Image Reading Device Ambient Light Variation Detection
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Solution Overview
Problem
Image reading devices face challenges in accurately detecting document size due to ambient light variations, leading to erroneous detection and potential waste during copying, especially when the pressure plate angle becomes small, causing glare and reduced ambient light entry.
Innovation Solution
An image reading device with a platen, a pressure plate, an angle detector, a reader for incident light variation, a variation amount calculator, and a variation amount determination unit, which records and calculates light variations and determines if they exceed a threshold, and includes a lighting window and a moving unit to adjust the reader position and threshold settings for improved detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the read time is increased to perform time averaging for reducing ambient light influence, then the ambient light countermeasure effectiveness is improved, but the detection timing becomes difficult to obtain and the operation complexity increases
Solution Approach 1:
The patent performs ambient light measurement in advance during the pressure plate closing process (at angles greater than angle B) before the actual document size detection. This preliminary action captures ambient light data when the pressure plate is still open enough to allow light entry, storing it for later use in compensating during the actual detection phase when the pressure plate is closed and ambient light cannot be measured.
2Reliability
If the detection operation is performed during pressure plate closing to use closure as trigger, then the trigger reliability is improved, but the read time becomes insufficient and productivity decreases
Solution Approach 1:
The patent divides the detection process into two separate phases: (1) ambient light measurement phase performed during pressure plate closing when angle > angle B, and (2) document size detection phase performed when pressure plate is fully closed. This segmentation allows each phase to be optimized independently - the first phase has sufficient time for ambient light capture, while the second phase focuses on document detection with the previously measured ambient light data.
3Reliability
If the pressure plate angle becomes smaller than predetermined angle B after closing, then the trigger precision is improved, but the rear surface glare occurs and measurement precision deteriorates
Solution Approach 1:
The patent measures the ambient light in advance when the pressure plate angle is still greater than angle B (before the harmful glare condition occurs). This preliminary measurement captures the ambient light data before the rear surface glare interferes with detection. The measured ambient light is then used to compensate for glare effects during the actual document detection phase, preventing the glare from causing measurement errors.
4Measurement precision
If reading with light source OFF is performed to avoid pressure plate glare, then the measurement precision is improved, but the ambient light cannot be correctly obtained and reliability decreases
Solution Approach 1:
The patent performs ambient light measurement in advance during the pressure plate closing process (when angle > angle B) before the actual document size detection. This preliminary action captures ambient light data when the pressure plate is still open enough to allow light entry, storing it for later use in compensating during the actual detection phase when the pressure plate is closed and ambient light cannot be measured.
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 solution reduces erroneous detection by accurately accounting for ambient light variations, ensuring reliable document size detection even in environments with changing light conditions, and allows for automatic size detection while minimizing waste.
Implementation Method 1
a reader that records a variation in distribution for a fixed period of time of incident light heading toward an inside of the platen
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(b)
AI summary
An image reading device includes: a platen (21) on which a document is placed; a platen cover (22) openable and closable with respect to the platen (21); a cover-open sensor (23) which detects a fact that the open/close angle of the platen cover (22) has passed a predetermined angle from a close state; a CCD line sensor (92) including charge coupled devices (CCD) arranged for recording a variation in distribution for a fixed period of time of incident light when detecting passing of the platen cover (22); a variation amount calculator (52d) which calculates a variation amount of incident light at each distribution point on the basis of a variation in distribution recorded by the CCD line sensor (92); and a variation amount determination unit (52c) which determines whether or not a variation amount calculated by the variation amount calculator (52d) exceeds a predetermined threshold.