Laser measuring instrument based on diffraction method

Abstract

The utility model relates to the technical field of laser measurement, and discloses a laser measuring instrument based on a diffraction method. The objective of the utility model is to solve the technical problems in the prior art that the diameter of a laser beam of a traditional rotating mirror type laser measuring instrument reaches 40 [mu] m, the measurement precision is influenced when the diameter of a measured object is extremely small, the repeatability is poor, and the measurement accuracy is influenced by the placement angle of a workpiece with an extremely small diameter. The device comprises a laser, a collimating lens, a receiving lens and a receiving CCD (Charge Coupled Device), wherein the collimating lens comprises an optical fiber coupler, a homogenizing optical fiber and an optical fiber collimating lens. Compared with a traditional rotating mirror type measuring instrument, the measuring instrument is free of a rotating part and a receiving imaging lens, strong in interference resistance, low in cost, capable of measuring diffraction fringes formed by tiny objects and imaging the diffraction fringes on the focal plane of the receiving lens, stable and high in precision, and voltage signals are received and transmitted by a CCD (Charge Coupled Device).

Description

Technical Field

[0001] This utility model relates to the field of laser measurement technology, and in particular to a laser measuring instrument based on diffraction. Background Technology

[0002] Traditional optical measurement techniques are mainly divided into CCD measurement and rotating mirror technology. Early CCD measurement techniques generated grayscale images, similar to surveillance images, suitable for measuring objects with diameters greater than 0.2 mm, but insufficient for applications requiring extremely small diameter objects and high precision. Rotating mirror laser technology converts a point light source into a line light source using a rotating optical element. While this method can achieve high-precision measurement, its relatively large beam diameter is unsuitable for measuring extremely fine objects, thus affecting the accuracy of the measurement data. Diffraction laser measuring instruments are precision instruments that utilize the diffraction phenomenon of light to measure the size of extremely fine objects. When a laser beam illuminates an extremely thin cylindrical object, it causes diffraction, forming a specific diffraction pattern. According to Fraunhofer diffraction theory, when a parallel laser beam passes through a small hole, slit, or filament, it produces a series of alternating bright and dark fringes on a distant screen. The position and intensity distribution of these fringes depend on the geometry and size of the obstacle, and can be applied to measuring the size of tiny objects and detecting surface roughness and smoothness. Diffraction measurement is a non-contact measurement method that does not damage the object being measured and can achieve nanometer-level resolution and accuracy.

[0003] Chinese patent document CN2465176Y discloses a laser diffraction measuring instrument. The instrument has a laser generator horizontally mounted in a tray within a laser column on the right side of the base. A narrow, elongated light-passing hole is provided in the support. A slit is formed between the edge mounted within the upper locking block and the workpiece being measured on the support. A laser receiving screen is mounted on the left side of the base, and a capacitive digital caliper is mounted on the back frame. An adjustable negative lens is mounted on the support of the base between the receiving screen, the edge, and the workpiece being measured. The laser beam passes through the center of the negative lens and is directed towards the receiving screen.

[0004] However, the above-mentioned solutions have at least the following technical problems during implementation: Traditional rotating mirror measuring instruments use a motor to drive the rotating mirror for measurement. When the diameter of the object being measured is small, the measurement accuracy is often affected by interference caused by the motor rotation. Furthermore, they lack experimental repeatability, and the accuracy of the measurement is affected by the placement angle of small-diameter workpieces. Therefore, there is an urgent need to propose a laser measuring instrument based on diffraction. Summary of the Invention

[0005] In view of the above technical problems, this disclosure provides a laser measuring instrument based on diffraction method, which solves the technical problems of traditional rotating mirror measuring instruments in the prior art, which use a motor to drive the rotating mirror for measurement. When the diameter of the measured object is extremely small, the resolution and measurement accuracy are limited by the increase in the diameter of the laser beam. Furthermore, the accuracy of the measurement is affected by the placement angle of the small-diameter workpiece.

