An endoscope with a large depth of field optical lens

Abstract

The embodiment of the application discloses a large-FOV optical lens of an endoscope, and belongs to the field of optical elements. From the object side to the image side, the large-FOV optical lens is composed of a first lens with negative focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with positive or negative focal power and a fifth lens with negative focal power arranged in sequence. The object side of the first lens is a plane, and the image side is a concave surface. At least one of the object side and the image side of the second lens is a convex surface. The object side of the third lens is a convex surface, and the image side is a convex surface. The fourth lens is a meniscus lens with a concave object side and a convex image side. At least one of the object side and the image side of the fifth lens is a concave surface. The advantage is that the depth of field of the optical lens is expanded by reasonably matching the surface types of the lenses, miniaturized design is realized, and distortion is reduced, so that the specific requirements of the endoscope on the optical lens can be met.

Description

Technical Field

[0001] This invention relates to an optical lens for an endoscope, and more particularly to a large depth-of-field optical lens for an endoscope. Background Technology

[0002] Endoscopic technology is an important tool in the field of medical diagnosis and treatment, especially in the screening and intervention of gastrointestinal diseases. Endoscopes can observe the morphology of gastrointestinal tissues through the body's natural cavities and screen for suspicious lesions.

[0003] In clinical practice, physicians need to observe and perform surgery at various distances, ranging from wide-angle views to close-up details. This requires endoscopic lenses to possess both good depth of field and image quality. Traditional endoscopic lenses have a shallow depth of field, meaning that even slight relative displacement during examination can cause blurring. Expanding the depth of field can reduce the impact of minute movements in the gastrointestinal tract, decrease the number of refocusing adjustments, and broaden the range of object distances that can be clearly imaged, thereby improving examination efficiency. To obtain a wider field of view, endoscopic lenses typically employ a large field of view design. However, the resulting distortion severely affects the accurate reproduction of the image; for example, a gastroscopy lens with a 145° field of view typically exhibits 70% distortion. Furthermore, the aperture of the endoscopic lens directly affects patient comfort and the ability to pass through narrow cavities, but miniaturization further complicates aberration correction.

[0004] Chinese invention patent application CN120178479A discloses a miniature, large depth-of-field, wide-angle, high-definition lens that uses a five-element lens to achieve a large depth of field of 3-100mm. However, its resolution is relatively low, and the image detail clarity cannot meet the needs of fine diagnosis. Chinese invention patent application CN120871390A discloses an endoscope objective and endoscope, using a five-element lens to achieve distortion of no more than 60% at a 140° field of view. However, all five lenses are aspherical, resulting in high cost and significant manufacturing difficulties. Chinese invention patent application CN116774388A discloses an endoscope optical system, endoscope objective, and endoscope. It achieves lens miniaturization by controlling the length of the front lens group to compress the lens aperture, but it fails to effectively improve distortion, and image distortion remains a prominent problem. Summary of the Invention

[0005] This invention provides a large depth-of-field optical lens for endoscopes, which can effectively reduce distortion while achieving a large depth of field and a small aperture, thus meeting the specific requirements of endoscopes for optical imaging lenses.

[0006] This invention provides a large depth-of-field optical lens for an endoscope, comprising, from the object side to the image side, a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with either positive or negative optical power, and a fifth lens with negative optical power, arranged sequentially. The first lens has a flat object side and a concave image side; the second lens has at least one convex surface between its object side and image side; the third lens has both a convex object side and an convex image side; the fourth lens is a meniscus lens with a concave object side and a convex image side; and the fifth lens has at least one concave object side and an image side. The focal length f of the large depth-of-field optical lens is in the range of 0.6mm ≤ f ≤ 0.8mm, and the image height imgH and focal length f satisfy 1 ≤ imgH / f ≤ 1.2.

[0007] Compared with the prior art, the advantage of the present invention lies in the fact that by reasonably combining lenses with different surface shapes, the inner diameter is enlarged.

[0008] The endoscope features a large depth-of-field optical lens with a diameter of ≤2.5mm, achieving a miniaturized design. At the same time, the peak-to-valley distortion is less than 60%, which meets the specific requirements of endoscopes for optical lenses.

