Variable-diameter narrow inner cavity three-dimensional shape measurement system and calibration method

Abstract

The system is composed of a three-axis moving platform TMS and a rotary scanning measuring head R, the rotary scanning measuring head R is installed on the three-axis moving platform TMS, and the three-axis moving platform TMS drives the rotary scanning measuring head to stretch into an inner cavity to measure the three-dimensional shape. The calibration method comprises the following steps: firstly, establishing a three-dimensional displacement platform TMS coordinate system {M}, a rotary scanning probe R coordinate system {S} and a calibration sphere coordinate system {B}; then calibrating the light emitting direction of the rotary scanning probe R by using a calibration ball, and taking the unit vector of the initial light emitting direction as the X-axis direction of the global coordinate system; the rotary scanning probe R is rotated by 90 degrees, the unit vector of the light emitting direction at the moment is used as the Y-axis direction of the global coordinate system, and finally the Z-axis direction of the global coordinate system is given according to the right-hand spiral rule. The method has the advantages of high efficiency, high precision, simplicity in operation and the like.

Description

Technical Field

[0001] The present invention belongs to the field of geometric measurement, and specifically relates to a three-dimensional shape measurement system and calibration method for variable-diameter narrow inner cavities. Background Art

[0002] Variable-diameter narrow inner cavities widely exist in high-end manufacturing fields such as aerospace, for example, the drum of an aero-engine, the oil pipeline valve of a space rocket, etc. The diameter of such cavities is 5 - 100 mm, the depth-diameter ratio is ≥5, and usually the entrance diameter is small while the middle part diameter is large. The geometric dimensions and three-dimensional shape of variable-diameter narrow inner cavities have a great influence on the working performance of components.

[0003] Traditional measurement means for variable-diameter narrow inner cavities mainly include: internal micrometer, plug gauge, internal diameter gauge, pneumatic gauge, special inspection fixture, structured light, industrial CT, confocal, ultrasonic imaging, eddy current imaging, coordinate measuring machine, etc. However, methods such as internal micrometer, plug gauge, internal diameter gauge, pneumatic gauge, and special inspection fixture have poor accessibility, are prone to damage parts, and rely on manual operation with low measurement efficiency; structured light has low measurement accuracy and poor accessibility; industrial CT has low efficiency and high cost; confocal has a small depth of field; ultrasonic imaging and eddy current imaging have low accuracy; although the coordinate measuring machine has relatively high measurement accuracy and acceptable accessibility, its measurement efficiency is too low and it is easy to scratch precision parts. Therefore, the existing measurement means cannot meet the comprehensive requirements of high precision, high efficiency, non-destructive measurement, and good accessibility for narrow spaces.

[0004] The existing calibration methods are complex in operation and cumbersome in process, and often require multiple different calibration objects to cooperate to complete; the existing calibration methods often only calibrate the light-emitting direction of the probe, can only establish a local coordinate system, and cannot establish a global coordinate system; the calibration solution method also has special requirements for the installation pose of the probe, and has poor versatility. Summary of the Invention

[0005] To solve the above problems in the prior art, the present invention provides a three-dimensional shape measurement system for a narrow inner cavity with a variable diameter. The system consists of a three-axis displacement platform and a rotary scanning probe that can extend into the narrow inner cavity with a variable diameter. The rotary scanning probe and the three-axis displacement platform each have their own coordinate systems. Therefore, it is necessary to calibrate the three-dimensional shape measurement system for the narrow inner cavity with a variable diameter to establish a unified coordinate system.

[0006] The technical solution adopted by the present invention to achieve the above object is: a calibration method for a three-dimensional shape measurement system of a variable-diameter narrow inner cavity, comprising the following steps:

[0007] Step 1: Define three coordinate systems, namely: the three-dimensional displacement platform TMS coordinate system {M}, the rotary scanning probe R coordinate system {S}, and the calibration sphere coordinate system {B}, for coordinate conversion between the three coordinate systems;

[0008] Step 2: Calibrate the light-emitting direction of the rotary scanning probe R using a calibration sphere, and use the unit vector of the initial light-emitting direction as the X-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system;

[0009] Step 3: Rotate the rotary scanning probe R by 90°, and use the unit vector of the light-emitting direction at this time as the Y-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system; the Z-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system is given by the right-hand screw rule.

