Robert Cell Optical Delay via Curved Mirror Aperture
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Solution Overview
Problem
Existing optical delay elements, such as those based on dielectric blocks and lens trains, face limitations in achieving long delays with minimal optical loss and compact design, particularly in phased-array antenna systems where true-time delay is required to prevent beam squinting.
Innovation Solution
The use of a multi-pass optical cell, referred to as the Robert cell, which employs a system of curved mirrors with a spatially extended wedge-shaped notch aperture to provide selectable optical time delays through multiple reflections, allowing for adjustable delays and compact design with low loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If dielectric delay blocks are used, then short delays can be achieved, but the device becomes impractical for longer delays
Solution Approach 1:
The patent employs curved mirrors (spherical or parabolic) instead of flat dielectric blocks to create a compact optical path. The curvature enables multiple reflections within a small volume, achieving long optical delays (meters) in a compact footprint without the impracticality of long linear paths
Solution Approach 2:
The invention transitions from one-dimensional linear delay paths (dielectric blocks) to two-dimensional curved optical paths within a cavity. The light beam traverses a complex curved trajectory between mirrors, effectively packing meters of optical path length into a compact three-dimensional space
2Loss of time
If lens trains are used to achieve long delays, then the delay can be extended, but the device becomes prohibitively long and alignment becomes difficult
Solution Approach 1:
The patent merges multiple optical functions (delay, beam steering, focusing) into a single integrated cavity with curved mirrors. The mirrors perform both reflection and beam direction control simultaneously, eliminating the need for separate alignment-prone lens elements
Solution Approach 2:
Curved mirrors inherently provide beam convergence and divergence properties that would require multiple lenses to achieve. The curvature enables a single compact element to replace long trains of discrete lenses, simplifying alignment while maintaining long optical path lengths
3Loss of time
If optical fiber delay elements are used, then long delays can be achieved, but alignment issues and losses are introduced
Solution Approach 1:
The patent uses high-reflectivity curved mirrors as intermediaries to guide light through multiple reflections. These mirrors achieve high reflectivity (>99%) reducing optical loss compared to fiber coupling interfaces, while the curved geometry maintains beam quality without the alignment sensitivity of fiber connections
4Volume of moving object
If a compact design is pursued, then the device size is reduced, but achieving long delays with minimal loss becomes difficult
Solution Approach 1:
The curved mirror geometry enables the light beam to traverse a long serpentine path within a compact cavity volume. The curvature ensures consistent beam-mirror interaction angles throughout the path, maintaining high reflectivity and minimal loss even as the optical path length extends to meters within a small physical footprint
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 Robert cell achieves significant time delays of several meters with minimal optical loss, offering a compact and efficient solution for true-time delay applications, suitable for phased-array antennas and other optical systems, by allowing precise control of time delays through the position of the input light beam within the wedge-shaped notch aperture.
Implementation Method 1
a multi-pass optical cell including a first curved mirror and a second curved mirror facing the first curved mirror to define an optical cavity
Data Source
AI summary
An optical delay device comprises a multi-pass optical cell including first and second facing curved mirrors defining an optical cavity. One curved mirror includes a spatially extended aperture, such as a wedge-shaped notch aperture formed into the perimeter of the curved mirror. One curved mirror is split into two component mirrors one of which is tilted to define a swirling reflection pattern on the curved mirror that includes the spatially extended aperture. The optical time delay introduced to a light ray by the multi-pass optical cell depends on the input location of the light ray into the spatially extended aperture. The optical delay device may include two such multi-pass optical cells and a mirror that optically couples the two said multi-pass optical cells.