A miniature high-definition wide-angle endoscope objective optical system

Abstract

The utility model discloses a kind of superminiature high-definition wide-angle endoscope objective optical systems, comprising: first lens L1, second lens L2, third lens L3, double cemented lens group, sixth lens L6 are sequentially arranged from object side along optical axis;Optical system diaphragm is located between second lens, third lens;The double cemented lens group is composed of fourth lens L4 and fifth lens L5 cemented, wherein fourth lens L4 is close to object side;The first lens is double aspheric glass lens;Second lens, third lens, double cemented lens group, sixth lens are spherical glass lens.The endoscope objective optical system has not less than 120 ° field angle, maximum distortion is not more than 10%, total length is not more than 3.5mm, optical system maximum diameter is not more than 1mm, suitable for miniaturization and light-weight endoscope design requirement.

Description

Technical Field

[0001] This utility model relates to the field of medical optical instrument technology, specifically to an objective lens optical system for high-resolution electronic endoscopes, and in particular to an ultra-miniature endoscope objective lens that is adapted to small pixel-sized image sensors, has a large field of view, low distortion, and a nearly perpendicular principal ray angle (CRA). Background Technology

[0002] Electronic endoscopes use their objective lens optical system to image images of the human body cavity onto a CMOS or CCD image sensor, making them core instruments for minimally invasive medical diagnosis and surgery. With advancements in medical technology, clinical demands for endoscope performance have increased: not only are smaller outer diameters (≤1mm) required to minimize trauma, but also wider fields of view (≥120°) are needed to expand the observation range. Simultaneously, higher image resolution and fidelity (low distortion) are required to aid in accurate diagnosis.

[0003] However, achieving these performance indicators faces significant challenges in the field of optical design:

[0004] 1. The extremely small optical aperture (≤1mm) not only severely limits light transmission efficiency but also significantly restricts the system's aberration correction capabilities. Expanding the field of view significantly amplifies distortion effects. A large field of view inevitably introduces significant distortion in optical principles, leading to image edge stretching or compression, severe distortion, and astigmatism and field curvature problems at the edges, resulting in image quality degradation. Especially in ultra-wide-angle designs, field curvature can cause the image plane to deviate significantly from the ideal plane, preventing simultaneous sharp focus at the image center and edges. To achieve high-definition imaging, the maximum field curvature must be controlled within an extremely small range (e.g., less than the system's depth of focus), which is an extremely difficult design goal in ultra-compact systems. Simultaneously, improving the transfer function performance under limited aperture faces physical bottlenecks, making it difficult to meet the high-frequency information transmission requirements of high-resolution sensors. This creates a difficult-to-balance constraint between key parameters such as field of view, image fidelity, and detail resolution.

[0005] 2. Principal Ray Angle Matching Issue: Image sensors (especially CCDs) have microlens structures, making them extremely sensitive to the angle of incidence (CRA). If the principal ray angle output by the optical system does not match the sensor's optimal receiving angle, it will cause a decrease in response in the sensor's edge areas, resulting in vignetting (shadowing) and severely affecting image uniformity. In wide-angle systems, strictly controlling the CRA is an extremely difficult task.

[0006] Currently, ultra-fine endoscopes on the market often sacrifice field of view, tolerate large distortion, and have low MTF in pursuit of small size; or, although they possess wide-angle characteristics, they cannot be effectively matched with high-resolution small-pixel sensors, resulting in problems such as vignetting and low edge resolution due to CRA mismatch. Furthermore, significant field curvature and difficult-to-correct distortion further exacerbate the blurring and image distortion at the edges of the field of view, affecting overall image clarity and geometric realism. Therefore, developing an endoscope objective that simultaneously meets the requirements of ultra-small outer diameter (1mm), wide field of view (120°), low distortion (<10%), high transfer function performance (MTF>0.1 at 285lp / mm), excellent image plane flatness (maximum field curvature ≤0.022mm, less than the depth of focus), and perfect matching with the sensor (CRA almost zero) has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0007] To address the challenge of achieving the optimal balance between ultra-small aperture, ultra-wide field of view, low distortion, high resolution, and perfect sensor matching in endoscopic objective design, this invention provides an ultra-compact high-definition wide-angle endoscopic objective optical system. Through its innovative optical design, it achieves superior performance in a compact size, integrating wide-angle, low distortion, high resolution, and high uniformity. This provides a core imaging solution for high-end endoscopes, demonstrating significant clinical value and market competitiveness.

