Dero Switch Mirror Assembly for Low-Loss Beam Rotation
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Solution Overview
Problem
Existing optical systems face issues with absorption, scatter, and polarization effects due to the use of Dero-prisms and K-mirrors, which are significant in moderate to high-powered lasers and imaging systems, leading to reduced power output, noise, and optical transmission loss.
Innovation Solution
A mirror system comprising rotatable switch mirrors and fixed mirrors positioned in specific orientations to rotate an optical input about its axis, avoiding supporting structures without the need for Dero-prisms or half-wave plates, allowing for efficient beam rotation and polarization control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Dero-prism is used to rotate the laser beam to avoid the window frame, then the beam rotation function is achieved, but significant absorption and scatter occur reducing power output and increasing noise
Solution Approach 1:
The patent divides the beam rotation function into multiple discrete mirror elements (first and second switching mirrors) that can independently redirect the beam. Instead of using a single large Dero-prism, the system segments the optical path into multiple reflection stages, each handled by a smaller mirror, thereby reducing cumulative absorption and scatter losses while achieving the same rotational effect.
Solution Approach 2:
The patent replaces the mechanical Dero-prism system with an electro-optical mirror switching system. The switching mirrors are positioned and oriented such that they can be rapidly actuated to change beam direction without the need for large rotating glass prisms, eliminating the absorption and scatter issues inherent in Dero-prism materials.
2Ease of operation
If a Dero-prism is used to undo rotation caused by a scanning mirror, then the image rotation is corrected, but significant optical transmission loss occurs
Solution Approach 1:
The patent segments the image rotation correction function across multiple fixed mirrors and switching mirrors rather than using a single Dero-prism. The first switching mirror redirects the beam to the first fixed mirror, which reflects it to the second switching mirror, and finally to the second fixed mirror. This segmented approach reduces transmission loss at each interface compared to a single thick glass element.
Solution Approach 2:
The patent substitutes the Dero-prism-based correction system with a mirror-based system that uses reflective optics instead of transmissive optics. By using mirrors to undo the rotation caused by the scanning mirror, the system avoids the transmission losses inherent in thick glass prisms while achieving the same angular correction.
3Loss of energy
If a K-mirror assembly is used to mitigate absorption and scatter, then these effects are reduced, but the angle of incidence must be greater than 45 deg causing undesired polarization and absorption effects
Solution Approach 1:
The patent applies different orientations and functions to different mirror elements in the system. Each switching mirror and fixed mirror is positioned with a specific local orientation optimized for its particular function in the optical path, rather than forcing all mirrors to operate at the >45° angle required by K-mirror assemblies. This allows each mirror to operate at optimal angles that minimize polarization effects while still achieving beam rotation.
4Ease of operation
If a half-wave plate is used to rotate the laser beam's polarization axis, then the polarization rotation is achieved, 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 made of birefringent crystal) with an active mirror switching system that rotates the polarization axis through geometric reflection rather than material birefringence. The switching mirrors are positioned and oriented to achieve the desired polarization rotation through the law of reflection, eliminating the need for birefringent materials that cannot handle high laser powers.
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 system effectively rotates beams and images to avoid obstructions while minimizing absorption, scatter, and polarization effects, providing a compact and efficient solution for optical projection systems.
Implementation Method 1
The plurality of switch mirrors may be placed in a plurality of configurations to rotate the optical output between a plurality of positions at the output responsive to receipt of the optical input
Data Source
AI summary
An apparatus for rotating an optical input about an optical axis of the optical input. The apparatus includes an input for receiving the optical input and an output for providing an optical output. The apparatus also includes a plurality of switch mirrors moveable between a first state and a second state that rotates an associated mirror about the optical axis of the optical input. The apparatus further includes a plurality of fixed mirrors each in a fixed position. The plurality of switch mirrors may be placed in a plurality of configurations to rotate the optical output between a plurality of positions at the output responsive to receipt of the optical input.