CN220024996U

CN220024996U - Endoscope optical system, objective lens module and endoscope

Info

Publication number: CN220024996U
Application number: CN202320748372.7U
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: 2023-04-06
Filing date: 2023-04-06
Publication date: 2023-11-17
Anticipated expiration: 2033-04-06

Abstract

The application relates to an endoscope optical system, an objective lens module and an endoscope. The endoscope optical system includes: the first lens with negative focal power has a concave image side surface at a paraxial region; the object side surface of the second lens is a convex surface at a paraxial region; the image side surface of the third lens is convex at a paraxial region; the object side surface of the fourth lens is a concave surface at a paraxial region; the endoscope optical system satisfies: TTL/f is more than or equal to 4.08 and less than or equal to 4.52. The endoscope optical system can be designed in a small size and has good imaging quality.

Description

Endoscope optical system, objective lens module and endoscope

Technical Field

The present application relates to the technical field of endoscopes, and in particular, to an endoscope optical system, an objective lens module, and an endoscope.

Background

Along with the rapid development of medical equipment, the application of an endoscope in the medical field is also becoming wider and wider, the endoscope can extend into a user body to acquire images of focus areas in the user body, diagnosis or treatment is facilitated, and the accuracy of diagnosis and treatment is affected by the imaging quality of the endoscope. In the related art, the imaging quality of an endoscope is generally improved by increasing the number of lenses in an optical system of the endoscope, which easily causes the endoscope to be oversized, thereby easily causing damage to a user. The endoscope in the related art has difficulty in achieving both small size and high imaging quality.

Disclosure of Invention

In view of this, it is necessary to provide an endoscope optical system, an objective lens module, and an endoscope, which solve the problem that it is difficult to achieve both small size and high imaging quality in the related art endoscope.

An endoscope optical 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;

a fourth lens with negative focal power, wherein the object side surface of the fourth lens is a concave surface at a paraxial region;

and the endoscope optical system satisfies the following conditional expression:

4.08≤TTL/f≤4.52；

wherein TTL is the distance between the object side surface of the first lens and the imaging surface of the endoscope optical system on the optical axis, that is, the total optical length of the endoscope optical system, and f is the focal length of the endoscope optical system.

According to the endoscope optical system, the first lens has negative focal power, and the image side surface is the concave surface at the paraxial region, so that the first lens is beneficial to collecting large-angle light rays, the visual angle of the endoscope optical system is beneficial to expanding, and the wide-angle characteristic is beneficial to realizing. The second lens has positive focal power, so that aberration such as distortion generated when the first lens introduces large-angle light rays can be corrected, and imaging quality of the endoscope optical system can be improved. The third lens has positive focal power, and the image side surface is convex at a paraxial region, which is favorable for converging light rays towards the image side, thereby being favorable for shortening the total length of the endoscope optical system. The fourth lens has negative focal power, and the object side surface is a concave surface at a paraxial region, so that light rays are reasonably deflected towards the imaging surface, the incident angle of the light rays on the imaging surface is favorably adjusted, the size of the imaging surface is increased, and the imaging quality of an endoscope optical system is favorably improved. When the conditional expression is satisfied, the ratio of TTL and f is favorable for reasonable configuration, the total length of the endoscope optical system is shortened, the small-size design is realized, the endoscope optical system can effectively deflect light, and the imaging quality of the endoscope optical system is improved. The endoscope optical system has the above focal power and surface type characteristics, satisfies the above conditions, can obtain good imaging quality with four lenses, and can give consideration to both small size and high imaging quality.

In one embodiment, the endoscope optical system satisfies the following conditional expression:

-0.9≤f1/f≤-0.7；

wherein f1 is the focal length of the first lens.

-9.9≤f4/f3≤-1.7；

wherein f4 is the focal length of the fourth lens, and f3 is the focal length of the third lens.

