Optical lens, optical engine, imaging module and 3D camera

Abstract

The present disclosure relates to the field of optical technology, in particular to an optical lens, an optical engine, an imaging module and a 3D camera. The present disclosure aims to improve the signal-to-noise ratio of three-dimensional detection by reducing interference signals. The optical lens provided by the present disclosure comprises a plurality of lenses and an aperture diaphragm coaxially arranged in sequence from the object side to the image side, and the absolute value of the difference between the number of lenses on the object side of the aperture diaphragm and the number of lenses on the image side of the aperture diaphragm is less than or equal to 2. The difference in the number of lenses on both sides of the aperture diaphragm is small, so as to reduce distortion, so that the total field of view distortion of the optical lens is less than 1%, ensuring the imaging performance and detection accuracy. Furthermore, the root mean square value of the wavefront is increased to not less than one wavelength, so that the number of transition pixels increases, the detail contrast is reduced, thereby reducing the point cloud fluctuation caused by micro-lens artifacts, laser speckle and the like, and improving the signal-to-noise ratio and detection accuracy of three-dimensional detection.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of optical technology, and in particular, to an optical lens, an optical engine, an imaging module and a 3D camera. BACKGROUND

[0002] Machine vision technology mainly acquires images through image acquisition devices composed of light sources, lenses and the like, and analyzes and processes the images of target objects by using image processing algorithms to obtain target features, and is widely used in production and manufacturing, quality detection, logistics, medicine, scientific research and other fields.

[0003] In related technologies, the optical engine, as a device for projecting light signals onto a target object, is an important part of machine vision technology. When the projection of the optical engine has micro-lens artifacts or speckle, or the effective light energy reflected by the detection target surface is low, it will reduce the signal-to-noise ratio of the camera and affect the absolute accuracy and resolution of optical machine vision detection. SUMMARY

[0004] The present disclosure provides an optical lens, an optical engine, an imaging module and a 3D camera to improve the signal-to-noise ratio of three-dimensional detection by reducing interference signals.

[0005] To achieve the above-mentioned purpose, the present disclosure adopts the following technical solutions:

[0006] The first aspect of the present disclosure provides an optical lens, comprising a plurality of lenses and an aperture stop coaxially arranged in order from an object side to an image side, and the absolute value of the difference between the number of lenses towards the object side of the aperture stop and the number of lenses towards the image side of the aperture stop is less than or equal to 2;

[0007] The root mean square value of the wavefront of the optical lens is increased to not less than one wavelength; and the distortion of the full field of view of the optical lens is less than 1%.

[0008] Compared with the prior art, the optical lens provided by the first aspect of the present disclosure has the following advantages:

[0009] The optical lens provided by the present disclosure has the following advantages: by arranging a plurality of lenses and the absolute value of the difference between the number of lenses on both sides of the aperture stop being less than or equal to 2, the difference between the number of lenses on both sides of the aperture stop is small, so as to reduce distortion, so that the distortion of the full field of view of the optical lens is less than 1%, and the imaging performance and detection accuracy are guaranteed; and the root mean square value of the wavefront is increased to not less than one wavelength, so that the number of transition pixels at the edge of the image element is increased, the contrast at the edge of the image element is reduced, and the point cloud fluctuation caused by micro-lens artifacts, laser speckle and the like is reduced, thereby improving the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0010] As an improvement of the optical lens above, the optical lens comprises: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged coaxially in sequence from the object side to the image side; the aperture stop is located between the fourth lens and the fifth lens.

[0011] As an improvement of the optical lens above, the first lens has positive refractive power, the second lens has negative refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, the fifth lens has negative refractive power, the sixth lens has positive refractive power, and the seventh lens has positive refractive power; the eighth lens has positive refractive power; the third lens and the fourth lens are cemented lenses, and the cemented lens formed by the third lens and the fourth lens has positive refractive power; the fifth lens and the sixth lens are cemented lenses, and the cemented lens formed by the fifth lens and the sixth lens has positive refractive power.

[0012] As an improvement of the optical lens above, the focal length f1 of the first lens is 28.1mm-100.7mm; the focal length f2 of the second lens is -12.9mm--7mm; the focal length f3 of the third lens is -10.7mm--5.9mm; the focal length f4 of the fourth lens is 4.5mm-7.9mm; the focal length f5 of the fifth lens is -10.7mm--5.5mm; the focal length f6 of the sixth lens is 6.6mm-13.7mm; the focal length f7 of the seventh lens is 20.2mm-27.8mm; and the focal length f8 of the eighth lens is 14.1mm-27.5mm.

[0013] As an improvement of the optical lens above, the first lens has a radius of curvature R11 of 19.2mm-59.9mm, a radius of curvature R12 greater than or equal to 176.1mm; the second lens has a radius of curvature R21 of 10.3mm-16.9mm, a radius of curvature R22 of 3.5mm-6.2mm; the third lens has a radius of curvature R31 of 21.1mm-45.5mm, a radius of curvature R32 of 4mm-7.5mm; the fourth lens has a radius of curvature R41 of 4mm-7.5mm, a radius of curvature R42 less than or equal to -87mm, or a radius of curvature R42 greater than or equal to 55.8mm; the fifth lens has a radius of curvature R51 of -21.7mm--13.67mm, a radius of curvature R52 of 8.8mm-21mm; the sixth lens has a radius of curvature R61 of 8.8mm-21mm, a radius of curvature R62 of -12.9mm--7.2mm; the seventh lens has a radius of curvature R71 greater than or equal to 283.9mm, a radius of curvature R72 of -21.6mm--15.3mm; the eighth lens has a radius of curvature R81 of 26.9mm-41.7mm, a radius of curvature R82 of -39.6mm--16.9mm.

[0014] As an improvement of the optical lens above, the first lens has a center thickness GT1 of 3mm-6.2mm; the second lens has a center thickness GT2 of 1.6mm-3mm; the third lens has a center thickness GT3 of 1.5mm-3mm; the fourth lens has a center thickness GT4 of 2.5mm-4mm; the fifth lens has a center thickness GT5 of 1.2mm-3mm; the sixth lens has a center thickness GT6 of 3.2mm-5.1mm; the seventh lens has a center thickness GT7 of 2.4mm-4.3mm; the eighth lens has a center thickness GT8 of 2.9mm-4.5mm.

[0015] As an improvement of the optical lens above of the present disclosure, an aperture stop is arranged between the fourth lens and the fifth lens; the air separation distance AT1 of the first lens and the second lens along the optical axis is 0.2mm-10.8mm; the air separation distance AT2 of the second lens and the third lens along the optical axis is 2.6mm-3.8mm; the third lens and the fourth lens are cemented lenses; the air separation distance AT3 of the fourth lens and the aperture stop along the optical axis is 0.7mm-2.3mm; the air separation distance AT4 of the aperture stop and the fifth lens along the optical axis is 0.6mm-1mm; the fifth lens and the sixth lens are cemented lenses; the air separation distance AT5 of the sixth lens and the seventh lens along the optical axis is 0.16mm-0.2mm; the air separation distance AT6 of the seventh lens and the eighth lens along the optical axis is 0.16mm-0.2mm; the air separation distance BFL of the eighth lens and the image plane along the optical axis is 9.4mm-16.2mm.

[0016] As an improvement of the optical lens above of the present disclosure, the refractive index N1 of the first lens is 1.59-1.76, and the Abbe number V1 is 52.3-68; the refractive index N2 of the second lens is 1.81-1.88, and the Abbe number V2 is 25.4-40.8; the refractive index N3 of the third lens is 1.81-2, and the Abbe number V3 is 25.4-40.8; the refractive index N4 of the fourth lens is 1.92-1.95, and the Abbe number V4 is 17.9-20.9; the refractive index N5 of the fifth lens is 1.95, and the Abbe number V5 is 17.9; the refractive index N6 of the sixth lens is 1.62-1.65, and the Abbe number V6 is 58.4-63.4; the refractive index N7 of the seventh lens is 1.75, and the Abbe number V7 is 52.3; the refractive index N8 of the eighth lens is 1.75-1.83, and the Abbe number V8 is 42.7-52.3.

