W-Mirror Fold Assembly for Low-Loss Optical Beam Rotation
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Solution Overview
Problem
Existing optical systems face issues with absorption, scatter, and polarization due to the use of Dero-prisms and K-mirrors, which reduce laser power and cause optical transmission loss and undesired polarization effects, especially in high-powered laser systems.
Innovation Solution
A mirror system using a group of five fixed fold mirrors configured in a W orientation, with angles of incidence no greater than 45°, to continuously rotate an optical beam or image, reducing the moment of inertia and avoiding supporting structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Dero-prism is used to rotate the beam, then the beam can be repositioned to avoid window frames, but absorption and scatter cause significant power loss and noise
Solution Approach 1:
The patent extracts the beam rotation function from the Dero-prism by using a separate rotating mirror assembly. This separates the beam steering function from the beam path, allowing the main optical path to remain clear and minimize absorption and scatter losses while still achieving beam repositioning through the rotating mirror.
Solution Approach 2:
The patent introduces a rotating mirror as an intermediary device between the laser source and the scanning mirror. This intermediary performs the beam rotation function without requiring the beam to pass through additional glass elements, thereby maintaining laser power while achieving the necessary beam repositioning capability.
2Ease of operation
If a Dero-prism is used to undo rotation, then the rotation caused by scanning mirrors can be corrected, but optical transmission loss increases significantly
Solution Approach 1:
The patent replaces the mechanical Dero-prism system with a rotating mirror mechanism. This substitution uses reflective optics instead of transmissive optics, eliminating the need for the beam to pass through glass elements and thereby reducing optical transmission loss while maintaining the image rotation correction capability.
3Loss of energy
If a K-mirror assembly is used to mitigate absorption, then polarization and absorption effects are reduced, but the moment of inertia becomes significant due to the second mirror being mounted far from the rotation axis
Solution Approach 1:
The patent repositions the rotating mirror at the intersection of the optical axis and the rotation axis, creating a compact three-dimensional arrangement. This dimensional optimization allows all mirror surfaces to be positioned close to the rotation axis while maintaining the necessary optical path geometry, thereby minimizing the moment of inertia while avoiding absorption and polarization effects.
4Ease of operation
If a half-wave plate is used to rotate polarization, then the laser beam's polarization axis can be rotated, but the birefringent crystal is not suited for moderate to high-powered lasers
Solution Approach 1:
The patent replaces the half-wave plate (a passive optical element) with an actively controlled rotating mirror system. This substitution allows for polarization axis rotation through mechanical rotation of the mirror rather than through birefringence, enabling the system to handle moderate to high-powered lasers that would be damaged by birefringent crystals.
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 W-mirror assembly provides efficient beam rotation with reduced absorption and polarization, enabling compact design and lower moment of inertia, allowing for the use of less powerful motors and minimizing collisions with obstructions.
Implementation Method 1
A group of five fixed fold mirrors is configured in a W orientation to receive the optical input and continuously rotates the optical output about the optical axis of the apparatus
Data Source
AI summary
An apparatus continuously rotates an optical output about axis of rotation of the optical output. An input is centered on an optical axis of the apparatus and receives an optical input. An output is centered on the optical axis of the apparatus and provides an optical output. A group of five fixed fold mirrors is configured in a W orientation to receive the optical input and continuously rotates the optical output about the optical axis of the apparatus.