CN114324365A - Curved surface detection device - Google Patents
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- CN114324365A CN114324365A CN202210022328.8A CN202210022328A CN114324365A CN 114324365 A CN114324365 A CN 114324365A CN 202210022328 A CN202210022328 A CN 202210022328A CN 114324365 A CN114324365 A CN 114324365A
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Abstract
The embodiment of the invention discloses a curved surface detection device, which comprises a light source, an ellipsoidal mirror and an imaging system, wherein the ellipsoidal mirror is designed to be a hollow structure, the surface of the ellipsoidal mirror comprises a slot, the light source is arranged on a first focus of a long shaft of the ellipsoidal mirror by utilizing the characteristic that light emitted from one focus of the ellipsoidal reflecting bowl converges at the other focus after being reflected by the inner surface of the ellipsoidal bowl, an object to be detected passes through an opening area of the slot and is arranged on a second focus of the long shaft, the detection light emitted by the light source reaches a detection area of the object to be detected after being reflected by an inner reflecting surface of the ellipsoidal mirror to form reflected light, the reflected light is emitted through the slot, the imaging system receives the reflected light and generates an image formed on the surface of the detection area, and further identifies surface defects, the structure has the characteristics of concentrated energy and high utilization rate of the light source, and can realize bright field illumination of an edge cambered surface of the object to be detected, the edge surface defect of the object to be detected is convenient to identify.
Description
Technical Field
The embodiment of the invention relates to the technical field of detection, in particular to a curved surface detection device.
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. The structure schematic diagram is shown in figure 1.
In order to meet different process requirements, an illumination system of the current AOI detection equipment generally comprises bright field illumination and dark field illumination, for example, bare silicon wafer detection is taken, bright field illumination is usually coaxial illumination, if a silicon wafer has no defects, most of light returns to an objective lens in the original path to be imaged on a CCD (charge coupled device), if the silicon wafer has defects, incident light is absorbed or scattered, and only a small part of light can enter the objective lens to be imaged, so that the defects seen by people under bright field illumination are dark.
The conventional AOI detection apparatus (as shown in fig. 1) can better acquire an image of a flat surface, so that corresponding defects are identified through image processing, but for some uneven surfaces, especially surfaces with a large radian, such as arc surfaces of edges of materials such as silicon wafers, glass and the like, because a normal line of a surface to be detected is not always parallel to an optical axis of an objective lens, incident light and reflected light of the surface to be detected are not always symmetrical with respect to the optical axis of the objective lens, even if the surface to be detected has no defects, the reflected light may not return to the objective lens as it is, as shown in fig. 2, field missing or false detection may occur.
Disclosure of Invention
The embodiment of the invention provides a curved surface detection device, which utilizes the scattered illumination of an ellipsoid reflecting bowl, meets the requirement of edge detection of a silicon wafer, simultaneously fully utilizes the energy of a light source and improves the detection accuracy.
In a first aspect, an embodiment of the present invention provides a curved surface detection apparatus, including a light source, an ellipsoidal mirror, and an imaging system;
the ellipsoidal mirror is a hollow structure and the surface of the ellipsoidal mirror comprises a slot, wherein the slot comprises a first arc edge and a second arc edge; the ellipsoidal mirror also comprises a central plane where a long shaft is located, and the central plane is parallel to the plane where the first arc edge is located and the plane where the second arc edge is located respectively;
the light source is positioned on the first focus of the long shaft and used for emitting detection light; the object to be detected penetrates through the opening area of the slot and is positioned on the second focus of the long shaft, and at least part of the detection area of the object to be detected is a curved surface; the detection light is reflected by the inner reflecting surface of the ellipsoidal mirror, reaches the detection area of the object to be detected, is reflected and forms reflected light to be emitted through the slot;
the imaging system is positioned on the propagation path of the reflected light and is used for collecting the reflected light and imaging the detection area of the object to be detected according to the reflected light.