[0017] As an improvement of the optical lens above of the present disclosure, the first lens and the second lens form a first lens group, the focal length fa of the first lens group is-18.5mm--11.4mm; the third lens and the fourth lens form a second lens group, the focal length fb of the second lens group is 26.4mm-36.4mm; the fifth lens, the sixth lens, the seventh lens and the eighth lens form a third lens group, the focal length fc of the third lens group is 6.6mm-11.3mm; the axial distance of the first lens group and the second lens group is 2.6mm-3.81mm; the axial distance of the second lens group and the third lens group is 1.3mm-2.1mm.

[0018] As an improvement of the optical lens above, the focal length fa of the first lens group and the focal length f of the optical lens satisfy 1.7<|fa / f|<2.2; the focal length fb of the second lens group and the focal length f of the optical lens satisfy 3.3<fb / f<4.3; the focal length fc of the third lens group and the focal length f of the optical lens satisfy 1<fc / f<1.2.

[0019] As an improvement of the optical lens above, the focal length f of the optical lens is 6mm-11mm; the aperture number of the optical lens is F1.4-F7.5; the working waveband WL of the optical lens is 390nm-700nm; the image side target surface size IMG is 6mm-12mm; the total system optical length TTL is 33mm-66.4mm, and the system back focus BFL is 9.4mm-16.2mm.

[0020] The second aspect of the present disclosure provides an optical engine, comprising: a light source, a digital micro-mirror chip, and a projection lens, light of the light source forms a projection image after passing through the digital micro-mirror chip and is projected through the projection lens; the projection lens is the optical lens of the first aspect.

[0021] The optical engine provided by the second aspect of the present disclosure also has the same advantages as the optical lens of the first aspect because it comprises the optical lens of the first aspect.

[0022] The third aspect of the present disclosure provides an imaging module, comprising: a photosensitive chip and the optical lens of the first aspect, object side light is imaged on the photosensitive chip through the optical lens.

[0023] The imaging module provided by the third aspect of the present disclosure also has the same advantages as the optical lens of the first aspect because it comprises the optical lens of the first aspect.

[0024] The fourth aspect of the present disclosure provides a 3D camera, comprising a structured light projection and an imaging camera; the structured light projection is configured to emit light to a target object, and the imaging camera collects light reflected by the target object and forms an image; wherein the structured light projection comprises the optical engine of the second aspect; and / or, the imaging camera comprises the imaging module of the third aspect.

[0025] The 3D camera provided by the fourth aspect of the present disclosure also has the same advantages as the optical engine of the second aspect and / or the imaging module of the third aspect because it comprises the optical engine of the second aspect and / or the imaging module of the third aspect.

[0026] The fourth aspect of the present disclosure provides a 3D camera, comprising a structured light projection and an imaging camera; the structured light projection is configured to emit light to a target object, and the imaging camera collects the light reflected by the target object and forms an image;

[0027] The structured light projection comprises a light source, a digital micro-mirror chip, and the optical lens of any one of claims 1-12; the light of the light source forms a projection image after passing through the digital micro-mirror chip, and the projection image is projected to the target object by the lens; the imaging camera collects the light reflected by the target object and forms an image; and / or

[0028] The imaging camera comprises a photosensitive chip and the optical lens of any one of claims 1-12; the structured light projection is configured to project structured light to a target object; and the light on the target object is imaged on the photosensitive chip via the optical lens.

[0029] The fifth aspect of the present disclosure provides a 3D camera, which has the same advantages as the optical lens of the first aspect because it comprises the optical lens of the first aspect.

[0030] In addition to the technical problems solved by the present disclosure, the technical features constituting the technical solutions, and the beneficial effects brought by these technical features, the other technical problems solved by the optical lens and the electronic device provided by the present disclosure, the other technical features included in the technical solutions, and the beneficial effects brought by these technical features will be further described in detail in the specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the drawings needed in the description of the embodiments of the present disclosure or the prior art will be briefly introduced. Obviously, the drawings in the following description are only a part of the embodiments of the present disclosure, and these drawings and the written description are not intended to limit the scope of the present disclosure in any way, but to explain the concept of the present disclosure to those skilled in the art by referring to specific embodiments. Those skilled in the art can also obtain other drawings without creative labor based on these drawings.

[0032] Figure 1 The structural schematic diagram of the optical lens provided by the embodiments of the present disclosure is shown in the following figure:

[0033] Figure 2 The distortion diagram of the optical lens provided by the embodiments of the present disclosure is shown in the following figure:

[0034] Figure 3An edge spread function curve of the optical lens without increasing the wavefront provided in the embodiments of this disclosure;

[0035] Figure 4 The edge spread function curves of the optical lens before and after the amplification wave are provided in the embodiments of this disclosure;

[0036] Figure 5 This is a schematic diagram of the structure of an optical engine provided in an embodiment of the present disclosure;

[0037] Figure 6 Micromirror artifacts in the projected image of an optical engine using an optical lens in the prior art;

[0038] Figure 7 Micromirror artifacts in the projected image of the optical engine of the optical lens employing embodiments of the present disclosure;

[0039] Figure 8 A brightness distribution curve of micromirror artifacts in the projected image of an optical engine using an optical lens in the prior art.

[0040] Figure 9 A brightness distribution curve of micromirror artifacts in the projected image of the optical engine of the optical lens using an embodiment of the present disclosure.

[0041] Figure 10 This is a schematic diagram of the imaging module provided in an embodiment of the present disclosure;

[0042] Figure 11 The laser stripe image generated by the laser engine;

[0043] Figure 12 for Figure 11 Brightness distribution curve of a laser stripe image;

[0044] Figure 13 To capture images using an imaging module employing existing optical lenses. Figure 11 The image formed by laser stripes;

[0045] Figure 14 For capturing images of the imaging module of the optical lens in this embodiment of the present disclosure. Figure 11 An image showing the formation of laser stripes;

[0046] Figure 15 for Figure 13 Brightness distribution curve of a laser stripe image;

[0047] Figure 16 for Figure 14 Brightness distribution curve of a laser stripe image;

[0048] Figure 17Micro-mirror artifacts in images collected by 3D cameras using existing optical lenses as projection lenses and imaging lenses;

[0049] Figure 18 Micro-mirror artifacts in images collected by 3D cameras using optical lenses of embodiments of the present disclosure as projection lenses and existing optical lenses as imaging lenses;

[0050] Figure 19 Micro-mirror artifacts in images collected by 3D cameras using optical lenses of embodiments of the present disclosure as imaging lenses and existing optical lenses as projection lenses;

[0051] Figure 20 Micro-mirror artifacts in images collected by 3D cameras using optical lenses of embodiments of the present disclosure as projection lenses and optical lenses of embodiments of the present disclosure as imaging lenses;

[0052] Figure 21 For Figure 17 Point cloud fluctuation test curve diagram of three-dimensional reconstruction of micro-mirror artifacts;

[0053] Figure 22 For Figure 18 Point cloud fluctuation test curve diagram of three-dimensional reconstruction of micro-mirror artifacts;

[0054] Figure 23 For Figure 19 Point cloud fluctuation test curve diagram of three-dimensional reconstruction of micro-mirror artifacts;

[0055] Figure 24 For Figure 20 Point cloud fluctuation test curve diagram of three-dimensional reconstruction of micro-mirror artifacts. DETAILED DESCRIPTION

[0056] An optical engine, as a device for projecting light signals onto a target object, is an important component of machine vision technology. A camera acquires the light signals reflected by the target object to obtain the surface features of the target object.

[0057] For target objects with high material absorption, such as black objects, objects with complementary colors to the structured light, and target objects with high transmittance, such as glass cups, plastic bottles, and acrylic boxes, the effective light energy reflected by the target surface is very low. Compared with interference signals such as secondary reflected light and ambient light, the effective signal received by the camera is not strong enough, i.e., the signal-to-noise ratio is low. Improving the signal-to-noise ratio is a key problem for improving the accuracy and repeatability of three-dimensional surface reconstruction.

[0058] In three-dimensional detection, a digital light processing (DLP) optical engine or a laser engine is usually used to generate a structured light signal. The projection of the DLP optical engine has micromirror artifacts, which are manifested as regular stripes of the structured light. The structured light generated by the laser engine has speckles due to interference of laser light reflected by the microstructure of a target surface.

[0059] In some products, rotating or vibrating ground glass or diffractive optical elements are used to reduce the contrast of micromirror artifacts and laser speckles in projection. This has a good effect on static application scenarios such as projectors. However, 3D cameras are often installed on industrial robots or production lines and are subjected to vibration and acceleration motion for many years, and the internal structure needs to be stable and reliable. Rotating or vibrating ground glass or diffractive optical elements cannot meet the requirements.

