Visual displacement measuring device and atmospheric turbulence error weakening method thereof

Abstract

The application relates to a visual displacement measuring device and an atmospheric turbulence error weakening method thereof. The atmospheric turbulence error weakening method comprises the following steps: placing the visual displacement measuring device in front of a target, adjusting the distance between the visual displacement measuring device and the target and the distance between a microlens array and a camera, so that the target forms an intermediate real image plane between the microlens array and the camera; the camera collects an imaging picture of the target object, the imaging of each microlens is a sub-path image, and the centroid coordinates of all sub-path images on each frame of image are extracted; the relative displacement between the centroid coordinates of the corresponding sub-path images of the first frame of image and other frames of image is calculated; the displacement average of all sub-path images is calculated to obtain the displacement after turbulence error weakening; and the displacement after turbulence error weakening is converted into the actual displacement of the target. The imaging beam of the target to be measured in space is divided into multiple paths, and the turbulence random error is weakened in the form of average multi-path displacement.

Description

Technical Field

[0001] This application relates to the field of imaging technology, and in particular to a visual displacement measurement device and a method for reducing atmospheric turbulence errors thereon. Background Technology

[0002] Visual displacement measurement generally assumes that the atmosphere is a uniform and constant medium, and that the path of light from the target to the camera is a straight line. However, in reality, due to dynamic and thermodynamic factors, the path of light in the atmosphere is not a straight line. As a result, the target image acquired by the camera may be blurred and distorted, thus affecting the accuracy of visual displacement measurement.

[0003] Currently, methods for mitigating atmospheric turbulence errors mainly include reciprocal observation, mitigation methods using reference points, and meteorological parameter measurement. These methods can only handle errors caused by periodic and regular atmospheric effects, but they struggle to effectively address the random effects of irregular atmospheric turbulence. Filtering methods are commonly used to address the random effects of irregular atmospheric turbulence. However, since both time-domain and frequency-domain filtering are time-based, over-averaging can occur when processing changes in target displacement, significantly reducing the effectiveness of these methods. Summary of the Invention

[0004] To improve the accuracy of visual displacement measurement, this application provides a visual displacement measurement device and a method for reducing atmospheric turbulence errors.

[0005] on the one hand

[0006] The visual displacement measuring device provided in this application adopts the following technical solution:

[0007] A visual displacement measurement device includes a slide rail, a camera, and a microlens array. The camera and the microlens array are slidably connected to the slide rail. The camera is used to capture a real image plane formed by the microlens array. All microlenses in the microlens array have the same focal length.

[0008] Second aspect

[0009] This application also provides a method for mitigating atmospheric turbulence errors, which employs the following technical solution:

[0010] A method for reducing atmospheric turbulence errors, employing the aforementioned visual displacement measurement device, is characterized by comprising the following steps performed sequentially:

[0011] S1: Place the visual displacement measuring device in front of the target, and adjust the distance between the visual displacement measuring device and the target, as well as the distance between the microlens array and the camera, so that the target forms an intermediate real image plane between the microlens array and the camera.

[0012] S2: The camera acquires the intermediate real image plane to obtain the image of the target object. The image of each microlens is a sub-path image. The centroid coordinates of all sub-path images in each frame are extracted.

[0013] S3: Calculate the relative displacement between the centroid coordinates of the first frame image and the corresponding sub-path images of other frames;

[0014] S4: Calculate the mean displacement of all sub-path images to obtain the displacement after turbulence error reduction;

[0015] S5: Convert the displacement after turbulence error reduction into the actual target displacement.

[0016] Preferably, in step S1, the distance between the visual displacement measuring device and the target satisfies the following relationship:

[0017]

[0018] Where m is the distance between the microlens array and the target, n represents the distance between the microlens array and the intermediate real image plane, and f M The focal length of a single microlens;

[0019] The distance between the microlens array and the camera lens satisfies the following relationship:

[0020]

[0021] Where a is the distance between the camera and the intermediate real image plane, b is the distance between the camera and the sensor plane, and f is the distance between the camera and the sensor plane. L This refers to the camera's focal length.

[0022] Preferably, in step S2, the centroid coordinates of all sub-path images are extracted using the density centroid localization method, as follows:

[0023]

[0024] Where (x, y) represents the centroid coordinates of the circular marker image, m and n are the width and height of each frame image, respectively, and G... ij This represents the grayscale value of the i-th column and j-th row in the image.

[0025] Preferably, the relative displacement in step S3 is specifically achieved using the following method:

[0026]

[0027] or

[0028]

[0029] in, and Let x and y represent the x and y coordinates of the j-th sub-path image in the first frame, respectively. and Let x and y represent the x and y coordinates of the j-th sub-path image on other frames, respectively, where j ∈ [1, N] and N represents the number of sub-path images.

