A high-precision confocal line spectrum measurement device with polarization control

Abstract

A high-precision confocal spectral measurement device with polarization control is disclosed, specifically a line spectral confocal measurement device. This invention addresses the problems of existing technologies failing to effectively suppress defocused and crosstalk light, and exhibiting poor measurement capabilities. The invention comprises a linear beam, two polarization arrays, a beam splitter prism, a dispersive objective, and a first spectral demodulation module. These components are arranged sequentially from top to bottom. The object surface is positioned on one side of the beam splitter prism. One polarization array is positioned between the linear beam and the beam splitter prism, and the other polarization array is positioned between the beam splitter prism and the object surface. This invention belongs to the field of ultra-precision measurement technology.

Description

Technical Field

[0001] This invention relates to a line spectrum confocal measurement device, belonging to the field of ultra-precision measurement technology. Background Technology

[0002] Optical microscopes, due to their advantages of being non-contact, non-destructive, and highly precise, have become indispensable tools in the field of industrial measurement. With the rapid development of precision manufacturing, the demand for high-precision inspection is increasing year by year. Spectral confocal sensors are currently the most widely used type of sensor. Compared to laser confocal sensors, spectral confocal sensors use dispersive objectives to focus a broad-spectrum light source to different positions, and achieve rapid, high-precision displacement and thickness measurement without axial scanning through spectral demodulation.

[0003] Although spectral confocal scanning eliminates the need for axial scanning, a two-dimensional displacement stage is still required for lateral scanning to achieve rapid three-dimensional surface measurement. This results in a decrease in measurement speed and prevents instantaneous scanning measurements. Line-scanning spectral confocal scanning, on the other hand, can simultaneously measure multiple points. Combined with a one-dimensional displacement stage, it enables high-speed continuous measurement on production lines, making it ideal for industrial assembly line inspection scenarios.

[0004] However, existing line-scan spectral confocal structures often use slits instead of traditional pinholes. While this modification improves measurement efficiency, it also leads to crosstalk between adjacent measurement points, resulting in a decrease in axial and lateral resolution. Existing technologies to address this issue include using arrayed optical fibers, micromirror arrays, LCD panels, and micro-LEDs; however, these methods can only suppress crosstalk to a certain extent and often have low spatial sampling rates. Other improvements, such as denoising and deconvolution, have improved the signal-to-noise ratio to some extent and are effective on smooth, highly reflective surfaces, but their performance on rough or low-reflective surfaces is limited. Therefore, it is necessary to improve the line-scan spectral confocal structure from a hardware perspective to effectively suppress defocused and crosstalk light and enhance its measurement capabilities. Summary of the Invention

[0005] To address the problems of existing technologies being unable to effectively suppress defocused and crosstalk light, and having poor measurement capabilities, this invention proposes a polarization-controlled high-precision confocal spectral measurement device.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: The present invention includes linear light, two polarization arrays, a beam splitter prism, a dispersive objective lens, and a first spectral demodulation module;

[0007] The linear beam, beam splitter, dispersive objective, and first spectral demodulation module are arranged sequentially from top to bottom. The object surface is set on one side of the beam splitter. One polarization array is set between the linear beam and the beam splitter, and another polarization array is set between the beam splitter and the object surface.

[0008] Furthermore, the linear light is composed of an LED array.

[0009] Furthermore, the polarization array is used for polarization modulation of linear light and selective passage of reflected light. The polarization array is linearly polarized, and the polarization directions of adjacent units of the polarization array are perpendicular to each other.

[0010] Furthermore, the polarization array is composed of multiple internal units, with the middle internal unit being transparent and the internal units on both sides coated with an anti-reflective coating having a reflectivity of less than one-thousandth.

[0011] Furthermore, the ratio of reflected light to transmitted light in the beam splitter is 50:50.

[0012] Furthermore, the dispersive objectives are single-wavelength off-axis aberration corrected.

[0013] Furthermore, the first spectral demodulation module is a spectral peak extraction device.

