ToF Sensor Cross-Time-Shift Measurement for Pixel Deviation Compensation
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Solution Overview
Problem
Existing time-of-flight (ToF) sensors face accuracy degradation in distance measurements due to offsets or gain deviations of depth pixels, leading to inconsistent and inaccurate results.
Innovation Solution
A ToF sensor with a multi-tap structure and a method that generates multiple time shifts and sampled data using demodulation signals of different phases, determining a cross time shift to enhance measurement accuracy by equalizing sampled data between reference taps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ToF sensor uses single-tap structure with fixed demodulation signals, then the device complexity is low and ease of manufacture is high, but the measurement precision degrades due to offsets and gain deviations of depth pixels
Solution Approach 1:
The sensor divides the photodetector into multiple taps (first reference tap, second reference tap, and measurement tap) that independently sample the received light signal at different phases. This segmentation allows each tap to capture specific phase information, enabling the system to distinguish between offset/gain deviations and actual distance measurements by comparing signals across multiple taps.
Solution Approach 2:
The sensor applies demodulation signals with different phases (0°, 90°, 180°, 270°) to the multiple taps in a periodic manner. By systematically varying the phase of demodulation signals across different taps, the system can extract distance information while compensating for pixel deviations through the periodic sampling pattern.
2Measurement precision
If the ToF sensor applies multiple demodulation signals with different phases to multiple taps, then the measurement precision improves through cross time shift determination, but the use of energy increases due to multiple sampling operations
Solution Approach 1:
The sensor combines multiple sampling operations into a single integrated measurement process. By simultaneously applying different phase demodulation signals to different taps and processing their outputs together through cross time shift determination, the system achieves high-precision distance measurement while consolidating energy consumption into a unified operational framework rather than sequential independent measurements.
3Measurement precision
If the ToF sensor uses multiple taps with different phase demodulation signals, then the measurement precision improves by compensating for pixel deviations, but the device complexity increases due to additional circuitry and processing
Solution Approach 1:
The multiple taps in the sensor serve multiple functions simultaneously: they act as photodetectors for receiving light signals, as phase samplers for capturing different phase information, and as reference sources for compensating gain and offset deviations. This multi-functionality reduces the need for separate dedicated components, thereby managing device complexity while achieving high measurement precision.
Solution Approach 2:
The reference taps (first and second reference taps) automatically provide calibration information for compensating pixel deviations without requiring external calibration procedures. The system uses its own internal reference signals from the multiple taps to self-correct for offsets and gain variations, eliminating the need for separate calibration hardware or complex external adjustment mechanisms.
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
The method and sensor design improve distance measurement accuracy by compensating for pixel deviations, ensuring precise distance calculations despite variations in depth pixel characteristics.
Implementation Method 1
The transmission light is reflected from the object back to the ToF sensor as the reception light
Implementation Method 2
The depth pixel has a multi-tap structure including a plurality of taps to generate a plurality of sampled data based on a reception light and a plurality of demodulation signals having different phases
Data Source
AI summary
A method measures the distance between a time-of-flight (ToF) sensor and an object based on cross time shift. The ToF sensor includes at least one depth pixel and a light source to direct transmission light to an object. The depth pixel may have a multi-tap structure and may generate sampled data based on reception light and demodulation signals having different phases. The reception light corresponds to the transmission light reflected from the object. The method includes generating time shifts between the transmission light and demodulation signals, performing sampling operations to generate the sampled data corresponding to the time shifts, determining a cross time shift based on sampled data of a first reference tap substantially equaling sampled data of a second reference tap, and determining the distance between the ToF sensor and the object based on the cross time shift.