A vacuum high-temperature forging furnace inner forging piece polarization on-line detection device

Abstract

The present application relates to laser detection technical field, disclose a kind of vacuum high-temperature forging furnace inner forging piece polarization on-line detection device, including window subassembly, coaxial light beam split and combine subassembly, active linear polarization laser emission module and polarization filtering imaging receiving module, window subassembly is embedded in furnace wall through-hole and forms optical transparent passage;Coaxial light beam split and combine subassembly is set in window furnace outside, with three optical ports.The present application embeds high-temperature light-transmitting material window subassembly in furnace wall through-hole, sets coaxial light beam split and combine subassembly in window furnace outside, couples active linear polarization laser emission module and polarization filtering imaging receiving module to same window, share same segment main light path passing through furnace wall, constructs complete polarization detection channel from furnace outside to furnace inside again return, and utilize the physical difference between the polarization characteristics reserved by forging piece surface mirror reflection and the depolarization of mould / furnace wall diffuse reflection, realize the accurate distinction of forging piece and background under isothermal, same bright and same spectrum environment.

Description

Technical Field

[0001] This invention relates to the field of laser detection technology, specifically to an online polarization detection device for forgings inside a vacuum high-temperature forging furnace. Background Technology

[0002] Vacuum high-temperature isothermal forging (1000~1500℃) is a core manufacturing process for key components in aerospace, nuclear power, and high-end equipment. During forging, the billet is preheated to the process temperature in a vacuum furnace and then fed into the mold cavity. The mold is closed and pressure is applied to complete the forging process, after which the ejector pin pushes the forging out of the mold cavity. The position, orientation, and contour integrity of the forging after demolding directly determine the product quality. Defects such as misalignment, insufficient material, and underpressure, if not detected in time, will lead to batch scrap. Therefore, real-time online monitoring of the forgings during the forging process is crucial.

[0003] Conventional detection methods primarily involve visual inspection or infrared detection. Visual inspection utilizes the differences in brightness, color temperature, or spectral distribution between the target and the background. These differences are captured by imaging sensors and processed through image processing to achieve target recognition. The physical basis is that different objects, due to differences in temperature or material, exhibit observable differences in the intensity and spectral characteristics of their radiated or reflected light. However, in a vacuum high-temperature isothermal forging environment, the forging, die, and furnace wall are all heated to the same forging process temperature. According to Kirchhoff's law of thermal radiation, the radiative exitance of an object in thermal equilibrium depends only on its temperature and surface emissivity. Because the surface state of high-temperature metal surfaces tends to be uniform after prolonged high-temperature holding (oxidation, diffusion of alloying elements, etc.), the emissivity differences between surfaces are extremely small, leading to a uniform blackbody radiation brightness, color temperature, and spectral distribution across all surfaces.

[0004] The working principle of infrared thermometry is to detect the infrared energy radiated from the surface of an object, and then infer the surface temperature based on Planck's law of radiation, using the temperature gradient between different objects to distinguish and locate them. Its physical basis is also the existence of a measurable temperature difference between the target and the background. However, in a vacuum high-temperature isothermal forging environment, the billet is independently heated to the forging process temperature in the preheating zone before being sent into the mold cavity. After sufficient heat exchange during mold closing and pressure application, the forging and the mold reach a state of thermal equilibrium, and their temperatures are the same. The furnace wall is also within the same temperature range. Therefore, there is no measurable temperature gradient between the forging, the mold, and the furnace wall.

[0005] Therefore, conventional visual inspection methods and infrared inspection methods, under vacuum, high temperature, isothermal conditions, and strong blackbody radiation of the same brightness and spectrum, cannot accurately distinguish forgings from the background online based on visual / infrared data acquisition because the target area lacks the physical basis for brightness and temperature differences. Summary of the Invention

[0006] The purpose of this invention is to provide an online polarization detection device for forgings in a vacuum high-temperature forging furnace, so as to solve the technical problem in the prior art that it is difficult to accurately distinguish forgings from the background online based on visual / infrared acquisition data due to the lack of physical basis for brightness difference and temperature difference in the target area.

[0007] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: An online polarization detection device for forgings in a vacuum high-temperature forging furnace includes: The window assembly is embedded in the through-hole of the furnace wall of the vacuum high-temperature forging furnace to form an optically transparent channel between the high-temperature environment inside the furnace and the normal-temperature environment outside the furnace. A coaxial beam splitter / combiner is disposed outside the furnace of the window assembly. The coaxial beam splitter / combiner has a first port, a second port, and a third port. The third port faces the window assembly, and the coaxial beam splitter / combiner is configured to guide light input from the first port to output from the third port, and to guide light input from the third port to output from the second port. An active linearly polarized laser emitting module has its emitting end facing the first port, so that the emitted linearly polarized laser passes through the first port and the third port in sequence, passes through the window assembly, and enters the furnace along the main optical axis of the optical transparent channel to irradiate the surface of the forging, as well as the furnace wall and the surface of the mold. The polarization filtering imaging receiving module has its receiving end facing the second port, so that the reflected light from the forging surface, furnace wall and mold returns along the main optical axis and then enters the polarization filtering imaging receiving module through the third port and the second port in sequence.

[0008] Furthermore, the coaxial beam splitter and combiner assembly includes a polarization beam splitter and a quarter-wave plate; The polarization beam splitter is located at the intersection of the first port, the second port, and the third port, and the quarter-wave plate is located on the main optical axis between the polarization beam splitter and the window assembly.

[0009] Furthermore, the polarization beam splitter is a polarization beam splitting cubic prism. The beam splitting surface of the polarization beam splitting cubic prism transmits linearly polarized light with a first polarization direction incident between the first port and the third port along the principal optical axis, and reflects and guides linearly polarized light with a second polarization direction orthogonal to the first polarization direction incident from the third port along the principal optical axis to the second port.

[0010] Furthermore, the fast axis direction of the quarter-wave plate forms an angle of 42° to 48° with the polarization direction of the linearly polarized laser emitted by the active linearly polarized laser emission module.

[0011] Furthermore, the first linearly polarized laser emitted by the active linearly polarized laser emission module enters the polarization beam splitter with a first polarization direction and is transmitted to the third port; The first linearly polarized laser, output from the third port with the first polarization direction, passes through the quarter-wave plate and the window assembly in sequence and enters the furnace. After being reflected by the mirror surface of the forging, the polarization direction changes to the second polarization direction. The second linearly polarized laser reflected in the second polarization direction returns along the original optical path, passes through the window assembly and the quarter-wave plate in sequence, enters the polarization beam splitter, and is reflected to the second port b to enter the polarization filtering imaging receiving module; The polarization state of the light diffusely reflected from the furnace wall and the mold surface is randomized. After passing through the quarter-wave plate, a portion of the light is reflected by the polarization beam splitter to the second port, so as to selectively split the specular reflection light from the forging surface and the diffuse reflection light from the furnace wall and the mold surface.

[0012] Furthermore, the viewing window assembly includes a sapphire transparent substrate, the inner surface of the sapphire transparent substrate is coated with an anti-metal evaporation protective coating layer, and a vacuum sealing structure is provided between the sapphire transparent substrate and the furnace wall through hole; The sapphire translucent substrate is installed at an angle in the through hole of the furnace wall. The normal direction of the sapphire translucent substrate forms a preset angle with the main optical axis, so that the reflected light from the front and rear surfaces of the sapphire translucent substrate deviates from the main optical axis.

[0013] Furthermore, the vacuum high-temperature forging furnace adopts a double-layer structure of an outer furnace shell and an inner heating furnace liner. The furnace wall through holes include furnace shell through holes opened on the outer furnace shell and furnace liner through holes opened at corresponding positions on the inner heating furnace liner. The furnace shell through holes and the furnace liner through holes are coaxially arranged. The window assembly is embedded in the furnace shell through holes, and its inward end abuts against the furnace liner through holes. The main optical axis coincides with the axes of the furnace shell through hole, the furnace liner through hole, and the viewing window assembly.

