CN113945168A - Surface topography measurement system and method - Google Patents
Surface topography measurement system and method Download PDFInfo
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- CN113945168A CN113945168A CN202010690199.0A CN202010690199A CN113945168A CN 113945168 A CN113945168 A CN 113945168A CN 202010690199 A CN202010690199 A CN 202010690199A CN 113945168 A CN113945168 A CN 113945168A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
- G01B11/2513—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object with several lines being projected in more than one direction, e.g. grids, patterns
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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Abstract
The application provides a surface topography detection system and a method thereof, wherein the surface topography detection method comprises the following steps. The test light is divided into a first sub light and a second sub light, the first sub light is incident to the reflector along a first axial direction, and the second sub light is incident to the surface of the object along a second axial direction. The reflector is moved to enable the reflector to reflect the first sub-light at different positions in the first axial direction so as to generate N reflected lights. An object reflected light is generated that is associated with the second sub-ray reflected from the object surface. N images associated with the N reflected lights and the object reflected light are generated, each image including a plurality of interference fringes. And analyzing the plurality of interference fringes in each image to calculate N sine wave curve equations. And calculating the surface topography of the object surface according to the N sine wave curve equations.
Description
Technical Field
The present invention relates to a system and a method for measuring surface topography, and more particularly, to a system and a method for measuring surface topography using interference fringes.
Background
After the product is manufactured, the product is subjected to a certain test procedure to check the quality of the product. Some test procedures may require verification of the quality of the surface of the product, for example, the surface flatness of the product or the microstructure on the surface may be checked. Generally, various testing devices are used to inspect the surface of a product during a testing procedure, such as a camera to capture the surface of the product, and then the captured image is enlarged to inspect a specific region of the surface of the product.
For measuring the flatness of the surface of a product, an interferometer is conventionally used to measure the surface of the product. As can be understood by those skilled in the art, the interferometer divides a beam of light into two sub-beams, reflects one of the sub-beams on the surface of the product, changes the optical path of the other sub-beam by moving the reflector, and measures the topography of the surface of the product by using the optical path difference and the phase difference between the two sub-beams. However, if the requirement for the plane accuracy of the product surface is high, the mechanical error caused by moving the mirror is particularly highlighted, so that the morphology of the product surface cannot be correctly judged due to the mechanical error. In view of the limitations of planar accuracy of conventional interferometers, there is a need for a system and method for surface topography detection that can support higher planar accuracy.
Disclosure of Invention
In view of the above, the present disclosure is directed to a surface topography detecting method, which can eliminate an error when a mirror is moved, so as to accurately measure a surface topography.
The application provides a surface topography detection method, which comprises the following steps. Firstly, the test light is divided into a first sub-light and a second sub-light, the first sub-light is incident to the reflector along a first axial direction, and the second sub-light is incident to the surface of the object along a second axial direction. Then, the reflector is moved to make the reflector reflect the first sub-light at different positions in the first axial direction to generate N reflected lights. And, an object reflected light is generated, the object reflected light being associated with the second sub-ray reflected from the object surface. Then, N images are generated, wherein the N images are related to the N reflected lights and the object reflected light, and each image comprises a plurality of interference fringes. And analyzing the plurality of interference fringes in each image to calculate N sinusoidal curve equations. And calculating the surface topography of the object surface by the N sine wave curve equations. Wherein a first angle is included between a first normal of the reflector and the first axial direction, or a first angle is included between a second normal of the object surface and the second axial direction, and N is a positive integer greater than 2.
In some embodiments, the step of moving the mirror to reflect the first sub-light at different positions in the first axial direction to generate N reflected lights further comprises the following steps. First, an i-th set position of the mirror in the first axial direction is set to generate an i-th reflected light of the N reflected lights. And, set up the reflector in the (i + 1) th settlement position of the first axial, produce the (i + 1) th reflected light in the said N reflected light. Wherein the ith setting position is separated from the (i + 1) th setting position by one eighth of the first wavelength, and i is a positive integer less than N. In addition, the step of analyzing the plurality of interference fringes in each image to calculate the N sinusoidal curve equations may further include the following steps. First, a reference line perpendicular to the interference fringes is selected in each image. And performing curve fitting on the plurality of interference fringes on the reference line to calculate each sine wave curve formula.
