CN115096194A - Displacement measuring probe, measuring device and displacement measuring method - Google Patents
Displacement measuring probe, measuring device and displacement measuring method Download PDFInfo
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- CN115096194A CN115096194A CN202210890553.3A CN202210890553A CN115096194A CN 115096194 A CN115096194 A CN 115096194A CN 202210890553 A CN202210890553 A CN 202210890553A CN 115096194 A CN115096194 A CN 115096194A
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- 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
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
Abstract
The application provides a displacement measurement probe, a measurement device and a displacement measurement method. The displacement measuring probe comprises: a beam output assembly for outputting a collimated first gaussian beam; the light beam conversion assembly is used for converting the collimated first Gaussian light beam into a first Bessel light beam and emitting the first Bessel light beam to an object surface to be detected; the imaging assembly comprises an imaging lens and a linear array image sensor, wherein the optical axis of the imaging lens and the first Bessel beam form a first angle, the imaging lens is used for imaging a bright spot formed by irradiating the first Bessel beam on an object surface to be detected, the linear array image sensor and the optical axis form a second angle and are used for receiving a bright spot image formed by the imaging lens on the bright spot, and the bright spot image is used for calculating the displacement of the object surface to be detected relative to a reference surface. The displacement measurement probe provided by the application can carry out high longitudinal resolution displacement measurement on the object plane with a fine step profile with high transverse resolution, and meanwhile, the measurement range is increased.
Description
Technical Field
The application relates to the field of distance measurement, in particular to a displacement measurement probe, a measurement device and a displacement measurement method.
Background
The laser displacement meter is widely used for online optical detection of micro-displacement measurement, appearance profile measurement and the like. The light beam emitted by a laser emission system in the laser displacement meter is mostly a focused Gaussian light beam, and the size of a light spot projected onto an object surface to be measured influences the extraction precision of the image point position on the linear array image sensor. The longer the distance from the light spot projected on the object plane to be measured by the Gaussian beam to the beam waist of the Gaussian beam is, the larger the size is, so that the extraction precision of the image point position on the linear array image sensor can be influenced. Therefore, in order to ensure the extraction accuracy of the image point position on the line image sensor, the measurement range of the laser displacement meter is small.
Disclosure of Invention
In a first aspect, embodiments of the present application provide a displacement measurement probe, including:
a beam output assembly for outputting a collimated first Gaussian beam;
the light beam conversion assembly and the light beam output assembly are arranged at intervals and used for converting the collimated first Gaussian beam into a first Bessel beam and emitting the first Bessel beam to an object surface to be detected, and the light beam conversion assembly comprises a first convex cone lens used for converting the Gaussian beam into the Bessel beam;
the imaging assembly comprises an imaging lens and a linear array image sensor, an optical axis of the imaging lens and the first Bessel beam form a first angle and are used for imaging a bright spot formed by irradiating the first Bessel beam on the object surface to be detected, the linear array image sensor and the imaging lens are arranged at intervals and form a second angle with the optical axis and are used for receiving a bright spot image formed by the imaging lens on the bright spot, and the bright spot image is used for calculating the displacement of the object surface to be detected;
wherein the optical axis passes through a middle position of the non-diffraction section of the first bessel beam and the line image sensor, and an extension line of a radial direction of the imaging lens, an extension line of a radial direction of the line image sensor and an extension line of the first bessel beam intersect at a point in a plane determined by the first bessel beam and the optical axis.
Wherein the light beam emitted from the first convex cone lens has a non-diffraction section, and the length of the non-diffraction section is proportional to the beam waist radius of the collimated first Gaussian light beam and inversely proportional to the base angle of the first convex cone lens.
Wherein the beam output assembly comprises:
a laser for outputting a second Gaussian beam;
and the collimating mirror is arranged at an interval with the laser and is used for converting the second Gaussian beam into the collimated first Gaussian beam.
Wherein the beam output assembly comprises:
a laser for outputting a second Gaussian beam;
a focusing lens spaced from the laser for focusing the second Gaussian beam into a converging third Gaussian beam;
the opening of the diaphragm is arranged at the focal plane of the focusing lens and is used for transmitting the converged third Gaussian beam to form a divergent fourth Gaussian beam;
and the collimating lens and the diaphragm are arranged at intervals, and the front focus of the collimating lens is arranged at the opening of the diaphragm and used for converting the divergent fourth Gaussian beam into the collimated first Gaussian beam.
Wherein the beam conversion assembly further comprises:
a concave cone lens disposed proximate to the beam output assembly relative to the first convex cone lens for converting the collimated first Gaussian beam to a diverging annular hollow beam;
and the second convex cone lens is arranged between the concave cone lens and the first convex cone lens, the convex conical surface structure of the second convex cone lens is opposite to the concave conical surface structure of the concave cone lens, the base angle of the convex conical surface structure of the second convex cone lens is equal to the base angle of the concave conical surface structure of the concave cone lens, and the second convex cone lens is used for converting the divergent annular hollow light beam into the collimated annular hollow light beam and emitting the collimated annular hollow light beam to the first convex cone lens.
Wherein the beam conversion assembly further comprises:
a third convex cone lens disposed proximate to the beam output assembly relative to the first convex cone lens for converting the collimated first Gaussian beam to a diverging annular hollow beam;
and the second convex cone lens is arranged between the third convex cone lens and the first convex cone lens, the convex conical surface structure of the second convex cone lens is opposite to the convex conical surface structure of the third convex cone lens, the base angle of the convex conical surface structure of the second convex cone lens is equal to that of the convex conical surface structure of the third convex cone lens, and the second convex cone lens is used for converting the divergent annular hollow light beam into a collimated annular hollow light beam and emitting the collimated annular hollow light beam to the first convex cone lens.
In a plane defined by the first bessel beam and the optical axis, the second convex conical lens and the first convex conical lens are relatively fixed, and the second convex conical lens and the first convex conical lens can move in a connecting line direction of the first convex conical lens and the second convex conical lens, the imaging lens can move in a radial direction of the imaging lens, and the line array image sensor can move in the radial direction of the line array image sensor.
