Coded Optical Transmission for Depth Estimation
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Solution Overview
Problem
Existing optical detection systems face challenges in achieving high frame rates and resolutions due to limitations in scanned and flash transmit approaches, and increased complexity with frequency multiplexing schemes, particularly in time-of-flight distance estimation.
Innovation Solution
A coded transmission scheme using orthogonal code sequences is employed, where individual optical emitters transmit specified amplitude-modulated waveforms, allowing for contemporaneous illumination and separation of reflected light contributions using correlation-based techniques, enabling efficient spatial selectivity and depth estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a scanned transmit approach is used to simplify receiver architecture, then device complexity is reduced, but frame rate and resolution are limited due to sequential illumination of locations
Solution Approach 1:
The field-of-regard is divided into multiple discrete locations, each illuminated by a unique coded transmit sequence from the optical emitter array. This segmentation allows parallel processing of multiple spatial regions simultaneously, overcoming the sequential limitation of scanned approaches while maintaining receiver simplicity through correlation-based separation of the coded signals.
Solution Approach 2:
Coded transmit sequences with periodic structures (such as orthogonal codes or pseudorandom sequences) are transmitted simultaneously to multiple locations. The periodic nature of these codes enables correlation-based detection at the receiver, allowing simultaneous illumination of multiple locations without increasing receiver complexity, thus improving frame rate while maintaining architectural simplicity.
2Device complexity
If a scanned transmit approach is used to simplify receiver architecture, then device complexity is reduced, but resolution is limited due to sequential illumination of locations
Solution Approach 1:
The field-of-regard is divided into multiple discrete locations, each illuminated by a unique coded transmit sequence from the optical emitter array. This segmentation allows parallel processing of multiple spatial regions simultaneously, overcoming the sequential limitation of scanned approaches while maintaining receiver simplicity through correlation-based separation of the coded signals.
Solution Approach 2:
Multiple locations are illuminated continuously and simultaneously rather than sequentially, maintaining continuous depth estimation across the entire field-of-regard. This continuous parallel operation improves measurement precision by providing simultaneous depth data from multiple locations, eliminating the temporal gaps inherent in scanned approaches.
3Productivity
If a flash transmit scheme is used to illuminate the entire field-of-regard simultaneously, then frame rate is improved, but transmit intensity limits inhibit maximum range and resolution
Solution Approach 1:
The flash illumination is segmented into multiple coded transmit sequences, each assigned to specific regions or locations within the field-of-regard. This segmentation allows simultaneous illumination of multiple locations with lower individual intensities, avoiding the transmit intensity limits of conventional flash schemes while maintaining high frame rates through parallel processing.
Solution Approach 2:
The transmit signal parameters are changed by applying unique coded sequences to different optical emitters or emitter groups. This parameter variation enables the system to maintain high frame rates through parallel transmission while distributing the required total energy across multiple lower-intensity signals, thereby improving depth estimation resolution without exceeding transmit intensity limits.
4Productivity
If frequency multiplexing is used to transmit multiple wavelengths contemporaneously, then productivity is improved, but device complexity and cost increase substantially
Solution Approach 1:
Instead of using multiple wavelengths (frequency multiplexing), the system uses temporal copies of coded sequences at a single wavelength. Multiple locations are illuminated by time-coded versions of the same base sequence, allowing the receiver to separate signals through correlation processing. This copying approach achieves parallel illumination and high frame rates without the complexity of multiple wavelength channels.
Solution Approach 2:
The system replaces the optical frequency domain multiplexing mechanism with a temporal code domain multiplexing approach. Instead of using different wavelengths (optical frequency), the system uses different temporal codes at a single wavelength, allowing signal separation through correlation processing in the time domain. This substitution dramatically reduces system complexity while maintaining high productivity through parallel processing.
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 enhances depth estimation accuracy and allows for simultaneous illumination and processing of multiple locations in the field-of-regard, improving frame rate and resolution while reducing system complexity.
Implementation Method 1
individual optical emitters transmit specified amplitude-modulated waveforms
Implementation Method 2
a receiver can detect light scattered or reflected by objects within the receiver's field-of-view
Implementation Method 3
a receiver can detect light scattered or reflected by objects within the receiver's field-of-view
Implementation Method 4
separation of received signals can be performed in the time-domain using a correlation-based technique
Implementation Method 5
one or more 'time-of-flight' determination techniques. In order to perform such detection, an illuminator can be used to transmit light toward a field-of-regard
Data Source
AI summary
In an optical detection system, a coded transmission scheme can be used to provide scene illumination. For example, a transmitter can include transmit elements that can be controlled individually or in groups to provide specified modulated (e.g., on-off-keyed) waveforms corresponding to specified transmit code sequences. Light reflected or scattered by an object can be detected by an optical receiver, such as a single-pixel detector. Contributions to the received optical signal corresponding to the respective transmit code sequences can be separated using a correlation-based technique, even when such contributions overlap in time. Regions of a field-of-regard illuminated by ones or groups of the transmit elements can be selected or adjusted, such as to provide controllable spatial (e.g., angular) selectivity of which portions of the field-of-regard are illuminated by particular transmit signals.