CN217332997U

CN217332997U - Endoscope head and endoscope imaging system

Info

Publication number: CN217332997U
Application number: CN202221025259.8U
Authority: CN
Inventors: 李艳萍; 郝希应; 张本好
Original assignee: Sunny Optical Zhejiang Research Institute Co Ltd
Current assignee: Sunny Optical Zhejiang Research Institute Co Ltd
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-08-30
Anticipated expiration: 2032-04-29

Abstract

The present disclosure provides an endoscope head, an endoscope imaging system, the endoscope head comprising: the lens comprises a first lens, a first prism, a second lens, a third lens, a fourth lens cemented with the third lens and a fifth lens which are arranged in sequence from an object side to an image side, wherein the first lens is a glass aspheric negative lens, and the image side surface of the first lens is a concave surface; the second lens has positive bending force, and the image side surface of the second lens is a convex surface; the third lens has positive bending force, and the object side surface of the third lens is a convex surface; the fourth lens has negative bending force, and the image side surface of the fourth lens is a concave surface; the fifth lens is a glass aspheric positive lens, the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface, so that the imaging of the endoscope head can have good image quality.

Description

Endoscope head and endoscope imaging system

Technical Field

The present disclosure relates to the field of optical elements, and in particular, to an endoscope head and an endoscope imaging system.

Background

Optical lenses are widely used, such as various traditional professional cameras, mobile phone lenses which have been increased explosively, monitoring lenses of vehicles, AR and VR lenses of emerging smart homes or wearable devices, miniature lenses for inspecting industrial devices, and the like.

In the medical field, because the internal tissues of a human body are difficult to observe, people design a medical endoscope head to probe into the human body, and a better treatment scheme is facilitated by observing whether pathological changes and other conditions exist. The endoscope imaging system can be used in minimally invasive surgery, and the minimally invasive surgery has the advantages of small damage to patients, reduction of pain of the patients in the surgery, short postoperative rehabilitation time and the like, so that the endoscope imaging system with better performance is beneficial to implementation of diagnosis and treatment, minimally invasive surgery and the like.

The optical lens is an indispensable component in various imaging systems, and directly influences the quality of imaging and even the realization and effect of an algorithm.

SUMMERY OF THE UTILITY MODEL

In view of the above, there is a need to provide an endoscope lens to solve at least one of the problems of large aperture, small field of view, large distortion and large chromatic aberration of the conventional lens.

The disclosed embodiments provide an endoscope comprising: the lens comprises a first lens, a first prism, a second lens, a third lens, a fourth lens cemented with the third lens and a fifth lens which are arranged in sequence from an object side to an image side, wherein the first lens is a glass aspheric negative lens, and the image side surface of the first lens is a concave surface; the second lens has positive bending force, and the image side surface of the second lens is a convex surface; the third lens has positive bending force, and the object side surface of the third lens is a convex surface; the fourth lens has negative bending force, and the image side surface of the fourth lens is a concave surface; the fifth lens element is a glass aspheric positive lens element, the object-side surface of the fifth lens element is a convex surface, and the image-side surface of the fifth lens element is a convex surface.

According to the arrangement, the first lens is configured into the glass aspheric negative lens, the increase of the field angle of the endoscope lens is facilitated, the caliber is reduced, the endoscope lens with a small caliber and a large field is realized by matching with other lenses, the fifth lens is configured with the glass aspheric positive lens besides the first lens, the aspheric mirror surface can improve the degree of freedom of the lens, the relative illumination of the endoscope lens is effectively improved, the number of the lenses of the endoscope lens with the same performance can be reduced to a certain degree, meanwhile, various materials with low refractive index and high dispersion can be selected from glass materials, the selection is more flexible than the actual selection of plastic materials, and the performance of the endoscope lens is further improved.

The lens with positive bending force and the lens with negative bending force are alternately combined, so that the aberration of each field of view is balanced, astigmatism, chromatic aberration and distortion can be effectively corrected, the obtained image data are suitable for conversion, and a three-dimensional effect is realized. In addition, the cemented lens can better correct chromatic aberration, so that the endoscopic lens can obtain better chromatic aberration characteristics in a larger wavelength range including visible light and fluorescence ranges.

In some embodiments, the first prism is removably attached to the second lens and the first lens is removably attached to the second lens.

So set up, the combination of at least five pieces of lens can realize better formation of image effect, and wherein third lens and fourth lens veneer can further reduce the colour difference. In addition, the endoscope provided by the embodiment of the disclosure realizes the replacement of the first prism by configuring the first prism to be detachably and rotatably connected with the second lens, and the first lens is detachably connected with the first prism.

In some embodiments, the endoscope head further comprises a second prism having a different turning angle to the optical axis than the first prism; the second prism is replaceable with the first prism.

According to the arrangement, a plurality of prisms with different steering angles can be arranged, and then the observation of the endoscope head on the visual field with different angles can be realized by replacing different prisms. Furthermore, by switching the prism, it is possible to realize that the endoscope head can observe the object side in the direction of 0 ° or 30 ° with respect to the imaging optical axis, and can realize that the image of the periphery can be observed in the direction of 30 °, for example.

In some embodiments, the second lens is a glass aspheric lens or a glass spherical lens, the third lens is a glass aspheric lens or a glass spherical lens, and the fourth lens is a glass aspheric lens or a glass spherical lens.

So set up, can select the material of these three lenses more nimble, the mirror surface sets up to the sphere can be when guaranteeing imaging performance reduce cost, under some circumstances, can guarantee under the condition of 160lp/mm that the mould of the modulation transfer function of 0.7 visual field is greater than 0.3, and sets up the mirror surface as the aspheric surface and can further promote the degree of freedom of endoscope design and promote image quality.

