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

Abstract

The invention relates to the technical field of optics, in particular to an optical lens, an optical engine, an imaging module and a 3D camera. The invention aims to improve the signal-to-noise ratio of three-dimensional detection by reducing interference signals. The optical lens provided by the invention comprises a plurality of lenses and an aperture diaphragm which are sequentially and coaxially arranged from the object side to the image side, the absolute value of the difference between the number of lenses, facing the object side, of the aperture diaphragm and the number of lenses, facing the image side, of the aperture diaphragm is smaller than or equal to 2, and the difference between the numbers of the lenses on the two sides of the aperture diaphragm is small so as to reduce distortion. The full-view-field distortion of the optical lens is less than 1%, and the imaging performance and the detection precision are ensured; moreover, the wavefront root-mean-square value is increased to be not less than one wavelength, so that transition pixels are increased, and the detail contrast ratio is reduced, thereby reducing point cloud fluctuation caused by micro-mirror artifacts, laser speckles and the like, and improving the signal-to-noise ratio and detection precision 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 Art

[0002] Machine vision technology mainly acquires images through image acquisition devices composed of light sources, lenses, etc., and uses image processing algorithms to analyze and process the images of target objects to obtain target features. It is widely used in production and manufacturing, quality inspection, logistics, medicine, scientific research and other fields.

[0003] In the relevant technology, the optical engine is an important part of machine vision technology as a device that generates light signals and projects them onto the target object. When the projection of the optical engine has micro-mirror artifacts or speckles, or the effective light energy reflected on the detection target surface is low, the camera signal-to-noise ratio will be reduced, affecting the absolute accuracy and resolution of optical machine vision detection. Summary of the invention

[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] In order to achieve the above objectives, the present disclosure adopts the following technical solutions:

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

[0007] The root mean square value of the wavefront of the optical lens increases to no less than one wavelength; and the full field distortion 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 is provided with a plurality of lenses, and the absolute value of the difference in the number of lenses on both sides of the aperture stop is less than or equal to 2, and the difference in the number of lenses on both sides of the aperture stop is small, so as to reduce distortion, so that the full field distortion of the optical lens is less than 1%, thereby ensuring imaging performance and detection accuracy; 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 pixel increases, the contrast of the edge of the pixel is reduced, thereby reducing the point cloud fluctuation caused by micromirror artifacts, laser speckle, etc., and improving the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0010] As an improvement of the above optical lens disclosed in the present invention, the optical lens includes: 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 coaxially arranged 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 above optical lens disclosed in the present invention, the first lens has positive focal power, the second lens has negative focal power, the third lens has negative focal power, the fourth lens has positive focal power, the fifth lens has negative focal power, the sixth lens has positive focal power, and the seventh lens has positive focal power; the eighth lens has positive focal 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 focal 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 focal power.

[0012] As an improvement of the above-mentioned optical lens disclosed in the present invention, 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; the focal length f8 of the eighth lens is 14.1mm~27.5mm.

[0013] As an improvement of the above-mentioned optical lens disclosed in the present invention, the radius of curvature R11 of the incident surface of the first lens is 19.2mm~59.9mm, and the radius of curvature R12 of the exit surface is greater than or equal to 176.1mm; the radius of curvature R21 of the incident surface of the second lens is 10.3mm~16.9mm, and the radius of curvature R22 of the exit surface is 3.5mm~6.2mm; the radius of curvature R31 of the incident surface of the third lens is 21.1mm~45.5mm, and the radius of curvature R32 of the exit surface is 4mm~7.5mm; the radius of curvature R41 of the incident surface of the fourth lens is 4mm~7.5mm, and the radius of curvature R42 of the exit surface is less than or equal to -87mm, or the radius of curvature R41 of the exit surface is 4mm~7.5mm. 2 is greater than or equal to 55.8mm; the curvature radius R51 of the incident surface of the fifth lens 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 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 is greater than or equal to 283.9mm, and the curvature radius R72 of the exit surface is -21.6mm~-15.3mm; the curvature radius R81 of the incident surface of the eighth lens is 26.9mm~41.7mm, and the curvature radius R82 of the exit surface is -39.6mm~-16.9mm.

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

[0015] As an improvement of the above optical lens disclosed in the present invention, an aperture stop is arranged between the fourth lens and the fifth lens; the air spacing distance AT1 between the first lens and the second lens along the optical axis is 0.2mm-10.8mm; the air spacing distance AT2 between 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 spacing distance AT3 between the fourth lens and the aperture stop along the optical axis is 0.7mm-2.3mm; the air spacing distance AT4 between 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 spacing distance AT5 between the sixth lens and the seventh lens along the optical axis is 0.16mm-0.2mm; the air spacing distance AT6 between the seventh lens and the eighth lens along the optical axis is 0.16mm-0.2mm; and the air spacing distance BFL between the eighth lens and the image plane along the optical axis is 9.4mm-16.2mm.

