Folded Optics Meta Optical Element TTL Reduction
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Solution Overview
Problem
Existing camera modules face challenges in reducing the optical Z height or total track length (TTL) to achieve low-height designs, which is essential for integrating camera modules into compact electronic devices.
Innovation Solution
The use of folded optics with at least one meta optical element (MOE) is proposed, where the chief ray of light travels along a piece-wise linear path, skewed with respect to at least one metasurface of the MOE, to focus light on the image sensor while minimizing the TTL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional lens systems are used, then effective light collection and image sensing capabilities are maintained, but the optical Z height or total track length (TTL) is increased
Solution Approach 1:
The patent introduces a tilted optical axis that is angled relative to the image sensor surface, transitioning from a conventional perpendicular optical path to a skewed three-dimensional path. This dimensional change allows the light to traverse a longer effective optical path while maintaining a shorter perpendicular distance (optical Z height) from the lens to the sensor, thereby resolving the contradiction between reduced height and maintained light collection capability.
Solution Approach 2:
The patent employs a curved or tilted optical path rather than a straight perpendicular path. The piece-wise linear path with skew angles creates an effective curved trajectory for light propagation, allowing the optical system to achieve longer effective focal lengths within reduced physical footprints, thus maintaining imaging performance while reducing optical Z height.
2Length of moving object
If the optical path is skewed with respect to the metasurface, then the optical Z height is reduced, but the complexity of the optical system increases
Solution Approach 1:
The patent divides the optical path into multiple discrete segments or stages, with each metasurface introducing a specific skew angle. This segmentation allows the complex tilted optical path to be constructed from simpler, modular components, making the system more manageable and potentially easier to manufacture despite the overall complexity of the skewed configuration.
Solution Approach 2:
The patent intentionally introduces asymmetry by tilting the optical axis relative to the image sensor surface. This asymmetric configuration, while increasing design complexity, enables the reduction of optical Z height. The asymmetric metasurface designs are optimized to compensate for the tilted path, transforming the complexity into a functional advantage for compactness.
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
This configuration allows for a significant reduction in the TTL, enabling the development of low-height camera modules that can be seamlessly integrated into compact devices while maintaining effective light collection and image sensing capabilities.
Implementation Method 1
The at least one MOE is configured such that a chief ray of light impinging on, and passing through, the at least one MOE, travels along a piece-wise linear path to the optically active surface of the image sensor
Implementation Method 2
the at least one MOE is configured such that the chief ray of light is focused on the optically active surface of the image sensor
Data Source
AI summary
An example apparatus includes an image sensor having an optically active surface, and folded optics including at least one meta optical element (MOE). The at least one MOE is configured such that a chief ray of light impinging on, and passing through, the at least one MOE, travels along a piece-wise linear path to the optically active surface of the image sensor. NIL Technology ApS F&R Ref.: 47717-0041WO1 PCT Application