A device and method for measuring three-dimensional topography of a non-uniform reflectivity sample

Abstract

The present application relates to a kind of uneven reflectivity sample three-dimensional topography measuring device and method, comprising: structured light illumination element DLP, collimating lens group, polarizing beam splitter, 1 / 4 wave plate, motor, dispersion tube mirror, objective lens, the objective table of placing measured sample, focusing lens, two-phase color mirror, first filter, first camera, total reflection prism, second filter, second camera and microprocessor;The 1 / 4 wave plate, motor, dispersion tube mirror, objective lens, objective table, focusing lens, first camera and second camera are perpendicular to optical axis, the structured light illumination element DLP, polarizer and collimating lens group are parallel to optical axis, and with the optical axis line reflected by measured sample vertical.The present application is simple in structure, can quickly measure the step height of uneven reflectivity sample, and can eliminate the multiplicative error caused by uneven reflectivity by wide-field image, with higher measurement accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of confocal technology, and in particular to a device and method for measuring three-dimensional topography of a sample with uneven reflectivity. BACKGROUND

[0002] With the continuous development of technology, the detection requirements for the surface topography of high-precision machining are also continuously improving, specifically involving efficient detection of large-size and complex topography micro-nano topography samples. The differential parallel confocal measurement technology disclosed in a differential confocal axial range expansion measurement device (CN202320166403.8) becomes an important part of the detection technology. Compared with the traditional technology, this technology avoids hierarchical scanning to improve detection efficiency and at the same time improves the detection range. On this basis, a multi-band differential confocal microscopic 3D measurement method and device (CN202210898540.0) proposes a chromatic differential parallel confocal technology, which uses the different axial chromatic dispersion distances between different wavebands to detect the three-dimensional topography of the measured sample. However, the existing technology is not suitable for samples with uneven surface reflectivity. When samples with different materials have different reflectivity, the intensity of one part of the same detection sample will be high due to its high reflectivity, which will make the surface height tend to be high, while the other part will be dark due to its low reflectivity, making the measured surface height low. Therefore, the existing differential confocal method cannot detect the height of the sample with uneven reflectivity, resulting in errors in the measurement results. SUMMARY

[0003] The purpose of the present application is to overcome the problem of large measurement error in the prior art, and to provide a device and method for measuring the three-dimensional topography of a sample with uneven reflectivity. The structured light illumination element DLP can modulate different forms of light. By adjusting the structured light illumination element DLP to single-point mode or full-on mode, the multiplicative measurement error caused by different reflectivity can be eliminated, and the height difference of the sample with uneven reflectivity can be quickly and accurately obtained.

[0004] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0005] On the one hand, a device for measuring the three-dimensional topography of a sample with uneven reflectivity comprises a structured light illumination element DLP, a collimating lens group, a polarization beam splitter, a 1 / 4 waveplate, a chromatic tube lens, a motor, an objective lens, a sample stage on which a measured sample is placed, a two-phase mirror, a first camera, a total reflection prism, a second camera, and a microprocessor.

[0006] The collimating lens group and the polarization beam splitter are sequentially arranged on the emission light path of the structured light illumination element DLP; the 1 / 4 waveplate, the motor, the chromatic tube lens, the objective lens, and the measured sample are sequentially arranged on the reflected light path of the polarization beam splitter.

[0007] The objective lens, dispersive tube lens, motor, quarter-wave plate and polarizing beam splitter are also sequentially arranged in the reflected light path of the sample under test;

[0008] The first camera is positioned in the transmission light path of the dichroic mirror;

[0009] The total internal reflection prism is disposed on the reflected light path of the dichroic mirror, and the second camera is disposed on the reflected light path of the total internal reflection prism;

[0010] The microprocessor is connected to the first camera and the second camera respectively to acquire the collected images; the microprocessor is connected to the motor to control the motor to drive the dispersive tube lens and / or objective lens to move in the Z-axis direction;

[0011] The first camera is positioned at a specified distance behind the focal point of the first band; the second camera is positioned at a specified distance in front of the focal point of the second band; the reference planes of the first camera, the reference plane of the second camera, the structured light illumination element (DLP), and the focal plane of the sample under test are conjugate; the first band and the second band are two bands of light reflected from the surface of the sample under test after passing through a dichroic mirror.

[0012] Preferably, the structured light illumination element DLP includes an illumination source and a spatial light modulator.

