Spectral Reflectance Estimation Using Dual Transformation Matrices
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Solution Overview
Problem
Current image forming apparatuses face challenges in achieving high-speed color management due to the inefficiency of spectral devices in measuring spectral reflectance, particularly when using white LEDs as light sources, which result in degraded precision and increased manufacturing costs.
Innovation Solution
A spectral characteristic obtaining apparatus that utilizes a primary and secondary transformation matrix to estimate spectral characteristics from light quantities in multiple wavelength bands, allowing for high-precision and high-speed measurement, even with white LEDs, by composing primary and secondary estimation results to improve accuracy across the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral reflectance is measured using a spectral device with multiple wavelength bands (31 or more bands), then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent divides the spectral measurement process into two stages: first, a rough measurement is performed using a small number of wavelength bands (3-16 bands) to quickly identify the measurement target; second, based on the preliminary results, a more detailed measurement is conducted using 31 or more wavelength bands only for specific bands where higher precision is needed. This segmentation approach reduces overall measurement time while maintaining necessary precision.
Solution Approach 2:
The patent applies partial action by performing full high-precision measurement (31 or more bands) only partially - specifically, only for wavelength bands where the preliminary rough measurement indicates higher precision is required. For other bands, the rough measurement results are sufficient, avoiding unnecessary time consumption from excessive full-band high-precision measurement.
2Use of energy by moving object
If white LED is used as light source to achieve high luminance and efficiency, then energy efficiency is improved, but spectral uniformity deteriorates causing degraded measurement precision in certain wavelength bands
Solution Approach 1:
The patent changes the parameter of light exposure time dynamically based on the spectral characteristics of the white LED light source. Specifically, for wavelength bands where the LED emits lower light quantity (such as certain regions in the spectrum), the light exposure time is extended to compensate. This parameter adjustment ensures that sufficient light reaches the detector across all wavelength bands, maintaining measurement precision while retaining the energy efficiency benefits of using white LED.
3Measurement precision
If light exposure time is increased to improve signal strength in low-luminance wavelength bands, then measurement precision is improved, but measurement speed decreases
Solution Approach 1:
The patent applies local quality by differentiating light exposure time settings across different wavelength bands rather than using a uniform exposure time. For wavelength bands where the white LED provides sufficient luminance, a shorter exposure time is used. For bands with lower luminance output, extended exposure time is applied locally to those specific bands only. This localized adjustment maintains overall measurement speed while improving precision where needed.
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
Enables precise and rapid estimation of spectral reflectance, reducing errors and maintaining high-speed measurement capabilities while minimizing the need for specialized light sources or sensors, thus reducing costs.
Implementation Method 1
measurement of colorimetric values (e.g., XYZ or L*a*b* defined by CIE (International Commission On Illumination)), inspection of color tone of printed material, and adjustment of an image forming process are performed based on spectral reflectance from light diffused from a surface of a printed material measured by the spectral device
Implementation Method 2
the white LED is formed of an LED that emits blue light and a fluorescent material that absorbs the blue light and emits yellow light
Data Source
AI summary
A spectral characteristic obtaining apparatus includes a detection unit detecting light quantities in plural wavelength bands from a measurement target, a storage unit storing pre-obtained spectral characteristics of the measurement target, a calculation unit calculating a primary transformation matrix from the light quantities and the pre-obtained spectral characteristics of at least one reference sample and a secondary transformation matrix from one of the pre-obtained spectral characteristics corresponding to a primary wavelength band and another one of the pre-obtained spectral characteristics corresponding to a secondary wavelength band, an estimation unit estimating the spectral characteristics of the measurement target by performing a primary estimation on the light quantities in the plural wavelength bands by using the primary transformation matrix, performing a secondary estimation on a result of the primary estimation by using the secondary transformation matrix, and compositing a result of the secondary estimation with the result of the primary estimation.