WO2018196303A1 - Projector calibration method and apparatus based on multi-directional projection - Google Patents

Projector calibration method and apparatus based on multi-directional projection Download PDF

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WO2018196303A1
WO2018196303A1 PCT/CN2017/107275 CN2017107275W WO2018196303A1 WO 2018196303 A1 WO2018196303 A1 WO 2018196303A1 CN 2017107275 W CN2017107275 W CN 2017107275W WO 2018196303 A1 WO2018196303 A1 WO 2018196303A1
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target
projector
calibration
feature point
phase
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PCT/CN2017/107275
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French (fr)
Chinese (zh)
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彭翔
张雅琴
刘晓利
杨洋
蔡泽伟
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深圳大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2433—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring outlines by shadow casting

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  • the invention belongs to the field of optical measurement technology, and in particular relates to a projector calibration method and device for multi-directional projection.
  • the calibration technology of 3D imaging system is a very important step in 3D imaging.
  • the projector calibration technology in 3D digital imaging is a method for estimating the fixed internal parameters of the projector in 3D imaging system.
  • the projector calibration technology is 3D imaging technology provides important 3D imaging conditions, and better calibration techniques and methods provide better imaging conditions for 3D imaging.
  • three-dimensional imaging systems can be divided into two categories, one is a three-dimensional imaging system consisting of a single camera and a single projector, and the other is a system consisting of a dual camera and a single projector.
  • the first type of system has a simple structure, fast measurement speed, and high measurement efficiency, but its imaging system must involve calibration of the camera and projector.
  • the calibration technology of the camera has been developed more maturely, but the projector is not.
  • the biggest difficulty is that the projector is not an imaging device and therefore cannot capture images. How to accurately acquire the coordinates of the feature points in the image coordinate system of the projector is to be solved. A big problem.
  • the phase method is commonly used to calibrate the projector.
  • the phase method is specifically: projecting the phase coded map to the target plane, and using phase demodulation technology to obtain the phase of the target feature point, and then obtaining the corresponding projector image coordinate system. coordinate of.
  • This method considers nonlinear distortion and does not need to use the calibration result of the camera; however, on the one hand, the method has the problem of inaccurate image extraction of feature points; on the other hand, the three-dimensional world coordinate X of the target feature point is As a known quantity input, the deviation between it and its real coordinates (due to various factors such as the target is not ideal plane, three-dimensional point printing error, etc.) will introduce systematic errors and reduce the reliability of the calibration result.
  • the invention provides a multi-directional projection projector calibration method and device, aiming at solving the inaccurate extraction of feature points and the deviation between the three-dimensional world coordinates of the target feature points and the real values by using the phase method for calibration.
  • the introduction of systematic errors makes the calibration results more accurate.
  • the invention provides a projector calibration method for multi-directional projection, the projector calibration method is applied to a projector calibration system, the projector calibration system comprises: a projector, a camera and a target, the camera is located in the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration method includes:
  • Step S1 using the projector to sequentially project a preset calibration pattern to the target plane in N specified orientations preset around the target, and collecting the target information map by using the camera in each specified orientation;
  • Step S2 performing feature point extraction on the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtaining the phase distribution of the target information map by using the phase demodulation technique, combined with the target feature
  • the initial calibration parameters include: N external reference ⁇ 1 , ⁇ 2 ⁇ ⁇ N composed of a projector and a target, and a projector internal parameter ⁇ ;
  • step S4 the initial calibration parameter and the three-dimensional world coordinate X are optimized by a beam adjustment method to obtain a final calibration parameter.
  • the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
  • the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps;
  • the target information map includes: a plurality of phase shift maps containing target information and a plurality of targets Gray code map of the information.
  • the precise phase based on the target feature points Obtaining a sub-pixel coordinate x i corresponding to the target feature point in the projector image coordinate system, including:
  • the sub-pixel coordinates x i corresponding to the target feature points are calculated by the following formula
  • the beam adjustment method is specifically: assuming that there are M target feature points in each specified orientation, and the initial calibration parameters and the target feature points are minimized by minimizing the objective function.
  • the objective function is:
  • x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation
  • the present invention also provides a multi-directional projection projector calibration device, the projector calibration device being applied to a projector calibration system, the projector calibration system comprising: a projector, a camera and a target, the camera is located at the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration device includes:
  • a projection acquisition module configured to use the projector to sequentially project a preset calibration pattern to a target plane in N specified orientations preset around the target, and collect the target information map by using the camera in each specified orientation;
  • the initial calibration parameters include: N external reference ⁇ 1 , ⁇ 2 ⁇ ⁇ N composed of a projector and a target, and a projector internal parameter ⁇ ;
  • an optimization module configured to optimize the initial calibration parameter and the three-dimensional world coordinate X by using a beam adjustment method to obtain a final calibration parameter.
  • the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
  • the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps;
  • the target information map includes: a plurality of phase shift maps containing target information and a plurality of targets Gray code map of the information.
  • the feature point information acquiring module includes:
  • the precise phase determining module is configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system, and obtain a phase distribution of the target information map by using a phase demodulation technique. Combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
  • a sub-pixel determination module configured to calculate a sub-pixel coordinate x i corresponding to the target feature point according to a mapping relationship between sub-pixel coordinates and a phase of the target feature point in the projector image coordinate system ;
  • the objective function is:
  • x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation
  • the present invention has the beneficial effects that the multi-azimuth projection projector calibration method and apparatus provided by the present invention are based on a phase method, and on the one hand, projections are respectively performed in N specified orientations by a projector, and The camera optical axis is perpendicular to the target plane to collect the target information map, so that the feature point image extraction is more accurate; on the other hand, the invention adopts the beam adjustment method to take the three-dimensional world coordinate X of the target feature point as the to-be-optimized
  • the variables are optimized to eliminate the systematic error introduced by the deviation between the 3D world coordinate X of the target feature point and its real coordinates, and adjust X to a higher reliability value during beam adjustment optimization, thus The calibration results are more accurate.
  • FIG. 1 is a schematic diagram of hardware modules in a projector calibration system according to an embodiment of the present invention
  • FIG. 2 is a schematic flow chart of a multi-directional projection projector calibration method according to an embodiment of the present invention
  • FIG. 3 is a diagram of a 11*9 circular marker point target according to an embodiment of the present invention.
  • FIG. 4 is a sub-pixel coordinate diagram of a target feature point in a camera image coordinate system in a specified orientation according to an embodiment of the present invention
  • FIG. 5 is a sub-pixel coordinate diagram of a target feature point in a projector image coordinate system in a specified orientation according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of a principle of a calibration model provided by an embodiment of the present invention.
  • FIG. 7 is a re-projection error diagram of the projector after initial calibration according to an embodiment of the present invention.
