Test tool for calibration of gimbal camera north function

Abstract

The utility model relates to the technical field of calibration test equipment provides a kind of for the test tool of pan-tilt camera north function calibration, including arc-shaped tool body, tool body has marking surface, marking surface is provided with zero mark and at least one angle offset mark group, zero mark is configured as used as the reference for calibrating pan-tilt camera north direction, angle offset mark group distributes in one side or both sides of zero mark, every angle offset mark in angle offset mark group corresponds a specific angle offset value, and, the visual graphic features of any two angle offset marks corresponding different angle offset values are all different. In production stage, when pan-tilt points to the north direction considered by itself according to its own system, camera captures an angle offset mark with unique graphic features on tool body, realizes the high-precision, quantifiable measurement of north deviation, improves calibration accuracy.

Description

Technical Field

[0001] This utility model relates to the field of calibration and testing equipment technology, and in particular to a test fixture for calibrating the north-pointing function of a PTZ camera. Background Technology

[0002] Pan-tilt cameras, especially long-focal-length cameras with azimuth pointing capabilities, are widely used in scenarios requiring precise positioning of distant targets, such as forest fire prevention, border monitoring, power line inspection, and monitoring of major events. In these applications, the core technical requirement is the ability to accurately obtain the target's azimuth relative to geographic north, so that the observation information can be correlated with the geographic coordinate system, providing precise location guidance for subsequent decision-making and actions.

[0003] In existing technologies, pan-tilt cameras typically incorporate electronic compasses or similar geomagnetic sensors to provide north-pointing capabilities. However, electronic compasses are highly susceptible to interference from ferromagnetic materials in the surrounding environment, high-voltage power lines, and the electromagnetic fields of the device itself, and their accuracy is inherently limited. Such angular errors may be negligible when observing close-range targets, but when the target distance reaches several kilometers or even tens of kilometers, minute angular deviations are drastically amplified, leading to a significant linear discrepancy between the calculated target position and the actual position. This is unacceptable in emergency scenarios where every second counts, such as forest fire prevention, severely impacting rescue efficiency and potentially causing irreparable damage.

[0004] To address the issues of insufficient accuracy and susceptibility to interference with electronic compasses, the industry has further developed a north-pointing solution employing a dual-antenna Global Navigation Satellite System (GNSS). This solution involves installing two GNSS antennas at a certain distance on a gimbal, and using a high-precision differential algorithm to calculate the accurate orientation of the baseline vector formed by the two antennas relative to true north.

[0005] However, in research and development and production practice, it was found that even with an advanced dual-antenna north-pointing solution, the azimuth angle reported by the PTZ camera in actual applications still exhibits a fixed but unknown systematic error. In-depth analysis revealed that the root cause of the problem lies not in the algorithm of the dual-antenna system, but in the physical installation. The dual-antenna system can accurately determine the orientation of its antenna baseline, but due to unavoidable machining tolerances, stress release during product assembly, and gaps in component fits, it is difficult to achieve absolute parallelism between the antenna baseline and the camera's central optical axis. This physical non-parallelism constitutes a systematic deviation angle. This deviation angle is a purely mechanical structural error; it is fixed for each device, but varies between different devices. Because the dual-antenna system itself cannot detect this installation deviation, there is an angle between its output true north direction and the true north direction actually pointed to by the camera lens. This results in the aforementioned problem of inaccurate long-distance positioning persisting, affecting the final product performance and customer experience. Utility Model Content

[0006] This invention provides a test fixture for calibrating the north-pointing function of a PTZ camera, which solves the above-mentioned technical defects in the prior art. It can efficiently measure the systematic deviation angle of the PTZ camera introduced by mechanical installation tolerances during the manufacturing stage, thereby improving the production calibration efficiency and reducing the manufacturing cost.

[0007] This utility model provides a test fixture for calibrating the north-pointing function of a PTZ camera, comprising: The arc-shaped tool body has a marking surface, on which a zero-position mark and at least one group of angle offset marks are provided. The zero-position mark is configured as a reference for calibrating the true north direction of the pan-tilt camera. The group of angle offset marks is distributed on one or both sides of the zero-position mark. Each angle offset mark in the group of angle offset marks corresponds to a specific angle offset value. Furthermore, any two angle offset marks corresponding to different angle offset values ​​will have different visual graphic features.