[0010] For the coordinate system {M} of the three-dimensional displacement platform TMS, its origin is O M , and the positive directions of the three coordinate axes are X M , Y M , Z M , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform. The origin O of the three-dimensional moving platform TMS coordinate system M does not change during the entire measurement process with the movement of each axis;

[0011] For the coordinate system {S} of the rotary scanning probe R, its origin is O S which is defined as the point where the three axes of the three-axis displacement stage are all at the zero displacement and the measurement distance is zero when the rotary scanning probe is in the initial pose. The positive directions of the three coordinate axes are X S , Y S , Z S , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform. The origin O of the rotary scanning probe R coordinate system {S} S changes during the measurement process with the movement of the three-dimensional moving platform;

[0012] For the coordinate system {B} of the calibration sphere, its origin O B is the center of the sphere, and the positive directions of the three coordinate axes are X B , Y B , Z B , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform.

[0013] Calibrating the initial light-emitting direction of the rotary scanning probe R using a calibration sphere includes:

[0014] Step 21: Move the three-axis displacement platform to align the light-emitting port of the rotary scanning probe R with the calibration sphere so that the direction of the light emitted by the probe passes through the center of the sphere. Record the measurement value of the rotary scanning probe R at this time as d1, and the moving amounts of the three axes of the three-axis displacement platform are {X1, Y1, Z1}; at this time, the origin O of the rotary scanning probe R coordinate system {S} S can be expressed in the three-axis displacement platform TMS coordinate system {M} as Denote the intersection point of the measurement light of the rotary scanning probe R at this time and the spherical surface as Then this point can be expressed in the spherical coordinate system as:

[0015]

[0016] where m = [i, j, k] T is the unit vector of the measurement light in the coordinate system {S} of the rotary scanning probe R, satisfying mm T = 1;

[0017] Since the point is a point on the spherical surface, it satisfies the spherical surface equation

[0018]

[0019] where R is the diameter of the calibration sphere;

[0020] Step 22: Move the three-dimensional moving platform n times, and record the moving amounts of the three axes of the three-axis displacement platform each time as {X n , Y n , Z n}, and record the measurement value of the rotary scanning probe R at this time as d n . At this time, all spherical surface points all satisfy Equation (1) and Equation (2); obtain an n-dimensional nonlinear equation system:

[0021]

[0022] Equation (3) is an equation system about variables i, j, k, There are 6 variables, n ≥ 6;

[0023] Step 23: Solve using the Levenberg-Marquardt iterative estimation method to obtain i, j, k.

[0024] Including:

[0025] Step 31: Take {X1, Y1, X1} as the origin of the three-dimensional topography measurement system of the variable-diameter narrow inner cavity, and take the initial light-emitting direction m = [i, j, k] T of the rotary scanning probe R as the X-axis direction of the global coordinate system of the three-dimensional topography measurement system of the variable-diameter narrow inner cavity;

[0026] Step 32: Rotate the initial light-emitting direction of the rotary scanning probe R by 90°, and obtain:

[0027]

[0028] In Equation (4), θ = 90°; Take p as the Y-axis direction of the global coordinate system of the variable-diameter narrow lumen three-dimensional topography measurement system;

[0029] Step 3: Determine the Z-axis direction of the global coordinate system of the variable-diameter narrow lumen three-dimensional topography measurement system according to m and p, and the right-hand screw rule:

[0030]

[0031] So far, with {X1, Y1, Z1} as the origin, m as the positive X-axis direction, p as the positive Y-axis direction, and q as the positive Z-axis direction, the global coordinate system of the variable-diameter narrow lumen three-dimensional topography measurement system is established, and the calibration is completed.

