Sham lens, structured light projection device and visual inspection system

Abstract

The present invention belongs to the field of optical imaging, and in particular relates to a Sham lens, a structured light projection device, and a visual detection system. The Sham lens includes a first cylindrical lens group, a second cylindrical lens group, a first spherical lens group, and a second spherical lens group, which are sequentially distributed along the optical axis from the object side to the image side. The generatrix of the first cylindrical lens group is orthogonal to the generatrix of the second cylindrical lens group, and the focal length f in the long side direction of the image captured by the Sham lens is Y The focal length f of the short side of the image captured by the Sham lens X Satisfying 1.4≤|f Y / f X |≤2.2. This means it can achieve an aspect ratio of 1.4 to 2.2 times, reducing the waste of resolution along the long side of the chip, improving projection effects, and thus enhancing the accuracy of structured light 3D detection.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a Sham lens, a structured light projection device, and a visual detection system. Background Art

[0002] Machine vision inspection has gradually transformed from traditional 2D to 3D. For example, 3D vision inspection is used in semiconductor chips and SMT (Surface Mount Technology). Specifically, semiconductor chip 3D inspection targets the tin ball morphology on the chip surface. SMT 3D inspection mainly includes solder paste thickness inspection before patching (SPI, short for Solder Paste Inspection) and surface mount component quality inspection after patching (AOI, short for Automated Optical Inspection, i.e. automatic optical inspection). In order to achieve 3D inspection, such as Figure 1 As shown in Figure 1, the use of structured light oblique projection is the current mainstream solution. The structured light projection system is mainly composed of a grating generator and a projection lens.

[0003] Currently, most manufacturers use FA lenses (Factory Automation, industrial lenses) as projection lenses. Because the angle does not satisfy Sham's law, the lens cannot focus clearly at both near and far distances during tilted projection. At the same time, the application scenarios of FA lenses and projection lenses are significantly different. Projection lenses require a telecentric optical path design, but FA lenses do not meet this requirement. When using FA lenses as projection lenses, the brightness and contrast consistency of the projected pattern is poor. To address the above issues, some manufacturers use tilt-shift lenses as projection lenses. However, since the aspect ratio of the DLP (Digital Light Processing) chip used for structured light projection in structured light projection systems is typically 16:9, this results in a waste of resolution along the long side of the chip and limits 3D detection accuracy. Summary of the Invention

[0004] The embodiments of the present invention provide a Sham lens, a structured light projection device, and a visual inspection system, which aim to reduce the waste of resolution in the long side direction of the chip, improve the projection effect, and enhance the accuracy of structured light 3D detection.

[0005] To this end, according to one aspect of the present invention, a Sham lens is provided, comprising a first cylindrical lens group, a second cylindrical lens group, a first spherical lens group, and a second spherical lens group, which are sequentially distributed along the optical axis from the object side to the image side. The generatrix of the first cylindrical lens group is orthogonal to the generatrix of the second cylindrical lens group, and the focal length f in the long side direction of the image captured by the Sham lens is Y The focal length f of the short side of the image captured by the Sham lens isX Satisfying 1.4≤|f Y / f X |≤2.2.

[0006] Optionally, the first cylindrical lens group includes a first cylindrical lens with positive optical power and a second cylindrical lens with negative optical power, and the generatrix of the first cylindrical lens and the generatrix of the second cylindrical lens are both parallel to the short side of the image captured by the Sham lens;

[0007] The second cylindrical lens group includes a third cylindrical lens with negative optical power and a fourth cylindrical lens with positive optical power. The generatrix of the third cylindrical lens and the generatrix of the fourth cylindrical lens are both parallel to the long side direction of the picture shot by the Sham lens.

[0008] Optionally, the first spherical lens group and the second spherical lens group form a double Gaussian structure.

[0009] Optionally, the first spherical lens group is a spherical lens with positive optical power;

[0010] The second spherical lens group includes a first cemented lens with negative optical power, an aperture, a second cemented lens with negative optical power, a meniscus lens with positive optical power, and a plano-convex lens with positive optical power, which are distributed in sequence from the object side to the image side along the optical axis.

[0011] Optionally, the first spherical lens group or the second spherical lens group includes at least one positive power lens, and the relative refractive index temperature coefficient dn / dt of the positive power lens satisfies the following condition:

[0012] -10.0×10 -6 / ℃≤dn / dt≤-3.0×10 -6 / ℃.

