Method for obtaining projection correction amount, projection system and projection correction method

Abstract

The present application discloses a method for obtaining a projection correction amount, a projection system, and a projection correction method, which can overcome the above-mentioned problems and obtain accurate projection correction amounts, thereby facilitating automatic correction and precise correction. The present application provides a method for obtaining a projection correction amount, comprising the following steps: obtaining a reference normal vector #imgabs0# of a target plane; when a projector performs a standard projection at a reference spatial position, the plane where the lens is located is parallel to the target plane; obtaining a projection vector #imgabs1#; the coordinate values ​​of the projection vector #imgabs2# and the reference normal vector #imgabs3# are based on the same preset spatial coordinate system and are related to the current spatial position of the lens; obtaining an angle between the reference normal vector #imgabs4# and the projection vector #imgabs5#, and obtaining the projection correction amount based on the angle.

Description

Technical Field

[0001] The present application relates to the field of projection, and in particular to a method for obtaining a projection correction value, a projection system, and a projection correction method. Background Art

[0002] When using a projector for projection, sometimes a trapezoidal projection phenomenon will occur. At this time, the image projected onto the target plane will appear trapezoidal, such as Figure 1 As shown, it includes vertical trapezoids and horizontal trapezoids. When the image is trapezoidal, it will affect the user experience and the user needs to adjust the picture to obtain a normal viewing experience.

[0003] When image adjustments are needed, users must adjust the projector's optical and mechanical position repeatedly until the optical and mechanical positions are parallel to the target plane, aligning the principal optical axis of the light emitted by the optical and mechanical positions perpendicular to the target plane. Conventional keystone correction requires complex geometric calculations to determine the projector's deflection relative to the projection surface, making it very inconvenient to use. Summary of the Invention

[0004] In view of this, the present application provides a method for obtaining a projection correction amount, a projection system, and a projection correction method, which can overcome the above-mentioned problems and obtain accurate projection correction amounts, thereby facilitating automatic correction and precise correction.

[0005] The present application provides a method for obtaining projection correction amount, comprising the following steps: obtaining a reference normal vector of the target plane When the projector performs standard projection at the reference space position, the plane where the projector lens is located is parallel to the target plane; obtain the projection vector , the projection vector and the base normal vector The coordinate values ​​are based on the same preset spatial coordinate system and are related to the current spatial position of the lens; obtaining the reference normal vector With the projection vector and obtain the projection correction amount according to the angle.

[0006] Optionally, the obtaining of the reference normal vector of the target plane The method comprises the following steps: obtaining the depth information of the target plane in a direction perpendicular to the plane where the lens of the projector is located at the reference space position of the projector; obtaining the point cloud plane corresponding to the target plane according to the depth information; obtaining the reference normal vector according to the point cloud plane corresponding to the target plane. .

[0007] Optionally, the projection vector perpendicular to the current plane of the lens, and the obtained projection vector Before, the method further includes the following steps: detecting whether there is a correction signal, and if so, performing the step of obtaining the projection vector steps.

[0008] Optionally, the projection vector is obtained The method comprises: obtaining a point cloud plane corresponding to the plane where the lens is currently located; obtaining the projection vector based on the point cloud plane corresponding to the plane where the lens is currently located .

[0009] Optionally, obtaining the point cloud plane corresponding to the plane where the lens is currently located includes: at the current spatial position of the projector, obtaining depth information along a direction perpendicular to the plane where the lens is currently located, and converting the depth information into point cloud data to construct a point cloud plane corresponding to the plane where the lens is currently located, the point cloud plane corresponding to the plane where the lens is currently located contains multiple point clouds related to the depth information of the plane where the lens is currently located.

[0010] Optionally, the projection vector is obtained based on the point cloud plane corresponding to the plane where the lens is currently located. The method comprises: using principal component analysis to analyze the point cloud plane corresponding to the plane where the lens is currently located, and obtaining the projection vector of the point cloud plane corresponding to the plane where the lens is currently located. .

