Five-Lens Optical Assembly Miniaturization via Flange Back Length Adjustment
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Solution Overview
Problem
Optical devices in mobile communication terminals face challenges due to their long total length (TTL) and short flange back length (FBL), resulting in large lens sizes that do not meet market demands for thinner devices with increasing display sizes and aesthetically pleasing designs.
Innovation Solution
A lens assembly with a small-diameter barrel is implemented by increasing the flange back length relative to the total length of the lenses, allowing for a miniaturized optical device that can be easily mounted in electronic devices, using a configuration of five lenses with specific refractive powers and aspheric surfaces to minimize size and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional lens configurations are used, then image capturing function is achieved, but the total length (TTL) becomes long and flange back length (FBL) becomes short
Solution Approach 1:
The lens assembly is divided into five separate lens elements (first through fifth lenses) with specific refractive powers arranged in sequence. This segmentation allows independent optimization of each element's parameters to achieve the desired TTL and FBL ratio while correcting various aberrations throughout the optical path.
Solution Approach 2:
The patent applies specific parameter constraints to achieve the invention: the ratio of FBL to TTL is maintained between 0.10 and 0.30, the third lens has negative refractive power with specific focal length relationships, and aspheric surfaces are introduced. These parameter changes enable miniaturization while maintaining optical performance.
2Length of moving object
If lens size is reduced for thinner devices, then device thickness is decreased, but aberration correction becomes more difficult
Solution Approach 1:
Aspheric surfaces are introduced on at least some of the lens elements to replace traditional spherical surfaces. This allows for better aberration correction in a compact configuration by providing more degrees of freedom in surface shape design, enabling precise control of light rays throughout the miniaturized optical path.
Solution Approach 2:
The lens assembly uses a combination of different refractive powers and material properties across five lens elements, with specific attention to the third lens having negative refractive power. This composite approach allows cancellation of various aberrations while maintaining a compact overall structure suitable for thin devices.
3Length of moving object
If five lenses with specific configurations are used, then FBL/TTL ratio is improved and size is reduced, but device complexity increases
Solution Approach 1:
Each lens element is designed to serve multiple functions: the first lens with positive refractive power contributes to overall focusing while the second lens with negative refractive power helps correct spherical aberration; the third lens with negative power and aspheric surfaces addresses multiple aberration types; the fourth and fifth lenses complete the focusing function while correcting residual aberrations. This multi-functionality reduces the need for additional corrective elements.
Solution Approach 2:
Aspheric surfaces are strategically applied to lens elements to provide enhanced aberration correction capabilities within the compact five-lens configuration. The aspheric profiles allow single elements to perform functions that would traditionally require multiple spherical elements, thereby reducing overall complexity despite the tight optical constraints.
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
The solution enables the creation of an aesthetically pleasing, miniaturized optical device with improved lens assembly design, allowing for easier integration into electronic devices while maintaining image quality and correcting spherical aberration, astigmatism, and distortion.
Implementation Method 1
a first lens with positive refractive power, a second lens with negative refractive power, a third lens with negative refractive power, a fourth lens with negative refractive power, and a fifth lens with positive refractive power
Data Source
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AI summary
A lens assembly may include: a first lens having positive refractive power and including a convex subject side surface; a second lens; a third lens having negative refractive power and including a subject side surface being convex toward an image secsor side in a center portion thereof, through which an optical axis passes; a fourth lens having positive or negative refractive power; and a fifth lens having positive or negative refractive power. The first lens, the second lens, the third lens, the fourth lens, and the fifth lens may be sequentially arranged from a subject to an image sensor along the optical axis. The lens assembly may satisfy a condition defined by 0.6 < TTL/ImgH < 1, where "TTL" represents a distance from the subject side surface of the first lens to an imaging surface of the image sensor, and "ImgH" represents a maximum image height of an image formed on the imaging surface.