Three-dimensional measurement device, and method for improving projection brightness uniformity

Abstract

A method for improving the projection brightness uniformity of a projection apparatus (11), the method comprising: acquiring geometric projection parameters of the projection apparatus (11) (S200); on the basis of the obtained geometric projection parameters, calculating a brightness compensation coefficient for each pixel point of an image to be projected (S210); on the basis of the brightness compensation coefficient for each pixel point of said image, performing brightness compensation on said image, so as to obtain a brightness-compensated image to be projected (S220); and projecting the brightness-compensated image to be projected. By means of performing brightness compensation on an image to be projected, the brightness of structured light finally projected onto an object to be inspected is more uniform. Therefore, the impact on grayscale differences caused by self-attenuation factors of a light source can be effectively reduced, such that grayscale changes in a finally obtained measurement image can more truly reflect changes in the height of said object itself; moreover, the grayscale difference between a highly reflective area and other areas can be reduced, such that a more reliable three-dimensional measurement result is obtained, thereby achieving a higher simplicity and reliability. Further disclosed are a three-dimensional measurement device and a computer-readable storage medium.

Description

A three-dimensional measuring device and a method for increasing the uniformity of projection brightness Technical Field

[0001] This invention relates to the field of structured light, specifically to a three-dimensional measurement device and a method for increasing the uniformity of projection brightness. Background Technology

[0002] With the development of various fields such as mold design, precision machining, product inspection, and industrial measurement, traditional two-dimensional image sensor technology is increasingly unable to meet the needs of production scenarios. The demand for three-dimensional measurement technology has been growing rapidly in recent years. Since three-dimensional measurement sensors have an additional depth information, and the depth itself is not very sensitive to factors such as pose and lighting, three-dimensional measurement has greater advantages for object recognition and measurement tasks.

[0003] Currently, mainstream 3D measurement sensors are divided into contact and non-contact types. Non-contact sensors often use pre-known geometric relationships between multiple sensors to perform coordinate measurements. They are more popular due to their advantages such as being non-destructive and deformation-free. Among them, surface structured light technology based on triangulation has gradually shown its application potential.

[0004] In structured light systems, a combination of a light source, a DMD (Digital Micro-mirror Device), and a projection lens is typically used. Among these, DLP (Digital Light Projector) technology is mainly used as the light source in structured light systems because it has advantages such as high native contrast, miniaturization, closed optical path, high brightness, and good uniformity. However, due to the limitations of the mechanical structure, projectors are often designed as Sham off-axis structures, resulting in a high tilt angle between the projector and the plane where the object to be detected is located. This affects the brightness uniformity of the light spot projected onto the object, meaning that the brightness in the area closer to the light source is significantly higher than in the area farther away from the light source, causing a deviation in the obtained three-dimensional information.

[0005] Therefore, it is very important to design a method to improve the uniformity of structured light reconstruction systems. Summary of the Invention

[0006] The main technical problem solved by this invention is how to solve the problem of uneven brightness caused by the high tilt angle of the projection device.

[0007] According to a first aspect, one embodiment provides a three-dimensional measurement device, comprising:

[0008] One or more projection devices, the projection devices being used to project an image containing a preset pattern onto an object to be detected;

[0009] An image capturing component is used to capture an image of the object to be detected on which the preset pattern is projected, thereby obtaining a measurement image;

[0010] An image processing unit is configured to process the measured image to obtain the three-dimensional information of the object to be detected; and,

[0011] Controller, used for:

[0012] Obtain the projection geometry parameters of the projection device;

[0013] Calculate the brightness compensation coefficient for each pixel of the image to be projected based on the projection geometry parameters of the projection device;

[0014] The brightness of the image to be projected is compensated according to the brightness compensation coefficient of each pixel of the image to be projected, so as to obtain the brightness-compensated image to be projected.

[0015] The projection device is controlled to project the brightness-compensated image to be projected.

