Endoscopic optical imaging system and imaging device for coal-fired boilers

Abstract

The application provides an endoscopic optical imaging system and imaging equipment suitable for a coal-fired boiler, and relates to the field of infrared imaging technology. The imaging system comprises an endoscopic objective group, a symmetrical relay system group and an image plane. The coal-fired boiler is provided with an observation opening, and at least the endoscopic objective group extends into the interior of the furnace through the observation opening. The endoscopic objective group is opposite to the inner wall of the coal-fired boiler, and is used for transmitting infrared radiation of an imaging area to the symmetrical relay system group, and then transmitting the infrared radiation to the image plane through the symmetrical relay system group to realize imaging. The imaging system adopts an endoscopic structure design, at least the endoscopic objective group extends into the interior of the furnace through the observation opening, and can be as close as possible to the surface of the water-cooled wall to perform imaging, so that the infrared radiation of the water-cooled wall does not need to pass through long-distance high-temperature flames, smoke dust and flying ash, and can enter the imaging system through the close and relatively arranged endoscopic objective group to perform imaging.

Description

Technical Field

[0001] This application relates to the field of infrared imaging technology, and in particular to an endoscopic optical imaging system and imaging device suitable for coal-fired boilers. Background Technology

[0002] Thermal power generation remains one of the main methods of power generation. Since coal is a non-renewable resource and considering power generation costs, coal-fired boilers typically use low-rank coal. This type of coal produces a large amount of ash, which easily cokes when it comes into contact with water-cooled walls. Due to poor thermal conductivity, heat accumulates at the coking points, leading to a rapid temperature rise and a significant risk of tube rupture, severely impacting economic efficiency and personnel safety. Therefore, visual monitoring of the water-cooled walls in coal-fired boilers is essential to achieve real-time monitoring of the coking status and accurate quantitative measurement of the temperature field distribution. This is of great practical significance and engineering application value for guiding the precise operation of soot blowing systems, taking preventative measures in advance, and developing targeted maintenance plans to avoid tube rupture accidents. Summary of the Invention

[0003] In view of this, this application provides an endoscopic optical imaging system and imaging device suitable for coal-fired boilers, the scheme of which is as follows: An endoscopic optical imaging system suitable for coal-fired boilers includes an endoscopic objective lens group, a symmetrical relay system group, and an image plane; The coal-fired boiler has an observation opening, and at least the endoscope assembly is placed inside the coal-fired boiler through the observation opening; The endoscope group is opposite to the inner wall of the coal-fired boiler. The endoscope group is used to transmit the infrared radiation of the area to be imaged on the inner wall of the coal-fired boiler to the symmetrical relay system group, and then to the image plane through the symmetrical relay system group. The symmetrical relay system group includes at least one symmetrical relay system, and the symmetrical relay system includes N rod mirrors, where N is an even number greater than or equal to 2; the N rod mirrors are arranged sequentially along the direction away from the endoscope group, and the i-th rod mirror and the (N-i+1)-th rod mirror are arranged symmetrically along a mirror axis, where i is greater than or equal to 1.

[0004] Optionally, the incident surface of the i-th rod lens and the exit surface of the (N-i+1)-th rod lens have opposite radii of curvature, and their absolute values ​​are equal; the exit surface of the i-th rod lens and the incident surface of the (N-i+1)-th rod lens have opposite radii of curvature, and their absolute values ​​are equal.

[0005] Optionally, the thickness of the i-th rod lens and the (N-i+1)-th rod lens are equal along a direction parallel to the optical axis of the imaging system.

[0006] Optionally, the endoscope assembly includes a window glass, a first lens, an aperture, a second lens, and a third lens. The window glass is located on the side close to the area to be imaged, and the first lens, the aperture, the second lens, and the third lens are arranged sequentially in a direction away from the window glass. Both the light-incident surface and the light-exit surface of the window glass are flat. The light-incident surface of the first lens is a plane, and the light-exit surface of the first lens is recessed toward the side where the window glass is located; The light-incident surface of the second lens is recessed towards the side where the third lens is located, and the light-exit surface of the second lens is convex towards the side where the third lens is located; The light-incident surface of the third lens bulges towards the side where the second lens is located, and the light-exit surface of the third lens is recessed towards the side where the second lens is located.

[0007] Optionally, the imaging system further includes a first reflecting mirror and a second reflecting mirror; The infrared radiation, after passing through the endoscope group, is transmitted sequentially through the first reflector and the second reflector to the symmetrical relay system group.

[0008] Optionally, the symmetrical relay system group includes three symmetrical relay systems, which are arranged sequentially along a direction away from the endoscope group.

[0009] Optionally, N=4.

[0010] Optionally, one of the incident surface and the exit surface of the rod lens is a plane, and the other is a sphere.