[0014] Furthermore, the furnace liner through hole is an oblong hole or a waist-shaped hole, and its length direction is the same as the thermal expansion direction of the inner heating furnace liner, so as to compensate for the thermal expansion displacement of the inner heating furnace liner during the heating process.

[0015] Furthermore, the polarization filtering imaging receiving module includes a narrowband bandpass filter, a focal plane polarization image sensor, and an imaging optical lens arranged sequentially along the optical path; The center wavelength of the narrowband bandpass filter is matched with the laser wavelength emitted by the active linearly polarized laser emission module, and is used to filter out blackbody thermal radiation noise in the furnace. The pixel of the focal plane polarization image sensor integrates a micro-polarization array with multiple directions for real-time acquisition of polarization images in a single exposure. The imaging optical lens is disposed on the side of the narrow bandpass filter facing the second port, and is used to image the light filtered by the narrow bandpass filter onto the target surface of the focal plane polarization image sensor.

[0016] Furthermore, the active linearly polarized laser emission module includes a linearly polarized laser and a collimating and shaping lens group. The laser emitted by the linearly polarized laser is collimated and shaped by the collimating and shaping lens group and then enters the first port as a parallel beam.

[0017] Compared with the prior art, the present invention has the following advantages: This invention embeds a high-temperature resistant, light-transmitting material window assembly into a through-hole in the furnace wall, and sets a coaxial beam splitting and combining assembly on the outside of the window. It couples the active linearly polarized laser emitting module and the polarization filtering imaging receiving module to the same window, sharing the same main optical path passing through the furnace wall. This constructs a complete polarization detection channel from outside the furnace to inside and back. Furthermore, it utilizes the physical difference between the polarization characteristics preserved by the specular reflection of the forging surface and the depolarization by the diffuse reflection of the mold / furnace wall, to achieve accurate differentiation between the forging and the background under isothermal, same brightness, and same spectral conditions. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure provided for an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the optical path principle of the coaxial beam splitting and combining component provided in the embodiments of this application.

[0021] Figure 3 This is a schematic diagram of the coaxial optical through-hole structure of the double-layer furnace body provided in the embodiments of this application.

[0022] Figure 4 This is a schematic diagram showing the installation positions of the coaxial beam splitter / combiner, the active linearly polarized laser emitting module, and the polarization-filtered imaging receiving module provided in the embodiments of this application.

[0023] Figure 5 This is a schematic diagram of the window component structure provided in an embodiment of this application.

[0024] Figure 6 This is a schematic diagram of the polarization state conversion between the incident laser light path and the reflected light return light path provided in the embodiments of this application.

[0025] The reference numerals in the figure are as follows: 1. Vacuum high-temperature forging furnace; 11. Outer furnace shell; 12. Inner heating furnace liner; 2. Furnace wall through holes; 21. Furnace shell through holes; 22. Furnace liner through holes; 3. Window assembly; 31. Sapphire transparent substrate; 32. Anti-metal evaporation protective coating layer; 33. Vacuum sealing structure; 4 Active linearly polarized laser emission module, 41 Linearly polarized laser, 42 Collimating and shaping lens group; 5. Coaxial beam splitter and combiner assembly; 51. Polarizing beam splitter; 52. Quarter-wave plate; 5a. First port; 5b. Second port; 5c. Third port. 6. Polarization filter imaging receiver module, 61. Narrowband bandpass filter, 62. Focal plane polarization image sensor, 63. Imaging optical lens; 7. Constant temperature damping base; 8. Operational control host; 9-person human-computer interaction display terminal. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Example 1:

[0028] like Figure 1 As shown, the present invention provides an online polarization detection device for forgings in a vacuum high-temperature forging furnace, which mainly consists of four core functional units: a window assembly 3, a coaxial beam splitting and combining assembly 5, an active linear polarization laser emitting module 4, and a polarization filtering imaging receiving module 6. The four are connected in series through an optical path to form a complete polarization detection channel from outside the furnace to inside the furnace and back to outside the furnace.

[0029] like Figure 3 , Figure 5As shown, the viewing window assembly 3 is embedded in the furnace wall through-hole 2 of the vacuum high-temperature forging furnace 1, serving as the only optical interface between the high-temperature environment inside the furnace and the ambient temperature environment outside. The viewing window assembly 3 is made of high-temperature resistant and light-transmitting sapphire material. Its mechanical strength and optical performance remain stable within a working temperature range of 1000~1500℃. It exhibits high transmittance and minimal attenuation for 808nm and 1064nm wavelength lasers, has a Mohs hardness of 9, and good wear resistance, enabling it to withstand the erosion of metal vapors and high-temperature dust inside the furnace.

[0030] The normal direction of the window assembly 3 defines the direction of the main optical axis of the device. After passing through the window assembly 3, the main optical axis points to the area where the forging is located in the furnace through the coaxial optical through hole.

[0031] The inner surface of the window assembly 3 is coated with an anti-metal evaporation protective coating layer 32. This coating layer is a SiO2 / TiO2 multilayer high-temperature resistant dielectric film with a transmittance of not less than 96% for the working laser wavelength (1064nm). At the same time, it reduces the adhesion of metal vapor to the sapphire surface and extends the effective service life of the window.

[0032] A vacuum sealing structure 33 is provided between the viewing window assembly 3 and the furnace wall through hole 2, including an oxygen-free copper vacuum sealing gasket and a floating elastic compression flange. The oxygen-free copper sealing gasket undergoes controllable deformation under the pre-tightening force of the disc spring group of the elastic compression flange, forming a high-vacuum sealing contact surface with the outer peripheral surface of the sapphire transparent substrate and the inner wall surface of the furnace wall through hole. The adaptive deformation capability of the elastic element can compensate for the axial and radial thermal expansion displacement generated by the furnace body during the thermal cycle of 1000-1500℃, maintaining the sealing reliability across the entire temperature range.

[0033] The coaxial beam splitter / combiner 5 is located outside the furnace of the viewing window assembly 3 and is the core optical coupling element of this device. For example... Figures 2-4 As shown, the coaxial beam splitter / combiner 5 has three optical ports: First port 5a: facing the active linearly polarized laser emission module 4, serving as the laser incident port; Second port 5b: Oriented toward polarization filter imaging receiver module 6, it is the reflected light output port; The third port 5c: facing the window assembly 3, along the main optical axis, is the optical port leading into the furnace.

[0034] The first port 5a and the second port 5b are arranged in mutually orthogonal directions, and the third port 5c is arranged along the main optical axis. The function of the coaxial beam splitting and combining component 5 is to guide the laser light input from the first port 5a to the output of the third port 5c, and then through the viewing window into the furnace; and to guide the reflected light returning from the third port 5c to the output of the second port 5b, and then into the polarization filtering imaging receiving module 6.

[0035] The laser emitter and the imaging receiver need to share the same optical path (coaxial) passing through the furnace wall to simplify the structure, reduce the window size, reduce the opening area of ​​the furnace wall, reduce the impact on the structural strength of the furnace body and the vacuum seal, and at the same time ensure that the incident light and the reflected light are always accurately aligned.

[0036] However, the emitted and received light must be effectively separated to prevent high-power laser light from directly entering the imaging sensor and causing saturation or permanent damage. Therefore, an optical beam splitter / combiner is needed to selectively split the incident and reflected light by utilizing the difference in polarization states, guiding them to their respective ports.

[0037] An active linearly polarized laser emitting module 4 is installed outside the first port 5a of the coaxial beam splitter / combiner 5, with its emitting end facing the first port 5a. The active linearly polarized laser emitting module 4 emits linearly polarized laser light with a wavelength of 808 nm or 1064 nm. The emitted linearly polarized laser light enters the coaxial beam splitter / combiner 5 from the first port 5a, is guided to the third port 5c for output, and then passes through the window assembly 3 along the main optical axis into the furnace.