[0013] Optionally, during the focusing process, the first cylindrical lens group, the second cylindrical lens group and the first spherical lens group move back and forth along the optical axis as a whole.

[0014] According to another aspect of the present invention, there is provided a structured light projection device comprising a DLP chip and the Sham lens as described above, wherein the plane where the effective surface of the DLP chip is located, the plane perpendicular to the axis of the Sham lens, and the projection surface of the Sham lens satisfy Sham's law.

[0015] Optionally, the angle α between the projection surface of the Sham lens and the axis of the Sham lens and the angle β between the plane where the effective surface of the DLP chip is located and the axis of the Sham lens meet the following conditions:

[0016] 0.2≤|tanα / tanβ|≤0.3.

[0017] Optionally, the structured light projection device also includes an illumination light path, a uniform light path and a TIR prism, wherein the uniform light path is used to uniformly distribute the outgoing light of the illumination light path; the TIR prism is used to adjust the angle of the outgoing light of the uniform light path and reflect the outgoing light of the DLP chip onto the Sham lens for imaging.

[0018] According to another aspect of the present invention, a visual inspection system is provided, comprising the Sham lens as described above or the structured light projection device as described above.

[0019] The beneficial effects of the Sham lens, structured light projection device, and visual detection system provided by the present invention are as follows: compared with the prior art, the busbars of the first cylindrical lens group near the object side and the busbars of the second cylindrical lens group in the Sham lens of the present invention are orthogonal to each other, which can effectively reduce the number of lenses, compress the overall volume of the lens, and achieve high contrast and large depth of focus. The focal length f in the long side direction of the image captured by the Sham lens is Y The focal length f of the short side of the image captured by the Sham lens X Satisfying 1.4≤|f Y / f X |≤2.2, which means that an aspect ratio of 1.4 to 2.2 times can be achieved, reducing the waste of resolution in the long side direction of the chip, improving the projection effect, and thus enhancing the accuracy of structured light 3D detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] in:

[0022] Figure 1 This is a schematic diagram of using structured light oblique projection in 3D detection;

[0023] Figure 2 1 is a schematic cross-sectional view of a Sham lens in the YZ plane according to an embodiment of the present invention;

[0024] Figure 3 1 is a schematic cross-sectional view of a Sham lens in an XZ plane according to an embodiment of the present invention;

[0025] Figure 4 1 is a schematic diagram of an optical path of a Sham lens in an oblique projection state used in a structured light projection device according to an embodiment of the present invention;

[0026] Figure 5 1 is an MTF diagram of a Sham lens according to an embodiment of the present invention;

[0027] Figure 6 1 is a defocus diagram of a Sham lens according to an embodiment of the present invention;

[0028] Figure 7 is a schematic structural diagram of a structured light projection device according to an embodiment of the present invention;

[0029] Figure 8 FIG1 is a schematic diagram of a structured light projection device in use according to an embodiment of the present invention.

[0030] Description of main component symbols:

[0031] 10. Sham lens;

[0032] 20. DLP chip;

[0033] 30. TIR prism;

[0034] 100, first cylindrical lens group; 110, first cylindrical lens; 120, second cylindrical lens;

[0035] 200, second cylindrical lens group; 210, third cylindrical lens; 220, fourth cylindrical lens;

[0036] 300, first spherical lens group;

[0037] 400 , second spherical lens group; 410 , first cemented lens; 420 , aperture; 430 , second cemented lens; 440 , meniscus lens; 450 , plano-convex lens. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many other forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0039] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0040] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] As mentioned in the background, most manufacturers currently use FA lenses for oblique structured light projection in 3D visual inspection, resulting in poor brightness and contrast consistency in the projected pattern. While some manufacturers use tilt-shift lenses, the DLP chips used for structured light projection in structured light projection systems typically have a 16:9 aspect ratio. This results in wasted resolution along the chip's long side, limiting 3D inspection accuracy.