[0008] The objective of this utility model is achieved through the following technical solution, as shown in the accompanying drawings:

[0009] An ultra-compact high-definition wide-angle endoscope objective lens optical system includes: a first lens L1, a second lens L2, a third lens L3, a cemented doublet lens group, and a sixth lens L6 arranged sequentially along the optical axis from the object side; the optical system aperture is located between the second lens and the third lens; the cemented doublet lens group is composed of a fourth lens L4 and a fifth lens L5 cemented together, wherein the fourth lens L4 is closer to the object side; the first lens is a double aspherical glass lens; the second lens, the third lens, the cemented doublet lens group, and the sixth lens are spherical glass lenses.

[0010] Preferably, the optical parameters of the endoscope objective optical system satisfy the following relationship:

[0011] 3.0≤IH / f≤3.2

[0012] 4≤L≤8

[0013] 0.08≤IH / TTL≤0.12

[0014] 1.8≤d1 / f≤2

[0015] 4.5≤Bf / f≤5

[0016] 2.2≤|fL1 / f|≤2.5

[0017] 3.1≤|fL² / f|≤3.4

[0018] 5.2≤|fL3 / f|≤5.5

[0019] 49≤|f45 / f|≤50

[0020] 12≤|fL6 / f|≤13

[0021] 1.4 ≤ FNO / TTL ≤ 1.6

[0022] in:

[0023] f is the focal length of the endoscope optical system; IH is half the optical image height of the endoscope optical system; L is the working distance of the endoscope optical system; TTL is the distance on the optical axis from the object side of the first lens L1 to the imaging surface of the endoscope optical system; d1 is the center thickness of the first lens L1; Bf is the distance on the optical axis from the image side of the sixth lens L6 to the imaging surface of the endoscope optical system; fL1 is the effective focal length of the first lens L1; fL2 is the effective focal length of the second lens L2; ​​fL3 is the effective focal length of the third lens L3; f45 is the overall effective focal length of the fourth lens L4 and the fifth lens L5; fL6 is the effective focal length of the sixth lens L6; FNO is the aperture number of the endoscope optical system.

[0024] Preferably, the first lens L1 has a convex surface near the object and a concave surface away from the object; the second lens L2 has concave surfaces on both sides; the third lens L3 has convex surfaces on both sides; in the cemented doublet lens group, the fourth lens L4 has convex surfaces on both sides, the fifth lens L5 has a concave surface near the object and a convex surface away from the object; and the sixth lens L6 has convex surfaces on both sides.

[0025] Preferably, the first lens L1 has an object-side radius of curvature ranging from -220mm to -240mm and an image-side radius of curvature ranging from 0.15mm to 0.25mm; the second lens L2 has an object-side radius of curvature ranging from -0.4mm to -0.6mm and an image-side radius of curvature ranging from 0.4mm to 0.6mm; the third lens L3 has an object-side radius of curvature ranging from 0.4mm to 0.6mm and an image-side radius of curvature ranging from -0.4mm to -0.6mm; in the cemented doublet lens group, the object-side radius of curvature ranges from 0.9mm to 1.1mm, the cemented surface radius of curvature ranges from -0.25mm to -4mm, and the image-side radius of curvature ranges from -0.8mm to -1.2mm; and the sixth lens L6 has an object-side radius of curvature ranging from 2.2mm to 2.6mm and an image-side radius of curvature ranging from -0.9mm to -1.2mm.

[0026] Preferably, the center thickness of the first lens L1 is 0.15 mm to 0.4 mm; the center thickness of the second lens L2 is 0.4 mm to 0.6 mm; the center thickness of the third lens L3 is 0.15 mm to 0.4 mm; the thickness of the fourth lens L4 is 0.3 mm to 0.5 mm; the thickness of the fifth lens L5 is 0.15 mm to 0.4 mm; and the center thickness of the sixth lens L1 is 0.2 mm to 0.4 mm.