In some embodiments, in the step of performing curve fitting on the plurality of interference fringes on the reference line to calculate each sine wave curve equation, an i-th phase error value of the i-th reflected light and the i + 1-th reflected light may be further obtained during the curve fitting. Here, each sinusoidal equation may include a level parameter, an amplitude parameter and a phase parameter, and the phase parameter is associated with the surface topography of the object surface and the ith phase error value.
The application provides a surface topography detecting system, the error when can eliminating the removal speculum to can measure out the surface topography correctly.
The application provides a surface topography detecting system for measuring the surface topography of an object surface, the surface topography measuring system comprises a light source, a reflector, a spectroscope, a photographic device and a processing device. The light source is used for providing test light. The mirror is selectively movable in different positions in the first axial direction. The spectroscope is used for dividing the test light into a first sub-light and a second sub-light, the first sub-light enters the reflector along a first axial direction, and the second sub-light enters the surface of the object along a second axial direction. The photographing device is configured to receive first sub-beams reflected from the mirror at different positions in the first axial direction and receive second sub-beams reflected from the surface of the object to generate N images, where the first sub-beams reflected from the mirror at different positions in the first axial direction are defined as N reflected light, the second sub-beams reflected from the surface of the object are defined as object reflected light, the N images are associated with the N reflected light and the object reflected light, and each image includes a plurality of interference fringes. The processing device is electrically connected with the photographic device and used for analyzing the interference fringes in each image to calculate N sinusoidal curve equations and calculating the surface topography of the object surface according to the N sinusoidal curve equations. Wherein a first angle is included between a first normal of the reflector and the first axial direction, or a first angle is included between a second normal of the object surface and the second axial direction, and N is a positive integer greater than 2.
In some embodiments, when the test light has a first wavelength, the mirror generates an ith reflected light of the N reflected lights at an ith set position in the first axial direction, and the mirror generates an (i + 1) th reflected light of the N reflected lights at an (i + 1) th set position in the first axial direction, wherein the ith set position is spaced from the (i + 1) th set position by one eighth of the first wavelength, and i is a positive integer less than N. The processing device may further select a reference line perpendicular to the interference fringes in each image, and perform curve fitting on the interference fringes on the reference line to calculate each sine wave curve equation. In addition, the processing device may further obtain an ith phase error value between the ith reflected light and the (i + 1) th reflected light when performing curve fitting. Each of the sinusoidal equations may include a level parameter, an amplitude parameter, and a phase parameter, and the phase parameter is associated with a surface topography of the object surface and an ith phase error value.
In summary, the surface topography detection system and method provided by the present application enable the surface of the reflector or the object to be tilted by an angle, so that the first sub-light or the second sub-light is not incident on the surface of the reflector or the object perpendicularly, thereby ensuring that the image captured by the camera device has a plurality of interference fringes. In addition, the processing device can calculate and eliminate the phase error value when the reflecting mirror is moved, so that the surface appearance can be measured correctly.
Further details regarding other functions and embodiments of the present application are described below with reference to the accompanying drawings.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a functional block diagram of a surface topography measurement system according to an embodiment of the present application;
FIG. 2A is a schematic diagram of an image with a plurality of interference fringes according to an embodiment of the present application;
FIG. 2B is a schematic diagram of another image with multiple interference fringes according to one embodiment of the present application;
FIG. 2C is a schematic diagram showing a sine wave curve-fitting to interference fringes according to an embodiment of the present application;
fig. 3 is a flowchart illustrating steps of a surface topography measurement method according to an embodiment of the present application.
Description of the symbols
1 surface topography detection System 10 light Source 12 Reflector
14 spectroscope 16 photographing devices 160a, 160b image
162a, 162b reference lines 164a, 164b sine wave 18 processing apparatus
2 object surface L1 test light L11 first sub-light
L12 second sub-ray R11 reflected light R12 object reflected light
Theta angle A first axial direction B second axial direction
S20-S25 process flow
Detailed Description
In order to specifically describe the embodiments and achieve the effects of the present application, an embodiment is provided and described below with reference to the drawings.