[0009] In one feasible implementation, the focal lengths f1 of the first lens, f2 of the second lens, f3 of the third lens, f4 of the fourth lens, and f5 of the fifth lens satisfy the following conditions: -1.7 ≤ f1 / f ≤ -1.2, 2 ≤ f2 / f ≤ 16, 0.5 ≤ f3 / f ≤ 1.5, -10 ≤ f4 / f ≤ 10, and -1.4 ≤ f5 / f ≤ -0.4, respectively. The first, third, and fifth lenses have a small focal length ratio in a large depth-of-field optical lens, enabling them to handle a large optical power. This is beneficial for controlling the focal length, field of view, and image height of the large depth-of-field optical lens, further increasing its depth of field. Simultaneously, their high light-deflection capability helps to compress the length and reduce the aperture of the large depth-of-field optical lens, achieving miniaturization. The second and fourth lenses have a large focal length ratio in the optical system, handling a small optical power, allowing for a smoother light transition, reducing lens sensitivity, and improving image sharpness.

[0010] In one feasible implementation, the refractive indices Nd1 of the first lens, Nd2 of the second lens, Nd3 of the third lens, Nd4 of the fourth lens, and Nd5 of the fifth lens satisfy the following conditions: 0≤Nd1-Nd2≤0.1, 0≤Nd2-Nd3≤0.2, -0.2≤Nd3-Nd4≤0, and -0.2≤Nd4-Nd5≤-0.1, respectively. The refractive index of the first lens is greater than or equal to that of the second and third lenses, and the refractive index of the fifth lens is greater than or equal to that of the third and fourth lenses. Under the premise of bearing a large optical power, the curvature of the lens surface can be reduced, making the lens flatter or thinner. This is beneficial for compressing the length of large depth-of-field optical lenses, reducing the aperture of large depth-of-field optical lenses, and realizing miniaturized design. The refractive index of the second lens is less than or equal to that of the first lens, and the refractive index of the third lens is less than or equal to that of the second lens. This reduces manufacturing costs without affecting imaging performance. The refractive index of the fourth lens is between that of the third and fifth lenses, which is conducive to a smooth transition of light, reduces aberrations, and improves image sharpness.

[0011] In one feasible implementation, the two surfaces of the third lens are aspherical. This configuration allows for adjustment of light trajectory at different fields of view and apertures. Because the third lens is located in the center of a large depth-of-field optical lens, the overlap between fields of view is high, and the beam aperture is large, which can correct axial aberrations and improve image sharpness.

[0012] In one feasible implementation, the two surfaces of the fifth lens are aspherical. This configuration allows for adjustment of light trajectory at different fields of view and apertures. Because the fifth lens is close to the image plane, the overlap between fields of view is reduced, the beam aperture is smaller, distortion and off-axis aberrations can be controlled, and image sharpness is improved. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the large depth-of-field optical lens of the endoscope provided in Example 1 of the present invention;

[0014] Figure 2 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 1 of the present invention at an object distance of 8mm.

[0015] Figure 3 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 1 of the present invention at an object distance of 3mm;

[0016] Figure 4 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 1 of the present invention at an object distance of 100mm.

[0017] Figure 5This is a distortion curve diagram of the large depth-of-field optical lens of the endoscope in Example 1 of the present invention.

[0018] Figure 6 This is a schematic diagram of the large depth-of-field optical lens of the endoscope provided in Example 2 of the present invention;

[0019] Figure 7 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 2 of the present invention at an object distance of 8mm;

[0020] Figure 8 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 2 of the present invention at an object distance of 3mm;

[0021] Figure 9 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 2 of the present invention at an object distance of 100mm.

[0022] Figure 10 This is a distortion curve diagram of the large depth-of-field optical lens of the endoscope in Example 2 of the present invention.

[0023] Figure 11 This is a schematic diagram of the large depth-of-field optical lens of the endoscope provided in Example 3 of the present invention;

[0024] Figure 12 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 3 of the present invention at an object distance of 8mm;

[0025] Figure 13 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 3 of the present invention at an object distance of 3 mm;

[0026] Figure 14 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 3 of the present invention at an object distance of 100mm.

[0027] Figure 15 This is a distortion curve diagram of the large depth-of-field optical lens of the endoscope in Example 3 of the present invention.

