CN115682983A - Spectrum confocal-based method for measuring appearance of inner surface and outer surface of hemispherical harmonic oscillator - Google Patents
Spectrum confocal-based method for measuring appearance of inner surface and outer surface of hemispherical harmonic oscillator Download PDFInfo
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- CN115682983A CN115682983A CN202211312224.7A CN202211312224A CN115682983A CN 115682983 A CN115682983 A CN 115682983A CN 202211312224 A CN202211312224 A CN 202211312224A CN 115682983 A CN115682983 A CN 115682983A
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Abstract
The invention relates to a method for measuring the appearance of the inner and outer surfaces of a hemispherical harmonic oscillator based on spectrum confocal. The invention comprises the following steps: adjusting the displacement motion table and the posture adjusting table to enable the optical axis of the spectrum confocal measuring head to intersect with the rotating shaft of the hemispherical harmonic oscillator; dividing scanning measurement intervals, performing curved surface parallel flat plate approximation on measurement points, and recording a theoretical included angle between a flat plate and a vertical plane of a spectrum confocal measuring head; the spectrum confocal measuring head and the hemispherical harmonic oscillator respectively perform linear scanning motion and rotary motion, and spectrum peak position data of each measuring point on the surface of the hemispherical harmonic oscillator are collected; and establishing an inclined flat plate compensation model to calculate the distance position information of the inner surface and the outer surface of the hemispherical harmonic oscillator at each measuring point, and converting the measuring result into point cloud to generate the appearance of the inner surface and the outer surface. The method provided by the invention can effectively reduce the measurement error introduced by the curved surface, can obtain the full appearance of the inner surface and the outer surface of the hemispherical harmonic oscillator through one-time scanning movement, and can be integrated on processing equipment to realize online measurement after simple debugging.
Description
Technical Field
The invention relates to the technical field of precision measurement, in particular to a method for measuring the appearance of the inner surface and the outer surface of a hemispherical harmonic oscillator based on spectrum confocal.
Background
The hemispherical harmonic oscillator is used as an important component of a hemispherical resonance gyroscope of an inertial navigation device, is transparent and hemispherical shell-shaped, is light and thin, is generally less than 1mm thick, and has geometric accuracy which determines the final working performance of a product to a great extent. However, due to the existence of processing errors, unpredictable differences often exist between the surface morphology of the produced hemispherical resonator and a theoretical design value, and the development of the hemispherical resonator gyroscope in the military and civil inertial navigation fields in China is greatly restricted.
Chinese patent application CN112344865A discloses an in-situ measurement system and method for the wall thickness and the wall thickness uniformity of a hemispherical harmonic oscillator, wherein the hemispherical harmonic oscillator is clamped on a C shaft of a machine tool main shaft, and then a chromatic confocal sensor arranged on a B shaft of the machine tool is adopted to measure the wall thickness and the circumferential wall thickness non-uniformity of the hemispherical harmonic oscillator, but the emergent light of the chromatic confocal sensor is strictly required to be perpendicular to the axis of the hemispherical harmonic oscillator and pass through the center of a sphere in the measurement process, so that the measurement error of tens of micrometers is often introduced due to the difficulty in realization in the actual operation process; in addition, the reflected light intensity of the chromatic confocal sensor under the condition of large-angle inclination measurement is weak, so that the proposed method cannot perform wall thickness on the surface far away from the lip edge part of the hemispherical harmonic oscillator, and the obtained measurement data is incomplete. The inventor also proposes that a Fizeau interferometer is used for measuring part of the surface of the hemispherical harmonic oscillator for multiple times, and the whole surface appearance and wall thickness information of the hemispherical harmonic oscillator are obtained by a surface splicing method, but the Fizeau interferometer is extremely complex in operation process, so that the measurement can be carried out only through a very complicated debugging process, and the Fizeau interferometer is very difficult to be integrated and applied to hemispherical harmonic oscillator processing equipment to realize online measurement. Therefore, it is highly desirable to provide an on-line shape measurement technique applicable to the machining process of hemispherical resonators to guide the machining process thereof so as to ensure the production yield of hemispherical resonators.
