Five-Lens Optical Assembly with Positive Fifth Element
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Solution Overview
Problem
Conventional optical lens assemblies for compact electronic devices face challenges in achieving good aberration correction and modulation transfer function (MTF) performance while minimizing size, particularly in five-lens designs where the fifth lens element with an inflection point may result in insufficient depth of field due to negative refractive power lens elements.
Innovation Solution
The design comprises a five-lens optical assembly with specific refractive powers and surface curvatures, including a first lens with positive power, a second lens with negative power, a third lens with positive power, a fourth lens as a meniscus with aspheric surfaces, and a fifth lens with positive power and an inflection point, optimized by relations such as 0.7 < f/f1 < 2.0 and 0.8 < CT1/CT2 < 2.8, to achieve shorter length and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a five-lens design with a fifth lens element having an inflection point is adopted to correct aberration and shorten total length, then the total length of the optical lens assembly is reduced, but the negative refractive power lens elements may have insufficient width or depth of field
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive powers and curvature radii of all five lens elements. Specifically, it sets the refractive power of the fifth lens element to be positive (contrary to conventional designs where it is negative), and establishes specific relationships between curvature radii (R5/R6 between 0.3-1.5, R7/R8 between -1.5/-0.3) to ensure adequate depth of field while maintaining compact length. The aspheric coefficients are also optimized to balance aberration correction with depth of field requirements.
Solution Approach 2:
The patent uses composite design by combining five lens elements with different material properties and surface characteristics. The system integrates elements with both spherical and aspheric surfaces, and combines positive and negative refractive power elements in a specific configuration. This composite approach allows the system to achieve both compact length and sufficient depth of field by leveraging the complementary strengths of different lens element types.
2Manufacturing precision
If the fifth lens element with negative refractive power is used to correct distortion, then aberration correction is improved, but the modulation transfer function (MTF) performance deteriorates during miniaturization
Solution Approach 1:
The patent inverts the conventional design approach by giving the fifth lens element positive refractive power instead of negative. This inversion allows the system to correct distortion through the combined action of all five elements rather than relying on the negative power of the fifth element alone, thereby maintaining MTF performance while achieving compact size and good aberration correction.
Solution Approach 2:
The patent extensively uses aspheric surfaces on multiple lens elements (first, second, fourth, and fifth elements) to correct aberrations. The aspheric coefficients are optimized to provide distortion correction without compromising MTF performance. This curvature-based approach replaces the need for negative refractive power in the fifth element, resolving the contradiction between aberration correction and MTF performance.
3Manufacturing precision
If more lens elements are added to improve aberration correction and MTF, then image quality is improved, but the total length and complexity of the optical lens assembly increase
Solution Approach 1:
The patent achieves excellent aberration correction and MTF performance with only five lens elements by optimizing key parameters: the refractive power distribution (with the fifth element having positive power), curvature radius relationships (R5/R6, R7/R8), and aspheric coefficients. This parameter optimization allows compact length while maintaining high image quality, avoiding the need for additional lens elements that would increase length and 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 effectively shortens the optical lens assembly, enhances aberration correction, and improves MTF, meeting high-resolution requirements for compact electronic devices by allocating refractive power efficiently and reducing chromatic aberrations.
Implementation Method 1
a first lens element (110) with a positive refractive power, a second lens element (120) with a negative refractive power, a third lens element (130) with a positive refractive power, a fourth lens element (140) with a positive refractive power, and a fifth lens element (150) with a positive refractive power
Data Source
AI summary
An image pick-up optical lens assembly, sequentially arranged from an object side to an image side along an optical axis, comprises: a first lens element with a positive refractive power having a convex object-side surface, a second lens element with a negative refractive power, a third lens element with a positive refractive power, a meniscus fourth lens element with a positive refractive power having at least one aspherical optical surface, and a fifth lens element with a positive refractive power having at least one inflection point on the optical image-side surface. Additionally, the image pick-up optical lens assembly satisfies several particular conditions. The invention possesses features such as good aberration compensation, well-performed modulation transfer function and short total length of lens assembly applicable for compact cameras and mobile phones.