Solid-State DToF LiDAR Using AOM Scanning for Miniaturization
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Solution Overview
Problem
Current LIDAR systems face limitations in miniaturization, range, and cost due to high optical power requirements and mechanical scanning, making them impractical for vehicular applications, especially for ranges beyond 120 meters.
Innovation Solution
A solid-state time-of-flight system using a pattern of discrete laser spots projected in sequences, with a detector synchronized to accumulate charge in multiple time windows, and a narrow bandpass filter to enhance detection range and accuracy, integrating VCSELs and sensors on a semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-power pulsed lasers and mechanical scanning systems are used in DToF LIDAR, then detection range and measurement precision are improved, but device complexity, size, and cost increase significantly
Solution Approach 1:
The patent replaces mechanical scanning systems with an electro-optical approach using acousto-optic modulators (AOMs) to deflect and scan laser beams. This substitution eliminates moving mechanical parts while achieving the same beam scanning function, thereby reducing device complexity and improving reliability while maintaining measurement precision
Solution Approach 2:
The patent employs periodic pulsed laser emission synchronized with periodic AOM deflection patterns to scan multiple spots across the target scene. This periodic action allows sequential illumination and detection of multiple locations, enabling 3D mapping without requiring simultaneous high-power illumination of the entire scene, thus reducing overall system complexity
2Length of stationary object
If high optical power is used to extend detection range beyond 120 meters, then detection range is improved, but safety constraints and thermal management become problematic
Solution Approach 1:
The patent divides the illumination task into multiple discrete laser spots scanned sequentially across the scene using AOMs. Instead of illuminating the entire scene simultaneously with high power, the system segments the scene into multiple spots and illuminates them in sequence, allowing each spot to receive sufficient power for long-range detection while the total optical power remains within safety and thermal limits
Solution Approach 2:
The system uses periodic pulsed laser emission with duty cycles optimized for thermal management. By emitting short pulses and allowing cooling intervals between pulses, the system extends detection range beyond 120 meters while keeping average power within safe operating limits and managing thermal load on the laser diodes
3Measurement precision
If mechanical rotating structures with multiple lasers and detectors are used, then detection accuracy and coverage are improved, but miniaturization and reliability are compromised
Solution Approach 1:
The patent replaces mechanical rotating structures with stationary laser diodes and acousto-optic modulators for beam deflection. This eliminates mechanical rotating parts that are prone to wear and failure, significantly improving system reliability while maintaining the ability to scan and measure multiple points with high accuracy
Solution Approach 2:
The patent introduces acousto-optic modulators as intermediary devices between the laser sources and the target scene. These AOMs serve as electronically controlled beam deflectors, replacing mechanical scanning mirrors or rotating polygons, thereby improving reliability through solid-state operation while maintaining measurement precision through acoustic field control
4Length of stationary object
If VCSEL power output is increased to extend detection range, then detection range is improved, but thermal stability and operational reliability deteriorate
Solution Approach 1:
The patent employs periodic pulsed operation of VCSELs with carefully controlled pulse widths and duty cycles. This allows the VCSELs to operate at high peak powers sufficient for long-range detection while maintaining low average power that prevents excessive heating, thereby extending detection range beyond 120 meters while preserving thermal stability and operational reliability
Solution Approach 2:
The system segments the total illumination requirement into multiple sequential spot illuminations rather than simultaneous full-scene illumination. This segmentation allows each VCSEL to operate within its thermal stability limits while the cumulative effect of scanning multiple spots achieves the required detection range through time-integrated signal accumulation
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 achieves a significantly longer detection range and miniaturization while maintaining high accuracy, overcoming the limitations of existing LIDAR systems by using low-power semiconductor lasers and integrating light sources and sensors, enabling effective vehicular surround sensing.
Implementation Method 1
a solid-state light source arranged for projecting a pattern of discrete spots of laser light towards the object in a sequence of pulses
Implementation Method 2
the detector is equipped with a corresponding narrow bandpass filter
Implementation Method 3
the picture elements are configured to generate the exposure values by accumulating, for all of the pulses of the sequence, a first amount of electrical charge representative of a first amount of light reflected by the object during a first predetermined time window
Implementation Method 4
System for determining a distance to an object... time-of-flight based sensing to determine the distance of objects from a sensor
Data Source
AI summary
The invention pertains to a system for determining a distance, comprising: a light source for projecting a pattern of discrete spots of laser light towards the object in a sequence of pulses; a detector comprising picture elements, for detecting light representing the pattern as reflected by the object in synchronization with the sequence of pulses; and processing means to calculate the distance to the object as a function of exposure values generated by said picture elements. The picture elements generate exposure values by accumulating a first amount of electrical charge representing a first amount of light reflected during a first time window and a second electrical charge representing a second amount of light reflected during a second time window. The solid-state radiation source emits substantially monochromatic light having a wavelength spread of less than ±20 nm and the detector is equipped with a corresponding narrow bandpass filter.