Optical detection system and image dynamic alignment method

Abstract

The present application relates to an optical detection system and a method for dynamic image alignment, wherein the optical detection system mainly includes a translation stage, a light source, a reflector, an adjustment mechanism, a photodetector, and a processing unit. The technical solution utilizes the adjustment mechanism to adjust the posture of the reflector, thereby being able to correct and compensate for the detected image, which helps to solve the problem of relative displacement of image features caused by deformation of the translation stage structure. During the detection and scanning process of the system, the processing unit adjusts the translation or deflection of the reflector based on the offset value of the detected image in the direction perpendicular to the scanning direction, and compensates for the position offset of the image features from the perspective of physical optics, which can achieve accurate alignment of the same image features, thereby eliminating the influence of the displacement stage structure deformation and helping to improve the system's sensitivity to detecting abnormal areas on the surface of the test piece.

Description

Technical Field

[0001] The present application relates to the field of optical detection technology, and in particular to an optical detection system and an image dynamic alignment method. Background Art

[0002] As the chip size in large-scale integrated circuits continues to shrink, the minimum detection size of semiconductor surface inspection that matches the manufacturing process is also shrinking, which has led to an increase in the difficulty of inspection.

[0003] In semiconductor inspection systems such as wafers, a highly sensitive TDI camera is typically used in conjunction with a scanning stage to quickly capture images of the wafer surface. This allows for the detection of surface defects by comparing the grayscale differences between images of different dies (the bare die or wafer itself, which is a very small unit within a silicon wafer, including a fully designed single chip and the adjacent horizontal and vertical scribe groove areas). However, the wafer scanning process is subject to many unstable factors, such as slight bending of the stage structure and structural deformation caused by temperature fluctuations. These factors can cause the wafer being tested to shift relative to the TDI camera's target surface in the vertical scanning direction, leading to relative displacement between the die images used for inspection.

[0004] Obviously, for defect detection methods that use image grayscale difference, when the images used for difference calculation have relative displacement on the wafer structure, it is easy to cause a decrease in defect detection sensitivity, and even lead to serious consequences such as false detection. To correct and compensate for this error and improve the sensitivity of optical detection, the most common method is image post-processing technology, which aligns the two images before performing the difference calculation. However, alignment methods based on image post-processing technology often introduce some errors during the sub-pixel alignment process, resulting in a decrease in the signal-to-noise ratio of defect detection compared to the result without relative displacement, thus failing to achieve the desired effect. Summary of the Invention

[0005] The main technical problem to be solved by this application is how to overcome the problem of relative displacement of image features caused by the structural deformation of the semiconductor translation stage. To solve the above technical problem, this application proposes an optical detection system and an image dynamic alignment method.

[0006] According to the first aspect, an embodiment provides an optical detection system, including: a translation stage for carrying a piece to be tested; a light source for projecting illumination light onto the piece to be tested carried on the translation stage; the illumination light is used to generate a first reflected light after being projected onto the surface of the piece to be tested; a reflector, obliquely arranged on a transmission light path of the first reflected light, for reflecting the first reflected light to generate a second reflected light, and projecting the second reflected light to a preset detection position; an adjustment mechanism for adjusting the posture of the reflector; a photodetector, arranged at the detection position, for detecting the second reflected light along a preset scanning direction and generating a corresponding detection image; and a processing unit.

[0007] The processing unit obtains the detection image from the photodetector; the processing unit obtains the offset value of the detection image relative to a preset standard image in a scanning direction perpendicular to the photodetector; the standard image is a detection image obtained at the initial moment of optical detection, or a detection image obtained at a time point during the optical detection process; the processing unit obtains the posture adjustment amount of the reflector according to the offset value; the processing unit controls the adjustment mechanism according to the posture adjustment amount, and compensates for the image point position of the second reflected light by changing the posture of the reflector, so that the detection image generated by the re-detection is aligned with the standard image.

[0008] The optical detection system further includes a microscope objective lens; the microscope objective lens is arranged on the transmission optical path of the first reflected light and is used to adjust the first reflected light according to a certain optical magnification, and the adjusted first reflected light is transmitted to the reflector.

[0009] The optical detection system also includes an illumination tube lens and a spectroscope; the illumination tube lens is arranged on the transmission light path of the illumination light, and is used to optically adjust the illumination light and emit the adjusted illumination light through its own light outlet; the spectroscope is obliquely arranged on the transmission light path of the first reflected light and is oblique to the light outlet of the illumination tube lens; the spectroscope is used to split a part of the illumination light emitted by the illumination tube lens and reflect it into the microscope objective lens, and the illumination light reflected into the microscope objective lens is projected onto the surface of the test piece after passing through the microscope objective lens; the spectroscope is also used to split a part of the first reflected light adjusted by the microscope objective lens and transmit it to the reflector.

[0010] The optical detection system further includes an imaging tube lens, which is disposed between the beam splitter and the reflector and is used to optically adjust the first reflected light transmitted by the beam splitter and transmit the optically adjusted first reflected light to the reflector.

[0011] The optical detection system further includes a driving component and a supporting component; the driving component is used to drive the translation stage to move, thereby changing the projected position of the surface of the test piece under the illumination light through the movement of the translation stage; the supporting component is provided on the translation stage and is used to fix the test piece to prevent the test piece from falling off during the movement of the translation stage.

