An infrared fiber endoscope

Abstract

The present invention belongs to the technical field of endoscopes, and is specifically an infrared fiber endoscope. The present invention includes five coaxial spherical refractive lenses, an aperture and an imaging surface, and the lenses are arranged in sequence from the object side to the image side: the first lens is a concave lens, and the mirror surface facing the object side and the mirror surface facing the image side are both convex toward the object side; the second lens is a concave lens, and the mirror surface facing the object side and the mirror surface facing the image side are both convex toward the image side; the third lens is a concave lens, and the mirror surface facing the object side and the mirror surface facing the image side are both convex toward the image side; the fourth lens is a convex lens, and the mirror surface facing the object side is convex toward the object side, and the mirror surface facing the image side is convex toward the image side; the fifth lens is a concave lens, and the mirror surface facing the object side and the mirror surface facing the image side are both convex toward the image side; the second lens and the third lens are combined into a double cemented lens, and the fourth lens and the fifth lens are combined into a double cemented lens. The working band of the present invention is near infrared, and it adopts the image side telecentric and anti-telecentric structure design, with compact structure, small size and excellent observation quality.

Description

Technical Field

[0001] The invention belongs to the technical field of endoscopes, and in particular relates to an infrared fiber endoscope. Background Art

[0002] Endoscopic technology has been continuously improved with the progress of science, and has been widely used in a series of related fields such as industrial manufacturing, mechanical processing, power electronics, civil engineering, etc., especially in the medical field, where endoscopes have become indispensable equipment in daily diagnosis and treatment and surgery. In recent years, the development of endoscopes has produced more forms: ultra-fine fiber endoscopes, ultra-long video endoscopes, multi-elbow pipeline inspection endoscopes, stereo dual-channel endoscopes, etc. The fiber optic image transmission bundle in the fiber endoscope is a passive device formed by assembling a certain number of optical fibers of the same length in a certain arrangement and curing and polishing. It is light in weight, can be bent at any angle, and can transmit images in complex spaces. It has been widely used in various fields such as medicine, industry, scientific research, aerospace, and military.

[0003] In the medical field, especially when observing the anatomical structure of some important organs, it is necessary to observe in a blood environment. The common visible light endoscope has serious distortion and deformation of visible light imaging due to the strong absorption and scattering effect of blood on the visible light band, and there are problems such as poor relative illumination. Blood has relatively weak absorption and scattering of infrared light information, so the design of an endoscope system working in the infrared band is of great significance for the observation of surgical procedures. However, the more common problem with the current endoscope lens is that the field of view is relatively small. During the observation process, it is necessary to constantly adjust the conversion lens to obtain information from different directions, which greatly reduces the efficiency of observation and surgery; the receiving aperture of the lens is small, and some existing large-field endoscope systems use aspherical and free-form surface structures, which are difficult to process. In addition, the infrared lens design with a large field of view faces problems such as complex structure, large size, and high cost. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, an object of the present invention is to provide an infrared fiber endoscope which has a compact structure, is easy to process and has excellent performance.

[0005] The infrared fiber endoscope (objective optical system) provided by the present invention has a structure as shown in Figure 1 As shown in the figure, the system adopts an image-space telecentric and anti-telecentric structure. Through the optimization of the lens structure, a large field of view of 138°, a relative illumination of more than 82% and a high telecentricity are achieved while ensuring a compact structure and a small number of lenses. It can be well coupled and matched with the fiber optic image transmission bundle, and all lenses adopt a spherical structure, which greatly reduces the processing difficulty and saves processing costs.

