Time-of-Flight Camera Depth Correction Algorithm
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Solution Overview
Problem
Time-of-flight cameras using amplitude-modulated continuous light suffer from systematic depth errors due to non-harmonic signals, leading to aliasing effects and requiring intricate, time-consuming calibration processes that are not suitable for industrial production.
Innovation Solution
A method for corrected depth measurement that involves calculating a ground truth value by subtracting a pixel-dependent offset, applying a pixel-independent function, and adding a pixel-independent offset, which can be performed in real-time without additional devices or extensive processing power, using a look-up table for memory efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If camera-, integration time- or pixel-wise corrections are employed to correct systematic depth error, then measurement precision is improved, but device complexity and calibration time increase significantly
Solution Approach 1:
The patent transforms the complex per-pixel correction functions into simple parameter-based corrections. By determining pixel-dependent offset values and pixel-independent correction parameters through a simplified calibration process, the system achieves accurate depth correction using basic arithmetic operations instead of complex functions for each pixel.
Solution Approach 2:
The correction approach is segmented into two distinct components: pixel-dependent offset values (cm) that account for individual pixel characteristics, and pixel-independent correction parameters (g and ct) that apply globally. This segmentation allows efficient processing where most pixels share the same correction function, reducing overall complexity.
2Measurement precision
If intricate calibration processes are used to correct depth errors, then measurement precision is improved, but productivity decreases due to time consumption
Solution Approach 1:
The calibration process is performed preliminarily during camera production or initialization, determining all necessary offset values and correction parameters in advance. Once calibrated, the camera can operate at full speed without requiring repeated calibration, as the correction parameters are stored and applied automatically during normal operation.
3Measurement precision
If comprehensive calibration data is stored for each pixel, then measurement precision is improved, but memory space requirements increase
Solution Approach 1:
The patent reduces memory requirements by transforming complex per-pixel correction functions into simple parameter sets. Instead of storing extensive calibration data for each pixel, only compact offset values (cm) and global correction parameters (g and ct) are stored, which can be efficiently implemented using look-up tables or simple mathematical functions.
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
Enables accurate and efficient depth correction in time-of-flight cameras, reducing memory requirements and processing power while minimizing the need for individual pixel calibration, facilitating rapid 3D image recording.
Implementation Method 1
Time-of-flight cameras are used to provide pixelwise depth information in an image of a three-dimensional object or scenery
Implementation Method 2
the phase of the received light can be deduced from the amplitude and by the relative phase difference the time of flight and thus the distance to the reflecting object can be determined
Implementation Method 3
the camera emits a continuous field of amplitude-modulated light, which is reflected from objects in the field of view of the camera
Data Source
AI summary
A method for corrected depth measurement with a time-of-flight camera using amplitude-modulated continuous light. In order to enable an accurate and efficient depth measurement with a time-of-flight camera, the method includes, for each of a plurality of pixels of a sensor array of the camera: acquiring with the camera a raw depth value rm for the pixel; and automatically calculating a ground truth value rt according to: rt=g(rm−cm)+ct, to correct a systematic depth error of the raw depth value rm, wherein cm is a pixel-dependent first offset, g is a pixel-independent first function and ct is a pixel-independent second offset.