[0012] The adjustment mechanism adjusts the posture of the reflector by translating the reflector or deflecting the reflector; the reflector changes the image point position of the second reflected light during the translation adjustment or deflection adjustment process.

[0013] The processing unit calculates the offset value of the detected image relative to a preset standard image in a scanning direction perpendicular to the photodetector, including: selecting a reference feature point from the standard image; obtaining an alignment feature point that belongs to the same image feature as the reference feature point from the detected image; calculating the pixel difference between the alignment feature point and the reference feature point in the scanning direction perpendicular to the photodetector; the scanning direction perpendicular to the photodetector is consistent with the transmission direction of the second reflected light; and obtaining the offset value based on the pixel difference.

[0014] The processing unit converts the offset value to obtain the posture adjustment amount of the reflector, including: converting the offset value according to a preset function curve to obtain a corresponding function value; the function curve is used to represent the linear relationship between the offset value and the posture adjustment amount; determining the posture adjustment amount of the reflector according to the converted function value; the posture adjustment amount is a translation amount or a deflection amount, the translation amount is used to adjust the translation movement distance of the reflector, and the deflection amount is used to adjust the deflection rotation angle of the reflector.

[0015] The processing unit is further configured to: after the detection image generated by the re-detection is aligned with the standard image, the processing unit detects the surface defect features of the workpiece to be tested based on the detection image generated by the re-detection to obtain the position and / or type of the surface defect features of the workpiece to be tested.

[0016] According to the second aspect, an embodiment provides an image dynamic alignment method, including: obtaining a detection image of a workpiece to be tested from a photodetector; transmitting the surface reflected light of the workpiece to be tested to the photodetector after being reflected by a reflector; calculating the offset value of the detection image relative to a preset standard image in a scanning direction perpendicular to the photodetector; obtaining a posture adjustment amount of the reflector according to the offset value; controlling the change of the posture of the reflector according to the posture adjustment amount, and aligning the detection image obtained again from the photodetector with the standard image by compensating for the image point position of the reflected light of the reflector; and using the detection image obtained again from the photodetector to be detected to obtain surface defect characteristics of the workpiece to be tested.

[0017] The beneficial effects of this application are:

[0018] According to the above-mentioned embodiment, an optical detection system and a method for dynamic image alignment are provided, wherein the optical detection system mainly includes a translation stage, a light source, a reflector, an adjustment mechanism, a photodetector, and a processing unit. The technical solution utilizes the adjustment mechanism to adjust the posture of the reflector, thereby being able to correct and compensate for the detected image, which helps to solve the problem of relative displacement of image features caused by deformation of the translation stage structure. During the detection scanning process of the system, the processing unit adjusts the translation or deflection of the reflector based on the offset value of the detected image in the direction perpendicular to the scanning direction, compensating for the position offset of the image features from the perspective of physical optics, achieving accurate alignment of the same image features, thereby eliminating the influence of the displacement stage structure deformation and improving the system's sensitivity to detecting abnormal areas on the surface of the test piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of an optical detection system in one embodiment of the present application;

[0020] Figure 2 This is a structural diagram of an optical detection system in another embodiment of the present application;

[0021] Figure 3 This is a schematic diagram of a method for changing the image point position of the second reflected light by translating a reflective mirror in one embodiment of the present application;

[0022] Figure 4 This is a schematic diagram of a method for changing the image point position of the second reflected light by a deflecting reflector in one embodiment of the present application;

[0023] Figure 5 This is a structural diagram of an optical detection system in another embodiment of the present application;

[0024] Figure 6 This is a flowchart of a method for dynamic image alignment in one embodiment of the present application;

[0025] Figure 7 This is a flowchart of calculating an offset value in one embodiment of the present application;

[0026] Figure 8 This is a flow chart of detecting surface defect features in one embodiment of the present application;

[0027] Figure 9 This is a structural diagram of an optical detection system in another embodiment of the present application. DETAILED DESCRIPTION

[0028] The present application is further described in detail below by means of specific embodiments in conjunction with the accompanying drawings. Similar elements in different embodiments are numbered with associated similar elements. In the following embodiments, many detailed descriptions are provided to enable the present application to be better understood. However, those skilled in the art will readily appreciate that some of the features may be omitted in different circumstances, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid the core portion of the present application being overwhelmed by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0029] In addition, the features, operations, or characteristics described in the specification may be combined in any appropriate manner to form various embodiments. Furthermore, the steps or actions in the method description may be reordered or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various sequences in the specification and drawings are provided solely for the purpose of clearly describing a particular embodiment and are not intended to be mandatory, unless otherwise specified.

[0030] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings).

[0031] In order to overcome the problem of relative displacement of image features caused by the structural deformation of the semiconductor translation stage, the technical solution of the present application corrects and compensates the relative displacement of the part to be tested and the detection target surface of the photodetector perpendicular to the scanning direction during the photoelectric detection process through dynamic adjustment of the optical structure before the image to be tested of the part to be tested is output. The purpose is to avoid the relative displacement of the same features in the detection image, thereby improving the detection sensitivity of the optical detection system to the surface defect features of the part to be tested.

