ToF Sensor Signal Processing for Transparent Subject Distance Correction

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Solution Overview

Problem

Accurate acquisition of distance information is challenging in the presence of transparent subjects due to low signal-to-noise ratio and interference from external light, especially in outdoor environments, which affects 3D shape construction and environment mapping.

Innovation Solution

A signal processing device and method that acquire histogram data of flight time, determine if a subject is transparent based on peak information, and correct three-dimensional coordinates and color information using a transparent subject determination unit, enabling accurate distance measurement and color correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If spot-shaped pulse light is used to expand reach distance, then the number of detected reflected light increases, but the SN ratio becomes low and peak detection becomes difficult

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidSN ratio

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Multiple adjacent pixels are combined to form a multipixel region, merging their detection capabilities to improve the SN ratio for peak detection in histogram generation

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The problem is solved by transitioning from analyzing a single peak to analyzing multiple peaks across different multipixel regions, adding a spatial dimension to the detection approach

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If multipixel unit is used for light reception to improve SN ratio, then power consumption is reduced, but spatial resolution is lowered

Engineering Contradiction:

ImproveSN ratioVSAvoidspatial resolution

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The pixel array is segmented into multiple multipixel regions, each responsible for detecting reflected light in specific spatial directions, thereby maintaining spatial resolution while improving SN ratio through localized pixel cooperation

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If transparent subject is present, then distance information cannot be accurately acquired, but conventional methods cannot distinguish transparent subjects from opaque subjects

Engineering Contradiction:

Improvedistance information accuracyVSAvoidtransparent subject identification

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The system performs excessive detection by identifying multiple peak positions in the histogram data, then selectively processes only the relevant peaks corresponding to the actual subject, ignoring peaks caused by transparent objects

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The histogram analysis serves as an intermediary step that reveals the presence of transparent subjects through multiple peaks, enabling the system to distinguish between transparent and opaque subjects before final distance calculation

Inventive Principle:

Principle #24Intermediary (Mediator)

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 acquisition of distance and color information even with transparent subjects, improving 3D reconstruction and environment mapping by correcting for refraction and interference effects.

Implementation Method 1

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

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Implementation Method 2

using a light receiving element referred to as a single photon avalanche diode (SPAD) in each pixel for light reception

Methodology Applied

Scientific EffectSingle photon avalanche diode detection: Avalanche Breakdown

Implementation Method 3

generates a histogram of a flight time of the pulse light, and calculates a distance to the object from the flight time corresponding to a peak of the histogram

Methodology Applied

Scientific EffectHistogram analysis of flight time:

Data Source

PatentUS20240362822A1Signal processing device and signal processing method

Publication Date: 2024.10.31 SONY GROUP CORP

AI summary

There is provided a signal processing device and a signal processing method capable of accurately acquiring distance information in a case where a transparent subject is present. The signal processing device includes an acquisition unit that acquires histogram data of a flight time of irradiation light to a subject, a transparent subject determination unit that determines whether or not the subject is a transparent subject on the basis of peak information indicated by the histogram data and three-dimensional coordinates of the subject calculated on the basis of the histogram data, and an output unit that outputs the three-dimensional coordinates of the subject in which color information or three-dimensional coordinates of the subject is corrected on the basis of a transparent subject determination result of the transparent subject determination unit. The technology of the present disclosure can be applied to, for example, a signal processing device and the like that corrects distance information acquired by a ToF sensor of a direct ToF system.