Color Measurement in Dark Environments Using Reference Images
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Solution Overview
Problem
In dark environments with few light sources, it is challenging to accurately measure the color of objects using digital imaging apparatuses as it is difficult to specify a reference white color due to underexposure, leading to inappropriate color measurement.
Innovation Solution
An image processing technology that acquires both a measurement target image and a reference image, derives a reference color based on imaging parameters and pixel values, and calculates color evaluation values using a corrected reference color to address the issue of underexposure in dark environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If color measurement is performed in a dark environment using a measurement target image, then color measurement can be attempted in low-light conditions, but the reference white color cannot be properly specified due to underexposure, resulting in inaccurate color measurement
Solution Approach 1:
The system captures a reference image in a bright environment before capturing the measurement target image in a dark environment. This preliminary action of acquiring the reference image with proper exposure allows the system to have a valid reference white color available even when the measurement occurs in dark conditions where the reference white would be underexposed.
Solution Approach 2:
The system uses a reference image captured in a bright environment as a substitute for the reference white color that would be needed in the dark environment measurement. Instead of relying on an underexposed reference white in the dark image, the system copies the reference color information from the properly exposed reference image taken earlier.
2Measurement precision
If imaging parameters are adjusted to properly expose the reference white board, then the reference color can be accurately captured, but the measurement target object may become overexposed in bright environments
Solution Approach 1:
The system separates the reference color capture and measurement target capture into two distinct imaging operations. The reference image is captured with imaging parameters optimized for the reference white board, while the measurement target image is captured with parameters optimized for the measurement object. This segmentation allows each to be properly exposed without compromising the other.
Solution Approach 2:
The reference image is captured in advance under controlled lighting conditions where the reference white board can be properly exposed. This preliminary capture of reference color information allows the subsequent measurement of the target object to use different imaging parameters without being constrained by the need to also properly expose the reference white.
Data Source
AI summary
An image processing apparatus to measure a color of an object based on a measurement target image obtained by imaging the object includes an acquisition unit, a derivation unit, and a calculation unit. The acquisition unit acquires the measurement target image and a reference image different from the measurement target image. The derivation unit derives a reference color based on an imaging parameter used in imaging of the measurement target image, an imaging parameter used in imaging of the reference image, and a pixel value of at least one pixel in the reference image. The calculation unit calculates, with reference to the reference color, a color evaluation value of at least one pixel corresponding to the object in the measurement target image.