阅读说明：本技术 成像设备、光学镜头以及内窥镜 (Imaging apparatus, optical lens, and endoscope ) 是由 吴沛 罗正春 蒋青锋 于 2021-07-16 设计创作，主要内容包括：本申请涉及一种成像设备、光学镜头以及内窥镜,其中,该成像设备,包括成像元件和光学镜头；成像元件用于将光学镜头形成的光学图像转换为电信号；光学镜头,用于对物体进行成像,从物侧到像侧依次包括位于同一光路上的光阑、第一透镜、第二透镜、第三透镜、第四透镜、第五透镜以及成像面,采用特定的表面形状搭配和合理的焦距分配。通过本申请,解决了成像设备中镜头尺寸较大,无法完成小型化设计的问题,实现在满足高像素的同时结构更加紧凑。(The present application relates to an imaging apparatus, an optical lens, and an endoscope, wherein the imaging apparatus includes an imaging element and an optical lens; the imaging element is used for converting an optical image formed by the optical lens into an electric signal; the optical lens is used for imaging an object, sequentially comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging surface which are positioned on the same optical path from an object side to an image side, and adopts specific surface shape collocation and reasonable focal length distribution. Through the application, the problem that the size of a lens in imaging equipment is large and miniaturization design cannot be completed is solved, and the structure is more compact while high pixels are met.)

1. An imaging apparatus characterized by comprising an imaging element and an optical lens;

the imaging element is used for converting an optical image formed by the optical lens into an electric signal;

the optical lens is used for imaging an object and sequentially comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging surface which are positioned on the same optical path from an object side to an image side;

the first lens has positive focal power and comprises a first object end surface and a first image end surface;

the second lens has negative focal power and comprises a second object end surface and a second image end surface;

the third lens has negative focal power and comprises a third object end surface and a third image end surface;

the fourth lens has positive focal power and comprises a fourth object end surface and a fourth image end surface;

the fifth lens has positive focal power and comprises a fifth object end surface and a fifth image end surface;

the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces;

the third lens and the fourth lens are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein f represents the focal length of the optical lens; f. of_g1Representing a focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

2. An optical lens is used for imaging an object and is characterized by comprising a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging surface which are positioned on the same optical path in sequence from an object side to an image side;

the first lens has positive focal power and comprises a first object end surface and a first image end surface;

the second lens has negative focal power and comprises a second object end surface and a second image end surface;

the third lens has negative focal power and comprises a third object end surface and a third image end surface;

the fourth lens has positive focal power and comprises a fourth object end surface and a fourth image end surface;

the fifth lens has positive focal power and comprises a fifth object end surface and a fifth image end surface;

the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces;

the third lens and the fourth lens are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein, f isShowing the focal length of the optical lens; f. of_g1Representing a focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

3. An optical lens according to claim 2, characterized in that the optical lens further comprises a filter;

the optical filter is arranged on a light path between the fifth lens and the imaging surface.

4. An optical lens according to claim 2, characterized in that the diaphragm is an aperture diaphragm.

5. An optical lens according to claim 2, wherein the first lens, the second lens, the third lens, the fourth lens and the fifth lens are spherical lenses;

or the first lens, the second lens, the third lens, the fourth lens and the fifth lens are aspheric lenses.

6. An optical lens according to any one of claims 2 to 5, characterized in that the optical lens satisfies the following relation:

TTL/f≤1.3；

wherein TTL represents the total optical length of the optical lens; f denotes a focal length of the optical lens.

7. An optical lens according to any one of claims 2 to 5, characterized in that the optical lens satisfies the following relation:

BFL/TL≤0.6；

wherein BFL represents an optical back focus of the optical lens; TL denotes a lens group length of the optical lens.

8. An optical lens according to any one of claims 2 to 5, characterized in that the optical lens satisfies the following relation:

wherein R4 represents the center radius of curvature of the second image end face; r5 represents the central radius of curvature of the third object end face.

