System and method for correcting errors caused by noisy data in deflection measurement method

Abstract

The present invention relates to a system and a method for correcting errors caused by noisy data in a deflection measurement method and, more specifically, to a correction system for reducing errors in a deflection measurement system due to noise in a stepped section of an object to be measured. The system for correcting errors caused by noisy data in a deflection measurement method includes: a pattern generator for generating a pattern and projecting the pattern onto an object to be measured; a detector for acquiring image data of a deformed pattern reflected from the object to be measured; and a correction means for erasing noisy data in a stepped street region and interpolating data of the erased portion.

Description

Error correction system and correction method due to noisy data in bias measurement method

[0001] The present invention relates to an error correction system and a correction method for error correction due to noisy data in a bias measurement method.

[0002] A free-form surface is any surface that has asymmetry about any axis, and the core components of cutting-edge optical devices such as smart glasses and head-mounted displays (HMDs) that have recently appeared are all made of free-form surfaces. These free-form surfaces not only overcome the optical performance limitations of existing optical systems consisting only of spherical or aspherical surfaces, but can also satisfy design elements at the same time, so much research is being conducted worldwide. Deflection measurement is a representative technology that can measure the three-dimensional shape of such free-form surfaces. Unlike existing interferometers, it can measure the three-dimensional shape of a measurement target without a separate reference plane, and is therefore attracting attention as a next-generation free-form surface shape measuring device.

[0003] The basic principle of the deflection measurement method is to measure the change in inclination of each surface by analyzing the phase of the pattern deformed by the shape of the measurement object after incident a striped pattern with a periodic pattern onto the surface of the measurement object. In other words, assuming that the shape of the measurement object is z = z (x, y), the measurement value obtained through the deflection measurement method can obtain the x-direction inclination component (∂z / ∂x) and the y-direction inclination component (∂z / ∂y) depending on the direction of the incident pattern. Therefore, by integrating the two inclination components in the x- and y-directions obtained from the measured phase, the three-dimensional shape of the measurement object can be restored and obtained.

[0004] At this time, to minimize errors caused by external vibrations and environmental changes during the measurement process and accurately measure three-dimensional surface shapes, the ability to measure phase at high speeds is paramount. If external environmental errors affect the measurement object during the measurement process, this can lead to significant errors in the measurement results.

[0005] Additionally, in the measurement method of the bias measurement technique, noisy data is generated in sections with steps.

[0006] Accordingly, the present invention has been devised to solve the above-mentioned conventional problems, and according to an embodiment of the present invention, in order to reduce the occurrence of errors due to noisy data occurring in a section with a step, the relevant section is selected, the data is erased, and the data of the erased section is interpolated to drastically reduce the errors, thereby providing an error correction system and correction method due to noisy data in a bias measurement method.

[0007] Meanwhile, the technical tasks to be achieved in the present invention are not limited to the technical tasks mentioned above, and other technical tasks not mentioned can be clearly understood by a person having ordinary knowledge in the technical field to which the present invention belongs from the description below.

[0008] The first object of the present invention is to provide a correction system for reducing errors due to noise in a section of a measurement object having a step difference in a deflection measurement system, the correction system comprising: a pattern generating unit that generates a pattern and projects it onto the measurement object; a detector that acquires image data of a deformed pattern reflected from the measurement object; and a correction means that erases noisy data in a street area having a step difference and interpolates data of the erased portion; and the correction system can be achieved as an error correction system due to noisy data in a deflection measurement method.

[0009] And the correction means may be characterized by including a noise data selection unit that sets threshold data based on the light quantity data of the image data and selects data below the threshold data as noise data; and a noise removal unit that removes the noise data from the light quantity data.

[0010] It may also be characterized by further including an interpolation unit that interpolates the removed data.

[0011] And after setting the threshold data, the method may further include a slope correction unit that corrects the image slope of the light quantity data; and the noise removal unit may be characterized by removing data below the threshold point from the slope-corrected light quantity data.

[0012] In addition, the present invention may further include an area expansion unit that expands a street area in image data from which noise has been removed through an image processing algorithm.

[0013] And the interpolation unit may be characterized in that it obtains interpolation data by calculating a slope through at least three normal lines of plane data based on three or more points in the peripheral area, and interpolates the street area.

[0014] The second object of the present invention is to provide a correction method for reducing errors due to noise in a section of a measurement object having a step difference in a deflection measurement system, the correction method comprising: a first step in which a pattern generating unit generates a pattern and projects it onto a measurement object, and a detector obtains image data of a deformed pattern reflected from the measurement object; a second step in which a noise data selecting unit sets threshold data based on light quantity data of the image data and selects data below the threshold data as noise data; a third step in which a noise removing unit removes the noise data from the light quantity data; and a fourth step in which an interpolating unit interpolates the removed data.

