Shim lenses and industrial cameras

Abstract

The application provides a Schmitt lens for an industrial camera, comprising: a first lens group, a second lens group and a third lens group arranged in sequence from an object side to an image side along a lens optical axis, wherein the first lens group, the second lens group and the third lens group are all positive lens groups; wherein the second lens group is used as an aperture stop of the Schmitt lens, a ratio of an aperture of the third lens group to an aperture of the first lens group is 0.6-1.1, and the number of lenses in the first lens group is equal to the number of lenses in the third lens group. The Schmitt lens for industrial 3D measurement is optimized and designed, the requirement of clear imaging of the target full field of view is met, and the Schmitt lens has the characteristics of small volume, high resolution and low distortion.

Description

Technical Field

[0001] This disclosure relates to the field of optical systems technology, and more particularly to a SAM lens for an industrial camera and an industrial camera. Background Technology

[0002] With the development of image processing and computer technology, 3D non-contact measurement technology has emerged. It has advantages such as high precision, high speed, and high stability. The lens is an important component of this technology. Resolution and distortion affect the accuracy of 3D point cloud reconstruction, and traditional lenses are limited by the near-to-far imaging principle and depth of field, making it difficult to achieve clear imaging of the target across the entire field of view.

[0003] Applying Scherram's law in the imaging optical path can yield a significantly wider field of view. In Scherram's optical path, the principal plane of the lens, the target plane to be imaged in sharp focus, and the plane containing the CMOS chip surface must intersect. Unlike traditional imaging optical paths, to achieve the Scherram's optical path imaging effect, the lens optical axis and the CMOS chip surface are no longer perpendicular, but rather at a certain angle.

[0004] Whether in industrial cameras or CMOS modules, a protective cover glass is typically placed on the chip surface, parallel to the CMOS chip surface. However, the cover glass causes spherical aberration in converging beams, and when it is not perpendicular to the lens optical axis, it can also cause coma and astigmatism, resulting in significant differences in image quality between the meridional and sagittal directions in the optical path. This manifests as a large difference in contrast between the horizontal and vertical directions in the image, which is detrimental to optical path focusing and actual imaging results. The thicker the cover glass or the larger the CMOS sensor size, the greater the difference in image quality, and the less conducive it is to accurately representing object information in the image.

[0005] If the cover glass is set perpendicular to the lens optical axis in the SAM optical path, it will inevitably no longer be parallel to the CMOS chip surface. Firstly, a specially designed angled sealing structure is needed to fix the cover glass. Then, the cover glass on the CMOS chip surface must be removed and reinstalled on the angled sealing structure to achieve sealing and protection of the CMOS chip. Generally, CMOS chips require the cover glass to be removed and installed in a Class 100 cleanroom environment. The construction and maintenance of a Class 100 cleanroom are very demanding, and the removal and installation of the cover glass requires professional personnel. The angle between the CMOS chip surface and the cover glass depends on the magnification of the SAM optical path and the lens angle, and a universal angle cannot generally be designed.

[0006] In conclusion, although the cover glass parallel to the CMOS chip surface causes a significant decrease in image quality, it is more convenient and feasible in practical applications.

[0007] The content of the background section only discloses the technology known to the inventors and does not necessarily represent the prior art in this field. Summary of the Invention

[0008] In view of one or more existing defects, the present invention provides a SAM lens for industrial cameras, comprising: a first lens group, a second lens group, and a third lens group arranged sequentially along the optical axis from the object side to the image side.

[0009] The first lens group, the second lens group, and the third lens group are all positive power lens groups;

[0010] Wherein, the aperture of the second lens group is used as the aperture stop of the SAM lens, the ratio of the aperture of the third lens group to the aperture of the first lens group is 0.6-1.1, and the number of lenses in the first lens group is equal to the number of lenses in the third lens group.

[0011] According to one aspect of the present invention, the SAM lens has a focal length of 40-70mm, an operating wavelength of 380nm-780nm, an optical length to image half-height ratio (TTL / IH) of 3.0-7.5mm, and an angle between the light-transmitting cover and the lens optical axis of 46°-80°.

