Image Sensor Phase Selection Circuit for Noise Reduction
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Solution Overview
Problem
Time-of-flight (ToF)-based image sensors face challenges in accurately measuring object depth due to noise from various causes, necessitating a method to minimize noise and improve measurement accuracy.
Innovation Solution
The image sensor employs a modulation clock generating circuit, demodulation clock generating circuit, phase selection circuit, and time gating circuit to generate and control modulation and demodulation signals with varying phases, using random numbers to select and apply pre-modulation and pre-demodulation signals, thereby reducing noise and enhancing depth measurement accuracy within an unambiguous range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ToF-based image sensors measure depth using fixed modulation and demodulation signals, then the measurement process is simple, but noise from various causes degrades measurement accuracy
Solution Approach 1:
The patent applies dynamics by making the modulation and demodulation signal phases variable rather than fixed. The phase selection circuit randomly selects from multiple pre-defined phases for each packet, allowing the system to adapt to different measurement conditions and minimize noise interference, thereby improving depth measurement accuracy without requiring overly complex real-time signal generation
Solution Approach 2:
The patent implements preliminary action by pre-defining multiple modulation and demodulation signal phases before the measurement process. These pre-defined phases are stored and randomly selected for each packet, eliminating the need for complex real-time phase generation and reducing processing complexity while maintaining high measurement precision
2Measurement precision
If the modulation signal period is increased to extend measurement range, then the unambiguous range increases, but the measurement time increases
Solution Approach 1:
The patent applies segmentation by dividing the measurement process into multiple packets, each with its own randomly selected phase. Instead of using a single long-period modulation signal, the system uses multiple shorter-period packets with different phases, allowing the unambiguous range to be extended through statistical accumulation while maintaining fast measurement timing for each individual packet
Solution Approach 2:
The patent utilizes periodic action by employing multiple modulation signal periods with different phases for each packet. This periodic approach with varying phases allows the system to extend the effective measurement range through phase diversity while keeping each individual measurement cycle short, thus reducing overall measurement time
3Measurement precision
If multiple phases are randomly selected for each packet to minimize noise, then measurement accuracy improves, but the control complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-defining multiple modulation and demodulation signal phases before the measurement process. These pre-defined phases are stored and randomly selected for each packet, eliminating the need for complex real-time phase generation and reducing processing complexity while maintaining high measurement precision
Solution Approach 2:
The patent applies parameter changes by randomly selecting from multiple pre-defined phase parameters for each packet rather than using a fixed phase. This approach introduces variability to minimize noise while relying on pre-computed phase values, thereby improving measurement accuracy without requiring complex real-time parameter generation or adjustment
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 effectively minimizes noise and improves the accuracy of depth measurements by randomly applying signals with different phases, ensuring only accurate depth information from the desired range is obtained, thus extending the unambiguous measurement range and maintaining accuracy in various conditions, including bad weather.
Implementation Method 1
a modulation clock generating circuit configured to generate first to Nth modulation clock signals respectively having N phases
Implementation Method 2
a demodulation clock generating circuit configured to generate first to Nth demodulation clock signals respectively having N phases respectively corresponding to the first to Nth modulation clock signals
Implementation Method 3
ToF-based image sensors may measure information about a distance to an object... measure a ToF, which corresponds to a time for light reflected from the object to be received after the light is irradiated to the object
Data Source
AI summary
An image sensor for measuring a depth of an object disposed in an unambiguous range is provided. The image sensor includes: a modulation clock generating circuit configured to generate N modulation clock signals respectively having N phases; a demodulation clock generating circuit configured to generate N demodulation clock signals respectively having N phases respectively corresponding to the N modulation clock signals; a phase selection circuit configured to select one modulation clock signal from among the N modulation clock signals to output as a pre-modulation signal, based on a random number, and select, from among the N demodulation clock signals, and output as N pre-demodulation signals corresponding to the pre-modulation signal, based on the random number; and a time gating circuit configured to control a time at which the pre-modulation signal and the N pre-demodulation signals are applied, based on the unambiguous range.