  • FIG. 8 is a re-projection error diagram of the projector after the adjustment is optimized according to an embodiment of the present invention.
  • FIG. 9 is a schematic block diagram of a multi-directional projection projector calibration apparatus according to an embodiment of the present invention.
  • the invention provides a multi-directional projection projector calibration method.
  • the projector calibration method is applied to a projector calibration system.
  • the projector calibration system comprises: a projector, a camera and a target.
  • the camera is positioned above the target and the optical axis of the camera is perpendicular to the plane of the target.
  • N suitable projection orientations need to be determined around the target plane such that when performing the calibration step, the projector respectively projects the calibration pattern at the preset N specified orientations;
  • it is necessary to adjust the positional relationship between the camera and the target so that the optical axis of the camera is perpendicular to the target plane, thereby ensuring that the target is imaged at the optimal shooting position of the camera.
  • the method for determining the N specified orientations is: adjusting the focal length of the projector when determining the first specified orientation, and ensuring that the projected pattern can be focused on the target plane
  • the specific operation step is: placing on the target plane A piece of white paper, adjust the projector's focus knob, so that the cast pattern can be placed on the white paper to form a clear pattern; in addition, to ensure that the target can be fully covered by the cast pattern.
  • N-1 specified orientations are determined around the target plane, and in each of the remaining specified orientations, it is necessary to ensure that the target can be completely covered by the projected pattern and within the depth of field of the projector. Among them, N ⁇ 3.
  • the positional relationship between the camera and the target is adjusted by placing the target on the test bench.
  • the camera is placed above the target, and the optical axis of the camera is placed perpendicular to the target plane, and the field of view, the aperture and the focal length of the camera are adjusted to make the target image clear; the positional relationship between the camera and the target makes the extraction target
  • the phase value of the target feature point is more accurate, and the sub-pixel position in the projector image coordinate system corresponding to the target feature point is more accurate.
  • the projector adopts DELL DLP (Digital Light Processing), model M110, standard resolution 1280*800;
  • the camera adopts IMAVISION industrial digital camera, model MER-130 -30UM, resolution 1280*1024, pixel size 5.2 ⁇ m*5.2 ⁇ m, camera lens using PENTAX industrial lens, model C1614-M.
  • Step S1 using the projector to sequentially project a preset calibration pattern to the target plane in N specified orientations preset around the target, and collecting the target information map by using the camera in each specified orientation;
  • the preset calibration pattern includes: a plurality of sinusoidal phase shift patterns and a plurality of Gray code patterns
  • the target information map includes: a plurality of phase shift maps containing target information.
  • several Gray code maps containing target information in addition, the camera collects the original target image when the projector only projects uniform illumination.
  • a 11*9 circular marker point target is used.
  • the feature point is the center of the circular pattern, and a total of 99 feature points.
  • Step S2 performing feature point extraction on the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtaining the phase distribution of the target information map by using the phase demodulation technique, combined with the target feature
  • the target information map in each specified orientation is processed. Specifically, the processing is divided into three parts: one is that the target feature points are obtained by the feature point extraction in the camera.
  • the position in the image coordinate system, as shown in Fig. 4 is the position of the target feature point in the camera image coordinate system obtained under a certain orientation; the second is to obtain the phase distribution of the target information map by phase demodulation technique.
  • the third is to combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
  • the initial calibration parameters include: N external reference ⁇ 1 , ⁇ 2 ⁇ ⁇ N composed of a projector and a target, and a projector internal parameter ⁇ .
  • the schematic diagram of the calibration model provided by the embodiment of the present invention is shown in FIG. 6
  • the re-projection error after calibration is shown in FIG. 7;
  • the distribution and standard deviation of the re-projection error are important criteria for evaluating the calibration result, generally
  • the re-projection error of the feature points is concentrated around the origin, and the smaller the standard deviation of the re-projection errors, the more accurate the calibration result is.
  • step S4 the initial calibration parameter and the three-dimensional world coordinate X are optimized by a beam adjustment method to obtain a final calibration parameter.
  • the beam adjustment method is specifically: assuming that there are M target feature points in each specified orientation, and the initial calibration parameters and the target feature points are minimized by minimizing the objective function.
  • the objective function is:
  • x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation
  • the re-projection error after calibration is shown in Figure 8, and Figure 7 Compared to the improvement.
  • the Reprojector Error distribution is as shown in FIG. 8, and the standard deviations in the horizontal and vertical directions are 0.02541 pixel, respectively. And 0.01926pixel; and only the initial calibration, the standard deviation of the horizontal and vertical directions are 0.11119pixel and 0.08406pixel, respectively, as shown in Figure 7; thus can be seen that the improved calibration accuracy can reach 77%.
  • a projector calibration device for multi-directional projection is described below.
  • the projector calibration device is applied to a projector calibration system.
  • the projector calibration system includes: a projector, a camera, and a target, and the camera is located at the standard Above the target, and the optical axis of the camera is perpendicular to the plane of the target;
  • the projector calibration device includes:
  • the projection acquisition module 1 is configured to sequentially project a preset calibration pattern to a target plane by using the projector in sequence with N specified presets around the target, and collect the target information map by using the camera in each specified orientation;
  • the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
  • the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps;
  • the target information map includes: a plurality of phases containing target information The shift map and several Gray code maps containing the target information; in addition, the camera collects the original target map when the projector only projects uniform illumination.
  • the feature point information acquiring module 2 specifically includes: an accurate phase determining module, configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system,
  • the phase demodulation technique is used to obtain the phase distribution of the target information map, the position of the target feature point and the phase distribution of the target information map are combined, and the precise phase of the target feature point is obtained through sub-pixel interpolation calculation.
  • the method further includes a sub-pixel determination module, configured to calculate a sub-pixel coordinate corresponding to the target feature point according to a mapping relationship between a sub-pixel coordinate and a phase of the target feature point in the projector image coordinate system, that is, using the following formula x i ;
  • the initial calibration parameters include: N external reference ⁇ 1 , ⁇ 2 ⁇ ⁇ N composed of a projector and a target, and a projector internal parameter ⁇ ;
  • the optimization module 4 is configured to optimize the initial calibration parameter and the three-dimensional world coordinate X by using a beam adjustment method to obtain a final calibration parameter.
  • the objective function is:
  • x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation
  • the multi-azimuth projection projector calibration method and device provided by the invention are based on the phase method, but are superior to the general phase method.
  • the problem of inaccurate image extraction of feature points is solved; on the other hand, the target is solved.
  • the problem that there is a deviation between the three-dimensional world coordinates of the target feature points and the real value is different from the generalized optimization objective function.
  • All or part of the steps in the above embodiments are controlled by a program to control related hardware, and the program may be stored in a computer readable storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, or the like. .

