CN113533353A - Defect detection device and defect detection method - Google Patents
Defect detection device and defect detection method Download PDFInfo
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- CN113533353A CN113533353A CN202110959661.7A CN202110959661A CN113533353A CN 113533353 A CN113533353 A CN 113533353A CN 202110959661 A CN202110959661 A CN 202110959661A CN 113533353 A CN113533353 A CN 113533353A
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
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Abstract
The embodiment of the invention discloses a defect detection device and a defect detection method, wherein the defect detection device comprises a light source, a first lens group, an optical path compensator group, a second lens group and a detector; the optical path compensator group comprises at least one optical path compensator; a detection light beam emitted by the light source is reflected by the surface of the object to be detected to form a reflected light beam, and the optical path compensator is arranged in the focal depth range of the first lens group for imaging the surface of the object to be detected; the thickness of the optical path compensator is unevenly distributed along the propagation direction of the reflected light beam, the optical path compensator can compensate the optical path difference of the reflected light beam caused by the cambered surface of the object to be detected, so that the reflected light beam with the compensated optical path difference is focused and imaged in the same focal plane through the second lens, and the detector collects a clear image formed by the second lens. The device solves the technical problems that the existing optical imaging system is difficult to accurately identify and position the materials to be measured on the uneven surface and the surface with larger radian and is difficult to obtain clear images.
Description
Technical Field
The embodiment of the invention relates to the technical field of detection, in particular to a defect detection device and a defect detection method.
Background
With the deepening and popularization of industrial automation and intellectualization, the use of Automatic Optical Inspection (AOI) instead of the traditional manual visual Inspection has become a technological development trend. The AOI equipment is widely used in the fields of automobiles, medicines, traffic, semiconductors and the like by virtue of the rapid and accurate defect identification and positioning capability of the AOI equipment.
Currently, existing AOI devices typically include optical imaging systems, stages, material transport systems, and the like. Wherein the optical imaging system comprises an illumination unit, an imaging objective, a detector and the like. The illumination unit is responsible for providing required radiant light, the objective lens is used for collecting a light signal of a surface to be measured, and the detector is responsible for converting the light into a digital signal. Generally, the AOI device can better acquire an image of a flat surface, so as to identify corresponding defects through image processing.
For some uneven surfaces, especially surfaces with large radian, clear images are difficult to obtain by an optical imaging system, for example, the edges of materials such as silicon wafers, glass and the like have arc surfaces, and the traditional optical imaging system cannot obtain the images of the whole arc surface, so that edge defects are difficult to locate and identify.
Disclosure of Invention
The embodiment of the invention provides a defect detection device and a defect detection method, and aims to solve the technical problems that an existing optical imaging system is difficult to accurately identify and position a material to be detected on an uneven surface and a surface with a large radian, and a clear image is difficult to obtain.
In a first aspect, an embodiment of the present invention provides a defect detection apparatus, including a light source and an optical system, where the optical system includes a first lens group, an optical path compensator, a second lens group, and a detector;
the light source is used for emitting a detection light beam, the detection light beam is reflected by the surface of an object to be detected to form a reflected light beam, at least part of the surface of the object to be detected is a cambered surface, and the first lens group, the optical path compensator, the second lens group and the detector are sequentially positioned on a transmission path of the reflected light beam;
the first lens group is used for transmitting the reflected light beam to the optical path compensator;
the thickness of the optical path compensator is unevenly distributed along the propagation direction of the reflected light beam, and the optical path compensator is used for compensating the optical path difference of the reflected light beam caused by the cambered surface of the object to be detected;
the second lens group is used for imaging the surface of the object to be measured according to the reflected light beam after compensating the optical path difference;
the detector is positioned in the focal plane of the second lens group and is used for collecting the image formed by the second lens group.
Optionally, the optical path compensator is located within a focal depth range of the first lens group.
