Polarization regulation and control high-precision line spectrum confocal measurement device

Abstract

The invention discloses a polarization regulation and control high-precision spectrum confocal measurement device, and relates to a line spectrum confocal measurement device. The invention aims to solve the problems that defocused light and crosstalk light cannot be effectively suppressed and the measurement capability is poor in the prior art. The device comprises linear light, two polarization arrays, a beam splitter prism, a dispersion objective lens and a first spectrum demodulation module. The linear light, the beam splitter prism, the dispersion objective lens and the first spectrum demodulation module are sequentially arranged from top to bottom, the object surface is arranged on one side of the beam splitter prism, one polarization array is arranged between the linear light and the beam splitter prism, and the other polarization array is arranged between the beam splitter prism and the object surface. The invention belongs to the technical field of ultra-precision measurement.

Description

Technical Field

[0001] The invention relates to a line spectrum confocal measurement device, belonging to the technical field of ultra-precision measurement. Background Art

[0002] Optical microscopes have become an indispensable tool in the field of industrial measurement due to their advantages such as non-contact, non-destructive and high precision. With the rapid development of precision manufacturing, the demand for high-precision detection is also increasing year by year. Spectral confocal sensors are the most commonly used sensors. Compared with laser confocal sensors, spectral confocal sensors focus a wide spectrum light source to different positions through a dispersive objective lens, and achieve fast, high-precision displacement and thickness measurement without axial scanning through spectral demodulation.

[0003] Although spectral confocal does not require axial scanning, in order to achieve rapid measurement of three-dimensional surfaces, a two-dimensional translation stage is still required for lateral scanning, which leads to a decrease in measurement speed and makes it impossible to achieve instantaneous scanning measurement. Line scanning spectral confocal can measure multiple points simultaneously, and with a one-dimensional translation stage, it can perform high-speed continuous measurement on the production line, which is very suitable for industrial assembly line inspection scenarios.

[0004] However, existing line scanning spectral confocals mostly use slits instead of traditional pinholes. Although this modification improves the measurement efficiency, it also causes the light intensity of adjacent measurement points to crosstalk, resulting in a decrease in axial and lateral resolution. To address this problem, existing technologies include the use of arrayed optical fibers, micromirror arrays, LCD panels, micro-LEDs, etc. However, these methods can only suppress the crosstalk problem to a certain extent and often have a low spatial sampling rate. Other improvements include denoising and deconvolution, which improve the signal-to-noise ratio to a certain extent. They have a certain effect on smooth and highly reflective surfaces, but their performance on rough surfaces and low-reflective surfaces is very limited. Therefore, it is necessary to improve the line spectrum confocal structure from a hardware perspective, effectively suppress defocused light and crosstalk light, and improve its measurement capabilities. Summary of the invention

[0005] The present invention aims to solve the problem that the prior art cannot effectively suppress defocused light and crosstalk light and has poor measurement capability, and further proposes a polarization-controlled high-precision spectral confocal measurement device.

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

[0007] The linear light, the beam splitter prism, the dispersion objective lens and the first spectrum demodulation module are arranged in sequence from top to bottom, the object surface is arranged on one side of the beam splitter prism, a polarization array is arranged between the linear light and the beam splitter prism, and another polarization array is arranged between the beam splitter prism 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 a plurality of internal units, the internal unit in the middle is light-transmissive, and the internal units on both sides are coated with an anti-reflection coating, and the reflectivity of the anti-reflection coating is less than one thousandth.

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

[0012] Furthermore, the dispersive objective is corrected for single wavelength off-axis aberrations.

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

[0014] The invention comprises linear light, a polarization array, a beam splitter prism, a dispersion objective lens, a second spectrum demodulation module and two coupling mirror groups;

[0015] The linear light, the beam splitter prism, the polarization array, the dispersion objective lens and the object surface are arranged in sequence from left to right, the second spectrum demodulation module is arranged above the beam splitter prism, a coupling mirror group is arranged between the linear light and the beam splitter prism, and another coupling mirror group is arranged between the beam splitter prism and the second spectrum demodulation module.

[0016] The present invention comprises linear light, a first spectrum demodulation module and two beam splitting prism components;

[0017] The linear light is arranged on the left side above the first spectrum demodulation module, the object surface is arranged on the right side above the first spectrum demodulation module, a spectroscopic prism component is arranged between the linear light and the first spectrum demodulation module, and another spectroscopic prism component is arranged between the object surface and the first spectrum demodulation module.

