Distance adjustment measurement method and measurement device

Abstract

A distance adjustment measurement method is suitable for use in combination with an object to be measured. The distance adjustment measurement method comprises the following steps. A linear motor drives a laser displacement meter to move. The laser displacement meter continuously detects a distance between the laser displacement meter and the object to be measured to generate and output a sensing signal or an error signal. It is determined whether the distance exceeds a measurement range according to the sensing signal or the error signal. If the distance exceeds the measurement range, the linear motor drives the laser displacement meter to move. If the distance does not exceed the measurement range, the linear motor stops moving the laser displacement meter, and the laser displacement meter performs a depth measurement on a surface to be measured of the object to be measured.

Description

Technical Field

[0001] This case relates to a distance adjustment measurement method, and more particularly to a distance adjustment measurement method and measuring device suitable for adjusting the measurement distance. Background Technology

[0002] In current depth measurement technology, depth sensors can be categorized by their sensing method into contact distance sensors and non-contact distance sensors. Contact distance sensors can be represented by dial indicators. Non-contact distance sensors can be divided into long-range laser interferometers and short-range laser displacement gauges. Dial indicators have a mechanical structure that relies on elasticity to adhere to the object's surface; if the object moves or rotates too quickly, measurement problems may occur. Although laser interferometers offer high precision, they are expensive and require extensive setup, making them less suitable for inspecting various parts on different production lines. Laser displacement gauges, limited by the triangular optical path and the spacing of the sensing strips, only achieve high resolution within a relatively small sensing depth range.

[0003] Therefore, how to provide a measuring device to solve the above problems is an important issue in this field. Summary of the Invention

[0004] This disclosure provides a distance adjustment measurement method suitable for use with an object to be measured. The distance adjustment measurement method includes the following steps: a. A linear motor drives a laser displacement meter to move towards the object to be measured. b. The laser displacement meter continuously detects the distance between the laser displacement meter and the object to be measured to generate and output a sensing signal or an error signal. c. The sensing signal or error signal determines whether the distance between the laser displacement meter and the object to be measured exceeds the measurement range. If it exceeds the measurement range, return to step a; if it does not exceed the measurement range, proceed to the next step. d. The linear motor stops moving the laser displacement meter, and the laser displacement meter performs a depth measurement on the surface of the object to be measured.

[0005] This disclosure provides a measuring device suitable for use with an object to be measured. The measuring device includes a laser displacement meter, a linear motor, and a control system. The laser displacement meter measures the distance between the laser displacement meter and the object to be measured. The linear motor drives the laser displacement meter to move towards the object to be measured, wherein during the movement of the laser displacement meter by the linear motor, the laser displacement meter continuously detects the distance between the laser displacement meter and the object to generate and output a sensing signal or an error signal. The control system determines, based on the sensing signal, whether the distance between the laser displacement meter and the object to be measured exceeds a measurement range. If it exceeds the measurement range, the linear motor continues to drive the laser displacement meter towards the object to be measured. If it does not exceed the measurement range, the linear motor stops moving the laser displacement meter, and the laser displacement meter performs a depth measurement on the surface of the object to be measured.

[0006] In summary, the distance adjustment measurement method and measuring device disclosed in this document utilize a laser displacement meter and a linear motor to precisely position the distance between the laser displacement meter and the object to be measured, thereby adjusting the sensing distance at any initial position to the expected measurement distance, and thus performing accurate depth measurement on the object to be measured. Attached Figure Description

[0007] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the accompanying drawings are described below:

[0008] Figure 1 This is a schematic diagram of a measuring device shown according to some embodiments of this disclosure;

[0009] Figure 2 This is a schematic diagram of the functional blocks of a measuring device according to some embodiments of this disclosure;

[0010] Figure 3 This is a schematic diagram of a portion of the steps in a distance adjustment measurement method according to some embodiments of this disclosure;

[0011] Figure 4 This is a schematic diagram of the functional blocks of an optical encoder, a pulse signal control circuit, and a laser displacement meter, as shown in some embodiments of this disclosure.

[0012] Figures 5A-5B A schematic diagram of a laser displacement meter shown according to some embodiments of this disclosure document;

[0013] Figure 6 This is a schematic diagram of a measuring device shown according to some embodiments of this disclosure.

