WO2022213274A1 - Universal ct axis alignment method - Google Patents
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Definitions
- the present disclosure relates to the technical fields of synchrotron radiation CT imaging, X-ray CT imaging and non-destructive three-dimensional detection, and in particular, to a general CT axis alignment method.
- CT Computer tomography
- the rotation axis should be imaged at the center of the horizontal direction of the detector as much as possible during the CT process, and the center of the sample (or the selected positioning point) is placed directly above the rotation axis, so the opposite axis is CT A very important content in imaging. It is assumed that the Z axis is the optical axis direction, the Y axis is the rotation axis direction, and the X axis is perpendicular to the Y and Z axes.
- the sample rotation stage 102 has an x-axis translation motor 103 and a z-axis translation motor 104, and there is an X-axis translation motor under the sample rotation stage 101, as shown in Figure 1.
- the rotation angle of the turntable is 0°
- the x-axis is parallel to the X-axis
- the z-axis is parallel to the Z-axis.
- parallel beam illumination usually in a full-angle (360°rotatable) CT, the projection position of the positioning point at the projection angles of 0°, 90°, 180° and 270° can be recorded, which can realize fast axis alignment.
- 0° and 180° are used to adjust the x-axis position, in one of the positions, move the x-axis translation motor 103 to make it project at the midpoint of the two projection positions; 90° and 270° are used to adjust the z-axis position, in which A position is projected at the midpoint of the two projection positions by moving the z-axis translation motor 104, and the first step of the axis alignment is completed by two-step adjustment, and the positioning point is moved directly above the rotation axis. At this time, when the sample stage is rotated, the positioning point does not change at the imaging position of the detector.
- the sample rotation stage 102 and the x-axis translation motor 103 and the z-axis translation motor 104 are moved as a whole by the X-axis translation motor 101 under the rotation stage, so that the positioning point is imaged at the center of the detector in the horizontal direction position, complete the second step of aligning the axis.
- the rotation angle in CT imaging is limited, and the conventional CT axial method is no longer applicable.
- the maximum rotation angle range of the sample stage that can be accepted during imaging is usually less than ⁇ 65°.
- the anchor point may move out of the field of view when the sample is rotated by a small distance from the axis. Therefore, there is a need to develop a general and fast alignment method suitable for angle-limited and small field-of-view CT imaging.
- the present disclosure provides a general CT axis alignment method, in order to partially solve at least one of the above technical problems.
- a general CT axis alignment method comprising the following steps:
- the position of the anchor point relative to the rotation axis is calculated and the anchor point is moved just above the rotation axis.
- the imaging geometric relationship includes: the position of the positioning point in the rotating Cartesian coordinate system is (x 0 , z 0 ); when the three rotation angles are ⁇ 1 , ⁇ 2 and ⁇ 3 respectively, the positioning point is The imaging positions on the detector are X 1 , X 2 and X 3 , respectively.
- the steps of moving the positioning point to just above the rotation axis include:
- the method further includes moving the rotation axis to the center position of the detector according to the imaging position of the positioning point.
- moving the rotation axis to the center position of the detector according to the imaging position of the positioning point is realized by an X-axis translation motor located under the sample rotation stage.
- Fig. 1 is the sample stage system structure in the prior art
- FIG. 2 is a flowchart of a general CT axis alignment method provided by an embodiment of the present disclosure
- FIG. 3 is a schematic diagram of projection imaging geometry provided by an embodiment of the present disclosure.
- FIG. 4 is a schematic diagram of an implementation case provided by an embodiment of the present disclosure.
- the present disclosure proposes a general CT alignment method to quickly complete the alignment before CT.
- FIG. 2 is the flow chart of the general CT axis alignment method; wherein, the method comprises the following steps:
- the rotation axis is moved to the center position of the detector through the imaging position of the positioning point to complete the CT axis alignment.
- the first step of axis alignment is completed; where -x 0 or -z 0 indicates that the moving direction along the x-axis or z-axis is positive or The negative direction depends on the opposite state of the positive and negative values of x 0 and z 0.
