A spectral confocal measurement system for static surface profiles

Abstract

This invention relates to the field of spectral measurement technology, specifically to a confocal spectral measurement system for static surface profiles. The system includes: a uniform polychromatic surface light source emitting a light beam; a surface-view chromatic aberration objective lens receiving the light beam and illuminating different wavelengths of light at different depths on the object under test; and the light reflected from the object being measured being projected onto a digital micromirror device (DMD). The DMD controls the tilt angle of a micromirror array and simulates a pinhole array structure to regulate the reflection direction of the light projected by the surface-view chromatic aberration objective lens. A surface-view hyperspectral imager receives the reflected light beam regulated by the DMD and performs spectral analysis and imaging processing on the reflected beam. This invention achieves a rapid and high-precision measurement method without physically moving the object under test, improving measurement speed and accuracy while reducing system complexity and maintenance requirements.

Description

Technical Field

[0001] This invention relates to the field of spectral measurement technology, and more specifically to a spectral confocal measurement system for static surface profiles. Background Technology

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

[0003] Traditional confocal spectral measurement methods are single-point measurements, acquiring height information from only one specific point on the sample surface during each measurement. To construct a topographic map of the entire sample surface, external mechanical devices, such as a long-stroke two-dimensional displacement stage, are required to gradually move the object under test, allowing the confocal spectral sensor to measure different points on the sample surface one by one. However, this method is not only time-consuming, but the large-scale mechanical movement can also introduce significant errors, thus reducing measurement accuracy. Therefore, snapshot confocal spectral measurement systems have emerged. Snapshot confocal spectral measurement systems can simultaneously acquire height information from multiple points on the object under test. This system can simultaneously capture and analyze light signals from different regions of the sample surface. Therefore, snapshot systems no longer require a long-stroke two-dimensional displacement stage to measure each point individually; instead, a short-stroke displacement stage with small-range fine adjustments is sufficient to complete the measurement of the entire sample surface.

[0004] Although snapshot-type spectral confocal systems improve measurement efficiency and accuracy, they still rely on mechanical devices to move objects in a two-dimensional plane, which limits their detection speed to some extent. In addition, 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 profiles to solve the problem that existing spectral confocal measurement methods rely on mechanical devices to move objects in a two-dimensional plane, which limits the detection speed and accuracy.

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

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

[0008] The surface field chromatic aberration objective is located between the uniform polychromatic surface light source and the object under test. The surface field chromatic aberration objective is used to receive the light beam emitted by the uniform polychromatic surface light source, and to illuminate different wavelengths of light onto different depths of the object under test, and then project the light reflected back from the object under test onto the digital micromirror device.

[0009] The digital micromirror device is located between the surface field chromatic aberration objective and the surface field hyperspectral imager. The digital micromirror device is used to control the tilt angle of the micromirror array and simulate the pinhole array structure to regulate the reflection direction of the light projected by the surface field chromatic aberration objective.

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

[0011] In one alternative implementation, the system further includes: a semi-reflective translucent mirror;

[0012] The semi-reflective semi-transparent lens is located between the uniform polychromatic surface 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 semi-reflective mirror is used to receive the light beam emitted by the uniform polychromatic surface light source, and to reflect and transmit the light beam emitted by the uniform polychromatic surface light source, so that the light beam emitted from the uniform polychromatic surface light source is reflected to the surface field chromatic aberration objective lens, while the light returning from the surface field chromatic aberration objective lens is transmitted to the digital micromirror device.

[0014] In one optional embodiment, the surface field chromatic aberration objective lens, located between the semi-reflective lens and the object under test, is also used to receive the light beam transmitted by the semi-reflective lens, to illuminate different wavelengths of light onto different depths of the object under test, and then to reflect the light returned by the object under test back to the digital micromirror device through the semi-reflective lens.

[0015] In one alternative implementation, 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 beam after being controlled by the digital micromirror device, perform relay imaging, and transmit it to the surface field hyperspectral imager.

[0018] In one optional embodiment, the surface field hyperspectral imager is further configured to receive the beam after relay imaging by the imaging relay lens, and perform spectral analysis and imaging processing on the beam after relay imaging by the imaging relay lens to obtain the surface depth information of the object under test.

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

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

[0021] In one optional embodiment, the digital micromirror device includes the micromirror array;

[0022] Each micromirror in the micromirror array has an on state and an off state. When the first micromirror in the micromirror array is on, the first micromirror reflects the light projected onto it in the first reflection direction to the receiving area of ​​the surface field hyperspectral imager. When the second micromirror in the micromirror array is off, the second micromirror reflects the light projected onto it in the second reflection direction to a position outside the receiving area of ​​the surface field hyperspectral imager.

