A lens assembly

Abstract

The application discloses a lens assembly, a capsule endoscope capsule and a system thereof. The lens assembly is sequentially provided with a first lens with a negative refractive power from an object side to an image side, a diaphragm, a second lens with a positive refractive power, and a third lens with a negative refractive power. The object side of the first lens is a convex surface at a near optical axis, and the image side of the first lens is a concave surface at the near optical axis. The image side of the second lens is a convex surface at the near optical axis. The object side of the third lens is a concave surface at the near optical axis, and the image side of the third lens is a concave surface at the near optical axis. The first lens, the second lens and the third lens are all aspherical lenses. Any two adjacent lenses are spaced. The lens assembly is beneficial to shortening the total optical length of the lens assembly, realizing the miniaturized design of the lens assembly, and has excellent imaging effect, wide field of view and small distortion.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and more particularly to a lens assembly. Background Technology

[0002] Capsule endoscopy involves direct ingestion, taking pictures through a camera inside the endoscope, and then transmitting the pictures to a receiver via data transmission. The images taken by the capsule can be received and viewed in real time using specific software. As capsule endoscopy continues to develop, making the endoscope smaller is a challenge. To facilitate ingestion and testing, the capsule volume needs to be reduced to a smaller size.

[0003] This invention optimizes the camera module to a smaller size while having a larger field of view, providing a wider field of view and allowing observation of a larger area. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a lens assembly:

[0005] A lens assembly, comprising, from the object side to the image side, the following components:

[0006] The first lens with negative refractive power has an object-side surface that is convex near the optical axis and an image-side surface that is concave near the optical axis.

[0007] Aperture;

[0008] The second lens, which has positive refractive power, has a convex image-side surface near the optical axis.

[0009] The third lens with negative refractive power has an object-side surface that is concave near the optical axis and an image-side surface that is concave near the optical axis.

[0010] The first lens, the second lens, and the third lens are all aspherical lenses, and any two adjacent lenses are spaced apart.

[0011] Furthermore, the lens assembly satisfies the following condition: TTL / ImgH≤2.0, where TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the lens assembly, and ImgH is the length of the diagonal of the effective imaging area of ​​the lens assembly.

[0012] Furthermore, the lens assembly satisfies the following conditions: CT1 / TTL≤0.124, CT2 / TTL≤0.185, CT3 / TTL≤0.077, where 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.

[0013] Furthermore, the lens assembly satisfies the following condition: 1.11≤(ct1+t12) / (ct2+ct3++T23+T34)≤2.5, where 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.

[0014] Furthermore, the lens assembly satisfies the following condition: -0.91 < f2 / f3 < -0.73, where 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.

[0015] Furthermore, the lens assembly satisfies the following conditions: ND3≥1.6, ND1=ND2; where 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.

[0016] Furthermore, the lens assembly satisfies the following condition: 1.16≤R22 / R31≤2.0, where R22 is the radius of curvature of the image side of the second lens and R31 is the radius of curvature of the object side of the third lens.

[0017] Furthermore, 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.

[0018] Furthermore, the lens assembly satisfies the following condition: TTL ≤ 2.5.

[0019] Furthermore, the lens assembly satisfies the following condition: DMAX ≤ 1.78.

[0020] Furthermore, there is no relative movement between any two adjacent lenses in the lens assembly.

[0021] The lens assembly of the present invention is advantageous for shortening the overall optical length of the lens assembly, realizing the miniaturization design of the lens assembly, and providing excellent imaging effect, wide field of view, and low distortion. Attached Figure Description

[0022] Figure 1A : A schematic diagram of the lens assembly provided in the first embodiment of this application;

[0023] Figure 1B : Figure 1A The relative illumination curve of the lens assembly is shown.

[0024] Figure 1C : Figure 1A The MTF curve of polychromatic light diffraction defocusing of the lens assembly is shown.

[0025] Figure 1D : Figure 1A The field curvature and distortion curves of the lens assembly are shown.

[0026] Figure 1E : Figure 1A The vertical chromatic aberration curve of the lens assembly shown;

[0027] Figure 1F : Figure 1A The axial aberration curve of the lens assembly is shown.

[0028] Figure 2A : A schematic diagram of the lens assembly provided in the second embodiment of this application

[0029] Figure 2B : Figure 2A The relative illumination curve of the lens assembly is shown.

[0030] Figure 2C : Figure 2A The MTF curve of polychromatic light diffraction defocusing of the lens assembly is shown.

