CN219552748U - Imaging system, endoscope objective lens, and endoscope - Google Patents

Abstract

The present utility model relates to an imaging system, an endoscope objective lens, and an endoscope. The image pickup system includes: a first lens element with negative refractive power, wherein an image-side surface of the first lens element is concave at a paraxial region; a second lens with positive focal power, wherein the object side surface of the second lens is a convex surface at a paraxial region; a third lens element with positive refractive power, wherein an image-side surface of the third lens element is convex at a paraxial region; the imaging system satisfies the following conditional expression: 156deg/mm < FOV/SD11 < 217deg/mm; wherein FOV is the maximum field angle of the imaging system, SD11 is the maximum effective half-caliber of the object side of the first lens. The imaging system can be miniaturized and has good imaging quality.

Description

Imaging system, endoscope objective lens, and endoscope

Technical Field

The present utility model relates to the technical field of endoscopes, and in particular, to an imaging system, an endoscope objective lens, and an endoscope.

Background

The endoscope can extend into a specific position of a patient body, and observe the specific position, for example, the endoscope is used for observing organs such as digestive organs, bronchi, nasal cavities, throats, urinary organs, uterus and the like, and can bring great convenience to diagnosis and treatment. Meanwhile, the requirements of the industry on the imaging quality of the endoscope are also higher and higher, and the accuracy of diagnosis and treatment is greatly influenced by the quality of the imaging quality of the endoscope. However, the current endoscopes have poor imaging quality, and it is difficult to satisfy high-precision diagnosis and treatment.

Disclosure of Invention

Accordingly, it is necessary to provide an imaging system, an endoscope objective lens, and an endoscope, which solve the problem of poor imaging quality of the conventional endoscope.

An imaging system for an endoscope, the number of lenses having optical power in the imaging system being three, and the imaging system comprising, in order from an object side to an image side along an optical axis:

a first lens element with negative refractive power, wherein an image-side surface of the first lens element is concave at a paraxial region;

a second lens with positive focal power, wherein the object side surface of the second lens is a convex surface at a paraxial region;

a third lens element with positive refractive power, wherein an image-side surface of the third lens element is convex at a paraxial region;

the imaging system satisfies the following conditional expression:

156deg/mm≤FOV/SD11≤217deg/mm；

wherein FOV is the maximum field angle of the imaging system, SD11 is the maximum effective half-caliber of the object side of the first lens.

In one embodiment, the imaging system satisfies the following conditional expression:

1≤SD11/f≤2.1；

wherein f is the effective focal length of the imaging system.

In one embodiment, the imaging system satisfies the following conditional expression:

1.6≤f*tan(HFOV)/ImgH≤2.7；

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

In one embodiment, the imaging system satisfies the following conditional expression:

3.5≤TTL/ImgH≤4；

wherein TTL is the distance between the object side surface of the first lens and the imaging surface of the imaging system on the optical axis, and ImgH is half of the image height corresponding to the maximum field angle of the imaging system.

In one embodiment, the imaging system satisfies the following conditional expression:

1.4mm ^-1 ≤FNO/TTL≤2.6mm ^-1 ；

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

In one embodiment, the imaging system satisfies the following conditional expression:

1.8≤SD11/SD32≤3；

wherein SD32 is the maximum effective half-caliber of the image side surface of the third lens.

In one embodiment, the imaging system satisfies the following conditional expression:

-0.7≤f1/f2≤-0.4；

wherein f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens.

In one embodiment, the imaging system satisfies the following conditional expression:

-0.9≤f1/f3≤-0.3；

wherein f1 is an effective focal length of the first lens, and f3 is an effective focal length of the third lens.

In one embodiment, the imaging system satisfies the following conditional expression:

4.1≤TTL/f≤6.5；

wherein TTL is a distance between an object side surface of the first lens and an imaging surface of the imaging system on an optical axis, and f is an effective focal length of the imaging system.