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

[0024] In the spectral confocal measurement system of this invention, this characteristic of digital micromirror devices (DMDs) is utilized to progressively control the tilt angle of each micromirror in the micromirror array through programming. When the tilt angle of a micromirror changes, the reflection direction of the light incident on the micromirror also changes accordingly. This invention uses a digital micromirror device (DMD) to simulate pinhole array scanning, eliminating the need for the object under test to move. Information from different positions on the surface of the object under test can be quickly acquired by directly controlling the state of the DMD, thus enabling rapid measurement of the object's surface contour. Because this invention does not require movement of the object under test, it avoids the use of mechanical structures and eliminates the problem of mechanical wear, thereby ensuring long-term stable operation of the system and maintaining stable measurement accuracy over a long period, improving system reliability and the accuracy of measurement results. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

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

[0027] Figure 2 This is a schematic diagram of a digital micromirror device simulating a pinhole array scan according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] According to an embodiment of the present invention, a spectral confocal measurement system for static surface profiles is provided. Figure 1 This is a schematic diagram of a spectral confocal measurement system for static surface profiles according to an embodiment of the present invention, as shown below. Figure 1 As shown, the system includes: a homogenized polychromatic surface 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 polychromatic surface light source 1 is used to emit light beams;

[0031] The chromatic aberration objective 2 is located between the uniform polychromatic light source 1 and the object under test 5. The chromatic aberration objective 2 is used to receive the light beam emitted by the uniform polychromatic light source 1 and to illuminate different wavelengths of light onto different depths of the object under test 5. The light returned by the object under test 5 is then projected onto the digital micromirror device 3.

[0032] The digital micromirror device 3 is located between the chromatic aberration objective 2 and the hyperspectral imager 4. The digital micromirror device 3 is used to control the tilt angle of the micromirror array and simulate the pinhole array structure to regulate the reflection direction of the light projected by the chromatic aberration objective 2.

[0033] The surface-view hyperspectral imager 4 is used to receive the reflected beam after being controlled by the digital micromirror device 3, and to perform spectral analysis and imaging processing on the reflected beam after being controlled by the digital micromirror device 3.

[0034] In one alternative implementation, such as Figure 1 As shown, the system also includes: a semi-reflective translucent mirror 6;

[0035] The semi-reflective semi-transparent lens 6 is located between the uniform polychromatic light source 1 and the chromatic aberration objective lens 2, and between the chromatic aberration objective lens 2 and the digital micromirror device 3.

[0036] The semi-reflective lens 6 is used to receive the light beam emitted by the uniform polychromatic surface light source 1, and to reflect and transmit the light beam emitted by the uniform polychromatic surface light source 1, so that the light beam emitted from the uniform polychromatic surface light source 1 is reflected to the surface chromatic aberration objective lens 2, while the light returning from the surface chromatic aberration objective lens 2 is transmitted to the digital micromirror device 3.

[0037] In one optional embodiment, the surface field chromatic aberration objective 2 is located between the semi-reflective lens 6 and the object under test 5, and is also used to receive the light beam transmitted by the semi-reflective lens 6, to irradiate different wavelengths of light onto different depths of the object under test 5, and then to reflect the light returned by the object under test 5 through the semi-reflective lens 6 to the digital micromirror device 3.

[0038] In one alternative implementation, such as 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 beam after being controlled 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 beam after relay imaging by the imaging relay lens 7, and to perform spectral analysis and imaging processing on the beam after relay imaging by the imaging relay lens 7 to obtain the surface depth information of the object under test 5.

[0042] In one alternative implementation, the relay lens has an imaging ratio of 1:1.

[0043] In one alternative implementation, the light source beam is a uniform and continuous polychromatic beam.

[0044] In one alternative embodiment, the digital micromirror device 3 includes the micromirror array;

[0045] Each micromirror in the micromirror array has an on and off state. When the first micromirror in the array is on, it reflects the light projected onto it in the first reflection direction to the receiving area of ​​the surface field hyperspectral imager 4. When the second micromirror in the array is off, it reflects the light projected onto it in the second reflection direction to a position outside the receiving area of ​​the surface field hyperspectral imager 4.

[0046] Furthermore, the uniform polychromatic surface light source 1 serves as the starting light source for the entire spectral confocal measurement system, emitting a uniform and continuous polychromatic beam. Polychromatic light contains multiple wavelengths, which is the foundation of spectral confocal measurement. Different wavelengths of light will produce different focusing effects in subsequent optical elements due to their different refractive properties, thereby enabling the measurement of different depth information on the surface of the object under test 5. When the system includes the uniform polychromatic surface light source 1, a surface-view chromatic aberration objective lens 2, a digital micromirror device 3, a semi-reflective mirror 6, an imaging relay lens 7, and a surface-view hyperspectral imager 4, the light beam emitted by the uniform polychromatic surface light source 1 is directly directed towards the semi-reflective mirror 6. The light beam has a certain divergence angle and energy distribution at the light source exit, ensuring that it can cover the effective receiving area of ​​subsequent optical elements.

