1 | = 1.04) < 1.5;

[0057] 0.10 < (|f6 / f S1 | = 0.23) < 0.30;

[0058] 0.25 < (|f7 / f S1 | = 0.40) < 0.50.

[0059] Compared with the prior art, the beneficial effects of the optical system and the high-resolution close-range imaging telephoto industrial lens provided in this embodiment are as follows: Through reasonable lens combination and focal length matching, an optical system is realized, whose focal length varies within the range of 75 ± 10 mm; the resolution can reach 200 lp / mm, and it can match 2.5-μm pixels; the floating focusing method is adopted, and good imaging can be achieved at close range.

[0060] In this embodiment, in order to achieve close-range imaging, the optical system adopts the floating focusing method; adjusting the distance between the fixed group S1 and the focusing group S2 can balance the aberration caused by the change of the object distance, so as to achieve good imaging at close range and finally meet the application requirements of high-resolution imaging at close range.

[0061] Embodiment 2

[0062] This embodiment provides a high-resolution close-range imaging telephoto industrial lens, including an optical system and a mechanical system for realizing the focusing of the optical system. The high-resolution close-range imaging telephoto industrial lens is applicable to the application scenario of machine vision inspection, and through reasonable lens combination and focal length matching, the application requirements of high-resolution imaging at close range are achieved.

[0063] See Figure 3 Figure 3 , the optical system provided in this embodiment is sequentially provided with a fixed group S1 and a focusing group S2 from the object side to the image side. Among them, the mechanical system is connected to the focusing group S2 and is used to drive the focusing group S2 to approach or move away from the fixed group S1 along the optical axis to achieve focusing.

[0064] The fixed group S1 includes a first lens G1 with positive optical power, a second lens G2 with negative optical power, a third lens G3 with positive optical power, a fourth lens G4 with positive optical power, a fifth lens G5 with negative optical power, a sixth lens G6 with negative optical power, and a seventh lens G7 with positive optical power;

[0065] Among them, a diaphragm S is provided between the fifth lens G5 and the sixth lens G6;

[0066] The focusing group S2 has positive optical power; in this embodiment, the focusing group S2 is a third cemented lens U3 formed by cementing an eighth lens G8 and a ninth lens G9.

[0067] Optionally, the eighth lens G8 is a meniscus lens convex toward the object side, and the ninth lens G9 is a plano-concave lens convex toward the object side.

[0068] The combined focal length of the fixed group S1 is f S1 and the combined focal length of the focusing group S2 is f S2 where 0.4 < |f S1 / f S2 | < 1.4.

[0069] In this embodiment, the first lens G1 is a biconvex lens, the second lens G2 is a meniscus lens convex toward the image side, the third lens G3 is a biconvex lens or a plano-convex lens convex toward the object side, the fourth lens G4 is a biconvex lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconcave lens, and the seventh lens G7 is a biconvex lens.

[0070] Optionally, the first lens G1 and the second lens G2 are cemented to form a first cemented lens U1, and the fourth lens G4 and the fifth lens G5 are cemented to form a second cemented lens U2. Among them, the first lens G1 and the third lens G3 are made of low-dispersion materials, and the second lens G2 is made of a high-dispersion material. That is, the dispersions of the first lens G1 and the third lens G3 are both lower than the dispersion of the second lens G2. Then, the combination of the first lens G1, the second lens G2, and the third lens G3 can effectively reduce the secondary spectrum existing in the optical system and improve the resolution.

[0071] Optionally, when each lens satisfies the following parameter restrictions, the imaging effect is better:

[0072] The focal length of the first cemented lens U1 is f U1 , the focal length of the third lens is f3, where: 0 < |f S1 / f U1 | < 1.5, 0.5 < |f3 / f S1 | < 1.5;

[0073] The focal length of the sixth lens G6 is f6, and the focal length of the seventh lens G7 is f7, where: 0.10 < |f6 / f S1 | < 0.30, 0.25 < |f7 / f S1 | < 0.50;

[0074] The refractive index of the fourth lens G4 is n4, and the refractive index of the fifth lens G5 is n5, where: 1.85 < n4 < 2.1, 1.6 < n5 < 1.85;

[0075] The semi-image height y of the optical system and the focal length f of the optical system satisfy the relationship: |y / f| < 0.15.

[0076] Specific embodiments are given below according to the above settings of the present invention for explanation.

[0077] The lens data of the exemplary optical system are shown in Table 2 below, and the corresponding MTF diagram is as Figure 4 shown.