[0011] Optionally, the principal component analysis method is used to analyze the point cloud plane corresponding to the plane where the lens is currently located, and obtain the projection vector of the point cloud plane corresponding to the plane where the lens is currently located The method comprises the following steps: obtaining the coordinate mean of each point cloud on the point cloud plane according to the following formula (1):

[0012]

[0013] in is the coordinate mean, P n is the coordinate of each point cloud on the point cloud plane, N is the number of point clouds on the point cloud plane, and n is the point cloud number on the point cloud plane;

[0014] According to the following formula (2), the covariance matrix of each point cloud on the point cloud plane is obtained based on the coordinates of each point cloud and the mean of the coordinates:

[0015]

[0016] Wherein C is the covariance matrix;

[0017] According to the following formula (3), the minimum eigenvector of the covariance matrix is ​​obtained:

[0018]

[0019] Wherein v1, v2 and v3 are three eigenvectors of the covariance matrix, λ1, λ2 and λ3 are eigenvalues ​​corresponding to the three eigenvectors; the minimum eigenvector is normalized and the normalized result is used as the projection vector .

[0020] Optionally, the preset spatial coordinate system is a three-dimensional rectangular coordinate system, including three axes XYZ, and the reference normal vector The coordinates in the preset space coordinate system are (0, 0, 1), and the reference normal vector is obtained With the projection vector The angle includes: determining a correction order when performing projection correction; determining a corresponding angle calculation formula according to the correction order; the correction order includes a first correction order and a second correction order, which correspond to the first angle calculation formula and the second angle calculation formula respectively, wherein: the first correction order is: first perform correction in the X-axis direction, and then perform correction in the Y-axis direction; the second correction order is: first perform correction in the Y-axis direction, and then perform correction in the X-axis direction.

[0021] Optionally, the first angle calculation formula includes the following formulas (4) and (5):

[0022]

[0023]

[0024] The second angle calculation formula includes the following formulas (6) and (7):

[0025]

[0026]

[0027] Where α is the projection vector With the reference normal vector The angle of deviation in the X-axis direction, β is the projection vector With the reference normal vector The angle of the Y-axis deviation, nx is the projection vector The coordinate on the X axis, ny is the projection vector The coordinate on the Y axis, nz is the projection vector The coordinate on the Z axis.

[0028] The present application also provides a projection system, including a projector, and the projection system can implement the method for obtaining the projection correction amount.

[0029] The present application also provides a projection correction method, comprising the steps of: obtaining the projection correction amount, wherein the projection correction amount is obtained based on the projection correction amount obtaining method; and performing projection correction according to the projection correction amount.

[0030] The method for obtaining the projection correction amount, the projection system, and the projection correction method in the present application can obtain the projection correction amount, and the projection system can automatically calibrate according to the projection correction amount without the user having to perform corresponding projection calibration according to the image prompts on the projection screen. It is simple and convenient, and effectively optimizes the user's viewing experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is a schematic diagram of the situation where the projected figure is trapezoidal during the projection process.

[0033] Figure 2 1 is a flowchart of the steps of a method for obtaining projection correction value in one embodiment of the present application.

[0034] Figure 3 FIG. 1 is a schematic diagram showing that a lens of a projector is parallel to a target plane in an embodiment of the present application.

[0035] Figure 4 FIG. 1 is a schematic diagram of a projector lens after the position of the projector lens is changed in one embodiment of the present application.

[0036] Figure 5 Schematic diagram of a process for implementing projection correction by the projection system according to one embodiment of the present application. DETAILED DESCRIPTION

[0037] A method for obtaining a projection correction amount, a projection system, and a projection correction method are proposed below to solve the above-mentioned problem. The method for obtaining a projection correction amount and the projection system obtain accurate projection correction amounts, thereby facilitating automatic and precise correction.

[0038] The method for obtaining the projection correction amount, the projection system, and the projection correction method are further described below in conjunction with the accompanying drawings and embodiments.

[0039] In a first aspect, the present application provides a method for obtaining a projection correction value.

[0040] See also Figure 2 、 Figure 3 as well as Figure 4 ,in Figure 2 This is a flowchart of the steps of a method for obtaining projection correction value in one embodiment of the present application. Figure 3 Schematic diagram of a projector lens parallel to a target plane in one embodiment of the present application. Figure 4 FIG. 1 is a schematic diagram of a projector lens after the position of the projector lens is changed in one embodiment of the present application.

