An infrared wide-angle endoscope objective optical system

Abstract

The present invention belongs to the technical field of endoscopes, and is specifically an infrared wide-angle endoscope objective optical system. The objective optical system of the present invention includes, along the optical axis from the object plane to the image plane, a first lens with negative optical power, an aperture, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and an imaging plane; the surfaces of the first to fifth lenses are all spherical, and the system adopts an image-side telecentric and anti-telephoto structural design. Through reasonable matching and structural optimization, the maximum field of view of the system reaches 120°, the full field of view is greater than 0.75 at a spatial resolution of 21lp / mm, the relative illumination of the imaging plane is greater than 99%, and the image plane size is 3mm, which matches the subsequent optical fiber image transmission bundle.

Description

Technical Field

[0001] The invention belongs to the technical field of endoscopes, and in particular relates to an infrared wide-angle endoscope objective optical system. Background Art

[0002] Endoscopic technology is a comprehensive technology that integrates optics, precision manufacturing, image processing, optoelectronic information, materials, bioengineering and other high-tech disciplines. Since its invention, medical endoscopes have been widely used. With the help of endoscopes, doctors can observe the tissue morphology and pathological conditions of internal organs of the human body very intuitively and efficiently, greatly reducing the harm of surgery to patients and effectively controlling surgical risks. Since its appearance, endoscopes have experienced the development of rigid tube endoscopes, semi-curved endoscopes, fiber endoscopes and electronic endoscopes.

[0003] With the development of medical level and endoscopic technology, endoscopes are used more and more widely in clinical surgery. Especially when observing the anatomical structure of some important organs, it is necessary to observe in a blood environment. Common visible light endoscopes have 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 the surgical process. However, the more common problem with current endoscopic lenses is that the field of view is relatively small, which is not conducive to observation; the receiving aperture of the lens is small, and some existing large-field-of-view endoscope systems use aspherical and free-form surface structures, which are difficult to process. 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, the object of the present invention is to provide an endoscope objective optical system which has a compact structure, wide-angle characteristics, good relative illumination performance, image-space telecentricity and operates in the near-infrared band.

[0005] The infrared wide-angle 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 image-space telecentric and anti-telecentric structures. Through the optimization of the lens structure, it realizes wide angle, high relative illumination and high telecentricity while ensuring compact structure and a small number of lenses. It can be well coordinated and coupled with the subsequent optical fiber image transmission bundle, and all lenses adopt spherical structure, which greatly reduces the processing difficulty and saves processing costs.

[0006] 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 plane 7 which are arranged in sequence along the optical axis from the object plane to the image plane; the first lens 1 comprises a first surface 11 facing the object plane and a second surface 12 facing the image plane; the second lens 3 comprises a third surface 31 facing the object plane and a fourth surface 32 facing the image plane; the third lens 4 comprises a fourth surface 32 facing the object plane and a fifth surface 41 facing the image plane; the fourth lens 5 comprises a sixth surface 51 facing the object plane and a seventh surface 52 facing the image plane; the fifth lens 6 comprises a seventh surface 52 facing the object plane and an eighth surface 61 facing the image plane.

[0007] Furthermore, the focal length of the first lens 1 is -0.25332 mm. -1 The first surface 11 is a convex spherical surface with a curvature radius of 5.3246 mm; the second surface 12 is a convex spherical surface with a curvature radius of 2.3753 mm; and the center thickness of the first lens 1 is 0.9502 mm.

[0008] Furthermore, the focal length of the second lens 3 is 0.027513 mm. -1 The third surface 31 is a convex spherical surface with a curvature radius of 7.6271 mm; the fourth surface 32 is a convex spherical surface with a curvature radius of 1.4567 mm; and the center thickness of the second lens 3 is 1.1573 mm.

[0009] Furthermore, the focal length of the third lens 4 is 0.22451 mm. -1 The fifth surface 41 is a concave spherical surface with a curvature radius of -2.4894 mm; the center thickness of the third lens 4 is 0.6328 mm.

