Lens assembly

Abstract

The invention discloses a lens assembly, a capsule endoscope capsule and a system thereof, and the lens assembly is sequentially provided with a first lens with negative refractive power from an object side to an image side, the object side surface of the first lens is a convex surface in a paraxial region, and the image side surface of the first lens is a concave surface in a paraxial region; a diaphragm; a second lens element with positive refractive power having an image-side surface being convex in a paraxial region thereof; a third lens element with negative refractive power having an object-side surface being concave in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof; the first lens, the second lens and the third lens are all aspheric lenses, any two adjacent lenses are arranged at intervals, the lens assembly is beneficial to shortening the total optical length of the lens assembly, miniaturization design of the lens assembly is achieved, and the lens assembly is excellent in imaging effect, wide in view field and small in distortion.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a lens assembly. Background Art

[0002] Capsule endoscopy is a kind of device that is swallowed directly. It takes pictures through the camera inside the endoscope, and then transmits the pictures to the receiver through data. The pictures taken by the capsule can be received and viewed in real time through specific software. With the continuous development of capsule endoscopy, how to make the endoscope smaller is a difficult problem. In order to facilitate swallowing detection, the size of the capsule needs to be made smaller. The present invention optimizes the camera module to have a smaller volume while having a larger field of view, a wider field of view, and can observe a larger range. Summary of the invention

[0003] In order to solve the deficiencies of the prior art, the present invention provides a lens assembly: A lens assembly, which is provided with: The first lens element has a negative refractive power, the object side surface of which is convex at the near optical axis, and the image side surface of which is concave at the near optical axis; Aperture; The second lens element has positive refractive power and its image side surface is convex near the optical axis; The third lens element has a negative refractive power, the object side surface of which is concave at the near optical axis, and the image side surface of which is concave at the near optical axis; The first lens, the second lens and the third lens are all aspherical lenses, and any two adjacent lenses are arranged at an interval.

[0004] Furthermore, the lens assembly satisfies the following condition: TTL / ImgH≤2.0, wherein TTL is the distance from the object side of the first lens to the imaging surface of the lens assembly on the optical axis, and ImgH is the length of the diagonal of the effective imaging area of ​​the lens assembly.

[0005] Further, the lens assembly satisfies the following conditions: CT1 / TTL≤0.124, CT2 / TTL≤0.185, CT3 / TTL≤0.077, wherein CT1 is the maximum thickness of the first lens on the optical axis, CT2 is the maximum thickness of the second lens on the optical axis, and CT3 is the maximum thickness of the third lens on the optical axis.

[0006] Further, the lens assembly satisfies the following condition: 1.11≤(ct1+t12) / (ct2+ct3++T23+T34)≤2.5, CT1 is the maximum thickness of the first lens on the optical axis, CT2 is the maximum thickness of the second lens on the optical axis, and CT3 is the maximum thickness of the third lens on the optical axis.

[0007] Furthermore, the lens assembly satisfies the following condition: -0.91<f2 / f3<-0.73, wherein f1 is the focal length of the first lens, f2 is the focal length of the second lens, and f3 is the focal length of the third lens.

[0008] Furthermore, the lens assembly satisfies the following conditions: ND3≥1.6, ND1=ND2; wherein ND1 is the refractive index of the first lens, ND2 is the refractive index of the second lens, and ND3 is the refractive index of the third lens.

[0009] Furthermore, the lens assembly satisfies the following condition: 1.16≤R22 / R31≤2.0, wherein R22 is the radius of curvature of the image side surface of the second lens, and R31 is the radius of curvature of the object side surface of the third lens.

[0010] Furthermore, the lens assembly satisfies the following condition: f / EPD≤4.1, wherein f is the focal length of the lens assembly, and EPD is the entrance pupil diameter of the lens assembly.

[0011] Furthermore, the lens assembly satisfies the following condition: TTL≤2.5.

[0012] Furthermore, the lens assembly satisfies the following condition: DMAX≤1.78.

[0013] Furthermore, any two adjacent lenses in the lens assembly do not move relative to each other.

