Optical measuring device for thickness of low-reflection film

Abstract

The invention discloses a low-reflection film thickness optical measuring device which comprises a Y-shaped optical fiber, the split end of the Y-shaped optical fiber is connected with a light source and a spectrograph, the tail end of the Y-shaped optical fiber is connected with an optical fiber connector, a first curved surface reflector is obliquely arranged in the light emitting direction of the optical fiber connector, and the first curved surface reflector is used for changing the direction of a light path. An optical translation mechanism is further arranged on the light path of the first curved-surface reflecting mirror, the optical translation mechanism comprises a reflecting cylindrical mirror and a second curved-surface reflecting mirror, the reflecting cylindrical mirror and the second curved-surface reflecting mirror are symmetrically installed, and the optical translation mechanism is used for adjusting the positions of the reflecting cylindrical mirror and the second curved-surface reflecting mirror in the vertical direction. A novel reflection type light path design is adopted, effective collection of sample reflection light energy is achieved through the reflection lens set, and therefore effective and accurate measurement of the film thickness of the low-reflectivity sample is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement, and in particular relates to an optical measurement device for the thickness of a low-reflection film. Background Art

[0002] Traditional white light film thickness measurement technology has some challenges when dealing with low reflectivity materials. Traditional white light film thickness measurement uses a focusing lens after the fiber probe. This method severely limits the ability to collect energy reflected from the sample back to the fiber receiving end.

[0003] Since low-reflectivity materials have a high light absorption rate or transmittance, the proportion of energy reflected from the sample to the probe is relatively small. When the optical fiber probe is focused by the focusing lens group, the energy collection ability is weak, and the effective signal cannot be transmitted to the spectrometer detector, resulting in poor measurement results for low-reflectivity samples. This limitation affects the accurate measurement of the film thickness of low-reflectivity materials and hinders research and application in related fields.

[0004] Common white light film thickness measuring instruments such as Figure 1 As shown, during the film thickness measurement process, light is emitted from a white light source 6, passes through a Y-type optical fiber 1 to a fiber probe 2, and is focused 4 onto a sample surface 5 by a focusing lens group 3. The light reflected by the sample returns to the fiber probe 2 along the original path, passes through the Y-type optical fiber 1 at the other end, and finally reaches a spectrometer 7. The spectrometer is used to analyze the spectral signal of the reflected light and calculate the film thickness value. It is worth noting that if the spectral signal intensity is too weak or the signal-to-noise ratio is poor, the calculation of the film thickness value becomes difficult.

[0005] In common white light film thickness gauges, the position of the fiber optic probe plays a key role in energy collection. The focusing lens group has strong correction capabilities in the visible light band, but chromatic aberration or other optical deviations may occur in the ultraviolet and infrared bands.

[0006] These optical deviations are difficult to completely eliminate in a transmissive optical structure, or the cost of eliminating them is high.

[0007] The distribution of energy collection of the fiber optic probe position relative to the center distance of the optical axis of a common white light film thickness measurement instrument is as follows Figure 2 As shown, the horizontal axis represents the distance to the center of the optical axis, and the vertical axis represents the captured energy ratio.

[0008] Within 100 microns from the optical axis, the energy capture of light with a wavelength of 400nm can reach about 70%.

[0009] However, light with a wavelength of 200nm (ultraviolet) and 1700nm (infrared) captures only about 20% of the energy over the same distance range.

[0010] These analysis results show that for common white light film thickness measurement instruments, there are differences in the efficiency of capturing light energy at different wavelengths. These optical deviations are difficult to eliminate in the optical structure of the transmission type, or the cost of eliminating them is too high. Summary of the invention

[0011] In view of the above-mentioned technical problems, the purpose of the present invention is to provide an optical measuring device for the thickness of low-reflective films, which adopts a new reflective optical path design and realizes the effective collection of the sample reflected light energy through a reflective lens group, thereby realizing effective and accurate measurement of the film thickness of low-reflectivity samples.