[0010] Furthermore, the focal length of the fourth lens 5 is -0.06921 mm. -1 The sixth surface 51 is a convex spherical surface with a curvature radius of 45.6842 mm; the seventh surface 52 is a concave spherical surface with a curvature radius of -1.6254 mm; and the center thickness of the fourth lens 5 is 2.1183 mm.

[0011] Furthermore, the optical power of the fifth lens 6 is 0.21563 mm. -1 The eighth surface 61 is a concave spherical surface with a curvature radius of -2.5735 mm; the central thickness of the fifth lens 6 is 0.8950 mm.

[0012] Furthermore, the center interval between the second surface 12 and the aperture 2 is 5.9842 mm, the center interval between the aperture 2 and the third surface 31 is 0.1324 mm, the center interval between the fifth surface 41 and the sixth surface 51 is 1.0359 mm, and the center interval between the eighth surface 61 and the imaging surface 7 is 1.5968 mm.

[0013] Furthermore, the refractive index n and the Abbe number v of the first lens (1) are 1.8706 and 41.1097 respectively; the refractive index n and the Abbe number v of the second lens (3) are 1.8356 and 23.7699 respectively; the refractive index n and the Abbe number v of the third lens (4) are 1.6835 and 53.3600 respectively; the refractive index n and the Abbe number v of the fourth lens (5) are 1.5743 and 68.3786 respectively; the refractive index n and the Abbe number v of the fifth lens (6) are 1.7452 and 27.4780 respectively.

[0014] Furthermore, the net aperture of the first lens 1 is 4.0000 mm, the net aperture of the second lens 3 is 0.6650 mm, the net aperture of the third lens 4 is 0.9961, the net aperture of the fourth lens 5 is 1.4874 mm, and the net aperture of the fifth lens 6 is 1.6830 mm.

[0015] 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.

[0016] Furthermore, the operating band of the objective optical system is 1.2-1.8μm, the full field of view is greater than 0.75 at a spatial resolution of 21lp / mm, the relative illumination of the imaging surface is greater than 99%, the effective focal length is 0.797mm, the F number is 4, the image side numerical aperture NA is 0.1238, the maximum field of view angle is 120°, the maximum system aperture is 8mm, the total length of the system is 14.32mm, the image plane size is 3mm, which matches the subsequent optical fiber image transmission bundle.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] (1) Based on the shortcomings of the existing endoscope imaging system, the present invention designs an infrared wide-angle endoscope objective optical system. By adopting the image-side telecentric and anti-telecentric structure, the optical system and the subsequent optical fiber image transmission bundle can be coupled, while the size of the system is greatly reduced;

[0019] (2) The present invention increases the field of view of the system to 120° by optimizing the structure of the first to fifth lenses and adjusting the position of the aperture. The system does not need to repeatedly move the lens to change the viewing angle for observation during operation, which greatly improves the work efficiency. When the system operates in the 1.2-1.8μm near-infrared band, it can ensure that the MTF value is greater than 0.75 at the limiting resolution of 21lp / mm, and the relative illumination of the full field of view is greater than 99%;

[0020] (3) The present invention designs an infrared wide-angle endoscope objective optical system, in which all lenses are designed with a spherical structure and the maximum size of the system is 8 mm, which greatly reduces the processing difficulty and saves processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic structural diagram of an infrared wide-angle endoscope objective optical system of the present invention.

[0022] Figure 2 The figure is a schematic diagram of imaging of an infrared wide-angle endoscope objective optical system of the present invention.

[0023] Figure 3 Schematic diagram of the MTF transfer function curve in an embodiment of the present invention.

[0024] Figure 4 Schematic diagram of diffuse spots in an embodiment of the present invention.

[0025] Figure 5 Schematic diagram of relative illumination in an embodiment of the present invention.

[0026] Figure 6 FIG. 4 is a schematic diagram of diffraction circle energy in an embodiment of the present invention.

