Image Sensor Phase Modulation for Distance Measurement Noise Reduction
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Solution Overview
Problem
Time-of-flight (ToF)-based image sensors face challenges in minimizing noise when measuring distances, which affects the accuracy of distance-related information due to various noise factors.
Innovation Solution
The image sensor employs a demodulation clock generation circuit, demodulation phase selection circuit, delay circuit, and phase mixer to generate demodulation signals with varying phases based on a random number and address, reducing noise by changing phases for each packet and pixel group, thereby minimizing read noise and electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed-phase demodulation signals are used for distance measurement, then the measurement process is simple, but read noise and electromagnetic interference increase, reducing measurement accuracy
Solution Approach 1:
The patent applies dynamics by making the demodulation signal phases changeable rather than fixed. The control circuit dynamically adjusts the phases of demodulation signals based on random numbers generated for each packet, transforming the static phase configuration into a dynamic one that adapts to reduce noise and interference while maintaining measurement accuracy
Solution Approach 2:
The patent implements periodic action by systematically changing the demodulation signal phases across different packets within each integration time. The control circuit generates different random numbers for each packet, causing the phases to periodically vary, which helps distribute and reduce the impact of noise and electromagnetic interference over time
2Measurement precision
If demodulation signal phases are changed for each packet using random numbers, then noise and peak current are reduced, but the device complexity increases
Solution Approach 1:
The control circuit serves itself by autonomously generating random numbers for each packet without requiring external intervention or complex external control systems. This self-service approach allows the system to dynamically adjust demodulation phases while keeping the overall device architecture relatively simple
Solution Approach 2:
The patent changes the phase parameters of demodulation signals based on randomly generated values for each packet. By modifying these parameters dynamically rather than changing the fundamental system architecture, the patent achieves noise reduction and peak current mitigation while limiting the increase in device complexity to parameter management rather than structural complexity
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 enhances the accuracy of distance measurement by reducing noise and peak current, allowing for high-speed modulation operations and preventing depth pixel fixed-pattern noise, leading to improved depth measurement accuracy.
Implementation Method 1
receive a light signal generated by the light source and reflected from an object
Implementation Method 2
measuring a light flight time until the light reflected from the object is received
Implementation Method 3
generate first to fourth demodulation signals of which phases are changed based on a random number and an address
Data Source
AI summary
An image sensor and a camera are provided. The image sensor includes: a demodulation clock generation circuit configured to generate first to fourth demodulation clock signals respectively having first to fourth phases; a demodulation phase selection circuit configured to generate first to fourth pre-demodulation signals based on the first to fourth demodulation clock signals and a random number that changes for each of a plurality of packets; a delay circuit configured to generate a first delay signals, second delay signals, third delay signals and fourth delay signals by delaying the first to fourth pre-demodulation signals by a plurality of delay phases; and a phase mixer configured to generate first to fourth demodulation signals of which phases are changed based on an address that changes for each of the plurality of packets. The first to fourth phases have a phase difference of 90° from each other.