Referring to fig. 1, fig. 1 is a functional block diagram of a surface topography measurement system according to an embodiment of the present application. As shown in fig. 1, the surface topography detection system 1 is an optical system and can be used to measure the surface topography of an object surface 2. The present embodiment is not limited to the kind of the target surface 2, and may be, for example, a surface of all or part of a wafer, a chip, or a mechanical part. In practice, the surface texture detecting system 1 of the present embodiment can support a higher plane precision, but is not limited to measuring only the planar object surface 2, and the surface texture detecting system 1 of the present embodiment may also measure the curved object surface 2. As can be seen, the surface topography measuring system 1 may comprise the light source 10, the reflector 12, the beam splitter 14, the photographing device 16 and the processing device 18, and it is not limited whether the light source 10, the reflector 12, the beam splitter 14, the photographing device 16 and the processing device 18 are installed in a housing, and the photographing device 16 and the processing device 18 may be electrically connected by wire or wirelessly, for example, the processing device 18 may be remotely installed. In an example, the surface topography detecting system 1 may further include a lens, a filter or other optical components, which is not limited in this embodiment. The components of the surface topography system 1 are described below.
The light source 10 is used to provide a test light L1, the test light L1 can be a laser light with a single wavelength (first wavelength), and the wavelength of the test light L1 is not limited herein. As shown in fig. 1, the light source 10 emits a test light L1 into the beam splitter 14 along a second axis B. Then, the beam splitter 14 can split the test light L1 into a first sub-light L11 and a second sub-light L12, wherein the first sub-light L11 enters the reflector 12 along the first axis a, and the second sub-light L12 enters the object surface 2 along the second axis B. It should be understood by those skilled in the art that the beam splitter 14 is capable of splitting the test light L1 into two identical sub-light beams, i.e. the first sub-light beam L11 and the second sub-light beam L12 have substantially the same light intensity and the same wavelength and can emit light in a first axial direction a and a second axial direction B perpendicular to each other, respectively. It should be noted that although fig. 1 illustrates that the light source 10, the beam splitter 14 and the object surface 2 are in the second axis direction B, the embodiment is not limited thereto. For example, it is also possible to interchange the mirror 12 and the object surface 2 such that the object surface 2 is in a first axis a and the light source 10, the beam splitter 14 and the mirror 12 are in a second axis B.
First, the mirror 12 incident with the first sub-light L11 is described, the mirror 12 can be selectively moved to different positions in the first axial direction a, and the mirror 12 can reflect the first sub-light L11 back, where the reflected first sub-light L11 is defined as the reflected light R11. In practice, there are N setting positions in the first axis a, and the mirror 12 can be driven to move to one of the N setting positions. In one example, the distance between two adjacent ones of the N set positions may be predetermined, for example, when the first wavelength is λ, the distance may be λ/8, that is, one eighth of the wavelength (first wavelength) of the test light L1. The N set positions of the mirror 12 relate to the optical path length of the first sub-ray L11, in particular the distance between the mirror 12 and the beam splitter 14. For example, if the mirror 12 reflects the first sub-light L11 at the 1 st setting position in the first axis a, the 1 st reflected light R11 is generated. When the reflector 12 moves forward (or backward) in the first axial direction a by one eighth of the first wavelength and reflects the first sub-light L11 at the 2 nd setting position, the 2 nd reflected light R11 is generated.
Because of the overlapping relationship of the optical paths in the first axial direction a, although the distance between the mirror 12 and the beam splitter 14 in the 2 nd setting position is only one eighth of the first wavelength longer (or less) than the distance between the mirror 12 and the beam splitter 14 in the 1 st setting position, it should be understood by those skilled in the art that the optical path length of the 2 nd reflected light R11 is two times longer (or less) than that of the 1 st reflected light R11, i.e. one quarter of the first wavelength. This means that the 2 nd reflected light R11 and the 1 st reflected light R11 will be 90 degrees out of phase (i.e., pi/2). In practice, the mirror 12 may have more than 3 setting positions, and those skilled in the art will understand that the four-step phase shift method or the seven-step phase shift method is usually adopted in the measurement, that is, there are 4 setting positions or 7 setting positions corresponding to the mirror 12. Taking the four-step phase shift method as an example, the reflector 12 also reflects the first sub-ray L11 at the 3 rd set position in the first axis a and generates the 3 rd reflected light R11. The reflector 12 also reflects the first sub-ray L11 at the 4 th setting position in the first axial direction a, and generates a 4 th reflected light R11. That is, the phases of the 1 st to 4 th reflected lights R11 are sequentially different by 90 degrees (i.e., π/2).