[0014] Explanation of reference numerals in the attached figures

[0015] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the appended symbols are explained as follows:

[0016] 100: Measuring device

[0017] 110: Linear Motor

[0018] 112: Coil assembly

[0019] 114: Magnet backplate

[0020] 116: Optical slider

[0021] 118: Optical guide rail

[0022] 120,520: Laser displacement meter

[0023] 122: Laser source

[0024] 124,524: Lenses

[0025] 126,526: Lens

[0026] 128,528: Sensors

[0027] 210: Control System 211: Position Controller

[0028] 212: Speed ​​Controller

[0029] 214: Current Controller

[0030] 215: Electrical System Module

[0031] 216: Motor and Mechanical System Module

[0032] 217: Pulse Generation Circuit

[0033] 220: Drive

[0034] 230: Optical encoder

[0035] 240: Monitor

[0036] 300: Distance Adjustment Measurement Method

[0037] 400: Measurement Platform

[0038] Ptri: Periodic trigger signal

[0039] SE: Error signal

[0040] Sm: Motion data signal

[0041] Ic: Motor drive current

[0042] SP1, SP2a, SP2b: Support section

[0043] SP3a, SP3b: Support section

[0044] FS,FSa: Base

[0045] FS2a, FS2b: Base

[0046] BS: Bottom

[0047] Ds: Sensing distance

[0048] Dl: Total length

[0049] Dc: Displacement distance

[0050] Dsum: Distance

[0051] NL: Normal

[0052] Li1, Li2: Incident light

[0053] Lr1, Lr2: Reflected light

[0054] ITEMT: Test Item

[0055] ITEM1, ITEM2: Test objects

[0056] SURT: Surface to be measured

[0057] SURF1, SURF2: Surfaces to be measured

[0058] S310~S380: Steps

[0059] DS: Sensing signal Detailed Implementation

[0060] The following is a detailed description of embodiments with reference to the accompanying drawings. However, the provided embodiments are not intended to limit the scope of this disclosure, and the description of the structural operation is not intended to limit the order of execution. Any structure resulting from the recombination of elements and producing a device with equivalent functionality is within the scope of this disclosure. Furthermore, the illustrations are for illustrative purposes only and are not drawn to their original dimensions. For ease of understanding, the same or similar elements will be designated with the same symbols in the following description.

[0061] Unless otherwise specified, the terms used throughout the specification and claims generally have their ordinary meaning in the context of the art, the disclosure, and the specific content.

[0062] Furthermore, the terms "comprising," "including," "having," "containing," etc., used in this document are all open-ended terms, meaning "including but not limited to." Additionally, the term "and / or" as used in this document includes any one or more of the related listed items and all combinations thereof.

[0063] In this document, when a component is referred to as “coupled” or “coupled,” it may mean “electrically coupled” or “electrically coupled.” “Coupled” or “coupled” can also be used to indicate that two or more components operate or interact with each other. Furthermore, although terms such as “first,” “second,” etc., are used in this document to describe different components, these terms are only used to distinguish components or operations described using the same technical terms.

[0064] Please see Figure 1 and Figure 2 , Figure 1This is a schematic diagram of a measuring device 100 according to some embodiments of this disclosure. The measuring device 100 includes a linear motor 110, a laser displacement sensor 120, an optical slider 116, and an optical guide rail 118. The laser displacement sensor 120 is a surface depth sensor. During the movement of the laser displacement sensor 120 driven by the linear motor 110, the laser displacement sensor 120 continuously senses the distance between itself and the side surface SURT of the object under test (ITEMT) to generate a sensing signal DS or an error signal SE, thereby automatically adjusting the optimal measuring distance between the laser displacement sensor 120 and the ITEMT in different measurement environments. This has the advantage that the laser displacement sensor 120 does not need to be pre-set to the optimal measuring distance of the ITEMT, and the surface shape of the ITEMT can still be depicted in a point-by-point manner, and the surface depth of the ITEMT can be measured at the optimal measuring distance to obtain high-resolution measurement results.

[0065] In some embodiments, the ITEMT (Item to be Tested) can be a part to be inspected after production (e.g., a lens), electronic component, etc., and its surface shape can be regular or irregular. Therefore, this invention is not limited to this. Because the surface shape of the ITEMT can be irregular, the measurer cannot obtain information such as curvature of the irregular shape, and therefore cannot pre-input the moving distance of the laser displacement meter 120 to reach the optimal measurement position.