[0027] 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

[0028] 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

[0029] like Figure 1As shown, an infrared wide-angle endoscope objective optical system provided by the present invention includes: 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. Further, the first lens 1 includes a first surface 11 facing the object surface and a second surface 12 facing the image surface; the second lens 3 includes a third surface 31 facing the object surface and a fourth surface 32 facing the image surface; the third lens 4 includes a fourth surface 32 facing the object surface and a fifth surface 41 facing the image surface; the fourth lens 5 includes a sixth surface 51 facing the object surface and a seventh surface 52 facing the image surface; the fifth lens 6 includes a seventh surface 52 facing the object surface and an eighth surface 61 facing the image surface.

[0030] Furthermore, the focal length of the first lens 1 is -0.25332 mm. -1 The first surface 11 is a convex spherical surface with a curvature radius of 5.3246 mm; the second surface 12 is a convex spherical surface with a curvature radius of 2.3753 mm; and the center thickness of the first lens 1 is 0.9502 mm.

[0031] Furthermore, the focal length of the second lens 3 is 0.027513 mm. -1 The third surface 31 is a convex spherical surface with a curvature radius of 7.6271 mm; the fourth surface 32 is a convex spherical surface with a curvature radius of 1.4567 mm; and the center thickness of the second lens 3 is 1.1573 mm.

[0032] Furthermore, the focal length of the third lens 4 is 0.22451 mm. -1 The fifth surface 41 is a concave spherical surface with a curvature radius of -2.4894 mm; the center thickness of the third lens 4 is 0.6328 mm.

[0033] Furthermore, the focal length of the fourth lens 5 is -0.06921 mm. -1 The sixth surface 51 is a convex spherical surface with a curvature radius of 45.6842 mm; the seventh surface 52 is a concave spherical surface with a curvature radius of -1.6254 mm; and the center thickness of the fourth lens 5 is 2.1183 mm.

[0034] Furthermore, the optical power of the fifth lens 6 is 0.21563 mm. -1 The eighth surface 61 is a concave spherical surface with a curvature radius of -2.5735 mm; the central thickness of the fifth lens 6 is 0.8950 mm.

[0035] Furthermore, the center interval between the second surface 12 and the aperture 2 is 5.9842 mm, the center interval between the aperture 2 and the third surface 31 is 0.1324 mm, the center interval between the fifth surface 41 and the sixth surface 51 is 1.0359 mm, and the center interval between the eighth surface 61 and the imaging surface 7 is 1.5968 mm.

[0036] Furthermore, the refractive index n and the Abbe number v of the first lens (1) are 1.8706 and 41.1097 respectively; the refractive index n and the Abbe number v of the second lens (3) are 1.8356 and 23.7699 respectively; the refractive index n and the Abbe number v of the third lens (4) are 1.6835 and 53.3600 respectively; the refractive index n and the Abbe number v of the fourth lens (5) are 1.5743 and 68.3786 respectively; the refractive index n and the Abbe number v of the fifth lens (6) are 1.7452 and 27.4780 respectively.

[0037] Furthermore, the net aperture of the first lens 1 is 4.0000 mm, the net aperture of the second lens 3 is 0.6650 mm, the net aperture of the third lens 4 is 0.9961, the net aperture of the fourth lens 5 is 1.4874 mm, and the net aperture of the fifth lens 6 is 1.6830 mm.

[0038] Furthermore, if Figure 2 As shown, in order to couple with the subsequent optical fiber image transmission bundle, the image-side telecentric structure design is adopted. From the imaging schematic diagram, it can be seen that the main rays of the receiving light beam at the imaging plane are parallel to the main axis, and the telecentricity is as high as 0.0235, which ensures the efficiency of light coupling.

[0039] 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.

[0040] 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 0.75, and the overall aberration optimization effect is good.

[0041] 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 5.243 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.

[0042] Furthermore, if Figure 5As shown, the relative illumination of the light received by the objective optical system in the embodiment at the imaging surface is above 99%, which is much better than the relative illumination characteristics of common endoscope structures, and well ensures the uniformity of imaging.

