Projection Zoom Lens Aberration Control via Segmented Power
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Solution Overview
Problem
Existing projection lenses for projectors using digital micromirror devices (DMDs) face challenges in achieving both high power and wide-angle views while maintaining effective aberration correction, due to limitations in lens design and arrangement.
Innovation Solution
A projection zoom lens configuration comprising five lens groups with specific refractive powers and focal lengths, including a weak refractive power for the fifth lens group, allows for a zoom ratio of 1.5 and a half-field angle of 39-45 degrees, optimizing aberration correction and reducing aberration variation across zooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a projection lens is designed for high power with a zoom ratio of about ×1.5, then the refractive power is increased, but the half-field angle becomes limited to 30° and aberration correction is compromised
Solution Approach 1:
The projection lens is divided into five lens groups with specific refractive power distributions. The first lens group has the strongest refractive power, while the fifth lens group has the weakest, creating a segmented power distribution that enables both high power and wide half-field angle (39-45°) simultaneously
Solution Approach 2:
Each lens group is assigned specific optical characteristics tailored to its position and function. The fifth lens group, positioned closest to the image display element, is specifically designed with weak refractive power to minimize aberration while the first lens group provides strong refractive power for high power projection
2Area of stationary object
If the lens diameter on the side of the light valve is reduced to avoid interference with the illumination light system, then the lens size is downsized, but the backfocus becomes longer and lens design becomes more difficult
Solution Approach 1:
The projection lens is designed with zoom functionality, allowing the focal length to be dynamically adjusted. This enables the lens to adapt to different projection distances and requirements while maintaining a compact diameter that does not interfere with the illumination light system
Solution Approach 2:
The lens system utilizes variable refractive power distribution across the five lens groups to achieve different focal lengths. By changing the effective refractive power parameters, the system can accommodate long backfocus requirements while maintaining a compact overall size
3Device complexity
If existing lens configurations are used, then the design is simpler, but aberration correction is insufficient and aberration variation during zooming is large
Solution Approach 1:
The lens system is segmented into five distinct lens groups with specific refractive power assignments. This segmentation allows for optimized aberration correction at each stage of light transmission, reducing overall aberration variation during zooming while maintaining reasonable design complexity
Solution Approach 2:
The projection lens employs a composite lens structure combining multiple lens groups with different optical properties. This composite design enables sophisticated aberration correction that cannot be achieved with simpler single-group configurations
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 high-performance projection with improved aberration correction and reduced aberration variation, achieving a wide half-field angle and high-power zoom ratio, suitable for DMD-based projectors.
Implementation Method 1
a first lens group having a negative refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a fifth lens group, wherein a refractive power of the fifth lens group is weaker than the refractive power of the first lens group, the refractive power of the second lens group, the refractive power of the third lens group, and the refractive power of the fourth lens group
Data Source
AI summary
A projection zoom lens constituting a projection optical system of a projector, which projects an image displayed on a surface of an image display element on a projected surface, so as to magnify and display the image includes, in order from the projected surface side to the image display element side, a first lens group having a negative refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group, wherein a refractive power of the fifth lens group is weaker than the refractive power of the first lens group, the refractive power of the second lens group, the refractive power of the third lens group, and the refractive power of the fourth lens group.