CN101413788B - Surface topography measuring method and device thereof - Google Patents

Abstract

A surface topography measuring device is used to measure the surface topography of an object to be measured, comprising: a laser unit, which emits laser to the surface of the object to be measured to form a laser positioning point; a measuring unit, which measures the surface of the object to be measured according to the laser positioning point; and a moving platform, which clamps one of the laser unit and the measuring unit to move in at least one dimension; wherein the relative position between the object to be measured and the laser unit does not change.

Description

Surface Topography Measuring Method and Device

technical field

The invention relates to a method and device for measuring surface topography, in particular to a method and a device for superimposing multiple surface topography images of objects by using laser light to assist positioning.

Background technique

In the measurement of tiny structures, optical interference technology is widely used because of its advantages of fast, high precision, and non-destructive detection. If the angle is too large, it cannot be detected correctly by the sensing device, and the phenomenon of insufficient measurement information occurs.

The known processing method is to displace and swing the object to be measured or the measuring instrument to a specific angle for measurement to obtain multiple measurement images; then calculate the spatial relationship of each measurement image based on the displacement and the swing angle ; Then according to the correlation with each other, the final result is superimposed.

US Patent No. 5,940,181 uses the above-mentioned method to measure an aspheric object to be measured. The requirement for using this alignment method is: the measuring instrument must be able to accurately provide various environmental variables such as displacement and swing angle, otherwise, a small error will cause the images to be superimposed due to the difference in space coordinates. The conversion caused a large offset.

To increase the accuracy of image superposition, the main processing methods are divided into two aspects: hardware and software: on the hardware, the mechanism is set up with precise components, so that the error of the instrument during measurement can be within a specific range; on the software, Algorithms are used to correct the alignment error. Among them, the Iterative Closest Point (ICP) proposed by Besl. et al. is a universal calculation method suitable for three-dimensional space alignment.

However, the above two processing methods still have their own problems to face: in terms of hardware, a more sophisticated mechanism means that the cost and complexity of the instrument will increase; in terms of software, as analyzed by Rusinkiewicz. Powerful algorithms still have their limits. For example, the shape without obvious features will cause the instability of its operation, and this phenomenon without obvious features generally exists in the measurement of tiny structures.

Contents of the invention

The object of the present invention is to provide a surface topography measurement method and its device, which uses laser positioning points to correct the offset of the measurement image, so more errors in the mechanism can be tolerated and the complexity of the algorithm can be greatly reduced , in order to achieve the purpose of image superposition of the surface topography of the object.

In order to achieve the above object, the surface topography measuring device provided by the present invention is used to measure the surface topography of an object to be measured, comprising:

A laser unit, which emits laser light to the surface of the object to be measured to form a laser positioning point;

a measuring unit, which measures the surface of the object to be measured according to the laser positioning point; and

a mobile platform, which clamps the laser unit and one of the measurement unit to move at least one dimension;

Wherein, the relative position between the object under test and the laser unit does not change.

In the surface topography measuring device, the laser unit further includes a lens through which the laser light passes.

In the surface topography measuring device, the mobile platform moves in four dimensions.

In the surface topography measuring device, the four-dimensional movement includes movement in the three-dimensional directions of X, Y, and Z and rotation along the XZ plane.

In the surface topography measuring device, the mobile platform clamps the laser unit and the object to be measured.

In the surface topography measuring device, the moving platform clamps the measuring unit.

In the surface topography measuring device, the measuring unit is a measuring lens.

The surface topography measurement method provided by the present invention is used to measure the surface topography of an object to be measured, comprising:

(1) Provide a laser unit, a measurement unit and a mobile platform, wherein the laser unit emits laser light to the surface of the object to be measured to form a laser positioning point, and the measurement unit measures the surface of the object to be measured according to the laser positioning point For measurement, the mobile platform clamps the laser unit and one of the measurement units to move in the X, Y, Z three-dimensional directions and rotate along the XZ plane, and the relative position between the object to be measured and the laser unit do not change;

(2) Adjust the mobile platform so that the measurement unit focuses on the object to be measured;

(3) Rotate the mobile platform by a specific angle along the Y axis;

(4) Adjusting the Z direction of the mobile platform so that the measuring unit precisely focuses on the object to be measured to obtain a first image;

(5) Repeat steps (3) to (4) to obtain a second image; and

(6) Taking the laser positioning point as a reference point, superimposing the first image and the second image to obtain the surface topography of the object to be tested.