In some embodiments, the object side surface of the first lens is convex or concave.

In this way, the convex object-side surface of the first lens is beneficial to collecting object-side rays and ensuring the angle of field, and the concave object-side surface of the first lens is beneficial to mounting the endoscope head.

In some embodiments, the object side surface of the second lens is convex, planar, or concave.

So set up, because first prism is removable, the imaging effect of follow-up lens can be guaranteed to the object side face type through the control second lens. The object side surface of the second lens is a plane, and the second lens can be better matched with the first prism at the front end of the second lens in the assembling process and reduce assembling tolerance. The object side surface of the second lens is convex or concave, which is beneficial to reducing coma aberration and astigmatism of the endoscope lens, and simultaneously is beneficial to compressing the incident angle of light rays at the position of the diaphragm, so that the shape and the size of distortion are better controlled.

In some embodiments, the effective focal length f1 of the first lens satisfies: -2.3mm < f1< -1.5 mm; the effective focal length f2 of the second lens satisfies: 5.0mm < f2<6.5 mm.

By the arrangement, the focal power of the first lens and the focal power of the second lens can be effectively controlled in a reasonable interval, so that the two lenses bear the focal power required by the endoscope lens, the spherical aberration contributed by the two lenses is in a reasonable controllable range, and the image quality of an on-axis view field is better ensured. In addition, the relative illumination of the endoscope head can be ensured, and the relative illumination of the marginal field of view can be improved at least in a visible light range.

In some embodiments, the field angle FOV of the endoscope head satisfies: the FOV is more than or equal to 80 degrees.

By arranging the large angle of view, a larger range can be better observed under the endoscopic working environment.

In some embodiments, the absolute value of the distortion of the endoscope head in the diagonal direction of the imaging surface is less than 6%.

By controlling the distortion absolute value of the endoscope head, accurate images can be observed better, and the state of the observed part can be judged more accurately.

In some embodiments, the effective focal length f3 of the third lens satisfies: 3.5mm < f3<20.0 mm; the effective focal length f4 of the fourth lens satisfies: -30.0mm < f4< -2.0 mm.

By the arrangement, the cemented third lens and the cemented fourth lens can be better applied to light with the wavelength of 430 nm-880 nm.

In some embodiments, the effective focal length f5 of the fifth lens satisfies: 2.5mm < f5<5 mm.

With the arrangement, the contribution rate of the spherical aberration and astigmatism of the fifth lens can be controlled to a certain degree, so that the astigmatism amount and the spherical aberration generated by the front-end optical lens and the rear-end optical lens of the endoscope lens can be balanced, and the endoscope lens has good imaging quality.

In some embodiments, the relative illumination RI of the peripheral field of view of the endoscope head satisfies: RI > 80%.

By the arrangement, clear images can be better obtained in an endoscopic working environment by ensuring the relative illumination of the marginal field of view.

In some embodiments, the optical path length t12 from the image-side surface of the first lens to the object-side surface of the second lens satisfies: 4mm < t12<5 mm.

So set up, the first prism that sets up between first lens and the second lens can have better design space, and the first prism can be configured to satisfy different demands.

In some embodiments, the maximum diameter of each of the first through fifth lenses and the first prism is less than 3.2 mm.

By the arrangement, the sizes of all accessories of the endoscope head are controlled, so that the caliber of the endoscope head is better reduced, and meanwhile, enough design space is reserved for all the lenses to guarantee the imaging quality.

In some embodiments, the total effective focal length f of the endoscope head satisfies: f <1.9 mm.

By the arrangement, the endoscope head can have a smaller focal length, a larger depth of field range can be obtained, and a better imaging effect can be obtained under the conditions of different object distances.

In some embodiments, the first prism includes a turning prism, a light outgoing direction of the turning prism is adapted to correspond to the optical axis of the second lens, and a light incoming direction of the turning prism is adapted to correspond to the optical axis of the first lens, wherein the light outgoing direction of the turning prism intersects with the light incoming direction.

In this arrangement, by disposing the steering prism, the endoscope head can peen at the center of the field of view in the direction in which the imaging optical axes intersect.

In some embodiments, a turning prism comprises: a light incident surface; the first functional layer is used for transmitting light incident through the light incident surface; the second functional layer is used for reflecting the light transmitted by the first functional layer to the first functional layer, wherein the first functional layer is also used for reflecting the light reflected by the second functional layer; and a light exit surface for transmitting the light reflected by the first functional layer.

By the arrangement, the optical path in the first prism can be ensured to meet the design value, and good light transmission is realized for imaging.

In some embodiments, the endoscope head further comprises a quarter-wave plate located between the first functional layer and the second functional layer; and wherein the first functional layer comprises a polarization splitting film.

So set up, the light through polarization beam splitting film is the polarized light, avoids the polarized light to receive the interference of the light of polarization beam splitting film income light side etc. and avoids the light mutual interference of polarization beam splitting film light-emitting side through the setting of quarter wave plate to make the image information that the light that should turn to the prism transmission carried intact. The endoscope head has better imaging quality.

In another aspect, embodiments of the present disclosure provide an endoscopic imaging system comprising: the endoscope head described above; and the imaging chip is positioned on the imaging surface of the endoscope head.

With the arrangement, a larger observation visual field can be better obtained in a narrow space through the endoscope head. In addition, the endoscope imaging system can obtain brighter images.

In some embodiments, the endoscopic imaging system further comprises a protective glass on the object side of the first lens.

