Optical imaging system for imaging inner wall of sphere

Abstract

The invention discloses an optical imaging system for imaging the inner wall of a sphere. The technical problem that a traditional optical imaging system is not suitable for imaging the inner wall of the sphere in the prior art is solved. The optical imaging system for imaging the inner wall of the sphere comprises a front-end lens group and a rear-end lens group which are arranged in the direction from the object side to the image side along the optical axis, and the front-end lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged in the direction from the object side to the image side along the optical axis. The first lens, the second lens and the fourth lens are negative lenses, the third lens and the fifth lens are positive lenses, the rear-end lens group comprises a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens which are sequentially arranged in the direction from the object side to the image side along the optical axis, the sixth lens and the eighth lens are negative lenses, and the tenth lens is positive lenses. The seventh lens, the ninth lens and the tenth lens are positive lenses, and the maximum diameter of the front-end lens group is smaller than the minimum diameter of the rear-end lens group.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, in particular to an optical imaging system for imaging the inner wall of a sphere. BACKGROUND

[0002] The existing optical imaging system, based on the principle of plane-to-plane projection, can only realize cleaning projection imaging in a small area range of the inner wall of a sphere, and cannot realize clear projection imaging in a large field range of the inner wall of a sphere. At the same time, due to the size limitation of the sphere, the projection mode of the traditional large field optical system with a large front aperture, a short length and a small image surface is also not suitable for the projection forming of the inner wall of a sphere. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the present application provides an optical imaging system for imaging the inner wall of a sphere to solve the technical problem that the traditional optical imaging system in the prior art is not suitable for imaging the inner wall of a sphere.

[0004] In order to achieve the above technical target, the optical imaging system for imaging the inner wall of a sphere provided by the present application comprises a front end lens group and a rear end lens group arranged in sequence along the direction of the optical axis from the object side to the image side, The front end lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the direction of the optical axis from the object side to the image side, the first lens, the second lens and the fourth lens are negative lenses, the third lens and the fifth lens are positive lenses, and the optical power of the front end lens group is positive, The rear end lens group comprises a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens arranged in sequence along the direction of the optical axis from the object side to the image side, the sixth lens and the eighth lens are negative lenses, the seventh lens, the ninth lens and the tenth lens are positive lenses, and the optical power of the rear end lens group is positive, The maximum diameter of the front lens group is smaller than the minimum diameter of the rear end lens group.

[0005] As a preferred, the diaphragm of the optical imaging system is located on the object side surface of the fourth lens.

[0006] As a preferred, the fourth lens and the fifth lens are cemented to form a first cemented lens, and the first cemented lens has a positive optical power.

[0007] As a preferred, the combined optical power of the first lens, the second lens and the third lens is negative and greater than the optical power of the first lens.

[0008] As a preferred, the seventh lens has the largest positive optical power in the optical imaging system, and the eighth lens has the smallest negative optical power in the optical imaging system.

[0009] As a preference, the eighth lens and the ninth lens are cemented to form a second cemented lens, and the second cemented lens has a negative optical power.

[0010] As a preference, the combination of the sixth lens, the seventh lens and the second cemented lens has a negative optical power.

[0011] As a preference, the Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens and the tenth lens are arranged in a high-low order.

[0012] As a preference, the total length of the optical imaging system is L, the focal length of the optical imaging system is f, and 1.5 < L / f < 3.5.

[0013] As a preference, the maximum value of the field of view angle of the optical imaging system is 47°.