[0016] As an improvement of the above optical lens disclosed in the present invention, 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, 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 above optical lens disclosed in the present invention, the first lens and the second lens form a first lens group, and the focal length fa of the first lens group is -18.5 mm to -11.4 mm; the third lens and the fourth lens form a second lens group, and the focal length fb of the second lens group is 26.4 mm to 36.4 mm; 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 6.6 mm to 11.3 mm; the axial spacing between the first lens group and the second lens group is 2.6 mm to 3.81 mm; the axial spacing between the second lens group and the third lens group is 1.3 mm to 2.1 mm.

[0018] As an improvement of the above-mentioned optical lens disclosed in the present invention, 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 above-mentioned optical lens disclosed in the present invention, 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 band WL of the optical lens is 390nm~700nm; the image side target surface size IMG is 6mm~12mm; the total optical length TTL of the system 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, which includes: a light source, a digital micromirror chip and a projection lens. The light of the light source forms a projection image after passing through the digital micromirror chip and is projected through the projection lens; the projection lens is the optical lens described in the first aspect.

[0021] The optical engine provided in the second aspect of the present disclosure includes the optical lens described in the first aspect, so the optical engine provided in the second aspect of the present disclosure also has the same advantages as the optical lens described in the first aspect.

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

[0023] The imaging module provided in the third aspect of the present disclosure includes the optical lens described in the first aspect, so the imaging module provided in the third aspect of the present disclosure also has the same advantages as the optical lens described in the first aspect.

[0024] A fourth aspect of the present disclosure provides a 3D camera, comprising a structured light projector and an imaging camera; the structured light projector 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 projector comprises the optical engine described in the second aspect; and / or the imaging camera comprises the imaging module described in the third aspect.

[0025] The 3D camera provided in the fourth aspect of the present disclosure includes the optical engine described in the second aspect and / or the imaging module described in the third aspect. Therefore, the 3D camera provided in the fourth aspect of the present disclosure also has the same advantages as the optical engine described in the second aspect and / or the imaging module described in the third aspect.

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

[0027] The structured light projection comprises a light source, a digital micromirror chip and an optical lens according to any one of claims 1 to 12, wherein the light from the light source forms a projection image after passing through the digital micromirror chip, and the projection lens projects the light onto the target object; 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 according to any one of claims 1 to 12, and the structured light projection is configured to project structured light onto a target object; the light on the target object is imaged onto the photosensitive chip via the optical lens.

[0029] The 3D camera provided in the fifth aspect of the present disclosure includes the optical lens described in the first aspect, so the 3D camera provided in the fifth aspect of the present disclosure also has the same advantages as the optical lens described in the first aspect.

[0030] In addition to the technical problems solved by the present disclosure, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by the optical lens and electronic device provided by the present disclosure, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments of the present disclosure or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only part of the embodiments of the present disclosure. These drawings and text descriptions are not intended to limit the scope of the concept of the present disclosure in any way, but to illustrate the concepts of the present disclosure to those skilled in the art by referring to specific embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the structure of an optical lens provided in an embodiment of the present disclosure;

[0033] Figure 2 A distortion diagram of the optical lens provided by an embodiment of the present disclosure;

[0034] Figure 3A graph of edge spread function of an optical lens without increasing wavefront provided by an embodiment of the present disclosure;

[0035] Figure 4 A graph of edge diffusion functions before and after the optical lens amplifies the wave provided by an embodiment of the present disclosure;

[0036] Figure 5 A schematic diagram of the structure of an optical engine provided by an embodiment of the present disclosure;

[0037] Figure 6 It is a micro-mirror artifact in the projection picture of an optical engine using an optical lens in the prior art;

[0038] Figure 7 A micromirror artifact in a projection image of an optical engine using the optical lens of an embodiment of the present disclosure;

[0039] Figure 8 A brightness distribution curve diagram of micromirror artifacts in a projection image of an optical engine using an optical lens in the prior art;

[0040] Fig. 9 is a brightness distribution curve diagram of micromirror artifacts in a projection picture of an optical engine using the optical lens of an embodiment of the present disclosure;

[0041] Fig.10 A schematic diagram of the structure of an imaging module provided in an embodiment of the present disclosure;

[0042] Fig.11 An image of the laser stripes generated for the laser engine;

[0043] Fig.12 for Fig.11 Brightness distribution curve of the laser stripe image;

[0044] Fig.13 Shooting with an imaging module using an optical lens in the prior art Fig.11 The image formed by the laser stripes;

[0045] Fig.14 Photographing the imaging module of the optical lens of the embodiment of the present disclosure Fig.11 The image formed by the laser stripes;

[0046] Fig.15 for Fig.13 Brightness distribution curve of the laser stripe image;

[0047] Fig.16 for Fig.14 Brightness distribution curve of the laser stripe image;