In one embodiment, the imaging system satisfies the following conditional expression:

1.8≤Bf/f≤2.1；

wherein Bf is the distance from the image side surface of the third lens to the imaging surface of the imaging system on the optical axis, and f is the effective focal length of the imaging system.

An endoscope objective lens comprising a photosensitive element and the imaging system according to any of the above embodiments, wherein the photosensitive element is disposed on an image side of the imaging system.

An endoscope comprising the above-described endoscope objective lens.

According to the imaging system, the lenses can be reasonably configured, and various aberrations of the imaging system can be effectively corrected by matching with the reasonable design of the relational expression, so that the imaging quality of the imaging system is improved, and the accuracy of diagnosis and treatment is improved when the imaging system is applied to an endoscope.

Drawings

Fig. 1 is a schematic configuration diagram of an image pickup system in a first embodiment;

fig. 2 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the first embodiment;

fig. 3 is a schematic structural diagram of an image capturing system in a second embodiment;

fig. 4 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the second embodiment;

fig. 5 is a schematic structural diagram of an image capturing system in a third embodiment;

fig. 6 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the third embodiment;

fig. 7 is a schematic structural diagram of an image pickup system in a fourth embodiment;

fig. 8 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the fourth embodiment;

fig. 9 is a schematic structural view of an image pickup system in a fifth embodiment;

fig. 10 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the fifth embodiment;

fig. 11 is a schematic structural view of an image pickup system in the sixth embodiment;

fig. 12 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the sixth embodiment;

fig. 13 is a schematic configuration diagram of an image pickup system in the seventh embodiment;

fig. 14 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the seventh embodiment;

fig. 15 is a schematic configuration diagram of an image pickup system in the eighth embodiment;

fig. 16 is a astigmatic curve chart, a distortion curve chart, and a magnification chromatic aberration curve chart of the image capturing system in the eighth embodiment.

Detailed Description

In order that the above objects, features and advantages of the utility model will be readily understood, a more particular description of the utility model will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present utility model. The present utility model may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the utility model, whereby the utility model is not limited to the specific embodiments disclosed below.

In the description of the present utility model, it should 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", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present utility model and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present utility model.

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

In the present utility model, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present utility model, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" 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 are used herein for illustrative purposes only and are not meant to be the only embodiment.

Referring to fig. 1, in some embodiments of the present utility model, the image capturing system 100 includes a first lens L1, a second lens L2, and a third lens L3 in order from an object side to an image side along an optical axis. 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, and the third lens element L3 includes an object-side surface S5 and an image-side surface S6. The first lens L1, the second lens L2 and the third lens L3 are coaxially disposed, and a common axis of each lens in the image capturing system 100 is an optical axis of the image capturing system 100. In some embodiments, the image capturing system 100 may further include an imaging surface S7 located at the image side of the third lens L3, and the light beam can be incident on the imaging surface S7 after being adjusted by the first lens L1, the second lens L2, and the third lens L3.

Specifically, in some examples, the first lens L1 has negative optical power, and the image side surface S2 of the first lens L1 is concave at a paraxial region. The second lens element L2 has positive refractive power, and an object-side surface S3 of the second lens element L2 is convex at a paraxial region. The third lens element L3 has positive refractive power, and an image-side surface S6 of the third lens element L3 is convex at a paraxial region.

