CN113251932A - Displacement measurement method integrating confocal method and trigonometry - Google Patents
Displacement measurement method integrating confocal method and trigonometry Download PDFInfo
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- CN113251932A CN113251932A CN202110418490.7A CN202110418490A CN113251932A CN 113251932 A CN113251932 A CN 113251932A CN 202110418490 A CN202110418490 A CN 202110418490A CN 113251932 A CN113251932 A CN 113251932A
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention discloses a displacement measurement method integrating a confocal method and a trigonometry. The existing displacement measurement mode has the contradiction between precision and measuring range. A focusing lens and a position sensitive element are arranged on one side of a probe of a laser confocal displacement sensor, the laser confocal displacement sensor carries out high-precision measurement during measurement to obtain a measured value, a triangulation displacement measurement system also carries out measurement on a laser incidence point, measurement data assist judges whether a measured point is in the range of the laser confocal displacement sensor, if the confocal displacement sensor exceeds the range, the triangulation displacement measurement system obtains the position value of the current measured point, then the position value is used for guiding the Z axis of a three-coordinate measuring machine to move along the direction of the Z coordinate axis, a measuring head device is enabled to return to the range of the laser confocal displacement sensor, and then measurement is continued. The invention can realize the expansion of the measuring range of the laser confocal displacement sensor under the condition of ensuring high-precision measurement.
Description
Technical Field
The invention belongs to the field of non-contact displacement measurement based on optical measurement, and particularly relates to a displacement measurement method integrating a confocal method and a trigonometry.
Background
The confocal displacement measurement is a non-contact displacement measurement method based on spectral dispersion analysis, and the principle is as follows: a beam of white light (or multi-wavelength mixed light) passes through the dispersive objective lens to form continuous monochromatic light focuses on an optical axis, and the distances from each monochromatic light focus to a measured object are different. When the measured surface is at a certain position in the measuring range, only light with a certain wavelength is focused on the measured surface, the reflected light of the light with the wavelength can enter the spectrometer because the light meets the confocal condition, and most of light cannot enter the spectrometer because the light with other wavelengths is in a defocusing state on the measured surface. The wavelength value at the maximum light intensity position is obtained through the decoding of the spectrometer, and the distance value corresponding to the target can be measured.
On the basis, a product of a color coaxial confocal displacement meter developed by KEYENCE company adopts a color light source to replace a white light source for displacement measurement by a traditional confocal method, so that the luminous waveband width is improved, and high-precision measurement can be realized in a wider waveband. The main principle is as follows: firstly, irradiating a beam of blue laser on a fluorescent body capable of simultaneously emitting red light and green light to generate multicolor light, and then transmitting the multicolor light to a probe through an optical fiber; when in light projection, only monochromatic light with a certain specific wavelength in the polychromatic light can be focused at a measured point; when receiving light, only the light focused on the surface of the measured object can be received and transmitted to the optical splitter to be decomposed according to the wavelength to obtain corresponding measured data. The method adopts a straight-up and straight-down measurement method, and can realize high-precision measurement on the surfaces of various objects to be measured, such as curved surfaces, pits and small surface height fluctuation.
However, in the displacement monitoring field, the measurement accuracy and the measurement range are often contradictory. The confocal displacement measurement has a high accuracy but a small range, as developed by KEYENCE: the ultra-high precision displacement meter CL-L015/CL-P015 has a measuring range of 2.6 mm; the shape measurement type displacement meter CL-PT010 has a measuring range of 0.6 mm. Therefore, when the surface of the measured object has a complex shape and large height fluctuation, the confocal displacement measurement will easily cause the over-range phenomenon to terminate the measurement.
Aiming at the problem, the displacement monitoring field has a trigonometry displacement measurement to make up the defect of small measuring range of the confocal displacement sensor. The main principle of trigonometry displacement measurement is as follows: after laser emitted by the laser is converged on the surface of a measured object through the focusing lens, generated diffuse reflection light is received by the receiving lens and converged on a position sensitive element (such as PSD, CMOS, CCD and the like) to form light spots, and a displacement value of the measured point can be obtained according to a triangular relation formed among the measured point, the optical center of the receiving lens and the light spots on the sensitive element. However, the triangulation laser displacement sensor has a larger measurement range but lower measurement accuracy than the confocal displacement sensor, and may not meet the measurement requirements in some cases where high-accuracy detection is required.