1.45≤Bf/f≤1.72；

wherein Bf is a distance between an image side surface of the fourth lens and an imaging surface of the endoscope optical system on an optical axis.

f2/f is more than or equal to 1.6 and less than or equal to 2.4; wherein f2 is the focal length of the second lens; and/or the number of the groups of groups,

f3/f is more than or equal to 0.7 and less than or equal to 1.4; wherein f3 is the focal length of the third lens.

-3≤f2/f1≤-1.5；

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

1.51mm ^-1 ≤FNO/TTL≤1.7mm ^-1 ；

wherein FNO is the f-number of the endoscope optical system.

R7/R8 is more than or equal to 0.05 and less than or equal to 0.77; wherein R7 is a radius of curvature of the object side surface of the fourth lens element at the optical axis, and R8 is a radius of curvature of the image side surface of the fourth lens element at the optical axis; and/or the number of the groups of groups,

R4/R5 is more than or equal to 0.02 and less than or equal to 1.44; wherein R4 is a radius of curvature of the image side surface of the second lens element at the optical axis, and R5 is a radius of curvature of the object side surface of the third lens element at the optical axis.

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

An endoscope comprises the objective lens module.

Drawings

Fig. 1 is a schematic view showing the structure of an optical system of an endoscope in the first embodiment.

Fig. 2a is an astigmatic diagram of an endoscope optical system in a first embodiment.

Fig. 2b is a graph showing distortion of the optical system of the endoscope in the first embodiment.

Fig. 2c is a graph of chromatic aberration of magnification of an endoscope optical system in the first embodiment.

Fig. 3 is a schematic view showing the structure of an optical system of an endoscope in the second embodiment.

Fig. 4a is an astigmatic diagram of an endoscope optical system in a second embodiment.

Fig. 4b is a graph showing distortion of the endoscope optical system in the second embodiment.

Fig. 4c is a graph of chromatic aberration of magnification of an endoscope optical system in a second embodiment.

Fig. 5 is a schematic view showing the structure of an optical system of an endoscope in the third embodiment.

Fig. 6a is an astigmatic diagram of an endoscope optical system in a third embodiment.

Fig. 6b is a graph of distortion of an endoscope optical system in a third embodiment.

Fig. 6c is a graph of chromatic aberration of magnification of an endoscope optical system in a third embodiment.

Fig. 7 is a schematic view of the structure of an endoscope optical system in the fourth embodiment.

Fig. 8a is an astigmatic diagram of an endoscope optical system in a fourth embodiment.

Fig. 8b is a graph showing distortion of an optical system of an endoscope in the fourth embodiment.

Fig. 8c is a graph of chromatic aberration of magnification of an endoscope optical system in a fourth embodiment.

Fig. 9 is a schematic structural view of an endoscope optical system in a fifth embodiment.

Fig. 10a is an astigmatic diagram of an endoscope optical system in a fifth embodiment.

Fig. 10b is a graph showing distortion of an optical system of an endoscope in the fifth embodiment.

Fig. 10c is a chromatic aberration of magnification graph of an endoscope optical system in the fifth embodiment.

Fig. 11 is a schematic structural view of an endoscope optical system in the sixth embodiment.

Fig. 12a is an astigmatic diagram of an endoscope optical system in a sixth embodiment.

Fig. 12b is a graph showing distortion of an optical system of an endoscope in the sixth embodiment.

Fig. 12c is a chromatic aberration of magnification graph of an endoscope optical system in the sixth embodiment.

Fig. 13 is a schematic structural view of an endoscope optical system in the seventh embodiment.

Fig. 14a is an astigmatic diagram of an endoscope optical system in a seventh embodiment.

Fig. 14b is a graph showing distortion of an endoscope optical system in the seventh embodiment.

Fig. 14c is a chromatic aberration of magnification graph of an endoscope optical system in the seventh embodiment.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application 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 application. The present application 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 application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that, if any, these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., are used herein with respect to the orientation or positional relationship shown in the drawings, these terms refer to the orientation or positional relationship for convenience of description and simplicity of description only, and do not indicate or imply that the apparatus 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 application.