[0013] Preferably, the three-dimensional morphology measurement device for non-uniform reflectance samples further includes: a focusing lens; the focusing lens is disposed between the polarizing beam splitter and the dichroic mirror.

[0014] Preferably, the three-dimensional morphology measurement device for non-uniform reflectance samples further includes: a first filter; the first filter is disposed between the first camera and the dichroic mirror.

[0015] Preferably, the three-dimensional morphology measurement device for non-uniform reflectance samples further includes: a second filter; the second filter is disposed between the total internal reflection prism and the second camera.

[0016] Preferably, the motor is a piezoelectric ceramic motor.

[0017] On the other hand, a method for measuring the three-dimensional morphology of a sample with uneven reflectance, based on the aforementioned device for measuring the three-dimensional morphology of a sample with uneven reflectance, includes:

[0018] S1, Place the sample to be tested.

[0019] Place the sample within the working range of the measuring device and keep the position of the sample from changing.

[0020] S2, acquire the confocal signal of the two bands.

[0021] The illumination mode of the structured light illumination element DLP is modulated to acquire images, reconstruct confocal images of two bands, and drive the microprocessor to simultaneously acquire the confocal images A of the two bands. λ1 and A λ2 ;

[0022] S3, acquire wide-field signals in two bands.

[0023] Modulate the structured light illumination element DLP to full-on illumination mode and acquire sample wide-field images B under the same conditions and positions as in step S2. λ1 and B λ2 ;

[0024] S4, Calculate the step height of the sample being measured.

[0025] The image is obtained by performing operations on two sets of grayscale images. calibration formula I in D The step height of the test sample is obtained by replacing the gray value of image Q. Based on the step height, a grayscale image Q of the test sample is obtained. Z ;

[0026] S5, acquire the 3D point cloud of the sample under test. The microprocessor will then process the image Q... Z The pixel position is used as the XY position of the three-dimensional shape, and the image Q is... Z The grayscale value is used as the height in the Z-axis direction to obtain the three-dimensional point cloud of the sample under test;

[0027] S6, Fitting the three-dimensional morphology of the sample under test.

[0028] The microprocessor fits the point cloud in the three-dimensional point cloud of the sample under test to obtain the three-dimensional morphology of the sample with uneven reflectance.

[0029] Preferably, before calculating the step height of the measured sample, data calibration is also included, as follows:

[0030] Calibration steps for the linear relationship between light intensity and axial position:

[0031] The structured light illumination element DLP is in single-point mode, using uniform reflectance samples as calibration samples; the first camera and the first band λ1 are used for focusing. After focusing on the focal plane, the microprocessor drives the motor to move in the Z-axis direction, and the preset single-point images are scanned.

[0032] Steps to obtain the calibration formula:

[0033] Without changing the scanning position of the motor, the motor is driven to move in the Z-axis direction using the second camera and the second waveband λ2, and a preset single-point image is scanned out; the relationship between the single-point gray value in the preset image and the range of the motor moving in the axial direction is drawn in the same coordinate system, that is, the axial light intensity response curves of the two wavebands are drawn and The and difference is obtained, and the linear relationship I between the differential light intensity and the axial direction of the axial light intensity curves of the two wavebands is obtained D , I D = I λ1 -I λ2 =kz D +b; wherein, z D is the axial position; k and b are the fitted coefficients; based on I D = I λ1 -I λ2 =kz D +b, the calibration formula is obtained

[0034] The beneficial effects of the present application are as follows:

[0035] (1) The structured light illumination element DLP used in the present application can not only be used as a light source, but also can be used for spatial light modulation, modulating a single beam of light into different forms of structured light, and modulating a single point to complete the calibration of the confocal mode; the DLP is opened in a full-on mode, and the multiplicative error caused by the uneven reflectivity can be eliminated through a wide-field image, the step height of the uneven reflectivity sample in the measurement range can be measured, and finally the three-dimensional topography measurement of the uneven reflectivity sample can be realized;

[0036] (2) The focusing positions of the two wavebands in the present application are arranged at the same position away from the focus of the two wavebands of the measured sample, and the structured light illumination element DLP, the measured sample and the positions of the two cameras are conjugate, the waveband 1 camera and the waveband 2 camera simultaneously shoot two images required, and the difference is realized;

[0037] (3) The present application has the advantages of simple structure, easy operation, fast measurement speed and high measurement precision, and can be used for industrial rapid detection.