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

[0049] Fig.18 Micromirror artifacts in images collected by a 3D camera using the optical lens of the embodiment of the present disclosure as a projection lens and using an existing optical lens as an imaging lens;

[0050] Fig.19 Micromirror artifacts in images collected by a 3D camera using the optical lens of the embodiment of the present disclosure as an imaging lens and using an existing optical lens as a projection lens;

[0051] Fig. 20 Micromirror artifacts in images collected by a 3D camera using the optical lens of the embodiment of the present disclosure as a projection lens and the optical lens of the embodiment of the present disclosure as an imaging lens;

[0052] Fig.21 for Fig.17 Point cloud fluctuation test curve diagram of 3D reconstruction of micro-mirror artifacts;

[0053] Fig. 22 for Fig.18 Point cloud fluctuation test curve diagram of 3D reconstruction of micro-mirror artifacts;

[0054] Fig.23 for Fig.19 Point cloud fluctuation test curve diagram of 3D reconstruction of micro-mirror artifacts;

[0055] Fig.24 for Fig. 20 Point cloud fluctuation test curve of 3D reconstruction of micro-mirror artifacts. DETAILED DESCRIPTION

[0056] As a device that generates light signals and projects them onto target objects, the optical engine is an important part of machine vision technology. The camera acquires the surface features of the target object by collecting the light signals reflected by the target object.

[0057] For target objects with high material absorption, such as black objects, objects with complementary colors to the structured light, and targets 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, that is, the signal-to-noise ratio is low. Improving the signal-to-noise ratio is a key issue in improving the accuracy and repeatability of 3D surface reconstruction.

[0058] In 3D detection, a digital light processing (DLP) optical engine or laser engine is usually used to generate structured light signals. The projection of the DLP optical engine has micro-mirror artifacts, which are reflected as regular stripes in the structured light. The structured light generated by the laser engine has speckles due to the interference of the laser after being reflected by the microstructure of the target surface.

[0059] In some products, rotating or vibrating frosted glass or diffractive optical elements are used to reduce the contrast of projected micromirror artifacts and laser speckle. This has a relatively good effect for 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 all year round. They require a stable and reliable internal structure, which rotating or vibrating frosted glass or diffractive optical elements cannot meet.

[0060] In view of this, an embodiment of the present disclosure provides an optical lens for improving the signal-to-noise ratio of three-dimensional detection by reducing interference signals.

[0061] Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0062] Embodiment 1

[0063] An embodiment of the present disclosure provides an optical lens, wherein the root mean square value (RMS) of the wavefront of the optical lens is increased to no less than one wavelength.

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

[0065] When the wavefront RMS of the optical lens increases to not less than one wavelength, the number of pixels contained in the edge spread function within 20% to 80% of the radiant illumination increases within a certain range, for example, the number of pixels is 1.0 pixel to 3.4 pixels.

[0066] This increases the number of transition pixels at the edge of the pixel, reduces the contrast of the pixel edge, thereby reducing the point cloud fluctuations caused by micromirror artifacts, laser speckle, etc., and improves the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0067] In conventional lenses of related technologies, the wavefront RMS is less than one wavelength to improve the system imaging quality as much as possible and avoid the reduction of detail contrast. However, the wavefront RMS of the optical lens disclosed in the present invention is increased to more than one wavelength, which reduces the detail contrast and plays a role in reducing the point cloud fluctuation caused by micromirror artifacts, laser speckle, etc., and improves the signal-to-noise ratio and detection accuracy of three-dimensional detection.

[0068] The optical lens of the disclosed embodiment achieves optical distortion less than 1% through a double Gaussian structure variation.

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

[0070] Among them, the optical lens of the embodiment of the present disclosure includes a plurality of lenses and an aperture stop coaxially arranged in sequence from the object side to the image side, and the absolute value of the difference between the number of lenses with the aperture stop facing the object side and the number of lenses with the aperture stop facing the image side is less than or equal to 2.

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

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

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

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

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

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

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

[0078] The three lens groups each include at least one lens, which may include a double separated lens and a cemented lens. The lens surface may be a concave surface, a convex surface or a plane surface. The lenses of each lens group may all be spherical lenses, or all aspherical lenses, or may be composed of spherical lenses and aspherical lenses.

[0079] Continue to refer to Figure 1 The optical lens of the embodiment of the present disclosure includes 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 which are coaxially arranged in sequence from the object side to the image side; the third lens G3 and the fourth lens G4 are a cemented lens; the fifth lens G5 and the sixth lens G6 are a cemented lens.

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

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

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

[0083] The fifth lens G5 has negative power, the sixth lens G6 has positive power, and the cemented lens formed by the fifth lens G5 and the sixth lens G6 has positive power, and has the ability to converge certain light and correct chromatic aberration.

[0084] The seventh lens G7 has positive refractive power; the eighth lens G8 has positive refractive power, and the light is focused on the image plane in order to reduce the degree of deflection of light passing through the lens through the distribution of the refractive power, thereby reducing the system tolerance sensitivity.

