Optical lens assembly

Abstract

The utility model discloses an optical lens group, including first lens, second lens, third lens and fourth lens in proper order from object side to image side along the optical axis, first lens is the convex concave aspheric lens with negative optical power, second lens is the convex convex aspheric lens with positive optical power, third lens is the concave convex aspheric lens with negative optical power, through limiting the ratio of effective focal length and optical total length of optical lens group is in the preset range, and combining " negative - positive - negative - positive " four lens optical power combination design, while guaranteeing that the overall structure of lens group is compact, significantly expand the imaging field of view range, compared with the lens group of existing field of view angle is small, can effectively cover more spacious area, especially in indoor robot obstacle avoidance, vehicle-mounted close-range pedestrian detection close-range sensing scene, can reduce imaging blind area greatly, capture the surrounding environment information comprehensively, improve the judgment accuracy and reliability of sensing system.

Description

Technical Field

[0001] This utility model relates to the field of optical lens technology, specifically to an optical lens assembly. Background Technology

[0002] In the field of optical lens technology, optical lens groups, as the core components of imaging systems, are widely used in environmental perception, security monitoring, automotive vision, consumer electronics and other fields. As downstream application scenarios continue to demand miniaturization, integration and sensing performance of equipment, the structural design and performance of optical lens groups have become one of the key factors restricting system upgrades.

[0003] Existing lens groups generally have a small field of view (FOV), which is usually difficult to cover a wide range of space. In close-range environmental perception scenarios, such as obstacle avoidance for indoor robots and close-range pedestrian detection in vehicles, the small field of view can easily lead to obvious blind spots in the imaging range, making it impossible to fully capture information about the surrounding environment, thus affecting the accuracy and reliability of the perception system. Therefore, we need to propose an optical lens group. Utility Model Content

[0004] The purpose of this invention is to provide an optical lens group that, by setting a "negative-positive-negative-positive" four-lens optical power combination and limiting the ratio of effective focal length to total optical length to a preset range, achieves the effect of significantly expanding the imaging field of view while ensuring a compact lens group structure, thereby reducing near-field perception blind spots and improving the accuracy and reliability of the perception system, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] An optical lens group includes: a first lens, a second lens, a third lens, and a fourth lens sequentially along the optical axis from the object side to the image side; the first lens is a convex-concave aspherical lens with negative optical power, the second lens is a convex-convex aspherical lens with positive optical power, the third lens is a concave-convex aspherical lens with negative optical power, and the fourth lens is a convex-concave aspherical lens with positive optical power, and the ratio of the effective focal length to the total optical length of the optical lens group is within a preset range.

[0007] Preferably, the horizontal field of view of the optical lens group is 105°-120°, and the diagonal field of view is 120°-136°.

[0008] Preferably, the F-number of the optical lens group is 1.0-1.25.

[0009] Preferably, the effective focal length of the optical lens group is 2.9mm-3.3mm.

[0010] Preferably, the system also includes a sensor with a horizontal dimension of 6.0 mm, a vertical dimension of 2.4 mm, and a pixel size of 25 μm; the image plane diameter of the optical lens group is 6.6 mm, which matches the sensor.

[0011] Preferably, the first lens, the second lens, the third lens, and the fourth lens are fixed together by a spacer ring.

[0012] Preferably, the spacer ring between the first lens and the second lens is made of PET material, the thickness of the annular substrate of the spacer ring is 1.2mm-1.8mm, and the roughness Ra of the inner wall of the annular substrate is ≤0.8μm.

[0013] The positioning structure of the spacer ring includes 3-4 radial positioning bosses evenly distributed circumferentially along the inner wall of the annular base. The height of the radial positioning bosses is 0.3mm-0.5mm, and the end face of the boss is an arc surface, the radius of which is adapted to the outer circumferential curvature radius of the adjacent lens.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] This invention limits the ratio of the effective focal length to the total optical length of the optical lens group to a preset range, and combines a "negative-positive-negative-positive" four-lens optical power combination design. While ensuring the overall structure of the lens group is compact, it significantly expands the imaging field of view. Compared with existing lens groups with a smaller field of view, it can effectively cover a wider spatial area. Especially in close-range perception scenarios such as indoor robot obstacle avoidance and vehicle-mounted close-range pedestrian detection, it can greatly reduce imaging blind spots, comprehensively capture surrounding environmental information, and improve the judgment accuracy and reliability of the perception system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the distribution of the optical lens group of this utility model;

[0017] Figure 2 This is a schematic diagram of the optical path of the optical lens assembly of this utility model.