[0038] This device employs "active" linearly polarized laser illumination instead of relying on the thermal radiation of the forging itself. In an isothermal environment of 1000–1500°C, the blackbody radiation emitted by the forging, mold, and furnace wall is identical in brightness and spectrum, making them difficult to distinguish. Active laser illumination introduces a narrowband signal source at a specific wavelength (e.g., 1064 nm) that is significantly higher than the blackbody radiation background, providing a signal basis for subsequent narrowband filtering and polarization analysis. Simultaneously, the laser is required to have highly linearly polarized characteristics (polarization extinction ratio ≥ 100:1) because only when the polarization state of the incident light is determined and known can the forging and background be distinguished by analyzing the changes in the polarization state of the reflected light (spectral reflection maintains polarization contrast, diffuse reflection depolarizes).

[0039] The polarization-filtered imaging receiver module 6 is mounted outside the second port 5b of the coaxial beam splitter / combiner assembly 5, with its receiving end facing the second port 5b. The polarization-filtered imaging receiver module 6 receives and analyzes the polarization characteristics of the light output from the second port 5b, and outputs polarization image data.

[0040] The light output from port 5b has been polarization-selectively split by the coaxial beam splitter, containing a highly polarized signal reflected from the forging specular surface and a low-polarized signal diffusely reflected from the mold / furnace wall. The polarization filtering imaging receiver module further performs narrowband filtering (to suppress blackbody radiation noise) and polarization imaging (to quantize the polarization degree of each pixel) on this light signal, providing the image data basis for subsequent polarization degree thresholding.

[0041] The linearly polarized laser emitted by the active linearly polarized laser emission module 4 passes sequentially through the first port 5a and the third port 5c, through the window assembly 3, and enters the furnace along the main optical axis to irradiate the surface of the forging. The reflected light from the surface of the forging and the background inside the furnace (mold, furnace wall) returns along the original path along the main optical axis (this is a common geometric characteristic of specular reflection and diffuse reflection - under near-normal incident conditions, the reflected light returns near the incident direction), and then enters the polarization filtering imaging receiving module 6 sequentially through the third port 5c and the second port 5b.

[0042] The incident and reflected light paths share the same principal optical axis segment passing through the viewing window, achieving "coaxiality". Utilizing the geometric property that reflected light returns near the incident direction, only one viewing window is needed to simultaneously complete laser incident and reflected light reception.

[0043] Therefore, the device of the present invention, by embedding a high-temperature resistant light-transmitting material window assembly in the through hole of the furnace wall and setting a coaxial beam splitting and combining assembly on the outside of the window furnace, couples the active linear polarization laser emitting module and the polarization filtering imaging receiving module to the same window, sharing the same main optical path passing through the furnace wall, thus constructing a complete polarization detection channel from outside the furnace to inside the furnace and back. Furthermore, by utilizing the physical difference between the polarization characteristics preserved by the specular reflection of the forging surface and the depolarization by the diffuse reflection of the mold / furnace wall, it achieves accurate differentiation between the forging and the background under isothermal, same brightness and same spectrum conditions.

[0044] Example 2:

[0045] like Figures 2-4 As shown, the coaxial beam splitter and combiner 5 includes a polarization beam splitter 51 and a quarter-wave plate 52.

[0046] The polarization beam splitter 51 is located at the intersection of the first port 5a, the second port 5b, and the third port 5c, i.e., the geometric intersection center of the three-port optical path. The quarter-wave plate 52 is located on the principal optical axis between the polarization beam splitter 51 and the window assembly 3, downstream of the polarization beam splitter 51 and upstream of the window assembly 3.

[0047] In this embodiment, the combination of a polarization beam splitter and a quarter-wave plate is a classic optical architecture for achieving coaxial transmit and receive separation, which is widely used in optical systems such as LiDAR, confocal microscopes, and optical coherence tomography (OCT).

[0048] The isolation of incident and reflected light is achieved by two orthogonal transformations of polarization states: linearly polarized light → quarter-wave plate → circularly polarized light → target reflection → circularly polarized light → quarter-wave plate → orthogonally linearly polarized light. The orthogonally linearly polarized light is split into different directions by a polarization beam splitter.

[0049] In this embodiment, the architecture not only achieves separation of transmission and reception, but also combines the specular reflection characteristics of the forging surface and the diffuse reflection characteristics of the mold / furnace wall surface to provide an inherent contrast enhancement effect between the forging and the background before it enters the imaging sensor.

[0050] As a preferred embodiment, such as Figure 4 As shown, the polarization beam splitter 51 is a polarization beam-splitting cube prism (PBSCube), which is formed by bonding two right-angle prisms along their diagonal surfaces. The bonding diagonal surfaces are coated with a polarization-selective multilayer dielectric film (beam-splitting surface). The polarization beam-splitting cube prism is placed at the intersection center of the three ports.

[0051] The beam splitter 51 has high transmittance (T) for linearly polarized light incident along the principal optical axis in the first polarization direction (denoted as P polarization direction - the electric field vector is located in the incident plane). p ≥95%), causing it to pass through the beam-splitting surface and exit from the third port 5c along the principal optical axis. It has high reflectivity (R) for linearly polarized light incident from the third port 5c along the principal optical axis and with a second polarization direction orthogonal to the first polarization direction (denoted as the S polarization direction – the electric field vector is perpendicular to the incident plane). s (≥95%), causing it to be reflected by the beam splitter and rotated 90°, outputting from the second port 5b.

[0052] In this embodiment, the beam-splitting surface of the polarization beam-splitting cubic prism is formed by alternating layers of high and low refractive index dielectric films, and its optical thickness satisfies the Brewster angle condition, so that P-polarized light is transmitted with extremely low loss and S-polarized light is reflected with high reflectivity.

[0053] The cubic prism is chosen over the flat polarization beam splitter because both transmitted and reflected light from the cubic prism propagate in a straight line along the inside of the prism, and the exit surface is parallel to the incident surface, which does not introduce beam deflection or astigmatism, making it suitable for polarization imaging systems that require high beam quality.

[0054] The P / S polarization direction is defined to be consistent with the incident surface of the beam splitter, ensuring that the P-polarized light output by the laser emission module is efficiently transmitted and the reflected S-polarized light is efficiently reflected to the imaging module.

[0055] As a preferred embodiment, the fast axis direction of the quarter-wave plate 52 forms a 45° angle with the polarization direction (i.e., the P-polarization direction) of the linearly polarized laser emitted by the active linearly polarized laser emission module 4 (in actual engineering, an installation tolerance of ±3° is allowed, i.e., 42°~48°).

[0056] The condition for a quarter-wave plate to convert linearly polarized light into circularly polarized light is that the polarization direction of the linearly polarized light forms a 45° angle with the fast axis of the wave plate. At this time, the amplitudes of the components of the linearly polarized light along the fast and slow axes are equal, and the fast-axis component passes through the wave plate before the slow-axis component, introducing a 90° phase difference (i.e., a quarter-wavelength optical path difference) between them. The resulting light is circularly polarized.

[0057] The specific derivation is as follows: Let the electric field of the incident ray-polarized light be... The polarization direction makes a 45° angle with the fast axis. On the fast axis... and slow axis The directional components are: ; ; After passing through a quarter-wave plate, the fast-axis component produces a relative output to the slow-axis component. (90°) Phase advance: ; ; The two beams have a 90° phase difference and equal amplitude, and when combined, they produce circularly polarized light. The direction of rotation of circularly polarized light depends on the relative orientation of the fast axis and the incident polarization direction.

[0058] When circularly polarized light is reflected by the mirror on the surface of the forging and then passes through the quarter-wave plate again, the components of the circularly polarized light in the fast and slow axis directions introduce a 90° phase difference again, and the cumulative phase difference becomes 180°. After synthesis, it becomes linearly polarized light, and its polarization direction is orthogonal to the incident direction - that is, it changes from P polarization to S polarization.

[0059] If the angle between the fast axis and the polarization direction deviates by 45°, the amplitudes of the fast and slow axis components will be unequal, resulting in elliptically polarized light rather than ideally circularly polarized light. After reflection and a second passage through the waveplate, although the polarization direction of the outgoing light remains approximately orthogonal to the incident light, the polarization purity decreases. This causes some light energy to be transmitted to the first port (returning to the laser direction) by the polarization beam splitter instead of being reflected to the second port (imaging direction), reducing system efficiency. An installation tolerance of ±3° is acceptable in engineering, and the decrease in polarization purity is within 5%.