[0014] The optical imaging system of the present application realizes the imaging of the inner wall of the sphere through ten lenses, wherein the first lens has a negative optical power, and the first lens is the entrance of light rays, and setting it as a negative lens can improve the turning ability of light rays with a large field of view. The diameter of the first lens can be smaller under the same incident light ray angle, which is more suitable for the narrow entrance under the imaging scenario of the inner wall of the sphere, and leaves space for the subsequent lens to correct chromatic aberration. The second lens cooperates with the first lens to adjust the angle of the light rays incident on the third lens, so that the angle of the light rays incident on the third lens tends to the direction of the optical axis; The third lens connects the light rays emitted by the second lens, reduces the divergence of the light rays, and controls the angle of the light rays incident on the fourth lens, avoiding excessive diffusion of the light rays, which helps to reduce coma and control aberration; The cooperation of the fourth lens and the fifth lens enables the light rays to retain the negative field curvature compensation generated by the fourth lens when the light rays are emitted from the fifth lens, thereby maintaining the field curvature correction effect of the fourth lens on the light rays, thereby reducing the distortion of the imaging; The sixth lens makes the deflection of the light rays relatively gentle, reduces the spherical aberration, and at the same time compensates for the positive field curvature generated by the positive optical power of the front lens group, so as to flatten the image surface and help to balance the field curvature; The seventh lens can compensate for the negative field curvature generated by the sixth lens to reduce distortion; The divergence of the eighth lens and the convergence of the ninth lens control the angle of the light rays incident on the tenth lens, increase the light ray projection area on the tenth lens, and establish the basis for the last step of imaging; at the same time, the eighth lens can compensate for the negative field curvature generated by the seventh lens to reduce distortion; The tenth lens cooperates with the eighth lens and the ninth lens to converge light rays, so that the light rays are nearly vertically projected to the imaging surface, thereby reducing the distortion of the projection on the imaging surface.

[0015] The features and advantages of the present application will be described in detail in the following detailed description of embodiments, with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Structure diagram of the large field of view optical imaging of the annular belt in the embodiment of the present application; Figure 2 Structure diagram of the optical imaging system in the embodiment of the present application; Figure 3 Structure diagram of the f-theta mode principle of the optical imaging system in the embodiment of the present application; Figure 4 Point array diagram of the optical detection system of the inner wall of the spherical cavity in the embodiment of the present application; Figure 5 Wave difference diagram of the optical detection system of the inner wall of the spherical cavity in the embodiment of the present application; Figure 6 Transfer function MTF diagram of the optical detection system of the inner wall of the spherical cavity in the embodiment of the present application; Figure 7 Distortion diagram of the optical detection system of the inner wall of the spherical cavity in the embodiment of the present application.

[0017] Reference signs: 110, first lens, 120, second lens, 130, third lens, 140, first cemented lens, 141, fourth lens, 142, fifth lens, 150, sixth lens, 160, seventh lens, 170, second cemented lens, 171, eighth lens, 172, ninth lens, 180, tenth lens; 200, imaging surface. DETAILED DESCRIPTION

[0018] The technical solutions of the embodiments of the present application will be explained and described below in combination with the drawings of the embodiments of the present application. However, the following embodiments are only preferred embodiments of the present application, and are not all. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative labor also belong to the protection scope of the present application.

[0019] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0020] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of", "several" is two or more, unless otherwise explicitly limited.

[0021] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0022] As shown in Figure 1 , Figure 2 The present application provides an optical imaging system for imaging the inner wall of a sphere, which comprises a front lens group and a rear lens group arranged in order from the object side to the image side along the optical axis. The front lens group comprises a first lens 110, a second lens 120, a third lens 130, a fourth lens 141 and a fifth lens 142 arranged in order from the object side to the image side along the optical axis. The rear lens group comprises a sixth lens 150, a seventh lens 160, an eighth lens 171, a ninth lens 172 and a tenth lens 180 arranged in order from the object side to the image side along the optical axis.

[0023] The sphere is provided with an opening, and the optical imaging system projects the inner wall of the sphere at the opening position. The inner wall of the sphere is illuminated by a light source, and the light reflected by the inner wall of the sphere passes through the first lens 110 to the tenth lens 180 in turn and is incident on the imaging surface 200. A detector array is provided on the image side for detecting and identifying the image projected on the imaging surface 200. The maximum diameter of the front lens group is smaller than the minimum diameter of the rear lens group.

[0024] The first lens 110 is a negative lens, the radius of curvature of the object side surface thereof at the optical axis is negative, and the radius of curvature of the image side surface thereof at the optical axis is positive.