9. An optical lens barrel according to any one of claims 2 to 5, wherein the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element are made of glass.

10. An optical lens according to claim 9, characterized in that the optical lens satisfies the following conditional expression:

Vd1≤82；

Vd2≤65；

Vd4≤71；

wherein Vd1 represents the lens abbe number of the first lens; vd2 denotes the lens abbe number of the second lens; vd4 denotes the abbe number of the optic of the fourth lens.

11. An optical lens according to claim 9, characterized in that the optical lens satisfies the following conditional expression:

Nd2≥1.45；

Nd3≤1.82；

Nd4≤1.63；

Nd5≤1.87；

wherein Nd2 represents the optic refractive index of the second lens; nd3 denotes an index of refraction of the third lens; nd4 denotes an index of refraction of the fourth lens; nd5 denotes an index of refraction of the optic of the fifth lens.

12. An optical lens according to any one of claims 2 to 5, characterized in that the optical lens satisfies the following conditional expression:

f1≤21mm；

f2≤-31mm；

f5≤19mm；

wherein f1 denotes a focal length of the first lens group; f2 denotes the focal length of the second lens; f5 denotes the focal length of the fifth lens.

13. An endoscope, comprising a connection tube and an optical lens according to any one of claims 2 to 12;

the connecting pipe is connected with the optical lens and used for transmitting the optical image of the optical lens.

Technical Field

The present application relates to the field of medical imaging equipment technology, and in particular, to an imaging device, an optical lens, and an endoscope.

Background

Owing to the rapid development of smart medical treatment in recent years, optical lenses are increasingly used in the medical field, and especially in the medical endoscope field, the requirements for optical imaging lenses are increasing. In addition, as the imaging system gradually moves to 4K high definition, the requirement for pixels is higher. In an endoscope used in the medical field, images of various parts in a body cavity are obtained by an endoscope inserted into the body cavity, and an observation part is diagnosed using the images.

In the related art, chinese patent publication No. CN 110764226 a discloses a large-field micro-objective lens, which includes, in order from an object end to an image end along an optical axis direction thereof, a first lens with positive dioptric brightness, a second lens with positive dioptric brightness, a third lens, a fourth lens with positive dioptric brightness, a fifth lens with negative dioptric brightness, a sixth lens with negative dioptric brightness, and an imaging surface. The lens consists of six lenses, the size of the whole lens is large, the miniaturization design cannot be completed, and the pixel ratio is low.

At present, no effective solution is provided for the problems that in the related art, the size of a lens is large, the miniaturization design cannot be completed, and the requirement for high pixels cannot be met.

Disclosure of Invention

The embodiment of the application provides an imaging device, an optical lens and an endoscope, and aims to solve the problems that in the related art, the size of the lens is large, the miniaturization design cannot be completed, and the requirement for high pixels cannot be met.

In a first aspect, an embodiment of the present application provides an imaging apparatus, including an imaging element and an optical lens;

the imaging element is used for converting an optical image formed by the optical lens into an electric signal;

the optical lens is used for imaging an object and sequentially comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging surface which are positioned on the same optical path from an object side to an image side;

the first lens has positive focal power and comprises a first object end surface and a first image end surface;

the second lens has negative focal power and comprises a second object end surface and a second image end surface;

the third lens has negative focal power and comprises a third object end surface and a third image end surface;

the fourth lens has positive focal power and comprises a fourth object end surface and a fourth image end surface;

the fifth lens has positive focal power and comprises a fifth object end surface and a fifth image end surface;

the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces;

the third lens and the fourth lens are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein f represents the focal length of the optical lens; f. of_g1Representing a focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