[0066] The linear motor 110 includes a coil assembly 112 and a magnet backplate 114. The coil assembly 112 is arranged along the Z-axis between support structures SP2a and SP2b. Support structure SP2a is located on one side adjacent to the base FS, and support structure SP2b is located on the other side opposite to the base FS.

[0067] An optical guide rail 118 is disposed on the other side relative to the base FS, and the optical guide rail 118 is disposed along the Z-axis. An optical slider 116 is mounted on the optical guide rail 118, and the optical slider 116 is used to move along the Z-axis on the optical guide rail 118.

[0068] A magnetic backplate 114 is connected to an optical slider 116, and is coupled to an optical rail 118 via the optical slider 116. The magnetic backplate 114 has a magnet and is disposed on an inner side adjacent to the coil assembly 112. The coil assembly 112 can be considered as a stator, and the magnetic backplate 114 as a mover. Electromagnetic induction between the coil assembly 112 and the magnetic backplate 114 generates a linear driving force along the Z-axis, causing the magnetic backplate 114 to move the optical slider 116 coupled to the optical rail 118 along the Z-axis.

[0069] The laser displacement gauge 120 is connected to the optical slider 116 via the support SP1. When the linear motor 110 generates a linear driving force, the laser displacement gauge 120 will be driven by the optical slider 116 to move along the Z-axis. The laser displacement gauge 120 is locked onto the support SP1 according to the designed hole positions. Of course, the structural design of the laser displacement gauge 120 and the support SP1 is not limited to this.

[0070] Continue reading Figure 1 as well as Figure 2 , Figure 2 This is a schematic diagram of the functional blocks of a measuring device 100 according to some embodiments of this disclosure. For example... Figure 2 As shown, the optical slider 116 also includes an optical encoder 230. The optical encoder 230 is positioned on one side of the optical slider 116 facing the optical guide rail 118, and is used to detect the grating on the optical guide rail 118 and output the displacement distance Dc of the optical slider 116. The reference position of the displacement distance Dc at the origin can be determined by the intersection of the extension line of the base FS at the bottom BS and the optical guide rail 118 along the Z-axis.

[0071] The measuring device 100 also includes a control system 210, a driver 220, and a display 240. In some embodiments, the control system 210 may be implemented by a microcontroller, controller, processor, or other processing circuitry, or the driver 220 may be used directly to replace the control system 210.

[0072] The control system 210 continuously receives the displacement distance Dc of the optical slider 116 from the optical encoder 116, and converts the continuously transmitted displacement distance Dc from the optical encoder 116 into the movement rate of the optical slider 116. The control system 210 receives either a sensing signal DS or an error signal SE generated by the laser displacement meter 120 sensing the distance Ds, and generates a periodic trigger signal Ptri to the laser displacement meter 120, causing the laser displacement meter 120 to sense the distance Ds according to the frequency of the periodic trigger signal Ptri. The control system 210 transmits a motion data signal Sm to the driver 210, causing the driver 210 to generate a motor drive current Ic based on the information of the motion data signal Sm, and outputs the motor drive current Ic to the linear motor 110.

[0073] In some embodiments, after the laser displacement meter 120 detects the sensing distance Ds, the control system 210 can record the current displacement distance Dc of the optical slider 116, the sensing distance Ds detected by the laser displacement meter 120, and the total length Dl of the support SP1 and the laser displacement meter 120, and then sum them up to obtain the distance Dsum from the test surface SURF of the test object ITEMT to the bottom BS of the base FS, so as to transmit the sensing distance Ds and the distance Dsum to the display 240 for the user to view.

[0074] Please see Figures 1 to 3 , Figure 3 This is a schematic diagram of steps S310 to S380 of a distance adjustment measurement method 300 according to some embodiments of this disclosure.

[0075] In step S310, the object to be measured is placed on the measuring platform (not shown). Figure 1 ).

[0076] In step S320, the relative positions of the test object ITEMT and the laser displacement meter 120 on the horizontal plane are adjusted. In some embodiments, the measurement platform may be implemented by a machine tool with the function of moving in the X-axis and Y-axis directions to adjust the test point of the test object ITEMT on the test surface SURT to the incident path of the beam Li1 generated by the laser displacement meter 120. In other embodiments, the measuring device 100 further includes a linear module (not shown) that moves along the X-axis and Y-axis to drive the adjustment of the laser displacement meter 120, thereby aligning the test point of the test object ITEMT with the incident path of the beam Li1 generated by the laser displacement meter 120.