[0016] According to a second aspect, one embodiment provides a method for increasing the uniformity of projection brightness of a projection device, comprising:

[0017] Obtain the projection geometry parameters of the projection device;

[0018] Calculate the brightness compensation coefficient for each pixel of the image to be projected based on the projection geometry parameters of the projection device;

[0019] The brightness of the image to be projected is compensated according to the brightness compensation coefficient of each pixel of the image to be projected, so as to obtain the brightness-compensated image to be projected.

[0020] The brightness-compensated image to be projected is then projected.

[0021] According to the above embodiment of a three-dimensional measurement device and a method for increasing the uniformity of projection brightness, by performing brightness compensation on the image to be projected at the projection end, each pixel on the actual projected image has compensated brightness, thereby making the brightness of the striped beams projected onto the object to be detected more uniform. When using the image capturing component for grayscale imaging, no further flat-field correction is required. On the one hand, this can effectively reduce the influence of grayscale difference caused by the attenuation factor of the light source itself, so that the grayscale changes in the final measurement image can more realistically reflect the changes in the height of the object to be detected. On the other hand, for locally highly reflective objects, without further processing... When performing brightness compensation, if a highly reflective area is close to the light source, it will result in a higher grayscale difference between that area and other areas in the obtained measurement image. This will lead to a significant deviation in the 3D information of that area after reconstruction. Brightness compensation can reduce the brightness of the area close to the light source, thereby reducing the grayscale difference between the highly reflective area and other areas, resulting in more reliable 3D measurement results. In addition, since the projected image is more uniform in space, the spatial position of the object under test can be less affected during reconstruction. Moreover, compared with complex optical or structural designs, processing the projected image algorithmically is more cost-effective and simpler. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the structure of a three-dimensional measuring device;

[0023] Figure 2 is a flowchart of a method for increasing the uniformity of projection brightness of a projection device;

[0024] Figure 3 is a schematic diagram showing the positions of different components of the structured light system;

[0025] Figure 4 shows the image to be projected before brightness compensation;

[0026] Figure 5 shows the brightness-compensated image;

[0027] Figure 6 shows the image to be projected after brightness compensation. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0029] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0030] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0031] In this embodiment of the invention, the relationship between the theoretical brightness of each micromirror on the projection device and its corresponding projection field of view is established based on the structure and spatial relationship of the structured light system, thereby obtaining the brightness compensation coefficient. The brightness of the projected image is then compensated according to the brightness compensation coefficient, so that the grayscale difference in the measurement image acquired by the camera can truly reflect the height information of the object to be detected, thereby improving the reliability of the three-dimensional measurement results.

[0032] In a structured light system, referring to Figure 1, one or more projection devices 11 are used to alternately project images containing preset patterns onto the object to be detected. In this embodiment, the projection device 11 includes a matrix array of micromirrors, each micromirror corresponding to a pixel in the image to be projected, used to project a pixel in the image onto the object to be detected, and forming a projection field of view on the surface of the object to be detected, and the projection field of view is a trapezoidal area. After a single projection device 11 projects a projected image containing a preset pattern onto the object to be detected, an image capturing component 12 is used to capture an image of the object to be detected, obtaining a measurement image of the object to be detected. In this embodiment, the image capturing component 12 is a camera. Then, the image processing unit 13 decodes the obtained measurement image according to the corresponding decoding algorithm to obtain a phase image, and then restores the phase value to the true three-dimensional coordinates of the object according to the pre-calibrated position parameters.

[0033] In this embodiment, since striped coded structured light is one of the most widely used 3D measurement methods, and has advantages such as high accuracy, non-contact operation, high speed and high stability, its measurement principle is triangulation, that is, calculating the intersection of the light plane projected by the projector and the light rays corresponding to the camera pixel positions to obtain the 3D coordinates of the object to be measured. Among them, there are various ways of light plane encoding, the classic methods are Gray code and / or sinusoidal phase shift, which have the advantages of high stability and high accuracy. Therefore, in this embodiment, the phase shift image and / or Gray code image generated by striped coded structured light is used as the initial image to be projected, that is, the image to be projected before brightness compensation, as shown in Figure 4. After processing the image to be projected, it is then projected onto the surface of the object to be detected.

