Indirect Time-of-Flight Depth Mapping Phase Shift Distribution
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Solution Overview
Problem
High modulation frequency in indirect time-of-flight depth mapping systems results in high direct and capacitive currents, leading to significant electromagnetic interference and voltage disruptions, which degrade measurement accuracy and synchronization.
Innovation Solution
Spatially allocating phase shifts on the demodulation signal across a matrix of photosensitive pixels, distributing phase shifts at different values within groups of pixels to reduce current peaks and electromagnetic interference, and compensating for these shifts in phase shift calculations to maintain measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the modulation frequency is increased to improve measurement accuracy, then the measurement precision is improved, but the direct current and capacitive current increase, generating strong electromagnetic interference and voltage disruptions
Solution Approach 1:
The patent segments the pixel array into multiple groups, each group being controlled by demodulation signals with different phase shifts. This segmentation distributes the capacitive current peaks across different time instances for each group, reducing the intensity of electromagnetic interference generated by any single group while maintaining the high modulation frequency needed for measurement accuracy
Solution Approach 2:
Different groups of pixels are assigned different phase shift values locally, creating a spatial distribution of phase shifts across the pixel array. This local differentiation allows each group to operate at high frequency while the overall system experiences reduced electromagnetic interference through temporal distribution of current peaks
2Measurement precision
If the modulation frequency is increased to improve measurement accuracy, then the measurement precision is improved, but the supply voltage drops and ground voltage increases, disrupting logic element switching and degrading synchronization
Solution Approach 1:
By segmenting the pixel array into multiple groups with different phase shifts, the patent distributes the capacitive current loading across different time instances. This reduces the peak current demand on the power supply at any given moment, minimizing voltage drops and ground voltage increases that would otherwise disrupt logic element switching and degrade synchronization
Solution Approach 2:
The patent employs periodic phase-shifted demodulation signals for different pixel groups, creating a time-distributed switching pattern. This periodic action with distributed phase shifts spreads the current demand over time, reducing instantaneous voltage disruptions and maintaining stable power supply conditions for reliable synchronization
3Measurement precision
If the resolution is increased to improve depth mapping quality, then the measurement precision is improved, but the capacitive current peaks increase, generating strong electromagnetic interference
Solution Approach 1:
The patent segments the high-resolution pixel array into multiple groups, each controlled by demodulation signals with different phase shifts. This segmentation distributes the capacitive current peaks associated with high-resolution operation across different time instances for each group, reducing the intensity of electromagnetic interference while maintaining the high resolution needed for quality depth mapping
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 reduces the intensity and frequency of electromagnetic interference, allowing for higher resolution and modulation frequency in depth mapping systems while minimizing disruptions to the measurement process.
Implementation Method 1
The phase shift measurement can be obtained from the amount of charge photogenerated by pixels of a receiver during integration periods
Implementation Method 2
time-of-flight measurement systems measure the time between the instant of emission of an optical signal, i.e. a light signal, and the instant of reception of this signal after reflection
Data Source
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AI summary
The method for acquiring indirect time-of-flight depth mapping in a photosensitive pixel array (RES_PX) segmented into pixel groups includes at least one capture (Capt1-Capt4) during which the array pixels are driven by a demodulation signal (DEMOD). The method includes introducing phase shifts into the demodulation signal at different values (Δ1-Δ12) and distributed across each pixel group (Col1-Col12, Bk).