Furthermore, the terms "first," "second," and the like, if any, 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 application, the terms "plurality" and "a plurality" if any, mean at least two, such as two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly. For example, the two parts can be fixedly connected, detachably connected or integrated; 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 application can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present application, unless expressly stated or limited otherwise, the meaning of a first feature being "on" or "off" a second feature, and the like, is that the first and second features are either in direct contact or in indirect contact through 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 if 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. If 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, if any, are for descriptive purposes only and do not represent a unique embodiment.

Referring to fig. 1, fig. 1 illustrates a schematic diagram of an endoscope optical system 100 in some embodiments of the present application. The endoscope optical system 100 provided by the application can be applied to any applicable type of endoscope, and the endoscope optical system 100 can adjust the light rays entering the endoscope so that the light rays can form clear images. In some embodiments of the present application, the endoscope optical system 100 includes, in order from an object side to an image side along an optical axis, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The first lens element L1, the second lens element L2, the third lens element L3 and the fourth lens element L4 each comprise an object-side surface facing the object side and an image-side surface facing the image side. The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 may be coaxially disposed, and an axis common to the lenses in the endoscope optical system 100 is an optical axis of the endoscope optical system 100. In some embodiments, the endoscope optical system 100 may further include an imaging surface 110 located at the image side of the fourth lens L4, and the light incident on the endoscope optical system 100 can be incident on the imaging surface 110 after being adjusted by the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4. In the present application, the object side of the endoscope optical system 100 may be understood as a side of the endoscope optical system 100 facing the object, for example, toward the focal region, and the image side of the endoscope optical system 100 may be understood as a side of the endoscope optical system 100 where the imaging surface 110 is located.

In some embodiments, the first lens element L1 has negative refractive power, and an image-side surface of the first lens element L1 is concave at a paraxial region. The second lens element L2 has positive refractive power, and an object-side surface 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 of the third lens element L3 is convex at a paraxial region. The fourth lens element L4 has negative refractive power, and an object-side surface of the fourth lens element L4 is concave at a paraxial region. In the present application, 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.

In the above-mentioned endoscope optical system 100, the first lens L1 has negative focal power, and the image side surface is concave at the paraxial region, which is advantageous for the first lens L1 to collect light rays with a large angle, thereby being advantageous for enlarging the field angle of the endoscope optical system 100 and for realizing the wide-angle characteristic. The second lens L2 has positive power, which is advantageous for correcting aberrations such as distortion generated when the first lens L1 introduces high-angle light, thereby facilitating improvement of imaging quality of the endoscope optical system 100. The third lens element L3 has positive refractive power, and has a convex image-side surface at a paraxial region thereof, which facilitates converging light toward the image side, thereby shortening the overall length of the endoscope optical system 100. The fourth lens element L4 has negative refractive power, and has a concave object-side surface at a paraxial region thereof, which facilitates reasonable deflection of light toward the imaging surface 110, thereby facilitating adjustment of an incident angle of the light on the imaging surface 110, and increasing a size of the imaging surface 110, and further facilitating improvement of imaging quality of the endoscope optical system 100.

Further, in some embodiments, the endoscope optical system 100 satisfies the conditional expression: TTL/f is more than or equal to 4.08 and less than or equal to 4.52; wherein TTL is the distance between the object side surface of the first lens L1 and the imaging surface of the endoscope optical system 100 on the optical axis, i.e. the total optical length of the endoscope optical system 100, and f is the focal length of the endoscope optical system 100. When the above conditional expression is satisfied, the ratio of TTL to f is favorable to be reasonably configured, which is favorable to shortening the total length of the endoscope optical system 100, realizing a small-size design, and also favorable to enable the endoscope optical system 100 to effectively deflect light rays and improving the imaging quality of the endoscope optical system 100.

