One-dimensional surface topography measurement system and its measurement method

Abstract

The present invention provides a one-dimensional surface topography measurement system and a measurement method thereof. The measurement device includes a differential confocal ranging module and a dispersion angle measurement module. During the measurement of the surface topography of the object to be measured: First, the position to be measured on the surface of the object to be measured is moved to a preset measurement position through the differential confocal ranging module; then the peak wavelength of the position to be measured is extracted through the dispersion angle measurement module, and finally the tilt angle of the position to be measured is determined by the relationship between the tilt angle θ and the peak wavelength λ, θ = F(λ). The present invention utilizes the fact that different tilt angles at the position to be measured will cause different horizontal offsets to the dispersed light beam, and the spectral signals received by the spectrometer will have different peak wavelengths, thereby calculating the tilt angle of the position to be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and particularly relates to a one-dimensional surface topography measurement system and a measurement method thereof. Background Art

[0002] With the continuous improvement of optical technology and machining capabilities, manufacturing technology is constantly developing towards large sizes and high precision, and the demand for high-precision topography measurement of production devices is becoming increasingly urgent. Topography measurement mainly measures the distance and angle at different positions of the object to be measured. Since the requirement for the spatial resolution of the measurement reaches the nanometer level, it is required that the measurement probe can accurately aim at the surface of the object to be measured.

[0003] Currently, the measurement methods are mainly divided into contact measurement and non-contact measurement. Among them, non-contact measurement is more widely used, including laser confocal ranging method, chromatic confocal method, etc.:

[0004] 1) Contact measurement method: The coordinate information of the measurement point is obtained by the probe contacting the surface of the object to be measured.

[0005] 2) Laser confocal ranging method: The distance information of the sampling point is calculated by using the spot size of confocal imaging.

[0006] 3) Chromatic confocal method: Using white light as the light source, and utilizing the characteristic that lights with different wavelengths are focused at different positions through a chromatic dispersion lens, the spectrum of the light returned from the surface of the object to be measured is measured by a spectrometer, and the distance information is obtained through conversion.

[0007] The existing technologies are mainly divided into contact measurement and non-contact measurement. Among them, contact measurement is likely to damage the surface of the object to be measured, and the contact probe will wear out during use. Non-contact measurement often adopts the method of optical measurement, which has the characteristics of high precision and high sensitivity.

[0008] In a traditional optical confocal microscope, the surface topography is restored and reconstructed by sampling the position information of multiple points on the surface of the object to be measured. Currently, especially in the identification of micro surface defects, measuring the gradient information of the surface to be measured instead of the distance information has been proven to be a more effective method. However, since the gradient field is usually non-integrable, there are still limitations in using the gradient field for surface reconstruction. Summary of the Invention

[0009] In view of the above problems, the object of the present invention is to propose a one-dimensional surface topography measurement system and its measurement method, an optical element detection method and system with both distance measurement and angle measurement functions, which solve the drawback that the existing detection methods cannot measure the angle while measuring the distance. The differential confocal technology is adopted to measure the distance of the position to be measured. By using the different tilt angles of the position to be measured, different horizontal offsets will be generated for the chromatic dispersion light, and the spectral signals received by the spectrometer will have different peak wavelengths, so as to calculate the tilt angle of the position to be measured.

[0010] To achieve the above object, the present invention adopts the following specific technical solutions:

[0011] Compared with the existing technologies, the present invention selects to jointly measure the position information and gradient information of the surface of the object to be measured. The position information is used for surface reconstruction, and the gradient information is beneficial to the identification of micro surface defects. By combining the two kinds of information for reconstruction, the accuracy can be improved. By using the gradient information, the position information around the measurement point can be predicted, allowing the sensor to dynamically optimize the scanning strategy during scanning and improve the sampling efficiency. It has higher accuracy in optical topography measurement, especially in the identification of micro surface defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic structural diagram of a one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0013] Figure 2 is a schematic structural diagram of the differential confocal distance measurement part in the one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0014] Figure 3 is a schematic diagram of the differential confocal curve of the one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0015] Figure 4 is a schematic structural diagram of the chromatic dispersion angle measurement part in the one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0016] Figure 5 is a schematic diagram of the spectrometer data in the one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0017] Figure 6 is a schematic flowchart of the one-dimensional surface topography measurement method provided by an embodiment of the present invention.