[0041] In this embodiment, the method for obtaining the projection correction amount is used to perform projection correction of the projector, and includes the following steps: Step S101: obtaining the reference normal vector of the target plane When the projector performs standard projection at the reference space position, the plane where the lens of the projector is located is parallel to the target plane; Step S102: Obtain the projection vector , the projection vector and the base normal vector The coordinate values ​​are based on the same preset spatial coordinate system and are related to the current spatial position of the lens; Step S103: Obtain the reference normal vector With the projection vector and obtain the projection correction amount according to the angle.

[0042] The method for obtaining the projection correction amount described in this embodiment can obtain the projection correction amount so as to perform automatic calibration based on the projection correction amount. The user does not need to perform corresponding projection calibration on the target plane according to the image prompts. This is simple and convenient and effectively optimizes the user's usage experience.

[0043] In some embodiments, the obtaining of the reference normal vector of the target plane The method comprises the following steps: obtaining the depth information of the target plane in a direction perpendicular to the plane where the lens of the projector is located at the reference space position of the projector; obtaining the point cloud plane corresponding to the target plane according to the depth information; obtaining the reference normal vector according to the point cloud plane corresponding to the target plane. .

[0044] When performing step S101, the projector is placed at the reference space position for standard projection, and the plane where the lens of the projector is located is parallel to the target plane. Figure 3Point A in the figure is the reference spatial position. During standard projection, projector 301 is placed at point A, the lens plane of projector 301 is parallel to target plane 302, and the principal optical axis of light emitted from the lens is perpendicular to target plane 302. In this case, the image formed by projector 301 on the target plane is a standard image, a standard projection, and the image formed on the target plane is rectangular.

[0045] In some embodiments, the lens is part of the projector's optical engine and is fixed relative to the main optical axis of the optical engine when emitting light. The optical engine, which includes a DMD (Digital Micromirror Device) display core, a light source, a lens, and a heat sink, is one of the main components of the projector. The image projected by the projector is emitted from the lens of the optical engine and projected onto the target plane for viewing by the user.

[0046] In some embodiments, the reference normal vector only needs to be acquired once for a scene. The scene referred to here includes a fixed target plane and a fixed spatial position of the projector. In other scenes, whether the target plane or the spatial position of the projector changes, the reference normal vector needs to be acquired again.

[0047] In some embodiments, the measurement of the reference normal vector may be initiated according to user control. Therefore, in some embodiments, a step of initiating the measurement of the reference normal vector may be provided, and after initiation, the reference normal vector of the target plane is obtained.

[0048] In some embodiments, the obtaining of the reference normal vector of the target plane The method comprises the following steps: obtaining the depth information of the target plane in a direction perpendicular to the plane where the lens of the projector is located at the reference space position of the projector; obtaining the point cloud plane corresponding to the target plane according to the depth information; obtaining the reference normal vector according to the point cloud plane corresponding to the target plane. .

[0049] After the depth information of the target plane is obtained, the point cloud plane corresponding to the target plane can be obtained according to the depth information, and the reference normal vector of the target plane can be obtained based on the principal component analysis method in the prior art.

[0050] In some embodiments, the reference normal vector of the target plane is obtained by the depth information acquisition module. and the projection vector , the positional relationship between the depth information acquisition module and the projector is fixed and known.

[0051] In some embodiments, the depth information acquisition module includes a TOF (Time Of Flight) module. The TOF module uses a two-way ranging technology to measure the distance between nodes. The TOF module includes a light output module for emitting a detection light signal.

[0052] In these embodiments, the TOF module further includes a light receiving module, which is used to receive detection light signals reflected from the outside world, thereby completing the distance measurement between nodes.

[0053] In some embodiments, the projection vector perpendicular to the current plane of the lens, and the obtained projection vector Before, the method further includes the following steps: detecting whether there is a correction signal, and if so, performing the step of obtaining the projection vector steps.