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

[0086] The materials of the above lenses can be colorless optical glass and optical plastic. Optical plastic has low cost in mass production, is easy to process aspheric surfaces, and is lightweight. Optical glass has stable mechanical and thermal properties, and can eliminate chromatic aberration and improve imaging quality through the combination of different refractive indices and Abbe numbers. Industrial robots have diverse application environments and need to meet high ambient temperature stability.

[0087] In the disclosed embodiment, all lenses are made of glass. First, compared with plastic, glass has higher transmittance and better imaging effect. Second, the physical and chemical stability of glass is much better than that of plastic, so it can better adapt to various environments and has a longer service life.

[0088] In the disclosed embodiment, all lenses are spherical lenses, which are low in cost.

[0089] Depend on Figure 1 It can be seen from the structural diagram of the optical lens that, under the premise of ensuring the optical path size and volume of the lens, the lens structure is simple and the lens processability is good.

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

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

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

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

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

[0095] The focal length of each lens is defined below.

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

[0097] The curvature radius of each lens is defined below.

[0098] The radius of curvature R11 of the incident surface of the first lens G1 is 19.2mm-59.9mm, and the radius of curvature R12 of the exit surface is greater than or equal to 176.1mm; the radius of curvature R21 of the incident surface of the second lens G2 is 10.3mm-16.9mm, and the radius of curvature R22 of the exit surface is 3.5mm-6.2mm; the radius of curvature R31 of the incident surface of the third lens G3 is 21.1mm-45.5mm, and the radius of curvature R32 of the exit surface is 4mm-7.5mm; the radius of curvature R41 of the incident surface of the fourth lens G4 is 4mm-7.5mm, and the radius of curvature R42 of the exit surface is less than or equal to -87mm, or the radius of curvature R42 of the exit surface is greater than or equal to 5 5.8mm; the radius of curvature R51 of the incident surface of the fifth lens G5 is -21.7mm~-13.67mm, and the radius of curvature R52 of the exit surface is 8.8mm~21mm; the radius of curvature R61 of the incident surface of the sixth lens G6 is 8.8mm~21mm, and the radius of curvature R62 of the exit surface is -12.9mm~-7.2mm; the radius of curvature R71 of the incident surface of the seventh lens G7 is greater than or equal to 283.9mm, and the radius of curvature R72 of the exit surface is -21.6mm~-15.3mm; the radius of curvature R81 of the incident surface of the eighth lens G8 is 26.9mm~41.7mm, and the radius of curvature R82 of the exit surface is -39.6mm~-16.9mm.

[0099] Among them, combined with Figure 1The incident surface of the lens is the surface of the lens facing the object side; the exit surface of the lens is the surface of the lens facing the image side.

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

[0101] The center thickness of each lens is defined below.

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

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

[0104] The air spacing distance of each lens along the optical axis is defined below.

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

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

[0107] The air distance AT3 between the fourth lens G4 and the aperture stop 40 along the optical axis and the air distance AT4 between the aperture stop 40 and the fifth lens G5 along the optical axis satisfy 1.3<AT5+AT6<3.1.

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

[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 disclosed embodiments define the material properties of each lens by defining the refractive index and Abbe number of each lens.

[0111] Example 1

[0112] The focal length f of the optical lens of this example 1 is 6mm; the aperture number of the optical lens is F1.4; the working band WL of the optical lens is 390nm~700nm; the image side target surface size IMG is 6mm; the total optical length TTL of the system is 33mm, and the system back focus BFL is 9.4mm.

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

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

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

[0116] The surface shapes of each lens are 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 a cemented lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconvex lens, the fifth lens G5 and the sixth lens G6 are a cemented lens, the seventh lens G7 is a plano-convex lens, and the eighth lens G8 is a biconvex lens.

[0118] The focal length of each lens is defined below.

[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 curvature radius of each lens is defined below.

[0121] The first lens G1 has a curvature radius R11 of the incident surface of 19.2 mm, and a curvature radius R12 of the exit surface of 176.1 mm; the second lens G2 has a curvature radius R21 of the incident surface of 10.3 mm, and a curvature radius R22 of the exit surface of 3.5 mm; the third lens G3 has a curvature radius R31 of the incident surface of 21.1 mm, and a curvature radius R32 of the exit surface of 4 mm; the fourth lens G4 has a curvature radius R41 of the incident surface of 4 mm, and a curvature radius R42 of the exit surface of 55.8 mm; the fifth lens G4 has a curvature radius R50 of the incident surface of 4 mm, and a curvature radius R51 of the exit surface of 55.8 mm; The radius of curvature R51 of the incident surface of lens G5 is -13.67mm, and the radius of curvature R52 of the exit surface is 8.8mm; the radius of curvature R61 of the incident surface of the sixth lens G6 is 8.8mm, and the radius of curvature R62 of the exit surface is -7.2mm; the radius of curvature R71 of the incident surface of the seventh lens G7 is infinite, and the radius of curvature R72 of the exit surface is -15.3mm; the radius of curvature R81 of the incident surface of the eighth lens G8 is 26.9mm, and the radius of curvature R82 of the exit surface is -16.9mm.