The endoscope optical system 100 has the above-described optical power and surface type characteristics, and satisfies the above-described conditional expression, can obtain good imaging quality with a small number of four lenses, can achieve both small-size and high imaging quality, and can realize wide-angle characteristics, satisfying the large-range image capturing requirement of an endoscope.

In some embodiments, the endoscope optical system 100 is provided with a diaphragm 120, and the diaphragm 120 may be disposed between the second lens L2 and the third lens L3. The diaphragm 120 is disposed in the middle, so that the endoscope optical system 100 can have a sufficient light inlet amount while realizing a small size, thereby being beneficial to improving the imaging quality of the endoscope optical system 100.

In some embodiments, the endoscope optical system 100 further includes a protective glass 130, where the protective glass 130 is disposed between the fourth lens L4 and the imaging surface 110, and the protective glass 130 is used to protect a photosensitive element disposed at the imaging surface 110 in the objective lens module when the endoscope optical system 100 is applied in the objective lens module. In some embodiments, the endoscope optical system 100 further includes a filter 140, and the filter 140 may be disposed between the fourth lens L4 and the cover glass 130. The filter 140 is used for filtering out the interference light, and preventing the interference light from striking the imaging surface 110 to affect normal imaging. For example, the filter 140 may be an infrared cut filter for cutting light in a near infrared region that may be sensed by the photosensitive element. Of course, the filter 140 may be disposed between any two lenses in the endoscope optical system 100.

In some embodiments, the object side and the image side of each lens of the endoscope optical system 100 are aspheric, and the object side and the image side of each lens may be different in surface shape at the paraxial and the circumferential directions. The use of an aspherical structure can increase flexibility in lens design and effectively correct spherical aberration, improving imaging quality, so that the endoscope optical system 100 can obtain good imaging quality with a smaller number of lenses.