So set up, the protective glass can endure different endoscopic environment and be used for passing through the light for the endoscope head can work effectively for a long time.

Drawings

Fig. 1 is a schematic structural view of an endoscope head according to an embodiment of the present disclosure;

fig. 2 shows a color difference curve on the shaft of the endoscope head shown in fig. 1;

fig. 3 is a graph showing the relative illuminance of the endoscope head of fig. 1;

fig. 4 shows a modulation transfer function curve of the endoscope head of fig. 1;

FIG. 5 is a graph showing an astigmatism curve of the endoscope head of FIG. 1;

fig. 6 shows a distortion curve of the endoscope head shown in fig. 1;

fig. 7 is another schematic structural view of an endoscope head according to an embodiment of the present disclosure;

FIG. 8 is an enlarged schematic view of the first prism of FIG. 7;

FIG. 9 is an enlarged schematic view at A of FIG. 8;

fig. 10 is a schematic structural view of an endoscope head according to another embodiment of the present disclosure;

fig. 11 shows a color difference curve on the shaft of the endoscope head shown in fig. 10;

fig. 12 is a graph showing the relative illuminance of the endoscope head of fig. 10;

fig. 13 shows a modulation transfer function curve of the endoscope head of fig. 10;

fig. 14 shows an astigmatism curve of the endoscope head of fig. 10;

fig. 15 shows a distortion curve of the endoscope head shown in fig. 10;

fig. 16 is a schematic structural view of an endoscope head according to another embodiment of the present disclosure;

fig. 17 shows a color difference curve on the shaft of the endoscope head shown in fig. 16;

fig. 18 shows a relative illuminance curve for the endoscope head of fig. 16;

fig. 19 shows a modulation transfer function curve of the endoscope head of fig. 16;

fig. 20 shows an astigmatism curve of the endoscope head shown in fig. 16;

fig. 21 shows a distortion curve of the endoscope head shown in fig. 16;

fig. 22 is a schematic structural view of an endoscope head according to another embodiment of the present disclosure;

fig. 23 shows a color difference curve on the shaft of the endoscope head shown in fig. 22;

fig. 24 is a graph showing the relative illuminance of the endoscope head of fig. 22;

fig. 25 shows a modulation transfer function curve of the endoscope head of fig. 22;

fig. 26 shows an astigmatism curve of the endoscope head of fig. 22;

fig. 27 shows a distortion curve of the endoscope head of fig. 22;

fig. 28 is a schematic structural view of an endoscope head according to another embodiment of the present disclosure;

fig. 29 shows a color difference curve on the shaft of the endoscope head shown in fig. 28;

fig. 30 is a graph showing the relative illuminance of the endoscope head of fig. 28;

fig. 31 shows a modulation transfer function curve of the endoscope head of fig. 28;

fig. 32 shows an astigmatism curve of the endoscope head of fig. 28;

fig. 33 shows a distortion curve of the endoscope head shown in fig. 28.

Reference numerals: p1, cover glass; p2, first lens; p3, a first prism; p3', a second prism; p31, a first mirror; p32, a second mirror; p33, third mirror; p4, third lens; p5, third lens; p6, fourth lens; p7, fifth lens; p8, third prism; p9, optical filters; s0, imaging surface; s1, the object side surface of the first lens; s2, an image side surface of the first lens; s3, a light incident surface; s4, emitting a light surface; s5, the object side surface of the second lens; s6, an image side surface of the second lens; s7, the object side surface of the third lens; s8, gluing the surface; s9, an image side surface of the fourth lens element; s10, an object side surface of the fifth lens; s11, an image side surface of the fifth lens element; s12, the object side surface of the third prism; s13, the image side surface of the third prism; s14, the image side surface of the optical filter; s15, a first functional layer; s151, a first medium layer; s152, an adhesive layer; s153, a second medium layer; s16, a second functional layer; x1, imaging optic axis; x2, viewing direction optical axis.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

It will be understood that when an element is referred to as being "mounted on" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.

The dimensions of the structures shown in the figures herein do not represent actual dimensions and may be adjusted as desired for actual production. The terms "upper", "lower", "left", "right", and the like as used herein refer to the orientation in the drawings and, unless otherwise specifically indicated, should not be construed as limiting the product in actual use.

The first, second, third, etc. are used herein only to distinguish the same features, and it is understood that the first lens may also be referred to herein as the second lens, and the second lens may also be referred to herein as the first lens.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. For example, reference herein to a mirror and its parameters, without being explicitly limited, describe a portion of the proximal optical axis. The terminology used herein in the description of the disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1, an embodiment of the present disclosure provides an endoscope head including a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. As shown in fig. 1, the imaging optical axis X1 is perpendicular to the imaging surface S0. The protective glass P1 to the optical filter P9 may be disposed in order from the object side to the image side along the imaging optical axis X1.

The first lens element P2 with negative refractive power can be made of glass, the object-side surface S1 of the first lens element can be convex, the image-side surface S2 of the first lens element can be concave, and the mirror surface of the first lens element P2 can be aspheric. The second lens element P4 can have positive refractive power and can be made of glass, the object-side surface S5 of the second lens element can be a plane, the image-side surface S6 of the second lens element can be a convex surface, and specifically, the mirror surface of the second lens element P4 can be a spherical surface. The third lens P5 and the fourth lens P6 are cemented into a double cemented glass spherical lens. Specifically, the third lens element P5 with positive refractive power can be made of glass, and the object-side surface S7 of the third lens element can be convex. The fourth lens element P6 can have negative refractive power and can be made of glass, and the image-side surface S9 of the fourth lens element can be concave. The object-side surface S7, the bonding surface S8 and the image-side surface S9 of the third lens element may be spherical. The fifth lens element P7 with positive refractive power can be made of glass, the object-side surface S10 of the fifth lens element can be convex, the image-side surface S11 of the fifth lens element can be convex, and the mirror surface of the fifth lens element P7 can be aspheric.

