Color Camera Calibration for Optical Resolution and Uniformity

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Solution Overview

Problem

Standard imaging colorimeters are too large to easily scan the Eye Motion Box (EMB) of Near Eye Displays (NED) systems, and color cameras degrade resolution due to demosaicing algorithms like deBayering.

Innovation Solution

Use an off-the-shelf color camera to measure color uniformity and resolution by converting its output to XYZ color space using a conversion matrix generated from colorimeter measurements and overcoming deBayering effects through mathematical operations on a raw green channel image.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an imaging colorimeter is used to measure color uniformity and resolution, then measurement accuracy is improved, but device size becomes too large to easily scan the Eye Motion Box of Near Eye Displays

Engineering Contradiction:

Improvecolor uniformity measurement accuracyVSAvoidcolorimeter size

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent uses a color camera to capture images of the optical system output, which are then processed to replicate the measurement capabilities of an imaging colorimeter. The camera captures RGB images that are converted to XYZ color space values through a conversion matrix, creating a functional copy of the colorimeter's measurement capability without requiring the physical size of a traditional colorimeter.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the physical imaging colorimeter with a computational approach using a standard color camera. Instead of relying on the camera's native RGB output, the system substitutes the mechanical/colorimetric measurement process with mathematical operations including conversion matrix multiplication and deBayering correction, achieving colorimeter-level measurements through software processing rather than specialized hardware.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If a color camera is used to measure optical properties, then device size and ease of operation are improved, but resolution measurement accuracy degrades due to demosaicing algorithms

Engineering Contradiction:

Improveease of scanning EMBVSAvoidresolution measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent acknowledges the deBayering process inherently degrades resolution, but converts this harmful effect into a beneficial measurement approach. By deliberately using the deBayered image and applying correction factors, the system transforms the camera's limitation into a workable measurement methodology. The conversion matrix and correction algorithms compensate for the resolution loss, allowing the use of inexpensive color cameras while maintaining measurement accuracy.

Inventive Principle:

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

Solution Approach 2:

The patent changes the color space parameters from the camera's native RGB to the standard XYZ color space through a conversion matrix. This parameter transformation allows the system to work with standard colorimetric data while accounting for the camera's specific spectral response. The conversion matrix adjusts the RGB values to XYZ values, effectively recalibrating the camera output to match colorimeter standards despite the resolution degradation from deBayering.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a color camera with deBayering is used, then cost and accessibility are improved, but color space accuracy deteriorates requiring conversion to XYZ values

Engineering Contradiction:

Improvecamera availabilityVSAvoidcolor space accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent introduces a conversion matrix as an intermediary between the color camera's RGB output and the standard XYZ color space. This conversion matrix acts as a mediator that translates the camera's proprietary color space into the universal XYZ color space used by colorimeters. The matrix accounts for the camera's specific sensor characteristics and filter responses, enabling accurate color measurements from any standard color camera without requiring proprietary hardware or software.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250354867A1Characterizing optical system performance with a color camera

Publication Date: 2025.11.20 LUMUS LTD

AI summary

A device, system, and method are provided for processing an output of a color camera, such that the color camera may be used to measure color uniformity and resolution of an optical system. The processing includes converting an output of the color camera into an XYZ color space using a conversion matrix. The conversion matrix is generated by capturing color images and colorimeter measurements of three different wavelength ranges of light. The processing also includes overcoming the deBayering effect of the color camera to measure a resolution of the optical system using an optical test target displayed by the optical system. The optical test target has a uniform appearance along a direction of homogeneity. The resolution is determined based on a one-dimension image generated by performing a mathematical operation along the direction of homogeneity.