ToF Image Sensor Pulse-Width Control for Accurate Depth Sensing
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Solution Overview
Problem
Existing time-of-flight (ToF) based image sensors suffer from noise in distance measurements due to various factors, leading to inaccurate distance information.
Innovation Solution
An image sensor with a pixel array and control circuit that generates photo gate signals with varying pulse widths within a frame section, simulating triangular waveforms to reduce signal distortion and enhance depth information resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If constant pulse width photo gate signals are used in ToF image sensors, then the device operation is simple, but the measurement precision and depth information resolution deteriorate due to signal distortion and noise
Solution Approach 1:
The patent applies dynamics by transitioning from static constant pulse width signals to dynamic variable pulse width signals. The control circuit generates photo gate signals whose pulse widths vary over time within each frame period, creating a time-varying control pattern that reduces signal distortion and improves depth measurement resolution without requiring complex additional hardware
Solution Approach 2:
The patent implements parameter changes by modifying the pulse width parameter of the photo gate signals. The control circuit varies the pulse width of successive photo gate signals within a frame period, creating a modulation pattern that enhances the phase difference measurement accuracy and reduces noise in distance measurements
2Measurement precision
If varying pulse width photo gate signals are generated to reduce noise, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent applies periodic action by generating photo gate signals with pulse widths that vary periodically within each frame period. This periodic variation in pulse width creates a modulation pattern that enables more accurate phase difference measurement and reduces noise in distance measurements while maintaining a regular, predictable signal generation rhythm
3Measurement precision
If triangular waveform simulation is used to enhance depth information, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or hardware waveform generation systems with a simplified control circuit implementation. The triangular waveform effect is achieved through digital or logical control of the photo gate signal pulse widths, substituting complex physical waveform generation with easier-to-implement electronic control while maintaining the beneficial phase difference measurement accuracy
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 solution increases the accuracy and resolution of depth information by minimizing noise and improving the phase difference measurement between transmission and reception light signals.
Implementation Method 1
each unit pixel may include a photodiode PD, an overflow transistor OT, first and second transfer transistors TS1 and TS2, first and second storage transistors SS1 and SS2, first and second source followers SF1 and SF2, and first and second select transistors SELX1 and SELX2
Data Source
AI summary
An image sensor for distance measurement and a camera module including the same are provided. The image sensor includes a pixel array including a plurality of unit pixels, a control circuit configured to provide a plurality of photo gate signals to the plurality of unit pixels, respectively, and a readout circuit configured to read out pixel signals from the pixel array on a frame-by-frame basis, wherein the control circuit generates the plurality of photo gate signals such that a pulse width is changed within one frame section.