In a second aspect, an embodiment of the present application further provides a measurement apparatus, including:
the displacement measurement probe according to the first aspect, configured to output a first bessel beam, and image a bright spot formed by irradiating the first bessel beam on a surface of an object to be measured;
and the data processor is electrically connected with the linear array image sensor and used for receiving data of a bright spot image formed by the bright spot on the linear array image sensor and calculating the displacement of the object surface to be detected according to the bright spot image data, and the data processor is also electrically connected with the light beam output assembly and used for controlling the light beam output assembly to output a first Gaussian light beam of which the output power changes along with the reflectivity of the object surface.
In a third aspect, an embodiment of the present application further provides a displacement measurement method, where the displacement measurement method includes:
projecting a first Bessel light beam with a slender needle shape without diffraction characteristics on the surface of an object to be measured to form a bright spot with a very small cross section diameter;
acquiring a bright spot image formed by the bright spot on the linear array image sensor;
extracting precise position information of the center of the bright spot image on the line array image sensor by adopting an image processing method;
and calculating the displacement of the object surface to be measured by adopting a triangular distance measurement principle according to the position information of the bright spot image.
Wherein, the step of extracting the precise position information of the center of the bright spot image on the line array image sensor by adopting an image processing method comprises the following steps:
identifying a central bright peak and a plurality of secondary bright peaks at two sides according to the bright spot image;
and performing fitting calculation on the light intensity distribution of the central bright peak and the multiple sub-bright peaks at two sides to obtain super-resolution point location information of the central bright peak of the bright spot image.
The application provides a displacement measurement probe, displacement measurement probe includes beam output subassembly, beam conversion subassembly and formation of image subassembly, first convex cone lens in the beam conversion subassembly will the first gaussian beam of collimation converts first Bessel beam for the beam can keep the horizontal size of several microns unchangeable in longer propagation distance, thereby makes when displacement measurement probe carries out displacement measurement, has improved horizontal resolution and vertical measurement resolution, and has improved the measurement range. Therefore, the displacement measurement probe provided by the application can perform high longitudinal resolution displacement measurement on the object plane with the fine stepped profile at high transverse resolution, and meanwhile, the measurement range is increased.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a displacement measurement probe according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a displacement measurement probe according to the embodiment of FIG. 1, in which a first convex cone lens converts a Gaussian beam into a Bessel beam;
FIG. 3 is a schematic diagram of a beam output assembly provided in one embodiment of the displacement measurement probe provided in the embodiment of FIG. 1;
FIG. 4 is a schematic diagram of a beam output assembly provided in another embodiment of the displacement measurement probe provided in the embodiment of FIG. 1;
FIG. 5 is a schematic structural diagram of a light beam conversion assembly in one embodiment of the displacement measurement probe provided in the embodiment of FIG. 4;
FIG. 6 is a schematic diagram of a light beam conversion assembly in another embodiment of the displacement measurement probe provided in the embodiment of FIG. 4;
FIG. 7 is a schematic structural diagram of a displacement measurement probe provided in the embodiment of FIG. 5;
fig. 8 is a schematic structural diagram of a measurement apparatus according to an embodiment of the present disclosure;
FIG. 9 is a flowchart of a displacement measurement method according to an embodiment of the present disclosure;
fig. 10 is a flowchart of a displacement measurement algorithm in the displacement measurement method provided in the embodiment of fig. 9.
Reference numerals: a measuring device 1; a displacement measuring probe 10; a data processor 20; a beam output assembly 110; a beam conversion component 120; an imaging assembly 130; a laser 111; a collimating mirror 112; a focusing lens 113; a diaphragm 114; a first convex axicon lens 121; a second convex axicon lens 122; a concave axicon lens 123; a third convex axicon lens 124; an imaging lens 131; a line image sensor 132; an optical axis 1311; a lens center 1312; an imaging reference point 1321; a collimated first gaussian beam L11; a second gaussian beam L12; a third gaussian beam L13; a fourth gaussian beam L14; the first bessel light beam L21; a diverging annular hollow light beam L41; a collimated annular hollow light beam L42; a non-diffraction zone L211; reference plane W0; object plane W1.
Detailed Description
The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without inventive step, are within the scope of the present disclosure.
The terms "first," "second," and the like in the description and claims of the present application and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
Reference herein to "an embodiment" or "an implementation" means that a particular feature, structure, or characteristic described in connection with the embodiment or implementation can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein may be combined with other embodiments.
The present embodiment provides a displacement measurement probe 10. Referring to fig. 1, fig. 1 is a schematic structural diagram of a displacement measurement probe according to an embodiment of the present disclosure. In the present embodiment, the displacement measuring probe 10 includes a light beam output assembly 110, a light beam conversion assembly 120, and an imaging assembly 130. The beam output assembly 110 is configured to output a collimated first gaussian beam L11. The beam conversion module 120 is disposed at an interval from the beam output module 110, and is configured to convert the collimated first gaussian beam L11 into a first bessel beam L21 and emit the first bessel beam to an object plane W1. The beam conversion assembly 120 includes a first convex axicon 121, and the first convex axicon 121 is used for converting a gaussian beam into a bessel beam. The imaging component 130 includes an imaging lens 131 and a line image sensor 132. The optical axis 1311 of the imaging lens 131 makes a first angle with the first bessel beam L21, the imaging lens 131 is used for imaging a bright spot formed by the first bessel beam L21 irradiating on the object plane W1, the line image sensor 132 is arranged at a distance from the imaging lens 131 and makes a second angle with the optical axis 1311, and is used for receiving a bright spot image formed by the imaging lens 131 on the bright spot, and the bright spot image is used for calculating the displacement of the object plane to be measured with respect to the reference plane W0. Wherein the optical axis 1311 passes through a middle position of a non-diffraction section of the first bessel beam L21 and the line image sensor 132, and an extension line of a radial direction of the imaging lens 131, an extension line of a radial direction of the line image sensor 132 and an extension line of the first bessel beam L21 intersect at a point in a plane determined by the first bessel beam L21 and the optical axis 1311.
In the present embodiment, the displacement measuring probe 10 is used for optical displacement measurement. Specifically, the displacement measuring probe 10 uses a bessel beam as an illumination beam of the object plane W1 to measure the distance between the displaced object plane W1 and the displacement measuring probe 10, or measure the distance between the displaced object plane W1 and the reference plane W0 before displacement, or measure the distance between each step profile in an object plane having a step profile. Wherein the reference plane W0 is located within the non-diffraction section of the first bessel beam L21, for example, the reference plane W0 may be located at the center of the non-diffraction section of the first bessel beam L21. The non-diffraction section of the first bessel beam L21 is a transmission range in which the amplitude distribution of the first bessel beam L21 does not change with the transmission distance.
