Dual Negative Lens Units for Quiet High-Speed Autofocus
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Solution Overview
Problem
Existing optical systems for image capturing devices face challenges in achieving quiet and high-speed auto-focusing while minimizing aberration variations across a wide focal range, particularly in digital cameras using solid-state image sensors.
Innovation Solution
The optical system incorporates a front lens unit and two focusing units with negative refractive power, where the first and second focusing units move to change the distance between them on the optical axis, satisfying specific inequalities to reduce aberrations and enhance focus sensitivity, thereby enabling high-speed and quiet focusing with minimal aberration variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single focusing unit is used to reduce weight and simplify structure, then device complexity and weight are reduced, but focusing speed and quietness deteriorate due to insufficient focus sensitivity
Solution Approach 1:
The focusing unit is divided into two separate focusing units (first and second focusing units), each with negative refractive power. This segmentation allows independent movement of each unit, increasing focus sensitivity and enabling faster, quieter focusing while maintaining reduced overall complexity compared to traditional single-unit designs
2Speed
If focusing units move significantly to achieve focus from infinity to short distance, then focus sensitivity is improved, but aberration variations increase
Solution Approach 1:
Each focusing unit is assigned a specific negative refractive power value within optimized ranges (first focusing unit: -0.5 to -2.0, second focusing unit: -0.5 to -2.0). This local optimization of refractive power characteristics allows the units to move independently with sufficient focus sensitivity while maintaining small aberration variations across the entire focusing range from infinity to short distance
3Speed
If the distance between focusing units is optimized to improve focus sensitivity, then focusing performance is enhanced, but optical system complexity increases
Solution Approach 1:
The optical system optimizes specific parameter ranges: the distance between the first and second focusing units is controlled to be 0.005 to 0.020 times the focal length of the optical system. By changing and optimizing this critical parameter, the system achieves high focus sensitivity and fast, quiet focusing while maintaining manageable optical system complexity through standardized design ratios
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 achieves high optical performance and reduces aberration variations across a wide focal range, facilitating high-speed and quiet focusing in image capturing devices, including digital cameras, by optimizing the movement and refractive power of the focusing units.
Implementation Method 1
a first focusing unit having a negative refractive power, and a second focusing unit having a negative refractive power in this order from an object side to an image side
Data Source
AI summary
An optical system includes a front lens unit, a first focusing unit having a negative refractive power, and a second focusing unit having a negative refractive power in this order from an object side to an image side. The optical system is a single focus optical system. When a focus is shifted from an object at infinity to an object at a short distance, the first focusing unit and the second focusing unit move to change a distance between the first focusing unit and the second focusing unit on an optical axis.