The method for measuring surface topography, wherein the step (2) also includes the following steps:

(2-1) Adjust the X direction and the Y direction of the mobile platform so that the measuring unit is aligned with the intersection of the X axis and the Y axis of the mobile platform; and

(2-2) Adjusting the Z direction of the mobile platform so that the measuring unit initially focuses on the object to be measured.

The method for measuring surface topography, wherein step (6) includes:

(6-1) For each image, take any point as the rotation center, and reverse the Y-axis rotation amount during measurement;

(6-2) Retrieve the laser positioning point with a higher threshold;

(6-3) Perform offset correction in the X and Y directions according to the relative position of the laser positioning point in the image;

(6-4) According to the height value of the topography on the laser positioning point, the offset correction of the relative height in the Z direction is performed; and

(6-5) Superimposing the corrected images.

In the surface topography measuring method, the laser unit further includes a lens through which the laser light passes.

In the surface topography measurement method, the mobile platform clamps the laser unit and the object to be measured.

The method for measuring surface topography, wherein the mobile platform clamps the measuring unit.

In the surface topography measurement method, the measurement unit is a measurement lens.

The benefits that the present invention can produce are:

1) Since the present invention superimposes multiple images to obtain the overall measurement result of the object under test, the magnification ratio of the lens can be increased, so the fineness can be increased.

2) The displacement and swing of the mobile platform can avoid the physical limitation that the measurement unit cannot receive the reflected light when the inclination of the object to be measured is too large;

3) The calculation of the counterpoint is relatively easy, and there will be no situation where the solution cannot be found.

Description of drawings

Fig. 1 is a schematic diagram of the system of the surface topography measuring device of the present invention;

Fig. 2 is a schematic diagram of the system after the surface topography measuring device of the present invention is rotated by an angle;

Fig. 3 is a flowchart of the surface topography measurement method of the present invention; and

FIG. 4 is a flow chart of image superposition of the surface topography measurement method of the present invention.

Explanation of main signs and symbols in the attached drawings:

10-laser unit

12-Measuring unit

14-Mobile Platform

16-Analyte

100-lens

102-Laser positioning point

Detailed ways

In order to have a further understanding and recognition of the structure, purpose and effect of the present invention, the detailed description is as follows in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of the system of the surface topography measuring device of the present invention. The surface topography measurement device of the present invention comprises: a laser unit 10, a measurement unit 12 and a mobile platform 14, the laser unit 10 emits laser light and reaches the surface of a test object 16 through the lens 100, and A laser positioning point 102 is formed on the surface of the object to be measured 16; the measurement unit 12 measures the surface profile of the object to be measured 16 according to the laser positioning point 102; the mobile platform 14 holds the laser unit 10 or the measurement unit One of 12 performs four-dimensional movement, and the four-dimensional here refers to movement in the X-axis direction, the Y-axis direction, and the Z-axis direction, and rotation along the XZ plane.

In FIG. 1 , the relative position between the object under test 16 and the laser unit 100 does not change, that is, the object under test 16 and the laser unit 100 remain fixed or act together, so that the laser positioning point 102 is on the object under test 16 The position on the mobile platform 14 will not change due to the adjustment of the mobile platform 14, as shown in Figure 2 (this figure is the schematic diagram after the mobile platform 14 is rotated by an angle α); therefore, multiple measured images can be positioned according to the laser The coordinates of the points 14 in the image are used to determine the relative relationship between each other so that the images can be accurately superimposed.

Please refer to FIG. 3 again, which is a flow chart of the surface topography measuring method of the present invention. The surface topography measurement method of the present invention utilizes the device shown in Figure 1 to achieve the purpose of measurement, wherein:

Step 31 - adjusting the X direction and the Y direction of the mobile platform, so that the measuring unit is aligned with the intersection of the X axis and the Y axis of the mobile platform;

Step 32 - adjusting the Z direction of the mobile platform so that the measuring unit initially focuses on the object to be measured;

Step 33 - rotating the mobile platform by a specific angle along the Y axis;

Step 34—adjusting the Z direction of the mobile platform so that the measuring unit can precisely focus on the object under test to obtain a first image;

Step 35 - repeat steps 33 to 34 to obtain a second image; and

Step 36 - taking the laser positioning point as a reference point, stitching the first image and the second image to obtain the surface topography of the object to be tested.

In order to make the superposition process of the above-mentioned step 36 clearer, the detailed process of the step 36 is shown in Figure 4, wherein:

Step 41 - For each image, take any point as the rotation center, and reverse the Y-axis rotation during measurement;

Step 42—acquiring laser positioning points with a higher threshold;

Step 43 - performing offset correction in the X direction and the Y direction according to the relative position of the laser positioning point in the image;

Step 44—according to the height value of the topography on the laser positioning point, perform offset correction of the relative height in the Z direction; and

Step 45 - superimposing the corrected images.