Optionally, the reflected light beam includes a first reflected light beam and a second reflected light beam, the first reflected light beam is reflected by an edge of the arc surface of the object to be measured and reaches the first surface of the optical path compensator, the second reflected light beam is reflected by a center of the arc surface of the object to be measured and reaches the second surface of the optical path compensator, and an optical path difference between the first reflected light beam and the second reflected light beam is L;
the difference H in thickness between the first surface and the second surface along the direction of propagation of the reflected light beam satisfies the formula: l ═ H (n-1); wherein n is the refractive index of the optical path compensator.
Optionally, the optical path length compensator includes at least two concentric annular steps.
Optionally, the number N of annular steps of the optical path compensator satisfies the formula: n ═ Lmax/(DOF/k);
wherein, along the transmission direction of the reflected light beam, Lmax is the maximum optical path difference between the edge position of the cambered surface and the center position of the cambered surface of the object to be measured, DOF is the focal depth of the optical system, k is a positive integer, and k is more than or equal to 2; (DOF/k) is an optical path length compensation amount of any adjacent two of the annular steps in the optical path length compensator.
Optionally, the height difference dh between any two adjacent annular stepped rings satisfies the formula: dh ═ (DOF/k/(n-1);
wherein DOF is the focal depth of the optical system, k is a positive integer, and k is more than or equal to 2; (DOF/k) is an optical path length compensation amount of any adjacent two of the annular steps in the optical path length compensator, and n is a refractive index of the optical path length compensator.
Optionally, the refractive index of the optical path compensator is n, and n is greater than or equal to 1.4 and less than or equal to 2.
Optionally, the width difference dw between any two adjacent annular steps satisfies the formula: dw ═ W/N × Mag;
w is the view field width of the position of the edge of the cambered surface and the position of the center of the cambered surface of the object to be measured, and Mag is the magnification of the first lens group.
Optionally, the optical path compensators are multiple and arranged on the turntable mechanism, a rotation central axis of the turntable mechanism is parallel to an optical axis of the reflected light beam, and the optical path compensators are uniformly arranged around the rotation central axis of the turntable mechanism in a circumferential manner;
and in the rotating process of the turntable mechanism, the optical path compensators are sequentially positioned in the imaging view field of the first lens group.
In a second aspect, an embodiment of the present invention provides a defect detection method, where a defect detection apparatus provided in the first aspect is used to perform defect detection on an object to be detected, and the defect detection method includes:
compensating the optical path difference of a reflected light beam reflected by the surface of the object to be detected by using an optical path compensator in the defect detection device, wherein at least part of the surface of the object to be detected is a cambered surface;
acquiring an image of the surface of the object to be detected formed by the compensated reflected light beam by using a detector in the defect detection device;
and identifying the defects on the surface of the object to be detected in the image acquired by the detector through an image processing algorithm by using a computer.
The embodiment of the invention discloses a defect detection device, which comprises a light source, a first lens group, an optical path compensator group, a second lens group and a detector, wherein the optical path compensator group comprises at least one optical path compensator; the thickness of the optical path compensator is unevenly distributed along the propagation direction of the reflected light beam, the optical path compensator can compensate the optical path difference of the reflected light beam caused by the cambered surface of the object to be detected, so that the reflected light beam with the compensated optical path difference is focused and imaged in the same focal plane through the second lens, and the detector collects a clear image formed by the second lens. The device solves the technical problems that the existing optical imaging system is difficult to accurately identify and position the materials to be measured on the uneven surface and the surface with larger radian and is difficult to obtain clear images.