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Abstract

Disclosed is a projector calibration method based on multi-directional projection, belonging to the technical field of optical measurement. The method comprises: step S1, using a projector (1) to project a pre-set calibration pattern onto a target plane in N pre-set specified directions around a target (3) in sequence, and collecting a target information graph using a camera (2) in each specified direction; step S2, processing the target information graph collected in each specified direction, obtaining an accurate phase value of a target feature point by means of calculation and then obtaining a sub-pixel coordinate, corresponding to the target feature point, in an image coordinate system of the projector (1); step S3, using the obtained sub-pixel coordinate in the image coordinate system of the projector (1), and a known three-dimensional world coordinate X of the target feature point to calibrate the projector (1) to acquire an initial calibration parameter; and step S4, using bundle adjustment to optimize the initial calibration parameter and the three-dimensional world coordinate X to obtain a final calibration parameter. By means of the calibration method, a final calibration result is more accurate.

Description

多方位投影的投影仪标定方法及装置Projector calibration method and device for multi-directional projection 技术领域Technical field
本发明属于光学测量技术领域，尤其涉及一种多方位投影的投影仪标定方法及装置。The invention belongs to the field of optical measurement technology, and in particular relates to a projector calibration method and device for multi-directional projection.
背景技术Background technique
三维成像系统的标定技术在三维成像中是非常关键一步，其中，三维数字成像中的投影仪标定技术是一种用于估计三维成像系统中投影仪的固定内部参数的方法，投影仪标定技术为三维成像技术提供重要的三维成像条件，更优的标定技术和方法能为三维成像提供更好的成像条件。The calibration technology of 3D imaging system is a very important step in 3D imaging. Among them, the projector calibration technology in 3D digital imaging is a method for estimating the fixed internal parameters of the projector in 3D imaging system. The projector calibration technology is 3D imaging technology provides important 3D imaging conditions, and better calibration techniques and methods provide better imaging conditions for 3D imaging.
目前，三维成像系统可分为两类，一类是由单相机、单投影仪组成的三维成像系统，另一类是由双相机、单投影仪组成的系统。第一类系统结构简单、测量速度快、测量效率高，但其成像系统必须涉及到相机和投影仪的标定。相机的标定技术已经发展的比较成熟，但是投影仪却不然，最大的困难是投影仪不是成像设备，因而不能采集图像，那么如何精确获取特征点在投影仪图像坐标系下的坐标是要解决的一大难题。At present, three-dimensional imaging systems can be divided into two categories, one is a three-dimensional imaging system consisting of a single camera and a single projector, and the other is a system consisting of a dual camera and a single projector. The first type of system has a simple structure, fast measurement speed, and high measurement efficiency, but its imaging system must involve calibration of the camera and projector. The calibration technology of the camera has been developed more maturely, but the projector is not. The biggest difficulty is that the projector is not an imaging device and therefore cannot capture images. How to accurately acquire the coordinates of the feature points in the image coordinate system of the projector is to be solved. A big problem.
目前常用相位法对投影仪进行标定，这种相位法具体为：投射相位编码图到标靶平面，利用相位解调技术求出标靶特征点的相位，进而求得对应投影仪图像坐标系下的坐标。这种方法考虑了非线性畸变，同时也不需要利用相机的标定结果；但是，一方面，该方法存在特征点图像提取不准确的问题；另一方面，标靶特征点的三维世界坐标X是作为已知量输入的，它与其真实坐标之间的偏差(由于标靶不是理想平面、三维点印制误差等多种因素导致)会引入系统误差，降低标定结果的可靠性。 At present, the phase method is commonly used to calibrate the projector. The phase method is specifically: projecting the phase coded map to the target plane, and using phase demodulation technology to obtain the phase of the target feature point, and then obtaining the corresponding projector image coordinate system. coordinate of. This method considers nonlinear distortion and does not need to use the calibration result of the camera; however, on the one hand, the method has the problem of inaccurate image extraction of feature points; on the other hand, the three-dimensional world coordinate X of the target feature point is As a known quantity input, the deviation between it and its real coordinates (due to various factors such as the target is not ideal plane, three-dimensional point printing error, etc.) will introduce systematic errors and reduce the reliability of the calibration result.
发明内容Summary of the invention
本发明提供一种多方位投影的投影仪标定方法及装置，旨在解决利用相位法进行标定时存在的特征点图像提取不准确、标靶特征点的三维世界坐标与真实值之间有偏差从而引入系统误差的问题，使得标定结果更加精确。The invention provides a multi-directional projection projector calibration method and device, aiming at solving the inaccurate extraction of feature points and the deviation between the three-dimensional world coordinates of the target feature points and the real values by using the phase method for calibration. The introduction of systematic errors makes the calibration results more accurate.
本发明提供了一种多方位投影的投影仪标定方法，所述投影仪标定方法应用于投影仪标定系统，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直；所述投影仪标定方法包括：The invention provides a projector calibration method for multi-directional projection, the projector calibration method is applied to a projector calibration system, the projector calibration system comprises: a projector, a camera and a target, the camera is located in the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration method includes:
步骤S1，利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；Step S1, using the projector to sequentially project a preset calibration pattern to the target plane in N specified orientations preset around the target, and collecting the target information map by using the camera in each specified orientation;
步骤S2，对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000001
及基于所述标靶特征点的精确相位
Figure PCTCN2017107275-appb-000002
得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；Step S2, performing feature point extraction on the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtaining the phase distribution of the target information map by using the phase demodulation technique, combined with the target feature The position of the point and the phase distribution of the target information map, and the precise phase of the target feature point is obtained through sub-pixel interpolation calculation
Figure PCTCN2017107275-appb-000001
And precise phase based on the feature points of the target
Figure PCTCN2017107275-appb-000002
Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
步骤S3，利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；Step S3, using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to calibrate the projector, and obtain an initial calibration parameter, i=1, 2, ......N;
所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ；The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ;
步骤S4，利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。In step S4, the initial calibration parameter and the three-dimensional world coordinate X are optimized by a beam adjustment method to obtain a final calibration parameter.
进一步地，所述预置的N个指定方位需要满足：所述投影仪在所述预置的N个指定方位投射的标定图案在标靶平面聚焦。Further, the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
进一步地，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图。 Further, the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps; the target information map includes: a plurality of phase shift maps containing target information and a plurality of targets Gray code map of the information.