Disclosure of Invention
The invention aims to provide a method for measuring the appearance of the inner and outer surfaces of a hemispherical harmonic oscillator based on spectrum confocal aiming at the defects of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
step 2, according to theoretical design values of the radiuses of the inner and outer hemispherical surfaces of the hemispherical harmonic oscillator, taking half of the transverse resolution of the spectrum confocal measuring head as a scanning measurement interval, performing curved surface parallel flat plate approximation on all measuring points, and recording theoretical included angle values between the flat plate and the vertical plane of the spectrum confocal measuring head, namely corresponding equivalent inclination angles at the measuring points;
step 3, enabling the spectrum confocal measuring head to perform scanning motion along a straight line, enabling the hemispherical harmonic oscillator to perform rotary motion around the axis of the hemispherical harmonic oscillator, and collecting and extracting the spectrum peak position data of each measuring point on the surface of the hemispherical harmonic oscillator;
and 4, establishing an inclined flat plate compensation model to calculate the distance D between the outer surface of the hemispherical harmonic oscillator and the distance delta D between the inner surface and the outer surface at each measuring point, and finally converting the measuring result into point cloud to generate the appearance of the inner surface and the outer surface of the hemispherical harmonic oscillator.
Further, the specific method for approximating the curved parallel flat plate in the step 2 comprises the following steps:
taking any measuring point on the surface of the hemispherical harmonic oscillator as a tangent point to make parallel tangent planes of the inner surface and the outer surface of the point, and taking a curved surface at the measuring point, which is obtained by clamping a large plane between the two tangent planes, to be an approximately parallel flat plate.
Further, the specific content of the tilted flat compensation model in step 4 includes:
4-1, integrating the inclination angle value and the spectral peak position data of the approximately parallel flat plate of each measuring point, adopting a light ray tracing method to compensate the influence of the inclined flat plate on the spectral peak position deviation collected by the spectral confocal measuring head, and obtaining the distance delta D between the inner surface and the outer surface of the hemispherical harmonic oscillator corresponding to the measuring point (namely the distance between the inner surface and the outer surface of the hemispherical harmonic oscillator corresponding to the measuring point) as follows:
wherein delta is the difference value of the measured original spectrum peak position and theta 1 Alpha is the angle of inclination of the plate, n, for the angle of incidence of the light focused on the lower surface of the plate 1 The refractive index of the flat material is shown, and omega is the rotation angle around the optical axis of the spectral confocal measuring head.
4-2, selecting a plurality of flat plates with different thicknesses, carrying out calibration measurement experiments by using the spectrum confocal measuring head under different inclination angles, and comparing the actual nominal value delta D a And model measured value deltaD m Introducing an inclination angle correction factor k to correct the inclination angle alpha of the flat plate in the formula into k alpha, substituting the correction factor k into the model so as to enable the model to measure a correction value delta D m ' with the actual nominal value Δ D a The difference is minimal, thereby improving the measurement accuracy of the model.
Furthermore, the wall thickness, various sizes and shape error values of the hemispherical harmonic oscillator at any position can be obtained through data processing according to the internal and external surface appearances of the hemispherical harmonic oscillator.
Compared with the prior art, the invention has the following beneficial effects:
1. the requirements on the relative position relationship between the spectrum confocal measuring head and the hemispherical harmonic oscillator during measurement are low, the system is easy to adjust and simple to operate, and the system can be integrated on machining equipment of the hemispherical harmonic oscillator to realize online measurement through simple installation and debugging.
2. Based on the scheme of curved surface parallel plate approximation, an inclined plate compensation model is established to compensate the measurement result of the spectrum confocal measuring head and increase the measurement error to a submicron order, so that the measurement error caused by surface curvature when the spectrum confocal sensor measures the curved surface of the hemispherical harmonic oscillator is effectively reduced.
3. The spectrum confocal measuring head with a large working inclination angle is adopted, the full-view measurement of the inner surface and the outer surface of the hemispherical harmonic oscillator can be realized through one-time linear scanning motion of the measuring head and the rotating motion of the hemispherical harmonic oscillator around the shaft, the measured data is complete, and the measured shape result can be further used for calculating the wall thickness and various size and shape error values of the hemispherical harmonic oscillator at any position.
Drawings
FIG. 1 is a flow chart of the method for measuring the internal and external surface topography of the hemispherical harmonic oscillator according to the present invention.
FIG. 2 is a schematic diagram of the measurement of the surface topography of the hemispherical resonator according to the present invention.
FIG. 3 is a schematic view of the curved parallel plate approximation of the present invention.
