Method for detecting a surface attitude to be measured and optical detection device using this detection method

Abstract

The present application discloses a kind of detection method of the attitude of the surface to be measured and optical detection equipment using the detection method, which is based on at least two contrast value lookup tables to obtain the tilt state of the surface to be measured in the detection procedure. By the different waveband light having different focusing degrees for target detection area, the contrast degree of the focusing index of different two wavebands in the target detection area is obtained, and then the two height position parameters matching in the corresponding contrast value lookup table are found out, and then the tilt state of the surface to be measured can be obtained based on the difference between the height position parameters, which is used as the basis for subsequent attitude adjustment. Therefore, under the operation of this matching mechanism, an image can be detected for attitude, eliminating the time-consuming procedure of detecting the focusing degree layer by layer for observation points, which can greatly improve the detection efficiency of the attitude of the surface to be measured.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical detection technique, and more particularly, to a detection method using a chromatic aberration factor to detect a surface attitude of a subject, and an optical detection apparatus using the detection method to detect and adjust the surface attitude of the subject. BACKGROUND

[0002] Observation at a microscopic scale is performed by a microscope system. When the topography of a subject is within the depth of field of the focal plane of the microscope system, the topography of the subject can be clearly shown in the microscope system.

[0003] When the topography of the subject has a certain degree of height difference, for example, the subject has a tilt state, the observed plane of the subject cannot have a high degree of perpendicularity with the optical axis of the microscope system, which results in a decrease in optical imaging quality due to the generation of optical aberration.

[0004] In order to improve the optical imaging quality, the observed plane of the subject needs to have a high degree of perpendicularity with the optical axis of the microscope system as much as possible, so that the topography of the subject can be within the depth of field of the focal plane of the microscope system.

[0005] Conventionally, the observation points defined by the corners of the observed surface are used. In a periodic adjustment procedure, a series of modulation transfer function calculations at different height positions are performed for each observation point to detect the best focus height position, so as to obtain the attitude of the observed surface and adjust it. After a plurality of periodic adjustment procedures are performed, the tilt degree converges, and the observed plane and the optical axis of the microscope system reach a high degree of perpendicularity. However, this method needs to perform height position scanning, imaging, and modulation transfer function calculation for each height position for each observation point in each periodic adjustment procedure. This not only consumes a lot of time for imaging, transmission, and calculation, but also increases the overall detection time due to the mechanical movement of the height position scanning (moving the focal plane of the microscope system in an axial direction) and the mechanical repeated stopping action.

[0006] Therefore, the conventional detection method consumes a considerable amount of time, especially when the number of observation points used as the focus basis is large at a microscopic scale, each periodic detection procedure consumes more time, which leads to a decrease in efficiency. SUMMARY

[0007] One of the purposes of the present application is to improve the detection efficiency of the surface attitude of the subject.

[0008] To achieve the above object and other objects, the present application provides a method for detecting a surface attitude, which is based on at least two contrast value lookup tables that are set up in advance, to obtain the tilt state of the surface under test in a detection procedure. The method comprises: obtaining image data of two target detection areas on the surface under test; dividing the image data of each target detection area into a first band image data and a second band image data of different bands; obtaining a focus index value corresponding to each of the first band image data and the second band image data, and obtaining a ratio between the two values; finding a height position parameter that matches in the corresponding contrast value lookup table according to the ratio corresponding to each target detection area; obtaining the tilt state of the surface under test according to the difference between the height position parameters corresponding to the two target detection areas; wherein each contrast value lookup table refers to the ratio information of each target detection area on a standard surface under test in a height swing range at each height position parameter that is not established in the detection procedure.

[0009] In an embodiment of the present application, the establishment of the contrast value lookup table obtains the image data of two matching areas corresponding to each height position in the height swing range of the corresponding two target detection areas on the standard surface under test, obtains a focus index value corresponding to each of the two bands, and obtains a ratio information between the two values. A height position parameter corresponding to each ratio information is used as the height position parameter in the contrast value lookup table.