The first prism P3 serves to transmit light passing through the first lens P2 toward the second lens P4. The first prism P3 includes an incident surface S3 and an emergent surface S4, and the incident surface S3 and the emergent surface S4 may be perpendicular to the imaging optical axis X1, respectively. The third prism P8 may be made of glass, the object-side surface S12 of the third prism may be a plane, and the image-side surface S13 of the third prism may be a plane and attached to the filter P9. The image side surface S14 of the filter may be a plane surface. The stop STO may be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 may sequentially pass through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then be imaged on the imaging surface S0.

The angle of view FOV of the endoscope head shown in fig. 1 may be 80 °, and the total effective focal length f may be 1.87. The following table 1 shows various parameters of the endoscope head, wherein the unit of curvature radius, distance, effective focal length is mm, as shown in table 1:

TABLE 1

Flour mark	Surface type	Radius of curvature	Distance between two adjacent devices	Refractive index	Abbe number	Effective focal length
							P1 item side	Spherical surface	All-round	0.5500	1.77	72.24
S1	Aspherical surface	66.0120	0.4000	1.77	47.17	-2.09
							S2	Aspherical surface	1.5710	0.4885
S3	Spherical surface	All-round	4.2000	2.0	24.44
							S4	Spherical surface	All-round	0.0300
STO	Spherical surface	All-round	0.3000	1.92	18.89	6.39
							S5	Spherical surface	Go to nothing	0.7350
S6	Spherical surface	-5.9000	0.7580
							S7	Spherical surface	6.1760	1.1120	1.59	68.35	17.35
S8	Spherical surface	-6.1760	0.4800	1.84	23.78	-28.30
							S9	Spherical surface	6.1760	0.2842
S10	Aspherical surface	5.0770	1.2670	1.49	82.51	4.69
							S11	Aspherical surface	-2.3320	2.7064
S12	Spherical surface	All-round	3.3000	1.76	52.34
							S13	Spherical surface	All-round	0.4000	1.52	64.21
S14	Spherical surface	All-round	0.0370
							S0		All-round

The conic coefficients and high-order term coefficients a4, a6, A8 and a10 that satisfy the aspherical surface shape of the endoscope head are shown in table 2.

TABLE 2

Fig. 2 shows an on-axis color difference curve of the endoscope head. Fig. 3 shows a relative illuminance curve of the endoscope head. Fig. 4 shows a modulation transfer function curve of the endoscope head. Fig. 5 shows an astigmatism curve of the endoscope head. Fig. 6 shows a distortion curve of the endoscope head. The relative illumination RI of the endoscope head is larger than 0.8, the MTFS and MTFT in a 0.7 view field are both larger than 0.3 under the condition of 160lp/mm, and in addition, the distortion resistance and the chromatic aberration performance are good.

Illustratively, the first prism P3 of the endoscope head is detachably connected with the second lens P4, and the first lens P2 is detachably connected with the second lens P4. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

As shown in fig. 7, the endoscope head may further include a second prism P3'. For example, the second prism P3 'and the first prism P3 can be replaced, and the optical path of the second prism P3' and the first prism P3 are the same. In other embodiments, the endoscope head may also be considered to include only the second prism P3', which in turn may be referred to as the first prism.

Illustratively, the endoscope head may include a plurality of sets of protective glass P1 and a first lens P2, one set of protective glass P1 and a first lens P2 fixedly connected to a first prism P3, and another set of protective glass P1 and a first lens P2 fixedly connected to a second prism P3'.

The second prism P3' is a turning prism, and the perpendicular to the light incident surface S3 is parallel to the viewing direction optical axis X2 of the first lens P2. The viewing direction optical axis X2 intersects the imaging optical axis X1, for example, at a 30 angle. By configuring the first lens P2 and the first prism P3 and the second prism P3' to be detachably connected relative to the second lens P4, the detection of different angle views by the endoscope head is realized.

As shown in fig. 8, the second prism P3' includes a first mirror P31, a second mirror P32, and a third mirror P33. The first mirror P31 includes an incident surface S3, the second mirror P32 can be glued to the first mirror P31 and includes an emergent surface S4, and the third mirror P33 is glued to the second mirror P32 on the side away from the first mirror P31. The second prism P3' also includes a first functional layer S15 located between the second mirror P32 and the first mirror P31, and a second functional layer S16 located between the second mirror P32 and the third mirror P33. Light incident along the viewing direction optical axis X2 may enter the second mirror P32 through the first mirror P31 and the first functional layer S15 and be directed toward the second functional layer S16. The second functional layer S16 may reflect light passing through the first functional layer S15 toward the first functional layer S15. The first functional layer S15 may reflect the light reflected by the second functional layer S16 toward the light emitting surface S4. Illustratively, the light is totally internally reflected at the second functional layer S16 and the first functional layer S15. Further, the first functional layer S151 and the first mirror P31 collectively function to totally internally reflect light, and the second functional layer S16 and the third mirror P31 collectively function to totally internally reflect light.

