A micro displacement detection device based on optical interference principle

Abstract

This utility model relates to the field of precision measurement technology, specifically a micro-displacement detection device based on the principle of optical interference. It solves the problems of instability of the wedge structure and large measurement errors in fringe spacing in existing technologies, leading to insufficient detection accuracy. The device includes a light source assembly, a semi-reflecting mirror, a support, and a CCD camera. The support houses the wedge interference assembly. Light emitted from the light source assembly is reflected by the semi-reflecting mirror to the wedge interference assembly, forming wedge interference fringes. The CCD camera captures the wedge interference fringes. A detection rod is mounted on the support, arranged perpendicular to the interference fringes. One end of the detection rod extends between the two glass plates of the wedge interference assembly, and the other end is connected to the target object. The beneficial effect is that the upper and lower glass plates of the wedge interference assembly are fixed by the support and remain stationary throughout the detection process, completely avoiding the instability of the wedge structure caused by glass plate movement in traditional solutions, thus providing a foundation for measurement accuracy.

Description

Technical Field

[0001] This utility model relates to the field of precision measurement technology, and in particular to a micro-displacement detection device based on the principle of optical interference. Background Technology

[0002] Micro-displacement detection is one of the core technologies in fields such as industrial precision measurement, material performance characterization, and instrument calibration. Its detection accuracy directly affects product quality control, the reliability of scientific research data, and the operational stability of high-end equipment. With the development of modern manufacturing towards miniaturization and high precision, the demand for micro-displacement detection is becoming increasingly urgent. Optical interferometry, with its advantages of high sensitivity and non-contact measurement, has become one of the mainstream technical approaches for micro-displacement detection.

[0003] In existing technologies, detection devices based on the wedge interference principle have been applied to scenarios such as the determination of the coefficient of thermal expansion. For example, patent CN113984828A discloses a device for determining the coefficient of thermal expansion through wedge interference. This device forms an air wedge using a laser light source, a semi-reflective mirror, and upper and lower standard flat glass plates. It uses a fringe counter to detect the number of interference fringes, calculates the wedge height using a formula, and then derives the coefficient of thermal expansion of the material. This solves the problems of low accuracy and narrow application range of traditional displacement sensors and is applicable to the determination of the coefficient of thermal expansion of gases, liquids, and solids.

[0004] However, the existing wedge interferometric detection devices still have significant technical shortcomings in direct detection of minute displacements. The core principle of these devices is to lift one end of a standard flat glass plate using a liftable actuator, forming a wedge between the upper and lower glass plates. Displacement changes are reflected in the change in the spacing of the interference fringes, and the displacement is ultimately calculated by measuring the difference between the fringes before and after the displacement change. However, in practical applications, this measurement method is prone to significant errors, specifically: First, the measurement of the fringes spacing depends on fringe recognition and spacing calibration. Environmental vibrations and temperature fluctuations can cause minute deformations or relative shifts in the upper and lower glass plates, resulting in inconsistent reference positions between the two measurements. Second, when the displacement is extremely small (e.g., nanometer-level), the change in fringe spacing is weak, and pixel-level errors in fringe recognition and diffraction interference from the optical system can significantly increase the relative error in spacing measurement. Third, the stability of the wedge structure is difficult to guarantee during the time interval between two measurements, further exacerbating the measurement deviation and ultimately affecting the accuracy of minute displacement detection. Utility Model Content

[0005] This invention proposes a micro-displacement detection device based on the principle of optical interference, which solves the problems of insufficient detection accuracy caused by the instability of the wedge structure and the large measurement error of the fringe spacing in the prior art.

