Projection Lens System Aberration Control via Segmented Optical Axes
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Solution Overview
Problem
Existing projection lens systems struggle to effectively control aberrations other than coma aberration when the display surface and projection plane are not parallel, leading to deterioration in image focus.
Innovation Solution
A projection lens system is designed with a front group and a rear group, where the front group is positioned on the projection-plane side and the rear group on the display-surface side, with an aperture stop on the display-surface side. The optical axes of the front and rear groups are parallel but shifted relative to each other, allowing for effective control of aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display surface and projection plane are not parallel, then the projection image can be formed on a tilted screen, but coma aberration significantly deteriorates
Solution Approach 1:
The projection lens system is divided into a front group and a rear group with different optical axes. The front group's optical axis is tilted relative to the display surface normal, while the rear group's optical axis is parallel to the display surface normal. This segmentation allows independent optimization of each group to address different aberration requirements, enabling projection on non-parallel surfaces while controlling coma aberration.
Solution Approach 2:
The patent introduces asymmetry by making the front group's optical axis tilted at a specific angle relative to the display surface normal, while keeping the rear group's optical axis parallel to the display surface normal. This asymmetric configuration allows the system to adapt to non-parallel projection surfaces while maintaining aberration control through the specific tilt angle design.
2Manufacturing precision
If the optical axis is tilted to satisfy Scheimpflug principle, then focus is achieved on tilted projection plane, but coma aberration increases
Solution Approach 1:
The lens system is segmented into front and rear groups with different optical axis orientations. The front group provides the necessary tilt for Scheimpflug focus on the projection plane, while the rear group maintains an optical axis parallel to the display surface normal to minimize coma aberration generation. This segmentation allows the system to achieve focus on tilted surfaces without the harmful coma effect.
Solution Approach 2:
The front group acts as an intermediary between the display surface and the projection plane. It introduces the necessary angular deviation to satisfy the Scheimpflug principle for focus, while the rear group corrects the beam direction to be parallel with the display surface normal, thereby mediating between the conflicting requirements of focus and aberration control.
3Device complexity
If a single optical axis is used, then the lens system is simpler, but it cannot effectively control aberrations when display surface and projection plane are not parallel
Solution Approach 1:
The optical system is segmented into a front group and a rear group, each with its own optical axis. The front group's optical axis is tilted relative to the display surface normal, while the rear group's optical axis is parallel to it. This segmentation enables effective aberration control in tilted projection scenarios while maintaining reasonable system complexity through modular design.
Data Source
AI summary
A projection lens system (G1, G2) includes a front group (G1) disposed on a projection-plane (SC) side, a rear group (G2) disposed on a display-surface (SF) side of an image display element inclined with reference to the projection plane (SC), and an aperture stop (S) disposed on the display-surface (SF) side with reference to the front group (G1). The rear-group optical axis is tilted on the shared plane at a tilt angle ξ with reference to the display-surface normal. In projection lens system (G1, G2), when the amount of shift Δ is zero, the tilt angle ξ satisfies a conditional expression 0<ξ/ξs<1, where ξs denotes a tilt angle when Scheimpflug principle is satisfied with reference to the display surface (SF) and the projection plane (SC).