Defective Pixel Detection in Photoelectric Conversion Devices
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Solution Overview
Problem
Photoelectric conversion devices, such as CCD and CMOS linear sensors, often suffer from defective pixels due to low saturation levels or high dark current, leading to reduced image quality, and existing methods struggle to accurately detect and correct these defects, especially white-spot pixels.
Innovation Solution
A method involving a photoelectric conversion device that obtains pixel values at two different times in dark conditions, calculates the noise amount by subtracting these values, and determines pixels with noise above a threshold as defective, allowing for correction to normal pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-time-point dark pixel value detection is used, then the detection process is simple and fast, but the detection precision is insufficient to accurately identify defective pixels
Solution Approach 1:
The patent performs preliminary detection at a first time point to identify candidate defective pixels, then conducts further verification at a second time point. This staged approach allows accurate detection while avoiding the need for complex simultaneous multi-parameter measurement, resolving the contradiction between precision and complexity.
Solution Approach 2:
The detection process is segmented into multiple stages: initial dark pixel value acquisition at first time point, comparison with reference values, identification of candidate defective pixels, and final confirmation at second time point. This segmentation enables precise detection without requiring all measurement operations to occur simultaneously, thus managing complexity while maintaining accuracy.
2Measurement precision
If multiple time points are used for dark pixel value detection, then the detection accuracy improves, but the detection time increases
Solution Approach 1:
The patent uses the first time point detection results as a preliminary screening step to identify candidate defective pixels before performing the second time point measurement. This preliminary action reduces the overall detection time by avoiding unnecessary second measurements for normal pixels, while still achieving high accuracy through targeted verification of suspects.
Solution Approach 2:
The patent applies partial action by performing complete two-time-point detection only for candidate defective pixels identified in the first stage, while using simplified single-time-point assessment for the majority of normal pixels. This selective approach achieves high detection accuracy for critical cases without proportionally increasing overall detection time.
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
Effectively detects and corrects defective pixels, improving image quality by accurately identifying and addressing both white-spot and black-spot pixels, thereby enhancing the performance of devices like multifunction peripherals and cameras.
Implementation Method 1
a photoelectric conversion element to generate an image signal according to an intensity of light being input
Data Source
AI summary
A photoelectric conversion device includes a photoelectric conversion element to generate an image signal according to an intensity of light being input and circuitry. The circuitry obtains pixel values in dark time, respectively, for at least a first time and a second time. The second time is longer than the first time. The pixel values in dark time represent pixel values obtained when no light is input to the photoelectric conversion element. The circuitry obtains a subtraction between the pixel values for the first time and the pixel values for the second time. The circuitry detects a noise amount based on the subtraction. The circuitry determines at least one pixel having the detected noise amount that is equal to or greater than a predetermined first threshold value, as a defective pixel of the photoelectric conversion element.