The negative focal power of the first lens L1 is matched with the concave surface shape of the image side surface S2 of the first lens L1 at the paraxial region, which is favorable for the first lens L1 to collect light rays with a large angle, thereby being favorable for the image capturing system 100 to realize the wide-angle characteristic, and thus, the requirement of capturing images in a large range can be met. The positive focal power of the second lens element L2, in combination with the convex surface shape of the object side surface S3 of the second lens element L2 at the paraxial region, is beneficial to correcting the aberration generated when the first lens element L1 introduces the high-angle light beam by the second lens element L2, thereby improving the imaging quality of the image capturing system 100. The positive focal power of the third lens L3, in combination with the convex surface shape of the image side surface S6 of the third lens L3 at the paraxial region, enables the third lens L3 to cooperate with the second lens L2 to effectively converge light rays, thereby being beneficial to shortening the overall length of the image capturing system 100 and realizing a miniaturized design; and meanwhile, the incident angle of the light on the imaging surface S7 is more easily matched with the photosensitive element, so that the imaging quality of the imaging system 100 is improved. The reasonable configuration of the focal powers and the surface shapes of the first lens L1, the second lens L2 and the third lens L3 is also beneficial to smooth transition of light between the first lens L1, the second lens L2 and the third lens L3, so that aberration sensitivity of the image capturing system 100 is reduced, and further, the imaging quality of the image capturing system 100 is improved while the wide-angle characteristic and the miniaturized design are realized. In the present utility model, the surface shape of a certain lens at the paraxial region is described, and the surface shape of the portion of the lens corresponding to the region through which paraxial light passes is understood as the surface shape.

Further, in some embodiments, the imaging system 100 satisfies the conditional expression: 156deg/mm < FOV/SD11 < 217deg/mm; the FOV is the maximum angle of view of the imaging system 100, and SD11 is the maximum effective half-aperture of the object side surface S1 of the first lens L1. The above conditional expression is satisfied, which is favorable for reducing the effective caliber of the image capturing system 100, thereby realizing a miniaturized design, and is favorable for realizing the wide-angle characteristic of the image capturing system 100, so as to satisfy the requirement of large-scale image capturing, and is favorable for the image capturing system 100 to have good imaging quality. Above the upper limit of the above conditional expression, the field angle of the imaging system 100 is too large, and aberrations such as distortion, which are difficult to correct, are likely to occur in the fringe field, which is disadvantageous in improving the imaging quality. Below the lower limit of the above conditional expression, the implementation of the wide-angle characteristic is not advantageous, and the reduction of the effective aperture of the image pickup system 100 is also not advantageous.

When the optical power and the surface shape characteristics are provided and the conditional expression is satisfied, the imaging system 100 can achieve both a compact design, a wide-angle characteristic, and a high imaging quality.

In some embodiments, the imaging system 100 satisfies the conditional expression: SD11/f is more than or equal to 1 and less than or equal to 2.1; where f is the effective focal length of the imaging system 100. The above conditional expression is satisfied, which is beneficial to reducing the effective caliber and the total length of the image capturing system 100 to realize miniaturized design, and is beneficial to improving the imaging quality of the image capturing system 100. Exceeding the upper limit of the above conditional expression, the effective aperture of the first lens L1 is too large, which is not beneficial to the realization of miniaturized design, and the effective focal length of the image capturing system 100 is too short, which results in limited light deflection space in the axial direction of the image capturing system 100, which is not beneficial to the good adjustment of light, thereby being not beneficial to the improvement of imaging quality. Below the lower limit of the above conditional expression, the effective focal length of the image capturing system 100 is too long, resulting in too long total length of the image capturing system 100, which is also disadvantageous for implementation of a miniaturized design.

In some embodiments, the imaging system 100 satisfies the conditional expression: 1.6.ltoreq.f.tan (HFOV)/ImgH.ltoreq.2.7; where f is the effective focal length of the imaging system 100, HFOV is half of the maximum field angle of the imaging system 100, and ImgH is half of the image height corresponding to the maximum field angle of the imaging system 100. The imaging system 100 can achieve good imaging quality while achieving wide-angle characteristics while satisfying the above conditional expression. Exceeding the upper limit of the above conditional expression, the field angle of the imaging system 100 is too large, which tends to cause aberrations such as distortion, which are difficult to correct, in the fringe field of view, and is disadvantageous in improving the imaging quality. Below the lower limit of the above conditional expression, the imaging system 100 is disadvantageous in achieving wide-angle characteristics.