In a second aspect, an embodiment of the present application provides an optical lens for imaging an object, which includes, in order from an object side to an image side, a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and an imaging surface, which are located on the same optical path;

the first lens has positive focal power and comprises a first object end surface and a first image end surface;

the second lens has negative focal power and comprises a second object end surface and a second image end surface;

the third lens has negative focal power and comprises a third object end surface and a third image end surface;

the fourth lens has positive focal power and comprises a fourth object end surface and a fourth image end surface;

the fifth lens has positive focal power and comprises a fifth object end surface and a fifth image end surface;

the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces;

the third lens and the fourth lens are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein f represents the focal length of the optical lens; f. of_g1Representing a focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

In some of these embodiments, the optical lens further comprises an optical filter;

the optical filter is arranged on a light path between the fifth lens and the imaging surface.

In some of these embodiments, the diaphragm is an aperture diaphragm.

In some of these embodiments, the first, second, third, fourth, and fifth lenses are spherical lenses;

or the first lens, the second lens, the third lens, the fourth lens and the fifth lens are aspheric lenses.

In some of these embodiments, the optical lens satisfies the following relationship:

TTL/f≤1.3；

wherein TTL represents the total optical length of the optical lens; f denotes a focal length of the optical lens.

In some of these embodiments, the optical lens satisfies the following relationship:

BFL/TL≤0.6；

wherein BFL represents an optical back focus of the optical lens; TL denotes a lens group length of the optical lens.

In some of these embodiments, the optical lens satisfies the following relationship:

wherein R4 represents the center radius of curvature of the second image end face; r5 represents the central radius of curvature of the third object end face.

In some embodiments, the first lens element, the second lens element, the third lens element, the fourth lens element and the fifth lens element are made of glass.

In some embodiments, the optical lens satisfies the following conditional expression:

Vd1≤82；

Vd2≤65；

Vd4≤71；

wherein Vd1 represents the lens abbe number of the first lens; vd2 denotes the lens abbe number of the second lens; vd4 denotes the abbe number of the optic of the fourth lens.

In some embodiments, the optical lens satisfies the following conditional expression:

Nd2≥1.45；

Nd3≤1.82；

Nd4≤1.63；

Nd5≤1.87；

wherein Nd2 represents the optic refractive index of the second lens; nd3 denotes an index of refraction of the third lens; nd4 denotes an index of refraction of the fourth lens; nd5 denotes an index of refraction of the optic of the fifth lens.

In some embodiments, the optical lens satisfies the following conditional expression:

f1≤21mm；

f2≤-31mm；

f5≤19mm；

wherein f1 denotes a focal length of the first lens group; f2 denotes the focal length of the second lens; f5 denotes the focal length of the fifth lens.

In a third aspect, embodiments of the present application provide an endoscope, comprising a connecting tube and the optical lens according to the second aspect;

the connecting pipe is connected with the optical lens and used for transmitting the optical image of the optical lens.

Compared with the related art, the imaging device, the optical lens and the endoscope provided by the embodiment of the application are provided, wherein the imaging device comprises an imaging element and the optical lens; the imaging element is used for converting an optical image formed by the optical lens into an electric signal; the optical lens is used for imaging an object and sequentially comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging surface which are positioned on the same optical path from an object side to an image side; the first lens has positive focal power and comprises a first object end surface and a first image end surface; the second lens has negative focal power and comprises a second object end surface and a second image end surface; the third lens has negative focal power and comprises a third object end surface and a third image end surface; the fourth lens has positive focal power and comprises a fourth object end surface and a fourth image end surface; the fifth lens has positive focal power and comprises a fifth object end surface and a fifth image end surface; the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces; the third lens and the fourth lens are combined into a cemented lens group; the cemented lens group satisfies the following relation:wherein f represents the focal length of the optical lens; f. of_g1Representing a focal length of the cemented lens group; the FOV represents the field angle of the optical lens. The application solves the problems that the size of a lens in imaging equipment is large and miniaturization design cannot be completed, adopts specific surface shape collocation and reasonable focal length distribution, and is practicalThe structure is more compact while satisfying the high pixel now.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a schematic structural diagram of an optical lens according to an embodiment of the present invention;

fig. 2 is a graph of an optical transfer function (MTF) at a normal temperature in a visible light band according to a first embodiment of the present invention;

