Three-Lens Optical System with BFL/TL Ratio for Miniaturization
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Solution Overview
Problem
The challenge is to develop an optical lens system for portable electronic devices that achieves miniaturization while maintaining a longer back focal length and improving illumination, especially with the increasing demand for higher image resolution and smaller image sensors.
Innovation Solution
The optical lens system consists of three lenses with specific refractive powers and aspheric surfaces, where the first lens has positive refractive power with a convex object-side surface, the second lens has positive refractive power with a concave object-side surface, and the third lens has negative refractive power with a concave image-side surface, satisfying conditions such as 0.38 < BFL/TL < 0.58 and 29.58 < FOV/f < 78.49 to optimize miniaturization and illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the photographing module is miniaturized, then the size is reduced, but the back focal length becomes shorter
Solution Approach 1:
The optical lens system is divided into three distinct lens elements with specific refractive powers and surface curvatures. The first lens has positive refractive power with a convex object-side surface, the second lens has positive refractive power with a concave object-side surface, and the third lens has negative refractive power. This segmentation allows independent optimization of each lens element to achieve the desired back focal length while maintaining compact overall size.
Solution Approach 2:
The patent applies specific parameter relationships to optimize the optical system: the ratio of back focal length to total track length (BFL/TL) is constrained between 0.38 and 0.58, and the ratio of field of view to focal length (FOV/f) is constrained between 29.58 and 78.49. These parameter changes enable the system to achieve longer back focal length relative to its compact size, resolving the contradiction between miniaturization and back focal length requirements.
2Volume of moving object
If the lens system is miniaturized, then the size is reduced, but the illumination is degraded
Solution Approach 1:
The patent employs aspheric surfaces on all lens elements to optimize light transmission and illumination distribution. The object-side surface of the first lens is convex, the object-side surface of the second lens is concave, and the image-side surface of the third lens is concave. These curved surfaces are designed with specific radius of curvature parameters (e.g., R1/EPD between 0.4 and 1.2, R3/EPD between -1.5 and -0.3) to enhance illumination while maintaining compact dimensions.
Solution Approach 2:
The patent optimizes illumination by controlling the f-number (Fno) between 1.8 and 3.0 and the ratio of distance from stop to third lens to total track length (SD/TL) between 0.3 and 0.5. These parameter changes ensure adequate illumination in the miniaturized system by optimizing the light path and distribution across the image sensor.
3Length of stationary object
If the back focal length is increased, then the image quality is improved, but the device complexity increases
Solution Approach 1:
The optical system is segmented into three lens elements with alternating positive and negative refractive powers. This segmentation allows the system to achieve longer back focal length while managing complexity through modular design, where each lens element can be independently optimized and manufactured.
Solution Approach 2:
The patent establishes specific parameter ranges to balance back focal length and complexity: BFL/TL between 0.38 and 0.58, and the number of lens elements is limited to three. These parameter constraints ensure that the system achieves adequate back focal length for image quality while preventing excessive complexity in the lens design and manufacturing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively meets the requirements of miniaturization and longer back focal length, enhances image quality, and improves illumination by adjusting the lens parameters to balance focal length and view angle, ensuring better image reception and brightness.
Implementation Method 1
a first lens with positive refractive power, comprising an object-side surface and an image-side surface, the object-side surface of the first lens being convex near an optical axis
Implementation Method 2
a second lens with positive refractive power, comprising an object-side surface and an image-side surface, the object-side surface of the second lens being concave near the optical axis
Implementation Method 3
a third lens with negative refractive power, comprising an object-side surface and an image-side surface, the image-side surface of the third lens being concave near the optical axis
Data Source
AI summary
An optical lens system includes, in order from the object side to the image side: a stop, a first lens with positive refractive power, a second lens with positive refractive power, a third lens with negative refractive power, wherein a distance from an image-side surface of the third lens to an image plane along an optical axis is BFL, a distance from an object-side surface of the first lens to the image plane along the optical axis is TL, following condition is satisfied: 0.38<BFL/TL<0.58. Such arrangements can meet the requirement of miniaturization under the condition of longer back focal length.