[0032] Example 1

[0033] Please refer to Figure 1 In this embodiment, an optical detection system is disclosed, which mainly includes a translation stage 11, a light source 21, a reflector 31, an adjustment mechanism 32, a photodetector 41 and a processing unit 51, which are described below respectively.

[0034] The translation stage 11 is a supporting platform for the test piece A. The translation stage 11 can drive the test piece A to move in the xyz directions, so that the optical imaging mechanism composed of the light source 21, the reflector 31 and the photodetector 41 can scan the entire surface of the test piece A.

[0035] It should be noted that the test piece A here can be a semiconductor product such as a wafer or a chip. Since there may be defects such as flaws on its surface, it is necessary to perform optical inspection on its surface to control the quality of the product.

[0036] Light source 21 projects illumination light L1 onto the object under test A supported by the translation stage 11. This illumination light is used to generate first reflected light L2 upon impact with the surface of the object under test A. Light source 21 can be any of an LED, xenon lamp, mercury lamp, halogen lamp, laser lamp, laser plasma lamp, or laser-driven white light source. Therefore, illumination light L1 can be white light, colored light, or laser. It should be understood that since illumination light L1 generates reflected and scattered light upon impact with the surface of the object under test A, first reflected light L2 is merely a general term for light, encompassing both reflected and scattered light.

[0037] The reflector 31 is disposed obliquely on the transmission path of the first reflected light L2. The reflector 31 reflects (e.g., plane-reflects) the first reflected light L2 to generate a second reflected light L3, and projects the second reflected light L3 to a predetermined detection position where a photodetector 41 is disposed.

[0038] The adjustment mechanism 32 is connected to the reflector 31 and is used to adjust the position of the reflector 31. The position here may include a translation distance and / or a deflection angle. It will be understood that due to the oblique reflection effect of the reflector 31 on light, after the adjustment mechanism 32 adjusts the position of the reflector 31, the transmission direction of the first reflected light L2 will be changed, causing the position of the image point of the second reflected light L3 at the detection position to change.

[0039] It should be noted that the adjustment mechanism 32 can be a driving component such as a piezoelectric, a servo motor, a DD motor, etc., which can drive the reflector 31 to perform a translational movement. The translation direction can be referred to as Figure 3 In addition, the adjustment mechanism 32 can also drive the reflector 31 to perform a deflection action, and the deflection direction can be referred to Figure 4In order to increase the response speed of the adjustment mechanism 32, it is preferred to use a driving component with a response frequency of more than 20 Hz. In order to ensure the adjustment effect, during each optical detection process, the adjustment mechanism 32 should use one of the translation and deflection methods to adjust the posture of the reflector 31.

[0040] A photodetector 41 is positioned at the detection position. Its function is to detect the second reflected light L3 along a predetermined scanning direction and generate a corresponding detection image. It is understood that the photodetector 41 converts optical signals into electrical signals. The generated detection image is an image of the surface of the test object A illuminated by the illumination light L1. The photodetector 41 can be a line scan camera, preferably a TDI line scan camera.

[0041] The processing unit 51 is connected to the translation stage 11, the adjustment mechanism 32 and the photodetector 41 to realize the functions of image processing, logical operation and adjustment control. Specifically, the function of the processing unit 51 is described as follows.

[0042] (1) The processing unit 51 controls the motion of the translation stage 11 to move the carried test piece A. The photoelectric detector 41 can continuously detect and obtain detection images, and the processing unit 51 obtains detection images frame by frame from the photoelectric detector 41.

[0043] (2) The processing unit 51 calculates the offset value of the detection image relative to the preset standard image in the scanning direction perpendicular to the photodetector 41. The standard image here can be the detection image obtained at the initial moment of optical detection, or the detection image obtained at a certain time point during the optical detection process, or the previous detection image obtained during the optical detection process. If the scanning direction of the photodetector is the z-axis, then the scanning direction perpendicular to the photodetector 41 is the x-axis. Since it is necessary to calculate the offset value of the detection image relative to the standard image, the detection image and the standard image can contain the same image feature, which can be used as a reference point for the offset calculation.

[0044] (3) The processing unit 51 converts the offset value to obtain the attitude adjustment amount of the reflector 31. The attitude adjustment amount can be either the translation amount (such as the translation distance) of the reflector 31 or the deflection amount (such as the deflection angle) of the reflector 31.

[0045] (4) The processing unit 51 controls the adjustment mechanism 32 according to the attitude adjustment amount, and the adjustment mechanism 32 drives the reflector 31 to adjust its attitude according to the attitude adjustment amount. By changing the attitude of the reflector 31, the image point position of the second reflected light L3 is compensated, so that the detection image generated by the re-detection is aligned with the standard image.

[0046] Further, see Figure 1 and Figure 2 The disclosed optical inspection system further includes a microscope objective lens 34. The microscope objective lens 34 is disposed in the optical path of the first reflected light L2 and is configured to adjust the first reflected light L2 according to a predetermined optical magnification. The adjusted first reflected light L2 is then transmitted to the reflector 31. In some cases, the system may include multiple microscope objective lenses 34 with different magnifications or operating wavelengths. By switching between these microscope objective lenses, different optical inspection requirements can be met.