进一步地，所述基于所述标靶特征点的精确相位
Figure PCTCN2017107275-appb-000003
得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，包括：Further, the precise phase based on the target feature points
Figure PCTCN2017107275-appb-000003
Obtaining a sub-pixel coordinate x i corresponding to the target feature point in the projector image coordinate system, including:
根据投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即利用以下公式计算得到与所述标靶特征点相对应的亚像素坐标xi；According to the mapping relationship between the sub-pixel coordinates and the phase of the target feature points in the projector image coordinate system, the sub-pixel coordinates x i corresponding to the target feature points are calculated by the following formula;
Figure PCTCN2017107275-appb-000004
Figure PCTCN2017107275-appb-000004
其中，
Figure PCTCN2017107275-appb-000005
代表所述标靶特征点的精确相位，T代表相位周期宽度，i＝1,2,......N。among them,
Figure PCTCN2017107275-appb-000005
Representing the exact phase of the target feature point, T represents the phase period width, i = 1, 2, ... N.
进一步地，所述步骤S4中，所述光束平差法具体为：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；Further, in the step S4, the beam adjustment method is specifically: assuming that there are M target feature points in each specified orientation, and the initial calibration parameters and the target feature points are minimized by minimizing the objective function. The three-dimensional world coordinates X j , j=1, 2..., M are optimized to obtain final calibration parameters;
所述目标函数为：The objective function is:
Figure PCTCN2017107275-appb-000006
Figure PCTCN2017107275-appb-000006
其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，
Figure PCTCN2017107275-appb-000007
代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation,
Figure PCTCN2017107275-appb-000007
Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
本发明还提供了一种多方位投影的投影仪标定装置，所述投影仪标定装置应用于投影仪标定系统，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直；所述投影仪标定装置包括：The present invention also provides a multi-directional projection projector calibration device, the projector calibration device being applied to a projector calibration system, the projector calibration system comprising: a projector, a camera and a target, the camera is located at the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration device includes:
投影采集模块，用于利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；a projection acquisition module, configured to use the projector to sequentially project a preset calibration pattern to a target plane in N specified orientations preset around the target, and collect the target information map by using the camera in each specified orientation;
特征点信息获取模块，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚 像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000008
及基于所述标靶特征点的精确相位
Figure PCTCN2017107275-appb-000009
得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；The feature point information acquiring module is configured to extract the feature points of the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtain the phase distribution of the target information map by using the phase demodulation technique. Combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
Figure PCTCN2017107275-appb-000008
And precise phase based on the feature points of the target
Figure PCTCN2017107275-appb-000009
Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
初始标定模块，用于利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；An initial calibration module is configured to calibrate the projector by using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to obtain an initial calibration parameter, i=1 , 2, ... N;
所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ；The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ;
优化模块，用于利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。And an optimization module, configured to optimize the initial calibration parameter and the three-dimensional world coordinate X by using a beam adjustment method to obtain a final calibration parameter.
进一步地，所述预置的N个指定方位需要满足：所述投影仪在所述预置的N个指定方位投射的标定图案在标靶平面聚焦。Further, the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
进一步地，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图。Further, the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps; the target information map includes: a plurality of phase shift maps containing target information and a plurality of targets Gray code map of the information.
进一步地，所述特征点信息获取模块包括：Further, the feature point information acquiring module includes:
精确相位确定模块，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000010
The precise phase determining module is configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system, and obtain a phase distribution of the target information map by using a phase demodulation technique. Combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
Figure PCTCN2017107275-appb-000010
亚像素确定模块，用于根据投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即利用以下公式计算得到与所述标靶特征点相对应的亚像素坐标xi；a sub-pixel determination module, configured to calculate a sub-pixel coordinate x i corresponding to the target feature point according to a mapping relationship between sub-pixel coordinates and a phase of the target feature point in the projector image coordinate system ;
Figure PCTCN2017107275-appb-000011
Figure PCTCN2017107275-appb-000011
其中，
Figure PCTCN2017107275-appb-000012
代表所述标靶特征点的精确相位，T代表相位周期宽度， i＝1,2,......N。among them,
Figure PCTCN2017107275-appb-000012
Represents the exact phase of the target feature point, T represents the phase period width, i = 1, 2, ... N.
进一步地，优化模块具体用于：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；Further, the optimization module is specifically configured to: assume that there are M target feature points in each specified orientation, and the three-dimensional world coordinates X j , j=1 of the initial calibration parameter and the target feature point by minimizing the objective function , 2..., M is optimized to obtain the final calibration parameters;
所述目标函数为：The objective function is:
其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，
Figure PCTCN2017107275-appb-000014
代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation,
Figure PCTCN2017107275-appb-000014
Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
本发明与现有技术相比，有益效果在于：本发明提供的一种多方位投影的投影仪标定方法及装置是基于相位法，一方面，通过投影仪分别在N个指定方位进行投射，并且相机光轴垂直于标靶平面来采集标靶信息图的方式，使得特征点图像提取更加准确；另一方面，本发明采用光束平差法，将标靶特征点的三维世界坐标X作为待优化的变量进行了优化，消除了标靶特征点的三维世界坐标X与其真实坐标之间的偏差引入的系统误差，将X在光束平差优化的过程中调整为可靠性更高的值，从而使得标定结果更加精确。Compared with the prior art, the present invention has the beneficial effects that the multi-azimuth projection projector calibration method and apparatus provided by the present invention are based on a phase method, and on the one hand, projections are respectively performed in N specified orientations by a projector, and The camera optical axis is perpendicular to the target plane to collect the target information map, so that the feature point image extraction is more accurate; on the other hand, the invention adopts the beam adjustment method to take the three-dimensional world coordinate X of the target feature point as the to-be-optimized The variables are optimized to eliminate the systematic error introduced by the deviation between the 3D world coordinate X of the target feature point and its real coordinates, and adjust X to a higher reliability value during beam adjustment optimization, thus The calibration results are more accurate.
附图说明DRAWINGS
图1是本发明实施例提供的一种投影仪标定系统中的硬件模块示意图；1 is a schematic diagram of hardware modules in a projector calibration system according to an embodiment of the present invention;
图2是本发明实施例提供的一种多方位投影的投影仪标定方法的流程示意图；2 is a schematic flow chart of a multi-directional projection projector calibration method according to an embodiment of the present invention;
图3是本发明实施例提供的11*9圆形标志点标靶图；FIG. 3 is a diagram of a 11*9 circular marker point target according to an embodiment of the present invention; FIG.
图4是本发明实施例提供的在某个指定方位下标靶特征点在相机图像坐标系下的亚像素坐标图； 4 is a sub-pixel coordinate diagram of a target feature point in a camera image coordinate system in a specified orientation according to an embodiment of the present invention;
图5是本发明实施例提供的在某个指定方位下标靶特征点在投影仪图像坐标系中的亚像素坐标图；5 is a sub-pixel coordinate diagram of a target feature point in a projector image coordinate system in a specified orientation according to an embodiment of the present invention;
图6是本发明实施例提供的标定模型的原理示意图；6 is a schematic diagram of a principle of a calibration model provided by an embodiment of the present invention;
图7是本发明实施例提供的投影仪经初始标定后的重投影误差图；FIG. 7 is a re-projection error diagram of the projector after initial calibration according to an embodiment of the present invention; FIG.