[0060] Therefore, the embodiments of the present disclosure provide an optical lens, which reduces interference signals to improve the signal-to-noise ratio of three-dimensional detection.

[0061] The embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present disclosure, and cannot be understood as a limitation of the present disclosure.

[0062] Embodiment One

[0063] The embodiments of the present disclosure provide an optical lens, in which a root mean square (RMS) value of a wavefront of the optical lens is increased to be not less than one wavelength.

[0064] The wavelength is a wavelength of a working wavelength band of the optical lens. When the optical lens is used as a projection lens of a projection device, the wavelength is a wavelength of light projected by the projection device. When the optical lens is used as an imaging lens, the wavelength is a wavelength of light reflected by a target object to the imaging lens.

[0065] When the RMS value of the wavefront of the optical lens is increased to be not less than one wavelength, the number of pixels included in the edge spread function in a range of 20% to 80% of radiant exposure is increased in a certain range, for example, from 1.0 pixel to 3.4 pixels.

[0066] In this way, the number of pixels at the edge of the pixel is increased, the contrast of the edge of the pixel is reduced, and the point cloud fluctuation caused by micromirror artifacts, laser speckles, and the like is reduced, thereby improving the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0067] In a conventional lens of the related art, the wavefront RMS is less than one wavelength to improve the system imaging quality as much as possible and avoid the decrease of detail contrast. In the optical lens of the present disclosure, the wavefront RMS is increased to more than one wavelength to reduce the detail contrast, reduce the point cloud fluctuation caused by the micro-lens artifact and laser speckle, and improve the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0068] The optical lens of the embodiment of the present disclosure realizes optical distortion of less than 1% through a double-Gaussian structure variant.

[0069] In this way, the optical lens can still maintain good imaging quality, while the wavefront RMS is increased to more than one wavelength to reduce the detail contrast.

[0070] In the optical lens of the embodiment of the present disclosure, the lenses and the aperture stop are coaxially arranged in sequence from the object side to the image side, and the absolute value of the difference between the number of lenses on the object side of the aperture stop and the number of lenses on the image side of the aperture stop is less than or equal to 2.

[0071] In some embodiments, the difference between the number of lenses on the object side of the aperture stop and the number of lenses on the image side of the aperture stop is zero, that is, the number of lenses on the object side of the aperture stop is the same as the number of lenses on the image side of the aperture stop.

[0072] In some embodiments, the number of lenses on the object side of the aperture stop is more than the number of lenses on the image side of the aperture stop. For example, the number of lenses on the object side of the aperture stop is 5, and the number of lenses on the image side of the aperture stop is 4.

[0073] In other embodiments, the number of lenses on the object side of the aperture stop is less than the number of lenses on the image side of the aperture stop. For example, the number of lenses on the object side of the aperture stop is 4, and the number of lenses on the image side of the aperture stop is 5.

[0074] The small difference between the number of lenses on both sides of the aperture stop makes the number of lenses on both sides of the aperture stop approximately symmetrical, which is beneficial to reducing distortion.

[0075] In the embodiment of the present disclosure, the surface shape of the lens on the object side of the aperture stop is symmetrical to the surface shape of the lens on the image side of the aperture stop.

[0076] In this way, through the symmetry of the number of lenses and the surface shape on both sides of the aperture stop, the optical distortion is reduced, so that the total field distortion of the optical lens is less than 1%, and the imaging accuracy is ensured.

[0077] In combination Figure 1 The optical lens provided by the embodiment of the present disclosure includes three lens groups, which are a first lens group 10, a second lens group 20, and a third lens group 30 in sequence along the optical path from the object side to the image side.

[0078] The three lens groups each include at least one lens, and can include doublet lenses and cemented lenses. The lens surfaces can be concave, convex or planar. The lenses of each lens group can all be spherical lenses, all be aspherical lenses, or be composed of spherical lenses and aspherical lenses.

[0079] With reference to the foregoing Figure 1 The optical lens of the embodiment of the present disclosure includes, arranged coaxially in sequence from the object side to the image side, a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5, a sixth lens G6, a seventh lens G7, and an eighth lens G8; the third lens G3 and the fourth lens G4 are cemented lenses; the fifth lens G5 and the sixth lens G6 are cemented lenses.

[0080] The first lens G1 has positive refractive power, and can provide large negative distortion to compensate for a large amount of positive distortion generated by other lenses.

[0081] The second lens G2 has negative refractive power, and can collect off-axis large-angle light beams to enter the lens, thereby realizing miniaturization of the optical path structure.

[0082] The third lens G3 has negative refractive power, the fourth lens G4 has positive refractive power, and the cemented lens formed by the third lens G3 and the fourth lens G4 has positive refractive power. The cemented lens can realize deflection of light rays, so that the light rays smoothly enter the aperture stop 40.

[0083] The fifth lens G5 has negative refractive power, the sixth lens G6 has positive refractive power, and the cemented lens formed by the fifth lens G5 and the sixth lens G6 has positive refractive power, and can correct chromatic aberration while bearing a certain light converging capability.

[0084] The seventh lens G7 has positive refractive power, and the eighth lens G8 has positive refractive power. Through refractive power distribution, each of the seventh lens G7 and the eighth lens G8 bears a certain converging capability, reduces the degree of deflection of light rays passing through the lenses, thereby reducing the system tolerance sensitivity, and converges the light rays on the image plane.

[0085] In some embodiments, the first lens G1 can be a convex-concave lens, the second lens G2 can be a convex-concave lens, the third lens G3 can be a convex-concave lens, the fourth lens G4 can be a biconvex lens, the fifth lens G5 can be a biconcave lens, the sixth lens G6 can be a biconvex lens, the seventh lens G7 can be a convex-concave lens, and the eighth lens G8 can be a biconvex lens.

[0086] The material of each lens can be achromatic optical glass and optical plastic. Optical plastic is low in cost in mass production, easy to process aspheric surface, and light in weight. Optical glass has stable mechanical properties and thermal properties, and can eliminate chromatic aberration and improve imaging quality by combination of different refractive indexes and Abbe numbers. Industrial robots are applied in various environments, and need to meet higher environmental temperature stability.

[0087] In the embodiments of the present disclosure, all lenses are made of glass material. Firstly, the transmittance of glass material is higher than that of plastic material, and the imaging effect is better. Secondly, the physical and chemical stability of glass material is much better than that of plastic material, which can better adapt to various environments and has a longer service life.

[0088] In the embodiments of the present disclosure, all lenses are spherical lenses, which are low in cost.

[0089] By Figure 1 As can be seen from the structural diagram of the optical lens shown in the figure, under the premise of ensuring the size and volume of the lens optical path, the lens structure is simple in form and good in lens processability.

[0090] The focal length f of the optical lens in the embodiments of the present disclosure is 6mm-11mm; the aperture number of the optical lens is F1.4-F7.5; the working waveband WL of the optical lens is 390nm-700nm; the image side target surface size IMG is 6mm-12mm; the total system optical length TTL is 33mm-66.4mm, and the system back focus BFL is 9.4mm-16.2mm.

[0091] Continuing to refer to Figure 1 , the first lens G1 and the second lens G2 form the first lens group 10, the third lens G3 and the fourth lens G4 form the second lens group 20, and the fifth lens G5, the sixth lens G6, the seventh lens G7 and the eighth lens G8 form the third lens group 30.

[0092] The focal length fa of the first lens group 10 is-18.5mm--11.4mm; the focal length fb of the second lens group 20 is 26.4mm-36.4mm; and the focal length fc of the third lens group 30 is 6.6mm-11.3mm.

[0093] The axial distance between the first lens group 10 and the second lens group 20 is 2.6mm-3.81mm; and the axial distance between the second lens group 20 and the third lens group 30 is 1.3mm-2.1mm.

[0094] The focal length fa of the first lens group 10 and the focal length f of the optical lens satisfy 1.7<|fa / f|<2.2; the focal length fb of the second lens group 20 and the focal length f of the optical lens satisfy 3.3<fb / f<4.3; and the focal length fc of the third lens group 30 and the focal length f of the optical lens satisfy 1<fc / f<1.2.

[0095] The focal length of each lens is limited as follows.

