Projection Lens Aberration Correction via Group Movement
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Solution Overview
Problem
Conventional projection lens systems struggle to achieve sufficient optical performance in terms of lateral chromatic aberration and curvature of field, especially with high-resolution image display devices and high zoom ratios, as they fail to maintain performance across a wide zooming range.
Innovation Solution
A five- or six-group projection lens system design where the most enlargement-side group has negative optical power and the most reduction-side group has positive optical power, with specific movement patterns and aperture stop placement, adhering to defined conditional formulas to optimize aberration correction and maintain performance across zooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional projection lens systems are used with high zoom ratios, then zooming capability is achieved, but lateral chromatic aberration and curvature of field cannot be corrected sufficiently
Solution Approach 1:
The projection lens system is divided into multiple lens groups (first through fifth groups) with different optical powers and movement characteristics. Each group is assigned specific functions: the first and second groups primarily correct lateral chromatic aberration through their movement, while the third group corrects curvature of field. This segmentation allows independent optimization of different aberration types during zooming operations.
Solution Approach 2:
The patent implements dynamic movement of specific lens groups during zooming. The first, second, and third groups move along the optical axis in response to zooming operations, while the fourth and fifth groups remain stationary. This dynamic configuration enables the system to maintain optimal aberration correction across the entire zoom range from wide-angle to telephoto ends.
2Measurement precision
If high-resolution image display devices are used, then image quality is improved, but the variation in curvature of field becomes intolerable
Solution Approach 1:
The patent assigns specific optical power characteristics to different lens groups to address local optical quality issues. The third lens group is given positive optical power specifically to correct curvature of field, while the first two groups have configurations optimized for lateral chromatic aberration correction. This localized functional assignment ensures that each aspect of image quality is addressed by the most suitable lens group.
Solution Approach 2:
The patent changes the movement parameters of the first, second, and third lens groups during zooming operations. By controlling the displacement distances and directions of these groups relative to each other, the system dynamically adjusts the curvature of field correction to match the zoom level, maintaining acceptable performance from wide-angle to telephoto ends.
3Manufacturing precision
If lateral chromatic aberration is corrected by moving groups greatly backward, then lateral chromatic aberration is improved, but telecentricity cannot be maintained
Solution Approach 1:
The patent uses the fourth and fifth lens groups as stationary intermediary elements that help maintain telecentricity while the first three groups move to correct lateral chromatic aberration. The aperture stop is positioned between the third and fourth groups, with the fourth group acting as a mediator to preserve the telecentric property despite the movement of earlier groups. This intermediary structure allows independent optimization of aberration correction and telecentricity maintenance.
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 corrects lateral chromatic aberration and curvature of field, enabling high-resolution image display with improved optical performance across the entire zoom range, making projectors more compact, versatile, and high-performance.
Implementation Method 1
a projection lens system for projectors having a zooming capability
Data Source
AI summary
An aperture stop is arranged on the reduction side of the most reduction-side lens element in a fourth group; during zooming from the tele-end to the wide-end through a middle position that fulfills conditional formula 0.99<fm/(ft×fw)½<1.01, first and fifth groups remain stationary, the composite power of third and fourth groups is constantly positive, and the third and fourth groups move from the enlargement side to the reduction side, satisfying conditional formulae: 7<ΔTM3/|ΔTM2|, 7<ΔTW3/|ΔTW2|, 7<ΔTM4/|ΔTM2|, 7<ΔTW4/|ΔTW2|, 0.9<ΔTM4/ΔTM3<1.1, 0.9<ΔTW4/ΔTW<1.1 (ft, fm, and fw are the entire-system focal lengths at the tele-end, the middle position, and the wide-end; ΔTM2-4 are the movement amounts of the second to fourth groups from the tele-end to the middle position; and ΔTW2-4 are the movement amounts of the second to fourth groups from the tele-end to the wide-end).