[0006] The infrared fiber endoscope provided by the present invention comprises: a first lens 1, an aperture 2, a second lens 3, a third lens 4, a fourth lens 5, a fifth lens 6, and an imaging surface 7 which are coaxially arranged in sequence; wherein the first lens 1 is a concave lens, and the first surface 11 facing the object side and the second surface 12 facing the image side are both convex toward the object side; the second lens 3 is a concave lens, and the third surface 31 facing the object side and the fourth surface 32 facing the image side are both convex toward the image side; the third lens 4 is a concave lens, and the fourth surface 32 facing the object side and the fifth surface 41 facing the image side are both convex toward the image side; the fourth lens 5 is a convex lens, and the sixth surface 51 facing the object side is convex toward the object side, and the seventh surface 52 facing the image side is convex toward the image side; the fifth lens 6 is a concave lens, and the seventh surface 52 facing the object side and the eighth surface 61 facing the image side are both convex toward the image side.

[0007] Furthermore, the focal power of the first lens 1 is negative, and its focal length f1 is -3.3265 mm; the focal power of the second lens 3 is positive, and its focal length f2 is 47.022 mm; the focal power of the third lens 4 is positive, and its focal length f3 is 2.2688 mm; the focal power of the fourth lens 5 is negative, and its focal length f4 is -126.23 mm; the focal power of the fifth lens 6 is positive, and its focal length f5 is 4.6249 mm.

[0008] Furthermore, the refractive index n and Abbe number v of the first lens 1 are 1.7945 and 45.5269 respectively; the refractive index n and Abbe number v of the second lens 3 are 1.8059 and 34.2421 respectively; the refractive index n and Abbe number v of the third lens 4 are 1.6675 and 41.9314 respectively; the refractive index n and Abbe number v of the fourth lens 5 are 1.5923 and 68.3986 respectively; the refractive index n and Abbe number v of the fifth lens 6 are 1.7495 and 34.9505 respectively.

[0009] Furthermore, the operating band of the objective optical system is 1.2-1.8 μm, the full field of view is greater than 0.65 at a spatial resolution of 21 lp / mm, the relative illumination of the imaging surface is greater than 82%, the effective focal length is 1.101 mm, the F number is 4, the maximum field of view angle is 138°, the maximum outer diameter is 8.1196 mm, the full field of the system is 10.38 mm, and the back working distance is 0.2362 mm.

[0010] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0011] (1) Based on the shortcomings of the existing endoscope imaging system, the present invention designs an infrared fiber endoscope, which can ensure the coupling between the optical system and the subsequent optical fiber image transmission bundle when the field of view angle is increased to 138°. When the system is working, there is no need to repeatedly move the lens to change the viewing angle for observation, which greatly improves the work efficiency;

[0012] (2) The present invention adopts an image-space telecentric and anti-telephoto structure, which greatly reduces the size of the system. The maximum outer diameter is 8.1196 mm. When the system works in the 1.2-1.8 μm near-infrared band, it can obtain excellent observation quality in an environment where visible light endoscopes are difficult to work and the imaging quality is poor. It can ensure that the MTF value is greater than 0.65 at the limit resolution of 21 lp / mm, and the relative illumination of the whole field of view is greater than 82%;

[0013] (3) All lenses in the present invention adopt a spherical structure design, which greatly reduces the processing difficulty and saves processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of the infrared fiber endoscope of the present invention.

[0015] Figure 2 It is a schematic diagram of imaging of the infrared fiber endoscope of the present invention.

[0016] Figure 3 Schematic diagram of the MTF transfer function curve in an embodiment of the present invention.

[0017] Figure 4 Schematic diagram of diffuse spots in an embodiment of the present invention.

[0018] Figure 5 Schematic diagram of axial aberration in an embodiment of the present invention.

[0019] Figure 6 Schematic diagram of relative illumination in an embodiment of the present invention.

[0020] Figure 7 FIG. 4 is a schematic diagram of diffraction circle energy in an embodiment of the present invention.