[0060] Example 2 describes the complete optical path process and polarization state change from laser emission to the reflected light entering the imaging module, which is the physical core of polarization detection in this invention. The following, in conjunction with... Figure 6 Please provide a detailed explanation.

[0061] The light path (path A) of specular reflection from the surface of the forging: The linearly polarized laser emitted by the active linearly polarized laser emission module 4 (the first linearly polarized laser) enters the polarization beam splitter 51 with the first polarization direction (P-polarization direction). The polarization beam splitter 51 has high transmittance for P-polarized light, which is transmitted and output from the third port 5c along the principal optical axis and directed towards the quarter-wave plate 52.

[0062] When P-polarized light passes through a quarter-wave plate 52, it is converted into circularly polarized light (assuming right-handed circular polarization) because the fast axis is at a 45° angle to the polarization direction.

[0063] Right-hand circularly polarized light passes through the viewing window assembly 3, enters the furnace cavity through the coaxial optical through hole, and irradiates the surface of the forging.

[0064] Specular reflection occurs on the surface of a forging under near-normal incidence conditions. The physical essence of specular reflection is coherent scattering of light on a smooth surface. The polarization state of the reflected light is preserved (not randomized), but the rotation direction of circularly polarized light is reversed during reflection—right-hand circular polarization becomes left-hand circular polarization. This is because reflection introduces an additional π-phase change, altering the rotation direction of circular polarization, but not changing the essential characteristics of circular polarization.

[0065] The left-hand circularly polarized light returns along the original optical path (principal optical axis), passes through the window assembly 3, and then passes through the quarter-wave plate 52 again. The quarter-wave plate 52 introduces another 90° phase difference into the left-hand circularly polarized light. After superimposing with the 180° phase change introduced by reflection, the total phase difference between the fast and slow axis components is 270° (equivalent to -90°). After synthesis, it becomes linearly polarized light (the second linearly polarized laser), and its polarization direction is orthogonal to the incident P direction—that is, it becomes the S polarization direction.

[0066] S-polarized light enters polarization beamsplitter 51, which has high reflectivity for S-polarized light, and reflects it 90°, outputting it from the second port 5b and entering polarization filtering imaging receiver module 6.

[0067] Energy efficiency analysis: Assuming the polarization beam splitter has a 95% transmittance for P-light and a 95% reflectance for S-light, a 97% transmittance for the quarter-wave plate, and a 90% transmittance for the viewing window, the total transmission efficiency of the light reflected from the forged mirror from the laser emission point to the imaging sensor is approximately: η 锻件 ≈0.95 (PBS transmission) × 0.97 (QWP) × 0.90 (viewing window) × ρ 锻件 (Forging reflectivity) × 0.90 (Viewport return) × 0.97 (QWP return) × 0.95 (PBS reflectivity) ≈ 0.69 × ρ 锻件 .

[0068] Where, ρ 锻件The specular reflectivity of the forging surface is typically 0.3-0.6 under 1064nm wavelength and high-temperature metal surface conditions.

[0069] The light path (path B) of diffuse reflection from the mold / furnace wall: The process from laser emission to irradiating the inner surface of the furnace is the same as path A: the P-linearly polarized laser is transmitted through a polarization beam splitter, converted into right-hand circularly polarized light by a quarter-wave plate, passes through the viewing window and enters the furnace to irradiate the mold and furnace wall surface.

[0070] The rough surfaces of the mold and furnace walls, along with the presence of an oxide layer, produce diffuse reflection. The physical essence of diffuse reflection is the incoherent scattering of light on a rough surface. The random orientation of numerous microscopic scattering units randomizes (depolarizes) the polarization state of the reflected light. Specifically, diffusely reflected light contains both S-polarization and P-polarization components, as well as various elliptic polarization states, and the phase relationships of these polarization states are random.

[0071] The reflected light, in these randomly mixed polarization states, returns along the original optical path (diffuse reflection component near the normal incident direction), passing through window assembly 3 and quarter-wave plate 52. Since the incident light is already in a randomly polarized state, the 90° phase difference introduced by the quarter-wave plate to the linearly polarized component of the randomly polarized state only changes the polarization state form of each component (linear polarization → elliptic polarization, elliptic polarization → another type of elliptic polarization), but does not change the randomness of the polarization state. Therefore, the light after passing through the quarter-wave plate is still in a randomly mixed polarization state.

[0072] When light with randomly mixed polarization states enters the polarization beam splitter 51, the polarization beam splitter splits the light according to the polarization direction: The S-polarization component is reflected to the second port 5b and enters the polarization filter imaging receiver module 6. The P-polarization component is transmitted back to the first port 5a, that is, back to the laser direction, and is attenuated by the isolator or optical path inside the laser. The remaining elliptical polarized light is distributed to the two ports according to the S1 component of the Stokes parameter.

[0073] For completely depolarized diffuse reflection light ( Its S-polarization component and P-polarization component have equal energy. The polarization beam splitter reflects about 50% of the energy to the second port 5b and transmits about 50% of the energy back to the first port (5a).

[0074] Energy efficiency analysis: Only about 50% of the diffuse reflected light reaches the imaging sensor after passing through the polarization beam splitter, while nearly 100% of the specular reflected light reaches the imaging sensor. Therefore, before entering the imaging sensor, the coaxial beam splitter and combiner already provides an inherent contrast enhancement effect of approximately 2:1 (100%:50%), making the signal intensity in the forging region approximately twice that of the background region, thus laying a high signal-to-noise ratio foundation for subsequent polarization degree thresholding.

[0075] This enhanced contrast is the key to the innovative application of the classic transceiver separation optical path architecture to the polarization detection of high-temperature forgings in this invention. In traditional LiDAR or OCT systems, the polarization beam splitter and quarter-wave plate are only used for transceiver isolation, without distinguishing between the target signal and the background signal. However, in this invention, the physical characteristics of the forging's specular reflection preserving the polarization state and the mold / furnace wall's diffuse reflection depolarizing it are precisely coupled with the polarization-selective beam splitter's characteristics. This allows the same optical structure to achieve selective enhancement of the forging and background signals while simultaneously completing transceiver separation.

[0076] Polarization degree imaging analysis: The light output from port 5b enters the polarization-filtered imaging receiver module 6. This light contains two signals: 1. Highly polarized light reflected from the mirror surface of the forging: After a complete P→circular polarization→S polarization conversion path, it reaches the sensor with nearly 100% efficiency, and the polarization direction is highly consistent (S direction), with a high degree of polarization.

[0077] 2. Low-polarized light diffusely reflected from the mold / furnace wall: After a polarization state randomization process, only about 50% of the energy reaches the sensor, and the polarization direction is disordered with low polarization degree.

[0078] The two signals are superimposed in the same imaging field of view. By calculating the degree of polarization (DoP) of each pixel, the forging pixels (high DoP) and the background pixels (low DoP) can be distinguished.

[0079] Example 3:

[0080] like Figure 5 As shown, the viewing window assembly 3 includes a sapphire transparent substrate 31. The inner surface of the sapphire transparent substrate 31 is coated with an anti-metal evaporation protective coating layer 32. A vacuum sealing structure 33 is provided between the sapphire transparent substrate 31 and the furnace wall through hole 2.

[0081] The sapphire transparent substrate 31 is a sapphire disc with a diameter of 80 mm and a thickness of 8 mm, made of high-purity optical-grade α-Al2O3 single crystal. The initial transmittance of sapphire to 808 nm and 1064 nm wavelength lasers is not less than 85%, and the transmittance decay does not exceed 10% of the initial value after continuous operation at 1500℃ for 500 hours.

[0082] The anti-metal evaporation protective coating layer 32 is a SiO2 / TiO2 multilayer dielectric film, deposited on the furnace-side surface of the sapphire transparent substrate 31 using electron beam evaporation physical vapor deposition (EBSD). The total thickness of the film layer is approximately 2 μm. This coating layer has two functions: firstly, the contact angle of metal vapor on the coating layer surface is larger than that on the bare sapphire surface, reducing the adhesion strength of metal vapor and facilitating subsequent cleaning and maintenance; secondly, even if there is slight metal deposition on the coating layer surface, the impact on the transmittance at a specific laser wavelength (1064 nm) is controlled within a small range.