In some embodiments, the imaging system 100 satisfies the conditional expression: TTL/ImgH is less than or equal to 3.5 and less than or equal to 4; the TTL is the distance between the object side surface S1 of the first lens L1 and the imaging surface S7 of the image capturing system 100 on the optical axis, that is, the total optical length of the image capturing system 100, and ImgH is half of the image height corresponding to the maximum field angle of the image capturing system 100. The satisfaction of the above conditional expression is advantageous in reducing the effective aperture and the optical total length of the image pickup system 100, thereby facilitating the realization of a miniaturized design. Exceeding the upper limit of the above conditional expression, the overall length of the image capturing system 100 is too long, which is not favorable for the image capturing system 100 to realize a miniaturized design. Below the lower limit of the above conditional expression, the imaging surface S7 of the imaging system 100 is oversized, which is not beneficial to reducing the effective caliber of the imaging system 100, and is also not beneficial to implementing a miniaturized design of the imaging system 100.

In some embodiments, a camera is takenThe image system 100 satisfies the conditional expression: 1.4mm ^-1 ≤FNO/TTL≤2.6mm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the Here, FNO is an f-number of the image capturing system 100, and TTL is a distance between the object side surface S1 of the first lens L1 and the imaging surface S7 of the image capturing system 100 on the optical axis. The above conditional expression is satisfied, which is favorable for reducing the effective caliber and the total length of the image pickup system 100, thereby being favorable for realizing the miniaturized design of the image pickup system 100, and simultaneously, being favorable for preventing the aperture of the image pickup system 100 from being too small, thereby being favorable for obtaining sufficient light entering quantity by the image pickup system 100 and having good imaging quality. Exceeding the upper limit of the above conditional expression, the aperture number of the image capturing system 100 is too large, resulting in too small aperture, which is unfavorable for increasing the light entering amount of the image capturing system 100, and tends to cause too low relative illuminance of imaging, which is unfavorable for increasing the imaging quality. Below the lower limit of the above conditional expression, the effective caliber of the imaging system 100 is too large, and the overall length is too large, which is not beneficial to the realization of a miniaturized design.

In some embodiments, the imaging system 100 satisfies the conditional expression: SD11/SD32 is more than or equal to 1.8 and less than or equal to 3; here, SD32 is the maximum effective half aperture of the image side surface S6 of the third lens L3. The above conditional expression is satisfied, so that the first lens L1 is favorable to effectively collecting light rays with a large angle, and the fourth lens L4 is also favorable to effectively transmitting light rays to the imaging surface S7, thereby realizing wide-angle characteristics and simultaneously improving imaging quality.

In some embodiments, the imaging system 100 satisfies the conditional expression: -0.7.ltoreq.f1/f2.ltoreq.0.4; wherein f1 is the effective focal length of the first lens L1, and f2 is the effective focal length of the second lens L2. The ratio of the effective focal lengths of the first lens L1 and the second lens L2 can be reasonably configured to satisfy the above conditional expression, which is favorable for realizing the wide-angle characteristic and improving the imaging quality of the imaging system 100. Exceeding the upper limit of the above conditional expression, the negative power of the first lens L1 is too small, and the refractive power is too large, so that serious aberration is easily generated in the fringe field of view, which is not beneficial to improving the imaging quality. Below the lower limit of the above conditional expression, the negative focal power of the first lens L1 is too large, and the refractive power is too small, which is not beneficial to effectively collecting light rays with a large angle, thereby not beneficial to implementation of the wide-angle characteristic.

