CN218383453U

CN218383453U - Imaging lens group, endoscope objective lens and endoscope

Info

Publication number: CN218383453U
Application number: CN202222659479.2U
Authority: CN
Inventors: 马健; 周新; 赵源
Original assignee: Microport Urocare Shanghai Co Ltd
Current assignee: Microport Urocare Shanghai Co Ltd
Priority date: 2022-10-10
Filing date: 2022-10-10
Publication date: 2023-01-24
Anticipated expiration: 2032-10-10

Abstract

The utility model relates to an imaging lens group, endoscope objective and endoscope. The imaging lens group comprises: a first lens element having a negative optical power, the image-side surface being concave at the paraxial region; a second lens element having a positive optical power, the image-side surface being convex at a paraxial region; a third lens element having a positive optical power, the object-side surface and the image-side surface both being convex at a paraxial region; a fourth lens element with negative power having a concave object-side surface at paraxial region and a convex image-side surface at paraxial region; the imaging lens group satisfies: 150deg/mm is less than or equal to FOV/SD11 is less than or equal to 189deg/mm. The imaging lens group can give consideration to both miniaturization design and good imaging quality.

Description

Imaging lens group, endoscope objective lens and endoscope

Technical Field

The utility model relates to an endoscope technical field especially relates to an imaging lens group, endoscope objective and endoscope.

Background

Endoscopes can be inserted into patients for more precise diagnosis or treatment, and thus, the application of endoscopes in the medical field is also becoming more and more widespread. Because the internal tissues of the body of a patient are fragile, the endoscope is easy to damage the patient during diagnosis or treatment, and especially the endoscope for observing digestive organs, bronchi, nasal cavities, throats, urinary organs, uteruses and the like has stricter requirements on the volume. However, the current endoscope is over-sized and easily causes injury to patients.

SUMMERY OF THE UTILITY MODEL

In view of the above, it is necessary to provide an imaging lens group, an endoscope objective lens, and an endoscope, which are directed to the problem of the current endoscope being too large in size.

An imaging lens group, wherein the number of lenses having optical power in the imaging lens group is four, and the imaging lens group sequentially comprises from an object side to an image side along an optical axis:

a first lens having a negative optical power, an image-side surface of the first lens being concave at a paraxial region;

a second lens having positive optical power, an image-side surface of the second lens being convex at a paraxial region;

a third lens having positive optical power, the third lens having both an object-side surface and an image-side surface that are convex at a paraxial region; and the number of the first and second groups,

a fourth lens element having a negative optical power, said fourth lens element having a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

the imaging lens group meets the following conditional expression:

150deg/mm≤FOV/SD11≤189deg/mm；

wherein, the FOV is the maximum field angle of the imaging lens group, and SD11 is the maximum effective half aperture of the object-side surface of the first lens.

In one embodiment, the imaging lens group satisfies the following conditional expression:

0.7≤SD11/f≤1.1；

wherein f is an effective focal length of the imaging lens group.

1.6≤f*tan(HFOV)/ImgH≤2.2；

wherein f is an effective focal length of the imaging lens group, HFOV is half of a maximum field angle of the imaging lens group, and ImgH is half of an image height corresponding to the maximum field angle of the imaging lens group.

2.9≤TTL/ImgH≤3.8；

wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the imaging lens group, and ImgH is half of an image height corresponding to a maximum field angle of the imaging lens group.

1.4mm ^-1 ≤FNO/TTL≤2mm ^-1 ；

the FNO is the f-number of the imaging lens group, and the TTL is the distance from the object side surface of the first lens element to the imaging surface of the imaging lens group on the optical axis.

In one embodiment, the maximum effective half aperture of the object-side surface of the first lens is larger than the maximum effective half aperture of the image-side surface of the fourth lens, and the maximum effective half apertures of the object-side surface of the second lens and the object-side surface of the third lens are both smaller than the maximum effective half aperture of the image-side surface of the fourth lens.

SD11/SD42 is more than or equal to 1.4 and less than or equal to 1.8; and/or the presence of a gas in the gas,

2.3≤SD11/SD21≤3.4；

wherein SD42 is the maximum effective half aperture of the image-side surface of the fourth lens element; SD21 is the maximum effective half aperture of the object-side surface of the second lens.

3.4≤TTL/f≤4；

wherein, TTL is an axial distance from an object-side surface of the first lens element to an image plane of the imaging lens group, and f is an effective focal length of the imaging lens group.

0.9≤Bf/f≤1.4；

wherein Bf is a distance on an optical axis from an image side surface of the fourth lens element to an image plane of the imaging lens assembly, and f is an effective focal length of the imaging lens assembly.