In order to solve the contradiction between the measurement accuracy and the measurement range, the current common method is to use a large-range and high-accuracy sensor to perform repeated measurement respectively, such as: firstly, a large-range sensor is used for carrying out primary measurement, and then the data of the primary measurement is used for guiding a high-precision sensor to carry out secondary measurement. The measuring method can solve the contradiction between measuring range and precision to a certain extent, but when the method is applied to a production field, firstly, the production beat is reduced by measuring for many times, the requirement of the production field on the measuring efficiency cannot be met, and the time cost is increased; secondly, sensors with large measuring range and high precision are respectively adopted, two sensors are required to be respectively used, and the measurement cost is increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a displacement measurement method integrating a confocal method and a triangulation method. During measurement, high-precision measurement is carried out through the laser confocal displacement sensor to obtain a final measurement value, meanwhile, the triangulation displacement measurement system also measures a laser incidence point, and measurement data can assist in judging whether a measured point is in the measuring range of the laser confocal displacement sensor in real time (namely, whether the laser confocal displacement sensor generates a defocusing phenomenon). If the confocal displacement sensor exceeds the measuring range, the triangulation displacement measurement system acquires the position value of the current measurement point, and then the position value is used for guiding the Z axis of the three-coordinate measuring machine to move along the direction of the Z coordinate axis, so that the position of the measuring head device on the Z coordinate axis is adjusted, the measuring head device returns to the measuring range of the laser confocal displacement sensor, and then the measurement is continued. The invention can realize the expansion of the measuring range of the laser confocal displacement sensor under the condition of ensuring high-precision measurement.
In order to achieve the purpose, the invention adopts the following technical solutions:
the invention discloses a displacement measurement method integrating a confocal method and a trigonometry, which comprises the following steps:
the method comprises the following steps: constructing a displacement measuring head device integrating a confocal method and a trigonometry; the displacement measuring head device integrating the confocal method and the trigonometry comprises a laser confocal displacement sensor probe, a probe fixing clamp II, a probe fixing clamp I, a measuring head panel, a fixed seat, a position sensitive element, a lens holder and a focusing lens; the first probe fixing clamp and the second probe fixing clamp are fixed and clamp the probe of the laser confocal displacement sensor; and the first probe fixing clamp is fixed with the measuring head panel. The position sensitive element is fixed on the fixed seat, and the fixed seat is fixed with the measuring head panel. The focusing lens is fixed on the lens holding frame, and the lens holding frame is fixed with the measuring head panel. The laser confocal displacement sensor probe is connected with the optical unit and the controller of the laser confocal displacement sensor body to form a laser confocal displacement sensor; measuring light emitted by the probe of the laser confocal displacement sensor is generated by an optical unit of the body of the laser confocal displacement sensor and is transmitted to the probe of the laser confocal displacement sensor through an optical fiber; the central axis of the measuring light emitted by the probe of the laser confocal displacement sensor and the central axis of the focusing lens are positioned in the same plane. And the signal output end of the position sensitive element is connected with the controller. The laser confocal displacement sensor, the focusing lens and the position sensitive element form a triangulation displacement measuring system.
Step two: and fixing the probe panel on the Z axis of the three-coordinate measuring machine, and enabling the central axis of the measuring light emitted by the probe of the laser confocal displacement sensor to be parallel to the Z axis of the three-coordinate measuring machine.
Step three: working range s of position sensitive element in laser confocal displacement sensor measuring range1s2And calibrating the working range of the trigonometry displacement measurement system.
Step four: the object to be measured is placed in the measuring area of the three-coordinate measuring machine platform and a measuring coordinate system is established with X, Y, Z coordinate axes of the three-coordinate measuring machine.
Step five: the Z axis of the three-coordinate measuring machine is translated along the Z coordinate axis, the position of the measuring head panel on the Z coordinate axis is adjusted, so that after the focusing lens focuses the diffuse reflection light on the surface of the measured object, the light spot position point formed on the position sensitive element is at s0And recording the Z coordinate value Z of the Z axis of the three-coordinate measuring machine at the moment0，s0Is the working range s1s2The center position of (a).