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

[0123] The center thickness of each lens is defined below.

[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 spacing distance of each lens along the optical axis is defined below.

[0126] The air spacing distance AT1 between the first lens G1 and the second lens G2 along the optical axis is 0.2 mm; the air spacing distance AT2 between 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 spacing distance AT3 between the fourth lens G4 and the aperture stop 40 along the optical axis is 0.7 mm; the air spacing distance AT4 between 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 spacing distance AT5 between the sixth lens G6 and the seventh lens G7 along the optical axis is 0.16 mm; the air spacing distance AT6 between the seventh lens G7 and the eighth lens G8 along the optical axis is 0.16 mm; and the air spacing distance BFL between the eighth lens G8 and the image plane along the optical axis is 9.4 mm.

[0127] An air spacing distance AT3 between the fourth lens G4 and the aperture stop 40 along the optical axis and an air spacing distance AT4 between the aperture stop 40 and the fifth lens G5 along the optical axis satisfy AT3+AT4=1.3 mm.

[0128] The refractive index and Abbe number of each lens are defined below.

[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; the refractive index N8 of the eighth lens G8 is 1.75, and the Abbe number V8 is 52.3.

[0130] Example 2

[0131] The focal length f of the optical lens in this example is 7.6mm; the aperture number of the optical lens is F1.65; the working band 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 system back focus BFL is 12mm.

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

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

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

[0135] The surface shapes of each lens are as follows:

[0136] The first lens G1 is a convex-planar 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 biconvex lens, the third lens G3 and the fourth lens G4 are a cemented lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconvex lens, the fifth lens G5 and the sixth lens G6 are a cemented lens, the seventh lens G7 is a biconvex lens, and the eighth lens G8 is a biconvex lens.

[0137] The focal length of each lens is defined below.

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

[0139] The curvature radius of each lens is defined below.

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

[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 center thickness of each lens is defined below.

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

[0144] The air spacing distance of each lens along the optical axis is defined below.

[0145] The air spacing distance AT1 between the first lens G1 and the second lens G2 along the optical axis is 0.2 mm; the air spacing distance AT2 between 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 spacing distance AT3 between the fourth lens G4 and the aperture stop 40 along the optical axis is 2.3 mm; the air spacing distance AT4 between 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 spacing distance AT5 between the sixth lens G6 and the seventh lens G7 along the optical axis is 0.2 mm; the air spacing distance AT6 between the seventh lens G7 and the eighth lens G8 along the optical axis is 0.2 mm; and the air spacing distance BFL between the eighth lens G8 and the image plane along the optical axis is 12 mm.

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

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

[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 3

[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 band WL of the optical lens is 390nm~700nm; the image side target surface size IMG is 12mm; the total optical length TTL of the system is 66.4mm, and the system back focus BFL is 16.2mm.

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

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

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

[0154] The surface shapes of each lens are as follows:

[0155] The first lens G1 is a convex-plano 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-plano lens, the third lens G3 and the fourth lens G4 are a cemented lens, the fifth lens G5 is a biconcave lens, the sixth lens G6 is a biconvex lens, the fifth lens G5 and the sixth lens G6 are a cemented lens, the seventh lens G7 is a plano-convex lens, and the eighth lens G8 is a biconvex lens.

[0156] The focal length of each lens is defined below.

[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 curvature radius of each lens is defined below.

[0159] The curvature radius R11 of the incident surface of the first lens G1 is 59.9 mm, and the curvature radius R12 of the exit surface is infinite; the curvature radius R21 of the incident surface of the second lens G2 is 16.9 mm, and the curvature radius R22 of the exit surface is 6.2 mm; the curvature radius R31 of the incident surface of the third lens G3 is 29.6 mm, and the curvature radius R32 of the exit surface is 7.5 mm; the curvature radius R41 of the incident surface of the fourth lens G4 is 7.5 mm, and the curvature radius R42 of the exit surface is infinite; the curvature radius R32 of the incident surface of the fifth lens G4 is 16.9 mm, and the curvature radius R3 ...16.9 mm, and the curvature radius R42 of the exit surface is infinite; the curvature radius R32 of the incident surface of the fifth lens G4 is 16.9 mm, and the curvature radius R32 of the exit surface is 6.2 mm; the curvature radius R31 of the incident surface of the third lens G3 is 29. The radius of curvature R51 of the incident surface of mirror G5 is -21.7mm, and the radius of curvature R52 of the exit surface is 21mm; the radius of curvature R61 of the incident surface of the sixth lens G6 is 21mm, and the radius of curvature R62 of the exit surface is -12.9mm; the radius of curvature R71 of the incident surface of the seventh lens G7 is infinite, and the radius of curvature R72 of the exit surface is -21.1mm; the radius of curvature R81 of the incident surface of the eighth lens G8 is 41.7mm, and the radius of curvature R82 of the exit surface is -39.6mm.