[0018] The reference numerals therein include: white light source 1, first dispersion compensation prism 2, collimated color beam 3, second dispersion compensation prism 4, single wavelength light source 5, first beam splitting prism 6, second beam splitting prism 7, first condenser lens 8, object to be measured 9, third beam splitting prism 10, fourth beam splitting prism 11, second condenser lens 12, pre-focus pinhole 13, pre-focus photoelectric sensor 14, third condenser lens 15, post-focus pinhole 16, post-focus photoelectric sensor 17, cylindrical lens 18, pinhole 19, and spectrometer probe 20. Detailed implementation manners

[0019] In the following, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0021] Figure 1 The structural schematic diagram of a one-dimensional surface topography measurement system provided by an embodiment of the present invention is shown.

[0022] As Figure 1 shown, the one-dimensional surface topography measurement system provided by an embodiment of the present invention includes: a first light source device, a second light source device, a first beam splitting device, a second beam splitting device, a third beam splitting device, a first condenser device, a first detector device, a second detector device, and a third detector device.

[0023] Figure 2 The structural schematic diagram of the differential confocal ranging part in the one-dimensional surface topography measurement system provided by an embodiment of the present invention is shown.

[0024] As Figure 2 shown, in the differential confocal ranging module of the one-dimensional surface topography measurement system provided by the present invention:

[0025] The first light source device includes: a single wavelength light source 5. The single wavelength light source 5 is used to emit a collimated laser beam with a diameter of d and a wavelength of λ after beam expansion, and the collimated laser beam is incident on the first beam splitting device.

[0026] The first beam splitting device includes: a first beam splitting prism 6 and a second beam splitting prism 7.

[0027] The collimated laser beam is incident on the first condenser device after being reflected by the first beam splitting prism 6 and transmitted by the second beam splitting prism 7.

[0028] The first condenser device includes: a first condenser lens 8. The first condenser lens 8 is used for achromatizing and focusing the collimated laser beam. The first condenser lens 8 is provided with a transmission device and can move vertically in the incident light direction of the collimated laser beam, and its displacement can be accurately measured at the nanometer level by an interference rangefinder.

[0029] The collimated laser beam is incident on the surface of the object to be measured 9 after being converged by the first condenser lens 8, and after being reflected by the object to be measured 9, it enters the first condenser lens 8 again. The laser beam emitted from the first condenser lens 8 is reflected by the second beam splitting prism 7 and then passes through the second beam splitting device and the third beam splitting device in sequence. The collimated laser beam is divided into a pre-focus measurement beam and a post-focus measurement beam.

[0030] The second beam splitting device includes: a third beam splitting prism 10.

[0031] The third beam splitting device includes: a fourth beam splitting prism 11.

[0032] The laser beam is reflected by the second beam splitting prism 7, transmitted through the third beam splitting prism 10 and then incident on the fourth beam splitting prism 11, and is divided into a pre-focus measurement beam and a post-focus measurement beam by the fourth beam splitting prism 11.

[0033] The beam emitted after being reflected by the fourth beam splitting prism 11 is the pre-focus measurement beam and is incident on the first detector device;

[0034] The beam emitted after being transmitted through the fourth beam splitting prism 11 is the post-focus measurement beam and is incident on the second detector device.

[0035] The first detector device includes: a second condenser lens 12, a pre-focus pinhole 13 and a pre-focus photoelectric sensor 14.

[0036] The second detector device includes: a third condenser lens 15, a post-focus pinhole 16 and a post-focus photoelectric sensor 17.

[0037] The pre-focus measurement beam is converged by the second condenser lens 12 and then enters the pre-focus photoelectric sensor 14 after passing through the pre-focus pinhole 13.

[0038] The pre-focus pinhole 13 with a diameter of D is placed at the position of f - u m , where f is the focal length of the second condenser lens 12. The pre-focus photoelectric sensor 14 is placed behind the pre-focus pinhole 13 for measuring the light intensity.

[0039] The post-focus measurement beam is converged by the third condenser lens 15 and then enters the post-focus photoelectric sensor 17 after passing through the post-focus pinhole 16.

[0040] The post-focus pinhole 16 with a diameter of D is placed at the position of f + u mThe position, where f is the focal length of the condenser lens 15. A post-focal pinhole 16 is placed behind the post-focal photoelectric sensor 17 for measuring the light intensity.

[0041] Under the control of the transmission device, the first condenser lens 8 is moved, and its position is recorded as u by the interference rangefinder, so that the measurement position on the object to be measured 9 moves from the pre-focal position of the condenser lens to the post-focal position. The pre-focal photodetector 14 and the post-focal photodetector 17 record the change in light intensity, which are respectively denoted as I(u, -u m ) and I(u, +u m ).

[0042] Figure 3 Shows a schematic diagram of the differential confocal curve of the one-dimensional surface topography measurement system provided by the embodiment of the present invention.