[0008] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, multiple angle offset marks in the angle offset mark group are arranged linearly or in an arc array along the direction deviating from the zero mark.

[0009] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the number, size, shape, or combination of the graphic elements of the angle offset mark are different to form different visual graphic features.

[0010] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the angle offset mark includes a main indicator graphic and one or more sub-indicator graphics; The main indicator graphic is used to indicate the offset direction; The number, size, and shape of the sub-indicator graphics are used to characterize the specific angular offset value.

[0011] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the main indicator graphic is a vertical line running through the image, and the secondary indicator graphic is a number of short horizontal lines at equal intervals.

[0012] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the graphic features of the zero-position mark are different from the graphic features of all angle offset marks.

[0013] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the zero mark is composed of three vertical lines of different widths: the middle one is the main vertical line that runs through the image, one side is a short vertical line occupying the upper part of the image, and the other side is a short vertical line occupying the lower part of the image.

[0014] The test fixture for calibrating the north function of a PTZ camera provided by this utility model also includes an alignment verification device, which is used to ensure that the zero mark is aligned with the true north direction.

[0015] According to the test fixture for calibrating the north-pointing function of a PTZ camera provided by this utility model, the alignment verification device includes: At least two laser emitters are disposed on the tooling body; And at least two laser receivers, each for receiving the optical signal from the laser transmitter, wherein the laser transmitter and laser receiver are paired and the line connecting the two paired laser transmitters intersects perpendicularly with the line connecting the zero mark of the tooling body and the pan-tilt camera.

[0016] According to the test fixture for calibrating the north function of a PTZ camera provided by this utility model, the at least two laser emitters are configured to operate with different emission waveforms to prevent signal crosstalk between receivers.

[0017] This invention provides a test fixture for calibrating the north-pointing function of a PTZ camera. The fixture's arc-shaped body has a zero-position mark and at least one group of angle offset marks on its marked surface. The zero-position mark serves as a reference for calibrating the PTZ camera's true north direction. The angle offset marks are distributed on one or both sides of the zero-position mark. Each angle offset mark in the group corresponds to a specific angle offset value, and any two angle offset marks corresponding to different angle offset values ​​will have different visual graphic features. This transforms the abstract north-pointing angle deviation into concrete, machine-visually identifiable, and quantifiable physical graphic information. During production, when the PTZ points to what it perceives as true north, the camera no longer captures a blurry, difficult-to-determine image, but rather an angle offset mark with unique graphic features on the fixture body. This achieves high-precision, quantifiable measurement of the north-pointing deviation, improving calibration accuracy.

[0018] Compared to traditional calibration methods that require specialized technicians to repeatedly align and read data using precision equipment such as theodolites—a time-consuming, tedious process demanding high skill levels—this invention simplifies this complex process to pointing, photographing, and recognizing. Utilizing the camera itself as a reading device, coupled with fixed testing fixtures and backend recognition software, it improves production calibration efficiency and reduces manufacturing costs. Furthermore, replacing manual judgment with machine vision achieves a significant leap in efficiency, directly reducing labor and time costs.

[0019] Furthermore, as a physical standard component, the markings on the testing fixture are fixed once manufactured. All products in the same batch are calibrated using the exact same fixture, ensuring the consistency and reliability of calibration results for the entire batch. This eliminates systematic or random errors that may be introduced by different testers, test times, or test environments, thus ensuring that every PTZ camera leaving the factory adheres to the same high standards, greatly guaranteeing the consistency of product performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the layout of a test fixture for calibrating the north-pointing function of a PTZ camera, provided in an embodiment of this utility model.

[0022] Figure 2This is a schematic diagram of another layout of the test fixture for calibrating the north-pointing function of a PTZ camera provided in this embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of a test fixture for calibrating the north-pointing function of a PTZ camera, provided in an embodiment of this utility model.

[0024] Figure 4 This is one of the layout schematic diagrams of another embodiment of the test fixture for calibrating the north function of a PTZ camera provided in this utility model embodiment.

[0025] Figure 5 This is a second schematic diagram of the layout of another embodiment of the test fixture for calibrating the north function of a PTZ camera provided by this utility model.

