Slim Optical Imaging System with Nested Lens Units
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Solution Overview
Problem
The miniaturization of portable terminals poses challenges in implementing high-resolution and high-performance camera modules due to the difficulty in mounting telephoto lenses with long focal lengths and total track lengths, which restricts the implementation of advanced camera functionalities like optical zoom and image stabilization without increasing the device's thickness.
Innovation Solution
An optical imaging system comprising a sequence of lenses with specific refractive powers and shapes, including noncircular lenses and spacers with unique aperture radii and curvature, is designed to achieve a slim form factor while maintaining high optical performance, satisfying various conditional expressions for focal lengths, aperture ratios, and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a telephoto lens with long focal length is used to achieve high resolution and optical zoom, then the imaging performance is improved, but the total track length and device thickness increase
Solution Approach 1:
The patent employs a nested lens structure where multiple lens elements are arranged in a compact configuration. The first lens unit with positive refractive power is positioned closer to the object, while the second lens unit with negative refractive power is positioned closer to the image sensor, creating a nested arrangement that reduces the overall optical path length while maintaining telephoto imaging capability.
Solution Approach 2:
The patent utilizes specific refractive power parameters for the lens units, with the first lens unit having positive refractive power and the second lens unit having negative refractive power. The conditional expression f/IMG HT>4.9 optimizes the focal length ratio to achieve telephoto characteristics while controlling the total track length. This parameter optimization allows high-resolution imaging without proportionally increasing the optical system length.
2Shape
If the focal length is increased to achieve narrow angle of view and telephoto characteristics, then the angle of view is reduced, but the total track length increases
Solution Approach 1:
The nested arrangement of lens units with opposite refractive powers allows the optical system to achieve telephoto compression. The positive refractive power of the first lens unit converges light rays to achieve narrow angle of view, while the negative refractive power of the second lens unit diverges them to reduce the overall optical path, creating a compact telephoto design.
Solution Approach 2:
The patent optimizes the focal length parameter through the conditional expression f/IMG HT>4.9, where f is the total focal length and IMG HT is half the diagonal length of the image sensor. This parameter ratio control enables the system to achieve narrow angle of view characteristics typical of telephoto lenses while keeping the total track length proportional to the image sensor size, thus resolving the contradiction between angle of view and track length.
3Reliability
If more lens elements are added to improve optical performance and correct aberrations, then the imaging quality is improved, but the device complexity and thickness increase
Solution Approach 1:
The patent divides the optical system into two functional segments: the first lens unit with positive refractive power and the second lens unit with negative refractive power. This segmentation allows each unit to be optimized for specific functions - the first unit for light gathering and initial focusing, and the second unit for aberration correction and final image formation - reducing the need for additional lens elements while maintaining high optical performance.
Solution Approach 2:
The patent employs aspherical surfaces on the lens elements, characterized by specific curvature parameters and conic constants. These parameter optimizations enable single lens elements to correct multiple types of aberrations (spherical aberration, coma, astigmatism) that would traditionally require multiple spherical elements, thus improving optical performance while reducing system complexity.
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 enables the implementation of a slim optical imaging system with a narrow angle of view, supporting telephoto lens characteristics and advanced camera functionalities like autofocusing, optical zoom, and image stabilization without increasing the device's thickness, thus enabling the miniaturization of portable electronic devices.
Implementation Method 1
a first lens L1 having positive refractive power
Implementation Method 2
a second lens L2 having negative refractive power
Implementation Method 3
a total focal length f of a lens unit including the first lens L1 through the fifth lens L5 and half (IMG HT) of a diagonal length of an imaging surface of an image sensor satisfy f/IMG HT>4.9
Data Source
AI summary
An optical imaging system includes a first lens having positive refractive power, a second lens, a third lens, and a fourth lens, arranged sequentially from an object side along an optical axis. The first lens through the fourth lens are spaced apart from each other along the optical axis in a paraxial region. A total focal length f of a lens unit including the first lens through the fourth lens and half (IMG HT) of a diagonal length of an imaging surface of an image sensor satisfy f/IMG HT>4.9. An effective aperture radius of an object-side surface of the first lens and an effective aperture radius of an object-side surface of the second lens are both greater than effective aperture radii of an object-side surface and an image-side surface of each of the lenses other than the first lens and the second lens.