Endoscope lens and image acquisition equipment for high-temperature furnace

Abstract

The invention discloses a high-temperature furnace endoscope lens and image acquisition equipment. The lens comprises the following components which are sequentially arranged from an object side surface P1 to an imaging surface P3 along an optical axis: a first group of high-temperature-resistant glass plates P2; an aperture stop S; the second large-view-field positive lens group is composed of a balsaming lens of a lens L1, a lens L2 and a lens L3, the lens L1 is a plano-convex positive lens, and the balsaming lens of the lens L2 and the lens L3 has positive focal power; a third group of symmetrical positive lenses L4; the fourth positive lens group and the fourth large-view-field positive lens group are bonding lenses which are formed by bonding a lens L5 and a lens L6 and have positive focal power; and a fifth group of negative lenses L7, wherein the lens L7 is a plano-concave negative lens. According to the scheme, large-view-field and low-distortion imaging in a high-temperature environment is achieved mainly through diaphragm optimization, cooperative work of the five sets of lenses and symmetric design, and the system is suitable for industrial endoscopic monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical lenses, and in particular to an endoscope lens for high-temperature furnaces and an image acquisition device. Background Art

[0002] With the rapid development of modern industry, high-temperature furnaces have become the core equipment in many industries such as metallurgy, chemical engineering, and glass manufacturing. The efficient operation of these furnaces is directly related to production efficiency, product quality, and equipment safety. Therefore, real-time and accurate monitoring of the internal conditions of high-temperature furnaces is particularly important.

[0003] However, the application of traditional optical endoscope lenses in high-temperature environments faces many challenges, and the main problems are as follows:

[0004] 1. Thermal deformation of optical materials: Ordinary optical glass is prone to thermal expansion at high temperatures, resulting in a change in refractive index, which in turn causes blurred imaging. When the temperature exceeds a certain threshold, the optical properties of the glass significantly decline, seriously affecting the imaging quality.

[0005] 2. Deformation of the lens barrel structure: High temperatures also cause the lens barrel structure of the lens to expand and deform, destroying the precise alignment relationship between optical elements and further affecting the imaging effect.

[0006] 3. Compromise of optical performance: To adapt to high-temperature environments, traditional lens designs often need to sacrifice certain optical performance. For example, reducing the aperture of the lens can reduce the amount of light passing through, thereby lowering the temperature inside the lens, but this design will cause the vignetting phenomenon of the imaging to worsen, and the clarity and detail performance of the image will be greatly reduced.

[0007] 4. Insufficient imaging field of view: With the continuous improvement of industrial monitoring requirements, the traditional lens field of view (mostly 60°) can no longer meet the needs of large-range monitoring. A wider field of view is crucial for comprehensively observing the internal conditions of the furnace.

[0008] Although related technologies have been improved, for example, patent CN109188653B improves distortion by adopting a symmetric design, but its field of view is only 76°, still difficult to meet the actual needs of large-range monitoring. In addition, this solution sets the aperture stop at the very front of the lens, and this design is prone to thermal deformation of the aperture stop in a high-temperature environment, thereby affecting the imaging stability. At the same time, due to the small number of lenses, this solution cannot achieve lower-distortion imaging, and there is still much room for improvement in imaging quality.

[0009] It can be seen that there is an obvious compromise between the high-temperature resistance performance and the imaging quality of the current endoscope lens for high-temperature furnaces and kilns, and it is difficult to simultaneously meet the requirements of high imaging quality in high-temperature environments and large field-of-view monitoring. Therefore, developing an endoscope lens that can not only solve the high-temperature resistance problem but also improve the wide-angle imaging performance has become a technical problem that urgently needs to be solved in the industrial inspection field. Summary of the Invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a high-temperature furnace and kiln endoscope lens and an image acquisition device.

[0011] The technical solution of the present invention is as follows: A high-temperature furnace and kiln endoscope lens, characterized in that it includes the following components arranged in sequence along the optical axis from the object side P1 to the imaging surface P3:

[0012] The first group of high-temperature-resistant glass plates P2;

[0013] The aperture stop S;

[0014] The second group of large-field-of-view positive lens groups, the second group of large-field-of-view positive lens groups is composed of the cemented lenses of lens L1, lens L2, and lens L3. Lens L1 is a plano-convex positive lens, and the cemented lens of lens L2 and lens L3 has a positive optical power;

[0015] The third group of symmetrical positive lens L4;

[0016] The fourth group of positive lens groups, the fourth group of large-field-of-view positive lens groups is a cemented lens with positive optical power formed by gluing lens L5 and lens L6, and the combined focal length of the cemented lens of lens L5 and lens L6 is smaller than the combined focal length of the cemented lens of lens L2 and lens L3

[0017] The fifth group of negative lens L7, lens L7 is a plano-concave negative lens.