- z 0 3
- the z-axis translation motor is moved 3 unit lengths along the z-axis in the negative direction.
- z 0 -3
- the z-axis translation motor is moved 3 unit lengths along the z-axis in the positive direction.
- the rotation axis is moved to the center of the detector by the X-axis translation motor located under the sample rotation stage to complete the second step of axis alignment.
- Figure 3 shows a schematic diagram of the projection imaging geometry. It is worth noting that in a lens or lens-like imaging system, the x-axis is opposite to the x-axis. The dot is the positioning point, and the distance from the rotation axis is ⁇ . The position in the rotated Cartesian coordinate system is (x 0 ,z 0 ). When the rotation angles are respectively ⁇ 1 , ⁇ 2 and ⁇ 3 , the imaging positions of the positioning point on the detector are X 1 , X 2 and X 3 respectively. Meanwhile, the imaging position of the rotation axis on the detector is X a , and M is the magnification of the system. According to the imaging geometric relationship, the following relationship can be obtained
- the first step of aligning the axis is completed, that is, after moving the positioning point directly above the rotation axis. Then move the rotation axis to the center of the detector according to the imaging position of the positioning point, and complete the second step of the axis alignment.
- the rotation angle during CT imaging usually takes the range of ⁇ 60°.
- the detector was oriented in the X direction to avoid the calculation difference caused by the inverted image of the zone plate, as shown in Figure 4.
- ⁇ 1 , ⁇ 2 and ⁇ 3 take ⁇ , 0 and - ⁇ respectively, then we have
- the imaging positions on the detector at three angles are respectively X + , X 0 and X - .
- the movement amount (L x ) of the x-axis translation motor 103 and the movement amount (L z ) of the z -axis translation motor 104 are respectively
- the axis alignment can be completed as follows:
- the CT alignment method of the present disclosure has at least one of the following beneficial effects:
- the alignment process no longer requires at least 270° rotation like the conventional alignment method, and only needs to be imaged at any three angles, so this method can realize the alignment of angle-limited CT.
- the method can determine the position of the rotation axis through quantitative calculation on the basis of only recording the imaging positions of three angles, so as to quickly complete the axis alignment.
Abstract
A universal CT axis alignment method, comprising the following steps: imaging a positioning point at three rotation angle positions; and according to an imaging geometric relationship, calculating the position of the positioning point relative to a rotating shaft, and moving the positioning point to a position directly above the rotating shaft.
Description
本公开涉及同步辐射CT成像、X射线CT成像和无损三维检测技术领域，尤其涉及一种通用的CT对轴方法。The present disclosure relates to the technical fields of synchrotron radiation CT imaging, X-ray CT imaging and non-destructive three-dimensional detection, and in particular, to a general CT axis alignment method.
CT(Computed tomography)是一种三维成像技术，通过采集旋转样品在多个观察角度下的二维像，利用CT重构算法完成物体的三维成像。为了充分利用探测器的有效成像面积，CT过程中需要尽量让旋转轴成像于探测器水平方向中心位置，且样品的中心(或者选取的定位点)置于旋转轴正上方，因此对轴是CT成像中一个非常重要的内容。假设Z轴为光轴方向，Y轴为旋转轴方向，X轴与Y轴和Z轴垂直。为了使样品台能够平动同时样品平动又不影响旋转轴位置，样品旋转台102上有x轴平动电机103和z轴平动电机104，样品旋转台下还有一个X轴平动电机101，如图1所示。当旋转台旋转角度为0°时，x轴与X轴平行，z轴与Z轴平行。在平行束照明下，通常全角度(可360°旋转)CT中，记录定位点在投影角为0°、90°、180°和270°处的投影位置，可实现快速对轴。0°和180°用于调节x轴位置，在其中一个位置通过移动x轴平动电机103使其投影在两者投影位置的中点；90°和270°用于调节z轴位置，在其中一个位置通过移动z轴平动电机104使其投影在两者投影位置的中点，通过两步调节即完成了对轴的第一步，把定位点移至旋转轴正上方。此时，旋转样品台，定位点在探测器成像位置不发生改变。在任意角度下，通过旋转台下的X轴平动电机101整体移动样品旋转台102以及其上的x轴平动电机103和z轴平动电机104，使定位点成像于探测器水平方向中心位置，完成对轴第二步。