Rapid calibration target plate device

Abstract

The invention discloses a rapid target plate calibration device, and belongs to the technical field of laser boresighting, the device comprises a laser boresighting mirror and a laser resolver, the laser boresighting mirror is used for emitting laser beams, the laser resolver is installed on an aircraft target plate, a laser receiver of the laser resolver is used for splitting light, a vertical camera is installed at the top of the laser resolver, and the vertical camera is connected with a camera. A parallel camera is installed at the rear end of the laser resolving instrument, the laser receiver divides a received laser beam into two light beams perpendicular to each other, and the two light beams are transmitted to the vertical camera and the parallel camera respectively. Compared with the prior art, the device does not need a tedious aircraft leveling process, remarkably reduces the operation complexity, adopts an advanced laser image detection technology and a high-precision sensor, can realize high-precision fixed-axis measurement, adopts a near-infrared band CCD (Charge Coupled Device) industrial camera, is provided with a narrow-band optical filter at the front end, can effectively filter the interference of environmental visible light, and is high in measurement precision. The pose of the target plate is automatically adjusted through automatic calculation of an algorithm, and personal errors are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of laser target calibration, and in particular to a device for quickly calibrating a target plate. Background Art

[0002] During aircraft maintenance calibration, accurate target plate positioning is crucial. Traditionally, this method involves mechanical calibration (cold calibration). Mechanical calibration begins by aligning the aircraft with the ground using a theodolite. Then, tools and fixtures such as a plumb bob, water bubble, tape measure, and a calibration scope are used to determine the relative position of the target plate and the aircraft. Once the relative position between the target plate and the aircraft is determined, the calibration scope is used to manually interpret the calibration error. Based on this interpretation, the mounting angle of the equipment being calibrated is adjusted. Once these adjustments are complete, target plate calibration is complete.

[0003] The above-mentioned existing technical solutions have the following technical problems: (1) There is a problem of manual interpretation error, and the efficiency needs to be further improved. (2) When manually adjusting the target plate posture, there is a lack of accurate reference data, and it often takes multiple attempts to approach the theoretical position, which increases labor intensity and time cost. (3) The parameters are read manually, and the ambient lighting conditions have a certain impact on the target calibration.

[0004] How to solve the above technical problems has long troubled technical personnel in this field. Summary of the Invention

[0005] The main purpose of the present invention is to provide a device for quickly calibrating a target plate, which can effectively solve the problems mentioned in the background technology.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A device for quickly calibrating a target plate, characterized in that it includes a laser calibration scope and a laser resolver, wherein: the laser calibration scope is used to emit a laser beam, a telescope is installed parallel to the top of the laser of the laser calibration scope, the rear end of the laser is connected to a de-expansion top tube, a double-end expansion tube is installed on the de-expansion top tube, the de-expansion top tube and the double-end expansion tube cooperate with each other to allow the laser to be coaxially installed inside the gun barrel, and the laser is connected to a mobile power supply through an electric wire; the laser resolver is installed on the aircraft target plate, the laser receiver of the laser resolver is used for splitting light, a vertical camera is installed on the top of the laser resolver, and a parallel camera is installed on the rear end of the laser resolver through a clamping device and a connecting tube. The laser receiver divides the received laser beam into two mutually perpendicular beams, which are transmitted to the vertical camera and the parallel camera respectively.

[0007] Preferably, the laser solver further includes a laser filter, a beam splitter prism, a photosensitive plate S1 and a photosensitive plate S2, wherein: The laser filter is arranged at the front end of the laser receiver, the dichroic prism is arranged inside the laser receiver at a 45° angle, the photosensitive plate S1 is arranged on the top of the laser receiver, and the photosensitive plate S2 is arranged in the connecting tube.