In view of the above, the object surface 2 incident with the second sub-light L12 can also reflect the second sub-light L12, and the reflected second sub-light L12 is defined as the object reflected light R12. Unlike the mirror 12 which moves to N set positions, the relative distance between the object surface 2 and the beam splitter 14 can be kept constant, so that the phase of the object reflected light R12 at any point in time should be the same. Of course, it is also possible to fix the relative distance between the reflector 12 and the beam splitter 14 and change the relative distance between the object surface 2 and the beam splitter 14, and those skilled in the art will understand that the change is only a simple replacement of the embodiment. For convenience of explanation of the spirit of the present application, this embodiment will be described by taking an example in which the mirror 12 is moved by N setting positions. In addition, the reflected light R11 and the object reflected light R12 are emitted to the photographing device 16 through the beam splitter 14, so that the photographing device 16 receives the reflected light R11 and the object reflected light R12 to generate N images. Further, taking the four-step phase shift method as an example, the 1 st to 4 th images generated by the image capturing device 16 may correspond to the 1 st reflected light R11 and the object reflected light R12, the 2 nd reflected light R11 and the object reflected light R12, the 3 rd reflected light R11 and the object reflected light R12, the 4 th reflected light R11 and the object reflected light R12, and so on.
In practice, the angle θ (first angle) is included between the normal (first normal) of the mirror surface of the reflector 12 and the first axis a, and the purpose of the angle θ is to ensure that interference fringes are always present in the image generated by the imaging device 16. In one example, if the normal (first normal) of the mirror surface of the mirror 12 does not have the angle θ with the first axis a, or if the normal of the mirror surface of the mirror 12 overlaps with the first axis a, interference fringes cannot be generated in the image generated by the imaging device 16. Since the interference fringes are the basis for determining the surface topography of the object surface 2 in the present embodiment, it is technically significant that the normal (first normal) of the mirror surface of the reflecting mirror 12 and the first axial direction a have an angle θ (first angle). Further, in the 1 st image, the 1 st reflected light R11 and the object reflected light R12 generate an interference phenomenon, and a plurality of interference fringes are generated in the 1 st image. Similarly, for the 2 nd to 4 th images, the 2 nd to 4 th reflected lights R11 and the object reflected light R12 also generate interference phenomena, and a plurality of interference fringes also exist in the 2 nd to 4 th images, and so on. In order to analyze the images, the camera 16 is electrically connected to the processing device 18, the processing device 18 converts the interference fringes in each image into corresponding sinusoidal equations, and the sinusoidal equations calculate the surface topography associated with the object surface 2.
In one example, the processing device 18 processes the images from the imaging device 16, in particular to extract the sinusoidal equations associated with the interference fringes from each image. To describe how to extract the sinusoidal curve formula associated with the interference fringes from the image, please refer to fig. 2A and fig. 2B together. Fig. 2A is a schematic diagram illustrating an image with a plurality of interference fringes according to an embodiment of the present application, and fig. 2A is a schematic diagram illustrating another image with a plurality of interference fringes according to an embodiment of the present application. Assuming that the 1 st image generated by the image capturing device 16 is the image 160a in fig. 2A, the processing device 18 first selects a reference line 162A in the image 160 a. Here, the reference line 162a should be perpendicular to the interference fringes in the image 160a, so that there are regularly appearing bright and dark values on the reference line 162 a. The processing device 18 then performs a curve fitting on the interference fringes on the reference line 162a to generate a sine wave 164 a. The peak of the sine wave 164a may be the center of a bright fringe in the interference fringe, and the valley of the sine wave 164a may be the center of a dark fringe in the interference fringe. Similarly, assuming that the 2 nd image generated by the image capturing device 16 is the image 160B in fig. 2B, the processing device 18 also selects a reference line 162B in the image 160B. The reference line 162b is also perpendicular to the interference fringes in the image 160b, so that there are regularly appearing bright and dark values on the reference line 162 b. In addition, the processing device 18 also performs a curve fitting on the interference fringes on the reference line 162b to generate a sine wave 164 b. Taking the four-step phase shift method as an example, the processing device 18 can calculate the sinusoidal curve formula corresponding to the sinusoidal in each of the 4 images.