[0014] This invention includes a linear beam, a polarization array, a beam splitter prism, a dispersive objective lens, a second spectral demodulation module, and two coupling mirror groups;

[0015] The linear beam, beam splitter, polarization array, dispersive objective, and object surface are arranged sequentially from left to right. The second spectral demodulation module is positioned above the beam splitter. One coupling mirror group is positioned between the linear beam and the beam splitter, and another coupling mirror group is positioned between the beam splitter and the second spectral demodulation module.

[0016] This invention includes linear light, a first spectral demodulation module, and two beam-splitting prism assemblies;

[0017] The linear beam is positioned to the left above the first spectral demodulation module, the object surface is positioned to the right above the first spectral demodulation module, a beam splitter assembly is positioned between the linear beam and the first spectral demodulation module, and another beam splitter assembly is positioned between the object surface and the first spectral demodulation module.

[0018] Furthermore, the beam-splitting prism assembly includes a polarization array, a beam-splitting prism, and a dispersive objective lens;

[0019] The polarization array, beam splitter, and dispersive objective are arranged sequentially from top to bottom.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention introduces a polarization array to control the polarization of the light source, effectively suppressing defocused light and stray light, reducing light intensity crosstalk between adjacent measurement points, thereby greatly improving the signal-to-noise ratio of the detected spectral signal, which is beneficial for subsequent signal peak extraction and effectively improving the lateral and axial resolution of the system.

[0022] 2. Due to the improved lateral resolution of the detector, the measurement results of more points within a unit length are reliable, thus enabling the device to measure fine structures.

[0023] 3. Compared with traditional array devices, the polarization array introduced in this invention does not require electromagnetic modulation, and the spatial sampling rate, response time and dynamic range can be greatly improved, effectively increasing the data throughput of the device.

[0024] 4. The polarization array of the present invention can simultaneously serve as a modulation device for the light source and a suppression device for defocused light, eliminating the need for alignment operations required by traditional array devices, effectively reducing the device assembly and adjustment steps, lowering the difficulty of device assembly and adjustment, and improving the reliability of the device. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the polarization array structure;

[0027] Figure 3 This is a schematic diagram illustrating how the polarization array affects the transmitted illumination light.

[0028] Figure 4 This is a schematic diagram showing the modulation of reflected light from a focused point by a polarization array.

[0029] Figure 5 It is a modulation diagram of the defocused reflected light by the polarization array;

[0030] Figure 6 This is a schematic diagram of another form of polarization-controlled high-precision line spectrum confocal measurement device;

[0031] Figure 7 This is a schematic diagram of an off-axis polarization-controlled high-precision line spectrum confocal measurement device.

[0032] Figures 1 to 7 In the diagram, 1-linear light, 2-polarization array, 3-beam splitter prism, 4-dispersive objective lens, 5-first spectral demodulation module, 6-object surface, 7-second spectral demodulation module, and 8-coupled mirror group. Detailed Implementation

[0033] Example 1: As Figure 1 As shown, a high-precision confocal spectral measurement device with polarization control includes a linear beam 1, two polarization arrays 2, a beam splitter prism 3, a dispersive objective lens 4, and a first spectral demodulation module 5.

[0034] Linear beam 1, beam splitter 3, dispersive objective lens 4 and first spectral demodulation module 5 are arranged sequentially from top to bottom. Object surface 6 is set on one side of beam splitter 3. One polarization array 2 is set between linear beam 1 and beam splitter 3, and another polarization array 2 is set between beam splitter 3 and object surface 6.

[0035] Among them, the linear light 1 is composed of an LED array, or it can be formed by focusing a broadband light source. Its line width and line length are similar to the width and length of the polarization array 2.

[0036] The polarization array 2 is used for polarization modulation of the linear light 1 and selective transmission of the reflected light. The polarization array 2 is linearly polarized, and the polarization directions of adjacent units of the polarization array 2 are perpendicular to each other. The polarization array can also be modulated with 1 / 4 wavelength or 1 / 2 wavelength to ensure that there is a significant difference in light transmission between adjacent units after two modulations. The number of units inside the polarization array is multiple, and the specific number can be determined according to the required line length. Typically, the value can be 1024 or 2048.

