Smartphone-Based Gamma Correction Table Generation
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Solution Overview
Problem
Ordinary users face challenges in calibrating image forming apparatuses due to the need for expensive dedicated colorimeters to match color values between different devices, making it difficult to perform accurate gamma correction for gradation characteristics.
Innovation Solution
A calibration system using a smartphone as an imaging device captures images of a test chart and a reference chart, calculating weighting coefficients based on color intensity to generate a gamma correction table that corrects gradation characteristics, allowing for accurate color matching without the need for advanced equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated colorimeter is used to match color values between image forming apparatuses, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a digital camera to capture images of test charts and simulate the function of a dedicated colorimeter. By copying the measurement capability through image capture and processing, the system achieves color value measurement without requiring expensive specialized equipment. The camera captures RGB values which are then processed to derive colorimetric data.
Solution Approach 2:
The patent replaces expensive, sophisticated colorimeters with inexpensive digital cameras that are widely available. The camera serves as a disposable or readily replaceable component that can be easily updated or replaced without significant cost, thereby reducing the barrier to entry for color calibration.
2Ease of operation
If a digital camera is used instead of a dedicated colorimeter, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent introduces a test chart with known color patches as an intermediary between the camera and the color measurement task. The test chart provides reference color values that mediate the conversion from camera RGB readings to accurate colorimetric data, enabling precise measurement despite using a simple camera.
Solution Approach 2:
The patent replaces the complex optical and mechanical systems of a dedicated colorimeter with a simpler digital camera system. The measurement function is achieved through software processing of images rather than through specialized hardware, substituting computational methods for physical measurement mechanisms.
3Manufacturing precision
If weighting coefficients are calculated based on color intensity, then manufacturing precision is improved, but calculation complexity increases
Solution Approach 1:
The patent applies local quality by calculating weighting coefficients specific to each color patch based on its individual color intensity characteristics. Rather than using a uniform correction approach, the system tailors the weighting to the local properties of each patch, improving the precision of gradation correction for different color regions.
Solution Approach 2:
The patent dynamically adjusts the weighting coefficients based on the color intensity parameter of each patch. By changing the weighting parameter according to the specific color intensity values, the system optimizes the correction process for different color regions, achieving higher precision in gradation characteristics correction.
Data Source
AI summary
A calibration system includes an imaging device, an image forming apparatus, and a table generating section. The image forming apparatus prints a test chart containing patches of colors on a sheet. The imaging device captures images of a reference chart containing patches corresponding to the patches in the test chart and the test chart on the sheet together to generate a picture. The table generating section: calculates a weighting coefficient for each of the patches in the picture based on a color intensity of the patch; calculates, as a representative value for each of gradations of color values of the patches in the picture, a weighted average of color values of the patches in the gradation based on the weighting coefficient; and generates a gamma correction table for correcting gradation characteristics of the image forming apparatus to gradation characteristics in accordance with the reference chart based on the representative values.