[0025] The second lens 120 is a negative lens, the radius of curvature of the object side surface thereof at the optical axis is negative, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0026] The third lens 130 is a positive lens, the radius of curvature of the object side surface thereof at the optical axis is negative, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0027] The fourth lens 141 is a negative lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is positive.

[0028] The fifth lens 142 is a positive lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0029] The fourth lens 141 and the fifth lens 142 are cemented to form a first cemented lens 140, the image side surface of the fourth lens 141 and the object side surface of the fifth lens 142 are cemented surfaces, the focal length of the first cemented lens 140 is the combined focal length of the fourth lens 141 and the fifth lens 142, and the focal length of the first cemented lens 140 is positive.

[0030] The sixth lens 150 is a negative lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is positive.

[0031] The seventh lens 160 is a positive lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0032] The eighth lens 171 is a negative lens, the radius of curvature of the object side surface thereof at the optical axis is negative, and the radius of curvature of the image side surface thereof at the optical axis is positive.

[0033] The ninth lens 172 is a positive lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0034] The eighth lens 171 and the ninth lens 172 are cemented to form a second cemented lens 170, the image side surface of the eighth lens 171 and the object side surface of the ninth lens 172 are cemented surfaces, the focal length of the second cemented lens 170 is the combined focal length of the eighth cemented lens and the ninth cemented lens, and the focal length of the second cemented lens 170 is negative.

[0035] The tenth lens 180 is a positive lens, the radius of curvature of the object side surface thereof at the optical axis is positive, and the radius of curvature of the image side surface thereof at the optical axis is negative.

[0036] From the second lens 120, the light rays pass through the second lens 120 to the ninth lens 172 in turn, and the optical power of the lenses is arranged in the order of negative-positive, and the optical imaging system constructs a reverse telephoto structure between the first lens 110 and the eighth lens 171, thereby lengthening the focal length of the optical imaging system and leaving space for the detector array on the image side. Among them, the total length of the optical imaging system is L, the focal length of the optical imaging system is f, and 1.5 < L / f < 3.5.

[0037] The first lens 110, the second lens 120 and the third lens 130 are combined at the front end of the optical imaging system to control the aperture of the front end of the optical imaging system, so that the aperture of the front end of the optical imaging system can be as small as possible.

[0038] The material of the first lens 110 is fused quartz, the refractive index is 1.45, and the Abbe number is 67.8. The use of fused quartz glass can improve the radiation resistance of the first lens 110. The curvature radius of the object side of the first lens 110 is R1, and the curvature radius of the image side of the first lens 110 is R2. R1 is relatively large compared to R2, so that the object side of the first lens 110 is relatively flat, and the refraction of the light rays on the object side of the first lens 110 is small, avoiding the sudden change of the imaging edge light rays and reducing coma and astigmatism. R2 is relatively small compared to R1, so that the image side of the first lens 110 forms a strong concave surface, so that the first lens 110 has negative optical power. The first lens 110 is the entrance of the light rays, and being set as a negative lens can improve the turning ability of the large field of view light rays. Under the same incident light ray angle, the diameter of the first lens can be smaller, which is more suitable for the narrow entrance under the imaging scene of the spherical inner wall, and the larger R1 can balance the problem of low refractive index of fused quartz glass, leaving space for subsequent lens correction of chromatic aberration.

[0039] The second lens 120 is heavy flint glass, with a refractive index of 1.86 and an Abbe number of 36.6. The curvature radius of the object side of the second lens 120 is R3, the curvature radius of the image side of the second lens 120 is R4, the object side of the second lens 120 is strongly concave relative to the image side of the second lens 120, and the image side of the second lens 120 is weakly convex relative to the object side of the second lens 120, so that the second lens 120 has a negative focal power. Among them, the object side of the second lens 120 is strongly concave relative to the image side of the second lens 120, which can compress the front aperture and increase the light divergence effect; the image side of the second lens 120 is weakly convex, so that the second lens 120 has a smaller negative focal power, which is beneficial to strengthening the divergence effect of light in a short distance. The object side of the second lens 120 cooperates with the image side of the first lens 110 to adjust the angle of the light entering the second lens 120; the image side of the second lens 120 cooperates with the object side of the second lens 120 to adjust the angle of the light towards the third lens 130, so that the angle of the light towards the third lens 130 tends to be in the direction of the optical axis.