[0018] Further, the beam splitter assembly includes a polarization array, a beam splitter prism and a dispersion objective lens;

[0019] The polarization array, the beam splitter prism and the dispersion objective lens are arranged in sequence from top to bottom.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention introduces a polarization array to control the polarization of the light source, effectively suppresses out-of-focus light and stray light, and reduces the light intensity crosstalk of adjacent measurement points, thereby greatly improving the signal-to-noise ratio of the detected spectral signal, which is beneficial to the subsequent signal peak extraction and effectively improves the lateral and axial resolution of the system;

[0022] 2. Due to the improvement of the lateral resolution of the detector, the measurement results of more points within a unit length can be reliable, so that the device can measure fine structures;

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

[0024] 4. The polarization array of the present invention can be used as a modulation device for the light source and a suppression device for the returned defocused light at the same time, without the need for the alignment operation of the traditional array device, which effectively reduces the steps of device installation and adjustment, reduces the difficulty of device installation and adjustment, and improves the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0027] Figure 3 It is a schematic diagram of the way in which the polarization array acts on the transmitted illumination light;

[0028] Figure 4 is a schematic diagram of the modulation of the quasi-focus reflected light by the polarization array;

[0029] Figure 5 is the modulation pattern 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 It is a schematic diagram of an off-axis polarization-controlled high-precision line spectrum confocal measurement device;

[0032] Figures 1 to 7 In the figure, 1- linear light, 2- polarization array, 3- beam splitter prism, 4- dispersion objective lens, 5- first spectrum demodulation module, 6- object surface, 7- second spectrum demodulation module, 8- coupling mirror group. DETAILED DESCRIPTION

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

[0034] The linear light 1, the beam splitter prism 3, the dispersion objective lens 4 and the first spectral demodulation module 5 are arranged in sequence from top to bottom, the object surface 6 is arranged on one side of the beam splitter prism 3, a polarization array 2 is arranged between the linear light 1 and the beam splitter prism 3, and another polarization array 2 is arranged between the beam splitter prism 3 and the object surface 6.

[0035] The linear light 1 is composed of an LED array, or can be formed by focusing a wide spectrum light source, and its line width and line length are close to the width and length of the polarization array 2;

[0036] Among them, the polarization array 2 is used for polarization modulation of the linear light 1 and selective passage 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 by 1 / 4 wavelength and 1 / 2 wavelength to ensure that there is a significant light transmittance difference between adjacent units after two modulations. There are multiple units inside the polarization array, and the specific number can be determined according to the line length to be detected, and the values ​​​​usually can be 1024 or 2048.

[0037] The polarization array 2 is composed of a plurality of internal units, the internal unit in the middle is light-transmitting, and the internal units on both sides are coated with an anti-reflection coating, and the reflectivity of the anti-reflection coating is less than one thousandth; the number of polarization arrays can be one, which is directly placed between the dispersion objective lens and the beam splitter prism, and it simultaneously realizes converting the transmitted light into linear polarization and suppressing other polarization states of the returned light; the size of the polarization array unit is usually in the micron range, preferably thirty microns.

[0038] The ratio of reflected light to transmitted light of the prism 3 is 50:50.

[0039] The dispersion objective lens 4 is corrected for single-wavelength off-axis aberrations, especially the field curvature aberration should ensure that there is no obvious focus shift within the measurement line length.

[0040] The first spectrum demodulation module 5 is a spectrum peak extraction device, and its detector may be polarization-insensitive or may be capable of polarization state detection.

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

[0042] like Figure 2As shown, the structure of the polarization array 2 is composed of tiny units in a periodic polarization state. The size of each unit is tens of microns. The specific size can be determined by the method multiple of the dispersion objective lens. The size of each unit should ensure that it reaches an ideal size after being focused by the dispersion objective lens. At the same time, each unit size has high light transmittance. When the light passing through is natural light and non-polarized light, it can ensure that the transmittance is close to 50%.

[0043] like Figure 3 As shown, natural light will form a periodic array of different polarization states after passing through the polarization array. After being collected and focused by the dispersion objective lens, the polarization states of the focal points corresponding to each unit and the focus points of the return light are largely the same as the polarization states of the unit itself. The smooth surface can maintain the above polarization characteristics to a large extent, while the polarization characteristics of the rough surface will be destroyed to a certain extent, but the overall polarization tends to the unit itself.

[0044] like Figure 4 and Figure 5 As shown, the polarization array 2 mainly functions to suppress the defocused light and stray light of adjacent points. When the light is focused on the surface of the object after passing through the dispersive objective lens 4, the focal point size of the returned 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 defocused focus of the illumination light is irradiated on the surface of the object, the focus size of the returned light will be larger than the size of the polarization unit, so that the diffuse light will irradiate other polarization units. Since the polarization states of adjacent units are inconsistent, the defocused light cannot pass through, thereby increasing the signal proportion of the measurement point itself and greatly improving the signal-to-noise ratio.