[0011] Optionally, the window glass is made of zinc selenide, and the first lens, the second lens, the third lens, and each rod lens in the symmetrical relay system are made of germanium.

[0012] An imaging device comprising the endoscopic optical imaging system applicable to coal-fired boilers as described in any of the preceding claims.

[0013] Compared with existing technologies, the beneficial effects of the technical solution in this application are as follows: The imaging system includes an endoscopic objective assembly, a symmetrical relay system assembly, and an image plane. An observation opening is provided in the coal-fired boiler, through which at least the endoscopic objective assembly extends into the furnace. The endoscopic objective assembly is positioned opposite the inner wall of the coal-fired boiler. It transmits infrared radiation from the area to be imaged on the boiler's inner wall to the symmetrical relay system assembly, which then transmits it to the image plane, thus achieving image formation of the area. This imaging system employs an endoscopic structure design, extending the endoscopic objective lens assembly into the furnace through the observation opening. This allows for imaging as close as possible to the surface of the water-cooled wall, eliminating the need for infrared radiation from the water-cooled wall to traverse long distances through high-temperature flames, smoke, and fly ash. Instead, the infrared radiation enters the imaging system through the closely positioned endoscopic objective lens assembly, thus eliminating interference from high-temperature flames and other contaminants on the temperature measurement signal. This effectively solves the problem of inaccurate temperature measurement in existing temperature measurement equipment under harsh furnace conditions. Furthermore, it provides reliable technical support for the accurate commissioning of boiler soot blowing systems, early warning of tube rupture accidents, and optimization of boiler combustion efficiency, resulting in significant safety and economic benefits. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0016] Figure 1 This application provides an endoscopic optical imaging system applicable to coal-fired boilers; Figure 2 A schematic diagram of the optical path of an endoscopic optical imaging system applicable to a coal-fired boiler, provided for this application; Figure 3 A modulation transfer function curve of an endoscopic optical imaging system for a coal-fired boiler provided in this application; Figure 4 A dot diagram of an endoscopic optical imaging system for a coal-fired boiler provided in this application; Figure 5A tolerance allocation diagram for an endoscopic optical imaging system applicable to a coal-fired boiler, provided in this application; Figure 6 This application provides a tolerance analysis diagram for an endoscopic optical imaging system applicable to coal-fired boilers. Detailed Implementation

[0017] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0018] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] As described in the background section, it is essential to conduct visual monitoring of the water-cooled walls in coal-fired boilers. This has significant practical and engineering application value in guiding the precise operation of soot blowing systems, taking preventive measures in advance, and developing targeted maintenance plans to avoid tube rupture accidents.

[0020] Current technologies generally employ infrared thermography equipment for monitoring the temperature of water-cooled walls. However, the infrared imaging beam of the water-cooled wall needs to penetrate the high-temperature flame, high-concentration smoke and dust, and high-speed moving fly ash layer inside the furnace. The aforementioned high-temperature flame, smoke and dust, and fly ash themselves have extremely strong infrared radiation characteristics, and the smoke and dust and fly ash have a severe scattering and attenuation effect on the infrared signal. As a result, the signal received by the temperature measuring equipment is mixed with multiple components such as flame radiation, wall radiation after medium attenuation, and medium self-radiation. It is difficult to accurately reflect the true temperature distribution and coking state of the water-cooled wall from it. For a long time, this problem has been a difficult technical bottleneck to overcome in the field of boiler water-cooled wall temperature monitoring.

[0021] To address the aforementioned problems, this application provides an endoscopic optical imaging system suitable for coal-fired boilers, such as... Figure 1 and Figure 2 As shown, Figure 1 This application provides an endoscopic optical imaging system suitable for coal-fired boilers. Figure 2 This application provides an optical path diagram of an endoscopic optical imaging system applicable to coal-fired boilers. The imaging system includes an endoscopic objective lens group 100, a symmetrical relay system group 200, and an image plane 36.

[0022] The aforementioned coal-fired boiler has an observation opening 300, which is an observation opening 300 on the side wall (also called the water-cooled wall) of the coal-fired boiler. At least the endoscope assembly 100 is placed inside the coal-fired boiler through the observation opening 300; specifically, at least the endoscope assembly 100 extends into the coal-fired boiler through the observation opening 300. The placement of at least the endoscope assembly 100 inside the coal-fired boiler through the observation opening 300 can mean that both the endoscope assembly 100 and a portion of the symmetrical relay system assembly 200 are placed inside the coal-fired boiler through the observation opening 300. However, this application does not limit this; it can be that only the endoscope assembly 100 is placed inside the coal-fired boiler through the observation opening 300, or both the endoscope assembly 100 and the symmetrical relay system assembly 200 are placed inside the coal-fired boiler through the observation opening 300, depending on the specific circumstances. It should be noted that... Figure 1 The observation opening 300 is merely a schematic representation; its specific shape and positional relationship with other components in the imaging system are not limited and will depend on the specific circumstances. Furthermore, Figure 1 For clarity of illustration, avoid Figure 1 The lateral width is too wide, which affects the clarity of the endoscopic objective lens assembly. This affects the clarity of each symmetrical relay system within the symmetrical relay system. Figure 1 The two sides are arranged side by side, but this application does not limit this and it depends on the specific circumstances.