[0014] The lens assembly of the present invention is conducive to shortening the total optical length of the lens assembly, realizing the miniaturized design of the lens assembly, and has excellent imaging effect, a wide field of view, and small distortion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A : A schematic structural diagram of a lens assembly provided in the first embodiment of the present application; Figure 1B : Figure 1A Relative illumination graph of the lens assembly shown; Figure 1C : Figure 1A The polychromatic light diffraction through-focus MTF curve of the lens assembly shown; Figure 1D : Figure 1A Field curvature and distortion graphs of the lens assembly shown; Figure 1E : Figure 1A Vertical axis chromatic aberration curve of the lens assembly shown; Figure 1F : Figure 1A Axial aberration curve diagram of the lens assembly shown; Figure 2A : A schematic diagram of the structure of the lens assembly provided in the second embodiment of the present application Figure 2B : Figure 2A Relative illumination graph of the lens assembly shown; Figure 2C : Figure 2A The polychromatic light diffraction through-focus MTF curve of the lens assembly shown; Figure 2D : Figure 2A Field curvature and distortion graphs of the lens assembly shown; Figure 2E : Figure 2A Vertical axis chromatic aberration curve of the lens assembly shown; Figure 2F : Figure 2A Axial aberration curve diagram of the lens assembly shown; Figure 3A : A schematic structural diagram of a lens assembly provided in a third embodiment of the present application; Figure 3B : Figure 3A Relative illumination graph of the lens assembly shown; Figure 3C : Figure 3A The polychromatic light diffraction through-focus MTF curve of the lens assembly shown; Figure 3D : Figure 3A Field curvature and distortion graphs of the lens assembly shown; Figure 3E : Figure 3A Vertical axis chromatic aberration curve of the lens assembly shown; Figure 3F : Figure 3A Axial aberration graph of the lens assembly shown. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It should be understood that the specific implementation methods described here are only used to explain the present invention and are not used to limit the present invention.

[0017] Definition: The side of an optical component or element facing the subject is called the object side, and the side facing the imaging surface is called the image side.

[0018] TTL: The distance from the object side of the first lens to the imaging surface of the lens assembly at the optical axis; ImgH: diagonal length of the effective imaging area of ​​the lens assembly; ND1: refractive index of the first lens; ND2: refractive index of the second lens; ND3: refractive index of the third lens; CT1: Maximum thickness of the first lens on the optical axis; CT2: the maximum thickness of the second lens on the optical axis; CT3: Maximum thickness of the third lens on the optical axis; T12: The distance between the first lens and the aperture on the optical axis; T23: The distance between the aperture and the second lens on the optical axis; T34: The distance between the second lens and the third lens on the optical axis; T45: The distance between the third lens and the imaging surface of the lens assembly on the optical axis; f1: focal length of the first lens; f2: focal length of the second lens; f3: focal length of the third lens; f: focal length of the lens assembly; EPD: entrance pupil diameter; WFno: F number of lens assembly; Fov: the field of view of the lens assembly; k: cone coefficient; A4: the 4th order coefficient of the aspheric surface; A6: the sixth-order coefficient of the aspheric surface; A8: 8th order coefficient of aspheric surface; A10: the 10th order coefficient of the aspheric surface; A12: 12th order coefficient of aspheric surface; A14: 14th order coefficient of aspheric surface; A16: 16th order coefficient of aspheric surface; DMAX: Maximum effective radius of the lens.

[0019] The present application provides a miniaturized wide-angle lens assembly for optical imaging. The lens assembly can be applied to products in multiple fields that are sensitive to the volume of the lens assembly, such as smart terminals, medical examination and surgical systems, industrial cameras, security monitoring equipment, wearable devices, drones, virtual reality (VR) and augmented reality (AR) equipment, etc. The present application takes the application of the lens assembly to a capsule endoscope system in the medical field as an example for explanation.

[0020] Please refer to Figure 1A A schematic diagram of the structure of the lens assembly provided in the first embodiment of the present application, Figure 2A A schematic diagram of the structure of the lens assembly provided in the second embodiment of the present application and Figure 3AThis is a schematic diagram of the structure of a lens assembly provided in the third embodiment of the present application. The lens assembly is provided with a first lens L1, an aperture ST, a second lens L2, a third lens L3, a filter S1 and an imaging surface S2 in sequence from the object side to the image side, and each lens has an object-side surface facing the object side and an image-side surface facing the image side.