[0012] According to one aspect of the invention, the focal length of the first lens group is 70-100mm, the focal length of the second lens group is 135-165mm, the focal length of the third lens group is 25-55mm, the air gap between the first lens group and the second lens group on the optical axis of the lens is 3-8mm, and the air gap between the second lens group and the third lens group on the optical axis of the lens is 6-11mm.

[0013] According to one aspect of the invention, the first lens group comprises three spherical lenses, the second lens group comprises two spherical lenses, and the third lens group comprises three spherical lenses, wherein the front surface radius of curvature and the rear surface radius of curvature of each spherical lens are both greater than 0.

[0014] According to one aspect of the invention, the second lens group comprises a fourth lens and a fifth lens arranged sequentially along the optical axis of the lens from the object side to the image side.

[0015] The fourth lens has negative optical power and its object side is convex and its image side is concave. The image side of the fourth lens is used as the aperture stop of the Sham lens.

[0016] The fifth lens has negative optical power and its object side is convex and its image side is concave.

[0017] The radius of curvature of the front surface of the fifth lens is greater than the radius of curvature of the rear surface.

[0018] According to one aspect of the invention, the first lens group comprises: a first lens, a second lens, and a third lens arranged sequentially along the optical axis of the lens from the object side to the image side.

[0019] The first lens has positive optical power and the object side is convex and the image side is concave;

[0020] The second lens has positive optical power and the object side is convex and the image side is concave.

[0021] The third lens has negative optical power and its object side is convex and its image side is concave.

[0022] The radius of curvature of the front surface of the third lens is greater than the radius of curvature of the rear surface.

[0023] According to one aspect of the invention, the second lens and the third lens are cemented lenses, and the second lens and the third lens are made of materials with different refractive indices and Abbe numbers.

[0024] According to one aspect of the invention, the difference between the Abbe number of the second lens and the Abbe number of the third lens is greater than 10.

[0025] According to one aspect of the invention, the third lens group comprises: a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis of the lens from the object side to the image side.

[0026] The sixth lens has negative optical power and its object side is concave while its image side is convex.

[0027] The seventh lens has negative optical power and its object side is concave while its image side is convex.

[0028] The eighth lens has positive optical power and its object side and image side are both convex.

[0029] The radius of curvature of the front surface of the eighth lens is greater than the radius of curvature of the rear surface.

[0030] According to one aspect of the invention, the sixth lens and the seventh lens are cemented lenses, and the sixth lens and the seventh lens are made of materials with different refractive indices and Abbe numbers.

[0031] According to one aspect of the invention, the difference between the Abbe number of the sixth lens and the Abbe number of the seventh lens is greater than 10.

[0032] The present invention also relates to an industrial camera, comprising:

[0033] The Sham shot as described above;

[0034] Photosensitive element; and

[0035] A light-transmitting cover plate covers the photosensitive element, the light-transmitting cover plate is parallel to the imaging plane of the photosensitive element, and is not perpendicular to the optical axis of the SAM lens.

[0036] This invention presents a SAM lens optimized for use with a tilted light-transmitting cover plate. The cover plate is parallel to the surface of the photosensitive element but not perpendicular to the lens's optical axis, allowing it to be compatible with 1.4” large-area CMOS chips. This design enhances the sharpness range in industrial 3D measurement, enabling accurate depth measurement. The lens ensures clear imaging across the entire target field of view and features small size, high resolution, and low distortion. Attached Figure Description

[0037] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. In the drawings:

[0038] Figure 1 A schematic diagram of the imaging principle of Scham's law is shown;

[0039] Figure 2 A schematic diagram of a Sham lens according to an embodiment of the present invention is shown;

[0040] Figure 3a A schematic diagram of a Sham lens including eight lenses according to an embodiment of the present invention is shown;

[0041] Figure 3b The application is shown. Figure 3a A schematic diagram of the structure of an industrial camera with a Sham lens;

[0042] Figure 4 It shows Figure 3a Optical blur pattern of a Schahm lens;

[0043] Figure 5 It shows Figure 3a A schematic diagram of the modulation transfer function (MTF) of a Schahm lens;

[0044] Figure 6 It shows Figure 3a A diagram illustrating field curvature and astigmatism in a Sham lens. Detailed Implementation

[0045] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. 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 indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0049] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0050] This invention presents a SAM lens optimized for use with a tilted light-transmitting cover plate. The cover plate is parallel to the surface of the photosensitive element but not perpendicular to the lens's optical axis, allowing it to be compatible with 1.4” large-area CMOS chips. This design enhances the sharpness range in industrial 3D measurement, enabling accurate depth measurement. The lens ensures clear imaging across the entire target field of view and features small size, high resolution, and low distortion.

