Centering method for a helical scan measurement system

Abstract

The application discloses a centering method of a spiral scanning measurement system, comprising a rotating platform, an x-direction driving platform and a y-direction driving platform for driving the rotating platform, and a probe, wherein the centering is performed according to the following steps: S01, placing a scale sheet in the center of the rotating platform; S02, moving the probe to the center of the rotating platform, so that the scale sheet is in the measurement range of the probe, and the z-axis height value h of the scale sheet is set as 0; S03, starting the rotating platform, and recording the total number N of positive and negative peak values of the signal sent by the probe when the rotating platform rotates one round; and S04, under the condition that the rotating platform continues to rotate, adjusting the x-direction driving platform and the y-direction driving platform to make N tend to 0, and completing the centering of the driving rotating platform. The scale sheet is taken as a measured object, the eccentricity error r is reflected through the scale sheet, and the centering is realized by gradually eliminating the zero-crossing number N.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology, and specifically relates to a centering method for a spiral scanning measurement system. Background Technology

[0002] In recent years, with the continuous advancement of ultra-precision machining and micro-machining technologies, components with precision surfaces, such as precision mechanical parts, and devices and integrated circuits with microstructured surfaces, such as microlens arrays, micromirror arrays, gratings, and very large-scale integrated circuits, have emerged. The surface morphology of a specimen not only reflects its external characteristics but also its internal properties. For example, the surface morphology of machined mechanical parts affects mechanical properties such as friction and wear, contact stiffness, fatigue strength, fit properties, and transmission accuracy of the system, as well as physical properties such as thermal conductivity, electrical conductivity, and corrosion resistance. The surface roughness of silicon wafers used to fabricate integrated circuits has a significant impact on thin-film resistance and capacitance in the circuit, thereby affecting circuit performance and yield. The surfaces of optical components fabricated through multiple photolithography and etching methods, as well as the surfaces of micromechanical structures fabricated through micromachining technology, all affect the performance of the specimen.

[0003] Currently, when measuring the surface morphology of a specimen, as shown in the attached diagram of the instruction manual... Figure 1 As shown, the x and y coordinates are mostly obtained using a raster scanning method. This scanning method is convenient for subsequent data output, but after the x-axis completes one line scan, the y-axis moves a small step. These two steps are performed separately and require frequent acceleration, deceleration, and reverse movement, which increases the measurement time and introduces reverse movement errors. Simultaneous operation of both the x and y axes allows for rapid scanning. Furthermore, using special scanning paths can significantly improve the scanning rate, such as sine, cycloidal, Hilbert curve, Lissajous curve, and spiral scans. (See the attached diagram in the manual.) Figure 2 As shown, the turntable rotates continuously while the linear platform moves laterally in the x-direction, forming a spiral trajectory scan. Each trajectory line in the spiral scanning mode is equidistant, and the scanning platform only accelerates or decelerates at the beginning and end of the measurement phase, maintaining a constant speed in the remaining phases. This effectively improves measurement speed and reduces interference, which is of great significance for practical applications. However, the prerequisite for achieving spiral scanning is precise alignment between the probe and the turntable's rotation center. If the probe is not aligned with the turntable's rotation center, i.e., if the probe has an eccentric error, the reconstructed morphology will be distorted, leading to unreliable measurement results. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for centering a spiral scanning measurement system that can ensure the coincidence accuracy of the scanning starting point of the probe and the rotation center of the rotating platform, thereby achieving centering of the spiral scanning measurement system, in view of the current status of the prior art.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problem is as follows: a centering method for a helical scanning measurement system, comprising a rotating platform, an x-axis driving platform and a y-axis driving platform for driving the rotating platform, and a probe, wherein centering is performed according to the following steps:

[0006] S01, place the scale sheet roughly in the center of the rotating platform;

[0007] S02, move the probe approximately to the center of the rotating platform so that the scale sheet is within the measurement range of the probe. Set the z-axis height h of the scale sheet to 0.

[0008] S03, start the rotating platform and record the total number N of positive and negative peaks N that the probe sends a signal that crosses h for each rotation of the rotating platform;

[0009] S04, while the rotating platform continues to rotate, adjust the x-axis and y-axis driving platforms to make N approach 0, thus completing the centering of the rotating platform. When the scale sheet is a planar grating, the positive and negative peaks of the laser crossing h are abrupt, so N is the number of zero crossings.

[0010] In the preferred embodiment, in step S04, the x-axis drive platform is first adjusted to minimize N; then the y-axis drive platform is adjusted to minimize N, thus completing the centering of the drive rotary platform.