[0008] Preferably, the device comprises the following steps: 1) Equipment installation and preparation: Insert the double-ended expansion tube of the laser calibration scope into the aircraft gun barrel, ensuring it is inserted tightly and firmly so that the laser calibration scope represents the aircraft axis. Install the laser resolver on the aircraft target plate and tighten the fixing bolts. 2) Laser emission and image acquisition: Turn on the laser to emit a laser beam that is strictly aligned with the aircraft axis. The laser beam enters the resolver's laser receiver. The receiver is equivalent to two parallel photosensitive plates. The resolver camera uses the light spot inside the receiver as the observation target and captures a two-dimensional image of the light spot, completing the information acquisition process. 3) Optical center extraction and deviation calculation: The optical center extraction algorithm is used to process the captured spot image to obtain the optical center coordinates. The optical center coordinates and the distance between the solver and the laser are input into the attitude calculation algorithm to calculate the deviation distance and deviation angle of the laser axis. 4) Target plate deviation correction: Based on the calculated deviation distance and deviation angle, the target plate's motion system is driven to correct the deviation so that the target plate and the aircraft axis reach the expected positional relationship.

[0009] Preferably, the optical center extraction algorithm specifically includes the following steps: An edge tracking algorithm based on binary image topological structure analysis is used to extract the corresponding connected area by detecting the boundary of the binary image. Then, geometric constraints such as roundness, convexity and eccentricity are applied to determine the specific position of the circular landmark.

[0010] Preferably, the posture calculation algorithm specifically includes the following steps: Based on the position coordinates P0 and P1 of the light spot on the front and rear photosensitive plates and the distance between the two photosensitive plates, analysis is performed in the spatial coordinate system and the navigation coordinate system of the target plate to calculate the deviation distance and deviation angle.

[0011] Preferably, image processing is required before optical center extraction and deviation solution, which specifically includes the following steps: The captured two-dimensional spot image is grayscaled, and then the calibrated grayscale image is converted into a binary image through the adaptive threshold method. It is then subjected to a Gaussian filter to remove the noise points in the image and make the grayscale value evenly distributed, so as to facilitate the extraction of circular features.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) Simple and efficient operation: No tedious aircraft leveling process is required, which significantly reduces the complexity of operation, reduces manual workload, and improves measurement efficiency. (2) High measurement accuracy: The use of advanced laser image detection technology and high-precision sensors can achieve high-precision fixed-axis measurement. (3) Strong environmental adaptability: During the image acquisition and processing process, a series of effective measures are taken to deal with complex light environments. For example, in terms of hardware, a CCD industrial camera in the near-infrared band is used, and a narrow-band filter is set at the front end to effectively filter out ambient visible light interference, facilitating subsequent image processing. (4) High degree of intelligence: Automatic calculation and automatic adjustment of the target plate posture through algorithms reduce human errors, have low technical requirements for operators, and are easy to operate and promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the interior of the laser solver of the present invention; Figure 3 This is a schematic diagram of the working principle of the laser solver of the present invention; Figure 4 This is a flow chart of the control algorithm of the present invention.

[0014] In the figure: 1-laser calibration scope, 101-laser, 102-telescope, 103-de-expansion jacking tube, 104-double-end expansion tube, 105-mobile power supply, 2-laser resolver, 201-laser receiver, 202-vertical camera, 203-clamping device, 204-parallel camera, 205-laser filter, 206-beam splitter prism, 207-photosensitive plate S1, 208-photosensitive plate S2. DETAILED DESCRIPTION

[0015] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0016] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. The terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] like Figure 1 and Figure 2 As shown, the rapid target calibration device includes a laser calibration scope 1 and a laser resolver 2. In the figure, the laser calibration scope 1 is used to emit a laser beam. A telescope 102 is mounted parallel to the top of the laser 101 of the laser calibration scope 1. A de-expansion jacking tube 103 is connected to the rear end of the laser 101. A double-ended expansion tube 104 is mounted on the de-expansion jacking tube 103. The de-expansion jacking tube 103 and the double-ended expansion tube 104 cooperate to coaxially mount the laser 101 inside the gun barrel. The laser 101 is connected to a mobile power supply 105 via an electrical cable. The laser resolver 2 is mounted on the aircraft target. The laser receiver 201 of the laser resolver 2 is used for beam splitting. A vertical camera 202 is mounted on the top of the laser resolver 2, and a parallel camera 204 is mounted on the rear end of the laser resolver 2 via a clamping device 203 and a connecting tube. The laser receiver 201 splits the received laser beam into two perpendicular beams, which are transmitted to the vertical camera 202 and the parallel camera 204, respectively.