[0034] During this process, due to the attenuation of light during propagation, the brightness of the area near the light source on the object to be detected is higher, while the brightness of the area far from the light source is lower. That is, the grayscale difference in the measurement image obtained by the camera is not entirely caused by the height change of the object to be detected, but is also affected by the attenuation of light itself. Therefore, brightness compensation can be performed on the projection image at the projection end according to the brightness of the projection field of view corresponding to a single micromirror, so that the brightness projected onto the object to be detected is more uniform, and the grayscale information in the measurement image can more accurately reflect the actual three-dimensional information of the object to be detected, thereby obtaining more accurate and reliable three-dimensional measurement results. The specific process of brightness compensation of the projection image using controller 14 in this embodiment is as follows:

[0035] First, obtain the projection geometry parameters of the projection device.

[0036] For a micromirror on the projector, this micromirror is set to "on" while the other micromirrors are set to "off". The plane containing the object to be tested is projected onto the surface. In this embodiment, this plane is called the measured plane. Then, a camera is used to acquire an image of the measured plane, obtaining a surface image of the measured plane. At this time, the obtained surface image only contains the projected field of view region formed by the micromirror on the measured plane, which is a trapezoidal region. Then, a corner detection algorithm, such as the Harris corner detection algorithm, is used to detect corners in the obtained surface image, obtaining the pixel coordinates of the four corners of the trapezoidal region. Based on the obtained pixel coordinates of the four corners in the surface image, the camera's intrinsic and extrinsic parameter matrices, the spatial coordinates of these four corners are obtained. Then, the DLT algorithm, i.e., the direct linear transformation algorithm, is used to estimate the homography matrix based on the spatial coordinates of these four corners and the pixel coordinates of the micromirror, thereby establishing the correspondence between the micromirror and the projected field of view region formed on the measured plane. At this time, by further combining the camera's intrinsic and extrinsic parameter matrices, the correspondence between the micromirror and the trapezoidal region in the surface image can be obtained. For example, for any micromirror on a projector, the projected field of view formed by the micromirror in the surface image is a trapezoidal region. For the i-th corner point in this trapezoidal region, i = 1, 2, 3, 4, the pixel coordinates of the corner point are transformed to the world coordinate system according to the camera's intrinsic and extrinsic parameter matrices to obtain the spatial coordinates of the corner point:

[0037] Among them, (x i ,y i Let be the pixel coordinates of the i-th corner point in the surface image; K is the intrinsic parameter matrix of the camera. -1 X is the inverse of the camera's intrinsic parameter matrix, and E is the camera's extrinsic parameter matrix; wi ,Y wi Z wi ) represents the spatial coordinates of the i-th corner point.

[0038] The other corner points in the trapezoidal region are processed to obtain the spatial coordinates of the four corner points. In this embodiment, the coordinates of the upper left corner of each micromirror are directly determined by the row and column numbers, which are the pixel coordinates of the micromirror. The coordinates of the other three corners of the micromirror are represented by the pixel coordinates of the adjacent micromirrors. For example, for the micromirror in row u and column v, the pixel coordinates of the micromirror are (u, v), that is, the coordinates of the upper left corner of the micromirror are (u, v), the coordinates of the upper right corner of the micromirror are (u, v+1), the coordinates of the lower left corner are (u+1, v), and the coordinates of the lower right corner are (u+1, v). At this time, the four corners of the micromirror correspond one-to-one with the four corner points in the trapezoidal region. Then, the DLT algorithm is used to estimate the homography matrix H based on the spatial coordinates of the four corner points in the trapezoidal region and the pixel coordinates corresponding to the four corners of the micromirror. The resulting homography matrix is ​​a 3×3 matrix. Let the spatial coordinates of the corner point corresponding to the pixel coordinates of the current micromirror be (X, Y, Z), then the transformation relationship between the two can be expressed as:

[0039] This allows us to establish a correspondence between any micromirror on the projector and the four corner points of the projected field of view in the surface image. The projection geometry parameters in this embodiment represent this correspondence. At this point, the four corner points of the projected field of view in the surface image can be obtained based on the pixel coordinates of any micromirror on the projector.