[0028] Figure 16 This is a schematic diagram of the large depth-of-field optical lens of the endoscope provided in Example 4 of the present invention;

[0029] Figure 17 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 4 of the present invention at an object distance of 8mm.

[0030] Figure 18This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 4 of the present invention at an object distance of 3 mm.

[0031] Figure 19 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 4 of the present invention at an object distance of 100mm.

[0032] Figure 20 This is a distortion curve diagram of the large depth-of-field optical lens of the endoscope in Example 4 of the present invention.

[0033] Figure 21 This is a schematic diagram of the large depth-of-field optical lens of the endoscope provided in Example 5 of the present invention;

[0034] Figure 22 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 5 of the present invention at an object distance of 8mm;

[0035] Figure 23 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 5 of the present invention at an object distance of 3 mm;

[0036] Figure 24 This is a modulation transfer function curve of the large depth-of-field optical lens of the endoscope in Example 5 of the present invention at an object distance of 100mm.

[0037] Figure 25 This is a distortion curve diagram of the large depth-of-field optical lens of the endoscope in Example 5 of the present invention.

[0038] Explanation of reference numerals in the attached figures:

[0039] G1, first lens; G2, second lens; G3, third lens; G4, fourth lens; G5, fifth lens; L1, filter; L2, protective glass; IMA, imaging plane. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale.

[0042] In each example, the convexity or concavity of the lens surface is determined by the radius of curvature at the center of the lens surface. When the radius of curvature of the object-side surface is greater than 0, the surface is convex; when the radius of curvature of the object-side surface is infinite, the surface is planar; and when the radius of curvature of the object-side surface is less than 0, the surface is concave. When the radius of curvature of the image-side surface is greater than 0, the surface is concave; when the radius of curvature of the image-side surface is infinite, the surface is planar; and when the radius of curvature of the image-side surface is less than 0, the surface is convex.

[0043] In an exemplary embodiment, to improve lens image quality and reduce aberrations in the imaging system, an aspherical lens is used, the surface shape of which satisfies the following equation: Where y represents the radial coordinate value of the lens perpendicular to the optical axis. Z ( y Let y be the sag of the aspherical lens at a height of y along the optical axis from the vertex of the aspherical surface. c =1 / R, where R represents the radius of curvature at the center of the surface profile of the aspherical lens. k Represents the conicity factor, parameter B , C , D The coefficients of the fourth, sixth, and eighth order terms of the higher-order aspherical polynomials are, in order.

[0044] Figure 1 , Figure 6 , Figure 11 , Figure 16 and Figure 21This invention illustrates a large depth-of-field optical lens for an endoscope, comprising, from the object side to the image side, a first lens G1 with negative optical power, a second lens G2 with positive optical power, a third lens G3 with positive optical power, a fourth lens G4 with either positive or negative optical power, and a fifth lens G5 with negative optical power, arranged sequentially. The focal length f of the large depth-of-field optical lens is in the range of 0.6mm ≤ f ≤ 0.8mm, and the image height imgH satisfies the following relationship with the focal length f: 1 ≤ imgH / f ≤ 1.2. The first lens G1, as a negative lens, expands the field of view, providing a wider field of view. The second lens G2, as a positive lens, collects and converges the large field of view light rays diverged by the first lens G1, which is beneficial for controlling the focal length and field of view of the optical system, further increasing the depth of field of the optical lens, reducing the aperture of the optical lens, and achieving a miniaturized design. Existing gastrointestinal endoscope modules typically use 1 / 6-inch chips, whose side structure limits the overall outer diameter of the module, resulting in a generally large packaged size, slightly larger than 4mm × 3mm, with the optical lens typically having a diameter of 3mm. This application's large depth-of-field optical lens is designed based on a small chip, less than 1 / 7 inch in size, achieving a packaged size of 2.5mm × 2.5mm. The diameter of the large depth-of-field optical lens is also less than or equal to 2.5mm, thus achieving a miniaturized design from the large depth-of-field optical lens to the entire endoscope module. The third lens G3 is a positive lens, with both its object-side and image-side surfaces being convex. This double-convex surface design effectively further converges light, facilitating control of the optical lens's focal length, field of view, and image height, further increasing the depth of field. The fourth lens G4 can be either a positive or negative lens, working in conjunction with the third lens G3 and the fifth lens G5 to transition light rays. When the fourth lens G4 is a positive lens, it converges light rays together with the third lens G3. When the fourth lens G4 is a negative lens, it mitigates the light-converging effect of the third lens G3, controls the light angle and lens length, and provides image for the fifth lens G5. As a negative lens, the fifth lens G5 diverges the converged light rays and forms an image, increasing the imaging height, improving the utilization of the chip area, and facilitating control of the focal length, field of view, and image height of the optical lens, further increasing the depth of field. The image height imgH and focal length f of a large depth-of-field optical lens satisfy: 1 ​​≤ imgH / f ≤ 1.2. Limiting this relationship to the lower limit reduces lens sensitivity; limiting it to the upper limit achieves a large field of view, increases depth of field, broadens the user's observation range, and controls endoscope distortion within a certain range, reducing image distortion.