[0027] Preferably, the endoscope objective optical system has a field of view of not less than 120° and a maximum distortion of not more than 10%.

[0028] Preferably, the total length of the endoscope objective optical system is no more than 3.5 mm, and the maximum diameter of the optical system is no more than 1 mm, which is suitable for the design requirements of miniaturized and lightweight endoscopes.

[0029] This utility model has the following beneficial effects:

[0030] 1. Highly efficient coupling with small-pixel sensors was achieved, resulting in high-definition resolution. At a high spatial frequency of 285 lp / mm, the system maintains a central field-of-view MTF of no less than 0.1. This excellent transfer function fully meets the requirements of high-resolution sensors with pixel sizes around 1.75 μm for the optical system, ensuring that the objective lens itself has sufficient resolving power to support high-definition imaging and laying the foundation for displaying minute pathological structures.

[0031] 2. The principal ray angle is precisely controlled, ensuring excellent imaging uniformity across the entire image plane. Through precise optical path optimization, this invention strictly controls the system's principal ray angle (CRA) to within 0.025°. This characteristic enables the system to completely eliminate edge vignetting (dimosis) when coupled with an image sensor; and to significantly improve edge image sharpness and brightness when coupled with a fiber optic image bundle, thereby obtaining a high-quality image that is uniform and bright from the center to the edges.

[0032] 3. A perfect balance is achieved between the two core requirements of wide-angle viewing and low distortion within a 1mm aperture limit. This invention successfully achieves an ultra-wide 120° field of view under the strict constraint of an optical outer diameter of only 1mm, while suppressing maximum optical distortion to within 10%. This provides doctors with a wide and highly realistic diagnostic field of view, greatly improving the convenience and accuracy of surgical procedures.

[0033] 4. The aspherical design of key components is the technological cornerstone for achieving high performance. This invention designs both sides of the first lens as aspherical. This allows for precise shaping and aberration correction of the wide-angle beam at the beginning of the optical path, effectively suppressing distortion and spherical aberration. This provides a decisive guarantee for achieving extremely low CRA and high MTF, and is the key technical means by which this invention breaks through the traditional performance ceiling. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of an ultra-compact high-definition wide-angle endoscope objective lens optical system according to an embodiment of the present invention;

[0036] Figure 2 This is a modulation transfer function (MTF) curve of an ultra-compact high-definition wide-angle endoscope objective optical system according to an embodiment of the present invention;

[0037] Figure 3 This is a dot diagram of an ultra-compact high-definition wide-angle endoscope objective lens optical system according to an embodiment of the present invention;

[0038] Figure 4 This is a field curvature and distortion diagram of an ultra-compact high-definition wide-angle endoscope objective optical system according to an embodiment of this utility model.

[0039] Figure 5This is a relative illumination diagram of an ultra-compact high-definition wide-angle endoscope objective lens optical system according to an embodiment of this utility model. Detailed Implementation

[0040] To make the technical solution and advantages of this utility model clearer, the specific embodiments of this utility model will be described in further detail and completely below with reference to the accompanying drawings. The various embodiments described below are only some preferred embodiments of this utility model, not all of them; the various embodiments described below are intended to explain this utility model and should not be construed as limiting this utility model; reasonable combinations of the technical features defined by the various embodiments of this utility model, as well as all other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort, are within the scope of protection of this utility model.

[0041] This invention aims to solve the problem of achieving the optimal balance between ultra-small aperture, ultra-large field of view, low distortion, high resolution, and perfect matching with sensors in the design of endoscope objectives. Specifically, the existing technology mainly suffers from the following technical problems:

[0042] The fundamental contradiction between aperture and image quality: Existing ultra-fine endoscopes, in pursuit of small apertures (such as... This often results in a significant sacrifice of the field of view or a tolerance for large distortions. Achieving a 120° ultra-large field of view while maintaining a 1mm outer diameter introduces severe astigmatism, field curvature, and barrel distortion exceeding 30%, leading to severely distorted and blurred image edges that cannot meet the needs of accurate diagnosis.

