DMD-based cross-type light path splitting device and ultraviolet imaging sub-block detection method

Abstract

This invention discloses a DMD-based cross-type optical path beam splitter, comprising an ultraviolet imaging lens, a dichroic mirror, a digital micromirror device (DMD), an ultraviolet filter, an ultraviolet detector, a visible light camera, and a light collector, as well as an optical path shield. The DMD is electrically connected to a DMD controller. This invention also discloses an ultraviolet imaging block detection method, including constructing an imaging device based on the aforementioned beam splitter; the beam splitter splits the incident mixed light; an FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image; the FPGA control module simultaneously acquires visible light video signals; the FPGA control module fuses the visible light video signals and ultraviolet image signals and displays them, completing the corona discharge location positioning. This invention solves the problems of delayed corona discharge detection and early warning, high detection equipment cost, and slow imaging speed in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a DMD-based cross-type optical path splitting device, and also to an ultraviolet imaging block detection method. Background Technology

[0002] When the voltage on high-voltage equipment and lines rises to a certain level, the air on the surface of the conductor becomes highly ionized, its good insulation properties are destroyed, and it transforms into a conductor, resulting in corona discharge. By detecting the strength of the corona discharge, it is possible to determine whether the high-voltage equipment is in good working condition. Therefore, corona discharge detection is a key means to ensure the normal operation of high-voltage equipment.

[0003] Currently, corona discharge detection mainly employs infrared imaging and ultrasonic detection technologies. However, both technologies suffer from drawbacks such as susceptibility to sunlight interference, difficulty in accurately locating the discharge site, and delayed fault warnings. Furthermore, imported ultraviolet imaging equipment is expensive, hindering its widespread application. Additionally, traditional ultraviolet imaging uses a line-by-line full-frame scanning method, resulting in slow imaging speeds that cannot meet the demands of high-speed imaging detection.

[0004] A digital micromirror device (DMD) is an array of multiple high-speed digital optical reflective switches, composed of numerous small aluminum reflective mirrors. The display resolution is determined by the number of reflective mirrors; one micromirror or an array of micromirrors corresponds to one pixel. By imaging ultraviolet light onto the DMD device, leveraging its pixel-level controllability and high-speed flipping characteristics, and then sequentially scanning each pixel onto an ultraviolet detector, high-speed passive point-scanning ultraviolet imaging can be achieved. This technology holds promise for corona discharge detection, thereby addressing the problems existing in current technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a DMD-based cross-type optical path splitting device and an ultraviolet imaging block detection method, which solves the problems of delayed corona discharge detection and early warning, high detection equipment cost, and slow imaging speed in the prior art.

[0006] The technical solution adopted in this invention is a DMD cross-type optical path splitter, including an ultraviolet imaging lens, a dichroic mirror, a digital micromirror device (DMD), an ultraviolet filter, an ultraviolet light detector, a visible light camera, and a light collector; an optical path shield is provided on the outside of the device. The digital micromirror device (DMD) is electrically connected to a DMD controller.

[0007] The invention is further characterized by: The ultraviolet imaging lens, dichroic mirror, digital micromirror device and ultraviolet photodetector are arranged in the same plane, and the four are respectively arranged at the four vertices of an approximately rectangular shape, forming a folded optical path layout.

[0008] The ultraviolet imaging lens and the dichroic mirror are arranged diagonally opposite each other along the rectangle; the reflective surface of the dichroic mirror faces the digital micromirror device (DMD) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the DMD is tilted towards the dichroic mirror and fixed at a 24° angle relative to the incident light path; the visible light camera is arranged on the visible light transmission side of the dichroic mirror; the light collector is arranged beside the DMD and fixed at a 72° angle to the incident light direction of the DMD; the photosensitive surface of the ultraviolet photodetector faces the vertical light emission direction of the window mirror of the DMD; the ultraviolet filter is arranged between the DMD and the ultraviolet photodetector.

[0009] The ultraviolet light detector is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode.

[0010] The transmission wavelength range of the ultraviolet filter is 220nm to 280nm.

[0011] The ultraviolet light detector has a photosensitive wavelength range of 200nm to 400nm.

[0012] The inner wall of the light path shield is covered with black light-absorbing cloth.