In this embodiment, the beam output assembly 110 is configured to output a collimated first gaussian beam L11.
In this embodiment, the light beam conversion assembly 120 is configured to receive the collimated first gaussian light beam L11, so as to convert the collimated first gaussian light beam L11 into a first bessel light beam L21 and emit the first bessel light beam. Specifically, the beam conversion assembly 120 includes a first convex axicon 121, and the first convex axicon 121 is used for converting a gaussian beam into a bessel beam. The first convex cone lens 121 is configured to receive a collimated light beam, and in this embodiment, the first convex cone lens 121 is disposed at a beam waist of the collimated first gaussian light beam L11. Compared with the gaussian beam, the bessel beam can keep the transverse dimension of several micrometers in a longer transmission distance, so that the displacement measurement probe 10 can increase the measurement range of the displacement measurement probe 10 by converting the collimated first gaussian beam L11 into the first bessel beam L21 under the condition of meeting the requirements of the transverse resolution of the object surface to be measured and the size of a bright spot used for measurement.
In this embodiment, the first bessel beam L21 is irradiated onto the object plane W1, and forms a bright spot on the object plane W1, where the bright spot is imaged on the imaging component 130, and specifically, the bright spot passes through the imaging lens 131 and is imaged on the line image sensor 132. An optical axis 1311 of the imaging lens 131 makes a first angle with the first bessel beam L21. The line image sensor 132 is spaced apart from the imaging lens 131 and disposed at a second angle to the optical axis 1311. Specifically, in a plane defined by the first bessel beam L21 and the optical axis 1311, an extension line of the radial direction of the imaging lens 131, an extension line of the radial direction of the line image sensor 132, and an extension line of the first bessel beam L21 intersect at a point. Wherein the optical axis 1311 passes through the lens center 1312 of the imaging lens 131 and through the middle position of the non-diffractive section of the first bessel light beam L21.
In this embodiment, the bright spot image can be used to calculate the displacement of the object plane W1. Specifically, the distance between the reference plane W0 and the displacement measuring probe 10 is d0, the distance between the lens center 1312 of the imaging lens 131 and the intersection of the optical axis 1311 and the first bessel beam L21 is d1, the distance between the imaging reference point 1321 of the line image sensor 132 and the lens center 1312 of the imaging lens 131 is d2, the first angle is α, the second angle is β, and the distance between the speckle image and the imaging reference point 1321 of the line image sensor 132 is x 0. The imaging of the bright spots to the line image sensor 132 via the imaging lens 131 complies with the schemer's law. When the object plane W1 to be measured is closer to the displacement measuring probe 10 than the reference plane W0, that is, the speckle image is farther from the light beam conversion assembly 120 than the imaging reference point 1321 of the linear array image sensor 132, a distance y0= (x0 × 1 ×) sin β)/(d 2 × sin α + x0 × sin (α + β) between the object plane W1 to be measured and the reference plane W0 is, and then a distance y1= d0-y0 between the object plane W1 to be measured and the displacement measuring probe 10. When the object plane W1 is farther from the displacement measuring probe 10 than the reference plane W0, that is, the speckle image is closer to the light beam conversion assembly 120 than the imaging reference point 1321 of the linear array image sensor 132, a distance y0= (x0 × d1 × sin β)/[ d2 × sin α -x0 × sin (α + β) ] between the object plane W1 and the reference plane W0, then a distance y1= d0+ y0 between the object plane W1 and the displacement measuring probe 10. The distance between the bright spot image and the imaging reference point 1321 of the line image sensor 132 refers to a distance between a pixel unit where a central bright peak of the bright spot image is located and a pixel unit where the imaging reference point 1321 of the line image sensor 132 is located. The imaging reference point 1321 of the line image sensor 132 is a position of the speckle image on the line image sensor 132 when the displacement measurement probe 10 detects the reference surface W0. In addition, when the object plane W1 has a stepped profile, the bright spot image can also be used to calculate the height difference between the respective step planes in the object plane W1 by translating the object plane W1.
In the existing displacement measuring instrument, a gaussian beam is generally used as a displacement measuring beam. In the first aspect, due to the optical characteristics of the gaussian beam, the gaussian beam has the smallest beam cross section only near the beam waist in the propagation process, and the smaller the beam waist size is, the shorter the beam propagation length corresponding to the beam cross section meeting the detection accuracy requirement on both sides of the beam waist is, so that the range of performing high lateral resolution displacement detection by using the gaussian beam is not large. Compared with a gaussian beam, the displacement measurement probe 10 provided by the present application converts the gaussian beam into a bessel beam by using the beam conversion component 120 to perform displacement measurement, and specifically, performs displacement measurement by using the first bessel beam L21. The size of the cross section of the Bezier beam in the transmission process of the Bezier beam in a certain range is basically kept unchanged, so that the Bezier beam can have the cross section of the beam meeting the requirement of transverse detection accuracy in a longer transmission range, and the range of displacement detection by adopting the Bezier beam is wide. In the second aspect, since the gaussian beam has a cross-sectional dimension meeting high-precision measurement only near the beam waist, when displacement detection is performed by using the gaussian beam, a bright spot image imaged on the linear array image sensor 132 is too large in most cases where the object plane is far away from the beam waist, so that a large error exists in displacement measurement. Compared with a gaussian beam, the displacement measurement probe 10 provided by the application utilizes a bessel beam to perform displacement measurement, and can ensure that a bright spot image imaged on the linear array image sensor 132 has a consistent small size in a measuring range, so that the displacement measurement error is small, that is, the measurement precision of the displacement measurement probe 10 is high. In the third aspect, when the displacement measurement is performed by using the gaussian beam, if the measurement with high precision is to be satisfied, the measurement range of the displacement measurement is small. If the measurement range is large, the measurement error is small only near the beam waist of the gaussian beam, and the measurement error increases at other positions. Compared with a gaussian beam, the displacement measurement probe 10 provided by the application utilizes the bessel beam to perform displacement measurement, and can have a larger measurement range under the condition of meeting high-precision measurement, for example, 5 times, 10 times or 20 times of the measurement range of the gaussian beam, so that the displacement measurement probe 10 can measure fine step-type object plane displacement with high resolution and simultaneously increase the measurement range. It should be noted that the high resolution means that the size of the bright spot is small, and the resolving power for the horizontal structure of the object plane is strong, and meanwhile, the pixel positioning precision of the bright spot image on the linear array image sensor 132 is high, for example, 1 pixel unit or 1 sub-pixel unit has strong resolving power for the longitudinal displacement of the object plane.
