Folded Macro-Tele Lens Layout for Wide-FOV Close-Up Imaging
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Solution Overview
Problem
Existing digital cameras with ultra-wide field of view (UW) lenses face challenges in capturing macro images from larger object-lens distances with high object-to-image magnification and optical Bokeh, due to their limited focusing range and large depth of field, which makes framing and lighting conditions difficult, especially for subjects like insects.
Innovation Solution
A folded digital camera design with a lens system comprising N≥6 lens elements, featuring a specific focal length and optical path folding element, which provides a focusing range from infinity to a minimal object distance with a ratio of minimal object distance to effective focal length (MIOD/EFL) less than 20, and a maximum chief ray angle to field of view (Max CRA/FOV) less than 0.25, allowing for improved focusing and optical Bokeh.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ultra-wide field of view lens is used, then field of view is improved, but depth of field becomes excessively large making macro photography difficult
Solution Approach 1:
The lens system is divided into multiple lens elements (N≥6) with specific refractive power arrangements (++−+−+ or +−++−+). This segmentation allows independent optimization of different optical functions: some elements control field of view while others manage depth of field and magnification, resolving the contradiction between wide FOV and macro capability
Solution Approach 2:
Different regions of the lens system are assigned different optical properties. The lens elements have varying refractive powers and focal lengths tailored to specific functions: front elements handle wide angle capture while rear elements provide macro magnification control. This local optimization enables both wide FOV and shallow depth of field for macro subjects
2Measurement precision
If minimal object distance is reduced for higher magnification, then object-to-image magnification is improved, but focusing range becomes limited
Solution Approach 1:
The lens system incorporates movable lens elements or groups that can be dynamically adjusted during focusing. This dynamic configuration allows the lens to maintain high magnification at minimal object distance while preserving the ability to focus at longer distances, achieving both high magnification capability and extended focusing range
Solution Approach 2:
The patent employs lens elements with specific focal length ratios and refractive power distributions that can be varied through focusing mechanisms. By changing the effective focal length and object distance parameters in a coordinated manner, the system achieves magnification ratios from 1:1 to 15:1 while maintaining focus from infinity to minimal object distance
3Length of moving object
If optical path is folded to reduce camera size, then device dimensions are improved, but optical complexity increases
Solution Approach 1:
The optical path is folded using mirrors or prisms to redirect light at angles perpendicular to the main optical axis. This dimensional change allows the optical path length to be extended without increasing the camera's form factor in the primary direction, achieving compact size while maintaining optical performance
Solution Approach 2:
Optical path folding elements (mirrors or prisms) serve as intermediaries that redirect light between the lens elements and the image sensor. These intermediaries enable the optical path to be folded back on itself, reducing the overall camera length while preserving the required optical path length for the N≥6 lens element system
4Manufacturing precision
If maximum chief ray angle is reduced for better image quality, then image quality is improved, but field of view becomes restricted
Solution Approach 1:
The lens elements are designed with asymmetric surface profiles and varying refractive powers that are optimized for different field angles. This asymmetric design allows the system to control chief ray angles for off-axis rays without compromising on-axis performance, achieving both wide field of view and controlled maximum CRA for optimal image quality
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 camera achieves a larger object-to-image magnification range of 1:1 to 15:1, reduced maximum field curvature, and a smaller f-number, enabling better image capture with enhanced optical Bokeh and framing capabilities for macro photography.
Implementation Method 1
OPFE folds the optical path from a first optical path 112 to a second optical path 114
Implementation Method 2
a lens 104 with a plurality of lens elements
Data Source
AI summary
Folded digital cameras comprising a lens system with a lens and an image sensor, the lens having N≥6 lens elements Li, an effective focal length (EFL) and a total track length (TTL), wherein each lens element has a respective focal length fi and wherein a first lens element L1 faces an object side, and an optical path folding element (OPFE) for providing a folded optical path between an object and the lens. In some embodiments, the lens system has a focusing range that covers object-lens distances from infinity to a minimal object distance (MIOD), wherein MIOD/EFL is smaller than 20 or even 7. In some embodiments, the ratio of a maximal chief ray angle to a field of view of the folded camera Max CRA/FOV is smaller than 0.25 or even 0.15 when the camera is focused at infinity.