CN220626762U - Wide-angle endoscope objective lens optical system - Google Patents

Abstract

The utility model relates to the field of objective optics, in particular to an objective optical system of a wide-angle endoscope. The optical axis comprises the following components from an object plane to an image plane in sequence: the first lens is provided with negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface; the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; the optical system has a wide field angle through the combined design of different focal lengths of the concave-convex lens, improves resolution and relative illumination under the condition of meeting the requirements of wide angle and definition, obviously improves definition and picture illumination uniformity, and is beneficial to doctors to check diseases.

Description

Wide-angle endoscope objective lens optical system

Technical Field

The utility model relates to the field of objective optics, in particular to an objective optical system of a wide-angle endoscope.

Background

With the progress of medical instruments in the prior art, a capsule endoscope is a medical instrument for examining human intestinal tracts, is used for snooping the health conditions of human intestines, stomach and esophagus parts, and is used for helping doctors to diagnose diseases of digestive tract systems of patients. In the detection process, the imaging definition, resolution and imaging range of the photo are important points, so the inventor provides a wide-angle endoscope objective optical system to obtain a larger imaging range and higher imaging definition and resolution.

Disclosure of Invention

Aiming at the problems in the prior art, the utility model provides a wide-angle endoscope objective optical system with a large field angle and high definition.

The utility model relates to an objective optical system of a wide-angle endoscope, which sequentially comprises the following components from an object plane to an image plane along an optical axis:

the first lens is provided with negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface;

the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

the focal power of the first lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.7< Φ1/Φ < -0.45;

the focal power of the second lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: 0.9< phi 2/phi <1.20;

the focal power of the third lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.96< Φ3/Φ < -0.5;

wherein: Φ1 is the optical power of the first lens, unit diopter; Φ2 is the optical power of the second lens, the unit diopter; Φ3 is the optical power of the third lens, unit diopter; phi is the optical power of the wide-angle endoscope objective lens optical system and the unit diopter.

Preferably, an aperture stop is further included that is disposed between the first lens and the second lens.

Preferably, the lens further comprises an infrared filter arranged at one end of the image side surface of the third lens.

Preferably, the method further comprises: FOV > 150 degrees;

wherein: the FOV is the field angle of the wide-angle endoscope objective optical system in degrees.

Preferably, the method further comprises: CRA is more than or equal to 24.5 degrees and less than or equal to 25.5 degrees;

wherein: CRA is the angle of incidence of principal ray of the image plane of the wide angle endoscope objective optical system, in degrees.

Preferably, the method further comprises: ET1/CT1 < 2.5; ET2/CT2 is more than 0.5 and less than 0.6; ET3/CT3 is more than 1.8 and less than 1.9;

wherein: ET1 is the edge thickness of the first lens in mm; CT1 is the center thickness of the first lens, in mm;

ET2 is the edge thickness of the second lens in mm; CT2 is the center thickness of the second lens, in mm;

ET3 is the edge thickness of the third lens in mm; CT3 is the center thickness of the third lens in mm.

Preferably, the method further comprises: EFL/EPD < 3.42;

wherein: EFL is the effective focal length of the wide-angle endoscope objective optical system, in mm; EPD is the entrance pupil diameter in mm of the wide angle endoscope objective optical system.

Preferably, the method further comprises: TTL/EFL is less than 5.23;

wherein TTL is the total optical length of the wide-angle endoscope objective optical system, and the unit is mm; EFL is the effective focal length of the wide angle endoscope objective optical system in mm.

Preferably, the method further comprises: OFL/TTL is more than 0.16 and less than 0.18;

wherein OFL is the optical back focus of the wide-angle endoscope objective optical system, and the unit is mm; TTL is the total optical length in mm of the wide-angle endoscope objective optical system.

Preferably, the first lens, the second lens and the third lens are all plastic aspherical lenses.

Compared with the prior art, the utility model has the following technical effects:

the optical system has a wide field angle through the combined design of different focal lengths of the concave-convex lens, improves resolution and relative illumination under the condition of meeting the requirements of wide angle and definition, obviously improves definition and picture illumination uniformity, and is beneficial to doctors to check diseases.