图8是本发明实施例提供的投影仪经平差优化后的重投影误差图；FIG. 8 is a re-projection error diagram of the projector after the adjustment is optimized according to an embodiment of the present invention; FIG.
图9是本发明实施例提供的一种多方位投影的投影仪标定装置的模块示意图。FIG. 9 is a schematic block diagram of a multi-directional projection projector calibration apparatus according to an embodiment of the present invention.
具体实施方式detailed description
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
本发明提供了一种多方位投影的投影仪标定方法，所述投影仪标定方法应用于投影仪标定系统，如图1所示，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直。The invention provides a multi-directional projection projector calibration method. The projector calibration method is applied to a projector calibration system. As shown in FIG. 1 , the projector calibration system comprises: a projector, a camera and a target. The camera is positioned above the target and the optical axis of the camera is perpendicular to the plane of the target.
具体地，在执行标定步骤之前，一方面，需要在标靶平面周围确定N个合适的投影方位，使得在执行标定步骤时，投影仪分别在预置的N个指定方位投射标定图案；另一方面，需要调节相机与标靶的位置关系，使相机光轴与标靶平面垂直，从而保证标靶在相机的最佳拍摄位置成像。Specifically, prior to performing the calibration step, on the one hand, N suitable projection orientations need to be determined around the target plane such that when performing the calibration step, the projector respectively projects the calibration pattern at the preset N specified orientations; In this aspect, it is necessary to adjust the positional relationship between the camera and the target so that the optical axis of the camera is perpendicular to the target plane, thereby ensuring that the target is imaged at the optimal shooting position of the camera.
更具体地，确定N个指定方位的方法为：在确定第一个指定方位时，调节投影仪焦距，确保投射的图案能在标靶平面聚焦，具体的操作步骤为：在标靶平面上放一张白纸，调节投影仪的调焦旋钮，使投出的图案投在白纸上能成清晰的图案；另外，要保证标靶能够被投出去的图案全面覆盖。再在标靶平面周围确定剩下N-1个指定方位，在剩下的每个指定方位都需要保证标靶能够被投出去的图案全面覆盖，并且在投影仪的景深范围内。其中，N≥3。More specifically, the method for determining the N specified orientations is: adjusting the focal length of the projector when determining the first specified orientation, and ensuring that the projected pattern can be focused on the target plane, the specific operation step is: placing on the target plane A piece of white paper, adjust the projector's focus knob, so that the cast pattern can be placed on the white paper to form a clear pattern; in addition, to ensure that the target can be fully covered by the cast pattern. Then, N-1 specified orientations are determined around the target plane, and in each of the remaining specified orientations, it is necessary to ensure that the target can be completely covered by the projected pattern and within the depth of field of the projector. Among them, N≥3.
更具体地，调节相机与标靶的位置关系的方式为：将标靶平放在实验台上， 相机置于所述标靶上方，并使相机光轴垂直于标靶平面摆放，调节相机的视场、光圈和焦距，使标靶成像清晰；所述相机与标靶的位置关系使提取标靶特征点的相位值更加准确，进而得到与标靶特征点相对应的投影仪图像坐标系下亚像素位置更加准确。More specifically, the positional relationship between the camera and the target is adjusted by placing the target on the test bench. The camera is placed above the target, and the optical axis of the camera is placed perpendicular to the target plane, and the field of view, the aperture and the focal length of the camera are adjusted to make the target image clear; the positional relationship between the camera and the target makes the extraction target The phase value of the target feature point is more accurate, and the sub-pixel position in the projector image coordinate system corresponding to the target feature point is more accurate.
具体地，本发明实施例中，投影仪采用的是DELL的DLP(Digital Light Processing，数字光处理技术)，型号M110，标准分辨率1280*800；相机采用IMAVISION的工业数字摄像机，型号MER-130-30UM，分辨率1280*1024，像素尺寸5.2μm*5.2μm,相机的镜头采用PENTAX工业镜头，型号C1614-M。Specifically, in the embodiment of the present invention, the projector adopts DELL DLP (Digital Light Processing), model M110, standard resolution 1280*800; the camera adopts IMAVISION industrial digital camera, model MER-130 -30UM, resolution 1280*1024, pixel size 5.2μm*5.2μm, camera lens using PENTAX industrial lens, model C1614-M.
下面具体介绍这种多方位投影的投影仪标定方法，如图2所示，包括：The following describes the multi-directional projection projector calibration method, as shown in Figure 2, including:
步骤S1，利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；Step S1, using the projector to sequentially project a preset calibration pattern to the target plane in N specified orientations preset around the target, and collecting the target information map by using the camera in each specified orientation;
具体地，所述步骤S1中，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图；另外，相机在投影仪只投射均匀光照的时候，采集原标靶图。Specifically, in the step S1, the preset calibration pattern includes: a plurality of sinusoidal phase shift patterns and a plurality of Gray code patterns; and the target information map includes: a plurality of phase shift maps containing target information. And several Gray code maps containing target information; in addition, the camera collects the original target image when the projector only projects uniform illumination.
具体地，本发明实施例中用的是11*9的圆形标志点标靶，如图3所示，特征点即是圆形图案的圆心，一共99个特征点。Specifically, in the embodiment of the present invention, a 11*9 circular marker point target is used. As shown in FIG. 3, the feature point is the center of the circular pattern, and a total of 99 feature points.
步骤S2，对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000015
及基于所述标靶特征点的精确相位
Figure PCTCN2017107275-appb-000016
得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；Step S2, performing feature point extraction on the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtaining the phase distribution of the target information map by using the phase demodulation technique, combined with the target feature The position of the point and the phase distribution of the target information map, and the precise phase of the target feature point is obtained through sub-pixel interpolation calculation
Figure PCTCN2017107275-appb-000015
And precise phase based on the feature points of the target
Figure PCTCN2017107275-appb-000016
Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
具体地，在所述N个指定方位投射和采集完成后，处理每个指定方位下的标靶信息图，具体地，处理分为三部分：一是经过特征点提取得到标靶特征点在相机图像坐标系下的位置，如图4所示，为得到的在某个指定方位下标靶特征点在相机图像坐标系下的位置；二是利用相位解调技术得到标靶信息图的相 位分布；三是结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000017
然后，根据得到的精确相位
Figure PCTCN2017107275-appb-000018
并结合投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即结合公式
Figure PCTCN2017107275-appb-000019
计算得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N，如图5所示；其中，T代表相位周期宽度(单位：像素)。Specifically, after the N specified azimuth projections and acquisitions are completed, the target information map in each specified orientation is processed. Specifically, the processing is divided into three parts: one is that the target feature points are obtained by the feature point extraction in the camera. The position in the image coordinate system, as shown in Fig. 4, is the position of the target feature point in the camera image coordinate system obtained under a certain orientation; the second is to obtain the phase distribution of the target information map by phase demodulation technique. The third is to combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
Figure PCTCN2017107275-appb-000017
Then, based on the exact phase obtained
Figure PCTCN2017107275-appb-000018
Combined with the mapping relationship between the sub-pixel coordinates and the phase of the target feature points in the image coordinate system of the projector, that is, the combination formula
Figure PCTCN2017107275-appb-000019
Calculating sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the image coordinate system of the projector, as shown in FIG. 5; wherein T represents a phase period Width (in pixels).