[0018] In the diagram: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Spacer ring; 6. Cylinder. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] Please see Figure 1-2 This utility model provides a technical solution:

[0021] An optical lens assembly includes, along the optical axis from the object side to the image side, a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4; the first lens 1 is a convex-concave aspherical lens with negative optical power, the second lens 2 is a convex-convex aspherical lens with positive optical power, the third lens 3 is a concave-convex aspherical lens with negative optical power, and the fourth lens 4 is a convex-concave aspherical lens with positive optical power, and the ratio of the effective focal length to the total optical length of the optical lens assembly is within a preset range;

[0022] By setting a four-lens power combination of "negative-positive-negative-positive" and limiting the ratio of effective focal length to total optical length, the design achieves the effect of optimizing the light refraction path while ensuring a compact overall lens group structure, laying the foundation for subsequent imaging performance improvement. This synergistic design of power combination and parameter limitation avoids the bulky size problem caused by blindly increasing the number of lenses in pursuit of a large field of view, as seen in traditional lens groups. It also solves the imaging distortion problem caused by overloading the optical power of a single lens, providing core structural support for the integrated application of lens groups in miniaturized devices.

[0023] The optical lens assembly has a horizontal field of view of 105°-120° and a diagonal field of view of 120°-136°. By setting the field of view parameters within this range, it effectively covers a wider spatial area and reduces imaging blind spots in scenarios such as indoor robot obstacle avoidance and vehicle-mounted close-range pedestrian detection. In indoor robot obstacle avoidance scenarios, this field of view allows the robot to capture obstacle information within a horizontal range of 105°-120° around its body in one go, eliminating the need for frequent camera rotation and improving obstacle avoidance response speed. In vehicle-mounted close-range pedestrian detection, the 120°-136° diagonal field of view can cover the area in front of and to the sides of the vehicle at close range, effectively avoiding the risk of missed pedestrian detection due to limited field of view.

[0024] The optical lens group has an F-number of 1.0-1.25. By setting a small F-number of 1.0-1.25, the light transmission rate of the lens group is improved, ensuring sufficient light acquisition in low-light environments and guaranteeing image clarity. Compared with traditional lens groups with an F-number greater than 1.5, this lens group can increase light transmission by more than 30% in low-light scenarios such as nighttime security monitoring and vehicle detection in underground parking garages. It can clearly capture the detailed features of target objects, such as the texture of pedestrians' clothing and the outline structure of obstacles, providing high-quality image data for accurate judgment by the perception system.

[0025] The effective focal length of the optical lens group is 2.9mm-3.3mm. By setting the effective focal length to 2.9mm-3.3mm, it achieves the desired close-range imaging requirements and, in conjunction with the field of view parameters, enables a wide-range and clear imaging effect. This effective focal length range ensures stable imaging quality within a close-range range of 0.5m-5m, meeting the needs of indoor robots for environmental detection within a range of 1m-3m, and also adapting to the requirements of vehicle-mounted systems for recognizing pedestrians and obstacles at close range of 2m-5m. Furthermore, combined with the large field of view parameters, it achieves "close-range wide-area" imaging coverage, avoiding the imaging blurring problems that are common with short focal lengths.

[0026] It also includes a sensor with a horizontal dimension of 6.0 mm, a vertical dimension of 2.4 mm, and a pixel size of 25 μm. The image plane diameter of the optical lens group is 6.6 mm, matching the sensor size. By setting the image plane diameter to match the sensor size, the lens group's image can completely cover the sensor's photosensitive area, avoiding wasted imaging information and improving imaging utilization. The 25 μm pixel size ensures the sensor's high sensitivity to light, and combined with the lens group's high light transmittance, further improves imaging performance in low-light environments. The precise matching of the image plane circle to the sensor avoids information loss caused by the image edge exceeding the sensor's range, and also prevents sensor resource idleness due to an excessively small image plane, achieving efficient collaboration between the optical system and the sensing system.