In some embodiments, the imaging system 100 satisfies the conditional expression: -0.9.ltoreq.f1/f3.ltoreq.0.3; wherein f1 is an effective focal length of the first lens L1, and f3 is an effective focal length of the third lens L3. The ratio of the effective focal lengths of the first lens L1 and the third lens L3 can be reasonably configured to satisfy the above conditional expression, which is favorable for realizing the wide-angle characteristic and improving the imaging quality of the imaging system 100. Exceeding the upper limit of the above conditional expression, the negative power of the first lens L1 is too small, and the refractive power is too large, so that serious aberration is easily generated in the fringe field of view, which is not beneficial to improving the imaging quality. Below the lower limit of the above conditional expression, the negative focal power of the first lens L1 is too large, and the refractive power is too small, which is not beneficial to effectively collecting light rays with a large angle, thereby not beneficial to implementation of the wide-angle characteristic.

In some embodiments, the imaging system 100 satisfies the conditional expression: TTL/f is more than or equal to 4.1 and less than or equal to 6.5; wherein TTL is the distance between the object side surface S1 of the first lens L1 and the imaging surface S7 of the image capturing system 100 on the optical axis, i.e. the total optical length of the image capturing system 100, and f is the effective focal length of the image capturing system 100. The above conditional expression is satisfied, which is favorable for shortening the total length of the camera system 100, realizing miniaturized design, and simultaneously, the camera system 100 can have enough space to reasonably deflect light, which is favorable for improving imaging quality.

In some embodiments, the imaging system 100 satisfies the conditional expression: bf/f is more than or equal to 1.8 and less than or equal to 2.1; where Bf is the distance between the image side surface S6 of the third lens L3 and the imaging surface S7 of the image capturing system 100 on the optical axis, i.e. the back focal length of the image capturing system 100, and f is the effective focal length of the image capturing system 100. The above conditional expression is satisfied, and the overall length of the image capturing system 100 is shortened to achieve a miniaturized design, and meanwhile, the image capturing system 100 can have a large enough back focal space, which is favorable for focusing of the image capturing system 100 and is also favorable for better assembling of the image capturing system 100 with the photosensitive element.

In some embodiments, the imaging system 100 satisfies the conditional expression: the FOV is more than or equal to 130 degrees and less than or equal to 150 degrees. The above conditional expression is satisfied, and the imaging system 100 has a wide-angle characteristic, and is beneficial to satisfying the requirement of capturing images in a large range when applied to an endoscope, so as to reduce the risk of missed detection, and meanwhile, the field angle of the imaging system 100 is not too large, so that aberrations such as too serious distortion of the edge field of view can be avoided, and the improvement of imaging quality is facilitated.

In some embodiments, the imaging system 100 satisfies the conditional expression: imgH is more than or equal to 0.6mm and less than or equal to 0.8mm; the ImgH is half of the image height corresponding to the maximum field angle of the imaging system 100. The image capturing system 100 can have a large image plane characteristic, so that the image capturing system 100 can be matched with a photosensitive element with a higher pixel to obtain good imaging quality, and meanwhile, the aberration of an edge view field is reduced, the relative illuminance of the edge view field is improved, and the imaging quality of the image capturing system 100 is improved.

It should be noted that, in some embodiments, the image capturing system 100 may match a photosensitive element having a rectangular photosensitive surface, and the imaging surface S7 of the image capturing system 100 coincides with the photosensitive surface of the photosensitive element. At this time, if the effective pixel area on the imaging surface S7 has a horizontal direction and a diagonal direction, the FOV may be understood as the maximum field angle in the diagonal direction of the imaging system 100, and ImgH may be understood as half the size of the effective pixel area of the imaging system 100 in the diagonal direction.

It is understood that, in the present utility model, the imaging surface S7 may be understood as a virtual surface formed by a converging point of the system light on the image side of the third lens L3, and when the image capturing system 100 is matched with the photosensitive element, the imaging surface S7 coincides with the photosensitive surface of the photosensitive element, so that the light adjusted by the image capturing system 100 can form a clear image on the photosensitive surface.

In some embodiments, the image capturing system 100 is provided with a stop ST, which may be disposed between the second lens L2 and the third lens L3. By the arrangement, the imaging system 100 can have sufficient light entering quantity while the miniaturization characteristic is realized, so that the imaging quality of the imaging system 100 is improved.