[0006] The technical solution of this utility model is implemented as follows: A micro-displacement detection device based on the principle of optical interference includes a light source assembly, a semi-reflecting mirror, a support, and a CCD camera. A wedge interference assembly is mounted on the support. Light emitted from the light source assembly is reflected by the semi-reflecting mirror to the wedge interference assembly, forming wedge interference fringes. The CCD camera captures the wedge interference fringes. A detection rod is mounted on the support, arranged perpendicular to the interference fringes. One end of the detection rod extends between two glass plates of the wedge interference assembly, and the other end is connected to the target object. Due to the height of the detection rod, a bulge appears at the position corresponding to the detection rod in the observed interference fringes. During displacement detection, the displacement of the target object pushes or pulls the detection rod between the two glass plates of the wedge interference assembly, thereby changing the number of bulging fringes. The displacement distance is calculated by observing the change in the number of bulging fringes before and after displacement. During the detection process, the two glass plates of the wedge interference assembly remain stationary, ensuring the stability of the wedge structure and thus guaranteeing accurate measurement results.

[0007] The wedge interference assembly includes an upper glass plate and a lower glass plate, with an included angle greater than zero between them. Both the upper and lower glass plates are made of quartz glass, and an air wedge is formed between them.

[0008] The distance between the upper and lower glass plates is greater than the radial dimension of the detection rod. This prevents the detection rod from colliding with the upper or lower glass plates during movement, ensuring the structural stability of the wedge interference assembly.

[0009] The bracket is provided with a lower positioning groove, the bottom surface of which is horizontally arranged, and the depth of the lower positioning groove is less than or equal to the thickness of the lower glass sheet. The lower positioning groove is used to embed the lower glass sheet, ensuring that the lower glass sheet is positioned horizontally.

[0010] One side of the lower positioning groove is provided with a groove, the bottom of which is flush with the bottom surface of the lower positioning groove. The groove is designed to facilitate the operator to remove the lower glass plate from the lower positioning groove, making it easy to replace the lower glass plate.

[0011] The support is equipped with a guide tube, which is arranged laterally, and the detection rod passes through the guide tube. The guide tube guides the detection rod, ensuring that the detection rod moves along the inclined direction of the upper glass plate. The guide tube is staggered with the lower positioning groove.

[0012] The detection rod is a cylindrical or prismatic rod. The detection rod is made of quartz glass.

[0013] The bracket is provided with an upper positioning groove, which is located above the lower positioning groove, and the bottom surface of the upper positioning groove is inclined. The upper positioning groove is used to position the upper glass plate, so that a stable air wedge is formed between the upper and lower glass plates.

[0014] The inclination angle of the bottom surface of the upper positioning groove is in the range of 0.05° to 5°.

[0015] The light source assembly includes a monochromatic point light source and a collimating lens. The light generated by the monochromatic point light source is collimated into a parallel beam by the collimating lens. The wavelength of the monochromatic point light source is selected from 532nm, 632.8nm, or 650nm.

[0016] The beneficial effects of this utility model are: Significantly improved structural stability: The upper and lower glass plates of the wedge interference assembly are fixed by upper and lower positioning grooves, respectively, and the upper and lower glass plates remain stationary during the testing process. This completely avoids the instability of the wedge structure caused by the movement of the glass plates in traditional solutions, providing a foundation for measurement accuracy.

[0017] Measurement error is significantly reduced: By detecting the change in the number of raised stripes instead of the traditional two-step stripe spacing measurement, cumulative errors such as spacing recognition error and reference offset are avoided. Combined with the precise guidance of the guide tube for the detection rod, the measurement repeatability error is small and the detection accuracy is high.

[0018] Optimized ease of operation: The groove design on one side of the bracket makes it easier to disassemble and replace the lower glass plate, reducing equipment maintenance costs; at the same time, the gap fit between the detection rod and the guide tube ensures smooth movement without the need for complicated adjustments.

[0019] Simple and reliable structure: The whole device is composed of conventional optical components and mechanical structure, without complex transmission parts, low processing difficulty, controllable manufacturing cost, and easy to mass production and application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a micro-displacement detection device based on the principle of optical interference according to this utility model.

[0022] Figure 2 This is a schematic diagram of the support structure.