FIG. 4 is a schematic diagram of a tilted plate compensation model according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear, the following detailed description is made with reference to the accompanying drawings and examples.
The invention discloses a method for measuring the appearance of the inner and outer surfaces of a hemispherical harmonic oscillator based on spectrum confocal, which comprises the following steps of:
and 2, according to theoretical design values of the radiuses of the inner and outer hemispherical surfaces of the hemispherical harmonic oscillator, in the embodiment, half of the transverse resolution of the spectrum confocal measuring head is used as a scanning measurement interval, curved surface parallel flat plate approximation is carried out on all measuring points, and the theoretical included angle value (namely the corresponding equivalent inclination angle of the measuring points) between the flat plate and the vertical surface of the spectrum confocal measuring head is recorded. It should be noted that although there may be a difference between the actual topography of the inner and outer hemispherical surfaces of the hemispherical resonator and the theoretical design value thereof, due to the characteristic that the spectroscopic confocal measurement head is insensitive to small tilt angles, the problem of the equivalent tilt angle error caused by the difference can be ignored.
As shown in fig. 3, the specific method for approximating the curved parallel flat plate is as follows: any measuring point on the surface of the hemispherical resonator (under the condition of extremely small scale, the influence on the final measuring result is not great by selecting an inner surface measuring point or an outer surface measuring point as a parallel tangent plane) is taken as a tangent point to be made into a parallel tangent plane of the inner surface and the outer surface of the point, a curved surface at the measuring point obtained by a large plane clamped by the two tangent planes is taken to be an approximately parallel flat plate, and the material of the flat plate is fused quartz which is the same as that of the hemispherical resonator in the embodiment;
step 3, enabling the spectrum confocal measuring head to perform scanning motion along a straight line, enabling the hemispherical harmonic oscillator to perform rotation motion around the axis of the hemispherical harmonic oscillator, enabling the spectrum confocal measuring head to rotate for a circle exactly every time the spectrum confocal measuring head moves for one scanning measuring interval, and simultaneously collecting and extracting spectrum peak position data at each measuring point on the surface of the hemispherical harmonic oscillator;
and 4, establishing an inclined plate compensation model to calculate the distance D between the outer surface of the hemispherical harmonic oscillator and the distance delta D between the inner surface and the outer surface of the hemispherical harmonic oscillator (namely the distance between the measuring points of the inner surface and the outer surface of the hemispherical harmonic oscillator shown in the figure 2) at each measuring point, and finally converting the measuring result into point cloud to generate the appearance of the inner surface and the outer surface of the hemispherical harmonic oscillator.
The specific contents of the tilt plate compensation model include:
(1) And (3) integrating the inclination angle value of the approximately parallel flat plate and the spectral peak position data of each measuring point, and compensating the influence of the inclined flat plate on the spectral peak position deviation of the spectrum collected by the spectrum confocal measuring head by adopting a light ray tracing method. As shown in fig. 4, the wavelengths are λ respectively 1 And λ 2 Are focused on the upper and lower parallel plates respectivelyA surface. According to the sine theorem:
n 0 sinθ 1 ＝n 1 sinθ 2 ， (1)
in the formula [ theta ] 1 And theta 2 Incident and refraction angles, n, respectively, of light rays focused on the lower surface of the plate 0 And n 1 Is the refractive index of air and a plate material, where n 0 And =1. Then, on the triangle OO 1 O 2 And OO 2 O 3 The sine theorem is applied to obtain:
where α is the inclination angle of the flat plate and d is the distance between the upper and lower surfaces of the parallel flat plate at the measurement section shown in FIG. 4. The combined type (1) to (3) can obtain:
wherein δ is the difference between the measured original spectral peak positions, which can be directly read in the spectral confocal sensor, and the essence is the difference between the two spectral peaks in the measured signal after mapping the wavelength of light to a distance value.
The light rays under different rotation angles omega rotating around the optical axis of the spectrum confocal measuring head are fully considered, and the distance delta D between the upper surface and the lower surface of the parallel flat plate (namely the distance between the inner surface and the outer surface of the corresponding hemispherical harmonic oscillator at the measuring point) is finally obtained after normalization operation:
(2) Selecting a plurality of fused quartz glass plates with different thicknesses to carry out calibration measurement under different inclination angles by using a spectrum confocal measuring headQuantitative experiments, comparison of actual nominal values Δ D a And model measured value deltaD m Introducing a dip angle correction factor k to correct the dip angle alpha of the middle flat plate in the formula into k alpha, substituting the correction factor k into the model to enable the model to measure the correction value delta D m ' with the actual nominal value Δ D a The difference is minimum, so that the measurement accuracy of the model is improved.