步骤S3，根据标定模型，利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；Step S3, according to the calibration model, using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to calibrate the projector, and obtain an initial calibration parameter, i= 1,2,...N;
所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ。The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ.
具体地，本发明实施例提供的标定模型的原理图如图6所示，标定后的重投影误差如图7所示；重投影误差的分布和标准差是评价标定结果的重要标准，一般地，特征点的重投影误差集中围绕在原点附近，并且重投影误差的标准差越小标定结果越准确。Specifically, the schematic diagram of the calibration model provided by the embodiment of the present invention is shown in FIG. 6 , and the re-projection error after calibration is shown in FIG. 7; the distribution and standard deviation of the re-projection error are important criteria for evaluating the calibration result, generally The re-projection error of the feature points is concentrated around the origin, and the smaller the standard deviation of the re-projection errors, the more accurate the calibration result is.
步骤S4，利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。In step S4, the initial calibration parameter and the three-dimensional world coordinate X are optimized by a beam adjustment method to obtain a final calibration parameter.
具体地，所述步骤S4中，所述光束平差法具体为：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；Specifically, in the step S4, the beam adjustment method is specifically: assuming that there are M target feature points in each specified orientation, and the initial calibration parameters and the target feature points are minimized by minimizing the objective function. The three-dimensional world coordinates X j , j=1, 2..., M are optimized to obtain final calibration parameters;
所述目标函数为：The objective function is:
Figure PCTCN2017107275-appb-000020
Figure PCTCN2017107275-appb-000020
其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，
Figure PCTCN2017107275-appb-000021
代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表 投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation,
Figure PCTCN2017107275-appb-000021
Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
具体地，与一般标定的优化目标函数相比，光束平差法的优化方法区别在于将标靶特征点的三维世界坐标Xj,j＝1,2...，M作为待优化的变量，来消除误差带来的不利影响，将X在光束平差优化的过程中调整为可靠性更高的值，从而使标定结果更加精确；标定后的重投影误差如图8所示，与图7相比有所提升。Specifically, compared with the generally calibrated optimization objective function, the optimization method of the beam adjustment method differs in that the three-dimensional world coordinates X j , j=1, 2..., M of the target feature points are used as variables to be optimized. To eliminate the adverse effects caused by the error, adjust X to a higher reliability value in the process of beam adjustment optimization, so that the calibration result is more accurate; the re-projection error after calibration is shown in Figure 8, and Figure 7 Compared to the improvement.
本发明实施例中，经过多方位投影采集、图像处理、初始标定、平差优化之后，其重投影误差(Reprojector Error)分布如图8所示，水平和竖直方向的标准偏差分别是0.02541pixel和0.01926pixel；而只经过初始标定，水平和竖直方向的标准偏差分别是0.11119pixel和0.08406pixel，如图7所示；由此可见提高的标定精确度可达77％。In the embodiment of the present invention, after multi-azimuth projection acquisition, image processing, initial calibration, and adjustment optimization, the Reprojector Error distribution is as shown in FIG. 8, and the standard deviations in the horizontal and vertical directions are 0.02541 pixel, respectively. And 0.01926pixel; and only the initial calibration, the standard deviation of the horizontal and vertical directions are 0.11119pixel and 0.08406pixel, respectively, as shown in Figure 7; thus can be seen that the improved calibration accuracy can reach 77%.
下面再介绍一种多方位投影的投影仪标定装置，所述投影仪标定装置应用于投影仪标定系统，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直；A projector calibration device for multi-directional projection is described below. The projector calibration device is applied to a projector calibration system. The projector calibration system includes: a projector, a camera, and a target, and the camera is located at the standard Above the target, and the optical axis of the camera is perpendicular to the plane of the target;
如图9所示，所述投影仪标定装置包括：As shown in FIG. 9, the projector calibration device includes:
投影采集模块1，用于利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；The projection acquisition module 1 is configured to sequentially project a preset calibration pattern to a target plane by using the projector in sequence with N specified presets around the target, and collect the target information map by using the camera in each specified orientation;
具体地，所述投影采集模块1中，所述预置的N个指定方位需要满足：所述投影仪在所述预置的N个指定方位投射的标定图案在标靶平面聚焦。Specifically, in the projection collection module 1, the preset N specified orientations need to be satisfied: the calibration pattern projected by the projector in the preset N specified orientations is focused on the target plane.
具体地，所述投影采集模块1中，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图；另外，相机在投影仪只投射均匀光照的时候，采集原标靶图。Specifically, in the projection collection module 1, the preset calibration pattern includes: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps; the target information map includes: a plurality of phases containing target information The shift map and several Gray code maps containing the target information; in addition, the camera collects the original target map when the projector only projects uniform illumination.
特征点信息获取模块2，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过 亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000022
及基于所述标靶特征点的精确相位
Figure PCTCN2017107275-appb-000023
得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；The feature point information acquiring module 2 is configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system, and obtain a phase of the target information map by using a phase demodulation technique. Distribution, combining the position of the target feature point with the phase distribution of the target information map, and obtaining the precise phase of the target feature point through sub-pixel interpolation calculation
Figure PCTCN2017107275-appb-000022
And precise phase based on the feature points of the target
Figure PCTCN2017107275-appb-000023
Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
具体地，所述特征点信息获取模块2具体包括：精确相位确定模块，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
Figure PCTCN2017107275-appb-000024
还包括亚像素确定模块，用于根据投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即利用以下公式计算得到与所述标靶特征点相对应的亚像素坐标xi；Specifically, the feature point information acquiring module 2 specifically includes: an accurate phase determining module, configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system, The phase demodulation technique is used to obtain the phase distribution of the target information map, the position of the target feature point and the phase distribution of the target information map are combined, and the precise phase of the target feature point is obtained through sub-pixel interpolation calculation.
Figure PCTCN2017107275-appb-000024
The method further includes a sub-pixel determination module, configured to calculate a sub-pixel coordinate corresponding to the target feature point according to a mapping relationship between a sub-pixel coordinate and a phase of the target feature point in the projector image coordinate system, that is, using the following formula x i ;
Figure PCTCN2017107275-appb-000025
Figure PCTCN2017107275-appb-000025
其中，
Figure PCTCN2017107275-appb-000026
代表所述标靶特征点的精确相位，T代表相位周期宽度(单位：像素)，i＝1,2,......N。among them,
Figure PCTCN2017107275-appb-000026
Represents the exact phase of the target feature point, T represents the phase period width (unit: pixel), i = 1, 2, ... N.
