Three-dimensional shape measuring device for sample with uneven reflectivity

Abstract

The utility model relates to a device for measuring the three-dimensional shape of a sample with non-uniform reflectivity. The device comprises a structured light illumination element DLP, a collimating lens group, a polarizing beam splitter, a 1 / 4 wave plate, a motor, a dispersion tube lens, an objective lens, an objective table for placing the sample to be measured, a focusing lens, a dichroic mirror, a first optical filter, a first camera, a total reflection prism, a second optical filter, a second camera and a microprocessor, the 1 / 4 wave plate, the motor, the dispersion tube lens, the objective lens, the objective table, the focusing lens, the first camera and the second camera are perpendicular to the same optical axis, and the structured light illumination element DLP, the polaroid and the collimating lens group are parallel to the same optical axis and are perpendicular to the optical axis reflected by a tested sample. According to the utility model, the structure is simple, the first camera and the second camera can rapidly acquire images of two wavebands of a sample with non-uniform reflectivity based on the structured light illumination element DLP, and the microprocessor rapidly measures the height difference of the sample with non-uniform reflectivity based on the images of the two wavebands.

Description

Technical Field

[0001] The utility model relates to the field of confocal technology, in particular to a three-dimensional topography measurement device for samples with uneven reflectivity. Background Technique

[0002] With the continuous development of technology, the requirements for the detection of the surface topography of high-precision machining are also constantly improving, specifically involving the efficient detection of micro-nano topography samples with large sizes and complex topographies. The differential parallel confocal measurement technology disclosed by a differential confocal axial vector range extension measurement device (CN202320166403.8) has become an important part of the detection technology. Compared with traditional technologies, this technology avoids hierarchical scanning, improves the detection efficiency, and at the same time, the detection range is improved. On this basis, a multi-band differential confocal microscopy 3D measurement method and device (CN202210898540.0) proposed the chromatic dispersion differential parallel confocal technology, which uses the different axial chromatic dispersion distances between different bands to detect the three-dimensional topography of the measured sample. However, the existing technologies are not applicable to samples with uneven surface reflectivity. When samples with different materials have different reflectivities, for the same detection sample, a part of the position has a high reflectivity, resulting in a high intensity, so that the surface height tends to be high, while another part of the position has a low reflectivity and is too dark, making the measured surface height on the low side. Therefore, it is difficult for the existing differential confocal methods to detect the height of samples with uneven reflectivity, resulting in errors in the measurement results. Content of the Utility Model

[0003] The purpose of the utility model is to overcome the problem of large measurement errors in the prior art, and provide a three-dimensional topography measurement device for samples with uneven reflectivity. The structured light illumination element DLP can modulate different forms of light, and by adjusting the structured light illumination element DLP to the single-point mode or the full-open mode, the multiplicative measurement error caused by different reflectivities can be eliminated, so as to quickly and accurately obtain the height difference of the measured sample with uneven reflectivity.

[0004] In order to achieve the above purpose, the technical solution of the utility model is as follows:

[0005] On the one hand, a three-dimensional topography measurement device for samples with uneven reflectivity includes: a structured light illumination element DLP, a collimating lens group, a polarization beam splitter, a quarter-wave plate, a motor, a dispersion tube lens, an objective lens, a stage for placing the measured sample, a dichroic 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 optical path of the structured light illumination element DLP; the quarter-wave plate, the dispersion tube lens, the motor, the objective lens, and the measured sample are sequentially arranged on the reflection optical path of the beam splitter;

[0007] The objective lens, the dispersion tube lens, the motor, the quarter-wave plate, and the polarization beam splitter are also sequentially arranged on the reflected light path of the sample to be measured;

[0008] The first camera is arranged on the transmission light path of the dichroic mirror;

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

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

[0011] The first camera is arranged at a specified distance behind the focus of the first wavelength band; the second camera is arranged at a specified distance in front of the focus of the second wavelength 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 position of the sample to be measured are conjugate; the first wavelength band and the second wavelength band are two wavelength bands after the light reflected from the surface of the sample to be measured passes through the dichroic mirror.

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

[0013] Preferably, the three-dimensional topography measurement device for a sample with non-uniform reflectivity further includes: a focusing lens; the focusing lens is arranged between the polarization beam splitter and the dichroic mirror.

[0014] According to the three-dimensional topography measurement device for a sample with non-uniform reflectivity described in the claims, it is characterized in that it further includes: a first filter; the first filter is arranged between the first camera and the dichroic mirror.

[0015] Preferably, the three-dimensional topography measurement device for a sample with non-uniform reflectivity further includes: a second filter; the second filter is arranged between the total reflection prism and the second camera.

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

[0017] The beneficial effects of the present utility model are as follows:

[0018] (1) The structured light illumination element DLP used in the present utility model can not only be used as a light source, but also perform spatial light modulation, modulate a single beam of light into different forms of structured light, modulate it into a single point to complete the calibration of the confocal mode, and open the DLP to the full-open mode, and the multiplicative error caused by non-uniform reflectivity can be eliminated through the wide-field image, realizing the measurement of the step height of the sample with non-uniform reflectivity within the measurement range, and finally realizing the three-dimensional topography measurement of the sample with non-uniform reflectivity;

[0019] (2) The focusing positions of the two wavelength bands of the present utility model are set above and below the step of the sample to be measured, and the structured light illumination element DLP, the sample to be measured, and the positions of the two cameras are conjugate. The first wavelength band camera and the second wavelength band camera simultaneously capture two required images to achieve differential measurement.