Step six: the Z axis of the three-coordinate measuring machine translates along the X or Y coordinate axis direction to drive the laser confocal displacement sensor probe to scan and measure the surface of the measured object; when measuring a point i to be measured, firstly, the output value of a trigonometry displacement measurement system is obtained, and whether a light spot focused by a focusing lens at the point i to be measured is positioned in a range s is judged1s2If it is within range s1s2And storing the coordinate value (X) of the laser confocal displacement sensori,Yi,Zi) Wherein i is 1,2,3 … …, n, n is the total number of points to be measured in the surface scanning measurement process of the measured object; if the light spot focused by the focusing lens at the point i to be measured is positioned in the range s2s2In the' inner part, the Z axis of the three-coordinate measuring machine drives the measuring head panel to move downwards along the Z coordinate axis direction until the position of the light spot focused by the focusing lens returns to the range s1s2Inside and recording the direction of the coordinate axis Z of the three-coordinate measuring machineThe moving distance Deltaz, the coordinate value (X) of the laser confocal displacement sensor is storedi,Yi,Zi- Δ Z), after the storage is finished, moving the Z axis of the three-coordinate measuring machine upwards in the direction of the Z coordinate axis by Δ Z for resetting; if the light spot focused by the focusing lens at the point i to be measured is positioned in the range s1s1In the' inner part, the Z-axis of the three-coordinate measuring machine drives the measuring head panel to move upwards along the Z coordinate axis direction until the position of the focusing light spot of the focusing lens returns to the range s1s2And recording the moving distance delta Z of the three-coordinate measuring machine along the Z coordinate axis direction, and storing the measuring coordinate value (X) of the laser confocal displacement sensor at the momenti,Yi,ZiAnd + delta Z), after the storage is finished, the Z axis of the three-coordinate measuring machine moves downwards along the Z coordinate axis direction by delta Z for resetting.
Step seven: and repeating the point-by-point scanning measurement process of the step six until the scanning measurement of the whole measured object surface is completed.
Preferably, the process of calibrating the working range of the position sensitive element in the measuring range of the laser confocal displacement sensor specifically comprises the following steps:
firstly, the Z axis of the three-coordinate measuring machine translates along the Z coordinate axis, so that the output measurement value of the laser confocal displacement sensor is the measurement range midpoint value h0Recording the spot position point on the position sensitive element at the moment as s0. Then the Z axis of the three-coordinate measuring machine is moved downwards, so that the output measurement value of the laser confocal displacement sensor is the minimum value h of the measuring range1Recording the spot position point on the position sensitive element at the moment as s1。
Moving the three-coordinate measuring machine in the Z-axis direction to make the output measurement value of the laser confocal displacement sensor be the maximum value of the measuring range h2Recording the spot position point on the position sensitive element at the moment as s2Then, the working range of the position sensitive element is determined to be s within the measuring range of the laser confocal displacement sensor1s2。
Preferably, the working range calibration process of the trigonometric displacement measurement system is as follows:
the Z axis of the three-coordinate measuring machine is translated along the Z coordinate axis to make the focusing lens focus on the diffuse reflection of the measured object surfaceAfter the light, forming a light spot on the position sensitive element at the position s0To (3). Then the Z axis of the three-coordinate measuring machine is moved downwards, when the focusing lens focuses the diffuse reflection light on the surface of the measured object, and the light spot formed on the position sensitive element is positioned at the lower limit position point s of the working range of the position sensitive element1' hour, record the distance h of downward movement of the coordinate measuring machine1′。
Moving the three-coordinate measuring machine in Z-axis direction, and focusing the diffuse reflected light on the surface of the measured object by the focusing lens to form light spot in the extreme position point s of the position sensitive element2' hour, record the distance h of upward movement of the coordinate measuring machine2' the maximum working range of the position sensitive element is s1′s2' the working range of the trigonometry displacement measurement system is h ═ h1′-h2′。
Preferably, the output value of the trigonometric displacement measurement system is calculated by using the trigonometric displacement measurement principle, and the calculation formula is as follows:
in the formula, alpha is an included angle between a central axis of measuring light emitted by a probe of the laser confocal displacement sensor and a central axis of the focusing lens; beta is an included angle between the surface of the position sensitive element and the central axis of the focusing lens; l1The output measurement value of the laser confocal displacement sensor is a measuring range midpoint value h0The distance from the center of the time focusing lens to the central axis of the measuring light emitted by the probe of the laser confocal displacement sensor; l2When the spot position point is at s0The distance from the center of the focusing lens to the position point of the light spot; delta s is the spot position point of the measured point on the position sensitive element relative to the spot position point s0The distance of (d); delta h is a middle point value h of a real-time measuring point of the trigonometric displacement measuring system relative to the measuring range of the laser confocal displacement sensor0The distance of (d); setting the measured point as h0When the point is above, plus or minus takes the plus sign, otherwise, plus or minus takes the minus sign.
