Scannerless Optical Rangefinder Multi-Channel Receiver Design
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Solution Overview
Problem
Existing optical rangefinders face challenges in operating effectively under high ambient lighting conditions, particularly in bright sunlight, due to intense background light interference, and struggle to provide wide-field-of-view angularly-resolved detection without the use of costly and bulky mechanical scanners or expensive high-energy laser sources.
Innovation Solution
A scannerless optical rangefinder system utilizing a multi-channel optical receiver with LED light sources emitting broad field-of-illumination pulses, combined with PIN photodiodes and analog-to-digital conversion, to detect optical return signals across a wide field-of-view while minimizing background light interference through optical filtering and large photosensitive surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow FOV optical receiver with small photosensitive surface is used, then the signal-to-noise ratio in high ambient light is improved, but the field-of-view coverage is reduced
Solution Approach 1:
The patent divides the optical receiver into multiple detection channels, each with its own photodetector and instantaneous field-of-view. This segmentation allows the system to maintain narrow FOV per channel for good signal-to-noise ratio while collectively covering a wide field-of-view through multiple channels working in parallel.
Solution Approach 2:
The patent transitions from a single-channel narrow FOV system to a multi-channel system where the field-of-view is expanded by adding spatial dimension through multiple detection channels. Each channel maintains its narrow FOV characteristics while the aggregate system achieves wide field-of-view coverage.
2Area of stationary object
If a wide field-of-view optical receiver is used, then the coverage area is improved, but the signal-to-noise ratio in high ambient light deteriorates
Solution Approach 1:
The optical receiver is segmented into multiple independent detection channels, each with narrow instantaneous FOV and good signal-to-noise ratio. The collective FOV of all channels provides wide coverage while each channel maintains high reliability through its narrow FOV configuration.
Solution Approach 2:
Multiple narrow FOV detection channels are merged into a single multi-channel optical receiver system. The combination preserves the signal-to-noise ratio advantages of narrow FOV while achieving wide field-of-view coverage through the aggregated capability of all channels.
3Area of stationary object
If mechanical scanners are used to achieve wide-field-of-view detection, then the field-of-view coverage is improved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical scanning systems with a stationary multi-channel optical receiver. Instead of mechanically moving a narrow FOV receiver to scan the scene, multiple fixed FOV receivers simultaneously cover different angular regions, eliminating mechanical complexity while achieving wide field-of-view coverage.
Solution Approach 2:
The patent replaces periodic mechanical scanning with simultaneous parallel detection across multiple channels. All detection channels operate at the same time to capture returns from different angular positions, eliminating the need for periodic scanning motion while providing comprehensive field-of-view coverage.
4Reliability
If high-energy laser sources are used to improve detection in bright sunlight, then the signal-to-noise ratio is improved, but the cost and energy consumption increase
Solution Approach 1:
The patent replaces expensive, high-energy laser sources with lower-cost, lower-energy LED light sources. By using multiple detection channels with smaller individual photosensitive surfaces, the system achieves adequate signal-to-noise ratio without requiring high-energy illumination, reducing both cost and energy consumption.
Solution Approach 2:
Instead of using a single high-energy laser source, the patent employs multiple LED sources with lower individual energy output. The collective illumination from multiple lower-energy sources, combined with multi-channel detection, achieves the necessary signal-to-noise ratio without the excessive energy consumption of high-power lasers.
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
Enables reliable, cost-effective, and efficient detection and ranging of objects over a wide field-of-view in varying lighting conditions, including bright sunlight, without the need for mechanical scanners or high-energy laser sources, providing improved signal-to-noise ratios and reduced operational costs.
Implementation Method 1
an optical emitter having a LED light source and driver electronics, emitting a train of light pulses having a broad field-of-illumination (FOI)
Implementation Method 2
a multi-channel optical receiver (MCOR) for detecting optical return signals, an overall field-of-view (FOV) encompassing each channel instantaneous FOV... each detection channel of the multi-channel optical receiver having a photodetector with a photosensitive surface
Implementation Method 3
ranging objects distanced from up to a few hundreds meters... in presence of bright sunlight... An effective approach to make laser rangefinders more immune to the presence of intense background light... inserting a narrowband optical filter in front of the objective lens of the optical receiver
Implementation Method 4
The FOV of an optical receiver is given by the ratio of the size of the photosensitive surface of the photodetector integrated in the receiver and the local length of the objective lens, the photosensitive surface being placed close to or exactly at the focal plane of the lens
Implementation Method 5
Most optical rangefinders that range objects located beyond a few meters away operate according to the time-of-flight (TOF) principle, which relies on the finite propagation speed of light... the distance that separates the aimed object from the rangefinder is inferred from the time taken by the light pulses to propagate up to the aimed object and then back to the rangefinder
Data Source
AI summary
A multiple-field-of-view scannerless optical rangefinder operating in pulsed Time-Of-Flight operation for use in high ambient background light is described. The rangefinder comprises an optical emitter having a LED light source and driver electronics, emitting a train of light pulses having a broad field-of-illumination (FOI); a multi-channel optical receiver (MCOR) for detecting optical return signals, an overall field-of-view (FOV) encompassing each channel instantaneous FOV, the FOI encompassing the overall FOV, the multi-channel optical receiver having analog front-end electronics; an Analog-to-Digital Converter (ADC) for receiving and converting the waveforms into digital format; a control and processing unit (CPU) for generating a pulse trigger signal, sending a synchronization trigger signal to the MCOR for starting the detection of the optical return signals, and for processing the waveforms in digital format; a data interface; wherein a peak present in any of waveforms is a signature of an object located within the instantaneous FOV.