[0010] In an embodiment of the present application, the denominator of the ratio can be the focus index value corresponding to the second band image data, and the numerator of the ratio can be the focus index value corresponding to the first band image data. The first band image data is based on light of a first wavelength, and the second band image data is based on light of a second wavelength.

[0011] In an embodiment of the present application, the first wavelength is longer than the second wavelength.

[0012] To achieve the above object and other objects, the present application also provides an optical detection device for adjusting the posture of a measurement surface of a measurement object, comprising a carrier, an image capturing assembly, a light source assembly, and a control host; the carrier is used for carrying the measurement object, and comprises at least two adjusting mechanisms for adjusting the posture of a carrying surface; the image capturing assembly is used for capturing images toward the carrying surface; the light source assembly is used for providing illumination toward the carrying surface; and the control host is coupled to the at least two adjusting mechanisms, the image capturing assembly, and the light source assembly, receives image data generated by the image capturing assembly, and controls the at least two adjusting mechanisms. The control host is used for executing the above-mentioned detection method for the posture of the measurement surface, and acquires the height position parameters of two target detection areas according to the at least two contrast value lookup tables stored in advance and the image data generated by the image capturing assembly, controls the at least two adjusting mechanisms, so that the difference between the two height position parameters of the two target detection areas is less than a preset threshold value, and the measurement surface is in a horizontal state.

[0013] In an embodiment of the present application, the image of the measurement surface captured by the image capturing assembly toward the carrying surface is one frame of image data, which is used for the control host to perform the above-mentioned detection method on the two target detection areas.

[0014] In an embodiment of the present application, the light source assembly is used for simultaneously providing illumination light of two different wavebands.

[0015] In this way, the present application applies the chromatic aberration characteristics of light of two different wavebands formed by the optical imaging system, and establishes matching position information by applying the contrast characteristics on the focusing index value, so that the optical detection device can perform posture detection by capturing only one frame of image under the operation of the matching mechanism, and the time-consuming procedure of performing layer-by-layer focusing degree detection on each observation point by scanning different height positions is avoided. The detection method and the detection device for the posture of the carrying surface proposed by the present application have a significant efficiency improvement. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of an optical detection device according to an embodiment of the present application;

[0017] Figure 2 is a schematic diagram of the optical detection device of Figure 1 in a first embodiment under the image capturing angle;

[0018] Figure 3 is a focusing diagram of light of different wavebands;

[0019] Figure 4 is a schematic diagram of the posture of the measurement surface corresponding to different height position parameters;

[0020] Figure 5This is a graph showing the relationship between the degree of contrast in focus index of two different bands in a target detection area and the height position parameter.

[0021] Figure 6 This is a schematic diagram of the detection state;

[0022] Figure 7 This is a flowchart of a method for detecting the attitude of a surface under test according to an embodiment of the present invention.

Detailed Implementation Methods

[0023] To fully understand the purpose, features, and effects of the present invention, the present invention will now be described in detail with reference to the following specific embodiments and accompanying drawings:

[0024] In this application, the terms "a" or "an" are used to describe units, components, structures, devices, modules, systems, parts, or regions, etc. This is used merely for ease of explanation and to provide a general meaning for the scope of the invention. Therefore, unless it is obvious otherwise, this description should be understood to include one or at least one, and the singular also includes the plural.

[0025] In this application, the terms "comprising," "including," "having," or any other similar terms used are not limited to the elements listed in this application, but may include other elements that are not expressly listed but are generally inherent in the unit, component, structure, device, module, system, part, or region.

[0026] In this application, the ordinal terms such as "first" or "second" are used to distinguish or refer to elements, structures, parts, or regions that are related to the same or similar entities, and do not necessarily imply a spatial order of these elements, structures, parts, or regions. It should be understood that in certain situations or configurations, ordinal terms may be used interchangeably without affecting the implementation of the invention.

[0027] For optical systems, focusing methods can be divided into active focusing and passive focusing. Active focusing involves actively emitting specific light waves from the object being measured and receiving the light waves reflected back from the object to determine the distance between the object and the optical system, thereby achieving focusing. Examples include infrared ranging and ultrasonic ranging. Passive focusing, on the other hand, analyzes the acquired image data of the object being measured to determine the focusing position, thus achieving focusing.