FIG. 3 is a field curvature diagram in the visible light band provided by the first embodiment of the present invention;

FIG. 4 is a diagram of distortion in the visible light band provided by the first embodiment of the present invention;

FIG. 5 is a diagram of a first transverse fan in the visible wavelength band provided by the first embodiment of the present invention;

FIG. 6 is a diagram of a second transversal fan in the visible wavelength band according to the first embodiment of the present invention;

FIG. 7 is a third transversal fan diagram in the visible wavelength band according to the first embodiment of the present invention;

FIG. 8 is a fourth transversal fan diagram in the visible wavelength band according to the first embodiment of the present invention;

FIG. 9 is a fifth exemplary transverse fan in the visible wavelength band according to the first embodiment of the present invention;

fig. 10 is a first point diagram in the visible light band provided by the first embodiment of the present invention;

fig. 11 is a second point diagram in the visible light band provided by the first embodiment of the present invention;

fig. 12 is a third point diagram in the visible light band provided by the first embodiment of the present invention;

fig. 13 is a fourth point diagram in the visible light band provided by the first embodiment of the present invention;

fig. 14 is a fifth point diagram in the visible light band provided by the first embodiment of the present invention;

fig. 15 is a graph of an optical transfer function (MTF) at a normal temperature in the visible light band according to a second embodiment of the present invention;

FIG. 16 is a field curvature diagram in the visible wavelength band provided by a second embodiment of the present invention;

fig. 17 is a distortion diagram in the visible light band provided by the second embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments provided in the present application without any inventive step are within the scope of protection of the present application. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of ordinary skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments without conflict.

Unless defined otherwise, technical or scientific terms referred to herein shall have the ordinary meaning as understood by those of ordinary skill in the art to which this application belongs. When an element is referred to herein as being "on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present. Reference herein to the terms "first," "second," "third," and the like, are merely to distinguish similar objects and do not denote a particular ordering for the objects. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, an optical lens according to an embodiment of the present application is used for imaging an object, and includes, in order from an object side to an image side, a stop, a first lens element L1, a second lens element L2, a third lens element L3, a fourth lens element L4, a fifth lens element L5, and an image plane; the first lens L1 has positive optical power, and the first lens L1 includes a first object end surface and a first image end surface; the second lens L2 has negative power, and the second lens L2 includes a second object plane and a second image plane; the third lens L3 has negative power, and the third lens L3 includes a third object end surface and a third image end surface; the fourth lens L4 has positive optical power, and the fourth lens L4 includes a fourth object end surface and a fourth image end surface; the fifth lens L5 has positive optical power, and the fifth lens L5 includes a fifth object end surface and a fifth image end surface; the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces; the third lens L3 and the fourth lens L4 are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein f represents the focal length of the optical lens; f. of_g1Indicating the focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

In this embodiment, the relation (1) can limit the structure of the cemented lens assembly and the structure of the entire optical lens, specifically, the focal length and the total length of the entire optical lens, i.e., the miniaturization design of the structure can be controlled. The optical lens structure who adopts does: the lens system sequentially comprises a diaphragm, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and an imaging surface which are located on the same optical path from the object side to the image side, and the structure is more compact while high pixel is met by combining specific surface shape collocation of each lens and the focal length distribution meeting the relation (1).

In one embodiment, the optical lens further includes an optical filter L6; the filter L6 is disposed on the optical path between the fifth lens L5 and the image forming surface, and can protect the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5. And the filter L6 has a filtering effect, so that the imaging effect can be further improved. The filter L6 is generally a planar structure. And the lenses of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are in various forms. Such as: the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are spherical lenses. Alternatively, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are aspheric lenses. It should be understood that spherical lenses refer to lenses in which both the inner and outer surfaces are spherical, or one surface is spherical and the other is flat. The surface shape of the aspheric lens is determined by a multi-image high-order equation, and the radiuses of all points on the surface shape are different. Preferably, an aspherical lens may be selected which enables a reduction of the lens thickness.