[0020] (3) The present utility model has a simple structure, is easy to operate, has a fast measurement speed and high measurement accuracy, and can be used for industrial rapid detection.

[0021] The following further describes the present utility model in detail with reference to the drawings and embodiments, but the three-dimensional topography measurement device for samples with uneven reflectivity of the present utility model is not limited to the embodiments. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic structural diagram of the three-dimensional topography measurement device for samples with uneven reflectivity according to the embodiment of the present utility model;

[0024] Reference Signs in the Drawings: 1. Structured Light Illumination Element DLP; 2. Collimating Lens Group; 3. Polarizing Beam Splitter; 4. Quarter-Wave Plate; 5. Dispersive Tube Mirror; 6. Motor; 7. Objective Lens; 8. Stage; 9. Focusing Lens; 10. Dichroic Mirror; 11. First Filter; 12. First Camera; 13. Total Reflection Prism; 14. Second Filter; 15. Second Camera; 16. Microprocessor. Detailed Embodiment

[0025] In order to make the purpose, technical solutions and advantages of the present utility model clearer, the following further describes the present utility model in detail with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

[0026] See Figure 1As shown in the figure, this embodiment discloses a three-dimensional topography measurement device for samples with uneven reflectivity, including: a structured light illumination element DLP 1, a collimating lens group 2, a polarization beam splitter 3, a quarter-wave plate 4, a dispersion tube lens 5, a motor 6, an objective lens 7, a stage 8 for placing the sample to be measured, 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;

[0027] The collimating lens group 2 and the polarization beam splitter 4 are sequentially arranged on the emission light path of the structured light illumination element DLP1; the quarter-wave plate 4, the dispersion tube lens 5, the motor 6, the objective lens 7, and the sample to be measured are sequentially arranged on the reflection light path of the polarization beam splitter 3;

[0028] The objective lens 7, the motor 6, the dispersion tube lens 5, the quarter-wave plate 4, and the polarization beam splitter 3 are also sequentially arranged on the reflection light path of the sample to be measured;

[0029] The first camera 12 is arranged on the transmission light path of the dichroic mirror 10; the focusing lens 9 is arranged between the polarization beam splitter 3 and the dichroic mirror 10; the first filter 11 is arranged between the first camera 12 and the dichroic mirror 10.

[0030] 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;

[0031] The microprocessor 16 is respectively connected to the first camera 12 and the second camera 15 to obtain the collected images; the microprocessor 16 is connected to the motor 6 to control the motor 6 to drive the objective lens 7 to move in the Z-axis direction;

[0032] The first camera 12 is arranged at a specified distance M behind the focus of the first band; the second camera 15 is arranged at a specified distance M in front of the focus of the second band; the reference planes of the first camera 12, the reference plane of the second camera 15, the structured light illumination element DLP 1, and the focal plane position of the sample to be measured are conjugate; the first band and the second band are two bands after the light reflected from the surface of the sample to be measured passes through the dichroic mirror 10.

[0033] Furthermore, 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 both an illumination light source and be capable of spatial light modulation.

[0034] The motor 6 is a piezoelectric ceramic motor.

[0035] In this embodiment, the quarter-wave plate 4, the dispersion tube lens 5, the motor 6, the objective lens 7, the stage 10, 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 perpendicular to the optical axis of the light reflected by the sample to be measured.

[0036] The light emitted by the structured light illumination element DLP 1 is spatially modulated by itself into a spot or stripe light, passes through the collimating lens group 2, reaches the PBS polarization beam splitter 3, and is reflected to the quarter-wave plate to convert the linearly polarized light into circularly polarized light. Then, it passes through the dispersion tube lens 5 and the objective lens 7 in sequence. The light of different bands generates a series of focal points along the optical axis, so that the focal points of several bands are focused on the surface of the sample to be measured. The light of these several bands is reflected on the sample surface and passes through the objective lens 7, the dispersion tube lens 5, the quarter-wave plate 4, passes through the polarization beam splitter 3 and the focusing lens 9 in sequence. The focusing lens 9 focuses the light to reach the dichroic mirror 10, which divides the light into two bands. The first band passes through the first filter 11 and is received by the first camera 12, and the second band passes through the total reflection prism 13 and the filter 14 and is received by the second camera 15.

[0037] The usage method of a three-dimensional topography measurement device for a sample with uneven reflectivity is as follows.