In some embodiments, the material of each lens in the endoscope optical system 100 may be plastic. The use of a plastic lens can reduce the weight of the endoscope optical system 100 and reduce the production cost. Further, the material of each lens may be any suitable plastic with good biocompatibility, such as a polymeric resin, so that the risk of damage to the user caused by the endoscope is reduced when the endoscope optical system 100 is applied to the endoscope.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: -0.9.ltoreq.f1/f.ltoreq.0.7; wherein f1 is the focal length of the first lens L1. When the above conditional expression is satisfied, the ratio of the focal length of the first lens L1 to the focal length of the endoscope optical system 100 can be reasonably configured, so that the first lens L1 can effectively collect light with a large angle, thereby being beneficial to realizing wide-angle characteristics, and meanwhile, the first lens L1 cannot deviate from an excessive angle when introducing light with a large angle, thereby being beneficial to inhibiting generation of aberration such as distortion and improving imaging quality of the endoscope optical system 100.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: -9.9.ltoreq.f4/f3.ltoreq.1.7; wherein f4 is the focal length of the fourth lens L4, and f3 is the focal length of the third lens L3. When the above conditional expression is satisfied, the ratio of the focal lengths of the fourth lens L4 and the third lens L3 can be reasonably configured, so that the focal power of the fourth lens L4 is not excessively strong, and the focal power of the third lens L3 is not excessively weak, so that the third lens L3 and the fourth lens L4 are mutually matched, light can be gently converged to the imaging surface 110, and meanwhile, various aberrations of an off-axis view field can be corrected, and the imaging quality of the endoscope optical system 100 is improved.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: bf/f is more than or equal to 1.45 and less than or equal to 1.72; where Bf is the distance on the optical axis from the image side surface of the fourth lens L4 to the imaging surface 110 of the endoscope optical system 100. When the above conditional expression is satisfied, the ratio of the back focal length to the focal length of the endoscope optical system 100 can be reasonably configured, so that the endoscope optical system 100 has sufficient back focal space to transition light, and sufficient focusing space can be provided to satisfy focusing requirements, and meanwhile, the assembly of the endoscope optical system 100 and the photosensitive element in the objective lens module is facilitated.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: f2/f is more than or equal to 1.6 and less than or equal to 2.4; wherein f2 is the focal length of the second lens L2. The ratio of the focal length of the second lens L2 to the focal length of the endoscope optical system 100 can be reasonably configured, so that the focal power of the second lens L2 is not excessively strong, and light can smoothly transition at the second lens L2, thereby being beneficial to correcting aberrations such as coma aberration of an off-axis view field and improving the imaging quality of the endoscope optical system 100.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: f3/f is more than or equal to 0.7 and less than or equal to 1.4; wherein f3 is the focal length of the third lens L3. When the above conditional expression is satisfied, the ratio of the focal length of the third lens L3 to the focal length of the endoscope optical system 100 can be reasonably configured, so that the third lens L3 has enough optical power, can effectively converge light rays, is favorable for compressing the total length of the endoscope optical system 100, and realizes a small-size design.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: -3.ltoreq.f2/f1.ltoreq.1.5; wherein f2 is the focal length of the second lens L2, and f1 is the focal length of the first lens L1. When the above conditional expression is satisfied, the ratio of the focal length of the second lens L2 to the focal length of the first lens L1 can be reasonably configured, so that the first lens L1 and the second lens L2 are reasonably matched, and when large-angle light is introduced to realize the wide-angle characteristic, the generation of aberration such as distortion and coma is also favorably suppressed, and the imaging quality of the endoscope optical system 100 is improved.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: 1.51mm ^-1 ≤FNO/TTL≤1.7mm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the Where FNO is the f-number of the endoscope optical system 100. When the above conditional expression is satisfied, the effective caliber and the total length of the endoscope optical system 100 are favorably reduced, thereby being favorable for compressing the size of the endoscope optical system 100, realizing the small-size design, and simultaneously being favorable for preventing the aperture of the endoscope optical system 100 from being too small, thereby being favorable for obtaining sufficient light entering quantity of the endoscope optical system 100 and having good imaging quality.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: R7/R8 is more than or equal to 0.05 and less than or equal to 0.77; where R7 is a radius of curvature of the object side surface of the fourth lens element L4 at the optical axis, and R8 is a radius of curvature of the image side surface of the fourth lens element L4 at the optical axis. When the above conditional expression is satisfied, the ratio of the curvature radius of the object side surface of the fourth lens element L4 at the image side surface at the optical axis can be reasonably configured, so that the fourth lens element L4 can smoothly transition light to the imaging surface 110, which is beneficial to correcting the aberration of the endoscope optical system 100, and can reasonably adjust the incident angle of the light on the imaging surface 110, thereby being beneficial to improving the imaging quality of the endoscope optical system 100.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: R4/R5 is more than or equal to 0.02 and less than or equal to 1.44; wherein R4 is a radius of curvature of the image side surface of the second lens element L2 at the optical axis, and R5 is a radius of curvature of the object side surface of the third lens element L3 at the optical axis. When the above conditional expression is satisfied, the ratio of the radii of curvature of the image side surface of the second lens L2 and the object side surface of the third lens L3 at the optical axis can be matched with the design that the diaphragm 120 is arranged between the second lens L2 and the third lens L3, so that light can smoothly transition between the second lens L2 and the third lens L3 and fill the diaphragm 120, thereby being beneficial to correcting the aberration of the endoscope optical system 100 and improving the light entering quantity of the endoscope optical system 100, and being beneficial to improving the imaging quality of the endoscope optical system 100.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: T12/T23 is more than or equal to 1.4 and less than or equal to 6.3; wherein T12 is the distance between the image side of the first lens element L1 and the object side of the second lens element L2 on the optical axis, and T23 is the distance between the image side of the second lens element L2 and the object side of the third lens element L3 on the optical axis. When the above conditional expression is satisfied, the ratio of the air space between the first lens L1 and the second lens L2 to the air space between the second lens L2 and the third lens L3 can be reasonably configured, so that the first three lenses have sufficient space to deflect light rays, suppress the generation of aberration, and facilitate the assembly of the first three lenses with sufficient space, and simultaneously, the overall length of the endoscope optical system 100 is also facilitated to be compressed, thereby realizing the small-size design.