The following describes in detail the relational expressions and conditional expressions that the optical lens needs to satisfy.

In one embodiment, the diaphragm is an aperture diaphragm, and the distance between the aperture diaphragm and the first lens L1 is less than or equal to 0.4 mm; in one embodiment, the distance between the aperture stop and the first lens L1 may be 0.2 mm.

In one embodiment, the optical lens satisfies the following relationship:

TTL/f≤1.3 (2)；

wherein, TTL represents the total optical length of the optical lens; f denotes a focal length of the optical lens. In the embodiment, the optical lens satisfies the relation (1) and also satisfies the relation (2), the total optical length is limited by limiting the focal length, and the focal length can be reasonably distributed to reduce aberration; and simultaneously, the whole size of the optical lens is favorably limited.

In one embodiment, the optical lens satisfies the following relationship:

BFL/TL≤0.6 (3)；

wherein BFL represents the optical back focus of the optical lens; TL denotes a lens group length of the optical lens. In the present embodiment, the optical lens satisfies the relational expression (3) as well as the relational expression (1). The length of the lens group is limited by limiting the optical back focus, so that the focal length can be reasonably distributed to improve pixels; and simultaneously, the whole size of the optical lens is favorably limited. In other embodiments, the optical lens may also satisfy the relation (1), the relation (2) and the relation (3) at the same time, which is not limited.

In one embodiment, the optical lens satisfies the following relationship:

wherein R4 represents the center radius of curvature of the second image-end face; r5 represents the central radius of curvature of the third object end face. The central curvature radius of the second image end surface and the central curvature radius of the third object end surface are reasonably defined by the relation (4) to define the shapes of the second lens L2 and the third lens L3, and the second lens L2 and the third lens L3 both have negative focal power, so that the aperture and the total length of the subsequent lens can be reduced, and the optical lens can be miniaturized. In one embodiment, the optical lens can satisfy the relation (1), the relation (2), the relation (3) and the relation (4) at the same time. In another embodiment, the optical lens can satisfy the relation (1), the relation (2) and the relation (4) at the same time. As described above, the more relational expressions that are satisfied, the better the effect that the optical lens achieves, i.e., the more compact the structure, and the imaging quality can be ensured.

In one embodiment, the optical lens satisfies the following conditional expression (5):

f1≤21mm；f2≤-31mm；f5≤19mm； (5)；

wherein f1 denotes a focal length of the first lens L1 group; f2 denotes a focal length of the second lens L2; f5 denotes a focal length of the fifth lens L5. In the present embodiment, the conditional expression (5) is used to assign the focal lengths of the first lens L1, the second lens L2, and the fifth lens L5, and further optimize the assignment scheme of the focal lengths, so as to limit the structure of the optical lens.

In order to control the cost and make the lens have good processing performance, the materials of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 may all be glass, so that the requirements on the materials of the lenses are provided.

In one embodiment, the optical lens satisfies the following conditional expression (6):

Vd1≤82；Vd2≤65；Vd4≤71； (6)；

vd1 represents the abbe number of the first lens L1; vd2 denotes the lens abbe number of the second lens L2; vd4 denotes the lens abbe number of the fourth lens L4.