[0040] Then, the brightness compensation coefficient of each pixel of the image to be projected is calculated based on the projection geometry parameters of the projection device.

[0041] For any micromirror in the projector, the four corner points of the corresponding trapezoidal projection field of view are obtained according to the obtained correspondence. Two corner points corresponding to the lower base of the trapezoidal region are selected, i.e., corner points with the same x-coordinate are grouped together, resulting in two groups of corner points, each containing two corner points. The Euclidean distance between the two corner points in each group is then calculated. The group with the largest Euclidean distance is selected as the two corner points corresponding to the lower base of the trapezoidal region. These two corner points have the same x-coordinate; in this embodiment, they are called the longer side corner points. It should be noted that in geometry, the lower base of a trapezoid refers to the longer of the two bases. The ratio between the x-coordinate of the longer side corner point and the height of the micromirror corresponding to the pixel is calculated. The arctangent of this ratio is calculated, and the cosine of the arctangent is calculated. The fixed gain of the projector is obtained. The ratio between the fixed gain and the nth power of the cosine value is taken as the theoretical brightness of the projection field of view. n can be 2, 3, 4, etc., and can be set according to actual needs.

[0042] Taking a typical scenario in a structured light system, namely a combination of two projectors and one camera, as shown in Figure 3, the measured plane is denoted as P, and the center point of the projector is located at (x, h), where x is the Euclidean distance between the center point of the projector and the center point of the camera, and h is the height of the center point of the projector relative to the horizontal plane. Then, the horizontal distance within the projector's field of view is... The theoretical brightness at a given position can be expressed as k / cos n (θ), where k is the fixed gain of the projector, which is related to the projector's optical power and field of view.

[0043] For the e-th micromirror on the projector, if the two corner points corresponding to the bottom edge of the trapezoidal region corresponding to the micromirror are obtained, the theoretical brightness of the projected field of view region formed by the micromirror on the measured plane can be expressed as:

[0044] Among them, L e h is the theoretical brightness of the projected field of view corresponding to the e-th micromirror. e Let b be the height of the e-th micromirror from the horizontal plane. e is the x-coordinate of the corner point of the long side corresponding to the e-th micromirror; k is the fixed gain of the projector; cos() is the cosine function; arctan() is the arctangent function.

[0045] Since there is a one-to-one correspondence between the micromirrors on the projector and the pixels in the image to be projected, the theoretical brightness of the projection field of view corresponding to the e-th micromirror is also the theoretical brightness corresponding to the e-th pixel in the image to be projected.

[0046] Then, the reciprocal of the obtained theoretical brightness is used as the gain coefficient of the e-th micromirror, and the scale transformation coefficient is set to normalize the obtained gain coefficient. The gain coefficient of the e-th micromirror is mapped to the range of (0,1] through the scale transformation coefficient, and the normalization of the obtained gain coefficient is completed. The normalization result is the brightness compensation coefficient of the e-th micromirror, which is also the brightness compensation coefficient of the e-th pixel. The scale transformation coefficient can be set according to the actual situation.

[0047] Each pixel in the image to be projected is processed to obtain the theoretical brightness of the projection field of view corresponding to each pixel, and then the brightness compensation coefficient of each pixel in the image to be projected is obtained. The brightness compensation coefficients corresponding to all pixels constitute the brightness compensation image, as shown in Figure 5.

[0048] Then, the brightness of the image to be projected is compensated according to the brightness compensation coefficient of each pixel of the image to be projected, so as to obtain the brightness-compensated image to be projected.