[0015] And in the second and third steps, the slope correction unit may correct the image slope of the light quantity data after setting the threshold data, and the noise removal unit may remove data below the threshold from the slope-corrected light quantity data.

[0016] In addition, after the third step, the region expansion unit may further include a step of expanding the street region from the noise-removed image data through an image processing algorithm, and the fourth step may be characterized in that the interpolation unit obtains interpolation data by calculating a slope through at least three normal lines of the plane data based on three or more points in the peripheral area, and interpolates the street region.

[0017] According to the error correction system and correction method due to noisy data in the bias measurement method according to an embodiment of the present invention, in order to reduce the occurrence of errors due to noisy data occurring in a section with a step, the relevant portion is selected, the data is erased, and the data of the erased portion is interpolated, thereby having the effect of drastically reducing the error.

[0018] Meanwhile, the effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0019] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0020] Figure 1 is a schematic diagram of a three-dimensional shape measurement system using a phase shift flatness measurement method.

[0021] Figure 2 is a block diagram of an error correction system using noisy data in the bias measurement method of the present invention.

[0022] Figure 3 is a flow chart of an error correction method using noisy data in the bias measurement method of the present invention.

[0023] Figure 4a is image data acquired through a detector according to an embodiment of the present invention.

[0024] Figure 4b shows the light quantity data and critical point data for section A in Figure 4a.

[0025] Figure 4c is the light quantity data with the image tilt corrected in Figure 4b.

[0026] Figure 5a is image data from which noise data has been removed according to an embodiment of the present invention.

[0027] Figure 5b is image data that expands the street area in Figure 5a.

[0028] Figures 6a and 6b show image data and light quantity data before (a) and after (b) correction according to an embodiment of the present invention.

[0029] Figures 7a and 7b are image data before (a) and after (b) correction of a pattern wafer according to an embodiment of the present invention.

[0030] Figures 8a and 8b show image data of a bare wafer before (a) and after (b) correction according to an embodiment of the present invention.

[0031] Below, an error correction system and correction method due to noisy data in a bias measurement method according to an embodiment of the present invention will be described.

[0032] First, Fig. 1 illustrates a schematic diagram of a three-dimensional shape measurement system using a phase shifting flatness measurement method. The pattern generating unit is a screen (10) of a display device, and the generated sinusoidal pattern is projected onto a measurement target (1).

[0033] And the pattern reflected on the measurement target (1) is incident on a detector consisting of a camera (20) to obtain image data having intensity and light quantity information.

[0034] In addition, the analysis means measures and analyzes the phase from the deformed pattern measured by the camera (20) to obtain a 3D shape of the measurement object (1). In addition, the control unit is connected to both the screen (10) and the camera (20) to control them.

[0035] Basically, an image is acquired from a detector (20), a wrapped phase is acquired for each frequency through Fourier transform for this pattern, and an unwrapped phase is acquired from the folded phase to measure and analyze the shape of a measurement object having a free-form surface.

[0036]

[0037] However, in the measurement method of this bias measurement method, noisy data is generated in sections with steps (street areas).

[0038] Since such noisy data causes errors, the embodiment of the present invention is characterized by selecting the relevant portion, erasing the data, and interpolating the data of the erased portion to reduce the errors.

[0039]

[0040] Figure 2 illustrates a block diagram of an error correction system for noisy data in the bias measurement method of the present invention. Figure 3 illustrates a flowchart of an error correction method for noisy data in the bias measurement method of the present invention.

[0041]

[0042] In a bias measurement method according to an embodiment of the present invention, an error correction system due to noise data is a system for compensating for reducing an error due to noise in a section of a measurement object having a step difference in a bias measurement system, and is configured to include a correction means for erasing noisy data in a street area having a step difference and interpolating data in the erased section.

[0043] As shown in Fig. 2, it can be seen that the correction means can be configured to include a noise data selection unit (30), a slope correction unit (40), a noise removal unit (50), an area expansion unit (60), and an interpolation unit (70).

[0044] The noise selection unit (30) sets the threshold data based on the light quantity data of the image data acquired from the detector (20), and selects data below the threshold data as noise data.

[0045]

[0046] Fig. 4a illustrates image data acquired through a detector according to an embodiment of the present invention. As illustrated in Fig. 4a, a measurement target (e.g., a wafer) (1) has a plurality of street areas divided into horizontal and vertical sections, and errors occur due to differences in the steps of these street areas.

[0047] Figure 4b illustrates the light quantity data and critical point data for cross-section A (red line) in Figure 4a. Critical point data (red line in Figure 4a) is set based on the light quantity data for the cross-section of the measurement object (1).