[0043] As Figure 3 shown, when the collimated laser beam is just focused on the surface of the object to be measured 9 by the first condenser lens 8, the light intensities at the pre-focal pinhole 13 and the post-focal pinhole 16 are exactly equal. At this time, the light intensity signals received by the pre-focal photoelectric sensor 14 and the post-focal photoelectric sensor 17 are also equal, that is, I(u, -u m ) = I(u, +u m ). Subtract I(u, -u m ) from I(u, +u m ), and the differential confocal signal curve FES is obtained as:

[0044] FES = I(u, -u m ) - I(u, +u m )

[0045] Then, the displacement reading value of the first condenser lens 8 measured by the interference rangefinder corresponding to the zero point of the FES norm curve is recorded as the distance information of the measured point.

[0046] Figure 4 Shows a schematic diagram of the structure of the dispersion angle measurement part in the one-dimensional surface topography measurement system provided by the embodiment of the present invention.

[0047] As Figure 4 shown, in the dispersion angle measurement module of the one-dimensional surface topography measurement system provided by the present invention:

[0048] The second light source device includes: a white light source 1, a first dispersion compensation prism 2, a collimated color beam 3, and a second dispersion compensation prism 4.

[0049] Using white light as the light source, the beam emitted by the white light source 1 passes through the first dispersion compensation prism 2 and the second dispersion compensation prism 4 composed of two 45° prism arrangements. Due to the dispersion angle being related to the wavelength, a collimated color beam 3 separated horizontally according to the wavelength is output.

[0050] After the collimated color beam 3 passes through the first beam splitting prism 6 and the second beam splitting prism 7, it is converged by the first condenser lens 8 and incident on the surface of the object to be measured 9 again. When the FES curve passes through zero, the measurement point on the surface of the object to be measured 9 is just at the focal position of the first condenser lens 8, and the collimated color beam 3 is focused on the surface of the object to be measured 9 and reflected.

[0051] Since the surface of the object to be measured 9 is in an inclined state, the parallel chromatic divergent light emitted from the first condenser lens 8 will have a horizontal shift relative to the incident light in the direction perpendicular to the incident direction.

[0052] The divergent light beam emitted from the first condenser lens 8 is reflected by the second beam splitting prism 7 and the third beam splitting prism 10 and then incident on the third detector device.

[0053] The third detector device includes: a cylindrical lens 18, a pinhole 19, and a spectrometer probe 20.

[0054] The divergent light beam is first incident on the cylindrical lens 18, and the cylindrical lens 18 focuses the divergent light beam in the direction perpendicular to the lateral dispersion. After passing through the pinhole 19, it is incident on the spectrometer probe 20.

[0055] Figure 5 Shows a schematic diagram of spectrometer data in the one-dimensional surface topography measurement system provided by an embodiment of the present invention.

[0056] As Figure 5 shown, since different measurement positions of the object to be measured 9 have different inclination angles, corresponding to different offset amounts of the divergent light beam emitted from the first condenser lens 8, different components of the chromatic divergent light passing through the pinhole 19, analyzing the spectrometer data, extracting the peak wavelength, and different peak wavelengths will correspond to different inclination angles of the measurement points on the object to be measured 9.

[0057] Before use, replace the object to be measured 9 with a standard object to be measured to calibrate the system. Change the inclination angle of the standard part, measure the peak wavelength of the spectrometer, and different inclination angles correspond one-to-one with the peak point wavelength of the spectrometer data. By the calibration method, the relationship between the inclination angle θ and the peak wavelength λ is fitted as θ = F(λ). During actual measurement, according to the spectrometer measurement of the peak wavelength, the inclination angle θ is calculated through the relationship θ = F(λ).

[0058] Figure 6 Shows a schematic flow chart of the one-dimensional surface topography measurement method provided by an embodiment of the present invention.

[0059] As Figure 6 shown, the one-dimensional surface topography measurement method provided by an embodiment of the present invention includes the following steps:

[0060] Preprocessing step S0: Calibrate the one-dimensional surface topography measurement system provided by the present invention using a standard test piece.

[0061] The calibration process is as follows: Change the tilt angle of the standard piece, and different tilt angles correspond one-to-one with the peak wavelength of the spectrometer data. Measure the peak wavelength through the spectrometer, and fit the relationship between the tilt angle θ and the peak wavelength λ as θ = F(λ).

[0062] S1: Perform distance measurement through the differential confocal module, and at the same time move the measurement position on the object to be measured to the focal position of the first condenser lens.