[0077] In step S330, the measurement distance is adjusted. The linear motor 110 begins to drive the laser displacement meter 120 to move towards the object to be measured, ITEMT.

[0078] In step S340, the laser displacement meter 120 continuously detects the distance between itself and the object under test (ITEMT). The laser displacement meter 120 generates incident light Li1 onto the test surface SURT of the ITEMT. The incident light Li1 is reflected by the test surface SURT of the ITEMT to form reflected light Lr1. When the laser displacement meter 120 does not receive reflected light Lr1, it means that the current distance Ds between the laser displacement meter 120 and the ITEMT is outside the measurement range of the laser displacement meter 120, and the laser displacement meter 120 generates and outputs an error signal SE. Conversely, when the laser displacement meter 120 receives reflected light Lr1, it means that the current distance Ds between the laser displacement meter 120 and the ITEMT is within the measurement range of the laser displacement meter 120, and a sensing signal DS is generated.

[0079] In step S350, the control system 210 determines whether the distance between the laser displacement meter 120 and the object to be measured (ITEMT) exceeds the measurement range based on the signal transmitted by the laser displacement meter 120. If the laser displacement meter 120 transmits an error signal SE to the control system 210, it is determined that the distance is greater than the measurement range, and the process proceeds to step S362. If the control system 210 receives a sensing signal DS, indicating that the distance falls within the measurement range, the process proceeds to step S372. In some embodiments, the measurement range may be 65–95 mm or 30–120 mm, and the measurement accuracy may be 0.1 μm, 0.2 μm, or other values, depending on the different specifications of the laser displacement meter 120. Therefore, this invention is not limited to these specifications.

[0080] In step S362, the linear motor 110 drives the laser displacement meter 120 to move towards the object under test (ITEMT) at a second rate. In some embodiments, the control system 210 controls the linear motor 110 to drive the laser displacement meter 120 towards or in the opposite direction of the object under test (ITEMT) based on the current position of the optical slider 116. In some embodiments, the second rate is mainly to allow the optical slider 116 and the laser displacement meter 120 to move towards the target position at a faster speed. Therefore, it is set with reference to N2 times the measurement resolution, e.g., the resolution is X mm, and the laser displacement meter response is T seconds. Thus, the moving speed reaches (1 / laser displacement meter response) * resolution * N2 = second rate, where N2 is a second coefficient between 1 and 200. Following step S340, the laser displacement meter 120 continuously detects the distance between itself and the object under test (ITEMT).

[0081] In step S372, the user confirms whether a precise measurement distance needs to be input. The control system 210 determines whether the sensing distance Ds meets the specifications of the laser displacement meter 120's measurement range. For example, if the sensing distance Ds falls within the range of 65-95 mm or 30-120 mm, it means it falls within the measurement range. The user can then choose whether to input a precise measurement distance, allowing the laser displacement meter 120 to more accurately reach the optimal measurement target position. If the user selects "yes," the process proceeds to step S373, meaning the user needs to continue moving the laser displacement meter 120 to the optimal precise measurement distance for the best measurement result. If the user selects "no," the process proceeds to step S374, meaning the user no longer needs to move the laser displacement meter 120, as its current position is sufficient for precise measurement.

[0082] In step S373, the control system 210 determines whether the difference between the sensing distance Ds and the precise measurement distance is zero. If yes, proceed to step S374; otherwise, proceed to step S378. In step S373, when the difference is 0, it means that the sensing distance Ds equals the precise measurement distance, that is, the measurement position required by the user has been reached, and proceed to step S374. If the difference is not 0, it means that the laser displacement meter 120 still needs to move to reach the measurement position required by the user, therefore, proceed to step S378.

[0083] In step S378, the control system 210 controls the linear motor 110 to move the laser displacement meter 120 at a first rate based on the difference between the sensing distance Ds measured by the laser displacement meter 120 and the precise measurement distance, and then returns to step S373 for closed-loop control. Since the user needs to continue moving the laser displacement meter 120 to the precise measurement distance in step S378, the first rate is mainly achieved by slow and high-precision control to reach the target position. Therefore, it can be referenced to N1 times the measurement resolution, where EX: resolution Y mm, and the response of the laser displacement meter 120 is T s. Thus, the first rate = (1 / laser displacement meter response) * resolution * N1, where N1 is a first coefficient between 1 and 0.01, and the first coefficient (N1) is not equal to and less than the second coefficient (N2).