[0032] A method for measuring the three-dimensional topography of a variable-diameter narrow lumen includes:

[0033] 1) Move the three-axis displacement platform so that the rotary scanning probe R extends into the variable-diameter narrow lumen to be measured, and record the coordinates {X g , Y g , Z g} of the three-axis displacement platform in real time during the movement, and accumulate and convert them to the global coordinate system;

[0034] 2) Control the rotary scanning probe R to scan the variable-diameter narrow lumen, feedback the measurement angle θ, and calculate the three-axis accumulated values in the global coordinate system through m, p, and q;

[0035] Obtain the three-dimensional topography point cloud coordinates of the variable-diameter narrow lumen.

[0036] A variable-diameter narrow lumen three-dimensional topography measurement system includes a host computer, a three-axis moving platform TMS, a rotary scanning probe R, and a calibration ball. The rotary scanning probe R is installed on the three-axis displacement platform TMS. The three-axis displacement platform TMR drives the rotary scanning probe to perform three-dimensional spatial motion and extends into the variable-diameter narrow lumen to measure the three-dimensional topography. The calibration ball is arranged at a fixed position within the viewing angle of the rotary scanning probe R so that the rotary scanning probe R scans it for position calibration; The host computer is provided with a memory and a processor. The memory stores a calibration program module and a narrow lumen measurement program module. When the processor loads the program, it executes the above method steps to achieve pre-measurement calibration, and executes scanning of the variable-diameter narrow lumen to obtain the three-dimensional topography of the variable-diameter narrow lumen to be measured.

[0037] The three-axis moving platform TMS is a linear motion module in three directions. The drive motor on each linear module is connected to the host computer to receive the moving control signal and feedback the moving position. The rotary scanning probe R is connected to the host computer to receive the rotation control signal and feedback the measurement data.

[0038] The present invention has the following beneficial effects and advantages:

[0039] 1. A three-dimensional topography measurement system for a narrow inner cavity with variable diameter provided by the present invention has the comprehensive advantages of high precision, high efficiency, non-destructive measurement, and good accessibility.

[0040] 2. The calibration method for the three-dimensional topography measurement system of the narrow inner cavity with variable diameter provided in this article only requires a calibration sphere and is easy to operate.

[0041] 3. The calibration method for the three-dimensional topography measurement system of the narrow inner cavity with variable diameter provided by the present invention does not have the problem of matrix singularity, avoiding the special requirements for the installation attitude of the rotary scanning probe during the calibration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Diagram of the three-dimensional topography measurement system for a narrow inner cavity with variable diameter of the present invention;

[0043] Figure 2 Diagram of the calibration method for the three-dimensional topography measurement system of the narrow inner cavity with variable diameter of the present invention;

[0044] Figure 3 Diagram for calibrating the light-emitting direction of the rotary scanning probe R of the present invention;

[0045] Among them, 1 is the three-axis displacement platform TMS, 2 is the rotary scanning probe R, and 3 is the narrow inner cavity with variable diameter to be measured. DETAILED DESCRIPTION OF THE INVENTION

[0046] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the specific implementation methods of the present invention in detail with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0048] As Figure 1 shown, a three-dimensional topography measurement system for a narrow inner cavity with variable diameter includes a host computer, a three-axis moving platform TMS, and a rotary scanning probe R. The rotary scanning probe R is installed on the three-axis displacement platform TMS, and the three-axis displacement platform TMR drives the rotary scanning probe R to perform three-dimensional motion in space and extends into the narrow inner cavity 3 with variable diameter to measure its three-dimensional topography.