[0023] In the diagram: 1. Monochromatic point light source, 2. Collimating lens, 3. Semi-reflective mirror, 4. CCD camera, 5. Upper glass plate, 6. Lower glass plate, 7. Support, 8. Detection rod, 9. Detection target, 71. Lower positioning groove, 72. Groove, 73. Guide tube, 74. Upper positioning groove. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Example 1, as Figure 1 As shown, a micro-displacement detection device based on the principle of optical interference includes a light source assembly, a semi-reflecting mirror 3, a support 7, and a CCD camera 4. The support 7 is characterized by a wedge interference component; light emitted from the light source assembly is reflected by the semi-reflecting mirror 3 to the wedge interference component, forming wedge interference fringes; the CCD camera 4 captures the wedge interference fringes; a detection rod 8 is provided on the support 7, arranged perpendicular to the interference fringes, with one end of the detection rod 8 extending between two glass plates of the wedge interference component, and the other end connected to the target object 9. The light source assembly includes a monochromatic point light source 1 and a collimating lens 2; the light generated by the monochromatic point light source 1 is collimated into a parallel beam by the collimating lens 2.

[0026] Specifically, the monochromatic point light source 1 is a helium-neon laser with a wavelength of 632.8nm. The collimating lens 2 collimates the diverging light emitted by the monochromatic point light source 1 into a parallel beam. The semi-reflecting mirror 3 is arranged at a 45° angle to ensure that the parallel light emitted from the collimating lens 2 is reflected to the wedge interference assembly.

[0027] Because the probe 8 has a certain height, raised fringes will appear at the positions corresponding to the probe 8 in the observed interference fringes. During displacement detection, the target object 9 is displaced, pushing or pulling the probe 8 between the two glass plates of the wedge interference assembly, thereby changing the number of raised fringes. The displacement distance can be calculated by the change in the number of raised fringes before and after displacement. During the detection process, the two glass plates of the wedge interference assembly remain stationary, ensuring the stability of the wedge structure and thus ensuring accurate measurement results.

[0028] Furthermore, the wedge interference assembly includes an upper glass plate 5 and a lower glass plate 6, with an included angle greater than zero between them. Both the upper and lower glass plates are made of quartz glass, and an air wedge is formed between them.

[0029] Furthermore, the distance between the upper glass plate 5 and the lower glass plate 6 is greater than the radial dimension of the detection rod 8. This prevents the detection rod 8 from colliding with the upper glass plate 5 or the lower glass plate 6 during movement, ensuring the structural stability of the wedge interference assembly.

[0030] Example 2, based on Example 1, provides a micro-displacement detection device based on the principle of optical interference, such as... Figure 2 As shown, the bracket 7 is provided with a lower positioning groove 71. The bottom surface of the lower positioning groove 71 is horizontally arranged, and the depth of the lower positioning groove 71 is less than or equal to the thickness of the lower glass sheet 6. The lower positioning groove 71 is used to embed the lower glass sheet 6 to ensure that the lower glass sheet 6 is horizontally positioned.

[0031] Furthermore, a groove 72 is provided on one side of the lower positioning groove 71, and the bottom of the groove 72 is flush with the bottom surface of the lower positioning groove 71. The groove 72 is designed to facilitate the operator to remove the lower glass piece 6 from the lower positioning groove 71, making it easier to replace the lower glass piece 6.

[0032] Furthermore, the support 7 is equipped with a guide tube 73, which is arranged laterally, and the detection rod 8 passes through the guide tube 73. The guide tube 73 guides the detection rod 8, ensuring that the detection rod 8 moves along the inclined direction of the upper glass plate 5. The guide tube 73 is staggered with the lower positioning groove 71 to avoid interference between the guide tube 73 and the lower glass plate 6.

[0033] Furthermore, the detection rod 8 is a cylindrical rod or a prism rod. The detection rod 8 is made of quartz glass.

[0034] Furthermore, the bracket 7 is provided with an upper positioning groove 74, which is located above the lower positioning groove 71, and the bottom surface of the upper positioning groove 74 is arranged at an angle. The upper positioning groove 74 is used to position the upper glass plate 5, so that a stable air wedge is formed between the upper glass plate 5 and the lower glass plate 6.

[0035] Furthermore, the tilt angle of the bottom surface of the upper positioning groove 74 ranges from 0.05° to 2°.