[0013] Each micromirror on the digital micromirror device (DMD) chip is controlled by the DMD controller and has an on state and an off state. When the micromirror is on, ultraviolet light is emitted perpendicularly to the window mirror of the DMD and then shines perpendicularly onto the photosensitive surface of the ultraviolet detector after passing through an ultraviolet filter. When the micromirror is off, ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the DMD and enters the light collector.

[0014] Another technical solution of the present invention is an ultraviolet imaging block detection method, which uses the above-mentioned DMD-based cross-type optical path splitter, comprising: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based cross-type optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. Step 2: The beam splitter splits the incident mixed light, and the FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image. Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them to complete the corona discharge location positioning.

[0015] Another feature of the technical solution of the present invention is that: The DMD controller and the visible light camera based on the DMD cross-type optical path splitting device are electrically connected to the FPGA control module respectively; the ultraviolet detector based on the DMD cross-type optical path splitting device is electrically connected to the shaping circuit; the shaping circuit is connected to the A / D analog-to-digital conversion circuit, and the A / D analog-to-digital conversion circuit is connected to the FPGA control module; the FPGA control module is also electrically connected to the display.

[0016] In step 2, the FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light area generated by corona discharge and generate an ultraviolet image. It is necessary to preset the total number of image segmentation layers Q and the number of segmentation blocks N in each layer, which specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all the micromirrors of the digital micromirror device DMD to be in the on state through the DMD controller. If an ultraviolet light signal is detected, the subsequent steps are executed. If not, the FPGA control module only outputs a visible light signal. Step 2.2: Assign the current segmentation layer variable M to 2. Divide the DMD micromirrors into N block areas according to the number of segmentation blocks N in each layer. Control the micromirrors in each block area to be turned on in sequence and detect ultraviolet light. When all the micromirrors in a certain block area are in the on state, all the micromirrors in other block areas are in the off state, and label the block area where ultraviolet light is detected. Step 2.3: Increment M by 1. If M < Q, return to step 2.2 to continue segmentation and labeling. If M ≥ Q, perform a single-pixel scan imaging row by row on the last labeled area with ultraviolet light. Step 2.4: The FPGA control module receives the scan imaging data and generates a full-frame ultraviolet image.

[0017] In step 2.2, the number of segmentation blocks N in each layer is 4, and the corresponding area is equally divided into 4 block areas for ultraviolet light detection.

[0018] In step 2.3, the single-pixel scan imaging row by row is to control the micromirrors of the digital micromirror device DMD to be turned on one by one through the FPGA control module, and scan the ultraviolet light of each pixel point to the ultraviolet detector in sequence to complete the imaging of the corresponding area.

[0019] The beneficial effects of the present invention are as follows: In the present invention, through the DMD cross-type optical path splitting device, the coaxial acquisition and splitting of ultraviolet light and visible light can be completed synchronously, ensuring the matching of the imaging positions of the two optical paths and effectively avoiding the problem of fusion misalignment. Among them, in the ultraviolet light and visible light optical path shunting device, the core optical devices adopt a coplanar rectangular layout, the optical path structure is regular, and only the position of the imaging lens needs to be slightly adjusted to adapt to different focal length lenses, without changing the overall optical path, and the equipment debugging is convenient. At the same time, the folded intersecting optical path structure is adopted, effectively shortening the optical path transmission path, reducing the occupied space of the optical system and the light shield, greatly reducing the overall volume of the equipment, and the structure is compact.

[0020] This invention relies on FPGA closed-loop feedback iteration to dynamically adjust the working state of the DMD micromirror based on the detection results of the previous frame, intelligently completing partitioned iterative scanning. Compared with the traditional full-domain scanning method, it significantly improves the imaging frame rate and detection speed while ensuring imaging resolution. Combining the precise optical path gating characteristics of the digital micromirror with the high-sensitivity detection advantage of the photomultiplier tube, it can effectively capture weak corona ultraviolet signals, greatly improving the ability to identify and detect micro-discharges under complex working conditions. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the DMD-based cross-type optical path splitter in this invention; Figure 2 This is a flowchart of the visible light and ultraviolet light fusion scheme in this invention; Figure 3 This is a flowchart of the ultraviolet imaging multi-layer segmentation iterative algorithm in this invention; Figure 4 This is a schematic diagram of the results of the ultraviolet imaging multi-layer segmentation iterative algorithm in this invention.