[0011] In a preferred embodiment, the surface of the scale sheet has equal-width raised and recessed strips, spaced at intervals of P. Although a scale sheet with an uneven surface can also be measured, the equal-width raised and recessed strips enable quantitative measurement.

[0012] In a preferred embodiment, the scale sheet is a grating. The grating has equal-width raised strips and equal-width recessed strips.

[0013] In the preferred embodiment, the scale sheet is a planar grating. There are various types of gratings, but a planar grating can reflect laser light to the greatest extent.

[0014] In the preferred embodiment, in step S02, let the position of the probe be T, the center position of the rotating platform be T', and the distance from T to T' be r. Then r = Np / 8 (Equation 1). In Equation 1, p is one grating period. The probe rotates around the grating surface once, and four zero-crossing points are generated within one grating period. That is, N / 4 is the number of grating periods swept by the probe. Therefore, the diameter of one rotation of the probe is 2r = p * N / 4, that is, the deviation radius r = Np / 8. By making N smaller, r is made smaller, so that the center position T' of the rotating platform gradually coincides with T.

[0015] In the preferred embodiment, the scale sheet is a sub-nanometer grating, and the probe is a sub-nanometer probe.

[0016] A planar grating with period p is placed on a turntable. There is no relative motion between the grating and the turntable, and the rotation center T' of the turntable is the rotation center of the grating. The probe is positioned at the midpoint between the upper and lower surfaces of the grating. The center coordinate T of the probe at this point is the eccentricity error. The magnitude of the eccentricity error is the length r of TT'. The turntable rotates one revolution at a constant speed. During this revolution, the projection of the curve measured by the probe's rotational scanning onto the grating's xy-plane is a circle with radius r.

[0017] When the probe passes over the uneven surface of the grating, the signal collected by the detector fluctuates around the zero value of the height h. The height value of the curve measured by rotational scanning changes with the rotation angle. By recording the number of zero-crossings N of the measured curve during one rotation of the grating (calculated by ensuring that the product of adjacent points is less than 0), the eccentricity error r can be calculated. When the probe is ideally aligned with the center of the turntable, the probe reading does not change with the turntable rotation angle, and the number of zero-crossings N is 0.

[0018] The eccentricity error r calculated by equation (1) has eccentric components in both the x and y directions, and the positive and negative directions of the eccentric components are unknown. Therefore, the moving platforms in the x and y directions need to be separated and adjusted multiple times to achieve precise alignment between the probe and the turntable. Probe alignment is actually a process of successively approaching the optimal zero-crossing position.

[0019] In summary, compared with the prior art, the centering method of the spiral scanning measurement system of the present invention 1) uses a scale sheet as the object to be measured, and reflects the eccentricity error r through the scale sheet. The scale sheet adopts a sub-nanometer grating, and the probe adopts a sub-nanometer probe, thereby making the probe centering accuracy high.

[0020] 2) The eccentricity error r is calculated by the number of zero-crossings N of the curve measured when the grating rotates one revolution (calculated by the method of the product of adjacent scattered points being less than 0). The number of zero-crossings is obtained quickly through computer algorithm, thereby quickly obtaining the eccentricity error r, which makes the probe alignment efficiency high.

[0021] 3) The scanning results are reflected by the response function curve, which can accurately record the number of zero crossings and avoid misjudgment of the eccentricity error r, thus making the centering reliability high. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the surface morphology of the object being measured using a raster-based scanning method in the prior art;

[0023] Figure 2 This is a schematic diagram of the surface morphology of the object being measured using spiral scanning in existing technology;

[0024] Figure 3This is a schematic diagram of the structure of a scanning device in the prior art;

[0025] Figure 4 This is a schematic diagram of the circular path swept by the probe on the scale sheet during the centering process of the rotating platform;

[0026] Figure 5 yes Figure 4 During the centering process, the probe sends signals that cross the positive and negative peak values ​​of h for each rotation of the rotating platform, and the measured curve is scanned.

[0027] Figure 6 This is a schematic diagram of the heart-aligning steps. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] It should be noted that the term "comprising" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a product that includes a series of units is not necessarily limited to those units that are explicitly listed, but may include other units that are not explicitly listed or that are inherent to such products.

[0030] In this application, the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0031] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0032] Furthermore, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a direct connection, an indirect connection via an intermediate medium, or an internal connection between two devices, elements, or components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0033] The attached figures are labeled as follows: x-axis drive platform 1, y-axis drive platform 2, probe head 3, scanning trajectory 4, rotating platform 5, scale sheet 6, strip-shaped protrusion 61, strip-shaped depression 62, marble vibration isolation platform 7.

