Optical system of a large-angle medical capsule endoscope

Abstract

The patent discloses a large-angle medical capsule endoscope optical system, and belongs to the optical lens field, which comprises first lens elements (L1), second lens elements (L2), optical filters (IR), light barriers (STO), third lens elements (L3), fourth lens elements (L4) and fifth lens elements (L5) arranged in sequence from an object plane to an image plane; and the focal lengths of the lens elements satisfy the following relationships: -135.02 < f1 / f < -138.73; -1.652 < f2 / f < -1.926; 1.349 < f3 / f < 1.682; 1.228 < f4 / f < 1.619; -1.346 < f5 / f < -1.304. The large-angle medical capsule endoscope optical system has good depth of field, small aperture, good tolerance, small distortion, and comparable resolution in liquid and air.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical lenses, and more specifically, relates to a medical capsule endoscope lens. Background Art

[0002] With the continuous development of medical technology, endoscopes are particularly important in diagnosing the causes of diseases within the human body. In order to improve the patient experience with endoscopes and enhance the diagnostic efficiency and accuracy of doctors for diseases within the human body, the medical industry's requirements for the size and optical performance of endoscopes are becoming increasingly stringent, especially for angles, depth of field, and the resolution of air and liquid. The present invention is made to meet these requirements. Summary of the Invention

[0003] To meet the current market demand, the present invention provides a large-angle medical capsule endoscope optical system, aiming to obtain an optical system with good depth of field, small aperture, low distortion, and shared use of air and liquid.

[0004] To achieve the above object, the present invention provides a large-angle medical capsule endoscope optical system, which is sequentially composed of a first lens element (L1), a second lens element (L2), a filter (IR), a diaphragm (STO), a third lens element (L3), a fourth lens element (L4), a fifth lens element (L5), and a chip protection glass (CG) from the object plane to the image plane; the first lens element (L1) is a plastic spherical negative lens, with its object side being convex and its image side being concave; the second lens element (L2) is a plastic aspherical negative lens, with its object side being concave and its image side being concave; the third lens element (L3) is a plastic aspherical positive lens, with its object side being convex and its image side being convex; the fourth lens element (L4) is a plastic aspherical positive lens, with its object side being convex and its image side being convex; the fifth lens element (L5) is a plastic aspherical negative lens, with its object side being concave and its image side being concave; and the focal lengths of each lens element satisfy the following relationship: -138.73 < f1 / f < -135.02; -1.926 < f2 / f < -1.652; 1.349 < f3 / f < 1.682; 1.228 < f4 / f < 1.619; -1.346 < f5 / f < -1.304; where f1 is the effective focal length of the first lens element (L1), f2 is the effective focal length of the second lens element (L2), f3 is the effective focal length of the third lens element (L3), f4 is the effective focal length of the fourth lens element (L4), f5 is the effective focal length of the fifth lens element (L5), and f is the effective focal length of a large-angle medical capsule endoscope optical system.

[0005] Preferably, the filter (IR) and the diaphragm (STO) are located between the second lens element (L2) and the third lens element (L3).

[0006] Preferably, the following relationship is satisfied: f / F < 0.16; where F is the f-number of a large-angle medical capsule endoscope optical system.

[0007] Preferably, the following relationship is satisfied: The following relationship is also satisfied: ∑TC / ∑TE = 1.218; where ∑TC is the sum of the lens thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) on the optical axis, and ∑TE is the sum of the axial thicknesses at the maximum aperture of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5).

[0008] Preferably, the following relationships are also satisfied: 0.17 < T1 / ∑TC < 0.19; 0.24 < T2 / ∑TC < 0.27; 0.22 < T3 / ∑TC < 0.25; 0.21 < T4 / ∑TC < 0.23; 0.08 < T5 / ∑TC < 0.11; where T1, T2, T3, T4, and T5 are the lens thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) on the optical axis, respectively.