[0028] The focusing method adopted in the present embodiment is a passive focusing method. The passive focusing method is generally based on an existing algorithm to calculate a corresponding focus index value from the acquired image data, and finally determines the clearest imaging position according to the position corresponding to the highest focus index value. For example, the algorithm includes a gray scale function-based algorithm and a frequency domain function-based algorithm. These functions are selectively used to calculate the focus index value of the acquired image data, and these functions are applicable to the acquisition of the focus index value described in the subsequent embodiments of the present case.

[0029] For example, the Tenengrad gradient function is a gray scale function-based algorithm that uses Sobel operators to extract gradient values in the horizontal and vertical directions of the image data. The Sobel operator is a kind of existing discrete differentiation operator. Another gray scale function-based algorithm, such as the Brenner function, is to calculate the sum of the squares of the gray scale differences between pixels separated by a certain number of units in the horizontal or vertical direction as the basis for determining the image sharpness.

[0030] Please refer to Figure 1 and Figure 2 , Figure 1 is a schematic diagram of an optical detection device according to an embodiment of the present application, Figure 2 is Figure 1 is a schematic diagram of the optical detection device in the first embodiment under the imaging angle. The optical detection device includes a stage 110, an imaging assembly 120, a light source assembly 130, and a control host 140.

[0031] The imaging assembly 120 is used to image the bearing surface 112 to acquire the image of the test surface 200 of the test object placed on the bearing surface 112. The light source assembly 130 is used to provide illumination to the bearing surface 112 to illuminate the test surface 200, wherein the light source assembly 130 can simultaneously provide two different wave bands of illumination light. The light source assembly is not limited to ring light, and coaxial light is also applicable to the present application. The control host 140 is coupled to the imaging assembly 120, the light source assembly 130, and the stage 110 and its adjustment mechanism 111 to receive the image data generated by the imaging assembly 120 and perform the detection of the test surface posture, and control the adjustment mechanism 111.

[0032] The stage 110 carries the test object through the bearing surface 112. The stage includes at least two adjustment mechanisms 111 for adjusting the posture of the bearing surface 112. The adjustment mechanism 111 in Figure 1 and Figure 2 is exemplified by vertical adjustment devices arranged at the four corners of the stage 110 (see Figure 2The configuration position of the four adjustment mechanisms 111 in the embodiment of the present application, but not limited thereto, other stages and adjustment devices that can change the posture of the surface 200 of the object under test can also be applicable. In other words, the adjustment mechanisms 111 are used to make the stage 110 have the adjustability of the posture, so that when the surface 200 of the object under test on the stage 110 is detected as not having the proper perpendicularity with the optical axis of the imaging assembly 120, the horizontal degree of the stage 110 can be adjusted to achieve the proper perpendicularity between the surface 200 and the optical axis of the imaging assembly 120.

[0033] Wherein, how to adjust the stage 110 to achieve a better horizontal degree depends on the current posture of the surface 200 of the object under test determined by the acquired image data, and the corresponding adjustment is made by the adjustment mechanisms 111. In the embodiment of the present application, the inclination state of the surface 200 of the object under test is detected in the detection process based on the pre-established contrast value lookup table, which can be directly used as the adjustment basis of the adjustment mechanisms 111.

[0034] Please refer to Figure 3 , which is a schematic diagram of the focusing of light of different wavebands. Through the chromatic aberration phenomenon of different wavebands, the focusing planes of light of different wavebands show a certain degree of difference. As shown in Figure 3 , when green light G is in focus, red light R and blue light B cannot be in focus on the focal plane position PG of green light G based on the property of chromatic aberration. Therefore, the image data of red light R and blue light B (for example, image data of R channel and image data of B channel) will show that the focus index values are not in focus (low definition) after the algorithm operation. In the example of using the Brenner function as the algorithm for evaluating whether the image is in focus or not, the focus index values of the image data of red light R and blue light B will be lower than that of green light G image data because they are not in the focus position. In the embodiment of the present application, by using the feature that the difference degree of the focus index of a target detection area of a detection surface of different wavebands changes with the height position, the height position parameter is converted, and then the inclination state can be quickly determined by the difference of the height position parameters of different target detection areas as the adjustment basis, which will be further described below.

