LiDAR Range Sensing with Temporal Multiplexing and Single Photodetector
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Solution Overview
Problem
Current frequency-modulated continuous-wave LiDAR systems are complex, costly, and sensitive to shock and vibration, making them less suitable for mobile applications due to their size and power consumption, as well as requiring separate drive circuits and multiple photodetectors for each emitter.
Innovation Solution
A range sensing apparatus with an array of emitters and a single or balanced photodetector, utilizing amplitude-chirped electrical drive pulses to induce frequency chirp in coherent optical radiation, and temporally multiplexing drive signals to reduce complexity and packaging costs, while integrating driving and switching circuitry with the emitter array on a single chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple photodetectors and separate drive circuits are used for each emitter, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple photodetector functions into a single photodetector by temporally multiplexing the emitters. Each emitter is activated sequentially in time slots, allowing one photodetector to serve multiple emitters. This reduces the number of photodetectors from N (where N is the number of emitters) to 1, while maintaining the ability to measure range and velocity for each emitter through temporal separation and signal processing.
Solution Approach 2:
The patent implements periodic temporal multiplexing where emitters are activated in alternating time slots. The drive signals are modulated with a chirp pattern that repeats periodically, and the photodetector samples the reflected signal during each period. This periodic action allows a single photodetector to sequentially measure signals from multiple emitters, reducing system complexity while preserving measurement precision through structured temporal sampling.
2Measurement precision
If multiple photodetectors and separate drive circuits are used for each emitter, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple separate drive circuits and photodetectors into integrated circuits. The drive circuitry for multiple emitters is merged into a single integrated circuit that generates temporally multiplexed drive signals. Similarly, multiple photodetector channels are consolidated into a single photodetector element, reducing the total number of components that need to be manufactured and assembled, thereby lowering manufacturing cost while maintaining measurement precision.
Solution Approach 2:
The single photodetector and integrated drive circuitry perform multiple functions that previously required separate components. The photodetector serves all emitters sequentially, and the integrated circuit generates drive signals for all emitters through temporal multiplexing. This multi-functionality reduces the bill of materials and assembly complexity, making the system more cost-effective to manufacture while preserving the ability to accurately measure range and velocity for each emitter.
3Measurement precision
If traditional LiDAR systems are used, then measurement capability is maintained, but size and power consumption increase
Solution Approach 1:
The patent merges multiple emitters and photodetectors into a compact integrated structure. The emitters are arranged in an array that can be physically compact, and the temporal multiplexing allows the system to function with fewer physical components. The single photodetector and integrated drive circuitry further reduce the overall system footprint, making the LiDAR system smaller and more suitable for mobile applications while maintaining range and velocity measurement capabilities.
Solution Approach 2:
The temporal multiplexing scheme allows the system to achieve the functionality of multiple simultaneous emitters and photodetectors using a single photodetector and sequential emitter activation. This periodic action reduces the number of physical components required, thereby reducing system size and weight, while maintaining measurement precision through structured temporal sampling and signal processing that recovers the information that would otherwise require multiple simultaneous components.
4Measurement precision
If traditional LiDAR systems are used, then measurement capability is maintained, but power consumption increases
Solution Approach 1:
The temporal multiplexing approach activates emitters sequentially rather than simultaneously, reducing the total power consumption. Instead of all emitters operating at full power at the same time, only one emitter is active at a time during each time slot. This periodic activation reduces the peak power demand and average power consumption while maintaining measurement capability through structured sampling and signal processing that recovers range and velocity information from the sequential measurements.
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 approach simplifies the detection circuitry, reduces electromagnetic interference, and enables accurate range and velocity measurement across a target using a single photodetector, improving the utility of LiDAR systems for mobile use cases by minimizing size and power consumption.
Implementation Method 1
direct optical radiation reflected from the respective location onto the optical detector so as to interfere optically with the local beam
Implementation Method 2
The light reflected from the target is mixed with a sample of the transmitted light (referred to as the local beam or local oscillator) and detected by a photodetector, such as a balanced photodiode pair. The photodetector outputs an RF signal at a beat frequency
Implementation Method 3
A controller is coupled to apply amplitude-chirped electrical drive pulses to the transmitter while controlling the switching circuitry to temporally multiplex the electrical drive pulses among the emitters
Implementation Method 4
project the local beam toward the optical detector, to project the transmitted beam toward a respective location on a target, and to direct optical radiation reflected from the respective location onto the optical detector
Data Source
AI summary
Range sensing apparatus includes a transmitter including an array of emitters configured to emit respective beams of coherent optical radiation and switching circuitry coupled to the emitters. An optical assembly is configured to divide each beam of the coherent optical radiation into a transmitted beam and a local beam, to project the local beam toward an optical detector, to project the transmitted beam toward a respective location on a target, and to direct optical radiation reflected from the respective location onto the optical detector so as to interfere optically with the local beam. A controller is coupled to apply amplitude-chirped electrical drive pulses to the transmitter while controlling the switching circuitry to temporally multiplex the electrical drive pulses among the emitters, and to receive and process electrical beat signals output by the optical detector in response to interference between the reflected optical radiation and the local beam.