[0021] The first lens L1 has negative refractive power, its object side surface is convex at the near optical axis, and its image side surface is concave at the near optical axis; the second lens L2 has positive refractive power, and its image side surface is convex at the near optical axis; the third lens L3 has negative refractive power, its object side surface is concave at the near optical axis, and its image side surface is concave at the near optical axis; the first lens L1, the second lens L2, and the third lens L3 are all aspherical lenses, and any two adjacent lenses are arranged at an interval.

[0022] In the lens assembly provided by the present application, the object side of the first lens is convex at the near optical axis, which is beneficial to expanding the field of view angle and has positive refractive power, and is used to converge the light incident on the first lens; the second lens has positive refractive power, converges the light beam emitted by the first lens, can effectively balance low-order aberrations, can effectively correct paraxial spherical aberration, and reduce peripheral astigmatism field curvature; the third lens has negative refractive power, which is beneficial to the miniaturization of the lens assembly, and can reduce spherical aberration by changing the position of marginal light.

[0023] Furthermore, in the lens assembly, the image side surface of the second lens is convex at the near optical axis, and the object side surface of the third lens is concave at the near optical axis, so that the concave-convex shapes of the image side surface of the second lens and the object side surface of the third lens at the near optical axis tend to match each other, which is conducive to the close fit between the second lens and the third lens with a smaller gap. Therefore, the concave-convex shape setting of the surfaces of the second lens and the third lens at the near optical axis is conducive to the close design of the three lenses, shortening the total optical length of the lens assembly, realizing the miniaturization of the lens assembly, and achieving better aberration correction effect.

[0024] The object side surface of the lens described in the present invention is a convex surface, which means that when the object side surface of the lens is cut through any point on the surface, the object side surface is always on the right side of the cut surface, and its radius of curvature is positive, otherwise the object side surface is a concave surface, and its radius of curvature is negative; the image side surface is a convex surface, which means that when the image side surface of the lens is cut through any point on the surface, the image side surface is always on the left side of the cut surface, and its radius of curvature is negative, otherwise the image side surface is a concave surface, and its radius of curvature is positive. If a section is made through any point on the surface of the object side or image side of the lens, the surface has both a part on the left side of the cut surface and a part on the right side of the cut surface, then the surface has a curve inflection point, and the judgment of the concave and convex of the object side surface and the image side surface at the near optical axis is still applicable to the above.

[0025] The concavo-convex shapes of the object side and the image side at the near optical axis of each lens are defined above. It can be understood that the object side and the image side of the first lens L1, the second lens L2, and the third lens L3 may have several inflection points. An inflection point is a point on the lens surface, and the tangent at this point is perpendicular to the optical axis.

[0026] The lens assembly satisfies TTL / ImgH ≤ 2.0, where TTL is the distance on the optical axis from the object side of the first lens L1 to the imaging surface IM of the lens assembly, and ImgH is the length of the diagonal of the effective imaging area of the lens assembly. By controlling the ratio of TTL / ImgH, it is possible to ensure that the optical imaging lens has the characteristics of a large image surface and thinning.

[0027] Preferably, CT1 / TTL ≤ 0.124, CT2 / TTL ≤ 0.185, CT3 / TTL ≤ 0.077, where CT1 is the maximum thickness of the first lens L1 on the optical axis, CT2 is the maximum thickness of the second lens L3 on the optical axis, and CT3 is the maximum thickness of the third lens L3 on the optical axis. Defining the thickness ratios of CT1, CT2, and CT3 in the entire lens assembly is beneficial to reducing the length of the lens assembly, reducing the volume of the lens assembly, and realizing the miniaturization of the lens assembly.

[0028] Preferably, 1.11 ≤ (ct1 + t12) / (ct2 + ct3 + T23 + T34) ≤ 2.5, where CT1 is the maximum thickness of the first lens L1 on the optical axis, CT2 is the maximum thickness of the second lens L2 on the optical axis, CT3 is the maximum thickness of the third lens L3 on the optical axis, T12 is the distance between the first lens and the diaphragm on the optical axis, T23 is the distance between the diaphragm and the second lens on the optical axis, T34 is the distance between the second lens and the third lens on the optical axis, and T45 is the distance between the third lens and the imaging surface of the lens assembly on the optical axis. The optical system is symmetric with respect to the diaphragm before and after, which can effectively reduce coma.