The application provides a displacement measurement probe 10, displacement measurement probe 10 includes beam output subassembly 110, beam conversion subassembly 120 and imaging subassembly 130, first convex cone lens 121 in beam output subassembly 110 will collimated first gaussian beam L11 converts into first Bessel light beam L21 for the transverse dimension that the light beam can keep several microns in longer propagation distance is unchangeable, thereby makes when displacement measurement probe 10 carries out displacement measurement, has improved and has measured the transverse resolution ratio, and has improved the measurement range under the circumstances of keeping longitudinal resolution ratio. Therefore, the displacement measurement probe 10 provided by the application can perform high longitudinal resolution displacement measurement on the object plane of the fine stepped structure with high transverse resolution, and meanwhile, the measurement range is increased.
Referring to fig. 2, fig. 2 is a schematic diagram illustrating that a first convex cone lens in the displacement measurement probe provided in the embodiment of fig. 1 converts a gaussian beam into a bessel beam. In this embodiment, the light beam emitted from the first convex cone lens 121 has a non-diffraction section L211, and the length of the non-diffraction section L211 is proportional to the beam waist radius of the collimated first gaussian light beam L11 and inversely proportional to the base angle of the first convex cone lens 121.
In the present embodiment, the first convex cone lens 121 is disposed at a beam waist of the collimated first gaussian light beam L11, and is configured to convert the collimated first gaussian light beam L11 into the first bessel light beam L21 and emit the first bessel light beam L21. The first bessel light beam L21 has the non-diffraction section L211, that is, the transverse cross-sectional dimension of the first bessel light beam L21 in the non-diffraction section L211 is almost unchanged, so that the displacement measurement accuracy in the non-diffraction section L211 is kept stable and consistent when the displacement measurement probe 10 performs displacement measurement using the first bessel light beam L21. Specifically, the length of the non-diffraction section L211 (see Z0 in fig. 2) is proportional to the beam waist radius of the collimated first gaussian light beam L11 and inversely proportional to the base angle of the first convex cone lens 121. The first convex cone lens 121 includes a substrate and a convex cone structure connected to each other, the substrate is cylindrical, the convex cone structure is supported on the substrate and protrudes in a direction away from the substrate, the convex cone structure is conical, and an included angle formed between an outer contour of the convex cone structure and the substrate is a base angle of the first convex cone lens 121 (please refer to γ 0 in fig. 2). Therefore, the length of the non-diffraction section L211 of the first bessel beam L21 can be changed by adjusting the beam waist radius of the collimated first gaussian beam L11 or replacing the first convex cone lens 121 with a different base angle, thereby changing the displacement measurement range of the displacement measurement probe 10. For example, by increasing the length of the non-diffractive section L211, thereby increasing the displacement measurement range of the displacement measurement probe 10, a large range of displacement measurements is achieved, such as ranges greater than 30mm, greater than 50mm, or greater than 100 mm. It will be appreciated that the displacement measuring probe 10 can not only perform large-scale displacement measurement, but also perform small-scale displacement measurement, for example, a scale of less than 30mm, less than 20mm, or less than 10mm, depending on the application. The displacement measuring range of the displacement measuring probe 10 is not limited in the present application.
In addition, in the present embodiment, the transverse sectional radius of the first bessel beam L21 in the non-diffraction section L211 is inversely proportional to the size of the base angle of the first convex cone lens 121, and therefore, the larger the base angle of the first convex cone lens 121 is, the smaller the transverse sectional radius of the first bessel beam L21 in the non-diffraction section L211 is, that is, the higher the displacement measurement resolution of the displacement measurement probe 10 is.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a beam output assembly provided in one embodiment of the displacement measurement probe provided in the embodiment of fig. 1. In the present embodiment, the beam output assembly 110 includes a laser 111 and a collimator 112. The laser 111 is used to output a second gaussian beam L12. The collimating mirror 112 is spaced apart from the laser 111, and is configured to convert the second gaussian beam L12 into the collimated first gaussian beam L11.
In this embodiment, the laser 111 is used to output the second gaussian light beam L12, and the collimating mirror 112 is used to convert the second gaussian light beam L12 into the collimated first gaussian light beam L11, so that the collimated first gaussian light beam L11 has a smaller divergence angle than the second gaussian light beam L12 within a certain transmission distance. In addition, the position of the beam waist of the second gaussian light beam L12 output by the laser 111 is not easy to determine, and after the second gaussian light beam L12 is converted into the collimated first gaussian light beam L11 by the collimating mirror 112, the beam waist of the collimated first gaussian light beam L11 can be determined by the collimating mirror 112, so as to facilitate the setting of other devices.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a beam output assembly provided in another embodiment of the displacement measurement probe provided in the embodiment of fig. 1. In the present embodiment, the beam output assembly 110 includes a laser 111, a focusing lens 113, an aperture 114, and a collimator 112. The laser 111 is used to output a second gaussian beam L12. The focusing lens 113 is spaced apart from the laser 111 for converting the second gaussian beam L12 into a converging third gaussian beam L13. The aperture 114 is disposed at the focal plane of the focusing lens 113 and is used for transmitting the converged third gaussian light beam L13 to form a divergent fourth gaussian light beam L14. The collimating mirror 112 and the diaphragm 114 are arranged at an interval, and a front focus of the collimating mirror 112 is arranged at an opening of the diaphragm 114, and is used for converting the divergent fourth gaussian light beam L14 into a collimated first gaussian light beam L11.
