TOF Camera Stripe Illumination Reduces Motion Artifacts
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Solution Overview
Problem
Conventional full-field 3D time-of-flight (TOF) cameras face challenges in achieving optimal illumination, leading to reduced signal-to-background light ratio and increased motion artifacts due to simultaneous illumination of the entire field of view, which affects the accuracy and efficiency of depth measurement.
Innovation Solution
The camera system illuminates only specific regions of the field of view, using a scanning illumination module to project light in a vertical or horizontal stripe pattern, allowing for sequential acquisition and processing of pixel regions, thereby reducing multiple reflections and improving the signal-to-background light ratio and reducing motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the entire field of view is illuminated simultaneously, then all pixels can be captured at the same time, but the signal-to-background light ratio decreases and motion artifacts increase
Solution Approach 1:
The field of view is divided into multiple pixel regions that are illuminated and captured sequentially rather than simultaneously. The illumination module projects light stripes onto specific regions, and the imaging sensor captures these regions in sequence, allowing for better signal-to-background light ratio while maintaining acceptable acquisition speed through optimized scanning patterns
2Loss of time
If the entire field of view is illuminated simultaneously, then the acquisition time is reduced, but motion artifacts increase and depth measurement accuracy decreases
Solution Approach 1:
The illumination module uses periodic light stripes that are projected sequentially across different pixel regions. Each region receives periodic illumination at optimized intervals, allowing the system to reduce motion artifacts through controlled timing while maintaining efficient acquisition through the periodic nature of the illumination pattern
3Reliability
If uniform illumination is applied to all objects, then the dynamic range of the sensor is optimized, but multiple reflections increase and reduce measurement accuracy
Solution Approach 1:
Instead of uniform illumination across the entire field of view, the system applies localized illumination to specific pixel regions using light stripes. Each region receives illumination tailored to its specific requirements, reducing multiple reflections from areas not currently being measured while maintaining optimal sensor dynamic range utilization for the active region
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 enables more direct light to be received by each pixel region, reducing acquisition time and improving the signal-to-background light ratio, resulting in enhanced depth measurement accuracy and reduced motion artifacts compared to conventional systems.
Implementation Method 1
The illumination module is designed with the intention to keep the required dynamic range of the sensor as small as possible, often leading to adjustments that result in the reflection of the same amount of light back to the camera from all objects within the field of interest
Implementation Method 2
The reflected light is imaged onto a sensor. The photo-generated electrons are demodulated in the sensor. Based on the phase information, the distance for each pixel is deduced
Data Source
AI summary
A time of flight (TOF) based camera system includes an illumination module that illuminates only portion of the sensor's field of view that translates to a given region of the pixels of the imaging sensor. The acquired data of the pixel region is processed and/or readout, typically. After the exposure time of the first pixel region is completed, a second pixel region is illuminated and the second pixel region is processed. This procedure can be repeated a couple of times up to a few hundred even thousand times until the entire pixel array is readout and possibly read-out a number of times. The full depth image is then reconstructed based on the results from the different pixel region acquisitions. This system can be used to reduce stray light. Compared to state-of-the-art TOF camera, the presented method and device show improvements in background light stability and a reduction in multiple reflections.