Compact Zoom Lens Design for Projectors
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Solution Overview
Problem
Conventional zoom lenses for image projection devices are bulky and costly due to their long length and complex assembly, failing to meet the requirements of compactness, weight reduction, and high optical performance while maintaining sufficient back focal length for high-resolution image projection.
Innovation Solution
A compact zoom lens configuration comprising two movable lens groups with negative and positive refractive powers, where the first lens group is adjacent to the object side and the second lens group is adjacent to the image side, with a variable distance between them that decreases during zooming, employing aspheric lenses to correct aberrations and maintain a long back focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional four-group zoom lens is used to achieve high zoom ratio and high resolution, then the optical performance is improved, but the overall length increases making the projector bulky
Solution Approach 1:
The patent extracts and eliminates unnecessary lens groups from the conventional four-group configuration. By using only two lens groups (first lens group with negative refractive power and second lens group with positive refractive power), the design removes redundant elements while maintaining the required zoom ratio and image resolution, thereby reducing the overall length
Solution Approach 2:
The patent changes the refractive power parameters of the lens groups. The first lens group is designed with negative refractive power and the second with positive refractive power, with specific focal length ratios (0.3 < |f1/f2| < 0.7) that enable compact configuration while achieving high zoom ratio and maintaining image quality
2Adaptability or versatility
If more lens elements are added to achieve high zoom ratio, then the zoom capability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent extracts only the essential lens groups needed for zoom functionality. By eliminating two entire lens groups from the conventional design and using merely two movable lens groups, the manufacturing cost is significantly reduced while the zoom ratio capability is maintained through optimized movement and focal length ratios
Solution Approach 2:
The two lens groups are designed to perform multiple functions simultaneously. The first lens group with negative refractive power and the second with positive refractive power work together to provide both zooming capability and image quality correction, making each lens group multi-functional and reducing the need for additional specialized elements
3Manufacturing precision
If more lens elements are added to achieve high resolution, then the image quality is improved, but the device complexity increases
Solution Approach 1:
The patent extracts and removes unnecessary lens elements from the conventional configuration. By using only two lens groups instead of four, and selectively including aspheric lens elements only where necessary for aberration correction, the design simplifies the overall structure while maintaining high image resolution
Solution Approach 2:
The patent applies aspheric lens elements locally rather than throughout the entire system. Aspheric surfaces are incorporated in specific lens elements (such as in the first or second lens group) where they are most effective for correcting aberrations, while other elements may remain spherical, optimizing the balance between image quality and manufacturing complexity
4Length of moving object
If the refractive power of lens groups is increased to reduce movement stroke, then the overall length is reduced, but aberration fluctuations during zooming increase
Solution Approach 1:
The patent optimizes the refractive power parameters within specific ranges rather than maximizing them. The focal length ratio between the first and second lens groups is constrained (0.3 < |f1/f2| < 0.7), and the back focal length is maintained within specific proportions of the focal length, ensuring stable aberration correction while achieving compact size
Solution Approach 2:
The patent designs the lens groups with feedback mechanisms for aberration correction. The movable lens groups are positioned and designed such that their movement during zooming automatically compensates for aberration changes, with the optical design providing inherent feedback that maintains image quality across the zoom range
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 results in a compact, cost-effective zoom lens that effectively corrects aberrations, ensuring high optical performance and enabling the production of small-size, lightweight, and low-cost projectors capable of high-resolution image projection.
Implementation Method 1
Both groups contain at least one aspheric lens element for elimination of aberrations
Implementation Method 2
a first lens group of negative refractive power and a second lens group of positive refractive power
Data Source
AI summary
A compact zoom lens includes a first lens group (1, 3) of negative refractive power disposed on an object side and a second lens group (2, 4) of positive refractive power disposed on an image side. Both the first and second lens groups are movable. The first and second lens groups defines a variable distance therebetween. During zooming from the wide-angle end to the telephoto end, the second lens group moves toward the object side and the variable distance between the first and second lens groups decreases. The compact zoom lens has a long back focal length with various aberrations satisfactorily corrected.