[0026] Figure 6 These are waveforms of laser emitters at different locations.

[0027] Figure label: 100. Tooling body; 110. Marking surface; 111. Zero mark; 112. Angular offset mark; 112-1. Main indicator graphic; 112-2. Secondary indicator graphic; 200. Pan-tilt camera. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0029] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0030] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0032] Figure 1 This is a schematic diagram of the layout of a test fixture for calibrating the north-pointing function of a PTZ camera, provided in an embodiment of this utility model. Figure 2 This is a schematic diagram of another layout of the test fixture for calibrating the north-pointing function of a PTZ camera provided in this embodiment of the present invention. Figure 3 This is a schematic diagram of a test fixture for calibrating the north-pointing function of a PTZ camera, provided in an embodiment of this utility model.

[0033] See Figures 1 to 3 This utility model provides a test fixture for calibrating the north-pointing function of a PTZ camera. The PTZ camera 200 is used in forest fire prevention, event monitoring and other occasions. Although the dual-antenna north-pointing system equipped with the PTZ camera 200 has high accuracy, there will still be physical deviations in the north-pointing direction due to factors such as structural tolerances and installation accuracy. Moreover, this deviation is difficult to measure and calibrate accurately during the production stage.

[0034] The present invention provides a test fixture for calibrating the north-pointing function of a PTZ camera by creating a tool with a specific physical form and coded visual markings.

[0035] Specifically, the test fixture includes an arc-shaped fixture body 100, which serves as the physical carrier for all visual markings and is designed with an arc-shaped structure. During calibration, the pan-tilt camera 200 can be placed at the center of this arc-shaped fixture body 100. When the pan-tilt rotates horizontally (azimuth rotation) around its own vertical axis, the distance between the camera lens (imaging sensor) and the marking surface 110 on the fixture body 100 remains essentially constant. This ensures consistent imaging ratios; that is, regardless of the angle at which the pan-tilt points away from the marking 112, the size and clarity of the image remain consistent. This reduces the complexity and difficulty of subsequent image recognition algorithms, improving the accuracy and reliability of recognition.

[0036] The tooling body 100 can be made of rigid materials such as metal, engineering plastics, or composite panels to ensure its structural stability and resistance to deformation. Its radius of curvature can be set according to the common production line workstation space and the closest focusing distance of the pan-tilt camera 200; for example, the radius can be set to 1 meter to 3 meters.

[0037] The tooling body 100 has a marking surface 110, which is an area on the tooling body 100 used to present visual graphics. It typically adopts a high-contrast, low-reflection design, such as a matte white background with black markings, to facilitate clear capture by the camera.

[0038] The marking surface 110 is provided with a zero-position mark 111 and at least one set of angle offset marks 112. The zero-position mark 111 is configured as a reference for calibrating the true north direction of the pan-tilt camera 200. That is, the zero-position mark 111 is the reference for the entire fixture body 100, representing the position where the angle deviation is zero, which is the true north direction. During calibration setup, an external high-precision north-pointing device, such as a theodolite or differential GPS, is required to determine the true north direction, and the zero-position mark 111 of the fixture body 100 must be precisely aligned with this direction.

[0039] The angle offset marker group 112 is the core of the deviation encoding. The angle offset marker group 112 is distributed on one or both sides of the zero-position marker 111. Each angle offset marker 112 within the group corresponds to a specific angle offset value. For example, the left side represents northwest, and the right side represents east of north. Each independent angle offset marker 112 within the group uniquely corresponds to a specific angle offset value, such as 0.1°, 0.2°, ..., N°.

[0040] Any two angle offset markers 112 corresponding to different angle offset values ​​will have different visual graphic features. For example, by changing the number, size, shape, or combination of lines, the angle offset markers 112 can be made to correspond one-to-one with specific angle offset values, and each will have different graphic features. This setting ensures the uniqueness and unambiguity of the identification. The image recognition algorithm can directly read the precise angle value represented by the graphic. By assigning a graphic identity to each angle offset value, any ambiguity in the measurement is avoided, transforming calibration from an estimation relying on human experience to a precise measurement based on encoding and decoding. This allows for the recording of accurate compensation values, fundamentally improving the north-pointing accuracy of the final product. This is the key to achieving precise decoding. If the graphics corresponding to different angle values ​​are too similar, confusion may occur during image recognition, leading to calibration failure or errors. Therefore, highly distinguishable graphic encoding must be used.

