Small-size hard tube endoscope optical system

Abstract

The utility model relates to a small-size hard tube endoscope optical system, the optical system is composed of an objective lens group, a relay group and an eyepiece group which are sequentially arranged along an optical axis from an object space to an image space, the objective lens group is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens, and the second lens and the third lens are symmetrically distributed and are plano-concave lenses; the relay group comprises a front-section lens group and a rear-section lens group, the front-section lens group is a steering lens group and consists of a plurality of bonding lenses arranged along the direction of an optical axis, each bonding lens is formed by bonding a sixth lens and a seventh lens, the sixth lens is a plano-convex lens, and the seventh lens is a flat rod lens; the rear lens group is composed of an eighth lens, a ninth lens, a tenth lens and an eleventh lens which are sequentially arranged along the optical axis from the object space to the image space, and the eighth lens is a biconvex aspheric lens. The utility model has the characteristics of reasonable design, large field of view, small size, simple structure and easy manufacture.

Description

Technical field:

[0001] The utility model relates to a small-size hard tube endoscope optical system. Background technology:

[0002] The commonly used rigid tube endoscope objective lens group structure is a combination of a plano-concave lens and a biconvex lens. However, due to the small R value of the concave surface of the plano-concave lens when the structure has a large field of view and a small size, the lens processing is difficult.

[0003] The optical image transfer system structure of the early rigid tube endoscope is composed of a pair of double-cemented thin lens groups, with the aperture located in the middle, and the vertical axis aberration is well corrected. However, due to the use of thin lens groups, the lenses are prone to tilt during assembly, which affects the image quality of the system.

[0004] The relay group of the currently commonly used rigid tube endoscope optical system contains multiple groups of image transfer lens groups with the same structure, using double or triple cemented lenses, one of which is a Hopkins rod lens. One end of the Hopkins rod lens is glued to a thin negative lens with a negative focal length. The thin negative lens uses high refractive index and high dispersion optical glass to correct axial chromatic aberration, but cannot correct field curvature. Compared with the early structure, this image transfer structure has a high light energy transmittance. The advantage of this rigid tube endoscope optical image transfer system is that the structure is simple and the light energy transmittance is higher than that of the early image transfer structure. The disadvantage is that the radius of the non-cemented surface of the Hopkins rod lens is large, and it is difficult to process using traditional optical processing technology.

[0005] It can be seen that the design of the objective lens group and the relay lens group has a great influence on the manufacturing of large-field-of-view and small-size rigid tube endoscopes. Utility model content:

[0006] The utility model makes improvements on the problems existing in the above-mentioned prior art, that is, the technical problem to be solved by the utility model is to provide a small-sized rigid tube endoscope optical system with reasonable design, simple structure, small size, large field of view, and easy manufacturing.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a small-size hard tube endoscope optical system, the optical system is composed of an objective lens group, a relay group and an eyepiece group arranged in sequence along the optical axis from the object side to the image side, the objective lens group is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side, the first lens is a plane mirror, the second lens and the third lens are symmetrically distributed and are both plano-concave lenses, the fourth lens is a plano-convex lens, and the fifth lens is a biconvex lens; the relay group is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side, A front lens group and a rear lens group are arranged in sequence, wherein the front lens group is a steering lens group and is composed of a plurality of cemented lenses arranged along the optical axis, each cemented lens is formed by cementing a sixth lens and a seventh lens, the sixth lens is a plano-convex lens, and the seventh lens is a plano-rod lens; the rear lens group is composed of an eighth lens, a ninth lens, a tenth lens, and an eleventh lens arranged in sequence along the optical axis from the object side to the image side, the eighth lens is a biconvex aspheric lens, the ninth lens is a plano-rod lens, the tenth lens is formed by cementing a biconvex lens and a negative meniscus lens, and the eleventh lens is a plano-rod lens.

[0008] Furthermore, the focal length ratio of the biconvex aspheric lens to the plano-concave lens ranges from 7.1 to 8.0, and the focal length ratio of the biconvex aspheric lens to the plano-convex lens ranges from 0.77 to 0.93.

[0009] Furthermore, the lens diameters of the objective lens group and the relay lens group are 0.8-1.3 mm.

[0010] Furthermore, in the objective lens group, the first lens, the second lens, and the third lens constitute a negative lens system; and the fourth lens and the fifth lens constitute a positive lens system.

[0011] Furthermore, all lenses of the objective lens group are made of high-refractive-index glass material, and the refractive index of the material is between 1.75-1.85. The refractive index of the sixth lens is between 1.48-1.55; and the refractive index of the seventh lens is between 1.75-1.83.