[0047] Further, see Figure 1 and Figure 2 The disclosed optical detection system also includes an illumination tube lens 22 and a spectroscope 23. The illumination tube lens 22 is arranged on the transmission light path of the illumination light L1, and is used to optically adjust the illumination light L1 and emit the adjusted illumination light L1 through its own light outlet. The spectroscope 23 is obliquely arranged on the transmission light path of the first reflected light L1 and is oblique to the light outlet of the illumination tube lens 22. Here, the spectroscope 23 is used to split a portion of the illumination light L1 emitted by the illumination tube lens 22 and reflect it into the microscope objective lens 34. The illumination light L1 reflected into the microscope objective lens 34 is projected onto the surface of the test piece A after passing through the microscope objective lens 34. In addition, the spectroscope 23 is also used to split a portion of the first reflected light L2 adjusted by the microscope objective lens 34 and transmit it to the reflector 31.

[0048] It should be noted that the illumination tube lens 22 can be an optically adjusted form of Köhler illumination or critical illumination, and its function is to form a uniform illumination light field at the focal plane of the objective lens. The beam splitter 23 can use a 50:50 splitting ratio lens, that is, half of the light incident on the beam splitter 23 is reflected and the other half is projected.

[0049] Further, see Figure 1 and Figure 2 The disclosed optical detection system further includes an imaging tube lens 33. The imaging tube lens 33 is disposed between the beam splitter 23 and the reflector 31 and is configured to optically adjust the first reflected light L2 transmitted by the beam splitter 23 and transmit the optically adjusted first reflected light L2 to the reflector 31. It will be appreciated that the optical adjustment methods of the imaging tube lens 33 include focusing adjustment, filtering adjustment, and other methods.

[0050] In this embodiment, the light source 21, the illumination tube lens 22, the beam splitter 23, the microscope objective lens 34, the imaging tube lens 33, the reflector 31, the adjustment mechanism 32, and the photodetector 41 can together constitute an optical imaging mechanism, wherein the illumination light L1 output by the light source 21 is coupled into the illumination tube lens 22, and after being reflected by the beam splitter 23, the illumination light L1 is projected onto the surface of the test piece A through the microscope objective lens 34. The first reflected light L2 formed by surface reflection and scattering of the test piece A is collected by the microscope objective lens 34. The first reflected light L2 passes through the beam splitter 23 and is coupled into the imaging tube lens 33. It is then reflected by the reflector 31, and the generated second reflected light L3 is finally imaged on the photosensitive area of ​​the photodetector 41. The photodetector 41 generates frames of detection images, which are transmitted to the processing unit 51.

[0051] Further, see Figure 1 and Figure 2 The disclosed optical detection system further includes a driving component 12 and a supporting component 13. The driving component 12 is used to drive the translation stage 11 to move, and the projected position of the surface of the workpiece A under the illumination light L1 is changed by the movement of the translation stage 11; the driving component 12 can be a driving component such as a piezoelectric, a servo motor, or a DD motor, which can drive the translation stage 11 to move in the xyz direction, and to achieve control in multiple degrees of freedom, and can even drive the translation stage 11 to rotate. The supporting component 13 is provided on the translation stage 11, and is used to fix the workpiece A to prevent the workpiece A from falling off during the movement of the translation stage 11; the supporting component 13 can be fixed by pressing, adsorption, gluing, or other fixing methods, such as a common CHUCK component.

[0052] It is understood that during the movement of the translation stage 11, the aforementioned optical imaging mechanism should be able to scan the entire surface of the test object A. Taking a conventional 12-inch wafer as an example, the scanning area supported by the translation stage 11 during movement is at least 300mm×300mm.

[0053] It should be noted that factors such as slight bending of the stage 11 itself and structural deformation caused by temperature fluctuations can cause relative displacement of the test object A relative to the target surface of the photodetector 41 in a direction perpendicular to the scanning direction. This can cause relative displacement between the detected images used for optical testing. The aforementioned optical imaging mechanism drives the reflector 31 to perform corresponding translation (or deflection), thereby compensating for the relative displacement of the detected images.

[0054] In this embodiment, the adjustment mechanism 32 can adjust the posture of the reflector 31 by translating or deflecting the reflector 31. Thus, during the translation or deflection adjustment of the reflector 31, the image point position of the second reflected light L3 changes, thereby correcting and compensating for the relative displacement of the detected image. In a preferred embodiment, the direction of the translation adjustment of the reflector 31 remains orthogonal to the preset scanning direction, and the normal direction of the deflection surface formed by the deflection adjustment of the reflector 31 remains consistent with or parallel to the preset scanning direction.