[0051] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0052] Figure 1 The diagram illustrates the imaging principle of Scherm's Law. According to Scherm's Law, when the extensions of the target plane, the lens principal plane, and the CMOS chip plane intersect at a single line, and this line of intersection is unique, a clear image can be captured across the entire field of view of the tilted target. This requires satisfying the following Scherm's Law:

[0053] tanα / tanβ=b' / a'

[0054] Where α is the angle between the target plane and the lens optical axis, β is the angle between the CMOS chip plane and the lens optical axis, a' is the object distance of point D on the lens optical axis, b' is the image distance of point D on the optical axis, and b' / a' is the magnification of the lens.

[0055] The angle β between the CMOS chip plane and the lens optical axis must satisfy the following relationship:

[0056]

[0057] Where f′ is the focal length of the lens.

[0058] According to the above-mentioned Scherm's Law, the present invention arranges the lens, the light-transmitting cover plate and the photosensitive element in sequence, wherein the light-transmitting cover plate is used to protect the photosensitive element, such as a CMOS chip, and is arranged parallel to the surface of the photosensitive element.

[0059] Figure 2A schematic diagram of a SAM lens according to an embodiment of the present invention is shown. A SAM lens for an industrial camera includes: a first lens group 1, a second lens group 2, and a third lens group 3 arranged sequentially from the object side to the image side along the optical axis of the lens, wherein the first lens group 1, the second lens group 2, and the third lens group 3 are all positive power lens groups.

[0060] Wherein, the light-transmitting aperture of the second lens group 2 is used as the aperture stop of the SAM lens, the ratio of the light-transmitting aperture of the third lens group 3 to the light-transmitting aperture of the first lens group 1 is 0.6-1.1, and the number of lenses in the first lens group 1 and the number of lenses in the third lens group 3 are equal.

[0061] The first lens group 1 is used to collect light energy, allowing information from the target area to fully enter the camera imaging system. The first lens group 1 is a positive power lens group, comprising at least one lens, which can be entirely spherical lenses, entirely aspherical lenses, or a combination of spherical and aspherical lenses. Using aspherical lenses can effectively eliminate spherical aberration and other forms of aberration generated by the lens, and can also be used to compensate for distortion aberrations. In industrial lenses, multiple aberrations must be corrected. Using only spherical lenses for correction not only results in a large number of lens combinations and high technical requirements for the lens, but sometimes it is also insufficient to correct aberrations to meet performance requirements. Replacing some of the spherical lenses in the lens group with aspherical lenses can significantly correct the spherical aberration introduced by spherical lenses in the collimation and focusing system. Optionally, the first lens group 1 includes aspherical lenses. By adjusting the surface constant and aspherical coefficient, optical quality can be improved, system stability enhanced, and overall cost reduced. If the first lens group 1 includes multiple lenses, these multiple lenses can be either split lenses or cemented lenses; this invention does not limit this.

[0062] The second lens group 2 is positioned between the first lens group 1 and the third lens group 3, acting as an aperture stop for the Schahm lens. It reduces lens aberrations, improves imaging resolution, and limits the light-gathering aperture, controlling the overall light transmission of the lens. The second lens group 2 is a positive power lens group, comprising at least one lens, which can be entirely spherical, entirely aspherical, or a combination of spherical and aspherical lenses. Using aspherical lenses can effectively eliminate spherical aberrations and other forms of aberrations produced by the lens, and can also be used to compensate for distortion aberrations. Optionally, the second lens group 2 includes aspherical lenses. By adjusting the surface constant and aspherical coefficient, optical quality can be improved, system stability enhanced, and overall cost reduced. If the second lens group 2 comprises multiple lenses, these lenses can be either split lenses or cemented lenses; this invention does not limit this.