[0018] Specifically, the laser calibration scope is mainly responsible for emitting the laser beam. The laser is shaped through optical design, and after laser beam expansion, the laser can produce a thin straight line. The double-ended expansion tube is slowly inserted into the fuselage reference position. After it is fully inserted, the top tube is rotated in the opposite direction to the front end to completely disengage it from the expansion tube. The tube is pushed inward along the axial direction to fully integrate the inner wall with the outer circle of the expansion tube. At this time, the expansion tube is in an expanded state, forming an interference fit, ensuring that the expansion tube and the inner wall are tightly connected without gaps and ensuring coaxiality. The top tube structure is designed for easy installation and disassembly. The telescope adopts the principle of a mature optical telescope system and is used in conjunction with the laser, so that the operator can easily and clearly observe the position of the laser spot.

[0019] Specifically, the laser solver is installed on the aircraft target board. The solver uses computer vision technology to extract the optical center and measure the position of the light beam emitted by the laser, and then drives the motion system of the target board to correct the deviation.

[0020] Specifically, the laser solver 2 also includes a laser filter 205, a dichroic prism 206, a photosensitive plate S1207 and a photosensitive plate S2208, wherein: the laser filter 205 is arranged at the front end of the laser receiver 201, the dichroic prism 206 is arranged inside the laser receiver 201 at a 45° posture, the photosensitive plate S1207 is arranged at the top of the laser receiver 201, and the photosensitive plate S2208 is arranged in the connecting tube.

[0021] It should be noted that the laser filter 205 is an optical element designed specifically for the spectral characteristics of lasers. By selectively transmitting light of specific wavelengths, it modulates, optimizes, and protects the laser beam, facilitating observation by the vertical camera 202, thereby enabling the laser solver 2 to achieve higher resolution accuracy. The beam splitter prism 206, composed of two identical right-angle prisms, transforms an incident light beam through the beam splitter prism into two mutually perpendicular rays, which are then incident on the photosensitive plates S1207 and S2208, respectively, thereby achieving higher resolution efficiency for the laser solver 2. The photosensitive plates S1207 and S2208 form a screen, and light is incident on the vertical camera 202. Without the photosensitive plate S1207, the vertical camera 202 would not be able to observe the spot size.

[0022] It should be further explained that the working principle of this product is as follows Figure 2 and Figure 3 As shown, based on the characteristics of laser linear propagation, the laser transmitter shoots a straight line that is strictly consistent with the aircraft axis. The emitted laser is received by the receiver, and the solver receives the target video image and calculates the deviation distance and deviation angle of the laser axis, and then makes corrections. The interior of the receiver can be regarded as two parallel photosensitive plates with a fixed distance between the photosensitive plates. When the laser beam hits the photosensitive plate, the coordinates of the laser projection point P1 are measured on the photosensitive plate. After the beam passes through the front photosensitive plate S1, it is emitted to the rear photosensitive plate, leaving the projection point coordinates P2 on the rear photosensitive plate. The distance between the two photosensitive plates is a fixed value. In this way, the expression of the incident light in the spatial coordinate system can be solved based on the coordinates of the two projection points P1 and P1. Through computer solution, the deviation distances and deviation angles can be known.

[0023] Based on the above principle, the receiver's internal optical system can be designed. A semi-beam splitter prism is placed at a 45-degree angle in front of the original position of photosensitive plate S1. Photosensitive plate S1 is then placed above the semi-beam splitter prism. Due to the principle of plane mirror imaging, the virtual image of photosensitive plate S1 is now located behind the semi-beam splitter prism, at S1's original position. Due to the reversibility of the optical path, the projection of the light reflected from the semi-beam splitter prism onto S1 is the projection of the incident light onto the virtual image of S1. Photosensitive plate S2 is still placed in its original position, and the light transmitted from the semi-beam splitter prism is projected onto S2, which is the projection of the incident light onto S2. The photosensitive plate screen is made of a material similar to frosted glass. When the light beam is projected onto the screen, it produces a clear light spot on the back of the screen. A camera positioned on the back of the screen then captures the pattern of the light spot on the back of the screen. Through image processing, the coordinates of the light spot on the screen are obtained.

