Spectral confocal measurement system for static surface profile

Abstract

The invention relates to the technical field of spectral measurement, in particular to a spectral confocal measurement system for a static surface profile, which comprises a shimming polychromatic light surface light source for emitting a light source beam, a surface field chromatic aberration objective lens for receiving the light source beam and irradiating light rays with different wavelengths to different depths of a measured object, light returned by the measured object is projected to the digital micro-mirror device, the digital micro-mirror device controls the dip angle change of the micro-mirror array and simulates a small hole array structure so as to regulate and control the reflection direction of the light projected by the surface view field chromatic aberration objective lens, and the surface view field hyperspectral imager receives a reflected light beam regulated and controlled by the digital micro-mirror device and transmits the reflected light beam to the digital micro-mirror device. And the reflected light beam is subjected to spectral analysis and imaging processing. According to the invention, a rapid and high-precision measurement method without physically moving the measured object is realized, the measurement speed and precision are improved, and the complexity and maintenance requirements of the system are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of spectral measurement, and in particular to a spectral confocal measurement system for static surface profile. Background Art

[0002] Spectral confocal measurement technology is a high-precision non-contact measurement method that uses optical principles to measure the height or profile of an object's surface.

[0003] The traditional measurement method based on spectral confocal is single-point measurement. In each measurement process, only the height information of a specific point on the sample surface can be obtained. In order to construct a topographic map of the entire sample surface, it is necessary to rely on external mechanical devices, such as a long-stroke two-dimensional translation stage, to gradually move the object to be measured, so that the spectral confocal sensor can measure different points on the sample surface one by one. However, this method not only takes a long time to measure, but also the large-scale mechanical movement may introduce large errors, thereby reducing the measurement accuracy. Therefore, the snapshot spectral confocal measurement system came into being. The snapshot spectral confocal measurement system can simultaneously obtain the height information of multiple points on the object to be measured. The system can simultaneously capture and analyze the light signals from different areas of the sample surface. Therefore, the snapshot system no longer requires a long-stroke two-dimensional translation stage to measure each point one by one, but only requires a short-stroke translation stage to perform small-range fine-tuning to complete the measurement of the entire sample surface.

[0004] Although the snapshot spectral confocal system improves measurement efficiency and accuracy, it still relies on mechanical devices to move objects in a two-dimensional plane, which limits its detection speed to a certain extent. At the same time, the mechanical structure is susceptible to wear and tear, requires regular maintenance, and its accuracy decreases over time. Summary of the invention

[0005] In view of this, the present invention provides a spectral confocal measurement system for static surface profile to solve the problem that the existing spectral confocal measurement method relies on a mechanical device to move the object in a two-dimensional plane, which limits the detection speed and detection accuracy.

[0006] In a first aspect, the present invention provides a spectral confocal measurement system for static surface profile, the system comprising: a uniform field polychromatic light source, a surface field chromatic aberration objective lens, a digital micromirror device, and a surface field hyperspectral imager;

[0007] The uniform field polychromatic light surface light source is used to emit a light source light beam;

[0008] The surface field chromatic aberration objective lens is located between the uniform field polychromatic light surface light source and the object to be measured, and is used to receive the light source light beam emitted by the uniform field polychromatic light surface light source, irradiate light of different wavelengths to different depths of the object to be measured, and then project the light returned by the object to be measured to the digital micromirror device;

[0009] The digital micromirror device is located between the surface field chromatic aberration objective lens and the surface field hyperspectral imager, and is used to control the inclination change of the micromirror array and simulate the pinhole array structure to adjust the reflection direction of the light projected by the surface field chromatic aberration objective lens;

[0010] The surface field hyperspectral imager is used to receive the reflected light beam after being regulated by the digital micromirror device, and perform spectral analysis and imaging processing on the reflected light beam after being regulated by the digital micromirror device.