[0063] The third lens group 3 converges the light beams from each field of view onto the surface of the photosensitive element and is used to correct aberrations. The third lens group 3 is a positive power lens group, comprising at least one lens, which can be entirely spherical lenses, entirely aspherical lenses, or a combination of spherical and aspherical lenses. Using aspherical lenses can effectively eliminate spherical aberrations and other forms of aberrations produced by the lens, and can also be used to compensate for distortion aberrations. Optionally, the third lens group 3 includes aspherical lenses; by adjusting the surface constant and aspherical coefficient, optical quality can be improved, system stability enhanced, and overall cost reduced. If the third lens group 3 comprises multiple lenses, these lenses can be either split lenses or cemented lenses; this invention does not limit this.

[0064] The aperture of the second lens group 2 is used as the aperture stop of the SAM lens, and the ratio of the aperture of the third lens group 3 to the aperture of the first lens group 1 is 0.6-1.1. Preferably, the ratio of the aperture of the third lens group 3 to the aperture of the first lens group 1 is between 0.71 and 1.0.

[0065] The number of lenses in the first lens group 1 is equal to the number of lenses in the third lens group 3. Preferably, the total number of lenses in the SAM lens is symmetrically arranged on both sides of the first surface, which is the surface of one of the lenses in the second lens group 2. For example, the first lens group 1 includes four lenses, the second lens group 2 includes two lenses, and the third lens group 3 includes four lenses. The first surface is either the rear surface of the first lens in the second lens group 2 or the front surface of the second lens. There are five lenses on each side of the first surface, that is, one side of the first surface contains four lenses from the first lens group 1 and the first lens from the second lens group 2, and the other side of the first surface contains the second lens from the second lens group 2 and four lenses from the third lens group 3. Preferably, the number of lenses in the first lens group 1 and the second lens group 2 is greater than or equal to three.

[0066] The lens materials are colorless optical glass and optical plastic. Optical plastic is low-cost for mass production, easy to process into aspherical surfaces, and lightweight. Optical glass has stable mechanical and thermal properties, and chromatic aberration can be eliminated and image quality improved by combining different refractive indices and Abbe numbers. Industrial robots are used in diverse environments, requiring high environmental temperature stability. Preferably, spherical lenses can be made of optical glass, and aspherical lenses can be made of optical plastic. Preferably, all lenses in the first lens group 1 are made of optical glass.

[0067] According to a preferred embodiment of the present invention, the focal length of the SAM lens is 40-70mm, the working wavelength is 380nm-780nm, the ratio of total optical length to image half-height (TTL / IH) is 3.0-7.5mm, and the angle between the light-transmitting cover and the lens optical axis is 46°-80°.

[0068] The industrial camera includes a photosensitive element and a light-transmitting cover plate. The light-transmitting cover plate covers the photosensitive element and is arranged parallel to the surface of the photosensitive element. The light-transmitting cover plate is not perpendicular to the optical axis of the lens. Preferably, the SAM lens has a focal length of 40-60mm, an operating wavelength of 390nm-485nm, a total optical length to image half-height ratio (TTL / IH) of 3.4-6.9mm, and an angle between the light-transmitting cover plate and the optical axis of the lens of 51°-76°.

[0069] According to a preferred embodiment of the present invention, the focal length of the first lens group 1 is 70-100mm, the focal length of the second lens group 2 is 135-220mm, preferably 190-210mm, the focal length of the third lens group 3 is 25-55mm, the air gap between the first lens group 1 and the second lens group 2 on the optical axis of the lens is 3-8mm, and the air gap between the second lens group 2 and the third lens group 3 on the optical axis of the lens is 6-11mm.

[0070] In one embodiment, the key parameters of the Sham lens are shown in Table 1:

[0071] Table 1

[0072] Focal length (mm) Aperture Field of view (mm) Target surface (mm) 38～59 2.0～5.0 107～142 20～24

[0073]

[0074] According to a preferred embodiment of the present invention, the first lens group 1 includes three lenses, the second lens group 2 includes two lenses, and the third lens group 3 includes three lenses.

[0075] According to a preferred embodiment of the present invention, the first lens group 1 includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis of the lens from the object side to the image side. The first lens has positive optical power and its object side is convex, while its image side is concave; the second lens has positive optical power and its object side is convex, while its image side is concave; the third lens has negative optical power and its object side is convex, while its image side is concave.