[0035] Please refer to Figure 1 , Figure 2 , Figure 4 and Figure 5 , Figure 4 , which is a schematic diagram of the posture of the surface under test corresponding to different height position parameters, Figure 5 , which is a relationship diagram between the contrast degree of the focus index of different wavebands in a target detection area and the height position parameter.

[0036] The pre-established contrast value lookup table is based on a standard test surface of a standard test object. The standard test object is used to define the type of test object, and is used to establish the contrast value lookup table based on the characteristic topography of its surface (standard test surface). For example, when testing on a production line, a specific test surface of a large number of test objects of a certain model or type needs to be tested. The contrast value lookup table needs to be established for this test surface first. The standard test object can be a good product of this type of test object with a characteristic topography. Subsequently, before each test object is tested, the optical testing device adjusts the level of the test surface of the test object based on the contrast value lookup table, so that the observed plane of the test object can be more perpendicular to the optical axis of the image capturing assembly 120 in the optical testing device.

[0037] One contrast value lookup table corresponds to one target detection area on the test surface of the standard test object. The target detection area can be defined by setting its position and size, and in the embodiments of the present application, the size of the area is not limited. As shown in Figure 2 Two target detection areas D1 and D2 are set on the test surface 200 (on the standard test object). The two defined target detection areas D1 and D2 are the areas used by the optical testing device as the basis for determining the posture of the test surface 200 of each test object before it is tested.

[0038] The adjustment mechanism 111 of the carrier 110 can adjust the level of the carrier surface 112, so that Figure 2 For example, the adjustment of the level can be performed by rotating the test object around the first axis L1 or other axes as the rotation axis, so that the test surface 200 of the test object has a height swing range, which refers to the maximum range of the carrier surface 112 that can be adjusted based on the rotation axis, and is not limited to the aforementioned adjustment method. In other words, when the corresponding height position parameters can be obtained from the images at each height position point (different positions with different distances from the image capturing assembly 120) of the two target detection areas D1 and D2 within the height swing range, the corresponding adjustment parameters can be obtained based on the height positions of the two target detection areas D1 and D2 and their difference, and there is no need to perform the time-consuming layer-by-layer focus detection procedure for each target detection area as in the prior art.

[0039] The detection light of different wavebands has different focus index values for the same detection surface, and this difference is converted into the correspondence between the contrast between different wavebands and the height position parameters in the embodiments of the present application. Please refer to Figure 5, in the construction of the contrast ratio lookup table, each position on the abscissa (height position parameter P) represents the height position point of the corresponding target detection area in the height swing range, and on the other hand, it also has a corresponding degree of proximity with respect to the imaging assembly 120. At each height position point on the abscissa, the image data of the two different wavebands is obtained, and the corresponding focus index values are obtained based on the existing image analysis method, and the ratio between the two focus index values (the ratio information in the contrast ratio lookup table) represents the contrast degree r (i.e. Figure 5 of the ordinate).

[0040] In Figure 4 and Figure 5 , three height position points RP01, RP10, RP20 in the height swing range are shown, wherein, Figure 5 the relationship diagram corresponds to the target detection area D1, and each target detection area has a corresponding relationship diagram (i.e. has a corresponding contrast ratio lookup table). After the ratio between the focus index values and the corresponding height position parameters are obtained one by one, the relationship diagram shown in Figure 5 can be obtained by drawing a fitting curve, and the contrast ratio lookup table can also be completed accordingly. In subsequent detection, only the value of the contrast degree r (ratio) corresponding to the current height position of the target detection area needs to be obtained, and the value of the corresponding height position parameter P can be directly obtained through the contrast ratio lookup table. Then, based on the difference between the two target detection areas, the difference can be used as the basis for judging the attitude of the object to be measured. Subsequently, the difference can be eliminated by adjusting mechanism 111 to adjust the level of the object to be measured, so that the observed plane of the object to be measured can have a higher vertical degree with the optical axis of the imaging assembly 120 in the optical detection device.