[0047] Furthermore, the semi-reflective lens 6 is a lens with special optical properties, capable of partially reflecting and partially transmitting light. For the light beam emitted from the homogenized polychromatic surface light source 1, the semi-reflective lens 6 allows most of the light to be reflected, enabling the light beam to smoothly enter the field-view chromatic aberration objective 2. For the light returning from the field-view chromatic aberration objective 2, the semi-reflective lens 6 can transmit a specific wavelength of light, allowing it to pass through the digital micromirror device 3. Through this reflection and transmission function, the semi-reflective lens 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 semi-reflective lens 6 faces the homogenized polychromatic surface light source 1, receiving the light beam emitted from it, while the other side faces the field-view chromatic aberration objective 2, transmitting the light beam reflected by the semi-reflective lens 6 to the field-view chromatic aberration objective 2. Simultaneously, the semi-reflective lens 6 is also connected to the digital micromirror device 3, reflecting the light returning from the field-view chromatic aberration objective 2 back to the digital micromirror device 3.

[0048] Furthermore, the surface field chromatic aberration objective 2, based on the principle of light dispersion, focuses light of different wavelengths onto different depths of the object being measured 5. When light of different wavelengths passes through the surface field chromatic aberration objective 2, due to differences in refractive index, it will form focal points at different axial positions. This focusing characteristic allows the system to distinguish information about different depths of the object's surface, such as... Figure 1In the figure, 400nm and 100nm represent different depths on the surface of the object under test 5. The surface field chromatic aberration objective 2 receives the light beam reflected from the semi-reflective mirror 6 and uniformly illuminates the surface of the object under test 5. Simultaneously, the surface field chromatic aberration objective 2 also collects the light reflected back from the surface of the object under test 5. Only specific wavelength beams precisely focused at a certain depth on the object surface can return along the original path; other wavelengths, not focused at that depth, will not return along the original path. The returned specific wavelength beam is then transmitted through the semi-reflective mirror 6 to the digital micromirror device 3. The surface field chromatic aberration objective 2 is located between the semi-reflective mirror 6 and the object under test 5, with one end connected to the semi-reflective mirror 6 to receive the reflected light beam; the other end directly faces the surface of the object under test 5, illuminating the object under test 5. This surface field chromatic aberration objective 2 can be replaced by a specially designed lens group and diffractive optical elements.

[0049] For further details, please see Figure 2 The diagram shown illustrates a digital micromirror device 3 simulating a pinhole array scan. The digital micromirror device 3 consists of an array of numerous tiny mirrors (micromirrors). By programming and controlling the tilt angle of the micromirror array, the structure of a pinhole array can be simulated. Each micromirror is equivalent to a controllable "pinhole." When a micromirror is at a specific tilt angle, it allows light to be reflected in a predetermined direction; when the micromirror is at other tilt angles, the light is reflected in other directions. Based on the simulated pinhole array structure, the digital micromirror device 3 can precisely control the reflection path of light returning from the surface chromatic aberration objective 2. By changing the tilt angle of the micromirrors, light from different positions can be reflected in different directions, thereby achieving spatial modulation of the light. This controllability allows the system to selectively measure information at different positions on the surface of the object being measured 5. The digital micromirror device 3 receives light returning from the surface chromatic aberration objective 2 (reflected by a semi-reflective mirror 6). The reflected beam passes through an imaging relay lens 7, which is connected to the imaging relay lens 7 to ensure that the light is accurately transmitted into the lens. Figure 2 As shown, each micromirror of the digital micromirror device 3 can switch between two main states, "on" and "off," respectively controlling the direction of light reflection. When the state is "on," the reflected light from the micromirror enters the spectrometer; when the state is "off," the reflected light from the micromirror does not enter the spectrometer. By gradually controlling the "on" and "off" states of the micromirrors, the simulated pinhole array scanning process can be completed.

[0050] Furthermore, the imaging relay lens 7 primarily functions as a relay imaging element, accurately transmitting and imaging the light beam reflected from the digital micromirror device 3. The imaging ratio is 1:1, meaning the image formed by the imaging relay lens 7 is spatially similar to the light distribution reflected from the digital micromirror device 3. This similarity helps the subsequent field-of-view hyperspectral imager 4 accurately receive and analyze the light. Through accurate light transmission, the imaging relay lens 7 ensures that the propagation direction and beam characteristics remain unchanged, providing high-quality input light for the field-of-view hyperspectral imager 4. The imaging relay lens 7 is located between the digital micromirror device 3 and the field-of-view hyperspectral imager 4, with one end connected to the digital micromirror device 3 to receive the light beam reflected from it; the other end is connected to the field-of-view hyperspectral imager 4, inputting the transmitted light beam into it.