[0022] In the diagram, 1. Ultraviolet imaging lens; 2. Dichroic mirror; 3. Digital micromirror device (DMD); 4. Light collector; 5. Ultraviolet filter; 6. Ultraviolet light detector; 7. Visible light camera; 8. Optical path shield; 9. DMD controller. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 This embodiment provides a DMD-based cross-type optical path splitter, such as... Figure 1 As shown, it includes an ultraviolet imaging lens 1, a dichroic mirror 2, a digital micromirror device (DMD) 3, an ultraviolet filter 5, an ultraviolet light detector 6, a visible light camera 7, and a light collector 4; a light path shield 8 is provided on the outside of the device. The digital micromirror device DMD3 is electrically connected to the DMD controller 9.

[0025] The core design of this embodiment lies in the cross-splitting layout of the optical path: the incident light (containing both ultraviolet and visible light) is first collected and initially converged by the ultraviolet imaging lens 1. Then, the incident light illuminates the dichroic mirror 2. The dichroic mirror 2 is an optical element with wavelength selectivity; its coating design gives it high reflectivity for ultraviolet light and high transmittance for visible light. Therefore, the ultraviolet light in the incident light is reflected by the dichroic mirror 2, deflected, and directed towards the digital micromirror device (DMD3); while the visible light in the incident light is directly transmitted through the dichroic mirror 2 and enters the visible light camera 7 for imaging.

[0026] Through the aforementioned beam-splitting mechanism, this device achieves real-time separation and independent acquisition of coaxially incident ultraviolet and visible light. This coaxial optical path design fundamentally avoids the image misalignment problem caused by parallax in traditional off-axis imaging systems, providing an ideal data source for subsequent high-precision ultraviolet-visible image registration and fusion. Specifically, since the ultraviolet and visible light images originate from the same incident optical path, their geometric distortion characteristics and field of view are highly consistent. Subpixel-level precise alignment can be achieved with only simple translation, rotation, and scaling, significantly reducing the complexity and computational load of the fusion algorithm and improving the clarity of the fused image and the accuracy of target localization.

[0027] Example 2 Based on Example 1, this example further defines the spatial layout and angular parameters of each optical element, such as... Figure 1 As shown, the ultraviolet imaging lens 1, the dichroic mirror 2, the digital micromirror device 3, and the ultraviolet photodetector 6 are arranged in the same plane, and the four are respectively arranged at the four vertices of an approximately rectangular shape, forming a highly compact folded optical path layout.

[0028] Specifically: The ultraviolet imaging lens 1 and the dichroic mirror 2 are arranged diagonally opposite each other along the rectangle; the reflective surface of the dichroic mirror 2 faces the digital micromirror device (DMD3) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the digital micromirror device (DMD3) is tilted towards the dichroic mirror 2 and fixed at a 24° angle relative to the incident light path; the visible light camera 7 is arranged on the visible light transmission side of the dichroic mirror 2; the light collector 4 is arranged beside the digital micromirror device (DMD3) and fixed at a 72° angle to the incident light direction of the digital micromirror device (DMD3); the photosensitive surface of the ultraviolet photodetector 6 is directly opposite the vertical light output direction of the window mirror of the digital micromirror device (DMD3); the ultraviolet filter 5 is arranged between the digital micromirror device (DMD3) and the ultraviolet photodetector 6.

[0029] In this embodiment, the ultraviolet imaging lens 1, dichroic mirror 2, digital micromirror device 3, and ultraviolet detector 6 are located at the vertices of an approximately rectangular shape, independent of each other, with ample space for fine-tuning. When replacing the ultraviolet imaging lens 1 with a different focal length, only its axial position within the lens barrel needs to be adjusted to change the focusing distance, without moving other optical components, greatly simplifying system maintenance and upgrade operations.

[0030] Meanwhile, the optical path, from the ultraviolet imaging lens 1 to the dichroic mirror 2, then to the digital micromirror device (DMD) 3, and finally to the ultraviolet photodetector 6, forms a folded path instead of a straight line. This folded design allows the optical path to achieve a long optical path within a limited space, thereby significantly reducing the physical volume occupied by the optical path. Correspondingly, the volume of the external optical path shield 8 can also be significantly reduced, ultimately achieving miniaturization and weight reduction of the entire ultraviolet imager, which is beneficial for portable applications such as handheld or airborne applications.