[0076] According to a preferred embodiment of the present invention, the second lens group 2 includes a fourth lens and a fifth lens arranged sequentially from the object side to the image side along the optical axis of the lens. The fourth lens has negative optical power and the object side is convex and the image side is concave. The image side of the fourth lens is used as the aperture stop of the SAM lens. The fifth lens has negative optical power and the object side is convex and the image side is concave.

[0077] According to a preferred embodiment of the present invention, the third lens group 3 includes a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side along the optical axis of the lens, wherein the sixth lens has negative optical power and the object side is concave and the image side is convex; the seventh lens has negative optical power and the object side is concave and the image side is convex; and the eighth lens has positive optical power and the object side is convex and the image side is convex.

[0078] Figure 3a A schematic diagram of the lenses in a Sham lens according to an embodiment of the present invention is shown. The Sham lens consists of a total of eight lenses, wherein the first lens group includes three lenses, namely, first lens G1, second lens G2 and third lens G3 from the object side to the image side; the second lens group includes two lenses, namely, fourth lens G4 and fifth lens G5 from the object side to the image side; and the third lens group includes three lenses, namely, sixth lens G6, seventh lens G7 and eighth lens G8 from the object side to the image side.

[0079] Continue to refer to Figure 3a The surface shapes of each lens are as follows: G1 is a convex-concave lens, G2 is a convex-concave lens, G3 is a convex-concave lens, G2 and G3 are cemented lenses, G4 is a convex-concave lens and also acts as an aperture stop, G5 is a convex-concave lens, G6 is a concave-convex lens, G7 is a concave-convex lens, G6 and G7 are cemented lenses, and G8 is a biconvex lens.

[0080] Continue to refer to Figure 3a The air gaps between the lenses are as follows: the air gap between lenses G1 and G2 is 0-2 mm on the optical axis; lenses G2 and G3 are cemented lenses, which can cancel distortion; the air gap between lenses G3 and G4 is 3-6 mm on the optical axis; the air gap between lenses G4 and G5 is 0-2 mm on the optical axis; the air gap between lenses G5 and G6 is 6-10 mm on the optical axis; lenses G6 and G7 are cemented lenses, which can cancel distortion; the air gap between lenses G7 and G8 is 0-2 mm on the optical axis. All units are millimeters.

[0081] According to a preferred embodiment of the present invention, the first lens group includes three spherical lenses, the second lens group includes two spherical lenses, and the third lens group includes three spherical lenses, wherein the front surface radius of curvature and the rear surface radius of curvature of each spherical lens are both greater than 0.

[0082] According to a preferred embodiment of the present invention, the radius of curvature of the front surface of the third lens G3 is greater than the radius of curvature of the rear surface.

[0083] According to a preferred embodiment of the present invention, the radius of curvature of the front surface of the fifth lens G5 is greater than the radius of curvature of the rear surface.

[0084] According to a preferred embodiment of the present invention, the radius of curvature of the front surface of the eighth lens G8 is greater than the radius of curvature of the rear surface.

[0085] Continue to refer to Figure 3a Each lens includes a front surface facing the object side and a rear surface facing the image side. The radii of curvature of each lens are as follows: G1 lens: front surface radius of curvature 26-29, rear surface radius of curvature 76-80; G2 lens: front surface radius of curvature 17-20, rear surface radius of curvature 192-195; G3 lens: front surface radius of curvature 192-195, rear surface radius of curvature 13-16; G4 lens: front surface radius of curvature 30. -33, the radius of curvature of the rear surface is 55-58; the radius of curvature of the front surface of the G5 lens is 16-19, and the radius of curvature of the rear surface is 11-14; the radius of curvature of the front surface of the G6 lens is 9-12, and the radius of curvature of the rear surface is 7-10; the radius of curvature of the front surface of the G7 lens is 7-10, and the radius of curvature of the rear surface is 13-16; the radius of curvature of the front surface of the G8 lens is 78-81, and the radius of curvature of the rear surface is 29-32. All units are millimeters.