[0049] Calculate the product between the gray value of each pixel in the projected image and the corresponding brightness compensation coefficient. Use the resulting product as the brightness compensation result of each pixel. The brightness compensation results of all pixels constitute the brightness-compensated projected image, as shown in Figure 6.

[0050] Finally, the brightness-compensated image to be projected is projected to obtain a measurement image, thereby obtaining the three-dimensional information of the object to be detected.

[0051] The brightness-compensated image to be projected is projected from the projector onto the object to be detected. Then, the camera is used to acquire the image of the object to be detected, and the measurement image is obtained. The image processing unit 13 processes the obtained measurement image, that is, it performs structured light demodulation and three-dimensional reconstruction on the obtained measurement image, thereby obtaining the true three-dimensional information of the object to be detected.

[0052] Please refer to Figure 1. In this embodiment, a three-dimensional measurement device first uses the controller 14 to obtain the projection geometry parameters of the projection device 11, thereby calculating the brightness compensation coefficient of each pixel of the image to be projected, and then performing brightness compensation on the image to be projected. After the brightness compensation image to be projected is projected, the image capturing component 12 captures the object to be detected to obtain the measurement image. Finally, the image processing unit 13 processes the obtained measurement image to obtain the three-dimensional information of the object to be detected.

[0053] This embodiment compensates for the brightness of the image to be projected at the projection end, making the brightness of the striped beams projected onto the object to be detected more uniform. When using the image capturing component 12 for grayscale imaging, no further flat-field correction is required. On the one hand, this effectively reduces the influence of grayscale differences caused by the attenuation of the light source itself, allowing the grayscale changes in the final measurement image to more realistically reflect the height changes of the object to be detected. On the other hand, for locally highly reflective objects, without brightness compensation, if the locally highly reflective area is close to the light source area, it will result in a higher grayscale difference between this area and other areas in the obtained measurement image, leading to a large deviation in the three-dimensional information of this area after reconstruction. Brightness compensation can reduce the brightness of the area close to the light source, thereby reducing the grayscale difference between the highly reflective area and other areas, thus obtaining more reliable three-dimensional measurement results. In addition, since the projected image is more uniform in space, the spatial position of the object to be detected is less affected during reconstruction. Compared with complex optical or structural designs, processing the projected image algorithmically is more cost-effective and simpler. Furthermore, this method is also applicable to situations where the camera has a high tilt angle.

[0054] A method for increasing the uniformity of projection brightness of a projection device, as shown in Figure 2, includes:

[0055] Step S200: Obtain the projection geometry parameters of the projection device.

[0056] For a micromirror on the projector, this micromirror is set to "on" while the other micromirrors are set to "off". The plane containing the object to be tested is projected onto the surface. In this embodiment, this plane is called the measured plane. Then, a camera is used to acquire an image of the measured plane, obtaining a surface image of the measured plane. At this time, the obtained surface image only contains the projected field of view region formed by the micromirror on the measured plane, which is a trapezoidal region. Then, a corner detection algorithm, such as the Harris corner detection algorithm, is used to detect corners in the obtained surface image, obtaining the pixel coordinates of the four corners of the trapezoidal region. Based on the obtained pixel coordinates of the four corners in the surface image, the camera's intrinsic and extrinsic parameter matrices, the spatial coordinates of these four corners are obtained. Then, the DLT algorithm, i.e., the direct linear transformation algorithm, is used to estimate the homography matrix based on the spatial coordinates of these four corners and the pixel coordinates of the micromirror, thereby establishing the correspondence between the micromirror and the projected field of view region formed on the measured plane. At this time, by further combining the camera's intrinsic and extrinsic parameter matrices, the correspondence between the micromirror and the trapezoidal region in the surface image can be obtained.

