Aspheric Third Lens Design for Compact Image Taking Lenses
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Solution Overview
Problem
Conventional image taking lenses for solid-state image pickup elements face challenges in achieving compactness and low manufacturing costs while maintaining optical performance, with issues related to lens size, exit pupil positioning, and sensitivity to manufacturing errors.
Innovation Solution
The design incorporates an image taking lens with an aperture stop followed by a positive first lens, a negative second lens, and a negative third lens with aspheric surfaces, where the third lens's region around the optical axis is concave and the peripheral region is convex, fulfilling specific focal length and curvature radius conditions to optimize optical performance and reduce manufacturing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the image taking lens is made small with a size of the solid-state image pickup element unchanged, then the lens occupies less space, but the exit pupil position moves closer to the image plane causing oblique light flux entry and poor image brightness uniformity
Solution Approach 1:
The patent applies local quality by using an aspheric surface specifically on the image-side surface of the third lens (negative lens), while other lenses use spherical surfaces. This localized aspheric design corrects peripheral aberrations and improves image brightness uniformity without requiring a complete redesign of the entire lens system, thus maintaining compactness while solving the brightness non-uniformity problem.
Solution Approach 2:
The patent changes the optical parameters by introducing a negative lens with a specific focal length ratio (|f2/f3| between 0.05 and 0.5) and using an aspheric surface with specific curvature coefficients. These parameter changes allow the exit pupil to be positioned appropriately while maintaining a compact lens structure, preventing oblique light flux entry and improving image brightness uniformity.
2Device complexity
If a conventional three-lens design with one negative lens is used, then the lens structure is simple, but sensitivity to manufacturing errors increases and peripheral optical performance deteriorates
Solution Approach 1:
The patent applies local quality by using an aspheric surface specifically on the image-side surface of the third lens (negative lens), while other lenses use spherical surfaces. This localized aspheric design corrects peripheral aberrations and improves image brightness uniformity without requiring a complete redesign of the entire lens system, thus maintaining compactness while solving the brightness non-uniformity problem.
Solution Approach 2:
The patent uses a composite approach by combining spherical surfaces on the first two lenses with an aspheric surface on the third lens. This composite design leverages the manufacturing simplicity of spherical surfaces for most of the system while introducing aspheric precision only where needed for peripheral correction, balancing complexity and performance.
3Volume of moving object
If the power of the negative lens is made too strong to achieve compactness, then the lens size is reduced, but sensitivity against manufacturing errors for the lens optical axis increases
Solution Approach 1:
The patent changes the optical parameters by introducing a negative lens with a specific focal length ratio (|f2/f3| between 0.05 and 0.5) and using an aspheric surface with specific curvature coefficients. These parameter changes allow the exit pupil to be positioned appropriately while maintaining a compact lens structure, preventing oblique light flux entry and improving image brightness uniformity.
Solution Approach 2:
The patent applies spheroidality by using an aspheric surface on the third lens instead of a simple spherical surface. The aspheric curvature profile is designed to correct aberrations while reducing sensitivity to manufacturing tolerances, allowing the negative lens to provide sufficient optical power for compactness without excessive sensitivity to alignment errors.
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 results in a compact, low-cost image taking lens with improved optical performance, appropriate exit pupil positioning, and reduced sensitivity to manufacturing errors, enabling effective downsizing and maintaining peripheral optical performance.
Implementation Method 1
The third lens is provided with an image side surface in an aspheric shape
Data Source
AI summary
An image taking lens forming an optical image on an solid-state image pickup element according to the present invention, is provided with, in order from an object side thereof: a first lens with a positive power; a second lens with a negative power; and a third lens with a negative power. Third lens includes an image side surface in an aspheric shape such that a region around an optical axis in the aspheric shape is formed in a concave shape facing an image side of the image taking lens and a peripheral region in the aspheric shape surrounding the region around the optical axis is formed in a convex shape facing the image side of the image taking lens. The image taking lens fulfills a predefined conditional formula.