For example, the processing device 18 may input the light and dark value data on the reference line 162a into a calculation program, such as a conventional matlab program, and curve-fit the light and dark values on the reference line 162a by the matlab program. By analogy, the processing device 18 can calculate 4 sinusoidal expressions corresponding to the 1 st to 4 th images, for example, the following expressions (1) to (4).
I1(x,y)＝I’(x,y)+I”(x,y)cos[φ(x,y)] (1)
I2(x,y)＝I’(x,y)+I”(x,y)cos[φ(x,y)+ε1] (2)
I3(x,y)＝I’(x,y)+I”(x,y)cos[φ(x,y)+ε1)+ε2] (3)
I4(x,y)＝I’(x,y)+I”(x,y)cos[φ(x,y)+ε1+ε2)+ε3] (4)
Is illustrated by formula (1), wherein I1(x, y) represents the sine wave fitted to the interference fringe in the 1 st image, I' (x, y) represents the level parameter (or DC offset) corresponding to the sine wave, I "(x, y) represents the amplitude parameter, cos [ phi (x, y) ], corresponding to the sine wave]To represent said sine wave pairsThe corresponding phase parameter, where phi (x, y) is the surface topography associated with the object surface 2. As can be seen from equations (1) and (2), the sine wave I in equation (2)2(x, y) in addition to the same level parameter I' (x, y) and amplitude parameter I "(x, y), there is one more epsilon in the phase parameter part1This embodiment will be1Defined as phase 1 error value. The present embodiment mentions in the foregoing example that the mirror 12 can be set between N set positions, which can be understood as positions to which the mirror 12 is intended to be moved, but the mirror 12 is not necessarily precisely movable to the N set positions. Those skilled in the art will understand that the level parameter I' (x, y) and the amplitude parameter I "(x, y) in the equations (1) - (4) should be the same, because the 1 st to 4 th reflected light R11 have different optical paths and the level and the amplitude should be the same. In addition, cos [ φ (x, y) of the phase parameter in equations (1) to (4)]The components, since they are only related to the surface topography of the object surface 2, should also be identical.
The phase parameter also has a phase error value epsilon of 1 st phase1The reason for the components, this embodiment is briefly described as follows. Referring to fig. 2A to 2C together, fig. 2C is a schematic diagram illustrating a sine wave for curve fitting of interference fringes according to an embodiment of the present application. As described in the foregoing embodiment, assuming that the 1 st set position and the 2 nd set position of the mirror 12 are ideally the first wavelength (λ/8) which is one eighth different, that is, ideally the first wavelength (λ/4) in which the optical path difference between the 2 nd reflected light R11 and the 1 st reflected light R11 is one quarter, it can be deduced that the phases of the 2 nd reflected light R11 and the 1 st reflected light R11 are different by 90 degrees (i.e., pi/2). That is, the phases of the sine wave 164a in the image 160a and the sine wave 164b in the image 160b are theoretically different by 90 degrees (i.e., π/2). For convenience of example, the peak of one sine wave 164a is selected in fig. 2C, for example, at the (x, y) position. Ideally, sine wave 164a and sine wave 164b are 90 degrees out of phase (i.e., π/2), and the position of the peak of sine wave 164a would correspond to the position of the amplitude null of sine wave 164 b. In practice, however, the distance that the mirror 12 moves in the first axial direction a may be made of a piezoelectric materialAlthough relatively delicate, no ideal component exists physically. Thus, the piezoelectric assembly is still likely to have an error each time the mirror 12 is moved, resulting in the position of the peak of the sine wave 164a not being exactly aligned with the position of the amplitude null of the sine wave 164 b. In other words, the response (degree of displacement) of the piezoelectric element to the applied voltage is not necessarily the same every time, resulting in the fact that the distance between the 1 st set position and the 2 nd set position is not exactly the first wavelength (λ/8) of one eighth. This is also the case where a phase error value ε is added between the equation (1) for the sine wave 164a and the equation (2) for the sine wave 164b1The reason for (1).