[0023] The endoscope objective group 100 is positioned opposite the inner wall of the coal-fired boiler. The endoscope objective group 100 transmits the infrared radiation from the area to be imaged on the inner wall of the coal-fired boiler to the symmetrical relay system group 200, and then from the symmetrical relay system group 200 to the image plane 36. In other words, after the endoscope extends into the coal-fired boiler through the observation opening 300, i.e., after the endoscope extends into the furnace of the coal-fired boiler through the observation opening 300, it is positioned opposite the inner wall of the coal-fired boiler. This allows the infrared radiation from the area to be imaged on the inner wall of the coal-fired boiler to be directly transmitted to the endoscope objective group 100, then to the symmetrical relay system group 200, and finally to the image plane 36, thus achieving infrared thermal imaging of the area to be imaged.

[0024] The symmetrical relay system group 200 includes at least one symmetrical relay system 210. Each symmetrical relay system 210 includes N rod lenses 202, where N is an even number greater than or equal to 2. The N rod lenses 202 are arranged sequentially along a direction away from the endoscope group 100, and the i-th rod lens 202 and the (N-i+1)-th rod lens 202 are arranged symmetrically along a mirror axis, where i is greater than or equal to 1. For example, the symmetrical relay system 210 includes four rod lenses 202, namely the first, second, third, and fourth rod lenses 202 arranged sequentially along a direction away from the endoscope group 100, with the first and fourth rod lenses 202 and the second and third rod lenses 202 arranged symmetrically along a mirror axis. Specifically, the light-incident surface of the first rod lens 202 and the light-exit surface of the fourth rod lens 202 are arranged symmetrically along a mirror axis, the light-exit surface of the first rod lens 202 and the light-incident surface of the fourth rod lens 202 are arranged symmetrically along a mirror axis, the light-incident surface of the second rod lens 202 and the light-exit surface of the third rod lens 202 are arranged symmetrically along a mirror axis, and the light-exit surface of the second rod lens 202 and the light-incident surface of the third rod lens 202 are arranged symmetrically along a mirror axis.

[0025] As described above, the imaging system adopts an endoscopic structure design, extending the endoscopic objective lens group 100 into the furnace through the observation opening 300. This means that the front end of the imaging system can directly extend into the furnace through the boiler's observation opening 300 and image as close as possible to the surface of the water-cooled wall. This allows the infrared radiation from the water-cooled wall to enter the imaging system through the closely positioned and relatively arranged endoscopic objective lens group 100 without having to travel long distances through high-temperature flames, smoke, and fly ash. This eliminates interference from high-temperature flames and other factors on the temperature measurement signal, enabling the detector to acquire the infrared radiation from the surface of the water-cooled wall. This achieves real-time visualization and accurate temperature field inversion of the water-cooled wall, effectively solving the problem of inaccurate temperature measurement in existing temperature measurement equipment under harsh furnace conditions. It also provides reliable technical support for the accurate commissioning of the boiler soot blowing system, early warning of tube rupture accidents, and optimization of boiler combustion efficiency, resulting in significant safety and economic benefits.

[0026] Based on the above imaging system, such as Figure 3 As shown, Figure 3 This application provides an MTF (Modulation Transfer Function) curve for an endoscopic optical imaging system suitable for coal-fired boilers. Figure 3 The horizontal axis represents spatial frequency, and the vertical axis represents the OTF magnitude (i.e., MTF value). According to Figure 3It can be seen that the OTF modulus of the modulation transfer function of this imaging system is greater than 0.1 at the 14.7 line pairs, the imaging quality of each field of view is close to the diffraction limit, the aberration correction is relatively good, and thus the imaging quality is good.

[0027] In addition, such as Figure 4 As shown, Figure 4 This application provides a ray tracing point array diagram for an endoscopic optical imaging system applicable to coal-fired boilers. Figure 4 Figures a, b, c, and d show the ray tracing point arrays for working half-field of view angles of 0°, 30°, 60°, and 85°, respectively. Figure 5 The infrared radiation wavelengths in the figures include 8μm, 10μm, and 14μm, as shown in the rectangles 8, 10, and 14 in the figures. According to... Figure 4 It can be seen that under the above four different field of view angles, the RMS (Root Mean Square Radius) radius of the imaging system is less than twice the Airy disk diameter, and the GEO (Geometric Spot Radius) radius is generally less than three times the Airy disk diameter, indicating more concentrated energy and better image quality. Furthermore, according to... Figure 4 It is also known that the half field of view of this imaging system can reach 85°, thus enabling the imaging system to achieve wide-angle imaging while providing high-quality imaging.