[0040] The third lens 130 is environmentally friendly crown glass, with a refractive index of 1.59 and an Abbe number of 68.3. The curvature radius of the object side of the third lens 130 is R5, the curvature radius of the image side of the third lens 130 is R6, the object side of the third lens 130 is weakly concave relative to the image side of the third lens 130, and the image side of the third lens 130 is strongly convex relative to the object side of the third lens 130, so that the third lens 130 has a smaller positive focal power. By adopting the combination mode of weak concave and strong convex, the third lens 130 connects the light emitted by the second lens 120, reduces the light divergence intensity, controls the angle of the light towards the fourth lens 141, avoids excessive light diffusion, and helps to reduce coma and control aberration.

[0041] The combined focal power of the first lens 110, the second lens 120 and the third lens 130 is negative and greater than the focal power of the first lens 110. This makes the light more divergent when entering the first lens 110, and the light remains in a divergent state when passing through the third lens 130, but the divergence state is weaker than that of the first lens 110, which helps to control the angle of the light entering the fourth lens and reduce the size of the fourth lens.

[0042] The fourth lens 141 is heavy flint glass with a refractive index of 1.86 and an Abbe number of 36.6. The fifth lens 142 is environmental heavy crown glass with a refractive index of 1.59 and an Abbe number of 68.3. The curvature radius of the object side of the fourth lens 141 is R7, the curvature radius of the cemented surface of the fourth lens 141 and the fifth lens 142 is R8, the object side of the fourth lens 141 is weak convex relative to the cemented surface of the first cemented lens 140, the cemented surface of the first cemented lens 140 is strong concave relative to the object side of the fourth lens 141, so that the fourth lens 141 has a negative focal power, the curvature radius of the image side of the fifth lens 142 is R9, the curvature component of R9 is large, so that the image side of the fifth lens 142 is close to a plane and the fifth lens 142 has a positive focal power. The combined focal power of the first cemented lens 140 is positive, the combined focal power of the first cemented lens 140 is dominated by the object side of the fourth lens 141, the refractive angle of the light ray is small when the light ray exits the image side of the fifth lens 142, and the image side of the fifth lens 142 serves as a protective surface, so that the negative field curvature compensation generated by the fourth lens 141 can be preserved when the light ray exits the fifth lens 142, the field curvature correction effect of the first cemented lens 140 on the light efficiency is maintained, and the distortion of the imaging is reduced.

[0043] The stop of the optical imaging system is located on the object side of the fourth lens 141, and no additional stop hole needs to be arranged in the optical imaging system, thereby reducing the complexity of the optical imaging system. By adjusting the distance between the third lens 130 and the fourth lens 141 and the combined focal power of the first lens 110, the second lens 120 and the third lens 130, the refractive angle of the large field of view light can be adjusted, and the light incidence angle of the fourth lens 141 can be controlled.

[0044] The fourth lens 141 and the fifth lens 142 are cemented to form the first cemented lens 140, and the two have different refractive indices and Abbe numbers, so that the first cemented lens 140 has good chromatic aberration correction capability, and at the same time, the fourth lens 141 and the fifth lens 142 are cemented to form an integral whole, which improves the stability of assembly and helps to accurately position the installation position of the stop.

[0045] The combined focal power of the first lens 110, the second lens 120, the third lens 130, the fourth lens 141 and the fifth lens 142 is positive, which plays a certain converging role for the light efficiency of the large field of view, avoiding that the incidence wide angle of the sixth lens is too divergent, so that the aperture of the sixth lens needs to be set too large.