In some embodiments, the endoscope optical system 100 satisfies the following conditional expression: 2 omega is more than or equal to 130 degrees. Wherein 2ω is the maximum field angle of the endoscope optical system. When the above conditional expression is satisfied, the endoscope optical system 100 can realize a wide-angle characteristic, and can satisfy the requirement for wide-range image capturing of an endoscope.

It should be noted that, in some embodiments, when the endoscope optical system 100 is applied to the objective lens module, the endoscope optical system 100 may match a photosensitive element having a rectangular photosensitive surface, and the imaging surface 110 of the endoscope optical system 100 may coincide with the photosensitive surface of the photosensitive element. The effective pixel area on the imaging plane 110 may have a horizontal direction as well as a diagonal direction, and 2ω may be understood as a maximum field angle of the endoscope optical system 100 in the diagonal direction. It is understood that, in the present application, the imaging surface 110 may be understood as a virtual surface formed by a converging point of light rays of the endoscope optical system at the image side of the fourth lens L4, and when the endoscope optical system 100 is matched with the photosensitive element, the imaging surface 110 coincides with the photosensitive surface of the photosensitive element, so that light rays adjusted by the endoscope optical system 100 can form a clear image on the photosensitive surface.

In some embodiments, the object side of the first lens L1 is planar, facilitating assembly and positioning of the endoscope optical system 100 in an endoscope, improving assembly accuracy.

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

First embodiment

Referring again to fig. 1, fig. 1 is a schematic diagram of an endoscope optical system 100 in a first embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

The image side surface of the first lens element L1, and the object side surfaces and the image side surfaces of the second lens element L2, the third lens element L3 and the fourth lens element L4 are aspheric.

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

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

the fourth lens element L4 has a concave 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 a radius of curvature (at the optical axis), thickness, refractive index, abbe number, focal length, and effective focal length f, maximum field angle 2ω, and f-number FNO of each lens of the endoscope optical system 100 in the first embodiment. The reference wavelength of the focal length, refractive index, abbe number of each lens, and focal length of the endoscope optical system 100 is 587.6nm, and the same applies to other embodiments. The elements from the object plane (not shown) to the imaging plane 110 are 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 of the first lens element L1, the second row represents the image-side surface 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, the second value is the distance between the image-side surface of the first lens element L1 and the rear surface (the object-side surface of the second lens element L2) of the image-side direction on the optical axis 110, and the meaning of other values in the thickness parameter row can be deduced.

Note that in the first embodiment and the following embodiments, the endoscope optical system 100 may be provided without the filter 140 and the cover glass 130, but the distance between the image side surface of the fourth lens L4 and the imaging surface 110 on the optical axis remains unchanged.

TABLE 1

The aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 in the first embodiment are given in table 2. Wherein, the plane number from S2 indicates the image side surface of the first lens element L1, S3 and S4 indicate the object side surface and the image side surface of the second lens element L2, S5 and S6 indicate the object side surface and the image side surface of the third lens element L3, and S7 and S8 indicate the object side surface and the image side surface of the fourth lens element L4, respectively. And K-a14 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. 2a, 2b and 2c, fig. 2a is an astigmatic diagram of the endoscope optical system 100 in the first embodiment, an abscissa represents a focus shift in millimeters, fig. 2b is a distortion diagram of the endoscope optical system 100 in the first embodiment, an abscissa represents a distortion value in percent, and fig. 2c is a chromatic aberration diagram of the endoscope optical system 100 in the first embodiment, and an abscissa represents um. As can be seen from fig. 2a, 2b and 2c, the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are smaller, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Second embodiment

Referring to fig. 3, fig. 3 is a schematic structural view of an endoscope optical system 100 in a second embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

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;

The parameters of the endoscope optical system 100 in the second embodiment are given in table 3, wherein the definition of the parameters can be obtained from the first embodiment, and the detailed description is omitted herein.

