Image reproducing apparatus white balance offset prevention

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Solution Overview

Problem

Digital cameras recording raw pixel data face challenges in reproducing images with accurate white balance when the color space of the reproducing apparatus differs from the camera's optimum color space, leading to white balance offsets.

Innovation Solution

An image reproducing apparatus that reads and corrects image data using color temperature and color space information recorded during imaging, employing a first color space corrector, a color temperature adjuster, and a second color space corrector to ensure accurate white balance and color space conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the reproducing apparatus freely adjusts the color space to suit user demand, then the adaptability of the reproducing apparatus is improved, but the white balance accuracy deteriorates because the color temperature information is optimized only for the camera's color space

Engineering Contradiction:

Improvecolor space adaptabilityVSAvoidwhite balance accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent segments the color space conversion process into two distinct stages: first converting from the camera's color space to an intermediate color space using camera-specific conversion coefficients, then converting from the intermediate color space to the target color space using reproducing apparatus-specific conversion coefficients. This segmentation allows each stage to be optimized independently, preserving white balance accuracy while enabling color space adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediate color space as a mediator between the camera's color space and the target color space. The intermediate color space serves as a common reference that contains the camera's color temperature information while also being convertible to various target color spaces, thereby resolving the conflict between white balance accuracy and color space adaptability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the reproducing apparatus uses color temperature information optimized for the camera's color space, then the white balance accuracy is maintained, but the ability to reproduce images in optional color spaces deteriorates

Engineering Contradiction:

Improvewhite balance accuracyVSAvoidcolor space conversion capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent divides the color space conversion into two sequential steps: first applying camera-specific conversion coefficients to transform from the camera's color space to an intermediate color space, then applying reproducing apparatus-specific conversion coefficients to transform from the intermediate color space to the target color space. This segmentation preserves white balance accuracy in the first step while enabling color space adaptability in the second step.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate color space serves multiple functions: it acts as the target color space for the camera's color temperature optimization, simultaneously serves as the source color space for conversion to various optional color spaces, and provides a universal reference framework that works across different camera and reproducing apparatus configurations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If raw pixel data are recorded without color space processing, then the manufacturing simplicity is improved, but the white balance accuracy in reproduction deteriorates when color space differs between imaging and reproducing

Engineering Contradiction:

Improverecording process simplicityVSAvoidwhite balance accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent performs color space conversion coefficients preparation and storage as preliminary actions during the imaging process. The camera records not only raw pixel data but also pre-calculated color space conversion coefficients that enable accurate white balance reproduction. This preliminary preparation maintains recording simplicity while ensuring reproduction accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent copies and stores color space conversion coefficients along with the raw pixel data. These copied coefficients are then applied during reproduction to transform the color space, thereby maintaining the simplicity of raw data recording while achieving accurate color reproduction through the copied transformation information.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS7719727B2Image reproducing apparatus for preventing white balance offset and solid-state imaging apparatus

Publication Date: 2010.05.18 FUJIFILM CORP

AI summary

A digital camera supplies raw pixel data in a raw data mode to a digital processor. In the digital processor, a white balance decision circuit determines a white balance gain as color temperature information. The digital processor outputs the image data and the white balance gain thus determined over data bus to an interface unit. The linear matrix coefficients, supplied from a system controller, are sent over the data bus to the interface unit, which interfaces the data in accordance with a recording format, according to which the three sorts of data are recorded in a storage unit responsive to a control signal.