Image-Space Telecentric Lens With Aspheric Cemented Groups
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Solution Overview
Problem
There is a need for a high-performance image-space telecentric lens that balances resolution, image circle size, and compactness in micro-projectors, while minimizing the total length and correcting aberrations effectively.
Innovation Solution
An image-space telecentric lens design featuring a first lens group of negative refractive power and a second lens group with a cemented positive refractive power lens nearest the aperture stop, including at least one aspheric surface in each group to reduce aberrations and chromatic distortion, thereby minimizing the total track length and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the number of lenses is reduced to shorten the total length, then the compactness is improved, but the image resolution deteriorates
Solution Approach 1:
The lens system is divided into multiple lens groups (first lens group with negative refractive power, second lens group with positive refractive power, and cemented lens) rather than using a single lens element. This segmentation allows each group to contribute differently to the overall optical function, enabling compact design while maintaining resolution through coordinated aberration correction across groups
Solution Approach 2:
The patent employs composite lens structures including cemented lenses that combine different glass materials with varying refractive indices and dispersion properties. This allows chromatic aberration correction within a compact form factor, as the composite structure achieves multiple correction functions that would otherwise require separate lens elements
2Length of moving object
If the number of lenses is reduced to shorten the total length, then the compactness is improved, but the aberration correction capability deteriorates
Solution Approach 1:
The patent utilizes aspheric surfaces with specific curvature parameters and conic constants to enhance aberration correction. By carefully controlling the geometric parameters of aspheric surfaces in the lens groups, the system achieves effective spherical aberration and coma correction with fewer elements, as aspheric profiles provide additional degrees of freedom for optimizing ray paths
Solution Approach 2:
The aperture stop is strategically positioned between the first and second lens groups to serve as an intermediary element that controls chief ray angles. This positioning, combined with the telecentric design, helps correct distortion and field curvature aberrations without requiring additional correction lenses, as the stop location itself becomes part of the aberration management strategy
3Manufacturing precision
If more lenses are added to improve image resolution, then the image quality is improved, but the total length increases
Solution Approach 1:
The patent employs dynamic optimization of the lens group configurations, where the spacing and positioning of lens groups are optimized to achieve compact folding of the optical path. The telecentric design allows the exit pupil to be positioned at infinity, enabling the image sensor to be placed closer to the lens while maintaining resolution, thus dynamically optimizing the relationship between resolution and length
4Ease of manufacture
If traditional spherical lenses are used, then the manufacturing is simpler, but the aberration correction is insufficient
Solution Approach 1:
The patent replaces traditional spherical lens surfaces with aspheric surfaces that have non-uniform curvature. This allows a single lens element to correct multiple types of aberrations (spherical aberration, coma, astigmatism) that would otherwise require multiple spherical lenses. The aspheric profiles are manufactured using modern precision molding or grinding techniques, making them practically feasible while dramatically improving correction capability
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 design achieves good correction ability, reduced size, and improved image quality by balancing chromatic aberration and optical distortion, while maintaining a compact form factor.
Implementation Method 1
The first lens group has at least one aspheric surface, and the second lens group has at least one aspheric surface
Implementation Method 2
the second lens group has a cemented lens of positive refractive power, and the cemented lens is nearest the aperture stop as compared with other lens in the second lens group
Data Source
AI summary
An image-space telecentric lens includes, in order from a magnified side to a minified side, a first lens group of negative refractive power, an aperture stop, and a second lens group of positive refractive power. The first lens group has at least one aspheric surface, and the second lens group has at least one aspheric surface. The second lens group has a cemented lens of positive refractive power, and the cemented lens is nearest the aperture stop as compared with other lens in the second lens group. The image-space telecentric lens satisfies the condition: TT<100 mm, where TT denotes a length measured along an optical axis and between two outermost opposite lens surfaces of the image-space telecentric lens.