[0054] In these embodiments, the projection vector is obtained only after the correction signal is detected. In some other embodiments, a projection vector may be performed each time the system is powered on. to obtain the projection correction at any time.

[0055] exist Figure 4 In the embodiment shown, the projection vector There is an angle between the reference normal vectors compared to the target plane 302, so the image finally formed on the target plane 302 is not trapezoidal. At this time, a correction signal can be generated as needed to control the depth information acquisition module installed on the projector to obtain the current projection vector to achieve projection correction.

[0056] The obtained projection vector The method comprises: obtaining a point cloud plane corresponding to the plane where the lens is currently located; obtaining the projection vector based on the point cloud plane corresponding to the plane where the lens is currently located .

[0057] A point cloud is a collection of massive points representing the surface characteristics of a target. Point cloud data generated using different measurement principles has different parameters. For example, point cloud data generated using laser measurement includes the point cloud's 3D coordinates (X, Y, and Z) and the laser reflection intensity (Intensity), while point cloud data generated using photogrammetry includes the point cloud's 3D coordinates and color information (RGB). At a minimum, the 3D coordinates of the point cloud are required to determine the projection plane corresponding to the projector's current spatial position.

[0058] The obtaining of the point cloud plane corresponding to the plane where the lens is currently located includes: at the current spatial position of the projector, obtaining depth information along a direction perpendicular to the plane where the lens is currently located, and converting the depth information into point cloud data to construct a point cloud plane corresponding to the plane where the lens is currently located, wherein the point cloud plane corresponding to the plane where the lens is currently located includes multiple point clouds related to the depth information of the plane where the lens is currently located.

[0059] In some embodiments, the depth information may be converted into point cloud data according to the following formula (8):

[0060]

[0061] Among them, X, Y, and Z are the spatial coordinates corresponding to the point cloud data, u and v are the pixel coordinates of the depth camera that obtains the depth information, and K is the camera intrinsic parameter matrix.

[0062] In some other embodiments, if there are other corresponding relationships, different conversion equations may be selected according to the specific corresponding relationships.

[0063] The projection vector is obtained based on the point cloud plane corresponding to the plane where the lens is currently located. The method comprises: using principal component analysis to analyze the point cloud plane corresponding to the plane where the lens is currently located, and obtaining the projection vector of the point cloud plane corresponding to the plane where the lens is currently located. .

[0064] In some embodiments, the principal component analysis method is used to analyze the point cloud plane corresponding to the plane where the lens is currently located, and the projection vector of the point cloud plane corresponding to the plane where the lens is currently located is obtained. The following steps are involved:

[0065] Step S201: Obtain the coordinate mean of each point cloud on the point cloud plane according to the following formula (1):

[0066]

[0067] in is the coordinate mean, P n is the coordinate of each point cloud on the point cloud plane, N is the number of point clouds on the point cloud plane, and n is the point cloud number on the point cloud plane.

[0068] Step S202: According to the following formula (2), the covariance matrix of each point cloud on the point cloud plane is obtained based on the coordinates of each point cloud and the mean value of the coordinates:

[0069]

[0070] Where C is the covariance matrix.

[0071] Step S203: Obtain the minimum eigenvector of the covariance matrix according to the following formula (3):

[0072]

[0073] Wherein v1, v2 and v3 are three eigenvectors of the covariance matrix, and λ1, λ2 and λ3 are eigenvalues ​​corresponding to the three eigenvectors.

[0074] Step S204: normalize the minimum eigenvector and use the normalized result as the projection vector .

[0075] In some embodiments, the preset spatial coordinate system is a three-dimensional rectangular coordinate system, including three mutually perpendicular axes XYZ, and the reference normal vector The coordinates in the preset space coordinate system are (0, 0, 1). With the projection vector The angle includes: determining a correction order when performing projection correction; determining a corresponding angle calculation formula according to the correction order; the correction order includes a first correction order and a second correction order, which correspond to the first angle calculation formula and the second angle calculation formula respectively, wherein: the first correction order is: first perform correction in the X-axis direction, and then perform correction in the Y-axis direction; the second correction order is: first perform correction in the Y-axis direction, and then perform correction in the X-axis direction.