[0096] The focal length f1 of the first lens G1 is 28.1mm-100.7mm; the focal length f2 of the second lens G2 is -12.9mm--7mm; the focal length f3 of the third lens G3 is -10.7mm--5.9mm; the focal length f4 of the fourth lens G4 is 4.5mm-7.9mm; the focal length f5 of the fifth lens G5 is -10.7mm--5.5mm; the focal length f6 of the sixth lens G6 is 6.6mm-13.7mm; the focal length f7 of the seventh lens G7 is 20.2mm-27.8mm; and the focal length f8 of the eighth lens G8 is 14.1mm-27.5mm.

[0097] The curvature radius of each lens is limited as follows.

[0098] The curvature radius R11 of the incident surface of the first lens G1 is 19.2mm-59.9mm, and the curvature radius R12 of the exit surface is greater than or equal to 176.1mm; the curvature radius R21 of the incident surface of the second lens G2 is 10.3mm-16.9mm, and the curvature radius R22 of the exit surface is 3.5mm-6.2mm; the curvature radius R31 of the incident surface of the third lens G3 is 21.1mm-45.5mm, and the curvature radius R32 of the exit surface is 4mm-7.5mm; the curvature radius R41 of the incident surface of the fourth lens G4 is 4mm-7.5mm, and the curvature radius R42 of the exit surface is less than or equal to -87mm, or the curvature radius R42 of the exit surface is greater than or equal to 55.8mm; the curvature radius R51 of the incident surface of the fifth lens G5 is -21.7mm--13.67mm, and the curvature radius R52 of the exit surface is 8.8mm-21mm; the curvature radius R61 of the incident surface of the sixth lens G6 is 8.8mm-21mm, and the curvature radius R62 of the exit surface is -12.9mm--7.2mm; the curvature radius R71 of the incident surface of the seventh lens G7 is greater than or equal to 283.9mm, and the curvature radius R72 of the exit surface is -21.6mm--15.3mm; and the curvature radius R81 of the incident surface of the eighth lens G8 is 26.9mm-41.7mm, and the curvature radius R82 of the exit surface is -39.6mm--16.9mm.

[0099] In the above description, the accompanying drawings are combined. Figure 1The entrance surface of the lens is a surface of the lens facing the object side; and the exit surface of the lens is a surface of the lens facing the image side.

[0100] When the curvature radius is infinite, the surface is a plane. For example, when the exit surface curvature radius R12 of the first lens G1 is infinite, the exit surface of the first lens G1 is a plane.

[0101] The central thickness of each lens is defined as follows.

[0102] The central thickness GT1 of the first lens G1 is 3mm-6.2mm; the central thickness GT2 of the second lens G2 is 1.6mm-3mm; the central thickness GT3 of the third lens G3 is 1.5mm-3mm; the central thickness GT4 of the fourth lens G4 is 2.5mm-4mm; the central thickness GT5 of the fifth lens G5 is 1.2mm-3mm; the central thickness GT6 of the sixth lens G6 is 3.2mm-5.1mm; the central thickness GT7 of the seventh lens G7 is 2.4mm-4.3mm; and the central thickness GT8 of the eighth lens G8 is 2.9mm-4.5mm.

[0103] The central thickness of the lens refers to the thickness of the center of the lens along the optical axis.

[0104] The air gap distance of each lens along the optical axis is defined as follows.

[0105] The aperture stop 40 is arranged between the fourth lens G4 and the fifth lens G5.

[0106] The air gap distance AT1 of the first lens G1 and the second lens G2 along the optical axis is 0.2mm-10.8mm; the air gap distance AT2 of the second lens G2 and the third lens G3 along the optical axis is 2.6mm-3.8mm; the third lens G3 and the fourth lens G4 are cemented lenses; the air gap distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis is 0.7mm-2.3mm; the air gap distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis is 0.6mm-1mm; the fifth lens G5 and the sixth lens G6 are cemented lenses; the air gap distance AT5 of the sixth lens G6 and the seventh lens G7 along the optical axis is 0.16mm-0.2mm; the air gap distance AT6 of the seventh lens G7 and the eighth lens G8 along the optical axis is 0.16mm-0.2mm; and the air gap distance BFL of the eighth lens G8 and the image plane along the optical axis is 9.4mm-16.2mm.

[0107] The air gap distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis and the air gap distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis satisfy 1.3

[0108] The refractive index and Abbe number of each lens are defined as follows.

[0109] The refractive index N1 of the first lens G1 is 1.59-1.76, and the Abbe number V1 is 52.3-68; the refractive index N2 of the second lens G2 is 1.81-1.88, and the Abbe number V2 is 25.4-40.8; the refractive index N3 of the third lens G3 is 1.81-2, and the Abbe number V3 is 25.4-40.8; the refractive index N4 of the fourth lens G4 is 1.92-1.95, and the Abbe number V4 is 17.9-20.9; the refractive index N5 of the fifth lens G5 is 1.95, and the Abbe number V5 is 17.9; the refractive index N6 of the sixth lens G6 is 1.62-1.65, and the Abbe number V6 is 58.4-63.4; the refractive index N7 of the seventh lens G7 is 1.75, and the Abbe number V7 is 52.3; the refractive index N8 of the eighth lens G8 is 1.75-1.83, and the Abbe number V8 is 42.7-52.3.

[0110] The material properties of each lens are defined by limiting the refractive index and Abbe number of each lens.

[0111] Example One

[0112] The focal length f of the optical lens of this example one is 6mm; the aperture number of the optical lens is F1.4; the working waveband WL of the optical lens is 390nm-700nm; the image side target surface size IMG is 6mm; the total system optical length TTL is 33mm, and the system back focus BFL is 9.4mm.

[0113] The focal length fa of the first lens group 10 is -11.4mm; the focal length fb of the second lens group 20 is 26.4mm; and the focal length fc of the third lens group 30 is 6.6mm.

[0114] The axial distance between the first lens group 10 and the second lens group 20 is 2.6mm; and the axial distance between the second lens group 20 and the third lens group 30 is 1.3mm.

[0115] The focal length fa of the first lens group 10 and the focal length f of the optical lens satisfy |fa / f|=1.9; the focal length fb of the second lens group 20 and the focal length f of the optical lens satisfy fb / f=4.3; and the focal length fc of the third lens group 30 and the focal length f of the optical lens satisfy fc / f=1.1.

[0116] The surface shape of each lens is as follows:

[0117] The first lens G1 is a convex-concave lens, the second lens G2 is a convex-concave lens, the third lens G3 is a convex-concave lens, the fourth lens G4 is a convex-concave lens, the third lens G3 and the fourth lens G4 are cemented lenses, the fifth lens G5 is a double-concave lens, the sixth lens G6 is a double-convex lens, the fifth lens G5 and the sixth lens G6 are cemented lenses, the seventh lens G7 is a plano-convex lens, and the eighth lens G8 is a double-convex lens.

[0118] The focal lengths of the lenses are defined as follows.

[0119] The focal length f1 of the first lens G1 is 28.1 mm, the focal length f2 of the second lens G2 is -7 mm, the focal length f3 of the third lens G3 is -5.9 mm, the focal length f4 of the fourth lens G4 is 4.5 mm, the focal length f5 of the fifth lens G5 is -5.5 mm, the focal length f6 of the sixth lens G6 is 6.6 mm, the focal length f7 of the seventh lens G7 is 20.2 mm, and the focal length f8 of the eighth lens G8 is 14.1 mm.

[0120] The radii of curvature of the lenses are defined as follows.

[0121] The radius of curvature R11 of the entrance surface of the first lens G1 is 19.2 mm, and the radius of curvature R12 of the exit surface is 176.1 mm; the radius of curvature R21 of the entrance surface of the second lens G2 is 10.3 mm, and the radius of curvature R22 of the exit surface is 3.5 mm; the radius of curvature R31 of the entrance surface of the third lens G3 is 21.1 mm, and the radius of curvature R32 of the exit surface is 4 mm; the radius of curvature R41 of the entrance surface of the fourth lens G4 is 4 mm, and the radius of curvature R42 of the exit surface is 55.8 mm; the radius of curvature R51 of the entrance surface of the fifth lens G5 is -13.67 mm, and the radius of curvature R52 of the exit surface is 8.8 mm; the radius of curvature R61 of the entrance surface of the sixth lens G6 is 8.8 mm, and the radius of curvature R62 of the exit surface is -7.2 mm; the radius of curvature R71 of the entrance surface of the seventh lens G7 is infinite, and the radius of curvature R72 of the exit surface is -15.3 mm; and the radius of curvature R81 of the entrance surface of the eighth lens G8 is 26.9 mm, and the radius of curvature R82 of the exit surface is -16.9 mm.