Optionally, along the long axis direction of the ellipsoidal mirror, along the long axis direction, the maximum included angle between the connecting line of the second focal point and any point on the first arc side and the long axis direction and the maximum included angle between the connecting line of the second focal point and any point on the second arc side and the long axis direction are both γ, γ is less than or equal to 2 α, and α is greater than 0 ° and less than 90 °;
along perpendicular the direction of first cambered surface place plane, the width of slot is 2h, satisfies:
wherein α is the minimum included angle between the tangent plane of the detection area of the object to be detected and the long axis direction, a is half of the length of the long axis of the ellipsoidal mirror, b is half of the length of the short axis of the ellipsoidal mirror, c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror, and h is half of the width of the slot.
Optionally, the imaging system includes an objective lens, an optical axis of the objective lens is parallel to a plane where the first cambered surface is located, an included angle between the optical axis of the objective lens and the long axis direction is β, and β is greater than or equal to 10 ° and less than or equal to 30 °.
Optionally, along the long axis direction, the length of the slot is L, which satisfies:
optionally, the imaging system further comprises a tube lens and a CCD camera.
Optionally, the light source comprises a point light source,
the inner reflecting surface of the ellipsoidal mirror comprises scattering particles, and the scattering particles are used for scattering the detection light reaching the inner reflecting surface of the ellipsoidal mirror to form a scattering light beam;
the scattering angle of the scattered light beam relative to the detected light is theta1And satisfies the following conditions:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
Optionally, the scattering angle θ1Also satisfies:
optionally, the light source comprises a surface light source;
the diameter of the light source of the surface light source is D, and the following requirements are met:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
Optionally, the inner reflecting surface of the ellipsoidal mirror comprises a specular reflecting mirror.
Optionally, the light source comprises a bright field light source.
The embodiment of the invention discloses a curved surface detection device, which comprises a light source, an ellipsoidal mirror and an imaging system, wherein the ellipsoidal mirror is designed to be a hollow structure, the surface of the ellipsoidal mirror comprises a slot, the light source is arranged on a first focus of a long shaft of the ellipsoidal mirror by utilizing the characteristic that light emitted from one focus of the ellipsoidal reflecting bowl converges at the other focus after being reflected by the inner surface of the ellipsoidal bowl, an object to be detected passes through an opening area of the slot and is arranged on a second focus of the long shaft, reflected light is formed after the detected light emitted by the light source reaches a detected area of the object to be detected after being reflected by an inner reflecting surface of the ellipsoidal mirror and is emitted through the slot, the imaging system 3 receives the reflected light and generates an image formed by the surface of the detected area so as to identify surface defects, and the structure has the characteristics of concentrated energy and high utilization rate of the light source, and can realize bright field illumination of an edge cambered surface of the object to be detected, the edge surface defect of the object to be detected is convenient to identify.
Drawings
FIG. 1 is a schematic diagram of a bright field illumination and imaging structure of a conventional AOI inspection apparatus in the prior art;
FIG. 2 is a schematic structural diagram of a conventional AOI inspection apparatus for inspecting a circular arc surface in the prior art;
fig. 3 is a schematic XY plane structure diagram of a curved surface detection device according to an embodiment of the present invention;
fig. 4 is a schematic perspective view of an ellipsoidal mirror according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an XZ plane of a curved surface detection apparatus according to an embodiment of the present invention;
FIG. 6 is a schematic view of an edge detection light of an object to be measured according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating the requirement of the angle of the incident light at the edge of the object to be measured according to the embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of an ellipsoidal mirror according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of an ellipsoidal mirror according to an embodiment of the present invention, wherein the slot length L is satisfied;
FIG. 10 shows the scattering angle θ of the internal reflection surface of an ellipsoidal mirror according to an embodiment of the present invention1A schematic diagram of (a);
fig. 11 is a schematic view of a surface light source 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. 3 is a schematic structural diagram of a curved surface detection device according to an embodiment of the present invention; fig. 4 is a schematic perspective view of an ellipsoidal mirror according to an embodiment of the present invention; fig. 5 is a schematic cross-sectional view of an ellipsoidal mirror according to an embodiment of the present invention. The curved surface 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 and glass, identifying the edge arc surface defect and the like. As shown in fig. 3 to 5, the curved surface detection device includes a light source 1, an ellipsoidal mirror 2, and an imaging system 3; the ellipsoidal mirror 2 is a hollow structure and the surface thereof comprises a slot 20, the slot 20 comprises a first arc edge 21 and a second arc edge 22; the ellipsoidal mirror 2 further comprises a central plane where a long axis is located, and the plane where the first arc edge 21 is located and the plane where the second arc edge 22 is located are both parallel to the central plane; the light source 1 is positioned on a first focus F1 of the long shaft and is used for emitting detection light; the object 4 to be detected passes through the opening area of the slot 20 and is positioned on the second focus F2 of the long shaft, and at least part of the detection area of the object 4 to be detected is a curved surface; the detection light is reflected by the inner reflecting surface of the ellipsoidal mirror 1, reaches the detection area of the object to be detected 4, is reflected, forms reflected light and is emitted through the slot 20; the imaging system 3 is located on the propagation path of the reflected light and is used for collecting the reflected light and imaging the detection area of the object 4 to be detected according to the reflected light.
