Projection Lens Aspherical Freeform Aberration Correction
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Solution Overview
Problem
Existing projection-type image display apparatuses fail to adequately reduce throw distance and achieve large images while maintaining image quality, as they suffer from insufficient aberration correction and increased manufacturing complexity due to the use of freeform surface lenses with unstable molding conditions.
Innovation Solution
A projection lens system incorporating a combined lens surface formed by adding a freeform surface to an aspherical surface, which is symmetric with respect to the optical axis, to improve aberration correction and simplify manufacturing by ensuring accurate mold processing and assembly, while maintaining a compact design through decentering of lenses and use of freeform surface lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If freeform surface lenses are used to reduce throw distance and correct aberrations, then image quality and compactness are improved, but manufacturing precision and assembly accuracy deteriorate due to unstable molding conditions
Solution Approach 1:
The patent applies asymmetry by combining a rotationally symmetric aspherical surface with an asymmetric freeform surface on the same lens. The aspherical surface provides rotational symmetry for stable molding, while the freeform surface (represented by polynomial terms in equations (2) and (3)) introduces necessary asymmetry for aberration correction in oblique projection, resolving the contradiction between manufacturing stability and image quality.
Solution Approach 2:
The patent merges two surface types (aspherical and freeform) into a single composite lens surface. The aspherical surface component ensures stable molding and basic aberration control, while the freeform surface component adds the capability to correct complex aberrations in oblique projection, achieving both manufacturing reliability and superior image quality.
2Manufacturing precision
If multiple aspherical lenses are used to correct aberrations, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple surface functions into a single composite lens surface by merging aspherical and freeform surfaces. This integration reduces the number of separate lens elements needed while maintaining comprehensive aberration correction capabilities, thereby reducing device complexity while preserving image quality.
Solution Approach 2:
The composite lens surface with combined aspherical and freeform characteristics serves multiple functions simultaneously: it corrects spherical aberration, coma aberration, and distortion that would otherwise require multiple separate lens elements. This multi-functionality reduces the overall lens system complexity while maintaining superior aberration correction.
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 enables a downsized projection-type image display apparatus that effectively corrects aberrations, achieves a short throw distance, and supports large-screen projections with improved manufacturing ease and accuracy.
Implementation Method 1
a lens having a lens surface having a largely-improving aberration correcting ability by using an aspherical surface that is symmetric with respect to an optical axis in order to reduce meridional aberration (basic aberration)
Implementation Method 2
by adding a freeform surface to the aspherical surface in order to more accurately correct sagittal aberration (in a cutting-sphere direction)
Data Source
AI summary
A projection-type image display apparatus has a projection optical system that can sufficiently meet requirements for significant reduction in a throw distance and a large image and that can downsize. A projection image display apparatus of an oblique type comprising, inside a housing: a light source; an image display element configured to modulate an intensity of light from the light source in accordance with an image signal; and a projection lens system including a plurality of lenses configured to project image light onto a projection plane from an oblique direction, the image light being modulated from the image display element. The projection lens system has a lens integrally having an aspherical lens surface and a freeform lens surface, and the lens integrally having the aspherical lens surface and the freeform lens surface is arranged in the projection lens system so that light components of luminous flux are separated.