Beam Shaping Device Using Spherical Collimator Lens
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Solution Overview
Problem
The divergence angle of laser light emitted from semiconductor lasers is significantly larger in the fast axis direction than in the slow axis direction, making it difficult to handle and manufacture the cylindrical lenses required for beam shaping, and leading to reduced utilization efficiency due to overlapping beams and aberrations when the pitch between light emitting layers is narrow.
Innovation Solution
A beam shaping device is designed with a first collimator lens for the slow axis direction and a second collimator lens for the fast axis direction, where the first collimator lens has a micro lens array with incident and exit surfaces shaped as concentric arcs, allowing for precise collimation and easy handling and manufacturing, while the second collimator lens has flat surfaces to prevent aberrations and overlapping beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pitch between light emitting layers is narrowed to increase power output, then the fill factor increases and power enhancement is achieved, but beams from adjacent light emitting layers overlap at shorter distances requiring shorter focal distances for collimators
Solution Approach 1:
The patent applies spherical curvature to the collimator lens surfaces. Specifically, the first collimator lens has a spherical incident surface with radius R1 and a spherical exit surface with radius R2, allowing the lens to achieve the required short focal distance while maintaining manufacturability and avoiding excessive thinning or elongation that would occur with cylindrical lenses of equivalent focal length.
2Manufacturing precision
If the focal distance of the FAC is shortened to prevent beam overlap, then the curvature radius of the lens surface becomes very small (approximately 0.1 mm), but this makes the FAC very thin and elongated requiring utmost care in handling and difficult manufacturing
Solution Approach 1:
The patent replaces the cylindrical geometry of conventional FACs with spherical geometry. The collimator lens has spherical surfaces with radii R1 and R2 that are much larger than the 0.1 mm curvature radius of conventional FACs, resulting in a lens that is easier to handle and manufacture while achieving the same short focal distance requirement through optimized spherical surface design.
Solution Approach 2:
The patent changes the geometric parameters of the collimator lens from cylindrical to spherical, and optimizes the radii of curvature (R1, R2) and lens thickness to achieve the required focal distance while maintaining reasonable dimensions for handling and manufacturing. This parameter optimization allows the lens to avoid being excessively thin or elongated.
3Ease of operation
If the SAC and FAC are designed to be large in size for easy handling and manufacturing, then the distance from the LD bar to the SAC is expanded, but laser light enters adjacent cylinder surfaces causing unintended exit directions and reduced utilization efficiency
Solution Approach 1:
The patent uses spherical surfaces instead of cylindrical surfaces for the collimator lens. The spherical geometry with optimized radii R1 and R2 allows the lens to be positioned closer to the LD bar (reducing the distance expansion problem) while the spherical curvature naturally confines the laser beams to the intended optical path, preventing stray light from entering adjacent regions and maintaining high utilization efficiency.
4Power
If cylindrical lenses are used for collimation in both fast and slow axis directions, then beam collimation is achieved, but the lenses become difficult to handle and manufacture when high power enhancement is required
Solution Approach 1:
The patent merges the functions of the fast axis collimator (FAC) and slow axis collimator (SAC) into a single integrated collimator lens. This unified lens has spherical surfaces that simultaneously collimate beams in both the fast axis direction (Y-axis) and slow axis direction (X-axis), eliminating the need for separate cylindrical lenses and their associated alignment and handling complexities while supporting high power enhancement.
Solution Approach 2:
The patent employs spherical curvature for the collimator lens surfaces, which simplifies the manufacturing process compared to cylindrical lenses. The spherical geometry with radii R1 and R2 can be manufactured using conventional spherical lens fabrication techniques, avoiding the difficult molding and polishing required for cylindrical lenses with small curvature radii, thereby reducing device complexity while maintaining collimation performance.
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 enables easy handling and manufacturing of the beam shaping device, prevents unnecessary aberrations, and maintains high utilization efficiency of laser light even with narrow pitches between light emitting layers, allowing for further power enhancement without reducing laser light efficiency.
Implementation Method 1
a first collimator lens configured to collimate at least one of the plurality of beams of laser light that diverges in the first direction
Implementation Method 2
a second collimator lens configured to collimate at least one of the plurality of beams of laser light that diverges in a second direction, which is a direction orthogonal to the optical axis direction and the first direction both
Data Source
AI summary
A beam shaping device includes an SAC and an FAC. The SAC is placed between an LD bar and the FAC. A first incident surface and a first exit surface are formed in the SAC. The first incident surface includes a plurality of incident-side lens surfaces aligned in a slow axis direction X. The incident-side lens surfaces each have, in section orthogonal to a fast axis direction Y, a shape convexed toward the outside of the SAC and, in section orthogonal to the slow axis direction X, a shape concaved toward the inside of the SAC. The shape of the first incident surface and the shape of the first exit surface in section orthogonal to the slow axis direction X are concentric arcs having a point on an emission end surface of a light emitting layer as the center.