[0122] The radius of curvature R71 of the entrance surface of the seventh lens G7 is infinite, indicating that the entrance surface of the seventh lens G7 is a plane.

[0123] The central thicknesses of the lenses are defined as follows.

[0124] The center thickness GT1 of the first lens G1 is 3 mm; the center thickness GT2 of the second lens G2 is 2 mm; the center thickness GT3 of the third lens G3 is 2 mm; the center thickness GT4 of the fourth lens G4 is 2.5 mm; the center thickness GT5 of the fifth lens G5 is 1.2 mm; the center thickness GT6 of the sixth lens G6 is 3.2 mm; the center thickness GT7 of the seventh lens G7 is 2.4 mm; and the center thickness GT8 of the eighth lens G8 is 2.9 mm.

[0125] The air interval distances of the lenses along the optical axis are defined as follows.

[0126] The air interval distance AT1 of the first lens G1 and the second lens G2 along the optical axis is 0.2 mm; the air interval distance AT2 of the second lens G2 and the third lens G3 along the optical axis is 2.6 mm; the third lens G3 and the fourth lens G4 are cemented lenses; the air interval distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis is 0.7 mm; the air interval distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis is 0.6 mm; the fifth lens G5 and the sixth lens G6 are cemented lenses; the air interval distance AT5 of the sixth lens G6 and the seventh lens G7 along the optical axis is 0.16 mm; the air interval distance AT6 of the seventh lens G7 and the eighth lens G8 along the optical axis is 0.16 mm; and the air interval distance BFL of the eighth lens G8 and the image plane along the optical axis is 9.4 mm.

[0127] The air interval distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis and the air interval distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis satisfy AT3 + AT4 = 1.3 mm.

[0128] The refractive indices and Abbe numbers of the lenses are defined as follows.

[0129] The refractive index N1 of the first lens G1 is 1.75, and the Abbe number V1 is 52.3; the refractive index N2 of the second lens G2 is 1.88, and the Abbe number V2 is 39.2; the refractive index N3 of the third lens G3 is 1.88, and the Abbe number V3 is 39.2; the refractive index N4 of the fourth lens G4 is 1.92, and the Abbe number V4 is 20.9; the refractive index N5 of the fifth lens G5 is 1.95, and the Abbe number V5 is 17.9; the refractive index N6 of the sixth lens G6 is 1.65, and the Abbe number V6 is 58.4; the refractive index N7 of the seventh lens G7 is 1.75, and the Abbe number V7 is 52.3; and the refractive index N8 of the eighth lens G8 is 1.75, and the Abbe number V8 is 52.3.

[0130] Example Two

[0131] The focal length f of the optical lens of the present example is 7.6mm; the aperture ratio of the optical lens is F1.65; the working waveband WL of the optical lens is 390nm-700nm; the image-side target surface size IMG is 8mm; the total optical length TTL of the system is 43mm, and the back focus BFL of the system is 12mm.

[0132] The focal length fa of the first lens group 10 is -16.6mm; the focal length fb of the second lens group 20 is 26.1mm; and the focal length fc of the third lens group 30 is 9mm.

[0133] The axial distance between the first lens group 10 and the second lens group 20 is 3.6mm; and the axial distance between the second lens group 20 and the third lens group 30 is 3.1mm.

[0134] The focal length fa of the first lens group 10 and the focal length f of the optical lens satisfy |fa / f|=2.2; the focal length fb of the second lens group 20 and the focal length f of the optical lens satisfy fb / f=3.4; and the focal length fc of the third lens group 30 and the focal length f of the optical lens satisfy fc / f=1.2.

[0135] The surface shape of each lens is as follows:

[0136] The first lens G1 is a convex plane lens, the second lens G2 is a convex-concave lens, the third lens G3 is a convex-concave lens, the fourth lens G4 is a double convex lens, the third lens G3 and the fourth lens G4 are cemented lenses, the fifth lens G5 is a double concave lens, the sixth lens G6 is a double convex lens, the fifth lens G5 and the sixth lens G6 are cemented lenses, the seventh lens G7 is a double convex lens, and the eighth lens G8 is a double convex lens.

[0137] The focal length of each lens is limited as follows.

[0138] The focal length f1 of the first lens G1 is 36.1mm; the focal length f2 of the second lens G2 is -10.2mm; the focal length f3 of the third lens G3 is -6.4mm; the focal length f4 of the fourth lens G4 is 5.2mm; the focal length f5 of the fifth lens G5 is -6.7mm; the focal length f6 of the sixth lens G6 is 9mm; the focal length f7 of the seventh lens G7 is 26.6mm; and the focal length f8 of the eighth lens G8 is 17.5mm.

[0139] The curvature radius of each lens is limited as follows.

[0140] The curvature radius R11 of the entrance surface of the first lens G1 is 27.4 mm, and the curvature radius R12 of the exit surface is infinite; the curvature radius R21 of the entrance surface of the second lens G2 is 15 mm, and the curvature radius R22 of the exit surface is 5.1 mm; the curvature radius R31 of the entrance surface of the third lens G3 is 45.4 mm, and the curvature radius R32 of the exit surface is 5 mm; the curvature radius R41 of the entrance surface of the fourth lens G4 is 5 mm, and the curvature radius R42 of the exit surface is -87 mm; the curvature radius R51 of the entrance surface of the fifth lens G5 is -15.8 mm, and the curvature radius R52 of the exit surface is 11.5 mm; the curvature radius R61 of the entrance surface of the sixth lens G6 is 11.5 mm, and the curvature radius R62 of the exit surface is -10.5 mm; the curvature radius R71 of the entrance surface of the seventh lens G7 is 283.9 mm, and the curvature radius R72 of the exit surface is -21.6 mm; the curvature radius R81 of the entrance surface of the eighth lens G8 is 31.8 mm, and the curvature radius R82 of the exit surface is -25.9 mm.

[0141] The curvature radius R12 of the exit surface of the first lens G1 is infinite, indicating that the exit surface of the first lens G1 is a plane.

[0142] The central thickness of each lens is defined as follows.

[0143] The central thickness GT1 of the first lens G1 is 3.7 mm; the central thickness GT2 of the second lens G2 is 1.6 mm; the central thickness GT3 of the third lens G3 is 1.5 mm; the central thickness GT4 of the fourth lens G4 is 4 mm; the central thickness GT5 of the fifth lens G5 is 2.3 mm; the central thickness GT6 of the sixth lens G6 is 3.9 mm; the central thickness GT7 of the seventh lens G7 is 2.9 mm; and the central thickness GT8 of the eighth lens G8 is 3.5 mm.

[0144] The air gap distance of each lens along the optical axis is defined as follows.

[0145] The air gap distance AT1 of the first lens G1 and the second lens G2 along the optical axis is 0.2 mm; the air gap distance AT2 of the second lens G2 and the third lens G3 along the optical axis is 3.6 mm; the third lens G3 and the fourth lens G4 are cemented lenses; the air gap distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis is 2.3 mm; the air gap distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis is 0.8 mm; the fifth lens G5 and the sixth lens G6 are cemented lenses; the air gap distance AT5 of the sixth lens G6 and the seventh lens G7 along the optical axis is 0.2 mm; the air gap distance AT6 of the seventh lens G7 and the eighth lens G8 along the optical axis is 0.2 mm; and the air gap distance BFL of the eighth lens G8 and the image plane along the optical axis is 12 mm.

[0146] wherein the air separation distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis and the air separation distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis satisfy AT3+AT4=3.1mm.

[0147] The refractive index and Abbe number of each lens are defined as follows.

[0148] The refractive index N1 of the first lens G1 is 1.76, and the Abbe number V1 is 52.3; the refractive index N2 of the second lens G2 is 1.81, and the Abbe number V2 is 25.4; the refractive index N3 of the third lens G3 is 1.88, and the Abbe number V3 is 40.8; the refractive index N4 of the fourth lens G4 is 1.92, and the Abbe number V4 is 20.9; the refractive index N5 of the fifth lens G5 is 1.95, and the Abbe number V5 is 17.9; the refractive index N6 of the sixth lens G6 is 1.65, and the Abbe number V6 is 58.4; the refractive index N7 of the seventh lens G7 is 1.75, and the Abbe number V7 is 52.3; the refractive index N8 of the eighth lens G8 is 1.83, and the Abbe number V8 is 42.7.