[0011] In an optional embodiment, the system further comprises: a half-reflective half-mirror;

[0012] The half-reflecting half-mirror is located between the uniform field complex light source and the surface field chromatic aberration objective lens, and between the surface field chromatic aberration objective lens and the digital micromirror device;

[0013] The half-reflecting half-mirror is used to receive the light source light beam emitted by the half-reflecting half-mirror, and to reflect and transmit the light source light beam emitted by the half-reflecting half-mirror, so that the light source light beam emitted from the uniform field complex light source is reflected to the surface field chromatic aberration objective lens, and at the same time, the light returned from the surface field chromatic aberration objective lens is transmitted to the digital micromirror device.

[0014] In an optional embodiment, the surface field chromatic aberration objective lens is located between the half-reflecting half-mirror and the object to be measured, and is also used to receive the light source light beam transmitted by the half-reflecting half-mirror, irradiate light of different wavelengths to different depths of the object to be measured, and then reflect the light returned from the object to be measured through the half-reflecting half-mirror to the digital micromirror device.

[0015] In an optional embodiment, the system further includes an imaging relay lens;

[0016] The imaging relay lens is located between the digital micromirror device and the surface field hyperspectral imager;

[0017] The imaging relay lens is used to receive the reflected light beam regulated by the digital micromirror device, perform relay imaging, and transmit it to the surface field hyperspectral imager.

[0018] In an optional embodiment, the surface field of view hyperspectral imager is also used to receive the light beam after the imaging relay lens relays the imaging image, and perform spectral analysis and imaging processing on the light beam after the imaging relay lens relays the imaging image, so as to obtain the surface depth information of the object under test.

[0019] In an optional implementation, the imaging ratio of the relay lens is 1:1.

[0020] In an optional embodiment, the light source light beam is a uniform and continuous polychromatic light beam.

[0021] In an optional implementation, the digital micromirror device includes the micromirror array;

[0022] The switching state of each micromirror in the micromirror array includes an on state and an off state. When the first micromirror in the micromirror array is in the on state, the first micromirror reflects the light projected onto the first micromirror according to the first reflection direction to the receiving area of ​​the surface field of view hyperspectral imager; when the second micromirror in the micromirror array is in the off state, the second micromirror reflects the light projected onto the second micromirror according to the second reflection direction to a position outside the receiving area of ​​the surface field of view hyperspectral imager.

[0023] The technical solution provided by the present invention may include the following beneficial effects:

[0024] In the spectral confocal measurement system of the present invention, this characteristic of the digital micromirror device (DMD) is utilized to gradually control the change of the inclination angle of each micromirror in the micromirror array by programming. When the inclination angle of the micromirror changes, the reflection direction of the light incident on the micromirror will also change accordingly. The present invention utilizes the digital micromirror device (DMD) to simulate the pinhole array scanning, and does not require the object to be measured to perform scanning motion. The information of different positions on the surface of the object to be measured can be directly obtained by controlling the state of the digital micromirror device (DMD), thereby being able to quickly complete the measurement of the surface profile of the object to be measured. Since the present invention does not require the object to be measured to move, the use of a mechanical structure is avoided, and there is no problem of mechanical structure wear, thereby ensuring the long-term stable operation of the system, so that the measurement accuracy of the system can be kept stable for a long time, and the reliability of the system and the accuracy of the measurement results are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a structural schematic diagram of a spectral confocal measurement system for a static surface profile according to an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of a digital micromirror device simulating pinhole array scanning according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] According to an embodiment of the present invention, a spectral confocal measurement system embodiment of a static surface profile is provided. Figure 1 FIG. 1 is a schematic diagram of a spectral confocal measurement system for a static surface profile according to an embodiment of the present invention. Figure 1 As shown, the system includes: a uniform field polychromatic light source 1, a surface field chromatic aberration objective lens 2, a digital micromirror device 3 and a surface field hyperspectral imager 4;

[0030] The uniform field polychromatic light surface light source 1 is used to emit a light source light beam;

