Color Evaluation Device Affine Transformation Black Correction

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Solution Overview

Problem

Existing color evaluation methods are inadequate for accurately converting intermediate colors from color sensors to quantitative digital values due to environmental factors like varying light sources and photography conditions, particularly failing to correct colors near black accurately through affine transformations.

Innovation Solution

A color evaluation device that uses a storage unit to store color information of four or more reference colors photographed in a first environment, determines conversion coefficients based on changes in these reference colors between environments, and applies an affine transformation formula to correct sensor colors as if they were photographed in the first environment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If linear transformation with origin unmoved is used for color correction, then the transformation is simple, but colors close to black cannot be corrected accurately

Engineering Contradiction:

Improvesimplicity of transformationVSAvoidcolor correction accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the transformation model from linear transformation with fixed origin to affine transformation with translation. This allows the transformation to accommodate color values close to black by adding translation parameters, thereby improving correction accuracy without significantly complicating the transformation process.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extends the color space transformation from 3D linear transformation to 4D affine transformation by adding translation dimensions. This dimensional extension enables accurate representation and correction of colors near black that would otherwise be lost in the origin-constrained linear transformation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If three-color color sample is used for correction, then the correction process is simple, but translation in color space is not allowed

Engineering Contradiction:

Improvecorrection process complexityVSAvoidcorrection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the color correction process into separate components: scaling (linear transformation) and translation (color shift). By using four or more color samples, the system can independently determine scaling factors and translation vectors, allowing both linear and affine transformations to be applied systematically.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary measurements of four or more reference colors in advance to establish the transformation relationship between different lighting conditions. This preliminary action enables the system to pre-calculate conversion coefficients that can be applied to correct sensor colors without requiring complex real-time processing.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If coordinate transformation with fixed origin is used, then the transformation is constrained, but correction amount for black colors becomes insufficient

Engineering Contradiction:

Improvetransformation flexibilityVSAvoidcorrection amount for black colors

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent makes the transformation dynamic by allowing the origin to shift based on the input color values. Instead of a fixed origin transformation, the system applies translation that adapts to the position of colors in the color space, particularly improving the correction of black and dark colors that would otherwise remain inaccurate.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11398055B2Color evaluation device, color evaluation method, and indication object used in color evaluation method

Publication Date: 2022.07.26 HITACHI LTD

AI summary

A calculation device comprises a color evaluation unit that acquires a sensor color and four or more reference colors from photography data from a measurement time when an indication object was photographed in a second photography environment; determines coefficients for color conversion between a first and the second photography environments based on the amount of change from color information for the reference colors in the first photography environment, which has been read from a calculation device storage unit, to color information for the reference colors in the second photography environment, which has been acquired from the photography data; and uses the sensor color acquired from the photography data from the measurement time and the color conversion coefficients to correct the sensor color to the color that would have been photographed in the first photography environment by solving a conversion formula including terms representing an affine transformation consisting of translation.