A method for measuring the micro-motion speed of an object using interference method

Abstract

This invention discloses a method for measuring the micro-motion velocity of an object using interferometry, comprising an interferometric measurement system and a detection mirror. The detection mirror is disposed on the moving end of the object. The interferometric measurement system measures the surface of the detection mirror and records the number of aperture changes and the corresponding counting time. The moving velocity is calculated based on the number of aperture changes and the corresponding counting time: Moving velocity = Number of aperture changes * Half-wavelength size / Air refractive index / Counting time, where the half-wavelength size is the laser wavelength of the interferometric measurement system. This invention enables precise measurement of micro-motion velocities, meeting the requirements of high-precision operating environments.

Description

Technical Field

[0001] This invention relates to the field of micro-velocity measurement technology, specifically to a method for measuring the micro-velocity of an object using interferometry. Background Technology

[0002] Crystal growth generally refers to placing crystal raw materials in the crucible of a crystal growth furnace, melting the crystal raw materials with the furnace's heater, placing a seed crystal at the lower end of a lifting rod, lowering the lifting rod to partially immerse the seed crystal in the molten crystal raw materials, rotating the seed crystal with a rotary motor, and lifting the entire lifting rod frame upwards. The molecules in the crystal raw materials grow on the surface of the seed crystal according to the molecular arrangement in the seed crystal, and the crystal below the seed crystal becomes thicker and longer. After several process stages such as necking, shoulder expansion, shoulder rotation, constant diameter growth, shoulder reduction, and pull-out, a single crystal with qualified geometric shape and internal quality is grown.

[0003] During the growth process described above, many factors affect crystal quality, among which the uniformity of the pulling speed is extremely important. Pulling the rod too slowly or too fast will affect the growth quality.

[0004] Existing speed measurement methods generally use laser interferometers, such as the Renishaw XL-80 laser interferometer and the Agilent 5530 dual-frequency laser interferometer. These methods provide high-performance measurement and calibration for motion systems such as coordinate measuring machines and machine tools through light intensity signals. However, they are still insufficient and unsuitable for environments with slow movement speeds and high requirements for detecting short-term speed fluctuations. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems and provide a method for measuring the micro-motion speed of an object using interferometry, which can accurately measure the micro-motion speed and meet the requirements of high-precision operating environments.

[0006] To address the aforementioned technical problems, this invention provides a method for measuring the micro-motion velocity of an object using interferometry. The method includes an interferometric measurement system and a detection mirror. The detection mirror is positioned on the moving end of the object. The interferometric measurement system measures the surface of the detection mirror and records the number of aperture changes and the corresponding counting time. The moving velocity is calculated based on the number of aperture changes and the corresponding counting time, using the following formula:

[0007] Movement speed = The wavelength dimension is the laser wavelength dimension of the interferometric measurement system.

[0008] Furthermore, within the measurement window of the interferometric measurement system, the initial center position and the offset center position of the aperture are recorded, and the distance b between the initial center position and the offset center position is measured. The initial center position of the aperture is recorded at the beginning of the counting time, and the offset center position of the aperture is recorded at the end of the counting time.

[0009] The measured lifting height h1 is corrected, and the lifting height h1 = Based on the distance b between the initial center position of the aperture and the offset center position of the aperture, the actual lifting height h0 is obtained by correcting using the following formula:

[0010] ;

[0011] The moving speed is calculated based on the actual lifting height h0. Moving speed = lifting height h0 / counting time.

[0012] Furthermore, the object is a lifting rod frame, the inspection mirror is fixedly installed on the top of the lifting rod frame, a lifting rotary motor is installed inside the lifting rod frame, the lifting rotary motor is connected to the crystal lifting rod, the bottom of the crystal lifting rod extends into the crystal growth furnace, the side of the lifting rod frame is connected to the lifting and lifting guide rail, and the lifting and lifting guide rail is connected to the lifting reduction motor.

[0013] Furthermore, when the aperture offset center position changes and reciprocates, a track maintenance reminder is triggered, indicating that the guide rail is vibrating and requires maintenance. The reciprocating movement status is determined by continuously measuring the distance b between the initial aperture center position and the aperture offset center position before and after the change.

[0014] Furthermore, the uniformity of the object's speed during motion can be determined based on the aperture's counting frequency.

[0015] Furthermore, an upper threshold is set for the aperture counting frequency. When the aperture counting frequency exceeds the upper threshold, a track maintenance reminder is triggered, indicating that the guide rail is exhibiting crawling behavior and requires maintenance.

[0016] Furthermore, the detection mirror is a plane mirror, and the surface of the plane mirror is provided with a detection recess.

[0017] Furthermore, the amount of aperture change is measured based on the change in aperture diameter.