[0086] Continue to refer to Figure 3a The center thicknesses of the lenses are as follows: G1 lens has a center thickness of 3-5 mm; G2 lens has a center thickness of 3-5 mm; G3 lens has a center thickness of 2-4 mm; G4 lens has a center thickness of 2-4 mm; G5 lens has a center thickness of 5-7 mm; G6 lens has a center thickness of 3-5 mm; G7 lens has a center thickness of 2-4 mm; and G8 lens has a center thickness of 5-7 mm. All units are millimeters.

[0087] Continue to refer to Figure 3a The air gaps between the lenses are as follows: the air gap between lenses G1 and G2 is 0-2 on the optical axis; lenses G2 and G3 are cemented lenses; the air gap between lenses G3 and G4 is 3-6 on the optical axis; the air gap between lenses G4 and G5 is 0-2 on the optical axis; the air gap between lenses G5 and G6 is 6-10 on the optical axis; lenses G6 and G7 are cemented lenses; and the air gap between lenses G7 and G8 is 0-2 on the optical axis. All units are millimeters.

[0088] Continue to refer to Figure 3aThe optical power of each lens is as follows: G1 lens: 61-63; G2 lens: 28-30; G3 lens: -18 to -20; G4 lens: 85-87; G5 lens: -105 to -107; G6 lens: -20 to -22; G7 lens: 33-35; G8 lens: 33-35. All units are millimeters.

[0089] According to a preferred embodiment of the present invention, the second lens G2 and the third lens G3 are cemented lenses, and the second lens G2 and the third lens G3 are made of materials with different refractive indices and Abbe numbers.

[0090] According to a preferred embodiment of the present invention, the difference between the Abbe number of the second lens G2 and the Abbe number of the third lens G3 is greater than 10.

[0091] According to a preferred embodiment of the present invention, the sixth lens G6 and the seventh lens G7 are cemented lenses, and the sixth lens G6 and the seventh lens G7 are made of materials with different refractive indices and Abbe numbers.

[0092] According to a preferred embodiment of the present invention, the difference between the Abbe number of the sixth lens G6 and the Abbe number of the seventh lens G7 is greater than 10.

[0093] Continue to refer to Figure 3a The optical parameters of each lens are as follows: G1 lens has a refractive index of 1.6-1.7 and an Abbe number of 60-63; G2 lens has a refractive index of 1.6-1.7 and an Abbe number of 60-63; G3 lens has a refractive index of 1.7-1.8 and an Abbe number of 33-36; G4 lens has a refractive index of 1.7-1.8 and an Abbe number of 33-36; G5 lens has a refractive index of 1.9-2.0 and an Abbe number of 16-19; G6 lens has a refractive index of 1.5-1.6 and an Abbe number of 63-66; G7 lens has a refractive index of 1.6-1.7 and an Abbe number of 37-40; and G8 lens has a refractive index of 1.6-1.7 and an Abbe number of 60-63.

[0094] In summary, Figure 3aThe Sham lens consists of eight lenses, each with its own specific functional focus, optimizing performance parameters. It utilizes two sets of cemented lenses: the first set includes lenses G2 and G3, and the second set includes lenses G6 and G7. Each set contains two lenses made of two different glass materials, ensuring consistent image magnification. Furthermore, the combination of these two glass materials cancels out chromatic aberration caused by the lens's inherent properties, allowing for better application in the short-wavelength band. For example, in the first set, lens G2 is made of crown glass, and lens G3 is made of flint glass. The different refractive indices and Abbe numbers of these two optical glasses eliminate chromatic aberration and improve image quality. Crown glass is an optical glass with a low refractive index and a high Abbe number. Crown optical glasses include fluorine crown (FK), light crown (QK), phosphorus crown (PK), heavy phosphorus crown (ZPK), crown (K), heavy crown (ZK), barium crown (BaK), lanthanum crown (LaK), titanium crown (TiK), and special crown (TK), among others. Flint glass is an optical glass with a high refractive index and a low Abbe number. Flint-type optical glasses are classified into light flint (QF), flint (F), heavy flint (ZF), barium flint (BaF), heavy barium flint (ZBaF), lanthanum flint (LaF), heavy lanthanum flint (ZLaF), titanium flint (TiF), crown flint (KF), and special flint (TF), etc. They are distributed in different regions on the refractive index versus dispersion coefficient graph. This invention does not limit the lens material; as long as the cemented lens group uses materials with different refractive indices and Abbe numbers, they are all within the scope of protection of this invention.