In one embodiment, the first lens is made of glass, and the second lens, the third lens and the fourth lens are made of plastic.

In one embodiment, the first lens, the second lens, the third lens and the fourth lens are all made of plastic.

An endoscope objective lens comprises a photosensitive element and the imaging lens group as in any one of the above embodiments, wherein the photosensitive element is disposed at an image side of the imaging lens group.

An endoscope comprising an endoscope objective as described above.

Above-mentioned imaging lens group, the focal power and the face type of each lens can obtain rational configuration, and the cooperation can effectively converge the light to FOV SD 11's rational design to shorten imaging lens group's overall length, and then when imaging lens group is applied to the endoscope, be favorable to reducing the size of endoscope, avoid the too big and damage to the disease of size of endoscope.

Drawings

FIG. 1 is a schematic structural diagram of an imaging lens group according to a first embodiment;

FIG. 2 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly in the first embodiment;

FIG. 3 is a schematic structural diagram of an imaging lens group according to a second embodiment;

FIG. 4 is a graph of astigmatism, distortion and chromatic aberration of magnification of an imaging lens assembly according to a second embodiment;

FIG. 5 is a schematic structural diagram of an imaging lens group according to a third embodiment;

FIG. 6 is a graph of astigmatism, distortion and chromatic aberration of magnification of an imaging lens group in a third embodiment;

FIG. 7 is a schematic structural diagram of an imaging lens group in a fourth embodiment;

FIG. 8 is a graph of astigmatism, distortion and chromatic aberration of magnification of an imaging lens assembly according to a fourth embodiment;

FIG. 9 is a schematic view of an imaging lens group according to a fifth embodiment;

FIG. 10 is a graph of astigmatism, distortion and chromatic aberration of magnification of an imaging lens group in a fifth embodiment;

FIG. 11 is a schematic view of an imaging lens group according to a sixth embodiment;

FIG. 12 is a graph of astigmatism, distortion and chromatic aberration of magnification of an imaging lens assembly according to a sixth embodiment;

FIG. 13 is a schematic structural diagram of an imaging lens group according to a seventh embodiment;

FIG. 14 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly of the seventh embodiment.

Detailed Description

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, as those skilled in the art will be able to make similar modifications without departing from the spirit and scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "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 "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1, in some embodiments of the present application, the imaging lens group 100 includes, in order from an object side to an image side, a first lens element L1, a second lens element L2, a third lens element L3 and a fourth lens element L4. Specifically, the first lens element L1 includes an object-side surface S1 and an image-side surface S2, the second lens element L2 includes an object-side surface S3 and an image-side surface S4, the third lens element L3 includes an object-side surface S5 and an image-side surface S6, and the fourth lens element L4 includes an object-side surface S7 and an image-side surface S8. The first lens element L1, the second lens element L2, the third lens element L3 and the fourth lens element L4 are coaxially disposed, and a common axis of the lenses of the imaging lens assembly 100 is an optical axis of the imaging lens assembly 100. In some embodiments, the imaging lens group 100 can further include an image plane S9 located on the image side of the fourth lens element L4, and light can be incident on the image plane S9 after being adjusted by the first lens element L1, the second lens element L2, the third lens element L3 and the fourth lens element L4.

Specifically, in some examples, the first lens L1 has a negative optical power, and the image-side surface S2 of the first lens L1 is concave at the paraxial region. The second lens element L2 has positive optical power, and the image-side surface S4 of the second lens element L2 is convex at the paraxial region. The third lens element L3 has positive optical power, and both the object-side surface S5 and the image-side surface S6 of the third lens element L3 are convex at the paraxial region. The fourth lens element L4 has negative power, and the object-side surface S7 of the fourth lens element L4 is concave at the paraxial region and the image-side surface S8 is convex at the paraxial region.

