Fixed Focal Length Lens Reducing Weight via Segmented Positive Unit
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Solution Overview
Problem
Existing image pickup optical systems face challenges in achieving a wide angle and low F-number with uniform resolving power across the image plane, leading to issues such as increased weight and size of focusing units due to insufficient refractive power and large lens diameters.
Innovation Solution
A fixed focal length lens configuration with a first positive refractive power lens unit that does not move for focusing, accompanied by a second and third lens unit that move for focusing, where the first lens unit includes two negative lenses, and specific conditional expressions are satisfied to optimize focal lengths and refractive powers, reducing the size and weight while maintaining high optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the positive refractive power of the first lens unit is increased, then the diameter and weight of the focusing units are reduced, but the lens configuration becomes more complex
Solution Approach 1:
The first lens unit is divided into multiple lens elements (including at least one negative lens and one positive lens) with specific refractive powers. By segmenting the lens unit and assigning specific functions to each element, the patent achieves the required positive refractive power while maintaining a manageable configuration. The focusing units are also segmented into multiple lens elements with optimized individual refractive powers.
Solution Approach 2:
The patent assigns specific refractive power ranges to different lens units based on their local functions. The first lens unit has a positive refractive power of +0.05 to +0.15 (optimized locally for reducing focusing unit size), while the second and third lens units have negative refractive powers tailored to their specific focusing requirements. This local optimization of refractive powers allows weight reduction without excessive complexity.
2Area of stationary object
If the combined refractive power of negative lenses in the first lens unit is increased, then the diameter of the lens closest to the object side is reduced, but the overall lens system becomes more complex
Solution Approach 1:
The patent specifies precise parameter ranges for the refractive powers of lenses in the first lens unit. The combined refractive power of negative lenses is set within a specific range, and the ratio between positive and negative lens powers is controlled. By changing and optimizing these parameters within defined boundaries, the patent reduces the object-side lens diameter to minimize lens barrel size while avoiding excessive complexity through standardized parameter ranges.
3Reliability
If the diameter of focusing units is increased to achieve sufficient refractive power, then the optical performance is improved, but the weight and load on the driving system increase
Solution Approach 1:
The patent optimizes the refractive power parameters of the first lens unit to a specific positive range (+0.05 to +0.15), which allows the focusing units to achieve sufficient optical performance with smaller diameters. This parameter optimization ensures that the focusing units have enough refractive power to correct aberrations effectively while maintaining a compact size and reduced weight, thereby improving reliability without excessive weight.
4Reliability
If the diameter of the lens closest to the object side is increased to achieve sufficient refractive power, then the optical performance is improved, but the lens barrel diameter becomes larger
Solution Approach 1:
The patent controls the refractive power parameters of the first lens unit, specifically setting the combined refractive power of negative lenses and the ratio of positive to negative lens powers within defined ranges. These parameter changes allow the object-side lens to achieve sufficient refractive power for high optical performance while maintaining a smaller diameter, thus preventing the lens barrel from becoming excessively large.
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 achieves a wide-angle, small F-number lens with reduced size and weight, ensuring high optical performance and effective correction of aberrations across the entire object distance.
Implementation Method 1
a first lens unit having a positive refractive power... the first lens unit includes two negative lenses disposed in succession from the object side
Implementation Method 2
at least the second lens unit moves for focusing... two lens units being moved when focusing in a manner such that a distance between the two lens units changes
Data Source
AI summary
A fixed focal length lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit and a third lens unit, wherein the first lens unit does not move for focusing, at least the second lens unit moves for focusing, a distance between each pair of adjacent lens units changes for focusing, and the first lens unit includes two negative lenses disposed in succession from the object side, and wherein a focal length of the fixed focal length lens, a focal length of the first lens unit, and a combined focal length of the two negative lenses of the first lens unit are appropriately set.