[0083] The vacuum sealing structure 33 includes an oxygen-free copper C-section vacuum sealing gasket and a floating elastic compression flange. The oxygen-free copper sealing gasket is arranged around the outer peripheral surface of the sapphire transparent substrate 31 and the inner wall surface of the furnace wall through hole 2.

[0084] Oxygen-free copper (C10200) exhibits excellent plastic deformation capabilities under high-temperature vacuum conditions, without releasing gases or polluting the vacuum environment. The floating elastic clamping flange applies an axial preload of approximately 8 kN to the sapphire transparent substrate via a disc spring assembly, causing the oxygen-free copper sealing gasket to undergo controllable plastic deformation to form a high-vacuum level sealing contact surface.

[0085] The elastic deformation capability of the disc spring assembly can automatically compensate for the axial and radial thermal expansion displacement generated by the furnace body during the thermal cycle of 1000~1500℃, and maintain the stability of the sealing surface pressure throughout the entire temperature range.

[0086] The viewing window assembly 3 is the only component in the entire device that directly withstands the high temperature and high vacuum inside the furnace, and its long-term reliability directly determines the availability of the entire detection system. The high-temperature stability of sapphire ensures that its light transmittance does not decrease over long periods at 1000-1500℃; the anti-metal evaporation protective coating ensures an extended effective service life of the viewing window in a metal vapor environment; and the oxygen-free copper seal combined with the elastic floating clamping flange ensures that the vacuum seal does not fail during frequent temperature cycles. These three elements work together to enable the viewing window assembly to operate stably for extended periods in extreme environments.

[0087] As a preferred embodiment, such as Figure 5 As shown, the sapphire light-transmitting substrate 31 is installed obliquely in the furnace wall through hole 2. The normal direction of the sapphire light-transmitting substrate 31 forms a preset oblique angle with the main optical axis (typical value is 5°~15°, preferably 10°), so that the reflected light from the front and rear surfaces of the sapphire light-transmitting substrate 31 deviates from the main optical axis, reducing backlight interference.

[0088] The front and back surfaces of any optical window / plate will produce Fresnel reflections (reflectivity of approximately 4% per surface, and approximately 7% per surface for sapphire with a refractive index of 1.76). If the sapphire is mounted perpendicular to the principal optical axis (with the normal coinciding with the principal optical axis), the reflected light from the front and back surfaces will return along the principal optical axis, enter the coaxial beam splitter 5, be reflected by the polarization beam splitter to the second port 5b, and form strong background stray light / ghost image on the imaging sensor, severely interfering with polarization imaging.

[0089] When the sapphire is mounted at an angle, the reflected light from its front and rear surfaces deviates from the principal optical axis. Taking a 10° angle as an example, the incident angle is 10°, and according to Fresnel's law of reflection, the reflection angle is also 10°, resulting in a 20° deviation of the reflected light from the incident direction. The reflected light from the rear surface of the sapphire is refracted within the sapphire, and its exit direction also deviates from the principal optical axis. These reflected lights, deviating from the principal optical axis, do not enter the third port 5c of the coaxial beam splitter / combiner component 5, and therefore do not reach the imaging sensor, effectively eliminating backlight interference.

[0090] The effect of angled installation on transmitted light (incident laser light and reflected signal light) is minimal: the additional optical path introduced by a 10° angle is approximately (θ' is the angle of refraction), its impact on image quality is negligible. The lateral beam offset introduced by the oblique placement is approximately This can be compensated by adjusting the position of the coaxial beam splitting and combining component 5.

[0091] Example 4:

[0092] like Figure 1 , Figure 3 As shown, the vacuum high-temperature forging furnace 1 adopts a double-layer structure of an outer furnace shell 11 and an inner heating furnace liner 12. The furnace wall through-holes 2 include a furnace shell through-hole 21 opened on the furnace shell 11 and a furnace liner through-hole 22 opened at the corresponding position on the furnace liner (12), both of which are coaxially arranged. The viewing window assembly 3 is embedded in the furnace shell through-hole (21), and its main optical axis is consistent with the common axis of the furnace shell through-hole 21 and the furnace liner through-hole 22.

[0093] In this embodiment, the double-layer structure of the vacuum high-temperature forging furnace is its basic structural feature: the outer furnace shell 11 is a vacuum container, maintaining a high vacuum environment inside the furnace; the inner heating furnace liner 12 is a heating element, heating the space inside the furnace to the forging process temperature (1000~1500℃). A gap is left between the two layers for placing heating elements and heat insulation materials.

[0094] In the double-layer structure, the laser incident beam must pass through both the furnace shell and the furnace liner simultaneously to reach the mold cavity inside the furnace. If only a hole is made in the furnace shell and not in the furnace liner, the laser will be blocked by the opaque furnace liner wall and will not be able to reach the forging. Therefore, through holes must be made at corresponding positions in the furnace shell and furnace liner, and both must be coaxially arranged so that the laser and reflected light can pass through without obstruction along a common axis. The viewing window assembly is installed in the through hole in the furnace shell (the furnace shell is the outer wall of the vacuum container, and the viewing window achieves vacuum sealing here), while the through hole in the furnace liner is a free through hole (the interior of the furnace liner is the high-temperature forging space and does not require additional sealing).

[0095] As a preferred embodiment, such as Figure 1 , Figure 3 As shown, the furnace liner through hole 22 is an oblong hole or a waist-shaped hole. The length direction of the oblong hole is consistent with the thermal expansion direction of the inner heating furnace liner 12, so as to compensate for the thermal expansion displacement of the heating furnace liner 12 during the heating process and ensure that the main optical axis is not blocked by the heating furnace liner 12 in the entire temperature range.

[0096] The furnace chamber 12 will undergo thermal expansion during the heating process. Taking typical parameters as an example: the furnace chamber material is a nickel-based high-temperature alloy, with a linear expansion coefficient of... Temperature rise from room temperature (25°C) to 1500°C The characteristic length of the furnace lining from a reference point (e.g., one end of the furnace lining) to the location of the through hole. Then the thermal expansion displacement is: ; If the furnace liner through-hole is circular and its diameter matches the beam diameter (approximately 15-20 mm), during thermal expansion, the furnace liner through-hole may shift by more than 10 mm relative to the furnace shell through-hole, causing the main optical axis to fall into the solid part of the furnace liner and the optical path to be blocked.

[0097] The elongated hole design extends the furnace liner through-hole along the direction of thermal expansion, with a length of: ; in, To meet the minimum diameter required for the beam to pass through (typically 1.5-2 times the beam diameter). This represents the maximum thermal expansion displacement. Taking the above parameters as an example, The width of the oblong hole Not less than It is usually 15-20mm.

[0098] The inner wall of the oblong hole is chamfered (to remove sharp edges and prevent laser diffraction) and polished (to reduce surface roughness). (To reduce multiple reflections of the laser on the hole wall) and avoid stray light interference.

[0099] Within the entire temperature range (room temperature to 1500℃), after the furnace liner expands thermally, the furnace liner through hole shifts along the length of the elongated hole. However, due to the length margin design of the elongated hole, no matter how much the furnace liner expands, the opening range of the furnace liner through hole always covers the main optical axis position of the furnace shell through hole, ensuring that the optical path is unobstructed.

[0100] Example 5:

[0101] like Figure 4 As shown, the polarization filtering imaging receiving module 6 includes a narrow-band bandpass filter 61 and a focal plane polarization image sensor 62 arranged sequentially along the optical path. The center wavelength of the narrow-band bandpass filter 61 matches the laser wavelength emitted by the active linear polarization laser emission module 4, and is used to filter out blackbody thermal radiation noise in the furnace. The focal plane polarization image sensor 62 integrates micro-polarization arrays in multiple directions on its pixels for real-time acquisition of polarization images in a single exposure.