Wherein, the negative focal power of first lens L1, the concave type of the image side S2 in passing optical axis department of cooperation first lens L1 is favorable to first lens L1 to collect wide-angle light to be favorable to imaging lens group 100 to realize the wide-angle characteristic, thereby can satisfy the demand of getting for instance on a large scale. The positive focal power of the second lens element L2, in cooperation with the convex surface of the image-side surface S4 of the second lens element L2 at the paraxial region, is beneficial to the second lens element L2 to correct the aberration generated when the first lens element L1 introduces large-angle light, thereby being beneficial to improving the imaging quality of the imaging lens assembly 100. The positive focal power of the third lens element L3, in cooperation with the double convex surface type of the third lens element L3 at the paraxial region, enables the third lens element L3 to cooperate with the second lens element L2 to converge light effectively, thereby facilitating shortening of the total length of the imaging lens assembly 100 and achieving miniaturization. The focal power and the reasonable configuration of the surface type of the first lens L1, the second lens L2 and the third lens L3 are also beneficial to the smooth transition of light among the first lens L1, the second lens L2 and the third lens L3, thereby being beneficial to reducing the aberration sensitivity of the imaging lens group 100 and further improving the imaging quality of the imaging lens group 100 while realizing the wide-angle characteristic and the miniaturization design. Fourth lens L4 'S negative focal power, cooperation fourth lens L4 is in the concave-convex surface type of passing optical axis department, be favorable to fourth lens L4 rationally with light deflection and diverge to imaging surface S9, thereby be favorable to making the incident angle of light on imaging surface S9 match with photosensitive element more easily, and be favorable to increasing imaging lens group 100' S imaging surface S9 size, and then be favorable to promoting imaging lens group 100 'S imaging quality, still be favorable to shortening imaging lens group 100' S back focal length simultaneously, thereby be favorable to imaging lens group 100 to realize miniaturized design. In the present application, the surface shape of a lens at a paraxial region is described, and the surface shape of a portion of the lens corresponding to a region through which paraxial light passes can be understood.

Further, in some embodiments, the imaging optical group 100 satisfies the conditional expression: 150deg/mm is less than or equal to FOV/SD11 is less than or equal to 189deg/mm; wherein, FOV is the maximum field angle of the imaging lens group 100, and SD11 is the maximum effective half aperture of the object-side surface S1 of the first lens element L1. Satisfying above-mentioned conditional expression, being favorable to dwindling the effective bore of imaging lens group 100 to realize miniaturized design, being favorable to imaging lens group 100 to realize wide angle characteristic simultaneously, in order to satisfy the demand of getting for instance on a large scale, still be favorable to imaging lens group 100 to have good image quality in addition. Exceeding the upper limit of the above conditional expression, the field angle of the imaging lens group 100 is too large, and aberrations such as distortion which are difficult to correct are likely to occur in the peripheral field, which is not favorable for improving the imaging quality. Being lower than the lower limit of the above conditional expression is not favorable for realizing the wide-angle characteristic and reducing the effective aperture of the imaging lens group 100.

When the imaging lens group 100 has the above focal power and surface type characteristics and satisfies the above conditional expressions, the imaging lens group can achieve both miniaturization design, wide-angle characteristics, and high imaging quality.

In some embodiments, the imaging lens group 100 satisfies the conditional expression: SD11/f is more than or equal to 0.7 and less than or equal to 1.1; where f is the effective focal length of the imaging lens group 100. Satisfying the above conditional expressions is beneficial to reducing the effective aperture and the total length of the imaging lens group 100 to realize the miniaturization design, and is also beneficial to improving the imaging quality of the imaging lens group 100. Surpass the upper limit of above-mentioned conditional expression, first lens L1's effective bore is too big, is unfavorable for the realization of miniaturized design, and the effective focal length of the group of formation of image mirror 100 is too short simultaneously, leads to the formation of image mirror 100 to be axial upward light deflection space limited, is unfavorable for well adjusting light to be unfavorable for the promotion of image quality. Below the lower limit of the above conditional expression, the effective focal length of the imaging lens group 100 is too long, which results in too long total length of the imaging lens group 100, and is also not conducive to the realization of miniaturized design.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: 1.6-2.2 of f star tan (HFOV)/ImgH; wherein f is the effective focal length of the imaging lens assembly 100, HFOV is half of the maximum field angle of the imaging lens assembly 100, and ImgH is half of the image height corresponding to the maximum field angle of the imaging lens assembly 100. Satisfying the above conditional expressions, the imaging lens group 100 can achieve a wide-angle characteristic and also have good imaging quality. Exceeding the upper limit of the above conditional expression, the field angle of the imaging lens group 100 is too large, which is likely to cause aberration such as distortion that is difficult to correct in the peripheral field of view, and is not favorable for improving the imaging quality. Lower than the lower limit of the above conditional expression is not favorable for the imaging lens assembly 100 to realize a wide-angle characteristic.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: TTL/ImgH is more than or equal to 2.9 and less than or equal to 3.8; wherein, TTL is an axial distance from the object-side surface S1 of the first lens element L1 to the image plane S9 of the imaging lens assembly 100, i.e., an optical total length of the imaging lens assembly 100, and ImgH is a half of an image height corresponding to a maximum field angle of the imaging lens assembly 100. Satisfying the above conditional expressions is advantageous for reducing the effective aperture and the optical total length of the imaging lens group 100, thereby facilitating the realization of the miniaturization design. Exceeding the upper limit of the above conditional expressions, the total length of the imaging lens group 100 is too long, which is not favorable for the imaging lens group 100 to realize a miniaturized design. Being lower than the lower limit of the above conditional expression, the size of the imaging surface S9 of the imaging lens group 100 is too large, which is not favorable for reducing the effective aperture of the imaging lens group 100, and is also not favorable for realizing the miniaturization design of the imaging lens group 100.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: 1.4mm ^-1 ≤FNO/TTL≤2mm ^-1 (ii) a Wherein FNO is an f-number of the imaging lens assembly 100, and TTL is an axial distance from the object-side surface S1 of the first lens element L1 to the image plane S9 of the imaging lens assembly 100. Satisfying the above conditional expressions is advantageous for reducing the effective aperture and the total length of the imaging lens group 100, thereby being advantageous for realizing the miniaturization design of the imaging lens group 100, and simultaneously being advantageous for preventing the aperture of the imaging lens group 100 from being too small, thereby being advantageous for the imaging lens group 100 to obtain a sufficient light incident amount and having good imaging quality. Exceeding the upper limit of above-mentioned conditional expression, the f-number of imaging mirror group 100 is too big, leads to the diaphragm undersize, is unfavorable for promoting the light incident quantity of imaging mirror group 100, leads to the relative illuminance of formation of image too low easily to be unfavorable for the promotion of formation of image quality. Below the lower limit of the above conditional expression, the effective aperture of the imaging lens group 100 is too large, and the total length is also too large, which is not favorable for implementing a miniaturized design.