[0045] The focal lengths f1 of the first lens G1, f2 of the second lens G2, f3 of the third lens G3, f4 of the fourth lens G4, and f5 of the fifth lens G5 satisfy the following conditions: -1.7 ≤ f1 / f ≤ -1.2, 2 ≤ f2 / f ≤ 16, 0.5 ≤ f3 / f ≤ 1.5, -10 ≤ f4 / f ≤ 10, and -1.4 ≤ f5 / f ≤ -0.4, respectively. The first lens G1, the third lens G3, and the fifth lens G5 have a small focal length ratio in the optical system, enabling them to handle a large optical power. This is beneficial for controlling the focal length, field of view, and image height of the optical system, further increasing the depth of field. Simultaneously, their high light-deflection capability helps to compress the length of the optical system, reduce the lens aperture, and achieve miniaturization. The second lens G2 and the fourth lens G4 have a large focal length ratio in the optical system, handling a small optical power. This helps to smooth the light transition, reduce lens sensitivity, and improve image sharpness.

[0046] The refractive indices Nd1 of the first lens G1, Nd2 of the second lens G2, Nd3 of the third lens G3, Nd4 of the fourth lens G4, and Nd5 of the fifth lens G5 satisfy the following conditions: 0 ≤ Nd1 - Nd2 ≤ 0.1, 0 ≤ Nd2 - Nd3 ≤ 0.2, -0.2 ≤ Nd3 - Nd4 ≤ 0, and -0.2 ≤ Nd4 - Nd5 ≤ -0.1, respectively. The refractive index of the first lens G1 is greater than or equal to that of the second and third lenses G2, and the refractive index of the fifth lens G5 is greater than or equal to that of the third and fourth lenses G4. This allows for a reduction in lens surface curvature while maintaining a high optical power, resulting in flatter or thinner lenses. This facilitates reducing the length and aperture of the optical lens, enabling miniaturized designs. The refractive index of the second lens G2 is less than or equal to that of the first lens G1, and the refractive index of the third lens G3 is less than or equal to that of the second lens G2. This reduces manufacturing costs without affecting imaging performance. The refractive index of the fourth lens G4 is between that of the third lens G3 and the fifth lens G5, which facilitates a smooth light transition, reduces aberrations, and improves image clarity.

[0047] The object side of the first lens G1 is flat, and the image side is concave.

[0048] At least one of the object-side surface and the image-side surface of the second lens G2 is a convex surface, such as... Figure 1 and Figure 21 The object-side and image-side surfaces of the second lens G2 shown are both convex. Figure 11 and Figure 16 The object-side surface of the second lens G2 shown is concave, while the image-side surface is convex; and Figure 6 The object-side surface of the second lens G2 shown is convex, and the image-side surface is concave.

[0049] The third lens G3 has a convex object side and a convex image side, while the fourth lens G4 is a meniscus lens with a concave object side and a convex image side.

[0050] At least one of the object-side surface and the image-side surface of the fifth lens G5 is concave. For example... Figure 1 , Figure 11 and Figure 21 The object-side surface of the fifth lens G5 shown is concave, and the image-side surface is also concave. Figure 6 and Figure 16 The fifth lens G5 shown has a concave object side and a convex image side.