[0018] Furthermore, the direction of movement can be determined based on the direction of change of the aperture during the movement. When the distance between the interferometric measurement system and the detection mirror increases, the aperture will contract inward; when the distance between the interferometric measurement system and the detection mirror decreases, the aperture will expand outward. The direction of movement can be determined based on the changes in the contraction and expansion of the aperture.

[0019] Furthermore, an adjustment base is provided between the detection mirror and the moving end of the object. The adjustment base includes a lower fixed plate and an upper adjustment plate. The upper adjustment plate is provided with a mirror body fixing groove. A pressure spring is provided in the middle of the lower fixed plate and the upper adjustment plate. The lower fixed plate is provided with three threaded posts. The upper adjustment plate is provided with three limiting holes. The upper adjustment plate is sleeved on the three threaded posts through the three limiting holes. Locking nuts are provided on both sides of the bottom and top surfaces of the threaded posts. The lower fixed plate is fixedly connected to the moving end of the object. The detection mirror is fixedly installed in the mirror body fixing groove.

[0020] The beneficial effects of this invention are:

[0021] 1. The aperture is very sensitive to changes; even the slightest movement will cause it to narrow or widen. Therefore, it can accurately measure the speed of minute movements. Furthermore, the direction of aperture change is constant, so the direction of movement can be determined. The measurement accuracy can reach speeds within a fraction of a second.

[0022] 2. The speed measurement is obtained by recording the number of aperture changes and then converting the result. Therefore, the uniformity of the actual moving speed can be determined by the speed of aperture changes.

[0023] 3. By monitoring the speed and displacement of aperture changes, abnormal situations during operation can be detected, enabling early detection of equipment problems and significantly reducing maintenance costs. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the speed measuring structure of the present invention;

[0025] Figure 2 This is a schematic diagram of the aperture variation of the present invention;

[0026] Figure 3 This is a schematic diagram of the aperture displacement of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the present invention used in a crystal growth device;

[0028] Figure 5 This is a schematic diagram of the adjusting base structure of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0030] An embodiment of the method for measuring the micro-motion velocity of an object using interferometry according to the present invention includes an interferometric measurement system 11 and a detection mirror 6. The detection mirror is disposed on the moving end of the object. The measured plane of the detection mirror is processed into a low aperture (a plane with concave error). The interferometric measurement system measures the surface of the detection mirror. The interferometric measurement system can capture and image the aperture formed on the surface of the detection mirror. The aperture is an interference ring. During the movement of the object, the shape of the aperture changes, constantly disappearing and forming new apertures. The change of aperture is related to distance. Therefore, recording the number of aperture changes can be converted into the distance between the interferometric measurement system and the detection mirror. Then, the counting time corresponding to the number of aperture changes is recorded. The moving speed can be calculated based on the number of aperture changes and the corresponding counting time, as shown in the following formula:

[0031] Movement speed = The wavelength dimension is the laser wavelength dimension of the interferometric measurement system;

[0032] Specifically, the interferometry system uses a 0.6328-micron helium-neon laser. When the ambient air refractive index is 1.0003, 15 interference rings appear in 10 seconds. Therefore, the velocity of the measured plane is:

[0033] v= =0.4745 micrometers / second = 1.7 millimeters / hour.

[0034] To apply the above-mentioned velocity measurement method to the crystal growth process, the object is the lifting rod frame 14, the detection mirror is fixedly mounted on the top of the lifting rod frame, the lifting rod frame is equipped with a lifting rotary motor 15, the lifting rotary motor is connected to the crystal lifting rod 16, the bottom of the crystal lifting rod extends into the crystal growth furnace 17, the side of the lifting rod frame is connected to the lifting lifting guide rail 18, the lifting lifting guide rail is connected to the lifting reduction motor 19, and the interferometry system is fixed on the four-dimensional adjustment base 12, for reference. Figure 4 As shown, the lifting reduction motor drives the lifting guide rail to move, the lifting guide rail drives the lifting rod frame to move up and down, the lifting rod frame drives the crystal lifting rod to move up and down, and at the same time, the lifting rotation motor also drives the crystal lifting rod to rotate, meeting the crystal growth requirements. And referring to... Figure 1As shown, the aforementioned interferometric measurement system includes a semiconductor laser 1, a condenser lens 2, a beam splitter prism 3, a collimating objective lens 4, and a standard plane mirror 5 arranged sequentially in a straight line. An objective lens is also positioned along the beam splitter prism's direction of beam splitting. The objective lens is mounted on a CCD camera, which is connected to a computer. The semiconductor laser emits monochromatic laser light. The condenser lens converges the small laser beam, which then diverges into a large-aperture beam after passing the focal point. The beam splitter allows light incident from above to exit downwards and light incident from below to reflect to the right. The collimating objective lens converts diverging light into parallel light and parallel light into convergent light. The lower surface of the standard plane mirror is a standard plane, close to an ideal plane. The objective lens, in conjunction with the CCD camera, images the light incident on the object side and displays the image on the computer. The polished surface of the detection mirror has a plane error within the micrometer level, facilitating aperture imaging. Specifically, the laser emitted by the semiconductor laser is focused by a condenser lens and then diverged. After passing through a beam splitter, it is collimated into parallel light by a collimating objective lens. The parallel light is then irradiated onto the measured plane of the detection mirror by a standard plane mirror and reflected back to the standard surface of the standard plane mirror. When the parallelism difference between the two surfaces is within the micrometer level, Newtonian interference fringes will appear. The images are then formed on a CCD by the beam splitter and objective lens.

