Four-Lens Optical System with Movable Element for Compact Focusing
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Solution Overview
Problem
Conventional compact photographing systems, particularly in mobile electronic products, face challenges in achieving high image quality and accurate focusing at both close distances and infinity due to limitations in lens structures, leading to compromised image quality and increased power consumption.
Innovation Solution
An optical system comprising a first lens group with a positive refractive power and a second lens group with specific refractive powers and surface configurations, allowing for precise focusing adjustments by moving the first lens element along the optical axis, while maintaining a compact size and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional three-element lens structure is used, then the device size is compact, but the image quality and focusing accuracy at both close distances and infinity are insufficient
Solution Approach 1:
The patent employs a dynamic focusing mechanism where the first lens element can move along the optical axis to adjust focus. This dynamic adjustment allows the lens to achieve accurate focusing at both close distances and infinity, resolving the contradiction between maintaining compactness and achieving high image quality across different focal distances.
Solution Approach 2:
The patent uses a composite lens structure combining four lens elements with different refractive powers and surface configurations. The first lens element has positive refractive power with a convex object-side surface, the second lens element has negative refractive power with a concave image-side surface, the third lens element has positive refractive power with a convex image-side surface, and the fourth lens element has negative refractive power with aspheric surfaces. This composite structure optimizes both image quality and compactness.
2Manufacturing precision
If a five-element lens structure is used, then the image quality improves, but the total track length increases making it unsuitable for compact electronic products
Solution Approach 1:
The patent optimizes the parameters of each lens element, including their refractive powers, surface curvatures, and spacing. By carefully selecting and adjusting these parameters, the system achieves high image quality with only four lens elements and a compact total track length, avoiding the need for a longer five-element structure.
Solution Approach 2:
The patent utilizes curved surfaces with specific concave and convex configurations in the lens elements to optimize light paths and reduce aberrations. The aspheric surfaces in the fourth lens element specifically help in achieving high image quality while maintaining a compact overall length.
3Manufacturing precision
If a fixed-focus lens system is used, then the device is simple and compact, but the focusing capability at close distances and infinity is limited resulting in poor image quality
Solution Approach 1:
The patent implements a dynamic focusing mechanism where the first lens element can move along the optical axis between different positions to focus on objects at various distances. This dynamic adjustment capability enables accurate focusing at both close distances and infinity while maintaining relatively simple device structure.
Solution Approach 2:
The patent divides the focusing function into discrete segments by using multiple lens elements with different refractive powers. The first lens element handles close-distance focusing, while the subsequent elements contribute to overall focusing accuracy and image quality, enabling multi-distance focusing without complex mechanisms.
4Manufacturing precision
If digital image processing technique of extended depth of field is used to compensate for fixed-focus lens deficiency, then focusing capability improves, but image quality is compromised and power consumption increases
Solution Approach 1:
The patent replaces the computational method (digital image processing) with an optical solution (physical lens movement). By using a movable first lens element that can physically adjust focus positions, the system achieves accurate focusing at different distances through optical means rather than requiring post-processing, thereby reducing power consumption while maintaining image quality.
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 optical system achieves improved focusing accuracy and image quality at both close distances and infinity, with reduced total track length and power consumption, suitable for high-megapixel applications in compact electronic devices.
Implementation Method 1
The first lens element with positive refractive power has a convex object-side surface. The second lens element with negative refractive power has a concave image-side surface. The third lens element with positive refractive power has a convex image-side surface. The fourth lens element with negative refractive power has a concave object-side surface and a concave image-side surface at a paraxial region, wherein the image-side surface of the fourth lens element changes from concave at the paraxial region to convex at a peripheral region
Data Source
AI summary
An optical system comprises, in order from an object side to an image side, a first lens group includes a first lens element with positive refractive power having a convex object-side surface; and a second lens group in order from the object side to the image side includes a second lens element with negative refractive power having a concave image-side surface, a third lens element with positive refractive power having a convex image-side surface, and a fourth lens element with negative refractive power having a concave object-side surface and a concave image-side surface, wherein the image-side surface of the fourth lens element changes from concave at a paraxial region to convex at a peripheral region, and both of the object-side surface and the image-side surface of the fourth lens element are aspheric.