[0044] In order to solve the above problems, according to one aspect of the present invention, an embodiment of the present invention provides a Sham lens, such as Figure 2-Figure 3 As shown, the Sham lens 10 includes a first cylindrical lens group 100, a second cylindrical lens group 200, a first spherical lens group 300, and a second spherical lens group 400, which are sequentially distributed along the optical axis from the object side to the image side. The generatrix of the first cylindrical lens group 100 is orthogonal to the generatrix of the second cylindrical lens group 200, and the focal length f in the long side direction (the direction of the Y axis in the figure) of the image captured by the Sham lens 10 is Y The focal length f of the short side direction (the direction of the X axis in the figure) of the image captured by the Sham lens 10 is X Satisfying 1.4≤|f Y / f X |≤2.2.

[0045] In the embodiment of the present invention, the generatrix of the first cylindrical lens group 100 near the object side and the generatrix of the second cylindrical lens group 200 in the Sham lens 10 are orthogonal to each other, which can effectively reduce the number of lenses, compress the overall volume of the lens, and achieve high contrast and large depth of focus. The focal length f in the long side direction of the image captured by the Sham lens 10 is Y The focal length f of the short side of the image captured by the Sham lens 10 is X Satisfying 1.4≤|f Y / f X |≤2.2, which means it can achieve an aspect ratio of 1.4 to 2.2 times, and can achieve a 16:9 widening to 1:1 (i.e., a 1.8-fold aspect ratio), reducing the waste of resolution in the long side direction of the chip, improving the projection effect, and thus enhancing the accuracy of structured light 3D detection.

[0046] It is understandable that the Sham lens 10 is not limited to use in structured light projection devices in the field of machine vision detection, but can also be used in other projection equipment to reduce the waste of resolution in the long side direction of the chip and improve the projection effect.

[0047] Preferably, in order to save costs, the focal length f of the long side of the image captured by the Sham lens 10 is Y The focal length f of the short side of the image captured by the Sham lens 10 is X Satisfying 1.6≤|f Y / f X |≤2.

[0048] In one embodiment, if Figure 2-Figure 3 As shown, the first cylindrical lens group 100 includes a first cylindrical lens 110 having positive refractive power and a second cylindrical lens 120 having negative refractive power. The generatrix of the first cylindrical lens 110 and the generatrix of the second cylindrical lens 120 are both parallel to the short side of the image captured by the Sham lens 10 (i.e., the direction of the X-axis in the figure).

[0049] The second cylindrical lens group 200 includes a third cylindrical lens 210 with negative optical power and a fourth cylindrical lens 220 with positive optical power. The busbars of the third cylindrical lens 210 and the busbars of the fourth cylindrical lens 220 are both parallel to the long side direction of the image captured by the Sham lens 10 (i.e., the direction of the Y axis in the figure).

[0050] Through the above arrangement, the astigmatism between the meridional and sagittal directions introduced by the cylindrical lens is effectively reduced. At the same time, the combination of cylindrical lenses with positive and negative optical powers can reduce the field curvature of the system and ensure consistency in different fields of view.

[0051] In one embodiment, if Figure 2-Figure 3 As shown, the first spherical lens group 300 and the second spherical lens group 400 form a double Gaussian structure.

[0052] The double Gaussian structure formed by the first spherical lens group 300 and the second spherical lens group 400 can effectively balance various aberrations (including spherical aberration, astigmatism, field curvature, etc.) in the system.

[0053] In a specific embodiment, Figure 2-Figure 3 As shown, the first spherical lens group 300 is a spherical lens with positive optical power;

[0054] The second spherical lens group 400 includes a first cemented lens 410 with negative optical power, an aperture 420, a second cemented lens 430 with negative optical power, a meniscus lens 440 with positive optical power, and a plano-convex lens 450 with positive optical power, which are distributed in sequence from the object side to the image side along the optical axis.

[0055] Through the above arrangement, the first spherical lens group 300 and the second spherical lens group 400 form a typical double-Gaussian architecture.

[0056] In some specific embodiments, the first spherical lens group 300 or the second spherical lens group 400 includes at least one positive power lens, and the relative refractive index temperature coefficient dn / dt of the positive power lens satisfies the following conditions:

[0057] -10.0×10 -6 / ℃≤dn / dt≤-3.0×10 -6 / ℃.

[0058] In this way, the imaging system can be kept athermal and the image plane drift caused by different ambient temperatures of the imaging system can be effectively balanced.

[0059] In some specific embodiments, during the focusing process of the Sham lens 10 , the first cylindrical lens group 100 , the second cylindrical lens group 200 and the first spherical lens group 300 move back and forth along the optical axis as a whole.