Drawings
Fig. 1 is a schematic structural diagram of a defect detection apparatus according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an optical path length compensator according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of another optical path length compensator according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an optical path length compensator set according to an embodiment of the present invention;
fig. 5 is a schematic flowchart of a defect detection method according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a schematic structural diagram of a defect detection apparatus according to an embodiment of the present invention. The defect detection device provided by the embodiment of the invention can be used for positioning the arc surface image at the edge of materials such as silicon wafers, glass and the like, identifying edge defects and the like. As shown in fig. 1, the defect detecting apparatus 1 includes a light source 11 and an optical system including a first lens group 12, an optical path length compensator 131, a second lens group 14, and a detector 15; the light source 11 is used for emitting a detection light beam T, the detection light beam T is reflected by the surface of the object 2 to be detected to form a reflected light beam R, at least part of the surface of the object 2 to be detected is a cambered surface, such as a side surface, and the first lens group 12, the optical path compensator 131, the second lens group 14 and the detector 15 are sequentially located on the propagation path of the reflected light beam R; the first lens group 12 is used for transmitting the reflected light beam R to the optical path length compensator 131; the optical path length compensator 131 is located on the beam propagation path of the first lens group 12; the thickness of the optical path compensator 131 is unevenly distributed along the propagation direction of the reflected light beam R, and the optical path compensator 131 is used for compensating the optical path difference of the reflected light beam R caused by the cambered surface of the object 2 to be measured; the second lens group 14 is used for transmitting a reflected light beam R' after compensating the optical path difference; the detector 15 is located in the focal plane of the second lens group 14 and is used for collecting the image formed by the second lens group 14.
Illustratively, as shown in fig. 1, the defect detecting apparatus 1 includes a light source 11 and an optical system including a first lens group 12, an optical path length compensator 131, a second lens group 14, and a detector 15. The light source 11 may be LED light or a laser light source, the first lens group 12 and the second lens group 14 respectively include a focusing lens, and can collect and focus an optical signal to form an image, and the stage 3 is used for bearing the object 2 to be measured. The object 2 to be measured can be a silicon wafer, glass and other materials. The light source 11 emits a detection beam T to irradiate the surface of the object 2, and when the detection beam T is reflected by the curved surface of the object 2 to form a reflected beam R, the reflected beam R passes through the first lens group 12 and reaches the optical path compensator 131. Preferably, the optical path compensator 131 is arranged at the middle image plane of the defect detection device, so that the reflected light beam R can image the arc surface of the object 2 to be detected on the surface of the optical path compensator 131. Because at least part of the surface of the object 2 to be detected is a cambered surface, the reflected light beam R reaching the optical path compensator 131 has an optical path difference, and at this time, due to the optical path difference caused by the cambered surface, the images of the reflected light beam R on the optical path compensator 131 are not on the same plane, and the optical path needs to be compensated through the optical path compensator 131, so that the image acquired by the detector 15 is clear, and the defect detection imaging effect is improved.
Further, the optical path length compensator 131 is disposed in a non-uniform thickness along the propagation direction of the reflected light beam R, and the optical path length compensator 131 may be made of a transparent material and have a certain refractive index. When the reflected light beam R with the optical path difference reaches the surface of the optical path compensator 131 and then passes through the optical path compensator 131, the optical path compensator 131 compensates the optical path difference of the reflected light beam R caused by the arc surface of the object 2 to be measured, so that the optical path difference of the reflected light beam R' emitted by the optical path compensator 131 is nearly zero; the detector 15 is arranged in the focal plane of the second lens group 14, the second lens group 14 images the reflected light beam R ' with the compensated optical path difference to the detector 15, and the imaging definition of the reflected light beam R ' on the detector 15 is improved due to the elimination of the optical path difference of the reflected light beam R '. The detector can be a CCD camera or other devices capable of acquiring and imaging images, and converts the optical signals into digital signals to be displayed in the form of images.
To sum up, the embodiment of the invention discloses a defect detection device, which comprises a light source and an optical system, wherein the optical system comprises a first lens group, an optical path compensator, a second lens group and a detector, when the defect is detected, a matched optical path compensator is selected, a detection light beam emitted by the light source is reflected by the surface of an object to be detected to form a reflected light beam, and the first lens group, the optical path compensator, the second lens group and the detector are arranged on a propagation path of the reflected light beam in sequence, so that the light beam compensates the optical path through the optical path compensator; the thickness of the optical path compensator is unevenly distributed along the propagation direction of the reflected light beam, the optical path compensator can compensate the optical path difference of the reflected light beam caused by the cambered surface of the object to be measured, so that the reflected light beam with the compensated optical path difference is focused and imaged in the same focal plane through the second lens group, and the detector is positioned in the focal plane of the second lens group and collects the second lens group to form a clear image. The device can detect the defects that the uneven surface of the object to be detected and the surface with larger radian are difficult to accurately identify and position, and can obtain clear surface images.