[0028] In one embodiment of this application, for the aforementioned symmetrical relay system group 200, the incident light surface of the i-th rod mirror 202 and the emitting light surface of the (N-i+1)-th rod mirror 202 in each symmetrical relay system 210 have opposite radii of curvature and equal absolute values ​​of radii of curvature; the emitting light surface of the i-th rod mirror 202 and the incident light surface of the (N-i+1)-th rod mirror 202 have opposite radii of curvature and equal absolute values ​​of radii of curvature. Based on this, the i-th rod mirror 202 and the (N-i+1)-th rod mirror 202 in the symmetrical relay system 210 are arranged in a mirror axis symmetrical configuration. For example, the aforementioned symmetrical relay system 210 includes four rod lenses 202, which are arranged sequentially along a direction away from the endoscope group 100: the first rod lens 202, the second rod lens 202, the third rod lens 202, and the fourth rod lens 202. The light-incident surfaces of the first rod lens 202 and the light-exit surfaces of the fourth rod lens 202 have opposite radii of curvature, but their absolute values ​​are equal. The light-exit surfaces of the first rod lens 202 and the light-incident surfaces of the fourth rod lens 202 have opposite radii of curvature, but their absolute values ​​are equal. The light-incident surfaces of the second rod lens 202 and the light-exit surfaces of the third rod lens 202 have opposite radii of curvature, but their absolute values ​​are equal.

[0029] In one embodiment of this application, the thickness of the i-th rod lens 202 and the (N-i+1)-th rod lens 202 are equal along a direction parallel to the optical axis of the imaging system. Similarly, for example, a symmetrical relay system 210 includes four rod lenses 202, which are the first rod lens 202, the second rod lens 202, the third rod lens 202, and the fourth rod lens 202 arranged sequentially along a direction away from the endoscope group 100. Then, along a direction parallel to the optical axis of the imaging system, the thickness of the first rod lens 202 and the fourth rod lens 202 are equal, and the thickness of the second rod lens 202 and the third rod lens 202 are equal.

[0030] In one embodiment of this application, the endoscope assembly 100 includes a window glass 102, a first lens 104, an aperture 5, a second lens 106, and a third lens 108. The window glass 102 is located on the side closer to the area to be imaged, and the first lens 104, aperture 5, second lens 106, and third lens 108 are arranged sequentially in a direction away from the window glass 102. Based on this, infrared radiation from the area to be imaged enters the endoscope assembly 100 through the window glass 102 and is then transmitted sequentially through the first lens 104, aperture 5, second lens 106, and third lens 108.

[0031] The light-incident and light-exit surfaces of the window glass 102 are both flat, meaning the window glass 102 is a plane mirror. This plane mirror is used to block external wind, sand, water vapor, mechanical impacts, etc., protecting the optical components in the endoscope assembly 100, as well as other optical components, lenses, and detectors inside the imaging system. In addition, the window glass 102 can also transmit infrared light while blocking visible light and ultraviolet light, thereby suppressing external interference.

[0032] The light-incident surface 1 of the first lens 104 is flat, and the light-exiting surface 4 of the first lens 104 is concave towards the side where the window glass 102 is located, that is, the first lens 104 is a plano-concave lens; the light-incident surface 6 of the second lens 106 is concave towards the side where the third lens 108 is located, and the light-exiting surface 7 of the second lens 106 is convex towards the side where the third lens 108 is located, that is, the second lens 106 is a concave-convex lens; the light-incident surface 8 of the third lens 108 is convex towards the side where the second lens 106 is located, and the light-exiting surface 9 of the third lens 108 is concave towards the side where the second lens 106 is located, that is, the third lens 108 is a concave-convex lens. Based on the above-mentioned first lens 104, second lens 106, third lens 108 and aperture 5, the infrared radiation of the area to be imaged is transmitted to the symmetrical relay system group 200, and works in conjunction with the symmetrical relay system group 200 to achieve better imaging quality.

[0033] In one embodiment of this application, for the aforementioned endoscope group 100, the angle between the main ray of infrared radiation and the optical axis of the imaging system is less than or equal to 1°, and the image-side telecentricity of the last symmetrical relay system 210 in the aforementioned symmetrical relay system group 200 is ≤0.9°. Based on this, by using structural operands MNCA (Minimum Center Air Thickness), MNEA (Minimum Edge Air Thickness), MNCG (Minimum Center Glass Thickness), MNEG (Minimum Edge Glass Thickness), MXCG (MaXimum Center Glass Thickness), and MXCA (MaXimum Center Air Thickness), the center and edge thicknesses of air and each lens can be controlled, ensuring the manufacturability of the mechanical structure. By repeatedly optimizing the imaging system using spot radius, wavefront, and pupil sampling number, the final optimization result can be as follows: Figure 2 As shown. Furthermore, the total length of this imaging system can be approximately 1006 mm, which is the reference... Figure 1 The distance from which infrared radiation is transmitted from the window glass 102 to the image plane 36 can be 1006 mm.