[0060] The first cylindrical lens group 100, the second cylindrical lens group 200 and the first spherical lens group 300 move back and forth as a whole to compensate for image plane offset caused by lens thickness, air space and back focus tolerance. The floating focus has high stability and is convenient for actual machine installation and adjustment operations.

[0061] In one embodiment, if Figure 2-Figure 3 As shown, the Sham lens 10 includes, from the object side to the image side, the following components:

[0062] a first cylindrical lens 110 having positive refractive power, comprising a first surface (convex surface) located on the object side and a second surface (concave surface) located on the image side;

[0063] a second cylindrical lens 120 having negative optical power, comprising a third surface (convex surface) located on the object side and a fourth surface (concave surface) located on the image side;

[0064] a third cylindrical lens 210 having negative optical power, comprising a fifth surface (concave surface) located on the object side and a sixth surface (concave surface) located on the image side;

[0065] a fourth cylindrical lens 220 having positive refractive power, comprising a seventh surface (convex surface) located on the object side and an eighth surface (convex surface) located on the image side;

[0066] A spherical lens having positive optical power, comprising a ninth surface (convex surface) located on the object side and a tenth surface (concave surface) located on the image side;

[0067] a first cemented lens 410 having negative optical power, comprising an eleventh surface (convex surface) located on the object side, a twelfth surface (flat surface) at the cemented portion, and a thirteenth surface (concave surface) located on the image side;

[0068] Aperture 420;

[0069] a second cemented lens 430 having negative refractive power, comprising a fifteenth surface (concave surface) located on the object side, a sixteenth surface (flat surface) at the cemented portion, and a seventeenth surface (convex surface) located on the image side;

[0070] a meniscus lens 440 having positive optical power, comprising an eighteenth surface (concave surface) located on the object side and a nineteenth surface (convex surface) located on the image side;

[0071] The plano-convex lens 450 has positive refractive power and includes a 20th surface (convex surface) located on the object side and a 21st surface (flat surface) located on the image side.

[0072] like Figure 4 As shown in FIG. 1 , in a structured light projection device, a Sham lens 10 is used in conjunction with a TIR (Total Internal Reflector) prism and a DLP chip 20 as a light path diagram, wherein the TIR prism 30 includes a 22nd surface (plane) located on the object side and a 23rd surface (plane) located on the image side. The following examples illustrate the parameters of each lens of the present invention:

[0073]

[0074]

[0075] In this embodiment, the Sham lens 10 has an aspect ratio of 1.8, a total lens length of 68.11 mm, a maximum aperture Fno=3.2, a projection angle of 25°, a maximum imaging surface Φ of 12.4 mm, and a resolution of 140 lp / mm.

[0076] refer to Figure 5, shows the MTF (Modulation Transfer Function) diagram of the Sham lens provided in this embodiment, where the horizontal axis represents frequency in line pairs / mm, and the vertical axis represents contrast. It can be seen from the figure that the full field of view of 70 line pairs / mm is greater than 0.5.

[0077] refer to Figure 6 , which shows the defocus diagram of the Sham lens, the horizontal axis represents the focus displacement in mm, and the vertical axis represents the MTF value. It can be seen from the figure that the depth of focus is 0.1mm.

[0078] In this embodiment, the Sham lens 10 satisfies Sham's law, has a telecentric image space design, and achieves a 16:9 aspect ratio widened to a 1:1 aspect ratio, which significantly improves the projection effect and is of great significance to the improvement of the structured light 3D detection accuracy.

[0079] According to another aspect of the present invention, an embodiment of the present invention further provides a structured light projection device, such as Figure 7-Figure 8 As shown, the structured light projection device includes a DLP chip 20 and a Sham lens 10 in any of the above embodiments. The plane where the effective surface of the DLP chip 20 is located, the vertical plane of the axis of the Sham lens 10, and the projection surface of the Sham lens 10 satisfy Sham's law.

[0080] Since the structured light projection device adopts the Sham lens 10 in the above embodiment, it also has the advantages and benefits brought by the above Sham lens 10. By widening the Sham lens 10, the waste of the long side resolution of the DLP chip 20 is reduced, the projection effect is improved, and the structured light 3D detection accuracy is further improved.