Optionally, the optical path compensator is located within the focal depth range of the first lens group. The optical path compensator 131 is disposed within the focal depth range of the first lens group image, and when the first lens group 12 transmits the reflected light beam R to the optical path compensator 131, the reflected light beam R can be imaged on the optical path compensator 131, which is favorable for the optical path compensator 131 to compensate the optical path difference of the reflected light beam R.
Optionally, the reflected light beam R includes a first reflected light beam R1 and a second reflected light beam R2, the first reflected light beam R1 is reflected at an edge position of the arc surface of the object 2 to be measured and reaches the first surface of the optical path compensator 131, the second reflected light beam R2 is reflected at a center position of the arc surface of the object 2 to be measured and reaches the second surface of the optical path compensator, and an optical path difference between the first reflected light beam R1 and the second reflected light beam R2 is L; the difference H in thickness between the first surface and the second surface in the direction of propagation of the reflected light beam satisfies the formula (1): l ═ H (n-1); wherein n is the refractive index of the optical path compensator.
For example, with reference to fig. 1, point a at the edge position of the arc surface of the object 2 and point B at the center position are taken as an example for description. When the detection beam T emitted from the light source 11 irradiates the point a and the point B on the surface of the object 2 to be detected, the detection beam T is reflected by the point a at the edge of the arc surface to obtain a first reflected beam R1, and is reflected by the point B at the center to obtain a second reflected beam R2. Along the propagation direction of the reflected light beam R2, because the side surface of the object 2 to be measured is a cambered surface, there is an optical path difference L between the first reflected light beam R1 and the second reflected light beam R2, when the first reflected light beam R1 passes through the first lens group 12 and reaches a point a 'on the first surface of the optical path compensator 131, and the second reflected light beam R2 passes through the first lens group 12 and reaches a point B' on the second surface of the optical path compensator 131, the thickness of the optical path compensator 131 is set to be non-uniform, and there is a thickness difference H (parallel to the optical axis direction) between the first surface where the point a 'is located and the second surface where the point B' is located, as shown in fig. 1, by adjusting the refractive index n of the optical path compensator 131, the thickness difference H between the first surface and the second surface of the optical path compensator 131 satisfies the formula (1): and L is H (n-1), so that the thickness difference H of the optical path compensator 131 corresponding to the image plane can be set according to the optical path difference L between the point a and the point B, and further, after the first reflected light beam R1 and the second reflected light beam R2 are distributed to pass through the optical path compensator 131 from the point a 'and the point B', the optical path difference between the first reflected light beam R1 and the second reflected light beam R2 is eliminated, and the optical path difference between the first reflected light beam R1 and the second reflected light beam R2 is compensated. When the point B at the central position of the arc surface of the object 2 to be measured is taken as a reference point, and the optical path difference L is determined at any point at the position of the arc surface of the object 2 to be measured, the optical path compensator 131 meeting the optical path difference L compensation of the object 2 to be measured can be designed according to the formula met by the thickness difference H.
In actual defect detection, optical path compensators with certain standard sizes need to be preset, and proper optical path compensators are selected according to different objects to be detected so as to adapt to different cambered surfaces to be detected and realize optimal compensation of optical path difference, thereby improving the positioning of defect detection, identifying edge defects and the like.
Optionally, fig. 2 is a schematic structural diagram of an optical path length compensator according to an embodiment of the present invention. As shown in fig. 2, the optical path length compensator 131 includes at least two concentric annular steps.
Illustratively, as shown in fig. 2, the optical path length compensator 131 may be configured to include at least two concentric annular steps, 5 annular steps being shown. By setting the form of the plurality of annular steps, the optical path difference L of the reflected light beam R' passing through the optical path compensator 131 is made to be almost zero. The structure of the optical path compensator 131 has various forms, and fig. 3 is a schematic structural diagram of another optical path compensator according to an embodiment of the present invention. As shown in fig. 3, the sidewall surface of the optical path compensator 131 has a cambered surface structure consistent with the structure of the object to be measured.