[0038] The present application will be further described in detail in combination with the drawings and embodiments, but the three-dimensional topography measurement device and method for uneven reflectivity sample of the present application are not limited to the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description only show some of the embodiments of the present application, and all the other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0040] Figure 1 A structural schematic diagram of the uneven reflectivity sample three-dimensional topography measurement device of the embodiment of the present application;

[0041] Figure 2 A flow chart of the uneven reflectivity sample three-dimensional topography measurement method of the embodiment of the present application;

[0042] The drawings are as follows: 1, a structured light illumination element DLP; 2, a collimating lens group; 3, a polarization beamsplitter; 4, a 1 / 4 wave plate; 5, a dispersion tube mirror; 6, a motor; 7, an objective lens; 8, an objective table; 9, a focusing lens; 10, a dichroic mirror; 11, a first filter; 12, a first camera; 13, a total reflection prism; 14, a second filter; 15, a second camera; and 16, a microprocessor. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application more clear, the following will further describe the present application in detail with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0044] Referring to Figure 1 The embodiment discloses an uneven reflectivity sample three-dimensional topography measurement device, which comprises a structured light illumination element DLP 1, a collimating lens group 2, a polarization beamsplitter 3, a 1 / 4 wave plate 4, a dispersion tube mirror 5, a motor 6, an objective lens 7, an objective table 8 on which a measured sample is placed, a focusing lens 9, a dichroic mirror 10, a first filter 11, a first camera 12, a total reflection prism 13, a second filter 14, a second camera 15, and a microprocessor 16.

[0045] The collimating lens group 2 and the polarization beamsplitter 3 are sequentially arranged on the emission light path of the structured light illumination element DLP 1; the 1 / 4 wave plate 4, the dispersion tube mirror 5, the motor 6, the objective lens 7, and the measured sample are sequentially arranged on the reflection light path of the polarization beamsplitter 3.

[0046] The objective lens 7, the motor 6, the 1 / 4 wave plate 4, and the polarization beamsplitter 3 are further sequentially arranged on the reflection light path of the measured sample.

[0047] The first camera 12 is arranged on the transmission light path of the dichroic mirror 10; the focusing lens 9 is arranged between the polarizing beam splitter 3 and the dichroic mirror 10; the first filter 11 is arranged between the first camera 12 and the dichroic mirror 10.

[0048] The total reflection prism 13 is arranged on the reflection light path of the dichroic mirror 10, and the second camera 15 is arranged on the reflection light path of the total reflection prism 13; the second filter 14 is arranged between the total reflection prism 13 and the second camera 15.

[0049] The microprocessor 16 is connected with the first camera 12 and the second camera 15 respectively to acquire the collected images; the microprocessor 16 is connected with the motor 6 to control the motor 6 to drive the objective lens 7 to move in the Z-axis direction.

[0050] The first camera 12 is arranged at a specified distance M away from the first waveband focus point; the second camera 15 is arranged at a specified distance M away from the second waveband focus point; the reference surface of the first camera 12, the reference surface of the second camera 15, the structured light illumination element DLP 1 and the focal surface position of the measured sample are conjugated; the first waveband and the second waveband are two wavebands of the light reflected by the surface of the measured sample after passing through the dichroic mirror 10.

[0051] Further, the structured light illumination element DLP 1 includes an illumination light source and a spatial light modulator, that is, the structured light illumination element DLP 1 can act as an illumination light source and can also perform spatial light modulation.

[0052] The motor 6 is a piezoelectric ceramic motor.

[0053] In the embodiment, the 1 / 4 wave plate 4, the dispersion tube mirror 5, the motor 6, the objective lens 7, the objective table 8, the focusing lens 9, the first camera 12 and the second camera 15 are perpendicular to the same optical axis, the structured light illumination element DLP 1 and the collimating lens group 2 are parallel to the same optical axis, and are perpendicular to the optical axis of the light reflected by the measured sample.