[0031] Figure 2D : Figure 2A The field curvature and distortion curves of the lens assembly are shown.

[0032] Figure 2E : Figure 2A The vertical chromatic aberration curve of the lens assembly shown;

[0033] Figure 2F : Figure 2A The axial aberration curve of the lens assembly is shown.

[0034] Figure 3A : A schematic diagram of the lens assembly provided in the third embodiment of this application;

[0035] Figure 3B : Figure 3A The relative illumination curve of the lens assembly is shown.

[0036] Figure 3C : Figure 3A The MTF curve of polychromatic light diffraction defocusing of the lens assembly is shown.

[0037] Figure 3D : Figure 3A The field curvature and distortion curves of the lens assembly are shown.

[0038] Figure 3E : Figure 3A The vertical chromatic aberration curve of the lens assembly shown;

[0039] Figure 3F : Figure 3AThe diagram shows the axial aberration curves of the lens assembly. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0041] Definition: The side of an optical component or element facing the subject is called the object side, and the side facing the imaging plane is called the image side.

[0042] TTL: The distance from the object side of the first lens to the imaging surface of the lens assembly at the optical axis;

[0043] ImgH: The length of the diagonal of the effective imaging area of ​​the lens assembly;

[0044] ND1: Refractive index of the first lens;

[0045] ND2: Refractive index of the second lens;

[0046] ND3: Refractive index of the third lens;

[0047] CT1: The maximum thickness of the first lens along the optical axis;

[0048] CT2: The maximum thickness of the second lens along the optical axis;

[0049] CT3: The maximum thickness of the third lens along the optical axis;

[0050] T12: The distance between the first lens and the aperture on the optical axis;

[0051] T23: The distance between the aperture stop and the second lens on the optical axis;

[0052] T34: The distance between the second and third lenses on the optical axis;

[0053] T45: The distance between the imaging plane of the third lens and the lens assembly on the optical axis;

[0054] f1: Focal length of the first lens;

[0055] f2: Focal length of the second lens;

[0056] f3: Focal length of the third lens;

[0057] f: Focal length of the lens assembly;

[0058] EPD: Entrance pupil diameter;

[0059] WFno: Lens assembly F-number;

[0060] Fov: Field of view of the lens assembly;

[0061] k: Conic coefficient;

[0062] A4: The fourth-order coefficient of an aspherical surface;

[0063] A6: The 6th order coefficient of an aspherical surface;

[0064] A8: The 8th coefficient of an aspherical surface;

[0065] A10: The 10th order coefficient of an aspherical surface;

[0066] A12: The 12th order coefficient of an aspherical surface;

[0067] A14: The 14th order coefficient of aspherical surfaces;

[0068] A16: The 16th order coefficient of an aspherical surface;

[0069] DMAX: Maximum effective radius of the lens.

[0070] This application provides a miniaturized wide-angle lens assembly for optical imaging. This lens assembly can be applied to products in various fields where the size of the lens assembly is relatively sensitive, such as smart terminals, medical examination and surgical systems, industrial cameras, security monitoring equipment, wearable devices, drones, virtual reality (VR) and augmented reality (AR) devices, etc. This application takes the application of the lens assembly in the medical field of capsule endoscope system as an example for illustration.

[0071] Please refer to Figure 1A A schematic diagram of the lens assembly provided in the first embodiment of this application. Figure 2A A schematic diagram of the lens assembly provided in the second embodiment of this application and Figure 3A This is a schematic diagram of the lens assembly provided in the third embodiment of this 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. Each lens has an object side facing the object and an image side facing the image.

[0072] The first lens L1 has negative refractive power, its object side is convex near the optical axis, and its image side is concave near the optical axis; the second lens L2 has positive refractive power, and its image side is convex near the optical axis; the third lens L3 has negative refractive power, its object side is concave near the optical axis, and its image side is concave near the 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 spaced apart.

[0073] In the lens assembly provided in this application, the object side of the first lens is convex near the optical axis, which is beneficial for expanding the field of view and has positive refractive power, used to converge the light rays incident on the first lens; the second lens has positive refractive power, which converges the light beam emitted from the first lens, effectively balances low-order aberrations, effectively corrects paraxial spherical aberration, and reduces peripheral astigmatism; the third lens has negative refractive power, which is beneficial for miniaturization of the lens assembly, and can reduce spherical aberration by changing the position of the edge rays.