Illustratively, as shown in FIG. 9, the first functional layer S15 includes a first dielectric layer S151, a glue layer S152, and a second dielectric layer S153 disposed in that order from the first mirror P31 to the second mirror P32. The first dielectric layer S151 can be plated on the first mirror P31, the second dielectric layer S153 can be plated on the second mirror P32, and then the two are glued by the glue layer S152. There may be no air gap between the first mirror P31 and the second mirror P32, so that the second prism P3' has better temperature resistance. The endoscope head can maintain the use performance even at the high temperature of 134 ℃. In addition, the second prism P3' has better impact resistance and higher reliability.

Illustratively, the material of the first dielectric layer S151 includes aluminum oxide (e.g., Al) ₃ O ₂ ) The material of the second dielectric layer S153 includes silicon oxide (e.g. SiO) ₂ ). The material of the second functional layer S16 may include a metal. In other embodiments, the first dielectric layer S151 includes a polarization splitting dielectric film and the second dielectric layer S153 includes 1/4 wave plates.

In some embodiments, the first functional layer S15 includes a polarizing dichroic film with a quarter wave plate disposed between the first functional layer S15 and the second functional layer S16.

In the endoscope head provided by the embodiment of the present disclosure, the first prism may further make the viewing direction optical axis and the imaging optical axis form other angles. Illustratively, the third prism may be provided as a right-angled prism.

Fig. 10 illustrates another endoscope head of an embodiment of the present disclosure. The endoscope head includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging surface S0. The protective glass P1 to the filter P9 may be disposed in order from the object side to the image side along the imaging optical axis.

The first lens element P2 can have a negative refractive power and can be made of glass, the object-side surface S1 of the first lens element can be concave, and the image-side surface S2 of the first lens element can be concave, and specifically, the specular surface of the first lens element P2 can be aspheric and can have an inflection point. The second lens element P4 can have positive refractive power and can be made of glass, the object-side surface S5 of the second lens element can be a plane, the image-side surface S6 of the second lens element can be a convex surface, and specifically, the mirror surface of the second lens element P4 can be a spherical surface. The third lens P5 and the fourth lens P6 are cemented into a double cemented glass spherical lens. Specifically, the third lens element P5 can have a positive refractive power and can be made of glass, and the object-side surface S7 of the third lens element can be convex. The fourth lens element P6 with negative refractive power can be made of glass, and the image-side surface S9 of the fourth lens element can be concave. The object-side surface S7, the bonding surface S8 and the image-side surface S9 of the third lens element may be spherical. The fifth lens element P7 with positive refractive power can be made of glass, the object-side surface S10 of the fifth lens element can be convex, the image-side surface S11 of the fifth lens element can be convex, and the mirror surface of the fifth lens element P7 can be aspheric.

The first prism P3 serves to transmit light passing through the first lens P2 toward the second lens P4. The first prism P3 includes a light incident surface S3 and a light emitting surface S4, and the light incident surface S3 and the light emitting surface S4 may be perpendicular to the imaging optical axis, respectively. The third prism P8 may be made of glass, the object-side surface S12 of the third prism may be a plane, and the image-side surface S13 of the third prism may be a plane and attached to the filter P9. The image side S14 of the filter may be planar. The stop STO may be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 may sequentially pass through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then be imaged on the imaging surface S0.

The angle of view FOV of the endoscope head shown in fig. 10 may be 80 °, and the total effective focal length f may be 1.88. The following table 3 shows various parameters of the endoscope head, wherein the unit of curvature radius, distance, effective focal length is mm, as shown in table 3:

TABLE 3

The conic coefficients and high-order term coefficients a4, a6, A8 and a10 that satisfy the aspherical surface shape of the endoscope head are shown in table 4.

TABLE 4

Fig. 11 shows an on-axis color difference curve of the endoscope head. Fig. 12 shows a relative illuminance curve of the endoscope head. Fig. 13 shows a modulation transfer function curve of the endoscope head. Fig. 14 shows an astigmatism curve of the endoscope head. Fig. 15 shows a distortion curve of the endoscope head. The relative illumination RI of the endoscope head is larger than 0.8, the MTFS and MTFT in a 0.7 view field are both larger than 0.3 under the condition of 160lp/mm, and in addition, the distortion resistance and the chromatic aberration performance are good.

Fig. 16 illustrates another endoscope head of an embodiment of the present disclosure. The endoscope head includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging surface S0. The protective glass P1 to the filter P9 may be disposed in order from the object side to the image side along the imaging optical axis.

The first lens element P2 with negative refractive power can be made of glass, the object-side surface S1 of the first lens element can be convex, and the image-side surface S2 of the first lens element can be concave. The second lens element P4 with positive refractive power can be made of glass, the object-side surface S5 of the second lens element can be convex, the image-side surface S6 of the second lens element can be convex, and the mirror surface of the second lens element P4 can be spherical. The third lens P5 and the fourth lens P6 are cemented into a double cemented glass spherical lens. Specifically, the third lens element P5 can have a positive refractive power and can be made of glass, and the object-side surface S7 of the third lens element can be convex. The fourth lens element P6 can have negative refractive power and can be made of glass, and the image-side surface S9 of the fourth lens element can be concave. The object-side surface S7, the bonding surface S8 and the image-side surface S9 of the third lens element may be spherical. The fifth lens element P7 with positive refractive power can be made of glass, the object-side surface S10 of the fifth lens element can be convex, the image-side surface S11 of the fifth lens element can be convex, and the mirror surface of the fifth lens element P7 can be aspheric.