[0034] In one embodiment of this application, the imaging system further includes a first reflecting mirror 10 and a second reflecting mirror 11. Infrared radiation, after passing through the endoscope objective group 100, is transmitted sequentially through the first reflecting mirror 10 and the second reflecting mirror 11 to the symmetrical relay system group 200. Specifically, the first reflecting mirror 10 and the second reflecting mirror 11 are both planar reflecting mirrors, and are arranged at intervals, both tilted at 45° relative to the optical axis. Based on this, the angle between the first reflecting mirror 10 and the second reflecting mirror 11 and the optical axis is 45°, so that after the infrared radiation passes through the endoscope objective group 100, the first reflecting mirror 10 and the second reflecting mirror 11 are turned 90° twice, thus the transmission direction of the infrared radiation in the endoscope objective is parallel to the transmission direction in the symmetrical relay system group 200. This allows the symmetrical relay system group to be at least partially located outside the coal-fired boiler through optical path deflection, thereby enabling the imaging system to transmit infrared radiation to the outside of the coal-fired boiler for imaging, further suppressing interference from flames, fly ash, etc., and ensuring image quality. In addition, the imaging system can achieve a 180° turn in the infrared radiation transmission path based on the first reflector 10 and the second reflector 11, thereby reducing the size of the imaging system, making it suitable for the small installation space of the boiler, realizing convenient assembly, inspection and maintenance of the imaging system, and reducing the later operation and maintenance costs.

[0035] In one embodiment of this application, the aforementioned symmetrical relay system group 200 may include three symmetrical relay systems 210, which are arranged sequentially along a direction away from the endoscope group 100. That is, if the aforementioned symmetrical relay system group 200 includes three symmetrical relay systems 210, these three symmetrical relay systems 210 are arranged sequentially along the transmission direction of infrared radiation in the imaging system. However, this application does not limit the number of symmetrical relay systems 210 included in the symmetrical relay system group 200; it depends on the specific circumstances.

[0036] In one embodiment of this application, N=4, meaning the symmetrical relay system 210 may include four rod lenses 202. However, this application does not limit this, and it depends on the specific circumstances. Furthermore, this application does not limit whether the number of rod lenses 202 in each symmetrical relay system 210 within the symmetrical relay system group 200 is the same, and it depends on the specific circumstances.

[0037] In one embodiment of this application, one of the incident surface and the exit surface of the bar lens 202 is a plane, and the other is a spherical surface. However, this application does not limit this and the specific choice depends on the circumstances.

[0038] In one embodiment of this application, the window glass 102 is made of zinc selenide, and the first lens 104, the second lens 106, the third lens 108, and each rod lens 202 in the symmetrical relay system 210 are made of germanium.

[0039] Based on the imaging system described in the above embodiments, such as Figure 5 As shown, Figure 5 This application provides a tolerance allocation diagram for an endoscopic optical imaging system applicable to coal-fired boilers. Figure 5 The test wavelength is 10µm. The curvature tolerance of each optical element in the imaging system is set at 2 aperture stops, with a local aperture of 0.2. The thickness tolerance is ±0.025mm, surface eccentricity is ±0.008mm, and surface tilt is ±0.013°. The aforementioned optical elements include each lens in the endoscope objective group 100, each rod lens 202 in the symmetrical relay system group 200, and the first reflecting mirror 10 and the second reflecting mirror 11. Therefore, the eccentricity of the imaging system is ±0.008mm, and the tilt is ±0.013°. Additionally, the refractive index tolerance of this imaging system is ±0.0008, and the Abbe number tolerance is 0. Figure 6 As shown, after 100 Monte Carlo analyses, the MTF at 10 lp / mm was greater than 0.19 in 90% of cases, indicating high processing feasibility.

[0040] To gain a clearer understanding of the endoscopic optical imaging system for coal-fired boilers provided in this application, a specific embodiment will be described in detail below.