[0012] In order to solve the above technical problems, the technical solution of the present invention is: A low-reflection film thickness optical measurement device comprises a Y-type optical fiber, wherein the split end of the Y-type optical fiber is connected to a light source and a spectrometer, the tail end of the Y-type optical fiber is connected to an optical fiber connector, a first curved reflector is obliquely arranged in the light emitting direction of the optical fiber connector, the first curved reflector is used to change the direction of the light path, an optical translation mechanism is also arranged on the light path of the first curved reflector, the optical translation mechanism comprises a reflecting cylindrical mirror and a second curved reflector, the reflecting cylindrical mirror and the second curved reflector are symmetrically installed, and the optical translation mechanism is used to adjust the vertical position of the reflecting cylindrical mirror and the second curved reflector.

[0013] In a preferred technical solution, the optical translation mechanism includes a fixed frame arranged above the base, a moving block is arranged in the fixed frame, the moving block is connected to the adjustment rod, the adjustment rod is connected to the adjustment knob, and the reflective cylindrical mirror and the second curved reflective mirror are symmetrically installed in the moving block.

[0014] In a preferred technical solution, an extension portion is provided on one side of the fixing frame, a fixing block is provided on the extension portion, the fixing block is tilted, elastic portions are provided at both ends of the fixing block, and the first curved reflector is clamped on the fixing block through the elastic portion.

[0015] In the preferred technical solution, a groove is provided on one side of the moving block, and the groove is provided with a first fixed inclined surface and a second fixed inclined surface, the first fixed inclined surface and the second fixed inclined surface are symmetrically arranged, and a second elastic part is provided at the outer ends of the first fixed inclined surface and the second fixed inclined surface, and the end of the second elastic part extends inward by a certain distance.

[0016] In a preferred technical solution, grooves are respectively provided at both ends of the first fixed inclined surface and the second fixed inclined surface.

[0017] In a preferred technical solution, the first fixing inclined surface is parallel to the surface of the fixing block.

[0018] In a preferred technical solution, the extension portion of the fixing frame is provided with a mounting hole, the mounting hole is used to install a flange base, the flange base includes a mounting portion and a connecting portion, the connecting portion is connected to the optical fiber connector, and the mounting portion is installed in the mounting hole.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a novel reflective optical path design, which realizes the effective collection of sample reflected light energy through a reflective lens group, thereby achieving effective and accurate measurement of the film thickness of low-reflectivity samples.

[0020] The optical translation mechanism can achieve up and down movement by rotation, and can fine-tune the moving block to achieve precise control of the focus. The lens of this structure is easy to install, simple to operate, and short in time, and can improve the measurement speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of a common white light film thickness measuring instrument; Figure 2 Energy analysis of the fiber optic probe position of common white light film thickness measuring instruments; Figure 3 This is a schematic diagram of the optical path of the measuring instrument of the reflective film thickness measuring device of this embodiment; Figure 4 Schematic diagram of the structure of the reflective film thickness measuring device of this embodiment; Figure 5 is a schematic structural diagram of the optical translation mechanism of this embodiment; Figure 6 is a structural schematic diagram of the optical translation mechanism from another angle of this embodiment; Figure 7 is a schematic diagram of the structure of the moving block of this embodiment; Figure 8 for Figure 4 The enlarged view of point A in the middle; Fig. 9 Schematic diagram of the structure of the flange base of this embodiment; Fig.10 This is the energy analysis of the optical fiber probe position of the reflection type film thickness measurement device of this embodiment. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0023] Example

[0024] like Figure 3 As shown, an optical measuring device for the thickness of a low-reflection film comprises a Y-type optical fiber 10, wherein the split end of the Y-type optical fiber 10 is connected to a light source 20 and a spectrometer 30, and the tail end of the Y-type optical fiber 10 is connected to an optical fiber connector 40, and a first curved reflector 50 is arranged obliquely in the light emitting direction of the optical fiber connector 40, and the first curved reflector 50 is used to change the direction of the light path, and an optical translation mechanism 60 is also arranged on the light path of the first curved reflector 50, and the optical translation mechanism 60 comprises a reflecting cylindrical mirror 61 and a second curved reflector 62, and the reflecting cylindrical mirror 61 and the second curved reflector 62 are symmetrically installed, and the optical translation mechanism 60 is used to adjust the vertical position of the reflecting cylindrical mirror 61 and the second curved reflector 62.

[0025] Y-type optical fiber 10: used for transmission and reception of optical signals.

[0026] The optical fiber connector 40 may be an SMA connector or an FC connector, or other forms of optical fiber connectors may be used.