初始标定模块3，用于利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；The initial calibration module 3 is configured to calibrate the projector by using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to obtain an initial calibration parameter, i= 1,2,...N;
所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ；The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ;
优化模块4，用于利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。The optimization module 4 is configured to optimize the initial calibration parameter and the three-dimensional world coordinate X by using a beam adjustment method to obtain a final calibration parameter.
具体地，所述优化模块4具体用于：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；Specifically, the optimization module 4 is specifically configured to: assume that there are M target feature points in each specified orientation, and minimize the three-dimensional world coordinate X j of the initial calibration parameter and the target feature point by using a minimum objective function. j=1, 2..., M is optimized to obtain the final calibration parameters;
所述目标函数为：The objective function is:
Figure PCTCN2017107275-appb-000027
Figure PCTCN2017107275-appb-000027
其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation, Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
本发明提供的一种多方位投影的投影仪标定方法及装置是基于相位法，但优于一般的相位法，一方面，解决了特征点图像提取不准确的问题；另一方面，解决了标靶特征点三维世界坐标与真实值之间有偏差的问题，与一般标定的优化目标函数相比，光束平差法的优化方法区别在于将标靶特征点的三维世界坐标Xj,j＝1,2...，M作为待优化的变量，消除了误差带来的不利影响，将X在光束平差优化的过程中调整为可靠性更高的值，最后使标定结果更加精确。The multi-azimuth projection projector calibration method and device provided by the invention are based on the phase method, but are superior to the general phase method. On the one hand, the problem of inaccurate image extraction of feature points is solved; on the other hand, the target is solved. The problem that there is a deviation between the three-dimensional world coordinates of the target feature points and the real value is different from the generalized optimization objective function. The difference between the optimization methods of the beam adjustment method is that the three-dimensional world coordinates of the target feature points X j , j=1 , 2..., M as the variable to be optimized, eliminates the adverse effects caused by the error, adjusts X to a higher reliability value in the process of beam adjustment optimization, and finally makes the calibration result more accurate.
上述实施例方法中的全部或部分步骤是通过程序来控制相关硬件完成，所述的程序可以存储于一计算机可读取存储介质中，所述的存储介质，如ROM/RAM、磁盘、光盘等。All or part of the steps in the above embodiments are controlled by a program to control related hardware, and the program may be stored in a computer readable storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, or the like. .
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。 The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims (10)

  1. 一种多方位投影的投影仪标定方法，其特征在于，所述投影仪标定方法应用于投影仪标定系统，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直；所述投影仪标定方法包括：A projector calibration method for multi-directional projection, characterized in that the projector calibration method is applied to a projector calibration system, the projector calibration system comprising: a projector, a camera and a target, the camera being located at the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration method includes:
    步骤S1，利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；Step S1, using the projector to sequentially project a preset calibration pattern to the target plane in N specified orientations preset around the target, and collecting the target information map by using the camera in each specified orientation;
    步骤S2，对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100001
    及基于所述标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100002
    得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；    Step S2, performing feature point extraction on the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtaining the phase distribution of the target information map by using the phase demodulation technique, combined with the target feature The position of the point and the phase distribution of the target information map, and the precise phase of the target feature point is obtained through sub-pixel interpolation calculation
    Figure PCTCN2017107275-appb-100001
    And precise phase based on the feature points of the target
    Figure PCTCN2017107275-appb-100002
    Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
    步骤S3，利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；Step S3, using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to calibrate the projector, and obtain an initial calibration parameter, i=1, 2, ......N;
    所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ；The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ;
    步骤S4，利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。In step S4, the initial calibration parameter and the three-dimensional world coordinate X are optimized by a beam adjustment method to obtain a final calibration parameter.
  2. 如权利要求1所述的投影仪标定方法，其特征在于，所述预置的N个指定方位需要满足：所述投影仪在所述预置的N个指定方位投射的标定图案在标靶平面聚焦。The projector calibration method according to claim 1, wherein the preset N specified orientations are required to satisfy: a calibration pattern projected by the projector in the preset N specified orientations is at a target plane Focus.
  3. 如权利要求1所述的投影仪标定方法，其特征在于，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图。The projector calibration method according to claim 1, wherein the preset calibration pattern comprises: a plurality of sinusoidal phase shift patterns and a plurality of Gray code patterns; and the target information map comprises: a plurality of A phase shift map of the target information and a number of Gray code maps containing the target information.
  4. 如权利要求1所述的投影仪标定方法，其特征在于，所述基于所述标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100003
    得到投影仪图像坐标系中与所述标靶特征点相对应的亚 像素坐标xi，包括：    The projector calibration method according to claim 1, wherein said precise phase based on said target point of said target
    Figure PCTCN2017107275-appb-100003
    Obtaining a sub-pixel coordinate x i corresponding to the target feature point in the projector image coordinate system, including:
    根据投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即利用以下公式计算得到与所述标靶特征点相对应的亚像素坐标xi；According to the mapping relationship between the sub-pixel coordinates and the phase of the target feature points in the projector image coordinate system, the sub-pixel coordinates x i corresponding to the target feature points are calculated by the following formula;
    Figure PCTCN2017107275-appb-100004
    Figure PCTCN2017107275-appb-100004
    其中，
    Figure PCTCN2017107275-appb-100005
    代表所述标靶特征点的精确相位，T代表相位周期宽度，i＝1,2,......N。    among them,
    Figure PCTCN2017107275-appb-100005
    Representing the exact phase of the target feature point, T represents the phase period width, i = 1, 2, ... N.