[0046] The sixth lens 150 is made of heavy flint glass SF6 with a refractive index of 1.86 and an Abbe number of 23.8. The curvature radius of the object side of the sixth lens 150 is R10, the curvature radius of the image side of the sixth lens 150 is R11, the object side of the sixth lens 150 is weakly convex relative to the image side of the sixth lens 150, and the image side of the sixth lens 150 is strongly concave relative to the object side of the sixth lens 150, so that the sixth lens 150 has a negative focal power. At the same time, the absolute value of the curvature radius of the object side of the sixth lens 150 is large, so that the object side of the sixth lens 150 is relatively flat, the light deflection is relatively flat, the spherical aberration is reduced, and at the same time, the positive field curvature generated by the positive focal power of the front lens group can be compensated, so that the image surface is flattened, which helps to balance the field curvature.

[0047] The material of the seventh lens 160 is selected to be environmentally friendly heavy crown glass with a refractive index of 1.59 and an Abbe number of 68.3. The curvature radius of the object side of the seventh lens 160 is R12, the curvature radius of the image side of the seventh lens 160 is R13, the object side of the seventh lens 160 is convex, and the image side of the seventh lens 160 is also convex, so that the seventh lens 160 has a positive focal power. The seventh lens 160 is used to cooperate with the sixth lens 150 to converge light, reducing the angle of light incident on the eighth lens 171. At the same time, the seventh lens 160 has the largest positive focal power in the optical imaging system, so that the edge light can be strongly converged, compressing the size of the light spot and improving the central resolution. The object side of the seventh lens 160 can compensate for the negative field curvature generated by the image side of the sixth lens 150, reducing distortion. The object side and the image side of the seventh lens 160 can adopt a nearly symmetric convex design, which helps to balance aberrations and reduce distortion.

[0048] The eighth lens 171 is heavy flint glass with a refractive index of 1.86 and an Abbe number of 36.6. The ninth lens 172 is environmental heavy crown glass with a refractive index of 1.59 and an Abbe number of 68.3. The curvature radius of the object side surface of the eighth lens 171 is R14, the curvature radius of the cemented surface of the eighth lens 171 and the ninth lens 172 is R15, the object side surface of the eighth lens 171 is concave, and the cemented surface of the second cemented lens 170 is also concave, so that the eighth lens 171 has the smallest negative focal power in the optical imaging system. The curvature radius of the image side surface of the ninth lens 172 is R16, and the image side surface of the ninth lens 172 is convex, so that the ninth lens 172 has a positive focal power. The combined focal power of the second cemented lens 170 is negative, and the combined focal power of the second cemented lens 170 is dominated by the object side surface of the eighth lens 171, which controls the angle of the light rays to the tenth lens 180 by divergence of the eighth lens 171 and convergence of the ninth lens 172, increases the light ray projection area on the tenth lens 180, and establishes the basis for the last step of imaging; at the same time, the convex object side surface of the eighth lens 171 cooperates with the image side surface of the seventh lens 160 to compensate for the negative field curvature generated by the seventh lens 160, reduce distortion, and the image side surface of the eighth lens 171 can maintain the field curvature compensation of the object side surface of the eighth lens 171.

[0049] The tenth lens 180 is heavy flint glass SF6 with a refractive index of 1.86 and an Abbe number of 23.8. The curvature radius of the object side surface of the tenth lens 180 is R17, and the curvature radius of the image side surface of the tenth lens 180 is R18. The object side surface of the tenth lens 180 is convex, and the image side surface of the tenth lens 180 is concave, so that the first lens 110 has a positive focal power. The tenth lens 180 cooperates with the second cemented lens 170 to converge the light rays emitted by the second cemented lens 170, so that the light rays are nearly perpendicular to the imaging surface 200, thereby reducing the distortion of the projection on the imaging surface 200.

[0050] The combined focal power of the sixth lens 150, the seventh lens 160, the eighth lens 171, the ninth lens 172 and the tenth lens 180 is positive, which further converges the light rays emitted by the front lens group to the imaging surface 200, so that the imaging on the imaging surface 200 is clear.

[0051] The imaging optical lens group will be described in detail below in combination with specific parameters.