[0078] Table 2 Summary of parameters of each lens of the optical system for cemented lens focusing

[0079]

[0080] In the optical system shown in Table 2 above, the change range of the focal length f of the optical system is between 69 mm and 85 mm; the working distance range is between 280 mm and 550 mm; the semi-image height y = 8.8 mm; the maximum aperture is F2.8; the focal length of the fixed group S1 is f S1 = 76.64 mm; the focal length f of the focusing group S2 S2 = 74.48 mm; the focal length of the first cemented lens U1 is f U1 = 248.24 mm; the focal length of the third lens is f3 = 64.82 mm; the focal length f6 of the sixth lens G6 = -17.37 mm; the focal length of the seventh lens G7 is f7 = 32.05 mm.

[0081] They satisfy the following relationships:

[0082] |y / f| < 0.15;

[0083] 0.4 < (|f S1 / fS2 | = 1.03)< 1.4;

[0084] 0 < (|f S1 / f U1 | = 0.31)< 1.5;

[0085] 0.5 < (|f3 / f S1 |0.85)< 1.5;

[0086] 0.10 < (|f6 / f S1 | = 0.23)< 0.30;

[0087] 0.25 < (|f7 / f S1 | = 0.42)< 0.50。

[0088] Compared with the prior art, the beneficial effects of the optical system and the high-resolution short-distance imaging long-focus industrial lens provided in this embodiment are as follows: Through reasonable lens combination and focal length matching, an optical system is realized, whose focal length varies within the range of 75 ± 10 mm; the resolution can reach 200 lp / mm, and it can match 2.5-μm pixels; the floating focusing method is adopted, and good imaging can be achieved at short distances.

[0089] In this embodiment, in order to achieve short-distance imaging, the optical system adopts the floating focusing method; adjusting the distance between the fixed group S1 and the focusing group S2 can balance the aberration caused by the change of the object distance, so as to achieve good imaging at short distances and finally meet the application requirements of high-resolution imaging at short distances. Further, when the focusing group S2 adopts a cemented lens, the optical system can have a wider working distance range and can also be compatible with larger-size photosensitive chips.

[0090] It should be understood that although this specification is described according to the embodiments, not each embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0091] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical system, characterized in that, A fixed group S1 and a focusing group S2 are sequentially arranged from the object side to the image side. The focusing group S2 can approach or move away from the fixed group S1 along the optical axis to achieve focusing. The fixed group S1 is composed of a first lens G1 with positive optical power, a second lens G2 with negative optical power, a third lens G3 with positive optical power, a fourth lens G4 with positive optical power, a fifth lens G5 with negative optical power, a sixth lens G6 with negative optical power, and a seventh lens G7 with positive optical power. Wherein, a diaphragm S is arranged between the fifth lens G5 and the sixth lens G6. The focusing group S2 has positive optical power. The combined focal length of the fixed group S1 is f S1 , and the combined focal length of the focusing group S2 is f S2 , where 0.4 < |f S1 / f S2 | < 1.4; The focusing group S2 is a single lens or a cemented lens. The first lens G1 is a biconvex lens, the second lens G2 is a meniscus lens convex toward the image side, the third lens G3 is a biconvex lens or a plano-convex lens convex toward the object side, the fourth lens G4 is a biconvex lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconcave lens, and the seventh lens G7 is a biconvex lens.

2. The optical system according to claim 1, wherein The first lens G1 and the second lens G2 are cemented to form a first cemented lens U1, and the fourth lens G4 and the fifth lens G5 are cemented to form a second cemented lens U2.

3. The optical system according to claim 2, characterized in that, The dispersions of the first lens G1 and the third lens G3 are both lower than that of the second lens G2.

4. The optical system according to claim 3, wherein The focal length of the first cemented lens U1 is f U1 , the focal length of the third lens is f3, where: 0 < |f S1 / f U1 | < 1.5, 0.5 < |f3 / f S1 | < 1.5; The focal length of the sixth lens G6 is f6, and the focal length of the seventh lens G7 is f7, where: 0.10 < |f6 / f S1 |<0.30, 0.25 < |f7 / f S1 |<0.

50.

5. The optical system according to claim 4, wherein The refractive index of the fourth lens G4 is n4, and the refractive index of the fifth lens G5 is n5, where: 1.85 < n4 < 2.1, 1.6 < n5 < 1.

85.

6. The optical system according to claim 1, characterized in that, The semi-image height y of the optical system and the focal length f of the optical system satisfy the relationship: |y / f| < 0.

15.

7. A long-focus industrial lens for high-resolution close-range imaging, characterized in that, It includes a mechanical system and the optical system according to any one of claims 1 to 6. The mechanical system is used to drive the focusing group S2 of the optical system to approach or move away from the fixed group S1 of the optical system along the optical axis to achieve focusing.

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