[0160] Among them, 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. The curvature radius 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 curvature radius R71 of the incident surface of the seventh lens G7 is infinite, indicating that the incident surface of the seventh lens G7 is a plane.

[0161] The center thickness of each lens is defined below.

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

[0163] The air spacing distance of each lens along the optical axis is defined below.

[0164] The air spacing distance AT1 between the first lens G1 and the second lens G2 along the optical axis is 10.8 mm; the air spacing distance AT2 between 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 spacing distance AT3 between the fourth lens G4 and the aperture stop 40 along the optical axis is 1.1 mm; the air spacing distance AT4 between 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 spacing distance AT5 between the sixth lens G6 and the seventh lens G7 along the optical axis is 0.2 mm; the air spacing distance AT6 between the seventh lens G7 and the eighth lens G8 along the optical axis is 0.2 mm; and the air spacing distance BFL between the eighth lens G8 and the image plane along the optical axis is 16.2 mm.

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

[0166] The refractive index and Abbe number of each lens are defined below.

[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; the refractive index N8 of the eighth lens G8 is 1.76, and the Abbe number V8 is 52.3.

[0168] 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 within the working band. Figure 2It can be seen that the full field distortion of the optical lens of the embodiment of the present disclosure is less than 1%, which is conducive to achieving high calibration accuracy and improving detection accuracy. In addition, aberrations such as spherical aberration, coma, astigmatism, and chromatic aberration are still kept within a small range that does not affect the accuracy.

[0169] The horizontal axis of the edge spread function curve is the distance to the center of the pixel, in micrometers; the vertical axis is the percentage of radiation illumination at the current position, with a value range of 0-1.

[0170] Combination Figure 3 , without wavefront augmentation, contains 0.5 to 0.9 pixels within 20% to 80% of the radiant illumination.

[0171] Combination Figure 4 , after the wavefront RMS value increases to 1λ, the number of pixels contained in the 20% to 80% irradiance increases to 1.0 to 3.4 pixels.

[0172] Embodiment 2

[0173] Combination Figure 5 The embodiment of the present disclosure provides an optical engine, which includes: a light source 51, a digital micromirror chip 52 and a projection lens 53. The light from the light source 51 passes through the digital micromirror chip 52 to form a projection image, which is then projected through the projection lens 53.

[0174] The projection lens 53 is the optical lens of the first embodiment.

[0175] The light source 51 may 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] Three light sources 51 may be provided, and the main wavelengths of the three light sources 51 may be 430nm-460nm, 510nm-530nm and 610nm-650nm respectively. White light and monochromatic light can be used to project full-brightness images, full-darkness images, Gray code stripes of different widths, sinusoidal stripes and single-row pixel stripes through software control. White light is generated by lighting up monochromatic light simultaneously or in turn.

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

[0179] The optical engine of the embodiment of the present disclosure adopts the optical lens of the above-mentioned embodiment 1 as the projection lens 53, which can effectively reduce the micro-mirror 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 artifacts of the projected image are as follows: Figure 6 As shown in the figure, we can see the micromirror artifact with obvious difference in light and dark.

[0181] Reference Figure 8 In the brightness distribution curve of micromirror artifacts, the horizontal axis is from Figure 6 The number of pixels from the left to the right of the image, the vertical axis is the gray value. The position with the largest gray value is the brightest, and the position with the smallest gray value is the darkest. Among them, the gray value C1 of the brightest point is 223, the gray value C2 of the darkest point is 199, and the light-dark contrast ratio is (C1-C2) / (C1+C2)*100%=5.7%.

[0182] When the optical engine adopts the optical lens of the embodiment of the present disclosure as a projection lens, the micro-mirror artifacts of the projection image are as follows: Figure 7 As shown in the figure, it can be seen that the difference between light and dark is significantly reduced.

[0183] Reference Fig. 9 The grayscale value C1 of the brightest part is 237, the grayscale value C2 of the darkest part is 228, and the contrast between light and dark is (C1-C2) / (C1+C2)*100%=1.9%.

[0184] (5.7%-1.9%) / 5.7%=0.667, thus the noise intensity caused by the micromirror artifacts is reduced by two thirds.

[0185] The optical engine of the disclosed embodiment achieves high-quality structured light projection by reducing micromirror artifacts.

[0186] Embodiment 3

[0187] Combination Fig.10 The embodiment of the present disclosure further provides an imaging module, which includes a photosensitive chip 101 and an optical lens 102 of the above embodiment, and the object side light is imaged on the photosensitive chip 101 through the optical lens 102.

[0188] A cover glass 103 is also provided on the side of the photosensitive chip 101 facing the optical lens 102 to protect the photosensitive chip 101 .