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

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

[0047] like Figure 6As shown, another variation of the polarization-controlled high-precision linear confocal measurement device uses a polarization device to simultaneously modulate the polarization of the light source and suppress the returned defocused light, which effectively reduces the complexity of the installation and adjustment caused by the simultaneous operation of the two devices, reduces the system's installation and adjustment errors, and improves the stability of the system; the specific implementation process is that the linear light 1 is collected by the coupling lens group 8 and then transmitted through the beam splitter prism 3 and projected onto the polarization array 2, and then is focused on the object surface 6 along the axial direction by the dispersive objective lens 4, the returned light is collected by the dispersive objective lens 4 and then focused on the polarization array 2 again, and then the filtered light is reflected by the beam splitter prism 3 and then collected by the coupling lens group 8 and focused on the second spectral demodulation module 7, and then the spectral peak is extracted.

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

[0049] The linear light 1 is arranged on the left side above the first spectral demodulation module 5, the object surface 6 is arranged on the right side above the first spectral demodulation module 5, a spectroscopic prism component is arranged between the linear light 1 and the first spectral demodulation module 5, and another spectroscopic prism component is arranged between the object surface 6 and the first spectral demodulation module 5.

[0050] Wherein, the beam splitter prism assembly includes a polarization array 2, a beam splitter prism 3 and a dispersion objective lens 4;

[0051] The polarization array 2, the beam splitter prism 3 and the dispersion objective lens 4 are arranged in sequence 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, and then dispersed along the off-axis by the beam splitter prism 3 and dispersed along the axial direction by the dispersion objective lens 4, and then focused on the object surface 6. The return light passes through the dispersion objective lens 4 with the same parameters and then passes through the beam splitter prism 3 with the same parameters to reach the polarization array 2, and then enters the spectrum demodulation module for peak wavelength extraction.

[0053] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A polarization-controlled high-precision spectral confocal measurement device, characterized in that: It comprises linear light (1), two polarization arrays (2), a beam splitter prism (3), a dispersion objective lens (4) and a first spectrum demodulation module (5); The linear light (1), the beam splitter prism (3), the dispersion objective lens (4) and the first spectrum demodulation module (5) are arranged in sequence from top to bottom, the object surface (6) is arranged on one side of the beam splitter prism (3), a polarization array (2) is arranged between the linear light (1) and the beam splitter prism (3), and another polarization array (2) is arranged between the beam splitter prism (3) and the object surface (6).

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

3. The polarization-controlled high-precision spectral confocal measurement device according to claim 1, characterized in that: The polarization array (2) is used for polarization modulation of linear light (1) and for selectively passing 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.

4. The polarization-controlled high-precision spectral confocal measurement device according to claim 1, characterized in that: The polarization array (2) is composed of a plurality of internal units, wherein the internal unit located in the middle is light-transmissive, and the internal units located on both sides are coated with an anti-reflection coating, wherein the reflectivity of the anti-reflection coating is less than one thousandth.

5. The polarization-controlled high-precision spectral confocal measurement device according to claim 1, characterized in that: The ratio of reflected light and transmitted light of the beam splitter (3) is 50:

50.

6. The polarization-controlled high-precision spectral confocal measurement device according to claim 1, characterized in that: The dispersive objective lens (4) is corrected for single wavelength off-axis aberrations.

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

8. A polarization-controlled high-precision spectral confocal measurement device, characterized in that: It comprises linear light (1), a polarization array (2), a beam splitter prism (3), a dispersion objective lens (4), a second spectrum demodulation module (7) and two coupling mirror groups (8); The linear light (1), the beam splitter prism (3), the polarization array (2), the dispersion objective lens (4) and the object surface (6) are arranged in sequence from left to right, the second spectrum demodulation module (7) is arranged above the beam splitter prism (3), a coupling mirror group (8) is arranged between the linear light (1) and the beam splitter prism (3), and another coupling mirror group (8) is arranged between the beam splitter prism (3) and the second spectrum demodulation module (7).

9. A polarization-controlled high-precision spectral confocal measurement device, characterized in that: It comprises linear light (1), a first spectrum demodulation module (5) and two beam splitting prism components; The linear light (1) is arranged on the left side above the first spectrum demodulation module (5), the object surface (6) is arranged on the right side above the first spectrum demodulation module (5), a beam splitter prism component is arranged between the linear light (1) and the first spectrum demodulation module (5), and another beam splitter prism component is arranged between the object surface (6) and the first spectrum demodulation module (5).

10. The polarization-controlled high-precision spectral confocal measurement device according to claim 9, characterized in that: The beam splitter prism assembly comprises a polarization array (2), a beam splitter prism (3) and a dispersion objective lens (4); The polarization array (2), the beam splitter prism (3) and the dispersion objective lens (4) are arranged in sequence from top to bottom.

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