[0055] In a specific embodiment, when the processing unit 51 calculates the offset value of the detection image relative to the preset standard image in the scanning direction perpendicular to the photodetector 41, it specifically includes the following processing process: the processing unit 51 selects a reference feature point from the standard image, and the reference feature point can be an imaging feature position corresponding to a defect area on the surface of the test piece A. The processing unit 51 obtains a registration feature point that belongs to the same image feature as the reference feature point from the detection image, and the registration feature point can be an imaging feature position after the reference feature point has undergone relative displacement. The processing unit 51 calculates the pixel difference between the registration feature point and the reference feature point in the scanning direction perpendicular to the photodetector 41. Here, the scanning direction perpendicular to the photodetector 41 is consistent with the transmission direction of the second reflected light L3. For example, the scanning direction of the photodetector 41 is Figure 1 The z-axis direction in FIG is perpendicular to the scanning direction of the photodetector 41, and the transmission direction of the second reflected light L3, i.e., the x-axis direction, is perpendicular to the scanning direction of the photodetector 41. The processing unit 51 obtains an offset value based on the pixel difference. For example, the offset value can be expressed as the number of offset pixels or the offset pixel distance, or even in pixels.

[0056] In one specific embodiment, when the processing unit 51 converts the offset value to obtain the attitude adjustment amount of the reflector 31, the processing specifically includes the following process: the processing unit 51 converts the offset value according to a preset function curve to obtain a corresponding function value; the function curve is used to represent the linear relationship between the offset value and the attitude adjustment amount, that is, one offset value corresponds to only one attitude adjustment amount. The processing unit 51 determines the attitude adjustment amount of the reflector 31 based on the converted function value; the attitude adjustment amount of the reflector 31 is a translation amount or a deflection amount, wherein the translation amount is used to adjust the translational movement distance of the reflector 31, and the deflection amount is used to adjust the deflection rotation angle of the reflector 31.

[0057] In one specific embodiment, the processing unit 51 is further configured to perform the following processing: after aligning the re-detected image with the standard image, the processing unit 51 eliminates imaging jitter in the detected image. This facilitates optical inspection of the surface of the test piece A based on the detected image. The processing unit can then detect surface defect features of the test piece A based on the re-detected image, thereby obtaining the location and / or type of the surface defect features of the test piece A. It will be understood that since methods for detecting image defect features (i.e., defect features) are already commonly used in optical inspection systems, it is considered that the detection methods of the prior art are employed herein.

[0058] for example Figure 2 and Figure 3 , there is a defective area on the test piece A and it is represented by a. The first reflected light L2 corresponding to point a reaches the detection area of ​​the photodetector 41 after passing through the microscope objective lens 34, the imaging tube lens 33, and the reflector 31, forming the image point position of the second reflected light on the detection area and represented by a′. The detection image obtained at this time can be regarded as a standard image. Due to the structural deformation of the displacement stage 11, point a on the test piece A will be displaced. For example, if it is displaced to point b, it will cause the original image point position a′ to be displaced to b′. The detection image obtained at this time can be regarded as the detection image to be processed. Since the relative displacement of the detection image occurs, it will cause imaging jitter, which will not be conducive to the surface optical detection of the test piece A based on the detection image, so the image point position b′ needs to be displaced and adjusted. The processing unit 51 obtains the standard image containing a′ and the detection image containing b′ from the photodetector 41, takes point a′ as the pixel reference point, calculates the offset value (such as the offset pixel value) of the detection image relative to the standard image in the scanning direction perpendicular to the photodetector 41, and converts the translation amount (such as the translation distance) of the reflector 31 according to the offset value; then, the processing unit 51 controls the adjustment mechanism 32 to adjust the reflector 31. Figure 3 By translation adjustment, the reflector 31 is translated to another position, such as the position shown by the reflector 31′; since the reflection position of the first reflected light L2 by the reflector 31′ has changed, the image point position of the second reflected light L3 will be displaced from point b′ to point a′, thereby satisfying the requirement that point b′ and point a′ coincide. In this way, the detected image is relatively displaced to the position of the standard image, so that the detected image is aligned with the standard image.

[0059] for example Figure 2 and Figure 4, there is a defective area on the test piece A and it is represented by a. The first reflected light L2 corresponding to point a reaches the detection area of ​​the photodetector 41 after passing through the microscope objective lens 34, the imaging tube lens 33, and the reflector 31, forming the image point position of the second reflected light on the detection area and represented by a′. The detection image obtained at this time can be regarded as a standard image. Due to the structural deformation of the displacement stage 11, point a on the test piece A will be displaced. For example, if it is displaced to point b, it will cause the original image point position a′ to be displaced to b′. The detection image obtained at this time can be regarded as the detection image to be processed. Since the relative displacement of the detection image occurs, it will cause imaging jitter, which will not be conducive to the surface optical detection of the test piece A based on the detection image, so the image point position b′ needs to be displaced and adjusted. The processing unit 51 obtains the standard image containing a′ and the detection image containing b′ from the photodetector 41, takes point a′ as the pixel reference point, calculates the offset value (such as the offset pixel value) of the detection image relative to the standard image in the scanning direction perpendicular to the photodetector 41, and converts the deflection amount (such as the deflection angle) of the reflector 31 according to the offset value; then, the processing unit 51 controls the adjustment mechanism 32 to adjust the reflector 31. Figure 4 The deflection adjustment is performed to deflect the reflector 31 to another angle, such as the angle shown by the reflector 31′; since the reflection angle of the reflector 31′ to the first reflected light L2 has changed, the image point position of the second reflected light L3 will be displaced from point b′ to point a′, thereby satisfying the requirement that point b′ and point a′ coincide. In this way, the detected image is relatively displaced to the position of the standard image, so that the detected image is aligned with the standard image.