Exemplarily, as shown in fig. 3 to fig. 5, in the curved surface detecting device light source 1, the ellipsoidal mirror 2 and the imaging system 3 provided by the embodiment of the present invention, the ellipsoidal mirror 2 may also be referred to as an ellipsoidal reflecting bowl, and the ellipsoidal mirror 2 is a hollow structure. The ellipsoidal mirror 2 comprises a long axis, a plane where the long axis of the ellipsoidal mirror 2 is located is arbitrarily selected, the plane is taken as a reference plane, a first arc edge 21 is formed by slotting on the surface of the ellipsoidal mirror 2 in an area above the reference plane, a second arc edge 22 is formed by slotting on the surface of the ellipsoidal mirror 2 in an area below the reference plane, it is ensured that the plane where the first arc edge 21 is located and the plane where the second arc edge 22 is located are both parallel to the reference plane, and a slot 20 is formed on the surface of the ellipsoidal mirror 2. A detection area of the test object 4 is placed from the opening area of the slot 20, and the detection area includes an arc-shaped curved surface. The slot 20 is to ensure that the object (silicon wafer) to be measured can be inserted into the ellipsoidal mirror 2, and to ensure that the reflected light at the edge of the object (silicon wafer) to be measured can come out from the ellipsoidal mirror 2 and enter the imaging system 3,
by utilizing the characteristic that light emitted from one focus by the ellipsoidal reflector converges at the other focus after being reflected by the inner surface of the ellipsoidal reflector, the embodiment of the invention places the light source 1 at the first focus F1 of the long axis for emitting detection light, and places the edge vertex of the detection area of the object 4 to be detected at the second focus F2 of the long axis through the slot 20, for example, places the edge arc of the wafer at the second focus F2 of the long axis. According to the tangent normal theorem of the ellipse, the light emitted from F1 must pass through F2 after being reflected by the ellipsoid, and as shown in FIG. 5, the light emitted from the central point of the light source must pass through the vertex of the edge of the silicon wafer after being reflected by the ellipsoid. No matter the propagation direction of the detection light emitted from the position of the first focus F1, the detection light can reach the object 4 to be measured at the position of the second focus F2 after being reflected by the inner surface of the ellipsoidal mirror 2, and the second focus F2 can obtain incident light at different angles, so that bright field illumination of the surface of the detection area is realized. The detection light is reflected by the detection area to form reflected light, the reflected light is emitted through the slot 20, and the imaging system 3 is used for receiving the reflected light L3 and generating an image formed on the surface of the detection area. The energy of the detection light L3 reflected by the ellipsoidal mirror 2 is concentrated, the energy utilization rate of the light source is high and can reach more than 90%, the imaging system 3 is favorable for imaging, and the surface defect of the object to be detected is convenient to observe.
To sum up, the curved surface detection device provided by the embodiment of the present invention includes a light source, an ellipsoidal mirror and an imaging system, wherein the ellipsoidal mirror is designed to be a hollow structure, the surface of the ellipsoidal mirror includes a slot, the light source is arranged on a first focus of a long axis of the ellipsoidal mirror by utilizing the characteristic that light emitted from one focus of the ellipsoidal reflecting bowl converges at another focus after being reflected by the inner surface of the ellipsoidal bowl, an object to be detected passes through an opening area of the slot and is arranged on a second focus of the long axis, the detection light emitted by the light source reaches a detection area of the object to be detected after being reflected by the inner reflecting surface of the ellipsoidal mirror to form reflected light to be emitted through the slot, the imaging system 3 receives the reflected light and generates an image formed on the surface of the detection area, and further identifies surface defects, the structure has the characteristics of concentrated light source energy and high utilization rate, and can realize bright field illumination of the edge arc surface of the object to be detected, the edge surface defect of the object to be detected is convenient to identify.