[0018] Furthermore, the aperture diameter of the aperture stop S is less than 2 mm.

[0019] Furthermore, the field-of-view angle of the lens is 85°, the focal length f = 3.85 mm, and the image plane size is 9 mm.

[0020] Furthermore, in the second group of large-field-of-view positive lens groups, the focal length f1 of lens L1 satisfies: 10 mm < f1 < 11 mm, the focal length f2 of lens L2 satisfies: 6 mm < f2 < 7 mm, the focal length f3 of lens L3 satisfies: -8 mm < f3 < -7 mm, and the combined focal length f23 of lens L2 and lens L3 satisfies: 26464 mm < f23 < 26465 mm.

[0021] Further, the focal length f4 of the lens L4 satisfies: 9 mm < f4 < 110 mm.

[0022] Further, in the fourth group of wide-field positive lens groups, the lens L5 is a symmetrical positive lens. The focal length f5 of the lens L5 satisfies: 7 mm < f5 < 8 mm, the focal length f6 of the lens L6 satisfies: -8 mm < f6 < -7 mm, and the combined focal length f56 of the lens L5 and the lens L6 satisfies: 83 mm < f56 < 84 mm.

[0023] Further, the focal length f7 of the lens L7 satisfies: -7 mm < f7 < -6 mm.

[0024] Further, a photoelectric imaging device or a relay lens is placed at the imaging plane P3.

[0025] An image acquisition device, characterized in that it includes the above-mentioned high-temperature furnace endoscope lens.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This solution mainly realizes large-field-of-view and low-distortion imaging in a high-temperature environment through aperture optimization, the collaborative work of five groups of lenses, and symmetrical design, and is suitable for industrial endoscope monitoring.

[0028] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0029] 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 for the description of the embodiments or the prior art. Obviously, the following drawings 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:

[0030] Figure 1 is a schematic structural diagram of a high-temperature furnace endoscope lens of the present invention;

[0031] Figure 2 is a modulation transfer function MTF diagram of a high-temperature furnace endoscope lens of the present invention;

[0032] Figure 3 is a spot diagram of a high-temperature furnace endoscope lens of the present invention;

[0033] Figure 4 is a central field-of-view function diagram of a high-temperature furnace endoscope lens of the present invention;

[0034] Figure 5It is the maximum field of view point spread function diagram of an endoscope lens for high-temperature furnaces and kilns of the present invention;

[0035] Figure 6 It is the diffraction energy encirclement diagram of an endoscope lens for high-temperature furnaces and kilns of the present invention;

[0036] Figure 7 It is the wavefront aberration vs. field of view diagram of an endoscope lens for high-temperature furnaces and kilns of the present invention;

[0037] Figure 8 It is the grid distortion diagram of an endoscope lens for high-temperature furnaces and kilns of the present invention;

[0038] Figure 9 It is the radial aberration diagram of an endoscope lens for high-temperature furnaces and kilns of the present invention. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", "vertical", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0041] In the present invention, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0042] In the description of the present invention, the "first feature" and "second feature" may include one or more of such features. In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0043] In the description of the present invention, the terms "comprise", "comprising", "have", "including" and / or "containing", when used in this specification, mean the presence of the stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0044] In the description of the present invention, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0045] In the drawings, for the sake of clarity, the thickness, dimensions and shape of the lens have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are for illustrative purposes only and are not drawn to an exact scale.

[0046] As Figure 1 shown, a high-temperature furnace endoscope lens includes the following components arranged in sequence along the optical axis from the object side P1 to the imaging surface P3: a first group of high-temperature resistant glass plates P2, an aperture stop S, a second group of large-field positive lens groups, a third group of symmetric positive lenses L4, a fourth group of positive lens groups, and a fifth group of negative lenses L7.

[0047] Specifically, P1 is the object side, and P2 is the first group of high-temperature resistant glass plates, which mainly play a heat insulation role to protect the lens behind.

[0048] The second group of large-field positive lens groups is composed of the cemented lenses of lenses L1, L2 and L3. Lens L1 is a plano-convex positive lens, which provides a relatively large field of view and has a relatively small spherical aberration itself. Therefore, it helps to correct spherical aberration and installation. The aperture stop S is arranged between P2 and L1, which also helps to eliminate distortion. The cemented lenses of lenses L2 and L3 have positive optical power and relatively large focal lengths, and their main functions are to correct spherical aberration, astigmatism, etc.