  5. 如权利要求1所述的投影仪标定方法，其特征在于，所述步骤S4中，所述光束平差法具体为：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；The projector calibration method according to claim 1, wherein in the step S4, the beam adjustment method is specifically: assuming that there are M target feature points in each specified orientation, by minimizing the target. The function optimizes the initial calibration parameters and the three-dimensional world coordinates X j , j=1, 2..., M of the target feature points to obtain final calibration parameters;
    所述目标函数为：The objective function is:
    Figure PCTCN2017107275-appb-100006
    Figure PCTCN2017107275-appb-100006
    其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，
    Figure PCTCN2017107275-appb-100007
    代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。    Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation,
    Figure PCTCN2017107275-appb-100007
    Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
  6. 一种多方位投影的投影仪标定装置，其特征在于，所述投影仪标定装置应用于投影仪标定系统，所述投影仪标定系统包括：投影仪、相机和标靶，所述相机位于所述标靶上方，并且相机的光轴和标靶所在平面垂直；所述投影仪标定装置包括：A multi-directional projection projector calibration device, wherein the projector calibration device is applied to a projector calibration system, the projector calibration system includes: a projector, a camera, and a target, the camera is located at the Above the target, and the optical axis of the camera is perpendicular to the plane of the target; the projector calibration device comprises:
    投影采集模块，用于利用所述投影仪依次在标靶周围预置的N个指定方位投射预置的标定图案到标靶平面，在每个指定方位用所述相机采集标靶信息图；a projection acquisition module, configured to use the projector to sequentially project a preset calibration pattern to a target plane in N specified orientations preset around the target, and collect the target information map by using the camera in each specified orientation;
    特征点信息获取模块，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚 像素插值计算得到标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100008
    及基于所述标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100009
    得到投影仪图像坐标系中与所述标靶特征点相对应的亚像素坐标xi，i＝1,2,......N；    The feature point information acquiring module is configured to extract the feature points of the target information map in each specified azimuth to obtain the position of the target feature point in the camera image coordinate system, and obtain the phase distribution of the target information map by using the phase demodulation technique. Combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
    Figure PCTCN2017107275-appb-100008
    And precise phase based on the feature points of the target
    Figure PCTCN2017107275-appb-100009
    Obtaining sub-pixel coordinates x i , i=1, 2, . . . N corresponding to the target feature points in the projector image coordinate system;
    初始标定模块，用于利用得到的投影仪图像坐标系下亚像素坐标xi和已知的标靶特征点的三维世界坐标X对所述投影仪进行标定，求得初始标定参数，i＝1,2,......N；An initial calibration module is configured to calibrate the projector by using the obtained sub-pixel coordinate x i of the projector image coordinate system and the three-dimensional world coordinate X of the known target feature point to obtain an initial calibration parameter, i=1 , 2, ... N;
    所述初始标定参数包括：由投影仪与标靶组成的N个外参Θ1、Θ2......ΘN，和投影仪内部参数θ；The initial calibration parameters include: N external reference Θ 1 , Θ 2 Θ Θ N composed of a projector and a target, and a projector internal parameter θ;
    优化模块，用于利用光束平差法对所述初始标定参数和所述三维世界坐标X进行优化，得到最终标定参数。And an optimization module, configured to optimize the initial calibration parameter and the three-dimensional world coordinate X by using a beam adjustment method to obtain a final calibration parameter.
  7. 如权利要求6所述的投影仪标定装置，其特征在于，所述预置的N个指定方位需要满足：所述投影仪在所述预置的N个指定方位投射的标定图案在标靶平面聚焦。The projector calibration apparatus according to claim 6, wherein said preset N specified orientations are required to satisfy: a calibration pattern projected by said projector in said preset N specified orientations is at a target plane Focus.
  8. 如权利要求6所述的投影仪标定装置，其特征在于，所述预置的标定图案包括：若干幅正弦周期相移图和若干幅格雷码图；所述标靶信息图包括：若干幅含有标靶信息的相移图和若干幅含有标靶信息的格雷码图。The projector calibration apparatus according to claim 6, wherein the preset calibration pattern comprises: a plurality of sinusoidal phase shift diagrams and a plurality of Gray code maps; and the target information map comprises: a plurality of A phase shift map of the target information and a number of Gray code maps containing the target information.
  9. 如权利要求6所述的投影仪标定装置，其特征在于，所述特征点信息获取模块包括：The projector calibration device according to claim 6, wherein the feature point information acquisition module comprises:
    精确相位确定模块，用于对每个指定方位下的标靶信息图进行特征点提取得到标靶特征点在相机图像坐标系下的位置，利用相位解调技术得到标靶信息图的相位分布，结合标靶特征点的位置和标靶信息图的相位分布，并经过亚像素插值计算得到标靶特征点的精确相位
    Figure PCTCN2017107275-appb-100010
    The precise phase determining module is configured to perform feature point extraction on the target information map in each specified azimuth to obtain a position of the target feature point in the camera image coordinate system, and obtain a phase distribution of the target information map by using a phase demodulation technique. Combine the position of the target feature point with the phase distribution of the target information map, and obtain the precise phase of the target feature point through sub-pixel interpolation calculation.
    Figure PCTCN2017107275-appb-100010
    亚像素确定模块，用于根据投影仪图像坐标系下的标靶特征点的亚像素坐标与相位的映射关系，即利用以下公式计算得到与所述标靶特征点相对应的亚像素坐标xi；a sub-pixel determination module, configured to calculate a sub-pixel coordinate x i corresponding to the target feature point according to a mapping relationship between sub-pixel coordinates and a phase of the target feature point in the projector image coordinate system ;
    Figure PCTCN2017107275-appb-100011
    Figure PCTCN2017107275-appb-100011
    其中，
    Figure PCTCN2017107275-appb-100012
    代表所述标靶特征点的精确相位，T代表相位周期宽度，i＝1,2,......N。    among them,
    Figure PCTCN2017107275-appb-100012
    Representing the exact phase of the target feature point, T represents the phase period width, i = 1, 2, ... N.
  10. 如权利要求6所述的投影仪标定装置，其特征在于，优化模块具体用于：假设每个指定方位下的标靶特征点有M个，通过最小化目标函数对所述初始标定参数和标靶特征点的三维世界坐标Xj,j＝1,2...，M进行优化，得到最终标定参数；The projector calibration apparatus according to claim 6, wherein the optimization module is specifically configured to: assume that there are M target feature points in each specified orientation, and the initial calibration parameters and labels are performed by minimizing the objective function. The three-dimensional world coordinates X j , j=1, 2..., M of the target feature points are optimized to obtain final calibration parameters;
    所述目标函数为：The objective function is:
    Figure PCTCN2017107275-appb-100013
    Figure PCTCN2017107275-appb-100013
    其中，xij代表第i个方位下标靶信息图中的第j个标靶特征点经过图像处理得到的亚像素坐标，
    Figure PCTCN2017107275-appb-100014
    代表根据标定模型计算得到的第i个方位下标靶信息图中的第j个标靶特征点的坐标，τ＝{θ,Θi,Xj}为待优化的参数向量，其中，θ代表投影仪内部参数，Θi代表投影仪与标靶组成的外参，i＝1,2,......N。     Where x ij represents the sub-pixel coordinates obtained by image processing of the jth target feature point in the target information map of the i-th orientation,
    Figure PCTCN2017107275-appb-100014
    Representing the coordinates of the jth target feature point in the target information map of the i-th azimuth calculated according to the calibration model, τ={θ, Θ i , X j } is the parameter vector to be optimized, where θ represents The internal parameters of the projector, Θ i represents the external parameters of the projector and the target, i = 1, 2, ... N.
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