Preferably, when the laser confocal displacement sensor is out of focus at the near end of the point to be measured, the distance Δ Z of the Z axis of the three-coordinate measuring machine moving up along the Z coordinate axis satisfies the following condition:
Δh-(h1-h0)≤Δz≤Δh+(h0-h2)
preferably, when the laser confocal displacement sensor is out of focus at the far end of the point to be measured, the distance Δ Z of the downward shift of the Z axis of the three-coordinate measuring machine along the Z coordinate axis satisfies the following condition:
Δh-(h0-h2)≤Δz≤Δh+(h1-h0)。
the invention has the beneficial effects that:
1. the invention integrates confocal displacement measurement and triangle displacement measurement, in the actual measurement process, the triangle displacement measurement system is used for judging whether the laser confocal displacement sensor has the over-range phenomenon, and the Z-axis coordinate of the measurement device is adjusted according to the data obtained by the triangle measurement, so that the laser confocal displacement sensor returns to the confocal measurement area, thereby expanding the measurement range of the laser confocal displacement sensor and realizing the rapid and high-precision non-contact measurement of the complex surface with holes, holes and abrupt change structures.
2. The invention has simple measurement principle, lower measurement cost and convenient operation, and is suitable for high-precision and wide-range measurement scenes.
Drawings
Fig. 1 is a perspective view showing the overall structure of a displacement measuring probe device according to the present invention;
FIG. 2 is an assembly view of a first probe mounting fixture and a second probe mounting fixture according to the present invention;
FIG. 3 is a schematic view of the optical path of the displacement measuring probe device of the present invention;
FIG. 4 is a schematic diagram of trigonometric displacement measurement employed in the present invention;
fig. 5 is a schematic workflow diagram of the present invention.
In the figure: 1. the confocal displacement sensor comprises a laser confocal displacement sensor probe 2, probe fixing clamps II and 3, screws 4, probe fixing clamps I and 5, a first bolt group 6, a measuring head panel 6-1, a connecting rod 7, a fixing seat 8, a second bolt group 9, a position sensitive element 10, a third bolt group 11, a lens holder 12 and a focusing lens.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 4 and 5, a displacement measurement method integrating confocal method and triangulation method includes the following steps:
the method comprises the following steps: as shown in fig. 1,2 and 3, a displacement measuring probe device integrating a confocal method and a trigonometry method is constructed; the displacement measurement measuring head device integrating the confocal method and the trigonometry comprises a laser confocal displacement sensor probe 1, a probe fixing clamp II 2, a probe fixing clamp I4, a measuring head panel 6, a fixed seat 7, a position sensitive element 9, a lens holder 11 and a focusing lens 12; the first probe fixing clamp 4 and the second probe fixing clamp 2 are connected through a screw 3 to form a probe fixing clamp and clamp the laser confocal displacement sensor probe 1; the first probe fixing clamp 4 is connected with the measuring head panel 6 through a first bolt group 5. A position sensitive element 9 (the position sensitive element 9 is preferably a linear array CMOS image sensor or a linear array CCD element) is fixed on the fixed seat 7, and the fixed seat 7 is connected with the measuring head panel 6 through a second bolt group 8. The focusing lens 12 is fixed on the lens holder 11, and the lens holder 11 is connected with the stylus face plate 6 (preferably, the stylus face plate 6 is provided with an integrally formed connecting rod 6-1) through the third bolt group 10. The laser confocal displacement sensor probe 1 is connected with an optical unit and a controller of the laser confocal displacement sensor body to form a laser confocal displacement sensor; the measuring light emitted by the laser confocal displacement sensor probe 1 is generated by an optical unit of the laser confocal displacement sensor body and is transmitted to the laser confocal displacement sensor probe 1 through an optical fiber; the central axis of the measuring light emitted by the laser confocal displacement sensor probe 1 and the central axis of the focusing lens 12 are positioned in the same plane. The focusing lens 12 can form light spots on the position sensitive element 9 after focusing the diffuse reflection light on the surface of the measured object; the signal output end of the position sensitive element 9 is connected with the controller. The laser confocal displacement sensor, the focusing lens 12 and the position sensitive element 9 form a triangulation displacement measuring system.