FIG. 6 is a schematic view of an edge detection light of an object to be measured according to an embodiment of the present invention; FIG. 7 is a schematic diagram illustrating the requirement of the angle of the incident light at the edge of the object to be measured according to the embodiment of the present invention; fig. 8 is a schematic cross-sectional view of an ellipsoidal mirror according to an embodiment of the present invention. As shown in fig. 3-8, optionally, along the long axis direction (as shown in the X direction in the figure) of the ellipsoidal mirror 2, the maximum included angle between the connection line of the second focal point F2 and any point on the first arc edge 21 and the long axis direction and the maximum included angle between the connection line of the second focal point F2 and any point on the second arc edge 22 and the long axis direction are both γ, γ is less than or equal to 2 α, and α is greater than 0 ° and less than 90 °; along a direction perpendicular to the plane of the first arc surface 21, the width of the slot 20 is 2h, which satisfies:
wherein, alpha is the minimum included angle between the tangent plane of the detection area of the object to be detected and the long axis direction, a is half of the length of the long axis of the ellipsoidal mirror, b is half of the length of the short axis of the ellipsoidal mirror, c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror, and h is half of the width of the slot.
In particular, as shown in connection with fig. 3-8. Because at least part of the surface of the edge of the detection area of the object 4 to be detected is an arc surface, for example, the edge of a silicon wafer has an arc surface with a larger radian when the edge of the silicon wafer is detected. As shown in fig. 6, incident light of each angle is irradiated on the arc surface, and specular reflection occurs, and the light enters the imaging system 3 at 0 ° to be imaged. An included angle α between a tangent line of the edge of the silicon wafer and a long axis direction (e.g., an X direction in the figure, or a horizontal line) is usually 0 to 90 °, and then bright field illumination needs to provide light rays with an incident angle of more than- (180 ° -2 α) to the silicon wafer, as shown in fig. 7, optionally, the light source 1 includes a bright field light source. For example, when a light source of an LED filament emits light at 360 degrees, under the condition that the ellipsoidal mirror 2 is complete, incident light received at the vertex of the edge of a silicon wafer is reflected by an ellipsoidal surface of the inner surface of the whole ellipsoidal mirror 2 and is also in the opposite direction of 360 degrees, and the requirements of incident angle light rays of more than- (180-2 alpha) are met in the vertex area of the edge of the silicon wafer. Because the ellipsoidal mirror 2 has a slot, a part of the incident light received at the vertex of the silicon edge is missing, and the width 2h of the slot 20 can be controlled, so that the included angle γ between the F2 and the first arc side 21 (indicated by the point M in fig. 8) of the ellipsoidal mirror 2 and the long axis direction (indicated by the direction X in the figure, or the horizontal line), and the included angle γ between the F2 and the second arc side 22 (indicated by the point N in fig. 8) of the ellipsoidal mirror 2 and the long axis direction (indicated by the direction X in the figure, or the horizontal line), satisfy γ ≦ 2 α, as shown in fig. 8, at which time the incident light of- (180 ° -2 α) can be received at the vertex of the silicon edge for bright field illumination.
Further, in the XY plane of the ellipsoidal mirror, the elliptic equation satisfied by combining the ellipsoidal mirror 2 is
a is half of the length of the major axis of the ellipsoidal mirror, b is half of the length of the minor axis of the ellipsoidal mirror, and c is half of the distance between the first focus F1 and the second focus F2 of the major axis of the ellipsoidal mirror. Wherein, in the XY plane, the coordinates of F2 are (c,0), c2＝a2-b2The M point coordinate is (
h) Then half the width h of the slot 20 should satisfy the following equation:
after the major axis and the minor axis of the ellipsoidal mirror 2 and the included angle α between the object 4 to be measured and the major axis direction (such as the X direction in the figure, or the horizontal line) are determined, the width 2h of the slot 20 is set, so that the vertex of the edge of the silicon wafer (object to be measured) can receive incident light of- (180 ° -2 α), so that the object to be measured can obtain incident light of different angles, and the requirement of edge bright field illumination is met.