In this embodiment, the laser 111 is used to output the second gaussian light beam L12, and the second gaussian light beam L12 is converted into the converged third gaussian light beam L13 by the focusing lens 113, and the third gaussian light beam L13 is focused to the opening of the diaphragm 114. The opening of the diaphragm 114 refers to a region where the diaphragm 114 has translucency. The converged third gaussian light beam L13 passes through the diaphragm 114 to form the diverged fourth gaussian light beam L14. The collimating mirror 112 and the diaphragm 114 are disposed at an interval, and a front focus of the collimating mirror 112 is disposed at an opening of the diaphragm 114, that is, a focus point of the third gaussian light beam L13 coincides with the front focus of the collimating mirror 112. The collimator lens 112 is used to transform the diverging fourth gaussian light beam L14 into the collimated first gaussian light beam L11 tending to be parallel. The focusing lens 113 and the diaphragm 114 cooperate to convert the second gaussian light beam L12 emitted from the laser 111 into the fourth gaussian light beam L14, which is divergent, so as to facilitate the collimating mirror 112 to output the collimated first gaussian light beam L11.
Referring to fig. 5, fig. 5 is a schematic structural diagram of a light beam conversion assembly in an embodiment of the displacement measurement probe provided in the embodiment of fig. 4. In this embodiment, the light beam conversion assembly 120 further includes a concave cone lens 123 and a second convex cone lens 122. The concave cone lens 123 is disposed near the beam output assembly 110 opposite to the first convex cone lens 121 for converting the collimated first gaussian beam L11 into a divergent annular hollow beam L41. The second convex cone lens 122 is disposed between the concave cone lens 123 and the first convex cone lens 121, the convex cone structure of the second convex cone lens 122 is disposed opposite to the concave cone structure of the concave cone lens 123, a base angle γ 2 of the convex cone structure of the second convex cone lens 122 is equal to a base angle γ 1 of the concave cone structure of the concave cone lens 123, and the second convex cone lens 122 is configured to convert the divergent annular hollow light beam L41 into a collimated annular hollow light beam L42 and emit the collimated annular hollow light beam to the first convex cone lens 121.
In this embodiment, the concave cone structure of the concave cone lens 123 is opposite to the convex cone structure of the second convex cone lens 122, the concave cone lens 123 is disposed close to the light beam output assembly 110 relative to the second convex cone lens 122, the second convex cone lens 122 is disposed between the concave cone lens 123 and the first convex cone lens 121, and the convex cone structure of the second convex cone lens 122 is opposite to the convex cone structure of the first convex cone lens 121.
In this embodiment, the concave cone lens 123 is configured to receive the collimated first gaussian light beam L11 emitted through the light beam output assembly 110, wherein the concave cone lens 123 is disposed at the beam waist of the collimated first gaussian light beam L11, and the concave cone lens 123 is configured to convert the collimated first gaussian light beam L11 into the divergent annular hollow light beam L41 and emit the divergent annular hollow light beam L41 to the second convex cone lens 122. The second convex cone lens 122 converts the diverging annular hollow light beam L41 into the collimated annular hollow light beam L42 and emits to the first convex cone lens 121. The first convex cone lens 121 is used for converting the collimated annular hollow light beam L42 into the first bessel light beam L21 and emitting the first bessel light beam, so that the working distance of the displacement measuring probe 10 is increased without changing the size of the first convex cone lens 121.
In fig. 5, the grid lines are schematically shown as light beams.
Referring to fig. 6, fig. 6 is a schematic structural diagram of a light beam conversion assembly in another embodiment of the displacement measurement probe provided in the embodiment of fig. 4. In this embodiment, the light beam conversion assembly 120 further includes a third convex cone lens 124 and a second convex cone lens 122. The third convex cone lens 124 is disposed close to the beam output assembly 110 with respect to the first convex cone lens 121 for converting the collimated first gaussian beam L11 into a divergent annular hollow beam L41. The second convex cone lens 122 is disposed between the third convex cone lens 124 and the first convex cone lens 121, the convex cone structure of the second convex cone lens 122 is disposed opposite to the convex cone structure of the third convex cone lens 124, and a base angle γ 2 of the convex cone structure of the second convex cone lens 122 is equal to a base angle γ 3 of the convex cone structure of the third convex cone lens 124. The second convex cone lens 122 is used for converting the divergent annular hollow light beam L41 into a collimated annular hollow light beam L42 and emitting the collimated annular hollow light beam to the first convex cone lens 121.
In this embodiment, the convex cone structure of the third convex cone lens 124 is opposite to the convex cone structure of the second convex cone lens 122, the third convex cone lens 124 is disposed close to the light beam output assembly 110 relative to the second convex cone lens 122, the second convex cone lens 122 is disposed between the third convex cone lens 124 and the first convex cone lens 121, and the convex cone structure of the second convex cone lens 122 is opposite to the convex cone structure of the first convex cone lens 121.
In this embodiment, the third convex cone lens 124 is configured to receive the collimated first gaussian light beam L11 emitted through the light beam output assembly 110. The third convex cone lens 124 is disposed at the beam waist of the collimated first gaussian light beam L11, and the third convex cone lens 124 is configured to convert the collimated first gaussian light beam L11 into the divergent annular hollow light beam L41 and emit the divergent annular hollow light beam to the second convex cone lens 122. The second convex cone lens 122 converts the diverging annular hollow light beam L41 into the collimated annular hollow light beam L42 and emits to the first convex cone lens 121. The first convex cone lens 121 is used for converting the collimated annular hollow light beam L42 into the first bessel light beam L21 and emitting the first bessel light beam, so that the working distance of the displacement measuring probe 10 is increased without changing the size of the first convex cone lens 121.
In fig. 6, the grid lines are schematically shown as light beams.
Referring to fig. 7, fig. 7 is a schematic structural diagram of the displacement measurement probe according to the embodiment of fig. 5. In the present embodiment, the second convex axicon lens 122 is fixed relative to the first convex axicon lens 121 in a plane defined by the first bessel light beam L21 and the optical axis 1311, and the second convex axicon lens 122 and the first convex axicon lens 121 are movable in a direction of a line connecting the first convex axicon lens 121 and the second convex axicon lens 122. The imaging lens 131 is movable in a radial direction of the imaging lens 131. The line image sensor 132 may be moved in a radial direction of the line image sensor 132. It should be noted that the structure of the displacement measurement probe 10 according to the present embodiment may be based on the embodiment of fig. 5 or the embodiment of fig. 6, and it is understood that the displacement measurement probe 10 according to the embodiment of fig. 7 is schematically described, and the displacement measurement probe 10 according to the present embodiment is not limited thereto.