Step two: the measuring head panel 6 is fixed on the Z axis of the three-coordinate measuring machine, and the central axis of the measuring light emitted by the laser confocal displacement sensor probe 1 is parallel to the Z axis of the three-coordinate measuring machine.
Step three: working range s of position sensitive element 9 is calibrated in measuring range of laser confocal displacement sensor1s2And calibrating the working range of the trigonometry displacement measurement system.
Step four: the object to be measured is placed in the measuring area of the three-coordinate measuring machine platform and a measuring coordinate system is established with X, Y, Z coordinate axes of the three-coordinate measuring machine.
Step five: the Z axis of the three-coordinate measuring machine translates along the Z coordinate axis, the position of the measuring head panel 6 on the Z coordinate axis is adjusted, so that after the focusing lens 12 focuses the diffuse reflection light on the surface of the measured object, the position point of the light spot formed on the position sensitive element 9 is at s0And recording the Z coordinate value Z of the Z axis of the three-coordinate measuring machine at the moment0，s0Is the working range s1s2The center position of (a).
Step six: the Z axis of the three-coordinate measuring machine translates along the direction of the X or Y coordinate axis to drive the laser confocal displacement sensor probe 1 to scan and measure the surface of the measured object; when measuring a point i to be measured, firstly, the output value of the triangulation displacement measurement system is obtained, and whether the light spot focused by the focusing lens 12 at the point i to be measured is positioned in the range s is judged1s2If it is within range s1s2And storing the coordinate value (X) of the laser confocal displacement sensori,Yi,Zi) Wherein X isiIs the X coordinate value, Y coordinate value of the point i to be measured in the measuring coordinate systemiIs the Y coordinate value, Z of the point i to be measured in the measuring coordinate systemiThe Z coordinate value of the point i to be measured in the measuring coordinate system is shown, i is 1,2,3 … …, n is the total number of the points to be measured in the surface scanning measuring process of the measured object; if the light spot focused by the focusing lens 12 at the point i to be measured is located in the range s2s2In' interior, the laser confocal displacement sensor probe 1 is considered to be too far away from the surface of the measured objectEnd defocusing) is out of the range of the measuring range, then the Z axis of the three-coordinate measuring machine drives the measuring head panel 6 to move downwards along the Z coordinate axis direction until the light spot position focused by the focusing lens 12 returns to the range s1s2And recording the moving distance delta Z of the three-coordinate measuring machine along the Z coordinate axis direction, and storing the measuring coordinate value (X) of the laser confocal displacement sensor at the momenti,Yi,Zi- Δ Z), after the storage is finished, moving the Z axis of the three-coordinate measuring machine upwards along the Z coordinate axis direction by Δ Z for resetting, and preparing to carry out next point measurement; if the light spot focused by the focusing lens 12 at the point i to be measured is located in the range s1s1In' the laser confocal displacement sensor probe 1 is considered to be too close to the surface of the measured object (near-end defocusing) and exceeds the measuring range, then the Z axis of the three-coordinate measuring machine drives the measuring head panel 6 to move upwards along the Z coordinate axis direction until the focusing lens 12 focuses the light spot position to return to the range s1s2And recording the moving distance delta Z of the three-coordinate measuring machine along the Z coordinate axis direction, and storing the measuring coordinate value (X) of the laser confocal displacement sensor at the momenti,Yi,ZiAnd + delta Z), after the storage is finished, the Z axis of the three-coordinate measuring machine moves downwards along the Z coordinate axis direction by delta Z for resetting, and the next point measurement is prepared.