[0084] For a clearer explanation of step S378, please refer to the following: Figure 4 , Figure 4 This is a schematic diagram of the functional blocks of an optical encoder 230, a control system 210, a laser displacement meter 120, and a driver 220, as shown in some embodiments of this disclosure. The optical encoder 230, control system 210, laser displacement meter 120, and driver 220 form a closed-loop cycle. In the control system 210, the position controller 211 generates a position control signal to the speed controller 212 based on the difference between the precisely measured distance Dref and the sensing distance Ds measured by the laser displacement meter 120. The speed controller 212 generates a current signal i through a current controller 214 and an electrical system module 215. The motor and mechanical system module 216 generates a motion data signal Sm to the driver 220 based on the current signal i. Therefore, the driver 220 generates a motor drive current Ic to drive the linear motor 110. The pulse generation circuit 217 generates a periodic trigger signal Ptri to the laser displacement meter 120 based on the motion data signal Sm, causing the laser displacement meter 120 to continuously detect and output the sensing distance Ds according to the frequency of the periodic trigger signal Ptri. The sensing distance Ds is fed into the position controller 211 after the difference between the position loop and the precise measurement distance Dref is generated.

[0085] In step S378, the control system 210 can also compare the difference between the sensing distance Ds and the precise measurement distance Dref with a threshold, and thus adjust the first moving speed of the linear motor 110. More specifically, by comparing the difference with the threshold, if the difference is greater than the threshold, it indicates a large difference between the sensing distance Ds and the precise measurement distance Dref. The control system 210 then increases the first coefficient, allowing the linear motor 110 to move the laser displacement meter 120 at a faster speed. Conversely, if the difference is less than the threshold, it indicates a very small difference between the sensing distance Ds and the precise measurement distance Dref. The control system 210 then decreases the first coefficient, causing the linear motor 110 to move the laser displacement meter 120 at a slower speed.

[0086] In some embodiments, the sampling rate of the control system 210 is 1 kHz. In other embodiments, the sampling rate of the control system 210 is 100 Hz to 4 MHz. Therefore, this invention is not limited thereto.

[0087] In step S374, the movement of the laser displacement meter 120 driven by the linear motor 110 is paused. Step S374 occurs because, in step S372, the user selected not to input the precise measurement distance, or because, in step S378, the laser displacement meter has completed its movement at the first rate. In both cases, it indicates that the sensed distance Ds has reached the precise measurement distance, and the control system 210 pauses / stops the movement of the laser displacement meter 120 driven by the linear motor 110, and proceeds to step S376.

[0088] In step S376, the laser displacement meter 120 detects the SURT surface of the ITEMT. After the control system 210 pauses / stops the movement of the laser displacement meter 120 driven by the linear motor 110, the laser displacement meter 120 is used to detect the surface roughness / surface smoothness of the ITEMT.

[0089] In some embodiments, step S376 may follow step S320 to adjust the position of the test object ITEMT on the horizontal plane, thereby detecting the next test point. In some embodiments, step S376 may follow step S380 to end the measurement.

[0090] Please see Figure 5A The laser displacement meter 120 is a scattering displacement meter, comprising a laser source 122, a lens 124, a lens 126, and a sensor 128. The laser source 122 generates incident light Li1 along the normal NL direction to the side surface SURF1 of the object to be measured, ITEMT1. The incident light Li1 is reflected by the side surface SURF1, generating reflected light Lr1. The reflected light Lr1 is transmitted to the sensor 128 via the lens 124 and the lens 126. This scattering displacement meter is suitable for measuring rough surfaces.

[0091] Please see Figure 5B This is a schematic diagram of a laser displacement meter 520 according to some embodiments of this disclosure. The laser displacement meter 520 is a reflective displacement meter, comprising a laser source 522, a lens 524, a lens 526, and a sensor 528. The laser source 522 generates incident light Li2, which is incident on the surface SURF2 at an incident angle θi. The incident light Li2 is reflected by the surface SURF2, resulting in reflected light Lr2. The reflected light Lr2 propagates through the lens 524 and lens 526 at a reflection angle θr to the sensor 528, where the incident angle θi is equal to the reflection angle θr. This reflective displacement meter is suitable for measuring glass surfaces or highly reflective surfaces. Both laser displacement meters 120 and 520 use the absence of received reflected light Lr1 as the basis for outputting an error signal SE.