[0031] The surface field chromatic aberration objective lens 2 is located between the uniform field polychromatic light surface light source 1 and the object to be measured 5. The surface field chromatic aberration objective lens 2 is used to receive the light source light beam emitted by the uniform field polychromatic light surface light source 1, and irradiate light of different wavelengths to different depths of the object to be measured 5, and then project the light returned by the object to be measured 5 to the digital micromirror device 3;

[0032] The digital micromirror device 3 is located between the surface field chromatic aberration objective lens 2 and the surface field hyperspectral imager 4. The digital micromirror device 3 is used to control the inclination change of the micromirror array and simulate the pinhole array structure to adjust the reflection direction of the light projected by the surface field chromatic aberration objective lens 2.

[0033] The surface field hyperspectral imager 4 is used to receive the reflected light beam regulated by the digital micromirror device 3 , and perform spectral analysis and imaging processing on the reflected light beam regulated by the digital micromirror device 3 .

[0034] In an optional embodiment, if Figure 1 As shown, the system further comprises: a half-reflective half-mirror 6;

[0035] The half-reflecting half-mirror 6 is located between the uniform field complex light source 1 and the surface field chromatic aberration objective lens 2, and between the surface field chromatic aberration objective lens 2 and the digital micromirror device 3;

[0036] The half-reflecting half-mirror 6 is used to receive the light source light beam emitted by the half-reflecting half-mirror 6, and to reflect and transmit the light source light beam emitted by the half-reflecting half-mirror 6, so that the light source light beam emitted from the uniform field complex light surface light source 1 is reflected to the surface field chromatic aberration objective lens 2, and at the same time, the light returned from the surface field chromatic aberration objective lens 2 is transmitted to the digital micromirror device 3.

[0037] In an optional embodiment, the surface field chromatic aberration objective lens 2 is located between the half-reflecting half-mirror 6 and the object to be measured 5, and is also used to receive the light source light beam transmitted by the half-reflecting half-mirror 6, irradiate light of different wavelengths to different depths of the object to be measured 5, and then reflect the light returned by the object to be measured 5 through the half-reflecting half-mirror 6 to the digital micromirror device 3.

[0038] In an optional embodiment, if Figure 1 As shown, the system also includes an imaging relay lens 7;

[0039] The imaging relay lens 7 is located between the digital micromirror device 3 and the surface field hyperspectral imager 4;

[0040] The imaging relay lens 7 is used to receive the reflected light beam regulated by the digital micromirror device 3 , perform relay imaging, and transmit it to the surface field hyperspectral imager 4 .

[0041] In an optional embodiment, the surface field hyperspectral imager 4 is also used to receive the light beam after the imaging relay lens 7 relays the imaging, and perform spectral analysis and imaging processing on the light beam after the imaging relay lens 7 relays the imaging, so as to obtain the surface depth information of the object 5 to be measured.

[0042] In an optional implementation, the imaging ratio of the relay lens is 1:1.

[0043] In an optional embodiment, the light source light beam is a uniform and continuous polychromatic light beam.

[0044] In an optional implementation, the digital micromirror device 3 includes the micromirror array;

[0045] The switching state of each micromirror in the micromirror array includes an on state and an off state. When the first micromirror in the micromirror array is in the on state, the first micromirror reflects the light projected onto the first micromirror according to the first reflection direction to the receiving area of ​​the surface field of view hyperspectral imager 4; when the second micromirror in the micromirror array is in the off state, the second micromirror reflects the light projected onto the second micromirror according to the second reflection direction to a position outside the receiving area of ​​the surface field of view hyperspectral imager 4.