[0038] (1) Place the sample to be measured

[0039] Place the sample within the working range of the measurement device and keep the position of the sample to be measured unchanged;

[0040] (2) Obtain confocal signals of two bands

[0041] Modulate the illumination mode of the structured light illumination element DLP, obtain images, reconstruct confocal images of two bands, and drive the microprocessor to simultaneously obtain confocal images A λ1 and A λ2 ;

[0042] (3) Obtain wide-field signals of two bands

[0043] Modulate the structured light illumination element DLP to the full-open illumination mode, and obtain the wide-field image B of the sample under the same conditions and at the same position in step S2 λ1 and B λ2 ;

[0044] (4) Calculate the step height of the sample to be measured

[0045] Perform operations on the two groups of grayscale images to obtain an image Substitute the grayscale value of the image Q for I in the calibration formula to obtain the step height of the sample to be measured. Based on the step height, obtain a grayscale image Q of the sample to be measured D Z;

[0046] (5) Obtain the three-dimensional point cloud of the sample to be measured. The acquisition and processing unit for the three-dimensional point cloud of the sample to be measured takes the pixel positions of image Q Z as the XY positions of the three-dimensional topography, and takes the gray values of image Q Z as the height in the Z-axis direction to obtain the three-dimensional point cloud of the sample to be measured;

[0047] (6) Fit the three-dimensional topography of the sample to be measured

[0048] The processing unit fits the point cloud in the three-dimensional point cloud of the sample to be measured to obtain the three-dimensional topography of the sample with non-uniform reflectivity.

[0049] The calibration process of the formula includes:

[0050] (1) Calibrate the linear relationship between light intensity and axial position

[0051] The modulated structured light illumination element DLP is in single-point mode, and a sample with uniform reflectivity is used as the calibration sample; the first camera and the first wavelength band λ1 are used for focusing. After focusing on the focal plane, the processing unit drives the motor to move in the Z-axis direction to layer-scan a preset number of single-point images;

[0052] (2) Obtain the calibration formula

[0053] Without changing the scanning position of the motor, use the second camera and the second wavelength band λ2, drive the motor to move in the Z-axis direction to layer-scan a preset number of single-point images; in the same coordinate system, plot the relationship between the single-point gray value in the preset number of images and the range of axial motor movement under the two wavelength bands, that is, plot the axial light intensity response curves I λ1 and I λ2 ; Subtract I λ1 and I λ2 to obtain the linear relationship between the differential light intensity of the axial light intensity curves of the two wavelength bands and the axis I D , I D = I λ1 - I λ2 = kz D + b; where z D is the axial position; k and b are the fitted coefficients; based on I D = I λ1 - I λ2 = kz D + b to obtain the calibration formula

[0054] The principle and operation mode of the present utility model are described through the above specific implementation cases. These cases are intended to provide a clear understanding framework for readers to grasp the core idea and operation key points of the present utility model. However, it should be clear that these cases are not limitations on the application scope of the present utility model. For those skilled in the art, various forms of improvements and innovations based on the core idea of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A three-dimensional shape measurement device for a sample with uneven reflectivity, characterized in that: include: Structured light illumination element DLP (1), collimating lens group (2), polarization beam splitter (3), quarter wave plate (4), dispersion tube lens (5), motor (6), objective lens (7), stage for placing the sample to be tested (8), dichroic mirror (10), first camera (12), total reflection prism (13), second camera (15) and microprocessor (16); The collimating lens group (2) and the polarization beam splitter (3) are sequentially arranged on the emission light path of the structured light illumination element DLP (1); the quarter wave plate (4), the dispersion tube lens (5), the motor (6), the objective lens (7) and the sample to be measured are sequentially arranged on the reflection light path of the polarization beam splitter (3); The objective lens (7), the motor (6), the dispersion tube lens (5), the quarter wave plate (4) and the polarization beam splitter (3) are also arranged in sequence on the reflection light path of the sample to be measured; The first camera (12) is arranged on the transmission light path of the dichroic mirror (10); 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 microprocessor (16) is connected to the first camera (12) and the second camera (15) respectively to obtain the collected images; the microprocessor (16) is connected to the motor (6) to control the motor (6) to drive the objective lens (7) to move in the Z-axis direction; The first camera (12) is arranged at a specified distance behind the focus of the first band; the second camera (15) is arranged at a specified distance in front of the focus of the second band; 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 plane position of the sample to be measured are conjugate; the first band and the second band are two bands of light reflected from the surface of the sample to be measured after passing through a dichroic mirror (10).

2. The three-dimensional shape measuring device for a sample with uneven reflectivity according to claim 1, characterized in that: The structured light illumination element DLP (1) comprises an illumination light source and a spatial light modulator.

3. The three-dimensional shape measuring device for a sample with uneven reflectivity according to claim 1, characterized in that: Also includes: Focusing lens (9); the focusing lens (9) is arranged between the polarization beam splitter (3) and the dichroic mirror (10).

4. The three-dimensional shape measuring device for a sample with uneven reflectivity according to claim 1, characterized in that: Also includes: A first optical filter (11); the first optical filter (11) is arranged between the first camera (12) and the dichroic mirror (10).

5. The three-dimensional shape measuring device for a sample with uneven reflectivity according to claim 1, characterized in that: Also includes: A second optical filter (14); the second optical filter (14) is arranged between the total reflection prism (13) and the second camera (15).

6. The three-dimensional shape measuring device for a sample with uneven reflectivity according to claim 1, characterized in that: The motor (6) is a piezoelectric ceramic motor.

Images