[0074] Furthermore, in the lens assembly, the image-side surface of the second lens is convex near the optical axis, and the object-side surface of the third lens is concave near the optical axis. Consequently, the concave and convex shapes of the image-side surface of the second lens and the object-side surface of the third lens near the optical axis tend to match each other, which is beneficial for the second and third lenses to fit together tightly with a small gap. Therefore, the concave and convex shape settings of the surfaces of the second and third lenses near the optical axis are conducive to the close-fitting design of the three lenses, reducing the overall optical length of the lens assembly, realizing the miniaturization of the lens assembly, and achieving better aberration correction effect.

[0075] The object-side surface of the lens described in this invention is convex if, when a cross-section is made across the object-side surface from any point on the surface, the object-side surface is always on the right side of the cross-section, and its radius of curvature is positive. Conversely, if the object-side surface is concave, its radius of curvature is negative. Similarly, the image-side surface is convex if, when a cross-section is made across the object-side or image-side surface from any point on the surface, the image-side surface is always on the left side of the cross-section, and its radius of curvature is negative. Conversely, if the image-side surface is concave, its radius of curvature is positive. If a cross-section is made across the object-side or image-side surface from any point on the surface, and the surface has both a portion on the left and a portion on the right side of the cross-section, then the surface has a curve inflection point. The determination of the convexity / concavity of the object-side and image-side surfaces near the optical axis still applies as described above.

[0076] The above text defines the concave and convex shapes of the object side and image side near the optical axis of each lens. It can be understood that the object side and 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 located on the surface of the lens, and the tangent at that point is perpendicular to the optical axis.

[0077] 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, the optical imaging lens can be guaranteed to have the characteristics of a large image plane and thinness.

[0078] 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, 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, decreasing the volume of the lens assembly, and achieving miniaturization of the lens assembly.

[0079] 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 aperture on the optical axis, T23 is the distance between the aperture 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 aperture before and after, which can effectively reduce coma.

[0080] 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 imaging quality.

[0081] 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, while also giving the lens assembly a shorter optical length.

[0082] Preferably, the lens assembly satisfies the following conditions: ND3 ≥ 1.6, ND1 = ND2, ND3 > ND1;

[0083] where 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.

[0084] The lens assembly satisfies the following conditions: 1.16 ≤ R22 / R31 ≤ 2.0, where R22 is the radius of curvature of the image side of the second lens L2 and R31 is the radius of curvature of the object side of the third lens L3. Controlling the radius of curvature of the image side of the second lens L2 and the object side of the third lens L3 can effectively balance spherical aberration and make the imaging quality of the lens better.

[0085] The lens assembly satisfies the following conditions: f / EPD ≤ 4.1,

[0086] Where 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 to the entrance pupil diameter of the lens assembly, the aperture is enlarged, the amount of light transmitted is increased, and a better imaging effect is achieved.

[0087] Preferably, the lens assembly meets the following condition: TTL ≤ 2.5.

[0088] TTL is the distance from the object side of the first lens to the imaging surface of the lens assembly at the optical axis. By controlling the overall length of the lens, a smaller volume can be achieved.

[0089] Preferably, the lens assembly meets the following condition: DMAX ≤ 1.78.

[0090] DMAX is the maximum effective radius of the lens, and the lens diameter is miniaturized by controlling the outer diameter of the lens.

[0091] Preferably, there is no relative movement between any two adjacent lenses in the lens assembly, 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.

[0092] The lens assembly provided in this application is described in detail below with reference to three embodiments:

[0093] Further reference Figure 1B for Figure 1A The relative illumination curve of the lens assembly shown is as follows: Figure 1C for Figure 1A The MTF curve of polychromatic light diffraction defocusing of the lens assembly shown is as follows: Figure 1D for Figure 1A The field curvature and distortion curves of the lens assembly shown are as follows: Figure 1E for Figure 1A The vertical chromatic aberration curve of the lens assembly shown is as follows: Figure 1F for Figure 1A The axial aberration curves of the lens assembly shown are presented. Table 1.1 in the first embodiment contains the optical parameters of some components in the lens assembly provided in the first embodiment of this application. Table 1.2 contains the aspherical coefficients of each lens in the lens assembly provided in the first embodiment of this application. Table 1.3 contains the optical parameters satisfied by the lens assembly provided in the first embodiment of this application.

[0094] Table 1.1: .