In some embodiments, the maximum effective half aperture of the object-side surface S1 of the first lens L1 is larger than the maximum effective half aperture of the image-side surface S8 of the fourth lens L4, and the maximum effective half apertures of the object-side surface S3 of the second lens L2 and the object-side surface S5 of the third lens L3 are smaller than the maximum effective half aperture of the image-side surface S8 of the fourth lens L4. So set up, when reducing the effective bore of formation of image mirror group 100 in order to realize miniaturized design, the biggest effective bore of first lens L1' S object side face S1 is enough big, be favorable to first lens L1 to effectively collect the light of wide angle, thereby be favorable to the realization of wide angle characteristic, and the light that is favorable to first lens L1 to collect is full of the diaphragm of formation of image mirror group 100 at second lens L2 and third lens L3, thereby be favorable to promoting the relative illumination of formation of image in order to promote the imaging quality of formation of image mirror group 100, in addition still be favorable to fourth lens L4 to effectively transmit light to imaging surface S9, be favorable to enlarging imaging surface S9 size, and make the incident angle of light on imaging surface S9 match photosensitive element better, thereby promote the imaging quality of formation of image mirror group 100.

In some embodiments, the imaging lens group 100 satisfies the conditional expression: SD11/SD42 is more than or equal to 1.4 and less than or equal to 1.8; here, SD42 is the maximum effective half aperture of the image side surface S8 of the fourth lens L4. Satisfy above-mentioned conditional expression, be favorable to first lens L1 effectively to collect large-angle light, also be favorable to fourth lens L4 effectively to transmit light to imaging surface S9 to be favorable to the realization of wide angle characteristic and big image plane characteristic.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: SD11/SD21 is more than or equal to 2.3 and less than or equal to 3.4; where SD21 is the maximum effective half aperture of the object-side surface S3 of the second lens L2. Satisfy above-mentioned conditional expression, first lens L1 and second lens L2 can rationally cooperate, are favorable to the mutual correction of aberration, are favorable to the realization of wide angle characteristic simultaneously.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: TTL/f is more than or equal to 3.4 and less than or equal to 4; wherein, TTL is an axial distance from the object-side surface S1 of the first lens element L1 to the image plane S9 of the imaging lens assembly 100, i.e., an optical total length of the imaging lens assembly 100, and f is an effective focal length of the imaging lens assembly 100. Satisfying above-mentioned conditional expression, being favorable to shortening the overall length of imaging mirror group 100, realizing miniaturized design, also can making imaging mirror group 100 have the reasonable deflection light in sufficient space simultaneously, be favorable to the promotion of image quality.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: bf/f is more than or equal to 0.9 and less than or equal to 1.4; wherein Bf is an axial distance from the image-side surface S8 of the fourth lens element L4 to the image plane S9 of the imaging lens assembly 100, i.e., a back focal length of the imaging lens assembly 100, and f is an effective focal length of the imaging lens assembly 100. Satisfying the above conditional expressions, while shortening the total length of the imaging lens group 100 to achieve a compact design, the imaging lens group 100 can have a large enough back focal space, which is beneficial to focusing of the imaging lens group 100 and better assembling of the imaging lens group 100 with a photosensitive element.