[0092] Figure 6 This is a schematic diagram of a measuring device 100 shown according to some embodiments of this disclosure. Figure 6 In the embodiment, the laser displacement meter 520 corresponds to Figure 5B The laser displacement meter 520 is used in this application. Figure 6 The linear motor 110, optical slider 116, and optical guide rail 118 in the measuring device are respectively similar to Figure 1 The linear motor 110, optical slider 116, and optical guide rail 118 are included. Therefore, they will not be described in detail here.

[0093] In summary, the measuring device 100 provided in this disclosure, utilizing laser displacement meters 120 and 520 and a linear motor 110, is suitable for measuring the sensing distance Ds from any initial position, and for quickly and accurately positioning the laser displacement meters 120 and 520 towards the object under test (ITEMT) by adjusting their different forward speeds, thus enabling precise measurement of the ITEMT. In this way, the distance between the ITEMT and the laser displacement meters 120 and 520, the surface shape of the ITEMT, and the surface depth of the ITEMT can still be measured accurately and quickly without the need for pre-setting the correct measurement position.

[0094] Although this disclosure has been described above with reference to embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make various modifications and refinements without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the appended claims.

Claims

1. A distance adjustment measurement method, suitable for use with an object to be measured, comprising the following steps: a. The linear motor drives the laser displacement meter to move toward the object to be measured at a second speed; b. The laser displacement sensor continuously detects the distance between the laser displacement sensor and the object to be measured to generate and output a sensing signal or an error signal, wherein, The error signal is output when the laser displacement meter does not receive reflected light from the object under test; c. Determine whether the distance exceeds the measurement range based on the sensing signal or the error signal. If it exceeds the measurement range, return to step a; otherwise, proceed to the next step. as well as d. The linear motor drives the laser displacement meter to move at a first rate until the sensing distance and the precise measurement distance are a difference, wherein the first rate is less than the second rate; and the laser displacement meter performs a depth measurement on a surface of the object to be measured.

2. The distance adjustment measurement method according to claim 1, wherein the first rate is equal to (1 / laser displacement meter response). Resolution The product of the first coefficients, the second rate equals (1 / laser displacement gauge response). Resolution The product of the second coefficient.

3. The distance adjustment measurement method according to claim 2, wherein, The first coefficient is not equal to and is less than the second coefficient.

4. The distance adjustment measurement method according to claim 2 or 3, wherein, The first coefficient is between 1 and 0.

01.

5. The distance adjustment measurement method according to claim 4, wherein, The second coefficient is between 1 and 200.

6. The distance adjustment measurement method according to claim 2, further comprising: The laser displacement meter, which is mounted on the optical slider, is driven by the linear motor to move along the optical guide rail; The displacement distance of the optical slider is recorded by the optical encoder of the optical slider; A control system converts the displacement distance to the current movement rate of the optical slider; and The control system adjusts the first coefficient based on the difference between the distance measured by the laser displacement meter and the precise measured distance.

7. The distance adjustment measurement method according to claim 6, further comprising: The difference between the distance and the precise measured distance is compared with a threshold. If the difference is greater than the threshold, the first coefficient is increased; otherwise, if the difference is less than the threshold, the first coefficient is decreased.

8. A measuring device suitable for use in conjunction with an object to be measured, the measuring device comprising: A laser displacement meter is used to measure the distance between the laser displacement meter and the object to be measured. A linear motor is used to move a laser displacement meter toward the object under test at a second rate, wherein during the period when the linear motor moves the laser displacement meter, the laser displacement meter continuously detects the distance between the laser displacement meter and the object under test to generate and output a sensing signal or an error signal, wherein... The error signal is output when the laser displacement meter does not receive reflected light from the object under test; The control system is used to determine, based on the sensing signal or the error signal, whether the distance between the laser displacement meter and the object under test exceeds the measurement range, wherein: If the measurement range is exceeded, the linear motor continues to drive the laser displacement meter to move towards the object being measured; and If the measurement range is not exceeded, the linear motor drives the laser displacement meter to move at a first rate until the sensing distance and the precise measurement distance are a difference, wherein the first rate is less than the second rate; and the laser displacement meter performs a depth measurement on a surface of the object to be measured.

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