[0041] In the production calibration process, the true north direction is determined using high-precision reference equipment, and the zero-position mark 111 on the tooling body 100 of this invention is aligned with the true north direction. Then, the gimbal to be calibrated is directed towards the tooling body 100 of this invention based on its perceived north direction measured by its own dual-antenna system. At this point, the image captured by the gimbal camera 200 will no longer be the zero-position mark 111, but rather a specific angular offset mark 112 on the tooling body 100. By identifying this angular offset mark 112 through an image recognition algorithm, the inherent north deviation value of the gimbal system can be accurately and quantitatively determined and stored as a compensation value in the system, thereby achieving high-precision factory calibration for each device.

[0042] This setup simplifies angle conversion during calibration. Under equidistant conditions, the physical distance between the marks on the tooling body 100 is linearly proportional to the angle value they represent, making the design and calibration process simpler and more accurate.

[0043] It is understood that the test fixture for calibrating the north-pointing function of a PTZ camera provided in this embodiment of the invention has a zero-position mark 111 and at least one set of angle offset marks 112 on the marking surface 110 of the arc-shaped fixture body 100. The zero-position mark 111 is used to calibrate the true north direction of the PTZ camera 200. The set of angle offset marks 112 is distributed on one or both sides of the zero-position mark 111. Each angle offset mark 112 in the set of angle offset marks 112 corresponds to a specific angle offset value, and any two angle offset marks 112 corresponding to different angle offset values ​​have different visual graphic features. By transforming the abstract north-pointing angle deviation into concrete physical graphic information that can be accurately identified and quantified by machine vision, in the production stage, when the PTZ points to what it considers to be true north according to its own system, its camera no longer captures a blurry and difficult-to-determine image, but rather an angle offset mark 112 with unique graphic features on the fixture body 100. This achieves high-precision and quantifiable measurement of the north-pointing deviation, improving calibration accuracy.

[0044] Compared to traditional calibration methods that require specialized technicians to repeatedly align and read data using precision equipment such as theodolites—a time-consuming, tedious process demanding high skill levels—this invention simplifies this complex process to pointing, photographing, and recognizing. Utilizing the camera itself as a reading device, coupled with fixed testing fixtures and backend recognition software, it improves production calibration efficiency and reduces manufacturing costs. Furthermore, replacing manual judgment with machine vision achieves a significant leap in efficiency, directly reducing labor and time costs.

[0045] Furthermore, as a physical standard component, the markings on the testing fixture remain fixed once manufactured. All products in the same batch are calibrated using the exact same fixture, ensuring the consistency and reliability of calibration results across the entire batch. This eliminates systematic or random errors that may be introduced by different testers, test times, or test environments, thus guaranteeing that every PTZ camera 200 leaving the factory adheres to the same high standards, greatly ensuring the consistency of product performance.

[0046] Compared to developing complex dynamic electronic calibration systems, the test fixture provided by this invention is essentially a pre-designed marking plate. The manufacturing cost of the test fixture mainly lies in mold making and printing / engraving, which are technologically mature and cost-controllable. Its structure is simple, robust, durable, and not easily damaged, making it extremely convenient for deployment and maintenance on the production line. Most of the intelligent computing is transferred to infinitely replicable software algorithms, achieving significant quality improvements without increasing capital investment.

[0047] Continue reading Figure 3In some embodiments of this invention, multiple angle offset markers 112 within the angle offset marker group 112 are arranged linearly or in an arc array along the direction deviating from the zero-position marker 111. The purpose is to construct a physical coding system with an inherent logical order and spatial predictability. This is not an arbitrary layout choice, but rather to achieve an intuitive and systematic mapping relationship between physical position and angle value.

[0048] In other words, the primary purpose of arranging the angle offset markers 112 along a predetermined path (straight line or arc) is to establish a clear logical relationship: the physical position of the marker on the tooling body 100 directly corresponds to the magnitude and direction of the angle offset value it represents.