[0034] Example 1: A centering method for a spiral scanning measurement system of the present invention includes a rotating platform 5, an x-axis driving platform 1 and a y-axis driving platform 2 for driving the rotating platform 5, and a probe 3. The x-axis driving platform 1 and the y-axis driving platform 2 are both mounted on a marble vibration isolation platform 7. The centering is performed according to the following steps:

[0035] S01, place the scale sheet 6 roughly in the center of the rotating platform 5;

[0036] S02, move the probe 3 approximately to the center of the rotating platform 5 so that the scale plate 6 is within the measurement range of the probe 3. Assume that the height h of the laser spot emitted by the probe 3 on the scale plate 6 in the initial state is 0. If the probe is a laser and the scale plate 6 is a grating, then the spot is focused at half the position between the upper and lower surfaces of the grating. If the probe is a contact probe, then the probe is adjusted to the position of the lower surface of the grating.

[0037] S03, start rotating platform 5, and record the total number N of positive and negative peaks N that the probe 3 sends across h for each rotation of rotating platform 5. Figure 5 As shown, Figure 5 In this context, 2Π represents the rotating platform 5 rotating one revolution;

[0038] S04, while the rotating platform 5 continues to rotate, by adjusting the x-axis driving platform 1 and the y-axis driving platform 2, N is made to approach 0, thus completing the centering of the rotating platform 5. When the scale plate 6 is a planar grating, the positive and negative peaks of the laser crossing h are abrupt, so N is the zero-crossing number. When the probe 3 is located outside the rotation center of the rotating platform 5, the scanning trajectory 4 of the laser signal emitted by the probe 3 on the rotating platform 5 is a circle.

[0039] In the embodiment, in step S04, the x-axis driving platform 1 is first adjusted to minimize N; then the y-axis driving platform 2 is adjusted to minimize N, thus completing the centering of the driving rotation platform 5.

[0040] In this embodiment, the surface of the scale sheet 6 is provided with equal-width strip-shaped protrusions and equal-width strip-shaped depressions, with an interval period of P. Although the scale sheet 6 with an uneven surface can also be measured, the equal-width strip-shaped protrusions and equal-width strip-shaped depressions enable the measurement to be quantified.

[0041] In this embodiment, the scale sheet 6 is a grating. The grating has equal-width strip-shaped protrusions and equal-width strip-shaped recesses.

[0042] In this embodiment, the scale sheet 6 is a planar grating. There are various types of gratings, but a planar grating can reflect laser light to the greatest extent.

[0043] In the embodiment, in step S02, let the position of the probe be T, the center position of the rotating platform 5 be T', and the distance from T to T' be r. Then r = Np / 8 (Equation 1). In Equation 1, p is one grating period. The probe rotates around the grating surface once, and four zero-crossing points are generated within one grating period. That is, N / 4 is the number of grating periods swept by the probe. Therefore, the diameter of one rotation of the probe is 2r = p * N / 4, that is, the deviation radius r = Np / 8.

[0044] By decreasing N, r is reduced, thus gradually aligning the center position T' of the rotating platform 5 with T.

[0045] In this embodiment, the scale sheet 6 is a sub-nanometer grating, and the probe 3 is a sub-nanometer probe.

[0046] A planar grating with period p is placed on a turntable. There is no relative motion between the grating and the turntable, and the rotation center T' of the turntable is the rotation center of the grating. The probe 3 is placed at the midpoint between the upper and lower surfaces of the grating. The center coordinate T of the probe 3 at this time is the eccentricity error. The magnitude of the eccentricity error is the length r of TT'. The turntable rotates one revolution at a constant speed. During this revolution, the projection of the curve measured by the probe's rotational scanning onto the grating's xy plane is a circle with radius r.

[0047] When probe 3 passes over the uneven grating surface, the signal collected by the detector fluctuates around the zero value of height h. The height value of the curve measured by rotational scanning changes with the rotation angle. The number of zero-crossings N of the measured curve during one rotation of the grating is calculated by multiplying adjacent points by less than 0, thus calculating the eccentricity error r. When probe 3 is ideally aligned with the turntable center, the probe reading does not change with the turntable rotation angle, and the number of zero-crossings N is 0.

[0048] The eccentricity error r calculated using Equation 1 has eccentric components in both the x and y directions, and the positive and negative directions of these components are unknown. Therefore, the moving platforms in the x and y directions need to be separated and adjusted multiple times to achieve precise alignment between the probe and the turntable. Probe alignment is essentially a process of successively approaching the optimal zero-crossing position.

[0049] The specific centering process of the rotating platform 5 in Example 1 is as follows:

[0050] like Figure 6 As shown, S01, begin. Specifically, the scale sheet 6 is placed approximately in the center of the rotating platform 5.