The first prism P3 serves to transmit light passing through the first lens P2 toward the second lens P4. The first prism P3 includes an incident surface S3 and an emergent surface S4, and the incident surface S3 and the emergent surface S4 may be perpendicular to the imaging optical axis, respectively. The third prism P8 may be made of glass, the object side surface S12 of the third prism may be a plane, and the image side surface S13 of the third prism may be a plane and attached to the filter P9. The image side S14 of the filter may be planar. The stop STO may be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 may sequentially pass through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then be imaged on the imaging surface S0.

The angle of view FOV of the endoscope head shown in fig. 16 may be 80 °, and the total effective focal length f may be 1.88. The following table 5 shows the parameters of the endoscope head, wherein the unit of curvature radius, distance and effective focal length is mm, as shown in table 5:

TABLE 5

Flour mark	Surface type	Radius of curvature	Distance between two adjacent plates	Refractive index	Abbe number	Effective focal length
							P1 item side	Spherical surface	All-round	0.5500	1.77	72.24
S1	Aspherical surface	6.8811	0.3995	1.77	47.17	-1.89
							S2	Aspherical surface	1.2191	0.5195
S3	Spherical surface	Go to nothing	4.2000	2.0	24.44
							S4	Spherical surface	Go to nothing	0.0300
STO	Spherical surface	All-round	0.3000	1.92	18.89	5.61
							S5	Spherical surface	75.3675	0.7464
S6	Spherical surface	-5.6868	0.6718
							S7	Spherical surface	4.6604	1.4038	1.59	68.35	4.16
S8	Spherical surface	-4.6604	0.7809	1.84	23.78	-2.23
							S9	Spherical surface	4.6604	0.1532
S10	Aspherical surface	3.6276	1.6935	1.49	82.51	3.10
							S11	Aspherical surface	-2.2695	3.0003
S12	Spherical surface	All-round	3.3000	1.76	52.34
							S13	Spherical surface	Go to nothing	0.3000	1.52	64.21
S14	Spherical surface	Go to nothing	0.0450
							S0		All-round

The conic coefficients and high-order term coefficients a4, a6, A8 and a10 that satisfy the aspherical surface shape of the endoscope head are shown in table 6.

TABLE 6

Fig. 17 shows an on-axis color difference curve of the endoscope head. Fig. 18 shows a relative illuminance curve of the endoscope head. Fig. 19 shows a modulation transfer function curve of the endoscope head. Fig. 20 shows an astigmatism curve of the endoscope head. Fig. 21 shows a distortion curve of the endoscope head. The relative illumination RI of the endoscope head is larger than 0.8, the MTFS and the MTFT in a 0.7 field of view are both better under the condition of 160lp/mm, and in addition, the distortion resistance and the chromatic aberration performance are good.

Fig. 22 shows another endoscope head of an embodiment of the present disclosure. The endoscope head includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging surface S0. The protective glass P1 to the filter P9 may be disposed in order from the object side to the image side along the imaging optical axis.

The first lens element P2 with negative refractive power can be made of glass, the object-side surface S1 of the first lens element can be convex, and the image-side surface S2 of the first lens element can be concave. The second lens element P4 can have positive refractive power and can be made of glass, the object-side surface S5 of the second lens element can be concave, the image-side surface S6 of the second lens element can be convex, and the mirror surface of the second lens element P4 can be spherical. The third lens P5 and the fourth lens P6 are cemented into a double cemented glass spherical lens. Specifically, the third lens element P5 with positive refractive power can be made of glass, and the object-side surface S7 of the third lens element can be convex. The fourth lens element P6 can have negative refractive power and can be made of glass, and the image-side surface S9 of the fourth lens element can be concave. The surface types of the object-side surface S7, the bonding surface S8, and the image-side surface S9 of the third lens element may be spherical. The fifth lens element P7 with positive refractive power can be made of glass, the object-side surface S10 of the fifth lens element can be convex, the image-side surface S11 of the fifth lens element can be convex, and the mirror surface of the fifth lens element P7 can be aspheric.

The angle of view FOV of the endoscope head shown in fig. 22 may be 80 °, and the total effective focal length f may be 1.88. The following table 7 shows various parameters of the endoscope head, wherein the unit of curvature radius, distance, effective focal length is mm, as shown in table 7:

TABLE 7

Flour mark	Surface type	Radius of curvature	Distance between two adjacent devices	Refractive index	Abbe number	Effective focal length
							P1 item side	Spherical surface	All-round	0.5500	1.77	72.24
S1	Aspherical surface	7.3503	0.3997	1.77	47.17	-1.89
							S2	Aspherical surface	1.2348	0.5237
S3	Spherical surface	All-round	4.2000	2.0	24.44
							S4	Spherical surface	All-round	0.3000
STO	Spherical surface	All-round	0.0300	1.92	18.89	5.87
							S5	Spherical surface	-500.0000	0.7356
S6	Spherical surface	-5.4928	0.5200
							S7	Spherical surface	4.8598	1.4481	1.59	68.35	4.34
S8	Spherical surface	-4.8598	1.2213	1.84	23.78	-2.28
							S9	Spherical surface	4.8598	0.1240
S10	Aspherical surface	3.4764	1.5746	1.49	82.51	3.07
							S11	Aspherical surface	-2.3067	3.0003
S12	Spherical surface	All-round	3.3000	1.76	52.34
							S13	Spherical surface	All-round	0.3000	1.52	64.21
S14	Spherical surface	All-round	0.0450
							S0		Go to nothing

The conic coefficients and high-order term coefficients a4, a6, A8 and a10 that satisfy the aspherical surface shape of the endoscope head are shown in table 8.

