Inner Focusing Lens Compact Diameter Wide-Angle Correction
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Solution Overview
Problem
Conventional inner focusing lenses with a positive lens element farthest on the image side face challenges in reducing diameter and size for compact camera applications, particularly for mirrorless interchangeable-lens cameras, and fail to adequately address wide-angle views and field curvature correction.
Innovation Solution
The inner focusing lens configuration includes a first lens group with a positive refractive power, a second lens group with a negative refractive power, and a third lens group with a negative refractive power, where the second lens group moves along the optical axis to adjust intervals, incorporating at least one negative meniscus lens and a simple lens element with negative refractive power farthest on the image side, to achieve compactness and high imaging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive lens element is disposed farthest on the image side to assure telecentricity, then imaging performance is improved, but the diameter of the optical system cannot be sufficiently reduced
Solution Approach 1:
The patent inverts the conventional arrangement by disposing a negative lens element farthest on the image side instead of a positive lens element. This inversion allows the optical system to achieve compact diameter while maintaining acceptable imaging performance through software correction of oblique incidence effects.
Solution Approach 2:
The patent changes the refractive power parameter of the lens element farthest on the image side from positive to negative. This parameter change enables the optical system to reduce diameter while compensating for the loss of telecentricity through image processing techniques.
2Speed
If the focusing group is made light-weight with smallest diameter for rapid driving, then autofocus speed is improved, but aberration variations consequent to wobble increase
Solution Approach 1:
The patent applies local quality by assigning different refractive powers to different lens groups: the first lens group has positive refractive power while the second and third lens groups have negative refractive power. This local differentiation allows the focusing group to be lightweight for fast autofocus while the overall configuration suppresses aberration variations.
Solution Approach 2:
The patent introduces a negative lens element farthest on the image side as an intermediary that suppresses aberration variations caused by focusing group wobble. This intermediary element compensates for the instability introduced by rapid focusing movements.
3Reliability
If a positive lens group is disposed farthest on the image side, then telecentricity is assured, but the diameter of the third lens group cannot be sufficiently reduced for compact camera applications
Solution Approach 1:
The patent inverts the conventional approach by placing a negative lens element farthest on the image side instead of a positive lens group. This inversion enables the third lens group diameter to be sufficiently reduced for compact camera applications while accepting oblique incidence on the image sensor.
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 enables a compact, lightweight focusing group with wide-angle capabilities, reducing the optical system's diameter and overall length, while effectively correcting field curvature and aberrations, making it suitable for high-speed video capture and compact camera designs.
Implementation Method 1
a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a negative refractive power
Data Source
AI summary
An inner focusing lens has sequentially from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a negative refractive power. The first lens group has negative meniscus lenses disposed farthest on the object side thereof. The second lens group is moved along the optical axis whereby focusing from a focus state for an object at infinity to a focus state for the minimum object distance is performed. The inner focusing lens satisfies predetermined conditions and thereby, realizes a compact inner focusing lens having high imaging performance at wide angles, suitable for compact cameras having a function of capturing video.