3D Image Sensor Calibration for ToF Depth Accuracy
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Solution Overview
Problem
Time-of-Flight (ToF) sensors face accuracy issues due to non-ideal factors such as mismatch and dark current in photodetectors, leading to erroneous depth measurements.
Innovation Solution
A photo-detecting apparatus and calibration method that includes a 3D image sensor with a calibration data generator producing IQ-mismatch, non-linearity, temperature, and offset calibration data to correct for these errors, stored in a storage medium for use by a 3D image generator to produce accurate 3D images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodetectors are used in ToF sensors for depth measurement, then optical-to-electrical conversion is enabled, but sensing accuracy deteriorates due to mismatch and dark current
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual depth measurement operations. The system captures calibration images under controlled conditions (with lens cap covering the lens) to establish reference data for IQ-mismatch, non-linearity, and offset corrections. This pre-calibration process creates lookup tables and correction parameters that are stored and applied during subsequent measurements, eliminating the need for real-time correction calculations and ensuring accurate depth measurements from the start.
Solution Approach 2:
The patent implements feedback through a multi-stage calibration process where the system continuously refines its measurement accuracy. The calibration procedure captures images at different phases and depths, analyzes the results to identify errors (IQ-mismatch, non-linearity, offset), and generates correction parameters that are fed back into the measurement system. This feedback loop ensures that the system compensates for photodetector imperfections and maintains high sensing accuracy.
2Measurement precision
If calibration data is stored in a storage medium, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies copying by creating digital representations (lookup tables) of calibration data that can be stored and reused. Instead of performing complex real-time calculations to correct for IQ-mismatch and non-linearity, the system pre-calculates correction values and stores them in lookup tables within the storage medium. During actual measurements, the system simply copies and applies the appropriate correction values from these tables, significantly reducing computational complexity while maintaining high 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 calibration method significantly improves the accuracy of depth measurements by accounting for IQ-mismatch, non-linearity, temperature, and offset errors, enhancing the overall sensing quality and reliability of 3D image generation.
Implementation Method 1
which include a plurality of photodetectors for performing optical-to-electrical conversion
Data Source
AI summary
A photo-detecting apparatus includes an image sensor and a 3D image generator. The image sensor having a plurality of 3D photodetectors is configured to output a raw data. The 3D image generator having a storage medium for storing a calibration data is configured to output a 3D image according to the raw data and the calibration data. The calibration data includes at least one of an IQ-mismatch calibration data, a non-linearity calibration data, a temperature calibration data and an offset calibration data.