ToF Image Sensor Pulse-Width Control for Accurate Depth Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time-of-flight (ToF) based image sensors suffer from noise in distance measurements due to various factors, which affect the accuracy of distance-related 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, and a readout circuit that reads pixel signals on a frame-by-frame basis, enhancing the accuracy of distance measurements by reducing signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If constant pulse width photo gate signals are used, then the device complexity is low, but the measurement precision and depth information resolution deteriorate due to signal distortion and noise
Solution Approach 1:
The patent implements dynamic pulse width modulation where the photo gate signal pulse width varies over time within each frame period. The control circuit generates pulse widths that change according to a predetermined pattern (e.g., triangular waveform simulation), allowing the system to adapt the signal characteristics to reduce noise and improve depth resolution without requiring hardware modifications.
Solution Approach 2:
The invention changes the temporal parameter (pulse width) of the photo gate signal dynamically. By varying the pulse width according to different time points within a frame, the system optimizes the correlation between transmitted and received light signals, thereby improving measurement precision while maintaining the same basic device structure.
2Measurement precision
If pulse width modulation is applied to photo gate signals, then the accuracy of distance measurement improves, but the device complexity increases due to advanced control circuit requirements
Solution Approach 1:
The control circuit generates photo gate signals with periodic pulse width variations within each frame period. This periodic modulation pattern (such as simulating triangular waveforms) enables the system to extract phase difference information more accurately by creating predictable correlation patterns between transmitted and received signals, improving distance measurement accuracy through temporal sampling.
Solution Approach 2:
The system dynamically adjusts the pulse width of photo gate signals based on time within the frame, creating a dynamic sampling pattern that optimizes measurement accuracy. This dynamic approach allows the control circuit to capture phase difference information at multiple temporal points, improving distance measurement precision without requiring additional hardware components.
3Reliability
If varying pulse width signals are used, then noise in distance-related information is reduced, but the ease of operation and signal generation complexity increases
Solution Approach 1:
The control circuit implements dynamic pulse width modulation that automatically varies the photo gate signal characteristics within each frame. This dynamic signal generation reduces noise in distance-related information by creating temporal correlation patterns that enhance signal-to-noise ratio, while the automated control eliminates the need for manual signal adjustment.
Solution Approach 2:
The system changes the temporal parameter (pulse width) of photo gate signals according to a predetermined pattern, which reduces noise in distance measurements by creating distinguishable correlation patterns. This parameter modulation is automatically generated by the control circuit, maintaining ease of operation while improving reliability through noise reduction.
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 resolution and accuracy of depth information by adjusting the overlap of photo gate signals, simulating a triangular waveform to minimize noise and improve phase difference calculations between transmission and reception light signals.
Implementation Method 1
A time-of-flight (ToF) based image sensor may generate a 3D image of an object by measuring information related to a distance to the object from the ToF-based image sensor. The ToF-based image sensor may obtain the information related to the distance of the object from the ToF-based image sensor by measuring a light flight time until light reflected from the object is received after light is irradiated to the object.
Implementation Method 2
an image sensor configured to receive a reception light signal reflected from the object, wherein the image sensor includes a pixel array including a plurality of unit pixels
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.