[0021] The numbers in the figure are: 1 is the first lens, 2 is the aperture, 3 is the second lens, 4 is the third lens, 5 is the fourth lens, 6 is the fifth lens, 7 is the imaging plane, 11 is the first surface, 12 is the second surface, 31 is the third surface, 32 is the fourth surface, 41 is the fifth surface, 51 is the sixth surface, 52 is the seventh surface, and 61 is the eighth surface. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto. Example

[0023] like Figure 1As shown, the infrared wide-angle endoscope objective optical system provided by the present invention comprises: a first lens 1, an aperture 2, a second lens 3, a third lens 4, a fourth lens 5, a fifth lens 6, and an imaging surface 7; the first lens 1 is a concave lens, and the first surface 11 facing the object side and the second surface 12 facing the image side are both convex toward the object side; the second lens 3 is a concave lens, and the third surface 31 facing the object side and the fourth surface 32 facing the image side are both convex toward the image side; the third lens 4 is a concave lens, and the fourth surface 32 facing the object side and the fifth surface 41 facing the image side are both convex toward the image side; the fourth lens 5 is a convex lens, and the sixth surface 51 facing the object side is convex toward the object side, and the seventh surface 52 facing the image side is convex toward the image side; the fifth lens 6 is a concave lens, and the seventh surface 52 facing the object side and the eighth surface 61 facing the image side are both convex toward the image side.

[0024] Furthermore, the focal power of the first lens 1 is negative, and its focal length f1 is -3.3265 mm; the focal power of the second lens 3 is positive, and its focal length f2 is 47.022 mm; the focal power of the third lens 4 is positive, and its focal length f3 is 2.2688 mm; the focal power of the fourth lens 5 is negative, and its focal length f4 is -126.23 mm; the focal power of the fifth lens 6 is positive, and its focal length f5 is 4.6249 mm.

[0025] Furthermore, the refractive index n and Abbe number v of the first lens 1 are 1.7945 and 45.5269 respectively; the refractive index n and Abbe number v of the second lens 3 are 1.8059 and 34.2421 respectively; the refractive index n and Abbe number v of the third lens 4 are 1.6675 and 41.9314 respectively; the refractive index n and Abbe number v of the fourth lens 5 are 1.5923 and 68.3986 respectively; the refractive index n and Abbe number v of the fifth lens 6 are 1.7495 and 34.9505 respectively.

[0026] Further, the radius of curvature of the first surface 11 is 5.3306 mm, the radius of curvature of the second surface 12 is 1.9050 mm, and the center thickness of the first lens 1 is 0.7500 mm; further, the radius of curvature of the third surface 31 is -79.9755 mm, the radius of curvature of the fourth surface is -4.2277 mm, and the center thickness of the second lens 3 is 1.0577 mm; further, the radius of curvature of the fifth surface 41 is -4.2777 mm, and the center thickness of the third lens 4 is 0.2945 mm; further, the radius of curvature of the sixth surface is 6.4200 mm, the radius of curvature of the seventh surface is -1.2735 mm, and the center thickness of the fourth lens 5 is 2.0756 mm; further, the radius of curvature of the eighth surface 61 is -2.4658 mm, and the center thickness of the fifth lens 6 is 1.8186 mm. Furthermore, the center interval between the second surface 12 and the aperture 2 is 4.0638 mm, the center interval between the aperture 2 and the third surface 31 is 0.0271 mm, the center interval between the fifth surface 41 and the sixth surface 51 is 0.0637 mm, and the center interval between the eighth surface 61 and the imaging surface 7 is 0.2362 mm.

[0027] Furthermore, if Figure 2 As shown, the principal rays of the received light beam at the imaging plane are parallel to the principal axis, the telecentricity is as high as 0.0384, and the image-side numerical aperture NA is 0.1237, which is convenient for coupling with the optical fiber image transmission bundle and improving the efficiency of light transmission. Furthermore, the numerical aperture of the subsequent optical fiber image transmission bundle is 0.22, the cross-sectional size is 3mm, and a total of 10,000 single-filament optical fibers are arranged in a hexagonal structure.

[0028] Furthermore, the second lens 3 and the third lens 4 are glued together to form a double glued lens, and the fourth lens 5 and the fifth lens 6 are glued together to form a double glued lens. The first lens 1 compresses the light in the object space to ensure the small size of the subsequent lens, and the combination of the double glued lens can greatly reduce the aberration of the system and improve the quality of the image received by the imaging surface 7.