[0041] Specifically, the imaging system may include an endoscope objective group 100, two reflecting mirrors (first reflecting mirror 10 and second reflecting mirror 11), three sets of symmetrical relay systems 210, and an image plane 36. The endoscope objective group 100 consists of a window glass 102, an aperture stop 5, and three lenses. Each symmetrical relay system 210 consists of four rod lenses 202, which are special cylindrical lenses. The imaging system has a half-field of view of 0°, 30°, 60°, and 85°, and operating wavelengths of 8μm, 10μm, and 14μm, with a center wavelength of 10μm. It should be noted that the operating wavelengths of 8μm, 10μm, and 14μm refer to the additional selection of 8μm and 14μm as calculation parameters in the optical design process within the infrared radiation with a center wavelength of 10μm. These parameters, along with aberrations, are calculated in conjunction with the center wavelength to complete the design and optimization of the imaging system. It should also be noted that the center wavelength of this imaging system is 10μm. On the one hand, the peak range of flame radiation is 1.7μm~2μm, and on the other hand, high-temperature flue gas has strong absorption peaks at 2.7μm and 4.3μm. The infrared radiation with a center wavelength of 10μm can pass through the flue gas without being drastically attenuated, and avoid strong flame radiation interference. It can specifically suppress the infrared radiation interference of flame, high-temperature flue gas and fly ash, significantly improve the signal-to-noise ratio of temperature measurement imaging in the harsh environment of the furnace, and ensure imaging clarity and temperature measurement accuracy.

[0042] like Figure 1 As shown, the dashed line represents the optical axis of the imaging system. All optical elements in the endoscope objective group 100, all optical elements in the symmetrical relay system group 200, the two mirrors, and the image plane 36 are located on the same optical axis, which is the optical axis of the imaging system. Figure 1In the diagram, 1 and 2 are the light-incident and light-exit surfaces of the window glass 102 of the endoscope objective assembly 100, 3 and 4 are the light-incident and light-exit surfaces of the first lens 104 of the endoscope objective assembly 100, 5 is the aperture stop 5, 6 and 7 are the light-incident and light-exit surfaces of the second lens 106 of the endoscope objective assembly 100, 8 and 9 are the light-incident and light-exit surfaces of the third lens 108 of the endoscope objective assembly 100, 10 is the first reflecting surface with an inclination angle of 45° (i.e., the first reflecting mirror 10), and 11 is the second... Two reflecting surfaces with a tilt angle of 45° (i.e., the second reflecting mirror 11); 12 and 13 are the incident and exit surfaces of the first rod mirror 202 in the first group of symmetrical relay systems 210; 14 and 15 are the incident and exit surfaces of the second rod mirror 202 in the first group of symmetrical relay systems 210; 16 and 17 are the incident and exit surfaces of the third rod mirror 202 in the first group of symmetrical relay systems 210; 18 and 19 are the incident and exit surfaces of the fourth rod mirror 202 in the first group of symmetrical relay systems 210. The light-incident and light-outceasing surfaces of rod lens 202 are as follows: 20 and 21 are the light-incident and light-outceasing surfaces of the first rod lens 202 in the second group of symmetrical relay systems 210; 22 and 23 are the light-incident and light-outceasing surfaces of the second rod lens 202 in the second group of symmetrical relay systems 210; 24 and 25 are the light-incident and light-outceasing surfaces of the third rod lens 202 in the second group of symmetrical relay systems 210; and 26 and 27 are the light-incident and light-outceasing surfaces of the fourth rod lens 202 in the second group of symmetrical relay systems 210. The light-emitting surfaces are as follows: 28 and 29 are the incident and emitting surfaces of the first rod lens 202 in the third symmetrical relay system 210; 30 and 31 are the incident and emitting surfaces of the second rod lens 202 in the third symmetrical relay system 210; 32 and 33 are the incident and emitting surfaces of the third rod lens 202 in the third symmetrical relay system 210; 34 and 35 are the incident and emitting surfaces of the fourth rod lens 202 in the third symmetrical relay system 210; and 36 is the image plane. The window glass 102 in the endoscope objective group 100 is made of zinc selenide, and the other lenses are made of germanium. All rod lenses 202 in the symmetrical relay system 210 are made of germanium. Furthermore, the maximum aperture of each lens in the endoscope objective group 100 is 14.528 mm.

[0043] The area to be imaged is located on the opposite side of the light-incident surface 1 of the window glass 102, and the distance between it and the light-incident surface 1 of the window glass 102 is 240mm. The infrared radiation emitted by the area to be imaged at different field angles is reflected twice by the endoscope objective group 100 to the symmetrical relay system group 200, and then imaged on the image plane 36 by the three symmetrical relay systems 210.

[0044] In the aforementioned symmetrical repeater system group 200, a single symmetrical repeater system 210 consists of four rod mirrors 202. Each rod mirror 202 has one surface that is a plane with an infinite radius of curvature and another surface that is a spherical surface convex outwards. In each symmetrical repeater system 210, the light-incident surface 12 of the first rod mirror 202 and the light-exit surface 19 of the fourth rod mirror 202 have opposite radii of curvature; the light-exit surface 13 of the first rod mirror 202 and the light-incident surface 18 of the fourth rod mirror 202 have opposite radii of curvature; the light-incident surface 14 of the second rod mirror 202 and the light-exit surface 17 of the third rod mirror 202 have opposite radii of curvature; the light-exit surface 15 of the second rod mirror 202 and the light-incident surface 16 of the third rod mirror 202 have opposite radii of curvature; the first rod mirror 202 and the fourth rod mirror 202 have the same thickness; the second rod mirror 202 and the third rod mirror 202 have the same thickness; and the maximum aperture of each rod mirror 202 is 18 mm.