In some embodiments, the image capturing system 100 may further include an infrared cut filter 110, where the infrared cut filter 110 may be disposed on the image side of the third lens L3, and the infrared cut filter 110 is used for filtering infrared light, so as to prevent the infrared light from reaching the imaging surface S7 and affecting the imaging quality of the image capturing system 100. Of course, the ir cut filter 110 may also be disposed between the first lens L1 and the second lens L2, or disposed on the object side of the first lens L1, as long as there is enough space for assembling the ir cut filter 110.

In some embodiments, the image capturing system 100 further includes a protective glass 120, where the protective glass 120 may be disposed between the third lens L3 and the imaging surface S7, and the protective glass 120 is used to protect the photosensitive element disposed at the imaging surface S7.

In some embodiments, the object side and the image side of each lens of the image capturing system 100 are aspheric, and the object side and the image side of each lens may be different in surface shape at the paraxial region and at the peripheral region. The adoption of the aspheric structure can improve the flexibility of lens design, effectively correct spherical aberration and improve imaging quality.

In some embodiments, the materials of the lenses in the image capturing system 100 may be plastic. The lens made of plastic material can reduce the weight of the camera system 100 and the production cost, and is also beneficial to realizing the small-caliber design, and the small-size of the camera system 100 is matched to realize the light and thin design of the camera system 100.

The reference wavelengths for the above effective focal lengths are 587.6nm.

From the above description of the embodiments, more particular embodiments and figures are set forth below in detail.

First embodiment

Referring to fig. 1 again, fig. 1 is a schematic diagram of an image capturing system 100 according to a first embodiment. The image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

The object side surface S1 of the first lens element L1 is a plane, and the image side surface S2 of the first lens element L1, and the object side surfaces and the image side surfaces of the second lens element L2 and the third lens element L3 are aspheric. In the remaining embodiments, the object-side surface and the image-side surface of each of the first lens element L1, the second lens element L2, and the third lens element L3 are aspheric.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

Table 1 below shows detailed parameters such as the radius of curvature, thickness, refractive index, abbe number, effective focal length, and effective focal length f, maximum field angle FOV, and f-number FNO of each lens of the image capturing system 100 in the first embodiment. The elements from the first lens L1 to the imaging surface S7 in table 1 are sequentially arranged in the order of the elements from top to bottom in table 1. The first row of the first lens element L1 represents the object-side surface S1 of the first lens element L1, the second row represents the image-side surface S2 of the first lens element L1, and so on. The first value in the "thickness" parameter row of the first lens element L1 is the thickness of the first lens element L1 on the optical axis 110, and the second value is the distance between the image side surface S2 of the first lens element L1 and the rear surface (the object side surface of the second lens element L2) in the image side direction on the optical axis 110, so that the meaning of the other values in the thickness parameter row can be deduced. Wherein, the refractive index, abbe number and effective focal length of each lens are 587.6nm.

Note that in this embodiment and the following embodiments, the imaging system 100 may not be provided with the infrared cut filter 110 and the cover glass 120, but the distance between the third lens L3 and the imaging surface S7 remains unchanged.

TABLE 1

The aspherical coefficients of the object side or image side of each lens of the imaging system 100 are given in table 2. Wherein the plane numbers from S2-S6 represent object side or image side surfaces S2-S6, respectively. And K-a12 from top to bottom respectively represent types of aspherical coefficients, where K represents a conic coefficient, A4 represents four times an aspherical coefficient, A6 represents six times an aspherical coefficient, A8 represents eight times an aspherical coefficient, and so on. In addition, the aspherical coefficient formula is as follows:

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

TABLE 2

Referring to fig. 2, fig. 2 is a astigmatism curve chart, a distortion curve chart and a magnification chromatic aberration curve chart of the image capturing system 100 in the first embodiment in order from left to right. As can be seen from the astigmatic curve chart of fig. 2, the sagittal field curvature and meridional field curvature of the image capturing system 100 are both smaller, the field curvature and astigmatism of each field of view are well corrected, the center and the edge of the field of view have clear imaging, and the image capturing system 100 has a large depth of field effect. As can be seen from the distortion graph of fig. 2, the distortion of the entire field of view of the imaging system 100 is small, the distortion of the image caused by the main beam is small, and the imaging quality of the system is excellent. As can be seen from the chromatic aberration of magnification graph of fig. 2, the chromatic aberration of magnification of the image capturing system 100 is well corrected, and good imaging quality is achieved.