In some embodiments, the imaging lens group 100 satisfies the following conditional expression: the FOV is more than or equal to 120 degrees and less than or equal to 140 degrees. Satisfy above-mentioned conditional expression, imaging lens group 100 possesses wide angle characteristic, and when being applied to the endoscope, is favorable to satisfying the demand of getting for instance on a large scale to reduce the risk of missing examining, simultaneously, imaging lens group 100's angle of view also can not be too big, can avoid marginal field of view to produce aberration such as too serious distortion, thereby is favorable to the promotion of imaging quality.

In some embodiments, the imaging lens group 100 satisfies the conditional expression: imgH is more than or equal to 0.8mm and less than or equal to 1mm; wherein ImgH is half of the image height corresponding to the maximum field angle of the imaging lens group 100. Satisfying above-mentioned conditional expression, imaging lens group 100 can possess big image plane characteristic to can match the photosensitive element of higher pixel in order to obtain good imaging quality, also be favorable to reducing the aberration of marginal visual field simultaneously, promote the relative illuminance of marginal visual field, also be favorable to promoting imaging lens group 100's imaging quality.

It should be noted that, in some embodiments, the imaging lens group 100 may match a photosensitive element having a rectangular photosensitive surface, and the imaging surface S9 of the imaging lens group 100 coincides with the photosensitive surface of the photosensitive element. At this time, the effective pixel area on the imaging plane S9 has a horizontal direction and a diagonal direction, so that the FOV can be understood as the maximum field angle of the imaging lens group 100 in the diagonal direction, and ImgH can be understood as half of the size of the effective pixel area of the imaging lens group 100 in the diagonal direction.

It is understood that, in the present application, the image plane S9 can be understood as a virtual plane formed by the convergence point of the system light rays on the image side of the fourth lens element L4, and when the imaging lens assembly 100 is matched with the photosensitive elements, the image plane S9 is overlapped with the photosensitive surfaces of the photosensitive elements, so that the system-adjusted light rays can form a clear image on the photosensitive surfaces.

In some embodiments, the imaging lens group 100 is provided with a stop ST, which may be disposed between the second lens L2 and the third lens L3. Due to the arrangement of the middle diaphragm ST, the imaging lens group 100 can have sufficient light entering amount while realizing the miniaturization characteristic, and the imaging quality of the imaging lens group 100 can be improved.

In some embodiments, the imaging lens assembly 100 further includes an ir-cut filter 110, the ir-cut filter 110 is disposed between the first lens element L1 and the second lens element L2, and the ir-cut filter 110 is used for filtering infrared light and preventing the infrared light from reaching the image plane S9 and affecting the imaging quality of the imaging lens assembly 100. Of course, the ir-cut filter 110 may be disposed between any two other lenses, or between the fourth lens L4 and the image plane S9, as long as there is enough space for the ir-cut filter 110 to fit.

In some embodiments, the imaging lens group 100 further includes a protective glass 120, the protective glass 120 may be disposed between the fourth lens element L4 and the imaging surface S9, and the protective glass 120 is used for protecting the photosensitive element disposed at the imaging surface S9.

In some embodiments, the object-side surface and the image-side surface of each lens element of the imaging lens assembly 100 are aspheric, and the shapes of the object-side surface and the image-side surface of each lens element at a paraxial region and at a periphery may be different. The adoption of the aspheric surface structure can improve the flexibility of lens design, effectively correct spherical aberration and improve imaging quality.

In some embodiments, each lens in the imaging lens group 100 may be made of plastic. The lenses made of plastic material can reduce the weight and production cost of the imaging lens assembly 100, and the small size of the imaging lens assembly 100 is matched to achieve the light and thin design of the imaging lens assembly 100.

In other embodiments, the material of the first lens L1 may be glass, and the material of the second lens L2, the third lens L3, and the fourth lens L4 may be plastic. Adopt the glass material, can make first lens L1 possess good wear resistance and biocompatibility for when imaging lens group 100 is applied to the endoscope, the lens of foremost is difficult to damage because of the collision, can save front end protection glass's setting, also is difficult to cause negative effects to user's health. The three rear lenses are made of plastic materials, so that the miniaturization design of the imaging lens group 100 is facilitated, and meanwhile, the weight and the cost of the imaging lens group 100 are reduced. Of course, the above material matching is only an example of the imaging lens group 100 in some embodiments, and the materials of the lenses of the imaging lens group 100 may be glass, or may be any combination of glass and plastic.

The reference wavelength of the effective focal length is 587.6nm.