[0045] In the aforementioned endoscope assembly 100, the thickness of the window glass 102 is 0.901 mm, the thickness of the first lens 104 is 0.999 mm, the thickness of the second lens 106 is 7.72 mm, the thickness of the third lens 108 is 0.988 mm, the thickness of the first and fourth rod lenses 202 of the symmetrical relay system 210 is 42.849 mm, and the thickness of the second and third rod lenses 202 is 74.609 mm.

[0046] In this imaging system, the air gap between the light-emitting surface 2 of the window glass 102 and the light-incident surface 3 of the first lens 104 is 0.143 mm; the air gap between the light-emitting surface 4 of the first lens 104 and the aperture stop 5 is 7.77 mm; the air gap between the aperture stop 5 and the light-incident surface 6 of the second lens 106 is 3.311 mm; the air gap between the light-emitting surface 7 of the second lens 106 and the light-incident surface 8 of the third lens 108 is 6.21 mm; the air gap between the light-emitting surface 9 of the third lens 108 and the first reflecting mirror 10 is 8.958 mm; the air gap between the first reflecting mirror 10 and the second reflecting mirror 11 is 17 mm; and the second reflecting mirror 11 and the first rod mirror of the first symmetrical relay system 210 are... The air gap between the light-receiving surfaces 12 of the first rod lens 202 of the first symmetrical relay system 210 is 20 mm. The air gap between the light-exiting surface 13 of the first rod lens 202 and the light-receiving surface 14 of the second rod lens 202 of the first symmetrical relay system 210 is 6.302 mm. The air gap between the light-exiting surface 15 of the second rod lens 202 and the light-receiving surface 16 of the third rod lens 202 of the first symmetrical relay system 210 is 31.146 mm. The air gap between the light-exiting surface 17 of the third rod lens 202 and the light-receiving surface 18 of the fourth rod lens 202 of the first symmetrical relay system 210 is 6.302 mm. The air gap between the light-exiting surface 19 of the fourth rod lens 202 of the relay system 210 and the light-incident surface 20 of the first rod lens 202 of the second symmetrical relay system 210 is 60 mm; the air gap between the light-exiting surface 21 of the first rod lens 202 of the second symmetrical relay system 210 and the light-incident surface 22 of the second rod lens 202 of the second symmetrical relay system 210 is 6.302 mm; the air gap between the light-exiting surface 23 of the second rod lens 202 of the second symmetrical relay system 210 and the light-incident surface 24 of the third rod lens 202 of the second symmetrical relay system 210 is 31.146 mm; and the air gap between the light-exiting surface 25 of the third rod lens 202 of the second symmetrical relay system 210 and the light-incident surface 20 of the second symmetrical relay system 210 is 60 mm. The air gap between the incident surfaces 26 of the fourth rod lens 202 of the relay system 210 is 6.302 mm; the air gap between the exit surface 27 of the fourth rod lens 202 of the second symmetrical relay system 210 and the incident surface 28 of the first rod lens 202 of the third symmetrical relay system 210 is 60 mm; the air gap between the exit surface 29 of the first rod lens 202 of the third symmetrical relay system 210 and the incident surface 30 of the second rod lens 202 of the third symmetrical relay system 210 is 6.302 mm; and the air gap between the exit surface 31 of the second rod lens 202 of the third symmetrical relay system 210 and the incident surface 32 of the third rod lens 202 of the third symmetrical relay system 210 is 31 mm.The air gap between the light-exiting surface 33 of the third rod lens 202 of the third symmetrical relay system 210 and the light-incident surface 34 of the fourth rod lens 202 of the third symmetrical relay system 210 is 6.302 mm, and the air gap between the light-exiting surface 35 of the fourth rod lens 202 of the third symmetrical relay system 210 and the image plane 36 is 30 mm.

[0047] Based on the endoscopic optical imaging system applicable to coal-fired boilers described in any of the above embodiments, this application also provides an imaging device, which includes the endoscopic optical imaging system applicable to coal-fired boilers described in any of the above embodiments.