Optionally, the number N of annular steps of the optical path compensator satisfies formula (3): n ═ Lmax/(DOF/k); wherein, along the transmission direction of the reflected light beam, Lmax is the maximum optical path difference between the edge position of the cambered surface of the object to be measured and the center position of the cambered surface, DOF is the focal depth of the optical system, k is a positive integer, and k is more than or equal to 2; (DOF/k) is an optical path length compensation amount of two arbitrary adjacent annular steps in the optical path length compensator.
Illustratively, with continued reference to fig. 2, the number of the annular steps 1311 of the optical path length compensator 131 is set to N, which is a positive integer. When an object to be measured with a standard specification, such as a silicon wafer, is detected, the maximum optical path difference Lmax between the edge position of the arc surface and the center position of the arc surface of the object to be measured is known, and if the object to be measured is a non-standard object, the maximum optical path difference Lmax of the object to be measured can be obtained through a distance detector and other devices. Given the depth of focus DOF of the optical system, the height compensation value of the optical path compensator 131 adjacent to the ring-shaped step 1311 is set to 1/k of the depth of focus DOF, and the height difference dh of the optical path compensator 13 adjacent to the ring-shaped step 1311 satisfies formula (2): (DOF/k)/(n-1), deformation according to equation (1): lmax ═ dh × N (N-1), the number N of annular steps of the optical path compensator satisfies formula (3): n is Lmax/(DOF/K), K is a positive integer, K is more than or equal to 2, and when K is large enough, the number of N is enough, and the smooth slope structure shown in fig. 3 can be infinitely approached; and the number N of the annular steps of the optical path compensator needs to be set according to the actual optical path difference compensation effect and the defect detection imaging effect. In the formula that N satisfies, set (DOF/k) as the optical path compensation amount of any two adjacent annular steps in the optical path compensator, further accurately calculate the optical path compensation amount of the reflected light beam, and improve the compensation accuracy of the optical path compensator.
Optionally, the refractive index of the optical path compensator is n, and n is greater than or equal to 1.4 and less than or equal to 2. When a transparent material with a sufficiently large refractive index n is selected as the main body of the optical path compensator, on one hand, the height difference dh between any two adjacent annular stepped rings can be reduced, and on the other hand, the thickness of the optical path compensator can be reduced, and the volume can be reduced.
Optionally, the width difference dw between any two adjacent annular steps satisfies formula (4): dw ═ W/N × Mag; w is the view field width of the position of the edge of the cambered surface of the object to be measured and the position of the center of the cambered surface, and Mag is the magnification of the first lens group.
Illustratively, with continued reference to fig. 2, further, it is assumed that the width difference dw between any two adjacent annular steps satisfies the formula (4): and dw is W/N Mag, where W is the width of the field of view at the position of the edge of the arc surface and at the position of the center of the arc surface of the object 2 to be measured, and Mag is the magnification of the first lens group 12. When the object 2 to be measured and the first lens group 12 are determined, W and Mag are determined values, and when the number N of the annular steps of the optical path compensator 131 is large enough, the width difference dw between any two adjacent annular step rings is small enough, so that the reflected light beam R can be finely compensated after passing through the optical path compensator 131, the second lens group 14 transmits the reflected light beam R' with the compensated optical path difference, and the detector 15 collects an image formed by the second lens group 14. .
For example, when the maximum optical path difference Lmax between the edge position and the center position of the arc surface of the object is 100 μm, the field width W is 300 μm, the DOF is 50 μm, the maximum magnification Mag of the first lens group is 2, the k value is 4, the refractive index of the optical compensator is 1.5, and the equations (2) to (4) are used to calculate, the number N of annular steps of the optical compensator 131 is 100/(50/4) is 8, the height difference dh between any two adjacent annular step rings is (50/4)/(1.5-1) is 25 μm, and the width difference dw between any two adjacent annular step rings is 300/8 is 75 μm.