[0009] Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following advantages:

[0010] (1) The apertures of the lenses of the optical imaging system of the present invention are small and the total length is short, which is beneficial to miniaturization; (2) The central region of the optical system of the present invention has a small distortion; (3) The effective focal length of the optical system of the present invention is small and the depth of field is good, and the depth of field can reach 3 mm to 35 mm, meeting the use of the capsule endoscope; (4) The optical system of the present invention is beneficial to reducing the tolerance sensitivity and is beneficial to mass production through the combination of positive and negative lenses and reasonable lens thicknesses. (5) The resolution of the optical system of the present invention in air and liquid is quite the same and can be used in both air and liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic structural diagram of the first embodiment of the present invention;

[0012] Figure 2 It is a distortion diagram of the first embodiment of the present invention;

[0013] Figure 3 It is an MTF diagram of the first embodiment of the present invention;

[0014] Figure 4 It is a schematic structural diagram of the second embodiment of the present invention;

[0015] Figure 5 This is a distortion diagram of the second embodiment of the present invention;

[0016] Figure 6 This is the MTF diagram of the second embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] 1. A large-angle medical capsule endoscope optical system, characterized in that, from the object plane to the image plane, it is composed of a first lens element (L1), a second lens element (L2), an IR filter, an aperture stop (STO), a third lens element (L3), a fourth lens element (L4), a fifth lens element (L5), and a chip protective glass (CG); the first lens element (L1) is a plastic spherical negative lens, with a convex object-side surface and a concave image-side surface; the second lens element (L2) is a plastic aspherical negative lens, with a concave object-side surface and a concave image-side surface; the third lens element (L3) is a plastic aspherical positive lens, with a convex object-side surface and a convex image-side surface; the fourth lens element (L4) is a plastic aspherical positive lens, with a convex object-side surface and a convex image-side surface; the fifth lens element (L5) is a plastic aspherical negative lens, with a concave object-side surface and a concave image-side surface; and the focal lengths of each lens element satisfy the following relationship:

[0019] -138.73 <f1 / f<-135.02;

[0020] -1.926 <f2 / f<-1.652;

[0021] 1.349 <f3 / f<1.682;

[0022] 1.228 <f4 / f<1.619;

[0023] -1.346 <f5 / f<-1.304;

[0024] Wherein, f1 is the effective focal length of the first lens element (L1), f2 is the effective focal length of the second lens element (L2), f3 is the effective focal length of the third lens element (L3), f4 is the effective focal length of the fourth lens element (L4), f5 is the effective focal length of the fifth lens element (L5), and f is the effective focal length of a large-angle medical capsule endoscope optical system.

[0025] The optical system adopts a negative-negative-positive-positive-negative structure, and the focal length of each lens is relatively close to the focal length ratio of the optical system. This is beneficial for balancing the optical power of each lens, making the light-reflecting ability of each lens comparable, and reducing the sensitivity of each lens to tolerance.

[0026] 2. The aforementioned large-angle medical capsule endoscope optical system is characterized in that the second lens element (L2) is a negative lens, and the filter (IR) and aperture stop (STO) are located between the second lens element (L2) and the third lens element (L3).

[0027] In conventional optical systems, the optical filter (IR) is typically placed at the rear, between the image plane and the last lens. In this invention, the IR is placed between the second lens element (L2) and the third lens element (L3) primarily because the air gap between them is large enough to accommodate the IR. Placing the IR here makes full use of the optical system's space, reducing its overall length. Furthermore, the second lens element (L2) is a negative lens, which can compress large-angle light rays, effectively reducing its effective aperture. The aperture stop (STO), located behind the second lens element (L2), further compresses the light, facilitating a reduction in the aperture of the subsequent three lens elements and contributing to a shorter overall length.

[0028] 3. The aforementioned large-angle medical capsule endoscope optical system satisfies the following relationship:

[0029] f / F < 0.16;

[0030] Where F represents the aperture number of a large-angle medical capsule endoscope optical system.

[0031] When the light transmission is sufficient, the smaller the effective focal length of the optical system, the larger the aperture number, and the better the depth of field. Generally, the ratio of the effective focal length to the aperture number of an endoscope is between 0.23 and 0.3. The optical system of this invention can achieve a ratio of less than 0.16, and the depth of field can meet the requirements of 3mm to 35mm.

[0032] 4. The aforementioned large-angle medical capsule endoscope optical system also satisfies the following relationship:

[0033] ∑TC / ∑TE=1.218;

[0034] Where ∑TC is the sum of the lens thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) on the optical axis, and ∑TE is the sum of the axial thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) at their maximum aperture.

[0035] The ratio of the sum of the center thickness to the sum of the edge thicknesses of all lenses is close to 1, indicating that the optical path traveled by rays in the central and peripheral fields of view is similar, preventing the formation of a noticeably curved image upon reaching the image plane and thus reducing distortion. Conventional endoscopes exhibit distortion exceeding 50%, while the distortion in the central region of this invention is less than 6%, aiding medical personnel in clearly viewing images and diagnosing diseases.