Similarly, in practice, there will be an error in the distance between the 2 nd and 3 rd set positions, i.e., the 3 rd reflected light R11 and the 2 nd reflected light R11 will differ in phase by 90 degrees (i.e., π/2) plus a phase error value ε2. It is worth mentioning that since the 2 nd setting position itself is also in error, the equation (3) is not limited to the phase error value epsilon2In addition, the phase error value epsilon is also included1. Similarly, there is an error in the distance between the 3 rd and 4 th set positions, and the 4 th reflected light R11 and the 3 rd reflected light R11 will differ in phase by 90 degrees (i.e., π/2) plus a phase error value ε3. And, in addition to the phase error value ε in the equation (4)3In addition, the phase error value epsilon is also included1And the phase error value epsilon2. It can be understood by those skilled in the art that the curve fitting of the interference fringes in the 1 st to 4 th images of the present embodiment will be combined with the phase error value ε1Phase error value epsilon2And the phase error value epsilon3Together are calculated. That is, the sine waves I in equations (1) to (4)1(x, y) to I4(x, y) is directly derived from interference fringes on the reference lines of the 1 st to 4 th images, and the phase error value epsilon1Phase error value epsilon2And the phase error value epsilon3These are known parameters that will be derived during curve fitting. In contrast, the unknown variables in equations (1) to (4) remainThe down level parameter I '(x, y), the amplitude parameter I' (x, y) and the phase parameter cos [ phi (x, y)]. That is, if the present embodiment derives equations (1) to (4) based on the four-step phase shift method, it is inevitable to solve the above three unknown variables, that is, to solve the phase parameter cos [ phi (x, y) ]]And thus can be derived from the phase parameter cos [ phi (x, y)]The surface topography of the object surface 2 is then deduced.
It will be understood by those skilled in the art that the three unknown variables need only be solved by three corresponding equations, and thus, whether the four-step phase shift method (as described above, there are four equations) or the seven-step phase shift method (there are seven equations) is used, there is enough information to derive the surface topography of the object surface 2. In other words, the four-step phase shift method or the seven-step phase shift method can be applied to measure the surface topography of the object surface 2.
The surface topography measurement method of the present application is described below by using the surface topography measurement system of the foregoing embodiment, please refer to fig. 1 and fig. 3 together, and fig. 3 is a flowchart illustrating steps of the surface topography measurement method according to an embodiment of the present application. As shown in the figure, the surface topography detection method of the present application includes the following steps. In step S20, the beam splitter 14 may split the test light L1 emitted from the light source 10 into a first sub-light L11 and a second sub-light L12, wherein the first sub-light L11 enters the reflector 12 along the first axis a, and the second sub-light L12 enters the object surface 2 along the second axis B. Next, in step S21, the reflector 12 can be moved to different positions along the first axis a to reflect the first sub-light L11, where the reflected first sub-light L11 is the reflected light R11. In step S22, the reflected second sub-light L12 is reflected from the object surface 2, and the reflected second sub-light L12 is the object reflected light R12. Next, in step S23, the camera 16 receives the reflected light R11 and the reflected object light R12 and generates images, each of which includes a plurality of interference fringes. In step S24, the processing device 18 analyzes the interference fringes in each image to calculate sinusoidal equations, such as equations (1) to (4). And in step S25, the processing device 18 calculates the surface topography of the object surface 2 according to the sine wave curve equation. Other steps related to the surface topography measurement method have been described in the above embodiments of the surface topography measurement system, and are not described herein in detail in this embodiment.
In summary, the surface topography detection system and method provided by the present application enable the surface of the reflector or the object to be tilted by an angle, so that the first sub-light or the second sub-light is not incident on the surface of the reflector or the object perpendicularly, thereby ensuring that the image captured by the camera device has a plurality of interference fringes. In addition, the processing device can calculate and eliminate the phase error value when the reflecting mirror is moved, so that the surface appearance can be measured correctly.
The above-described embodiments and/or implementations are only illustrative of the preferred embodiments and/or implementations for implementing the technology of the present application, and are not intended to limit the implementations of the technology of the present application in any way, and those skilled in the art can make many changes or modifications to the equivalent embodiments without departing from the scope of the technology disclosed in the present application, but should still be considered as the technology or implementations substantially the same as the present application.