[0054] The light emitted by the structured light illumination element DLP 1 is spatially modulated by itself into a light spot or a stripe light, and then reaches the PBS polarizing beam splitter 3 through the collimating lens group 2, is reflected to the 1 / 4 wave plate to convert linearly polarized light into circularly polarized light, and then passes through the dispersion tube mirror 5 and the objective lens 7 in turn, so that a series of focal points are generated along the optical axis, and the focal points of several wave bands are focused on the surface of the measured sample, and the light of the several wave bands is reflected on the surface of the sample, passes through the objective lens 7, the dispersion tube mirror 5, the 1 / 4 wave plate 4, the polarizing beam splitter 3 and the focusing lens 9 in turn, and then is focused by the focusing lens 9 to the two-phase color mirror 10, so that the light is divided into two wave bands, the first wave band is transmitted through the first filter 11 and is received by the first camera 12, and the second wave band is transmitted through the filter 14 by the total reflection prism 13 and is received by the second camera 15.

[0055] Referring to Figure 2 The application further discloses a three-dimensional topography measurement method for a sample with uneven reflectivity, and the method comprises the following steps.

[0056] S1, placing a sample to be measured

[0057] The sample to be measured is placed in the working range of the measurement device, and the position of the sample to be measured is kept unchanged;

[0058] S2, acquiring confocal signals of two wave bands

[0059] The illumination mode of the structured light illumination element DLP is modulated, an image is acquired, and confocal images of two wave bands are reconstructed, so that the microprocessor simultaneously acquires the confocal images A λ1 and A λ2 of the two wave bands.

[0060] S3, acquiring wide-field signals of two wave bands

[0061] The structured light illumination element DLP is modulated to be in a full-on illumination mode, and the wide-field images B λ1 and B λ2 of the sample under the same conditions and positions in the step S2 are acquired.

[0062] S4, calculating the step height of the measured sample

[0063] Two groups of gray-scale images are operated to obtain an image Q The gray-scale value of the image Q is used to replace I D in the calibration formula , so that the step height of the measured sample is obtained, and based on the step height, a gray-scale image Q Z of the measured sample is obtained.

[0064] S5, acquiring a three-dimensional point cloud of the measured sample

[0065] The microprocessor acquires the image Q Zpixel position as the XY position of the three-dimensional topography, and the image Q Z gray value as the Z-axis direction height, to obtain the three-dimensional point cloud of the measured sample;

[0066] S6, fitting the three-dimensional topography of the measured sample

[0067] The microprocessor fits the point cloud in the three-dimensional point cloud of the measured sample to obtain the three-dimensional topography of the sample with uneven reflectivity.

[0068] The above calculation of the step height of the measured sample further includes data calibration, and multiple tests do not need to be calibrated repeatedly. The data calibration includes:

[0069] The linear relationship calibration step of the light intensity and the axial position:

[0070] The DLP of the modulated structured light illumination element is a single-point mode, and a sample with uniform reflectivity is used as a calibration sample; the first camera and the first waveband λ1 are used for focusing, and after focusing to the focal plane, the microprocessor drives the motor to move in the Z-axis direction, and the preset single-point image is scanned out;

[0071] The calibration formula acquisition step:

[0072] Without changing the scanning position of the motor, the second camera and the second waveband λ2 are used, the motor is driven to move in the Z-axis direction, and the preset single-point image is scanned out; in the same coordinate system, the relationship between the single-point gray value in the preset image and the axial motor movement range under the two wavebands is drawn, that is, the axial light intensity response curves of the two wavebands are drawn and and The difference between the two wavebands is obtained, and the linear relationship I D , I D = I λ1 -I λ2 =kz D +b; wherein z D is the axial position; k and b are the fitted coefficients; based on I D = I λ1 -I λ2 =kz D +b, the calibration formula is obtained

[0073] The principles and operation modes of the present application are described through the above specific implementation cases. These cases aim to provide a clear understanding framework for the reader to grasp the core ideas and operation points of the present application. However, it needs to be clear that these cases are not a limitation on the application range of the present application, and various forms of improvement and innovation based on the core ideas of the present application should be included in the protection range of the present application for professional technicians in the field.​