[0006] According to one aspect of this disclosure, a laser measuring instrument based on diffraction is provided, comprising a laser generating component disposed on one side of the object being measured, and a laser receiving component disposed on the other side of the object being measured; the laser generating component includes a laser, and a collimating lens is disposed between the laser and the object being measured, the collimating lens including a coupler for coupling the laser beam into an optical fiber, a homogenizing optical fiber for homogenizing the beam into a uniform spot, and an optical fiber collimating lens for focusing the beam emitted from the optical fiber to a desired diameter, the lens surface of the optical fiber collimating lens being coated with an anti-reflection coating; the laser receiving component includes a receiving lens and a receiving CCD, the receiving CCD being located on the focal plane of the receiving lens, and the receiving CCD being an area array CCD.

[0007] In some embodiments of this disclosure, the receiving CCD is a planar control array CCD.

[0008] In some embodiments of this disclosure, the object to be measured is vertically positioned on a Z-axis worktable, and the measurement of different axial positions of the object is achieved as the worktable moves along the Z-axis. The Z-axis worktable is located on an XY-axis worktable.

[0009] In some embodiments of this disclosure, the XY-axis worktable includes two parallel X-axis lead screws, with an X-axis nut surrounding the X-axis lead screws to form a sliding pair. A Y-axis crossbeam is installed between the X-axis nuts, and a Y-axis nut is installed on the Y-axis crossbeam via a slider. A Y-axis lead screw is installed through the center of the Y-axis nut, and a Z-axis worktable is installed above the Y-axis nut.

[0010] In some embodiments of this disclosure, the Z-axis worktable includes a coarse positioning portion and a fine positioning portion. The coarse positioning portion includes a Z-axis lead screw, the end of which is connected to a motor to drive the Z-axis lead screw to rotate. A Z-axis nut is arranged around the Z-axis lead screw to form a sliding pair. The fine positioning portion is installed above the Z-axis nut. The fine positioning portion includes a micro-positioning plate, which is connected to a piezoelectric ceramic to drive the micro-positioning plate. The displacement control end of the piezoelectric ceramic is connected to a high-voltage driving power supply. The high-voltage driving power supply is connected to a controller via a D / A conversion chip. The sensing signal receiving end of the controller is connected to a laser receiving component.

[0011] In some embodiments of this disclosure, the Z-axis lead screw is installed at an angle with a slope of 0.01 to 0.1.

[0012] In some embodiments of this disclosure, the piezoelectric ceramic is a WTDS0810025 type electrostrictive ceramic micro-displacement device.

[0013] In some embodiments of this disclosure, the D / A conversion chip is an AD669 digital-to-analog converter.

[0014] The beneficial effects of this utility model are as follows:

[0015] Compared to traditional rotating mirror measuring instruments, laser measuring instruments based on diffraction have no rotating parts or receiving imaging lenses, resulting in strong anti-interference capabilities, low cost, and stable, high-precision measurement. The diffraction fringes formed by measuring small objects are imaged onto the focal plane of the receiving lens, where a CCD receives and outputs a voltage signal. The simplified optical path design eliminates the need for traditional rotating mirrors and reflecting mirror systems, employing the principle of diffraction to achieve high-resolution and high-precision measurement of extremely fine objects. The conversion from point light source to line light source utilizes specific optical components such as homogenizing fibers, avoiding instability and light loss caused by mechanical movements such as mirror rotation. The use of a high-resolution area array CCD sensor for image capture, analysis, and data processing effectively eliminates errors caused by deviations or tilts of the measured object in various directions, significantly improving measurement accuracy. The integrated design of the receiving lens and CCD ensures optimal focusing, enabling clear capture of diffraction patterns. The multi-dimensional moving platform design allows for precise three-dimensional positioning of the measured object. The XY-axis stage design provides stable translational motion, ensuring precise positioning capabilities in the X and Y directions. The coarse positioning section achieves rapid adjustment over a wide range using a Z-axis lead screw, while the fine positioning section utilizes piezoelectric ceramics for micron-level fine adjustment, significantly improving measurement accuracy and resolution. The use of high-performance piezoelectric ceramic materials enables extremely small but highly precise displacements when voltage is applied. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a laser measuring instrument based on diffraction.

[0017] Figure 2 This is a schematic diagram of the workbench structure;

[0018] Figure 3 This is a schematic diagram of the workbench from another perspective.