[0060] It should be noted that, in the process of optical inspection of the workpiece using the optical inspection system, the processing unit 51 adjusts the translation or deflection of the reflector according to the offset value of the detection image in the direction perpendicular to the scanning direction, and corrects and compensates for the relative displacement of the image features from the perspective of physical optics, thereby achieving accurate alignment of the same image features, thereby eliminating the influence of the structural deformation of the translation stage 11, and helping to improve the system's sensitivity to detecting abnormalities on the surface of the workpiece.

[0061] In one embodiment, Figure 6 Another optical detection system is disclosed, wherein the optical imaging mechanism can be Figure 2 The light source 21, the lighting tube lens 22, the spectroscope 23, the microscope objective lens 34, the imaging tube lens 33, the reflector 31, the adjustment mechanism 32, and the photodetector 41 are composed of the light source 21, the lighting tube lens 22, the spectroscope 23, the microscope objective lens 34, the imaging tube lens 33, the reflector 31, the adjustment mechanism 32, and the photodetector 41, wherein the acquisition calculation unit and the control unit can be combined as Figure 2 The processing unit 51 in the embodiment of the present invention may include a displacement stage. Figure 2 The translation stage 11, wherein CHUCK can be Figure 2 The bearing member 13 in the Figure 6In the embodiment, the optical imaging mechanism 2 sends the detection image obtained by optical detection to the acquisition and calculation unit 511. The acquisition and calculation unit 511 processes the detection image and sends a control command to the control unit 512. The control unit 512 controls the posture of the reflector in the optical imaging mechanism 2 and the movement of the translation stage 11 in response to the control command. Figure 2 and Figure 6 The working principle of the optical imaging mechanism 2 is as follows: the illumination light L1 output by the light source 21 is coupled into the illumination tube lens 22, and after being reflected by the beam splitter 23, the illumination light L1 is projected onto the surface of the test piece A through the microscope objective 34. The first reflected light L2 formed by the surface reflection and scattering of the test piece A is collected by the microscope objective 34. The first reflected light L2 passes through the beam splitter 23 and is coupled into the imaging tube lens 33. It is then reflected by the reflector 31, and the generated second reflected light L3 is finally imaged on the photosensitive area of ​​the photodetector 41. The photodetector 41 generates detection images frame by frame, and the detection images are transmitted to the acquisition and calculation unit 511. For details, see Figure 2 and Figure 6 The acquisition and calculation unit 511 implements part of the functions of the processing unit 51, such as calculating the offset value of the detected image relative to the preset standard image in the scanning direction perpendicular to the photodetector 41; then converting the offset value to obtain the attitude adjustment value of the reflector 31 (such as the translation distance or deflection angle), and sending some control signals to the control unit 512 based on the attitude adjustment value. Figure 2 and Figure 6 The control unit 512 implements another part of the functions of the processing unit 51. For example, the control unit 512 can control the adjustment mechanism 32 in response to a control signal sent by the acquisition and calculation unit 511, and the adjustment mechanism 32 drives the reflector 31 to adjust its posture according to the posture adjustment amount. By changing the posture of the reflector 31, the image point position of the second reflected light L3 is compensated, so that the detection image generated by the re-detection is aligned with the standard image; moreover, the control unit 512 can also automatically control the movement of the translation stage after the optical detection starts, so that the CHUCK on the translation stage drives the carried test piece to move, so that the photoelectric detector can continuously detect and obtain the detection image.

[0062] Example 2

[0063] Based on the optical detection system disclosed in the first embodiment, this embodiment discloses a method for dynamic image alignment. Figure 1 and Figure 2 The processing unit 51 is applied thereto.

[0064] Please refer to Figure 6 The image dynamic alignment method in this embodiment mainly includes steps 610-640, which are described below respectively.

[0065] Step 610: Obtain a detection image of the object under test from a photoelectric detector. Here, the surface reflected light of the object under test is reflected by a reflector and then transmitted to the photoelectric detector.

[0066] Step 620 : Calculate the offset value of the detected image relative to the preset standard image in the scanning direction perpendicular to the photodetector.

[0067] Step 630: Obtain the attitude adjustment amount of the reflector according to the offset value.

[0068] In step 640, the reflector's posture is controlled and changed according to the posture adjustment amount. By compensating the image point position of the reflected light from the reflector, the detected image obtained from the photodetector is aligned with the standard image. The detected image obtained from the photodetector is used to detect surface defect characteristics of the test piece.