CT (Computed tomography) is a three-dimensional imaging technology. By collecting two-dimensional images of rotating samples at multiple viewing angles, CT reconstruction algorithms are used to complete three-dimensional imaging of objects. In order to make full use of the effective imaging area of the detector, the rotation axis should be imaged at the center of the horizontal direction of the detector as much as possible during the CT process, and the center of the sample (or the selected positioning point) is placed directly above the rotation axis, so the opposite axis is CT A very important content in imaging. It is assumed that the Z axis is the optical axis direction, the Y axis is the rotation axis direction, and the X axis is perpendicular to the Y and Z axes. In order to enable the sample stage to translate and the sample to translate without affecting the position of the rotation axis, the sample rotation stage 102 has an x-axis translation motor 103 and a z-axis translation motor 104, and there is an X-axis translation motor under the sample rotation stage 101, as shown in Figure 1. When the rotation angle of the turntable is 0°, the x-axis is parallel to the X-axis, and the z-axis is parallel to the Z-axis. Under parallel beam illumination, usually in a full-angle (360°rotatable) CT, the projection position of the positioning point at the projection angles of 0°, 90°, 180° and 270° can be recorded, which can realize fast axis alignment. 0° and 180° are used to adjust the x-axis position, in one of the positions, move the x-axis translation motor 103 to make it project at the midpoint of the two projection positions; 90° and 270° are used to adjust the z-axis position, in which A position is projected at the midpoint of the two projection positions by moving the z-axis translation motor 104, and the first step of the axis alignment is completed by two-step adjustment, and the positioning point is moved directly above the rotation axis. At this time, when the sample stage is rotated, the positioning point does not change at the imaging position of the detector. At any angle, the sample rotation stage 102 and the x-axis translation motor 103 and the z-axis translation motor 104 are moved as a whole by the X-axis translation motor 101 under the rotation stage, so that the positioning point is imaged at the center of the detector in the horizontal direction position, complete the second step of aligning the axis.
很多时候CT成像中旋转角度受限，常规CT对轴方法不再适用。比如同步辐射软X射线纳米显微成像，由于机械结构限制，成像时能接受的样品台最大旋转角度范围通常小于±65°。此外，在成像视场很小的情况下，定位点偏离轴较小距离都可能导致旋转样品时定位点移出视场。 因此，需要发展一种适用于角度受限以及小视场CT成像的通用、快速的对轴方法。In many cases, the rotation angle in CT imaging is limited, and the conventional CT axial method is no longer applicable. For example, in synchrotron radiation soft X-ray nano-microscopic imaging, due to the limitation of mechanical structure, the maximum rotation angle range of the sample stage that can be accepted during imaging is usually less than ±65°. In addition, in cases where the imaging field of view is small, the anchor point may move out of the field of view when the sample is rotated by a small distance from the axis. Therefore, there is a need to develop a general and fast alignment method suitable for angle-limited and small field-of-view CT imaging.
发明内容SUMMARY OF THE INVENTION
针对上述技术问题，本公开提供了一种通用的CT对轴方法，以期部分地解决上述技术问题中的至少之一。In view of the above technical problems, the present disclosure provides a general CT axis alignment method, in order to partially solve at least one of the above technical problems.
为了实现上述目的，作为本公开的一方面，提供了一种通用的CT对轴方法，包括以下步骤：In order to achieve the above object, as an aspect of the present disclosure, a general CT axis alignment method is provided, comprising the following steps:
在三个旋转角度位置对定位点成像；Image the anchor point at three rotational angle positions;
根据成像几何关系，计算定位点相对旋转轴的位置并将所述定位点移动到旋转轴正上方。According to the imaging geometry, the position of the anchor point relative to the rotation axis is calculated and the anchor point is moved just above the rotation axis.