[0051] S02, adjust the probe 3 so that the scale plate 6 is within the measurement range. Specifically, move the probe 3 approximately to the center of the rotating platform 5 so that the scale plate 6 is within the measurement range of the probe 3. Let the z-axis height h of the scale plate 6 be 0.

[0052] S03, Rotational Scan, Calculate Zero Crossings. Specifically, start the rotating platform 5 and record the total number N of positive and negative peaks N that the signal sent by the probe 3 crosses h during each rotation of the rotating platform 5.

[0053] S04, while the rotating platform 5 continues to rotate, adjust the x-axis drive platform 1 and the y-axis drive platform 2 to make N approach 0, thus completing the centering of the rotating platform 5. Specifically, this is further subdivided into executing steps S04-1 to S04-4 in multiple rounds of step S03.

[0054] S04-1, set the movement amount x1 of x. In the figure, x1 = -x1 is an assignment operation. When moving x towards the moving platform, the number of zero crossings does not decrease, which means that it has moved past the head. The previous step has reached the closest position to the center. Therefore, moving -x1 is to move back to the previous position.

[0055] S04-2, Mobile x-axis mobile platform;

[0056] If the zero-crossing number N has decreased to the minimum, then the adjustment of the x-direction driving platform 1 is completed, and then S04-3 is executed to set the y-direction movement amount y1. In the figure, y1 = -y1 is the assignment operation. When the y-direction moving platform is moved, the zero-crossing number does not decrease, which means that it has moved too far and the previous step has reached the closest position to the center. Therefore, moving -y1 is to move back to the previous position; S04-4, move the y-direction moving platform;

[0057] If the zero-crossing number N reaches its minimum and approaches 0, then the adjustment of the y-direction driving platform 2 is completed, and the centering of the rotating platform 5 is finally completed.

[0058] Example 2: The scale sheet 6 used in Example 2 is a graphene foam board. Alignment was performed according to the following steps:

[0059] S01, place the scale sheet 6 roughly in the center of the rotating platform 5;

[0060] S02, move the probe 3 approximately to the center of the rotating platform 5 so that the scale plate 6 is within the measurement range of the probe 3, and set the z-axis height h of the scale plate 6 to 0;

[0061] S03, start rotating platform 5, and record the total number N of positive and negative peaks N of the signal sent by probe 3 across h for each rotation of rotating platform 5;

[0062] S04, while the rotating platform 5 continues to rotate, adjust the x-axis drive platform 1 and the y-axis drive platform 2 to make N approach 0, thus completing the centering of the rotating platform 5.

[0063] In the embodiment, in step S04, the x-axis driving platform 1 is first adjusted to minimize N; then the y-axis driving platform 2 is adjusted to minimize N, thus completing the centering of the driving rotation platform 5.

[0064] The preferred embodiments of the present invention have been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A centering method for a helical scanning measurement system, comprising a rotating platform (5), an x-axis driving platform (1) and a y-axis driving platform (2) for driving the rotating platform (5), and a probe (3), wherein, The alignment is performed as follows: S01, the scale sheet (6) is placed approximately in the center of the rotating platform (5); the surface of the scale sheet (6) is provided with equal-width strip-shaped protrusions (61) and equal-width strip-shaped depressions (62), with an interval period of P; S02, the probe (3) is moved approximately to the center of the rotating platform (5), so that the scale sheet (6) is within the measurement range of the probe (3), and the height value h of the laser emitted by the probe (3) on the scale sheet (6) in the initial state is set to 0; S03, the rotating platform (5) is started, and the total number N of positive and negative peaks that the rotating platform (5) passes through h in one revolution is recorded; S04, while the rotating platform (5) continues to rotate, the x-axis driving platform (1) and y-axis driving platform (2) are adjusted to make N approach 0, thus completing the alignment of the rotating platform (5).

2. A method of centering a helical scan measurement system according to claim 1, characterized by: In step S04, the x-direction drive platform (1) is first adjusted to minimize N; Then adjust the y-direction drive platform (2) to make N approach 0, thus completing the centering of the drive rotation platform (5).

3. The method of centering a helical scan measurement system of claim 1, wherein: The scale sheet (6) is a grating.

4. A method of centring a helical scan measurement system according to claim 3, characterised in that: The scale sheet (6) is a planar grating.

5. A method of centring a helical scan measurement system according to claim 4, characterised in that: In step S02, let the position of the probe be T, the center position of the rotating platform (5) be T', and the distance from T to T' be r, then r = Np / 8 Equation (I).

6. A method of centring a helical scan measurement system according to claim 5, characterised in that: The scale sheet (6) is a sub-nanometer grating, and the probe (3) is a sub-nanometer probe.

Images