Camera Quantum Efficiency Calibration Using Transmissive Filters
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Solution Overview
Problem
Conventional camera colorimetric calibration techniques are time-consuming, costly, and subjective, often resulting in less than optimal results due to high condition numbers and insufficient distinction between intensities for specific wavelengths, leading to skewed color representation.
Innovation Solution
A system utilizing a broad spectrum light emitting diode, light diffuser plates, and ultra-narrow band interference filters to produce filtered light at discrete wavelengths, allowing for accurate determination of quantum efficiency curves for red, green, and blue channels, minimizing subjectivity and improving calibration accuracy through non-overlapping wavelength spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional colorimetric calibration techniques using standard reflective color charts are used, then colorimetric calibration can be performed, but the process is time-consuming and costly
Solution Approach 1:
The patent extracts the calibration target from the conventional reflective color chart approach and replaces it with a transmissive color chart containing colored transparent patches. This allows the camera to capture light directly transmitted through the colored patches rather than reflecting off them, significantly reducing calibration time and complexity while maintaining accuracy
Solution Approach 2:
The patent replaces the mechanical/optical system of reflective color charts with a transmissive system using colored transparent patches. This substitution eliminates the need for complex illumination setups and reflective measurements, streamlining the calibration process to a simple capture and processing operation
2Measurement precision
If conventional calibration techniques using reflective color charts are used, then calibration can be achieved, but results are subjective and may be skewed
Solution Approach 1:
The patent removes the subjective element from calibration by using transmissive colored patches with known spectral transmission characteristics. The calibration becomes an objective measurement of light transmission through controlled filters rather than a subjective interpretation of reflected colors, eliminating operator bias and inconsistency
Solution Approach 2:
The patent introduces a transmissive color chart with known spectral characteristics as an intermediary between the light source and camera sensor. This intermediary provides a controlled, objective reference that eliminates the subjectivity inherent in reflective calibration methods
3Measurement precision
If broad band interference filters are used in conventional calibration, then calibration can be performed, but high condition numbers result in insufficient distinction between intensities
Solution Approach 1:
The patent segments the spectral response into distinct, non-overlapping wavelength bands using multiple narrow bandpass filters. Each filter is optimized for a specific wavelength range, creating discrete spectral channels that provide clear intensity distinction without the confusion caused by broad overlapping bands
Solution Approach 2:
The patent applies local quality optimization by designing each narrow bandpass filter to have peak transmission at specific wavelengths tailored to the camera's sensor characteristics. This localized spectral optimization ensures maximum intensity distinction at each wavelength region while keeping the overall system manageable
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
The system achieves colorimetric calibration with reduced time and cost, providing accurate and objective results with a condition number between 1 and 1.5, and a standard deviation of Gaussians less than 7 nm, ensuring reliable color representation.
Implementation Method 1
at least one broad spectrum light emitting diode configured to transmit light
Implementation Method 2
a plurality of interference filters, the plurality of interference filters configured to limit the light to a narrow band
Implementation Method 3
a camera configured to detect the transmitted light and to map an intensity value for each pixel of the camera
Data Source
AI summary
A system and method for colorimetric calibration is described herein. A system for performing color calibration is described, comprising at least one broad spectrum light emitting diode, at least one light diffuser plate, at least one interference filter, and a camera, the camera comprising at least one sensor for detection of colors, wherein a spectral response within 5% error of a ground truth method can be achieved. A method for performing color calibration is described, comprising transmitting light from at least one broad spectrum light emitting diode, scattering light with at least one light diffuser plate, filtering light with at least one interference filter, detecting light at a camera sensor, mapping an intensity value for each pixel of the camera sensor, and creating a quantum efficiency curve for each of red, green, and blue channels.