In the present embodiment, the second convex axicon lens 122 and the first convex axicon lens 121 are relatively fixed in a plane defined by the first bessel beam L21 and the optical axis 1311, and the second convex axicon lens 122 and the first convex axicon lens 121 are movable in the first direction M1 to adjust the working distance of the displacement measuring probe 10. Specifically, when the second convex axicon lens 122 and the first convex axicon lens 121 move in the first direction M1 toward the direction away from the first convex axicon lens 121, the working distance of the displacement measurement probe 10 can be reduced. When the second convex axicon 122 and the first convex axicon 121 move toward the first convex axicon 121 along the first direction M1, the working distance of the displacement measuring probe 10 can be increased. The first direction M1 is a connecting line direction of the center of the first convex conical lens 121 and the center of the second convex conical lens 122.
In the present embodiment, when the second convex axicon lens 122 and the first convex axicon lens 121 move in the first direction M1 in a plane determined by the first bessel beam L21 and the optical axis 1311, the corresponding imaging lens 131 moves in the second direction M2, so that the optical axis 1311 of the imaging lens 131 remains to have no diffracted portion passing through the first bessel beam L21. The respective line image sensors 132 are moved in the third direction M3 such that the line image sensors 132 are located on the optical axis 1311 of the imaging lens 131. Wherein the second direction M2 is a radial direction of the imaging lens 131, and the third direction M3 is a radial direction of the line image sensor 132.
The embodiment of the application also provides a measuring device 1. Referring to fig. 1 and 8, fig. 8 is a schematic structural diagram of a measurement apparatus according to an embodiment of the present disclosure. In this embodiment, the measuring device 1 includes a data processor 20 and a displacement measuring probe 10 as provided in any of the above embodiments. The displacement measurement probe 10 is used for outputting a first bessel beam L21 and imaging a bright spot formed by irradiating the first bessel beam L21 on the object surface W1. The data processor 20 is electrically connected to the linear array image sensor 132, and is configured to receive the bright spot image data formed by the bright spot on the linear array image sensor 132, and calculate the displacement of the object plane W1 to be measured according to the bright spot image data. The data processor 20 is also electrically connected to the beam output assembly 110, and is configured to control the beam output assembly 110 to output a collimated first gaussian beam L11 with power varying with the object plane reflectivity.
In the present embodiment, the data processor 20 is electrically connected to the beam output device 110 to control the beam output device 110 to output the collimated first gaussian beam L11, and control the power of the collimated gaussian beam L11 to vary with the object plane reflectivity. The data processor 20 is further electrically connected to the line array image sensor 132, so as to receive the image data of the bright spots formed by the bright spots on the line array image sensor 132, and according to the pixel unit position on the linear array image sensor 132 corresponding to the bright spot image, calculating a distance x0 between the pixel unit where the bright spot image is located and the pixel unit where the imaging reference point 1321 of the linear array image sensor 132 is located, and calculating a distance y0 between the object plane W1 and the reference plane W0 or a distance y1 between the displacement measurement probe 10 and the object plane W1 according to a distance between the lens center 1312 of the imaging lens 131 and the beam waist of the first bessel beam L21, the lens center 1312 of the imaging lens 131 and the imaging reference point 1321 of the line image sensor 132, the first angle, the second angle, and the hot spot image. Specifically, the distance between the reference plane W0 and the displacement measuring probe 10 is d0, the distance between the lens center 1312 of the imaging lens 131 and the intersection of the optical axis 1311 and the first bessel beam L21 is d1, the distance between the imaging reference point 1321 of the line image sensor 132 and the lens center 1312 of the imaging lens 131 is d2, the first angle is α, the second angle is β, and the distance between the speckle image and the imaging reference point 1321 of the line image sensor 132 is x 0. The imaging of the bright spots to the line image sensor 132 via the imaging lens 131 conforms to the schemer's law. When the object plane W1 is closer to the displacement measurement probe 10 than the reference plane W0, that is, the speckle image is farther from the light beam conversion assembly 120 than the imaging reference point 1321 of the line image sensor 132, the distance y0 between the object plane W1 and the reference plane W0 can be calculated according to a first formula. Wherein, the first formula is y0= (x0 × d1 × sin β)/[ d2 × sin α + x0 × sin (α + β) ], so that the distance y1= d0-y0 between the object plane W1 and the displacement measuring probe 10. When the object plane W1 is farther from the displacement measurement probe 10 than the reference plane W0, that is, the speckle image is closer to the light beam conversion assembly 120 than the imaging reference point 1321 of the line image sensor 132, the distance y0 between the object plane W1 and the reference plane W0 can be calculated by formula two. Wherein, the formula two is y0= (x0 × d1 × sin β)/[ d2 × sin α -x0 × sin (α + β) ], and then the distance y1= d0+ y0 between the object plane W1 to be measured and the displacement measuring probe 10. The distance between the bright spot image and the imaging reference point 1321 of the line image sensor 132 refers to a distance between a pixel unit where a central bright peak of the bright spot image is located and a pixel unit where the imaging reference point 1321 of the line image sensor 132 is located. The imaging reference point 1321 of the line image sensor 132 is a position of the speckle image on the line image sensor 132 when the displacement measurement probe 10 detects the reference surface W0.
Compared with the traditional device which adopts the Gaussian beam to measure the displacement, the image of the bright spot formed by the Gaussian beam on the object plane on the linear array image sensor usually occupies a plurality of pixel units, so that a large error exists in the position calculation of the image of the bright spot, and the error of the displacement measurement is large. The displacement measurement device 1 provided by the application adopts the Bessel light beam to carry out displacement measurement, and in a measuring range, a bright spot image formed by a bright spot formed on an object surface by the Bessel light beam on the linear array image sensor 132 usually occupies 1 pixel unit or 1 sub-pixel unit, so that the error of position calculation of the bright spot image is reduced, and the displacement measurement precision is improved.
The application provides a measuring device 1 adopts the Bessel beam to carry out distance measurement, compares in adopting the Gaussian beam to carry out displacement measurement, and the measuring device 1's that this application provided range improves by a wide margin, and measurement accuracy is high.