[0043] The problem of matching high resolution with small pixels: Modern high-resolution sensors have pixel sizes as small as 1.75μm, which places extremely high demands on the MTF of optical systems at characteristic frequencies (such as 285lp / mm). Existing ultra-fine endoscopes often have an MTF that decays to below 0.1 at this high frequency, failing to fully utilize the sensor's resolution potential and resulting in loss of image details.

[0044] The challenge of controlling the main ray angle: Whether coupling a CCD / CMOS sensor or a fiber optic image bundle, strict control of the main ray angle is necessary. In ultra-wide-angle designs, uncontrolled CRA can lead to vignetting at the sensor edges or deterioration of image quality at the edges of the fiber optic image bundle, severely affecting image uniformity. Current technology struggles to control the CRA within the ideal range at a 120° field of view.

[0045] Explanation of terms in the embodiments of this utility model:

[0046] Object side: refers to the side from which light enters the optical system (an ultra-compact high-definition wide-angle endoscope objective lens optical system), i.e., the side where the observed object is located. For the application of this embodiment of the invention in a video laryngoscope: the object side is the side where the patient's glottis is located; light is emitted from the glottis (or reflected after illumination) and enters the optical system of the laryngoscope. "Object side" is defined from the perspective of the entire optical system, indicating the direction of light entry and the starting point of the element arrangement; it defines the coordinate system of the entire sequence.

[0047] Object side: A more relative term, specifically referring to the surface of an optical element (such as the first lens) that is closer to the "object side," as opposed to the "image side," which refers to the surface of the element that is closer to the "image side." Example: For a single lens (such as the first lens), it has two surfaces: the surface closer to the object being photographed (or the surface closer to the object side) is called the "object side"; the surface closer to the imaging sensor is called the "image side."

[0048] Image plane side: refers to the side from which light rays exit the optical system, i.e., the side where the image sensor (such as CCD / CMOS) imaging surface is located. In the application of this invention in a video laryngoscope: the image plane side is the side where the image sensor is located, and the light rays processed by the optical system ultimately converge here to form a clear image.

[0049] The following are embodiments of this utility model:

[0050] This embodiment describes an ultra-compact, high-definition, wide-angle endoscope objective lens optical system, such as... Figure 1 As shown, it includes: a first lens L1, a second lens L2, a third lens L3, a cemented doublet lens group, and a sixth lens L6 arranged sequentially along the optical axis from the object side; the optical system aperture is located between the second lens and the third lens; the cemented doublet lens group is composed of a fourth lens L4 and a fifth lens L5 cemented together, wherein the fourth lens L4 is closer to the object side; the first lens is a double aspherical glass lens; the second lens, the third lens, the cemented doublet lens group, and the sixth lens are spherical glass lenses.

[0051] Preferably, the optical parameters of the endoscope objective lens optical system described in this embodiment satisfy the following relationship:

[0052] 3.0≤IH / f≤3.2

[0053] 4≤L≤8

[0054] 0.08≤IH / TTL≤0.12

[0055] 1.8≤d1 / f≤2

[0056] 4.5≤Bf / f≤5

[0057] 2.2≤|fL1 / f|≤2.5

[0058] 3.1≤|fL² / f|≤3.4

[0059] 5.2≤|fL3 / f|≤5.5

[0060] 49≤|f45 / f|≤50

[0061] 12≤|fL6 / f|≤13

[0062] 1.4 ≤ FNO / TTL ≤ 1.6

[0063] in:

[0064] f is the focal length of the endoscope optical system; IH is half the optical image height of the endoscope optical system; L is the working distance of the endoscope optical system; TTL is the distance on the optical axis from the object side of the first lens L1 to the imaging surface of the endoscope optical system; d1 is the center thickness of the first lens L1; Bf is the distance on the optical axis from the image side of the sixth lens L6 to the imaging surface of the endoscope optical system; fL1 is the effective focal length of the first lens L1; fL2 is the effective focal length of the second lens L2; ​​fL3 is the effective focal length of the third lens L3; f45 is the overall effective focal length of the fourth lens L4 and the fifth lens L5; fL6 is the effective focal length of the sixth lens L6; FNO is the aperture number of the endoscope optical system.

