dToF Sensor Position Deviation Correction via Histogram Similarity
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Solution Overview
Problem
dToF sensors experience deviations in position information due to calibration errors, distance measurement errors, and exposure timing deviations when correlating three-dimensional position data with RGB camera images, particularly in low-reflectivity or distant subjects and outdoor environments with strong external light disturbances.
Innovation Solution
A signal processing apparatus and method that acquire a distance histogram from a dToF sensor, determine if a distance measurement point requires positional correction, and execute correction processing based on similarity analysis with nearby points, adjusting three-dimensional coordinates to correct positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spot-shaped pulse light is used to expand reach distance and increase reflected light detection, then the number of detection increases, but the spatial resolution decreases due to sparse pixel detection
Solution Approach 1:
The pixel array is divided into multiple multipixel groups, where each multipixel consists of multiple adjacent pixels working together as a single detection unit. This segmentation allows the system to maintain high detection reliability through increased photon collection while managing the spatial resolution trade-off through systematic processing of each multipixel's data
Solution Approach 2:
Multiple adjacent pixels are merged into a single multipixel detection unit to increase the effective detection area and improve the signal-to-noise ratio. By combining signals from multiple pixels, the system achieves better detection reliability for spot-shaped pulse light while the multipixel structure enables selective processing to maintain overall spatial resolution
2Length of stationary object
If distance measurement is performed in low-reflectivity or distant subject environments with external light disturbance, then the measurement range is extended, but the SN ratio decreases making peak detection difficult
Solution Approach 1:
The system dynamically adjusts the pulse light emission parameters and detection settings based on the measurement environment. By adapting the illumination intensity, pulse width, and detection sensitivity according to external conditions, the system maintains adequate SN ratio while extending measurement range to distant or low-reflectivity subjects
Solution Approach 2:
The system uses periodic pulse light emission with optimized timing and duration. By emitting short, intense pulse light periodically and synchronizing detection with the expected return time, the system improves SN ratio through time-gated detection while maintaining extended measurement range through repeated measurements and histogram analysis
3Adaptability or versatility
If three-dimensional position information is correlated with RGB camera images, then volumetric capture and SLAM applications are enabled, but positional deviation occurs due to calibration errors and measurement errors
Solution Approach 1:
The system implements feedback mechanisms where the detected position information from the dToF sensor is continuously compared with corresponding RGB camera image data. Calibration errors and measurement deviations are detected through this feedback loop, and correction processing is applied to align the three-dimensional position information with the camera coordinate system, thereby maintaining accuracy while enabling versatile applications
Solution Approach 2:
A coordinate transformation and calibration system acts as an intermediary between the dToF sensor and RGB camera. This intermediary layer processes and reconciles the different coordinate systems and measurement references, correcting positional deviations caused by calibration errors and enabling accurate integration of data from both sensors for volumetric capture and SLAM applications
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 effectively corrects positional deviations in dToF sensor data, improving the accuracy of three-dimensional coordinates and enhancing the reliability of distance measurements in challenging environments.
Implementation Method 1
A ToF sensor of a direct ToF method (hereinafter, also referred to as a dToF sensor) detects reflected light, which is pulse light reflected by an object, using a light receiving element referred to as a single photon avalanche diode (SPAD) in each pixel for light reception
Implementation Method 2
the dToF sensor generates a histogram of time of flight of the pulse light, and calculates a distance to the object from the time of flight corresponding to a peak of the histogram
Data Source
AI summary
There is provided a signal processing apparatus and a signal processing method enabling correction of a deviation of position information of a dToF sensor. The signal processing apparatus includes: a data acquisition unit configured to acquire a distance histogram that is histogram data of time of flight of irradiation light at a predetermined distance measurement point of a distance measurement sensor; a check target determination unit configured to determine whether or not the predetermined distance measurement point is a distance measurement point as a positional deviation check target; and a coordinate correction unit configured to execute correction processing of correcting three-dimensional coordinates of the predetermined distance measurement point, the three-dimensional coordinates being computed from the distance histogram, on the basis of a determination result of similarity between the distance histogram of the predetermined distance measurement point and the distance histogram of a nearby distance measurement point near the predetermined distance measurement point, in a case where the predetermined distance measurement point is a distance measurement point as a positional deviation check target. The technology of the present disclosure can be applied to, for example, a signal processing apparatus or the like that calculates three-dimensional coordinates of an object by using a distance histogram output from a distance measurement sensor.