DFB Laser 3D Depth Sensing with Pulsed Bursts
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Solution Overview
Problem
Active depth sensing systems face challenges in achieving high-resolution images due to inherent pincushion distortion and susceptibility to ambient light interference, particularly when using VCSEL arrays, which limits their performance in varying lighting conditions.
Innovation Solution
Implementing a single DFB laser configured to emit a sequence of short bursts of light pulses followed by long cooling periods, allowing the system to operate at high power and reduce noise from ambient light, enabling brightness comparable to VCSEL arrays while minimizing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single DFB laser is used to emit light at high power, then brightness is improved and distortion is reduced, but susceptibility to ambient light interference increases
Solution Approach 1:
The system uses periodic pulsed illumination where the DFB laser emits light in short bursts followed by cooling periods. This periodic operation allows the laser to accumulate high energy in brief intervals while dissipating heat between pulses, enabling high brightness output without continuous overheating that would increase ambient light susceptibility
Solution Approach 2:
The system performs preliminary cooling during the non-transmission portions of the pulse sequence, preparing the laser for subsequent high-power emission. This preliminary action of cooling between pulses enables the laser to maintain high brightness capability while reducing thermal effects that would otherwise increase vulnerability to ambient light interference
2Illumination intensity
If VCSEL arrays are used for illumination, then brightness is improved, but pincushion distortion occurs limiting resolution
Solution Approach 1:
The invention extracts the light source from the VCSEL array configuration and uses a single DFB laser instead. This removal of the multi-element VCSEL array eliminates the pincushion distortion inherent in array-based systems while maintaining the ability to project structured light patterns through the single laser combined with coding techniques
Solution Approach 2:
The system changes the illumination parameter from continuous wave or long pulse operation to short pulsed operation. This parameter change enables the single DFB laser to achieve brightness levels comparable to VCSEL arrays while avoiding the distortion issues, as the pulsed operation allows for higher peak power emission without the thermal and optical distortions of continuous operation
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 the resolution and robustness of active depth sensing applications by reducing SNR degradation from ambient light, enabling effective operation in both indoor and outdoor conditions.
Implementation Method 1
a single-mode distributed feedback (DFB) laser configured to output a sequence of relatively short bursts of light pulses
Implementation Method 2
receiving, during each transmission portion, a plurality of light pulses reflected from the scene, and continuously accumulating photoelectric charge indicative of the received light pulses
Data Source
AI summary
This disclosure provides systems, methods, and apparatuses for sensing a scene. In one aspect, a device may illuminate the scene using a sequence of two or more periods. Each period may include a transmission portion during which a plurality of light pulses are emitted onto the scene. Each period may include a non-transmission portion corresponding to an absence of emitted light. The device may receive, during each transmission portion, a plurality of light pulses reflected from the scene. The device may continuously accumulate photoelectric charge indicative of the received light pulses during an entirety of the sequence. The device may transfer the accumulated photoelectric charge to a readout circuit after an end of the sequence.