[0046] Furthermore, the uniform field polychromatic light surface light source 1 can emit a uniform and continuous polychromatic light beam as the starting light source of the entire spectral confocal measurement system. Polychromatic light includes a variety of different wavelengths of light, which is the basis of spectral confocal measurement. Light of different wavelengths will produce different focusing effects in subsequent optical elements due to different refractive properties, thereby realizing the measurement of different depth information on the surface of the object to be measured 5. When the system includes a uniform field polychromatic light surface light source 1, a surface field chromatic aberration objective lens 2, a digital micromirror device 3, a half-reflecting half-mirror lens 6, an imaging relay lens 7, and a surface field hyperspectral imager 4, the light source light beam emitted by the uniform field polychromatic light surface light source 1 is directly directed to the half-reflecting half-mirror lens 6, and the light source light beam has a certain divergence angle and energy distribution at the light source outlet, ensuring that the effective receiving area of ​​the subsequent optical elements can be covered.

[0047] Further, the half-reflecting half-mirror 6 is a lens with special optical properties, which can partially reflect and partially transmit light. For the light source beam emitted from the uniform field complex light surface light source 1, the half-reflecting half-mirror 6 allows most of the light to be reflected, so that the light source beam can smoothly enter the surface field chromatic aberration objective lens 2, and for the light returned from the surface field chromatic aberration objective lens 2, the half-reflecting half-mirror 6 can transmit the light beam of a specific wavelength so that it is transmitted to the digital micromirror device 3. Through this reflection and transmission function, the half-reflecting half-mirror 6 plays a role in separating and guiding light in the optical path, ensuring that the light propagates along a predetermined path. One side of the half-reflecting half-mirror 6 faces the uniform field complex light surface light source 1, receives the light source beam emitted from the uniform field complex light surface light source 1, and the other side faces the surface field chromatic aberration objective lens 2, and transmits the light beam reflected by the half-reflecting half-mirror 6 to the surface field chromatic aberration objective lens 2. At the same time, the half-reflecting half-mirror 6 is also connected to the digital micromirror device 3, and the light returned from the surface field chromatic aberration objective lens 2 is reflected to the digital micromirror device 3.

[0048] Furthermore, the surface field chromatic aberration objective lens 2 focuses light of different wavelengths at different depths of the measured object 5 according to the principle of light dispersion. When light of different wavelengths passes through the surface field chromatic aberration objective lens 2, due to the difference in refractive index, it will form focal points at different axial positions. The focusing characteristics enable the system to distinguish information at different depths of the object surface, such as Figure 1The 400nm and 100nm in the figure represent different depths of the surface of the object 5 to be measured. The surface field chromatic aberration objective lens 2 receives the light beam reflected from the half-reflecting half-mirror 6 and irradiates it evenly onto the surface of the object 5 to be measured. At the same time, the surface field chromatic aberration objective lens 2 also collects the light reflected back from the surface of the object 5 to be measured. Only the light beam of a specific wavelength that is precisely focused at a certain depth on the surface of the object can return along the original path, and the light of other wavelengths will not return along the original path because they are not focused at this depth. The returned light beam of specific wavelength is then transmitted to the digital micromirror device 3 through the half-reflecting half-mirror 6. The surface field chromatic aberration objective lens 2 is located between the half-reflecting half-mirror 6 and the object 5 to be measured, with one end connected to the half-reflecting half-mirror 6 to receive the reflected light beam; the other end is directly facing the surface of the object 5 to irradiate the light beam onto the object 5 to be measured. The surface field chromatic aberration objective lens 2 can be replaced by a specially designed lens group and a diffractive optical element.