[0043] Furthermore, if Figure 6 As shown, the diffraction circle energy of the full field of view of the objective optical system in the embodiment is higher than 88% within a radius of 13.75 μm, which well ensures the efficiency of light energy transfer.

[0044] 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. The working band of the objective optical system is 1.2-1.8μm, the effective focal length is 0.797mm, the F number is 4, the image side numerical aperture NA is 0.1238, the maximum field of view angle is 120°, the maximum system aperture is 8mm, the total system length is 14.32mm, the image plane size is 3mm, and it is well coupled with the subsequent optical fiber image transmission bundle.

[0045] 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 wide-angle endoscope objective optical system, characterized in that: The system 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 arranged in sequence along the optical axis from the object surface to the image surface. The system adopts an image-side telecentric and anti-telephoto structure, and all lenses adopt a spherical structure. The first lens (1) comprises a first surface (11) facing the object surface and a second surface (12) facing the image surface. The second lens (3) comprises a third surface (31) facing the object surface and a fourth surface (32) facing the image surface. The third lens (4) comprises a fourth surface (32) facing the object surface and a fifth surface (41) facing the image surface. The fourth lens (5) comprises a sixth surface (51) facing the object surface and a seventh surface (52) facing the image surface. The fifth lens (6) comprises a seventh surface (52) facing the object surface and an eighth surface (61) facing the image surface. The focal power of the first lens (1) is -0.25332 mm -1 , the first surface (11) is a convex spherical surface with a radius of curvature of 5.3246 mm; the second surface (12) is a convex spherical surface with a radius of curvature of 2.3753 mm; the center thickness of the first lens (1) is 0.9502 mm; The focal length of the second lens (3) is 0.027513 mm -1 The third surface (31) is a convex spherical surface with a radius of curvature of 7.6271 mm; the fourth surface (32) is a convex spherical surface with a radius of curvature of 1.4567 mm; the center thickness of the second lens (3) is 1.1573 mm; The focal length of the third lens (4) is 0.22451 mm -1 The fifth surface (41) is a concave spherical surface with a radius of curvature of -2.4894 mm; the central thickness of the third lens (4) is 0.6328 mm; The focal power of the fourth lens (5) is -0.06921 mm -1 The sixth surface (51) is a convex spherical surface with a radius of curvature of 45.6842 mm; the seventh surface (52) is a concave spherical surface with a radius of curvature of -1.6254 mm; the center thickness of the fourth lens (5) is 2.1183 mm; The optical power of the fifth lens (6) is 0.21563 mm -1 The eighth surface (61) is a concave spherical surface with a radius of curvature of -2.5735 mm; and the central thickness of the fifth lens (6) is 0.8950 mm.

2. The infrared wide-angle endoscope objective optical system according to claim 1, characterized in that: The center distance between the second surface (12) and the aperture (2) is 5.9842 mm, the center distance between the aperture (2) and the third surface (31) is 0.1324 mm, the center distance between the fifth surface (41) and the sixth surface (51) is 1.0359 mm, and the center distance between the eighth surface (61) and the imaging surface (7) is 1.5968 mm.

3. The infrared wide-angle endoscope objective optical system according to claim 1, characterized in that: The refractive index n and the Abbe number v of the first lens (1) are 1.8706 and 41.1097 respectively; the refractive index n and the Abbe number v of the second lens (3) are 1.8356 and 23.7699 respectively; the refractive index n and the Abbe number v of the third lens (4) are 1.6835 and 53.3600 respectively; the refractive index n and the Abbe number v of the fourth lens (5) are 1.5743 and 68.3786 respectively; the refractive index n and the Abbe number v of the fifth lens (6) are 1.7452 and 27.4780 respectively.

4. The infrared wide-angle 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 0.75 at a spatial resolution of 21lp / mm, the relative illumination of the imaging surface is greater than 99%, the effective focal length is 0.797mm, the F number is 4, the image side numerical aperture NA is 0.1238, the maximum field of view angle is 120°, the maximum system aperture is 8mm, the total length of the system is 14.32mm, the image plane size is 3mm, which matches the subsequent optical fiber image transmission bundle.

Images