[0051] The plano-concave surface design of the first lens G1 causes the refraction angle of rays from the periphery of the field of view to be greater than that from the center of the field of view. Even after reshaping by subsequent lenses, some negative distortion still exists. This negative distortion, also known as barrel distortion, manifests as a magnification at the center of the field of view being greater than at the periphery. Appropriate negative distortion can simulate the stereoscopic view of an endoscope inside the intestines, conforming to the human eye's viewing habits and improving the user experience. The concave-convex meniscus design of the fourth lens G4 allows for a smoother light transition, reducing lens sensitivity and improving image clarity.

[0052] In one embodiment, the two surfaces of the third lens G3 can be aspherical, which is beneficial for adjusting the light trajectory at different fields of view and different apertures. The third lens G3 is located in the middle of the optical system, resulting in a high degree of overlap between fields of view and a large beam aperture, which can correct axial aberrations and improve image sharpness.

[0053] In one embodiment, the two surfaces of the fifth lens G5 can be aspherical, which is beneficial for adjusting the light trajectory at different fields of view and different apertures. The fifth lens G5 is close to the image plane, reducing the overlap between fields of view and resulting in a smaller beam aperture, which helps control isometric aberrations and improves image sharpness.

[0054] The following are five specific examples provided in the embodiments of the present invention.

[0055] Example 1: Figure 1 This example illustrates a large depth-of-field optical lens for an endoscope, comprising a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, and a fifth lens G5 from the object side to the image side. A filter L1 is disposed between the second lens G2 and the third lens G3 to filter light in a specific operating wavelength range, thereby improving the clarity and signal-to-noise ratio of the lens image. A protective glass L2 is disposed behind the fifth lens G5 to protect the chip and prevent the intrusion of external gases, moisture, and debris. Figure 1 In this context, IMA stands for Imaging Surface.

[0056] The first lens G1 has a negative optical power and is a plano-concave lens; the second lens G2 has a positive optical power and is a biconvex lens; the third lens G3 has a positive optical power and is a biconvex lens; the fourth lens G4 has a positive optical power and is a concave-convex lens; and the fifth lens G5 has a negative optical power and is a biconcave lens. The main optical structural parameters of Example 1 are shown in Table 1.

[0057] Table 1

[0058]

[0059] Figures 2 to 4 The modulation transfer function curves for this example 1 at different object distances are shown.

[0060] Figure 2 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 2 This example demonstrates that the large depth-of-field optical lens of the endoscope in Example 1 has a modulation transfer function (MTF) value greater than 0.6 in the central field of view and greater than 0.25 in the peripheral field of view at an object distance of 8 mm and a speed of 100 lp / mm, exhibiting good imaging performance.

[0061] Figure 3 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 3This example demonstrates that the large depth-of-field optical lens of the endoscope in Example 1 has a modulation transfer function value greater than 0.2 in the center field of view and a modulation transfer function value greater than 0.2 in the edge field of view at a distance of 3 mm and a speed of 100 lp / mm, indicating good imaging performance.

[0062] Figure 4 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 4 The large depth-of-field optical lens of the endoscope in Example 1 demonstrates that at a 100mm object distance and 100lp / mm, the modulation transfer function value of the central field of view is greater than 0.4, and the modulation transfer function value of the peripheral field of view is greater than 0.3, indicating good imaging performance.

[0063] Figure 5 Corresponding to the distortion curve of Example 1 in the wavelength range of 0.486 micrometers to 0.54 micrometers, from Figure 5 As can be seen, the peak-valley distortion of this distortion curve in the Zemax optical design simulation software is 59.13%. This value is obtained by calculating the difference between the maximum distortion value of 0 and the minimum distortion value of -59.13% of this distortion curve, indicating that the aberration is well corrected.

[0064] Example 2: Figure 6 This example illustrates a large depth-of-field optical lens for an endoscope. Compared to Example 1, Example 2 primarily changes the surface shape of the second lens G2 so that the object-side surface is convex and the image-side surface is concave, and changes the surface shape of the fifth lens G5 so that the object-side surface is concave and the image-side surface is convex, and also changes the fifth lens G5 to an aspherical lens. The main optical structural parameters of Example 2 are shown in Table 2.

[0065] Table 2

[0066]

[0067] The aspherical optical parameters of the fifth lens G5 in this example are shown in Table 3.

[0068] Table 3

[0069]

[0070] Figures 7 to 9 The modulation transfer function curves for Example 2 at different object distances are shown.