Drawings

FIG. 1 is a schematic diagram of the structure of an objective lens optical system of a wide angle endoscope;

FIG. 2 is a schematic view of the optical path of the wide angle endoscope objective optical system;

FIG. 3 is a diagram of the difference MTF (modulation transfer function) at the designed working distance of the wide-angle endoscope objective optical system;

FIG. 4 is a graph of the relative illuminance of a wide angle endoscope objective optical system;

FIG. 5 is an aberration diagram of a wide angle endoscope objective optical system;

FIG. 6 is a distortion diagram of the wide angle endoscope objective optical system;

fig. 7 is a principal ray incidence angle diagram of the wide-angle endoscope objective optical system.

Reference numerals: p1, a first lens; p2, a second lens; p3, a third lens; STO and aperture stop; an IR, infrared filter; s1, a first lens object side surface; s2, a first lens image side surface; s3, an aperture diaphragm surface; s4, a second lens object side surface; s5, a second lens image side surface; s6, a third lens object side surface; s7, a third lens is arranged on the image side surface; s8, an infrared filter object side surface; s9, an infrared filter image side surface.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments.

Examples

The utility model relates to an objective optical system of a wide-angle endoscope, which is shown in fig. 1, and sequentially comprises the following components from an object plane to an image plane along an optical axis: the first lens element P1 with negative focal power, wherein the object-side surface of the first lens element P1 is convex, and the image-side surface of the first lens element P1 is concave; the second lens element P2 with positive refractive power has a convex object-side surface of the second lens element P2 and a convex image-side surface of the second lens element P2; the third lens element P3 with negative focal power, wherein the object-side surface of the third lens element P3 is concave, and the image-side surface of the third lens element P3 is convex;

the optical power of the first lens P1 and the optical power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.7< Φ1/Φ < -0.45; the optical power of the second lens P2 and the optical power of the wide-angle endoscope objective lens optical system satisfy the following formula: 0.9< phi 2/phi <1.20; the optical power of the third lens P3 and the optical power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.96< Φ3/Φ < -0.5; wherein: Φ1 is the optical power of the first lens P1, unit diopter; Φ2 is the optical power of the second lens P2, unit diopter; Φ3 is the optical power of the third lens P3, unit diopter; phi is the optical power of the wide-angle endoscope objective lens optical system and the unit diopter. In this embodiment, a negative-positive lens-combined architecture is adopted, and compared with the prior art, the architecture of this embodiment has a maximum image height & MTF (modulation transfer function) of 0.2lp/mm at the cut-off frequency, and the MTF (modulation transfer function) of this optical system is greater than 0.34lp/mm, so that the performance is superior, and the resolution of details is high.

And also includes an aperture stop STO disposed between the first lens P1 and the second lens P2. And an infrared filter IR arranged at one end of the image side surface of the third lens P3.

Further comprises: FOV > 150 degrees; wherein: the FOV is the field angle of the wide-angle endoscope objective optical system in degrees. Further comprises: CRA is more than or equal to 24.5 degrees and less than or equal to 25.5 degrees; wherein: CRA is the angle of incidence of principal ray of the image plane of the wide angle endoscope objective optical system, in degrees.

Further comprises: ET1/CT1 < 2.5; ET2/CT2 is more than 0.5 and less than 0.6; ET3/CT3 is more than 1.8 and less than 1.9;

wherein: ET1 is the edge thickness of the first lens P1 in mm; CT1 is the center thickness of the first lens P1 in mm;

ET2 is the edge thickness of the second lens P2 in mm; CT2 is the center thickness of the second lens P2, in mm;

ET3 is the edge thickness of the third lens P3 in mm; CT3 is the center thickness of the third lens P3 in mm. According to the experience of injection molding industry, the ratio of ET/CT is generally between 0.3 and 3.0, and when the relation is satisfied, the lens injection molding difficulty of the wide-angle endoscope objective optical system is small, and the dimensional tolerance and the surface type precision are convenient to control.

Further comprises: EFL/EPD < 3.42; wherein: EFL is the effective focal length of the wide-angle endoscope objective optical system, in mm; EPD is the entrance pupil diameter in mm of the wide angle endoscope objective optical system. The smaller the ratio of EFL/EPD, the smaller the aperture of the optical system, and the greater the amount of light entering. The maximum field relative illumination of the wide-angle endoscope objective optical system is higher than 75%, the illumination uniformity of an imaging picture is good, and good image quality can be maintained under the condition of weak light.