The embodiment of the application also provides a displacement measurement method. Referring to fig. 1, fig. 2 and fig. 9, fig. 9 is a flowchart of a displacement measurement method according to an embodiment of the present disclosure. In the present embodiment, the displacement measurement method includes projecting the first bessel beam L21 having an elongated needle shape without diffraction characteristics on the object plane W1 to form a bright spot having a very small cross-sectional diameter. And acquiring a bright spot image formed by the bright spot on the linear array image sensor 132. And extracting the precise position information of the center of the bright spot image on the linear array image sensor 132 by adopting an image processing method. And calculating the displacement of the object plane W1 to be measured by adopting a triangulation distance measuring principle according to the position information of the bright spot image.
In the present embodiment, the optical distance measurement is performed using the measuring apparatus 1 as described in the foregoing embodiments. Specifically, the displacement measurement method includes steps S10, S20, S30, and S40. The steps S10, S20, S30 and S40 are described in detail next.
S10, the first bessel beam L21 having an elongated needle shape without diffraction characteristics is projected on the object plane W1, and a bright spot having a very small cross-sectional diameter is formed.
In the present embodiment, the object plane W1 and the measuring apparatus 1 according to the above embodiments are provided, and the displacement measuring probe 10 is disposed toward the object plane W1. Specifically, the first convex cone lens 121 is disposed toward the object plane W1, and the displacement measurement probe 10 converts the collimated first gaussian beam L11 into the first bessel beam L21 through the first convex cone lens 121 in the beam conversion assembly 120, and emits the first bessel beam L3526 to the object plane W1 to form a bright spot. The first bessel light beam L21 has a non-diffraction characteristic and is in a shape of an elongated needle, and the object plane W1 is disposed in the non-diffraction section L211 of the first bessel light beam L21 emitted by the first convex cone lens 121, so that the first bessel light beam L21 can form a bright spot with a very small cross-sectional diameter on the object plane W1 to ensure the measurement accuracy of the measurement apparatus 1. For example, the cross-sectional diameter of the non-diffractive section L211 of the first bessel beam L21 may be, but is not limited to, 1 μm, 2.2 μm, or 3.5 μm, etc., the length of the non-diffractive section L211 of the first bessel beam L21 may be, but is not limited to, 30mm, 44mm, or 53mm, etc., and the cross-sectional diameter of the bright spot may be, but is not limited to, 1.4 μm, 2.5 μm, or 3.8 μm, etc.
And S20, acquiring a bright spot image formed by the bright spot on the linear array image sensor 132.
In the present embodiment, the bright spots form a bright spot image on the line image sensor 132.
And S30, extracting the precise position information of the center of the bright spot image on the linear array image sensor 132 by adopting an image processing method.
And S40, calculating the displacement of the object plane W1 to be measured by adopting a triangular distance measurement principle according to the position information of the bright spot image.
According to the distance between the bright spot image and the imaging reference point 1321, the displacement of the object plane W1 to be measured can be calculated by adopting a triangulation distance measurement principle. The reference plane W0 corresponds to a reference position for calculating the displacement of the object plane W1, and the imaging reference point 1321 corresponds to a position of the speckle image on the line image sensor 132 when the displacement measuring probe 10 detects the reference plane W0.
Regarding the precise position information extraction of the speckle image on the line image sensor 132, in an embodiment, since the diameter of the central bright peak of the speckle image is small, only one pixel unit is occupied on the line image sensor 132, the data processor 20 may directly calculate the distance between the speckle image and the pixel unit where the imaging reference point 1321 of the line image sensor 132 is located according to the position of the pixel unit where the center of the speckle image is located, and further calculate the displacement distance of the object plane W1 from the reference plane W0.
In another embodiment, referring to fig. 10, fig. 10 is a flowchart illustrating a displacement measurement algorithm in the displacement measurement method according to the embodiment of fig. 9. The image processing method is adopted to extract the precise position information of the center of the bright spot image on the linear array image sensor 132. "comprises identifying a central bright peak and a plurality of secondary bright peaks on both sides from the bright spot image. And performing fitting calculation on the light intensity distribution of the central bright peak and the multiple sub-bright peaks at two sides to obtain super-resolution point location information of the central bright peak of the bright spot image.
In the present embodiment, steps S31 and S32 are included according to the precise position information of the center of the speckle image on the line image sensor 132.
And S31, identifying the central bright peak and a plurality of secondary bright peaks at two sides according to the bright spot image.
In the present embodiment, since the light spot distribution of the bessel beam appears as a central circular bright spot and surrounds a series of concentric weak bright rings, the bright spot image appears as a central bright peak image surrounded by a series of sub-bright peaks on both sides on the pixel unit of the line image sensor 132. The data processor 20 can identify the light intensity distribution of the central bright peak and the multiple sub-bright peaks at two sides of the bright spot image according to the bright spot image, and draw the light intensity distribution graph of the bright spot image, wherein the light intensity distribution graph comprises the central bright peak with the strongest light intensity and the multiple sub-bright peaks with the weaker light intensity.
And S32, performing fitting calculation on the light intensity distribution of the central bright peak and the multiple sub-bright peaks at the two sides to obtain the super-resolution point location information of the central bright peak of the bright spot image.
In this embodiment, fitting calculation is performed according to the point location and the light intensity on the pixel unit corresponding to the central bright peak in the light intensity distribution diagram, and the point locations and the light intensities on the pixel unit corresponding to the plurality of sub-bright peaks, so as to calculate light intensity distribution fitting curves of different point locations of the bright spot image on the same pixel unit, and further select a maximum value of the light intensity distribution fitting curves to determine the point location of the central bright peak of the bright spot image. Usually, the pixel unit corresponding to the maximum value of the light intensity distribution map in the light intensity distribution map is the central bright peak point position of the bright spot image, but only which pixel unit the central bright peak point position of the bright spot image is located in can be obtained according to the light intensity distribution map. Compared with the method for calculating the central bright peak position of the bright spot image according to the light intensity distribution graph, the method for determining the central bright peak position of the bright spot image by adopting the maximum value of the light intensity distribution fitting curve has higher precision. For example, the central bright peak position of the bright spot image is calculated to be located in the 4 th pixel unit by using the light intensity distribution diagram, and the central bright peak position of the bright spot image is calculated to be located in the 4.2 th pixel unit by using the light intensity distribution fitting curve. Therefore, after the light intensity distribution is subjected to fitting calculation, the calculation accuracy of the central bright peak point position information of the bright spot image is higher, so that the displacement measurement accuracy of the object plane W1 to be measured is higher.