TABLE 3 Table 3

The aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 in the second embodiment 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. 4a, 4b and 4c, fig. 4a is an astigmatic diagram of the endoscope optical system 100 in the second embodiment, fig. 4b is a distortion diagram of the endoscope optical system 100 in the second embodiment, and fig. 4c is a chromatic aberration of magnification diagram of the endoscope optical system 100 in the second embodiment. As can be seen from fig. 4a, 4b and 4c, the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are smaller, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Third embodiment

Referring to fig. 5, fig. 5 is a schematic structural view of an endoscope optical system 100 in a third embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

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

The parameters of the endoscope optical system 100 in the third embodiment are given in table 5, wherein the definition of the parameters can be obtained from the first embodiment, and the detailed description is omitted herein.

TABLE 5

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

TABLE 6

Referring to fig. 6a, 6b and 6c, fig. 6a is an astigmatic diagram of an endoscope optical system 100 in the third embodiment, an abscissa represents a focus shift in um, fig. 6b is a distortion diagram of the endoscope optical system 100 in the third embodiment, and fig. 6c is a chromatic aberration diagram of magnification of the endoscope optical system 100 in the third embodiment. As can be seen from fig. 6a, 6b and 6c, the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are smaller, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Fourth embodiment

Referring to fig. 7, fig. 7 is a schematic structural view of an endoscope optical system 100 in a fourth embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

The parameters of the endoscope optical system 100 in the fourth embodiment are given in table 7, wherein the definition of the parameters can be obtained from the first embodiment, and the detailed description is omitted herein.

TABLE 7

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

TABLE 8

Referring to fig. 8a, 8b and 8c, fig. 8a is an astigmatic diagram of the endoscope optical system 100 in the fourth embodiment, fig. 8b is a distortion diagram of the endoscope optical system 100 in the fourth embodiment, and fig. 8c is a chromatic aberration of magnification diagram of the endoscope optical system 100 in the fourth embodiment. As can be seen from fig. 8a, 8b and 8c, the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are smaller, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Fifth embodiment

Referring to fig. 9, fig. 9 is a schematic structural view of an endoscope optical system 100 in a fifth embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

the fourth lens element L4 has a concave object-side surface at a paraxial region and a concave image-side surface at a paraxial region.

The parameters of the endoscope optical system 100 in the fifth embodiment are given in table 9, wherein the definition of the parameters can be obtained from the first embodiment, and the detailed description is omitted herein.

TABLE 9

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

Table 10

Referring to fig. 10a, 10b and 10c, fig. 10a is an astigmatic diagram of an endoscope optical system 100 in a fifth embodiment, fig. 10b is a distortion diagram of the endoscope optical system 100 in the fifth embodiment, and fig. 10c is a chromatic aberration of magnification diagram of the endoscope optical system 100 in the fifth embodiment. As can be seen from fig. 10a, 10b and 10c, the sagittal curvature and meridional curvature of the endoscope optical system 100 are smaller, the curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Sixth embodiment

Referring to fig. 11, fig. 11 is a schematic structural view of an endoscope optical system 100 in a sixth embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

The parameters of the endoscope optical system 100 in the sixth embodiment are given in table 11, wherein the definition of the parameters can be obtained from the first embodiment, and the description thereof is omitted herein.