[0049] AsFigure 2 As shown in the figure, three coordinate systems are defined, namely the three-dimensional displacement platform TMS coordinate system {M}, whose origin is O M , the positive directions of the three coordinate axes are X M , Y M , Z M , which are consistent with the moving directions X, Y, X of the three-axis displacement platform. The origin O of the three-dimensional moving platform TMS coordinate system M does not change with the movement of each axis during the entire measurement process; the rotating scanning probe R coordinate system {S}, whose origin is O S is defined as the point where the three axes of the three-axis displacement stage are all displaced to zero, and the measured distance is zero when the rotating scanning probe R is in the initial pose. The positive directions of the three coordinate axes are X S , Y S , Z S , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform. The origin O of the rotating scanning probe R coordinate system {S} S changes with the movement of the three-dimensional moving platform during the measurement process; the calibration sphere is arranged at a fixed position within the viewing angle range of the rotating scanning probe R, and the coordinate system {B}, whose origin O B is the center of the sphere, and the positive directions of the three coordinate axes are X B , Y B , X B , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform.

[0050] As Figure 3 shown in the figure, the light-emitting direction of the rotating scanning probe R is calibrated using the calibration sphere, and the unit vector of the initial light-emitting direction is used as the X-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system. Specifically, it is divided into two steps:

[0051] Step 1: Move the three-axis displacement platform to align the light-emitting port of the rotating scanning probe R with the calibration sphere so that the direction of the light emitted by the probe approximately passes through the center of the sphere. Record the measurement value of the rotating scanning probe R at this time as d1. The measurement value is the distance between the rotating scanning probe R and the calibration sphere. The moving amounts of the three axes of the three-axis displacement platform are {X1, Y1, X1} respectively. At this time, the origin O of the rotating scanning probe R coordinate system {S} S can be expressed in the three-axis displacement platform TMS coordinate system {M} as Express the intersection point of the measurement light of the rotating scanning probe R and the spherical surface at this time as Then this point can be expressed in the spherical coordinate system as:

[0052]

[0053] where m = [i, j, k] TTo measure the unit vector of light in the R coordinate system {S} of the rotary scanning probe head R, satisfying mm T = 1.

[0054] Since the point is a point on the spherical surface, it thus satisfies the spherical surface equation

[0055]

[0056] where R is the diameter of the calibration sphere.

[0057] Step 2: Move the three-dimensional moving platform multiple times so that the rotary scanning probe head R performs light-emitting scanning on each position of the surface of the calibration sphere, and record the moving amounts of the three axes of the three-axis displacement platform each time as {Y n , Y n , Z n}, and record the measurement value of the rotary scanning probe head R at this time as d n . At this time, all spherical surface points all satisfy Equation (1) and Equation (2). Combine Equation (1) and Equation (2) to obtain an n-dimensional nonlinear equation system:

[0058]

[0059] Equation (3) is an equation system regarding variables i, j, k, There are 6 variables in the equation system, which are the coordinates of the zero point M in the calibration sphere coordinate system. Therefore, the three-dimensional moving platform can be moved n times (n≥6), and the Levenberg-Marquard (LM) iterative estimation method can be used to solve for i, j, k.

[0060] Step 3: Take {X1, Y1, Z1} as the origin of the three-dimensional topography measurement system for variable-diameter narrow inner cavities, and take the initial light-emitting direction m = [i, j, k] T of the rotary scanning probe head R as the X-axis direction of the global coordinate system of the three-dimensional topography measurement system for variable-diameter narrow inner cavities.

[0061] Rotate the initial light-emitting direction of the rotary scanning probe head R by 90°, and obtain:

[0062]

[0063] θ = 90° in Equation (4). Take p as the Y-axis direction of the global coordinate system of the three-dimensional topography measurement system for variable-diameter narrow inner cavities.

[0064] According to m and p, and the right-hand screw rule, determine the Z-axis direction of the global coordinate system of the three-dimensional topography measurement system for variable-diameter narrow inner cavities:

[0065]

[0066] So far, with {X1, Y1, Z1} as the origin, m as the positive direction of the X-axis, p as the positive direction of the Y-axis, and q as the positive direction of the Z-axis, the global coordinate system of the three-dimensional topography measurement system for variable-diameter narrow inner cavities has been established, and the calibration has been completed.

