Rear Attachment Lens for Image Pickup Apparatus
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in reducing the size of the optical system while maintaining backfocus and achieving high optical performance, especially when using interchangeable lenses, as they often compromise on image circle magnification and aberration correction.
Innovation Solution
The image pickup apparatus includes a mount for interchangeable lenses, an optical system with specific refractive power configurations, and an optical filter, which satisfies certain conditional expressions to achieve reduced size, secure backfocus, and high optical performance by optimizing lens configurations and aberration contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an optical system is inserted between an interchangeable lens and image pickup element to increase focal length, then the image circle is enlarged, but the optical system size increases and backfocus is compromised
Solution Approach 1:
The patent integrates the optical system (including lenses L1-L7) and optical filter F within the lens barrel of the interchangeable lens itself, rather than as a separate external attachment. This nesting approach allows the focal length modification functionality to be incorporated without increasing the overall optical system volume, as the components are housed within the existing lens structure.
Solution Approach 2:
The patent arranges the optical components in a compact multi-element configuration along the optical axis, utilizing the depth dimension efficiently. By optimizing the axial distances between lenses and positioning the optical filter at a specific location within the lens barrel, the design achieves high image circle magnification while maintaining a compact overall length that does not compromise backfocus.
2Adaptability or versatility
If an optical system is inserted between an interchangeable lens and image pickup element to increase focal length, then the image circle is enlarged, but backfocus is compromised
Solution Approach 1:
The optical system is nested within the lens barrel such that the combined length of the interchangeable lens and attachment does not exceed the original flange back distance. The lenses and optical filter are positioned within the available space, ensuring that the rear attachment lens maintains the required backfocus for mounting to the image pickup apparatus.
Solution Approach 2:
The patent optimizes the refractive powers and axial positions of the individual lenses (L1-L7) to achieve the desired image circle magnification while controlling the overall length. By carefully selecting lens parameters and spacing, the design achieves high magnification without extending the backfocus beyond acceptable limits.
3Adaptability or versatility
If an optical system is inserted between an interchangeable lens and image pickup element to increase focal length, then the focal length is increased, but optical performance deteriorates due to aberration
Solution Approach 1:
The optical system is divided into multiple discrete lens elements (L1-L7) with alternating positive and negative refractive powers, arranged in a specific sequence. This segmentation allows each lens to contribute to correcting specific types of aberrations, with the intermediate lenses serving as aberration correction elements that compensate for distortions introduced by the magnification lenses.
Solution Approach 2:
The optical filter F is positioned as an intermediary element between the interchangeable lens and the optical system, and the intermediate lenses act as mediators to correct aberrations. This arrangement allows the system to achieve high focal length magnification while maintaining optical quality through the aberration-correcting function of the intermediate optical elements.
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 effectively increases the focal length of interchangeable lenses, reduces the optical system size, and secures backfocus, while maintaining high optical performance by adhering to specific refractive power and lens configuration conditions.
Implementation Method 1
an optical system having a refractive power and configured to image an object point, which is located on an image side of a surface of the optical system that is closest to an object side, onto the image pickup element
Data Source
AI summary
An image pickup apparatus includes: a mount to which an interchangeable lens is mountable; an image sensor; an optical system having a refractive power and imaging an object point located on an image side of a most-object-side surface of the optical system onto the image sensor; and an optical filter arranged between the optical system and the image sensor, and a distance on an optical axis from a flange surface of the mount to the object point located on the image side of the most-object-side surface, a distance on the optical axis from the flange surface of the mount to the image pickup element, and a lateral magnification of the optical system when the interchangeable lens is mounted to the image pickup apparatus and the object point located on the image side of the most-object-side surface, is imaged onto the image pickup element, are appropriately set.