[0065] Preferably, the first lens L1 has a convex surface near the object and a concave surface away from the object; the second lens L2 has concave surfaces on both sides; the third lens L3 has convex surfaces on both sides; in the cemented doublet lens group, the fourth lens L4 has convex surfaces on both sides, the fifth lens L5 has a concave surface near the object and a convex surface away from the object; and the sixth lens L6 has convex surfaces on both sides.

[0066] Preferably, the first lens L1 has an object-side radius of curvature ranging from -220mm to -240mm and an image-side radius of curvature ranging from 0.15mm to 0.25mm. The second lens L2 has an object-side radius of curvature ranging from -0.4mm to -0.6mm and an image-side radius of curvature ranging from 0.4mm to 0.6mm. The third lens L3 has an object-side radius of curvature ranging from 0.4mm to 0.6mm and an image-side radius of curvature ranging from -0.4mm to -0.6mm. In the cemented doublet lens group, the object-side radius of curvature ranges from 0.9mm to 1.1mm, the cemented surface radius of curvature ranges from -0.25mm to -4mm, and the image-side radius of curvature ranges from -0.8mm to -1.2mm. The sixth lens L6 has an object-side radius of curvature ranging from 2.2mm to 2.6mm and an image-side radius of curvature ranging from -0.9mm to -1.2mm.

[0067] Preferably, the center thickness of the first lens L1 is 0.15 mm to 0.4 mm; the center thickness of the second lens L2 is 0.4 mm to 0.6 mm; the center thickness of the third lens L3 is 0.15 mm to 0.4 mm; in the cemented doublet lens group, the thickness of the fourth lens L4 near the object side is 0.3 mm to 0.5 mm, the thickness of the fifth lens L5 away from the object side is 0.15 mm to 0.4 mm; and the center thickness of the sixth lens L1 is 0.2 mm to 0.4 mm.

[0068] Preferably, the endoscope objective optical system has a field of view of not less than 120° and a maximum distortion of not more than 10%.

[0069] Preferably, the total length of the endoscope objective optical system is no more than 3.5 mm, and the maximum diameter of the optical system is no more than 1 mm, which is suitable for the design requirements of miniaturized and lightweight endoscopes.

[0070] Simulation experiment:

[0071] A simulation experiment was conducted on the ultra-compact high-definition wide-angle endoscope objective lens optical system described in this embodiment of the invention. The simulation results are as follows: Figures 2 to 5 As shown.

[0072] 1. For example Figure 2(The modulation transfer function (MTF) curves are shown in the figure. This figure displays the modulation transfer function (MTF) curves of the optical system in the central field of view (0 degrees), 0.5 field of view (30 degrees), and peripheral field of view (60 degrees). The figure includes curves in both the meridional (T) and sagittal (S) directions. The two black "diffraction limit" curves represent the theoretical upper limit of the performance of the ideal optical system. The X-axis is the spatial frequency (unit: period / mm), and the Y-axis is the magnitude of the optical transfer function (OTF), i.e., the MTF value, ranging from 0 (completely blurred) to 1 (ideally sharp).

[0073] Simulation results explanation:

[0074] (1) Leading resolution limits, meeting the requirements of high-definition sensors: Modulation transfer function (MTF) data confirms that this system maintains a modulation contrast of ≥0.1 in the center field of view even at a high spatial frequency of 285 lp / mm. This indicates that its resolution limits fully meet the physical requirements of a 160,000-pixel CCD sensor with a pixel size of 1.75 μm, ensuring from an optical perspective that the imaging system can capture and reproduce the microscopic details of tissue surfaces, providing reliable high-definition imaging for endoscopic diagnosis.

