Sensing Circuit Photodegradation Correction
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Solution Overview
Problem
Existing optical sensors using amorphous silicon thin film transistors face deviations in luminance detection due to photodegradation, which cannot be accurately corrected, especially in cases where the document contains less than 10% white color, and this issue persists in sensors detecting ambient brightness.
Innovation Solution
A sensing circuit employing two sensing elements with the same characteristics, where one element's energy is reduced by a predetermined rate, allowing for the calculation of degradation rates and accurate detection values by comparing output signals and stored degradation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two photoelectric conversion elements with the same structure are used to correct photodegradation, then luminance detection accuracy is improved, but the correction fails when the document contains less than 10% white color
Solution Approach 1:
The patent applies local quality by differentiating the functional roles of the two photoelectric conversion elements: the first element (sensor pixel) is optimized for detecting actual luminance signals from the document, while the second element (reference pixel) is specifically designed to experience controlled photodegradation by receiving reflected light from a white reference surface. This localized functional differentiation enables accurate correction even when document content varies significantly in white color proportion.
2Reliability
If a high reflectance reflection surface is provided to match white document reading, then the degree of photodegradation between elements is equalized, but this approach is ineffective for color print images with less than 10% white color
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the integrated luminance parameter received by the reference photoelectric conversion element. Instead of using a fixed high-reflectance surface, the system modifies the luminance parameter to match the actual document type being scanned. For color print images with minimal white content, the reference element receives adjusted luminance levels that reflect the actual document characteristics, enabling accurate photodegradation correction across diverse document types.
3Device complexity
If the same environmental light is incident on two photoelectric conversion elements, then the setup is simple, but photodegradation correction cannot be achieved in ambient brightness sensors
Solution Approach 1:
The patent applies segmentation by dividing the optical path into two distinct channels: one channel directs environmental light to the first photoelectric conversion element for actual luminance measurement, while another channel directs reflected light from a white reference surface to the second photoelectric conversion element for photodegradation reference. This spatial segmentation of the optical system enables simultaneous acquisition of both measurement and reference signals, achieving accurate photodegradation correction in ambient brightness sensors.
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
This approach enables precise correction of detection values by delaying the degradation of the second sensing element, ensuring accurate measurement of luminance or temperature even as the first sensing element degrades, applicable to various optical and temperature sensors.
Implementation Method 1
a first photoelectric conversion element that outputs a first output signal with a level corresponding to the luminance of incident light
Implementation Method 2
a second photoelectric conversion element that has the same photoelectric conversion characteristic as the first photoelectric conversion element and outputs a second output signal with a level corresponding to the luminance of incident light
Data Source
AI summary
A sensing circuit includes a first sensing element, a second sensing element, a reduction unit, a storage unit, a specifying unit and a detection unit. The reduction unit reduces the amount of the energy applied to the second sensing element. The storage unit stores a degradation characteristic of the sensing element. The specifying unit specifies a rate of degradation. The detection unit detects the amount of the energy on the basis of the rate of degradation.