[0076] In some embodiments, the first angle calculation formula includes the following formulas (4) and (5):

[0077]

[0078]

[0079] The second angle calculation formula includes the following formulas (6) and (7):

[0080]

[0081]

[0082] Where α is the projection vector With the reference normal vector The angle of deviation in the X-axis direction, β is the projection vector With the reference normal vector The angle of the Y-axis deviation, nx is the projection vector The coordinate on the X axis, ny is the projection vector The coordinate on the Y axis, nz is the projection vector The coordinate on the Z axis.

[0083] The first angle calculation formula and the second angle calculation formula can both be obtained by calculating the rotation matrix.

[0084] In some embodiments, a projection system has a preset calibration sequence, and the angle is directly obtained according to the preset calibration sequence. In other embodiments, a calibration sequence selection option may be preset, and the user may first determine the calibration sequence before calibration, and the angle is obtained according to the selected calibration sequence.

[0085] In some embodiments, the angle directly corresponds to the offset of the projector's projection plane relative to the target plane, so the projection correction amount is equal to the angle. In some other embodiments, the projection correction amount can also be obtained based on the specific positional relationship between the projector's projection plane and the target plane.

[0086] In a second aspect, the present application provides a projection system.

[0087] The projection system includes a projector, and the projection system can implement the method for obtaining the projection correction amount.

[0088] The projector includes a depth information acquisition module for acquiring depth information and forming a corresponding point cloud plane, etc. In some embodiments, the depth information acquisition module includes a TOF module.

[0089] The projection system in this application can obtain the projection correction amount and can automatically calibrate according to the projection correction amount. The user does not need to perform corresponding projection calibration according to the image prompts on the projection screen. It is simple and convenient and effectively optimizes the user's viewing experience.

[0090] In a third aspect, the present application provides a projection correction method.

[0091] The projection correction method includes the following steps: obtaining the projection correction amount, wherein the projection correction amount is obtained based on the projection correction amount obtaining method; and performing projection correction according to the projection correction amount.

[0092] In some embodiments, when performing projection correction, the position, optical axis, etc. of the projection light machine can be adjusted according to the projection correction amount, thereby achieving position movement of the image projected by the projection light machine on a projection surface such as a screen.

[0093] In some other embodiments, when performing projection correction, the original image in the projection light machine can be adjusted according to the projection correction amount. For example, if the projection area of ​​the projection light machine is a trapezoid, the original image can be adjusted to a trapezoid and projected by the projection light machine to display a rectangular picture on the projection plane.

[0094] Moreover, the projection correction method described in the present application can be widely used for trapezoidal correction of long-focus projectors, short-focus projectors, laser TVs, and other devices involving image projection.

[0095] See also Figure 5 , which is a flow chart of the projection correction implemented by the projection system according to one embodiment.

[0096] exist Figure 5 In the projection system, a reference normal vector is pre-stored , only the projection vector needs to be obtained Therefore, Figure 5 In the embodiment shown, a TOF module is used to obtain depth information related to the current spatial position of the projector, and the depth information is converted into point cloud data. After constructing a point cloud plane, the PCA (Principle Components Analysis) method is used to decompose and obtain the normal vector of the current point cloud plane, and the normal vector is used as the projection vector. Then, use the above angle calculation formula to calculate the projection vector With the base normal vector The angle between them can be used to perform trapezoidal correction on the projector based on the angle.

[0097] In this embodiment, the normal vector is a unit normal vector and has undergone the following processing: 1. Calculating the mean of the point cloud coordinates of each point cloud on the point cloud plane; 2. Calculating the covariance matrix on the point cloud plane; 3. Calculating the three eigenvectors of the covariance matrix to obtain the minimum eigenvector, and normalizing it to obtain the unit normal vector of the current point cloud plane.