It can be seen that the image superposition step in Figure 4 is to use the laser positioning points in the image to correct the deflection and offset of the mobile platform back to the environmental parameters of the original measurement, so that the displacement deviation caused by the unknown rotation radius can be repositioned , so that the precise superposition of images can be achieved, and the complexity of the algorithm can be reduced.

In the surface topography measurement method of the present invention, the rotation of the mobile platform generally does not exceed 10°; and the measurement unit is generally a measurement lens. The mobile platform can be designed to hold the laser unit and move in four dimensions together with the object to be measured (as shown in Figure 1 and Figure 2), or only hold the measurement unit to move in four dimensions (another embodiment, not shown Shown), the change on this mechanism is to change according to the actual needs of users.

The above description is only the best implementation mode of the present invention, and should not limit the implementation scope of the present invention. That is, all equivalent changes and modifications made according to the claims of the present invention should still fall within the scope covered by the claims of the present invention.

Claims (14)

1. A surface topography measuring device for measuring the surface topography of an object to be measured, comprising: a laser unit that emits laser light to the surface of the object to be measured to form a laser positioning point; a measuring A unit for measuring the surface of the object to be measured according to the laser positioning point; and a mobile platform, which clamps the laser unit and one of the measurement unit for at least one-dimensional movement; Wherein, the relative position between the object under test and the laser unit does not change. 2. The surface topography measuring device as claimed in claim 1, wherein the laser unit comprises a lens through which the laser light passes. 3. The surface topography measuring device as claimed in claim 1, wherein the mobile platform moves in four dimensions. 4 . The surface topography measuring device according to claim 3 , wherein the four-dimensional movement includes movement in X, Y, and Z three-dimensional directions and rotation along the XZ plane. 5 . The surface topography measuring device according to claim 1 , wherein the mobile platform clamps the laser unit and the object to be measured. 6. The surface topography measuring device according to claim 1, wherein the mobile platform holds the measuring unit. 7. The surface topography measuring device according to claim 1, wherein the measuring unit is a measuring lens. 8. A surface topography measurement method for measuring the surface topography of an object to be measured, comprising: (1) Provide a laser unit, a measuring unit, and a mobile platform, wherein the laser unit emits laser light to the surface of the object to be measured to form a laser positioning point, and the measuring unit measures the surface of the object to be measured according to the laser positioning point. The measurement of the mobile platform clamps the laser unit and one of the measurement units to move in the X, Y, Z three-dimensional directions and rotate along the XZ plane, and the relative position of the object to be measured and the laser unit do not change; (2) Adjust the mobile platform so that the measurement unit focuses on the object to be measured; (3) Rotate the mobile platform by a specific angle along the Y axis; (4) Adjusting the Z direction of the mobile platform so that the measuring unit precisely focuses on the object to be measured to obtain a first image; (5) Repeat steps (3) to (4) to obtain a second image; and (6) Taking the laser positioning point as a reference point, superimposing the first image and the second image to obtain the surface topography of the object to be measured. 9. The surface topography measuring method as claimed in claim 8, wherein, the step (2) includes the following steps: (2-1) Adjust the X direction and the Y direction of the mobile platform so that the measuring unit is aligned with the intersection of the X axis and the Y axis of the mobile platform; and (2-2) Adjusting the Z direction of the mobile platform so that the measuring unit initially focuses on the object to be measured. 10. The surface topography measuring method as claimed in claim 8, wherein, step (6) comprises: (6-1) For each image, take any point as the rotation center, and reverse the Y-axis rotation amount during measurement; (6-2) Retrieve the laser positioning point with a higher threshold; (6-3) Perform offset correction in the X and Y directions according to the relative position of the laser positioning point in the image; (6-4) According to the height value of the topography on the laser positioning point, the offset correction of the relative height in the Z direction is performed; and (6-5) Superimposing the corrected images. 11. The surface topography measuring method as claimed in claim 8, wherein the laser unit comprises a lens through which the laser light passes. 12. The surface topography measuring method as claimed in claim 8, wherein the mobile platform clamps the laser unit and the object to be measured. 13. The surface topography measurement method according to claim 8, wherein the mobile platform clamps the measurement unit. 14. The surface topography measuring method according to claim 8, wherein the measuring unit is a measuring lens.

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