[0031] Example 3 Based on Example 2, the ultraviolet detector 6 is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode.

[0032] Among them, the ultraviolet photomultiplier tube (UVP) possesses extremely high sensitivity and extremely low noise, enabling it to detect extremely weak (even single-photon level) ultraviolet radiation. Its working principle is as follows: ultraviolet light irradiates the photocathode, generating photoelectrons. These photoelectrons, under the influence of a high-voltage electric field, sequentially bombard multiple dynodes, producing secondary electron emission, ultimately forming an amplified current pulse at the anode. The gain of a UVP can reach 10⁻¹⁰. 5 ~10 7 It is very suitable for weak ultraviolet signal detection scenarios such as corona discharge and flame detection.

[0033] An ultraviolet avalanche photodiode is a photodetector based on the avalanche multiplication effect under reverse bias of a semiconductor PN junction. When ultraviolet photons are absorbed in the depletion region, they generate photogenerated carriers. These carriers undergo collisional ionization in a high electric field region, triggering the avalanche multiplication effect and thus achieving internal gain (typically 10–200). Ultraviolet avalanche photodiodes offer advantages such as small size, low operating voltage (tens to hundreds of volts), fast response speed, and insensitivity to magnetic fields, making them particularly suitable for portable ultraviolet imaging devices with high requirements for size and integration.

[0034] This device can flexibly select an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode as the ultraviolet light detector according to the actual application scenario, such as detection distance, target ultraviolet intensity, system power consumption budget, etc.

[0035] Meanwhile, this embodiment specifies the key parameters of each optical element.

[0036] The ultraviolet filter 5 has a transmission wavelength range of 220 nm to 280 nm. This band covers most of the characteristic ultraviolet radiation generated by corona discharge and flame combustion. The filter typically employs interference coating technology, alternately depositing high- and low-refractive-index materials (such as HfO2 / SiO2 or Al2O3 / SiO2) on a substrate (such as quartz or calcium fluoride) to form a bandpass filter system. Its typical performance indicators include: transmittance ≥80% at the center wavelength and optical density OD ≥4 in the cutoff band (400 nm to 1100 nm), meaning a transmittance of less than 0.01%. This filter effectively suppresses visible and near-infrared stray light from entering the ultraviolet detector, significantly improving the signal-to-noise ratio.

[0037] The ultraviolet photodetector 6 has a photosensitive wavelength range of 200nm to 400nm. Whether it is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode, its photocathode material or semiconductor material (such as wide bandgap semiconductors such as SiC, GaN, and AlGaN) has been optimized for this wavelength range to ensure high quantum efficiency (typically ≥30%) in the 200nm to 400nm range, while having extremely low response to visible light longer than 400nm, thus achieving both spectral selectivity and high sensitivity.

[0038] The inner wall of the light-shielding shield 8 is covered with black light-absorbing fabric. This light-absorbing fabric is made of black flocked fabric or black matte velvet material with high absorption and low reflectivity, and its reflectivity in the visible to near-infrared band can be as low as less than 1%. The light-absorbing fabric is tightly attached to the inner wall of the light-shielding shield with double-sided tape or special adhesive, and all seams should be overlapped to avoid exposing the metal wall surface.

[0039] Example 4 Based on Example 3, this example provides a detailed description of the operating state and optical path control mechanism of the digital micromirror device DMD3.

[0040] The Digital Micromirror Device (DMD3) is an array of multiple high-speed digital optical reflective switches, composed of numerous small aluminum reflective mirrors. The display resolution is determined by the number of reflective mirrors; one micromirror or an array of micromirrors corresponds to one pixel. Each micromirror on the DMD3 chip is controlled by the DMD controller 9 and has two stable mechanical deflection states: on and off. In this device, the normal to the window mirror of the DMD3 serves as a reference, and incident ultraviolet light is incident on the DMD window mirror at a 24° angle.