[0189] Fig.11 The laser stripe image generated by the laser engine has obvious laser speckles. Fig.12 for Fig.11 The brightness distribution curve of the laser stripe image in the figure, the horizontal axis is the distance, and the vertical axis is the gray value. Laser speckle is manifested as obvious burrs in the brightness distribution curve along the length of the stripe, and its maximum PV value (Peak-to-Valley value) is 126.

[0190] Fig.13 For shooting with existing optical lenses Fig.11 In the image formed by the laser stripe image, obvious bright and dark spots can still be seen.

[0191] Fig.14 The optical lens of the first embodiment is used to shoot Fig.11 The image formed by the laser stripe image has blurred bright and dark spots, and even the bright and dark spots in the stripes cannot be seen.

[0192] Fig.15 for Fig.13 The brightness distribution curve of the image in the figure has a maximum PV value of 109; Fig.16 for Fig.14 The brightness distribution curve of the image in the figure has a maximum PV value of 56. The noise intensity caused by 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 micromirror artifacts and laser speckles of structured light in the image.

[0194] Embodiment 4

[0195] The embodiment of the present disclosure also provides a 3D camera, which includes: 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 light reflected by the target object and forms an image;

[0196] Wherein, the structured light projection device includes the optical engine of the second embodiment; and / or,

[0197] The imaging camera includes the imaging module of the third embodiment.

[0198] In some examples, the 3D camera uses the optical engine of the second embodiment to project light to the target object, and uses the imaging camera of the prior art to collect the light reflected by the target object and form an image.

[0199] In other examples, the 3D camera uses an existing optical engine to project light to a target object, and uses the imaging module of Example 3 to collect light reflected by the target object and form an image.

[0200] In some other examples, the 3D camera uses the optical engine of the second embodiment to project light to the target object, and uses the imaging module of the third embodiment to collect light reflected by the target object and form an image.

[0201] The embodiment of the present disclosure also provides a 3D camera, which includes: 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 light reflected by the target object and forms an image;

[0202] The structured light projection device includes a light source, a digital micromirror chip and the optical lens of the first embodiment. The light from the light source forms a projection image after passing through the digital micromirror chip and is projected to the target object through the optical lens; the imaging camera collects the light reflected by the target object and forms an image; and / or

[0203] The imaging camera includes: a photosensitive chip and the optical lens of the first embodiment, and 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 through the optical lens.

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

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

[0206] In some other examples, the 3D camera uses the optical lens of the first embodiment as the projection lens of the structured light projection device, and uses the optical lens of the first embodiment as the imaging lens.

[0207] Fig.17 The 3D camera uses the existing optical lens as the projection lens and the existing optical lens as the imaging lens to collect the micro-mirror artifacts of the image, and the difference between light and dark is obvious.

[0208] Fig.18 The micro-mirror artifacts in the image collected by the 3D camera using the optical lens of the first embodiment as a projection lens and the existing optical lens as an imaging lens are reduced, and the difference between light and dark is reduced.

[0209] Fig.19 The micro-mirror artifacts in the image collected by the 3D camera using the existing optical lens as the projection lens and the optical lens of the first embodiment as the imaging lens are reduced, and the difference between light and dark is reduced.

[0210] Fig. 20 The 3D camera adopts the optical lens of the first embodiment as a projection lens and adopts the optical lens of the first embodiment as an imaging lens to collect micro-mirror artifacts and reduce the difference between light and dark.

[0211] Fig.21 for Fig.17 Point cloud fluctuation test curve of 3D reconstruction of micro-mirror artifacts. The horizontal axis is pixel coordinates and the vertical axis is depth distance, in mm. Fig.21 The point cloud fluctuation PV value is about 0.7mm.

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

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

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

[0215] The 3D camera of the disclosed embodiment uses the optical lens of the disclosed embodiment as a projection lens and / or an optical lens, which can effectively reduce the noise intensity of the original image, improve the signal-to-noise ratio, significantly improve the fluctuation of the three-dimensional reconstruction point cloud, and thus improve the repeatability and resolution of the 3D camera; and achieve a higher absolute accuracy with a distortion of less than 1% without losing measurement accuracy. For targets with high absorption and high transmittance, such as dark objects and transparent objects, it is helpful to solve the detection problem of difficulty in distinguishing effective signals from interference signals.

[0216] In the above description, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this 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, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. An optical lens, characterized in that: include: A plurality of lenses and an aperture stop coaxially arranged in sequence from the object side to the image side, wherein the absolute value of the difference between the number of lenses of the aperture stop facing the object side and the number of lenses of the aperture stop facing the image side is less than or equal to 2; The root mean square value of the wavefront of the optical lens increases to no less than one wavelength; and the full field distortion of the optical lens is less than 1%.

2. The optical lens according to claim 1, characterized in that: 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 which are coaxially arranged in sequence from the object side to the image side; and the aperture stop is located between the fourth lens and the fifth lens.