[0098] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, such as the mutual combination of technical features between the embodiments, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for obtaining a projection correction value, characterized in that: The following steps are involved: At a reference spatial position of the projector, acquiring depth information of the target plane along a direction perpendicular to a plane where a lens of the projector is located; Acquire a point cloud plane corresponding to the target plane according to the depth information; Acquire the reference normal vector according to the point cloud plane corresponding to the target plane When the projector performs standard projection at the reference space position, the plane where the lens of the projector is located is parallel to the target plane; At the current spatial position of the projector, depth information is acquired along a direction perpendicular to the plane where the lens is currently located, and the depth information is converted into point cloud data to construct a point cloud plane corresponding to the plane where the lens is currently located, wherein the point cloud plane corresponding to the plane where the lens is currently located includes a plurality of point clouds related to the depth information of the plane where the lens is currently located; The projection vector is obtained based on the point cloud plane corresponding to the plane where the lens is currently located. The projection vector and the base normal vector The coordinate values ​​are based on the same preset spatial coordinate system and are related to the current spatial position of the lens; Get the reference normal vector With the projection vector and obtain the projection correction amount according to the angle.

2. The method for obtaining the projection correction amount according to claim 1, wherein: The projection vector perpendicular to the current plane of the lens, and the obtained projection vector Before, the following steps are also included: Detect whether there is a correction signal, if so, obtain the projection vector steps.

3. The method for obtaining the projection correction amount according to claim 1, wherein: The projection vector is obtained based on the point cloud plane corresponding to the plane where the lens is currently located. include: Use principal component analysis to analyze the point cloud plane corresponding to the plane where the lens is currently located, and obtain the projection vector of the point cloud plane corresponding to the plane where the lens is currently located 4. The method for obtaining the projection correction amount according to claim 3, wherein: The principal component analysis method is used to analyze the point cloud plane corresponding to the plane where the lens is currently located, and the projection vector of the point cloud plane corresponding to the plane where the lens is currently located is obtained. The following steps are involved: According to the following formula (1), the coordinate mean of each point cloud on the point cloud plane is obtained: in is the coordinate mean, P n is the coordinate of each point cloud on the point cloud plane, N is the number of point clouds on the point cloud plane, and n is the point cloud number on the point cloud plane; According to the following formula (2), the covariance matrix of each point cloud on the point cloud plane is obtained based on the coordinates of each point cloud and the mean of the coordinates: Wherein C is the covariance matrix; According to the following formula (3), the minimum eigenvector of the covariance matrix is ​​obtained: Wherein v1, v2 and v3 are three eigenvectors of the covariance matrix, and λ1, λ2, λ3 are eigenvalues ​​corresponding to the three eigenvectors; Normalize the minimum eigenvector and use the normalized result as the projection vector 5. The method for obtaining the projection correction amount according to claim 1, wherein: The preset spatial coordinate system is a three-dimensional rectangular coordinate system, including three axes XYZ, and the reference normal vector The coordinates in the preset space coordinate system are (0, 0, 1), and the reference normal vector is obtained With the projection vector The angles include: Determine the correction order when performing projection correction; Determine the corresponding angle calculation formula according to the correction sequence; The correction sequence includes a first correction sequence and a second correction sequence, which correspond to the first angle calculation formula and the second angle calculation formula respectively, wherein: The first correction order is: first perform correction in the X-axis direction, then perform correction in the Y-axis direction; The second correction order is: first perform correction in the Y-axis direction, and then perform correction in the X-axis direction.

6. The method for obtaining the projection correction amount according to claim 5, characterized in that: The first angle calculation formula includes the following formulas (4) and (5): The second angle calculation formula includes the following formulas (6) and (7): Where α is the projection vector With the reference normal vector The angle of deviation in the X-axis direction, β is the projection vector With the reference normal vector The angle of deviation in the Y axis, nx is the projection vector The coordinate on the X axis, ny is the projection vector The coordinate on the Y axis, nz is the projection vector The coordinate on the Z axis.

7. A projection system, characterized in that: The projection system comprises a projector, and the projection system can implement the method for obtaining the projection correction amount according to any one of claims 1 to 6.

8. A projection correction method, characterized in that: The following steps are involved: Acquire the projection correction amount, wherein the projection correction amount is acquired based on the method for acquiring the projection correction amount according to any one of claims 1 to 6; Projection correction is performed according to the projection correction amount.

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