[0012] Furthermore, the eyepiece group consists of a twelfth lens and a thirteenth lens arranged in sequence along the optical axis from the object side to the image side, wherein the twelfth lens is a negative meniscus lens, and the thirteenth lens is formed by gluing a double convex lens and a negative meniscus lens.

[0013] Furthermore, the air gap between the first lens and the second lens is 0.02mm; the air gap between the second lens and the third lens is 0.24mm; the air gap between the third lens and the fourth lens is 0.02mm; the air gap between the fourth lens and the fifth lens is 0.24mm; the air gap between the fifth lens and the sixth lens is 1.83mm; in the steering lens group of the relay group, the air gap between two adjacent cemented lens groups is 0.42mm; the air gap between the seventh lens and the eighth lens is 0.43mm; the air gap between the eighth lens and the ninth lens is 0.43mm; the air gap between the ninth lens and the tenth lens is 0.43mm; the air gap between the tenth lens and the eleventh lens is 0.41mm; the air gap between the eleventh lens and the twelfth lens is 1.79mm; and the air gap between the twelfth lens and the thirteenth lens is 1mm.

[0014] Furthermore, the parameters of both ends of the biconvex aspheric lens are consistent.

[0015] Furthermore, the field of view of the optical system is greater than 100°.

[0016] Compared with the prior art, the utility model has the following effects: the utility model has a reasonable design and meets the characteristics of large field of view, small size, simple structure and easy manufacturing. Description of the drawings:

[0017] Figure 1 It is a schematic diagram of the structure of the optical system in the embodiment of the utility model;

[0018] Figure 2 It is a schematic diagram of the structure of the objective lens group of the optical system in the embodiment of the utility model;

[0019] Figure 3 It is a schematic diagram of the partial structure of the front mirror group of the relay group of the optical system in the embodiment of the utility model;

[0020] Figure 4 A schematic diagram of the structure of the rear mirror group of the relay group of the optical system in the embodiment of the utility model;

[0021] Figure 5 It is a schematic diagram of the structure of the eyepiece group of the optical system in the embodiment of the utility model.

[0022] In the figure:

[0023] 1-objective lens group; 2-relay group; 3-eyepiece group; L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-fifth lens; L6-sixth lens; L7-seventh lens; L8-eighth lens; L9-ninth lens; L10-tenth lens; L11-eleventh lens; L12-twelfth lens; L13-thirteenth lens. Specific implementation method:

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0026] like Figures 1 to 5 As shown, the utility model is a small-sized rigid tube endoscope optical system with a field of view angle greater than 100°. The optical system consists of an objective lens group, a relay group and an eyepiece group arranged in sequence along the optical axis from the object side to the image side. The objective lens group adopts a symmetrical plano-concave lens structure, and the image transfer lens group of the relay group adopts a plano-convex lens plus a plano-rod lens combination. At the same time, a double convex aspheric lens is added in the relay group.

[0027] Specifically: the objective lens group is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side, the first lens is a plane mirror, the second lens and the third lens are symmetrically distributed and are both plano-concave lenses, the fourth lens is a plano-convex lens, and the fifth lens is a biconvex lens; the relay group is composed of a front lens group and a rear lens group arranged in sequence along the optical axis from the object side to the image side, the front lens group is a steering lens group and is composed of a plurality of cemented lenses arranged along the optical axis, each cemented lens is a sixth lens and a seventh lens cemented together The sixth lens is a plano-convex lens, and the seventh lens is a plano-rod lens; the rear lens group is composed of an eighth lens, a ninth lens, a tenth lens, and an eleventh lens arranged in sequence along the optical axis from the object side to the image side, the eighth lens is a biconvex aspheric lens, the ninth lens is a plano-rod lens, and the tenth lens is formed by gluing a biconvex lens and a negative meniscus lens; the eyepiece group is composed of a twelfth lens and a thirteenth lens arranged in sequence along the optical axis from the object side to the image side, the twelfth lens is a negative meniscus lens, and the thirteenth lens is formed by gluing a biconvex lens and a negative meniscus lens.

[0028] In this embodiment, the focal length ratio of the biconvex aspheric lens to the plano-concave lens is in the range of 7.1-8.0, and the preferred focal length ratio is 7.66.

[0029] In this embodiment, the focal length ratio of the biconvex aspheric lens to the plano-convex lens is in the range of 0.77-0.93, and the preferred focal length ratio is 0.85.

