VCSEL Array LIDAR Optics for Small-Divergence Beam Projection
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Solution Overview
Problem
Existing LIDAR systems face challenges in achieving small angular divergence and high measurement resolution in a compact package, leading to issues with size, weight, power, cost, and complexity, while also being blind to near objects due to high launch power requirements for longer ranges.
Innovation Solution
The use of a multi-wavelength VCSEL array LIDAR transmitter with a two-lens optical design, where the first lens is positioned close to the VCSEL array to converge beams and the second lens projects them to a target range, allowing for a compact size and improved angular resolution by adjusting the position and aperture of the lenses to achieve a small angular divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single lens is used to collimate VCSEL beams, then the system structure is simple, but the angular divergence is large and measurement precision is poor
Solution Approach 1:
The patent divides the optical system into two separate lens modules: a first lens module for collimating individual VCSEL beams to reduce angular divergence, and a second lens module for projecting the collimated beams onto the target. This segmentation allows each lens to be optimized for its specific function, achieving small angular divergence (improved measurement precision) while keeping each lens relatively simple in structure.
2Reliability
If high launch power is used to extend detection range, then long-range detection is improved, but near objects become blind spots
Solution Approach 1:
The patent employs pulsed laser operation where the VCSEL array emits light in periodic pulses rather than continuous wave. By controlling the duty cycle and timing of these pulses, the system can optimize power delivery for long-range detection while the pulsed nature allows for time-gated detection that can distinguish near objects from the background, eliminating the blind spot issue associated with continuous high-power operation.
3Measurement precision
If VCSEL array with many elements is used to improve angular resolution, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent arranges VCSEL elements in a two-dimensional array configuration rather than a simple linear array. This dimensional change allows the system to achieve angular resolution in both horizontal and vertical directions simultaneously. The 2D arrangement with specific pitch dimensions (e.g., 250 micrometers) enables compact packaging while maintaining high angular resolution, reducing the number of elements needed compared to a 1D array with equivalent 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
This configuration enables a compact LIDAR system with enhanced angular resolution and reduced size, weight, and power consumption, while maintaining performance across a 100-meter range and allowing for finer resolution in preferred directions, such as distinguishing between objects like pedestrians and trees.
Implementation Method 1
A first lens is positioned in an optical path of the plurality of optical beams at a distance from at least one of the plurality of light emitters that is less than a focal length of the first lens so that the first lens converges the plurality of optical beams to a converged optical beam with a beam waist
Implementation Method 2
A second lens is positioned in the optical path of the first converged optical beam so that it projects the first converged optical beam to a target range
Data Source
AI summary
A LIDAR transmitter includes a first transmitter array attached to a substrate and configured to generate a first array of laser beams. A first lens is positioned in an optical path of the first array of laser beams and configured to converge the first array of laser beams along the optical path. A second lens converges the first array of laser beams, wherein a position of a center of the second lens has a first radial offset from a center of the first transmitter array. A second transmitter array is attached to the substrate with a lateral offset from the first transmitter array and configured to generate a second array of laser beams. A third lens is configured to converge the second array of laser beams along the optical path. A fourth lens converges the second array of laser beams, wherein a position of a center of the fourth lens has a second radial offset from a center of the second transmitter array. The lateral offset, the first radial offset, and the second radial offset are chosen to provide a desired beam pattern at a target range.