Step seven: and repeating the point-by-point scanning measurement process of the step six until the scanning measurement of the whole measured object surface is completed.
As a preferred embodiment, the process of calibrating the working range of the position sensitive element 9 within the measuring range of the laser confocal displacement sensor specifically comprises the following steps:
firstly, the Z axis of the three-coordinate measuring machine translates along the Z coordinate axis, so that the output measurement value of the laser confocal displacement sensor is the measurement range midpoint value h0The spot position on the position sensor 9 at this time is recorded as s0. Then the Z axis of the three-coordinate measuring machine is moved downwards, so that the output measurement value of the laser confocal displacement sensor is the minimum value h of the measuring range1(near-end defocus critical point), recording the spot position on the position sensitive element 9 at this time as s1。
Moving the three-coordinate measuring machine in the Z-axis direction to make the laser confocal displacement sensor output measured value as a quantityMaximum of the range h2(far-end defocus critical point), recording the spot position on the position sensitive element 9 at this time as s2Determining the working range of the position sensitive element 9 within the measuring range of the laser confocal displacement sensor as s1s2。
As a preferred embodiment, the working range calibration process of the trigonometric displacement measurement system is as follows:
firstly, the Z axis of the three-coordinate measuring machine translates along the Z coordinate axis, so that after the diffuse reflection light on the surface of the measured object is focused by the focusing lens 12, a light spot position point is formed on the position sensitive element 9 at s0To (3). Then the Z axis of the coordinate measuring machine is moved downwards, when the focusing lens 12 focuses the diffuse reflection light on the surface of the measured object, and the light spot formed on the position sensitive element 9 is positioned at the lower limit position point s of the working range of the position sensitive element 91' hour, record the distance h of downward movement of the coordinate measuring machine1′。
Moving the three-coordinate measuring machine in the Z-axis direction, and when the focusing lens 12 focuses the diffuse reflection light on the surface of the measured object, the light spot formed on the position sensitive element 9 is located at the limit position point s on the working range of the position sensitive element 92' hour, record the distance h of upward movement of the coordinate measuring machine2' then the maximum working range of the position-sensitive element 9 is s1′s2' the working range of the trigonometry displacement measurement system is h ═ h1′-h2′。
As a preferred embodiment, the output value of the trigonometric displacement measurement system is calculated by using the trigonometric displacement measurement principle, and the calculation formula is as follows:
in the formula, α is an included angle between a central axis of the measuring light emitted by the laser confocal displacement sensor probe 1 and a central axis of the focusing lens 12; beta is an included angle between the surface of the position sensitive element 9 and the central axis of the focusing lens 12; l1Output measurement for laser confocal displacement sensorIs a range midpoint value h0The distance from the center of the time focusing lens 12 to the central axis of the measuring light emitted by the laser confocal displacement sensor probe 1; l2When the spot position point is at s0The distance from the center of the focusing lens 12 to the spot position point; Δ s is the spot position point of the measured point on the position sensor 9 relative to the spot position point s0The distance of (d); delta h is a middle point value h of a real-time measuring point of the trigonometric displacement measuring system relative to the measuring range of the laser confocal displacement sensor0The distance of (d); setting the measured point as h0When the point is above, plus or minus takes the plus sign, otherwise, plus or minus takes the minus sign.