Fig. 4 is a schematic structural diagram of an optical path length compensator set according to an embodiment of the present invention. As shown in fig. 4, optionally, a plurality of optical path compensators 1311 are provided on the turntable mechanism 132, a rotation central axis L of the turntable mechanism 132 is parallel to the optical axis of the reflected light beam R, and the plurality of optical path compensators 131 are uniformly arranged circumferentially around the rotation central axis L of the turntable mechanism 132; during the rotation of the turntable mechanism 132, the plurality of optical path compensators 131 are sequentially located in the imaging field of view of the first lens group 12.
Illustratively, as shown in fig. 4, in the actual defect detection system, a turntable mechanism 132 may be disposed at the intermediate image plane, optical path compensators 131 of different specifications may be switched, and the turntable mechanism 132 and the plurality of optical path compensators 131 form an optical path compensator group 13. As shown in fig. 4, the optical path compensator group 13 includes 6 optical path compensators 131, and different N, dh and dw combinations are obtained according to the maximum optical path difference Lmax parameter at the position of the edge of the arc surface and the position of the center of the arc surface of the object to be detected, so as to adapt to detection of different arc surfaces to be detected. Specifically, a turntable mechanism 132 is provided, and the plurality of optical path compensators 131 are uniformly arranged around a rotation central axis L of the turntable mechanism 132 in a circumferential manner, so that when the defect detection of the object to be detected is performed, the rotation central axis L of the turntable mechanism 132 is ensured to be parallel to the optical axis of the reflected light beam R, and during the rotation of the turntable mechanism 132, the plurality of optical path compensators 131 are sequentially located in the imaging field of view of the first lens group 12, preferably, the optical path compensators 131 are located within the focal depth range of the first lens group 12. And selecting a proper optical path compensator 131 for detecting the defects of the object to be detected according to the maximum optical path difference parameter of the object to be detected.
Based on the same inventive concept, the embodiment of the invention also provides a defect detection method, which adopts the defect detection device provided by the first aspect to detect the defects of the object to be detected. Fig. 4 is a schematic flowchart of a defect detection method according to an embodiment of the present invention. As shown in fig. 4, the defect detection method includes:
s01, compensating the optical path difference of the reflected light beam reflected by the surface of the object to be detected by using the optical path compensator in the defect detection device, wherein at least part of the surface of the object to be detected is a cambered surface.
Specifically, as shown in fig. 1, the object 2 is placed on the stage 3, parameters N, dh and dw of the optical path compensator satisfying the maximum optical path difference Lmax are determined according to the maximum optical path difference Lmax parameter at the edge position of the arc surface and the center position of the arc surface of the object, and the optical path compensator 131 satisfying the parameter requirement is selected by rotating the turntable mechanism 132. When defect detection is performed, a detection light beam T emitted by the light source 11 irradiates the surface of the object to be detected and is reflected to form a reflected light beam R, the reflected light beam R is converged and imaged to the optical path compensator 131 through the first lens group, the optical path compensator 131 compensates the optical path difference of the reflected light beam R, and the second lens group 14 converges the reflected light beam R' after compensating the optical path difference and images the cambered surface of the object to be detected 2.
And S02, acquiring an image of the surface of the object to be detected formed by the compensated reflected light beams by using a detector in the defect detection device.
As shown in fig. 1, the focal plane of the second lens group 14 may be located within the focal depth range of the detector 15, and since the reflected light beam R' has no optical path difference, the entire arc surface can be clearly imaged on the detector 15, and an image formed by the arc surface of the object 2 to be measured is acquired.
And S03, identifying the surface defect of the object to be detected in the image acquired by the detector through an image processing algorithm by using a computer.
The method comprises the steps of acquiring an image of a detector by using a computer through an image processing algorithm, identifying parameters such as defect positions, shapes, specifications and types of an object to be detected through the image processing algorithm, such as threshold segmentation and template comparison, and further outputting information such as defect sizes, areas and positions.