Claims

1. A method for measuring the three-dimensional morphology of a sample with uneven reflectance, characterized in that, A three-dimensional topography measurement device based on samples with uneven reflectance is used. The measurement device includes: Structured light illumination element DLP (1), collimating lens group (2), polarizing beam splitter (3), quarter wave plate (4), dispersive tube lens (5), motor (6), objective lens (7), stage for placing the sample under test (8), dichroic mirror (10), first camera (12), total internal reflection prism (13), second camera (15) and microprocessor (16); The collimating lens group (2) and the polarizing beam splitter (3) are sequentially arranged on the emission light path of the structured light illumination element DLP (1); the quarter wave plate (4), motor (6), dispersive tube lens (5), objective lens (7) and the sample under test are sequentially arranged on the reflection light path of the polarizing beam splitter (3); The objective lens (7), dispersive tube lens (5), motor (6), quarter wave plate (4) and polarizing beam splitter (3) are also arranged sequentially on the reflected light path of the sample under test; The first camera (12) is disposed in the transmission light path of the dichroic mirror (10); The total internal reflection prism (13) is disposed on the reflected light path of the dichroic mirror (10), and the second camera (15) is disposed on the reflected light path of the total internal reflection prism (13); The microprocessor (16) is connected to the first camera (12) and the second camera (15) respectively to acquire the acquired images; the microprocessor (16) is connected to the motor (6) to control the motor (6) to drive the dispersive tube lens (5) and / or objective lens (7) to move in the Z-axis direction; The first camera (12) is set at a specified distance behind the focal point of the first band; the second camera (15) is set at a specified distance in front of the focal point of the second band; the reference plane of the first camera (12), the reference plane of the second camera (15), the structured light illumination element DLP (1), and the focal plane of the sample under test are conjugate; the first band and the second band are two bands of light reflected from the surface of the sample under test after passing through the dichroic mirror (10); Measurement methods include: S1, Place the sample to be tested. Place the sample within the working range of the measuring device and keep the position of the sample from changing. S2, acquire the confocal signal of the two bands. Modulate the illumination mode of the structured light illumination element DLP, acquire the image, and reconstruct the confocal images of two wavebands to drive the microprocessor to simultaneously acquire the confocal images A of two wavebands λ1 and A λ2 ; S3, acquire wide-field signals in two bands. Modulate the structured light illumination element DLP to full-on illumination mode and acquire sample wide-field images B under the same conditions and positions as in step S2. λ1 and B λ2 ; S4, Calculate the step height of the sample being measured. The image is obtained by performing operations on two sets of grayscale images. calibration formula Linear relationship I D The step height of the test sample is obtained by replacing the gray value of image Q. Based on the step height, a grayscale image Q of the test sample is obtained. Z Among them, z D Here, k represents the axial position; b are the fitted coefficients. S5, acquire the 3D point cloud of the test sample. The microprocessor will acquire the image Q Z The pixel position is used as the XY position of the three-dimensional shape, and the image Q is... Z The grayscale value is used as the height in the Z-axis direction to obtain the three-dimensional point cloud of the sample under test; S6, Fitting the three-dimensional morphology of the sample under test. The microprocessor fits the point cloud in the three-dimensional point cloud of the sample under test to obtain the three-dimensional morphology of the sample with uneven reflectance.

2. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, Before calculating the step height of the measured sample, data calibration is also included, as follows: Calibration steps for the linear relationship between light intensity and axial position: The structured light illumination element DLP is in single-point mode, using uniform reflectance samples as calibration samples; the first camera and the first band λ1 are used for focusing. After focusing on the focal plane, the microprocessor drives the motor to move in the Z-axis direction, and the preset single-point images are scanned. Steps to obtain the calibration formula: Without changing the scanning position of the motor, using a second camera and the second wavelength band λ2, the motor is driven to move in the Z-axis direction, and a preset number of single-point images are scanned. Under the same coordinate system, the relationship between the grayscale value of a single point in the preset images and the range of axial motor movement is plotted for both wavelength bands, i.e., the axial light intensity response curves for the two wavelength bands are plotted. and Will and By subtracting the values, we obtain the axial intensity curves for the two bands, showing the linear relationship between the differential intensity and the axial direction. D I D =I λ1 -I λ2 =kz D +b; Based on I D =I λ1 -I λ2 =kz D +b yields the calibration formula 3. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, The structured light illumination element DLP(1) includes an illumination source and a spatial light modulator.

4. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, Also includes: Focusing lens (9); the focusing lens (9) is disposed between the polarizing beam splitter (3) and the dichroic mirror (10).

5. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, Also includes: First filter (11); the first filter (11) is disposed between the first camera (12) and the dichroic mirror (10).

6. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, Also includes: Second filter (14); the second filter (14) is disposed between the total reflection prism (13) and the second camera (15).

7. The method for measuring the three-dimensional morphology of a sample with uneven reflectance according to claim 1, characterized in that, The motor (6) is a piezoelectric ceramic motor.

Images