[0027] The split ends of the Y-type optical fiber 10 are respectively connected to a white light source 20 and a spectrometer 30 . The white light source can be a combination of one or more of a tungsten halogen lamp, an LED, a deuterium lamp, a xenon lamp, and LDLS.

[0028] The first curved reflector 50 is used to reflect horizontally incident light into vertically upward light, thereby redirecting the light path.

[0029] The optical translation mechanism 60 includes a reflective cylindrical mirror 61 and a second curved reflective mirror 62, which are installed therein in a 45-degree symmetrical manner.

[0030] A displacement knob 63 is provided above the optical translation mechanism 60 , which can be rotated to achieve up and down movement and adjust the focus height.

[0031] The sample 70 to be measured is placed in the optical path for measuring the film thickness.

[0032] In this device, the white light source transmits light through a Y-shaped optical fiber, and after being reflected by the first curved reflector, the light is turned vertically upward. The reflective cylindrical mirror and the second curved reflector are symmetrically installed to allow the light to be correctly reflected and focused. By rotating the displacement knob of the optical translation stage, the optical translation mechanism can move up and down to adjust the focus height to ensure that the light is correctly focused on the sample being measured. This design allows the light in the optical path to be effectively guided and focused, providing a reliable optical environment for film thickness measurement.

[0033] A specific embodiment, such as Figure 4 , 5As shown, the optical translation mechanism 60 includes a fixed frame 64 arranged above the base 11, a moving block 65 is arranged in the fixed frame 64, the moving block 65 is connected to the adjustment rod 66, the adjustment rod 66 is connected to the adjustment knob 63, and the reflecting cylindrical mirror 61 and the second curved reflecting mirror 62 are symmetrically installed in the moving block 65.

[0034] In one embodiment, Figure 6 As shown, an extension portion 641 is provided on one side of the fixing frame 64, and a fixing block 642 is provided on the extension portion 641. The fixing block 642 is tilted, and elastic portions 643 are provided at both ends of the fixing block 642. The first curved reflector 50 is clamped on the fixing block 642 through the elastic portions 643. The elastic portion 643 has a certain elasticity and is not necessarily made of an elastic material.

[0035] In one embodiment, Figure 7 As shown, a groove 651 is provided on one side of the moving block 65, and the groove 651 is provided with a first fixed inclined surface 652 and a second fixed inclined surface 653, and the first fixed inclined surface 652 and the second fixed inclined surface 653 are symmetrically arranged, and the ends of the first fixed inclined surface 652 and the second fixed inclined surface 653 close to the outside are provided with a second elastic part 654, and the end of the second elastic part 654 extends a certain distance inward. The second elastic part 654 has a certain elasticity like the elastic part 643, and is not necessarily made of an elastic material. The first fixed inclined surface 652 is used to install the reflective cylindrical mirror 61, and the second fixed inclined surface 653 is used to install the second curved reflective mirror 62.

[0036] In one embodiment, the first fixing inclined surface 652 is parallel to the surface of the fixing block 642 .

[0037] In one embodiment, grooves 655 are respectively provided at both ends of the first fixing inclined surface 652 and the second fixing inclined surface 653 , and the grooves 655 are semicircular arc grooves.

[0038] In one embodiment, Figure 8 , 9 As shown, the extension portion 641 of the fixing frame 64 is provided with a mounting hole 644 , and the mounting hole 644 is used to install the flange base 80 . The flange base 80 includes a mounting portion 81 and a connecting portion 82 . The connecting portion 82 is connected to the optical fiber connector 40 , and the mounting portion 82 is installed in the mounting hole 644 .

[0039] Light path description: 1. The light emitted by the light source 20 is transmitted to the optical fiber connector 40 through the Y-type optical fiber 10, and then reaches the first curved reflector 50, which reflects the light to the reflective cylindrical mirror 61, and then reflected by the reflective cylindrical mirror 61 to the second curved reflector 62, and finally the light is vertically incident on the sample 70 to be tested.

[0040] 2. The optical path of the signal of the measured sample 70 is opposite to the above optical path: from the measured sample 70 to the second curved reflector 62, then from the second curved reflector 62 to the reflecting cylindrical mirror 61, then from the reflecting cylindrical mirror 61 to the first curved reflector 50, then to the optical fiber connector 40, the optical fiber connector 40 to the Y-type optical fiber 10, and finally to the spectrometer 30.