Based on the above description of the embodiments, more specific embodiments and drawings are set forth below for detailed description.

First embodiment

Referring to fig. 1 again, fig. 1 is a schematic structural diagram of an imaging lens assembly 100 in the first embodiment. The imaging lens group 100 includes, in order from an object side to an image side, a first lens L1 having negative power, an infrared cut filter 110, a second lens L2 having positive power, a diaphragm ST, a third lens L3 having positive power, a fourth lens L4 having negative power, and a protective glass 120.

The object-side surface and the image-side surface of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are aspheric, and the same applies to other embodiments.

The object-side surface of the first lens element L1 is a plane at the paraxial region, and the image-side surface thereof is a concave surface at the paraxial region;

the object-side surface of the second lens element L2 is convex at the paraxial region, and the image-side surface thereof is convex at the paraxial region;

the object-side surface of the third lens element L3 is convex at the paraxial region, and the image-side surface thereof is convex at the paraxial region;

the object-side surface of the fourth lens element L4 is concave at the paraxial region, and the image-side surface thereof is convex at the paraxial region.

Table 1 below shows the curvature radius, thickness, refractive index, abbe number, effective focal length of each lens element of the imaging lens assembly 100 in the first embodiment, and the detailed parameters of the effective focal length f, maximum field angle FOV and f-number FNO of the imaging lens assembly 100. The elements in table 1 from the first lens L1 to the image forming surface S9 are arranged in the order of the elements from the top to the bottom in table 1. The first row of the first lens L1 represents the object side surface S1 of the first lens L1, the second row represents the image side surface S2 of the first lens L1, and so on. The first value in the "thickness" parameter list of the first lens element L1 is the thickness of the first lens element L1 along the optical axis 110, and the second value is the distance from the image-side surface S2 of the first lens element L1 to the rear surface (the object-side surface of the second lens element L2) along the image-side direction along the optical axis 110, from which the meanings of the other values in the thickness parameter list can be inferred. Wherein, the refractive index, abbe number and effective focal length of each lens are 587.6nm.

It should be noted that in this embodiment and the following embodiments, the imaging lens group 100 may not be provided with the ir-cut filter 110 and the protective glass 120, but the distance between the first lens L1 and the second lens L2, and the distance between the fourth lens L4 and the imaging surface S9 are kept unchanged.

TABLE 1

The aspheric coefficients of the object-side surface and the image-side surface of each lens element of the imaging lens assembly 100 are given in table 2. Wherein the surface numbers from S1-S8 represent object side surfaces or image side surfaces S1-S8, respectively. And K-A8 from top to bottom respectively indicate the types of aspheric coefficients, where K indicates a conic coefficient, A4 indicates a fourth-order aspheric coefficient, A6 indicates a sixth-order aspheric coefficient, and A8 indicates an eighth-order aspheric coefficient. In addition, the aspherical surface coefficient formula is as follows:

wherein Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the surface vertex, r is the distance from the corresponding point on the aspheric surface to the optical axis 110, c is the curvature of the aspheric surface vertex, K is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspheric surface type formula.

TABLE 2

Referring to fig. 2, fig. 2 is a graph of astigmatism, a graph of distortion, and a graph of chromatic aberration of magnification of the imaging lens assembly 100 in the first embodiment, in order from left to right. As can be seen from the astigmatism graph of fig. 2, the sagittal field curvature and the meridional field curvature of the imaging lens group 100 are both small, the field curvature and the astigmatism of each field of view are well corrected, the center and the edge of the field of view have clear images, and the imaging lens group 100 has a large depth of field effect. As can be seen from the distortion graph of fig. 2, the distortion of the whole field of view of the imaging lens group 100 is small, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent. As can be seen from the magnification chromatic aberration curve of fig. 2, the maximum difference value of different wavelengths is less than 2um, and the magnification chromatic aberration of the imaging lens group 100 is well corrected, so that the imaging quality is good.

Second embodiment

Referring to fig. 3, fig. 3 is a schematic structural diagram of the imaging lens assembly 100 in the second embodiment, in which the imaging lens assembly 100 includes, in order from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a diaphragm ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

The object-side surface of the first lens element L1 is concave at the paraxial region, and the image-side surface thereof is concave at the paraxial region;

In addition, the parameters of the imaging lens assembly 100 are given in table 3, and the definitions of the parameters can be obtained from the first embodiment, which is not described herein again.

TABLE 3

The aspheric coefficients of the image-side surface or the object-side surface of each lens element of the imaging lens assembly 100 are given in table 4, and the definition of each parameter can be derived from the first embodiment.

