Inter-reflection Detection Using Multi-frequency Phase Analysis

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Solution Overview

Problem

Existing three-dimensional measurement techniques, such as active stereo measurement, face accuracy issues due to detection failures in regions with inter-reflection, where lights from multiple light sources are received by a pixel, leading to decreased measurement accuracy.

Innovation Solution

An inter-reflection detection apparatus that uses a combination of low-frequency and high-frequency sinusoidal patterns to determine phase differences, with phase connection processing to accurately detect inter-reflection regions by comparing phase differences across multiple combinations of patterns, ensuring accurate detection without failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single frequency sinusoidal pattern is used for phase measurement, then the measurement process is simple, but inter-reflection detection accuracy deteriorates due to detection failures in certain regions

Engineering Contradiction:
Improvemeasurement process complexityVSAvoidinter-reflection detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent divides the measurement into multiple segments by using multiple frequency sinusoidal patterns (low-frequency and high-frequency) separately. Each frequency pattern provides phase information for specific regions, and by segmenting the measurement process, the system can detect inter-reflection more accurately without overwhelming complexity in a single measurement process.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a new dimension of analysis by comparing phase differences across multiple frequency patterns. Instead of relying on a single frequency measurement, the system adds the frequency dimension to the phase measurement, creating a multi-dimensional approach that improves inter-reflection detection accuracy while maintaining measurement simplicity.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Reliability

If phase difference is determined using only low-frequency and high-frequency combinations, then detection coverage is limited, but computational complexity increases when evaluating all combinations

Engineering Contradiction:
Improvedetection coverageVSAvoidcomputational complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies partial action by evaluating only the necessary frequency combinations (low-frequency and high-frequency) rather than all possible combinations. This selective approach provides sufficient detection coverage for inter-reflection detection while avoiding the excessive computational complexity that would result from evaluating every possible frequency combination.

Inventive Principle:
Principle #16Partial or excessive action

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 apparatus effectively detects inter-reflection regions with high accuracy, expanding the range of reliable detection and preventing detection failures, thereby improving the overall measurement precision in three-dimensional position determination.

Implementation Method 1

an irradiation unit configured to emit light having variable-frequency (cycle) sinusoidal patterns

Methodology Applied
Scientific EffectLight emission and reflection: Light

Implementation Method 2

the light projected to the measurement object reflects a plurality of times on the surface. This phenomena is called inter-reflection or multiple reflection

Methodology Applied
Scientific EffectInter-reflection: Reflection

Implementation Method 3

an image acquisition unit configured to acquire an image of an object irradiated with the light from the irradiation unit

Methodology Applied
Scientific EffectOptical imaging: Photography

Data Source

PatentEP3594616B1Inter-reflection detection apparatus, inter-reflection detection method, and program
Publication Date: 2024.10.30 OMRON CORP
  • EP3594616B1 patent drawingFigure 1~2
  • EP3594616B1 patent drawingFigure 3~4
  • EP3594616B1 patent drawingFigure 5

AI summary

Provided is an inter-reflection detection apparatus including: an irradiation unit configured to emit light having variable-frequency sinusoidal patterns; an image acquisition unit configured to acquire an image of an object irradiated with the light from the irradiation unit; a phase determination unit configured to determine a phase at each position in the image; and a detection unit configured to detect a region in which inter-reflection occurs. The detection unit is configured to determine a phase difference between a phase acquired from an image generated by irradiation of a low-frequency sinusoidal pattern and a phase acquired from an image generated by irradiation of a high-frequency sinusoidal pattern for a plurality of combinations of low-frequency waves and high-frequency waves, and determine that inter-reflection occurs in a region in which the phase difference for any one of the plurality of combinations is equal or more than a threshold.