Optical Delay Line Retroreflector Positional Invariance
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Solution Overview
Problem
Existing optical delay line systems face challenges in maintaining positional invariance of the return beam, leading to high insertion losses and increased installation costs due to the need for precise alignment and mechanical imperfections, which are exacerbated over time.
Innovation Solution
An optical-delay-line device with a retroreflector and an optical element comprising three planar reflective surfaces arranged at 45° angles ensures positional invariance, allowing the return beam to be steered to the same location and orientation as the incident beam, even with imperfect mechanical translation, using a compact and economical design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two planar mirrors are placed at 90° on movable holders to produce an optical delay line, then variable optical delay can be achieved, but precise alignment between mirrors and optical components is required which is time-consuming and tedious
Solution Approach 1:
The patent combines two separate mirrors into a single corner-cube reflector assembly. This integration eliminates the need for precise alignment between multiple mirrors and optical components, as the corner-cube reflector inherently maintains the correct geometric relationship. The movable holder simply needs to translate the entire integrated assembly, greatly simplifying the alignment operation while preserving the variable optical delay capability.
2Ease of operation
If a corner-cube reflector is used on the movable holder to simplify alignment, then ease of operation is improved, but the movable holder must be moved very precisely to maintain alignment quality which increases installation costs
Solution Approach 1:
The patent introduces a beam-steering optical element (such as a prism or additional mirror) as an intermediary between the corner-cube reflector and the optical fiber. This intermediary component compensates for misalignments caused by imperfect translational movement of the movable holder. By adjusting the beam-steering element, the system can maintain proper alignment even when the corner-cube reflector's position varies, thereby reducing the required translational precision while preserving coupling efficiency.
3Reliability
If precise mechanical translation is used to maintain alignment quality, then coupling efficiency is improved, but mechanical play and wear over time aggravate insertion losses
Solution Approach 1:
The patent incorporates a feedback mechanism through the beam-steering optical element that can be adjusted to compensate for drift and misalignment. This allows the system to actively correct for mechanical play and wear over time, maintaining stable coupling efficiency. The feedback approach transforms a purely passive mechanical system into one that can adapt to degradation, significantly improving long-term reliability and reducing the impact of mechanical wear on insertion losses.
4Adaptability or versatility
If the movable holder is moved translationally to vary optical delay, then variable delay is achieved, but lateral offset of the incident beam causes lateral offset of the return beam which increases insertion losses
Solution Approach 1:
The patent uses a beam-steering optical element as an intermediary to compensate for lateral offsets in the return beam. This element can adjust the beam path to realign the return beam with the optical fiber axis, thereby eliminating insertion losses caused by lateral misalignment. The intermediary component acts as a corrective element that maintains optimal coupling regardless of the movable holder's position, enabling variable delay without sacrificing coupling efficiency.
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 solution provides stable and low-loss optical coupling over a wide range of tunability, reducing the need for precise mechanical alignment and minimizing insertion losses, while allowing for large optical delays with fewer mechanical imperfections.
Implementation Method 1
a retroreflector that ensures a self-alignment of a direction of an output beam of the retroreflector with a direction of a beam incident on the retroreflector
Implementation Method 2
an optical element that is said to ensure positional invariance, comprising a first reflective surface, a second reflective surface and a third reflective surface, the beam that propagates along said optical path and that enters said optical element in said second direction, being reflected by said first surface with an angle of 90° toward said second surface, then being reflected in succession by said second and third surfaces
Data Source
AI summary
An optical delay line device, providing a fixed or variable optical delay, including an optical input, an optical output, an optical assembly that directs a beam along an optical path from the input to the output. The optical assembly including; a retroreflector, an optical element including first, second and third reflective surfaces, the second and third reflective surfaces being arranged to make therebetween an angle of 45°, a beam that propagates along the optical path and enters said optical element being reflected by the first surface with an angle of 90° toward the second surface, then being reflected by the second and third surfaces to exit from the optical element in a direction parallel to the direction of the beam incident on the optical element, and said optical element is arranged so as to steer said output beam onto said second surface of said retroreflector.