[0019] Figure 4 Schematic diagram of a piezoelectric ceramic high-voltage drive power supply;

[0020] The components in the diagram are named as follows: 1. Laser; 2. Collimating lens; 3. Receiving lens; 4. Receiving CCD; 5. Z-axis stage; 6. XY-axis stage; 7. X-axis lead screw; 8. X-axis nut; 9. Y-axis beam; 10. Slider; 11. Y-axis nut; 12. Y-axis lead screw; 13. Micro-positioning plate; 14. Z-axis lead screw; 15. Motor; 16. Z-axis nut. Detailed Implementation

[0021] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Example 1

[0022] This example discloses a laser measuring instrument based on diffraction. See [link to documentation]. Figures 1 to 4 The laser receiver includes a laser generating component located on one side of the object being measured and a laser receiving component located on the other side of the object being measured. The laser generating component includes a laser 1, and a collimating lens 2 is disposed between the laser 1 and the object being measured. The collimating lens 2 includes a linear generator lens that can shape the light beam into a linear spot and an optical fiber collimating lens that can focus the optical fiber to the required beam diameter. The lens surface of the optical fiber collimating lens is coated with an anti-reflection film. The laser receiving component includes a receiving lens 3 and a receiving CCD 4, with the receiving CCD 4 located on the focal plane of the receiving lens 3.

[0023] The object to be measured is placed on the Z-axis worktable 5, and the Z-axis worktable 5 is placed on the XY-axis worktable 6.

[0024] The XY-axis worktable 6 includes two parallel X-axis lead screws 7, with X-axis nuts 8 surrounding the X-axis lead screws 7 to form a sliding pair. A Y-axis crossbeam 9 is installed between the X-axis nuts 8, and a Y-axis nut 11 is installed on the Y-axis crossbeam 9 via a slider 10. A Y-axis lead screw 12 is installed through the center of the Y-axis nut 11, and a Z-axis worktable 5 is installed above the Y-axis nut 11.

[0025] The Z-axis worktable 5 includes a coarse positioning section and a fine positioning section. The coarse positioning section includes a Z-axis lead screw 14, with a motor 15 connected to the end of the Z-axis lead screw 14 to drive the Z-axis lead screw 14 to rotate. A Z-axis nut 16 is arranged around the Z-axis lead screw 14 to form a sliding pair. The fine positioning section is installed above the Z-axis nut 16. The fine positioning section includes a micro-positioning plate 13, which is connected to a piezoelectric ceramic to drive the micro-positioning plate 13. The displacement control end of the piezoelectric ceramic is connected to a high-voltage drive power supply. The high-voltage drive power supply is connected to a controller via a D / A conversion chip. The sensor signal receiving end of the controller is connected to a laser receiving component.

[0026] The Z-axis lead screw 14 is installed at an angle with an inclination of 0.01~0.1.

[0027] The piezoelectric ceramic is the WTDS0810025 type electrostrictive ceramic micro-displacement device.

[0028] The D / A conversion chip is the AD669 digital-to-analog converter.

[0029] The receiving CCD is an area-controlled CCD. Depending on the transfer and readout structure, there are different types of area-controlled imaging devices, the common types being frame-transfer FTCCD and interline-transfer ILTCCD.

[0030] The Z-axis stage 5 and the XY-axis stage 6 are designed to adjust the equipment so that the object being measured is within the recording space when the tilt angle is large.

[0031] During operation, laser 1 generates a laser beam, which is shaped into a linear spot by collimating lens 2 and then irradiates the object under test. The laser beam passes through or reflects off the object, producing a diffraction pattern. This diffraction pattern is captured by receiving lens 3 and focused onto receiving CCD 4 to form an image. Receiving CCD 4 converts the image into electrical signals, which are then transmitted to the controller for processing and analysis to obtain information about the object's dimensions or other characteristics. If a larger range of position adjustments is required, the controller drives the Z-axis lead screw 14 via motor 15, causing the Z-axis nut 16 to move along the Z-axis, thus changing the height of the object. For even finer position adjustments, the controller drives a micro-positioning plate 13 via piezoelectric ceramic, achieving sub-micron level precision. The controller continuously optimizes the position of the object based on the received data to ensure the most accurate measurement results.