[0102] In this embodiment, within the furnace environment of 1000~1500℃, all high-temperature surfaces (forgings, molds, furnace walls) emit strong blackbody thermal radiation. According to Planck's blackbody radiation law, at a wavelength of 1064nm, the spectral radiance of a blackbody at 1500℃ is approximately: ; Although 1064 nm is located on the short-wavelength side of the blackbody radiation curve (with a peak at approximately 1.6 μm), and its radiance is much lower than the peak, it is still not negligible. Especially in imaging sensors, the integral effect of blackbody thermal radiation will generate a uniform background signal (dark current + thermal radiation signal) across the entire target surface, reducing image contrast.

[0103] The narrowband bandpass filter 61 restricts the spectral range received by the sensor to an extremely narrow bandwidth of ±1.5 nm of the laser wavelength. Outside this bandwidth, blackbody radiation is attenuated by more than 100,000 times by the out-of-band optical density (OD≥5) of the filter; within this bandwidth, the integrated energy of blackbody radiation is extremely small (because the bandwidth is only 3 nm), while the laser reflection signal is concentrated within this bandwidth and its intensity is much higher than that of blackbody radiation. Therefore, after narrowband filtering, the sensor mainly receives the laser reflection signal, and blackbody thermal radiation noise is effectively suppressed.

[0104] In addition, after obtaining the optical signal after narrowband filtering, it is necessary to analyze the degree of polarization (DoP) of each pixel to distinguish between high-polarization forging pixels and low-polarization background pixels. There are various methods to measure the degree of polarization, among which the division-of-focal-plane (DoFP) method best meets the real-time requirements of this application.

[0105] The split-focus plane polarization image sensor integrates a micro-polarizer (with linewidth in the micrometer range) above each pixel. Every four adjacent pixels form a "polarization superpixel," corresponding to the four polarization directions of 0°, 45°, 90°, and 135°, respectively. A single exposure can simultaneously acquire light intensity information in all four polarization directions, eliminating the need for rotating the polarizer or multiple frame acquisitions. This makes it suitable for real-time detection in dynamic scenarios such as forging ejection during forging (frame rate ≥ 30fps).

[0106] As a preferred embodiment, such as Figure 4 As shown, the narrowband bandpass filter 61 has a bandwidth ≤ 3nm (full width at half maximum, FWHM). The focal plane polarization image sensor 62 integrates micro-polarization arrays in four directions: 0°, 45°, 90°, and 135° on its pixels.

[0107] The choice of bandwidth needs to strike a balance between two constraints: The narrower the bandwidth, the better the blackbody thermal radiation noise suppression effect and the higher the signal-to-noise ratio. The narrower the bandwidth, the higher the requirement for laser wavelength stability, and the peak transmittance of the filter may decrease due to manufacturing precision limitations.

[0108] The 3nm bandwidth corresponds to a relative bandwidth of approximately 0.28% at a wavelength of 1064nm, which fully meets the wavelength stability requirements (temperature drift ≤0.1nm / ℃, and wavelength drift ≤0.3nm after temperature control) for linearly polarized laser diodes (LDs) or solid-state lasers. Furthermore, narrowband filters (center wavelength 1064nm, bandwidth 3nm, peak transmittance ≥85%) can be mass-produced using current optical thin-film manufacturing technology at a controllable cost.

[0109] Based on a bandwidth of 1064nm and 3nm, the transmission band of the filter is 1062.5-1065.5nm. Within this band, the radiation energy density of a 1500℃ blackbody is extremely low. After filtering, the blackbody radiation noise is suppressed by more than 100 times (compared to broadband reception without a filter), ensuring high signal-to-noise ratio imaging.

[0110] The micro-polarization arrays at 0°, 45°, 90°, and 135° were chosen because polarization degree calculation based on Stokes parameters requires light intensity measurements in at least three different polarization directions. This four-directional configuration provides information redundancy, improving the accuracy and robustness of polarization degree calculations while meeting the requirements of real-time computation.

[0111] The extinction ratio (defined as the ratio of maximum to minimum transmittance of light in the same polarization direction) of micropolarizers in all directions must be ≥100:1. A higher extinction ratio results in a wider dynamic range for polarization degree measurement and a stronger ability to distinguish between high polarization (forgings) and low polarization (background). Currently, micropolarizers based on nanowire grating technology can achieve an extinction ratio of over 200:1 at a wavelength of 1064 nm, meeting the requirements.

[0112] Example 6:

[0113] like Figure 4 As shown, the active linearly polarized laser emission module 4 includes a linearly polarized laser 41 and a collimating and shaping lens group 42. The laser emitted by the linearly polarized laser 41 is collimated and shaped by the collimating and shaping lens group 42 and then enters the first port 5a as a parallel beam.

[0114] In this embodiment, the linearly polarized laser 41 is an active illumination light source, requiring the output of highly linearly polarized laser light with a polarization extinction ratio ≥100:1. Optional solutions include: Linearly polarized laser diodes (LDs) directly output linearly polarized light. They are compact, highly efficient, and suitable for wavelengths of 1064nm or 808nm.

[0115] Solid-state lasers (such as Nd:YAG) with external polarizers offer high output power and good beam quality, but their structure is relatively complex. The actual choice depends on the detection distance, spot size, and power requirements.

[0116] The collimating and shaping lens group 42 collimates the diverging beam output from the laser into a parallel beam and shapes the beam diameter and cross-sectional energy distribution (e.g., Gaussian beam → flat-top beam). The purpose of collimation is to ensure that the beam maintains a small divergence angle after passing through the coaxial beam splitter 5 and the window assembly 3, forming a suitably sized and uniformly energetic illumination spot on the forging surface. The beam diameter is typically designed to be 5-10 mm, slightly smaller than the effective aperture of the polarizing beam splitter 51 and the window assembly 3 (typically ≥25 mm), leaving sufficient centering margin.

[0117] Example 7:

[0118] like Figure 4 As shown, the polarization filtering imaging receiver module 6 also includes an imaging optical lens 63, which is disposed on the second port 5b side of the narrow bandpass filter 61 and is used to image the light filtered by the narrow bandpass filter 61 onto the target surface of the focal plane polarization image sensor 62.

[0119] In this embodiment, the narrowband filter only performs spectral filtering (suppressing blackbody thermal radiation noise) and does not have imaging function. The light output from the second port 5b is divergent reflected light from the forging and background inside the furnace. It needs to be focused by the imaging optical lens 63 and formed into a clear spatial image on the sensor target surface, so that the spatial position information of the forging and background is encoded into the pixel coordinates of the image.

[0120] The field of view and focal length of the imaging optical lens 63 are designed based on the size of the forging in the furnace and the detection distance. For example, if the detection distance (distance from the viewing window to the forging) is 500mm and the imaging area of ​​the forging is 150mm × 150mm, then the required field of view is approximately [missing information]. The corresponding lens focal length (calculated based on a sensor target size of 11.3mm) is approximately Using a standard industrial lens with a focal length of 50mm can achieve a field of view of approximately 12°, which meets the imaging coverage requirements.

[0121] The imaging optical lens 63 must operate in a band that covers the selected laser wavelength (1064nm) and have good transmittance and image quality at that wavelength. An achromatic lens or a dedicated near-infrared lens can be selected.

[0122] Example 8:

[0123] The following sources of interference exist during the operation of the vacuum high-temperature forging furnace: 1. Vibration: Strong mechanical vibrations are generated during the forging process and transmitted to the external mounting structure through the furnace body. Vibration can cause changes in the relative positions of optical elements, resulting in optical path misalignment and blurred imaging.

[0124] 2. Heat conduction: Although the temperature of the outer wall of the furnace is much lower than that inside the furnace, it is still higher than room temperature (possibly 100-300℃), affecting nearby optical modules through solid-state conduction and thermal radiation. Temperature fluctuations can lead to laser output power and wavelength drift, changes in the splitting ratio of the polarization beam splitter, and increased dark current noise in the sensor.