TABLE 8

Fig. 23 shows an on-axis color difference curve of the endoscope head. Fig. 24 shows a relative illuminance curve of the endoscope head. Fig. 25 shows a modulation transfer function curve of the endoscope head. Fig. 26 shows an astigmatism curve of the endoscope head. Fig. 27 shows a distortion curve of the endoscope head. The relative illumination RI of the endoscope head is larger than 0.8, the MTFS and the MTFT in a 0.7 field of view are both better under the condition of 160lp/mm, and in addition, the distortion resistance and the chromatic aberration performance are good.

Fig. 28 shows another endoscope head of an embodiment of the present disclosure. The endoscope head comprises a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third lens P8 and a filter P9. The imaging optical axis is perpendicular to the imaging surface S0. The protective glass P1 to the filter P9 may be disposed in order from the object side to the image side along the imaging optical axis.

The first lens element P2 with negative refractive power can be made of glass, the object-side surface S1 of the first lens element can be convex, the image-side surface S2 of the first lens element can be concave, and the surface of the first lens element P2 can be aspheric. The second lens element P4 can have positive refractive power and can be made of glass, the object-side surface S5 of the second lens element can be concave, the image-side surface S6 of the second lens element can be convex, and the mirror surface of the second lens element P4 can be spherical. The third lens P5 and the fourth lens P6 are cemented into a double cemented glass spherical lens. Specifically, the third lens element P5 can have a positive refractive power and can be made of glass, and the object-side surface S7 of the third lens element can be convex. The fourth lens element P6 can have negative refractive power and can be made of glass, and the image-side surface S9 of the fourth lens element can be concave. The object-side surface S7, the bonding surface S8 and the image-side surface S9 of the third lens element may be spherical. The fifth lens element P7 with positive refractive power can be made of glass, the object-side surface S10 of the fifth lens element can be convex, the image-side surface S11 of the fifth lens element can be convex, and the mirror surface of the fifth lens element P7 can be aspheric.

The angle of view FOV of the endoscope head shown in fig. 28 may be 84 °, and the total effective focal length f may be 1.74. The following table 9 shows various parameters of the endoscope head, wherein the unit of curvature radius, distance, effective focal length is mm, as shown in table 9:

TABLE 9

Flour mark	Surface type	Radius of curvature	Distance between two adjacent devices	Refractive index	Abbe number	Effective focal length
							P1 item side	Spherical surface	All-round	0.5500	1.77	72.24
S1	Aspherical surface	-66.5728	0.3993	1.77	47.17	-1.61
							S2	Aspherical surface	1.3306	0.5589
S3	Spherical surface	All-round	4.2000	2.0	24.44
							S4	Spherical surface	All-round	0.0300
STO	Spherical surface	All-round	0.3000	1.92	18.89	5.15
							S5	Spherical surface	-14.7538	0.9363
S6	Spherical surface	-3.7747	0.7764
							S7	Spherical surface	4.2670	1.1214	1.59	68.35	3.78
S8	Spherical surface	-4.2670	0.5630	1.84	23.78	-2.06
							S9	Spherical surface	4.2670	0.1134
S10	Aspherical surface	2.7341	2.6699	1.49	82.51	3.39
							S11	Aspherical surface	-2.9776	3.0014
S12	Spherical surface	All-round	3.3000	1.76	52.34
							S13	Spherical surface	All-round	0.3000	1.52	64.21
S14	Spherical surface	All-round	0.0450
							S0		All-round

The conic coefficients and high-order term coefficients a4, a6, A8, and a10 that satisfy the aspherical surface shape in the endoscope head are shown in table 10.

Watch 10

Fig. 29 shows an on-axis color difference curve of the endoscope head. Fig. 30 shows a relative illuminance curve of the endoscope head. Fig. 31 shows a modulation transfer function curve of the endoscope head. Fig. 32 shows an astigmatism curve of the endoscope head. Fig. 33 shows a distortion curve of the endoscope head. The relative illumination RI of the endoscope head is larger than 0.8, the MTFS and the MTFT in a 0.7 field of view are both better under the condition of 160lp/mm, and in addition, the distortion resistance and the chromatic aberration performance are good.

The present disclosure also provides an endoscopic imaging system, which includes an endoscopic lens and an imaging chip disposed on an imaging surface. The endoscope head can be any of the endoscope heads described above. The imaging chip may include a Complementary Metal Oxide Semiconductor (CMOS) or a Charge Coupled Device (CCD) for converting light transmitted from the endoscope head into an electrical signal.

The endoscope head may include a first lens, a first prism, a second lens, a third lens, a fourth lens cemented with the third lens, and a fifth lens arranged in order from an object side to an image side. The first lens is a glass aspheric negative lens, the object side surface of which is a convex surface or a concave surface, and the image side surface of which is a concave surface. The second lens is a glass spherical positive lens, the object side surface of the second lens is a convex surface, a concave surface or a plane, and the image side surface of the second lens is a convex surface. The third lens is a glass spherical positive lens, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a convex surface jointed with the fourth lens. The fourth lens is a glass spherical negative lens, the object side surface of the fourth lens is a concave surface jointed with the third lens, and the image side surface of the fourth lens is a concave surface. The fifth lens element is a glass aspheric positive lens element with a convex object-side surface and a convex image-side surface.

Illustratively, the first prism may be detachably coupled to the second lens, and the first lens may be glued to the first prism.

In some embodiments, the effective focal length f1 of the first lens satisfies: -2.3mm < f1< -1.5mm, further satisfying: -2.1mm < f1< -1.6 mm. The effective focal length f2 of the second lens satisfies: 5.0mm < f2<6.5 mm. Exemplarily, the field angle FOV of the endoscope head satisfies: the FOV is more than or equal to 80 degrees. Illustratively, the absolute value of distortion of the endoscope head in the diagonal direction of the imaging plane is less than 6%.