[0041] In the construction of the contrast ratio lookup table, the target detection area used is the same as the target detection area used in the subsequent detection process. In addition, the contrast ratio lookup table is further defined by the matching area A in Figure 5 , and accordingly, the height swing range of the bearing surface 112 is controlled within a certain limit. The matching area A can be defined by the fluctuation interval in the fitting curve of Figure 5 .

[0042] In which, based on a value (ratio) of a contrast degree r, it includes: first information, the focus index value (numerator) of the first waveband detection light; and second information, the focus index value (denominator) of the other waveband detection light; and the distribution relationship of the two information at each height position point in the height swing range (i.e. the focus index value at the low position point is different from the focus index value at the high position point). This makes a value of a contrast degree r Figure 5When the value of the corresponding height position parameter P has two values, one of the two values can be obtained by one of the two information. In other words, when the corresponding ratio r of the target detection area matches two height position parameters in the corresponding ratio lookup table, the corresponding height position parameter (the correct height position parameter) can be determined by the focus index value corresponding to the first waveband image data or the focus index value corresponding to the second waveband image data.

[0043] Next, please refer to Figure 1 , Figure 6 and Figure 7 , Figure 6 is a schematic diagram of a detection state, Figure 7 is a flowchart of a detection method of a surface posture of an object according to an embodiment of the present application. As shown in Figure 6 , before the posture detection, the surface of the object 200 and the optical axis O of the image capturing assembly 120 are not perpendicular. The detection method of the posture of the object 200 includes the following steps:

[0044] Step S100, an image capturing step. This step obtains image data of two target detection areas D1 and D2 on the object 200. The image data of the two target detection areas D1 and D2 can be obtained together in one image data. In other embodiments, the image data of the two target detection areas D1 and D2 can be obtained separately.

[0045] Step S200, an image area division step. This step divides the image data of each target detection area into two different waveband image data, i.e., first waveband image data and second waveband image data. For example, the first waveband image data is red light image data, and the second waveband image data is blue light image data. In other embodiments, the image data can be of other wavelengths.

[0046] Step S300, a contrast degree obtaining step. This step obtains the corresponding focus index value of each of the first waveband image data and the second waveband image data by using existing algorithms. In addition, the ratio between the two values is obtained as the contrast degree. In other embodiments, the numerator of the ratio is the focus index value corresponding to the first waveband image data, and the denominator of the ratio is the focus index value corresponding to the second waveband image data. The first waveband image data is based on light of a first wavelength, and the second waveband image data is based on light of a second wavelength, wherein the first wavelength is longer than the second wavelength.

[0047] Step S400, matching step. This step is to find the matching height position parameter in the corresponding contrast value look-up table according to the contrast value (the ratio between the focus index values of the two waveband image data) corresponding to each target detection area D1 and D2. That is, in the contrast value look-up table, one contrast value r (such as the y-coordinate of Figure 5 ) can be matched to one corresponding height position parameter P (such as the x-coordinate of Figure 5 ).

[0048] Step S500, tilt state obtaining step. This step is to obtain the tilt state of the surface 200 according to the difference between the height position parameters P corresponding to the two target detection areas obtained in step S400. In other words, when the height position parameters P corresponding to the two target detection areas have a difference, it means that the surface 200 is in a tilted state, and the degree of tilt can be determined by the difference between the height position parameters P corresponding to the two target detection areas. For example, once the height position difference of the two target detection areas is obtained, the adjustment mechanism 111 of the stage 110 in Figure 1 can easily complete the adjustment of the degree of tilt. In other embodiments, after adjusting the degree of tilt once, the aforementioned steps S100-S500 can be performed again until there is no height position difference between the two target detection areas or the height position difference is within a threshold value. The threshold value is defined according to, for example, the allowable error range in the optical detection system or other allowable error conditions.

[0049] The configuration of the adjustment mechanism 111 of the stage 110 is not limited to the position shown in Figure 2 .