[0036] The detection device is used as follows: First, a helium-neon laser with a wavelength of 632.8nm is selected as the monochromatic point light source 1. The upper glass plate 5 and the lower glass plate 6 are both made of quartz glass. The bottom surface of the upper positioning groove 74 is tilted at an angle of 0.5° so that the included angle of the air wedge formed by the upper and lower glass plates is 0.5°. Then, the detection rod 8 is inserted into the guide tube 73, and the other end of the detection rod 8 is connected to the detection target object by adhesive bonding. Finally, the light source is activated, and the collimated parallel beam is reflected by the semi-reflecting mirror 3 to the air wedge, forming interference fringes. The fringe spacing is calculated using the formula: fringe spacing L = 36.3 micrometers. The CCD camera 4 captures an image of the initial state, records the number of raised fringes N1, and records the position of the outermost raised fringe. The target object is detected to have a slight displacement, which pushes the detection rod to move along the guide tube. The CCD camera captures an image after the displacement, records the position of the outermost raised fringe after the detection rod moves, and calculates the change in the number of fringes N. The displacement change A = the number of fringes N multiplied by the fringe spacing L.

[0037] This device uses interference fringes as a scale, enabling measurements at the micrometer level.

[0038] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A micro displacement detection device based on the principle of optical interference, comprising a light source assembly, a half mirror (3), a bracket (7) and a CCD camera (4), characterized in that, The bracket (7) is equipped with a wedge interference assembly; the light emitted by the light source assembly is reflected by the semi-reflective mirror (3) to the wedge interference assembly to form wedge interference fringes; the CCD camera (4) captures the wedge interference fringes; the bracket (7) is equipped with a detection rod (8), which is arranged perpendicular to the interference fringes. One end of the detection rod (8) extends between the two glass plates of the wedge interference assembly, and the other end of the detection rod (8) is connected to the detection target (9).

2. The minute displacement detecting apparatus based on the optical interference principle according to claim 1, wherein The wedge interference assembly includes an upper glass plate (5) and a lower glass plate (6), and the included angle between the upper glass plate (5) and the lower glass plate (6) is greater than zero.

3. The minute displacement detecting apparatus based on the optical interference principle according to claim 2, wherein The distance between the upper glass plate (5) and the lower glass plate (6) is greater than the radial dimension of the detection rod (8).

4. The minute displacement detecting apparatus based on the optical interference principle according to claim 2 or 3, characterized by The bracket (7) is provided with a lower positioning groove (71), the bottom surface of the lower positioning groove (71) is arranged horizontally, and the depth of the lower positioning groove (71) is less than or equal to the thickness of the lower glass plate (6).

5. The minute displacement detecting apparatus based on the optical interference principle according to claim 4, wherein A groove (72) is provided on one side of the lower positioning groove (71), and the bottom of the groove (72) is flush with the bottom surface of the lower positioning groove (71).

6. The minute displacement detecting apparatus based on the optical interference principle according to claim 5, wherein The bracket (7) is provided with a guide tube (73), which is arranged horizontally, and the test rod (8) is inserted inside the guide tube (73).

7. The minute displacement detecting apparatus based on the optical interference principle according to claim 6, wherein The test rod (8) is a cylindrical rod or a prism rod.

8. The minute displacement detecting apparatus based on the optical interference principle according to any one of claims 2, 3, 5 to 7, wherein The bracket (7) is provided with an upper positioning groove (74), which is located above the lower positioning groove (71), and the bottom surface of the upper positioning groove (74) is arranged at an inclination.

9. The minute displacement detecting apparatus based on the optical interference principle according to claim 8, wherein The tilt angle of the bottom surface of the upper positioning groove (74) ranges from 0.05° to 5°.

10. The minute displacement detecting apparatus based on the optical interference principle according to claim 1 or 9, wherein The light source assembly includes a monochromatic point light source (1) and a collimating lens (2). The light generated by the monochromatic point light source (1) is collimated into a parallel beam by the collimating lens (2).

Images