[0027] The first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are fixed together by spacer rings 5. By fixing adjacent lenses with spacer rings 5, the precise positioning of each lens along the optical axis is ensured, preventing lens misalignment from affecting imaging accuracy. The thickness of the spacer rings 5 ​​is precisely calculated to strictly control the air gap between each lens, ensuring that light is refracted along a preset path. At the same time, its fixing function can resist vibrations and shocks during equipment operation, such as vibrations from vehicle-mounted equipment traveling on bumpy roads or robots moving, avoiding problems such as image blurring and field of view shift caused by lens misalignment, and improving the environmental adaptability of the lens group.

[0028] The spacer ring 5 between the first lens 1 and the second lens 2 is made of PET material, while the spacer ring 5 between the second lens 2, the third lens 3, and the fourth lens 4 is made of PC material. By selecting PET and PC materials for the spacer rings 5 ​​according to the assembly and optical performance requirements between the lenses, the effect of ensuring fixation stability while also considering lightweight materials and adaptability to different optical environments between lenses is achieved. PET material has good flexibility and surface smoothness, which can reduce the squeezing damage during the assembly of the first lens 1 and the second lens 2, and at the same time reduce the interference of light reflection on the surface of the spacer ring; PC material has higher rigidity and temperature resistance, and can withstand the slight temperature changes caused by light refraction between the second lens 2 and the fourth lens 4, ensuring the long-term stability of the spacing dimensions. Both materials are lightweight, avoiding increasing the overall weight of the lens assembly.

[0029] The thickness of the annular substrate of spacer ring 5 is strictly controlled within the range of 1.2mm-1.8mm. Under lens assembly and equipment vibration conditions, the annular substrate is prone to deformation, causing the axial spacing between adjacent lenses to deviate beyond the allowable error. If the thickness exceeds 1.8mm, it will significantly increase the axial dimension of the lens assembly, violating the miniaturization design goal and making it unsuitable for space-constrained devices such as consumer electronics and robots. Simultaneously, the inner wall roughness of the annular substrate is set to Ra≤0.8μm, achieved through precision grinding: the low-roughness inner wall reduces diffuse reflection of light on the inner wall of the spacer ring, preventing stray light from entering the imaging optical path.

[0030] In the positioning structure of spacer ring 5, 3-4 radial positioning bosses are evenly distributed along the circumferential direction of the inner wall of the annular base. The specific number can be selected according to the lens diameter. For lenses with a diameter less than 8mm, 3 bosses are sufficient to form a stable triangular support. For lenses with a diameter of 8mm-12mm, 1 more boss is added, for a total of 4, to further improve the positioning accuracy. The height of the boss is set to 0.3mm-0.5mm. This height ensures that the boss is in close contact with the outer periphery of the lens to achieve radial limiting, and also prevents stress concentration on the outer periphery of the lens due to excessive height, thus avoiding stress deformation at the lens edge. The end face of the boss is designed as an arc surface, and the radius of the arc surface is perfectly matched with the outer periphery curvature radius of the adjacent lens. For example, when the adjacent lens is a convex-concave aspherical lens with an outer periphery curvature radius of 5mm, the radius of the arc surface of the boss is simultaneously set to 5mm. This adaptive design allows the boss to form a "surface contact" with the outer periphery of the lens, rather than the traditional "point contact." This increases the contact area, improves positioning stability, and prevents scratches or damage to the outer periphery of the lens due to excessive local stress.

[0031] The outer casings 6 of the first lens 1, second lens 2, third lens 3, and fourth lens 4 are made of PC material. By using PC material casings 6, effective protection is achieved for the internal lens assembly, while maintaining lightweight construction and structural strength, and adapting to the installation requirements of miniaturized devices. The PC material casings 6 can effectively resist damage to the lens surface from external dust, moisture, and minor impacts, protecting the optical performance of the lenses from being affected. Its high structural strength can support the assembly and fixation of the entire lens assembly, while its density is only about 1 / 5 that of metal materials, meeting the lightweight requirements of miniaturized devices such as consumer electronics and robots. Furthermore, the inner wall of the casing 6 is matte-finished, which reduces the interference of stray light reflection on image quality.