[0049] Whether the angle offset marker 112 is located to the left or right of the zero mark 111 directly corresponds to whether the angle deviation is "north-east" or "north-west". The physical distance between the angle offset marker 112 and the zero mark 111 is directly proportional to the magnitude of the angle deviation. The greater the distance, the greater the angle deviation.

[0050] This design is like a ruler, with the scale (angle offset mark 112) arranged in an orderly manner along the ruler body (linear or arc path), making the entire calibration system highly logical and predictable, and avoiding decoding chaos caused by random scattering of marks.

[0051] Once the PTZ camera 200 captures an image, the algorithm does not need to perform a global, aimless search and matching across the entire frame. Instead, it can start from the image center (the theoretical zero position) and perform a directional scan along a known linear or arc path. This significantly narrows the search range, reduces the computational load, and improves recognition speed.

[0052] Continue reading Figure 3 In some embodiments of this utility model, the number, size, shape, or combination of graphic elements of the angle offset mark 112 varies to form different visual graphic features. These graphic elements may include vertical lines, horizontal lines, dots, color blocks, etc.

[0053] In order for the image recognition algorithm to quickly and unambiguously identify the zero mark 111, the graphic features of the zero mark 111 are different from the graphic features of all the angle offset marks 112.

[0054] For example, the zero-position marker 111 can be composed of three vertical lines of different widths: a wider main vertical line in the middle, a thinner short vertical line to its upper left (occupying only the upper half of the image), and a medium-width short vertical line to its lower right (occupying only the lower half of the image). This asymmetrical and feature-rich design not only makes it easy to identify but also effectively prevents misjudgments caused by a 180-degree rotation of the camera or the tooling body 100.

[0055] Specifically, the angle offset mark 112 includes a main indicator graphic 112-1 and one or more sub-indicator graphics 112-2; the main indicator graphic 112-1 is used to indicate the offset direction; the number, size and shape of the sub-indicator graphics 112-2 are used to characterize the specific angle offset value.

[0056] For example: 0.1° west of north: Angle offset marker 112 is located to the left of zero marker 111. Its graphic can be composed of a vertical line running through the image (main indicator graphic 112-1, indicating the west direction) and 10 equally spaced short horizontal lines (secondary indicator graphic 112-2, the number 10 being used to encode the value 0.1). That is, the 10 short horizontal lines maintain the same length, width, and adjacent spacing.

[0057] 0.2° North by West: Angle offset marker 112 is also located to the left of zero marker 111. Its graphic can be composed of a vertical line running through the image and nine equally spaced short horizontal lines; that is, the nine short horizontal lines have the same length, width, and adjacent spacing. To further increase differentiation, the length of these nine short horizontal lines can be slightly shorter than the length of the ten short horizontal lines at 0.1°.

[0058] At a position of N degrees west of north: Angle offset marker 112 is also located to the left of zero marker 111. Its graphic can be composed of a vertical line running through the image and five equidistant short horizontal lines. The five short horizontal lines have the same length, width, and adjacent intervals. The length is appropriately reduced compared to the position of 0.2 degrees west of north.

[0059] 0.1° east of north: Angle offset marker 112 is located to the right of zero marker 111. Its graphic can be composed of a vertical line running through the image (main indicator graphic 112-1, indicating the direction of east) and 10 short horizontal lines at equal intervals. The 10 short horizontal lines have the same length, the same width, and the same spacing between adjacent lines.

[0060] 0.2° North by East: Angle offset marker 112 is located to the right of zero marker 111. Its graphic can consist of a vertical line running through the image (main indicator graphic 112-1, indicating the east direction) and nine equidistant short horizontal lines. The nine short horizontal lines have the same length, width, and spacing. The length of the nine short horizontal lines can be slightly shorter than the length of the ten short horizontal lines for 0.1°.

[0061] At a position of N degrees east of north: Angle offset marker 112 is also located to the right of zero marker 111. Its graphic can be composed of a vertical line running through the image and five equidistant short horizontal lines. The five short horizontal lines have the same length, width, and adjacent intervals. The length is appropriately reduced compared to the position of 0.2 degrees west of north.

[0062] Similarly, by changing the number, size, and even shape of the sub-indicator graphic 112-2 (horizontal line), a "graphic ID card" that is easy to identify and count using machine vision algorithms can be designed for each precise angular offset value (e.g., accurate to 0.05°). This encoding method based on the number of graphic elements is more resistant to interference and more reliable in recognition compared to encoding that relies solely on size or grayscale.