[0030] Preferably, the average displacement in step S4 is:

[0031]

[0032] Preferred, actual displacement The calculation formula is as follows:

[0033]

[0034]

[0035] Among them, D physical SF represents the actual physical size of the measured target, and d represents the scale factor. image This indicates the width of the image of the target on the camera.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] By combining multi-view imaging with conventional camera imaging, multi-path segmentation of the imaging beam in the space of the target under test is achieved, so as to average the data at different times at different spatial positions of the imaging beam. Its processing and displacement measurement results have different dimensions, which can effectively avoid the over-averaging problem that occurs when processing time-series displacement results by time-domain or frequency-domain correction calculation. At the same time, the use of microlens array and single camera can reduce the cost of the device. It has the advantages of single exposure, simple structure, high processing efficiency and good applicability. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the visual displacement measuring device according to an embodiment of this application.

[0039] Figure 2 This is a schematic diagram illustrating the principle of the multi-view imaging model in the embodiments of this application.

[0040] Figure 3 This is a measurement result diagram showing the distance between the microlens array and the marker, which is 3.4m.

[0041] Figure 4This is a measurement result diagram showing the distance between the microlens array and the marker, which is 6.8m.

[0042] Figure 5 This is a measurement result diagram showing the distance between the microlens array and the marker, which is 8.5m.

[0043] Figure 6 This is a measurement result diagram with a measurement distance of 15m between the microlens array and the marker.

[0044] Figure 7 This is a measurement result diagram showing the distance between the microlens array and the marker, which is 22.2m.

[0045] Figure 8 This is a measurement result diagram showing the distance between the microlens array and the marker, which is 29.4m.

[0046] Explanation of reference numerals in the attached diagram: 1. Slide rail; 2. Camera; 3. Microlens array; 4. Slide block; 5. Sliding knob. Detailed Implementation

[0047] The following is in conjunction with the appendix Figure 1-8 This application will be described in further detail.

[0048] Reference Figure 1 This application discloses a visual displacement measurement device comprising a slide rail 1, a camera 2, and a microlens array 3. Two slide blocks 4 are slidably connected to the slide rail 1. The camera 2 and the microlens array 3 are detachably connected to the two slide blocks 4, allowing the camera 2 and the microlens array 3 to move closer to and further away from each other along the sliding direction of the slide blocks 4. In this embodiment, the camera 2 and the microlens array 3 are fixed to the slide blocks 4 with bolts; in other embodiments, a snap-fit ​​connection is used. Each slide block 4 is threaded with a sliding knob 5. The screwing direction of the sliding knob 5 is perpendicular to the sliding direction of the slide block 4. The sliding knob 5, by screwing in, presses against or moves away from the slide rail 1, thereby limiting the movement of the slide block 4 on the slide rail 1. The camera 2 is used to capture the real image plane imaged by the microlens array 3. All microlenses in the microlens array 3 have the same focal length.

[0049] This application also discloses a method for mitigating atmospheric turbulence errors, comprising the following steps performed sequentially:

[0050] S1: Place the visual displacement measuring device in front of the target, and adjust the distance between the visual displacement measuring device and the target, as well as the distance between the microlens array and the camera.

[0051] The distance between the visual displacement measurement device and the target satisfies the following relationship:

[0052]

[0053] Where m is the distance between the microlens array and the target, n represents the distance between the microlens array and the intermediate real image plane, and f M The focal length of a single microlens;

[0054] The distance between the microlens array and the camera lens satisfies the following relationship:

[0055]

[0056] Where a is the distance between the camera and the intermediate real image plane, b is the distance between the camera and the sensor plane, and f is the distance between the camera and the sensor plane. L The focal length of the camera;

[0057] Specific multi-view imaging model reference Figure 2 ;

[0058] To ensure that the target forms an intermediate real image plane between the microlens array and the camera, meaning the target's detection position must be limited to the imaging range of each sub-path, the maximum displacement range of the target image that the visual displacement measurement device can measure is:

[0059]

[0060] Among them, W img N represents the width of the entire image captured by the camera, in pixels. c d represents the number of columns of microlenses in a microlens array. image This indicates the imaging width of the target in the image.

[0061] S2: The camera captures the intermediate real image plane to obtain an image of the target object. The image of each microlens is a sub-path image.

[0062] The centroid coordinates of all sub-path images in each frame are extracted using the density centroid localization method.

[0063]

[0064] Where (x, y) represents the centroid coordinates of the circular marker image, m and n are the width and height of each frame image, respectively, and G... ij This represents the grayscale value of the i-th column and j-th row in the image.

[0065] S3: Calculate the relative displacement between the centroid coordinates of the corresponding sub-path images of the reference frame (first frame) and subsequent frames (other frames besides the first frame):

[0066]

[0067] or

[0068]

[0069] in, and Let x and y represent the x and y coordinates of the j-th sub-path image in the first frame, respectively. and Let x and y represent the x and y coordinates of the j-th sub-path image on other frames, respectively, where j ∈ [1, N] and N represents the number of sub-path images.