[0032] Working principle: When external light enters this optical lens group from the object side, it first illuminates the surface of the first lens 1. As a convex-concave aspherical lens with negative optical power, the first lens 1 initially diverges the incident light, expanding the originally narrow range of incident light and laying the foundation for large field-of-view imaging. Simultaneously, the aspherical structure can initially correct optical aberrations such as spherical aberration. The diverged light then enters the second lens 2, which is a convex-convex aspherical lens with positive optical power. Its function is to converge the diverged light, adjust the direction of light propagation, bringing it closer to the optical axis, and further correct the residual aberrations generated by the first lens 1, improving the stability of light propagation.

[0033] The converged light then passes through the third lens 3, a concave-convex aspherical lens with negative optical power. Its negative optical power characteristic allows for secondary divergence and adjustment of the light, compensating for the deviations in light processing at the edges of the large field of view by the first two lenses, optimizing the imaging quality at the edges of the field of view, and ensuring imaging uniformity throughout the entire field of view. Simultaneously, its aspherical structure effectively corrects aberrations such as coma and astigmatism, reducing light distortion. Finally, the light enters the fourth lens 4, a convex-concave aspherical lens with positive optical power. This fourth lens performs final convergence and precise correction, focusing all effective light rays onto an imaging area with an image circle diameter of 6.6 mm. This imaging area precisely matches the sensor's horizontal dimensions of 6.0 mm, vertical dimensions of 2.4 mm, and pixel size of 25 μm, enabling the sensor to fully receive and convert the optical image into an electrical signal.

[0034] Throughout the light propagation and imaging process, the four-lens power combination of "negative-positive-negative-positive" works synergistically with the preset effective focal length (2.9mm-3.3mm) and total optical length ratio to achieve a 105°-120° horizontal field of view and a 120°-136° diagonal field of view while maintaining a compact lens group structure. A small F-number of 1.0-1.25 improves light transmission, ensuring sufficient light in low-light environments. The spacer rings 5 ​​made of PET and PC materials ensure the precision and stability of each lens position, while the PC material cylinder 6 provides protection and support for the internal components. The coordinated operation of these structures and parameters ultimately enables the lens group to achieve high-quality imaging with a large field of view, miniaturization, and high light transmission, meeting the application needs of environmental perception, security monitoring, and automotive vision scenarios.

[0035] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An optical lens assembly, characterized in that, include: Along the optical axis from the object side to the image side, it includes a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4); The first lens (1) is a convex-concave aspherical lens with negative optical power, the second lens (2) is a convex-convex aspherical lens with positive optical power, the third lens (3) is a concave-convex aspherical lens with negative optical power, and the fourth lens (4) is a convex-concave aspherical lens with positive optical power. The ratio of the effective focal length to the total optical length of the optical lens group is within a preset range. The horizontal field of view of the optical lens group is 105°-120°, the diagonal field of view is 120°-136°, the F-number of the optical lens group is 1.0-1.25, and the effective focal length of the optical lens group is 2.9mm-3.3mm.

2. An optical lens assembly according to claim 1, characterized in that: It also includes a sensor with a horizontal dimension of 6.0 mm, a vertical dimension of 2.4 mm, and a pixel size of 25 μm; the image plane diameter of the optical lens group is 6.6 mm, which matches the sensor.

3. An optical lens assembly according to claim 1, characterized in that: The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are fixed together by a spacer ring (5).

4. An optical lens assembly according to claim 3, characterized in that: The spacer ring (5) between the first lens (1) and the second lens (2) is made of PET material. The thickness of the annular substrate of the spacer ring (5) is 1.2mm-1.8mm, and the roughness Ra of the inner wall of the annular substrate is ≤0.8μm.

5. An optical lens assembly according to claim 4, characterized in that: The positioning structure of the spacer ring (5) includes 3-4 radial positioning bosses evenly distributed along the inner wall of the annular base. The height of the radial positioning bosses is 0.3mm-0.5mm, and the end face of the boss is an arc surface. The radius of the arc surface is adapted to the outer circumferential curvature radius of the adjacent lens.

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