Imaging Lens with Segmented Focusing Groups for 1.4 μm Resolution
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Solution Overview
Problem
There is a lack of imaging lenses that can achieve a resolution of 1.4 μm×1.4 μm for ⅔-inch to ⅓-inch CMOS cameras with an MTF contrast of 15% or above, preferably 20% or above, while also allowing for simple focusing mechanisms.
Innovation Solution
The proposed imaging lens consists of a focusing lens assembly with a positive refractive power that moves along the optical axis for focusing, and a fixed lens assembly with a negative refractive power positioned near the imaging plane. This configuration includes two positive lens groups with an aperture between them, enabling high resolution and simple focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional imaging lens design is used, then the structure is simple, but the resolution cannot achieve 1.4 μm×1.4 μm with MTF contrast of 15% or above
Solution Approach 1:
The lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, third lens group with positive refractive power) that can move independently along the optical axis. This segmentation allows each group to contribute differently to the overall resolution and MTF performance while enabling flexible focusing mechanisms.
Solution Approach 2:
The patent implements dynamic focusing by allowing the first and third lens groups to move along the optical axis while the second lens group remains fixed. This dynamic configuration enables the lens to achieve high resolution at different object distances, maintaining MTF contrast of 15% or above across various focusing conditions.
2Measurement precision
If the pixel size is miniaturized to enhance image resolution, then the resolution increases, but the lens must image a smaller area with higher precision
Solution Approach 1:
Different lens groups are designed with specific refractive powers and movement characteristics tailored to their local functions. The first lens group (positive power) handles initial light convergence, the second lens group (negative power) provides intermediate correction, and the third lens group (positive power) finalizes the imaging. This local optimization ensures high precision imaging across the entire sensor surface.
Solution Approach 2:
The patent utilizes changes in refractive power distribution and object distance to optimize imaging performance. By adjusting the movement of lens groups with different refractive powers, the system maintains high MTF contrast and resolution for miniaturized pixels while adapting to various focusing conditions.
3Ease of operation
If a floating mechanism is used for focusing, then the focusing function is achieved, but the device complexity increases
Solution Approach 1:
The focusing mechanism is segmented into discrete movable lens groups (first and third groups) and a fixed lens group (second group). This segmentation simplifies the overall mechanism by allowing independent control of specific groups rather than requiring complex floating mechanisms for the entire lens assembly.
Solution Approach 2:
Instead of moving the entire lens assembly or using complex floating mechanisms, the patent inverts the approach by keeping the middle lens group (second group with negative power) fixed and moving only the outer lens groups (first and third groups with positive power). This inverted configuration simplifies the focusing mechanism while maintaining effective focusing function.
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 imaging lens achieves a resolution corresponding to miniaturized image sensor elements and allows for focusing with a simple structure, while maintaining an MTF contrast of more than 15% and preferably more than 20% at 1.4 μmL&S over the entire CMOS surface.
Implementation Method 1
a focusing lens assembly with a positive refractive power, which can move in a direction of an optical axis depending on an object distance
Implementation Method 2
a fixed lens assembly with a negative refractive power, which is fixed near the imaging plane
Data Source
AI summary
An imaging lens includes a focusing lens assembly with a positive refractive power, which can move in a direction of an optical axis depending on an object distance and have two positive lens groups with an aperture disposed therebetween, and a fixed lens assembly with a negative refractive power fixed near the imaging plane. The focusing lens assembly includes a 2-division-3-piece front group with positive refractive power consisting of single lens and doublet lenses, the aperture, and a 2-division-3-piece back group with positive refractive power consisting of doublet lenses and single lens. The focusing lens closest to the object side is a meniscus lens convex at the object side and concave at an image side and has the weakest refractive power out of all. The front group and the back group relative to the aperture have focal lengths f1 and f2 complying with correlation of 0.9<f1/f2<1.3.