其中，所述成像几何关系包括：所述定位点在旋转笛卡尔坐标系中的位置为(x
0,z
0)；当三个旋转角度分别为θ
1、θ
2和θ
3时，定位点在探测器上的成像位置分别为X
1、X
2和X
3。
Wherein, the imaging geometric relationship includes: the position of the positioning point in the rotating Cartesian coordinate system is (x 0 , z 0 ); when the three rotation angles are θ 1 , θ 2 and θ 3 respectively, the positioning point is The imaging positions on the detector are X 1 , X 2 and X 3 , respectively.
其中，根据成像几何关系，将定位点移动到旋转轴正上方的步骤包括：Wherein, according to the imaging geometric relationship, the steps of moving the positioning point to just above the rotation axis include:
根据成像几何关系，得到如下方程：According to the imaging geometry, the following equations are obtained:
其中，
为成像变换矩阵，X
a为旋转轴在探测器上的成像位置，M为系统放大倍数。
in, is the imaging transformation matrix, X a is the imaging position of the rotation axis on the detector, and M is the magnification of the system.
其中，通过求解所述方程得到如下等式：where the following equation is obtained by solving the equation:
其中，根据所述等式得到x
0和z
0后，通过沿x轴移动x轴平动电机距离|x
0|，沿z轴移动z轴平动电机距离|z
0|，即完成将定位点移动到旋转轴正上方，其中，沿x轴或z轴移动方向为正向或负向取决于x
0和z
0数值正负的相反状态。
Wherein, after obtaining x 0 and z 0 according to the equation, by moving the x-axis translation motor distance |x 0 | along the x-axis, and moving the z-axis translation motor distance |z 0 | along the z-axis, the positioning is completed. The point moves directly above the axis of rotation, where the direction of movement along the x- or z-axis is positive or negative depending on the opposite state of the positive and negative values of x 0 and z 0 .
其中，还包括根据所述定位点成像位置把所述旋转轴移动到探测器中心位置。The method further includes moving the rotation axis to the center position of the detector according to the imaging position of the positioning point.
其中，根据所述定位点成像位置把所述旋转轴移动到探测器中心位置是通过位于样品旋转台下方的X轴平动电机来实现的。Wherein, moving the rotation axis to the center position of the detector according to the imaging position of the positioning point is realized by an X-axis translation motor located under the sample rotation stage.
图1是现有技术中的样品台系统结构；Fig. 1 is the sample stage system structure in the prior art;
图2是本公开实施例提供的通用的CT对轴方法的流程图；2 is a flowchart of a general CT axis alignment method provided by an embodiment of the present disclosure;
图3是本公开实施例提供的投影成像几何示意图；3 is a schematic diagram of projection imaging geometry provided by an embodiment of the present disclosure;
图4是本公开实施例提供的一种实施案例示意图。FIG. 4 is a schematic diagram of an implementation case provided by an embodiment of the present disclosure.
在CT旋转角度受限或视场较小时，常规的CT对轴方法不再适用。同步辐射软X射线纳米显微成像中成像视场小，CT过程旋转角度小于180°，为了提高对轴效率，本公开提出一种通用的CT对轴方法，快速完成CT前的对轴。When the CT rotation angle is limited or the field of view is small, the conventional CT axial method is no longer suitable. In synchrotron radiation soft X-ray nano-microscopic imaging, the imaging field of view is small, and the rotation angle of the CT process is less than 180°. In order to improve the alignment efficiency, the present disclosure proposes a general CT alignment method to quickly complete the alignment before CT.
为使本公开的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并参照附图，对本公开作进一步的详细说明。In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure will be further described in detail below with reference to the specific embodiments and the accompanying drawings.
如图2所示为通用的CT对轴方法的流程图；其中，该方法包括以下步骤：As shown in Fig. 2 is the flow chart of the general CT axis alignment method; wherein, the method comprises the following steps:
在三个旋转角度位置对定位点成像；Image the anchor point at three rotational angle positions;
根据成像几何关系，将定位点移动到旋转轴正上方；According to the imaging geometric relationship, move the positioning point to just above the rotation axis;
通过所述定位点成像位置把所述旋转轴移动到探测器中心位置，完成CT对轴。The rotation axis is moved to the center position of the detector through the imaging position of the positioning point to complete the CT axis alignment.