TABLE 4

Referring to fig. 4, fig. 4 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 in the second embodiment sequentially from left to right, and it can be seen from fig. 4 that the field curvature astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 are well corrected, and the imaging lens assembly 100 has good imaging quality.

Third embodiment

Referring to fig. 5, fig. 5 is a schematic structural diagram of the imaging lens assembly 100 in the third embodiment, the imaging lens assembly 100 includes, in order from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a diaphragm ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

In addition, the parameters of the imaging lens assembly 100 are given in table 5, and the definitions of the parameters can be obtained from the first embodiment, which is not described herein again.

TABLE 5

The aspheric coefficients of the image-side surface and the object-side surface of each lens element of the imaging lens assembly 100 are given in table 6, and the definition of each parameter can be derived from the first embodiment.

TABLE 6

Referring to fig. 6, fig. 6 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 in the third embodiment sequentially from left to right, and it can be seen from fig. 6 that the field curvature astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 are well corrected, and the imaging lens assembly 100 has good imaging quality.

Fourth embodiment

Referring to fig. 7, fig. 7 is a schematic structural diagram of the imaging lens assembly 100 in the fourth embodiment, the imaging lens assembly 100 includes, in order from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a stop ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

In addition, the parameters of the imaging lens assembly 100 are given in table 7, and the definitions of the parameters can be derived from the first embodiment, which is not repeated herein.

TABLE 7

The aspheric coefficients of the image-side surface or the object-side surface of each lens element of the imaging lens assembly 100 are given in table 8, and the definition of each parameter can be derived from the first embodiment.

TABLE 8

Referring to fig. 8, fig. 8 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 in the fourth embodiment sequentially from left to right, and it can be seen from fig. 8 that the field curvature astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 are well corrected, and the imaging lens assembly 100 has good imaging quality.

Fifth embodiment

Referring to fig. 9, fig. 9 is a schematic structural diagram of the imaging lens assembly 100 in the fifth embodiment, and the imaging lens assembly 100 sequentially includes, from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a stop ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

The object-side surface of the first lens element L1 is planar at the paraxial region, and the image-side surface thereof is concave at the paraxial region;

In addition, the parameters of the imaging lens assembly 100 are given in table 9, and the definitions of the parameters can be obtained from the first embodiment, which is not described herein again.

TABLE 9

The aspheric coefficients of the image-side surface or the object-side surface of each lens element of the imaging lens assembly 100 are given in table 10, and the definition of each parameter can be derived from the first embodiment.

Watch 10

Referring to fig. 10, fig. 10 is a graph of astigmatism, a graph of distortion, and a graph of chromatic aberration of magnification of the imaging lens assembly 100 in the fifth embodiment sequentially from left to right, and it can be seen from fig. 10 that the astigmatism, distortion, and chromatic aberration of magnification of the imaging lens assembly 100 are well corrected, and the imaging lens assembly 100 has good imaging quality.

Sixth embodiment

Referring to fig. 11, fig. 11 is a schematic structural diagram of the imaging lens assembly 100 in the sixth embodiment, and the imaging lens assembly 100 sequentially includes, from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a stop ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

In addition, the parameters of the imaging lens assembly 100 are given in table 11, and the definitions of the parameters can be obtained from the first embodiment, which is not described herein again.

TABLE 11

The aspheric coefficients of the image-side surface or the object-side surface of each lens element of the imaging lens assembly 100 are given in table 12, and the definition of each parameter can be derived from the first embodiment.

TABLE 12

Referring to fig. 12, fig. 12 is a graph of astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 in the sixth embodiment sequentially from left to right, and it can be seen from fig. 12 that the field curvature astigmatism, distortion and chromatic aberration of magnification of the imaging lens assembly 100 are well corrected, and the imaging lens assembly 100 has good imaging quality.

Seventh embodiment

Referring to fig. 13, fig. 13 is a schematic structural diagram of the imaging lens assembly 100 in the seventh embodiment, wherein the imaging lens assembly 100 sequentially includes, from an object side to an image side, a first lens L1 with negative power, an ir-cut filter 110, a second lens L2 with positive power, a stop ST, a third lens L3 with positive power, a fourth lens L4 with negative power, and a protective glass 120.

the object-side surface of the second lens element L2 is concave at the paraxial region, and the image-side surface thereof is convex at the paraxial region;

the object-side surface of the third lens element L3 is convex at the paraxial region thereof, and the image-side surface thereof is convex at the paraxial region thereof;

In addition, the parameters of the imaging lens assembly 100 are given in table 13, and the definitions of the parameters can be obtained from the first embodiment, which is not described herein again.

Watch 13

The aspheric coefficients of the image-side surface or the object-side surface of each lens element of the imaging lens assembly 100 are given in table 14, and the definition of each parameter can be derived from the first embodiment.