[0052] The structure diagram of the optical imaging system of the embodiment of the present application is shown in Figure 1 、 Figure 2The optical imaging system includes a front lens group and a rear lens group arranged in sequence along the optical axis from the object side to the image side. The front lens group includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 141, and a fifth lens 142. The rear lens group includes a sixth lens 150, a seventh lens 160, an eighth lens 171, a ninth lens 172, and a tenth lens 180. The optical imaging system of the embodiment is used for imaging the inner wall of a sphere with a sphere radius of 100 mm. The related parameters of the optical imaging system are shown in Table 1. The center thickness in Table 1 refers to the distance between two adjacent surfaces on the optical axis. For example, the center thickness of 2 mm of the image side surface of the first lens 110 refers to the distance between the first lens 110 and the second lens 120 being 2 mm.

[0053] Table 1: Lens parameter table

[0054] According to Table 1, the optical power of the first lens 110 in the embodiment is -0.0488.

[0055] The optical power of the second lens 120 is -0.001, and the combined optical power of the first lens 110 and the second lens 120 is -0.05.

[0056] The optical power of the third lens 130 is 0.0077, and the combined optical power of the first lens 110 to the third lens 130 is -0.042.

[0057] The optical power of the fourth lens 141 is -0.0184, the optical power of the fifth lens 142 is 0.0743, the combined optical power of the first cemented lens 140 is 0.0559, and the combined optical power of the first lens 110 to the first cemented lens 140 is 0.015.

[0058] The optical power of the sixth lens 150 is -0.022.

[0059] The optical power of the seventh lens 160 is 0.0837, and the combined optical power of the sixth lens 150 and the seventh lens 160 is 0.0621.

[0060] The optical power of the eighth lens 171 is -0.1685, the combined optical power of the ninth lens 172 is 0.0628, the combined optical power of the second cemented lens 170 is -0.1057. The combined optical power of the sixth lens 150 to the second cemented lens 170 is -0.0304.

[0061] The optical power of the tenth lens 180 is 0.0459, and the combined optical power of the sixth lens 150 to the tenth lens 180 is 0.0183.

[0062] The total length of the optical imaging system is 62.3 mm, and the optical power is 0.0351 mm -1 , and the focal length is 28.46 mm.

[0063] The optical imaging system of the present application is based on the principle of spherical-plane projection, and the optical structure adopted is as shown in Figure 2 . The object plane of the system is spherical, and the image plane is planar, realizing the projection from spherical to planar. The optical system realizes the non-distorted imaging of the spherical object according to the f-theta imaging mode. The full field of view of the optical system is 47°, and from the perspective of annular imaging, it realizes 360° annular imaging space of 23.5°, and there is no blind area in the middle, meeting the demand of large field of view observation range. The spectral range of the optical system is 486nm~656nm, the focal length is 28.46mm, the image detector array is 4096x3000, and the pixel size is 3.45μm. The spherical radius is 100mm, and the object distance is 200mm, so the object resolution can reach 32.8μm, which can meet the requirement of 35μm resolution. Since the full field of view of the optical system is 47°, under the condition of 200mm object distance, the object field coverage area is greater than 120mm 2 . The system is composed of 10 lenses, including 2 sets of double-cemented lenses. The maximum clear aperture in the front lens group of the optical system is 9mm, the maximum clear aperture in the rear lens group of the optical system is 12mm, and the total length of the optical system is 62.3mm. Considering the structure and installation of the cylindrical illumination light source, the radial size of the system can meet the overall requirements.

[0064] The spot diagram of the optical system is as shown in Figure 4 . From the figure, it can be seen that the spot size of the system spot diagram is smaller than the Airy disk.

[0065] The wave difference diagram OPD of the optical system is as shown in Figure 5 . From the figure, it can be seen that the wave difference PV value is less than λ / 4.

[0066] The transfer function MTF diagram of the optical system is as shown in Figure 6 . From the figure, it can be seen that the system is better than 0.35 in the space frequency range from 0-145lp / mm, which has reached the technical index of clear imaging.