[0071] Figure 7 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 7 This example demonstrates that, at an object distance of 8 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the central field of view is greater than 0.5, and the MJF values ​​of the peripheral field of view are both greater than 0.2, indicating good imaging performance.

[0072] Figure 8 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 8 This example demonstrates that, at a 3mm object distance and 100lp / mm, the modulation transfer function (MJF) value of the central field of view is greater than 0.25, and the MJF values ​​of the peripheral field of view are both greater than 0.2, indicating good imaging performance.

[0073] Figure 9In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 9 This example demonstrates that, at an object distance of 100 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the central field of view is greater than 0.4, and the MJF values ​​of the peripheral field of view are both greater than 0.2, indicating good imaging performance.

[0074] Figure 10 Corresponding to the distortion curve of Example 2 in the wavelength range of 0.486 micrometers to 0.54 micrometers, from Figure 10 As can be seen, the peak-valley distortion of this distortion curve in the Zemax optical design simulation software is 59%. This value is obtained by calculating the difference between the maximum distortion value of 0 and the minimum distortion value of -59% of this distortion curve, indicating that the aberration is well corrected.

[0075] Example 3: Figure 11 This example three illustrates a large depth-of-field optical lens for an endoscope. Compared to example one, example three primarily differs in that the surface shape of the second lens G2 is changed so that the object side is concave and the image side is convex. The main optical structural parameters of example three are shown in Table 4.

[0076] Table 4

[0077]

[0078] Figures 12 to 14 The modulation transfer function curves for Example 3 at different object distances are shown.

[0079] Figure 12In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 12 This example demonstrates that, at an object distance of 8 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.5, and the MJF values ​​of the edge field of view are both greater than 0.25, indicating good imaging performance.

[0080] Figure 13 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 13 This example demonstrates that, at an object distance of 3 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) values ​​of the central field of view and the edge field of view are both greater than 0.2, indicating good imaging performance.

[0081] Figure 14In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 14 This example demonstrates that, at an object distance of 100 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.4, and the MJF values ​​of the edge field of view are both greater than 0.3, indicating good imaging performance.

[0082] Figure 15 Corresponding to the distortion curve of Example 3 in the wavelength range of 0.486 micrometers to 0.54 micrometers, from Figure 15 As can be seen, the peak-valley distortion of this distortion curve in the Zemax optical design simulation software is 56.18%. This value is obtained by calculating the difference between the maximum distortion value of 0 and the minimum distortion value of -56.18% of this distortion curve, indicating that the aberration is well corrected.

[0083] Example 4: Figure 16 This example four illustrates a large depth-of-field optical lens for an endoscope. Compared to example three, example four primarily changes the surface shape of the fifth lens G5 so that the object side is concave and the image side is convex, and also changes the fifth lens G5 to an aspherical lens. The main optical structural parameters of example four are shown in Table 5.

[0084] Table 5

[0085]

[0086] The aspherical optical parameters of the fifth lens G5 in Example 4 are shown in Table 6.

[0087] Table 6

[0088]

[0089] Figures 17 to 19 The modulation transfer function curves for Example 4 at different object distances are shown.

[0090] Figure 17In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 17 This example demonstrates that, at an object distance of 8 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.5, and the MJF value of the edge field of view is greater than 0.35, indicating good imaging performance.

[0091] Figure 18 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 18 This example demonstrates that, at a 3mm object distance and 100lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.25, and the MJF values ​​of the edge field of view are both greater than 0.25, indicating good imaging performance.

[0092] Figure 19In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 19 This example demonstrates that, at an object distance of 100 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.35, and the MJF values ​​of the edge fields of view are also greater than 0.35, indicating good imaging performance.

[0093] Figure 20 Corresponding to the distortion curve of Example 4 in the wavelength range of 0.486 micrometers to 0.54 micrometers, from Figure 20 As can be seen, the peak-valley distortion of this distortion curve in the Zemax optical design simulation software is 58.90%. This value is obtained by calculating the difference between the maximum distortion value of 0 and the minimum distortion value of -58.90% of this distortion curve, indicating that the aberration is well corrected.

[0094] Example 5: Figure 21 This example five illustrates a large depth-of-field optical lens for an endoscope. Compared to example three, example five primarily changes the surface shape of the second lens G2 to be convex on both the object side and the image side, and changes the third lens G3 to an aspherical lens. The main optical structural parameters of example five are shown in Table 7.