[0063] The specific usage process of the test fixture for calibrating the north-pointing function of a PTZ camera provided in this embodiment is as follows: On the production line, the testing fixture provided by this utility model is fixed. Using a theodolite, the true north direction is found, and the position of the fixture body 100 is adjusted so that the camera is located at the center of the arc of the fixture body 100, and the zero mark 111 of the fixture is aligned with the true north direction.

[0064] Then, the pan-tilt camera 200 to be calibrated is activated and commanded to perform a north-pointing operation. The pan-tilt will rotate to what it perceives as true north based on data from its dual-antenna system. Due to inherent bias, the lens is not aligned with the zero-position mark 111 at this time.

[0065] The camera captures an image of the current field of view. Suppose the image shows a shape with a vertical line and nine horizontal lines on the right. The backend analysis software identifies this shape, matches it using a pre-defined encoding rule library, and decodes it to show that the shape represents 0.2° east of north. The system then determines that the pan-tilt-zoom (PTZ) system has a 0.2° azimuth deviation.

[0066] The deviation value of -0.2° is permanently written into the firmware of the gimbal as calibration compensation data. Thereafter, the gimbal will automatically add this compensation value when reporting any direction, thus outputting a highly accurate true geographic direction.

[0067] Since the test fixture serves as the measurement reference in the calibration process, its accuracy is a prerequisite for all subsequent measurements. Even a slight rotational shift of the test fixture during placement—for example, the zero-position mark 111, which should point due north, actually deviates by 0.05 degrees—will directly transmit and superimpose this initial error into the final calibration result of the PTZ camera 200, leading to calibration failure or decreased accuracy. Therefore, to ensure the placement accuracy of the test fixture itself and thus guarantee the absolute reliability of the reference direction represented by the zero-position mark 111, in a preferred embodiment of this invention, the test fixture for calibrating the north-pointing function of the PTZ camera further includes an alignment verification device.

[0068] Figure 4 This is one of the layout schematic diagrams of another embodiment of the test fixture for calibrating the north function of a PTZ camera provided in this utility model embodiment. Figure 5 This is a second schematic diagram of the layout of another embodiment of the test fixture for calibrating the north function of a PTZ camera provided by this utility model. Figure 6 These are waveforms of laser emitters at different locations.

[0069] See Figures 4 to 6 Based on the above embodiments, the test fixture for calibrating the north function of the PTZ camera also includes an alignment verification device. The alignment verification device is used to ensure that the zero mark 111 is aligned with the due north direction, providing a high-precision positioning reference for the test fixture itself and ensuring the accuracy of the placement of the test fixture itself.

[0070] Specifically, the alignment and calibration device includes at least two laser emitters disposed on the fixture body 100; and at least two laser receivers respectively for receiving light signals from the laser emitters; the laser emitters and laser receivers are paired and the position of their pairing connection line is used to calibrate whether the placement orientation of the fixture body 100 is correct, that is: the connection line between the two paired laser emitters intersects perpendicularly with the connection line between the zero mark 111 of the fixture body 100 and the pan-tilt camera 200.

[0071] In a specific embodiment, two small-angle laser emitters (hereinafter referred to as points A and B) can be symmetrically arranged on the tooling body 100 along a precisely machined horizontal reference line (e.g., the bottom edge of the tooling). Simultaneously, two corresponding laser receivers (hereinafter referred to as points C and D) are also arranged on an external fixed reference object at the calibration station (e.g., the ground or a dedicated bracket) along a parallel reference line. Their pairing relationship is: emitter at point A corresponds to receiver at point C, and emitter at point B corresponds to receiver at point D.

[0072] It is understood that this embodiment of the invention utilizes geometric relationships for orientation locking. When the test fixture is correctly placed, the line segment connecting points A and B should intersect precisely at a 90-degree angle with the center line representing "true north." At this time, the laser beam emitted from point A will accurately strike the receiver at point C, and simultaneously, the laser beam emitted from point B will accurately strike the receiver at point D. During actual installation and debugging, operators or automated equipment only need to fine-tune the orientation of the fixture until the receivers at points C and D simultaneously detect the strongest light signal, which proves that the fixture body 100 is in a completely correct, non-rotationally offset preset position. This process is intuitive, accurate, and easy to automate.