[0048]

[0049] In addition, the tilt correction unit (40) is configured to correct the image tilt of the light quantity data after setting the threshold data. Fig. 4c illustrates the light quantity data with the image tilt corrected in Fig. 4b.

[0050] And the noise removal unit (50) removes data below the critical point from the slope-corrected light quantity data (i.e., only data above the critical point are selected).

[0051]

[0052] And the area expansion unit (60) expands the street area in the removed image data. Fig. 5a illustrates image data from which noise data has been removed according to an embodiment of the present invention. In addition, Fig. 5b illustrates image data from which the street area in Fig. 5a has been expanded.

[0053] In an embodiment of the present invention, the makeup of the street area can be expanded by applying an image processing algorithm.

[0054] And the interpolation unit (70) according to the embodiment of the present invention is configured to interpolate the removed data.

[0055] Specifically, the interpolation unit (70) according to an embodiment of the present invention derives planar data based on three or more peripheral points other than the street area, acquires three such planar data, calculates normals of the three planar data, and derives a slope. Then, based on this slope, interpolation data is derived to interpolate the extended street area.

[0056]

[0057] Figures 6a and 6b illustrate image data and light quantity data before (a) and after (b) correction according to an embodiment of the present invention. It can be seen that noise components occurring at the street and die boundaries are removed. Figures 7a and 7b illustrate image data of a patterned wafer before (a) and after (b) correction according to an embodiment of the present invention. In addition, Figures 8a and 8b illustrate image data of a bare wafer before (a) and after (b) correction according to an embodiment of the present invention.

[0058]

[0059] In addition, the devices and methods described above are not limited to the configurations and methods of the embodiments described above, and the embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

Claims

1. In a bias measurement system, a correction system for reducing errors due to noise in sections where the measurement target has a step difference, A pattern generator that generates a pattern and projects it onto a measurement target; A detector that acquires image data of a deformed pattern reflected from the measurement object; and A system for correcting errors due to noisy data in a bias measurement method, characterized by including a correction means for erasing noisy data in a street area with steps and interpolating data in the erased portion.

2. In paragraph 1, The above correction means is, A noise data selection unit that sets threshold data based on the light quantity data of the above image data and selects data below the threshold data as noise data; and A system for correcting errors due to noisy data in a bias measurement method, characterized in that it includes a noise removal unit that removes the noisy data from the light quantity data.

3. In paragraph 2, An error correction system due to noisy data in a bias measurement method, characterized in that it further includes an interpolation unit that interpolates removed data.

4. In paragraph 3, A system for correcting errors due to noisy data in a bias measurement method, characterized in that it further includes a slope correction unit that corrects the image slope of the light quantity data after setting the threshold data, and the noise removal unit removes data below the threshold from the slope-corrected light quantity data.

5. In paragraph 4, A system for correcting errors due to noisy data in a bias measurement method, characterized in that it further includes an area expansion unit that expands a street area in image data from which noise has been removed through an image processing algorithm.

6. In paragraph 5, A system for correcting errors due to noisy data in a bias measurement method, characterized in that the interpolation unit obtains interpolation data using linear and nonlinear algorithms.

7. In paragraph 6, A system for correcting errors due to noisy data in a bias measurement method, characterized in that the interpolation unit obtains interpolation data by calculating a slope through at least three normal lines of plane data based on three or more points in the peripheral area, and interpolates the street area.

8. In a bias measurement system, a correction method for reducing errors due to noise in a section where the measurement object has a step difference, A first step in which a pattern generator generates a pattern and projects it onto a measurement object, and a detector acquires image data of a deformed pattern reflected from the measurement object; A second step in which a noise data selection unit sets threshold data based on the light quantity data of the image data and selects data below the threshold data as noise data; A third step in which a noise removal unit removes the noisy data from the light quantity data; A method for correcting errors due to noisy data in a bias measurement method, characterized by including a fourth step of interpolating data from which an interpolation part has been removed.

9. In paragraph 8, In the above second and third steps, A method for correcting errors due to noisy data in a bias measurement method, characterized in that the tilt correction unit corrects the image tilt of the light quantity data after setting the threshold data, and the noise removal unit removes data below the threshold from the tilt-corrected light quantity data.

10. In paragraph 9, After step 3, The region expansion unit further includes a step of expanding the street region in the noise-removed image data using an image processing algorithm, The fourth step is a method for correcting errors due to noisy data in a bias measurement method, characterized in that the interpolation unit obtains interpolation data by calculating a slope through at least three normal lines of plane data based on three or more points in the peripheral area, and interpolates the street area.

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