[0067] The distortion diagram of the optical system is as shown in Figure 7 . According to the f-theta imaging mode, the relative distortion is less than 0.2%.

[0068] The imaging principle of the optical imaging system of the present application is as follows: using the f-theta imaging mode, the non-distortion (less distortion) of imaging is realized. Through the mapping relationship between any point on the inner wall of the sphere and the point on the imaging plane 200, the sphere-plane projection is realized.

[0069] The specific principle is described in detail in the descriptionFigure 3 For the sag x of any point on the sphere, the object height h can be expressed as:

[0070] For the sag x of any point on the sphere, the object height h can be expressed as:

[0071] The incident angle θ of any point on the sphere relative to the optical imaging system can be expressed as:

[0072] The image height y of the optical imaging system in the f-theta imaging mode under the non-distortion condition of the spherical object can be expressed as:

[0073] By the projected image size on the imaging surface 200 and the position of the edge point x of the inner wall of the spherical object to be measured, the focal length f of the optical imaging system and the optical power of the optical imaging system can be calculated.

[0074] The combined optical power of each lens in the optical imaging system is equal to the optical power of the optical imaging system

[0075] In the zemax software, the total length of the optical imaging system, the number and type of lenses, the maximum diameter of the front lens group, the minimum diameter of the rear lens, the minimum center thickness and the minimum edge thickness according to the aperture of different lenses, and the constraints that the seventh lens 160 has the largest positive optical power in the optical imaging system, the second cemented lens 170 has the smallest negative optical power, and the tenth lens 180 has a larger positive optical power, etc. can be obtained. A plurality of sets of lenses that meet the conditions can be obtained, such as the curvature radius of the object side and the image side of each lens, the lens thickness and the spacing.

[0076] This embodiment only lists one set of preferred lens combination based on a specific environment, but other lens combination methods set by the same inventive concept are also within the protection scope of the present application.

[0077] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that the present application includes but is not limited to the contents described in the above specific embodiments and the drawings. Any modification that does not deviate from the functional and structural principles of the present application will be included in the scope of the claims.​​​

Claims

1. An optical imaging system for imaging the inner wall of a sphere, characterized in that: It includes a front lens group and a rear lens group arranged in sequence along the optical axis from the object side to the image side. The front lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the optical axis from the object side to the image side. The first lens, the second lens, and the fourth lens are negative lenses, the third lens and the fifth lens are positive lenses, and the optical power of the front lens group is positive. The rear lens group includes a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence along the optical axis from the object side to the image side, the sixth lens and the eighth lens are negative lenses, the seventh lens, the ninth lens, and the tenth lens are positive lenses, and the optical power of the rear lens group is positive. The maximum diameter of the front lens group is smaller than the minimum diameter of the rear lens group.

2. The optical imaging system according to claim 1, wherein: The aperture of the optical imaging system is located on the object-side surface of the fourth lens element.

3. The optical imaging system according to claim 2, wherein: The fourth lens and the fifth lens are cemented together to form a first cemented lens, and the first cemented lens has positive refractive power.

4. The optical imaging system according to claim 1, wherein: The combined optical power of the first lens, the second lens, and the third lens is negative and greater than the optical power of the first lens.

5. The optical imaging system according to claim 1, wherein: The seventh lens has the largest positive optical power in the optical imaging system, and the eighth lens has the smallest negative optical power in the optical imaging system.

6. The optical imaging system according to claim 5, wherein: The eighth lens and the ninth lens are cemented together to form a second cemented lens, and the optical power of the second cemented lens is negative.

7. The optical imaging system according to claim 6, wherein: The combined refractive power of the sixth lens, the seventh lens, and the second cemented lens is negative.

8. The optical imaging system according to claim 1, wherein: Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the tenth lens are arranged in order of high to low.

9. The optical imaging system according to claim 1, wherein: The total length of the optical imaging system is L, the focal length of the optical imaging system is f, and 1.5<L / f<3.

5.

10. The optical imaging system according to claim 8, wherein: The maximum field of view of the optical imaging system is 47°.

Images