[0035] The method for measuring the lifting speed based on the above structure involves fixing the detection mirror on top of the lifting rod frame, i.e., on the moving end. The interferometry system is positioned above the detection mirror and fixed to the support via a four-dimensional adjustment frame. The four-dimensional adjustment frame is adjusted so that the light emitted from the interferometry system is parallel to the lifting guide rail and aligned with the detection mirror. Then, the fixed position of the detection mirror is adjusted so that its surface is perpendicular to the incident light. At this point, it can be observed on the computer that the Newtonian interference ring and the shape of the detection mirror displayed in the measurement window of the interferometry system are centrally symmetrical. If asymmetry is not achieved, the position of the detection mirror is adjusted to ensure that the Newtonian interference ring and the shape of the plane mirror are centrally symmetrical. As the lifting rod frame rises and falls, the shape of the Newtonian interference ring and the plane mirror remains centrally symmetrical. Figure 2 As shown, as the lifting rod moves slowly towards the interferometric measurement system (i.e., the measurement distance L decreases), the interference rings expand outward, a new interference ring appears at the center, expands, and disappears from the field of view, repeating this process. Conversely, as the lifting rod moves slowly in the opposite direction of the interferometric measurement system (i.e., the measurement distance L increases), the interference rings contract inward, a new interference ring appears on the outer ring, contractes, and disappears at the center, repeating this process. The direction of movement can be determined through these changes.

[0036] Among them, the number of aperture changes can be measured based on the change in aperture diameter. During the measurement process, the accuracy of aperture counting can be further improved based on the diameter change. The change in aperture can be calculated down to a fraction of a second, so the speed can be measured in fractions of a second. Based on whether the aperture diameter is shrinking or increasing, the direction of aperture change can be quickly determined, so as to quickly determine the direction of movement.

[0037] Reference Figure 3 As shown, due to the inevitable tilt error between the optical path and the moving direction of the object after the installation and debugging of the interferometric measurement system, the outgoing light of the interferometric measurement system and the lifting guide rail can only be relatively parallel. This is unavoidable during assembly and debugging. That is, there is an angle between the optical path direction and the moving direction. During the movement, the deviation between the measured size and the actual size will become larger and larger, and the center of the interference ring will deviate from the center of the plane mirror. In order to further improve the speed measurement accuracy, in the measurement window of the interferometric measurement system, the initial center position of the aperture and the offset center position of the aperture are recorded first, and the distance b between the initial center position of the aperture and the offset center position of the aperture is measured. The initial center position of the aperture is recorded at the beginning of the counting time, and the offset center position of the aperture is recorded at the end of the counting time.

[0038] The measured lifting height h1 was then corrected; lifting height h1 = Based on the distance b between the initial center position of the aperture and the offset center position of the aperture, the actual lifting height h0 is obtained by correcting using the following formula:

[0039] ;

[0040] Finally, the moving speed is calculated based on the actual lifting height h0. Moving speed = lifting height h0 / counting time.

[0041] The performance of the lifting guide rail can be monitored based on changes in the aperture. When the aperture offset center position changes and reciprocating movement occurs, a rail maintenance reminder is triggered, indicating rail vibration and requiring maintenance. The reciprocating movement is determined by continuously measuring the distance 'b' between the initial aperture center position and the aperture offset center position before and after the change. The uniformity of the object's movement speed can also be judged based on the aperture counting frequency. A threshold is set for the aperture counting frequency; when the aperture counting frequency exceeds the threshold, a rail maintenance reminder is triggered, indicating crawling on the guide rail and requiring maintenance. The occurrence of these phenomena provides a basis for guide rail maintenance.