Second embodiment

Referring to fig. 3, fig. 3 is a schematic structural diagram of an image capturing system 100 in the second embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 2, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 3 Table 3

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 4, and the definition of each parameter therein can be derived from the first embodiment.

TABLE 4 Table 4

Referring to fig. 4, fig. 4 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 in the second embodiment, and as can be seen from fig. 4, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Third embodiment

Referring to fig. 5, fig. 5 is a schematic structural diagram of an image capturing system 100 in the third embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 5, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 5

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 6, and the definition of each parameter therein can be derived from the first embodiment.

TABLE 6

Referring to fig. 6, fig. 6 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 according to the third embodiment, and as can be seen from fig. 6, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Fourth embodiment

Referring to fig. 7, fig. 7 is a schematic structural diagram of an image capturing system 100 in the fourth embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

the third lens element L3 has a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 7, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 7

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 8, and the definition of each parameter therein can be derived from the first embodiment.

TABLE 8

Referring to fig. 8, fig. 8 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 according to the fourth embodiment, and as can be seen from fig. 8, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Fifth embodiment

Referring to fig. 9, fig. 9 is a schematic structural diagram of an image capturing system 100 in a fifth embodiment, where the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 9, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 9

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 10, and the definition of each parameter therein can be derived from the first embodiment.

Table 10

Referring to fig. 10, fig. 10 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 according to the fifth embodiment, and as can be seen from fig. 10, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Sixth embodiment

Referring to fig. 11, fig. 11 is a schematic structural diagram of an image capturing system 100 in the sixth embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 11, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 11

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 12, and the definition of each parameter therein can be derived from the first embodiment.

Table 12

Referring to fig. 12, fig. 12 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 according to the sixth embodiment, and as can be seen from fig. 12, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Seventh embodiment

Referring to fig. 13, fig. 13 is a schematic structural diagram of an image capturing system 100 in the seventh embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 13, and the definition of each parameter can be obtained in the first embodiment, which is not described herein.

TABLE 13

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 14, and the definition of each parameter therein can be derived from the first embodiment.

TABLE 14

Referring to fig. 14, fig. 14 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification chart of the image capturing system 100 in the seventh embodiment, and as can be seen from fig. 14, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

Eighth embodiment

Referring to fig. 15, fig. 15 is a schematic structural diagram of an image capturing system 100 in the eighth embodiment, and the image capturing system 100 includes, in order from an object side to an image side, a first lens L1 having negative optical power, a second lens L2 having positive optical power, a stop ST, a third lens L3 having positive optical power, an infrared cut filter 110, and a cover glass 120.

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

the second lens element L2 has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the third lens element L3 has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region.

In addition, the parameters of the image capturing system 100 are given in table 15, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 15

The aspherical coefficients of each lens image side or object side of the image capturing system 100 are given in table 16, and the definition of each parameter therein can be derived from the first embodiment.

Table 16

Referring to fig. 16, fig. 16 shows, in order from left to right, an astigmatic curve chart, a distortion curve chart and a chromatic aberration of magnification curve chart of the image capturing system 100 in the eighth embodiment, and as can be seen from fig. 16, the astigmatic curve, the distortion and the chromatic aberration of magnification of the image capturing system 100 are all well corrected, and the image capturing system 100 has good imaging quality.