[0125] Based on this, such as Figure 1 , Figure 3 , Figure 4 As shown, the active linearly polarized laser emitting module 4, the coaxial beam splitting and combining component 5, and the polarization filtering imaging receiving module 6 are all mounted on the constant temperature and vibration damping base 7. The constant temperature and vibration damping base 7 is set independently of the vacuum high-temperature forging furnace 1 and is not rigidly connected to the furnace body.

[0126] In this embodiment, the constant temperature damping base 7 is not rigidly connected to the furnace body; instead, a flexible connection or air gap isolates the vibration transmission path. Furthermore, an air-floating damper or spring damping system is used to attenuate the furnace body vibration to within the amplitude range allowed by the optical elements. In addition, the constant temperature damping base 7 has a built-in temperature control system (such as constant temperature water circulation or Peltier temperature control) to control the working temperature of the optical module within a constant range (such as 25±0.5℃) and eliminate the impact of temperature fluctuations on optical performance.

[0127] Example 9:

[0128] like Figure 1 As shown, the computing control host 8 is electrically connected to the polarization filter imaging receiver module 6. It is used to receive the polarization image output by the polarization filter imaging receiver module 6, calculate the Stokes parameters, run the pre-trained polarization segmentation network to complete the segmentation of the forging region, and extract the forging contour for subsequent forging pose detection.

[0129] In this embodiment, in the original image output by the focal plane polarization image sensor 62, each polarization superpixel (2×2 pixel group) contains light intensity values ​​in four polarization directions: (0° direction) (45° direction) (90° direction) (135° direction). The computing and control host calculates the Stokes parameters based on these four light intensity values: Total luminous intensity: ; Linear polarization components (0° / 90° direction): ; Linear polarization components (45° / 135° directions): ; Degree of polarization: .

[0130] The range of DoP values ​​is: . This represents fully linearly polarized light. This indicates completely unpolarized light.

[0131] Subsequently, the original intensity images in the four polarization directions are used as low-order multidimensional polarization features, while the Stokes parameters and degree of polarization are used as high-order multidimensional polarization features, and input into a pre-trained polarization segmentation network. The polarization segmentation network consists of a low-order segmentation sub-network, a high-order segmentation sub-network, and a correction sub-network: the low-order segmentation sub-network extracts detailed information such as texture edges from the original intensity domain and outputs a low-order segmentation mask; the high-order segmentation sub-network performs globally reliable segmentation based on polarization physical quantities and outputs a high-order segmentation mask; the correction sub-network receives the channel concatenation result of the high-order segmentation mask and the error mask, and, guided by the error mask, performs targeted correction on the divergence region between the two sub-networks, outputting a corrected forging segmentation mask. The computational control host extracts the contour of the segmentation mask to obtain the two-dimensional contour of the forging.

[0132] The polarization segmentation network consists of a low-order segmentation sub-network, a high-order segmentation sub-network, and a correction sub-network, all three employing an encoder-decoder structure. The low-order segmentation sub-network includes a first encoder and a first decoder. The first encoder extracts multi-scale original texture features from multi-dimensional polarization low-order features step-by-step. The first decoder fuses encoder features at corresponding scales through skip connections and upsamples step-by-step to restore spatial resolution, outputting a low-order segmentation mask. The high-order segmentation sub-network includes a second encoder and a second decoder. The second encoder extracts multi-scale polarization physical features from multi-dimensional polarization high-order features step-by-step. The second decoder fuses encoder features at corresponding scales through skip connections and upsamples step-by-step to restore spatial resolution, outputting a high-order segmentation mask. The correction sub-network includes a third encoder and a third decoder. The third encoder extracts multi-scale contextual features from the channel concatenation input of the high-order segmentation mask and the error mask step-by-step. The third decoder fuses encoder features at corresponding scales through skip connections and upsamples step-by-step to restore spatial resolution, outputting a corrected forging segmentation mask. The error mask is obtained by calculating the absolute value of the pixel-by-pixel difference between the low-order and high-order segmentation masks.

[0133] The encoder-decoder structure described above is a preferred embodiment of this device, and not the only limitation on the network structure. Other network structures capable of achieving feature extraction and resolution restoration are also applicable to the three sub-networks.

[0134] The training loss of the polarization segmentation network consists of two parts: a low-order segmentation loss and a correction loss. The total training loss is the weighted sum of the two. The high-order segmentation subnetwork does not accept direct supervision from the ground truth mask, but accepts indirect supervision from the correction loss, in order to preserve the natural divergence between the low-order and high-order segmentation masks and maintain the information content of the error mask.

[0135] When this device is configured with binoculars, it consists of two independent sets of viewing window components, coaxial beam splitting and combining components, active linearly polarized laser emission modules, and polarization filtering imaging receiving modules, serving as the first detection unit and the second detection unit, respectively. These units simultaneously acquire first and second multi-directional polarized raw images from two different perspectives. The computing control host 8 runs the aforementioned polarization segmentation network on the first and second images, respectively, segmenting the first forging region and the second forging region and extracting their contours to obtain the first forging contour and the second forging contour.

[0136] The computing control host 8 inputs the first and second forging contours into a pre-established three-dimensional pose recognition model for the forging. This model includes a first two-dimensional pose recognition sub-network, a second two-dimensional pose recognition sub-network, and a binocular fusion sub-network: the first sub-network identifies the two-dimensional pose category from the first forging contour under a first viewpoint; the second sub-network identifies the two-dimensional pose category from the second forging contour under a second viewpoint; and the binocular fusion sub-network nonlinearly fuses the probability vectors of the two two-dimensional pose categories from the two viewpoints to output the three-dimensional pose category of the forging. The three-dimensional pose category describes the spatial state of the forging within the furnace, including normal, left-leaning, right-leaning, forward-leaning, backward-leaning, left-tilting, right-tilting, forward-tilting, backward-tilting, and demolding abnormality.

[0137] When using a monocular configuration, only a single-sided detection unit and polarization segmentation network are run to obtain the two-dimensional contour of the forging, but it can be used to determine the integrity of the forging contour (such as whether there are defects such as missing material or underpressure).

[0138] Both the first and second 2D pose recognition subnetworks employ convolutional neural networks comprising multiple convolutional and fully connected layers. In the first subnetwork, the convolutional layers progressively extract contour shape features from the input first forging contour. The fully connected layers are followed by a Softmax activation function, outputting a 2D pose category probability vector from the first viewpoint based on the contour shape features. The category corresponding to the maximum value in the probability vector is taken as the 2D pose category from the first viewpoint. The second subnetwork structure is symmetrical to the first subnetwork, extracting features from the second forging contour and outputting a 2D pose category probability vector from the second viewpoint. The 2D pose categories include centering, shifting left, shifting right, tilting left, and tilting right.

[0139] The binocular fusion subnetwork adopts a multilayer perceptron structure containing multiple fully connected layers. It takes the joint feature vector, which is formed by concatenating the two-dimensional pose category probability vectors output by the first and second two-dimensional pose recognition subnetworks, as input. The two-dimensional pose information of the first and second perspectives contained in the joint feature is nonlinearly fused through the fully connected layers to output the three-dimensional pose category probability vector of the forging. The category corresponding to the maximum value in the probability vector is taken as the three-dimensional pose category of the forging.

[0140] The convolutional neural network and multilayer perceptron structures described above are preferred embodiments of this device, and not the only limitation on network structures. Other network structures capable of contour feature extraction and pose classification are also applicable to the first and second 2D pose recognition subnetworks; other network structures capable of "dual-view probability vector fusion-3D classification" are also applicable to the binocular fusion subnetwork.

[0141] The training loss of the forging 3D pose recognition model consists of three parts: classification loss, binocular consistency loss, and 2D-3D consistency loss. The classification loss includes first 2D pose classification loss, second 2D pose classification loss, and 3D pose classification loss, all using cross-entropy loss. The binocular consistency loss penalizes invalid 2D pose combinations that violate binocular geometry in the outputs of the first and second 2D pose recognition subnetworks. The 2D-3D consistency loss penalizes invalid triplets where the 3D pose category output by the binocular fusion subnetwork logically contradicts the two input 2D pose categories. The total training loss is a weighted sum of the above losses.