具体包括：Specifically include:
记录任意三个角度(θ
1，θ
2，θ
3)定位点的成像位置X
1、X
2和X
3；
Record the imaging positions X 1 , X 2 and X 3 of the anchor points at any three angles (θ 1 , θ 2 , θ 3 );
基于成像变换矩阵
利用公式
Based on imaging transformation matrix Use the formula
计算定位点位置(x
0,z
0)以及旋转轴成像位置X
a；
Calculate the position of the anchor point (x 0 , z 0 ) and the imaging position X a of the rotation axis;
通过移动x轴平动电机-x
0，移动z轴平动电机-z
0，完成对轴第一步；其中，-x
0或-z
0表示沿x轴或z轴移动方向为正向或负向取决于x
0和z
0数值正负的相反状态，比如z
0＝3，那么此时为沿z轴负向移动z轴平动电机3个单位长度，当z
0＝-3时，那么此时为沿z轴正向移动z轴平动电机3个单位长度。
By moving the x-axis translation motor -x 0 and moving the z-axis translation motor -z 0 , the first step of axis alignment is completed; where -x 0 or -z 0 indicates that the moving direction along the x-axis or z-axis is positive or The negative direction depends on the opposite state of the positive and negative values of x 0 and z 0. For example, z 0 =3, then the z-axis translation motor is moved 3 unit lengths along the z-axis in the negative direction. When z 0 =-3, Then, at this time, the z-axis translation motor is moved 3 unit lengths along the z-axis in the positive direction.
通过位于样品旋转台下方的X轴平动电机把旋转轴移动到探测器中心位置，完成对轴第二步。The rotation axis is moved to the center of the detector by the X-axis translation motor located under the sample rotation stage to complete the second step of axis alignment.
如图3所示为投影成像几何示意图，值得注意的是，在透镜或类透镜成像系统中，X轴与x轴是反向的。圆点为定位点，离旋转轴的距离为ρ。在旋转笛卡尔坐标系中的位置为(x
0,z
0)。当旋转角度分别在θ
1、θ
2和θ
3时，定位点在探测器上的成像位置分别为X
1、X
2和X
3。同时，旋转轴在探测器上的成像位置为X
a，M为系统放大倍数。根据成像几何关系，可得如下关系式
Figure 3 shows a schematic diagram of the projection imaging geometry. It is worth noting that in a lens or lens-like imaging system, the x-axis is opposite to the x-axis. The dot is the positioning point, and the distance from the rotation axis is ρ. The position in the rotated Cartesian coordinate system is (x 0 ,z 0 ). When the rotation angles are respectively θ 1 , θ 2 and θ 3 , the imaging positions of the positioning point on the detector are X 1 , X 2 and X 3 respectively. Meanwhile, the imaging position of the rotation axis on the detector is X a , and M is the magnification of the system. According to the imaging geometric relationship, the following relationship can be obtained
其中
为成像变换矩阵，解上述方程，可得如下等式
in is the imaging transformation matrix, solve the above equation, the following equation can be obtained
计算得x
0和z
0后，移动103电机-x
0，移动104电机-z
0；
After calculating x 0 and z 0 , move 103 motor-x 0 and move 104 motor-z 0 ;
通过以上步骤，完成了对轴的第一步，即把定位点移动到旋转轴正上方之后。再根据定位点成像位置把旋转轴移动到探测器中心位置，完成对轴第二步。Through the above steps, the first step of aligning the axis is completed, that is, after moving the positioning point directly above the rotation axis. Then move the rotation axis to the center of the detector according to the imaging position of the positioning point, and complete the second step of the axis alignment.
至此，完成所有的对轴步骤。At this point, all the alignment steps are completed.