In the present embodiment, requirements are placed on the abbe numbers of the lenses of the first lens L1, the second lens L2, and the fourth lens L4. The specific requirements are as follows: the abbe number Vd1 of the first lens L1 is not more than 82; the abbe number Vd2 of the second lens L2 is less than or equal to 65; the abbe number Vd4 of the fourth lens L4 is not more than 71. For an optical lens, these three conditions may not be satisfied simultaneously. Such as: as long as one, two, or three of them are satisfied simultaneously. When one of the requirements is met, only the abbe number Vd1 of the first lens L1 can be met, and is not more than 82; or the abbe number Vd2 of the second lens L2 is less than or equal to 65; or the abbe number Vd4 of the fourth lens L4 is less than or equal to 71. When two of the above conditions are satisfied, only the lens abbe number Vd1 of the first lens L1 is not more than 82, and the lens abbe number Vd2 of the second lens L2 is not more than 65; the Abbe number Vd1 of the first lens L1 is not more than 82, and the Abbe number Vd4 of the fourth lens L4 is not more than 71; the Abbe number Vd2 of the second lens L2 is not more than 65; and the Abbe number Vd4 of the fourth lens L4 is not more than 71. Here, the above arrangement combination is not an example. Further, the abbe numbers of the lenses of the third lens L3 and the fifth lens L5 are not limited. Through the setting of above-mentioned parameter, the distance between the reasonable control lens is given, makes optical lens structure compacter simultaneously, is favorable to shortening optical lens's overall length.

In one embodiment, the optical lens satisfies the following conditional expression (7):

Nd2≥1.45；Nd3≤1.82；Nd4≤1.63；Nd5≤1.87； (7)；

wherein Nd2 denotes an eyeglass refractive index of the second lens L2; nd3 denotes an eyeglass refractive index of the third lens L3; nd4 denotes an index of refraction of the fourth lens L4; nd5 denotes an index of refraction of the fifth lens L5. These four conditions may not be satisfied simultaneously for the optical lens. Such as: as long as one, two, three, four, or three of them are satisfied. For example, the case where one is satisfied is: the refractive index Nd2 of the second lens L2 is not less than 1.45, and the refractive index of the lens of the other lens is not limited. Two conditions are satisfied: the refractive index Nd2 of the second lens L2 is not less than 1.45, the refractive index Nd2 of the third lens L3 is not less than 1.82, and the refractive indices of the lenses of the other lenses are not limited. Three conditions are satisfied: the refractive index Nd2 of the second lens L2 is not less than 1.45, the refractive index Nd2 of the third lens L3 is not less than 1.82, the refractive index Nd5 of the fifth lens L5 is not more than 1.87, and the refractive indexes of the lenses of the other lenses are not limited. Here, the above arrangement combination is not an example. Through the setting of above-mentioned parameter, the distance between the reasonable control lens is given, makes optical lens structure compacter simultaneously, is favorable to shortening optical lens's overall length.

Specific examples are provided below for a detailed description:

example one

The optical lens provided in this embodiment is configured to image an object, and includes, in order from an object side to an image side, a stop located on the same optical path, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a filter L6, and an imaging surface; the first lens L1 has positive optical power, and the first lens L1 includes a first object end surface and a first image end surface; the second lens L2 has negative power, and the second lens L2 includes a second object plane and a second image plane; the third lens L3 has negative power, and the third lens L3 includes a third object end surface and a third image end surface; the fourth lens L4 has positive optical power, and the fourth lens L4 includes a fourth object end surface and a fourth image end surface; the fifth lens L5 has positive optical power, and the fifth lens L5 includes a fifth object end surface and a fifth image end surface; the optical filter L6 includes a sixth object end face and a sixth image end face; the first object end face, the second object end face, the fourth image end face, the fifth object end face and the fifth image end face are convex faces; the first image end face, the second image end face, the third object end face and the third image end face are all concave faces; the third lens L3 and the fourth lens L4 are combined into a cemented lens group; the cemented lens group satisfies the following relation:

wherein f represents the focal length of the optical lens; f. of_g1Indicating the focal length of the cemented lens group; the FOV represents the field angle of the optical lens.