Although embodiments of the present application have been shown and described, it is understood that the above embodiments are illustrative and not restrictive, and that those skilled in the art may make changes, modifications, substitutions and alterations to the above embodiments without departing from the scope of the present application, and that such changes and modifications are also to be considered as within the scope of the present application.
Claims (10)
1. A displacement measurement probe, characterized in that it comprises:
a beam output assembly for outputting a collimated first Gaussian beam;
the light beam conversion assembly and the light beam output assembly are arranged at intervals and used for converting the collimated first Gaussian beam into a first Bessel beam and emitting the first Bessel beam to an object surface to be detected, and the light beam conversion assembly comprises a first convex cone lens used for converting the Gaussian beam into the Bessel beam; and
the imaging assembly comprises an imaging lens and a linear array image sensor, a first angle is formed between the optical axis of the imaging lens and the first Bessel light beam, the imaging lens is used for imaging a bright spot formed by the first Bessel light beam irradiating on the object surface to be detected, the linear array image sensor and the imaging lens are arranged at intervals and are arranged at a second angle to the optical axis, the linear array image sensor is used for receiving a bright spot image formed by the imaging lens on the bright spot, and the bright spot image is used for calculating the displacement of the object surface to be detected relative to a reference surface;
wherein the optical axis passes through a middle position of the non-diffraction section of the first bessel beam and the line image sensor, and an extension line of a radial direction of the imaging lens, an extension line of a radial direction of the line image sensor and an extension line of the first bessel beam intersect at a point in a plane determined by the first bessel beam and the optical axis.
2. The displacement measuring probe of claim 1, wherein the beam of light emitted from the first convex axicon has a non-diffractive segment, and wherein a length of the non-diffractive segment is proportional to a beam waist radius of the collimated first gaussian beam and inversely proportional to a base angle of the first convex axicon.
3. The displacement measurement probe of claim 1, wherein the beam output assembly comprises:
a laser for outputting a second Gaussian beam; and
and the collimating mirror is arranged at an interval with the laser and is used for converting the second Gaussian beam into the collimated first Gaussian beam.
4. The displacement measuring probe of claim 1, wherein the beam output assembly comprises:
a laser for outputting a second Gaussian beam;
the focusing lens is arranged at a distance from the laser and is used for focusing the second Gaussian beam into a converged third Gaussian beam;
the opening of the diaphragm is arranged at the focal plane of the focusing lens and is used for transmitting the converged third Gaussian beam to form a divergent fourth Gaussian beam; and
the collimating lens and the diaphragm are arranged at intervals, and the front focus of the collimating lens is arranged at the opening of the diaphragm and used for converting the divergent fourth Gaussian beam into the collimated first Gaussian beam.
5. The displacement measurement probe of claim 1, wherein the beam conversion assembly further comprises:
a concave cone lens disposed proximate to the beam output assembly relative to the first convex cone lens for converting the collimated first Gaussian beam to a diverging annular hollow beam; and
the second convex cone lens, the second convex cone lens is located concave cone lens with between the first convex cone lens, the protruding conical surface structure of second convex cone lens with concave cone lens's sunken conical surface structure sets up relatively, just the base angle of the protruding conical surface structure of second convex cone lens with concave cone lens's sunken conical surface structure's base angle equals, the second convex cone lens be used for with the annular hollow light beam that diverges converts collimating annular hollow light beam and emergent extremely first convex cone lens.
6. The displacement measuring probe of claim 1, wherein the beam conversion assembly further comprises:
a third convex cone lens disposed proximate to the beam output assembly relative to the first convex cone lens for converting the collimated first Gaussian beam to a diverging annular hollow beam; and
the second convex cone lens, the second convex cone lens is located the third convex cone lens with between the first convex cone lens, the protruding conical surface structure of second convex cone lens with the protruding conical surface structure of third convex cone lens sets up relatively, just the base angle of the protruding conical surface structure of second convex cone lens with the base angle of the protruding conical surface structure of third convex cone lens equals, the second convex cone lens be used for with the annular hollow light beam of divergence converts the annular hollow light beam of collimation into and goes out extremely first convex cone lens.
7. The displacement measuring probe according to claim 5 or 6, wherein the second convex axicon lens is fixed relative to the first convex axicon lens in a plane defined by the first Bezier beam and the optical axis, and the second convex axicon lens and the first convex axicon lens are movable in a direction of a line connecting the first convex axicon lens and the second convex axicon lens, the imaging lens is movable in a radial direction of the imaging lens, and the line image sensor is movable in a radial direction of the line image sensor.
8. A measuring device, characterized in that the measuring device comprises:
the displacement measuring probe according to any one of claims 1 to 7, wherein the displacement measuring probe is used for outputting a first Bessel beam and imaging a bright spot formed by the first Bessel beam irradiating on an object surface to be measured; and
the data processor is electrically connected with the linear array image sensor and used for receiving the bright spot image data formed by the bright spots on the linear array image sensor and calculating the displacement of the object surface to be detected according to the bright spot image data, and the data processor is also electrically connected with the light beam output assembly and used for controlling the light beam output assembly to output a first collimated Gaussian light beam with the output power varying with the reflectivity of the object surface.
9. A displacement measuring method, characterized in that the displacement measuring method comprises:
projecting a first Bessel beam with a slender needle shape without diffraction characteristics on the surface of an object to be measured to form a bright spot with a very small cross section diameter;
acquiring a bright spot image formed on the linear array image sensor by the bright spot;
extracting precise position information of the center of the bright spot image on the line array image sensor by adopting an image processing method; and
and calculating the displacement of the object surface to be measured by adopting a triangular distance measurement principle according to the position information of the bright spot image.
10. The displacement measuring method according to claim 9, wherein the extracting the precise position information of the center of the speckle image on the line array image sensor by using an image processing method comprises:
identifying a central bright peak and a plurality of secondary bright peaks at two sides according to the bright spot image; and
and performing fitting calculation on the light intensity distribution of the central bright peak and the multiple sub-bright peaks at two sides to obtain super-resolution point location information of the central bright peak of the bright spot image.
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