下面结合具体实施案例对本公开的技术方案进行进一步阐述。The technical solutions of the present disclosure will be further elaborated below with reference to specific implementation cases.
以同步辐射纳米显微成像为例，CT成像时旋转角度通常取±60°范围。分析过程中探测器在X方向调了方向，避免了波带片成倒像带来 的计算差异，如图4所示。θ
1、θ
2和θ
3分别取θ、0和-θ，则有
Taking synchrotron radiation nanomicroscopic imaging as an example, the rotation angle during CT imaging usually takes the range of ±60°. During the analysis, the detector was oriented in the X direction to avoid the calculation difference caused by the inverted image of the zone plate, as shown in Figure 4. θ 1 , θ 2 and θ 3 take θ, 0 and -θ respectively, then we have
设三个角度处在探测器上成像位置分别为X
+、X
0和X
-。基于式(2)可得
The imaging positions on the detector at three angles are respectively X + , X 0 and X - . Based on formula (2), we can get
其中in
即x轴平动电机103移动量(L
x)和z轴平动电机104移动量(L
z)分别为
That is, the movement amount (L x ) of the x-axis translation motor 103 and the movement amount (L z ) of the z -axis translation motor 104 are respectively
具体可按如下步骤完成对轴：Specifically, the axis alignment can be completed as follows:
1.在0°时把定位点移动视场中心，再分别在±1°位置成像，通过公式(7)完成z轴的粗对准。由于电机误差，定位点运动轨迹并不是完全理想的圆弧，θ越小受电机不理想的影响越大，所以第一步为粗对准。1. Move the positioning point to the center of the field of view at 0°, and then image at ±1° positions respectively, and complete the rough alignment of the z-axis by formula (7). Due to the motor error, the trajectory of the positioning point is not a completely ideal arc. The smaller θ is, the greater the influence of the motor is not ideal, so the first step is rough alignment.
2.继续增大角度与0°的偏移量，确保定位点在±θ时还在视场内，同时让θ尽可能大，记录三个成像位置(0°和±θ)，再次利用公式(7)完成z轴的再对准。2. Continue to increase the offset between the angle and 0° to ensure that the positioning point is still within the field of view at ±θ, while making theta as large as possible, record three imaging positions (0° and ±θ), and use the formula again (7) Complete the realignment of the z-axis.
3.分别在0°，±60°记录成像位置，公式(6)和(7)简化为
和
基于该计算结果完成x轴和z轴的精对准。
3. Record the imaging position at 0°, ±60°, respectively, formulas (6) and (7) are simplified as and Based on this calculation result, fine alignment of the x-axis and the z-axis is done.
4.最后通过设置在样品旋转台下方的X轴平动电机101把定位点成像位置移至探测器中心即完成全部对轴。4. Finally, move the imaging position of the positioning point to the center of the detector through the X-axis translation motor 101 arranged under the sample rotation stage to complete all axis alignment.
综上所述，与传统设计方法相比，本公开的CT对轴方法至少具有如下有益效果之一：To sum up, compared with the traditional design method, the CT alignment method of the present disclosure has at least one of the following beneficial effects:
1.适用于角度受限CT成像。1. It is suitable for CT imaging with limited angle.
对轴过程不再需要像常规对轴方法要求至少实现270°旋转，只需要在任意三个角度成像，因此该方法可实现角度受限CT的对轴。The alignment process no longer requires at least 270° rotation like the conventional alignment method, and only needs to be imaged at any three angles, so this method can realize the alignment of angle-limited CT.
2.适用于小视场CT成像。2. Suitable for small field of view CT imaging.
基于成像原理，可知
是一个缓变函数，当θ
1、θ
2和θ
3非常接近时，X
1、X
2和X
3也非常接近。因此，在小视场情况下，即使定位点离旋转轴较远，可以通过改变成像角度的取值实现小视场CT的对轴。
Based on the imaging principle, it can be known that is a slowly varying function, when θ 1 , θ 2 and θ 3 are very close, X 1 , X 2 and X 3 are also very close. Therefore, in the case of a small field of view, even if the positioning point is far from the rotation axis, the alignment of the small field of view CT can be achieved by changing the value of the imaging angle.