[0030] In this embodiment, the diameter of the lenses of the objective lens group and the relay lens group is 0.8-1.3 mm, preferably 1 mm.

[0031] In this embodiment, the objective lens group is designed as a reverse telephoto lens structure with a negative lens in front and a positive lens in the back. Specifically, the first lens, the second lens, and the third lens form a negative lens system, and its focal length is less than 0; the fourth lens and the fifth lens form a positive lens system, and its focal length is greater than 0. Preferably, the focal length of the negative lens system is -0.27 mm, and the focal length of the positive lens system is 0.67 mm.

[0032] In this embodiment, all lenses of the objective lens group are made of high-refractive-index glass material, and the refractive index of the material is between 1.75-1.85, wherein the first lens n1=1.77; the second lens n2=1.85; the third lens n3=1.85; the fourth lens n4=1.85; the fifth lens n5=1.81, and n1, n2, n3, n4, and n5 are the refractive indices of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens, respectively.

[0033] In this embodiment, the refractive index of the sixth lens is in the range of 1.48-1.55; the refractive index of the seventh lens is in the range of 1.75-1.83. Preferably, n6 of the sixth lens is 1.50, n7 of the seventh lens is 1.81, and n6 and n7 are the refractive indices of the sixth lens and the seventh lens respectively.

[0034] In this embodiment, the air gap between the first lens and the second lens is 0.02 mm; the air gap between the second lens and the third lens is 0.24 mm; the air gap between the third lens and the fourth lens is 0.02 mm; the air gap between the fourth lens and the fifth lens is 0.24 mm; the air gap between the fifth lens and the sixth lens is 1.83 mm; in the steering lens group of the relay group, the air gap between two adjacent cemented lens groups is 0.42 mm; the air gap between the seventh lens and the eighth lens is 0.43 mm; the air gap between the eighth lens and the ninth lens is 0.43 mm; the air gap between the ninth lens and the tenth lens is 0.43 mm; the air gap between the tenth lens and the eleventh lens is 0.41 mm; the air gap between the eleventh lens and the twelfth lens is 1.79 mm; and the air gap between the twelfth lens and the thirteenth lens is 1 mm.

[0035] In this embodiment, the parameters of the two ends of the double convex aspheric lens are consistent, and its aspheric parameters ASP1 surface R = 4.8856, K = -6.9246, A1 = 0, A2 = -7.4003E-3, A3 = -1.2637E-2, A4 = -3.4151E-2; ASP2 surface R = -4.8856, K = -6.9246, A1 = 0, A2 = -7.4003E-3, A3 = -1.2637E-2, A4 = -3.4151E-2. Among them, K is the cone coefficient, A1 is the second-order coefficient of the aspheric surface, A2 is the fourth-order coefficient of the aspheric surface, A3 is the sixth-order coefficient of the aspheric surface, A4 is the eighth-order coefficient of the aspheric surface, and R is the radius of curvature. The surface equation of the aspheric surface is:

[0036]

[0037] In this embodiment, the relay lens group includes 13 sets of sixth lenses L6 and seventh lenses L7.

[0038] In this embodiment, the operating wavelength range of the optical system is 450nm-650nm, the central wavelength is 546nm, the half field angle is 50.1°, the aperture size is 0.084mm, the object distance is 5mm, and the lens focal length f is 1.45mm.

[0039] In this embodiment, the curvature radii R1 and R2, the center thickness d, the material and the focal length f of each lens are specifically shown in Table 1 below.

[0040] lens R1 R2 d Material f L1 infinity infinity 0.2 SAPPHIRE 0 L2 infinity 0.55 0.2 H-ZF52GT -0.64 L3 -0.55 infinity 0.2 H-ZF52GT -0.64 L4 infinity -0.68 0.77 H-ZF52GT 0.8 L5 2.4 -2.4 0.86 H-ZLAF56B 1.61 L6 2.87 infinity 0.5 H-K2 5.71 L7 infinity infinity 9 H-ZLAF56B 0 L8 4.89 -4.89 1.07 D-K9 4.9 L9 infinity infinity 9 H-ZLAF56B 0 L10-1 4.73 -1 0.6 H-ZBAF52 1.28 L10-2 -1 -2.78 0.5 H-ZF73GT -1.87 L11 infinity infinity 3.5 H-ZLAF56B 0 L12 -0.91 -2.09 1.66 H-ZLAF55D -5.42 L13-1 6.85 -1.98 1.5 H-TF3L 2.66 L13-2 -1.98 1.62 1.62 H-ZF88GT -2.06

[0041] Table 1

[0042] In this embodiment, the imaging method of the small-size rigid tube endoscope optical system is as follows: during imaging: light travels from the object side to the image side through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens and the thirteenth lens to form an image.