[0041] When the micromirror is in the open state, ultraviolet light is emitted perpendicularly to the window mirror of the digital micromirror device DMD3, and after passing through the ultraviolet filter 5, it is perpendicularly irradiated onto the photosensitive surface of the ultraviolet detector 6, thereby realizing the detection of useful signals.

[0042] When the micromirror is closed, ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the digital micromirror device DMD3 and enters the light collector 4, where it is absorbed as useless light.

[0043] Meanwhile, this embodiment provides the working principle of a DMD-based cross-type optical path splitter, and the overall workflow is as follows: Incident light from the target scene (containing both ultraviolet radiation and visible light reflection) first enters the ultraviolet imaging lens 1. The ultraviolet imaging lens 1 uses a material with good transmittance for both ultraviolet and visible light (such as fused silica or calcium fluoride) to converge and collimate the incident light, outputting a parallel or nearly parallel incident beam. This beam illuminates the dichroic mirror 2 at a 45° incident angle. The dichroic mirror 2 utilizes its wavelength-selective coating to efficiently reflect ultraviolet light (220nm–280nm) from the incident light (reflectivity ≥95%), while simultaneously efficiently transmitting visible light (400nm–700nm) (transmittance ≥90%). Thus, ultraviolet and visible light are spatially separated for the first time. The ultraviolet light travels along the reflection path to the digital micromirror device (DMD3), while the visible light travels along the transmission path to the visible light camera 7, which outputs a visible light image signal.

[0044] The reflected ultraviolet light reaches the window mirror of the digital micromirror device (DMD3) at an incident angle of 24°. The DMD3 chip integrates hundreds of thousands to millions of independently controllable micromirrors. Each micromirror, under the control of the DMD controller 9, switches between on and off states at an extremely high frequency.

[0045] When the micromirrors are in the open state: according to the law of reflection, the incident ultraviolet light is precisely reflected and emitted perpendicular to the mirror surface of the DMD window. The emitted ultraviolet light passes perpendicularly through the ultraviolet filter 5, which further filters out any residual visible light or near-infrared stray light. Subsequently, the ultraviolet light perpendicularly illuminates the photosensitive surface of the ultraviolet detector 6. The detector converts the ultraviolet light signal into an electrical signal and outputs it.

[0046] When the micromirrors are in the closed state: the incident ultraviolet light is reflected in a direction that forms a 48° angle with the normal to the DMD window, i.e., deviating from the photosensitive surface of the detector. This outgoing light enters the light collector 4.

[0047] The light shield 8 of the entire device and the black light-absorbing cloth on its inner wall provide a working environment with low stray light interference for all the above-mentioned optical paths, ensuring that only the target signal light propagates along the designed path throughout the entire optical path from the entrance of the ultraviolet imaging lens 1 to the ultraviolet detector 6 and the visible light camera 7, thereby suppressing background noise to the maximum extent.

[0048] In summary, this device achieves coaxial beam splitting through a dichroic mirror 2, high-precision spatial gating and scanning of ultraviolet light through a digital micromirror device (DMD3), and a compact layout through a folded optical path, ultimately completing the coaxial acquisition and separation of ultraviolet and visible light. This provides an efficient, compact, and flexible solution for ultraviolet detection and positioning applications.

[0049] Example 5 This embodiment provides a method for segmented detection in ultraviolet imaging, using the DMD-based cross-type optical path splitter from Embodiment 4, specifically including the following steps: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based cross-type optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. The DMD controller 9 and visible light camera 7, based on the DMD cross-type optical path splitter, are electrically connected to the FPGA control module. The ultraviolet detector 6, also based on the DMD cross-type optical path splitter, is electrically connected to the shaping circuit. The shaping circuit is connected to the A / D converter, which in turn is connected to the FPGA control module. The FPGA control module is also electrically connected to the display. The shaping circuit amplifies, filters, and shapes the weak current pulse signal, converting it into a voltage pulse signal with amplitude and width matching the input requirements of the A / D converter. The A / D converter converts the analog voltage signal output by the shaping circuit into a digital signal for further processing by the FPGA control module. Both the shaping circuit and the A / D converter are commonly used circuits in the field of ultraviolet light detection. Those skilled in the art can choose commercially available mature chips or conventional discrete components to build the circuit according to actual needs; their specific internal structures will not be described in detail here.

