Inner Focus Lens Aberration Control via Aperture Stop Positioning
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Solution Overview
Problem
Image pickup optical systems with inner focus types face challenges in maintaining optical characteristics during focusing and image stabilization, often experiencing aberration deviation and decentering aberrations due to the movement of lens units.
Innovation Solution
An optical system comprising a first lens unit with positive refractive power, a second lens unit that moves during focusing, a third lens unit with negative refractive power for image stabilization moving vertically, and a fourth lens unit with positive refractive power, where the second and third lens units are positioned near an aperture stop to minimize size and aberrations, and the conditional expression 0.30 < D3/f < 1.30 is satisfied to optimize lens positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a light-weight lens unit is used for inner focus mechanism, then focusing speed is improved, but aberration deviation increases during focusing
Solution Approach 1:
The patent applies local quality by making the second lens unit (focusing lens unit) with positive refractive power and positioning it near the aperture stop. This local configuration with specific refractive power and positioning minimizes aberration deviation during focusing while maintaining light weight for fast focusing operation.
Solution Approach 2:
The aperture stop acts as an intermediary element between the second lens unit and the third lens unit. By positioning the aperture stop between these lens units, the patent controls the light paths and reduces aberration deviation caused by the movement of the light-weight second lens unit during focusing.
2Reliability
If lens units are moved for image stabilization, then image blur correction is achieved, but decentering aberrations are generated
Solution Approach 1:
The patent applies local quality by making the third lens unit (image stabilization lens unit) with negative refractive power and positioning it near the aperture stop. This specific configuration minimizes decentering aberrations when the lens unit moves vertically for image stabilization while maintaining effective blur correction.
Solution Approach 2:
The aperture stop serves as an intermediary that controls the light paths through the third lens unit during image stabilization. By positioning the aperture stop between the second and third lens units, the patent reduces decentering aberrations generated when the third lens unit moves vertically to correct image blur.
3Volume of moving object
If lens units are positioned to minimize size, then system compactness is improved, but optical characteristics may deteriorate
Solution Approach 1:
The patent applies local quality by assigning specific refractive powers to different lens units (positive for second lens unit, negative for third lens unit) and positioning them near the aperture stop. This localized optimization allows each lens unit to be compact while collectively maintaining satisfactory optical characteristics during focusing and image stabilization.
Solution Approach 2:
The patent uses parameter changes by optimizing the refractive powers of individual lens units and their positions relative to the aperture stop. By carefully controlling these parameters (refractive power, position), the patent achieves compact lens unit sizes while maintaining required optical performance.
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 allows for effective focusing and image stabilization with small and lightweight lens units, maintaining satisfactory optical characteristics and reducing aberrations, thereby enhancing the optical performance of image pickup systems.
Implementation Method 1
the second lens unit is configured to move in an optical axis direction during focusing
Implementation Method 2
the third lens unit is configured to move, during image blur correction, in a direction having a vertical direction component with respect to an optical axis
Implementation Method 3
a first lens unit having a positive refractive power; a second lens unit having a positive refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power
Data Source
AI summary
Provided is an optical system, including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a positive refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power, in which the second lens unit is configured to move in an optical axis direction during focusing, in which the third lens unit is configured to move, during image blur correction, in a direction having a vertical direction component with respect to an optical axis, and in which a configuration of the first lens unit and arrangement of an aperture stop and the third lens unit are each appropriately set.