As a preferred embodiment, when the laser confocal displacement sensor is out of focus at the near end of the real-time measuring point, the distance Δ Z of the Z axis of the three-coordinate measuring machine moving up along the Z coordinate axis satisfies the following condition:
Δh-(h1-h0)≤Δz≤Δh+(h0-h2)
as a preferred embodiment, when the laser confocal displacement sensor is out of focus at the far end of the real-time measuring point, the distance Delta Z of the Z axis of the three-coordinate measuring machine moving downwards along the Z coordinate axis meets the following condition:
Δh-(h0-h2)≤Δz≤Δh+(h1-h0) 。
Claims (6)
1. a displacement measurement method integrating a confocal method and a trigonometry is characterized in that: the method comprises the following specific steps:
the method comprises the following steps: constructing a displacement measuring head device integrating a confocal method and a trigonometry; the displacement measuring head device integrating the confocal method and the trigonometry comprises a laser confocal displacement sensor probe, a probe fixing clamp II, a probe fixing clamp I, a measuring head panel, a fixed seat, a position sensitive element, a lens holder and a focusing lens; the first probe fixing clamp and the second probe fixing clamp are fixed and clamp the probe of the laser confocal displacement sensor; the first probe fixing clamp is fixed with the measuring head panel; the position sensitive element is fixed on the fixed seat, and the fixed seat is fixed with the measuring head panel; the focusing lens is fixed on the lens holder, and the lens holder is fixed with the measuring head panel; the laser confocal displacement sensor probe is connected with the optical unit and the controller of the laser confocal displacement sensor body to form a laser confocal displacement sensor; measuring light emitted by the probe of the laser confocal displacement sensor is generated by an optical unit of the body of the laser confocal displacement sensor and is transmitted to the probe of the laser confocal displacement sensor through an optical fiber; the central axis of the measuring light emitted by the probe of the laser confocal displacement sensor and the central axis of the focusing lens are positioned in the same plane; the signal output end of the position sensitive element is connected with the controller; the laser confocal displacement sensor, the focusing lens and the position sensitive element form a triangulation displacement measuring system;
step two: fixing a measuring head panel on a Z axis of a three-coordinate measuring machine, and enabling a central axis of measuring light emitted by a probe of a laser confocal displacement sensor to be parallel to the Z axis of the three-coordinate measuring machine;
step three: working range s of position sensitive element in laser confocal displacement sensor measuring range1s2Calibrating the working range of the trigonometry displacement measurement system;
step four: placing a measured object in a measuring area of a three-coordinate measuring machine platform, and establishing a measuring coordinate system by using X, Y, Z coordinate axes of the three-coordinate measuring machine;
step five: the Z axis of the three-coordinate measuring machine is translated along the Z coordinate axis, the position of the measuring head panel on the Z coordinate axis is adjusted, so that after the focusing lens focuses the diffuse reflection light on the surface of the measured object, the light spot position point formed on the position sensitive element is at s0And recording the Z coordinate value Z of the Z axis of the three-coordinate measuring machine at the moment0，s0Is the working range s1s2The center position of (a);
step six: the Z axis of the three-coordinate measuring machine translates along the X or Y coordinate axis direction to drive the laser confocal displacement sensor probe to scan and measure the surface of the measured object; when measuring a point i to be measured, firstly, the output value of a trigonometry displacement measurement system is obtained, and whether a light spot focused by a focusing lens at the point i to be measured is positioned in a range s is judged1s2If it is within range s1s2Interior, thenStoring the measurement coordinate value (X) of the laser confocal displacement sensori,Yi,Zi) Wherein i is 1,2,3 … …, n, n is the total number of points to be measured in the surface scanning measurement process of the measured object; if the light spot focused by the focusing lens at the point i to be measured is positioned in the range s2s′2And when the three-coordinate measuring machine is in the Z-axis direction, the Z-axis of the three-coordinate measuring machine drives the measuring head panel to move downwards along the Z coordinate axis direction until the light spot position focused by the focusing lens returns to the range s1s2And recording the moving distance delta Z of the three-coordinate measuring machine along the Z coordinate axis direction, and storing the measuring coordinate value (X) of the laser confocal displacement sensor at the momenti,Yi,Zi- Δ Z), after the storage is finished, moving the Z axis of the three-coordinate measuring machine upwards in the direction of the Z coordinate axis by Δ Z for resetting; if the light spot focused by the focusing lens at the point i to be measured is positioned in the range s1s′1And when the position of the focusing light spot of the focusing lens returns to the range s, the Z-axis of the three-coordinate measuring machine drives the measuring head panel to move upwards along the Z coordinate axis direction1s2And recording the moving distance delta Z of the three-coordinate measuring machine along the Z coordinate axis direction, and storing the measuring coordinate value (X) of the laser confocal displacement sensor at the momenti,Yi,Zi+ delta Z), after the storage is finished, the Z axis of the three-coordinate measuring machine moves downwards along the Z coordinate axis direction by delta Z for resetting;
step seven: and repeating the point-by-point scanning measurement process of the step six until the scanning measurement of the whole measured object surface is completed.
