Pattern Light Projection for Ghost Image Detection in Distance Measurement

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Solution Overview

Problem

Existing distance measurement techniques using pattern projection methods struggle to effectively detect regions of multiple reflection between high-gloss and complexly shaped image capturing target objects, leading to measurement errors due to ghost images and incorrect detection of light angles.

Innovation Solution

An image processing apparatus that projects pattern light, captures images, calculates line directions, decides epipolar lines based on positional relationships, and determines regions as either first or second regions based on angle differences, using edge detection filters or spatial frequency analysis to detect multiple reflected light regions and adjust projection patterns accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If pattern projection method is used for distance measurement, then distance measurement capability is provided, but measurement precision deteriorates due to multiple reflection causing ghost images and incorrect light angle detection

Engineering Contradiction:

Improvedistance measurement precisionVSAvoidmultiple reflection interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by detecting multiple reflected light regions before performing distance measurement. The system first identifies regions affected by multiple reflections using image processing techniques, then excludes these regions from subsequent measurement calculations, preventing measurement errors before they occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and isolates the problematic multiple reflected light regions from the overall measurement process. By detecting these regions separately and excluding them from distance measurement calculations, the system removes the harmful influence of multiple reflections on measurement precision.

Inventive Principle:

Principle #2Taking out (Extraction)

2Extent of automation

If image processing is applied to captured images, then image analysis is enabled, but reliability deteriorates due to ghost images appearing as noise causing malfunction

Engineering Contradiction:

Improveimage processing automationVSAvoidimage processing reliability

Core Design Contradiction:

Extent of automationVSReliability

Solution Approach 1:

The patent converts the harmful effect of multiple reflections into a detectable feature. By analyzing characteristics of reflected light patterns, the system identifies multiple reflected light regions and uses this information to improve the reliability of image processing by excluding problematic areas from analysis.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If existing multiple reflection detection method (Japanese Patent No. 3800842) is used, then even number of times reflection detection is enabled, but detection completeness deteriorates because odd number of times reflection errors cannot be detected

Engineering Contradiction:

Improvemultiple reflection detection accuracyVSAvoiddetection coverage for different reflection orders

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the detection parameter from relying on image inversion characteristics (which only work for even-order reflections) to analyzing line direction angles of pattern light. This parameter change enables detection of both even and odd order multiple reflections by comparing the angle between epipolar lines and pattern light lines, significantly improving detection coverage.

Inventive Principle:

Principle #35Parameter changes

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

This approach reduces measurement errors by accurately identifying multiple reflected light regions, thereby improving the accuracy of distance measurements and reducing noise in image processing.

Implementation Method 1

the incident angle of the pattern light that is reflected by the measurement target object and becomes incident on an image capturing apparatus

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS8938099B2Image processing apparatus, method of controlling the same, distance measurement apparatus, and storage medium

Publication Date: 2015.01.20 CANON KK

AI summary

An image processing apparatus includes a projection unit adapted to project pattern-light onto an object; an image capturing unit adapted to capture the object; a calculation unit adapted to calculate a line direction of the pattern-light in each predetermined region of the image; a decision unit adapted to decide an epipolar-line based on a relationship between the projection unit and the image capturing unit; a determination unit adapted to determine whether an angle made by the direction of the epipolar-line and the line direction is not more than a predetermined value; and a detection unit adapted to detect a first-region when the angle is not more than the predetermined value, and detect a second-region when the angle is more than the predetermined value. The projection unit projects the pattern-light having a line component parallel to the epipolar-line.