[0029] Preferably, -0.81 < f2 / f3 < -0.72. The smaller the value, the more beneficial it is to correct aberration while reducing the volume. The second lens L2 and the third lens L3 cooperate to effectively shorten the total length of the lens assembly while ensuring the imaging quality.

[0030] Preferably, -0.302 ≤ f / f1 ≤ -0.287. By controlling the ratio of the focal length of the lens assembly to the focal length of the first lens L1, it is possible to avoid excessive optical power of the first lens L1, resulting in low sensitivity and good imaging quality of the lens assembly, and at the same time, the lens assembly has a short optical length.

[0031] Preferably, the lens assembly satisfies the following conditions: ND3 ≥ 1.6, ND1 = ND2, ND3 > ND1; Among them, ND1 is the refractive index of the first lens L1, ND2 is the refractive index of the second lens L2, and ND3 is the refractive index of the third lens L3. Controlling the refractive index is beneficial to maintaining good imaging quality.

[0032] The lens assembly satisfies the following condition: 1.16≤R22 / R31≤2.0, wherein R22 is the curvature radius of the image side surface of the second lens L2, and R31 is the curvature radius of the object side surface of the third lens L3. By controlling the curvature radii of the image side surface of the second lens L2 and the object side surface of the third lens L3, the spherical aberration can be effectively balanced, thereby improving the imaging quality of the lens.

[0033] The lens assembly meets the following conditions: f / EPD≤4.1, Among them, f is the focal length of the lens assembly, and EPD is the entrance pupil diameter of the lens assembly. By controlling the ratio of the focal length of the lens assembly to the entrance pupil diameter, the aperture is expanded, the amount of light passing is increased, and a better imaging effect is achieved.

[0034] Preferably, the lens assembly meets the following conditions: TTL ≤ 2.5, TTL is the distance from the object side of the first lens to the imaging surface of the lens assembly at the optical axis, and a smaller volume is achieved by controlling the overall length of the lens.

[0035] Preferably, the lens assembly meets the following conditions: DMAX≤1.78, Among them, DMAX is the maximum effective radius of the lens, and the lens diameter can be miniaturized by controlling the outer diameter of the lens.

[0036] Preferably, any two adjacent lenses in the lens assembly do not move relative to each other, that is, there is no relative movement between the first lens L1, the second lens L2 and the third lens L3 in the lens assembly.

[0037] The lens assembly provided by the present application is specifically described in three embodiments as follows: Further references Figure 1B for Figure 1A The relative illumination curve of the lens assembly shown, Figure 1C for Figure 1A The polychromatic light diffraction defocus MTF curve of the lens assembly shown in the figure, Figure 1D for Figure 1A The field curvature and distortion curves of the lens assembly shown, Figure 1E for Figure 1A The vertical axis chromatic aberration curve of the lens assembly shown and Figure 1F for Figure 1AThe axial aberration curve diagram of the lens assembly is shown. Table 1.1 in the first embodiment is the optical parameters of some components in the lens assembly provided in the first embodiment of the present application. Table 1.2 is the aspheric coefficient of each lens in the lens assembly provided in the first embodiment of the present application. Table 1.3 is the optical parameters satisfied by the lens assembly provided in the first embodiment of the present application.

[0038] Table 1.1:

[0039] The aspheric curve equation of each lens is expressed as follows:

[0040] Among them, Z is the distance vector height of the aspheric surface from the origin of the aspheric surface when the aspheric surface is at a height r along the optical axis, c is the paraxial curvature of the aspheric surface (the radius of curvature R = 1 / c, which is the inverse of the curvature), k is the cone coefficient; Ai is the i-th order coefficient of the aspheric surface, and the high-order coefficients used in the present invention are A4, A6, A8, A10, A12, A14 and A16.

[0041] Table 1.2:

[0042] Table 1.3:

[0043] Further reference is made to the second embodiment Figure 2B for Figure 2A The relative illumination curve of the lens assembly shown, Figure 2C for Figure 2A The polychromatic light diffraction defocus MTF curve of the lens assembly shown in the figure, Figure 2D for Figure 2A The field curvature and distortion curves of the lens assembly shown, Figure 2E for Figure 2A The vertical axis chromatic aberration curve of the lens assembly shown and Figure 2F for Figure 2A The axial aberration curve diagram of the lens assembly is shown, Table 2.1 is the optical parameters of some components in the lens assembly provided in the second embodiment of the present application, Table 2.2 is the aspheric coefficients of each lens in the lens assembly provided in the second embodiment of the present application, and Table 2.3 is the optical parameters satisfied by the lens assembly provided in the second embodiment of the present application.