In the present embodiment, the relevant parameters of each lens of the optical lens are shown in table 1, wherein R represents the curvature radius, Tc represents the center thickness, and N_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

Table 1 (relevant parameters for each lens);

based on the relevant parameters of the lenses, the optical technical indexes of the optical lens of the embodiment are as follows:

the total optical length TTL of the optical lens is less than or equal to 30.5 mm; focal length f of optical lens: 25 mm; angle of field of optical lens: 18 degrees; optical distortion of optical lens: 1.0 percent; aperture FNO of optical lens: FNO is less than or equal to 4.0; size of a lens image plane: not less than 8 mm.

It is to be understood that the optical transfer function is a function representing the relative changes of the modulation and the lateral phase shift during the imaging process, with the spatial frequency as a variable. The use of the optical transfer function to evaluate the imaging quality of the imaging system is a relatively accurate, intuitive, and common way. The higher and smoother curve shows the better imaging quality, and various aberrations (such as spherical aberration, coma aberration, astigmatism, field curvature, axial chromatic aberration, vertical axis chromatic aberration and the like) are well corrected.

Fig. 2 is a graph showing an optical transfer function (MTF) of the optical lens of this embodiment in a normal temperature state in the visible light band. In the figure, the abscissa is the spatial frequency and the ordinate is the optical transfer function (MTF) value. TS0.0000MM, is shown to be located at the center of the imaging area. It can be seen from the figure that the optical transfer function (MTF) graph is smooth and concentrated, and the average value of the MTF in the full field (half image height Y' 4.0mm) is 0.6 or more, and the MTF in the full field is 0.6 or more in the case of 100 lp/mm. It follows that the imaging requirements for high pixels can be achieved.

When the lens has field curvature, the intersection point of the whole light beam is not superposed with an ideal image point, and although a clear image point can be obtained at each specific point, the whole image plane is a curved surface. As shown in fig. 3 and 4, the field curvature in this embodiment is controlled within ± 0.2 mm. In the figure, T represents the meridional field curvature and S represents the sagittal field curvature. The field curvature curve shows the distance of the current focal plane or image plane to the paraxial focal plane as a function of the field of view coordinates. The meridional field curvature data is the distance from the currently determined focal plane to the paraxial focal plane measured along the Z axis, and is measured on the meridional (YZ plane). Sagittal curvature of field data measures distances measured in a plane perpendicular to the meridian plane, the base line in the schematic is on the optical axis, the top of the curve represents the maximum field of view (angle or height), and no units are set on the vertical axis, since the curve is always normalized by the maximum radial field of view.

As can be seen from fig. 4, the distortion control in the present embodiment is preferable, and is within 1.0%. Curves referencing a plurality of wavelengths (0.486mm, 0.588mm, 0.656mm, 0.436mm and 0.900mm) are coincident in fig. 4. In general, lens distortion is a general term for the intrinsic perspective distortion of an optical lens, that is, distortion due to perspective, which is very unfavorable for the imaging quality of a photograph, and after all, the purpose of photography is reproduction rather than exaggeration; however, this is an inherent characteristic of the lens (converging light with a convex lens and diverging light with a concave lens), and cannot be eliminated, and only can be improved. The distortion of the fixed-focus lens provided by the embodiment is only 1.0%, the distortion is set to balance the focal length, the angle of view and the size of the target surface of the corresponding camera, and the deformation caused by the distortion can be corrected through post-image processing. Thus imaging can be used with a probe device that can support the target surface up to a maximum of 1/2 inches.

As shown in fig. 5, 6, 7, 8, and 9, the fan map is for each field of view. Such as: IMA:0.000MM means that the intersection height of the chief ray of the 0 field of view and the imaging plane (IMA) is 0. EX and EY refer to the difference between the height of a ray on a particular pupil incident on the imaging plane within the current field fan and the height of the chief ray of the current field on the imaging plane. PY represents the pupil coordinates on the meridian fan; PX represents the pupil coordinate on the sagittal fan. And the fan patterns appear in pairs at each field of view. It can be seen from the above graph that the curves are more concentrated and the spherical aberration and dispersion are better controlled.