[0081] In one embodiment, if Figure 8 As shown, the angle α between the projection surface of the Sham lens 10 and the axis of the Sham lens 10 and the angle β between the plane where the effective surface of the DLP chip 20 is located and the axis of the Sham lens 10 meet the following conditions: 0.2≤|tanα / tanβ|≤0.3.

[0082] This design ensures that the pattern can be clearly focused both near and far during oblique projection.

[0083] In one embodiment, if Figure 7 As shown, the structured light projection device also includes an illumination light path (not shown in the figure), a uniform light path (not shown in the figure) and a TIR prism 30. The uniform light path is used to uniformly light the outgoing light of the illumination light path; the TIR prism 30 is used to adjust the angle of the outgoing light of the uniform light path and reflect the outgoing light of the DLP chip 20 onto the Sham lens 10 for imaging.

[0084] According to yet another aspect of the present invention, an embodiment of the present invention further provides a visual inspection system, comprising the above-mentioned Sham lens 10 or the above-mentioned structured light projection device.

[0085] Since the visual inspection system adopts the Sham lens 10 or the structured light projection device in the above embodiment, it is beneficial to improve the accuracy of structured light 3D inspection.

[0086] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] The above embodiments merely illustrate several embodiments of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of the present invention. Therefore, the scope of the present invention shall be determined by the appended claims.

Claims

1. A Sham lens, characterized in that: The invention comprises a first cylindrical lens group, a second cylindrical lens group, a first spherical lens group and a second spherical lens group which are sequentially distributed along the optical axis from the object side to the image side. The generatrix of the first cylindrical lens group is orthogonal to the generatrix of the second cylindrical lens group. The focal length f of the long side of the image captured by the Sham lens is Y The focal length f of the short side of the image captured by the Sham lens is X Satisfying 1.4≤|f Y / f X |≤2.

2.

2. The Sham lens according to claim 1, wherein: The first cylindrical lens group includes a first cylindrical lens with positive optical power and a second cylindrical lens with negative optical power, wherein the generatrix of the first cylindrical lens and the generatrix of the second cylindrical lens are both parallel to the short side of the image captured by the Sham lens; The second cylindrical lens group includes a third cylindrical lens with negative optical power and a fourth cylindrical lens with positive optical power. The generatrix of the third cylindrical lens and the generatrix of the fourth cylindrical lens are both parallel to the long side direction of the picture shot by the Sham lens.

3. The Sham lens according to claim 1, wherein: The first spherical lens group and the second spherical lens group form a double Gaussian structure.

4. The Sham lens according to claim 3, wherein: The first spherical lens group is a spherical lens with positive optical power; The second spherical lens group includes a first cemented lens with negative optical power, an aperture, a second cemented lens with negative optical power, a meniscus lens with positive optical power, and a plano-convex lens with positive optical power, which are distributed in sequence from the object side to the image side along the optical axis.

5. The Sham lens according to claim 1, 3 or 4, characterized in that: The first spherical lens group or the second spherical lens group includes at least one positive power lens, and the relative refractive index temperature coefficient dn / dt of the positive power lens satisfies the following conditions: -10.0×10 -6 / ℃≤dn / dt≤-3.0×10 -6 / ℃。 6. The Sham lens according to any one of claims 1 to 4, characterized in that: During the focusing process, the first cylindrical lens group, the second cylindrical lens group and the first spherical lens group move back and forth along the optical axis as a whole.

7. A structured light projection device, characterized in that: It comprises a DLP chip and the Sham lens according to any one of claims 1 to 6, wherein the plane where the effective surface of the DLP chip is located, the vertical plane of the axis of the Sham lens, and the projection surface of the Sham lens satisfy Sham's law.

8. The structured light projection device according to claim 7, wherein: The angle α between the projection surface of the Sham lens and the axis of the Sham lens and the angle β between the plane where the effective surface of the DLP chip is located and the axis of the Sham lens meet the following conditions: 0.2≤|tanα / tanβ|≤0.

3.

9. The structured light projection device according to claim 7 or 8, characterized in that: The structured light projection device also includes an illumination light path, a uniform light path and a TIR prism. The uniform light path is used to uniformly emit light from the illumination light path; the TIR prism is used to adjust the angle of the output light from the uniform light path and reflect the output light from the DLP chip onto the Sham lens for imaging.

10. A visual inspection system, characterized in that: It comprises the Sham lens as described in any one of claims 1-6 or the structured light projection device as described in any one of claims 7-9.

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