[0049] The third group of symmetric positive lenses L4 is a completely symmetric positive lens. Its main function is to correct and eliminate distortion. Centered on L4, the number of lenses on one side is L1, L2, and L3, and the number of lenses on the other side is L5, L6, and L7. Therefore, the number of lenses on both sides is symmetric, which makes the entire lens symmetric as well.

[0050] The fourth group of large-field-of-view positive lens group is a cemented lens with positive optical power formed by cementing lens L5 and lens L6. The combined focal length of the cemented lens of lens L5 and lens L6 should be less than the combined focal length of the cemented lens of lens L2 and lens L3, so as to achieve front-back balance. Its main functions are to correct spherical aberration, astigmatism, distortion, etc.

[0051] The fifth group of negative lens L7 is a plano-concave negative lens. L7 corresponds to L1, one in front and the other behind, one is concave and the other is convex, which effectively reduces spherical aberration.

[0052] P3 is the imaging plane. An optoelectronic imaging device (such as a CCD, CMOS, or other imaging device) is placed at P3, or a relay lens is connected at the back to form an image acquisition device.

[0053] The above L1, L2, L3, L4, L5, L6, and L7 are all spherical lenses symmetric about the optical axis. Since the entire lens system is a large aberration system, in addition to correcting various aberrations, the distortion caused by the large field of view is corrected as much as possible. Therefore, symmetric lenses are used as much as possible in the structural design. After adopting the above structure, the field of view angle of the lens is 85°, the focal length f = 3.85 mm, and the image plane size is 9 mm, meeting the requirements of a 1 / 1.8-inch imaging device.

[0054] Compared with the prior art, the present solution has the following improvement points:

[0055] 1. The aperture stop is no longer set at the very front of the lens, but a rear-mounted design is adopted. The aperture stop is located behind the high-temperature resistant glass, which can enhance the high-temperature stability of the lens.

[0056] 2. As a whole, five groups of lenses, namely L1, L2 / L3, L4, L5 / L6, and L7, work together. Among them, L2 / L3 and L5 / L6 are cemented lens groups, and the overall lens uses the symmetry design concept, which can effectively reduce the influence of distortion, making the field of view angle of the lens larger and covering a wider monitoring range.

[0057] Therefore, the lens of the present solution can better meet the imaging requirements in a high-temperature environment, with clear imaging. The image plane size can reach 9 millimeters. None of the lenses use aspherical design. Therefore, it has the beneficial effects of small size, compact structure, low cost, and high imaging quality.

[0058] In some embodiments, the aperture diameter of the aperture stop S is less than 2 mm, that is, the aperture stop S is a pinhole stop, and the diameter of the light beam is limited by a very small aperture, thereby reducing light scattering and interference and improving the contrast and clarity of imaging.

[0059] In some embodiments, in the second large field-of-view positive lens group, the focal length f1 of the lens L1 satisfies: 10 mm < f1 < 11 mm, the focal length f2 of the lens L2 satisfies: 6 mm < f2 < 7 mm, the focal length f3 of the lens L3 satisfies: -8 mm < f3 < -7 mm, and the combined focal length f23 of the lens L2 and the lens L3 satisfies: 26464 mm < f23 < 26465 mm. The second large field-of-view positive lens group with such parameters can better correct aberrations such as spherical aberration, chromatic aberration, and astigmatism.

[0060] In some embodiments, the focal length f4 of the lens L4 satisfies: 9 mm < f4 < 110 mm.

[0061] In some embodiments, in the fourth large field-of-view positive lens group, the lens L5 is a symmetric positive lens, the focal length f5 of the lens L5 satisfies: 7 mm < f5 < 8 mm, the focal length f6 of the lens L6 satisfies: -8 mm < f6 < -7 mm, and the combined focal length f56 of the lens L5 and the lens L6 satisfies: 83 mm < f56 < 84 mm. The fourth large field-of-view positive lens group with such parameters can better correct aberrations such as spherical aberration, chromatic aberration, and astigmatism.

[0062] In some embodiments, the focal length f7 of the lens L7 satisfies: -7 mm < f7 < -6 mm.

[0063] The lens parameters of the present invention include the thickness and spacing of each lens, the refractive index of each lens, the radius of curvature, the focal length, and the refractive index of the material of each lens.