[0043] The advantages of the utility model are:

[0044] 1. The objective lens group is designed with a symmetrical plano-concave structure. Under the requirements of large field of view and small size, this structure increases the R value of the single-piece plano-concave lens and reduces the difficulty of lens processing;

[0045] 2. In the design of the relay group, the sixth lens group and the seventh lens group respectively use a plano-convex lens and a flat rod lens. This combination is used as a relay lens group to achieve different tube length requirements for hard tube endoscopes while reducing the difficulty of lens processing;

[0046] 3. In the design of the relay group, the eighth lens group adopts a double convex aspheric lens, which can better eliminate the accumulated aberration between the objective lens group and the relay group and simplify the number of lenses.

[0047] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except where it is obviously impossible to use an one-piece molding process).

[0048] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the above utility model include states or shapes that are approximate, similar or close thereto.

[0049] Any component provided by the utility model can be assembled from multiple separate components, or can be a separate component manufactured by an integrated molding process.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the utility model can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the utility model, which should be included in the scope of the technical solution for protection of the utility model.

Claims

1. A small-sized rigid tube endoscope optical system, the optical system is composed of an objective lens group, a relay group and an eyepiece group arranged in sequence along the optical axis from the object side to the image side, characterized in that: The objective lens group is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object side to the image side, wherein the first lens is a plane mirror, the second lens and the third lens are symmetrically distributed and are both plano-concave lenses, the fourth lens is a plano-convex lens, and the fifth lens is a biconvex lens; the relay group is composed of a front lens group and a rear lens group arranged in sequence along the optical axis from the object side to the image side, the front lens group is a steering lens group and is composed of a plurality of cemented lenses arranged along the optical axis, each cemented lens is formed by cementing a sixth lens and a seventh lens, the sixth lens is a plano-convex lens, and the seventh lens is a flat-rod lens; the rear lens group is composed of an eighth lens, a ninth lens, a tenth lens and an eleventh lens arranged in sequence along the optical axis from the object side to the image side, the eighth lens is a biconvex aspheric lens, the ninth lens is a flat-rod lens, the tenth lens is formed by cementing a biconvex lens and a negative meniscus lens, and the eleventh lens is a flat-rod lens.

2. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: The focal length ratio of the biconvex aspheric lens to the plano-concave lens ranges from 7.1 to 8.0, and the focal length ratio of the biconvex aspheric lens to the plano-convex lens ranges from 0.77 to 0.

93.

3. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: The diameter of the lenses of the objective lens group and the relay lens group is 0.8-1.3 mm.

4. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: In the objective lens group, the first lens, the second lens, and the third lens constitute a negative lens system; the fourth lens and the fifth lens constitute a positive lens system.

5. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: All lenses of the objective lens group are made of high-refractive-index glass material, and the refractive index of the material is between 1.75-1.85; the refractive index range of the sixth lens is between 1.48-1.55; the refractive index range of the seventh lens is between 1.75-1.

83.

6. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: The eyepiece group consists of a twelfth lens and a thirteenth lens arranged in sequence along the optical axis from the object side to the image side. The twelfth lens is a negative meniscus lens, and the thirteenth lens is formed by gluing a double convex lens and a negative meniscus lens.

7. The small-size rigid tube endoscope optical system according to claim 2, characterized in that: The air gap between the first lens and the second lens is 0.02mm; the air gap between the second lens and the third lens is 0.24mm; the air gap between the third lens and the fourth lens is 0.02mm; the air gap between the fourth lens and the fifth lens is 0.24mm; the air gap between the fifth lens and the sixth lens is 1.83mm; in the steering lens group of the relay group, the air gap between two adjacent cemented lens groups is 0.42mm; the air gap between the seventh lens and the eighth lens is 0.43mm; the air gap between the eighth lens and the ninth lens is 0.43mm; the air gap between the ninth lens and the tenth lens is 0.43mm; the air gap between the tenth lens and the eleventh lens is 0.41mm; the air gap between the eleventh lens and the twelfth lens is 1.79mm; the air gap between the twelfth lens and the thirteenth lens is 1mm.

8. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: The parameters of the biconvex aspheric lens are consistent at both ends.

9. The small-size rigid tube endoscope optical system according to claim 1, characterized in that: The field of view of the optical system is greater than 100°.

Images