[0149] Example Three

[0150] The focal length f of the optical lens of this example three is 11mm; the aperture number of the optical lens is F7.5; the working waveband WL of the optical lens is 390nm-700nm; the image side target surface size IMG is 12mm; the total system optical length TTL is 66.4mm, and the system back focus BFL is 16.2mm.

[0151] The focal length fa of the first lens group 10 is -18.5mm; the focal length fb of the second lens group 20 is 36.4mm; and the focal length fc of the third lens group 30 is 11.3mm.

[0152] The axial distance between the first lens group 10 and the second lens group 20 is 3.81mm; and the axial distance between the second lens group 20 and the third lens group 30 is 2.1mm.

[0153] The focal length fa of the first lens group 10 and the focal length f of the optical lens satisfy |fa / f|=1.7; the focal length fb of the second lens group 20 and the focal length f of the optical lens satisfy fb / f=3.3; and the focal length fc of the third lens group 30 and the focal length f of the optical lens satisfy fc / f=1.

[0154] The surface shape of each lens is as follows:

[0155] The first lens G1 is a convex plane lens, the second lens G2 is a convex-concave lens, the third lens G3 is a convex-concave lens, the fourth lens G4 is a convex plane lens, the third lens G3 and the fourth lens G4 are cemented lenses, the fifth lens G5 is a double-concave lens, the sixth lens G6 is a double-convex lens, the fifth lens G5 and the sixth lens G6 are cemented lenses, the seventh lens G7 is a plane-convex lens, and the eighth lens G8 is a double-convex lens.

[0156] The focal lengths of the lenses are defined as follows.

[0157] The focal length f1 of the first lens G1 is 100.7 mm, the focal length f2 of the second lens G2 is -12.9 mm, the focal length f3 of the third lens G3 is -10.7 mm, the focal length f4 of the fourth lens G4 is 7.9 mm, the focal length f5 of the fifth lens G5 is -10.7 mm, the focal length f6 of the sixth lens G6 is 13.7 mm, the focal length f7 of the seventh lens G7 is 27.8 mm, and the focal length f8 of the eighth lens G8 is 27.5 mm.

[0158] The radii of curvature of the lenses are defined as follows.

[0159] The radius of curvature R11 of the entrance surface of the first lens G1 is 59.9 mm, and the radius of curvature R12 of the exit surface is infinite; the radius of curvature R21 of the entrance surface of the second lens G2 is 16.9 mm, and the radius of curvature R22 of the exit surface is 6.2 mm; the radius of curvature R31 of the entrance surface of the third lens G3 is 29.6 mm, and the radius of curvature R32 of the exit surface is 7.5 mm; the radius of curvature R41 of the entrance surface of the fourth lens G4 is 7.5 mm, and the radius of curvature R42 of the exit surface is infinite; the radius of curvature R51 of the entrance surface of the fifth lens G5 is -21.7 mm, and the radius of curvature R52 of the exit surface is 21 mm; the radius of curvature R61 of the entrance surface of the sixth lens G6 is 21 mm, and the radius of curvature R62 of the exit surface is -12.9 mm; the radius of curvature R71 of the entrance surface of the seventh lens G7 is infinite, and the radius of curvature R72 of the exit surface is -21.1 mm; and the radius of curvature R81 of the entrance surface of the eighth lens G8 is 41.7 mm, and the radius of curvature R82 of the exit surface is -39.6 mm.

[0160] The radius of curvature R12 of the exit surface of the first lens G1 is infinite, indicating that the exit surface of the first lens G1 is a plane. The radius of curvature R42 of the exit surface of the fourth lens G4 is infinite, indicating that the exit surface of the fourth lens G4 is a plane. The radius of curvature R71 of the entrance surface of the seventh lens G7 is infinite, indicating that the entrance surface of the seventh lens G7 is a plane.

[0161] The central thicknesses of the lenses are defined as follows.

[0162] The central thickness GT1 of the first lens G1 is 6.2 mm; the central thickness GT2 of the second lens G2 is 3 mm; the central thickness GT3 of the third lens G3 is 3 mm; the central thickness GT4 of the fourth lens G4 is 3.8 mm; the central thickness GT5 of the fifth lens G5 is 3 mm; the central thickness GT6 of the sixth lens G6 is 5.1 mm; the central thickness GT7 of the seventh lens G7 is 4.3 mm; and the central thickness GT8 of the eighth lens G8 is 4.5 mm.

[0163] The air interval distances of the lenses along the optical axis are defined as follows.

[0164] The air interval distance AT1 of the first lens G1 and the second lens G2 along the optical axis is 10.8 mm; the air interval distance AT2 of the second lens G2 and the third lens G3 along the optical axis is 3.8 mm; the third lens G3 and the fourth lens G4 are cemented lenses; the air interval distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis is 1.1 mm; the air interval distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis is 1 mm; the fifth lens G5 and the sixth lens G6 are cemented lenses; the air interval distance AT5 of the sixth lens G6 and the seventh lens G7 along the optical axis is 0.2 mm; the air interval distance AT6 of the seventh lens G7 and the eighth lens G8 along the optical axis is 0.2 mm; and the air interval distance BFL of the eighth lens G8 and the image plane along the optical axis is 16.2 mm.

[0165] The air interval distance AT3 of the fourth lens G4 and the aperture stop 40 along the optical axis and the air interval distance AT4 of the aperture stop 40 and the fifth lens G5 along the optical axis satisfy AT3+AT4=2.1 mm.

[0166] The refractive indexes and Abbe numbers of the lenses are defined as follows.

[0167] The refractive index N1 of the first lens G1 is 1.59, and the Abbe number V1 is 68; the refractive index N2 of the second lens G2 is 1.88, and the Abbe number V2 is 40.8; the refractive index N3 of the third lens G3 is 2, and the Abbe number V3 is 25.4; the refractive index N4 of the fourth lens G4 is 1.95, and the Abbe number V4 is 17.9; the refractive index N5 of the fifth lens G5 is 1.95, and the Abbe number V5 is 17.9; the refractive index N6 of the sixth lens G6 is 1.62, and the Abbe number V6 is 63.4; the refractive index N7 of the seventh lens G7 is 1.75, and the Abbe number V7 is 52.3; and the refractive index N8 of the eighth lens G8 is 1.76, and the Abbe number V8 is 52.3.

[0168] In combination Figure 2 In the distortion diagram, the ordinate is the field of view, and the abscissa is the distortion value. Each curve represents the distortion value at different wavelengths in the working waveband range. As shown in the figure, the distortion value of the lens is less than 0.1% in the working waveband range. Figure 2It can be seen that the full field of view distortion of the optical lens is less than 1%, which is beneficial to realize high calibration accuracy and improve detection accuracy. Moreover, the aberrations such as spherical aberration, coma, astigmatism, and chromatic aberration are still kept in a small range that does not affect the accuracy.

[0169] The abscissa of the edge spread function curve is the distance to the center of the pixel, in microns; and the ordinate is the percentage of the radiation intensity at the current position, with a value range of 0-1.

[0170] In combination Figure 3 Without increasing the wave front, 0.5-0.9 pixels are contained within 20%-80% radiation intensity.

[0171] In combination Figure 4 After the wave front RMS value is increased to 1λ, the number of pixels contained within 20%-80% radiation intensity is increased to 1.0-3.4 pixels.

[0172] Embodiment two

[0173] In combination Figure 5 The optical engine provided by the embodiment of the present disclosure includes a light source 51, a digital micromirror chip 52, and a projection lens 53. The light of the light source 51 forms a projection image after passing through the digital micromirror chip 52 and is projected via the projection lens 53.

[0174] The projection lens 53 is the optical lens of the above-mentioned embodiment one.

[0175] The light source 51 can be an LED light source, a laser light source, or other light sources.

[0176] In some embodiments, the light source 51 is a high-brightness light source.

[0177] The light source 51 can be provided with three light sources 51, and the main wavelengths of the three light sources 51 can be 430nm-460nm, 510nm-530nm, and 610nm-650nm, respectively. The software can be used to control the projection of a full-bright image, a full-dark image, different-width Gray code stripes, sinusoidal stripes, and single-column pixel stripes by using white light and monochromatic light. The white light is generated by simultaneously or alternately lighting the monochromatic light.