[0063] Step S1 includes the following sub-steps:

[0064] S11: The first light source device emits a collimated laser beam, which is irradiated on the surface of the object to be measured after passing through the transmission of the first beam splitter prism, the second beam splitter prism, and the convergence of the first condenser lens in sequence;

[0065] S12: After being reflected by the object to be measured, the collimated laser beam passes through the transmission of the first condenser lens and the reflection of the second beam splitter prism again, and then enters the third beam splitter prism;

[0066] S13: After passing through the transmission of the third beam splitter prism, the collimated laser beam enters the fourth beam splitter prism and is divided into a pre-focal measurement beam and a post-focal measurement beam;

[0067] S14: The pre-focal measurement beam enters the first detector device after being reflected by the fourth beam splitter prism; the post-focal measurement beam enters the second detector device after passing through the fourth beam splitter prism;

[0068] S15: By moving the position of the first focusing lens, when the light intensities shown by the first detector device and the second detector device are the same, the measurement position on the object to be measured is located at the focal point of the first condenser lens.

[0069] S2: Collect the signal value of the dispersed light beam reflected by the object to be measured through the dispersion angle measurement module, and obtain the peak wavelength of the measurement position on the object to be measured.

[0070] Step S2 includes the following sub-steps:

[0071] S21: The second light source device emits a dispersed light beam, which is irradiated on the surface of the object to be measured after passing through the transmission of the first beam splitter prism, the second beam splitter prism, and the convergence of the first condenser lens in sequence;

[0072] S22: The measurement position on the surface of the object to be measured is located at the focal position of the first condenser lens. The dispersed light beam is focused at the measurement position and then reflected back to the first condenser lens;

[0073] S23. The dispersed light beam emitted from the first condenser lens is incident on the third detector device after being reflected by the second beam splitter prism and the third beam splitter prism in sequence, and the signal value of the dispersed light beam is obtained.

[0074] S24. Analyze the signal value of the dispersed light beam obtained by the third detector device, and extract the peak wavelength of the position to be measured.

[0075] S3. According to the relationship between the tilt angle θ and the peak wavelength λ, θ = F(λ), obtain the tilt angle of the position to be measured on the surface of the object to be measured.

[0076] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0077] The above specific embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A one-dimensional surface topography measurement system, characterized in that It includes a differential confocal ranging module and a dispersion angle measurement module; during the measurement of the surface topography of the object to be measured: First, move the position to be measured on the surface of the object to be measured to the preset measurement position through the differential confocal ranging module; then extract the peak wavelength of the position to be measured through the dispersion angle measurement module, and finally determine the tilt angle of the position to be measured through the relationship θ between the tilt angle θ and F ( λ ) of the peak wavelength λ. The differential confocal ranging module includes: a first light source device, a first beam splitting prism, a second beam splitting prism, a first condenser lens, a third beam splitting prism, a fourth beam splitting prism, a first detector device, and a second detector device; The first light source device is used to emit a collimated laser beam, and the collimated laser beam irradiates the surface of the object to be measured after passing through the first beam splitting prism, the transmission of the second beam splitting prism, and the convergence of the first condenser lens in sequence; After the collimated laser beam is reflected by the object to be measured, it passes through the transmission of the first condenser lens, the reflection of the second beam splitting prism, and the transmission of the third beam splitting prism, and then is incident on the fourth beam splitting prism; The fourth beam splitting prism divides the collimated laser beam into a pre-focus measurement beam and a post-focus measurement beam perpendicular to each other, and respectively incident on the first detector device and the second detector device; The first light source device is a single-wavelength light source; The single-wavelength light source is used to emit a collimated laser beam with a diameter of d and a wavelength of λ . The first condenser lens is provided with a transmission device for realizing vertical movement in the incident light direction of the collimated laser beam; The beam emitted after being reflected by the fourth beam splitting prism is a pre-focus measurement beam and is incident on the first detector device; The beam emitted after passing through the fourth beam splitting prism is a post-focus measurement beam and is incident on the second detector device; The first detector device includes: a second condenser lens, a pre-focus pinhole, and a pre-focus photoelectric sensor; The second detector device includes: a third condenser lens, a post-focus pinhole, and a post-focus photoelectric sensor; After the pre-focus measurement beam is converged by the second condenser lens, it passes through the pre-focus pinhole and is incident on the pre-focus photoelectric sensor; The pre-focus pinhole is placed at f - u m the position, where f is the focal length of the second condenser lens; After the post-focus measurement beam is converged by the third condenser lens, it passes through the post-focus pinhole and is incident on the post-focus photoelectric sensor; The post-focal pinhole is placed at f + u m where f is the focal length of the third condenser lens.