In some embodiments, the effective focal length f3 of the third lens satisfies: 3.5mm < f3<20.0mm, further 3.7mm < f3<17.4mm can be satisfied. The effective focal length f4 of the fourth lens satisfies: -30.0mm < f4<0mm, further satisfying: -28.0mm < f4< -2.0 mm. Illustratively, the relative illuminance RI of the marginal field of view of the endoscope head satisfies: RI > 80%.

In some embodiments, the optical path length t12 from the image-side surface of the first lens to the object-side surface of the second lens satisfies: 4mm < t12<5mm, further satisfying: 4.4mm < t12<4.6 mm. The maximum diameter of each of the first lens, the fifth lens and the first prism is less than 3.2mm, wherein the maximum diameter of the first prism refers to the maximum diagonal length of the cross section projection of the first prism on the optical axis of the second lens. The first lens to the fifth lens refer to the maximum diameters of the whole body with respect to the own axis.

In some embodiments, the effective focal length f5 of the fifth lens satisfies: 2.5mm < f5<5mm, further satisfying: 3.0mm < f5<4.7 mm. Illustratively, the total effective focal length f of the endoscope head satisfies: f <1.9 mm. The object distance range of the endoscope imaging system during operation can be between 20mm and 200 mm.

Illustratively, the first prism includes a turning prism for turning the optical path. The light outgoing direction of the steering prism is suitable for corresponding to the optical axis of the second lens, and the light incoming direction is suitable for corresponding to the optical axis of the first lens. The endoscopic imaging system may further include a protective glass on the object side of the first lens.

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

The above-mentioned embodiments only express several implementation modes of the present disclosure, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the patent disclosure. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the concept of the present disclosure, and these changes and modifications are all within the scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the appended claims.

Claims

1. An endoscope head comprising a first lens, a first prism, a second lens, a third lens, a fourth lens cemented with the third lens, and a fifth lens arranged in this order from an object side to an image side,

the first lens is a glass aspheric negative lens, and the image side surface of the first lens is a concave surface;

the second lens has positive bending force, and the image side surface of the second lens is a convex surface;

the third lens has positive bending force, and the object side surface of the third lens is a convex surface;

the fourth lens has negative bending force, and the image side surface of the fourth lens is a concave surface;

the fifth lens is a glass aspheric positive lens, the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface.

2. The endoscope head of claim 1, wherein the first prism is removably coupled to the second lens, and the first lens is removably coupled to the second lens.

3. The endoscope head of claim 2, wherein the endoscope head further comprises a second prism having a different turning angle to an optical axis than the first prism;

the second prism is replaceable with the first prism.

4. The endoscope head of claim 1, wherein the second lens is a glass aspheric lens or a glass spherical lens, the third lens is a glass aspheric lens or a glass spherical lens, and the fourth lens is a glass aspheric lens or a glass spherical lens.

5. The endoscope head of claim 1, wherein the object side surface of the first lens is convex or concave.

6. The endoscope head of claim 1, wherein the object side surface of the second lens is convex, planar, or concave.

7. The endoscope head of claim 1, wherein the first lens has an effective focal length f1 satisfying: -2.3mm < f1< -1.5 mm;

the effective focal length f2 of the second lens satisfies: 5.0mm < f2<6.5 mm.

8. The endoscope head of claim 1, wherein a field angle FOV of the endoscope head satisfies: the FOV is more than or equal to 80 degrees.

9. The endoscope head of claim 1, wherein the endoscope head has an absolute value of distortion in an imaging plane diagonal direction of less than 6%.

10. The endoscope head of claim 1, wherein the third lens has an effective focal length f3 satisfying: 3.5mm < f3<20.0 mm;

the effective focal length f4 of the fourth lens satisfies: -30.0mm < f4<0 mm.

11. The endoscope head of claim 1, wherein the relative illuminance RI of the marginal field of view of the endoscope head satisfies: RI > 80%.

12. The endoscope head of claim 1, wherein an optical path length t12 from an image side surface of the first lens to an object side surface of the second lens satisfies: 4mm < t12<5 mm.

13. The endoscope head of claim 1, wherein a maximum diameter of each of the first through fifth lenses and the first prism is less than 3.2 mm.

14. The endoscope head of claim 1, wherein the endoscope head has a total effective focal length f that satisfies: f <1.9 mm.

15. The endoscope head of any one of claims 1-14, wherein the first prism comprises a turning prism, a light exit direction of the turning prism adapted to correspond to an optical axis of the second lens, a light entrance direction of the turning prism adapted to correspond to an optical axis of the first lens,

the light outgoing direction of the steering prism is intersected with the light incoming direction.

16. The endoscope head of claim 15, wherein the turning prism comprises:

a light incident surface;

the first functional layer is used for transmitting the light incident through the light incident surface;

a second functional layer for reflecting light transmitted by the first functional layer towards the first functional layer, wherein the first functional layer is further for reflecting light reflected by the second functional layer; and

and the light-emitting surface is used for transmitting the light reflected by the first functional layer.

17. The endoscope head of claim 16, wherein the endoscope head further comprises a quarter wave plate located between the first functional layer and the second functional layer; and

wherein the first functional layer comprises a polarization splitting film.

18. An endoscopic imaging system, comprising:

the endoscope head of any one of claims 1 to 17; and

and the imaging chip is positioned on the imaging surface of the endoscope head.

19. The endoscopic imaging system of claim 18, further comprising a cover glass on the object side of the first lens.