[0049] For further information, see Figure 2 The digital micromirror device 3 shown is a schematic diagram of simulating pinhole array scanning. The digital micromirror device 3 is composed of an array of a large number of tiny reflectors (micromirrors). By programming and controlling the inclination angle change of the micromirror array, the structure of the pinhole array can be simulated. Each micromirror is equivalent to a controllable "pinhole". When the micromirror is at a specific inclination angle, it can reflect light in a predetermined direction; when the micromirror is at other inclination angles, the light will be reflected in other directions. Based on the simulated pinhole array structure, the digital micromirror device 3 can accurately control the reflection path of the light returned from the surface field chromatic aberration objective lens 2. By changing the inclination angle of the micromirror, light at different positions can be reflected in different directions, thereby realizing spatial modulation of the light. This control capability enables the system to selectively measure information at different positions on the surface of the object 5 to be measured. The digital micromirror device 3 receives the light returned from the surface field chromatic aberration objective lens 2 (reflected by the semi-reflective and semi-transparent mirror 6), and the reflected light beam passes through the imaging relay lens 7, which is connected to the imaging relay lens 7 to ensure that the light can be accurately transmitted to the lens. As shown in FIG. Figure 2 As shown, each micromirror of the digital micromirror device 3 can be switched between two main states of "on" or "off", respectively controlling the reflection direction of the light. When the state is "on", the reflected light of the micromirror enters the spectrometer; when the state is "off", the reflected light of the micromirror does not enter the spectrometer. The simulated pinhole array scanning process can be completed by gradually controlling the "on" and "off" states of the micromirrors.

[0050] Furthermore, the imaging relay lens 7 mainly plays the role of relay imaging, accurately transmitting and imaging the light beam reflected by the digital micromirror device 3. The imaging ratio is 1:1, that is, the image formed by the imaging relay lens 7 is similar to the distribution of light reflected on the digital micromirror device 3 in space. This similarity helps the subsequent surface field hyperspectral imager 4 to accurately receive and analyze the light. By accurately transmitting the light, the imaging relay lens 7 ensures that the propagation direction of the light and the characteristics of the light beam remain unchanged, providing high-quality input light for the surface field hyperspectral imager 4. The imaging relay lens 7 is located between the digital micromirror device 3 and the surface field hyperspectral imager 4, one end of which is connected to the digital micromirror device 3 to receive the light beam reflected by the digital micromirror device 3; the other end is connected to the surface field hyperspectral imager 4 to input the transmitted light beam into the surface field hyperspectral imager 4.

[0051] Further, the surface field hyperspectral imager 4 receives the light transmitted from the imaging relay lens 7. Since the imaging relay lens 7 ensures the quality and distribution of the light, the surface field hyperspectral imager 4 can accurately receive the light and further analyze the light. The surface field hyperspectral imager 4 performs spectral analysis on the received light, and infers the contour and spectral information of the surface of the measured object 5 by analyzing the proportion and intensity of different wavelength components in the light. At the same time, the surface field hyperspectral imager 4 also performs imaging processing, and presents the analyzed data in the form of an image, so as to intuitively observe and analyze the surface morphology of the measured object 5. The surface field hyperspectral imager 4 performs multi-dimensional analysis of the light based on the technology of spectral analysis and imaging processing. For example, it can judge the material composition and physical properties of different areas on the surface of the object according to the absorption and reflection characteristics of light of different wavelengths. Through the imaging processing of the light, the contour and details of the surface of the object can be displayed in the form of an image, providing the user with intuitive measurement results. The surface field hyperspectral imager 4 receives the light beam from the imaging relay lens 7 and is the last stop of light propagation, completing the final measurement data collection and analysis.

[0052] Furthermore, by gradually controlling the digital micromirror device 3 and simulating the scanning process of the pinhole array, the spectral confocal measurement system can quickly and accurately measure the overall surface morphology of the object, thereby realizing high-speed and high-precision spectral confocal measurement. The spectral confocal measurement system can accurately obtain the surface profile and spectral information of the measured object 5 without moving it, and has extremely high practicality and application potential.

[0053] In summary, in the spectral confocal measurement system of the present invention, this characteristic of the digital micromirror device (DMD) is utilized to gradually control the change of the inclination angle of each micromirror in the micromirror array by programming. When the inclination angle of the micromirror changes, the reflection direction of the light incident on the micromirror will also change accordingly. The present invention utilizes a digital micromirror device (DMD) to simulate pinhole array scanning, and does not require the object to be measured to perform scanning motion. The information of different positions on the surface of the object to be measured can be directly obtained by controlling the state of the digital micromirror device (DMD), thereby being able to quickly complete the measurement of the surface profile of the object to be measured. Since the present invention does not require the object to be measured to move, the use of a mechanical structure is avoided, and there is no problem of mechanical structure wear, thereby ensuring that the system can operate stably for a long time, so that the measurement accuracy of the system can be kept stable for a long time, and the reliability of the system and the accuracy of the measurement results are improved.