[0037] The polarization array 2 is composed of multiple internal units. The internal unit in the middle is transparent, while the internal units on both sides are coated with an anti-reflective coating with a reflectivity of less than one-thousandth. The number of polarization arrays can be one, which is placed directly between the dispersive objective and the beam splitter. It simultaneously converts the transmitted light into linear polarization and suppresses other polarization states of the returned light. The size of the polarization array unit is usually on the order of micrometers, preferably thirty micrometers.

[0038] In this case, the ratio of reflected light to transmitted light in prism 3 is 50:50.

[0039] Among them, the dispersive objective 4 is corrected for single-wavelength off-axis aberrations, especially for field curvature aberrations, ensuring no significant focus shift within the measurement line length.

[0040] Among them, the first spectral demodulation module 5 is a spectral peak extraction device, whose detector can be polarization insensitive or polarization state detection.

[0041] When using this device for measurement, the line light source 1 is first modulated into a linearly polarized light array after passing through the polarization array 2. Then, it passes through the beam splitter and is received by the dispersive objective lens 4. After dispersion, it is focused on different lines along the axis. The reflected light is also collected by the dispersive objective lens 4. Then, it is reflected to the polarization array through the beam splitter prism 3. After the defocused light and stray light carrying other polarization states are suppressed, it enters the spectral demodulation module.

[0042] like Figure 2As shown, the structure of polarization array 2 is composed of tiny units with periodic polarization states. The size of each unit is tens of micrometers. The specific size can be determined by magnification using a dispersive objective. The size of each unit should ensure that it reaches the ideal size after being focused by the dispersive objective. At the same time, each unit has high light transmittance. When the light that passes through is natural light that is unpolarized, the transmittance can be ensured to be close to 50%.

[0043] like Figure 3 As shown, natural light forms a periodic array with different polarization states after passing through a polarization array. After being collected and focused by a dispersive objective lens, the polarization states of the focal point and the focal point of the returning light of each unit are largely the same as the polarization state of the unit itself. Among them, smooth surfaces can largely maintain the above polarization characteristics, while the polarization characteristics of rough surfaces will be damaged to a certain extent, but the overall polarization tends to be the same as that of the unit itself.

[0044] like Figure 4 and Figure 5 As shown, the main function of polarization array 2 is to suppress defocused light and stray light from adjacent points. When light passes through dispersive objective lens 4 and is focused on the surface of the object, the focal point of its returning light is approximately equal to the size of the polarization array unit. At this time, most of the light will pass through the corresponding polarization unit. When the illumination light defocuses and focuses on the surface of the object, the focal point of the returning light will be larger than the size of the polarization unit, so the stray light will illuminate other polarization units. Since the polarization states of adjacent units are inconsistent, the defocused light cannot pass through, thereby increasing the signal ratio of the measurement point itself and greatly improving the signal-to-noise ratio.

[0045] Example 2: Figure 6 As shown, a high-precision confocal spectral measurement device with polarization control includes a linear beam 1, a polarization array 2, a beam splitter prism 3, a dispersive objective lens 4, a second spectral demodulation module 7, and two coupling mirror groups 8.

[0046] Linear light 1, beam splitter 3, polarization array 2, dispersive objective lens 4, and object surface 6 are arranged sequentially from left to right. The second spectral demodulation module 7 is located above the beam splitter 3. One coupling mirror group 8 is located between the linear light 1 and the beam splitter 3, and another coupling mirror group 8 is located between the beam splitter 3 and the second spectral demodulation module 7.

[0047] like Figure 6As shown, another variation of the high-precision linear confocal measurement device with polarization control utilizes polarization devices to simultaneously modulate the polarization of the light source and suppress the returning defocused light. This effectively reduces the assembly and adjustment complexity caused by the simultaneous operation of two devices, reduces the system's assembly and adjustment errors, and improves the system's stability. Specifically, the linear light 1 is collected by the coupling lens group 8, transmitted through the beam splitter prism 3, and projected onto the polarization array 2. It is then focused along the axis onto the object surface 6 by the dispersive objective lens 4. The returning light is collected by the dispersive objective lens 4 and focused again onto the polarization array 2. The filtered light is then reflected by the beam splitter prism 3 and collected again by the coupling lens group 8 and focused onto the second spectral demodulation module 7, where spectral peak extraction is performed.