[0042] During the use of the aforementioned inspection mirror, there is a need for multiple adjustments. Therefore, an adjustment base 13 is also provided between the inspection mirror and the moving end of the object, as shown in the reference. Figure 5As shown, the adjustment base includes a lower fixed plate 20 and an upper adjusting plate 21. The upper adjusting plate is provided with a mirror body fixing groove. A pressure spring 23 is provided in the middle of the lower fixed plate and the upper adjusting plate. The lower fixed plate is provided with three threaded posts 24. The upper adjusting plate is provided with three limiting holes. The upper adjusting plate is sleeved on the three threaded posts through the three limiting holes. Locking nuts 25 are provided on both sides of the bottom and top surfaces of the threaded posts. The lower fixed plate is fixedly connected to the moving end of the object. The inspection mirror is fixedly installed in the mirror body fixing groove.

[0043] During adjustment, the pressure spring can always provide a reaction force to the upper adjustment plate, which is limited by the upper locking nut. By adjusting the upper locking nut, the posture can be adjusted. After adjustment, the lower locking nut is locked to fix it and keep its position unchanged during operation. The diameter of the limiting hole is larger than the diameter of the threaded post, thus ensuring that the upper adjustment plate has room for posture adjustment.

[0044] In summary, the growth rate of Czochralski crystals is generally between 0.1 and 5 mm / hour. This invention can measure the instantaneous rising speed and uniformity of the lifting rod during the growth process, and can also monitor the crawling and vibration of the guide rail. It can also be applied to the monitoring of the feed rate and feed depth in micro-feeding machining equipment.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the micro-motion velocity of an object using interferometry, characterized in that, The apparatus includes an interferometric measurement system and a detection mirror. The detection mirror is mounted on the moving end of the object. The interferometric measurement system measures the surface of the detection mirror and records the number of aperture changes and the corresponding counting time. The moving speed is calculated based on the number of aperture changes and the corresponding counting time, using the following formula: Movement speed = The wavelength dimension is the laser wavelength dimension of the interferometric measurement system; Within the measurement window of the interferometric measurement system, record the initial center position and the offset center position of the aperture, and measure the distance b between the initial center position and the offset center position. The initial center position of the aperture is recorded at the beginning of the counting time, and the offset center position of the aperture is recorded at the end of the counting time. The measured lifting height h1 is corrected, and the lifting height h1 = Based on the distance b between the initial center position of the aperture and the offset center position of the aperture, the actual lifting height h0 is obtained by correcting using the following formula: ； The moving speed is calculated based on the actual lifting height h0. Moving speed = lifting height h0 / counting time; The object is a lifting rod frame, and the detection mirror is fixedly installed on the top of the lifting rod frame. A lifting rotary motor is installed inside the lifting rod frame, and the lifting rotary motor is connected to the crystal lifting rod. The bottom of the crystal lifting rod extends into the crystal growth furnace. The side of the lifting rod frame is connected to the lifting and lowering guide rail, and the lifting and lowering guide rail is connected to the lifting reduction motor. When the aperture offset center position changes and reciprocates, a track maintenance reminder is triggered, indicating that the guide rail is vibrating and requires maintenance. The reciprocating movement state is determined by continuously measuring the distance b between the initial aperture center position and the aperture offset center position before and after the change.

2. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 1, characterized in that, The uniformity of an object's speed can be determined by the aperture's counting frequency.

3. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 2, characterized in that, A threshold is set for the aperture counting frequency. When the aperture counting frequency exceeds the threshold, a track maintenance reminder is triggered, indicating that the guide rail is crawling and requires maintenance.

4. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 1, characterized in that, The detection mirror is a plane mirror, and the surface of the plane mirror is provided with a detection recess.

5. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 1, characterized in that, The amount of aperture change is measured based on the change in aperture diameter.

6. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 1, characterized in that, The direction of movement is determined by the change in the aperture during its movement. When the distance between the interferometric measurement system and the detection mirror increases, the aperture will contract inward; when the distance between the interferometric measurement system and the detection mirror decreases, the aperture will expand outward. The direction of movement is determined by the changes in the contraction and expansion of the aperture.

7. The method for measuring the micro-motion velocity of an object using interferometry as described in claim 1, characterized in that, An adjustment base is also provided between the detection mirror and the moving end of the object. The adjustment base includes a lower fixed plate and an upper adjustment plate. The upper adjustment plate is provided with a mirror body fixing groove. A pressure spring is provided in the middle of the lower fixed plate and the upper adjustment plate. The lower fixed plate is provided with three threaded posts. The upper adjustment plate is provided with three limiting holes. The upper adjustment plate is sleeved on the three threaded posts through the three limiting holes. Locking nuts are provided on both sides of the bottom and top surfaces of the threaded posts. The lower fixed plate is fixedly connected to the moving end of the object. The detection mirror is fixedly installed in the mirror body fixing groove.

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