[0048] In summary, this application provides an endoscopic optical imaging system and imaging device suitable for coal-fired boilers. The imaging system includes an endoscopic objective lens assembly, a symmetrical relay system assembly, and an image plane. The coal-fired boiler has an observation opening through which at least the endoscopic objective lens assembly extends into the furnace. The endoscopic objective lens assembly is positioned opposite the inner wall of the coal-fired boiler. The endoscopic objective lens assembly transmits infrared radiation from the area to be imaged on the inner wall of the coal-fired boiler to the symmetrical relay system assembly, and then to the image plane, thereby achieving imaging of the area to be imaged. This imaging system employs an endoscopic structure design, extending the endoscopic objective lens assembly into the furnace through the observation opening. This allows for imaging as close as possible to the surface of the water-cooled wall, eliminating the need for infrared radiation from the water-cooled wall to traverse long distances through high-temperature flames, smoke, and fly ash. Instead, the infrared radiation enters the imaging system through the closely positioned endoscopic objective lens assembly, thus eliminating interference from high-temperature flames and other contaminants on the temperature measurement signal. This effectively solves the problem of inaccurate temperature measurement in existing temperature measurement equipment under harsh furnace conditions. Furthermore, it provides reliable technical support for the accurate commissioning of boiler soot blowing systems, early warning of tube rupture accidents, and optimization of boiler combustion efficiency, resulting in significant safety and economic benefits.

[0049] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on its differences from other embodiments, and similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0050] It should be noted that, in the description of this application, the terms "upper," "lower," "top," "bottom," "inner," and "outer," 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 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, and therefore should not be construed as a limitation of this application. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0051] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely 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 an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0052] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An endoscopic optical imaging system suitable for coal-fired boilers, characterized in that, It includes an endoscope assembly, a symmetrical relay system assembly, and an image plane; The coal-fired boiler has an observation opening, through which at least the endoscope assembly is placed inside the coal-fired boiler; The endoscope group is opposite to the inner wall of the coal-fired boiler. The endoscope group is used to transmit the infrared radiation of the area to be imaged on the inner wall of the coal-fired boiler to the symmetrical relay system group, and then to the image plane through the symmetrical relay system group. The symmetrical relay system group includes at least one symmetrical relay system, and the symmetrical relay system includes N rod mirrors, where N is an even number greater than or equal to 2; the N rod mirrors are arranged sequentially along the direction away from the endoscope group, and the i-th rod mirror and the (N-i+1)-th rod mirror are arranged symmetrically along a mirror axis, where i is greater than or equal to 1.

2. The endoscopic optical imaging system for coal-fired boilers according to claim 1, characterized in that, The incident surface of the i-th rod lens and the exit surface of the (N-i+1)-th rod lens have opposite radii of curvature, and their absolute values ​​are equal; the exit surface of the i-th rod lens and the incident surface of the (N-i+1)-th rod lens have opposite radii of curvature, and their absolute values ​​are equal.

3. The endoscopic optical imaging system for coal-fired boilers according to claim 2, characterized in that, Along the direction parallel to the optical axis of the imaging system, the thickness of the i-th rod lens and the (N-i+1)-th rod lens are equal.

4. The endoscopic optical imaging system for coal-fired boilers according to claim 1, characterized in that, The endoscope assembly includes a window glass, a first lens, an aperture, a second lens, and a third lens. The window glass is located on the side close to the area to be imaged, and the first lens, the aperture, the second lens, and the third lens are arranged sequentially in a direction away from the window glass. Both the light-incident surface and the light-exit surface of the window glass are flat. The light-incident surface of the first lens is a plane, and the light-exit surface of the first lens is recessed toward the side where the window glass is located; The light-incident surface of the second lens is recessed towards the side where the third lens is located, and the light-exit surface of the second lens is convex towards the side where the third lens is located; The light-incident surface of the third lens bulges towards the side where the second lens is located, and the light-exit surface of the third lens is recessed towards the side where the second lens is located.

5. The endoscopic optical imaging system for coal-fired boilers according to claim 1, characterized in that, The imaging system also includes a first reflecting mirror and a second reflecting mirror; The infrared radiation, after passing through the endoscope group, is transmitted sequentially through the first reflector and the second reflector to the symmetrical relay system group.

6. The endoscopic optical imaging system for coal-fired boilers according to claim 1, characterized in that, The symmetrical relay system group includes three symmetrical relay systems, which are arranged sequentially along the direction away from the endoscope group.

7. The endoscopic optical imaging system for coal-fired boilers according to claim 1 or 6, characterized in that, N=4。 8. The endoscopic optical imaging system for coal-fired boilers according to claim 7, characterized in that, The light-incident surface and the light-excising surface of the rod lens are, respectively, a plane and a sphere.

9. The endoscopic optical imaging system for coal-fired boilers according to claim 4, characterized in that, The window glass is made of zinc selenide, and the first lens, the second lens, the third lens, and each rod lens in the symmetrical relay system are made of germanium.

10. An imaging device, characterized in that, Including the endoscopic optical imaging system applicable to coal-fired boilers as described in any one of claims 1-9.

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