[0036] 5. The aforementioned large-angle medical capsule endoscope optical system has a field of view of over 150° and comparable resolution in air and liquid, which ensures that medical personnel are not affected by the medium when using the endoscope. The sufficiently large field of view also helps medical personnel obtain more information.

[0037] 6. The aforementioned large-angle medical capsule endoscope optical system also satisfies the following relationship:

[0038] 0.17 <T1 / ∑TC<0.19;

[0039] 0.24 <T2 / ∑TC<0.27;

[0040] 0.22 <T3 / ∑TC<0.25;

[0041] 0.21 <T4 / ∑TC<0.23;

[0042] 0.08 <T5 / ∑TC<0.11;

[0043] Where T1, T2, T3, T4, and T5 are the lens thicknesses on the optical axis of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5), respectively.

[0044] The center thicknesses of each lens are relatively close and the distribution is reasonable, which helps to reduce aberrations while also reducing the tolerance sensitivity of the lenses.

[0045] Example 1

[0046] As a specific embodiment of the present invention, the parameters of a large-angle medical capsule endoscope optical system are shown in Tables 1 and 2 below:

[0047] Table 1. Structural parameters of a large-angle medical capsule endoscope optical system.

[0048]

[0049]

[0050] Table 2. Surface coefficient of aspherical lens in a large-angle medical capsule endoscope optical system.

[0051]

[0052]

[0053] Example 2

[0054] As a specific embodiment of the present invention, the parameters of a large-angle medical capsule endoscope optical system are shown in Tables 3 and 4 below:

[0055] Table 3. Structural parameters of a large-angle medical capsule endoscope optical system.

[0056]

[0057] Table 4. Surface coefficient of aspherical lens in a large-angle medical capsule endoscope optical system.

[0058]

[0059]

[0060] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are 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 scope of protection of the present invention.

Claims

1. A wide-angle medical capsule endoscope optical system, characterized in that, The lens consists of, sequentially from the object plane to the image plane, a first lens element (L1), a second lens element (L2), an IR filter, an aperture stop (STO), a third lens element (L3), a fourth lens element (L4), a fifth lens element (L5), and a chip protective glass (CG). The first lens element (L1) is a plastic spherical negative lens with a convex object-side surface and a concave image-side surface. The second lens element (L2) is a plastic aspherical negative lens with a concave object-side surface and a concave image-side surface. The third lens element (L3) is a plastic aspherical positive lens with a convex object-side surface and a convex image-side surface. The fourth lens element (L4) is a plastic aspherical positive lens with a convex object-side surface and a convex image-side surface. The fifth lens element (L5) is a plastic aspherical negative lens with a concave object-side surface and a concave image-side surface. Furthermore, the focal lengths of each lens element satisfy the following relationship: -138.73 <f1 / f<-135.02; -1.926 <f2 / f<-1.652; 1.349 <f3 / f<1.682; 1.228 <f4 / f<1.619; -1.346 <f5 / f<-1.304; Wherein, f1 is the effective focal length of the first lens element (L1), f2 is the effective focal length of the second lens element (L2), f3 is the effective focal length of the third lens element (L3), f4 is the effective focal length of the fourth lens element (L4), f5 is the effective focal length of the fifth lens element (L5), and f is the effective focal length of a large-angle medical capsule endoscope optical system.

2. The large-angle medical capsule endoscope optical system as described in claim 1, characterized in that, The second lens element (L2) is a negative lens, and the filter (IR) and aperture stop (STO) are located between the second lens element (L2) and the third lens element (L3).

3. The large-angle medical capsule endoscope optical system as described in claim 1, characterized in that, The following relationship must be satisfied: f / F < 0.16; Where F represents the aperture number of a large-angle medical capsule endoscope optical system.

4. The large-angle medical capsule endoscope optical system as described in claim 1, characterized in that, It also satisfies the following relation: 1.19 < ∑TC / ∑TE < 1.23; Where ∑TC is the sum of the lens thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) on the optical axis, and ∑TE is the sum of the axial thicknesses of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5) at their maximum aperture.

5. The large-angle medical capsule endoscope optical system as described in claim 1, characterized in that, It also satisfies the following relation: 0.17 <T1 / ∑TC<0.19; 0.24 <T2 / ∑TC<0.27; 0.22 <T3 / ∑TC<0.25; 0.21 <T4 / ∑TC<0.23; 0.08 <T5 / ∑TC<0.11; Where T1, T2, T3, T4, and T5 are the lens thicknesses on the optical axis of the first lens element (L1), the second lens element (L2), the third lens element (L3), the fourth lens element (L4), and the fifth lens element (L5), respectively.

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