[0095] In a cemented lens, the two lenses are coaxial, which maximizes the cancellation of distortion caused by the lens itself during light incidence and exit. These two sets of cemented lenses are primarily responsible for balancing the overall lens distortion; their combined effect maximizes the cancellation of final lens distortion. The G4 lens acts as an aperture stop, and the G5 lens following it effectively cancels the aberrations of the first lens group. The final optical imaging system composed of eight lenses is an approximately symmetrical system relative to the aperture stop position; for example, the first and third lens groups have the same number of lenses, or the number of lenses on both sides of the first surface is the same. By adjusting the approximately symmetrical structure, the aberration correction capability of the optical imaging system can be effectively improved, thereby effectively reducing astigmatism, coma, and spherical aberration caused by the tilted setting of the cover plate in the Sham optical path.

[0096] The present invention also relates to an industrial camera, comprising: a SAM lens, a photosensitive element, and a light-transmitting cover plate as described above, wherein the light-transmitting cover plate covers the photosensitive element, the light-transmitting cover plate is parallel to the imaging plane of the photosensitive element, and is not perpendicular to the optical axis of the SAM lens.

[0097] Figure 3b The application is shown. Figure 3aA schematic diagram of an industrial camera structure using a SAM lens. The industrial camera includes a SAM lens, a photosensitive element, and a light-transmitting cover. The object-side tilted surface of the SAM lens represents the target plane, while the two image-side tilted surfaces of the SAM lens represent the light-transmitting cover and the photosensitive element surface, respectively. The light-transmitting cover is, for example, a glass cover, and the photosensitive element is, for example, a CMOS chip. The glass cover and the CMOS chip surface (i.e., the imaging plane) are arranged parallel to each other and not perpendicular to the optical axis of the SAM lens.

[0098] The Sham lens consists of eight lenses. Lenses G2 and G3 are cemented lenses that compensate for distortion; lenses G6 and G7 are also cemented lenses that compensate for distortion; lenses G1 and G8 reduce aberrations caused by the tilt of the cover plate. Lens G4 acts as an aperture stop, and lens G5 compensates for aberrations in the first lens group.

[0099] In this embodiment, the working distance of the SAM lens is 260nm, the entrance pupil diameter is 20, and the working wavelength is 400nm-480nm.

[0100] Figure 4 It shows Figure 3a The optical blur pattern of the Schahm lens, where OBJ represents the object-side field of view and IMA represents the image-side field of view, both in millimeters. RMS RADIUS and GEO RADIUS are in micrometers. The optical blur pattern shows that: at the center field of view, RMS RADIUS is 2.573 μm and GEO RADIUS is 4.586 μm; at the edge field of view, RMS RADIUS is 3.703 μm and GEO RADIUS is 14.314 μm. The on-axis and off-axis energy concentration and aberration correction are excellent, achieving ideal resolution.

[0101] Figure 5 It shows Figure 3a The modulation transfer function (MTF) diagram of the Schahm lens shows that the horizontal axis represents spatial resolution in line pairs / mm, the vertical axis represents contrast ratio in the range of 0-1, and TS represents the meridional and sagittal components of the MTF at different fields of view. As can be seen from the diagram, the contrast ratio is greater than 0.65 at 60 line pairs / mm for each field of view, indicating that the lens has high contrast and resolution.

[0102] Figure 6 It shows Figure 3a The diagrams illustrate the field curvature and astigmatism of the Schahm lens. The left image shows the field curvature, with the vertical axis representing the field of view and the horizontal axis representing the astigmatism value, in micrometers. The right image shows the distortion, with the vertical axis representing the field of view and the horizontal axis representing the distortion value. As can be seen from the images, the lens exhibits a field curvature and astigmatism value of less than 0.05 across the entire field of view in the corresponding coaxial optical path, demonstrating excellent astigmatism correction capabilities. The lens also exhibits a distortion value of less than 0.1% across the entire field of view in the corresponding coaxial optical path, indicating extremely low distortion.

[0103] Combination Figures 3a-6 As can be seen, the SAM lens designed in this invention has high contrast and resolution, extremely low distortion rate and astigmatism processing capability, and is compatible with large target surface photosensitive elements.