2. The displacement measurement method of claim 1, which integrates confocal method and trigonometry, wherein: the process of calibrating the working range of the position sensitive element in the measuring range of the laser confocal displacement sensor specifically comprises the following steps:
firstly, the Z axis of the three-coordinate measuring machine translates along the Z coordinate axis, so that the output measurement value of the laser confocal displacement sensor is the measurement range midpoint value h0Recording the spot position point on the position sensitive element at the moment as s0(ii) a Then the Z axis of the three-coordinate measuring machine is moved downwards, so that the output measurement value of the laser confocal displacement sensor is the minimum value h of the measuring range1Recording the position of the light spot on the position-sensitive element at that timePoint is s1；
Moving the three-coordinate measuring machine in the Z-axis direction to make the output measurement value of the laser confocal displacement sensor be the maximum value of the measuring range h2Recording the spot position point on the position sensitive element at the moment as s2Then, the working range of the position sensitive element is determined to be s within the measuring range of the laser confocal displacement sensor1s2。
3. The displacement measurement method of claim 1, which integrates confocal method and trigonometry, wherein: the working range calibration process of the trigonometry displacement measurement system is as follows:
firstly, the Z axis of the three-coordinate measuring machine is translated along the Z coordinate axis, so that after the diffuse reflection light on the surface of the measured object is focused by the focusing lens, the position point of the light spot is formed on the position sensitive element at s0At least one of (1) and (b); then the Z axis of the three-coordinate measuring machine is moved downwards, when the diffuse reflection light of the surface of the measured object is focused by the focusing lens, and the light spot formed on the position sensitive element is positioned at the lower limit position point s 'of the working range of the position sensitive element'1Then, the distance h 'of downward movement of the three-coordinate measuring machine is recorded'1；
Moving the three-coordinate measuring machine in the Z-axis direction, and when the focusing lens focuses the diffuse reflection light on the surface of the measured object, the light spot formed on the position sensitive element is located at the extreme position point s 'on the working range of the position sensitive element'2Then, the upward movement distance h 'of the three-coordinate measuring machine is recorded'2Then the maximum operating range of the position sensitive element is s'1s′2The working range of the trigonometric displacement measurement system is h ═ h'1-h′2。
4. The displacement measurement method of claim 1, which integrates confocal method and trigonometry, wherein: the output value of the triangulation displacement measurement system is obtained by calculation according to the triangulation displacement measurement principle, and the calculation formula is as follows:
in the formula, alpha is an included angle between a central axis of measuring light emitted by a probe of the laser confocal displacement sensor and a central axis of the focusing lens; beta is an included angle between the surface of the position sensitive element and the central axis of the focusing lens; l1The output measurement value of the laser confocal displacement sensor is a measuring range midpoint value h0The distance from the center of the time focusing lens to the central axis of the measuring light emitted by the probe of the laser confocal displacement sensor; l2When the spot position point is at s0The distance from the center of the focusing lens to the position point of the light spot; delta s is the spot position point of the measured point on the position sensitive element relative to the spot position point s0The distance of (d); delta h is a middle point value h of a real-time measuring point of the trigonometric displacement measuring system relative to the measuring range of the laser confocal displacement sensor0The distance of (d); setting the measured point as h0When the point is above, plus or minus takes the plus sign, otherwise, plus or minus takes the minus sign.
5. The displacement measurement method of claim 1, which integrates confocal method and trigonometry, wherein: when the laser confocal displacement sensor is out of focus at the near end of the point to be measured, the upward moving distance delta Z of the Z axis of the three-coordinate measuring machine along the Z coordinate axis meets the following conditions:
Δh-(h1-h0)≤Δz≤Δh+(h0-h2)。
6. the displacement measurement method of claim 1, which integrates confocal method and trigonometry, wherein: when the laser confocal displacement sensor is out of focus at the far end of the point to be measured, the distance delta Z of the Z axis of the three-coordinate measuring machine moving downwards along the Z coordinate axis meets the following conditions:
Δh-(h0-h2)≤Δz≤Δh+(h1-h0)。
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