In summary, the defect detection method provided by the embodiment of the present invention uses the defect detection system provided by the above embodiment to perform defect detection, and can select the matched optical path compensator according to different objects to be detected, and can accurately identify, position, and obtain the defect of the object to be detected, so as to obtain clear defect image information.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. The defect detection device is characterized by comprising a light source and an optical system, wherein the optical system comprises a first lens group, an optical path compensator, a second lens group and a detector;
the light source is used for emitting a detection light beam, the detection light beam is reflected by the surface of an object to be detected to form a reflected light beam, at least part of the surface of the object to be detected is a cambered surface, and the first lens group, the optical path compensator, the second lens group and the detector are sequentially positioned on a transmission path of the reflected light beam;
the first lens group is used for transmitting the reflected light beam to the optical path compensator;
the thickness of the optical path compensator is unevenly distributed along the propagation direction of the reflected light beam, and the optical path compensator is used for compensating the optical path difference of the reflected light beam caused by the cambered surface of the object to be detected;
the second lens group is used for transmitting the reflected light beam after compensating the optical path difference to the detector;
the detector is positioned in the focal plane of the second lens group and is used for collecting the image formed by the second lens group.
2. The defect detection apparatus of claim 1, wherein the optical path compensator is located within a depth of focus of the first lens group.
3. The apparatus of claim 1, wherein the reflected light beams include a first reflected light beam and a second reflected light beam, the first reflected light beam is reflected at an edge of the arc surface of the object to be measured and reaches the first surface of the optical path compensator, the second reflected light beam is reflected at a center of the arc surface of the object to be measured and reaches the second surface of the optical path compensator, and an optical path difference between the first reflected light beam and the second reflected light beam is L;
the difference H in thickness between the first surface and the second surface along the direction of propagation of the reflected light beam satisfies the formula: l ═ H (n-1); wherein n is the refractive index of the optical path compensator.
4. The apparatus of claim 1, wherein the optical path compensator comprises at least two concentric annular steps.
5. The defect detection apparatus of claim 4, wherein the number N of annular steps of the optical path compensator satisfies the formula: n ═ Lmax/(DOF/k);
wherein, along the transmission direction of the reflected light beam, Lmax is the maximum optical path difference between the edge position of the cambered surface and the center position of the cambered surface of the object to be measured, DOF is the focal depth of the optical system, k is a positive integer, and k is more than or equal to 2; (DOF/k) is an optical path length compensation amount of any adjacent two of the annular steps in the optical path length compensator.
6. The defect detecting apparatus according to claim 4, wherein a height difference dh between any two adjacent annular stepped rings satisfies a formula: dh ═ (DOF/k/(n-1);
wherein DOF is the focal depth of the optical system, k is a positive integer, and k is more than or equal to 2; (DOF/k) is an optical path length compensation amount of any adjacent two of the annular steps in the optical path length compensator, and n is a refractive index of the optical path length compensator.
7. The defect detection apparatus of claim 3 or 6, wherein the refractive index of the optical path compensator is n, 1.4. ltoreq. n.ltoreq.2.
8. The defect detection apparatus according to claim 4, wherein the width difference dw between any two adjacent annular steps satisfies the formula: dw ═ W/N × Mag;
w is the view field width of the position of the edge of the cambered surface and the position of the center of the cambered surface of the object to be measured, and Mag is the magnification of the first lens group.
9. The apparatus of claim 1, wherein the optical path compensators are disposed on a turntable mechanism, a rotation center axis of the turntable mechanism is parallel to an optical axis of the reflected light beam, and the optical path compensators are uniformly arranged circumferentially around the rotation center axis of the turntable mechanism;
and in the rotating process of the turntable mechanism, the optical path compensators are sequentially positioned in the imaging view field of the first lens group.
10. A defect inspection method for performing defect inspection using the defect inspection apparatus according to any one of claims 1 to 9, the defect inspection method comprising:
compensating the optical path difference of a reflected light beam reflected by the surface of the object to be detected by using an optical path compensator in the defect detection device, wherein at least part of the surface of the object to be detected is a cambered surface;
acquiring an image of the surface of the object to be detected formed by the compensated reflected light beam by using a detector in the defect detection device;
and identifying the defects on the surface of the object to be detected in the image acquired by the detector through an image processing algorithm by using a computer.
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