[0142] The calculation results and judgment outputs of the computing control host (8) are transmitted to the human-machine interaction display terminal 9 via a wired communication interface (such as Gigabit Ethernet, Camera Link, or USB 3.0). The human-machine interaction display terminal 9 is an industrial-grade touch screen or an external display for an industrial control computer, and is set up at the operating table in the forging workshop for operators to monitor the detection status in real time. The display interface of the human-machine interaction display terminal 9 includes the following information areas: Real-time polarization image area: Displays the original polarization image acquired by the focal plane polarization image sensor 62 and the pseudo-color polarization image after polarization degree calculation. In the pseudo-color image, high polarization degree areas (forgings) are displayed in warm colors, and low polarization degree areas (background) are displayed in cool colors, allowing operators to intuitively distinguish the forgings from the background.

[0143] Forging contour overlay area: The segmented and extracted forging contour lines are overlaid on the real-time polarized image. The contour lines are drawn with a highlight color, allowing operators to intuitively judge the completeness and accuracy of the contour extraction.

[0144] The forging outline and posture overlay area displays the extracted forging outline on the real-time polarized image, and labels the currently identified 3D pose category or 2D outline information with text.

[0145] Judgment Result and Alarm Area: Displays the judgment result of the current inspection ("Pass" or "Fail"). When judged as unqualified, it will alert the operator in a conspicuous manner (such as flashing red text and sound alarm) to the deviation or demolding abnormality, and automatically record the alarm time, deviation value and corresponding polarization image for post-process review and defect analysis.

[0146] Process Retrospective Query Area: Provides a query function for historical inspection records. Operators can retrieve historical inspection data (including polarization images, contour data, deviation values, and judgment conclusions) by time, forging number, mold number, and other conditions for quality traceability and process optimization.

[0147] The communication between the human-machine interface display terminal 9 and the computing control host 8 adopts a standard industrial protocol to ensure the real-time performance and reliability of data transmission. The human-machine interface software of the display terminal is driven by the operating system and application programs built into the computing control host 8, supports a Chinese interface, and has a simple and intuitive operation logic, which can be used by operators after simple training.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. All such modifications or substitutions should be covered within the protection scope of this application, and should not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. An online polarization detection device for forgings in a vacuum high-temperature forging furnace, characterized in that, include: The window assembly (3) is embedded in the furnace wall through hole (2) of the vacuum high temperature forging furnace (1) to form an optically transparent channel between the high temperature environment inside the furnace and the normal temperature environment outside the furnace; A coaxial beam splitter / combiner (5) is disposed outside the furnace of the window assembly (3). The coaxial beam splitter / combiner (5) has a first port (5a), a second port (5b) and a third port (5c). The third port (5c) faces the window assembly (3). The coaxial beam splitter / combiner (5) is configured to guide light input from the first port (5a) to the third port (5c) for output, and to guide light input from the third port (5c) to the second port (5b) for output. An active linearly polarized laser emitting module (4) has its emitting end facing the first port (5a) so that the linearly polarized laser emitted by it passes through the first port (5a) and the third port (5c) in sequence through the window assembly (3) and enters the furnace along the main optical axis of the optical transparent channel, irradiating the surface of the forging, as well as the furnace wall and the surface of the mold. The polarization filter imaging receiving module (6) has its receiving end facing the second port (5b) so that the reflected light from the forging surface, furnace wall and mold returns along the main optical axis and then enters the polarization filter imaging receiving module (6) through the third port (5c) and the second port (5b) in sequence.

2. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 1, characterized in that, The coaxial beam splitter and combiner (5) includes a polarization beam splitter (51) and a quarter-wave plate (52). The polarization beam splitter (51) is located at the intersection of the first port (5a), the second port (5b) and the third port (5c), and the quarter-wave plate (52) is located on the main optical axis between the polarization beam splitter (51) and the window assembly (3).

3. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 2, characterized in that, The polarization beam splitter (51) is a polarization beam splitting cubic prism. The beam splitting surface of the polarization beam splitting cubic prism transmits linearly polarized light with a first polarization direction incident between the first port (5a) and the third port (5c) along the principal optical axis, and reflects and guides linearly polarized light with a second polarization direction orthogonal to the first polarization direction incident from the third port (5c) along the principal optical axis to the second port (5b).

4. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 2, characterized in that, The fast axis direction of the quarter-wave plate (52) forms an angle of 42°~48° with the polarization direction of the linearly polarized laser emitted by the active linearly polarized laser emission module (4).

5. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 2, characterized in that, The first linearly polarized laser emitted by the active linearly polarized laser emission module (4) enters the polarization beam splitter (51) with a first polarization direction and is transmitted to the third port (5c). The first linearly polarized laser output from the third port (5c) with the first polarization direction passes through the quarter-wave plate (52) and the window assembly (3) in sequence and enters the furnace. After being reflected by the mirror surface of the forging, the polarization direction changes to the second polarization direction. The second linearly polarized laser reflected in the second polarization direction returns along the original optical path, passes through the window assembly (3) and the quarter-wave plate (52) in sequence, enters the polarization beam splitter (51), and is reflected to the second port (5b) to enter the polarization filtering imaging receiving module (6). The polarization state of the light diffusely reflected from the furnace wall and the mold surface is randomized. After passing through the quarter-wave plate (52), part of it is reflected by the polarization beam splitter (51) to the second port (5b) to selectively split the specular reflection light of the forging and the diffuse reflection light of the furnace wall and the mold surface.

6. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 1, characterized in that, The window assembly (3) includes a sapphire light-transmitting substrate (31), the inner surface of the sapphire light-transmitting substrate (31) is coated with an anti-metal evaporation protective coating layer (32), and a vacuum sealing structure (33) is provided between the sapphire light-transmitting substrate (31) and the furnace wall through hole (2). The sapphire translucent substrate (31) is installed obliquely in the furnace wall through hole (2). The normal direction of the sapphire translucent substrate (31) forms a preset oblique angle with the main optical axis, so that the reflected light from the front and rear surfaces of the sapphire translucent substrate (31) deviates from the main optical axis.

7. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 1, characterized in that, The vacuum high-temperature forging furnace (1) adopts a double-layer structure of an outer furnace shell (11) and an inner heating furnace liner (12). The furnace wall through hole (2) includes a furnace shell through hole (21) opened on the outer furnace shell (11) and a furnace liner through hole (22) opened at the corresponding position on the inner heating furnace liner (12). The furnace shell through hole (21) and the furnace liner through hole (22) are coaxially arranged. The window assembly (3) is embedded in the furnace shell through hole (21) and its inward end abuts against the furnace liner through hole (22). The main optical axis coincides with the axis of the furnace shell through hole (21), the furnace liner through hole (22), and the window assembly (3).

8. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 7, characterized in that, The furnace liner through hole (22) is an elongated or waist-shaped hole, and its length direction is the same as the thermal expansion direction of the inner heating furnace liner (12) to compensate for the thermal expansion displacement of the inner heating furnace liner (12) during the heating process.

9. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 1, characterized in that, The polarization filtering imaging receiver module (6) includes a narrow bandpass filter (61), a focal plane polarization image sensor (62), and an imaging optical lens (63) arranged sequentially along the optical path. The center wavelength of the narrow bandpass filter (61) is matched with the laser wavelength emitted by the active linearly polarized laser emission module (4) to filter out blackbody thermal radiation noise in the furnace. The pixel of the focal plane polarization image sensor (62) is integrated with a micro-polarization array in multiple directions for real-time acquisition of polarization images in a single exposure. The imaging optical lens (63) is disposed on the side of the narrow bandpass filter (61) facing the second port (5b) and is used to image the light filtered by the narrow bandpass filter (61) onto the target surface of the focal plane polarization image sensor (62).

10. The online polarization detection device for forgings in a vacuum high-temperature forging furnace according to claim 1, characterized in that, The active linearly polarized laser emission module (4) includes a linearly polarized laser (41) and a collimating and shaping lens group (42). The laser emitted by the linearly polarized laser (41) is collimated and shaped by the collimating and shaping lens group (42) and then enters the first port (5a) as a parallel beam.

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