[0069] Here we will Figure 1 and Figure 2 Taking the optical detection system disclosed in as an example, Figure 6 The image dynamic alignment method in the embodiment of the present invention is introduced. The processing unit 51 controls the motion of the translation stage 11, and in the process of driving the carried test piece A to move, the photodetector 41 can continuously detect and obtain detection images, and the processing unit 51 obtains frames of detection images from the photodetector 41. Specifically, the illumination light L1 output by the light source 21 is coupled into the illumination tube lens 22. After being reflected by the beam splitter 23, the illumination light L1 is projected onto the surface of the test piece A through the microscope objective 34. The first reflected light L2 (i.e., the surface reflected light of the test piece A) formed by the surface reflection and scattering of the test piece A is collected by the microscope objective 34. The first reflected light L2 passes through the beam splitter 23 and is coupled into the imaging tube lens 33. It is then reflected by the reflector 31, and the generated second reflected light L3 (i.e., the reflected light of the reflector 31) is finally imaged on the photosensitive area of ​​the photodetector 41. The photodetector 41 generates frames of detection images, which are transmitted to the processing unit 51. The processing unit 51 calculates the offset value of the detected image relative to the preset standard image in the scanning direction perpendicular to the photodetector 41. The processing unit 51 converts the offset value to obtain the posture adjustment amount of the reflector 31. The posture adjustment amount can be either the translation amount of the reflector 31 (such as the translation distance) or the deflection amount of the reflector 31 (such as the deflection angle). The processing unit 51 controls the adjustment mechanism 32 based on the posture adjustment amount. The adjustment mechanism 32 drives the reflector 31 to adjust its posture according to the posture adjustment amount. By changing the posture of the reflector 31, the image point position of the second reflected light L3 is compensated, so that the detected image generated by the re-detection is aligned with the standard image.

[0070] In this embodiment, the above step 620 mainly involves the process of calculating the offset value, so please refer to Figure 7 , the step 620 may specifically include steps 621-624, which are described as follows.

[0071] Step 621: Select a reference feature point from the standard image. The reference feature point can be an imaging feature position corresponding to a defect area on the surface of the test piece, such as Figure 3 or Figure 4 Point a′ in .

[0072] Step 622: Obtain a corresponding feature point from the detection image that has the same image feature as the reference feature point. The corresponding feature point can be the imaging feature position of the reference feature point after relative displacement, such as Figure 3 Or b′ in the figure.

[0073] Step 623, calculate the pixel difference between the alignment feature point and the reference feature point in the scanning direction perpendicular to the photodetector, for example Figure 3 or Figure 4 The pixel difference between point b' and point a' in the scanning direction perpendicular to the photodetector. Here, the scanning direction perpendicular to the photodetector is consistent with the transmission direction of the second reflected light; for example, the scanning direction of the photodetector 41 is Figure 1 The z-axis direction in FIG, then the scanning direction perpendicular to the photodetector 41 is the transmission direction of the second reflected light L3, that is, the x-axis direction.

[0074] In step 624, an offset value is obtained based on the pixel difference. For example, the offset value can be expressed as the number of pixels offset or the distance of pixels offset, or even in pixel units.

[0075] In this embodiment, the above step 630 mainly involves the process of determining the posture adjustment amount of the reflector, which may specifically include: converting the offset value according to a preset function curve to obtain a corresponding function value, and the function curve is used to represent the linear relationship between the offset value and the posture adjustment amount; determining the posture adjustment amount of the reflector according to the converted function value, and the posture adjustment amount is a translation amount or a deflection amount, wherein the translation amount is used to adjust the translation movement distance of the reflector, and the deflection amount is used to adjust the deflection rotation angle of the reflector.

[0076] In this embodiment, the detection image can be aligned with the standard image according to the above steps 610-640. Then, after the detection image is aligned with the standard image, the surface defect feature detection process of the test piece is also included. For details, please refer to Figure 8 .exist Figure 8 Steps 710-730 are disclosed in the following and are described below.

[0077] Step 710: Acquire a detection image aligned with the standard image.

[0078] Step 720: Detect surface defect features of the workpiece based on the acquired detection image. Since the detection method of image defect features (ie, defect features) has been widely used in optical inspection systems, it is considered that the detection method of the prior art is used here.

[0079] Step 730 : After detecting the surface defect features of the test piece, obtain the position and / or type of the surface defect features of the test piece.

[0080] Example 3:

[0081] Based on the image dynamic alignment method disclosed in the second embodiment, this embodiment discloses an optical detection device, which includes a memory 81 and a processor 82. Figure 9 .

[0082] In this embodiment, the memory 81 and the processor 82 are the main components of the optical detection device 8. Of course, the optical detection device may also include some detection components and execution components connected to the processor 82. For details, please refer to the above embodiment 1, as well as Figure 1 and Figure 2 The system structure in will not be described in detail here.

[0083] The memory 81 can be used as a computer-readable storage medium, and is used to store a program. The program can be the program code corresponding to the image dynamic alignment method in the second embodiment, such as Figure 6 The program codes corresponding to steps 610-640 are shown in FIG.

[0084] The processor 82 is connected to the memory 81 and is used to execute the program stored in the memory 81 to implement the image dynamic alignment method disclosed in the above embodiment 2. It should be noted that the functions implemented by the processor 82 can refer to the processing unit 51 in embodiment 1 and will not be described in detail here.

[0085] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer program. When all or part of the functions in the above embodiments are implemented by computer program, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above functions can be implemented. In addition, when all or part of the functions in the above embodiments are implemented by computer program, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and saved in the memory of the local device by downloading or copying, or the system of the local device is updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be implemented.

[0086] The above specific examples are used to illustrate the present application, which is only used to help understand the technical solution of the present application and is not intended to limit the present application. For those skilled in the art, based on the ideas of the present application, several simple deductions, modifications or substitutions can be made.