Figure 9 is a schematic diagram of the slot length L setting of an ellipsoidal mirror provided by an embodiment of the invention. As shown in fig. 3-9, optionally, the imaging system 3 includes an objective lens having an optical axis L0Parallel to the plane of the first cambered surface and the optical axis L of the objective lens0The included angle between the long axis direction and the beta is beta, and the beta is more than or equal to 10 degrees and less than or equal to 30 degrees.
Illustratively, as shown in fig. 9, the imaging system 3 includes an objective lens (not shown in the figure, which is disposed in the imaging system 3) for magnifying the edge image of the object to be measured and improving the imaging quality. Setting the optical axis L of an objective lens0Parallel to the plane of the first cambered surface, i.e. in the XY plane parallel to the surface of the object to be measured (silicon wafer)0The included angle between the incident light and the reflected light is beta, i.e. the incident light and the reflected light on the surface of the object to be measured have a certain included angle beta, preferably, beta is more than or equal to 10 degrees and less than or equal to 30 degrees, so as to ensure that the reflected light reflected by the surface of the object to be measured 4 exits through the slot 20 and then follows the optical axis L of the objective lens0Enter the objective lens to be amplified and then enter the imaging system to be imaged. Optionally, the imaging system further includes a tube lens and a CCD camera, the reflected light amplified by the objective lens is incident to a photosensitive plane of the CCD camera through the tube lens in parallel, and the CCD camera images the surface of the object to be measured, which may be a color or black-and-white image, facilitating edge defect identification.
On the basis of the above embodiment, optionally, the length of the slot along the long axis direction is L, which satisfies:
exemplary, with continued reference toAs shown in fig. 3-9, further, if the reflected light at the edge of the object to be measured (silicon wafer) can exit from the ellipsoidal mirror 2 and enter the objective lens, the length L of the slot 20 needs to be limited. As shown in fig. 8 and 9, when the reflected light exits through the T point of the opening area of the slot 20, according to the included angle β between the incident light and the reflected light, in the ellipse equation, along the major axis direction, L1 is H/tan β, H is parallel to the minor axis of the ellipse, and H is<2b, 2b is the minor axis length of the ellipsoidal mirror, and the length of the slot 20 is set to L > L1+ a-c, the length of the slot 20
During the process, the reflected light at the edge of the object to be measured (silicon wafer) can enter the objective lens after coming out of the ellipsoidal mirror 2. In practical silicon chip edge detection applications, a region of a silicon chip edge is detected, not just an edge vertex, and incident light of- (180-2 alpha) needs to be in the detected region. On the basis of the above embodiment, by reasonably adjusting the width 2h and the length L of the slot 20, firstly, the width 2h of the slot can satisfy that the included angle γ between the connection line of each point in the detection area of the object (the detection point of the detection area of the object is located at the second focus F2) and the first arc side S1 (shown as point M in fig. 8) of the slot 20 or the second arc side S2 (shown as point N in fig. 8) of the slot 20 and the long axis direction is less than or equal to 2 α; secondly, each point in the detection area of the object to be detected 4 can receive the reflected light reflected by each point of the internal reflection surface of the elliptical mirror 2, so that the incident light of- (180-2 alpha) is satisfied in the detection area of the object to be detected 3, and bright field illumination of the edge of the object to be detected is formed.