[0054] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the defined scope.

Claims

1. A spectral confocal measurement system for static surface profile, characterized in that: The system comprises: a uniform field polychromatic light source, a surface field chromatic aberration objective lens, a digital micromirror device and a surface field hyperspectral imager; The uniform field polychromatic light surface light source is used to emit a light source light beam; The surface field chromatic aberration objective lens is located between the uniform field polychromatic light surface light source and the object to be measured, and is used to receive the light source light beam emitted by the uniform field polychromatic light surface light source, irradiate light of different wavelengths to different depths of the object to be measured, and then project the light returned by the object to be measured to the digital micromirror device; The digital micromirror device is located between the surface field chromatic aberration objective lens and the surface field hyperspectral imager, and is used to control the inclination change of the micromirror array and simulate the pinhole array structure to adjust the reflection direction of the light projected by the surface field chromatic aberration objective lens; The surface field hyperspectral imager is used to receive the reflected light beam after being regulated by the digital micromirror device, and perform spectral analysis and imaging processing on the reflected light beam after being regulated by the digital micromirror device.

2. The system according to claim 1, characterized in that The system further comprises: a half-reflecting half-mirror; The half-reflecting half-mirror is located between the uniform field complex light source and the surface field chromatic aberration objective lens, and between the surface field chromatic aberration objective lens and the digital micromirror device; The half-reflecting half-mirror is used to receive the light source light beam emitted by the half-reflecting half-mirror, and to reflect and transmit the light source light beam emitted by the half-reflecting half-mirror, so that the light source light beam emitted from the uniform field complex light source is reflected to the surface field chromatic aberration objective lens, and at the same time, the light returned from the surface field chromatic aberration objective lens is transmitted to the digital micromirror device.

3. The system according to claim 2, characterized in that The surface field chromatic aberration objective lens is located between the half-reflecting half-mirror and the object to be measured, and is also used to receive the light source light beam transmitted by the half-reflecting half-mirror, irradiate light of different wavelengths to different depths of the object to be measured, and then reflect the light returned by the object to be measured through the half-reflecting half-mirror to the digital micromirror device.

4. The system according to claim 2, characterized in that The system also includes an imaging relay lens; The imaging relay lens is located between the digital micromirror device and the surface field hyperspectral imager; The imaging relay lens is used to receive the reflected light beam regulated by the digital micromirror device, perform relay imaging, and transmit it to the surface field hyperspectral imager.

5. The system according to claim 4, characterized in that The surface field hyperspectral imager is also used to receive the light beam after the imaging relay lens relays the imaging image, and perform spectral analysis and imaging processing on the light beam after the imaging relay lens relays the imaging image, so as to obtain the surface depth information of the measured object.

6. The system according to claim 4, characterized in that The imaging ratio of the relay lens is 1:

1.

7. The system according to any one of claims 1 to 6, characterized in that: The light source beam is a uniform and continuous polychromatic beam.

8. The system according to any one of claims 1 to 6, characterized in that: The digital micromirror device includes the micromirror array; The switching state of each micromirror in the micromirror array includes an on state and an off state. When the first micromirror in the micromirror array is in the on state, the first micromirror reflects the light projected onto the first micromirror according to the first reflection direction to the receiving area of ​​the surface field of view hyperspectral imager; when the second micromirror in the micromirror array is in the off state, the second micromirror reflects the light projected onto the second micromirror according to the second reflection direction to a position outside the receiving area of ​​the surface field of view hyperspectral imager.

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