Color Target Substrate with Partial Filters for Spectral Reflectance
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Solution Overview
Problem
Accurately estimating the color appearance in a scene photographed is challenging due to the limitations of conventional methods, particularly with smartphone cameras, which struggle to capture spectral values accurately without specialized equipment and are prone to inaccuracies from changes in lighting and camera position when using multiple exposures.
Innovation Solution
A color target substrate with filters covering part of the sample surface, allowing for single-image spectral reflectance estimation using a digital still camera and a spectral analysis engine, which processes the image to determine spectral reflectance without requiring complex optical elements or multiple exposures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple exposures are used to photograph the same locations with different filters, then spectral values can be estimated, but lighting and camera position changes degrade accuracy
Solution Approach 1:
The patent applies preliminary action by pre-attaching multiple filters with different spectral transmittance characteristics to the color target substrate before measurement. This allows the camera to capture all filter data in a single exposure, eliminating the need for multiple exposures and thus preventing degradation from lighting and camera position changes. The filters are arranged in a predetermined pattern on the substrate, enabling the system to obtain multiple spectral measurements simultaneously rather than sequentially.
2Measurement precision
If specialized camera equipment is used to photograph through multiple filters, then spectral estimation accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies copying by transferring the filter array from the camera system to the color target substrate. Instead of requiring the camera to have multiple filters or complex optical elements, the filters are copied onto the substrate itself. This allows a standard digital camera to capture spectral information by photographing the filtered color target, eliminating the need for specialized camera equipment while maintaining measurement accuracy.
Solution Approach 2:
The patent applies dimensionality change by moving the filter array from the optical path dimension (in the camera) to the target object dimension (on the substrate). This spatial reorganization allows spectral measurement to be achieved through a simple photograph of the substrate rather than through complex in-camera optical filtering, effectively solving the problem with a different dimensional approach.
3Measurement precision
If in camera processing is used to handle multiple filter data, then spectral estimation can be performed, but processing inaccuracies increase
Solution Approach 1:
The patent applies self-service by having the color target substrate carry its own filtering function through the attached filters. The substrate essentially measures itself by reflecting light through the known filter characteristics, and the camera simply captures the result. This eliminates the need for complex in-camera processing to combine multiple filter measurements, as all filter data is simultaneously encoded in the single captured image through the predetermined filter arrangement on the substrate.
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 method enables accurate spectral reflectance estimation with stable lighting and camera position, avoiding the inaccuracies associated with multiple exposures and specialized equipment, while also addressing the limitations of constrained color gamuts in digital cameras.
Implementation Method 1
The filter unit includes three filter areas having spectral transmittance which is a square root of the spectral transmittance having a linear transform relation with a color-matching function
Data Source
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AI summary
Exemplary embodiments of the present disclosure are related to a color target and methods and systems for estimating a spectral reflectance of the color target based on an image of the color target. The color target can include a substrate having a target surface, a sample window formed in the substrate and defining perimeter within which a sample surface is disposed, and one or more filters disposed the sample surface. The one or more filters are configured to cover a first portion of the sample surface, while leaving a second portion of the sample surface uncovered.