3. The optical lens according to claim 2, characterized in that: 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 third lens and the fourth lens are cemented lenses, and the cemented lens formed by the third lens and the fourth lens has positive focal 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 focal power.

4. The optical lens according to claim 2, characterized in that: 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.

5. The optical lens according to claim 2, characterized in that: The radius of curvature R11 of the incident surface of the first lens is 19.2mm-59.9mm, and the radius of curvature R12 of the exit surface is greater than or equal to 176.1mm; the radius of curvature R21 of the incident surface of the second lens is 10.3mm-16.9mm, and the radius of curvature R22 of the exit surface is 3.5mm-6.2mm; the radius of curvature R31 of the incident surface of the third lens is 21.1mm-45.5mm, and the radius of curvature R32 of the exit surface is 4mm-7.5mm; the radius of curvature R41 of the incident surface of the fourth lens is 4mm-7.5mm, and the radius of curvature R42 of the exit surface is less than or equal to -87mm, or the radius of curvature R42 of the exit surface is greater than or equal to 5 5.8mm; the curvature radius R51 of the incident surface of the fifth lens 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 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 is greater than or equal to 283.9mm, and the curvature radius R72 of the exit surface is -21.6mm~-15.3mm; the curvature radius R81 of the incident surface of the eighth lens is 26.9mm~41.7mm, and the curvature radius R82 of the exit surface is -39.6mm~-16.9mm.

6. The optical lens according to claim 2, characterized in that: The center thickness GT1 of the first lens is 3mm~6.2mm; the center thickness GT2 of the second lens is 1.6mm~3mm; the center thickness GT3 of the third lens is 1.5mm~3mm; the center thickness GT4 of the fourth lens is 2.5mm~4mm; the center thickness GT5 of the fifth lens is 1.2mm~3mm; the center thickness GT6 of the sixth lens is 3.2mm~5.1mm; the center thickness GT7 of the seventh lens is 2.4mm~4.3mm; the center thickness GT8 of the eighth lens is 2.9mm~4.5mm.

7. The optical lens according to claim 2, characterized in that: The air spacing distance AT1 between the first lens and the second lens along the optical axis is 0.2mm-10.8mm; the air spacing distance AT2 between 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 spacing distance AT3 between the fourth lens and the aperture stop along the optical axis is 0.7mm-2.3mm; the air spacing distance AT4 between 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 spacing distance AT5 between the sixth lens and the seventh lens along the optical axis is 0.16mm-0.2mm; the air spacing distance AT6 between the seventh lens and the eighth lens along the optical axis is 0.16mm-0.2mm; the air spacing distance BFL between the eighth lens and the image plane along the optical axis is 9.4mm-16.2mm.

8. The optical lens according to claim 2, characterized in that: 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.

9. The optical lens according to claim 2, 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 -18.5 mm to -11.4 mm; The third lens and the fourth lens form a second lens group, and the focal length fb of the second lens group is 26.4 mm to 36.4 mm; 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 6.6 mm to 11.3 mm; An axial distance between the first lens group and the second lens group is 2.6 mm to 3.81 mm; an axial distance between the second lens group and the third lens group is 1.3 mm to 2.1 mm.

10. The optical lens according to claim 2, 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.

11. The optical lens according to any one of claims 1 to 10, 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 band WL of the optical lens is 390nm to 700nm; the image side target surface size IMG is 6mm to 12mm; the total optical length TTL of the system is 33mm to 66.4mm, and the back focus BFL of the system is 9.4mm to 16.2mm.

12. An optical engine, characterized in that: include: A light source, a digital micromirror chip and a projection lens, wherein the light from the light source forms a projection image after passing through the digital micromirror chip and is projected through the projection lens; The projection lens is the optical lens according to any one of claims 1 to 11.

13. An imaging module, characterized in that: It comprises a photosensitive chip and the optical lens according to any one of claims 1 to 11, and the object side light is imaged on the photosensitive chip through the optical lens.

14. A 3D camera, characterized in that: include: Structured light projection and imaging cameras; The structured light projection device 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 device comprises the optical engine according to claim 12; and / or, The imaging camera comprises the imaging module according to claim 13.

15. A 3D camera, characterized in that: include: Structured light projection device and imaging camera; The structured light projection device is configured to emit light to a target object, and the imaging camera collects light reflected by the target object and forms an image; The structured light projection device comprises a light source, a digital micromirror chip, and the optical lens according to any one of claims 1 to 11, wherein the light from the light source forms a projection image after passing through the digital micromirror chip, and is projected to the target object through the optical lens; The imaging camera collects light reflected by the target object and forms an image; and / or The imaging camera comprises: a photosensitive chip and an optical lens according to any one of claims 1 to 11, and the structured light projection device is configured to project structured light onto a target object; The light on the target object is imaged onto the photosensitive chip via the optical lens.

Images