[0070] S4: Calculate the mean displacement of all sub-path images.

[0071]

[0072] The displacement after the turbulence error is reduced is obtained.

[0073] S5: Converts the displacement after turbulence error reduction into the actual target displacement, actual displacement The calculation formula is as follows:

[0074]

[0075]

[0076] Among them, D physical SF represents the actual physical size of the measured target, and d represents the scale factor. image This indicates the width of the image of the target on the camera.

[0077] Displacement measurement experiment of static marker:

[0078]

[0079] Using a circular light spot marker as the target, a visual displacement measuring device was placed in front of the marker, and the distance between the camera and the marker, as well as the distance between the microlens array and the camera, were adjusted according to the method described above. An electric heating furnace was placed between the visual displacement measuring device and the marker, and the temperature was set to 300℃ as a heat source to simulate turbulence.

[0080] The microlens array and the marker were kept at the following distances in sequence: 3.4m, 6.8m, 8.5m, 15m, 22.2m, and 29.4m, with each group of data acquisition lasting 10 seconds. The experiment was conducted.

[0081] The displacement measurement results in the y-axis direction (vertical) are shown in Figure 3-8:

[0082] (Alternatively, displacement along the x-axis can be used for measurement; the x-axis direction is also known as the transverse direction.)

[0083] The gray curve represents the displacement of all sub-paths in each frame of the image, i.e., the displacement before turbulence error reduction; the black curve represents the result after averaging the multi-path displacements, i.e., the displacement after turbulence error reduction.

[0084] Observing the experimental results, when the heat source temperature is 300℃, the displacement measurement error caused by turbulence is approximately ±0.3-±0.6 pixels (the displacement measurement accuracy of the visual displacement measurement device under non-turbulent conditions has been measured to be better than 0.05 pixels, so the influence of pixel error on the experimental results can be ignored). After error reduction, the maximum and average errors of the six sets of displacement results are only 0.12 pixels and 0.02 pixels, respectively; the root mean square error after reduction is less than 0.04 pixels, and the accuracy improvement rate reaches more than 50%.

[0085] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method of atmospheric-turbulence-error mitigation for a visual displacement measurement device, the method comprising: The visual displacement measuring device comprises a slide rail (1), a camera (2) and a microlens array (3), the camera (2) and the microlens array (3) are slidably connected to the slide rail (1), the camera (2) is used for shooting an actual image plane imaged by the microlens array (3), and all microlenses of the microlens array (3) have the same focal length; ​ The atmospheric turbulence error weakening method adopts the visual displacement measuring device, and comprises the following steps in sequence: S1: placing the visual displacement measuring device in front of a target, adjusting the distance between the visual displacement measuring device and the target and the distance between the microlens array and the camera, so that the target forms an intermediate actual image plane between the microlens array and the camera; S2: the camera captures the intermediate actual image plane to obtain an imaging picture of the target object, each imaging of a microlens is a sub-path image, and the centroid coordinates of all sub-path images in each frame of image are extracted; S3: calculating the relative displacement between the centroid coordinates of the corresponding sub-path images of the first frame of image and other frames of image; S4: calculating the displacement mean value of all sub-path images to obtain the displacement after turbulence error weakening; S5: converting the displacement after turbulence error weakening into the actual displacement of the target; In step S1, the distance between the visual displacement measuring device and the target satisfies the following relationship: wherein m is the distance between the microlens array and the target, n represents the distance between the microlens array and the intermediate real image plane, f M is the focal length of a single microlens; The distance between the microlens array and the camera lens satisfies the following relationship: where a is the distance of the camera to the intermediate real image plane, b represents the distance of the camera to the sensor plane, f L is the focal length of the camera.

2. The atmospheric turbulence error weakening method of the visual displacement measuring device according to claim 1, characterized in that: In step S2, the density centroid positioning method is used to extract the centroid coordinates of all sub-path images, and the specific method is as follows: where (x, y) represents the image centroid coordinates of the circular sign, m and n are the width and height of each frame image, respectively, G ij denotes the gray value of the i-th column and j-th row in the image.

3. The atmospheric turbulence error weakening method of the visual displacement measuring device according to claim 1, characterized in that: In step S3, the relative displacement is specifically calculated by the following method: Or wherein, and xj and yj represent the x coordinate and the y coordinate of the jth sub-path image on the first frame image, respectively, and xj and yj represent the x coordinate and the y coordinate of the jth sub-path image on the other frame image, respectively, j e [1, N], N represents the number of sub-path images.

4. The atmospheric turbulence error weakening method of the visual displacement measuring device according to claim 3, characterized in that: In step S4, the displacement mean value is:

5. The atmospheric turbulence error weakening method of the visual displacement measuring device according to claim 4, characterized in that: Actual displacement The formula for calculating the actual displacement is as follows: where D physical represents the actual physical dimension of the measurement target, SF represents a scale factor, d image represents the width of the measurement target as imaged on the camera.

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