[0048] Example 3: Figure 7 As shown, a polarization-controlled high-precision confocal spectral measurement device includes a linear beam 1, a first spectral demodulation module 5, and two beam splitter prism assemblies.

[0049] Linear light 1 is positioned on the left side above the first spectral demodulation module 5, and object surface 6 is positioned on the right side above the first spectral demodulation module 5. One beam splitter assembly is positioned between linear light 1 and the first spectral demodulation module 5, and another beam splitter assembly is positioned between object surface 6 and the first spectral demodulation module 5.

[0050] The beam splitter assembly includes a polarization array 2, a beam splitter 3, and a dispersive objective lens 4.

[0051] The polarization array 2, the beam splitter 3, and the dispersive objective lens 4 are arranged sequentially from top to bottom.

[0052] like Figure 7 As shown, the light source 1 is polarized and modulated after passing through the polarization array 2, then dispersed off-axis by the beam splitter 3 and axially by the dispersive objective lens 4, and then focused on the object surface 6. The returning light passes through the dispersive objective lens 4 with the same parameters, then through the beam splitter 3 with the same parameters, and then reaches the polarization array 2, and then enters the spectral demodulation module for peak wavelength extraction.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A high-precision confocal linear spectrum measurement device with polarization control, characterized in that, It includes linear light (1), two polarization arrays (2), a beam splitter (3), a dispersive objective (4), and a first spectral demodulation module (5); Linear light (1), beam splitter (3), dispersive objective (4) and object surface (6) are arranged in order from top to bottom. The object surface (6) is arranged on one side of the beam splitter (3). A polarization array (2) is arranged between the linear light (1) and the beam splitter (3). Another polarization array (2) is arranged between the beam splitter (3) and the first spectral demodulation module (5). The polarization array (2) is used to polarize the linear light (1) and selectively pass the reflected light. The polarization array (2) is linearly polarized, and the polarization directions of adjacent units of the polarization array (2) are perpendicular to each other.

2. The high-precision confocal linear spectrum measurement device with polarization control according to claim 1, characterized in that, Linear light (1) is composed of an LED array.

3. The high-precision confocal linear spectrum measurement device with polarization control according to claim 1, characterized in that, The polarization array (2) consists of multiple internal units. The internal unit in the middle is transparent, while the internal units on both sides are coated with an anti-reflective coating with a reflectivity of less than one-thousandth.

4. The high-precision confocal linear spectrum measurement device with polarization control according to claim 1, characterized in that, The ratio of reflected light to transmitted light in the beam splitter (3) is 50:

50.

5. The high-precision confocal linear spectrum measurement device with polarization control according to claim 1, characterized in that, The dispersive objective (4) is a single-wavelength off-axis aberration corrector.

6. The high-precision confocal linear spectrum measurement device with polarization control according to claim 1, characterized in that, The first spectral demodulation module (5) is a spectral peak extraction device.

7. A high-precision confocal linear spectrum measurement device with polarization control, characterized in that, It includes linear light (1), a first spectral demodulation module (5), and two beam splitter assemblies; A linear beam (1) is positioned on the left side above the object surface (6), a first spectral demodulation module (5) is positioned on the right side above the object surface (6), a beam splitter assembly is positioned between the linear beam (1) and the object surface (6), and another beam splitter assembly is positioned between the object surface (6) and the first spectral demodulation module (5); the beam splitter assembly includes a polarization array (2), a beam splitter (3), and a dispersive objective (4); The polarization array (2), the beam splitter (3), and the dispersive objective (4) are arranged sequentially from top to bottom; The polarization array (2) is used to polarize the linear light (1) and selectively pass the reflected light. The polarization array (2) is linearly polarized, and the polarization directions of adjacent units of the polarization array (2) are perpendicular to each other.

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