[0073] See Figure 6 At least two laser emitters are configured to operate with different emission waveforms to prevent signal crosstalk between receivers.

[0074] In practical applications, laser transmitters A and B, along with their corresponding receivers C and D, are typically very close together. This presents a risk of signal crosstalk, where the beam from point A is partially scattered and received by point D, or the beam from point B is received by point C. This crosstalk can interfere with the accuracy of alignment judgment. This embodiment, however, configures at least two laser transmitters with different emission waveform operating modes, employing a signal coding-based anti-interference scheme.

[0075] For example, the laser emitter at point A can be set to a continuous illumination mode, emitting a laser beam with a constant intensity. Meanwhile, the laser emitter at point B can be set to an intermittent (pulse) mode with a specific frequency, such as flashing at a frequency of 5 kHz.

[0076] Accordingly, the receiver at point C is designed to respond effectively only to continuous optical signals, while the internal circuitry of the receiver at point D is designed in bandpass filtering mode, responding effectively only to pulsed optical signals at a frequency of 5kHz. Through this precise matching of transmitter encoding (different waveforms) and receiver decoding (selective response), even if the receiver at point C receives scattered pulsed light from point B, or the receiver at point D receives scattered continuous light from point A, neither will generate a valid trigger signal. This fundamentally eliminates signal crosstalk, greatly improving the stability and reliability of the alignment verification system.

[0077] Understandably, the alignment and calibration device is not a simple superposition of isolated technical features; it forms a close technical synergy with the angular offset marks 112 group on the marking surface 110, jointly serving the purpose of high-precision north calibration. Furthermore, this allows the entire testing fixture to function as a whole, systematically addressing a series of technical issues from precise placement to accurate measurement.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model 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. Such modifications or substitutions do 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 utility model.

Claims

1. A test fixture for calibrating the north-pointing function of a PTZ camera, characterized in that, include: The arc-shaped tool body has a marking surface, on which a zero-position mark and at least one group of angle offset marks are provided. The zero-position mark is configured as a reference for calibrating the true north direction of the pan-tilt camera. The group of angle offset marks is distributed on one or both sides of the zero-position mark. Each angle offset mark in the group of angle offset marks corresponds to a specific angle offset value. Furthermore, any two angle offset marks corresponding to different angle offset values ​​will have different visual graphic features.

2. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 1, characterized in that, The multiple angle offset markers in the angle offset marker group are arranged linearly or in an arc array along the direction deviating from the zero position marker.

3. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 1, characterized in that, The differences in the number, size, shape, or combination of the graphic elements of the angle offset markers create different visual graphic features.

4. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 3, characterized in that, The angle offset marker includes a main indicator graphic and one or more sub-indicator graphics; The main indicator graphic is used to indicate the offset direction; The number, size, and shape of the sub-indicator graphics are used to characterize the specific angular offset value.

5. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 4, characterized in that, The main indicator graphic is a vertical line running through the image, and the secondary indicator graphic is a number of short horizontal lines at equal intervals.

6. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 1, characterized in that, The graphic features of the zero-position marker are different from those of all the angle offset markers.

7. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 6, characterized in that, The zero-position marker consists of three vertical lines of different widths: the middle one is the main vertical line that runs through the image, one side is a short vertical line that occupies the upper part of the image, and the other side is a short vertical line that occupies the lower part of the image.

8. The test fixture for calibrating the north-pointing function of a PTZ camera according to any one of claims 1 to 7, characterized in that, It also includes an alignment verification device, which is used to ensure that the zero mark is aligned with true north.

9. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 8, characterized in that, The alignment verification device includes: At least two laser emitters are disposed on the tooling body; And at least two laser receivers, each for receiving the optical signal from the laser transmitter, wherein the laser transmitter and laser receiver are paired and the line connecting the two paired laser transmitters intersects perpendicularly with the line connecting the zero mark of the tooling body and the pan-tilt camera.

10. The test fixture for calibrating the north-pointing function of a PTZ camera according to claim 9, characterized in that, The at least two laser emitters are configured to operate with different emission waveforms to prevent signal crosstalk between receivers.

Images