FIG. 10 shows an ellipsoidal mirror according to an embodiment of the present invention, in which the scattering angle of the internal reflection surface is θ1Schematic representation of (a). As shown in fig. 3-10, alternatively, the light source 1 includes a point light source, and the inner reflecting surface of the ellipsoidal mirror 2 includes scattering particles (not shown in the figure) for scattering the detection light reaching the inner reflecting surface of the ellipsoidal mirror to form a scattered light beam; the scattering angle of the scattered light beam relative to the detected light is theta1And satisfies the following conditions:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
Illustratively, in conjunction with fig. 10, the light source 1 includes a point light source, and the point light source provided by the embodiment of the present invention refers to a light source that can uniformly emit light in all directions, such as an LED lamp. By disposing the point light source at the first focus F1, the internal reflection surface of the ellipsoidal mirror 2 can be made into a scattering surface with a certain scattering angle by adding scattering particles on the internal reflection surface of the ellipsoidal mirror 2, so that all the detection light emitted from the light source and incident on the internal reflection surface of the ellipsoidal mirror 2 can be changed into a light with a certain divergence angle θ after being scattered1Of the scattered light beam, i.e. the scattered light beam has a scattering angle theta with respect to the detection light1Or the scattering angle theta of the internal reflection surface of the ellipsoidal mirror 21。
Further adjusting the scattering surface formed by the scattering particles according to the size of the detection area 31 to be detected 3, and further adjusting the scattering angle theta of the scattered light beam relative to the detection light1So that scattered light can cover the detected region 31. Specifically, the size of the detection region is known as w × t, where w is the length of the detection region of the analyte, and t is the width of the detection region of the analyte. The distance between a certain point P of the internal reflection surface of the ellipsoidal mirror 2 and the second focus F2 is l1And l is1The beam scattered by the point P, which is much larger than w and t, covers exactly the detection area 31. The divergence angle of the scattered light emitted from the point P relative to the incident detection light is theta1And the intersection point with the edge of the detection region 31 is K, Q, the condition is satisfied
Where KQ is the distance between the foci K and Q, and l is known1Smaller theta1The larger the KQ, the larger θ1The larger, when KQ is the largest
In the XZ plane of FIG. 10, according to the ellipse equation
If the coordinates of the point P are (x, z), l1The expression of (a) is as follows:
where-a ≦ x ≦ a, and when x ≦ a, l1Minimum is l1A-c, then theta1Has a maximum value of
Setting the scattering angle of the internal reflection surface of the elliptical mirror 2
By the angle of scattering theta1And (2) limiting, each position point of the detected area of the object to be detected 4 can receive the reflected light from each position point of the internal reflecting surface of the ellipsoidal mirror 2, and further setting the included angle between the connecting line of each position point of the detected area 31 of the object to be detected 4 and each position of the ellipsoidal reflecting surface and the long axis direction (horizontal line) to satisfy (180-2 alpha) - (180-2 alpha), so that each point in the detected area 31 can receive the incident light of (180-2 alpha) - (180-2 alpha), and the edge bright field illumination is realized.
Alternatively, the scattering angle θ1And further satisfies:
further, the scattering angle theta of the scattered light beam with respect to the detected light is defined1I.e. the internal reflection surface scattering angle theta of the elliptical mirror1Satisfy the following requirements
Excessive scattering angle theta1Will havePart of the scattered light exceeding the detection area 31 causes a waste of light energy by varying the scattering angle theta1Is limited to
Within the range, each point in the detection area 31 can receive incident light of- (180-2 alpha), and the light energy utilization rate is higher than 90%, so that the light source energy is fully utilized, the imaging quality can be improved, and the defects of the detection area 31 can be favorably identified.
Fig. 11 is a schematic view of a surface light source according to an embodiment of the present invention. As shown in fig. 11, alternatively, the light source includes a surface light source; the light source diameter of the surface light source is D, and the following requirements are met:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
Exemplarily, as shown in fig. 11, the light source 1 includes a surface light source, which refers to a light source having a light emitting region with a certain length and width, such as a flat light source. Selecting a circular surface light source with the diameter D of the light source, wherein the light emitting surface of the light source 1 has a certain size, so that the light rays emitted from the light source 1 to any point of the internal reflection surface of the ellipsoidal mirror 2 have a certain divergence angle theta2Optionally, the internal reflecting surface of the ellipsoidal mirror 2 comprises a specular mirror. The divergent beams incident on the mirror surface reflector are reflected to form a beam having the same divergent angle theta2The divergent light beam reaches the position of a second focus F2 of the ellipsoidal mirror 2, and the size of the light emitting surface of the light source 1 is controlled to make the scattering angle of the light source 1 to each point of the internal reflecting surface of the ellipsoidal mirror 2 be theta2Satisfy the inequality
Making the reflection by internal reflecting surfacesThe emitted light can cover the detection area 31 of the object 4 to be measured. Since the diameter of the circular light emitting surface of the light source 1 is D, the inequality is satisfied:
namely, it is
Therefore, the included angle between the connecting line of each position point in the detection area 31 and each position on the internal reflection surface of the ellipsoidal mirror 2 and the long axis direction (horizontal line) is satisfied to be (180-2 alpha) - (180-2 alpha), the incident light of (180-2 alpha) - (180-2 alpha) can be received by each point in the detection area 31 of the object 4 to be detected, bright field illumination of the detection area 31 is formed, under the condition of adopting a surface light source, the light energy utilization rate is still high and reaches more than 90%, and the light source energy is fully utilized.