[0067] During the actual application process, the measurement process includes:

[0068] 1) Move the three-axis displacement platform so that the rotary scanning probe R extends into the variable-diameter narrow inner cavity to be measured, and record the coordinates {X g , Y g , Z g} of the three-axis displacement platform in real time during the movement, and accumulate and convert them to the global coordinate system;

[0069] 2) Control the rotary scanning probe R to scan the variable-diameter narrow inner cavity, feedback the measurement angle θ, and calculate the accumulated values of the three axes in the global coordinate system through m, p, and q;

[0070] The three-dimensional topography point cloud coordinates of the variable-diameter narrow inner cavity are obtained.

[0071] The present invention also provides a three-dimensional topography measurement system for variable-diameter narrow inner cavities, including a host computer, a three-axis moving platform TMS, a rotary scanning probe R, and a calibration ball. The rotary scanning probe R is installed on the three-axis displacement platform TMS, and the three-axis displacement platform TMR drives the rotary scanning probe to perform three-dimensional spatial movements and extends into the variable-diameter narrow inner cavity to measure the three-dimensional topography. The calibration ball is arranged at a fixed position within the viewing angle range of the rotary scanning probe R so that the rotary scanning probe R scans it for position calibration; the host computer is provided with a memory and a processor. The memory stores a calibration program module and a narrow inner cavity measurement program module. When the processor loads the program, it executes the above-mentioned method steps to achieve pre-measurement calibration, and executes scanning of the variable-diameter narrow inner cavity to obtain the three-dimensional topography of the variable-diameter narrow inner cavity to be measured. The three-axis moving platform TMS is a linear motion module in three directions. The drive motors on each linear module are connected to the host computer to receive moving control signals and feedback the moving positions. The rotary scanning probe R is connected to the host computer to receive rotary control signals and feedback measurement data.

[0072] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A calibration method for a three-dimensional topography measurement system of a variable-diameter narrow inner cavity, characterized in that It includes the following steps: Step 1: Define three coordinate systems, namely: the three-dimensional displacement platform TMS coordinate system {M}, the rotary scanning probe R coordinate system {S}, and the calibration sphere coordinate system {B}, which are used for coordinate conversion between the three coordinate systems. Step 2: Calibrate the light-emitting direction of the rotary scanning probe R using the calibration sphere, and use the unit vector of the initial light-emitting direction as the X-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system. Step 3: Rotate the rotary scanning probe R by 90°, and use the unit vector of the light-emitting direction at this time as the Y-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system; the Z-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system is given by the right-hand screw rule.

2. A calibration method for a variable-diameter narrow inner cavity three-dimensional topography measurement system according to claim 1, characterized in that The TMS coordinate system {M} of the three-dimensional displacement platform has its origin at O M , and the positive directions of the three coordinate axes are X M , Y M , Z M , which are consistent with the moving directions X, Y, Z of the three-axis displacement platform. The origin O of the three-dimensional moving platform TMS coordinate system M does not change with the movement of each axis during the entire measurement process; The origin of the R coordinate system {S} of the rotary scanning probe is O. S It is defined as the point where the displacement zeros of the three axes of the three-axis displacement stage are located, and the measuring distance is zero when the rotary scanning probe is in the initial pose. The positive directions of the three coordinate axes, X S , Y S , Z S , are consistent with the moving directions X, Y, Z of the three-axis displacement platform. The origin O of the R coordinate system {S} of the rotary scanning probe S changes with the movement of the three-dimensional moving platform during the measurement process. The calibrated spherical coordinate system {B}, whose origin O B is the center of the sphere, and the positive directions of the three coordinate axes X B , Y B , Z B are consistent with the moving directions X, Y, Z of the three-axis displacement platform.