[0050] Step 2: The ultraviolet and visible light beam splitter separates the incident mixed light. The FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image. The ultraviolet imaging multi-layer segmentation iterative algorithm flow is as follows: Figure 3 As shown.

[0051] Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them (the visible light and ultraviolet light fusion scheme process is as follows). Figure 2 As shown in the figure, the location of the corona discharge is determined.

[0052] Example 6 This embodiment details the multi-layer segmentation iterative scanning algorithm executed by the FPGA control module in step 2. This algorithm is used to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image. The total number of image segmentation layers Q and the number of segmentation blocks N per layer need to be preset first. The algorithm flow is as Figure 3 shown, and the schematic diagram of the segmentation iteration result is as Figure 4 shown. It specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all the micromirrors of the digital micromirror device DMD3 to be in the on state through the DMD controller 9. If an ultraviolet light signal is detected, it means that ultraviolet light has entered the lens, as Figure 4 shown by the red frame in. Ultraviolet light is detected in the overall region, and the subsequent steps are continued. If not detected, the FPGA control module only outputs a visible light signal.

[0053] Step 2.2: As Figure 3 shown, assign the current segmentation layer variable M to 2, divide the DMD micromirrors into N block regions according to the number of segmentation blocks N per layer, and sequentially control the micromirrors of each block region to be turned on and detect ultraviolet light. When all the micromirrors of a certain block region are in the on state, all the micromirrors of other block regions are in the off state, and label the block region where ultraviolet light is detected; In this embodiment, the number of segmentation blocks N per layer is 4. As Figure 4 shown, the green cross lines divide the region within the entire red frame into 4 block regions. The FPGA control module sequentially controls the micromirrors of these 4 block regions of the DMD controller to be in the on state. When all the micromirrors of a certain block are in the on state, all the micromirrors of other regions are in the off state. When all the micromirrors of a certain block region are in the fully on state, if the ultraviolet light detector detects an ultraviolet light signal, label this block region as the block region with ultraviolet light in layer M. As Figure 4 shown, among the 4 block regions divided by the green cross lines, ultraviolet light is detected in the upper left corner region, and no ultraviolet light is detected in the other 3 block regions.

[0054] Step 2.3: Increment M by 1. If M < Q, return to step 2.2 to continue segmentation and labeling. If M ≥ Q, perform a single-pixel scanning imaging row by row on the finally labeled region with ultraviolet light; as Figure 4 shown, perform single-pixel scanning imaging on the block region below the yellow cross line with M = 4.

[0055] Among them, single-pixel scanning imaging row by row is to control the micromirrors of the digital micromirror device DMD3 to be turned on one by one through the FPGA control module, scan the ultraviolet light of each pixel point to the ultraviolet detector in sequence, and complete the imaging of the corresponding region.

[0056] Step 2.4: The FPGA control module receives the scanning imaging data and generates a full-frame ultraviolet image.

[0057] This algorithm divides a frame of image into multiple layers and blocks for iterative detection. Only blocks where ultraviolet light signals are detected are further segmented or scanned line by line, while blocks without ultraviolet light signals are skipped. This coarse-to-fine region localization strategy transforms the process of fully scanning the entire frame into precise scanning of only small local areas, significantly reducing scanning time wasted in areas without ultraviolet light and substantially improving the frame rate of single-pixel imaging methods.

Claims

1. A DMD-based cross-type optical path splitter, characterized in that, It includes an ultraviolet imaging lens (1), a dichroic mirror (2), a digital micromirror device (DMD) (3), an ultraviolet filter (5), an ultraviolet light detector (6), a visible light camera (7), and a light collector (4); an optical path shield (8) is provided on the outside of the device. The digital micromirror device (DMD) (3) is electrically connected to a DMD controller (9).

2. The DMD-based cross-type optical path splitter according to claim 1, characterized in that, The ultraviolet imaging lens (1), dichroic mirror (2), digital micromirror device (3) and ultraviolet photodetector (6) are arranged in the same plane, and the four are respectively arranged at the four vertices of an approximate rectangle, forming a folded optical path layout.

