Non-planar Imaging Plane Field Curvature Correction
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Solution Overview
Problem
Existing lens optical units for digital cameras with solid-state image sensors face challenges in reducing size while maintaining high optical performance and correcting field curvature, particularly due to the need for a large number of lenses and complex optical designs to achieve optimal image quality across the entire image field.
Innovation Solution
A lens optical unit design featuring a non-planar imaging plane with a sag amount increasing in the optical axis direction, satisfying specific conditional expressions for Petzval curvature, angle of incidence, and focal length, which includes a configuration of four lenses with two positive and two negative lenses, and an aspheric surface on the image-side lens to correct aberrations and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional planar imaging plane is used, then the lens optical unit can be designed with simpler structure, but field curvature correction becomes difficult and image resolution deteriorates at the edges
Solution Approach 1:
Instead of adding complex corrective elements to a planar imaging plane, the patent inverts the approach by making the imaging plane itself non-planar with a specific curved surface shape that matches the field curvature of the optical system. This eliminates the need for additional field curvature correction lenses while maintaining high image resolution across the entire field.
Solution Approach 2:
The patent changes the geometric parameter of the imaging plane from planar to non-planar with a specific sag amount profile. By optimizing the curved surface shape parameters to match the field curvature, the system achieves excellent image quality without requiring additional corrective optical elements.
2Manufacturing precision
If multiple lenses are added to correct field curvature and improve image quality, then optical performance improves, but the size of the lens optical unit increases
Solution Approach 1:
The patent extracts the field curvature correction function from separate corrective lenses and integrates it into the imaging plane structure itself. This eliminates the need for additional lenses dedicated to field curvature correction, thereby reducing the overall size of the optical unit while maintaining image quality.
Solution Approach 2:
The non-planar imaging plane serves multiple functions: it acts as both the image sensor substrate and the field curvature correction element. By combining these functions into a single component, the patent reduces the number of optical elements needed while achieving both compact size and high image quality.
3Volume of moving object
If the imaging plane is made non-planar with increased sag amount, then field curvature correction improves and size is reduced, but manufacturing precision of the imaging plane becomes more difficult
Solution Approach 1:
The patent optimizes the sag amount parameter of the non-planar imaging plane to balance field curvature correction effectiveness with manufacturability. By carefully selecting the sag amount profile that matches the optical system's field curvature characteristics, the patent achieves excellent correction while maintaining reasonable manufacturing precision requirements.
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 optical performance with sufficient field curvature correction and size reduction, ensuring optimal image resolution across the entire image field by aligning the field curvature direction with the imaging plane shape and reducing the number of lenses required.
Implementation Method 1
an imaging plane of the solid-state image sensor has a non-planar shape that causes a sag amount in an optical axis direction to increase as a distance from an optical axis increases, and a conditional expression (1) is satisfied: ρ×Sag>0 where ρ represents a Petzval curvature of an optical unit
Implementation Method 2
an aspheric surface on the image-side lens to correct aberrations and reduce size
Implementation Method 3
at least one lens that is arranged at an object side of a solid-state image sensor
Data Source
AI summary
Provided is a lens optical unit, including at least one lens arranged at an object side of a solid-state image sensor. An imaging plane of the image sensor has a non-planar shape causing a sag amount in an optical axis direction to increase as a distance from an optical axis increases, and satisfies the expression: ρ×Sag>0, where ρ represents a Petzval curvature of an optical unit represented by ρ:ρ=∑k1rk·(1nk′-1nk),rk represents a curvature radius of a kth lens surface from the object side, nk represents a refractive index of a medium before being incident to the kth lens surface from the object side, n′k represents a refractive index of a medium after being emitted from the kth lens surface from the object side, and Sag represents a sag amount in the optical axis direction related to a given point other than the optical axis on the imaging plane.