[0044] Table 2.1:

[0045] Table 2.2:

[0046] Table 2.3:

[0047] Further reference is made to the third embodiment Figure 3B for Figure 3A The relative illumination curve of the lens assembly shown, Figure 3C for Figure 3A The polychromatic light diffraction defocus MTF curve of the lens assembly shown in the figure, Figure 3D for Figure 3A The field curvature and distortion curves of the lens assembly shown, Figure 3E for Figure 3A The vertical axis chromatic aberration curve of the lens assembly shown and Figure 3F for Figure 3A The axial aberration curve of the lens assembly shown in Table 3.1 is the optical parameters of some components in the lens assembly provided in the third embodiment of the present application, Table 3.2 is the aspheric coefficient of each lens in the lens assembly provided in the third embodiment of the present application, and Table 3.3 is the optical parameters satisfied by the lens assembly provided in the third embodiment of the present application.

[0048] Table 3.1:

[0049] Table 3.2:

[0050] Table 3.3:

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lens assembly, characterized in that: From the object side to the image side, they are arranged in order: The first lens element has a negative refractive power, the object side surface of which is convex at the near optical axis, and the image side surface of which is concave at the near optical axis; Aperture; The second lens element has positive refractive power and its image side surface is convex near the optical axis; The third lens element has a negative refractive power, the object side surface of which is concave at the near optical axis, and the image side surface of which is concave at the near optical axis; The first lens, the second lens and the third lens are all aspherical lenses, and any two adjacent lenses are arranged at an interval.

2. The lens assembly according to claim 1, wherein: The lens assembly satisfies the following condition: TTL / ImgH≤2.0, wherein TTL is the distance from the object side of the first lens to the imaging surface of the lens assembly on the optical axis, and ImgH is the length of the diagonal of the effective imaging area of ​​the lens assembly.

3. The lens assembly according to claim 2, characterized in that: The lens assembly satisfies the following conditions: CT1 / TTL≤0.124, CT2 / TTL≤0.185, CT3 / TTL≤0.077, wherein CT1 is the maximum thickness of the first lens on the optical axis, CT2 is the maximum thickness of the second lens on the optical axis, and CT3 is the maximum thickness of the third lens on the optical axis.

4. The lens assembly according to claim 3, characterized in that: The lens assembly meets the following conditions: 1.11≤(ct1+t12) / (ct2+ct3++T23+T34) ≤2.5, wherein CT1 is the maximum thickness of the first lens on the optical axis, CT2 is the maximum thickness of the second lens on the optical axis, and CT3 is the maximum thickness of the third lens on the optical axis.

5. The lens assembly according to claim 4, characterized in that: The lens assembly meets the following conditions: -0.91<f2 / f3<-0.73, wherein f1 is the focal length of the first lens, f2 is the focal length of the second lens, and f3 is the focal length of the third lens.

6. The lens assembly according to claim 5, characterized in that: The lens assembly meets the following conditions: ND3≥1.6, ND1=ND2; wherein ND1 is the refractive index of the first lens, ND2 is the refractive index of the second lens, and ND3 is the refractive index of the third lens.

7. The lens assembly according to claim 6, wherein: The lens assembly satisfies the following condition: 1.16≤R22 / R31≤2.0, wherein R22 is the radius of curvature of the image side surface of the second lens, and R31 is the radius of curvature of the object side surface of the third lens.

8. The lens assembly according to claim 7, wherein: The lens assembly satisfies the following condition: f / EPD≤4.1, where f is the focal length of the lens assembly and EPD is the entrance pupil diameter of the lens assembly.

9. The lens assembly as claimed in claim 8, characterized in that: The lens assembly meets the following condition: TTL≤2.

5.

10. The lens assembly according to claim 9, wherein: The lens assembly meets the following condition: DMAX≤1.

78.

11. The lens assembly according to claim 10, wherein: Any two adjacent lenses in the lens assembly do not move relative to each other.

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