[0178] The digital micromirror chip (DMD) 52 contains millions of tiny mirrors, each of which represents a pixel. By controlling the tilt angle of each micromirror, the reflection of light is adjusted to generate an image.

[0179] The optical engine of the embodiment of the present disclosure uses the optical lens of the above-mentioned embodiment one as the projection lens 53, which can effectively reduce the micromirror artifacts in the structured light.

[0180] When the optical engine uses the optical lens in the prior art as the projection lens, the micro-mirror artifact of the projection picture is as shown in FIG. 5. Figure 6 As can be seen from the figure, the micro-mirror artifact with obvious bright-dark difference.

[0181] Referring to Figure 8 , in the brightness distribution curve of the micro-mirror artifact, the abscissa is the pixel number from the left side to the right side of the image in Figure 6 , and the ordinate is the gray value. The position with the maximum gray value is the brightest position, and the position with the minimum gray value is the darkest position. Among them, the gray value C1 of the brightest position is 223, the gray value C2 of the darkest position is 199, and the bright-dark contrast is (C1-C2) / (C1+C2)*100% = 5.7%.

[0182] When the optical engine uses the optical lens of the embodiment of the present disclosure as the projection lens, the micro-mirror artifact of the projection picture is as shown in FIG. 6. Figure 7 As can be seen from the figure, the bright-dark difference of the micro-mirror artifact is obviously reduced.

[0183] Referring to Figure 9 , the gray value C1 of the brightest position is 237, the gray value C2 of the darkest position is 228, and the bright-dark contrast is (C1-C2) / (C1+C2)*100% = 1.9%.

[0184] (5.7%-1.9%) / 5.7% = 0.667, so the noise intensity caused by the micro-mirror artifact is reduced by two-thirds.

[0185] The optical engine of the embodiment of the present disclosure realizes high-quality structured light projection by reducing the micro-mirror artifact.

[0186] Embodiment Three

[0187] In combination Figure 10 , the embodiment of the present disclosure also provides an imaging module, which comprises a photosensitive chip 101 and the optical lens 102 of the above-mentioned embodiment, and the object-side light is imaged on the photosensitive chip 101 via the optical lens 102.

[0188] A cover glass 103 is further arranged on the side of the photosensitive chip 101 facing the optical lens 102, so as to protect the photosensitive chip 101.

[0189] Figure 11 The laser stripe image generated by the laser engine has obvious laser speckle. Figure 12 The laser stripe image has a brightness distribution curve as shown in FIG. 8. Figure 11 The abscissa is the distance, and the ordinate is the gray value. The laser speckle is manifested as obvious burrs in the brightness distribution curve in the length direction of the stripe, and the maximum PV value (Peak-to-Valley value) is 126.

[0190] Figure 13 the image formed by the laser stripe image photographed by the optical lens of the prior art Figure 11 The image formed by the laser stripe image photographed by the optical lens of the prior art

[0191] Figure 14 the image formed by the laser stripe image photographed by the optical lens of the prior art Figure 11 The bright and dark spots are blurred and even invisible in the image formed by the laser stripe image photographed by the optical lens of the prior art

[0192] Figure 15 the image formed by the laser stripe image photographed by the optical lens of the prior art Figure 13 The PV value of the brightness distribution curve of the image is maximally 109; Figure 16 the image formed by the laser stripe image photographed by the optical lens of the prior art Figure 14 The PV value of the brightness distribution curve of the image is maximally 56. The noise intensity caused by the laser speckle is reduced by nearly half.

[0193] When the optical lens of the embodiment of the present disclosure is used as an imaging lens, high-quality image output is achieved by significantly reducing the contrast of the micro-lens artifacts of the structured light and the laser speckle in the image.

[0194] Embodiment Four

[0195] The embodiment of the present disclosure also provides a 3D camera, which comprises a structured light projection device and an imaging camera; the structured light projection device is configured to emit light to a target object, and the imaging camera collects the light reflected by the target object and forms an image;

[0196] The structured light projection device comprises the optical engine of the embodiment two; and / or,

[0197] The imaging camera comprises the imaging module of the embodiment three.

[0198] In some examples, the 3D camera projects light to a target object by using the optical engine of the embodiment two, and collects the light reflected by the target object and forms an image by using the imaging camera of the prior art.

[0199] In other examples, the 3D camera projects light to a target object by using the existing optical engine, and collects the light reflected by the target object and forms an image by using the imaging module of the embodiment three.

[0200] In yet other examples, the 3D camera projects light to a target object by using the optical engine of the embodiment two, and collects the light reflected by the target object and forms an image by using the imaging module of the embodiment three.

[0201] The embodiment of the present disclosure also provides a 3D camera, which comprises a structured light projection device and an imaging camera; the structured light projection device is configured to emit light to a target object, and the imaging camera collects the light reflected by the target object and forms an image;

[0202] The structured light projection device comprises a light source, a digital micro-mirror chip, and the optical lens of embodiment one. The light from the light source forms a projection image after passing through the digital micro-mirror chip and is projected to the target object via the optical lens. The imaging camera collects the light reflected by the target object and forms an image. And / or

[0203] The imaging camera comprises a photosensitive chip and the optical lens of embodiment one. The structured light projection device is configured to project structured light to the target object. The light on the target object is imaged on the photosensitive chip via the optical lens.

[0204] In some examples, the 3D camera adopts the optical lens of embodiment one as the projection lens of the structured light projection device and adopts the optical lens of the prior art as the imaging lens.

[0205] In other examples, the 3D camera adopts the optical lens of the prior art as the projection lens of the structured light projection device and adopts the optical lens of embodiment one as the imaging lens.

[0206] In yet other examples, the 3D camera adopts the optical lens of embodiment one as the projection lens of the structured light projection device and adopts the optical lens of embodiment one as the imaging lens.

[0207] Figure 17 For the 3D camera, the existing optical lens is adopted as the projection lens and the existing optical lens is adopted as the imaging lens. The micro-mirror artifacts in the collected image are obvious in brightness and darkness.

[0208] Figure 18 For the 3D camera, the optical lens of embodiment one is adopted as the projection lens and the existing optical lens is adopted as the imaging lens. The micro-mirror artifacts in the collected image are weakened in brightness and darkness.

[0209] Figure 19 For the 3D camera, the existing optical lens is adopted as the projection lens and the optical lens of embodiment one is adopted as the imaging lens. The micro-mirror artifacts in the collected image are weakened in brightness and darkness.

[0210] Figure 20 For the 3D camera, the optical lens of embodiment one is adopted as the projection lens and the optical lens of embodiment one is adopted as the imaging lens. The micro-mirror artifacts in the collected image are weakened in brightness and darkness.

[0211] Figure 21 For Figure 17 The point cloud fluctuation test curve of the three-dimensional reconstruction of the micro-mirror artifacts in FIG. 8 is shown in FIG. 9. The horizontal coordinate is the pixel coordinate and the vertical coordinate is the depth distance, which is in mm. Figure 21 The point cloud fluctuation PV value in FIG. 8 is about 0.7 mm.

[0212] Figure 22The midpoint cloud fluctuation PV value is about 0.15 mm, and the fluctuation amplitude is improved by about 78%.

[0213] Figure 23 The midpoint cloud fluctuation PV value is about 0.2 mm, and the fluctuation amplitude is improved by about 71%.

[0214] Figure 24 The midpoint cloud fluctuation PV value is about 0.1 mm, and the fluctuation amplitude is improved by about 86%.

[0215] The 3D camera of the embodiments of the present disclosure adopts the optical lens of the embodiments of the present disclosure as the projection lens and / or optical lens, which can effectively reduce the noise intensity of the original image, improve the signal-to-noise ratio, significantly improve the three-dimensional reconstruction point cloud fluctuation, and further improve the repeatability and resolution of the 3D camera; and achieve high absolute accuracy with a distortion of less than 1%, without loss of measurement accuracy. For targets with high absorption and high transmission, such as dark objects and transparent objects, it is beneficial to solve the detection problem of being difficult to distinguish between effective signals and interference signals.

[0216] In the above description, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction.