[0064] Specifically, as shown in Table 1

[0065]

[0066] Table 1

[0067] Surf SPHAS1 COMAS2 ASTIS3 FCURS4 DISTS5 CLA(CL) CTR(CT) TOT 0.0001074 0.000488 0.000074 0.003130 0.307513 -0.000032 -0.000354

[0068] Table 2

[0069] Table 2 shows the Seidel aberration coefficients of the lens.

[0070] In the accompanying drawings Figure 1 is a schematic structural diagram of an endoscope lens for a high-temperature furnace kiln according to the present invention; Figure 2 is a modulation transfer function MTF diagram of an endoscope lens for a high-temperature furnace kiln according to the present invention; Figure 3 is a spot diagram of an endoscope lens for a high-temperature furnace kiln according to the present invention; Figure 4It is the central field of view function diagram of an endoscope lens for high-temperature furnace kilns of the present invention; Figure 5 It is the maximum field of view point spread function diagram of an endoscope lens for high-temperature furnace kilns of the present invention; Figure 6 It is the diffraction energy enclosing diagram of an endoscope lens for high-temperature furnace kilns of the present invention; Figure 7 It is the wavefront aberration vs. field of view diagram of an endoscope lens for high-temperature furnace kilns of the present invention;

[0071] Figure 8 It is the grid distortion diagram of an endoscope lens for high-temperature furnace kilns of the present invention; Figure 9 It is the radial aberration diagram of an endoscope lens for high-temperature furnace kilns of the present invention.

[0072] In summary, this solution mainly realizes large field of view and low distortion imaging in high-temperature environments through aperture optimization, the collaborative work of five groups of lenses, and symmetric design, and is applicable to industrial endoscope monitoring.

[0073] Although some embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that: without departing from the principles and purposes of the present invention, various changes, modifications, substitutions, and variations to these embodiments are all within the protection scope of the claims of the present invention.

Claims

1. A high-temperature furnace endoscope lens, characterized in that: It includes the following components arranged in sequence along the optical axis from the object side P1 to the imaging plane P3: The first group of high-temperature resistant glass plates P2; The aperture stop S; The second group of large-field-of-view positive lens groups, where the second group of large-field-of-view positive lens groups is composed of the cemented lens of lens L1, lens L2, and lens L3. Lens L1 is a plano-convex positive lens, and the cemented lens of lens L2 and lens L3 has a positive optical power; The third group of symmetrical positive lens L4; The fourth group of positive lens groups, where the fourth group of large-field-of-view positive lens groups is a cemented lens with positive optical power formed by cementing lens L5 and lens L6, and the combined focal length of the cemented lens of lens L5 and lens L6 is less than the combined focal length of the cemented lens of lens L2 and lens L3; The fifth group of negative lens L7, and lens L7 is a plano-concave negative lens.

2. The high-temperature furnace endoscope lens according to claim 1, characterized in that: The aperture diameter of the aperture stop S is less than 2 mm.

3. The high temperature furnace endoscope lens according to claim 1, characterized in that: The field of view angle of the lens is 85°, the focal length f = 3.85 mm, and the image plane size is 9 mm.

4. The high temperature furnace endoscope lens according to claim 1, characterized in that: In the second group of large field-of-view positive lens groups, the focal length f1 of lens L1 satisfies: 10 mm < f1 < 11 mm, the focal length f2 of lens L2 satisfies: 6 mm < f2 < 7 mm, the focal length f3 of lens L3 satisfies: -8 mm < f3 < -7 mm, and the combined focal length f23 of lens L2 and lens L3 satisfies: 26464 mm < f23< 26465 mm.

5. The high temperature furnace endoscope lens according to claim 1, characterized in that: The focal length f4 of lens L4 satisfies: 9 mm < f4 < 110 mm.

6. The high temperature furnace endoscope lens according to claim 1, characterized in that: In the fourth group of large-field-of-view positive lens groups, lens L5 is a symmetrical positive lens, the focal length f5 of lens L5 satisfies: 7 mm < f5 < 8 mm, the focal length f6 of lens L6 satisfies: -8 mm < f6 < -7 mm, and the combined focal length f56 of lens L5 and lens L6 satisfies: 83 mm < f56 < 84 mm.

7. The high-temperature furnace endoscope lens according to claim 1, characterized in that: The focal length f7 of lens L7 satisfies: -7 mm < f7 < -6 mm.

8. The high-temperature furnace endoscope lens according to claim 1, characterized in that: An optoelectronic imaging device is placed at the imaging plane P3 or a relay lens is connected at the back.

9. An image acquisition device, characterized in that: It includes the high-temperature furnace endoscope lens according to any one of claims 1-8.

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