As shown in fig. 10, 11, 12, 13, and 14, in the dot diagram for each field of view, it can be seen from the above-mentioned figures that the spot radius is small and relatively concentrated, and the corresponding aberration and coma are also good.

The high-pixel-height optical lens adopts the specific surface shape collocation and reasonable focal length distribution, and the structure is more compact while the high pixel is met. The mechanical total length of the optical lens is not more than 31 mm; the number of lenses is small, the processability is good, and the cost control is low; the lenses can compensate each other at different temperatures, so that the temperature characteristic is better, and the imaging performance has no obvious change at 5-40 ℃.

Example two

The optical lens provided by the second embodiment has the same structure as the optical lens in the first embodiment, except that parameters of the respective lenses are different.

Specifically, in the present embodiment, the relevant parameters of each lens of the optical lens are shown in table 2, wherein R represents the curvature radius, Tc represents the center thickness, and N represents the center thickness_dD-line refractive index, V, of the material_dRepresents the abbe number of the material.

Table 2 (relevant parameters for each lens);

based on the relevant parameters of the lenses, the optical technical indexes of the optical lens of the embodiment are as follows:

the total optical length TTL of the optical lens is less than or equal to 30.5 mm; focal length f of optical lens: 25 mm; angle of field of optical lens: 18 degrees; optical distortion of optical lens: 1.0 percent; aperture FNO of optical lens: FNO is less than or equal to 4.0; size of a lens image plane: not less than 8 mm.

In the present embodiment, as shown in fig. 15, 16 and 17, a graph of an optical transfer function (MTF), a field curvature diagram and a distortion diagram of the optical lens in a normal temperature state of the visible light band are provided. As can be seen from the figure, the present embodiment can also have effects similar to those of the first embodiment. For example, as shown in fig. 15, the optical transfer function (MTF) graph is smooth and concentrated, and the average MTF value in the full field (half-image height Y' 4.0mm) is 0.6 or more, and the MTF value in the full field is 0.6 or more at 100 lp/mm. As shown in fig. 16, the field curvature in this embodiment is controlled within ± 0.2 mm. As shown in fig. 17, the distortion control in the present embodiment is preferable, and is within 1.0%. Therefore, the structure is more compact while high pixel is satisfied by adopting the specific surface shape collocation and reasonable focal length distribution of the application. The mechanical total length of the optical lens is not more than 31 mm; the number of lenses is small, the processability is good, and the cost control is low; the MTF value of the whole field of view reaches more than 0.6 under the condition of 100 lp/mm. The lenses can compensate each other at different temperatures, so that the temperature characteristic is better, and the imaging performance has no obvious change at 5-40 ℃.

In the present embodiment, there is provided an endoscope comprising a connection tube and an optical lens in any one of the above embodiments; the connecting pipe is connected with the optical lens and used for transmitting the optical image of the optical lens. The connecting pipe can be a fiber inserting pipe or an adjustable conveying pipe. The optical lens has the characteristics of small structure, capability of ensuring imaging quality, good processability, low cost, large target surface and the like, so that the endoscope also has the characteristics.

In the present embodiment, there is provided an imaging apparatus including an imaging element and the optical lens in any one of the above embodiments; the imaging element is used for converting an optical image formed by the optical lens into an electric signal.

Specifically, the imaging element may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or may be a CCD (Charge Coupled Device) image sensor. The imaging device may be a computer or any other electronic device with an optical lens. The optical lens has the characteristics of small structure, high imaging quality guarantee, high processability, low cost, large target surface and the like, so that the imaging equipment has the characteristics.

It should be understood by those skilled in the art that various features of the above-described embodiments can be combined in any combination, and for the sake of brevity, all possible combinations of features in the above-described embodiments are not described in detail, but rather, all combinations of features which are not inconsistent with each other should be construed as being within the scope of the present disclosure.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.