[0050] In summary, by applying the chromatic aberration characteristics of light rays of different wavebands formed by the optical imaging system and based on the contrast characteristics that can be shown in the focus index values, the matching height position information is established, so that the optical detection device can operate under this matching mechanism and only needs to take one image to detect the posture, thereby eliminating the time-consuming procedure of detecting the focus degree layer by layer for the observation points, and greatly improving the detection efficiency of the surface posture.

[0051] The preferred embodiments of the present application are disclosed in the foregoing description, however, it should be understood by those skilled in the art that the embodiments herein are only used to describe the present application and should not be interpreted as limiting the scope of the present application. It should be noted that all equivalent changes and substitutions of the embodiments should be understood as falling within the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0052]

List of reference signs

[0053] 110 stage

[0054] 111 adjustment mechanism

[0055] 112 bearing surface

[0056] 120 image-taking assembly

[0057] 130 light source assembly

[0058] 140 control host

[0059] 200 surface to be measured

[0060] A matching area

[0061] C central position

[0062] L1 first axis

[0063] L1' another axial direction

[0064] L2 second axis

[0065] O optical axis

[0066] P height position parameter

[0067] PG focal plane position of green light G

[0068] RP01 height position point within a height swing range

[0069] RP10 height position point within a height swing range

[0070] RP20 height position point within a height swing range

[0071] r degree of contrast

[0072] R red light

[0073] G green light

[0074] B blue light

[0075] S100-S500 steps

Claims

1. A method for detecting the attitude of a surface to be tested, which is based on a pre-established lookup table of at least two comparison values ​​to obtain the tilt state of the surface to be tested in a detection program, the detection method comprising: Irradiation light including two different wavelengths is provided on the surface to be tested, and image data of two target detection areas are obtained on the surface to be tested; The image data of each target detection area is divided into two different bands: a first band image data and a second band image data. Obtain the focus index value corresponding to the first band image data and the second band image data respectively, and obtain a ratio between the two values. Based on the ratio corresponding to each target detection area, a matching height position parameter is found in the corresponding comparison value lookup table; and Based on the degree of difference between the height position parameters corresponding to the two target detection areas, the tilt state of the surface to be measured is obtained. Wherein, each of the comparison value lookup tables refers to the ratio information of each of the target detection areas within a height swing range for each height position parameter of a standard test surface not established in the detection procedure; The establishment of the comparison value lookup table is as follows: for the matching area corresponding to the two target detection areas on the standard test surface, within the height swing range, image data corresponding to the two matching areas at each height position is obtained, and a focus index value corresponding to each of the two different bands is obtained, as well as a ratio information between the two values. The height position parameter corresponding to each ratio information is used as the height position parameter in the comparison value lookup table.

2. The detection method as described in claim 1, wherein, The denominator of the ratio is the focus index value corresponding to the second band image data, and the numerator of the ratio is the focus index value corresponding to the first band image data. The first band image data is based on a first wavelength of light, and the second band image data is based on a second wavelength of light.

3. The detection method as described in claim 2, wherein, The first wavelength is longer than the second wavelength.

4. An optical inspection device for adjusting the orientation of a surface to be measured of an object, the optical inspection device comprising: A platform for supporting the object to be tested, the platform including at least two adjustment mechanisms for adjusting the orientation of a support surface; An image-capturing component for capturing an image toward the bearing surface; A light source assembly for providing illumination toward the bearing surface; and A control host, coupled to the at least two adjustment mechanisms, the image acquisition assembly, and the light source assembly, receives image data generated by the image acquisition assembly and controls the at least two adjustment mechanisms. The control host is used to execute the method for detecting the attitude of the surface under test as described in any one of claims 1 to 3. The control host obtains the current height position parameters of two target detection areas based on at least two comparison value lookup tables stored in the host and the image data generated by the imaging component. The control host controls the at least two adjustment mechanisms to make the difference between the two height position parameters of the two target detection areas less than a preset threshold value, so that the surface under test is in a horizontal state.

5. The optical inspection device as described in claim 4, wherein, The image acquired by the imaging component towards the bearing surface constitutes an image of the surface to be tested. This image data is used by the control host to perform the detection method on the two target detection areas.

6. The optical inspection device as described in claim 4, wherein, The light source assembly is used to simultaneously provide illumination light of two different wavelengths.

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