Time-of-Flight Camera Crosstalk Correction Matrix
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Solution Overview
Problem
Time-of-flight cameras suffer from significant phase distortion due to inter-pixel crosstalk, particularly in images with high spatial contrast, which affects the accuracy of depth measurements by introducing errors in phase values.
Innovation Solution
A calibration system that generates a crosstalk correction matrix using a combination of small and large phase gradient calibration targets, applied as an all-pass filter to correct phase images without affecting the amplitude images, thereby reducing inter-pixel crosstalk-induced phase variance without adding noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional time-of-flight camera imaging is used, then the camera can capture depth information, but inter-pixel crosstalk causes significant phase distortion particularly in high spatial contrast images
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual depth imaging to characterize and correct the crosstalk effects. A calibration target with known properties is imaged first to determine crosstalk coefficients, which are then stored and applied to correct subsequent depth images, preventing phase distortion from affecting measurement accuracy
Solution Approach 2:
The patent introduces an intermediary correction process between light detection and depth calculation. A crosstalk correction matrix is computed from calibration data and applied as an intermediate step to correct the raw phase images before final depth measurement, effectively mediating the harmful crosstalk effects without requiring hardware modification
2Measurement precision
If crosstalk correction is applied to reduce phase distortion, then phase measurement accuracy improves, but the complexity of the imaging system increases due to calibration requirements
Solution Approach 1:
The patent uses copying by creating a digital model of the crosstalk effects through calibration imaging. Instead of physically modifying the sensor array, a correction matrix (digital copy of the ideal response) is computed from calibration data and applied to correct operational images, simplifying the physical system while achieving correction
Solution Approach 2:
The patent applies parameter changes by modifying the phase values through mathematical transformation. The crosstalk correction process changes the phase parameters in the captured images by applying a correction matrix, effectively adjusting the measured values to compensate for crosstalk without changing the physical sensor characteristics
Data Source
AI summary
A time-of-flight camera calibration system includes a time-of-flight camera and a calibration processor. The calibration processor is coupled to the time-of-flight camera. The calibration processor is configured to receive an input phase image captured by the time-of-flight camera, and generate a blurred phase image by applying a low pass filter to the input phase image. The calibration processor is also configured to generate a crosstalk correction matrix based on the blurred phase image, and provide the crosstalk correction matrix to the time-of-flight camera.