[0024] like Figure 4 As shown, in actual operation, the device includes the following operating steps: 1) Equipment installation and preparation: Insert the double-ended expansion tube 104 of the laser calibration scope 1 into the aircraft gun barrel, ensuring that it is inserted tightly and firmly so that the laser calibration scope 1 represents the aircraft axis. Install the laser solver 2 on the aircraft target plate and tighten the fixing bolts. 2) Laser emission and image acquisition: Turn on the laser 101 to emit a laser beam that is strictly aligned with the aircraft axis. The laser beam enters the resolver's laser receiver 201. The interior of the receiver is equivalent to two parallel photosensitive plates. The resolver camera uses the light spot inside the receiver as the observation target and captures a two-dimensional image of the light spot, completing the information acquisition process. 3) Optical center extraction and deviation calculation: The optical center extraction algorithm is used to process the captured spot image to obtain the optical center coordinates. The optical center coordinates and the distance between the solver and the laser are input into the attitude calculation algorithm to calculate the deviation distance and deviation angle of the laser axis. 4) Target plate deviation correction: Based on the calculated deviation distance and deviation angle, the target plate's motion system is driven to correct the deviation so that the target plate and the aircraft axis reach the expected positional relationship.

[0025] It's important to note that image quality can impact the accuracy of the design and the effectiveness of the algorithm during image analysis. Therefore, certain preprocessing steps are required before analysis. The primary goal of image preprocessing is to eliminate meaningless information, restore meaningful information, improve the detectability of valid information, and significantly simplify the data, thereby improving the reliability of subsequent image processing. To reduce the computational complexity of image processing, the calibration image is first grayscaled. This grayscale image is then converted to a binary image using an adaptive thresholding method. A Gaussian filter is then applied to remove image noise and achieve a uniform grayscale distribution, facilitating the extraction of circular features.

[0026] It should be noted that using a CCD camera assembly and a specially designed laser, we can obtain a spot image with an appropriate spot size and clear outlines. Based on the optical center extracted from the spot image and combined with other necessary parameters, such as the distance between the laser and the resolver, the measurement system can determine the deviation information of the target to be measured. Therefore, the accuracy of extracting the spot optical center is crucial to ensuring the system's calibration accuracy. Edge tracking extraction is performed on the preprocessed image using an edge tracking algorithm based on binary image topology analysis. By detecting the boundaries of the binary image, the corresponding connected area is extracted. Geometric constraints on roundness, convexity, and eccentricity are then applied to further determine the specific location of the circular landmark.

[0027] The calculation methods of roundness, convexity and eccentricity are as follows: 1) Roundness: Roundness generally refers to the degree to which a polygon approaches a perfect circle. The corresponding formula is: (1) Where: Indicates the roundness of the marker point, represents the area of the landmark point, Indicates the perimeter of the landmark point.

[0028] 2) Convexity: Convexity generally refers to the degree of concavity and convexity of a landmark point. The formula is defined as: (2) Where: is the convexity of the landmark point, is the area of the landmark point, Represents the convex hull area of the landmark point.

[0029] 3) Eccentricity: Eccentricity refers to the degree of deviation of the polygon's elliptical orbit from a perfect circle. Direct calculation of eccentricity is difficult. Generally, the image moment is used to solve the inertia rate of the landmark point, and then the eccentricity is calculated from the inertia rate. The corresponding formula is: (3) Where: represents the eccentricity of the landmark point, Represents the inertia rate of the landmark point.

[0030] After extracting the edges of the landmark points, the centroid of each landmark point is obtained using the first-order moment of the image, and its corresponding center can be obtained. Digital image ,in Order geometric moment for: (4) The above algorithm can be used to determine the position coordinates P0 and P1 of the light spot on the front and rear photosensitive plates. Since the distance between the two photosensitive plates is a known and fixed value, the coordinates of the two projection points P0 and P1 can be used to solve the expression of the incident light beam in the spatial coordinate system. Furthermore, the spatial coordinate system and the navigation coordinate system of the target plate are relatively stationary, so the deviation distances and angles can be calculated using linear expressions.