According to the preferable embodiment, the wall thickness, various sizes and shape error values of the hemisphere harmonic oscillator at any position can be obtained through data processing according to the inner and outer surface appearances of the hemisphere harmonic oscillator.
It should be emphasized that the above-described embodiments are merely illustrative of the technical concept and features of the present invention, which are intended to enable those skilled in the art to understand the content of the present invention and to implement the invention, and thus the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (4)
1. A method for measuring the appearance of the inner and outer surfaces of a hemispherical harmonic oscillator based on spectral confocal is characterized by comprising the following steps:
step 1, adjusting the position and the posture between a spectrum confocal measuring head and a hemispherical harmonic oscillator to ensure that an optical axis of the spectrum confocal measuring head is intersected with a rotating shaft of the hemispherical harmonic oscillator to form a certain included angle to finish initial calibration of a system;
step 2, according to theoretical design values of the radiuses of the inner and outer hemispherical surfaces of the hemispherical harmonic oscillator, taking half of the transverse resolution of the spectrum confocal measuring head as a scanning measurement interval, performing curved surface parallel flat plate approximation on all measuring points, and recording theoretical included angle values between the flat plate and the vertical surface of the spectrum confocal measuring head;
step 3, enabling the spectrum confocal measuring head to perform scanning motion along a straight line, enabling the hemispherical harmonic oscillator to perform rotary motion around the axis of the hemispherical harmonic oscillator, and collecting and extracting the spectrum peak position data of each measuring point on the surface of the hemispherical harmonic oscillator;
and 4, establishing an inclined flat plate compensation model to calculate the distance D between the outer surface of the hemispherical harmonic oscillator and the distance delta D between the inner surface and the outer surface at each measuring point, and finally converting the measuring result into point cloud to generate the appearance of the inner surface and the outer surface of the hemispherical harmonic oscillator.
2. The method for measuring the appearance of the inner and outer surfaces of the hemispherical harmonic oscillator based on spectral confocal according to claim 1, wherein the specific method for approximating the curved parallel flat plate in the step 2 is as follows: taking any measuring point on the surface of the hemispherical harmonic oscillator as a tangent point to make parallel tangent planes of the inner surface and the outer surface of the point, and taking a curved surface at the measuring point, which is obtained by clamping a large plane between the two tangent planes, to be an approximately parallel flat plate.
3. The method for measuring the appearance of the inner and outer surfaces of the hemispherical harmonic oscillator based on spectral confocal according to claim 1, wherein the specific content of the tilted flat compensation model in the step 4 comprises:
4-1, integrating the inclination angle value and the spectral peak position data of the approximately parallel flat plate of each measuring point, adopting a light ray tracing method to compensate the influence of the inclined flat plate on the spectral peak position deviation collected by the spectral confocal measuring head, and obtaining the distance delta D between the inner surface and the outer surface of the corresponding hemispherical harmonic oscillator at the measuring point as follows:
wherein delta is the difference value of the measured original spectrum peak position and theta 1 Alpha is the angle of inclination of the plate, n, for the angle of incidence of the light focused on the lower surface of the plate 1 The refractive index of the flat material is adopted, and omega is the rotation angle of the optical axis of the spectral confocal measuring head;
4-2, selecting a plurality of flat plates with different thicknesses, carrying out calibration measurement experiments by using the spectrum confocal measuring head under different inclination angles, and comparing the actual nominal value delta D a And model measured value deltaD m Introducing a dip angle correction factor k to correct the dip angle alpha of the middle flat plate in the formula into k alpha, substituting the correction factor k into the model to enable the model to measure the correction value delta D m ’ From the actual nominal value Δ D a The difference is minimal, thereby improving the measurement accuracy of the model.
4. The method for measuring the appearance of the inner and outer surfaces of the hemispherical resonator based on spectral confocal of claim 1, wherein the wall thickness, the sizes and the shape error values of the hemispherical resonator at any position can be obtained by data processing according to the appearance of the inner and outer surfaces of the hemispherical resonator.
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