Folded Telephoto Camera Optics With Dual Prisms for Compact Zoom
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Solution Overview
Problem
Conventional small cameras in mobile devices struggle to capture high-resolution, high-quality images due to physical constraints, requiring improved optical systems that can maintain compact size while achieving low F-numbers and high zoom capabilities.
Innovation Solution
A folded camera design incorporating two light folding elements, such as prisms or a prism and a mirror, with an independent lens system that includes refractive lens elements and an aperture stop, configured to redirect light paths and correct optical aberrations, allowing for high-resolution imaging with low F-numbers and optical zoom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional camera designs are used in small form factor devices, then the camera module can be compact, but the image resolution and quality deteriorate
Solution Approach 1:
The patent introduces light folding elements (prisms or mirrors) that redirect the optical path at angles, transforming a linear optical path into a folded configuration. This allows the optical axis to change direction multiple times, effectively packing a longer optical path length into a smaller Z-height volume, thereby achieving high resolution imaging in compact camera modules
Solution Approach 2:
The patent employs a nested arrangement where the lens system is positioned between two light folding elements, with each component carefully integrated into the limited space. The aperture stop is positioned within the lens system, and multiple lens elements are stacked in a compact configuration, maximizing the use of available volume to achieve both compactness and high imaging quality
2Volume of moving object
If the pixel size is reduced to increase pixel count, then the photosensor becomes more compact, but the image quality and brightness capture deteriorate
Solution Approach 1:
The folded optical path design extends the effective focal length and light gathering path without increasing the physical footprint, allowing smaller pixels to capture sufficient light by optimizing the optical path geometry rather than relying on larger pixel areas
Solution Approach 2:
The patent optimizes multiple optical parameters including F-number, focal length, and lens element positions to maximize light transmission efficiency. By carefully controlling these parameters, the system achieves high brightness capture despite using compact photosensors with smaller pixels
3Length of stationary object
If a compact lens system is designed, then the camera module height is reduced, but the ability to correct optical aberrations deteriorates
Solution Approach 1:
The light folding elements redirect the optical path through multiple axes, creating additional space within the compact volume to position multiple lens elements and the aperture stop in optimal configurations for aberration correction, which would be impossible in a simple linear arrangement
Solution Approach 2:
The lens system is divided into multiple discrete lens elements with different optical powers and characteristics, arranged in a stacked configuration. This segmentation allows each element to correct specific types of aberrations while maintaining a compact overall structure
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 enables high-resolution, high-quality imaging with low F-numbers and optical zoom in a compact form factor, suitable for small form factor cameras, including smartphones and tablets, while providing autofocus and optical image stabilization.
Implementation Method 1
The first light folding element (a prism) redirects light from an object field from a first axis (AX 1) to the lens system on a second axis (AX 2). The second light folding element (e.g., another prism or a mirror) redirects the light onto a third axis (AX 3)
Implementation Method 2
The lens elements in the lens stack receive the light through the aperture stop and refract the light to the second light folding element
Data Source
AI summary
An optical system includes a first light folding element (e.g., a prism), a second light folding element (e.g., another prism or a mirror), and a lens system located between the first light folding element and the second light folding element. In some cases, the lens system includes a lens stack having either four or five lens elements with refractive power. The first light folding element redirects light from an object field from a first axis to the lens system on a second axis. The plurality of refractive lens elements in the lens stack refract the light to the second light folding element. The second light folding element redirects the light from the second axis onto a third axis to form an image of the object field at an image plane. The optical system has a 35 mm equivalent focal length within a range of 85 to 160 mm.