[0041] Through this carefully designed mechanical structure, light can be effectively transmitted and focused, providing a reliable optical path for film thickness measurement. The layout of the entire system makes signal collection and processing more efficient and precise, thereby improving the accuracy and reliability of measurement. This design of reflective optical path is particularly suitable for wide-band optical devices, which can significantly improve energy collection efficiency and provide important technical support for optical measurement.

[0042] The reflective optical path is more suitable for wide-band optical devices, and its energy collection efficiency far exceeds that of traditional white light film thickness measuring instruments. Fig.10 In the figure, the three curves represent the changes in the collected energy fraction at wavelengths of 200nm, 400nm and 1700nm as the distance from the center of the optical axis changes. It is observed that the energy collection efficiency at different wavelengths is consistent, and within 100 microns from the optical axis, the energy fraction reaches about 80%.

[0043] These results clearly show that the energy collection efficiency of the reflective white light film thickness measurement instrument of the present invention is significantly better than that of the traditional white light film thickness measurement instrument. For low reflectivity materials, the device can collect light intensity more efficiently, which helps to improve the signal-to-noise ratio or increase the measurement speed while maintaining the same collected light intensity.

[0044] This superior energy collection efficiency is of great significance for a wide range of applications, especially when low reflectivity materials need to be measured. By improving the energy collection efficiency, the design of this reflective optical path can significantly improve the accuracy and efficiency of the measurement, providing important technical support for the performance improvement of optical equipment.

[0045] The film thickness measuring device of the present invention has greatly improved energy collection efficiency at the receiving end, and the energy collection efficiency at ultraviolet and infrared wavelengths has been improved several times compared with traditional devices. For low reflectivity materials, the device can collect more light intensity, improve the signal-to-noise ratio, or increase the measurement speed for the same collected light intensity.

[0046] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. An optical measuring device for the thickness of a low-reflection film, comprising a Y-type optical fiber, characterized in that: The split end of the Y-type optical fiber is connected to a light source and a spectrometer, and the tail end of the Y-type optical fiber is connected to a fiber optic connector. A first curved reflector is tilted in the light output direction of the fiber optic connector. The first curved reflector is used to change the direction of the light path. An optical translation mechanism is also provided on the light path of the first curved reflector. The optical translation mechanism includes a reflecting cylindrical mirror and a second curved reflector. The reflecting cylindrical mirror and the second curved reflector are symmetrically installed, and the optical translation mechanism is used to adjust the vertical position of the reflecting cylindrical mirror and the second curved reflector.

2. The optical measuring device for the thickness of a low-reflection film according to claim 1, characterized in that: The optical translation mechanism comprises a fixed frame arranged above the base, a moving block is arranged in the fixed frame, the moving block is connected to an adjusting rod, the adjusting rod is connected to an adjusting knob, and the reflecting cylindrical mirror and the second curved reflecting mirror are symmetrically installed in the moving block.

3. The optical measuring device for low-reflection film thickness according to claim 1, characterized in that: An extension portion is provided on one side of the fixing frame, a fixing block is provided on the extension portion, the fixing block is tilted, elastic portions are provided at both ends of the fixing block, and the first curved reflector is clamped on the fixing block through the elastic portion.

4. The optical measuring device for the thickness of a low-reflection film according to claim 3, characterized in that: A groove is provided on one side of the moving block, and the groove is provided with a first fixed inclined surface and a second fixed inclined surface, the first fixed inclined surface and the second fixed inclined surface are symmetrically arranged, and a second elastic part is provided at the outer ends of the first fixed inclined surface and the second fixed inclined surface, and the end of the second elastic part extends inward by a certain distance.

5. The optical measuring device for low-reflection film thickness according to claim 4, characterized in that: Grooves are respectively provided at both ends of the first fixing inclined surface and the second fixing inclined surface.

6. The optical measuring device for the thickness of a low-reflection film according to claim 4, characterized in that: The first fixing inclined surface is parallel to the surface of the fixing block.

7. The optical measuring device for low-reflection film thickness according to claim 3, characterized in that: The extension portion of the fixing frame is provided with a mounting hole, the mounting hole is used to install the flange base, the flange base includes a mounting portion and a connecting portion, the connecting portion is connected to the optical fiber connector, and the mounting portion is installed in the mounting hole.

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