3. The DMD-based cross-type optical path splitter according to claim 1, characterized in that, The ultraviolet imaging lens (1) and the dichroic mirror (2) are arranged diagonally opposite each other along the rectangle; the reflective surface of the dichroic mirror (2) faces the digital micromirror device (DMD) (3) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the digital micromirror device (DMD) (3) is tilted towards the dichroic mirror (2) and is fixed at a 24° angle relative to the incident light path; the visible light camera (7) is arranged on the visible light transmission side of the dichroic mirror (2); the light collector (4) is arranged on the side of the digital micromirror device (DMD) (3) and is fixed at a 72° angle to the incident light direction of the digital micromirror device (DMD) (3); the photosensitive surface of the ultraviolet light detector (6) faces the vertical light output direction of the window mirror of the digital micromirror device (DMD) (3); the ultraviolet filter (5) is arranged between the digital micromirror device (DMD) (3) and the ultraviolet light detector (6).

4. The DMD-based cross-type optical path splitter according to claim 1, characterized in that, The ultraviolet light detector (6) is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode; The ultraviolet filter (5) has a transmission wavelength range of 220nm to 280nm; The ultraviolet photodetector (6) has a photosensitive wavelength range of 200nm to 400nm; The inner wall of the light path shield (8) is covered with black light-absorbing cloth.

5. The DMD-based cross-type optical path splitter according to claim 1, characterized in that, Each micromirror on the DMD (3) chip is controlled by the DMD controller (9) and has an open state and a closed state. When the micromirror is open, ultraviolet light is emitted perpendicularly to the window mirror of the DMD (3) and then perpendicularly irradiates the photosensitive surface of the ultraviolet detector (6) after passing through the ultraviolet filter (5). When the micromirror is closed, ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the DMD (3) and enters the light collector (4).

6. An ultraviolet imaging block detection method, using the DMD-based cross-type optical path splitter as described in any one of claims 1 to 5, characterized in that, include: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based cross-type optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. Step 2: The beam splitter splits the incident mixed light, and the FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image. Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them to complete the corona discharge location positioning.

7. The ultraviolet imaging block detection method according to claim 6, characterized in that, The DMD controller (9) and the visible light camera (7) of the DMD cross-type optical path spectroscopic device are respectively electrically connected to the FPGA control module; the ultraviolet light detector (6) of the DMD cross-type optical path spectroscopic device is electrically connected to the shaping circuit; the shaping circuit is connected to the A / D analog-to-digital conversion circuit, and the A / D analog-to-digital conversion circuit is connected to the FPGA control module; the FPGA control module is also electrically connected to the display.

8. The ultraviolet imaging block detection method according to claim 6, characterized in that, In step 2, the FPGA control module performs multi-layer segmentation iterative scanning to locate the ultraviolet light area generated by corona discharge and generate an ultraviolet image. It is necessary to preset the total number of image segmentation layers Q and the number of segmentation blocks N per layer, which specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all the micro-mirrors of the digital micromirror device DMD (3) to be in the on state through the DMD controller. If an ultraviolet light signal is detected, the subsequent steps are executed; if not, the FPGA control module only outputs a visible light signal. Step 2.2: Assign the current segmentation layer variable M to 2. Divide the DMD micro-mirrors into N block areas according to the number of segmentation blocks N per layer. Control the micro-mirrors of each block area to be turned on in sequence and detect ultraviolet light. When all the micro-mirrors of a certain block area are in the on state, all the micro-mirrors of other block areas are in the off state, and mark the block area where ultraviolet light is detected. Step 2.3: Increment M by 1. If M < Q, return to step 2.2 to continue segmentation and marking. If M ≥ Q, perform a single-pixel scan imaging row by row on the finally marked area with ultraviolet light. Step 2.4: The FPGA control module receives the scan imaging data and generates a full-frame ultraviolet image.

9. The ultraviolet imaging block detection method according to claim 8, characterized in that, In step 2.2, the number of segmentation blocks N per layer is 4, and the corresponding area is equally divided into 4 block areas for ultraviolet light detection.

10. The ultraviolet imaging block detection method according to claim 8, characterized in that, In step 2.3, the single-pixel scan imaging row by row is to control the micro-mirrors of the digital micromirror device DMD (3) to be turned on one by one through the FPGA control module, and scan the ultraviolet light of each pixel point to the ultraviolet detector in sequence to complete the imaging of the corresponding area.

Images