[0051] Furthermore, the field-of-view hyperspectral imager 4 receives light transmitted from the imaging relay lens 7. Since the imaging relay lens 7 ensures the quality and distribution of the light, the field-of-view hyperspectral imager 4 can accurately receive the light and perform further analysis. The field-of-view hyperspectral imager 4 performs spectral analysis on the received light, inferring the contour and spectral information of the surface of the object being measured 5 by analyzing the proportion and intensity of different wavelength components in the light. Simultaneously, the field-of-view hyperspectral imager 4 also performs imaging processing, presenting the analyzed data in image form for intuitive observation and analysis of the surface morphology of the object being measured 5. Based on spectral analysis and imaging processing techniques, the field-of-view hyperspectral imager 4 performs multi-dimensional analysis of light. For example, it can determine the material composition and physical properties of different areas of the object's surface based on the absorption and reflection characteristics of different wavelengths of light. Through imaging processing of the light, the contour and details of the object's surface can be displayed in image form, providing users with intuitive measurement results. The surface-view hyperspectral imager 4 receives the light beam from the imaging relay lens 7, serving as the final stop for light propagation and completing the final measurement data acquisition and analysis.

[0052] Furthermore, by gradually controlling the digital micromirror device 3 to simulate the scanning process of the pinhole array, the spectral confocal measurement system can quickly and accurately measure the overall surface morphology of an object, thereby achieving high-speed and high-precision spectral confocal measurement. This spectral confocal measurement system can accurately acquire the surface contour and spectral information of the object being measured 5 without requiring it to move, demonstrating extremely high practicality and application potential.

[0053] In summary, the spectral confocal measurement system of this invention utilizes this characteristic of digital micromirror devices (DMDs) to progressively control the tilt angle of each micromirror in the micromirror array through programming. When the tilt angle of a micromirror changes, the reflection direction of the light incident on the micromirror also changes accordingly. This invention uses a digital micromirror device (DMD) to simulate pinhole array scanning, eliminating the need for the object under test to move. Information from different positions on the surface of the object under test can be quickly acquired by directly controlling the state of the DMD, thus enabling rapid measurement of the object's surface contour. Because this invention does not require movement of the object under test, it avoids the use of mechanical structures and eliminates the problem of mechanical wear, ensuring long-term stable operation of the system and maintaining stable measurement accuracy over a long period, thereby improving the system's reliability and the accuracy of the measurement results.

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

Claims

1. A spectral confocal measurement system for static surface profiles, characterized in that, The system includes: a homogenized polychromatic surface light source, a surface field chromatic aberration objective lens, a digital micromirror device, and a surface field hyperspectral imager. The uniform polychromatic surface light source is used to emit a light beam; The surface field chromatic aberration objective is located between the uniform polychromatic surface light source and the object under test. The surface field chromatic aberration objective is used to receive the light beam emitted by the uniform polychromatic surface light source, and to illuminate different wavelengths of light onto different depths of the object under test, and then project the light reflected back from the object under test onto the digital micromirror device. The digital micromirror device is located between the surface field chromatic aberration objective and the surface field hyperspectral imager. The digital micromirror device is used to control the tilt angle of the micromirror array and simulate the pinhole array structure to regulate the reflection direction of the light projected by the surface field chromatic aberration objective. The surface-view hyperspectral imager is used to receive the reflected beam after being modulated by the digital micromirror device, and to perform spectral analysis and imaging processing on the reflected beam after being modulated by the digital micromirror device.

2. The system according to claim 1, characterized in that, The system also includes: a semi-reflective translucent lens; The semi-reflective semi-transparent lens is located between the uniform polychromatic surface 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 semi-reflective mirror is used to receive the light beam emitted by the uniform polychromatic surface light source, and to reflect and transmit the light beam emitted by the uniform polychromatic surface light source, so that the light beam emitted from the uniform polychromatic surface light source is reflected to the surface field chromatic aberration objective lens, while the light returning 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 semi-reflective lens and the object under test. It is also used to receive the light beam transmitted by the semi-reflective lens, to illuminate different wavelengths of light onto different depths of the object under test, and to reflect the light returned by the object under test to the digital micromirror device through the semi-reflective lens.

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 beam after being controlled 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 beam after relay imaging by the imaging relay lens, and to perform spectral analysis and imaging processing on the beam after relay imaging by the imaging relay lens to obtain the surface depth information of the object under test.

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; Each micromirror in the micromirror array has an on state and an off state. When the first micromirror in the micromirror array is on, the first micromirror reflects the light projected onto it in the first reflection direction to the receiving area of ​​the surface field hyperspectral imager. When the second micromirror in the micromirror array is off, the second micromirror reflects the light projected onto it in the second reflection direction to a position outside the receiving area of ​​the surface field hyperspectral imager.

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