[0217] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present disclosure, and not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. An optical lens, characterized in that, It consists of eight lenses with optical power arranged coaxially from the object side to the image side, as well as an aperture stop; The root mean square value of the wavefront of the optical lens is increased to be no less than one wavelength; the full field-of-view distortion of the optical lens is less than 1%. The eight lenses with optical power are respectively the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens; the aperture stop is located between the fourth lens and the fifth lens; The first lens has positive optical power, the second lens has negative optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has negative optical power, the sixth lens has positive optical power, and the seventh lens has positive optical power. The eighth lens has positive optical power; The object-side surface of the first lens is convex, the second lens is a convex-concave lens, the third lens is a convex-concave lens, the object-side surface of the fourth lens is convex, the fifth lens is a biconcave lens, the sixth lens is a biconvex lens, the image-side surface of the seventh lens is convex, and the eighth lens is a biconvex lens. The focal length f1 of the first lens is 28.1mm to 100.7mm; the focal length f2 of the second lens is -12.9mm to -7mm; the focal length f3 of the third lens is -10.7mm to -5.9mm; the focal length f4 of the fourth lens is 4.5mm to 7.9mm; the focal length f5 of the fifth lens is -10.7mm to -5.5mm; the focal length f6 of the sixth lens is 6.6mm to 13.7mm; the focal length f7 of the seventh lens is 20.2mm to 27.8mm; and the focal length f8 of the eighth lens is 14.1mm to 27.5mm.

2. The optical lens according to claim 1, characterized in that, The third lens and the fourth lens are cemented lenses, and the cemented lens formed by the third lens and the fourth lens has positive optical power; the fifth lens and the sixth lens are cemented lenses, and the cemented lens formed by the fifth lens and the sixth lens has positive optical power.

3. The optical lens according to claim 1, characterized in that, The first lens has an incident surface radius of curvature R11 of 19.2 mm to 59.9 mm and an exit surface radius of curvature R12 greater than or equal to 176.1 mm; the second lens has an incident surface radius of curvature R21 of 10.3 mm to 16.9 mm and an exit surface radius of curvature R22 of 3.5 mm to 6.2 mm; the third lens has an incident surface radius of curvature R31 of 21.1 mm to 45.5 mm and an exit surface radius of curvature R32 of 4 mm to 7.5 mm; the fourth lens has an incident surface radius of curvature R41 of 4 mm to 7.5 mm and an exit surface radius of curvature R42 less than or equal to -87 mm, or an exit surface radius of curvature R42 greater than or equal to 5 mm. The radius of curvature of the incident surface of the fifth lens is 5.8mm; the radius of curvature R51 of the incident surface of the sixth lens is -21.7mm to -13.67mm, and the radius of curvature R52 of the exit surface is 8.8mm to 21mm; the radius of curvature R61 of the incident surface of the sixth lens is 8.8mm to 21mm, and the radius of curvature R62 of the exit surface is -12.9mm to -7.2mm; the radius of curvature R71 of the incident surface of the seventh lens is greater than or equal to 283.9mm, and the radius of curvature R72 of the exit surface is -21.6mm to -15.3mm; the radius of curvature R81 of the incident surface of the eighth lens is 26.9mm to 41.7mm, and the radius of curvature R82 of the exit surface is -39.6mm to -16.9mm.

4. The optical lens according to claim 1, characterized in that, The center thickness GT1 of the first lens is 3mm to 6.2mm; the center thickness GT2 of the second lens is 1.6mm to 3mm; the center thickness GT3 of the third lens is 1.5mm to 3mm; the center thickness GT4 of the fourth lens is 2.5mm to 4mm; the center thickness GT5 of the fifth lens is 1.2mm to 3mm; the center thickness GT6 of the sixth lens is 3.2mm to 5.1mm; the center thickness GT7 of the seventh lens is 2.4mm to 4.3mm; and the center thickness GT8 of the eighth lens is 2.9mm to 4.5mm.

5. The optical lens according to claim 1, characterized in that, The air gap distance AT1 between the first lens and the second lens along the optical axis is 0.2 mm to 10.8 mm; the air gap distance AT2 between the second lens and the third lens along the optical axis is 2.6 mm to 3.8 mm; the third lens and the fourth lens are cemented lenses; the air gap distance AT3 between the fourth lens and the aperture stop along the optical axis is 0.7 mm to 2.3 mm; the air gap distance AT4 between the aperture stop and the fifth lens along the optical axis is 0.6 mm to 1 mm; the fifth lens and the sixth lens are cemented lenses; the air gap distance AT5 between the sixth lens and the seventh lens along the optical axis is 0.16 mm to 0.2 mm; the air gap distance AT6 between the seventh lens and the eighth lens along the optical axis is 0.16 mm to 0.2 mm; and the air gap distance BFL between the eighth lens and the image plane along the optical axis is 9.4 mm to 16.2 mm.

6. The optical lens according to claim 1, characterized in that, The first lens has a refractive index N1 of 1.59–1.76 and an Abbe number V1 of 52.3–68; the second lens has a refractive index N2 of 1.81–1.88 and an Abbe number V2 of 25.4–40.8; the third lens has a refractive index N3 of 1.81–2 and an Abbe number V3 of 25.4–40.8; and the fourth lens has a refractive index N4 of 1.92–1.95 and an Abbe number V4 of 17. The refractive index of the fifth lens is 1.95, and the Abbe number is 17.

9. The refractive index of the sixth lens is 1.62 to 1.65, and the Abbe number is 58.4 to 63.

4. The refractive index of the seventh lens is 1.75, and the Abbe number is 52.

3. The refractive index of the eighth lens is 1.75 to 1.83, and the Abbe number is 42.7 to 52.

3.

7. The optical lens according to claim 1, characterized in that, The first lens and the second lens form a first lens group, and the focal length fa of the first lens group is -18.5mm to -11.4mm; The third lens and the fourth lens form a second lens group, and the focal length fb of the second lens group is 26.4mm to 36.4mm; The fifth lens, the sixth lens, the seventh lens, and the eighth lens form a third lens group, and the focal length fc of the third lens group is 6.6mm to 11.3mm. The axial distance between the first lens group and the second lens group is 2.6 mm to 3.81 mm; the axial distance between the second lens group and the third lens group is 1.3 mm to 2.1 mm.

8. The optical lens according to claim 1, characterized in that, The focal length fa of the first lens group and the focal length f of the optical lens satisfy 1.7 < |fa / f| < 2.2; the focal length fb of the second lens group and the focal length f of the optical lens satisfy 3.3 < fb / f < 4.3; the focal length fc of the third lens group and the focal length f of the optical lens satisfy 1 < fc / f < 1.

2.

9. The optical lens according to any one of claims 1-8, characterized in that, The focal length f of the optical lens is 6mm to 11mm; the aperture number of the optical lens is F1.4 to F7.5; the working wavelength WL of the optical lens is 390nm to 700nm; the image target size IMG is 6mm to 12mm; the total optical length TTL of the system is 33mm to 66.4mm; and the back focal length BFL of the system is 9.4mm to 16.2mm.

10. An optical engine, characterized in that, include: The system includes a light source, a digital micromirror chip, and a projection lens. The light from the light source passes through the digital micromirror chip to form a projected image, which is then projected through the projection lens. The projection lens is the optical lens described in any one of claims 1-9.

11. An imaging module, characterized in that, It includes a photosensitive chip and an optical lens as described in any one of claims 1-9, wherein object-side light is imaged onto the photosensitive chip via the optical lens.

12. A 3D camera, characterized in that, include: Structured light projection device and imaging camera; The structured light projection device is configured to emit light rays to a target object, and the imaging camera collects the light rays reflected by the target object and forms an image; Wherein, the structured light projection device includes the optical engine as described in claim 10; and / or, The imaging camera includes the imaging module as described in claim 11.

13. A 3D camera, characterized in that, include: Structured light projection device and imaging camera; The structured light projection device is configured to emit light rays to a target object, and the imaging camera collects the light rays reflected by the target object and forms an image; The structured light projection device includes a light source, a digital micromirror chip, and an optical lens as described in any one of claims 1-9. The light from the light source passes through the digital micromirror chip to form a projected image, which is then projected onto the target object via the optical lens. The imaging camera captures the light reflected from the target object and forms an image; and / or The imaging camera includes: a photosensitive chip and an optical lens according to any one of claims 1-9, and the structured light projection device is configured to project structured light onto a target object; The light rays from the target object are imaged onto the photosensitive chip via the optical lens.

Images