3. A calibration method for a three-dimensional topography measurement system of a variable-diameter narrow inner cavity according to claim 2, characterized in that, Calibrating the initial light-emitting direction of the rotary scanning probe R using the calibration sphere includes: Step 21: Move the three-axis displacement platform to align the light outlet of the rotary scanning probe R with the calibration sphere so that the direction of the light emitted by the probe passes through the center of the sphere. Record the measured value of the rotary scanning probe R at this time as d1, and the displacement amounts of the three axes of the three-axis displacement platform are {X1, Y1, Z1}; the origin O of the coordinate system {S} of the rotary scanning probe R at this time S can be represented in the coordinate system {M} of the three-axis displacement platform TMS as Represent the intersection point of the measuring light of the rotary scanning probe R and the spherical surface at this time as Then this point can be represented in the spherical coordinate system as: wherein is the unit vector for measuring light in the R coordinate system {S} of the rotary scanning probe, satisfying Since the point is a point on the spherical surface, it satisfies the spherical equation where R is the diameter of the calibration sphere; Step 22: Move the three-dimensional moving platform n times, and record the moving amounts of the three axes of the three-axis displacement platform each time as {X n , Y n , Z n}, and record the measured value of the rotary scanning probe R at this time as d n . At this time, all spherical points satisfy Equation (1) and Equation (2); obtain an n-dimensional non-linear equation system: Equation (3) is about variables i, j, k, There are 6 variables in the system of equations, and n ≥ 6; Step 23: Solve using the Levenberg-Marquardt iterative estimation method to obtain i, j, k.

4. A calibration method for a three-dimensional topography measurement system of a variable-diameter narrow inner cavity as claimed in claim 2 and claim 3, characterized in that It includes: Step 31: Take {X1, Y1, Z1} as the origin of the three-dimensional topography measurement system for the variable-diameter narrow inner cavity, and take the initial light-emitting direction of the rotary scanning probe R as the X-axis direction of the global coordinate system of the three-dimensional topography measurement system for the variable-diameter narrow inner cavity; Step 32: Rotate the initial light-emitting direction of the rotary scanning probe R by 90° to obtain: In equation (4), θ = 90°; take p as the Y-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system; Step 3: Determine the Z-axis direction of the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system according to m and p, and the right-hand screw rule: So far, with {X1, Y1, Z1} as the origin, m as the positive X-axis direction, p as the positive Y-axis direction, and q as the positive Z-axis direction, the global coordinate system of the variable-diameter narrow inner cavity three-dimensional topography measurement system is established, and the calibration is completed.

5. A three-dimensional topography measurement method for a variable-diameter narrow inner cavity, characterized in that, It includes: 1) Move the three-axis displacement platform so that the rotary scanning probe R extends into the narrow inner cavity with variable diameter to be measured, and record the coordinates of the three-axis displacement platform {X g , Y g , Z g} in real time during the movement, and accumulate and convert them to the global coordinate system; 2) Control the rotary scanning probe R to scan the variable-diameter narrow inner cavity, feedback the measurement angle θ, and calculate the cumulative values of the three axes in the global coordinate system through m, p, and q; Obtain the three-dimensional topography point cloud coordinates of the variable-diameter narrow inner cavity.

6. A three-dimensional topography measurement system for a variable-diameter narrow inner cavity, characterized in that It includes a host computer, a three-axis moving platform TMS, a rotary scanning probe R, and a calibration sphere. The rotary scanning probe R is installed on the three-axis displacement platform TMS. The three-axis displacement platform TMR drives the rotary scanning probe to perform three-dimensional spatial motion and extends into the variable-diameter narrow inner cavity to measure the three-dimensional topography. The calibration sphere is arranged at a fixed position within the viewing angle range of the rotary scanning probe R so that the rotary scanning probe R can perform position calibration on its scan; the host computer is provided with a memory and a processor. The memory stores a calibration program module and a narrow inner cavity measurement program module. When the processor loads the program, it executes the method steps described in any one of claims 1-5 to achieve pre-measurement calibration, and executes scanning of the variable-diameter narrow inner cavity to obtain the three-dimensional topography of the variable-diameter narrow inner cavity to be measured.

7. A three-dimensional topography measurement system for a variable-diameter narrow inner cavity according to claim 6, characterized in that, The three-axis moving platform TMS is a linear motion module in three directions. The drive motor on each linear module is connected to the host computer to receive the moving control signal and feedback the moving position. The rotary scanning probe R is connected to the host computer to receive the rotation control signal and feedback the measurement data.

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