[0075] (2) Uniform image quality across the entire field of view, supporting a wide-angle diagnostic field of view: Throughout the entire 120° ultra-wide field of view, from the center to the edge, the system's MTF curve exhibits a smooth and controllable attenuation trend. Especially within the commonly used frequency bands that determine the sharpness of the main image subject, a good contrast level is maintained across the entire field of view. This characteristic ensures that while obtaining a wide observation range, it can provide image quality that meets clinical diagnostic needs from the image center to the edge, effectively solving the common edge blurring and distortion problems of ultra-wide-angle endoscopes, and assisting doctors in accurately judging lesions in various areas of the field of view during scanning.

[0076] 2. For example Figure 3 As shown in the dot plot, this plot illustrates the convergence of different wavelengths of light (F-ray (0.486133μm), d-ray (0.587562μm), and C-ray (0.656273μm)) from different field-of-view angles (0°, 30°, and 60°) on the image plane after passing through the optical system. In the plot, different colored dots represent the actual landing points of different wavelengths of light on the image plane. The black circles in each subplot represent the Airy disk size of the system at the diffraction limit, used to evaluate image quality. Supplementary data for the dot plot is provided below, offering quantitative data on aberrations at different field-of-view angles, generally comparing the RMS radius to the Airy disk radius:

[0077]

[0078] Airy disk radius (3.171 μm): It is the theoretical minimum circle of confusion diameter of an optical system under the diffraction limit, and is the theoretical benchmark for evaluating image quality.

[0079] RMS radius: This is the root mean square radius of the image point dispersion in a real optical system. It comprehensively reflects various geometric aberrations present in the system (such as spherical aberration, coma, astigmatism, etc.). The closer the RMS radius is to, or even smaller than, the Airy disk radius, the better the aberration correction of the system, and the closer the imaging quality is to the physical theoretical limit.

[0080] Simulation results explanation:

[0081] (1) Excellent aberration correction, with the central field of view approaching the diffraction limit: Dot plot analysis shows that in the central field of view, the convergence points of different wavelengths of light almost completely coincide, and its RMS radius (0.628 μm) is much smaller than the theoretical Airy disk radius (3.171 μm). This proves that the monochromatic aberration and chromatic aberration of the system have been corrected to the extreme, and the central imaging quality is infinitely close to the diffraction limit in physical theory, ensuring that the observed target can present an image with extremely high sharpness and color fidelity when it is in the center of the image.

[0082] (2) Uniform image quality across the entire field of view and excellent edge resolution: As the field of view increases to the edge, the RMS radius of the dot plot remains excellently controlled at an extremely low level, significantly smaller than the Airy disk radius. This data quantitatively demonstrates that the system effectively controls key aberrations such as astigmatism, field curvature, and magnification chromatic aberration throughout the entire 120° ultra-large field of view, thereby ensuring that the imaging quality from the center to the edge meets the requirements of high-definition diagnosis and avoiding the impact of edge image quality degradation on diagnostic observation.

[0083] 3. For example Figure 4 As shown in the field curvature and distortion charts, the left-hand chart (field curvature chart) uses millimeters (mm) as its Y-axis coordinate, representing the distance the image point deviates from the ideal image plane. The straighter the field curvature curve and the closer it is to the 0 mm line on the X-axis, the flatter the image plane. The right-hand chart (distortion chart) typically uses a percentage (%) as its Y-axis coordinate, representing the degree of image distortion (distortion value). The smaller the distortion value, the less image distortion.

[0084] Simulation results explanation:

[0085] (1) Field curvature is effectively suppressed, and the image plane is flat: The field curvature / distortion diagram shows that the maximum field curvature of the system is strictly controlled within 0.0219 mm. This value is less than the depth of focus of the system, which means that the image plane shift caused by changes in object distance will not cause significant defocus blur. This optically ensures that all image points can be clearly focused on the same image plane throughout the entire field of view, laying the physical foundation for achieving consistent high-definition imaging across the entire screen.

[0086] (2) High level of distortion control: For a 120° ultra-wide-angle optical system, the maximum optical distortion has been successfully suppressed to 10%, which is a significant technological achievement. Lower distortion means that the image has high geometric fidelity, which can truly restore the shape and relative position of tissue structures, providing doctors with more reliable and intuitive diagnostic information.