[0057] For example, for any micromirror on a projector, the projected field of view formed by the micromirror in the surface image is a trapezoidal region. For the i-th corner point in this trapezoidal region, i = 1, 2, 3, 4, the pixel coordinates of the corner point are transformed to the world coordinate system according to the camera's intrinsic and extrinsic parameter matrices to obtain the spatial coordinates of the corner point:

[0058] Among them, (x i ,y i Let be the pixel coordinates of the i-th corner point in the surface image; K is the intrinsic parameter matrix of the camera. -1 X is the inverse of the camera's intrinsic parameter matrix, and E is the camera's extrinsic parameter matrix; wi ,Y wi Z wi ) represents the spatial coordinates of the i-th corner point.

[0059] The other corner points in the trapezoidal region are processed to obtain the spatial coordinates of the four corner points. In this embodiment, the coordinates of the upper left corner of each micromirror are directly determined by the row and column numbers, which are the pixel coordinates of the micromirror. The coordinates of the other three corners of the micromirror are represented by the pixel coordinates of the adjacent micromirrors. For example, for the micromirror in row u and column v, the pixel coordinates of the micromirror are (u, v), that is, the coordinates of the upper left corner of the micromirror are (u, v), the coordinates of the upper right corner of the micromirror are (u, v+1), the coordinates of the lower left corner are (u+1, v), and the coordinates of the lower right corner are (u+1, v). At this time, the four corners of the micromirror correspond one-to-one with the four corner points in the trapezoidal region. Then, the DLT algorithm is used to estimate the homography matrix H based on the spatial coordinates of the four corner points in the trapezoidal region and the pixel coordinates corresponding to the four corners of the micromirror. The resulting homography matrix is ​​a 3×3 matrix. Let the spatial coordinates of the corner point corresponding to the pixel coordinates of the current micromirror be (X, Y, Z), then the transformation relationship between the two can be expressed as:

[0060] This allows us to establish a correspondence between any micromirror on the projector and the four corner points of the projected field of view in the surface image. The projection geometry parameters in this embodiment represent this correspondence. At this point, the four corner points of the projected field of view in the surface image can be obtained based on the pixel coordinates of any micromirror on the projector.

[0061] Step S210: Calculate the brightness compensation coefficient of each pixel of the image to be projected based on the projection geometry parameters of the projection device.

[0062] For any micromirror in the projector, the four corner points of the corresponding trapezoidal projection field of view are obtained according to the obtained correspondence. Two corner points corresponding to the lower base of the trapezoidal region are selected, i.e., corner points with the same x-coordinate are grouped together, resulting in two groups of corner points, each containing two corner points. The Euclidean distance between the two corner points in each group is then calculated. The group with the largest Euclidean distance is selected as the two corner points corresponding to the lower base of the trapezoidal region. These two corner points have the same x-coordinate; in this embodiment, these two corner points are called the longer side corner points. It should be noted that in geometry, the lower base of a trapezoid refers to the longer of the two bases. The ratio between the x-coordinate of the longer side corner point and the height of the micromirror corresponding to the pixel is calculated. The arctangent of this ratio is calculated, and the cosine of the arctangent is calculated. The fixed gain of the projector is obtained. The ratio between the fixed gain and the nth power of the cosine value is taken as the theoretical brightness of the projection field of view. n can be 2, 3, 4, etc., and can be set according to actual needs.

[0063] Taking a typical scenario in a structured light system, namely a combination of two projectors and one camera, as shown in Figure 3, the measured plane is denoted as P, and the center point of the projector is located at (x, h), where x is the Euclidean distance between the center point of the projector and the center point of the camera, and h is the height of the center point of the projector relative to the horizontal plane. Then, the horizontal distance within the projector's field of view is... The theoretical brightness at a given position can be expressed as k / cos n (θ), where k is the fixed gain of the projector, which is related to the projector's optical power and field of view.