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 curved surface detection device is characterized by comprising a light source, an ellipsoidal mirror and an imaging system;
the ellipsoidal mirror is a hollow structure and the surface of the ellipsoidal mirror comprises a slot, wherein the slot comprises a first arc edge and a second arc edge; the ellipsoidal mirror also comprises a central plane where a long shaft is located, and the central plane is parallel to the plane where the first arc edge is located and the plane where the second arc edge is located respectively;
the light source is positioned on the first focus of the long shaft and used for emitting detection light; the object to be detected penetrates through the opening area of the slot and is positioned on the second focus of the long shaft, and at least part of the detection area of the object to be detected is a curved surface; the detection light is reflected by the inner reflecting surface of the ellipsoidal mirror, reaches the detection area of the object to be detected, is reflected and forms reflected light to be emitted through the slot;
the imaging system is positioned on the propagation path of the reflected light and is used for collecting the reflected light and imaging the detection area of the object to be detected according to the reflected light.
2. The curved surface detection device according to claim 1, wherein, in the long axis direction of the ellipsoidal mirror, the maximum angle between the line connecting the second focal point and any point on the first arc side and the long axis direction and the maximum angle between the line connecting the second focal point and any point on the second arc side and the long axis direction are both γ,
γ≤2α，0°＜α＜90°；
along perpendicular the direction of first cambered surface place plane, the width of slot is 2h, satisfies:
wherein α is the minimum included angle between the tangent plane of the detection area of the object to be detected and the long axis direction, a is half of the length of the long axis of the ellipsoidal mirror, b is half of the length of the short axis of the ellipsoidal mirror, c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror, and h is half of the width of the slot.
3. The curved surface detection device of claim 2, wherein the imaging system comprises an objective lens, an optical axis of the objective lens is parallel to a plane of the first curved surface, an included angle between the optical axis of the objective lens and the long axis direction is β, and β is greater than or equal to 10 ° and less than or equal to 30 °.
4. The curved surface detecting device according to claim 3, characterized in thatCharacterized in that along the long axis direction, the length of the slot is L, satisfying:
5. the curved surface detecting device according to claim 3, wherein the imaging system further comprises a tube mirror and a CCD camera.
6. The curved surface detecting device according to claim 1, wherein the light source includes a point light source;
the inner reflecting surface of the ellipsoidal mirror comprises scattering particles, and the scattering particles are used for scattering the detection light reaching the inner reflecting surface of the ellipsoidal mirror to form a scattering light beam;
the scattering angle of the scattered light beam relative to the detected light is theta1And satisfies the following conditions:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
7. The curved surface detection device of claim 6, wherein the scattering angle θ1Also satisfies:
8. the curved surface inspection device of claim 1, wherein the light source comprises a surface light source;
the diameter of the light source of the surface light source is D, and the following requirements are met:
w is the length of the detection area of the object to be detected, t is the width of the detection area of the object to be detected, a is half of the length of the long axis of the ellipsoidal mirror, and c is half of the distance between the first focus and the second focus of the long axis of the ellipsoidal mirror.
9. The curved surface detecting device according to claim 8, wherein the inner reflecting surface of the ellipsoidal mirror comprises a specular mirror.
10. The curved surface inspection device of claim 1, wherein the light source comprises a bright field light source.
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