TABLE 14

Referring to fig. 14, fig. 14 is a graph of astigmatism, a graph of distortion, and a graph of chromatic aberration of magnification of the imaging lens assembly 100 in the seventh embodiment sequentially from left to right, and it can be seen from fig. 14 that the field curvature astigmatism, distortion, and chromatic aberration of magnification of the imaging lens assembly 100 are all well corrected, and the imaging lens assembly 100 has good imaging quality.

In addition, the imaging lens group 100 in the first to seventh embodiments satisfies the data in table 15 below, and the following data can be referred to for the obtained effects.

Watch 15

The present application further provides an endoscope objective (not shown) comprising a photosensitive element and the imaging lens group 100 according to any of the above embodiments. The light sensing surfaces of the light sensing elements coincide with an imaging surface S9 of the imaging mirror group 100. Specifically, the photosensitive element may be a Charge Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS) Device. By adopting the imaging lens group 100 in the endoscope objective lens, the miniaturization design, the wide-angle characteristic and the realization of high imaging quality can be considered, thereby being beneficial to the application of the endoscope objective lens in the endoscope.

The present application further provides an endoscope (not shown) comprising a housing and the endoscope objective lens of any of the above embodiments, wherein the endoscope objective lens is disposed in the housing, and the housing may be a fixing structure of the endoscope objective lens. Endoscopes may be used in the medical field, for example for medical diagnosis of patients, and in particular include, but are not limited to, endoscopes for viewing the digestive organs, bronchi, nasal cavities, throat, urinary organs and uterus. Adopt above-mentioned endoscope objective in the endoscope, endoscope objective can compromise miniaturized design, wide angle characteristic and high imaging quality's realization to when making the endoscope be applied to medical field, can reduce the damage to the disease by the at utmost, also can acquire the image in focus area on a large scale, avoid missing the risk of looking into, still can form the pathological change image that has the high definition simultaneously, promote diagnostic accuracy.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

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

Claims

1. An imaging lens assembly comprising four lenses, wherein the number of the lenses having optical power in the imaging lens assembly is four, and the imaging lens assembly sequentially comprises, from an object side to an image side along an optical axis:

a second lens having positive optical power, an image side surface of the second lens being convex at a paraxial region;

a third lens having a positive optical power, the third lens having both an object-side surface and an image-side surface that are convex at a paraxial region; and the number of the first and second groups,

the imaging lens group meets the following conditional expression:

150deg/mm≤FOV/SD11≤189deg/mm；

2. The imaging lens group of claim 1, wherein the imaging lens group satisfies the following conditional expression:

0.7≤SD11/f≤1.1；

wherein f is an effective focal length of the imaging lens group.

3. Imaging lens group according to claim 1, characterized in that it satisfies the following conditional expression:

1.6≤f*tan(HFOV)/ImgH≤2.2；

4. The imaging lens group of claim 1, wherein the imaging lens group satisfies the following conditional expression:

2.9≤TTL/ImgH≤3.8；

5. The imaging lens group of claim 1, wherein the imaging lens group satisfies the following conditional expression:

1.4mm ^-1 ≤FNO/TTL≤2mm ^-1 ；

6. The imaging lens group of claim 1, wherein the maximum effective half aperture of the object-side surface of the first lens element is larger than the maximum effective half aperture of the image-side surface of the fourth lens element, and the maximum effective half apertures of the object-side surface of the second lens element and the object-side surface of the third lens element are smaller than the maximum effective half aperture of the image-side surface of the fourth lens element.

7. The imaging lens group of claim 6, wherein the imaging lens group satisfies the following conditional expression:

2.3≤SD11/SD21≤3.4；

wherein SD42 is the maximum effective half aperture of the image-side surface of the fourth lens element, and SD21 is the maximum effective half aperture of the object-side surface of the second lens element.

8. The imaging lens group of claim 1, wherein the imaging lens group satisfies the following conditional expression:

3.4≤TTL/f≤4；

9. The imaging lens group of claim 1, wherein the imaging lens group satisfies the following conditional expression:

0.9≤Bf/f≤1.4；

10. The imaging lens group of claim 1, wherein the first lens element is made of glass, and the second, third and fourth lens elements are made of plastic; or,

the first lens, the second lens, the third lens and the fourth lens are all made of plastics.

11. An endoscope objective lens, comprising a light-sensitive element and the imaging lens assembly of any one of claims 1-10, wherein the light-sensitive element is disposed on an image side of the imaging lens assembly.

12. An endoscope, characterized in that it comprises an endoscope objective according to claim 11.