2. The one-dimensional surface topography measurement system according to claim 1, wherein Under the control of the transmission device, move the first condenser lens while recording the light intensity changes of the pre-focus photodetector and the post-focus photodetector, denoted respectively as I ( u , -u m )= I ( u , +u m ); When the light intensity signals received by the pre-focus photoelectric sensor and the post-focus photoelectric sensor are equal, that is I ( u , -u m ) = I ( u , +u m ) : The position to be measured on the surface of the object to be measured is just at the focal position of the first condenser lens.

3. The one-dimensional surface topography measurement system according to claim 2, wherein The dispersion angle measurement module includes: a second light source device, a first beam splitting prism, a second beam splitting prism, a first condenser lens, a third beam splitting prism, and a third detector device; The second light source device is used to emit a dispersion beam, and the dispersion beam passes through the transmission of the first beam splitting prism and the second beam splitting prism in sequence, and then is focused on the position to be measured of the object to be measured by the first condenser lens again; After the dispersion beam is reflected by the object to be measured, it passes through the transmission of the first condenser lens, the reflection of the second beam splitting prism, and the reflection of the third beam splitting prism again, and then is incident on the third detector device.

4. The one-dimensional surface topography measurement system according to claim 3, wherein The second light source device includes: a white light source, a first dispersion compensation prism, and a second dispersion compensation prism; The beam emitted by the white light source passes through the first dispersion compensation prism and the second dispersion compensation prism to obtain the dispersion beam; The third detector device includes: a cylindrical lens, a pinhole, and a spectrometer; After the dispersion beam is focused by the cylindrical lens, it passes through the pinhole and is incident on the spectrometer to obtain the signal value of the dispersion beam. By analyzing the signal value and extracting the peak wavelength of the dispersion beam, the tilt angle of the position to be measured is obtained.

5. A measurement method of a one-dimensional surface topography measurement system according to any one of claims 1-4, characterized in that, Including the following sub-steps: S1. Perform distance measurement through the differential confocal module, and at the same time move the measured position on the object to be measured to the focal position of the first condenser lens; S2. Collect the signal value of the dispersed light beam reflected by the object to be measured through the dispersion angle measurement module, and obtain the peak wavelength of the measured position on the object to be measured; The step S2 includes the following sub-steps: S21. The dispersed light beam irradiates the surface of the object to be measured after passing through the first beam splitter prism, the transmission of the second beam splitter prism, and the convergence of the first condenser lens in sequence; S22. The measured position on the surface of the object to be measured is located at the focal position of the first condenser lens, and the dispersed light beam is focused at the measured position and then reflected back to the first condenser lens; S23. The dispersed light beam exiting from the first condenser lens is incident on the third detector device after passing through the reflection of the second beam splitter prism and the third beam splitter prism in sequence, and the signal value of the dispersed light beam is obtained; S24. Analyze the signal value of the dispersed light beam obtained by the third detector device, and extract the peak wavelength of the measured position; S3. According to the relationship between θ the tilt angle λ and the peak wavelength θ = F ( λ ), the tilt angle of the position to be measured on the surface of the object to be measured is obtained.

6. The one-dimensional surface topography measurement method according to claim 5, characterized in that It further includes a preprocessing step S0. Calibrate the one-dimensional surface topography measurement system using a standard object to be measured; The calibration process is as follows: change the tilt angle of the standard part, measure the peak wavelength of the dispersed light beam reflected by the standard part through a spectrometer, and then fit the tilt angle θ and the peak wavelength λ relationship θ = F ( λ ).

7. The one-dimensional surface topography measurement method according to claim 6, characterized in that The step S1 includes the following sub-steps: S11. The collimated laser beam irradiates the surface of the object to be measured after passing through the first beam splitter prism, the transmission of the second beam splitter prism, and the convergence of the first condenser lens in sequence; S12. After being reflected by the object to be measured, the collimated laser beam passes through the transmission of the first condenser lens and the reflection of the second beam splitter prism again and then is incident on the third beam splitter prism; S13. The collimated laser beam is incident on the fourth beam splitter prism after passing through the transmission of the third beam splitter prism, and is divided into a pre-focal measurement beam and a post-focal measurement beam; S14. The pre-focal measurement beam is incident on the first detector device after being reflected by the fourth beam splitter prism; the post-focal measurement beam is incident on the second detector device after passing through the transmission of the fourth beam splitter prism; S15. By moving the position of the first focusing lens, when the light intensities displayed by the first detector device and the second detector device are the same, the measured position on the object to be measured is located at the focal point of the first condenser lens.

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