Claims

1. An optical detection system, characterized in that: include: A translation stage, used to carry the object to be tested; a light source, configured to project illumination light onto the piece to be tested carried on the translation stage, wherein the illumination light is configured to generate first reflected light after being projected onto a surface of the piece to be tested; a reflector, obliquely disposed on a transmission optical path of the first reflected light, for reflecting the first reflected light to generate a second reflected light, and projecting the second reflected light to a preset detection position; an adjustment mechanism for adjusting the posture of the reflector by translating the reflector or deflecting the reflector; the reflector changes the image point position of the second reflected light during the translation adjustment or deflection adjustment, wherein the direction of the translation adjustment remains orthogonal to the preset scanning direction, and the normal direction of the deflection surface formed by the deflection adjustment remains consistent with or parallel to the preset scanning direction; a photoelectric detector, disposed at the detection position, for detecting the second reflected light along a preset scanning direction and generating a corresponding detection image; A processing unit for: obtaining the detection image from the photodetector; Calculating an offset value of the detection image relative to a preset standard image in a scanning direction perpendicular to the photodetector; the standard image is a detection image obtained at the initial moment of optical detection, or a detection image obtained at a time point during the optical detection process; Obtaining a posture adjustment amount of the reflector according to the offset value; The adjustment mechanism is controlled according to the attitude adjustment amount, and the image point position of the second reflected light is compensated by changing the attitude of the reflector, so that the detection image generated by the re-detection is aligned with the standard image.

2. The optical detection system according to claim 1, wherein: Also included are microscope objectives; The microscope objective is arranged on the transmission optical path of the first reflected light, and is used to adjust the first reflected light according to a preset optical magnification, and the adjusted first reflected light is transmitted to the reflector.

3. The optical detection system according to claim 2, wherein: Also included are an illumination tube lens and a beam splitter; The lighting tube lens is arranged on the transmission optical path of the lighting light, and is used to optically adjust the lighting light and emit the adjusted lighting light through its own light outlet; The beam splitter is arranged obliquely on the transmission optical path of the first reflected light and obliquely opposite to the light outlet of the illumination tube lens; the beam splitter is used to split a part of the illumination light emitted by the illumination tube lens and reflect it into the microscope objective lens, and the illumination light reflected into the microscope objective lens is projected onto the surface of the test piece after passing through the microscope objective lens; the beam splitter is also used to split a part of the first reflected light adjusted by the microscope objective lens and transmit it to the reflector.

4. The optical detection system according to claim 3, wherein: Also included are imaging tube lenses; The imaging tube lens is arranged between the beam splitter and the reflector, and is used for optically adjusting the first reflected light transmitted by the beam splitter, and transmitting the optically adjusted first reflected light to the reflector.

5. The optical detection system according to claim 1, wherein: Also includes a driving component and a bearing component; The driving component is used to drive the translation stage to move, and the projected position of the surface of the test piece under the illumination light is changed through the movement of the translation stage; The carrying component is disposed on the translation stage and is used to fix the piece to be tested to prevent the piece to be tested from falling off during the movement of the translation stage.

6. The optical detection system according to any one of claims 1 to 5, characterized in that: The processing unit is configured to calculate an offset value of the detection image relative to a preset standard image in a scanning direction perpendicular to the photoelectric detector, including: Selecting reference feature points from the standard image; Acquire, from the detection image, an alignment feature point that belongs to the same image feature as the reference feature point; Calculating a pixel difference between the alignment feature point and the reference feature point in a scanning direction perpendicular to the photodetector, wherein the scanning direction perpendicular to the photodetector is consistent with a transmission direction of the second reflected light; The offset value is obtained according to the pixel difference.

7. The optical detection system according to any one of claims 1 to 5, characterized in that: The processing unit is used to convert the attitude adjustment amount of the reflector according to the offset value, including: Converting the offset value according to a preset function curve to obtain a corresponding function value, wherein the function curve is used to represent a linear relationship between the offset value and the posture adjustment amount; The attitude adjustment amount of the reflector is determined according to the converted function value. The attitude adjustment amount is a translation amount or a deflection amount. The translation amount is used to adjust the translation movement distance of the reflector, and the deflection amount is used to adjust the deflection rotation angle of the reflector.

8. The optical detection system according to any one of claims 1 to 5, characterized in that: The processing unit is further configured to: After the detection image generated by the re-detection is aligned with the standard image, the processing unit detects the surface defect features of the test piece according to the detection image generated by the re-detection to obtain the position and / or type of the surface defect features of the test piece.

9. A dynamic image alignment method, applied to the optical detection system according to any one of claims 1 to 8, characterized in that: include: Obtaining a detection image of the test piece from a photodetector; The surface reflected light of the test piece is reflected by the reflector and then transmitted to the photodetector; Calculating an offset value of the detected image relative to a preset standard image in a scanning direction perpendicular to the photodetector; Obtaining a posture adjustment amount of the reflector according to the offset value; The posture of the reflector is changed according to the posture adjustment amount, and the image point position of the reflected light of the reflector is compensated so that the detection image obtained again from the photodetector is aligned with the standard image; the detection image obtained again from the photodetector is used to detect the surface defect characteristics of the workpiece to be tested.

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