Further comprises: TTL/EFL is less than 5.23; wherein TTL is the total optical length of the wide-angle endoscope objective optical system, and the unit is mm; EFL is the effective focal length of the wide angle endoscope objective optical system in mm. The angle of view of the wide-angle endoscope objective lens optical system is larger than 150 degrees, the maximum image surface diameter can reach 1.8mm, and when the relation is satisfied, the optical total length and the volume of the lens can be effectively controlled by restricting the ratio of the total length to the effective focal length.

Further comprises: OFL/TTL is more than 0.16 and less than 0.18; wherein OFL is the optical back focus of the wide-angle endoscope objective optical system, and the unit is mm; TTL is the total optical length in mm of the wide-angle endoscope objective optical system. When the above relation is satisfied, the back focus of the wide-angle endoscope objective optical system is sufficient, and focusing and assembly in the subsequent steps are easy.

The first lens element P1, the second lens element P2 and the third lens element P3 are all plastic aspheric lenses.

Table 1 lens parameter table of wide angle endoscope objective optical system

Table 2 aspherical coefficients of each lens surface of an objective optical system of a wide-angle endoscope

The following is the aspheric formula:

wherein: the perpendicular distance between the point on the aspheric curve and the optical axis is in mm;

z is the sagittal height distance from the aspheric top along the optical axis direction in mm when the perpendicular distance between the point on the aspheric curve and the optical axis is r;

paraxial curvature (c=1/R, R is radius of curvature, unit mm);

k, quadric surface constant;

a4 to A20, 4 th to 20 th order coefficients.

Claims (10)

1. An objective optical system for a wide-angle endoscope, comprising, in order from an object plane to an image plane along an optical axis:

the first lens is provided with negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface;

the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

the focal power of the first lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.7< Φ1/Φ < -0.45;

the focal power of the second lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: 0.9< phi 2/phi <1.20;

the focal power of the third lens and the focal power of the wide-angle endoscope objective lens optical system satisfy the following formula: -0.96< Φ3/Φ < -0.5;

wherein: Φ1 is the optical power of the first lens, unit diopter; Φ2 is the optical power of the second lens, the unit diopter; Φ3 is the optical power of the third lens, unit diopter; phi is the optical power of the wide-angle endoscope objective lens optical system and the unit diopter.

2. The wide-angle endoscope objective optical system of claim 1, further comprising an aperture stop disposed between the first lens and the second lens.

3. The wide-angle endoscope objective optical system of claim 2, further comprising an infrared filter disposed at an image side end of the third lens.

4. A wide-angle endoscope objective optical system according to claim 3 and also comprising:

FOV＞150°；

wherein: the FOV is the field angle of the wide-angle endoscope objective optical system in degrees.

5. The wide-angle endoscope objective optical system of claim 4, further comprising:

24.5°≤CRA≤25.5°；

wherein: CRA is the angle of incidence of principal ray of the image plane of the wide angle endoscope objective optical system, in degrees.

6. The wide-angle endoscope objective optical system of claim 5, further comprising:

2.4＜ET1/CT1＜2.5；0.5＜ET2/CT2＜0.6；1.8＜ET3/CT3＜1.9；

wherein: ET1 is the edge thickness of the first lens in mm; CT1 is the center thickness of the first lens, in mm;

ET2 is the edge thickness of the second lens in mm; CT2 is the center thickness of the second lens, in mm;

ET3 is the edge thickness of the third lens in mm; CT3 is the center thickness of the third lens in mm.

7. The wide-angle endoscope objective optical system of claim 6, further comprising:

EFL/EPD＜3.42；

wherein: EFL is the effective focal length of the wide-angle endoscope objective optical system, in mm; EPD is the entrance pupil diameter in mm of the wide angle endoscope objective optical system.

8. The wide-angle endoscope objective optical system of claim 7, further comprising:

TTL/EFL＜5.23；

wherein TTL is the total optical length of the wide-angle endoscope objective optical system, and the unit is mm; EFL is the effective focal length of the wide angle endoscope objective optical system in mm.

9. The wide-angle endoscope objective optical system of claim 8, further comprising:

0.16＜OFL/TTL＜0.18；

wherein OFL is the optical back focus of the wide-angle endoscope objective optical system, and the unit is mm; TTL is the total optical length in mm of the wide-angle endoscope objective optical system.

10. The wide-angle endoscope objective optical system of claim 9, wherein the first lens, the second lens and the third lens are all plastic aspherical lenses.