Claims (10)
1. A method for measuring surface topography, comprising:
dividing a test light into a first sub-light and a second sub-light, wherein the first sub-light is incident to a reflector along a first axial direction, and the second sub-light is incident to an object surface along a second axial direction; and
moving the reflector to make the reflector reflect the first sub-beam at different positions in the first axial direction to generate N reflected lights;
generating an object reflected light, the object reflected light being associated with the second sub-ray reflected from the object surface;
generating N images associated with the N reflected lights and the object reflected light, each of the images including a plurality of interference fringes;
analyzing the interference fringes in each image to calculate N sinusoidal curves; and
calculating a surface topography of the object surface from the N sinusoidal curves;
wherein a first angle is included between a first normal of the reflector and the first axial direction, or a first angle is included between a second normal of the object surface and the second axial direction, and N is a positive integer greater than 2.
2. The method of claim 1, wherein the test light has a first wavelength, and the step of moving the mirror such that the mirror reflects the first sub-light at different positions in the first axis to generate the N reflected lights further comprises:
setting an ith setting position of the reflector in the first axial direction to generate an ith reflected light in the N reflected lights;
setting an i +1 th set position of the reflector in the first axial direction to generate an i +1 th reflected light in the N reflected lights; and
wherein the i-th setting position is spaced from the i + 1-th setting position by one eighth of the first wavelength, and i is a positive integer less than N.
3. The method of claim 2, wherein the step of analyzing the interference fringes in each of the images to calculate the N sinusoidal equations further comprises:
selecting a reference line in each image perpendicular to the interference fringes; and
and performing curve fitting on the interference fringes on the reference line to calculate each sine wave curve formula.
4. The method of claim 3, wherein in the step of curve-fitting the interference fringes on the reference line to calculate each sinusoidal curve formula, an i-th phase error value of the i-th reflected light and the i + 1-th reflected light is obtained during curve fitting.
5. The method of claim 4, wherein each of the sinusoidal equations includes a calibration parameter, an amplitude parameter and a phase parameter, and the phase parameter is associated with the surface topography of the object surface and the i-th phase error value.
6. A surface topography measurement system for measuring a surface topography of a surface of an object, the surface topography measurement system comprising:
a light source for providing a test light;
a reflector selectively movable in different positions in a first axial direction;
a beam splitter for splitting the test beam into a first sub-beam and a second sub-beam, wherein the first sub-beam is incident on the reflector along the first axial direction, and the second sub-beam is incident on the object surface along the second axial direction; and
a camera device for receiving the first sub-beams reflected from the mirror at different positions in the first axial direction and receiving the second sub-beams reflected from the object surface to generate N images, wherein the first sub-beams reflected from the mirror at different positions in the first axial direction are defined as N reflected light, the second sub-beams reflected from the object surface are defined as an object reflected light, the N images are associated with the N reflected light and the object reflected light, and each image includes a plurality of interference fringes; and
a processing device electrically connected to the camera device for analyzing the interference fringes in each image to calculate N sinusoidal curves, and calculating the surface topography of the object surface by the N sinusoidal curves;
wherein a first angle is included between a first normal of the reflector and the first axial direction, or a first angle is included between a second normal of the object surface and the second axial direction, and N is a positive integer greater than 2.
7. The system of claim 6, wherein the test light has a first wavelength, the mirror generates an i-th reflection light of the N reflection lights at an i-th set position in the first axial direction, the mirror generates an i + 1-th reflection light of the N reflection lights at an i + 1-th set position in the first axial direction, wherein the i-th set position is spaced apart from the i + 1-th set position by one eighth of the first wavelength, and i is a positive integer less than N.
8. The system of claim 7, wherein the processing device further selects a reference line perpendicular to the interference fringes in each of the images, and performs curve fitting on the interference fringes on the reference line to calculate each of the sinusoidal equations.
9. The system of claim 8, wherein the processing device further obtains an i-th phase error value between the i-th reflected light and the i + 1-th reflected light during curve fitting.
10. The system of claim 9, wherein each of the sinusoidal equations includes a calibration parameter, an amplitude parameter and a phase parameter, and the phase parameter is associated with the surface topography of the object surface and the i-th phase error value.
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