[0029] Furthermore, if Figure 3 As shown, the MTF value of the objective optical system in the embodiment at the cutoff frequency of 21lp / mm in the whole field of view is greater than 0.65, and the overall aberration optimization effect is good.

[0030] Furthermore, if Figure 4 As shown, the root mean square size of the diffuse spot of light received by the objective optical system at the imaging plane in the embodiment is about 7.626 μm, and the size of a single fiber of the subsequent optical fiber image transmission bundle is 27.5 μm, which can far exceed the imaging requirements.

[0031] Furthermore, if Figure 5 As shown, through the combination of double cemented lenses, the axial aberration of the system is well controlled.

[0032] Furthermore, if Figure 6 As shown, the relative illumination of the light received by the objective optical system in the embodiment at the imaging surface is above 82%, thereby ensuring the illumination uniformity of the imaging.

[0033] Furthermore, if Figure 7 As shown, the diffraction circle energy of the full field of view of the objective optical system in the embodiment is higher than 85% within a radius of 13.75 μm, which well ensures the efficiency of light energy transfer.

[0034] Furthermore, the operating band of the objective optical system is 1.2-1.8 μm, the full field of view is greater than 0.65 at a spatial resolution of 21 lp / mm, the relative illumination of the imaging surface is greater than 82%, the effective focal length is 1.101 mm, the F number is 4, the maximum field of view angle is 138°, the maximum outer diameter is 8.1196 mm, the full field of the system is 10.38 mm, and the back working distance is 0.2362 mm.

[0035] The above embodiment is only one implementation of the present invention, but the implementation of the present invention is not limited to the above embodiment. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An infrared fiber endoscope, characterized in that: The system comprises, arranged in order from the object side to the image side: a first lens (1), an aperture (2), a second lens (3), a third lens (4), a fourth lens (5), a fifth lens (6), and an imaging surface (7); the system adopts an image side telecentric and anti-telecentric structure, and through lens structure optimization, a large field of view angle, a large relative illumination, and a high telecentricity are achieved while ensuring a compact structure and a small number of lenses; wherein the first lens (1) is a concave lens, and a first surface (11) facing the object side and a second surface (12) facing the image side are both convex toward the object side; the second lens ( The lens (3) is a concave lens, and the third surface (31) facing the object side and the fourth surface (32) facing the image side are both convex toward the image side; the third lens (4) is a concave lens, and the fourth surface (32) facing the object side and the fifth surface (41) facing the image side are both convex toward the image side; the fourth lens (5) is a convex lens, and the sixth surface (51) facing the object side is convex toward the object side, and the seventh surface (52) facing the image side is convex toward the image side; the fifth lens (6) is a concave lens, and the seventh surface (52) facing the object side and the eighth surface (61) facing the image side are both convex toward the image side.

2. The infrared fiber endoscope objective optical system according to claim 1, characterized in that: The optical focal power of the first lens (1) is negative, and its focal length f1 is -3.3265 mm; the optical focal power of the second lens (3) is positive, and its focal length f2 is 47.022 mm; the optical focal power of the third lens (4) is positive, and its focal length f3 is 2.2688 mm; the optical focal power of the fourth lens (5) is negative, and its focal length f4 is -126.23 mm; the optical focal power of the fifth lens (6) is positive, and its focal length f5 is 4.6249 mm.

3. The infrared fiber endoscope objective optical system according to claim 1, characterized in that: The working band of the objective optical system is 1.2-1.8μm, the full field of view is greater than 0.65 at a spatial resolution of 21lp / mm, the relative illumination of the imaging surface is greater than 82%, the effective focal length is 1.101mm, the F number is 4, the maximum field of view angle is 138°, the maximum outer diameter is 8.1196mm, the full field of the system is 10.38mm, and the back working distance is 0.2362mm.

Images