[0032] Compared to traditional rotating mirror measuring instruments, laser measuring instruments based on diffraction have no rotating parts or receiving imaging lenses, resulting in strong anti-interference capabilities, low cost, and the ability to image diffraction fringes formed by measuring small objects onto the focal plane of the receiving lens. The voltage signal is received by a CCD and transmitted, ensuring stability and high accuracy. A line generator lens, a type of fiber laser beam shaping lens, can shape a collimated or focused beam into a linear spot, used for supplementary lighting in line scan cameras or in 3D structured light applications. A fiber collimator is used to collimate / focus the output fiber to the desired beam diameter or spot size. The lens achieves the diffraction limit, thus reducing the spot diameter to a few micrometers. This lens is coated with an anti-reflection coating to reduce back reflection. Fiber collimators and focusing components can be used in pairs. Fiber optic collimating lenses have FC / PC, FC / APC, and SMA905 interfaces. They are mainly used for fiber optic collimation, but can also be used for parallel fiber coupling and focusing. For collimation, they can be connected to either single-mode or multimode fiber. For coupling, multimode fiber has higher coupling efficiency than single-mode fiber (multimode fiber has a larger numerical aperture and core diameter than single-mode fiber).

[0033] Although some preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0034] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A laser measuring instrument based on diffraction, characterized in that: The device includes a laser generating component located on one side of the object being tested and a laser receiving component located on the other side of the object being tested. The laser generating component includes a laser, and a collimating lens is disposed between the laser and the object being tested. The collimating lens includes a homogenizing fiber for homogenizing and shaping the laser beam into a uniform spot and a fiber collimating lens for focusing the fiber beam to the desired beam diameter. The lens surface of the fiber collimating lens is coated with an anti-reflection coating. The laser receiving component includes a receiving lens and a receiving CCD, with the receiving CCD located on the focal plane of the receiving lens.

2. The laser measuring instrument based on diffraction as described in claim 1, characterized in that: The receiving CCD is a surface-controlled CCD.

3. The laser measuring instrument based on diffraction as described in claim 1, characterized in that: The object to be measured is vertically set on the Z-axis worktable, and the measurement of the object at different positions along the axial direction is realized as the worktable moves along the Z-axis; the Z-axis worktable is set on the XY-axis worktable.

4. The laser measuring instrument based on diffraction as described in claim 3, characterized in that: The XY-axis worktable includes two parallel X-axis lead screws, with an X-axis nut surrounding the X-axis lead screws to form a sliding pair. A Y-axis crossbeam is installed between the X-axis nuts, and a Y-axis nut is installed on the Y-axis crossbeam via a slider. A Y-axis lead screw is installed through the center of the Y-axis nut, and a Z-axis worktable is installed above the Y-axis nut.

5. The laser measuring instrument based on diffraction as described in claim 3, characterized in that: The Z-axis worktable includes a coarse positioning section and a fine positioning section. The coarse positioning section includes a Z-axis lead screw, the end of which is connected to a motor to drive the Z-axis lead screw to rotate. A Z-axis nut is arranged around the Z-axis lead screw to form a sliding pair. The fine positioning section is installed above the Z-axis nut. The fine positioning section includes a micro-positioning plate, which is connected to a piezoelectric ceramic to drive the micro-positioning plate. The displacement control end of the piezoelectric ceramic is connected to a high-voltage driving power supply. The high-voltage driving power supply is connected to a controller via a D / A conversion chip. The sensor signal receiving end of the controller is connected to a laser receiving component.

6. The laser measuring instrument based on diffraction as described in claim 4, characterized in that: The Z-axis lead screw is installed at an angle with a slope of 0.01 to 0.

1.

7. The laser measuring instrument based on diffraction as described in claim 5, characterized in that: The piezoelectric ceramic is a WTDS0810025 type electrostrictive ceramic micro-displacement device.

8. The laser measuring instrument based on diffraction as described in claim 4, characterized in that: The D / A conversion chip is the AD669 digital-to-analog converter.

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