Projection Zoom Lens with Fixed Groups and Movable Middle for Compact Design
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Solution Overview
Problem
Conventional zoom lenses for projection fail to maintain constant brightness across the entire zoom range while providing a wide angle of view and reducing lens diameter, leading to increased size and weight of projection-type display apparatuses.
Innovation Solution
A zoom lens configuration with a first negative lens group fixed on the magnification side, a last positive lens group fixed on the reduction side, and a middle group with movable lens groups, including both positive and negative refractive power lenses, which move during magnification changes to maintain a non-telecentric reduction side and secure appropriate back focus, reducing lens diameter and ensuring constant F-number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a wide angle lens is used to provide a wide angle of view, then the angle of view is improved, but the screen size changes significantly with projection distance, reducing flexibility in setting conditions
Solution Approach 1:
The patent applies zoom lens technology with movable lens groups that allow dynamic adjustment of focal length. The lens system includes a first lens group, second lens group, third lens group, and fourth lens group, where the second and third lens groups move relative to each other to change magnification. This dynamic adjustment capability enables the projection lens to adapt to different projection distances and screen sizes while maintaining a wide angle of view, thus resolving the contradiction between wide angle of view and flexibility in setting conditions.
2Manufacturing precision
If multiple lenses are combined to achieve sufficient image formation performance, then image quality is improved, but the total length and lens diameter increase, making the apparatus larger and heavier
Solution Approach 1:
The patent divides the projection lens into four distinct lens groups (first lens group, second lens group, third lens group, and fourth lens group) with different refractive powers and functions. Each lens group is optimized for specific optical functions, allowing the system to achieve high image formation performance while maintaining a compact structure. The segmented design enables better control over optical path and reduces the need for excessive lens elements, thereby reducing overall size and weight.
Solution Approach 2:
The patent employs aspheric surfaces in certain lens elements to change the geometric parameters of the lens surfaces. This allows for more efficient light control and aberration correction with fewer lens elements, reducing the total length and diameter of the lens system while maintaining or improving image formation performance.
3Manufacturing precision
If a telecentric lens is used toward the reduction side to improve color combination characteristics, then color accuracy is improved, but the lens diameter and back focus length increase, reducing adaptability to DMD-based systems
Solution Approach 1:
The patent applies telecentric design only to specific lens groups (the first and fourth lens groups) rather than the entire system. The second and third lens groups are designed with different characteristics to optimize for DMD compatibility. This localized application of telecentric design maintains color combination characteristics in critical areas while allowing other areas to be optimized for compactness and DMD adaptability.
Solution Approach 2:
By dividing the lens system into four functional groups with different design priorities, the patent can optimize each group for its specific function. The first and fourth groups handle color combination with telecentric design, while the second and third groups focus on magnification control and compactness, enabling the system to work effectively with DMD technology.
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 compact projection-type display apparatus with excellent optical performance, maintaining constant brightness and image quality across the zoom range while reducing the size and weight of the lens system.
Implementation Method 1
a zoom lens for projection consists of a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power arranged in this order from the magnification side
Data Source
AI summary
A zoom lens for projection consists of a negative first lens group, which is fixed during magnification change, a middle group, which includes plural lens groups that move during magnification change, and a positive last lens group, which is fixed during magnification change, in this order from a magnification side. A reduction side is non-telecentric. Both of a lens group closest to the magnification side and a lens group closest to the reduction side in the middle group have positive refractive power, and move from the reduction side toward the magnification side during magnification change from a wide-angle end to a telephoto end. The last lens group includes at least two positive lenses and at least two negative lenses. A positive lens is arranged closest to the reduction side in the last lens group. A predetermined conditional expression about a focal length of the last lens group is satisfied.