Print Medium Position Detection Using Differential Light Sensors
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Solution Overview
Problem
Existing printing apparatuses face challenges in accurately detecting the position of a print medium due to fluctuations in signal values caused by the posture and environmental factors, such as external light, affecting the detection accuracy.
Innovation Solution
The printing apparatus employs a position detection unit with a light emitting unit and two light receiving units arranged side by side, which generate a difference signal to accurately detect the position of the print medium by canceling out the influence of environmental factors, using a differential signal output unit to enhance detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light receiving element is used to detect the print medium position, then the device complexity is low, but the detection accuracy deteriorates due to signal fluctuations from posture and environmental factors
Solution Approach 1:
The light receiving element is divided into multiple segments (first light receiving element and second light receiving element) arranged side by side in the width direction. Each segment detects light independently, and their signals are combined to determine position. This segmentation allows the system to distinguish between signal variations caused by medium posture versus actual position changes, thereby improving detection accuracy without requiring overly complex external shielding structures.
Solution Approach 2:
The patent combines the detection signals from multiple light receiving elements through a differential calculation process. By merging the information from the first and second light receiving elements and computing their difference, the system extracts position information while canceling out common environmental interference. This signal merging approach enhances measurement precision while maintaining relatively simple device structure.
2Measurement precision
If the light receiving element detects reflected light from the conveyance path, then the print medium position can be detected, but signal fluctuations occur due to external light and medium posture affecting detection accuracy
Solution Approach 1:
The system uses feedback from multiple light receiving elements to continuously monitor and compensate for environmental interference. By comparing the signals from the first and second light receiving elements in real-time through differential calculation, the system can identify and eliminate the influence of external light and medium posture variations, maintaining accurate position detection despite these harmful factors.
Solution Approach 2:
The patent converts the harmful effect of external light and posture variations into a useful signal characteristic. By arranging light receiving elements side by side and using differential calculation, the system transforms environmental interference that affects both elements similarly into a cancelable common-mode signal, while the position information appears as a differential signal. This approach turns the harmful environmental sensitivity into a feature that helps distinguish true position changes from noise.
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 configuration improves the detection accuracy of the print medium's position, enabling precise ink discharge up to the end of the medium without overspray, and allows for efficient intermittent conveyance and scanning printing.
Implementation Method 1
a light emitting unit configured to emit light to a conveyance path of a print medium, a first light receiving unit configured to detect reflected light from the conveyance path, and a second light receiving unit configured to detect reflected light from the conveyance path
Data Source
AI summary
A printing apparatus, comprising a printing unit, a conveyance unit and a position detection unit, the position detection unit including a light emitting unit configured to emit light to a conveyance path of a print medium, a first light receiving unit configured to detect reflected light from the conveyance path, and a second light receiving unit configured to detect reflected light from the conveyance path, the first and the second light receiving units being arranged side by side with other in a direction crossing a conveyance direction of a print medium, and a position of a print medium in a direction crossing the conveyance direction is specified based on a difference signal between signals of the first and the second light receiving units.