Image Sensor Reference Portion Stabilization
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Solution Overview
Problem
Existing image sensors for reading transmissive documents suffer from unstable image quality due to environmental changes and aging of illuminating elements, leading to reduced luminance and accuracy in image reading.
Innovation Solution
An image sensor configuration that includes a transmissive light source and a semitransparent reference portion on the transmissive member, combined with a reflective light source and a rod lens array, which allows for photoelectric conversion of both transmitted and reflected light, and uses signal processing to correct for variations in light intensity and element performance, thereby maintaining image quality across environmental changes and aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an illuminating element is used for reading transmissive documents, then image reading is enabled, but image quality becomes unstable due to TCR and environmental changes
Solution Approach 1:
The patent applies preliminary action by providing a reference portion with a known reflectance property (higher than the document) before the actual document reading. This reference portion is read first to establish a baseline signal level, which is then used to correct the document reading signal. By performing this reference measurement in advance, the system compensates for illuminating element variations (TCR, environmental changes, aging) before they affect the actual document reading accuracy.
2Adaptability or versatility
If a transmissive document unit with white reference window is used, then document type detection is enabled, but reading quality of transmissive documents is deteriorated
Solution Approach 1:
The patent applies segmentation by separating the reference portion from the actual document reading area. The reference portion is positioned at a specific location (e.g., edge of the reading area) and is distinct from the document being read. This segmentation allows the system to independently measure the reference signal and use it to correct the document signal, thereby improving reading quality while maintaining the ability to detect document types through the transmissive document unit.
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
The solution ensures stable and high-quality image reading by correcting for light intensity variations and element performance changes, reducing the impact of environmental and aging-related issues on image accuracy and luminance.
Implementation Method 1
a light emitting element for emitting light
Implementation Method 2
a light receiving element for allowing light to be incident and performing photoelectric conversion
Data Source
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AI summary
An image sensor includes: a light transmissive member extending in a direction orthogonal to a direction of conveying the document; a reference portion provided outside the conveying region where a document is conveyed with respect to the orthogonal direction and having a transmittance lower than a transmittance of in the conveying region of the light transmissive member; and a light source unit. The image sensor further includes: a lens unit converging the light transmitting through the document and the reference portion; a light receiving unit that receives the light transmitted through the lens unit and outputs an electric signal; an amplifying unit that amplifies the electric signal of the document corresponding to the conveying region and outputs an image signal of the document; and a controlling unit configured to control an amplification factor of the amplifying unit based on the electric signal corresponding to the reference portion.