Asymmetric Collimating Lenses for Multi-Chip Laser Diodes
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Solution Overview
Problem
Multi-chip laser diode (MCL) devices face challenges in miniaturization due to the large divergence angles of laser beams, particularly in the fast axis, which result in elliptical beam spots and require larger optical elements, affecting collimation and energy distribution.
Innovation Solution
A laser device design featuring a base plate, frame, light-emitting chips, and a collimating lens group where the collimating lenses are arranged to reduce the divergence angle more significantly in the fast axis than in the slow axis, using a combination of concave and convex curved surfaces to optimize collimation and beam spot shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional collimating lenses are used for MCL devices, then the laser beams can be collimated, but the beam spots remain elliptical due to large divergence angles in the fast axis, requiring larger optical elements
Solution Approach 1:
The patent employs asymmetric optical elements including a cylindrical lens and a toroidal lens with different curvature radii in the fast axis and slow axis directions. The cylindrical lens has a curvature radius of 1.5mm in the fast axis direction and no curvature in the slow axis direction, while the toroidal lens has curvature radii of 2.0mm and 3.0mm in the fast and slow axis directions respectively. This asymmetric design allows differential correction of divergence angles, transforming elliptical beam spots into circular ones without requiring larger optical elements
Solution Approach 2:
The patent changes the optical parameters of the collimating lens system by introducing lenses with specific curvature radii tailored to each axis. The cylindrical lens introduces a curvature radius of 1.5mm only in the fast axis direction to counteract the larger divergence angle, while the toroidal lens provides different curvature radii (2.0mm in fast axis, 3.0mm in slow axis) to fine-tune the beam profile. These parameter changes enable effective collimation with compact optical elements
2Shape
If the divergence angle in the fast axis is reduced more than in the slow axis, then the beam spot becomes more circular, but the collimation complexity increases
Solution Approach 1:
The patent segments the collimation function into two distinct optical elements: a cylindrical lens for primary correction in the fast axis direction and a toroidal lens for fine-tuning in both directions. This segmentation allows each lens to be optimized for its specific function, with the cylindrical lens handling the larger divergence angle correction and the toroidal lens providing differential adjustment, thereby managing complexity through functional decomposition
Solution Approach 2:
The patent utilizes curved surfaces with specific geometry - a cylindrical lens with curvature only in the fast axis direction and a toroidal lens with different curvatures in both directions. These curved surfaces are designed with precise curvature radii (1.5mm for cylindrical, 2.0mm and 3.0mm for toroidal) to match the divergence characteristics of the laser diode, enabling effective collimation through geometric optics rather than complex adaptive systems
3Reliability
If larger optical elements are used to handle large divergence angles, then collimation can be achieved, but the device size increases
Solution Approach 1:
The patent achieves effective collimation with compact optical elements by changing the optical parameters - specifically using a cylindrical lens with 1.5mm curvature radius and a toroidal lens with 2.0mm and 3.0mm curvature radii. These carefully selected parameters enable the small optical elements to sufficiently counteract the large divergence angles, maintaining reliable collimation while keeping the device compact
Solution Approach 2:
The asymmetric design of the optical elements allows them to be smaller in size while still handling large divergence angles effectively. The cylindrical and toroidal lenses concentrate their optical power in the directions where it is most needed (fast axis with larger divergence), rather than requiring uniform large aperture in all directions, thus reducing overall device volume while maintaining collimation reliability
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 design improves the collimation effect, reduces the size of the laser device, and enhances the energy distribution of the laser beams, leading to a more efficient and compact optical assembly with improved display performance.
Implementation Method 1
The collimating lens group includes a plurality of collimating lenses. The plurality of collimating lenses correspond to the plurality of light-emitting chips. At least one of the plurality of collimating lenses is configured to reduce a divergence angle of the laser beam incident on the collimating lens
Data Source
AI summary
A laser device includes a base plate, a plurality of light-emitting chips, a frame and a collimating lens group. The plurality of light-emitting chips are configured to emit laser beams. The laser beams emitted by the plurality of light-emitting chips each have a first axis and a second axis. The collimating lens group is disposed on a side of the frame away from the base plate, and includes a plurality of collimating lenses. The plurality of collimating lenses correspond to the plurality of light-emitting chips. The collimating lens is configured to reduce a divergence angle of the laser beam incident on the collimating lens, so as to make a reduction of the divergence angle of the laser beam passing through the collimating lens in the first axis less than a reduction of the divergence angle of the laser beam passing through the collimating lens in the second axis.