[0087] 4. For example Figure 5 As shown in the (relative illuminance diagram), this diagram illustrates how the relative illuminance of the optical system varies with the Y-field of view angle. Relative illuminance is the ratio of the light intensity at the edge of the field of view to the light intensity at the center of the field of view, with an ideal value of 1 (i.e., 100%). The blue curve in the diagram represents the relative illuminance variation curve. The X-axis represents the field of view angle, from 0° (center) to 60° (edge, corresponding to a full field of view of 120°); the Y-axis represents the relative illuminance value, ranging from 0 to 1.0.

[0088] Simulation results explanation:

[0089] (1) Uniform illumination across the entire field of view with no vignetting: The relative illuminance gradually decreases from 1.0 in the central field of view to 0.94 in the peripheral field of view, exhibiting excellent illumination uniformity. This nearly flat illumination distribution ensures consistent brightness across the entire screen, completely eliminating vignetting and providing clinicians with a comfortable and reliable field of view without the need to repeatedly adjust the endoscope position due to uneven brightness.

[0090] In summary, the comprehensive data from dot plots, field curvature / distortion to relative illumination strongly demonstrate that the optical system of this invention has successfully achieved near-diffraction-limited imaging resolution, excellent aberration correction effect, and uniform high-definition image quality across the entire field of view under the harsh conditions of an ultra-small aperture of 1mm and an ultra-large field of view of 120°. All performance indicators meet the application standards of high-end diagnostic endoscopes.

[0091] The ultra-compact high-definition wide-angle endoscope objective optical system described in this embodiment has the following advantages:

[0092] 1. By designing both sides of the first lens as aspherical and strictly controlling the principal ray angle (CRA≤0.025°), the following effects are achieved:

[0093] (1) Achieving ultimate image quality correction under ultra-wide angle: The first lens, as the "gateway" of the system, has a double-sided aspherical design that can accurately correct aberrations such as distortion and spherical aberration caused by the ultra-wide field of view (120°) as soon as light enters the system. The extra degree of freedom provided by the aspherical surface makes it possible to strictly control the maximum distortion within 10% while maintaining an outer diameter of 1mm, thus ensuring the geometric fidelity of the image.

[0094] (2) Ensure perfect matching with the sensor: Control the CRA at a level close to zero degrees (≤0.025°), which enables the system to completely eliminate the edge response reduction and vignetting caused by incident angle mismatch when coupled with a CCD / CMOS sensor with a pixel size of 1.75μm, and obtain a picture with highly uniform brightness from the center to the edge.

[0095] (3) Improved system transfer function performance: This precise aberration control directly improves the system's modulation transfer function. At a high spatial frequency of 285 lp / mm, the central field of view MTF can still be maintained above 0.1, meeting the matching requirements of a 160,000-pixel high-resolution sensor and ensuring that the objective lens's resolving power is sufficient to render fine tissue structures.

[0096] 2. Through optimized optical power allocation and F-number control (F#4.4), high performance is achieved while maintaining appropriate light transmission. This ensures sufficient signal-to-noise ratio for the imaging system under small apertures, while also achieving a suitable depth of field through a moderate F-number, meeting the observation needs of endoscopes at different depths within body cavities.

[0097] 3. By limiting the optical outer diameter to an extreme 1.0 mm, a key foundation for the miniaturization design of endoscopes is provided. The effect is that it allows endoscope manufacturers to integrate the objective lens system into the smallest endoscope without sacrificing optical performance, meeting the stringent requirements of minimally invasive surgeries such as pediatrics and neurosurgery, while leaving more space for instrument access.

[0098] 4. Through careful material selection and tolerance analysis, the manufacturability of the product was ensured while employing complex designs such as aspherical surfaces. The result is that, despite extremely high system performance requirements, stable mass production can still be achieved through reasonable process design, meeting the stringent reliability and consistency requirements of medical devices.

