Dual-Frequency TOF Sensor Phase Clocking for Simpler Depth Sensing
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Solution Overview
Problem
The structure of existing dual-frequency Time of Flight (TOF) sensors is complicated, and there is a need for a simplified approach that maintains accuracy and measurement range.
Innovation Solution
A TOF sensor using dual frequency with pixel clocks having different numbers of phases according to different exposure frames, where high and low frequencies are employed, and pixel clocks are shifted by 90 degrees to have specific phases, reducing the complexity of the modulation operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual frequency is used to provide different accuracy and measurement range, then measurement performance is improved, but device structure becomes complicated
Solution Approach 1:
The patent implements dynamic frequency switching where the TOF sensor operates at high frequency for near objects and low frequency for far objects. The frequency is dynamically adjusted based on exposure frame timing, allowing the system to adapt measurement parameters in real-time rather than using fixed dual-frequency hardware, thus reducing structural complexity while maintaining measurement performance
Solution Approach 2:
The patent changes the operating frequency parameter over time within a single TOF sensor. By modulating the frequency of the pixel clock signal dynamically during operation (switching between high and low frequencies based on exposure frame sequence), the system achieves different measurement ranges and accuracies without requiring physically separate sensor structures for each frequency band
2Measurement precision
If pixel clocks are shifted by 90 degrees for modulation operation, then phase measurement capability is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic 90-degree phase shifting to pixel clocks in an alternating pattern between high and low frequency operations. Instead of continuously applying phase shifting at maximum intensity, the system periodically activates phase modulation only when needed for specific exposure frames, reducing overall power consumption while maintaining sufficient phase measurement capability for accurate depth mapping
Solution Approach 2:
The patent implements partial phase shifting where not all pixel clocks are shifted by 90 degrees in every frame. By selectively applying phase modulation to specific pixel clocks based on the current frequency band and exposure requirements, the system achieves adequate phase measurement precision without the full power cost of universal continuous phase shifting across all pixels
Data Source
AI summary
A Time of Flight (TOF) sensor using dual frequency includes: a light source for irradiating light to an external subject; a phase modulation controller for providing the light source with a clock so that the light source irradiates irradiation light according to a timing of a global clock, and generating a plurality of pixel clocks having dual frequency; and a pixel array for receiving the pixel clocks and generating a pixel signal, wherein the pixel clocks have a different number of phases according to different exposure frames at the dual frequency.