3.能够快速地完成CT对轴。3. Can quickly complete CT axis alignment.
本方法可以在只记录三个角度成像位置的基础上，通过定量计算确定旋转轴的位置，从而快速完成对轴。The method can determine the position of the rotation axis through quantitative calculation on the basis of only recording the imaging positions of three angles, so as to quickly complete the axis alignment.
以上所述的具体实施例，对本公开的目的、技术方案和有益效果进行了进一步详细说明，应理解的是，以上所述仅为本公开的具体实施例而已，并不用于限制本公开，凡在本公开的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included within the protection scope of the present disclosure.
Claims (7)
- 一种通用的CT对轴方法，包括以下步骤：A general CT axis alignment method includes the following steps:在三个旋转角度位置对定位点成像；Image the anchor point at three rotational angle positions;根据成像几何关系，计算定位点相对旋转轴的位置并将所述定位点移动到旋转轴正上方。According to the imaging geometry, the position of the anchor point relative to the rotation axis is calculated and the anchor point is moved just above the rotation axis.
- 根据权利要求1所述的CT对轴方法，其中，所述成像几何关系包括：所述定位点在旋转笛卡尔坐标系中的位置为(x 0,z 0)；当三个旋转角度分别为θ 1、θ 2和θ 3时，定位点在探测器上的成像位置分别为X 1、X 2和X 3。 The CT axis alignment method according to claim 1, wherein the imaging geometric relationship comprises: the position of the positioning point in the rotated Cartesian coordinate system is (x 0 , z 0 ); when the three rotation angles are respectively When θ 1 , θ 2 and θ 3 , the imaging positions of the positioning point on the detector are X 1 , X 2 and X 3 respectively.
- 根据权利要求2所述的CT对轴方法，其中，根据成像几何关系，将定位点移动到旋转轴正上方的步骤包括：The CT axis alignment method according to claim 2, wherein, according to the imaging geometric relationship, the step of moving the positioning point to just above the rotation axis comprises:根据成像几何关系，得到如下方程：According to the imaging geometry, the following equations are obtained:
其中，为成像变换矩阵，X a为旋转轴在探测器上的成像位置，M为系统放大倍数。 in,
is the imaging transformation matrix, X a is the imaging position of the rotation axis on the detector, and M is the magnification of the system. - 根据权利要求3所述的CT对轴方法，其中，通过求解所述方程得到如下等式：The method for CT axis alignment according to claim 3, wherein the following equation is obtained by solving the equation:
- 根据权利要求4所述的CT对轴方法，其中，根据所述等式得到x 0和z 0后，通过沿x轴移动x轴平动电机距离|x 0|，沿z轴移动z轴平动电机距离|z 0|，即完成将定位点移动到旋转轴正上方，其中，沿x轴或z轴移动方向为正向或负向取决于x 0和z 0数值正负的相反状态。 The CT axis alignment method according to claim 4, wherein after obtaining x 0 and z 0 according to the equation, by moving the x-axis translation motor distance |x 0 | along the x-axis, moving the z-axis translation along the z-axis The motor distance |z 0 |, that is, the positioning point is moved directly above the rotation axis, where the moving direction along the x-axis or the z-axis is positive or negative depending on the opposite states of the positive and negative values of x 0 and z 0 .
- 根据权利要求1所述的CT对轴方法，其中，还包括根据所述定位点成像位置把所述旋转轴移动到探测器中心位置。The CT axis alignment method according to claim 1, further comprising moving the rotation axis to a center position of the detector according to the imaging position of the anchor point.
- 根据权利要求6所述的CT对轴方法，其中，根据所述定位点成像位置把所述旋转轴移动到探测器中心位置是通过位于样品旋转台下方的X轴平动电机来实现的。The CT axis alignment method according to claim 6, wherein moving the rotation axis to the detector center position according to the positioning point imaging position is realized by an X-axis translation motor located under the sample rotation stage.
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