[0064] For the e-th micromirror on the projector, if the two corner points corresponding to the bottom edge of the trapezoidal region corresponding to the micromirror are obtained, the theoretical brightness of the projected field of view region formed by the micromirror on the measured plane can be expressed as:

[0065] Among them, L e h is the theoretical brightness of the projected field of view corresponding to the e-th micromirror. e Let b be the height of the e-th micromirror from the horizontal plane. e is the x-coordinate of the corner point of the long side corresponding to the e-th micromirror; k is the fixed gain of the projector; cos() is the cosine function; arctan() is the arctangent function.

[0066] Since there is a one-to-one correspondence between the micromirrors on the projector and the pixels in the image to be projected, the theoretical brightness of the projection field of view corresponding to the e-th micromirror is also the theoretical brightness corresponding to the e-th pixel in the image to be projected.

[0067] Then, the reciprocal of the obtained theoretical brightness is used as the gain coefficient of the e-th micromirror, and the scale transformation coefficient is set to normalize the obtained gain coefficient. The gain coefficient of the e-th micromirror is mapped to the range of (0,1] through the scale transformation coefficient, and the normalization of the obtained gain coefficient is completed. The normalization result is the brightness compensation coefficient of the e-th micromirror, which is also the brightness compensation coefficient of the e-th pixel. The scale transformation coefficient can be set according to the actual situation.

[0068] Each pixel in the image to be projected is processed to obtain the theoretical brightness of the projection field of view corresponding to each pixel, and then the brightness compensation coefficient of each pixel in the image to be projected is obtained. The brightness compensation coefficients corresponding to each pixel constitute the brightness compensation image, as shown in Figure 5.

[0069] Step S220: Perform brightness compensation on the image to be projected according to the brightness compensation coefficient of each pixel of the image to be projected, and obtain the brightness-compensated image to be projected.

[0070] Calculate the product between the gray value of each pixel in the projected image and the corresponding brightness compensation coefficient. Use the resulting product as the brightness compensation result of each pixel. The brightness compensation results of all pixels constitute the brightness-compensated projected image, as shown in Figure 6.

[0071] Step S230: Project the brightness-compensated image to be projected to obtain a measurement image, thereby obtaining the three-dimensional information of the object to be detected.

[0072] The brightness-compensated image to be projected is projected from the projector onto the object to be detected. Then, a camera is used to acquire an image of the object to be detected, and a measurement image is obtained. The obtained measurement image is then subjected to structured light demodulation and 3D reconstruction to obtain the true 3D information of the object to be detected.

[0073] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.

[0074] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A three-dimensional measuring apparatus, characterized by comprising: The method comprises the following steps: one or more projection devices for projecting a preset pattern-containing image to be projected onto an object to be detected; an image capturing component for capturing the object to be detected with the preset pattern projected thereon to obtain a measurement image; an image processing unit for processing the measurement image to obtain three-dimensional information of the object to be detected; a controller for: obtaining the projection geometry parameters of the projection device; calculating the brightness compensation coefficient of each pixel point of the image to be projected according to the projection geometry parameters of the projection device; performing brightness compensation on the image to be projected according to the brightness compensation coefficient of each pixel point of the image to be projected to obtain the image to be projected after brightness compensation; controlling the projection device to project the image to be projected after brightness compensation. The projection device comprises a plurality of micromirrors arranged in a matrix, each micromirror being used for projecting a pixel point on the image to be projected; 2. The three-dimensional measuring apparatus of claim 1, wherein The controller calculates the brightness compensation coefficient of each pixel point of the image to be projected according to the projection geometry parameters of the projection device, which comprises: for any pixel point in the image to be projected, obtaining four corner points of the projection field region corresponding to the pixel point according to the projection geometry parameters of the projection device, and obtaining the theoretical brightness of the projection field region according to the coordinates of the four corner points and the height of the micromirror corresponding to the pixel point; taking the inverse of the obtained theoretical brightness as the gain coefficient of the pixel point, obtaining a scale transformation coefficient, normalizing the obtained gain coefficient according to the scale transformation coefficient, and taking the normalized result as the brightness compensation coefficient of the pixel point. The controller obtains the theoretical brightness of the projection field region according to the coordinates of the four corner points and the height of the micromirror corresponding to the pixel point, which comprises:

3. The three-dimensional measuring apparatus of claim 2, wherein The projection field region is a trapezoidal region, two corner points in the four corner points corresponding to the lower base of the trapezoidal region are called long-side corner points, the obtained two long-side corner points have the same abscissa, the ratio between the abscissa of the obtained long-side corner point and the height of the micromirror corresponding to the pixel point is calculated, the inverse tangent value of the obtained ratio is calculated, the cosine value of the obtained inverse tangent value is calculated, the fixed gain of the projector is obtained, and the ratio between the fixed gain and the nth power of the obtained cosine value is taken as the theoretical brightness of the projection field region. The controller performs brightness compensation on the image to be projected according to the brightness compensation coefficient of each pixel point of the image to be projected to obtain the image to be projected after brightness compensation, which comprises:

4. The three-dimensional measuring apparatus of claim 1, wherein calculating the product between the gray value of each pixel point and the corresponding brightness compensation coefficient, taking the obtained product as the brightness compensation result of each pixel point, and the brightness compensation results of all pixel points constitute the image to be projected after brightness compensation. The image to be projected comprises a phase shift image and / or a Gray code image.

5. The three-dimensional measuring apparatus of claim 1, wherein The method comprises the following steps:

6. A method for increasing projection brightness uniformity of a projection device, characterized in that, obtaining the projection geometry parameters of the projection device; calculating the brightness compensation coefficient of each pixel point of the image to be projected according to the projection geometry parameters of the projection device; performing brightness compensation on the image to be projected according to the brightness compensation coefficient of each pixel point of the image to be projected to obtain the image to be projected after brightness compensation; ​ Project the image to be projected after brightness compensation.

7. The method of claim 6, wherein, The projection device comprises a plurality of micro-mirrors arranged in a matrix, each micro-mirror being used to project a pixel point on the image to be projected; the method for calculating the brightness compensation coefficient of each pixel point of the image to be projected according to the projection geometry parameter of the projection device comprises: For any pixel point in the image to be projected, four corner points of the projection field region corresponding to the pixel point are obtained according to the projection geometry parameter of the projection device, the theoretical brightness of the projection field region is obtained according to the coordinates of the four corner points and the height of the micro-mirror corresponding to the pixel point, the reciprocal of the obtained theoretical brightness is taken as the gain coefficient of the pixel point, the scale transformation coefficient is obtained, the obtained gain coefficient is normalized according to the scale transformation coefficient, and the normalized result is taken as the brightness compensation coefficient of the pixel point.

8. The method of claim 7, wherein, The method for obtaining the theoretical brightness of the projection field region according to the coordinates of the four corner points and the height of the micro-mirror corresponding to the pixel point comprises: The projection field region is a trapezoidal region, two corner points in the four corner points corresponding to the lower base of the trapezoidal region are called long-side corner points, the horizontal coordinates of the obtained long-side corner points are calculated, the ratio between the horizontal coordinates of the obtained long-side corner points and the height of the micro-mirror corresponding to the pixel point is calculated, the inverse tangent value of the obtained ratio is calculated, the cosine value of the obtained inverse tangent value is calculated, the fixed gain of the projector is obtained, and the ratio between the fixed gain and the nth power of the obtained cosine value is taken as the theoretical brightness of the projection field region.

9. The method of claim 6, wherein, The method for performing brightness compensation on the image to be projected according to the brightness compensation coefficient of each pixel point of the image to be projected to obtain the image to be projected after brightness compensation comprises: The product between the gray value of each pixel point and the corresponding brightness compensation coefficient is calculated, the obtained product is taken as the brightness compensation result of each pixel point, and the brightness compensation results of all the pixel points constitute the image to be projected after brightness compensation.

10. A computer-readable storage medium, characterized in that, The medium stores a computer program, and the computer program can be executed by the processor to implement the method according to any one of claims 6-9.

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