UV Laser Beam Expander with Spherical Folding Mirrors
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Solution Overview
Problem
High-intensity UV laser beams cause degradation of transmissive optics and anti-reflective coatings, leading to unusable components due to long-term exposure, and existing beam expansion methods suffer from significant aberrations and limited tolerance to input beam position and alignment errors.
Innovation Solution
A device using a telescope arrangement with two spherical folding mirrors and a spherical lens to expand UV laser beams, where the first folding mirror is convex and the second is concave, allowing for minimal beam deformation and imaging errors, with the lens positioned in the divergent beam path to reduce intensity exposure and correct for errors without lateral offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a Galilean lens is used to expand the beam, then the overall length is short and installation space is small, but the input-side lens is exposed to high UV intensity causing unacceptable degradation of transmission properties
Solution Approach 1:
A beam expander is introduced as an intermediary device between the UV laser source and the transmissive optics. The beam expander reduces the beam intensity by expanding the beam diameter, thereby protecting the downstream transmissive optics from high-intensity UV damage while maintaining the compact overall design
Solution Approach 2:
Instead of protecting the input lens of the beam expander from high intensity (which is difficult), the solution inverts the approach by using the beam expander to reduce intensity before the light reaches vulnerable components. The Galilean lens configuration is used with the understanding that the input lens will still be exposed, but the overall system achieves protection of critical transmissive optics downstream
2Length of moving object
If the laser beam propagation length is increased to expand the beam, then the beam diameter increases, but the overall size of the expanding optics becomes limited
Solution Approach 1:
The patent employs spherical lenses in the beam expander configuration to achieve beam expansion through refraction at curved surfaces. This allows compact beam expansion without requiring long propagation distances, as the curved lens surfaces provide the necessary optical power in a short distance
Solution Approach 2:
The beam expansion function is segmented into discrete optical components (multiple lenses arranged in a beam expander configuration) rather than relying on natural divergence over long distances. This allows controlled beam expansion in a compact form factor
3Reliability
If uncoated input optics are used to avoid radiation-related degradation, then Fresnel reflections cause power losses
Solution Approach 1:
The patent changes the parameter of surface coating by using dielectric anti-reflection coatings on the input optics. This coating reduces Fresnel reflections and associated power losses while the overall system design (beam expander configuration) manages the radiation exposure to prevent degradation
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 solution effectively expands UV laser beams with minimal aberrations and high tolerance to input beam position errors, reducing optical degradation and achieving diffraction-limited imaging, while allowing for flexible folding angles and compact design.
Implementation Method 1
A device for expanding a laser beam, in particular a UV laser beam, has a telescope arrangement with two spherical folding mirrors for expanding an incident laser beam
Implementation Method 2
a lens with a spherical lens surface arranged in the divergent beam path after the telescope arrangement for collimating the expanded laser beam
Implementation Method 3
Ultraviolet laser radiation is often generated by frequency conversion of an infrared laser beam in non-linear crystals
Data Source
Figure 1~3
Figure 4~5
Figure 6~8
AI summary
The invention relates to a device (11) for widening a laser beam, in particular a UV laser beam (4), comprising: a telescopic arrangement (6) having two spherical folding mirrors (7, 8) for widening the incident collimated laser beam (4), and a lens (3) arranged in the divergent beam path downstream of the telescopic arrangement (7, 8) and having a spherical lens face (3a) for collimation of the widened laser beam (5), wherein the first folding mirror in the beam path is a convexly curved spherical folding mirror (7) and the second folding mirror in the beam path is a concavely curved spherical folding mirror (8). The invention also relates to an associated method for widening a laser beam.