[0031] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A rapid target plate calibration device, characterized in that: It comprises a laser calibration mirror (1) and a laser solver (2), wherein: The laser calibration mirror (1) is used to emit a laser beam. A telescope (102) is installed parallel to the top of the laser (101) of the laser calibration mirror (1). The rear end of the laser (101) is connected to a de-expansion top tube (103). A double-end expansion tube (104) is mounted on the de-expansion top tube (103). The de-expansion top tube (103) and the double-end expansion tube (104) cooperate with each other to enable the laser (101) to be coaxially installed inside the gun barrel. The laser (101) is connected to a mobile power supply (105) via an electric wire. The laser resolver (2) is mounted on an aircraft target plate. The laser receiver (201) of the laser resolver (2) is used for light splitting. A vertical camera (202) is mounted on the top of the laser resolver (2). A parallel camera (204) is mounted on the rear end of the laser resolver (2) via a clamping device (203) and a connecting tube. The laser receiver (201) splits a received laser beam into two mutually perpendicular beams, which are respectively transmitted to the vertical camera (202) and the parallel camera (204).

2. A rapid target plate calibration device according to claim 1, characterized in that: The laser solver (2) further includes a laser filter (205), a beam splitter prism (206), a photosensitive plate S1 (207), and a photosensitive plate S2 (208), wherein: The laser filter (205) is arranged at the front end of the laser receiver (201), the beam splitter prism (206) is arranged inside the laser receiver (201) at a 45-degree angle, the photosensitive plate S1 (207) is arranged on the top of the laser receiver (201), and the photosensitive plate S2 (208) is arranged in the connecting tube.

3. A rapid target plate calibration device according to claim 1, characterized in that: The steps are as follows: 1) Equipment installation and preparation: Insert the double-ended expansion tube (104) of the laser calibration mirror (1) into the aircraft gun barrel, ensuring that it is inserted tightly and firmly, so that the laser calibration mirror (1) represents the aircraft axis, install the laser solver (2) on the aircraft target plate, and tighten the fixing bolts; 2) Laser emission and image acquisition: Turn on the laser (101) to emit a laser beam that is strictly consistent with the axis of the aircraft, so that the laser enters the laser receiver (201) of the solver. The inside of the receiver is equivalent to two parallel photosensitive plates. The resolver camera takes the light spot inside the receiver as the observation target and captures a two-dimensional light spot image to complete the information acquisition process; 3) Optical center extraction and deviation calculation: The optical center extraction algorithm is used to process the captured spot image to obtain the optical center coordinates. The optical center coordinates and the distance between the solver and the laser are input into the attitude calculation algorithm to calculate the deviation distance and deviation angle of the laser axis. 4) Target plate deviation correction: Based on the calculated deviation distance and deviation angle, the target plate's motion system is driven to correct the deviation so that the target plate and the aircraft axis reach the expected positional relationship.

4. A rapid target plate calibration device according to claim 1, characterized in that: The optical center extraction algorithm specifically includes the following steps: An edge tracking algorithm based on binary image topological structure analysis is used to extract the corresponding connected area by detecting the boundary of the binary image. Then, geometric constraints such as roundness, convexity and eccentricity are applied to determine the specific position of the circular landmark.

5. A rapid target plate calibration device according to claim 1, characterized in that: The posture calculation algorithm specifically includes the following steps: Based on the position coordinates P0 and P1 of the light spot on the front and rear photosensitive plates and the distance between the two photosensitive plates, analysis is performed in the spatial coordinate system and the navigation coordinate system of the target plate to calculate the deviation distance and deviation angle.

6. A rapid target plate calibration device according to claim 1, characterized in that: Image processing is required before optical center extraction and deviation solution, which specifically includes the following steps: The captured two-dimensional spot image is grayscaled, and then the calibrated grayscale image is converted into a binary image through the adaptive threshold method. It is then subjected to a Gaussian filter to remove the noise points in the image and make the grayscale value evenly distributed, so as to facilitate the extraction of circular features.

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