Solid-State LIDAR Distance Detection Using Multi-Window Charge Integration
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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 LIDAR system using a pattern of discrete laser spots projected in a sequence of pulses, detected by a CMOS or CCD sensor with multiple charge storage wells, allowing for longer-range distance detection by integrating reflected energy over two time windows and minimizing read-out noise.
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 divides the detection process into multiple sequential time windows, with each time window capturing photons from a specific distance range. This temporal segmentation allows the system to use lower power lasers while maintaining detection capability across extended ranges, replacing the need for high-power continuous lasers and mechanical scanning systems
Solution Approach 2:
The system uses periodic pulsed laser emission with multiple time windows within each pulse cycle. By periodically emitting low-power pulses and using time-gated detection, the system achieves extended range measurement without requiring high peak power, thereby reducing device complexity and eliminating mechanical scanning components
2Power
If VCSEL power output is increased to extend detection range, then operating range is improved, but thermal stability and reliability deteriorate
Solution Approach 1:
Instead of using continuous high-power VCSEL operation, the patent employs periodic pulsed emission with low peak power. The multi-time-window detection scheme allows the system to accumulate photons over multiple low-power pulses, achieving extended range without exceeding thermal limits of the VCSEL, thus maintaining reliability and thermal stability
Solution Approach 2:
The system maintains continuous detection capability by sequentially processing multiple time windows across repeated low-power pulse cycles. This continuous photon accumulation from multiple low-power emissions achieves the same effective detection range as high-power continuous operation would provide, without the thermal penalties
3Area of stationary object
If mechanical scanning is used to acquire 3D maps, then measurement precision and coverage are improved, but device complexity, size, and reliability are worsened
Solution Approach 1:
The patent replaces mechanical scanning systems with a stationary detector that uses temporal gating to achieve spatial resolution. By detecting photons in multiple time windows corresponding to different flight times, the system reconstructs distance information without any moving parts, eliminating mechanical scanning complexity while maintaining scene coverage capability
Solution Approach 2:
The system adds the time dimension to the detection process, using time-of-flight information to distinguish spatial positions. This temporal dimension replaces the need for mechanical angular scanning, allowing the stationary detector to map 3D space by measuring photon arrival times across multiple time windows
4Measurement precision
If serial read-out of SPAD arrays is used, then measurement precision is improved, but bandwidth and productivity are limited
Solution Approach 1:
The patent performs preliminary spatial filtering by using a stationary detector to capture the entire scene simultaneously in each time window. This preliminary capture of all spatial information in parallel, followed by temporal processing, maintains high measurement precision while achieving high bandwidth through parallel photon detection across multiple time windows
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 greater operating range and miniaturization while maintaining accuracy, overcoming the limitations of existing semiconductor-based LIDAR systems by using low-power VCSELs and range gating to enhance light energy detection.
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
a detector comprising a plurality of picture elements, the detector being configured for detecting light representing the pattern of discrete spots as reflected by the object
Implementation Method 3
System for determining a distance to an object... time-of-flight based sensing systems to be used for the characterization of a scene
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 the exposure values by accumulating a first amount of electrical charge representative of a first amount of light reflected during a first time window and a second electrical charge representative of a second amount of light reflected during a second time window, the second time window occurring after the first time window. The picture elements comprise at least two sets of charge storage wells, each configured as a cascade.