[0104] In summary, this invention provides an optimized SAM lens for use with a tilted light-transmitting cover plate. This cover plate is parallel to the surface of the photosensitive element and not perpendicular to the lens's optical axis, allowing it to be compatible with 1.4” large-area CMOS chips. This design enhances the sharpness range in industrial 3D measurement, enabling accurate depth measurement. The lens ensures clear imaging across the entire target field of view and features small size, high resolution, and low distortion.

[0105] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Shema lens for industrial camera, comprising a first lens group, a second lens group and a third lens group arranged in order from an object side to an image side along a lens optical axis, characterized in that, each of the first lens group, the second lens group and the third lens group is a positive lens group; a ratio of an entrance pupil of the third lens group to an entrance pupil of the first lens group is 0.6-1.1, a number of lenses in the first lens group is equal to a number of lenses in the third lens group, and an entrance pupil of the second lens group is used as an aperture stop of the Shema lens; the first lens group comprises a first lens, a second lens and a third lens arranged in order from the object side to the image side, the first lens has positive refractive power, an object side surface is convex, and an image side surface is concave, the second lens has positive refractive power, an object side surface is convex, and an image side surface is concave, and the third lens has negative refractive power, an object side surface is convex, and an image side surface is concave; the second lens group comprises a fourth lens and a fifth lens arranged in order from the object side to the image side, the fourth lens has positive refractive power, an object side surface is convex, and an image side surface is concave, and the fifth lens has negative refractive power, an object side surface is convex, and an image side surface is concave; the third lens group comprises a sixth lens, a seventh lens and an eighth lens arranged in order from the object side to the image side, the sixth lens has negative refractive power, an object side surface is concave, and an image side surface is convex, the seventh lens has positive refractive power, an object side surface is concave, and an image side surface is convex, and the eighth lens has positive refractive power, an object side surface is convex, and an image side surface is convex; a focal length of the first lens group is 70-100mm, a focal length of the second lens group is 135-165mm, a focal length of the third lens group is 25-55mm, an air distance between the first lens group and the second lens group along the lens optical axis is 3-8mm, and an air distance between the second lens group and the third lens group along the lens optical axis is 6-11mm. 2.The Shema lens according to claim 1, wherein a focal length of the Shema lens is 40-70mm, a working waveband is 380nm-780nm, a ratio of an optical total length to an image half height TTL / IH is 3.0-7.5, and an angle between a light-transmitting cover plate and the lens optical axis is 46°-80°. 3.The Shema lens according to claim 1 or 2, wherein the first lens group comprises three spherical lenses, the second lens group comprises two spherical lenses, and the third lens group comprises three spherical lenses, a front surface curvature radius and a back surface curvature radius of each spherical lens are greater than 0.

4. The Sharm lens of claim 3, wherein, an image side surface of the fourth lens is used as an aperture stop of the Shema lens; a front surface curvature radius of the fifth lens is greater than a back surface curvature radius. 5.The Shema lens according to claim 3, wherein a front surface curvature radius of the third lens is greater than a back surface curvature radius. 6.The Shema lens according to claim 5, wherein the second lens and the third lens are cemented lenses, and the second lens and the third lens are made of materials with different refractive indexes and Abbe numbers.

7. The Schmidt lens of claim 6, wherein a difference between the Abbe number of the second lens and the Abbe number of the third lens is greater than 10.

8. The Schmidt lens of claim 3, wherein a front surface radius of curvature of the eighth lens is greater than a back surface radius of curvature.

9. The Schmidt lens of claim 8, wherein the sixth lens and the seventh lens are cemented lenses, the sixth lens and the seventh lens being made of different materials having different refractive indices and Abbe numbers.

10. The Schmidt lens of claim 9, wherein a difference between the Abbe number of the sixth lens and the Abbe number of the seventh lens is greater than 10.

11. An industrial camera, comprising: a Schmidt lens as claimed in any one of claims 1-10; a light sensing element; and a light transmissive cover plate covering the light sensing element, the light transmissive cover plate being parallel to an imaging plane of the light sensing element and non-perpendicular to an optical axis of the Schmidt lens. ​

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