[0099] In summary, this invention not only achieves breakthroughs in optical parameters (such as a 120° field of view, <10% distortion, MTF ≥ 0.1 at 285 lp / mm, and CRA ≤ 0.025°), but also conducts synergistic optimizations across multiple dimensions, including sensor matching, manufacturing feasibility, and clinical application. The adoption of these technical means and their resulting effects closely revolve around and thoroughly serve the specific field of "ultra-compact high-performance endoscopes," representing a fundamental improvement over conventional endoscope objectives in terms of design goals, technical routes, and performance standards. This invention possesses significant originality and non-obviousness.

Claims

1. An ultra-compact high-definition wide-angle endoscope objective lens optical system, characterized in that, include: The first lens, the second lens, the third lens, the cemented doublet lens group, and the sixth lens are arranged sequentially along the optical axis from the object side. The optical system aperture is located between the second and third lenses; the cemented doublet lens group is composed of a fourth and a fifth lens cemented together, with the fourth lens being the one closer to the object; the first lens is a double aspherical glass lens; the second lens, the third lens, the cemented doublet lens group, and the sixth lens are spherical glass lenses.

2. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The optical parameters of the endoscope objective optical system satisfy the following relationship: 3.0≤IH / f≤3.2 4≤L≤8 0.08≤IH / TTL≤0.12 1.8≤d1 / f≤2 4.5≤Bf / f≤5 2.2≤|fL1 / f|≤2.5 3.1≤|fL² / f|≤3.4 5.2≤|fL3 / f|≤5.5 49≤|f45 / f|≤50 12≤|fL6 / f|≤13 1.4 ≤ FNO / TTL ≤ 1.6 in: f is the focal length of the endoscope optical system; IH is half the optical image height of the endoscope optical system; L is the working distance of the endoscope optical system; TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the endoscope optical system; d1 is the center thickness of the first lens; Bf is the distance on the optical axis from the image side of the sixth lens to the imaging surface of the endoscope optical system; fL1 is the effective focal length of the first lens; fL2 is the effective focal length of the second lens; fL3 is the effective focal length of the third lens; f45 is the overall effective focal length of the fourth and fifth lenses; fL6 is the effective focal length of the sixth lens; FNO is the aperture number of the endoscope optical system.

3. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The first lens has a convex surface near the object and a concave surface away from the object; the second lens has concave surfaces on both sides; the third lens has convex surfaces on both sides; in the cemented doublet lens group, the fourth lens has convex surfaces on both sides, the fifth lens has a concave surface near the object and a convex surface away from the object; and the sixth lens has convex surfaces on both sides.

4. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The first lens has an object-side radius of curvature ranging from -220mm to -240mm and an image-side radius of curvature ranging from 0.15mm to 0.25mm; the second lens has an object-side radius of curvature ranging from -0.4mm to -0.6mm and an image-side radius of curvature ranging from 0.4mm to 0.6mm; the third lens has an object-side radius of curvature ranging from 0.4mm to 0.6mm and an image-side radius of curvature ranging from -0.4mm to -0.6mm; in the cemented doublet lens group, the object-side radius of curvature ranges from 0.9mm to 1.1mm, the cemented surface radius of curvature ranges from -0.25mm to -4mm, and the image-side radius of curvature ranges from -0.8mm to -1.2mm; the sixth lens has an object-side radius of curvature ranging from 2.2mm to 2.6mm and an image-side radius of curvature ranging from -0.9mm to -1.2mm.

5. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The center thickness of the first lens is 0.15 mm to 0.4 mm; the center thickness of the second lens is 0.4 mm to 0.6 mm; the center thickness of the third lens is 0.15 mm to 0.4 mm; the thickness of the fourth lens is 0.3 mm to 0.5 mm; the thickness of the fifth lens is 0.15 mm to 0.4 mm; and the center thickness of the sixth lens L1 is 0.2 mm to 0.4 mm.

6. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The endoscope objective optical system has a field of view of not less than 120° and a maximum distortion of not more than 10%.

7. The ultra-compact high-definition wide-angle endoscope objective lens optical system as described in claim 1, characterized in that, The total length of the endoscope objective optical system is no more than 3.5 mm, and the maximum diameter of the optical system is no more than 1 mm.

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