TABLE 11

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

Table 12

Referring to fig. 12a, 12b and 12c, fig. 12a is an astigmatic diagram of an endoscope optical system 100 in a sixth embodiment, fig. 12b is a distortion diagram of the endoscope optical system 100 in the sixth embodiment, and fig. 12c is a chromatic aberration of magnification diagram of the endoscope optical system 100 in the sixth embodiment. As can be seen from fig. 12a, 12b and 12c, the sagittal curvature and meridional curvature of the endoscope optical system 100 are smaller, the curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

Seventh embodiment

Referring to fig. 13, fig. 13 is a schematic structural view of an endoscope optical system 100 in a seventh embodiment. The endoscope optical 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 120, a third lens L3 having positive optical power, a fourth lens L4 having negative optical power, an optical filter 140, and a cover glass 130.

The parameters of the endoscope optical system 100 in the seventh embodiment are given in table 13, wherein the definition of the parameters can be obtained from the first embodiment, and the description thereof is omitted herein.

TABLE 13

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

TABLE 14

Referring to fig. 14a, 14b and 14c, fig. 14a is an astigmatic diagram of an endoscope optical system 100 in a seventh embodiment, fig. 14b is a distortion curve diagram of the endoscope optical system 100 in the seventh embodiment, and fig. 14c is a chromatic aberration of magnification curve diagram of the endoscope optical system 100 in the seventh embodiment. As can be seen from fig. 14a, 14b and 14c, the sagittal field curvature and meridional field curvature of the endoscope optical system 100 are smaller, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the whole field of view of the endoscope optical system 100 is smaller, the image distortion caused by the main beam is smaller, the imaging quality of the system is excellent, the chromatic aberration of magnification of the endoscope optical system 100 is well corrected, and the imaging quality is good.

In the first to seventh embodiments, the endoscope optical system 100 satisfies the data in table 15 below, and the meaning of each parameter below and the effect that can be obtained by satisfying the following data are referred to above.

TABLE 15

The present application also provides an objective lens module (not shown) comprising a photosensitive element and the endoscope optical system 100 according to any of the above embodiments. The photosensitive surface of the photosensitive element can be regarded as the imaging surface 110 of the endoscope optical 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 above-described endoscope optical system 100 is used in an objective lens module, which can achieve a small-sized design, a wide-angle characteristic, and a high imaging quality, thereby facilitating the application of the objective lens module in an endoscope.

The application also provides an endoscope (not shown in the figure), which comprises a shell and the objective lens module in any embodiment, wherein the objective lens module is arranged in the shell, and the shell can be a lens barrel of an endoscope objective lens. The endoscope may be applied in the medical field, for example, in medical diagnosis of a patient, and in particular, the endoscope includes, but is not limited to, an endoscope for observing digestive organs, bronchi, nasal cavities, throats, urinary organs, and uterus, and the endoscope may be a flexible tube endoscope. The endoscope objective lens is adopted in the endoscope, and the small-size design, the wide-angle characteristic and the high imaging quality can be achieved, so that when the endoscope is applied to the medical field, the damage to a patient can be reduced to the greatest extent, the image of a focus area can be obtained in a large range, the miss-checking risk is avoided, meanwhile, a lesion image with high definition can be formed, and the 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 application, which are described in detail and are not to be construed as limiting the scope of the claims. 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 application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. An endoscope optical system, comprising, in order from an object side to an image side along an optical axis:

4.08≤TTL/f≤4.52；

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

2. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

-0.9≤f1/f≤-0.7；

wherein f1 is the focal length of the first lens.

3. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

-9.9≤f4/f3≤-1.7；

4. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

1.45≤Bf/f≤1.72；

5. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

6. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

-3≤f2/f1≤-1.5；

7. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

1.51mm ^-1 ≤FNO/TTL≤1.7mm ^-1 ；

wherein FNO is the f-number of the endoscope optical system.

8. The endoscope optical system of claim 1, wherein the endoscope optical system satisfies the following conditional expression:

9. An objective lens module comprising a photosensitive element and the endoscope optical system according to any one of claims 1 to 8, the photosensitive element being disposed on an image side of the endoscope optical system.

10. An endoscope comprising the objective lens module of claim 9.