In addition, the image pickup systems 100 in the first to eighth embodiments satisfy the data of table 17 below, and the effects that can be obtained by satisfying the following data can be referred to above.

TABLE 15

The present utility model also provides an endoscope objective lens (not shown) comprising a photosensitive element and the imaging system 100 according to any of the embodiments described above. The photosensitive surface of the photosensitive element coincides with the imaging surface S7 of the imaging system 100. Specifically, the photosensitive element may be a charge coupled element (Charge Coupled Device, CCD) or a complementary metal oxide semiconductor device (Complementary Metal-Oxide Semiconductor Sensor, CMOS Sensor). The use of the imaging system 100 in an endoscope objective lens can achieve both a compact design, a wide-angle characteristic, and a high imaging quality, thereby facilitating the application of the endoscope objective lens in an endoscope.

The utility model also provides an endoscope (not shown in the drawings), which comprises a shell and the endoscope objective lens in any embodiment, wherein the endoscope objective lens is arranged in the shell, and the shell can be a fixed structure of the endoscope objective lens. Endoscopes may be used in the medical field, for example in medical diagnosis of patients, and in particular, endoscopes include, but are not limited to, endoscopes for viewing digestive organs, bronchi, nasal cavities, throats, urinary organs and uterus. The endoscope objective lens is adopted in the endoscope, and the endoscope objective lens can achieve miniaturization design, wide-angle characteristics and high imaging quality, so that damage to a patient can be reduced to the greatest extent, images of focus areas can be obtained in a large range, missed detection risks are avoided, meanwhile, lesion images with high definition can be formed, and diagnosis accuracy is improved.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the utility model, which are described in detail and are not to be construed as limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.

Claims (12)

1. An imaging system for an endoscope, wherein the number of lenses having optical power in the imaging system is three, and the imaging system sequentially comprises, from an object side to an image side along an optical axis:

a first lens element with negative refractive power, wherein an image-side surface of the first lens element is concave at a paraxial region;

a second lens with positive focal power, wherein the object side surface of the second lens is a convex surface at a paraxial region;

a third lens element with positive refractive power, wherein an image-side surface of the third lens element is convex at a paraxial region;

the imaging system satisfies the following conditional expression:

156deg/mm≤FOV/SD11≤217deg/mm；

wherein FOV is the maximum field angle of the imaging system, SD11 is the maximum effective half-caliber of the object side of the first lens.

2. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

1≤SD11/f≤2.1；

wherein f is the effective focal length of the imaging system.

3. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

1.6≤f*tan(HFOV)/ImgH≤2.7；

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

4. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

3.5≤TTL/ImgH≤4；

wherein TTL is the distance between the object side surface of the first lens and the imaging surface of the imaging system on the optical axis, and ImgH is half of the image height corresponding to the maximum field angle of the imaging system.

5. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

1.4mm ^-1 ≤FNO/TTL≤2.6mm ^-1 ；

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

6. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

1.8≤SD11/SD32≤3；

wherein SD32 is the maximum effective half-caliber of the image side surface of the third lens.

7. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

-0.7≤f1/f2≤-0.4；

wherein f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens.

8. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

-0.9≤f1/f3≤-0.3；

wherein f1 is an effective focal length of the first lens, and f3 is an effective focal length of the third lens.

9. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

4.1≤TTL/f≤6.5；

wherein TTL is a distance between an object side surface of the first lens and an imaging surface of the imaging system on an optical axis, and f is an effective focal length of the imaging system.

10. The imaging system according to claim 1, wherein the imaging system satisfies the following conditional expression:

1.8≤Bf/f≤2.1；

wherein Bf is the distance from the image side surface of the third lens to the imaging surface of the imaging system on the optical axis, and f is the effective focal length of the imaging system.

11. An endoscope objective lens comprising a photosensitive element and the imaging system of any one of claims 1-10, the photosensitive element being disposed on an image side of the imaging system.

12. An endoscope comprising the endoscope objective of claim 11.