[0095] The equations for the aspherical curves of each lens are expressed as follows:

[0096]

[0097] Where Z is the distance vector from the origin of the aspherical surface at a height of r along the optical axis, c is the paraxial curvature of the aspherical surface (radius of curvature R = 1 / c, which is the reciprocal of curvature), k is the conic coefficient, and Ai is the i-th order coefficient of the aspherical surface. The higher order coefficients used in this invention are A4, A6, A8, A10, A12, A14, and A16.

[0098] Table 1.2: .

[0099] Table 1.3: .

[0100] Further refer to the second embodiment Figure 2B for Figure 2A The relative illumination curve of the lens assembly shown is as follows: Figure 2C for Figure 2A The MTF curve of polychromatic light diffraction defocusing of the lens assembly shown is as follows: Figure 2D for Figure 2A The field curvature and distortion curves of the lens assembly shown are as follows: Figure 2E for Figure 2A The vertical chromatic aberration curve of the lens assembly shown is as follows: Figure 2F for Figure 2A The axial aberration curves of the lens assembly shown are presented in Table 2.1, which contains the optical parameters of some components in the lens assembly provided in the second embodiment of this application; Table 2.2 contains the aspherical coefficients of each lens in the lens assembly provided in the second embodiment of this application; and Table 2.3 contains the optical parameters satisfied by the lens assembly provided in the second embodiment of this application.

[0101] Table 2.1: .

[0102] Table 2.2: .

[0103] Table 2.3: .

[0104] Further refer to the third embodiment Figure 3B for Figure 3A The relative illumination curve of the lens assembly shown is as follows: Figure 3C for Figure 3A The MTF curve of polychromatic light diffraction defocusing of the lens assembly shown is as follows: Figure 3D for Figure 3A The field curvature and distortion curves of the lens assembly shown are as follows: Figure 3E for Figure 3A The vertical chromatic aberration curve of the lens assembly shown is as follows: Figure 3F for Figure 3A The axial aberration curves of the lens assembly shown are presented in Table 3.1, which contains the optical parameters of some components in the lens assembly provided in the third embodiment of this application; Table 3.2 contains the aspherical coefficients of each lens in the lens assembly provided in the third embodiment of this application; and Table 3.3 contains the optical parameters satisfied by the lens assembly provided in the third embodiment of this application.

[0105] Table 3.1: .

[0106] Table 3.2: .

[0107] Table 3.3: .

[0108] The above description is merely 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 within the protection scope of the present invention.

Claims

1. A lens assembly, characterized in that, There are three aspherical lenses in total, arranged sequentially from the object side to the image side: The first lens with negative refractive power has an object-side surface that is convex near the optical axis and an image-side surface that is concave near the optical axis. Aperture; The second lens, which has positive refractive power, has a convex image-side surface near the optical axis. The third lens with negative refractive power has an object-side surface that is concave near the optical axis and an image-side surface that is concave near the optical axis. The first lens, the second lens, and the third lens are all aspherical lenses, and any two adjacent lenses are spaced apart. The lens assembly satisfies the following conditions: TTL / ImgH≤2.0, CT1 / TTL≤0.124, CT2 / TTL≤0.185, CT3 / TTL≤0.077, -0.91<f2 / f3<-0.73, Where TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the lens assembly, ImgH is the length of the diagonal of the effective imaging area of ​​the lens assembly, 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, CT3 is the maximum thickness of the third lens on the optical axis, and f2 is the focal length of the second lens and f3 is the focal length of the third lens.

2. The lens assembly as claimed in claim 1, characterized in that, The lens assembly satisfies the following conditions: 1.11≤(CT1+T12) / (CT 2+ CT 3++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, CT3 is the maximum thickness of the third lens on the optical axis, T12 is the distance between the first lens and the aperture on the optical axis, T23 is the distance between the aperture and the second lens on the optical axis, and T34 is the distance between the second lens and the third lens on the optical axis.

3. The lens assembly as described in claim 1, characterized in that, 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.

4. The lens assembly as claimed in claim 1, characterized in that, The lens assembly satisfies the following conditions: 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.

5. The lens assembly as claimed in claim 1, characterized in that, The lens assembly meets the following condition: TTL≤2.5mm.

6. The lens assembly as claimed in claim 1, characterized in that, The lens assembly satisfies the following conditions: DMAX≤1.78mm, where DMAX is the maximum effective radius of the lens.

7. The lens assembly as claimed in claim 1, characterized in that, In the lens assembly, there is no relative movement between any two adjacent lenses.

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