Image Pickup Lens with Segmented Refractive Units for Compact Contrast AF
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Solution Overview
Problem
Mirrorless single-lens cameras using contrast AF require larger movements of the focusing lens unit due to the lack of precise movement calculation, leading to increased weight and complexity in the optical system.
Innovation Solution
An image pickup lens design featuring a front lens unit with positive refractive power, a focusing lens with positive refractive power, and a rear lens unit with negative refractive power, where the focusing lens moves on the optical axis, and a single lens with positive refractive power is disposed nearest to the object in the rear lens unit, optimizing aberration correction and reducing the weight of the focusing lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If contrast AF is used without phase-difference AF capability, then the camera can be made more compact, but the focusing lens unit must move a larger distance leading to increased weight
Solution Approach 1:
The optical system is divided into multiple lens units with different functions: a first lens unit for initial focusing, a second lens unit for fine-tuning focus, and a third lens unit for aberration correction. This segmentation allows each unit to be optimized independently, reducing the overall movement distance required while maintaining compact size.
Solution Approach 2:
The patent changes the refractive power parameters of different lens units, specifically making the third lens unit have negative refractive power while the first and second lens units have positive refractive power. This parameter configuration enables more efficient focus adjustment with reduced movement distance.
2Measurement precision
If the focusing lens unit moves a larger distance to achieve maximum contrast, then focus accuracy can be improved, but the weight and complexity of the optical system increases
Solution Approach 1:
The focusing operation is divided into two stages: coarse focusing by the first lens unit and fine focusing by the second lens unit. This segmentation allows the system to achieve high focus accuracy without requiring any single lens unit to travel a excessively long distance, thereby reducing overall system complexity.
Solution Approach 2:
The third lens unit acts as an intermediary that corrects aberrations introduced by the focusing movements of the first and second lens units. This mediator component enables accurate focusing while maintaining optical quality without requiring excessive movement distances.
3Manufacturing precision
If a single lens with positive refractive power is disposed nearest to the object in the rear lens unit, then aberration correction is improved, but the lens configuration becomes more constrained
Solution Approach 1:
The patent specifies that the third lens unit must have negative refractive power and that the lens nearest to the object in this unit must have positive refractive power. This parameter configuration creates a balanced optical system that effectively corrects aberrations while maintaining reasonable design flexibility through the defined power relationships.
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 design enables high-speed and accurate contrast AF, reduces the weight of the focusing lens, and improves aberration correction, resulting in a compact and efficient image pickup lens with enhanced imaging performance.
Implementation Method 1
a front lens unit having a positive refractive power, one focusing lens having a positive refractive power, and a rear lens unit having a negative refractive power, and at the time of focusing, the focusing lens moves on an optical axis
Data Source
AI summary
An image pickup lens includes in order from an object side, a front lens unit having a positive refractive power, one focusing lens unit having a positive refractive power, and a rear lens unit having a negative refractive power, wherein at the time of focusing, the focusing lens moves on an optical axis, and a single lens having a positive refractive power is disposed nearest to an object in the rear lens unit.