[0095] Table 7

[0096]

[0097] The aspherical optical parameters of the third lens G3 in this example are shown in Table 8.

[0098] Table 8

[0099]

[0100] Figures 22 to 24 The modulation transfer function curves for Example 5 at different object distances are shown.

[0101] Figure 22In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 22 This example demonstrates that, at an object distance of 8 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.5, and the MJF values ​​of the edge field of view are both greater than 0.25, indicating good imaging performance.

[0102] Figure 23 In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 23 This example demonstrates that, at a 3mm object distance and 100lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.25, and the MJF values ​​of the edge field of view are both greater than 0.25, indicating good imaging performance.

[0103] Figure 24In the diagram, the curve marked 0.0° meridional / 0.0° sagittal represents the meridional and sagittal curves, respectively, measured within the meridional and sagittal sections at a field of view of 0.0° relative to the optical system's optical axis, showing the modulation transfer function (MTF) values ​​as a function of spatial frequency. Since this is at the central field of view, the meridional and sagittal curves theoretically overlap and are displayed as a single curve. The curve marked 70° meridional represents the MTF values ​​of the edge field of view as a function of spatial frequency, measured within the meridional section at an image height position at a field of view of 70° relative to the optical system's optical axis. The curve marked 70° sagittal represents the MTF values ​​of the edge field of view as a function of the same spatial frequency, measured within the sagittal section at the same field of view. Figure 24 This example demonstrates that, at an object distance of 100 mm and a speed of 100 lp / mm, the modulation transfer function (MJF) value of the center field of view is greater than 0.3, and the MJF values ​​of the edge field of view are both greater than 0.25, indicating good imaging performance.

[0104] Figure 25 Corresponding to the distortion curve of Example 5 in the wavelength range of 0.486 micrometers to 0.54 micrometers, from Figure 25 As can be seen, the peak-valley distortion of this distortion curve in the Zemax optical design simulation software is 58.73%. This value is obtained by calculating the difference between the maximum distortion value of 0 and the minimum distortion value of -58.73% of this distortion curve, indicating that the aberration is well corrected.

[0105] The performance parameters for the five examples above are shown in Table 9.

[0106] Table 9

[0107]

[0108] The examples shown above are merely individual examples of the present invention and do not limit the scope of protection of the present invention. Therefore, equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A large depth-of-field optical lens for an endoscope, characterized in that, The lens, arranged sequentially from the object side to the image side, consists of a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with either positive or negative optical power, and a fifth lens with negative optical power. The first lens has a flat object side and a concave image side. The second lens has at least one convex surface between its object side and image side. The third lens has both a convex object side and an convex image side. The fourth lens is a meniscus lens with a concave object side and a convex image side. The fifth lens has at least one concave object side and an image side. The focal length f of the large depth-of-field optical lens is in the range of 0.6mm ≤ f ≤ 0.8mm, and the image height imgH satisfies the condition 1 ≤ imgH / f ≤ 1.

2.

2. The large depth-of-field optical lens for an endoscope as described in claim 1, characterized in that, The focal lengths f1 of the first lens, f2 of the second lens, f3 of the third lens, f4 of the fourth lens, and f5 of the fifth lens satisfy the following conditions respectively: -1.7≤f1 / f≤-1.2, 2≤f2 / f≤16, 0.5≤f3 / f≤1.5, -10≤f4 / f≤10, and -1.4≤f5 / f≤-0.

4.

3. The large depth-of-field optical lens for an endoscope as described in claim 1, characterized in that, The refractive indices Nd1 of the first lens, Nd2 of the second lens, Nd3 of the third lens, Nd4 of the fourth lens, and Nd5 of the fifth lens satisfy the following conditions: 0≤Nd1-Nd2≤0.1, 0≤Nd2-Nd3≤0.2, -0.2≤Nd3-Nd4≤0, and -0.2≤Nd4-Nd5≤-0.1, respectively.

4. The large depth-of-field optical lens for an endoscope as described in claim 1, characterized in that, The two surfaces of the third lens are aspherical.

5. The large depth-of-field optical lens for an endoscope as described in claim 1, characterized in that, The fifth lens has two aspherical surfaces.

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